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Sample records for determine polyelectrolyte solutions

  1. Polyelectrolyte Solutions

    NASA Astrophysics Data System (ADS)

    Colby, Ralph H.

    2008-03-01

    Pierre-Gilles de Gennes once described polyelectrolytes as the ``least understood form of condensed matter''. In this talk, I will describe the state of the polyelectrolyte field before and after de Gennes' seminal contributions published 1976-1980. De Gennes clearly explained why electrostatic interactions only stretch the polyelectrolyte chains on intermediate scales in semidilute solution (between the electrostatic blob size and the correlation length) and why the scattering function has a peak corresponding to the correlation length (the distance to the next chain). Despite many other ideas being suggested since then, the simple de Gennes scaling picture of polyelectrolyte conformation in solution has stood the test of time. How that model is used today, including consequences for dynamics in polyelectrolyte solutions, and what questions remain, will clarify the importance of de Gennes' ideas.

  2. Solution rheology of polyelectrolytes and polyelectrolyte-surfactant systems

    NASA Astrophysics Data System (ADS)

    Plucktaveesak, Nopparat

    (styrene-alt-sodium maleate) and poly(diisobutylene- alt-sodium maleate) show the polyelectrolyte behavior as predicted. However, the viscosity as a function of concentration of sodium maleate based copolymers with 1-alkenes; 1-octene (C8), 1-decene (C10), 1-dodecene (C12) and 1-hexene (C14) exhibit an abnormal scaling power, which might be caused by aggregation of the alkene tails to form micelles. In the last chapter, we report the rheological properties of aqueous solutions of poly(acrylic acid) and oppositely charged surfactant, dodecyl trimethylammonium bromide (C12TAB). The solution viscosity decreases as surfactant is added, partly because the polyelectrolyte wraps around the surface of the spherical surfactant micelles, shortening the effective chain length. The effects of polymer molecular weight, polymer concentration, and polymer charge have been studied with no added salt. The results are compared with the predictions of a simple model based on the scaling theory for the viscosity of dilute and unentangled semidilute polyelectrolyte solutions in good solvent. This model takes into account two effects of added surfactant. The effective chain length of the polyelectrolyte is shortened when a significant fraction of the chain wraps around micelles. Another effect is the change of solution ionic strength resulting from surfactant addition that further lowers the viscosity. The parameters used in this model are independently determined, allowing the model to make a quantitative prediction of solution viscosity with no adjustable parameters. The model is also applied to predict the decrease in viscosity of various polyelectrolyte/oppositely charged surfactant systems reported in literature. The results are in good agreement with experimental data, proving that our model applies to all polyelectrolytes mixed with oppositely charged surfactants that form spherical micelles.

  3. Phase diagrams of polyelectrolyte solutions

    NASA Astrophysics Data System (ADS)

    Mahdi, Khaled A.

    We study the phase diagram of polyelectrolyte solutions in salt and salt-free environments. We examine the phase behavior of polyelectrolyte solutions, in the semidilute regime, using different physical models, namely the Random Phase Approximation (RPA) and the cross-linked model. In the RPA, we calculate the electrostatic free energy by summing all the fluctuations of the chains and all present ionic species. Within this approximation, the phase diagrams of salt-free polyelectrolyte solutions show phase separation even without including short-range attractions or ion condensation. We find that the phase behavior of large chains resembles the phase diagram of polymer network solutions. That is, the equilibrium is established between a network phase and a chain-free phase. Upon the addition of salt, the dissociated ions increase the entropy of the system and overcome the energy from the electrostatic fluctuations. When the short-range attraction between monomers is included in the model, the free energy predicts phase segregation for all salt valences at high salt concentrations (1 mol/l and higher). The phenomenon is called salting-out and occurs simply because the addition of salt reduces the quality of the solvent and induces precipitation. However, phase segregation in the presence of multivalent ions in polyelectrolyte solutions occurs at low salt concentrations (less than 1 mol/l). We propose that this phase separation is due to polyions cross-linked by multivalent ions. We constructed a phenomenological two-state model to examine this phenomenon. The two phases coexisting in the solution are a network-like phase and a polymer-free phase. The polymer-free phase is modeled using Debye-Huckel theory. In the cross-linked phase, each condensed multivalent ion attracts an equal number of monomers creating a neutral cluster. The energy of the cluster is evaluated by a simple Coulombic energy. The bare monomer charges between the linkages are treated as line of

  4. Charge regularization in phase separating polyelectrolyte solutions.

    PubMed

    Muthukumar, M; Hua, Jing; Kundagrami, Arindam

    2010-02-28

    Theoretical investigations of phase separation in polyelectrolyte solutions have so far assumed that the effective charge of the polyelectrolyte chains is fixed. The ability of the polyelectrolyte chains to self-regulate their effective charge due to the self-consistent coupling between ionization equilibrium and polymer conformations, depending on the dielectric constant, temperature, and polymer concentration, affects the critical phenomena and phase transitions drastically. By considering salt-free polyelectrolyte solutions, we show that the daughter phases have different polymer charges from that of the mother phase. The critical point is also altered significantly by the charge self-regularization of the polymer chains. This work extends the progress made so far in the theory of phase separation of strong polyelectrolyte solutions to a higher level of understanding by considering chains which can self-regulate their charge.

  5. Charge regularization in phase separating polyelectrolyte solutions

    PubMed Central

    Muthukumar, M.; Hua, Jing; Kundagrami, Arindam

    2010-01-01

    Theoretical investigations of phase separation in polyelectrolyte solutions have so far assumed that the effective charge of the polyelectrolyte chains is fixed. The ability of the polyelectrolyte chains to self-regulate their effective charge due to the self-consistent coupling between ionization equilibrium and polymer conformations, depending on the dielectric constant, temperature, and polymer concentration, affects the critical phenomena and phase transitions drastically. By considering salt-free polyelectrolyte solutions, we show that the daughter phases have different polymer charges from that of the mother phase. The critical point is also altered significantly by the charge self-regularization of the polymer chains. This work extends the progress made so far in the theory of phase separation of strong polyelectrolyte solutions to a higher level of understanding by considering chains which can self-regulate their charge. PMID:20192314

  6. 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

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

    PubMed

    Plazzotta, Beatrice; Diget, Jakob Stensgaard; Zhu, Kaizheng; Nyström, Bo; Pedersen, Jan Skov

    2016-10-01

    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.

  8. Polyelectrolyte solutions: Excluded-volume considerations

    NASA Astrophysics Data System (ADS)

    Mattoussi, Hedi; Karasz, Frank E.

    1993-12-01

    We provide experimental evidence for the electrostatically related excluded-volume effects on the colligative properties and the single chain behavior of polyelectrolyte solutions in the dilute regime. The data are compared to the theory developed by Fixman, Skolnick, Odijk, and Houwaart. Good agreement between these theoretical considerations and the experimental data is observed.

  9. Solution dynamics of synthetic and natural polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Krause, Wendy E.

    Polyelectrolytes are abundant in nature and essential to life, and used extensively in industry. This work discussed two polyelectrolytes: sodium poly(2-acrylamido-2-methylpropanesulfonate) (NaPAMS), synthetic polyelectrolyte, and sodium hyaluronate (NaHA), a glycosaminoglycan. Rheological data of NaPAMS solutions of variable chain length and concentration were reported. A strong dependence of viscosity eta on chain length: eta ˜ M2.4 was found. The comparison of the rheological data with two proposed scaling theories (Dobrynin 1995, Witten 1987) forces the conclusion that neither theory is correct. A possible interpretation of the viscosity data falling between the predictions of the two scaling theories is that some chain rigidity may persist beyond the correlation length. A sample model for the conductivity of semidilute polyelectrolytes with no added salt was presented. The model correctly describes the logarithmic decrease of specific conductance observed for many polyelectrolytes at low concentration (below ca. 10-2M), and is in good agreement with data from NaPAMS solutions. NaHA in phosphate buffered saline behaves as a typical polyelectrolyte in the high-salt limit, as Newtonian viscosities are observed over a wide range of shear rates. There is no evidence of intermolecular hydrogen bonding causing gel formation in NaHA solutions without protein present. The viscosity of 3 mg/mL NaHA was measured in the presence of the selected anti-inflammatory agents. Of the seven additives investigated only (D)-penicillamine significantly altered the rheology of HA. (D)-Penicillamine dramatically reduced the viscosity of HA, probably by disrupting intramolecular hydrogen bonding. The plasma proteins albumin and gamma-globulins bind to HA in solution to form a weak reversible gel. The rheology and osmotic pressure of the simple model for synovial fluid, consisting of 3mg/mL NaHA, 11 mg/mL albumin, and 7 mg/mL gamma-globulins in phosphate buffered saline, were studied

  10. A molecular-thermodynamic model for polyelectrolyte solutions

    NASA Astrophysics Data System (ADS)

    Jiang, Jianwen; Liu, Honglai; Hu, Ying; Prausnitz, J. M.

    1998-01-01

    Polyelectrolyte solutions are modeled as freely tangent-jointed, charged hard-sphere chains and corresponding counterions in a continuum medium with permitivity ɛ. By adopting the sticky-point model, the Helmholtz function for polyelectrolyte solutions is derived through the r-particle cavity-correlation function (CCF) for chains of sticky, charged hard spheres. The r-CCF is approximated by a product of effective nearest-neighbor two-particle CCFs; these are determined from the hypernetted-chain and mean-spherical closures (HNC/MSA) inside and outside the hard core, respectively, for the integral equation theory for electrolytes. The colligative properties are given as explicit functions of a scaling parameter Γ that can be estimated by a simple iteration procedure. Osmotic pressures, osmotic coefficients, and activity coefficients are calculated for model solutions with various chain lengths. They are in good agreement with molecular simulation and experimental results.

  11. A molecular-thermodynamic model for polyelectrolyte solutions

    SciTech Connect

    Jiang, J.; Liu, H.; Hu, Y.; Prausnitz, J.M.

    1998-01-01

    Polyelectrolyte solutions are modeled as freely tangent-jointed, charged hard-sphere chains and corresponding counterions in a continuum medium with permitivity {var_epsilon}. By adopting the sticky-point model, the Helmholtz function for polyelectrolyte solutions is derived through the r-particle cavity-correlation function (CCF) for chains of sticky, charged hard spheres. The r-CCF is approximated by a product of effective nearest-neighbor two-particle CCFs; these are determined from the hypernetted-chain and mean-spherical closures (HNC/MSA) inside and outside the hard core, respectively, for the integral equation theory for electrolytes. The colligative properties are given as explicit functions of a scaling parameter {Gamma} that can be estimated by a simple iteration procedure. Osmotic pressures, osmotic coefficients, and activity coefficients are calculated for model solutions with various chain lengths. They are in good agreement with molecular simulation and experimental results. {copyright} {ital 1998 American Institute of Physics.}

  12. Calorimetric determination of surfactant/polyelectrolyte binding isotherms.

    PubMed

    Lapitsky, Yakov; Parikh, Maider; Kaler, Eric W

    2007-07-26

    Mixing of oppositely charged surfactants and polyelectrolytes in aqueous solutions leads to cooperative surfactant adsorption onto the polyelectrolyte chains. Experimental determination of surfactant/polyelectrolyte binding isotherms is usually done using custom-built surfactant-ion-specific electrodes. As an alternative, we present an indirect isotherm approximation method that uses conventional isothermal titration calorimetry (ITC). The calorimetric data is fitted to the two-binding-state Satake-Yang adsorption model, which quantifies the extent of binding in terms of the binding constant (Ku) and the cooperativity parameter (u). This approach is investigated using two surfactant/polyelectrolyte mixtures: sodium perfluorooctanoate (FC7) and N,N,N-trimethylammonium derivatized hydroxyethyl cellulose (UCARE Polymer JR-400), whose binding behavior follows the Satake-Yang model, and dodecyltrimethylammonium bromide (DTAB) and poly(styrenesulfonate) (NaPSS), whose behavior deviates dramatically from the Satake-Yang model. These studies demonstrate that, in order to apply the indirect ITC method of binding isotherm determination, the surfactant/polyelectrolyte adsorption process must have no more than two dominant binding states. Thus, the technique works well for the FC7/JR-400 mixture. It fails in the case of the DTAB/NaPSS adsorption, but its mode of failure offers insight into the multiple-binding-state adsorption mechanism.

  13. Viscosity of Aqueous Polyelectrolyte Solutions with Oppositely Charged Surfactant

    NASA Astrophysics Data System (ADS)

    Eggert, Matthew; Colby, Ralph

    2006-03-01

    The viscosity of polyelectrolyte solutions with oppositely charged surfactants is measured for a series of anionic polyelectrolytes of variable hydrophobicity (alternating copolymers of sodium maleate with hydrocarbon comonomers) in the presence of cationic trimethyl ammonium bromides with various alkyl tail lengths. These results are compared with a simple model that modifies the scaling theory for unentangled semidilute polyelectrolyte solutions to account for the addition of oppositely charged surfactant. The surfactant lowers the viscosity of these solutions through two means. The polyelectrolyte binds to the surface of the surfactant micelle, reducing the effective chain length of the polymer. The binding also causes counterions of the polyelectrolyte and the surfactant to be released into solution, acting as a salt that screens the repulsion between charges of the polyelectrolyte, causing the chains to have smaller size. The fraction of effectively charged monomers (i.e., free counterions) on the polyelectrolyte is measured via an ion-selective electrode, meaning the simple model has no adjustable parameters. Additional electrodes are used to measure the amount of free surfactant in solution in order to estimate the amount of surfactant associated with each polyelectrolyte chain.

  14. Nematic ordering in dilute solutions of rodlike polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Potemkin, Igor I.; Khokhlov, Alexei R.

    2004-06-01

    Quantitative theory of orientational behavior of rodlike polyelectrolytes in dilute solution is developed. We find that in salt-free solutions many-body Coulomb interactions between macro- and counterions favor nematic ordering. It is shown that the orientationally isotropic phase of the solution becomes unstable toward nematic ordering at polymer concentration smaller than the overlap concentration. Our predictions are consistent with experimental observations for synthetic polyelectrolytes poly(p-phenylene)sulfonates in aqueous solutions.

  15. Self-assembly and molecular "recognition" phenomena in solutions of (bio)polyelectrolyte complexes

    NASA Astrophysics Data System (ADS)

    Izumrudov, V. A.

    2008-04-01

    Recently published data on polyelectrolyte complexes formed by both oppositely charged synthetic polyions and natural polyelectrolytes (proteins, enzymes, nucleic acids) are summarised. The properties of these complexes and the phase behaviour of their solutions is shown to obey the general trends found in the studies of cooperative interpolyelectrolyte interactions. The principles of functioning of polyelectrolyte complexes that underlie the self-assembly of complexes in solution and determine the ability of complexes to retain stability over a specified broad range of external conditions and then to quickly and reversibly respond with high sensitivity to a change in the environment by changing their molecular characteristics and phase state are considered. The successful use of the results of fundamental research of (bio)polyelectrolyte complexes for the solution of topical problems of biotechnology, materials science and medicine are demonstrated.

  16. Clusters in strong polyelectrolyte solutions in the condensation theory approach.

    PubMed

    Perico, Angelo; Rapallo, Arnaldo

    2011-02-07

    The interaction free energy of parallel clusters of like-charged rod polyelectrolytes in solution is calculated in the framework of the extended condensation theory. For sufficiently high linear charge density of the polyelectrolyte, clustering takes place. The greater is the number of polyelectrolytes participating to the cluster, the smaller is the equilibrium interpolyelectrolyte distance, and the deeper is the corresponding free energy minimum. It is a counterintuitive organization due to the increasing of the counterion condensed charge and condensation volume, taking place as the polyelectyrolytes approach each other.

  17. Advancements to the theory of free solution electrophoresis of polyelectrolytes

    NASA Astrophysics Data System (ADS)

    McCormick, Laurette

    Capillary electrophoresis (CE) is the workhorse of countless analytical laboratories and is used routinely in various industries including pharmaceutical, forensic and clinical applications. Basically, CE is a method for separating charged molecular species in a buffer-filled capillary by the application of an electric field; the analytes move from one end of the capillary to the detector at the other end at speeds determined by their charge, size and shape. Generally, in free solution CE uniformly charged polyelectrolytes (such as DNA) are free-draining, meaning that their speed is independent of their size. Hence, until recently, a gel or other sieving medium has been necessary for the separation of polyelectrolytes; however, modifying uniformly charged polymers on the molecular level, via conjugation to uncharged polymers, allows for separation in free solution CE. In this thesis, advancements to the theory of free solution electrophoresis of polyelectrolytes, in particular, to the theories for two new free solution electrophoresis methods relying on conjugation, are presented. The first method, called End Labelled Free Solution Electrophoresis (ELFSE), can be used to sequence DNA, a negatively charged polymer in solution. Two different means of improving the resolution of ELFSE are predicted, one based on the molecular end effect, the other based on using a controlled electro-osmotic flow. In addition, a theory for the segregation of the DNA and label coils in ELFSE is presented. The second method is called Free Solution Conjugate Electrophoresis (FSCE); it allows for characterization of a sample of neutral polymers differing in length. The relevant theory, developed herein, elucidates how to accurately determine the molar mass distribution of the sample through FSCE measurements. In addition, supporting theories are developed that clarify the correct equation for the diffusion coefficient of molecules undergoing free solution electrophoresis, as well as

  18. Exploration of polyelectrolytes as draw solutes in forward osmosis processes.

    PubMed

    Ge, Qingchun; Su, Jincai; Amy, Gary L; Chung, Tai-Shung

    2012-03-15

    The development of the forward osmosis (FO) process has been constrained by the slow development of appropriate draw solutions. Two significant concerns related to draw solutions are the draw solute leakage and intensive energy requirement in recycling draw solutes after the FO process. FO would be much attractive if there is no draw solute leakage and the recycle of draw solutes is easy and economic. In this study, polyelectrolytes of a series of polyacrylic acid sodium salts (PAA-Na), were explored as draw solutes in the FO process. The characteristics of high solubility in water and flexibility in structural configuration ensure the suitability of PAA-Na as draw solutes and their relative ease in recycle through pressure-driven membrane processes. The high water flux with insignificant salt leakage in the FO process and the high salt rejection in recycle processes reveal the superiority of PAA-Na to conventional ionic salts, such as NaCl, when comparing their FO performance via the same membranes. The repeatable performance of PAA-Na after recycle indicates the absence of any aggregation problems. The overall performance demonstrates that polyelectrolytes of PAA-Na series are promising as draw solutes, and the new concept of using polyelectrolytes as draw solutes in FO processes is applicable. Copyright © 2011 Elsevier Ltd. All rights reserved.

  19. Integral equation theory for counterion distribution in polyelectrolyte solutions

    NASA Astrophysics Data System (ADS)

    Shew, Chwen-Yang; Yethiraj, Arun

    1998-03-01

    An integral equation theory is developed to explore the behavior of rigid and flexible polyelectolyte solutions with explicit counter ions. The theory makes predictions for the distribution of counterions around the polyion in addition to polyion-polyion correlation and polymer conformations. For rigid polyelectrolytes, the theory is to fit the scattering spectra of tobacco mosaic virus solutions. In dilute solutions, the effective charge decreases as concentration is increased. The results are consistent with the nature of TMV molecules as weak polyacids. For flexible polyelectrolytes, we have extended the previous work of one component thread model and Koyama chain model to this system. The counterion distribution is very sensitive to polyion concentration. Theoretical calculations are consistent with simulation results.

  20. Electro-osmotic flow of semidilute polyelectrolyte solutions

    NASA Astrophysics Data System (ADS)

    Uematsu, Yuki; Araki, Takeaki

    2013-09-01

    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.

  1. Pattern Formation in Drying Drops of Polyelectrolyte - Salt Solutions

    NASA Astrophysics Data System (ADS)

    Kaya, Deniz; Belyi, Vladimir A.

    2005-03-01

    We use optical microscopy, AFM, and SEM to investigate salt patterns formed during evaporation of aqueous solutions of sodium poly(styrene sulfonate) and sodium chloride (NaPSS/NaCl). Observed patterns exhibit significantly larger variety than in the simple "drying coffee drop" experiments. We find that varying the concentration ratios of polyelectrolyte/salt solutions leads to formation of qualitatively different patterns, including radially grown salt deposits, concentric rings of salt and other structures. Our results indicate that these patterns are also sensitive to evaporation rate of the droplet. However molecular weight of the polymer appears to have little to no effect on the observed patterns.

  2. Employment of Gibbs-Donnan-based concepts for interpretation of the properties of linear polyelectrolyte solutions

    USGS Publications Warehouse

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

    1991-01-01

    Earlier research has shown that the acid dissociation and metal ion complexation equilibria of linear, weak-acid polyelectrolytes and their cross-linked gel analogues are similarly sensitive to the counterion concentration levels of their solutions. Gibbs-Donnan-based concepts, applicable to the gel, are equally applicable to the linear polyelectrolyte for the accommodation of this sensitivity to ionic strength. This result is presumed to indicate that the linear polyelectrolyte in solution develops counterion-concentrating regions that closely resemble the gel phase of their analogues. Advantage has been taken of this description of linear polyelectrolytes to estimate the solvent uptake by these regions. ?? 1991 American Chemical Society.

  3. Competitive reactions in solutions of poly-L-histidine, calf thymus DNA, and synthetic polyanions: determining the binding constants of polyelectrolytes.

    PubMed

    Zelikin, Alexander N; Trukhanova, Elizabeth S; Putnam, David; Izumrudov, Vladimir A; Litmanovich, Andrey A

    2003-11-12

    The physicochemical characteristics of a nonviral gene delivery system will govern its functional bioactivity; however, empiricism dominates the literature in this field, and a significant deficiency of quantitative investigation and evaluation of nonviral gene delivery vehicles remains. Herein, we derive a physical model and experimental method to quantitatively determine the binding constants between a model polycationic nonviral gene delivery vehicle poly-L-histidine (PLH) and calf thymus DNA. The approach has utility to a variety of systems and is not limited to the described polymer model. The interaction of PLH with DNA was monitored by fluorescence quenching of an ethidium bromide probe in the pH range 4 to 8. The interaction increased with pH decrease with the most pronounced change between pH 6 and 7. The obtained pH-dependence of fraction of salt bonds formed between PLH and DNA was used to estimate pK(a) of PLH in the presence of DNA, which equaled 6.24. The interaction of PLH with DNA in the presence of added synthetic polyanions was studied by the same approach and found to be controlled by pH, nature of the charge groups of the polyanion, and its degree of polymerization. In the mixture with sodium poly(styrenesulfonate) the interaction was negligible in the whole studied pH range, whereas in the mixtures with sodium poly(acrylate) (PA) or sodium poly(methacrylate), DNA was able to compete effectively for the binding with PLH. For PA samples with degree of polymerization higher than degree of polymerization of PLH, DP(PA) > DP(PLH), the fraction of polycation bound to DNA was constant regardless of DP(PA.) In contrast, at DP(PA) < DP(PLH), a pronounced increase in the bound fraction was observed. It substantiates the notion that the binding energy of two polymers is mainly controlled by the DP of the shorter component of polyelectrolyte complex. The data on PLH distribution between DNA and added polyanion with different values of DP were treated

  4. Counterion adsorption theory of dilute polyelectrolyte solutions: apparent molecular weight, second virial coefficient, and intermolecular structure factor.

    PubMed

    Muthukumar, M

    2012-07-21

    Polyelectrolyte chains are well known to be strongly correlated even in extremely dilute solutions in the absence of additional strong electrolytes. Such correlations result in severe difficulties in interpreting light scattering measurements in the determination of the molecular weight, radius of gyration, and the second virial coefficient of charged macromolecules at lower ionic strengths from added strong electrolytes. By accounting for charge-regularization of the polyelectrolyte by the counterions, we present a theory of the apparent molecular weight, second virial coefficient, and the intermolecular structure factor in dilute polyelectrolyte solutions in terms of concentrations of the polymer and the added strong electrolyte. The counterion adsorption of the polyelectrolyte chains to differing levels at different concentrations of the strong electrolyte can lead to even an order of magnitude discrepancy in the molecular weight inferred from light scattering measurements. Based on counterion-mediated charge regularization, the second virial coefficient of the polyelectrolyte and the interchain structure factor are derived self-consistently. The effect of the interchain correlations, dominating at lower salt concentrations, on the inference of the radius of gyration and on molecular weight is derived. Conditions for the onset of nonmonotonic scattering wave vector dependence of scattered intensity upon lowering the electrolyte concentration and interpretation of the apparent radius of gyration are derived in terms of the counterion adsorption mechanism.

  5. Salting-out and Salting-in in Polyelectrolyte Solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Pengfei; Wu, Jianzhong; Wang, Zhen-Gang

    The phase behavior of polyelectrolyte (PE) solutions is governed by complicated interplay involving the mixing entropy, excluded volume, chain connectivity, and electrostatic interactions. Here we study the phase behavior of PE solutions in both salt-free condition and with added salt using a liquid-state (LS) theory based thermodynamic model. The LS model accounts or the hard-core repulsion by the Canahan-Starling equation of state, correlations due to chain connectivity by the first-order thermodynamic perturbation theory, and electrostatic correlations by the mean-spherical approximation. In comparison to the prediction from the well-known Voorn-Overbeek theory, the LS model predicts loop-type binodal curves in the salt-PE concentration diagram at temperatures slightly above the critical temperature of PE solution in salt-free case, consistent with the experimental study. The phase separated region shrinks with increasing temperature. Three scenarios of salting-out and salting-in phenomenon are predicted with addition of salts based, depending on the PE concentration.

  6. Solution properties of star polyelectrolytes having a moderate number of arms

    NASA Astrophysics Data System (ADS)

    Chremos, Alexandros; Douglas, Jack F.

    2017-07-01

    We investigate polyelectrolyte stars having a moderate number of arms by molecular dynamics simulations of a coarse-grained model over a range of polyelectrolyte concentrations, where both the counter-ions and solvent are treated explicitly. This class of polymeric materials is found to exhibit rather distinct static and dynamic properties from linear and highly branched star polyelectrolyte solutions emphasized in past studies. Moderately branched polymers are particle-like in many of their properties, while at the same time they exhibit large fluctuations in size and shape as in the case of linear chain polymers. Correspondingly, these fluctuations suppress crystallization at high polymer concentrations, leading apparently to an amorphous rather than crystalline solid state at high polyelectrolyte concentrations. We quantify the onset of this transition by measuring the polymer size and shape fluctuations of our model star polyelectrolytes and the static and dynamic structure factor of these solutions over a wide range of polyelectrolyte concentration. Our findings for star polyelectrolytes are similar to those of polymer-grafted nanoparticles having a moderate grafting density, which is natural given the soft and highly deformable nature of both of these "particles."

  7. Modeling of Polyelectrolyte Adsorption from Micellar Solutions onto Biomimetic Substrates.

    PubMed

    Banerjee, Soumi; Cazeneuve, Colette; Baghdadli, Nawel; Ringeissen, Stéphanie; Léonforte, Fabien; Leermakers, Frans A M; Luengo, Gustavo S

    2017-09-21

    Depositing cationic polyelectrolytes (PEs) from micellar solutions that include surfactants (SU) onto surfaces is a rich, complex, highly relevant, and challenging topic that covers a broad field of practical applications (e.g., from industrial to personal care). The role of the molecular architecture of the constituents of the PEs are often overruled, or at least and either, underestimated in regard to the surface properties. In this work, we aim to evaluate the effect of a model biomimetic surface that shares the key characteristics of the extreme surface of hair and its concomitant chemo- and physisorbed properties onto the deposition of a complex PEs:SU system. To tackle out the effect of the molecular architecture of the PEs, we consider (i) a purely linear and hydrophilic PE (P100) and (ii) a PE with lateral amphiphilic chains (PegPE). Using numerical self-consistent field calculations, we show that the architecture of the constituents interfere with the surface properties in a nonintuitive way such that, depending on the amphiphilicity and hydrophilicity of the PEs and the hydrophobicity of the surface, a re-entrant adsorbing transition can be observed, the lipid coverage of the model hair surface being the unique control parameter. Such a behavior is rationalized by the anticooperative associative properties of the coacervate micelles in solution, which is also controlled by the architecture of the PEs and SU. We now expect that PEs adsorption, as a rule, is governed by the molecular details of the species in solution as well as the surface specificities. We emphasize that molecular realistic modeling is essential to rationalize and optimize the adsorption process of, for example, polymer conditioning agents in water-rinsed cosmetic or textile applications.

  8. Single chains of strong polyelectrolytes in aqueous solutions at extreme dilution: Conformation and counterion distribution

    NASA Astrophysics Data System (ADS)

    Xu, Guofeng; Luo, Shuangjiang; Yang, Qingbo; Yang, Jingfa; Zhao, Jiang

    2016-10-01

    The molecular conformation of two typical polyelectrolytes, sodium polystyrene sulfonate (NaPSS) and quarternized poly-4-vinylpyridine (QP4VP), was studied in aqueous solutions without salt addition at the single molecular level. By fluorescence correlation spectroscopy, the hydrodynamic radius (Rh) of NaPSS and QP4VP with the molecular weight ranging more than one order of magnitude was measured. The scaling analysis of Rh exhibits scaling exponent of 0.70 and 0.86 for NaPSS and QP4VP in solutions without added salts, respectively, showing the conformation is much more expanded than random coil. Numerical fittings using the model of diffusion of a rod molecule agree with the data well, indicating that the polyelectrolyte chains take the rod-like conformation under the condition without salt addition. Further investigations by determining the electric potential of single PSS- chains using the photon counting histogram technique demonstrate the enhanced counterion adsorption to the charged chain at higher molecular weight.

  9. Radius of gyration and intrinsic viscosity of polyelectrolyte solutions

    SciTech Connect

    Milas, M.; Borsali, R.; Rinaudo, M.

    1993-12-31

    Relatively low molecular weights polyelectrolytes (10{sup 4}-10{sup 6}) behave as worm-like chain when electrostatic repulsions are assumed to govern the excluded volume parameter. Under such conditions, predictions of chain expansion and effect of polyelectrolyte concentrations are made assuming that unperturbed dimensions could be obtained at infinite salt content. Experimental studies of an ionic polysaccharide, namely the Na-hyaluronate, were done and the values obtained for the radius of gyration as well as the intrinsic viscosity at different charge densities are in good agreement with the predictions.

  10. Interactions and dispersion stability of aluminum oxide colloidal particles in electroless nickel solutions in the presence of comb polyelectrolytes.

    PubMed

    de Hazan, Yoram; Reuter, Torben; Werner, Dennis; Clasen, Rolf; Graule, Thomas

    2008-07-15

    The effect of comb polyelectrolytes on the dispersion stability of colloidal alumina particles in DI water and commercial electroless nickel (EN) solutions was investigated. Adsorption of polyelectrolytes and major EN components onto colloidal alumina was assessed by TGA, chemical analysis, and zeta potential measurements. Zeta potential measurements were made during titrations of comb-polyelectrolyte-stabilized dispersions with EN solutions to full ionic strength for the first time. The compilation of titration curves made with varying amounts of comb polyelectrolytes provides high resolution and novel insight into the particle/surfactant/EN systems. Continuous decrease in particle/EN components surface interactions with the increase in comb polyelectrolyte coverage is observed. Laser diffraction measurements reveal steric stabilization of nano- and submicronmeter alumina dispersions in both DI water and EN solutions with >7 wt% and >2 wt% comb polyelectrolyte, respectively.

  11. Monte Carlo simulation and equation of state for flexible charged hard-sphere chain fluids: Polyampholyte and polyelectrolyte solutions

    SciTech Connect

    Jiang, Hao; Adidharma, Hertanto

    2014-11-07

    The thermodynamic modeling of flexible charged hard-sphere chains representing polyampholyte or polyelectrolyte molecules in solution is considered. The excess Helmholtz energy and osmotic coefficients of solutions containing short polyampholyte and the osmotic coefficients of solutions containing short polyelectrolytes are determined by performing canonical and isobaric-isothermal Monte Carlo simulations. A new equation of state based on the thermodynamic perturbation theory is also proposed for flexible charged hard-sphere chains. For the modeling of such chains, the use of solely the structure information of monomer fluid for calculating the chain contribution is found to be insufficient and more detailed structure information must therefore be considered. Two approaches, i.e., the dimer and dimer-monomer approaches, are explored to obtain the contribution of the chain formation to the Helmholtz energy. By comparing with the simulation results, the equation of state with either the dimer or dimer-monomer approach accurately predicts the excess Helmholtz energy and osmotic coefficients of polyampholyte and polyelectrolyte solutions except at very low density. It also well captures the effect of temperature on the thermodynamic properties of these solutions.

  12. Monte Carlo simulation and equation of state for flexible charged hard-sphere chain fluids: polyampholyte and polyelectrolyte solutions.

    PubMed

    Jiang, Hao; Adidharma, Hertanto

    2014-11-07

    The thermodynamic modeling of flexible charged hard-sphere chains representing polyampholyte or polyelectrolyte molecules in solution is considered. The excess Helmholtz energy and osmotic coefficients of solutions containing short polyampholyte and the osmotic coefficients of solutions containing short polyelectrolytes are determined by performing canonical and isobaric-isothermal Monte Carlo simulations. A new equation of state based on the thermodynamic perturbation theory is also proposed for flexible charged hard-sphere chains. For the modeling of such chains, the use of solely the structure information of monomer fluid for calculating the chain contribution is found to be insufficient and more detailed structure information must therefore be considered. Two approaches, i.e., the dimer and dimer-monomer approaches, are explored to obtain the contribution of the chain formation to the Helmholtz energy. By comparing with the simulation results, the equation of state with either the dimer or dimer-monomer approach accurately predicts the excess Helmholtz energy and osmotic coefficients of polyampholyte and polyelectrolyte solutions except at very low density. It also well captures the effect of temperature on the thermodynamic properties of these solutions.

  13. Electrical conductivity of aqueous polyelectrolyte solutions in the presence of counterion condensation: The scaling approach revisited

    NASA Astrophysics Data System (ADS)

    Bordi, F.; Cametti, C.; Gili, T.

    2002-08-01

    The conductometric properties of aqueous polyelectrolyte solutions in the absence of added salt are reviewed in the light of the dynamic scaling description of the polymer conformation in different concentration regimes, recently proposed by Dobrynin and Rubinstein [Macromolecules 28, 1859 (1995); 32, 915 (1999)]. The scaling approach to the transport properties of polyelectrolyte solutions allows us to separate contributions due to polymer conformation from those due to the ionic character of the chain, and offers the possibility to extend the validity of the Manning conductivity model to the dilute and semidilute regimes. Moreover, the quality of the solvent, influencing the polyion-counterion interactions, can be properly taken into account. The electrical conductivity predicted by this scaling approach compares reasonably well with the observed values for a model polyelectrolyte (polyacrylate sodium salt in aqueous solutions, good solvent condition) over an extended concentration range from the dilute to the semidilute regime.

  14. Conformational effect on small angle neutron scattering behavior of interacting polyelectrolyte solutions: a perspective of integral equation theory

    SciTech Connect

    Chen, Wei-Ren; Do, Changwoo; Hong, Kunlun; Liu, Yun; Porcar, L.; Shew, Chwen-Yang; Smith, Greg

    2012-01-01

    We present small angle neutron scattering (SANS) measurements of deuterium oxide (D2O) solutions of linear and star sodium poly(styrene sulfonate) (NaPSS) as a function of polyelectrolyte concentration. Emphasis is on understanding the dependence of their SANS coherent scattering cross section I(Q) on the molecular architecture of single polyelectrolyte. The key finding is that for a given concentration, star polyelectrolytes exhibit more pronounced characteristic peaks in I(Q), and the position of the first peak occurs at a smaller Q compared to their linear counterparts. Based on a model of integral equation theory, we first compare the SANS experimental I(Q) of salt free polyelectrolyte solutions with that predicted theoretically. Having seen their satisfactory qualitative agreement, the dependence of counterion association behavior on polyelectrolyte geometry and concentration is further explored. Our predictions reveal that the ionic environment of polyelectrolyte exhibits a strong dependence on polyelectrolyte geometry at lower polyelectrolyte concentration. However, when both linear and star polyelectrolytes exceed their overlap concentrations, the spatial distribution of counterion is found to be essentially insensitive to polyelectrolyte geometry due to the steric effect.

  15. Condensation of semiflexible polyelectrolytes in mixed solutions of mono- and multivalent salts

    NASA Astrophysics Data System (ADS)

    Plunk, Amelia A.; Luijten, Erik

    2013-03-01

    The salt-dependent condensation of highly charged polyelectrolytes in aqueous solution is a topic of great biological and industrial importance that has been widely studied over the past decades. It is well established that interaction with multivalent counterions leads to the formation of bundle-like aggregates for rigid polyelectrolytes and to collapsed structures or disordered aggregates for flexible polyelectrolytes. Here, we investigate the behavior of semiflexible chain molecules, where the electrostatically induced aggregation is impeded by the intrinsic bending stiffness of the polymer. Moreover, we study the competition between monovalent and multivalent counterions in mixed solutions and establish the threshold salt concentration required for condensation. Our findings are relevant for a range of biomedical problems, including the fabrication of nanoparticles for gene delivery and the packaging of DNA by histones. This work is supported by the National Science Foundation.

  16. Motion of Molecular Probes and Viscosity Scaling in Polyelectrolyte Solutions at Physiological Ionic Strength

    PubMed Central

    Sozanski, Krzysztof; Wisniewska, Agnieszka; Kalwarczyk, Tomasz; Sznajder, Anna; Holyst, Robert

    2016-01-01

    We investigate transport properties of model polyelectrolyte systems at physiological ionic strength (0.154 M). Covering a broad range of flow length scales—from diffusion of molecular probes to macroscopic viscous flow—we establish a single, continuous function describing the scale dependent viscosity of high-salt polyelectrolyte solutions. The data are consistent with the model developed previously for electrically neutral polymers in a good solvent. The presented approach merges the power-law scaling concepts of de Gennes with the idea of exponential length scale dependence of effective viscosity in complex liquids. The result is a simple and applicable description of transport properties of high-salt polyelectrolyte solutions at all length scales, valid for motion of single molecules as well as macroscopic flow of the complex liquid. PMID:27536866

  17. Interaction between two parallel plates covered with a polyelectrolyte brush layer in an electrolyte solution.

    PubMed

    Ohshima, Hiroyuki

    An approximate analytic expression is derived for the interaction energy between two parallel plates covered with a polyelectrolyte brush layer in an electrolyte solution. The interaction energy has three components: electrostatic interaction energy between two brush layers before and after their contact, steric interaction energy between two brush layers after their contact, and the van der Waals interaction energy between the cores of the plates. It is shown that these three components are of the same order of magnitude and contribute equally to the total interaction energy between two polyelectrolyte-coated plates in an electrolyte solution. On the basis of Derjaguin's approximation, an approximate expression for the interaction energy between two spherical particles covered with polyelectrolyte brush layers is also derived.

  18. Using Optical Tweezers for the Characterization of Polyelectrolyte Solutions with Very Low Viscoelasticity

    PubMed Central

    2013-01-01

    Recently, optical tweezing has been used to provide a method for microrheology addressed to measure the rheological properties of small volumes of samples. In this work, we corroborate this emerging field of microrheology by using these optical methods for the characterization of polyelectrolyte solutions with very low viscoelasticity. The influence of polyelectrolyte (i.e., polyacrylamide, PAM) concentration, specifically its aging, of the salt concentration is shown. The close agreement of the technique with classical bulk rheological measurements is demonstrated, illustrating the advantages of the technique. PMID:23786307

  19. Optimal linearized Poisson-Boltzmann theory applied to the simulation of flexible polyelectrolytes in solution.

    PubMed

    Bathe, M; Grodzinsky, A J; Tidor, B; Rutledge, G C

    2004-10-22

    Optimal linearized Poisson-Boltzmann (OLPB) theory is applied to the simulation of flexible polyelectrolytes in solution. As previously demonstrated in the contexts of the cell model [H. H. von Grunberg, R. van Roij, and G. Klein, Europhys. Lett. 55, 580 (2001)] and a particle-based model [B. Beresfordsmith, D. Y. C. Chan, and D. J. Mitchell, J. Colloid Interface Sci. 105, 216 (1985)] of charged colloids, OLPB theory is applicable to thermodynamic states at which conventional, Debye-Huckel (DH) linearization of the Poisson-Boltzmann equation is rendered invalid by violation of the condition that the electrostatic coupling energy of a mobile ion be much smaller than its thermal energy throughout space, |nu(alpha)e psi(r)|polyelectrolytes, OLPB theory is applied to a concentrated solution of freely jointed chains. The osmotic pressure is computed at various reservoir ionic strengths and compared with results from the conventional DH model for polyelectrolytes. Through comparison with the cylindrical cell model for polyelectrolytes, it is demonstrated that the OLPB model yields the correct osmotic pressure behavior with respect to nonlinear theory where conventional DH theory fails, namely at large ratios of mean counterion density to reservoir salt density, when the Donnan potential is large. (c) 2004 American Institute of Physics.

  20. 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.

  1. Preparation of conductive PDDA/(PEDOT:PSS) multilayer thin film: influence of polyelectrolyte solution composition.

    PubMed

    Jurin, F E; Buron, C C; Martin, N; Filiâtre, C

    2014-10-01

    Self-assembled multilayer films made of PEDOT:PSS poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) and PDDA poly(diallyldimethylammonium chloride) were prepared using layer-by-layer method. In order to modify the growth regime of the multilayer, to fabricate an electrical conductive film and to control its thickness, the effects of pH, type of electrolyte, ionic strength and polyelectrolyte concentration were investigated. Optical reflectometry measurements show that the pH of the solutions has no effect on the film growth while the adsorbed amount increases more rapidly when BaCl2 is used instead of NaCl as electrolyte. An increase in the ionic strength (with NaCl) induces a change in the growth regime from a linear to an exponential one at low polyelectrolyte concentration. As UV-vis measurements indicate, no decomplexation of PEDOT was recorded after film preparation. With polyelectrolyte concentration below 1 g L(-1), no conductive films were obtained even if 50 bilayers were deposited. A conductive film was prepared with a polyelectrolyte concentration of 1 g L(-1) and the measured conductivity was 0.3 S m(-1). A slight increase in conductivity was recorded when BaCl2 was used probably due to a modification of the film structure. Copyright © 2014 Elsevier Inc. All rights reserved.

  2. Parameter identifiability in application of soft particle electrokinetic theory to determine polymer and polyelectrolyte coating thicknesses on colloids.

    PubMed

    Louie, Stacey M; Phenrat, Tanapon; Small, Mitchell J; Tilton, Robert D; Lowry, Gregory V

    2012-07-17

    Soft particle electrokinetic models have been used to determine adsorbed nonionic polymer and polyelectrolyte layer properties on nanoparticles or colloids by fitting electrophoretic mobility data. Ohshima first established the formalism for these models and provided analytical approximations ( Ohshima, H. Adv. Colloid Interface Sci.1995, 62, 189 ). More recently, exact numerical solutions have been developed, which account for polarization and relaxation effects and require fewer assumptions on the particle and soft layer properties. This paper characterizes statistical uncertainty in the polyelectrolyte layer charge density, layer thickness, and permeability (Brinkman screening length) obtained from fitting data to either the analytical or numerical electrokinetic models. Various combinations of particle core and polymer layer properties are investigated to determine the range of systems for which this analysis can provide a solution with reasonably small uncertainty bounds, particularly for layer thickness. Identifiability of layer thickness in the analytical model ranges from poor confidence for cases with thick, highly charged coatings, to good confidence for cases with thin, low-charged coatings. Identifiability is similar for the numerical model, except that sensitivity is improved at very high charge and permeability, where polarization and relaxation effects are significant. For some poorly identifiable cases, parameter reduction can reduce collinearity to improve identifiability. Analysis of experimental data yielded results consistent with expectations from the simulated theoretical cases. Identifiability of layer charge density and permeability is also evaluated. Guidelines are suggested for evaluation of statistical confidence in polymer and polyelectrolyte layer parameters determined by application of the soft particle electrokinetic theory.

  3. Characterization of swollen structure of high-density polyelectrolyte brushes in salt solution by neutron reflectivity

    NASA Astrophysics Data System (ADS)

    Kobayashi, Motoyasu; Terayama, Yuki; Hino, Masahiro; Ishihara, Kazuhiko; Takahara, Atsushi

    2009-08-01

    Zwitterionic and cationic polyelectrolyte brushes on quartz substrate were prepared by surface-initiated atom transfer radical polymerization of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and 2-(methacryloyloxy)ethyltrimethylammonium chloride (METAC), respectively. The effects of ionic strength on brush structure and surface properties of densely grafted polyelectrolyte brushes were analysed by neutron reflectivity (NR) measurements. NR at poly(METAC)/D2O and poly(MPC)/D2O interface revealed that the grafted polymer chains were fairly extended from the substrate surface, while the thickness reduction of poly(METAC) brush was observed in 5.6 M NaCl/D2O solution due to the screening of the repulsive interaction between polycations by hydrated salt ions. Interestingly, no structural change was observed in poly(MPC) brush even in a salt solution probably due to the unique interaction properties of phosphorylcholine units.

  4. 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)

  5. 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.

  6. Interactions between hairy rod anionic conjugated polyelectrolytes and nonionic alkyloxyethylene surfactants in aqueous solution: observations from cloud point behaviour.

    PubMed

    Fonseca, Sofia M; Eusébio, M Ermelinda; Castro, Ricardo; Burrows, Hugh D; Tapia, Maria José; Olsson, Ulf

    2007-11-15

    The effect of three anionic, hairy-rod fluorene based conjugated polyelectrolytes on the cloud points of the alkyloxyethylene surfactants C10E3, C12E4, C12E5, and C12E6 has been studied in aqueous solution. Although the association behaviour of these rigid polymers with surfactants is different from that of more flexible polyelectrolytes, both types of polymers are seen to increase the cloud points, probably as a consequence of associative interactions. The possible importance of Coulombic interactions is suggested by the decrease in cloud points with these systems in the presence of NaCl. With the conjugated polyelectrolytes, the effect appears to be most pronounced with poly[9,9-bis(4-phenoxybutylsulfonate)fluorene-co-2,5-thienylene], which may result from specific interactions between oxyethylene groups and the thiophene ring. The value of cloud point behaviour in designing water based formulations for preparation of devices of these conjugated polyelectrolytes is discussed.

  7. Length-Scale Dependent Viscosity in Semidilute Polyelectrolyte Solutions

    NASA Astrophysics Data System (ADS)

    Poling-Skutvik, Ryan; Krishnamoorti, Ramanan; Conrad, Jacinta

    2015-03-01

    Using optical microscopy and particle tracking algorithms, we measured the mean-squared displacements (MSDs) of fluorescent polystyrene particles with diameters ranging from 300 nm to 2 μm suspended in semidilute solutions of high molecular weight partially hydrolyzed polyacrylamide. The solutions had polymer concentrations ranging from 0.67 to 67c*, where c* is the overlap concentration, and estimated correlation lengths of ~ 100 to 900 nm. At short times, the particles exhibited subdiffusive behavior characterized by MSD ~tα with α < 1 . On long time scales, the particles transitioned to Fickian diffusion (α = 1) and their diffusivity was calculated from the slope of the MSD. Whereas the large particles agreed with predictions using the Stokes-Einstein equation and bulk zero-shear viscosity, the smaller particles diffused much faster than predicted. The relative diffusivities do not collapse onto a single curve, but rather form a continuum that varies with particle size. This indicates that the particles experience a size-dependent effective viscosity mediated by the ratio of particle diameter to characteristic length scales in the polymer solution.

  8. Precipitation of oppositely charged polyelectrolytes in salt solutions.

    PubMed

    Kudlay, Alexander; Olvera de la Cruz, Monica

    2004-01-01

    We study phase separation in symmetric solutions of weakly charged flexible chains of opposite sign. Precipitation is caused by effective attractions due to charge fluctuations and by short-range attractions between monomers. The contribution from charge fluctuations is computed within the random phase approximation (RPA), which takes into account the connectivity of charges in the polyions. The impenetrability of the ions is accounted for by using a modified Coulomb potential in the RPA. In good solvent conditions the precipitate monotonically swells and eventually dissolves upon addition of salt. However, near the theta-solvent condition, but still in the good solvent, the precipitate can be stable at any salt concentration. Moreover, the density of the precipitate after initial decrease can increase with addition of salt. This effect is a result of redistribution of salt between the precipitate and the supernatant, which is due to an interplay of electrostatic and hardcore interactions. For not too weakly charged polyions the precipitate properties become strongly dependent on temperature even in good solvent conditions.

  9. Polyelectrolyte and carbon nanotube multilayers made from ionic liquid solutions

    NASA Astrophysics Data System (ADS)

    Nakashima, Takuya; Zhu, Jian; Qin, Ming; Ho, Szushen; Kotov, Nicholas A.

    2010-10-01

    The inevitable contact of substrates with water during the traditional practice of layer-by-layer assembly (LBL) creates problems for multiple potential applications of LBL films in electronics. To resolve this issue, we demonstrate here the possibility of a LBL process using ionic liquids (ILs), which potentially eliminates corrosion and hydration processes related to aqueous media and opens additional possibilities in structural control of LBL films. ILs are also considered to be one of the best ``green'' processing solvents, and hence, are advantageous in respect to traditional organic solvents. Poly(ethyleneimine) (PEI) and poly(sodium styrenesulfonate) (PSS) were dispersed in a hydrophilic IL and successfully deposited in the LBL fashion. To produce electroactive thin films with significance to electronics, a similar process was realized for PSS-modified single-walled carbon nanotubes (SWNT-PSS) and poly(vinyl alcohol) (PVA). Characterization of the coating using standard spectroscopy and microscopy techniques typical of the multilayer field indicated that there are both similarities and differences in the structure and properties of LBL films build from ILs and aqueous solutions. The films exhibited electrical conductivity of 102 S m-1 with transparency as high as 98% for visible light, which is comparable to similar parameters for many carbon nanotube and graphene films prepared by both aqueous LBL and other methods.The inevitable contact of substrates with water during the traditional practice of layer-by-layer assembly (LBL) creates problems for multiple potential applications of LBL films in electronics. To resolve this issue, we demonstrate here the possibility of a LBL process using ionic liquids (ILs), which potentially eliminates corrosion and hydration processes related to aqueous media and opens additional possibilities in structural control of LBL films. ILs are also considered to be one of the best ``green'' processing solvents, and hence, are

  10. The finite size effect of monomer units on the electrostatics of polyelectrolyte solutions

    NASA Astrophysics Data System (ADS)

    Tong, Chaohui

    2010-02-01

    The effective interactions between two test counterions and two test solvent dipoles in a semidilute/concentrated weakly charged polyelectrolyte solution are studied using the field-theoretical approach on the mean-field level. From the effective Hamiltonians in terms of the two test counterions and the two test solvent dipoles, respectively, analytical expressions for the effective interactions in the real space are derived. It is unambiguously demonstrated that, at a Θ solvent condition, both the effective interactions between two counterions and two parallel-oriented solvent dipoles consist of an attractive part at intermediate distances of separation. As the electrostatic screening effect from counterions and salt ions quantified by the Debye-Hückel screening parameter becomes stronger, the magnitude of the attraction decreases and the minimum of the attractive profile shift to a shorter distance of separation. On the other hand, when the excluded volume effect is dominant, the effective interactions are purely repulsive. This nontrivial and seemingly counterintuitive result originates from the finite size effect of the monomer units of the polymer chains on the electrostatics of the polyelectrolyte solution. As the size of the monomer units goes to zero, at the Θ solvent condition, the effective interactions between two counterions and two parallel-oriented solvent dipoles are purely repulsive.

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

    PubMed Central

    Krishnan, M.

    2017-01-01

    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

  12. 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

  13. 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

  14. Self-consistent mode-coupling theory for the viscosity of rodlike polyelectrolyte solutions.

    PubMed

    Miyazaki, Kunimasa; Bagchi, Biman; Yethiraj, Arun

    2004-10-22

    A self-consistent mode-coupling theory is presented for the viscosity of solutions of charged rodlike polymers. The static structure factor used in the theory is obtained from polymer integral equation theory; the Debye-Huckel approximation is inadequate even at low concentrations. The theory predicts a nonmonotonic dependence of the reduced excess viscosity eta(R) on concentration from the behavior of the static structure factor in polyelectrolyte solutions. The theory predicts that the peak in eta(R) occurs at concentrations slightly lower than the overlap threshold concentration, c*. The peak height increases dramatically with increasing molecular weight and decreases with increased concentrations of added salt. The position of the peak, as a function of concentration divided by c*, is independent of salt concentration or molecular weight. The predictions can be tested experimentally. (c) 2004 American Institute of Physics.

  15. Characterization of Swollen States of Polyelectrolyte Brushes in Salt Solution by Neutron Reflectivity

    NASA Astrophysics Data System (ADS)

    Kobayashi, Motoyasu; Mitamura, Koji; Terada, Masami; Yamada, Norifumi L.; Takahara, Atsushi

    2011-01-01

    Cationic and zwitterionic polyelectrolyte brushes on quartz substrate were synthesized by surface-initiated atom transfer radical polymerization of 2-(methacryloyloxy)-ethyltrimethylammonium chloride (MTAC) and 2-(methacryloyloxy)ethyl phosphorylcholine (MPC). The effects of ionic strength on brush structure are investigated by neutron reflectivity (NR) in NaCl deuterium oxide (D2O) solutions. We observed that poly(MTAC) chains were drastically shrunk at concentrations above 0.1 M NaCl/D2O, which may be the change in charge-screening effect against ions on poly(MTAC). On the other hand, effect of salt concentration on a swollen state of poly(MPC) brush was negligible, even at the high concentration (5.0 M) close to saturation. The behaviour of poly(MPC) in salt aqueous solution is completely different from that of poly(MTAC), which may arise from the unique interaction properties, neutral nature, and hydrated water structure of phosphorylcholine units.

  16. Polyelectrolyte-like behaviour of poly(ethylene-oxide) solutions with added monovalent salt

    NASA Astrophysics Data System (ADS)

    Lal, Jyotsana; Hakem, Ilhem-Faiza

    2004-03-01

    Solvent effects on the conformation of poly(ethylene-oxide) (PEO) and complexation of PEO by monovalent cations, have been examined by using small-angle neutron scattering. In methanol and acetonitrile, a big change in interchain interaction, osmotic compressibility and local chain conformation have been observed upon addition of small amounts of potassium iodide. The amplitude of the total intensity decreases significantly and a peak at a certain value of the wavevector q* appears as signature of a polyelectrolyte-like behaviour. With further addition of salt, the ionic strength of the solution increases and potassium binding becomes less favorable: the binding constant decreases with the ionic strength and PEO behaves as a neutral polymer with excluded volume. No association between PEO and potassium iodide was observed in aqueous solutions. Reference: I.F. Hakem and J. Lal. Europhysics letters, 64 (2), 204, 2003

  17. Determination of the concentration dependence of polyelectrolyte diffusion coefficients by application of the Boltzmann gradient method.

    PubMed

    Wagner, A T; Kohler, H-H

    2008-03-15

    The concentration dependence of a polyelectrolyte diffusion coefficient in aqueous low salt solution (KCl, 1 mM) is determined from a single dynamic gradient experiment. The Boltzmann method is applied to calculate the diffusion coefficient. A special diffusion cell is constructed that minimizes aberrations in the optical detection of the polyion concentration profile. Bovine serum albumin (BSA) is chosen as a model polyion. To get information about the diffusion process down to very small polyion concentrations, the BSA molecule is fluorescently labeled. The fluorescence intensity is used as a measure of the polyion concentration. The change of the polyion net charge caused by labeling is discussed. The cell is illuminated by an LED, and the fluorescence intensity profile is detected by a CCD camera. Experiments at 5 and 17 degrees C show that the diffusion coefficient of labeled BSA remains constant in the very low polyion concentration range below a threshold of about 1.5 g/l. This is in contradiction to the linear concentration dependence of polyion diffusion coefficients at very low concentrations often postulated in the literature without reference to direct experimental evidence. Our finding is confirmed by dynamic light scattering experiments published recently. An explanation for this behavior based on a modified Donnan osmotic compressibility approach is given.

  18. Depletion and double layer forces acting between charged particles in solutions of like-charged polyelectrolytes and monovalent salts.

    PubMed

    Moazzami-Gudarzi, Mohsen; Maroni, Plinio; Borkovec, Michal; Trefalt, Gregor

    2017-05-14

    Interaction forces between silica particles were measured in aqueous solutions of the sodium salt of poly(styrene sulphonate) (PSS) and NaCl using the colloidal probe technique based on an atomic force microscope (AFM). The observed forces can be rationalized through a superposition of damped oscillatory forces and double layer forces quantitatively. The double layer forces are modeled using Poisson-Boltzmann (PB) theory for a mixture of a monovalent symmetric electrolyte and a highly asymmetric electrolyte, whereby the multivalent coions represent the polyelectrolyte chains. The effective charge of the polyelectrolyte is found to be smaller than the bare number of charged groups residing on one polyelectrolyte molecule. This effect can be explained by counterion condensation. The interplay between depletion and double layer forces can be further used to predict the phase of the depletion force oscillations. However, this picture holds only at not too elevated concentrations of the polyelectrolyte and salt. At higher salt concentrations, attractive van der Waals forces become important, while at higher polyelectrolyte concentrations, the macromolecules adsorb onto the like-charged silica interface.

  19. A picture of dilute solution behavior of polymers through polyelectrolyte simulation

    NASA Astrophysics Data System (ADS)

    Yamakawa, Hiromi; Yoshizaki, Takenao; Ida, Daichi

    2013-11-01

    A Monte Carlo (MC) study is made of the persistence length q and the binary cluster integral β (or the excluded-volume strength B) for polyelectrolytes by the use of the discrete Kratky-Porod wormlike chain with hard-core-effective Debye-Hückel electrostatic pair potentials. The quantity q is determined from the initial decay rate of the bond correlation function after preliminary confirmation of the validity of this procedure using the chain with Lennard-Jones pair potentials. The quantity B is determined from the mean-square radius of gyration along with q by the use of the quasi-two-parameter (QTP) excluded-volume theory. They are evaluated for two model cases of polyelectrolytes, sodium hyaluronate as an example of semiflexible polymers and poly(sodium 4-styrenesulfonate) as a typical example of flexible polymers, both in aqueous sodium chloride. The behavior of MC data so obtained for q and B as functions of added salt concentration c is examined in detail, comparing them with the Odijk-Skolnick-Fixman theory of q and the Fixman-Skolnick (FS) theory of B and also with literature experimental data. In particular, the MC values of B are in almost complete agreement with the FS theory for large c, although the latter still overestimates B somewhat for small c. The values of B themselves and also the validity of the QTP theory in general are discussed in comparison with the case of nonionic polymers.

  20. A picture of dilute solution behavior of polymers through polyelectrolyte simulation.

    PubMed

    Yamakawa, Hiromi; Yoshizaki, Takenao; Ida, Daichi

    2013-11-28

    A Monte Carlo (MC) study is made of the persistence length q and the binary cluster integral β (or the excluded-volume strength B) for polyelectrolytes by the use of the discrete Kratky-Porod wormlike chain with hard-core-effective Debye-Hückel electrostatic pair potentials. The quantity q is determined from the initial decay rate of the bond correlation function after preliminary confirmation of the validity of this procedure using the chain with Lennard-Jones pair potentials. The quantity B is determined from the mean-square radius of gyration along with q by the use of the quasi-two-parameter (QTP) excluded-volume theory. They are evaluated for two model cases of polyelectrolytes, sodium hyaluronate as an example of semiflexible polymers and poly(sodium 4-styrenesulfonate) as a typical example of flexible polymers, both in aqueous sodium chloride. The behavior of MC data so obtained for q and B as functions of added salt concentration c is examined in detail, comparing them with the Odijk-Skolnick-Fixman theory of q and the Fixman-Skolnick (FS) theory of B and also with literature experimental data. In particular, the MC values of B are in almost complete agreement with the FS theory for large c, although the latter still overestimates B somewhat for small c. The values of B themselves and also the validity of the QTP theory in general are discussed in comparison with the case of nonionic polymers.

  1. Metastability of large aggregates and viscosity, and stability of the pearl necklace conformation after organic solvent treatment of aqueous hydrophobic polyelectrolyte solutions.

    PubMed

    Essafi, Wafa; Raissi, Wifek; Abdelli, Amira; Boué, François

    2014-10-23

    Aggregates-a phenomenon still not understood-as well as the pearl-necklace-like chain conformation in aqueous solutions of hydrophobic polyelectrolytes are addressed here, using treatment by an organic solvent. The second appear to be at equilibrium in water. The first appear to be metastable, and surprisingly associated with higher zero shear viscosity. The hydrophobic polyelectrolyte is poly(styrene-co-sodium styrenesulfonate) (PSS), and the solution treatment is to first add to water an organic solvent, THF, which is then evaporated and replaced by the same amount of water. To investigate polyelectrolyte solutions as a function of THF treatment, we use small angle neutron scattering in the semidilute regime, viscosimetry in the dilute and semidilute regimes (unentangled), and osmometry in the similar semidilute regime (the contribution of the counterions being dominant). First, the structure, namely, the scattering from all chains, is characterized by a maximum ("polyelectrolyte peak"). Its position, amplitude, and scattered intensity at zero angle depend, at a given sulfonation rate of PSS, on the solvent quality through the added amount of organic solvent (THF). This dependence is very pronounced when the sulfonation rate is low (more hydrophobic polyelectrolyte) and is canceled when the sulfonation rate is high (more hydrophilic polyelectrolyte). Second, the viscosity of the polyelectrolyte solutions decreases with THF treatment for the hydrophobic polyelectrolytes. Third, osmometry shows no noticeable increase of the effective charge with THF treatment. It is proposed that the large scale aggregates, especially in the case of very hydrophobic polyelectrolytes, disappear irreversibly with THF treatment, while the pearl-necklace conformation of the chain remains as in its initial state. Parallel test measurements for a fully hydrophilic polyelectrolyte, poly(sodium-2-acrylamido-2-methylpropanesulfonate)-co-(acrylamide) (P(AMAMPS)), at different sulfonation

  2. 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

  3. Effect of polyelectrolyte adsorption on lateral distribution and dynamics of anionic lipids: a Monte Carlo study of a coarse-grain model.

    PubMed

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

    2014-09-01

    We employ Monte Carlo simulations to investigate the interaction between an adsorbing linear flexible cationic polyelectrolyte and a ternary mixed fluid membrane containing neutral (phosphatidylcholine, PC), monovalent (phosphatidylserine, PS), and multivalent (phosphatidylinositol, PIP2) anionic lipids. We systematically explore the influences of polyelectrolyte chain length, polyelectrolyte charge density, polyelectrolyte total charge amount, and salt solution ionic strength on the static and dynamic properties of different anionic lipid species. Our results show that the multivalent PIP2 lipids dominate the polyelectrolyte-membrane interaction and competitively inhibit polyelectrolyte-PS binding. When the total charge amount of the polyelectrolyte is less than that of the local oppositely charged PIP2 lipids, the polyelectrolyte can drag the bound multivalent lipids to diffuse on the membrane, but cannot interact with the PS lipids. Under this condition, the diffusion behaviors of the polyelectrolyte closely follow the prediction of the Rouse model, and the polyelectrolyte chain properties determine the adsorption amount, concentration gradients, and hierarchical mobility of the bound PIP2 lipids. However, when the total charge amount of the polyelectrolyte is larger than that of the local PIP2 lipids, the polyelectrolyte further binds the PS lipids around the polyelectrolyte-PIP2 complex to achieve local electrical neutrality. In this condition, parts of the polyelectrolyte desorb from the membrane and show faster mobility, and the bound PS presents much faster mobility than the segregated PIP2. This work provides an explanation for heterogeneity formation in different anionic lipids induced by polyelectrolyte adsorption.

  4. The influence of charged-induced variations in the local permittivity on the static and dynamic properties of polyelectrolyte solutions.

    PubMed

    Fahrenberger, Florian; Hickey, Owen A; Smiatek, Jens; Holm, Christian

    2015-12-28

    There is a large body of literature investigating the static and dynamic properties of polyelectrolytes due both to their widespread application in industrial processes and their ubiquitous presence in biology. Because of their highly charged nature, polyelectrolytes tend to alter the local dielectric permittivity of the solution within a few nanometers of their backbone. This effect has, however, been almost entirely ignored in both simulations and theoretical work. In this article, we apply our recently developed electrostatic solver based on Maxwell's equations to examine the effects of the permittivity reduction in the vicinity of the polyelectrolyte. We first verify our new approach by calculating and comparing ion distributions around a linear fixed polyelectrolyte and find both quantitative and qualitative changes in the ion distribution. Further simulations with an applied electric field show that the reduction in the local dielectric constant increases the mobility of the chains by approximately ten percent. More importantly, variations in the local dielectric constant lead to qualitatively different behavior of the conductivity.

  5. New 2-in-1 polyelectrolyte step-by-step film buildup without solution alternation: from PEDOT-PSS to polyelectrolyte complexes.

    PubMed

    de Saint-Aubin, Christine; Hemmerlé, Joseph; Boulmedais, Fouzia; Vallat, Marie-France; Nardin, Michel; Schaaf, Pierre

    2012-06-12

    Although never emphasized and increasingly used in organic electronics, PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)) layer-by-layer (lbl) film construction violates the alternation of polyanion and polycation rule stated as a prerequisit for a step-by-step film buildup. To demonstrate that this alternation is not always necessary, we studied the step-by-step construction of films using a single solution containing polycation/polyanion complexes. We investigated four different systems: PEDOT-PSS, bPEI-PSS (branched poly(ethylene imine)-poly(sodium 4-styrene sulfonate)), PDADMA-PSS (poly(diallyl dimethyl ammonium)-PSS), and PAH-PSS (poly(allylamine hydrochloride)-PSS). The film buildup obtained by spin-coating or dipping-and-drying process was monitored by ellipsometry, UV-vis-NIR spectrophotometry, and quartz-crystal microbalance. The surface morphology of the films was characterized by atomic force microscopy in tapping mode. After an initial transient regime, the different films have a linear buildup with the number of deposition steps. It appears that, when the particles composed of polyanion-polycation complex and complex aggregates in solution are more or less liquid (case of PEDOT-PSS and bPEI-PSS), our method leads to smooth films (roughness on the order of 1-2 nm). On the other hand, when these complexes are more or less solid particles (case of PDADMA-PSS and PAH-PSS), the resulting films are much rougher (typically 10 nm). Polycation/polyanion molar ratios in monomer unit of the liquid, rinsing, and drying steps are key parameters governing the film buildup process with an optimal polycation/polyanion molar ratio leading to the fastest film growth. This new and general lbl method, designated as 2-in-1 method, allows obtaining regular and controlled film buildup with a single liquid containing polyelectrolyte complexes and opens a new route for surface functionalization with polyelectrolytes.

  6. High frequency dielectric dispersion of polyelectrolyte solutions and its relation to counterion condensation

    NASA Astrophysics Data System (ADS)

    Penafiel, L. Miguel; Litovitz, Theodore A.

    1992-07-01

    The dielectric properties of polyelectrolyte solutions are studied in terms of counterion condensation by measurements of the dielectric response of pH buffered Na polyacrylate solutions. pH values are selected to allow variation of the charge density parameter ξ in the range between 0.5-2.8, that is, across ξ=1, the theoretical critical level for counterion condensation. The dielectric increment of the high frequency dispersion, Δɛ2, is found to have nonzero values only above the counterion condensation threshold and is therefore linked to the occurrence of counterion condensation. Above the condensation threshold Δɛ2 (≊6) and its corresponding polarizability α∥2 (≊6×10-16 cm3) are found to be approximately constant with increasing ξ. This result is predicted by Manning's polarizability model for condensed counterions which results in a good fit to the experimental data when the average length of the polyion segments parallel to the external field, Ls, is set to 284 Å. This value of Ls is also shown to be in relatively close agreement with the value calculated for the length of a rigid subunit in Mandel's polyion model, obtained using the relaxation time of the high frequency dispersion. The length Ls, which is larger than the persistence length, is estimated to be of the order of magnitude of the correlation length between segments.

  7. Solvent-induced changes in the structure and rheology of polyelectrolyte solutions.

    NASA Astrophysics Data System (ADS)

    Breedveld, Victor

    2006-03-01

    By integrating microfluidics and particle tracking microrheology, we have constructed a dialysis cell for microrheology, which provides unique opportunities for studying the dynamics of microstructural changes induced by changes in solvent composition. Such experiments are virtually impossible with mechanical rheometers. The concept and design of the microdialysis cell will be discussed, and data will be presented on the structural and rheological response of polyelectrolyte solutions to changes in ionic strength. Sulphonated polystyrene is a water-soluble polymer and its molecular conformation in solution strongly depends on ionic strength of the solution. It will be shown that quantitative measurements of transient solution viscosity during solvent exchange can be performed with the new dialysis cell. Experiments were also performed on amphiphilic block copolypeptide (BCP) hydrogels, which self-assemble into fibrillar structures due to a subtle balance between attractive and repulsive intermolecular forces. Electrostatic repulsion between the hydrophilic L-lysine blocks plays a key role. Therefore, changes in ionic strength have a significant effect on the self-assembled local structure and mechanical properties of the BCP gels, as was previously observed in rheometer experiments. Microrheology in the dialysis cell provided a much more complete picture, revealing the occurrence of microscopic phase separation upon the addition of salt. For example, in a K160L40 lysine-leucine block copolypeptide, the motion of tracer particles in the hydrogel is homogeneous in DI water. After the addition of salt, microrheology reveals the co-existence of populations of freely moving and immobilized particles. The changes in local microstructure were found to be reversible when the ionic strength of the solution was lowered again. Data will be presented on the dynamics of the morphological and rheological changes of various block copolypeptide hydrogels.

  8. 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

    Polyelectrolyte Solutions* was held IZ-16 February, 1990, at Casa Sirena Hotel, Oxnard, CA There were ninety-one scientists iarticipatIng. ’cludiq thirty-four...MACROMOLECULAR AND POLYELECT’ROLYTE 5’LUToNS Casa Sirena . Oxnard. CA Lee Magid - Chairman Peter Pusey - VIce-Chairman Monday. February 12 S.J. Candau...12-16, 1990 Casa Sirena Marina Hotel Oxnard, California REGISTRATION LIST Bruce J. Ackerson 149 Sauver Candau 136 Oklahoma State University Universit4

  9. Small-angle X-ray scattering from salt-free solutions of star-branched polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Heinrich, M.; Rawiso, M.; Zilliox, J. G.; Lesieur, P.; Simon, J. P.

    2001-02-01

    The dispersion state of sodium-sulphonated polystyrene (ensuremathNaPSS) star-branched polyelectrolytes was investigated in salt-free aqueous solutions, by use of the small-angle X-ray scattering technique. With respect to polystyrene (PS) star-branched polymers of identical functionality, the ordering phenomenon occurring in the neighborhood of the overlap concentration c^* is reinforced and observed in a larger range of concentrations. Moreover, the degree of order is no longer maximum at c^* and is improved as the concentration decreases. The dispersion state is then mainly controlled by the electrostatic interaction. A crystalline order should therefore be achieved with stars of lower functionality, provided the electrostatic interaction is added to the osmotic repulsion. On the other hand, unusual scattering patterns are measured for aqueous solutions of ensuremathNaPSS star polyelectrolytes. Indeed, a diffuse scattering is revealed at high angles, in addition to the regular diffraction rings related to preferred interstar distances. It is similar to the broad scattering peak produced by semidilute solutions of ensuremathNaPSS linear polyelectrolytes and associated to the electrostatic correlation hole within the isotropic model. In the dilute regime (c< c^*), it is just an intramolecular characteristic and represents the electrostatic repulsion between arms belonging to the same star. In the semidilute regime (c> c^*), it also reflects the electrostatic repulsion between arms of distinct stars. So, as the concentration increases, it is mainly caused by the interpenetration of ensuremathNaPSS stars. Such an observation is in agreement with the composite structure earlier proposed by Daoud and Cotton for star semidilute solutions. For c> c^*, ensuremathNaPSS star aqueous solutions can therefore be pictured as effective stars immersed in a matrix formed by the overlap of the arm ends. With respect to the dilute regime, the effective stars are smaller; the higher

  10. Scaling Theory of Polyelectrolyte Nanogels

    NASA Astrophysics Data System (ADS)

    Qu, Li-Jian

    2017-08-01

    The present paper develops the scaling theory of polyelectrolyte nanogels in dilute and semidilute solutions. The dependencies of the nanogel dimension on branching topology, charge fraction, subchain length, segment number, solution concentration are obtained. For a single polyelectrolyte nanogel in salt free solution, the nanogel may be swelled by the Coulombic repulsion (the so-called polyelectrolyte regime) or the osmotic counterion pressure (the so-called osmotic regime). Characteristics and boundaries between different regimes of a single polyelectrolyte nanogel are summarized. In dilute solution, the nanogels in polyelectrolyte regime will distribute orderly with the increase of concentration. While the nanogels in osmotic regime will always distribute randomly. Different concentration dependencies of the size of a nanogel in polyelectrolyte regime and in osmotic regime are also explored. Supported by China Earthquake Administration under Grant No. 20150112 and National Natural Science Foundation of China under Grant No. 21504014

  11. Pore size distributions in polyelectrolyte multilayers determined by nuclear magnetic resonance cryoporometry

    NASA Astrophysics Data System (ADS)

    Vaca Chávez, Fabián; Schönhoff, Monika

    2007-03-01

    Polyelectrolyte multilayers (PEMs) are thin films, which are assembled one molecular layer at a time, by alternatingly adsorbing polycations and polyanions making use of their attractive electrostatic interaction. Since the porosity of PEMs is one of the properties of major interest, in the current work the first pore size distribution of PEMs in samples consisting of silica particles coated with poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) is presented. To this end, the nuclear magnetic resonance (NMR) cryoporometry technique was applied. The proton NMR signal of liquid water is analyzed assuming a log normal distribution of motional correlation times. From the results, it is possible to determine the size of water sites in the layers to around 1nm. In addition, a slight variation with the number of layers is found. The average pore size agrees with cutoff sizes found in permeation experiments.

  12. Counterion-induced entropic interactions in solutions of strongly stretched, osmotic polyelectrolyte stars

    NASA Astrophysics Data System (ADS)

    Jusufi, A.; Likos, C. N.; Lowen, H.

    2002-06-01

    We examine the conformations and effective interactions of star-branched polyelectrolytes with and without added salt, by employing monomer-resolved molecular dynamics simulations and an analytical theory. The simulations take into account the excluded-volume and Coulomb interactions between the individual monomers, as well as the counter- and coions. The theory is based on a variational free energy that is written as a sum of electrostatic, polymer, and entropic contributions of the counter- and coions. For the conformations of isolated polyelectrolyte stars, we find strong stretching of the chains, resulting in a linear scaling of the star radius with the degree of polymerization, as well as trapping and condensation of a large fraction of counterions. The effective interactions at arbitrarily strong overlaps between the stars are shown to be dominated by the entropic contributions of the trapped counterions, with the electrostatic contribution playing only a minor role due to an almost complete neutralization of the stars. In the case of added salt, we find a shrinking of the star size as well as a weakening of the effective force due to a generalized depletion mechanism. The good agreement between theory and simulations allows us to put forward analytic expressions for the effective interaction between polyelectrolyte stars at arbitrary separations.

  13. Hydrogen bond network relaxation in aqueous polyelectrolyte solutions: the effect of temperature

    NASA Astrophysics Data System (ADS)

    Sarti, S.; Truzzolillo, D.; Bordi, F.

    2012-07-01

    Dielectric spectroscopy data over the range 100 MHz-40 GHz allow for a reliable analysis of two of the major relaxation phenomena for polyelectrolytes (PE) in water. Within this range, the dielectric relaxation of pure water is dominated by a near-Debye process at ν = 18.5 GHz corresponding to a relaxation time of τ = 8.4 ps at 25 °C. This mode is commonly attributed to the cooperative relaxation specific to liquids forming a hydrogen bond network (HBN) and arising from long range H-bond-mediated dipole-dipole interactions. The presence of charged polymers in water partially modifies the dielectric characteristics of the orientational water molecule relaxation due to a change of the dielectric constant of water surrounding the charges on the polyion chain. We report experimental results on the effect of the presence of a standard flexible polyelectrolyte (sodium polyacrylate) on the HBN relaxation in water for different temperatures, showing that the HBN relaxation time does not change by increasing the polyelectrolyte density in water, even if relatively high concentrations are reached (0.02 monomol l-1 ≤ C ≤ 0.4 monomol l-1). We also find that the effect of PE addition on the HBN relaxation is not even a broadening of its distribution, rather a decrease of the spectral weight that goes beyond the pure volume fraction effect. This extra decrease is larger at low T and less evident at high T, supporting the idea that the correlation length of the water is less affected by the presence of charged flexible chains at high temperatures.

  14. Swelling and collapse of polyelectrolyte gels in equilibrium with monovalent and divalent electrolyte solutions

    NASA Astrophysics Data System (ADS)

    Yin, De-Wei; Olvera de la Cruz, Monica; de Pablo, Juan J.

    2009-11-01

    The swelling of polyelectrolyte (PE) gels by 1:1 and 2:1 salts is studied via osmotic ensemble Monte Carlo simulations at constant osmotic pressure and electrolyte chemical potential of a reservoir phase in equilibrium with a model PE network. Large molecular weight gels exhibit a remarkable swelling response to small changes in 2:1 salt concentration. Gel collapse is accompanied by the formation of a previously unknown heterogeneous nanostructure, predicted by theory and observed in simulations, consisting of regions dense in monomers coexisting with regions rich in mono- and divalent ions.

  15. Solution-processed pH-neutral conjugated polyelectrolyte improves interfacial contact in organic solar cells.

    PubMed

    Zhou, Huiqiong; Zhang, Yuan; Mai, Cheng-Kang; Seifter, Jason; Nguyen, Thuc-Quyen; Bazan, Guillermo C; Heeger, Alan J

    2015-01-27

    The intrinsic acidic nature of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole-transporting layer (HTL) induces interfacial protonation and limits the device performance in organic solar cells based on basic pyridylthiadiazole units. By utilizing a pH neutral, water/alcohol soluble conjugated polyelectrolyte CPE-K as the HTL in p-DTS(PTTh2)2:PC71BM solar cells, a 60% enhancement in PCE has been obtained with an increased V(bi), reduced R(s), and improved charge extraction. These effects originate from the elimination of interfacial protonation and energy barrier compared with the PEDOT:PSS HTL.

  16. Thermally induced suppression of interchain interactions in dilute aqueous solutions of conjugated polyelectrolyte rotaxanes and their analogues

    NASA Astrophysics Data System (ADS)

    Tregnago, Giulia; Afshar, Ali; McDonnell, Shane O.; Anderson, Harry L.; Cacialli, Franco

    2017-08-01

    We use steady-state and nanosecond time-resolved photoluminescence spectroscopy to investigate the evolution of packing interactions in dilute solutions of a sulfonated poly(diphenylenevinylene) lithium salt and its cyclodextrin-threaded polyrotaxanes as a function of the threading ratio (TR) when increasing the temperature from 10 to 40 °C. Contrary to the expectation of a temperature-induced increase of packing and aggregation, supported by previous Raman studies identifying a temperature-induced reduction in the inter-phenyl torsion angles, we find clear spectral (photoluminescence blue-shift and narrowing) and dynamic (shorter lifetimes and reduced weight of the long-lived components) signatures of a reduction of interchain interactions for the polyelectrolytes at higher temperatures with TR up to 1.3.

  17. Adsorption of tannic acid on polyelectrolyte monolayers determined in situ by streaming potential measurements.

    PubMed

    Oćwieja, M; Adamczyk, Z; Morga, M

    2015-01-15

    Physicochemical characteristics of tannic acid (tannin) suspensions comprising its stability for a wide range of ionic strength and pH were thoroughly investigated using UV-vis spectrophotometry, dynamic light scattering and microelectrophoretic measurements. These studies allowed to determine the hydrodynamic diameter of the tannic acid that was 1.63 nm for the pH range 3.5-5.5. For pH above 6.0 the hydrodynamic diameter significantly decreased as a result of the tannin hydrolysis. The electrophoretic mobility measurements confirmed that tannic acid is negatively charged for these values of pH and ionic strength 10(-4)-10(-2) M. Therefore, in order to promote adsorption of tannin molecules on negatively charged mica, the poly(allylamine hydrochloride) (PAH) supporting monolayers were first adsorbed under diffusion transport conditions. The coverage of polyelectrolyte monolayers was regulated by changing bulk concentration of PAH and the adsorption time. The electrokinetic characteristics of bare and PAH-covered mica were determined using the streaming potential measurements. The zeta potential of these PAH monolayers was highly positive, equal to 46 mV for ionic strength of 10(-2) M. The kinetics of tannin adsorption on these PAH supporting monolayers was evaluated by the in situ the streaming potential measurements. The zeta potential of PAH monolayers abruptly decreases with the adsorption of tannin molecules that was quantitatively interpreted in terms of the three-dimensional electrokinetic model. The acid-base characteristics of tannin monolayers were acquired via the streaming potential measurements for a broad range of pH. The obtained results indicate that it is possible to control adsorption of tannin on positively charged surfaces in order to designed new multilayer structures of desirable electrokinetic properties and stability.

  18. Conformations of polyelectrolyte macromolecules with different charge density in solutions of different ionic strengths

    NASA Astrophysics Data System (ADS)

    Dommes, O. A.; Okatova, O. V.; Pavlov, G. M.

    2016-11-01

    Studies of charged polymer chains are interesting in both fundamental and applied aspects. Especially, polyelectrolytes attract huge attention of researchers due to their ability to form interpolymer complexes with synthetic and biopolymers. The study was carried out on the fractions of hydrophilic copolymers of N-methyl-N-vinyl acetamide and N-methyl-N-vinyl amine hydrochloride of different degrees of polymerization and of different charge density using methods of molecular hydrodynamics. Hydrodynamic and conformational characteristics as well as molar masses of isolated molecules were estimated. In addition, the intrinsic viscosity of fractions was studied at the extreme ionic strengths - in distilled water (∼10-6M) and in 6M NaCl. Scaling relations for intrinsic viscosity, sedimentation and translational diffusion coefficients with molar mass were obtained. Conformational behavior of macromolecules with different linear charge density was compared.

  19. Entropy and enthalpy of polyelectrolyte complexation: Langevin dynamics simulations.

    PubMed

    Ou, Zhaoyang; Muthukumar, M

    2006-04-21

    We report a systematic study by Langevin dynamics simulation on the energetics of complexation between two oppositely charged polyelectrolytes of same charge density in dilute solutions of a good solvent with counterions and salt ions explicitly included. The enthalpy of polyelectrolyte complexation is quantified by comparisons of the Coulomb energy before and after complexation. The entropy of polyelectrolyte complexation is determined directly from simulations and compared with that from a mean-field lattice model explicitly accounting for counterion adsorption. At weak Coulomb interaction strengths, e.g., in solvents of high dielectric constant or with weakly charged polyelectrolytes, complexation is driven by a negative enthalpy due to electrostatic attraction between two oppositely charged chains, with counterion release entropy playing only a subsidiary role. In the strong interaction regime, complexation is driven by a large counterion release entropy and opposed by a positive enthalpy change. The addition of salt reduces the enthalpy of polyelectrolyte complexation by screening electrostatic interaction at all Coulomb interaction strengths. The counterion release entropy also decreases in the presence of salt, but the reduction only becomes significant at higher Coulomb interaction strengths. More significantly, in the range of Coulomb interaction strengths appropriate for highly charged polymers in aqueous solutions, complexation enthalpy depends weakly on salt concentration and counterion release entropy exhibits a large variation as a function of salt concentration. Our study quantitatively establishes that polyelectrolyte complexation in highly charged Coulomb systems is of entropic origin.

  20. Study of polyelectrolytes for Los Alamos National Laboratory. Final report

    SciTech Connect

    Labonne, N.

    1994-11-01

    To assess the safety of a potential radioactive waste repository, analysis of the fluid solution containing low levels of activity need to be performed. In some cases, the radioactivity would be so weak (3--30 pCi/L) that the solution must be concentrated for measurement. For this purpose, Los Alamos National Laboratory scientists are synthesizing some water soluble polyelectrolytes, which, because they are strong complexing agents for inorganic cations, can concentrate the radioelements in solution. To assist in characterization of these polyelectrolytes, the author has performed experiments to determine physico-chemical constants, such as pKa values and stability constants. The complexation constants between both polyelectrolytes and europium were determined by two methods: solvent extraction and ion exchange. Results are presented.

  1. Luminescence Titrations of Polyelectrolytes.

    DTIC Science & Technology

    1984-05-01

    aluentered JA Week N it ditiu’I ken A60010 IL. SUPPLEMENTARY NOTES IS. Kay WORDS (CaaIAhu. an revrn ide "I .. eesese md =0uI1Y 6F we"A amA .) Polyele...Polyelectrolytes are also seeing increasing use as agents for the preparation of chemically modified electrodes (3,4). The equivalent weight (EW) of the...sufficiently large, Imax will be reached after a small excess of polyelectrolyte solution has been added. Standard (28) extrapolation procedures may then be used

  2. 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.

  3. 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.

  4. 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.

  5. Interaction between like-charged polyelectrolyte-colloid complexes in electrolyte solutions: A Monte Carlo simulation study in the Debye-Hückel approximation

    NASA Astrophysics Data System (ADS)

    Truzzolillo, D.; Bordi, F.; Sciortino, F.; Sennato, S.

    2010-07-01

    We study the effective interaction between differently charged polyelectrolyte-colloid complexes in electrolyte solutions via Monte Carlo simulations. These complexes are formed when short and flexible polyelectrolyte chains adsorb onto oppositely charged colloidal spheres, dispersed in an electrolyte solution. In our simulations the bending energy between adjacent monomers is small compared to the electrostatic energy, and the chains, once adsorbed, do not exchange with the solution, although they rearrange on the particles surface to accommodate further adsorbing chains or due to the electrostatic interaction with neighbor complexes. Rather unexpectedly, when two interacting particles approach each other, the rearrangement of the surface charge distribution invariably produces antiparallel dipolar doublets that invert their orientation at the isoelectric point. These findings clearly rule out a contribution of dipole-dipole interactions to the observed attractive interaction between the complexes, pointing out that such suspensions cannot be considered dipolar fluids. On varying the ionic strength of the electrolyte, we find that a screening length κ-1, short compared with the size of the colloidal particles, is required in order to observe the attraction between like-charged complexes due to the nonuniform distribution of the electric charge on their surface ("patch attraction"). On the other hand, by changing the polyelectrolyte/particle charge ratio ξs, the interaction between like-charged polyelectrolyte-decorated particles, at short separations, evolves from purely repulsive to strongly attractive. Hence, the effective interaction between the complexes is characterized by a potential barrier, whose height depends on the net charge and on the nonuniformity of their surface charge distribution.

  6. Controlled release of a microencapsulated arduous semi-hydrophobic active from coatings: Superhydrophilic polyelectrolyte shells as globally rate-determining barriers.

    PubMed

    Bergek, Jonatan; Andersson Trojer, Markus; Uhr, Hermann; Nordstierna, Lars

    2016-03-10

    Polymethylmethacrylate-based microcapsules containing the antimicrobial agent 2-n-octyl-4-isothiazolin-3-one (OIT) decorated by an anchored polyelectrolyte brush consisting of an amphiphilic diblock copolymer of polymethylmethacrylate-block-poly(sodium methacrylate) type have been formulated via a coacervation technique. The polyelectrolyte brush surface provided the microcapsule with a high and stable surface charge density. This enabled further surface modification of the colloidal particle with a thin and dense polyelectrolyte multilayer using the layer-by-layer technique. The addition of the highly charged and hydrophilic polyelectrolyte multilayer assembled on the microcapsule surface resulted in a considerable decrease of the release rate of the encapsulated OIT in aqueous suspension, corresponding to a 40 times reduction of the effective OIT diffusion coefficient in the polymethylmethacrylate matrix. Moreover, the release of encapsulated or freely dispersed OIT from coatings as a function of the matrix density was evaluated and analyzed within the framework of applied diffusion models. Encapsulation of OIT in polyelectrolyte multilayer composite microcapsules was found to significantly prolong the release and render the release rate more or less independent of the matrix density. In addition, the long-term antimicrobial properties of the coatings were evaluated in terms of their susceptibility for biofouling using the fungus and common biofouler Aspergillus niger as model organism. The results clearly demonstrated that the use of encapsulated OIT gave a significantly prolonged surface protection and allowed for the determination of the critical surface flux. The polyelectrolyte multilayer has therefore been recognized as the rate-determining barrier for OIT. The matrix density has a minor influence on the release rate of encapsulated OIT from these microcapsules and this concept may very well be expanded to cover a broad range of hydrophobic and semi

  7. Aggregation dynamics of rigid polyelectrolytes

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    Similarly charged polyelectrolytes are known to attract each other and aggregate into bundles when the charge density of the polymers exceeds a critical value that depends on the valency of the counterions. The dynamics of aggregation of such rigid polyelectrolytes are studied using large scale molecular dynamics simulations. We find that the morphology of the aggregates depends on the value of the charge density of the polymers. For values close to the critical value, the shape of the aggregates is cylindrical with height equal to the length of a single polyelectrolyte chain. However, for larger values of charge, the linear extent of the aggregates increases as more and more polymers aggregate. In both the cases, we show that the number of aggregates decrease with time as power laws with exponents that are not numerically distinguishable from each other and are independent of charge density of the polymers, valency of the counterions, density, and length of the polyelectrolyte chain. We model the aggregation dynamics using the Smoluchowski coagulation equation with kernels determined from the molecular dynamics simulations and justify the numerically obtained value of the exponent. Our results suggest that once counterions condense, effective interactions between polyelectrolyte chains short-ranged and the aggregation of polyelectrolytes are diffusion-limited.

  8. Interplay between Depletion and Double-Layer Forces Acting between Charged Particles in Solutions of Like-Charged Polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Moazzami-Gudarzi, Mohsen; Kremer, Tomislav; Valmacco, Valentina; Maroni, Plinio; Borkovec, Michal; Trefalt, Gregor

    2016-08-01

    Direct force measurements between negatively charged silica particles in the presence of a like-charged strong polyelectrolyte were carried out with an atomic force microscope. The force profiles can be quantitatively interpreted as a superposition of depletion and double-layer forces. The depletion forces are modeled with a damped oscillatory profile, while the double-layer forces with the mean-field Poisson-Boltzmann theory for a strongly asymmetric electrolyte, whereby an effective valence must be assigned to the polyelectrolyte. This effective valence is substantially smaller than the bare valence due to ion condensation effects. The unusual aspect of the electrical double layer in these systems is the exclusion of the like-charged polyelectrolyte from the vicinity of the surface, leading to a strongly nonexponential diffuse ionic layer that is dominated by counterions and has a well-defined thickness. As the oscillatory depletion force sets in right after this layer, this condition can be used to predict the phase of the oscillatory depletion force.

  9. Ionizing radiation in the polyelectrolytes technology

    NASA Astrophysics Data System (ADS)

    Martin, D.; Dragusin, M.; Radoiu, M.; Moraru, R.; Oproiu, C.; Toma, M.; Ferdes, O.; Jianu, A.; Bestea, V.; Manea, A.

    1999-01-01

    Gamma ray and accelerated electron beam application in the chemistry of polyelectrolytes is presented. The polyelectrolytes preparation is based on radiation induced polymerization of aqueous solutions containing an appropriate mixture of monomers such as acrylamide, acrylic acid, vinyl acetate, diallyldimethylammonium-chloride and certain initiators, complexing agents and chain transfer agents. The effects of absorbed dose, rate of absorbed dose and chemical composition of aqueous solution on the polymerization process are discussed. The results obtained by testing these polyelectrolytes with waste water from food industry are also given.

  10. 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

  11. Biosensors from conjugated polyelectrolyte complexes.

    PubMed

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

    2002-01-08

    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 (MV(2+)). 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.

  12. Bundle Formation in Polyelectrolyte Brushes

    NASA Astrophysics Data System (ADS)

    Günther, J. U.; Ahrens, H.; Förster, S.; Helm, C. A.

    2008-12-01

    Bundle formation of the vertically oriented polyelectrolytes within polyelectrolyte brushes is studied with x-ray reflectivity and grazing-incidence diffraction as a function of grafting density and ion concentration. At 0.8 Molar monomer concentration and without added salt, a bundle consists of two chains and is 50 Å long. On the addition of up to 1M CsCl, the aggregation number increases up to 15 whereas the bundle length approaches a limiting value, 20 Å. We suggest that the bundle formation is determined by a balance between long-ranged electrostatic repulsion, whose range and amplitude is decreased on salt addition, and short-ranged attraction.

  13. Cytotoxic activity of paclitaxel incorporated into polyelectrolyte nanocapsules

    NASA Astrophysics Data System (ADS)

    Karabasz, Alicja; Bzowska, Monika; Łukasiewicz, Sylwia; Bereta, Joanna; Szczepanowicz, Krzysztof

    2014-04-01

    Nanoencapsulation is a promising solution for the delivery of chemotherapeutics to tumors. A method of preparation of drug-loaded nanocapsules based on the liquid core encapsulation by a sequential adsorption of a polyelectrolyte is described. An easily evaporative solvent, chloroform, was used as an oil phase. An interfacial complex formed with an oil-soluble, Food and Drug Administration-approved surfactant, and polycation poly- l-lysine (PLL) was used as a microemulsion stabilizer. A polyelectrolyte multilayer shell was constructed by a sequential adsorption of polyelectrolytes using biocompatible polyelectrolytes (PLL as a polycation and poly- l-glutamic acid as a polyanion). A hydrophobic anticancer agent, paclitaxel, was successfully encapsulated in the nanocarriers with the average size of 100 nm. In vitro analysis of the effects of nanoformulations was performed using a mouse colon carcinoma cell line CT26-CEA. Biocompatibility of the nanocapsules was evaluated using various biochemical assays. The results indicate that the cell viability was diminished by positively but not by negatively charged nanocarriers. Analysis of the cellular uptake of nanocapsules determined by flow cytometry and confocal microscopy confirmed their accumulation inside the cells. Encapsulated paclitaxel retains its cytotoxic/cytostatic activity; although its effects were weaker than those of the corresponding concentrations of the free drug. The generated nanocapsules seem to be a valuable vehicle for tumor drug delivery; although further work is needed to increase their overall activity.

  14. [The electrostatic contribution to interactions of some enzymes with polyelectrolytes].

    PubMed

    Saburova, E A; Dybovskaia, Iu N; Sivezhelezov, V S; Elfamova, L I

    2005-01-01

    To explain the inhibitory action of polyelectrolytes on enzymes and, in particular, to define potentially reactive zones for the binding of polyelectrolyte, the electric potential of enzymes lactate dehydrogenase and glutamate dehydrogenase was calculated using the solution of the Poisson-Boltzmann equation by a numerical method with the use of the Gauss-Seidel relaxation method at three pH values: 6.5, 7.0, and 8.0 and three values of ionic strength: 50, 100, and 150 mm. On the basis of these calculations and their visualization, representative sites for favorable binding of polyanions were determined as extended areas on the surface of proteins with the positive potential in the neutral pH region. It was shown that there is a correlation between the area of positive potential and the efficiency of enzyme inactivation for a number of pH values and concentrations of salt for two enzymes. The calculations performed allowed one to explain the inhibitory action of polyelectrolytes on the specified enzymes to understand the difference between the values of polyelectrolyte inactivation constants for the two enzymes and estimate the minimal areas of the positive potential on the protein surface that provide their effective inhibition.

  15. Electrostatic correlations and the polyelectrolyte self energy.

    PubMed

    Shen, Kevin; Wang, Zhen-Gang

    2017-02-28

    We address the effects of chain connectivity on electrostaticfluctuations in polyelectrolyte solutions using a field-theoretic, renormalizedGaussian fluctuation (RGF) theory. As in simple electrolyte solutions [Z.-G. Wang,Phys. Rev. E 81, 021501 (2010)], the RGF provides a unified theory forelectrostatic fluctuations, accounting for both dielectric and charge correlationeffects in terms of the self-energy. Unlike simple ions, the polyelectrolyte self energydepends intimately on the chain conformation, and our theory naturally provides aself-consistent determination of the response of intramolecular chain structure topolyelectrolyte and salt concentrations. The effects of the chain-conformation on theself-energy and thermodynamics are especially pronounced for flexiblepolyelectrolytes at low polymer and salt concentrations, where application of thewrong chain structure can lead to a drastic misestimation of the electrostaticcorrelations. By capturing the expected scaling behavior of chain size from dilute tosemi-dilute regimes, our theory provides improved estimates of the self energy at lowpolymer concentrations and correctly predicts the eventual N-independenceof the critical temperature and concentration of salt-free solutions of flexiblepolyelectrolytes. We show that the self energy can be interpreted in terms of aninfinite-dilution energy μm,0(el) and a finite concentrationcorrelation correction μ(corr) which tends to cancel out the formerwith increasing concentration.

  16. Electrostatic correlations and the polyelectrolyte self energy

    NASA Astrophysics Data System (ADS)

    Shen, Kevin; Wang, Zhen-Gang

    2017-02-01

    We address the effects of chain connectivity on electrostaticfluctuations in polyelectrolyte solutions using a field-theoretic, renormalizedGaussian fluctuation (RGF) theory. As in simple electrolyte solutions [Z.-G. Wang,Phys. Rev. E 81, 021501 (2010)], the RGF provides a unified theory forelectrostatic fluctuations, accounting for both dielectric and charge correlationeffects in terms of the self-energy. Unlike simple ions, the polyelectrolyte self energydepends intimately on the chain conformation, and our theory naturally provides aself-consistent determination of the response of intramolecular chain structure topolyelectrolyte and salt concentrations. The effects of the chain-conformation on theself-energy and thermodynamics are especially pronounced for flexiblepolyelectrolytes at low polymer and salt concentrations, where application of thewrong chain structure can lead to a drastic misestimation of the electrostaticcorrelations. By capturing the expected scaling behavior of chain size from dilute tosemi-dilute regimes, our theory provides improved estimates of the self energy at lowpolymer concentrations and correctly predicts the eventual N-independenceof the critical temperature and concentration of salt-free solutions of flexiblepolyelectrolytes. We show that the self energy can be interpreted in terms of aninfinite-dilution energy μm,0 el and a finite concentrationcorrelation correction μcorr which tends to cancel out the formerwith increasing concentration.

  17. Patterned Microstructure Fabrication: Polyelectrolyte Complexes vs Polyelectrolyte Multilayers

    PubMed Central

    Gai, Meiyu; Frueh, Johannes; Kudryavtseva, Valeriya L.; Mao, Rui; Kiryukhin, Maxim V.; Sukhorukov, Gleb B.

    2016-01-01

    Polyelectrolyte complexes (PEC) are formed by mixing the solutions of oppositely charged polyelectrolytes, which were hitherto deemed “impossible” to process, since they are infusible and brittle when dry. Here, we describe the process of fabricating free-standing micro-patterned PEC films containing array of hollow or filled microchambers by one-step casting with small applied pressure and a PDMS mould. These structures are compared with polyelectrolyte multilayers (PEM) thin films having array of hollow microchambers produced from a layer-by-layer self-assembly of the same polyelectrolytes on the same PDMS moulds. PEM microchambers “cap” and “wall” thickness depend on the number of PEM bilayers, while the “cap” and “wall” of the PEC microchambers can be tuned by varying the applied pressure and the type of patterned mould. The proposed PEC production process omits layering approaches currently employed for PEMs, reducing the production time from ~2 days down to 2 hours. The error-free structured PEC area was found to be significantly larger compared to the currently-employed microcontact printing for PEMs. The sensitivity of PEC chambers towards aqueous environments was found to be higher compared to those composed of PEM. PMID:27830831

  18. Colloidal stability of magnetic iron oxide nanoparticles: influence of natural organic matter and synthetic polyelectrolytes.

    PubMed

    Ghosh, Saikat; Jiang, Wei; McClements, Julian D; Xing, Baoshan

    2011-07-05

    The colloidal behavior of natural organic matter (NOM) and synthetic poly(acrylic acid) (PAA)-coated ferrimagnetic (γFe(2)O(3)) nanoparticles (NPs) was investigated. Humic acid (HA), an important component of NOM, was extracted from a peat soil. Two different molecular weight PAAs were also used for coating. The colloidal stability of the coated magnetic NPs was evaluated as a resultant of the attractive magnetic dipolar and van der Waals forces and the repulsive electrostatic and steric-electrosteric interactions. The conformational alterations of the polyelectrolytes adsorbed on magnetic γFe(2)O(3) NPs and their role in colloidal stability were determined. Pure γFe(2)O(3) NPs were extremely unstable because of aggregation in aqueous solution, but a significant stability enhancement was observed after coating with polyelectrolytes. The steric stabilization factor induced by the polyelectrolyte coating strongly dictated the colloidal stability. The pH-induced conformational change of the adsorbed, weakly charged polyelectrolytes had a significant effect on the colloidal stability. Atomic force microscopy (AFM) revealed the stretched conformation of the HA molecular chains adsorbed on the γFe(2)O(3) NP surface at pH 9, which enhanced the colloidal stability through long-range electrosteric stabilization. The depletion of the polyelectrolyte during the dilution of the NP suspension decreased the colloidal stability under acidic solution conditions. The conformation of the polyelectrolytes adsorbed on the NP surface was altered as a function of the substrate surface charge as viewed from AFM imaging. The polyelectrolyte coating also led to a reduction in magnetic moments and decreased the coercivity of the coated γFe(2)O(3) NPs. Thus, the enhanced stabilization of the coated maghematite NPs may facilitate their delivery in the groundwater for the effective removal of contaminants. © 2011 American Chemical Society

  19. Ion-exchange controls the kinetics of deswelling of polyelectrolyte microgels in solutions of oppositely charged surfactant.

    PubMed

    Nilsson, Peter; Hansson, Per

    2005-12-22

    The kinetics of deswelling of sodium polyacrylate microgels (radius 30-140 microm) in aqueous solutions of dodecyltrimethylammonium bromide is investigated by means of micropipet-assisted light microscopy. The purpose of the study is to test a recent model (J. Phys. Chem. B 2003, 107, 9203) proposing that the rate of the volume change is controlled by the transport of surfactant from the solution to the gel core (ion exchange) via the surfactant-rich surface phase appearing in the gel during the volume transition. Equilibrium swelling characteristics of the gel network in surfactant-free solutions and with various amounts of surfactant present are presented and discussed with reference to related systems. A relationship between gel volume and degree of surfactant binding is determined and used in theoretical predictions of the deswelling kinetics. Experimental data for single gel beads observed during deswelling under conditions of forced convection are presented and compared with model calculations. It is demonstrated that the dependences of the kinetics on initial gel size, the surfactant concentration in the solution, and the liquid flow rate are well accounted for by the model. It is concluded that the deswelling rates of the studied gels are strongly influenced by the mass transport of surfactant between gel and solution (stagnant layer diffusion), but only to a minor extent by the transport through the surface phase. The results indicate that, during the volume transition, swelling equilibrium (network relaxation/transport of water) is established on a relatively short time scale and, therefore, can be treated as independent of the ion-exchange kinetics. Theoretical aspects of the kinetics and mechanisms of surfactant transport through the surface phase are discussed.

  20. Prediction of solvent-induced morphological changes of polyelectrolyte diblock copolymer micelles.

    PubMed

    Li, Nan K; Fuss, William H; Tang, Lei; Gu, Renpeng; Chilkoti, Ashutosh; Zauscher, Stefan; Yingling, Yaroslava G

    2015-11-14

    Self-assembly processes of polyelectrolyte block copolymers are ubiquitous in industrial and biological processes; understanding their physical properties can also provide insights into the design of polyelectrolyte materials with novel and tailored properties. Here, we report systematic analysis on how the ionic strength of the solvent and the length of the polyelectrolyte block affect the self-assembly and morphology of the polyelectrolyte block copolymer materials by constructing a salt-dependent morphological phase diagram using an implicit solvent ionic strength (ISIS) method for dissipative particle dynamics (DPD) simulations. This diagram permits the determination of the conditions for the morphological transition into a specific shape, namely vesicles or lamellar aggregates, wormlike/cylindrical micelles, and spherical micelles. The scaling behavior for the size of spherical micelles is predicted, in terms of radius of gyration (R(g,m)) and thickness of corona (Hcorona), as a function of solvent ionic strength (c(s)) and polyelectrolyte length (NA), which are R(g,m) ∼ c(s)(-0.06)N(A)(0.54) and Hcorona ∼ c(s)(-0.11)N(A)(0.75). The simulation results were corroborated through AFM and static light scattering measurements on the example of the self-assembly of monodisperse, single-stranded DNA block-copolynucleotides (polyT50-b-F-dUTP). Overall, we were able to predict the salt-responsive morphology of polyelectrolyte materials in aqueous solution and show that a spherical-cylindrical-lamellar change in morphology can be obtained through an increase in solvent ionic strength or a decrease of polyelectrolyte length.

  1. Conformation of polyelectrolytes in poor solvents: Variational approach and quantitative comparison with scaling predictions

    NASA Astrophysics Data System (ADS)

    Tang, Haozhe; Liao, Qi; Zhang, Pingwen

    2014-05-01

    We present the results of variational calculations of a polyelectrolyte solution with low salt in poor solvent conditions for a polymer backbone. By employing the variation method, we quantitatively determined the diagram of the state of the polyelectrolyte in poor solvents as a function of the charge density and the molecular weight. The exact structure and diagram of the polyelectrolyte were compared to the scaling predictions of the necklace model developed by Dobrynin and Rubinstein [Prog. Polym. Sci. 30, 1049-1118 (2005); Dobrynin and Rubinstein, Macromolecules 32, 915-922 (1999); Dobrynin and Rubinstein, Macromolecules 34, 1964-1972 (2001)]. We find that the scaling necklace model may be used as a rather good estimation and analytical approximation of the exact variational model. It is also pointed out that the molecular connection of polymer is crucial for ellipsoid and necklace conformation.

  2. A new equation of state of a flexible-chain polyelectrolyte solution: Phase equilibria and osmotic pressure in the salt-free case.

    PubMed

    Budkov, Yu A; Kolesnikov, A L; Georgi, N; Nogovitsyn, E A; Kiselev, M G

    2015-05-07

    We develop a first-principle equation of state of salt-free polyelectrolyte solution in the limit of infinitely long flexible polymer chains in the framework of a field-theoretical formalism beyond the linear Debye-Hueckel theory and predict a liquid-liquid phase separation induced by a strong correlation attraction. As a reference system, we choose a set of two subsystems-charged macromolecules immersed in a structureless oppositely charged background created by counterions (polymer one component plasma) and counterions immersed in oppositely charged background created by polymer chains (hard-core one component plasma). We calculate the excess free energy of polymer one component plasma in the framework of modified random phase approximation, whereas a contribution of charge densities' fluctuations of neutralizing backgrounds we evaluate at the level of Gaussian approximation. We show that our theory is in a very good agreement with the results of Monte Carlo and MD simulations for critical parameters of liquid-liquid phase separation and osmotic pressure in a wide range of monomer concentration above the critical point, respectively.

  3. Saloplastics: processing compact polyelectrolyte complexes.

    PubMed

    Schaaf, Pierre; Schlenoff, Joseph B

    2015-04-17

    Polyelectrolyte complexes (PECs) are prepared by mixing solutions of oppositely charged polyelectrolytes. These diffuse, amorphous precipitates may be compacted into dense materials, CoPECs, by ultracentrifugation (ucPECs) or extrusion (exPECs). The presence of salt water is essential in plasticizing PECs to allow them to be reformed and fused. When hydrated, CoPECs are versatile, rugged, biocompatible, elastic materials with applications including bioinspired materials, supports for enzymes and (nano)composites. In this review, various methods for making CoPECs are described, as well as fundamental responses of CoPEC mechanical properties to salt concentration. Possible applications as synthetic cartilage, enzymatically active biocomposites, self-healing materials, and magnetic nanocomposites are presented.

  4. Electrostatics of Rigid Polyelectrolytes

    SciTech Connect

    Wong, G.C.L.

    2009-06-04

    The organization of rigid biological polyelectrolytes by multivalent ions and macroions are important for many fundamental problems in biology and biomedicine, such as cytoskeletal regulation and antimicrobial sequestration in cystic fibrosis. These polyelectrolytes have been used as model systems for understanding electrostatics in complex fluids. Here, we review some recent results in theory, simulations, and experiments.

  5. Characterization of polyelectrolyte behavior of the polysaccharides chitosan, heparin, and hyaluronan, by light scattering and viscometry.

    NASA Astrophysics Data System (ADS)

    Boddohi, Soheil; Yonemura, Susan; Kipper, Matt

    2008-03-01

    This study on the polyelectrolyte behavior of polysaccharides in solution is motivated by our recent work in development of nanostructured polysaccharide-based surface coatings. Chitosan behaves as a weak polycation, and hyaluronan behaves as a weak polyanion, while heparin behaves as a strong polyanion. The ability to control the conformation of these polysaccharides in solution, by changing the solution ionic strength and pH may offer the opportunity to further tune the nanoscale features of polysaccharide-based surface coatings assembled from solution. In the work reported here, the solution conformation of these polymers is determined from gel permeation chromatography coupled to differential refractive index, light scattering, and viscometry detection. These results are related to the nanostructure of chitosan-heparin and chitosan-hyaluronan surface coatings based on polyelectrolyte multilayers.

  6. The structure of AuPd nanoalloys anchored on spherical polyelectrolyte brushes determined by X-ray absorption spectroscopy.

    PubMed

    Kaiser, Julian; Szczerba, Wojciech; Riesemeier, Heinrich; Reinholz, Uwe; Radtke, Martin; Albrecht, Martin; Lu, Yan; Ballauff, Matthias

    2013-01-01

    Well-defined and facetted bimetallic gold-palladium nanoalloys have been synthesized and anchored in spherical polyelectrolyte brushes (SPB) as composite particles (AuPd@SPB). These particles are better catalysts in aqueous phase than the pure metals. The atomistic arrangement of these nanoalloys has been analysed by extended X-ray absorption fine structure (EXAFS) spectroscopy at the Au-L3 and the Pd-K absorption edge. The samples with high amounts of gold appear as almost statistically mixed random alloys. Alloy compositions with less gold show slight enrichment of Pd at the surface of the particle. In addition, signals of non-metallic palladium appear at the Pd-K edge which indicate the presence of the Pd2+ species in addition to metallic palladium. The relation of these structural features to the catalytic activity is discussed.

  7. Investigation on the interaction of Safranin T with anionic polyelectrolytes by spectrophotometric method

    NASA Astrophysics Data System (ADS)

    Fradj, Anouar Ben; Lafi, Ridha; Hamouda, Sofiane Ben; Gzara, Lassaad; Hamzaoui, Ahmed Hichem; Hafiane, Amor

    2014-10-01

    Understanding the role played by chemical additives such as NaCl salt, acid and Cetylpyridinium Chloride (CPC) surfactant on the interaction between dye and polyelectrolyte contributes to optimization of processes using polyelectrolytes in the removal of dye from aqueous solution. Herein we focus in the interaction between Safranin T, a cationic dye, with two anionic polyelectrolytes, poly(ammonium acrylate) and poly(acrylic acid) using spectrophotometric method and conductivity measurement. In aqueous solution, each of anionic polyelectrolytes forms a complex with the dye and induces a metachromasy indicated by the blue shift of the absorbance of the dye. The stoichiometry of complexes evaluated by the molar ratio method are 1:1 for Safranin T poly(ammonium acrylate) and 2:1 in the case of Safranin T poly(acrylic acid). The effect of additives on the stability of complexes has been studied by varying concentrations of the salt and the surfactant and pH of the solution. The thermodynamic parameters of interaction ΔG, ΔH and ΔS at different temperatures were evaluated to determine the stability constant of the complexes.

  8. Factors responsible for the aggregation behavior of hydrophobic polyelectrolyte PEA in aqueous solution studied by molecular dynamics simulations.

    PubMed

    Sappidi, Praveenkumar; Natarajan, Upendra

    2017-08-01

    Self-association (i.e. interchain aggregation) behavior of atactic poly(ethacrylic acid) PEA in dilute aqueous solution as function of degree-of-neutralization by Na(+) counter-ions (i.e. charge fraction f) was investigated by molecular dynamics simulations. Aggregation is found to occur in the range 0≤f≤0.7 in agreement with experimental results compared at specified polymer concentration Cp=0.36mol/l in dilute solution. The macromolecular solution was characterized and analysed for radius-of-gyration, torsion angle distribution, inter and intra-molecular hydrogen bonds, radial distribution functions of intermolecular and inter-atomic pairs, inter-chain contacts and solvation enthalpy. The PEA chains form aggregate through attractive inter-chain interaction via hydrogen bonding, in the range f<0.7, in agreement with experimental observation. The numbers of inter-chain contacts decreases with f. A critical structural transition occurs at f=0.7, observed via simulations for the first time, in Rg as well as inter-chain H-bonds. The inter-chain distance increases with f due to repulsive interactions between COO- groups on the chains. PEA-PEA electrostatic interactions dominant solvation enthalpy. The PEA solvation enthalpy becomes increasingly favorable with increase in f. The transition enthalpy change, in going from uncharged (acid) state to fully charged state (f=1) is unfavorable towards aggregate formation. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Hydrophobically modified polyelectrolytes: Characterization, aggregation and adsorption

    NASA Astrophysics Data System (ADS)

    Islam, Mohammad Ferdous

    The focus of our work was to experimentally study the aggregation and adsorption behavior of model HM polyelectrolytes. Hydrophobically modified alkali soluble emulsions (HASE), the model HM polyelectrolytes, were chosen because they had complex architecture yet possessed key variables for systematic study. The HASE polymers have methacrylic acid (MAA) and ethyl acrylate (EA) in the backbone with pendent hydrophobic groups. Characterization of a single molecule is an important first step in understanding the aggregation and adsorption of these polymers. However, characterizations of the HASE polymers using conventional techniques such as gel permeation chromatography or static light scattering were difficult because of the hydrophobic association. In this study, two different approaches have been taken to prevent the hydrophobic association in aqueous solution: (1) hydrolyze the polymer to cleave the hydrophobic constituents, and (2) use methyl beta-cyclodextrin that has a hydrophobic cavity and a hydrophilic outer shell, to shield the hydrophobes from associating. By taking these two approaches and using gel permeation chromatography (GPC), dynamic (DLS) and static (SLS) light scattering techniques, the molecular weight, hydrodynamic radius and radius of gyration of a single molecule were determined. Except for one chemical site, we were able to determine that branching or grafting did not occur in the polymer chain during synthesis. Our aggregation studies showed that, in aqueous solutions, the HASE polymers formed small aggregates (presumably single micelles of single or a few chains) and large aggregates (presumably formed by bridging between micelles). The radii and masses of the larger aggregates, measured using DLS and SLS, were found to increase with an increase in the polymer concentration, indicating an open association process for the HASE polymers. Our SLS results also showed that, at high salt concentration, the aggregates of the HASE polymer with

  10. Electrochromism and electrocatalysis in viologen polyelectrolyte multilayers

    SciTech Connect

    Stepp, J.; Schlenoff, J.B.

    1997-06-01

    Polyelectrolyte multilayers were constructed from a polyviologen and poly(styrene sulfonate) using an alternating polyion solution deposition technique. In situ absorption spectroscopy showed multilayers to be strongly electrochromic. Oxygen reduction at multilayer-coated conducting glass electrodes was also shown to be facilitated.

  11. Polyelectrolyte multilayers: An odyssey through interdisciplinary science

    NASA Astrophysics Data System (ADS)

    Jaber, Jad A.

    This dissertation provides an overview of a self assembled multilayer technique based on the alternating deposition of oppositely charged polyelectrolytes onto charged solid supports. The basic principles and methodologies governing this technique are laid down, and new strategies are built upon the latter, in an effort to develop innovative technologies that would be beneficial for making new products or improving the quality of existing ones. Fundamental studies to characterize the water content, efficiency of ion-pairing, differential strength of electrostatic interactions, topology, and viscoelastic properties of polyelectrolyte multilayers, PEMUs, are illustrated and conducted. In addition, polyelectrolyte multilayers that are stimulus responsive, or support active and controlled bio-motor protein interactions are described. Attenuated total reflectance Fourier transform infrared, (ATR), spectroscopy was used to compare the extent of swelling and doping within PAH/PSS and PDADMA/PSS polyelectrolyte multilayers. Unlike PDADMA/PSS, whose water content depended on the solution ionic strength, PAH/PSS was resistant to swelling by salt. It was stable up to 4.0 M sodium chloride, with 6 water molecules per ion-pair. Using the infrared active perchlorate sodium salt, the amount of residual persistent extrinsic sites in both PDADMA/PSS and PAH/PSS was determined to be 3% and 6%, respectively. The free energy of association between the polymer segments, in the presence of sodium perchlorate, was in the order of 4.5 kJ mol-1 and -9.5 kJ mol-1 for PDADMA/PSS and PAH/PSS correspondingly. Thus, indicating the relatively strong electrostatic association between the polymer segments in a PAH/PSS relative to PDADMA/PSS multilayer. Adjusting the pH of the solution in contact with the PAH/PSS multilayer to 11.5 resulted in a first order discontinuous dissociation of the Pol+Pol- bonds. Techniques used to study the mechanical properties of single muscle fiber were adapted to

  12. Diffusion of polyelectrolytes in polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Rahalkar, Anand; Muthukumar, Murugappan

    2015-03-01

    Using dynamic light scattering, we have investigated the diffusion coefficient of sodium poly(styrene sulfonate) in a matrix of poly(acrylamide-co-acrylate) gels. The diffusion coefficient of the probe polyelectrolyte exhibits a crossover behavior from a particle-diffusion to entropic-barrier dominated diffusion, as the molecular weight is increased. The effect of electrostatics, by varying the charge density of the matrix, on probe diffusion constant will be presented.

  13. 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.

  14. Actuation and ion transportation of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Hong, Wei; Wang, Xiao

    2010-04-01

    Consisting of charged network swollen with ionic solution, polyelectrolyte gels are known for their salient characters including ion exchange and stimuli responsiveness. The active properties of polyelectrolyte gels are mostly due to the migration of solvent molecules and solute ions, and their interactions with the fixed charges on the network. In this paper, we extend the recently developed nonlinear field theory of polyelectrolyte gels by assuming that the kinetic process is limited by the rate of the transportation of mobile species. To study the coupled mechanical deformation, ion migration, and electric field, we further specialize the model to the case of a laterally constrained gel sheet. By solving the field equations in two limiting cases: the equilibrium state and the steady state, we calculate the mechanical responses of the gel to the applied electric field, and study the dependency on various parameters. The results recover the behavior observed in experiments in which polyelectrolyte gels are used as actuators, such as the ionic polymer metal composite. In addition, the model reveals the mechanism of the selectivity in ion transportation. Although by assuming specific material laws, the reduced system resembles those in most existing models in the literature, the theory can be easily generalized by using more realistic free-energy functions and kinetic laws. The adaptability of the theory makes it suitable for studying many similar material systems and phenomena.

  15. Spatial distribution of protein molecules adsorbed at a polyelectrolyte multilayer

    NASA Astrophysics Data System (ADS)

    Jackler, Guido; Czeslik, Claus; Steitz, Roland; Royer, Catherine A.

    2005-04-01

    The spatial distribution of protein molecules interacting with a planar polyelectrolyte multilayer was determined using neutron reflectometry. Staphylococcal nuclease (SNase) was used as model protein that was adsorbed to the multilayer at 22°C and 42°C . At each temperature, the protein solution was adjusted to pD -values of 4.9 and 7.5 to vary the net charge of the protein molecules. The multilayer was built up on a silicon wafer by the deposition of poly(ethylene imine) (PEI), poly(styrene sulfonate) (PSS), and poly(allylamine hydrochloride) (PAH) in the order Si-PEI-PSS- (PAH-PSS)5 . Applying the contrast variation technique, two different neutron reflectivity curves were measured at each condition of temperature and pD -value. From the analysis of the curves, protein density profiles normal to the interface were recovered. Remarkably, it has been found that SNase is partially penetrating into the polyelectrolyte multilayer after adsorption at all conditions studied. The measured neutron reflectivities are consistent with a penetration depth of 50Å at pD=4.9 and 25Å at pD=7.5 . Since SNase has an isoelectric point of pH=9.5 , it carries a net positive charge at both pD -values and interacts with the PSS final layer under electrostatic attraction conditions. However, when increasing the temperature, the amount of adsorbed protein is increasing at both pD -values indicating the dominance of entropic driving forces for the protein adsorption. Interestingly, at pD=4.9 where the protein charge is relatively high, this temperature-induced mass increase of immobilized protein is more pronounced within the polyelectrolyte multilayer, whereas at pD=7.5 , closer to the isoelectric point of SNase, raising the temperature has mainly the effect to accumulate protein molecules outside the polyelectrolyte multilayer at the water interface. It is suggested that the penetration of SNase into the polyelectrolyte multilayer is related to a complexation mechanism. The

  16. Aquifer properties determined from two analytical solutions

    SciTech Connect

    Chen, X.; Ayers, J.F.

    1998-09-01

    Many ground water flow and contaminant transport studies involve unconfined aquifers. Determination of reliable hydraulic properties of unconfined aquifers is therefore important. In the analysis of pumping test data, the quality of the determined aquifer parameters can be greatly improved by using a proper model of the aquifer system. Moench (1995) provided an analytical solution for flow to a well partially penetrating an unconfined aquifer. His solution, in contrast to the Neuman solution (1974), accounts for the noninstantaneous decline of the water table (delayed yield). Consequently, the calculated drawdown in these two solutions is different under certain circumstances, and this difference may therefore affect the computation of aquifer properties from pumping test data. This paper uses an inverse computational method to calculate four aquifer parameters as well as a delayed yield parameter, {alpha}{sub 1}, from pumping test data using both the Neuman (1974) and Moench (1995) solutions. Time-drawdown data sets from a pumping test in an unconfined alluvial aquifer near Grand Island, Nebraska, were analyzed. In single-well analyses, horizontal hydraulic conductivity values derived from the Moench solution are lower, but vertical hydraulic conductivity values are higher than those calculated from the Neuman solution. However, the hydraulic conductivity values in composite-well analyses from both solutions become very close. Furthermore, the Neuman solution produces similar hydraulic conductivity values in the single-well and composite-well analyses, but the Moench solution does not. While variable {alpha}{sub 1} seems to play a role in affecting the computation of aquifer parameters in the single-well analysis, a much smaller effect was observed in the composite-well analysis.

  17. A multiphasic model for the volume change of polyelectrolyte hydrogels

    NASA Astrophysics Data System (ADS)

    Feng, Ligang; Jia, Yuxi; Chen, Xiliang; Li, Xue; An, Lijia

    2010-09-01

    A multiphasic model for the volume change of polyelectrolyte hydrogels that takes into account conservation of mass and momentum is derived. The gradient of chemical/electrochemical potentials of water and mobile ions is taken as the driving force for the volume change of the polyelectrolyte hydrogel, which is damped by the frictional forces between different phases and balanced by the elastic restoring force of the polymer network. Employing the model constructed here, the free swelling of a spherical polyelectrolyte hydrogel immersed in salt solution is simulated by the finite element method. The simulation shows that the polyelectrolyte hydrogel swells from the surface to the interior when the concentration of the external salt solution decreases. The swelling kinetics for ordinary hydrogels with high frictional coefficient between the polymer network and water is controlled by the collective diffusion of the polymer network, while for fast-response hydrogels it is controlled by the ionic diffusion in the hydrogel.

  18. Optimal solutions of unobservable orbit determination problems

    NASA Astrophysics Data System (ADS)

    Cicci, David A.; Tapley, Byron D.

    1988-12-01

    The method of data augmentation, in the form ofa priori covariance information on the reference solution, as a means to overcome the effects of ill-conditioning in orbit determination problems has been investigated. Specifically, for the case when ill-conditioning results from parameter non-observability and an appropriatea priori covariance is unknown, methods by which thea priori covariance is optimally chosen are presented. In problems where an inaccuratea priori covariance is provided, the optimal weighting of this data set is obtained. The feasibility of these ‘ridge-type’ solution methods is demonstrated by their application to a non-observable gravity field recovery simulation. In the simulation, both ‘ridge-type’ and conventional solutions are compared. Substantial improvement in the accuracy of the conventional solution is realized by the use of these ridge-type solution methods. The solution techniques presented in this study are applicable to observable, but ill-conditioned problems as well as the unobservable problems directly addressed. For the case of observable problems, the ridge-type solutions provide an improvement in the accuracy of the ordinary least squares solutions.

  19. Spherical polyelectrolyte brushes in the presence of multivalent counterions: The effect of fluctuations and correlations as determined by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Mei, Yu; Hoffmann, Martin; Ballauff, Matthias; Jusufi, Arben

    2008-03-01

    We consider the interaction of multivalent counterions with spherical polyelectrolyte brushes (SPBs). SPBs result if linear polyelectrolyte chains (contour length 60 nm) are densely grafted to colloidal spheres of 116 nm in diameter. When dispersed in water the surface layer, consisting of chains of the strong polyelectrolyte poly(styrene sulfonic acid), will swell. Recent work [Mei , Phys. Rev. Lett. 97, 158301 (2006)] has demonstrated that spherical polyelectrolyte brushes undergo a collapse in the presence of a mixture of monovalent and multivalent counterions. The collapse crossover could be well described by a mean-field approach. Here we demonstrate that the application of a mean-field approach is well founded by simulation results done with molecular dynamics (MD). MD simulations show that over a wide range of multivalent counterion concentration the effects of ion correlation and fluctuations can be neglected. Higher-valent counterions are shown to interact strongly with the polyelectrolyte chains of the SPBs and thus exhibit a much reduced osmotic activity in the system. This reduction is the driving force for the collapse.

  20. Triggered Release of Encapsulated Cargo from Photoresponsive Polyelectrolyte Nanocomplexes

    PubMed Central

    2016-01-01

    Combining the numerous advantages of using light as a stimulus, simple free radical random copolymerization, and the easy, all-aqueous preparation of polyelectrolyte complexes (PECs), we prepared photolabile PEC nanoparticles and demonstrated their rapid degradation under UV light. As a proof of concept demonstration, the dye Nile Red was encapsulated in the PECs and successfully released into the surrounding solution as the polyelectrolyte nanocomplex carriers dissolved upon light irradiation. PMID:27526052

  1. Effect of Supporting Polyelectrolyte Multilayers and Deposition Conditions on the Formation of 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine Lipid Bilayers.

    PubMed

    Wlodek, Magdalena; Szuwarzynski, Michal; Kolasinska-Sojka, Marta

    2015-09-29

    The formation of complete supported lipid bilayers by vesicle adsorption and rupture was studied in relation to deposition conditions of vesicles and underlying cushion formed from various polyelectrolytes. 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 of various pH with or without NaCl addition. Polyelectrolyte multilayer films (PEM) were constructed by sequential adsorption of alternately charged polyelectrolytes from their solutions-layer-by-layer deposition (LBL). The mechanism of the formation of supported lipid bilayer on polyelectrolyte films was studied by quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). QCM-D allowed following the adsorption kinetics while AFM measurements verified the morphology of lipid vesicles and isolated bilayer patches on the PEM cushions providing local topological images in terms of lateral organization. Additionally, polyelectrolyte cushions were characterized with ellipsometry to find thickness and swelling properties, and their roughness was determined using AFM. It has been demonstrated that the pH value and an addition of NaCl in the buffer solution as well as the type of the polyelectrolyte cushion influence the kinetics of bilayer formation and the quality of formed bilayer patches.

  2. Heparin's solution structure determined by small-angle neutron scattering.

    PubMed

    Rubinson, Kenneth A; Chen, Yin; Cress, Brady F; Zhang, Fuming; Linhardt, Robert J

    2016-12-01

    Heparin is a linear, anionic polysaccharide that is widely used as a clinical anticoagulant. Despite its discovery 100 years ago in 1916, the solution structure of heparin remains unknown. The solution shape of heparin has not previously been examined in water under a range of concentrations, and here is done so in D2 O solution using small-angle neutron scattering (SANS). Solutions of 10 kDa heparin-in the millimolar concentration range-were probed with SANS. Our results show that when sodium concentrations are equivalent to the polyelectrolyte's charge or up to a few hundred millimoles higher, the molecular structure of heparin is compact and the shape could be well modeled by a cylinder with a length three to four times its diameter. In the presence of molar concentrations of sodium, the molecule becomes extended to nearly its full length estimated from reported X-ray measurements on stretched fibers. This stretched form is not found in the presence of molar concentrations of potassium ions. In this high-potassium environment, the heparin molecules have the same shape as when its charges were mostly protonated at pD ≈ 0.5, that is, they are compact and approximately half the length of the extended molecules.

  3. Local pH and effective pKA of weak polyelectrolytes - insights from computer simulations.

    PubMed

    Nová, Lucie; Uhlík, Filip; Košovan, Peter

    2017-03-09

    In this work we study the titration behavior of weak polyelectrolytes by computer simulations. We analyze the local pH near the chains at various conditions and provide molecular-level insight which complements the recent experimental determination of this quantity. Next, we analyze the non-ideal titration behaviour of weak polyelectrolytes in solution, calculate the effective ionization constant and compare the simulation results with theoretical predictions. In contrast with the universal behaviour with respect to chain length, we find non-universality and deviations from theory with respect to polymer concentration and permittivity of the solvent. The latter we explain in terms of counterion condensation and ion correlation effects, which lead to reversal of the non-ideal titration behaviour at very low permittivities. We discuss the impact of these findings on the interpretation of experimental results.

  4. Structural study of coacervation in protein-polyelectrolyte complexes

    NASA Astrophysics Data System (ADS)

    Chodankar, S.; Aswal, V. K.; Kohlbrecher, J.; Vavrin, R.; Wagh, A. G.

    2008-09-01

    Coacervation is a dense liquid-liquid phase separation and herein we report coacervation of protein bovine serum albumin (BSA) in the presence of polyelectrolyte sodium polystyrene sulfonate (NaPSS) under varying solution conditions. Small-angle neutron scattering (SANS) measurements have been performed on above protein-polyelectrolyte complexes to study the structural evolution of the process that leads to coacervation and the phase separated coacervate as a function of solution pH , protein-polyelectrolyte ratio and ionic strength. SANS study prior to phase separation on the BSA-NaPSS complex shows a fractal structure representing a necklace model of protein macromolecules randomly distributed along the polystyrene sulfonate chain. The fractal dimension of the complex decreases as pH is shifted away from the isoelectric point (˜4.7) of BSA protein, which indicates the decrease in the compactness of the complex structure due to increase in the charge repulsion between the protein macromolecules bound to the polyelectrolyte. Concentration-dependence studies of the polyelectrolyte in the complex suggest coexistence of two populations of polyelectrolytes, first one fully saturated with proteins and another one free from proteins. Coacervation phase has been obtained through the turbidity measurement by varying pH of the aqueous solution containing protein and polyelectrolyte from neutral to acidic regime to get them to where the two components are oppositely charged. The spontaneous formation of coacervates is observed for pH values less than 4. SANS study on coacervates shows two length scales related to complex aggregations (mesh size and overall extent of the complex) hierarchically branched to form a larger network. The mesh size represents the distance between cross-linked points in the primary complex, which decreases with increase in ionic strength and remains the same on varying the protein-polyelectrolyte ratio. On the other hand, the overall extent of the

  5. Charge regulation and local dielectric function in planar polyelectrolyte brushes.

    PubMed

    Kumar, Rajeev; Sumpter, Bobby G; Kilbey, S Michael

    2012-06-21

    Understanding the effect of inhomogeneity on the charge regulation and dielectric properties, and how it depends on the conformational characteristics of the macromolecules is a long-standing problem. In order to address this problem, we have developed a field-theory to study charge regulation and local dielectric function in planar polyelectrolyte brushes. The theory is used to study a polyacid brush, which is comprised of chains end-grafted at the solid-fluid interface, in equilibrium with a bulk solution containing monovalent salt ions, solvent molecules, and pH controlling acid. In particular, we focus on the effects of the concentration of added salt and pH of the bulk in determining the local charge and dielectric function. Our theoretical investigations reveal that the dipole moment of the ion-pairs formed as a result of counterion adsorption on the chain backbones play a key role in affecting the local dielectric function. For polyelectrolytes made of monomers having dipole moments lower than the solvent molecules, dielectric decrement is predicted inside the brush region. However, the formation of ion-pairs (due to adsorption of counterions coming from the dissociation of added salt) more polar than the solvent molecules is shown to increase the magnitude of the dielectric function with respect to its bulk value. Furthermore, an increase in the bulk salt concentration is shown to increase the local charge inside the brush region.

  6. 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.

  7. Determining rhenium in weak processing solutions

    SciTech Connect

    Koval', L.B.

    1986-09-01

    Analytical methods of determining rhenium in production solutions and solid materials almost always include a stage of separating molybdenum, since these elements occur together in molybdenum ores and concentrates. The authors have developed a method of analysis for rhenium in low-concentration industrial solutions containing a complicated set of impurities. The molybdenum is separated from rhenium in a separating funnel and the acidity is brought to 1 M. A 20% solution of KCNS is added together with ascorbic acid. The funnel is shaken for 1-2 min and left to stand until the molybdenum is completely reduced (5-10 min), and then the thiocyanate complex of the molybdenum is extracted with diethyl ether. The lower water layer is transferred to a volumetric flask and the necessary reagents are added to reduce the rhenium and produce the yellow-orange rhenium thiocyanate complex. The peak optical density of the complex is measured with a photocolorimeter and the absorption spectra are recorded with a spectrophotometer.

  8. Effects of chain rigidity on the adsorption of a polyelectrolyte chain on mixed lipid monolayer: a Monte Carlo study.

    PubMed

    Duan, Xiaozheng; Ding, Mingming; Zhang, Ran; Li, Liangyi; Shi, Tongfei; An, Lijia; Huang, Qingrong; Xu, Wen-Sheng

    2015-05-14

    We apply Monte Carlo simulation to explore the adsorption of a positively charged polyelectrolyte on a lipid monolayer membrane, composed of electronically neutral, monovalent anionic and mulvitalent anionic phospholipids. We systematically assess the influence of various factors, including the intrinsic rigidity of the polyelectrolyte chain, the bead charge density of the polyelectrolyte, and the ionic strength of the saline solution, on the interfacial structural properties of the polyelectrolyte/monolayer complex. The enhancement of the polyelectrolyte chain intrinsic rigidity reduces the polyelectrolyte conformational entropy loss and the energy gains in electrostatic interaction, but elevates the segregated anionic lipid demixing entropy loss. This energy-entropy competition results in a nonmonotonic dependence of the polyelectrolyte/monolayer association strength on the degree of chain rigidity. The semiflexible polyelectrolyte, i.e., the one with an intermediate degree of chain rigidity, is shown to associate onto the ternary membane below a higher critical ionic concentration. In this ionic concentration regime, the semiflexible polyelectrolyte binds onto the monolayer more firmly than the pancake-like flexible one and exhibits a stretched conformation. When the chain is very rigid, the polyelectrolyte with bead charge density Zb = +1 exhibits a larger tail and tends to dissociate from the membrane, whereas the one with Zb = +2 can still bind onto the membrane in a bridge-like conformation. Our results imply that chain intrinsic rigidity serves as an efficient molecular factor for tailoring the adsorption/desorption transition and interfacial structure of the polyelectrolyte/monolayer complex.

  9. 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

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

    SciTech Connect

    Oded, Meirav; Kelly, Stephen T.; Gilles, Mary K.; Müller, Axel H. E.; Shenhar, Roy

    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 segments 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.

  11. Effects of carboxylic polyelectrolytes on the growth of calcium carbonate

    NASA Astrophysics Data System (ADS)

    Euvrard, M.; Martinod, A.; Neville, A.

    2011-02-01

    In this paper experimental results are reported on the effects of anionic polyelectrolytes (polyaspartate and polymaleic acid) on the formation of calcium carbonate on a metallic substrate. An experimental procedure which permits the in situ and real-time growth of particles in the micrometric range to be followed was used. By using image analysis, the determination of the morphometric parameters of crystals was done. Jointly, an adsorption study of the polyelectrolytes on calcite was conducted to complement the study of the interactions between polyelectrolytes and crystals. It has been shown that polyaspartate (PASP) and polymaleic acid (PMA) may influence the nucleation/growth process of calcium carbonate. At low concentrations (of about 1×10 -5 mol dm -3), PMA and PASP reduce the surface coverage of deposits on the substrate by decreasing the number of micron size particles and/or the sizes of mineral. When the polyelectrolytes were added after 10 min of the experiment, they significantly decreased the growth rate of the crystals. Following the adsorption of the polyelectrolytes on the submicron size crystals of calcite complements this research. Langmuir isotherms show that PASP and PMA adsorb on calcite suggesting that the polyelectrolytes may block the active sites of growth of crystals.

  12. Orbit Determination Using GPS Navigation Solution

    NASA Astrophysics Data System (ADS)

    Gomes, V. M.; Kuga, H. K.; Chiaradia, A. P.; Prado, A. F.

    The Global Positioning System (GPS) is a satellite navigation system that allows the users to determine position, velocity and the time with high precision. Its main purposes are aid to radionavigation in three dimensions with high precision positioning, navigation in real time, global coverage and quick acquisition of data sent by the GPS satellites. The purpose of this work is to compute in real time a state vector composed of position, velocity, GPS receiver clock bias and drift of the TOPEX/POSEIDON satellite by filtering the raw navigation solutions obtained by the on-board receiver. In this work the Kalman filter is used to estimate the state vector based on the incoming observations from the receiver. Such a computational algorithm processes measurements to produce minimum variance estimates of the system using knowledge of the dynamics and of the measurements, statistics of the measurement errors, and information about initial conditions. The Kalman filter is used due to its robustness in real time applications, without unnecessary storage of observations, as they can be processed while being collected. The filter dynamic model includes perturbation due to geopotential and the bias and drift are modeled as random walk processes. The observations include the raw navigation solution composed of position and bias. The velocity components of the navigation solution are not used due to its low accuracy. Several simulations are done comprising three days of observations of TOPEX/POSEINDON receiver, which are processed by the proposed algorithm. A comparison is done between the estimated state vector and the precise orbit ephemeris (POE) produced by JPL/NASA. Other characteristics are also analyzed, including effects of truncated dynamic model, step-size of integration, SA effect, to show the impact on the procedure in terms of accuracy and computational burden.

  13. Interfacial tension of polyelectrolyte complex coacervate phases.

    SciTech Connect

    Qin, Jian; Priftis, Dimitrios; Farina, R; Perry, Sarah L.; Leon, Lorraine F.; Whitmer, Jonathan; Hoffmann, Kyle; Tirrell, Matthew; de Pablo, Juan J.

    2014-06-01

    We consider polyelectrolyte solutions which, under suitable conditions, phase separate into a liquid-like coacervate phase and a coexisting supernatant phase that exhibit an extremely low interfacial tension. Such interfacial tension provides the basis for most coacervate-based applications, but little is known about it, including its dependence on molecular weight, charge density, and salt concentration. By combining a Debye-Huckel treatment for electrostatic interactions with the Cahn-Hilliard theory, we derive explicit expressions for this interfacial tension. In the absence of added salts, we find that the interfacial tension scales as N-3/2(eta/eta(c)-1)(3/2) near the critical point of the demixing transition, and that it scales as eta(1/2) far away from it, where N is the chain length and eta measures the electrostatic interaction strength as a function of temperature, dielectric constant, and charge density of the polyelectrolytes. For the case with added salts, we find that the interfacial tension scales with the salt concentration psi as N-1/4(1-psi/psi(c))(3/2) near the critical salt concentration psi(c). Our predictions are shown to be in quantitative agreement with experiments and provide a means to design new materials based on polyelectrolyte complexation.

  14. 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.

  15. [Determination of taste sensitivity with mixed solutions].

    PubMed

    Marco Algarra, R

    1990-01-01

    In the second part of our study we present the results of the mixture of four basic tastes in comparison with those of the simple solutions, mea ng as well the fatigue phenomenon with the mixed solutions.

  16. Aligned Carbon Nanotube Thin Films from Liquid Crystal Polyelectrolyte Inks.

    PubMed

    Tune, Daniel D; Blanch, Adam J; Shearer, Cameron J; Moore, Katherine E; Pfohl, Moritz; Shapter, Joseph G; Flavel, Benjamin S

    2015-11-25

    Single walled carbon nanotube thin films are fabricated by solution shearing from high concentration sodium nanotubide polyelectrolyte inks. The solutions are produced by simple stirring of the nanotubes with elemental sodium in dimethylacetamide, and the nanotubes are thus not subject to any sonication-induced damage. At such elevated concentrations (∼4 mg mL(-1)), the solutions exist in the liquid crystal phase and during deposition this order is transferred to the films, which are well aligned in the direction of shear with a 2D nematic order parameter of ∼0.7 determined by polarized absorption measurements. Compared to similarly formed films made from superacids, the polyelectrolyte films contain smaller bundles and a much narrower distribution of bundle diameters. After p-doping with an organic oxidizer, the films exhibit a very high DC electrical to optical conductivity ratio of σ(DC)/σ(OP) ∼ 35, corresponding to a calculated DC conductivity of over 7000 S cm(-1). When very thin (T550 ∼ 96%), smooth (RMS roughness, R(q) ∼ 2.2 nm), and highly aligned films made via this new route are used as the front electrodes of carbon nanotube-silicon solar cells, the power conversion efficiency is almost an order of magnitude greater than that obtained when using the much rougher (R(q) ∼ 20-30 nm) and less conductive (peak σ(DC)/σ(OP) ∼ 2.5) films formed by common vacuum filtration of the same starting material, and having the same transmittance.

  17. Direct Determination of Nonmetals in Solution with Atomic Spectrometry.

    ERIC Educational Resources Information Center

    McGregor, David A.; And Others

    1988-01-01

    Addresses solution nonmetal determinations on a fundamental level. Characterizes research in this area of chemical instrumentation. Discusses the fundamental limitations of nonmetal atomic spectrometry, the status of nonmetals and atomic spectroscopic techniques, and current directions in solution nonmetal determinations. (CW)

  18. Remarks on Polyelectrolyte Conformation

    NASA Astrophysics Data System (ADS)

    de Gennes, P. G.; Pincus, P.; Velasco, R. M.; Brochard, F.

    Nous discutons des conformations de polymères linéaires chargés en faisant les hypothèses suivantes : a) la chaĬne sans charge est flexible, b) la force éctrostatique domine les interactions monomère-monomère c) il n'y a pas de sels. 1) Pour le cas dilué (chaĬne non enchevetrees) en corrigeant le calcul self-consistant fait récemment par Richmond [1a], on trouve une taille des polyions égale a = R ND, qui est une fonction linéaire de l'indice de polymérisation N. Ce rèsultat est en accord avec les prècèdents travaux de Hermans et Overbeek [1b], Kuhn, Kunzle et Katchalsky [1c]. 2) Il existe un domaine pour des concentrations très petites c (c** < c < c*) oò les interactions èlectrostatiques entre les polyions sont supèrieures aux ènergies thermiques, il semble donc possible que les polyions puissent former un rèseau pèriodique à trois dimensions. Nèanmoins, il semble difficile de mettre en èvidence un rèseau si diluè. 3) Jusqu'ici toutes les expériences avec les polyélectrolytes sans sels ont été pratiquement faites à des concentrations c > c*, pour lesquelles les différentes cha.nes sont enchevêtrées. Pour discuter ce régime on s.intéresse uniquement au cas où la charge par unité de longueur est près du (ou audessus du) seuil de condensation, donc il existe une seule longueur ξ(c) caractérisant les corrélations; à trois dimensions 03BE a le même comportement que le rayon de Debye pour les contre-ions. On a considéré quelques conformations possibles : a) un réseau hexagonal de batonnets; b) un réseau cubique de batonnets; c) une phase isotrope de cha.nes partiellement flexibles. Les différentes structures formées de batonnets semblent avoir la même énergie électrostatique. Ce fait suggère que la phase isotrope peut être la plus favorable. On analyse cette dernière phase en utilisant les mêmes méthodes qui se sont révélées efficaces pour les solutions des polymères neutres. Dans le modèle isotrope

  19. Responsive interfaces grafted with polyelectrolyte or polyampholyte

    NASA Astrophysics Data System (ADS)

    Tran, Yvette; Sanjuan, Sarah; Pantoustier, Nadège; Perrin, Patrick

    2007-01-01

    We synthesize and investigate the swelling behavior of polyelectrolyte and polyampholyte grafted layers on planar substrates. The polymer brushes are prepared using the "grafting from" method with surface-initiated atom transfer radical polymerization (ATRP), which allows a good control of the chain length and a weak polydispersity of chains. Ellipsometry and neutron reflectivity are used to determine the swollen thickness and the monomer volume fraction profile. The scaling behavior of the neutral polymer brush and the strong polyelectrolyte brush is in good agreement with scaling laws predicted by mean-field theories. The swelling behavior of the pH-responsive polybase brush is between the situation of the neutral polymer brush in good solvent and the quenched polyelectrolyte. Polyampholyte brushes are contracted in the pH range of zero net charge. A barrier zone likely due to the attraction between positively and negatively charged monomer units is observed in the density profile. This barrier could prevent from a collective ionization of the chains and reduce the expected collapse of the brush.

  20. The effects of salts on polyelectrolyte systems

    NASA Astrophysics Data System (ADS)

    Zissu, Jonathan Adam

    The effects of salts on the behavior of polyelectrolyte systems were investigated. The phase behavior of polyelectrolyte solutions in the presence of added salt was calculated by combining the free energies due to Flory-Huggins mixing and Debye-Huckel electrostatics, with both terms modified for our polyelectrolyte solutions. Using the calculated phase diagrams, we found that most results give a typical polymer-solvent-nonsolvent phase diagram, with the solvent acting as a "nonsolvent" (since we assume that the polymer-solvent interaction parameter, chi, is positive) and the dissociated salt acting as a "solvent". However, for high charges of the salt ions, we found a completely different phase diagram, one which can be explained by a "salting out effect" where the addition of salt over a certain concentration threshold causes complete phase separation over all concentrations of polymer and solvent. Also, the density and repulsive force profiles for a system comprised of two parallel, planar, uncharged surfaces uniformly covered with poly electrolyte brushes in an electrolyte solution was calculated using a computational enumeration of a one-dimensional random walk model. For large surface separations, we found three different density profiles: a Gaussian regime when kappa is large, a stretched regime when kappa is intermediate in value, and a "pancake" regime, with chains collapsed onto their grafted surface, when kappa is small. For small surface separations, the first two regimes are replaced with an interpenetrating regime, where the density is essentially uniform across the entire region between the surfaces. For intermediate surface separations, the repulsive force scales as exp (- Ak12 D), unlike what is expected using Gouy-Chapman theory.

  1. Optically active polyelectrolyte multilayers as membranes for chiral separations.

    PubMed

    Rmaile, Hassan H; Schlenoff, Joseph B

    2003-06-04

    Ultrathin films of chiral polyelectrolyte complex, prepared by the multilayering process, exhibit selectivity in the membrane separations of optically active compounds, such as l- and d-ascorbic acid. The flux through these polyelectrolyte multilayers, PEMUs, is exceptionally high and may be controlled by the concentration of salt present in the permeating solutions. Both in-situ ATR-FTIR and chiral capillary electrochromatography indicate that flux selectivity is mainly kinetically controlled, stemming from a difference in diffusion rates of various enantiomers through PEMUs, rather than a difference in partitioning.

  2. Sonication-assisted synthesis of polyelectrolyte-coated curcumin nanoparticles.

    PubMed

    Zheng, Zhiguo; Zhang, Xingcai; Carbo, Daniel; Clark, Cheryl; Nathan, Cherie-Ann; Lvov, Yuri

    2010-06-01

    A new method of nanoparticle formulation for poorly water-soluble materials was demonstrated for curcumin. The drug was dissolved in organic solvent that is miscible with water (ethanol), and drug nucleation was initiated by gradual worsening of the solution by the addition of an aqueous polyelectrolyte assisted by ultrasonication. Curcumin crystals of 60-100 nm size were obtained depending on the component concentrations, sonication power, and initial solvent. Layer-by-layer shell assembly with biocompatible polyelectrolytes was used to provide a particle coating with a high surface potential and the stabilization of drug nanocolloids. Polyelectrolyte layer-by-layer encapsulation allowed sustained drug release from nanoparticles over the range of 10-20 h.

  3. Ion transport through electrolyte/polyelectrolyte multi-layers

    NASA Astrophysics Data System (ADS)

    Femmer, Robert; Mani, Ali; Wessling, Matthias

    2015-06-01

    Ion transport of multi-ionic solutions through layered electrolyte and polyelectrolyte structures are relevant in a large variety of technical systems such as micro and nanofluidic devices, sensors, batteries and large desalination process systems. We report a new direct numerical simulation model coined EnPEn: it allows to solve a set of first principle equations to predict for multiple ions their concentration and electrical potential profiles in electro-chemically complex architectures of n layered electrolytes E and n polyelectrolytes PE. EnPEn can robustly capture ion transport in sub-millimeter architectures with submicron polyelectrolyte layers. We proof the strength of EnPEn for three yet unsolved architectures: (a) selective Na over Ca transport in surface modified ion selective membranes, (b) ion transport and water splitting in bipolar membranes and (c) transport of weak electrolytes.

  4. Ion transport through electrolyte/polyelectrolyte multi-layers

    PubMed Central

    Femmer, Robert; Mani, Ali; Wessling, Matthias

    2015-01-01

    Ion transport of multi-ionic solutions through layered electrolyte and polyelectrolyte structures are relevant in a large variety of technical systems such as micro and nanofluidic devices, sensors, batteries and large desalination process systems. We report a new direct numerical simulation model coined EnPEn: it allows to solve a set of first principle equations to predict for multiple ions their concentration and electrical potential profiles in electro-chemically complex architectures of n layered electrolytes E and n polyelectrolytes PE. EnPEn can robustly capture ion transport in sub-millimeter architectures with submicron polyelectrolyte layers. We proof the strength of EnPEn for three yet unsolved architectures: (a) selective Na over Ca transport in surface modified ion selective membranes, (b) ion transport and water splitting in bipolar membranes and (c) transport of weak electrolytes. PMID:26111456

  5. A Molecular Imprinting Strategy Employing Polyelectrolyte Multilayers

    NASA Astrophysics Data System (ADS)

    Olugebefola, Solar C.

    2005-03-01

    Polyelectrolyte multilayers were assembled from poly(allylamine hydrochloride) (PAH), poly(acrylic acid) (PAA) and poly(acrylic acid-r-vinyl benzyl acetate) (xPAA), derivatized from PAA. The pHs of polymer assembly solutions were controlled to yield high surface area film morphologies for adsorption. Assembled films were photo crosslinked in the presence of adsorbed template molecules and the template removed to yield selective binding sites. Quartz crystal microbalance measurements of adsorption onto films templated with bovine serum albumin show higher affinity for BSA compared to films crosslinked with no templating.

  6. The binding of divalent metal ions to polyelectrolytes in mixed counterion systems. II. Dextransulfate-Mg2+ and dextransulfate-Ca2+ in solutions containing added NaCl or KCl.

    PubMed

    Joshi, Y M; Kwak, J C

    1981-02-01

    Measurements of magnesium and calcium ion activities in solutions of the polyelectrolyte dextransulfate, with added sodium chloride or potassium chloride are presented. A two wavelength dye spectrophotometric method is used. Dextransulfate concentrations Cp (expressed as moles sulfate ion/litre) vary between 0.001 and 0.007, total ionic strengths between 0.005 and 0.08 mole/XXX. Divalent metal ion concentrations are varied between 0 and 1.2 Cp. The results for the metal ion activities are expressed in the form of parameters theta2 = C2/Cp (C(2bp) = bound divalent metal ion concentration) and K2 = theta2/(C2-C2b). For each divalent/univalent counterion pair the values obtained for theta2 and K2 as a function of C2,Cp, and ionic strength are compared to predictions of the "two variable theory" developed for these mixed counterion systems by Manning. This comparison shows that the observed decrease in theta2 with increasing ionic strength at fixed C2 and Cp is generally well predicted by the two variable theory. The extent of divalent ion binding at a given C2, Cp, and ionic strength is largest for the Ca/Na counterion combination, and lowest for the Mg/K combination.

  7. Self-assembly in block polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Vishnyakov, Aleksey; Neimark, Alexander V.

    2011-02-01

    The self-consistent field theory (SCFT) complemented with the Poisson-Boltzmann equation is employed to explore self-assembly of polyelectrolyte copolymers composed of charged blocks A and neutral blocks B. We have extended SCFT to dissociating triblock copolymers and demonstrated our approach on three characteristic examples: (1) diblock copolymer (AB) melt, (2) symmetric triblock copolymer (ABA) melt, (3) triblock copolymer (ABA) solution with added electrolyte. For copolymer melts, we varied the composition (that is, the total fraction of A-segments in the system) and the charge density on A blocks and calculated the phase diagram that contains ordered mesophases of lamellar, gyroid, hexagonal, and bcc symmetries, as well as the uniform disordered phase. The phase diagram of charged block copolymer melts in the charge density - system composition coordinates is similar to the classical phase diagram of neutral block copolymer melts, where the composition and the Flory mismatch interaction parameter χ _{AB} are used as variables. We found that the transitions between the polyelectrolyte mesophases with the increase of charge density occur in the same sequence, from lamellar to gyroid to hexagonal to bcc to disordered morphologies, as the mesophase transitions for neutral diblocks with the decrease of χ _{AB}. In a certain range of compositions, the phase diagram for charged triblock copolymers exhibits unexpected features, allowing for transitions from hexagonal to gyroid to lamellar mesophases as the charge density increases. Triblock polyelectrolyte solutions were studied by varying the charge density and solvent concentration at a fixed copolymer composition. Transitions from lamellar to gyroid and gyroid to hexagonal morphologies were observed at lower polymer concentrations than the respective transitions in the similar neutral copolymer, indicating a substantial influence of the charge density on phase behavior.

  8. Strong and weak adsorptions of polyelectrolyte chains onto oppositely charged spheres

    NASA Astrophysics Data System (ADS)

    Cherstvy, Andrey; Winkler, Roland

    2007-03-01

    We investigate the complexation of long thin polyelectrolyte chains with the oppositely charged sphere. In the limit of strong adsorption, when strongly charged polyelectrolyte chains adapt definite wrapped conformations on the sphere surface (solenoidal, tennis-ball-like, etc.), we analytically solve the linear Poisson-Boltzmann equation and calculate the electrostatic potential and energy of the complex. We discuss some biological applications of the obtained results, including those for DNA wrapping in the nucleosome core particles and for aggregate formation of DNA with oppositely charged nano-spheres studied in vitro. For weak adsorption, when a flexible weakly charged polyelectrolyte chain is localized next to the sphere in solution, we solve the Edwards equation for the chain conformations in the Hulth'en potential. The latter is used as an approximation for the screened Debye-H"uckel potential of the sphere. For arbitrary sphere radius, we predict the critical conditions for polyelectrolyte adsorption as a coupling between critical sphere and polyelectrolyte charge densities, sphere radius, temperature, and ionic strength in solution. We find that the critical charge density of the sphere exhibits a distinctively different dependence on the Debye screening length than for polyelectrolyte adsorption onto a flat surface. We compare our findings with experimental measurements on complex formation of various polyelectrolytes (DNA, PSS, AMPS, etc.) with oppositely charged colloidal particles and cationic micelles, where similar universal scaling relations for the sphere charge density have been revealed.

  9. Dynamic Multiscale Simulation of Polyelectrolyte Nanoassemblies

    DTIC Science & Technology

    2008-08-21

    REPORT Dynamic Multiscale Simulation of Polyelectrolyte Nanoassemblies 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: The goal of this project is to...Std. Z39.18 - 31-May-2008 Dynamic Multiscale Simulation of Polyelectrolyte Nanoassemblies Report Title ABSTRACT The goal of this project is to...Total Number: Sub Contractors (DD882) Inventions (DD882) Final Progress Report Dynamic Multiscale Simulation of Polyelectrolyte Nanoassemblies

  10. Determination of total solutes in synfuel wastewaters

    SciTech Connect

    Wallace, J.R.; Bonomo, F.S.

    1984-03-01

    Efforts to investigate both lyophilization and the measurement of colligative properties as an indication of total solute content are described. The objective of the work described is to develop a method for measuring total dissolved material in retort wastewaters which is simple and rugged enough to be performed in a field laboratory in support of pollution control tests. The analysis should also be rapid enough to provide timely and pertinent data to the pollution control plant operator. To be of most value, the technique developed also should be applicable to other synfuel wastewaters, most of which contain similar major components as oil shale retort waters. 4 references, 1 table.

  11. Nanoparticle gel electrophoresis: soft spheres in polyelectrolyte hydrogels under the Debye-Hückel approximation.

    PubMed

    Li, Fei; Allison, Stuart A; Hill, Reghan J

    2014-06-01

    A mathematical model for electrophoresis of polyelectrolyte coated nanoparticles (soft spheres) in polyelectrolyte hydrogels is proposed, and evaluated by comparison to literature models for bare-sphere gel electrophoresis and free-solution electrophoresis. The utilities of approximations based on the bare-particle electrophoretic mobility, free-solution mobility, and electroosmotic flow in hydrogels are explored. Noteworthy are the influences of the particle-core dielectric constant and overlap of the polyelectrolyte shell. The present theory, which neglects ion-concentration and charge-density perturbations, indicates that the gel electrophoretic mobilities of metallic-core nanoparticles in polyelectrolyte gels can be qualitatively different than for their non-metallic counterparts. These insights will be beneficial for interpreting nanoparticle gel-electrophoresis data, optimizing electrophoretic separations, and engineering nanoparticles for technological applications. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Wrap-and-Strip Technology of Protein-Polyelectrolyte Complex for Biomedical Application.

    PubMed

    Shiraki, Kentaro; Kurinomaru, Takaaki; Tomita, Shunsuke

    2016-01-01

    A polyelectrolyte is a polymer composed of repeating units of an electrolyte group that enables reversible complex formation with proteins in aqueous solutions. This review introduces "wrap-and-strip" technology of protein-polyelectrolyte complex (PPC) by noncovalent interaction. Storage: protein is stabilized against physical and chemical stresses. Enrichment: precipitation through PPC can be used as an enrichment method without irreversible unfolding. Catalytic activity switch: a complementary charged pair of polyelectrolytes functions as a reversible enzyme activity switch. Hyperactivation: a specific combination of a polyelectrolyte and substrate enhances enzyme activity by one order of magnitude compared with an enzyme alone. Stabilization: PPC increases protein stability against chemical and physical stresses, such as covalently modified polyethylene glycosylated protein. Simple PPC-based technology can expand the applicable fields of soluble proteins in aqueous solutions.

  13. 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

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

    SciTech Connect

    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

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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

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

    SciTech Connect

    Hoffmann, Ingo; Farago, Bela; Schweins, Ralf; Falus, Peter; Sharp, Melissa; Prévost, Sylvain; Gradzielski, Michael

    2015-08-21

    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 different 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

  18. Configurational properties of a single semiflexible polyelectrolyte

    NASA Astrophysics Data System (ADS)

    Ghosh, K.; Carri, Gustavo A.; Muthukumar, M.

    2001-09-01

    Using a variational calculation, we have considered the effect of chain length, intrinsic backbone stiffness, solvent quality, and salt concentration on the behavior of a single semiflexible polyelectrolyte in dilute solution. Explicitly, we have calculated the radius of gyration (Rg) and effective persistence length for different solvent qualities and salt concentrations. For an isolated semiflexible polyelectrolyte with increasing molecular weight, there can be five regimes with effective exponent ν (defining the molecular weight dependence of Rg) being 1, 1/2, 1, 2/5, and 1/2 in the absence of nonelectrostatic excluded volume interaction. This suggests a double crossover behavior from rodlike to Gaussian and then to Gaussian again as the chain length is increased. During the second crossover, ν can be as high as 1, although the actual value of Rg is order of magnitude smaller than the rodlike value. There can be another regime in this second crossover where the apparent exponent is 2/5 due to additional self-screening arising from counterions of the polymer. This self-screening can significantly reduce Rg, although the asymptotic exponent 2/5 may not be observable due to physical constraints. A thorough analysis of the crossover behavior is presented.

  19. Chain Conformation and Dynamics in Spin-Assisted Weak Polyelectrolyte Multilayers

    DOE PAGES

    Zhuk, Aliaksandr; Selin, Victor; Zhuk, Iryna; ...

    2015-03-13

    In this paper, we report on the effect of the deposition technique on film layering, stability, and chain mobility in weak polyelectrolyte layer-by-layer (LbL) films. Ellipsometry and neutron reflectometry (NR) showed that shear forces arising during spin-assisted assembly lead to smaller amounts of adsorbed polyelectrolytes within LbL films, result in a higher degree of internal film order, and dramatically improve stability of assemblies in salt solutions as compared to dip-assisted LbL assemblies. The underlying flattening of polyelectrolyte chains in spin-assisted LbL films was also revealed as an increase in ionization degree of the assembled weak polyelectrolytes. As demonstrated by fluorescencemore » recovery after photobleaching (FRAP), strong binding between spin-deposited polyelectrolytes results in a significant slowdown of chain diffusion in salt solutions as compared to dip-deposited films. Moreover, salt-induced chain intermixing in the direction perpendicular to the substrate is largely inhibited in spin-deposited films, resulting in only subdiffusional (<2 Å) chain displacements even after 200 h exposure to 1 M NaCl solutions. Finally, this persistence of polyelectrolyte layering has important ramifications for multistage drug delivery and optical applications of LbL assemblies.« less

  20. Chain Conformation and Dynamics in Spin-Assisted Weak Polyelectrolyte Multilayers

    SciTech Connect

    Zhuk, Aliaksandr; Selin, Victor; Zhuk, Iryna; Belov, Benjamin; Ankner, John F.; Sukhishvili, Svetlana A.

    2015-03-13

    In this paper, we report on the effect of the deposition technique on film layering, stability, and chain mobility in weak polyelectrolyte layer-by-layer (LbL) films. Ellipsometry and neutron reflectometry (NR) showed that shear forces arising during spin-assisted assembly lead to smaller amounts of adsorbed polyelectrolytes within LbL films, result in a higher degree of internal film order, and dramatically improve stability of assemblies in salt solutions as compared to dip-assisted LbL assemblies. The underlying flattening of polyelectrolyte chains in spin-assisted LbL films was also revealed as an increase in ionization degree of the assembled weak polyelectrolytes. As demonstrated by fluorescence recovery after photobleaching (FRAP), strong binding between spin-deposited polyelectrolytes results in a significant slowdown of chain diffusion in salt solutions as compared to dip-deposited films. Moreover, salt-induced chain intermixing in the direction perpendicular to the substrate is largely inhibited in spin-deposited films, resulting in only subdiffusional (<2 Å) chain displacements even after 200 h exposure to 1 M NaCl solutions. Finally, this persistence of polyelectrolyte layering has important ramifications for multistage drug delivery and optical applications of LbL assemblies.

  1. Electrophoresis of DNA and other polyelectrolytes: Physical mechanisms

    NASA Astrophysics Data System (ADS)

    Viovy, Jean-Louis

    2000-07-01

    The dramatic recent advances in molecular biology, which have opened a new era in medicine and biotechnology, rely on improved techniques to study large molecules. Electrophoresis is one of the most important of these. Separation of DNA by size, in particular, is at the heart of genome mapping and sequencing and is likely to play an increasing role in diagnosis. This article reviews, from the point of view of a physicist, the mechanisms responsible for electrophoretic separation of polyelectrolytes. This separation is mainly performed in gels, and a wide variety of migration mechanisms can come into play, depending on the polyelectrolyte's architecture, on the electric fields applied, and on the properties of the gel. After a brief review of the thermodynamic and electrohydrodynamic principles relating to polyelectrolyte solutions, the author treats the phenomenology of electrophoresis and describes the conceptual and theoretical tools in the field. The reptation mechanisms, by which large flexible polyelectrolytes thread their way through the pores of the gel matrix, play a prominent role. Biased reptation, the extension of this model to electrophoresis, provides a very intuitive framework within which numerous physical ideas can be introduced and discussed. It has been the most popular theory in this domain, and it remains an inspiring concept for current development. There have also been important advances in experimental techniques such as single-molecule viodeomicroscopy and the development of nongel separation media and mechanisms. These, in turn, form the basis for fast-developing and innovative technologies like capillary electrophoresis, electrophoresis on microchips, and molecular ratchets.

  2. Theory of competitive counterion adsorption on flexible polyelectrolytes: divalent salts.

    PubMed

    Kundagrami, Arindam; Muthukumar, M

    2008-06-28

    The counterion distribution around an isolated flexible polyelectrolyte in the presence of a divalent salt is evaluated using the adsorption model [M. Muthukumar, J. Chem. Phys. 120, 9343 (2004)] that considers the Bjerrum length, salt concentration, and local dielectric heterogeneity as physical variables in the system. Self-consistent calculations of effective charge and size of the polymer show that divalent counterions replace condensed monovalent counterions in competitive adsorption. The theory further predicts that at modest physical conditions for a flexible polyelectrolytes such as sodium polystyrene sulfonate in aqueous solutions polymer charge is compensated and reversed with increasing divalent salt. Consequently, the polyelectrolyte shrinks and reswells. Lower temperatures and higher degrees of dielectric heterogeneity between chain backbone and solvent enhance condensation of all species of ions. Complete diagrams of states for the effective charge calculated as functions of the Coulomb strength and salt concentration suggest that (a) overcharging requires a minimum Coulomb strength and (b) progressively higher presence of salt recharges the polymer due to either electrostatic screening (for low Coulomb strengths) or coion condensation (for high Coulomb strengths). Consideration of ion-bridging by divalent counterions leads to a first-order collapse of polyelectrolytes in modest presence of divalent salts and at higher Coulomb strengths. The authors' theoretical predictions are in agreement with the generic results from experiments and simulations.

  3. 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.

  4. Macrojunctions ordering in polyelectrolyte hydrogels

    NASA Astrophysics Data System (ADS)

    Török, Gy; Lebedev, V. T.; Cser, L.; Buyanov, A. L.; Revelskaya, L. G.

    2000-03-01

    We studied the structure of polyelectrolyte hydrogels of sodium polyacrylate cross-linked by macromolecular allyldextran (supergels). Using high-resolution SANS we have found the specific ordering of macrojunctions (structure's period ∼130 nm) that may be reliable for the network's anomaly swelling.

  5. Electrophoresis of a polyelectrolyte through a nanopore

    NASA Astrophysics Data System (ADS)

    Ghosal, Sandip

    2006-11-01

    Translocation of polyelectrolytes (such as DNA) through natural and artificial nanopores can be detected with single molecule resolution by monitoring the resistivity of the pore (Nature Biotechnology (2001) 19, pp. 248). The technique could evolve into a technology for sequencing DNA at speeds that are orders of magnitude faster than what is currently possible. Here a hydrodynamic model to determine the electrophoretic speed of a polyelectrolyte through a nanopore is presented. It is assumed that the speed is determined by a balance of electrical and viscous forces arising from within the pore and that classical continuum electrostatics and hydrodynamics may be considered applicable. An explicit formula for the translocation speed as a function of the pore geometry and other physical parameters is obtained and is shown to be consistent with experimental measurements on DNA translocation through nanopores in silicon membranes. Secondary effects such as the hydrodynamic friction on the part of the polymer outside the nanopore must also be considered to explain the weak dependence of the translocation speed on the polymer length.

  6. Silver Ion Polyelectrolyte Container as a Sensitive Quartz Crystal Microbalance Gas Detector.

    PubMed

    Tsuge, Yosuke; Moriyama, Yukari; Tokura, Yuki; Shiratori, Seimei

    2016-11-01

    A polyelectrolyte film containing metastable silver ions was applied as a quartz crystal microbalance (QCM) gas detector. The polyelectrolyte film was obtained by immersing a polyelectrolyte with numerous amine groups in a metal ion solution. The QCM detector with silver ions responded to a very low methylmercaptan gas concentration (20 ppb) but did not respond to ammonia, volatile amines, aromatic compounds, or alcohols. The response speed of the QCM detector increased gradually with increasing methylmercaptan concentrations. The highly sensitive and selective response is promoted by a ligand substitution reaction caused by the formation of coordinative bonds between a metastable silver ion and amine groups in the polyelectrolyte film. To the best of our knowledge, this system has the highest sensitivity among reported QCM gas detectors. Such high-sensitivity among reported QCM gas detectors. Such high-sensitivity gas detectors for volatile sulfur compounds have wide ranging applications in areas such as volcanic eruption prediction, food inspection, environmental analysis, and medical diagnostics.

  7. Long-Range Hydrophilic Attraction between Water and Polyelectrolyte Surfaces in Oil.

    PubMed

    Shi, Chen; Yan, Bin; Xie, Lei; Zhang, Ling; Wang, Jingyi; Takahara, Atsushi; Zeng, Hongbo

    2016-11-21

    The outstanding water wettability and the capability of polyelectrolyte surfaces to spontaneously clean oil fouling are determined by their wetting mechanism in the surrounding medium. Here, we have quantified the nanomechanics between three types of polyelectrolyte surfaces (i.e. zwitterionic, cationic, and anionic) and water or oil drops using an atomic force microscope (AFM) drop probe technique, and elucidated the intrinsic wetting mechanisms of the polyelectrolyte surfaces in oil and water media. The measured forces between oil drops and polyelectrolyte surfaces in water can be described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Surprisingly, strong long-range attraction was discovered between polyelectrolyte surfaces and water drops in oil, and the strongest interaction was measured for the polyzwitterion. This unexpected long-range "hydrophilic" attraction in oil could be attributed to a strong dipolar interaction because of the large dipole moment of the polyelectrolytes. Our results provide new nanomechanical insights into the development of novel polyelectrolyte-based materials and coatings for a wide range of engineering, bioengineering, and environmental applications. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Self-Assembly of Polyoxometalate and Polyelectrolyte Macroions into Mechanically Strong Supramolecular Hydrogels

    NASA Astrophysics Data System (ADS)

    Jing, Benxin; Zhu, Y. Elaine

    Polyoxometalate (POM) macroions are the nanoclusters of transition metal oxide with size 1-10 nm and well-defined structure at the atom level. Because of their stoichiometric surface groups and high solubility in polar solvents to form thermodynamically stable solution, POMs are studied as excellent model macroions at nanoscale. In this work, we explore the electrostatic controlled self-assembly of anionic POMs and cationic or zwitterionic polyelectrolytes (PEs) in aqueous solution. Specifically we examine the complex formation of zwitterionic poly (3-(methacryloylamino)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide) (PSBMA) and cationic poly(diallyldimethylammonium chloride) (PDADMAC) with tungstate based POMs of varied valence. The phase diagram of POM/polyelectrolyte complexes is determined with varied POM/PE charge ratios. It is interesting to observe the coacervation of POMs with PSBMA. With cationic PDADMAC, hybrid POM-PDADMAC hydrogels can be formed. Nevertheless, POM-PDADMAC complexes exhibit much enhanced mechanical properties in comparison to polymer hydrogel. The viscoelastic properties of hybrid macroion complexes strongly depend on PDADMAC concentration, POM-to-PDADMAC molar ratio, the size and valence of POMs. At the intermediate range of POM-to-PDADMAC concentration ratio, shear thickening and strain hardening are observed with soft supramolecular hydrogels, which is resulted from the non-Gaussian stretching of polymer chains.

  9. Depth-profiling X-ray photoelectron spectroscopy (XPS) analysis of interlayer diffusion in polyelectrolyte multilayers.

    PubMed

    Gilbert, Jonathan B; Rubner, Michael F; Cohen, Robert E

    2013-04-23

    Functional organic thin films often demand precise control over the nanometer-level structure. Interlayer diffusion of materials may destroy this precise structure; therefore, a better understanding of when interlayer diffusion occurs and how to control it is needed. X-ray photoelectron spectroscopy paired with C60(+) cluster ion sputtering enables high-resolution analysis of the atomic composition and chemical state of organic thin films with depth. Using this technique, we explore issues common to the polyelectrolyte multilayer field, such as the competition between hydrogen bonding and electrostatic interactions in multilayers, blocking interlayer diffusion of polymers, the exchange of film components with a surrounding solution, and the extent and kinetics of interlayer diffusion. The diffusion coefficient of chitosan (M = ∼100 kDa) in swollen hydrogen-bonded poly(ethylene oxide)/poly(acrylic acid) multilayer films was examined and determined to be 1.4*10(-12) cm(2)/s. Using the high-resolution data, we show that upon chitosan diffusion into the hydrogen-bonded region, poly(ethylene oxide) is displaced from the film. Under the conditions tested, a single layer of poly(allylamine hydrochloride) completely stops chitosan diffusion. We expect our results to enhance the understanding of how to control polyelectrolyte multilayer structure, what chemical compositional changes occur with diffusion, and under what conditions polymers in the film exchange with the solution.

  10. Depth-profiling X-ray photoelectron spectroscopy (XPS) analysis of interlayer diffusion in polyelectrolyte multilayers

    PubMed Central

    Gilbert, Jonathan B.; Rubner, Michael F.; Cohen, Robert E.

    2013-01-01

    Functional organic thin films often demand precise control over the nanometer-level structure. Interlayer diffusion of materials may destroy this precise structure; therefore, a better understanding of when interlayer diffusion occurs and how to control it is needed. X-ray photoelectron spectroscopy paired with C60+ cluster ion sputtering enables high-resolution analysis of the atomic composition and chemical state of organic thin films with depth. Using this technique, we explore issues common to the polyelectrolyte multilayer field, such as the competition between hydrogen bonding and electrostatic interactions in multilayers, blocking interlayer diffusion of polymers, the exchange of film components with a surrounding solution, and the extent and kinetics of interlayer diffusion. The diffusion coefficient of chitosan (M = ∼100 kDa) in swollen hydrogen-bonded poly(ethylene oxide)/poly(acrylic acid) multilayer films was examined and determined to be 1.4*10−12 cm2/s. Using the high-resolution data, we show that upon chitosan diffusion into the hydrogen-bonded region, poly(ethylene oxide) is displaced from the film. Under the conditions tested, a single layer of poly(allylamine hydrochloride) completely stops chitosan diffusion. We expect our results to enhance the understanding of how to control polyelectrolyte multilayer structure, what chemical compositional changes occur with diffusion, and under what conditions polymers in the film exchange with the solution. PMID:23569265

  11. Monoclonal antibody purification using cationic polyelectrolytes: an alternative to column chromatography.

    PubMed

    Peram, Thanmaya; McDonald, Paul; Carter-Franklin, Jayme; Fahrner, Robert

    2010-01-01

    The potential of cationic polyelectrolytes to precipitate host cell and process related impurities was investigated, to replace one or more chromatography steps in monoclonal antibody purification. The impact of antibody isoelectric point, solution properties (pH and ionic strength), and polyelectrolyte properties (structure, molecular weight and pK(a)) on the degree of precipitation was studied. At neutral pH, increasing solution ionic strength impeded the ionic interaction between the polyelectrolyte and impurities, reducing impurity precipitation. Increasing polyelectrolyte molecular weight and pK(a) enabled precipitation of impurities at higher ionic strength. PoIy(arginine) was selected as the preferred polyelectrolyte in unconditioned cell culture fluid. PoIy(arginine) precipitation achieved consistent host cell protein clearance and antibody recovery for multiple antibodies across a wider range of polyelectrolyte concentrations. Poly(arginine) precipitation was evaluated as a flocculant and as a functional replacement for anion exchange chromatography in an antibody purification process. Upstream treatment of cell culture fluid with poly(arginine) resulted in flocculation of solids (cells and cell debris), and antibody recovery and impurity clearance (host cell proteins, DNA and insulin) comparable to the downstream anion exchange chromatography step.

  12. 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

  13. Modeling ion binding to humic substances: elastic polyelectrolyte network model.

    PubMed

    Orsetti, Silvia; Andrade, Estela M; Molina, Fernando V

    2010-03-02

    A new model for the electrostatic contribution to ion binding to humic substances is proposed and applied to published data for proton binding to fulvic and humic acids. The elastic polyelectrolyte network model treats humic substance particles as composed by two parts, an external one directly in contact with the solution, and an internal part or gel fraction which is considered, from a statistical point of view, as a charged polymer network swelled by the electrolyte solution, in the framework of the Flory polymer network theory. The electrostatic effect is given by a Donnan-like potential, which can be regarded as an average value over the gel fraction of the humic particle. The gel fraction expands as the pH and humic charge are increased, determining the Donnan potential and consequently the ion activity inside the gel. The model was fitted to published experimental data with good agreement. The model predictions are discussed, and the behavior suggests, for some cases, the presence of a transition between closed and open structures attributed to the presence, at low pH, of intramolecular hydrogen bonds which are removed as the carboxylic sites become deprotonated.

  14. Parametrization of direct and soft steric-undulatory forces between DNA double helical polyelectrolytes in solutions of several different anions and cations.

    PubMed

    Podgornik, R; Rau, D C; Parsegian, V A

    1994-04-01

    Directly measured forces between DNA helices in ordered arrays have been reduced to simple force coefficients and mathematical expressions for the interactions between pairs of molecules. The tabulated force parameters and mathematical expressions can be applied to parallel molecules or, by transformation, to skewed molecules of variable separation and mutual angle. This "toolbox" of intermolecular forces is intended for use in modelling molecular interactions, assembly, and conformation. The coefficients characterizing both the exponential hydration and the electrostatic interactions depend strongly on the univalent counterion species in solution, but are only weakly sensitive to anion type and temperature (from 5 to 50 degrees C). Interaction coefficients for the exponentially varying hydration force seen at spacings less than 10 to 15 A between surfaces are extracted directly from pressure versus interaxial distance curves. Electrostatic interactions are only observed at larger spacings and are always coupled with configurational fluctuation forces that result in observed exponential decay lengths that are twice the expected Debye-Huckel length. The extraction of electrostatic force parameters relies on a theoretical expression describing steric forces of molecules "colliding" through soft exponentially varying direct interactions.

  15. Multichain aggregates in dilute solutions of associating polyelectrolyte keeping a constant size at the increase in the chain length of individual macromolecules.

    PubMed

    Korchagina, Evgeniya V; Philippova, Olga E

    2010-12-13

    Multichain aggregates together with individual macromolecules were detected by light scattering in dilute aqueous solutions of chitosan and of its hydrophobic derivatives bearing 4 mol % of n-dodecyl side groups. It was demonstrated that the size of aggregates and their aggregation numbers increase at the introduction of hydrophobic side groups into polymer chains. The key result concerns the effect of the chain length of individual macromolecules on the aggregation behavior. It was shown that for both unmodified and hydrophobically modified (HM) chitosan, the size of aggregates is independent of the length of single chains, which may result from the electrostatic nature of the stabilization of aggregates. At the same time, the number of macromolecules in one aggregate increases significantly with decreasing length of single chains to provide a sufficient number of associating groups to stabilize the aggregate. The analysis of the light scattering data together with TEM results suggests that the aggregates of chitosan and HM chitosan represent spherical hydrogel particles with denser core and looser shell covered with dangling chains.

  16. Versatile electron-collecting interfacial layer by in situ growth of silver nanoparticles in nonconjugated polyelectrolyte aqueous solution for polymer solar cells.

    PubMed

    Yuan, Kai; Chen, Lie; Chen, Yiwang

    2014-10-02

    Novel PEIE-Ag composites by in situ growth of silver nanoparticles in poly(ethylenimine)-ethoxylated (PEIE) aqueous solution are explored as an efficient interfacial layer for improving inverted polymer solar cells (PSCs) performance. The hybrid PEIE-Ag interfacial material is simple to fabricate only via ultraviolet irradiation with good water-solubility and unique film formation. The generated Ag nanoparticles can anchor in the PEIE polymer chains to form a conductive continuous interpenetrating network structure. Combining of the advantages of PEIE and Ag nanoparticles, the PEIE-Ag shows enhanced charge transport, electron selective and collection, and improved light-harvesting, mainly due to the surface plasmon resonance effect, better energy alignment induced by the formation of ideal dipole layer, as well as the improved conductivity. These distinguished interfacial properties result in the power conversion efficiency of inverted PSCs based on poly[4,8-bis(2-ethyl-hexyl-thiophene-5-yl)-benzo[1,2-b:4,5-b]dithiophene-2,6-diyl]-alt-[2-(2-ethyl-hexanoyl)-thieno[3,4-b]thiophen-4,6-diyl] (PBDTTT-C-T) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) photoactive layer substantially improved up to 7.66% from 6.11%. Moreover, the device performance is insensitively dependent on the thickness of the PEIE-Ag interfacial layer, broadening the thicknesses selection window for interfacial materials. These results demonstrate that PEIE-Ag is a potential interfacial material compatible with roll-to-roll techniques and suitable for printed electronic devices.

  17. Trace hydrazines in aqueous solutions accurately determined by gas chromatography

    NASA Technical Reports Server (NTRS)

    Welz, E. A., Jr.

    1967-01-01

    Trace amounts of hydrazines in aqueous solutions can be determined by using polythyleneimine /PEI/ in conjunction with the gas chromatographic column. The PEI specifically retains water without altering the separability or elution order of the hydrazine and associated constituents.

  18. Macroion Interaction at Polyelectrolyte Brush Interfaces

    NASA Astrophysics Data System (ADS)

    Qu, Chen

    2015-03-01

    The effect of macroions, including synthetic polyelectrolytes, DNA and proteins, on the structure and surface properties of charged polymer thin films remains inadequately understood partially due to the complexity involving the hydrophobic effect and the conformational change of polymeric macroions. In this work, we explore a group of inorganic nanocluster based macroions, hydrophilic polyoxometalates (POMs) of robust nanocluster structure and carrying high surface charges (~ 2-42 negative charges) to investigate their interaction with surface tethered poly-2-vinylpyridine (P2VP) brush-like thin films immersed in aqueous solution. We observe the collapse of swollen P2VP chains by adding POM macroions of increased concentration by AFM, QCM and contact goniometer measurements, in sharp contrast to the increased chain stretching by adding monovalent salts. A careful comparison is made between distinct POMs based on their charge, size and chemical nature. These findings serve as a good reference for theoretical model modification and design of new mesoporous composite membranes.

  19. Super-stoichiometric charge neutralization in particle-polyelectrolyte systems.

    PubMed

    Kleimann, Jörg; Gehin-Delval, Cécile; Auweter, Helmut; Borkovec, Michal

    2005-04-12

    The adsorption of poly(vinylamine) (PVA) on poly(styrene sulfate) latex particles is studied, and its consequences on the charging behavior and suspension stability are investigated. The adsorption process is assessed by batch depletion experiments and time-resolved electrophoretic mobility measurements. The adsorption of PVA appears to be basically irreversible. The rate of adsorption decreases with decreasing polymer dose. At low polymer dose, the polymer coverage corresponds to the amount of the polyelectrolyte added, while at high polymer dose, the polymer coverage saturates the surface. Stability ratios are determined by dynamic light scattering, and strongly depend on the polymer dose and salt level. The aggregation is rapid near the isoelectric point (IEP), and it slows down when moving away from it. The charge neutralization is highly nonstoichiometric with charging ratios (CR) larger than unity, meaning that several charges on an adsorbed polyelectrolyte chain are necessary to neutralize a single charge on the particle surface. By comparing the IEP for particles and polyelectrolytes of different charge densities, we find a strong dependence of the CR on the mismatch between the average distances between individual charges on the surface and on the polyelectrolyte. A simple model is proposed to explain this trend.

  20. Polyelectrolyte multilayer capsules with quantum dots for biomedical applications.

    PubMed

    Adamczak, M; Hoel, H J; Gaudernack, G; Barbasz, J; Szczepanowicz, K; Warszyński, P

    2012-02-01

    The aim of this work was to encapsulate the CdTe quantum dots within the nanocapsules that were prepared by the layer-by-layer adsorption of polyelectrolytes. Two different polyelectrolyte pairs were used as components of the shell: synthetic polycation poly(allyamine hydrochloride) (PAH), together with anionic poly(sodium styrene sulfonate) (PSS), and biocompatible cationic poly-L-lysine hydrobromide in a pair with biocompatible anionic poly-D-glutamic acid sodium salt (PGA). The saturation method was used for formation of consecutive layers on the initial CdTe-polyelectrolyte complex. A growth of the polyelectrolyte shell was followed with the electrophoretic mobility and light scattering measurements, in order to determine the zeta potential and the size of capsules, respectively. The fluorescent spectra of the quantum dots, which are embedded within the capsules, were characterized with spectrofluorimeter. Later on, they were deposited on a negatively charged mica surface and studied by the means of atomic force microscopy (AFM). In order to estimate the cytotoxicity of capsules, their influence on the B-lymphoblastoid cell line proliferation and on unspecific binding to the P-blood mononuclear cells was examined using the flow cytometry.

  1. Advanced Polyelectrolyte-Modified Zinc Phosphate Coatings

    DTIC Science & Technology

    1995-09-01

    September 1995 4 . TITLE AND SUBTITLE Advanced Polyelectrolyte-Modified Zinc Phosphate Coatings 6. AUTHOR(S) T. Sugama, N. Carciello and C.I...ADVANCED POLYELECTROLYTE-MODIFIED ZINC PHOSPHATE COATINGS ft PAL - ?y- 3 $> Phase I. Annual Report (October 1994 - September 1995) ^ by T. Sugama, N...and Cr-nitrates, 3 ) the substitution of environmentally safe polyelectrolyte for the conventional chrome-based compounds in the rinsing process, 4

  2. Complexes of xylan and synthetic polyelectrolytes. Characterization and adsorption onto high quality unbleached fibres.

    PubMed

    Mocchiutti, Paulina; Galván, María V; Peresin, María S; Schnell, Carla N; Zanuttini, Miguel A

    2015-02-13

    In this work, polyelectrolyte complexes (PECs) were formed by adding polyacrylic acid (PAA) or 4-O-methylglucuronoxylan (Xyl) on poly(allylamine hydrochloride) (PAH) solutions, at different ionic strength and neutral pH. Turbidity curves, charge densities of the cationic complexes determined by polyelectrolyte titration method, and z-potential values showed clear differences between both complexes. Stirring favourably reverses the effects of sedimentation of Xyl/PAH complexes, as demonstrated by colloidal stability tests. Adsorption studies on silica surfaces, performed by Quartz Crystal Microbalance with Dissipation (QCM-D) showed that PAA/PAH adsorbed complexes layers were rigid, while the corresponding Xyl/PAH layers were viscoelastic. Despite the different conformations, both complexes were adsorbed as spherical particles, as observed by Atomic Force Microscopy (AFM). Adsorption isotherms performed on fibre suspensions showed that the ionic strength of the liquid medium determines the amount of PEC retained. Finally, it was found that the papermaking properties were significantly increased due to the addition of these PECs.

  3. The structure and interaction mechanism of a polyelectrolyte complex: a dissipative particle dynamics study.

    PubMed

    Meneses-Juárez, Efrain; Márquez-Beltrán, César; Rivas-Silva, Juan Francisco; Pal, Umapada; González-Melchor, Minerva

    2015-08-07

    The mechanism of complex formation of two oppositely charged linear polyelectrolytes dispersed in a solvent is investigated by using dissipative particle dynamics (DPD) simulation. In the polyelectrolyte solution, the size of the cationic polyelectrolyte remains constant while the size of the anionic chain increases. We analyze the influence of the anionic polyelectrolyte size and salt effect (ionic strength) on the conformational changes of the chains during complex formation. The behavior of the radial distribution function, the end-to-end distance and the radius of gyration of each polyelectrolyte is examined. These results showed that the effectiveness of complex formation is strongly influenced by the process of counterion release from the polyelectrolyte chains. The radius of gyration of the complex is estimated using the Fox-Flory equation for a wormlike polymer in a theta solvent. The addition of salts in the medium accelerates the complex formation process, affecting its radius of gyration. Depending on the ratio of chain lengths a compact complex or a loosely bound elongated structure can be formed.

  4. Complexation and coacervation of like-charged polyelectrolytes inspired by mussels.

    PubMed

    Kim, Sangsik; Huang, Jun; Lee, Yongjin; Dutta, Sandipan; Yoo, Hee Young; Jung, Young Mee; Jho, YongSeok; Zeng, Hongbo; Hwang, Dong Soo

    2016-02-16

    It is well known that polyelectrolyte complexes and coacervates can form on mixing oppositely charged polyelectrolytes in aqueous solutions, due to mainly electrostatic attraction between the oppositely charged polymers. Here, we report the first (to the best of our knowledge) complexation and coacervation of two positively charged polyelectrolytes, which provides a new paradigm for engineering strong, self-healing interactions between polyelectrolytes underwater and a new marine mussel-inspired underwater adhesion mechanism. Unlike the conventional complex coacervate, the like-charged coacervate is aggregated by strong short-range cation-π interactions by overcoming repulsive electrostatic interactions. The resultant phase of the like-charged coacervate comprises a thin and fragile polyelectrolyte framework and round and regular pores, implying a strong electrostatic correlation among the polyelectrolyte frameworks. The like-charged coacervate possesses a very low interfacial tension, which enables this highly positively charged coacervate to be applied to capture, carry, or encapsulate anionic biomolecules and particles with a broad range of applications.

  5. Complexation and coacervation of like-charged polyelectrolytes inspired by mussels

    PubMed Central

    Kim, Sangsik; Huang, Jun; Lee, Yongjin; Dutta, Sandipan; Yoo, Hee Young; Jung, Young Mee; Jho, YongSeok; Zeng, Hongbo

    2016-01-01

    It is well known that polyelectrolyte complexes and coacervates can form on mixing oppositely charged polyelectrolytes in aqueous solutions, due to mainly electrostatic attraction between the oppositely charged polymers. Here, we report the first (to the best of our knowledge) complexation and coacervation of two positively charged polyelectrolytes, which provides a new paradigm for engineering strong, self-healing interactions between polyelectrolytes underwater and a new marine mussel-inspired underwater adhesion mechanism. Unlike the conventional complex coacervate, the like-charged coacervate is aggregated by strong short-range cation–π interactions by overcoming repulsive electrostatic interactions. The resultant phase of the like-charged coacervate comprises a thin and fragile polyelectrolyte framework and round and regular pores, implying a strong electrostatic correlation among the polyelectrolyte frameworks. The like-charged coacervate possesses a very low interfacial tension, which enables this highly positively charged coacervate to be applied to capture, carry, or encapsulate anionic biomolecules and particles with a broad range of applications. PMID:26831090

  6. Sequestration of Methylene Blue into Polyelectrolyte Complex Coacervates.

    PubMed

    Zhao, Mengmeng; Zacharia, Nicole S

    2016-08-01

    Polyelectrolyte complex coacervation is a process that has been proposed as a model for protocell formation due to its ability to compartmentalize chemicals in solution without a membrane. During the liquid-liquid phase separation that results in water rich and polyelectrolyte rich phases, small molecules present in solution selectively partition to one phase over the other. This sequestration is based on relative affinities. Here, a study of the sequestration of methylene blue (MB) into the complex coacervate phase of three pairs of synthetic polyelectrolytes is presented; branched polyethylene imine with polyacrylic acid, polyvinyl sulfonate, or poly(4-styrenesulfonic acid). These materials are characterized with UV-vis, zeta potential measurements, and dynamic light scattering. The branched polyethylene imine/poly(4-styrenesulfonic acid) system is shown to have a significantly higher sequestration capacity for the MB as compared to either of the other two systems, based on π-π interactions which are not possible in the other systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. 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 Ca2+, Mg2+, and Ba2+, and trivalent Y3+ 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 theory well, exhibiting two distinct regimes:more » the osmotic and salted brush regimes. Introducing trivalent Y3+ cations causes an abrupt shrinkage of the PSS brush due to the uptake of Y3+ counterions. The uptake of Y3+ counterions and shrinkage of the brush are reversible upon increasing the concentration of monovalent salt. Divalent cations, Mg2+, Ca2+, and Ba2+, 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

  8. Study of polyelectrolyte complexes of chitosan and sulfoethyl cellulose

    SciTech Connect

    Baklagina, Yu. G. Kononova, S. V.; Petrova, V. A.; Kruchinina, E. V.; Nud'ga, L. A.; Romanov, D. P.; Klechkovskaya, V. V.; Orekhov, A. S.; Bogomazov, A. V.; Arkhipov, S. N.

    2013-03-15

    The complexing of polycation chitosan and polyanion sulphoethyl cellulose during the formation of polyelectrolyte simplex membranes using the layer-by-layer deposition of a solution of one polyion on a gel-like film of another one has been studied. The structural characteristics of the multilayer composites and their components have been analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray microanalysis. A technique is proposed for studying the structure of surface layers of thin polymer films (15-20 {mu}m) using a portable DIFREI-401 diffractometer. It is shown that the sequence of layer deposition during the formation of membrane films does not affect their structural characteristics. The interaction between positively charged chitosan groups (-NH{sub 3}{sup +}) and negatively charged sulfoethyl cellulose groups (-SO{sub 3}{sup -}) during the growth of polyelectrolyte complexes results in a packing of chitosan chains in the multilayer film.

  9. Plastic behaviour of polyelectrolyte microcapsules derived from colloid templates.

    PubMed

    Bäumler, H; Artmann, G; Voigt, A; Mitlöhner, R; Neu, B; Kiesewetter, H

    2000-01-01

    The deformability and osmotic properties of hollow microcapsules were studied by means of the micropipette video microscopic technique. The microcapsules were prepared by consecutive multiple adsorption of the polyanion, poly(styrene sulphonate), and the polycation, poly(allylamine hydrochloride), onto melamine formaldehyde resin latex of 5 microm diameter, which was decomposed after completing the coating by transferring to hydrochloric acid of pH 1.1. The polyelectrolyte microcapsules reacted to micropipette suction with plastic deformation. If lipids are added to the polyelectrolyte layers, the capsules cannot be visibly deformed by micropipette suction up to 10(4) N/m2. However, plastic shrinking was observed if the stress was generated by the osmotic pressure of a sucrose solution of 10(6) N/m2.

  10. A molecular simulation study on salt response of polyelectrolyte complexes

    NASA Astrophysics Data System (ADS)

    Antila, Hanne; van Tassel, Paul; Sammalkorpi, Maria

    2015-03-01

    In aqueous solutions, oppositely charged polymers, polyelectrolytes (PEs) form complexes which are known to be sensitive to added salt with responses ranging from shrinking to full destabilization of the complex. As a specific application of PE complexes, the complex formation of DNA with polycations has been demonstrated to be an effective means of transfecting genetic material in gene therapy. We use all-atom molecular dynamics and coarse-grained Monte Carlo simulations to investigate the effect of excess salt on DNA-polycation complex stability. The detailed all-atom simulations demonstrate the mechanism of polycation and ion species specific salt-driven dissociation involving charge reversal. More generally, other possible mechanisms of salt driven dissociation exist as well. The coarse grained approach, which describes the PE complex as oppositely charged, rigid rods and ions as hard spheres, provides a more complete understanding of PE interactions in salt, and suggests possible mechanisms leading to repulsion between the oppositely charged polyelectrolytes.

  11. Polyelectrolyte Coacervates Deposited as High Gas Barrier Thin Films.

    PubMed

    Haile, Merid; Sarwar, Owais; Henderson, Robert; Smith, Ryan; Grunlan, Jaime C

    2017-01-01

    Multilayer coatings consisting of oppositely charged polyelectrolytes have proven to be extraordinarily effective oxygen barriers but require many processing steps to fabricate. In an effort to prepare high oxygen barrier thin films more quickly, a polyelectrolyte complex coacervate composed of polyethylenimine and polyacrylic acid is prepared. The coacervate fluid is applied as a thin film using a rod coating process. With humidity and thermal post-treatment, a 2 µm thin film reduces the oxygen transmission rate of 0.127 mm poly(ethylene terephthalate) by two orders of magnitude, rivalling conventional oxygen barrier technologies. These films are fabricated in ambient conditions using low-cost, water-based solutions, providing a tremendous opportunity for single-step deposition of polymeric high barrier thin films. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Colloid Titration--A Rapid Method for the Determination of Charged Colloid.

    ERIC Educational Resources Information Center

    Ueno, Keihei; Kina, Ken'yu

    1985-01-01

    "Colloid titration" is a volumetric method for determining charged polyelectrolytes in aqueous solutions. The principle of colloid titration, reagents used in the procedure, methods of endpoint detection, preparation of reagent solutions, general procedure used, results obtained, and pH profile of colloid titration are considered. (JN)

  13. Colloid Titration--A Rapid Method for the Determination of Charged Colloid.

    ERIC Educational Resources Information Center

    Ueno, Keihei; Kina, Ken'yu

    1985-01-01

    "Colloid titration" is a volumetric method for determining charged polyelectrolytes in aqueous solutions. The principle of colloid titration, reagents used in the procedure, methods of endpoint detection, preparation of reagent solutions, general procedure used, results obtained, and pH profile of colloid titration are considered. (JN)

  14. Reversible Self-Assembly of Hydrophilic Inorganic Polyelectrolytes into Highly Conservative, Vesicle-like Structures

    NASA Astrophysics Data System (ADS)

    Kistler, Melissa; Bhatt, Anish; Liu, Guang; Liu, Tianbo

    2007-03-01

    The hydrophilic polyoxometalate (POM) macroanions are inorganic polyelectrolytes which offer a direct connection between simple ions and organic polyelectrolytes. POM solutions are perfect model systems for studying polyelectrolyte solutions because they are identical in size, shape, mass and charges, with easily tunable charge density. Many types of POM macroanions are highly soluble but undergo reversible self-assembly to form uniform, stable, soft, single-layer vesicle-like ``blackberry'' structures containing >1000 individual POMs in dilute solutions. The driving force of the blackberry formation is likely counterion-mediated attraction (like-charge attraction). The blackberry size can be accurately controlled by solvent quality, or the charge density on macroions. Many unexpected phenomena have been observed in these novel systems. Blackberry structures may be analogous to virus shell structures formed by capsid proteins. References: Nature, 2003, 426, 59; JACS, 2002, 124, 10942; 2003, 125, 312; 2004, 126, 16690; 2005, 127, 6942; 2006, 128, 10103.

  15. Ion transport in polyelectrolyte multilayer membranes: Electrochemical, spectroscopic, and computational analysis

    NASA Astrophysics Data System (ADS)

    Farhat, Tarek Rafic

    Diffusion of ions across thin membranes, whether polymeric or biological, is diverse and important field in science. In separation science, thin polymer films have potential application in the chemical and pharmaceutical industries. In this dissertation, ion transport on a recently discovered polymer thin films known as polyelectrolyte multilayer films is investigated. Unexpectedly, a polyelectrolyte multilayer membrane behaved unlike classical membranes and a new mechanism termed the "reluctant exchange" was proposed to explain their behavior. Ion transport in these membranes was studied electrochemically, using the rotating disc electrode voltammetry technique, to obtain flux characteristic of at least ten electroactive species The flux through membranes was found to be either a linear or nonlinear function of electrolyte concentration depending on the charge, the resonance form, and the membrane diffusion coefficient of the electroactive ion. The "reluctant exchange" lead to significant transport selectivity between ions, favoring species with lower charge. A triangular relation was established between the electroactive probe ions, the polyelectrolyte ion pair exchangers, and a variety of supporting electrolytes. In certain cases a blocking effect was detected, which was harnessed to study the effectiveness of these films at inhibiting pitting corrosion of stainless steel. Experimental analysis was extended to include in situ Attenuated Total Internal Reflectance-Fourier Transform Infra Red spectroscopy that verified the linear dependence of the population of extrinsic sites and the independence of the concentration of the probe ions on the concentration of the external salt solution. Finally, owing to the difficulty of detecting the hops of active probe ions across the ion pair exchangers, a theoretical approach was proposed to understand the molecular dynamics of the "reluctant exchange" mechanism. A visualization of ion transport across the polyelectrolyte

  16. Effect of polyelectrolyte-surfactant complexation on Marangoni transport at a liquid-liquid interface.

    PubMed

    Dunér, Gunnar; Kim, Michelle; Tilton, Robert D; Garoff, Stephen; Przybycien, Todd M

    2016-04-01

    Complexation of surfactants and oppositely charged polyelectrolytes is expected to alter Marangoni transport at a fluid interface compared to either single component system due to altered interfacial tension isotherms and mass transfer rates as well as adsorption irreversibility effects. We investigate Marangoni transport at the oil/water interface by passing mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and cationic polyelectrolyte poly(3-(2-methylpropionamide)propyl) trimethylammonium chloride-acrylamide (poly[AM-MAPTAC]), or rinsing solutions, over an oil/water interface in a radial, stagnation point flow. The displacements of adsorbed tracer particles are recorded through optical microscopy. The net displacement, defined as the sum of the displacements occurring during the adsorption and desorption stages of one application and rinsing cycle, is up to 10 times greater for complexing surfactant/polymer mixtures compared to either single component system. The enhanced net displacement is largely determined by the enhanced transport upon adsorption, while the reverse displacement that would normally occur upon rinsing is partially suppressed by partially irreversible polymer adsorption at the oil/water interface. In addition to effects of complexation on interfacial tension gradient induced flow, complexation effects on the bulk, and possibly interfacial, viscosity also influence the interfacial transport. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Perfluoro-alcohol-induced complex coacervates of polyelectrolyte-surfactant mixtures: phase behavior and analysis.

    PubMed

    Nejati, Mahboubeh M; Khaledi, Morteza G

    2015-05-26

    Perfluorinated alcohols and acids such as hexafluoroisopropanol (HFIP), trifluoroethanol, trifluoroacetic acid, pentafluoropropionic acid, and heptafluorobutyric acid induce coacervation and phase separation in aqueous solutions of a wide variety of individual and mixed amphiphiles [ Khaledi Langmuir 2013 , 29 , 2458 ]. This paper focuses on HFIP-induced complex coacervate formation in the mixtures of anionic polyelectrolytes, such as sodium salt of poly(methacrylic acid) (PMA) or poly(acrylic acid) (PAA) and cationic surfactants of alkyltrimethylammonium bromides. In purely aqueous media and over a wide concentration range, mixtures of PMA and CTAB form the catanionic complex (CTA(+)PM(-)) that is insoluble in water (white precipitate). Upon addition of a small percentage of HFIP, the mixture goes through phase transition and formation of two distinctly clear liquid phases. The phase diagram for the HFIP-PMA-CTAB coacervate system was studied. The coacervate volume was determined as a function of system variables such as charge ratio as well as total and individual concentrations of the system components. These results, combined with the chemical composition analysis of the separated aqueous top-phase and coacervate bottom-phase, shed light on the coacervation mechanism. The results suggest that exchange of counterions and ion-pair formation play critical roles in the coacervation process. This process facilitated by HFIP through solvation of the head groups and dehydration of the hydrophobic moieties of the catanionic complex. Because of the presence of HFIP, coacervation occurs over a wide range of concentrations and charge ratios of the oppositely charged polyelectrolyte and surfactant.

  18. 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.

  19. Direct determination of nonmetals in solution with atomic spectrometry

    SciTech Connect

    McGregor, D.A.; Cull, K.B.; Gehlhausen, J.M.; Viscomi, A.S.; Wu, M.; Zhang, L.; Carnahan, J.W.

    1988-10-01

    In a 1984 report, Browner and Boorn discussed factors associated with sample introduction in atomic spectroscopy. Because of inherent problems that often restrict detection limits and produce interference effects, the authors questioned whether sample introduction was the Achilles' heel of atomic spectroscopy. It is also well known, but less often discussed, that another chink exists in the armor of this class of techniques. This chink is characterized by the difficulty of nonmetal determinations with solution samples. In this article, solution nonmetal determinations are addressed on a fundamental level, research in this direction is characterized, and future implications are discussed.

  20. Highly sensitive and fast responsive fiber-optic modal interferometric pH sensor based on polyelectrolyte complex and polyelectrolyte self-assembled nanocoating.

    PubMed

    Yin, Mingjie; Gu, Bobo; Zhao, Qiang; Qian, Jinwen; Zhang, Aping; An, Quanfu; He, Sailing

    2011-04-01

    A new fiber-optic pH sensor is demonstrated by coating negatively charged polyelectrolyte complex (PEC(-)) nanoparticles, made of sodium carboxymethyl cellulose and poly(diallyldimethylammonium chloride) (PDDA), and positively charged PDDA on the surface of a thin-core fiber modal interferometer (TCFMI) with a layer-by-layer (LbL) electrostatic self-assembly method. The fabricated TCFMI pH sensor has different transmission dip wavelengths under different pH values and shows high sensitivities of 0.6 nm/pH unit and -0.85 nm/pH unit for acidic and alkaline solutions, respectively, and short response time of 30-50 s. The LbL electrostatic self-assembly process of a PEC(-)/PDDA multilayer is traced by quartz crystal microbalance and shows a fast thickness growth. Atomic force microscopy shows the root mean square (RMS) surface roughness of electrostatic self-assembly nanocoating of polyelectrolyte complex/polyelectrolyte is much higher than that of polyelectrolyte/polyelectrolyte due to the larger size of PEC(-) colloidal nanoparticles. The enhanced RMS surface roughness and thickness of the nanocoating can shorten the response time and raise the sensitivity of the TCFMI pH sensor, respectively. In addition, the TCFMI pH sensor has highly reversible performance and good durability.

  1. Optimisation of the self-assembly process: production of stable, alginate-based polyelectrolyte nanocomplexes with protamine

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

    The aim of this work was to investigate the possibility of covalent cross-linker-free, polyelectrolyte complex formation at the nanoscale between alginic acid (as sodium alginate, ALG) and protamine (PROT). Optimisation of the self-assembly conditions was performed by varying the type of polymer used, pH of component solutions, mass mixing ratio of the components and the speed and order of component addition on the properties of complexes. Homogenous particles with nanometric sizes resulted when an aqueous dispersion of ALG was rapidly mixed with a solution of PROT. The polyelectrolyte complex between ALG and PROT was confirmed by infrared spectroscopy. To facilitate incorporation of drugs soluble at low pH, pH of ALG dispersion was decreased to 2; however, no nanoparticles (NPs) were formed upon complexation with PROT. Adjusting pH of PROT solution to 3 resulted in the formation of cationic or anionic NPs with a size range 70-300 nm. Colloidal stability of selected alginic acid low/PROT formulations was determined upon storage at room temperature and in liquid media at various pH. Physical stability of NPs correlated with the initial surface charge of particles and was time- and pH-dependent. Generally, better stability was observed for anionic NPs stored as native dispersions and in liquids covering a range of pH.

  2. Separate determination of nitrophenols and aminophenols in aqueous solutions

    SciTech Connect

    Korenman, Y.I.; Bortnikova, R.N.; Nefedova, T.A.; Sotnikova, N.G.

    1985-05-01

    Nitro and aminophenols are widely distributed, highly toxic components of waste waters from the phenolic industry. This article proposes a rapid extraction photometric method for determination of the most widespread isomers of nitro and aminophenols (ortho-substituted). Preliminary separation of the components being determined is based on the substantial difference in the ability of 2-nitrophenol and 2-aminophenol to be extracted from aqueous solutions by organic solvents. It is shown that the distribution coefficient for 2-nitrophenol in the system dibutyl ether-water is almost 40 times larger than the corresponding value for 2-aminophenol. The method described made possible the determination of 2-nitrophenol and 2-aminophenol in aqueous solution after their separation with satisfactory accuracy. The maximum error for the determination of 2-aminophenol was 12% and for 2-nitrophenol, 4%.

  3. Coulometric determination of americium in acetonitrile solution of phosphoric acid

    SciTech Connect

    Perevalov, S.A.; Kulyakov, Yu.M.; Lebedev, I.A.; Myasoedov, B.F.

    1986-10-20

    A procedure was developed for the coulometric determination of americium using the electrochemical couple Am(IV)-Am(III). An acetonitrile solution of 0.3-0.2 M H/sub 3/PO/sub 4/ was used as the electrolyte. Americium can be determined in the presence of large amounts of Cm, Pu, Ce, and other impurities; limit of detection approx. 10 ..mu..g.

  4. Numerical Solution for the Determination of Towboat Return Currents

    DTIC Science & Technology

    1994-03-01

    Numerical Solution of Potential Flow ...................... 7 Geometry and Grid Development ........................ 7 Boundaries...and size of the hull, and the channel geometry . h. Wake flow . The current produced as water fills in behind the stern to replace the water displaced...time-steps). Geometry and Grid Development Sensitivity tests were conducted using STREMR to determine the potential of modeling the flow field around

  5. Antibacterial polyelectrolyte-coated Mg alloys for biomedical applications

    NASA Astrophysics Data System (ADS)

    Seraz, Md. S.; Asmatulu, R.; Chen, Z.; Ceylan, M.; Mahapatro, A.; Yang, S. Y.

    2014-04-01

    This study deals with two biomedical subjects: corrosion rates of polyelectrolyte-coated magnesium (Mg) alloys, mainly used for biomedical purposes, and antibacterial properties of these alloys. Thin sheets of Mg alloys were coated with cationic polyelectrolyte chitosan (CHI) and anionic polyelectrolyte carboxymethyl cellulose (CMC) using a layer-by-layer coating method and then embedded with antibacterial agents under vacuum. Electrochemical impedance spectroscopy was employed to analyze these samples in order to detect their corrosion properties at different conditions. In the electrochemical analysis section, a corrosion rate of 72 mille inches per year was found in a salt solution for the sample coated with a 12 phosphonic acid self-assembled monolayer and 9 CHI/CMC multilayers. In the antibacterial tests, gentamicin was used to investigate the effects of the drug embedded with the coated surfaces against the Escherichia coli (E. coli) bacteria. Antibacterial studies were tested using the disk diffusion method. Based on the standard diameter of the zone of inhibition chart, the antibacterial diffusion from the surface strongly inhibited bacterial growth in the regions. The largest recorded diameter of the zone of inhibition was 50 mm for the pre-UV treated and gentamicin-loaded sample, which is more than three times the standard diameter.

  6. Linear Viscoelasticity and Swelling of Polyelectrolyte Complex Coacervates

    NASA Astrophysics Data System (ADS)

    Hamad, Fawzi; Colby, Ralph

    2012-02-01

    The addition of near equimolar amounts of poly(diallyldimethylammonium chloride) to poly(isobutylene-alt-maleate sodium), results in formation of a polyelectrolyte complex coacervate. Zeta-potential titrations conclude that these PE-complexes are nearly charge-neutral. Swelling and rheological properties are studied at different salt concentrations in the surrounding solution. The enhanced swelling observed at high salt concentration suggests the system behaves like a polyampholyte gel, and weaker swelling at very low salt concentrations implies polyelectrolyte gel behavior. Linear viscoelastic oscillatory shear measurements indicate that the coacervates are viscoelastic liquids and that increasing ionic strength of the medium weakens the electrostatic interactions between charged units, lowering the relaxation time and viscosity. We use the time-salt superposition idea recently proposed by Spruijt, et al., allowing us to construct master curves for these soft materials. Similar swelling properties observed when varying molecular weights. Rheological measurements reveal that PE-complexes with increasing molecular weight polyelectrolytes form a network with higher crosslink density, suggesting time-molecular weight superposition idea.

  7. Ultrafast active mixer using polyelectrolytic ion extractor.

    PubMed

    Chun, Honggu; Kim, Hee Chan; Chung, Taek Dong

    2008-05-01

    We report on a low voltage, straight/smooth surface, and efficient active micromixer. The mixing principle is based on alternative ion depletion-enrichment using a pair of positively charged polyelectrolytic gel electrodes (pPGEs), which face each other joined by a microchannel. This system has an external AC signal source electrically connected to the pPGEs via the respective 1 M KCl solutions and Ag/AgCl electrodes. When an electric bias is applied between the two pPGEs, anions are extracted through one of the pPGEs to create a local ion-deficient region. Simultaneously, an ion-rich area appears near the other pPGE due to an inward anionic flux. As the direction of the charge flow is periodically reversed by the AC signal source, the ion depletion-enrichment regions are alternately swapped with each other on the 'push-pull' basis. The turmoil between the pPGEs quickly mixes the solutions in the microchannel without any mechanical moving part or specially machined structures. In the proposed system, both AC frequency and current density can be easily and finely controlled so that one can quickly find the optimal conditions for a given sample. The micromixer as made showed a mixing efficiency higher than 90% for sample solutions of 1 mM Rhodamine 6G and PBS at pH 7.4 when the flow rate was under 6 mm s(-1). In addition to the solution-solution mixing, the micromixer can effectively mix suspended microparticles with solution. As a representative example, rapid and efficient lysis of human red blood cells was demonstrated allowing minimal damage of the white blood cells.

  8. Systematic modification of the rheological properties of colloidal suspensions with polyelectrolyte multilayers

    NASA Astrophysics Data System (ADS)

    Hess, Andreas; Pretzl, Melanie; Heymann, Lutz; Fery, Andreas; Aksel, Nuri

    2011-09-01

    Tailoring rheological properties of colloidal suspensions with the adsorption of polyelectrolyte multilayers (PEMs) is based on the idea of controlling macroscopic mechanical properties by modifying the particle surface in a reproducible and well-understood manner. With layer-by-layer self-assembly, monodisperse polystyrene particles are coated with up to ten layers of the oppositely charged strong polyelectrolytes: poly(diallyl dimethyl ammonium chloride) and poly(styrene sulfonate). The conformation of the adsorbed polyelectrolyte is controlled by the ionic strength of the used aqueous polyelectrolyte solution. For 1M NaCl solution, a brushlike adsorption of the polyelectrolyte is expected. The ability of PEMs to serve on a nanoscale level as surface modifiers and influence macroscopic rheological properties like viscoelasticity, yield stress, and shear banding is discussed. The mechanical behavior of these suspensions is qualitatively described by the theory of Derjaguin-Landau-Verwey-Overbeek with short-range repulsion and long-range attraction. A scaling rule is proposed which distinguishes between the precusor and the multilayer regime.

  9. Systematic modification of the rheological properties of colloidal suspensions with polyelectrolyte multilayers.

    PubMed

    Hess, Andreas; Pretzl, Melanie; Heymann, Lutz; Fery, Andreas; Aksel, Nuri

    2011-09-01

    Tailoring rheological properties of colloidal suspensions with the adsorption of polyelectrolyte multilayers (PEMs) is based on the idea of controlling macroscopic mechanical properties by modifying the particle surface in a reproducible and well-understood manner. With layer-by-layer self-assembly, monodisperse polystyrene particles are coated with up to ten layers of the oppositely charged strong polyelectrolytes: poly(diallyl dimethyl ammonium chloride) and poly(styrene sulfonate). The conformation of the adsorbed polyelectrolyte is controlled by the ionic strength of the used aqueous polyelectrolyte solution. For 1M NaCl solution, a brushlike adsorption of the polyelectrolyte is expected. The ability of PEMs to serve on a nanoscale level as surface modifiers and influence macroscopic rheological properties like viscoelasticity, yield stress, and shear banding is discussed. The mechanical behavior of these suspensions is qualitatively described by the theory of Derjaguin-Landau-Verwey-Overbeek with short-range repulsion and long-range attraction. A scaling rule is proposed which distinguishes between the precusor and the multilayer regime.

  10. Influence of Higher Valence Ions on Flexible Polyelectrolytes Stiffness and Counter-ion Distribution

    NASA Astrophysics Data System (ADS)

    Chremos, Alexandros; Douglas, Jack F.

    We investigate the influence of counter-ion valency on the flexibility of highly charged flexible polymer chains by molecular dynamics simulations that include both salt and an explicit solvent. A theoretical understanding of solutions of these molecules (e.g., DNA, RNA, and sulfonate polyestyrene) has been slow to develop due to the complex coupling between the polyelectrolyte conformation and the ionic species in solution due to their long range Coulomb interactions. As observed experimentally, we find that divalent counter-ions greatly reduce the chain persistence length, in comparison to monovalent counter-ions, an effect correlated with the tendency of the polyelectrolyte chain to become distorted by divalent counter-ions. We rationalize these results by with the substantial increase of counter-ion population at the interface with the polyelectrolyte, which not only leads to a more effective screening of the bare charge, but also leads to charge inversion in the trivalent counter-ion case. These conformational changes with counter-ion valency are also associated with a drastic increase of the number of contacts the counter-ions have at the interface with polyelectrolyte, an effect associated with polyelectrolyte chain ``coiling'' around the counter-ions. NIST Postdoctoral Fellowship.

  11. Determination of closed form solution for acceptance sampling using ANN.

    PubMed

    Vasudevan, D; Selladurai, V; Nagaraj, P

    2004-01-01

    Tabled sampling schemes such as MIL-STD-105D offer limited flexibility to quality control engineers in designing sampling plans to meet specific needs. We describe a closed form solution to determine the AQL indexed single sampling plan using an artificial neural network (ANN). To determine the sample size and the acceptance number, feed-forward neural networks with sigmoid neural function are trained by a back propagation algorithm for normal, tightened, and reduced inspections. From these trained ANNs, the relevant weight and bias values are obtained. The closed form solutions to determine the sampling plans are obtained using these values. Numerical examples are provided for using these closed form solutions to determine sampling plans for normal, tightened, and reduced inspections. The proposed method does not involve table look-ups or complex calculations. Sampling plan can be determined by using this method, for any required acceptable quality level and lot size. Suggestions are provided to duplicate this idea for applying to other standard sampling table schemes.

  12. Rapid determination of global moment-tensor solutions

    USGS Publications Warehouse

    Sipkin, S.A.

    1994-01-01

    In an effort to improve data services, the National Earthquake Information Center has begun a program, in cooperation with the Incorporated Research Institutions for Seismology Data Management Center (IRIS DMC), to produce rapid estimates of the seismic moment tensor for most earthquakes with a bodywave magnitude of 5.8 or greater. An estimate of the moment tensor can usually be produced within 20 minutes of the arrival of the broadband P-waveform data from the IRIS DMC. The solutions do not vary significantly from the final solutions determined using the entire network. -from Author

  13. Structural transitions of encapsidated polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Angelescu, D. G.; Linse, P.; Nguyen, T. T.; Bruinsma, R. F.

    2008-03-01

    Conformations and structural transitions of polyelectrolytes strictly confined onto a spherical 2D surface have been investigated by scaling descriptions based on physical arguments concerning polyelectrolyte adsorption onto planar surface and liquid crystals as well as by Monte Carlo simulations using a bead-spring model with short-range and electrostatic repulsions. In case of the electrostatic screened regime, a disordered-ordered (spiral) transition at increasing persistence length of the chain was found. It was predicted that the transition occurred when the persistence length is comparable with the mean spacing between adjacent strands of the ordered chain. The presence of a non-screened electrostatic repulsion led to a more complex behavior with i) a re-entrant order-disorder transition and ii) a tennis ball texture as an additional smectic/nematic structure. The various competing structures given by the theory were recovered by the Monte Carlo simulations, which also indicated that the tennis ball texture was favored over the spiral structure by the long-range interactions for semi-flexible chains.

  14. Quasielastic and electrophoretic light scattering studies of polyelectrolyte-micelle complexes

    NASA Astrophysics Data System (ADS)

    Rigsbee, Daniel R.; Dubin, Paul L.

    1991-06-01

    The aqueous system comprised of poly(dimethylammonium chloride) (a strongly cationic polymer) and a mixture of sodium dodecyl sulfate and Triton X-100 (anionic/nonionic mixed micelles) forms polyelectrolyte-micelle complexes. At suitable micelle compositions and ionic strengths, soluble complexes are formed, which may be studied by a variety of solution techniques, including quasielastic light scattering. In this report, the authors examine the influence of polymer molecular weight and micelle composition on the nature of these complexes. Multiangle measurements were made with two different instruments (hence different procedures for extracting apparent size distributions from measured autocorrelation curves). At the concentrations employed, multipolymer complexes appear to form. The QELS data, taken in conjunction with limited electrophoretic light scattering results, suggest that the main determinant of the extent of higher-order aggregation are those factors influencing the net charge of a 'primary' i.e. intrapolymer complex, with molecular weight per se playing a secondary role.

  15. 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.

  16. Ultrathin self-assembled polyelectrolyte multilayer membranes

    NASA Astrophysics Data System (ADS)

    Tieke, B.; van Ackern, F.; Krasemann, L.; Toutianoush, A.

    The paper is concerned with ultrathin membranes prepared upon alternating layer-by-layer adsorption of cationic and anionic polyelectrolytes on a porous substructure. The formation of the polyelectrolyte multilayer membranes is characterised and the transport of gases, liquid mixtures and ions across the membranes is studied. In particular, the use of the membranes for alcohol/water separation under pervaporation conditions, and for the separation of mono- and divalent ions is described. It is demonstrated that upon a suitable choice of polyelectrolytes and substructures, and a careful optimisation of preparation and operation conditions, membranes can be tailored exhibiting an excellent separation capability.

  17. Polyelectrolyte-graphene Nanocomposites for Biosensing Applications

    PubMed Central

    Priftis, Dimitrios

    2015-01-01

    Due to their unique structure, the optical and mechanical properties graphene and its derivatives (e.g. graphene oxide, reduced graphene oxide) have captured the attention of a constantly increasing number of scientists with regards to biomolecule sensing. This mini review focuses on one specific type of sensor, that consisting of graphene and polyelectrolytes. Polyelectrolyte-graphene nanocomposites exhibit outstanding detection capabilities by synergistically combining the characteristics of both components, outperforming traditional sensors in many cases. Characteristics and mechanistic details of the most important polyelectrolyte-graphene based sensors will be discussed in detail in addition to some current challenges and future perspectives. PMID:27713667

  18. [Determination of Chloride Salt Solution by NIR Spectroscopy].

    PubMed

    Zhang, Bin; Chen, Jian-hong; Jiao, Ming-xing

    2015-07-01

    Determination of chloride salt solution by near infrared spectrum plays a very important role in Biomedicine. The near infrared spectrum analysis of Sodium chloride, potassium chloride, calcium chloride aqueous solution shows that the concentration change of chloride salt can affect hydrogen bond, resulting in the variation of near infrared spectrum of water. The temperature influence on NIR spectrum has been decreased by choosing reasonable wavelength range and the wavelength where the temperature effects are zero (isosbestic point). Chlorine salt prediction model was established based on partial least squares method and used for predicting the concentration of the chlorine ion. The impact on near infrared spectrum of the cation ionic radius, the number of ionic charge, the complex effect of ionic in water has also discussed in this article and the reason of every factor are analysed. Experimental results show that the temperature and concentration will affect the near-infrared spectrum of the solution, It is found that the effect of temperature plays the dominant role at low concentrations of chlorine salt; rather, the ionic dominates at high concentration. Chloride complexes are formed in aqueous solution, It has an effect on hydrogen bond of water combining with the cations in chlorine salt solution, Comparing different chloride solutions at the same concentration, the destruction effects of chloride complexes and catnions on the hydrogen bond of water increases in the sequences: CaCl2 >NaCl>KC. The modeling result shows that the determination coefficients (R2) = 99.97%, the root mean square error of cross validation (RM- SECV) = 4.51, and the residual prediction deviation (RPD) = 62.7, it meets the daily requirements of biochemical detection accuracy.

  19. Solutes determine the temperature windows for microbial survival and growth

    PubMed Central

    Chin, Jason P.; Megaw, Julianne; Magill, Caroline L.; Nowotarski, Krzysztof; Williams, Jim P.; Bhaganna, Prashanth; Linton, Mark; Patterson, Margaret F.; Underwood, Graham J. C.; Mswaka, Allen Y.; Hallsworth, John E.

    2010-01-01

    Microbial cells, and ultimately the Earth's biosphere, function within a narrow range of physicochemical conditions. For the majority of ecosystems, productivity is cold-limited, and it is microbes that represent the failure point. This study was carried out to determine if naturally occurring solutes can extend the temperature windows for activity of microorganisms. We found that substances known to disorder cellular macromolecules (chaotropes) did expand microbial growth windows, fungi preferentially accumulated chaotropic metabolites at low temperature, and chemical activities of solutes determined microbial survival at extremes of temperature as well as pressure. This information can enhance the precision of models used to predict if extraterrestrial and other hostile environments are able to support life; furthermore, chaotropes may be used to extend the growth windows for key microbes, such as saprotrophs, in cold ecosystems and manmade biomes. PMID:20404182

  20. The determination of captopril in Solution by Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Gao, Junxiang; Gu, Huaimin; Dong, Xiao; liu, fangfang

    2011-01-01

    Captopril, 1-[(2S)-3-mercapto-2-methyl propionyl]-Lproline, is an angiotensin converting enzyme (ACE) inhibitor, which reduces peripheral resistance and lowers blood pressure. It is widely used in the hypertensive ailments and incongestive heart failure treatment. Due to such crucial pharmacological importance, development of simple and accurate methods for the determination of captopril is desired. In this work, the normal Raman spectra of the captopril in different concentrations were studied, and the relationship between the Raman intensity and the concentrations of the captopril was quantificationally analysed. By selecting appropriate characteristic Raman bands of the cptopril, the solution of some captopril purchased in a local pharmacy was quantificationally determined. A quantificational linear relationship between the Raman intensity and the concentrations of captopril was obtained, and it is little affected by other compounds in the solution of captopril. This study provides an effective technique for the quantificational determination of captopril in solutions, and it has a potential application in the analysis of medicament.

  1. A rotating disk electrokinetic method for characterizing polyelectrolyte pharmaceutical gels.

    PubMed

    Qu, Beibei; Lee, Ping I

    2012-05-01

    Charge groups in polyelectrolyte gels can affect the entrapment and release of ionic drugs as well as influencing the stability of colloidal and nanoparticulate drug delivery systems. An accurate knowledge of gel charge properties is therefore important to the understanding and design of such drug delivery systems. Existing rotating disk method for quantifying the surface potential of flat surfaces is based on the classical electrokinetic model that neglects the effect of surface conductivity and is therefore only applicable to ion-impenetrable hard surfaces. This classical electrokinetic model would be inaccurate for polyelectrolyte gel systems involving ion-penetrable charged layers or "soft" surfaces. In this study, we developed a new rotating disk model for characterizing charge properties of ion penetrable soft surfaces and tested it on polyvinyl alcohol (PVA)/polyacrylic acid (PAA), gelatin, and gelatin/PAA polyelectrolyte gels. In addition to classical electrokinetic parameters, the contribution of surface conductivity known to be very significant for soft and ion-penetrable gel surfaces has been taken into account in this new rotating disk model. Based on this new approach, two rotating gel disks of different radius but with identical gel composition and preparation procedures were employed for determining the gel surface potential and density of fixed charge groups. A comparison of the resulting data with that obtained from existing rotating disk model ignoring the surface conductivity reveals a significant underestimation of the gel surface potential and the density of fixed charge groups by the ion-impenetrable hard surface approach. Our results thus confirm that the contribution of surface conductivity is significant in the electrokinetic characterization of polyelectrolyte gels that can be evaluated with our new rotating disk model. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Acid-base equilibria of multilayered pseudo-polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Mateo, Ayeisca E.; Priefer, Ronny

    2015-11-01

    The use of weak polyelectrolytes in multilayer polymer systems provides a means of altering the physicochemical properties of these thin films. Previously, we have examined the limits of the polyanions by incorporating the pseudo-polyelectrolytes (pPE's), poly(4-vinylphenol) (PVPh) and poly[5-(2-trifluoromethyl-1,1,1-trifluoro-2-hydroxypropyl)-2-norbornene] (PNBHFA). These pPE's, although being polyacids, should have pKa values in the basic versus acidic pH range. In order to determine the pKa(app) value of these polymers, once multilayered onto Snowtex silica particles with the weak polyelectrolyte, poly(allylamine hydrochloride) (PAH), we employed zeta potential. PVPh demonstrated pKa(app) values ranging from 10.55 to 11.08 which varied based upon assembly pH conditions as well as layer number. PAH yielded pKa(app) values ranging between 9.81 and 10.99 when multilayered with PVPh and 9.91-11.04 when partnered with PNBHFA. However, from our study it would appear that PNBHFA does not interact with PAH electrostatically, but rather via H-bonding, and therefore should actually not be classified as a pPE.

  3. Luminescence quenching of a phosphorescent conjugated polyelectrolyte.

    PubMed

    Haskins-Glusac, Ksenija; Pinto, Mauricio R; Tan, Chunyan; Schanze, Kirk S

    2004-11-17

    The photophysical and luminescence quenching properties of a platinum(II) acetylide-based conjugated polyelectrolyte, Pt-p, which features carboxylic acid solubilizing groups are reported. The Pt-acetylide polymer is water soluble, and it exhibits phosphorescence from a triplet pi,pi exciton based on the conjugated backbone. The phosphorescence from Pt-p is quenched by viologens with different charges (MV(+), MV(2+), and MV(4+)), and in each case the quenching is dominated by a dynamic (diffusional) mechanism. Comparison of the Stern-Volmer quenching properties of Pt-p with those of a structurally analogous fluorescent organic polyelectrolyte leads to the conclusion that the amplified quenching effect, which is commonly observed for fluorescent conjugated polyelectrolytes, is not important for the platinum acetylide phosphorescent conjugated polyelectrolyte.

  4. Lyophilized Chitosan/xanthan Polyelectrolyte Complex Based Mucoadhesive Inserts for Nasal Delivery of Promethazine Hydrochloride

    PubMed Central

    G Dehghan, Mohamed Hassan; Marzuka, Marzuka

    2014-01-01

    The objective of this investigation was the development of chitosan/xanthan polyelectrolyte complex based mucoadhesive nasal insert of promethazine hydrochloride a drug used in the treatment of motion sickness. A 32 factorial design was applied for preparing chitosan/xanthan polyelectrolyte complex and to study the effect of independent variables i.e. concentration of xanthan [X1] and concentration of chitosan [X2] on various responses i.e. viscosity of polyelectrolyte complex solution, water uptake of nasal inserts (at pH 2, 5.5, 7.4), bioadhesion potential of nasal inserts and in-vitro drug release at Q6h through nasal inserts. FTIR and DSC analysis were carried out to confirm complex formation and on loaded and unloaded nasal insert to investigate any drug excipient interaction. The nasal inserts were also characterized by powder X-ray diffractometry (PXRD) and Scanning electron microscopy (SEM) and for ex-vivo permeation studies. The results show that higher amount of xanthan in polyelectrolyte complexes with respect to higher amount of chitosan retarded in-vitro drug release. The water uptake behaviour of nasal insert was strongly influenced by pH of the medium and by polycation/ polyanion concentration. The investigation verifies the formation of polyelectrolyte complexes formation between chitosan and xanthan at pH values in the vicinity of pKa intervals of the two polymers and confirms their potential for the nasal delivery of promethazine hydrochloride. PMID:25276178

  5. Stretch-induced biodegradation of polyelectrolyte multilayer films for drug release.

    PubMed

    Barthes, Julien; Mertz, Damien; Bach, Charlotte; Metz-Boutigue, Marie-Hélène; Senger, Bernard; Voegel, Jean-Claude; Schaaf, Pierre; Lavalle, Philippe

    2012-09-25

    The design of stimuli-responsive polymer assemblies for the controlled release of bioactive molecules has raised considerable interest these two last decades. Herein, we report the design of mechanically responsive drug-releasing films made of polyelectrolyte multilayers. A layer-by-layer (LbL) reservoir containing biodegradable polyelectrolytes is capped with a mechanosensitive LbL barrier and responds to stretching by a total enzymatic degradation of the film. This strategy is successfully applied for the release in solution of an anticancer drug initially loaded within the architecture.

  6. 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

  7. Polyelectrolyte adsorption, interparticle forces, and colloidal aggregation.

    PubMed

    Szilagyi, Istvan; Trefalt, Gregor; Tiraferri, Alberto; Maroni, Plinio; Borkovec, Michal

    2014-04-21

    This review summarizes the current understanding of adsorption of polyelectrolytes to oppositely charged solid substrates, the resulting interaction forces between such substrates, and consequences for colloidal particle aggregation. The following conclusions can be reached based on experimental findings. Polyelectrolytes adsorb to oppositely charged solid substrates irreversibly up to saturation, whereby loose and thin monolayers are formed. The adsorbed polyelectrolytes normally carry a substantial amount of charge, which leads to a charge reversal. Frequently, the adsorbed films are laterally heterogeneous. With increasing salt levels, the adsorbed mass increases leading to thicker and more homogeneous films. Interaction forces between surfaces coated with saturated polyelectrolyte layers are governed at low salt levels by repulsive electric double layer interactions, and particle suspensions are stable under these conditions. At appropriately high salt levels, the forces become attractive, principally due to van der Waals interactions, but eventually also through other forces, and suspensions become unstable. This situation can be rationalized with the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO). Due to the irreversible nature of the adsorption process, stable unsaturated layers form in colloidal particle suspensions at lower polyelectrolyte doses. An unsaturated polyelectrolyte layer can neutralize the overall particle surface charge. Away from the charge reversal point, electric double layer forces are dominant and particle suspensions are stable. As the charge reversal point is approached, attractive van der Waals forces become important, and particle suspensions become unstable. This behaviour is again in line with the DLVO theory, which may even apply quantitatively, provided the polyelectrolyte films are sufficiently laterally homogeneous. For heterogeneous films, additional attractive patch-charge interactions may become important

  8. [Mechanical characteristics of synthetic polyelectrolyte gel as a physical model of the cytoskeleton].

    PubMed

    Shkliar, T F; Toropova, O A; Safronov, A P; Pollack, G H; Bliakhman, F A

    2011-01-01

    A physical model of the cytoskeleton based on synthetic polyelectrolyte hydrogel of polymethacrylic acid has been proposed. From the physicochemical point of view, the structures of polyelectrolyte gel and the cytoskeleton show a high degree of similarity. It was shown that polyelectrolyte gel can shorten and produce mechanical stress in response to changes in the composition of the surrounding solution. The mechanical properties of the model gel were evaluated: Young modulus (2-6 kPa), stress relaxation time (0.1-1 s), and apparent viscosity (0.3-3 kPa x s). The viscoelastic properties of the gel depend on the degree of its swelling. It has been demonstrated that the mechanical properties of gels of polymethacrylic acid are close to those of biological objects.

  9. 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.

  10. Polyelectrolyte properties of filamentous biopolymers and their consequences in biological fluids.

    PubMed

    Janmey, Paul A; Slochower, David R; Wang, Yu-Hsiu; Wen, Qi; Cēbers, Andrejs

    2014-03-14

    Anionic polyelectrolyte filaments are common in biological cells. DNA, RNA, the cytoskeletal filaments F-actin, microtubules, and intermediate filaments, and polysaccharides such as hyaluronan that form the pericellular matrix all have large net negative charge densities distributed over their surfaces. Several filamentous viruses with diameters and stiffnesses similar to those of cytoskeletal polymers also have similar negative charge densities. Extracellular protein filaments such collagen, fibrin and elastin, in contrast, have notably smaller charge densities and do not behave as highly charged polyelectrolytes in solution. This review summarizes data that demonstrate generic counterion-mediated effects on four structurally unrelated biopolymers of similar charge density: F-actin, vimentin, Pf1 virus, and DNA, and explores the possible biological and pathophysiological consequences of the polyelectrolyte properties of biological filaments.

  11. Light-scattering study of the effect of salt and polyelectrolyte on magnetic latex particles

    SciTech Connect

    Sohn, D.; Russo, P.S.

    1993-12-31

    Dynamic and static light scattering methods have been used to study the interaction between magnetic latex and polyelectrolytes (polystyrene sulfonate sodium salt, NaPSS) in solution. The light scattering signal from magnetic latex particles was far stronger than that of the polyelectrolyte, especially during depolarized measurements where the polyelectrolyte was essentially invisible. Rotational and translational diffusion of the magnetic latex is investigated as a function of the NaPSS concentration and added salt (NaCl). The diffusion coefficient of magnetic latex decreases abruptly with increasing salt concentration when NaPSS is absent, but it recovers upon addition of NaPSS to the system. Static light scattering results also give evidence of particle aggregation at high salt.

  12. Effective interactions between oppositely charged polyelectrolytes in the presence of salt

    NASA Astrophysics Data System (ADS)

    Hansen, Jean-Pierre; Coslovich, Daniele; Kahl, Gerhard

    2011-12-01

    We generalize the familiar effective DLVO (Derjaguin-Landau-Verwey-Overbeek) pair potential between charged, hard core colloidal particles to the case of solutions of oppositely charged, penetrable polyelectrolyte coils in the presence of microions, within the framework of classical Density Functional Theory. The limiting behaviour of the effective potentials is derived in the limits of weak and strong microion screening; in the latter regime the effective potentials are shown to go over to a universal Gaussian form, multiplied by the square of the microion Debye screening length. The physical implications of screening on polyelectrolyte aggregation are discussed and illustrated by preliminary Monte Carlo simulations and the results of fluid integral equations for the polyelectrolyte pair structure.

  13. Structural and optical behavior of thin films of protein (BSA)-Polyelectrolyte (PAA, PSS) complexes

    NASA Astrophysics Data System (ADS)

    Talukdar, Hrishikesh; Kundu, Sarathi

    2017-05-01

    Optical behaviors of protein (BSA) in the presence of negatively charged polyelectrolytes (PAA and PSS) in thin film confirmation are studied using UV-Vis and photoluminescence spectroscopy. The out-of-plane structures and in-plane surface morphologies of the thin films of protein-polyelectrolyte complexes (PPC) are investigated using X-ray reflectivity (XRR) and Atomic force microscopy (AFM) respectively. It is found that although the out-of-plane structure and surface morphology of PPC is nearly same as in pure polyelectrolyte but a larger red-shift of ≈ 23 nm is obtained in optical emissions from the thin films of PPC in comparison with that of the pure protein and PPC solutions. Mechanism is proposed for such larger red-shift from the thin film of PPC.

  14. Underwater contact adhesion and microarchitecture in polyelectrolyte complexes actuated by solvent exchange

    NASA Astrophysics Data System (ADS)

    Zhao, Qiang; Lee, Dong Woog; Ahn, B. Kollbe; Seo, Sungbaek; Kaufman, Yair; Israelachvili, Jacob N.; Waite, J. Herbert

    2016-04-01

    Polyelectrolyte complexation is critical to the formation and properties of many biological and polymeric materials, and is typically initiated by aqueous mixing followed by fluid-fluid phase separation, such as coacervation. Yet little to nothing is known about how coacervates evolve into intricate solid microarchitectures. Inspired by the chemical features of the cement proteins of the sandcastle worm, here we report a versatile and strong wet-contact microporous adhesive resulting from polyelectrolyte complexation triggered by solvent exchange. After premixing a catechol-functionalized weak polyanion with a polycation in dimethyl sulphoxide (DMSO), the solution was applied underwater to various substrates whereupon electrostatic complexation, phase inversion, and rapid setting were simultaneously actuated by water-DMSO solvent exchange. Spatial and temporal coordination of complexation, inversion and setting fostered rapid (~25 s) and robust underwater contact adhesion (Wad >= 2 J m-2) of complexed catecholic polyelectrolytes to all tested surfaces including plastics, glasses, metals and biological materials.

  15. Energy Conversion in Polyelectrolyte Hydrogels

    SciTech Connect

    Erbas, Aykut; Olvera de la Cruz, Monica

    2015-08-18

    Using extensive molecular dynamics simulations of polyelectrolyte hydrogels we demonstrate that, on deformation, these hydrogels adjust their deformed state predominantly by altering electrostatic interactions between their charged groups rather than excluded-volume and bond energies. On deformation, due to the hydrogel’s inherent tendency to preserve electroneutrality in its interior, the translational entropy of counterions decreases and the total electrostatic energy becomes more attractive. This result is valid for a wide range of compression ratios and Bjerrum lengths. The change in the electrostatic energy is more marked in highly swollen gels at low ionic strengths. At high Bjerrum lengths, where most of the counterions are condensed on hydrogel chains and the gel resembles a neutral system, the electrostatic-energy change with deformation is weaker.

  16. Interaction between two polyelectrolyte brushes.

    PubMed

    Kumar, N Arun; Seidel, Christian

    2007-08-01

    We report molecular dynamics simulations on completely charged polyelectrolyte brushes grafted to two parallel surfaces. The pressure Pi is evaluated as a function of separation D between the two grafting planes. For decreasing separation, Pi shows several regimes distinguished by their scaling with D which reflects the different physical nature of the various regimes. At weak compression the pressure obeys the 1D power law predicted by scaling theory of an ideal gas of counterions in the osmotic brush regime. In addition we find that the brushes shrink as they approach each other trying to avoid interpenetration. At higher compressions where excluded volume interactions become important, we obtain scaling exponents between -2 at small grafting density rho(a) and -3 at large rho(a). This behavior indicates a transition from a brush under good solvent condition to the melt regime with increasing grafting density.

  17. A Zimm model for polyelectrolytes in an electric field

    NASA Astrophysics Data System (ADS)

    Long, Didier; Viovy, Jean-Louis; Ajdari, Armand

    1996-11-01

    By linearizing the electro-hydrodynamic equations and using general arguments, we have recently described the deformation and drift of a polyelectrolyte in solution under the simultaneous action of an electric field and a non-electric force, and obtained results qualitatively different from previous theories. We show here how one can adapt the Zimm model to obtain a more operational description for such problems, which allows us to recover our previous results in a simple way and could be used to describe more general situations such as transient phenomena or the electrophoresis of a polyampholyte.

  18. 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.

  19. The synthesis and study of telechelic polyelectrolytes for hydrogel formation

    NASA Astrophysics Data System (ADS)

    Hunt, Jasmine N.

    Polymeric hydrogels comprised of oppositely charged ABA triblock copolymer polyelectrolytes based upon poly(allyl glycidyl ether-b-ethylene glycol-ballyl glycidyl ether), P(AGE-b-EG-b-AGE), with functionalized ionic 'A'-endblocks and a neutral, hydrophilic 'B'-block were synthesized. Aqueous solutions of poly-cations and -anions were mixed at room temperature, producing hydrogels through co-assembly driven by electrostatic interactions between the endblocks. Due the ease and modular nature of the synthesis and hydrogel formation, polymeric libraries differing in relative block lengths and ionic functionalization were created and the affects of polymer composition on the hydrogel's mechanical and structural properties were examined.

  20. Improved separate solution method for determination of low selectivity coefficients.

    PubMed

    Egorov, Vladimir V; Zdrachek, Elena A; Nazarov, Valentine A

    2014-04-15

    Simple, fast, and theoretically substantiated experimental method for determination of improved selectivity coefficients is proposed. The method is based on the well-known fact that low selectivity coefficients determined by the separate solution method (SSM) are time-dependent and, upon our finding, this dependence is a well-defined linear function of time raised to the certain negative power. In particular, the selectivity coefficients obtained for equally charged primary and foreign ions by SSM linearly depend on time to the minus one-fourth. It was found that extrapolation of experimental data using this function to the intersection with Y axes gives reliable values of rather low selectivity coefficients (down to n × 10(-7)), which strongly differ from those measured using SSM and correspond well with the values obtained using the modified separate solution method (MSSM) proposed by Bakker. At the same time, the new method is free of one very essential limitation inherent to MSSM, namely, it is applicable after the conditioning of electrodes in the primary ion solution and can be repeated many times.

  1. 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%.

  2. Antibacterial polyelectrolyte micelles for coating stainless steel.

    PubMed

    Falentin-Daudré, Céline; Faure, Emilie; Svaldo-Lanero, Tiziana; Farina, Fabrice; Jérôme, Christine; Van De Weerdt, Cécile; Martial, Joseph; Duwez, Anne-Sophie; Detrembleur, Christophe

    2012-05-08

    In this study, we report on the original synthesis and characterization of novel antimicrobial coatings for stainless steel by alternating the deposition of aqueous solutions of positively charged polyelectrolyte micelles doped with silver-based nanoparticles with a polyanion. The micelles are formed by electrostatic interaction between two oppositely charged polymers: a polycation bearing 3,4-dihydroxyphenylalanine units (DOPA, a major component of natural adhesives) and a polyanion (poly(styrene sulfonate), PSS) without using any block copolymer. DOPA units are exploited for their well-known ability to anchor to stainless steel and to form and stabilize biocidal silver nanoparticles (Ag(0)). The chlorine counteranion of the polycation forms and stabilizes biocidal silver chloride nanoparticles (AgCl). We demonstrate that two layers of micelles (alternated by PSS) doped with silver particles are enough to impart to the surface strong antibacterial activity against gram-negative E. coli. Moreover, micelles that are reservoirs of biocidal Ag(+) can be easily reactivated after depletion. This novel water-based approach is convenient, simple, and attractive for industrial applications.

  3. Characterization of self-assembled polyelectrolyte complex nanoparticles formed from chitosan and pectin.

    PubMed

    Birch, Nathan P; Schiffman, Jessica D

    2014-04-01

    Chronic wounds continue to be a global healthcare concern. Thus, the development of new nanoparticle-based therapies that treat multiple symptoms of these "non-healing" wounds without encouraging antibiotic resistance is imperative. One potential solution is to use chitosan, a naturally antimicrobial polycation, which can spontaneously form polyelectrolyte complexes when mixed with a polyanion in appropriate aqueous conditions. The requirement of at least two different polymers opens up the opportunity for us to form chitosan complexes with an additional functional polyanion. In this study, chitosan:pectin (CS:Pec) nanoparticles were synthesized using an aqueous spontaneous ionic gelation method. Systematically, a number of parameters, polymer concentration, addition order, mass ratio, and solution pH, were explored and their effect on nanoparticle formation was determined. The size and surface charge of the particles were characterized, as well as their morphology using transmission electron microscopy. The effect of polymer concentration and addition order on the nanoparticles was found to be similar to that of other chitosan:polyanion complexes. The mass ratio was tuned to create nanoparticles with a chitosan shell and a controllable positive zeta potential. The particles were stable in a pH range from 3.5 to 6.0 and lost stability after 14 days of storage in aqueous media. Due to the high positive surface charge of the particles, the innate properties of the polysaccharides used, and the harmless disassociation of the polyelectrolytes, we suggest that the development of these CS:Pec nanoparticles offers great promise as a chronic wound healing platform.

  4. 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

  5. Reaction-complexation coupling between an enzyme and its polyelectrolytic substrate: determination of the dissociation constant of the hyaluronidase-hyaluronan complex from the hyaluronidase substrate-dependence.

    PubMed

    Lenormand, Hélène; Amar-Bacoup, Fériel; Vincent, Jean-Claude

    2013-01-01

    Hyaluronan (HA) is catalytically hydrolyzed by hyaluronidase (HAase). Depending on pH, HA is able to form a non-productive electrostatic complex with HAase in addition to the classical enzyme-substrate complex. Experiments have shown the strong inhibition of the HA hydrolysis catalyzed by HAase when performed at high HA over HAase concentration ratio and low ionic strength. The substrate-dependence thus shows a non-classic inhibition of HAase at high substrate concentrations due to the sequestration of HAase by HA in the electrostatic complex. The modeling of the HA/HAase system is characteristic of a reaction-complexation coupling and it is very difficult to study reaction or binding, separately. Here, we have established the equation controlling the global system and shown that the substrate-dependence of such a system is a direct combination of a pure Michaelis-Menten equation associated with the reaction and a hyperbolic curve associated with the binding. At low substrate concentrations, the hyperbola, representing the relative part of HAase not sequestered by HA, can be assimilated to a straight line. We have established the relationship between the slope of that straight line and the dissociation constant of the electrostatic HA-HAase complex. Fitting the theoretical equation to the experimental data allowed us to determine, for the first time, the Kd value of the non-productive HA-HAase complex at low ionic strength. Copyright © 2013. Published by Elsevier B.V.

  6. Structure of Polyelectrolyte Brushes in the Presence of Multivalent Counterions

    SciTech Connect

    Yu, Jing; Mao, Jun; Yuan, Guangcui; Satija, Sushil; Jiang, Zhang; Chen, Wei; Tirrell, Matthew

    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 Ca2+, Mg2+, and Ba2+, and trivalent Y3+ 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 theory well, exhibiting two distinct regimes: the osmotic and salted brush regimes. Introducing trivalent Y3+ cations causes an abrupt shrinkage of the PSS brush due to the uptake of Y3+ counterions. The uptake of Y3+ counterions and shrinkage of the brush are reversible upon increasing the concentration of monovalent salt. Divalent cations, Mg2+, Ca2+, and Ba2+, 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.

  7. Complexation behavior of oppositely charged polyelectrolytes: Effect of charge distribution

    NASA Astrophysics Data System (ADS)

    Zhao, Mingtian; Zhou, Jihan; Su, Cuicui; Niu, Lin; Liang, Dehai; Li, Baohui

    2015-05-01

    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)5/(KGKG)5, (EEGG)5/(KKGG)5, and (EEGG)5/(KGKG)5, in a solution including explicit solvent molecules. Among the three model systems, only the charge distributions along the chains are not 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

  8. Spectrophotometric determination of silicate traces in hemodialysis solutions.

    PubMed

    Raggi, M A; Sabbioni, C; Mandrioli, R; Zini, Q; Varani, G

    1999-06-01

    Reliable methods for the analysis of silicon are of great importance, because it seems that the silicate anion can reduce aluminum bioavailability in patients undergoing dialysis. Thus, a simple and sensitive spectrophotometric method is described for the determination of silicate traces in dialysis solutions. The method is based on the reaction between silicate ions and excess ammonium molybdate reagent to give a yellow silico-molybdic complex. This complex is then reduced to the heteropoly blue compound by means of ascorbic acid. Absorbance values are measured at 830 nm, and are stable for more than 2 h. A good linearity was obtained up to 300 ng ml(-1) of silicon concentration. The accuracy and the precision of the method were good; relative standard deviation values of 2% intraday and of 3.9% interday for six replicates on 40 ng ml(-1) standard silicate solutions were found. Results of the analysis of some commercial hemodialysis solution samples, obtained by means of the 'standard additions' method, are provided.

  9. Determining PPN gamma with Gaia's Astrometric Core Solution

    NASA Astrophysics Data System (ADS)

    Hobbs, David; Holl, B.; Lindegren, L.; Raison, F.; Klioner, S.; Butkevich, A.

    2009-05-01

    Gaia is the ESA space astrometry mission due for launch in December 2011. Its objective is to map a large part of our Galaxy and its surroundings by simultaneous positional, photometric and spectroscopic measurements. In addition to its huge output of fundamental astrometric and astrophysical data, it will provide stringent new tests of general relativity. One of the largest relativistic effects observed via Gaia's measurements is the gravitational light bending due to the Sun and major planets. This opens the possibility of accurately measuring the parameter γ of the Parameterized Post-Newtonian (PPN) formulation, which is of key importance to fundamental physics. By analyzing the astrometric residuals, which compare the observations to predictions based on general relativity, a constraint on PPN γ could be obtained which is significantly better than today's best estimate from the Cassini mission of 2x10-5. The effects of introducing global unknowns into Gaia's Astrometric Global Iterative Solution (AGIS) are not well understood and the convergence properties of the solution may be affected in undesirable ways. For this reason we have implemented the algorithm to determine PPN γ within our simulation software, known as AGISLab. This light-weight and scalable simulation tool allows to investigate the convergence properties of the solution when PPN γ is included together with the astrometric and attitude updates. In particular we have considered the statistical correlation between PPN γ and the stellar parallaxes which slows the convergence of the iterative solution. By introducing a further global pseudo parameter, equivalent to a common parallax shift but constrained to zero, this correlation is eliminated resulting in an improved convergence and a better estimate of the standard error of PPN γ. Preliminary results are presented based on simulated data, which include only the deflection of light by the Sun.

  10. Preliminary Oklahoma Optimal Fault Orientations Determined by Focal Mechanism Solutions

    NASA Astrophysics Data System (ADS)

    Darold, A. P.; Holland, A. A.

    2015-12-01

    Six hundred and eighty-eight focal mechanisms were calculated between 2010 and 2015 and used to determine optimally oriented fault orientations within the contemporary stress field in Oklahoma. The contemporary stress, maximum horizontal stress (shmax) orientation of N85°E, is determined from the orientation of the P- and T-axes of the 688 focal mechanisms used. The majority of the focal mechanism solutions were computed using earthquakes occurring in central and north-central Oklahoma, a region where the greatest numbers of recent earthquakes have occurred. The focal mechanisms used in this compilation include Regional Moment Tensor solutions and first-motion focal mechanisms. We determined a mean shmax of 83.2° with a standard deviation of 21.3° azimuth. The median shmax is 84.8° with 633 observations. From the probability density functions, it is possible to define orientations of optimal, moderately optimal and sub-optimal fault strikes. The focal mechanism distribution is dominated by strike-slip motion on steeply dipping faults and thus fault strike is restricted to the range of 0° to 180°. Optimal fault strike orientation ranges between 45°-60°, 105°-120° and 135°-150° and represent fault orientations most likely for failure. Moderately optimal fault strike orientation ranges between 15°-45°, 60°-75°, 90°-105° and 120°-135° and represent fault orientations moderately likely for failure. All other orientations of fault strike are sub-optimal orientations and have a low likelihood of failure. These results do not indicate that failure cannot occur on sub-optimal fault strikes, but suggest that they are less likely. We apply these results to the most comprehensive Oklahoma fault map to date. Identifying optimal fault orientations is important for determining the potential earthquake hazard of both naturally occurring and triggered seismicity.

  11. 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

  12. Spectrofluorimetric determination of trace aluminum in diluted hemodialysis solutions

    NASA Astrophysics Data System (ADS)

    Gündüz, S. Beniz; Küçükkolbaşý, Semahat; Atakol, Orhan; Kýlýç, Esma

    2005-03-01

    In this study, a spectrofluorimetric method has been developed for the determination of aluminum based on the formation of an aluminum complex with N, N'-disalicylidene-1,3-diamino-2-hydroxypropane (DSAHP). The most suitable pH, solvent medium, complex formation time, Schiff base concentration and temperature were determined. The excitation and emission wavelengths were 270 and 437 nm, respectively, in which the DSAHP-Al complex gave the maximum flurescence intensity at pH 3.0 and 6.0 in 50% dioxan-50% water medium. Under these conditions, calibration curves were obtained in three different linear limits, and was found that aluminum could be detected within the concentration limit of 0-10.0 μM and the lowest detection limit being 0.27 ng ml -1. The stochiometry of the DSAHP-Al complex was also determined spectrofluorimetrically under optimal conditions and the molar ratio of DSAHP-Al was calculated as 2:1. Using the developed method, aluminum was detected in hemodialysis solutions, and the results obtained were similar and comparable with those obtained using the method described in the British Pharmacopoeia within 95% confidence limits. This method can be used successfully for the routine determination of aluminum because it is quick, requires less amount of reactives, is sensitive, reliable and reproducible.

  13. Surface-induced rearrangement of polyelectrolyte complexes: influence of complex composition on adsorbed layer properties.

    PubMed

    Ondaral, Sedat; Ankerfors, Caroline; Odberg, Lars; Wågberg, Lars

    2010-09-21

    The adsorption characteristics of two different types of polyelectrolyte complexes (PECs), prepared by mixing poly(allylamine hydrochloride) and poly(acrylic acid) in a confined impinging jet (CIJ) mixer, have been investigated with the aid of stagnation point adsorption reflectometry (SPAR), a quartz crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM) using SiO(2) surfaces. The two sets of PEC were prepared by combining high molecular mass PAH/PAA (PEC-A) and low molecular mass PAH/PAA (PEC-B). The PEC-A showed a higher adsorption to the SiO(2) surfaces than the PEC-B. The adsorption of the PEC-A also showed a larger change in the dissipation (ΔD), according to the QCM-D measurements, suggesting that the adsorbed layer of these complexes had a relatively lower viscosity and a lower shear modulus. Complementary investigations of the adsorbed layer using AFM imaging showed that the adsorbed layer of PEC-A was significantly different from that of PEC-B and that the changes in properties with adsorption time were very different for the two types of PECs. The PEC-A complexes showed a coalescence into larger block of complexes on the SiO(2) surface, but this was not detected with the PEC-B. The size determinations of the complexes in solution showed that they were very stable over time, and it was therefore concluded that the coalescence of the complexes was induced by the interaction between the complexes and the surface. The results also indicated that polyelectrolytes can migrate between the different complexes adsorbed to the surface. The results also give indications that the preparation of PEC-B leads to the formation of two different types of polyelectrolyte complexes differing in the amount of polymer in the complexes; i.e., two populations of complexes were formed with similar sizes but with totally different adsorption structures at the solid-liquid interface.

  14. The preparation of polyelectrolyte complexes carboxymethyl chitosan(CMC)-pectin by reflux method as a Pb (II) metal ion adsorbent

    NASA Astrophysics Data System (ADS)

    Hastuti, Budi; Mudasir, Siswanta, Dwi; Triyono

    2016-02-01

    Aim of this research is to synthesized a chemically stable polyelectrolyte complexs carboxymetyl chitosan CMC-pectin as Pb(II) ion adsorbent by reflux method. During synthesis process, the optimum mass ratio of CMC and pectin was pre-determined and the active groups of the CMC-pectin complex was characterized by using IR spectrofotometer. Finally, adsorption capacity of the adsorbent material for Pb (II) ions was studied under optimum condition, i.e. adsorbent mass, contact time, and pH. Result shows that CMC could be succesfully combined with pectin to produce CMC-pectin complex. The optimum mass ratio CMC: pectin to form the polyelectrolyte complexs CMC-pectin was 70% : 30%. The active groups identified in the CMC-pectin complex was a hydroxyl (OH) and carboxylate (-COOH) groups. The optimum conditions for Pb (II) ion absoprtion was 10 mg of the adsorbent mass, 75 min of contact time, and pH 5. This material can be effectively used as adsorbents for Pb (II) ions, where up to 91% Pb (II) metal ions was adsorbed from aqueous solution and the adsorption capacity of the adsorbent was 41.63 mg/g.

  15. Electrostatic Properties of an Entirely Hydrophilic Polyelectrolyte.

    NASA Astrophysics Data System (ADS)

    Hoagland, David; Popov, Alexei

    2007-03-01

    A new of class of polyelectrolyte ionenes is described, one with an entirely hydrophilic backbone of quaternized nitrogens connected by polyoxyethylene spacers of controlled length. The chemistry of these pegylated ionenes yields solubility at constant charge density in solvents of varying dielectric constant; it also allows for controlled variation of polyelectrolyte charge density through choice of monomers. Such features make the new ionenes ideal model polyelectrolytes on which to test theories for electrostatic properties of polyelectrolytes. In particular, we report on the use of electrophoresis to measure effective charge density for different charge spacings and dielectric constants. In conformance with previous results for aliphatic ionenes, we find counterion condensation for pegylated ionenes at conditions different than classical predictions. Counterion condensation -- a constant effective charge density - is encountered in univalent electrolyte by the lowering of dielectric constant even when the dimensionless charge density is less than unity; conditions for the condensation depend on counterion identity (size). Additional studies on various anionic polyelectrolytes dissolved in nonaqueous solvents reproduce the same trends, suggesting their universality.

  16. Energy conversion in polyelectrolyte hydrogels

    NASA Astrophysics Data System (ADS)

    Olvera de La Cruz, Monica; Erbas, Aykut; Olvera de la Cruz Team

    Energy conversion and storage have been an active field of research in nanotechnology parallel to recent interests towards renewable energy. Polyelectrolyte (PE) hydrogels have attracted considerable attention in this field due to their mechanical flexibility and stimuli-responsive properties. Ideally, when a hydrogel is deformed, applied mechanical work can be converted into electrostatic, elastic and steric-interaction energies. In this talk, we discuss the results of our extensive molecular dynamics simulations of PE hydrogels. We demonstrate that, on deformation, hydrogels adjust their deformed state predominantly by altering electrostatic interactions between their charged groups rather than excluded-volume and bond energies. This is due to the hydrogel's inherent tendency to preserve electro-neutrality in its interior, in combination with correlations imposed by backbone charges. Our findings are valid for a wide range of compression ratios and ionic strengths. The electrostatic-energy alterations that we observe in our MD simulations may induce pH or redox-potential changes inside the hydrogels. The resulting energetic difference can be harvested, for instance, analogously to a Carnot engine, or facilitated for sensor applications. Center for Bio-inspired Energy Science (CBES).

  17. Cationic β-cyclodextrin polymer applied to a dual cyclodextrin polyelectrolyte multilayer system.

    PubMed

    Junthip, Jatupol; Tabary, Nicolas; Leclercq, Laurent; Martel, Bernard

    2015-08-01

    A polyelectrolyte multilayer film (PEM) based on cationic and anionic β-cyclodextrin polyelectrolytes was coated onto a textile substrate for future drug delivery purposes. We firstly synthesized a novel cationic β-cyclodextrin polymer (polyEPG-CD) by crosslinking β-cyclodextrin (βCD) with epichlorohydrin (EP) under basic conditions, in the presence of glycidyltrimetrylammonium chloride (GTMAC) as cationizing group. The influence of preparation conditions has been investigated in order to preferably obtain a water soluble fraction whose charge density and molecular weights were optimal for the layer-by-layer (LbL) deposition process. The different cationic cyclodextrin polymers obtained were characterized by FTIR, NMR, colloidal titration, conductimetry, thermogravimetric analysis and size exclusion chromatography. Besides, the counterpart polyelectrolyte was a β-cyclodextrin polymer crosslinked with citric acid, polyCTR-CD, whose synthesis and characterization have been previously reported. Finally we realized the Layer by Layer (LbL) build-up of the PEM coating onto the textile support, using the dip coating method, by alternatively soaking it in cationic polyEPG-CD and anionic polyCTR-CD solutions. This multilayer self-assembly was monitored by SEM, gravimetry and OWLS in function of both polyelectrolytes concentrations and ratios. Solutions parameters such as pH, ionic strenght were also discussed.

  18. Delivery of functional polyelectrolytes from complexes induced by salt addition: impact of the initial binding strength.

    PubMed

    Rondon, Céline; Argillier, Jean-François; Leal-Calderon, Fernando

    2014-12-15

    This paper focuses on polyelectrolyte complexes (PECs) soft nanoparticles and how dissociation occurs upon salt addition. The system is composed of a strong polyanion (polystyrene sulfonate, PSS) and a weak polycation (poly(allylamine) hydrochloride, PAH) in large excess. Soft nanoparticles were obtained by pouring a PSS solution into a PAH one under constant stirring. As the charge density of PAH chain depends on the pH of the polyelectrolyte solution, PEC particles exhibit distinct behaviors under salt addition depending on the pH of the continuous phase. At pH=5.5, PAH chains are fully charged and the addition of salt produces particle aggregation followed by sedimentation. Conversely, at pH=10 where PAH is only partially charged, the addition of salt drives a progressive disentanglement of the two polyelectrolytes, as revealed by both viscosimetric and spectroscopic measurements. At sufficiently high ionic strength, the two electrolytes are fully dissociated. Our results emphasize differences in behavior (binding reversibility) between strongly and weakly bound polyelectrolytes of opposite charge upon addition of salt. We discuss the potential use of these systems as stimulus responsive materials for the delivery of scale nucleation inhibitors in application around petroleum recovery. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Conductive thin-film composite hydrogels: Trapping an anionic polyelectrolyte in a polyaziridine host matrix

    SciTech Connect

    Wexler, A.; Suen, C.; Hill, S.

    1995-08-01

    Acid-catalyzed polymerization of sufficiently concentrated aqueous solutions of a trifunctional aziridine monomer affords hydrogels. Dynamic mechanical analysis has been used to demonstrate that composite hydrogels, obtained when the polymerization is effected in the presence of poly(sodium styrenesulfonate), have a composition dependent modulus. A region rich in the polyelectrolyte has a modulus which exceeds that of the {open_quotes}host{close_quotes} homogeneous polyaziridine hydrogel. This is consistent with ionic bonds between protonated sites on the polyaziridine matrix and sulfonate groups on the included polyelectrolyte augmenting the structural stability of the hydrogel. Thin films were prepared from coatings of the incipient hydrogel solutions. When the coatings are dried to a water content of 20%, water-insoluble thin films are obtained provided a critical weight fraction of the monomer is exceeded. Conductive thin films can be obtained, provided a critical weight fraction of polyelectrolyte is exceeded. FTIR analysis of the coatings in the attenuated total reflectance mode shows that conductivity increases as tight ion pairing decreases between the polyelectrolyte and its counter ions in the matrix. The S-shaped dependence of the normalized conductivity on the composition of the thin films is independent of the state of hydration of the film. Effective medium percolation theory, (EMPT), generally fits the S-shaped compositional dependence of the conductivity but overestimates the rate of growth of the conductivity beyond the critical point. 20 refs., 7 figs.

  20. Regenerable Polyelectrolyte Membrane for Ultimate Fouling Control in Forward Osmosis.

    PubMed

    Kang, Yan; Zheng, Sunxiang; Finnerty, Casey; Lee, Michael J; Mi, Baoxia

    2017-03-02

    This study demonstrated the feasibility of using regenerable polyelectrolyte membranes to ultimately control the irreversible membrane fouling in a forward osmosis (FO) process. The regenerable membrane was fabricated by assembling multiple polyethylenimine (PEI) and poly(acrylic acid) (PAA) bilayers on a polydopamine-functionalized polysulfone support. The resulting membrane exhibited higher water flux and lower solute flux in FO mode (with the active layer facing feed solution) than in PRO mode (with the active layer facing draw solution) using trisodium citrate as draw solute, most likely due to the unique swelling behavior of the polyelectrolyte membrane. Membrane regeneration was conducted by first dissembling the existing PEI-PAA bilayers using strong acid and then reassembling fresh PEI-PAA bilayers on the membrane support. It was found that, after the acid treatment, the first covalently bonded PEI layer and some realigned PAA remained on the membrane support, acting as a beneficial barrier that prevented the acid-foulant mixture from penetrating into the porous support during acid treatment. The water and solute flux of the regenerated membrane was very similar to that of the original membrane regardless of alginate fouling, suggesting an ultimate solution to eliminating the irreversible membrane fouling in an FO process. With a procedure similar to the typical membrane cleaning protocol, in situ membrane regeneration is not expected to noticeably increase the membrane operational burden but can satisfactorily avoid the expensive replacement of the entire membrane module after irreversible fouling, thereby hopefully reducing the overall cost of the membrane-based water-treatment system.

  1. A quaternion pose determination solution based on monocular vision model

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Zhang, Qiuzhi; Zhang, Baoshang

    2011-08-01

    Determination of relative three-dimensional position and orientation between two reference frames can be solved by the pose measuring methods based on monocular vision model. Owing to the special T-shaped configuration, the definition of object rotational matrix in the terms of quaternion elements helped in representing the problem by six nonlinear equations from which a closed-form solution can be obtained for all the unknown parameters. The calculating formulas of elements in the rotational matrix were deduced from the coordinates of feature points in camera frame as well as the converting vector which was also introduced into the process acting as corrected term. An approximate pose could be found by the assumption of zero difference in depth of all points in camera frame, then the converting vector should be initialized by the third row of current rotational matrix. The principle of computing priority of the max value in quaternion expression was proposed to ensure the convergence of the iteration loop through which the final pose was achieved in a few iterations. Simulation experiments show the validity of the solution and analysis of the calculating precision was made in detail. The measuring orientation error would constringe with the reduction of distance from camera focus to target object and performance of the algorithm went well in short distance, while the deformation went larger with the increasing of errors caused by imprecise correspondence.

  2. Determination of trace elements in triglycine sulfate solutions

    NASA Technical Reports Server (NTRS)

    Tadros, Shawky H.

    1993-01-01

    Ten elements were divided into 2 groups. The elements in the first group included iron, nickel, chromium, manganese, copper, and gold. The elements in the second group included zinc, cobalt, lead, cadmium, and gold. Five ppm of each element in each group was spiked in a 1 percent triglycine sulfate (TGS) solution. Glycine was removed with 1-naphthyl isocyanate in ether medium. The glycine derivative 1-naphthyl isocyanate glycine was removed by filtration, and the filtrates were analyzed for the different elements. Analysis of these elements was performed by using the 5100 Perkin-Elmer Atomic Absorption Spectrophotometer. The result of these experiments was the observation that there was a decrease in the concentration of chromium and gold, which was interpreted to be due to the chelation of these elements by the derivative 1-naphthyl isocyanate glycine. Further research is needed to determine the concentration of other elements in triglycine sulfate (TGS) solutions. These elements will include lithium, sodium, rubidium, magnesium, calcium, strontium, barium, aluminum, and silicon. These are the most likely elements to be found in the sulfuric acid used in manufacturing the TGS crystal. Moreover, we will extend our research to investigate the structural formula of the violet colored chelated compounds, which had been formed by interaction of the derivative 1-naphthyl isocyanate glycine with the different elements, such as gold, chromium.

  3. Ion Environments in Mn(2+)-Doped Polyelectrolyte Complexes: Dilute Magnetic Saloplastics.

    PubMed

    Abhyankar, Nandita; Ghoussoub, Yara E; Wang, Qifeng; Dalal, Naresh S; Schlenoff, Joseph B

    2016-07-14

    Amorphous hydrated complexes of the polyelectrolytes poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium) were doped with the spin-5/2 ion Mn(2+). X-band electron paramagnetic resonance (EPR) measurements of the Mn(2+) spins within these stoichiometric polyelectrolyte complexes (PECs) revealed an octahedral coordination environment, similar to that observed in aqueous solutions of Mn(2+). This octahedral symmetry of the [Mn(H2O)6](2+) complexes, observed in fully hydrated PECs, is somewhat distorted because of the wide range of ion pairs possible with the sulfonate group on PSS. As the Mn(2+) concentration was increased, the linewidths broadened, indicating the dominance of dipolar broadening over exchange narrowing in determining the linewidths; that is, any exchange narrowing was masked by the large dipolar broadening. The calculated linewidths were used to estimate the strengths of the dipolar interactions, and hence the distances between the Mn(2+) spins, on the basis of a simple model of regularly spaced spins. The distances calculated by this method were roughly comparable to the geometric average distances calculated on the basis of the Mn(2+) concentrations and densities of the doped PEC samples. From a comparison of their EPR spectra, the ion environments in the doped, fully hydrated PECs were found to be similar to those in hydrated classical ion exchange resins. EPR spectra before and after drying of the PECs indicate the replacement of octahedrally coordinated water by oxide anions from the polyanion chain and the corresponding loss of the symmetric environment of Mn(2+) ions.

  4. 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.

  5. Optically transparent polyelectrolyte-silica composite materials: Preparation, characterization, and application in optical chemical sensing

    SciTech Connect

    Shi, Yining; Seliskar, C.J.

    1997-03-01

    A series of polyelectrolyte-containing silica composite materials have been prepared by sol-gel processing. These optically transparent composites have been characterized by scanning electron microscopy and UV-visible spectrophotometry. These materials can be processed into monolithic disks and thin films. The thicknesses of spin-coated films of these materials on glass can be varied from 0.13 to 3.5 {mu}m as determined by an optical interferences method. These materials are ion exchangeable and less brittle than the parent silica glass due to the incorporation of the organic polyelectrolyte. These new composites retain the nanoscale porosity and optical transparency into the ultraviolet of the parent silica sol-gel glasses, making them attractive host matrixes for the immobilization of ionizable dye molecules and chemical reagents. An optical pH sensing platform (0.9 x 2.5 cm) based on the electrostatic immobilization of HPTS (8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt) in a PDMDAAC (poly(diallyldimethylammonium chloride))-silica composite film was fabricated and evaluated. The results clearly demonstrate that this platform is easy to construct with high batch reproducibility and can be regenerated by simple solution ion exchange. The platform is usable in both the modes of absorption and fluorescence, making it versatile. Having a fast response time (ca. {approximately}2 s to more than 2 units of pH change), the platform is also highly resistant to dye leaching and storage degradation over a period of months. 49 refs., 9 figs., 2 tabs.

  6. Spin-Coated Polyelectrolyte Coacervate Films.

    PubMed

    Kelly, Kristopher D; Schlenoff, Joseph B

    2015-07-01

    Thin films of complexes made from oppositely charged polyelectrolytes have applications as supported membranes for separations, cell growth substrates, anticorrosion coatings, biocompatible coatings, and drug release media, among others. The relatively recent technique of layer-by-layer assembly reliably yields conformal coatings on substrates but is impractically slow for films with thickness greater than about 1 μm, even when accelerated many fold by spraying and/or spin assembly. In the present work, thin, uniform, smooth films of a polyelectrolyte complex (PEC) are rapidly made by spin-coating a polyelectrolyte coacervate, a strongly hydrated viscoelastic liquidlike form of PEC, on a substrate. While the apparatus used to deposit the PEC film is conventional, the behavior of the coacervate, especially the response to salt concentration, is highly nontraditional. After glassification by immersion in water, spun-on films may be released from their substrates to yield free-standing membranes of thickness in the micrometer range.

  7. Glucose solution determination based on liquid photoacoustic resonance.

    PubMed

    Zhao, SiWei; Tao, Wei; He, QiaoZhi; Zhao, Hui; Yang, HongWei

    2017-01-10

    Noninvasive blood glucose determination has received considerable attention in the past from both patients and scientists all over the world, and it is becoming increasingly important as a research focus. The two most difficult problems leading to no breakthrough in this area are sensitivity and specificity in determination. In order to obtain reliable measurement results of blood glucose levels, we propose a new liquid photoacoustic resonance theory that can significantly enhance the intensity of the signal and improve the sensitivity. This paper demonstrates the theory of liquid photoacoustic resonance, gives a rigorous mathematical expression, and analyzes the variation of the transducer output in the case of liquid photoacoustic resonance. A signal processing method is demonstrated at the same time under the liquid photoacoustic resonance condition. Meanwhile, the feasibility and validity are verified by experiments with different concentrations of glucose solution. The result shows that liquid photoacoustic resonance can strengthen the signal, and the resolution achieves 20  mg/dL. This method overcomes the issue of low sensitivity and the inaccurate detection in the nonresonant case, and gets accurate results. This result could provide a theoretical basis for realization of noninvasive measurement of blood glucose.

  8. Directed motion of proteins along tethered polyelectrolytes.

    PubMed

    Henzler, Katja; Rosenfeldt, Sabine; Wittemann, Alexander; Harnau, Ludger; Finet, Stephanie; Narayanan, Theyencheri; Ballauff, Matthias

    2008-04-18

    We present the first time-resolved investigation of motions of proteins in densely grafted layers of spherical polyelectrolyte brushes. Using small-angle x-ray scattering combined with rapid stopped-flow mixing, we followed the uptake of bovine serum albumin by poly(acrylic acid) layer with high spatial and temporal resolution. We find that the total amount of adsorbed protein scales with time as t(1/4). This subdiffusive behavior is explained on the basis of directed motion of the protein along the polyelectrolyte chains.

  9. 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.

  10. Does cation dehydration drive the binding of metal ions to polyelectrolytes in water? What we can learn from the behaviour of aluminium(III) and chromium(III).

    PubMed

    Burrows, Hugh D; Costa, Diana; Ramos, M Luísa; Miguel, M da Graça; Teixeira, M Helena; Pais, Alberto A C C; Valente, Artur J M; Bastos, Margarida; Bai, Guangyue

    2012-06-14

    Much stronger binding is seen in aqueous solutions between the anionic polyelectrolyte potassium poly(vinyl sulfate) and the substitution labile aluminium(III) than with the kinetically inert chromium(III). This strongly supports the idea that entropy driven water loss from the hydration sphere of the metal ion plays a major role in driving binding of the trivalent metal ion to the polyelectrolyte.

  11. 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…

  12. 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…

  13. Photoluminescence of water-soluble CdSe/ZnS nanoparticles in complexes with cationic and anionic polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Strekal', N.; Kulakovich, O.; Belyaev, A.; Stsiapura, V.; Maskevich, S.

    2008-01-01

    The data on the influence of polyelectrolytes on the photon emission probability of water-soluble CdSe/ZnS nanoparticles are obtained. The decrease in the photoluminescence quantum yield of nanoparticles occurring upon their transfer to aqueous solutions from toluene (in the course of solubilization) depends on the ionic nature of an agent applied for the replacement of trioctylphosphine oxide residues on the surface of nanoparticles. It turns out that such a cationic modifying agent as cysteamine leads to an insignificant (˜10%) decrease in the photoluminescence quantum yield of nanoparticles. The use of such an anionic agent as mercaptoacetic acid causes a significant (˜80%) decrease in the quantum yield and the average decay time of photoluminescence. For nanoparticles modified by mercaptoacetic acid (anionic nanoparticles), this decrease is partially compensated if these particles interact with polyelectrolytes whose backbone is oppositely charged (cationic polyelectrolytes), such as polyallylamine and polydiallyldimethylammonium chloride. In this case, the photoluminescence quantum yield shows a reverse increase by 40%, remaining the same within a matter of months or longer. In contrast to this, cationic nanoparticles, only slightly quenched by cysteamine at the stage of solubilization, are appreciably degraded in complexes with anionic polyelectrolytes in solutions and upon immobilization of complexes on a substrate, so that their photoluminescence quantum yield irreversible decreases to zero within a few days. Possible mechanisms of the effects observed are discussed and their consideration in polyelectrolyte-based molecular lithography.

  14. Branched Polyelectrolytes Based on Hydrolyzed Dextran-Graft

    NASA Astrophysics Data System (ADS)

    Bezugly, N.; Kutsevol, N.; Filipchenko, S.

    2008-08-01

    Two series of Dextran-graft-Polyacrylamide copolymers with polysaccharide backbone having different molecular weights (Mw = 20 000 and Mw = 70 000) and long grafted Polyacrylamide chains were synthesized by radical copolymerization using Ceric-ion-induced redox initiation. A certain fraction of ionic sites was introduced into the PAA grafts by alkaline hydrolysis during different time periods (NH2 groups were changed by OH groups) in order to convert D-g-PAA into polyelectrolyte. It was established that D-g-PAA copolymers both in non-ionic and in ionic form can adsorb transition metal ions from aqueous solution. These copolymers have high flocculation efficiency due to their expanded conformation in water solution. The flocculation ability is inversely related to the spacing of the PAA grafts (i.e. the length of backbone between the grafts).

  15. PROPERTIES OF DOUBLE-STRANDED DNA AS A POLYELECTROLYTE.

    PubMed

    OHNISHI, T

    1963-11-01

    The stability of the structure of double-stranded DNA in the salt-free solution is discussed on the basis of the polyelectrolyte theory. Assuming that DNA is an infinitely long rod, and the formation of double strands is divided into combining process and folding process, the free energy changes required in these processes are calculated by the use of the exact solutions of two-dimensional Poisson-Boltzmann equation for the one rod and the two rod systems.By strong depression of electrostatic interaction due to counter-ion condensation phenomena, the free energy change is remarkably decreased so that the double-stranded structure of DNA can be stabilized by energy of hydrogen bonds between base pairs. The increase of the activity coefficient of a counterion upon heat denaturation of DNA is also explained.

  16. Evaluation of the counterion condensation theory of polyelectrolytes.

    PubMed Central

    Stigter, D

    1995-01-01

    We compare free energies of counterion distributions in polyelectrolyte solutions predicted from the cylindrical Poisson-Boltzmann (PB) model and from the counterion condensation theories of Manning: CC1 (Manning, 1969a, b), which assumes an infinitely thin region of condensed counterions, and CC2 (Manning, 1977), which assumes a region of finite thickness. We consider rods of finite radius with the linear charge density of B-DNA in 1-1 valent and 2-2 valent salt solutions. We find that under all conditions considered here the free energy of the CC1 and the CC2 models is higher than that of the PB model. We argue that counterion condensation theory imposes nonphysical constraints and is, therefore, a poorer approximation to the underlying physics based on continuum dielectrics, point-charge small ions, Poisson electrostatics, and Boltzmann distributions. The errors in counterion condensation theory diminish with increasing distance from, or radius of, the polyion. PMID:8527651

  17. Formation of polyelectrolyte multilayers: ionic strengths and growth regimes.

    PubMed

    Tang, Kan; Besseling, Nicolaas A M

    2016-01-28

    This article presents a study of layer-by-layer (LbL) formation of poly-electrolyte multilayers (PEMs). Upon increasing ionic strength LbL growth patterns vary from linear for the lowest salt concentrations ([NaCl] = 0, 0.001, and 0.01 M) to exponential (for [NaCl] = 0.5 and 1 M). The slope of the linear growth at the lowest ionic strengths increases with increasing [NaCl]. During the LbL process at 0.5 M NaCl we observe a cross over from exponential to linear growth for which the slope is orders of magnitude larger than those observed at low salt concentrations. We provide a comprehensive interpretation of these growth behaviors, which are also reported for many other LbL PEM systems, based on the generic features of the phase diagram of aqueous solutions of mixtures of oppositely charged poly-electrolytes. Processes occurring in LbL formation of PEMs can be understood as moving in the direction of equilibrium, while never achieving it. The experimental model system in this study was: polydiallyldimethylammonium chloride/polystyrene sulfonate (PDADMAC/PSS). PEM formation was followed in situ by optical reflectometry in combination with well-controlled transport conditions (impinging jet stagnation point flow).

  18. 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.

  19. Dynamics of a polyelectrolyte under a constant electric field

    NASA Astrophysics Data System (ADS)

    Park, Pyeong Jun

    2015-11-01

    We perform a molecular dynamics simulation of a polyelectrolyte in a viscous fluid under an external electric field to study the dynamics of gel-free electrophoresis. To incorporate the hydrodynamic effects, we employ a coarse-grained description of water by using multiparticle collision dynamics. We use a screened Coulomb interaction among the monomers and explicit monovalent counterions to model the electrostatic interactions in an ionic solution. The mobility of the polyelectrolyte µ is obtained as a function of the molecular weight N, the electric field strength E,and the Debye screening length of the solvent λ. The mobility is found to be independent of N for large N and to exhibit a maximum at a certain N for a large λ, which are in agreement with experimental results. The dependence of µ on E is also examined and discussed by considering the effects of an electric field on counterion condensation. The dependence of µ on λ shows a discrepancy between our simulation and experiments, which implies that the added salts not only screen out the Coulomb interaction but also participate in the counterion condensation significantly.

  20. Building a road map for tailoring multilayer polyelectrolyte films

    SciTech Connect

    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, 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

  1. Enzyme-polyelectrolyte complex: Salt effects on the reaction of urease with polyallylamine

    NASA Astrophysics Data System (ADS)

    Tikhonenko, S. A.; Saburova, E. A.; Durdenko, E. N.; Sukhorukov, B. I.

    2009-10-01

    The effects of inorganic mono- and divalent salts of different types on how the cation polyelectrolyte polyallylamine hydrochloride (PAA) binds with the oligomer enzyme urease were studied. It was shown that in solutions of the monovalent salts NaCl, KCl, and NH4Cl, polyelectrolyte-protein complexes formed by electrostatic interactions, which decreased monotonically as the salt concentrations increased according to the classic law of statistical physics, correlating the Debye radius with the ionic strength of the solution. In solutions of the divalent salts Na2SO4 and (NH4)2SO4, the efficiency of the formation of the polyelectrolyte-protein complexes changed abruptly (the enzyme was drastically activated) at low salt concentrations (˜0.6-0.8 mM), which was not consistent with the classic theory of charge interactions in solutions with different ionic strengths. Turbidimetric titration at different salt concentrations in the given range revealed a high aggregative ability for sulfates and low ability for chlorides. It was concluded that the anomalies in the concentration dependence of the enzyme activity and aggregative ability were related to the formation of stable bonds PAA to the divalent SO{4/2-} anion, which increased drastically when the ratio of anion concentration to the number of positively charged PAA monomers in solution reached 1: 2.

  2. Self-assembled amorphous drug-polyelectrolyte nanoparticle complex with enhanced dissolution rate and saturation solubility.

    PubMed

    Cheow, Wean Sin; Hadinoto, Kunn

    2012-02-01

    The dissolution rate and solubility of poorly soluble drugs can be enhanced by formulating them into stable amorphous nanoparticle complex (nanoplex). For this purpose, a highly sustainable self-assembly drug-polyelectrolyte complexation process is developed, with ciprofloxacin and dextran sulfate as the drug and polyelectrolyte models, respectively. The nanoplex are prepared by mixing two aqueous salt solutions - one containing the drug and the other containing the oppositely charged polyelectrolyte. The nanoplex suspension is transformed into stable dry-powder form by freeze-drying. The effects of drug concentration, drug-to-polyelectrolyte charge ratio, and salt concentration on the complexation efficiency, yield, drug loading, and nanoplex morphology are examined. The dissolution rates and solubility of the nanoplex are characterized and compared to raw drug crystals. Nearly spherical amorphous nanoplex having fairly uniform sizes in the range of 200-400 nm and 80% drug loading are successfully produced at ≥80% complexation efficiency and yield. The complexation efficiency is governed by the drug concentration and its ratio to the salt concentration. The nanoplex powders exhibit approximately twice higher dissolution rate and solubility than raw drug crystals and remain stable after one-month storage. Overall, amorphous nanoplex represent a promising bioavailability-enhanced formulation of poorly soluble drugs owed to their superior characteristics and ease of preparation. Copyright © 2011 Elsevier Inc. All rights reserved.

  3. Influence of polyelectrolyte chemical structure on their interaction with lipid membrane of zwitterionic liposomes.

    PubMed

    Quemeneur, Francois; Rinaudo, Marguerite; Pépin-Donat, Brigitte

    2008-08-01

    In this paper we extend our previous experimental work on interaction between polyelectrolytes and liposomes. First, the adsorption of chitosan and alkylated chitosan (cationic polyelectrolytes) with different alkyl chain lengths on lipid membranes of liposomes is examined. The amount of both chitosans adsorbed remains the same even if more alkylated polysaccharide has to be added to get saturation if compared with unmodified chitosan. It is demonstrated that alkyl chains do not specifically interact with the lipid bilayer and that electrostatic interaction mechanism governs the chitosan adsorption. The difference observed between unmodified and alkylated chitosans behavior to reach the plateau can be interpreted in terms of a competition between electrostatic polyelectrolyte adsorption on lipid bilayer and hydrophobic autoassociation in solution (which depends on the alkyl chain length). Second, interaction of liposomes with hyaluronan (HA) and alkylated hyaluronan (anionic polyelectrolytes) is analyzed. The same types of results as discussed for chitosan are obtained, but in this case, autoassociation of alkylated HA only occurs in the presence of salt excess. Finally, a first positive layer of chitosan is adsorbed on the lipid membrane, followed by a second negative layer of HA at three different pHs. This kind of multilayer decoration allows the control of the net charge of the composite vesicles. A general conclusion is that whatever the pH and, consequently, the initial charge of the liposomes, chitosan adsorption gives positively charged composite systems, which upon addition of hyaluronan, give rise to negatively charged composite vesicles.

  4. Lipophilic polyelectrolyte gels as super-absorbent polymers for nonpolar organic solvents.

    PubMed

    Ono, Toshikazu; Sugimoto, Takahiro; Shinkai, Seiji; Sada, Kazuki

    2007-06-01

    Polyelectrolyte gels that are known as super-absorbent polymers swell and absorb water up to several hundred times their dried weights and have become ubiquitous and indispensable materials in many applications. Their superior swelling abilities originate from the electrostatic repulsion between the charges on the polymer chains and the osmotic imbalance between the interior and exterior of the gels. However, no super-absorbent polymers for volatile organic compounds (VOCs), and especially for nonpolar organic solvents (epsilon<10) have been reported, because common polyelectrolyte gels collapse in such solvents owing to the formation of a higher number of aggregates of ions and ion pairs. Here, we report that a novel class of polyelectrolyte gels bearing tetra-alkylammonium tetraphenylborate as a lipophilic and bulky ionic group swell in some nonpolar organic solvents up to 500 times their dry size. Dissociation of the ionic groups even in low-dielectric media (3polyelectrolytes that have been used only in aqueous solutions or highly polar solvents, and provides soft materials that swell in a variety of media. These materials could find applications as protective barriers for VOCs spilled in the environment and as absorbents for waste oil.

  5. Lipophilic polyelectrolyte gels as super-absorbent polymers for nonpolar organic solvents

    NASA Astrophysics Data System (ADS)

    Ono, Toshikazu; Sugimoto, Takahiro; Shinkai, Seiji; Sada, Kazuki

    2007-06-01

    Polyelectrolyte gels that are known as super-absorbent polymers swell and absorb water up to several hundred times their dried weights and have become ubiquitous and indispensable materials in many applications. Their superior swelling abilities originate from the electrostatic repulsion between the charges on the polymer chains and the osmotic imbalance between the interior and exterior of the gels. However, no super-absorbent polymers for volatile organic compounds (VOCs), and especially for nonpolar organic solvents (ɛ<10) have been reported, because common polyelectrolyte gels collapse in such solvents owing to the formation of a higher number of aggregates of ions and ion pairs. Here, we report that a novel class of polyelectrolyte gels bearing tetra-alkylammonium tetraphenylborate as a lipophilic and bulky ionic group swell in some nonpolar organic solvents up to 500 times their dry size. Dissociation of the ionic groups even in low-dielectric media (3<ɛ<10) enhances the swelling ability by expansion of the polymer networks. This expands the potential of polyelectrolytes that have been used only in aqueous solutions or highly polar solvents, and provides soft materials that swell in a variety of media. These materials could find applications as protective barriers for VOCs spilled in the environment and as absorbents for waste oil.

  6. 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

    2017-07-23

    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.

  7. Elasticity and Extensibility Determine Printability and Spinnability of Polymer Solutions

    NASA Astrophysics Data System (ADS)

    Dinic, Jelena; Jimenez, Leidy; Sharma, Vivek

    Many advanced manufacturing technologies like inkjet and 3D printing, nano-fiber spinning involve complex free-surface flows, and the formation of columnar necks that undergo spontaneous capillary-driven thinning and pinch-off. The progressive self-thinning of neck is often characterized by self-similar profiles and scaling laws that depend on the relative magnitude of capillary, inertial and viscous stresses for simple (Newtonian and inelastic) fluids. Stream-wise velocity gradients that arise within the thinning columnar neck create an extensional flow field that can orient and stretch macromolecules, contributing extra elastic stresses and extensional viscosity that change thinning and pinch-off dynamics for polymeric complex fluids. Characterizing the filament thinning and break-up kinetics in jetting, dripping and stretching liquid bridge provides invaluable insight into the interplay of elastic, viscous, capillary and inertial stresses relevant for these applications. We elucidate how polymer composition, flexibility and molecular weight determine the thinning and pinch-off kinetics in our experiments. Both effective relaxation time and transient extensional viscosity are found to be strongly concentration dependent even for dilute solutions.

  8. Elasticity and Extensibility Determine Printability and Spinnability of Polymer Solutions

    NASA Astrophysics Data System (ADS)

    Dinic, Jelena; Nallely Jimenez, Leidy; Mei, Vicky; Zhang, Yiran; Sharma, Vivek

    2015-03-01

    Many advanced manufacturing technologies like inkjet printing, 3D printing, nano-fiber spinning, gravure printing and nanoimprint lithography involve complex free-surface flows, where both shear and extensional rheology affect processability. In applications that involve progressive thinning and break-up of a fluid column or sheet into drops, the dominant flow within the filament is extensional in nature. Polymeric fluids exhibit a much larger resistance to flow in an elongational flow field than Newtonian fluids with same shear viscosity. Characterizing the filament thinning and break-up kinetics in jetting, dripping and stretching liquid bridge provides invaluable insight into the interplay of elastic, viscous, capillary and inertial stresses relevant for these applications. In this talk, we elucidate how polymer composition, flexibility and molecular weight determine the kinetics of capillary-driven thinning and pinch-off in our experiments. Both effective relaxation time and transient extensional viscosity are found to be strongly concentration dependent even for dilute solutions. Further, we show how finite extensibility of polymers dramatically changes the kinematics from elastocapillary to viscocapillary under strong extensional flow fields that can lead to coil-stretch transition.

  9. A use of Ramachandran potentials in protein solution structure determinations.

    PubMed

    Bertini, Ivano; Cavallaro, Gabriele; Luchinat, Claudio; Poli, Irene

    2003-08-01

    A strategy is developed to use database-derived phi-psi constraints during simulated annealing procedures for protein solution structure determination in order to improve the Ramachandran plot statistics, while maintaining the agreement with the experimental constraints as the sole criterion for the selection of the family. The procedure, fully automated, consists of two consecutive simulated annealing runs. In the first run, the database-derived phi-psi constraints are enforced for all amino acids (but prolines and glycines). A family of structures is then selected on the ground of the lowest violations of the experimental constraints only, and the phi-psi values for each residue are examined. In the second and final run, the database-derived phi-psi constraints are enforced only for those residues which in the first run have ended in one and the same favored phi-psi region. For residues which are either spread over different favored regions or concentrated in disallowed regions, the constraints are not enforced. The final family is then selected, after the second run, again only based on the agreement with the experimental constraints. This automated approach was implemented in DYANA and was tested on as many as 12 proteins, including some containing paramagnetic metals, whose structures had been previously solved in our laboratory. The quality of the structures, and of Ramachandran plot statistics in particular, was notably improved while preserving the agreement with the experimental constraints.

  10. Using NMR to Determine Protein Structure in Solution

    NASA Astrophysics Data System (ADS)

    Cavagnero, Silvia

    2003-02-01

    Nuclear magnetic resonance (NMR) is a marvelous spectroscopic technique that chemists, physicists, and biochemists routinely employ for their research around the world. This year half of the Nobel Prize for chemistry went to Kurt Wüthrich, who was recognized for the development of NMR-based techniques that lead to the structure determination of biomolecules in solution. In addition to implementing novel pulse sequences and software packages, Wüthrich also applied his methods to several biological systems of key importance to human health. These include the prion protein, which is heavily involved in the spongiform encephalopathy (best known as 'mad cow disease'), which recently caused numerous human deaths, particularly in the UK, due to ingestion of contaminated meat. Transverse relaxation optimized spectroscopy (TROSY) is the most intriguing new NMR method recently developed by Wüthrich and coworkers. This and other closely related pulse sequences promise to play a pivotal role in the extension of NMR to the conformational analysis of very large (up to the megadalton range) macromolecules and macromolecular complexes. More exciting new developments are expected in the near future.

  11. Determination of the enthalpy of solute-solvent interaction from the enthalpy of solution: aqueous solutions of erythritol and L-threitol.

    PubMed

    Lopes Jesus, A J; Tomé, Luciana I N; Eusébio, M Ermelinda S; Redinha, J S

    2006-05-11

    In this work the enthalpy of the solute-solvent interaction of erythritol and L-threitol in aqueous solution was determined from the values obtained for the enthalpy of solvation. The values for this property were calculated from those determined for the enthalpies of solution and sublimation. To determine the values of the enthalpy of solute-solvent interaction, the solvation process is considered as taking place in three steps: opening a cavity in the solvent to hold the solute molecule, changing the solute conformation when it passes from the gas phase into solution, and interaction between the solute and the solvent molecules. The cavity enthalpy was calculated by the scaled particle theory and the conformational enthalpy change was estimated from the value of this function in the gas phase and in solution. Both terms were determined by DFT calculations. The solvent effect on the solute conformation in solution was estimated using the CPCM solvation model. The importance of the cavity and conformational terms in the interpretation of the enthalpy of solvation is noted. While the cavity term has been used by some authors, the conformational term is considered for the first time. The structural features in aqueous solution of erythritol and L-threitol are discussed.

  12. 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.

  13. Solvent Effects on the Structure-Property Relationship of Redox-Active Self-Assembled Nanoparticle-Polyelectrolyte-Surfactant Composite Thin Films: Implications for the Generation of Bioelectrocatalytic Signals in Enzyme-Containing Assemblies.

    PubMed

    Cortez, M Lorena; Ceolín, Marcelo; Cuellar Camacho, Luis; Donath, Edwin; Moya, Sergio E; Battaglini, Fernando; Azzaroni, Omar

    2017-01-11

    The search for strategies to improve the performance of bioelectrochemical platforms based on supramolecular materials has received increasing attention within the materials science community, where the main objective is to develop low-cost and flexible routes using self-assembly as a key enabling process. Important contributions to the performance of such bioelectrochemical devices have been made based on the integration and supramolecular organization of redox-active polyelectrolyte-surfactant complexes on electrode supports. Here, we examine the influence of the processing solvent on the interplay between the supramolecular mesoorganization and the bioelectrochemical properties of redox-active self-assembled nanoparticle-polyelectrolyte-surfactant nanocomposite thin films. Our studies reveal that the solvent used in processing the supramolecular films and the presence of metal nanoparticles not only have a substantial influence in determining the mesoscale organization and morphological characteristics of the film but also have a strong influence on the efficiency and performance of the bioelectrochemical system. In particular, a higher bioelectrochemical response is observed when nanocomposite supramolecular films were cast from aqueous solutions. These observations seem to be associated with the fact that the use of aqueous solvents increases the hydrophilicity of the film, thus favoring the access of glucose, particularly at low concentrations. We believe that these results improve our current understanding of supramolecular nanocomposite materials generated via polyelectrolyte-surfactant complexes, in order to use the processing conditions as a variable to improve the performance of bioelectrochemical devices.

  14. Complex coacervation of supercharged proteins with polyelectrolytes.

    PubMed

    Obermeyer, Allie C; Mills, Carolyn E; Dong, Xue-Hui; Flores, Romeo J; Olsen, Bradley D

    2016-04-21

    Complexation of proteins with polyelectrolytes or block copolymers can lead to phase separation to generate a coacervate phase or self-assembly of coacervate core micelles. However, many proteins do not coacervate at conditions near neutral pH and physiological ionic strength. Here, protein supercharging is used to systematically explore the effect of protein charge on the complex coacervation with polycations. Four model proteins were anionically supercharged to varying degrees as quantified by mass spectrometry. Proteins phase separated with strong polycations when the ratio of negatively charged residues to positively charged residues on the protein (α) was greater than 1.1-1.2. Efficient partitioning of the protein into the coacervate phase required larger α (1.5-2.0). The preferred charge ratio for coacervation was shifted away from charge symmetry for three of the four model proteins and indicated an excess of positive charge in the coacervate phase. The composition of protein and polymer in the coacervate phase was determined using fluorescently labeled components, revealing that several of the coacervates likely have both induced charging and a macromolecular charge imbalance. The model proteins were also encapsulated in complex coacervate core micelles and micelles formed when the protein charge ratio α was greater than 1.3-1.4. Small angle neutron scattering and transmission electron microscopy showed that the micelles were spherical. The stability of the coacervate phase in both the bulk and micelles improved to increased ionic strength as the net charge on the protein increased. The micelles were also stable to dehydration and elevated temperatures.

  15. Tailored polyelectrolyte thin film multilayers to modulate cell adhesion.

    PubMed

    Muzzio, Nicolás E; Pasquale, Miguel A; Moya, Sergio E; Azzaroni, Omar

    2017-08-29

    The layer-by-layer assembly of polyelectrolyte multilayers (PEMs) from natural or synthetic polyelectrolytes constitutes a very versatile and simple strategy to modify surfaces and modulate cell behavior. PEMs assembled from natural polyelectrolytes are very appealing for biological and medical applications due to their high biocompatibility. However, PEMs from natural polyelectrolytes display poor cell adhesion as they are soft materials with an elasticity modulus of a few kilopascal. In this report, the authors present results on the modulation of cell adhesion of different immortalized cell lines by PEMs. Two strategies are employed to vary cell adhesion: (1) a heterogeneous polyelectrolyte multilayer is assembled employing a rigid bottom block including a synthetic polyelectrolyte with a soft upper block of natural polyelectrolytes and (2) polyelectrolyte multilayers from natural polyelectrolytes are thermally annealed after assembly. The physicochemical characteristics of the PEMs change upon thermal treatment. Depending on the composition of the polyelectrolyte multilayer, cell adhesion may be enhanced or reduced. Based on the impact on PEM properties and cell adhesion caused by thermal annealing, a temperature gradient is applied to a PEM of poly-l-lysine/alginate to induce a spatial variation of PEM properties, resulting in a gradient in cell adhesion. The strategies shown here can be employed as simple alternatives to tailor PEM properties by means of fully biocompatible procedures.

  16. Fine control over the size of surfactant-polyelectrolyte nanoparticles by hydrodynamic flow focusing.

    PubMed

    Tresset, Guillaume; Marculescu, Catalin; Salonen, Anniina; Ni, Ming; Iliescu, Ciprian

    2013-06-18

    Synthesis of surfactant-polyelectrolyte nanoparticles was carried out in a microfluidic device with a fine control over the size and the polydispersity. An anionic polysaccharide (sodium carboxymethylcellulose, CMC) solution was focused using a cationic surfactant (dodecyl trimethylammonium bromide, DTAB) solution in a microfluidic channel at selected ratios of flow rates and reagent concentrations. The methodology ensured a controlled mixing kinetics and a uniform distribution of charges at the mixing interface. The resulting nanoparticles exhibited remarkably well-defined and repeatable size distributions, with hydrodynamic diameters tunable from 50 up to 300 nm and polydispersity index around 0.1 in most cases. Microfluidic-assisted self-assembly may be an efficient way to produce well-controlled polyelectrolyte-based nanoparticles suitable for colloidal science as well as for gene delivery applications.

  17. Salt-induced effective interactions and phase separation of an ultrasoft model of polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Rotenberg, Benjamin; Bernard, Olivier; Hansen, Jean-Pierre

    2014-05-01

    We use a semi-grand canonical version of mean-field density functional theory to determine the total effective interaction energy of a solution of penetrable polyions characterised by a Gaussian charge distribution, in the presence of added salt. We then apply this effective representation of semi-flexible polyelectrolyte chains to investigate the possibility of a phase separation similar to that predicted earlier for charge-stabilised hard-sphere colloids. Apart from the absence of a hard-core repulsion, the effective pair potential is similar to the familiar Derjaguin-Landau-Verwey-Overbeek (DLVO) potential between charged-stabilised colloids, i.e. of the screened-Coulomb (Yukawa) form, but the effective valence of the polyions differs significantly from that of the DLVO pair potential, especially at high salt concentration. The existence of a well-defined closed-loop spinodal curve predicted by our mean-field calculation points to a phase separation between solutions with high and low polyion concentrations under reasonable physical conditions. The salt concentration at the upper critical point is typically two orders of magnitude larger than in the case of hard-core polyions, indicating that polyion penetrability appears to enhance the tendency towards phase separation.

  18. Tuning Smart Microgel Swelling and Responsive Behavior through Strong and Weak Polyelectrolyte Pair Assembly

    PubMed Central

    Costa, Eunice; Lloyd, Margaret M.; Chopko, Caroline; Aguiar-Ricardo, Ana; Hammond, Paula T.

    2012-01-01

    The layer-by-layer (LbL) assembly of polyelectrolyte pairs on temperature and pH-sensitive cross-linked poly(N-isopropylacrylamide)-co-(methacrylic acid), poly(NIPAAm-co-MAA), microgels enabled a fine tuning of the gel swelling and responsive behavior according to the mobility of the assembled polyelectrolyte (PE) pair and the composition of the outermost layer. Microbeads with well-defined morphology were initially prepared by synthesis in supercritical carbon dioxide. Upon LbL assembly of polyelectrolytes, interactions between the multilayers and the soft porous microgel led to differences in swelling and thermoresponsive behavior. For the weak PE pairs, namely poly(L-lysine) / poly(L-glutamic acid) and poly(allylamine hydrochloride) / poly(acrylic acid), polycation-terminated microgels were less swollen and more thermoresponsive than native microgel; while polyanion-terminated microgels were more swollen and not significantly responsive to temperature, in a quasi-reversible process with consecutive PE assembly. For the strong PE pair, poly(diallyldimethylammonium chloride) / poly(sodium styrene sulfonate), the differences among polycation and polyanion-terminated microgels are not sustained after the first PE bilayer due to extensive ionic cross-linking between the polyelectrolytes. The tendencies across the explored systems became less noteworthy in solutions with larger ionic strength due to overall charge shielding of the polyelectrolytes and microgel. ATR FT-IR studies correlated the swelling and responsive behavior after LbL assembly on the microgels with the extent of H-bonding and alternating charge distribution within the gel. Thus, the proposed LbL strategy may be a simple and flexible way to engineer smart microgels in terms of size, surface chemistry, overall charge and permeability. PMID:22676290

  19. Catalytic membranes prepared using layer-by-layer adsorption of polyelectrolyte/metal nanoparticle films in porous supports.

    PubMed

    Dotzauer, David M; Dai, Jinhua; Sun, Lei; Bruening, Merlin L

    2006-10-01

    Layer-by-layer adsorption of polyelectrolytes and gold nanoparticles within porous supports provides a convenient method for forming catalytic membranes. The polyelectrolyte film effectively immobilizes the gold nanoparticles without inhibiting access to catalytic sites, as shown by the similar rate constants for nanoparticle-catalyzed 4-nitrophenol reduction in solution and in membranes. Modified alumina membranes reduce >99% of 0.4 mM 4-nitrophenol at linear flow rates of 0.98 cm/s, and the modification process is also applicable to track-etched polycarbonate supports.

  20. Mediating gel formation from structurally controlled poly(electrolytes) through multiple "head-to-body" electrostatic interactions.

    PubMed

    Srour, Hassan; Ratel, Olivier; Leocmach, Mathieu; Adams, Emma A; Denis-Quanquin, Sandrine; Appukuttan, Vinukrishnan; Taberlet, Nicolas; Manneville, Sébastien; Majesté, Jean-Charles; Carrot, Christian; Andraud, Chantal; Monnereau, Cyrille

    2015-01-01

    Tuning the chain-end functionality of a short-chain cationic homopolymer, owing to the nature of the initiator used in the atom transfer radical polymerization (ATRP) polymerization step, can be used to mediate the formation of a gel of this poly(electrolyte) in water. While a neutral end group gives a solution of low viscosity, a highly homogeneous gel is obtained with a phosphonate anionic moiety, as characterized by rheometry and diffusion nuclear magnetic resonance (NMR). This novel type of supramolecular control over poly(electrolytic) gel formation could find potential use in a variety of applications in the field of electro-active materials.

  1. Huge Differences in the Kinetics of Swelling Enhancement and De-enhancement of Permanently Charged Polyelectrolyte Brushes.

    PubMed

    Chu, Xiao; Yang, Jingfa; Zhao, Jiang

    2016-10-06

    As demonstrated previously (X. Chu et al., Soft Matter 2014, 10, 5568), permanently charged polyelectrolyte brushes can experience an enhancement of swelling by exposure to an external monovalent salt solution in moderate concentrations. Beyond the previous static measurements, the kinetics of the swelling enhancement and de-enhancement were investigated in the current study by using a quartz crystal microbalance with dissipation (QCM-D). By developing an effective approach to quantify the response in QCM-D, a vast difference in swelling enhancement and de-enhancement of a model permanently charged polyelectrolyte brush (sodium polystyrene sulfonate, NaPSS) was discovered. The results indicate new physics of the charged brushes: the difference in the attachment and detachment of counterions to the polyelectrolyte chains.

  2. Solubilization and separation of p-tert-butylphenol using polyelectrolyte/surfactant complexes in colloid-enhanced ultrafiltration

    SciTech Connect

    Uchiyama, Hirotaka; Christian, S.D.; Tucker, E.E.; Scamehorn, J.F. )

    1994-03-15

    Water-soluble polyelectrolyte/surfactant complexes, involving oppositely charged species, can form at quite low thermodynamic activities of the surfactant. This fact can be exploited in colloid-enhanced ultrafiltration separations, where both molecular organic pollutants and toxic ions are to be removed from contaminated aqueous streams. Investigations have been made of (a) the solubilization and ultrafiltration of solutions of organic solutes in polymer/surfactant solutions, for comparison with studies of micellar surfactant solutions in the absence of added polymers; (b) the penetration of surfactant through the membrane (leakage of monomer) in dialysis and ultrafiltration experiments; and (c) the utility of polyelectrolytes as scavengers'' for surfactant species that-enter the permeate or filtrate in colloid-enhanced ultrafiltration separations. The polyelectrolyte chosen for the studies is sodium poly(styrenesulfonate) and the surfactant is cetylpyridinium chloride (hexadecylpyridinium chloride). A detailed study has been made of the solubilization and separation of p-tert-butylphenol in aqueous mixtures of sodium poly(styrenesulfonate) and cetylpyridinium chloride, at polyelectrolyte to surfactant mole ratios of two to one and three to one.

  3. Highly Stable Conjugated Polyelectrolytes for Water-Based Hybrid Mode Electrochemical Transistors.

    PubMed

    Zeglio, Erica; Eriksson, Jens; Gabrielsson, Roger; Solin, Niclas; Inganäs, Olle

    2017-03-16

    Hydrophobic, self-doped conjugated polyelectrolytes (CPEs) are introduced as highly stable active materials for organic electrochemical transistors (OECTs). The hydrophobicity of CPEs renders films very stable in aqueous solutions. The devices operate at gate voltages around zero and show no signs of degradation when operated for 10(4) cycles under ambient conditions. These properties make the produced OECTs ideal devices for applications in bioelectronics.

  4. Determination of arsenic species in soil solution under flooded conditions

    SciTech Connect

    Onken, B.M.; Hossner, L.R.

    1996-09-01

    Greenhouse experiments were conducted to evaluate the relationships between the species and concentrations of As in the soil solution of flooded soils with other parameters including soil pe, pH, Fe, Mn, and type and amount of As added. Two soils were treated with 0, 5, 15, 25, 35, and 45 mg As kg{sup -1} soil added as either Na-arsenate or Na-arsenite and planted with rice (Oryza sativa L.). Soil solution samples were collected during a period of 60 d and analyzed for As. Selective hydrides generation was employed to evaluate both type and quality of As present in the samples. Inorganic As in the form of arsenate and arsenite was found in the soil solution of both soils. The conversion of added arsenite to arsenate occurred within the first 10 d of the experiment when the pe/pH of the soil was not conducive to arsenite stability. Added arsenate was converted to arsenite during the source of the experiment as the pe/pH of the soil declined due to flooding. Arsenate reached a maximum in soil solution at 10 to 20 d after flooding while maximum arsenite concentrations occurred at 20 to 30 d after flooding. The total concentration of As in soil solution generally reached a maximum at 20 to 30 d after flooding, after which time precipitous losses of As from soil solution occurred in all but the highest As treatments. Soil solution As concentrations were not statistically different between planted and unplanted controls. 30 refs., 6 figs., 3 tabs.

  5. Adsorption of polyelectrolytes onto oppositely charged cylindrical macroions

    NASA Astrophysics Data System (ADS)

    de Carvalho, Sidney Jurado; Caetano, Daniel Lucas Zago

    2013-06-01

    In this work we investigate the adsorption of polyelectrolyte chains onto uniformly charged cylindrical macroions by means of the Metropolis Monte Carlo simulations and weighted histogram analysis method. Adopting a simplified model for macromolecules and treating the electrolytic solution in the Debye-Hückel level, conformational properties of the adsorbed chain, such as the radius of gyration and the thickness of the adsorbed layer, are provided as a function of ionic strength and macroion charge density. By analysis of the free energy profile as a function of the radius of gyration it was possible to identify first-order-like transitions between adsorbed and desorbed states and obtain a macroion charge density dependence of the critical ionic strength in good agreement with experiments.

  6. 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.

  7. Dispersion of single-walled carbon nanotubes using polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Aldea, G.; Nunzi, J. M.

    2009-02-01

    In order to produce high performance SWNT-based products, it is necessary to make them soluble, reaching a certain degree of dispersion and stability in solution. Since SWNTs are mostly inert, being neither hydrophilic nor lipophilic, their use suffers from poor dispersion capability and weak interaction with other partners. Therefore, activating and modifying their surface is an essential prerequisite to processing. We report on a versatile nondestructive strategy for the non-covalent functionalization of SWNT by polyelectrolytes based on maleic anhydride copolymers. To evaluate competing stabilization characteristics, we explored the dispersing power of a range of maleic anhydride copolymers functionalized with several chromophore units: pyrene, cholesterol and Disperse Red 1. The surface modification of SWNT is straightforward and efficient for making them dispersible in water and in other organic solvents and for producing nanometer-scale materials suitable for nanotechnology, medicinal chemistry and environment friendly solar cell applications.

  8. Energetic and entropic forces governing the attraction between polyelectrolyte-grafted colloids.

    PubMed

    Arya, Gaurav

    2009-12-03

    The energetic and entropic interactions governing the attraction between like-charged colloidal particles grafted with oppositely charged polyelectrolyte chains in a monovalent electrolyte are investigated computationally. We employ coarse-grained models of the colloids with varying surface and polyelectrolyte charges and Monte Carlo simulations to compute the potential of mean force between two colloidal particles as a function of their separation distance. By categorizing the potentials as attractive or purely repulsive, we obtain the extent and location of the attractive-force regime within the two-dimensional parameter space comprised of the colloid surface and polyelectrolyte charge. The attractive regime is found to occupy the inside of a hyperbola in this charge space, whose shape and size is determined by a complex interplay between energetic and entropic interactions. In particular, we find that the strength of attraction at short distances is governed by a balance between favorable energetic and entropic terms arising from polymer-bridging interactions, unfavorable energies arising from the mutual repulsion of the colloid surfaces and polyelectrolyte chains, and unfavorable entropies arising from the overlap and crowding effects of chains confined between the colloid surfaces. A phenomenological model is proposed to explain the hyperbolic shape of the attractive regime and make useful predictions about changes in its shape and location for conditions not investigated in this study.

  9. The effect of nature of polyions and treatment after deposition on wetting characteristics of polyelectrolyte multilayers

    NASA Astrophysics Data System (ADS)

    Kolasińska, Marta; Warszyński, Piotr

    2005-10-01

    The sequential adsorption of oppositely charged polyelectrolytes (PE) occurs to be a powerful tool for obtaining various materials of precisely defined properties. The interfacial features of PE multilayer films are governed by the choice of polycation/polyanion pairs and the conditions of film formation. Additionally, the long time exposure to the conditions different than that encountered during formation usually affects polyelectrolyte multilayer structure. The wettability of heterogeneous surfaces produced by 'layer-by-layer' (LbL) adsorption of polyelectrolytes was investigated in this work. We focused on the influence of film treatment after deposition on wetting properties of obtained multilayers. The effect of the nature of the first layer was also studied. Apart from simple arrangements: (polyallylamine hydrochloride)/(polysodium 4-styrenesulfonate) (PAH/PSS) and (poly- L-lysine hydrobromide)/(poly- L-glutamic acid sodium salt) (PLL/PGA) more complicated structures were considered having as a first layer two types of polyethylene imines (PEI) of different molecular weight. Wetting properties of such polyelectrolyte films were determined experimentally by contact angle measurements using technique of direct image analysis of the shape of sessile drop.

  10. 21 CFR 864.9320 - Copper sulfate solution for specific gravity determinations.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Copper sulfate solution for specific gravity... Establishments That Manufacture Blood and Blood Products § 864.9320 Copper sulfate solution for specific gravity determinations. (a) Identification. A copper sulfate solution for specific gravity determinations is a device...

  11. 21 CFR 864.9320 - Copper sulfate solution for specific gravity determinations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Copper sulfate solution for specific gravity... Establishments That Manufacture Blood and Blood Products § 864.9320 Copper sulfate solution for specific gravity determinations. (a) Identification. A copper sulfate solution for specific gravity determinations is a device...

  12. 21 CFR 864.9320 - Copper sulfate solution for specific gravity determinations.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Copper sulfate solution for specific gravity... Establishments That Manufacture Blood and Blood Products § 864.9320 Copper sulfate solution for specific gravity determinations. (a) Identification. A copper sulfate solution for specific gravity determinations is a device...

  13. 21 CFR 864.9320 - Copper sulfate solution for specific gravity determinations.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Copper sulfate solution for specific gravity... Establishments That Manufacture Blood and Blood Products § 864.9320 Copper sulfate solution for specific gravity determinations. (a) Identification. A copper sulfate solution for specific gravity determinations is a device...

  14. 21 CFR 864.9320 - Copper sulfate solution for specific gravity determinations.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Copper sulfate solution for specific gravity... Establishments That Manufacture Blood and Blood Products § 864.9320 Copper sulfate solution for specific gravity determinations. (a) Identification. A copper sulfate solution for specific gravity determinations is a device...

  15. 75 FR 65525 - TRG Insurance Solutions, Beckley, WV; Notice of Revised Determination on Reconsideration

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-25

    ... Employment and Training Administration TRG Insurance Solutions, Beckley, WV; Notice of Revised Determination... of TRG Insurance Solutions, Beckley, West Virginia, to apply for Trade Adjustment Assistance. On... determine that workers of TRG Insurance Solutions, Beckley, West Virginia, who are engaged in...

  16. 76 FR 9789 - Determination That Theophylline Oral Solution, 80 Milligrams/15 Milliliters, Was Not Withdrawn...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-22

    ... HUMAN SERVICES Food and Drug Administration Determination That Theophylline Oral Solution, 80 Milligrams... determined that theophylline oral solution, 80 milligrams (mg)/15 milliliters (mL), was not withdrawn from... new drug applications (ANDAs) for theophylline oral solution, 80 mg/15 mL, if all other legal and...

  17. Quantification of hydrolytic charge loss of DMAEA-Q-based polyelectrolytes by proton NMR spectroscopy and implications for colloid titration.

    PubMed

    Saveyn, Hans; Hendrickx, Pieter M S; Dentel, Steven K; Martins, José C; Van der Meeren, Paul

    2008-05-01

    Copolymers of acrylamide and quaternised dimethylaminoethyl acrylate (DMAEA-Q) constitute an economically important range of cationic polyelectrolytes used in sludge conditioning. The latter treatment involves charge neutralisation and bridging induced by these polymers. Since both of these phenomena rely on charge-driven sorption onto the negatively charged colloidal particles, the accurate assessment of their charge density is of primary importance in polyelectrolyte characterisation. The experimental determination of this characteristic generally relies on colloidal charge titration, in which the cationic polymer is titrated against an anionic polymer. Hereby, one of the requirements to have a stoichiometric reaction between the oppositely charged polymers is a sufficiently low polymer concentration. In this study, it is shown that such a low polymer concentration may entail a pronounced hydrolysis effect for DMAEA-Q-based polymers, which leads to a release of the cationic side groups and hence causes considerable errors on the charge titration results. Proton nuclear magnetic resonance spectroscopy was applied to investigate the fast hydrolysis kinetics of DMAEA-Q polymers together with time-dependent charge titration measurements. Diffusion NMR spectroscopy was used to assist in establishing the nature of the hydrolysis compounds. The results from both techniques indicate that a high degree of hydrolysis is reached within minutes after dilution of a concentrated polymer stock solution into aqueous solutions of slightly acidic to neutral pH values. Therefore, a modification to the classic colloid titration procedure is proposed, using a buffered dilution liquid to avoid polymer hydrolysis. It is shown that a buffer pH value of 4.5 avoids not only polymer hydrolysis effects but also possible protonation of the anionic titrant, thereby avoiding overestimation of the charge density. By means of this procedure, reproducible and time-independent charge titration

  18. 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.

  19. 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

    2017-08-14

    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.

  20. Counterion condensation to cationic polyelectrolytes in methanol/water mixtures

    SciTech Connect

    Rios, H.; Barraza, R.

    1995-12-31

    Manning`s theory states that counterion condensation phenomenon is basically governed by two factors: the average distance between charges on the polyion framework and the {open_quotes}bulk{close_quotes} dielectric constant. In this work, the effect of macroscopic dielectric constant on solutions of chloride, bromide and nitrate of poly-[N,N-dimethyl-N-(2-hydroxypropyl)ammonium], using mixtures of methanol/water as solvent, was investigated. Results are analyzed as compared with those reported in water for the same system. The equivalent electrical conductivity at infinite dilution, {Lambda}{degrees}, of their solutions agrees well with both the viscosity and the dielectric constant behavior of pure mixtures in all the composition range. However, the behavior of the counterion-polyion interaction parameter, referred to that calculated according to Manning`s definition, shows a maximum in the same range where {Lambda}{degrees} abruptly decreases at about 0.2 mole fraction of methanol. This apparently anomalous behavior involves an increase in the average distance between charges without ionic dissociation and it can be explained in terms of a polyion conformational change. Accordingly, viscosity measurements showed a maximum in the same composition range. The preferential adsorption coefficient, {lambda}{sup *}, measured by dialysis equilibrium and differential refractometry, shows that water is the component more adsorbed to the polyelectrolyte, at least in the range from 0.05 to 0.3 mole fraction of methanol. Consequently, if one of the components of the mixture is preferentially adsorbed to the polyelectrolyte, then the parameter on which depends the counterion condensation is the dielectric constant in the association microdomain.

  1. 75 FR 55612 - TRG Insurance Solutions, LLC; Beckley, WV; Notice of Affirmative Determination Regarding...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-13

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR Employment and Training Administration TRG Insurance Solutions, LLC; Beckley, WV; Notice of Affirmative... Solutions, LLC, Beckley, West Virginia (subject firm). The negative determination was issued on July...

  2. Mesoscale modeling of polyelectrolyte brushes with salt.

    PubMed

    Ibergay, Cyrille; Malfreyt, Patrice; Tildesley, Dominic J

    2010-06-03

    We report dissipative particle dynamics (DPD) simulations of a polyelectrolyte brush under athermal solvent conditions. The electrostatic interactions are calculated using the particle-particle particle-mesh (PPPM) method with charges distributed over the particles. The polymer beads, counterions, co-ions, and solvent particles are modeled explicitly. The DPD simulations show a dependence of the brush height on the grafting density and the charge fraction that is typical of the nonlinear osmotic brush regime. We report the effect of the addition of salt on the structural properties of the brush. In the case of a polyelectrolyte brush with a high surface coverage, the simulations reproduce the transition between the nonlinear osmotic brush regime where the thickness of the brush is independent of the salt concentration and the salted regime where the brush height decreases weakly with the salt concentration.

  3. Salt-induced aggregation of stiff polyelectrolytes.

    PubMed

    Fazli, Hossein; Mohammadinejad, Sarah; Golestanian, Ramin

    2009-10-21

    Molecular dynamics simulation techniques are used to study the process of aggregation of highly charged stiff polyelectrolytes due to the presence of multivalent salt. The dominant kinetic mode of aggregation is found to be the case of one end of one polyelectrolyte meeting others at right angles, and the kinetic pathway to bundle formation is found to be similar to that of flocculation dynamics of colloids as described by Smoluchowski. The aggregation process is found to favor the formation of finite bundles of 10-11 filaments at long times. Comparing the distribution of the cluster sizes with the Smoluchowski formula suggests that the energy barrier for the aggregation process is negligible. Also, the formation of long-lived metastable structures with similarities to the raft-like structures of actin filaments is observed within a range of salt concentration.

  4. Determination of diffusion coefficient in gel and in aqueous solutions using scanning electrochemical microscopy.

    PubMed

    Csóka, Balázs; Nagy, Géza

    2004-10-29

    Diffusion coefficient of different species in different media is an important property needed in scientific research and practice. A method taking advantage on the special capability of scanning electrochemical microscopy (SECM) is described for the easy and accurate measurement of diffusion coefficient. The method is based on detecting the concentration-time transients with appropriate electrochemical microsensor positioned at the close vicinity of a miniature dose-source device. At a given time (ti), a small dose of the investigated species is introduced. The Deltatmax=(tcmax-ti) value and the distance (d=x+Deltaxn) between the source and the detector microelectrode are used for the calculation of D. While the original set distance (x) cannot be accurately measured in the micrometer scale, the tip travel distance (Deltaxn) of the microscope is well defined. Collecting a few Deltatmax-(x+Deltaxn) data pairs, a reliable value of the diffusion coefficient can be obtained. The procedure is simple, and no exact knowledge of the introduced dose is needed. Two ways of sample dose delivery were used: on the one hand, coulometric generation with current-controlled electric pulse using micro-disc electrode, and on the other one, pressure ejection of a nano-droplet from a glass micropipette. Diffusion coefficient of I2, H2O2, [Ru(NH3)6]Cl3 and K3[Fe(CN)6] were measured in solution and in agarose gel phases of different composition. The effect of polyelectrolyte ion exchangers on the diffusion of the investigated species was checked.

  5. Method for Non-Invasive Determination of Chemical Properties of Aqueous Solutions

    NASA Technical Reports Server (NTRS)

    Todd, Paul W. (Inventor); Jones, Alan (Inventor); Thomas, Nathan A. (Inventor)

    2016-01-01

    A method for non-invasively determining a chemical property of an aqueous solution is provided. The method provides the steps of providing a colored solute having a light absorbance spectrum and transmitting light through the colored solute at two different wavelengths. The method further provides the steps of measuring light absorbance of the colored solute at the two different transmitted light wavelengths, and comparing the light absorbance of the colored solute at the two different wavelengths to determine a chemical property of an aqueous solution.

  6. Crystal structure solution from experimentally determined atomic pair distribution functions

    SciTech Connect

    Juhas, P.; Granlund, L.; Gujarathi, S.R.; Duxbury, P.M.; Billinge, S.J.L.

    2010-05-25

    An extension of the Liga algorithm for structure solution from atomic pair distribution functions (PDFs), to handle periodic crystal structures with multiple elements in the unit cell, is described. The procedure is performed in three separate steps. First, pair distances are extracted from the experimental PDF. In the second step the Liga algorithm is used to find unit-cell sites consistent with these pair distances. Finally, the atom species are assigned over the cell sites by minimizing the overlap of their empirical atomic radii. The procedure has been demonstrated on synchrotron X-ray PDF data from 16 test samples. The structure solution was successful for 14 samples, including cases with enlarged supercells. The algorithm success rate and the reasons for the failed cases are discussed, together with enhancements that should improve its convergence and usability.

  7. Light reflection visualization to determine solute diffusion into clays.

    PubMed

    Yang, Minjune; Annable, Michael D; Jawitz, James W

    2014-06-01

    Light reflection visualization (LRV) experiments were performed to investigate solute diffusion in low-permeability porous media using a well-controlled two-dimensional flow chamber with a domain composed of two layers (one sand and one clay). Two different dye tracers (Brilliant Blue FCF and Ponceau 4R) and clay domains (kaolinite and montmorillonite) were used. The images obtained through the LRV technique were processed to monitor two-dimensional concentration distributions in the low-permeability zone by applying calibration curves that related light intensity to equilibrium concentrations for each dye tracer in the clay. One dimensional experimentally-measured LRV concentration profiles in the clay were found to be in very good agreement with those predicted from a one-dimensional analytical solution, with coefficient of efficiency values that exceeded 0.97. The retardation factors (R) for both dyes were relatively large, leading to slow diffusive penetration into the clays. At a relative concentration C/C0=0.1, Brilliant Blue FCF in kaolinite (R=11) diffused approximately 10 mm after 21 days of source loading, and Ponceau 4R in montmorillonite (R=7) diffused approximately 12 mm after 23 days of source loading. The LRV experimentally-measured two-dimensional concentration profiles in the clay were also well described by a simple analytical solution. The results from this study demonstrate that the LRV approach is an attractive non-invasive tool to investigate the concentration distribution of dye tracers in clays in laboratory experiments.

  8. Theory of polyelectrolyte adsorption on heterogeneously charged surfaces applied to soluble protein-polyelectrolyte complexes

    NASA Astrophysics Data System (ADS)

    de Vries, R.; Weinbreck, F.; de Kruif, C. G.

    2003-03-01

    Existing theoretical approaches to polymer adsorption on heterogeneous surfaces are applied to the problems of polyelectrolyte and polyampholyte adsorption on randomly charged surfaces. Also, analytical estimates are developed for the critical pH at which weakly charged polyelectrolytes and globular proteins start forming soluble complexes. Below a critical salt concentration, soluble complexes form "on the wrong side" of the protein isoelectric point due to the heterogeneity of the protein surface charge distribution. The analytical estimates are consistent with experimental data on soluble complexes in mixtures of gum arabic and whey protein isolate.

  9. Ferrocene-containing polyelectrolyte multilayer film-covered electrodes: electrocatalytic determination of ascorbic acid and use of inner blocking layers to improve the upper detection limit of the electrodes.

    PubMed

    Liu, Aihua; Anzai, Jun-Ichi

    2004-09-01

    A multilayer film composed of ferrocene(Fc)-appended poly(allylamine hydrochloride) (Fc-PAH) and poly(potassium vinylsulfate) (PVS) has been prepared on the surface of a gold(Au) electrode by using a layer-by-layer self-assembly technique. Fc-containing polyelectrolyte multilayer (PEM) film-modified electrodes can electrochemically catalyze the oxidation of ascorbic acid successfully. For a 2 (Fc-PAH/PVS) bilayer-covered electrode the catalytic current increased linearly with increasing concentration of ascorbic acid over the concentration range 6 micromol L(-1)-3 mmol L(-1). To extend the dynamic range for ascorbic acid, the surface of the Au electrode was first covered with a (PAH/PVS)(2) film on which an additional (Fc-PAH/PVS)(5) film was coated. This strategy successfully extended the dynamic range of the electrode up to 25 mmol L(-1) ascorbic acid, because the (PAH/PVS)(2) layer blocked access of ascorbic acid to the electrode surface. The upper detection limit of the (PAH/PVS)(2) (Fc-PAH/PVS)(5) film-modified electrode is much higher than those of Fc-based ascorbic acid sensors reported so far. Electron transfer is diffusion-controlled within the (PAH/PVS)(2)(Fc-PAH/PVS)(5) film.

  10. Conformation and translational diffusion of a xanthan polyelectrolyte chain: Brownian dynamics simulation and single molecule tracking

    NASA Astrophysics Data System (ADS)

    Chun, Myung-Suk; Kim, Chongyoup; Lee, Duck E.

    2009-05-01

    In our recent Brownian dynamics (BD) simulation study, the structure and dynamics of anionic polyelectrolyte xanthan in bulk solution as well as confined spaces of slitlike channel were examined by applying a coarse-grained model with nonlinear bead-spring discretization of a whole chain [J. Jeon and M.-S. Chun, J. Chem. Phys. 126, 154904 (2007)]. This model goes beyond other simulations as they did not consider both long-range electrostatic and hydrodynamic interactions between pairs of beads. Simulation parameters are obtained from the viscometric method of rheology data on the native and sonicated xanthan polysaccharides, which have a contour length less than 1μm . The size of the semiflexible polyelectrolyte can be well described by the wormlike chain model once the electrostatic effects are taken into account by the persistence length measured at a long length scale. For experimental verifications, single molecule visualization was performed on fluorescein-labeled xanthan using an inverted fluorescence microscope, and the motion of an individual molecule was quantified. Experimental results on the conformational changes in xanthan chain in the electrolyte solution have a reasonable trend to agree with the prediction by BD simulations. In the translational diffusion induced by the Debye screening effect, the simulation prediction reveals slightly higher values compared to those of our measurements, although it agrees with the literature data. Considering the experimental restrictions, our BD simulations are verified to model the single polyelectrolyte well.

  11. 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.

  12. Electric-field-induced response of a droplet embedded in a polyelectrolyte gel

    NASA Astrophysics Data System (ADS)

    Mohammadi, Aliasghar

    2013-08-01

    The electric-field induced response of a droplet embedded in a quenched polyelectrolyte gel is calculated theoretically. The response comprises the droplet translation and the electric-field induced flow fields within the droplet. The gel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no free charge. An analytical solution, using the perturbation methodology and linear superposition, is obtained for the leading-order steady response to a DC electric-field. The fluid within the droplet is driven due to hydrodynamic coupling with the electroosmotic flow. The fluid velocity within the droplet is linearly proportional to the electroosmotic flow. Moreover, the microrheological response function of a droplet within a polyelectrolyte gel is also provided, highlighting the importance of boundary conditions at the droplet-gel interface on microrheological measurements.

  13. Electrostatic Swelling and Conformational Variation Observed in High-Generation Polyelectrolyte Dendrimers

    SciTech Connect

    Butler, Paul D; Chen, Wei-Ren; Herwig, Kenneth W; Hong, Kunlun; Liu, Yun; Porcar, L.; Shew, Chwen-Yang; Smith, Gregory Scott; Chen, Hsin-Lung; Chen, Chun-Yu; Li, Xin; Liu, Emily

    2010-01-01

    A coordinated study combining small angle neutron scattering (SANS) and small angle x-ray scattering (SAXS) measurements was conducted to investigate the structural characteristics of aqueous (D2O) generation 7 and 8 (G7 & G8) PAMAM dendrimer solutions as a function of molecular protonation at room temperature. The change in intra-molecular conformation was clearly exhibited in the data analysis by separating the variation in the inter-molecular correlation. Our results unambiguously demonstrate an increased molecular size and evolved intra-molecular density profile upon increasing the molecular protonation. This is contrary to the existing understanding that in higher generation polyelectrolyte dendrimers, steric crowding stiffens the local motion of dendrimer segments exploring additional available intra-dendrimer volume and therefore inhibits the electrostatic swelling. Our observation is relevant to elucidation of the general microscopic picture of polyelectrolyte dendrimer structure, as well as the development of dendrimer-based packages with based on the stimuli-responsive principle.

  14. Self-consistent field theory of polyelectrolyte brushes with finite chain extensibility

    NASA Astrophysics Data System (ADS)

    Lebedeva, Inna O.; Zhulina, Ekaterina B.; Borisov, Oleg V.

    2017-06-01

    Polyelectrolyte brushes are formed by charged macromolecules tethered by the end segment to a solid-liquid interface. At low ionic strength of the solution, the intermolecular electrostatic interactions lead to strong stretching of the macromolecules that may, as a result, approach the limit of their extensibility (the contour length). Here, we present an analytical theory of polyelectrolyte brushes developed within the Poisson-Boltzmann approximation which explicitly accounts for finite extensibility of the brush-forming chains. In contrast to earlier theories based on the approximation of Gaussian elasticity of the brush-forming chains, the current approach enables avoiding artificial result of stretching of the chains beyond the contour length at high degrees of ionization or/and large grafting densities.

  15. Protein-Polyelectrolyte Coacervates: A Novel State of Biomacromolecular Fluids

    NASA Astrophysics Data System (ADS)

    Dubin, P.; Bohidar, H.; Hashizdume, A.; Ké, P.; Bloomfield, V.; Lal, J.; Morishima, Y.; Naumann, C.; Russo, P.; Skobeleva, V.

    2002-03-01

    A challenging problem in complex fluids is the organization and dynamics of charged biopolymers in the highly concentrated intracellular milieu. Proteins with a patchwork of positive and negative charges interact with nucleic acids and membranes that are predominantly negatively charged. The resulting coulombic interactions can lead to both stabilizing repulsions and association or aggregation, depending on a delicate balance of charge density and concentration. We studied the microstructure of a model biocomplex polyelectrolyte formed by pH-induced complexation of serum albumin with the strong polycation PDMDAAC Structure and dynamics are probed using SANS, static and dynamic light scattering, rheology, FRAP, rheology, and TIRF. Optically clear phases ("coacervates") are formed with protein in excess of 200 g/L, concentrations normally not homogeneously sustainable in aqueous solutions but characteristic of those in cells. The solutions display very large shear viscosities, but exhibit protein diffusivities only an order of magnitude below those in dilute protein solution, which explains in part the retention of activity when such coacervates are prepared with enzymes. The results from SANS, LS, FRAP, TIRF and rheology reveal a solution-like state in which homogeneous fluid-like domains coexist with denser and more nearly charge-neutralized domains which inhibit local protein diffusion and confer transient network viscoelasticity.

  16. Antimicrobial agent-free hybrid cationic starch/sodium alginate polyelectrolyte films for food packaging materials.

    PubMed

    Şen, Ferhat; Uzunsoy, İrem; Baştürk, Emre; Kahraman, Memet Vezir

    2017-08-15

    This study aimed to develop polyelectrolyte structured antimicrobial food packaging materials that do not contain any antimicrobial agents. Cationic starch was synthesized and characterized by FT-IR spectroscopy and (1)H NMR spectroscopy. Its nitrogen content was determined by Kjeldahl method. Polyelectrolyte structured antimicrobial food packaging materials were prepared using starch, cationic starch and sodium alginate. Antimicrobial activity of materials was defined by inhibition zone method (disc diffusion method). Thermal stability of samples was evaluated by TGA and DSC. Hydrophobicity of samples was determined by contact angle measurements. Surface morphology of samples was investigated by SEM. Moreover, gel contents of samples were determined. The obtained results prove that produced food packaging materials have good thermal, antimicrobial and surface properties, and they can be used as food packaging material in many industries. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Precipitate-Coacervate Transformation in Polyelectrolyte-Mixed Micelle Systems.

    PubMed

    Comert, Fatih; Nguyen, Duy; Rushanan, Marguerite; Milas, Peker; Xu, Amy Y; Dubin, Paul L

    2017-05-04

    The polycation/anionic-nonionic mixed micelle, poly(diallyldimethylammonium chloride)-sodium dodecyl sulfate/Triton X-100 (PDADMAC-SDS/TX100), is a model polyelectrolyte-colloid system in that the micellar mole fraction of SDS (Y) controls the micelle surface charge density, thus modulating the polyelectrolyte-colloid interaction. The exquisite temperature dependence of this system provides an important additional variable, controlling both liquid-liquid (L-L) and liquid-solid (L-S) phase separation, both of which are driven by the entropy of small ion release. In order to elucidate these transitions, we applied high-precision turbidimetry (±0.1 %), isothermal titration calorimetry, and epifluorescence microscopy which demonstrates preservation of micelle structure under all conditions. The L-S region at large Y including precipitation displays a remarkable linear, inverse Y-dependence of the L-S transition temperature Ts. In sharp contrast, the critical temperature for L-L coacervation Tφ, shows nearly symmetrical effects of positive and negative deviations in Y from the point of soluble complex neutrality, which is controlled in solution by the micelle charge and the number of micelles bound per polymer chain n (Zcomplex = Zpolymer + nZmicelle). In solid-like states, n no longer signifies the number of micelles bound per polymer chain, since the proximity of micelles inverts the host-guest relationship with each micelle binding multiple PE chains. This intimate binding goes hand-in-hand with the entropy of release of micelle-localized charge-compensating ions whose concentration depends on Y. These ions need not be released in L-L coacervation, but during L-S transition their displacement by PE accounts for the inverse dependence of Ts on micelle charge, Y.

  18. Fundamental solution of the problem of linear programming and method of its determination

    NASA Technical Reports Server (NTRS)

    Petrunin, S. V.

    1978-01-01

    The idea of a fundamental solution to a problem in linear programming is introduced. A method of determining the fundamental solution and of applying this method to the solution of a problem in linear programming is proposed. Numerical examples are cited.

  19. 76 FR 32366 - Determination That ORLAAM (Levomethadyl Acetate Hydrochloride) Oral Solution, 10 Milligrams...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-06

    ... determined that ORLAAM (levomethadyl acetate hydrochloride (HCl)) oral solution, 10 milligrams (mg... solution, 10 mg/mL, if all other legal and regulatory requirements are met. FOR FURTHER INFORMATION CONTACT... HCl) oral solution, 10 mg/mL, is the subject of NDA 20-315, held by Roxane Laboratories, Inc....

  20. Novel pore-filled polyelectrolyte composite membranes for cathodic microbial fuel cell application

    NASA Astrophysics Data System (ADS)

    Gohil, J. M.; Karamanev, D. G.

    2013-12-01

    Novel pore-filled polyelectrolyte membrane (PEM) was produced using track etched polycarbonate (PC) as porous substrate and poly(vinyl alcohol) (PVA) as pore filling material. PVA in PC pores was stabilized through cross-linking of PVA matrix with glutaraldehyde (GA). Cross-link time was varied from 24 h to 96 h while keeping the membranes in GA solution. Pore sizes of substrate PC membrane tested were 0.01, 0.1 and 0.2 μm. The membranes were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Ionic conductivity, water uptake, contact angle and gel content have been measured to determine membranes performance. The ionic crossover (iron ions and protons) through membranes was studied in a complete fuel cell. The single-cell performance of membrane was tested in a cathodic microbial fuel cell (MFC, Biogenerator). The physiochemical properties and membranes fuel cell performance were highly depended on the cross-link density of PVA matrices. Membranes cross-liked with GA for 72 h showed maximum gel content and their peak power density has reached 110 mW cm-2 at current density of 378 mA cm-2. Among all, membrane cross-linked for 72 h was studied for continuous long-term stability, which showed consistency for application in MFC.

  1. Precipitation of DNA by polyamines: a polyelectrolyte behavior.

    PubMed Central

    Raspaud, E; Olvera de la Cruz, M; Sikorav, J L; Livolant, F

    1998-01-01

    Conditions of double-stranded DNA precipitation by the polyamines spermidine and spermine have been determined experimentally and compared to theoretical predictions. The influence of the concentrations of DNA and added monovalent salt, and of the DNA length has been investigated in a systematic manner. Three regimes of DNA concentrations are observed. We clarify the dependence of these regimes on the monovalent salt concentration and on the DNA length. Our observations make possible a rationalization of the experimental results reported in the literature. A comparison of the precipitation conditions of different kinds of polyelectrolytes suggests a general process. Our experimental data are compared to the "ion-bridging" model based on short-range electrostatic attractions. By starting from the spinodal equation, predicted by this model, and using the limiting form of Manning's fractions of condensed counterions, analytical expressions of the precipitation conditions have been found in the three regimes. Experimental and theoretical results are in good agreement. PMID:9449338

  2. Ion diffusion coefficients through polyelectrolyte multilayers: temperature and charge dependence.

    PubMed

    Ghostine, Ramy A; Schlenoff, Joseph B

    2011-07-05

    The diffusion coefficient is a fundamental parameter for devices exploiting the ion transport properties of polyelectrolyte multilayers (PEMUs) and complexes. Here, the transport of ferricyanide through a multilayer made from poly(diallyldimethylammonium chloride) (PDADMA) and polystyrene sulfonate (PSS) was studied as a function of temperature or salt concentration. Accurate and precise measurements of ion diffusion coefficients were obtained using steady-state electrochemistry to determine the flux and Fourier transform infrared (FTIR) spectroscopy to measure the PEMU concentration. It was found that the concentration of ferricyanide inside the film decreased with temperature. Membrane transport is strongly thermally activated with activation energy 98 kJ mol(-1). A potential shift with decreasing salt concentration in cyclic voltammograms was translated into a differential flux caused by significantly higher diffusion coefficients for ferricyanide as compared to ferrocyanide. © 2011 American Chemical Society

  3. The decisive role of free water in determining homogenous ice nucleation behavior of aqueous solutions

    PubMed Central

    Wang, Qiang; Zhao, Lishan; Li, Chenxi; Cao, Zexian

    2016-01-01

    It is a challenging issue to quantitatively characterize how the solute and pressure affect the homogeneous ice nucleation in a supercooled solution. By measuring the glass transition behavior of solutions, a universal feature of water-content dependence of glass transition temperature is recognized, which can be used to quantify hydration water in solutions. The amount of free water can then be determined for water-rich solutions, whose mass fraction, Xf, is found to serve as a universal relevant parameter for characterizing the homogeneous ice nucleation temperature, the meting temperature of primary ice, and even the water activity of solutions of electrolytes and smaller organic molecules. Moreover, the effects of hydrated solute and pressure on ice nucleation is comparable, and the pressure, when properly scaled, can be incorporated into the universal parameter Xf. These results help establish the decisive role of free water in determining ice nucleation and other relevant properties of aqueous solutions. PMID:27225427

  4. Investigation of multilayered polyelectrolyte thin films by means of refractive index measurements, FT-IR spectroscopy and SEM

    NASA Astrophysics Data System (ADS)

    Bodurov, I.; Vlaeva, I.; Exner, G.; Uzunova, Y.; Russev, S.; Pilicheva, B.; Viraneva, A.; Yovcheva, T.; Grancharova, Ts; Sotirov, S.; Marudova, M.

    2016-02-01

    Multilayered polyelectrolyte films are promising structures in the biomedical field. In order to meet the demands for biomedical applications, the structures have to be built from biocompatible and/or biodegradable, nontoxic starting materials, possessing some specific functional properties, depending on the particular application. In the present study, the multilayered polyelectrolyte films with potential use as buccal bioadhesive drug delivery systems were investigated. They were prepared via layer-by-layer deposition of successive nanolayers onto substrate. Three different biopolymers were used. The substrate, from poly(lactic acid), was solvent casted. After that, it was subjected to corona treatment, which ensures surface charge excess for the multilayer deposition. The nanolayers were prepared either from 0.01 g/L solutions of chitosan or 0.05 g/L xanthan. Acetate buffer (pH 4.5 and ionic strength 1 M) was used as a solvent. The substrate was dipped successively into one of the solutions, allowing formation of polyelectrolyte complexes of chitosan (polycation) and xanthan (polyanion). The substrates was treated in negative corona. The multilayered structures consisted of 8, 9, 14, 15 or 20 nanolayers. Number of techniques, such refractive index measurements, FT- IR spectroscopy and SEM morphology were employed in order to monitor the properties of the so prepared multilayered polyelectrolyte films.

  5. In situ monitoring of the formation of nanoscale polyelectrolyte coatings on optical fibers using Surface Plasmon Resonances.

    PubMed

    Shevchenko, Yanina; Ahamad, Nur Uddin; Ianoul, Anatoli; Albert, Jacques

    2010-09-13

    Deposition of a conformal nanoscale polymer coating was characterized using a fiber SPR sensor. The sensor platform consisted of an unmodified gold-coated single mode fiber where SPR was excited through the coupling of the core mode into the cladding modes using a Tilted Fiber Bragg Grating. The results from this study show how the sensor can monitor in real time the formation of polyelectrolyte coatings during a process consisting of several stages of immersion. The experimental data was further calibrated by simulations and Atomic Force Microscope imaging allowing us to determine the thickness and refractive index of the adsorbed polyelectrolyte.

  6. Tracer Diffusion of Polyelectrolytes in a Complex Medium

    NASA Astrophysics Data System (ADS)

    Ma, J.; Bruggink, J. L.; Yu, H.

    1997-03-01

    The issue of translational polyelectrolyte diffusion in a complex medium is of both fundamental and practical interest. In our study we examine the diffusion in a gelatin gel as a function of molecular weight and polyelectrolytes concentration. Fractionated, monodisperse gelatin is used as a model matrix. The diffusion of poly(styrene sulfonate) (PSS) and poly (2-acrylamido-2-methylpropane sulfonate) (PAMPS), both in the form of sodium salts, have been studied using fluorescence recovery after photobleaching (FRAP) and dynamic light scattering (DLS) techniques. A series of molecular weights of the two polyelectrolytes and the gelatin have been labeled with fluorescent dyes so that diffusion of each component can be studied individually. By correlating the diffusion of the polyelectrolyte and gelatin, we gain insight into the interactions between the polyelectrolytes and the matrix.

  7. Multifunctional polyelectrolyte multilayers as nanofiltration membranes and as sacrificial layers for easy membrane cleaning.

    PubMed

    Ilyas, Shazia; de Grooth, Joris; Nijmeijer, Kitty; de Vos, Wiebe M

    2015-05-15

    This manuscript investigates the modification of an ultra-filtration (UF) membrane support with polyelectrolyte multilayers (PEMs) consisting of the weak polyelectrolytes poly(allyl amine) hydrochloride (PAH) and poly(acrylic acid) (PAA). These prepared polyelectrolyte multilayer membranes have a dual function: They act as nanofiltration (NF) membranes and as sacrificial layers to allow easy cleaning of the membranes. In order to optimize the conditions for PEM coating and removal, adsorption and desorption of these layers on a model surface (silica) was first studied via optical reflectometry. Subsequently, a charged UF membrane support was coated with a PEM and after each deposited layer, a clear increase in membrane resistance against pure water permeation and a switch of the zeta potential were observed. Moreover these polyelectrolyte multilayer membranes, exhibited rejection of solutes in a range typical for NF membranes. Monovalent ions (NaCl) were hardly rejected (<24%), while rejections of >60% were observed for a neutral organic molecule sulfamethoxazole (SMX) and for the divalent ion SO3(2-). The rejection mechanism of these membranes seems to be dominated by size-exclusion. To investigate the role of these PEMs as sacrificial layers for the cleaning of fouled membranes, the prepared polyelectrolyte multilayers were fouled with silica nano particles. Subsequent removal of the coating using a rinse and a low pressure backwash with pH 3, 3M NaNO3 allowed for a drop in membrane resistance from 1.7⋅10(14)m(-1) (fouled membrane) to 9.9⋅10(12)m(-1) (clean membrane), which is nearly equal to that of the pristine membrane (9.7⋅10(12)m(-1)). Recoating of the support membrane with the same PEMs resulted in a resistance equal to the resistance of the original polyelectrolyte multilayer membrane. Interestingly, less layers were needed to obtain complete foulant removal from the membrane surface, than was the case for the model surface. The possibility for

  8. Determination of focal mechanism solutions for the Cauca nest, Colombia

    NASA Astrophysics Data System (ADS)

    Tary, J. B.; Diaz, S. A.

    2016-12-01

    Colombia is located on the South American plate, with the Nazca plate to the West and the Caribbean plate to the North - North-West. Colombia has three main earthquake nests showing high seismic activity which has been identified as the Bucaramanga nest, Cauca nest, and Murindo nest. The Bucaramanga and Cauca nests show concentrations of intermediate-depth ( 70-170 km) earthquake sources. These two nests are oriented approximately North-South and dip toward the East. They are offset by approximately 250 km in the East-West direction, which has been attributed to a slab tear in the subducting Nazca plate. The slab tear is also supported by the presence two domains of different volcanic activities and seismic velocities. Many studies have been devoted to the Bucaramanga nest due to its high seismic activity and high magnitude events in comparison to the other nests. However, there is no clear consensus about the tectonic interpretation for the concentration of these events. We calculate focal mechanisms from the Cauca nest, which hasn't been studied in detail, using data from the Red Sismológica Nacional of Colombia (RSNC). We selected a set of well-recorded events and interpret their focal mechanism solutions regarding the slab tear hypothesis. This study contributes to a better understanding of the geodynamic context in Colombia.

  9. Titrimetric determination of hydrogen peroxide in alkaline solution.

    PubMed

    McCurdy, W H; Bell, H F

    1966-07-01

    Direct titration of hydrogen peroxide in alkaline bromide media has been accomplished with sodium hypochlorite. The relative standard deviation is 0.2%. A photometric end-point is recommended for the determination of 0.10-1.0 mequiv of peroxide. Larger samples are evaluated by use of Bordeaux Red as visual indicator. The hypochlorite procedure compares favourably with iodometry and permanganate in the analysis of commercial peroxides.

  10. Integral Equation Theory for the Conformation of Polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Shew, C.-Y.; Yethiraj, A.

    1996-03-01

    The equilibrium conformation properties of polyelectrolyes are explored using the integral equation theory. The polymer molecules are modeled as freely-jointed beads that interact via a hard sphere plus screened Coulomb potential. To obtain the intramolecuar correlation function ( and hence the chain conformations) the many chain system is replaced by a single chain whose beads interact via the bare interaction plus a solvent-induced potential, which approximately accounts for the presence of the other molecules. Since this solvent induced potential is a functional of the intramolecular correlations it is obtained iteratively in a self-consistent fashion. The intramolecular correlation functions for a given solvation potential are obtained via Monte Carlo simulation of a single chain. A thread model of the polymer molecules is also investigated, in which case the single chain conformations are obtained using a variational method. The predictions of the theory for these two models are similar. For single chains ~ N^2 ( is the mean square end-to-end distance and N is the degree of polymerization) in salt free solutions, and ~ N^1.2 in high salt solutions. At high polymer concentration ~ N. The theory provides a means of interpolating between these limiting cases. An interesting feature is that there is a very sharp drop in polymer size at very low concentrations which happens because the overlap threshold concentration in polyelectrolytes solutions is very small.

  11. Preparation and characterization modified chitosan by polyelectrolyte complexation

    NASA Astrophysics Data System (ADS)

    Zuhannisa, Nugraheni, Prihati Sih; Budhijanto, Wiratni; Kusumastuti, Yuni

    2017-03-01

    The polyelectrolyte complexes (PECs) of chitosan with various polysaccharides such as alginate, carrageenan, Arabic gum, carboxymethylcellulose (CMC), pectin, and glucomannan were prepared and characterized. The complexation was performed by addition of polysaccharide solution as crosslinking agent into chitosan solution (0.01% and 2 %) under magnetic stirring. The size of the obtained modified chitosan was analyzed by Particle Size Analyzer (PSA). The turbidity and pH were measured to observe the stability of the modified chitosan during the storage. The stability of the complexes was investigated at room temperature (37°C) for 3 weeks. The existence of glucomannan and arabic gum resulted PECs when it reacted with the chitosan solution using ratio 1:1. The changed crosslinker resulted a hydrogel after it blended. The obtained PECs could be affected by the ratio between chitosan and polysaccharide and the molecular weight of both polymers. The crosslinker concentration gave a significantly influenced the obtained particle size at the chitosan concentration 0.01 % and 2%.

  12. Electrolyte effect on gelation behavior of oppositely charged nanocrystalline cellulose and polyelectrolyte.

    PubMed

    Lu, Ang; Song, Yongbo; Boluk, Yaman

    2014-12-19

    The electrolyte (NaCl) influences on the sol-gel transition of the complex solution composed of oppositely charged nanocrystalline cellulose (NCC) and polyelectrolyte (quaternized hydroxyethylcellulose ethoxylate, QHEC) were investigated by the rheological means in the present paper. Winter and Chambon theory was applicable to describe the sol-gel transition, and the critical gel points have been successfully determined. When increasing the NaCl concentration, more NCC were needed to form a critical gel due to the screening of the electrostatic interaction, and the larger loss tangent and relaxation exponent (n) values at the gel point demonstrated a less elastic nature of the complex solution with more NaCl. The results indicated the gel network was composed of entanglements and association of QHEC (as polymer network), as well as the electrostatic adsorption interaction between QHEC chains and NCC rods (as cross-linking). With the addition of NaCl, the screening effect led to the enhancement of the entanglements and weakening of the electrostatic adsorption, however, the gel strength decreased with increasing the NaCl amount, suggesting the electrostatic adsorption interaction played a more dominant role than the entanglements when the gel was formed. Moreover, the exponents of the scaling law η0∝ɛ(-γ) and Ge∝ɛ(z) of the QHEC/NCC/NaCl solution revealed that the scaling law n=z/(z+γ) between n, γ, and z was only feasible at the highest NaCl concentration, as a result of that the intermolecular electrostatic interaction was completely screened, indicating the scaling law was only feasible when intermolecular interaction was small enough to be neglected. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. 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.

  14. Surface tension of polyelectrolyte coacervates

    NASA Astrophysics Data System (ADS)

    Qin, Jian; Priftis, Dimitrios; Farina, Robert; Perry, Sarah; Leon, Lorraine; Whitmer, Jonathan; Hoffman, Kyle; Tirrell, Matthew; de Pablo, Juan J.

    2014-03-01

    Stoichiometric solutions of polycations and polyanions can phase separate, resulting in the coexistence of a supernatant phase and a polymer-rich complex phase. The complex phase may be liquid-like or solid-like, depending on the ionic strength and the temperature. Liquid-like complexes, known as ``coacervates'', retain a large amount of water, up to 70-80% by weight, and exhibit an ultra-low interfacial tension with the coexisting supernatant phase (smaller than the water surface tension by three orders of magnitude). Previous experiments have observed that this interfacial tension decreases with the amount of salt, and vanishes near a critical salt concentration according to a 3 / 2 power of the salt undersaturation. In this work we derive analytical expressions for the interfacial tension in both the low and high charge density limits. For solutions with added salts, we provide explicit expressions for the interfacial tension near the critical salt concentration and explain the 3 / 2 power dependence. Our results are shown to be in good agreement with experiment.

  15. Improved solution accuracy for TDRSS-based TOPEX/Poseidon orbit determination

    NASA Technical Reports Server (NTRS)

    Doll, C. E.; Mistretta, G. D.; Hart, R. C.; Oza, D. H.; Bolvin, D. T.; Cox, C. M.; Nemesure, M.; Niklewski, D. J.; Samii, M. V.

    1994-01-01

    Orbit determination results are obtained by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) using a batch-least-squares estimator available in the Goddard Trajectory Determination System (GTDS) and an extended Kalman filter estimation system to process Tracking and Data Relay Satellite (TDRS) System (TDRSS) measurements. GTDS is the operational orbit determination system used by the FDD in support of the Ocean Topography Experiment (TOPEX)/Poseidon spacecraft navigation and health and safety operations. The extended Kalman filter was implemented in an orbit determination analysis prototype system, closely related to the Real-Time Orbit Determination System/Enhanced (RTOD/E) system. In addition, the Precision Orbit Determination (POD) team within the GSFC Space Geodesy Branch generated an independent set of high-accuracy trajectories to support the TOPEX/Poseidon scientific data. These latter solutions use the geodynamics (GEODYN) orbit determination system with laser ranging and Doppler Orbitography and Radiopositioning integrated by satellite (DORIS) tracking measurements. The TOPEX/Poseidon trajectories were estimated for November 7 through November 11, 1992, the timeframe under study. Independent assessments were made of the consistencies of solutions produced by the batch and sequential methods. The batch-least-squares solutions were assessed based on the solution residuals, while the sequential solutions were assessed based on primarily the estimated covariances. The batch-least-squares and sequential orbit solutions were compared with the definitive POD orbit solutions. The solution differences were generally less than 2 meters for the batch-least-squares and less than 13 meters for the sequential estimation solutions. After the sequential estimation solutions were processed with a smoother algorithm, position differences with POD orbit solutions of less than 7 meters were obtained. The differences among the POD, GTDS, and filter

  16. Improved solution accuracy for TDRSS-based TOPEX/Poseidon orbit determination

    NASA Astrophysics Data System (ADS)

    Doll, C. E.; Mistretta, G. D.; Hart, R. C.; Oza, D. H.; Bolvin, D. T.; Cox, C. M.; Nemesure, M.; Niklewski, D. J.; Samii, M. V.

    1994-05-01

    Orbit determination results are obtained by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) using a batch-least-squares estimator available in the Goddard Trajectory Determination System (GTDS) and an extended Kalman filter estimation system to process Tracking and Data Relay Satellite (TDRS) System (TDRSS) measurements. GTDS is the operational orbit determination system used by the FDD in support of the Ocean Topography Experiment (TOPEX)/Poseidon spacecraft navigation and health and safety operations. The extended Kalman filter was implemented in an orbit determination analysis prototype system, closely related to the Real-Time Orbit Determination System/Enhanced (RTOD/E) system. In addition, the Precision Orbit Determination (POD) team within the GSFC Space Geodesy Branch generated an independent set of high-accuracy trajectories to support the TOPEX/Poseidon scientific data. These latter solutions use the geodynamics (GEODYN) orbit determination system with laser ranging and Doppler Orbitography and Radiopositioning integrated by satellite (DORIS) tracking measurements. The TOPEX/Poseidon trajectories were estimated for November 7 through November 11, 1992, the timeframe under study. Independent assessments were made of the consistencies of solutions produced by the batch and sequential methods. The batch-least-squares solutions were assessed based on the solution residuals, while the sequential solutions were assessed based on primarily the estimated covariances. The batch-least-squares and sequential orbit solutions were compared with the definitive POD orbit solutions. The solution differences were generally less than 2 meters for the batch-least-squares and less than 13 meters for the sequential estimation solutions. After the sequential estimation solutions were processed with a smoother algorithm, position differences with POD orbit solutions of less than 7 meters were obtained. The differences among the POD, GTDS, and filter

  17. Counterion-Induced Attraction between Rigid Polyelectrolytes

    SciTech Connect

    Gro Bruinsma, R.F.; Gro Mashl, R.J.; Gelbart, W.M.

    1997-03-01

    We report on results of long-time Brownian-dynamics simulations of electrostatic interactions between two rigid polyelectrolyte rods. We find that the interaction can be both repulsive, as obtained from mean-field theory, and attractive. The onset of attraction depends not only on the fixed charge density of the rod, but also on its radius. The attractive force is found to be due to the development of positional correlations between the counterions condensed on the two rods, for which we propose a simple analytical model. {copyright} {ital 1997} {ital The American Physical Society}

  18. Evolution of growth modes for polyelectrolyte bundles.

    PubMed

    Lai, Ghee Hwee; Coridan, Rob; Zribi, Olena V; Golestanian, Ramin; Wong, Gerard C L

    2007-05-04

    Multivalent ions induce attractions between polyelectrolytes, but lead to finite-sized bundles rather than macroscopic phase separation. The kinetics of aggregation and bundle formation of actin is tracked using two different fluorescently labeled populations of F-actin. It is found that the growth mode of these bundles evolves with time and salt concentration, varying from an initial lateral growth to a longitudinal one at later stages. The results suggest that kinetics play a role in bundle growth, but not in the lateral size of bundles, which is constant for linear and branched topologies.

  19. Luminescence Probe Studies of Nafion Polyelectrolytes.

    DTIC Science & Technology

    1983-10-07

    I iD-Ri33 519 LUMINESCENCE PROBE STUDIES OF NRFION FOLYELECTROLYTES i/i (U) TEXAS A AND M UNIV COLLEGE STATION DEPT OF CHEMIISTRY N E PRIETO ET AL...Task No. NR 627-838 TECHNICAL REPORT NO. 2 *Luminescence Probe Studi s of Nafion Polyelectrolytes Pby Nelson E. Prieto and Charles R. Martin 41...E. Prieto and Charles R. Martin N00014-82K-0612 9. PERFORMING ORGANIZATION NAME AND ADDRESS _%. -PROGRAM ELEMENT. PROJECT. TASK AREA & WORKC UNIT

  20. Three semi-discrete integrable systems related to orthogonal polynomials and their generalized determinant solutions

    NASA Astrophysics Data System (ADS)

    Chen, Xiao-Min; Chang, Xiang-Ke; Sun, Jian-Qing; Hu, Xing-Biao; Yeh, Yeong-Nan

    2015-07-01

    In this paper, we present a generalized Toeplitz determinant solution for the generalized Schur flow and propose a mixed form of the two known relativistic Toda chains together with its generalized Toeplitz determinant solution. In addition, we also give a Hankel type determinant solution for a nonisospectral Toda lattice. All these results are obtained by technical determinant operations. As a bonus, we finally obtain some new combinatorial numbers based on the moment relations with respect to these semi-discrete integrable systems and give the corresponding combinatorial interpretations by means of the lattice paths.

  1. Protonation process of conjugated polyelectrolytes on enhanced power conversion efficiency in the inverted polymer solar cells

    NASA Astrophysics Data System (ADS)

    Yi, Chao; Hu, Rong; Ren, He; Hu, Xiaowen; Wang, Shu; Gong, Xiong; Cao, Yong

    2014-01-01

    In this study, two conjugated polyelectrolytes, polythiophene derivative (PTP) and poly[(9,9-bis [6‧-N, N, N-trimethylammonium] hexyl)-fluorenylene-phenylene] dibromide (PFP), are utilized to modify the surface properties of ZnO electron extraction layer (EEL) in the inverted polymer solar cells (PSCs). Both higher short-circuit current densities and larger open-circuit voltages were observed from the inverted PSCs with ZnO/PFP or ZnO/PTP as compared with those only with ZnO EEL. The protonation process for PTP and PFP in solution is distinguished. Overall, more than 40% enhanced power conversion efficiency (PCE) from the inverted PSCs with ZnO/PFP, in which the PFP could be fully ionized in deionized water, and more than 30% enhanced PCE from the inverted PSCs with ZnO/PTP, as the case that the PTP could not be fully ionized in deionized water, as compared with the inverted PSCs with ZnO EEL were observed, respectively. These results demonstrate that the conjugated polyelectrolytes play an important role in enhancement of device performance of inverted PSCs and that the protonation process of the conjugated polyelectrolytes is critical to the modification for EEL in PSCs.

  2. Chitosan Based Polyelectrolyte Complexes as Potential Carrier Materials in Drug Delivery Systems

    PubMed Central

    Hamman, Josias H.

    2010-01-01

    Chitosan has been the subject of interest for its use as a polymeric drug carrier material in dosage form design due to its appealing properties such as biocompatibility, biodegradability, low toxicity and relatively low production cost from abundant natural sources. However, one drawback of using this natural polysaccharide in modified release dosage forms for oral administration is its fast dissolution rate in the stomach. Since chitosan is positively charged at low pH values (below its pKa value), it spontaneously associates with negatively charged polyions in solution to form polyelectrolyte complexes. These chitosan based polyelectrolyte complexes exhibit favourable physicochemical properties with preservation of chitosan’s biocompatible characteristics. These complexes are therefore good candidate excipient materials for the design of different types of dosage forms. It is the aim of this review to describe complexation of chitosan with selected natural and synthetic polyanions and to indicate some of the factors that influence the formation and stability of these polyelectrolyte complexes. Furthermore, recent investigations into the use of these complexes as excipients in drug delivery systems such as nano- and microparticles, beads, fibers, sponges and matrix type tablets are briefly described. PMID:20479980

  3. Theory of polyelectrolyte complexation—Complex coacervates are self-coacervates

    NASA Astrophysics Data System (ADS)

    Delaney, Kris T.; Fredrickson, Glenn H.

    2017-06-01

    The complexation of mixtures of cationic and anionic polymers to produce complex-coacervate phases is a subject of fundamental importance to colloid and polymer science as well as to applications including drug delivery, sensing technologies, and bio-inspired adhesives. Unfortunately the theoretical underpinnings of complex coacervation are widely misunderstood and conceptual mistakes have propagated in the literature. Here, a simple symmetric polyelectrolyte mixture model in the absence of salt is used to discuss the salient features of the phase diagram, including the location of the critical point, binodals, and spinodals. It is argued that charge compensation by dimerization in the dilute region renders the phase diagram of an oppositely charged polyelectrolyte mixture qualitatively and quantitatively similar to that of a single-component symmetric diblock polyampholyte solution, a system capable of "self-coacervation." The theoretical predictions are verified using fully fluctuating field-theoretic simulations for corresponding polyelectrolyte and diblock polyampholyte models. These represent the first comprehensive, approximation-free phase diagrams for coacervate and self-coacervate systems to appear in the literature.

  4. Controlling the nanofiltration properties of multilayer polyelectrolyte membranes through variation of film composition.

    PubMed

    Miller, Matthew D; Bruening, Merlin L

    2004-12-21

    We report the use of a variety of polyelectrolyte multilayers (PEMs) as selective skins in composite membranes for nanofiltration (NF) and diffusion dialysis. Deposition of PEMs occurs through simple alternating adsorption of polycations and polyanions, and separations can be optimized by varying the constituent polyelectrolytes as well as deposition conditions. In general, the use of polycations and polyanions with lower charge densities allows separation of larger analytes. Depending on the polyelectrolytes employed, PEM membranes can remove salt from sugar solutions, separate proteins, or allow size-selective passage of specific sugars. Additionally, because of the minimal thickness of PEMs, NF pure water fluxes through these membranes typically range from 1.5 to 3 m3/(m2 day) at 4.8 bar. Specifically, to separate sugars, we employed poly(styrene sulfonate) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) films, which allow 42% passage of glucose along with a 98% rejection of raffinose and a pure water flux of 2.4 m3/(m2 day). PSS/PDADMAC membranes are also capable of separating NaCl and sucrose (selectivity of approximately 10), while high-flux chitosan/hyaluronic acid membranes [pure water flux of 5 m3/(m2 day) at 4.8 bar] may prove useful in protein separations.

  5. The effects of acrylamide polyelectrolytes on aquatic organisms: relating toxicity to chain architecture.

    PubMed

    Costa, R; Pereira, J L; Gomes, J; Gonçalves, F; Hunkeler, D; Rasteiro, M G

    2014-10-01

    Understanding the inherent toxicity of water-soluble synthetic polyelectrolytes is critical for adequate risk management as well as enhancing product design when biological activity is a key performance index (e.g. for application in biofouling bivalves' control). The toxicity of two cationic acrylamide copolymers with different chain branching degree was evaluated. Standard ecotoxicity tests were conducted with microalgae and daphnids. The susceptibility of Corbicula fluminea, as a biofouling bivalve, was also evaluated. The effect of polyelectrolyte on the test media viscosity and the polymer chain size distributions under the experimental conditions were also examined. The susceptibility of the microalgae to both polymers was similar. As the complexity and size of the test organisms increased, differences in toxicity due to different chain architecture were noticeable. The more branched polymer was significantly less toxic to both daphnids and the bivalves, which could be linked to the distinctive features of its bimodal size chain distribution. This architecture resulted in both more compact globular molecules and the formation of aggregates, which reduce the polymer interaction with the biological surfaces. The results of this study promote the incorporation of environmental considerations in polyelectrolyte development and contribute to the design of improved solutions for controlling biofouling bivalves. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Elasticity of hollow polyelectrolyte capsules prepared by the layer-by-layer technique

    NASA Astrophysics Data System (ADS)

    Gao, C.; Donath, E.; Moya, S.; Dudnik, V.; Möhwald, H.

    Osmotically induced deformations (invaginations) of polyelectrolyte capsules were observed in poly(styrene sulfonate, sodium salt) (PSS) solution since PSS of Mw 70 000 is excluded from the capsule interior. It was found that there is a critical osmotic pressure difference at which the initial spherical capsule shape becomes unstable and invaginations are formed. This critical osmotic pressure was obtained as a function of the wall thickness and the capsule size. A theoretical model is provided which describes the relationship between the critical osmotic pressure, the elasticity modulus, the capsule wall thickness, and the capsule radius. The model was verified by measuring the invagination onset as a function of particle radius and wall thickness. The elasticity modulus of the PSS/PAH (polyallylamine hydrochloride) polyelectrolyte multilayer was measured as a function of wall thickness and capsule diameter. The modulus ranges between 500 and 750 MPa, which indicates a relatively strongly interconnected polyelectrolyte multilayer structure. With higher molecular weight PAH the elasticity modulus of the PSS/PAH multilayer was slightly enhanced.

  7. Underwater contact adhesion and microarchitecture in polyelectrolyte complexes actuated by solvent exchange

    PubMed Central

    Seo, Sungbaek; Kaufman, Yair; Israelachvili, Jacob N.; Waite, J. Herbert

    2016-01-01

    Polyelectrolyte complexation is critical to the formation and properties of many biological and polymeric materials, and is typically initiated by aqueous mixing1 followed by fluid–fluid phase separation, such as coacervation2–5. Yet little to nothing is known about how coacervates evolve into intricate solid microarchitectures. Inspired by the chemical features of the cement proteins of the sandcastle worm, here we report a versatile and strong wet-contact microporous adhesive resulting from polyelectrolyte complexation triggered by solvent exchange. After premixing a catechol-functionalized weak polyanion with a polycation in dimethyl sulphoxide (DMSO), the solution was applied underwater to various substrates whereupon electrostatic complexation, phase inversion, and rapid setting were simultaneously actuated by water–DMSO solvent exchange. Spatial and temporal coordination of complexation, inversion and setting fostered rapid (~25 s) and robust underwater contact adhesion (Wad ≥ 2 J m−2) of complexed catecholic polyelectrolytes to all tested surfaces including plastics, glasses, metals and biological materials. PMID:26779881

  8. 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.

  9. 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.

  10. Triclosan loaded electrospun nanofibers based on a cyclodextrin polymer and chitosan polyelectrolyte complex.

    PubMed

    Ouerghemmi, Safa; Degoutin, Stéphanie; Tabary, Nicolas; Cazaux, Frédéric; Maton, Mickaël; Gaucher, Valérie; Janus, Ludovic; Neut, Christel; Chai, Feng; Blanchemain, Nicolas; Martel, Bernard

    2016-11-20

    This work focuses on the relevance of antibacterial nanofibers based on a polyelectrolyte complex formed between positively charged chitosan (CHT) and an anionic hydroxypropyl betacyclodextrin (CD)-citric acid polymer (PCD) complexing triclosan (TCL). The study of PCD/TCL inclusion complex and its release in dynamic conditions, a cytocompatibility study, and finally the antibacterial activity assessment were studied. The fibers were obtained by electrospinning a solution containing chitosan mixed with PCD/TCL inclusion complex. CHT/TCL and CHT-CD/TCL were also prepared as control samples. The TCL loaded nanofibers were analyzed by Scanning Electron Microscopy (SEM), Fourier Transformed Infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD). Nanofibers stability and swelling behavior in aqueous medium were pH and CHT:PCD weight ratio dependent. Such results confirmed that CHT and PCD interacted through ionic interactions, forming a polyelectrolyte complex. A high PCD content in addition to a thermal post treatment at 90°C were necessary to reach a nanofibers stability during 15days in soft acidic conditions, at pH=5.5. In dynamic conditions (USP IV system), a prolonged release of TCL with a reduced burst effect was observed on CHT-PCD polyelectrolyte complex based fibers compared to CHT-CD nanofibers. These results were confirmed by a microbiology study showing prolonged antibacterial activity of the nanofibers against Escherichia coli and Staphylococcus aureus. Such results could be explained by the fact that the stability of the polyelectrolyte CHT-PCD complex in the nanofibers matrix prevented the diffusion of the PCD/triclosan inclusion complex in the supernatant, on the contrary of the similar system including cyclodextrin in its monomeric form.

  11. Effect of solutes on the heterogeneous nucleation temperature of supercooled water: an experimental determination.

    PubMed

    Wilson, P W; Haymet, A D J

    2009-04-21

    We investigate the effect of solute concentration on the heterogeneous ice nucleation temperature (T(het)) of aqueous solutions of both NaCl and d-glucose. An automatic lag time apparatus (ALTA) technique allows the dependence of T(het) on solute concentration to be determined with statistical significance. Our results point to the solute-induced lowering of T(het) being a factor of two times the equivalent melting point depression at any fixed concentration, the same factor reported for homogeneous nucleation experiments with small molecular weight solutes.

  12. Polyelectrolyte multilayer-cushioned fluid lipid bilayers: a parachute model.

    PubMed

    Shao, Jingxin; Wen, Caixia; Xuan, Mingjun; Zhang, Hongyue; Frueh, Johannes; Wan, Mingwei; Gao, Lianghui; He, Qiang

    2017-01-18

    Lipid bilayer membranes supported on polyelectrolyte multilayers are widely used as a new biomembrane model that connects biological and artificial materials since these ultrathin polyelectrolyte supports may mimic the role of the extracellular matrix and cell skeleton in living systems. Polyelectrolyte multilayers were fabricated by a layer-by-layer self-assembly technique. A quartz crystal microbalance with dissipation was used in real time to monitor the interaction between phospholipids and polyelectrolytes in situ on a planar substrate. The surface properties of polyelectrolyte films were investigated by the measurement of contact angles and zeta potential. Phospholipid charge, buffer pH and substrate hydrophilicity were proved to be essential for vesicle adsorption, rupture, fusion and formation of continuous lipid bilayers on the polyelectrolyte multilayers. The results clearly demonstrated that only the mixture of phosphatidylcholine and phosphatidic acid (4 : 1) resulted in fluid bilayers on chitosan and alginate multilayers with chitosan as a top layer at pH 6.5. A coarse-grained molecular simulation study elucidated that the exact mechanism of the formation of fluid lipid bilayers resembles a "parachute" model. As the closest model to the real membrane, polyelectrolyte multilayer-cushioned fluid lipid bilayers can be appropriate candidates for application in biomedical fields.

  13. Interferometry study of aqueous lubrication on the surface of polyelectrolyte brush.

    PubMed

    Kobayashi, Motoyasu; Tanaka, Hiroyoshi; Minn, Myo; Sugimura, Joichi; Takahara, Atsushi

    2014-11-26

    The water lubrication behavior of a polyelectrolyte brush was investigated by using double-spacer-layer ultra-thin-film interferometry to determine the thickness of the aqueous lubrication layer present at the interface between the brush and a spherical glass lens. A hydrophilic poly{[2-(methacryloyloxy)ethyl]trimethylammonium chloride} brush was prepared on an optical glass disk coated with layers of semireflective chromium and silica. The thickness of the hydrodynamic lubrication layer was estimated interferometrically. On increasing the sliding velocity from 10(-5) to 10(-1) m·s(-1), the gap between the rotating disk and loading sphere glass lens showed a marked increase to 130 nm at 2×10(-2) m·s(-1), and the friction coefficient simultaneously decreased to 0.01-0.02, indicating that the polyelectrolyte brush promoted the formation of a fluid lubrication layer that separates the rubbing surfaces, preventing direct contact and providing a low friction coefficient.

  14. Length Scale Dependence of the Dynamic Properties of Hyaluronic Acid Solutions in the Presence of Salt

    SciTech Connect

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

    2010-12-07

    In solutions of the charged semirigid biopolymer hyaluronic acid in salt-free conditions, the diffusion coefficient D{sub 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{sub DLS}. This behavior contrasts with neutral polymer solutions. With increasing salt content, D{sub DLS} approaches D{sub 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-Hueckel length.

  15. 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

  16. Modeling competitive substitution in a polyelectrolyte complex

    SciTech Connect

    Peng, B.; Muthukumar, M.

    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 longer 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.

  17. Modeling competitive substitution in a polyelectrolyte complex

    NASA Astrophysics Data System (ADS)

    Peng, B.; Muthukumar, M.

    2015-12-01

    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 longer 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.

  18. Nanoparticle gel electrophoresis: bare charged spheres in polyelectrolyte hydrogels.

    PubMed

    Li, Fei; Hill, Reghan J

    2013-03-15

    Nanoparticle gel electrophoresis has recently emerged as an attractive means of separating and characterizing nanoparticles. Consequently, a theory that accounts for electroosmotic flow in the gel, and coupling of the nanoparticle and hydrogel electrostatics and hydrodynamics, is required, particularly for gels in which the mesh size is comparable to or smaller than the particle radii. Here, we present an electrokinetic model for charged, spherical colloidal particles undergoing electrophoresis in charged (polyelectrolyte) hydrogels: the gel-electrophoresis analogue of Henry's theory for electrophoresis in Newtonian electrolytes. We compare numerically exact solutions of the model with several independent asymptotic approximations, identifying regions in the parameter space where these approximations are accurate or break down. As previously assumed in the literature, Henry's formula, modified by the addition of a constant electroosmotic flow mobility, is accurate only for nanoparticles that are small compared to the hydrogel mesh size. We derived an exact analytical solution of the full model by judiciously modifying the theory of Allison et al. for uncharged gels, drawing on the superposition methodology of Doane et al. to account for hydrogel charge. This furnishes accurate and economical mobility predictions for the entire parameter space. The present model suggests that nanoparticle size separations (with diameters ≲40 nm) are optimal at low ionic strength, with a gel mesh size that is selected according to the particle charging mechanism. For weakly charged particles, optimal size separation is achieved when the Brinkman screening length is matched to the mean particle size.

  19. Multiscale modeling of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Wallmersperger, Thomas; Wittel, Falk K.; Kröplin, Bernd H.

    2006-03-01

    Electrolyte polymer gels are a very attractive class of actuation materials with remarkable electronic and mechanical properties having a great similarity to biological contractile tissues. They consist of a polymer network with ionizable groups and a liquid phase with mobile ions. Absorption and delivery of solvent lead to a considerably large change of volume. Due to this capability, they can be used as actuators for technical applications, where large swelling and shrinkage is desired. In the present work chemically and electrically stimulated polymer gels in a solution bath are investigated. To describe the different complicated phenomena occurring in these gels adequately, the modeling can be conducted on different scales. Therefore, models based on the statistical theory and porous media theory, as well as a multi-field model and a discrete element formulation are derived. A refinement of the different theories from global macroscopic to microscopic are presented in this paper: The statistical theory is a macroscopic theory capable to describe the global swelling or bending e.g. of a gel film, while the general theory of porous media (TPM) is a macroscopic continuum theory which is based on the theory of mixtures extended by the concept of volume fractions. The TPM is a homogenized model, i.e. all geometrical and physical quantities can be seen as statistical averages of the real quantities. The presented chemo-electro-mechanical multi-field formulation is a mesoscopic theory. It is capable of giving the concentrations and the electric potential in the whole domain. Finally the (micromechanical) discrete element (DE) theory is employed. In this case, the continuum is represented by distributed particles with local interaction relations combined with balance equations for the chemical field. This method is predestined for problems involving large displacements, strains and discontinuities. The presented formulations are compared and conclusions on their

  20. Coulometric determination of berkelium in sulfuric acid and nitric acid solutions

    SciTech Connect

    Timofeev, G.A.; Chistyakov, V.M.; Erin, E.A.

    1987-03-01

    Results are reported on the study and quantitative determination of berkelium by the coulometric method in 1 M sulfuric acid, in solutions of nitric acid, and in mixtures of these acids. The best results in the determination of berkelium were obtained in solutions of a mixture of nitric and sulfuric acids. In 1 M HNO/sub 3/ + 0.1 M H/sub 2/SO/sub 4/ solutions, berkelium can be determined with an accuracy within approx. +/- 2%, when its content is 10 ..mu..g/ml.

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

    NASA Astrophysics Data System (ADS)

    Sanyal, Oishi

    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.

  2. Quantum field theory of polyelectrolyte-counterion condensation

    NASA Astrophysics Data System (ADS)

    Dewey, T. G.

    1988-10-01

    A simple quantum theory of polyelectrolyte-counterion interactions is presented. A model Hamiltonian is employed which describes both the polyelectrolyte and the counterion as free, spinless fermions. This Hamiltonian is transformed into a form which is isomorphous with traditional Hamiltonians used to describe phase transitions. The difference between this theory and early theories of superconductivity is that the counterion-counterion interaction energies will be quite large and will persist at high temperatures. The counterion condensate is a collective mode resulting from polyelectrolyte-mediated polarizations. Colligative properties for this model are compared with the Poisson-Boltzmann theory and to Manning's condensation theory.

  3. Electrokinetics of pH-regulated zwitterionic polyelectrolyte nanoparticles

    NASA Astrophysics Data System (ADS)

    Yeh, Li-Hsien; Tai, Yi-Hsuan; Wang, Nan; Hsu, Jyh-Ping; Qian, Shizhi

    2012-11-01

    The electrokinetic behavior of pH-regulated, zwitterionic polyelectrolyte (PE) nanoparticles (NPs) in a general electrolyte solution containing multiple ionic species is investigated for the first time. The NPs considered are capable of simulating entities such as proteins, biomolecules, and synthetic polymers. The applicability of the model proposed is verified by the experimental data of succinoglycan nanoparticles available in the literature. We show that, in addition to their effective charge density, counterion condensation, double-layer polarization, and electro-osmotic flow of unbalanced counterions inside the double layer all significantly affect the electrophoretic behaviors of NPs. Our model successfully predicts many interesting electrophoretic behaviors, which qualitatively agree with experimental observations available in the literature. In contrast, because the effects of double-layer polarization and charge regulation are neglected, the existing theoretical models fail to explain the experimental results. The results gathered provide necessary information for the interpretation of relevant electrophoresis data in practice, and for nanofluidic applications such as biomimetic ion channels and nanopore-based sensing of single biomolecules.The electrokinetic behavior of pH-regulated, zwitterionic polyelectrolyte (PE) nanoparticles (NPs) in a general electrolyte solution containing multiple ionic species is investigated for the first time. The NPs considered are capable of simulating entities such as proteins, biomolecules, and synthetic polymers. The applicability of the model proposed is verified by the experimental data of succinoglycan nanoparticles available in the literature. We show that, in addition to their effective charge density, counterion condensation, double-layer polarization, and electro-osmotic flow of unbalanced counterions inside the double layer all significantly affect the electrophoretic behaviors of NPs. Our model successfully

  4. Determining the Amount of Copper(II) Ions in a Solution Using a Smartphone

    ERIC Educational Resources Information Center

    Montangero, Marc

    2015-01-01

    When dissolving copper in nitric acid, copper(II) ions produce a blue-colored solution. It is possible to determine the concentration of copper(II) ions, focusing on the hue of the color, using a smartphone camera. A free app can be used to measure the hue of the solution, and with the help of standard copper(II) solutions, one can graph a…

  5. Determining the Amount of Copper(II) Ions in a Solution Using a Smartphone

    ERIC Educational Resources Information Center

    Montangero, Marc

    2015-01-01

    When dissolving copper in nitric acid, copper(II) ions produce a blue-colored solution. It is possible to determine the concentration of copper(II) ions, focusing on the hue of the color, using a smartphone camera. A free app can be used to measure the hue of the solution, and with the help of standard copper(II) solutions, one can graph a…

  6. Microfluidics Meets Dilute Solution Viscometry: An Undergraduate Laboratory to Determine Polymer Molecular Weight Using a Microviscometer

    ERIC Educational Resources Information Center

    Pety, Stephen J.; Lu, Hang; Thio, Yonathan S.

    2011-01-01

    This paper describes a student laboratory experiment to determine the molecular weight of a polymer sample by measuring the viscosity of dilute polymer solutions in a PDMS microfluidic viscometer. Sample data are given for aqueous solutions of poly(ethylene oxide) (PEO). A demonstration of shear thinning behavior using the microviscometer is…

  7. [The possibility for determining haptoglobin phenotypes in blood stains after treatment with a luminol solution].

    PubMed

    Alesho, N A; Guzheedov, V N; Dvorkin, A I

    1989-01-01

    The paper gives the results of tests for influence of luminol solution of different composition on detectability of haptoglobin fractions in the bloodstains of different ages. It was stated that alkaline luminol solutions reduce intensity of fractions and may hamper Hp phenotype determination especially in old stains.

  8. Microfluidics Meets Dilute Solution Viscometry: An Undergraduate Laboratory to Determine Polymer Molecular Weight Using a Microviscometer

    ERIC Educational Resources Information Center

    Pety, Stephen J.; Lu, Hang; Thio, Yonathan S.

    2011-01-01

    This paper describes a student laboratory experiment to determine the molecular weight of a polymer sample by measuring the viscosity of dilute polymer solutions in a PDMS microfluidic viscometer. Sample data are given for aqueous solutions of poly(ethylene oxide) (PEO). A demonstration of shear thinning behavior using the microviscometer is…

  9. Adsorption of hydrophobically modified polyelectrolytes at the n-octane/water interface.

    PubMed

    Barraza, R G; Olea, A F; Martinez, F; Ruiz-Tagle, I

    2003-05-15

    The interfacial activity of polyelectrolytes carrying alkyl side chains of different length has been studied. Potassium salts of poly(maleic acid-co-1-olefins), PA-n K2 with n=12 , 14, 16, 18, were synthesized, and the interfacial tension at the aqueous solution/n -octane interface was measured as a function of the length of the alkyl side chain. The results show that the interfacial tension lowering, the limiting excess concentration Gamma (m), and the efficiency of adsorption pC (20) depend on the number of methylene groups in the alkyl side chain. According to Rosen the last two parameters define two different contributions to the standard free energy of adsorption: one arises from the distribution of the polymer between the bulk of the solution and the interface Delta G (dist )(0), and another comes from the configuration adopted at the interface Delta G (int )(0). These free energies were plotted as a function of the number of carbon atoms in the alkyl side chain and a linear relation was found for both of them. From these plots contributions of 0.83 and -0.58 per methylene group were determined for Delta G (0)(dist ) and Delta G (0)(int ), respectively. The positive value for the incremental free energy of distribution is attributed to the formation of a polymer micelle which is stabilized by longer alkyl side chains. On the other hand, the negative value for Delta G (0)(int ) indicates that at the interface the polymer adopts a configuration where the hydrocarbon tail is interacting with the octane molecules.

  10. 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.

  11. Determination of refractive index and concentration of iodine solutions using opals

    NASA Astrophysics Data System (ADS)

    Kępińska, Mirosława; Starczewska, Anna; Szala, Janusz

    2014-03-01

    The determination of refractive index of iodine-ethanol solutions using SiO2 opals has been presented. For the first time concentration of solution iodine in ethanol has been determined by applying a simple method of using opal and de Feijter's relation. Basing on wavelength of diffraction peaks the appropriate formula describing concentration of iodine ethanol solution has been evolved. The uncertainty of the determined concentration has been established, too. The coefficient dnc/dC = 0.0201(4) (% w/w-1) of the linear dependence between refractive index and the concentration of iodine solution has been determined. The procedure of calibration of the used opal sensor is described. The opal sensor is not distracted by the measurement and can be used repeatedly.

  12. Nitric acid uptake by sulfuric acid solutions under stratospheric conditions - Determination of Henry's Law solubility

    NASA Technical Reports Server (NTRS)

    Reihs, Christa M.; Golden, David M.; Tolbert, Margaret A.

    1990-01-01

    The uptake of nitric acid by sulfuric acid solutions representative of stratospheric particulate at low temperatures was measured to determine the solubility of nitric acid in sulfuric acid solutions as a function of H2SO4 concentration and solution temperature. Solubilities are reported for sulfuric acid solutions ranging from 58 to 87 wt pct H2SO4 over a temperature range from 188 to 240 K, showing that, in general, the solubility of nitric acid increases with decreasing sulfuric acid concentration and with decreasing temperature. The measured solubilities indicate that nitric acid in the global stratosphere will be found predominantly in the gas phase.

  13. Filterability of membrane bioreactor (MBR) sludge: impacts of polyelectrolytes and mixing with conventional activated sludge.

    PubMed

    Yigit, Nevzat O; Civelekoglu, Gokhan; Cinar, Ozer; Kitis, Mehmet

    2010-01-01

    The main objective of this work was to investigate the filterability of MBR sludge and its mixture with conventional activated sludge (CAS). In addition, the impacts of type and dose of various polyelectrolytes, filter type and sludge properties on the filterability of both MBR and Mixed sludges were determined. Specific cake resistance (SCR) measured by the Buchner funnel filtration test apparatus and the solids content of the resulting sludge cake were used to assess the dewaterability of tested sludges. The type of filter paper used in Buchner tests affected the results of filterability for MBR, CAS and Mixed sludges. SCR values and optimum polyelectrolyte doses increased with increasing MLSS concentrations in the MBR, which suggested that increase in MLSS concentrations accompanied by increases in EPS and SMP concentrations and a shift toward smaller particles caused poorer dewaterability of the MBR sludge. The significant differences observed among the filterability of CAS and MBR sludges suggested that MLSS alone is not a good predictor of sludge dewaterability. Combining CAS and MBR sludges at different proportions generally improved their dewaterability. Combining MBR sludges having typically high MLSS and EPS concentrations with CAS having much lower MLSS concentrations may be an option for full-scale treatment plants experiencing sludge dewaterability problems. Better filterability and higher cake dry solids were achieved with cationic polyelectrolytes compared to anionic and non-ionic ones for all sludge types tested.

  14. 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.

  15. 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.

  16. Similarity of salt influences on the pH of buffers, polyelectrolytes, and proteins.

    PubMed

    Voinescu, Alina E; Bauduin, Pierre; Pinna, M Cristina; Touraud, Didier; Ninham, Barry W; Kunz, Werner

    2006-05-04

    Changes in pH induced by the addition of electrolytes to buffers, polyelectrolytes (a polycarboxy polymethylene and a polyethyleneimine), and proteins (casein, whey, and lysozyme) solutions are explored systematically. The two buffer systems are triethanolamine/triethanolammonium chloride and citric acid/sodium citrate. These are chosen because of the similarity of their acid-base equilibria with those of amino acids predominant in most proteins, that is, amino acids that include carboxylate or ammonium groups in their structures. The pH of triethanolamine and of citrate buffers respectively increases and decreases when salt is added. At low electrolyte concentrations (<0.15 mol/kg), the phenomenon is well accounted for by standard electrostatic theories. pH values at higher salt concentrations are not reliable when measured with a commercial glass electrode without cross-checking by a standard hydrogen electrode. The changes of the pH values of polyelectrolyte and protein solutions with added salts turn out to be remarkably similar to the salt induced pH changes in the buffer solutions. It is even possible to qualitatively predict these changes in protein solutions simply from the primary protein structure. At least in the systems considered here, the specific ion effects on pH seem to correlate with the bulk activity coefficients of the added electrolytes, at least at moderate salt concentrations.

  17. The use of synthesized aqueous solutions for determining strontium sorption isotherms

    USGS Publications Warehouse

    Liszewski, M.J.; Bunde, R.L.; Hemming, C.; Rosentreter, J.; Welhan, J.

    1998-01-01

    The use of synthesized aqueous solutions for determining experimentally derived strontium sorption isotherms of sediment was investigated as part of a study accessing strontium chemical transport properties. Batch experimental techniques were used to determine strontium sorption isotherms using synthesized aqueous solutions designed to chemically represent water from a natural aquifer with respect to major ionic character and pH. A strontium sorption isotherm for a sediment derived using a synthesized aqueous solution was found to be most comparable to an isotherm derived using natural water when the synthesized aqueous solution contained similar concentrations of calcium and magnesium. However, it is difficult to match compositions exactly due to the effects of disequilibrium between the solution and the sediment. Strong linear relations between sorbed strontium and solution concentrations of calcium and magnesium confirm that these cations are important co-constituents in these synthesized aqueous solutions. Conversely, weak linear relations between sorbed strontium and solution concentrations of sodium and potassium indicate that these constituents do not affect sorption of strontium. The addition of silica to the synthesized aqueous solution does not appreciably affect the resulting strontium sorption isotherm.

  18. The self-assembly of copolymers with one hydrophobic and one polyelectrolyte block in aqueous media: a dissipative particle dynamics study.

    PubMed

    Lísal, Martin; Limpouchová, Zuzana; Procházka, Karel

    2016-06-28

    The reversible self-assembly of symmetrical block copolymers consisting of one hydrophobic block and one ionizable polyelectrolyte block of the same length has been studied in aqueous solutions by dissipative particle dynamics simulations. In addition to three standard dissipative particle dynamics forces (conservative soft repulsion, dissipative and stochastic forces), explicit interaction between smeared charges on ions and on ionized polymer beads described by the electrostatic potential with appropriately localized charges was taken into account. The self-assembly and properties of formed core-shell micelles were investigated as functions of the degree of ionization for systems differing in the hydrophobicity of the non-ionized polyelectrolyte block and in the compatibility of the polymer blocks. This study shows that micelles undergo massive dissociation with increasing degree of ionization. The simulation data compare well with the predictions of scaling theories for systems with soluble polyelectrolytes on a semi-quantitative level and broaden the knowledge of systems in poor solvents.

  19. Deposition of polyelectrolyte multilayer films made from chitosan and xanthan on biodegradable substrate: Effect of pH and ionic strength

    NASA Astrophysics Data System (ADS)

    Viraneva, A.; Marudova, M.; Sotirov, S.; Bodurov, I.; Pilicheva, B.; Uzunova, Y.; Exner, G.; Grancharova, Ts.; Vlaeva, I.; Yovcheva, T.

    2016-03-01

    The aim of the present work is to investigate the effect of pH and ionic strength on the deposition of chitosan/xanthan multilayers on preliminary corona charged substrates from polylactic acid. The multilayer films were formed by alternative dipping the substrate into chitosan and xanthan polyelectrolyte solutions. For this purpose 0.1% chitosan solution and 0.05% xanthan solution in acetate buffers with pH 4; 4.5 and 5 and ionic strengths 0; 0.01; 0.1 and 1 mol/l were used. The film properties were investigated by FTIR, laser refractometry, XPS and AFM methods. It was found that the binding of the polyelectrolytes to the substrate was irreversible over the time of deposition. The investigated parameters were found to depend on both pH and ionic strength of the polyelectrolyte solutions. This behaviour was attributed to the changes in charge density of the polyelectrolytes and screening effect of the counterions.

  20. Solvation and dissociation in weakly ionized polyelectrolytes.

    PubMed

    Onuki, Akira; Okamoto, Ryuichi

    2009-03-26

    We present a Ginzburg-Landau theory of inhomogeneous polyelectrolytes with a polar solvent. First, we take into account the molecular (solvation) interaction among the ions, the charged monomers, the uncharged monomers, and the solvent molecules, together with the electrostatic interaction with a composition-dependent dielectric constant. Second, we treat the degree of ionization as a fluctuating variable dependent on the local electric potential. With these two ingredients included, our results are as follows. (i) We derive a mass reaction law and a general expression for the surface tension. (ii) We calculate the structure factor of the composition fluctuations as a function of various parameters of the molecular interactions, which provides a general criterion of the formation of mesophases. (iii) We numerically examine some typical examples of interfaces and mesophase structures, which strongly depend on the molecular interaction parameters.

  1. Highly Swollen Porous Microstructures in Polyelectrolyte Multilayers

    NASA Astrophysics Data System (ADS)

    Cho, Chungyeon; Kaiser, Jeremy; Zacharia, Nicole

    2011-03-01

    We investigated the creation of porous morphologies from polyelectrolyte multilayers (PEMs) consisting of linear poly(ethylenimine) and poly(acrylic acid), and poly (allylamine hydrochloride) and poly (acrylic acid) as a function of pH and immersion time under post-base assembly treatment. The porous transition is linked to the neutralization of the polycations electrolytes as well as ionization of PAA by the exposing LbL films to high pH. This causes PEMs to undergo spinodal decomposition, creating pores and an increase in film thickness. By using reactive wet stamping technique, we were able to locally cause porosity changes under high pH conditions in the LbL films. Further investigation of the mechanical properties of patterned LbL films was done by performing nano-indentation analysis. The results showed clear difference of physical properties such as hardness and modulus between stamped and unstamped regions based on porous transition.

  2. Taste does not determine daily intake of dilute sugar solutions in mice

    PubMed Central

    Beltran, F.; Benton, L.; Cheng, S.; Gieseke, J.; Gillman, J.; Spain, H. N.

    2010-01-01

    When a rodent licks a sweet-tasting solution, taste circuits in the central nervous system that facilitate stimulus identification, motivate intake, and prepare the body for digestion are activated. Here, we asked whether taste also determines daily intake of sugar solutions in C57BL/6 mice. We tested several dilute concentrations of glucose (167, 250, and 333 mM) and fructose (167, 250, and 333 mM). In addition, we tested saccharin (38 mM), alone and in binary mixture with each of the sugar concentrations, to manipulate sweet taste intensity while holding caloric value constant. In experiment 1, we measured taste responsiveness to the sweetener solutions in two ways: chorda tympani nerve responses and short-term lick tests. For both measures, the mice exhibited the following relative magnitude of responsiveness: binary mixtures > saccharin > individual sugars. In experiment 2, we asked whether the taste measures reliably predicted daily intake of the sweetener solutions. No such relationship was observed. The glucose solutions elicited weak taste responses but high daily intakes, whereas the fructose solutions elicited weak taste responses and low daily intakes. On the other hand, the saccharin + glucose solutions elicited strong taste responses and high daily intakes, while the saccharin + fructose solutions elicited strong taste responses but low daily intakes. Overall, we found that 1) daily intake of the sweetener solutions varied independently of the magnitude of the taste responses and 2) the solutions containing glucose stimulated substantially higher daily intakes than did the solutions containing isomolar concentrations of fructose. Given prior work demonstrating greater postoral stimulation of feeding by glucose than fructose, we propose that the magnitude of postoral nutritive stimulation plays a more important role than does taste in determining daily intake of dilute sugar solutions. PMID:20702804

  3. Improved solution accuracy for Landsat-4 (TDRSS-user) orbit determination

    NASA Technical Reports Server (NTRS)

    Oza, D. H.; Niklewski, D. J.; Doll, C. E.; Mistretta, G. D.; Hart, R. C.

    1994-01-01

    This paper presents the results of a study to compare the orbit determination accuracy for a Tracking and Data Relay Satellite System (TDRSS) user spacecraft, Landsat-4, obtained using a Prototype Filter Smoother (PFS), with the accuracy of an established batch-least-squares system, the Goddard Trajectory Determination System (GTDS). The results of Landsat-4 orbit determination will provide useful experience for the Earth Observing System (EOS) series of satellites. The Landsat-4 ephemerides were estimated for the January 17-23, 1991, timeframe, during which intensive TDRSS tracking data for Landsat-4 were available. Independent assessments were made of the consistencies (overlap comparisons for the batch case and convariances for the sequential case) of solutions produced by the batch and sequential methods. The filtered and smoothed PFS orbit solutions were compared with the definitive GTDS orbit solutions for Landsat-4; the solution differences were generally less than 15 meters.

  4. Self-organization of grafted polyelectrolyte layers via the coupling of chemical equilibrium and physical interactions.

    PubMed

    Tagliazucchi, Mario; de la Cruz, Mónica Olvera; Szleifer, Igal

    2010-03-23

    The competition between chemical equilibrium, for example protonation, and physical interactions determines the molecular organization and functionality of biological and synthetic systems. Charge regulation by displacement of acid-base equilibrium induced by changes in the local environment provides a feedback mechanism that controls the balance between electrostatic, van der Waals, steric interactions and molecular organization. Which strategies do responsive systems follow to globally optimize chemical equilibrium and physical interactions? We address this question by theoretically studying model layers of end-grafted polyacids. These layers spontaneously form self-assembled aggregates, presenting domains of controlled local pH and whose morphologies can be manipulated by the composition of the solution in contact with the film. Charge regulation stabilizes micellar domains over a wide range of pH by reducing the local charge in the aggregate at the cost of chemical free energy and gaining in hydrophobic interactions. This balance determines the boundaries between different aggregate morphologies. We show that a qualitatively new form of organization arises from the coupling between physical interactions and protonation equilibrium. This optimization strategy presents itself with polyelectrolytes coexisting in two different and well-defined protonation states. Our results underline the need of considering the coupling between chemical equilibrium and physical interactions due to their highly nonadditive behavior. The predictions provide guidelines for the creation of responsive polymer layers presenting self-organized patterns with functional properties and they give insights for the understanding of competing interactions in highly inhomogeneous and constrained environments such as those relevant in nanotechnology and those responsible for biological cells function.

  5. 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.

  6. Formation of hydrate films on the surface of calcium silicate and aluminate in the presence of polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Kurochkina, G. N.

    2017-08-01

    To elucidate the mechanism of moistening and overmoistening of soils and mineral soil components capable of chemical hydration, the sorption of water vapor has been studied in combination with synchronous conductometric measurements. Effect of organic polyelectrolyte molecules on the hydration kinetics and the formation of hydrate films on their surface has been revealed for dehydrated calcium silicate and aluminate simulating minor soil components. The plotting of sorption-desorption curves has shown that hydrate-polymer films formed by aliphatic or aromatic polyelectrolytes with different functional groups (-COOH,-OH,-NH2,-CONH, etc.) significantly vary in dispersion and structure. The changes in dispersion during hydration are frequently not correlated with the amount of resulting hydrates, the content of which is controlled by the crystallochemical features of sorbents, the structure and activity of the polymer functional groups, and the conditions of sorption kinetic studies. It has been shown that the formation of low-permeable surface organomineral layers is typical for aliphatic polyelectrolytes, while more permeable layers determining the water-physical and structure-forming properties of soils are typical for aromatic polyelectrolytes.

  7. Dynamics of Polyelectrolyte Chains within Layer-by-Layer Assemblies

    NASA Astrophysics Data System (ADS)

    Sukhishvili, Svetlana

    2015-03-01

    Layer-by-layer (LbL) assembly of charged polymers/nanoparticles finds diverse industrial applications ranging from NIR reflective heat-reduction to multi-stage drug delivery. Internal layering of film components lies at the heart of their performance. I will discuss experiments aimed to unravel relationships between center-of-mass diffusion of polyelectrolyte (PE) chains within LbL films, PE molecular characteristics, environmental conditions (salt concentration), and film structure. Upon film annealing in salt solutions, chain diffusion is highly anisotropic (as probed by fluorescence recovery after photobleaching and neutron reflectometry), and is strongly coupled with film structure. For layered LbL films, PE diffusion in the direction parallel to the substrate reveals quasi-Rouse scaling with molecular weight (D ~ M-1) , even for long chains, suggesting that chains disentangle upon adsorption. Finally, I will discuss quantitative aspects of salt-induced PE chain diffusion in directions parallel and perpendicular to the substrate, and their consequences for persistent layering within LbL films. This work was supported by the National Science Foundation under Award DMR-0906474.

  8. Electric field induced morphological transitions in polyelectrolyte multilayers.

    PubMed

    Cho, Chungyeon; Jeon, Ju-Won; Lutkenhaus, Jodie; Zacharia, Nicole S

    2013-06-12

    In this work, the morphological transitions in weak polyelectrolyte (PE) multilayers (PEMs) assembled from linear poly(ethylene imine) (LPEI) and poly(acrylic acid) (PAA) upon application of an electric field were studied. Exposure to an electric field results in the creation of a porous structure, which can be ascribed to local changes in pH from the hydrolysis of water and subsequent structural rearrangements of the weak PE constituents. Depending on the duration of application of the field, the porous transition gradually develops into a range of structures and pore sizes. It was discovered that the morphological transition of the LbL films starts at the multilayer-electrode interface and propagates through the film. First an asymmetrical structure forms, consisting of microscaled pores near the electrode and nanoscaled pores near the surface in contact with the electrolyte solution. At longer application of the field the porous structures become microscaled throughout. The results revealed in this study not only demonstrate experimental feasibility for controlling variation in pore size and porosity of multilayer films but also deepens the understanding of the mechanism of the porous transition. In addition, electrical potential is used to release small molecules from the PEMs.

  9. Lipid monolayers and adsorbed polyelectrolytes with different degrees of polymerization.

    PubMed

    Ortmann, Thomas; Ahrens, Heiko; Lawrenz, Frank; Gröning, Andreas; Nestler, Peter; Günther, Jens-Uwe; Helm, Christiane A

    2014-06-17

    Polystyrene sulfonate (PSS) of different molecular weight M(w) is adsorbed to oppositely charged DODAB monolayers from dilute solutions (0.01 mmol/L). PSS adsorbs flatly in a lamellar manner, as is shown by X-ray reflectivity and grazing incidence diffraction (exception: PSS with M(w) below 7 kDa adsorbs flatly disordered to the liquid expanded phase). The surface coverage and the separation of the PSS chains are independent of PSS M(w). On monolayer compression, the surface charge density increases by a factor of 2, and the separation of the PSS chains decreases by the same factor. Isotherms show that on increase of PSS M(w) the transition pressure of the LE/LC (liquid expanded/liquid condensed) phase transition decreases. When the contour length exceeds the persistence length (21 nm), the transition pressure is low and constant. For low-M(w) PSS (<7 kDa) the LE/LC transition of the lipids and the disordered/ordered transition of adsorbed PSS occur simultaneously, leading to a maximum in the contour length dependence of the transition enthalpy. These findings show that lipid monolayers at the air/water interface are a suitable model substrate with adjustable surface charge density to study the equilibrium conformation of adsorbed polyelectrolytes as well as their interactions with a model membrane.

  10. 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.

  11. Complex formation between polyelectrolytes and oppositely charged oligoelectrolytes

    NASA Astrophysics Data System (ADS)

    Zhou, Jiajia; Barz, Matthias; Schmid, Friederike

    2016-04-01

    We study the complex formation between one long polyanion chain and many short oligocation chains by computer simulations. We employ a coarse-grained bead-spring model for the polyelectrolyte chains and model explicitly the small salt ions. We systematically vary the concentration and the length of the oligocation and examine how the oligocations affects the chain conformation, the static structure factor, the radial and axial distribution of various charged species, and the number of bound ions in the complex. At low oligocation concentration, the polyanion has an extended structure. Upon increasing the oligocation concentration, the polyanion chain collapses and forms a compact globule, but the complex still carries a net negative charge. Once the total charge of the oligocations is equal to that of the polyanion, the collapse stops and is replaced by a slow expansion. In this regime, the net charge on the complexes is positive or neutral, depending on the microion concentration in solution. The expansion can be explained by the reduction of the oligocation bridging. We find that the behavior and the structure of the complex are largely independent of the length of oligocations, and very similar to that observed when replacing the oligocations by multivalent salt cations, and conclude that the main driving force keeping the complex together is the release of monovalent counterions and coions. We speculate on the implications of this finding for the problem of controlled oligolyte release and oligolyte substitution.

  12. Engineering Polyelectrolyte Capsules with Independently Controlled Size and Shape.

    PubMed

    Zan, Xingjie; Garapaty, Anusha; Champion, Julie A

    2015-07-14

    Polyelectrolyte capsules (PECs) are a promising delivery system that has the ability to carry a large payload of a variety of cargoes. Controlling PEC properties is critical to understanding and tuning their cellular uptake efficiency, kinetics, and mechanism as well as their biodistribution in the body. The lack of a method to independently engineer PEC size, shape, and chemistry impedes both basic understanding of how physicochemical parameters affect PEC behavior in drug delivery and other applications, and the ability to optimize parameters for best function. Here, we report the successful fabrication of PECs having constant surface chemistry with independently controlled size and shape by combining soft organic templates created by the particle stretching method and a modified layer-by-layer (LBL) deposition process. Changing the template dispersion solution during LBL deposition from water to ethanol allowed us to overcome previous issues with organic templates, such as aggregation and template removal. These results will contribute not only to the basic study of the role of capsule shape and size on its function but also to the optimization of capsule properties for drug or imaging carriers, sensors, reactors, and other applications.

  13. Energy dispersive X-Ray fluorescence determination of thorium in phosphoric acid solutions

    NASA Astrophysics Data System (ADS)

    Mirashi, N. N.; Dhara, Sangita; Kumar, S. Sanjay; Chaudhury, Satyajeet; Misra, N. L.; Aggarwal, S. K.

    2010-07-01

    Energy dispersive X-ray fluorescence studies on determination of thorium (in the range of 7 to 137 mg/mL) in phosphoric acid solutions obtained by dissolution of thoria in autoclave were made. Fixed amounts of Y internal standard solutions, after dilution with equal amount of phosphoric acid, were added to the calibration as well as sample solutions. Solution aliquots of approximately 2-5 µL were deposited on thick absorbent sheets to absorb the solutions and the sheets were presented for energy dispersive X-ray fluorescence measurements. A calibration plot was made between intensity ratios (Th Lα/Y Kα) against respective amounts of thorium in the calibration solutions. Thorium amounts in phosphoric acid samples were determined using their energy dispersive X-ray fluorescence spectra and the above calibration plot. The energy dispersive X-ray fluorescence results, thus obtained, were compared with the corresponding gamma ray spectrometry results and were found to be within average deviation of 2.6% from the respective gamma ray spectrometry values. The average precision obtained in energy dispersive X-ray fluorescence determinations was found to be 4% (1 σ). The energy dispersive X-ray fluorescence method has an advantage over gamma ray spectrometry for thorium determination as the amount of sample required and measurement time is far less compared to that required in gamma ray spectrometry.

  14. 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.

  15. 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

  16. Determination of pKa values of organic bases in aqueous acetonitrile solutions using capillary electrophoresis.

    PubMed

    Buckenmaier, Stephan M C; McCalley, David V; Euerby, Melvin R

    2003-07-04

    Capillary electrophoresis (CE) was used for the determination of ionisation constants (pKa) of a variety of organic bases in aqueous acetonitrile solutions over the range 0-60% (v/v) acetonitrile. These bases are used as test compounds in HPLC column evaluation, thus knowledge of their pKa in hydro-organic solutions is useful. The base pKa decreased with acetonitrile concentration and significant shifts from the aqueous pKa (up to -0.8) were found using 60% acetonitrile. The CE application was confirmed to be very suitable for fast and accurate pKa measurement in aqueous organic solutions.

  17. Mineralization of monodispersed CdS nanoparticles on polyelectrolyte superstructure forming an electroluminescent "necklace-of-beads".

    PubMed

    Maheshwari, Vivek; Saraf, Ravi F

    2006-10-10

    We report a nonmicellar method to synthesize monodisperse semiconducting nanoparticles templated on polymer chains dissolved in solution at high yield. The monodispersity is achieved due to the beaded necklace morphology of the polyelectrolyte chains in solution where the beads are nanometer-scale nodules in the polymer chain. The resultant structure is a nanoparticles studded necklace where the particles are imbedded in the beads. Multiple cycles of synthesis on the polymer template yield nanoparticles of identical size, resulting in a nanocomposite with high particle fraction. The resultant nanocomposite has beaded-fibrilar morphology with imbedded nanoparticles and can be solution-casted to make electroluminescent thin film device.

  18. Novel silver nanoparticle-enhanced fluorometric determination of trace tetracyclines in aqueous solutions.

    PubMed

    Wang, Ping; Wu, Tun-Hua; Zhang, Yong

    2016-01-01

    Metal-enhanced fluorescence (MEF) has exhibited promise for applications in fluorometric assays. The effects of silver nanoparticles (AgNP) on the fluorescence behaviours of tetracycline hydrochloride (TCH) and chlortetracycline hydrochloride (CTC) in aqueous solutions were investigated. The experimental results demonstrated that the fluorescence intensities of each tetracycline in water solutions were greatly enhanced by AgNP through the MEF effect. In addition, a novel silver nanoparticle-enhanced fluorometric method was established for the direct determination of TCH and CTC in aqueous solutions. Under optimum experimental conditions, the linear dynamic ranges for the determination of TCH and CTC in aqueous solutions varied from 0.10 to 6.0 mg L(-1) and 0.050 to 3.0 mg L(-1) with detection limits of 0.63 µg L(-1) and 0.19 µg L(-1), respectively, and with the relative standard deviation of less than 1.9% (n=9). The experimental recovery results for the determination of TCH and CTC in aqueous solutions ranged from 93-106% and 95-104%, respectively. Compared with the established method without the addition of AgNP, the limits of quantitation of the silver nanoparticle-enhanced fluorometric method were approximately 5-fold lower for TCH and 3-fold lower for CTC. Moreover, the newly established silver nanoparticle-enhanced fluorometric method was successfully applied to the direct determination of TCH and CTC in pharmaceutical preparations.

  19. Principal factors that determine the extension of detection range in molecular beacon aptamer/conjugated polyelectrolyte bioassays† †Electronic supplementary information (ESI) available: Additional UV-vis, PL and CV data, equilibrium constant calculation for MBAs conformational change, and CD data. See DOI: 10.1039/c4sc03258f Click here for additional data file.

    PubMed Central

    Jeong, Ji-Eun; Kim, Boram; Woo, Shinjae; Hwang, Sungu

    2015-01-01

    A strategy to extend the detection range of weakly-binding targets is reported that takes advantage of fluorescence resonance energy transfer (FRET)-based bioassays based on molecular beacon aptamers (MBAs) and cationic conjugated polyelectrolytes (CPEs). In comparison to other aptamer-target pairs, the aptamer-based adenosine triphosphate (ATP) detection assays are limited by the relatively weak binding between the two partners. In response, a series of MBAs were designed that have different stem stabilities while keeping the constant ATP-specific aptamer sequence in the loop part. The MBAs are labeled with a fluorophore and a quencher at both termini. In the absence of ATP, the hairpin MBAs can be opened by CPEs via a combination of electrostatic and hydrophobic interactions, showing a FRET-sensitized fluorophore signal. In the presence of ATP, the aptamer forms a G-quadruplex and the FRET signal decreases due to tighter contact between the fluorophore and quencher in the ATP/MBA/CPE triplex structure. The FRET-sensitized signal is inversely proportional to [ATP]. The extension of the detection range is determined by the competition between opening of the ATP/MBA G-quadruplex by CPEs and the composite influence by ATP/aptamer binding and the stem interactions. With increasing stem stability, the weak binding of ATP and its aptamer is successfully compensated to show the resistance to disruption by CPEs, resulting in a substantially broadened detection range (from millimolar up to nanomolar concentrations) and a remarkably improved limit of detection. From a general perspective, this strategy has the potential to be extended to other chemical- and biological-assays with low target binding affinity. PMID:28706644

  20. Determination of refraction nonlinear index, for effect thermal, of solutions with nanoparticles of gold

    NASA Astrophysics Data System (ADS)

    Olivares-Vargas, A.; Trejo-Durán, M.; Alvarado-Méndez, E.; Cornejo-Monroy, D.; Mata-Chávez, R. I.; Estudillo-Ayala, J. M.; Castaño-Meneses, V.

    2013-09-01

    Research of nonlinear optical properties of materials for manufacturing opto-electronic devices, had a great growth in the last years. The solutions with nanoparticle metals present nonlinear optical properties. In this work we present the results of characterizing, analyzing and determining the magnitude and sign of the nonlinear refractive index, using the z-scan technique in solutions with nanoparticles of gold, lipoic acid and sodium chloride. We used a continuous Argon laser at 514 nm with variable power, an 18 cms lens, and a chopper. We determined the nonlinear refractive index in the order of 10-9. These materials have potential applications mainly as optical limiters.

  1. 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.

  2. Size, flexibility, and scattering functions of semiflexible polyelectrolytes with excluded volume effects: monte carlo simulations and neutron scattering experiments

    PubMed

    Cannavacciuolo; Sommer; Pedersen; Schurtenberger

    2000-10-01

    We present a systematic Monte Carlo study of the scattering function S(q) of semiflexible polyelectrolytes at infinite dilution, in solutions with different concentrations of added salt. In the spirit of a theoretical description of polyelectrolytes in terms of the equivalent parameters, namely, persistence length and excluded volume interactions, we used a modified wormlike chain model, in which the monomers are represented by charged hard spheres placed at distance a. The electrostatic interactions are approximated by a Debye-Huckel potential. We show that the scattering function is quantitatively described by that of uncharged wormlike chains with excluded volume effects provided that an electrostatic contribution is added to the persistence length. In addition we have studied the expansion of the radius of gyration and of the end-to-end distance. The results are in agreement with the picture outlined in the Odijk-Skolnick-Fixman theory, in which the behavior of charged polymers is described only in terms of increasing local rigidity and excluded volume effects. Moreover, the Monte Carlo data are found to be in very good agreement with experimental scattering measurements with equilibrium polyelectrolytes, i.e., giant wormlike micelles formed in mixtures of nonionic and ionic surfactants in dilute aqueous solution, with added salt.

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

    PubMed

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

    2016-12-01

    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.

  4. 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.

  5. Polyelectrolytes: Wastewater and sewage treatment. (Latest citations from the Selected Water Resources Abstracts database). Published Search

    SciTech Connect

    Not Available

    1993-02-01

    The bibliography contains citations concerning polyelectrolytes in wastewater and water treatment. Topics include flocculation, coagulation, separation techniques, pollutant identification, water pollution sources, and sludge dehydration. Hospital wastewater processing, methods of synthesizing polyelectrolyte complexes, and performance evaluations of polyelectrolytes are also discussed. (Contains 250 citations and includes a subject term index and title list.)

  6. Polyelectrolytes: Wastewater and sewage treatment. (Latest citations from the Selected Water Resources Abstracts database). Published Search

    SciTech Connect

    Not Available

    1994-04-01

    The bibliography contains citations concerning polyelectrolytes in wastewater and water treatment. Topics include flocculation, coagulation, separation techniques, pollutant identification, water pollution sources, and sludge dehydration. Hospital wastewater processing, methods of synthesizing polyelectrolyte complexes, and performance evaluations of polyelectrolytes are also discussed. (Contains 250 citations and includes a subject term index and title list.)

  7. Effect of polyelectrolytes on (de)stability of liquid foam films.

    PubMed

    Fauser, Heiko; von Klitzing, Regine

    2014-09-28

    The review addresses the influence of polyelectrolytes on the stabilisation of free-standing liquid foam films, which affects the stability of a whole macroscopic foam. Both the composition of the film surface and the stratification of the film bulk drives the drainage and the interfacial forces within a foam film. Beside synthetic polyelectrolytes also natural polyelectrolytes like cellulose, proteins and DNA are considered.

  8. 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

  9. Polyelectrolyte/surfactant films spread from neutral aggregates.

    PubMed

    Campbell, Richard A; Tummino, Andrea; Noskov, Boris A; Varga, Imre

    2016-06-28

    We describe a new methodology to prepare loaded polyelectrolyte/surfactant films at the air/water interface by exploiting Marangoni spreading resulting from the dynamic dissociation of hydrophobic neutral aggregates dispensed from an aqueous dispersion. The system studied is mixtures of poly(sodium styrene sulfonate) with dodecyl trimethylammonium bromide. Our approach results in the interfacial confinement of more than one third of the macromolecules in the system even though they are not even surface-active without the surfactant. The interfacial stoichiometry of the films was resolved during measurements of surface pressure isotherms in situ for the first time using a new implementation of neutron reflectometry. The interfacial coverage is determined by the minimum surface area reached when the films are compressed beyond a single complete surface layer. The films exhibit linear ripples on a length scale of hundreds of micrometers during the squeezing out of material, after which they behave as perfectly insoluble membranes with consistent stoichiometric charge binding. We discuss our findings in terms of scope for the preparation of loaded membranes for encapsulation applications and in deposition-based technologies.

  10. Synthesis and Characterization of Polyelectrolyte Grafted Charged Colloidal Particles

    NASA Astrophysics Data System (ADS)

    Mohanty, Priti Sundar; Harada, Tamotsu; Matsumoto, Kozo; Matsuoka, Hideki

    2006-05-01

    Novel polyelectrolyte grafted charged colloidal particles have been synthesized via emulsion polymerization method using block copolymer as an emulsifier and have been characterized by determining the surface charge number (Z), chain density (σ) using conductometric titration, the size distribution, hydrodynamic (Rh) radius by dynamic light scattering and the core radius (Rc) by atomic force microscopy. The structural ordering and dynamics have been investigated in a very dilute concentration and the effect of salt concentration (Cs) on hydrodynamic radius have also been studied using dynamic light scattering. The conductivity titration curve was found to show two equivalence points and the potentiometric titration curves are found to sensitive only after a critical salt concentrations. The corresponding measured hydrodynamic radius is also found to decrease after a critical salt concentration. At high salt concentration, the hydrodynamic radius shows a close agreement with that of the core radius measured by the atomic force microscope. These experimental results are in agreement with the recent theoretical prediction and experimental observation that most of the counterions are confined inside the brush region which led to stretching of the chains at low salt concentration.

  11. Structure and dynamics of polyelectrolyte surfactant mixtures under conditions of surfactant excess

    NASA Astrophysics Data System (ADS)

    Hoffmann, Ingo; Simon, Miriam; Farago, Bela; Schweins, Ralf; Falus, Peter; Holderer, Olaf; Gradzielski, Michael

    2016-09-01

    Oppositely charged polyelectrolyte (PE) surfactant mixtures can self-assemble into a large variety of mesoscopic structures, so-called polyelectrolyte surfactant complexes (PESCs). These structures directly affect the macroscopic behavior of such solutions. In this study, we investigated mixtures of the cationically charged PE JR 400 and the anionic surfactant SDS with the help of different neutron scattering and fluorescence methods. While an excess of PE charges in semi-dilute solutions causes an increase of viscosity, it has been observed that an excess of surfactant charges reduces the viscosity while precipitation is observed at charge equilibrium. The increase in viscosity had been investigated before and was attributed to the formation of cross links between PE chains. In this publication we focus our attention on the reduction of viscosity which is observed with an excess of surfactant charges. It is found that the PE chains form relatively large and densely packed clusters near the phase boundary on the surfactant rich side, thereby occupying less space and reducing the viscosity. For even higher surfactant concentrations, individual surfactant decorated PE chains are observed and their viscosity is found to be similar to that of the pure PE.

  12. Removal of textile dyes and metallic ions using polyelectrolytes and macroelectrolytes containing sulfonic acid groups.

    PubMed

    Caldera Villalobos, M; Peláez Cid, A A; Herrera González, Ana M

    2016-07-15

    This work reports the removal of textile dyes and metallic ions by means of adsorption and coagulation-flocculation using two polyelectrolytes and two macroelectrolytes containing sulfonic acid groups. The adsorption of textile dyes was studied in aqueous solutions containing cationic dyes and in wastewater containing a vat dye. Also, removal of vat and naphthol dyes was studied using the process of coagulation-flocculation. The results show these materials possess elevated adsorption capacity, and they accomplished removal rates above 97% in aqueous solutions. The removal of the vat dye improved the quality of the wastewater notably, and an uncolored effluent was obtained at the end of the treatment. The treatment using adsorption decreased the values for coloration, conductivity, suspended solids, and pH. The removal of vat and naphthol dyes by means of coagulation-flocculation was studied as well, and removal rates of 90% were obtained. The polyelectrolytes and macroelectrolytes also proved effective in the adsorption of metallic ions in wastewater. The treatment using adsorption accomplished high removal rates of metallic ions, and it showed greater selectivity towards Cu(2+), Fe(3+) and Pb(2+). A decrease in the content of solids as well as the values for COD and conductivity was observed in the wastewater as well. The analyses of FT-IR indicated that cationic dyes and metallic ions were chemisorbed by means of ionic exchange.

  13. Amplified fluorescence sensing of protease activity with conjugated polyelectrolytes

    PubMed Central

    Pinto, Mauricio R.; Schanze, Kirk S.

    2004-01-01

    Fluorescent conjugated polyelectrolytes with pendant ionic sulfonate and carboxylate groups are used to sense protease activity. Inclusion of the fluorescent conjugated polyelectrolyte into the assay scheme leads to amplification of the sensory response. The sensing mechanism relies on an electrostatic interaction between the conjugated polyelectrolyte and a peptide substrate that is labeled with a fluorescence quencher. Enzyme activity and hydrolysis kinetics are measured in real time by using fluorescence spectroscopy. Two approaches are presented. In the first approach, a fluorescence turn-on sensor was developed that is based on the use of p-nitroanilide-labeled peptide substrates. In this system enzyme-catalyzed peptide hydrolysis is signaled by an increase in the fluorescence from the conjugated polyelectrolyte. The turn-on system was used to sense peptidase and thrombin activity when the concentrations of the enzyme and substrate are in the nanomolar regime. Kinetic parameters were recovered from real-time assays. In the second approach, a fluorescence turn-off sensor was developed that relies on a peptide-derivatized rhodamine substrate. In the turn-off system enzyme-catalyzed peptide hydrolysis is signaled by a decrease in the fluorescence intensity of the conjugated polyelectrolyte. PMID:15136727

  14. Amplified fluorescence sensing of protease activity with conjugated polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Pinto, Mauricio R.; Schanze, Kirk S.

    2004-05-01

    Fluorescent conjugated polyelectrolytes with pendant ionic sulfonate and carboxylate groups are used to sense protease activity. Inclusion of the fluorescent conjugated polyelectrolyte into the assay scheme leads to amplification of the sensory response. The sensing mechanism relies on an electrostatic interaction between the conjugated polyelectrolyte and a peptide substrate that is labeled with a fluorescence quencher. Enzyme activity and hydrolysis kinetics are measured in real time by using fluorescence spectroscopy. Two approaches are presented. In the first approach, a fluorescence turn-on sensor was developed that is based on the use of p-nitroanilide-labeled peptide substrates. In this system enzyme-catalyzed peptide hydrolysis is signaled by an increase in the fluorescence from the conjugated polyelectrolyte. The turn-on system was used to sense peptidase and thrombin activity when the concentrations of the enzyme and substrate are in the nanomolar regime. Kinetic parameters were recovered from real-time assays. In the second approach, a fluorescence turn-off sensor was developed that relies on a peptide-derivatized rhodamine substrate. In the turn-off system enzyme-catalyzed peptide hydrolysis is signaled by a decrease in the fluorescence intensity of the conjugated polyelectrolyte.

  15. 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.

  16. Protein adsorption in polyelectrolyte brush type cation-exchangers.

    PubMed

    Khalaf, Rushd; Coquebert de Neuville, Bertrand; Morbidelli, Massimo

    2016-11-04

    Ion exchange chromatography materials functionalized with polyelectrolyte brushes (PEB) are becoming an integral part of many protein purification steps. Adsorption onto these materials is different than that onto traditional materials, due to the 3D partitioning of proteins into the polyelectrolyte brushes. Despite this mechanistic difference, many works have described the chromatographic behavior of proteins on polyelectrolyte brush type ion exchangers with much of the same methods as used for traditional materials. In this work, unconventional chromatographic behavior on polyelectrolyte brush type materials is observed for several proteins: the peaks shapes reveal first anti-Langmuirian and then Langmuirian types of interactions, with increasing injection volumes. An experimental and model based description of these materials is carried out in order to explain this behavior. The reason for this behavior is shown to be the 3D partitioning of proteins into the polyelectrolyte brushes: proteins that fully and readily utilize the 3D structure of the PEB phase during adsorption show this behavior, whereas those that do not show traditional ion exchange behavior.

  17. Semi-quantitative determination of cationic surfactants in aqueous solutions using gold nanoparticles as reporter probes.

    PubMed

    Kuong, Chi-Lap; Chen, Wei-Yu; Chen, Yu-Chie

    2007-03-01

    Concentrations of cationic surfactants in aqueous solutions have been estimated on the basis of changes in the color of gold nanoparticles, used as reporter probes. We have shown that the colors of gold nanoparticles with anionic protective groups on their surfaces shift from red to indigo/purple and then back to red in a range of cationic surfactant solutions in which concentrations vary from very low to above the theoretical CMCs. The color changes occur near the theoretical CMCs, presumably because the presence of surfactant micelles in the solution prevents the gold nanoparticles from aggregating. We have used gold nanoparticles as reporter probes to determine the concentrations of cationic surfactants in products such as hair conditioners, which often contain large amounts of alkyltrimethylammonium halides. Although this approach can only provide an estimate, it can be performed simply by addition of a given amount of gold nanoparticles to a series of diluted solutions, without the need for instruments or labor-intensive procedures.

  18. The enzymatic determination of bicarbonate and CO2 in reagents and buffer solutions.

    PubMed

    Hall, N P; Cornelius, M J; Keys, A J

    1983-07-01

    A method for the determination of bicarbonate in buffer solutions between pH 7.5 and 8.75 and in stock solutions of NaHCO3 is described. The HCO-3 is reacted with phosphoenolpyruvate (PEP) in the presence of PEP carboxylase (EC 4.1.1.31) and the oxaloacetate formed reduced to malate by NADH in the reaction catalyzed by malate dehydrogenase (EC 1.1.1.37). The extent of oxidation of NADH is measured spectrophotometrically. Experiments using standard solutions show that 1 mol of NADH is oxidized per mol of HCO-3 added. The method was used to establish the precautions needed to prepare buffer solutions containing less than 1% of the bicarbonate which would be present in the same buffers in equilibrium with air.

  19. Investigation of equilibria in solution. Determination of equilibrium constants with the HYPERQUAD suite of programs.

    PubMed

    Gans, P; Sabatini, A; Vacca, A

    1996-10-01

    A new suite of 10 programs concerned with equilibrium constants and solution equilibria is described. The suite includes data preparation programs, pretreatment programs, equilibrium constant refinement and post-run analysis. Data preparation is facilitated by a customized data editor. The pretreatment programs include manual trial and error data fitting, speciation diagrams, end-point determination, absorbance error determination, spectral baseline corrections, factor analysis and determination of molar absorbance spectra. Equilibrium constants can be determined from potentiometric data and/or spectrophotometric data. A new data structure is also described in which information on the model and on experimental measurements are kept in separate files.

  20. Selective depositions on polyelectrolyte multilayers: self-assembled monolayers of m-dPEG acid as molecular template.

    PubMed

    Kidambi, Srivatsan; Chan, Christina; Lee, Ilsoon

    2004-04-14

    This paper describes the fabrication of self-assembled monolayer (SAM) patterns of m-d-poly(ethylene glycol) (m-dPEG) acid molecules onto polyelectrolyte multilayers (PEMs). The patterned SAMs on PEMs were created by ionic interactions using microcontact printing (microCP) technique. The created m-dPEG acid monolayer patterns on PEMs act as resistive templates, and thus further depositions of consecutive poly(anion)/poly(cation) pairs of charged particles result in the formation of three-dimensional (3-D) patterned PEM films or selective particle depositions atop the original multilayer thin films. In this study, we illustrate nonlithographic methods of patterning and controlling 3-D PEM architectures and selective particle depositions. We investigated the effect of variables--the choice of solvent, concentration, pH, substrate pretreatment, and stamp contact times--on microcontact printing of m-dPEG acid molecules onto PEM films to determine the optimal conditions for these parameters to achieve efficient transfer of m-dPEG acid patterns onto PEMs. Among the variables, the pH of the m-dPEG acid ink solution played the most important role in the transfer efficiency of the patterns onto the multilayer films. The patterned films were characterized by optical microscopy and atomic force microscopy (AFM).

  1. Spectrofluorometric trace determination of cerium(III) in sodium hexametaphosphate solutions.

    PubMed

    Akseli, A; Rakicioğlu, Y

    1996-02-01

    The use of sodium hexametaphosphate in the spectrofluorometric determination of trace amounts of cerium(III) ions is described. Sodium hexametaphosphate acts as a specific reagent for enhancing the fluorescence intensity of cerium(III) in aqueous solutions. The apparent excitation and fluorescence wavelength used are 304 and 344 nm, respectively. Maximum fluorescence intensity is obtained by irradiating Ce(III) dissolved in 5.346 g/l sodium hexametaphosphate solution at room temperature. The fluorescence varies linearly with the concentration of cerium(III) in the range of 0.001-60 microg/ml. The coefficient of variation for 45 microg/ml Ce(III) in 5.346 g/l sodium hexametaphosphate solution is 1. The quenching effects of other lanthanides and some inorganic anions are given. This technique permits a direct and rapid determination of cerium(III) in rare earth mixtures and cerium concentrates.

  2. An analytical solution for determination of small contact angles from sessile drops of arbitrary size.

    PubMed

    Allen, Jeffrey S

    2003-05-15

    An analytical solution to the capillary equation of Young and Laplace is derived that allows determination of the static contact angle based on the volume of a sessile drop and the wetted area of the substrate. This solution does not require numerical integration to determine the drop profile and accounts for surface deformation due to gravitational effects. Calculation of the static contact angle by this method is remarkably simple and accurate when the contact angle is less than 30 degrees. A natural scaling arises in the solution, which provides indication of when a drop is small enough so as to neglect gravitational influences on the surface shape which, for small contact angles, is generally less than 1 microl. The technique described has the simplicity of the spherical cap approximation but remains accurate for any size of sessile drop.

  3. Surfactant mediated polyelectrolyte self-assembly

    SciTech Connect

    Goswami, Monojoy; Borreguero Calvo, Jose M.; Pincus, Phillip A.; Sumpter, Bobby G.

    2015-11-25

    Self-assembly and dynamics of polyelectrolyte (PE) surfactant complex (PES) is investigated using molecular dynamics simulations. The complexation is systematically studied for five different PE backbone charge densities. At a fixed surfactant concentration the PES complexation exhibits pearl-necklace to agglomerated double spherical structures with a PE chain decorating the surfactant micelles. The counterions do not condense on the complex, but are released in the medium with a random distribution. The relaxation dynamics for three different length scales, polymer chain, segmental and monomer, show distinct features of the charge and neutral species; the counterions are fastest followed by the PE chain and surfactants. The surfactant heads and tails have the slowest relaxation due to their restricted movement inside the agglomerated structure. At the shortest length scale, all the charge and neutral species show similar relaxation dynamics confirming Rouse behavior at monomer length scales. Overall, the present study highlights the structure-property relationship for polymer-surfactant complexation. These results will help improve the understanding of PES complex and should aid in the design of better materials for future applications.

  4. Immobilization of enzyme on chiral polyelectrolyte surface.

    PubMed

    Ding, Chao; Sun, Hanjun; Ren, Jinsong; Qu, Xiaogang

    2017-02-01

    Chiral D- and L-N-acryloyl aspartic acid (NAsp) polyelectrolyte (PE) surfaces with similar chemical compositions and physical properties but opposite chirality are designed for enzyme immobilization. Enzymes immobilized onto the chiral PE surfaces present high chiral preference, namely L-NAsp PE surface can keep most of the catalytic activity of the immobilized enzymes, however, for enzymes immobilized on D-NAsp PE surface a large decrease in catalytic activity occurred which was 11 times lower compared with L-NAsp PE surface. This phenomenon of chiral effect on enzymes immobilization can be explained by attenuated total reflectance (ATR) and circular dichroism (CD) results. The results exhibited that L-NAsp PE surface could preserve most of the secondary structures of immobilized enzymes while on D-NAsp PE surface with a large conformation alteration. These chiral surface induced differences after enzyme immobilization can be further used for logic operation. These results imply a novel strategy for the design of new enzymes immobilization materials based on the chiral effect and expand the applications of enzymes in biochips, chemical transformations and chiral biodevices.

  5. Surfactant mediated polyelectrolyte self-assembly

    DOE PAGES

    Goswami, Monojoy; Borreguero Calvo, Jose M.; Pincus, Phillip A.; ...

    2015-11-25

    Self-assembly and dynamics of polyelectrolyte (PE) surfactant complex (PES) is investigated using molecular dynamics simulations. The complexation is systematically studied for five different PE backbone charge densities. At a fixed surfactant concentration the PES complexation exhibits pearl-necklace to agglomerated double spherical structures with a PE chain decorating the surfactant micelles. The counterions do not condense on the complex, but are released in the medium with a random distribution. The relaxation dynamics for three different length scales, polymer chain, segmental and monomer, show distinct features of the charge and neutral species; the counterions are fastest followed by the PE chain andmore » surfactants. The surfactant heads and tails have the slowest relaxation due to their restricted movement inside the agglomerated structure. At the shortest length scale, all the charge and neutral species show similar relaxation dynamics confirming Rouse behavior at monomer length scales. Overall, the present study highlights the structure-property relationship for polymer-surfactant complexation. These results will help improve the understanding of PES complex and should aid in the design of better materials for future applications.« less

  6. 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.

  7. Methods for Determining the Molecular Weight and Solution Properties of Polyurethane Block Polymers.

    DTIC Science & Technology

    1986-10-08

    RD-A173 863 METHODS FOR DETERMINING THE MOLECULAR WEIGHT AND / SOLUTION PROPERTIES OF P ( U ) WISCONSIN UNIV-MADISON DEPT OF CHEMICAL ENGINEERING D LEE...concentration detector peak. Ci = mhi/ Vi (Ehi) (6) where m is the injected mass, Vi is the retention volume passing through the detector cell during the... Vi scometry The reduced viscosities of polystyrene and polyurethane in THF at four different concentrations were determined at 30C using an Ubbelohde

  8. Spectrophotometric determination of lithium ion using a water-soluble octabromoporphyrin in aqueous solution.

    PubMed

    Tabata, M; Nishimoto, J; Kusano, T

    1998-08-01

    A water-soluble porphyrin, (2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin; H(2)obtpps(4-)) was synthesized and developed for the determination of lithium ion in aqueous solution. The octabromo groups lower the basicity of the porphyrin by their electron-withdrawing effect, and enable the porphyrin to react with the lithium ion in alkaline solution to form the lithium complex along with a shift of absorption maximum: lambda max/nm (logepsilon/mol(-1) dm(3) cm(-1)) of the lithium porphyrin are 490.5 nm (5.31) and 734 nm (4.36). Sodium and potassium ions did not react with the porphyrin. The equilibrium constant for the reaction Li(+)+Hobtpps(5-)right harpoon over left harpoon[Li(obtpps)](5-)+H(+) was found to be 10(-8.80) and the conditional formation constant of the [Li(obtpps)](5-) at pH 13 is 10(4.21). The above results were applied to the determination of lithium ion in aqueous solution. The interference from transition and heavy metal ions was masked by using N,N'-1,2-ethanediylbis[N(carboxylmethy)glycinato]magnesium(II) ([Mg(edta)](2-)) solution. Absorbance at 490 nm was measured against a blank solution. A calibration graph was linear over the range of 0.007-0.7 mug cm(-3) (1x10(-6)-1x10(-4) mol dm(-3)) of lithium(I) with a correlation factor of 0.967. Lithium ion less than ppm level was determined spectrophtometrically in aqueous solution. The proposed method was applied to the determination of lithium in human serum and sea water samples.

  9. Twin solution calorimeter determines heats of formation of alloys at high temperatures

    NASA Technical Reports Server (NTRS)

    Darby, J. B., Jr.; Kleb, R.; Kleppa, O. J.

    1968-01-01

    Calvert-type, twin liquid metal solution calorimeter determines the heats of formation of transition metal alloys at high temperatures. The twin differential calorimeter measures the small heat effects generated over extended periods of time, has maximum operating temperature of 1073 degrees K and an automatic data recording system.

  10. Cast adhesive polyelectrolyte complex particle films of unmodified or maltose-modified poly(ethyleneimine) and cellulose sulphate: fabrication, film stability and retarded release of zoledronate.

    PubMed

    Torger, Bernhard; Vehlow, David; Urban, Birgit; Salem, Samaa; Appelhans, Dietmar; Müller, Martin

    2013-12-01

    The bone therapeutic drug zoledronate (ZOL) was loaded at and released by polyelectrolyte complex (PEC) particle films composed of either pure poly(ethyleneimine) (PEI) or maltose-modified poly(ethyleneimine) (PEI-M) and oppositely charged cellulose sulfate attached to model germanium (Ge) substrates by solution casting. Dispersions of colloidally stable polyelectrolyte complex (PEC) particles in the size range 11-141 nm were obtained by mixing PEI or PEI-M, CS and ZOL in defined stoichiometric ratios. TRANS-FTIR spectroscopy was used to determine the stability of the PEC films against detachment, in-situ-ATR-FTIR spectroscopy for the ZOL loss in the PEC film and UV-VIS spectroscopy for the ZOL enrichment of the release medium. Films of casted ZOL/CS/PEI-M or ZOL/CS/PEI particles were stable in contact to water, while films of the pure drug (ZOL) and of the binary systems ZOL/PEI-M or ZOL/PEI were not stable against detachment. Retarded releases of ZOL from various PEC films compared to the pure drug film were observed. The molecular weight of PEI showed a considerable effect on the initial burst (IB) of ZOL. No significant effect of the maltose modification of PEI-25 K on IB could be found. Generally, after one day the ZOL release process was finished for all measured ZOL/PEC samples and residual amounts of 0-30% were obtained. Surface adhesive drug loaded PEC particles are promising drug delivery systems to supply and release a defined amount of bone therapeutics and to functionalize bone substitution materials.

  11. 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

  12. The evolution of cyclopropenium ions into functional polyelectrolytes

    SciTech Connect

    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.

    2015-01-09

    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 of 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.

  13. Electrochemical mechanism of ion current rectification of polyelectrolyte gel diodes.

    PubMed

    Yamamoto, Tetsuya; Doi, Masao

    2014-06-17

    Polyelectrolyte gel diodes that are double layers of two oppositely charged polyelectrolyte gels, sandwiched by two symmetric electrodes, are emergent ionic devices. These diodes are designed to rectify ion currents with a physical mechanism that is analogous to conventional semiconductor diodes-the asymmetry in the permeability of ions across the interfaces between the two oppositely charged gels. Here we show that polyelectrolyte gel diodes indeed rectify steady currents with a physical mechanism that is very different from conventional diodes by using a simple electrochemical model; electric currents are limited by electrochemical reactions that are driven by potential drops at electrodes and these potential drops markedly change with changing the direction of applied voltages due to the redistribution of non-reactive counterions, leading to rectified ion currents. This concept is relatively generic and thus may provide insight in the physics of analogous ionic and biomimetic systems that show electrochemical reactions.

  14. An Invisible Bend Sensor Based on Porous Crosslinked Polyelectrolyte Film

    SciTech Connect

    Zhang, Q.; Saraf, Laxmikant V.; Smith, James R.; Jha, P.; Hua, Feng

    2009-04-29

    This paper describes the fabrication of a porous cross-linked polyelectrolyte membrane and the characterization of its humidity sensitivity performance. Electrostatic self-assembly, combined with acid treatment, and post-deposition annealing produced the membrane. The fabrication process offers the ability to control the thickness of the membrane, as well as enabling the engineering of the humidity sensitivity properties. A transparent humidity sensor was fabricated by integrating the membrane into a capacitive structure. In order to improve the moisture absorption and diffusion, both the polyelectrolyte layer and the electrode were made porous. The membrane was cross-linked to enhance the durability in high humid environments. Such a polyelectrolyte membrane showed high sensitivity to relative humidity variation over a range of 25-99%. The see-through property of the structure adds extra features and benefits to the sensor.

  15. Transparent Humidity Sensor Using Cross-Linked Polyelectrolyte Membrane

    SciTech Connect

    Zhang, Q.; Smith, James R.; Saraf, Laxmikant V.; Hua, Feng

    2009-07-02

    This paper describes the fabrication of a porous cross-linked polyelectrolyte membrane and the characterization of its humidity sensitivity performance. Electrostatic self-assembly, combined with acid treatment, and post-deposition annealing produced the membrane. The fabrication process offers the ability to control the thickness of the membrane, as well as enabling the engineering of the humidity sensitivity properties. A transparent humidity sensor was fabricated by integrating the membrane between two parallel electrodes. In order to improve the moisture absorption and diffusion, both the polyelectrolyte layer and the electrode were made porous. The membrane was cross-linked to enhance the durability in high humid environments. Such a polyelectrolyte membrane showed high sensitivity to relative humidity variation over a range of 25%–99%. The see-through property of the structure adds extra features and benefits to the sensor.

  16. Correlating the compliance and permeability of photocrosslinked polyelectrolyte multilayers

    PubMed Central

    Lehaf, Ali M.; Moussallem, Maroun D.; Schlenoff, Joseph B.

    2011-01-01

    Photocrosslinkable polyelectrolyte multilayers were made from poly(allylamine), PAH and poly(acrylic acid), PAA, modified with a photosensitive benzophenone. Nanoindentation, using atomic force microscopy, AFM, of these and unmodified PAH/PAA multilayers was used to assess their mechanical properties in situ under aqueous buffer. Under the conditions employed (and a 20 nm AFM radius tip) reliable nanoindentations that appeared to be decoupled from the properties of the silicon substrate were obtained for films greater than 150 nm in thickness. A strong difference in apparent modulus was observed for films terminated with positive as compared to negative polyelectrolyte. Films terminated with PAA were more glassy, suggesting better charge matching of polyelectrolytes. Multilayers irradiated up to 100 minutes showed a smooth and controlled increase in modulus, with little change in water contact angle. The permeability to iodide ion, measured electrochemically, also decreased in a controlled fashion PMID:21443175

  17. The evolution of cyclopropenium ions into functional polyelectrolytes

    NASA Astrophysics Data System (ADS)

    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.

  18. Polyelectrolyte gels comprising a lipophilic, cost-effective aluminate as fluorine-free absorbents for chlorinated hydrocarbons and diesel fuel.

    PubMed

    Wrede, Michael; Ganza, Viktoria; Bucher, Janina; Straub, Bernd F

    2012-07-25

    Superabsorbent polymers comprising a lipophilic, halogen-free, and cost-effective aluminate ("altebate") anion have been synthesized. The polyelectrolytes are based on octadecyl acrylate monomers, 0.8-1 mol % ethylene dimethacrylate cross-linker, and 5 mol % N-3-acroyloxypropyl trialkylammonium altebate. At 30 °C, swelling degrees of 70 (chlorobenzene), 102 (CHCl3), 130 (THF), 163 (ClCH2CH2Cl), 171 (dichlorobenzene), and 208 (CH2Cl2) have been determined. The polyelectrolyte absorbs reversibly diesel fuel with a swelling degree of 34, even in the presence of water. Swelling times and critical swelling temperatures have also been determined. The challenges for the development of oil absorbents are discussed.

  19. Coordination number of Li+ in nonaqueous electrolyte solutions determined by molecular rotational measurements.

    PubMed

    Yuan, Kaijun; Bian, Hongtao; Shen, Yuneng; Jiang, Bo; Li, Jiebo; Zhang, Yufan; Chen, Hailong; Zheng, Junrong

    2014-04-03

    The coordination number of Li(+) in acetonitrile solutions was determined by directly measuring the rotational times of solvent molecules bound and unbound to it. The CN stretch of the Li(+) bound and unbound acetonitrile molecules in the same solution has distinct vibrational frequencies (2276 cm(-1) vs 2254 cm(-1)). The frequency difference allows the rotation of each type of acetonitrile molecule to be determined by monitoring the anisotropy decay of each CN stretch vibrational excitation signal. Regardless of the nature of anions and concentrations, the Li(+) coordination number was found to be 4-6 in the LiBF4 (0.2-2 M) and LiPF6 (1-2 M) acetonitrile solutions. However, the dissociation constants of the salt are dependent on the nature of anions. In 1 M LiBF4 solution, 53% of the salt was found to dissociate into Li(+), which is bound by 4-6 solvent molecules. In 1 M LiPF6 solution, 72% of the salt dissociates. 2D IR experiments show that the binding between Li(+) and acetonitrile is very strong. The lifetime of the complex is much longer than 19 ps.

  20. The role of silica precipitation kinetics in determining the rate of quartz pressure solution

    NASA Astrophysics Data System (ADS)

    Mullis, Andrew M.

    1991-06-01

    Traditionally, models of intergranular pressure solution have assumed that grain boundary diffusion, probably through an adsorbed water layer, is the rate-limiting process (Weyl, 1959; Rutter, 1976). However, observations by Heald (1956, 1965) and experiments by Cecil and Heald (1971) show that the presence of clays may strongly inhibit the growth of secondary quartz. Under these circumstances, silica precipitation kinetics may also be important in determining the pressure solution rate. A model of quartz pressure solution including the rate of silica precipitation kinetics is developed, and strain rate equations are derived for a compacting sediment. Laboratory data for the precipitation constant k_, for quartz, indicate that precipitation kinetics should not be important in determining the rate of pressure solution in clean quartz sand. However, an estimate of the in situ value of k_ for the Dogger Beta formation, made from the data of Füchtbauer (1983), suggests that in a geological setting, k_ may be much smaller than under laboratory conditions. In consequence, it is asserted that silica precipitation kinetics may influence the rate of quartz pressure solution when secondary quartz growth is inhibited.

  1. Flow Cytometry for Determination of the Efficacy of Contact Lens Disinfecting Solutions against Acanthamoeba spp.

    PubMed Central

    Borazjani, Roya N.; May, Lauren L.; Noble, Judith A.; Avery, Simon V.; Ahearn, Donald G.

    2000-01-01

    Flow cytometric analyses of cellular staining with fluorescent viability dyes and direct microscopic observations of methylene blue exclusion were compared for evaluation of the effects of a chlorhexidine gluconate-based contact lens disinfectant solution and a polyhexamethylene biguanide solution against cysts and trophozoites of Acanthamoeba castellanii and Acanthamoeba polyphaga. The flow cytometric procedure with propidium iodide (used to stain dead cells) indicated that more than 90% of trophozoites of both species (inocula of 105 to 106/ml) at 22°C lost their viability after 4 h of exposure to chlorhexidine. When propidium iodide was used in combination with fluorescein diacetate (for live cells), the apparent number of propidium iodide-stained cells was reduced, but the relative efficacies of the two biguanide solutions appeared unchanged from those evident with the single dyes; the chlorhexidine solution was more effective than the polyhexamethylene biguanide solution. Similar data were obtained with the more cumbersome methylene blue exclusion procedure. Flow cytometric analyses provided a statistically reproducible and rapid procedure for determining the relative antiamoebal efficacies of the disinfecting solutions. PMID:10698771

  2. Adsorption and encapsulation of flexible polyelectrolytes in charged spherical vesicles

    NASA Astrophysics Data System (ADS)

    Shojaei, H. R.; Muthukumar, M.

    2017-06-01

    We present a theory of adsorption of flexible polyelectrolytes on the interior and exterior surfaces of a charged vesicle in an electrolyte solution. The criteria for adsorption and the density profiles of the adsorbed polymer chain are derived in terms of various characteristics of the polymer, vesicle, and medium, such as the charge density and length of the polymer, charge density and size of the vesicle, electrolyte concentration and dielectric constant of the medium. For adsorption inside the vesicle, the competition between the loss of conformational entropy and gain in adsorption energy results in two kinds of encapsulated states, depending on the strength of the polymer-vesicle interaction. By considering also the adsorption from outside the vesicle, we derive the entropic and energy contributions to the free energy change to transfer an adsorbed chain in the interior to an adsorbed chain on the exterior. In this paper, we have used the Wentzel-Kramers-Brillouin (WKB) method to solve the equation for the probability distribution function of the chain. The present WKB results are compared with the previous results based on variational methods. The WKB and variational results are in good agreement for both the interior and exterior states of adsorption, except in the zero-salt limit for adsorption in the exterior region. The adsorption criteria and density profiles for both the interior and exterior states are presented in terms of various experimentally controllable variables. Calculation of the dependencies of free energy change to transfer an adsorbed chain from the interior to the exterior surface on salt concentration and vesicle radius shows that the free energy penalty to expel a chain from a vesicle is only of the order of thermal energy.

  3. Amplified quenching of a conjugated polyelectrolyte by cyanine dyes.

    PubMed

    Tan, Chunyan; Atas, Evrim; Müller, Jürgen G; Pinto, Mauricio R; Kleiman, Valeria D; Schanze, Kirk S

    2004-10-27

    The conjugated polyelectrolyte PPESO3 features a poly(phenylene ethynylene) backbone substituted with anionic 3-sulfonatopropyloxy groups. PPESO3 is quenched very efficiently (KSV > 10(6) M(-1)) by cationic energy transfer quenchers in an amplified quenching process. In the present investigation, steady-state and picosecond time-resolved fluorescence spectroscopy are used to examine amplified quenching of PPESO3 by a series of cyanine dyes via singlet-singlet energy transfer. The goal of this work is to understand the mechanism of amplified quenching and to characterize important parameters that govern the amplification process. Steady-state fluorescence quenching of PPESO3 by three cationic oxacarbocyanine dyes in methanol solution shows that the quenching efficiency does not correlate with the Forster radius computed from spectral overlap of the PPESO3 fluorescence with the cyanines' absorption. The quenching efficiency is controlled by the stability of the polymer-dye association complex. When quenching studies are carried out in water where PPESO3 is aggregated, changes observed in the absorption and fluorescence spectra of 1,1',3,3,3',3'-hexamethylindotricarbocyanine iodide (HMIDC) indicate that the polymer templates the formation of a J-aggregate of the dye. The fluorescence dynamics in the PPESO3/HMIDC system were probed by time-resolved upconversion and the results show that PPESO3 to HMIDC energy transfer occurs on two distinctive time scales. At low HMIDC concentration, the dynamics are dominated by an energy transfer pathway with a time scale faster than 4 ps. With increasing HMIDC concentration, an energy pathway with a time scale of 0.1-1 ns is active. The prompt pathway (tau < 4 ps) is attributed to quenching of delocalized PPESO3 excitons created near the HMIDC association site, whereas the slow phase is attributed to intra- and interchain exciton diffusion to the HMIDC. Copyright 2004 American Chemical Society

  4. Polyelectrolyte multilayer-calcium phosphate composite coatings for metal implants.

    PubMed

    Elyada, Alon; Garti, Nissim; Füredi-Milhofer, Helga

    2014-10-13

    The preparation of organic-inorganic composite coatings with the purpose to increase the bioactivity of bioinert metal implants was investigated. As substrates, glass plates and rough titanium surfaces (Ti-SLA) were employed. The method comprises the deposition of polyelectrolyte multilayers (PEMLs) followed by immersion of the coated substrate into a calcifying solution of low supersaturation (MCS). Single or mixed PEMLs were constructed from poly-L-lysine (PLL) alternating with poly-L-glutamate, (PGA), poly-L-aspartate (PAA), and/or chondroitin sulfate (CS). ATR-FTIR spectra reveal that (PLL/PGA)10 multilayers and mixed multilayers with a (PLL/PGA)5 base contain intermolecular β-sheet structures, which are absent in pure (PLL/PAA)10 and (PLL/CS)10 assemblies. All PEML coatings had a grainy topography with aggregate sizes and size distributions increasing in the order: (PLL/PGA)n < (PLL/PAA)n < (PLL/CS)n. In mixed multilayers with a (PLL/PGA)n base and a (PLL/PAA)n or (PLL/CS)n top, the aggregate sizes were greatly reduced. The PEMLs promoted calcium phosphate nucleation and early crystal growth, the intensity of the effect depending on the composition of the terminal layer(s) of the polymer. In contrast, crystal morphology and structure depended on the supersaturation, pH, and ionic strength of the MCS, rather than on the composition of the organic matrix. Crystals grown on both uncoated and coated substrates were mostly platelets of calcium deficient carbonate apatite, with the Ca/P ratio depending on the precipitation conditions.

  5. Synthesis of hydrochloric acid solution for total mercury determination in natural waters.

    PubMed

    Patel-Sorrentino, Nathalie; Benaim, Jean-Yves; Cossa, Daniel; Lucas, Yves

    2011-01-01

    Total mercury (Hg(T)) determination requires the addition of concentrated hydrochloric acid solution (≥10 mol L(-1) HCl) in relatively high amounts to preserve the samples and to prepare reagent solutions. A method for the preparation of concentrated HCl with Hg(T) concentration of lower than 5 ng L(-1) is described in this article. It is based on the well-known chemical reaction: 2 NH(4)Cl + H(2)SO(4) → (NH(4))(2)SO(4) + 2 HCl. This method is validated thanks to the US Environmental Protection Agency method 1631 and standard reference materials BCR-579 (mercury in coastal seawater).

  6. CONJUGATED POLYMERS AND POLYELECTROLYTES IN SOLAR PHOTOCONVERSION, Final Technical Report

    SciTech Connect

    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.

  7. Effect of dielectric discontinuity on a spherical polyelectrolyte brush.

    PubMed

    Tergolina, Vinicius B; Dos Santos, Alexandre P

    2017-09-21

    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.

  8. Multilayered polyelectrolyte microcapsules: interaction with the enzyme cytochrome C oxidase.

    PubMed

    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.

  9. Electrophoretic Mobilities of the Charge Variants of DNA and Other Polyelectrolytes: Similarities, Differences, and Comparison with Theory.

    PubMed

    Stellwagen, Nancy C

    2017-03-09

    Free solution electrophoretic mobilities of polyelectrolytes with different charge densities have been analyzed using data taken from the literature. The polyions include single- and double-stranded DNA oligomers, small aromatic molecules, peptides, proteins, and synthetic copolymers. Mobility variations due to differences in the background electrolytes were minimized by calculating mobility ratios, dividing the mobility of each charge variant in each data set by the mobility of the most highly charged polyion in that data set. In all cases, the mobility ratios increase linearly with the logarithm of the fractional charge, not the first power of the charge as usually assumed. In addition, the mobility ratios observed for all polyelectrolytes, except for the synthetic copolymers, exhibit a common dependence on the logarithm of fractional charge. The unique results observed for the synthetic copolymers may be due to the flexibility of their hydrocarbon backbones, in contrast to the relatively rigid hydrophilic backbones of the other polyelectrolytes. The mobilities observed for the DNA charge variants are well predicted by the Manning electrophoresis equation, whereas the mobilities predicted by zeta potential theories are higher. However, mobility ratios calculated from both theories agree with the observed results.

  10. Baseline configuration for GNSS attitude determination with an analytical least-squares solution

    NASA Astrophysics Data System (ADS)

    Chang, Guobin; Xu, Tianhe; Wang, Qianxin

    2016-12-01

    The GNSS attitude determination using carrier phase measurements with 4 antennas is studied on condition that the integer ambiguities have been resolved. The solution to the nonlinear least-squares is often obtained iteratively, however an analytical solution can exist for specific baseline configurations. The main aim of this work is to design this class of configurations. Both single and double difference measurements are treated which refer to the dedicated and non-dedicated receivers respectively. More realistic error models are employed in which the correlations between different measurements are given full consideration. The desired configurations are worked out. The configurations are rotation and scale equivariant and can be applied to both the dedicated and non-dedicated receivers. For these configurations, the analytical and optimal solution for the attitude is also given together with its error variance-covariance matrix.

  11. Determining osmotic pressure of drug solutions by air humidity in equilibrium method.

    PubMed

    Zhan, Xiancheng; Li, Hui; Yu, Lan; Wei, Guocui; Li, Chengrong

    2014-06-01

    To establish a new osmotic pressure measuring method with a wide measuring range. The osmotic pressure of drug solutions is determined by measuring the relative air humidity in equilibrium with the solution. The freezing point osmometry is used as a control. The data obtained by the proposed method are comparable to those by the control method, and the measuring range of the proposed method is significantly wider than that of the control method. The proposed method is performed in an isothermal and equilibrium state, so it overcomes the defects of the freezing point and dew point osmometries which result from the heterothermal process in the measurement, and therefore is not limited to diluted solutions.

  12. Rheological and kinetic study of the ultrasonic degradation of locust bean gum in aqueous saline and salt-free solutions.

    PubMed

    Li, Ruoshi; Feke, Donald L

    2015-11-01

    The ultrasonic degradation of locust bean gum (LBG) in aqueous solutions has been studied at 25°C for ultrasonication times up to 120 min. Although LBG is not a polyelectrolyte, the degradation extent and kinetics were found to be somewhat sensitive to the ionic conditions in solution, and this is attributed to changes in molecular conformation that can occur in different salt environments. Ultrasonic degradation was tracked by rheological measurements that lead to the determination of intrinsic viscosity for the LBG molecules. A kinetic model was also developed and successfully applied to characterize and predict the degradation results.

  13. Small angle neutron scattering study to determine the structure of high strength hydrogels.

    NASA Astrophysics Data System (ADS)

    Tominaga, Taiki; Tirumala, Vijay R.; Lin, Eric K.; Wu, Wen-Li; Gong, Jian Ping; Furukawa, Hidemitsu; Osada, Yoshihito

    2006-03-01

    Hydrogels are swollen polymer networks containing more than 90% water. Most hydrogels, however, are mechanically too weak to be used as load bearing devices. Gong et al. have overcome this problem by synthesizing hydrogels with a double network (DN) structure. Modifying the polyelectrolyte network structure by polymerization of high molecular weight uncharged polymer in situ, resulted in orders of magnitude increase in their load bearing ability. Despite 90% water, these tough gels exhibit a fracture stress of 170 kg/cm^2, similar to that of articular cartilage found in the bone-joints of human body. In this work, we determined the structure of DN-gels using small angle neutron scattering. Structural origins for high toughness found in DN-gels were then examined by comparing the structure of DN-gels with that of pure polyelectrolyte network and polyacrylamide solution.

  14. Plant uptake and determination of arsenic species in soil solution under flooded conditions

    SciTech Connect

    Onken, B.M.; Hossner, L.R.

    1995-03-01

    Previous studies have not identified the different As species present in soil systems and determined if effective differences exist between As species with respect to plant parameters such as growth rate and As uptake. This study determined the species and concentrations of As present in soil solution of flooded soils and correlated them to As concentration, P concentration, an growth rate of plants grown in treated soils. Rice (Oryza sativa L.) was grown in two soils treated with 0, 5, 25, 35, and 45 mg As kg{sup -1} soil added as either Na-arsenate or Na-arsenite. Soil solution samples and plant samples were collected over a period of 60 d. The As concentration of rice plants best correlated to the mean soil solution arsenate concentration in a Beaumont clay (fine, montmorillonitic, thermic Entic Pelludert) and to the mean soil solution arsenite concentration in a Midland silt loam (fine, montmorillonitic, thermic Typic Ochraqualf). In both soils, plant P concentration was best correlated to the amount of As added to the soil rather than any soil solution As concentration. Plant weight was best correlated to the mean soil solution arsenate concentration in both soils. The rate of As uptake by plants increased as the rate of plant growth increased. Plants grown in soils treated with As had higher rates of As uptake for similar rates of growth when compared with plants in untreated soils. However, growth per unit of As uptake was higher for plants in untreated soils than plants in As treated soils. 31 refs., 8 figs., 5 tabs.

  15. Porous Polyelectrolyte Hydrogels With Enhanced Swelling Properties Prepared Via Thermal Reverse Casting Technique

    NASA Astrophysics Data System (ADS)

    Salerno, Aurelio; Netti, Paolo A.

    2010-06-01

    In this work we investigated the preparation and characterization of porous polyelectrolyte hydrogels via thermal reverse casting technique. Polyacrylamide hydrogels were synthesized by free-radical crosslinking polymerization into the space of an agarose gel which, after the setting of the chemical gel, was removed to allow the formation of an interconnected porosity pathway. Two different monomer/agarose solution ratios were selected for the reverse casting process and, the resulting hydrogels characterized in terms of morphological, micro-structural and thermal properties, as well as swelling capability in solutions at different ionic strength. The results of this study demonstrated that proposed technique allowed the design of porous polyacrylamide hydrogels with well controlled pore structures. Furthermore, if compared to non porous polyacrylamide hydrogel, the as obtained hydrogels were characterized by enhanced swelling properties and that, these properties were fine tuned by the appropriate selection of the templating agent concentration.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

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

    PubMed

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

    2015-06-17

    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 PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to 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.

  18. Intelligent colloidal hybrids via reversible pH-induced complexation of polyelectrolyte and silica nanoparticles.

    PubMed

    Mori, Hideharu; Müller, Axel H E; Klee, Joachim E

    2003-04-02

    We present novel intelligent colloidal polymer/silica nanocomposites, in which the complexation of cationic silica nanoparticles and a weak anionic polyelectrolyte can be manipulated simply by pH change through a hydrogen-bonding interaction and ionic complexation caused by hydrogen-transfer interactions between the constituents. Special silica particles which have nanometer size (diameter approximately 3.0 nm) and two independent proton-accepting sites were developed in this study. Both the silica and poly(acrylic acid) form transparent colloidal solutions in water, while a white turbid dispersion was obtained just after mixing the two solutions due to the complexation. The pH-induced association-dissociation behavior was confirmed by the turbidity and potentiometric titration measurements. The assembled structures of the hybrids were visualized by scanning force microscopy.

  19. The bulk phase behavior of short polyelectrolyte chains: A Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Orkoulas, Gerassimos; Kumar, Sanat

    2002-03-01

    While polyelectrolytes form an important class of materials in chemistry and biochemistry, their understanding at the theoretical level is still lacking. The strong Coulombic repulsions and attractions, the resulting Debye screening and the concomitant unlike-charge association (known as counterion condensation) render standard neutral polymer theories difficult to apply. Indeed, most theoretical and numerical investigations have been focused on the dilute-to-semidilute regime at somewhat weak Coulomb couplings. In this work, we consider a lattice model of flexible charged chains with an appropriate number of oppositely charged counterions to ensure electrical neutrality. Electrostatic interactions are explicitly taken into account and handled via Ewald sums in the simulations. The solvent is modeled as a uniform dielectric continuum. By performing grand canonical Monte Carlo simulations, we demonstrate that at strong Coulomb couplings (low reduced temperatures) the system separates into polymer rich and poor phases respectively. The type of phase coexistence occurring in these polyelectrolyte systems bears resemblances to the gas-liquid transition of the restricted primitive model of ionic solutions. The approach to the Flory theta point is studied by increasing the chain length. The critical point dependence on the chain length is found to be rather weak. A plausible explanation lies in the formation of long-lived network structures via a bead-counterion mechanism. Finally, the ability of the system to form gels via bead-counterion junctions is examined and analyzed.

  20. 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.

  1. Shaping calcite crystals by means of comb polyelectrolytes having neutral hydrophilic teeth.

    PubMed

    Malferrari, Danilo; Fermani, Simona; Galletti, Paola; Goisis, Marco; Tagliavini, Emilio; Falini, Giuseppe

    2013-02-12

    Comb polyelectrolytes (CPs) having neutral hydrophilic teeth, similar to double hydrophilic block copolymers, are a powerful tool to modify the chemical-physical properties of inorganic crystalline materials. One of their main applications is in concrete technology, where they work as superplasticizers, particle-dispersing agents. Here, CPs, having the same poly(acrylic acid) (PAA) backbone chain and differing in the grafting with methoxy poly(ethylene glycol) chains (MPEG) of two molecular weights, were used to investigate the influence of tooth chains in polymer aggregation and in control on morphology and aggregation of calcite particles. These polymers aggregate, forming interpolymer hydrogen bonds between carboxylic groups and ether oxygen functionalities. The presence of calcium ions in solution further enhances aggregation. Crystallization experiments of calcite in the presence of CPs show that the specificity of interactions between polymers and crystal planes and control on aggregation and size of particles is a function of the content and chain length of the MPEG in the PAA backbone. These parameters limit and can make specific the electrostatic interactions with ionic crystalline planes. Moreover, the mechanism of crystallization, classical or nonclassical, is addressed by the CP structure and concentration. These findings have implications in the understanding of the complex chemical processes associated to concrete superplasticizers action and in the study of the biomineralization processes, where biological comb polyelectrolytes, the acidic glycoproteins, govern formation of calcitic structures.

  2. Dielectric analysis based on spherical-shell model for cationic and anionic spherical polyelectrolyte brushes

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoxia; Zhao, Kongshuang

    2017-07-01

    We report here a dielectric study on cationic and anionic spherical polyelectrolyte brush (SPB) (consisting of a polystyrene (PS) core and poly (2-aminoethylmethacrylate hydrochloride (PAEMH) chains or poly (acrylic acid) (PAA) chains grafted onto the core) suspensions over a frequency range of 40 Hz-110 MHz. The relaxation behavior of the suspensions shows significant changes in the brush layer properties when changing the particle mass fraction or pH of the system. After eliminating the electrode polarization effect at a low frequency, two definite relaxations related to interfacial polarization, around 100 kHz and 10 MHz respectively, are observed. Based on a single layer spherical-shell model, we developed a curve-fitting procedure to analyze such dielectric spectra for soft particles, and then calculated the dielectric properties of the components of the SPBs (such as the permittivities and conductivities of the layer and solution phase), especially the layer thickness d s of the polyelectrolyte chain (PE) layer. We also found a larger confinement degree of counterions in the PAEMH brush due to the protonation of the amino group. Moreover, the repulsive force between the SPB particles is evaluated by using the d s combined with the relative theoretical formulas. We conclude that by raising (reducing) the acidity of the system, the stability of the PAEMH-SPB (PAA-SPB) suspension was improved. An increase in particle concentration can also improve the stability of these two dispersions.

  3. 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.

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

    PubMed

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

    2015-09-21

    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.

  5. Interaction and complex formation between catalase and cationic polyelectrolytes: chitosan and Eudragit E100.

    PubMed

    Boeris, Valeria; Romanini, Diana; Farruggia, Beatriz; Picó, Guillemo

    2009-08-01

    Interactions between catalase and the cationic polyelectrolytes: chitosan and Eudragit E100 have been investigated owing to their scientific and technological importance. These interactions have been characterized by turbidimetry, circular dichroism and fluorescence spectroscopy. It was found that the catalase conformation does not change significantly during the chain entanglements between the protein and the polyelectrolytes. The effects of pH, ionic strength and anions which modify the water structure were evaluated on the polymer-protein complex formation. A net coulombic interaction force between them was found since the insoluble complex formation decreased after the NaCl addition. Both polymers were found to precipitate around 80% of the protein in solution. No modification of the tertiary and secondary protein structure or the enzymatic activity was observed when the precipitate was dissolved by changing the pH of the medium. Chitosan and Eudragit E100 proved to be a useful framework to isolate catalase or proteins with a slightly acid isoelectrical pH by means of precipitation.

  6. Potentiometric determination of the 'formal' hydrolysis ratio of aluminium species in aqueous solutions.

    PubMed

    Fournier, Agathe C; Shafran, Kirill L; Perry, Carole C

    2008-01-21

    The 'formal' hydrolysis ratio (h = C(OH-)added/C(Al)total) of hydrolysed aluminium-ions is an important parameter required for the exhaustive and quantitative speciation-fractionation of aluminium in aqueous solutions. This paper describes a potentiometric method for determination of the formal hydrolysis ratio based on an automated alkaline titration procedure. The method uses the point of precipitation of aluminium hydroxide as a reference (h = 3.0) in order to calculate the initial formal hydrolysis ratio of hydrolysed aluminium-ion solutions. Several solutions of pure hydrolytic species including aluminium monomers (AlCl3), Al13 polynuclear cluster ([Al13O4(OH)24(H2O)12]7+), Al30 polynuclear cluster ([Al30O8(OH)56(H2O)26]18+) and a suspension of nanoparticulate aluminium hydroxide have been used as 'reference standards' to validate the proposed potentiometric method. Other important variables in the potentiometric determination of the hydrolysis ratio have also been optimised including the concentration of aluminium and the type and strength of alkali (Trizma-base, NH3, NaHCO3, Na2CO3 and KOH). The results of the potentiometric analysis have been cross-verified by quantitative 27Al solution nuclear magnetic resonance (27Al NMR) measurements. The 'formal' hydrolysis ratio of a commercial basic aluminium chloride has been measured as an example of a practical application of the developed technique.

  7. The Determination of the pH of Standard Buffer Solution: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Harris, K. R.

    1985-01-01

    Describes an experiment which shows: (1) how measurements of the reaction electromotive force for the cell (Pt/glass/NaCl(aq,m),buffer/AgCl/Ag/Pt) can be utilized in determining the absolute pH of the buffer; and (2) the demonstration of the use of the Debye-Huckel model of an electrolyte solution in solving an important electrochemical problem.…

  8. Simple and reliable quartz crystal microbalance technique for determination of solubility by cooling and heating solution.

    PubMed

    Liu, Li-Shang; Kim, Jong-Min; Kim, Woo-Sik

    2015-03-17

    A quartz crystal microbalance (QCM) is presented as a promising technique for determining the solubility and induction of nucleation via the cooling and reverse heating of a solution. When cooling and heating a solution, the resonant frequency (F) and resonant resistance (R) of the QCM responses change significantly due to vibrational loss related to the viscous and elastic friction that depend on the solution viscosity and solid mass on the sensor, respectively. Thus, obvious refraction points appear in the QCM response profile at the induction point of primary nucleation during cooling crystallization and at the saturated point during heating dissolution. Using an F-R plot of the QCM responses, the phase changes between liquid and solid at the induction and saturated points are confirmed. When compared with focused beam reflectance measurement (FBRM) and gravimetric methods, the QCM method is confirmed to be highly accurate and reliable for determining the solubility, making it a highly promising method for determining solubility and crystal nucleation with minimal effort based on simple temperature cycling, thereby avoiding precalibration and sampling.

  9. AC impedance-emission spectroscopy for determining the electrochemical behaviour of anodised aluminium in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Habib, K.

    2010-09-01

    In the present investigation, holographic interferometry was utilised for the first time to determine the rate change of the alternating current (AC) impedance of aluminium samples during the initial stage of anodisation processes in aqueous solution without any physical contact. In fact, because the AC impedance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the AC impedance was called AC impedance-emission spectroscopy. The anodisation process (oxidation) of the aluminium samples was carried out chemically in different sulphuric acid concentrations (0.5-3.125% H2SO4) at room temperature. In the mean time, the real time holographic interferometry was used to determine the difference in the AC impedance of two subsequent values, dZ, as a function of the elapsed time of the experiment for the aluminium samples in 0. 5, 1.0, 1.5 and 3.125% H2SO4 solutions. The AC impedance-emission spectra of the present investigation represent a detailed picture of not only the rate change of the AC impedance throughout the anodisation processes but also the spectra represent the rate change of the growth of the oxide films on the aluminium samples in different solutions. Consequently, holographic interferometry is found to be very useful for surface finish industries, especially for monitoring the early stage of anodisation processes of metals, in which the rate change of AC impedance of the aluminium samples can be determined in situ.

  10. Analytical solutions for determining residual stresses in two-dimensional domains using the contour method

    PubMed Central

    Kartal, Mehmet E.

    2013-01-01

    The contour method is one of the most prevalent destructive techniques for residual stress measurement. Up to now, the method has involved the use of the finite-element (FE) method to determine the residual stresses from the experimental measurements. This paper presents analytical solutions, obtained for a semi-infinite strip and a finite rectangle, which can be used to calculate the residual stresses directly from the measured data; thereby, eliminating the need for an FE approach. The technique is then used to determine the residual stresses in a variable-polarity plasma-arc welded plate and the results show good agreement with independent neutron diffraction measurements. PMID:24204187

  11. 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).

  12. Splaying hyperthin polyelectrolyte multilayers to increase their gas permeability.

    PubMed

    Yi, Song; Lin, Cen; Regen, Steven L

    2015-01-28

    The concept of splayed, hyperthin polyelectrolyte multilayers (PEMs) is introduced in which a bulky, hydrophilic and charged pendant group is used to increase the gas permeability of a PEM without reducing its permeation selectivity. Proof of principle studies are reported using nm-thick PEMs made from poly(sodium 4-styrene sulfonate) () and poly(allylamine hydrochloride) () bearing bulky cobaltocenium ions.

  13. Observation of Molecular Diffusion in Polyelectrolyte-Wrapped SERS Nanoprobes

    PubMed Central

    2015-01-01

    The popularity of nanotechnology-based sensing technologies has rapidly expanded within the past decade. Surface-enhanced Raman spectroscopy (SERS) is one such technique capable of chemically specific and highly sensitive measurements. The careful preparation of SERS-active nanoprobes is immensely vital for biological applications where nanoprobes are exposed to harsh ionic and protein rich microenvironments. Encapsulation of optical reporter molecules via layer-by-layer (LbL) polyelectrolyte wrapping is an emerging technique that also permits facile modification of surface chemistry and charge. LbL wrapping can be performed within a few hours and does not require the use of organic solvents or hazardous silanes. Nonetheless, the stability of its products requires further characterization and analysis. In this study, Raman-active methylene blue molecules were electrostatically encapsulated within alternating layers of cationic and anionic polyelectrolytes surrounding gold nanospheres. We observed molecular diffusion of methylene blue through polyelectrolyte layers by monitoring the change in SERS intensity over a period of more than 5 weeks. To minimize diffusion and improve the long-term storage stability of our nanoprobes, two additional nanoprobe preparation techniques were performed: thiol coating and cross-linking of the outer polyelectrolyte layer. In both cases, molecular diffusion is significantly diminished. PMID:24998291

  14. Titration of hydrophobic polyelectrolytes using Monte Carlo simulations.

    PubMed

    Ulrich, Serge; Laguecir, Abohachem; Stoll, Serge

    2005-03-01

    The conformation and titration curves of weak (or annealed) hydrophobic polyelectrolytes have been examined using Monte Carlo simulations with screened Coulomb potentials in the grand canonical ensemble. The influence of the ionic concentration pH and presence of hydrophobic interactions has been systematically investigated. A large number of conformations such as extended, pearl-necklace, cigar-shape, and collapsed structures resulting from the subtle balance of short-range hydrophobic attractive interactions and long-range electrostatic repulsive interactions between the monomers have been observed. Titration curves were calculated by adjusting the pH-pK(0) values (pK(0) represents the intrinsic dissociation constant of an isolated monomer) and then calculating the ionization degree alpha of the polyelectrolyte. Important transitions related to cascades of conformational changes were observed in the titration curves, mainly at low ionic concentration and with the presence of strong hydrophobic interactions. We demonstrated that the presence of hydrophobic interactions plays an important role in the acid-base properties of a polyelectrolyte in promoting the formation of compact conformations and hence decreasing the polyelectrolyte degree of ionization for a given pH-pK(0) value.

  15. Electrostatics and charge regulation in polyelectrolyte multilayered assembly.

    PubMed

    Cherstvy, Andrey G

    2014-05-01

    We examine the implications of electrostatic interactions on formation of polyelectrolyte multilayers, in application to field-effect based biosensors for label-free detection of charged macromolecules. We present a quantitative model to describe the experimental potentiometric observations and discuss its possibilities and limitations for detection of polyelectrolyte adsorption. We examine the influence of the ionic strength and pH on the sensor response upon polyelectrolyte layer-by-layer formation. The magnitude of potential oscillations on the sensor-electrolyte interface predicted upon repetitive adsorption charge-alternating polymers agrees satisfactorily with experimental results. The model accounts for different screening by mobile ions in electrolyte and inside tightly interdigitated multilayered structure. In particular, we show that sensors' potential oscillations are larger and more persistent at lower salt conditions, while they decay faster with the number of layers at higher salt conditions, in agreement with experiments. The effects of polyelectrolyte layer thickness, substrate potential, and charge regulation on the sensor surface triggered by layer-by-layer deposition are also analyzed.

  16. Practical Considerations for Determination of Glass Transition Temperature of a Maximally Freeze Concentrated Solution.

    PubMed

    Pansare, Swapnil K; Patel, Sajal Manubhai

    2016-08-01

    Glass transition temperature is a unique thermal characteristic of amorphous systems and is associated with changes in physical properties such as heat capacity, viscosity, electrical resistance, and molecular mobility. Glass transition temperature for amorphous solids is referred as (T g), whereas for maximally freeze concentrated solution, the notation is (T g'). This article is focused on the factors affecting determination of T g' for application to lyophilization process design and frozen storage stability. Also, this review provides a perspective on use of various types of solutes in protein formulation and their effect on T g'. Although various analytical techniques are used for determination of T g' based on the changes in physical properties associated with glass transition, the differential scanning calorimetry (DSC) is the most commonly used technique. In this article, an overview of DSC technique is provided along with brief discussion on the alternate analytical techniques for T g' determination. Additionally, challenges associated with T g' determination, using DSC for protein formulations, are discussed. The purpose of this review is to provide a practical industry perspective on determination of T g' for protein formulations as it relates to design and development of lyophilization process and/or for frozen storage; however, a comprehensive review of glass transition temperature (T g, T g'), in general, is outside the scope of this work.

  17. Spectrophotometric determination of EDTA in aqueous solution through ferroin formation using sodium sulfite as the reducer.

    PubMed

    Wang, Jingang; Yu, Jiemei; Kong, Xiang Z; Hou, Longlei

    2013-04-01

    This paper presents a simple, easy and reliable method for determination of EDTA (ethylenediaminetetraacetic acid) in aqueous system. Using EDTA chelating with ferric irons, an excessive amount of Fe(3+) was added to EDTA solution, and Fe(3+) in excess was reduced by addition of a Na2SO3 solution, the outcome ferrous ions were then reacted with 1,10-phenanthroline monohydrate (PTM) to form ferroin, a color developing reagent. The absorbance of the ferroin was determined using spectrophotometry, from which EDTA concentration was obtained. The method was tested for interferences and applied to determination of trace amount EDTA in its degradation by ozone oxidation, and the result compared with those from high-performance liquid chromatography. It was revealed that a low limit of 1.4μM for EDTA concentration detection was achieved with a high correlation coefficient of 0.999 combined with a low relative standard deviation of 0.6%. In contrast to all reported processes, where ferric ions in excess have to be separated from those chelated with EDTA prior to their reduction followed by interaction with PTM and spectrophotometric determination, the key merit of the present method is that EDTA concentration is determined without need of ferric separation, rendering the present process very easy. The method is also characterized by low cost, high precision and high reproducibility at the same time. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Polyelectrolyte-promoted forward osmosis-membrane distillation (FO-MD) hybrid process for dye wastewater treatment.

    PubMed

    Ge, Qingchun; Wang, Peng; Wan, Chunfeng; Chung, Tai-Shung

    2012-06-05

    Polyelectrolytes have proven their advantages as draw solutes in forward osmosis process in terms of high water flux, minimum reverse flux, and ease of recovery. In this work, the concept of a polyelectrolyte-promoted forward osmosis-membrane distillation (FO-MD) hybrid system was demonstrated and applied to recycle the wastewater containing an acid dye. A poly(acrylic acid) sodium (PAA-Na) salt was used as the draw solute of the FO to dehydrate the wastewater, while the MD was employed to reconcentrate the PAA-Na draw solution. With the integration of these two processes, a continuous wastewater treatment process was established. To optimize the FO-MD hybrid process, the effects of PAA-Na concentration, experimental duration, and temperature were investigated. Almost a complete rejection of PAA-Na solute was observed by both FO and MD membranes. Under the conditions of 0.48 g mL(-1) PAA-Na and 66 °C, the wastewater was most efficiently dehydrated yet with a stabilized PAA-Na concentration around 0.48 g mL(-1). The practicality of PAA-Na-promoted FO-MD hybrid technology demonstrates not only its suitability in wastewater reclamation, but also its potential in other membrane-based separations, such as protein or pharmaceutical product enrichment. This study may provide the insights of exploring novel draw solutes and their applications in FO related processes.

  19. Application of polyelectrolyte theories for analysis of DNA melting in the presence of Na+ and Mg2+ ions.

    PubMed Central

    Korolev, N; Lyubartsev, A P; Nordenskiöld, L

    1998-01-01

    Numerical calculations, using Poisson-Boltzmann (PB) and counterion condensation (CC) polyelectrolyte theories, of the electrostatic free energy difference, DeltaGel, between single-stranded (coil) and double-helical DNA have been performed for solutions of NaDNA + NaCl with and without added MgCl2. Calculations have been made for conditions relevant to systems where experimental values of helix coil transition temperature (Tm) and other thermodynamic quantities have been measured. Comparison with experimental data has been possible by invoking values of Tm for solutions containing NaCl salt only. Resulting theoretical values of enthalpy, entropy, and heat capacity (for NaCl salt-containing solutions) and of Tm as a function of NaCl concentration in NaCl + MgCl2 solutions have thus been obtained. Qualitative and, to a large extent, quantitative reproduction of the experimental Tm, DeltaHm, DeltaSm, and DeltaCp values have been found from the results of polyelectrolyte theories. However, the quantitative resemblance of experimental data is considerably better for PB theory as compared to the CC model. Furthermore, some rather implausible qualitative conclusions are obtained within the CC results for DNA melting in NaCl + MgCl2 solutions. Our results argue in favor of the Poisson-Boltzmann theory, as compared to the counterion condensation theory. PMID:9826624

  20. 76 FR 28045 - Determination That XIBROM (Bromfenac Ophthalmic Solution) 0.09% Was Not Withdrawn From Sale for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-13

    ... HUMAN SERVICES Food and Drug Administration Determination That XIBROM (Bromfenac Ophthalmic Solution) 0... (bromfenac ophthalmic solution) 0.09% was not withdrawn from sale for reasons of safety or effectiveness... ophthalmic solution 0.09% if all other legal and regulatory requirements are met. FOR FURTHER INFORMATION...