Nonlinear Layer-by-Layer Films: Effects of Chain Diffusivity on Film Structure and Swelling

DOE PAGES

Selin, Victor; Ankner, John F.; Sukhishvili, Svetlana A.

2017-08-09

Here in this paper, we report on the role of molecular diffusivity in the formation of nonlinearly growing polyelectrolyte multilayers (nlPEMs). Electrostatically bound polyelectrolyte multilayers were assembled from poly(methacrylic acid) (PMAA) as a polyanion and quaternized poly(2-(dimethylamino)ethyl methacrylate) (QPC) as a polycation. Film growth as measured by ellipsometry was strongly dependent on the time allowed for each polymer deposition step, suggesting that the diffusivities of the components are crucial in controlling the rate of film growth. Uptake of polyelectrolytes within nlPEMs was relatively slow and occurred on time scales ranging from minutes to hours, depending on the film thickness. Spectroscopicmore » ellipsometry measurements with nlPEM films exposed to aqueous solutions exhibited high (severalfold) degrees of film swelling and different swelling values for films exposed to QPC or PMAA solutions. FTIR spectroscopy showed that the average ionization of film-assembled PMAA increased upon binding of QPC and decreased upon binding of PMAA, in agreement with the charge regulation mechanism for weak polyelectrolytes. The use of neutron reflectometry (NR) enabled quantification of chain intermixing within the film, which was drastically enhanced when longer times were allowed for polyelectrolyte deposition. Diffusion coefficients of the polycation derived from the uptake rates of deuterated chains within hydrogenated films were of the order of 10 –14 cm 2/s, i.e., 5–6 orders of magnitude smaller than those found for diffusion of free polymer chains in solution. Exchange of the polymer solutions to buffer inhibited film intermixing. Taken together, these results contribute to understanding the mechanism of the growth of nonlinear polyelectrolyte multilayers and demonstrate the possibility of controlling film intermixing, which is highly desirable for potential future applications.« less

Improving Photocatalytic Activity through Electrostatic Self-Assembly: Polyelectrolytes as Tool for Solar Energy Conversion?

NASA Astrophysics Data System (ADS)

Groehn, Franziska

2015-03-01

With regard to the world's decreasing energy resources, developing strategies to exploit solar energy become more and more important. One approach is to take advantage of photocatalysis. Inspired by natural systems such as assemblies performing photosynthesis, it is highly promising to self-assemble synthetic functional species to form more effective or tailored supramolecular units. In this contribution, a new type of photocatalytically active self-assembled nanostructures in aqueous solution will be presented: supramolecular nano-objects obtained through self-assembly of macroions and multivalent organic or inorganic counterions. Polyelectrolyte-porphyrin nanoscale assemblies exhibit up to 10-fold higher photocatalytic activity than the corresponding porphyrins without polymeric template. Other self-assembled catalysts based on polyelectrolytes can exhibit expressed selectivity in a photocatalytic model reaction or even allow catalytic reactions in solution that are not possible with the building blocks only. Further, current results on combining different functional units at the polyelectrolyte template represent a next step towards more complex supramolecular structures for solar energy conversion.

Alternating current electroosmotic flow in polyelectrolyte-grafted nanochannel.

PubMed

Li, Fengqin; Jian, Yongjun; Chang, Long; Zhao, Guangpu; Yang, Liangui

2016-11-01

In this work, we investigate the time periodic electroosmotic flow (EOF) of an electrolyte solution through a slit polyelectrolyte-grafted (PE-grafted) nanochannel under applied alternating current (AC) electrical field. The PE-grafted nanochannel is represented by a rigid surface covered by a polyelectrolyte layer (PEL) in a brush-like configuration. Under Debye-Hückel approximation, we obtain analytical solutions of electrical potential in decoupled regime of PE-grafted nanochannel, where the thickness of PEL is independent of the electrostatic effects triggered by polyelectrolyte charges. Based upon the electrical potential obtained above, we calculate EOF velocities with uniform and non-uniform drag coefficients for PE-grafted nanochannel and compare their results. The effects of pertinent dimensionless parameters on EOF velocity amplitude are discussed in detail. Moreover, the amplitude of EOF velocity in a PE-grafted nanochannel is compared with that in a rigid one. It is shown that larger EOF velocity and volume flow rate are found for a PE-grafted nanochannel. In addition, AC EOF velocity is further investigated. The oscillation of velocity reduces and is restricted within the region near the PEL-electrolyte interface for higher oscillating Reynolds number Re. Copyright © 2016 Elsevier B.V. All rights reserved.

Molecular dynamics study of linear and comb-like polyelectrolytes in aqueous solution: effect of Ca2+ ions

NASA Astrophysics Data System (ADS)

Tong, Kefeng; Song, Xingfu; Sun, Shuying; Xu, Yanxia; Yu, Jianguo

2014-08-01

All-atom molecular dynamics simulations were employed to provide microscopic mechanism for the salt tolerance of polyelectrolytes dispersants. The conformational variation of polyelectrolytes and interactions between COO- groups and counterions/water molecules were also studied via radius of gyration and pair correlations functions. Sodium polyacrylate (NaPA) and sodium salts of poly(acrylic acid)-poly(ethylene oxide) (NaPA-PEO) were selected as the representative linear and comb-like polyelectrolyte, respectively. The results show that Ca2+ ions interact with COO- groups much stronger than Na+ ions and can bring ion-bridging interaction between intermolecular COO- groups in the NaPA systems. While in the NaPA-PEO systems, the introduced PEO side chains can prevent backbone chains from ion-bridging interactions and weaken the conformational changes. The present results can help in selecting and designing new-type efficient polyelectrolyte dispersants with good salt tolerance.

Hydrophobic interactions between polymethacrylic acid and sodium laureth sulfate in aqueous solutions

NASA Astrophysics Data System (ADS)

Yaremko, Z. M.; Fedushinskaya, L. B.; Burka, O. A.; Soltys, M. N.

2014-09-01

The role of hydrophobic interaction in the development of associative processes is demonstrated, based on the concentration dependences of the viscosity and pH of binary solutions of polymethacrylic acid as an anionic polyelectrolyte and sodium laureth sulfate as an anionic surfactant. It is found that the inflection point on the dependence of the difference between the pH values of binary solutions of polymethacrylic acid and sodium laureth sulfate on the polyelectrolyte concentration is a criterion for determining the predominant contribution from hydrophobic interaction, as is the inflection point on the dependence of pH of individual solutions of polymethacrylic acid on the polyelectrolyte concentration.

Polyelectrolyte multilayer assembly as a function of pH and ionic strength using the polysaccharides chitosan and heparin.

PubMed

Boddohi, Soheil; Killingsworth, Christopher E; Kipper, Matt J

2008-07-01

The goal of this work is to explore the effects of solution ionic strength and pH on polyelectrolyte multilayer (PEM) assembly, using biologically derived polysaccharides as the polyelectrolytes. We used the layer-by-layer (LBL) technique to assemble PEM of the polysaccharides heparin (a strong polyanion) and chitosan (a weak polycation) and characterized the sensitivity of the PEM composition and layer thickness to changes in processing parameters. Fourier-transform surface plasmon resonance (FT-SPR) and spectroscopic ellipsometry provided in situ and ex situ measurements of the PEM thickness, respectively. Vibrational spectroscopy and X-ray photoelectron spectroscopy (XPS) provided details of the chemistry (i.e., composition, electrostatic interactions) of the PEM. We found that when PEM were assembled from 0.2 M buffer, the PEM thickness could be increased from less than 2 nm per bilayer to greater than 4 nm per bilayer by changing the solution pH; higher and lower ionic strength buffer solutions resulted in narrower ranges of accessible thickness. Molar composition of the PEM was not very sensitive to solution pH or ionic strength, but pH did affect the interactions between the sulfonates in heparin and amines in chitosan when PEM were assembled from 0.2 M buffer. Changes in the PEM thickness with pH and ionic strength can be interpreted through descriptions of the charge density and conformation of the polyelectrolyte chains in solution.

Partial molar volume of anionic polyelectrolytes in aqueous solution.

PubMed

Salamanca, Constain; Contreras, Martín; Gamboa, Consuelo

2007-05-15

In this work the partial molar volumes (V) of different anionic polyelectrolytes and hydrophobically modified polyelectrolytes (PHM) were measured. Polymers like polymaleic acid-co-styrene, polymaleic acid-co-1-olefin, polymaleic acid-co-vinyl-2-pyrrolidone, and polyacrylic acid (abbreviated as MAS-n, PA-n-K2, AMVP, and PAA, respectively) were employed. These materials were investigated by density measurements in highly dilute aqueous solutions. The molar volume results allow us to discuss the effect of the carboxylic groups and the contributions from the comonomeric principal chain. The PAA presents the smaller V, while the largest V value was for AMVP. The V of PHM shows a linear relationship with the number of methylene groups in the lateral chain. It is found that the magnitude of the contribution per methylene group decreases as the hydrophobic character of the environment increases.

Use of marker ion and cationic surfactant plastic membrane electrode for potentiometric titration of cationic polyelectrolytes.

PubMed

Masadome, Takashi; Imato, Toshihiko

2003-07-04

A plasticized poly (vinyl chloride) (PVC) membrane electrode sensitive to stearyltrimethylammonium (STA) ion is applied to the determination of cationic polyelectrolytes such as poly (diallyldimethylammonium chloride) (Cat-floc) by potentiometric titration, using a potassium poly (vinyl sulfate) (PVSK) solution as a titrant. The end-point of the titration is detected as the potential change of the plasticized PVC membrane electrode caused by decrease in the concentration of STA ion added to the sample solution as a marker ion due to the ion association reaction between the STA ion and PVSK. The effects of the concentration of STA ion, coexisting electrolytes in the sample solution and pH of the sample on the degree of the potential change at the end-point were examined. A linear relationship between the concentration of cationic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 2x10(-5) to 4x10(-4) N for Cat-floc, glycol chitosan, and methylglycol chitosan.

A simple model for electrical charge in globular macromolecules and linear polyelectrolytes in solution

NASA Astrophysics Data System (ADS)

Krishnan, M.

2017-05-01

We present a model for calculating the net and effective electrical charge of globular macromolecules and linear polyelectrolytes such as proteins and DNA, given the concentration of monovalent salt and pH in solution. The calculation is based on a numerical solution of the non-linear Poisson-Boltzmann equation using a finite element discretized continuum approach. The model simultaneously addresses the phenomena of charge regulation and renormalization, both of which underpin the electrostatics of biomolecules in solution. We show that while charge regulation addresses the true electrical charge of a molecule arising from the acid-base equilibria of its ionizable groups, charge renormalization finds relevance in the context of a molecule's interaction with another charged entity. Writing this electrostatic interaction free energy in terms of a local electrical potential, we obtain an "interaction charge" for the molecule which we demonstrate agrees closely with the "effective charge" discussed in charge renormalization and counterion-condensation theories. The predictions of this model agree well with direct high-precision measurements of effective electrical charge of polyelectrolytes such as nucleic acids and disordered proteins in solution, without tunable parameters. Including the effective interior dielectric constant for compactly folded molecules as a tunable parameter, the model captures measurements of effective charge as well as published trends of pKa shifts in globular proteins. Our results suggest a straightforward general framework to model electrostatics in biomolecules in solution. In offering a platform that directly links theory and experiment, these calculations could foster a systematic understanding of the interrelationship between molecular 3D structure and conformation, electrical charge and electrostatic interactions in solution. The model could find particular relevance in situations where molecular crystal structures are not available or rapid, reliable predictions are desired.

Structure of flexible and semiflexible polyelectrolyte chains in confined spaces of slit micro/nanochannels.

PubMed

Jeon, Jonggu; Chun, Myung-Suk

2007-04-21

Understanding the behavior of a polyelectrolyte in confined spaces has direct relevance in design and manipulation of microfluidic devices, as well as transport in living organisms. In this paper, a coarse-grained model of anionic semiflexible polyelectrolyte is applied, and its structure and dynamics are fully examined with Brownian dynamics (BD) simulations both in bulk solution and under confinement between two negatively charged parallel plates. The modeling is based on the nonlinear bead-spring discretization of a continuous chain with additional long-range electrostatic, Lennard-Jones, and hydrodynamic interactions between pairs of beads. The authors also consider the steric and electrostatic interactions between the bead and the confining wall. Relevant model parameters are determined from experimental rheology data on the anionic polysaccharide xanthan reported previously. For comparison, both flexible and semiflexible models are developed accompanying zero and finite intrinsic persistence lengths, respectively. The conformational changes of the polyelectrolyte chain induced by confinements and their dependence on the screening effect of the electrolyte solution are faithfully characterized with BD simulations. Depending on the intrinsic rigidity and the medium ionic strength, the polyelectrolyte can be classified as flexible, semiflexible, or rigid. Confined flexible and semiflexible chains exhibit a nonmonotonic variation in size, as measured by the radius of gyration and end-to-end distance, with changing slit width. For the semiflexible chain, this is coupled to the variations in long-range bond vector correlation. The rigid chain, realized at low ionic strength, does not have minima in size but exhibits a sigmoidal transition. The size of confined semiflexible and rigid polyelectrolytes can be well described by the wormlike chain model once the electrostatic effects are taken into account by the persistence length measured at long length scale.

Molecular simulation of the swelling of polyelectrolyte gels by monovalent and divalent counterions

PubMed Central

Yin, De-Wei; Horkay, Ferenc; Douglas, Jack F.; de Pablo, Juan J.

2008-01-01

Permanently crosslinked polyelectrolyte gels are known to undergo discontinuous first-order volume phase transitions, the onset of which may be caused by a number of factors. In this study we examine the volumetric properties of such polyelectrolyte gels in relation to the progressive substitution of monovalent counterions by divalent counterions as the gels are equilibrated in solvents of different dielectric qualities. We compare the results of coarse-grained molecular dynamics simulations of polyelectrolyte gels with previous experimental measurements by others on polyacrylate gels. The simulations show that under equilibrium conditions there is an approximate cancellation between the electrostatic contribution and the counterion excluded-volume contribution to the osmotic pressure in the gel-solvent system; these two contributions to the osmotic pressure have, respectively, energetic and entropic origins. The finding of such a cancellation between the two contributions to the osmotic pressure of the gel-solvent system is consistent with experimental observations that the swelling behavior of polyelectrolyte gels can be described by equations of state for neutral gels. Based on these results, we show and explain that a modified form of the Flory–Huggins model for nonionic polymer solutions, which accounts for neither electrostatic effects nor counterion excluded-volume effects, fits both experimental and simulated data for polyelectrolyte gels. The Flory–Huggins interaction parameters obtained from regression to the simulation data are characteristic of ideal polymer solutions, whereas the experimentally obtained interaction parameters, particularly that associated with the third virial coefficient, exhibit a significant departure from ideality, leading us to conclude that further enhancements to the simulation model, such as the inclusion of excess salt, the allowance for size asymmetric electrolytes, or the use of a distance-dependent solvent dielectricity model, may be required. Molecular simulations also reveal that the condensation of divalent counterions onto the polyelectrolyte network backbone occurs preferentially over that of monovalent counterions. PMID:19045224

Molecular simulation of the swelling of polyelectrolyte gels by monovalent and divalent counterions.

PubMed

Yin, De-Wei; Horkay, Ferenc; Douglas, Jack F; de Pablo, Juan J

2008-10-21

Permanently crosslinked polyelectrolyte gels are known to undergo discontinuous first-order volume phase transitions, the onset of which may be caused by a number of factors. In this study we examine the volumetric properties of such polyelectrolyte gels in relation to the progressive substitution of monovalent counterions by divalent counterions as the gels are equilibrated in solvents of different dielectric qualities. We compare the results of coarse-grained molecular dynamics simulations of polyelectrolyte gels with previous experimental measurements by others on polyacrylate gels. The simulations show that under equilibrium conditions there is an approximate cancellation between the electrostatic contribution and the counterion excluded-volume contribution to the osmotic pressure in the gel-solvent system; these two contributions to the osmotic pressure have, respectively, energetic and entropic origins. The finding of such a cancellation between the two contributions to the osmotic pressure of the gel-solvent system is consistent with experimental observations that the swelling behavior of polyelectrolyte gels can be described by equations of state for neutral gels. Based on these results, we show and explain that a modified form of the Flory-Huggins model for nonionic polymer solutions, which accounts for neither electrostatic effects nor counterion excluded-volume effects, fits both experimental and simulated data for polyelectrolyte gels. The Flory-Huggins interaction parameters obtained from regression to the simulation data are characteristic of ideal polymer solutions, whereas the experimentally obtained interaction parameters, particularly that associated with the third virial coefficient, exhibit a significant departure from ideality, leading us to conclude that further enhancements to the simulation model, such as the inclusion of excess salt, the allowance for size asymmetric electrolytes, or the use of a distance-dependent solvent dielectricity model, may be required. Molecular simulations also reveal that the condensation of divalent counterions onto the polyelectrolyte network backbone occurs preferentially over that of monovalent counterions.

Molecular Structure and Sequence in Complex Coacervates

NASA Astrophysics Data System (ADS)

Sing, Charles; Lytle, Tyler; Madinya, Jason; Radhakrishna, Mithun

Oppositely-charged polyelectrolytes in aqueous solution can undergo associative phase separation, in a process known as complex coacervation. This results in a polyelectrolyte-dense phase (coacervate) and polyelectrolyte-dilute phase (supernatant). There remain challenges in understanding this process, despite a long history in polymer physics. We use Monte Carlo simulation to demonstrate that molecular features (charge spacing, size) play a crucial role in governing the equilibrium in coacervates. We show how these molecular features give rise to strong monomer sequence effects, due to a combination of counterion condensation and correlation effects. We distinguish between structural and sequence-based correlations, which can be designed to tune the phase diagram of coacervation. Sequence effects further inform the physical understanding of coacervation, and provide the basis for new coacervation models that take monomer-level features into account.

Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers.

PubMed

Nap, R J; Tagliazucchi, M; Szleifer, I

2014-01-14

This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads to systematic, but in general small, corrections to earlier theoretical predictions describing the behavior of weak polyelectrolyte layers. However, polyelectrolyte uncharging results in a decrease in the concentration of counterions and inclusion of the Born Energy can result in a substantial decrease of the counterion concentration. The effect of considering the Born energy contribution is explored for end-grafted weak polyelectrolyte layers by calculating experimental observables which are known to depend on the presence of charges within the polyelectrolyte layer: inclusion of the Born energy contribution leads to a decrease in the capacitance of polyelectrolyte-modified electrodes, a decrease of conductivity of polyelectrolyte-modified nanopores and an increase in the repulsion exerted by a planar polyelectrolyte layer confined by an opposing wall.

Finite-size polyelectrolyte bundles at thermodynamic equilibrium

NASA Astrophysics Data System (ADS)

Sayar, M.; Holm, C.

2007-01-01

We present the results of extensive computer simulations performed on solutions of monodisperse charged rod-like polyelectrolytes in the presence of trivalent counterions. To overcome energy barriers we used a combination of parallel tempering and hybrid Monte Carlo techniques. Our results show that for small values of the electrostatic interaction the solution mostly consists of dispersed single rods. The potential of mean force between the polyelectrolyte monomers yields an attractive interaction at short distances. For a range of larger values of the Bjerrum length, we find finite-size polyelectrolyte bundles at thermodynamic equilibrium. Further increase of the Bjerrum length eventually leads to phase separation and precipitation. We discuss the origin of the observed thermodynamic stability of the finite-size aggregates.

Advances in polyelectrolyte multilayer nanofilms as tunable drug delivery systems

PubMed Central

Jiang, Bingbing; Barnett, John B; Li, Bingyun

2009-01-01

There has been considerable interest in polyelectrolyte multilayer nanofilms, which have a variety of applications ranging from optical and electrochemical materials to biomedical devices. Polyelectrolyte multilayer nanofilms are constructed from aqueous solutions using electrostatic layer-by-layer self-assembly of oppositely-charged polyelectrolytes on a solid substrate. Multifunctional polyelectrolyte multilayer nanofilms have been studied using charged dyes, metal and inorganic nanoparticles, DNA, proteins, and viruses. In the past few years, there has been increasing attention to developing polyelectrolyte multilayer nanofilms as drug delivery vehicles. In this mini-review, we present recent developments in polyelectrolyte multilayer nanofilms with tunable drug delivery properties, with particular emphasis on the strategies in tuning the loading and release of drugs in polyelectrolyte multilayer nanofilms as well as their applications. PMID:24198464

Simulations of free-solution electrophoresis of polyelectrolytes with a finite Debye length using the Debye-Hückel approximation.

PubMed

Hickey, Owen A; Shendruk, Tyler N; Harden, James L; Slater, Gary W

2012-08-31

We introduce a mesoscale simulation method based on multiparticle collision dynamics (MPCD) for the electrohydrodynamics of polyelectrolytes with finite Debye lengths. By applying the Debye-Hückel approximation to assign an effective charge to MPCD particles near charged monomers, our simulations are able to reproduce the rapid rise in the electrophoretic mobility with respect to the degree of polymerization for the shortest polymer lengths followed by a small decrease for longer polymers due to charge condensation. Moreover, these simulations demonstrate the importance of a finite Debye length in accurately determining the mobility of uniformly charged polyelectrolytes and net neutral polyampholytes.

Regulation of anionic lipids in binary membrane upon the adsorption of polyelectrolyte: A Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Duan, Xiaozheng; Li, Yunqi; Zhang, Ran; Shi, Tongfei; An, Lijia; Huang, Qingrong

2013-06-01

We employ Monte Carlo simulations to investigate the interaction between an adsorbing linear flexible cationic polyelectrolyte and a binary fluid membrane. The membrane contains neutral phosphatidyl-choline, PC) and multivalent anionic (phosphatidylinositol, PIP2) lipids. We systematically study the influences of the solution ionic strength, the chain length and the bead charge density of the polyelectrolyte on the lateral rearrangement and the restricted mobility of the multivalent anionic lipids in the membrane. Our findings show that, the cooperativity effect and the electrostatic interaction of the polyelectrolyte beads can significantly affect the segregation extent and the concentration gradients of the PIP2 molecules, and further cooperate to induce the complicated hierarchical mobility behaviors of PIP2 molecules. In addition, when the polyelectrolyte brings a large amount of charges, it can form a robust electrostatic well to trap all PIP2 and results in local overcharge of the membrane. This work presents a mechanism to explain the membrane heterogeneity formation induced by the adsorption of charged macromolecule.

From dots to doughnuts: Two-dimensionally confined deposition of polyelectrolytes on block copolymer templates

DOE PAGES

Oded, Meirav; Kelly, Stephen T.; Gilles, Mary K.; ...

2016-07-05

The combination of block copolymer templating with electrostatic self-assembly provides a simple and robust method for creating nano-patterned polyelectrolyte multilayers over large areas. The deposition of the first polyelectrolyte layer provides important insights on the initial stages of multilayer buildup. Here, we focus on two-dimensionally confined “dots” patterns afforded by block copolymer films featuring hexagonally-packed cylinders that are oriented normal to the substrate. Rendering the cylinder caps positively charged enables the selective deposition of negatively charged polyelectrolytes on them under salt-free conditions. The initially formed polyelectrolyte nanostructures adopt a toroidal (“doughnut”) shape, which results from retraction of dangling polyelectrolyte segmentsmore » into the “dots” upon drying. With increasing exposure time to the polyelectrolyte solution, the final shape of the deposited polyelectrolyte transitions from a doughnut to a hemisphere. In conclusion, these insights would enable the creation of patterned polyelectrolyte multilayers with increased control over adsorption selectivity of the additional incoming polyelectrolytes.« less

From dots to doughnuts: Two-dimensionally confined deposition of polyelectrolytes on block copolymer templates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oded, Meirav; Kelly, Stephen T.; Gilles, Mary K.

The combination of block copolymer templating with electrostatic self-assembly provides a simple and robust method for creating nano-patterned polyelectrolyte multilayers over large areas. The deposition of the first polyelectrolyte layer provides important insights on the initial stages of multilayer buildup. Here, we focus on two-dimensionally confined “dots” patterns afforded by block copolymer films featuring hexagonally-packed cylinders that are oriented normal to the substrate. Rendering the cylinder caps positively charged enables the selective deposition of negatively charged polyelectrolytes on them under salt-free conditions. The initially formed polyelectrolyte nanostructures adopt a toroidal (“doughnut”) shape, which results from retraction of dangling polyelectrolyte segmentsmore » into the “dots” upon drying. With increasing exposure time to the polyelectrolyte solution, the final shape of the deposited polyelectrolyte transitions from a doughnut to a hemisphere. In conclusion, these insights would enable the creation of patterned polyelectrolyte multilayers with increased control over adsorption selectivity of the additional incoming polyelectrolytes.« less

Ionically Paired Layer-by-Layer Hydrogels: Water and Polyelectrolyte Uptake Controlled by Deposition Time

DOE PAGES

Selin, Victor; Ankner, John Francis; Sukhishvili, Svetlana

2018-01-11

Despite intense recent interest in weakly bound nonlinear (“exponential”) multilayers, the underlying structure-property relationships of these films are still poorly understood. This study explores the effect of time used for deposition of individual layers of nonlinearly growing layer-by-layer (LbL) films composed of poly(methacrylic acid) (PMAA) and quaternized poly-2-(dimethylamino)ethyl methacrylate (QPC) on film internal structure, swelling, and stability in salt solution, as well as the rate of penetration of invading polyelectrolyte chains. Thicknesses of dry and swollen films were measured by spectroscopic ellipsometry, film internal structure—by neutron reflectometry (NR), and degree of PMAA ionization—by Fourier-transform infrared spectroscopy (FTIR). The results suggestmore » that longer deposition times resulted in thicker films with higher degrees of swelling (up to swelling ratio as high as 4 compared to dry film thickness) and stronger film intermixing. The stronger intermixed films were more swollen in water, exhibited lower stability in salt solutions, and supported a faster penetration rate of invading polyelectrolyte chains. These results can be useful in designing polyelectrolyte nanoassemblies for biomedical applications, such as drug delivery coatings for medical implants or tissue engineering matrices.« less

Ionically Paired Layer-by-Layer Hydrogels: Water and Polyelectrolyte Uptake Controlled by Deposition Time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Selin, Victor; Ankner, John Francis; Sukhishvili, Svetlana

Despite intense recent interest in weakly bound nonlinear (“exponential”) multilayers, the underlying structure-property relationships of these films are still poorly understood. This study explores the effect of time used for deposition of individual layers of nonlinearly growing layer-by-layer (LbL) films composed of poly(methacrylic acid) (PMAA) and quaternized poly-2-(dimethylamino)ethyl methacrylate (QPC) on film internal structure, swelling, and stability in salt solution, as well as the rate of penetration of invading polyelectrolyte chains. Thicknesses of dry and swollen films were measured by spectroscopic ellipsometry, film internal structure—by neutron reflectometry (NR), and degree of PMAA ionization—by Fourier-transform infrared spectroscopy (FTIR). The results suggestmore » that longer deposition times resulted in thicker films with higher degrees of swelling (up to swelling ratio as high as 4 compared to dry film thickness) and stronger film intermixing. The stronger intermixed films were more swollen in water, exhibited lower stability in salt solutions, and supported a faster penetration rate of invading polyelectrolyte chains. These results can be useful in designing polyelectrolyte nanoassemblies for biomedical applications, such as drug delivery coatings for medical implants or tissue engineering matrices.« less

Electro-osmotic flow of semidilute polyelectrolyte solutions.

PubMed

Uematsu, Yuki; Araki, Takeaki

2013-09-07

We investigate electro-osmosis in aqueous solutions of polyelectrolytes using mean-field equations. A solution of positively charged polyelectrolytes is confined between two negatively charged planar surfaces, and an electric field is applied parallel to the surfaces. When electrostatic attraction between the polymer and the surface is strong, the polymers adhere to the surface, forming a highly viscous adsorption layer that greatly suppresses the electro-osmosis. Conversely, electro-osmosis is enhanced by depleting the polymers from the surfaces. We also found that the electro-osmotic flow is invertible when the electrostatic potential decays to its bulk value with the opposite sign. These behaviors are well explained by a simple mathematical form of the electro-osmotic coefficient.

Architecture, Assembly, and Emerging Applications of Branched Functional Polyelectrolytes and Poly(ionic liquid)s.

PubMed

Xu, Weinan; Ledin, Petr A; Shevchenko, Valery V; Tsukruk, Vladimir V

2015-06-17

Branched polyelectrolytes with cylindrical brush, dendritic, hyperbranched, grafted, and star architectures bearing ionizable functional groups possess complex and unique assembly behavior in solution at surfaces and interfaces as compared to their linear counterparts. This review summarizes the recent developments in the introduction of various architectures and understanding of the assembly behavior of branched polyelectrolytes with a focus on functional polyelectrolytes and poly(ionic liquid)s with responsive properties. The branched polyelectrolytes and poly(ionic liquid)s interact electrostatically with small molecules, linear polyelectrolytes, or other branched polyelectrolytes to form assemblies of hybrid nanoparticles, multilayer thin films, responsive microcapsules, and ion-conductive membranes. The branched structures lead to unconventional assemblies and complex hierarchical structures with responsive properties as summarized in this review. Finally, we discuss prospectives for emerging applications of branched polyelectrolytes and poly(ionic liquid)s for energy harvesting and storage, controlled delivery, chemical microreactors, adaptive surfaces, and ion-exchange membranes.

Structure of Polyelectrolyte Brushes in the Presence of Multivalent Counterions

DOE PAGES

Yu, Jing; Mao, Jun; Yuan, Guangcui; ...

2016-07-20

Polyelectrolyte brushes are of great importance to a wide range of fields, ranging from colloidal stabilization to responsive and tunable materials to lubrication. Here, we synthesized high-density polystyrenesulfonate (PSS) brushes using surface initiated atom transfer radical polymerization and performed neutron reflectivity (NR) and surface force measurements using a surface forces apparatus (SFA) to investigate the effect of monovalent Na +, divalent Ca 2+, Mg 2+, and Ba 2+, and trivalent Y 3+ counterions on the structure of the PSS brushes. NR and SFA results demonstrate that in monovalent salt solution the behavior of the PSS brushes agrees with scaling theorymore » well, exhibiting two distinct regimes: the osmotic and salted brush regimes. Introducing trivalent Y 3+ cations causes an abrupt shrinkage of the PSS brush due to the uptake of Y 3+ counterions. The uptake of Y 3+ counterions and shrinkage of the brush are reversible upon increasing the concentration of monovalent salt. Divalent cations, Mg 2+, Ca 2+, and Ba 2+, while all significantly affecting the structure of PSS brushes, show strong ion specific effects that are related to the specific interactions between the divalent cations and the sulfonate groups. Our results demonstrate that the presence of multivalent counterions, even at relatively low concentrations, can strongly affect the structure of polyelectrolyte brushes. Finally, the results also highlight the importance of ion specificity to the structure of polyelectrolyte brushes in solution.« less

Adsorption of surfactants and polymers at interfaces

NASA Astrophysics Data System (ADS)

Rojas, Orlando Jose

Surface tension and high-resolution laser light scattering experiments were used to investigate the adsorption of isomeric sugar-based surfactants at the air/liquid interface in terms of surfactant surface packing and rheology. Soluble monolayers of submicellar surfactant solutions exhibited a relatively viscous behavior. It was also proved that light scattering of high-frequency thermally-induced capillary waves can be utilized to study surfactant exchange between the surface and the bulk solution. Such analysis revealed the existence of a diffusional relaxation mechanism. A procedure based on XPS was developed for quantification, on an absolute basis, of polymer adsorption on mica and Langmuir-Blodgett cellulose films. The adsorption of cationic polyelectrolytes on negatively-charged solid surfaces was highly dependent on the polymer ionicity. It was found that the adsorption process is driven by electrostatic mechanisms. Charge overcompensation (or charge reversal) of mica occurred after adsorption of polyelectrolytes of ca. 50% charge density, or higher. It was demonstrated that low-charge-density polyelectrolytes adsorb on solid surfaces with an extended configuration dominated by loops and tails. In this case the extent of adsorption is limited by steric constraints. The conformation of the polyelectrolyte in the adsorbed layer is dramatically affected by the presence of salts or surfactants in aqueous solution. The phenomena which occur upon increasing the ionic strength are consistent with the screening of the electrostatic attraction between polyelectrolyte segments and solid surface. This situation leads to polyelectrolyte desorption accompanied by both an increase in the layer thickness and the range of the steric force. Adsorbed polyelectrolytes and oppositely charged surfactants readily associate at the solid/liquid interface. Such association induces polyelectrolyte desorption at a surfactant concentration which depends on the polyelectrolyte charge density. In practical systems the adsorption phenomena were found to be far more complex. Electrostatic and hydrogen bonding interactions play a major role in the adsorption of cationic polyelectrolytes on cellulosic substrates. Cationic and underivatized guar gum macromolecules form complexes with fines and dissolved and colloidal carbohydrates which are then retained on the cellulose fibers. The extent of the adsorption and association depends on the charge and nature of all the components present in pulp suspensions.

[An electron microscopy study of the structure of polyelectrolyte microcapsules containing protein and containing no protein].

PubMed

Kazakova, L I; Dubrovskiĭ, A V; Moshkov, D A; Shabarchina, L I; Sukhorukov, B I

2007-01-01

Electron micrographs of ultrathin sections of polyelectrolyte microparticles containing protein and free from protein for the formation of which CaCO3 spherulites served as a core basis have been obtained and analyzed. Polyelectrolyte microparticles with the number of alternately layered polyelectrolyte layers of polystyrene sulfonate and polyallylamine from 6 to 11 have been studied. It follows from the data obtained that protein-free polyelectrolyte particles having the dimensions 4.5-5 mm are formations of an intricate internal organization, which consist of a set of threadlike and closed nanoelements of polyelectrolyte nature with a thickness of 20-30 nm. The particles containing six to eight polyelectrolyte layers lack the external envelope; therefore, they were called polyelectrolyte microspherulites. With the number of layers nine and more, when a polyelectrolyte envelope appears on the surface, they transfer into polyelectrolyte microcapsules. It was found that, in a protein-containing polyelectrolyte microcapsule, as distinct from protein-free polyelectrolyte microspherulite and microcapsule, polyelectrolytes are located only in the nearsurface layer, and the external spatially organized envelope restricts the internal volume filled with protein solution. As the number of polyelectrolyte layers increases, the thickness of the envelope increases. The reasons for such substantial differences in the structures of polyelectrolyte microcapsules formed on protein-containing and protein-free CaCO3 spherulite are discussed.

Ductile polyelectrolyte macromolecule-complexed zinc phosphate conversion crystal pre-coatings and topcoatings embodying a laminate

DOEpatents

Sugama, Toshifumi; Kukacka, Lawrence E.; Carciello, Neal R.

1987-01-01

This invention relates to a precoat, laminate, and method for ductile coatings on steel and non-ferrous metals which comprises applying a zinc phosphating coating solution modified by a solid polyelectrolyte selected from polyacrylic acid (PAA), polymethacrylic acid (PMA), polyitaconic acid (PIA), and poly-L-glutamic acid. The contacting of the resin with the phosphating solution is made for a period of up to 20 hours at about 80.degree. C. The polyelectrolyte or the precoat is present in about 0.5-5.0% by weight of the total precoat composition and after application, the precoat base is dried for up to 5 hours at about 150.degree. C. to desiccate. Also, a laminate may be formed where polyurethane (PU) is applied as an elastomeric topcoating or polyfuran resin is applied as a glassy topcoating. It has been found that the use of PAA at a molecular weight of about 2.times.10.sup.5 gave improved ductility modulus effect.

Ductile polyelectrolyte macromolecule-complexed zinc phosphate conversion crystal pre-coatings and topcoatings embodying a laminate

DOEpatents

Sugama, T.; Kukacka, L.E.; Carciello, N.R.

1987-04-21

This invention relates to a precoat, laminate, and method for ductile coatings on steel and non-ferrous metals which comprises applying a zinc phosphating coating solution modified by a solid polyelectrolyte selected from polyacrylic acid (PAA), polymethacrylic acid (PMA), polyitaconic acid (PIA), and poly-L-glutamic acid. The contacting of the resin with the phosphating solution is made for a period of up to 20 hours at about 80 C. The polyelectrolyte or the precoat is present in about 0.5--5.0% by weight of the total precoat composition and after application, the precoat base is dried for up to 5 hours at about 150 C to desiccate. Also, a laminate may be formed where polyurethane (PU) is applied as an elastomeric topcoating or polyfuran resin is applied as a glassy topcoating. It has been found that the use of PAA at a molecular weight of about 2 [times] 10[sup 5] gave improved ductility modulus effect. 5 figs.

Ductile polyelectrolyte macromolecule-complexed zinc phosphate conversion crystal pre-coatings and topcoatings embodying a laminate

DOEpatents

Sugama, Toshifumi; Kukacka, L.E.; Carciello, N.R.

1985-11-05

This invention relates to a precoat, laminate, and method for ductile coatings on steel and non-ferrous metals which comprises applying a zinc phosphating coating solution modified by a solid polyelectrolyte selected from polyacrylic acid (PAA), polymethacrylic acid (PMA), polyitaconic acid (PIA), and poly-L-glutamic acid. The contacting of the resin with the phosphating solution is made for a period of up to 20 hours at about 80/sup 0/C. The polyelectrolyte or the precoat is present in about 0.5 to 5.0% by weight of the total precoat composition and after application, the precoat base is dried for up to 5 hours at about 150/sup 0/C to desiccate. Also, a laminate may be formed where polyurethane (PU) is applied as an elastomeric topcoating or polyfuran resin is applied as a glassy topcoating. It has been found that the use of PAA at a molecular weight of about 2 x 10/sup 5/ gave improved ductility modulus effect.

Polyelectrolyte Properties in Mono and Multi-Valent Ionic Media: Brushes and Complex Coacervates

NASA Astrophysics Data System (ADS)

Farina, Robert M.

Materials composed of polyelectrolytes have unique and interesting physical properties resulting primarily from their charged monomer segments. Polyelectrolytes, which exist in many different biological and industrial forms, have also been shown to be highly responsive to external environmental changes. Here, two specific polyelectrolyte systems, brushes and complex coacervates, are discussed in regards to how their properties can be tailored by adjusting the surrounding ionic environment with mono and multi-valent ions. End-tethered polyelectrolyte brushes, which constitute an interesting and substantial portion of polyelectrolyte applications, are well known for their ability to provide excellent lubrication and low friction when coated onto surfaces (e.g. articular cartilage and medical devices), as well as for their ability to stabilize colloidal particles in solution (e.g. paint and cosmetic materials). These properties have been extensively studied with brushes in pure mono-valent ionic media. However, polyelectrolyte brush interactions with multi-valent ions in solution are much less understood, although highly relevant considering mono and multi-valent counterions are present in most applications. Even at very low concentrations of multi-valent ions in solution, dramatic polyelectrolyte brush physical property changes can occur, resulting in collapsed chains which also adhere to one another via multi-valent bridging. Here, the strong polyelectrolyte poly(sodium styrene sulfonate) was studied using the Surface Forces Apparatus (SFA) and electrochemistry in order to investigate brush height and intermolecular interactions between two brushes as a function of multi-valent counterion population inside a brush. Complex coacervates are formed when polyanions and polycations are mixed together in proper conditions of an aqueous solution. This mixing results in a phase separation of a polymer-rich, coacervate phase composed of a chain network held together via electrostatic interactions. Complex coacervates are highly regarded for their extremely low interfacial energy resulting in an ability to spread and adhere to surfaces under water, utilized by marine organisms (e.g. mussels and tubeworms), as well as many encapsulation applications (e.g. pigment encapsulation for carbon-less paper and electronic paper displays). Here, the interfacial energy of coacervates composed of oppositely charged polypeptides, poly(L-lysine) and poly(L-glutamic acid), was investigated using the SFA in regards to changes in bulk mono-valent salt concentrations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Selin, Victor; Ankner, John F.; Sukhishvili, Svetlana A.

Here in this paper, we report on the role of molecular diffusivity in the formation of nonlinearly growing polyelectrolyte multilayers (nlPEMs). Electrostatically bound polyelectrolyte multilayers were assembled from poly(methacrylic acid) (PMAA) as a polyanion and quaternized poly(2-(dimethylamino)ethyl methacrylate) (QPC) as a polycation. Film growth as measured by ellipsometry was strongly dependent on the time allowed for each polymer deposition step, suggesting that the diffusivities of the components are crucial in controlling the rate of film growth. Uptake of polyelectrolytes within nlPEMs was relatively slow and occurred on time scales ranging from minutes to hours, depending on the film thickness. Spectroscopicmore » ellipsometry measurements with nlPEM films exposed to aqueous solutions exhibited high (severalfold) degrees of film swelling and different swelling values for films exposed to QPC or PMAA solutions. FTIR spectroscopy showed that the average ionization of film-assembled PMAA increased upon binding of QPC and decreased upon binding of PMAA, in agreement with the charge regulation mechanism for weak polyelectrolytes. The use of neutron reflectometry (NR) enabled quantification of chain intermixing within the film, which was drastically enhanced when longer times were allowed for polyelectrolyte deposition. Diffusion coefficients of the polycation derived from the uptake rates of deuterated chains within hydrogenated films were of the order of 10 –14 cm 2/s, i.e., 5–6 orders of magnitude smaller than those found for diffusion of free polymer chains in solution. Exchange of the polymer solutions to buffer inhibited film intermixing. Taken together, these results contribute to understanding the mechanism of the growth of nonlinear polyelectrolyte multilayers and demonstrate the possibility of controlling film intermixing, which is highly desirable for potential future applications.« less

Engineering polyelectrolyte multilayer structure at the nanometer length scale by tuning polymer solution conformation.

NASA Astrophysics Data System (ADS)

Boddohi, Soheil; Killingsworth, Christopher; Kipper, Matt

2008-03-01

Chitosan (a weak polycation) and heparin (a strong polyanion) are used to make polyelectrolyte multilayers (PEM). PEM thickness and composition are determined as a function of solution pH (4.6 to 5.8) and ionic strength (0.1 to 0.5 M). Over this range, increasing pH increases the PEM thickness; however, the sensitivity to changes in pH is a strong function of ionic strength. The PEM thickness data are correlated to the polymer conformation in solution. Polyelectrolyte conformation in solution is characterized by gel permeation chromatography (GPC). The highest sensitivity of PEM structure to pH is obtained at intermediate ionic strength. Different interactions govern the conformation and adsorption phenomena at low and high ionic strength, leading to reduced sensitivity to solution pH at extreme ionic strengths. The correspondence between PEM thickness and polymer solution conformation offers opportunities to tune polymer thin film structure at the nanometer length scale by controlling simple, reproducible processing conditions.

Molecular Dynamics Simulations of Adsorption of Poly(acrylic acid) and Poly(methacrylic acid) on Dodecyltrimethylammonium Chloride Micelle in Water: Effect of Charge Density.

PubMed

Sulatha, Muralidharan S; Natarajan, Upendra

2015-09-24

We have investigated the interaction of dodecyltrimethylammonium chloride (DoTA) micelle with weak polyelectrolytes, poly(acrylic acid) and poly(methacrylic acid). Anionic as well as un-ionized forms of the polyelectrolytes were studied. Polyelectrolyte-surfactant complexes were formed within 5-11 ns of the simulation time and were found to be stable. Association is driven purely by electrostatic interactions for anionic chains whereas dispersion interactions also play a dominant role in the case of un-ionized chains. Surfactant headgroup nitrogen atoms are in close contact with the carboxylic oxygens of the polyelectrolyte chain at a distance of 0.35 nm. In the complexes, the polyelectrolyte chains are adsorbed on to the hydrophilic micellar surface and do not penetrate into the hydrophobic core of the micelle. Polyacrylate chain shows higher affinity for complex formation with DoTA as compared to polymethacrylate chain. Anionic polyelectrolyte chains show higher interaction strength as compared to corresponding un-ionized chains. Anionic chains act as polymeric counterion in the complexes, resulting in the displacement of counterions (Na(+) and Cl(-)) into the bulk solution. Anionic chains show distinct shrinkage upon adsorption onto the micelle. Detailed information about the microscopic structure and binding characteristics of these complexes is in agreement with available experimental literature.

Counterion adsorption and desorption rate of a charged macromolecule

NASA Astrophysics Data System (ADS)

Shi, Yu; Yang, Jingfa; Zhao, Jiang

The rate constant of counterion adsorption to and desorption from a synthetic polyelectrolyte, polystyrene sulfonate (PSS-), is measured in aqueous solution by single molecule fluorescence spectroscopy. The results show that both adsorption and desorption rate of counterions have strong dependence on polymer concentration, salt concentration as well as the molecular weight of polyelectrolytes. The results clearly demonstrate that the contribution of electrostatic interaction and the translational entropy to the distribution of counterions of a polyelectrolyte molecule. The information is helpful to the understanding of polyelectrolyte physics. National Natural Science Foundation of China.

Potential of mean force between like-charged nanoparticles: Many-body effect

NASA Astrophysics Data System (ADS)

Zhang, Xi; Zhang, Jin-Si; Shi, Ya-Zhou; Zhu, Xiao-Long; Tan, Zhi-Jie

2016-03-01

Ion-mediated interaction is important for the properties of polyelectrolytes such as colloids and nucleic acids. The effective pair interactions between two polyelectrolytes have been investigated extensively, but the many-body effect for multiple polyelectrolytes still remains elusive. In this work, the many-body effect in potential of mean force (PMF) between like-charged nanoparticles in various salt solutions has been comprehensively examined by Monte Carlo simulation and the nonlinear Poisson-Boltzmann theory. Our calculations show that, at high 1:1 salt, the PMF is weakly repulsive and appears additive, while at low 1:1 salt, the additive assumption overestimates the repulsive many-body PMF. At low 2:2 salt, the pair PMF appears weakly repulsive while the many-body PMF can become attractive. In contrast, at high 2:2 salt, the pair PMF is apparently attractive while the many-body effect can cause a weaker attractive PMF than that from the additive assumption. Our microscopic analyses suggest that the elusive many-body effect is attributed to ion-binding which is sensitive to ion concentration, ion valence, number of nanoparticles and charges on nanoparticles.

Complex coacervation in charge complementary biopolymers: Electrostatic versus surface patch binding.

PubMed

Pathak, Jyotsana; Priyadarshini, Eepsita; Rawat, Kamla; Bohidar, H B

2017-12-01

In this review, a number of systems are described to demonstrate the effect of polyelectrolyte chain stiffness (persistence length) on the coacervation phenomena, after we briefly review the field. We consider two specific types of complexation/coacervation: in the first type, DNA is used as a fixed substrate binding to flexible polyions such as gelatin A, bovine serum albumin and chitosan (large persistence length polyelectrolyte binding to low persistence length biopolymer), and in the second case, different substrates such as gelatin A, bovine serum albumin, and chitosan were made to bind to a polyion gelatin B (low persistence length substrate binding to comparable persistence length polyion). Polyelectrolyte chain flexibility was found to have remarkable effect on the polyelectrolyte-protein complex coacervation. The competitive interplay of electrostatic versus surface patch binding (SPB) leading to associative interaction followed by complex coacervation between these biopolymers is elucidated. We modelled the SPB interaction in terms of linear combination of attractive and repulsive Coulombic forces with respect to the solution ionic strength. The aforesaid interactions were established via a universal phase diagram, considering the persistence length of polyion as the sole independent variable. Copyright © 2017 Elsevier B.V. All rights reserved.

Biosensors from conjugated polyelectrolyte complexes

PubMed Central

Wang, Deli; Gong, Xiong; Heeger, Peter S.; Rininsland, Frauke; Bazan, Guillermo C.; Heeger, Alan J.

2002-01-01

A charge neutral complex (CNC) was formed in aqueous solution by combining an orange light emitting anionic conjugated polyelectrolyte and a saturated cationic polyelectrolyte at a 1:1 ratio (per repeat unit). Photoluminescence (PL) from the CNC can be quenched by both the negatively charged dinitrophenol (DNP) derivative, (DNP-BS−), and positively charged methyl viologen (MV2+). Use of the CNC minimizes nonspecific interactions (which modify the PL) between conjugated polyelectrolytes and biopolymers. Quenching of the PL from the CNC by the DNP derivative and specific unquenching on addition of anti-DNP antibody (anti-DNP IgG) were observed. Thus, biosensing of the anti-DNP IgG was demonstrated. PMID:11756675

Sustained, Controlled and Stimuli-Responsive Drug Release Systems Based on Nanoporous Anodic Alumina with Layer-by-Layer Polyelectrolyte

NASA Astrophysics Data System (ADS)

Porta-i-Batalla, Maria; Eckstein, Chris; Xifré-Pérez, Elisabet; Formentín, Pilar; Ferré-Borrull, J.; Marsal, Lluis F.

2016-08-01

Controlled drug delivery systems are an encouraging solution to some drug disadvantages such as reduced solubility, deprived biodistribution, tissue damage, fast breakdown of the drug, cytotoxicity, or side effects. Self-ordered nanoporous anodic alumina is an auspicious material for drug delivery due to its biocompatibility, stability, and controllable pore geometry. Its use in drug delivery applications has been explored in several fields, including therapeutic devices for bone and dental tissue engineering, coronary stent implants, and carriers for transplanted cells. In this work, we have created and analyzed a stimuli-responsive drug delivery system based on layer-by-layer pH-responsive polyelectrolyte and nanoporous anodic alumina. The results demonstrate that it is possible to control the drug release using a polyelectrolyte multilayer coating that will act as a gate.

Interplay of polyelectrolytes with different adsorbing surfaces

NASA Astrophysics Data System (ADS)

Xie, Feng

We study the adsorption of polyelectrolytes from solution onto different adsorbing surfaces, focusing on the electrostatic interactions. Measurements of the surface excess, fractional ionization of chargeable groups, segmental orientation, and adsorption kinetics were made using Fourier transform infrared spectroscopy in the mode of attenuated total reflection. Different adsorbing surfaces, from single solid surfaces, solid surfaces modified with adsorbed polymer layer, to fluid-like surfaces-biomembranes were adopted. Both atomic force microscopy (AFM) and fluorescent techniques were employed to investigate the fluid-like surfaces in the absence and in the presence of polyelectrolytes. The work focuses on three primary issues: (i) the charge regulation of weak polyelectrolytes on both homogeneous and heterogeneous surfaces, (ii) the dynamics of adsorption when the surface possesses reciprocal mobility, i.e., biomembrane surface, and (iii) the structural and dynamical properties of the fluid-like surfaces interacting with polyelectrolytes. We find that the ionization of chargeable groups in weak polyelectrolytes is controlled by the charge balance between the adsorbates and the surfaces. A new interpretation of ionization in the adsorbed layer provides a new insight into the fundamental problem of whether ions of opposite charge associate or remain separate. Bjerrum length is found to be a criterion for the onset of surface ionization suppression, which helps to predict and control the conformation transition of proteins. In addition to the effect of different surfaces on the adsorption behavior of polyelectrolytes, we also focused on the response of the surfaces to the adsorbates. Chains that encountered sparsely-covered surfaces spread to maximize the number of segment-surface contacts at rates independent of the molar mass. Surface reconstruction rather than molar mass of the adsorbing molecules appeared to determine the rate of spreading. This contrasts starkly with traditional polymer adsorption onto surfaces whose structure is "frozen" and unresponsive. Finally, preliminary studies on dynamical properties of biomembrane surfaces interacting with polyelectrolytes are presented, using fluorescence correlation spectroscopy (FCS). The significance is to characterize domains induced by polyelectrolyte binding.

Formation and stability of water-soluble, molecular polyelectrolyte complexes: effects of charge density, mixing ratio, and polyelectrolyte concentration.

PubMed

Shovsky, Alexander; Varga, Imre; Makuska, Ricardas; Claesson, Per M

2009-06-02

The formation of complexes with stoichiometric (1:1) as well as nonstoichiometric (2:1) and (1:2) compositions between oppositely charged synthetic polyelectrolytes carrying strong ionic groups and significantly different molecular weights is reported in this contribution. Poly(sodium styrenesulfonate) (NaPSS) was used as polyanion, and a range of copolymers with various molar ratios of the poly(methacryloxyethyltrimethylammonium) chloride, poly(METAC), and the nonionic poly(ethylene oxide) ether methacrylate, poly(PEO45MEMA), were used as polycations. Formation and stability of PECs have been investigated by dynamic and static light scattering (LS), turbidity, and electrophoretic mobility measurements as a function of polyelectrolyte solution concentration, charge density of the cationic polyelectrolyte, and mixing ratio. The data obtained demonstrate that in the absence of PEO45 side chains the 100% charged polymer (polyMETAC) formed insoluble PECs with PSS that precipitate from solution when exact stoichiometry is achieved. In nonstoichiometric complexes (1:2) and (2:1) large colloidally stable aggregates were formed. The presence of even a relatively small amount of PEO45 side chains (25%) in the cationic copolymer was sufficient for preventing precipitation of the formed stoichiometric and nonstoichiometric complexes. These PEC's are sterically stabilized by the PEO45 chains. By further increasing the PEO45 side-chain content (50 and 75%) of the cationic copolymer, small, water-soluble molecular complexes could be formed. The data suggest that PSS molecules and the charged backbone of the cationic brush form a compact core, and with sufficiently high PEO45 chain density (above 25%) molecular complexes are formed that are stable over prolonged times.

Reversible water uptake/release by thermoresponsive polyelectrolyte hydrogels derived from ionic liquids.

PubMed

Deguchi, Yuki; Kohno, Yuki; Ohno, Hiroyuki

2015-06-07

Thermoresponsive polyelectrolyte hydrogels, derived from tetra-n-alkylphosphonium 3-sulfopropyl methacrylate-type ionic liquid monomers, show reversible water uptake/release, in which the gels absorb/desorb water for at least ten cycles via a lower critical solution temperature-type phase transition.

Formation of polyelectrolyte complexes with diethylaminoethyl dextran: charge ratio and molar mass effect.

PubMed

Le Cerf, Didier; Pepin, Anne Sophie; Niang, Pape Momar; Cristea, Mariana; Karakasyan-Dia, Carole; Picton, Luc

2014-11-26

The formation of polyelectrolyte complexes (PECs) between carboxymethyl pullulan and DEAE Dextran, was investigated, in dilute solution, with emphasis on the effect of charge density (molar ratio or pH) and molar masses. Electrophoretic mobility measurements have evidenced that insoluble PECs (neutral electrophoretic mobility) occurs for charge ratio between 0.6 (excess of polycation) and 1 (stoichiometry usual value) according to the pH. This atypical result is explained by the inaccessibility of some permanent cationic charge when screened by pH dependant cationic ones (due to the Hoffman alkylation). Isothermal titration calorimetry (ITC) indicates an endothermic formation of PEC with a binding constant around 10(5) L mol(-1). Finally asymmetrical flow field flow fractionation coupled on line with static multi angle light scattering (AF4/MALS) evidences soluble PECs with very large average molar masses and size around 100 nm, in agreement with scrambled eggs multi-association between various polyelectrolyte chains. Copyright © 2014 Elsevier Ltd. All rights reserved.

Poisson-Boltzmann theory of the charge-induced adsorption of semi-flexible polyelectrolytes.

PubMed

Ubbink, Job; Khokhlov, Alexei R

2004-03-15

A model is suggested for the structure of an adsorbed layer of a highly charged semi-flexible polyelectrolyte on a weakly charged surface of opposite charge sign. The adsorbed phase is thin, owing to the effective reversal of the charge sign of the surface upon adsorption, and ordered, owing to the high surface density of polyelectrolyte strands caused by the generally strong binding between polyelectrolyte and surface. The Poisson-Boltzmann equation for the electrostatic interaction between the array of adsorbed polyelectrolytes and the charged surface is solved for a cylindrical geometry, both numerically, using a finite element method, and analytically within the weak curvature limit under the assumption of excess monovalent salt. For small separations, repulsive surface polarization and counterion osmotic pressure effects dominate over the electrostatic attraction and the resulting electrostatic interaction curve shows a minimum at nonzero separations on the Angstrom scale. The equilibrium density of the adsorbed phase is obtained by minimizing the total free energy under the condition of equality of chemical potential and osmotic pressure of the polyelectrolyte in solution and in the adsorbed phase. For a wide range of ionic conditions and charge densities of the charged surface, the interstrand separation as predicted by the Poisson-Boltzmann model and the analytical theory closely agree. For low to moderate charge densities of the adsorbing surface, the interstrand spacing decreases as a function of the charge density of the charged surface. Above about 0.1 M excess monovalent salt, it is only weakly dependent on the ionic strength. At high charge densities of the adsorbing surface, the interstrand spacing increases with increasing ionic strength, in line with the experiments by Fang and Yang [J. Phys. Chem. B 101, 441 (1997)]. (c) 2004 American Institute of Physics.

Influence of natural organic matter (NOM) and synthetic polyelectrolytes on colloidal behavior of metal oxide nanoparticles

NASA Astrophysics Data System (ADS)

Ghosh, Saikat

The colloidal behavior of engineered nanomaterials exposed in an aquatic environment may significantly influence their bioavailability as well as toxicity to different species. Natural organic matter (NOM) is one of the major colloidal materials ubiquitous in the environment with significant structural heterogeneity. Therefore, role of NOM molecules on environmental fate of these engineered NPs needs to be addressed. Colloidal behavior of aluminum (Al2O 3) and magnetic iron oxide (gammaFe2O3) NPs was studied in the presence of structurally different HAs and synthetic polyacrylic acids (PAAs). The conformation behavior of the adsorobed NOM/polyelectrolyte under specific solution conditions were determined with dynamic light scattering, atomic force microscopy measurements. Al2O3 NPs followed the classical DLVO model of colloidal behavior in their pristine state. However, a significant deviation from the classical DLVO model was observed when these NPs were coated with structurally different HAs. Low polar, high molecular weight HA fractions showed much stronger stabilization against Ca2+ induced aggregation. Previously, we observed that these low polar, high molecular weight fractions strongly destabilized the NP suspension when added in a small quantity. A significant transformation in suspension stability was observed possibly due to steric effect of these adsorbed HAs. The colloidal behavior of PAA/NOM coated ferrimagnetic gammaFe 2O3 NPs were investigated. Pure gammaFe2O 3 NPs were extremely unstable in aqueous solution but a significant enhancement in colloidal stability was observed after coating with polyelectrolytes/NOM. The steric as well as electrostatic stabilization introduced by the polyelectrolyte coating strongly dictated the colloidal stability. The alteration of electrosteric stabilization mechanisms by pH-induced conformation change profoundly influences the colloidal stability. Atomic force microscopy (AFM) study revealed a highly stretched conformation of the HA molecular chains adsorbed on gammaFe 2O3 NP surface with increasing pH from 5 to 9 which enhanced the colloidal stability trough long range electrosteric stabilization. The depletion of the polyelectrolytes during dilution of the suspension in the acidic solution conditions and in the presence of Na+ or Ca 2+ decreased the colloidal stability. The conformation of the polyelectrolytes adsorbed on the NP surface altered significantly as a function of substrate surface charge as viewed from the AFM imaging.

Nanocomplexes of Photolabile Polyelectrolyte and Upconversion Nanoparticles for Near-Infrared Light-Triggered Payload Release.

PubMed

Xiang, Jun; Ge, Feijie; Yu, Bing; Yan, Qiang; Shi, Feng; Zhao, Yue

2018-06-07

A new approach to encapsulating charged cargo molecules into a nanovector and subsequently using near-infrared (NIR) light to trigger the release is demonstrated. NIR light-responsive nanovector was prepared through electrostatic interaction-driven complexation between negatively charged silica-coated upconversion nanoparticles (UCNP@silica, 87 nm hydrodynamic diameter, polydispersity index ∼0.05) and a positively charged UV-labile polyelectrolyte bearing pendants of poly(ethylene glycol) and o-nitrobenzyl side groups; whereas charged fluorescein (FLU) was loaded through a co-complexation process. By controlling the amount of polyelectrolyte, UCNP@silica can be covered by the polymer, whereas remaining dispersed in aqueous solution. Under 980 nm laser excitation, UV light emitted by UCNP is absorbed by photolytic side groups within polyelectrolyte, which results in cleavage of o-nitrobenzyl groups and formation of carboxylic acid groups. Such NIR light-induced partial reversal of positive charge to negative charge on the polyelectrolyte layer disrupts the equilibrium among UCNP@silica, polyelectrolyte, and FLU and, consequently, leads to release of FLU molecules.

Renewable urea sensor based on a self-assembled polyelectrolyte layer.

PubMed

Wu, Zhaoyang; Guan, Lirui; Shen, Guoli; Yu, Ruqin

2002-03-01

A renewable urea sensor based on a carboxylic poly(vinyl chloride) (PVC-COOH) matrix pH-sensitive membrane has been proposed, in which a positively charged polyelectrolyte layer is first constructed by using a self-assembly technique on the surface of a PVC-COOH membrane, and urease, with negative charges, is then immobilized through electrostatic adsorption onto the PVC-COOH membrane, by controlling the pH of the urease solution below its isoelectric point. The response characteristics of the PVC-COOH pH-sensitive membrane and the effects of experimental conditions have been investigated in detail. Compared with conventional covalent immobilization, the urea sensor made with this self-assembly immobilization shows significant advantage in terms of sensitivity and ease of regeneration. The potential responses of the urea sensor with self-assembly immobilization increase with the urea concentration over the concentration range 10(-5) - 10(-1) mol l(-1), and the detection limit is 0.028 mmol(-1). Moreover, this type of urea sensor can be repeatedly regenerated by using a simple washing treatment with 0.01 mol l(-1) NaOH (containing 0.5 mol l(-1) NaCl) and 0.01 mol l(-1) HCl. The urease layers and the polyelectrolyte layers on the PVC-COOH membrane are removed, the potential response of the sensor to urea solutions of different concentrations returns nearly to zero, and another assembly cycle of urease and polyelectrolyte can then be carried out.

Chirality-selected phase behaviour in ionic polypeptide complexes

DOE PAGES

Perry, Sarah L.; Leon, Lorraine; Hoffmann, Kyle Q.; ...

2015-01-14

In this study, polyelectrolyte complexes present new opportunities for self-assembled soft matter. Factors determining whether the phase of the complex is solid or liquid remain unclear. Ionic polypeptides enable examination of the effects of stereochemistry on complex formation. Here we demonstrate that chirality determines the state of polyelectrolyte complexes, formed from mixing dilute solutions of oppositely charged polypeptides, via a combination of electrostatic and hydrogen-bonding interactions. Fluid complexes occur when at least one of the polypeptides in the mixture is racemic, which disrupts backbone hydrogen-bonding networks. Pairs of purely chiral polypeptides, of any sense, form compact, fibrillar solids with amore » β-sheet structure. Analogous behaviour occurs in micelles formed from polypeptide block copolymers with polyethylene oxide, where assembly into aggregates with either solid or fluid cores, and eventually into ordered phases at high concentrations, is possible. Chirality is an exploitable tool for manipulating material properties in polyelectrolyte complexation.« less

The influence of screening of the polyion electrostatic potential on the counterion dynamics in polyelectrolyte solutions

NASA Astrophysics Data System (ADS)

Schipper, F. J. M.; Hollander, J. G.; Leyte, J. C.

1998-10-01

The self-diffusion coefficient of tetra-methylammonium counterion in solutions of polymethacrylic acid in 0953-8984/10/41/004/img1 has been measured over a broad polyion concentration range at a constant degree of neutralization and at different ratios of added monovalent or bivalent salt to polyions. A maximum counterion self-diffusion coefficient was observed as a function of polyion concentration. The value of the self-diffusion coefficient at the maximum did not depend on the valency of the added salt. The maximum was found at lower polymer concentrations and with a higher value, when the ratio of added salt to polyions was increased, as predicted by the Poisson-Boltzmann-Smoluchowski equation in the cylindrical cell model for polyelectrolytes. At higher polyion concentrations a maximum counterion self-diffusion coefficient against the ratio of added salt and polyions was observed, which has not been reported before. Upon increasing this ratio the electrostatic potential of the polyelectrolyte gets screened, leading to an increase of the counterion self-diffusion coefficient. Concentration effects of the added salt on the other hand ultimately lead to a decrease of the counterion self-diffusion coefficient, which explains the occurrence of a maximum.

Fabrication of Thickness-Controllable Micropatterned Polyelectrolyte-Film/Nanoparticle Surfaces by Using the Plasma Oxidation Method.

PubMed

Zhu, Chun-Tao; Ma, Sheng-Hua; Zhang, Ying; Wang, Xue-Jing; Lv, Peng; Han, Xiao-Jun

2016-04-05

We have demonstrated a novel way to form thickness-controllable polyelectrolyte-film/nanoparticle patterns by using a plasma etching technique to form, first, a patterned self-assembled monolayer surface, followed by layer-by-layer assembly of polyelectrolyte-films/nanoparticles. Octadecyltrimethoxysilane (ODS) and (3-aminopropyl)triethoxysilane (APTES) self-assembled monolayers (SAMs) were used for polyelectrolyte-film and nanoparticle patterning, respectively. The resolution of the proposed patterning method can easily reach approximately 2.5 μm. The height of the groove structure was tunable from approximately 2.5 to 150 nm. The suspended lipid membrane across the grooves was fabricated by incubating the patterned polyelectrolyte groove arrays in solutions of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) giant unilamellar vesicles (GUVs). The method demonstrated here reveals a new path to create patterned 2D or 3D structures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface modification of silk fibroin fabric using layer-by-layer polyelectrolyte deposition and heparin immobilization for small-diameter vascular prostheses.

PubMed

Elahi, M Fazley; Guan, Guoping; Wang, Lu; Zhao, Xinzhe; Wang, Fujun; King, Martin W

2015-03-03

There is an urgent need to develop a biologically active implantable small-diameter vascular prosthesis with long-term patency. Silk-fibroin-based small-diameter vascular prosthesis is a promising candidate having higher patency rate; however, the surface modification is indeed required to improve its further hemocompatibility. In this study, silk fibroin fabric was modified by a two-stage process. First, the surface of silk fibroin fabric was coated using a layer-by-layer polyelectrolyte deposition technique by stepwise dipping the silk fibroin fabric into a solution of cationic poly(allylamine hydrochloride) (PAH) and anionic poly(acrylic acid) (PAA) solution. The dipping procedure was repeated to obtain the PAH/PAA multilayers deposited on the silk fibroin fabrics. Second, the polyelectrolyte-deposited silk fibroin fabrics were treated in EDC/NHS-activated low-molecular-weight heparin (LMWH) solution at 4 °C for 24 h, resulting in immobilization of LMWH on the silk fibroin fabrics surface. Scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray data revealed the accomplishment of LMWH immobilization on the polyelectrolyte-deposited silk fibroin fabric surface. The higher the number of PAH/PAA coating layers on the silk fibroin fabric, the more surface hydrophilicity could be obtained, resulting in a higher fetal bovine serum protein and platelets adhesion resistance properties when tested in vitro. In addition, compared with untreated sample, the surface-modified silk fibroin fabrics showed negligible loss of bursting strength and thus reveal the acceptability of polyelectrolytes deposition and heparin immobilization approach for silk-fibroin-based small-diameter vascular prostheses modification.

Complexation behavior of oppositely charged polyelectrolytes: Effect of charge distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Mingtian; Li, Baohui, E-mail: dliang@pku.edu.cn, E-mail: baohui@nankai.edu.cn; Zhou, Jihan

Complexation behavior of oppositely charged polyelectrolytes in a solution is investigated using a combination of computer simulations and experiments, focusing on the influence of polyelectrolyte charge distributions along the chains on the structure of the polyelectrolyte complexes. The simulations are performed using Monte Carlo with the replica-exchange algorithm for three model systems where each system is composed of a mixture of two types of oppositely charged model polyelectrolyte chains (EGEG){sub 5}/(KGKG){sub 5}, (EEGG){sub 5}/(KKGG){sub 5}, and (EEGG){sub 5}/(KGKG){sub 5}, in a solution including explicit solvent molecules. Among the three model systems, only the charge distributions along the chains are notmore » identical. Thermodynamic quantities are calculated as a function of temperature (or ionic strength), and the microscopic structures of complexes are examined. It is found that the three systems have different transition temperatures, and form complexes with different sizes, structures, and densities at a given temperature. Complex microscopic structures with an alternating arrangement of one monolayer of E/K monomers and one monolayer of G monomers, with one bilayer of E and K monomers and one bilayer of G monomers, and with a mixture of monolayer and bilayer of E/K monomers in a box shape and a trilayer of G monomers inside the box are obtained for the three mixture systems, respectively. The experiments are carried out for three systems where each is composed of a mixture of two types of oppositely charged peptide chains. Each peptide chain is composed of Lysine (K) and glycine (G) or glutamate (E) and G, in solution, and the chain length and amino acid sequences, and hence the charge distribution, are precisely controlled, and all of them are identical with those for the corresponding model chain. The complexation behavior and complex structures are characterized through laser light scattering and atomic force microscopy measurements. The order of the apparent weight-averaged molar mass and the order of density of complexes observed from the three experimental systems are qualitatively in agreement with those predicted from the simulations.« less

Large Electro-Optic Kerr Effect in Ionic Liquid Crystals: Connecting Features of Liquid Crystals and Polyelectrolytes.

PubMed

Schlick, M Christian; Kapernaum, Nadia; Neidhardt, Manuel M; Wöhrle, Tobias; Stöckl, Yannick; Laschat, Sabine; Giesselmann, Frank

2018-06-06

The electro-optic Kerr effect in simple dipolar fluids such as nitrobenzene has been widely applied in electro-optical phase modulators and light shutters. In 2005, the discovery of the large Kerr effect in liquid-crystalline blue phases (Y. Hisakado et al., Adv. Mater. 2005, 17, 96-98.) gave new directions to the search for advanced Kerr effect materials. Even though the Kerr effect is present in all transparent and optically isotropic media, it is well known that the effect can be anomalously large in complex fluids, namely in the isotropic phase of liquid crystals or in polyelectrolyte solutions. Herein, it is shown that the Kerr effect in the isotropic phase of ionic liquid crystals combines the effective counterion polarization mechanism found in polyelectrolytes and the unique pretransitional growth of the Kerr constant found in the isotropic phase of nematic liquid crystals. Maximum Kerr constants in the order of several 10 -11  m V -2 (ten times higher than the Kerr constant of the toxic nitrobenzene and less temperature sensitive than Kerr constants of nematic liquid crystals) make ionic liquid crystals attractive as new class of functional materials in low-speed Kerr effect applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Swelling characteristics of acrylic acid polyelectrolyte hydrogel in a dc electric field

NASA Astrophysics Data System (ADS)

Jabbari, Esmaiel; Tavakoli, Javad; Sarvestani, Alireza S.

2007-10-01

A novel application of environmentally sensitive polyelectrolytes is in the fabrication of BioMEMS devices as sensors and actuators. Poly(acrylic acid) (PAA) gels are anionic polyelectrolyte networks that exhibit volume expansion in aqueous physiological environments. When an electric field is applied to PAA polyelectrolyte gels, the fixed anionic polyelectrolyte charges and the requirement of electro-neutrality in the network generate an osmotic pressure, above that in the absence of the electric field, to expand the network. The objective of this research was to investigate the effect of an externally applied dc electric field on the volume expansion of the PAA polyelectrolyte gel in a simulated physiological solution of phosphate buffer saline (PBS). For swelling studies in the electric field, two platinum-coated plates, as electrodes, were wrapped in a polyethylene sheet to protect the plates from corrosion and placed vertically in a vessel filled with PBS. The plates were placed on a rail such that the distance between the two plates could be adjusted. The PAA gel was synthesized by free radical crosslinking of acrylic acid monomer with ethylene glycol dimethacrylate (EGDMA) crosslinker. Our results demonstrate that volume expansion depends on the intensity of the electric field, the PAA network density, network homogeneity, and the position of the gel in the field relative to positive/negative electrodes. Our model predictions for PAA volume expansion, based on the dilute electrolyte concentration in the gel network, is in excellent agreement with the experimental findings in the high-electric-field regime (250-300 Newton/Coulomb).

Adsorption of weak polyelectrolytes on charged nanoparticles. Impact of salt valency, pH, and nanoparticle charge density. Monte Carlo simulations.

PubMed

Carnal, Fabrice; Stoll, Serge

2011-10-27

Complex formation between a weak flexible polyelectrolyte chain and one positively charged nanoparticle in presence of explicit counterions and salt particles is investigated using Monte Carlo simulations. The influence of parameters such as the nanoparticle surface charge density, salt valency, and solution property such as the pH on the chain protonation/deprotonation process and monomer adsorption at the nanoparticle surface are systematically investigated. It is shown that the nanoparticle presence significantly modifies chain acid/base and polyelectrolyte conformational properties. The importance of the attractive electrostatic interactions between the chain and the nanoparticle clearly promotes the chain deprotonation leading, at high pH and nanoparticle charge density, to fully wrapped polyelectrolyte at the nanoparticle surface. When the nanoparticle bare charge is overcompensated by the polyelectrolyte charges, counterions and salt particles condense at the surface of the polyelectrolyte-nanoparticle complex to compensate for the excess of charges providing from the adsorbed polyelectrolyte chain. It is also shown that the complex formation is significantly affected by the salt valency. Indeed, with the presence of trivalent salt cations, competition is observed between the nanoparticle and the trivalent cations. As a result, the amount of adsorbed monomers is less important than in the monovalent and divalent case and chain conformations are different due to the collapse of polyelectrolyte segments around trivalent cations out of the nanoparticle adsorption layer.

Adsorbed poly(aspartate) coating limits the adverse effects of dissolved groundwater solutes on Fe0 nanoparticle reactivity with trichloroethylene.

PubMed

Phenrat, Tanapon; Schoenfelder, Daniel; Kirschling, Teresa L; Tilton, Robert D; Lowry, Gregory V

2018-03-01

For in situ groundwater remediation, polyelectrolyte-modified nanoscale zerovalent iron particles (NZVIs) have to be delivered into the subsurface, where they degrade pollutants such as trichloroethylene (TCE). The effect of groundwater organic and ionic solutes on TCE dechlorination using polyelectrolyte-modified NZVIs is unexplored, but is required for an effective remediation design. This study evaluates the TCE dechlorination rate and reaction by-products using poly(aspartate) (PAP)-modified and bare NZVIs in groundwater samples from actual TCE-contaminated sites in Florida, South Carolina, and Michigan. The effects of groundwater solutes on short- and intermediate-term dechlorination rates were evaluated. An adsorbed PAP layer on the NZVIs appeared to limit the adverse effect of groundwater solutes on the TCE dechlorination rate in the first TCE dechlorination cycle (short-term effect). Presumably, the pre-adsorption of PAP "trains" and the Donnan potential in the adsorbed PAP layer prevented groundwater solutes from further blocking NZVI reactive sites, which appeared to substantially decrease the TCE dechlorination rate of bare NZVIs. In the second and third TCE dechlorination cycles (intermediate-term effect), TCE dechlorination rates using PAP-modified NZVIs increased substantially (~100 and 200%, respectively, from the rate of the first spike). The desorption of PAP from the surface of NZVIs over time due to salt-induced desorption is hypothesized to restore NZVI reactivity with TCE. This study suggests that NZVI surface modification with small, charged macromolecules, such as PAP, helps to restore NZVI reactivity due to gradual PAP desorption in groundwater.

Salt- and pH-induced desorption: Comparison between non-aggregated and aggregated mussel adhesive protein, Mefp-1, and a synthetic cationic polyelectrolyte.

PubMed

Krivosheeva, Olga; Dedinaite, Andra; Claesson, Per M

2013-10-15

Mussel adhesive proteins are of great interest in many applications due to their ability to bind strongly to many types of surfaces under water. Effective use such proteins, for instance the Mytilus edulis foot protein - Mefp-1, for surface modification requires achievement of a large adsorbed amount and formation of a layer that is resistant towards desorption under changing conditions. In this work we compare the adsorbed amount and layer properties obtained by using a sample containing small Mefp-1 aggregates with that obtained by using a non-aggregated sample. We find that the use of the sample containing small aggregates leads to higher adsorbed amount, larger layer thickness and similar water content compared to what can be achieved with a non-aggregated sample. The layer formed by the aggregated Mefp-1 was, after removal of the protein from bulk solution, exposed to aqueous solutions with high ionic strength (up to 1M NaCl) and to solutions with low pH in order to reduce the electrostatic surface affinity. It was found that the preadsorbed Mefp-1 layer under all conditions explored was significantly more resistant towards desorption than a layer built by a synthetic cationic polyelectrolyte with similar charge density. These results suggest that the non-electrostatic surface affinity for Mefp-1 is larger than for the cationic polyelectrolyte. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

Deposition of zeolite nanoparticles onto porous silica monolith

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gackowski, Mariusz; Bielanska, Elzbieta; Szczepanowicz, Krzysztof

2016-06-01

A facile and effective method of deposition of MFl zeolite nanoparticles (nanocrystals) onto macro-/mesoporous silica monolith was proposed. The electrostatic interaction between those two materials was induces by adsorption of cationic polyelectrolytes. That can be realized either by adsorption of polyelectrolyte onto silica monolith or on zeolite nanocrystals. The effect of time, concentration of zeolite nanocrystals, type of polyelectrolyte, and ultrasound treatment is scrutinized. Adsorption of polyelectrolyte onto silica monolith with subsequent deposition of nanocrystals resulted in a monolayer coverage assessed with SEM images. Infrared spectroscopy was applied as a useful method to determine the deposition effectiveness of zeolite nanocrystalsmore » onto silica. Modification of nanocrystals with polyelectrolyte resulted in a multilayer coverage due to agglomeration of particles. On the other hand, the excess of polyelectrolyte in the system resulted in a low coverage due to competition between polyelectrolyte and modified nanocrystals.« less

Surface analysis monitoring of polyelectrolyte deposition on Ba 0.5Sr 0.5TiO 3 thin films

NASA Astrophysics Data System (ADS)

Morales-Cruz, Angel L.; Fachini, Estevão R.; Miranda, Félix A.; Cabrera, Carlos R.

2007-09-01

Thin films are currently gaining interest in many areas such as integrated optics, sensors, friction, reducing coatings, surface orientation layers, and general industrial applications. Recently, molecular self-assembling techniques have been applied for thin film deposition of electrically conducting polymers, conjugated polymers for light-emitting devices, nanoparticles, and noncentrosymmetric-ordered second order nonlinear optical (NOL) devices. Polyelectrolytes self-assemblies have been used to prepare thin films. The alternate immersion of a charged surface in polyannion and a polycation solution leads usually to the formation of films known as polyelectrolyte multilayers. These polyanion and polycation structures are not neutral. However, charge compensation appears on the surface. This constitutes the building driving force of the polyelectrolyte multilayer films. The present approach consists of two parts: (a) the chemisorption of 11-mercaptoundecylamine (MUA) to construct a self-assembled monolayer with the consequent protonation of the amine, and (b) the deposition of opposite charged polyelectrolytes in a sandwich fashion. The approach has the advantage that ionic attraction between opposite charges is the driving force for the multilayer buildup. For our purposes, the multilayer of polyelectrolytes depends on the quality of the surface needed for the application. In many cases, this approach will be used in a way that the roughness factor defects will be diminished. The polyelectrolytes selected for the study were: polystyrene sulfonate sodium salt (PSS), poly vinylsulfate potassium salt (PVS), and polyallylamine hydrochloride (PAH), as shown in Fig. 1. The deposition of polyelectrolytes was carried out by a dipping procedure with the corresponding polyelectrolyte. Monitoring of the alternate deposition of polyelectrolyte bilayers was done by surface analysis techniques such as X-ray photoelectron spectroscopy (XPS), specular reflectance infrared (IR), and atomic force microscopy (AFM). The surface analysis results are presented through the adsorption steps of the polyelectrolytes layer by layer.

Polyelectrolyte multilayers: preparation and applications

NASA Astrophysics Data System (ADS)

Izumrudov, V. A.; Mussabayeva, B. Kh; Murzagulova, K. B.

2018-02-01

The review concerns the results of studies on the synthesis of polyelectrolyte coatings on charged surfaces. These coatings represent nanostructured systems with clearly defined tendency to self-assembly and self-adjustment, which is of particular interest for materials science, biomedicine and pharmacology. A breakthrough in this area of knowledge is due to the development and introduction of a new technique, so-called layer-by-layer (LbL) deposition of nanofilms. The technique is very simple, viz., multilayers are formed as a result of alternating treatment of a charged substrate of arbitrary shape with water-salt solutions of differently charged polyelectrolytes. Nevertheless, efficient use of the LbL method to fabricate nanofilms requires meeting certain conditions and limitations that were revealed in the course of research on model systems. Prospects for applications of polyelectrolyte layers in various fields are discussed. The bibliography includes 58 references.

Polyelectrolyte gels as bending actuators: modeling and numerical simulation

NASA Astrophysics Data System (ADS)

Wallmersperger, Thomas; Keller, Karsten; Attaran, Abdolhamid

2013-04-01

Polyelectrolyte gels are ionic electroactivematerials. They have the ability to react as both, sensors and actuators. As actuators they can be used e.g. as artificial muscles or drug delivery control; as sensors they may be used for measuring e.g. pressure, pH or other ion concentrations in the solution. In this research both, anionic and cationic polyelectrolyte gels placed in aqueous solution with mobile anions and cations are investigated. Due to external stimuli the polyelectrolyte gels can swell or shrink enormously by the uptake or delivery of solvent. In the present research a coupled multi-field problem within a continuum mechanics framework is proposed. The modeling approach introduces a set of equations governing multiple fields of the problem, including the chemical field of the ionic species, the electrical field and the mechanical field. The numerical simulation is performed by using the Finite Element Method. Within the study some test cases will be carried out to validate our model. In the works by Gülch et al., the application of combined anionic-cationic gels as grippers was shown. In the present research for an applied electric field, the change of the concentrations and the electric potential in the complete polymer is simulated by the given formulation. These changes lead to variations in the osmotic pressure resulting in a bending of different polyelectrolyte gels. In the present research it is shown that our model is capable of describing the bending behavior of anionic or cationic gels towards the different electrodes (cathode or anode).

Manipulating perfume delivery to the interface using polymer-surfactant interactions.

PubMed

Bradbury, Robert; Penfold, Jeffrey; Thomas, Robert K; Tucker, Ian M; Petkov, Jordan T; Jones, Craig

2016-03-15

Enhanced delivery of perfumes to interfaces is an important element of their effectiveness in a range of home and personal care products. The role of polyelectrolyte-surfactant mixtures to promote perfume adsorption at interfaces is explored here. Neutron reflectivity, NR, was used to quantify the adsorption of the model perfumes phenylethanol, PE, and linalool, LL, at the air-water interface in the presence of the anionic surfactant sodium dodecylsulfate, SDS, and the cationic polyelectrolytes, poly(dimethyldiallyl ammonium chloride), polydmdaac, and poly(ethyleneimine), PEI. The strong SDS-polydmdaac interaction dominates the surface adsorption in SDS-polymer-perfume (PE, LL) mixtures, such that the PE and LL adsorption is greatly suppressed. For PEI-SDS-perfume mixtures the PEI-LL interaction competes with the SDS-PEI interaction at all pH at the surface and significant LL adsorption occurs, whereas for PE the PEI-SDS interaction dominates and the PE adsorption is greatly reduced. The use of the strong surface polyelectrolyte-ionic surfactant interaction to manipulate perfume adsorption at the air-water interface has been demonstrated. In particular the results show how the competition between polyelectrolyte, surfactant and perfume interactions at the surface and in solution affect the partitioning of perfumes to the surface. Copyright © 2015 Elsevier Inc. All rights reserved.

Polyelectrolytes and Their Biological Interactions

PubMed Central

Katchalsky, A.

1964-01-01

Polyelectrolytes are water-soluble electrically charged polymers. Their properties are determined by the interplay of the electrical forces, the Brownian motion of the macromolecular chain, and intermolecular Van der Waals forces. Charged polyacids or polybases are stretched by the electrostatic forces, as evidenced by increase in solution viscosity, or by the stretching of polyelectrolyte gels. The electrical field of the polyions is neutralized by a dense atmosphere of counter-ions. The counter-ion attraction to the polyions is expressed by a reduction of the osmotic activity of the polyion—the osmotic pressure being only 15 to 20 per cent of the ideal in highly charged polyelectrolytes neutralized by monovalent counter-ions, and as low as 1 to 3 per cent of the ideal for polyvalent counter-ions. Since the ionic atmosphere is only slightly dependent on added low molecular salt, the osmotic pressure of polyelectrolyte salt mixtures is approximately equal to the sum of the osmotic pressure of polyelectrolyte and salt alone. Acidic and basic polyelectrolytes interact electrostatically with precipitation at the point of polymeric electroneutrality. At higher salt concentrations the interaction is inhibited by the screening of polymeric fixed charges. The importance of these interactions in enzymatic processes is discussed. The electrical double layer is polarizable as may be deduced from dielectric and conductometric studies. The polarizability leads to strong dipole formation in an electrical field. These macromolecular dipoles may play a role in the adsorption of polyelectrolytes on charged surfaces. The final part of the paper is devoted to interactions of polyelectrolytes with cell membranes and the gluing of cells to higher aggregates by charged biocolloids. ImagesFigure 17Figure 18Figure 19Figure 20 PMID:14104085

Assembly of purple membranes on polyelectrolyte films.

PubMed

Saab, Marie-belle; Estephan, Elias; Cloitre, Thierry; Legros, René; Cuisinier, Frédéric J G; Zimányi, László; Gergely, Csilla

2009-05-05

The membrane protein bacteriorhodopsin in its native membrane bound form (purple membrane) was adsorbed and incorporated into polyelectrolyte multilayered films, and adsorption was in situ monitored by optical waveguide light-mode spectroscopy. The formation of a single layer or a double layer of purple membranes was observed when adsorbed on negatively or positively charged surfaces, respectively. The purple membrane patches adsorbed on the polyelectrolyte multilayers were also evidenced by atomic force microscopy images. The driving forces of the adsorption process were evaluated by varying the ionic strength of the solution as well as the purple membrane concentration. At high purple membrane concentration, interpenetrating polyelectrolyte loops might provide new binding sites for the adsorption of a second layer of purple membranes, whereas at lower concentrations only a single layer is formed. Negative surfaces do not promote a second protein layer adsorption. Driving forces other than just electrostatic ones, such as hydrophobic forces, should play a role in the polyelectrolyte/purple membrane layering. The subtle interplay of all these factors determines the formation of the polyelectrolyte/purple membrane matrix with a presumably high degree of orientation for the incorporated purple membranes, with their cytoplasmic, or extracellular side toward the bulk on negatively or positively charged polyelectrolyte, respectively. The structural stability of bacteriorhodopsin during adsorption onto the surface and incorporation into the polyelectrolyte multilayers was investigated by Fourier transform infrared spectroscopy in attenuated total reflection mode. Adsorption and incorporation of purple membranes within polyelectrolyte multilayers does not disturb the conformational majority of membrane-embedded alpha-helix structures of the protein, but may slightly alter the structure of the extramembraneous segments or their interaction with the environment. This high stability is different from the lower stability of the predominantly beta-sheet structures of numerous globular proteins when adsorbed onto surfaces.

Yield stress and scaling of polyelectrolyte multilayer modified suspensions: effect of polyelectrolyte conformation during multilayer assembly.

PubMed

Hess, Andreas; Aksel, Nuri

2013-09-10

The yield stress of polyelectrolyte multilayer modified suspensions exhibits a surprising dependence on the polyelectrolyte conformation of multilayer films. The rheological data scale onto a universal master curve for each polyelectrolyte conformation as the particle volume fraction, φ, and the ionic strength of the background fluid, I, are varied. It is shown that rough films with highly coiled, brushy polyelectrolytes significantly enhance the yield stress. Moreover, via the ionic strength I of the background fluid, the dynamic yield stress of brushy polyelectrolyte multilayers can be finely adjusted over 2 decades.

Thermodynamic characterization of the interaction behavior of a hydrophobically modified polyelectrolyte and oppositely charged surfactants in aqueous solution: effect of surfactant alkyl chain length.

PubMed

Bai, Guangyue; Nichifor, Marieta; Lopes, António; Bastos, Margarida

2005-01-13

We have used a precision isothermal titration microcalorimeter (ITC) to measure the enthalpy curves for the interaction of a hydrophobically modified polyelectrolyte (D40OCT30) with oppositely charged surfactants (SC(n)S) in aqueous solution. D40OCT30 is a newly synthesized polymer based on dextran having pendant N-(2-hydroxypropyl)-N,N-dimethyl-N-octylammonium chloride groups randomly distributed along the polymer backbone with degree of substitution of 28.1%. The employed anionic surfactants are sodium octyl sulfate (SC(8)S) and sodium tetradecyl sulfate (SC(14)S). Microcalorimetric results along with turbidity and kinematic viscosity measurements demonstrate systematically the thermodynamic characterization of the interaction of D40OCT30/SC(n)S. A three-dimensional diagram with the derived phase boundaries is drawn to describe the effect of the alkyl chain length of surfactant and of the ratio between surfactant and pendant groups on the interaction. A more complete picture of the interaction mechanism for D40OCT30/SC(n)S systems is proposed here.

Lateral Structure Formation in Polyelectrolyte Brushes Induced by Multivalent Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brettmann, Blair; Pincus, Philip; Tirrell, Matthew

2017-01-13

We provide a theoretical model for the collapse of polyelectrolyte brushes in the presence of multivalent ions, focusing on the formation of lateral inhomogeneties in the collapsed state. Polyelectrolyte brushes are important in a variety of applications, including stabilizing colloidal particles and lubricating surfaces. Many uses rely on the extension of the densely grafted polymer chains from the surface in the extended brush morphology. In the presence Extended Brush of multivalent ions, brushes are significantly shorter than in monovalent ionic solutions, which greatly affects their properties. We base our theoretical analysis on an analogous collapse of polyelectrolyte brushes in amore » poor solvent, providing an energy balance representation for pinned micelles and cylindrical bundles. The equilibrium brush heights predicted for these structures are of a similar magnitude to those measured experimentally. The formation of lateral structures can open new avenues for stimuli-responsive applications that rely on nanoscale pattern formation on surfaces.« less

Structure of Weakly Charged Polyelectrolyte Brushes: Monomer Density Profiles

NASA Astrophysics Data System (ADS)

Borisov, O. V.; Zhulina, E. B.

1997-03-01

The internal structure (the monomer density profiles) of weakly charged polyelectrolyte brushes of different morphologies has been analyzed on the basis of the self-consistent-field approach. In contrast to previous studies based on the local electroneutrality approximation valid for sufficiently strongly charged or densely grafted (“osmotic") brushes we consider the opposite limit of sparse brushes which are unable to retain the counterions inside the brush. We have shown that an exact analytical solution of the SCF-equations is available in the case of a planar brush. In contrast to Gaussian monomer density profile known for “osmotic" polyelectrolyte brushes we have found that weakly charged brushes are characterized by constant monomer density. At the same time free ends of grafted polyions are distributed throughout the brush. Thus, the structural cross-over between polyelectrolyte “mushrooms" and dense brush regimes is established.

Encapsulated Hsp70 decreases endotoxin-induced production of ROS and TNFα in human phagocytes.

PubMed

Yurinskaya, M M; Kochetkova, O Yu; Shabarchina, L I; Antonova, O Yu; Suslikov, A V; Evgen'ev, M B; Vinokurov, M G

2017-01-01

Human heat shock protein Hsp70 was experimentally inserted into polyelectrolyte microcapsules. Encapsulated recombinant Hsp70 was studied in terms of its effects on neutrophil apoptosis, the production of reactive oxygen species, and the secretion of tumor necrosis factor alpha by promonocytic THP-1 cells. It was found that encapsulated Hsp70 effectively inhibits neutrophil apoptosis, unlike free exogenous protein used in solution. In THP-1 cells, encapsulated and free Hsp70 reduced LPS-induced tumor necrosis factor alpha production with a similar efficiency. Encapsulated Hsp70 reduces LPS-induced reactive oxygen species production by neutrophils in the course of its release from the microcapsules but not as much as free Hsp70. Thus, the polyelectrolyte microcapsules can be used as containers for the effective delivery of Hsp70 to neutrophils and monocytes to significantly improve the functioning of the innate immune system.

Urea photosynthesis inside polyelectrolyte capsules: effect of confined media.

PubMed

Shchukin, Dmitry G; Möhwald, Helmuth

2005-06-07

The influence of the restricted volume of poly(styrene sulfonate)/poly(allylamine hydrochloride) capsules of different size (2.2, 4.2, and 8.1 microm) on the TiO2-assisted photosynthesis of urea from inorganic precursors (CO2 and NO(3-)) in aqueous solution was demonstrated. Poly(vinyl alcohol) was employed as electron donor to facilitate the photosynthetic process. Decreasing the size of the confined microvolume of polyelectrolyte capsules accelerates the NO(3-) photoreduction, which is a limiting stage of the urea photosynthesis and, correspondingly, increases the efficiency of urea production. The highest yield of urea photosynthesis (37%) was achieved for Cu-modified TiO2 nanoparticles encapsulated inside 2.2 microm poly(styrene sulfonate)/poly(allylamine hydrochloride) capsules.

Building a road map for tailoring multilayer polyelectrolyte films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ankner, John Francis; Bardoel, Agatha A; Sukishvili, Svetlana

2012-01-01

Researchers are moving a step closer to a definite road map for building layer-by-layer (LbL) assembled polyelectrolyte films, with the assistance of the Liquids Reflectometer at Oak Ridge National Laboratory's Spallation Neutron Source, in Oak Ridge, Tennessee. Scientists using the liquids reflectometer have successfully taken snapshots in close to real time of these multilayered structures for different applications when they modify the structure and function parameters. Polyelecrolytes are polymers that carry charge in aqueous solutions. They contain chemical groups that dissociate in water, making such polymers charged. Most polyelectrolytes are water soluble. They are important components in foods, soaps, shampoos,more » and cosmetics products. They show promise for such environmental work as oil recovery and water treatment. Polyelectrolytes are compelling because researchers can chemically modify how they interact with water for multiple applications. When two types of polyelectrolytes of opposite charge are assembled at a surface in a sequential way using the LbL assembly technique, 'the result is the forming of surface films, useful for coatings, biomedical implants and devices, controlling adhesion of biological molecules, and controlling delivery of therapeutic molecules from surfaces,' said Svetlana Sukhishvili of the Stevens Institute of Technology in New Jersey, the lead chemist on the collaboration. 'Medical doctors often prefer to deliver multiple therapeutic compounds from the coatings in a time-resolved manner,' Sukhishvili said. 'To assist them, material scientists need to learn how to build coatings in which polymer layering will not be compromised when exposed to normal physiological conditions.' 'Being able to control these properties, understanding how what you do to the materials affects their properties, this allows you to apply them to situations where interacting with an environment is very helpful, whether in a biological context or any other kind of water soluble context,' said John Ankner, lead instrument scientist for the Liquids Reflectometer. Ankner said that when several parameters are systematically altered, that allows researchers to map out the whole range of structures in the polymer. 'This work really sets a road map for how to get started with synthesizing polyelectrolyte materials for specific applications. Then, one can say, ok, this methylated material, the one that is 30% charged, is going to be what we want to use for a particular application.' The ORNL collaboration with the Stevens Institute has been conducting a series of experiments at the SNS to study layered film stratification in these polymers. Researchers stitch the polyelectrolyte chains in the LbL films together through what is called ionic pairing and arrange them within fuzzy, ultrathin layers that lie parallel to a solid surface substrate. Exposure of these films to aqueous solutions that contain salt (i.e., conditions that imitate real life) can compromise this film layering, as the salt ions act to weaken the ionic pairing that binds such layers together. So salt solutions are of key interest in studying how to make such layers for use in human applications. In the first research, Ankner, Sukhishvili and her student Li Xu looked at the effects of the layering of two types of LbL films of changing the charge density with a salt solution, and of blocking access to a charged site by nearby groups. The films were composed of positively charged variants of PDMA, a methyl polymer, and PDEA, an ethyl polymer. The other component of both systems is the ion exchanger polystyrene sulfonate (PSS) which features a fixed negative charge. First, a silicon substrate was dipped into solutions of PDMA and PDEA in dilute sodium chloride for a fixed time. Depending on the deposition time and the concentration of the solution, a nanometer-thick monolayer of the polymer adsorbs to the silicon surface. The film buildup is then continued by depositing a layer of PSS, and the cycle is repeated. The PDMA (methyl)/PSS and PDEA (ethyl)/PSS films were then annealed in varying concentrations of aqueous salt solutions. The chemists wanted to know if in these multi-layer cake-like assemblies, the structure can be systematically altered by varying the salt concentration, time in solution, and ultimately other environmental parameters, such as temperature or pH. Neutron reflectivity of the layered films exhibits the quality of the layering, in particular the concentration of the layers and how intermixed they are with adjacent layers. In this research, neutron reflectivity data from films built from 10%, 40%, and 100% charged PDMA or PDEA polyelectrolytes and 100% charged PSS were quantitatively compared to predicted, layered arrangements until the models produced reflectivity patterns matching those of the data.« less

Effect of Polyelectrolyte and Fatty Acid Soap on the Formation of CaCO3 in the Bulk and the Deposit on Hard Surfaces.

PubMed

Wang, Hao; Alfredsson, Viveka; Tropsch, Juergen; Ettl, Roland; Nylander, Tommy

2015-09-30

The effects of sodium polyacrylate (NaPAA) as well as potassium oleate on the nucleation and calcium carbonate crystal growth on hard surfaces, i.e., stainless steel and silica, have been investigated at different temperatures. The relation between the surface deposition and the corresponding bulk processes has been revealed by combining dynamic light scattering (DLS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and ellipsometry. The aim was to further our understanding of the crystal deposition/growth mechanism and how it can be controlled by the presence of polyelectrolytes (NaPAA) or soap (potassium oleate). The addition of polyelectrolytes (NaPAA) or soap (potassium oleate) decreases the size of CaCO3 particles in bulk solution and affects both crystal structure and morphology in the bulk as well as on hard surfaces. The amount of particles on hard surfaces decreases significantly in the presence of both potassium oleate and NaPAA. This was found to be a consequence of potassium oleate or NaPAA adsorption on the hard surface as well as on the CaCO3 crystal surfaces. Here, the polymer NaPAA exhibited a stronger inhibition effect on the formation and growth of CaCO3 particles than potassium oleate.

Volumetric and calorimetric properties of aqueous ionene solutions

PubMed Central

Lukšič, Miha; Hribar-Lee, Barbara

2016-01-01

The volumetric (partial and apparent molar volumes) and calorimetric properties (apparent heat capacities) of aqueous cationic polyelectrolyte solutions – ionenes – were studied using the oscillating tube densitometer and differential scanning calorimeter. The polyion’s charge density and the counterion properties were considered as variables. The special attention was put to evaluate the contribution of electrostatic and hydrophobic effects to the properties studied. The contribution of the CH2 group of the polyion’s backbone to molar volumes and heat capacities was estimated. Synergistic effect between polyion and counterions was found. PMID:28503012

Influence of salt and rinsing protocol on the structure of PAH/PSS polyelectrolyte multilayers.

PubMed

Feldötö, Zsombor; Varga, Imre; Blomberg, Eva

2010-11-16

A quartz crystal microbalance (QCM) and dual polarization interferometry (DPI) have been utilized to study how the structure of poly(allylamine hydrochloride) (PAH)/poly(styrene sulfonate) (PSS) multilayers is affected by the rinsing method (i.e., the termination of polyelectrolyte adsorption). The effect of the type of counterions used in the deposition solution was also investigated, and the polyelectrolyte multilayers were formed in a 0.5 M electrolyte solution (NaCl and KBr). From the measurements, it was observed that thicker layers were obtained when using KBr in the deposition solution than when using NaCl. Three different rinsing protocols have been studied: (i) the same electrolyte solution as used during multilayer formation, (ii) pure water, and (iii) first a salt solution (0.5 M) and then pure water. When the multilayer with PAH as the outermost layer was exposed to pure water, an interesting phenomenon was discovered: a large change in the energy dissipation was measured with the QCM. This could be attributed to the swelling of the layer, and from both QCM and DPI it is obvious that only the outermost PAH layer swells (to a thickness of 25-30 nm) because of a decrease in ionic strength and hence an increase in intra- and interchain repulsion, whereas the underlying layers retain a very rigid and compact structure with a low water content. Interestingly, the outermost PAH layer seems to obtain very similar thicknesses in water independent of the electrolyte used for the multilayer buildup. Another interesting aspect was that the measured thickness with the DPI evaluated by a single-layer model did not correlate with the estimated thickness from the model calculations performed on the QCM-D data. Thus, we applied a two-layer model to evaluate the DPI data and the results were in excellent agreement with the QCM-D results. To our knowledge, this evaluation of DPI data has not been done previously.

Consequences of on-line dialysis on polyelectrolyte molar masses determined by size-exclusion chromatography with light scattering detection.

PubMed

Radke, Wolfgang

2016-02-01

Size-exclusion chromatography with light scattering detection experiments conducted on poly(acrylic acid) neutralized to different degrees or using hydroxides with different counterions suggest that the same counterion and degree of neutralization is observed at the detector, irrespective of salt concentration, degree of neutralization and counterion at the time of injection. This strongly supports that during the chromatographic experiment the counterions of the polyelectrolyte are exchanged with those of the eluent, resulting in an effective dialysis of the polyelectrolyte solution during the size-exclusion chromatography experiment. Consequently, the refractive index increment determined by a refractive index detector equals the refractive index increment obtained after excessive dialysis against the pure eluent. Therefore, the species detected and characterized by light scattering coupled to size-exclusion chromatography are not identical to the species injected into the chromatographic system. Despite this structural change during the chromatographic experiments, the correct molar mass for the injected species is obtained by size-exclusion chromatography with light scattering detection. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Liposomes: support for the formation of stable capsules made of reticulated polyelectrolytes or silicum].

PubMed

Germain, M; Paquereau, L; Winterhalter, M; Hochepied, J-F; Fournier, D

2007-03-01

Uses of enzymes for therapeutic purpose or for biosensing require a well-controlled nanoenvironnement to avoid degradation by proteolytic agents, pH variations or dilution effects. A solution is encapsulation under undenaturating conditions into a nanometer sized and stable capsule. The nanometer scall decreases recognition by the reticulo-endothelial system recognition and subsequent immune reaction. Liposomes are the method of choice since they allow protein encapsulation under mild conditions. However they lack in stability. In contrast, other type of capsules exhibit strong stability but with conditions required for formation that are incompatible with enzyme integrity. Here we combine different capsule formation techniques and use liposomes as templates for further stabilization. Here we demonstrate two types of multicomposite capsules. The first type is to coat the liposome surface with polyelectrolytes followed by secondary covalent crosslinking of the polyelectrolytes multilayer. In the second type of capsules we used silica to build an inorganic shell around liposome. Both techniques allow the formation of detergent stable nanocapsules which exhibits properties protective against acetylcholinesterase protein degradation, an enzyme of much interest for pesticide detection.

Surface modification of upconverting nanoparticles by layer-by-layer assembled polyelectrolytes and metal ions.

PubMed

Palo, Emilia; Salomäki, Mikko; Lastusaari, Mika

2017-12-15

Modificating and protecting the upconversion luminescence nanoparticles is important for their potential in various applications. In this work we demonstrate successful coating of the nanoparticles by a simple layer-by-layer method using negatively charged polyelectrolytes and neodymium ions. The layer fabrication conditions such as number of the bilayers, solution concentrations and selected polyelectrolytes were studied to find the most suitable conditions for the process. The bilayers were characterized and the presence of the desired components was studied and confirmed by various methods. In addition, the upconversion luminescence of the bilayered nanoparticles was studied to see the effect of the surface modification on the overall intensity. It was observed that with selected deposition concentrations the bilayer successfully shielded the particle resulting in stronger upconversion luminescence. The layer-by-layer method offers multiple possibilities to control the bilayer growth even further and thus gives promises that the use of upconverting nanoparticles in applications could become even easier with less modification steps in the future. Copyright © 2017 Elsevier Inc. All rights reserved.

From single Debye-Hückel chains to polyelectrolyte solutions: Simulation results

NASA Astrophysics Data System (ADS)

Kremer, Kurt

1996-03-01

This lecture will present results from simulations of single weakly charged flexible chains, where the electrostatic part of the interaction is modeled by a Debye-Hückel potential,( with U. Micka, IFF, Forschungszentrum Jülich, 52425 Jülich, Germany) as well as simulations of polyelectrolyte solutions, where the counterions are explicitly taken into account( with M. J. Stevens, Sandia Nat. Lab., Albuquerque, NM 87185-1111) ( M. J. Stevens, K. Kremer, JCP 103), 1669 (1995). The first set of the simulations is meant to clear a recent contoversy on the dependency of the persistence length LP on the screening length Γ. While the analytic theories give Lp ~ Γ^x with either x=1 or x=2, the simulations find for all experimentally accessible chain lengths a varying exponent, which is significantly smaller than 1. This causes serious doubts on the applicability of this model for weakly charged polyelectrolytes in general. The second part deals with strongly charged flexible polyelectrolytes in salt free solution. These simulations are performed for multichain systems. The full Coulomb interactions of the monomers and counterions are treated explicitly. Experimental measurements of the osmotic pressure and the structure factor are reproduced and extended. The simulations reveal a new picture of the chain structure based on calculations of the structure factor, persistence length, end-to-end distance, etc. Even at very low density, the chains show significant bending. Furthermore, the chains contract significantly before they start to overlap. We also show that counterion condensation dramatically alters the chain structure, even for a good solvent backbone.

Polyelectrolyte/Graphene Oxide Barrier Film for Flexible OLED.

PubMed

Yang, Seung-Yeol; Park, Jongwhan; Kim, Yong-Seog

2015-10-01

Ultra-thin flexible nano-composite barrier layer consists of graphene oxide and polyelectrolyte was prepared using the layer-by-layer processing method. Microstructures of the barrier layer was optimized via modifying coating conditions and inducing chemical reactions. Although the barrier layer consists of hydrophilic polyelectrolyte was not effective in blocking the water vapor permeation, the chemical reduction of graphene oxide as well as conversion of polyelectrolyte to hydrophobic nature were very effective in reducing the permeation.

Brownian Dynamics Simulations of Polyelectrolyte Adsorption in Shear Flow

NASA Astrophysics Data System (ADS)

Panwar, Ajay

2005-03-01

The adsorption of polyelectrolytes onto charged surfaces often occurs in microfludic devices and can influence their operation. We employ Brownian dynamics simulations to investigate the effect of a simple shear flow on the adsorption of an isolated polyelectrolyte molecule onto an oppositely charged surface. The polyelectrolyte is modeled as a freely-jointed bead-rod chain where the total charge is distributed uniformly among all the beads, and the beads are allowed to interact with one another and the charged surface through screened Coulombic interactions. The simulations are performed by placing the chain some distance above the surface, and the adsorption behavior is studied as a function of the screening length. Specifically, we look at the components of the radius of gyration, normal and parallel to the adsorbing surface, as functions of the screening length, both in the absence and presence of the flow. We find that in the absence of flow, the chain lies flat and stretched on the adsorbing surface in the limit of weak screening, but attains free solution behavior in the limit of strong screening. In the presence of a shear flow, the chain orientation in the direction of the flow increases with increasing Weissenberg number over the entire range of screening lengths studied. We also find that increasing the strength of the shear flow leads to an increased contact of the chain with the surface compared to the case when no flow is present.

Formation, Structure and Electrochemical Impedance Analysis of Microporous Polyelectrolyte Multilayers

NASA Astrophysics Data System (ADS)

Lutkenhaus, Jodie; McEnnis, Kathleen; Hammond, Paula

2007-03-01

Microporous networks are of interest as electrolyte materials, gas separation membranes and catalytic nanoparticle templates. Here, we create microporous polyelectrolyte networks of tunable pore size and connectivity using the layer-by-layer (LBL) technique. In this method, a film is formed from the alternate adsorption of oppositely charged polyelectrolytes from aqueous solution to create a cohesive thin film. Using poly(ethylene imine) (PEI) and poly(acrylic acid) (PAA), LBL thin films of variable composition and charge density were assembled; then, the films were treated in an acidic bath, which ionizes PEI and de-ionizes PAA. This shift in charge density induces morphological rearrangement realized by a microporous network. Depending on the assembly pH and acidic bath pH, we are able to precisely tune the morphology, which is characterized by atomic force microscopy and scanning electron microscopy. To demonstrate the porous nature of the polyelectrolyte multilayer, the pores were filled with non-aqueous electrolyte (i.e. ethylene carbonate, dimethyl carbonate and lithium hexafluorophosphate) and probed with electrochemical impedance spectroscopy. These microporous networks exhibited two time constants, indicative of ions traveling through the liquid-filled pores and ions traveling through the polyelectrolyte matrix.

Organic and Inorganic Dyes in Polyelectrolyte Multilayer Films

PubMed Central

Ball, Vincent

2012-01-01

Polyelectrolyte multilayer films are a versatile functionalization method of surfaces and rely on the alternated adsorption of oppositely charged species. Among such species, charged dyes can also be alternated with oppositely charged polymers, which is challenging from a fundamental point of view, because polyelectrolytes require a minimal number of charges, whereas even monovalent dyes can be incorporated during the alternated adsorption process. We will not only focus on organic dyes but also on their inorganic counterparts and on metal complexes. Such films offer plenty of possible applications in dye sensitized solar cells. In addition, dyes are massively used in the textile industry and in histology to stain textile fibers or tissues. However, the excess of non bound dyes poses serious environmental problems. It is hence of the highest interest to design materials able to adsorb such dyes in an almost irreversible manner. Polyelectrolyte multilayer films, owing to their ion exchange behavior can be useful for such a task allowing for impressive overconcentration of dyes with respect to the dye in solution. The actual state of knowledge of the interactions between charged dyes and adsorbed polyelectrolytes is the focus of this review article.

Simulating the thermodynamics of charging in weak polyelectrolytes: the Debye-Hückel limit

NASA Astrophysics Data System (ADS)

Rathee, Vikramjit S.; Sikora, Benjamin J.; Sidky, Hythem; Whitmer, Jonathan K.

2018-01-01

The coil-globule transition in weak (annealed) polyelectrolytes involves a subtle balance of pH, charge strength, and solvation forces. In this work, we utilize a coarse-grained hybrid grand-canonical Monte Carlo and molecular dynamics approach to explore the swelling behavior of weak linear and star polyelectrolytes under different ionic screening conditions and pH. Importantly, we are able to quantify topology-dependent effects in charging which arise at the core of star polymers. Our results are suggestive of suppression of charging in star weak polyelectrolytes in comparison to linear weak polyelectrolytes. Furthermore, we characterize the coil-globule transition in linear and star weak polyelectrolyte through expanded ensemble density-of-states simulations which suggest a change from a first order to second order phase transition moving from linear to star polyelectrolytes. Lastly, we characterize the inhomogeneous charging across the weak star polyelectrolyte through observed shifts in {{Δ }}{{{pK}}}{{o}}, and compare with experimental work. We discuss these results in relation to surfaces functionalized by weak polyelectrolyte brushes and weak polyelectrolyte-based drug delivery applications.

Separation of charge-regulated polyelectrolytes by pH-assisted diffusiophoresis.

PubMed

Hsu, Jyh-Ping; Hsu, Yen-Rei; Shang-Hung, Hsieh; Tseng, Shiojenn

2017-03-29

The potential of separating colloidal particles through simultaneous application of a salt gradient and a pH gradient, or pH-assisted diffusiophoresis, is evaluated by considering the case of spherical polyelectrolytes (PEs) having different equilibrium dissociation constants in an aqueous solution with KCl as the background salt. The simulation results gathered reveal that the dependence of the particle velocity on pH is more sensitive than that in pH-assisted electrophoresis, where an electric field and a pH gradient are applied simultaneously. This implies that the separation efficiency of pH-assisted diffusiophoresis can be better than that of pH-assisted electrophoresis. In particular, two types of PE having different equilibrium dissociation constants can be separated effectively by applying the former by enhancing/reducing their diffusiophoretic velocities.

One-Step Generation of Multifunctional Polyelectrolyte Microcapsules via Nanoscale Interfacial Complexation in Emulsion (NICE)

DOE PAGES

Kim, Miju; Yeo, Seon Ju; Highley, Christopher B.; ...

2015-07-14

Polyelectrolyte microcapsules represent versatile stimuli-responsive structures that enable the encapsulation, protection, and release of active agents. Their conventional preparation methods, however, tend to be time-consuming, yield low encapsulation efficiency, and seldom allow for the dual incorporation of hydrophilic and hydrophobic materials, limiting their widespread utilization. In this work, we present a method to fabricate stimuli-responsive polyelectrolyte microcapsules in one step based on nanoscale interfacial complexation in emulsions (NICE) followed by spontaneous droplet hatching. NICE microcapsules can incorporate both hydrophilic and hydrophobic materials and also can be induced to trigger the release of encapsulated materials by changes in the solution pHmore » or ionic strength. We also show that NICE microcapsules can be functionalized with nanomaterials to exhibit useful functionality, such as response to a magnetic field and disassembly in response to light. NICE represents a potentially transformative method to prepare multifunctional nanoengineered polyelectrolyte microcapsules for various applications such as drug delivery and cell mimicry.« less

One-Step Generation of Multifunctional Polyelectrolyte Microcapsules via Nanoscale Interfacial Complexation in Emulsion (NICE).

PubMed

Kim, Miju; Yeo, Seon Ju; Highley, Christopher B; Burdick, Jason A; Yoo, Pil J; Doh, Junsang; Lee, Daeyeon

2015-08-25

Polyelectrolyte microcapsules represent versatile stimuli-responsive structures that enable the encapsulation, protection, and release of active agents. Their conventional preparation methods, however, tend to be time-consuming, yield low encapsulation efficiency, and seldom allow for the dual incorporation of hydrophilic and hydrophobic materials, limiting their widespread utilization. In this work, we present a method to fabricate stimuli-responsive polyelectrolyte microcapsules in one step based on nanoscale interfacial complexation in emulsions (NICE) followed by spontaneous droplet hatching. NICE microcapsules can incorporate both hydrophilic and hydrophobic materials and also can be induced to trigger the release of encapsulated materials by changes in the solution pH or ionic strength. We also show that NICE microcapsules can be functionalized with nanomaterials to exhibit useful functionality, such as response to a magnetic field and disassembly in response to light. NICE represents a potentially transformative method to prepare multifunctional nanoengineered polyelectrolyte microcapsules for various applications such as drug delivery and cell mimicry.

One-Step Generation of Multifunctional Polyelectrolyte Microcapsules via Nanoscale Interfacial Complexation in Emulsion (NICE)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Miju; Yeo, Seon Ju; Highley, Christopher B.

Polyelectrolyte microcapsules represent versatile stimuli-responsive structures that enable the encapsulation, protection, and release of active agents. Their conventional preparation methods, however, tend to be time-consuming, yield low encapsulation efficiency, and seldom allow for the dual incorporation of hydrophilic and hydrophobic materials, limiting their widespread utilization. In this work, we present a method to fabricate stimuli-responsive polyelectrolyte microcapsules in one step based on nanoscale interfacial complexation in emulsions (NICE) followed by spontaneous droplet hatching. NICE microcapsules can incorporate both hydrophilic and hydrophobic materials and also can be induced to trigger the release of encapsulated materials by changes in the solution pHmore » or ionic strength. We also show that NICE microcapsules can be functionalized with nanomaterials to exhibit useful functionality, such as response to a magnetic field and disassembly in response to light. NICE represents a potentially transformative method to prepare multifunctional nanoengineered polyelectrolyte microcapsules for various applications such as drug delivery and cell mimicry.« less

A study of properties of "micelle-enhanced" polyelectrolyte capsules: Structure, encapsulation and in vitro release.

PubMed

Li, Xiaodong; Lu, Tian; Zhang, Jianxiang; Xu, Jiajie; Hu, Qiaoling; Zhao, Shifang; Shen, Jiacong

2009-07-01

"Micelle-enhanced" polyelectrolyte capsules were fabricated via a layer-by-layer technique, templated on hybrid calcium carbonate particles with built-in polymeric micelles based on polystyrene-b-poly(acrylic acid). Due to the presence of a large number of negatively charged micelles inside the polyelectrolyte capsule, which were liberated from templates, the capsule wall was reconstructed and had properties different to those of conventional polyelectrolyte capsules. This type of capsule could selectively entrap positively charged water-soluble substances. The encapsulation efficiency of positively charged substances was dependent on their molecular weight or size. For some positively charged compounds, such as rhodamine B and lysozyme, the concentration in the capsules was orders of magnitude higher than that in the incubation solution. In addition, in vitro release study suggested that the encapsulated compounds could be released through a sustained manner to a certain degree. All these results point to the fact that these capsules might be used as novel delivery systems for some water-soluble compounds.

Polyelectrolyte bundles

NASA Astrophysics Data System (ADS)

Limbach, H. J.; Sayar, M.; Holm, C.

2004-06-01

Using extensive Molecular Dynamics simulations we study the behavior of polyelectrolytes with hydrophobic side chains, which are known to form cylindrical micelles in aqueous solution. We investigate the stability of such bundles with respect to hydrophobicity, the strength of the electrostatic interaction, and the bundle size. We show that for the parameter range relevant for sulfonated poly-para-phenylenes (PPP) one finds a stable finite bundle size. In a more generic model we also show the influence of the length of the precursor oligomer on the stability of the bundles. We also point out that our model has close similarities to DNA solutions with added condensing agents, hinting to the possibility that the size of DNA aggregates is under certain circumstances thermodynamically limited.

Reaction enthalpy from the binding of multivalent cations to anionic polyelectrolytes in dilute solutions

NASA Astrophysics Data System (ADS)

Hansch, Markus; Kaub, Hans Peter; Deck, Sascha; Carl, Nico; Huber, Klaus

2018-03-01

Dilute solutions of sodium poly(styrene sulfonate) (NaPSS) in the presence of Al3+, Ca2+, and Ba2+ were analysed by means of isothermal titration calorimetry (ITC) in order to investigate the heat effect of bond formation between those cations and the anionic SO3- residues of NaPSS. The selection of the cations was guided by the solution behavior of the corresponding PSS salts from a preceding study [M. Hansch et al., J. Chem. Phys. 148(1), 014901 (2018)], where bonds between Ba2+ and anionic PSS showed an increasing solubility with decreasing temperature and Al3+ exhibited the inverse trend. Unlike to Al3+ and Ba2+, Ca2+ is expected to behave as a purely electrostatically interacting bivalent cation and was thus included in the present study. Results from ITC satisfactorily succeeded to explain the temperature-dependent solution behavior of the salts with Al3+ and Ba2+ and confirmed the non-specific behavior of Ca2+. Additional ITC experiments with salts of Ca2+ and Ba2+ and sodium poly(acrylate) complemented the results on PSS by data from a chemically different polyanion. Availability of these joint sets of polyanion-cation combinations not only offers the chance to identify common features and subtle differences in the solution behavior of polyelectrolytes in the presence of multi-valent cations but also points to a new class of responsive materials.

Apparent Ionic Charge in Electrolyte and Polyelectrolyte Solutions

ERIC Educational Resources Information Center

Magdelenat, H.; And Others

1978-01-01

Compares average displacements of charged particles under thermal motion alone with those obtained by the action of an external electric field to develop a concept of "apparent charge" to approximate actual structural charge in an electrolyte solution. (SL)

Aggregation behavior of sodium lauryl ether sulfate with a positively bicharged organic salt and effects of the mixture on fluorescent properties of conjugated polyelectrolytes.

PubMed

Tang, Yongqiang; Liu, Zhang; Zhu, Linyi; Han, Yuchun; Wang, Yilin

2015-02-24

The aggregation behavior of anionic single-chain surfactant sodium lauryl ether sulfate containing three ether groups (SLE3S) with positively bicharged organic salt 1,2-bis(2-benzylammoniumethoxy)ethane dichloride (BEO) has been investigated in aqueous solution, and the effects of the BEO/SLE3S aggregate transitions on the fluorescent properties of anionic conjugated polyelectrolyte MPS-PPV with a larger molecular weight and cationic conjugated oligoelectrolyte DAB have been evaluated. Without BEO, SLE3S does not affect the fluorescent properties of MPS-PPV and only affects the fluorescent properties of DAB at a higher SLE3S concentration. With the addition of BEO, SLE3S and BEO form gemini-like surfactant (SLE3S)2-BEO. When the BEO/SLE3S molar ratio is fixed at 0.25, with increasing the BEO/SLE3S concentration, the BEO/SLE3S mixture forms large, loosely arranged aggregates and then transforms to closely packed spherical aggregates and finally to long thread-like micelles. The photoluminescence (PL) intensity of MPS-PPV varies with the morphologies of the BEO/SLE3S aggregates, while the PL intensity of DAB is almost independent of the aggregate morphologies. The results demonstrate that gemini-like surfactants formed through intermolecular interactions can effectively adjust the fluorescent properties of conjugated polyelectrolytes.

Formation of Polyelectrolyte Complex Colloid Particles between Chitosan and Pectin with Different Degree of Esterification

NASA Astrophysics Data System (ADS)

Wang, Hui; Sun, Hongyuan; He, Jieyu

2017-12-01

The effects of degree of esterification, pectin/chitosan ratio and pH on the formation of polyelectrolyte complex colloid particles between chitosan (CS) and pectin (PE) were investigated. Low methoxyl pectin (LPE) was achieved by de-esterifying high methoxyl pectin (HPE) with pectin methyl esterase. Turbidity titration and colorimetric method was used to determine the stability of complex colloid particles. The structure and morphology of complex particles were characterized by FTIR and TEM. When pectin solution was dropped into chitosan solution, complex colloidal dispersion was stable as PE/CS mass ratio was no more than 3:2. Colloidal particles of HPE-CS complex coagulated at larger ratio of PE/CS than LPE-CS. The maximum complex occurred at pH 6.1 for HPE-CS and pH 5.7 for LPE-CS, and decreasing pH leaded to the dissociation of complex particles. Electrostatic interactions between carboxyl groups on pectin and amino groups on chitosan were confirmed by FTIR. Colloidal particle sizes ranged from about 100 nm to 400 nm with spherical shape.

The interplay of nanointerface curvature and calcium binding in weak polyelectrolyte-coated nanoparticles.

PubMed

Nap, Rikkert J; Gonzalez Solveyra, Estefania; Szleifer, Igal

2018-05-01

When engineering nanomaterials for application in biological systems, it is important to understand how multivalent ions, such as calcium, affect the structural and chemical properties of polymer-modified nanoconstructs. In this work, a recently developed molecular theory was employed to study the effect of surface curvature on the calcium-induced collapse of end-tethered weak polyelectrolytes. In particular, we focused on cylindrical and spherical nanoparticles coated with poly(acrylic acid) in the presence of different amounts of Ca2+ ions. We describe the structural changes that grafted polyelectrolytes undergo as a function of calcium concentration, surface curvature, and morphology. The polymer layers collapse in aqueous solutions that contain sufficient amounts of Ca2+ ions. This collapse, due to the formation of calcium bridges, is not only controlled by the calcium ion concentration but also strongly influenced by the curvature of the tethering surface. The transition from a swollen to a collapsed layer as a function of calcium concentration broadens and shifts to lower amounts of calcium ions as a function of the radius of cylindrical and spherical nanoparticles. The results show how the interplay between calcium binding and surface curvature governs the structural and functional properties of the polymer molecules. This would directly impact the fate of weak polyelectrolyte-coated nanoparticles in biological environments, in which calcium levels are tightly regulated. Understanding such interplay would also contribute to the rational design and optimization of smart interfaces with applications in, e.g., salt-sensitive and ion-responsive materials and devices.

Antibacterial Loaded Spray Dried Chitosan Polyelectrolyte Complexes as Dry Powder Aerosol for the Treatment of Lung Infections

PubMed Central

Mishra, Brahmeshwar; Mishra, Madhusmita; Yadav, Sarita Kumari

2017-01-01

Inhalation delivery of aerosolized antibacterials is preferred over conventional methods of delivery for targeting lung infection. The present study is concerned with the development and characterization of a novel, spray dried, aerosolized, chitosan polyelectrolyte complex (PEC) based microparticles containing antibacterials for the treatment of lung infections. Chitosan polyelectrolyte complex microparticles were formulated by spray drying process. Prepared spray dried chitosan PEC microparticles were studied for surface morphology, drug encapsulation efficiency, moisture content, Carr’s index, solid state interaction by XRD, aerosolization behaviour and in-vitro drug release. In-vitro cytotoxicity studies of microparticles were carried out on H1299 alveolar cell lines. Antibacterial efficacy of microparticles was assessed on the basis of determination of pharmacokinetic parameters in bronchial alveolar lavage (BAL) of rats using PK/PD analysis. The PEC microparticles were mostly spherical and exhibited high drug encapsulation efficiency. Release profiles showed an initial burst phase followed by a secondary sustained release phase. Good aerosolization behaviour as dry powder inhaler was demonstrated by microparticles with high values of recovered dose, emitted dose, and fine particle fraction. No overt cytotoxicity of microparticles was detected against H1299 alveolar cell line. More than 8 to 9 folds higher Cmax values were obtained in BAL fluid with microparticles as compared to intravenously administered antibacterial solution. The findings of the study suggest that chitosan polyelectrolyte complex based microparticles as dry powder inhaler can be an efficient antibacterial delivery system for sustained and effective management of lung infection. PMID:28496463

Responsive block copolymer photonics triggered by protein-polyelectrolyte coacervation.

PubMed

Fan, Yin; Tang, Shengchang; Thomas, Edwin L; Olsen, Bradley D

2014-11-25

Ionic interactions between proteins and polyelectrolytes are demonstrated as a method to trigger responsive transitions in block copolymer (BCP) photonic gels containing one neutral hydrophobic block and one cationic hydrophilic block. Poly(2-vinylpyridine) (P2VP) blocks in lamellar poly(styrene-b-2-vinylpyridine) block copolymer thin films are quaternized with primary bromides to yield swollen gels that show strong reflectivity peaks in the visible range; exposure to aqueous solutions of various proteins alters the swelling ratios of the quaternized P2VP (QP2VP) gel layers in the PS-QP2VP materials due to the ionic interactions between proteins and the polyelectrolyte. Parameters such as charge density, hydrophobicity, and cross-link density of the QP2VP gel layers as well as the charge and size of the proteins play significant roles on the photonic responses of the BCP gels. Differences in the size and pH-dependent charge of proteins provide a basis for fingerprinting proteins based on their temporal and equilibrium photonic response. The results demonstrate that the BCP gels and their photonic effect provide a robust and visually interpretable method to differentiate different proteins.

Electro-actuated hydrogel walkers with dual responsive legs.

PubMed

Morales, Daniel; Palleau, Etienne; Dickey, Michael D; Velev, Orlin D

2014-03-07

Stimuli responsive polyelectrolyte hydrogels may be useful for soft robotics because of their ability to transform chemical energy into mechanical motion without the use of external mechanical input. Composed of soft and biocompatible materials, gel robots can easily bend and fold, interface and manipulate biological components and transport cargo in aqueous solutions. Electrical fields in aqueous solutions offer repeatable and controllable stimuli, which induce actuation by the re-distribution of ions in the system. Electrical fields applied to polyelectrolyte-doped gels submerged in ionic solution distribute the mobile ions asymmetrically to create osmotic pressure differences that swell and deform the gels. The sign of the fixed charges on the polyelectrolyte network determines the direction of bending, which we harness to control the motion of the gel legs in opposing directions as a response to electrical fields. We present and analyze a walking gel actuator comprised of cationic and anionic gel legs made of copolymer networks of acrylamide (AAm)/sodium acrylate (NaAc) and acrylamide/quaternized dimethylaminoethyl methacrylate (DMAEMA Q), respectively. The anionic and cationic legs were attached by electric field-promoted polyion complexation. We characterize the electro-actuated response of the sodium acrylate hydrogel as a function of charge density and external salt concentration. We demonstrate that "osmotically passive" fixed charges play an important role in controlling the bending magnitude of the gel networks. The gel walkers achieve unidirectional motion on flat elastomer substrates and exemplify a simple way to move and manipulate soft matter devices and robots in aqueous solutions.

Single-chain-in-mean-field simulations of weak polyelectrolyte brushes

NASA Astrophysics Data System (ADS)

Léonforte, F.; Welling, U.; Müller, M.

2016-12-01

Structural properties of brushes which are composed of weak acidic and basic polyelectrolytes are studied in the framework of a particle-based approach that implicitly accounts for the solvent quality. Using a semi-grandcanonical partition function in the framework of the Single-Chain-in-Mean-Field (SCMF) algorithm, the weak polyelectrolyte is conceived as a supramolecular mixture of polymers in different dissociation states, which are explicitly treated in the partition function and sampled by the SCMF procedure. One obtains a local expression for the equilibrium acid-base reaction responsible for the regulation of the charged groups that is also incorporated to the SCMF sampling. Coupled to a simultaneous treatment of the electrostatics, the approach is shown to capture the main features of weak polyelectrolyte brushes as a function of the bulk pH in the solution, the salt concentration, and the grafting density. Results are compared to experimental and theoretical works from the literature using coarse-grained representations of poly(acrylic acid) (PAA) and poly(2-vinyl pyridine) (P2VP) polymer-based brushes. As the Born self-energy of ions can be straightforwardly included in the numerical approach, we also study its effect on the local charge regulation mechanism of the brush. We find that its effect becomes significant when the brush is dense and exposed to high salt concentrations. The numerical methodology is then applied (1) to the study of the kinetics of collapse/swelling of a P2VP brush and (2) to the ability of an applied voltage to induce collapse/swelling of a PAA brush in a pH range close to the pKa value of the polymer.

Immobilization of hydrogenase on carbon nanotube polyelectrolytes as heterogeneous catalysts for electrocatalytic interconversion of protons and hydrogen

NASA Astrophysics Data System (ADS)

Liu, Jiang; Wu, Wen-Jie; Fang, Fang; Zorin, Nikolay A.; Chen, Meng; Qian, Dong-Jin

2016-08-01

Immobilization of active enzymes on the surfaces of electrodes and nanomaterials is important in the fields of bioscience, and biotechnology. In this study, we investigated electrocatalytic properties of the interconversion of protons and hydrogen by means of hydrogenase (H2ase)-functionalized carbon nanotube polyelectrolyte composites. Multiwalled carbon nanotube polyelectrolytes (MWNT-PEs) were synthesized through a diazonium and an addition reaction with poly(4-vinylpyridine) (P4VP), followed by another addition reaction with either methyl iodide (CH3I) or N-methyl- N'-benzyl bromide bipyridinium (VBenBr) to produce MWNT-P4VPMe or MWNT-P4VPBenV polyelectrolytes, respectively. The MWNT-PE@H2ase bio-nanocomposites were then prepared by means of MWNT-PEs as substrates to bind with H2ase. The redox current density of the MWNT-PE@H2ase-modified electrodes increased with a decrease in pH values of the Ar-saturated electrolyte solution owing to the catalytic reduction of protons (H2 production); further, it increased with the increasing pH values of the H2-saturated solution owing to the catalytic oxidation of hydrogen. The reversible color change between blue-colored and colorless viologen (catalyzed by the MWNT-PE@H2ase bio-nanocomposites) suggested that they may be developed as nano-biosensors for molecular H2. The as-synthesized bio-nanocomposites showed strong long-term stability and high bioactivity.

Potentiometric titration of polyhexamethylene biguanide hydrochloride with potassium poly(vinyl sulfate) solution using a cationic surfactant-selective electrode.

PubMed

Masadome, Takashi; Yamagishi, Yuichi; Takano, Masaki; Hattori, Toshiaki

2008-03-01

A potentiometric titration method using a cationic surfactant as an indicator cation and a plasticized poly(vinyl chloride) membrane electrode sensitive to the cationic surfactant is proposed for the determination of polyhexamethylene biguanide hydrochloride (PHMB-HCl), which is a cationic polyelectrolyte. A sample solution of PHMB-HCl containing an indicator cation (hexadecyltrimethylammonium ion, HTA) was titrated with a standard solution of an anionic polyelectrolyte, potassium poly(vinyl sulfate) (PVSK). The end-point was detected as a sharp potential change due to an abrupt decrease in the concentration of the indicator cation, HTA, which is caused by its association with PVSK. The effects of the concentrations of HTA ion and coexisting electrolytes in the sample solution on the degree of the potential change at the end-point were examined. A linear relationship between the concentration of PHMB-HCl and the end-point volume of the titrant exists in the concentration range from 2.0 x 10(-5) to 4.0 x 10(-4) M in the case that the concentration of HTA is 1.0 x 10(-5) M, and that from 1.0 x 10(-6) to 1.2 x 10(-5) M in the case that the concentration of HTA is 5.0 x 10(-6) M, respectively. The proposed method was applied to the determination of PHMB-HCl in some contact-lens detergents.

Polyelectrolyte-Surfactant Complexes: A New Class of Organogelators

NASA Astrophysics Data System (ADS)

Cavicchi, Kevin; Liu, Yuqing; Guzman, Gustavo

2011-03-01

Polyelectrolyte-surfactant complexes (PE-SURFs) are a class of polymers generated by neutralizing a polyelectrolyte with an oppositely charged surfactant. It has been found that PE-SURFs composed of polystyrene sulfonate and long chain alkyl dimethyl amines act as good organogelators for a range of hydrophobic, organic solvents. Thermo-reversible organogels are formed by heating and cooling PE-SURF/solvent solutions. The gel transition temperature is influenced by the degree of polymerization, the length of the alkyl side-chain, the solubility parameter of the solvent, and the concentration of the gelator. Freeze-drying and scanning electron microscopy characterization of the resultant xerogels shows the formation of rod- and plate-like network morphologies depending on the system parameters. This behavior is consistent with gelation driven by the self-assembly of the amphiphilic PE-SURFs into micellar networks.

Formation of J-Aggregates of an Anionic Oxacarbocyanine Dye Upon Interaction with Proteins and Polyelectrolytes

NASA Astrophysics Data System (ADS)

Pronkin, P. G.; Tatikolov, A. S.

2017-05-01

J-aggregation of the anionic oxacarbocyanine dye 3,3'-di-(γ-sulfopropyl)-5,5'-diphenyl-9-ethyloxacarbocyanine betaine was studied in aqueous solutions in the presence of proteins (collagens, immunoglobulin G, serum albumins) and polyelectrolytes (polyethyleneimine, polyvinylpyrrolidone). It was found that denaturation of human serum albumin by urea stimulated J-aggregation of the dye. The dye formed two types of J-aggregates in the presence of denatured albumin and polyethyleneimine. J-aggregates formed in the presence of polyethyleneimine rearranged over time.

Computer simulations of dendrimer-polyelectrolyte complexes.

PubMed

Pandav, Gunja; Ganesan, Venkat

2014-08-28

We carry out a systematic analysis of static properties of the clusters formed by complexation between charged dendrimers and linear polyelectrolyte (LPE) chains in a dilute solution under good solvent conditions. We use single chain in mean-field simulations and analyze the structure of the clusters through radial distribution functions of the dendrimer, cluster size, and charge distributions. The effects of LPE length, charge ratio between LPE and dendrimer, the influence of salt concentration, and the dendrimer generation number are examined. Systems with short LPEs showed a reduced propensity for aggregation with dendrimers, leading to formation of smaller clusters. In contrast, larger dendrimers and longer LPEs lead to larger clusters with significant bridging. Increasing salt concentration was seen to reduce aggregation between dendrimers as a result of screening of electrostatic interactions. Generally, maximum complexation was observed in systems with an equal amount of net dendrimer and LPE charges, whereas either excess LPE or dendrimer concentrations resulted in reduced clustering between dendrimers.

Environmentally friendly cellulose-based polyelectrolytes in wastewater treatment.

PubMed

Grenda, Kinga; Arnold, Julien; Gamelas, José A F; Rasteiro, Maria G

2017-09-01

Natural-based polyelectrolytes (PELs), with all the advantages coming from being produced from renewable and biodegradable sources, are a potential solution for the removal of dyes from wastewater. In this work, surplus Eucalyptus bleached cellulose fibres from a paper mill were modified to increase the charge and solubility of cellulose. First, reactive aldehyde groups were introduced in the cellulose backbone by periodate oxidation of cellulose. Further modification with alkylammonium produced positively charged cellulose-based PELs. The final products were characterized by several analytical techniques. The PEL with the highest substitution degree of cationic groups was evaluated for its performance in decolouration processes, bentonite being used as aid. This was found to be effective for colour removal of either anionic or cationic dyes. Bio-PELs can thus be considered as very favourable eco-friendly flocculation agents for decolouration of harsh effluents from several industries, considering their biodegradable nature and thus the ability to produce less sludge.

Assessment of polyelectrolyte coating stability under dynamic buffer conditions in CE.

PubMed

Swords, Kyleen E; Bartline, Peter B; Roguski, Katherine M; Bashaw, Sarah A; Frederick, Kimberley A

2011-09-01

Dynamic buffer conditions are present in many electrophoretically driven separations. Polyelectrolyte multilayer coatings have been employed in CE because of their chemical and physical stability as well as their ease of application. The goal of this study is to measure the effect of dynamic changes in buffer pH on flow using a real-time method for measuring EOF. Polyelectrolyte multilayers (PEMs) were composed of pairs of strong or completely ionized polyelectrolytes including poly(diallyldimethylammonium) chloride and poly(styrene sulfonate) and weak or ionizable polyelectrolytes including poly(allylamine) and poly(methacrylic acid). Polyelectrolyte multilayers of varying thicknesses (3, 4, 7, 8, 15, or 16 layers) were also studied. While the magnitude of the EOF was monitored every 2 s, the buffer pH was exchanged from a relatively basic pH (7.1) to increasingly acidic pHs (6.6, 6.1, 5.5, and 5.1). Strong polyelectrolytes responded minimally to changes in buffer pH (<1%), whereas substantial (>10%) and sometimes irreversible changes were measured with weak polyelectrolytes. Thicker coatings resulted in a similar magnitude of response but were more likely to degrade in response to buffer pH changes. The most stable coatings were formed from thinner layers of strong polyelectrolytes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Properties of POPC/POPE supported lipid bilayers modified with hydrophobic quantum dots on polyelectrolyte cushions.

PubMed

Kolasinska-Sojka, Marta; Wlodek, Magdalena; Szuwarzynski, Michal; Kereiche, Sami; Kovacik, Lubomir; Warszynski, Piotr

2017-10-01

The formation and properties of supported lipid bilayers (SLB) containing hydrophobic nanoparticles (NP) was studied in relation to underlying cushion obtained from selected polyelectrolyte multilayers. Lipid vesicles were formed from zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) in phosphate buffer (PBS). As hydrophobic nanoparticles - quantum dots (QD) with size of 3.8nm (emission wavelength of 420nm) were used. Polyelectrolyte multilayers (PEM) were constructed by the sequential, i.e., layer-by-layer (LbL) adsorption of alternately charged polyelectrolytes from their solutions. Liposomes and Liposome-QDs complexes were studied with Transmission Cryo-Electron Microscopy (Cryo-TEM) to verify the quality of vesicles and the position of QD within lipid bilayer. Deposition of liposomes and liposomes with quantum dots on polyelectrolyte films was studied in situ using quartz crystal microbalance with dissipation (QCM-D) technique. The fluorescence emission spectra were analyzed for both: suspension of liposomes with nanoparticles and for supported lipid bilayers containing QD on PEM. It was demonstrated that quantum dots are located in the hydrophobic part of lipid bilayer. Moreover, we proved that such QD-modified liposomes formed supported lipid bilayers and their final structure depended on the type of underlying cushion. Copyright © 2017 Elsevier B.V. All rights reserved.

Processes in suspensions of nanocomposite microcapsules exposed to external electric fields

NASA Astrophysics Data System (ADS)

Ermakov, A. V.; Lomova, M. V.; Kim, V. P.; Chumakov, A. S.; Gorbachev, I. A.; Gorin, D. A.; Glukhovskoy, E. G.

2016-04-01

Microcapsules with and without magnetite nanoparticles incorporated in the polyelectrolyte shell were prepared. The effect of external electric field on the nanocomposite polyelectrolyte microcapsules containing magnetite nanoparticles in the shell was studied in this work as a function of the electric field strength. Effect of electric fields on polyelectrolyte microcapsules and the control over integrity of polyelectrolyte microcapsules with and without inorganic nanoparticles by constant electric field has been investigated. Beads effect, aggregation and deformations of nanocomposite microcapsule shell in response to electric field were observed by confocal laser scanning microscopy (CLSM). Thus, a new approach for effect on the nanocomposite microcapsule, including opening microcapsule shell by an electric field, was demonstrated. These results can be used for creation of new systems for drug delivery systems with controllable release by external electric field.

Self-assembled graphene/azo polyelectrolyte multilayer film and its application in electrochemical energy storage device.

PubMed

Wang, Dongrui; Wang, Xiaogong

2011-03-01

Graphene/azo polyelectrolyte multilayer films were fabricated through electrostatic layer-by-layer (LbL) self-assembly, and their performance as electrochemical capacitor electrode was investigated. Cationic azo polyelectrolyte (QP4VP-co-PCN) was synthesized through radical polymerization, postpolymerization azo coupling reaction, and quaternization. Negatively charged graphene nanosheets were prepared by a chemically modified method. The LbL films were obtained by alternately dipping a piece of the pretreated substrates in the QP4VP-co-PCN and nanosheet solutions. The processes were repeated until the films with required numbers of bilayers were obtained. The self-assembly and multilayer surface morphology were characterized by UV-vis spectroscopy, AFM, SEM, and TEM. The performance of the LbL films as electrochemical capacitor electrode was estimated using cyclic voltammetry. Results show that the graphene nanosheets are densely packed in the multilayers and form random graphene network. The azo polyelectrolyte cohesively interacts with the nanosheets in the multilayer structure, which prevents agglomeration of graphene nanosheets. The sheet resistance of the LbL films decreases with the increase of the layer numbers and reaches the stationary value of 1.0 × 10(6) Ω/square for the film with 15 bilayers. At a scanning rate of 50 mV/s, the LbL film with 9 bilayers shows a gravimetric specific capacitance of 49 F/g in 1.0 M Na(2)SO(4) solution. The LbL films developed in this work could be a promising type of the electrode materials for electric energy storage devices.

Derivatizing weak polyelectrolytes--solution properties, self-aggregation, and association with anionic surfaces of hydrophobically modified poly(ethylene imine).

PubMed

Griffiths, Peter C; Paul, Alison; Fallis, Ian A; Wellappili, Champa; Murphy, Damien M; Jenkins, Robert; Waters, Sarah J; Nilmini, Renuka; Heenan, Richard K; King, Stephen M

2007-10-15

The physical properties of weak polyelectrolytes may be tailored via hydrophobic modification to exhibit useful properties under appropriate pH and ionic strength conditions as a consequence of the often inherently competing effects of electrostatics and hydrophobicity. Pulsed-gradient spin-echo NMR (PGSE-NMR), electron paramagnetic resonance (EPR), small-angle neutron scattering (SANS) surface tension, fluorescence, and pH titration have been used to examine the solution conformation and aggregation behavior of a series of hydrophobically modified hyperbranched poly(ethylene imine) (PEI) polymers in aqueous solution, and their interaction with sodium dodecylsulfate (SDS). PGSE-NMR gave a particularly insightful picture of the apparent molecular weight distribution. The presence of the hydrophobes led to a lower effective charge on the polymer at any given pH, compared to the (parent) nonmodified samples. Analysis of the SANS data showed that the propensity to form highly elliptical or rod-like aggregates at higher pHs, reflecting both the changes in protonation behavior induced by the hydrophobic modification and an hydrophobic interaction, but that these structures were disrupted with decreasing pH (increasing charge). The parent samples were not surface active yet the hydrophobically modified samples show pronounced surface activity and the presence of small hydrophobic domains. The surface activity increased with an increase in the degree of modification. On addition of SDS, the onset of the formation of polymer/surfactant complexes was insensitive to the degree of modification with the resultant PEI/SDS complexes resembling the size and shape of simple SDS micelles. Indeed, the presence of the SDS effectively nullifies the effects of the hydrophobe. Hydrophobic modification is therefore a viable option to tailor pH dependent properties, whose effects may be removed by the presence of surfactant.

Design of polyelectrolyte multilayer membranes for ion rejection and wastewater effluent treatment

NASA Astrophysics Data System (ADS)

Sanyal, Oishi

Polyelectrolyte multilayer (PEM) membranes present a special class of nanostructured membranes which have potential applications in a variety of water treatment operations. These membranes are fabricated by the layer-by-layer (LbL) assembly of alternately charged polyelectrolytes on commercial membrane surfaces. A large variety of polyelectrolytes and their varied deposition conditions (pH, number of bilayers etc.) allow very fine tuning of the membrane performance in terms of permeability and rejection. The first part of this thesis is about the application of PEM membranes to the removal of perchlorate ion from water. Being a monovalent ion, it is most effectively removed by a reverse osmosis (RO) membrane. However, these membranes inherently have very low fluxes which lead to high pressure requirements. In our work, we modified the surface of a nanofiltration (NF) membrane by the LbL assembly of oppositely charged polyelectrolytes. The appropriate tuning of the LbL conditions led to the development of a membrane with significantly higher flux than RO membranes but with equivalent perchlorate rejection. This was one of the best trade-offs offered by PEM membranes for monovalent ion rejection as has been reported in literature so far. While PEM membranes have mostly shown great potential in ion-rejection studies, they have seldom been tested for real wastewater effluents. The second part of this thesis, therefore, deals with evaluating the applicability of PEM membranes to treating an electrocoagulation (EC)-treated high strength wastewater. Two types of very commonly used polyelectrolyte combinations were tried out -- one of which was an ionically crosslinked system and the other one was covalently crosslinked. Both the types of PEM membranes showed a high level of COD reduction from the feed stream with higher fluxes than commercial RO membranes. One major challenge in using membranes for wastewater treatment is their fouling propensity. Like many other wastewater samples, the EC treated solution also contained a fair amount of organic foulants. These PEM membranes, however, indicated better anti-fouling properties than commercial NF/RO membranes under normal flow conditions. The last part of our work was focused on improving the anti-fouling properties of these membranes by the incorporation of clay nanoplatelets within polyelectrolyte multilayers. In this project, a commercial polyethersulfone (PES) membrane was modified by clay-polyelectrolyte composite thin films and tested against the EC effluent under tangential flow conditions. In comparison to the PEM membranes, these clay-PEM (c-PEM) hybrid membranes offered superior anti-fouling properties with higher fluxes and also required lesser number of layers. On crosslinking the polyelectrolytes, the c-PEM membranes yielded improved anti-fouling properties and high COD removal. Introduction of these inorganic nanoplatelets, however, led to a significant decline in the initial flux of the modified membranes as compared to bare PES membranes, which therefore necessitates further optimization. Some strategies which can potentially help in optimizing the performance of these c-PEM membranes have been discussed in this thesis.

Polyelectrolyte adsorption onto like-charged surfaces mediated by trivalent counterions: A Monte Carlo simulation study

NASA Astrophysics Data System (ADS)

Luque-Caballero, Germán; Martín-Molina, Alberto; Quesada-Pérez, Manuel

2014-05-01

Both experiments and theory have evidenced that multivalent cations can mediate the interaction between negatively charged polyelectrolytes and like-charged objects, such as anionic lipoplexes (DNA-cation-anionic liposome complexes). In this paper, we use Monte Carlo simulations to study the electrostatic interaction responsible for the trivalent-counterion-mediated adsorption of polyelectrolytes onto a like-charged planar surface. The evaluation of the Helmholtz free energy allows us to characterize both the magnitude and the range of the interaction as a function of the polyelectrolyte charge, surface charge density, [3:1] electrolyte concentration, and cation size. Both polyelectrolyte and surface charge favor the adsorption. It should be stressed, however, that the adsorption will be negligible if the surface charge density does not exceed a threshold value. The effect of the [3:1] electrolyte concentration has also been analyzed. In certain range of concentrations, the counterion-mediated attraction seems to be independent of this parameter, whereas very high concentrations of salt weaken the adsorption. If the trivalent cation diameter is doubled the adsorption moderates due to the excluded volume effects. The analysis of the integrated charge density and ionic distributions suggests that a delicate balance between charge inversion and screening effects governs the polyelectrolyte adsorption onto like-charged surfaces mediated by trivalent cations.

Selective Adsorption and Separation of Organic Dyes with Spherical Polyelectrolyte Brushes and Compressed Carbon Dioxide.

PubMed

Zhang, Rui; Yu, Zhenchuan; Wang, Lei; Shen, Qizhe; Hou, Xiaoyan; Guo, Xuhong; Wang, Junwei; Zhu, Xuedong; Yao, Yuan

2017-10-04

Dye-containing wastewater has caused serious environmental pollution. Herein, rationally designed spherical polyelectrolyte brushes (SPBs) with cationic charges, polystyrene-poly(2-aminoethylmethacrylate hydrochloride) (PS-PAEMH) as the absorbent, and compressed carbon dioxide as the antisolvent are proposed for the separation of the anionic dye eosin Y (EY) from a solution of mixed dyes. The adsorption behavior of EY onto PS-PAEMH was highly dependent on CO 2 pressure, contact time, and initial concentration. The maximum adsorption capacity of PS-PAEMH was 335.20 mg g -1 . FTIR and UV/Vis measurements proved that the electrostatic interactions between EY and PS-PAEMH played an important role in the absorbance process. The adsorption process fitted the pseudo-second-order kinetic model and Freundlich isotherm model very well. The combined dye and polymer brush could be easily separated through ion exchange by adding an aqueous solution of NaCl. Recovered PS-PAEMH retained a high adsorption capacity even after ten cycles of regeneration. This method provides a simple and effective way to separate ionic materials for environmental engineering. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Alcohol--Induced Polyelectrolyte-Surfactant Complex Coacervate Systems: Characterization and Applications in Enzyme and Protein Extraction

NASA Astrophysics Data System (ADS)

Nejati Moshtaghin, Mahboubeh

The focus of this thesis is to achieve a better understanding of the newly discovered surfactant-polyelectrolyte complex coacervate (SPCC) systems induced by fluoroalcohol/acid as well as short chain aliphatic alcohol; and to elucidate their applications in extraction and enrichment of proteins and enzyme. We have discovered that fluoroalcohols and --acids induce complex coacervation and phase separation in the aqueous mixtures of oppositely charged anionic polyelectrolytes; specifically, sodium salts of polyacrylic acid and polymethacrylic acid and cationic surfactant (cetyltrimethylammonium bromide, CTAB) over a broad range of concentrations of mole fractions of the oppositely charged amphiphiles. Accordingly, these new classes of coacervators will significantly broaden the scope and facilitate engineering of new coacervate phases. Toward these goals, we have inspected the formation of surfactant-polyelectrolyte complex coacervates in the presence of fluoroalcohols namely hexafluoroisopropanol (HFIP) and Trifluoroethanol (TFE). Furthermore, the extent of coacervation as a function of concentrations the system components, and charge ratios of the oppositely charged amphiphiles has been investigated. Polyelectrolytes are considered to be milder reagents, as compared to surfactants, regarding proteins denaturation. This highlights the importance of a detailed investigation of the efficiency of our coacervate systems for extraction and preconcentration of proteins and enzymes, especially, when the biological activity of the extracted proteins needs to be maintained based on the objectives mentioned above, the results of the investigations have been organized in four chapters. In Chapter II, the phase behavior of the FA-SPCC will be investigated. The objective is to examine the phase behavior and phase properties with respect to the extent of coacervation in different solution conditions. In particular, the effects of different solution variables such as concentration of FA, oppositely charged amphiphiles (surfactant-polyelectrolyte), and the charge ratio of the surfactant-polyelectrolyte on the extent of coacervation have been investigated. Furthermore, the chemical composition of each phase formed in the coacervate system was determined as a function of HFIP percentage. Phase diagrams of HFIP-PMA-CTAB and 2-propanol-PMA-CTAB were studied. The phase separation occurs over a wide range of polyelectrolyte, surfactant and alcohol concentration. In addition, a study of the dependence of coacervate volume on phase composition in different system (as defined by concentrations and mole charge ratio of amphihiles and alcohols) provided useful insight about possible underlying interactions and mechanisms. It has been concluded that neutralization favors coacervation in both systems. However, according to the compositional analysis of both HFIP and 2-propanol SPCC system, it seems that coacervation mechanisms are different. In Chapter III the properties of 2-propanol--SPCC, with analogous surfactant (CTAB) and polyelectrolyte (PMA) used in Chapter II, will be investigated. In particular, we are interested in examining the difference between the phase separation characteristics of the coacervates induced by 2-propanol and HFIP as coacervator. For this purpose, the phase behavior and the chemical composition of the phases will be analyzed as a function of 2-propanol and constituents concentrations. Chapter IV contains results of our investigations on the activity of a model enzyme (Trypsin) in 2-propanol- and FA-induced SPCC system. These investigations will facilitate understanding whether the aliphatic alcohol, AA- and FA-induced SPCC system denature the model enzymes. Such investigations also help in evaluation of the applicability of the coacervate systems developed in this work in proteomics where the proteolytic activity of enzymes is used for protein digestion. Finally, in Chapter V, the efficiency of the coacervate system (2-propanol-induced-PMA-CTAB) for extraction of cytochrome c, as a model protein, will be investigated.

Small‐angle X‐ray scattering as a useful supplementary technique to determine molecular masses of polyelectrolytes in solution

PubMed Central

Plazzotta, Beatrice; Diget, Jakob Stensgaard; Zhu, Kaizheng; Nyström, Bo

2016-01-01

ABSTRACT Determination of molecular masses of charged polymers is often nontrivial and most methods have their drawbacks. For polyelectrolytes, a new possibility for the determination of number‐average molecular masses is represented by small‐angle X‐ray scattering (SAXS) which allows fast determinations with a 10% accuracy. This is done by relating the mass to the position of a characteristic peak feature which arises in SAXS due to the local ordering caused by charge‐repulsions between polyelectrolytes. Advantages of the technique are the simplicity of data analysis, the independency from polymer architecture, and the low sample and time consumption. The method was tested on polyelectrolytes of various structures and chemical compositions, and the results were compared with those obtained from more conventional techniques, such as asymmetric flow field‐flow fractionation, gel permeation chromatography, and classical SAXS data analysis, showing that the accuracy of the suggested method is similar to that of the other techniques. © 2016 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1913–1917 PMID:27840558

Copolymers for Drag Reduction in Marie Propulsion: New Molecular Structures with Enhanced Effectiveness

DTIC Science & Technology

1991-05-31

Soluble Polymers: Synthesis, Solution Properties, and Applications, ACS Symposium Series 467, Chapter 22, page 338 (1991). "Molecular- Weight -Distribution...Mississippi 39406-0076 at room temperature to remove low molecular weight polymers and excess KOH. The final products were obtained by freeze-drying...polyelectrolytes due to the presence of the were conducted on a Contraves LS 30 low shear rheometer at a shear long hydrophobic side chains in the polymer

Chitosan/pectin/gum Arabic polyelectrolyte complex: process-dependent appearance, microstructure analysis and its application.

PubMed

Tsai, Ruei-Yi; Chen, Pin-Wen; Kuo, Ting-Yun; Lin, Che-Min; Wang, Da-Ming; Hsien, Tzu-Yang; Hsieh, Hsyue-Jen

2014-01-30

Novel chitosan/pectin/gum Arabic polyelectrolyte complex (PEC) solutions and membranes with various compositions were prepared for biomedical applications. The appearance of the PEC solutions, either clear or turbid, was process-dependent and depended on how the three components were dissolved and mixed. The addition of gum Arabic to the chitosan and pectin significantly decreased the viscosities of the resultant PEC solutions due to the formation of globe-like microstructures that was accompanied by network-like microstructures and other molecular entanglements. The mechanical strength and hydrophilicity of the PEC membranes manufactured from the PEC solutions, especially for a weight ratio of 84/8/8 (chitosan/pectin/gum Arabic), were enhanced compared to pure chitosan membranes. Moreover, the use of the 84/8/8 PEC membranes as a drug carrier exhibited steady and fairly complete release of a drug (insulin) for 6h. Based on these promising results, the chitosan/pectin/gum Arabic PEC membranes have great potential in controlled drug release applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

Polyelectrolyte hydrogel instabilities in ionic solutions

NASA Astrophysics Data System (ADS)

English, Anthony E.; Tanaka, Toyoichi; Edelman, Elazer R.

1996-12-01

The phase behavior of polyelectrolyte hydrogels has been examined as a function of relative charge composition, bath salt concentration, and solvent quality. Nonlinear swelling instabilities of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAAc) copolymer hydrogels manifested themselves as discontinuous first order swelling transitions as a function of bath salt concentration. A modified Flory-Huggins model was used to describe the regions of instability when bath salt concentration and solvent quality are considered as control variables. The role of ion dissociation equilibrium in the change from local or smooth transitions to nonlocal or discontinuous swelling transitions is illustrated within the framework of our model.

Influence of processing parameters on pore structure of 3D porous chitosan-alginate polyelectrolyte complex scaffolds.

PubMed

Florczyk, Stephen J; Kim, Dae-Joon; Wood, David L; Zhang, Miqin

2011-09-15

Fabrication of porous polymeric scaffolds with controlled structure can be challenging. In this study, we investigated the influence of key experimental parameters on the structures and mechanical properties of resultant porous chitosan-alginate (CA) polyelectrolyte complex (PEC) scaffolds, and on proliferation of MG-63 osteoblast-like cells, targeted at bone tissue engineering. We demonstrated that the porous structure is largely affected by the solution viscosity, which can be regulated by the acetic acid and alginate concentrations. We found that the CA PEC solutions with viscosity below 300 Pa.s yielded scaffolds of uniform pore structure and that more neutral pH promoted more complete complexation of chitosan and alginate, yielding stiffer scaffolds. CA PEC scaffolds produced from solutions with viscosities below 300 Pa.s also showed enhanced cell proliferation compared with other samples. By controlling the key experimental parameters identified in this study, CA PEC scaffolds of different structures can be made to suit various tissue engineering applications. Copyright © 2011 Wiley Periodicals, Inc.

Capillary Thinning and Pinch-off Dynamics and Printability of Polyelectrolyte Solutions

NASA Astrophysics Data System (ADS)

Sharma, Vivek; Jimenez, Leidy N.; Dinic, Jelena; Parsi, Nikila

Biological macromolecules like proteins, DNA and polysaccharides, and many industrial polymers, are classified together as polyelectrolytes for in solution, the repeat units in their backbone are decorated with disassociated, charge-bearing ionic groups, surrounded by counter-ions. In diverse applications like inkjet printing, sprayable cosmetics and insecticides, paints and coatings that involve formation of fluid columns or sheets that undergo progressive thinning and pinch-off into drops, the dominant flow within the necking filament is extensional in nature. The extensional rheology response of the charged macromolecular solutions is not as well understood as that of their uncharged counterparts. Here focus on the characterization of capillary thinning and pinch-off dynamics, extensional rheology and printability of two model systems: sodium (polystyrene sulfonate) and poly(acrylic acid) by using dripping-onto-substrate (DoS) rheometry technique. Both the measured extensional relaxation times and the extensional viscosity values show salt- and polymer concentration-dependent behavior that is not expected or anticipated from the typical shear rheology response.

Structure Formation in Salt-Free Solutions of Amphiphilic Sulfonated Polyelectrolytes

NASA Astrophysics Data System (ADS)

Bockstaller, Michael; Koehler, Werner

2000-03-01

Self-assembled systems have long attracted attention due to their practical importance in many technical and biological fields. Dodecyl-substituted poly(para-phenylen)sulfonates (abbreviated PPPS) are highly charged polyelectrolytes which in the uncharged state have been investigated extensively and an intrinsic persistence length of 15 nm has been reported. Due to their hydrophobic side chains, PPPS are compatible with water only as micellar aggregates and tend to form supramolecular structures even at concentrations as low as 10-5mol_mon.units/l. Because of the rodlike conformation of PPPS, this self-assembly leads to aggregates of anisotropic shape. Therefore, depolarized light scattering was employed to yield complementary information about structure and dynamics of these complex fluids. Aqueous solutions of PPPS at room temperature undergo a structural transition at a critical concentration of c_crit.=0.016 g/l. This transition is characterized by a strong increase of scattered intensity in forward direction and dynamic depolarized scattering. Above c_crit. the cylindrical micelles (L=310 nm, d=3.1 nm, N_radial=12) self assembly into large ellipsoidal clusters of size in the μ m range. Due to the strong increase of depolarized scattered intensity there has to be a preferential orientation of the micelles inside those clusters, which thus represent a lyotropic mesophase. By combining static and dynamic light scattering for the low q-range as well as small angle x-ray scattering for the higher q-range it is possible to determine size and shape of each aggregation step. Decreasing the molecular weight of the PPPS has profound influence on the micellar length and hence on c_crit. which is close to the overlap concentration (c ~ 1/L^3) allowing for the observation of the polyelectrolyte effect.

Single-coil properties and concentration effects for polyelectrolyte-like wormlike micelles: a Monte Carlo study

NASA Astrophysics Data System (ADS)

Cannavacciuolo, Luigi; Skov Pedersen, Jan; Schurtenberger, Peter

2002-03-01

Results of an extensive Monte Carlo (MC) study on both single and many semiflexible charged chains with excluded volume (EV) are summarized. The model employed has been tailored to mimic wormlike micelles in solution. Simulations have been performed at different ionic strengths of added salt, charge densities, chain lengths and volume fractions Φ, covering the dilute to concentrated regime. At infinite dilution the scattering functions can be fitted by the same fitting functions as for uncharged semiflexible chains with EV, provided that an electrostatic contribution bel is added to the bare Kuhn length. The scaling of bel is found to be more complex than the Odijk-Skolnick-Fixman predictions, and qualitatively compatible with more recent variational calculations. Universality in the scaling of the radius of gyration is found if all lengths are rescaled by the total Kuhn length. At finite concentrations, the simple model used is able to reproduce the structural peak in the scattering function S(q) observed in many experiments, as well as other properties of polyelectrolytes (PELs) in solution. Universal behaviour of the forward scattering S(0) is established after a rescaling of Φ. MC data are found to be in very good agreement with experimental scattering measurements with equilibrium PELs, which are giant wormlike micelles formed in mixtures of nonionic and ionic surfactants in dilute aqueous solution, with added salt.

Smooth model surfaces from lignin derivatives. II. Adsorption of polyelectrolytes and PECs monitored by QCM-D.

PubMed

Norgren, Magnus; Gärdlund, Linda; Notley, Shannon M; Htun, Myat; Wågberg, Lars

2007-03-27

For the first time to the knowledge of the authors, well-defined and stable lignin model surfaces have been utilized as substrates in polyelectrolyte adsorption studies. The adsorption of polyallylamine (PAH), poly(acrylic acid) (PAA), and polyelectrolyte complexes (PECs) was monitored using quartz crystal microgravimetry with dissipation (QCM-D). The PECs were prepared by mixing PAH and PAA at different ratios and sequences, creating both cationic and anionic PECs with different charge levels. The adsorption experiments were performed in 1 and 10 mM sodium chloride solutions at pH 5 and 7.5. The highest adsorption of PAH and cationic PECs was found at pH 7.5, where the slightly negatively charged nature of the lignin substrate is more pronounced, governing electrostatic attraction of oppositely charged polymeric substances. An increase in the adsorption was further found when the electrolyte concentration was increased. In comparison, both PAA and the anionic PEC showed remarkably high adsorption to the lignin model film. The adsorption of PAA was further studied on silica and was found to be relatively low even at high electrolyte concentrations. This indicated that the high PAA adsorption on the lignin films was not induced by a decreased solubility of the anionic polyelectrolyte. The high levels of adsorption on lignin model surfaces found both for PAA and the anionic PAA-PAH polyelectrolyte complex points to the presence of strong nonionic interactions in these systems.

Effects of a polyelectrolyte additive on the selective dialysis membrane permeability for low-molecular-weight proteins.

PubMed

Krieter, Detlef H; Morgenroth, Andreas; Barasinski, Artur; Lemke, Horst-Dieter; Schuster, Oliver; von Harten, Bodo; Wanner, Christoph

2007-02-01

Improving the sieving characteristics of dialysis membranes enhances the clearance of low-molecular-weight (LMW) proteins and may have an impact on outcome in patients receiving haemodialysis. To approach this goal, a novel polyelectrolyte additive process was applied to a polyethersulphone (PES) membrane. Polyelectrolyte-modified PES was characterized in vitro by measuring complement activation and sieving coefficients of cytochrome c and serum albumin. In a prospective, randomized, cross-over study, instantaneous plasma water clearances and reduction rates of LMW proteins [beta(2)-microglobulin (b2m), cystatin c, myoglobin, retinol binding protein] were determined in eight patients receiving dialysis treatment with PES in comparison with polysulphone (PSU). Biocompatibility was assessed by determination of transient leucopenia, plasma levels of complement C5a, thrombin-antithrombin III (TAT), myeloperoxidase (MPO) and elastase (ELT). PES showed a steeper sieving profile and lower complement activation in vitro compared with PSU. Instantaneous clearance (69 +/- 8 vs. 58 +/- 3 ml/min; P < 0.001) and reduction rate (72.3 +/- 1 5% vs 66.2 +/- 6.1%; P < 0.001) of b2m were significantly higher with PES as compared with PSU. With higher molecular weight of proteins, differences in the solute removal between PES and PSU further increased, whereas albumin loss remained low (PES, 0.53 +/- 0.17 vs PSU, <0.22 g/dialysis). MPO, ELT and TAT did not differ between the two membranes. In contrast, leucopenia was less pronounced and C5a generation was significantly lower during dialysis with PES. Polyelectrolyte modification of PES results in a higher LMW protein removal and in optimized biocompatibility. Whether these findings translate into better outcome of patients receiving haemodialysis requires further studies.

Salt type and concentration affect the viscoelasticity of polyelectrolyte solutions

NASA Astrophysics Data System (ADS)

Turkoz, Emre; Perazzo, Antonio; Arnold, Craig B.; Stone, Howard A.

2018-05-01

The addition of small amounts of xanthan gum to water yields viscoelastic solutions. In this letter, we show that the viscoelasticity of aqueous xanthan gum solutions can be tuned by different types of salts. In particular, we find that the decrease in viscoelasticity not only depends, as is known, on the salt concentration, but also is affected by the counterion ionic radius and the valence of the salt.

Monte Carlo simulations of polyelectrolytes inside viral capsids.

PubMed

Angelescu, Daniel George; Bruinsma, Robijn; Linse, Per

2006-04-01

Structural features of polyelectrolytes as single-stranded RNA or double-stranded DNA confined inside viral capsids and the thermodynamics of the encapsidation of the polyelectrolyte into the viral capsid have been examined for various polyelectrolyte lengths by using a coarse-grained model solved by Monte Carlo simulations. The capsid was modeled as a spherical shell with embedded charges and the genome as a linear jointed chain of oppositely charged beads, and their sizes corresponded to those of a scaled-down T=3 virus. Counterions were explicitly included, but no salt was added. The encapisdated chain was found to be predominantly located at the inner capsid surface, in a disordered manner for flexible chains and in a spool-like structure for stiff chains. The distribution of the small ions was strongly dependent on the polyelectrolyte-capsid charge ratio. The encapsidation enthalpy was negative and its magnitude decreased with increasing polyelectrolyte length, whereas the encapsidation entropy displayed a maximum when the capsid and polyelectrolyte had equal absolute charge. The encapsidation process remained thermodynamically favorable for genome charges ca. 3.5 times the capsid charge. The chain stiffness had only a relatively weak effect on the thermodynamics of the encapsidation.

Pair interactions in polyelectrolyte-nanoparticle systems: Influence of dielectric inhomogeneities and the partial dissociation of polymers and nanoparticles.

PubMed

Pryamitsyn, Victor; Ganesan, Venkat

2015-10-28

We study the effective pair interactions between two charged spherical particles in polyelectrolyte solutions using polymer self-consistent field theory. In a recent study [V. Pryamitsyn and V. Ganesan, Macromolecules 47, 6095 (2015)], we considered a model in which the particles possess fixed charge density, the polymers contain a prespecified amount of dissociated charges and, the dielectric constant of the solution was assumed to be homogeneous in space and independent of the polymer concentration. In this article, we present results extending our earlier model to study situations in which either or both the particle and the polymers possess partially dissociable groups. Additionally, we also consider the case when the dielectric constant of the solution depends on the local concentration of the polymers and when the particle's dielectric constant is lower than that of the solvent. For each case, we quantify the polymer-mediated interactions between the particles as a function of the polymer concentrations and the degree of dissociation of the polymer and particles. Consistent with the results of our previous study, we observe that the polymer-mediated interparticle interactions consist of a short-range attraction and a long-range repulsion. The partial dissociablity of the polymer and particles was seen to have a strong influence on the strength of the repulsive portion of the interactions. Rendering the dielectric permittivity to be inhomogeneous has an even stronger effect on the repulsive interactions and results in changes to the qualitative nature of interactions in some parametric ranges.

Chitosan as cationic polyelectrolyte for the modification of electroosmotic flow and its utilization for the separation of inorganic anions by capillary zone electrophoresis.

PubMed

Takayanagi, Toshio; Motomizu, Shoji

2006-09-01

Cationic polyelectrolyte of chitosan was used for the reversal of electroosmotic flow in capillary zone electrophoresis. The chitosan was dissolved in acetic acid solution, and stable electroosmotic flow was obtained at the chitosan concentrations between 50 and 300 microg/mL. Separation of inorganic anions was carried out using the dynamically coated capillary by capillary zone electrophoresis. Nine kinds of anions were separated and detected with the capillary. The electrophoretic mobility of the analyte anions decreased with increasing concentrations of chitosan in the migrating solution through ion-ion interaction, but the migration order of the analyte anions was not changed in the concentration range of the chitosan examined. The signal shape for the analyte anions was developed by using field-enhanced sample stacking with 10 mM sodium sulfate.

A novel system for water soluble protein encapsulation with high efficiency: "micelles enhanced" polyelectrolyte capsules.

PubMed

Li, Xiaodong; Li, Xiaohui; Zhang, Jianxiang; Zhao, Shifang; Shen, Jiacong

2008-06-01

Novel "micelles enhanced" polyelectrolyte (PE) capsules based on functional templates of hybrid calcium carbonate were fabricated. Evidences suggested that the structure of capsule wall was different from that of conventional PE capsules, and the wall permeability of these PE capsules changed significantly. Lysozyme, a positively charged protein in neutral solution, was studied as a model protein to be encapsulated into the "micelles enhanced" PE capsules. Confocal laser scanning microscope was used to observe the entrapping process in real time, while UV-Vis spectroscope and scanning force microscope measurements suggested the high efficiency of encapsulation. In addition, the fluorescence recovery after photobleaching technique was employed to determine the existence form of deposited molecules. Further studies showed even negatively charged water-soluble peptides or proteins can be encapsulated into these hybrid capsules by modulating the pH value in bulk solution under its isoelectronic point as well. Copyright 2007 Wiley Periodicals, Inc.

Conjugated polyelectrolyte hole transport layer for inverted-type perovskite solar cells

PubMed Central

Choi, Hyosung; Mai, Cheng-Kang; Kim, Hak-Beom; Jeong, Jaeki; Song, Seyeong; Bazan, Guillermo C.; Kim, Jin Young; Heeger, Alan J.

2015-01-01

Organic–inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perovskite solar cells with pH-neutral and low-temperature solution-processable conjugated polyelectrolyte as the hole transport layer (instead of acidic PEDOT:PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to PEDOT:PSS, this work is the first report on the use of an organic hole transport material that enables the formation of uniform perovskite films with complete surface coverage and the demonstration of efficient, stable perovskite/fullerene planar heterojunction solar cells. PMID:26081865

Electrostatic Interactions and Self-Assembly in Polymeric Systems

NASA Astrophysics Data System (ADS)

Dobrynin, Andrey

Electrostatic interactions between macroions play an important role in different areas ranging from materials science to biophysics. They are main driving forces behind layer-by-layer assembly technique that allows self-assembly of multilayer films from synthetic polyelectrolytes, DNA, proteins and nanoparticles. They are responsible for complexation and reversible gelation between polyelectrolytes and proteins. In this talk, using results of the molecular dynamics simulations and analytical calculations, I will demonstrate what effect electrostatic interactions, counterion condensation and polymer solvent affinity have on a collapse of polyelectrolyte chain in a poor solvent conditions for the polymer backbone, on complexations and reversible gelation between polyelectrolytes and polyamholytes (unstructured proteins), on microphase separation transitions in spherical and planar charged brushes, and on a layer-by-layer assembly of charged nanoparticles and linear polyelectrolytes on charged surfaces. NSF DMR-1004576 DMR-1409710.

Preparation and analysis of multilayer composites based on polyelectrolyte complexes

NASA Astrophysics Data System (ADS)

Petrova, V. A.; Orekhov, A. S.; Chernyakov, D. D.; Baklagina, Yu. G.; Romanov, D. P.; Kononova, S. V.; Volod'ko, A. V.; Ermak, I. M.; Klechkovskaya, V. V.; Skorik, Yu. A.

2016-11-01

A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan-hyaluronic acid, chitosan-alginic acid, and chitosan-carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs.

Aggregation of flexible polyelectrolytes: Phase diagram and dynamics.

PubMed

Tom, Anvy Moly; Rajesh, R; Vemparala, Satyavani

2017-10-14

Similarly charged polymers in solution, known as polyelectrolytes, are known to form aggregated structures in the presence of oppositely charged counterions. Understanding the dependence of the equilibrium phases and the dynamics of the process of aggregation on parameters such as backbone flexibility and charge density of such polymers is crucial for insights into various biological processes which involve biological polyelectrolytes such as protein, DNA, etc. Here, we use large-scale coarse-grained molecular dynamics simulations to obtain the phase diagram of the aggregated structures of flexible charged polymers and characterize the morphology of the aggregates as well as the aggregation dynamics, in the presence of trivalent counterions. Three different phases are observed depending on the charge density: no aggregation, a finite bundle phase where multiple small aggregates coexist with a large aggregate and a fully phase separated phase. We show that the flexibility of the polymer backbone causes strong entanglement between charged polymers leading to additional time scales in the aggregation process. Such slowing down of the aggregation dynamics results in the exponent, characterizing the power law decay of the number of aggregates with time, to be dependent on the charge density of the polymers. These results are contrary to those obtained for rigid polyelectrolytes, emphasizing the role of backbone flexibility.

Fabrication of Large-area Free-standing Ultrathin Polymer Films

PubMed Central

Stadermann, Michael; Baxamusa, Salmaan H.; Aracne-Ruddle, Chantel; Chea, Maverick; Li, Shuaili; Youngblood, Kelly; Suratwala, Tayyab

2015-01-01

This procedure describes a method for the fabrication of large-area and ultrathin free-standing polymer films. Typically, ultrathin films are prepared using either sacrificial layers, which may damage the film or affect its mechanical properties, or they are made on freshly cleaved mica, a substrate that is difficult to scale. Further, the size of ultrathin film is typically limited to a few square millimeters. In this method, we modify a surface with a polyelectrolyte that alters the strength of adhesion between polymer and deposition substrate. The polyelectrolyte can be shown to remain on the wafer using spectroscopy, and a treated wafer can be used to produce multiple films, indicating that at best minimal amounts of the polyelectrolyte are added to the film. The process has thus far been shown to be limited in scalability only by the size of the coating equipment, and is expected to be readily scalable to industrial processes. In this study, the protocol for making the solutions, preparing the deposition surface, and producing the films is described. PMID:26066738

Self-assembly of polyelectrolyte surfactant complexes using large scale MD simulation

NASA Astrophysics Data System (ADS)

Goswami, Monojoy; Sumpter, Bobby

2014-03-01

Polyelectrolytes (PE) and surfactants are known to form interesting structures with varied properties in aqueous solutions. The morphological details of the PE-surfactant complexes depend on a combination of polymer backbone, electrostatic interactions and hydrophobic interactions. We study the self-assembly of cationic PE and anionic surfactants complexes in dilute condition. The importance of such complexes of PE with oppositely charged surfactants can be found in biological systems, such as immobilization of enzymes in polyelectrolyte complexes or nonspecific association of DNA with protein. Many useful properties of PE surfactant complexes come from the highly ordered structures of surfactant self-assembly inside the PE aggregate which has applications in industry. We do large scale molecular dynamics simulation using LAMMPS to understand the structure and dynamics of PE-surfactant systems. Our investigation shows highly ordered pearl-necklace structures that have been observed experimentally in biological systems. We investigate many different properties of PE-surfactant complexation for different parameter ranges that are useful for pharmaceutical, engineering and biological applications.

Ionic content and permeability of polyelectrolyte multilayers and complexes

NASA Astrophysics Data System (ADS)

Ghostine, Ramy A.

Ultrathin films of polyelectrolyte multilayers (PEMUs) are built by the alternating deposition of oppositely charged polymers from aqueous solutions onto a clean substrate. The most used protocol to fabricate this type of films is called the Layer-by-Layer assembly technique. The type of polyelectrolytes, the buildup conditions, and the post-assembly treatments can be modified in order to control both the chemical and physical properties of multilayers. In recent years, multilayers have been used in commercially available products, corrosion protection, biocompatible surfaces, hydrophobic and hydrophilic coatings and chromatographic applications. Their robustness and stability make polyelectrolyte multilayer thin films good candidates for a series of other applications such as cell growth control, ion exchange membranes, drug delivery, sensors and electronics. In this dissertation, the permeability of polyelectrolyte multilayers made from poly(diallyldimethylammonium chloride) (PDADMAC) and sodium poly(4-styrene sulfonate) (NaPSS) is discussed in details. The permeability was studied by measuring the flux of redox active ions across a PEMU coated electrode. The effect of temperature, salt type and concentration was studied and it was determined that the flux of ions increases with temperature and salt concentration, and the permeability of ions strongly depends on the type of salt ions present in solution. The membrane concentration of the redox active ion was also calculated using attenuated total reflectance Fourier transform infra red spectroscopy. In another part of this dissertation, the ionic content of PEMUs was investigated by using radioactive counterions to track the ratio of positive to negative polymer repeat units. It was found that the accepted model of charge overcompensation for each layer is incorrect. In fact, overcompensation at the surface occurs only on the addition of the polycation, whereas the polyanion merely compensates the polycation. After the assembly of about a dozen layers, positive sites begin to accrue in the multilayer. The buildup mechanism is highly asymmetric with respect to the layer number, thus a new model profile for PEMU was employed. The critical impact of asymmetric growth on various properties of multilayers is also discussed. Thickness change, surface roughness, mechanical properties and ionic content of PEMUs were also studied in another part of this dissertation. The effect of salt annealing on these properties was investigated by the use of radiolabeling technique and atomic force microscopy. It was determined that salt annealing causes the polymer mobility in the multilayer to increase, reducing the amount of extrinsic charges and decreasing the surface roughness of the multilayer. The incorporation of 2nd generation fibroblast growth factor was studied in another chapter of this dissertation. FGF-1 is an important protein used in the wound healing process. The addition of FGF into films of PEMU was successful after modifying the ionic content of these films. It was shown that treating PSS terminated PEMU films with 10 mM PSS at high salt concentration would remove all positive extrinsic charges from the multilayer and add extra PSS chains in the bulk of the film. The addition of extra PSS depends on the salt concentration used during the PSS treatment. The highest amount of incorporated FGF was 58 mug cm-2. The release of FGF in phosphate buffer saline solution was also tracked for 30 days period. A total of 13 mug cm-2 of FGF were released from (PDADMA/PSS) 10 when treated with PSS at 1.5 M NaCl. Doping constants and diffusion coefficients for an extruded, stoichiometric, dense polyelectrolyte complex, exPEC, were determined for a Hofmeister series of anions in the last part of this dissertation. Both parameters describe the extent and speed to which a complex may be doped, where they followed a Hofmeister ordering and covered a wide range of response. Doping and undoping kinetics of polyelectrolyte complexes of PDADMA and PSS were also investigated using conductivity and radioactivity techniques. Tracer diffusion of radiolabeled Na+, compared with coupled diffusion of NaCl, revealed slightly faster diffusion of Na+ compared to Cl- withing the PEC.

Equilibrium polyelectrolyte bundles with different multivalent counterion concentrations

NASA Astrophysics Data System (ADS)

Sayar, Mehmet; Holm, Christian

2010-09-01

We present the results of molecular-dynamics simulations on the salt concentration dependence of the formation of polyelectrolyte bundles in thermodynamic equilibrium. Extending our results on salt-free systems we investigate here deficiency or excess of trivalent counterions in solution. Our results reveal that the trivalent counterion concentration significantly alters the bundle size and size distribution. The onset of bundle formation takes place at earlier Bjerrum length values with increasing trivalent counterion concentration. For the cases of 80%, 95%, and 100% charge compensation via trivalent counterions, the net charge of the bundles decreases with increasing size. We suggest that competition among two different mechanisms, counterion condensation and merger of bundles, leads to a nonmonotonic change in line-charge density with increasing Bjerrum length. The investigated case of having an abundance of trivalent counterions by 200% prohibits such a behavior. In this case, we find that the difference in effective line-charge density of different size bundles diminishes. In fact, the system displays an isoelectric point, where all bundles become charge neutral.

Development of Well-Preserved, Substrate-Versatile Latent Fingerprints by Aggregation-Induced Enhanced Emission-Active Conjugated Polyelectrolyte.

PubMed

Malik, Akhtar Hussain; Kalita, Anamika; Iyer, Parameswar Krishnan

2017-10-25

The development of highly efficient latent fingerprint (LFP) technology remains extremely vital for forensic and criminal investigations. In this contribution, a straightforward, rapid, and cost-effective method has been established for the quick development of well-preserved latent fingerprint on multiple substrates, including plastic, glass, aluminum foil, metallic surfaces, and so forth, without any additional treatment, based on aggregation-induced enhanced emission-active conjugated polyelectrolyte (CPE) 3,3'-((2-(4-(1,2-diphenyl-2-(p-tolyl)vinyl)phenyl)-7-(7-methylbenzo[c][1,2,5]thiadiazol-4-yl)-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(1-methyl-1H-imidazol-3-ium) bromide, revealing clearly the third-level details (ridges, bifurcations, and pores) with high selectivity, high contrast, and no background interference even by blood stains, confirming the ability of the proposed technique for LFP detection with high resolution. The LFP development process was accomplished simply by immersing fingerprint-loaded substrate into the CPE solution for ∼1 min, followed by shaking off the residual polymer solution and then air drying. The CPE was readily transferred to the LFPs because of the strong electrostatic and hydrophobic interaction between the CPE molecules and the fingerprint components revealing distinct fluorescent images on various smooth nonporous surfaces.

Mechanical properties of bulk graphene oxide/poly(acrylic acid)/poly(ethylenimine) ternary polyelectrolyte complex.

PubMed

Duan, Yipin; Wang, Chao; Zhao, Mengmeng; Vogt, Bryan D; Zacharia, Nicole S

2018-05-30

Ternary complexes formed in a single pot process through the mixing of cationic (branched polyethylenimine, BPEI) and anionic (graphene oxide, GO, and poly(acrylic acid), PAA) aqueous solutions exhibit superior mechanical performance in comparison to their binary analogs. The composition of the ternary complex can be simply tuned through the composition of the anionic solution, which influences the water content and mechanical properties of the complex. Increasing the PAA content in the complex decreases the overall water content due to improved charge compensation with the BPEI, but this change also significantly improves the toughness of the complex. Ternary complexes containing ≤32 wt% PAA were too brittle to generate samples for tensile measurements, while extension in excess of 250% could be reached with 57 wt% PAA. From this work, the influence of GO and PAA on the mechanical properties of GO/PAA/BPEI complexes were elucidated with GO sheets acting to restrain the viscous flow and improve the mechanical strength at low loading (<12.6 wt%) and PAA more efficiently complexes with BPEI than GO to generate a less swollen and stronger network. This combination overcomes the brittle nature of GO-BPEI complexes and viscous creep of PAA-BPEI complexes. Ternary nanocomposite complexes appear to provide an effective route to toughen and strengthen bulk polyelectrolyte complexes.

A preliminary study on the potency of nanofluids as the electro-active materials for nanoelectrofuel flow batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kristiawan, B., E-mail: budi-k@uns.ac.id; Wijayanta, A. T., E-mail: agungtw@uns.ac.id; Juwana, W. E., E-mail: wibawa.ej@gmail.com

2016-03-29

This study presents a characterization of nanofluids as electroactive materials with dispersing metal oxide nanoparticles into aqueous polyelectrolytes of 20 wt.%, in particular, their electrochemical activites. The fundamental characterizations including X-ray diffraction, transmission electron microscopy, and Fourier ttransform iinfrared measurement were performed to ensure metal oxide component used in this work. Alumina (Al{sub 2}O{sub 3}) and copper oxide (CuO) nanoparticles of 0.5 vol.% in volume fraction were dispersed into Poly(diallyldimethylammonium chloride) solution (PDADMAC) and Poly(sodium 4-styrenesulfonate) (PSS), respectively. Alumina and copper oxide nanoparticles were dispersed into ionic solution with volume fraction of 0.5 vol.% by using two-step method. The generalmore » cyclic voltammetry measurement was used to analyze electrochemical behavior within three-electrode cell setup. The results show that PSS-based nanofluids demonstrate redox process. However, unclearly redox phenomenon was depicted PDADMAC-based nanofluids. Dispersing nanoparticles could shift pure ionic solution’s cyclic profile. It is clear that a significant impact on electrochemical behavior can be provided because of the existence metal oxide nanoparticles into polyelectrolyte solution.« less

Effect of PEG-PDMAEMA Block Copolymer Architecture on Polyelectrolyte Complex Formation with Heparin.

PubMed

Välimäki, Salla; Khakalo, Alexey; Ora, Ari; Johansson, Leena-Sisko; Rojas, Orlando J; Kostiainen, Mauri A

2016-09-12

Heparin is a naturally occurring polyelectrolyte consisting of a sulfated polysaccharide backbone. It is widely used as an anticoagulant during major surgical operations. However, the associated bleeding risks require rapid neutralization after the operation. The only clinically approved antidote for heparin is protamine sulfate, which is, however, ineffective against low molecular weight heparin and can cause severe adverse reactions in patients. In this study, the facile synthesis of cationic-neutral diblock copolymers and their effective heparin binding is presented. Poly(ethylene glycol)-poly(2-(dimethylamino)ethyl methacrylate) (PEG-PDMAEMA) block copolymers were synthesized in two steps via atom-transfer radical polymerization (ATRP) using PEG as a macroinitiator. Solution state binding between heparin and a range of PEG-PDMAEMA block copolymers and one homopolymer was studied with dynamic light scattering and methylene blue displacement assay. Also in vitro binding in plasma was studied by utilizing a chromogenic heparin anti-Xa assay. Additionally, quartz crystal microbalance and multiparametric surface plasmon resonance were used to study the surface adsorption kinetics of the polymers on a heparin layer. It was shown that the block copolymers and heparin form electrostatically bound complexes with varying colloidal properties, where the block lengths play a key role in controlling the heparin binding affinity, polyelectrolyte complex size and surface charge. With the optimized polymers (PEG114PDMAEMA52 and PEG114PDMAEMA100), heparin could be neutralized in a dose-dependent manner, and bound efficiently into small neutral complexes, with a hydrodynamic radius less than 100 nm. These complexes had only a limited effect on cell viability. Based on these studies, our approach paves the way for the development of new polymeric heparin binding agents.

Effect of methyl groups on conformational properties of small ionized comb-like polyelectrolytes at the atomic level.

PubMed

Zhao, Hongxia; Liu, Jiaping; Ran, Qianping; Yang, Yong; Shu, Xin

2017-03-01

Comb-like polycarboxylate ether (PCE) molecules with different content of methyl groups substituted on backbone and different location of methyl groups substituted on the side chains, respectively, were designed and were studied in explicit salt solutions by all-atom molecular dynamics simulations. Methyl groups substituted on the backbone of PCE have a great effect on the conformation of PCE. Stiffness of charged backbone was not only affected by the rotational freedom but also the electrostatic repulsion between the charged COO - groups. The interaction of counterions (Na + ) with COO - groups for PCE3 (with part of AA substituted by MAA on the backbone) was stronger and the screen effect was great, which decided the smaller size of PCE3. The interaction between water and COO - groups was strong regardless of the content of AA substituted by MAA on the backbone. The effect of methyl groups substituted on the different location of side chains on the conformation of PCE was less than that of methyl groups substituted on the backbone. The equilibrium sizes of the four PCE molecules with methyl groups substituted on the side chains were similar. Graphical Abstract Effect of methyl groups on conformational properties of small ionized comb-like polyelectrolytes at the atomic level.

Efficacy of chitosan in inhibiting the oxidation of (+)-catechin in white wine model solutions.

PubMed

Chinnici, Fabio; Natali, Nadia; Riponi, Claudio

2014-10-08

The efficacy of chitosan and sulfites in inhibiting the oxidation of (+)-catechin in aerated model white wines has been compared by monitoring the browning development and the generation of oxidized phenolic compounds. In addition, the protecting effects of these two additives toward the oxidative decay of varietal thiols were investigated. Chitosan effectively contrasted the browning onset in model solutions all along the entire duration of the experimentation. Color development was limited and comparable in both the sulfite and chitosan added samples. Thanks to its polyelectrolyte behavior, chitosan adsorbed up to 80% of the more hydrophilic oxidized phenolic species and chelated 70 and 30% of Fe and Cu added to the solutions, respectively. Thiol oxidation was significantly lowered by chitosan, suggesting that this additive could contribute to maintain the varietal character of wines coming from aromatic grapes and vinified with reduced sulfite amounts.

Fabrication of composite films containing zirconia and cationic polyelectrolytes.

PubMed

Pang, Xin; Zhitomirsky, Igor

2004-03-30

Composite films were prepared by electrophoretic deposition of poly(ethylenimine) or poly(allylamine hydrochloride) combined with cathodic precipitation of zirconia. Films of up to several micrometers thick were obtained on Ni, Pt, stainless-steel, graphite, and carbon-felt substrates. When the concentration of polyelectrolytes in solutions and the deposition time were varied, the amount of the deposited material and its composition can be varied. The electrochemical intercalation of yttria-stabilized zirconia particles into the composite films has been demonstrated. Obtained results pave the way for the electrodeposition of other polymer-ceramic composites. The deposits were studied by thermogravimetric analysis, X-ray diffraction analysis, scanning electron microscopy, and atomic force microscopy. The mechanisms of deposition are discussed.

Performance optimization of coagulant/flocculant in the treatment of wastewater from a beverage industry.

PubMed

Amuda, O S; Amoo, I A; Ajayi, O O

2006-02-28

This study investigated the effect of coagulation/flocculation treatment process on wastewater of Fumman Beverage Industry, Ibadan, Nigeria. The study also compared different dosages of coagulant, polyelectrolyte (non-ionic polyacrylamide) and different pH values of the coagulation processes. The effect of different dosages of polyelectrolyte in combination with coagulant was also studied. The results reveal that low pH values (3-8), enhance removal efficiency of the contaminants. Percentage removal of 78, 74 and 75 of COD, TSS and TP, respectively, were achieved by the addition of 500 mg/L Fe2(SO4)3.3H2O and 93, 94 and 96% removal of COD, TSS and TP, respectively, were achieved with the addition of 25 mg/L polyelectrolyte to the coagulation process. The volume of sludge produced, when coagulant was used solely, was higher compared to the use of polyelectrolyte combined with Fe2(SO4)3.3H2O. This may be as a result of non-ionic nature of the polyelectrolyte; hence, it does not chemically react with solids of the wastewater. Coagulation/flocculation may be useful as a pre-treatment process for beverage industrial wastewater prior to biological treatment.

Catalytic Micromotors Moving Near Polyelectrolyte-Modified Substrates: The Roles of Surface Charges, Morphology, and Released Ions.

PubMed

Wei, Mengshi; Zhou, Chao; Tang, Jinyao; Wang, Wei

2018-01-24

Synthetic microswimmers, or micromotors, are finding potential uses in a wide range of applications, most of which involve boundaries. However, subtle yet important effects beyond physical confinement on the motor dynamics remain less understood. In this letter, glass substrates were functionalized with positively and negatively charged polyelectrolytes, and the dynamics of micromotors moving close to the modified surfaces was examined. Using acoustic levitation and numerical simulation, we reveal how the speed of a chemically propelled micromotor slows down significantly near a polyelectrolyte-modified surface by the combined effects of surface charges, surface morphology, and ions released from the films.

Effect of calcium/sodium ion exchange on the osmotic properties and structure of polyelectrolyte gels.

PubMed

Horkay, Ferenc; Basser, Peter J; Hecht, Anne-Marie; Geissler, Erik

2015-12-01

We discuss the main findings of a long-term research program exploring the consequences of sodium/calcium ion exchange on the macroscopic osmotic and elastic properties, and the microscopic structure of representative synthetic polyelectrolyte (sodium polyacrylate, (polyacrylic acid)) and biopolymer gels (DNA). A common feature of these gels is that above a threshold calcium ion concentration, they exhibit a reversible volume phase transition. At the macroscopic level, the concentration dependence of the osmotic pressure shows that calcium ions influence primarily the third-order interaction term in the Flory-Huggins model of polymer solutions. Mechanical tests reveal that the elastic modulus is practically unaffected by the presence of calcium ions, indicating that ion bridging does not create permanent cross-links. At the microscopic level, small-angle neutron scattering shows that polyacrylic acid and DNA gels exhibit qualitatively similar structural features in spite of important differences (e.g. chain flexibility and chemical composition) between the two polymers. The main effect of calcium ions is that the neutron scattering intensity increases due to the decrease in the osmotic modulus. At the level of the counterion cloud around dissolved macroions, anomalous small-angle X-ray scattering measurements made on DNA indicate that divalent ions form a cylindrical sheath enveloping the chain, but they are not localized. Small-angle neutron scattering and small-angle X-ray scattering provide complementary information on the structure and interactions in polymer solutions and gels. © IMechE 2015.

Imaging trypsin activity through changes in the orientation of liquid crystals coupled to the interactions between a polyelectrolyte and a phospholipid layer.

PubMed

Hu, Qiong-Zheng; Jang, Chang-Hyun

2012-03-01

In this study, we developed a new type of liquid crystal (LC)-based sensor for the real-time and label-free monitoring of enzymatic activity through changes in the orientation of LCs coupled to the interactions between polyelectrolyte and phospholipid. The LCs changed from dark to bright after an aqueous solution of poly-l-lysine (PLL) was transferred onto a self-assembled monolayer of the phospholipid, dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (DOPG), at the aqueous/LC interface. Interactions between the positively charged PLL and the negatively charged DOPG drove the reorganization of the phospholipid membrane, which induced an orientational transition in the LCs from a homeotropic to planar state. Since the serine endopeptidase trypsin can enzymatically catalyze the hydrolysis of PLL, the dark-to-bright shift in the optical response was not observed after transferring a mixed solution of PLL and trypsin onto the DOPG-decorated LC interface, indicating that no orientational transitions in the LCs occurred. However, the optical response from dark to bright was observed when the mixture in the optical cell was replaced by an aqueous solution of PLL. Control experiments with trypsin or an aqueous mixture of PLL and deactivated trypsin further confirmed the feasibility of this approach. The detection limit of trypsin was determined to be ~1 μg/mL. This approach holds great promise for use in the development of LC-based sensors for the detection of enzymatic reactions in cases where the biological polyelectrolyte substrates of enzymes could disrupt the organization of the membrane and induce orientational transitions of LCs at the aqueous/LC interface. © 2012 American Chemical Society

Stability of polyelectrolyte-coated iron nanoparticles for T2-weighted magnetic resonance imaging

NASA Astrophysics Data System (ADS)

McGrath, Andrew J.; Dolan, Ciaran; Cheong, Soshan; Herman, David A. J.; Naysmith, Briar; Zong, Fangrong; Galvosas, Petrik; Farrand, Kathryn J.; Hermans, Ian F.; Brimble, Margaret; Williams, David E.; Jin, Jianyong; Tilley, Richard D.

2017-10-01

Iron nanoparticles are highly-effective magnetic nanoparticles for T2 magnetic resonance imaging (MRI). However, the stability of their magnetic properties is dependent on good protection of the iron core from oxidation in aqueous media. Here we report the synthesis of custom-synthesized phosphonate-grafted polyelectrolytes (PolyM3) of various chain lengths, for efficient coating of iron nanoparticles with a native iron oxide shell. The size of the nanoparticle-polyelectrolyte assemblies was investigated by transmission electron microscopy and dynamic light scattering, while surface attachment was confirmed by Fourier transform infrared spectroscopy. Low cytotoxicity was observed for each of the nanoparticle-polyelectrolyte ("Fe-PolyM3") assemblies, with good cell viability (>80%) remaining up to 100 μg mL-1 Fe in HeLa cells. When applied in T2-weighted MRI, corresponding T2 relaxivities (r2) of the Fe-PolyM3 assemblies were found to be dependent on the chain length of the polyelectrolyte. A significant increase in contrast was observed when polyelectrolyte chain length was increased from 6 to 65 repeating units, implying a critical chain length required for stabilization of the α-Fe nanoparticle core.

DNA Immobilization and Hybridization Detection by the Intrinsic Molecular Charge Using Capacitive Field-Effect Sensors Modified with a Charged Weak Polyelectrolyte Layer.

PubMed

Bronder, Thomas S; Poghossian, Arshak; Scheja, Sabrina; Wu, Chunsheng; Keusgen, Michael; Mewes, Dieter; Schöning, Michael J

2015-09-16

Miniaturized setup, compatibility with advanced micro- and nanotechnologies, and ability to detect biomolecules by their intrinsic molecular charge favor the semiconductor field-effect platform as one of the most attractive approaches for the development of label-free DNA chips. In this work, a capacitive field-effect EIS (electrolyte-insulator-semiconductor) sensor covered with a layer-by-layer prepared, positively charged weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was used for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization. The negatively charged probe single-stranded DNA (ssDNA) molecules were electrostatically adsorbed onto the positively charged PAH layer, resulting in a preferentially flat orientation of the ssDNA molecules within the Debye length, thus yielding a reduced charge-screening effect and a higher sensor signal. Each sensor-surface modification step (PAH adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), reducing an unspecific adsorption by a blocking agent, incubation with noncomplementary DNA (ncDNA) solution) was monitored by means of capacitance-voltage and constant-capacitance measurements. In addition, the surface morphology of the PAH layer was studied by atomic force microscopy and contact-angle measurements. High hybridization signals of 34 and 43 mV were recorded in low-ionic strength solutions of 10 and 1 mM, respectively. In contrast, a small signal of 4 mV was recorded in the case of unspecific adsorption of fully mismatched ncDNA. The density of probe ssDNA and dsDNA molecules as well as the hybridization efficiency was estimated using the experimentally measured DNA immobilization and hybridization signals and a simplified double-layer capacitor model. The results of field-effect experiments were supported by fluorescence measurements, verifying the DNA-immobilization and hybridization event.

Injection of polyelectrolytes enhances mobility of zero-valent iron nanoparticles in carbonate-rich porous media

NASA Astrophysics Data System (ADS)

Laumann, Susanne; Micić, Vesna; Schmid, Doris; Hofmann, Thilo

2013-04-01

The application of nanoscale zero-valent iron (nZVI) for in situ groundwater remediation has received increased attention as a beneficial and novel remediation technique. A precondition for effective nZVI field applications is its delivery to the contaminated source zones. This has proved to be difficult due to the limited mobility of nZVI, which remains one major obstacle to widespread utilization of this remediation approach (O'CAROLL ET AL., 2012). One important factor that controls mobility of nZVI is physical and chemical heterogeneity within the subsurface, such as mineralogical variations (KIM ET AL., 2012). In our previous study we showed that the nZVI transport in carbonate-rich porous media is significantly reduced compared to that in quartz porous media (LAUMANN ET AL., 2012). This is caused by favorable nZVI deposition onto carbonate sand and is attributed to the less negative surface charge of carbonate compared to that of quartz sand under the range of water chemical conditions typically encountered in aquifers. New strategies are therefore required to improve nZVI mobility in carbonate-rich porous media. One approach can be the injection of polyelectrolytes in the subsurface, which are expected to adsorb onto aquifer grains and provide greater repulsion between nZVI and the porous media. In this study the effect of co-injected polyelectrolytes on the transport of polyacrylic acid (PAA) coated nZVI in two model porous media, quartz and carbonate sands was evaluated. Column experiments were carried out aiming to evaluate mobility of PAA-nZVI co-injected with four polyelectrolytes, including natural organic matter (NOM), humic acid, carboxymethyl cellulose (CMC), and lignin sulfonate. The results demonstrated that the co-injection of the chosen polyelectrolytes does not influence mobility of PAA-nZVI in quartz sand; the breakthrough with co-injected polyelectrolytes was similar to that of the pure PAA-nZVI dispersion. This observation can be explained by the strong negative surface charge of the quartz sand, which was apparently not changed in the presence of polyelectrolytes. Conversely, the co-injected polyelectrolytes affected the breakthrough in carbonate sand, increasing nZVI mobility for approximately 15%. This can be explained by the attachment of the polyelectrolytes to the less negatively charged carbonate sand, which then promoted the PAA-nZVI mobility. Even though there are structural differences among the polyelectrolytes applied in this study, our results showed no significant variations in the PAA-nZVI mobility when these polyelectrolytes are present at concentration of 50 mg L-1. Lignin sulfonate was furthermore selected to investigate the effect of different polyelectrolyte concentrations (0, 10, 25, 50, 250, and 500 mg L-1) on the PAA-nZVI mobility. The results showed that higher lignin sulfonate concentrations (250 and 500 mg L-1) do not affect the transport of PAA-nZVI in quartz sand. In carbonate sand, on contrary, increasing mobility due to co-injected lignin sulfonate was observed at concentrations above 25 mg L-1, having the highest value with 500 mg L-1 co-injected with the PAA-nZVI dispersion. Overall, the results demonstrated that lignin sulfonate adsorption onto the carbonate sand reduce PAA-nZVI deposition onto aquifer grains and promote its mobility, the effect which is more pronounced at higher polyelectrolyte concentrations co-injected with the PAA-nZVI dispersion. The project is funded by the Federal Ministry of Agriculture, Forestry, Environment and Water Management (BMLFUW). Management by Kommunalkredit Public Consulting GmbH. Literature O'CAROLL, D. ET AL., (2012): Advances in Water Resources, in press. KIM, H.-J. ET AL., (2012): Journal of Colloid and Interface Science 370, 1-10. LAUMANN, S. ET AL., (2012): Environmental Pollution, submitted.

Swelling of biological and semiflexible polyelectrolytes.

PubMed

Dobrynin, Andrey V; Carrillo, Jan-Michael Y

2009-10-21

We have developed a theoretical model of swelling of semiflexible (biological) polyelectrolytes in salt solutions. Our approach is based on separation of length scales which allowed us to split a chain's electrostatic energy into two parts that describe local and remote electrostatic interactions along the polymer backbone. The local part takes into account interactions between charged monomers that are separated by distances along the polymer backbone shorter than the chain's persistence length. These electrostatic interactions renormalize chain persistence length. The second part includes electrostatic interactions between remote charged pairs along the polymer backbone located at distances larger than the chain persistence length. These interactions are responsible for chain swelling. In the framework of this approach we calculated effective chain persistence length and chain size as a function of the Debye screening length, chain degree of ionization, bare persistence length and chain degree of polymerization. Our crossover expression for the effective chain's persistence length is in good quantitative agreement with the experimental data on DNA. We have been able to fit experimental datasets by using two adjustable parameters: DNA ionization degree (α = 0.15-0.17) and a bare persistence length (l(p) = 40-44 nm).

Excluded volume and ion-ion correlation effects on the ionic atmosphere around B-DNA: Theory, simulations, and experiments

PubMed Central

Ovanesyan, Zaven; Fenley, Marcia O.; Guerrero-García, Guillermo Iván; Olvera de la Cruz, Mónica

2014-01-01

The ionic atmosphere around a nucleic acid regulates its stability in aqueous salt solutions. One major source of complexity in biological activities involving nucleic acids arises from the strong influence of the surrounding ions and water molecules on their structural and thermodynamic properties. Here, we implement a classical density functional theory for cylindrical polyelectrolytes embedded in aqueous electrolytes containing explicit (neutral hard sphere) water molecules at experimental solvent concentrations. Our approach allows us to include ion correlations as well as solvent and ion excluded volume effects for studying the structural and thermodynamic properties of highly charged cylindrical polyelectrolytes. Several models of size and charge asymmetric mixtures of aqueous electrolytes at physiological concentrations are studied. Our results are in good agreement with Monte Carlo simulations. Our numerical calculations display significant differences in the ion density profiles for the different aqueous electrolyte models studied. However, similar results regarding the excess number of ions adsorbed to the B-DNA molecule are predicted by our theoretical approach for different aqueous electrolyte models. These findings suggest that ion counting experimental data should not be used alone to validate the performance of aqueous DNA-electrolyte models. PMID:25494770

The effect of multivalent counterions to the structure of highly dense polystyrene sulfonate brushes

DOE PAGES

Yu, Jing; Mao, Jun; Yuan, Guangcui; ...

2016-02-23

Surface tethered polyelectrolyte brushes are scientifically interesting and technologically relevant to many applications, ranging from colloidal stabilization to responsive and tunable materials to lubrication. Many applications operate in environments containing multi-valent ions, media in which our scientific understanding is not yet well-developed. In this paper, we synthesized high-density polystyrene sulfonate (PSS) brushes via surface initiated atom-transfer radical polymerization, and performed neutron reflectivity (NR) measurements to investigate and compare the effects of mono-valent Rb + and tri-valent Y 3+ counterions to the structure of the densely tethered PSS brushes. Our NR results show that in mono-valent RbNO 3 solution, the densemore » PSS brush retained its full thickness up to a salt concentration of 1 M, whereas it immediately collapsed upon adding 1.67 mM of tri-valent Y 3+. Increasing the concentration of Y 3+ beyond this level did not lead to any significant further structure change of the PSS brush. Finally, our findings demonstrate that the presence of multi-valent counterions can significantly alter the structure of polyelectrolyte brushes, in a manner different from mono-valent ions, which has implications for the functionality of the brushes.« less

On the mesoscopic origins of high viscosities in some polyelectrolyte-surfactant mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffmann, Ingo, E-mail: ingo.hoffmann@tu-berlin.de; Institut Max von Laue-Paul Langevin; Farago, Bela

Oppositely charged polyelectrolyte (PE) surfactant mixtures allow the control of rheological parameters of a solution even at fairly low concentrations. For example, addition of 0.3 wt. % of anionic surfactant to a 1 wt. % solution of the polycation JR 400 increases the viscosity by 4 orders of magnitude. Recently, we could show that this increase is related to the formation of mixed, rod-like PE/surfactant aggregates which interconnect several polyelectrolyte chains [Hoffmann et al., Europhys. Lett. 104, 28001 (2013)]. In this paper, we refine our structural model of the aggregates to obtain a more consistent picture of their internal structure for differentmore » anionic surfactants. Combining small angle neutron scattering (SANS) and neutron spin-echo (NSE) allows us to determine the size of the aggregates. By comparing different contrasts, the internal structure of the aggregates can be elucidated and it is seen that the PE in the aggregates retains a relatively high freedom of movement. We proceeded to investigate the influence of the surfactant concentration and the surfactant type on structure and dynamics of the mixed aggregates. It is seen that the structural parameters of the aggregates depend very little on the surfactant concentration and headgroup. However, it is crucial to incorporate a sufficient amount of PE in the aggregates to increase the viscosity of the aggregates. By comparing viscous samples at 1 wt. % PE concentration with samples at a PE concentration of 0.3 wt. %, where no significant increase in viscosity is observed, we find that similar aggregates are formed already at this lower PE concentrations. However, the amount of PE incorporated in them is insufficient to interconnect several PE chains and therefore, they do not increase viscosity. So, our detailed investigation combining contrast variation SANS and NSE does not only allow to explain the viscosity behavior but also to deduced detailed information regarding the structures and the dynamics especially of the polyelectrolyte within the complexes.« less

Spectroscopic properties of triangular silver nanoplates immobilized on polyelectrolyte multilayer-modified glass substrates

NASA Astrophysics Data System (ADS)

Rabor, Janice B.; Kawamura, Koki; Muko, Daiki; Kurawaki, Junichi; Niidome, Yasuro

2017-07-01

Fabrication of surface-immobilized silver nanostructures with reproducible plasmonic properties by dip-coating technique is difficult due to shape alteration. To address this challenge, we used a polyelectrolyte multilayer to promote immobilization of as-received triangular silver nanoplates (TSNP) on a glass substrate through electrostatic interaction. The substrate-immobilized TSNP were characterized by absorption spectrophotometry and scanning electron microscopy. The bandwidth and peak position of localized surface plasmon resonance (LSPR) bands can be tuned by simply varying the concentration of the colloidal solution and immersion time. TSNP immobilized from a higher concentration of colloidal solution with longer immersion time produced broadened LSPR bands in the near-IR region, while a lower concentration with shorter immersion time produced narrower bands in the visible region. The shape of the nanoplates was retained even at long immersion time. Analysis of peak positions and bandwidths also revealed the point at which the main species of the immobilization had been changed from isolates to aggregates.

Polyelectrolyte-coated carbons used in the generation of blue energy from salinity differences.

PubMed

Ahualli, S; Jiménez, M L; Fernández, M M; Iglesias, G; Brogioli, D; Delgado, A V

2014-12-14

In this work we present a method for the production of clean, renewable electrical energy from the exchange of solutions with different salinities. Activated carbon films are coated with negatively or positively charged polyelectrolytes using well-established adsorption methods. When two oppositely charged coated films are placed in contact with an ionic solution, the potential difference between them will be equal to the difference between their Donnan potentials, and hence, energy can be extracted by building an electrochemical cell with such electrodes. A model is elaborated on the operation of the cell, based on the electrokinetic theory of soft particles. All the features of the model are experimentally reproduced, although a small quantitative difference concerning the maximum open-circuit voltage is found, suggesting that the coating is the key point to improve the efficiency. In the experimental conditions used, we obtain a power of 12.1 mW m(-2). Overall, the method proves to be a fruitful and simple approach to salinity-gradient energy production.

Hybrid particle-field molecular dynamics simulation for polyelectrolyte systems.

PubMed

Zhu, You-Liang; Lu, Zhong-Yuan; Milano, Giuseppe; Shi, An-Chang; Sun, Zhao-Yan

2016-04-14

To achieve simulations on large spatial and temporal scales with high molecular chemical specificity, a hybrid particle-field method was proposed recently. This method is developed by combining molecular dynamics and self-consistent field theory (MD-SCF). The MD-SCF method has been validated by successfully predicting the experimentally observable properties of several systems. Here we propose an efficient scheme for the inclusion of electrostatic interactions in the MD-SCF framework. In this scheme, charged molecules are interacting with the external fields that are self-consistently determined from the charge densities. This method is validated by comparing the structural properties of polyelectrolytes in solution obtained from the MD-SCF and particle-based simulations. Moreover, taking PMMA-b-PEO and LiCF3SO3 as examples, the enhancement of immiscibility between the ion-dissolving block and the inert block by doping lithium salts into the copolymer is examined by using the MD-SCF method. By employing GPU-acceleration, the high performance of the MD-SCF method with explicit treatment of electrostatics facilitates the simulation study of many problems involving polyelectrolytes.

Kinetics of electrically and chemically induced swelling in polyelectrolyte gels

NASA Astrophysics Data System (ADS)

Grimshaw, P. E.; Nussbaum, J. H.; Grodzinsky, A. J.; Yarmush, M. L.

1990-09-01

Controlled swelling and shrinking of polyelectrolyte gels is useful for regulating the transport of solutes into, out of, and through these materials. A macroscopic continuum model is presented to predict the kinetics of swelling in polyelectrolyte gel membranes induced by augmentation of electrostatic swelling forces arising from membrane fixed charge groups. The model accounts for ionic transport within the membrane, electrodiffusion phenomena, dissociation of membrane charge groups, intramembrane fluid flow, and mechanical deformation of the membrane matrix. Model predictions are compared with measurements of chemically and electrically induced swelling and shrinking in crosslinked polymethacrylic acid (PMAA) membranes. Large, reversible changes in PMAA membrane hydration were observed after changing the bath pH or by applying an electric field to modify the intramembrane ionic environment and fixed charge density. A relatively slow swelling process and more rapid shrinking for both chemical and electrical modulation of the intramembrane pH are observed. The model indicates that retardation of membrane swelling is dominated by diffusion-limited reaction of H+ ions with membrane charge groups, and that the more rapid shrinking is limited primarily by mechanical processes.

Top-down and Bottom-up Approaches in Production of Aqueous Nanocolloids of Low Soluble Drug Paclitaxel

PubMed Central

Pattekari, P.; Zheng, Z.; Zhang, X.; Levchenko, T.; Torchilin, V.

2015-01-01

Nano-encapsulation of poorly soluble anticancer drug was developed with sonication assisted layer-by-layer polyelectrolyte coating (SLbL). We changed the strategy of LbL-encapsulation from making microcapsules with many layers in the walls for encasing highly soluble materials to using very thin polycation / polyanion coating on low soluble nanoparticles to provide their good colloidal stability. SLbL encapsulation of paclitaxel resulted in stable 100-200 nm diameter colloids with high electrical surface ξ-potential (of -45 mV) and drug content in the nanoparticles of 90 wt %. In the top-down approach, nanocolloids were prepared by rupturing powder of paclitaxel using ultrasonication and simultaneous sequential adsorption of oppositely charged biocompatible polyelectrolytes. In the bottom-up approach paclitaxel was dissolved in organic solvent (ethanol or acetone), and drug nucleation was initiated by gradual worsening the solution with the addition of aqueous polyelectrolyte assisted by ultrasonication. Paclitaxel release rates from such nanocapsules were controlled by assembling multilayer shells with variable thicknesses and are in the range of 10-20 hours. PMID:21442095

Inhibiting surface crystallization of amorphous indomethacin by nanocoating.

PubMed

Wu, Tian; Sun, Ye; Li, Ning; de Villiers, Melgardt M; Yu, Lian

2007-04-24

An amorphous solid (glass) may crystallize faster at the surface than through the bulk, making surface crystallization a mechanism of failure for amorphous pharmaceuticals and other materials. An ultrathin coating of gold or polyelectrolytes inhibited the surface crystallization of amorphous indomethacin (IMC), an anti-inflammatory drug and model organic glass. The gold coating (10 nm) was deposited by sputtering, and the polyelectrolyte coating (3-20 nm) was deposited by an electrostatic layer-by-layer assembly of cationic poly(dimethyldiallyl ammonium chloride) (PDDA) and anionic sodium poly(styrenesulfonate) (PSS) in aqueous solution. The coating also inhibited the growth of existing crystals. The inhibition was strong even with one layer of PDDA. The polyelectrolyte coating still permitted fast dissolution of amorphous IMC and improved its wetting and flow. The finding supports the view that the surface crystallization of amorphous IMC is enabled by the mobility of a thin layer of surface molecules, and this mobility can be suppressed by a coating of only a few nanometers. This technique may be used to stabilize amorphous drugs prone to surface crystallization, with the aqueous coating process especially suitable for drugs of low aqueous solubility.

Polyelectrolyte multilayer-assisted fabrication of non-periodic silicon nanocolumn substrates for cellular interface applications

NASA Astrophysics Data System (ADS)

Lee, Seyeong; Kim, Dongyoon; Kim, Seong-Min; Kim, Jeong-Ah; Kim, Taesoo; Kim, Dong-Yu; Yoon, Myung-Han

2015-08-01

Recent advances in nanostructure-based biotechnology have resulted in a growing demand for vertical nanostructure substrates with elaborate control over the nanoscale geometry and a high-throughput preparation. In this work, we report the fabrication of non-periodic vertical silicon nanocolumn substrates via polyelectrolyte multilayer-enabled randomized nanosphere lithography. Owing to layer-by-layer deposited polyelectrolyte adhesives, uniformly-separated polystyrene nanospheres were securely attached on large silicon substrates and utilized as masks for the subsequent metal-assisted silicon etching in solution. Consequently, non-periodic vertical silicon nanocolumn arrays were successfully fabricated on a wafer scale, while each nanocolumn geometric factor, such as the diameter, height, density, and spatial patterning, could be fully controlled in an independent manner. Finally, we demonstrate that our vertical silicon nanocolumn substrates support viable cell culture with minimal cell penetration and unhindered cell motility due to the blunt nanocolumn morphology. These results suggest that vertical silicon nanocolumn substrates may serve as a useful cellular interface platform for performing a statistically meaningful number of cellular experiments in the fields of biomolecular delivery, stem cell research, etc.Recent advances in nanostructure-based biotechnology have resulted in a growing demand for vertical nanostructure substrates with elaborate control over the nanoscale geometry and a high-throughput preparation. In this work, we report the fabrication of non-periodic vertical silicon nanocolumn substrates via polyelectrolyte multilayer-enabled randomized nanosphere lithography. Owing to layer-by-layer deposited polyelectrolyte adhesives, uniformly-separated polystyrene nanospheres were securely attached on large silicon substrates and utilized as masks for the subsequent metal-assisted silicon etching in solution. Consequently, non-periodic vertical silicon nanocolumn arrays were successfully fabricated on a wafer scale, while each nanocolumn geometric factor, such as the diameter, height, density, and spatial patterning, could be fully controlled in an independent manner. Finally, we demonstrate that our vertical silicon nanocolumn substrates support viable cell culture with minimal cell penetration and unhindered cell motility due to the blunt nanocolumn morphology. These results suggest that vertical silicon nanocolumn substrates may serve as a useful cellular interface platform for performing a statistically meaningful number of cellular experiments in the fields of biomolecular delivery, stem cell research, etc. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02384j

Conjugated-polyelectrolyte-grafted cotton fibers act as "micro flypaper" for the removal and destruction of bacteria.

PubMed

Ista, Linnea K; Dascier, Dimitri; Ji, Eunkyung; Parthasarathy, Anand; Corbitt, Thomas S; Schanze, Kirk S; Whitten, David G

2011-08-01

We demonstrate herein a method for chemically modifying cotton fibers and cotton-containing fabric with a light-activated, cationic phenylene-ethynylene (PPE-DABCO) conjugated polyelectrolyte biocide. When challenged with Pseudomonas aeruginosa and Bacillus atropheaus vegetative cells from liquid suspension, light-activated PPE-DABCO effects 1.2 and 8 log, respectively, losses in viability of the exposed bacteria. These results suggest that conjugated polyelectrolytes retain their activity when grafted to fabrics, showing promise for use in settings where antimicrobial textiles are needed.

Effect of dielectric discontinuity on a spherical polyelectrolyte brush

NASA Astrophysics Data System (ADS)

Tergolina, Vinicius B.; dos Santos, Alexandre P.

2017-09-01

In this paper we perform molecular dynamics simulations of a spherical polyelectrolyte brush and counterions in a salt-free medium. The dielectric discontinuity on the grafted nanoparticle surface is taken into account by the method of image charges. Properties of the polyelectrolyte brush are obtained for different parameters, including valency of the counterions, radius of the nanoparticle, and the brush total charge. The monovalent counterions density profiles are obtained and compared with a simple mean-field theoretical approach. The theory allows us to obtain osmotic properties of the system.

Segregation in like-charged polyelectrolyte-surfactant mixtures can be precisely tuned via manipulation of the surfactant mass ratio.

PubMed

Wills, Peter W; Lopez, Sonia G; Burr, Jocelyn; Taboada, Pablo; Yeates, Stephen G

2013-04-09

In this study, we consider segregative phase separation in aqueous mixtures of quaternary ammonium surfactants didecyldimethylammonium chloride (DDQ) and alkyl (C12, 70%; C14 30%) dimethyl benzyl ammonium chloride (BAC) upon the addition of poly(diallyldimethylammonium) chloride (pDADMAC) as a function of both concentration and molecular weight. The nature of the surfactant type is dominant in determining the concentration at which separation into an upper essentially surfactant-rich phase and lower polyelectrolyte-rich phase is observed. However, for high-molecular-weight pDADMAC there is a clear indication of an additional depletion flocculation effect. When the BAC/DDQ ratio is tuned, the segregative phase separation point can be precisely controlled. We propose a phase separation mechanism for like-charged quaternary ammonium polyelectrolyte/surfactant/water mixtures induced by a reduction in the ionic atmosphere around the surfactant headgroup and possible ion pair formation. An additional polyelectrolyte-induced depletion flocculation effect was also observed.

Tribological properties of hydrophilic polymer brushes under wet conditions.

PubMed

Kobayashi, Motoyasu; Takahara, Atsushi

2010-08-01

This article demonstrates a water-lubrication system using high-density hydrophilic polymer brushes consisting of 2,3-dehydroxypropyl methacrylate (DHMA), vinyl alcohol, oligo(ethylene glycol)methyl ether methacrylate, 2-(methacryloyloxy)ethyltrimethylammonium chloride (MTAC), 3-sulfopropyl methacrylate potassium salt (SPMK), and 2-methacryloyloxyethyl phosphorylcholine (MPC) prepared by surface-initiated controlled radical polymerization. Macroscopic frictional properties of brush surfaces were characterized by sliding a glass ball probe in water using a ball-on-plate type tribotester under the load of 0.1-0.49 N at the sliding velocity of 10(-5)-10(-1) m s(-1) at 298 K. A poly(DHMA) brush showed a relatively larger friction coefficient in water, whereas the polyelectrolyte brushes, such as poly(SPMK) and poly(MPC), revealed significantly low friction coefficients below 0.02 in water and in humid air conditions. A drastic reduction in the friction coefficient of polyelectrolyte brushes in aqueous solution was observed at around 10(-3)-10(-2) m s(-1) owing to the hydrodynamic lubrication effect, however, an increase in salt concentration in the aqueous solution led to the increase in the friction coefficients of poly(MTAC) and poly(SPMK) brushes. The poly(SPMK) brush showed a stable and low friction coefficient in water even after sliding over 450 friction cycles, indicating a good wear resistance of the brush film. Copyright 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Modeling the effects of pH and ionic strength on swelling of anionic polyelectrolyte gels

NASA Astrophysics Data System (ADS)

Drozdov, A. D.; deClaville Christiansen, J.

2015-07-01

A constitutive model is developed for the elastic response of an anionic polyelectrolyte gel under swelling in water with an arbitrary pH and an arbitrary molar fraction of dissolved monovalent salt. A gel is treated as a three-phase medium consisting of a solid phase (polymer network), solvent (water), and solute (mobile ions). Transport of solvent and solute is thought of as their diffusion through the polymer network accelerated by an electric field formed by mobile and fixed ions and accompanied by chemical reactions (dissociation of functional groups attached to polymer chains and formation of ion pairs between bound charges and mobile counter-ions). Constitutive equations are derived by means of the free energy imbalance inequality for an arbitrary three-dimensional deformation with finite strains. These relations are applied to analyze equilibrium swelling diagrams on poly(acrylic acid) gel, poly(methacrylic acid) gel, and three composite hydrogels under water uptake in a bath (i) with a fixed molar fraction of salt and varied pH, and (ii) with a fixed pH and varied molar fraction of salt. To validate the ability of the model to predict observations quantitatively, material constants are found by matching swelling curves under one type of experimental conditions and results of simulation are compared with experimental data in the other type of tests.

Transport of Organic Compounds Through Porous Systems Containing Humic Acids.

PubMed

Smilek, Jiri; Sedlacek, Petr; Lastuvkova, Marcela; Kalina, Michal; Klucakova, Martina

2017-03-01

Soil pollution by the presence of different contaminants (e.g. heavy metal ions or pesticides) is one of the biggest problems worldwide. The positive affinity of natural humic acids towards these contaminants might contribute to the soil and ground water protection; therefore it is necessary to study the reactivity and barrier properties of humic acids. An original reactivity-mapping tool based on diffusion techniques designed to study the reactivity and barrier properties of polyelectrolytes was developed and tested on humic acids. The results of diffusion experiments demonstrate that the electrostatic interactions between humic acids functioning as a polyelectrolyte interpenetrated in a supporting hydrogel matrix (agarose) and cationic dye (methylene blue) as a model solute have a crucial impact on the rate of diffusion processes and on the barrier properties of hydrogels. The intensity of interactions was evaluated by fundamental diffusion parameters (effective diffusion coefficients and breakthrough time). The impact of modification of humic acids was also studied by means of diffusion experiments conducted on two types of standard humic acids (Leonardite 1S104H) and humic acids with selectively methylated carboxylic groups.

Packaging of Polyelectrolytes in Viral Capsids: The Interplay Between Polymer Length and Capsid Size

NASA Astrophysics Data System (ADS)

Knobler, Charles

2008-03-01

Each particle of the Cowpea Chlorotic Mottle Virus (CCMV) has a very small ``parts list,'' consisting of two components: a molecule of single-stranded RNA and a 190-residue protein that makes up the 28-nm diameter icosahedral capsid. When purified viral RNA and capsid protein are mixed in solution at an appropriate pH and ionic strength, infectious wild-type viruses form spontaneously. Virus-like particles (VLPs) are formed when the protein self assembles around other anionic polymers such as poly(styrene sulfonate) (PSS). Under different pH and ionic strength conditions the capsid protein can assemble by itself into empty capsids, multishell structures, tubes and sheets. To explore the effect on virion size of the competition between the preferred curvature of the protein and the size of the packaged cargo we have examined the formation of VLPs around PSS polymers with molecular weights ranging from 400 kDa to 3.4 MDa. Two distinct sizes are observed -- 22 nm for the lower molecular weights, jumping to 27 nm at 2 MDa. While under given conditions the size of PSS in solution is directly determined by its molecular weight, the self-complementarity of RNA makes its solution structure dependent on the nucleotide sequence as well. We have therefore employed Small-Angle X-ray Scattering and Fluorescence Correlation Spectroscopy to examine the sizes of viral and non-viral RNAs of identical lengths. A model for the assembly that includes both the self-interactions of the polyelectrolyte and the capsid proteins and the interactions between them provides insight into the experimental results.

Fracturing fluid cleanup by controlled release of enzymes from polyelectrolyte complex nanoparticles

NASA Astrophysics Data System (ADS)

Barati Ghahfarokhi, Reza

Guar-based polymer gels are used in the oil and gas industry to viscosify fluids used in hydraulic fracturing of production wells, in order to reduce leak-off of fluids and pressure, and improve the transport of proppants. After fracturing, the gel and associated filter cake must be degraded to very low viscosities using breakers to recover the hydraulic conductivity of the well. Enzymes are widely used to achieve this but injecting high concentrations of enzyme may result in premature degradation, or failure to gel; denaturation of enzymes at alkaline pH and high temperature conditions can also limit their applicability. In this study, application of polyelectrolyte nanoparticles for entrapping, carrying, releasing and protecting enzymes for fracturing fluids was examined. The objective of this research is to develop nano-sized carriers capable of carrying the enzymes to the filter cake, delaying the release of enzyme and protecting the enzyme against pH and temperature conditions inhospitable to native enzyme. Polyethylenimine-dextran sulfate (PEI-DS) polyelectrolyte complexes (PECs) were used to entrap two enzymes commonly used in the oil industry in order to obtain delayed release and to protect the enzyme from conditions inhospitable to native enzyme. Stability and reproducibility of PEC nanoparticles was assured over time. An activity measurement method was used to measure the entrapment efficiency of enzyme using PEC nanoparticles. This method was confirmed using a concentration measurement method (SDS-PAGE). Entrapment efficiencies of pectinase and a commercial high-temperature enzyme mixture in polyelectrolyte complex nanoparticles were maximized. Degradation, as revealed by reduction in viscoelastic moduli of borate-crosslinked hydroxypropyl guar (HPG) gel by commercial enzyme loaded in polyelectrolyte nanoparticles, was delayed, compared to equivalent systems where the enzyme mixture was not entrapped. This indicates that PEC nanoparticles delay the activity of enzymes by entrapping them. It was also observed that control PEC nanoparticles decreased both viscoelastic moduli, but with a slower rate compared to the PEC nanoparticles loaded with enzyme. Preparation shear and applied shear showed no significant effect on activity of enzyme-loaded PEC nanoparticles mixed with HPG solutions. However, fast addition of chemicals during the preparations showed smaller particle size compared to the drop-wise method. PEC nanoparticles (PECNPs) also protected both enzymes from denaturation at elevated temperature and pH. Following preparation, enzyme-loaded PEC nanoparticles were mixed with borate crosslinked HPG and the mixture was injected through a shear loop. Pectinase-loaded nanoparticles mixed with gelled HPG showed no sensitivity to shear applied along the shear loop at 25 °C. However, EL2X-loaded PEC nanoparticles showed sensitivity to shear applied along the shear loop at 40 °C. Filter cake was formed and degraded in a fluid loss cell for borate crosslinked HPG solutions mixed with either enzymes or enzyme-loaded PEC nanoparticles. Cleanup slopes of filter cake degraded using enzyme-loaded PEC nanoparticles and systems with enzymes mixed with HPG gel were significantly higher than for the filter cake formed with HPG gel mixed with no enzyme. In a different application, enzyme-loaded PEC nanoparticles showed significantly slower reduction in viscosity of HPG solution over time compared to the HPG systems mixed with enzyme. Increasing the viscosity of low concentration HPG, used as slick-water, decreases the proppant settling velocity. This is of specific interest in fracturing fluids used for unconventional reservoirs.

Influence of D-Penicillamine on the Viscosity of Hyaluronic Acid Solutions

NASA Astrophysics Data System (ADS)

Liang, Jing; Krause, Wendy E.; Colby, Ralph H.

2006-03-01

Polyelectrolyte hyaluronic acid (HA, hyaluronan) is an important component in synovial fluid. Its presence results in highly viscoelastic solutions with excellent lubricating and shock-absorbing properties. In comparison to healthy synovial fluid, diseased fluid has a reduced viscosity. In osteoarthritis this reduction in viscosity results from a decline in both the molecular weight and concentration of hyaluronic acid HA. Initial results indicate that D-penicillamine affects the rheology of bovine synovial fluid, a model synovial fluid solution, and its components, including HA. In order to understand how D-penicillamine modifies the viscosity of these solutions, the rheological properties of sodium hyaluronate (NaHA) in phosphate-buffered saline (PBS) with D-penicillamine were studied as function of time, D-penicillamine concentration (0 -- 0.01 M), and storage conditions. Penicillamine has a complex, time dependent effect on the viscosity of NaHA solutions---reducing the zero shear rate viscosity of a 3 mg/mL NaHA in PBS by ca. 40% after 44 days.

Solution of the nonlinear Poisson-Boltzmann equation: Application to ionic diffusion in cementitious materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arnold, J.; Kosson, D.S., E-mail: david.s.kosson@vanderbilt.edu; Garrabrants, A.

2013-02-15

A robust numerical solution of the nonlinear Poisson-Boltzmann equation for asymmetric polyelectrolyte solutions in discrete pore geometries is presented. Comparisons to the linearized approximation of the Poisson-Boltzmann equation reveal that the assumptions leading to linearization may not be appropriate for the electrochemical regime in many cementitious materials. Implications of the electric double layer on both partitioning of species and on diffusive release are discussed. The influence of the electric double layer on anion diffusion relative to cation diffusion is examined.

Sampling Long- versus Short-Range Interactions Defines the Ability of Force Fields To Reproduce the Dynamics of Intrinsically Disordered Proteins.

PubMed

Mercadante, Davide; Wagner, Johannes A; Aramburu, Iker V; Lemke, Edward A; Gräter, Frauke

2017-09-12

Molecular dynamics (MD) simulations have valuably complemented experiments describing the dynamics of intrinsically disordered proteins (IDPs), particularly since the proposal of models to solve the artificial collapse of IDPs in silico. Such models suggest redefining nonbonded interactions, by either increasing water dispersion forces or adopting the Kirkwood-Buff force field. These approaches yield extended conformers that better comply with experiments, but it is unclear if they all sample the same intrachain dynamics of IDPs. We have tested this by employing MD simulations and single-molecule Förster resonance energy transfer spectroscopy to sample the dimensions of systems with different sequence compositions, namely strong and weak polyelectrolytes. For strong polyelectrolytes in which charge effects dominate, all the proposed solutions equally reproduce the expected ensemble's dimensions. For weak polyelectrolytes, at lower cutoffs, force fields abnormally alter intrachain dynamics, overestimating excluded volume over chain flexibility or reporting no difference between the dynamics of different chains. The TIP4PD water model alone can reproduce experimentally observed changes in extensions (dimensions), but not quantitatively and with only weak statistical significance. Force field limitations are reversed with increased interaction cutoffs, showing that chain dynamics are critically defined by the presence of long-range interactions. Force field analysis aside, our study provides the first insights into how long-range interactions critically define IDP dimensions and raises the question of which length range is crucial to correctly sample the overall dimensions and internal dynamics of the large group of weakly charged yet highly polar IDPs.

Influence of Anti-inflammatory Drugs on the Rheological Properties of Synovial Fluid and Its Components

NASA Astrophysics Data System (ADS)

Krause, Wendy E.; Klossner, Rebecca R.; Liang, Jing; Colby, Ralph H.

2006-03-01

The polyelectrolyte hyaluronic acid (HA, hyaluronan), its interactions with anti-inflammatory drugs and other biopolymers, and its role in synovial fluid are being studied. We are investigating the rheological properties of sodium hyaluronate (NaHA) solutions and an experimental model of synovial fluid (comprised of NaHA, and the plasma proteins albumin and γ-globulins). Steady shear measurements on bovine synovial fluid, the synovial fluid model, and plasma protein solutions indicate that the fluids are rheopectic (stress increases with time under steady shear). In addition, the influence of anti-inflammatory agents on these solutions is being explored. Initial results indicate that D-penicillamine and hydroxychloroquine (HCQ) affect the rheology of the synovial fluid model and its components. While HCQ has no effect on the viscosity of NaHA solutions, it inhibits/suppresses the observed rheopexy of the synovial fluid model and plasma protein solutions. In contrast, D-penicillamine has a complex, time dependent effect on the viscosity of NaHA solutions,---reducing the zero shear rate viscosity of a 3 mg/mL NaHA (in phosphate buffered saline) by ca. 40% after 44 days. The potential implications of these results will be discussed.

Phase behavior of gemini surfactant hexylene-1,6-bis(dodecyldimethylammonium bromide) and polyelectrolyte NaPAA.

PubMed

Pi, Yingying; Shang, Yazhuo; Peng, Changjun; Liu, Honglai; Hu, Ying; Jiang, Jianwen

2006-07-01

The phase behavior of aqueous mixtures of gemini surfactant hexylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and oppositely charged polyelectrolyte sodium polyacrylate (NaPAA) has been studied experimentally. Compared to the mixtures of the traditional surfactant dodecyltrimethylammonium bromide (DTAB) and NaPAA, the gel phase region in the 12-6-12/NaPAA solution is larger. Element analysis reveals that NaPAA in the gel phase tends to replace the counterions of surfactant micelle and to release its own counterions. Spherical aggregates are observed in either top or bottom gel phase as detected by transmission electron microscopy. The addition of sodium bromide (NaBr) leads to a decrease in the gel phase region and the occurrence of a new cream phase.

Rheology of polyelectrolyte complex materials

NASA Astrophysics Data System (ADS)

Tirrell, Matthew

Fluid polyelectrolyte complexes, sometimes known as complex coacervates, have rheological properties that are very sensitive to structure and salt concentration. Dynamic moduli of such viscoelastic materials very many orders of magnitude between solutions of no added salt to of order tenth molar salt, typical, for example of physiological saline. Indeed, salt plays a role in the rheology of complex coacervates analogous to that which temperature plays on polymer melts, leading to an empirical observation of what may be termed time-salt or frequency salt superposition. Block copolymers containing complexing ionic blocks also exhibit strong salt sensitivity of their rheological properties. Data representing these phenomena will be presented and discussed. Support from NIST, Department of Commerce, via the Center for Hierarchical Materials Design at Northwestern University and the University of Chicago is gratefully acknowledged.

Effects of N-vinylpyrrolidone (NVP) containing polyelectrolytes on surface properties of conventional glass-ionomer cements (GIC).

PubMed

Moshaverinia, Alireza; Roohpour, Nima; Ansari, Sahar; Moshaverinia, Maryam; Schricker, Scott; Darr, Jawwad A; Rehman, Ihtesham U

2009-10-01

It has been found that polyacids containing an N-vinylpyrrolidinone (NVP) comonomer produces a glass inomer cement with improved mechanical and handling properties. The objective of this study was to investigate the effect of NVP modified polyelectrolytes on the surface properties and shear bond strength to dentin of glass ionomer cements. Poly(acrylic acid (AA)-co-itaconic acid (IA)-co-N-vinylpyrrolidone) was synthesized by free radical polymerization. The terpolymer was characterized using (1)H NMR, FTIR spectroscopy and viscometry for solution properties. The synthesized polymers were used in glass ionomer cement formulations (Fuji II commercial GIC). Surface properties (wettability) of modified cements were studied by water contact angle measurements as a function of time. Work of adhesion values of different surfaces was also determined. The effect of NVP modified polyacid, on bond strength of glass-ionomer cement to dentin was also investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to one- and two-way analysis of variance (ANOVA) at alpha=0.05. Results showed that NVP modified glass ionomer cements showed significantly lower contact angles (theta=47 degrees) and higher work of adhesion (WA=59.4 erg/cm(2)) in comparison to commercially available Fuji II GIC (theta=60 degrees and WA=50.3 erg/cm(2), respectively). The wettability of dentin surfaces conditioned with NVP containing terpolymer was higher (theta=21 degrees, WA=74.2 erg/cm(2)) than dentin conditioned with Fuji conditioner (theta=30 degrees, WA=69 erg/cm(2)). The experimental cement also showed higher but not statistically significant values for shear bond strength to dentin (7.8 MPa), when compared to control group (7.3 MPa). It was concluded that NVP containing polyelectrolytes are better dentin conditioners than the commercially available dentin conditioner (Fuji Cavity Conditioner, GC). NVP containing terpolymers can enhance the surface properties of GICs and also increase their bond strength to the dentin.

Doxorubicin-loaded poly (lactic-co-glycolic acid) nanoparticles coated with chitosan/alginate by layer by layer technology for antitumor applications.

PubMed

Chai, Fujuan; Sun, Linlin; He, Xinyi; Li, Jieli; Liu, Yuanfen; Xiong, Fei; Ge, Liang; Webster, Thomas J; Zheng, Chunli

2017-01-01

Natural polyelectrolyte multilayers of chitosan (CHI) and alginate (ALG) were alternately deposited on doxorubicin (DOX)-loaded poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) with layer by layer self-assembly to control drug release for antitumor activity. Numerous factors which influenced the multilayer growth on nano-colloidal particles were studied: polyelectrolyte concentration, NaCl concentration and temperature. Then the growth regime of the CHI/ALG multilayers was elucidated. The coated NPs were characterized by transmission electron microscopy, atomic force microscopy, X-ray diffraction and a zeta potential analyzer. In vitro studies demonstrated an undesirable initial burst release of DOX-loaded PLGA NPs (DOX-PLGA NPs), which was relieved from 55.12% to 5.78% through the use of the layer by layer technique. The release of DOX increased more than 40% as the pH of media decreased from 7.4 to 5.0. More importantly, DOX-PLGA (CHI/ALG) 3 NPs had superior in vivo tumor inhibition rates at 83.17% and decreased toxicity, compared with DOX-PLGA NPs and DOX in solution. Thus, the presently formulated PLGA-polyelectrolyte NPs have strong potential applications for numerous controlled anticancer drug release applications.

Solution aging and degradation of a transparent conducting polymer dispersion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jun; Jacobs, Ian E.; Friedrich, Stephan

As organic electronics improve, there is increased research interest on the longevity and stability of both the device and individual material components. Most of these studies focus on post deposition degradation and aging of the film. In this article, we examine the stability of polyelectrolyte dispersions before film coating. We observe substantial differences in the solution properties of the transparent conducting polymer, S-P3MEET, when comparing fresh versus aged dispersions and relate these solution differences to film properties. The aged dispersion contains large agglomerates and exhibits a typical shear-thinning rheological behavior, which results in non-uniformity of the spin-coated films. Near edgemore » X-ray absorption fine structure measurements were used to differentiate the changes in bonding and oxidation states and show that aged S-P3MEET is more highly self-doped than fresh S-P3MEET. We also show that addition of acid, salt or heat to fresh S-P3MEET can accelerate the degradation/aging process but are subjected to different mechanisms. Conductivity measurements of S-P3MEET films illustrate that there is a tradeoff between increased work function and decreased conductivity upon perfluorinated ionomer (PFI) loading. The formation of nanostructure in solution is also correlated to film morphology variations obtained from atomic force microscopy. Here, we expect that dispersion aging is a process that commonly exists in most solution-dispersed polyelectrolyte materials and that the methodologies presented in this paper might be beneficial to future degradation/stability studies.« less

Solution aging and degradation of a transparent conducting polymer dispersion

DOE PAGES

Li, Jun; Jacobs, Ian E.; Friedrich, Stephan; ...

2016-04-23

As organic electronics improve, there is increased research interest on the longevity and stability of both the device and individual material components. Most of these studies focus on post deposition degradation and aging of the film. In this article, we examine the stability of polyelectrolyte dispersions before film coating. We observe substantial differences in the solution properties of the transparent conducting polymer, S-P3MEET, when comparing fresh versus aged dispersions and relate these solution differences to film properties. The aged dispersion contains large agglomerates and exhibits a typical shear-thinning rheological behavior, which results in non-uniformity of the spin-coated films. Near edgemore » X-ray absorption fine structure measurements were used to differentiate the changes in bonding and oxidation states and show that aged S-P3MEET is more highly self-doped than fresh S-P3MEET. We also show that addition of acid, salt or heat to fresh S-P3MEET can accelerate the degradation/aging process but are subjected to different mechanisms. Conductivity measurements of S-P3MEET films illustrate that there is a tradeoff between increased work function and decreased conductivity upon perfluorinated ionomer (PFI) loading. The formation of nanostructure in solution is also correlated to film morphology variations obtained from atomic force microscopy. Here, we expect that dispersion aging is a process that commonly exists in most solution-dispersed polyelectrolyte materials and that the methodologies presented in this paper might be beneficial to future degradation/stability studies.« less

Macroion induced dehydration of weak polyelectrolyte brushes

NASA Astrophysics Data System (ADS)

Zheng, Zhongli; Zhu, Y. Elaine

2014-03-01

The interaction of macroions, including polyelectrolytes, DNAs, and proteins, with polymer and cellular surfaces is critically related to many biomolecular activities, such as protein adsorption and DNA hybridization at probe surfaces. In an experimental approach to examine the macroion electrostatic interaction with a polymer surface while minimizing the long-debated hydrophobic interaction, we study the interaction of molybdenum-based inorganic polyoxometalate (POM) nanoclusters carrying 42 negative charges as model hydrophilic macroions with surface-tethered poly-2-vinylpyridine (P2VP) brushes immersed in aqueous solutions. By AFM, QCM, and contact goniometer, we have observed the collapse of P2VP chains by adding POM macroions at a constant pH. Surprisingly, added POM macroions can cause the shift of swollen-to-collapse transition pH to a lower value, in contrast to the shift to high pH value by adding simple monovalent salts. At sufficiently high POM concentration, a stable POM-P2VP composite layer, showing little dependence on solution pH and additional salts, can be formed, suggesting a simple route to construct meso-porous polymer membranes.

Examination of soil contaminated by coal-liquids by size exclusion chromatography in 1-methyl-2-pyrrolidinone solution to evaluate interference from humic and fulvic acids and extracts from peat.

PubMed

Morgan, T J; Herod, A A; Brain, S A; Chambers, F M; Kandiyoti, R

2005-11-18

Soil from a redundant coke oven site has been examined by extraction of soluble materials using 1-methyl-2-pyrrolidinone (NMP) followed by size exclusion chromatography (SEC) of the extracted material. The extracted material was found to closely resemble a high temperature coal tar pitch. Standard humic and fulvic acids were also examined since these materials are very soluble in NMP and would be extracted with pitch if present in the soil. Humic substances derived from peat samples and NMP-extracts of peats were also examined. The results show that the humic and fulvic substances were not extracted directly by NMP from peats. They were extracted using caustic soda solution and were different from the peat extracts in NMP. These results indicate that humic and fulvic acids were soluble in NMP in the protonated polyelectrolyte form but not in the original native polyelectrolyte form. The extraction of soil using NMP followed by SEC appears to be a promising method for identifying contamination by coal-based industries.

Mucopolysaccharides in aqueous solutions: effect of ionic strength on titration curves.

PubMed

Rueda, C; Arias, C; Galera, P; López-Cabarcos, E; Yagüe, A

2001-01-01

We study the changes taking place in hyaluronic acid, chondroitin 4-sulfate (C4-S) and condroitin 6-sulfate (C6-S), at ionic strengths of 0.10, 0.15, and 0.20 in NaCl, in a neutralization process in aqueous solution. We apply the equation of Henderson Hasselbalch modified for polyelectrolytes and evaluate the changes in the electrostatic free energy starting from the pK curves as a function of the dissociation degree. For a dissociation degree next to 0.4 corresponding to the -COOH group of the hyaluronic acid, we observed a change in the conformation of the three glycosaminoglycans studied. This conformational change takes place as a consequence of the break of intramolecular links and the beginning of the ionization process. The macromolecules in solution show a structure of random coil sufficiently expanded so that the interaction among the close ionizable groups is negligible.

Directed assembly of three-dimensional structures with micron-scale features

DOEpatents

Gratson, Gregory; Lewis, Jennifer A.

2006-11-28

The invention provides polyelectrolyte inks comprising a solvent, a cationic polyelectrolyte, dissolved in the solvent, and an anionic polyelectrolyte, dissolved in the solvent. The concentration of at least one of the polyelectrolytes in the solvent is in a semidilute regime.

Diffusion of uncharged probe reveals structural changes in polyacids initiated by their neutralization: poly(acrylic acids).

PubMed

Hyk, Wojciech; Masiak, Michal; Stojek, Zbigniew; Ciszkowska, Malgorzata

2005-03-17

The diffusion studies of the uncharged probe (1,1'-ferrocenedimethanol) have been successfully applied for the evaluation of the changes in the three-dimensional structure of poly(acrylic acids) of various molecular weights (ranging from 2000 to 4,000,000 g/mol) during their neutralization with a strong base. The qualitative picture of the macromolecule arrangement during the titration of the polyacids has been obtained from the conductometric measurements. The characteristic changes in the poly(acrylic acid) conductivity are practically the same for all polyacids examined and are in a very good agreement with the predictions of our theoretical model of the polyelectrolyte conductance. The transformation of the polyelectrolyte solution into the gel-like or gel phase has been investigated more quantitatively by tracing the changes in the diffusion coefficient of the uncharged probe redox system. The probe diffusivities, D, were determined using steady-state voltammetry at microelectrodes for a wide range of neutralization degree, alpha, of the polyacids tested. The dependencies of D versus alpha are of similar shape for all poly(acrylic acids). The first parts of the dependencies reflect a rapid increase in D (up to neutralization degree of either 45% for the lowest molecular-weight poly(acrylic acid) or 75-80% for other polyacids). They are followed by the parts of a slight drop in the diffusion coefficient. The changes in the probe diffusivity become stronger as the molecular weight of poly(acrylic acid) increases. The maximum probe diffusion coefficients are greater than the initial values in the pure polyacid solutions by 14, 24, 19, 30, and 28% for poly(acrylic acid) of molecular weights of 2000, 450,000, 1,250,000, 3,000,000, and 4,000,000 g/mol, respectively. The variation in the probe diffusion coefficient qualitatively follows the line of the changes in the macroscopic viscosity of the polyelectrolyte system. This is in contrast to the predictions of the Stokes-Einstein relation and, therefore, suggests that the changes in the probe diffusion rate are mainly due to the structural changes in the polyacrylate medium and the macromolecular rearrangements induced by the chemical, acid-base reaction. By adapting the obstruction model for diffusion in homogeneous gels, the transport characteristics of the probe were converted into the structural characteristics of the polyelectrolytic systems. It has been found that the most ordered structure of the polyelectrolyte, or in other words the most permeable structure, is obtained when poly(acrylic acid) is neutralized at 75-80%.

Influence of network topology on the swelling of polyelectrolyte nanogels.

PubMed

Rizzi, L G; Levin, Y

2016-03-21

It is well-known that the swelling behavior of ionic nanogels depends on their cross-link density; however, it is unclear how different topologies should affect the response of the polyelectrolyte network. Here we perform Monte Carlo simulations to obtain the equilibrium properties of ionic nanogels as a function of salt concentration Cs and the fraction f of ionizable groups in a polyelectrolyte network formed by cross-links of functionality z. Our results indicate that the network with cross-links of low connectivity result in nanogel particles with higher swelling ratios. We also confirm a de-swelling effect of salt on nanogel particles.

Structure and interactions of human respiratory mucin

NASA Astrophysics Data System (ADS)

Purdy, Kirstin; Sheehan, John; Rubinstein, Michael; Wong, Gerard

2006-03-01

Human respiratory mucin plays a crucial role in the pathology of Cystic Fibrosis lung infections. Mucin is a flexible, linear polyelectrolyte, characterized by its many charged oligo-carbohydrate side chains that give it its bottle-brush structure. The macroscopic properties of a mucin suspension are known to change drastically with changes in ion concentration and solution pH, but little is known about the effect of these variables on individual mucin structure. We present preliminary results on the structural response of individual human respiratory mucin molecules to variations in concentration of ions of different valences via small angle x-ray diffraction.

Electro-responsive polyelectrolyte-coated surfaces.

PubMed

Sénéchal, V; Saadaoui, H; Rodriguez-Hernandez, J; Drummond, C

2017-07-01

The anchoring of polymer chains at solid surfaces is an efficient way to modify interfacial properties like the stability and rheology of colloidal dispersions, lubrication and biocompatibility. Polyelectrolytes are good candidates for the building of smart materials, as the polyion chain conformation can often be tuned by manipulation of different physico-chemical variables. However, achieving efficient and reversible control of this process represents an important technological challenge. In this regard, the application of an external electrical stimulus on polyelectrolytes seems to be a convenient control strategy, for several reasons. First, it is relatively easy to apply an electric field to the material with adequate spatiotemporal control. In addition, in contrast to chemically induced changes, the molecular response to a changing electric field occurs relatively quickly. If the system is properly designed, this response can then be used to control the magnitude of surface properties. In this work we discuss the effect of an external electric field on the adhesion and lubrication properties of several polyelectrolyte-coated surfaces. The influence of the applied field is investigated at different pH and salt conditions, as the polyelectrolyte conformation is sensitive to these variables. We show that it is possible to fine tune friction and adhesion using relatively low applied fields.

Ferroelectric polarization induces electric double layer bistability in electrolyte-gated field-effect transistors.

PubMed

Fabiano, Simone; Crispin, Xavier; Berggren, Magnus

2014-01-08

The dense surface charges expressed by a ferroelectric polymeric thin film induce ion displacement within a polyelectrolyte layer and vice versa. This is because the density of dipoles along the surface of the ferroelectric thin film and its polarization switching time matches that of the (Helmholtz) electric double layers formed at the ferroelectric/polyelectrolyte and polyelectrolyte/semiconductor interfaces. This combination of materials allows for introducing hysteresis effects in the capacitance of an electric double layer capacitor. The latter is advantageously used to control the charge accumulation in the semiconductor channel of an organic field-effect transistor. The resulting memory transistors can be written at a gate voltage of around 7 V and read out at a drain voltage as low as 50 mV. The technological implication of this large difference between write and read-out voltages lies in the non-destructive reading of this ferroelectric memory.

Density-controlled, solution-based growth of ZnO nanorod arrays via layer-by-layer polymer thin films for enhanced field emission

NASA Astrophysics Data System (ADS)

Weintraub, Benjamin; Chang, Sehoon; Singamaneni, Srikanth; Han, Won Hee; Choi, Young Jin; Bae, Joonho; Kirkham, Melanie; Tsukruk, Vladimir V.; Deng, Yulin

2008-10-01

A simple, scalable, and cost-effective technique for controlling the growth density of ZnO nanorod arrays based on a layer-by-layer polyelectrolyte polymer film is demonstrated. The ZnO nanorods were synthesized using a low temperature (T = 90 °C), solution-based method. The density-control technique utilizes a polymer thin film pre-coated on the substrate to control the mass transport of the reactant to the substrate. The density-controlled arrays were investigated as potential field emission candidates. The field emission results revealed that an emitter density of 7 nanorods µm-2 and a tapered nanorod morphology generated a high field enhancement factor of 5884. This novel technique shows promise for applications in flat panel display technology.

Length scale dependence of the dynamic properties of hyaluronic acid solutions in the presence of salt.

PubMed

Horkay, Ferenc; Falus, Peter; Hecht, Anne-Marie; Geissler, Erik

2010-12-02

In solutions of the charged semirigid biopolymer hyaluronic acid in salt-free conditions, the diffusion coefficient D(NSE) measured at high transfer momentum q by neutron spin echo is more than an order of magnitude smaller than that determined by dynamic light scattering, D(DLS). This behavior contrasts with neutral polymer solutions. With increasing salt content, D(DLS) approaches D(NSE), which is independent of ionic strength. Contrary to theoretical expectation, the ion-polymer coupling, which dominates the low q dynamics of polyelectrolyte solutions, already breaks down at distance scales greater than the Debye-Hückel length.

Determination of the parameters controlling swelling of chemically cross-linked pH-sensitive poly(N-vinylimidazole) hydrogels.

PubMed

Molina, M Jesús; Gómez-Antón, M Rosa; Piérola, Inés F

2007-10-25

The number of variables controlling the behavior of ionic gels is large and very often some of them are unknown. The aim of this work is to interpret quantitatively the swelling behavior of pH sensitive gels, with the minimum number of simplifying assumptions. With this purpose, the equilibrium degree of swelling (S) and protonation (alpha) of chemically cross-linked poly(N-vinylimidazole) (PVI) immersed in aqueous salt solutions were measured as a function of the ionic strength (mu), in the whole range of pH. In acid solutions with pH in the range 0 to 4, imidazole moieties become protonated, and PVI behaves as a polyelectrolyte gel: S decreases upon increasing mu both for NaCl and for CaCl(2), with HCl as protonating acid. In aqueous solutions with larger pH, between 4 and 12, the hydrogel is practically neutral, and S increases as mu rises, showing a salting-in effect. From the quantitative analysis of these results, the following facts emerged. Protonation induces chain stiffness (as measured by the non-Gaussian factor) and worsening of the solvent quality of the aqueous media (as measured by the polymer-solvent interaction parameter). For alpha below 33%, swelling seems to be governed by the excess of mobile counterions inside the gel with respect to the bath, with a minor but still significantly negative contribution of the osmotic swelling pressure due to polymer-solvent mixing. Above 33% protonation, it is necessary to consider Manning counterion condensation to get parameters with physical meaning. The crossover between polyelectrolyte and salting-in effects corresponds to alpha and mu values with the same ionic and mixing contributions to the osmotic swelling pressure. The formation of ionic nonpermanent cross-links, with H(2)SO(4) as the protonating acid, was discarded.

Resistance of poly(ethylene oxide)-silane monolayers to the growth of polyelectrolyte multilayers.

PubMed

Buron, Cédric C; Callegari, Vincent; Nysten, Bernard; Jonas, Alain M

2007-09-11

The ability of poly(ethylene oxide)-silane (PEO-silane) monolayers grafted onto silicon surfaces to resist the growth of polyelectrolyte multilayers under various pH conditions is assessed for different pairs of polyelectrolytes of varying molar mass. For acidic conditions (pH 3), the PEO-silane monolayers exhibit good polyelectrolyte repellency provided the polyelectrolytes bear no moieties that are able to form hydrogen bonds with the ether groups of the PEO chains. At basic pH, PEO-silane monolayers undergo substantial hydrolysis leading to the formation of negatively charged defects in the monolayers, which then play the role of adsorption sites for the polycation. Once the polycation is adsorbed, multilayer growth ensues. Because this is defect-driven growth, the multilayer is not continuous and is made of blobs or an open network of adsorbed strands. For such conditions, the molar mass of the polyelectrolyte plays a key role, with polyelectrolyte chains of larger molar mass adsorbing on a larger number of defects, resulting in stronger anchoring of the polyelectrolyte complex on the surfaces and faster subsequent growth of the multilayer. For polyelectrolytes of sufficiently low molar mass at pH 9, the growth of the multilayer can nevertheless be prevented for as much as five cycles of deposition.

Role of Electrostatic Interactions on the Transport of Druglike Molecules in Hydrogel-Based Articular Cartilage Mimics: Implications for Drug Delivery.

PubMed

Ye, Fengbin; Baldursdottir, Stefania; Hvidt, Søren; Jensen, Henrik; Larsen, Susan W; Yaghmur, Anan; Larsen, Claus; Østergaard, Jesper

2016-03-07

In the field of drug delivery to the articular cartilage, it is advantageous to apply artificial tissue models as surrogates of cartilage for investigating drug transport and release properties. In this study, artificial cartilage models consisting of 0.5% (w/v) agarose gel containing 0.5% (w/v) chondroitin sulfate or 0.5% (w/v) hyaluronic acid were developed, and their rheological and morphological properties were characterized. UV imaging was utilized to quantify the transport properties of the following four model compounds in the agarose gel and in the developed artificial cartilage models: H-Ala-β-naphthylamide, H-Lys-Lys-β-naphthylamide, lysozyme, and α-lactalbumin. The obtained results showed that the incorporation of the polyelectrolytes chondroitin sulfate or hyaluronic acid into agarose gel induced a significant reduction in the apparent diffusivities of the cationic model compounds as compared to the pure agarose gel. The decrease in apparent diffusivity of the cationic compounds was not caused by a change in the gel structure since a similar reduction in apparent diffusivity was not observed for the net negatively charged protein α-lactalbumin. The apparent diffusivity of the cationic compounds in the negatively charged hydrogels was highly dependent on the ionic strength, pointing out the importance of electrostatic interactions between the diffusant and the polyelectrolytes. Solution based affinity studies between the model compounds and the two investigated polyelectrolytes further confirmed the electrostatic nature of their interactions. The results obtained from the UV imaging diffusion studies are important for understanding the effect of drug physicochemical properties on the transport in articular cartilage. The extracted information may be useful in the development of hydrogels for in vitro release testing having features resembling the articular cartilage.

An investigation on the biotribocorrosion behaviour of CoCrMo alloy grafted with polyelectrolyte brush.

PubMed

Zhang, Hong-Yu; Zhu, Yu-Jiao; Hu, Xiang-Yu; Sun, Yan-Fang; Sun, Yu-Long; Han, Jian-Min; Yan, Yu; Zhou, Ming

2014-01-01

Surface grafting of polyelectrolyte brush, such as 3-sulfopropyl methacrylate potassium salt (SPMK), on hip implant materials has been reported to reduce the wear of the orthopaedic bearing surface. However, the biotribocorrosion behaviour of the SPMK brush has not been taken into consideration in previous research. In the present study, SPMK was grafted on Co28Cr6Mo alloy through photo-induced polymerization, and the biotribocorrosion behaviour was investigated by a series of frictional-electrochemical tests using a universal materials tester combined with an electrochemical measurement (three-electrode) system. Co28Cr6Mo disk and polyethylene (PE) pin were used as the contact pair, and the lubricants were 0.9% saline solution (NaCl) and 0.9% saline solution coupled with 25% bovine serum albumin (BSA). The results showed that SPMK was successfully grafted on Co28Cr6Mo alloy, which was confirmed by the comparison of Raman spectroscopy and static contact angle of the samples before and after surface modification. The greatly reduced electrochemical parameters such as corrosion current and pitting potential indicated that the corrosion rate of Co28Cr6Mo alloy was significantly reduced following SPMK grafting. Additionally, the frictional-electrochemical coupled measurement performed under reciprocating sliding demonstrated that the lowest corrosion current was obtained for the SPMK-grafted Co28Cr6Mo disk, with 0.9% NaCl coupled with 25% BSA as the electrolyte. It is indicated from the present study that SPMK polyelectrolyte brush can greatly improve the anti-biotribocorrosion properties of Co28Cr6Mo alloy, and thus has potential application on surface modification of hip implant materials.

pH Reversible Encapsulation of Oppositely Charged Colloids Mediated by Polyelectrolytes

PubMed Central

2017-01-01

We report the first example of reversible encapsulation of micron-sized particles by oppositely charged submicron smaller colloids. The reversibility of this encapsulation process is regulated by pH-responsive poly(acrylic acid) (PAA) present in solution. The competitive adsorption between the small colloids and the poly(acrylic acid) on the surface of the large colloids plays a key role in the encapsulation behavior of the system. pH offers an experimental knob to tune the electrostatic interactions between the two oppositely charged particle species via regulation of the charge density of the poly(acrylic acid). This results in an increased surface coverage of the large colloids by the smaller colloids when decreasing pH. Furthermore, the poly(acrylic acid) also acts as a steric barrier limiting the strength of the attractive forces between the oppositely charged particle species, thereby enabling detachment of the smaller colloids. Finally, based on the pH tunability of the encapsulation behavior and the ability of the small colloids to detach, reversible encapsulation is achieved by cycling pH in the presence of the PAA polyelectrolytes. The role of polyelectrolytes revealed in this work provides a new and facile strategy to control heteroaggregation behavior between oppositely charged colloids, paving the way to prepare sophisticated hierarchical assemblies. PMID:28419800

Encapsidation of Linear Polyelectrolyte in a Viral Nanocontainer

NASA Astrophysics Data System (ADS)

Hu, Yufang

2005-03-01

We present the results from a combined experimental and theoretical study on the self-assembly of a model icosahedral virus, Cowpea Chlorotic Mottle Virus (CCMV). The formation of native CCMV capsids is believed to be driven primarily by the electrostatic interactions between the viral RNA and the positively charged capsid interior, as well as by the hydrophobic interactions between capsid protein subunits. To probe these molecular interactions, in vitro self-assembly reactions are carried out using the CCMV capsid protein and a synthetic linear polyelectrolyte, sodium polystyrene sulfonate (NaPSS), which functions as the analog of viral RNA. Under appropriate solutions conditions, NaPSS is encapsidated by the viral capsid. The molecular weight of NaPSS is systematically varied and the resulting average capsid size, size distribution, and particle morphology are measured by transmission electron microscopy. The correlation between capsid size and packaged cargo size, as well as the upper limit of capsid packaging capacity, are characterized. To elucidate the physical role played by the encapsidated polyelectrolyte in determining the preferred size of spherical viruses, we have used a mean-field approach to calculate the free energy of the virus-like particle as a function of chain length (and of the strength of chain/capsid attractive interaction). We find good agreement with our analytical calculations and experimental results.

Aquifer modification: an approach to improve the mobility of nanoscale zero-valent iron particles used for in situ groundwater remediation

NASA Astrophysics Data System (ADS)

MicicBatka, Vesna; Schmid, Doris; Marko, Florian; Velimirovic, Milica; Wagner, Stephan; von der Kammer, Frank; Hofmann, Thilo

2015-04-01

Successful emplacement of nanoscale zero-valent iron (nZVI) within the contaminated source zone is a prerequisite for the use of nZVI technology in groundwater remediation. Emplacement of nZVI is influenced i.e., by the injection technique and the injection velocity applied, as well as by the mobility of nZVI in the subsurface. Whereas processes linked to the injection can be controlled by the remediation practitioners, the mobility of nZVI in the subsurface remains limited. Even though mobility of nZVI is somewhat improved by surface coating with polyelectrolytes, it is still greatly affected by the groundwater composition and physical and chemical heterogeneities of aquifer grains. In order to promote mobility of nZVI it is needed to alter the surface charge heterogeneities of aquifer grains. Modifying the aquifer grain's surfaces by means of polyelectrolyte coating is an approach proposed to increase the overall negative surface charge of the aquifer grain surfaces, hinder deposition of nZVI onto aquifer grains, and finally promote nZVI mobility. In this study the effect of different polyelectrolytes on the nZVI mobility is tested in natural sands deriving from real brownfield sites that are proposed to be remediated using the nZVI technology. Sands collected from brownfield sites were characterized in terms of grain size distribution, mineralogical and chemical composition, and organic carbon content. Furthermore, surface charge of these sands was determined in both, low- and high ionic strength background solutions. Finally, changes of the sand's surface charges were examined after addition of the proposed aquifer modifiers, lignin sulfonate and humic acid. Surface charge of brownfield sands in low ionic strength background solution is more negative compared to that in high ionic strength background solution. An increase in negative surface potential of brownfield sand was recorded when aquifer modifiers were applied in a background solution with low ionic strength, indicating their potential to improve nZVI mobility under comparable environmental conditions. In contrast, no significant change of the surface potential of brownfield sand was observed when aquifer modifiers were applied in a background solution with high ionic strength. The potential of the aquifer modifiers to promote the mobility of nZVI was furthermore tested in flow-through columns, starting with the one filled with natural quartz sand with rough surface, low ionic strength background solutions and pre-injecting lignin sulfonate in concentration of 50 mg/L. The preliminary results showed that the pre-injection of lignin sulfonate does increase mobility of nZVI under this experimental condition. Further mobility tests will be carried out in order to elucidate the potential of the aquifer modifiers to promote the mobility of nZVI in sands with a complex mineralogy and in the background solutions with varying ionic strength, in order to account for the condition that resemble those at polluted sites. This research receives funding from the European Union's Seventh Framework Programme FP7/2007-2013 under grant agreement n°309517.

Achieving significantly enhanced visible-light photocatalytic efficiency using a polyelectrolyte: the composites of exfoliated titania nanosheets, graphene, and poly(diallyl-dimethyl-ammonium chloride)

NASA Astrophysics Data System (ADS)

Zhang, Qian; An, Qi; Luan, Xinglong; Huang, Hongwei; Li, Xiaowei; Meng, Zilin; Tong, Wangshu; Chen, Xiaodong; Chu, Paul K.; Zhang, Yihe

2015-08-01

A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency.A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03256c

Tuning the properties of conjugated polyelectrolytes and application in a biosensor platform

DOEpatents

Chen, Liaohai

2004-05-18

The present invention provides a method of detecting a biological agent including contacting a sample with a sensor including a polymer system capable of having an alterable measurable property from the group of luminescence, anisotropy, redox potential and uv/vis absorption, the polymer system including an ionic conjugated polymer and an electronically inert polyelectrolyte having a biological agent recognition element bound thereto, the electronically inert polyelectrolyte adapted for undergoing a conformational structural change upon exposure to a biological agent having affinity for binding to the recognition element bound to the electronically inert polyelectrolyte, and, detecting the detectable change in the alterable measurable property. A chemical moiety being the reaction product of (i) a polyelectrolyte monomer and (ii) a biological agent recognition element-substituted polyelectrolyte monomer is also provided.

Weak polyelectrolyte complexation driven by associative charging.

PubMed

Rathee, Vikramjit S; Zervoudakis, Aristotle J; Sidky, Hythem; Sikora, Benjamin J; Whitmer, Jonathan K

2018-03-21

Weak polyelectrolytes are relevant for a wide range of fields; in particular, they have been investigated as "smart" materials for chemical separations and drug delivery. The charges on weak polyelectrolytes are dynamic, causing polymer chains to adopt different equilibrium conformations even with relatively small changes to the surrounding environment. Currently, there exists no comprehensive picture of this behavior, particularly where polymer-polymer interactions have the potential to affect charging properties significantly. In this study, we elucidate the novel interplay between weak polyelectrolyte charging and complexation behavior through coupled molecular dynamics and Monte Carlo simulations. Specifically, we investigate a model of two equal-length and oppositely charging polymer chains in an implicit salt solution represented through Debye-Hückel interactions. The charging tendency of each chain, along with the salt concentration, is varied to determine the existence and extent of cooperativity in charging and complexation. Strong cooperation in the charging of these chains is observed at large Debye lengths, corresponding to low salt concentrations, while at lower Debye lengths (higher salt concentrations), the chains behave in apparent isolation. When the electrostatic coupling is long-ranged, we find that a highly charged chain strongly promotes the charging of its partner chain, even if the environment is unfavorable for an isolated version of that partner chain. Evidence of this phenomenon is supported by a drop in the potential energy of the system, which does not occur at the lower Debye lengths where both potential energies and charge fractions converge for all partner chain charging tendencies. The discovery of this cooperation will be helpful in developing "smart" drug delivery mechanisms by allowing for better predictions for the dissociation point of delivery complexes.

Weak polyelectrolyte complexation driven by associative charging

NASA Astrophysics Data System (ADS)

Rathee, Vikramjit S.; Zervoudakis, Aristotle J.; Sidky, Hythem; Sikora, Benjamin J.; Whitmer, Jonathan K.

2018-03-01

Weak polyelectrolytes are relevant for a wide range of fields; in particular, they have been investigated as "smart" materials for chemical separations and drug delivery. The charges on weak polyelectrolytes are dynamic, causing polymer chains to adopt different equilibrium conformations even with relatively small changes to the surrounding environment. Currently, there exists no comprehensive picture of this behavior, particularly where polymer-polymer interactions have the potential to affect charging properties significantly. In this study, we elucidate the novel interplay between weak polyelectrolyte charging and complexation behavior through coupled molecular dynamics and Monte Carlo simulations. Specifically, we investigate a model of two equal-length and oppositely charging polymer chains in an implicit salt solution represented through Debye-Hückel interactions. The charging tendency of each chain, along with the salt concentration, is varied to determine the existence and extent of cooperativity in charging and complexation. Strong cooperation in the charging of these chains is observed at large Debye lengths, corresponding to low salt concentrations, while at lower Debye lengths (higher salt concentrations), the chains behave in apparent isolation. When the electrostatic coupling is long-ranged, we find that a highly charged chain strongly promotes the charging of its partner chain, even if the environment is unfavorable for an isolated version of that partner chain. Evidence of this phenomenon is supported by a drop in the potential energy of the system, which does not occur at the lower Debye lengths where both potential energies and charge fractions converge for all partner chain charging tendencies. The discovery of this cooperation will be helpful in developing "smart" drug delivery mechanisms by allowing for better predictions for the dissociation point of delivery complexes.

Polyelectrolyte multi-layers assembly of SiCHA nanopowders and collagen type I on aminolysed PLA films to enhance cell-material interactions.

PubMed

Baba Ismail, Yanny Marliana; Ferreira, Ana Marina; Bretcanu, Oana; Dalgarno, Kenneth; El Haj, Alicia J

2017-11-01

This paper presents a new approach in assembling bone extracellular matrix components onto PLA films, and investigates the most favourable environment which can be created using the technique for cell-material interactions. Poly (lactic acid) (PLA) films were chemically modified by covalently binding the poly(ethylene imine) (PEI) as to prepare the substrate for immobilization of polyelectrolyte multilayers (PEMs) coating. Negatively charged polyelectrolyte consists of well-dispersed silicon-carbonated hydroxyapatite (SiCHA) nanopowders in hyaluronic acid (Hya) was deposited onto the modified PLA films followed by SiCHA in collagen type I as the positively charged polyelectrolyte. The outermost layer was finally cross-linked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrocholoride and N-hydroxysulfosuccinimide sodium salt (EDC/NHS) solutions. The physicochemical features of the coated PLA films were monitored via X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscope (AFM). The amounts of calcium and collagen deposited on the surface were qualitatively and quantitatively determined. The surface characterizations suggested that 5-BL has the optimum surface roughness and highest amounts of calcium and collagen depositions among tested films. In vitro human mesenchymal stem cells (hMSCs) cultured on the coated PLA films confirmed that the coating materials greatly improved cell attachment and survival compared to unmodified PLA films. The cell viability, cell proliferation and Alkaline Phosphatase (ALP) expression on 5-BL were found to be the most favourable of the tested films. Hence, this newly developed coating materials assembly could contribute to the improvement of the bioactivity of polymeric materials and structures aimed to bone tissue engineering applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface friction of hydrogels with well-defined polyelectrolyte brushes.

PubMed

Ohsedo, Yutaka; Takashina, Rikiya; Gong, Jian Ping; Osada, Yoshihito

2004-08-03

Hydrogels of poly(2-hydroxyethyl methacrylate) (PHEMA) with well-defined polyelectrolyte brushes of poly(sodium 4-styrenesulfonate) (PNaSS) of various molecular weights were synthesized, keeping the distance between the polymer brushes constant at ca. 20 nm. The effect of polyelectrolyte brush length on the sliding friction against a glass plate, an electrorepulsive solid substrate, was investigated in water in a velocity range of 7.5 x 10(-5) to 7.5 x 10(-2) m/s. It is found that the presence of polymer brush can dramatically reduce the friction when the polymer brushes are short. With an increase in the length of the polymer brush, this drag reduction effect only works at a low sliding velocity, and the gel with long polymer brushes even shows a higher friction than that of a normal network gel at a high sliding velocity. The strong polymer length and sliding velocity dependence indicate a dynamic mechanism of the polymer brush effect.

Thermodynamic assessment of adsorptive fouling with the membranes modified via layer-by-layer self-assembly technique.

PubMed

Shen, Liguo; Cui, Xia; Yu, Genying; Li, Fengquan; Li, Liang; Feng, Shushu; Lin, Hongjun; Chen, Jianrong

2017-05-15

In this study, polyvinylidene fluoride (PVDF) microfiltration membrane was coated by dipping the membrane alternatingly in solutions of the polyelectrolytes (poly-diallyldimethylammonium chloride (PDADMAC) and polystyrenesulfonate (PSS)) via layer-by-layer (LBL) self-assembly technique to improve the membrane antifouling ability. Filtration experiments showed that, sludge cake layer on the coated membrane could be more easily washed off, and moreover, the remained flux ratio (RFR) of the coated membrane was obviously improved as compared with the control membrane. Characterization of the membranes showed that a polyelectrolyte layer was successfully coated on the membrane surfaces, and the hydrophilicity, surface charge and surface morphology of the coated membrane were changed. Based on the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) approaches, quantification of interfacial interactions between foulants and membranes in three different scenarios was achieved. It was revealed that there existed a repulsive energy barrier when a particle foulant adhered to membrane surface, and the enhanced electrostatic double layer (EL) interaction and energy barrier should be responsible for the improved antifouling ability of the coated membrane. This study provided a combined solution to membrane modification and interaction energy evaluation related with membrane fouling simultaneously. Copyright © 2017 Elsevier Inc. All rights reserved.

Low Molecular Weight Chitosan–Insulin Polyelectrolyte Complex: Characterization and Stability Studies

PubMed Central

Al-Kurdi, Zakieh I.; Chowdhry, Babur Z.; Leharne, Stephen A.; Al Omari, Mahmoud M. H.; Badwan, Adnan A.

2015-01-01

The aim of the work reported herein was to investigate the effect of various low molecular weight chitosans (LMWCs) on the stability of insulin using USP HPLC methods. Insulin was found to be stable in a polyelectrolyte complex (PEC) consisting of insulin and LMWC in the presence of a Tris-buffer at pH 6.5. In the presence of LMWC, the stability of insulin increased with decreasing molecular weight of LMWC; 13 kDa LMWC was the most efficient molecular weight for enhancing the physical and chemical stability of insulin. Solubilization of insulin-LMWC polyelectrolyte complex (I-LMWC PEC) in a reverse micelle (RM) system, administered to diabetic rats, results in an oral delivery system for insulin with acceptable bioactivity. PMID:25830681

Flexible polyelectrolyte chain in a strong electrolyte solution: Insight into equilibrium properties and force-extension behavior from mesoscale simulation

NASA Astrophysics Data System (ADS)

Malekzadeh Moghani, Mahdy; Khomami, Bamin

2016-01-01

Macromolecules with ionizable groups are ubiquitous in biological and synthetic systems. Due to the complex interaction between chain and electrostatic decorrelation lengths, both equilibrium properties and micro-mechanical response of dilute solutions of polyelectrolytes (PEs) are more complex than their neutral counterparts. In this work, the bead-rod micromechanical description of a chain is used to perform hi-fidelity Brownian dynamics simulation of dilute PE solutions to ascertain the self-similar equilibrium behavior of PE chains with various linear charge densities, scaling of the Kuhn step length (lE) with salt concentration cs and the force-extension behavior of the PE chain. In accord with earlier theoretical predictions, our results indicate that for a chain with n Kuhn segments, lE ˜ cs-0.5 as linear charge density approaches 1/n. Moreover, the constant force ensemble simulation results accurately predict the initial non-linear force-extension region of PE chain recently measured via single chain experiments. Finally, inspired by Cohen's extraction of Warner's force law from the inverse Langevin force law, a novel numerical scheme is developed to extract a new elastic force law for real chains from our discrete set of force-extension data similar to Padè expansion, which accurately depicts the initial non-linear region where the total Kuhn length is less than the thermal screening length.

Flexible polyelectrolyte chain in a strong electrolyte solution: Insight into equilibrium properties and force-extension behavior from mesoscale simulation.

PubMed

Malekzadeh Moghani, Mahdy; Khomami, Bamin

2016-01-14

Macromolecules with ionizable groups are ubiquitous in biological and synthetic systems. Due to the complex interaction between chain and electrostatic decorrelation lengths, both equilibrium properties and micro-mechanical response of dilute solutions of polyelectrolytes (PEs) are more complex than their neutral counterparts. In this work, the bead-rod micromechanical description of a chain is used to perform hi-fidelity Brownian dynamics simulation of dilute PE solutions to ascertain the self-similar equilibrium behavior of PE chains with various linear charge densities, scaling of the Kuhn step length (lE) with salt concentration cs and the force-extension behavior of the PE chain. In accord with earlier theoretical predictions, our results indicate that for a chain with n Kuhn segments, lE ∼ cs (-0.5) as linear charge density approaches 1/n. Moreover, the constant force ensemble simulation results accurately predict the initial non-linear force-extension region of PE chain recently measured via single chain experiments. Finally, inspired by Cohen's extraction of Warner's force law from the inverse Langevin force law, a novel numerical scheme is developed to extract a new elastic force law for real chains from our discrete set of force-extension data similar to Padè expansion, which accurately depicts the initial non-linear region where the total Kuhn length is less than the thermal screening length.

Self-assembling semiconducting polymers--rods and gels from electronic materials.

PubMed

Clark, Andrew P-Z; Shi, Chenjun; Ng, Benny C; Wilking, James N; Ayzner, Alexander L; Stieg, Adam Z; Schwartz, Benjamin J; Mason, Thomas G; Rubin, Yves; Tolbert, Sarah H

2013-02-26

In an effort to favor the formation of straight polymer chains without crystalline grain boundaries, we have synthesized an amphiphilic conjugated polyelectrolyte, poly(fluorene-alt-thiophene) (PFT), which self-assembles in aqueous solutions to form cylindrical micelles. In contrast to many diblock copolymer assemblies, the semiconducting backbone runs parallel, not perpendicular, to the long axis of the cylindrical micelle. Solution-phase micelle formation is observed by X-ray and visible light scattering. The micelles can be cast as thin films, and the cylindrical morphology is preserved in the solid state. The effects of self-assembly are also observed through spectral shifts in optical absorption and photoluminescence. Solutions of higher-molecular-weight PFT micelles form gel networks at sufficiently high aqueous concentrations. Rheological characterization of the PFT gels reveals solid-like behavior and strain hardening below the yield point, properties similar to those found in entangled gels formed from surfactant-based micelles. Finally, electrical measurements on diode test structures indicate that, despite a complete lack of crystallinity in these self-assembled polymers, they effectively conduct electricity.

(3-aminopropyl)-4-methylpiperazine end-capped poly(1,4-butanediol diacrylate-co-4-amino-1-butanol)-based multilayer films for gene delivery.

PubMed

Li, Cuicui; Tzeng, Stephany Y; Tellier, Liane E; Green, Jordan J

2013-07-10

Biodegradable polyelectrolyte surfaces for gene delivery were created through electrospinning of biodegradable polycations combined with iterative solution-based multilayer coating. Poly(β-amino ester) (PBAE) poly(1,4-butanediol diacrylate-co-4-amino-1-butanol) end-capped with 1-(3-aminopropyl)-4-methylpiperazine was utilized because of its ability to electrostatically interact with anionic molecules like DNA, its biodegradability, and its low cytotoxicity. A new DNA release system was developed for sustained release of DNA over 24 h, accompanied by high exogenous gene expression in primary human glioblastoma (GB) cells. Electrospinning a different PBAE, poly(1,4-butanediol diacrylate-co-4,4'-trimethylenedipiperidine), and its combination with polyelectrolyte 1-(3-aminopropyl)-4-methylpiperazine end-capped poly(1,4-butanediol diacrylate-co-4-amino-1-butanol)-based multilayers are promising for DNA release and intracellular delivery from a surface.

(3-Aminopropyl)-4-methylpiperazine End-capped Poly(1,4-butanediol diacrylate-co-4-amino-1-butanol)-based Multilayer Films for Gene Delivery

PubMed Central

Li, Cuicui; Tzeng, Stephany Y; Tellier, Liane E.; Green, Jordan J

2013-01-01

Biodegradable polyelectrolyte surfaces for gene delivery were created through electrospinning of biodegradable polycations combined with iterative solution-based multilayer coating. Poly(β-amino ester) (PBAE) poly(1,4-butanediol diacrylate-co-4-amino-1-butanol) end-capped with 1-(3-aminopropyl)-4-methylpiperazine was utilized due to its ability to electrostatically interact with anionic molecules like DNA, its biodegradability, and its low cytotoxicity. A new DNA release system was developed for sustained release of DNA over 24 hours, accompanied by high exogenous gene expression in primary human glioblastoma (GB) cells. Electrospinning a different PBAE, poly(1,4-butanediol diacrylate-co-4,4′-trimethylenedipiperidine), and its combination with polyelectrolyte 1-(3-aminopropyl)-4-methylpiperazine end-capped poly(1,4-butanediol diacrylate-co-4-amino-1-butanol)-based multilayers are promising for DNA release and intracellular delivery from a surface. PMID:23755861

Development of a conductivity-based photothermal absorbance detection microchip using polyelectrolytic gel electrodes.

PubMed

Chun, Honggu; Dennis, Patty J; Ferguson Welch, Erin R; Alarie, Jean Pierre; Jorgenson, James W; Ramsey, J Michael

2017-11-10

The development and application of polyelectrolytic gel electrodes (PGEs) for a microfluidic photothermal absorbance detection system is described. The PGEs are used to measure changes in conductivity based on heat generation by analytes absorbing light and changing the solution viscosity. The PGEs are suitable for direct contact conductivity measurements since they do not degrade with exposure to high electric fields. Both a 2-electrode system with DC voltages and a 3-electrode system with AC voltages were investigated. Experimental factors including excitation voltage, excitation frequency, laser modulation frequency, laser power, and path length were tested. The limits of detection for the 3-electrode and 2-electrode systems are 500nM and 0.55nM for DABSYL-tagged glucosamine, respectively. In addition, an electrokinetic separation of a potassium, DABSYL-tagged glucosamine, Rhodamine 6G, and Rhodamine B mixture was demonstrated. Copyright © 2017 Elsevier B.V. All rights reserved.

Efficient Energy Conversion by Grafting Nanochannels with End-charged Stimuli-responsive Polyelectrolyte Brush

NASA Astrophysics Data System (ADS)

Chen, Guang; Das, Siddhartha

2017-11-01

Polyelectrolyte (PE) brushes have aroused increasing attention in applications in energy conversion and chemical sensing due to the environmentally-responsive and designable nature. PE brushes are charged polymer chains densely grafted on solid-liquid interfaces. By designing copolymeric systems, one can localize the ionizable sites at the brush tip in order to get end-charged PE brushes. Such brushes demonstrate anomalous shrinking/swelling behaviors with tunable environmental parameters such as pH and salt concentration. In this study, we probe the conformation and electrostatics of such PE brush systems with various size, grafting density and charge distribution, and exploit the electrochemomechanical energy conversion capabilities of nanochannels grafted with such PE brush systems. Our results indicate that the presence of the end-charged PE brush layer can massively enhance the streaming potential mediated energy conversion efficiency, and the improvement is more significant in strongly ionic solution.

Halloysite clay nanotubes for resveratrol delivery to cancer cells.

PubMed

Vergaro, Viviana; Lvov, Yuri M; Leporatti, Stefano

2012-09-01

Halloysite is natural aluminosilicate clay with hollow tubular structure which allows loading with low soluble drugs using their saturated solutions in organic solvents. Resveratrol, a polyphenol known for having antioxidant and antineoplastic properties, is loaded inside these clay nanotubes lumens. Release time of 48 h is demonstrated. Spectroscopic and ζ-potential measurements are used to study the drug loading/release and for monitoring the nanotube layer-by-layer (LbL) coating with polyelectrolytes for further release control. Resveratrol-loaded clay nanotubes are added to breast cell cultures for toxicity tests. Halloysite functionalization with LbL polyelectrolyte multilayers remarkably decrease nanotube self-toxicity. MTT measurements performed with a neoplastic cell lines model system (MCF-7) as function of the resveratrol-loaded nanotubes concentration and incubation time indicate that drug-loaded halloysite strongly increase of cytotoxicity leading to cell apoptosis. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanoparticle modification by weak polyelectrolytes for pH-sensitive pickering emulsions.

PubMed

Haase, Martin F; Grigoriev, Dmitry; Moehwald, Helmuth; Tiersch, Brigitte; Shchukin, Dmitry G

2011-01-04

The affinity of weak polyelectrolyte coated oxide particles to the oil-water interface can be controlled by the degree of dissociation and the thickness of the weak polyelectrolyte layer. Thereby the oil in water (o/w) emulsification ability of the particles can be enabled. We selected the weak polyacid poly(methacrylic acid sodium salt) and the weak polybase poly(allylamine hydrochloride) for the surface modification of oppositely charged alumina and silica colloids, respectively. The isoelectric point and the pH range of colloidal stability of both particle-polyelectrolyte composites depend on the thickness of the weak polyelectrolyte layer. The pH-dependent wettability of a weak polyelectrolyte-coated oxide surface is characterized by contact angle measurements. The o/w emulsification properties of both particles for the nonpolar oil dodecane and the more polar oil diethylphthalate are investigated by measurements of the droplet size distributions. Highly stable emulsions can be obtained when the degree of dissociation of the weak polyelectrolyte is below 80%. Here the average droplet size depends on the degree of dissociation, and a minimum can be found when 15 to 45% of the monomer units are dissociated. The thickness of the adsorbed polyelectrolyte layer strongly influences the droplet size of dodecane/water emulsion droplets but has a less pronounced impact on the diethylphthalate/water droplets. We explain the dependency of the droplet size on the emulsion pH value and the polyelectrolyte coating thickness with arguments based on the particle-wetting properties, the particle aggregation state, and the oil phase polarity. Cryo-SEM visualization shows that the regularity of the densely packed particles on the oil-water interface correlates with the degree of dissociation of the corresponding polyelectrolyte.

Refractometric investigation of pectin solutions

NASA Astrophysics Data System (ADS)

Nikolova, K.; Pantchev, I.; Sajnov, S.

2005-04-01

This study discusses the possibility for a quantitative evaluation of pectin macromolecules bydratation, by measuring the refractive index (RI) of their solutions, using a differential laser refractometer and a laboratory-type interferometer, LI-3, Rayleigh-type. The results obtained have been discussed according to the theory of Ikegami for polyelectrolytes hydratation. Refractometer measurements of ethanol, methanol and water have been done. A theroretical link between the models of Selmeyerand Lorentz-Lorenz has been established, and by means of this link the number of electrons per volume unit of the alcohols indicated has been calculated.

Mass transport in polyelectrolyte solutions

NASA Astrophysics Data System (ADS)

Schipper, F. J. M.; Leyte, J. C.

1999-02-01

The self-diffusion coefficients of the three components of a salt-free heavy-water solution of polymethacrylic acid, completely neutralized with tetra-methylammonium hydroxide, were measured over a broad concentration range. Three concentration regions were observed for the self-diffusion of both the polyions and the counterions. At polyion concentrations below 0.01 mol monomer kg-1, the dilute concentration regime for the polymer, the polyion self-diffusion coefficient approaches the self-diffusion coefficient of a freely diffusing rod upon dilution. At polyelectrolyte concentrations above 0.1 mol monomer kg-1, the self-diffusion coefficients of the solvent, the counterions and the polymer decreased with concentration, suggesting that this decrease is due to a topological constraint on the motions of the components. In the intermediate-concentration region, the self-diffusion coefficients of the polyions and the counterions are independent of the concentration. The polyion dynamic behaviour is, in the intermediate- and high-concentration regions, reasonably well described by that of a hard sphere, with a radius of 3.7 nm. A correct prediction for the solvent dynamics is given by the obstruction effect of this hard sphere on the solvent. The relative counterion self-diffusion coefficient is predicted almost quantitatively over the entire concentration range with the Poisson-Boltzmann-Smoluchowski model for the spherical cell, provided that the sphere radius and the number of charges are chosen appropriately (approximately the number of charges in a persistence length). Using this model, the dependence of the counterion self-diffusion coefficient on the ionic strength, polyion concentration and counterion radius is calculated quantitatively over a large concentration range.

From the 2-dimensional unstable polyelectrolyte multilayer to the 3-dimensional stable dry polyelectrolyte capsules.

PubMed

Li, Xiaodong; Zhang, Jianxiang; Hu, Qiaoling; Li, Xiaohui

2011-11-01

Polystyrene-poly(acrylic acid)/poly(allylamine hydrochloride) polyelectrolyte multilayer was found to be instable and apt to reconstruct in the pure water. By depositing polystyrene-poly(acrylic acid)/poly(allylamine hydrochloride) multilayer on the polystyrene-poly(acrylic acid) hybrid CaCO(3) templates, novel polyelectrolyte capsules could be prepared after the removal of the templates. The resultant capsules could keep their three-dimensional (3D) spherical shape after being dried at room temperature, dramatically different from the conventional polyelectrolyte capsules based on nonhybrid templates by layer-by-layer procedure. The instable polyelectrolyte multilayer, hybrid templates, and assembly cycles were demonstrated to be three indispensable factors responsible for the formation of this type of 3D stable capsules. The formation mechanism was also discussed in this study. Copyright © 2011 Elsevier Inc. All rights reserved.

High-Efficiency All-Solution-Processed Light-Emitting Diodes Based on Anisotropic Colloidal Heterostructures with Polar Polymer Injecting Layers.

PubMed

Castelli, Andrea; Meinardi, Francesco; Pasini, Mariacecilia; Galeotti, Francesco; Pinchetti, Valerio; Lorenzon, Monica; Manna, Liberato; Moreels, Iwan; Giovanella, Umberto; Brovelli, Sergio

2015-08-12

Colloidal quantum dots (QDs) are emerging as true candidates for light-emitting diodes with ultrasaturated colors. Here, we combine CdSe/CdS dot-in-rod heterostructures and polar/polyelectrolytic conjugated polymers to demonstrate the first example of fully solution-based quantum dot light-emitting diodes (QD-LEDs) incorporating all-organic injection/transport layers with high brightness, very limited roll-off and external quantum efficiency as high as 6.1%, which is 20 times higher than the record QD-LEDs with all-solution-processed organic interlayers and exceeds by over 200% QD-LEDs embedding vacuum-deposited organic molecules.

Lipid Layers on Polyelectrolyte Multilayers: Understanding Lipid-Polyelectrolyte Interactions and Applications on the Surface Engineering of Nanomaterials.

PubMed

Diamanti, Eleftheria; Gregurec, Danijela; Gabriela, Romero; Cuellar, J L; Donath, E; Moya, S E

2016-06-01

In this manuscript we review work of our group on the assembly of lipid layers on top of polyelectrolyte multilayers (PEMs). The assembly of lipid layers with zwitterionic and charged lipids on PEMs is studied as a function of lipid and polyelectrolyte composition by the Quartz Crystal Microbalance. Polyelectrolyte lipid interactions are studied by means of Atomic Force Spectroscopy. We also show the coating of lipid layers for engineering different nanomaterials, i.e., carbon nanotubes and poly(lactic-co-glycolic) nanoparticles and how these can be used to decrease in vitro toxicity and to direct the intracellular localization of nanomaterials.

Effects of ion size and charge asymmetry on the salt distribution in polyelectrolyte blends and block copolymers

NASA Astrophysics Data System (ADS)

Kwon, Ha-Kyung; Shull, Kenneth R.; Zwanikken, Jos W.; Olvera de La Cruz, Monica

Polyelectrolytes have received much attention as potential candidates for rechargeable batteries, membrane fuel cells, and drug delivery carriers, as they can combine the electrochemical properties of the charged components with the mechanical stability and biocompatibility of the polymer backbone. The role of salt in determining the bulk and interfacial behaviors of polyelectrolytes has been of particular interest, as the miscibility has shown to depend significantly on salt identity and concentration. Recent studies employing the SCFT-LS method have shown that ionic correlations can enhance phase separation in polyelectrolytes and can induce selectivity in neutral solvents. Here, we extend the theory to investigate the role of salt in strongly correlated polyelectrolytes. We find that in lamellae-forming block copolymers, the addition of monovalent, symmetric salt can lead to a decreased lamellar spacing due to increased selectivity of the salt. When multiple electrostatic interactions are introduced via size and valency asymmetry in the salt pair, the bulk phase behavior and salt distribution across interfaces are significantly altered, as size and charge mismatch can transform the charge ordering seen in monovalent, symmetric salts. This work was performed under the following financial assistance award 70NANB14H012 from U.S. Department of Commerce, National Institute of Standards and Technology as part of the Center for Hierarchical Materials Design (CHiMaD).

Coagulation-flocculation mechanisms in wastewater treatment plants through zeta potential measurements.

PubMed

López-Maldonado, E A; Oropeza-Guzman, M T; Jurado-Baizaval, J L; Ochoa-Terán, A

2014-08-30

Based on the polyelectrolyte-contaminant physical and chemical interactions at the molecular level, this article analyzed and discussed the coagulation-flocculation and chemical precipitation processes in order to improve their efficiency. Bench experiments indicate that water pH, polyelectrolyte (PE) dosing strategy and cationic polyelectrolyte addition are key parameters for the stability of metal-PE complexes. The coagulation-flocculation mechanism is proposed based on zeta potential (ζ) measurement as the criteria to define the electrostatic interaction between pollutants and coagulant-flocculant agents. Polyelectrolyte and wastewater dispersions are exposed to an electrophoretic effect to determine ζ. Finally, zeta potential values are compared at pH 9, suggesting the optimum coagulant dose at 162mg/L polydadmac and 67mg/L of flocculant, since a complete removal of TSS and turbidity is achieved. Based on the concentration of heavy metals (0.931mg/L Sn, 0.7mg/L Fe and 0.63mg/L Pb), treated water met the Mexican maximum permissible limits. In addition, the treated water has 45mg O2/L chemical oxygen demand (COD) and 45mg C/L total organic carbon (TOC). The coagulation-flocculation mechanism is proposed taking into account both: zeta potential (ζ)-pH measurement and chemical affinity, as the criteria to define the electrostatic and chemical interaction between pollutants and polyelectrolytes. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of nanodimensional polyethylenimine layer on surface potential barriers of hybrid structures based on silicon single crystal

NASA Astrophysics Data System (ADS)

Malyar, Ivan V.; Gorin, Dmitry A.; Stetsyura, Svetlana V.

2013-01-01

In this report we present the analysis of I-V curves for MIS-structures like silicon substrate / nanodimensional polyelectrolyte layer / metal probe (contact) which is promising for biosensors, microfluidic chips, different devices of molecular electronics, such as OLEDs, solar cells, where polyelectrolyte layers can be used to modify semiconductor surface. The research is directed to investigate the contact phenomena which influence the resulting signal of devices mentioned above. The comparison of I-V characteristics of such structures measured by scanning tunnel microscopy (contactless technique) and using contact areas deposited by thermal evaporation onto the organic layer (the contact one) was carried out. The photoassisted I-V measurements and complex analysis based on Simmons and Schottky models allow one to extract the potential barriers and to observe the changes of charge transport in MIS-structures under illumination and after polyelectrolyte adsorption. The direct correlation between the thickness of the deposited polyelectrolyte layer and both equilibrium tunnel barrier and Schottky barrier height was observed for hybrid structures with polyethylenimine. The possibility of control over the I-V curves of hybrid structure and the height of the potential barriers (for different charge transports) by illumination was confirmed. Based on experimental data and complex analysis the band diagrams were plotted which illustrate the changes of potential barriers for MIS-structures due to the polyelectrolyte adsorption and under the illumination.

Chain stiffness, salt valency, and concentration influences on titration curves of polyelectrolytes: Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Carnal, Fabrice; Stoll, Serge

2011-01-01

Monte Carlo simulations have been used to study two different models of a weak linear polyelectrolyte surrounded by explicit counterions and salt particles: (i) a rigid rod and (ii) a flexible chain. We focused on the influence of the pH, chain stiffness, salt concentration, and valency on the polyelectrolyte titration process and conformational properties. It is shown that chain acid-base properties and conformational properties are strongly modified when multivalent salt concentration variation ranges below the charge equivalence. Increasing chain stiffness allows to minimize intramolecular electrostatic monomer interactions hence improving the deprotonation process. The presence of di and trivalent salt cations clearly promotes the chain degree of ionization but has only a limited effect at very low salt concentration ranges. Moreover, folded structures of fully charged chains are only observed when multivalent salt at a concentration equal or above charge equivalence is considered. Long-range electrostatic potential is found to influence the distribution of charges along and around the polyelectrolyte backbones hence resulting in a higher degree of ionization and a lower attraction of counterions and salt particles at the chain extremities.

Chain stiffness, salt valency, and concentration influences on titration curves of polyelectrolytes: Monte Carlo simulations.

PubMed

Carnal, Fabrice; Stoll, Serge

2011-01-28

Monte Carlo simulations have been used to study two different models of a weak linear polyelectrolyte surrounded by explicit counterions and salt particles: (i) a rigid rod and (ii) a flexible chain. We focused on the influence of the pH, chain stiffness, salt concentration, and valency on the polyelectrolyte titration process and conformational properties. It is shown that chain acid-base properties and conformational properties are strongly modified when multivalent salt concentration variation ranges below the charge equivalence. Increasing chain stiffness allows to minimize intramolecular electrostatic monomer interactions hence improving the deprotonation process. The presence of di and trivalent salt cations clearly promotes the chain degree of ionization but has only a limited effect at very low salt concentration ranges. Moreover, folded structures of fully charged chains are only observed when multivalent salt at a concentration equal or above charge equivalence is considered. Long-range electrostatic potential is found to influence the distribution of charges along and around the polyelectrolyte backbones hence resulting in a higher degree of ionization and a lower attraction of counterions and salt particles at the chain extremities.

Comparative study of cytotoxicity of ferromagnetic nanoparticles and magnetitecontaining polyelectrolyte microcapsules

NASA Astrophysics Data System (ADS)

Minaeva, O. V.; Brodovskaya, E. P.; Pyataev, M. A.; Gerasimov, M. V.; Zharkov, M. N.; Yurlov, I. A.; Kulikov, O. A.; Kotlyarov, A. A.; Balykova, L. A.; Kokorev, A. V.; Zaborovskiy, A. V.; Pyataev, N. A.; Sukhorukov, G. B.

2017-01-01

The cytotoxicity of magnetite nanoparticles (MNP) stabilized with citrate acidand polyelectrolyte multilayer microcapsules containing these particles in the shell is analyzed. Microcapsules were prepared by co-precipitation of iron (II) and (III) chlorides. Polyelectrolyte microcapsules synthesized by the layer-by-layer method from biodegradable polymers polyarginine and dextran sulfate. Cytotoxicity of the synthesized objects was studied on the L929 cells culture and human leucocytes. It was also investigated the phagocytic activity of leukocytes for the MNP and magnetite containing polyelectrolyte microcapsules (MCPM). A set of tests (MTT assay, neutral red uptake assay, lactate dehydrogenase release assay) was used to study the cytotoxicity in vitro. All the tests have shown that the magnetic nanoparticles have a greater cytotoxicity in comparison with microcapsules containing an equivalent amount of magnetite. In contrast to the mouse fibroblast culture, human leukocytes were more resistant to the toxic effects of magnetite. At the concentrations used in our studies no significant reduction in the viability of leukocytes has been registered. Both MNP and MCPM undergo phagocytosis, however, the phagocytic activity of leukocytes for these particles was lower than for the standard objects (latex microparticles).

Characterization of a Biomimetic Polymeric-Lipid Bilayer by Phase Sensitive Neutron Reflectivity

NASA Astrophysics Data System (ADS)

Perez-Salas, Ursula A.; Krueger, Susan; Majkrzak, Charles F.; Berk, Norman F.; Faucher, Keith M.; Chaikof, Elliot L.

2003-03-01

Lipid membranes, the boundaries for cellular and intracellular structures, regulate many crucial biological processes. Planar supported mimics of cell membranes are of great interest as model systems for the study of membrane structure/function phenomena in fundamental biophysics research. We studied a supported biomedically relevant membrane-mimetic system composed of a polyelectrolyte cushion, a terpolymer and a self-assembled phospholipid monolayer and obtained a detailed profile characterization of the system by neutron reflectometry. The water-swellable hydrophilic polyelectrolyte acts as a support for the biomembrane, not unlike the cytoskeletal support found in actual mammalian cell membranes. The "cushion" polymers are fixed to the flat, hard surface by having the polymer interact with it electrostatically. The terpolymer has the following desirable features: it tethers to the polyelectrolyte layer and it creates a hydrophilic and a hydrophobic region. Unilamellar phospholipid vesicle fusion on to the hydrophobic region of the terpolymer creates the hybrid tethered membrane. For added stability to external force fields (such as shear flow), the phospholipid monolayer is then polymerized in situ, effectively anchoring the lipid layer to the hydrophobic region of the terpolymer. Neutron reflectivity measurements were done on the polyelectrolyte layer, the polyelectrolyte layer plus terpolymer and the polylectrolyte layer plus terpolymer plus phospholipid. The layers were studied dry and hydrated and under 95α D_2O and 50% \\ 50% α H_2O \\ α D_2O) on the polyelectrolyte layer plus terpolymer and the polylectrolyte layer plus terpolymer plus phospholipid the distribution of water in the layers was obtained. The results will be correlated to impedance measurements flourescence measurements and infrared spectroscopy measurements made on equivalent samples.

[Inclusion of proteins into polyelectrolyte microcapsules by coprecipitation and adsorption].

PubMed

Kochetkova, O Iu; Kazakova, L I; Moshkov, D A; Vinokurov, M G; Shabarchina, L I

2013-01-01

In present study microcapsules composed of synthetic (PSS and PAA) and biodegradable (DS and PAr) polyelectrolytes on calcium carbonate microparticles were obtained. The ultrastructural organization of biodegradable microcapsules was studied using transmission electron microscopy. The envelope of such capsules consisting of six polyelectrolyte layers is already well-formed, having the average thickness of 44 ± 3.0 nm, and their internal polyelectrolyte matrix is sparser compared to the synthetic microcapsules. Spectroscopy was employed to evaluate the efficiency of incorporation of FITC-labeled BSA into synthetic microcapsules by adsorption, depending on the number of polyelectrolyte layers. It was shown that the maximal amount of protein incorporated into the capsules with 6 or 7 polyelectrolyte layers (4 and 2 pg/capsule, correspondingly). As a result we conclude that, in comparison with co-precipitation, the use of adsorption allows to completely avoid the loss of protein upon encapsulation.

Kinetics of swelling of polyelectrolyte gels: Fixed degree of ionization

NASA Astrophysics Data System (ADS)

Sen, Swati; Kundagrami, Arindam

2015-12-01

The swelling kinetics of uncharged and charged polymer (polyelectrolyte) gels in salt-free conditions is studied in one dimension by solving the constitutive equation of motion (Newton's law for the elementary gel volume) of the displacement variable by two theoretical methods: one in which the classical definition of stress is used with the bulk modulus taken as a parameter, and the other in which a phenomenological expression of the osmotic stress as a function of polymer density and degree of ionization is taken as an input to the dynamics. The time-evolution profiles for spatially varying polymer density and stress, along with the location of the gel-solvent interface, are obtained from the two methods. We show that both the polymer density (volume fraction) and stress inside the gel follow expected behaviours of being maximum for the uniformly shrunken gel, and relaxing slowly to the lowest values as the gel approaches equilibrium. We further show that, by comparing the temporal profiles of the gel-solvent interface and other variables between the two methods, one may attempt to assign an effective bulk modulus to the polyelectrolyte gel as a function of the degree of ionization and other parameters of the gel such as hydrophobicity, cross-link density, and the temperature. The major result we get is that the effective bulk modulus of a polyelectrolyte gel increases monotonically with its degree of ionization. In the process of identifying the parameters for a monotonic swelling, we calculated using a well-known expression of the free energy the equilibrium results of two-phase co-existence and the critical point of a polyelectrolyte gel with a fixed degree of ionization.

Kinetics of swelling of polyelectrolyte gels: Fixed degree of ionization.

PubMed

Sen, Swati; Kundagrami, Arindam

2015-12-14

The swelling kinetics of uncharged and charged polymer (polyelectrolyte) gels in salt-free conditions is studied in one dimension by solving the constitutive equation of motion (Newton's law for the elementary gel volume) of the displacement variable by two theoretical methods: one in which the classical definition of stress is used with the bulk modulus taken as a parameter, and the other in which a phenomenological expression of the osmotic stress as a function of polymer density and degree of ionization is taken as an input to the dynamics. The time-evolution profiles for spatially varying polymer density and stress, along with the location of the gel-solvent interface, are obtained from the two methods. We show that both the polymer density (volume fraction) and stress inside the gel follow expected behaviours of being maximum for the uniformly shrunken gel, and relaxing slowly to the lowest values as the gel approaches equilibrium. We further show that, by comparing the temporal profiles of the gel-solvent interface and other variables between the two methods, one may attempt to assign an effective bulk modulus to the polyelectrolyte gel as a function of the degree of ionization and other parameters of the gel such as hydrophobicity, cross-link density, and the temperature. The major result we get is that the effective bulk modulus of a polyelectrolyte gel increases monotonically with its degree of ionization. In the process of identifying the parameters for a monotonic swelling, we calculated using a well-known expression of the free energy the equilibrium results of two-phase co-existence and the critical point of a polyelectrolyte gel with a fixed degree of ionization.

Modeling the controllable pH-responsive swelling and pore size of networked alginate based biomaterials.

PubMed

Chan, Ariel W; Neufeld, Ronald J

2009-10-01

Semisynthetic network alginate polymer (SNAP), synthesized by acetalization of linear alginate with di-aldehyde, is a pH-responsive tetrafunctionally linked 3D gel network, and has potential application in oral delivery of protein therapeutics and active biologicals, and as tissue bioscaffold for regenerative medicine. A constitutive polyelectrolyte gel model based on non-Gaussian polymer elasticity, Flory-Huggins liquid lattice theory, and non-ideal Donnan membrane equilibria was derived, to describe SNAP gel swelling in dilute and ionic solutions containing uni-univalent, uni-bivalent, bi-univalent or bi-bi-valent electrolyte solutions. Flory-Huggins interaction parameters as a function of ionic strength and characteristic ratio of alginates of various molecular weights were determined experimentally to numerically predict SNAP hydrogel swelling. SNAP hydrogel swells pronouncedly to 1000 times in dilute solution, compared to its compact polymer volume, while behaving as a neutral polymer with limited swelling in high ionic strength or low pH solutions. The derived model accurately describes the pH-responsive swelling of SNAP hydrogel in acid and alkaline solutions of wide range of ionic strength. The pore sizes of the synthesized SNAP hydrogels of various crosslink densities were estimated from the derived model to be in the range of 30-450 nm which were comparable to that measured by thermoporometry, and diffusion of bovine serum albumin. The derived equilibrium swelling model can characterize hydrogel structure such as molecular weight between crosslinks and crosslinking density, or can be used as predictive model for swelling, pore size and mechanical properties if gel structural information is known, and can potentially be applied to other point-link network polyelectrolytes such as hyaluronic acid gel.

Structure of Salt-free Linear Polyelectrolytes in the Debye-Hückel Approximation

NASA Astrophysics Data System (ADS)

Stevens, Mark J.; Kremer, Kurt

1996-11-01

We examine the effects of the common Debye-Hückel approximation used in theories of polyelectrolytes. Molecular dynamics simulations using the Debye-Hückel pair potential of salt-free polyelectrolytes have been performed. The results of these simulations are compared to earlier “Coulomb" simulations which explicitly treated the counterions. We report here the comparisons of the osmotic pressure, the end-to-end distance and the single chain structure factor. In the dilute regime the Debye-Hückel chains are more elongated than the Coulomb chains implying that the counterion screening is stronger than the Debye-Hückel prediction. Like the Coulomb chains the Debye-Hückel chains contract significantly below the overlap density in contradiction to all theories. Entropy thus plays an important and sorely neglected role in theory.

Light Irradiation as Key to Shape and Function of Nano-Assemblies in Solution

NASA Astrophysics Data System (ADS)

Groehn, Franziska

Developing strategies to exploit solar energy become more and more important. Inspired by natural systems it is highly promising to self-assemble functional species into effective tailored supramolecular units. Here we report self-assembled polymer structures in solution, taking advantage of optical properties of hybrid structures and light responsiveness. A new type of photocatalytically active self-assembled polymer structure in aqueous solution consists of supramolecular nano-objects obtained from macroions and multivalent inorganic ``counterions'' such as nanoparticles or clusters. These can exhibit expressed selectivity or even allow catalytic reactions in solution that are not possible with the building blocks only. Further, polyelectrolyte-porphyrin nanoscale assemblies exhibit tunable optical properties including strong fluorescence and an up to 20-fold higher photocatalytic activity than without polymeric template. A different approach is to transfer light energy into mechanical energy. Here, light energy is converted into nanoscale shape changes. This route for the conversion of light is highly promising for applications in drug delivery, nanosensors and solar energy conversion. Membership of DPG, Germany ID 153159-.

Thermo-Responsive Complexes of c-Myc Antisense Oligonucleotide with Block Copolymer of Poly(OEGMA) and Quaternized Poly(4-Vinylpyridine).

PubMed

Topuzogullari, Murat; Elalmis, Yeliz Basaran; Isoglu, Sevil Dincer

2017-04-01

Solution behavior of thermo-responsive polymers and their complexes with biological macromolecules may be affected by environmental conditions, such as the concentration of macromolecular components, pH, ion concentration, etc. Therefore, a thermo-responsive polymer and its complexes should be characterized in detail to observe their responses against possible environments under physiological conditions before biological applications. To briefly indicate this important issue, thermo-responsive block copolymer of quaternized poly(4-vinylpyridine) and poly(oligoethyleneglycol methyl ether methacrylate) as a potential nonviral vector has been synthesized. Polyelectrolyte complexes of this copolymer with the antisense oligonucleotide of c-Myc oncogene are also thermo-responsive but, have lower LCST (lower critical solution temperature) values compared to individual copolymer. LCST values of complexes decrease with molar ratio of macromolecular components and presence of salt. Dilution of solutions also affects solution behavior of complexes and causes a significant decrease in size and an increase in LCST, which indicates possible effects of severe dilutions in the blood stream. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of the chitosan/poly(glutamic acid)/alginate polyelectrolyte complexing hydrogel and study on its drug releasing property.

PubMed

Chen, Yu; Yan, Xiaoting; Zhao, Jian; Feng, Huaiyu; Li, Puwang; Tong, Zongrui; Yang, Ziming; Li, Sidong; Yang, Jueying; Jin, Shaohua

2018-07-01

In the current study, a novel semi-dissolution/acidification/sol-gel transition (SD-A-SGT) method was explored for the preparation of polyelectrolyte complexing (PEC) composite hydrogels with natural polymers only. A chitosan (CS) powder was uniformly dispersed in a solution of poly(glutamic acid) (PGA) and alginate (SA) to form a semi-dissolved slurry mixture that was then exposed to an gaseous acidic atmosphere. CS was gradually dissolved and interacted with PGA and SA to form a CS/PGA/SA PEC composite hydrogel with a homogeneous structure. The SD-A-SGT procedure was able to overcome the shortcomings of direct mixing method via the PEC interaction. The effects of the hydrogel composition on its structure and properties were investigated by FTIR, XRD, rheology study, XPS, SEM, and swelling kinetics. The drug delivery performance of the CS/PGA/SA hydrogel was explored using piroxicam (PXC) as a model drug. PXC was in situ embedded in the hydrogel by the SD-A-SGT method. The hydrogel exhibited pH responsive drug release behaviors that were affected by the hydrogel composition. In all, the SD-A-SGT method for preparing PEC composite hydrogels has a great application potential in constructing the CS based hydrogels as medical materials. Copyright © 2018 Elsevier Ltd. All rights reserved.

Self-assembly of model graft copolymers of agarose and weak polyelectrolyte-based amphiphilic diblock copolymers: controlled drug release and degradation.

PubMed

Muppalla, Ravikumar; Jewrajka, Suresh K; Prasad, Kamalesh

2013-06-01

Polysaccharide-based copolymers are promising biomaterials due to their biocompatibility and biodegradability. For potential biomedical applications the copolymer as a whole and all the degraded species must be biocompatible and easily removable from the system. In this regards, new model pH-responsive seaweed agarose (Agr) grafted with weak polyelectrolyte-based well-defined amphiphilic block copolymers ca. poly[(methyl methacrylate)-b-(2-dimethylamino)ethyl methacrylate)] (PMMA-b-PDMA) were designed and synthesized to study the self-assembly, degradation, and in vitro hydrophobic/hydrophilic drug release behavior. The graft copolymer solutions display extremely low critical micelle concentration (CMC) and form pH responsive stable micelles. The degradation study of the graft copolymer reveals that the entire degraded components are well soluble/dispersible in water due to formation of mixed micelles. The micelles are also strongly adsorbed on the mica surface owing to electrostatic interaction. One application of the graft copolymer micelles is that it can entrap both hydrophilic and poorly water soluble hydrophobic drugs effectively and exhibit slow release kinetics. The release kinetics of both the hydrophilic and poorly water soluble hydrophobic drugs change with pH as well as with the composition of the graft copolymer. Copyright © 2012 Wiley Periodicals, Inc.

Proton conducting gel polyelectrolytes based on 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) copolymers with polyfunctional monomers. Part I. Anhydrous systems

NASA Astrophysics Data System (ADS)

Zygadło-Monikowska, Ewa; Florjańczyk, Zbigniew; Wielgus-Barry, Edyta; Paśniewski, Jarosław

The synthesis of crosslinked gel polyelectrolytes in polar aprotic solvents such as dimethylformamide (DMF) and a DMF and propylene carbonate (PC) mixture has been carried out in the copolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) and polyfunctional monomers. N, N‧-Methylene-bis-acrylamide, trioxyethylene dimethacrylate (M n ∼ 330) and trimethylolpropane ethoxylate (14/3 EO/OH) triacrylate were used as crosslinking monomers. The reactions were initiated thermally or by UV irradiation in the presence of Irgacure 184 or methyl benzoin ether. The crosslinking monomer was used in an amount of 0.5-13 wt.%. The effect of the type and concentration of the polyfunctional comonomer and type of solvent on the optical (color, transparency) and mechanical properties as well as the ability to conduct electrical charges have been studied. The application of a DMF and PC mixture enables to obtain transparent systems of good mechanical properties and high ambient temperature ionic conductivity of the order of 10 -3 to 10 -4 S cm -1, slightly lowered as compared with that of gels comprising DMF alone. The conducting properties of crosslinked gels have been compared with that of the AMPSA homopolymer solutions in analogous solvents.

Electrostatic effects on hyaluronic acid configuration

NASA Astrophysics Data System (ADS)

Berezney, John; Saleh, Omar

2015-03-01

In systems of polyelectrolytes, such as solutions of charged biopolymers, the electrostatic repulsion between charged monomers plays a dominant role in determining the molecular conformation. Altering the ionic strength of the solvent thus affects the structure of such a polymer. Capturing this electrostatically-driven structural dependence is important for understanding many biological systems. Here, we use single molecule manipulation experiments to collect force-extension behavior on hyaluronic acid (HA), a polyanion which is a major component of the extracellular matrix in all vertebrates. By measuring HA elasticity in a variety of salt conditions, we are able to directly assess the contribution of electrostatics to the chain's self-avoidance and local stiffness. Similar to recent results from our group on single-stranded nucleic acids, our data indicate that HA behaves as a swollen chain of electrostatic blobs, with blob size proportional to the solution Debye length. Our data indicate that the chain structure within the blob is not worm-like, likely due to long-range electrostatic interactions. We discuss potential models of this effect.

Effects of conformational ordering on protein/polyelectrolyte electrostatic complexation: ionic binding and chain stiffening

PubMed Central

Cao, Yiping; Fang, Yapeng; Nishinari, Katsuyoshi; Phillips, Glyn O.

2016-01-01

Coupling of electrostatic complexation with conformational transition is rather general in protein/polyelectrolyte interaction and has important implications in many biological processes and practical applications. This work studied the electrostatic complexation between κ-carrageenan (κ-car) and type B gelatin, and analyzed the effects of the conformational ordering of κ-car induced upon cooling in the presence of potassium chloride (KCl) or tetramethylammonium iodide (Me4NI). Experimental results showed that the effects of conformational ordering on protein/polyelectrolyte electrostatic complexation can be decomposed into ionic binding and chain stiffening. At the initial stage of conformational ordering, electrostatic complexation can be either suppressed or enhanced due to the ionic bindings of K+ and I− ions, which significantly alter the charge density of κ-car or occupy the binding sites of gelatin. Beyond a certain stage of conformational ordering, i.e., helix content θ > 0.30, the effect of chain stiffening, accompanied with a rapid increase in helix length ζ, becomes dominant and tends to dissociate the electrostatic complexation. The effect of chain stiffening can be theoretically interpreted in terms of double helix association. PMID:27030165

Electrokinetic energy conversion efficiency of viscoelastic fluids in a polyelectrolyte-grafted nanochannel.

PubMed

Jian, Yongjun; Li, Fengqin; Liu, Yongbo; Chang, Long; Liu, Quansheng; Yang, Liangui

2017-08-01

In order to conduct extensive investigation of energy harvesting capabilities of nanofluidic devices, we provide analytical solutions for streaming potential and electrokinetic energy conversion (EKEC) efficiency through taking the combined consequences of soft nanochannel, a rigid nanochannel whose surface is covered by charged polyelectrolyte layer, and viscoelastic rheology into account. The viscoelasticity of the fluid is considered by employing the Maxwell constitutive model when the forcing frequency of an oscillatory driving pressure flow matches with the inverse of the relaxation time scale of a typical viscoelastic fluid. We compare the streaming potential and EKEC efficiency with those of a rigid nanochannel, having zeta potential equal to the electrostatic potential at the solid-polyelectrolyte interface of the soft nanochannels. Within the present selected parameter ranges, it is shown that the different peaks of maximal streaming potential and EKEC efficiency for the rigid nanochannel are larger than those for the soft nanochannel when forcing frequencies of the driving pressure gradient are close to resonating frequencies. However, more enhanced streaming potential and EKEC efficiency for a soft nanochannel can be found in most of the regions away from these resonant frequencies. Moreover, the influence of several dimensionless parameters on EKEC efficiency is discussed in detail. Finally, within the given parametric regions, the maximum efficiency at some resonant frequency obtained in present analysis is about 25%. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of Highly-Conductive Polyelectrolytes for Lithium Batteries

NASA Technical Reports Server (NTRS)

Shriver, D. F.; Ratner, M. A.; Vaynman, S.; Annan, K. O.; Snyder, J. F.

2003-01-01

Future NASA and Air Force missions require reliable and safe sources of energy with high specific energy and energy density that can provide thousands of charge-discharge cycles at more than 40% depth- of-discharge and that can operate at low temperatures. All solid-state batteries have substantial advantages with respect to stability, energy density, storage fife and cyclability. Among all solid-state batteries, those with flexible polymer electrolytes offer substantial advantages in cell dimensionality and commensurability, low temperature operation and thin film design. The above considerations suggest that lithium-polymer electrolyte systems are promising for high energy density batteries and should be the systems of choice for NASA and US Air Force applications. Polyelectrolytes (single ion conductors) are among most promising avenues for achieving a major breakthrough 'in the applicability of polymer- based electrolyte systems. Their major advantages include unit transference number for the cation, reduced cell polarization, minimal salt precipitation, and favorable electrolyte stability at interfaces. Our research is focused on synthesis, modeling and cell testing of single ion carriers, polyelectrolytes. During the first year of this project we attempted the synthesis of two polyelectrolytes. The synthesis of the first one, the poly(ethyleneoxide methoxy acrylateco-lithium 1,1,2-trifluorobutanesulfonate acrylate, was attempted few times and it was unsuccessful. We followed the synthetic route described by Cowie and Spence. The yield was extremely low and the final product could not be separated from the impurities. The synthesis of this polyelectrolyte is not described in this report. The second polyelectrolyte, comb polysiloxane polyelectrolyte containing oligoether and perfluoroether sidechains, was synthesized in sufficient quantity to study the range of properties such as thermal stability, Li- ion- conductivity and stability toward lithium metal. Also, the batteries containing this polyelectrolyte were assembled and tested. The results are detailed below. The synthesis of another polyelectrolyte similar to polysiloxane polyelectrolyte has been started, however, the synthesis was not completed due to termination of the project.

Polyvinylpyrrolidone-sodium dodecylsulfate complex is a family of pseudo-polyanions with different charge densities: Evidence from capillary electrophoresis, capillary viscosimetry and conductometry.

PubMed

Wu, Yefan; Chen, Jie; Fang, Yun; Zhu, Meng

2016-10-01

Accordance with the previously supposed polyelectrolyte-like behaviour of neutral polymer-anionic surfactant complexes, direct evidence for the formation of the pseudo-polyanions in polyvinylpyrrolidone (PVP)-sodium dodecylsulfate (SDS) solution is put forward in this paper by capillary electrophoresis (CE) experiments in assistance with capillary viscosimetry and conductometry. The contradictory phenomena of the absolute value of relative electrophoretic mobility (re) increasing while the ionization degree (α) decreasing with the increasing specific clusterization [Г] in aqueous PVP-SDS solution are explained by the finding that the PVP-SDS complex is eventually a family of PVP-SDS pseudo-polyanions with different charge densities. And it is found countercations playing an important role in the formation of the PVP-SDS pseudo-polyanions in virtue of bridge effect. Copyright © 2016 Elsevier Inc. All rights reserved.

Polyelectrolyte-modified cowpea mosaic virus for the synthesis of gold nanoparticles.

PubMed

Aljabali, Alaa A A; Evans, David J

2014-01-01

Polyelectrolyte surface-modified cowpea mosaic virus (CPMV) can be used for the templated synthesis of narrowly dispersed gold nanoparticles. Cationic polyelectrolyte, poly(allylamine) hydrochloride, is electrostatically bound to the external surface of the virus capsid. The polyelectrolyte-coated CPMV promotes adsorption of aqueous gold hydroxide anionic species, prepared from gold(III) chloride and potassium carbonate, that are easily reduced to form CPMV-templated gold nanoparticles. The process is simple and environmentally benign using only water as solvent at ambient temperature.

Off-Resonant Two-Photon Absorption Cross-Section Enhancement of an Organic Chromophore on Gold Nanorods

PubMed Central

Sivapalan, Sean T.; Vella, Jarrett H.; Yang, Timothy K.; Dalton, Matthew J.; Haley, Joy E.; Cooper, Thomas M.; Urbas, Augustine M.; Tan, Loon-Seng; Murphy, Catherine J.

2013-01-01

Surface-plasmon-initiated interference effects of polyelectrolyte-coated gold nanorods on the two-photon absorption of an organic chromophore were investigated. With polyelectrolyte bearing gold nanorods of 2,4,6 and 8 layers, the role of the plasmonic fields as function of distance on such effects was examined. An unusual distance dependence was found: enhancements in the two-photon cross-section were at a minimum at an intermediate distance, then rose again at a further distance. The observed values of enhancement were compared to theoretical predictions using finite element analysis and showed good agreementdue to constructive and destructive interference effects. PMID:23687561

Folding Behaviors of Protein (Lysozyme) Confined in Polyelectrolyte Complex Micelle.

PubMed

Wu, Fu-Gen; Jiang, Yao-Wen; Chen, Zhan; Yu, Zhi-Wu

2016-04-19

The folding/unfolding behavior of proteins (enzymes) in confined space is important for their properties and functions, but such a behavior remains largely unexplored. In this article, we reported our finding that lysozyme and a double hydrophilic block copolymer, methoxypoly(ethylene glycol)5K-block-poly(l-aspartic acid sodium salt)10 (mPEG(5K)-b-PLD10), can form a polyelectrolyte complex micelle with a particle size of ∼30 nm, as verified by dynamic light scattering and transmission electron microscopy. The unfolding and refolding behaviors of lysozyme molecules in the presence of the copolymer were studied by microcalorimetry and circular dichroism spectroscopy. Upon complex formation with mPEG(5K)-b-PLD10, lysozyme changed from its initial native state to a new partially unfolded state. Compared with its native state, this copolymer-complexed new folding state of lysozyme has different secondary and tertiary structures, a decreased thermostability, and significantly altered unfolding/refolding behaviors. It was found that the native lysozyme exhibited reversible unfolding and refolding upon heating and subsequent cooling, while lysozyme in the new folding state (complexed with the oppositely charged PLD segments of the polymer) could unfold upon heating but could not refold upon subsequent cooling. By employing the heating-cooling-reheating procedure, the prevention of complex formation between lysozyme and polymer due to the salt screening effect was observed, and the resulting uncomplexed lysozyme regained its proper unfolding and refolding abilities upon heating and subsequent cooling. Besides, we also pointed out the important role the length of the PLD segment played during the formation of micelles and the monodispersity of the formed micelles. Furthermore, the lysozyme-mPEG(5K)-b-PLD10 mixtures prepared in this work were all transparent, without the formation of large aggregates or precipitates in solution as frequently observed in other protein-polyelectrolyte systems. Hence, the present protein-PEGylated poly(amino acid) mixture provides an ideal water-soluble model system to study the important role of electrostatic interaction in the complexation between proteins and polymers, leading to important new knowledge on the protein-polymer interactions. Moreover, the polyelectrolyte complex micelle formed between protein and PEGylated polymer may provide a good drug delivery vehicle for therapeutic proteins.

Ion transferring in polyelectrolyte networks in electric fields

NASA Astrophysics Data System (ADS)

Li, Honghao; Erbas, Aykut; Zwanikken, Jos; Olvera de La Cruz, Monica

Ion-conducting polyelectrolyte gels have drawn the attention of many researchers in the last few decades as they have wide applications not only in lithium batteries but also as stretchable, transparent ionic conductor or ionic cables devices. However, ion dynamics in polyelectrolyte gels has been much less studied analytically or computationally due to the complicated interplay of long-range electrostatic and short-range interactions. Here we propose a coarse-grained non-equilibrium molecular dynamics simulation to study the ion dynamics in polyelectrolyte gels under external electric fields. We found a nonlinear response region where the molar conductivity of polyelectrolyte gels increases with external fields. We propose counterion redistribution under electric fields as the driving mechanism. We also found the ionic conductivity to be modulated by changing polylelectrolyte network topology such as the chain length. Our discovery reveals the essential difference of ion dynamics between electrolytes and polyelectrolyte gels. These results will expand our understanding in charged polymeric systems and help in designing ion-conducting devices with higher conductivity.

Inhibition of atherosclerosis-promoting microRNAs via targeted polyelectrolyte complex micelles

PubMed Central

Kuo, Cheng-Hsiang; Leon, Lorraine; Chung, Eun Ji; Huang, Ru-Ting; Sontag, Timothy J.; Reardon, Catherine A.; Getz, Godfrey S.; Tirrell, Matthew; Fang, Yun

2015-01-01

Polyelectrolyte complex micelles have great potential as gene delivery vehicles because of their ability to encapsulate charged nucleic acids forming a core by neutralizing their charge, while simultaneously protecting the nucleic acids from non-specific interactions and enzymatic degradation. Furthermore, to enhance specificity and transfection efficiency, polyelectrolyte complex micelles can be modified to include targeting capabilities. Here, we describe the design of targeted polyelectrolyte complex micelles containing inhibitors against dys-regulated microRNAs (miRNAs) that promote atherosclerosis, a leading cause of human mortality and morbidity. Inhibition of dys-regulated miRNAs in diseased cells associated with atherosclerosis has resulted in therapeutic efficacy in animal models and has been proposed to treat human diseases. However, the non-specific targeting of microRNA inhibitors via systemic delivery has remained an issue that may cause unwanted side effects. For this reason, we incorporated two different peptide sequences to our miRNA inhibitor containing polyelectrolyte complex micelles. One of the peptides (Arginine-Glutamic Acid-Lysine-Alanine or REKA) was used in another micellar system that demonstrated lesion-specific targeting in a mouse model of atherosclerosis. The other peptide (Valine-Histidine-Proline-Lysine-Glutamine-Histidine-Arginine or VHPKQHR) was identified via phage display and targets vascular endothelial cells through the vascular cell adhesion molecule-1 (VCAM-1). In this study we have tested the in vitro efficacy and efficiency of lesion- and cell-specific delivery of microRNA inhibitors to the cells associated with atherosclerotic lesions via peptide-targeted polyelectrolyte complex micelles. Our results show that REKA-containing micelles (fibrin-targeting) and VHPKQHR-containing micelles (VCAM-1 targeting) can be used to carry and deliver microRNA inhibitors into macrophages and human endothelial cells, respectively. Additionally, the functionality of miRNA inhibitors in cells was demonstrated by analyzing miRNA expression as well as the expression or the biological function of its downstream target protein. Our study provides the first demonstration of targeting dys-regulated miRNAs in atherosclerosis using targeted polyelectrolyte complex micelles and holds promising potential for translational applications. PMID:25685357

Stability of foam films of oppositely charged polyelectrolyte/surfactant mixtures: effect of isoelectric point.

PubMed

Kristen-Hochrein, Nora; Laschewsky, André; Miller, Reinhard; von Klitzing, Regine

2011-12-15

In the present paper, the influence of the surfactant concentration and the degree of charge of a polymer on foam film properties of oppositely charged polyelectrolyte/surfactant mixtures has been investigated. To verify the assumption that the position of the isoelectric point (IEP) does not change the character of the foam film stabilities, the position of the IEP of the polyelectrolyte/surfactant mixtures has been shifted in two different ways. Within the first series of experiments, the foam film properties were studied using a fixed surfactant concentration of 3 × 10(-5) M in the mixture. Due to the low surfactant concentration, this is a rather dilute system. In the second approach, a copolymer of nonionic and ionic monomer units was used to lower the charge density of the polymer. This gave rise to additional interactions between the polyelectrolyte and the surfactant, which makes the description of the foam film behavior more complex. In both systems, the same characteristics of the foam film stabilities were found: The foam film stability is reduced toward the IEP of the system, followed by a destabilization around the IEP. At polyelectrolyte concentrations above the IEP, foam films are very stable. However, the concentration range where unstable films were formed was rather broad, and the mechanisms leading to the destabilization had different origins. The results were compared with former findings on PAMPS/C(14)TAB mixtures with an IEP of 10(-4) M.

Functional magnetic microspheres

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Landel, Robert F. (Inventor); Yen, Shiao-Ping S. (Inventor)

1981-01-01

Functional magnetic particles are formed by dissolving a mucopolysaccharide such as chitosan in acidified aqueous solution containing a mixture of ferrous chloride and ferric chloride. As the pH of the solution is raised magnetite is formed in situ in the solution by raising the pH. The dissolved chitosan is a polyelectrolyte and forms micelles surrounding the granules at pH of 8-9. The chitosan precipitates on the granules to form microspheres containing the magnetic granules. On addition of the microspheres to waste aqueous streams containing dissolved ions, the hydroxyl and amine functionality of the chitosan forms chelates binding heavy metal cations such as lead, copper, and mercury and the chelates in turn bind anions such as nitrate, fluoride, phosphate and borate.

Reversible Adhesion with Polyelectrolyte Brushes Tailored via the Uptake and Release of Trivalent Lanthanum Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farina, Robert; Laugel, Nicolas; Yu, Jing

Applications of end-tethered polyelectrolyte “brushes” to modify solid surfaces have been developed and studied for their colloidal stabilization and high lubrication properties. Current efforts have expanded into biological realms and stimuli-responsive materials. Our work explores responsive and reversible aspects of polyelectrolyte brush behavior when polyelectrolyte chains interact with oppositely charged multivalent ions and complexes, which act as counterions. There is a significant void in the polyelectrolyte literature regarding interactions with multivalent species. This paper demonstrates that interactions between solid surfaces bearing negatively charged polyelectrolyte brushes are highly sensitive to the presence of trivalent lanthanum, La3+. Lanthanum cations have unique interactionsmore » with polyelectrolyte chains, in part due to their small size and hydration radius which results in a high local charge density. Using La3+ in conjunction with the surface forces apparatus (SFA), adhesion has been observed to reversibly appear and disappear upon the uptake and release, respectively, of these multivalent cations acting as counterions. In media of fixed ionic strength set by monovalent sodium salt, at I0 = 0.003 M and I0 = 0.3 M, the sign of the interaction forces between overlapping brushes changes from repulsive to attractive when La3+ concentrations reach 0.1 mol % of the total ion concentration. These results are also shown to be generally consistent with, but subtlety different from, previous polyelectrolyte brush experiments using trivalent ruthenium hexamine in the role of the multivalent counterion.« less

Adhesive interactions of biologically inspired soft condensed matter

NASA Astrophysics Data System (ADS)

Anderson, Travers Heath

Improving our fundamental understanding of the surface interactions between complex materials is needed to improve existing materials and products as well as develop new ones. The object of this research was to apply the measurements of fundamental surface interactions to real world problems facing chemical engineers and materials scientists. I focus on three systems of biologically inspired soft condensed matter, with an emphasis on the adhesive interactions between them. The formation of phospholipid bilayers of the neutral lipid, dimyristoyl-phosphatidylcholine (DMPC) on silica surfaces from vesicles in aqueous solutions was investigated. The process involves five stages: vesicle adhesion to the substrate surfaces, steric interactions with neighboring vesicles, rupture, spreading via hydrophobic fusion of bilayer edges, and ejection of excess lipid, trapped water and ions into the solution. The forces between DMPC bilayers and silica were measured in the Surface Forces Apparatus (SFA) in phosphate buffered saline. The adhesion energy was found to be much stronger than the expected adhesion predicted by van der Waals interactions, likely due to an attractive electrostatic interaction. The effects of non-adsorbing cationic polyelectrolytes on the interactions between supported cationic surfactant bilayers were studied using the SFA. Addition of polyelectrolyte has a number of effects on the interactions including the induction of a depletion-attraction and screening of the double-layer repulsion. Calculations are made that allow for the conversion of the adhesion energy measured in the SFA to the overall interaction energy between vesicles in solution, which determines the stability behavior of vesicle dispersions. Mussels use a variety of dihydroxyphenyl-alanine (DOPA) rich proteins specifically tailored to adhering to wet surfaces. The SFA was used to study the role of DOPA on the adhesive properties of these proteins to TiO 2 and mica using both real mussel foot proteins (mfp) and a synthetic polypeptide analogue of mfp-3. Adhesion increased with DOPA concentration, although oxidation of DOPA reduces the adhesive capabilities of the proteins. Comparison of the two shows that DOPA is responsible for at least 80% of the adhesion energy of mfp-3 and can be attributed to DOPA groups favorably oriented within or at the interface of these films.

Microrheology with optical tweezers: measuring the relative viscosity of solutions 'at a glance'.

PubMed

Tassieri, Manlio; Del Giudice, Francesco; Robertson, Emma J; Jain, Neena; Fries, Bettina; Wilson, Rab; Glidle, Andrew; Greco, Francesco; Netti, Paolo Antonio; Maffettone, Pier Luca; Bicanic, Tihana; Cooper, Jonathan M

2015-03-06

We present a straightforward method for measuring the relative viscosity of fluids via a simple graphical analysis of the normalised position autocorrelation function of an optically trapped bead, without the need of embarking on laborious calculations. The advantages of the proposed microrheology method are evident when it is adopted for measurements of materials whose availability is limited, such as those involved in biological studies. The method has been validated by direct comparison with conventional bulk rheology methods, and has been applied both to characterise synthetic linear polyelectrolytes solutions and to study biomedical samples.

Microrheology with Optical Tweezers: Measuring the relative viscosity of solutions ‘at a glance'

PubMed Central

Tassieri, Manlio; Giudice, Francesco Del; Robertson, Emma J.; Jain, Neena; Fries, Bettina; Wilson, Rab; Glidle, Andrew; Greco, Francesco; Netti, Paolo Antonio; Maffettone, Pier Luca; Bicanic, Tihana; Cooper, Jonathan M.

2015-01-01

We present a straightforward method for measuring the relative viscosity of fluids via a simple graphical analysis of the normalised position autocorrelation function of an optically trapped bead, without the need of embarking on laborious calculations. The advantages of the proposed microrheology method are evident when it is adopted for measurements of materials whose availability is limited, such as those involved in biological studies. The method has been validated by direct comparison with conventional bulk rheology methods, and has been applied both to characterise synthetic linear polyelectrolytes solutions and to study biomedical samples. PMID:25743468

Encapsulation of Bacterial Spores in Nanoorganized Polyelectrolyte Shells (Postprint)

DTIC Science & Technology

2009-05-27

Nanoorganized polyelectrolyte shells have already found applica- tions in drug microencapsulation as a result of the tunable properties of the...polyelectrolyte shell.19 The same LbL technology allowed the introduction of enzymatic activity onto yeast cell shells in order to promote the conversion of

Electrochemical monitoring of chlorhexidine digluconate effect on polyelectrolyte immobilized bacteria and kinetic cell adhesion.

PubMed

Borghol, N; Mora, L; Sakly, N; Lejeune, P; Jouenne, T; Jaffrézic-Renault, N; Othmane, A

2011-01-10

The electrochemical impedance spectroscopy (EIS) technique has been used as a sensitive method to explore the effect of antibacterial molecules on immobilized bacteria and biofilm formation. In this work, we describe the electrochemical spectroscopy as a powerful method to monitor the effect of chlorhexidine digluconate (CHX-Dg) on polyelectrolyte immobilized Escherichia coli K12 MG1655 and the kinetics of cell adhesion on gold electrodes. The experimental impedance data were modeled with a Zview program to find the best equivalent electrical circuit and analyse its parameter's properties. Polyelectrolyte multilayer formation on the electrode surface and bacteria immobilization greatly increased the electron-transfer resistance (R(et)) and reduced the constant phase element (CPE(dl)). The effect of CHX-Dg was studied in a 0.5 x 10⁻⁴ mmol l⁻¹ to 0.5 mmol l⁻¹ range. The relation between the evolution of R(et) and CHX-Dg concentration was found to be negatively correlated. When CHX-Dg was added, the electrochemical monitoring of the bacterial kinetic adhesion showed that the electrode's capacity (C(P)) variation remained stable, demonstrating that the addition of CHX-Dg in the broth inhibited bacterial adhesion. © 2010 Elsevier B.V. All rights reserved.

Polymer mediated layer-by-layer assembly of different shaped gold nanoparticles.

PubMed

Budy, Stephen M; Hamilton, Desmond J; Cai, Yuheng; Knowles, Michelle K; Reed, Scott M

2017-02-01

Gold nanoparticles (GNPs) have a wide range of properties with potential applications in electronics, optics, catalysis, and sensing. In order to demonstrate that dense, stable, and portable samples could be created for these applications, multiple layers of GNPs were assembled via drop casting on glass substrates by layer-by-layer (LBL) techniques. Two cationic polyelectrolytes, poly(diallyldimethylammonium chloride) and polyethyleneimine, one anionic polyelectrolyte, poly(sodium 4-styrene sulfonate), and one neutral polymer, polyvinylpyrrolidone, were combined with four different shapes of GNPs (spherical, rod, triangular prismatic, and octahedral) to prepare thin films. A subset of these polymer nanoparticle combinations were assembled into thin films. Synthesized GNPs were characterized via dynamic light scattering, UV-vis spectroscopy, and transmission electron microscopy and the LBL thin films were characterized using UV-vis spectroscopy and atomic force microscopy. Sensing applications of the nanoparticles in solution and thin films were tested by monitoring the localized surface plasmon resonance of the GNPs. LBL thin films were prepared ranging from 25 to 100 layers with optical densities at plasmon from 0.5 to 3.0. Sensitivity in solutions ranged from 14 to 1002nm/refractive index units (RIU) and films ranged from 18.8 to 135.1nm/RIU suggesting reduced access to the GNPs within the films. Copyright © 2016 Elsevier Inc. All rights reserved.

Tunable swelling of polyelectrolyte multilayers in cell culture media for modulating NIH-3T3 cells adhesion.

PubMed

Qi, Wei; Cai, Peng; Yuan, Wenjing; Wang, Hua

2014-11-01

For polyelectrolyte multilayers (PEMs) assembled by the layer-by-layer (LbL) assembly technique, their nanostructure and properties can be governed by many parameters during the building process. Here, it was demonstrated that the swelling of the PEMs containing poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS) in cell culture media could be tuned with changing supporting salt solutions during the assembly process. Importantly, the influence of the PEMs assembled in different salt solutions on NIH-3T3 cell adhesion was observable. Specifically, the cells could possess a higher affinity for the films assembled in low salt concentration (i.e. 0.15M NaCl) or no salt, the poorly swelling films in cell culture media, which was manifested by the large cell spreading area and focal adhesions. In contrast, those were assembled in higher salt concentration, highly swelling films in cell culture media, were less attractive for the fibroblasts. As a result, the cell adhesion behaviors may be manipulated by tailoring the physicochemical properties of the films, which could be performed by changing the assembly conditions such as supporting salt concentration. Such a finding might promise a great potential in designing desired biomaterials for tissue engineering and regenerative medicine. © 2014 Wiley Periodicals, Inc.

Adsorption of nonuniformly charged fullerene-like nanoparticles on planar polyelectrolyte brushes in aqueous solutions.

PubMed

Hu, Yiyu; Cao, Dapeng

2009-05-05

On the basis of the coarse grained model, we investigated the adsorption of nonuniformly charged fullerene-like nanoparticles on planar polyelectrolyte brushes (PEBs) in aqueous solution by using Brownian dynamics simulation. It is found that the electroneutral nanoparticles can be adsorbed by the PEB, which is attributed to the asymmetrical electrostatic interactions of the PEB with the positively charged sites and negatively charged sites of the fullerene-like nanoparticles. The simulation results indicated that the adsorption amount exhibits non-monotonic behavior with the dipole moment of nanoparticles. First, the adsorption amount increases with the dipole moment and then reaches the maximum at the dipole moment of micro = 10.45. Finally, the adsorption falls at the dipole moment of micro = 14.39. The reason may be that, at the extremely large dipole moment of micro = 14.39, the fullerene-like nanoparticles aggregate together to form a big cluster in the bulk phase, which can be confirmed by the extremely high peak in the radial distribution function between nanoparticles. Accordingly, it is difficult for nanoparticles to enter into the PEB at the dipole moment of micro = 14.39. In addition, it is also found that the brush grafting density is an important factor affecting the brush thickness.

Self-assembled carrageenan/protamine polyelectrolyte nanoplexes-Investigation of critical parameters governing their formation and characteristics.

PubMed

Dul, Maria; Paluch, Krzysztof J; Kelly, Hazel; Healy, Anne Marie; Sasse, Astrid; Tajber, Lidia

2015-06-05

The aim of this work was to investigate the feasibility of cross-linker free polyelectrolyte complex formation at the nanoscale between carrageenan (CAR) and protamine (PROT). The properties of CAR/PROT nanoparticles (NPs) were dependent on the carrageenan type: kappa (KC), iota (IC) and lambda (LC), concentration of components, addition of divalent cations, weight mixing ratio (WMR) of constituents and mode of component addition. In the case of 0.1% w/v solutions, IC-based NPs had the smallest particle sizes (100-150nm) and low polydispersity indices (0.1-0.4). A decrease in the solution concentration from 0.1% to 0.05% w/v enabled the formation of KC/PROT NPs. All carrageenans exhibited the ability to form NPs with surface charge ranging from -190 to 40mV. The inclusion of divalent cations caused an increase in the particle size and zeta potential. Infrared analysis confirmed the presence of a complex between CAR and PROT and showed that IC chains undergo structural changes when forming NPs. Colloidal stability of NPs was related to the initial surface charge of particles and was time- and pH-dependent. IC was found to be the most suitable type of CAR when forming nanoplexes with PROT. Copyright © 2015 Elsevier Ltd. All rights reserved.

Modification of Bacterial Cellulose Biofilms with Xylan Polyelectrolytes.

PubMed

Santos, Sara M; Carbajo, José M; Gómez, Nuria; Ladero, Miguel; Villar, Juan C

2017-11-28

The effect of the addition of two [4-butyltrimethylammonium]-xylan chloride polyelectrolytes (BTMAXs) on bacterial cellulose (BC) was evaluated. The first strategy was to add the polyelectrolytes to the culture medium together with a cell suspension of the bacterium. After one week of cultivation, the films were collected and purified. The second approach consisted of obtaining a purified and homogenized BC, to which the polyelectrolytes were added subsequently. The films were characterized in terms of tear and burst indexes, optical properties, surface free energy, static contact angle, Gurley porosity, SEM, X-ray diffraction and AFM. Although there are small differences in mechanical and optical properties between the nanocomposites and control films, the films obtained by BC synthesis in the presence of BTMAXs were remarkably less opaque, rougher, and had a much lower specular gloss. The surface free energy depends on the BTMAXs addition method. The crystallinity of the composites is lower than that of the control material, with a higher reduction of this parameter in the composites obtained by adding the BTMAXs to the culture medium. In view of these results, it can be concluded that BC-BTMAX composites are a promising new material, for example, for paper restoration.

Enhancing gelation ability of a dendritic gelator through complexation with a polyelectrolyte.

PubMed

Zhang, Zijian; Yang, Miao; Zhang, Xinjun; Zhang, Lichu; Liu, Bo; Zheng, Ping; Wang, Wei

2009-01-01

A poly(urethane amide) (PUA) dendron with long alkyl chains on its periphery was synthesized and then attached to the backbone of a polyelectrolyte, in which each unit contained a positive charge, by ionizing the carboxyl groups on the apexes of the dendrons to form a dendronized polymer. We found that both the PUA dendron and the dendronized polymer could form organogels in toluene. Interestingly, both the minimum gelation concentration and the gelation time of the dendronized polymer gelator were greatly reduced compared with the dendron alone. Our investigations showed that in the gel phase the intermolecular hydrogen bonding between adjacent dendrons creates similar supramolecular structures in both the dendron and the dendronized polymer gelator, which immobilize solvent molecules by means of interactions between dendrons and solvent molecules. Further studies on the gelation kinetics indicated that the polyelectrolyte backbone plays an important role in prearranging the attached dendritic gelators orderly and quickly into the supramolecular structures through a nucleation-elongation mechanism. Therefore, the gel-forming ability of the dendritic PUA gelator is enhanced by being complexed with the polyelectrolyte. In this work, this positive macromolecular effect is discussed in detail.

Polyelectrolyte-Functionalized Nanofiber Mats Control the Collection and Inactivation of Escherichia coli

PubMed Central

Rieger, Katrina A.; Porter, Michael; Schiffman, Jessica D.

2016-01-01

Quantifying the effect that nanofiber mat chemistry and hydrophilicity have on microorganism collection and inactivation is critical in biomedical applications. In this study, the collection and inactivation of Escherichia coli K12 was examined using cellulose nanofiber mats that were surface-functionalized using three polyelectrolytes: poly (acrylic acid) (PAA), chitosan (CS), and polydiallyldimethylammonium chloride (pDADMAC). The polyelectrolyte functionalized nanofiber mats retained the cylindrical morphology and average fiber diameter (~0.84 µm) of the underlying cellulose nanofibers. X-ray photoelectron spectroscopy (XPS) and contact angle measurements confirmed the presence of polycations or polyanions on the surface of the nanofiber mats. Both the control cellulose and pDADMAC-functionalized nanofiber mats exhibited a high collection of E. coli K12, which suggests that mat hydrophilicity may play a larger role than surface charge on cell collection. While the minimum concentration of polycations needed to inhibit E. coli K12 was 800 µg/mL for both CS and pDADMAC, once immobilized, pDADMAC-functionalized nanofiber mats exhibited a higher inactivation of E. coli K12, (~97%). Here, we demonstrate that the collection and inactivation of microorganisms by electrospun cellulose nanofiber mats can be tailored through a facile polyelectrolyte functionalization process. PMID:28773422

Modeling pH-Responsive Adsorption of Polyelectrolytes at Oil-Water Interfaces

NASA Astrophysics Data System (ADS)

Qin, Shiyi; Yong, Xin

We use dissipative particle dynamics (DPD) to discover the interfacial adsorption of pH-responsive polyelectrolytes in oil-water binary systems under different pH values. The electrostatic interactions between charged beads and the dielectric discontinuity across the interface are modeled by exploiting a modified Particle-Particle-Particle-Mesh (PPPM) method, which uses an iterative method to solve the Poisson equation on a uniform grid. We first model the adsorption behavior of a single linear polyelectrolyte from the aqueous phase. The Henderson-Hasselbalch equation describes the relation between pH and the degree of ionization of the modeled polyelectrolytes. Through changing the degree of ionization, we explore the influence of pH on the adsorption behavior and show that the electrostatic interactions significantly modulate the adsorption. Time evolutions of the position and conformation of the polyelectrolytes and the variation in the oil-water surface tension will be measured to characterize the adsorption behavior. Furthermore, we model the pH-dependent adsorption behavior of polyelectrolytes with more complicated structures, namely, branched polyelectrolytes with hydrophobic backbones and hydrophilic side chains. We also find that the addition of salts in the medium and the lengths of the backbone and ionized side chain affect the adsorption. This research supported by the American Chemical Society Petroleum Research Fund (Award 56884-DNI9).

Liquid-liquid phase separation in dilute solutions of poly(styrene sulfonate) with multivalent cations: Phase diagrams, chain morphology, and impact of temperature

NASA Astrophysics Data System (ADS)

Hansch, Markus; Hämisch, Benjamin; Schweins, Ralf; Prévost, Sylvain; Huber, Klaus

2018-01-01

The dilute solution behavior of sodium poly(styrene sulfonate) is studied in the presence of trivalent Al3+ and bivalent Ba2+ cations at various levels of excess NaCl. The study evaluates the phase behavior and the morphology of the polyelectrolyte chains with increasing extent of decoration with the Al3+ and Ba2+ cations and analyses the effect of temperature on these decorated chains. The phase behavior is presented in the form of the cation concentration versus the respective poly(styrene sulfonate) concentration, recorded at the onset of precipitation. Whereas poly(styrene sulfonate) with Al3+ exhibits a linear phase boundary, denoted as the "threshold line," which increases with increasing poly(styrene sulfonate) concentration, Ba2+ cations show a threshold line which is independent of the poly(styrene sulfonate) concentration. An additional re-entrant phase, at considerably higher cation content than those of the threshold lines, is observed with Al3+ cations but not with Ba2+ cations. The threshold line and the re-entrant phase boundary form parts of the liquid-liquid phase boundary observed at the limit of low polymer concentration. The dimensions of the polyelectrolyte chains shrink considerably while approaching the respective threshold lines on increase of the Al3+ and Ba2+ cation content. However, subtle differences occur between the morphological transformation induced by Al3+ and Ba2+. Most strikingly, coils decorated with Al3+ respond very differently to temperature variations than coils decorated with Ba2+ do. As the temperature increases, the poly(styrene sulfonate) chains decrease their size in the presence of Al3+ cations but increase in size in the presence of Ba2+ cations.

Nanomechanics of layer-by-layer polyelectrolyte complexes: a manifestation of ionic cross-links and fixed charges.

PubMed

Han, Biao; Chery, Daphney R; Yin, Jie; Lu, X Lucas; Lee, Daeyeon; Han, Lin

2016-01-28

This study investigates the roles of two distinct features of ionically cross-linked polyelectrolyte networks - ionic cross-links and fixed charges - in determining their nanomechanical properties. The layer-by-layer assembled poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) network is used as the model material. The densities of ionic cross-links and fixed charges are modulated through solution pH and ionic strength (IS), and the swelling ratio, elastic and viscoelastic properties are quantified via an array of atomic force microscopy (AFM)-based nanomechanical tools. The roles of ionic cross-links are underscored by the distinctive elastic and viscoelastic nanomechanical characters observed here. First, as ionic cross-links are highly sensitive to solution conditions, the instantaneous modulus, E0, exhibits orders-of-magnitude changes upon pH- and IS-governed swelling, distinctive from the rubber elasticity prediction based on permanent covalent cross-links. Second, ionic cross-links can break and self-re-form, and this mechanism dominates force relaxation of PAH/PAA under a constant indentation depth. In most states, the degree of relaxation is >90%, independent of ionic cross-link density. The importance of fixed charges is highlighted by the unexpectedly more elastic nature of the network despite low ionic cross-link density at pH 2.0, IS 0.01 M. Here, the complex is a net charged, loosely cross-linked, where the degree of relaxation is attenuated to ≈50% due to increased elastic contribution arising from fixed charge-induced Donnan osmotic pressure. In addition, this study develops a new method for quantifying the thickness of highly swollen polymer hydrogel films. It also underscores important technical considerations when performing nanomechanical tests on highly rate-dependent polymer hydrogel networks. These results provide new insights into the nanomechanical characters of ionic polyelectrolyte complexes, and lay the ground for further investigation of their unique time-dependent properties.

Enzyme-polyelectrolyte complexes in water-ethanol mixtures: negatively charged groups artificially introduced into alpha-chymotrypsin provide additional activation and stabilization effects.

PubMed

Kudryashova, E V; Gladilin, A K; Vakurov, A V; Heitz, F; Levashov, A V; Mozhaev, V V

1997-07-20

Formation of noncovalent complexes between alpha-chymotrypsin (CT) and a polyelectrolyte, polybrene (PB), has been shown to produce two major effects on enzymatic reactions in binary mixtures of polar organic cosolvents with water. (i) At moderate concentrations of organic cosolvents (10% to 30% v/v), enzymatic activity of CT is higher than in aqueous solutions, and this activation effect is more significant for CT in complex with PB (5- to 7-fold) than for free enzyme (1.5- to 2.5-fold). (ii) The range of cosolvent concentrations that the enzyme tolerates without complete loss of catalytic activity is much broader. For enhancement of enzyme stability in the complex with the polycation, the number of negatively charged groups in the protein has been artificially increased by using chemical modification with pyromellitic and succinic anhydrides. Additional activation effect at moderate concentrations of ethanol and enhanced resistance of the enzyme toward inactivation at high concentrations of the organic solvent have been observed for the modified preparations of CT in the complex with PB as compared with an analogous complex of the native enzyme. Structural changes behind alterations in enzyme activity in water-ethanol mixtures have been studied by the method of circular dichroism (CD). Protein conformation of all CT preparations has not changed significantly up to 30% v/v of ethanol where activation effects in enzymatic catalysis were most pronounced. At higher concentrations of ethanol, structural changes in the protein have been observed for different forms of CT that were well correlated with a decrease in enzymatic activity. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 267-277, 1997.

Enzyme-polyelectrolyte multilayer assemblies on reduced graphene oxide field-effect transistors for biosensing applications.

PubMed

Piccinini, Esteban; Bliem, Christina; Reiner-Rozman, Ciril; Battaglini, Fernando; Azzaroni, Omar; Knoll, Wolfgang

2017-06-15

We present the construction of layer-by-layer (LbL) assemblies of polyethylenimine and urease onto reduced-graphene-oxide based field-effect transistors (rGO FETs) for the detection of urea. This versatile biosensor platform simultaneously exploits the pH dependency of liquid-gated graphene-based transistors and the change in the local pH produced by the catalyzed hydrolysis of urea. The use of an interdigitated microchannel resulted in transistors displaying low noise, high pH sensitivity (20.3µA/pH) and transconductance values up to 800 µS. The modification of rGO FETs with a weak polyelectrolyte improved the pH response because of its transducing properties by electrostatic gating effects. In the presence of urea, the urease-modified rGO FETs showed a shift in the Dirac point due to the change in the local pH close to the graphene surface. Markedly, these devices operated at very low voltages (less than 500mV) and were able to monitor urea in the range of 1-1000µm, with a limit of detection (LOD) down to 1µm, fast response and good long-term stability. The urea-response of the transistors was enhanced by increasing the number of bilayers due to the increment of the enzyme surface coverage onto the channel. Moreover, quantification of the heavy metal Cu 2+ (with a LOD down to 10nM) was performed in aqueous solution by taking advantage of the urease specific inhibition. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Electric double layer electrostatics of pH-responsive spherical polyelectrolyte brushes in the decoupled regime.

PubMed

Li, Hao; Chen, Guang; Das, Siddhartha

2016-11-01

Understanding the behavior and properties of spherical polyelectrolyte brushes (SPEBs), which are polyelectrolyte brushes grafted to a spherical core, is fundamental to many applications in biomedical, chemical and petroleum engineering as well as in pharmaceutics. In this paper, we study the pH-responsive electrostatics of such SPEBs in the decoupled regime. In the first part of the paper, we derive the scaling conditions in terms of the grafting density of the PEs on the spherical core that ensure that the analysis can be performed in the decoupled regime. In such a regime the elastic and the excluded volume effects of polyelectrolyte brushes (PEBs) can be decoupled from the electrostatic effects associated with the PE charge and the induced EDL. As a consequence the PE brush height, assumed to be dictated by the balance of the elastic and excluded volume effects, can be independent of the electrostatic effects. In the second part, we quantify the pH-responsive electrostatics of the SPEBs - we pinpoint that the radial monomer distribution for a given brush molecule exhibit a non-unique cubic distribution that decays away from the spherical core. Such a monomer distribution ensures that the hydrogen ion concentration is appropriately accounted for in the description of the SPEB thermodynamics. We anticipate that the present analysis, which provides possibly one of the first models for probing the electrostatics of pH-responsive SPEBs in a thermodynamically-consistent framework, will be vital for understanding the behavior of a large number of entities ranging from PE-coated NPs and stealth liposomes to biomolecules like bacteria and viruses. Copyright © 2016 Elsevier B.V. All rights reserved.

Diffusion of Sites versus Polymers in Polyelectrolyte Complexes and Multilayers.

PubMed

Fares, Hadi M; Schlenoff, Joseph B

2017-10-18

It has long been assumed that the spontaneous formation of materials such as complexes and multilayers from charged polymers depends on (inter)diffusion of these polyelectrolytes. Here, we separately examine the mass transport of polymer molecules and extrinsic sites-charged polyelectrolyte repeat units balanced by counterions-within thin films of polyelectrolyte complex, PEC, using sensitive isotopic labeling techniques. The apparent diffusion coefficients of these sites within PEC films of poly(diallyldimethylammonium), PDADMA, and poly(styrenesulfonate), PSS, are at least 2 orders of magnitude faster than the diffusion of polyelectrolytes themselves. This is because site diffusion requires only local rearrangements of polyelectrolyte repeat units, placing far fewer kinetic limitations on the assembly of polyelectrolyte complexes in all of their forms. Site diffusion strongly depends on the salt concentration (ionic strength) of the environment, and diffusion of PDADMA sites is faster than that of PSS sites, accounting for the asymmetric nature of multilayer growth. Site diffusion is responsible for multilayer growth in the linear and into the exponential regimes, which explains how PDADMA can mysteriously "pass through" layers of PSS. Using quantitative relationships between site diffusion coefficient and salt concentration, conditions were identified that allowed the diffusion length to always exceed the film thickness, leading to full exponential growth over 3 orders of magnitude thickness. Both site and polymer diffusion were independent of molecular weight, suggesting that ion pairing density is a limiting factor. Polyelectrolyte complexes are examples of a broader class of dynamic bulk polymeric materials that (self-) assemble via the transport of cross-links or defects rather than actual molecules.

Solution-processed small-molecule solar cells: breaking the 10% power conversion efficiency.

PubMed

Liu, Yongsheng; Chen, Chun-Chao; Hong, Ziruo; Gao, Jing; Yang, Yang Michael; Zhou, Huanping; Dou, Letian; Li, Gang; Yang, Yang

2013-11-28

A two-dimensional conjugated small molecule (SMPV1) was designed and synthesized for high performance solution-processed organic solar cells. This study explores the photovoltaic properties of this molecule as a donor, with a fullerene derivative as an acceptor, using solution processing in single junction and double junction tandem solar cells. The single junction solar cells based on SMPV1 exhibited a certified power conversion efficiency of 8.02% under AM 1.5 G irradiation (100 mW cm(-2)). A homo-tandem solar cell based on SMPV1 was constructed with a novel interlayer (or tunnel junction) consisting of bilayer conjugated polyelectrolyte, demonstrating an unprecedented PCE of 10.1%. These results strongly suggest solution-processed small molecular materials are excellent candidates for organic solar cells.

Capillary electrophoresis of chitooligosaccharides in acidic solution: simple determination using a quaternary-ammonium-modified column and indirect photometric detection with crystal violet.

PubMed

Hattori, Toshiaki; Anraku, Nobuhiro; Kato, Ryo

2010-02-01

Five chitosan oligosaccharides were separated in acidic aqueous solution by capillary electrophoresis (CE) with indirect photometric detection using a positively coated capillary. Electrophoretic mobility of the chitooligosaccharides (COSs) depended on the number of monomer units in acidic aqueous solution, similar to other polyelectrolyte oligomers. The separation was developed in nitric acid aqueous solution at pH 3.0 with 1 mM Crystal Violet, using a capillary positively coated with N-trimethoxypropyl-N,N,N-trimethylammonium chloride. The limit of the detection for chitooligosaccharides with two to six saccharide chains was less than 5 microM. CE determination of an enzymatically hydrolyzed COS agreed with results from HPLC. 2009 Elsevier B.V. All rights reserved.

Biocompatible Polyelectrolyte Complex Nanoparticles from Lactoferrin and Pectin as Potential Vehicles for Antioxidative Curcumin.

PubMed

Yan, Jing-Kun; Qiu, Wen-Yi; Wang, Yao-Yao; Wu, Jian-Yong

2017-07-19

Polyelectrolyte complex nanoparticles (PEC NPs) were fabricated via electrostatic interactions between positively charged heat-denatured lactoferrin (LF) particles and negatively charged pectin. The obtained PEC NPs were then utilized as curcumin carriers. PEC NPs were prepared by mixing 1.0 mg/mL solutions of heat-denatured LF and pectin at a mass ratio of 1:1 (w/w) in the absence of NaCl at pH 4.50. PEC NPs that were prepared under optimized conditions were spherical in shape with a particle size of ∼208 nm and zeta potential of ∼-32 mV. Hydrophobic curcumin was successfully encapsulated into LF/pectin PEC NPs with high encapsulation efficiency (∼85.3%) and loading content (∼13.4%). The in vitro controlled release and prominent antioxidant activities of curcumin from LF/pectin PEC NPs were observed. The present work provides a facile and fast method to synthesize nanoscale food-grade delivery systems for the improved water solubility, controlled release, and antioxidant activity of hydrophobic curcumin.

Preparation of polyelectrolytes for wastewater treatment.

PubMed

Radoiu, Marilena T; Martin, Diana I; Calinescu, Ioan; Iovu, Horia

2004-01-02

Liquid-phase polymerisation of acrylamide-acrylic acid to form polyelectrolytes used in wastewater cleaning was examined using accelerated electron beam and microwave irradiation methods. Polymerisation was carried out in aqueous solutions at temperatures approximately 60 degrees C. Monomers total concentration was established at 40% (36% acrylamide and 4% acrylic acid). Only using the features of simultaneous radiation-induction and microwave heating can result in the formation of linear polymer chains with good water solubility and low residual monomer concentration. The flocculation capacity of the obtained polymers was tested using two wastewaters, one sampled from a slaughterhouse and the other from a vegetable oil plant. Quality indicators such as total suspended matters (TSM), chemical oxygen demand (COD), biological oxygen demand (BOD) and fat, oils and grease (FOG) were measured before and after the treatment with polymeric flocculants and compared with the results obtained in classical treatment with Al(2)(SO(4))(3). It was found that the combined treatment with polymers and Al(2)(SO(4))(3) increases the degree of purification of both wastewaters up to 99%.

Proton and metal ion binding to natural organic polyelectrolytes-II. Preliminary investigation with a peat and a humic acid

USGS Publications Warehouse

Marinsky, J.A.; Reddy, M.M.

1984-01-01

We summarize here experimental studies of proton and metal ion binding to a peat and a humic acid. Data analysis is based on a unified physico-chemical model for reaction of simple ions with polyelectrolytes employing a modified Henderson-Hasselbalch equation. Peat exhibited an apparent intrinsic acid dissociation constant of 10-4.05, and an apparent intrinsic metal ion binding constant of: 400 for cadmium ion; 600 for zinc ion; 4000 for copper ion; 20000 for lead ion. A humic acid was found to have an apparent intrinsic proton binding constant of 10-2.6. Copper ion binding to this humic acid sample occurred at two types of sites. The first site exhibited reaction characteristics which were independent of solution pH and required the interaction of two ligands on the humic acid matrix to simultaneously complex with each copper ion. The second complex species is assumed to be a simple monodentate copper ion-carboxylate species with a stability constant of 18. ?? 1984.

An environmentally benign antimicrobial nanoparticle based on a silver-infused lignin core.

PubMed

Richter, Alexander P; Brown, Joseph S; Bharti, Bhuvnesh; Wang, Amy; Gangwal, Sumit; Houck, Keith; Cohen Hubal, Elaine A; Paunov, Vesselin N; Stoyanov, Simeon D; Velev, Orlin D

2015-09-01

Silver nanoparticles have antibacterial properties, but their use has been a cause for concern because they persist in the environment. Here, we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and, together with silver ions, can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies have shown that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles.

Material properties of novel polymeric films

NASA Astrophysics Data System (ADS)

Kim, Gene

This dissertation will study the material properties of two types of novel polymer films (polyelectrolyte multilayer films and photolithographic polymer films). The formation of polylelectrolyte multilayer films onto functionalized aluminum oxide surfaces and functionalized poly(ethylene terephthaltate) (PET) were studied. Functionalization of the aluminum oxide surfaces was achieved via silane coupling. Functionalization of PET surfaces was achieved via hydrolysis and amidation. Surface characterization techniques such as X-ray photoelectron spectroscopy (XPS) and dynamic contact angle measurements were used to monitor the polyelectrolyte multilayer formation. Mechanical properties of the aluminum oxide supported polyelectrolyte multilayer films were tested using a simplified peel test. XPS was used to analyze the surfaces before and after peel. Single lap shear joint specimens were constructed to test the adhesive shear strength of the PET-supported polyelectrolyte multilayer film samples with the aid of a cyanoacrylate adhesive. The adhesive shear strength and its relation with the type of functionalization, number of polyelectrolyte layers, and the effect of polyelectrolyte conformation using added salt were explored. Also, characterization on the single lap joints after adhesive failure was carried out to determine the locus of failure within the multilayers by using XPS and SEM. Two types of photolithographic polymers were formulated and tested. These two polymers (photocrosslinkable polyacrylate (PUA), and a photocrosslinkable polyimide (HRP)) were used to investigate factors that would affect the structural integrity of these particular polymers under environmental variables such as processing (time, UV cure, pressure, and temperature) and ink exposure. Thermomechanical characterization was carried out to see the behavior of these two polymers under these environmental variables. Microscopic techniques were employed to study the morphological behavior of the two polymer systems. Also, unique in-house characterization methods such as the vibrational holographic interferometry to measure residual stress in these polymer coatings upon processing, and the environmental tensile tester (ETT) to measure ink diffusion and swelling stresses were used to further characterize these two polymers.

Lipophilic polyelectrolyte gel derived from phosphonium borate can absorb a wide range of organic solvents.

PubMed

Sunaga, Sokuro; Kokado, Kenta; Sada, Kazuki

2018-01-24

Herein, we demonstrate a polyelectrolyte gel which can absorb a wide range of organic solvents from dimethylsulfoxide (DMSO, permittivity: ε = 47.0) to tetrahydrofuran (ε = 5.6). The gel consists of polystyrene chains with small amounts (∼5 mol%) of lipophilic electrolytes derived from triphenylphosphonium tetraaryl borate. The swelling ability of the polyelectrolyte gel was higher than that of the alkyl ammonium tetraaryl borate previously reported by us, and this is attributed to the higher compatibility with organic solvents, as well as the higher dissociating ability, of the triphenyl phosphonium salt. The role of the ionic moieties was additionally confirmed by post modification of the polyelectrolyte gel via a conventional Wittig reaction, resulting in a nonionic gel. Our findings introduced here will lead to a clear-cut molecular design for polyelectrolyte gels which absorb all solvents.

Highly sensitive self-complementary DNA nanoswitches triggered by polyelectrolytes.

PubMed

Wu, Jincai; Yu, Feng; Zhang, Zheng; Chen, Yong; Du, Jie; Maruyama, Atsushi

2016-01-07

Dimerization of two homologous strands of genomic DNA/RNA is an essential feature of retroviral replication. Herein we show that a cationic comb-type copolymer (CCC), poly(L-lysine)-graft-dextran, accelerates the dimerization of self-complementary stem-loop DNA, frequently found in functional DNA/RNA molecules, such as aptamers. Furthermore, an anionic polymer poly(sodium vinylsulfonate) (PVS) dissociates CCC from the duplex shortly within a few seconds. Then single stem-loop DNA spontaneously transforms from its dimer. Thus we can easily control the dimer and stem-loop DNA by switching on/off CCC activity. Both polyelectrolytes and DNA concentrations are in the nanomole per liter range. The polyelectrolyte-assisted transconformation and sequences design strategy ensures the reversible state control with rapid response and effective switching under physiologically relevant conditions. A further application of this sensitive assembly is to construct an aptamer-type drug delivery system, bind or release functional molecules responding to its transconformation.

Cyborg cells: functionalisation of living cells with polymers and nanomaterials.

PubMed

Fakhrullin, Rawil F; Zamaleeva, Alsu I; Minullina, Renata T; Konnova, Svetlana A; Paunov, Vesselin N

2012-06-07

Living cells interfaced with a range of polyelectrolyte coatings, magnetic and noble metal nanoparticles, hard mineral shells and other complex nanomaterials can perform functions often completely different from their original specialisation. Such "cyborg cells" are already finding a range of novel applications in areas like whole cell biosensors, bioelectronics, toxicity microscreening, tissue engineering, cell implant protection and bioanalytical chemistry. In this tutorial review, we describe the development of novel methods for functionalisation of cells with polymers and nanoparticles and comment on future advances in this technology in the light of other literature approaches. We review recent studies on the cell viability and function upon direct deposition of nanoparticles, coating with polyelectrolytes, polymer assisted assembly of nanomaterials and hard shells on the cell surface. The cell toxicity issues are considered for many practical applications in terms of possible adverse effects of the deposited polymers, polyelectrolytes and nanoparticles on the cell surface.

Regimes of electrostatic collapse of a highly charged polyelectrolyte in a poor solvent.

PubMed

Tom, Anvy Moly; Vemparala, Satyavani; Rajesh, R; Brilliantov, Nikolai V

2017-03-01

We perform extensive molecular dynamics simulations of a highly charged, collapsed, flexible polyelectrolyte chain in a poor solvent for the case when the electrostatic interactions, characterized by the reduced Bjerrum length l B , are strong. We find the existence of several sub-regimes in the dependence of the gyration radius of the chain R g on l B characterized by R g ∼ l. In contrast to a good solvent, the exponent γ for a poor solvent crucially depends on the size and valency of the counterions. To explain the different sub-regimes, we generalize the existing counterion fluctuation theory by including a more complete account of all possible volume interactions in the free energy of the polyelectrolyte chain. We also show that the presence of condensed counterions modifies the effective attraction among the chain monomers and modulates the sign of the second virial coefficient under poor solvent conditions.

Origin of translocation barriers for polyelectrolyte chains.

PubMed

Kumar, Rajeev; Muthukumar, M

2009-11-21

For single-file translocations of a charged macromolecule through a narrow pore, the crucial step of arrival of an end at the pore suffers from free energy barriers, arising from changes in intrachain electrostatic interaction, distribution of ionic clouds and solvent molecules, and conformational entropy of the chain. All contributing factors to the barrier in the initial stage of translocation are evaluated by using the self-consistent field theory for the polyelectrolyte and the coupled Poisson-Boltzmann description for ions without radial symmetry. The barrier is found to be essentially entropic due to conformational changes. For moderate and high salt concentrations, the barriers for the polyelectrolyte chain are quantitatively equivalent to that of uncharged self-avoiding walks. Electrostatic effects are shown to increase the free energy barriers, but only slightly. The degree of ionization, electrostatic interaction strength, decreasing salt concentration, and the solvent quality all result in increases in the barrier.

Effect of carboxymethylcellulose on potassium bitartrate crystallization on model solution and white wine

NASA Astrophysics Data System (ADS)

Bajul, Audrey; Gerbaud, Vincent; Teychene, Sébastien; Devatine, Audrey; Bajul, Gilles

2017-08-01

Instability in bottled wines refer to tartaric salts crystallization such as potassium bitartrate (KHT). It is not desirable as consumers see the settled salts as an evidence of a poor quality control. In some cases, it causes excessive gushing in sparkling wine. We investigate the effect of two oenological carboxymethylcellulose (CMC) for KHT inhibition in a model solution of white wine by studying the impact of some properties of CMC such as the degree of polymerization, the degree of substitution, and the apparent dissociation constant determined by potentiometric titration. Polyelectrolyte adsorption is used for determining the surface and total charge and for providing information about the availability of CMC charged groups for interacting with KHT crystal faces. The inhibitory efficiency of CMC on model solution is evaluated by measuring the induction time with the help of conductimetric methods. Crystals growth with and without CMC are studied by observation with MEB and by thermal analysis using DSC. The results confirm the effectiveness of CMC as an inhibitor of KHT crystallization in a model solution. The main hypothesis of the mechanism lies in the interaction of dissociated anionic carboxymethyl groups along the cellulose backbone with positively charged layers on KHT faces like the {0 1 0} face. Key factors such as pH, CMC chain length and total charge are discusses.

Polyelectrolyte Bundles: Finite size at thermodynamic equilibrium?

NASA Astrophysics Data System (ADS)

Sayar, Mehmet

2005-03-01

Experimental observation of finite size aggregates formed by polyelectrolytes such as DNA and F-actin, as well as synthetic polymers like poly(p-phenylene), has created a lot of attention in recent years. Here, bundle formation in rigid rod-like polyelectrolytes is studied via computer simulations. For the case of hydrophobically modified polyelectrolytes finite size bundles are observed even in the presence of only monovalent counterions. Furthermore, in the absence of a hydrophobic backbone, we have also observed formation of finite size aggregates via multivalent counterion condensation. The size distribution of such aggregates and the stability is analyzed in this study.

Novel application of polyelectrolyte multilayers as nanoscopic closures with hermetic sealing.

PubMed

Marcott, Stephanie A; Ada, Sena; Gibson, Phillip; Camesano, Terri A; Nagarajan, R

2012-03-01

Closure systems for personnel protection applications, such as protective clothing or respirator face seals, should provide effective permeation barrier to toxic gases. Currently available mechanical closure systems based on the hook and loop types (example, Velcro) do not provide adequate barrier to gas permeation. To achieve hermetic sealing, we propose a nonmechanical, nanoscopic molecular closure system based on complementary polyelectrolyte multilayers, one with a polycation outermost layer and the other with a polyanion outermost layer. The closure surfaces were prepared by depositing polyelectrolyte multilayers under a variety of deposition conditions, on conformable polymer substrates (thin films of polyethylene teraphthalate, PET or polyimide, PI). The hermetic sealing property of the closures was evaluated by measuring the air flow resistance using the dynamic moisture permeation cell (DMPC) at different humidity conditions. The DMPC measurements show that the polyelectrolyte multilayer closures provide significantly large resistance to air flow, approximately 20-800 times larger than that possible with conventional hook and loop type closure systems, at all humidity levels (from 5 to 95% relative humidity). Hence, from the point of view of providing a hermetic seal against toxic gas permeation, the polyelectrolyte multilayer closures are viable candidates for further engineering development. However, the adhesive strength of the multilayer closures measured by atomic force microscopy suggests that the magnitude of adhesion is much smaller than what is possible with mechanical closures. Therefore, we envisage the development of a composite closure system combining the mechanical closure to provide strong adhesion and the multilayer closure to provide hermetic sealing. © 2012 American Chemical Society

Novel polyelectrolyte complex based carbon nanotube composite architectures

NASA Astrophysics Data System (ADS)

Razdan, Sandeep

This study focuses on creating novel architectures of carbon nanotubes using polyelectrolytes. Polyelectrolytes are unique polymers possessing resident charges on the macromolecular chains. This property, along with their biocompatibility (true for most polymers used in this study) makes them ideal candidates for a variety of applications such as membranes, drug delivery systems, scaffold materials etc. Carbon nanotubes are also unique one-dimensional nanoscale materials that possess excellent electrical, mechanical and thermal properties owing to their small size, high aspect ratio, graphitic structure and strength arising from purely covalent bonds in the molecular structure. The present study tries to investigate the synthesis processes and material properties of carbon nanotube composites comprising of polyelectrolyte complexes. Carbon nanotubes are dispersed in a polyelectrolyte and are induced into taking part in a complexation process with two oppositely charged polyelectrolytes. The resulting stoichiometric precipitate is then drawn into fiber form and dried as such. The material properties of the carbon nanotube fibers were characterized and related to synthesis parameters and material interactions. Also, an effort was made to understand and predict fiber morphology resulting from the complexation and drawing process. The study helps to delineate the synthesis and properties of the said polyelectrolyte complex-carbon nanotube architectures and highlights useful properties, such as electrical conductivity and mechanical strength, which could make these structures promising candidates for a variety of applications.

Bistability in Doped Organic Thin Film Transistors (Preprint)

DTIC Science & Technology

2007-03-01

small molecules (e.g. pentacene ). As such, they do not necessarily compete with these more typical organic transistors, but rather have pertinence...involves dipping a substrate between two dilute polyelectrolyte solutions of opposite charge to build up a thin film via the electrostatic interactions...recovery is due to trapped O2(g) remaining in the film, which causes the reverse of reaction (1) to occur and the concomitant increase in the level of

Thermodynamic analysis of the interaction of partially hydrophobic cationic polyelectrolytes with sodium halide salts in water

NASA Astrophysics Data System (ADS)

Bončina, Matjaž; Lukšič, Miha; Seručnik, Mojca; Vlachy, Vojko

2014-05-01

Isothermal titration calorimetry was used to determine the temperature and concentration dependence of the enthalpy of mixing of 3,3- and 6,6-ionene fluorides, bromides, and iodides with low molecular weight salts (NaF, NaCl, NaBr, and NaI) in water. The magnitudes of the enthalpies, measured in the temperature range from 273 to 318 K, depended on the number of methylene groups on the ionene polyion (hydrophobicity), and on the anion of the added salt (ion-specificity). All enthalpies of mixing of 3,3- and 6,6-ionene fluorides with low molecular weight salts (NaCl, NaBr, and NaI) were negative, which is in contrast to the predictions of standard theories of polyelectrolyte solutions. This fact was interpreted in the light of the ion-water short-range interactions that are not accounted for in those theories. In contrast, the enthalpies of mixing of 3,3- and 6,6-ionene bromides and iodides with NaF were positive, being in accord with theory. Using the calorimetric data, we performed a model thermodynamic analysis of the polyelectrolyte-salt mixing process to obtain changes in the apparent standard Gibbs free energy, enthalpy, entropy, and heat capacity relative to the pure ionene fluorides in water. The results prove that halide ions replace fluoride counterions with a strength increasing in the order chloride < bromide < iodide. The process is enthalpy governed, accompanied by a positive change in the heat capacity.

Laser-induced fast fusion of gold nanoparticle-modified polyelectrolyte microcapsules.

PubMed

Wu, Yingjie; Frueh, Johannes; Si, Tieyan; Möhwald, Helmuth; He, Qiang

2015-02-07

In this study we investigated the effect of laser-induced membrane fusion of polyelectrolyte multilayer (PEM) based microcapsules bearing surface-attached gold nanoparticles (AuNPs) in aqueous media. We demonstrate that a dense coating of the capsules with AuNPs leads to enhanced light absorption, causing an increase of local temperature. This enhances the migration of polyelectrolytes within the PEMs and thus enables a complete fusion of two or more capsules. The encapsulated substances can achieve complete merging upon short-term laser irradiation (30 s, 30 mW @ 650 nm). The whole fusion process is followed by optical microscopy and scanning electron microscopy. In control experiments, microcapsules without AuNPs do not show a significant capsule fusion upon irradiation. It was also found that the duration of capsule fusion is affected by the density of AuNPs on the shell - the higher the density of AuNPs the shorter the fusion time. All these findings confirm that laser-induced microcapsule fusion is a new type of membrane fusion. This effect helps to study the interior exchange reactions of functional microcapsules, micro-reactors and drug transport across multilayers.

Gelatin Nano-coating for Inhibiting Surface Crystallization of Amorphous Drugs.

PubMed

Teerakapibal, Rattavut; Gui, Yue; Yu, Lian

2018-01-05

Inhibit the fast surface crystallization of amorphous drugs with gelatin nano-coatings. The free surface of amorphous films of indomethacin or nifedipine was coated by a gelatin solution (type A or B) and dried. The coating's effect on surface crystallization was evaluated. Coating thickness was estimated from mass change after coating. For indomethacin (weak acid, pK a  = 4.5), a gelatin coating of either type deposited at pH 5 and 10 inhibited its fast surface crystal growth. The coating thickness was 20 ± 10 nm. A gelatin coating deposited at pH 3, however, provided no protective effect. These results suggest that an effective gelatin coating does not require that the drug and the polymer have opposite charges. The ineffective pH 3 coating might reflect the poor wetting of indomethacin's neutral, hydrophobic surface by the coating solution. For nifedipine (weak base, pK a  = 2.6), a gelatin coating of either type deposited at pH 5 inhibited its fast surface crystal growth. Gelatin nano-coatings can be conveniently applied to amorphous drugs from solution to inhibit fast surface crystallization. Unlike strong polyelectrolyte coatings, a protective gelatin coating does not require strict pairing of opposite charges. This could make gelatin coating a versatile, pharmaceutically acceptable coating for stabilizing amorphous drugs.

Electrically driven ion separations and nanofiltration through membranes coated with polyelectrolyte multilayers

NASA Astrophysics Data System (ADS)

White, Nicholas

Polyelectrolyte multilayer (PEM) films deposited using the layer-by-layer (LBL) method are attractive for their simple deposition, tailorable nature, scalability, and charge or size-based selectivity for solutes. This dissertation explores ion separations in electrodialysis (ED) and solute removal through nanofiltration with PEMs deposited on polymer membranes. ED membranes typically exhibit modest selectivities between monovalent and divalent ions. In contrast, this work shows that K+/Mg 2+ ED selectivities reach values >1000 when using Nafion 115 cation-exchange membranes coated with multilayer poly(4-styrenesulfonate) (PSS)/protonated poly(allylamine) (PAH) films. For comparison, the corresponding K+ /Mg2+ selectivity of bare Nafion 115 is <2. However, water-splitting at strongly overlimiting current densities may lead to a local pH increase close to the membrane surface and alter film permeability or allow passage of Mg(OH)x species to decrease selectivity. When the source phase contains high salt concentrations, the K+ transference number approaches unity and the K+/Mg2+ selectivity is >20,000, presumably because the applied current is below the limiting value for K+ and H+ transport is negligible at this high K+ concentration. The high selectivities of these membranes may enable electrodialysis applications such as purification of salts that contain divalent or trivalent ions. The high ED selectivities of (PAH/PSS)5PAH-coated Nafion membranes translate to separations with Li+/Co2+ and K +/La3+. Even with adsorption of only 3 polyelectrolyte layers, Nafion membranes exhibit a Li+/Co2+ selectivity >23. However, the resistance to monovalent-ion passage does not decrease significantly with fewer polyelectrolyte layers. At overlimiting currents, hydroxides from water splitting form insoluble metal hydroxides to foul the membrane. With 0.1 M source-phase salt concentrations, transference numbers for monovalent cations approach unity and selectivities are >5000 because the diffusion-limited K+ or Li+ currents exceed the applied current. However, ED selectivities gradually decline with time. Thus, future research should aim to increase membrane stability and limiting currents to fully exploit the remarkable selectivity of these membranes. PEMs deposited on commercial ultrafiltration (UF) membranes also show high rejections of organic dyes. Coating the surface of polyethersulfone (PES) membranes imparts a selective barrier to dye molecules used in textile production. These films achieve dye rejections >98% and may be useful for wastewater treatment and dye recovery. Other studies in microfluidic channels exploit ion transport phenomena in the vicinity of ion-selective junctions, such as cation-exchange membranes. These studies suggest that ion concentration polarization (ICP) could remove charged species from feed streams.

Colloidal titration of aqueous zirconium solutions with poly(vinyl sulfate) by potentiometric endpoint detection using a toluidine blue selective electrode.

PubMed

Sakurada, Osamu; Kato, Yasutake; Kito, Noriyoshi; Kameyama, Keiichi; Hattori, Toshiaki; Hashiba, Minoru

2004-02-01

Zirconium oxy-salts were hydrolyzed to form positively charged polymer or cluster species in acidic solutions. The zirconium hydrolyzed polymer was found to react with a negatively charged polyelectrolyte, such as poly(vinyl sulfate), and to form a stoichiometric polyion complex. Thus, colloidal titration with poly(vinyl sulfate) was applied to measure the zirconium concentration in an acidic solution by using a Toluidine Blue selective plasticized poly(vinyl chloride) membrane electrode as a potentiometric end-point detecting device. The determination could be performed with 1% of the relative standard deviation. The colloidal titration stoichiometry at pH < or = 2 was one mol of zirconium per equivalent mol of poly(vinyl sulfate).

Periodic nanoscale patterning of polyelectrolytes over square centimeter areas using block copolymer templates

DOE PAGES

Oded, Meirav; Kelly, Stephen T.; Gilles, Mary K.; ...

2016-04-07

Nano-patterned materials are beneficial for applications such as solar cells, opto-electronics, and sensing owing to their periodic structure and high interfacial area. We present a non-lithographic approach for assembling polyelectrolytes into periodic nanoscale patterns over cm 2 -scale areas. We used chemically modified block copolymer thin films featuring alternating charged and neutral domains as patterned substrates for electrostatic self-assembly. In-depth characterization of the deposition process using spectroscopy and microscopy techniques, including the state-of-the-art scanning transmission X-ray microscopy (STXM), reveals both the selective deposition of the polyelectrolyte on the charged copolymer domains as well as gradual changes in the film topographymore » that arise from further penetration of the solvent molecules and possibly also the polyelectrolyte into these domains. Our results demonstrate the feasibility of creating nano-patterned polyelectrolyte layers, which opens up new opportunities for structured functional coating fabrication.« less

Release mechanism of doxazosin from carrageenan matrix tablets: Effect of ionic strength and addition of sodium dodecyl sulphate.

PubMed

Kos, Petra; Pavli, Matej; Baumgartner, Saša; Kogej, Ksenija

2017-08-30

The polyelectrolyte matrix tablets loaded with an oppositely charged drug exhibit complex drug-release mechanisms. In this study, the release mechanism of a cationic drug doxazosin mesylate (DM) from matrix tablets based on an anionic polyelectrolyte λ-carrageenan (λ-CARR) is investigated. The drug release rates from λ-CARR matrices are correlated with binding results based on potentiometric measurements using the DM ion-sensitive membrane electrode and with molecular characteristics of the DM-λ-CARR-complex particles through hydrodynamic size measurements. Experiments are performed in solutions with different ionic strength and with the addition of an anionic surfactant sodium dodecyl sulphate (SDS). It is demonstrated that in addition to swelling and erosion of tablets, the release rates depend strongly on cooperative interactions between DM and λ-CARR. Addition of SDS at concentrations below its critical micelle concentration (CMC) slows down the DM release through hydrophobic binding of SDS to the DM-λ-CARR complex. On the contrary, at concentrations above the CMC SDS pulls DM from the complex by forming mixed micelles with it and thus accelerates the release. Results involving SDS show that the concentration of surfactants that are naturally present in gastrointestinal environment may have a great impact on the drug release process. Copyright © 2017 Elsevier B.V. All rights reserved.

Cadmium Removal from Contaminated Water Using Polyelectrolyte-Coated Industrial Waste Fly Ash

PubMed Central

Olabemiwo, Fatai A.; Oyehan, Tajudeen A.; Khaled, Mazen

2017-01-01

Fly ash (FA) is a major industrial waste generated from power stations that add extra cost for proper disposal. Recent research efforts have consequently focused on developing ways to make use of FA in environmentally sound applications. This study, therefore, investigates the potential ability of raw fly ash (RFA) and polyelectrolyte-coated fly ash (PEFA) to remove cadmium (Cd) from polluted water. Using layer-by-layer approach, functionalized fly ash was coated with 20 layers from 0.03% (v/v) of cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic polystyrene sulfonate (PSS) solutions. Both surface morphology and chemical composition of the adsorbent (PEFA) were characterized using Field-Emission Scanning Electron Microscope (FE-SEM), X-Ray Diffraction (XRD), Fourier-Transform Infrared (FTIR), and X-Ray Fluorescence (XRF) techniques. The effects of pH, adsorbent dosage, contact time, initial contaminant concentration, and mixing rate of the adsorption of Cd were also studied in batch mode experiments. Results of the study revealed that a 4.0 g/L dosage of PEFA removed around 99% of 2.0 mg/L of Cd in 15 min at 150 rpm compared to only 27% Cd removal achieved by RFA under the same conditions. Results also showed that adsorption by PEFA followed both Langmuir and Freundlich models with correlation coefficients of 98% and 99%, respectively. PMID:28680373

Target-molecule-triggered rupture of aptamer-encapsulated polyelectrolyte microcapsules.

PubMed

Zhang, Xueru; Chabot, Denise; Sultan, Yasir; Monreal, Carlos; DeRosa, Maria C

2013-06-26

Polyelectrolyte microcapsules have great potential for serving as carriers for the delivery of their contents when triggered by an external stimulus. Aptamers are synthetic ssDNA or RNA that can bind to specific targets with high affinity and selectivity. Aptamers may retain these superior molecular recognition properties after encapsulation within polymer microcapsules. In this work, stable polyelectrolyte microcapsules with encapsulated aptamers were obtained by the layer-by-layer (LbL) method. Polyelectrolyte films were deposited onto a CaCO3 template that had been predoped with polystyrene sulfonate (PSS) and aptamer sequences (SA) that have an affinity for the dye sulforhodamine B (SRB). The PSS and aptamers are thought to serve as an internal scaffold supporting the microcapsule walls. These microcapsules would present target-molecule-triggered rupture properties. Microcapsule collapse was triggered by the binding of SRB to the encapsulated aptamer. The specificity of microcapsule collapse was investigated using a similar dye, tetramethylrosamine (TMR), which does not have affinity for SA. A high concentration of TMR did not lead to the collapse of the microcapsules. The effect of target binding on the microcapsules was confirmed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). These microcapsules may have potential applications in targeted delivery systems for the controlled release of drugs, pesticides, or other payloads.

Modification of polyelectrolyte microcapsules into a container for the low molecular weight compounds

NASA Astrophysics Data System (ADS)

Goryacheva, O. A.; Gao, H.; Sukhorukov, G. B.

2018-04-01

Polyelectrolyte microcapsules are one of the most successful developments in the direction of target drug delivery. Nevertheless, to encapsulate low molecular weight compounds and to deliver the targeted drugs it is necessary to modify the surface of the microcapsules. Silica nanostructures obtained as result of hydrolysis of (3-Aminopropyl)- triethoxysilane (APTES) were used for the modification of the microcapsules. This material shows no toxic effect on cells and is capable of biodegradation. Amino-groups in the structure of APTES make it possible for further direct bioconjugation.

Concentration and Purification of Influenza Virus on Insoluble Polyelectrolytes

PubMed Central

Wallis, Craig; Homma, Akira; Melnick, Joseph L.

1972-01-01

A method for rapid concentration and purification of influenza virus by adsorption on and elution from an insoluble polyelectrolyte is described. To accomplish this task, influenza virus had to be rendered stable at pH 4 to 5, since viruses adsorb to the polyelectrolyte more efficiently at this pH range. A precipitate which forms in influenza harvests under acid conditions in the cold can be removed by ammonium sulfate at a concentration which traps the precipitate but not the virus. Thus, ammonium sulfate-treated influenza virus in allantoic fluid could be readily concentrated on the polyelectrolyte. Elution yielded a virus concentrate essentially free of nonviral proteins. PMID:4553141

Size, shape, and diffusivity of a single Debye-Hückel polyelectrolyte chain in solution.

PubMed

Soysa, W Chamath; Dünweg, B; Prakash, J Ravi

2015-08-14

Brownian dynamics simulations of a coarse-grained bead-spring chain model, with Debye-Hückel electrostatic interactions between the beads, are used to determine the root-mean-square end-to-end vector, the radius of gyration, and various shape functions (defined in terms of eigenvalues of the radius of gyration tensor) of a weakly charged polyelectrolyte chain in solution, in the limit of low polymer concentration. The long-time diffusivity is calculated from the mean square displacement of the centre of mass of the chain, with hydrodynamic interactions taken into account through the incorporation of the Rotne-Prager-Yamakawa tensor. Simulation results are interpreted in the light of the Odjik, Skolnick, Fixman, Khokhlov, and Khachaturian blob scaling theory (Everaers et al., Eur. Phys. J. E 8, 3 (2002)) which predicts that all solution properties are determined by just two scaling variables-the number of electrostatic blobs X and the reduced Debye screening length, Y. We identify three broad regimes, the ideal chain regime at small values of Y, the blob-pole regime at large values of Y, and the crossover regime at intermediate values of Y, within which the mean size, shape, and diffusivity exhibit characteristic behaviours. In particular, when simulation results are recast in terms of blob scaling variables, universal behaviour independent of the choice of bead-spring chain parameters, and the number of blobs X, is observed in the ideal chain regime and in much of the crossover regime, while the existence of logarithmic corrections to scaling in the blob-pole regime leads to non-universal behaviour.

Gordon Research Conference on Dynamics of Macromolecular and Polyelectrolyte Solutions Held in Oxnard, California on 12-16 February 1990

DTIC Science & Technology

1990-04-01

Gonzalez Mozuelos and M. Xodina-Noyola. Centro do Investigacion y do Estudlos Avrandoes del : P N Mexico "Concentration profile of a colloidal...Louis Pasteur Department of Physics Laboratoire de Spectrometrie et Stillwater, OK 74078 D’Imagerie Ultrasonores 4 Rue Blaise Pascal A. Ziya Akcasu...Degiorgio 242 Universita de Pavia Eric Amis 258 Dipartim.nto de Elettronica University of Southern California Via Abbiategrasso 209 Dept. of Chemistry

Adsorption of mixtures of poly(amidoamine) dendrimers and sodium dodecyl sulfate at the air-water interface.

PubMed

Arteta, Marianna Yanez; Campbell, Richard A; Nylander, Tommy

2014-05-27

We relate the adsorption from mixtures of well-defined poly(amidoamine) (PAMAM) dendrimers of generations 4 and 8 with sodium dodecyl sulfate (SDS) at the air-water interface to the bulk solution properties. The anionic surfactant shows strong attractive interactions with the cationic dendrimers at pH 7, and electrophoretic mobility measurements indicate that the association is primarily driven by electrostatic interactions. Optical density measurements highlight the lack of colloidal stability of the formed bulk aggregates at compositions close to charge neutrality, the time scale of which is dependent on the dendrimer generation. Adsorption at the air-water interface was followed from samples immediately after mixing using a combination of surface tension, neutron reflectometry, and ellipsometry measurements. In the phase separation region for dendrimers of generation 4, we observed high surface tension corresponding to a depleted surfactant solution but only when the aggregates carried an excess of surfactant. Interestingly, these depleted adsorption layers contained spontaneously adsorbed macroscopic aggregates, and these embedded particles do not rearrange to spread monomeric material at the interface. These findings are discussed in relation to the interfacial properties of mixtures involving dendrimers of generation 8 as well as polydisperse linear and hyperbranched polyelectrolytes where there is polyelectrolyte bound to a surfactant monolayer. The results presented here demonstrate the capability of dendrimers to sequester anionic surfactants in a controllable manner, with potential applications as demulsification and antifoaming agents.

Adsorption of polyelectrolyte-like proteins to silica surfaces and the impact of pH on the response to ionic strength. A Monte Carlo simulation and ellipsometry study.

PubMed

Hyltegren, Kristin; Skepö, Marie

2017-05-15

The adsorbed amount of the polyelectrolyte-like protein histatin 5 on a silica surface depends on the pH and the ionic strength of the solution. Interestingly, an increase in ionic strength affects the adsorbed amount differently depending on the pH of the solution, as shown by ellipsometry measurements (Hyltegren, 2016). We have tested the hypothesis that the same (qualitative) trends can be found also from a coarse-grained model that takes all charge-charge interactions into account within the frameworks of Gouy-Chapman and Debye-Hückel theories. Using the same coarse-grained model as in our previous Monte Carlo study of single protein adsorption (Hyltegren, 2016), simulations of systems with many histatin 5 molecules were performed and then compared with ellipsometry measurements. The strength of the short-ranged attractive interaction between the protein and the surface was varied. The coarse-grained model does not qualitatively reproduce the pH-dependence of the experimentally observed trends in adsorbed amount as a function of ionic strength. However, the simulations cast light on the balance between electrostatic attraction between protein and surface and electrostatic repulsion between adsorbed proteins, the deficiencies of the Langmuir isotherm, and the implications of protein charge regulation in concentrated systems. Copyright © 2017 Elsevier Inc. All rights reserved.

Counterion self-diffusion in polyelectrolyte solutions

NASA Astrophysics Data System (ADS)

Schipper, F. J. M.; Hollander, J. G.; Leyte, J. C.

1997-12-01

The self-diffusion coefficient of 0953-8984/9/50/019/img1, tetra-methylammonium 0953-8984/9/50/019/img2, tetra-ethylammonium 0953-8984/9/50/019/img3, tetra-propylammonium 0953-8984/9/50/019/img4 and tetra-butylammonium 0953-8984/9/50/019/img5 in solutions of the weak polymethacrylic acid (PMA) were measured with PFG NMR. No additional salt was present in any of the experiments. The polyion concentration and degree of neutralization were varied. The maximum relative counterion self-diffusion coefficient against polyion concentration, that was reported earlier, was observed for both alkali and tetra-alkylammonium 0953-8984/9/50/019/img6 counterions. We propose that the maximum is due to the combination of the obstruction by the polyion and the changing counterion distribution at increasing polyion concentration. An explanation of this proposal is offered in terms of the Poisson - Boltzmann - Smoluchowski (PBS) model for polyelectrolytes. Qualitative agreement of this model with experiment was found for the dependence of the counterion self-diffusion coefficient on the degree of neutralization of the polyion, on counterion radius and on polyion concentration, over a concentration range from 0.01 to 1 0953-8984/9/50/019/img7. Adaption of the theoretical obstruction, to fit the self-diffusion data of the solvent, also greatly improves the model predictions on the counterion self-diffusion.

Acquisition of Infrared Variable Angle Spectroscopic Ellipsometer (IR-VASE)

DTIC Science & Technology

2016-04-22

External Advisory Board Meeting in Rio Piedras, PR. March 2016 Quiñonez B.*, Castilla D., Almodóvar J.; “ Polysaccharide -based polyelectrolyte...April 2016 Quiñonez B.*, Castilla D., Almodóvar J.; “ Polysaccharide -based polyelectrolyte multilayers: Physicochemical characterization and in...2016 Quiñonez B.*, Castilla D., Almodóvar J.; “ Polysaccharide -based polyelectrolyte multilayers: Physicochemical characterization and in vitro

Protein encapsulation via porous CaCO3 microparticles templating.

PubMed

Volodkin, Dmitry V; Larionova, Natalia I; Sukhorukov, Gleb B

2004-01-01

Porous microparticles of calcium carbonate with an average diameter of 4.75 microm were prepared and used for protein encapsulation in polymer-filled microcapsules by means of electrostatic layer-by-layer assembly (ELbL). Loading of macromolecules in porous CaCO3 particles is affected by their molecular weight due to diffusion-limited permeation inside the particles and also by the affinity to the carbonate surface. Adsorption of various proteins and dextran was examined as a function of pH and was found to be dependent both on the charge of the microparticles and macromolecules. The electrostatic effect was shown to govern this interaction. This paper discusses the factors which can influence the adsorption capacity of proteins. A new way of protein encapsulation in polyelectrolyte microcapsules is proposed exploiting the porous, biocompatible, and decomposable microparticles from CaCO3. It consists of protein adsorption in the pores of the microparticles followed by ELbL of oppositely charged polyelectrolytes and further core dissolution. This resulted in formation of polyelectrolyte-filled capsules with protein incorporated in interpenetrating polyelectrolyte network. The properties of CaCO3 microparticles and capsules prepared were characterized by scanning electron microscopy, microelectrophoresis, and confocal laser scanning microscopy. Lactalbumin was encapsulated by means of the proposed technique yielding a content of 0.6 pg protein per microcapsule. Horseradish peroxidase saves 37% of activity after encapsulation. However, the thermostability of the enzyme was improved by encapsulation. The results demonstrate that porous CaCO3 microparticles can be applied as microtemplates for encapsulation of proteins into polyelectrolyte capsules at neutral pH as an optimal medium for a variety of bioactive material, which can also be encapsulated by the proposed method. Microcapsules filled with encapsulated material may find applications in the field of biotechnology, biochemistry, and medicine.

Fabrication and physical-chemical characterisation of polyelectrolyte microparticles: platform for controlled release of bioactives.

PubMed

Sun, Yuhui; Travas-Sejdic, Jadranka; Wen, Jingyuan; Alany, Raid G

2009-08-01

Porous CaCO(3) microparticles were fabricated by colloidal crystallization. Two oppositely charged polyelectrolytes, poly (styrene sulfonate, PSS) and poly (allylamine hydrochloride, PAH) were adsorbed layer-by-layer on the CaCO(3) templates. Polyelectrolyte microcapsules were then obtained by removing the CaCO(3) core. Scanning electron microscopy (SEM), energy-dispersion X-ray analysis (EDX), laser diffraction particle sizing and Raman spectroscopy were employed to characterize the physico-chemical properties of the constructed microcapsules. In vitro drug release studies were conducted using the model water-soluble drug Rhodamine B. Factors such as the number of polyelectrolyte layers and pH were investigated. SEM micrographs revealed uniform CaCO(3) microparticles, nearly spherical in shape with pronounced surface roughness, and highly developed interior porous structure. The surface of polyelectrolyte coated particles became rougher than the initial CaCO(3) microparticles. The acquired SEM micrographs of the (PSS/PAH)(n) microcapsules indicated that the number of layers affected the morphology of the microcapsules. The (PSS/PAH)(3) microcapsules revealed a very porous network with many holes resembling the initial morphology of CaCO(3) microparticles. Raman spectra showed peaks at 1125 cm(-1) (S=O bond) and 1600 cm(-1) (aromatic ring stretching) which represented the PSS molecule. The thickness of each layer was about 10 to 20 nm and it can be tailored to such nanometer level by controlling the number of adsorbed layers. The in vitro release of Rhodamine B was dependent on both the number of wall bilayers as well as the pH of the release media. These systems provide an opportunity for the development of controlled release dosage forms with greater effectiveness in the treatment of chronic conditions.

Layer-by-Layer Assembled Nanotubes as Biomimetic Nanoreactors for Calcium Carbonate Deposition.

PubMed

He, Qiang; Möhwald, Helmuth; Li, Junbai

2009-09-17

Enzyme-loaded magnetic polyelectrolyte multilayer nanotubes prepared by layer-by-layer assembly combined with the porous template could be used as biomimetic nanoreactors. It is demonstrated that calcium carbonate can be biomimetically synthesized inside the cavities of the polyelectrolyte nanotubes by the catalysis of urease, and the size of the calcium carbonate precipitates was controlled by the cavity dimensions. The metastable structure of the calcium carbonate precipitates inside the nanotubes was protected by the outer shell of the polyelectrolyte multilayers. These features may allow polyelectrolyte nanotubes to be applied in the fields of nanomaterials synthesis, controlled release, and drug delivery. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Water absorption and moisture permeation properties of chitosan/poly(acrylamide-co-itaconic acid) IPC films.

PubMed

Bajpai, M; Bajpai, S K; Jyotishi, Pooja

2016-03-01

In this work, aqueous solutions of chitosan (Ch) and [poly(acrylamide(AAm)-co-itaconicacid(IA)] have been mixed to yield Ch/poly(AAm-co-IA) Inter-polyelectrolyte complex (IPC) films. The films were characterized by FTIR, X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). There was remarkable increase in the crystalline nature of IPC films. The films were investigated for their water absorption capacity in the physiological fluid (PF) of pH 7.4 at 37 °C. The amount of IA present in the film forming solutions affected the water absorption behavior of the resulting films. The dynamic water uptake data were interpreted by various kinetic models. The effect of pH on the swelling ratio (SR) indicated that the films showed highest swelling in lower as well as higher pH media. The water vapor transmission rates (WVTR) were obtained in the range of 6000-6645 g/m(2)/day. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of cationic polyelectrolytes on the performance of paper diagnostics for blood typing.

PubMed

McLiesh, Heather; Sharman, Scot; Garnier, Gil

2015-09-01

We investigated the effect that two common types of cationic polyelectrolytes used in papermaking might have on the performance of paper diagnostics using blood typing as an example. The results were analyzed in terms of red blood cells (RBC) retention and antibody-antigen specificity. Two questions were addressed: (1) can poly(amido-amine) epichlorohydrin (PAE) typically used for paper wet strength affect the diagnostic performance? (2) can high molecular weight cationic polyacrylamide (CPAM) employed as retention aid enhance or affect the selectivity and sensitivity of paper diagnostics? A series of paper varying in type of fibers and drying process were constructed with PAE and tested for blood typing performance. Residual PAE has no significant effect on blood typing paper diagnostics under normal conditions. Positives are unaffected with PAE, while negatives lose slight sharpness as some RBCs are unselectively retained. CPAM, the most common retention aid, can also be used to retain cells and biomolecules on paper. Paper towel was treated with CPAM solutions varying in polymer concentration and charge density and tested for blood typing. We found that CPAM dried on paper can retain RBC. CPAM affects the negative tests by retaining non-specifically individual RBC on fibers. RBC retention increases non-linearly with the CPAM charge density and concentration. As expected, wet CPAM retain RBCs at concentrations higher than 0.1wt%. As paper diagnostics are becoming a reality, more realistic papers than the Whatman filter paper will be engineered. This study provides guidance on how best use the required polymeric wet-strength and retention agents. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

Formulation and stabilization of nano-/microdispersion systems using naturally occurring edible polyelectrolytes by electrostatic deposition and complexation.

PubMed

Kuroiwa, Takashi; Kobayashi, Isao; Chuah, Ai Mey; Nakajima, Mitsutoshi; Ichikawa, Sosaku

2015-12-01

This review paper presents an overview of the formulation and functionalization of nano-/microdispersion systems composed of edible materials. We first summarized general aspects on the stability of colloidal systems and the roles of natural polyelectrolytes such as proteins and ionic polysaccharides for the formation and stabilization of colloidal systems. Then we introduced our research topics on (1) stabilization of emulsions by the electrostatic deposition using natural polyelectrolytes and (2) formulation of stable nanodispersion systems by complexation of natural polyelectrolytes. In both cases, the preparation procedures were relatively simple, without high energy input or harmful chemical addition. The properties of the nano-/microdispersion systems, such as particle size, surface charge and dispersion stability were significantly affected by the concerned materials and preparation conditions, including the type and concentration of used natural polyelectrolytes. These dispersion systems would be useful for developing novel foods having high functionality and good stability. Copyright © 2015 Elsevier B.V. All rights reserved.

Dendritic polyelectrolytes as seen by the Poisson-Boltzmann-Flory theory.

PubMed

Kłos, J S; Milewski, J

2018-06-20

G3-G9 dendritic polyelectrolytes accompanied by counterions are investigated using the Poisson-Boltzmann-Flory theory. Within this approach we solve numerically the Poisson-Boltzmann equation for the mean electrostatic potential and minimize the Poisson-Boltzmann-Flory free energy with respect to the size of the molecules. Such a scheme enables us to inspect the conformational and electrostatic properties of the dendrimers in equilibrium based on their response to varying the dendrimer generation. The calculations indicate that the G3-G6 dendrimers exist in the polyelectrolyte regime where absorption of counterions into the volume of the molecules is minor. Trapping of ions in the interior region becomes significant for the G7-G9 dendrimers and signals the emergence of the osmotic regime. We find that the behavior of the dendritic polyelectrolytes corresponds with the degree of ion trapping. In particular, in both regimes the polyelectrolytes are swollen as compared to their neutral counterparts and the expansion factor is maximal at the crossover generation G7.

Self-assembled virus-membrane complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Lihua; Liang, Hongjun; Angelini, Thomas

Anionic polyelectrolytes and cationic lipid membranes can self-assemble into lamellar structures ranging from alternating layers of membranes and polyelectrolytes to 'missing layer' superlattice structures. We show that these structural differences can be understood in terms of the surface-charge-density mismatch between the polyelectrolyte and membrane components by examining complexes between cationic membranes and highly charged M13 viruses, a system that allowed us to vary the polyelectrolyte diameter independently of the charge density. Such virus-membrane complexes have pore sizes that are about ten times larger in area than DNA-membrane complexes, and can be used to package and organize large functional molecules; correlatedmore » arrays of Ru(bpy){sub 3}{sup 2+} macroionic dyes have been directly observed within the virus-membrane complexes using an electron-density reconstruction. These observations elucidate fundamental design rules for rational control of self-assembled polyelectrolyte-membrane structures, which have applications ranging from non-viral gene therapy to biomolecular templates for nanofabrication.« less

3D solid supported inter-polyelectrolyte complexes obtained by the alternate deposition of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate)

PubMed Central

Maestro, Armando; Llamas, Sara; Álvarez-Rodríguez, Jesús; Ortega, Francisco; Maroto-Valiente, Ángel

2016-01-01

Summary This work addresses the formation and the internal morphology of polyelectrolyte layers obtained by the layer-by-layer method. A multimodal characterization showed the absence of stratification of the films formed by the alternate deposition of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate). Indeed the final organization might be regarded as three-dimensional solid-supported inter-polyelectrolyte films. The growth mechanism of the multilayers, followed using a quartz crystal microbalance, evidences two different growth trends, which show a dependency on the ionic strength due to its influence onto the polymer conformation. The hydration state does not modify the multilayer growth, but it contributes to the total adsorbed mass of the film. The water associated with the polyelectrolyte films leads to their swelling and plastification. The use of X-ray photoelectron spectroscopy has allowed for deeper insights on the internal structure and composition of the polyelectrolyte multilayers. PMID:26977377

3D solid supported inter-polyelectrolyte complexes obtained by the alternate deposition of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate).

PubMed

Guzmán, Eduardo; Maestro, Armando; Llamas, Sara; Álvarez-Rodríguez, Jesús; Ortega, Francisco; Maroto-Valiente, Ángel; Rubio, Ramón G

2016-01-01

This work addresses the formation and the internal morphology of polyelectrolyte layers obtained by the layer-by-layer method. A multimodal characterization showed the absence of stratification of the films formed by the alternate deposition of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate). Indeed the final organization might be regarded as three-dimensional solid-supported inter-polyelectrolyte films. The growth mechanism of the multilayers, followed using a quartz crystal microbalance, evidences two different growth trends, which show a dependency on the ionic strength due to its influence onto the polymer conformation. The hydration state does not modify the multilayer growth, but it contributes to the total adsorbed mass of the film. The water associated with the polyelectrolyte films leads to their swelling and plastification. The use of X-ray photoelectron spectroscopy has allowed for deeper insights on the internal structure and composition of the polyelectrolyte multilayers.

Monomer volume fraction profiles in pH responsive planar polyelectrolyte brushes

DOE PAGES

Mahalik, Jyoti P.; Yang, Yubo; Deodhar, Chaitra V.; ...

2016-03-06

Spatial dependencies of monomer volume fraction profiles of pH responsive polyelectrolyte brushes were investigated using field theories and neutron reflectivity experiments. In particular, planar polyelectrolyte brushes in good solvent were studied and direct comparisons between predictions of the theories and experimental measurements are presented. The comparisons between the theories and the experimental data reveal that solvent entropy and ion-pairs resulting from adsorption of counterions from the added salt play key roles in affecting the monomer distribution and must be taken into account in modeling polyelectrolyte brushes. Furthermore, the utility of this physics-based approach based on these theories for the predictionmore » and interpretation of neutron reflectivity profiles in the context of pH responsive planar polyelectrolyte brushes such as polybasic poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and polyacidic poly(methacrylic acid) (PMAA) brushes is demonstrated. The approach provides a quantitative way of estimating molecular weights of the polymers polymerized using surface-initiated atom transfer radical polymerization.« less

Kinetic Modulation of Pulsed Chrono-potentiometric Polymeric Membrane Ion Sensors by Polyelectrolyte Multilayers

PubMed Central

Xu, Yida; Xu, Chao; Shvarev, Alexey; Becker, Thomas; De Marco, Roland

2010-01-01

Polymeric membrane ion selective electrodes are normally interrogated by zero current potentiometry, and their selectivity is understood to be primarily dependent on an extraction/ion-exchange equilibrium between the aqueous sample and polymeric membrane. If concentration gradients in the contacting diffusion layers are insubstantial, the membrane response is thought to be rather independent of kinetic processes such as surface blocking effects. In this work, the surface of calcium-selective polymeric ion-selective electrodes is coated with polyelectrolyte multilayers as evidenced by zeta potential measurements, atomic force microscopy and electrochemical impedance spectroscopy. Indeed, such multilayers have no effect on their potentiometric response if the membranes are formulated in a traditional manner, containing a lipophilic ion-exchanger and a calcium-selective ionophore. However, drastic changes in the potential response are observed if the membranes are operated in a recently introduced kinetic mode using pulsed chronopotentiometry. The results suggest that the assembled nanostructured multilayers drastically alter the kinetics of ion transport to the sensing membrane, making use of the effect that polyelectrolyte multilayers have different permeabilities toward ions with different valences. The results have implications to the design of chemically selective ion sensors since surface localized kinetic limitations can now be used as an additional dimension to tune the operational ion selectivity. PMID:17711298

Modeling competitive substitution in a polyelectrolyte complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, B.; Muthukumar, M., E-mail: muthu@polysci.umass.edu

2015-12-28

We have simulated the invasion of a polyelectrolyte complex made of a polycation chain and a polyanion chain, by another longer polyanion chain, using the coarse-grained united atom model for the chains and the Langevin dynamics methodology. Our simulations reveal many intricate details of the substitution reaction in terms of conformational changes of the chains and competition between the invading chain and the chain being displaced for the common complementary chain. We show that the invading chain is required to be sufficiently longer than the chain being displaced for effecting the substitution. Yet, having the invading chain to be longermore » than a certain threshold value does not reduce the substitution time much further. While most of the simulations were carried out in salt-free conditions, we show that presence of salt facilitates the substitution reaction and reduces the substitution time. Analysis of our data shows that the dominant driving force for the substitution process involving polyelectrolytes lies in the release of counterions during the substitution.« less

Dynamics and lithium binding energies of polyelectrolytes based on functionalized poly(para-phenylene terephthalamide).

PubMed

Grozema, F C; Best, A S; van Eijck, L; Stride, J; Kearley, G J; de Leeuw, S W; Picken, S J

2005-04-28

Polyelectrolyte materials are an interesting class of electrolytes for use in fuel cell and battery applications. Poly(para-phenylene terephthalamide) (PPTA, Kevlar) is a liquid crystalline polymer that, when sulfonated, is a polyelectrolyte that exhibits moderate ion conductivity at elevated temperatures. In this work, quasi-elastic neutron scattering (QENS) experiments were performed to gain insight into the effect of the presence of lithium counterions on the chain dynamics in the material. It was found that the addition of lithium ions decreases the dynamics of the chains. Additionally, the binding of lithium ions to the sulfonic acids groups was investigated by density functional theory (DFT) calculations. It was found that the local surroundings of the sulfonic acid group have very little effect on the lithium-ion binding energy. Binding energies for a variety of different systems were all calculated to be around 150 kcal/mol. The DFT calculations also show the existence of a structure in which a single lithium ion interacts with two sulfonic acid moieties on different chains. The formation of such "electrostatic cross-links" is believed to be the source of the increased tendency to aggregate and the reduced dynamics in the presence of lithium ions.

Cucurbit[8]uril-Containing Multilayer Films for the Photocontrolled Binding and Release of a Guest Molecule.

PubMed

Nicolas, Henning; Yuan, Bin; Zhang, Xi; Schönhoff, Monika

2016-03-15

The powerful host-guest chemistry of cucurbit[8]uril (CB[8]) was employed to obtain photoresponsive polyelectrolyte multilayer films for the reversible and photocontrolled binding and release of an organic guest molecule. For this purpose, we designed and synthesized a polyelectrolyte with azobenzene side groups. Then, CB[8] was associated with the azo side group to obtain a supramolecular host-guest complex that was further used as building block in order to prepare photoresponsive and CB[8]-containing polyelectrolyte multilayer films. Ultraviolet spectroscopy and a dissipative quartz crystal microbalance are employed to monitor the formation of the host-guest complex and the layer-by-layer self-assembly of the multilayer films, respectively. We demonstrate that the photoresponsive properties of the azo side groups are maintained before and after host-guest complexation with CB[8] in solution and within the multilayer films, respectively. A guest molecule was then specifically included as second binding partner into the CB[8]-containing multilayer films. Subsequently, the release of the guest was performed by UV light irradiation due to the trans-cis isomerization of the adjacent azo side groups. Re-isomerization of the azo side groups was achieved by VIS light irradiation and enabled the rebinding of the guest into CB[8]. Finally, we demonstrate that the photocontrolled binding and release within CB[8]-containing multilayer films can reliably and reversibly be performed over a period of more than 2 weeks with constant binding efficiency. Therefore, we expect such novel type of photosensitive films to have promising future applications in the field of stimuli-responsive nanomaterials.

Coencapsulation of oxygen carriers and glucose oxidase in polyelectrolyte complex capsules for the enhancement of D-gluconic acid and delta-gluconolactone production.

PubMed

Bucko, Marek; Gemeiner, Peter; Vikartovská, Alica; Mislovicová, Danica; Lacík, Igor; Tkác, Ján

2010-04-01

A novel encapsulated oxidative biocatalyst comprising glucose oxidase (GOD) coencapsulated with oxygen carriers within polyelectrolyte complex capsules was developed for the production of D-gluconic acid and delta-gluconolactone. The capsules containing immobilized GOD were produced by polyelectrolyte complexation with sodium alginate (SA) and cellulose sulfate (CS) as polyanions, poly(methylene-co-guanidine) (PMCG) as the polycation, CaCl(2) as the gelling agent and NaCl as the antigelling agent (GOD-SA-CS/PMCG capsules). Poly(dimethylsiloxane) (PDMS) and an emulsion of n-dodecane (DOD) or perfluorodecaline (PFD) with PDMS were used as the oxygen carriers and MnO(2) was used as a hydrogen peroxide decomposition catalyst. Water-soluble PDMS was found to act as both an oxygen carrier and an emulsifier of water-insoluble DOD and PFD. Stable microcapsules could be produced with concentrations of up to 4% (w/w) of PDMS, 10% (w/w) of DOD and PFD, and 25% (w/w) of MnO(2) in the polyanion solution of SA and CS. Roughly a two-fold increase in the GOD activity from 21.0+/-1.1 to 38.4+/-2.0 U*g(-1) and product space-time yields (STY) from 44.3+/-2.0 to 83.4+/-3.4 g*H*day(-1) could be achieved utilizing coencapsulated oxygen carriers compared to GOD encapsulated in the absence of oxygen carriers. This enhanced production does not significantly depend on the selected oxygen carrier under the conditions used in this study.

Highly sensitive self-complementary DNA nanoswitches triggered by polyelectrolytes

NASA Astrophysics Data System (ADS)

Wu, Jincai; Yu, Feng; Zhang, Zheng; Chen, Yong; Du, Jie; Maruyama, Atsushi

2015-12-01

Dimerization of two homologous strands of genomic DNA/RNA is an essential feature of retroviral replication. Herein we show that a cationic comb-type copolymer (CCC), poly(l-lysine)-graft-dextran, accelerates the dimerization of self-complementary stem-loop DNA, frequently found in functional DNA/RNA molecules, such as aptamers. Furthermore, an anionic polymer poly(sodium vinylsulfonate) (PVS) dissociates CCC from the duplex shortly within a few seconds. Then single stem-loop DNA spontaneously transforms from its dimer. Thus we can easily control the dimer and stem-loop DNA by switching on/off CCC activity. Both polyelectrolytes and DNA concentrations are in the nanomole per liter range. The polyelectrolyte-assisted transconformation and sequences design strategy ensures the reversible state control with rapid response and effective switching under physiologically relevant conditions. A further application of this sensitive assembly is to construct an aptamer-type drug delivery system, bind or release functional molecules responding to its transconformation.Dimerization of two homologous strands of genomic DNA/RNA is an essential feature of retroviral replication. Herein we show that a cationic comb-type copolymer (CCC), poly(l-lysine)-graft-dextran, accelerates the dimerization of self-complementary stem-loop DNA, frequently found in functional DNA/RNA molecules, such as aptamers. Furthermore, an anionic polymer poly(sodium vinylsulfonate) (PVS) dissociates CCC from the duplex shortly within a few seconds. Then single stem-loop DNA spontaneously transforms from its dimer. Thus we can easily control the dimer and stem-loop DNA by switching on/off CCC activity. Both polyelectrolytes and DNA concentrations are in the nanomole per liter range. The polyelectrolyte-assisted transconformation and sequences design strategy ensures the reversible state control with rapid response and effective switching under physiologically relevant conditions. A further application of this sensitive assembly is to construct an aptamer-type drug delivery system, bind or release functional molecules responding to its transconformation. Electronic supplementary information (ESI) available: I. Sequences of DIS25, DIS25-2a and DIS25-3a. II. Structural formula of poly(l-lysine)-graft-dextran (PLL-g-Dex). 1H-NMR spectra of PLL-g-Dex in D2O. III. Gel electrophoretic analysis of dimerization of DIS25 with various N/P ratios. IV. The effect of polyelectrolyte on the fluorescence polarity of TAMRA-labeled duplex. V. UV absorption/Tm profiles of DIS25. VI. Arrhenius plots for spontaneous dissociation of the DIS25 dimer and PLL-g-Dex-assisted dimerization of DIS25.VII. Switching between double stem-loop DIS42 and extended multiplex drived by PLL-g-Dex and PVS. See DOI: 10.1039/c5nr05193b

An environmentally benign antimicrobial nanoparticle based ...

EPA Pesticide Factsheets

Silver nanoparticles have antibacterial properties but their use has been a cause for concern because they persist in the environment. Here we show that lignin nanoparticles infused with silver ions and coated with a cationic polyelectrolyte layer form a biodegradable and green alternative to silver nanoparticles. The polyelectrolyte layer promotes the adhesion of the particles to bacterial cell membranes and together with silver ions can kill a broad spectrum of bacteria, including Escherichia coli, Pseudomonas aeruginosa and quaternary-amine-resistant Ralstonia sp. Ion depletion studies showed that the bioactivity of these nanoparticles is time-limited because of the desorption of silver ions. High-throughput bioactivity screening did not reveal increased toxicity of the particles when compared to an equivalent mass of metallic silver nanoparticles or silver nitrate solution. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles. Our results demonstrate that the application of green chemistry principles may allow the synthesis of nanoparticles with biodegradable cores that have higher antimicrobial activity and smaller environmental impact than metallic silver nanoparticles

Ion transport and selectivity in biomimetic nanopores with pH-tunable zwitterionic polyelectrolyte brushes.

PubMed

Zeng, Zhenping; Yeh, Li-Hsien; Zhang, Mingkan; Qian, Shizhi

2015-10-28

Inspired by nature, functionalized nanopores with biomimetic structures have attracted growing interests in using them as novel platforms for applications of regulating ion and nanoparticle transport. To improve these emerging applications, we study theoretically for the first time the ion transport and selectivity in short nanopores functionalized with pH tunable, zwitterionic polyelectrolyte (PE) brushes. In addition to background salt ions, the study takes into account the presence of H(+) and OH(-) ions along with the chemistry reactions between functional groups on PE chains and protons. Due to ion concentration polarization, the charge density of PE layers is not homogeneously distributed and depends significantly on the background salt concentration, pH, grafting density of PE chains, and applied voltage bias, thereby resulting in many interesting and unexpected ion transport phenomena in the nanopore. For example, the ion selectivity of the biomimetic nanopore can be regulated from anion-selective (cation-selective) to cation-selective (anion-selective) by diminishing (raising) the solution pH when a sufficiently small grafting density of PE chains, large voltage bias, and low background salt concentration are applied.

Strong and weak adsorptions of polyelectrolyte chains onto oppositely charged spheres

NASA Astrophysics Data System (ADS)

Cherstvy, A. G.; Winkler, R. G.

2006-08-01

We investigate the complexation of long thin polyelectrolyte (PE) chains with oppositely charged spheres. In the limit of strong adsorption, when strongly charged PE chains adapt a definite wrapped conformation on the sphere surface, we analytically solve the linear Poisson-Boltzmann equation and calculate the electrostatic potential and the energy of the complex. We discuss some biological applications of the obtained results. For weak adsorption, when a flexible weakly charged PE chain is localized next to the sphere in solution, we solve the Edwards equation for PE conformations in the Hulthén potential, which is used as an approximation for the screened Debye-Hückel potential of the sphere. We predict the critical conditions for PE adsorption. We find that the critical sphere charge density exhibits a distinctively different dependence on the Debye screening length than for PE adsorption onto a flat surface. We compare our findings with experimental measurements on complexation of various PEs with oppositely charged colloidal particles. We also present some numerical results of the coupled Poisson-Boltzmann and self-consistent field equation for PE adsorption in an assembly of oppositely charged spheres.

Influence of structural features of carrageenan on the formation of polyelectrolyte complexes with chitosan.

PubMed

Volod'ko, A V; Davydova, V N; Glazunov, V P; Likhatskaya, G N; Yermak, I M

2016-03-01

The polyelectrolyte complexes (PEC) of carrageenans (CG)-κ-, κ/β-, λ-and x-CG with chitosan were obtained. The formation of PEC was detected by Fourier-transform infrared (FTIR) spectroscopy and by centrifugation in a Percoll gradient. The influence of the structural peculiarities of CG on its interaction with chitosan was studied. The results of centrifugation showed that x-CG with a high degree of sulphation (SD) was completely bound to chitosan, unlike low SD κ-CG and κ/β-CG. Binding constant values showed there was a high affinity of CG for chitosan. CG with flexible macromolecule conformation and high SD exhibited the greatest binding affinity for chitosan. The full-atomic 3D-structures of the PEC κ-CG: chitosan in solution have been obtained by the experiments in silico for the first time. The amino groups of chitosan make the largest contribution to the energy of the complex formation by means of hydrogen and ionic bonds. The most probable complexes have stoichiometries of 1:1 and 1:1.5. Copyright © 2015 Elsevier B.V. All rights reserved.

Fabrication of surfaces with extremely high contact angle hysteresis from polyelectrolyte multilayer.

PubMed

Wang, Liming; Wei, Jingjing; Su, Zhaohui

2011-12-20

High contact angle hysteresis on polyelectrolyte multilayers (PEMs) ion-paired with hydrophobic perfluorooctanoate anions is reported. Both the bilayer number of PEMs and the ionic strength of deposition solutions have significant influence on contact angle hysteresis: higher ionic strength and greater bilayer number cause increased contact angle hysteresis values. The hysteresis values of ~100° were observed on smooth PEMs and pinning of the receding contact line on hydrophilic defects is implicated as the cause of hysteresis. Surface roughness can be used to further tune the contact angle hysteresis on the PEMs. A surface with extremely high contact angle hysteresis of 156° was fabricated when a PEM was deposited on a rough substrate coated with submicrometer scale silica spheres. It was demonstrated that this extremely high value of contact angle hysteresis resulted from the penetration of water into the rough asperities on the substrate. The same substrate hydrophobized by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane exhibits high advancing contact angle and low hysteresis. © 2011 American Chemical Society

Reversible modulation of the redox activity in conducting polymer nanofilms induced by hydrophobic collapse of a surface-grafted polyelectrolyte.

PubMed

Fenoy, Gonzalo E; Giussi, Juan M; von Bilderling, Catalina; Maza, Eliana M; Pietrasanta, Lía I; Knoll, Wolfgang; Marmisollé, Waldemar A; Azzaroni, Omar

2018-05-15

We present the covalent modification of a Pani-like conducting polymer (polyaminobenzylamine, PABA) by grafting of a polyelectrolyte brush (poly [2-(methacryloyloxy)-ethyl-trimethylammonium chloride], PMETAC). As PABA has extra pendant amino moieties, the grafting procedure does not affect the backbone nitrogen atoms that are implicated in the electronic structure of the conducting polymers. Moreover, perchlorate anions interact very strongly with the quaternary ammonium pendant groups of PMETAC through ion pairing. Therefore, the grafting does not only keep the electroactivity of PABA in aqueous solutions but it adds the ion-actuation properties of the PMETAC brush to the modified electrode as demonstrated by contact angle measurements and electrochemical methods. In this way, the conjugation of the electron transfer properties of the conducting polymer with the anion responsiveness of the integrated brush renders perchlorate actuation of the electrochemical response. These results constitute a rational integration of nanometer-sized polymer building blocks that yields synergism of functionalities and illustrate the potentialities of nanoarchitectonics for pushing the limits of soft material science into the nanoworld. Copyright © 2018 Elsevier Inc. All rights reserved.

Molecular Origins of Thermal Transitions in Polyelectrolyte Assemblies

NASA Astrophysics Data System (ADS)

Yildirim, Erol; Zhang, Yanpu; Antila, Hanne S.; Lutkenhaus, Jodie L.; Sammalkorpi, Maria; Aalto Team; Texas A&M Team

2015-03-01

Polyelectrolyte (PE) multilayers and complexes formed from oppositely charged polymers can exhibit extraordinary superhydrophobicity, mechanical strength and responsiveness resulting in applications ranging functional membranes, optics, sensors and drug delivery. Depending on the assembly conditions, PE assemblies may undergo a thermal transition from glassy to soft behavior under heating. Our earlier work using thermal analysis measurements shows a distinct thermal transition for PE layer-by-layer (LbL) systems assembled with added salt but no analogous transition in films assembled without added salt or dry systems. These findings raise interesting questions on the nature of the thermal transition; here, we explore its molecular origins through characterization of the PE aggregates by temperature-controlled all-atom molecular dynamics simulations. We show via molecular simulations the thermal transition results from the existence of an LCST (lower critical solution temperature) in the PE systems: the diffusion behavior, hydrogen bond formation, and bridging capacity of water molecules plasticizing the complex changes at the transition temperature. We quantify the behavior, map its chemistry specificity through comparison of strongly and weakly charged PE complexes, and connect the findings to our interrelated QCM-D experiments.

Osmotic Pressure in Ionic Microgel Dispersions

NASA Astrophysics Data System (ADS)

Denton, Alan R.; Tang, Qiyun

2015-03-01

Microgels are microscopic gel particles, typically 10-1000 nm in size, that are swollen by a solvent. Hollow microgels (microcapsules) can encapsulate cargo, such as dye molecules or drugs, in their solvent-filled cavities. Their sensitive response to environmental conditions (e.g., temperature, pH) and influence on flow properties suit microgels to widespread applications in the chemical, pharmaceutical, food, and consumer care industries. When dispersed in water, polyelectrolyte gels become charged through dissociation of counterions. The electrostatic contribution to the osmotic pressure inside and outside of ionic microgels influences particle swelling and bulk materials properties, including thermodynamic, structural, optical, and rheological properties. Within the primitive and cell models of polyelectrolyte solutions, we derive an exact statistical mechanical formula for the contribution of mobile microions to the osmotic pressure within ionic microgels. Using Poisson-Boltzmann theory, we validate this result by explicitly calculating ion distributions across the surface of an ionic microgel and the electrostatic contribution to the osmotic pressure. Within a coarse-grained one-component model, we further chart the limits of the cell model for salty dispersions. This work was supported by the National Science Foundation under Grant No. DMR-1106331.

Avidin/PSS membrane microcapsules with biotin-binding activity.

PubMed

Endo, Yoshihiro; Sato, Katsuhiko; Sugimoto, Kentaro; Anzai, Jun-ichi

2011-08-15

Polyelectrolyte microcapsules with avidin-poly(styrene sulfonate) (PSS) membrane were prepared by a layer-by-layer deposition technique. The uptake and release of biotin-labeled fluorescein (b-FITC) as well as immobilization of biotin-labeled glucose oxidase (b-GOx) to the microcapsule were studied. The polyelectrolyte microcapsules were prepared by coating the surface of calcium carbonate (CaCO(3)) microparticles with an avidin/PSS multilayer membrane, followed by dissolution of CaCO(3) core in an ethylenediaminetetraacetic acid solution. Inner and outer poly(allylamine)/PSS films were required to isolate the microcapsules, whereas microcapsules could not be formed without the support. The uptake of b-FITC into the microcapsule was highly enhanced through a strong binding of b-FITC to avidin as compared with the uptake of biotin-free FITC. Release of b-FITC from the microcapsule was accelerated upon addition of biotin due to a competitive binding of the added biotin to the binding site of avidin. Similarly, the surface of microcapsule was modified with b-GOx with retaining its catalytic activity. Copyright © 2011 Elsevier Inc. All rights reserved.

Doped polymer semiconductors with ultrahigh and ultralow work functions for ohmic contacts.

PubMed

Tang, Cindy G; Ang, Mervin C Y; Choo, Kim-Kian; Keerthi, Venu; Tan, Jun-Kai; Syafiqah, Mazlan Nur; Kugler, Thomas; Burroughes, Jeremy H; Png, Rui-Qi; Chua, Lay-Lay; Ho, Peter K H

2016-11-24

To make high-performance semiconductor devices, a good ohmic contact between the electrode and the semiconductor layer is required to inject the maximum current density across the contact. Achieving ohmic contacts requires electrodes with high and low work functions to inject holes and electrons respectively, where the work function is the minimum energy required to remove an electron from the Fermi level of the electrode to the vacuum level. However, it is challenging to produce electrically conducting films with sufficiently high or low work functions, especially for solution-processed semiconductor devices. Hole-doped polymer organic semiconductors are available in a limited work-function range, but hole-doped materials with ultrahigh work functions and, especially, electron-doped materials with low to ultralow work functions are not yet available. The key challenges are stabilizing the thin films against de-doping and suppressing dopant migration. Here we report a general strategy to overcome these limitations and achieve solution-processed doped films over a wide range of work functions (3.0-5.8 electronvolts), by charge-doping of conjugated polyelectrolytes and then internal ion-exchange to give self-compensated heavily doped polymers. Mobile carriers on the polymer backbone in these materials are compensated by covalently bonded counter-ions. Although our self-compensated doped polymers superficially resemble self-doped polymers, they are generated by separate charge-carrier doping and compensation steps, which enables the use of strong dopants to access extreme work functions. We demonstrate solution-processed ohmic contacts for high-performance organic light-emitting diodes, solar cells, photodiodes and transistors, including ohmic injection of both carrier types into polyfluorene-the benchmark wide-bandgap blue-light-emitting polymer organic semiconductor. We also show that metal electrodes can be transformed into highly efficient hole- and electron-injection contacts via the self-assembly of these doped polyelectrolytes. This consequently allows ambipolar field-effect transistors to be transformed into high-performance p- and n-channel transistors. Our strategy provides a method for producing ohmic contacts not only for organic semiconductors, but potentially for other advanced semiconductors as well, including perovskites, quantum dots, nanotubes and two-dimensional materials.

Superabsorbent Polymers: An Idea Whose Time Has Come

NASA Astrophysics Data System (ADS)

Buchholz, Fredric L.

1996-06-01

Superabsorbent polymers are cross-linked polyelectrolytes. Because of their ionic nature and interconnected structure, they absorb large quantities of water and other aqueous solutions without dissolving. This makes them ideally suited as absorbents of body fluids in many personal care products sold today, including baby diapers, adult incontinence products, and feminine napkins. Several emerging applications are also described. A simple laboratory preparation of partially neutralized, cross-linked poly(acrylic acid) is given along with test methods suitable for measuring the absorption capacity of the product. Experiments are described that demonstrate the ability of a swelling gel to perform work, and the ability of a gel to exclude macromolecular solutes from diffusing into its porous, cross-linked structure.

Formation and Properties of Multilayer Films Based on Polyethyleneimine and Bovine Serum Albumin

NASA Astrophysics Data System (ADS)

Kulikouskaya, V. I.; Lazouskaya, M. E.; Kraskouski, A. N.; Agabekov, V. E.

2018-01-01

(Polyethyleneimine/bovine serum albumin) n ((PEI/BSA) n) multilayer films ( n = 1-10) are produced via the layer-by-later deposition of polyelectrolytes. It is shown that thickness and morphology of the formed coatings can be controlled by varying the solution's ionic strength during alternating adsorption of the components. (PEI/BSA)10 multilayer systems that contain up to 0.6 mg of antiseptic miramistin per 1 cm2 of film were created. It is established that the kinetics of miramistin release from (PEI/BSA)10 films in phosphate buffers and physiological solutions obey the Korsmeyer-Peppas equation with a high degree of accuracy ( R 2 > 0.95).

Multilayer Films and Capsules of Sodium Carboxymethylcellulose and Polyhexamethylenguanidine Hydrochloride

NASA Astrophysics Data System (ADS)

Guzenko, Nataliia; Gabchak, Oleksandra; Pakhlov, Evgenij

The complexation of polyhexamethylenguanidine hydrochloride (PHMG) and sodium carboxymethylcellulose (CMC) was investigated for different conditions. Mixing of equiconcentrated aqueous solutions of the polyelectrolytes was found to result in the formation of an insoluble interpolyelectrolyte complex with an overweight of carboxymethylcellulose. A step-by-step formation of stable, irreversibly adsorbed multilayer film of the polymers was demonstrated using the quartz crystal microbalance method. Unusually thick polymer shells with a large number of loops and tails of the polyanion were formed by the method of layer-by-layer self-assembly of PHMG and CMC on spherical CaCO3 particles. Hollow multilayer capsules stable in neutral media were obtained by dissolution of the inorganic matrix in EDTA solution.

Control of continuous phase PH using visible light to activate PH-dependent fibers and gels in a controlled and reversible manner

NASA Astrophysics Data System (ADS)

Zirino, Albert

1994-08-01

A transparent polyelectrolyte fiber or gel, such as crosslinked polyacrylic acid, which contracts and expands upon the addition of an acid or base to an aqueous medium solution, is placed in the same solution with a pH dependent dye, a colored photochromatic indicator dye. The dye preferably has a pAa value that is the same as the pH at a null contraction point of the fiber. By irradiating the solution with light of a wavelength of the absorption band of either the acid or base form of the dye, the solution pH is made to change, and the fiber is made to expand or contract, depending upon the wavelength. Thus, light energy is readily converted to work energy and may be used to power a pump, for example or an artificial muscle can be powered via an optical fiber.

Multi-Scale Structure of Coacervates formed by Oppositely Charged Polyelectrolytes

NASA Astrophysics Data System (ADS)

Rubinstein, Michael

We develop a scaling model of coacervates formed by oppositely charged polyelectrolytes and demonstrate that they self-organize into multi-scale structures. The intramolecular electrostatic interactions in dilute polyanion or polycation solutions are characterized by the electrostatic blobs with size D- and D+ respectively, that repel neighboring blobs on the same chains with electrostatic energy on the order of thermal energy kT . After mixing, electrostatic intramolecular repulsion of polyelectrolytes with higher charged density, say polyanions, keeps these polyanions in coacervates aligned into stretched arrays of electrostatic blobs of size D-

Polyelectrolyte Complexes of Low Molecular Weight PEI and Citric Acid as Efficient and Nontoxic Vectors for in Vitro and in Vivo Gene Delivery.

PubMed

Giron-Gonzalez, M Dolores; Salto-Gonzalez, Rafael; Lopez-Jaramillo, F Javier; Salinas-Castillo, Alfonso; Jodar-Reyes, Ana Belen; Ortega-Muñoz, Mariano; Hernandez-Mateo, Fernando; Santoyo-Gonzalez, Francisco

2016-03-16

Gene transfection mediated by the cationic polymer polyethylenimine (PEI) is considered a standard methodology. However, while highly branched PEIs form smaller polyplexes with DNA that exhibit high transfection efficiencies, they have significant cell toxicity. Conversely, low molecular weight PEIs (LMW-PEIs) with favorable cytotoxicity profiles display minimum transfection activities as a result of inadequate DNA complexation and protection. To solve this paradox, a novel polyelectrolyte complex was prepared by the ionic cross-linking of branched 1.8 kDa PEI with citric acid (CA). This system synergistically exploits the good cytotoxicity profile exhibited by LMW-PEI with the high transfection efficiencies shown by highly branched and high molecular weight PEIs. The polyectrolyte complex (1.8 kDa-PEI@CA) was obtained by a simple synthetic protocol based on the microwave irradiation of a solution of 1.8 kDa PEI and CA. Upon complexation with DNA, intrinsic properties of the resulting particles (size and surface charge) were measured and their ability to form stable polyplexes was determined. Compared with unmodified PEIs the new complexes behave as efficient gene vectors and showed enhanced DNA binding capability associated with facilitated intracellular DNA release and enhanced DNA protection from endonuclease degradation. In addition, while transfection values for LMW-PEIs are almost null, transfection efficiencies of the new reagent range from 2.5- to 3.8-fold to those of Lipofectamine 2000 and 25 kDa PEI in several cell lines in culture such as CHO-k1, FTO2B hepatomas, L6 myoblasts, or NRK cells, simultaneously showing a negligible toxicity. Furthermore, the 1.8 kDa-PEI@CA polyelectrolyte complexes retained the capability to transfect eukaryotic cells in the presence of serum and exhibited the capability to promote in vivo transfection in mouse (as an animal model) with an enhanced efficiency compared to 25 kDa PEI. Results support the polyelectrolyte complex of LMW-PEI and CA as promising generic nonviral gene carriers.

Noncovalent PEGylation through Protein-Polyelectrolyte Interaction: Kinetic Experiment and Molecular Dynamics Simulation.

PubMed

Kurinomaru, Takaaki; Kuwada, Kengo; Tomita, Shunsuke; Kameda, Tomoshi; Shiraki, Kentaro

2017-07-20

Noncovalent binding of polyethylene glycol (PEG) to a protein surface is a unique protein handling technique to control protein function and stability. A diblock copolymer containing PEG and polyelectrolyte chains (PEGylated polyelectrolyte) is a promising candidate for noncovalent attachment of PEG to a protein surface because of the binding through multiple electrostatic interactions without protein denaturation. To obtain a deeper understanding of protein-polyelectrolyte interaction at the molecular level, we investigated the manner in which cationic PEGylated polyelectrolyte binds to anionic α-amylase in enzyme kinetic experiments and molecular dynamics (MD) simulations. Cationic PEG-block-poly(N,N-dimethylaminoethyl) (PEG-b-PAMA) inhibited the enzyme activity of anionic α-amylase due to binding of PAMA chains. Enzyme kinetics revealed that the inhibition of α-amylase activity by PEG-b-PAMA is noncompetitive inhibition manner. In MD simulations, the PEG-b-PAMA molecule was initially located at six different placements of the x-, y-, and z-axis ±20 Å from the center of α-amylase, which showed that the PEG-b-PAMA nonspecifically bound to the α-amylase surface, corresponding to the noncompetitive inhibition manner that stems from the polymer binding to an enzyme surface other than the active site. In addition, the enzyme activity of α-amylase in the presence of PEG-b-PAMA was not inhibited by increasing the ionic strength, consistent with the MD simulation; i.e., PEG-b-PAMA did not interact with α-amylase in high ionic strength conditions. The results reported in this paper suggest that enzyme inhibition by PEGylated polyelectrolyte can be attributed to the random electrostatic interaction between protein and polyelectrolyte.

Novel polyelectrolytes

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Yen, Shiao-Ping Siao (Inventor)

1978-01-01

Cationic polyelectrolytes are formed by the polymerization in absence of oxygen of a monomer of the general formula: ##STR1## where x is 3 or more than 6 and Z is I, Br or Cl to form high charge density linear polymers. Segments of the linear polymer may be attached to or formed in the presence of polyfunctional reactive tertiary amines or halogen polymeric substrates or polyfunctional lower molecular reactive polyfunctional substrates to form branched or star polyelectrolytes by a quaternization polymerization reaction.

Influence of Protamine Functionalization on the Colloidal Stability of 1D and 2D Titanium Oxide Nanostructures.

PubMed

Rouster, Paul; Pavlovic, Marko; Horváth, Endre; Forró, László; Dey, Sandwip K; Szilagyi, Istvan

2017-09-26

The colloidal stability of titanium oxide nanosheets (TNS) and nanowires (TiONW) was studied in the presence of protamine (natural polyelectrolyte) in aqueous dispersions, where the nanostructures possessed negative net charge, and the protamine was positively charged. Regardless of their shape, similar charging and aggregation behaviors were observed for both TNS and TiONW. Electrophoretic experiments performed at different protamine loadings revealed that the adsorption of protamine led to charge neutralization and charge inversion depending on the polyelectrolyte dose applied. Light scattering measurements indicated unstable dispersions once the surface charge was close to zero or slow aggregation below and above the charge neutralization point with negatively or positively charged nanostructures, respectively. These stability regimes were confirmed by the electron microscopy images taken at different polyelectrolyte loadings. The protamine dose and salt-dependent colloidal stability confirmed the presence of DLVO-type interparticle forces, and no experimental evidence was found for additional interactions (e.g., patch-charge, hydrophobic, or steric forces), which are usually present in similar polyelectrolyte-particle systems. These findings indicate that the polyelectrolyte adsorbs on the TNS and TiONW surfaces in a flat and extended conformation giving rise to the absence of surface heterogeneities. Therefore, protamine is an excellent biocompatible candidate to form smooth surfaces, for instance in multilayers composed of polyelectrolytes and particles to be used in biomedical applications.

Glucose Oxidase Adsorption on Sequential Adsorbed Polyelectrolyte Films Studied by Spectroscopic Techniques

NASA Astrophysics Data System (ADS)

Tristán, Ferdinando; Solís, Araceli; Palestino, Gabriela; Gergely, Csilla; Cuisinier, Frédéric; Pérez, Elías

2005-04-01

The adsorption of Glucose Oxidase (GOX) on layers of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) deposited on Sequentially Adsorbed Polyelectrolyte Films (SAPFs) were studied by three different spectroscopic techniques. These techniques are: Optical Wave Light Spectroscopy (OWLS) to measure surface density; Fluorescence Resonance Energy Transfer (FRET) to verify the adsorption of GOX on the surface; and Fourier Transform Infrared Spectroscopy in Attenuated Total Reflection mode (FTIR-HATR) to inspect local structure of polyelectrolytes and GOX. Two positive and two negative polyelectrolytes are used: Cationic poly(ethyleneimine) (PEI) and poly(allylamine hydrochloride) (PAH) and anionic poly(sodium 4-styrene sulfonate) (PSS) and poly(acrylic acid) (PAA). These spectroscopic techniques do not require any labeling for GOX or SAPFs, specifically GOX and PSS are naturally fluorescent and are used as a couple donor-acceptor for the FRET technique. The SAPFs are formed by a (PEI)-(PSS/PAH)2 film followed by (PAA/PAH)n bilayers. GOX is finally deposited on top of SAPFs at different values of n (n=1..5). Our results show that GOX is adsorbed on positive ended SAPFs forming a monolayer. Contrary, GOX adsorption is not observed on negative ended film polyelectrolyte. GOX stability was tested adding a positive and a negative polyelectrolyte after GOX adsorption. Protein is partially removed by PAH and PAA, with lesser force by PAA.

Polyelectrolyte brushes in mixed ionic medium studied via intermolecular forces

NASA Astrophysics Data System (ADS)

Farina, Robert; Laugel, Nicolas; Pincus, Philip; Tirrell, Matthew

2011-03-01

The vast uses and applications of polyelectrolyte brushes make them an attractive field of research especially with the growing interest in responsive materials. Polymers which respond via changes in temperature, pH, and ionic strength are increasingly being used for applications in drug delivery, chemical gating, etc. When polyelectrolyte brushes are found in either nature (e.g., surfaces of cartilage and mammalian lung interiors) or commercially (e.g., skin care products, shampoo, and surfaces of medical devices) they are always surrounded by mixed ionic medium. This makes the study of these brushes in varying ionic environments extremely relevant for both current and future potential applications. The polyelectrolyte brushes in this work are diblock co-polymers of poly-styrene sulfonate (N=420) and poly-t-butyl styrene (N=20) which tethers to a hydrophobic surface allowing for a purely thermodynamic study of the polyelectrolyte chains. Intermolecular forces between two brushes are measured using the SFA. As multi-valent concentrations are increased, the brushes collapse internally and form strong adhesion between one another after contact (properties not seen in a purely mono-valent environment).

CONJUGATED POLYMERS AND POLYELECTROLYTES IN SOLAR PHOTOCONVERSION, Final Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schanze, Kirk S

2014-08-05

This DOE-supported program investigated the fundamental properties of conjugated polyelectrolytes, with emphasis placed on studies of excited state energy transport, self-assembly into conjugated polyelectroyte (CPE) based films and colloids, and exciton transport and charge injection in CPE films constructed atop wide bandgap semiconductors. In the most recent grant period we have also extended efforts to examine the properties of low-bandgap donor-acceptor conjugated polyelectrolytes that feature strong visible light absorption and the ability to adsorb to metal-oxide interfaces.

Imatinib-loaded polyelectrolyte microcapsules for sustained targeting of BCR-ABL+ leukemia stem cells.

PubMed

Palamà, Ilaria E; Leporatti, Stefano; de Luca, Emanuela; Di Renzo, Nicola; Maffia, Michele; Gambacorti-Passerini, Carlo; Rinaldi, Ross; Gigli, Giuseppe; Cingolani, Roberto; Coluccia, Addolorata M L

2010-04-01

The lack of sensitivity of chronic myeloid leukemia (CML) stem cells to imatinib mesylate (IM) commonly leads to drug dose escalation or early disease relapses when therapy is stopped. Here, we report that packaging of IM into a biodegradable carrier based on polyelectrolyte microcapsules increases drug retention and antitumor activity in CML stem cells, also improving the ex vivo purging of malignant progenitors from patient autografts. Microparticles/capsules were obtained by layer-by-layer (LbL) self-assembly of oppositely charged polyelectrolyte multilayers on removable calcium carbonate (CaCO(3)) templates and loaded with or without IM. A leukemic cell line (KU812) and CD34(+) cells freshly isolated from healthy donors or CML patients were tested. Polyelectrolyte microcapsules (PMCs) with an average diameter of 3 microm, fluorescently labelled multilayers sensitive to the action of intracellular proteases and 95-99% encapsulation efficiency of IM, were prepared. Cell uptake efficiency of such biodegradable carriers was quantified in KU812, leukemic and normal CD34(+) stem cells (range: 70-85%), and empty PMCs did not impact cell viability. IM-loaded PMCs selectively targeted CML cells, by promoting apoptosis at doses that exert only cytostatic effects by IM alone. More importantly, residual CML cells from patient leukapheresis products were reduced or eliminated more efficiently by using IM-loaded PMCs compared with freely soluble IM, with a purging efficiency of several logs. No adverse effects on normal CD34(+) stem-cell survival and their clonogenic potential was noticed in long-term cultures of hematopoietic progenitors in vitro. This pilot study provides the proof-of-principle for the clinical application of biodegradable IM-loaded PMC as feasible, safe and effective ex vivo purging agents to target CML stem cells, in order to improve transplant outcome of resistant/relapsed patients or reduce IM dose escalation.

The Effect of Salt on the Complex Coacervation of Vinyl Polyelectrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perry, Sarah; Li, Yue; Priftis, Dimitrios

2014-06-01

Complex coacervation is an electrostatically-driven phase separation phenomenon that is utilized in a wide range of everyday applications and is of great interest for the creation of self-assembled materials. Here, we utilized turbidity to characterize the effect of salt type on coacervate formation using two vinyl polyelectrolytes, poly(acrylic acid sodium salt) (pAA) and poly(allylamine hydrochloride) (pAH), as simple models for industrial and biological coacervates. We confirmed the dominant role of salt valence on the extent of coacervate formation, while demonstrating the presence of significant secondary effects, which can be described by Hofmeister-like behavior. These results revealed the importance of ion-specificmore » interactions, which are crucial for the informed design of coacervate-based materials for use in complex ionic environments, and can enable more detailed theoretical investigations on the role of subtle electrostatic and thermodynamic effects in complex coacervation.« less

Composite carbohydrate interpenetrating polyelectrolyte nano-complexes (IPNC) as a controlled oral delivery system of citalopram HCl for pediatric use: in-vitro/in-vivo evaluation and histopathological examination.

PubMed

Kamel, Rabab; Abbas, Haidy; El-Naa, Mona

2018-06-01

Citalopram HCl (CH) is one of the few drugs which can be used safely in childhood psychiatric disorders. This study was focused on the preparation of interpenetrating polyelectrolytes nano-complexes (IPNC) to transform the hydrophilic carbohydrate polymers into an insoluble form. The IPNCs were loaded with CH to sustain its effect. The IPNC2 (composed of chitosan:pectin in a 3:1 ratio) showed the most extended drug release pattern (P < 0.05) and followed a Higuchi-order kinetics model. It was characterized using SEM, X-rays diffractometry, and FTIR. In-vivo studies were performed using immature rats with induced depression, and were based on the investigation of behavioral, biochemical, and histopathological changes at different time intervals up to 24 h. Rats treated with IPNC2 showed a significant more rapid onset of action and more extended effect in the behavioral tests, in addition to a significantly higher serotonin brain level up to 24 h, compared to rats treated with the market product (P < 0.05). The histopathological examination showed a profound amelioration of the cerebral cortex features of the depressed rats after IPNC2 administration. This study proves the higher efficacy and more extended effect of the new polyelectrolytes nano-complexes compared to the market product.

Characterisation of capacitive field-effect sensors with a nanocrystalline-diamond film as transducer material for multi-parameter sensing.

PubMed

Abouzar, M H; Poghossian, A; Razavi, A; Williams, O A; Bijnens, N; Wagner, P; Schöning, M J

2009-01-01

The feasibility of a capacitive field-effect EDIS (electrolyte-diamond-insulator-semiconductor) platform for multi-parameter sensing is demonstrated by realising EDIS sensors with an O-terminated nanocrystalline-diamond (NCD) film as transducer material for the detection of pH and penicillin concentration as well as for the label-free electrical monitoring of adsorption and binding of charged macromolecules, like polyelectrolytes. The NCD films were grown on p-Si-SiO(2) substrates by microwave plasma-enhanced chemical vapour deposition. To obtain O-terminated surfaces, the NCD films were treated in an oxidising medium. The NCD-based field-effect sensors have been characterised by means of constant-capacitance method. The average pH sensitivity of the O-terminated NCD film was 40 mV/pH. A low detection limit of 5 microM and a high penicillin G sensitivity of 65-70 mV/decade has been obtained for an EDIS penicillin biosensor with the adsorptively immobilised enzyme penicillinase. Alternating potential changes, having tendency to decrease with increasing the number of adsorbed polyelectrolyte layers, have been observed after the layer-by-layer deposition of polyelectrolyte multilayers, using positively charged PAH (poly (allylamine hydrochloride)) and a negatively charged PSS (poly (sodium 4-styrene sulfonate)) as a model system. The response mechanism of the developed EDIS sensors is discussed.

Interfacial Self-Assembly of Polyelectrolyte-Capped Gold Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Honghu; Nayak, Srikanth; Wang, Wenjie

Here, we report on pH- and salt-responsive assembly of nanoparticles capped with polyelectrolytes at vapor–liquid interfaces. Two types of alkylthiol-terminated poly(acrylic acid) (PAAs, varying in length) are synthesized and used to functionalize gold nanoparticles (AuNPs) to mimic similar assembly effects of single-stranded DNA-capped AuNPs using synthetic polyelectrolytes. Using surface-sensitive X-ray scattering techniques, including grazing incidence small-angle X-ray scattering (GISAXS) and X-ray reflectivity (XRR), we demonstrate that PAA-AuNPs spontaneously migrate to the vapor–liquid interfaces and form Gibbs monolayers by decreasing the pH of the suspension. The Gibbs monoalyers show chainlike structures of monoparticle thickness. The pH-induced self-assembly is attributed to themore » protonation of carboxyl groups and to hydrogen bonding between the neighboring PAA-AuNPs. In addition, we show that adding MgCl 2 to PAA-AuNP suspensions also induces adsorption at the interface and that the high affinity between magnesium ions and carboxyl groups leads to two- and three-dimensional clusters that yield partial surface coverage and poorer ordering of NPs at the interface. We also examine the assembly of PAA-AuNPs in the presence of a positively charged Langmuir monolayer that promotes the attraction of the negatively charged capped NPs by electrostatic forces. Our results show that synthetic polyelectrolyte-functionalized nanoparticles exhibit interfacial self-assembly behavior similar to that of DNA-functionalized nanoparticles, providing a pathway for nanoparticle assembly in general.« less

Interfacial Self-Assembly of Polyelectrolyte-Capped Gold Nanoparticles

DOE PAGES

Zhang, Honghu; Nayak, Srikanth; Wang, Wenjie; ...

2017-10-06

Here, we report on pH- and salt-responsive assembly of nanoparticles capped with polyelectrolytes at vapor–liquid interfaces. Two types of alkylthiol-terminated poly(acrylic acid) (PAAs, varying in length) are synthesized and used to functionalize gold nanoparticles (AuNPs) to mimic similar assembly effects of single-stranded DNA-capped AuNPs using synthetic polyelectrolytes. Using surface-sensitive X-ray scattering techniques, including grazing incidence small-angle X-ray scattering (GISAXS) and X-ray reflectivity (XRR), we demonstrate that PAA-AuNPs spontaneously migrate to the vapor–liquid interfaces and form Gibbs monolayers by decreasing the pH of the suspension. The Gibbs monoalyers show chainlike structures of monoparticle thickness. The pH-induced self-assembly is attributed to themore » protonation of carboxyl groups and to hydrogen bonding between the neighboring PAA-AuNPs. In addition, we show that adding MgCl 2 to PAA-AuNP suspensions also induces adsorption at the interface and that the high affinity between magnesium ions and carboxyl groups leads to two- and three-dimensional clusters that yield partial surface coverage and poorer ordering of NPs at the interface. We also examine the assembly of PAA-AuNPs in the presence of a positively charged Langmuir monolayer that promotes the attraction of the negatively charged capped NPs by electrostatic forces. Our results show that synthetic polyelectrolyte-functionalized nanoparticles exhibit interfacial self-assembly behavior similar to that of DNA-functionalized nanoparticles, providing a pathway for nanoparticle assembly in general.« less

Characterization of casein and poly-L-arginine multilayer films.

PubMed

Szyk-Warszyńska, Lilianna; Kilan, Katarzyna; Socha, Robert P

2014-06-01

Thin films containing casein appear to be a promising material for coatings used in the medical area to promote biomineralization. α- and β-casein and poly-L-arginine multilayer films were formed by the layer-by layer technique and their thickness and mass were analyzed by ellipsometry and quartz crystal microbalance with dissipation monitoring (QCM-D). (PLArg/casein) films deposited in 0.15M NaCl exhibit fast (exponential-like) growth of the film thickness with the number of layers. The resulting films were c.a. 10 times thicker than obtained for poly-L-arginine and natural polyanions. We investigated the effect of the type of casein used for the film formation, finding that films with α-casein were slightly thicker than ones with β-casein. The effect of polyethylene imine anchoring layer on the thickness and mass of adsorbed films was similar as for linear polyelectrolyte pairs. Thickness of "wet" films was c.a. two times larger than measured after drying that suggests their large hydration. The analysis of the mass of films during their post-treatment with the solutions of various ionic strength and pH provided the information concerning films stability. Films remain stable in the neutral and weakly basic conditions that includes HEPES buffer, which is widely used in cell culture and biomedical experiments. At the conditions of high ionic strength films swell but their swelling is reversible. Films containing caseins as polyanion appear to be more elastic and the same time more viscous than one formed with polyelectrolyte pairs. XPS elemental analysis confirmed binding of calcium ions by the casein embedded in the multilayers. Copyright © 2014 Elsevier Inc. All rights reserved.

Cooperation of phosphates and carboxylates controls calcium oxalate crystallization in ultrafiltered urine.

PubMed

Grohe, Bernd; Chan, Brian P H; Sørensen, Esben S; Lajoie, Gilles; Goldberg, Harvey A; Hunter, Graeme K

2011-10-01

Osteopontin (OPN) is one of a group of proteins found in urine that are believed to limit the formation of kidney stones. In the present study, we investigate the roles of phosphate and carboxylate groups in the OPN-mediated modulation of calcium oxalate (CaOx), the principal mineral phase found in kidney stones. To this end, crystallization was induced by addition of CaOx solution to ultrafiltered human urine containing either human kidney OPN (kOPN; 7 consecutive carboxylates, 8 phosphates) or synthesized peptides corresponding to residues 65-80 (pSHDHMDDDDDDDDDGD; pOPAR) or 220-235 (pSHEpSTEQSDAIDpSAEK; P3) of rat bone OPN. Sequence 65-80 was also synthesized without the phosphate group (OPAR). Effects on calcium oxalate monohydrate (COM) and dihydrate (COD) formation were studied by scanning electron microscopy. We found that controls form large, partly intergrown COM platelets; COD was never observed. Adding any of the polyelectrolytes was sufficient to prevent intergrowth of COM platelets entirely, inhibiting formation of these platelets strongly, and inducing formation of the COD phase. Strongest effects on COM formation were found for pOPAR and OPAR followed by kOPN and then P3, showing that acidity and hydrophilicity are crucial in polyelectrolyte-affected COM crystallization. At higher concentrations, OPAR also inhibited COD formation, while P3, kOPN and, in particular, pOPAR promoted COD, a difference explainable by the variations of carboxylate and phosphate groups present in the molecules. Thus, we conclude that carboxylate groups play a primary role in inhibiting COM formation, but phosphate and carboxylate groups are both important in initiating and promoting COD formation.

Conformations of gelatin in trivalent chromium salt solutions: Viscosity and dynamic light scattering study

NASA Astrophysics Data System (ADS)

Qiao, Congde; Zhang, Jianlong; Kong, Aiqun

2017-02-01

An investigation of the influences of pH, salt type, and salt concentration on the conformations of gelatin molecules in trivalent chromium salt solutions was performed by viscosity and dynamic light scattering (DLS) techniques. It was found that the viscosity behaviors as polyelectrolytes or polyampholytes depended on the charge distribution on the gelatin chains, which can be tuned by the value of pH of the gelatin solution. The intrinsic viscosity of gelatin in basic chromium sulfate aqueous solution at pH = 2.0 first decreased and then increased with increasing Cr(OH)SO4 concentration, while a monotonic decrease of the intrinsic viscosity of gelatin was observed in CrCl3 solution. However, the intrinsic viscosity of gelatin at pH = 5.0 was found to be increased first and then decreased with an increase in salt concentration in Cr(OH)SO4 solution, as well as in CrCl3 solution. We suggested that the observed viscosity behavior of gelatin in trivalent chromium salt solutions was attributed to the comprehensive effects of shielding, overcharging, and crosslinking (complexation) caused by the introduction of the different counterions. In addition, the average hydrodynamic radius ( R h ) of gelatin molecules in various salt solutions was determined by DLS. It was found that the change trend of R h with salt concentration was the same as the change of intrinsic viscosity. Based on the results of the viscosity and DLS, a possible mechanism for the conformational transition of gelatin chains with external conditions including pH, salt concentration, and salt type is proposed.

Polyelectrolyte layer-by-layer deposition in cylindrical nanopores.

PubMed

Lazzara, Thomas D; Lau, K H Aaron; Abou-Kandil, Ahmed I; Caminade, Anne-Marie; Majoral, Jean-Pierre; Knoll, Wolfgang

2010-07-27

Layer-by-layer (LbL) deposition of polyelectrolytes within nanopores in terms of the pore size and the ionic strength was experimentally studied. Anodic aluminum oxide (AAO) membranes, which have aligned, cylindrical, nonintersecting pores, were used as a model nanoporous system. Furthermore, the AAO membranes were also employed as planar optical waveguides to enable in situ monitoring of the LbL process within the nanopores by optical waveguide spectroscopy (OWS). Structurally well-defined N,N-disubstituted hydrazine phosphorus-containing dendrimers of the fourth generation, with peripherally charged groups and diameters of approximately 7 nm, were used as the model polyelectrolytes. The pore diameter of the AAO was varied between 30-116 nm and the ionic strength was varied over 3 orders of magnitude. The dependence of the deposited layer thickness on ionic strength within the nanopores is found to be significantly stronger than LbL deposition on a planar surface. Furthermore, deposition within the nanopores can become inhibited even if the pore diameter is much larger than the diameter of the G4-polyelectrolyte, or if the screening length is insignificant relative to the dendrimer diameter at high ionic strengths. Our results will aid in the template preparation of polyelectrolyte multilayer nanotubes, and our experimental approach may be useful for investigating theories regarding the partitioning of nano-objects within nanopores where electrostatic interactions are dominant. Furthermore, we show that the enhanced ionic strength dependence of polyelectrolyte transport within the nanopores can be used to selectively deposit a LbL multilayer atop a nanoporous substrate.

Distribution of PEG-coated hollow polyelectrolyte microcapsules after introduction into the circulatory system and muscles of zebrafish

PubMed Central

2018-01-01

ABSTRACT The use of polyelectrolyte multilayer microcapsules as carriers for fluorescent molecular probes is a prospective technique for monitoring the physiological characteristics of animal vasculature and interstitial environment in vivo. Polyelectrolyte microcapsules have many features that favor their use as implantable carriers of optical sensors, but little information is available on their interactions with complex living tissues, distribution or residence time following different routes of administration in the body of vertebrates. Using the common fish model, the zebrafish Danio rerio, we studied in vivo the distribution of non-biodegradable microcapsules covered with polyethylene glycol (PEG) over time in the adults and evaluated potential side effects of their delivery into the fish bloodstream and muscles. Fluorescent microcapsules administered into the bloodstream and interstitially (in concentrations that were sufficient for visualization and spectral signal recording) both showed negligible acute toxicity to the fishes during three weeks of observation. The distribution pattern of microcapsules delivered into the bloodstream was stable for at least one week, with microcapsules prevalent in capillaries-rich organs. However, after intramuscular injection, the phagocytosis of the microcapsules by immune cells was manifested, indicating considerable immunogenicity of the microcapsules despite PEG coverage. The long-term negative effects of chronic inflammation were also investigated in fish muscles by histological analysis. PMID:29305467

Study of sporadical properties of crosslinked polyelectrolyte multilayers

NASA Astrophysics Data System (ADS)

Balu, Deebika

Polyelectrolyte multilayers (PEM) have become a highly studied class of materials due to the range of their applicability in many areas of research, including biology, chemistry and materials science. Recent advances in surface coatings have enabled modification of PEM surfaces to provide desirable properties such as controlled release, super-hydrophobicity, biocompatibility, antifouling and antibacterial properties. In the past decade, antimicrobial PEM coatings have been investigated as a safer alternative to the traditional disinfection methods that usually involve application of hazardous chemicals onto the surface to be cleaned. These antimicrobial coatings could be applied to common surfaces prone to colonization of bacteria (such as bench tops, faucet handles, etc) to supplement routine sanitization protocols by providing sustained antimicrobial activity. Vegetative bacteria (such as Escherichia coli) are more susceptible to antimicrobial agents than bacterial species that form spores. Hence, the antimicrobial activity of PEM coatings fabricated using Layer by Layer (LbL) technique were assayed using Bacillus anthracis spores (Sterne strain). In this thesis, the sporicidal effect of various polyelectrolyte multilayer coatings containing cross-linked polymers immersed in bleach have been evaluated as potential augmentation to existing disinfection methods.

Mechanisms of Polyelectrolyte Enhanced Surfactant Adsorption at the Air-Water Interface

PubMed Central

Stenger, Patrick C.; Palazoglu, Omer A.; Zasadzinski, Joseph A.

2009-01-01

Chitosan, a naturally occurring cationic polyelectrolyte, restores the adsorption of the clinical lung surfactant Survanta to the air-water interface in the presence of albumin at much lower concentrations than uncharged polymers such as polyethylene glycol. This is consistent with the positively charged chitosan forming ion pairs with negative charges on the albumin and lung surfactant particles, reducing the net charge in the double-layer, and decreasing the electrostatic energy barrier to adsorption to the air-water interface. However, chitosan, like other polyelectrolytes, cannot perfectly match the charge distribution on the surfactant, which leads to patches of positive and negative charge at net neutrality. Increasing the chitosan concentration further leads to a reduction in the rate of surfactant adsorption consistent with an over-compensation of the negative charge on the surfactant and albumin surfaces, which creates a new repulsive electrostatic potential between the now cationic surfaces. This charge neutralization followed by charge inversion explains the window of polyelectrolyte concentration that enhances surfactant adsorption; the same physical mechanism is observed in flocculation and re-stabilization of anionic colloids by chitosan and in alternate layer deposition of anionic and cationic polyelectrolytes on charged colloids. PMID:19366599

Mechanisms of polyelectrolyte enhanced surfactant adsorption at the air-water interface.

PubMed

Stenger, Patrick C; Palazoglu, Omer A; Zasadzinski, Joseph A

2009-05-01

Chitosan, a naturally occurring cationic polyelectrolyte, restores the adsorption of the clinical lung surfactant Survanta to the air-water interface in the presence of albumin at much lower concentrations than uncharged polymers such as polyethylene glycol. This is consistent with the positively charged chitosan forming ion pairs with negative charges on the albumin and lung surfactant particles, reducing the net charge in the double-layer, and decreasing the electrostatic energy barrier to adsorption to the air-water interface. However, chitosan, like other polyelectrolytes, cannot perfectly match the charge distribution on the surfactant, which leads to patches of positive and negative charge at net neutrality. Increasing the chitosan concentration further leads to a reduction in the rate of surfactant adsorption consistent with an over-compensation of the negative charge on the surfactant and albumin surfaces, which creates a new repulsive electrostatic potential between the now cationic surfaces. This charge neutralization followed by charge inversion explains the window of polyelectrolyte concentration that enhances surfactant adsorption; the same physical mechanism is observed in flocculation and re-stabilization of anionic colloids by chitosan and in alternate layer deposition of anionic and cationic polyelectrolytes on charged colloids.

Electrolyte-stimulated biphasic dissolution profile and stability enhancement for tablets containing drug-polyelectrolyte complexes.

PubMed

Kindermann, Christoph; Matthée, Karin; Sievert, Frank; Breitkreutz, Jörg

2012-10-01

Recently introduced drug-polyelectrolyte complexes prepared by hot-melt extrusion should be processed to solid dosage forms with tailor-made release properties. Their potential of stability enhancement should be investigated. Milled hot-melt extruded naproxen-EUDRAGIT® E PO polyelectrolyte complexes were subsequently processed to double-layer tablets with varying complex loadings on a rotary-die press. Physicochemical interactions were studied under ICH guideline conditions and using the Gordon-Taylor equation. Sorption and desorption were determined to investigate the influence of moisture and temperature on the complex and related to stability tests under accelerated conditions. Naproxen release from the drug-polyelectrolyte complex is triggered by electrolyte concentration. Depending on the complex loading, phosphate buffer pH 6.8 stimulated a biphasic dissolution profile of the produced double-layer tablets: immediate release from the first layer with 65% loading and prolonged release from the second layer within 24 h (98.5% loading). XRPD patterns proved pseudopolymorphism for tablets containing the pure drug under common storage conditions whereas the drug-complex was stable in the amorphous state. Drug-polyelectrolyte complexes enable tailor-made dissolution profiles of solid dosage forms by electrolyte stimulation and increase stability under common storage conditions.

The Rheological Properties of the Biopolymers in Synovial Fluid

NASA Astrophysics Data System (ADS)

Krause, Wendy E.; Klossner, Rebecca R.; Wetsch, Julie; Oates, Katherine M. N.; Colby, Ralph H.

2005-03-01

The polyelectrolyte hyaluronic acid (HA, hyaluronan), its interactions with anti-inflammatory drugs and other biopolymers, and its role in synovial fluid are being studied. We are investigating the rheological properties of sodium hyaluronate (NaHA) solutions and an experimental model of synovial fluid (comprised of NaHA, and the plasma proteins albumin and γ-globulins). Steady shear measurements on bovine synovial fluid and the synovial fluid model indicate that the fluids are highly viscoeleastic and rheopectic (stress increases with time under steady shear). In addition, the influence of anti-inflammatory agents on these solutions is being explored. Initial results indicate that D-penicillamine and hydroxychloroquine affect the rheology of the synovial fluid model and its components. The potential implications of these results will be discussed.

Ring-opening polymerization of 19-electron [2]cobaltocenophanes: a route to high-molecular-weight, water-soluble polycobaltocenium polyelectrolytes.

PubMed

Mayer, Ulrich F J; Gilroy, Joe B; O'Hare, Dermot; Manners, Ian

2009-08-05

Water-soluble, high-molecular-weight polycobaltocenium polyelectrolytes have been prepared by ring-opening polymerization (ROP) techniques. Anionic polymerization of a strained 19-electron dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium chloride resulted in the formation of oligomers with up to nine repeat units. Thermal ROP of dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium nitrate resulted in the formation of high-molecular-weight polycobaltocenium nitrate, a redox-active cobalt-containing polyelectrolyte.

Nanoparticles for Nonaqueous-phase liquids (NAPLs) Remediation

NASA Astrophysics Data System (ADS)

Jiemvarangkul, Pijit

Nanotechnology has gained attention in various fields of science and engineering for more than decades. Many nanotechnologies using nanosorbents, nanosensors, and nanoparticles have been developed, studied, and used to solve environmental problems. This dissertation contributes to the applications of two types of nanoparticles: 1) using zero valent iron nanoparticle technology (nZVI) for treatment of groundwater contaminated by chlorinated hydrocarbons and study effect of polyelectrolyte polymers on enhancing the mobility of nZVI in porous media and 2) testing a new type of nanoparticle, nano-scale calcium peroxide (CaO2) particles (nano-peroxide); particles have been synthesized and preliminarily tests on their chemical properties and oxidizing reactions with petroleum hydrocarbons investigated. Trichloroethylene (TCE) is one of the high toxic, dense, non-aqueous phase liquids (DNAPLs) and it is one of the major problems of groundwater contamination. The direct reaction of nano-scale zerovalent iron (nZVI) particles and TCE liquid phase batch experiments shows that nZVI has capability to remove pure phase TCE and there is the reduction reaction occurred with reaction byproduct. Mass balance of nZVI-TCE reaction demonstrates that 7--9 % TCE mass was trapped in 1 g of nZVI sludge indicating that absorption occurred during the removal process confirming the absorption of TCE into nZVI sludge. The reaction and absorption abilities of nZVI are depended upon its surface areas. Increasing amount of nZVI reduces the space of batch experiment systems, so TCE removal efficiency of nZVI is decreased. These experiments show the practicability of using nZVI to directly remove TCE from contaminated groundwater. The transport of nanoscale zero-valent iron (nZVI) particles stabilized by three polyelectrolytes: polyvinyl alcohol-co-vinyl acetate-co-itaconic acid (PV3A), poly(acrylic acid) (PAA) and soy proteins were examined. The study shows the increase in nZVI mobility by reducing particle size and generating negatively charged surfaces of nZVI by those polyelectrolyte polymers. PV3A stabilized nZVI has the best transport performance among the three materials. It was found that approximately 100% of nZVI flowed through the column. Retardation of nZVI is observed in all tests. Due to the large surface area of nZVI, large amounts of polyelectrolytes are often needed. For example, soy proteins exhibited an excellent stabilization capability only at the dose over 30% of nZVI mass. Approximately 57% of nZVI remained in the column when nZVI was stabilized with PAA at the dosage of 50%. Results suggest that nZVI may be prepared with tunable travel distance to form an iron reactive zone for the in situ remediation. The new nano size particles of calcium peroxide (nano-peroxide) were synthesized by the mechanical milling method. The particle size diameter (d 50) is around 120 nm with the enormous specific surface area at 30 m 2/g. The dissolution and reaction rate of nano-peroxide is faster than typical micro powder calcium peroxide around 1.5 times. With metal catalyzes (Fe2+), nano-peroxide promoted modified Fenton's chemistry (MF) and showed an excellent performance for oxidizing hydrocarbon. Benzene solutions were completely oxidized as high as 800 mg/L of benzene and gasoline contaminated solution was significantly decreased within 24 hours. pH is a major factor to increase the oxidizing of nano-peroxide. This research also reports the synthesis method, images and composition of nano-peroxide.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrova, V. A.; Orekhov, A. S.; Chernyakov, D. D.

A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan–hyaluronic acid, chitosan–alginic acid, and chitosan–carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs.

Bacteriophage enzymes for the prevention and treatment of bacterial infections: Stability and stabilization of the enzyme lysing Streptococcus pyogenes cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klyachko, N. L.; Dmitrieva, N. F.; Eshchina, A. S.

2008-06-01

Recombinant, phage associated lytic enzyme Ply C capable to lyse streptococci of groups A and C was stabilized in the variety of the micelles containing compositions to improve the stability of the enzyme for further application in medicine. It was shown that, in the micellar polyelectrolyte composition M16, the enzyme retained its activity for 2 months; while in a buffer solution under the same conditions ((pH 6.3, room temperature), it completely lost its activity in 2 days

Design of Chitosan and Its Water Soluble Derivatives-Based Drug Carriers with Polyelectrolyte Complexes

PubMed Central

Wu, Qing-Xi; Lin, Dong-Qiang; Yao, Shan-Jing

2014-01-01

Chitosan, the cationic polysaccharide derived from the natural polysaccharide chitin, has been studied as a biomaterial for more than two decades. As a polycationic polymer with favorable properties, it has been widely used to form polyelectrolyte complexes with polyanions for various applications in drug delivery fields. In recent years, a growing number of studies have been focused on the preparation of polyelectrolyte complexes based on chitosan and its water soluble derivatives. They have been considered well-suited as biomaterials for a number of vital drug carriers with targeted/controlled release profiles, e.g., films, capsules, microcapsules. In this work, an overview highlights not only the favorable properties of chitosan and its water soluble derivatives but also the good performance of the polyelectrolyte complexes produced based on chitosan. Their various types of applications as drug carriers are reviewed in detail. PMID:25532565

The evolution of cyclopropenium ions into functional polyelectrolytes

PubMed Central

Jiang, Yivan; Freyer, Jessica L.; Cotanda, Pepa; Brucks, Spencer D.; Killops, Kato L.; Bandar, Jeffrey S.; Torsitano, Christopher; Balsara, Nitash P.; Lambert, Tristan H.; Campos, Luis M.

2015-01-01

Versatile polyelectrolytes with tunable physical properties have the potential to be transformative in applications such as energy storage, fuel cells and various electronic devices. Among the types of materials available for these applications, nanostructured cationic block copolyelectrolytes offer mechanical integrity and well-defined conducting paths for ionic transport. To date, most cationic polyelectrolytes bear charge formally localized on heteroatoms and lack broad modularity to tune their physical properties. To overcome these challenges, we describe herein the development of a new class of functional polyelectrolytes based on the aromatic cyclopropenium ion. We demonstrate the facile synthesis of a series of polymers and nanoparticles based on monomeric cyclopropenium building blocks incorporating various functional groups that affect physical properties. The materials exhibit high ionic conductivity and thermal stability due to the nature of the cationic moieties, thus rendering this class of new materials as an attractive alternative to develop ion-conducting membranes. PMID:25575214

Design of chitosan and its water soluble derivatives-based drug carriers with polyelectrolyte complexes.

PubMed

Wu, Qing-Xi; Lin, Dong-Qiang; Yao, Shan-Jing

2014-12-19

Chitosan, the cationic polysaccharide derived from the natural polysaccharide chitin, has been studied as a biomaterial for more than two decades. As a polycationic polymer with favorable properties, it has been widely used to form polyelectrolyte complexes with polyanions for various applications in drug delivery fields. In recent years, a growing number of studies have been focused on the preparation of polyelectrolyte complexes based on chitosan and its water soluble derivatives. They have been considered well-suited as biomaterials for a number of vital drug carriers with targeted/controlled release profiles, e.g., films, capsules, microcapsules. In this work, an overview highlights not only the favorable properties of chitosan and its water soluble derivatives but also the good performance of the polyelectrolyte complexes produced based on chitosan. Their various types of applications as drug carriers are reviewed in detail.

Nanohybrid conjugated polyelectrolytes: highly photostable and ultrabright nanoparticles.

PubMed

Darwish, Ghinwa H; Karam, Pierre

2015-10-07

We present a general and straightforward one-step approach to enhance the photophysical properties of conjugated polyelectrolytes. Upon complexation with an amphiphilic polymer (polyvinylpyrrolidone), an anionic conjugated polyelectrolyte (poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene]) was prepared into small nanoparticles with exceptional photostability and brightness. The polymer fluorescence intensity was enhanced by 23 -fold and could be easily tuned by changing the order of addition. Single molecule experiments revealed a complete suppression of blinking. In addition, after only losing 18% of the original intensity, a remarkable amount of photons were emitted per particle (∼10(9), on average). This number is many folds greater than popular organic fluorescent dyes. We believe that an intimate contact between the two polymers is shielding the conjugated polyelectrolyte from the destructive photooxidation. The prepared nanohybrid particles will prove instrumental in single particle based fluorescent assays and can serve as a probe for the current state-of-the-art bioimaging fluorescence techniques.

The evolution of cyclopropenium ions into functional polyelectrolytes

DOE PAGES

Jiang, Yivan; Freyer, Jessica L.; Cotanda, Pepa; ...

2015-01-09

We report that versatile polyelectrolytes with tunable physical properties have the potential to be transformative in applications such as energy storage, fuel cells and various electronic devices. Among the types of materials available for these applications, nanostructured cationic block copolyelectrolytes offer mechanical integrity and well-defined conducting paths for ionic transport. To date, most cationic polyelectrolytes bear charge formally localized on heteroatoms and lack broad modularity to tune their physical properties. To overcome these challenges, we describe herein the development of a new class of functional polyelectrolytes based on the aromatic cyclopropenium ion.We demonstrate the facile synthesis of a series ofmore » polymers and nanoparticles based on monomeric cyclopropenium building blocks incorporating various functional groups that affect physical properties. In conclusion, the materials exhibit high ionic conductivity and thermal stability due to the nature of the cationic moieties, thus rendering this class of new materials as an attractive alternative to develop ion-conducting membranes.« less

A Brownian dynamics program for the simulation of linear and circular DNA and other wormlike chain polyelectrolytes.

PubMed Central

Klenin, K; Merlitz, H; Langowski, J

1998-01-01

For the interpretation of solution structural and dynamic data of linear and circular DNA molecules in the kb range, and for the prediction of the effect of local structural changes on the global conformation of such DNAs, we have developed an efficient and easy way to set up a program based on a second-order explicit Brownian dynamics algorithm. The DNA is modeled by a chain of rigid segments interacting through harmonic spring potentials for bending, torsion, and stretching. The electrostatics are handled using precalculated energy tables for the interactions between DNA segments as a function of relative orientation and distance. Hydrodynamic interactions are treated using the Rotne-Prager tensor. While maintaining acceptable precision, the simulation can be accelerated by recalculating this tensor only once in a certain number of steps. PMID:9533691

Intrinsic viscosity and rheological properties of natural and substituted guar gums in seawater.

PubMed

Wang, Shibin; He, Le; Guo, Jianchun; Zhao, Jinzhou; Tang, Hongbiao

2015-05-01

The intrinsic viscosity and rheological properties of guar gum (GG), hydroxypropyl guar (HPG) and carboxymethyl guar (CMG) in seawater and the effects of shear rate, concentration, temperature and pH on these properties were investigated. An intrinsic viscosity-increasing effect was observed with GG and HPG in seawater (SW) compared to deionized water (DW), whereas the intrinsic viscosity of CMG in seawater was much lower than that in DW due to a screening effect that reduced the repulsion between the polymer chains. Regardless of the functional groups, all sample solutions was well characterized by a modified Cross model that exhibited the transition from Newtonian to pseudoplastic in the low shear rate range at the concentrations of interest to industries, and their viscosity increased with the increase in their concentration but decreased with the increase in temperature. In contrast to nonionic GG or HPG, anionic CMG had a slightly decreased viscosity property in SW, exhibiting polyelectrolyte viscosity behavior. The α value in the zero-shear rate viscosity vs. concentration power-law equation for the samples gave the order of CMG>HPG>GG while the SW solution of CMG had the lowest viscous flow activation energy and exhibited a strong pH-dependent viscosity by a different shear rate. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of reactive monomer on PS-b-P2VP film.

PubMed

Kim, H J; Shin, D M

2014-08-01

Poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) lamellar film which is hydrophobic block-hydrophilic polyelectrolyte block polymer of 52 kg/mol-b-57 kg/mol and PS-b-P2VP film with reactive monomer (RM257) were prepared for photonic gel films. The lamellar stacks, which is alternating layer of hydrophilic and hydrophobic moiety of PS-b-P2VP, were obtained by exposing the spin coated film under chloroform vapor. The lamellar films were quaternized with 5 wt% of iodomethane diluted by n-hexane. We reported about the influence of reactive monomer on those photonic gel films. Added reactive monomer photonic gel film had higher absorbance than pure photonic gel films. As a result the photonic gel film with RM had more clear color. The lamellar films were swollen by DI water, ethanol (aq) and calcium carbonate solution. The band gaps of the lamellar films were drastically shifted to longer wavelength swollen by calcium carbonate solution. And the lamellar films were shifted to shorter wave length swollen by ethanol. So each lamellar film showed different color.

Influence of Hydrophobicity on Polyelectrolyte Complexation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadman, Kazi; Wang, Qifeng; Chen, Yaoyao

Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP)more » with methyl, ethyl and propyl substituents– thereby increasing the hydrophobicity with increasing side chain length– and complexing them with a common anionic polyelectrolyte, poly(styrene sulfonate). The mechanical 1 ACS Paragon Plus Environment behavior of these complexes is compared to the more hydrophilic system of poly(styrene sulfonate) and poly(diallyldimethylammonium) by quantifying the swelling behavior in response to salt stimuli. More hydrophobic complexes are found to be more resistant to doping by salt, yet the mechanical properties of the complex remain contingent on the overall swelling ratio of the complex itself, following near universal swelling-modulus master curves that are quantified in this work. The rheological behavior of QVP complex coacervates are found to be approximately the same, only requiring higher salt concentrations to overcome strong hydrophobic interactions, demonstrating that hydrophobicity can be used as an important parameter for tuning the stability of polyelectrolyte complexes in general, while still preserving the ability to be processed “saloplastically”.« less

Influence of Hydrophobicity on Polyelectrolyte Complexation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadman, Kazi; Wang, Qifeng; Chen, Yaoyao

Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low-viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials, their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture, it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP) withmore » methyl, ethyl, and propyl substituents—thereby increasing the hydrophobicity with increasing side chain length—and complexing them with a common anionic polyelectrolyte, poly(styrenesulfonate). The mechanical behavior of these complexes is compared to the more hydrophilic system of poly(styrenesulfonate) and poly(diallyldimethylammonium) by quantifying the swelling behavior in response to salt stimuli. More hydrophobic complexes are found to be more resistant to doping by salt, yet the mechanical properties of the complex remain contingent on the overall swelling ratio of the complex itself, following near universal swelling–modulus master curves that are quantified in this work. Furthermore, the rheological behaviors of QVP complex coacervates are found to be approximately the same, only requiring higher salt concentrations to overcome strong hydrophobic interactions, demonstrating that hydrophobicity can be used as an important parameter for tuning the stability of polyelectrolyte complexes in general, while still preserving the ability to be processed “saloplastically”.« less

Influence of Hydrophobicity on Polyelectrolyte Complexation

DOE PAGES

Sadman, Kazi; Wang, Qifeng; Chen, Yaoyao; ...

2017-11-16

Polyelectrolyte complexes are a fascinating class of soft materials that can span the full spectrum of mechanical properties from low-viscosity fluids to glassy solids. This spectrum can be accessed by modulating the extent of electrostatic association in these complexes. However, to realize the full potential of polyelectrolyte complexes as functional materials, their molecular level details need to be clearly correlated with their mechanical response. The present work demonstrates that by making simple amendments to the chain architecture, it is possible to affect the salt responsiveness of polyelectrolyte complexes in a systematic manner. This is achieved by quaternizing poly(4-vinylpyridine) (QVP) withmore » methyl, ethyl, and propyl substituents—thereby increasing the hydrophobicity with increasing side chain length—and complexing them with a common anionic polyelectrolyte, poly(styrenesulfonate). The mechanical behavior of these complexes is compared to the more hydrophilic system of poly(styrenesulfonate) and poly(diallyldimethylammonium) by quantifying the swelling behavior in response to salt stimuli. More hydrophobic complexes are found to be more resistant to doping by salt, yet the mechanical properties of the complex remain contingent on the overall swelling ratio of the complex itself, following near universal swelling–modulus master curves that are quantified in this work. Furthermore, the rheological behaviors of QVP complex coacervates are found to be approximately the same, only requiring higher salt concentrations to overcome strong hydrophobic interactions, demonstrating that hydrophobicity can be used as an important parameter for tuning the stability of polyelectrolyte complexes in general, while still preserving the ability to be processed “saloplastically”.« less

Positively charged and bipolar layered poly(ether imide) nanofiltration membranes for water softening applications

NASA Astrophysics Data System (ADS)

Gassara, S.; Abdelkafi, A.; Quémener, D.; Amar, R. Ben; Deratani, A.

2015-07-01

Poly(ether imide) (PEI) ultrafiltration membranes were chemically modified with branched poly(ethyleneimine) to obtain nanofiltration (NF) membrane Cat PEI with a positive charge in the pH range below 9. An oppositely charged polyelectrolyte layer was deposited on the resulting membrane surface by using sodium polystyrene sulfonate (PSSNa) and sodium polyvinyl sulfonate (PVSNa) to prepare a bipolar layered membrane NF Cat PEI_PSS and Cat PEI_PVS having a negatively charged surface and positively charged pores. Cat PEI exhibited good performance to remove multivalent cations (more than 90% of Ca2+) from single salt solutions except in presence of sulfate ions. Adding an anionic polyelectrolyte layer onto the positively charged surface resulted in a significant enhancement of rejection performance even in presence of sulfate anions. Application of the prepared membranes in water softening of natural complex mixtures was successful for the different studied membranes and a large decrease of hardness was obtained. Moreover, Cat PEI_PSS showed a good selectivity for nitrate removal. Fouling experiments were carried out with bovine serum albumin, as model protein foulant. Cat PEI_PSS showed much better fouling resistance than Cat PEI with a quantitative flux recovery ratio.

Distinctive viscoelastic and viscoplastic nanomechanics of ionically cross-linked polyelectrolyte complexes under intermittent relaxation and creep

NASA Astrophysics Data System (ADS)

Han, Biao; Ma, Tianzhu; Lee, Daeyeon; Shenoy, Vivek; Han, Lin

This study aims to reveal unique nanoscale viscoelastic and viscoplastic properties of ionically linked polyelectrolyte networks. Layer-by-layer PAH/PAA complexes were tested by four continuous loading cycles in aqueous solutions. In each cycle, AFM-nanoindentation via a microspherical tip (R =5 μm) was applied up to 1 μN force, followed by a 30-60 sec hold at either a constant indentation depth to measure relaxation, or a constant force to measure creep. At a highly cross-linked, net neutral state (0.01M, pH 5.5), instantaneous modulus increased by 2.7-fold from first to last cycle, while the degree of relaxation (>95%) remain consistent. These results indicate repeated loading increases local cross-link density, while relaxation is consistently dominated by cross-link breaking and re-formation. In contrast, under creep, modulus increased by a similar 3.5-fold, and degree of creep is significantly attenuated from ~50% to 45% from first to last cycle. Results from creep suggest constant viscous flow of polymer chains in the absence of permanent anchorage. As a result, an irreversible deformation (~370nm) was observed after multiple creep cycles, suggesting the presence of viscoplasticity.

Chain conformation, rheological and charge properties of fucoidan extracted from sea cucumber Thelenota ananas: A semi-flexible coil negative polyelectrolyte.

PubMed

Xu, Xiaoqi; Xue, Changhu; Chang, Yaoguang; Liu, Guanchen

2017-12-15

As a bioactive and functional polysaccharide, sea cucumber fucoidan has received increasing attention. Chain conformation and physicochemical properties of fucoidan extracted from Thelenota ananas (Ta-FUC) was investigated by utilizing HPSEC-MALLS-Visc-RI, microelectrophoresis and steady shear measurements. The conformation parameter α s (0.61±0.02), the Mark-Houwink-Kuhn-Sakurada exponent α η (0.92±0.01), α h (0.64±0.01) and the Smidsrød-Haug stiffness parameter B (0.036±0.010) consistently manifested that Ta-FUC adopted a semi-flexible coil conformation in NaCl solution. Based on a wormlike cylinder model, stiffness parameters, including persistence length q (13.27±0.80nm) and cylinder diameter d (0.79nm), were calculated. This polysaccharide demonstrated shear-thinning rheological behaviour, and critical concentration from dilute to semidilute concentration regime was determined as 3.6mg/ml. Ta-FUC exhibited as a negative polyelectrolyte in wide pH and ionic strength ranges. These molecular characteristics and physicochemical properties would facilitate further application of Ta-FUC as a functional ingredient in food. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multilayered Polyelectrolyte Microcapsules: Interaction with the Enzyme Cytochrome C Oxidase

PubMed Central

Pastorino, Laura; Dellacasa, Elena; Noor, Mohamed R.; Soulimane, Tewfik; Bianchini, Paolo; D'Autilia, Francesca; Antipov, Alexei; Diaspro, Alberto; Tofail, Syed A. M.; Ruggiero, Carmelina

2014-01-01

Cell-sized polyelectrolyte capsules functionalized with a redox-driven proton pump protein were assembled for the first time. The interaction of polyelectrolyte microcapsules, fabricated by electrostatic layer-by-layer assembly, with cytochrome c oxidase molecules was investigated. We found that the cytochrome c oxidase retained its functionality, that the functionalized microcapsules interacting with cytochrome c oxidase were permeable and that the permeability characteristics of the microcapsule shell depend on the shell components. This work provides a significant input towards the fabrication of an integrated device made of biological components and based on specific biomolecular functions and properties. PMID:25372607

Facile preparation of cobaltocenium-containing polyelectrolyte via click chemistry and RAFT polymerization.

PubMed

Yan, Yi; Zhang, Jiuyang; Qiao, Yali; Tang, Chuanbing

2014-01-01

A facile method to prepare cationic cobaltocenium-containing polyelectrolyte is reported. Cobaltocenium monomer with methacrylate is synthesized by copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction between 2-azidoethyl methacrylate and ethynylcobaltocenium hexafluorophosphate. Further controlled polymerization is achieved by reversible addition-fragmentation chain transfer polymerization (RAFT) by using cumyl dithiobenzoate (CDB) as a chain transfer agent. Kinetic study demonstrates the controlled/living process of polymerization. The obtained side-chain cobaltocenium-containing polymer is a metal-containing polyelectrolyte that shows characteristic redox behavior of cobaltocenium. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical determination of the glass transition temperature of thin polyelectrolyte brushes at solid-liquid interfaces by impedance spectroscopy.

PubMed

Alonso-García, Teodoro; Rodríguez-Presa, María José; Gervasi, Claudio; Moya, Sergio; Azzaroni, Omar

2013-07-16

Devising strategies to assess the glass transition temperature (Tg) of polyelectrolyte assemblies at solid-electrolyte interfaces is very important to understand and rationalize the temperature-dependent behavior of polyelectrolyte films in a wide range of settings. Despite the evolving perception of the importance of measuring Tg under aqueous conditions in thin film configurations, its straightforward measurement poses a challenging situation that still remains elusive in polymer and materials science. Here, we describe a new method based on electrochemical impedance spectroscopy (EIS) to estimate the glass transition temperature of planar polyelectrolyte brushes at solid-liquid interfaces. To measure Tg, the charge transfer resistance (Rct) of a redox probe diffusing through the polyelectrolyte brush was measured, and the temperature corresponding to the discontinuous change in Rct was identified as Tg. Furthermore, we demonstrate that impedance measurements not only facilitate the estimation of Tg but also enable a reliable evaluation of the transport properties of the polymeric interface, i.e., determination of diffusion coefficients, close to the thermal transition. We consider that this approach bridges the gap between electrochemistry and the traditional tools used in polymer science and offers new opportunities to characterize the thermal behavior of complex polymeric interfaces and macromolecular assemblies.

Encapsulation of curcumin in polyelectrolyte nanocapsules and their neuroprotective activity

NASA Astrophysics Data System (ADS)

Szczepanowicz, Krzysztof; Jantas, Danuta; Piotrowski, Marek; Staroń, Jakub; Leśkiewicz, Monika; Regulska, Magdalena; Lasoń, Władysław; Warszyński, Piotr

2016-09-01

Poor water solubility and low bioavailability of lipophilic drugs can be potentially improved with the use of delivery systems. In this study, encapsulation of nanoemulsion droplets was utilized to prepare curcumin nanocarriers. Nanosize droplets containing the drug were encapsulated in polyelectrolyte shells formed by the layer-by-layer (LbL) adsorption of biocompatible polyelectrolytes: poly-L-lysine (PLL) and poly-L-glutamic acid (PGA). The size of synthesized nanocapsules was around 100 nm. Their biocompatibility and neuroprotective effects were evaluated on the SH-SY5Y human neuroblastoma cell line using cell viability/toxicity assays (MTT reduction, LDH release). Statistically significant toxic effect was clearly observed for PLL coated nanocapsules (reduction in cell viability about 20%-60%), while nanocapsules with PLL/PGA coating did not evoke any detrimental effects on SH-SY5Y cells. Curcumin encapsulated in PLL/PGA showed similar neuroprotective activity against hydrogen peroxide (H2O2)-induced cell damage, as did 5 μM curcumin pre-dissolved in DMSO (about 16% of protection). Determination of concentration of curcumin in cell lysate confirmed that curcumin in nanocapsules has cell protective effect in lower concentrations (at least 20 times) than when given alone. Intracellular mechanisms of encapsulated curcumin-mediated protection engaged the prevention of the H2O2-induced decrease in mitochondrial membrane potential (MMP) but did not attenuate Reactive Oxygen Species (ROS) formation. The obtained results indicate the utility of PLL/PGA shell nanocapsules as a promising, alternative way of curcumin delivery for neuroprotective purposes with improved efficiency and reduced toxicity.

Encapsulation of curcumin in polyelectrolyte nanocapsules and their neuroprotective activity.

PubMed

Szczepanowicz, Krzysztof; Jantas, Danuta; Piotrowski, Marek; Staroń, Jakub; Leśkiewicz, Monika; Regulska, Magdalena; Lasoń, Władysław; Warszyński, Piotr

2016-09-02

Poor water solubility and low bioavailability of lipophilic drugs can be potentially improved with the use of delivery systems. In this study, encapsulation of nanoemulsion droplets was utilized to prepare curcumin nanocarriers. Nanosize droplets containing the drug were encapsulated in polyelectrolyte shells formed by the layer-by-layer (LbL) adsorption of biocompatible polyelectrolytes: poly-L-lysine (PLL) and poly-L-glutamic acid (PGA). The size of synthesized nanocapsules was around 100 nm. Their biocompatibility and neuroprotective effects were evaluated on the SH-SY5Y human neuroblastoma cell line using cell viability/toxicity assays (MTT reduction, LDH release). Statistically significant toxic effect was clearly observed for PLL coated nanocapsules (reduction in cell viability about 20%-60%), while nanocapsules with PLL/PGA coating did not evoke any detrimental effects on SH-SY5Y cells. Curcumin encapsulated in PLL/PGA showed similar neuroprotective activity against hydrogen peroxide (H2O2)-induced cell damage, as did 5 μM curcumin pre-dissolved in DMSO (about 16% of protection). Determination of concentration of curcumin in cell lysate confirmed that curcumin in nanocapsules has cell protective effect in lower concentrations (at least 20 times) than when given alone. Intracellular mechanisms of encapsulated curcumin-mediated protection engaged the prevention of the H2O2-induced decrease in mitochondrial membrane potential (MMP) but did not attenuate Reactive Oxygen Species (ROS) formation. The obtained results indicate the utility of PLL/PGA shell nanocapsules as a promising, alternative way of curcumin delivery for neuroprotective purposes with improved efficiency and reduced toxicity.

Influence of Layer-by-Layer Polyelectrolyte Deposition and EDC/NHS Activated Heparin Immobilization onto Silk Fibroin Fabric

PubMed Central

Elahi, M. Fazley; Guan, Guoping; Wang, Lu; King, Martin W.

2014-01-01

To enhance the hemocompatibility of silk fibroin fabric as biomedical material, polyelectrolytes architectures have been assembled through the layer-by-layer (LbL) technique on silk fibroin fabric (SFF). In particular, 1.5 and 2.5 bilayer of oppositely charged polyelectrolytes were assembled onto SFF using poly(allylamine hydrochloride) (PAH) as polycationic polymer and poly(acrylic acid) (PAA) as polyanionic polymer with PAH topmost. Low molecular weight heparin (LMWH) activated with 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was then immobilized on its surface. Alcian Blue staining, toluidine blue assay and X-ray photoelectron spectroscopy (XPS) confirmed the presence of heparin on modified SFF surfaces. The surface morphology of the modified silk fibroin fabric surfaces was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and obtained increased roughness. Negligible hemolytic effect and a higher concentration of free hemoglobin by a kinetic clotting time test ensured the improved biological performance of the modified fibroin fabric. Overall, the deposition of 2.5 bilayer was found effective in terms of biological and surface properties of the modified fibroin fabric compared to 1.5 bilayer self-assembly technique. Therefore, this novel approach to surface modification may demonstrate long term patency in future in vivo animal trials of small diameter silk fibroin vascular grafts. PMID:28788601

Layer-by-layer buildup of polysaccharide-containing films: Physico-chemical properties and mesenchymal stem cells adhesion.

PubMed

Kulikouskaya, Viktoryia I; Pinchuk, Sergei V; Hileuskaya, Kseniya S; Kraskouski, Aliaksandr N; Vasilevich, Irina B; Matievski, Kirill A; Agabekov, Vladimir E; Volotovski, Igor D

2018-03-22

Layer-by-Layer assembled polyelectrolyte films offer the opportunity to control cell attachment and behavior on solid surfaces. In the present study, multilayer films based on negatively charged biopolymers (pectin, dextran sulfate, carboxymethylcellulose) and positively charged polysaccharide chitosan or synthetic polyelectrolyte polyethyleneimine has been prepared and evaluated. Physico-chemical properties of the formed multilayer films, including their growth, morphology, wettability, stability, and mechanical properties, have been studied. We demonstrated that chitosan-containing films are characterized by the linear growth, the defect-free surface, and predominantly viscoelastic properties. When chitosan is substituted for the polyethyleneimine in the multilayer system, the properties of the formed films are significantly altered: the rigidity and surface roughness increases, the film growth acquires the exponential character. The multilayer films were subsequently used for culturing mesenchymal stem cells. It has been determined that stem cells effectively adhered to chitosan-containing films and formed on them the monolayer culture of fibroblast-like cells with high viability. Our results show that cell attachment is a complex process which is not only governed by the surface functionality because one of the key parameter effects on cell adhesion is the stiffness of polyelectrolyte multilayer films. We therefore propose our Layer-by-Layer films for applications in tissue engineering. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2018. © 2018 Wiley Periodicals, Inc.

Effect of Salt Concentration on the pH Responses of Strong and Weak Polyelectrolyte Brushes.

PubMed

Zhang, Jian; Kou, Ran; Liu, Guangming

2017-07-11

Strong polyelectrolyte brushes (SPB) and weak polyelectrolyte brushes (WPB) have different origins with response to pH, which makes their pH-responsive properties sensitive to salt concentration in different ways. Herein, we have employed poly[2-(methacryloyloxy)ethyl trimethylammonium chloride] (PMETAC) and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) brushes as model systems for SPB and WPB, respectively, to investigate the effect of salt concentration on the pH responses of SPB and WPB using several surface-sensitive techniques. The pH-responsive properties of the PMETAC brushes are governed by the reorganization of the interchain hydrogen bonds between the grafted chains, whereas the pH response of the PDMAEMA brushes is controlled by the charge of the grafted chains. The response of the properties of the PMETAC brushes including hydration, conformation, and surface wettability becomes weaker with increasing salt concentration induced by the competitive adsorption of counterions to the brushes between OH - and Cl - . The weakening of the pH response of the PMETAC brushes is more remarkable at the relatively high pH values. The pH response of the PDMAEMA brushes also exhibits a salt-concentration dependence. As the salt concentration increases, the weakening of the pH response of the PDMAEMA brushes is attributed to the decrease in osmotic pressure within the brushes at relatively low pH values.

Layer-by-Layer Assembled Architecture of Polyelectrolyte Multilayers and Graphene Sheets on Hollow Carbon Spheres/Sulfur Composite for High-Performance Lithium-Sulfur Batteries.

PubMed

Wu, Feng; Li, Jian; Su, Yuefeng; Wang, Jing; Yang, Wen; Li, Ning; Chen, Lai; Chen, Shi; Chen, Renjie; Bao, Liying

2016-09-14

In the present work, polyelectrolyte multilayers (PEMs) and graphene sheets are applied to sequentially coat on the surface of hollow carbon spheres/sulfur composite by a flexible layer-by-layer (LBL) self-assembly strategy. Owing to the strong electrostatic interactions between the opposite charged materials, the coating agents are very stable and the coating procedure is highly efficient. The LBL film shows prominent impact on the stability of the cathode by acting as not only a basic physical barrier, and more importantly, an ion-permselective film to block the polysulfides anions by Coulombic repulsion. Furthermore, the graphene sheets can help to stabilize the polyelectrolytes film and greatly reduce the inner resistance of the electrode by changing the transport of the electrons from a "point-to-point" mode to a more effective "plane-to-point'' mode. On the basis of the synergistic effect of the PEMs and graphene sheets, the fabricated composite electrode exhibits very stable cycling stability for over 200 cycles at 1 A g(-1), along with a high average Coulombic efficiency of 99%. With the advantages of rapid and controllable fabrication of the LBL coating film, the multifunctional architecture developed in this study should inspire the design of other lithium-sulfur cathodes with unique physical and chemical properties.

Poly(l-glutamic acid)-g-poly(ethylene glycol) external layer in polyelectrolyte multilayer films: Characterization and resistance to serum protein adsorption.

PubMed

Szczepanowicz, Krzysztof; Kruk, Tomasz; Świątek, Wiktoria; Bouzga, Aud M; Simon, Christian R; Warszyński, Piotr

2018-06-01

Formation of protein-resistant surfaces is a major challenge in the design of novel biomaterials and an important strategy to prevent protein adsorption is the formation of protein-resistant coatings. It can be achieved by proper modification of surfaces, e.g., by immobilization of hydrophilic polymers such as poly(ethylene glycol) (PEG). An appropriate method to immobilize PEG at charged surfaces is the adsorption of copolymers with PEG chains grafted onto polyelectrolyte backbone. The growing interest in the use of polyelectrolyte multilayer coatings in biomedical applications to improve biocompatibility and/or to prepare coating with antiadhesive properties has been the main reason for these studies. Therefore the aim was to produce protein resistant polyelectrolyte multilayer films. They were formed via the layer-by-layer approach, while their pegylation by the deposition of pegylated polyanion, PGA-g-PEG, as an external layer. The influence of PEG chain length and grafting density of PGA-g-PEG copolymers on the protein antiadhesive properties of pegylated polyelectrolyte multilayer films was investigated. To monitor the formation of pegylated and non-pegylated multilayer films, adsorption of the following proteins: HSA, Fibrinogen, and FBS were measured by quartz crystal microbalance (QCM - D). We found that protein adsorption onto all pegylated polyelectrolyte multilayers was significantly reduced in comparison to non-pegylated ones. Long-term performance tests confirmed the stability and the durability of the protein resistant properties of the pegylated multilayers. Antiadhesive properties of tested surfaces pegylated by PGA-g-PEG were compared to the available data for pegylated polycation PLL-g-PEG. Copyright © 2018 Elsevier B.V. All rights reserved.

Complexation of ferric oxide particles with pectins of different charge density.

PubMed

Milkova, Viktoria; Kamburova, Kamelia; Petkanchin, Ivana; Radeva, Tsetska

2008-09-02

The effect of polyelectrolyte charge density on the electrical properties and stability of suspensions of oppositely charged oxide particles is followed by means of electro-optics and electrophoresis. Variations in the electro-optical effect and the electrophoretic mobility are examined at conditions where fully ionized pectins of different charge density adsorb onto particles with ionizable surfaces. The charge neutralization point coincides with the maximum of particle aggregation in all suspensions. We find that the concentration of polyelectrolyte, needed to neutralize the particle charge, decreases with increasing charge density of the pectin. The most highly charged pectin presents an exception to this order, which is explained with a reduction of the effective charge density of this pectin due to condensation of counterions. The presence of condensed counterions, remaining bound to the pectin during its adsorption on the particle surface, is proved by investigation of the frequency behavior of the electro-optical effect at charge reversal of the particle surface.

Polyelectrolyte Multilayers in Tissue Engineering

PubMed Central

Detzel, Christopher J.; Larkin, Adam L.

2011-01-01

The layer-by-layer assembly of sequentially adsorbed, alternating polyelectrolytes has become increasingly important over the past two decades. The ease and versatility in assembling polyelectrolyte multilayers (PEMs) has resulted in numerous wide ranging applications of these materials. More recently, PEMs are being used in biological applications ranging from biomaterials, tissue engineering, regenerative medicine, and drug delivery. The ability to manipulate the chemical, physical, surface, and topographical properties of these multilayer architectures by simply changing the pH, ionic strength, thickness, and postassembly modifications render them highly suitable to probe the effects of external stimuli on cellular responsiveness. In the field of regenerative medicine, the ability to sequester growth factors and to tether peptides to PEMs has been exploited to direct the lineage of progenitor cells and to subsequently maintain a desired phenotype. Additional novel applications include the use of PEMs in the assembly of three-dimensional layered architectures and as coatings for individual cells to deliver tunable payloads of drugs or bioactive molecules. This review focuses on literature related to the modulation of chemical and physical properties of PEMs for tissue engineering applications and recent research efforts in maintaining and directing cellular phenotype in stem cell differentiation. PMID:21210759

Polyelectrolyte assisted charge titration spectrometry: Applications to latex and oxide nanoparticles.

PubMed

Mousseau, F; Vitorazi, L; Herrmann, L; Mornet, S; Berret, J-F

2016-08-01

The electrostatic charge density of particles is of paramount importance for the control of the dispersion stability. Conventional methods use potentiometric, conductometric or turbidity titration but require large amount of samples. Here we report a simple and cost-effective method called polyelectrolyte assisted charge titration spectrometry or PACTS. The technique takes advantage of the propensity of oppositely charged polymers and particles to assemble upon mixing, leading to aggregation or phase separation. The mixed dispersions exhibit a maximum in light scattering as a function of the volumetric ratio X, and the peak position XMax is linked to the particle charge density according to σ∼D0XMax where D0 is the particle diameter. The PACTS is successfully applied to organic latex, aluminum and silicon oxide particles of positive or negative charge using poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate). The protocol is also optimized with respect to important parameters such as pH and concentration, and to the polyelectrolyte molecular weight. The advantages of the PACTS technique are that it requires minute amounts of sample and that it is suitable to a broad variety of charged nano-objects. Copyright © 2016 Elsevier Inc. All rights reserved.

Layer-by-layer self-assembly in the development of electrochemical energy conversion and storage devices from fuel cells to supercapacitors.

PubMed

Xiang, Yan; Lu, Shanfu; Jiang, San Ping

2012-11-07

As one of the most effective synthesis tools, layer-by-layer (LbL) self-assembly technology can provide a strong non-covalent integration and accurate assembly between homo- or hetero-phase compounds or oppositely charged polyelectrolytes, resulting in highly-ordered nanoscale structures or patterns with excellent functionalities and activities. It has been widely used in the developments of novel materials and nanostructures or patterns from nanotechnologies to medical fields. However, the application of LbL self-assembly in the development of highly efficient electrocatalysts, specific functionalized membranes for proton exchange membrane fuel cells (PEMFCs) and electrode materials for supercapacitors is a relatively new phenomenon. In this review, the application of LbL self-assembly in the development and synthesis of key materials of PEMFCs including polyelectrolyte multilayered proton-exchange membranes, methanol-blocking Nafion membranes, highly uniform and efficient Pt-based electrocatalysts, self-assembled polyelectrolyte functionalized carbon nanotubes (CNTs) and graphenes will be reviewed. The application of LbL self-assembly for the development of multilayer nanostructured materials for use in electrochemical supercapacitors will also be reviewed and discussed (250 references).

Comparison of multilayer formation between different cellulose nanofibrils and cationic polymers.

PubMed

Eronen, Paula; Laine, Janne; Ruokolainen, Janne; Osterberg, Monika

2012-05-01

The multilayer formation between polyelectrolytes of opposite charge offers possibility for creating new tailored materials. Exchanging one or both components for charged nanofibrillated cellulose (NFC) further increases the variety of achievable properties. We explored this by introducing unmodified, low charged NFC and high charged TEMPO-oxidized NFC. Systematic evaluation of the effect of both NFC charge and properties of cationic polyelectrolytes on the structure of the multilayers was performed. As the cationic component cationic NFC was compared with two different cationic polyelectrolytes, poly(dimethyldiallylammoniumchloride) and cationic starch. Quartz crystal microbalance with dissipation (QCM-D) was used to monitor the multilayer formation and AFM colloidal probe microscopy (CPM) was further applied to probe surface interactions in order to gain information about fundamental interactions and layer properties. Generally, the results verified the characteristic multilayer formation between NFC of different charge and how the properties of formed multilayers can be tuned. However, the strong nonelectrostatic affinity between cellulosic fibrils was observed. CPM measurements revealed monotonically repulsive forces, which were in good correspondence with the QCM-D observations. Significant increase in adhesive forces was detected between the swollen high charged NFC. Copyright © 2011 Elsevier Inc. All rights reserved.

Nanostructured ultra-thin patches for ultrasound-modulated delivery of anti-restenotic drug

PubMed Central

Vannozzi, Lorenzo; Ricotti, Leonardo; Filippeschi, Carlo; Sartini, Stefania; Coviello, Vito; Piazza, Vincenzo; Pingue, Pasqualantonio; La Motta, Concettina; Dario, Paolo; Menciassi, Arianna

2016-01-01

This work aims to demonstrate the possibility to fabricate ultra-thin polymeric films loaded with an anti-restenotic drug and capable of tunable drug release kinetics for the local treatment of restenosis. Vascular nanopatches are composed of a poly(lactic acid) supporting membrane (thickness: ~250 nm) on which 20 polyelectrolyte bilayers (overall thickness: ~70 nm) are alternatively deposited. The anti-restenotic drug is embedded in the middle of the polyelectrolyte structure, and released by diffusion mechanisms. Nanofilm fabrication procedure and detailed morphological characterization are reported here. Barium titanate nanoparticles (showing piezoelectric properties) are included in the polymeric support and their role is investigated in terms of influence on nanofilm morphology, drug release kinetics, and cell response. Results show an efficient drug release from the polyelectrolyte structure in phosphate-buffered saline, and a clear antiproliferative effect on human smooth muscle cells, which are responsible for restenosis. In addition, preliminary evidences of ultrasound-mediated modulation of drug release kinetics are reported, thus evaluating the influence of barium titanate nanoparticles on the release mechanism. Such data were integrated with quantitative piezoelectric and thermal measurements. These results open new avenues for a fine control of local therapies based on smart responsive materials. PMID:26730191

CLARIFICATION OF POTOMAC RIVER WATER WITH CATIONIC POLYELECTROLYTES

DTIC Science & Technology

of normal amounts of chlorine, act effectively as a sole coagulant. It can replace a conventional metal salt in a system comprised of a solids-contact upflow type coagulation basin and a pressure- diatomite filter.

Salt dependence of compression normal forces of quenched polyelectrolyte brushes

NASA Astrophysics Data System (ADS)

Hernandez-Zapata, Ernesto; Tamashiro, Mario N.; Pincus, Philip A.

2001-03-01

We obtained mean-field expressions for the compression normal forces between two identical opposing quenched polyelectrolyte brushes in the presence of monovalent salt. The brush elasticity is modeled using the entropy of ideal Gaussian chains, while the entropy of the microions and the electrostatic contribution to the grand potential is obtained by solving the non-linear Poisson-Boltzmann equation for the system in contact with a salt reservoir. For the polyelectrolyte brush we considered both a uniformly charged slab as well as an inhomogeneous charge profile obtained using a self-consistent field theory. Using the Derjaguin approximation, we related the planar-geometry results to the realistic two-crossed cylinders experimental set up. Theoretical predictions are compared to experimental measurements(Marc Balastre's abstract, APS March 2001 Meeting.) of the salt dependence of the compression normal forces between two quenched polyelectrolyte brushes formed by the adsorption of diblock copolymers poly(tert-butyl styrene)-sodium poly(styrene sulfonate) [PtBs/NaPSS] onto an octadecyltriethoxysilane (OTE) hydrophobically modified mica, as well as onto bare mica.

Coarse-grained simulations of polyelectrolyte complexes: MARTINI models for poly(styrene sulfonate) and poly(diallyldimethylammonium)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vögele, Martin; Department of Theoretical Biophysics, Max Planck Institute of Biophysics, Frankfurt a. M.; Holm, Christian

2015-12-28

We present simulations of aqueous polyelectrolyte complexes with new MARTINI models for the charged polymers poly(styrene sulfonate) and poly(diallyldimethylammonium). Our coarse-grained polyelectrolyte models allow us to study large length and long time scales with regard to chemical details and thermodynamic properties. The results are compared to the outcomes of previous atomistic molecular dynamics simulations and verify that electrostatic properties are reproduced by our MARTINI coarse-grained approach with reasonable accuracy. Structural similarity between the atomistic and the coarse-grained results is indicated by a comparison between the pair radial distribution functions and the cumulative number of surrounding particles. Our coarse-grained models aremore » able to quantitatively reproduce previous findings like the correct charge compensation mechanism and a reduced dielectric constant of water. These results can be interpreted as the underlying reason for the stability of polyelectrolyte multilayers and complexes and validate the robustness of the proposed models.« less

Carrier-inside-carrier: polyelectrolyte microcapsules as reservoir for drug-loaded liposomes.

PubMed

Maniti, Ofelia; Rebaud, Samuel; Sarkis, Joe; Jia, Yi; Zhao, Jie; Marcillat, Olivier; Granjon, Thierry; Blum, Loïc; Li, Junbai; Girard-Egrot, Agnès

2015-01-01

Conventional liposomes have a short life-time in blood, unless they are protected by a polymer envelope, most often polyethylene glycol. However, these stabilizing polymers frequently interfere with cellular uptake, impede liposome-membrane fusion and inhibit escape of liposome content from endosomes. To overcome such drawbacks, polymer-based systems as carriers for liposomes are currently developed. Conforming to this approach, we propose a new and convenient method for embedding small size liposomes, 30-100 nm, inside porous calcium carbonate microparticles. These microparticles served as templates for deposition of various polyelectrolytes to form a protective shell. The carbonate particles were then dissolved to yield hollow polyelectrolyte microcapsules. The main advantage of using this method for liposome encapsulation is that carbonate particles can serve as a sacrificial template for deposition of virtually any polyelectrolyte. By carefully choosing the shell composition, bioavailability of the liposomes and of the encapsulated drug can be modulated to respond to biological requirements and to improve drug delivery to the cytoplasm and avoid endosomal escape.

Target binding influences permeability in aptamer-polyelectrolyte microcapsules.

PubMed

Sultan, Yasir; DeRosa, Maria C

2011-05-09

Aptamer-polyelectrolyte microcapsules are prepared for potential use as triggered delivery vehicles and microreactors. The hollow microcapsules are prepared from the sulforhodamine B aptamer and the polyelectrolytes poly(allylamine hydrochloride) and poly(sodium 4-styrene-sulfonate), using layer-by-layer (LbL) film deposition templated on a sacrificial CaCO(3) spherical core. Scanning electron microscopy and confocal microscopy confirm the formation of spherical CaCO(3) cores and LbL-aptamer microcapsules. Colocalization studies with fluorescently-tagged aptamer and sulforhodamine B verify the ability of the aptamer to recognize its cognate target in the presence of the K(+) ions that are required for its characteristic G-quadruplex formation. Fluorescence recovery after photobleaching studies confirms a significant difference in the permeability of the aptamer-polyelectrolyte microcapsules for the sulforhodamine B dye target compared to control microcapsules prepared with a random oligonucleotide. These results suggest that aptamer-based 'smart' responsive films and microcapsules could be applied to problems of catalysis and controlled release. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bioresorbable polyelectrolytes for smuggling drugs into cells.

PubMed

Jaganathan, Sripriya

2016-06-01

There is ample evidence that biodegradable polyelectrolyte nanocapsules are multifunctional vehicles which can smuggle drugs into cells, and release them upon endogenous activation. A large number of endogenous stimuli have already been tested in vitro, and in vivo research is escalating. Thus, the interest in the design of intelligent polyelectrolyte multilayer (PEM) drug delivery systems is clear. The need of the hour is a systematic translation of PEM-based drug delivery systems from the lab to clinical studies. Reviews on multifarious stimuli that can trigger the release of drugs from such systems already exist. This review summarizes the available literature, with emphasis on the recent progress in PEM-based drug delivery systems that are receptive in the presence of endogenous stimuli, including enzymes, glucose, glutathione, pH, and temperature, and addresses different active and passive drug targeting strategies. Insights into the current knowledge on the diversified endogenous approaches and methodological challenges may bring inspiration to resolve issues that currently bottleneck the successful implementation of polyelectrolytes into the catalog of third-generation drug delivery systems.

Alyssum homolocarpum seed gum: Dilute solution and some physicochemical properties.

PubMed

Hesarinejad, M A; Razavi, Seyed M A; Koocheki, A

2015-11-01

The objective of this study was to investigate the effect of various temperatures (25-65°C) on some dilute solution properties of Alyssum homolocarpum seed gum (AHSG) as a novel potential source of hydrocolloid. Monosaccharide composition, FTIR analysis and molecular parameters were determined to provide more structural information. The results indicated that AHSG had a low molecular weight (3.66×10(5)Da), medium intrinsic viscosity (18.34dl/g) at 25°C, relatively flexible chain with a chain flexibility parameter of 618.54, and activation energy of 0.51×10(7)J/kgmol. With rise in temperature from 25 to 55°C, the intrinsic viscosity decreased as well as coil radius and volume of AHSG. The shape factor of AHSG macromolecule was spherical at all temperatures. The electrostatic interaction and particle size of AHSG solution were -25.81mV (at neutral pH) and 225.36nm, respectively. The results revealed that AHSG had high total sugar content (85.33%), small amount of uronic acids (5.63%) and it is likely a galactan-type polysaccharide. The FTIR spectra showed that AHSG behaved like a typical polyelectrolyte because of the presence of carboxyl and hydroxyl groups. Copyright © 2015. Published by Elsevier B.V.

Electrophoresis of fd-virus particles: experiments and an analysis of the effect of finite rod lengths.

PubMed

Buitenhuis, Johan

2012-09-18

The electrophoretic mobility of rodlike fd viruses is measured and compared to theory, with the theoretical calculations performed according to Stigter (Stigter, D. Charged Colloidal Cylinder with a Gouy Double-Layer. J. Colloid Interface Sci. 1975, 53, 296-306. Stigter, D. Electrophoresis of Highly Charged Colloidal Cylinders in Univalent Salt- Solutions. 1. Mobility in Transverse Field. J. Phys. Chem. 1978, 82, 1417-1423. Stigter, D. Electrophoresis of Highly Charged Colloidal Cylinders in Univalent Salt Solutions. 2. Random Orientation in External Field and Application to Polyelectrolytes. J. Phys. Chem. 1978, 82, 1424-1429. Stigter, D. Theory of Conductance of Colloidal Electrolytes in Univalent Salt Solutions. J. Phys. Chem. 1979, 83, 1663-1670), who describes the electrophoretic mobility of infinite cylinders including relaxation effects. Using the dissociation constants of the ionizable groups on the surfaces of the fd viruses, we can calculate the mobility without any adjustable parameter (apart from the possible Stern layer thickness). In addition, the approximation in the theoretical description of Stigter (and others) of using a model of infinitely long cylinders, which consequently is independent of the aspect ratio, is examined by performing more elaborate numerical calculations for finite cylinders. It is shown that, although the electrophoretic mobility of cylindrical particles in the limit of low ionic strength depends on the aspect ratio much more than "end effects", at moderate and high ionic strengths the finite and infinite cylinder models differ only to a degree that can be attributed to end effects. Furthermore, the range of validity of the Stokes regime is systematically calculated.

Nanohybrid conjugated polyelectrolytes: highly photostable and ultrabright nanoparticles

NASA Astrophysics Data System (ADS)

Darwish, Ghinwa H.; Karam, Pierre

2015-09-01

We present a general and straightforward one-step approach to enhance the photophysical properties of conjugated polyelectrolytes. Upon complexation with an amphiphilic polymer (polyvinylpyrrolidone), an anionic conjugated polyelectrolyte (poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene]) was prepared into small nanoparticles with exceptional photostability and brightness. The polymer fluorescence intensity was enhanced by 23 -fold and could be easily tuned by changing the order of addition. Single molecule experiments revealed a complete suppression of blinking. In addition, after only losing 18% of the original intensity, a remarkable amount of photons were emitted per particle (~109, on average). This number is many folds greater than popular organic fluorescent dyes. We believe that an intimate contact between the two polymers is shielding the conjugated polyelectrolyte from the destructive photooxidation. The prepared nanohybrid particles will prove instrumental in single particle based fluorescent assays and can serve as a probe for the current state-of-the-art bioimaging fluorescence techniques.We present a general and straightforward one-step approach to enhance the photophysical properties of conjugated polyelectrolytes. Upon complexation with an amphiphilic polymer (polyvinylpyrrolidone), an anionic conjugated polyelectrolyte (poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene]) was prepared into small nanoparticles with exceptional photostability and brightness. The polymer fluorescence intensity was enhanced by 23 -fold and could be easily tuned by changing the order of addition. Single molecule experiments revealed a complete suppression of blinking. In addition, after only losing 18% of the original intensity, a remarkable amount of photons were emitted per particle (~109, on average). This number is many folds greater than popular organic fluorescent dyes. We believe that an intimate contact between the two polymers is shielding the conjugated polyelectrolyte from the destructive photooxidation. The prepared nanohybrid particles will prove instrumental in single particle based fluorescent assays and can serve as a probe for the current state-of-the-art bioimaging fluorescence techniques. Electronic supplementary information (ESI) available: Dynamic light scattering, photostability of different nanohybrids, and emission and absorption spectra. See DOI: 10.1039/c5nr03299g

Separation of pharmacologically active nitrogen-containing compounds on silica gels modified with 6,10-ionene, dextran sulfate, and gold nanoparticles

NASA Astrophysics Data System (ADS)

Ioutsi, A. N.; Shapovalova, E. N.; Ioutsi, V. A.; Mazhuga, A. G.; Shpigun, O. A.

2017-12-01

New stationary phases for HPLC are obtained via layer-by-layer deposition of polyelectrolytes and studied: (1) silica gel modified layer-by-layer with 6,10-ionene and dextran sulfate (Sorbent 1); (2) silica gel twice subjected to the above modification (Sorbent 2); and (3) silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate (Sorbent 3). The effect the content of the organic solvent in the mobile phase and the concentration and pH of the buffer solution have on the chromatographic behavior of several pharmacologically active nitrogen-containing compounds is studied. The sorbents are stable during the process and allow the effective separation of beta-blockers, calcium channel blockers, alpha-agonists, and antihistamines. A mixture of caffeine, nadolol, tetrahydrozoline, pindolol, orphenadrine, doxylamine, carbinoxamine, and chlorphenamine is separated in 6.5 min on the silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate.

pH-Sensitive breathing of clay within the polyelectrolyte matrix.

PubMed

Chaturbedy, Piyush; Jagadeesan, Dinesh; Eswaramoorthy, Muthusamy

2010-10-26

Stimuli-responsive organic-inorganic hybrid spheres were synthesized by coating the colloidal polystyrene spheres with polyelectrolyte-protected aminoclay, Mg phyllo(organo)silicate layers in a layer-by-layer method. The clay layers are sandwiched between the polyelectrolyte layers. The aminoclay swells in water due to protonation of amino groups, and the degree of swelling depends on the pH of the medium. As a result, the hybrid spheres undergo a size change up to 60% as the pH is changed from 9 to 4. The stimuli-responsive property of the hybrid spheres was used for the release of ibuprofen and eosin at different pH.

Electrical manipulation of oligonucleotides grafted to charged surfaces.

PubMed

Rant, Ulrich; Arinaga, Kenji; Fujita, Shozo; Yokoyama, Naoki; Abstreiter, Gerhard; Tornow, Marc

2006-09-21

The electrical manipulation of short DNA molecules on surfaces offers novel functionalities with fascinating possibilities in the field of bio-interfaces. Here we present systematic investigations of the electrical interactions which govern the structure of oligonucleotides on charged gold surfaces. Successively, we address influences of the applied field strength, the role of DC electrode potentials, in particular for polycrystalline surfaces, as well as screening effects of the surrounding electrolyte solution. Data obtained for single and double stranded DNA exhibit differences which can be attributed to the dissimilar flexibility of the different molecular conformations. A comparison of the experimental results with a basic model shows how the alignment of the molecules adjusts according to a balance between electrically induced ordering and stochastic thermal motions. The presented conclusions are expected to be of general relevance for the behaviour of polyelectrolytes exposed to localized electric fields at interfaces.

Solvation effects on like-charge attraction.

PubMed

Ghanbarian, Shahzad; Rottler, Jörg

2013-02-28

We present results of molecular dynamics simulations of the electrostatic interaction between two parallel charged rods in the presence of divalent counterions. Such polyelectrolytes have been considered as a simple model for understanding electrostatic interactions in highly charged biomolecules such as DNA. Since there are correlations between the free charge carriers, the phenomenon of like charge attraction appears for specific parameters. We explore the role of solvation effects and the resulting deviations from Coulomb's law on the nanoscale on this peculiar phenomenon. The behavior of the force between the charged rods in a simulation with atomistic representation of water molecules is completely different from a model in which water is modeled as a continuum dielectric. By calculating counterion-rodion pair correlation functions, we find that the presence of water molecules changes the structure of the counterion cloud and results in both qualitative and quantitative changes of the force between highly charged polyelectrolytes.

The study of a fluorescent biosensor based on polyelectrolyte microcapsules with encapsulated glucose oxidase

NASA Astrophysics Data System (ADS)

Kazakova, L. I.; Sirota, N. P.; Sirota, T. V.; Shabarchina, L. I.

2017-09-01

A fluorescent biosensor is synthesized and described. The biosensor consists of polyelectrolyte microcapsules with glucose oxidase (GOx) entrapped in the cavities and an oxygen-sensitive fluorescent indicator Ru(dpp) immobilized in shells, where Ru(dpp) is tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride. The theoretical activity of the encapsulated GOx and the effect storage time and medium composition have on the stability of sensor microcapsules are determined from polarographic measurements. No change in the activity of the encapsulated enzyme and or its loss to the storage medium are detected over the test period. The dispersion medium (water or a phosphate buffer) are shown to have no effect on the activity of microcapsules with immobilized GOx. The described optical sensor could be used as an alternative to electrochemical sensors for in vitro determination of glucose in the clinically important range of concentrations (up to 10 mmol/L).

Electrowetting of Weak Polyelectrolyte-Coated Surfaces.

PubMed

Sénéchal, Vincent; Saadaoui, Hassan; Rodriguez-Hernandez, Juan; Drummond, Carlos

2017-05-23

Polymer coatings are commonly used to modify interfacial properties like wettability, lubrication, or biocompatibility. These properties are determined by the conformation of polymer molecules at the interface. Polyelectrolytes are convenient elementary bricks to build smart materials, given that polyion chain conformation is very sensitive to different environmental variables. Here we discuss the effect of an applied electric field on the properties of surfaces coated with poly(acrylic acid) brushes. By combining atomic force microscopy, quartz crystal microbalance, and contact angle experiments, we show that it is possible to precisely tune polyion chain conformation, surface adhesion, and surface wettability using very low applied voltages if the polymer grafting density and environmental conditions (pH and ionic strength) are properly formulated. Our results indicate that the effective ionization degree of the grafted weak polyacid can be finely controlled with the externally applied field, with important consequences for the macroscopic surface properties.

In-vitro investigations of a pH- and ionic-strength-responsive polyelectrolytic hydrogel using a piezoresistive microsensor

PubMed Central

Schulz, Volker; Guenther, Margarita; Gerlach, Gerald; Magda, Jules J.; Tathireddy, Prashant; Rieth, Loren; Solzbacher, Florian

2010-01-01

Environmental responsive or smart hydrogels show a volume phase transition due to changes of external stimuli such as pH or ionic strength of an ambient solution. Thus, they are able to convert reversibly chemical energy into mechanical energy and therefore they are suitable as sensitive material for integration in biochemical microsensors and MEMS devices. In this work, micro-fabricated silicon pressure sensor chips with integrated piezoresistors were used as transducers for the conversion of mechanical work into an appropriate electrical output signal due to the deflection of a thin silicon bending plate. Within this work two different sensor designs have been studied. The biocompatible poly(hydroxypropyl methacrylate-N,N-dimethylaminoethyl methacrylate-tetra-ethyleneglycol dimethacrylate) (HPMA-DMA-TEGDMA) was used as an environmental sensitive element in piezoresistive biochemical sensors. This polyelectrolytic hydrogel shows a very sharp volume phase transition at pH values below about 7.4 which is in the range of the physiological pH. The sensor's characteristic response was measured in-vitro for changes in pH of PBS buffer solution at fixed ionic strength. The experimental data was applied to the Hill equation and the sensor sensitivity as a function of pH was calculated out of it. The time-dependent sensor response was measured for small changes in pH, whereas different time constants have been observed. The same sensor principal was used for sensing of ionic strength. The time-dependent electrical sensor signal of both sensors was measured for variations in ionic strength at fixed pH value using PBS buffer solution. Both sensor types showed an asymmetric swelling behavior between the swelling and the deswelling cycle as well as different time constants, which was attributed to the different nature of mechanical hydrogel-confinement inside the sensor. PMID:21152365

Humic substance charge determination by titration with a flexible cationic polyelectrolyte

NASA Astrophysics Data System (ADS)

Tan, Wen-Feng; Norde, Willem; Koopal, Luuk K.

2011-10-01

The anionic charge of humic substances (HS) plays a major role in the interaction of HS with other components. Therefore, the potential of the polyelectrolyte titration technique to obtain the charge density of HS in simple 1-1 electrolyte solutions has been investigated. Titrations are carried out with an automatic titrator combined with the "Mütek particle charge detector" which allows determination of the Mütek potential and the pH as a function of the added amount of titrant which is a solution of poly-diallyldimethylammonium chloride (polyDADMAC), a cationic strong polyelectrolyte. When the Mütek potential reverses its sign the iso-electric point (IEP) of the polyDADMAC-HS complex is reached. The polyDADMAC/HS mass ratio at the IEP gives information on the HS charge density and from the pH changes in solution an estimate of the charge regulation in the HS-polyDADMAC complex can be obtained. In general, for polyDADMAC-HS complexes an increase in the dissociation of the acid groups of HS is found (charge regulation). The charge regulation decreases with increasing concentration of 1-1 background electrolyte. Cation incorporation can be neglected at 1-1 electrolyte concentrations ⩽ 1 mmol L -1 and a 1-1 stoichiometry exists between the polyDADMAC and HS charge. However, at these low salt concentrations the charge regulation is substantial. A detailed analysis of purified Aldrich humic acid (PAHA) at pH 5 and a range of KCl concentrations reveals that the anionic charge of PAHA in the complex increases at 5 mmol L -1 KCl by 30% and at 150 mmol L -1 KCl by 12%. On the other hand, increasing amounts of K + become incorporated in the complex: at 5 mmol L -1 KCl 5% and at 150 mmol L -1 KCl 24% of the PAHA charge is balanced by K +. By comparing at pH 5 the mass ratios polyDADMAC/PAHA in the complex at the IEP with the theoretical mass ratios of polyDADMAC/PAHA required to neutralize PAHA in the absence of charge regulation and K + incorporation, it is found that at 50 mmol L -1 KCl the extra negative charge due to the interaction between polyDADMAC and PAHA is just compensated by K + incorporation in the complex. Therefore, a pseudo 1-1 stoichiometry exists at about 50 mmol L -1 1-1 electrolyte concentration and only at this salt concentration polyDADMAC titrations and conventional proton titrations give identical results. Most likely this is also true for other HA samples and other pH values. For FA further study is required to reveal the conditions for which polyDADMAC and proton titrations give identical results.

Nanoparticulate hollow TiO2 fibers as light scatterers in dye-sensitized solar cells: layer-by-layer self-assembly parameters and mechanism.

PubMed

Rahman, Masoud; Tajabadi, Fariba; Shooshtari, Leyla; Taghavinia, Nima

2011-04-04

Hollow structures show both light scattering and light trapping, which makes them promising for dye-sensitized solar cell (DSSC) applications. In this work, nanoparticulate hollow TiO(2) fibers are prepared by layer-by-layer (LbL) self-assembly deposition of TiO(2) nanoparticles on natural cellulose fibers as template, followed by thermal removal of the template. The effect of LbL parameters such as the type and molecular weight of polyelectrolyte, number of dip cycles, and the TiO(2) dispersion (amorphous or crystalline sol) are investigated. LbL deposition with weak polyelectrolytes (polyethylenimine, PEI) gives greater nanoparticle deposition yield compared to strong polyelectrolytes (poly(diallyldimethylammonium chloride), PDDA). Decreasing the molecular weight of the polyelectrolyte results in more deposition of nanoparticles in each dip cycle with narrower pore size distribution. Fibers prepared by the deposition of crystalline TiO(2) nanoparticles show higher surface area and higher pore volume than amorphous nanoparticles. Scattering coefficients and backscattering properties of fibers are investigated and compared with those of commercial P25 nanoparticles. Composite P25-fiber films are electrophoretically deposited and employed as the photoanode in DSSC. Photoelectrochemical measurements showed an increase of around 50% in conversion efficiency. By employing the intensity-modulated photovoltage and photocurrent spectroscopy methods, it is shown that the performance improvement due to addition of fibers is mostly due to the increase in light-harvesting efficiency. The high surface area due to the nanoparticulate structure and strong light harvesting due to the hollow structure make these fibers promising scatterers in DSSCs. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Interaction of protein with charged colloidal particles].

PubMed

Durdenko, E V; Kuznetsova, S M; Basova, L V; Tikhonenko, S A; Saburova, E A

2011-01-01

The functional state of three proteins of different molecular weight (urease, lactate dehydrogenase, and hemoglobin) in the presence of the linear polyelectrolytes poly(allylamine hydrochloride) (PAA) and sodium poly(styrenesulfonate) (PSS) in the dissolved state and of the same polyelectrolytes bound to the surface of microspheres has been investigated. Microspheres were prepared by consecutive absorption of oppositely charged polyelectrolytes so that the outer layer of the shell was PAA for the acidic protein urease, and PSS for the alkaline proteins LDH and hemoglobin. It was shown that the dissolved polyelectrolyte completely inactivates all three proteins within one minute with a slight difference in the time constant. (By Hb inactivation are conventionally meant changes in the heme environment observed from the spectrum in the Soret band.) In the presence of microspheres, the proteins were adsorbed on their surface; in this case, more than 95% of the activity was retained within two hours. The proportion of the protein adsorbed on microspheres accounted for about 98% for urease, 72% for Hb, and 35% for LDH, as determined from the tryptophan fluorescence data. The interaction of hemoglobin with another type of charged colloidal particles, phospholipid vesicles, leads to the destruction of the tertiary structure of the protein, which made itself evident in the optical absorption spectra in the Soret band, as well as the spectra of tryptophan fluorescence and circular dichroism. In this case, according to circular dichroism, the percentage of alpha-helical structure of Hb was maintained. The differences in the physical and chemical mechanisms of interaction of proteins with these two types of charged colloidal particles that leads to differences in the degree of denaturing effects are discussed.

Gd-functionalised Au nanoparticles as targeted contrast agents in MRI: relaxivity enhancement by polyelectrolyte coating.

PubMed

Warsi, Muhammad Farooq; Adams, Ralph W; Duckett, Simon B; Chechik, Victor

2010-01-21

Monolayer-protected, Gd(3+)-functionalised gold nanoparticles with enhanced spin-lattice relaxivity (r(1)) were prepared; adsorption of polyelectrolytes on these materials further increased r(1) and ligand exchange with a biotin-derivatised disulfide led to a prototype avidin-targeted contrast agent.

Tuning ice nucleation with counterions on polyelectrolyte brush surfaces.

PubMed

He, Zhiyuan; Xie, Wen Jun; Liu, Zhenqi; Liu, Guangming; Wang, Zuowei; Gao, Yi Qin; Wang, Jianjun

2016-06-01

Heterogeneous ice nucleation (HIN) on ionic surfaces is ubiquitous in a wide range of atmospheric aerosols and at biological interfaces. Despite its great importance in cirrus cloud formation and cryopreservation of cells, organs, and tissues, it remains unclear whether the ion-specific effect on ice nucleation exists. Benefiting from the fact that ions at the polyelectrolyte brush (PB)/water interface can be reversibly exchanged, we report the effect of ions on HIN on the PB surface, and we discover that the distinct efficiency of ions in tuning HIN follows the Hofmeister series. Moreover, a large HIN temperature window of up to 7.8°C is demonstrated. By establishing a correlation between the fraction of ice-like water molecules and the kinetics of structural transformation from liquid- to ice-like water molecules at the PB/water interface with different counterions, we show that our molecular dynamics simulation analysis is consistent with the experimental observation of the ion-specific effect on HIN.

Tuning ice nucleation with counterions on polyelectrolyte brush surfaces

PubMed Central

He, Zhiyuan; Xie, Wen Jun; Liu, Zhenqi; Liu, Guangming; Wang, Zuowei; Gao, Yi Qin; Wang, Jianjun

2016-01-01

Heterogeneous ice nucleation (HIN) on ionic surfaces is ubiquitous in a wide range of atmospheric aerosols and at biological interfaces. Despite its great importance in cirrus cloud formation and cryopreservation of cells, organs, and tissues, it remains unclear whether the ion-specific effect on ice nucleation exists. Benefiting from the fact that ions at the polyelectrolyte brush (PB)/water interface can be reversibly exchanged, we report the effect of ions on HIN on the PB surface, and we discover that the distinct efficiency of ions in tuning HIN follows the Hofmeister series. Moreover, a large HIN temperature window of up to 7.8°C is demonstrated. By establishing a correlation between the fraction of ice-like water molecules and the kinetics of structural transformation from liquid- to ice-like water molecules at the PB/water interface with different counterions, we show that our molecular dynamics simulation analysis is consistent with the experimental observation of the ion-specific effect on HIN. PMID:27386581

Kinetics of polyelectrolyte adsorption

NASA Astrophysics Data System (ADS)

Cohen Stuart, M. A.; Hoogendam, C. W.; de Keizer, A.

1997-09-01

The kinetics of polyelectrolyte adsorption has been investigated theoretically. In analogy with Kramers' rate theory for chemical reactions we present a model which is based on the assumption that a polyelectrolyte encounters a barrier in its motion towards an adsorbing surface. The height of the barrier, which is of electrostatic origin, is calculated with a self-consistent-field (SCF) model. The salt concentration strongly affects the height of the barrier. At moderate salt concentrations (0953-8984/9/37/009/img1) equilibrium in the adsorption is attained; at low salt concentration (0953-8984/9/37/009/img2) equilibrium is not reached on the time scale of experiments. The attachment process shows resemblances to the classical DLVO theory.

Removal of copper ions from aqueous solution by adsorption onto novel polyelectrolyte film-coated nanofibrous silk fibroin non-wovens

NASA Astrophysics Data System (ADS)

Zhou, Weitao; Huang, Haitao; Du, Shan; Huo, Yingdong; He, Jianxin; Cui, Shizhong

2015-08-01

In this approach, polyelectrolyte film-coated nanofibrous silk fibroin (SF) nonwovens were prepared from the alternate deposition of positively charged polyethylenimine (PEI) and negatively charged SF using electrostatic layer-by-layer (LBL) self-assembled technology. The composite membranes were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectrometer. The SF-PEI multilayer-assembled nanofibers (less than five layers) were fine and uniform with the fiber diameter from 400 nm to 600 nm, and had very large surface area and high porosity (more than 70%). The amino groups of PEI were proved to be deposited onto SF nonwovens, which granted the coated nonwovens with potential applicability for copper ions adsorption. The PEI films coated SF substrate showed much higher copper ions adsorption capacity than that of ethanol treated SF nanofibers. Adding the number of PEI coated could enhance the Cu2+ adsorption capacity significantly. The maximum milligrams per gram of copper ions adsorbed reached 59.7 mg/g when the SF substrate was coated with 5 bilayers of SF-PEI. However, the copper ions adsorption capacity had no obvious change as the number of PEI continued to increase. These results suggest potential for PEL film-coated nanofibrous nonwovens as a new adsorbent for metal ions.

Theory of end-labeled free-solution electrophoresis: is the end effect important?

PubMed

Chubynsky, Mykyta V; Slater, Gary W

2014-03-01

In the theory of free-solution electrophoresis of a polyelectrolyte (such as the DNA) conjugated with a "drag-tag," the conjugate is divided into segments of equal hydrodynamic friction and its electrophoretic mobility is calculated as a weighted average of the mobilities of individual segments. If all the weights are assumed equal, then for an electrically neutral drag-tag, the elution time t is predicted to depend linearly on the inverse DNA length 1/M. While it is well-known that the equal-weights assumption is approximate and in reality the weights increase toward the ends, this "end effect" has been assumed to be small, since in experiments the t(1/M) dependence seems to be nearly perfectly linear. We challenge this assumption pointing out that some experimental linear fits do not extrapolate to the free (i.e. untagged) DNA elution time in the limit 1/M→0, indicating nonlinearity outside the fitting range. We show that a theory for a flexible polymer taking the end effect into account produces a nonlinear curve that, however, can be fitted with a straight line over a limited range of 1/M typical of experiments, but with a "wrong" intercept, which explains the experimental results without additional assumptions. We also study the influence of the flexibilities of the charged and neutral parts. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simulation of weak polyelectrolytes: a comparison between the constant pH and the reaction ensemble method

NASA Astrophysics Data System (ADS)

Landsgesell, Jonas; Holm, Christian; Smiatek, Jens

2017-03-01

The reaction ensemble and the constant pH method are well-known chemical equilibrium approaches to simulate protonation and deprotonation reactions in classical molecular dynamics and Monte Carlo simulations. In this article, we demonstrate the similarity between both methods under certain conditions. We perform molecular dynamics simulations of a weak polyelectrolyte in order to compare the titration curves obtained by both approaches. Our findings reveal a good agreement between the methods when the reaction ensemble is used to sweep the reaction constant. Pronounced differences between the reaction ensemble and the constant pH method can be observed for stronger acids and bases in terms of adaptive pH values. These deviations are due to the presence of explicit protons in the reaction ensemble method which induce a screening of electrostatic interactions between the charged titrable groups of the polyelectrolyte. The outcomes of our simulation hint to a better applicability of the reaction ensemble method for systems in confined geometries and titrable groups in polyelectrolytes with different pKa values.

Behaviour of human mesenchymal stem cells on a polyelectrolyte-modified HEMA hydrogel for silk-based ligament tissue engineering.

PubMed

Bosetti, M; Boccafoschi, F; Calarco, A; Leigheb, M; Gatti, S; Piffanelli, V; Peluso, G; Cannas, M

2008-01-01

The aim of this study was to design a functional bio-engineered material to be used as scaffold for autologous mesenchymal stem cells in ligament tissue engineering. Polyelectrolyte modified HEMA hydrogel (HEMA-co-METAC), applied as coating on silk fibroin fibres, has been formulated in order to take advantage of the biocompatibility of the polyelectrolyte by increasing its mechanical properties with silk fibres. Human bone marrow mesenchymal stem cells behaviour on such reinforced polyelectrolyte has been studied by evaluating cell morphology, cell number, attachment, spreading and proliferation together with collagen matrix production and its mRNA expression. Silk fibroin fibres matrices with HEMA-co-METAC coating exhibited acceptable mechanical behaviour compared to the natural ligament, good human mesenchymal stem cell adhesion and with mRNA expression studies higher levels of collagen types I and III expression when compared to control cells on polystyrene. These data indicate high expression of mRNA for proteins responsible for the functional characteristics of the ligaments and suggest a potential for use of this biomaterial in ligament tissue-engineering applications.

Spectrophotometric Determination of the Characteristics of Stromal and Parenchymal Components of Colon Tumors

NASA Astrophysics Data System (ADS)

Motevich, I. G.; Strekal, N. D.; Shulha, A. V.; Maskevich, S. A.

2016-05-01

We consider the dependence of the spectral properties of eosin and hematoxylin (dyes routinely used in histology as contrast agents) on their localization in biological tissues with different levels of pathology: benign and malignant neoplasms and sigmoid colonic crypts. We have analyzed the fluorescent images and fluorescence spectra of the parenchyma and stromal elements. We have established that on going from physiologically normal cells to tumor cells, the contribution to the absorption cross section of histologic sections due to hematoxylin increases. In pathologically altered cells in a colonic crypt, we observe a hypsochromic effect in the fluorescence spectra of the samples with appreciable quenching of the fluorescence, while in the model systems the reverse effect occurs: a shift of the fluorescence maximum toward the red region. We discuss the influence on the indicated effects from local pH and the polarity of the dye environment in the model systems and histologic sections. As the systems modeling the polarity and acidity of the biological media, we use aqueous solutions of the dyes with different pH values and synthetic polyelectrolytes.

The Self-Assembly of Nanogold for Optical Metamaterials

NASA Astrophysics Data System (ADS)

Nidetz, Robert A.

2011-12-01

Optical metamaterials are an emerging field that enables manipulation of light like never before. Producing optical metamaterials requires sub-wavelength building blocks. The focus here was to develop methods to produce building blocks for metamaterials from nanogold. Electron-beam lithography was used to define an aminosilane patterned chemical template in order to electrostatically self-assemble citrate-capped gold nanoparticles. Equilibrium self-assembly was achieved in 20 minutes by immersing chemical templates into gold nanoparticle solutions. The number of nanoparticles that self-assembled on an aminosilane dot was controlled by manipulating the diameters of the dots and nanoparticles. Adding salt to the nanoparticle solution enabled the nanoparticles to self-assemble in greater numbers on the same sized dot. However, the preparation of the nanoparticle solution containing salt was sensitive to spikes in the salt concentration which led to aggregation of the nanoparticles and non-specific deposition. Gold nanorods were also electrostatically self-assembled. Polyelectrolyte-coated gold nanorods were patterned with limited success. A polyelectrolyte chemical template also patterned gold nanorods, but the gold nanorods preferred to pattern on the edges of the pattern. Ligand-exchanged gold nanorods displayed the best self-assembly, but suffered from slow kinetics. Self-assembled gold nanoparticles were cross-linked with poly(diallyldimethylammonium chloride). The poly(diallyldimethylammonium chloride) allowed additional nanoparticles to pattern on top of the already patterned nanoparticles. Cross-linked nanoparticles were lifted-off of the substrate by sonication in a sodium hydroxide solution. The presence of van der Waals forces and/or amine bonding prevent the nanogold from lifting-off without sonication. A good-solvent evaporation process was used to self-assemble poly(styrene) coated gold nanoparticles into spherical microbead assemblies. The use of larger nanoparticles and larger poly(styrene) ligands resulted in larger and smaller assemblies, respectively. Stirring the solution resulted in a wider size distribution of microbead assemblies due to the stirring's shear forces. Two undeveloped methods to self-assemble nanogold were investigated. One method used block-copolymer thin films as chemical templates to direct the electrostatic self-assembly of nanogold. Another method used gold nanorods that are passivated with different ligands on different faces. The stability of an alkanethiol ligand in different acids and bases was investigated to determine which materials could be used to produce Janus nanorods.

Interaction between amphiphilic ionic liquid 1-butyl-3-methylimidazolium octyl sulfate and anionic polymer of sodium polystyrene sulfonate in aqueous medium

NASA Astrophysics Data System (ADS)

Barhoumi, Z.; Saini, M.; Amdouni, N.; Pal, A.

2016-09-01

The micellization of an aqueous solution of the surface active ionic liquid (SAIL), 1-butyl-3-methylimidazolium octylsufate (C4mim)(C8OSO3) and its interaction with an anionic polymer sodium polystyrene sulfonate, (NaPSS) were studied using conductimetry, tensiometry and fluorimetry. Surface tension profile shows a more dramatic increase in the value of surface tension of aqueous (C4mim)(C8OSO3) before the critical micelle concentration (cmc) of IL. The critical micelle concentration (cmc) value of this surfactant was found out from conductance measurements. The thermodynamic parameters, i.e., Gibb's free energy, enthalpy, and entropy of micellization of the IL in aqueous solution have been calculated. Behavior of fluorescence probe confirms the binding interactions between SAIL and the polyelectrolyte.

Synthetic and Biopolymer Gels - Similarities and Difference.

NASA Astrophysics Data System (ADS)

Horkay, Ferenc

2006-03-01

Ion exchange plays a central role in a variety of physiological processes, such as nerve excitation, muscle contraction and cell locomotion. Hydrogels can be used as model systems for identifying fundamental chemical and physical interactions that govern structure formation, phase transition, etc. in biopolymer systems. Polyelectrolyte gels are particularly well-suited to study ion-polymer interactions because their structure and physical-chemical properties (charge density, crosslink density, etc) can be carefully controlled. They are sensitive to different external stimuli such as temperature, ionic composition and pH. Surprisingly few investigations have been made on polyelectrolyte gels in salt solutions containing both monovalent and multivalent cations. We have developed an experimental approach that combines small angle neutron scattering and osmotic swelling pressure measurements. The osmotic pressure exerted on a macroscopic scale is a consequence of changes occurring at a molecular level. The intensity of the neutron scattering signal, which provides structural information as a function of spatial resolution, is directly related to the osmotic pressure. We have found a striking similarity in the scattering and osmotic behavior of polyacrylic acid gels and DNA gels swollen in nearly physiological salt solutions. Addition of calcium ions to both systems causes a sudden volume change. This volume transition, which occurs when the majority of the sodium counterions are replaced by calcium ions, is reversible. Such reversibility implies that the calcium ions are not strongly bound by the polyanion, but are free to move along the polymer chain, which allows these ions to form temporary bridges between negative charges on adjacent chains. Mechanical measurements reveal that the elastic modulus is practically unchanged in the calcium-containing gels, i.e., ion bridging is qualitatively different from covalent crosslinks.

Development of functionalised polyelectrolyte capsules using filamentous Escherichia coli cells.

PubMed

Lederer, Franziska L; Günther, Tobias J; Weinert, Ulrike; Raff, Johannes; Pollmann, Katrin

2012-12-23

Escherichia coli is one of the best studied microorganisms and finds multiple applications especially as tool in the heterologous production of interesting proteins of other organisms. The heterologous expression of special surface (S-) layer proteins caused the formation of extremely long E. coli cells which leave transparent tubes when they divide into single E. coli cells. Such natural structures are of high value as bio-templates for the development of bio-inorganic composites for many applications. In this study we used genetically modified filamentous Escherichia coli cells as template for the design of polyelectrolyte tubes that can be used as carrier for functional molecules or particles. Diversity of structures of biogenic materials has the potential to be used to construct inorganic or polymeric superior hybrid materials that reflect the form of the bio-template. Such bio-inspired materials are of great interest in diverse scientific fields like Biology, Chemistry and Material Science and can find application for the construction of functional materials or the bio-inspired synthesis of inorganic nanoparticles. Genetically modified filamentous E. coli cells were fixed in 2% glutaraldehyde and coated with alternating six layers of the polyanion polyelectrolyte poly(sodium-4styrenesulfonate) (PSS) and polycation polyelectrolyte poly(allylamine-hydrochloride) (PAH). Afterwards we dissolved the E. coli cells with 1.2% sodium hypochlorite, thus obtaining hollow polyelectrolyte tubes of 0.7 μm in diameter and 5-50 μm in length. For functionalisation the polyelectrolyte tubes were coated with S-layer protein polymers followed by metallisation with Pd(0) particles. These assemblies were analysed with light microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. The thus constructed new material offers possibilities for diverse applications like novel catalysts or metal nanowires for electrical devices. The novelty of this work is the use of filamentous E. coli templates and the use of S-layer proteins in a new material construct.

Cell Uptake and Validation of Novel PECs for Biomedical Applications.

PubMed

Palamà, Ilaria E; Musarò, Mariarosaria; Coluccia, Addolorata M L; D'Amone, Stefania; Gigli, Giuseppe

2011-01-01

This pilot study provides the proof of principle for biomedical application of novel polyelectrolyte complexes (PECs) obtained via electrostatic interactions between dextran sulphate (DXS) and poly(allylamine hydrochloride) (PAH). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that DXS/PAH polyelectrolyte complexes were Monodispersed with regular rounded-shape features and average diameters of 250 nm at 2 : 1 weight ratios of DXS/PAH. Fluorescently labelled DXS and fluorescein-isothiocyanate- (FITC-)conjugate DXS were used to follow cell uptake efficiency of PECs and biodegradability of their enzymatically degradable DXS-layers by using confocal laser scanning microscopy (CLSM). Moreover, quantitative MTT and Trypan Blue assays were employed to validate PECs as feasible and safe nanoscaled carriers at single-cell level without adverse effects on metabolism and viability.

Cell Uptake and Validation of Novel PECs for Biomedical Applications

PubMed Central

Palamà, Ilaria E.; Musarò, Mariarosaria; Coluccia, Addolorata M. L.; D'Amone, Stefania; Gigli, Giuseppe

2011-01-01

This pilot study provides the proof of principle for biomedical application of novel polyelectrolyte complexes (PECs) obtained via electrostatic interactions between dextran sulphate (DXS) and poly(allylamine hydrochloride) (PAH). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that DXS/PAH polyelectrolyte complexes were Monodispersed with regular rounded-shape features and average diameters of 250 nm at 2 : 1 weight ratios of DXS/PAH. Fluorescently labelled DXS and fluorescein-isothiocyanate- (FITC-)conjugate DXS were used to follow cell uptake efficiency of PECs and biodegradability of their enzymatically degradable DXS-layers by using confocal laser scanning microscopy (CLSM). Moreover, quantitative MTT and Trypan Blue assays were employed to validate PECs as feasible and safe nanoscaled carriers at single-cell level without adverse effects on metabolism and viability. PMID:21876815

Effect of screening on the transport of polyelectrolytes through nanopores

NASA Astrophysics Data System (ADS)

Oukhaled, G.; Bacri, L.; Mathé, J.; Pelta, J.; Auvray, L.

2008-05-01

We study the transport of dextran sulfate molecules (Mw=8000 Da) through a bacterial α-hemolysin channel inserted into a bilayer lipid membrane submitted to an external electric field. We detect the current blockades induced by the molecules threading through one pore and vary the ionic strength in an unexplored range starting at 10-3 M. In the conditions of the experiment, the polyelectrolyte molecules enter the pore only if the Debye screening length is smaller than the pore radius in agreement with theory. We also observe that large potentials favour the passage of the molecules. The distribution of blockade durations suggests that a complex process governs the kinetics of the molecules. The dwelling time increases sharply as the Debye length increases and approaches the pore radius.

Criticality and Connectivity in Macromolecular Charge Complexation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, Jian; de Pablo, Juan J.

We examine the role of molecular connectivity and architecture on the complexation of ionic macromolecules (polyelectrolytes) of finite size. A unified framework is developed and applied to evaluate the electrostatic correlation free energy for point-like, rod-like, and coil-like molecules. That framework is generalized to molecules of variable fractal dimensions, including dendrimers. Analytical expressions for the free energy, correlation length, and osmotic pressure are derived, thereby enabling consideration of the effects of charge connectivity, fractal dimension, and backbone stiffness on the complexation behavior of a wide range of polyelectrolytes. Results are presented for regions in the immediate vicinity of the criticalmore » region and far from it. A transparent and explicit expression for the coexistence curve is derived in order to facilitate analysis of experimentally observed phase diagrams.« less

Biocompatible Polymeric Nanoparticles as Promising Candidates for Drug Delivery.

PubMed

Łukasiewicz, Sylwia; Szczepanowicz, Krzysztof; Błasiak, Ewa; Dziedzicka-Wasylewska, Marta

2015-06-16

The use of polymeric nanoparticles (NPs) in pharmacology provides many benefits because this approach can increase the efficacy and selectivity of active compounds. However, development of new nanocarriers requires better understanding of the interactions between NPs and the immune system, allowing for the optimization of NP properties for effective drug delivery. Therefore, in the present study, we focused on the investigation of the interactions between biocompatible polymeric NPs and a murine macrophage cell line (RAW 264.7) and a human monocytic leukemia cell line (THP-1). NPs based on a liquid core with polyelectrolyte shells were prepared by sequential adsorption of polyelectrolytes (LbL) using AOT (docusate sodium salt) as the emulsifier and the biocompatible polyelectrolytes polyanion PGA (poly-l-glutamic acid sodium salt) and polycation PLL (poly l-lysine). The average size of the obtained NPs was 80 nm. Pegylated external layers were prepared using PGA-g-PEG (PGA grafted by PEG poly(ethylene glycol)). The influence of the physicochemical properties of the NPs (charge, size, surface modification) on viability, phagocytosis potential, and endocytosis was studied. Internalization of NPs was determined by flow cytometry and confocal microscopy. Moreover, we evaluated whether addition of PEG chains downregulates particle uptake by phagocytic cells. The presented results confirm that the obtained PEG-grafted NPs are promising candidates for drug delivery.

Redox-controlled molecular permeability of composite-wall microcapsules

NASA Astrophysics Data System (ADS)

Ma, Yujie; Dong, Wen-Fei; Hempenius, Mark A.; Möhwald, Helmuth; Julius Vancso, G.

2006-09-01

Many smart materials in bioengineering, nanotechnology and medicine allow the storage and release of encapsulated drugs on demand at a specific location by an external stimulus. Owing to their versatility in material selection, polyelectrolyte multilayers are very promising systems in the development of microencapsulation technologies with permeation control governed by variations in the environmental conditions. Here, organometallic polyelectrolyte multilayer capsules, composed of polyanions and polycations of poly(ferrocenylsilane) (PFS), are introduced. Their preparation involved layer-by-layer self-assembly onto colloidal templates followed by core removal. PFS polyelectrolytes feature redox-active ferrocene units in the main chain. Incorporation of PFS into the capsule walls allowed us to explore the effects of a new stimulus, that is, changing the redox state, on capsule wall permeability. The permeability of these capsules could be sensitively tuned via chemical oxidation, resulting in a fast capsule expansion accompanied by a drastic permeability increase in response to a very small trigger. The substantial swelling could be suppressed by the application of an additional coating bearing common redox-inert species of poly(styrene sulfonate) (PSS-) and poly(allylamine hydrochloride) (PAH+) on the outer wall of the capsules. Hence, we obtained a unique capsule system with redox-controlled permeability and swellability with a high application potential in materials as well as in bioscience.

Cationic flocculants carrying hydrophobic functionalities: applications for solid/liquid separation.

PubMed

Schwarz, S; Jaeger, W; Paulke, B-R; Bratskaya, S; Smolka, N; Bohrisch, J

2007-07-26

The flocculation behaviors of three series of polycations with narrow molecular weight distributions carrying hydrophobic substituents on their backbones [poly(N-vinylbenzyl-N,N,N-trimethylammonium chloride), poly(N-vinylbenzyl-N,N-dimethyl-N-butylammonium chloride), and poly(N-vinylbenzylpyridinium chloride)] were investigated in dispersions of monodisperse polystyrene latexes and kaolin. Apparently, the charge density of the polycations decreases with increasing substituent hydrophobicity and increasing molecular weight of the polyelectrolytes. The necessary amount of flocculant for phase separation in dispersions with high substrate surface charge densities increases with increasing hydrophobicity of the polyelectrolyte. Nevertheless, the introduction of hydrophobic functionalities is beneficial, resulting in a substantial broadening of the range between the minimum and maximum amounts of flocculant necessary for efficient flocculation (flocculation window). An increase in ionic strength supports this effect. When the substrate has a low charge density, the hydrophobic interactions play a much more significant role in the flocculation process. Here, the minimum efficient doses remained the same for all three polyelectrolytes investigated, but the width of the flocculation window increased as the polycation hydrophobicity and the molecular weight increased. The necessary amount of flocculant increased with an increase in particle size at constant solid content of the dispersion, as well as with a decreasing number of particles at a constant particle size.

Studies of pilocarpine:carbomer intermolecular interactions.

PubMed

Zoppi, Ariana; Linck, Yamila Garro; Monti, Gustavo A; Genovese, Diego B; Jimenez Kairuz, Alvaro F; Manzo, Rubén H; Longhi, Marcela R

2012-05-10

The interactions between pilocarpine (PIL) and the anionic polyelectrolyte carbomer (CBR) were investigated. The effects of the chemical interactions on the chemical stability of the drug also were evaluated. The binary system was characterized by nuclear magnetic resonance techniques, Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction, scanning electron microscopy (SEM) and thermal analysis. The experiments showed that the complex, prepared by freeze-drying, is a solid amorphous form different from its precursors, thereby offering an interesting alternative for the preparation of extended release matrices. The solution stability of PIL was studied at pH 7 and 8, at 70 °C. The PIL solution stability was evaluated alone and in the presence of CBR. Results indicated that the drug in the presence of the polymer is 3.3 and 3.5 times more stable, at pH 7 and pH 8, respectively, than the drug without CBR. The activation energy and the frequency factor, according to Arrhenius plot, were estimated to be 13.9 ± 0.4 and 14.8 ± 0.5 kcalmol(-1), and 6.1 ± 0.3 and 7.6 ± 0.3, with and without the polymer, respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

Kinetics of protein adsorption/desorption mediated by pH-responsive polymer layer

NASA Astrophysics Data System (ADS)

Su, Xiao-Hang; Lei, Qun-Li; Ren, Chun-Lai

2015-11-01

We propose a new way of regulating protein adsorption by using a pH-responsive polymer. According to the theoretical results obtained from the molecular theory and kinetic approaches, both thermodynamics and kinetics of protein adsorption are verified to be well controlled by the solution pH. The kinetics and the amount of adsorbed proteins at equilibrium are greatly increased when the solution environment changes from acid to neutral. The reason is that the increased pH promotes the dissociation of the weak polyelectrolyte, resulting in more charged monomers and more stretched chains. Thus the steric repulsion within the polymer layer is weakened, which effectively lowers the barrier felt by the protein during the process of adsorption. Interestingly, we also find that the kinetics of protein desorption is almost unchanged with the variation of pH. It is because although the barrier formed by the polymer layer changes along with the change of pH, the potential at contact with the surface varies equally. Our results may provide useful insights into controllable protein adsorption/desorption in practical applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 21274062, 11474155, and 91027040).

Determining equilibrium osmolarity in poly(ethylene glycol)/chondrotin sulfate gels mimicking articular cartilage.

PubMed

Sircar, S; Aisenbrey, E; Bryant, S J; Bortz, D M

2015-01-07

We present an experimentally guided, multi-phase, multi-species polyelectrolyte gel model to make qualitative predictions on the equilibrium electro-chemical properties of articular cartilage. The mixture theory consists of two different types of polymers: poly(ethylene gylcol) (PEG), chondrotin sulfate (ChS), water (acting as solvent) and several different ions: H(+), Na(+), Cl(-). The polymer chains have covalent cross-links whose effect on the swelling kinetics is modeled via Doi rubber elasticity theory. Numerical studies on equilibrium polymer volume fraction and net osmolarity (difference in the solute concentration across the gel) show a complex interplay between ionic bath concentrations, pH, cross-link fraction and the average charge per monomer. Generally speaking, swelling is aided due to a higher average charge per monomer (or a higher particle fraction of ChS, the charged component of the polymer), low solute concentration in the bath, a high pH or a low cross-link fraction. A peculiar case arises at higher values of cross-link fraction, where it is observed that increasing the average charge per monomer leads to gel deswelling. Copyright © 2014 Elsevier Ltd. All rights reserved.

Current applications of foams formed from mixed surfactant-polymer solutions.

PubMed

Bureiko, Andrei; Trybala, Anna; Kovalchuk, Nina; Starov, Victor

2015-08-01

Foams cannot be generated without the use of special foaming agents, as pure liquids do not foam. The most common foaming agents are surfactants, however often for foam stability one active agent is not enough, it is necessary to add other component to increase foam lifetime. Foams on everyday use are mostly made from mixture of different components. Properly chosen combinations of two active ingredients lead to a faster foam formation and increased foam stability. During the last decade polymers (mainly polyelectrolytes and proteins) have become frequently used additives to foaming solutions. Mixtures of surfactants and polymers often demonstrate different foaming properties in comparison to surfactant only or polymer only solutions. The nature of surfactant-polymer interactions is complicated and prediction of resulting foaming properties of such formulations is not straightforward. Properties and foaming of surfactant-polymer mixtures are discussed as well as current applications of foams and foaming agents as foams are widely used in cosmetics, pharmaceutics, medicine and the food industry. Copyright © 2014 Elsevier B.V. All rights reserved.

Fast Proton Titration Scheme for Multiscale Modeling of Protein Solutions.

PubMed

Teixeira, Andre Azevedo Reis; Lund, Mikael; da Silva, Fernando Luís Barroso

2010-10-12

Proton exchange between titratable amino acid residues and the surrounding solution gives rise to exciting electric processes in proteins. We present a proton titration scheme for studying acid-base equilibria in Metropolis Monte Carlo simulations where salt is treated at the Debye-Hückel level. The method, rooted in the Kirkwood model of impenetrable spheres, is applied on the three milk proteins α-lactalbumin, β-lactoglobulin, and lactoferrin, for which we investigate the net-charge, molecular dipole moment, and charge capacitance. Over a wide range of pH and salt conditions, excellent agreement is found with more elaborate simulations where salt is explicitly included. The implicit salt scheme is orders of magnitude faster than the explicit analog and allows for transparent interpretation of physical mechanisms. It is shown how the method can be expanded to multiscale modeling of aqueous salt solutions of many biomolecules with nonstatic charge distributions. Important examples are protein-protein aggregation, protein-polyelectrolyte complexation, and protein-membrane association.

Charge Density Quantification of Polyelectrolyte Polysaccharides by Conductometric Titration: An Analytical Chemistry Experiment

ERIC Educational Resources Information Center

Farris, Stefano; Mora, Luigi; Capretti, Giorgio; Piergiovanni, Luciano

2012-01-01

An easy analytical method for determination of the charge density of polyelectrolytes, including polysaccharides and other biopolymers, is presented. The basic principles of conductometric titration, which is used in the pulp and paper industry as well as in colloid and interface science, were adapted to quantify the charge densities of a…

Osmotic and Salted Brush Phase of Polyelectrolyte Brushes

NASA Astrophysics Data System (ADS)

Helm, Christane A.; Ahrens, Heiko; Förster, Stephan

2004-03-01

Amphiphilic block copolymers consisting of a fluid hydrophobic Poly(ethyletylene) (PEE), and a Poly(styrenesulfonate) (PSS) part form monolayers at the air/water interface. With x-ray reflectivity it is shown that the hydrophobic blocks of PEE_114PSS_83 and PEE_144PSS_136 constitute a nm-thick melt, while the polyelectrolyte forms an osmotically swollen brush with counterion incorporation. A slight thickness increase on monolayer compression is found which can be explained by the strong stretching of the brushes. Only at high salt conditions (above 0.1 M), the brush shrinks and the thickness scales with the molecular area (exponent -1/3), and with the salt concentration (exponent ca. -1/5). With Grazing Incidence Diffraction, the lateral order of the polyelectrolyte chains can be detected.

Installing logic gates in permeability controllable polyelectrolyte-carbon nitride films for detecting proteases and nucleases.

PubMed

Chen, Lichan; Zeng, Xiaoting; Dandapat, Anirban; Chi, Yuwu; Kim, Donghwan

2015-09-01

Proteases and nucleases are enzymes heavily involved in many important biological processes, such as cancer initiation, progression, and metastasis; hence, they are indicative of potential diagnostic biomarkers. Here, we demonstrate a new label free and sensitive electrochemiluminescent (ECL) sensing strategy for protease and nuclease assays that utilize target-triggered desorption of programmable polyelectrolyte films assembled on graphite-like carbon nitride (g-C3N4) film to regulate the diffusion flux of a coreactant. Furthermore, we have built Boolean logic gates OR and AND into the polyelectrolyte films, capable of simultaneously sensing proteases and nucleases in a complicated system by breaking it into simple functions. The developed intelligent permeability controlled enzyme sensor may prove valuable in future medical diagnostics.

[Preparation of polyelectrolyte microcapsules contained gold nanoparticles].

PubMed

Sun, Ya-jie; Zhu, Jia-bi; Zheng, Chun-li

2010-03-01

In this work, polyelectrolyte microcapsules containing gold nanoparticles were prepared via layer by layer assembly. Gold nanoparticles and poly (allyamine hydrochloride) (PAH) were coated on the CaCO3 microparticles. And then EDTA was used to remove the CaCO3 core. Scanning electron microscopy (SEM) was used to characterize the surface of microcapsules. SEM images indicate that the microcapsules and the polyelectrolyte multilayer were deposited on the surface of CaCO3 microparticles. FITC-bovine serum albumin (FITC-BSA, 2 mg) was incorporated in the CaCO3 microparticles by co-precipitation. Fluorescence microscopy was used to observe the fluorescence intensity of microcapsules. The encapsulation efficiency was (34.31 +/- 2.44) %. The drug loading was (43.75 +/- 3.12) mg g(-1).

Effect of the cross-linking agent on performances of NaCS-CS/WSC microcapsules.

PubMed

Wu, Qing-Xi; Xu, Xin; Wang, Zu-Li; Yao, Shan-Jing; Tong, Wang-Yu; Chen, Yan

2016-11-01

Based on the properties of oppositely charged natural polysaccharides, the polyelectrolyte complexes (PECs) prepared with chitosan-related polycationic polyelectrolytes and cellulose-related polyanionic polyelectrolytes have been widely concerned for their potential applications as micro-drug-carriers for colon. However, the poor mechanical property of the PECs becomes the obstacle encountered in practical applications. This study investigated the effect of the cross-linking agent (sodium polyphosphate, PPS) on the performances of sodium cellulose sulfate -chitosan/water soluble chitosan (NaCS-CS/WSC) microcapsules. The results revealed that PPS could penetrate through the PEC film and form tighter interior structures compared with the microcapsules without the addition of cross-linking agent. The NaCS-CS microcapsules and NaCS-WSC microcapsules with or without PPS had distinct microstructures, which could be ascribed to the different physicochemical properties of CS and WSC. During the formation process, CS can be dissolved in water under acidic conditions, while WSC can be directly dissolved and protonated in acid-free aqueous providing NH3(+) groups quickly, which resulted in the microstructure's difference. Further analysis showed the NaCS-CS-PPS microcapsules and NaCS-WSC-PPS microcapsules had lower swelling ratios due to their tighter interior microstructures that formed. The cross-linking agent had important effect on the total mass of PECs that produced; moreover, the decline of zeta potential of NaCS-CS-PPS microcapsules was lower than that of NaCS-CS microcapsules, similar trend was found in the NaCS-WSC-PPS microcapsules compared with NaCS-WSC microcapsules, indicating the PPS participated in the interactions and played a role in the microcapsules' formation process. Copyright © 2016 Elsevier B.V. All rights reserved.

Simultaneous detection of refractive index and surface charges in nanolaser biosensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, Keisuke; Kishi, Yoji; Hachuda, Shoji

2015-01-12

The emission intensity of a GaInAsP photonic crystal nanolaser is affected by the pH of the solution, in which the nanolaser is immersed. This phenomenon can be explained by the change in the redox potential, which modifies the filling of electrons at surface states of the semiconductor and hence the nonradiative surface recombination. This phenomenon allows the nanolaser to simultaneously and independently detect the refractive index and electric charges near the surface on the basis of the variation in emission wavelength and intensity, respectively. This paper demonstrates this function through alternate deposition of charged polyelectrolytes and hybridization of deoxyribonucleic acids.

Relative size selection of a conjugated polyelectrolyte in virus-like protein structures.

PubMed

Brasch, Melanie; Cornelissen, Jeroen J L M

2012-02-01

A conjugated polyelectrolyte poly[(2-methoxy-5-propyloxy sulfonate)-phenyl-ene vinylene] (MPS-PPV) drives the assembly of virus capsid proteins to form single virus-like particles (VLPs) and aggregates with more than two VLPs, with a relative selection of high molecular weight polymer in the latter. This journal is © The Royal Society of Chemistry 2012

Ultrasensitive detection of nitroexplosive - picric acid via a conjugated polyelectrolyte in aqueous media and solid support.

PubMed

Hussain, Sameer; Malik, Akhtar Hussain; Afroz, Mohammad Adil; Iyer, Parameswar Krishnan

2015-04-28

Picric acid (PA) detection at parts per trillion (ppt) levels is achieved by a conjugated polyelectrolyte (PMI) in 100% aqueous media and on a solid platform using paper strips and chitosan (CS) films. The unprecedented selectivity is accomplished via combination of ground state charge transfer and resonance energy transfer (RET) facilitated by favorable electrostatic interactions.

Polyelectrolyte Structure and Interactions in Model Cystic Fibrosis Sputum

NASA Astrophysics Data System (ADS)

Slimmer, Scott; Angelini, Thomas; Liang, Hongjun; Butler, John; Wong, Gerard C. L.

2002-03-01

Cystic fibrosis sputum is a complex fluid consisting of a number of components, including mucin (a glycoprotein), lysozyme (a cationic polypeptide), water, salt, as well as a high concentration of a number of anionic biological polyelectrolytes such as DNA and F-actin. The interactions governing these components are poorly understood, but may have important clinical consequences. For example, the formation of these biological polyelectrolytes into ordered gel phases may contribute significantly to the observed high viscosity of CF sputum. In this work, a number of model systems were created to simulate CF sputum in vitro, in order to elucidate the contributions of the different components. Preliminary results will be presented. This work was supported by NSF DMR-0071761, DOE DEFG02-91ER45439, the Beckman Young Investigator Program, and the Cystic Fibrosis Foundation.

Flow cytometry of HEK 293T cells interacting with polyelectrolyte multilayer capsules containing fluorescein-labeled poly(acrylic acid) as a pH sensor.

PubMed

Reibetanz, Uta; Halozan, David; Brumen, Milan; Donath, Edwin

2007-06-01

Polyelectrolyte multilayer sensor capsules, 5 microm in diameter, which contained fluorescein-labeled poly(acrylic acid) (PAAAF) as pH-sensitive reporter molecules, were fabricated and employed to explore their endocytotic uptake into HEK 293T cells by flow cytometry. The percentage of capsules residing in the endolysosomal compartment was estimated from the fluorescence intensity decrease caused by acidification. Capsules attached to the extracellular surface of the plasma membrane were identified by trypan blue quenching. The number of capsules in the cytoplasm was rather small, being below the detection limit of the method. The advantages of polyelectrolyte multilayer capsules are that the fluorophore is protected from interaction with cellular compartments and that the multilayer can be equipped with additional functions.

Polyelectrolyte capsules as carriers for growth factor inhibitor delivery to hepatocellular carcinoma.

PubMed

Baldassarre, Francesca; Vergaro, Viviana; Scarlino, Flavia; De Santis, Flavia; Lucarelli, Giovanna; Torre, Antonio Della; Ciccarella, Giuseppe; Rinaldi, Ross; Giannelli, Gianluigi; Leporatti, Stefano

2012-05-01

The efficient internalization of TGF-beta inhibitor-loaded polyelectrolyte capsules and particles is studied in two HCC cell lines. Two polyelectrolyte pairs (biocompatible but not degradable and biodegradable crosslinked with gluteraldehyde) are employed for coating. The capsules are characterized by SEM. LY is successfully loaded inside the core and embedded between polymer layers. MS is used to quantify the loading efficiency by comparing post-loading and core-loading methods, since both coated templates and hollow shells are used as carriers. CLSM confirms dissolution of the pre-formed multilayer upon enzymatic degradation as the method of release, and migration assays demonstrate a higher inhibition efficiency of TGF-beta in tailored biodegradable capsules compared to free LY administration. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Evaluation of the sanitary-and-epidemiological safety of flocculating agents used for portable water purification].

PubMed

Zholdakova, Z I; Sinitsyna, O O; Tul'skaia, E A

2006-01-01

Polyelectrolytes used in the practice of water supply to the population were comparatively hygienically studied, by using a complex of hazard indices and a new approach to sanitary-and-epidemiological evaluation of the safety of water-soluble polymers is substantiated. The anionic and cationic flocculating agents from different chemical classes, such as Superflok A-100, Fennopol A 321E, Fennopol K 221E, Praestol 2530 TR, VPK-402, Superflok C-577, Saipan, KF-91, Ecosol-401, a low molecular-weight sodium polyacrylate were tested as model compounds. Moreover, the information already available in the scientific literature on the toxicity of synthetic polyelectrolytes was analyzed. The generalized maximum permissible concentrations were substantiated for individual chemical classes of synthetic polyelectrolytes: polyacrylamides, polyamines, polydiallyldimethylammonium chloride.

PEM Anchorage on Titanium Using Catechol Grafting

PubMed Central

Marie, Hélène; Barrere, Amélie; Schoentstein, Frédérique; Chavanne, Marie-Hélène; Grosgogeat, Brigitte; Mora, Laurence

2012-01-01

Background This study deals with the anchorage of polyelectrolyte films onto titanium surfaces via a cathecol-based linker for biomedical applications. Methodology The following study uses a molecule functionalized with a catechol and a carboxylic acid: 3-(3,4-dihydroxyphenyl)propanoic acid. This molecule is anchored to the TiO2 substrate via the catechol while the carboxylic acid reacts with polymers bearing amine groups. By providing a film anchorage of chemisorption type, it makes possible to deposit polyelectrolytes on the surface of titanium. Principal Findings Infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), contact angle and atomic force microscopy (AFM) measurements show that the different steps of grafting have been successfully performed. Conclusions This method based on catechol anchorage of polyelectrolytes open a window towards large possibilities of clinical applications. PMID:23226262

Surface colonized silver nano particles over chitosan poly-electrolyte micro-spheres and their multi-functional behavior

NASA Astrophysics Data System (ADS)

Prakash, B.; Asha, S.; Nimrodh Ananth, A.; Vanithakumari, G.; Okram, G. S.; Jose, Sujin P.; Jothi Rajan, M. A.

2018-02-01

Chitosan/tripolyphosphate polyelectrolyte (TPP) microspheres, decorated and surface functionalized with silver nanoparticles (NPs) of average diameter of 15 nm, were synthesized following a simple two-step procedure. These Ag NP-functionalized polyelectrolyte microspheres (Ag-CSPMs) are found to be biocompatible and enhancing the reactive oxygen species in curcumin with excellent anti-bacterial activity for selected Gram-positive and negative bacterial strains, making them much attractive relative to bare surface counterparts; the well-stabilized silver NPs do not form any agglomerations on the surface of the chitosan microspheres. They also show excellent cytotoxic behavior towards MCF7 cell lines, showing a half-maximal inhibitory concentration (IC50) of 32 μg ml-1. Therefore, Ag-CSPMs exhibit multi-functional ability having potential towards theranostics applications.

Particles decorated by an ionizable thermoresponsive polymer brush in water: experiments and self-consistent field modeling.

PubMed

Alves, S P C; Pinheiro, J P; Farinha, J P S; Leermakers, F A M

2014-03-20

We have synthesized anionic multistimuli responsive core-shell polymer nanoparticles with low size dispersity composed of glassy poly(methyl methacrylate) (PMMA) cores of ca. 40 nm radius and poly(N-isopropylacrylamide) (PNIPAM) anionic brush-like shells with methacrylic acid comonomers. Using dynamic light scattering, we observed a volume phase transition upon an increase in temperature and this response was pH and ionic strength dependent. Already at room temperature we observed a pronounced polyelectrolyte effect, that is, a shift of the apparent pKa extracted from the degree of dissociation of the acids as a function of the pH. The multiresponsive behavior of the hydrophobic polyelectrolyte brush has been modeled using the Scheutjens-Fleer self-consistent field (SF-SCF) approach. Using a phenomenological relation between the Flory-Huggins χ parameter and the temperature, we confront the predicted change in the brush height with the observed change of the hydrodynamic radius and degree of dissociation and obtain estimates for the average chain lengths (number of Kuhn segments) of the corona chains, the grafting density and charge density distributions. The theory reveals a rich internal structure of the hydrophobic polyelectrolyte brush, especially near the collapse transition, where we find a microphase segregated structure. Considering this complexity, it is fair to state that the theoretical predictions follow the experimental data semiquantitatively, and it is attractive to attribute the observed disparity between theory and experiments to the unknown polydispersity of the chains, the unknown distribution of the charges, or other experimental complications. More likely, however, the deviations point to significant problems of the mean field theory, which focuses solely on the radial distributions and ignores the possibility of the formation of lateral (local) inhomogeneities in partially collapsed polyelectrolyte brushes. We argue that the PNIPAM brush at room temperature is already behaving nonideally.

Brownian dynamics simulations of polyelectrolyte adsorption in shear flow with hydrodynamic interaction

NASA Astrophysics Data System (ADS)

Hoda, Nazish; Kumar, Satish

2007-12-01

The adsorption of single polyelectrolyte molecules in shear flow is studied using Brownian dynamics simulations with hydrodynamic interaction (HI). Simulations are performed with bead-rod and bead-spring chains, and electrostatic interactions are incorporated through a screened Coulombic potential with excluded volume accounted for by the repulsive part of a Lennard-Jones potential. A correction to the Rotne-Prager-Yamakawa tensor is derived that accounts for the presence of a planar wall. The simulations show that migration away from an uncharged wall, which is due to bead-wall HI, is enhanced by increases in the strength of flow and intrachain electrostatic repulsion, consistent with kinetic theory predictions. When the wall and polyelectrolyte are oppositely charged, chain behavior depends on the strength of electrostatic screening. For strong screening, chains get depleted from a region close to the wall and the thickness of this depletion layer scales as N1/3Wi2/3 at high Wi, where N is the chain length and Wi is the Weissenberg number. At intermediate screening, bead-wall electrostatic attraction competes with bead-wall HI, and it is found that there is a critical Weissenberg number for desorption which scales as N-1/2κ-3(lB∣σq∣)3/2, where κ is the inverse screening length, lB is the Bjerrum length, σ is the surface charge density, and q is the bead charge. When the screening is weak, adsorbed chains are observed to align in the vorticity direction at low shear rates due to the effects of repulsive intramolecular interactions. At higher shear rates, the chains align in the flow direction. The simulation method and results of this work are expected to be useful for a number of applications in biophysics and materials science in which polyelectrolyte adsorption plays a key role.

Effect of Pendant Side-Chain Sterics and Dipole Forces on Short Range Ordering in Random Polyelectrolytes

NASA Astrophysics Data System (ADS)

Nwosu, Chinomso; Pandey, Tara; Herring, Andrew; Coughlin, Edward; University of Massachusetts, Amherst Collaboration; Colorado School of Mines Collaboration

Backbone-to-backbone spacing in polymers is known to be dictated by the length of the pendant side-chains. Dipole forces in random polyelectrolytes lead to ionic clusters with a characteristic spacing that can be observed by SAXS. Repulsion due to side-chain sterics will compete with dipole forces driving cluster formation in random polyelectrolytes. A model study on short range order in anion exchange membranes (AEMs) of quaternized P4VP-ran-PI is presented. Quaternization of P4VP with alkyl bromides having different numbers of carbons, CnBr, introduces pendant side-chains as well as charges. X-ray scattering performed on PQ4VP-ran-PI(CnBr) show that when n <5 the dipole forces dominate leading to the formation of ionic clusters. However, when n >4, the chains remain separated due to sterics, forming a distinct backbone-to-backbone spacing morphology. For n=3, both dipole clustering and backbone spacing can coexist. Crosslinking of the isoprene units increased the coexistence window from n=3 to n=6. Impedance measurements show that a maximum conductivity of 110mS/cm was obtained for PQ4VP-ran-PI(C3Br). A discussion on short range order due to competition, or counter balancing, of steric repulsion and dipole forces will be presented. US Army MURI project (W911NF1010520).

Effect of nanoparticles size and polyelectrolyte on nanoparticles aggregation in a cellulose fibrous matrix

DOE PAGES

Raghuwanshi, Vikram Singh; Garusinghe, Uthpala Manavi; Ilavsky, Jan; ...

2017-09-18

Controlling nanoparticles (NPs) aggregation in cellulose/NPs composites allows to optimise NPs driven properties and their applications. Polyelectrolytes are used to control NPs aggregation and their retention within the fibrous matrix. Here in this study, we aim at evaluating how a polyelectrolyte (Cationic Polyacrylamide; CPAM, molecular weight: 13 MDa, charge: 50%, Radius of gyration: 30–36 nm) adsorbs and re-conforms onto the surface of silica(SiO 2) NPs differing in diameter (8, 22 and 74 nm) and to investigate the respective NPs aggregation in cellulose matrices. SEM shows the local area distribution of NPs in composites. Ultra-SAXS (USAXS) allows to evaluate the averagemore » NPs size distribution and the inter-particle interactions at length scale ranging from 1 to 1000 nm. USAXS data analysis reveals that CPAM covers multiple NPs of the smaller diameter (8 nm), presumably with a single chain to form large size NPs aggregates. As the NPs diameter is increased to 22 nm, CPAM re-conforms over NP surface forming a large shell of thickness 5.5 nm. For the composites with NPs of diameter 74 nm, the CPAM chain re-conforms further onto NP surface and the surrounding shell thickness decreases to 2.2 nm. Lastly, structure factor analysis reveals higher structural ordering for NPs as increases their diameter, which is caused by different conformations adopted by CPAM onto NPs surface.« less

Human mesenchymal stem cell osteoblast differentiation, ECM deposition, and biomineralization on PAH/PAA polyelectrolyte multilayers.

PubMed

Pattabhi, Sudhakara Rao; Lehaf, Ali M; Schlenoff, Joseph B; Keller, Thomas C S

2015-05-01

Polyelectrolyte multilayer (PEMU) coatings built layer by layer with alternating pairs of polyelectrolytes can be tuned to improve cell interactions with surfaces and may be useful as biocompatible coatings to improve fixation between implants and tissues. Here, we show that human mesenchymal stromal cells (hMSCs) induced with bone differentiation medium (BDM) to become osteoblasts biomineralize crosslinked PEMUs built with the polycation poly(allylamine hydrochloride) (PAH) and the polyanion poly(acrylic acid) (PAA). Degrees of hMSC osteoblast differentiation and surface biomineralization on the smooth PAH-terminated PEMUs (PAH-PEMUs) and microstructured PAA-terminated PEMUs (PAA-PEMUs) reflect differences in cell-deposited extracellular matrix (ECM). BDM-induced hMSCs expressed higher levels of the early osteoblast differentiation marker alkaline phosphatase and collagen 1 (COL1) sooner on PAA-PEMUs than on PAH-PEMUs. Cells on both types of PEMUs proceeded to express the later stage osteoblast differentiation marker bone sialoprotein (BSP), but the BDM-induced cells organized a more amorphous Collagen I and denser BSP localization on PAA-PEMUs than on PAH-PEMUs. These ECM properties correlated with greater biomineralization on the PAA-PEMUs than on PAH-PEMUs. Together, these results confirm the suitability of PAH/PAA PEMUs as a substrate for hMSC osteogenesis and highlight the importance of substrate effects on ECM organization and BSP presentation on biomineralization. © 2014 Wiley Periodicals, Inc.

Preparation of the polyelectrolyte complex hydrogel of biopolymers via a semi-dissolution acidification sol-gel transition method and its application in solid-state supercapacitors

NASA Astrophysics Data System (ADS)

Zhao, Jian; Chen, Yu; Yao, Ying; Tong, Zong-Rui; Li, Pu-Wang; Yang, Zi-Ming; Jin, Shao-Hua

2018-02-01

Hydrogels have drawn many attentions as the solid-state electrolytes in flexible solid-state supercapacitors (SCs) recently. Among them, the polyelectrolyte complex hydrogel (PECH) electrolytes of natural polymers are more competitive because of their environmentally friendly property and low cost. However, while mixing two biopolymer solutions with opposite charges, the strong electrostatic interactions between the cationic and anionic biopolymers may result in precipitates instead of hydrogels. Here we report a novel method, semi-dissolution acidification sol-gel transition (SD-A-SGT), for the preparation of the PECH of chitosan (CTS) and sodium alginate (SA), with the controllable sol-gel transition and uniform composition and successfully apply it as the hydrogel electrolyte of solid-state supercapacitors (SCs). The CTS-SA PECH exhibits an extremely high ionic conductivity of 0.051 S·cm-1 and reasonable mechanical properties with a tensile strength of 0.29 MPa and elongation at break of 109.5%. The solid-state SC fabricated with the CTS-SA PECH and conventional polyaniline (PANI) nanowire electrodes provided a high specific capacitance of 234.6 F·g-1 at 5 mV·s-1 and exhibited excellent cycling stability with 95.3% capacitance retention after 1000 cycles. Our work may pave a novel avenue to the preparation of biodegradable PECHs of full natural polymers, and promote the development of environmentally friendly electronic devices.

Highly Transparent, Nanofiller-Reinforced Scratch-Resistant Polymeric Composite Films Capable of Healing Scratches.

PubMed

Li, Yang; Chen, Shanshan; Li, Xiang; Wu, Mengchun; Sun, Junqi

2015-10-27

Integration of healability and mechanical robustness is challenging in the fabrication of highly transparent films for applications as protectors in optical and displaying devices. Here we report the fabrication of healable, highly transparent and scratch-resistant polymeric composite films that can conveniently and repeatedly heal severe damage such as cuts of several tens of micrometers wide and deep. The film fabrication process involves layer-by-layer (LbL) assembly of a poly(acrylic acid) (PAA) blend and branched poly(ethylenimine) (bPEI) blend, where each blend contains the same polyelectrolytes of low and high molecular weights, followed by annealing the resulting PAA/bPEI films with aqueous salt solution and incorporation of CaCO3 nanoparticles as nanofillers. The rearrangement of low-molecular-weight PAA and bPEI under aqueous salt annealing plays a critical role in eliminating film defects to produce optically highly transparent polyelectrolyte films. The in situ formation of tiny and well-dispersed CaCO3 nanoparticles gives the resulting composite films enhanced scratch-resistance and also retains the healing ability of the PAA/bPEI matrix films. The reversibility of noncovalent interactions among the PAA, bPEI, and CaCO3 nanoparticles and the facilitated migration of PAA and bPEI triggered by water enable healing of the structural damage and restoration of optical transparency of the PAA/bPEI films reinforced with CaCO3 nanoparticles.

Ionic Borate-Based Covalent Organic Frameworks: Lightweight Porous Materials for Lithium-Stable Solid State Electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Black, Hayden T.; Harrison, Katharine Lee

2016-10-01

The synthesis and characterization of the first polyelectrolyte of intrinsic microporosity (PEIM) is described. The novel material was synthesized via reaction between the nitrile group in the polymer backbone and n-butyl lithium, effectively anchoring an imine anion to the porous framework while introducing a mobile lithium counterion. The PEIM was characterized by 13C, 1H, and 7Li NMR experiments, revealing quantitative conversion of the nitrile functionality to the anionic imine. Variable temperature 7Li NMR analysis of the dry PEIM and the electrolyteswollen PEIM revealed that lithium ion transport within the dry PEIM was largely due to interchain hopping of the Limore » + ions, and that the mobility of polymer associated Li + was reduced after swelling in electrolyte solution. Meanwhile, the swollen PEIM supported efficient transport of dissolved Li + within the expanded pores. These results are discussed in the context of developing novel solid or solid-like lithium ion electrolytes using the new PEIM material.« less

Immobilization of Superoxide Dismutase on Polyelectrolyte-Functionalized Titania Nanosheets.

PubMed

Rouster, Paul; Pavlovic, Marko; Szilagyi, Istvan

2018-02-16

The superoxide dismutase (SOD) enzyme was successfully immobilized on titania nanosheets (TNS) functionalized with the poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte. The TNS-PDADMAC solid support was prepared by hydrothermal synthesis followed by self-assembled polyelectrolyte layer formation. It was found that SOD strongly adsorbed onto oppositely charged TNS-PDADMAC through electrostatic and hydrophobic interactions. The TNS-PDADMAC-SOD material was characterized by light scattering and microscopy techniques. Colloidal stability studies revealed that the obtained nanocomposites possessed good resistance against salt-induced aggregation in aqueous suspensions. The enzyme kept its functional integrity upon immobilization; therefore, TNS-PDADMAC-SOD showed excellent superoxide radical anion scavenging activity. The developed system is a promising candidate for applications in which suspensions of antioxidant activity are required in the manufacturing processes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polyphosphates as inorganic polyelectrolytes interacting with oppositely charged ions, polymers and deposited on surfaces: fundamentals and applications.

PubMed

Cini, N; Ball, V

2014-07-01

Polyphosphates are important but neglected polyelectrolytes that play a major role in biology and in surface science for the stabilization of colloids against flocculation and for the preservation of food. They are also known as "Calgon" ® and intensively used as additives in washing powders. This review aims to review recent developments in which linear polyphosphates are used for the design of new functional coatings using sol-gel processes and layer-by-layer deposition methods. All these methods rely on the high charge density of polyphosphates as inorganic polyelectrolytes, therefore the structure and properties of these molecules are also reviewed. New perspectives will also been given for the design of stimuli responsive coatings at the tiny frontier between biology and materials science. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of Natural Organic Matter on Stability, Transport and Deposition of Engineered Nano-particles in Porous Media

EPA Science Inventory

The interaction of nano-particles and organic substances, like natural organic matter, could have significant influence on the fate, transport and bioavailability of toxic substances. Natural organic matter (NOM) is a mixture of chemically complex polyelectrolytes with varying m...

Layer-by-Layer Polyelectrolyte Encapsulation of Mycoplasma pneumoniae for Enhanced Raman Detection

PubMed Central

Rivera-Betancourt, Omar E.; Sheppard, Edward S.; Krause, Duncan C.; Dluhy, Richard A.

2014-01-01

Mycoplasma pneumoniae is a major cause of respiratory disease in humans and accounts for as much as 20% of all community-acquired pneumonia. Existing mycoplasma diagnosis is primarily limited by the poor success rate at culturing the bacteria from clinical samples. There is a critical need to develop a new platform for mycoplasma detection that has high sensitivity, specificity, and expediency. Here we report the layer-by-layer (LBL) encapsulation of M. pneumoniae cells with Ag nanoparticles in a matrix of the polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS). We evaluated nanoparticle encapsulated mycoplasma cells as a platform for the differentiation of M. pneumoniae strains using surface enhanced Raman scattering (SERS) combined with multivariate statistical analysis. Three separate M. pneumoniae strains (M129, FH and II-3) were studied. Scanning electron microscopy and fluorescence imaging showed that the Ag nanoparticles were incorporated between the oppositely charged polyelectrolyte layers. SERS spectra showed that LBL encapsulation provides excellent spectral reproducibility. Multivariate statistical analysis of the Raman spectra differentiated the three M. pneumoniae strains with 97 – 100% specificity and sensitivity, and low (0.1 – 0.4) root mean square error. These results indicated that nanoparticle and polyelectrolyte encapsulation of M. pneumoniae is a potentially powerful platform for rapid and sensitive SERS-based bacterial identification. PMID:25017005

Pulmonary sustained release of insulin from microparticles composed of polyelectrolyte layer-by-layer assembly.

PubMed

Amancha, Kiran Prakash; Balkundi, Shantanu; Lvov, Yuri; Hussain, Alamdar

2014-05-15

The present study tests the hypothesis that layer-by-layer (LbL) nanoassembly of thin polyelectrolyte films on insulin particles provides sustained release of the drug after pulmonary delivery. LbL insulin microparticles were formulated using cationic and anionic polyelectrolytes. The microparticles were characterized for particle size, particle morphology, zeta potential and in vitro release. The pharmacokinetics and pharmacodynamics of drug were assessed by measuring serum insulin and glucose levels after intrapulmonary administration in rats. Bronchoalveolar lavage (BAL) and evans blue (EB) extravasation studies were performed to investigate the cellular or biochemical changes in the lungs caused by formulation administration. The mass median aerodynamic diameter (MMAD) of the insulin microparticles was 2.7 μm. Confocal image of the formulation particles confirmed the polyelectrolyte deposition around the insulin particles. Zeta potential measurements showed that there was charge reversal after each layering. Pulmonary administered LbL insulin formulation resulted in sustained serum insulin levels and concomitant decrease in serum glucose levels. The BAL and EB extravasation studies showed that the LbL insulin formulation did not elicit significant increase in marker enzymes activities compared to control group. These results demonstrate that the sustained release of insulin could be achieved using LbL nanoassembly around the insulin particles. Copyright © 2014 Elsevier B.V. All rights reserved.

Small angle neutron scattering study of polyelectrolyte brushes grafted to well-defined gold nanoparticle interfaces.

PubMed

Jia, Haidong; Grillo, Isabelle; Titmuss, Simon

2010-05-18

Small angle neutron scattering (SANS) has been used to study the conformations, and response to added salt, of a polyelectrolyte layer grafted to the interfaces of well-defined gold nanoparticles. The polyelectrolyte layer is prepared at a constant coverage by grafting thiol-functionalized polystyrene (M(w) = 53k) to gold nanoparticles of well-defined interfacial curvature (R(c) = 26.5 nm) followed by a soft-sulfonation of 38% of the segments to sodium polystyrene sulfonate (NaPSS). The SANS profiles can be fit by Fermi-Dirac distributions that are consistent with a Gaussian distribution but are better described by a parabolic distribution plus an exponential tail, particularly in the high salt regime. These distributions are consistent with the predictions and measurements for osmotic and salted brushes at interfaces of low curvature. When the concentration of added salt exceeds the concentration of counterions inside the brush, there is a salt-induced deswelling, but even at the highest salt concentration the brush remains significantly swollen due to a short-ranged excluded volume interaction. This is responsible for the observed resistance to aggregation of these comparatively high concentration polyelectrolyte stabilized gold nanoparticle dispersions even in the presence of a high concentration of added salt.

Development of a robust pH-sensitive polyelectrolyte ionomer complex for anticancer nanocarriers

PubMed Central

Lim, Chaemin; Youn, Yu Seok; Lee, Kyung Soo; Hoang, Ngoc Ha; Sim, Taehoon; Lee, Eun Seong; Oh, Kyung Taek

2016-01-01

A polyelectrolyte ionomer complex (PIC) composed of cationic and anionic polymers was developed for nanomedical applications. Here, a poly(ethylene glycol)–poly(lactic acid)–poly(ethylene imine) triblock copolymer (PEG–PLA–PEI) and a poly(aspartic acid) (P[Asp]) homopolymer were synthesized. These polyelectrolytes formed stable aggregates through electrostatic interactions between the cationic PEI and the anionic P(Asp) blocks. In particular, the addition of a hydrophobic PLA and a hydrophilic PEG to triblock copolyelectrolytes provided colloidal aggregation stability by forming a tight hydrophobic core and steric hindrance on the surface of PIC, respectively. The PIC showed different particle sizes and zeta potentials depending on the ratio of cationic PEI and anionic P(Asp) blocks (C/A ratio). The doxorubicin (dox)-loaded PIC, prepared with a C/A ratio of 8, demonstrated pH-dependent behavior by the deprotonation/protonation of polyelectrolyte blocks. The drug release and the cytotoxicity of the dox-loaded PIC (C/A ratio: 8) increased under acidic conditions compared with physiological pH, due to the destabilization of the formation of the electrostatic core. In vivo animal imaging revealed that the prepared PIC accumulated at the targeted tumor site for 24 hours. Therefore, the prepared pH-sensitive PIC could have considerable potential as a nanomedicinal platform for anticancer therapy. PMID:26955270

Silica Encapsulation of Ferrimagnetic Zinc Ferrite Nanocubes Enabled by Layer-by-layer Polyelectrolyte Deposition

PubMed Central

Park, Jooneon; Porter, Marc D.; Granger, Michael C.

2016-01-01

Stable suspensions of magnetic nanoparticles (MNPs) with large magnetic moment, m, per particle have tremendous utility in a wide range of biological applications. However, due to the strong magnetic coupling interactions often present in these systems, it is challenging to stabilize individual, high moment, ferro- and ferrimagnetic nanoparticles. A novel approach to encapsulate large, i.e., >100 nm, ferrimagnetic zinc ferrite nanocubes (ZFNCs) with silica after an intermediary layer-by-layer polyelectrolyte deposition step is described in this paper. The seed ZFNCs are uniform in shape and size and have high saturation mass magnetic moment (σs ~100 emu/g, m~4×10−13 emu/particle at 150 Oe). For the MNP system described within, successful silica encapsulation and creation of discrete ZFNCs were realized only after depositing polyelectrolyte multilayers composed of alternating polyallylamine and polystyrene sulfonate. Without the intermediary polyelectrolyte layers, magnetic dipole-dipole interactions led to the formation of linearly chained ZFNCs embedded in a silica matrix. Characterization of particle samples was performed by electron microscopy, energy-dispersive X-ray spectroscopy, infrared spectroscopy, powder X-ray diffraction, dynamic light scattering (hydrodynamic size and ζ-potential), and vibrating sample magnetometry. The results of these characterizations, which were performed after each of the synthetic steps, and synthetic details are presented. PMID:25756216

Polypeptide multilayer film co-delivers oppositely-charged drug molecules in sustained manners.

PubMed

Jiang, Bingbing; Defusco, Elizabeth; Li, Bingyun

2010-12-13

The current state-of-the-art for drug-carrying biomedical devices is mostly limited to those that release a single drug. Yet there are many situations in which more than one therapeutic agent is needed. Also, most polyelectrolyte multilayer films intended for drug delivery are loaded with active molecules only during multilayer film preparation. In this paper, we present the integration of capsules as vehicles within polypeptide multilayer films for sustained release of multiple oppositely charged drug molecules using layer-by-layer nanoassembly technology. Calcium carbonate (CaCO(3)) particles were impregnated with polyelectrolytes, shelled with polyelectrolyte multilayers, and then assembled onto polypeptide multilayer films using glutaraldehyde. Capsule-integrated polypeptide multilayer films were obtained after decomposition of CaCO(3) templates. Two oppositely charged drugs were loaded into capsules within polypeptide multilayer films postpreparation based on electrostatic interactions between the drugs and the polyelectrolytes impregnated within capsules. We determined that the developed innovative capsule-integrated polypeptide multilayer films could be used to load multiple drugs of very different properties (e.g., opposite charges) any time postpreparation (e.g., minutes before surgical implantation inside an operating room), and such capsule-integrated films allowed simultaneous delivery of two oppositely charged drug molecules and a sustained (up to two weeks or longer) and sequential release was achieved.

Polypeptide Multilayer Film Co-Delivers Oppositely-Charged Drug Molecules in Sustained Manners

PubMed Central

Jiang, Bingbing; DeFusco, Elizabeth; Li, Bingyun

2010-01-01

The current state-of-the-art for drug-carrying biomedical devices is mostly limited to those that release a single drug. Yet there are many situations in which more than one therapeutic agent is needed. Also, most polyelectrolyte multilayer films intending for drug delivery are loaded with active molecules only during multilayer film preparation. In this paper, we present the integration of capsules as vehicles within polypeptide multilayer films for sustained release of multiple oppositely-charged drug molecules using layer-by-layer nanoassembly technology. Calcium carbonate (CaCO3) particles were impregnated with polyelectrolytes, shelled with polyelectrolyte multilayers, and then assembled onto polypeptide multilayer films using glutaraldehyde. Capsule-integrated polypeptide multilayer films were obtained after decomposition of CaCO3 templates. Two oppositely-charged drugs were loaded into capsules within polypeptide multilayer films post-preparation based on electrostatic interactions between the drugs and the polyelectrolytes impregnated within capsules. We determined that the developed innovative capsule-integrated polypeptide multilayer films could be used to load multiple drugs of very different properties (e.g. opposite charges) any time post-preparation (e.g. minutes before surgical implantation inside an operating room), and such capsule-integrated films allowed simultaneous delivery of two oppositely-charged drug molecules and a sustained (up to two weeks or longer) and sequential release was achieved. PMID:21058719

[Polyelectrolyte microcapsules as systems for delivery of biologically active substances].

PubMed

Borodina, T N; Rumsh, L D; Kunizhev, S M; Sukhorukov, G B; Vorozhtsov, G N; Fel'dman, B M; Markvicheva, E A

2007-01-01

Novel biodegradable microcapsules for delivery of biologically active substances (BAS) were prepared by layer-by-layer (LbL) adsorption of oppositely charged polyelectrolytes, namely sodium alginate (Alg) and poly-L-lysine (PLL). To immobilize these BAS, porous spherical CaCO3 microparticles were used as templates. The templates (cores) were coated with several layers of oppositely charged polyelectrolytes forming shell on a core surface. The core-shell microparticles were converted into hollow microcapsules by a core dissolution after an EDTA treatment. Mild conditions for microcapsule fabrication allow to perform an entrapment of various biomolecules while keeping their bioactivity. Biocompatibility and biodegradable capability of the polyelectrolytes give a possibility to use the microcapsules as the target delivery systems. Chymotrypsin (Chym) entrapped into the microcapsules was used as a model enzyme. The immobilized enzyme was found to keep about 86% of the activity compared to a native Chym. The obtained microcapsules were stable at an acidic medium while they could be easily decomposed by trypsin treatment at an slightly alkaline medium. Chym was shown to be active after being released from the microcapsules decomposed by trypsin treatment. Thus, the microcapsules prepared by the LbL - technique can be used for the development of new type of BAS delivery systems in humans and animals.

Electrical properties of multilayers from low- and high-molecular-weight polyelectrolytes.

PubMed

Radeva, Tsetska; Milkova, Viktoria; Petkanchin, Ivana

2004-11-15

The formation of stable multilayer films by using as constituents sodium poly(4-styrene sulfonate) (PSS) and poly(4-vinyl pyridine) (PVP) was studied by electrooptics. A strong increase in basicity of the pyridine rings in the electrical field of the oppositely charged PSS chains was suggested to be the driving force for multilayer film formation. A linear increase in the film thickness was registered after deposition of the first three layers, with no dependence on the polyelectrolyte molecular weight. The electrooptical effect was found to increase with increasing area of each next layer, but depended on the molecular weights of both polymers. Polarization of "condensed" counterions along the chains of the last-adsorbed layer was suggested to explain this dependence. Following the counterion dynamics, we come to the conclusion that the electrical properties of the top layer govern the electrooptical behavior of the PSS/PVP film.

Photoinduced charge-transfer materials for nonlinear optical applications

DOEpatents

McBranch, Duncan W.

2006-10-24

A method using polyelectrolyte self-assembly for preparing multi-layered organic molecular materials having individual layers which exhibit ultrafast electron and/or energy transfer in a controlled direction occurring over the entire structure. Using a high molecular weight, water-soluble, anionic form of poly-phenylene vinylene, self-assembled films can be formed which show high photoluminescence quantum efficiency (QE). The highest emission QE is achieved using poly(propylene-imine) (PPI) dendrimers as cationic binders. Self-quenching of the luminescence is observed as the solid polymer film thickness is increased and can be reversed by inserting additional spacer layers of transparent polyelectrolytes between each active conjugated layer, such that the QE grows with thickness. A red shift of the luminescence is also observed as additional PPV layers are added. This effect persists as self-quenching is eliminated. Charge transfer superlattices can be formed by additionally incorporating C.sub.60 acceptor layers.

Encapsulation of basic fibroblast growth factor by polyelectrolyte multilayer microcapsules and its controlled release for enhancing cell proliferation.

PubMed

She, Zhen; Wang, Chunxia; Li, Jun; Sukhorukov, Gleb B; Antipina, Maria N

2012-07-09

Basic fibroblast growth factor (FGF2) is an important protein for cellular activity and highly vulnerable to environmental conditions. FGF2 protected by heparin and bovine serum albumin was loaded into the microcapsules by a coprecipitation-based layer-by-layer encapsulation method. Low cytotoxic and biodegradable polyelectrolytes dextran sulfate and poly-L-arginine were used for capsule shell assembly. The shell thickness-dependent encapsulation efficiency was measured by enzyme-linked immunosorbent assay. A maximum encapsulation efficiency of 42% could be achieved by microcapsules with a shell thickness of 14 layers. The effects of microcapsule concentration and shell thickness on cytotoxicity, FGF2 release kinetics, and L929 cell proliferation were evaluated in vitro. The advantage of using microcapsules as the carrier for FGF2 controlled release for enhancing L929 cell proliferation was analyzed.

Self-consistent treatment of the local dielectric permittivity and electrostatic potential in solution for polarizable macromolecular force fields.

PubMed

Hassan, Sergio A

2012-08-21

A self-consistent method is presented for the calculation of the local dielectric permittivity and electrostatic potential generated by a solute of arbitrary shape and charge distribution in a polar and polarizable liquid. The structure and dynamics behavior of the liquid at the solute/liquid interface determine the spatial variations of the density and the dielectric response. Emphasis here is on the treatment of the interface. The method is an extension of conventional methods used in continuum protein electrostatics, and can be used to estimate changes in the static dielectric response of the liquid as it adapts to charge redistribution within the solute. This is most relevant in the context of polarizable force fields, during electron structure optimization in quantum chemical calculations, or upon charge transfer. The method is computationally efficient and well suited for code parallelization, and can be used for on-the-fly calculations of the local permittivity in dynamics simulations of systems with large and heterogeneous charge distributions, such as proteins, nucleic acids, and polyelectrolytes. Numerical calculation of the system free energy is discussed for the general case of a liquid with field-dependent dielectric response.

Self-consistent treatment of the local dielectric permittivity and electrostatic potential in solution for polarizable macromolecular force fields

NASA Astrophysics Data System (ADS)

Hassan, Sergio A.

2012-08-01

A self-consistent method is presented for the calculation of the local dielectric permittivity and electrostatic potential generated by a solute of arbitrary shape and charge distribution in a polar and polarizable liquid. The structure and dynamics behavior of the liquid at the solute/liquid interface determine the spatial variations of the density and the dielectric response. Emphasis here is on the treatment of the interface. The method is an extension of conventional methods used in continuum protein electrostatics, and can be used to estimate changes in the static dielectric response of the liquid as it adapts to charge redistribution within the solute. This is most relevant in the context of polarizable force fields, during electron structure optimization in quantum chemical calculations, or upon charge transfer. The method is computationally efficient and well suited for code parallelization, and can be used for on-the-fly calculations of the local permittivity in dynamics simulations of systems with large and heterogeneous charge distributions, such as proteins, nucleic acids, and polyelectrolytes. Numerical calculation of the system free energy is discussed for the general case of a liquid with field-dependent dielectric response.

Self-consistent treatment of the local dielectric permittivity and electrostatic potential in solution for polarizable macromolecular force fields

PubMed Central

Hassan, Sergio A.

2012-01-01

A self-consistent method is presented for the calculation of the local dielectric permittivity and electrostatic potential generated by a solute of arbitrary shape and charge distribution in a polar and polarizable liquid. The structure and dynamics behavior of the liquid at the solute/liquid interface determine the spatial variations of the density and the dielectric response. Emphasis here is on the treatment of the interface. The method is an extension of conventional methods used in continuum protein electrostatics, and can be used to estimate changes in the static dielectric response of the liquid as it adapts to charge redistribution within the solute. This is most relevant in the context of polarizable force fields, during electron structure optimization in quantum chemical calculations, or upon charge transfer. The method is computationally efficient and well suited for code parallelization, and can be used for on-the-fly calculations of the local permittivity in dynamics simulations of systems with large and heterogeneous charge distributions, such as proteins, nucleic acids, and polyelectrolytes. Numerical calculation of the system free energy is discussed for the general case of a liquid with field-dependent dielectric response. PMID:22920098

Fractionation of poly(methacrylic acid) and poly(vinyl pyridine) in aqueous and organic mobile phases by multidetector thermal field-flow fractionation.

PubMed

Greyling, Guilaume; Pasch, Harald

2017-08-25

Multidetector thermal field-flow fractionation (ThFFF) is shown to be a versatile characterisation platform that can be used to characterise hydrophilic polymers in a variety of organic and aqueous solutions with various ionic strengths. It is demonstrated that ThFFF fractionates isotactic and syndiotactic poly(methacrylic acid) (PMAA) as well as poly(2-vinyl pyridine) (P2VP) and poly(4-vinyl pyridine) (P4VP) according to microstructure in organic solvents and that the ionic strength of the mobile phase has no influence on the retention behaviour of the polymers. With regard to aqueous solutions, it is shown that, despite the weak retention, isotactic and syndiotactic PMAA show different retention behaviours which can qualitatively be attributed to microstructure. Additionally, it is shown that the ionic strength of the mobile phase has a significant influence on the thermal diffusion of polyelectrolytes in aqueous solutions and that the addition of an electrolyte is essential to achieve a microstructure-based separation of P2VP and P4VP in aqueous solutions. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of reactive monomer on PS-b-P2VP film with UV irradiation

NASA Astrophysics Data System (ADS)

Kim, H. J.; Shin, D. M.

2012-03-01

Poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) lamellar film which is hydrophobic block hydrophilic polyelectrolyte block polymer of 52 kg/mol -b- 57 kg/mol and PS-b-P2VP film with reactive monomer (RM257) were prepared for photonic gel films. The lamellar stacks, which is alternating layer of hydrophilic and hydrophobic part of PS-b-P2VP. We reported about the influence of reactive monomer on those photonic gel films. Added reactive monomer photonic gel film had higher absorbance than pure photonic gel films. And band gaps of the lamellar films shifted by the time of UV light irradiation. That Photonic gel films were measured with the UV spectrophotometer. As a result the photonic gel film with reactive monomer had more clear color. The lamellar films were swollen by DI water, Ethyl alcohol (aq) and calcium carbonate solution. Since the domain spacing of dried photonic gel films were not showing any color in visible wavelength. The band gap of the lamellar films were drastically shifted to longer wavelength swollen by calcium carbonate solution (absorbance peak 565nm-->617nm). And the lamellar films were shifted to shorter wave length swollen by ethanol (absorbance peak 565nm-->497nm). So each Photonic gel film showed different color.

Density functional study on the structural and thermodynamic properties of aqueous DNA-electrolyte solution in the framework of cell model.

PubMed

Wang, Ke; Yu, Yang-Xin; Gao, Guang-Hua

2008-05-14

A density functional theory (DFT) in the framework of cell model is proposed to calculate the structural and thermodynamic properties of aqueous DNA-electrolyte solution with finite DNA concentrations. The hard-sphere contribution to the excess Helmholtz energy functional is derived from the modified fundamental measure theory, and the electrostatic interaction is evaluated through a quadratic functional Taylor expansion around a uniform fluid. The electroneutrality in the cell leads to a variational equation with a constraint. Since the reference fluid is selected to be a bulk phase, the Lagrange multiplier proves to be the potential drop across the cell boundary (Donnan potential). The ion profiles and electrostatic potential profiles in the cell are calculated from the present DFT-cell model. Our DFT-cell model gives better prediction of ion profiles than the Poisson-Boltzmann (PB)- or modified PB-cell models when compared to the molecular simulation data. The effects of polyelectrolyte concentration, ion size, and added-salt concentration on the electrostatic potential difference between the DNA surface and the cell boundary are investigated. The expression of osmotic coefficient is derived from the general formula of grand potential. The osmotic coefficients predicted by the DFT are lower than the PB results and are closer to the simulation results and experimental data.

Solution Properties of Amphoteric Random Copolymers Bearing Pendant Sulfonate and Quaternary Ammonium Groups with Controlled Structures.

PubMed

Nakahata, Rina; Yusa, Shin-Ichi

2018-01-05

Amphoteric random copolymers P(AMPS/APTAC50) x , where x = 41, 89, and 117, composed of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) and 3-acrylamidopropyltrimethylammonium chloride (APTAC) were prepared via reversible addition-fragmentation chain transfer radical polymerization. P(AMPS/APTAC50) x can dissolve in pure water to form small interpolymer aggregates. In aqueous solutions of NaCl, P(AMPS/APTAC50) x can dissolve in the unimer state. Amphoteric random copolymer P(AMPS/APTAC50) c with high molecular weight was prepared via conventional free-radical polymerization. Although P(AMPS/APTAC50) c cannot dissolve in pure water, it can dissolve in aqueous solutions of NaCl. In amphoteric random copolymers with high molecular weight, the possibility of continuous sequences of monomers with the same charge may increase, which may cause strong interactions between polymer chains. When fetal bovine serum (FBS) and polyelectrolytes were mixed in phosphate-buffered saline, the hydrodynamic radius and light-scattering intensity increased. There was no interaction between P(AMPS/APTAC50) x and FBS because corresponding increases could not be observed.

Conformal self-assembled thin films for optical pH sensors

NASA Astrophysics Data System (ADS)

Topasna, Daniela M.; Topasna, Gregory A.; Liu, Minghanbo; Tseng, Ching-Hung

2016-04-01

Simple, reliable, lightweight, and inexpensive thin films based sensors are still in intense development and high demand in many applications such as biomedical, industrial, environmental, military, and consumer products. One important class of sensors is the optical pH sensor. In addition, conformal thin film based sensors extend the range of application for pH optical sensors. We present the results on the fabrication and characterization of optical pH sensing coatings made through ionic self-assembled technique. These thin films are based on the combination of a polyelectrolyte and water-soluble organic dye molecule Direct Yellow 4. A series of films was fabricated and characterized in order to determine the optimized parameters of the polymer and of the organic dye solutions. The optical pH responses of these films were also studied. The transparent films were immersed in solutions at various temperature and pH values. The films are stable when immersed in solutions with pH below 9.0 and temperatures below 90 °C and they maintain their performance after longer immersion times. We also demonstrate the functionality of these coatings as conformal films.

Nitric oxide assisted C60 secondary ion mass spectrometry for molecular depth profiling of polyelectrolyte multilayers.

PubMed

Zappalà, G; Motta, V; Tuccitto, N; Vitale, S; Torrisi, A; Licciardello, A

2015-12-15

Secondary ion mass spectrometry (SIMS) with polyatomic primary ions provides a successful tool for molecular depth profiling of polymer systems, relevant in many technological applications. Widespread C60 sources, however, cause in some polymers extensive damage with loss of molecular information along depth. We study a method, based on the use of a radical scavenger, for inhibiting ion-beam-induced reactions causing sample damage. Layered polystyrene sulfonate and polyacrylic acid based polyelectrolyte films, behaving differently towards C60 beam-induced damage, were selected and prepared as model systems. They were depth profiled by means of time-of-flight (TOF)-SIMS in dual beam mode, using fullerene ions for sputtering. Nitric oxide was introduced into the analysis chamber as a radical scavenger. The effect of sample cooling combined with NO-dosing on the quality of depth profiles was explored. NO-dosing during C60-SIMS depth profiling of >1 micrometer-thick multilayered polyelectrolytes allows detection, along depth, of characteristic fragments from systems otherwise damaged by C60 bombardment, and increases sputtering yield by more than one order of magnitude. By contrast, NO has little influence on those layers that are well profiled with C60 alone. Such leveling effect, more pronounced at low temperature, leads to a dramatic improvement of profile quality, with a clear definition of interfaces. NO-dosing provides a tool for extending the applicability, in SIMS depth profiling, of the widely spread fullerene ion sources. In view of the acceptable erosion rates on inorganics, obtainable with C60, the method could be of relevance also in connection with the 3D-imaging of hybrid polymer/inorganic systems. Copyright © 2015 John Wiley & Sons, Ltd.