Polymer-based adsorbent for heavy metals removal from aqueous solution

NASA Astrophysics Data System (ADS)

Mahmud, H. N. M. E.; Huq, A. K. O.; Yahya, R.

2017-06-01

A novel conducting polymer-based adsorbent, polypyrrole (PPy) fine powder has successfully been prepared as a new adsorbent and utilized in the adsorption of heavy metal ions like arsenic, zinc and cadmium ions from aqueous solution. PPy was chemically synthesized by using FeCl3.6H2O as an oxidant. The prepared PPy adsorbent was characterized by Brunauer-Emmet-Teller (BET) surface analysis, field emission scanning electron microscopy (FESEM) and attenuated total reflectance fourier transform infrared ATR-(FTIR) spectroscopy. The adsorption was conducted by varying different parameters such as, contact time, pH and adsorbent dosage. The concentrations of metal ions were measured by inductively coupled plasma mass spectroscopy (ICP-MS). The results show that PPy acts as an effective sorbent for the removal of arsenic, zinc and cadmium ions from aqueous solution. The as-prepared PPy fine powder is easy to prepare and appeared as an effective adsorbent for heavy metal ions particularly arsenic in wastewater treatment.

Tuning Adsorption Duration To Control the Diffusion of a Nanoparticle in Adsorbing Polymers.

PubMed

Cao, Xue-Zheng; Merlitz, Holger; Wu, Chen-Xu

2017-06-15

Controlling the nanoparticle (NP) diffusion in polymers is a prerequisite to obtain polymer nanocomposites (PNCs) with desired dynamical and rheological properties and to achieve targeted delivery of nanomedicine in biological systems. Here we determine the suppression mechanism of direct NP-polymer attraction to hamper the NP mobility in adsorbing polymers and then quantify the dependence of the effective viscosity η eff felt by the NP on the adsorption duration τ ads of polymers on the NP using scaling theory analysis and molecular dynamics simulations. We propose and confirm that participation of adsorbed chains in the NP motion break up at time intervals beyond τ ads due to the rearrangement of polymer segments at the NP surface, which accounts for the onset of Fickian NP diffusion on a time scale of t ≈ τ ads . We develop a power law, η eff ∼ (τ ads ) ν , where ν is the scaling exponent of the dependence of polymer coil size on the chain length, which leads to a theoretical basis for the design of PNCs and nanomedicine with desired applications through tuning the polymer adsorption duration.

Secondary polymer layered impregnated tile

NASA Technical Reports Server (NTRS)

Tran, Huy K. (Inventor); Rasky, Daniel J. (Inventor); Szalai, Christine E. (Inventor); Carroll, Joseph A. (Inventor); Hsu, Ming-ta S. (Inventor)

2005-01-01

A low density organic polymer impregnated preformed fibrous ceramic article includes a plurality of layers. A front layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one organic polymer. A middle layer includes polymer impregnated ceramic fibers. A back layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one low temperature pyrolyzing organic polymer capable of decomposing without depositing residues.

Interphase and particle dispersion correlations in polymer nanocomposites

NASA Astrophysics Data System (ADS)

Senses, Erkan

Particle dispersion in polymer matrices is a major parameter governing the mechanical performance of polymer nanocomposites. Controlling particle dispersion and understanding aging of composites under large shear and temperature variations determine the processing conditions and lifetime of composites which are very important for diverse applications in biomedicine, highly reinforced materials and more importantly for the polymer composites with adaptive mechanical responses. This thesis investigates the role of interphase layers between particles and polymer matrices in two bulk systems where particle dispersion is altered upon deformation in repulsive composites, and good-dispersion of particles is retained after multiple oscillatory shearing and aging cycles in attractive composites. We demonstrate that chain desorption and re-adsorption processes in attractive composites under shear can effectively enhance the bulk microscopic mechanical properties, and long chains of adsorbed layers lead to a denser entangled interphase layer. We further designed experiments where particles are physically adsorbed with bimodal lengths of homopolymer chains to underpin the entanglement effect in interphases. Bimodal adsorbed chains are shown to improve the interfacial strength and used to modulate the elastic properties of composites without changing the particle loading, dispersion state or polymer conformation. Finally, the role of dynamic asymmetry (different mobilities in polymer blends) and chemical heterogeneity in the interphase layer are explored in systems of poly(methyl methacrylate) adsorbed silica nanoparticles dispersed in poly(ethylene oxide) matrix. Such nanocomposites are shown to exhibit unique thermal-stiffening behavior at temperatures above glass transitions of both polymers. These interesting findings suggest that the mobility of the surface-bound polymer is essential for reinforcement in polymer nanocomposites, contrary to existing glassy layer theories

Amine-pillared Nanosheet Adsorbents for CO2 Capture Applications

NASA Astrophysics Data System (ADS)

Jiang, Hui

3D microporous layers with 8 MB openings in the plane of the layers, as well as perpendicular to the layers, which are larger than CO2 molecules. Based on the structure differences between nanosheets precursor material MCM-22(P) and nanoporous layered silicate material AMH-3, the latter might be more suitable for CO 2 capturer application as an APN candidate material. However, none of the assumptions above have been approved experimentally. In this study, the influence of the amine loading on adsorption capacity and kinetics of adsorption for the mixed porosity material pillared MCM-22 (P) (also called MCM-36) is studied systematically, in order to determine a potential route to achieve a final material with both high amine loading and high adsorption capacity. We first synthesized MCM-22(P), followed by swelling and pillaring to create MCM-36. Polymeric amines such as polyethylenimine (PEI) are used as an organic component of the supported amine adsorbents, with varying polymer loadings within the adsorbents used. The kinetics and diffusion properties of carbon dioxide capture on a MCM-36 pillared material impregnated with amine containing Polyethylenimine polymers has been investigated. It was determined that the introduction of amine polymer cannot be used to improve the capture capacity of the support over that of the bare material, due to the fact that with the addition of a high loading of amine polymer the large pore diffusion channels become impossible for carbon dioxide molecules to diffuse through. This sets an upper limit to the capture capacity of polymer impregnated MCM-36 for carbon dioxide which does not surpass that for the initial bare material, and greatly reduces the utility of using this sort of amine-solid adsorbent for carbon capture plans in the future.

Pulling adsorbed polymers at an angle: A low temperature theory

NASA Astrophysics Data System (ADS)

Iliev, Gerasim; Whittington, Stuart

2012-02-01

We consider several partially-directed walk models in two- and three-dimensions to study the problem of a homopolymer interacting with a surface while subject to a force at the terminal monomer. The force is applied with a component parallel to the surface as well as a component perpendicular to the surface. Depending on the relative values of the force in each direction, the force can either enhance the adsorption transition or lead to desorption in an adsorbed polymer. For each model, we determine the associated generating function and extract the phase diagram, identifying states where the polymer is thermally desorbed, adsorbed, and under the influence of the force. We note the different regimes that appear in the problem and provide a low temperature approximation to describe them. The approximation is exact at T=0 and models the exact results extremely well for small values of T. This work is an extension of a model considered by S. Whittington and E. Orlandini.

Conformational Phase Diagram for Polymers Adsorbed on Ultrathin Nanowires

NASA Astrophysics Data System (ADS)

Vogel, Thomas; Bachmann, Michael

2010-05-01

We study the conformational behavior of a polymer adsorbed at an attractive stringlike nanowire and construct the complete structural phase diagram in dependence of the binding strength and effective thickness of the nanowire. For this purpose, Monte Carlo optimization techniques are employed to identify lowest-energy structures for a coarse-grained model of a polymer in contact with the nanowire. Among the representative conformations in the different phases are, for example, compact droplets attached to the wire and also nanotubelike monolayer films wrapping it in a very ordered way. We here systematically analyze low-energy shapes and structural order parameters to elucidate the transitions between the structural phases.

Conformational phase diagram for polymers adsorbed on ultrathin nanowires.

PubMed

Vogel, Thomas; Bachmann, Michael

2010-05-14

We study the conformational behavior of a polymer adsorbed at an attractive stringlike nanowire and construct the complete structural phase diagram in dependence of the binding strength and effective thickness of the nanowire. For this purpose, Monte Carlo optimization techniques are employed to identify lowest-energy structures for a coarse-grained model of a polymer in contact with the nanowire. Among the representative conformations in the different phases are, for example, compact droplets attached to the wire and also nanotubelike monolayer films wrapping it in a very ordered way. We here systematically analyze low-energy shapes and structural order parameters to elucidate the transitions between the structural phases.

Double-Layer Structured CO2 Adsorbent Functionalized with Modified Polyethyleneimine for High Physical and Chemical Stability.

PubMed

Jeon, Sunbin; Jung, Hyunchul; Kim, Sung Hyun; Lee, Ki Bong

2018-06-18

CO 2 capture using polyethyleneimine (PEI)-impregnated silica adsorbents has been receiving a lot of attention. However, the absence of physical stability (evaporation and leaching of amine) and chemical stability (urea formation) of the PEI-impregnated silica adsorbent has been generally established. Therefore, in this study, a double-layer impregnated structure, developed using modified PEI, is newly proposed to enhance the physical and chemical stabilities of the adsorbent. Epoxy-modified PEI and diepoxide-cross-linked PEI were impregnated via a dry impregnation method in the first and second layers, respectively. The physical stability of the double-layer structured adsorbent was noticeably enhanced when compared to the conventional adsorbents with a single layer. In addition to the enhanced physical stability, the result of simulated temperature swing adsorption cycles revealed that the double-layer structured adsorbent presented a high potential working capacity (3.5 mmol/g) and less urea formation under CO 2 -rich regeneration conditions. The enhanced physical and chemical stabilities as well as the high CO 2 working capacity of the double-layer structured adsorbent were mainly attributed to the second layer consisting of diepoxide-cross-linked PEI.

Towards understanding KOH conditioning of amidoxime-based polymer adsorbents for sequestering uranium from seawater

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

Pan, Horng-Bin; Kuo, Li-Jung; Wood, Jordana

2015-01-01

Conditioning of polymer fiber adsorbents grafted with amidoxime and carboxylic acid groups is necessary to make the materials hydrophilic for sequestering uranium from seawater. Spectroscopic techniques were employed to study the effectiveness of the traditional KOH conditioning method (2.5% KOH at 80 oC) on recently developed high-surface-area amidoxime-based polymer fiber adsorbents developed at Oak Ridge National Laboratory. FTIR spectra reveal that the KOH conditioning process removes the proton from the carboxylic acids and also converts the amidoxime groups to carboxylate groups in the adsorbent. With prolonged KOH treatment (>1 hr) at 80 oC, physical damage to the adsorbent material occursmore » which can lead to a significant reduction in the adsorbent’s uranium adsorption capability in real seawater during extended exposure times (>21 days). The physical damage to the adsorbent can be minimized by lowering KOH conditioning temperature. For the high-surface-area amidoxime-based adsorbents, 20 min of conditioning in 2.5% KOH at 80 oC or 1 hr of conditioning in 2.5% KOH at 60 oC appears sufficient to achieve de-protonation of the carboxylic acid with minimal harmful effects to the adsorbent material. The use of NaOH instead of KOH can also reduce the cost of the base treatment process required for conditioning the amidoxime-based sorbents with minimal loss of adsorption capacity (≤ 7%).« less

Kinetics of protein adsorption/desorption mediated by pH-responsive polymer layer

NASA Astrophysics Data System (ADS)

Su, Xiao-Hang; Lei, Qun-Li; Ren, Chun-Lai

2015-11-01

We propose a new way of regulating protein adsorption by using a pH-responsive polymer. According to the theoretical results obtained from the molecular theory and kinetic approaches, both thermodynamics and kinetics of protein adsorption are verified to be well controlled by the solution pH. The kinetics and the amount of adsorbed proteins at equilibrium are greatly increased when the solution environment changes from acid to neutral. The reason is that the increased pH promotes the dissociation of the weak polyelectrolyte, resulting in more charged monomers and more stretched chains. Thus the steric repulsion within the polymer layer is weakened, which effectively lowers the barrier felt by the protein during the process of adsorption. Interestingly, we also find that the kinetics of protein desorption is almost unchanged with the variation of pH. It is because although the barrier formed by the polymer layer changes along with the change of pH, the potential at contact with the surface varies equally. Our results may provide useful insights into controllable protein adsorption/desorption in practical applications. Project supported by the National Natural Science Foundation of China (Grant Nos. 21274062, 11474155, and 91027040).

Structure and chemical composition of layers adsorbed at interfaces with champagne.

PubMed

Aguié-Béghin, V; Adriaensen, Y; Péron, N; Valade, M; Rouxhet, P; Douillard, R

2009-11-11

The structure and the chemical composition of the layer adsorbed at interfaces involving champagne have been investigated using native champagne, as well as ultrafiltrate (UFch) and ultraconcentrate (UCch) obtained by ultrafiltration with a 10(4) nominal molar mass cutoff. The layer adsorbed at the air/liquid interface was examined by surface tension and ellipsometry kinetic measurements. Brewster angle microscopy demonstrated that the layer formed on polystyrene by adsorption or drop evaporation was heterogeneous, with a domain structure presenting similarities with the layer adsorbed at the air/liquid interface. The surface chemical composition of polystyrene with the adlayer was determined by X-ray photoelectron spectroscopy (XPS). The contribution of champagne constituents varied according to the liquid (native, UFch, and UCch) and to the procedure of adlayer formation (evaporation, adsorption, and adsorption + rinsing). However, their chemical composition was not significantly influenced either by ultrafiltration or by the procedure of deposition on polystyrene. Modeling this composition in terms of classes of model compounds gave approximately 35% (w/w) of proteins and 65% (w/w) of polysaccharides. In the adlayer, the carboxyl groups or esters represent about 18% of carbon due to nonpolypeptidic compounds, indicating the presence of either uronic acids in the complex structure of pectic polysaccharides or of polyphenolic esters. This structural and chemical information and its relationship with the experimental procedures indicate that proteins alone cannot be used as a realistic model for the macromolecules forming the adsorption layer of champagne. Polysaccharides, the other major macromolecular components of champagne wine, are assembled with proteins at the interfaces, in agreement with the heterogeneous character of the adsorbed layer at interfaces.

Pyrocarbons prepared by carbonisation of polymers adsorbed or synthesised on a surface of silica and mixed oxides

NASA Astrophysics Data System (ADS)

Gun'ko, V. M.; Skubiszewska-Zi ęba, J.; Leboda, R.; Voronin, E. F.; Zarko, V. I.; Levitskaya, S. I.; Brei, V. V.; Guzenko, N. V.; Kazakova, O. A.; Seledets, O.; Janusz, W.; Chibowski, S.

2004-04-01

Initial oxides fumed silica, alumina/silica and titania/silica and silica gel and hybrid adsorbents with pyrocarbon formed on these oxide substrates by carbonisation of immobilised (adsorbed or synthesised) polymers such as starch, methyl cellulose, polyvinylpyrrolidone, polystyrene, and polybutylvinyl ether were studied by adsorption, AFM, TEM, and FTIR methods. Polymer/oxide materials were investigated by nitrogen and Pb(II) adsorption, FTIR, and potentiometric titration methods. Analysis of nitrogen adsorption-desorption isotherms by different methods, FTIR spectra, AFM and TEM images of the initial and hybrid adsorbents reveals that the morphology of the substrates significantly changes on carbonisation of oxygen-containing polymers because of hydrothermal treatment of them by water eliminated as a product of pyrolysis. Contribution of own microporosity of pyrocarbon deposits formed on carbonisation of immobilised polymers is greater (dependent on reaction conditions) than that on pyrolysis of low-molecular compounds at the same oxide substrates. Pyrocarbon particles formed on silica gel are larger than those formed on fumed oxides and larger than those formed on silica gel on pyrolysis of low-molecular compounds.

In situ evaluation of density, viscosity, and thickness of adsorbed soft layers by combined surface acoustic wave and surface plasmon resonance.

PubMed

Francis, Laurent A; Friedt, Jean-Michel; Zhou, Cheng; Bertrand, Patrick

2006-06-15

We show the theoretical and experimental combination of acoustic and optical methods for the in situ quantitative evaluation of the density, the viscosity, and the thickness of soft layers adsorbed on chemically tailored metal surfaces. For the highest sensitivity and an operation in liquids, a Love mode surface acoustic wave (SAW) sensor with a hydrophobized gold-coated sensing area is the acoustic method, while surface plasmon resonance (SPR) on the same gold surface as the optical method is monitored simultaneously in a single setup for the real-time and label-free measurement of the parameters of adsorbed soft layers, which means for layers with a predominant viscous behavior. A general mathematical modeling in equivalent viscoelastic transmission lines is presented to determine the correlation between experimental SAW signal shifts and the waveguide structure including the presence of the adsorbed layer and the supporting liquid from which it segregates. A methodology is presented to identify from SAW and SPR simulations the parameters representatives of the soft layer. During the absorption of a soft layer, thickness or viscosity changes are observed in the experimental ratio of the SAW signal attenuation to the SAW signal phase and are correlated with the theoretical model. As application example, the simulation method is applied to study the thermal behavior of physisorbed PNIPAAm, a polymer whose conformation is sensitive to temperature, under a cycling variation of temperature between 20 and 40 degrees C. Under the assumption of the bulk density and the bulk refractive index of PNIPAAm, thickness and viscosity of the film are obtained from simulations; the viscosity is correlated to the solvent content of the physisorbed layer.

Characterization of polymer adsorption onto drug nanoparticles using depletion measurements and small-angle neutron scattering.

PubMed

Goodwin, Daniel J; Sepassi, Shadi; King, Stephen M; Holland, Simon J; Martini, Luigi G; Lawrence, M Jayne

2013-11-04

Production of polymer and/or surfactant-coated crystalline nanoparticles of water-insoluble drugs (nanosuspensions) using wet bead milling is an important formulation approach to improve the bioavailability of said compounds. Despite the fact that there are a number of nanosuspensions on the market, there is still a deficiency in the characterization of these nanoparticles where further understanding may lead to the rational selection of polymer/surfactant. To this end small-angle neutron scattering (SANS) measurements were performed on drug nanoparticles milled in the presence of a range of polymers of varying molecular weight. Isotopic substitution of the aqueous solvent to match the scattering length density of the drug nanoparticles (i.e., the technique of contrast matching) meant that neutron scattering resulted only from the adsorbed polymer layer. The layer thickness and amount of hydroxypropylcellulose adsorbed on nabumetone nanoparticles derived from fitting the SANS data to both model-independent and model dependent volume fraction profiles were insensitive to polymer molecular weight over the range Mv = 47-112 kg/mol, indicating that the adsorbed layer is relatively flat but with tails extending up to approximately 23 nm. The constancy of the absorbed amount is in agreement with the adsorption isotherm determined by measuring polymer depletion from solution in the presence of the nanoparticles. Insensitivity to polymer molecular weight was similarly determined using SANS measurements of nabumetone or halofantrine nanoparticles stabilized with hydroxypropylmethylcellulose or poly(vinylpyrrolidone). Additionally SANS studies revealed the amount adsorbed, and the thickness of the polymer layer was dependent on both the nature of the polymer and drug particle surface. The insensitivity of the adsorbed polymer layer to polymer molecular weight has important implications for the production of nanoparticles, suggesting that lower molecular weight polymers

Self-interacting polymer chains terminally anchored to adsorbing surfaces of three-dimensional fractal lattices

NASA Astrophysics Data System (ADS)

Živić, I.; Elezović-Hadžić, S.; Milošević, S.

2018-01-01

We have studied the adsorption problem of self-attracting linear polymers, modeled by self-avoiding walks (SAWs), situated on three-dimensional fractal structures, exemplified by 3d Sierpinski gasket (SG) family of fractals as containers of a poor solvent. Members of SG family are enumerated by an integer b (b ≥ 2), and it is assumed that one side of each SG fractal is an impenetrable adsorbing surface. We calculate the critical exponents γ1 ,γ11, and γs, which are related to the numbers of all possible SAWs with one, both, and no ends anchored to the adsorbing boundary, respectively. By applying the exact renormalization group (RG) method (for the first three members of the SG fractal family, b = 2 , 3, and 4), we have obtained specific values of these exponents, for θ-chain and globular polymer phase. We discuss their mutual relations and relations with corresponding values pertinent to extended polymer chain phase.

Patterned layers of adsorbed extracellular matrix proteins: influence on mammalian cell adhesion.

PubMed

Dupont-Gillain, C C; Alaerts, J A; Dewez, J L; Rouxhet, P G

2004-01-01

Three patterned systems aiming at the control of mammalian cell behavior are presented. The determinant feature common to these systems is the spatial distribution of extracellular matrix (ECM) proteins (mainly collagen) on polymer substrates. This distribution differs from one system to another with respect to the scale at which it is affected, from the supracellular to the supramolecular scale, and with respect to the way it is produced. In the first system, the surface of polystyrene was oxidized selectively to form micrometer-scale patterns, using photolithography. Adsorption of ECM proteins in presence of a competitor was enhanced on the oxidized domains, allowing selective cell adhesion to be achieved. In the second system, electron beam lithography was used to engrave grooves (depth and width approximately 1 microm) on a poly(methyl methacrylate) (PMMA) substratum. No modification of the surface chemistry associated to the created topography could be detected. Cell orientation along the grooves was only observed when collagen was preadsorbed on the substratum. In the third system, collagen adsorbed on PMMA was dried in conditions ensuring the formation of a nanometer-scale pattern. Cell adhesion was enhanced on such patterned collagen layers compared to smooth collagen layers.

Layered plasma polymer composite membranes

DOEpatents

Babcock, Walter C.

1994-01-01

Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is .gtoreq.2 and is the number of selective layers.

Layered plasma polymer composite membranes

DOEpatents

Babcock, W.C.

1994-10-11

Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is [>=]2 and is the number of selective layers. 2 figs.

Electrokinetic flow in a capillary with a charge-regulating surface polymer layer.

PubMed

Keh, Huan J; Ding, Jau M

2003-07-15

An analytical study of the steady electrokinetic flow in a long uniform capillary tube or slit is presented. The inside wall of the capillary is covered by a layer of adsorbed or covalently bound charge-regulating polymer in equilibrium with the ambient electrolyte solution. In this solvent-permeable and ion-penetrable surface polyelectrolyte layer, ionogenic functional groups and frictional segments are assumed to distribute at uniform densities. The electrical potential and space charge density distributions in the cross section of the capillary are obtained by solving the linearized Poisson-Boltzmann equation. The fluid velocity profile due to the application of an electric field and a pressure gradient through the capillary is obtained from the analytical solution of a modified Navier-Stokes/Brinkman equation. Explicit formulas for the electroosmotic velocity, the average fluid velocity and electric current density on the cross section, and the streaming potential in the capillary are also derived. The results demonstrate that the direction of the electroosmotic flow and the magnitudes of the fluid velocity and electric current density are dominated by the fixed charge density inside the surface polymer layer, which is determined by the regulation characteristics such as the dissociation equilibrium constants of the ionogenic functional groups in the surface layer and the concentration of the potential-determining ions in the bulk solution.

Effects of supercritical carbon dioxide on immobile bound polymer chains on solid substrates

NASA Astrophysics Data System (ADS)

Sen, Mani; Asada, Mitsunori; Jiang, Naisheng; Endoh, Maya K.; Akgun, Bulent; Satija, Sushil; Koga, Tadanori

2013-03-01

Adsorbed polymer layers formed on flat solid substrates have recently been the subject of extensive studies because it is postulated to control the dynamics of technologically relevant polymer thin films, for example, in lithography. Such adsorbed layers have been reported to hinder the mobility of polymer chains in thin films even at a large length scale. Consequently, this bound layer remains immobile regardless of processing techniques (i.e. thermal annealing, solvent dissolution, etc). Here, we investigate the use of supercritical carbon dioxide (scCO2) as a novel plasticizer for bound polystyrene layers formed on silicon substrates. In-situ swelling and interdiffusion experiments using neutron reflectivity were performed. As a result, we found the anomalous plasticization effects of scCO2 on the bound polymer layers near the critical point where the anomalous adsorption of CO2 molecules in polymer thin films has been reported previously. Acknowledgement: We acknowledge the financial support from NSF Grant No. CMMI-084626.

Bicarbonate Elution of Uranium from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

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

Pan, Horng-Bin; Wai, Chien M.; Kuo, Li-Jung

Uranium adsorbed on amidoxime-based polyethylene fibers in simulated seawater can be quantitatively eluted using 3 M KHCO3 at 40°C. Thermodynamic calculations are in agreement with the experimental observation that at high bicarbonate concentrations (3 M) uranyl ions bound to amidoxime molecules are converted to uranyl tris-carbonato complex in the aqueous solution. The elution process is basically the reverse reaction of the uranium adsorption process which occurs at a very low bicarbonate concentration (~10-3 M) in seawater. In real seawater experiments, the bicarbonate elution is followed by a NaOH treatment to remove natural organic matter adsorbed on the polymer adsorbent. Usingmore » the sequential bicarbonate and NaOH elution, the adsorbent is reusable after rinsing with deionized water and the recycled adsorbent shows no loss of uranium loading capacity based on real seawater experiments.« less

Bicarbonate Elution of Uranium from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

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

Pan, Horng-Bin; Wai, Chien M.; Kuo, Li-Jung

Uranium adsorbed on amidoxime-based polyethylene fibers in simulated seawater can be quantitatively eluted using 3 M KHCO 3 at 40°C. Thermodynamic calculations are in agreement with the experimental observation that at high bicarbonate concentrations (3 M) uranyl ions bound to amidoxime molecules are converted to uranyl tris-carbonato complex in the aqueous solution. The elution process is basically the reverse reaction of the uranium adsorption process which occurs at a very low bicarbonate concentration (~10 -3 M) in seawater. The bicarbonate elution is followed by a NaOH treatment to remove natural organic matter adsorbed on the polymer adsorbent, in real seawatermore » experiments. Furthermore, by using the sequential bicarbonate and NaOH elution, the adsorbent is reusable after rinsing with deionized water and the recycled adsorbent shows no loss of uranium loading capacity based on real seawater experiments.« less

Bicarbonate Elution of Uranium from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

DOE PAGES

Pan, Horng-Bin; Wai, Chien M.; Kuo, Li-Jung; ...

2017-05-02

Uranium adsorbed on amidoxime-based polyethylene fibers in simulated seawater can be quantitatively eluted using 3 M KHCO 3 at 40°C. Thermodynamic calculations are in agreement with the experimental observation that at high bicarbonate concentrations (3 M) uranyl ions bound to amidoxime molecules are converted to uranyl tris-carbonato complex in the aqueous solution. The elution process is basically the reverse reaction of the uranium adsorption process which occurs at a very low bicarbonate concentration (~10 -3 M) in seawater. The bicarbonate elution is followed by a NaOH treatment to remove natural organic matter adsorbed on the polymer adsorbent, in real seawatermore » experiments. Furthermore, by using the sequential bicarbonate and NaOH elution, the adsorbent is reusable after rinsing with deionized water and the recycled adsorbent shows no loss of uranium loading capacity based on real seawater experiments.« less

Interplay of polyelectrolytes with different adsorbing surfaces

NASA Astrophysics Data System (ADS)

Xie, Feng

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

Polymer Layered Silicate Nanocomposites: A Review

PubMed Central

Mittal, Vikas

2009-01-01

This review aims to present recent advances in the synthesis and structure characterization as well as the properties of polymer layered silicate nanocomposites. The advent of polymer layered silicate nanocomposites has revolutionized research into polymer composite materials. Nanocomposites are organic-inorganic hybrid materials in which at least one dimension of the filler is less than 100 nm. A number of synthesis routes have been developed in the recent years to prepare these materials, which include intercalation of polymers or pre-polymers from solution, in-situ polymerization, melt intercalation etc. The nanocomposites where the filler platelets can be dispersed in the polymer at the nanometer scale owing to the specific filler surface modifications, exhibit significant improvement in the composite properties, which include enhanced mechanical strength, gas barrier, thermal stability, flame retardancy etc. Only a small amount of filler is generally required for the enhancement in the properties, which helps the composite materials retain transparency and low density.

Isotherm modeling of organic activated bentonite and humic acid polymer used as mycotoxin adsorbents.

PubMed

Santos, R R; Vermeulen, S; Haritova, A; Fink-Gremmels, J

2011-11-01

The aim of the current study was to evaluate and compare two representative samples of different classes of adsorbents intended for use as feed additives in the prevention or reduction of the adverse effects exerted by mycotoxins, specifically ochratoxin A (OTA) and zearalenone (ZEN). The adsorbents, an organically activated bentonite (OAB) and a humic acid polymer (HAP), were tested in a common in vitro model with a pH course comparing the maximum pH changes that can be expected in the digestive system of a monogastric animal, i.e. pH 7.4 for the oral cavity, pH 3.0 for the stomach, and pH 8.4 for the intestines. In the first experiment, the concentration-dependent adsorbent capacity of OAB and HAB were tested using a fixed concentration of either mycotoxin. Thereafter, adsorption was evaluated applying different isotherms models, such as Freundlich, Langmuir, Brunauer-Emmett-Teller (BET) and Redlich-Peterson, to characterize the adsorption process as being either homo- or heterogeneous and representing either mono- or multilayer binding. At the recommended statutory level for the mycotoxins of 0.1 mg kg(-1) OTA and 0.5 mg kg(-1) ZEN, OAB showed an adsorbed capacity of >96% towards both mycotoxins, regardless of the pH. The HAP product was also able to absorb >96% of both mycotoxins at pH 3.0, but extensive desorption occurred at pH 8.4. Based on χ-square (χ(2)) values, Langmuir and Redlich-Peterson equations proved to be the best models to predict monolayer equilibrium sorption of OTA and ZEN onto the organically activated bentonite and the humic acid polymer. The applied methodology has a sufficient robustness to facilitate further comparative studies with different mycotoxin-adsorbing agents.

Influence of Irreversible Adsorption on the Glass Transition Temperature of Polymer Thin Films as Measured by Fluorescence

NASA Astrophysics Data System (ADS)

Burroughs, Mary; Priestley, Rodney

2014-03-01

Polymers confined to the nanometer length scale have been shown to exhibit deviations in the glass transition temperature (Tg) from the bulk. With the increasing use of confined polymers in nanotechnology, understanding and predicting this behavior is extremely relevant to industries ranging from pharmaceuticals to organic electronics. Recent work (Napolitano, Wübbenhorst, Nature Communications, 2, 260 (2011)) has connected deviations in Tg under confinement with irreversible physical adsorption of polymer chains at substrate interfaces. Here we investigate the influence of irreversibly adsorbed layers on the Tg of polystyrene (PS) thin films supported on silica via fluorescence. We examine the Tg of the brushes as a function of annealing time and irreversibly adsorbed layer thickness. By incorporating fluorescently labeled polymer layers into multilayered films of unlabeled polymer, we will examine the influence of brushes on adjacent layers dynamics. Finally, we will compare the results on PS with those of poly(methyl methacrylate).

Influence of hydrophilic groups and metal-ion adsorption on polymer-chain conformation of amidoxime-based uranium adsorbents

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

Wiechert, Alexander I.; Liao, Wei-Po; Hong, Eunice K.

In this study, we focus on the influence of hydrophilic groups and metal-ion loading on adsorbent polymer conformation, which controls access to adsorption sites and may limit adsorption capacity. Gaining a better understanding of the factors that influence conformation may yield higher-capacity adsorbents. Polyamidoxime (PAO), deuterated-PAO polyacrylic acid diblock copolymers (d-PAO-b-PAA), and randomly configured copolymers (PAO-co-PAA) were synthesized and characterized by neutron reflectometry in air and D 2O. For d-PAO-b-PAA, characterization was also performed after alkali conditioning and in simulated seawater. PAO and PAO-co-PAA, with similar molecular weight and grafting density, extended from 95-Å thickness in air to 180 andmore » 280-Å in D 2O, respectively. This result suggests that polymer swelling may cause the additional adsorption capacity observed when polymer hydrophilicity increases. Two d-PAO-b-PAA samples, A and B, with a d-PAO thickness of 55-Å swelled to 110-Å and 140-Å, respectively, with an overall thickness increase of ~160% in D 2O. After alkali conditioning, molecular interactions increased the density of PAA near the PAO-PAA interface, while the d-PAO thickness only decreased by ~10 Å. The d-PAO thickness of both samples declined to ~90-Å after adsorption in simulated seawater due to polymer-chain crosslinking. In conclusion, these results are expected to aid in improving adsorbent synthesis to increase uranium capacity.« less

Influence of hydrophilic groups and metal-ion adsorption on polymer-chain conformation of amidoxime-based uranium adsorbents

DOE PAGES

Wiechert, Alexander I.; Liao, Wei-Po; Hong, Eunice K.; ...

2018-04-06

In this study, we focus on the influence of hydrophilic groups and metal-ion loading on adsorbent polymer conformation, which controls access to adsorption sites and may limit adsorption capacity. Gaining a better understanding of the factors that influence conformation may yield higher-capacity adsorbents. Polyamidoxime (PAO), deuterated-PAO polyacrylic acid diblock copolymers (d-PAO-b-PAA), and randomly configured copolymers (PAO-co-PAA) were synthesized and characterized by neutron reflectometry in air and D 2O. For d-PAO-b-PAA, characterization was also performed after alkali conditioning and in simulated seawater. PAO and PAO-co-PAA, with similar molecular weight and grafting density, extended from 95-Å thickness in air to 180 andmore » 280-Å in D 2O, respectively. This result suggests that polymer swelling may cause the additional adsorption capacity observed when polymer hydrophilicity increases. Two d-PAO-b-PAA samples, A and B, with a d-PAO thickness of 55-Å swelled to 110-Å and 140-Å, respectively, with an overall thickness increase of ~160% in D 2O. After alkali conditioning, molecular interactions increased the density of PAA near the PAO-PAA interface, while the d-PAO thickness only decreased by ~10 Å. The d-PAO thickness of both samples declined to ~90-Å after adsorption in simulated seawater due to polymer-chain crosslinking. In conclusion, these results are expected to aid in improving adsorbent synthesis to increase uranium capacity.« less

Molecular Insights into the pH-Dependent Adsorption and Removal of Ionizable Antibiotic Oxytetracycline by Adsorbent Cyclodextrin Polymers

PubMed Central

Zhang, Yu; Cai, Xiyun; Xiong, Weina; Jiang, Hao; Zhao, Haitong; Yang, Xianhai; Li, Chao; Fu, Zhiqiang; Chen, Jingwen

2014-01-01

Effects of pH on adsorption and removal efficiency of ionizable organic compounds (IOCs) by environmental adsorbents are an area of debate, because of its dual mediation towards adsorbents and adsorbate. Here, we probe the pH-dependent adsorption of ionizable antibiotic oxytetracycline (comprising OTCH2 +, OTCH±, OTC−, and OTC2−) onto cyclodextrin polymers (CDPs) with the nature of molecular recognition and pH inertness. OTCH± commonly has high adsorption affinity, OTC− exhibits moderate affinity, and the other two species have negligible affinity. These species are evidenced to selectively interact with structural units (e.g., CD cavity, pore channel, and network) of the polymers and thus immobilized onto the adsorbents to different extents. The differences in adsorption affinity and mechanisms of the species account for the pH-dependent adsorption of OTC. The mathematical equations are derived from the multiple linear regression (MLR) analysis of quantitatively relating adsorption affinity of OTC at varying pH to adsorbent properties. A combination of the MLR analysis for OTC and molecular recognition of adsorption of the species illustrates the nature of the pH-dependent adsorption of OTC. Based on this finding, γ-HP-CDP is chosen to adsorb and remove OTC at pH 5.0 and 7.0, showing high removal efficiency and strong resistance to the interference of coexisting components. PMID:24465975

Versatile Poly(Diallyl Dimethyl Ammonium Chloride)-Layered Nanocomposites for Removal of Cesium in Water Purification.

PubMed

Jang, Sung-Chan; Kang, Sung-Min; Kim, Gi Yong; Rethinasabapathy, Muruganantham; Haldorai, Yuvaraj; Lee, Ilsong; Han, Young-Kyu; Renshaw, Joanna C; Roh, Changhyun; Huh, Yun Suk

2018-06-12

In this work, we elucidate polymer-layered hollow Prussian blue-coated magnetic nanocomposites as an adsorbent to remove radioactive cesium from environmentally contaminated water. To do this, Fe₃O₄ nanoparticles prepared using a coprecipitation method were thickly covered with a layer of cationic polymer to attach hollow Prussian blue through a self-assembly process. The as-synthesized adsorbent was confirmed through various analytical techniques. The adsorbent showed a high surface area (166.16 m²/g) with an excellent cesium adsorbent capacity and removal efficiency of 32.8 mg/g and 99.69%, respectively. Moreover, the superparamagnetism allows effective recovery of the adsorbent using an external magnetic field after the adsorption process. Therefore, the magnetic adsorbent with a high adsorption efficiency and convenient recovery is expected to be effectively used for rapid remediation of radioactive contamination.

Bioorthogonal layer-by-layer encapsulation of pancreatic islets via hyperbranched polymers

PubMed Central

Gattás-Asfura, Kerim M.; Stabler, Cherie L.

2013-01-01

The encapsulation of viable tissues via layer-by-layer polymer assembly provides a versatile platform for cell surface engineering, with nanoscale control over capsule properties. Herein, we report the development of a hyperbranched polymer-based, ultrathin capsule architecture expressing bioorthogonal functionality and tailored physiochemical properties. Random carbodiimide-based condensation of 3,5-dicarboxyphenyl glycineamide on alginate yielded a highly branched polysaccharide with multiple, spatially restricted, and readily functionalizable terminal carboxylate moieties. Poly(ethylene glycol) (PEG) was utilized to link azido end groups to the structured alginate. Together with phosphine functionalized poly(amido amine) (PAMAM) dendrimer, nanoscale layer-by-layer coatings, covalently stabilized via Staudinger ligation, were assembled onto solid surfaces and pancreatic islets. The effects of electrostatic and/or bioorthogonal covalent interlayer interactions on the resulting coating efficiency and stability, as well as pancreatic islet viability and function, were studied. These hyperbranched polymers provide a flexible platform for the formation of covalently stabilized ultrathin coatings on viable cells and tissues. In addition, the hyperbranched nature of the polymers presents a highly functionalized surface capable of bioorthogonal conjugation of additional bioactive or labeling motifs. PMID:24063764

Viscoelastic properties of cationic starch adsorbed on quartz studied by QCM-D.

PubMed

Tammelin, Tekla; Merta, Juha; Johansson, Leena-Sisko; Stenius, Per

2004-12-07

The adsorption and viscoelastic properties of layers of a cationic polyelectrolyte (cationic starch, CS, with 2-hydroxy-3-trimethylammoniumchloride as the substituent) adsorbed from aqueous solutions (pH 7.5, added NaCl 0, 1, 100, and 500 mM) on silica were studied with a quartz crystal microbalance with dissipation (QCM-D). Three different starches were investigated (weight-average molecular weights M(w) approximately 8.7 x 10(5) and 4.5 x 10(5) with degree of substitution DS = 0.75 and M(w) approximately 8.8 x 10(5) with DS = 0.2). At low ionic strength, the adsorbed layers are thin and rigid and the amount adsorbed can be calculated using the Sauerbrey equation. When the ionic strength is increased, significant changes take place in the amount of adsorbed CS and the viscoelasticity of the adsorbed layer. These changes were analyzed assuming that the layer can be described as a Voigt element on a rigid surface in contact with purely viscous solvent. It was found that CS with low charge density forms a thicker and more mobile layer with higher viscosity and elasticity than CS with high charge density. The polymers adsorbed on the silica even when the ionic strength was so high that electrostatic interactions were effectively screened. At this high ionic strength, it was possible to study the effect of molecular weight and molecular weight distribution of the CS on the properties of the adsorbed film. Increasing the molecular weight of CS resulted in a larger hydrodynamic thickness. CS with a narrow molecular weight distribution formed a more compact and rigid layer than broadly distributed CS, presumably due to the better packing of the molecules.

Synthesis, Development, and Testing of High-Surface-Area Polymer-Based Adsorbents for the Selective Recovery of Uranium from Seawater

DOE PAGES

Oyola, Yatsandra; Janke, Christopher J.; Dai, Sheng

2016-02-29

The ocean contains uranium with an approximate concentration of 3.34 ppb, which can serve as an incredible supply source to sustain nuclear energy in the United States. Unfortunately, technology currently available to recover uranium from seawater is not efficient enough and mining uranium on land is still more economical. For this study, we have developed polymer-based adsorbents with high uranium adsorption capacities by grafting amidoxime onto high-surface-area polyethylene (PE) fibers. Various process conditions have been screened, in combination with developing a rapid testing protocol (<24 h), to optimize the process. These adsorbents are synthesized through radiation-induced grafting of acrylonitrile (AN)more » and methacrylic acid (MAA) onto PE fibers, followed by the conversion of nitriles to amidoximes and basic conditioning. In addition, the uranium adsorption capacity, measured in units of g U/kg ads, is greatly increased by reducing the diameter of the PE fiber or changing its morphology. An increase in the surface area of the PE polymer fiber allows for more grafting sites that are positioned in more-accessible locations, thereby increasing access to grafted molecules that would normally be located in the interior of a fiber with a larger diameter. Polymer fibers with hollow morphologies are able to adsorb beyond 1 order of magnitude more uranium from simulated seawater than current commercially available adsorbents. Finally, several high-surface-area fibers were tested in natural seawater and were able to extract 5–7 times more uranium than any adsorbent reported to date.« less

A molecular model for cohesive slip at polymer melt/solid interfaces.

PubMed

Tchesnokov, M A; Molenaar, J; Slot, J J M; Stepanyan, R

2005-06-01

A molecular model is proposed which predicts wall slip by disentanglement of polymer chains adsorbed on a wall from those in the polymer bulk. The dynamics of the near-wall boundary layer is found to be governed by a nonlinear equation of motion, which accounts for such mechanisms on surface chains as convection, retraction, constraint release, and thermal fluctuations. This equation is valid over a wide range of grafting regimes, including those in which interactions between neighboring adsorbed molecules become essential. It is not closed since the dynamics of adsorbed chains is shown to be coupled to that of polymer chains in the bulk via constraint release. The constitutive equations for the layer and bulk, together with continuity of stress and velocity, are found to form a closed system of equations which governs the dynamics of the whole "bulk+boundary layer" ensemble. Its solution provides a stick-slip law in terms of the molecular parameters and extruder geometry. The model is quantitative and contains only those parameters that can be measured directly, or extracted from independent rheological measurements. The model predictions show a good agreement with available experimental data.

Adsorbed Layers of Ferritin at Solid and Fluid Interfaces Studied by Atomic Force Microscopy.

PubMed

Johnson; Yuan; Lenhoff

2000-03-15

The adsorption of the iron storage protein ferritin was studied by liquid tapping mode atomic force microscopy in order to obtain molecular resolution in the adsorbed layer within the aqueous environment in which the adsorption was carried out. The surface coverage and the structure of the adsorbed layer were investigated as functions of ionic strength and pH on two different charged surfaces, namely chemically modified glass slides and mixed surfactant films at the air-water interface, which were transferred to graphite substrates after adsorption. Surface coverage trends with both ionic strength and pH indicate the dominance of electrostatic effects, with the balance shifting between intermolecular repulsion and protein-surface attraction. The resulting behavior is more complex than that seen for larger colloidal particles, which appear to follow a modified random sequential adsorption model monotonically. The structure of the adsorbed layers at the solid surfaces is random, but some indication of long-range order is apparent at fluid interfaces, presumably due to the higher protein mobility at the fluid interface. Copyright 2000 Academic Press.

Sorption of organic molecules on surfaces of a microporous polymer adsorbent modified with different quantities of uracil

NASA Astrophysics Data System (ADS)

Gus'kov, V. Yu.; Ganieva, A. G.; Kudasheva, F. Kh.

2016-11-01

The sorption of organic molecules on the surfaces of a number of adsorbents based on a microporous copolymer of styrene and divinylbenzene modified with different quantities of uracil is studied by means of inverse gas chromatography at infinite dilution. Samples containing 10-6, 10-5, 10-4, 10-3, 10-2, and 0.5 × 10‒1 weight parts of uracil (the pC of uracil ranges from 1.3 to 6) are studied. The contributions from different intermolecular interactions to the Helmholtz energy of sorption are calculated via the linear free energy relationship. It is found that as the concentration of uracil on the surface of the polymer adsorbent grows, the contributions from different intermolecular interactions and the conventional polarity of the surface have a bend at pC = 3, due probably to the formation of a supramolecular structure of uracil. Based on the obtained results, it is concluded that the formation of the supramolecular structure of uracil on the surface of the polymer adsorbent starts when pC < 3.

Adsorption and structure of the adsorbed layer of ionic surfactants.

PubMed

Ivanov, Ivan B; Ananthapadmanabhan, Kavssery P; Lips, Alex

2006-11-16

Our goal in this study was to investigate theoretically and experimentally the adsorption of ionic surfactants and the role of different factors in the mechanism of adsorption, the adsorption parameters and the structure of the adsorbed layer. We used available literature data for the interfacial tension, sigma, vs. concentration, C(s), for sodium dodecyl sulfate (SDS) in three representative systems with Air/Water (A/W), Oil/Water (O/W) and Oil/Water + 0.1 M NaCl (O/WE) interfaces. We derived 6 new adsorption isotherms and 6 new equations of state (EOS) based on the adsorption isotherms for non-ionic surfactants of Langmuir, Volmer and Helfand-Frisch-Lebowitz (HFL) with interaction term betatheta2/2 in the EOS, theta=alphaGamma being the degree of coverage, with Gamma--adsorption and alpha--minimum area per molecule. We applied Gouy equation for high surface potentials and modified it to account for partial penetration of the counterions in the adsorbed layer. The equations were written in terms of the effective concentration C=[C(s)(C(s)+C(el))](1/2), where C(s) and C(el) are, respectively concentrations of the surfactant and the electrolyte. We showed that the adsorption constant K was model independent and derived an equation for the effective thickness of the adsorbed layer, delta(s). We found also that the minimum area per molecule, alpha, is larger than the true area, alpha(0), which depends on the adsorption model and is a function of the adsorption Gamma. The interaction term betatheta2/2 in the Langmuir EOS was found to be exact for small beta<1, but for the Volmer EOS it turned out to be only a crude approximation. Semi-quantitative considerations about the interaction between adsorbed discrete charges revealed that at A/W interface part of the adsorbed surfactant molecules are partially immersed in water, which leads to decreased repulsion and increased adsorption Gamma. At O/W the larger adsorption energy keeps the surfactant molecules on the surface

Kinetic Assembly of Near-IR Active Gold Nanoclusters using Weakly Adsorbing Polymers to Control Size

PubMed Central

Tam, Jasmine M.; Murthy, Avinash K.; Ingram, Davis R.; Nguyen, Robin; Sokolov, Konstantin V.; Johnston, Keith P.

2013-01-01

Clusters of metal nanoparticles with an overall size less than 100 nm and high metal loadings for strong optical functionality, are of interest in various fields including microelectronics, sensors, optoelectronics and biomedical imaging and therapeutics. Herein we assemble ~5 nm gold particles into clusters with controlled size, as small as 30 nm and up to 100 nm, which contain only small amounts of polymeric stabilizers. The assembly is kinetically controlled with weakly adsorbing polymers, PLA(2K)-b-PEG(10K)-b-PLA(2K) or PEG (MW = 3350), by manipulating electrostatic, van der Waals (VDW), steric, and depletion forces. The cluster size and optical properties are tuned as a function of particle volume fractions and polymer/gold ratios to modulate the interparticle interactions. The close spacing between the constituent gold nanoparticles and high gold loadings (80–85% w/w gold) produce a strong absorbance cross section of ~9×10−15 m2 in the NIR at 700 nm. This morphology results from VDW and depletion attractive interactions that exclude the weakly adsorbed polymeric stabilizer from the cluster interior. The generality of this kinetic assembly platform is demonstrated for gold nanoparticles with a range of surface charges from highly negative to neutral, with the two different polymers. PMID:20361735

Evolution of carboxymethyl cellulose layer morphology on hydrophobic mineral surfaces: variation of polymer concentration and ionic strength.

PubMed

Beaussart, Audrey; Mierczynska-Vasilev, Agnieszka; Beattie, David A

2010-06-15

The adsorption of carboxymethyl cellulose (CMC) on the basal planes of talc and molybdenite has been studied using in situ atomic force microscope (AFM) imaging. These experiments were partnered with quantitative adsorption isotherm determinations on particulate samples. The isotherms revealed a clear increase of the CMC adsorbed amount upon increasing the solution ionic strength for adsorption on both minerals. In addition, the shapes of the isotherms changed in response to the change in the electrolyte concentration, with CMC on talc displaying stepped (10(-3) M KCl), Langmuir (10(-2) M KCl), then Freundlich isotherm shapes (10(-1) M KCl), and CMC on molybdenite displaying stepped (10(-3) M KCl), Freundlich (10(-2) M KCl), then Langmuir isotherm shapes (10(-1) M KCl). AFM imaging of the polymer layer on the mineral surfaces with varying solution conditions mirrored and confirmed the conclusions from the isotherms: as the polymer solution concentration increased, coverage on the basal plane increased; as the ionic strength increased, coverage on the basal plane increased and the morphology of the layer changed from isolated well-distributed polymer domains to extensive adsorption and formation of dense, uneven polymer domains/features. In addition, comparison of the talc and molybdenite datasets points toward the presence of different binding mechanisms for CMC adsorption on the talc and molybdenite basal plane surfaces. 2010 Elsevier Inc. All rights reserved.

Tribochemical synthesis of nano-lubricant films from adsorbed molecules at sliding solid interface: Tribo-polymers from α-pinene, pinane, and n-decane

NASA Astrophysics Data System (ADS)

He, Xin; Barthel, Anthony J.; Kim, Seong H.

2016-06-01

The mechanochemical reactions of adsorbed molecules at sliding interfaces were studied for α-pinene (C10H16), pinane (C10H18), and n-decane (C10H22) on a stainless steel substrate surface. During vapor phase lubrication, molecules adsorbed at the sliding interface could be activated by mechanical shear. Under the equilibrium adsorption condition of these molecules, the friction coefficient of sliding steel surfaces was about 0.2 and a polymeric film was tribochemically produced. The synthesis yield of α-pinene tribo-polymers was about twice as much as pinane tribo-polymers. In contrast to these strained bicyclic hydrocarbons, n-decane showed much weaker activity for tribo-polymerization at the same mechanical shear condition. These results suggested that the mechanical shear at tribological interfaces could induce the opening of the strained ring structure of α-pinene and pinane, which leads to polymerization of adsorbed molecules at the sliding track. On a stainless steel surface, such polymerization reactions of adsorbed molecules do not occur under typical surface reaction conditions. The mechanical properties and boundary lubrication efficiency of the produced tribo-polymer films are discussed.

The role of adsorbed water on the friction of a layer of submicron particles

USGS Publications Warehouse

Sammis, Charles G.; Lockner, David A.; Reches, Ze’ev

2011-01-01

Anomalously low values of friction observed in layers of submicron particles deformed in simple shear at high slip velocities are explained as the consequence of a one nanometer thick layer of water adsorbed on the particles. The observed transition from normal friction with an apparent coefficient near μ = 0.6 at low slip speeds to a coefficient near μ = 0.3 at higher slip speeds is attributed to competition between the time required to extrude the water layer from between neighboring particles in a force chain and the average lifetime of the chain. At low slip speeds the time required for extrusion is less than the average lifetime of a chain so the particles make contact and lock. As slip speed increases, the average lifetime of a chain decreases until it is less than the extrusion time and the particles in a force chain never come into direct contact. If the adsorbed water layer enables the otherwise rough particles to rotate, the coefficient of friction will drop to μ = 0.3, appropriate for rotating spheres. At the highest slip speeds particle temperatures rise above 100°C, the water layer vaporizes, the particles contact and lock, and the coefficient of friction rises to μ = 0.6. The observed onset of weakening at slip speeds near 0.001 m/s is consistent with the measured viscosity of a 1 nm thick layer of adsorbed water, with a minimum particle radius of approximately 20 nm, and with reasonable assumptions about the distribution of force chains guided by experimental observation. The reduction of friction and the range of velocities over which it occurs decrease with increasing normal stress, as predicted by the model. Moreover, the analysis predicts that this high-speed weakening mechanism should operate only for particles with radii smaller than approximately 1 μm. For larger particles the slip speed required for weakening is so large that frictional heating will evaporate the adsorbed water and weakening will not occur.

Ordering nanoparticles with polymer brushes

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

Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a singlemore » layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. As a result, an interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.« less

Ordering nanoparticles with polymer brushes

NASA Astrophysics Data System (ADS)

Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

2017-12-01

Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a single layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. An interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.

Ordering nanoparticles with polymer brushes

DOE PAGES

Cheng, Shengfeng; Stevens, Mark J.; Grest, Gary S.

2017-12-08

Ordering nanoparticles into a desired super-structure is often crucial for their technological applications. We use molecular dynamics simulations to study the assembly of nanoparticles in a polymer brush randomly grafted to a planar surface as the solvent evaporates. Initially, the nanoparticles are dispersed in a solvent that wets the polymer brush. After the solvent evaporates, the nanoparticles are either inside the brush or adsorbed at the surface of the brush, depending on the strength of the nanoparticle-polymer interaction. For strong nanoparticle-polymer interactions, a 2-dimensional ordered array is only formed when the brush density is finely tuned to accommodate a singlemore » layer of nanoparticles. When the brush density is higher or lower than this optimal value, the distribution of nanoparticles shows large fluctuations in space and the packing order diminishes. For weak nanoparticle-polymer interactions, the nanoparticles order into a hexagonal array on top of the polymer brush as long as the grafting density is high enough to yield a dense brush. As a result, an interesting healing effect is observed for a low-grafting-density polymer brush that can become more uniform in the presence of weakly adsorbed nanoparticles.« less

Adsorption and flocculation by polymers and polymer mixtures.

PubMed

Gregory, John; Barany, Sandor

2011-11-14

Polymers of various types are in widespread use as flocculants in several industries. In most cases, polymer adsorption is an essential prerequisite for flocculation and kinetic aspects are very important. The rates of polymer adsorption and of re-conformation (relaxation) of adsorbed chains are key factors that influence the performance of flocculants and their mode of action. Polyelectrolytes often tend to adopt a rather flat adsorbed configuration and in this state their action is mainly through charge effects, including 'electrostatic patch' attraction. When the relaxation rate is quite low, particle collisions may occur while the adsorbed chains are still in an extended state and flocculation by polymer bridging may occur. These effects are now well understood and supported by much experimental evidence. In recent years there has been considerable interest in the use of multi-component flocculants, especially dual-polymer systems. In the latter case, there can be significant advantages over the use of single polymers. Despite some complications, there is a broad understanding of the action of dual polymer systems. In many cases the sequence of addition of the polymers is important and the pre-adsorbed polymer can have two important effects: providing adsorption sites for the second polymer or causing a more extended adsorbed conformation as a result of 'site blocking'. Copyright © 2011 Elsevier B.V. All rights reserved.

Self-Organization of Polymer Brush Layers in a Poor Solvent

NASA Astrophysics Data System (ADS)

Karim, A.; Tsukruk, V. V.; Douglas, J. F.; Satija, S. K.; Fetters, L. J.; Reneker, D. H.; Foster, M. D.

1995-10-01

Synthesis of densely grafted polymer brushes from good solvent polymer solutions is difficult when the surface interaction is only weakly attractive because of the strong steric repulsion between the polymer chains. To circumvent this difficulty we graft polymer layers in a poor solvent to exploit attractive polymer-polymer interactions which largely nullify the repulsive steric interactions. This simple strategy gives rise to densely grafted and homogeneous polymer brush layers. Model end-grafted polystyrene chains (M_w = 105,000) are prepared in the poor solvent cyclohexane (9.5 °C) where the chains are chemically attached to the surface utilizing a trichlorosilane end-group. Polished silicon wafers were then exposed to the reactive polymer solutions for a series of “induction times” tau_I and the evolving layer was characterized by X-ray reflectivity and atomic force microscopy. Distinct morphologies were found depending on tau_I. For short tau_I, corresponding to a grafting density less than 5 mg/m^2, the grafted layer forms an inhomogeneous island-like structure. At intermediate tau_I, where the coverage becomes percolating, a surface pattern develops which appears similar to spinodal decomposition in bulk solution. Finally, after sufficiently long tau_I, a dense and nearly homogeneous layer with a sharp interface is formed which does not exhibit surface pattern formation. The stages of brush growth are discussed qualitatively in terms of a random deposition model.

Elution of Uranium and Transition Metals from Amidoxime-Based Polymer Adsorbents for Sequestering Uranium from Seawater

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

Pan, Horng-Bin; Kuo, Li-Jung; Wai, Chien M.

2015-11-30

High-surface-area amidoxime and carboxylic acid grafted polymer adsorbents developed at Oak Ridge National Laboratory were tested for sequestering uranium in a flowing seawater flume system at the PNNL-Marine Sciences Laboratory. FTIR spectra indicate that a KOH conditioning process is necessary to remove the proton from the carboxylic acid and make the sorbent effective for sequestering uranium from seawater. The alkaline conditioning process also converts the amidoxime groups to carboxylate groups in the adsorbent. Both Na 2CO 3-H 2O 2 and hydrochloric acid elution methods can remove ~95% of the uranium sequestered by the adsorbent after 42 days of exposure inmore » real seawater. The Na 2CO 3-H 2O 2 elution method is more selective for uranium than conventional acid elution. Iron and vanadium are the two major transition metals competing with uranium for adsorption to the amidoxime-based adsorbents in real seawater.« less

Nanostructured Block Polymer Membranes as High Capacity Adsorbers for the Capture of Metal Ions from Water

NASA Astrophysics Data System (ADS)

Boudouris, Bryan; Weidman, Jacob; Mulvenna, Ryan; Phillip, William

The efficient removal of metal ions from aqueous streams is of significant import in applications ranging from industrial waste treatment to the purification of drinking water. An emerging paradigm associated with this separation is one that utilizes membrane adsorbers as a means by which to bind metal salt contaminants. Here, we demonstrate that the casting of an A-B-C triblock polymer using the self-assembly and non-solvent induced phase separation (SNIPS) methodology results in a nanoporous membrane geometry. The nature of the triblock polymer affords an extremely high density of binding sites within the membrane. As such, we demonstrate that the membranes with binding capacities equal to that of state-of-the-art packed bed columns. Moreover, because the affinity of the C moiety can be tuned, highly selective binding events can occur based solely on the chemistry of the block polymer and the metal ions in solution (i.e., in a manner that is independent of the size of the metal ions). Due to these combined facts, these membranes efficiently remove heavy metal (e.g., lead- and cadmium-based) salts from contaminated water streams with greater than 95% efficiency. Finally, we show that the membranes can be regenerated through a simple treatment in order to provide long-lasting adsorber systems as well. Thus, it is anticipated that these nanostructured triblock polymer membranes are a platform by which to obtain next-generation water purification processes.

Elution of uranium and transition metals from amidoxime-based polymer adsorbents for sequestering uranium from seawater

DOE PAGES

Pan, Horng-Bin; Kuo, Li-Jung; Miyamoto, Naomi; ...

2015-11-30

High-surface-area amidoxime and carboxylic acid grafted polymer adsorbents developed at Oak Ridge National Laboratory were tested for sequestering uranium in a flowing seawater flume system at the PNNL-Marine Sciences Laboratory. FTIR spectra indicate that a KOH conditioning process is necessary to remove the proton from the carboxylic acid and make the sorbent effective for sequestering uranium from seawater. The alkaline conditioning process also converts the amidoxime groups to carboxylate groups in the adsorbent. Both Na 2CO 3 H 2O 2 and hydrochloric acid elution methods can remove ~95% of the uranium sequestered by the adsorbent after 42 days of exposuremore » in real seawater. The Na 2CO 3 H 2O 2 elution method is more selective for uranium than conventional acid elution. Iron and vanadium are the two major transition metals competing with uranium for adsorption to the amidoxime-based adsorbents in real seawater. Tiron (4,5-Dihydroxy-1,3-benzenedisulfonic acid disodium salt, 1 M) can remove iron from the adsorbent very effectively at pH around 7. The coordination between vanadium (V) and amidoxime is also discussed based on our 51V NMR data.« less

Adsorption and Exchange Dynamics in Aging Hydroxyethylcellulose Layers on Silica.

PubMed

Mubarekyan; Santore

2000-07-15

The adsorption kinetics of hydroxyethylcellulose (HEC) on silica and relaxations in adsorbed HEC layers were probed using total internal reflectance fluorescence and near-Brewster reflectivity. Like many random-coil polymers, HEC was found to adsorb at the transport-limited rate. Relaxations occurred at nearly constant interfacial mass when HEC layers were exposed to aqueous solvent, causing the subsequent exchange of chains between the layer and the free solution to become increasingly hindered. Eventually, on the time scale of a day, layers became immobilized and unable to accommodate chains from free solution. A continued fluorescence decay, beyond time scales that could be probed with self exchange, suggested further relaxations of the adsorbed HEC. The polydisperse HEC system (with an average molecular weight near 450,000) behaved qualitatively similar to molecular weight standard polyethylene oxide (PEO) layers on silica. For instance, relaxations in PEO layers occurred on a time scale of 10-20 h, like the HEC layers. Young layers of the latter, however, exhibited self-exchange kinetics that were an order of magnitude slower than PEO layers of similar age. This difference in adsorbed layer dynamics was attributed to HEC's stiffer backbone, compared with flexible PEO. Copyright 2000 Academic Press.

Tunable electronic structure and spin splitting in single and multiple Fe-adsorbed g-C2N with different layers: A first-principles study

NASA Astrophysics Data System (ADS)

Zheng, Z. D.; Wang, X. C.; Mi, W. B.

2018-04-01

The electronic structure of Fe adsorbed g-C2N with different layers is investigated by first-principles calculations. The Fe1 and Fe2 represent the Fe adsorptions at Csbnd C and Csbnd N rings, and Fe11 and Fe121 adsorption sites are also considered. The Fe1 adsorbed g-C2N is metallic with layer from n = 1 to 4, and the maximum spin splitting is 515, 428, 46 and 133 meV. The band gap of Fe2 adsorbed g-C2N with different layers is 0, 0, 117 and 6 meV, and the maximum spin splitting is 565, 369, 195 and 146 meV, respectively. All of the Fe11 adsorbed g-C2N are metallic with layer from n = 1 to 4, and the maximum spin splitting is 199, 0, 83 and 203 meV. An indirect band gap of 215 meV appears in Fe121 adsorbed g-C2N at layer n = 3, and the maximum spin splitting is 283, 211, 304 and 153 meV, respectively. Our results show that the electronic structures of Fe adsorbed novel two-dimensional semiconductor g-C2N can be tuned by different layers. Moreover, the spin splitting of Fe2 adsorbed g-C2N decreases monotonically as g-C2N layer increases from n = 1 to 4, which will provide more potential applications in spintronic devices.

Influence of the molecular architecture on the adsorption onto solid surfaces: comb-like polymers.

PubMed

Guzmán, Eduardo; Ortega, Francisco; Prolongo, Margarita G; Starov, Victor M; Rubio, Ramón G

2011-09-28

The processes of adsorption of grafted copolymers onto negatively charged surfaces were studied using a dissipative quartz crystal microbalance (D-QCM) and ellipsometry. The control parameters in the study of the adsorption are the existence or absence on the molecular architecture of grafted polyethyleneglycol (PEG) chains with different lengths and the chemical nature of the main chain, poly(allylamine) (PAH) or poly(L-lysine) (PLL). It was found out that the adsorption kinetics of the polymers showed a complex behavior. The total adsorbed amount depends on the architecture of the polymer chains (length of the PEG chains), on the polymer concentration and on the chemical nature of the main chain. The comparison of the thicknesses of the adsorbed layers obtained from D-QCM and from ellipsometry allowed calculation of the water content of the layers that is intimately related to the grafting length. The analysis of D-QCM results also provides information about the shear modulus of the layers, whose values have been found to be typical of a rubber-like polymer system. It is shown that the adsorption of polymers with a charged backbone is not driven exclusively by the electrostatic interactions, but the entropic contributions as a result of the trapping of water in the layer structure are of fundamental importance.

Presence of Fe-Al binary oxide adsorbent cake layer in ceramic membrane filtration and their impact for removal of HA and BSA.

PubMed

Kim, Kyung-Jo; Jang, Am

2018-04-01

To enhance the removal of natural organic matter (NOM) in ceramic (Ce) membrane filtration, an iron-aluminum binary oxide (FAO) was applied to the ceramic membrane surface as the adsorbent cake layer, and it was compared with heated aluminum oxide (HAO) for the evaluation of the control of NOM. Both the HAO and FAO adsorbent cake layers efficiently removed the NOM regardless of NOM's hydrophobic/hydrophilic characteristics, and the dissolved organic carbon (DOC) removal in NOM for FAO was 1-1.12 times greater than that for HAO, which means FAO was more efficient in the removal of DOC in NOM. FAO (0.03 μm), which is smaller in size than HAO (0.4 μm), had greater flux reduction than HAO. The flux reduction increased as the filtration proceeded because most of the organic foulants (colloid/particles and soluble NOM) were captured by the adsorbent cake layer, which caused fouling between the membrane surface and the adsorbent cake layer. However, no chemically irreversible fouling was observed on the Ce membrane at the end of the FAO adsorbent cake layer filtration. This means that a stable adsorbent cake layer by FAO formed on the Ce membrane, and that the reduced pure water flux of the Ce membrane, resulting from the NOM fouling, can easily be recovered through physicochemical cleaning. Copyright © 2018 Elsevier Ltd. All rights reserved.

Fabrication and Theoretical Evaluation of Microlens Arrays on Layered Polymers

NASA Astrophysics Data System (ADS)

Oder, Tom; McMaster, Michael; Merlo, Corey; Bagheri, Camron; Reakes, Clayton; Petrus, Joshua; Li, Dingqiang; Crescimanno, Michael; Andrews, James

2014-03-01

Arrays of microlens were fabricated on nano-layered polymers using reactive ion etching. Semi hemispherical patterns with diameters ranging from 20 to 80 micrometers were first formed on a thick photoresist film that was spin-coated on the layered polymers using standard photolithographic process employing a gray scale glass mask. These patterns were then transferred to the polymers using dry etching in a reactive ion etching system. The optimized etch condition included a mixture of sulfur hexafluoride and oxygen, which resulted in an etch depth of 5 micrometers and successfully exposed the individual sub-micron thick layers in the polymers. Physical characterization of the microlens arrays was done using atomic force microscope and scanning electron microscope. We combine basic physical optics theory with the transfer matrix analysis of optical transport in nano-layered polymers to address subtleties in the chromatic response of microlenses made from these materials. In particular this method explains the len's behavior in and around the reflection band of the materials. We wish to acknowledge support of funds from NSF through its Center for Layered Polymeric Systems (CLiPS) at Case Western Reserve University.

The First Layer of 4He, H2, and Ne Adsorbed on HiPco™ Carbon Nanotube Bundles

NASA Astrophysics Data System (ADS)

Vilches, O. E.; Ramachandran, S.; Wilson, T. A.; Dash, J. G.

2006-09-01

We summarize results from AC and DC heat capacity measurements of 4He, H2, and Ne adsorbed on HiPco™ purified, closed-end single-wall carbon nanotube bundles (SWNTB) for the first adsorbed layer. We find two regions in the coverage domain: below ≈1/3 monolayer the adsorbate occupies high binding energy sites, mostly the external grooves of the bundles, while above ≈1/3 monolayer the external graphene surface is covered. No phase transitions have been observed at any temperature for all the adsorbates, a range of T where two-dimensional phases and phase transitions are seen for the same adsorbates deposited on exfoliated graphite.

Synchrotron X-Ray Diffraction Study of Structure and Growth of Adsorbed Layers

NASA Astrophysics Data System (ADS)

Dai, Pengcheng

Synchrotron x-ray diffraction and scanning-tunneling -microscopy (STM) experiments reveal a new commensurate monolayer structure of 10CB (decylcyanobiphenyl) molecules adsorbed on the (0001) graphite surface. Our results are consistent with two generic structures for nCB monolayers on surfaces of hexagonal symmetry. The monolayer d spacing of the new phase inferred by STM is 10% layer than that obtained by x-ray diffraction on the same sample. We suggest that part of this discrepancy results from a systematic error introduced in calibration of the STM length scale against the graphite substrate. For multilayer nCB films, we find that a polycrystalline structure is formed and most of the adsorbed molecules are aligned with their long axis perpendicular to the graphite surface. Synchrotron x-ray scattering has been used to investigate the structure and growth of xenon physisorbed on the Ag(111) surface using a specially designed ultra -high vacuum (UHV) chamber. For growth under quasi-equilibrium conditions, the bulk Xe-Xe spacing is reached at monolayer completion and solid films of thickness >= 220 A are observed in which an 'ABC' stacking sequence predominates. Under kinetic growth conditions, intensity oscillations at the Xe anti-Bragg position of the specular rod are observed as a function of time, indicating layer -by-layer growth. Analysis of the specular reflectivity at different coverages yields the fractional layer occupancies and the spacing between the Ag(111) surface and first Xe layer. We have conducted a series of low-energy electron diffraction (LEED) 'kinetic isotherm' experiments on both xenon and hexane rm(C_6H_{14 }) films adsorbed on the Ag(111) surface. Our preliminary results show that under the pressure and temperature range accessible to the experiments, all of the Xe kinetic isotherms fall on a universal curve which is concave upward. However, the hexane kinetic isotherms have a qualitatively different shape (S-like) at the higher

Double layer mixed matrix membrane adsorbers improving capacity and safety hemodialysis

NASA Astrophysics Data System (ADS)

Saiful; Borneman, Z.; Wessling, M.

2018-05-01

Double layer mixed matrix membranes adsorbers have been developed for blood toxin removal by embedding activated carbon into cellulose acetate macroporous membranes. The membranes are prepared by phase inversion method via water vapor induced phase separation followed by an immersion precipitation step. Double layer MMM consisting of an active support and a separating layer. The active support layer consists of activated carbon particles embedded in macroporous cellulose acetate; the separating layer consists of particle free cellulose acetate. The double layer membrane possess an open and interconnected macroporous structure with a high loading of activated carbon available for blood toxins removal. The MMM AC has a swelling degree of 6.5 %, porosity of 53 % and clean water flux of 800 Lm-2h-1bar-1. The prepared membranes show a high dynamic Creatinine (Crt) removal during hemodilysis process. The Crt removal by adsorption contributes to amore than 83 % of the total removal. The double layer adsorptive membrane proves hemodialysis membrane can integrated with adsorption, in which blood toxins are removed in one step.

Study of the adsorbed layer on a solid electrode surface by specular reflection measurement

NASA Astrophysics Data System (ADS)

Kusu, Fumiyo; Takamura, Kiyoko

1985-07-01

Specular reflection measurements were carried out to study the adsorbed layers of certain heterocyclic compounds such as adenine, barbital, 2'-deoxyadenosine, phenobarbital, pyridine and thymine. When pyridine was present in 0.1M NaClO 4, a marked decrease in the reflectivity of a gold electrode was observed. In the potential range near the point of zero charge on the reflectivity-potential curve, the decrease was due to the adsorption of pyridine. Assuming the reflectivity change to be proportional to the surface coverage, the potential and concentration dependence of pyridine adsorption was determined and analysed on the basis of a Langmuir-type adsorption isotherm. The refractive indices and extinction coefficients for the adsorbed layers of the compounds investigated were evaluated using the observed reflectivity change, according to relations proposed by McIntyre and Aspnes.

Effect of matrix chemical heterogeneity on effective filler interactions in model polymer nanocomposites

NASA Astrophysics Data System (ADS)

Hall, Lisa; Schweizer, Kenneth

2010-03-01

The microscopic Polymer Reference Interaction Site Model theory has been applied to spherical and rodlike fillers dissolved in three types of chemically heterogeneous polymer melts: alternating AB copolymer, random AB copolymers, and an equimolar blend of two homopolymers. In each case, one monomer species adsorbs more strongly on the filler mimicking a specific attraction, while all inter-monomer potentials are hard core which precludes macrophase or microphase separation. Qualitative differences in the filler potential-of-mean force are predicted relative to the homopolymer case. The adsorbed bound layer for alternating copolymers exhibits a spatial moduluation or layering effect but is otherwise similar to that of the homopolymer system. Random copolymers and the polymer blend mediate a novel strong, long-range bridging interaction between fillers at moderate to high adsorption strengths. The bridging strength is a non-monotonic function of random copolymer composition, reflecting subtle competing enthalpic and entropic considerations.

Polymer diffusion in the interphase between surface and solution.

PubMed

Weger, Lukas; Weidmann, Monika; Ali, Wael; Hildebrandt, Marcus; Gutmann, Jochen Stefan; Hoffmann-Jacobsen, Kerstin

2018-05-22

Total internal reflection fluorescence correlation spectroscopy (TIR-FCS) is applied to study the self-diffusion of polyethylene glycol solutions in the presence of weakly attractive interfaces. Glass coverslips modified with aminopropyl- and propyl-terminated silanes are used to study the influence of solid surfaces on polymer diffusion. A model of three phases of polymer diffusion allows to describe the experimental fluorescence autocorrelation functions. Besides the two-dimensional diffusion of adsorbed polymer on the substrate and three-dimensional free diffusion in bulk solution, a third diffusion time scale is observed with intermediate diffusion times. This retarded three-dimensional diffusion in solution is assigned to long range effects of solid surfaces on diffusional dynamics of polymers. The respective diffusion constants show Rouse scaling (D~N -1 ) indicating a screening of hydrodynamic interactions by the presence of the surface. Hence, the presented TIR-FCS method proves to be a valuable tool to investigate the effect of surfaces on polymer diffusion beyond the first adsorbed polymer layer on the 100 nm length scale.

Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers

DTIC Science & Technology

2016-06-15

with end-functionalized polymers . First, an end-functionalized polymer with conjugated end-molecule, pyrene, is successfully employed to boron... polymers . First, an end-functionalized polymer with conjugated end-molecule, pyrenes, is successfully employed to boron nitride nanosheets (BNNS), and...AFRL-AFOSR-JP-TR-2016-0071 Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers Cheolmin Park YONSEI UNIVERSITY

Manipulating interfacial polymer structures through mixed surfactant adsorption and complexation.

PubMed

Cattoz, Beatrice; de Vos, Wiebe M; Cosgrove, Terence; Crossman, Martin; Prescott, Stuart W

2012-04-17

The effects of a nonionic alcohol ethoxylate surfactant, C(13)E(7), on the interactions between PVP and SDS both in the bulk and at the silica nanoparticle interface are studied by photon correlation spectroscopy, solvent relaxation NMR, SANS, and optical reflectometry. Our results confirmed that, in the absence of SDS, C(13)E(7) and PVP are noninteracting, while SDS interacts strongly both with PVP and C(13)E(7) . Studying interfacial interactions showed that the interfacial interactions of PVP with silica can be manipulated by varying the amounts of SDS and C(13)E(7) present. Upon SDS addition, the adsorbed layer thickness of PVP on silica increases due to Coulombic repulsion between micelles in the polymer layer. When C(13)E(7) is progressively added to the system, it forms mixed micelles with the complexed SDS, reducing the total charge per micelle and thus reducing the repulsion between micelle and the silica surface that would otherwise cause the PVP to desorb. This causes the amount of adsorbed polymer to increase with C(13)E(7) addition for the systems containing SDS, demonstrating that addition of C(13)E(7) hinders the SDS-mediated desorption of an adsorbed PVP layer. © 2012 American Chemical Society

Internal Reflection Spectra of Surface Compounds and Adsorbed Molecules

NASA Astrophysics Data System (ADS)

Zolotarev, V. M.; Lygin, V. I.; Tarasevich, B. N.

1981-01-01

The application of attenuated total reflection (ATR) spectroscopy in surface studies of inorganic adsorbents and catalysts, polymers, and optically transparent electrodes is discussed. The basic principles of ATR spectroscopy as applied to surface phenomena are considered, with special reference to thin films, industrial adsorbents and catalysts, and polymer degradation processes. 276 references.

A machine learning approach to graph-theoretical cluster expansions of the energy of adsorbate layers

NASA Astrophysics Data System (ADS)

Vignola, Emanuele; Steinmann, Stephan N.; Vandegehuchte, Bart D.; Curulla, Daniel; Stamatakis, Michail; Sautet, Philippe

2017-08-01

The accurate description of the energy of adsorbate layers is crucial for the understanding of chemistry at interfaces. For heterogeneous catalysis, not only the interaction of the adsorbate with the surface but also the adsorbate-adsorbate lateral interactions significantly affect the activation energies of reactions. Modeling the interactions of the adsorbates with the catalyst surface and with each other can be efficiently achieved in the cluster expansion Hamiltonian formalism, which has recently been implemented in a graph-theoretical kinetic Monte Carlo (kMC) scheme to describe multi-dentate species. Automating the development of the cluster expansion Hamiltonians for catalytic systems is challenging and requires the mapping of adsorbate configurations for extended adsorbates onto a graphical lattice. The current work adopts machine learning methods to reach this goal. Clusters are automatically detected based on formalized, but intuitive chemical concepts. The corresponding energy coefficients for the cluster expansion are calculated by an inversion scheme. The potential of this method is demonstrated for the example of ethylene adsorption on Pd(111), for which we propose several expansions, depending on the graphical lattice. It turns out that for this system, the best description is obtained as a combination of single molecule patterns and a few coupling terms accounting for lateral interactions.

Cellular Responses Modulated by FGF-2 Adsorbed on Albumin/Heparin Layer-by-Layer Assemblies.

PubMed

Kumorek, Marta; Kubies, Dana; Filová, Elena; Houska, Milan; Kasoju, Naresh; Mázl Chánová, Eliška; Matějka, Roman; Krýslová, Markéta; Bačáková, Lucie; Rypáček, František

2015-01-01

In a typical cell culture system, growth factors immobilized on the cell culture surfaces can serve as a reservoir of bio-signaling molecules, without the need to supplement them additionally into the culture medium. In this paper, we report on the fabrication of albumin/heparin (Alb/Hep) assemblies for controlled binding of basic fibroblast growth factor (FGF-2). The surfaces were constructed by layer-by-layer adsorption of polyelectrolytes albumin and heparin and were subsequently stabilized by covalent crosslinking with glutaraldehyde. An analysis of the surface morphology by atomic force microscopy showed that two Alb/Hep bilayers are required to cover the surface of substrate. The formation of the Alb/Hep assemblies was monitored by the surface plasmon resonance (SPR), the infrared multiinternal reflection spectroscopy (FTIR MIRS) and UV/VIS spectroscopy. The adsorption of FGF-2 on the cross-linked Alb/Hep was followed by SPR. The results revealed that FGF-2 binds to the Alb/Hep assembly in a dose and time-dependent manner up to the surface concentration of 120 ng/cm(2). The bioactivity of the adsorbed FGF-2 was assessed in experiments in vitro, using calf pulmonary arterial endothelial cells (CPAE). CPAE cells could attach and proliferate on Alb/Hep surfaces. The adsorbed FGF-2 was bioactive and stimulated both the proliferation and the differentiation of CPAE cells. The improvement was more pronounced at a lower FGF-2 surface concentration (30 ng/cm(2)) than on surfaces with a higher concentration of FGF-2 (120 ng/cm(2)).

Cellular Responses Modulated by FGF-2 Adsorbed on Albumin/Heparin Layer-by-Layer Assemblies

PubMed Central

Kumorek, Marta; Kubies, Dana; Filová, Elena; Houska, Milan; Kasoju, Naresh; Mázl Chánová, Eliška; Matějka, Roman; Krýslová, Markéta; Bačáková, Lucie; Rypáček, František

2015-01-01

In a typical cell culture system, growth factors immobilized on the cell culture surfaces can serve as a reservoir of bio-signaling molecules, without the need to supplement them additionally into the culture medium. In this paper, we report on the fabrication of albumin/heparin (Alb/Hep) assemblies for controlled binding of basic fibroblast growth factor (FGF-2). The surfaces were constructed by layer-by-layer adsorption of polyelectrolytes albumin and heparin and were subsequently stabilized by covalent crosslinking with glutaraldehyde. An analysis of the surface morphology by atomic force microscopy showed that two Alb/Hep bilayers are required to cover the surface of substrate. The formation of the Alb/Hep assemblies was monitored by the surface plasmon resonance (SPR), the infrared multiinternal reflection spectroscopy (FTIR MIRS) and UV/VIS spectroscopy. The adsorption of FGF-2 on the cross-linked Alb/Hep was followed by SPR. The results revealed that FGF-2 binds to the Alb/Hep assembly in a dose and time-dependent manner up to the surface concentration of 120 ng/cm2. The bioactivity of the adsorbed FGF-2 was assessed in experiments in vitro, using calf pulmonary arterial endothelial cells (CPAE). CPAE cells could attach and proliferate on Alb/Hep surfaces. The adsorbed FGF-2 was bioactive and stimulated both the proliferation and the differentiation of CPAE cells. The improvement was more pronounced at a lower FGF-2 surface concentration (30 ng/cm2) than on surfaces with a higher concentration of FGF-2 (120 ng/cm2). PMID:25945799

Programmable light-controlled shape changes in layered polymer nanocomposites.

PubMed

Zhu, Zhichen; Senses, Erkan; Akcora, Pinar; Sukhishvili, Svetlana A

2012-04-24

We present soft, layered nanocomposites that exhibit controlled swelling anisotropy and spatially specific shape reconfigurations in response to light irradiation. The use of gold nanoparticles grafted with a temperature-responsive polymer (poly(N-isopropylacrylamide), PNIPAM) with layer-by-layer (LbL) assembly allowed placement of plasmonic structures within specific regions in the film, while exposure to light caused localized material deswelling by a photothermal mechanism. By layering PNIPAM-grafted gold nanoparticles in between nonresponsive polymer stacks, we have achieved zero Poisson's ratio materials that exhibit reversible, light-induced unidirectional shape changes. In addition, we report rheological properties of these LbL assemblies in their equilibrium swollen states. Moreover, incorporation of dissimilar plasmonic nanostructures (solid gold nanoparticles and nanoshells) within different material strata enabled controlled shrinkage of specific regions of hydrogels at specific excitation wavelengths. The approach is applicable to a wide range of metal nanoparticles and temperature-responsive polymers and affords many advanced build-in options useful in optically manipulated functional devices, including precise control of plasmonic layer thickness, tunability of shape variations to the excitation wavelength, and programmable spatial control of optical response.

Mixed polymer brushes by sequential polymer addition: anchoring layer effect.

PubMed

Draper, John; Luzinov, Igor; Minko, Sergiy; Tokarev, Igor; Stamm, Manfred

2004-05-11

Smart surfaces can be described as surfaces that have the ability to respond in a controllable fashion to specific environmental stimuli. A heterogeneous (mixed) polymer brush (HPB) can provide a synthetic route to designing smart polymer surfaces. In this research we study HPB comprised of end-grafted polystyrene (PS) and poly(2-vinyl pyridine) (P2VP). The synthesis of the HPB involves the use of an "intermolecular glue" acting as a binding/anchoring interlayer between the polymer brush and the substrate, a silicon wafer. We compare anchoring layers of epoxysilane (GPS), which forms a self-assembled monolayer with epoxy functionality, to poly(glycidyl methacrylate) (PGMA), which forms a macromolecular monolayer with epoxy functionality. The PS and P2VP were deposited onto the wafers in a sequential fashion to chemically graft PS in a first step and subsequently graft P2VP. Rinsing the HPB in selective solvents and observing the change in water contact angle as a function of the HPB composition studied the switching nature of the HPB. Scanning probe microscopy was used to probe the topography and phase imagery of the HPB. The nature of the anchoring layer significantly affected the wettability and morphology of the mixed brushes.

Fiber-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

DOEpatents

Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

2016-09-06

A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

Fiber-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

DOEpatents

Janke, Christopher J; Dai, Sheng; Oyola, Yatsandra

2014-05-13

A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

Carbazole/triarylamine based polymers as a hole injection/transport layer in organic light emitting devices.

PubMed

Wang, Hui; Ryu, Jeong-Tak; Kwon, Younghwan

2012-05-01

This study examined the influence of the charge injection barriers on the performance of organic light emitting diodes (OLEDs) using polymers with a stepwise tuned ionization potential (I(p) approximately -5.01 - -5.29 eV) between the indium tin oxide (ITO) (phi approximately -4.8 eV) anode and tris(8-hydroxyquinolinato) aluminium (Alq3) (I(p) approximately -5.7 eV) layer. The energy levels of the polymers were tuned by structural modification. Double layer devices were fabricated with a configuration of ITO/polymer/Alq3/LiF/Al, where the polymers, Alq3, and LiF/Al were used as the hole injection/transport layer, emissive electron transport layer, and electron injection/cathode, respectively. Using the current density-voltage (J-V), luminescence-voltage (L-V) and efficiencies in these double layer devices, the device performance was evaluated in terms of the energy level alignments at the interfaces, such as the hole injection barriers (phi(h)(iTO/polymer) and phi(h)(polymer/Alq3)) from ITO through the polymers into the Alq3 layer, and the electron injection barrier (phi(e)(polymer/Alq3) or electron/exciton blocking barrier) at the polymer/Alq3 interface.

Determination of imidazole derivatives by micellar electrokinetic chromatography combined with solid-phase microextraction using activated carbon-polymer monolith as adsorbent.

PubMed

Shih, Yung-Han; Lirio, Stephen; Li, Chih-Keng; Liu, Wan-Ling; Huang, Hsi-Ya

2016-01-08

In this study, an effective method for the separation of imidazole derivatives 2-methylimidazole (2-MEI), 4- methylimidazole (4-MEI) and 2-acetyl-4-tetrahydroxybutylimidazole (THI) in caramel colors using cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI-sweeping-MEKC) was developed. The limits of detection (LOD) and quantitation (LOQ) for the CSEI-sweeping-MEKC method were in the range of 4.3-80μgL(-1) and 14-270μgL(-1), respectively. Meanwhile, a rapid fabrication activated carbon-polymer (AC-polymer) monolithic column as adsorbent for solid-phase microextraction (SPME) of imidazole colors was developed. Under the optimized SPME condition, the extraction recoveries for intra-day, inter-day and column-to-column were in the range of 84.5-95.1% (<6.3% RSDs), 85.6-96.1% (<4.9% RSDs), and 81.3-96.1% (<7.1% RSDs), respectively. The LODs and LOQs of AC-polymer monolithic column combined with CSEI-sweeping-MEKC method were in the range of 33.4-60.4μgL(-1) and 111.7-201.2μgL(-1), respectively. The use of AC-polymer as SPME adsorbent demonstrated the reduction of matrix effect in food samples such as soft drink and alcoholic beverage thereby benefiting successful determination of trace-level caramel colors residues using CSEI-sweeping-MEKC method. The developed AC-polymer monolithic column can be reused for more than 30 times without any significant loss in the extraction recovery for imidazole derivatives. Copyright © 2015 Elsevier B.V. All rights reserved.

In situ creation of reactive polymer nanoparticles and resulting polymer layers formed at the interfaces of liquid crystals (Conference Presentation)

NASA Astrophysics Data System (ADS)

Kang, Shin-Woong; Kundu, Sudarshan; Park, Heung-Shik; Oh, Keun Chan; Lyu, Jae Jin

2017-02-01

We report the in situ creation of reactive polymer nanoparticles and resulting polymer networks formed at the interfaces of liquid crystals. It is known that polymerization-induced phase separation proceeds in two distinct regimes depending on the concentration of monomer. For a high monomer concentration, phase separation occurs mainly through the spinodal decomposition process, consequently resulting in interpenetrating polymer networks. For a dilute system, however, the phase separation mainly proceeds and completes in the binodal decomposition regime. The system resembles the aggregation process of colloidal particle. In this case, the reaction kinetics is limited by the reaction between in situ created polymer aggregates and hence the network morphologies are greatly influenced by the diffusion of reactive polymer particles. The thin polymer layers localized at the surface of substrate are inevitably observed and can be comprehended by the interfacial adsorption and further cross-linking reaction of reactive polymer aggregates at the interface. This process provides a direct perception on understanding polymer stabilized liquid crystals accomplished by the interfacial polymer layer. The detailed study has been performed for an extremely dilute condition (below 0.5 wt%) by employing systematic experimental approaches. Creation and growth of polymer nanoparticles have been measured by particle size analyzer. The interfacial localization of polymer aggregates and resulting interfacial layer formation with a tens of nanometer scale have been exploited at various interfaces such as liquid-solid, liquid-liquid, and liquid-gas interfaces. The resulting interfacial layers have been characterized by using fuorescent confocal microscope and field emission scanning electron microscope. The detailed processes of the polymer stabilized vertically aligned liquid crystals will be discussed in support of the reported study.

Associative polymers bridging between layers of multilamellar vesicles.

NASA Astrophysics Data System (ADS)

Choi, Seo; Bhatia, Surita

2006-03-01

Multilamellar vesicles can be found in a variety of pharmaceutical formulations, personal care products, and home care products. Hydrophobically modified associative polymers are often used to stabilize the vesicles or to control the rheological properties of these formulations. The hydrophobic groups are expected to insert themselves into the vesicle bilayers. Recent experimental work shows that hydrophobically modified polymers may from bridges between vesicles or may bridge between layers of a single vesicle. The latter configuration forces an interlayer spacing roughly equal to the radius of gyration of the backbone between associative groups. We have performed simple mean-field calculations on ideal telechelic associative polymers between concentric spherical surfaces. We find that the free energy per chain has an attractive minimum when the layer spacing is approximately N^1/2l, which is consistent with experimental results. The depth of the minimum depends on both chain length and curvature, and as expected when the curvature becomes small, the result for telechelic chains between flat surfaces is recovered.

Influence of the bound polymer layer on nanoparticle diffusion in polymer melts

DOE PAGES

Griffin, Philip J.; Bocharova, Vera; Middleton, L. Robert; ...

2016-09-23

We measure the center-of-mass diffusion of silica nanoparticles (NPs) in entangled poly(2-vinylpyridine) (P2VP) melts using Rutherford backscattering spectrometry. While these NPs are well within the size regime where enhanced, nonhydrodynamic NP transport is theoretically predicted and has been observed experimentally (2R NP/d tube ≈ 3, where 2R NP is the NP diameter and d tube is the tube diameter), we find that the diffusion of these NPs in P2VP is in fact well-described by the hydrodynamic Stokes–Einstein relation. The effective NP diameter 2R eff is significantly larger than 2R NP and strongly dependent on P2VP molecular weight, consistent with themore » presence of a bound polymer layer on the NP surface with thickness h eff ≈ 1.1R g. Our results show that the bound polymer layer significantly augments the NP hydrodynamic size in polymer melts with attractive polymer–NP interactions and effectively transitions the mechanism of NP diffusion from the nonhydrodynamic to hydrodynamic regime, particularly at high molecular weights where NP transport is expected to be notably enhanced. Lastly, these results provide the first experimental demonstration that hydrodynamic NP transport in polymer melts requires particles of size ≳5d tube, consistent with recent theoretical predictions.« less

Molecular Structure and Equilibrium Forces of Bovine Submaxillary Mucin Adsorbed at a Solid-Liquid Interface.

PubMed

Zappone, Bruno; Patil, Navinkumar J; Madsen, Jan B; Pakkanen, Kirsi I; Lee, Seunghwan

2015-04-21

By combining dynamic light scattering, circular dichroism spectroscopy, atomic force microscopy, and surface force apparatus, the conformation of bovine submaxillary mucin in dilute solution and nanomechanical properties of mucin layers adsorbed on mica have been investigated. The samples were prepared by additional chromatographic purification of commercially available products. The mucin molecule was found to have a z-average hydrodynamic diameter of ca. 35 nm in phosphate buffered solution, without any particular secondary or tertiary structure. The contour length of the mucin is larger than, yet of the same order of magnitude as the diameter, indicating that the molecule can be modeled as a relatively rigid polymeric chain due to the large persistence length of the central glycosylated domain. Mucin molecules adsorbed abundantly onto mica from saline buffer, generating polymer-like, long-ranged, repulsive, and nonhysteretic forces upon compression of the adsorbed layers. Detailed analysis of such forces suggests that adsorbed mucins had an elongated conformation favored by the stiffness of the central domain. Acidification of aqueous media was chosen as means to reduce mucin-mucin and mucin-substrate electrostatic interactions. The hydrodynamic diameter in solution did not significantly change when the pH was lowered, showing that the large persistence length of the mucin molecule is due to steric hindrance between sugar chains, rather than electrostatic interactions. Remarkably, the force generated by an adsorbed layer with a fixed surface coverage also remained unaltered upon acidification. This observation can be linked to the surface-protective, pH-resistant role of bovine submaxillary mucin in the variable environmental conditions of the oral cavity.

Adsorption of copolymers at polymer/air and polymer/solid interfaces

NASA Astrophysics Data System (ADS)

Oslanec, Robert

Using mainly low-energy forward recoil spectrometry (LE-FRES) and neutron reflectivity (NR), copolymer behavior at polymer/air and polymer/solid interfaces is investigated. For a miscible blend of poly(styrene-ran-acrylonitrile) copolymers, the volume fraction profile of the copolymer with lower acrylonitrile content is flat near the surface in contrast to mean field predictions. Including copolymer polydispersity into a self consistent mean field (SCMF) model does not account for this profile shape. LE-FRES and NR is also used to study poly(deuterated styrene-block-methyl-methacrylate) (dPS-b-PMMA) adsorption from a polymer matrix to a silicon oxide substrate. The interfacial excess, zsp*, layer thickness, L, and layer-matrix width, w, depend strongly on the number of matrix segments, P, for P 2N, the matrix chains are repelled from the adsorbed layer and the layer characteristics become independent of P. An SCMF model of block copolymer adsorption is developed. SCMF predictions are in qualitative agreement with the experimental behavior of zsp*, L, and w as a function of P. Using this model, the interaction energy of the MMA block with the oxide substrate is found to be -8ksb{B}T. In a subsequent experiment, the matrix/dPS interaction is made increasingly unfavorable by increasing the 4-bromostyrene mole fraction, x, in a poly(styrene-ran-4-bromostyrene) (PBrsbxS) matrix. Whereas experiments show that zsp* slightly decreases as x increases, the SCMF model predicts that zsp* should increase as the matrix becomes more unfavorable. Upon including a small matrix attraction for the substrate, the SCMF model shows that zsp* decreases with x because of competition between PBrsbxS and dPS-b-PMMA for adsorbing sites. In thin film dewetting experiments on silicon oxide, the addition of dPS-b-PMMA to PS coatings acts to slow hole growth and prevent holes from impinging. Dewetting studies show that longer dPS-b-PMMA chains are more effective stabilizing agents than shorter

Estimation of polymer-surface interfacial interaction strength by a contact AFM technique.

PubMed

Dvir, H; Jopp, J; Gottlieb, M

2006-12-01

Atomic force microscopy (AFM) measurements were employed to assess polymer-surface interfacial interaction strength. The main feature of the measurement is the use of contact-mode AFM as a tool to scratch off the polymer monolayer adsorbed on the solid surface. Tapping-mode AFM was used to determine the depth of the scraped recess. Independent determination of the layer thickness obtained from optical phase interference microscopy (OPIM) confirmed the depth of the AFM scratch. The force required for the complete removal of the polymer layer with no apparent damage to the substrate surface was determined. Polypropylene (PP), low-density polyethylene (PE), and PP-grafted-maleic anhydride (PP-g-ma) were scraped off silane-treated glass slabs, and the strength of surface interaction of the polymer layer was determined. In all cases it was determined that the magnitude of surface interaction force is of the order of van der Waals (VDW) interactions. The interaction strength is influenced either by polymer ability to wet the surface (hydrophobic or hydrophilic interactions) or by hydrogen bonding between the polymer and the surface treatment.

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

PubMed

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

2017-02-01

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

Effect of hole injection layer/hole transport layer polymer and device structure on the properties of white OLED.

PubMed

Cho, Ho Young; Park, Eun Jung; Kim, Jin-Hoo; Park, Lee Soon

2008-10-01

Copolymers containing carbazole and aromatic amine unit were synthesized by using Pd-catalyzed polycondensation reaction. The polymers were characterized in terms of their molecular weight and thermal stability and their UV and PL properties in solution and film state. The band gap energy of the polymers was also determined by the UV absorption and HOMO energy level data. The polymers had high HOMO energy level of 5.19-5.25 eV and work function close to that of ITO. The polymers were thus tested as hole injection/transport layer in the white organic light emitting diodes (OLED) by using 4,4'-bis(2,2-diphenyl-ethen-1-yl)diphenyl (DPVBi) as blue emitting material and 5,6,11,12-tetraphenylnaphthacene (Rubrene) as orange emitting dopant. The synthesized polymer, poly bis[6-bromo-N-(2-ethylhexyl)-carbazole-3-yl] was found to be useful as hole injection layer/hole transport layer (HIL/HTL) multifunctional material with high luminance efficiency and stable white color coordinate in the wide range of applied voltage.

Analytical phase diagrams for colloids and non-adsorbing polymer.

PubMed

Fleer, Gerard J; Tuinier, Remco

2008-11-04

We review the free-volume theory (FVT) of Lekkerkerker et al. [Europhys. Lett. 20 (1992) 559] for the phase behavior of colloids in the presence of non-adsorbing polymer and we extend this theory in several aspects: (i) We take the solvent into account as a separate component and show that the natural thermodynamic parameter for the polymer properties is the insertion work Pi(v), where Pi is the osmotic pressure of the (external) polymer solution and v the volume of a colloid particle. (ii) Curvature effects are included along the lines of Aarts et al. [J. Phys.: Condens. Matt. 14 (2002) 7551] but we find accurate simple power laws which simplify the mathematical procedure considerably. (iii) We find analytical forms for the first, second, and third derivatives of the grand potential, needed for the calculation of the colloid chemical potential, the pressure, gas-liquid critical points and the critical endpoint (cep), where the (stable) critical line ends and then coincides with the triple point. This cep determines the boundary condition for a stable liquid. We first apply these modifications to the so-called colloid limit, where the size ratio q(R)=R/a between the radius of gyration R of the polymer and the particle radius a is small. In this limit the binodal polymer concentrations are below overlap: the depletion thickness delta is nearly equal to R, and Pi can be approximated by the ideal (van't Hoff) law Pi=Pi(0)=phi/N, where phi is the polymer volume fraction and N the number of segments per chain. The results are close to those of the original Lekkerkerker theory. However, our analysis enables very simple analytical expressions for the polymer and colloid concentrations in the critical and triple points and along the binodals as a function of q(R). Also the position of the cep is found analytically. In order to make the model applicable to higher size ratio's q(R) (including the so-called protein limit where q(R)>1) further extensions are needed. We

Powder-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

DOEpatents

Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

2016-05-03

A powder-based adsorbent and a related method of manufacture are provided. The powder-based adsorbent includes polymer powder with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the powder-based adsorbent includes irradiating polymer powder, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Powder-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

Foam-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

DOEpatents

Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

2015-06-02

Foam-based adsorbents and a related method of manufacture are provided. The foam-based adsorbents include polymer foam with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the foam-based adsorbents includes irradiating polymer foam, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Foam-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

Tunable fractional-order capacitor using layered ferroelectric polymers

NASA Astrophysics Data System (ADS)

Agambayev, Agamyrat; Patole, Shashikant; Bagci, Hakan; Salama, Khaled N.

2017-09-01

Pairs of various Polyvinylidene fluoride P(VDF)-based polymers are used for fabricating bilayer fractional order capacitors (FOCs). The polymer layers are constructed using a simple drop casting approach. The resulting FOC has two advantages: It can be easily integrated with printed circuit boards, and its constant phase angle (CPA) can be tuned by changing the thickness ratio of the layers. Indeed, our experiments show that the CPA of the fabricated FOCs can be tuned within the range from -83° to -65° in the frequency band changing from 150 kHz to 10 MHz. Additionally, we provide an empirical formula describing the relationship between the thickness ratio and the CPA, which is highly useful for designing FOCs with the desired CPA.

Double layer zinc-UDP coordination polymers: structure and properties.

PubMed

Qiu, Qi-Ming; Gu, Leilei; Ma, Hongwei; Yan, Li; Liu, Minghua; Li, Hui

2018-05-17

A homochiral Zn-UDP coordination polymer with an alternating parallel ABAB sequence was constructed and studied by X-ray single crystal diffraction analysis. Its crystal structure shows that there are potentially open sites in the 2D layers. The activation of the sites makes the coordination polymer a fluorescent sensor for novel heterogeneous detection of amino acids.

Fabrication of three-dimensional polymer quadratic nonlinear grating structures by layer-by-layer direct laser writing technique

NASA Astrophysics Data System (ADS)

Bich Do, Danh; Lin, Jian Hung; Diep Lai, Ngoc; Kan, Hung-Chih; Hsu, Chia Chen

2011-08-01

We demonstrate the fabrication of a three-dimensional (3D) polymer quadratic nonlinear (χ(2)) grating structure. By performing layer-by-layer direct laser writing (DLW) and spin-coating approaches, desired photobleached grating patterns were embedded in the guest--host dispersed-red-1/poly(methylmethacrylate) (DR1/PMMA) active layers of an active-passive alternative multilayer structure through photobleaching of DR1 molecules. Polyvinyl-alcohol and SU8 thin films were deposited between DR1/PMMA layers serving as a passive layer to separate DR1/PMMA active layers. After applying the corona electric field poling to the multilayer structure, nonbleached DR1 molecules in the active layers formed polar distribution, and a 3D χ(2) grating structure was obtained. The χ(2) grating structures at different DR1/PMMA nonlinear layers were mapped by laser scanning second harmonic (SH) microscopy, and no cross talk was observed between SH images obtained from neighboring nonlinear layers. The layer-by-layer DLW technique is favorable to fabricating hierarchical 3D polymer nonlinear structures for optoelectronic applications with flexible structural design.

Fabrication of three-dimensional polymer quadratic nonlinear grating structures by layer-by-layer direct laser writing technique.

PubMed

Do, Danh Bich; Lin, Jian Hung; Lai, Ngoc Diep; Kan, Hung-Chih; Hsu, Chia Chen

2011-08-10

We demonstrate the fabrication of a three-dimensional (3D) polymer quadratic nonlinear (χ(2)) grating structure. By performing layer-by-layer direct laser writing (DLW) and spin-coating approaches, desired photobleached grating patterns were embedded in the guest-host dispersed-red-1/poly(methylmethacrylate) (DR1/PMMA) active layers of an active-passive alternative multilayer structure through photobleaching of DR1 molecules. Polyvinyl-alcohol and SU8 thin films were deposited between DR1/PMMA layers serving as a passive layer to separate DR1/PMMA active layers. After applying the corona electric field poling to the multilayer structure, nonbleached DR1 molecules in the active layers formed polar distribution, and a 3D χ(2) grating structure was obtained. The χ(2) grating structures at different DR1/PMMA nonlinear layers were mapped by laser scanning second harmonic (SH) microscopy, and no cross talk was observed between SH images obtained from neighboring nonlinear layers. The layer-by-layer DLW technique is favorable to fabricating hierarchical 3D polymer nonlinear structures for optoelectronic applications with flexible structural design.

Tandem Solar Cells from Accessible Low Band-Gap Polymers Using an Efficient Interconnecting Layer.

PubMed

Bag, Santanu; Patel, Romesh J; Bunha, Ajaykumar; Grand, Caroline; Berrigan, J Daniel; Dalton, Matthew J; Leever, Benjamin J; Reynolds, John R; Durstock, Michael F

2016-01-13

Tandem solar cell architectures are designed to improve device photoresponse by enabling the capture of wider range of solar spectrum as compared to single-junction device. However, the practical realization of this concept in bulk-heterojunction polymer systems requires the judicious design of a transparent interconnecting layer compatible with both polymers. Moreover, the polymers selected should be readily synthesized at large scale (>1 kg) and high performance. In this work, we demonstrate a novel tandem polymer solar cell that combines low band gap poly isoindigo [P(T3-iI)-2], which is easily synthesized in kilogram quantities, with a novel Cr/MoO3 interconnecting layer. Cr/MoO3 is shown to be greater than 80% transparent above 375 nm and an efficient interconnecting layer for P(T3-iI)-2 and PCDTBT, leading to 6% power conversion efficiencies under AM 1.5G illumination. These results serve to extend the range of interconnecting layer materials for tandem cell fabrication by establishing, for the first time, that a thin, evaporated layer of Cr/MoO3 can work as an effective interconnecting layer in a tandem polymer solar cells made with scalable photoactive materials.

Polymeric ionic liquid based on magnetic materials fabricated through layer-by-layer assembly as adsorbents for extraction of pesticides.

PubMed

He, Lijun; Cui, Wenhang; Wang, Yali; Zhao, Wenjie; Xiang, Guoqiang; Jiang, Xiuming; Mao, Pu; He, Juan; Zhang, Shusheng

2017-11-03

In this study, layer-by-layer assembly of polyelectrolyte multilayer films on magnetic silica provided a convenient and controllable way to prepare polymeric ionic liquid-based magnetic adsorbents. The resulting particles were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and magnetic measurements. The data showed that the magnetic particles had more homogeneous spherical shapes with higher saturation magnetization when compared to those obtained by free radical polymerization method. This facilitated the convenient collection of magnetic particles, with higher extraction repeatability. The extraction performance of the multilayer polymeric ionic liquid-based adsorbents was evaluated by magnetic solid-phase extraction of four pesticides including quinalphos, fenthion, phoxim, and chlorpropham. The data suggested that the extraction efficiency depended on the number of layers in the film. The parameters affecting the extraction efficiency were optimized, and good linearity ranging from 2 to 250μgL -1 was obtained with correlation coefficients of 0.9994-0.9998. Moreover, the proposed method presented low limit of detection (0.5μgL -1 , S/N=3) and limit of quantification (1.5μgL -1 , S/N=10), and good repeatability expressed by the relative standard deviation (2.0%-4.6%, n=5). The extraction recoveries of four pesticides were found to range from 58.9% to 85.8%. The reliability of the proposed method was demonstrated by analyzing environmental water samples, and the results revealed satisfactory spiked recovery, relative standard deviation, and selectivity. Copyright © 2017 Elsevier B.V. All rights reserved.

Porous double-layer polymer tubing for the potential use in heterogeneous continuous flow reactions.

PubMed

Herwig, Gordon; Hornung, Christian H; Peeters, Gary; Ebdon, Nicholas; Savage, G Paul

2014-12-24

Functional polymer tubing with an OD of 1/16 or 1/8 in. was fabricated by a simple polymer coextrusion process. The tubing was made of an outer impervious polypropylene layer and an inner layer, consisting of a blend of a functional polymer, polyethylene-co-methacrylic acid, and a sacrificial polymer, polystyrene. After a simple solvent leaching step using common organic solvents, the polystyrene was removed, leaving behind a porous inner layer that contains functional carboxylic acid groups, which could then be used for the immobilization of target molecules. Solution-phase reactions using amines or isocyanates have proven successful for the immobilization of a series of small molecules and polymers. This flexible multilayered functional tubing can be easily cut to the desired length and connected via standard microfluidic fittings.

Focus: Structure and dynamics of the interfacial layer in polymer nanocomposites with attractive interactions

DOE PAGES

Cheng, Shiwang; Carroll, Bobby; Bocharova, Vera; ...

2017-03-30

In recent years it has become clear that the interfacial layer formed around nanoparticles in polymer nanocomposites (PNCs) is critical for controlling their macroscopic properties. The interfacial layer occupies a significant volume fraction of the polymer matrix in PNCs and creates strong intrinsic heterogeneity in their structure and dynamics. In this paper, we focus on analysis of the structure and dynamics of the interfacial region in model PNCs with well-dispersed, spherical nanoparticles with attractive interactions. First, we discuss several experimental techniques that provide structural and dynamic information on the interfacial region in PNCs. Then, we discuss the role of variousmore » microscopic parameters in controlling structure and dynamics of the interfacial layer. The analysis presented emphasizes the importance of the polymer-nanoparticle interactions for the slowing down dynamics in the interfacial region, while the thickness of the interfacial layer appears to be dependent on chain rigidity, and has been shown to increase with cooling upon approaching the glass transition. Aside from chain rigidity and polymer-nanoparticle interactions, the interfacial layer properties are also affected by the molecular weight of the polymer and the size of the nanoparticles. Finally, in the last part of this focus article, we emphasize the important challenges in the field of polymer nanocomposites and a potential analogy with the behavior observed in thin films.« less

Layered double hydroxide-based nanomaterials as highly efficient catalysts and adsorbents.

PubMed

Li, Changming; Wei, Min; Evans, David G; Duan, Xue

2014-11-01

Layered double hydroxides (LDHs) are a class of anion clays consisting of brucite-like host layers and interlayer anions, which have attracted increasing interest in the fields of catalysis/adsorption. By virtue of the versatility in composition, morphology, and architecture of LDH materials, as well as their unique structural properties (intercalation, topological transformation, and self-assembly with other functional materials), LDHs display great potential in the design and fabrication of nanomaterials applied in photocatalysis, heterogeneous catalysis, and adsorption/separation processes. Taking advantage of the structural merits and various control synthesis strategies of LDHs, the active center structure (e.g., crystal facets, defects, geometric and electronic states, etc.) and macro-nano morphology can be facilely manipulated for specific catalytic/adsorbent processes with largely enhanced performances. In this review, the latest advancements in the design and preparation of LDH-based functional nanomaterials for sustainable development in catalysis and adsorption are summarized. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Room temperature rubbing for few-layer two-dimensional thin flakes directly on flexible polymer substrates

PubMed Central

Yu, Yan; Jiang, Shenglin; Zhou, Wenli; Miao, Xiangshui; Zeng, Yike; Zhang, Guangzu; Liu, Sisi

2013-01-01

The functional layers of few-layer two-dimensional (2-D) thin flakes on flexible polymers for stretchable applications have attracted much interest. However, most fabrication methods are “indirect” processes that require transfer steps. Moreover, previously reported “transfer-free” methods are only suitable for graphene and not for other few-layer 2-D thin flakes. Here, a friction based room temperature rubbing method is proposed for fabricating different types of few-layer 2-D thin flakes (graphene, hexagonal boron nitride (h-BN), molybdenum disulphide (MoS2), and tungsten disulphide (WS2)) on flexible polymer substrates. Commercial 2-D raw materials (graphite, h-BN, MoS2, and WS2) that contain thousands of atom layers were used. After several minutes, different types of few-layer 2-D thin flakes were fabricated directly on the flexible polymer substrates by rubbing procedures at room temperature and without any transfer step. These few-layer 2-D thin flakes strongly adhere to the flexible polymer substrates. This strong adhesion is beneficial for future applications. PMID:24045289

Differences between tethered polyelectrolyte chains adsorbed onto bare mica and hydrophobically modified mica, comparison with theory.

NASA Astrophysics Data System (ADS)

Balastre, Marc; Tamashiro, Mario N.; Hernandez, Ernesto; Pincus, Philip; Tirrell, Matthew

2001-03-01

End-grafted polymers generated from the adsorption of asymmetric diblock copolymers on solid surface play an important role in many areas of science and technology. While the small insoluble block acts as an anchor, the charged soluble block confers useful properties to the surface. This study looks at tethered layers of poly(styrene sulfonate)/poly(t-butyl styrene) (PtBS-PSS) adsorbed on both mica (hydrophilic) and octadecyltriethoxysilane (OTE) modified mica (hydrophobic). Normal compressing forces at two different constant grafting densities (bare and modified mica) were measured with the surface force apparatus and compared with theoretical prediction. The effect of salt concentration (Cs) upon the thickness of the self-assembled layers (Lo) was measured in each case. For adsorption of diblock copolymers onto OTE the resulting scaling relationship is much closer to the brush theory, Lo Cs-1/3. This result suggests that the adsorbed amount on mica is not high enough to form a brush.

Versatile dual organic interface layer for performance enhancement of polymer solar cells

NASA Astrophysics Data System (ADS)

Li, Zhiqi; Liu, Chunyu; Zhang, Zhihui; Li, Jinfeng; Zhang, Liu; Zhang, Xinyuan; Shen, Liang; Guo, Wenbin; Ruan, Shengping

2016-11-01

The electron transport layer plays a crucial role on determining electron injection and extraction, resulting from the effect of balancing charge transport and reducing the interfacial energy barrier. Decreasing the inherent incompatibility and enhancing electrical contact via employing appropriate buffer layer at the surface of hydrophobic organic active layer and hydrophilic inorganic electrode are also essential for charge collection. Herein, we demonstrate that an efficient dual polyelectrolytes interfacial layer composed of polyethylenimine (PEI) and conducting poly(9,9-dihexylfluorenyl-2,7-diyl) (PDHFD) is incorporated to investigate the interface energetics and electron transport in polymer solar cells (PSCs). The composited PEI/PDHFD interface layer (PPIL) overcomed the low conductivity of bare PEI polymer, which decreased series resistance and facilitated electron extraction at the ITO/PPIL-active layer interface. The introduction of the interface energy state of the PPIL reduced the work function of ITO so that it can mate the top of the valence band of the photoactive materials and promoted the formation of ohmic contact at ITO electrode interface. As a result, the composited PPIL tuned energy alignment and accelerated the electron transfer, leading to significantly increased photocurrent and power conversion efficiency (PCE) of the devices based on various representative polymer:fullerene systems.

Polymer/graphite oxide composites as high-performance materials for electric double layer capacitors

NASA Astrophysics Data System (ADS)

Tien, Chien-Pin; Teng, Hsisheng

A single graphene sheet represents a carbon material with the highest surface area available to accommodating molecules or ions for physical and chemical interactions. Here we demonstrate in an electric double layer capacitor the outstanding performance of graphite oxide for providing a platform for double layer formation. Graphite oxide is generally the intermediate compound for obtaining separated graphene sheets. Instead of reduction with hydrazine, we incorporate graphite oxide with a poly(ethylene oxide)-based polymer and anchor the graphene oxide sheets with poly(propylene oxide) diamines. This polymer/graphite oxide composite shows in a "dry" gel-electrolyte system a double layer capacitance as high as 130 F g -1. The polymer incorporation developed here can significantly diversify the application of graphene-based materials in energy storage devices.

Optical characterizations of silver nanoprisms embedded in polymer thin film layers

NASA Astrophysics Data System (ADS)

Carlberg, Miriam; Pourcin, Florent; Margeat, Olivier; Le Rouzo, Judikael; Berginc, Gerard; Sauvage, Rose-Marie; Ackermann, Jorg; Escoubas, Ludovic

2017-10-01

The precise control of light-matter interaction has a wide range of applications and is currently driven by the use of nanoparticles (NPs) by the recent advances in nanotechnology. Taking advantage of the material, size, shape, and surrounding media dependence of the optical properties of plasmonic NPs, thin film layers with tunable optical properties are achieved. The NPs are synthesized by wet chemistry and embedded in a polyvinylpyrrolidone (PVP) polymer thin film layer. Spectrophotometer and spectroscopic ellipsometry measurements are coupled to finite-difference time domain numerical modeling to optically characterize the heterogeneous thin film layers. Silver nanoprisms of 10 to 50 nm edge size exhibit high absorption through the visible wavelength range. A simple optical model composed of a Cauchy law and a Lorentz law, accounting for the optical properties of the nonabsorbing polymer and the absorbing property of the nanoprisms, fits the spectroscopic ellipsometry measurements. Knowing the complex optical indices of heterogeneous thin film layers let us design layers of any optical properties.

Adsorption properties of the nanozirconia/anionic polyacrylamide system-Effects of surfactant presence, solution pH and polymer carboxyl groups content

NASA Astrophysics Data System (ADS)

Wiśniewska, Małgorzata; Chibowski, Stanisław; Urban, Teresa

2016-05-01

The adsorption mechanism of anionic polyacrylamide (PAM) on the nanozirconia surface was examined. The effects of solution pH, carboxyl groups content in macromolecules and anionic surfactant (sodium dodecyl sulfate-SDS) addition were determined. The more probable structure of polymer adsorption layer was characterized based on the data obtained from spectrophotometry, viscosimetry and potentiometric titration methods. The adsorbed amount of polymer, size of macromolecules in the solution and surface charge density of ZrO2 particles in the absence and presence of PAM were assessed, respectively. Analysis of these results indicated that the increase of solution pH and content of carboxyl groups in the polymeric chains lead to more expanded conformations of adsorbing macromolecules. As a result, the adsorption of anionic polyacrylamide decreased. The SDS presence caused the significant increase of PAM adsorbed amount at pH 3, whereas at pH 6 and 9 the surfactant addition resulted in reduction of polymer adsorption level.

Diffusion of drag-reducing polymer solutions within a rough-walled turbulent boundary layer

NASA Astrophysics Data System (ADS)

Elbing, Brian R.; Dowling, David R.; Perlin, Marc; Ceccio, Steven L.

2010-04-01

The influence of surface roughness on diffusion of wall-injected, drag-reducing polymer solutions within a turbulent boundary layer was studied with a 0.94 m long flat-plate test model at speeds of up to 10.6 m s-1 and Reynolds numbers of up to 9×106. The surface was hydraulically smooth, transitionally rough, or fully rough. Mean concentration profiles were acquired with planar laser induced fluorescence, which was the primary flow diagnostic. Polymer concentration profiles with high injection concentrations (≥1000 wppm) had the peak concentration shifted away from the wall, which was partially attributed to a lifting phenomenon. The diffusion process was divided into three zones—initial, intermediate, and final. Studies of polymer injection into a polymer ocean at concentrations sufficient for maximum drag reduction indicated that the maximum initial zone length is of the order of 100 boundary layer thicknesses. The intermediate zone results indicate that friction velocity and roughness height are important scaling parameters in addition to flow and injection conditions. Lastly, the current results were combined with those in Petrie et al. ["Polymer drag reduction with surface roughness in flat-plate turbulent boundary layer flow," Exp. Fluids 35, 8 (2003)] to demonstrate that the influence of polymer degradation increases with increased surface roughness.

Bioelectrochemical control of neural cell development on conducting polymers.

PubMed

Collazos-Castro, Jorge E; Polo, José L; Hernández-Labrado, Gabriel R; Padial-Cañete, Vanesa; García-Rama, Concepción

2010-12-01

Electrically conducting polymers hold promise for developing advanced neuroprostheses, bionic systems and neural repair devices. Among them, poly(3, 4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) exhibits superior physicochemical properties but biocompatibility issues have limited its use. We describe combinations of electrochemical and molecule self-assembling methods to consistently control neural cell development on PEDOT:PSS while maintaining very low interfacial impedance. Electro-adsorbed polylysine enabled long-term neuronal survival and growth on the nanostructured polymer. Neurite extension was strongly inhibited by an additional layer of PSS or heparin, which in turn could be either removed electrically or further coated with spermine to activate cell growth. Binding basic fibroblast growth factor (bFGF) to the heparin layer inhibited neurons but promoted proliferation and migration of precursor cells. This methodology may orchestrate neural cell behavior on electroactive polymers, thus improving cell/electrode communication in prosthetic devices and providing a platform for tissue repair strategies. Copyright © 2010 Elsevier Ltd. All rights reserved.

A coordination polymer based magnetic adsorbent material for hemoglobin isolation from human whole blood, highly selective and recoverable

NASA Astrophysics Data System (ADS)

Zhang, Xiaoxing; Tan, Jipeng; Xu, Xinxin; Shi, Fanian; Li, Guanglu; Yang, Yiqiao

2017-09-01

A composite material has been obtained successfully through the loading of nanoscale coordination polymer on magnetic Fe3O4@SiO2 core-shell particle. In this composite material, coordination polymer nanoparticles distribute uniformly on Fe3O4@SiO2 and these two components are "tied" together firmly with chemical bonds. Adsorption experiments suggest this composite material exhibits very excellent selectivity to hemoglobin. But under the same condition, its adsorption to bovine serum albumin can almost be ignored. This selectivity can be attributed to the existence of hydrophobic interactions between coordination polymer nanoparticle and hemoglobin. For composite material, the hemoglobin adsorption process follows Langmuir model perfectly with high speed. The adsorbed hemoglobin can be eluted easily by sodium dodecyl sulfate stripping reagent with structure and biological activity of hemoglobin keeps well. The composite material was also employed to separate hemoglobin from human whole blood, which receives a very satisfactory result. Furthermore, magnetic measurement reveals ferromagnetic character of this composite material with magnetization saturation 3.56 emu g-1 and this guarantees its excellent magnetic separation performance from the treated solution.

Bioactivity of freeze-dried platelet-rich plasma in an adsorbed form on a biodegradable polymer material.

PubMed

Nakajima, Yu; Kawase, Tomoyuki; Kobayashi, Mito; Okuda, Kazuhiro; Wolff, Larry F; Yoshie, Hiromasa

2012-01-01

Owing to the necessity for the immediate preparation from patients' blood, autologous platelet-rich plasma (PRP) limits its clinical applicability. To address this concern and respond to emergency care and other unpredictable uses, we have developed a freeze-dried PRP in an adsorbed form on a biodegradable polymer material (Polyglactin 910). On the polymer filaments of PRP mesh, which was prepared by coating the polymer mesh with human fresh PRP and subsequent freeze-drying, platelets were incorporated, and related growth factors were preserved at high levels. This new PRP mesh preparation significantly and reproducibly stimulated the proliferation of human periodontal ligament cells in vitro and neovascularization in a chorioallantoic membrane assay. A full-thickness skin defect model in a diabetic mouse demonstrated the PRP mesh, although prepared from human blood, substantially facilitated angiogenesis, granulation tissue formation, and re-epithelialization without inducing severe inflammation in vivo. These data demonstrate that our new PRP mesh preparation functions as a bioactive material to facilitate tissue repair/regeneration. Therefore, we suggest that this bioactive material, composed of allogeneic PRP, could be clinically used as a promising alternative in emergency care or at times when autologous PRP is not prepared immediately before application.

Organic phototransistors with nanoscale phase-separated polymer/polymer bulk heterojunction layers

NASA Astrophysics Data System (ADS)

Hwang, Hyemin; Kim, Hwajeong; Nam, Sungho; Bradley, Donal D. C.; Ha, Chang-Sik; Kim, Youngkyoo

2011-05-01

Low-cost detectors for sensing photons at a low light intensity are of crucial importance in modern science. Phototransistors can deliver better signals of low-intensity light by electrical amplification, but conventional inorganic phototransistors have a limitation owing to their high temperature processes in vacuum. In this work, we demonstrate organic phototransistors with polymer/polymer bulk heterojunction blend films (mixtures of p-type and n-type semiconducting polymers), which can be fabricated by inexpensive solution processes at room temperature. The key idea here is to effectively exploit hole charges (from p-type polymer) as major signaling carriers by employing p-type transistor geometry, while the n-type polymer helps efficient charge separation from excitons generated by incoming photons. Results showed that the present organic transistors exhibited proper functions as p-type phototransistors with ~4.3 A W-1 responsivity at a low light intensity (1 µW cm-2), which supports their encouraging potential to replace conventional cooled charge coupled devices (CCD) for low-intensity light detection applications.Low-cost detectors for sensing photons at a low light intensity are of crucial importance in modern science. Phototransistors can deliver better signals of low-intensity light by electrical amplification, but conventional inorganic phototransistors have a limitation owing to their high temperature processes in vacuum. In this work, we demonstrate organic phototransistors with polymer/polymer bulk heterojunction blend films (mixtures of p-type and n-type semiconducting polymers), which can be fabricated by inexpensive solution processes at room temperature. The key idea here is to effectively exploit hole charges (from p-type polymer) as major signaling carriers by employing p-type transistor geometry, while the n-type polymer helps efficient charge separation from excitons generated by incoming photons. Results showed that the present organic

Improved Efficiency of Polymer Solar Cells by means of Coating Hole Transporting Layer as Double Layer Deposition

NASA Astrophysics Data System (ADS)

Chonsut, T.; Kayunkid, N.; Rahong, S.; Rangkasikorn, A.; Wirunchit, S.; Kaewprajak, A.; Kumnorkaew, P.; Nukeaw, J.

2017-09-01

Polymer solar cells is one of the promising technologies that gain tremendous attentions in the field of renewable energy. Optimization of thickness for each layer is an important factor determining the efficiency of the solar cells. In this work, the optimum thickness of Poly(3,4-ethylenedioxythione): poly(styrenesulfonate) (PEDOT:PSS), a famous polymer widely used as hole transporting layer in polymer solar cells, is determined through the analyzing of device’s photovoltaic parameters, e.g. short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF) as well as power conversion efficiency (PCE). The solar cells were prepared with multilayer of ITO/PEDOT:PSS/PCDTBT:PC70BM/TiOx/Al by rapid convective deposition. In such preparation technique, the thickness of the thin film is controlled by the deposition speed. The faster deposition speed is used, the thicker film is obtained. Furthermore, double layer deposition of PEDOT:PSS was introduced as an approach to improve solar cell efficiency. The results obviously reveal that, with the increase of PEDOT:PSS thickness, the increments of Jsc and FF play the important role to improve PCE from 3.21% to 4.03%. Interestingly, using double layer deposition of PEDOT:PSS shows the ability to enhance the performance of the solar cells to 6.12% under simulated AM 1.5G illumination of 100 mW/cm2.

Role of Polymer Segregation on the Mechanical Behavior of All-Polymer Solar Cell Active Layers.

PubMed

Balar, Nrup; Xiong, Yuan; Ye, Long; Li, Sunsun; Nevola, Daniel; Dougherty, Daniel B; Hou, Jianhui; Ade, Harald; O'Connor, Brendan T

2017-12-20

An all-polymer bulk heterojunction (BHJ) active layer that removes the use of commonly used small molecule electron acceptors is a promising approach to improve the thermomechanical behavior of organic solar cells. However, there has been limited research on their mechanical properties. Here, we report on the mechanical behavior of high-performance blade-coated all-polymer BHJ films cast using eco-friendly solvents. The mechanical properties considered include the elastic modulus, crack onset strain, and cohesive fracture energy. We show that the mechanical behavior of the blend is largely unaffected by significant changes in the segregation characteristics of the polymers, which was varied systematically through solvent formulation. In comparison to a polymer:fullerene BHJ counterpart, the all-polymer films were found to have lower stiffness and increased ductility. Yet, the fracture energy of the all-polymer films is not significantly improved compared to that of the polymer:fullerene films. This study highlights that improved mechanical behavior of all-polymer systems cannot be assumed, and that details of the molecular structure, molecular weight, and film morphology play an important role in both the optoelectronic and mechanical properties. Furthermore, we show that simple composite modeling provides a predictive tool for the mechanical properties of the polymer blend films, providing a framework to guide future optimization of the mechanical behavior.

Enhanced structural color generation in aluminum metamaterials coated with a thin polymer layer

DOE PAGES

Cheng, Fei; Yang, Xiaodong; Rosenmann, Daniel; ...

2015-09-18

A high-resolution and angle-insensitive structural color generation platform is demonstrated based on triple-layer aluminum-silica-aluminum metamaterials supporting surface plasmon resonances tunable across the entire visible spectrum. The color performances of the fabricated aluminum metamaterials can be strongly enhanced by coating a thin transparent polymer layer on top. The results show that the presence of the polymer layer induces a better impedance matching for the plasmonic resonances to the free space so that strong light absorption can be obtained, leading to the generation of pure colors in cyan, magenta, yellow and black (CMYK) with high color saturation.

An all-solid-state reference electrode based on the layer-by-layer polymer coating.

PubMed

Kwon, Nak-Hyun; Lee, Kyung-Sun; Won, Mi-Sook; Shim, Yoon-Bo

2007-09-01

A solid-state reference electrode (SSRE) was fabricated by layering a silicone rubber (SR) film containing KCl on an AgCl surface, then a perfluorinated ionomer film, and finally a polyurethane-based membrane containing an ionophore, a lipophilic ionic additive, and a plasticizer, respectively. The addition of SiCl4 to the polyurethane-based membrane layer enhanced the strength of the membrane in an aqueous solution. The morphologies of the membranes were studied separately by SEM. The fabrication of the Ag/AgCl electrode through this layer-by-layer polymer coating improved the electrode stability enormously. In addition, the potential drift of the SSRE according to the pH of the medium was minimized by introducing a H+-ion-selective ionophore (tridodecylamine; TDDA) into the outmost polymer membrane. The cyclic voltammetric and potentiometric responses using the SSRE and a conventional reference electrode, respectively, were consistent. The SSRE exhibited little potential variation even in the case of the addition of very high concentrations of various salts, such as Na salicylate, LiCl, KCl, CaCl2, MgCl2, KNO3, NaCl, and NaHCO3. The practicability of the proposed SSRE was tested for the determination of blood pH and pCO2 in a flow cell system. The SSRE fabricated in the present study was stable over two years.

The effect of chain rigidity on the interfacial layer thickness and dynamics of polymer nanocomposites

NASA Astrophysics Data System (ADS)

Cheng, Shiwang; Carrillo, Jan-Michael Y.; Carroll, Bobby; Sumpter, Bobby G.; Sokolov, Alexei P.

There are growing experimental evidences showing the existence of an interfacial layer that has a finite thickness with slowing down dynamics in polymer nanocomposites (PNCs). Moreover, it is believed that the interfacial layer plays a significant role on various macroscopic properties of PNCs. A thicker interfacial layer is found to have more pronounced effect on the macroscopic properties such as the mechanical enhancement. However, it is not clear what molecular parameter controls the interfacial layer thickness. Inspired by our recent computer simulations that showed the chain rigidity correlated well with the interfacial layer thickness, we performed systematic experimental studies on different polymer nanocomposites by varying the chain stiffness. Combining small-angle X-ray scattering, broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry, we find a good correlation between the polymer Kuhn length and the thickness of the interfacial layer, confirming the earlier computer simulations results. Our findings provide a direct guidance for the design of new PNCs with desired properties.

Novel processing to produce polymer/ceramic nanocomposites by atomic layer deposition

NASA Astrophysics Data System (ADS)

Liang, Xinhua

Polymeric materials can be greatly influenced by nanoscale inclusions of inorganic materials. The main goal of this thesis is to fabricate novel polymer/ceramic composite materials for two different applications using atomic layer deposition (ALD) or molecular layer deposition (MLD) methods. One is to produce well-dispersed polymer/ceramic nanocomposites with improved barrier properties for packaging applications. The other is to produce porous polymer/ceramic composites with improved bioactivity for tissue engineering applications. ALD has been successfully utilized for the conformal and uniform deposition of ultra-thin alumina and titania films on primary micron-sized polymer particles. The mechanism to initiate alumina and titania ALD on polymer particles without chemical functional groups was confirmed. A nucleation period was needed for both alumina and titania ALD on high density polyethylene (HDPE) particles and no nucleation period was needed for alumina ALD on polymethyl methacrylate particles. Titania ALD films deposited at low temperatures had an amorphous structure and showed much weaker photoactivity than common pigment-grade anatase TiO2 particles. Highly uniform and conformal ultra-thin aluminum alkoxide (alucone) polymer films were deposited on primary silica and titania nanoparticles using MLD in a fluidized bed reactor. The deposition chemistry and properties of alucone MLD films were investigated. The photoactivity of pigment-grade TiO2 particles was quenched after 20 cycles of an alucone MLD film, but the films shrank and decomposed in the presence of water, which decreased the passivation effect of the photoactivity of TiO2 particles. Well-dispersed polymer/ceramic nanocomposites were obtained by extruding alumina ALD coated HDPE particles. The diffusion coefficient of the fabricated nanocomposite membranes can be reduced by half with the inclusion of 7.3 vol.% alumina flakes. However, a corresponding increase in permeability was also observed

Solid-phase microextraction of phthalate esters in water sample using different activated carbon-polymer monoliths as adsorbents.

PubMed

Lirio, Stephen; Fu, Chung-Wei; Lin, Jhih-Yun; Hsu, Meng-Ju; Huang, Hsi-Ya

2016-07-13

In this study, the application of different activated carbon-polymer (AC-polymer) monoliths as adsorbents for the solid-phase microextraction (SPME) of phthalate esters (PAEs) in water sample were investigated. The activated carbon (AC) was embedded in organic polymers, poly(butyl methacrylate-co-ethylene dimethacrylate) (poly(BMA-EDMA)) or poly(styrene-co-divinylbenzene) (poly(STY-DVB)), via a 5-min microwave-assisted or a 15-min water bath heating polymerization. Preliminary investigation on the performance of the native poly(BMA-EDMA) and poly(STY-DVB) demonstrated remarkable adsorption efficiencies for PAEs. However, due to the strong hydrophobic, π-π, and hydrogen bonding interactions between the analytes and polymers, low extraction recoveries were achieved. In contrast, the presence of AC in native polymers not only enhanced the adsorption efficiencies but also assisted the PAE desorption, especially for AC-poly(STY-DVB) with extraction recovery ranged of 76.2-99.3%. Under the optimized conditions, the extraction recoveries for intra-, inter-day and column-to-column were in the range of 76.5-100.8% (<3.7% RSDs), 77.2-97.6% (<5.6% RSDs) and 75.5-99.7% (<6.2% RSDs), respectively. The developed AC-poly(STY-DVB) monolithic column showed good mechanical stability, which can be reused for more than 30 extraction times without any significant loss in the extraction recoveries of PAEs. The AC-poly(STY-DVB) monolithic column was successfully applied in SPME of PAEs in water sample with extraction recovery ranged of 78.8%-104.6% (<5.5% RSDs). Copyright © 2016 Elsevier B.V. All rights reserved.

Polymer-Layered Silicate Nanocomposites for Cryotank Applications

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Meador, Michael A.

2007-01-01

Previous composite cryotank designs have relied on the use of conventional composite materials to reduce microcracking and permeability. However, revolutionary advances in nanotechnology derived materials may enable the production of ultra-lightweight cryotanks with significantly enhanced durability and damage tolerance, as well as reduced propellant permeability. Layered silicate nanocomposites are especially attractive in cryogenic storage tanks based on results that have been reported for epoxy nanocomposite systems. These materials often exhibit an order of magnitude reduction in gas permeability when compared to the base resin. In addition, polymer-silicate nanocomposites have been shown to yield improved dimensional stability, strength, and toughness. The enhancement in material performance of these systems occurs without property trade-offs which are often observed in conventionally filled polymer composites. Research efforts at NASA Glenn Research Center have led to the development of epoxy-clay nanocomposites with 70% lower hydrogen permeability than the base epoxy resin. Filament wound carbon fiber reinforced tanks made with this nanocomposite had a five-fold lower helium leak rate than the corresponding tanks made without clay. The pronounced reduction observed with the tank may be due to flow induced alignment of the clay layers during processing. Additionally, the nanocomposites showed CTE reductions of up to 30%, as well as a 100% increase in toughness.

Chromatic control in coextruded layered polymer microlenses

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Oder, Tom N.; Andrews, James H.; Zhou, Chuanhong; Petrus, Joshua B.; Merlo, Cory; Bagheri, Cameron; Hetzel, Connor; Tancabel, James; Singer, Kenneth D.; Baer, Eric

2014-12-01

We describe the formation, characterization and theoretical understanding of microlenses comprised of alternating polystyrene and polymethylmethacrylate layers produced by multilayer coextrusion. These lenses are fabricated by photolithography, using a grayscale mask followed by plasma etching, so that the refractive index alternation of the bilayer stack appears across the radius of the microlens. The alternating quarter-wave thick layers form a one-dimensional photonic crystal whose dispersion augments the material dispersion, allowing one to sculpt the chromatic dispersion of the lens by adjusting the layered structure. Using Huygen's principle, we model our experimental measurements of the focal length of these lenses across the reflection band of the multilayer polymer film from which the microlens is fashioned. For a 56 micron diameter multilayered lens of focal length 300 microns, we measured a nearly 25 percent variation in the focal length across a shallow, 50 nm-wide reflection band.

Crystallization of Polymers in Confined Environments: Structural Development of Semi-crystalline Polymer-Layered Silicate Nanocomposites

NASA Astrophysics Data System (ADS)

Vaia, Richard A.; Lincoln, Derek M.; Wang, Zhi-Gang; Hsiao, Benjamin S.; Krishnamoorti, Ramanan

2000-03-01

Over the last decade, the utility of ultrafine dispersions of inorganic nanoparticles to enhance polymer performance and function as precursors to form self-passivating / self-healing inorganic coatings on the polymer surface has been established. Before developing the fundamental structure-property relationships though, a detailed understanding of processing / morphology relationships is necessary. As with other multiphase systems exhibiting nano (1-100 nm) and meso (100-500 nm) order (such as biopolymers, block-copolymers, colloidal suspensions, liquid crystals), physical properties ranging from toughness to optical clarity are determined by morphology on various length scales which in turn arise from processing history. This is anticipated to be especially important for blends containing two or more constituents with fundamental structural features on the nanoscale, such as crystal lamellae and aluminosilicate sheets. Small-angle x-ray scattering experiments with synchrotron radiation reveal the presence of ultra-long range (20-60 nm) mesoscopic ordering of the layered silicate in molten polyamide 6-layered silicate nanocomposites. This superstructure of these semi-rigid inorganic sheets provides a confined environment to examine the crystallization of polyamide 6 with traditional bulk characterization techniques. In addition to a change lamellae organization and lamellae size, the presence of the aluminosilicate layers and extent of interfacial interactions (end-tethered v. physiadsorbed chains) substantially alters the nucleation rate, growth kinetics and Brill transition of the crystal phase as revealed by isothermal crystallization experiments monitored in-situ with synchrotron radiation. These exfoliated nanocomposites provide new opportunities to investigate confined polymer crystallization as well as provide insight into the origin of various property enhancements in these systems.

Dynamics of comb-of-comb-network polymers in random layered flows

NASA Astrophysics Data System (ADS)

Katyal, Divya; Kant, Rama

2016-12-01

We analyze the dynamics of comb-of-comb-network polymers in the presence of external random flows. The dynamics of such structures is evaluated through relevant physical quantities, viz., average square displacement (ASD) and the velocity autocorrelation function (VACF). We focus on comparing the dynamics of the comb-of-comb network with the linear polymer. The present work displays an anomalous diffusive behavior of this flexible network in the random layered flows. The effect of the polymer topology on the dynamics is analyzed by varying the number of generations and branch lengths in these networks. In addition, we investigate the influence of external flow on the dynamics by varying flow parameters, like the flow exponent α and flow strength Wα. Our analysis highlights two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The anomalous long-time dynamics is governed by the temporal exponent ν of ASD, viz., ν =2 -α /2 . Compared to a linear polymer, the comb-of-comb network shows a shorter crossover time (from the subdiffusive to superdiffusive regime) but a reduced magnitude of ASD. Our theory displays an anomalous VACF in the random layered flows that scales as t-α /2. We show that the network with greater total mass moves faster.

Determination of active layer morphology in all-polymer photovoltaic cells

DOE PAGES

Mulderig, Andrew J.; Jin, Yan; Yu, Fei; ...

2017-08-18

This paper investigates the structure of films spin-coated from blends of the semiconducting polymers poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly{2,6-[4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene]-alt-4,7(2,1,3-benzo­thiadiazole)} (PCPDTBT). Such blends are of potential use in all-polymer solar cells in which both the acceptor and the donor material generate excitons to contribute to the photocurrent. Prompted by threefold performance gains seen in polymer/fullerene and polymer blend solar cells upon addition of pristine graphene, devices are prepared from P3HT/PCPDTBT blends both with and without graphene. This report focuses on the morphology of the active layer since this is of critical importance in determining performance. Small-angle neutron scattering (SANS) is utilized tomore » study this polymer blend with deuterated P3HT to provide contrast and permit the investigation of buried structure in neat and graphene-doped films. SANS reveals the presence of P3HT crystallites dispersed in an amorphous blend matrix of P3HT and PCPDTBT. The crystallites are approximately disc shaped and do not show any evidence of higher-order structure or aggregation. While the structure of the films does not change with the addition of graphene, there is a perceptible effect on the electronic properties and energy conversion efficiency in solar cells made from such films. Finally, determination of the active layer morphology yields crucial insight into structure–property relationships in organic photovoltaic devices.« less

Determination of active layer morphology in all-polymer photovoltaic cells

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

Mulderig, Andrew J.; Jin, Yan; Yu, Fei

This paper investigates the structure of films spin-coated from blends of the semiconducting polymers poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly{2,6-[4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene]-alt-4,7(2,1,3-benzo­thiadiazole)} (PCPDTBT). Such blends are of potential use in all-polymer solar cells in which both the acceptor and the donor material generate excitons to contribute to the photocurrent. Prompted by threefold performance gains seen in polymer/fullerene and polymer blend solar cells upon addition of pristine graphene, devices are prepared from P3HT/PCPDTBT blends both with and without graphene. This report focuses on the morphology of the active layer since this is of critical importance in determining performance. Small-angle neutron scattering (SANS) is utilized tomore » study this polymer blend with deuterated P3HT to provide contrast and permit the investigation of buried structure in neat and graphene-doped films. SANS reveals the presence of P3HT crystallites dispersed in an amorphous blend matrix of P3HT and PCPDTBT. The crystallites are approximately disc shaped and do not show any evidence of higher-order structure or aggregation. While the structure of the films does not change with the addition of graphene, there is a perceptible effect on the electronic properties and energy conversion efficiency in solar cells made from such films. Finally, determination of the active layer morphology yields crucial insight into structure–property relationships in organic photovoltaic devices.« less

Preparation, characterization and properties of polymer-layered silicate nanocomposites

NASA Astrophysics Data System (ADS)

Fonseca, Claudia Alencar

Nanocomposites are a relatively new class of composites, that in the polymer area typically consist of particle-filled polymers where at least one dimension of the dispersed particles is in the nanometer range. Amongst all potential nanocomposite precursors, those based on clay and layered silicates have been more widely investigated. These nanocomposites exhibit markedly improved mechanical, thermal, optical and physico-chemical properties when compared to conventional (microscale) composites. In the present work, properties of nanocomposites of Ethylene Methacrylic Acid copolymers and organically modified Montmorillonite formed from the melt was investigated. Nanocomposites of Poly(vinyl alcohol) and Montmorillonite formed from solution was also studied.

Control of the dipole layer of polar organic molecules adsorbed on metal surfaces via different charge-transfer channels

NASA Astrophysics Data System (ADS)

Lin, Meng-Kai; Nakayama, Yasuo; Zhuang, Ying-Jie; Su, Kai-Jun; Wang, Chin-Yung; Pi, Tun-Wen; Metz, Sebastian; Papadopoulos, Theodoros A.; Chiang, T.-C.; Ishii, Hisao; Tang, S.-J.

2017-02-01

Organic molecules with a permanent electric dipole moment have been widely used as a template for further growth of molecular layers in device structures. Key properties of the resulting organic films such as energy level alignment (ELA), work function, and injection/collection barrier are linked to the magnitude and direction of the dipole moment at the interface. Using angle-resolved photoemission spectroscopy (ARPES), we have systematically investigated the coverage-dependent work function and spectral line shapes of occupied molecular energy states (MESs) of chloroaluminium-phthalocyanine (ClAlPc) grown on Ag(111). We demonstrate that the dipole orientation of the first ClAlPc layer can be controlled by adjusting the deposition rate and postannealing conditions, and we find that the ELA at the interface differs by ˜0.4 eV between the Cl up and down configurations of the adsorbed ClAlPc molecules. These observations are rationalized by density functional theory (DFT) calculations based on a realistic model of the ClAlPc/Ag(111) interface, which reveal that the different orientations of the ClAlPc dipole layer lead to different charge-transfer channels between the adsorbed ClAlPc and Ag(111) substrate. Our findings provide a useful framework toward method development for ELA tuning.

Fibronectin and bovine serum albumin adsorption and conformational dynamics on inherently conducting polymers: a QCM-D study.

PubMed

Molino, Paul J; Higgins, Michael J; Innis, Peter C; Kapsa, Robert M I; Wallace, Gordon G

2012-06-05

Quartz crystal microbalance with dissipation monitoring (QCM-D) was employed to characterize the adsorption of the model proteins, bovine serum albumin (BSA) and fibronectin (FN), to polypyrrole doped with dextran sulfate (PPy-DS) as a function of DS loading and surface roughness. BSA adsorption was greater on surfaces of increased roughness and was above what could be explained by the increase in surface area alone. Furthermore, the additional mass adsorbed on the rough films was concomitant with an increase in the rigidity of the protein layer. Analysis of the dynamic viscoelastic properties of the protein adlayer reveal BSA adsorption on the rough films occurs in two phases: (1) arrival and initial adsorption of protein to the polymer surface and (2) postadsorption molecular rearrangement to a more dehydrated and compact conformation that facilitates further recruitment of protein to the polymer interface, likely forming a multilayer. In contrast, FN adsorption was independent of surface roughness. However, films prepared from solutions containing the highest concentration of DS (20 mg/mL) demonstrated both an increase in adsorbed mass and adlayer viscoelasticity. This is attributed to the higher DS loading in the conducting polymer film resulting in presentation of a more hydrated molecular structure indicative of a more unfolded and bioactive conformation. Modulating the redox state of the PPy-DS polymers was shown to modify both the adsorbed mass and viscoelastic nature of FN adlayers. An oxidizing potential increased both the total adsorbed mass and the adlayer viscoelasticity. Our findings demonstrate that modification of polymer physicochemical and redox condition alters the nature of protein-polymer interaction, a process that may be exploited to tailor the bioactivity of protein through which interactions with cells and tissues may be controlled.

Numerical simulation of viscoelastic layer rearrangement in polymer melts using OpenFOAM®

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

Köpplmayr, Thomas, E-mail: tkoepplmayr@gmail.com; Mayrhofer, Elias

In addition to their shear-thinning behavior, polymer melts are characterized by first and second normal stress differences, which cause secondary motions. Polymer coextrusion processes involve viscoelastic two-phase flows that influence layer formation. Using polymer melts with different pigmentation makes visible the layers deformed by second normal stress differences. We used a new solver for the OpenFOAM CFD toolbox which handles viscoelastic two-phase flows. A derivative of the volume-of-fluid (VoF) methodology was employed to describe the interface. Different types of polymer melt, such as polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) were investigated. In a coextrusion process, the less viscousmore » phase usually tends to encapsulate the more viscous one. However, the different viscoelastic properties of the melts also influence interface deformation. The materials were characterized by small-amplitude oscillatory-shear rheometry, and a multimode Giesekus model was used to fit shear viscosity, storage and loss modulus. Our simulations also took interfacial tension into account. Experimental observations and corresponding numerical simulations were found to be in good accordance.« less

Structure-induced switching of interpolymer adhesion at a solid-polymer melt interface.

PubMed

Jiang, Naisheng; Sen, Mani; Zeng, Wenduo; Chen, Zhizhao; Cheung, Justin M; Morimitsu, Yuma; Endoh, Maya K; Koga, Tadanori; Fukuto, Masafumi; Yuan, Guangcui; Satija, Sushil K; Carrillo, Jan-Michael Y; Sumpter, Bobby G

2018-02-14

Here we report a link between the interfacial structure and adhesive property of homopolymer chains physically adsorbed (i.e., via physisorption) onto solids. Polyethylene oxide (PEO) was used as a model and two different chain conformations of the adsorbed polymer were created on silicon substrates via the well-established Guiselin's approach: "flattened chains" which lie flat on the solid and are densely packed, and "loosely adsorbed polymer chains" which form bridges jointing up nearby empty sites on the solid surface and cover the flattened chains. We investigated the adhesion properties of the two different adsorbed chains using a custom-built adhesion testing device. Bilayers of a thick PEO overlayer on top of the flattened chains or loosely adsorbed chains were subjected to the adhesion test. The results revealed that the flattened chains do not show any adhesion even with the chemically identical free polymer on top, while the loosely adsorbed chains exhibit adhesion. Neutron reflectivity experiments corroborated that the difference in the interfacial adhesion is not attributed to the interfacial brodening at the free polymer-adsorbed polymer interface. Instead, coarse-grained molecular dynamics simulation results suggest that the tail parts of the loosely adsorbed chains act as "connector molecules", bridging the free chains and substrate surface and improving the interfacial adhesion. These findings not only shed light on the structure-property relationship at the interface, but also provide a novel approach for developing sticking/anti-sticking technologies through precise control of the interfacial polymer nanostructures.

Freestanding and Reactive Thin Films Fabricated by Covalent Layer-by-Layer Assembly and Subsequent Lift-Off of Azlactone-Containing Polymer Multilayers

PubMed Central

Buck, Maren E.

2010-01-01

We report an approach to the fabrication of freestanding and amine-reactive thin films that is based on the reactive layer-by-layer assembly and subsequent lift-off of azlactone-containing polymer multilayers. We demonstrate that covalently crosslinked multilayers fabricated using the azlactone-functionalized polymer poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) and a primary amine-containing polymer [poly(ethyleneimine) (PEI)] can be delaminated from planar glass and silicon surfaces by immersion in mildly acidic aqueous environments to yield flexible freestanding membranes. These freestanding membranes are robust and can withstand exposure to strong acid, strong base, or incubation in high ionic strength solutions that typically lead to the disruption and erosion of polymer multilayers assembled by reversible weak interactions (e.g., ‘polyelectrolyte multilayers’ assembled by electrostatic interactions or hydrogen bonding). We demonstrate further that these PEI/PVDMA assemblies contain residual reactive azlactone functionality that can be exploited to chemically modify the films (either directly after fabrication or after they have been lifted off of the substrates on which they were fabricated) using a variety of amine-functionalized small molecules. These freestanding membranes can also be transferred readily onto other objects (for example, onto the surfaces of planar substrates containing holes or pores) to fabricate suspended polymer membranes and other film-functionalized interfaces. In addition to planar, two-dimensional freestanding films, this approach can be used to fabricate and isolate three-dimensional freestanding membranes (e.g., curved films or tubes) by layer-by-layer assembly on, and subsequent lift-off from, the surfaces of topologically complex substrates (e.g., the curved ends of glass tubing, etc.). The results of this investigation, when combined, suggest the basis of methods for the fabrication of stable, chemically-reactive, and

Polymer thin film as coating layer to prevent corrosion of metal/metal oxide film

NASA Astrophysics Data System (ADS)

Sarkar, Suman; Kundu, Sarathi

2018-04-01

Thin film of polymer is used as coating layer and the corrosion of metal/metal oxide layer is studied with the variation of the thickness of the coating layer. The thin layer of polystyrene is fabricated using spin coating method on copper oxide (CuO) film which is deposited on glass substrate using DC magnetron sputtering technique. Thickness of the polystyrene and the CuO layers are determined using X-ray reflectivity (XRR) technique. CuO thin films coated with the polystyrene layer are exposed to acetic acid (2.5 v/v% aqueous CH3COOH solution) environments and are subsequently analyzed using UV-Vis spectroscopy and atomic force microscopy (AFM). Surface morphology of the film before and after interaction with the acidic environment is determined using AFM. Results obtained from the XRR and UV-Vis spectroscopy confirm that the thin film of polystyrene acts as an anticorrosion coating layer and the strength of the coating depends upon the polymer layer thickness at a constant acid concentration.

Flame retardant polymer-clay nanocoatings on cotton textile substrates using a newly developed, continuous layer-by-layer deposition process

USDA-ARS?s Scientific Manuscript database

Cotton’s exceptional softness, breathability, and absorbency have made it America’s best selling textile fiber; however, cotton textiles are generally more combustible than most synthetic fabrics. In this study, a continuous layer-by-layer self-assembly technique was used to deposit polymer-clay nan...

Non-targeted evaluation of selectivity of water-compatible class selective adsorbents for the analysis of steroids in wastewater.

PubMed

Kopperi, Matias; Riekkola, Marja-Liisa

2016-05-12

Selective adsorbents for solid-phase extraction are needed to meet the low concentration requirements of new environmental quality standard directives, especially for the analysis of estrogens in wastewater. In this work, bulk polymerization procedures were first optimized for the synthesis of non-imprinted polymers (NIP) with low non-specific adsorption of nonpolar compounds in aqueous environments. Water-compatible molecularly imprinted polymers (MIP) were then synthetized by increasing the selectivity of the polymer towards steroids with a testosterone template (average imprinting factor > 10). In addition, the affinity of synthetized entrapped β-cyclodextrin-epichlorohydrin polymers (ECD) towards steroids was clarified. The polymers were applied to the extraction of spiked wastewater effluent samples and their performance compared to commercially available adsorbents. The selectivity of the studied adsorbents was evaluated utilizing liquid chromatography ‒ mass spectrometry as well as comprehensive two-dimensional gas chromatography ‒ time-of-flight mass spectrometry. Affinity between adsorbents and steroids as well as matrix removal potential were measured with targeted methodologies, and two novel non-targeted methodologies were proposed to quantitatively measure adsorbent selectivity by utilizing chemometrics. Semi-quantitative selectivity was measured from the ratio of peak areas between steroidal and other compounds. Semi-qualitative selectivity was calculated from the ratio between the number of tentatively identified steroidal and other compounds. The synthetized polymers provided good matrix removal potential (ion suppression 15-30%) and semi-qualitative selectivity (∼4 units) compared to the commercial adsorbents (ion suppression 45-80%, selectivity < 3 units). Simple non-targeted approaches provided a novel method of quantifying the selectivity of extraction. Copyright © 2016 Elsevier B.V. All rights reserved.

Analysis of Double Layer and Adsorption Effects at the Alkaline Polymer Electrolyte-Electrode Interface

DTIC Science & Technology

2011-10-05

anion exchange mem - branes (AEM) are an attractive alternative to proton exchange mem - brane (PEM) fuel cells.1, 2 From electrocatalysts standpoint...gener- ally broken down into three distinct regions: the inner Helmholtz plane (IHP), the outer Helmholtz plane ( OHP ), and the diffuse layer. Figure 11...closest approach and is defined as OHP at a distance, x2. Nonspecifically adsorbed ions are distributed in a three dimensional region, called diffuse layer

A process for preparing an ultra-thin, adhesiveless, multi-layered, patterned polymer substrate

NASA Technical Reports Server (NTRS)

Bryant, Robert G. (Inventor); Kruse, Nancy H. M. (Inventor); Fox, Robert L. (Inventor); Tran, Sang Q. (Inventor)

1995-01-01

A process for preparing an ultra-thin, adhesiveless, multi-layered, patterned polymer substrate is disclosed. The process may be used to prepare both rigid and flexible cables and circuit boards. A substrate is provided and a polymeric solution comprising a self-bonding, soluble polymer and a solvent is applied to the substrate. Next, the polymer solution is dried to form a polymer coated substrate. The polymer coated substrate is metallized and patterned. At least one additional coating of the polymeric solution is applied to the metallized, patterned, polymer coated substrate and the steps of metallizing and patterning are repeated. Lastly, a cover coat is applied. When preparing a flexible cable and flexible circuit board, the polymer coating is removed from the substrate.

Self-consistent field theory of polymer-ionic molecule complexation.

PubMed

Nakamura, Issei; Shi, An-Chang

2010-05-21

A self-consistent field theory is developed for polymers that are capable of binding small ionic molecules (adsorbates). The polymer-ionic molecule association is described by Ising-like binding variables, C(i) ((a))(kDelta)(=0 or 1), whose average determines the number of adsorbed molecules, n(BI). Polymer gelation can occur through polymer-ionic molecule complexation in our model. For polymer-polymer cross-links through the ionic molecules, three types of solutions for n(BI) are obtained, depending on the equilibrium constant of single-ion binding. Spinodal lines calculated from the mean-field free energy exhibit closed-loop regions where the homogeneous phase becomes unstable. This phase instability is driven by the excluded-volume interaction due to the single occupancy of ion-binding sites on the polymers. Moreover, sol-gel transitions are examined using a critical degree of conversion. A gel phase is induced when the concentration of adsorbates is increased. At a higher concentration of the adsorbates, however, a re-entrance from a gel phase into a sol phase arises from the correlation between unoccupied and occupied ion-binding sites. The theory is applied to a model system, poly(vinyl alcohol) and borate ion in aqueous solution with sodium chloride. Good agreement between theory and experiment is obtained.

High-performance polymer/layered silicate nanocomposites

NASA Astrophysics Data System (ADS)

Heidecker, Matthew J.

High-performance layered-silicate nanocomposites of Polycarbonate (PC), poly(ethylene terephthalate) (PET), and their blends were produced via conventional melt-blending techniques. The focus of this thesis was on the fundamentals of dispersion, control of thermal stability, maintenance of melt-blending processing conditions, and on optimization of the composites' mechanical properties via the design of controlled and thermodynamically favorable nano-filler dispersions within the polymer matrices. PET and PC require high temperatures for melt-processing, rendering impractical the use of conventional/commercial organically-modified layered-silicates, since the thermal degradation temperatures of their ammonium surfactants lies below the typical processing temperatures. Thus, different surfactant chemistries must be employed in order to develop melt-processable nanocomposites, also accounting for polymer matrix degradation due to water (PET) or amine compounds (PC). Novel high thermal-stability surfactants were developed and employed in montmorillonite nanocomposites of PET, PC, and PC/PET blends, and were compared to the respective nanocomposites based on conventional quaternary-ammonium modified montmorillonites. Favorable dispersion was achieved in all cases, however, the overall material behavior -- i.e., the combination of crystallization, mechanical properties, and thermal degradation -- was better for the nanocomposites based on the thermally-stable surfactant fillers. Studies were also done to trace, and ultimately limit, the matrix degradation of Polycarbonate/montmorillonite nanocomposites, through varying the montmorillonite surfactant chemistry, processing conditions, and processing additives. Molecular weight degradation was, maybe surprisingly, better controlled in the conventional quaternary ammonium based nanocomposites -- even though the thermal stability of the organically modified montmorillonites was in most cases the lowest. Dependence of the

A novel (ex situ) method to quantify oxygen diffusion coefficient of polymer fuel cells backing and catalyst layers

NASA Astrophysics Data System (ADS)

Baricci, Andrea; Casalegno, Andrea

2016-09-01

Limiting current density of oxygen reduction reaction in polymer electrolyte fuel cells is determined by several mass transport resistances that lower the concentration of oxygen on the catalyst active site. Among them, diffusion across porous media plays a significant role. Despite the extensive experimental activity documented in PEMFC literature, only few efforts have been dedicated to the measurement of the effective transport properties in porous layers. In the present work, a methodology for ex situ measurement of the effective diffusion coefficient and Knudsen radius of porous layers for polymer electrolyte fuel cells (gas diffusion layer, micro porous layer and catalyst layer) is described and applied to high temperature polymer fuel cells State of Art materials. Regression of the measured quantities by means of a quasi 2D physical model is performed to quantify the Knudsen effect, which is reported to account, respectively, for 30% and 50% of the mass transport resistance in micro porous layer and catalyst layer. On the other side, the model reveals that pressure gradient consequent to permeation in porous layers of high temperature polymer fuel cells has a negligible effect on oxygen concentration in relevant operating conditions.

Modelization of three-layered polymer coated steel-strip ironing process using a neural network

NASA Astrophysics Data System (ADS)

Sellés, M. A.; Schmid, S. R.; Sánchez-Caballero, S.; Seguí, V. J.; Reig, M. J.; Pla, R.

2012-04-01

An alternative to the traditional can manufacturing process is to use plastic laminated rolled steels as base stocks. This material consist of pre-heated steel coils that are sandwiched between one or two sheets of polymer. The heated sheets are then immediately quenched, which yields a strong bond between the layers. Such polymer-coated steels were investigated by Jaworski [1,2] and Sellés [3], and found to be suitable for ironing with carefully controlled conditions. A novel multi-layer polymer coated steel has been developed for container applications. This material presents an interesting extension to previous research on polymer laminated steel in ironing, and offers several advantages over the previous material (Sellés [3]). This document shows a modelization for the ironing process (the most crucial step in can manufacturing) done by using a neural network

Zinc oxide nanowire-poly(methyl methacrylate) dielectric layers for polymer capacitive pressure sensors.

PubMed

Chen, Yan-Sheng; Hsieh, Gen-Wen; Chen, Shih-Ping; Tseng, Pin-Yen; Wang, Cheng-Wei

2015-01-14

Polymer capacitive pressure sensors based on a dielectric composite layer of zinc oxide nanowire and poly(methyl methacrylate) show pressure sensitivity in the range of 2.63 × 10(-3) to 9.95 × 10(-3) cm(2) gf(-1). This represents an increase of capacitance change by as much as a factor of 23 over pristine polymer devices. An ultralight load of only 10 mg (corresponding to an applied pressure of ∼0.01 gf cm(-2)) can be clearly recognized, demonstrating remarkable characteristics of these nanowire-polymer capacitive pressure sensors. In addition, optical transmittance of the dielectric composite layer is approximately 90% in the visible wavelength region. Their low processing temperature, transparency, and flexible dielectric film makes them a highly promising means for flexible touching and pressure-sensing applications.

Incorporating microorganisms into polymer layers provides bioinspired functional living materials

PubMed Central

Gerber, Lukas C.; Koehler, Fabian M.; Grass, Robert N.; Stark, Wendelin J.

2012-01-01

Artificial two-dimensional biological habitats were prepared from porous polymer layers and inoculated with the fungus Penicillium roqueforti to provide a living material. Such composites of classical industrial ingredients and living microorganisms can provide a novel form of functional or smart materials with capability for evolutionary adaptation. This allows realization of most complex responses to environmental stimuli. As a conceptual design, we prepared a material surface with self-cleaning capability when subjected to standardized food spill. Fungal growth and reproduction were observed in between two specifically adapted polymer layers. Gas exchange for breathing and transport of nutrient through a nano-porous top layer allowed selective intake of food whilst limiting the microorganism to dwell exclusively in between a confined, well-enclosed area of the material. We demonstrated a design of such living materials and showed both active (eating) and waiting (dormant, hibernation) states with additional recovery for reinitiation of a new active state by observing the metabolic activity over two full nutrition cycles of the living material (active, hibernation, reactivation). This novel class of living materials can be expected to provide nonclassical solutions in consumer goods such as packaging, indoor surfaces, and in biotechnology. PMID:22198770

High basicity adsorbents from solid residue of cellulose and synthetic polymer co-pyrolysis for phenol removal: Kinetics and mechanism

NASA Astrophysics Data System (ADS)

Lorenc-Grabowska, Ewa; Rutkowski, Piotr

2014-10-01

The activated carbons (ACs) produced from solid residue of cellulose and synthetic polymer co-pyrolysis (CACs) and commercial activated carbon from coconut shell (GC) were used for phenol removal. The adsorption kinetics and mechanism were investigated. All studied activated carbons are predominantly microporous and are characterized by basic surface characteristics. Surface area SBET varies between 1235 and 1499 m2/g, whereas the pHPZC changes from 7.70 to 10.63. The bath adsorption of phenol (P) was carried out at ambient temperature. The equilibrium time and equilibrium sorption capacity were determined. It was found that the boundary layer effect is bigger in AC with high basic characteristics of the surface. The rate controlling step is the intraparticle diffusion in CACs only, whereas in ACs with higher amount of acidic functionalities the adsorbate-surface interaction influences the rate of kinetic as well. The equilibrium isotherms are L2 type for commercial AC and L4 for CACs. The CACs are characterized by very high adsorption capacity that vary between 312 and 417 mg/g. The main mechanism of phenol adsorption is micropore filling within pores smaller than 1.4 nm. In the absence of solvent effect further adsorption of phenol on CACs takes place. The enhanced adsorption is due to dispersive/repulsive interaction induced by oxygen functionalities.

Preparation of amino acid-based polymer functionalized magnetic nanoparticles as adsorbents for analysis of plant growth regulators in bean sprouts.

PubMed

Ji, Shilei; Qi, Li; Li, Nan; Wang, Minglin

2016-09-01

A novel magnetic solid phase extraction (MSPE) adsorbent has been developed for enriching two plant growth regulators, including 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chlorophenoxyacetic acid (4-CPA), in bean sprouts. For preparing the MSPE adsorbent, poly(N-methacryloyl-L-phenylalanine methyl ester (P(MA-L-Phe-OMe)), amino acid-based polymer, was modified onto the magnetic nanoparticles via "grafting to" method by free radical polymerization. The resultant P(MA-L-Phe-OMe)-functionalized magnetic nanoparticles (Fe3O4@P(MA-L-Phe-OMe)) were characterized by Fourier transform infrared (FT-IR) spectroscopy and elemental analysis. The adsorption amount of Fe3O4@P(MA-L-Phe-OMe) nanoparticles to 2,4-D and 4-CPA were 39.82mgg(-1) and 29.02mgg(-1), respectively. Moreover, the prepared MSPE adsorbents showed good selectivity towards 2,4-D and 4-CPA due to the hydrophobic interactions and electrostatic forces between the target analytes and Fe3O4@P(MA-L-Phe-OMe). The results demonstrated that the proposed MSPE adsorbents have high affinity to the targets 2,4-D and 4-CPA. Under the optimized conditions, the proposed materials were successfully applied to enrich 2,4-D and 4-CPA in bean sprouts samples. The recovery values of the bean sprouts solution spiked the targets were from 90.9% to 96.4% with the relative standard deviations of 2.3-3.9%. Our work proved that the novel Fe3O4@P(MA-L-Phe-OMe) nanoparticles were the good adsorbents of magnetic solid phase extraction (MSPE) and have good potential for the analysis of trace compound in real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of Functional Thin Polymer Films Using a Layer-by-Layer Deposition Technique.

PubMed

Yoshida, Kentaro

2017-01-01

Functional thin films containing insulin were prepared using layer-by-layer (LbL) deposition of insulin and negatively- or positively-charged polymers on the surface of solid substrates. LbL films composed of insulin and negatively-charged polymers such as poly(acrylic acid) (PAA), poly(vinylsulfate) (PVS), and dextran sulfate (DS) were prepared through electrostatic affinity between the materials. The insulin/PAA, insulin/PVS, and insulin/DS films were stable in acidic solutions, whereas they decomposed under physiological conditions as a result of a change in the net electric charge of insulin from positive to negative. Interestingly, the insulin-containing LbL films were stable even in the presence of a digestive-enzyme (pepcin) at pH 1.4 (stomach pH). In contrast, LbL films consisting of insulin and positively-charged polymers such as poly(allylamine hydrochloride) (PAH) decomposed in acidic solutions due to the positive charges of insulin generated in acidic media. The insulin-containing LbL films can be prepared not only on the surface of flat substrates, such as quartz slides, but also on the surface of microparticles, such as poly(lactic acid) (PLA) microbeads. Thus, insulin-containing LbL film-coated PLA microbeads can be handled as a powder. In addition, insulin-containing microcapsules were prepared by coating LbL films on the surface of insulin-doped calcium carbonate (CaCO 3 ) microparticles, followed by dissolution of the CaCO 3 core. The release of insulin from the microcapsules was accelerated at pH 7.4, whereas it was suppressed in acidic solutions. These results suggest the potential use of insulin-containing microcapsules in the development of oral formulations of insulin.

Deoxyribonucleic acid (DNA) cladding layers for nonlinear-optic-polymer-based electro-optic devices

NASA Astrophysics Data System (ADS)

Grote, James G.; Ogata, Naoya; Diggs, Darnell E.; Hopkins, Frank K.

2003-07-01

Nonlinear optic (NLO) polymer based electro-optic devices have been achieving world record low half wave voltages and high frequencies over the last 2-3 years. Part of the advancement is through the use of relatively more conductive polymers for the cladding layers. Based on the current materials available for these cladding materials, however, the desired optical and electromagnetic properites are being balanced for materials processability. One does not want the solvent present in one layer to dissovle the one deposited underneath, or be dissolved by the one being deposited on top. Optimized polymer cladding materials, to further enhance device performance, are continuing to be investigated. Thin films of deoxyribonucleic acid (DNA), derived from salmon sperm, show promise in providing both the desired optical and magnetic properties, as well as the desired resistance to various solvents used for NLO polymer device fabrication. Thin films of DNA were deposited on glass and silicon substrates and the film quality, optical and electromagnetic properties and resistance to various solvents were characterized.

Molecular dynamics simulation aiming at interfacial characteristics of polymer chains on nanotubes with different layers

NASA Astrophysics Data System (ADS)

Li, Kun; Gu, Boqin; Zhu, Wanfu

2017-03-01

A molecular dynamics (MD) simulations study is performed on multiwalled carbon nanotubes (MWNTs)/acrylonitrile-butadiene rubber (NBR) composites. The physisorption and interfacial characteristics between the various MWNTs and polymer macromolecular chains are identified. The effects of nanotube layers on the nanotubes/polymer interactions are examined. Each of the situation result and surface features is characterized by binding energy (Eb). It is shown that the binding energy (Eb) increase with the number of layers.

Ultrathin Polyaniline-based Buffer Layer for Highly Efficient Polymer Solar Cells with Wide Applicability

PubMed Central

Zhao, Wenchao; Ye, Long; Zhang, Shaoqing; Fan, Bin; Sun, Mingliang; Hou, Jianhui

2014-01-01

Interfacial buffer layers often attribute the improved device performance in organic optoelectronic device. Herein, a water-soluble hydrochloric acid doped polyanilines (HAPAN) were utilized as p-type electrode buffer layer in highly efficient polymer solar cells (PSC) based on PBDTTT-EFT and several representative polymers. The PBDTTT-EFT-based conventional PSC featuring ultrathin HAPAN (1.3 nm) delivered high PCE approximately 9%, which is one of the highest values among conventional PSC devices. Moreover, ultrathin HAPAN also exhibited wide applicability in a variety of efficient photovoltaic polymers including PBDTTT-C-T, PTB7, PBDTBDD, PBTTDPP-T, PDPP3T and P3HT. The excellent performances were originated from the high transparency, small film roughness and suitable work function. PMID:25300365

Carboxymethylcellulose adsorption on molybdenite: the effect of electrolyte composition on adsorption, bubble-surface collisions, and flotation.

PubMed

Kor, Mohammad; Korczyk, Piotr M; Addai-Mensah, Jonas; Krasowska, Marta; Beattie, David A

2014-10-14

The adsorption of carboxymethylcellulose polymers on molybdenite was studied using spectroscopic ellipsometry and atomic force microscopy imaging with two polymers of differing degrees of carboxyl group substitution and at three different electrolyte conditions: 1 × 10(-2) M KCl, 2.76 × 10(-2) M KCl, and simulated flotation process water of multicomponent electrolyte content, with an ionic strength close to 2.76 × 10(-2) M. A higher degree of carboxyl substitution in the adsorbing polymer resulted in adsorbed layers that were thinner and with more patchy coverage; increasing the ionic strength of the electrolyte resulted in increased polymer layer thickness and coverage. The use of simulated process water resulted in the largest layer thickness and coverage for both polymers. The effect of the adsorbed polymer layer on bubble-particle attachment was studied with single bubble-surface collision experiments recorded with high-speed video capture and image processing and also with single mineral molybdenite flotation tests. The carboxymethylcellulose polymer with a lower degree of substitution resulted in almost complete prevention of wetting film rupture at the molybdenite surface under all electrolyte conditions. The polymer with a higher degree of substitution prevented rupture only when adsorbed from simulated process water. Molecular kinetic theory was used to quantify the effect of the polymer on the dewetting dynamics for collisions that resulted in wetting film rupture. Flotation experiments confirmed that adsorbed polymer layer properties, through their effect on the dynamics of bubble-particle attachment, are critical to predicting the effectiveness of polymers used to prevent mineral recovery in flotation.

Recent Advances in Gas Barrier Thin Films via Layer-by-Layer Assembly of Polymers and Platelets.

PubMed

Priolo, Morgan A; Holder, Kevin M; Guin, Tyler; Grunlan, Jaime C

2015-05-01

Layer-by-layer (LbL) assembly has emerged as the leading non-vacuum technology for the fabrication of transparent, super gas barrier films. The super gas barrier performance of LbL deposited films has been demonstrated in numerous studies, with a variety of polyelectrolytes, to rival that of metal and metal oxide-based barrier films. This Feature Article is a mini-review of LbL-based multilayer thin films with a 'nanobrick wall' microstructure comprising polymeric mortar and nano-platelet bricks that impart high gas barrier to otherwise permeable polymer substrates. These transparent, water-based thin films exhibit oxygen transmission rates below 5 × 10(-3) cm(3) m(-2) day(-1) atm(-1) and lower permeability than any other barrier material reported. In an effort to put this technology in the proper context, incumbent technologies such as metallized plastics, metal oxides, and flake-filled polymers are briefly reviewed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficiency of solution-processed multilayer polymer light-emitting diodes using charge blocking layers

NASA Astrophysics Data System (ADS)

Kasparek, Christian; Rörich, Irina; Blom, Paul W. M.; Wetzelaer, Gert-Jan A. H.

2018-01-01

By blending semiconducting polymers with the cross-linkable matrix ethoxylated-(4)-bisphenol-a-dimethacrylate (SR540), an insoluble layer is acquired after UV-illumination. Following this approach, a trilayer polymer light-emitting diode (PLED) consisting of a blend of poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD) and SR540 as an electron-blocking layer, Super Yellow-Poly(p-phenylene vinylene) (SY-PPV) blended with SR540 as an emissive layer, and poly(9,9-di-n-octylfluorenyl-2,7-diyl) as a hole-blocking layer is fabricated from solution. The trilayer PLED shows a 23% increase in efficiency at low voltage as compared to a single layer SY-PPV PLED. However, at higher voltage, the advantage in current efficiency gradually decreases. A combined experimental and modelling study shows that the increased efficiency is not only due to the elimination of exciton quenching at the electrodes but also due to suppressed nonradiative trap-assisted recombination due to carrier confinement. At high voltages, holes can overcome the hole-blocking barrier, which explains the efficiency roll-off.

Broadband All-Polymer Phototransistors with Nanostructured Bulk Heterojunction Layers of NIR-Sensing n-Type and Visible Light-Sensing p-Type Polymers

PubMed Central

Han, Hyemi; Nam, Sungho; Seo, Jooyeok; Lee, Chulyeon; Kim, Hwajeong; Bradley, Donal D. C.; Ha, Chang-Sik; Kim, Youngkyoo

2015-01-01

We report ‘broadband light-sensing’ all-polymer phototransistors with the nanostructured bulk heterojunction (BHJ) layers of visible (VIS) light-sensing electron-donating (p-type) polymer and near infrared (NIR) light-sensing electron-accepting (n-type) polymer. Poly[{2,5-bis-(2-ethylhexyl)-3,6-bis-(thien-2-yl)-pyrrolo[3,4-c]pyrrole-1,4-diyl}-co-{2,2′-(2,1,3-benzothiadiazole)]-5,5′-diyl}] (PEHTPPD-BT), which is synthesized via Suzuki coupling and employed as the n-type polymer, shows strong optical absorption in the NIR region (up to 1100 nm) in the presence of weak absorption in the VIS range (400 ~ 600 nm). To strengthen the VIS absorption, poly(3-hexylthiophene) (P3HT) is introduced as the p-type polymer. All-polymer phototransistors with the BHJ (P3HT:PEHTPPD-BT) layers, featuring a peculiar nano-domain morphology, exhibit typical p-type transistor characteristics and efficiently detect broadband (VIS ~ NIR) lights. The maximum corrected responsivity (without contribution of dark current) reaches up to 85 ~ 88% (VIS) and 26 ~ 40% (NIR) of theoretical responsivity. The charge separation process between P3HT and PEHTPPD-BT components in the highest occupied molecular orbital is proposed as a major working mechanism for the effective NIR sensing. PMID:26563576

Electrochemical Analysis of Conducting Polymer Thin Films

PubMed Central

Vyas, Ritesh N.; Wang, Bin

2010-01-01

Polyelectrolyte multilayers built via the layer-by-layer (LbL) method has been one of the most promising systems in the field of materials science. Layered structures can be constructed by the adsorption of various polyelectrolyte species onto the surface of a solid or liquid material by means of electrostatic interaction. The thickness of the adsorbed layers can be tuned precisely in the nanometer range. Stable, semiconducting thin films are interesting research subjects. We use a conducting polymer, poly(p-phenylene vinylene) (PPV), in the preparation of a stable thin film via the LbL method. Cyclic voltammetry and electrochemical impedance spectroscopy have been used to characterize the ionic conductivity of the PPV multilayer films. The ionic conductivity of the films has been found to be dependent on the polymerization temperature. The film conductivity can be fitted to a modified Randle’s circuit. The circuit equivalent calculations are performed to provide the diffusion coefficient values. PMID:20480052

Segmental dynamics of polymers in nanoscopic confinements, as probed by simulations of polymer/layered-silicate nanocomposites.

PubMed

Kuppa, V; Foley, T M D; Manias, E

2003-09-01

In this paper we review molecular modeling investigations of polymer/layered-silicate intercalates, as model systems to explore polymers in nanoscopically confined spaces. The atomic-scale picture, as revealed by computer simulations, is presented in the context of salient results from a wide range of experimental techniques. This approach provides insights into how polymeric segmental dynamics are affected by severe geometric constraints. Focusing on intercalated systems, i.e. polystyrene (PS) in 2 nm wide slit-pores and polyethylene-oxide (PEO) in 1 nm wide slit-pores, a very rich picture for the segmental dynamics is unveiled, despite the topological constraints imposed by the confining solid surfaces. On a local scale, intercalated polymers exhibit a very wide distribution of segmental relaxation times (ranging from ultra-fast to ultra-slow, over a wide range of temperatures). In both cases (PS and PEO), the segmental relaxations originate from the confinement-induced local density variations. Additionally, where there exist special interactions between the polymer and the confining surfaces ( e.g., PEO) more molecular mechanisms are identified.

Development of a computationally-designed polymeric adsorbent specific for mycotoxin patulin.

PubMed

Piletska, Elena V; Pink, Demi; Karim, Kal; Piletsky, Sergey A

2017-12-04

Patulin is a toxic compound which is found predominantly in apples affected by mould rot. Since apples and apple-containing products are a popular food for the elderly, children and babies, the monitoring of the toxin is crucial. This paper describes a development of a computationally-designed polymeric adsorbent for the solid-phase extraction of patulin, which provides an effective clean-up of the food samples and allows the detection and accurate quantification of patulin levels present in apple juice using conventional chromatography methods. The developed bespoke polymer demonstrates a quantitative binding towards the patulin present in undiluted apple juice. The polymer is inexpensive and easy to mass-produce. The contributing factors to the function of the adsorbent is a combination of acidic and basic functional monomers producing a zwitterionic complex in the solution that formed stronger binding complexes with the patulin molecule. The protocols described in this paper provide a blueprint for the development of polymeric adsorbents for other toxins or different food matrices.

Structure-induced switching of interpolymer adhesion at a solid–polymer melt interface

DOE PAGES

Jiang, Naisheng; Sen, Mani; Zeng, Wenduo; ...

2018-01-11

In this paper, we report a link between the interfacial structure and adhesive property of homopolymer chains physically adsorbed (i.e., via physisorption) onto solids. Polyethylene oxide (PEO) was used as a model and two different chain conformations of the adsorbed polymer were created on silicon substrates via the well-established Guiselin's approach: “flattened chains” which lie flat on the solid and are densely packed, and “loosely adsorbed polymer chains” which form bridges jointing up nearby empty sites on the solid surface and cover the flattened chains. We investigated the adhesion properties of the two different adsorbed chains using a custom-built adhesionmore » testing device. Bilayers of a thick PEO overlayer on top of the flattened chains or loosely adsorbed chains were subjected to the adhesion test. The results revealed that the flattened chains do not show any adhesion even with the chemically identical free polymer on top, while the loosely adsorbed chains exhibit adhesion. Neutron reflectivity experiments corroborated that the difference in the interfacial adhesion is not attributed to the interfacial brodening at the free polymer–adsorbed polymer interface. Instead, coarse-grained molecular dynamics simulation results suggest that the tail parts of the loosely adsorbed chains act as “connector molecules”, bridging the free chains and substrate surface and improving the interfacial adhesion. Finally, these findings not only shed light on the structure–property relationship at the interface, but also provide a novel approach for developing sticking/anti-sticking technologies through precise control of the interfacial polymer nanostructures.« less

3D Printing of Human Tissue Mimics via Layer-by-Layer Assembly of Polymer/Hydrogel Biopapers

NASA Astrophysics Data System (ADS)

Ringeisen, Bradley

2015-03-01

The foundations of tissue engineering were built on two fundamental areas of research: cells and scaffolds. Multipotent cells and their derivatives are traditionally randomly seeded into sophisticated polymer or hydrogel scaffolds, ultimately with the goal of forming a tissue-like material through cell differentiation and cell-material interactions. One problem with this approach is that no matter how complex or biomimetic the scaffold is, the cells are still homogeneously distributed throughout this three dimensional (3D) material. Natural tissue is inherently heterogeneous on both a microscopic and macroscopic level. It also contains different types of cells in close proximity, extracellular matrix, voids, and a complex vascularized network. Recently developed 3D cell and organ printers may be able to enhance traditional tissue engineering experiments by building scaffolds layer-by-layer that are crafted to mimic the microscopic and macroscopic structure of natural tissue or organs. Over the past decade, my laboratory has developed a capillary-free, live cell printer termed biological laser printing, or BioLP. We find that printed cells do not express heat shock protein and retain >99% viability. Printed cells also incur no DNA strand fracture and preserve their ability to differentiate. Recent work has used a layer-by-layer approach, stacking sheets of hybrid polymer/hydrogel biopapers in conjunction with live cell printing to create 3D tissue structures. Our specific work is now focused on the blood-brain-barrier and air-lung interface and will be described during the presentation.

Complexation of lysozyme with adsorbed PtBS-b-SCPI block polyelectrolyte micelles on silver surface.

PubMed

Papagiannopoulos, Aristeidis; Christoulaki, Anastasia; Spiliopoulos, Nikolaos; Vradis, Alexandros; Toprakcioglu, Chris; Pispas, Stergios

2015-01-20

We present a study of the interaction of the positively charged model protein lysozyme with the negatively charged amphiphilic diblock polyelectrolyte micelles of poly(tert-butylstyrene-b-sodium (sulfamate/carboxylate)isoprene) (PtBS-b-SCPI) on the silver/water interface. The adsorption kinetics are monitored by surface plasmon resonance, and the surface morphology is probed by atomic force microscopy. The micellar adsorption is described by stretched-exponential kinetics, and the micellar layer morphology shows that the micelles do not lose their integrity upon adsorption. The complexation of lysozyme with the adsorbed micellar layers depends on the micelles arrangement and density in the underlying layer, and lysozyme follows the local morphology of the underlying roughness. When the micellar adsorbed amount is small, the layers show low capacity in protein complexation and low resistance in loading. When the micellar adsorbed amount is high, the situation is reversed. The adsorbed layers both with or without added protein are found to be irreversibly adsorbed on the Ag surface.

Protection of Polymers from the Space Environment by Atomic Layer Deposition

NASA Astrophysics Data System (ADS)

Lindholm, Ned F.; Zhang, Jianming; Minton, Timothy K.; O'Patchen, Jennifer; George, Steven M.; Groner, Markus D.

2009-01-01

Polymers in space may be subjected to a barrage of incident atoms, photons, and/or ions. For example, oxygen atoms can etch and oxidize these materials. Photons may act either alone or in combination with oxygen atoms to degrade polymers and paints and thus limit their usefulness. Colors fade under the intense vacuum ultraviolet (VUV) solar radiation. Ions can lead to the build-up of static charge on polymers. Atomic layer deposition (ALD) techniques can provide coatings that could mitigate many challenges for polymers in space. ALD is a gas-phase technique based on two sequential, self-limiting surface reactions, and it can deposit very uniform, conformal, and pinhole-free films with atomic layer control. We have studied the efficacy of various ALD coatings to protect Kapton® polyimide, FEP Teflon®, and poly(methyl methacrylate) films from atomic-oxygen and VUV attack. Atomic-oxygen and VUV studies were conducted with the use of a laser-breakdown source for hyperthermal O atoms and a D2 lamp as a source of VUV light. These studies used a quartz crystal microbalance (QCM) to monitor mass loss in situ, as well as surface profilometry and scanning electron microscopy to study the surface recession and morphology changes ex situ. Al2O3 ALD coatings applied to polyimide and FEP Teflon® films protected the underlying substrates from O-atom attack, and ZnO coatings protected the poly(methyl methacrylate) substrate from VUV-induced damage.

Relationship between the Amount of Bitter Substances Adsorbed onto Lipid/Polymer Membrane and the Electric Response of Taste Sensors

PubMed Central

Toko, Kiyoshi; Hara, Daichi; Tahara, Yusuke; Yasuura, Masato; Ikezaki, Hidekazu

2014-01-01

The bitterness of bitter substances can be measured by the change in the membrane electric potential caused by adsorption (CPA) using a taste sensor (electronic tongue). In this study, we examined the relationship between the CPA value due to an acidic bitter substance and the amount of the bitter substance adsorbed onto lipid/polymer membranes, which contain different lipid contents, used in the taste sensor. We used iso-α-acid which is an acidic bitter substance found in several foods and beverages. The amount of adsorbed iso-α-acid, which was determined by spectroscopy, showed a maximum at the lipid concentration 0.1 wt % of the membrane, and the same phenomenon was observed for the CPA value. At the higher lipid concentration, however, the amount adsorbed decreased and then remained constant, while the CPA value decreased monotonically to zero. This constant adsorption amount was observed when the membrane potential in the reference solution did not change with increasing lipid concentration. The decrease in CPA value in spite of the constant adsorption amount is caused by a decrease in the sensitivity of the membrane as the surface charge density increases. The reason why the peaks appeared in both the CPA value and adsorption amount is based on the contradictory adsorption properties of iso-α-acid. The increasing charged lipid concentration of the membrane causes an increasing electrostatic attractive interaction between iso-α-acid and the membrane, but simultaneously causes a decreasing hydrophobic interaction that results in decreasing adsorption of iso-α-acid, which also has hydrophobic properties, onto the membrane. Estimates of the amount of adsorption suggest that iso-α-acid molecules are adsorbed onto both the surface and interior of the membrane. PMID:25184491

Adsorptive removal of hydrophobic organic compounds by carbonaceous adsorbents: a comparative study of waste-polymer-based, coal-based activated carbon, and carbon nanotubes.

PubMed

Lian, Fei; Chang, Chun; Du, Yang; Zhu, Lingyan; Xing, Baoshan; Liu, Chang

2012-01-01

Adsorption of the hydrophobic organic compounds (HOCs) trichloroethylene (TCE), 1,3-dichlorobenzene (DCB), 1,3-dinitrobenzene (DNB) and gamma-hexachlorocyclohexane (HCH) on five different carbonaceous materials was compared. The adsorbents included three polymer-based activated carbons, one coal-based activated carbon (F400) and multiwalled carbon nanotubes (MWNT). The polymer-based activated carbons were prepared using KOH activation from waste polymers: polyvinyl chloride (PVC), polyethyleneterephthalate (PET) and tire rubber (TR). Compared with F400 and MWNT, activated carbons derived from PVC and PET exhibited fast adsorption kinetics and high adsorption capacity toward the HOCs, attributed to their extremely large hydrophobic surface area (2700 m2/g) and highly mesoporous structures. Adsorption of small-sized TCE was stronger on the tire-rubber-based carbon and F400 resulting from the pore-filling effect. In contrast, due to the molecular sieving effect, their adsorption on HCH was lower. MWNT exhibited the lowest adsorption capacity toward HOCs because of its low surface area and characteristic of aggregating in aqueous solution.

Polymer based organic solar cells using ink-jet printed active layers

NASA Astrophysics Data System (ADS)

Aernouts, T.; Aleksandrov, T.; Girotto, C.; Genoe, J.; Poortmans, J.

2008-01-01

Ink-jet printing is used to deposit polymer:fullerene blends suitable as active layer for organic solar cells. We show that merging of separately deposited ink droplets into a continuous, pinhole-free organic thin film results from a balance between ink viscosity and surface wetting, whereas for certain of the studied solutions clear coffee drop effect occurs for single droplets; this can be minimized for larger printed areas, yielding smooth layers with minimal surface roughness. Resulting organic films are used as active layer for solar cells with power conversion efficiency of 1.4% under simulated AM1.5 solar illumination.

Water Transport in the Micro Porous Layer and Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell

NASA Astrophysics Data System (ADS)

Qin, C.; Hassanizadeh, S. M.

2015-12-01

In this work, a recently developed dynamic pore-network model is presented [1]. The model explicitly solves for both water pressure and capillary pressure. A semi-implicit scheme is used in updating water saturation in each pore body, which considerably increases the numerical stability at low capillary number values. Furthermore, a multiple-time-step algorithm is introduced to reduce the computational effort. A number of case studies of water transport in the micro porous layer (MPL) and gas diffusion layer (GDL) are conducted. We illustrate the role of MPL in reducing water flooding in the GDL. Also, the dynamic water transport through the MPL-GDL interface is explored in detail. This information is essential to the reduced continua model (RCM), which was developed for multiphase flow through thin porous layers [2, 3]. C.Z. Qin, Water transport in the gas diffusion layer of a polymer electrolyte fuel cell: dynamic pore-network modeling, J Electrochimical. Soci., 162, F1036-F1046, 2015. C.Z. Qin and S.M. Hassanizadeh, Multiphase flow through multilayers of thin porous media: general balance equations and constitutive relationships for a solid-gas-liquid three-phase system, Int. J. Heat Mass Transfer, 70, 693-708, 2014. C.Z. Qin and S.M. Hassanizadeh, A new approach to modeling water flooding in a polymer electrolyte fuel cell, Int. J. Hydrogen Energy, 40, 3348-3358, 2015.

Static and hydrodynamic studies of the conformation of adsorbed macromolecules at the solid/liquid interface

NASA Astrophysics Data System (ADS)

Yavorsky, D. P.

1981-08-01

The structure of an adsorbed macromolecular layer at the solid/liquid interface under both stationary and flow conditions is examined. The conformation of adsorbed bovine serum albumin (BSA) is deduced from the thickness of surface layers formed on the pore walls of track etched (mica) membranes. Changes in membrane permeability due to protein adsorption are related directly to a net reduction in pore size or an equivalent adsorbed layer thickness. Complementary permeability measurements using electrolyte conduction, tracer diffusion, and pressure driven flow have verified the unique structural qualities of the track etched membrane and collectively demonstrate an ability to determine bare pore size with an accuracy of + or - 2A. The average static thickness of an adsorbed BSA layer, as derived from electrolyte conduction and tracer diffusion, was 43 + or - 3A independent of pore size. In comparison with the known BSA solution dimensions, this measured thickness is consistent with a monolayer of structurally unperturbed protein molecules each oriented in a "side-on" position. Pronounced conformational changes in adsorbed BSA layers were observed under conditions of shear flow. Electrostatic interactions were also shown to significantly affect adsorbed protein conformation through changes in solution ionic strength and surface charge.

Mutual Photoluminescence Quenching and Photovoltaic Effect in Large-Area Single-Layer MoS2-Polymer Heterojunctions.

PubMed

Shastry, Tejas A; Balla, Itamar; Bergeron, Hadallia; Amsterdam, Samuel H; Marks, Tobin J; Hersam, Mark C

2016-11-22

Two-dimensional transition metal dichalcogenides (TMDCs) have recently attracted attention due to their superlative optical and electronic properties. In particular, their extraordinary optical absorption and semiconducting band gap have enabled demonstrations of photovoltaic response from heterostructures composed of TMDCs and other organic or inorganic materials. However, these early studies were limited to devices at the micrometer scale and/or failed to exploit the unique optical absorption properties of single-layer TMDCs. Here we present an experimental realization of a large-area type-II photovoltaic heterojunction using single-layer molybdenum disulfide (MoS 2 ) as the primary absorber, by coupling it to the organic π-donor polymer PTB7. This TMDC-polymer heterojunction exhibits photoluminescence intensity that is tunable as a function of the thickness of the polymer layer, ultimately enabling complete quenching of the TMDC photoluminescence. The strong optical absorption in the TMDC-polymer heterojunction produces an internal quantum efficiency exceeding 40% for an overall cell thickness of less than 20 nm, resulting in exceptional current density per absorbing thickness in comparison to other organic and inorganic solar cells. Furthermore, this work provides insight into the recombination processes in type-II TMDC-polymer heterojunctions and thus provides quantitative guidance to ongoing efforts to realize efficient TMDC-based solar cells.

Towards understanding KOH conditioning of amidoxime-based oolymer adsorbents for sequestering uranium from seawater

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

Pan, Horng-Bin; Kuo, Li-Jung; Wood, Jordana

2015-11-17

Conditioning of polymer fiber adsorbents grafted with amidoxime and carboxylic acid groups is necessary to make the materials hydrophilic for sequestering uranium from seawater. In this paper, spectroscopic techniques were employed to study the effectiveness of the traditional KOH conditioning method (2.5% KOH at 80⁰C) on recently developed high-surface-area amidoxime-based polymer fiber adsorbents developed at Oak Ridge National Laboratory. FTIR spectra reveal that the KOH conditioning process removes the proton from the carboxylic acids and also converts the amidoxime groups to carboxylate groups in the adsorbent. With prolonged KOH treatment (>1 hr) at 80⁰C, physical damage to the adsorbent materialmore » occurs which can lead to a significant reduction in the adsorbent's uranium adsorption capability in real seawater during extended exposure times (>21 days). The physical damage to the adsorbent can be minimized by lowering KOH conditioning temperature. For the high-surface-area amidoxime-based adsorbents, 20 min of conditioning in 2.5% KOH at 80⁰C or 1 hr of conditioning in 2.5% KOH at 60⁰C appears sufficient to achieve de-protonation of the carboxylic acid with minimal harmful effects to the adsorbent material. Lastly, the use of NaOH instead of KOH can also reduce the cost of the base treatment process required for conditioning the amidoxime-based sorbents with minimal loss of adsorption capacity (≤7%).« less

Graphene Oxide Derivatives as Hole- and Electron-Extraction Layers for High-Performance Polymer Solar Cells

DTIC Science & Technology

2013-11-20

Graphene oxide derivatives as hole- and electron- extraction layers for high-performance polymer solar cells Jun Liu,*a Michael Durstockb and Liming...oxide (GO) and its derivatives have been used as a new class of efficient hole- and electron-extraction materials in polymer solar cells (PSCs...new class of efficient hole- and electron-extraction materials in polymer solar cells (PSCs). Highly efficient and stable PSCs have been fabricated

Preparation and characterization of polymer layer systems for validation of 3D Micro X-ray fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Schaumann, Ina; Malzer, Wolfgang; Mantouvalou, Ioanna; Lühl, Lars; Kanngießer, Birgit; Dargel, Rainer; Giese, Ulrich; Vogt, Carla

2009-04-01

For the validation of the quantification of the newly-developed method of 3D Micro X-ray fluorescence spectroscopy (3D Micro-XRF) samples with a low average Z matrix and minor high Z elements are best suited. In a light matrix the interferences by matrix effects are minimized so that organic polymers are appropriate as basis for analytes which are more easily detected by X-ray fluorescence spectroscopy. Polymer layer systems were assembled from single layers of ethylene-propylene-diene rubber (EPDM) filled with changing concentrations of silica and zinc oxide as inorganic additives. Layer thicknesses were in the range of 30-150 μm. Before the analysis with 3D Micro-XRF all layers have been characterized by scanning micro-XRF with regard to filler dispersion, by infrared microscopy and light microscopy in order to determine the layer thicknesses and by ICP-OES to verify the concentration of the X-ray sensitive elements in the layers. With the results obtained for stacked polymer systems the validity of the analytical quantification model for the determination of stratified materials by 3D Micro-XRF could be demonstrated.

Molecular simulation of dispersion and mechanical stability of organically modified layered silicates in polymer matrices

NASA Astrophysics Data System (ADS)

Fu, Yao-Tsung

The experimental analysis of nanometer-scale separation processes and mechanical properties at buried interfaces in nanocomposites has remained difficult. We have employed molecular dynamics simulation in relation to available experimental data to alleviate such limitations and gain insight into the dispersion and mechanical stability of organically modified layered silicates in hydrophobic polymer matrices. We analyzed cleavage energies of various organically modified silicates as a function of the cation exchange capacity, surfactant head group chemistry, and chain length using MD simulations with the PCFF-PHYLLOSILICATE force field. The range of the cleavage energy is between 25 and 210 mJ/m2 upon the molecular structures and packing of surfactants. As a function of chain length, the cleavage energy indicates local minima for interlayer structures comprised of loosely packed layers of alkyl chains and local maxima for interlayer structures comprised of densely packed layers of alkyl chains between the layers. In addition, the distribution of cationic head groups between the layers in the equilibrium state determines whether large increases in cleavage energy due to Coulomb attraction. We have also examined mechanical bending and failure mechanisms of layered silicates on the nanometer scale using molecular dynamics simulation in comparison to a library of TEM data of polymer nanocomposites. We investigated the energy of single clay lamellae as a function of bending radius and different cation density. The layer energy increases particularly for bending radii below 20 nm and is largely independent of cation exchange capacity. The analysis of TEM images of agglomerated and exfoliated aluminosilicates of different CEC in polymer matrices at small volume fractions showed bending radii in excess of 100 nm due to free volumes in the polymer matrix. At a volume fraction >5%, however, bent clay layers were found with bending radii <20 nm and kinks as a failure mechanism

Correlation between surface morphology and surface forces of protein A adsorbed on mica.

PubMed Central

Ohnishi, S; Murata, M; Hato, M

1998-01-01

We have investigated the morphology and surface forces of protein A adsorbed on mica surface in the protein solutions of various concentrations. The force-distance curves, measured with a surface force apparatus (SFA), were interpreted in terms of two different regimens: a "large-distance" regimen in which an electrostatic double-layer force dominates, and an "adsorbed layer" regimen in which a force of steric origin dominates. To further clarify the forces of steric origin, the surface morphology of the adsorbed protein layer was investigated with an atomic force microscope (AFM) because the steric repulsive forces are strongly affected by the adsorption mode of protein A molecules on mica. At lower protein concentrations (2 ppm, 10 ppm), protein A molecules were adsorbed "side-on" parallel to the mica surfaces, forming a monolayer of approximately 2.5 nm. AFM images at higher concentrations (30 ppm, 100 ppm) showed protruding structures over the monolayer, which revealed that the adsorbed protein A molecules had one end oriented into the solution, with the remainder of each molecule adsorbed side-on to the mica surface. These extending ends of protein A overlapped each other and formed a "quasi-double layer" over the mica surface. These AFM images proved the existence of a monolayer of protein A molecules at low concentrations and a "quasi-double layer" with occasional protrusions at high concentrations, which were consistent with the adsorption mode observed in the force-distance curves. PMID:9449346

Submicroporous/microporous and compatible/incompatible multi-functional dual-layer polymer electrolytes and their interfacial characteristics with lithium metal anode

NASA Astrophysics Data System (ADS)

Lee, Young-Gi; Kyhm, Kwangseuk; Choi, Nam-Soon; Ryu, Kwang Sun

A novel multi-functional dual-layer polymer electrolyte was prepared by impregnating the interconnected pores with an ethylene carbonate (EC)/dimethyl carbonate (DMC)/lithium hexafluorophosphate (LiPF 6) solution. An incompatible layer is based on a microporous polyethylene (PE) and a compatible layer, based on a poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) is sub-microporous and compatible with an electrolyte solution. The Li electrode/the dual-layer polymer electrolyte/Li[Ni 0.15Li 0.23M n0.62]O 2 cell showed stable cycle performance under prolonged cycle number. This behavior is due to the enhanced compatibility between the matrix polymer and the liquid electrolytes within the submicroporous compatible layer, which could lead to a controlled Li + deposition on the Li anode surface by forming homegeneous electrolyte zone near the anode.

Conductive polymer layers to limit transfer of fuel reactants to catalysts of fuel cells to reduce reactant crossover

DOEpatents

Stanis, Ronald J.; Lambert, Timothy N.

2016-12-06

An apparatus of an aspect includes a fuel cell catalyst layer. The fuel cell catalyst layer is operable to catalyze a reaction involving a fuel reactant. A fuel cell gas diffusion layer is coupled with the fuel cell catalyst layer. The fuel cell gas diffusion layer includes a porous electrically conductive material. The porous electrically conductive material is operable to allow the fuel reactant to transfer through the fuel cell gas diffusion layer to reach the fuel cell catalyst layer. The porous electrically conductive material is also operable to conduct electrons associated with the reaction through the fuel cell gas diffusion layer. An electrically conductive polymer material is coupled with the fuel cell gas diffusion layer. The electrically conductive polymer material is operable to limit transfer of the fuel reactant to the fuel cell catalyst layer.

Automated solid-phase extraction of phenolic acids using layered double hydroxide-alumina-polymer disks.

PubMed

Ghani, Milad; Palomino Cabello, Carlos; Saraji, Mohammad; Manuel Estela, Jose; Cerdà, Víctor; Turnes Palomino, Gemma; Maya, Fernando

2018-01-26

The application of layered double hydroxide-Al 2 O 3 -polymer mixed-matrix disks for solid-phase extraction is reported for the first time. Al 2 O 3 is embedded in a polymer matrix followed by an in situ metal-exchange process to obtain a layered double hydroxide-Al 2 O 3 -polymer mixed-matrix disk with excellent flow-through properties. The extraction performance of the prepared disks is evaluated as a proof of concept for the automated extraction using sequential injection analysis of organic acids (p-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, gallic acid) following an anion-exchange mechanism. After the solid-phase extraction, phenolic acids were quantified by reversed-phase high-performance liquid chromatography with diode-array detection using a core-shell silica-C18 stationary phase and isocratic elution (acetonitrile/0.5% acetic acid in pure water, 5:95, v/v). High sensitivity and reproducibility were obtained with limits of detection in the range of 0.12-0.25 μg/L (sample volume, 4 mL), and relative standard deviations between 2.9 and 3.4% (10 μg/L, n = 6). Enrichment factors of 34-39 were obtained. Layered double hydroxide-Al 2 O 3 -polymer mixed-matrix disks had an average lifetime of 50 extractions. Analyte recoveries ranged from 93 to 96% for grape juice and nonalcoholic beer samples. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Study and modeling of the ironing process on a multi-layered polymer coated low-carbon steel

NASA Astrophysics Data System (ADS)

Selles Canto, Miguel Angel

The ironing process is the most crucial step in the manufacture of cans. Sheet steel covered by three polymer layers can be used as the starting material, but this coating must neither break nor fail in any manner in order to be considered as a viable and effective alternative to traditional practice. During ironing, the deformations are severe and high pressures exist at the tool-workpiece interface. Thickness reductions inherent in ironing require a large amount of surface generation. Deterioration of the coating in this delicate operation might enable direct contact of the stored food or drink with the metal. As can be appreciated, the key to the use of polymer-coated steel sheets in the manufacture of cans lies in the survival of these layers during the ironing process. Another important issue is the roughness of the newly-generated surface, because it should be possible to decorate the can without any difficulty. Changing the traditional manufacture of metallic containers such as cans and using this new coated material permits great reduction in environmental contaminants produced as a result of avoiding the formation of Volatile Organic Compounds (VOCs) during the manufacture of the polymer layers. This reduction is even greater because of not using additional lubricants due to the self-lubricanting property of the solid polymer coating layers during the drawing process. These objectives, together with the improvement of the mechanical characteristics and the adhesion of the painting or decorative priming, are realized by the use of the proposed material. In the existing bibliography about ironing processes on coated materials, some authors propose the use of the Upper Bound Theorem for modeling the material behavior. The present research shows for the first time the modeling of the ironing process on a three-layer polymer coated material. In addition, it takes into account the cases in which successful ironing is produced and those in which ones the ironing

Nano-sized Adsorbate Structure Formation in Anisotropic Multilayer System

NASA Astrophysics Data System (ADS)

Kharchenko, Vasyl O.; Kharchenko, Dmitrii O.; Yanovsky, Vladimir V.

2017-05-01

In this article, we study dynamics of adsorbate island formation in a model plasma-condensate system numerically. We derive the generalized reaction-diffusion model for adsorptive multilayer system by taking into account anisotropy in transfer of adatoms between neighbor layers induced by electric field. It will be found that with an increase in the electric field strength, a structural transformation from nano-holes inside adsorbate matrix toward separated nano-sized adsorbate islands on a substrate is realized. Dynamics of adsorbate island sizes and corresponding distributions are analyzed in detail. This study provides an insight into details of self-organization of adatoms into nano-sized adsorbate islands in anisotropic multilayer plasma-condensate systems.

Modifying protein adsorption by layers of glutathione pre-adsorbed on Au(111)

NASA Astrophysics Data System (ADS)

Vallée, Anne; Humblot, Vincent; Méthivier, Christophe; Dumas, Paul; Pradier, Claire-Marie

2011-12-01

Molecular interaction with metal surfaces raises fundamental questions regarding their binding tendency, their dispersion on the surface, as well as their conformation which may change their biological properties; addressing these questions, and being able to tune protein interactions, is of primary importance for the control of biointerfaces. In this study, one tripeptide, GSH (glu-cys-gly), was used to condition gold surfaces and thus influence the adsorption of bovine serum albumin (BSA). Depending on the pH value of the GSH solution, cationic, zwitterionic or anionic forms of the tripeptide could be stabilised on the surface, before interacting with BSA solutions. The amount of proteins was observed to depend both on the chemical state of the adsorbed underlying peptide and on the solvent of the protein solution, indicating an important role of electrostatic interactions upon protein adsorption. Moreover, atomic force microscopy (AFM), and synchrotron IR microscopy revealed a heterogeneous distribution of proteins on the GSH layer.

Polymer-phyllosilicate nanocomposites and their preparation

DOEpatents

Chaiko, David J.

2007-01-09

Polymer-phyllosilicate nanocomposites that exhibit superior properties compared to the polymer alone, and methods-for producing these polymer-phyllosilicate nanocomposites, are provided. Polymeric surfactant compatabilizers are adsorbed onto the surface of hydrophilic or natural phyllosilicates to facilitate the dispersal and exfoliation of the phyllosilicate in a polymer matrix. Utilizing polymeric glycol based surfactants, polymeric dicarboxylic acids, polymeric diammonium surfactants, and polymeric diamine surfactants as compatabilizers facilitates natural phyllosilicate and hydrophilic organoclay dispersal in a polymer matrix to produce nanocomposites.

Benzocyclobutene (BCB) Polymer as Amphibious Buffer Layer for Graphene Field-Effect Transistor.

PubMed

Wu, Yun; Zou, Jianjun; Huo, Shuai; Lu, Haiyan; Kong, Yuecan; Chen, Tangshen; Wu, Wei; Xu, Jingxia

2015-08-01

Owing to the scattering and trapping effects, the interfaces of dielectric/graphene or substrate/graphene can tailor the performance of field-effect transistor (FET). In this letter, the polymer of benzocyclobutene (BCB) was used as an amphibious buffer layer and located at between the layers of substrate and graphene and between the layers of dielectric and graphene. Interestingly, with the help of nonpolar and hydrophobic BCB buffer layer, the large-scale top-gated, chemical vapor deposited (CVD) graphene transistors was prepared on Si/SiO2 substrate, its cutoff frequency (fT) and the maximum cutoff frequency (fmax) of the graphene field-effect transistor (GFET) can be reached at 12 GHz and 11 GHz, respectively.

Polymer-Induced Depletion Interaction and Its Effect on Colloidal Sedimentation in Colloid-Polymer Mixtures

NASA Technical Reports Server (NTRS)

Tong, Penger

1996-01-01

In this paper we focus on the polymer-induced depletion attraction and its effect on colloidal sedimentation in colloid-polymer mixtures. We first report a small angle neutron scattering (SANS) study of the depletion effect in a mixture of hard-sphere-like colloid and non-adsorbing polymer. Then we present results of our recent sedimentation measurements in the same colloid-polymer mixture. A key parameter in controlling the sedimentation of heavy colloidal particles is the interparticle potential U(tau), which is the work required to bring two colloidal particles from infinity to a distance tau under a give solvent condition. This potential is known to affect the average settling velocity of the particles and experimentally one needs to have a way to continuously vary U(tau) in order to test the theory. The interaction potential U(tau) can be altered by adding polymer molecules into the colloidal suspension. In a mixture of colloid and non-adsorbing polymer, the potential U(tau) can develop an attractive well because of the depletion effect, in that the polymer chains are expelled from the region between two colloidal particles when their surface separation becomes smaller than the size of the polymer chains. The exclusion of polymer molecules from the space between the colloidal particles leads to an unbalanced osmotic pressure difference pushing the colloidal particles together, which results in an effective attraction between the two colloidal particles. The polymer-induced depletion attraction controls the phase stability of many colloid-polymer mixtures, which are directly of interest to industry.

Characterization of self-assembled redox polymer and antibody molecules on thiolated gold electrodes.

PubMed

Calvo, E J; Danilowicz, C; Lagier, C M; Manrique, J; Otero, M

2004-05-15

Multilayer immobilization of antibody and redox polymer molecules on a gold electrode was achieved, as a strategy for the potential development of an amperometric immunosensor. The step-by-step assembly of antibiotin IgG on Os(bpy)(2)ClPyCH(2)NH poly(allylamine) redox polymer (PAH-Os) adsorbed on thiolated gold electrodes was proved by quartz crystal microbalance (QCM) and atomic force microscopy (AFM) experiments, confirming the electrochemical evidence. The increase of redox charge during the layer-by-layer deposition demonstrated that charge propagation within the layers is feasible. The multilayer structure proved to be effective for the molecular recognition of horseradish peroxidase-biotin conjugate (HRP-biotin), as confirmed by the QCM measurements and the electrocatalytic reduction current obtained upon H(2)O(2) addition. The catalytic current resulting from PAH-Os mediation was shown to increase with the number of assembled layers. Furthermore, the inventory of IgG molecules on the supramolecular self-assembled structure and the specific and non-specific binding of HRP-biotin conjugate were confirmed by the QCM transient studies, giving information on the kinetics of IgG deposition and HRP-biotin conjugate binding to the IgG.

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

NASA Astrophysics Data System (ADS)

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

2008-10-01

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

A polarization-independent liquid crystal phase modulation using polymer-network liquid crystal with orthogonal alignment layers

NASA Astrophysics Data System (ADS)

Chen, Ming-Syuan; Lin, Wei-Chih; Tsou, Yu-Shih; Lin, Yi-Hsin

2012-10-01

A polarization-independent liquid crystal (LC) phase modulation using polymer-network liquid crystals with orthogonal alignments layers (T-PNLC) is demonstrated. T-PNLC consists of three layers. LC directors in the two layers near glass substrates are orthogonal to each other. In the middle layer, LC directors are perpendicular to the glass substrate. The advantages of such T-PNLC include polarizer-free, larger phase shift (~0.4π rad) than the residual phase type (<0.05π rad), and low operating voltage (< 30Vrms). It does not require bias voltage for avoiding scattering because the refractive index of liquid crystals matches that of polymers. The phase shift of T-PNLC is affected by the cell gap and the curing voltages. The potential applications are laser beam steering, spatial light modulators and electrically tunable micro-lens arrays.

Ionic polymer-metal composite actuators based on triple-layered polyelectrolytes composed of individually functionalized layers.

PubMed

Lee, Jang-Woo; Yoo, Young-Tai; Lee, Jae Yeol

2014-01-22

Ionic polymer-metal composite (IPMC) actuators based on two types of triple-layered Nafion composite membranes were prepared via consecutive solution recasting and electroless plating methods. The triple-layered membranes are composed of a Nafion layer containing an amphiphilic organic molecule (10-camphorsulfonic acid; CSA) in the middle section (for fast and large ion conduction) and two Nafion/modified inorganic composite layers in the outer sections (for large accumulation/retention of mobile ions). For construction of the two types of IPMCs, sulfonated montmorillonite (MMT) and polypyrrole (PPy)-coated alumina fillers were incorporated into the outer layers. Both the triple-layered IPMCs exhibited 42% higher tip displacements at the maximum deflections with a negligible back-relaxation, 50-74% higher blocking forces, and more rapid responses under 3 V dc, compared with conventional single-layered Nafion-IPMCs. Improvements in cyclic displacement under a rectangular voltage input of 3 V at 1 Hz were also made in the triple-layered configurations. Compared with single-layered IPMCs consisting of the identical compositions with the respective outer composite layers, the bending rates and energy efficiencies of both the triple-layered IPMCs were significantly higher, although the blocking forces were a bit lower. These remarkable improvements were attributed to higher capacitances and Young's moduli as well as a more efficient transport of mobile ions and water through the middle layer (Nafion/CSA) and a larger accumulation/retention of the mobile species in the outer functionalized inorganic composite layers. Especially, the triple-layered IPMC with the PPy-modified alumina registered the best actuation performance among all the samples, including a viable actuation even at a low voltage of 1.5 V due to involving efficient redox reactions of PPy with the aid of hygroscopic alumina.

Porous cellulosic adsorbent for the removal of Cd (II), Pb(II) and Cu(II) ions from aqueous media

NASA Astrophysics Data System (ADS)

Barsbay, Murat; Kavaklı, Pınar Akkaş; Tilki, Serhad; Kavaklı, Cengiz; Güven, Olgun

2018-01-01

The main objective of this work is to prepare a renewable cellulosic adsorbent by γ-initiated grafting of poly(glycidyl methacrylate) (PGMA) from cellulose substrate and subsequent modification of PGMA with chelating species, iminodiacetic acid (IDA), for Cd (II), Pb(II) and Cu(II) removal from aqueous media. Modification of PGMA grafted cellulose with IDA in aqueous solution under mild conditions has proceeded efficiently to yield a natural-based and effective porous adsorbent with well-defined properties as provided by the controlled polymerization technique, namely RAFT, applied during the radiation-induced graft copolymerization step and with sufficient degree of IDA immobilization as confirmed by XPS, FTIR, contact angle measurements and elemental analysis. In order to examine the Cd (II), Pb(II) and Cu(II) removing performance of the resulting adsorbent, batch experiments were carried out by ICP-MS. The adsorption capacities were determined as 53.4 mg Cd(II)/g polymer, 52.0 mg Pb(II)/g polymer and 69.6 mg Cu(II)/g polymer at initial feed concentration of 250 ppm, showing the promising potential of the natural-based adsorbent to steadily and efficiently chemisorb toxic metal ions.

Semiflexible polymers confined in a slit pore with attractive walls: two-dimensional liquid crystalline order versus capillary nematization.

PubMed

Milchev, Andrey; Egorov, Sergei A; Binder, Kurt

2017-03-01

Semiflexible polymers under good solvent conditions interacting with attractive planar surfaces are investigated by Molecular Dynamics (MD) simulations and classical Density Functional Theory (DFT). A bead-spring type potential complemented by a bending potential is used, allowing variation of chain stiffness from completely flexible coils to rod-like polymers whose persistence length by far exceeds their contour length. Solvent is only implicitly included, monomer-monomer interactions being purely repulsive, while two types of attractive wall-monomer interactions are considered: (i) a strongly attractive Mie-type potential, appropriate for a strictly structureless wall, and (ii) a corrugated wall formed by Lennard-Jones particles arranged on a square lattice. It is found that in dilute solutions the former case leads to the formation of a strongly adsorbed surface layer, and the profile of density and orientational order in the z-direction perpendicular to the wall is predicted by DFT in nice agreement with MD. While for very low bulk densities a Kosterlitz-Thouless type transition from the isotropic phase to a phase with power-law decay of nematic correlations is suggested to occur in the strongly adsorbed layer, for larger densities a smectic-C phase in the surface layer is detected. No "capillary nematization" effect at higher bulk densities is found in this system, unlike systems with repulsive walls. This finding is attributed to the reduction of the bulk density (in the center of the slit pore) due to polymer adsorption on the attractive wall, for a system studied in the canonical ensemble. Consequently in a system with two attractive walls nematic order in the slit pore can occur only at a higher density than for a bulk system.

ε-Polylysine-based thermo-responsive adsorbents for immunoglobulin adsorption-desorption under mild conditions.

PubMed

Maruyama, Masashi; Shibuya, Keisuke

2017-08-22

Thermo-responsive adsorbents for immunoglobulin G (IgG) employing ε-polylysine (EPL) as a polymer backbone were developed. The introduction of mercaptoethylpyridine (MEP) as an IgG-binding ligand and hydrophobization of side chains afforded thermo-responsive IgG adsorbents, whose thermo-responsive IgG desorption ratio was up to 88% (EPL/MEP derivative 3m). The changes in surface densities of active MEP groups, which are caused by thermal conformational changes of the adsorbents, play key roles for IgG desorption. Although a trade-off of IgG adsorption capacity and IgG desorption ratio was observed, the present study offers a novel molecular design for thermo-responsive adsorbents with high synthetic accessibility and potentially low toxicity.

Adsorption of dextrin on hydrophobic minerals.

PubMed

Beaussart, Audrey; Mierczynska-Vasilev, Agnieszka; Beattie, David A

2009-09-01

The adsorption of dextrin on talc, molybdenite, and graphite (three naturally hydrophobic minerals) has been compared. Adsorption isotherms and in situ tapping mode atomic force microscope (TMAFM) imaging have enabled polymer adsorbed amount and morphology of the adsorbed layer (area coverage and polymer domain size) to be determined and also the amount of hydration water in the structure of the adsorbed layer. The effect of the polymer on the mineral contact angles, measured by the captive bubble method on cleaved mineral surfaces, indicates clear correlations between the hydrophobicity reduction of the minerals, the adsorbed amount, and the surface coverage of the adsorbed polymer. Predictions of the flotation recovery of the treated mineral phases have been confirmed by performing batch flotation experiments. The influence of the polymer surface coverage on flotation recovery has highlighted the importance of this key parameter in the predictions of depressant efficiency. The roles of the initial hydrophobicity and the surface structure of the mineral basal plane in determining adsorption parameters and flotation response of the polymer-treated minerals are also discussed.

On the Interfacial Properties of Polymers/Functionalized Single-Walled Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Ansari, R.; Rouhi, S.; Ajori, S.

2016-06-01

Molecular dynamics (MD) simulations is used to study the adsorption of polyethylene (PE) and poly(ethylene oxide) (PEO) on the functionalized single-walled carbon nanotubes (SWCNTs). The effects of functionalization factor weight percent on the interaction energies of polymer chains with nanotubes are studied. Besides, the influences of different functionalization factors on the SWCNT/polymer interactions are investigated. It is shown that for both types of polymer chains, the largest interaction energies associates with the random O functionalized nanotubes. Besides, increasing temperature results in increasing the nanotube/polymer interaction energy. Considering the final shapes of adsorbed polymer chains on the SWCNTs, it is observed that the adsorbed conformations of PE chains are more contracted than those of PEO chains.

Polymer adsorption on silica and wettability of graphene oxide surfaces, experiments and simulations

NASA Astrophysics Data System (ADS)

Mortazavian, Hamid

Among the various classifications of polymer composites, studying polymers adsorbed to a surface such as silica is important due to their numerous applications. Adsorbed polymers usually show different properties than their bulk counterparts due to their interactions with the surface. In this study, we observed tightly- and loosely-bound polymer and mobile components in poly(vinyl acetate) (PVAc) on silica both with temperature-modulated differential scanning calorimetry (TMDSC) experiments and computer simulations. The more-mobile component which correlated to the region of low density at the air interface is reported for the first time using TMDSC thermograms. Pore size distribution and pore volume development of adsorbed PMMA samples showed different behavior below and above the tightly-bound amount of the polymer. The amount of tightly-bound polymer was obtained by a linear regression analysis of the ratio of the area under the two glass transitions. The values obtained vary from 0.52 to 0.86 mg PVAc/m2 silica depending upon the molecular mass for the amounts of PVAc and the specific surface area of fumed silica. Direct comparisons of the thermal properties and intermolecular interactions were performed between PVAc and poly(methyl methacrylate) (PMMA) with similar molecular masses and adsorbed amounts on silica. A larger amount of tightly-bound polymer and a greater change in glass transition were observed for adsorbed PMMA compared to adsorbed PVAc. These observations suggested that the interactions between PMMA and silica were stronger than those between PVAc and silica. Molecular modeling of these surface polymers showed that PMMA associates more strongly with silica than does PVAc through additional hydrogen-bonding interactions. Graphene oxide (GO) material surface characteristics make it easy to functionalize, making it a water repellant surface. To test the effect of chemical makeup and size of attached groups on the surface wettability of GO, we

In situ modification of chromatography adsorbents using cold atmospheric pressure plasmas

NASA Astrophysics Data System (ADS)

Olszewski, P.; Willett, T. C.; Theodosiou, E.; Thomas, O. R. T.; Walsh, J. L.

2013-05-01

Efficient manufacturing of increasingly sophisticated biopharmaceuticals requires the development of new breeds of chromatographic materials featuring two or more layers, with each layer affording different functions. This letter reports the in situ modification of a commercial beaded anion exchange adsorbent using atmospheric pressure plasma generated within gas bubbles. The results show that exposure to He-O2 plasma in this way yields significant reductions in the surface binding of plasmid DNA to the adsorbent exterior, with minimal loss of core protein binding capacity; thus, a bi-layered chromatography material exhibiting both size excluding and anion exchange functionalities within the same bead is produced.

Antifouling Thin-Film Composite Membranes by Controlled Architecture of Zwitterionic Polymer Brush Layer.

PubMed

Liu, Caihong; Lee, Jongho; Ma, Jun; Elimelech, Menachem

2017-02-21

In this study, we demonstrate a highly antifouling thin-film composite (TFC) membrane by grafting a zwitterionic polymer brush via atom-transfer radical-polymerization (ATRP), a controlled, environmentally benign chemical process. Initiator molecules for polymerization were immobilized on the membrane surface by bioinspired catechol chemistry, leading to the grafting of a dense zwitterionic polymer brush layer. Surface characterization revealed that the modified membrane exhibits reduced surface roughness, enhanced hydrophilicity, and lower surface charge. Chemical force microscopy demonstrated that the modified membrane displayed foulant-membrane interaction forces that were 1 order of magnitude smaller than those of the pristine TFC membrane. The excellent fouling resistance imparted by the zwitterionic brush layer was further demonstrated by significantly reduced adsorption of proteins and bacteria. In addition, forward osmosis fouling experiments with a feed solution containing a mixture of organic foulants (bovine-serum albumin, alginate, and natural organic matter) indicated that the modified membrane exhibited significantly lower water flux decline compared to the pristine TFC membrane. The controlled architecture of the zwitterionic polymer brush via ATRP has the potential for a facile antifouling modification of a wide range of water treatment membranes without compromising intrinsic transport properties.

Influence of polymer charge on the shear yield stress of silica aggregated with adsorbed cationic polymers.

PubMed

Zhou, Ying; Yu, Hai; Wanless, Erica J; Jameson, Graeme J; Franks, George V

2009-08-15

Flocs were produced by adding three cationic polymers (10% charge density, 3.0x10(5) g/mol molecular weight; 40% charge density, 1.1x10(5) g/mol molecular weight; and 100% charge density, 1.2x10(5) g/mol molecular weight) to 90 nm diameter silica particles. The shear yield stresses of the consolidated sediment beds from settled and centrifuged flocs were determined via the vane technique. The polymer charge density plays an important role in influencing the shear yield stresses of sediment beds. The shear yield stresses of sediment beds from flocs induced by the 10% charged polymer were observed to increase with an increase in polymer dose, initial solid concentration and background electrolyte concentration at all volume fractions. In comparison, polymer dose has a marginal effect on the shear yield stresses of sediment beds from flocs induced by the 40% and 100% charged polymers. The shear yield stresses of sediments from flocs induced by the 40% charged polymer are independent of salt concentration whereas the addition of salt decreases the shear yield stresses of sediments from flocs induced by the 100% charged polymer. When flocculated at the optimum dose for each polymer (12 mg/g silica for the 10% charged polymer at 0.03 M NaCl, 12 mg/g for 40% and 2 mg/g for 100%), shear yield stress increases as polymer charge increases. The effects observed are related to the flocculation mechanism (bridging, patch attraction or charge neutralisation) and the magnitude of the adhesive force. Comparison of shear and compressive yield stresses show that the network is only slightly weaker in shear than in compression. This is different than many other systems (mainly salt and pH coagulation) which have shear yield stress much less than compressive yield stress. The existing models relating the power law exponent of the volume fraction dependence of the shear yield stress to the network fractal structure are not satisfactory to predict all the experimental behaviour.

Synthesis and characterization of polymer layers for control of fluid transport

NASA Astrophysics Data System (ADS)

Vatansever, Fehime

The level of wetting of fiber surface with liquids is an important characteristic of fibrous materials. It is related to fiber surface energy and the structure of the material. Surface energy can be changed by surface modification via the grafting methodologies that have been reported for introducing new and stable functionality to fibrous substrates without changing bulk properties. Present work is dedicated to synthesis and characterization of macromolecular layers grafted to fiber surface in order to achieve directional liquid transport for the modified fabric. Modification technique used here is based on formation of stable polymer layer on fabric surface using "grafting to" technique. Specifically, modification of fabric with wettability gradient for facilitated one way-liquid transport, and pointed modification of yarn-based channels on textile microfluidic device for directional liquid transport are reported here. First, fabric was activated with alkali (NaOH) solution. Second, poly (glycidyl methacrylate) (PGMA) was deposited on fabric as an anchoring layer. Finally, polymers of interest were grafted to surface through the epoxy functionality of PGMA. Effect of polymer grafting on the wicking property of the fabric has been evaluated by vertical wicking technique at the each step of surface modification. The results shows that wicking performance of fabric can be altered by grafting of a thin nanoscale polymeric film. For the facilitated liquid transport, the gradient polymer coating was created using "grafting to" technique and its dependence on the grafting temperature. Wettability gradient from hydrophilic to hydrophobic (change in water contact angle from 0 to 140 degrees on fabric) was achieved by grafting of polystyrene (PS) and polyacrylic acid (PAA) sequentially with concentration gradient. This study proposes that fabric with wettability gradient property can be used to transfer sweat from skin and support moisture management when it is used in a

Hexadimethrine-montmorillonite nanocomposite: Characterization and application as a pesticide adsorbent

NASA Astrophysics Data System (ADS)

Gámiz, B.; Hermosín, M. C.; Cornejo, J.; Celis, R.

2015-03-01

The goal of this work was to prepare and characterize a novel functional material by the modification of SAz-1 montmorillonite with the cationic polymer hexadimethrine (SA-HEXAD), and to explore the potential use of this nanocomposite as a pesticide adsorbent. Comparative preparation and characterization with the well-known hexadecyltrimethylammonium-modified SAz-1 montmorillonite (SA-HDTMA) was also assessed. The characterization was performed by elemental analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), physisorption of N2, scanning electron microscopy (SEM) and Z potential measurements. The characterization and adsorption experiments showed that the extent of pesticide adsorption was markedly subjected to the structure and features of the surface of each organo-clay and also to the nature of the considered pesticide. SA-HEXAD displayed a high affinity for anionic pesticides which, presumably, were adsorbed by electrostatic attraction on positively-charged ammonium groups of the polymer not directly interacting with the clay. In contrast, SA-HDTMA displayed great adsorption of both uncharged and anionic pesticides with predominance of hydrophobic interactions. This work provided information about the surface properties of a new organic-inorganic nanohybrid material, SA-HEXAD, and its potential as an adsorbent for the removal of anionic organic pollutants from aqueous solutions.

Formation and stability of twisted ribbons in mixtures of rod-like fd-virus and non-adsorbing polymer

NASA Astrophysics Data System (ADS)

Dogic, Z.; Didonna, B.; Bryning, M.; Lubensky, T. C.; Yodh, A. G.; Janmey, P. A.

2003-03-01

We are investigating the behavior of mixtures of monodisperse fd-virus rods and non-adsorbing polymer. We observe the formation of isolated smectic disks. The single smectic disk is of a monolayer of aligned rods while its thickness equal to the length of a single rod. As disks coalesce they undergo shape transformations from flat structures to elongated twisted ribbons. A theoretical model is formulated wherein the chirality of the molecule favors the formation of the elongated ribbon structure while the line tension favors formation of untwisted disks. To check the validity of the theoretical model line tension and twist constants are experimentally measured. The line tension is deduced from thermal fluctuations of the interface. The twist constant is determined by unwinding the twisted ribbons using optical tweezers. This work is partially supported by NSF grants DMR-0203378, the PENN MRSEC, DMR-0079909, and NASA grant NAG8-2172.

Adsorption of Candida rugosa lipase at water-polymer interface: The case of poly( DL)lactide

NASA Astrophysics Data System (ADS)

Kamel, Gihan; Bordi, Federico; Chronopoulou, Laura; Lupi, Stefano; Palocci, Cleofe; Sennato, Simona; Verdes, Pedro V.

2011-12-01

Insights into the interactions between biological macromolecules and polymeric surfaces are of great interest because of potential uses in developing biotechnologies. In this study we focused on the adsorption of a model lipolytic enzyme, Candida rugosa lipase (CRL), on poly-(D,L)-lactic acid (PDLLA) polymer with the aim to gain deeper insights into the interactions between the enzyme and the carrier. Such studies are of particular relevance in order to establish the optimal conditions for enzyme immobilization and its applications. We employed two different approaches; by analyzing the influence of adsorbed CRL molecules on the thermodynamic behavior of Langmuir films of PDLLA deposited at air-water interface, we gained interesting information on the molecular interactions between the protein and the polymer. Successively, by a systematic analysis of the adsorption of CRL on PDLLA nanoparticles, we showed that the adsorption of a model lipase, CRL, on PDLLA is described in terms of a Langmuir-type adsorption behavior. In this model, only monomolecular adsorption takes place (i.e. only a single layer of the protein adsorbs on the support) and the interactions between adsorbed molecules and surface are short ranged. Moreover, both the adsorption and desorption are activated processes, and the heat of adsorption (the difference between the activation energy for adsorption and desorption) is independent from the surface coverage of the adsorbing species. Finally, we obtained an estimate of the number of molecules of the protein adsorbed per surface unit on the particles, a parameter of a practical relevance for applications in biocatalysis, and a semi-quantitative estimate of the energies (heat of adsorption) involved in the adsorption process.

Adsorption of surfactants and polymers at interfaces

NASA Astrophysics Data System (ADS)

Rojas, Orlando Jose

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

Rechargeable solid polymer electrolyte battery cell

DOEpatents

Skotheim, Terji

1985-01-01

A rechargeable battery cell comprising first and second electrodes sandwiching a solid polymer electrolyte comprising a layer of a polymer blend of a highly conductive polymer and a solid polymer electrolyte adjacent said polymer blend and a layer of dry solid polymer electrolyte adjacent said layer of polymer blend and said second electrode.

Influence of Weak Base Addition to Hole-Collecting Buffer Layers in Polymer:Fullerene Solar Cells.

PubMed

Seo, Jooyeok; Park, Soohyeong; Song, Myeonghun; Jeong, Jaehoon; Lee, Chulyeon; Kim, Hwajeong; Kim, Youngkyoo

2017-02-09

We report the effect of weak base addition to acidic polymer hole-collecting layers in normal-type polymer:fullerene solar cells. Varying amounts of the weak base aniline (AN) were added to solutions of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The acidity of the aniline-added PEDOT:PSS solutions gradually decreased from pH = 1.74 (AN = 0 mol% ) to pH = 4.24 (AN = 1.8 mol %). The electrical conductivity of the PEDOT:PSS-AN films did not change much with the pH value, while the ratio of conductivity between out-of-plane and in-plane directions was dependent on the pH of solutions. The highest power conversion efficiency (PCE) was obtained at pH = 2.52, even though all devices with the PEDOT:PSS-AN layers exhibited better PCE than those with the pristine PEDOT:PSS layers. Atomic force microscopy investigation revealed that the size of PEDOT:PSS domains became smaller as the pH increased. The stability test for 100 h illumination under one sun condition disclosed that the PCE decay was relatively slower for the devices with the PEDOT:PSS-AN layers than for those with pristine PEDOT:PSS layers.

Innovative Elution Processes for Recovering Uranium and Transition Metals from Amidoxime-based Adsorbents

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

Wai, Chien M.

Amidoxime-based polymer fibers are considered one of the most promising materials for sequestering uranium from seawater. The high-surface-area polymer fibers containing amidoxime and carboxylate groups synthesized by Oak Ridge National Lab (ORNL-AF1) show very high uranium adsorption capacities known in the literature. Effective elution of uranium and repeated use of the adsorbent are important factors affecting the cost of producing uranium from seawater using this material. Traditional acid leaching of uranium followed by KOH conditioning of the fiber causes chemical changes and physical damage to the ORNL-AF1 adsorbent. Two alkaline solution leaching methods were developed by this project, one usesmore » a highly concentrated (3 M) potassium bicarbonate solution at pH 8.3 and 40 °C; the other uses a mixture of sodium carbonate and hydrogen peroxide at pH 10.4. Both elution methods do not require KOH conditioning prior to reusing the fiber adsorbent. The conditions of eluting uranium from the amidoxime-based adsorbent using these alkaline solutions are confirmed by thermodynamic calculations. The bicarbonate elution method is selective for uranium recovery compared to other elution methods and causes no chemical change to the fiber material based on FTIR spectroscopy« less

Effect of polymer binders in anode catalyst layer on performance of alkaline direct ethanol fuel cells

NASA Astrophysics Data System (ADS)

Li, Y. S.; Zhao, T. S.; Liang, Z. X.

In preparing low-temperature fuel cell electrodes, a polymer binder is essential to bind discrete catalyst particles to form a porous catalyst layer that simultaneously facilitates the transfer of ions, electrons, and reactants/products. For two types of polymer binder, namely, an A3-an anion conducting ionomer and a PTFE-a neutral polymer, an investigation is made of the effect of the content of each binder in the anode catalyst layer on the performance of an alkaline direct ethanol fuel cell (DEFC) with an anion-exchange membrane and non-platinum (non-Pt) catalysts. Experiments are performed by feeding either ethanol (C 2H 5OH) solution or ethanol-potassium hydroxide (C 2H 5OH-KOH) solution. The experimental results for the case of feeding C 2H 5OH solution without added KOH indicate that the cell performance varies with the A3 ionomer content in the anode catalyst layer, and a content of 10 wt.% exhibits the best performance. When feeding C 2H 5OH-KOH solution, the results show that: (i) in the region of low current density, the best performance is achieved for a membrane electrode assembly without any binder in the anode catalyst layer; (ii) in the region of high current density, the performance is improved with incorporation of PTFE binder in the anode catalyst layer; (iii) the PTFE binder yields better performance than does the A3 binder.

Polyethers with pendent phenylvinyl substituted carbazole rings as polymers for hole transporting layers of OLEDs

NASA Astrophysics Data System (ADS)

Griniene, R.; Liu, L.; Tavgeniene, D.; Sipaviciute, D.; Volyniuk, D.; Grazulevicius, J. V.; Xie, Z.; Zhang, B.; Leduskrasts, K.; Grigalevicius, S.

2016-01-01

Polyethers containing pendent 3-(2-phenylvinyl)carbazole moieties have been synthesized by the multi-step synthetic routes. Full characterization of their structures is presented. The polymers represent materials of high thermal stability with initial thermal degradation temperatures exceeding 370 °C. The glass transition temperatures of the amorphous materials were in the range of 56-658 °C. The electron photoemission spectra of thin layers of the polymers showed ionization potentials of about 5.6 eV. Hole-transporting properties of the polymeric materials were tested in the structures of organic light emitting diodes with Alq3 as the green emitter and electron transporting layer. The device containing hole-transporting layers of poly{9-[6-(3-methyloxetan-3-ylmethoxy)hexyl]-3-(2-phenylvinyl)carbazole} exhibited the best overall performance with a maximum photometric efficiency of about 4.0 cd/A and maximum brightness exceeding 6430 cd/m2.

Integrated Gas Sensing System of SWCNT and Cellulose Polymer Concentrator for Benzene, Toluene, and Xylenes

PubMed Central

Im, Jisun; Sterner, Elizabeth S.; Swager, Timothy M.

2016-01-01

An integrated cellulose polymer concentrator/single-walled carbon nanotube (SWCNT) sensing system is demonstrated to detect benzene, toluene, and xylenes (BTX) vapors. The sensing system consists of functionalized cellulose as a selective concentrator disposed directly on top of a conductive SWCNT sensing layer. Functionalized cellulose concentrator (top layer) selectively adsorbs the target analyte and delivers the concentrated analyte as near as possible to the SWCNT sensing layer (bottom layer), which enables the simultaneous concentrating and sensing within a few seconds. The selectivity can be achieved by functionalizing cellulose acetate with a pentafluorophenylacetyl selector that interacts strongly with the target BTX analytes. A new design of the integrated cellulose concentrator/SWCNT sensing system allows high sensitivity with limits of detection for benzene, toluene, and m-xylene vapors of 55 ppm, 19 ppm, and 14 ppm, respectively, selectivity, and fast responses (<10 s to reach equilibrium), exhibiting the potential ability for on-site, real-time sensing applications. The sensing mechanism involves the selective adsorption of analytes in the concentrator film, which in turn mediates changes in the electronic potentials at the polymer-SWCNT interface and potentially changes in the tunneling barriers between nanotubes. PMID:26848660

Analysis of Adsorbate-Adsorbate and Adsorbate-Adsorbent Interactions to Decode Isosteric Heats of Gas Adsorption.

PubMed

Madani, S Hadi; Sedghi, Saeid; Biggs, Mark J; Pendleton, Phillip

2015-12-21

A qualitative interpretation is proposed to interpret isosteric heats of adsorption by considering contributions from three general classes of interaction energy: fluid-fluid heat, fluid-solid heat, and fluid-high-energy site (HES) heat. Multiple temperature adsorption isotherms are defined for nitrogen, T=(75, 77, 79) K, argon at T=(85, 87, 89) K, and for water and methanol at T=(278, 288, 298) K on a well-characterized polymer-based, activated carbon. Nitrogen and argon are subjected to isosteric heat analyses; their zero filling isosteric heats of adsorption are consistent with slit-pore, adsorption energy enhancement modelling. Water adsorbs entirely via specific interactions, offering decreasing isosteric heat at low pore filling followed by a constant heat slightly in excess of water condensation enthalpy, demonstrating the effects of micropores. Methanol offers both specific adsorption via the alcohol group and non-specific interactions via its methyl group; the isosteric heat increases at low pore filling, indicating the predominance of non-specific interactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modification of a Turbulent Boundary Layer within a Homogeneous Concentration of Drag reducing Polymer Solution

NASA Astrophysics Data System (ADS)

Farsiani, Yasaman; Elbing, Brian

2017-11-01

High molecular weight polymer solutions in wall-bounded flows can reduce the local skin friction by as much as 80%. External flow studies have typical focused on injection of polymer within a developing turbulent boundary layer (TBL), allowing the concentration and drag reduction level to evolve with downstream distance. Modification of the log-law region of the TBL is directly related to drag reduction, but recent results suggest that the exact behavior is dependent on flow and polymer properties. Weissenberg number and the viscosity ratio (ratio of solvent viscosity to the zero-shear viscosity) are concentration dependent, thus the current study uses a polymer ocean (i.e. a homogenous concentration of polymer solution) with a developing TBL to eliminate uncertainty related to polymer properties. The near-wall modified TBL velocity profiles are acquired with particle image velocimetry. In the current presentation the mean velocity profiles and the corresponding flow (Reynolds number) and polymer (Weissenberg number, viscosity ratio, and length ratio) properties are reported. Note that the impact of polymer degradation on molecular weight will also be quantified and accounted for when estimating polymer properties This work was supported by NSF Grant 1604978.

Chain Conformation near the Buried Interface in Nanoparticle-Stabilized Polymer Thin Films

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

Barkley, Deborah A.; Jiang, Naisheng; Sen, Mani

It is known that when nanoparticles are added to polymer thin films, they often migrate to the film-substrate interface and form an “immobile interfacial layer”, which has been believed as the origin of suppression of dewetting. We here report an alternative mechanism of dewetting suppression from the structural aspect of a polymer. Dodecane thiol-functionalized gold (Au) nanoparticles embedded in PS thin films prepared on Si substrates were used as a model. It was found that thermal annealing promotes irreversible polymer adsorption onto the substrate surface along with the surface migration of the nanoparticles. We also revealed that the surface migrationmore » causes additional nanoconfined space for the adsorbed polymer chains. As a result, the self-organization process of the strongly adsorbed polymer chains on the solid surface was so hindered that the chain conformations were randomized and expanded in the film normal direction. Here, the resultant chain conformation allows the interpenetration between free chains and the adsorbed chains, promoting adhesion and hence stabilizing the thin film.« less

Chain Conformation near the Buried Interface in Nanoparticle-Stabilized Polymer Thin Films

DOE PAGES

Barkley, Deborah A.; Jiang, Naisheng; Sen, Mani; ...

2017-09-26

It is known that when nanoparticles are added to polymer thin films, they often migrate to the film-substrate interface and form an “immobile interfacial layer”, which has been believed as the origin of suppression of dewetting. We here report an alternative mechanism of dewetting suppression from the structural aspect of a polymer. Dodecane thiol-functionalized gold (Au) nanoparticles embedded in PS thin films prepared on Si substrates were used as a model. It was found that thermal annealing promotes irreversible polymer adsorption onto the substrate surface along with the surface migration of the nanoparticles. We also revealed that the surface migrationmore » causes additional nanoconfined space for the adsorbed polymer chains. As a result, the self-organization process of the strongly adsorbed polymer chains on the solid surface was so hindered that the chain conformations were randomized and expanded in the film normal direction. Here, the resultant chain conformation allows the interpenetration between free chains and the adsorbed chains, promoting adhesion and hence stabilizing the thin film.« less

Scattering-layer-induced energy storage function in polymer-based quasi-solid-state dye-sensitized solar cells.

PubMed

Zhang, Xi; Jiang, Hongrui

2015-03-09

Photo-self-charging cells (PSCs) are compact devices with dual functions of photoelectric conversion and energy storage. By introducing a scattering layer in polymer-based quasi-solid-state dye-sensitized solar cells, two-electrode PSCs with highly compact structure were obtained. The charge storage function stems from the formed ion channel network in the scattering layer/polymer electrolyte system. Both the photoelectric conversion and the energy storage functions are integrated in only the photoelectrode of such PSCs. This design of PSC could continuously output power as a solar cell with considerable efficiency after being photo-charged. Such PSCs could be applied in highly-compact mini power devices.

Three-dimensional bioprinting of cell-laden constructs with polycaprolactone protective layers for using various thermoplastic polymers.

PubMed

Kim, Byoung Soo; Jang, Jinah; Chae, Suhun; Gao, Ge; Kong, Jeong-Sik; Ahn, Minjun; Cho, Dong-Woo

2016-08-22

Three-dimensional (3D) cell-printed constructs have been recognized as promising biological substitutes for tissue/organ regeneration. They provide tailored physical properties and biological cues via multi-material printing process. In particular, hybrid bioprinting, enabling to use biodegradable synthetic polymers as framework, has been an attractive method to support weak hydrogels. The constructs with controlled architecture and high shape fidelity were fabricated through this method, depositing spatial arrangement of multi-cell types into microscale constructs. Among biodegradable synthetic polymers, polycaprolactone (PCL) has been commonly chosen in fabrication of cell-printed constructs because of its low melting temperature of 60 °C to be dispensed with extrusion-based bioprinting system. However, in addition to PCL, various synthetic polymers have been widely applied for tissue regeneration. These polymers have distinctive characteristics essential for tissue/organ regeneration. Nevertheless, it is difficult to use some polymers, such as poly (lactic-co-glycolic acid) (PLGA) and polylactic acid (PLA) with 3D bioprinting technology because of their high melting temperature to be dispensed, which can result in thermal damage to the cells in the printed constructs during the fabrication process. We present a novel bioprinting method to use various synthetic polymers in fabrication of cell-printed constructs. PCL was introduced as a protective layer to prevent thermal damage caused by high temperature of polymers during fabrication. Remarkable improvement in cellular activities in the printed constructs with PCL layers was observed compared with the construct without PCL. This bioprinting method can be applied to fabricate more tissue-like constructs through the use of various biomaterials.

Changes in the adsorbate dipole layer with changing d-filling of the metal (II) (Co, Ni, Cu) phthalocyanines on Au(111).

PubMed

Xiao, Jie; Dowben, Peter A

2009-02-04

In combined photoemission and inverse photoemission spectroscopy studies, we observe changes in the metal phthalocyanine molecular orbital offsets with respect to the conducting gold substrate Fermi level, with the changing d-electron filling of the metal (II) (Co, Ni, Cu) phthalocyanines. The implication is that the interfacial dipole layer depends upon the choice of metal (Co, Ni, Cu) centers within the metal (II) phthalocyanines adsorbed on Au(111).

Unbinding transition from fluid membranes with associated polymers.

PubMed

Benhamou, M; Kaidi, H

2013-10-01

We consider two neighboring fluid membranes that are associated with long flexible polymers (proteins or other macromolecules). We are interested in two physical systems consisting of i) two adjacent membranes with end-grafted (or adsorbed) polymers (system I), or ii) two membranes confining a polymer solution (system II). In addition to the pure interactions between membranes, the presence of polymers gives rise to new induced mediated interactions, which are repulsive, for system I, and attractive, for system II. In fact, repulsive induced interactions are caused by the excluded-volume forces between grafted polymers, while attractive ones, by entropy loss, due to free motion of polymers between membranes. The main goal is a quantitative study of the unbinding transition thermodynamics that is drastically affected by the associated polymers. For system I, the repulsive polymer-mediated force delays this transition that can happen at low temperature. To investigate the unbinding phenomenon, we first present an exact mathematical analysis of the total potential that is the sum of the primitive and induced potentials. This mathematical study enables us to classify the total interaction potentials, in terms of all parameters of the problem. Second, use is made of the standard variational method to calculate the first moments of the membrane separation. Special attention is paid to the determination of the unbinding temperature. In particular, we discuss its dependence on the extra parameters related to the associated polymers, which are the surface coverage and the polymer layer thickness on each membrane (for system I) or the polymer density and the gyration radius of coils (for system II). Third, we compute the disjoining pressure upon membrane separation. Finally, we emphasize that the presence of polymers may be a mechanism to delay or to accentuate the appearance of the unbinding transition between fluid membranes.

Uptake of uranium from seawater by amidoxime-based polymeric adsorbent marine testing

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

Tsouris, C.; Kim, J.; Oyola, Y.

2013-07-01

Amidoxime-based polymer adsorbents in the form of functionalized fibers were prepared at the Oak Ridge National Laboratory (ORNL) and screened in laboratory experiments, in terms of uranium uptake capacity, using spiked uranium solution and seawater samples. Batch laboratory experiments conducted with 5-gallon seawater tanks provided equilibrium information. Based on results from 5-gallon experiments, the best adsorbent was selected for field-testing of uranium adsorption from seawater. Flow-through column tests have been performed at different marine sites to investigate the uranium uptake rate and equilibrium capacity under diverse biogeochemistry. The maximum amount of uranium uptake from seawater tests at Sequim, WA, wasmore » 3.3 mg U/g adsorbent after eight weeks of contact of the adsorbent with seawater. This amount was three times higher than the maximum adsorption capacity achieved in this study by a leading adsorbent developed by the Japan Atomic Energy Agency (JAEA), which was 1.1 mg U/g adsorbent at equilibrium. The initial uranium uptake rate of the ORNL adsorbent was 2.6 times higher than that of the JAEA adsorbent under similar conditions. A mathematical model derived from the mass balance of uranium was employed to describe the data. (authors)« less

Preparation of mixed molecularly imprinted polymer magnetic nanoparticles and its application in separation of Chinese traditional medicine

NASA Astrophysics Data System (ADS)

Xie, Yihui; Ma, Yajuan; Bai, Wenting; Zhu, Xiaofang; Liu, Min; Huang, Liping

2017-08-01

A mixed imprinted polymer which can rapidly adsorb all flavonoids from raspberry extract was prepared and recycled. The hybrid molecular surface imprinted polymers were prepared by using quercetin as the template molecule and Fe3O4 magnetic nanospheres as the carrier. The molecular imprinting polymer was prepared by using the "initial template molecule, molecularly imprinted polymer, mixed template molecule, molecularly imprint ted polymers (MIPS)". The adsorption performance and durability of the hybrid molecularly imprinted polymers were investigated by using the fingerprints of the ethyl acetate fraction of raspberry as an index. The adsorption of flavonoids from raspberry extract, lindenoside, cis-lindenin, quercetin, kaempferol and other flavonoids was completely adsorbed by mixed molecular-imprinted polymer, and the other components were basically adsorbed. When Mix-IMPs were repeatedly used 10 times, the fingerprints showed that the content and content of flavonoids were basically the same. The experimental results show that Mix-IMPs has good adsorption performance, can be recycled and used for rapid enrichment of flavonoids in raspberry.

Tuning the structure of thermosensitive gold nanoparticle monolayers.

PubMed

Rezende, Camila A; Shan, Jun; Lee, Lay-Theng; Zalczer, Gilbert; Tenhu, Heikki

2009-07-23

Gold nanoparticles grafted with poly(N-isopropylacrylamide) (PNIPAM) are rendered amphiphilic and thermosensitive. When spread on the surface of water, they form stable Langmuir monolayers that exhibit surface plasmon resonance. Using Langmuir balance and contrast-matched neutron reflectivity, the detailed structural properties of these nanocomposite monolayers are revealed. At low surface coverage, the gold nanoparticles are anchored to the interface by an adsorbed PNIPAM layer that forms a thin and compact pancake structure. Upon isothermal compression (T=20 degrees C), the adsorbed layer thickens with partial desorption of polymer chains to form brush structures. Two distinct polymer conformations thus coexist: an adsorbed conformation that assures stability of the monolayer, and brush structures that dangle in the subphase. An increase in temperature to 30 degrees C results in contractions of both adsorbed and brush layers with a concomitant decrease in interparticle distance, indicating vertical as well as lateral contractions of the graft polymer layer. The reversibility of this thermal response is also shown by the contraction-expansion of the polymer layers in heating-cooling cycles. The structure of the monolayer can thus be tuned by compression and reversibly by temperature. These compression and thermally induced conformational changes are discussed in relation to optical properties.

Fabrication of Covalently Crosslinked and Amine-Reactive Microcapsules by Reactive Layer-by-Layer Assembly of Azlactone-Containing Polymer Multilayers on Sacrificial Microparticle Templates

PubMed Central

Saurer, Eric M.; Flessner, Ryan M.; Buck, Maren E.; Lynn, David M.

2011-01-01

We report on the fabrication of covalently crosslinked and amine-reactive hollow microcapsules using ‘reactive’ layer-by-layer assembly to deposit thin polymer films on sacrificial microparticle templates. Our approach is based on the alternating deposition of layers of a synthetic polyamine and a polymer containing reactive azlactone functionality. Multilayered films composed of branched poly(ethylene imine) (BPEI) and poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) were fabricated layer-by-layer on the surfaces of calcium carbonate and glass microparticle templates. After fabrication, these films contained residual azlactone functionality that was accessible for reaction with amine-containing molecules. Dissolution of the calcium carbonate or glass cores using aqueous ethylenediamine tetraacetic acid (EDTA) or hydrofluoric acid (HF), respectively, led to the formation of hollow polymer microcapsules. These microcapsules were robust enough to encapsulate and retain a model macromolecule (FITC-dextran) and were stable for at least 22 hours in high ionic strength environments, in low and high pH solutions, and in several common organic solvents. Significant differences in the behaviors of capsules fabricated on CaCO3 and glass cores were observed and characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Whereas capsules fabricated on CaCO3 templates collapsed upon drying, capsules fabricated on glass templates remained rigid and spherical. Characterization using EDS suggested that this latter behavior results, at least in part, from the presence of insoluble metal fluoride salts that are trapped or precipitate within the walls of capsules after etching of the glass cores using HF. Our results demonstrate that the assembly of BPEI/PVDMA films on sacrificial templates can be used to fabricate reactive microcapsules of potential use in a wide range of fields, including catalysis, drug and gene delivery, imaging, and

Fully additive manufacture of a polymer cantilever with an embedded functional layer

NASA Astrophysics Data System (ADS)

Kanazawa, Shusuke; Kusaka, Yasuyuki; Horii, Yoshinori; Ushijima, Hirobumi

2018-03-01

In this paper, we report on an efficient and unique printing-based process for fabricating a cantilever structure with an embedded functional layer. The process is used to form a micro suspended structure via the one-batch transfer of stacked layers from a dummy substrate. The mechanism of the transfer process is clearly explained by the order of adhesion strengths of all interfaces. As a demonstration, a strain gauge which consisted of a polymer cantilever with an embedded conductive wire was successfully fabricated. It is expected that the proposed process will widely contribute to the efficient manufacture of useful sensors and actuators.

Polymers at interfaces and in colloidal dispersions.

PubMed

Fleer, Gerard J

2010-09-15

This review is an extended version of the Overbeek lecture 2009, given at the occasion of the 23rd Conference of ECIS (European Colloid and Interface Society) in Antalya, where I received the fifth Overbeek Gold Medal awarded by ECIS. I first summarize the basics of numerical SF-SCF: the Scheutjens-Fleer version of Self-Consistent-Field theory for inhomogeneous systems, including polymer adsorption and depletion. The conformational statistics are taken from the (non-SCF) DiMarzio-Rubin lattice model for homopolymer adsorption, which enumerates the conformational details exactly by a discrete propagator for the endpoint distribution but does not account for polymer-solvent interaction and for the volume-filling constraint. SF-SCF corrects for this by adjusting the field such that it becomes self-consistent. The model can be generalized to more complex systems: polydispersity, brushes, random and block copolymers, polyelectrolytes, branching, surfactants, micelles, membranes, vesicles, wetting, etc. On a mean-field level the results are exact; the disadvantage is that only numerical data are obtained. Extensions to excluded-volume polymers are in progress. Analytical approximations for simple systems are based upon solving the Edwards diffusion equation. This equation is the continuum variant of the lattice propagator, but ignores the finite segment size (analogous to the Poisson-Boltzmann equation without a Stern layer). By using the discrete propagator for segments next to the surface as the boundary condition in the continuum model, the finite segment size can be introduced into the continuum description, like the ion size in the Stern-Poisson-Boltzmann model. In most cases a ground-state approximation is needed to find analytical solutions. In this way realistic analytical approximations for simple cases can be found, including depletion effects that occur in mixtures of colloids plus non-adsorbing polymers. In the final part of this review I discuss a

Polymers functionalized with bronsted acid groups

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

Van Humbeck, Jeffrey; Long, Jeffrey R.; McDonald, Thomas M.

Porous aromatic framework polymers functionalized with Bronsted acid moieties are prepared by polymerization of a three-dimensional organic aryl or heteroaryl monomer and its copolymerization with a second aryl or heteroaryl monomer functionalized with one or more Bronsted acid moiety. The polymers are characterized by a stable three-dimensional structure, which, in exemplary embodiments, includes interpenetrating subunits within one or more domain of the bulk polymer structure. The polymers are of use in methods of adsorbing ammonia and amines and in devices and systems configured for this purpose.

Comparing dissolved reactive phosphorus measured by DGT with ferrihydrite and titanium dioxide adsorbents: anionic interferences, adsorbent capacity and deployment time.

PubMed

Panther, Jared G; Teasdale, Peter R; Bennett, William W; Welsh, David T; Zhao, Huijun

2011-07-18

Two adsorbents (Metsorb and ferrihydrite) used in binding layers with the diffusive gradients in a thin film technique were evaluated for the measurement of dissolved reactive phosphorous (DRP) in synthetic and natural waters. Possible interferences were investigated with Cl(-) (up to 1.35 mol L(-1)) and SO(4)(2-) (up to 0.056 mol L(-1)) having no affect on either DGT binding layer, and HCO(3)(-) (up to 5.7 mmol L(-1)) having no effect on Metsorb-DGT, over 4 days. However, HCO(3)(-) interfered with the ferrihydrite-DGT measurement at concentrations typical of many natural waters (≥0.7 mmol L(-1)) after a deployment period of 1-2 days. The capacity of the Metsorb binding phase for DGT response was ∼37,000 ng P, whereas the capacities of a low-mass (17.8 mg of adsorbent per DGT sampler) and high-mass (29.2mg of adsorbent per DGT sampler) ferrihydrite binding phase were substantially lower (∼15,000 ng P and ∼25,000 ng P, low-mass and high-mass, respectively). Increasing the capacity of the ferrihydrite adsorbent allowed the ferrihydrite-DGT to be utilized for up to 3 days before interference by HCO(3)(-) was observed. Seawater deployments demonstrated that even high-capacity ferrihydrite-DGT devices underestimated the DRP concentration by 37%, whereas Metsorb-DGT measurements were accurate. The Metsorb-DGT is superior to the ferrihydrite-DGT for determining DRP over deployment times greater than 1 day and in waters with ≥0.7 mmol L(-1) HCO(3)(-). Based on the experience obtained from this detailed validation process, the authors propose a number of key requirements that need to be considered when developing new DGT binding layers, with testing the performance over longer deployment times being critical. Copyright © 2011 Elsevier B.V. All rights reserved.

The Effect of Layer Orientation on the Mechanical Properties and Microstructure of a Polymer

NASA Astrophysics Data System (ADS)

Vega, V.; Clements, J.; Lam, T.; Abad, A.; Fritz, B.; Ula, N.; Es-Said, O. S.

2011-08-01

Rapid Prototyping (RP) is a method used everywhere from the entertainment industry to healthcare. Layer orientation is an important aspect of the final product. The objective of this research was to evaluate the effect of layer orientation on the mechanical strength and toughness of a polymer. The polymer used was a combination of two materials, ZP 130 and ZB 58, fused together in the Z Corporation Spectrum Z510 Rapid Prototyping Machine. ZP 130 is a powder composed of vinyl polymer (2-20%), sulfate salt (0-5%), and plaster that contains <1% crystalline silica (50-95%). ZB 58 is a liquid composed of glycerol (1-10%), preservative (sorbic acid salt) (0-2%), surfactant (<1%), pigment (<1%), and water (85-95%). After removal from the machine the samples were sealed with Z bond 101 which is Beta-methoxyethyl cyanoacrylate (60-100%). The layer orientations studied were the crack arrestor, crack divider, and short transverse with various combinations of the three, for a total of seven orientations. The mechanical strength was evaluated using tensile testing and three-point bend testing. The toughness was evaluated by Izod impact testing. Five samples for tensile testing and three-point bend testing as well as 15 samples for the Izod impact test for each of the seven orientations were made. The total number of samples was 175. The crack arrestor orientation was the strongest main orientation for the tensile and three-point bend test. Weibull analysis was done on the Izod impact testing due to high variation in the results for the crack arrestor and short transverse directions. It was found that the layer orientation and surface roughness played a significant role in the penetration of the Z bond 101 coating and in the overall strength of the samples.

Recent advances in polymer solar cells: realization of high device performance by incorporating water/alcohol-soluble conjugated polymers as electrode buffer layer.

PubMed

He, Zhicai; Wu, Hongbin; Cao, Yong

2014-02-01

This Progress Report highlights recent advances in polymer solar cells with special attention focused on the recent rapid-growing progress in methods that use a thin layer of alcohol/water-soluble conjugated polymers as key component to obtain optimized device performance, but also discusses novel materials and device architectures made by major prestigious institutions in this field. We anticipate that due to drastic improvements in efficiency and easy utilization, this method opens up new opportunities for PSCs from various material systems to improve towards 10% efficiency, and many novel device structures will emerge as suitable architectures for developing the ideal roll-to-roll type processing of polymer-based solar cells. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular dynamics study of the adsorption of anionic surfactant in a nonionic polymer brush.

PubMed

Wang, Hua; Zhang, Heng; Yuan, Shiling; Liu, Chengbu; Xu, Zhen

2014-06-01

The adsorption of the anionic surfactant, sodium dodecylsulfate (SDS) in poly(ethylene oxide) (PEO) brush was studied by molecular dynamics simulations. Our simulations revealed that surfactant can adsorb in polymer brush as micellar aggregates and the polymer would reside at the hydrocarbon-water interface of SDS micelles. This association between surfactant and polymer was mainly driven by the hydrophobic interaction between the polymer and surfactant tails. In the simulation, with the increasing of surfactant concentration, a plateau value representing saturated adsorption was observed. The height of polymer brush was mainly affected by the adsorbed surfactant at low grafting density of polymer; however, it was primarily controlled by the grafting density at high grafting density. Our conclusions at the molecular level were in close agreement with experiment about the adsorption of surfactant in polymer brushes.

Carrier transport in flexible organic bistable devices of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) polymer layer.

PubMed

Son, Dong-Ick; Park, Dong-Hee; Choi, Won Kook; Cho, Sung-Hwan; Kim, Won-Tae; Kim, Tae Whan

2009-05-13

The bistable effects of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) (PMMA) polymer single layer by using flexible polyethylene terephthalate (PET) substrates were investigated. Transmission electron microscopy (TEM) images revealed that ZnO nanoparticles were formed inside the PMMA polymer layer. Current-voltage (I-V) measurement on the Al/ZnO nanoparticles embedded in an insulating PMMA polymer layer/ITO/PET structures at 300 K showed a nonvolatile electrical bistability behavior with a flat-band voltage shift due to the existence of the ZnO nanoparticles, indicative of trapping, storing, and emission of charges in the electronic states of the ZnO nanoparticles. The carrier transport mechanism of the bistable behavior for the fabricated organic bistable device (OBD) structures is described on the basis of the I-V results by analyzing the effect of space charge.

M4FT-15OR03100415 - Update on COF-based Adsorbent Survey

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

Mayes, Richard T.; Dai, Sheng

2015-02-01

This letter report provides an update on activities focused on generating nanoporous adsorbents involving covalent organic frameworks (COF) and zeolitic imidazolium frameworks (ZIF). The adsorbents have been generated and screened in a uranyl-spiked brine (6 ppm U) to understand uranyl-binding behavior. Porous organic polymers (POP) also qualify under this title and are similar to the COF PPN-6 that is discussed herein. Seven COF/POP and one 1 ZIF were synthesized and screened for uranyl adsorption. Seawater screening is on-going via batch testing while flow screening systems are being developed at PNNL.

Highly reliable top-gated thin-film transistor memory with semiconducting, tunneling, charge-trapping, and blocking layers all of flexible polymers.

PubMed

Wang, Wei; Hwang, Sun Kak; Kim, Kang Lib; Lee, Ju Han; Cho, Suk Man; Park, Cheolmin

2015-05-27

The core components of a floating-gate organic thin-film transistor nonvolatile memory (OTFT-NVM) include the semiconducting channel layer, tunneling layer, floating-gate layer, and blocking layer, besides three terminal electrodes. In this study, we demonstrated OTFT-NVMs with all four constituent layers made of polymers based on consecutive spin-coating. Ambipolar charges injected and trapped in a polymer electret charge-controlling layer upon gate program and erase field successfully allowed for reliable bistable channel current levels at zero gate voltage. We have observed that the memory performance, in particular the reliability of a device, significantly depends upon the thickness of both blocking and tunneling layers, and with an optimized layer thickness and materials selection, our device exhibits a memory window of 15.4 V, on/off current ratio of 2 × 10(4), read and write endurance cycles over 100, and time-dependent data retention of 10(8) s, even when fabricated on a mechanically flexible plastic substrate.

Scaling of Polymer Degradation Rate within a High-Reynolds-Number Turbulent Boundary Layer

NASA Astrophysics Data System (ADS)

Elbing, Brian; Solomon, Michael; Perlin, Marc; Dowling, David; Ceccio, Steven

2009-11-01

An experiment conducted at the U.S. Navy's Large Cavitation Channel on a 12.9 m long flat-plate test model produced the first quantitative measurements of polymer molecular weight within a turbulent boundary layer. Testing was conducted at speeds to 20 m/s and downstream distance based Reynolds numbers to 220 million. These results showed that the rate of polymer degradation by scission of the polymer chains increases with increased speed, downstream distance and surface roughness. With the surface fully rough at 20 m/s there was no measureable level of drag reduction at the first measurement location (0.56 m downstream of injection). These results are scaled with the assumption that the rate of degradation is dependent on the polymer residence time in the flow and the local shear rate. A successful collapse of the data within the measurement uncertainty was achieved over a range of flow speed (6.6 to 20 m/s), surface roughness (smooth and fully rough) and downstream distance from injection (0.56 to 9.28 m).

Comparison of precursor infiltration into polymer thin films via atomic layer deposition and sequential vapor infiltration using in-situ quartz crystal microgravimetry

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

Padbury, Richard P.; Jur, Jesse S., E-mail: jsjur@ncsu.edu

Previous research exploring inorganic materials nucleation behavior on polymers via atomic layer deposition indicates the formation of hybrid organic–inorganic materials that form within the subsurface of the polymer. This has inspired adaptations to the process, such as sequential vapor infiltration, which enhances the diffusion of organometallic precursors into the subsurface of the polymer to promote the formation of a hybrid organic–inorganic coating. This work highlights the fundamental difference in mass uptake behavior between atomic layer deposition and sequential vapor infiltration using in-situ methods. In particular, in-situ quartz crystal microgravimetry is used to compare the mass uptake behavior of trimethyl aluminummore » in poly(butylene terephthalate) and polyamide-6 polymer thin films. The importance of trimethyl aluminum diffusion into the polymer subsurface and the subsequent chemical reactions with polymer functional groups are discussed.« less

Boundary layers of aqueous surfactant and block copolymer solutions against hydrophobic and hydrophilic solid surfaces

NASA Astrophysics Data System (ADS)

Steitz, Roland; Schemmel, Sebastian; Shi, Hongwei; Findenegg, Gerhard H.

2005-03-01

The boundary layer of aqueous surfactants and amphiphilic triblock copolymers against flat solid surfaces of different degrees of hydrophobicity was investigated by neutron reflectometry (NR), grazing incidence small angle neutron scattering (GISANS) and atomic force microscopy (AFM). Solid substrates of different hydrophobicities were prepared by appropriate surface treatment or by coating silicon wafers with polymer films of different chemical natures. For substrates coated with thin films (20-30 nm) of deuterated poly(styrene) (water contact angle \\theta_{\\mathrm {w}} \\approx 90^\\circ ), neutron reflectivity measurements on the polymer/water interface revealed a water depleted liquid boundary layer of 2-3 nm thickness and a density about 90% of the bulk water density. No pronounced depletion layer was found at the interface of water against a less hydrophobic polyelectrolyte coating (\\theta_{\\mathrm {w}} \\approx 63^\\circ ). It is believed that the observed depletion layer at the hydrophobic polymer/water interface is a precursor of the nanobubbles which have been observed by AFM at this interface. Decoration of the polymer coatings by adsorbed layers of nonionic CmEn surfactants improves their wettability by the aqueous phase at surfactant concentrations well below the critical micellar concentration (CMC) of the surfactant. Here, GISANS experiments conducted on the system SiO2/C8E4/D2O reveal that there is no preferred lateral organization of the C8E4 adsorption layers. For amphiphilic triblock copolymers (PEO-PPO-PEO) it is found that under equilibrium conditions they form solvent-swollen brushes both at the air/water and the solid/water interface. In the latter case, the brushes transform to uniform, dense layers after extensive rinsing with water and subsequent solvent evaporation. The primary adsorption layers maintain properties of the precursor brushes. In particular, their thickness scales with the number of ethylene oxide units (EO) of the block

Effect of tethering on the surface dynamics of a thin polymer melt layer

DOE PAGES

Uğur, Gökçe; Akgun, Bulent; Jiang, Zhang; ...

2016-05-13

The surface height fluctuations of a layer of low molecular weight (2.2k) untethered perdeuterated polystyrene (dPS) chains adjacent to a densely grafted polystyrene brush are slowed dramatically. Due to the interpenetration of the brush with the layer of “untethered chains” a hydrodynamic continuum theory can only describe the fluctuations when the effective thickness of the film is taken to be that which remains above the swollen brush. Furthermore, the portion of the film of initially untethered chains that interpenetrates with the brush becomes so viscous as to effectively play the role of a rigid substrate. They provide a route formore » tailoring polymer layer surface properties such as wetting, adhesion and friction, since these hybrid samples contain a covalently tethered layer at the bottom, does not readily dewet, and are more robust than thin layers of untethered short chains on rigid substrates.« less

Effect of tethering on the surface dynamics of a thin polymer melt layer

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

Uğur, Gökçe; Akgun, Bulent; Jiang, Zhang

The surface height fluctuations of a layer of low molecular weight (2.2k) untethered perdeuterated polystyrene (dPS) chains adjacent to a densely grafted polystyrene brush are slowed dramatically. Due to the interpenetration of the brush with the layer of “untethered chains” a hydrodynamic continuum theory can only describe the fluctuations when the effective thickness of the film is taken to be that which remains above the swollen brush. Furthermore, the portion of the film of initially untethered chains that interpenetrates with the brush becomes so viscous as to effectively play the role of a rigid substrate. They provide a route formore » tailoring polymer layer surface properties such as wetting, adhesion and friction, since these hybrid samples contain a covalently tethered layer at the bottom, does not readily dewet, and are more robust than thin layers of untethered short chains on rigid substrates.« less

Inverted polymer fullerene solar cells exceeding 10% efficiency with poly(2-ethyl-2-oxazoline) nanodots on electron-collecting buffer layers

PubMed Central

Nam, Sungho; Seo, Jooyeok; Woo, Sungho; Kim, Wook Hyun; Kim, Hwajeong; Bradley, Donal D. C.; Kim, Youngkyoo

2015-01-01

Polymer solar cells have been spotlighted due to their potential for low-cost manufacturing but their efficiency is still less than required for commercial application as lightweight/flexible modules. Forming a dipole layer at the electron-collecting interface has been suggested as one of the more attractive approaches for efficiency enhancement. However, only a few dipole layer material types have been reported so far, including only one non-ionic (charge neutral) polymer. Here we show that a further neutral polymer, namely poly(2-ethyl-2-oxazoline) (PEOz) can be successfully used as a dipole layer. Inclusion of a PEOz layer, in particular with a nanodot morphology, increases the effective work function at the electron-collecting interface within inverted solar cells and thermal annealing of PEOz layer leads to a state-of-the-art 10.74% efficiency for single-stack bulk heterojunction blend structures comprising poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] as donor and [6,6]-phenyl-C71-butyric acid methyl ester as acceptor. PMID:26656447

Comparative evaluation of concrete sealers and multiple layer polymer concrete overlays. Interim report no. 1.

DOT National Transportation Integrated Search

1987-01-01

The report presents comparisons of initial evaluations of several concrete sealers and multiple layer polymer concrete overlays. The sealers evaluated included a solvent-dlspersed epoxy, a water-dlspersed epoxy, a silane, and a high molecular weight ...

Adsorption of modified dextrins on molybdenite: AFM imaging, contact angle, and flotation studies.

PubMed

Beaussart, Audrey; Parkinson, Luke; Mierczynska-Vasilev, Agnieszka; Beattie, David A

2012-02-15

The adsorption of three dextrins (a regular wheat dextrin, Dextrin TY, carboxymethyl (CM) Dextrin, and hydroxypropyl (HP) Dextrin) on molybdenite has been investigated using adsorption isotherms, tapping mode atomic force microscopy (TMAFM), contact angle measurements, and dynamic bubble-surface collisions. In addition, the effect of the polymers on the flotation recovery of molybdenite has been determined. The isotherms revealed the importance of molecular weight in determining the adsorbed amounts of the polymers on molybdenite at plateau coverage. TMAFM revealed the morphology of the three polymers, which consisted of randomly dispersed domains with a higher area fraction of surface coverage for the substituted dextrins. The contact angle of polymer-treated molybdenite indicated that polymer layer coverage and hydration influenced the mineral surface hydrophobicity. Bubble-surface collisions indicated that the polymers affected thin film rupture and dewetting rate differently, correlating with differences in the adsorbed layer morphology. Direct correlations were found between the surface coverage of the adsorbed layers, their impact on thin film rupture time, and their impact on flotation recovery, highlighting the paramount role of the polymer morphology in the bubble/particle attachment process and subsequent flotation. Copyright © 2011 Elsevier Inc. All rights reserved.

Influence of Current Velocity on Uranium Adsorption from Seawater Using an Amidoxime-based Polymer Fiber Adsorbent

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

Ladshaw, Austin; Kuo, Li-Jung; Strivens, Jonathan

2017-02-08

Passive adsorption using amidoxime-based polymeric adsorbents is being developed for uranium recovery from seawater. The local oceanic current velocity where the adsorbent is deployed is a key variable in determining locations that will maximize uranium adsorption rates. Two independent experimental approaches using flow-through columns and recirculating flumes were used to assess the influence of linear velocity on uranium uptake kinetics by the adsorbent. Little to no difference was observed in the uranium adsorption rate vs. linear velocity for seawater exposure in flow-through columns. In contrast, adsorption results from seawater exposure in a recirculating flume showed a nearly linear trend withmore » current velocity. The difference in adsorbent performance between columns and flume can be attributed to (i) flow resistance provided by the adsorbent braid in the flume and (ii) enhancement in braid movement (fluttering) with increasing linear velocity.« less

Influence of Current Velocity on Uranium Adsorption from Seawater Using an Amidoxime-Based Polymer Fiber Adsorbent

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

Ladshaw, Austin; Kuo, Li-Jung; Strivens, Jonathan

2017-02-17

Passive adsorption using amidoxime-based polymeric adsorbents is being developed for uranium recovery from seawater. The local oceanic current velocity where the adsorbent is deployed is a key variable in determining locations that will maximize uranium adsorption rates. Two independent experimental approaches using flow-through columns and recirculating flumes were used to assess the influence of linear velocity on uranium uptake kinetics by the adsorbent. Little to no difference was observed in the uranium adsorption rate vs. linear velocity for seawater exposure in flow-through columns. In contrast, adsorption results from seawater exposure in a recirculating flume showed a nearly linear trend withmore » current velocity. The difference in adsorbent performance between columns and flume can be attributed to (i) flow resistance provided by the adsorbent braid in the flume and (ii) enhancement in braid movement (fluttering) with increasing linear velocity.« less

High performance polymer solar cells with as-prepared zirconium acetylacetonate film as cathode buffer layer

PubMed Central

Tan, Zhan'ao; Li, Shusheng; Wang, Fuzhi; Qian, Deping; Lin, Jun; Hou, Jianhui; Li, Yongfang

2014-01-01

Low-work-function active metals are commonly used as cathode in polymer solar cells (PSCs), but sensitivity of the active metals towards moisture and oxygen results in poor stability of the devices. Therefore, solution-proceessable and stable cathode buffer layer is of great importance for the application of PSCs. Here we demonstrate high performance PSCs by employing as-prepared zirconium acetylacetonate (a-ZrAcac) film spin-cast from its ethanol solution as cathode buffer layer. The PSCs based on a low bandgap polymer PBDTBDD as donor and PC60BM as acceptor with a-ZrAcac/Al cathode demonstrated an average power conversion efficiency (PCE) of 8.75% which is significantly improved than that of the devices with traditional Ca/Al cathode. The improved photovoltaic performance is benefitted from the decreased series resistance and enhanced light harvest of the PSCs with the a-ZrAcac/Al cathode. The results indicate that a-ZrAcac is a promising high performance cathode buffer layer for fabricating large area flexible PSCs. PMID:24732976

Method of making molecularly doped composite polymer material

DOEpatents

Affinito, John D [Tucson, AZ; Martin, Peter M [Kennewick, WA; Graff, Gordon L [West Richland, WA; Burrows, Paul E [Kennewick, WA; Gross, Mark E. , Sapochak, Linda S.

2005-06-21

A method of making a composite polymer of a molecularly doped polymer. The method includes mixing a liquid polymer precursor with molecular dopant forming a molecularly doped polymer precursor mixture. The molecularly doped polymer precursor mixture is flash evaporated forming a composite vapor. The composite vapor is cryocondensed on a cool substrate forming a composite molecularly doped polymer precursor layer, and the cryocondensed composite molecularly doped polymer precursor layer is cross linked thereby forming a layer of the composite polymer layer of the molecularly doped polymer.

Using quantitative magnetic resonance methods to understand better the gel-layer formation on polymer-matrix tablets.

PubMed

Mikac, Urša; Kristl, Julijana; Baumgartner, Saša

2011-05-01

Magnetic resonance imaging is a powerful, non-invasive technique that can help improve our understanding of the hydrogel layer formed on swellable, polymer-matrix tablets, as well as the layer's properties and its influence on drug release. In this paper, the authors review the NMR and MRI investigations of hydrophilic, swellable polymers published since 1994. The review covers NMR studies on the properties of water and drugs within hydrated polymers. In addition, MRI studies using techniques for determining the different moving-front positions within the swollen tablets, the polymer concentration profiles across them, the influence of the incorporated drug, and so on, are presented. Some complementary methods are also briefly presented and discussed. Using MRI, the formation of a hydrogel along with simultaneous determination of the drug's position within it can be observed non-invasively. However, the MRI parameters can influence the signal's intensity and therefore they need to be considered carefully in order to prevent any misinterpretation of the results. MRI makes possible an in situ investigation of swollen-matrix tablets and provides valuable information that can lead, when combined with other techniques, to a better understanding of polymeric systems and a more effective development of optimal dosage forms.

Electrodeposition of Polymer Nanostructures using Three Diffuse Double Layers: Polymerization beyond the Liquid/Liquid Interfaces

NASA Astrophysics Data System (ADS)

Divya, Velpula; Sangaranarayanan, M. V.

2018-04-01

Nanostructured conducting polymers have received immense attention during the past few decades on account of their phenomenal usefulness in diverse contexts, while the interface between two immiscible liquids is of great interest in chemical and biological applications. Here we propose a novel Electrode(solid)/Electrolyte(aqueous)/Electrolyte(organic) Interfacial assembly for the synthesis of polymeric nanostructures using a novel concept of three diffuse double layers. There exist remarkable differences between the morphologies of the polymers synthesized using the conventional electrode/electrolyte method and that of the new approach. In contrast to the commonly employed electrodeposition at liquid/liquid interfaces, these polymer modified electrodes can be directly employed in diverse applications such as sensors, supercapacitors etc.

Metal aminocarboxylate coordination polymers with chain and layered structures.

PubMed

Dan, Meenakshi; Rao, C N R

2005-11-18

The synthesis and structures of metal aminocarboxylates prepared in acidic, neutral, or alkaline media have been explored with the purpose of isolating coordination polymers with linear chain and two-dimensional layered structures. Metal glycinates of the formulae [CoCl2(H2O)2(CO2CH2NH3)] (I), [MnCl2(CO2CH2NH3)2] (II), and [Cd3Cl6(CO2CH2NH3)4] (III) with one-dimensional chain structures have been obtained by the reaction of the metal salts with glycine in an acidic medium under hydro/solvothermal conditions. These chain compounds contain glycine in the zwitterionic form. 4-Aminobutyric acid transforms to a cyclic amide under such reaction conditions, and the amide forms a chain compound of the formula [CdBr2(C4H7NO)2] (IV). Glycine in the zwitterionic form also forms a two-dimensional layered compound of the formula [Mn(H2O)2(CO2CH2NH3)2]Br2 (V). 6-Aminocaproic acid under alkaline conditions forms layered compounds with metals at room temperature, the metal being coordinated both by the amino nitrogen and the carboxyl oxygen atoms. Of the two layered compounds [Cd{CO2(CH2)5NH2}2]2 H2O (VI) and [Cu{CO2(CH2)5NH2}2]2 H2O (VII), the latter has voids in which water molecules reside.

Shear-induced surface alignment of polymer dispersed liquid crystal microdroplets on the boundary layer

NASA Technical Reports Server (NTRS)

Parmar, D. S.; Singh, J. J.

1993-01-01

Polymer dispersed liquid crystal thin films have been deposited on a glass substrate, utilizing the processes of polymerization and solvent evaporation induced phase separation. Liquid crystal microdroplets trapped on the upper surface of the thin film respond to the shear stress due to air or gas flow on the surface layer. Response to an applied step shear stress input on the surface layer has been measured by measuring the time response of the transmitted light intensity. Initial results on the measurements of the light transmission as a function of the air flow differential pressure indicate that these systems offer features suitable for boundary layer and gas flow sensors.

Adsorption of β-sitosterol on molecularly imprinted polymer

NASA Astrophysics Data System (ADS)

Soekamto, N. H.; Fauziah, St.; Taba, P.; Amran, M. B.

2017-04-01

Molecularly Imprinted Polymer (MIP) has been synthesized using methacrylate acid (MAA) as a monomer with hydroxyl and carbonyl functional groups that can react with ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent, and β-sitosterol as a template molecule. After the template was removed from the polymer, MIP_TFMAA was obtained. The MIP was used to adsorb β-sitosterol. The amount of β-sitosterol in solution after the adsorption was determined by HPLC. The results showed that the MIP was able to adsorb well the β-sitosterol at a pH 7 and the contact time of 90 min. The kinetic adsorption data obtained for β-sitosterol followed the pseudo-second-order model and consistent with the model of Feundlich isothermal with the adsorption capacity of 1.05 mg/g. The MIP was selective on β-sitosterol because it was able to adsorb β-sitosterol better than cholesterol.

Establishment of a biomimetic device based on tri-layer polymer actuators--propulsion fins.

PubMed

Alici, Gursel; Spinks, Geoffrey; Huynh, Nam N; Sarmadi, Laleh; Minato, Rick

2007-06-01

We propose to use bending type tri-layer polymer actuators as propulsion fins for a biomimetic device consisting of a rigid body, like a box fish having a carapace, and paired fins running through the rigid body, like a fish having pectoral fins. The fins or polymer bending actuators can be considered as individually controlled flexible membranes. Each fin is activated with sinusoidal inputs such that there is a phase lag between the movements of successive fins to create enough thrust force for propulsion. Eight fins with 0.125 aspect ratio have been used along both sides of the rigid body to move the device in the direction perpendicular to the longitudinal axis of the body. The designed device with the paired fins was successfully tested, moving in an organic solution consisting of solvent, propylene carbonate (PC), and electrolyte. The design procedure outlined in this study is offered as a guide to making functional devices based on polymer actuators and sensors.

Organic-Inorganic Hybrid Polymers as Adsorbents for Removal of Heavy Metal Ions from Solutions: A Review

PubMed Central

Samiey, Babak; Cheng, Chil-Hung; Wu, Jiangning

2014-01-01

Over the past decades, organic-inorganic hybrid polymers have been applied in different fields, including the adsorption of pollutants from wastewater and solid-state separations. In this review, firstly, these compounds are classified. These compounds are prepared by sol-gel method, self-assembly process (mesopores), assembling of nanobuilding blocks (e.g., layered or core-shell compounds) and as interpenetrating networks and hierarchically structures. Lastly, the adsorption characteristics of heavy metals of these materials, including different kinds of functional groups, selectivity of them for heavy metals, effect of pH and synthesis conditions on adsorption capacity, are studied. PMID:28788483

Amphiphilic invertible polymers: Self-assembly into functional materials driven by environment polarity

NASA Astrophysics Data System (ADS)

Hevus, Ivan

nanoparticles strongly differing in polarity. AIP modified silica nanoparticles are able to adsolubilize molecules of poorly water-soluble 2-naphthol into the adsorbed polymer layer. The adsolubilization ability of adsorbed invertible macromolecules makes AIP-modified silica nanoparticles potentially useful in wastewater treatment or biomedical applications. Finally, the invertible micellar assemblies were used as functional additives to improve the appearance of electrospun silicon wires based on cyclohexasilane, a liquid silicon precursor. AIP-assisted fabrication of silicon wires from the liquid cyclohexasilane precursor has potential as a scalable method for developing electronic functional materials.

Water/alcohol soluble conjugated polymers as highly efficient electron transporting/injection layer in optoelectronic devices.

PubMed

Huang, Fei; Wu, Hongbin; Cao, Yong

2010-07-01

Water/alcohol soluble conjugated polymers (WSCPs) can be processed from water or other polar solvents, which offer good opportunities to avoid interfacial mixing upon fabrication of multilayer polymer optoelectronic devices by solution processing, and can dramatically improve charge injection from high work-function metal cathode resulting in greatly enhancement of the device performance. In this critical review, the authors provide a brief review of recent developments in this field, including the materials design, functional principles, and their unique applications as interface modification layer in solution-processable multilayer optoelectronic devices (135 references).

Presence of electrostatically adsorbed polysaccharides improves spray drying of liposomes.

PubMed

Karadag, Ayse; Özçelik, Beraat; Sramek, Martin; Gibis, Monika; Kohlus, Reinhard; Weiss, Jochen

2013-02-01

Spray drying of liposomes with conventional wall materials such as maltodextrins often yields nonfunctional powders, that is, liposomes break down during drying and rehydration. Electrostatically coating the surface of liposomes with a charged polymer prior to spray drying may help solve this problem. Anionic lecithin liposomes (approximately 400 nm) were coated with lower (approximately 500 kDa, LMW-C) or higher (approximately 900 kDa, HMW-C) molecular weight cationic chitosan using the layer-by-layer depositing method. Low (DE20, LMW-MD) or high molecular weight (DE2, HMW-MD) maltodextrin was added as wall material to facilitate spray drying. If surfaces of liposomes (1%) were completely covered with chitosan (0.4%), no bridging or depletion flocculation would occur, and mean particle diameters would be approximately 500 nm. If maltodextrins (20%) were added to uncoated liposomes, extensive liposomal breakdown would occur making the system unsuitable for spray drying. No such aggregation or breakdown was observed when maltodextrin was added to chitosan-coated liposomes. Size changed little or even decreased slightly depending on the molecular weight of maltodextrin added. Scanning electron microscopy images of powders containing chitosan-coated liposomes revealed that their morphologies depended on the type of maltodextrin added. Powders prepared with LMW-MD contained mostly spherical particles while HMW-MD powders contained particles with concavities and dents. Upon redispersion, coated liposomes yielded back dispersions with particle size distributions similar to the original ones, except for LMW-C coated samples that had been spray dried with HMW-MD which yielded aggregates (approximately 30 μm). Results show that coating of liposomes with an absorbing polymer allows them to be spray dried with conventional maltodextrin wall materials. Liposomes have attracted considerable attention in the food and agricultural, biomedical industries for the delivery of

From carbon nanotubes and silicate layers to graphene platelets for polymer nanocomposites.

PubMed

Zaman, Izzuddin; Kuan, Hsu-Chiang; Dai, Jingfei; Kawashima, Nobuyuki; Michelmore, Andrew; Sovi, Alex; Dong, Songyi; Luong, Lee; Ma, Jun

2012-08-07

In spite of extensive studies conducted on carbon nanotubes and silicate layers for their polymer-based nanocomposites, the rise of graphene now provides a more promising candidate due to its exceptionally high mechanical performance and electrical and thermal conductivities. The present study developed a facile approach to fabricate epoxy-graphene nanocomposites by thermally expanding a commercial product followed by ultrasonication and solution-compounding with epoxy, and investigated their morphologies, mechanical properties, electrical conductivity and thermal mechanical behaviour. Graphene platelets (GnPs) of 3.57 ± 0.50 nm in thickness were created after the expanded product was dispersed in tetrahydrofuran using 60 min ultrasonication. Since epoxy resins cured by various hardeners are widely used in industries, we chose two common hardeners: polyoxypropylene (J230) and 4,4'-diaminodiphenylsulfone (DDS). DDS-cured nanocomposites showed a better dispersion and exfoliation of GnPs, a higher improvement (573%) in fracture energy release rate and a lower percolation threshold (0.612 vol%) for electrical conductivity, because DDS contains benzene groups which create π-π interactions with GnPs promoting a higher degree of dispersion and exfoliation of GnPs during curing. This research pointed out a potential trend where GnPs would replace carbon nanotubes and silicate layers for many applications of polymer nanocomposites.

Solution Adsorption Formation of a π-Conjugated Polymer/Graphene Composite for High-Performance Field-Effect Transistors.

PubMed

Liu, Yun; Hao, Wei; Yao, Huiying; Li, Shuzhou; Wu, Yuchen; Zhu, Jia; Jiang, Lei

2018-01-01

Semiconducting polymers with π-conjugated electronic structures have potential application in the large-scale printable fabrication of high-performance electronic and optoelectronic devices. However, owing to their poor environmental stability and high-cost synthesis, polymer semiconductors possess limited device implementation. Here, an approach for constructing a π-conjugated polymer/graphene composite material to circumvent these limitations is provided, and then this material is patterned into 1D arrays. Driven by the π-π interaction, several-layer polymers can be adsorbed onto the graphene planes. The low consumption of the high-cost semiconductor polymers and the mass production of graphene contribute to the low-cost fabrication of the π-conjugated polymer/graphene composite materials. Based on the π-conjugated system, a reduced π-π stacking distance between graphene and the polymer can be achieved, yielding enhanced charge-transport properties. Owing to the incorporation of graphene, the composite material shows improved thermal stability. More generally, it is believed that the construction of the π-conjugated composite shows clear possibility of integrating organic molecules and 2D materials into microstructure arrays for property-by-design fabrication of functional devices with large area, low cost, and high efficiency. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physicochemical controls on adsorbed water film thickness in unsaturated geological media

NASA Astrophysics Data System (ADS)

Tokunaga, Tetsu K.

2011-08-01

Adsorbed water films commonly coat mineral surfaces in unsaturated soils and rocks, reducing flow and transport rates. Therefore, it is important to understand how adsorbed film thickness depends on matric potential, surface chemistry, and solution chemistry. Here the problem of adsorbed water film thickness is examined by combining capillary scaling with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Novel aspects of this analysis include determining capillary influences on film thicknesses and incorporating solution chemistry-dependent electrostatic potential at air-water interfaces. Capillary analysis of monodisperse packings of spherical grains provided estimated ranges of matric potentials where adsorbed films are stable and showed that pendular rings within drained porous media retain most of the "residual" water except under very low matric potentials. Within drained pores, capillary contributions to thinning of adsorbed films on spherical grains are shown to be small, such that DLVO calculations for flat surfaces are suitable approximations. Hamaker constants of common soil minerals were obtained to determine ranges of the dispersion component to matric potential-dependent film thickness. The pressure component associated with electrical double-layer forces was estimated using the compression and linear superposition approximations. The pH-dependent electrical double-layer pressure component is the dominant contribution to film thicknesses at intermediate values of matric potential, especially in lower ionic strength solutions (<10 mol m-3) on surfaces with higher-magnitude electrostatic potentials (more negative than ≈-50 mV). Adsorbed water films are predicted to usually range in thickness from ≈1 to 20 nm in drained pores and fractures of unsaturated environments.

Effects of topology on the adsorption of singly tethered ring polymers to attractive surfaces.

PubMed

Li, Bing; Sun, Zhao-Yan; An, Li-Jia

2015-07-14

We investigate the effect of topology on the equilibrium behavior of singly tethered ring polymers adsorbed on an attractive surface. We focus on the change of square radius of gyration Rg(2), the perpendicular component Rg⊥(2) and the parallel component Rg‖(2) to the adsorbing surface, the mean contacting number of monomers with the surface , and the monomer distribution along z-direction during transition from desorption to adsorption. We find that both of the critical point of adsorption εc and the crossover exponent ϕ depend on the knot type when the chain length of ring ranges from 48 to 400. The behaviors of Rg(2), Rg⊥(2), and Rg‖(2) are found to be dependent on the topology and the monomer-surface attractive strength. At weak adsorption, the polymer chains with more complex topology are more adsorbable than those with simple topology. However, at strong adsorption, the polymer chains with complex topology are less adsorbable. By analyzing the distribution of monomer along z-direction, we give a possible mechanism for the effect of topology on the adsorption behavior.

Self-Assembled CNT-Polymer Hybrids in Single-Walled Carbon Nanotubes Dispersed Aqueous Triblock Copolymer Solutions

NASA Astrophysics Data System (ADS)

Vijayaraghavan, D.; Manjunatha, A. S.; Poojitha, C. G.

2018-04-01

We have carried out scanning electron microscopy (SEM), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), electrical conductivity, and 1H NMR studies as a function of temperature on single-walled carbon nanotubes (SWCNTs) dispersed aqueous triblock copolymer (P123) solutions. The single-walled carbon nanotubes in this system aggregate to form bundles, and the bundles aggregate to form net-like structures. Depending on the temperature and phases of the polymer, this system exhibits three different self-assembled CNT-polymer hybrids. We find CNT-unimer hybrid at low temperatures, CNT-micelle hybrid at intermediate temperatures wherein the polymer micelles are adsorbed in the pores of the CNT nets, and another type of CNT-micelle hybrid at high temperatures wherein the polymer micelles are adsorbed on the surface of the CNT bundles. Our DSC thermogram showed two peaks related to these structural changes in the CNT-polymer hybrids. Temperature dependence of the 1H NMR chemical shifts of the molecular groups of the polymer and the AC electrical conductivity of the composite also showed discontinuous changes at the temperatures at which the CNT-polymer hybrid's structural changes are seen. Interestingly, for a higher CNT concentration (0.5 wt.%) in the system, the aggregated polymer micelles adsorbed on the CNTs exhibit cone-like and cube-like morphologies at the intermediate and at high temperatures respectively.

Quantification of the Influence of Protein-Protein Interactions on Adsorbed Protein Structure and Bioactivity

PubMed Central

Wei, Yang; Thyparambil, Aby A.; Latour, Robert A.

2013-01-01

While protein-surface interactions have been widely studied, relatively little is understood at this time regarding how protein-surface interaction effects are influenced by protein-protein interactions and how these effects combine with the internal stability of a protein to influence its adsorbed-state structure and bioactivity. The objectives of this study were to develop a method to study these combined effects under widely varying protein-protein interaction conditions using hen egg-white lysozyme (HEWL) adsorbed on silica glass, poly(methyl methacrylate), and polyethylene as our model systems. In order to vary protein-protein interaction effects over a wide range, HEWL was first adsorbed to each surface type under widely varying protein solution concentrations for 2 h to saturate the surface, followed by immersion in pure buffer solution for 15 h to equilibrate the adsorbed protein layers in the absence of additionally adsorbing protein. Periodic measurements were made at selected time points of the areal density of the adsorbed protein layer as an indicator of the level of protein-protein interaction effects within the layer, and these values were then correlated with measurements of the adsorbed protein’s secondary structure and bioactivity. The results from these studies indicate that protein-protein interaction effects help stabilize the structure of HEWL adsorbed on silica glass, have little influence on the structural behavior of HEWL on HDPE, and actually serve to destabilize HEWL’s structure on PMMA. The bioactivity of HEWL on silica glass and HDPE was found to decrease in direct proportion to the degree of adsorption-induce protein unfolding. A direct correlation between bioactivity and the conformational state of adsorbed HEWL was less apparent on PMMA, thus suggesting that other factors influenced HEWL’s bioactivity on this surface, such as the accessibility of HEWL’s bioactive site being blocked by neighboring proteins or the surface

Driving mechanisms of ionic polymer actuators having electric double layer capacitor structures.

PubMed

Imaizumi, Satoru; Kato, Yuichi; Kokubo, Hisashi; Watanabe, Masayoshi

2012-04-26

Two solid polymer electrolytes, composed of a polyether-segmented polyurethaneurea (PEUU) and either a lithium salt (lithium bis(trifluoromethanesulfonyl)amide: Li[NTf2]) or a nonvolatile ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide: [C2mim][NTf2]), were prepared in order to utilize them as ionic polymer actuators. These salts were preferentially dissolved in the polyether phases. The ionic transport mechanism of the polyethers was discussed in terms of the diffusion coefficients and ionic transference numbers of the incorporated ions, which were estimated by means of pulsed-field gradient spin-echo (PGSE) NMR. There was a distinct difference in the ionic transport properties of each polymer electrolyte owing to the difference in the magnitude of interactions between the cations and the polyether. The anionic diffusion coefficient was much faster than that of the cation in the polyether/Li[NTf2] electrolyte, whereas the cation diffused faster than the anion in the polyether/[C2mim][NTf2] electrolyte. Ionic polymer actuators, which have a solid-state electric-double-layer-capacitor (EDLC) structure, were prepared using these polymer electrolyte membranes and ubiquitous carbon materials such as activated carbon and acetylene black. On the basis of the difference in the motional direction of each actuator against applied voltages, a simple model of the actuation mechanisms was proposed by taking the difference in ionic transport properties into consideration. This model discriminated the behavior of the actuators in terms of the products of transference numbers and ionic volumes. The experimentally observed behavior of the actuators was successfully explained by this model.

Suppression of single-wall carbon nanotube redox reaction by adsorbed proteins

NASA Astrophysics Data System (ADS)

Nakayama, Tomohito; Tanaka, Takeshi; Shiraki, Kentaro; Hase, Muneaki; Hirano, Atsushi

2018-07-01

Single-wall carbon nanotubes (SWCNTs) are widely used in biological applications. In biological systems, proteins readily adsorb to SWCNTs. However, little is known about the effects of proteins on the physicochemical properties of SWCNTs, such as their redox reaction. In this study, we measured the absorption and Raman spectra of SWCNTs dispersed in the presence of proteins such as bovine serum albumin to observe the redox reaction of the protein-adsorbed SWCNTs. The adsorbed proteins suppressed the redox reaction by forming thick and dense layers around the SWCNTs. Our findings are useful for understanding the behaviors of SWCNTs in biological systems.

Transparent actuators and robots based on single-layer superaligned carbon nanotube sheet and polymer composites.

PubMed

Chen, Luzhuo; Weng, Mingcen; Zhang, Wei; Zhou, Zhiwei; Zhou, Yi; Xia, Dan; Li, Jiaxin; Huang, Zhigao; Liu, Changhong; Fan, Shoushan

2016-03-28

Transparent actuators have been attracting emerging interest recently, as they demonstrate potential applications in the fields of invisible robots, tactical displays, variable-focus lenses, and flexible cellular phones. However, previous technologies did not simultaneously realize macroscopic transparent actuators with advantages of large-shape deformation, low-voltage-driven actuation and fast fabrication. Here, we develop a fast approach to fabricate a high-performance transparent actuator based on single-layer superaligned carbon nanotube sheet and polymer composites. Various advantages of single-layer nanotube sheets including high transparency, considerable conductivity, and ultra-thin dimensions together with selected polymer materials completely realize all the above required advantages. Also, this is the first time that a single-layer nanotube sheet has been used to fabricate actuators with high transparency, avoiding the structural damage to the single-layer nanotube sheet. The transparent actuator shows a transmittance of 72% at the wavelength of 550 nm and bends remarkably with a curvature of 0.41 cm(-1) under a DC voltage for 5 s, demonstrating a significant advance in technological performances compared to previous conventional actuators. To illustrate their great potential usage, a transparent wiper and a humanoid robot "hand" were elaborately designed and fabricated, which initiate a new direction in the development of high-performance invisible robotics and other intelligent applications with transparency.

Structural properties of atactic polystyrene adsorbed onto solid surfaces.

PubMed

Tatek, Yergou B; Tsige, Mesfin

2011-11-07

In the present work, we are studying the local conformation of chains in a thin film of polystyrene adsorbed on a solid substrate by using atomistically detailed simulations. The simulations are carried out by using the readily available and massively parallel molecular dynamics code known as LAMMPS. In particular, a special emphasis is given to the density and orientation of side chains (which consist of phenyl groups and methylene units) at solid/polymer and polymer/vacuum interfaces. Three types of substrates were used in our study: α-quartz, graphite, and amorphous silica. Our investigation was restricted to atactic polystyrene. Our results show that the density and structural properties of side chains depend on the type of surface. An excess of phenyl rings is observed near the α-quartz substrate while the film adsorbed on graphite is depleted in C(6)H(5). Moreover, the orientation of the rings and methylene units on the substrate/film interface show a strong dependence on the type of the substrate, while the rings at the film/vacuum interface show a marked tendency to point outward, away from the film. The results we obtained are in a large part in good agreement with previous experimental and simulation results.

A potentiometric non-enzymatic glucose sensor using a molecularly imprinted layer bonded on a conducting polymer.

PubMed

Kim, Dong-Min; Moon, Jong-Min; Lee, Won-Chul; Yoon, Jang-Hee; Choi, Cheol Soo; Shim, Yoon-Bo

2017-05-15

A non-enzymatic potentiometric glucose sensor for the determination of glucose in the micomolar level in saliva was developed based on a molecularly imprinted polymer (MIP) binding on a conducting polymer layer. A MIP containing acrylamide, and aminophenyl boronic acid, as a host molecule to glucose, was immobilized on benzoic acid-functionalized poly(terthiophene) (pTBA) by the amide bond formation onto a gold nanoparticles deposited-screen printed carbon electrode (pTBA/AuNPs/SPCE). Aromatic boronic acid was incorporated into the MIP layer to stably capture glucose and create a potentiometric signal through the changed pKa value of polymer film by the formation of boronate anion-glucose complex with generation of H + ions by the cis-diol reaction. Reversible binding and extraction of glucose on the sensor surface was observed using a quartz crystal microbalance. Each layer of the sensor probe was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The potentiometric response at the optimized conditions exhibited a wide linear dynamic range of 3.2×10 -7 to 1.0×10 -3 M, with a detection limit of 1.9 (±0.15)×10 -7 M. The sensor probe revealed an excellent selectivity and sensitivity for glucose compared to other saccharides. In addition, the reliability of the proposed glucose sensor was evaluated in physiological fluid samples of saliva and finger prick blood. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of Surface Roughness on Polymer Drag Reduction with a High-Reynolds-Number Turbulent Boundary Layer

NASA Astrophysics Data System (ADS)

Elbing, Brian; Dowling, David; Solomon, Michael; Bian, Sherry; Ceccio, Steven

2007-11-01

A recent experiment at the U.S. Navy's Large Cavitation Channel (LCC) investigated the effect of wall roughness on wall-injection polymer drag reduction (PDR) within a high-Reynolds-number (10^7 to 2x10^8 based on downstream distance) turbulent boundary layer (TBL). Testing was performed in two parts: 1) PDR experiment on a 12.9 m long, 3.05 m wide hydro-dynamically smooth flat plate and 2) PDR experiment on the same model with the entire surface roughened. The roughness was produced by blowing glass beads into epoxy paint that was applied to the entire model. The roughened model had an average roughness height ranging between 307 and 1154 μm. Drag reduction was determined using six, stream-wise located integrated skin-friction balances. In addition to skin-friction measurements, sampling was performed at three stream-wise located ports. The sampling ports were used to determine the amount of degradation, if any, caused by the turbulent flow on the polymer. Both the skin-friction measurements and sampling analysis indicates that wall roughness in a turbulent boundary layer significantly increases degradation of the polymer solution.

Modified silicas with different structure of grafted methylphenylsiloxane layer

NASA Astrophysics Data System (ADS)

Bolbukh, Yuliia; Terpiłowski, Konrad; Kozakevych, Roman; Sternik, Dariusz; Deryło-Marczewska, Anna; Tertykh, Valentin

2016-06-01

The method of a chemical assembly of the surface polymeric layer with high contents of the modifying agent was developed. Powders of nanodispersed silica with chemisorbed polymethylphenylsiloxane (PMPS) were synthesized by solvent-free chemical assembly technique with a dimethyl carbonate (DMC) as scission agent. Samples were characterized using FTIR spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM), and elemental analysis (CHN analysis). Coating microstructure, morphology, and hydrophilic-hydrophobic properties of nanoparticles were estimated. The results indicate a significant effect of the PMPS/DMC ratio at each modification stage on hydrophobic properties of modified silicas. Modification with a similar composition of the PMPS/DMC mixture, even with different polymer amount at each stage, provides the worst hydrophobicity. Results suggest that the highest hydrophobicity (contact angle θ = 135°-140°) is achieved in the case when silica modified with the PMPS/DMC mixture using multistage approach that providing a formation of the monomolecular layer of polysiloxane at the first modification step. The characteristics of surface structure were interpreted in terms of density of polymer-silica bonds at the interfaces that, usually, are reduced for modified surfaces, in a coupling with conformation model that accented the shape of chains (arch- and console-like) adsorbed on solid surfaces.

Transparent actuators and robots based on single-layer superaligned carbon nanotube sheet and polymer composites

NASA Astrophysics Data System (ADS)

Chen, Luzhuo; Weng, Mingcen; Zhang, Wei; Zhou, Zhiwei; Zhou, Yi; Xia, Dan; Li, Jiaxin; Huang, Zhigao; Liu, Changhong; Fan, Shoushan

2016-03-01

Transparent actuators have been attracting emerging interest recently, as they demonstrate potential applications in the fields of invisible robots, tactical displays, variable-focus lenses, and flexible cellular phones. However, previous technologies did not simultaneously realize macroscopic transparent actuators with advantages of large-shape deformation, low-voltage-driven actuation and fast fabrication. Here, we develop a fast approach to fabricate a high-performance transparent actuator based on single-layer superaligned carbon nanotube sheet and polymer composites. Various advantages of single-layer nanotube sheets including high transparency, considerable conductivity, and ultra-thin dimensions together with selected polymer materials completely realize all the above required advantages. Also, this is the first time that a single-layer nanotube sheet has been used to fabricate actuators with high transparency, avoiding the structural damage to the single-layer nanotube sheet. The transparent actuator shows a transmittance of 72% at the wavelength of 550 nm and bends remarkably with a curvature of 0.41 cm-1 under a DC voltage for 5 s, demonstrating a significant advance in technological performances compared to previous conventional actuators. To illustrate their great potential usage, a transparent wiper and a humanoid robot ``hand'' were elaborately designed and fabricated, which initiate a new direction in the development of high-performance invisible robotics and other intelligent applications with transparency.Transparent actuators have been attracting emerging interest recently, as they demonstrate potential applications in the fields of invisible robots, tactical displays, variable-focus lenses, and flexible cellular phones. However, previous technologies did not simultaneously realize macroscopic transparent actuators with advantages of large-shape deformation, low-voltage-driven actuation and fast fabrication. Here, we develop a fast approach to

The molecular mechanism of mediation of adsorbed serum proteins to endothelial cells adhesion and growth on biomaterials.

PubMed

Yang, Dayun; Lü, Xiaoying; Hong, Ying; Xi, Tingfei; Zhang, Deyuan

2013-07-01

To explore molecular mechanism of mediation of adsorbed proteins to cell adhesion and growth on biomaterials, this study examined endothelial cell adhesion, morphology and viability on bare and titanium nitride (TiN) coated nickel titanium (NiTi) alloys and chitosan film firstly, and then identified the type and amount of serum proteins adsorbed on the three surfaces by proteomic technology. Subsequently, the mediation role of the identified proteins to cell adhesion and growth was investigated with bioinformatics analyses, and further confirmed by a series of cellular and molecular biological experiments. Results showed that the type and amount of adsorbed serum proteins associated with cell adhesion and growth was obviously higher on the alloys than on the chitosan film, and these proteins mediated endothelial cell adhesion and growth on the alloys via four ways. First, proteins such as adiponectin in the adsorbed protein layer bound with cell surface receptors to generate signal transduction, which activated cell surface integrins through increasing intracellular calcium level. Another way, thrombospondin 1 in the adsorbed protein layer promoted TGF-β signaling pathway activation and enhanced integrins expression. The third, RGD sequence containing proteins such as fibronectin 1, vitronectin and thrombospondin 1 in the adsorbed protein layer bound with activated integrins to activate focal adhesion pathway, increased focal adhesion formation and actin cytoskeleton organization and mediated cell adhesion and spreading. In addition, the activated focal adhesion pathway promoted the expression of cell growth related genes and resulted in cell proliferation. The fourth route, coagulation factor II (F2) and fibronectin 1 in the adsorbed protein layer bound with cell surface F2 receptor and integrin, activated regulation of actin cytoskeleton pathway and regulated actin cytoskeleton organization. Copyright © 2013 Elsevier Ltd. All rights reserved.

Contractile response of bovine lateral saphenous vein to ergotamine tartrate exposed to different concentrations of molecularly imprinted polymers

USDA-ARS?s Scientific Manuscript database

Ergot alkaloids, in their active isomeric form, affect animal health and performance and adsorbents are used to mitigate toxicities by reducing bioavailability. Adsorbents with high specificity (molecularly imprinted: MIP and non-imprinted: NIP polymers) adsorb ergot alkaloids in vitro, but require ...

A new Pb{sup II}(ethylenediaminetetraacetate) coordination polymer with a two-dimensional layer structure

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

Zhao, D., E-mail: iamzd@hpu.edu.cn; Zhang, R. H.; Li, F. F.

2016-12-15

A new Pb{sup II}−edta{sup 4–} coordination polymer, Pb{sub 2}(edta)(H{sub 2}O){sub 0.76} (edta{sup 4–} = ethylenediaminetetraacetate) was synthesized under hydrothermal condition. Single crystal X-ray analysis reveals that it represents a novel two-dimensional (2D) Pb{sup 2+}–edta{sup 4–} layer structure with a (4,8{sup 2})-topology. Each edta{sup 4–} ligand employs its four carboxylate O and two N atoms to chelate one Pb{sup II} atom (hexa-coordinated) and connects five Pb{sup II} atoms (ennea-coordinated) via its four carboxylate groups to form 2D layer framework. Adjacent layers are packed into the overall structure through vander Waals interactions.

A solution-processed binary cathode interfacial layer facilitates electron extraction for inverted polymer solar cells.

PubMed

Zhang, Xinyuan; Li, Zhiqi; Liu, Chunyu; Guo, Jiaxin; Shen, Liang; Guo, Wenbin

2018-03-15

The charge transfer and separation are significantly affected by the electron properties of the interface between the electron-donor layer and the carrier-transporting layer in polymer solar cells (PSCs). In this study, we investigate the electron extraction mechanism of PSCs with a low temperature solution-processed ZnO/PEI as electron transport layer. The incorporation of PEI layer can decrease the work function of ZnO and reduce interfacial barrier, which facilitates electron extraction and suppresses bimolecular recombination, leading to a significant performance enhancement. Furthermore, PEI layer can induce phase separation and passivite inorganic surface trap states as well as shift the interfacial energy offset between metal oxide and organic materials. This work offers a simple and effective way to improve the charge transporting property of organic photovoltaic devices. Copyright © 2017 Elsevier Inc. All rights reserved.

Reactive polymer fused deposition manufacturing

DOEpatents

Kunc, Vlastimil; Rios, Orlando; Love, Lonnie J.; Duty, Chad E.; Johs, Alexander

2017-05-16

Methods and compositions for additive manufacturing that include reactive or thermosetting polymers, such as urethanes and epoxies. The polymers are melted, partially cross-linked prior to the depositing, deposited to form a component object, solidified, and fully cross-linked. These polymers form networks of chemical bonds that span the deposited layers. Application of a directional electromagnetic field can be applied to aromatic polymers after deposition to align the polymers for improved bonding between the deposited layers.

Formulation of bi-layer matrix tablets of tramadol hydrochloride: Comparison of rate retarding ability of the incorporated hydrophilic polymers.

PubMed

Arif, Hasanul; Al-Masum, Abdullah; Sharmin, Florida; Reza, Selim; Sm Islam, Sm Ashraful

2015-05-01

Bi-layer tablets of tramadol hydrochloride were prepared by direct compression technique. Each tablet contains an instant release layer with a sustained release layer. The instant release layer was found to release the initial dose immediately within minutes. The instant release layer was combined with sustained release matrix made of varying quantity of Methocel K4M, Methocel K15MCR and Carbomer 974P. Bi-layer tablets were evaluated for various physical tests including weight variation, thickness and diameter, hardness and percent friability. Drug release from bi-layer tablet was studied in acidic medium and buffer medium for two and six hours respectively. Sustained release of tramadol hydrochloride was observed with a controlled fashion that was characteristic to the type and extent of polymer used. % Drug release from eight-hour dissolution study was fitted with several kinetic models. Mean dissolution time (MDT) and fractional dissolution values (T25%, T50% and T80%) were also calculated as well, to compare the retarding ability of the polymers. Methocel K15MCR was found to be the most effective in rate retardation of freely water-soluble tramadol hydrochloride compared to Methocel K4M and Capbomer 974P, when incorporated at equal ratio in the formulation.

Observation of room temperature negative differential resistance in multi-layer heterostructures of quantum dots and conducting polymers.

PubMed

Kannan, V; Kim, M R; Chae, Y S; Ramana, Ch V V; Rhee, J K

2011-01-14

Multi-layer heterostructure negative differential resistance devices based on poly-[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) conducting polymer and CdSe quantum dots is reported. The conducting polymer MEH-PPV acts as a barrier while CdSe quantum dots form the well layer. The devices exhibit negative differential resistance (NDR) at low voltages. For these devices, strong negative differential resistance is observed at room temperature. A maximum value of 51 for the peak-to-valley ratio of current is reported. Tunneling of electrons through the discrete quantum confined states in the CdSe quantum dots is believed to be responsible for the multiple peaks observed in the I-V measurement. Depending on the observed NDR signature, operating mechanisms are explored based on resonant tunneling and Coulomb blockade effects.

Polymer and small molecule based hybrid light source

DOEpatents

Choong, Vi-En; Choulis, Stelios; Krummacher, Benjamin Claus; Mathai, Mathew; So, Franky

2010-03-16

An organic electroluminescent device, includes: a substrate; a hole-injecting electrode (anode) coated over the substrate; a hole injection layer coated over the anode; a hole transporting layer coated over the hole injection layer; a polymer based light emitting layer, coated over the hole transporting layer; a small molecule based light emitting layer, thermally evaporated over the polymer based light emitting layer; and an electron-injecting electrode (cathode) deposited over the electroluminescent polymer layer.

Adsorbate-driven morphological changes on Cu(111) nano-pits

DOE PAGES

Mudiyanselage, K.; Xu, F.; Hoffmann, F. M.; ...

2014-12-09

Adsorbate-driven morphological changes of pitted-Cu(111) surfaces have been investigated following the adsorption and desorption of CO and H. The morphology of the pitted-Cu(111) surfaces, prepared by Ar + sputtering, exposed a few atomic layers deep nested hexagonal pits of diameters from 8 to 38 nm with steep step bundles. The roughness of pitted-Cu(111) surfaces can be healed by heating to 450-500 K in vacuum. Adsorption of CO on the pitted-Cu(111) surface leads to two infrared peaks at 2089-2090 and 2101-2105 cm -1 for CO adsorbed on under-coordinated sites in addition to the peak at 2071 cm -1 for CO adsorbedmore » on atop sites of the close-packed Cu(111) surface. CO adsorbed on under-coordinated sites is thermally more stable than that of atop Cu(111) sites. Annealing of the CO-covered surface from 100 to 300 K leads to minor changes of the surface morphology. In contrast, annealing of a H covered surface to 300 K creates a smooth Cu(111) surface as deduced from infrared data of adsorbed CO and scanning tunnelling microscopy (STM) imaging. The observation of significant adsorbate-driven morphological changes with H is attributed to its stronger modification of the Cu(111) surface by the formation of a sub-surface hydride with a hexagonal structure, which relaxes into the healed Cu(111) surface upon hydrogen desorption. These morphological changes occur ~150 K below the temperature required for healing of the pitted-Cu(111) surface by annealing in vacuum. In contrast, the adsorption of CO, which only interacts with the top-most Cu layer and desorbs by 160 K, does not significantly change the morphology of the pitted-Cu(111) surface.« less

Fabrication Processes to Generate Concentration Gradients in Polymer Solar Cell Active Layers

PubMed Central

Inaba, Shusei; Vohra, Varun

2017-01-01

Polymer solar cells (PSCs) are considered as one of the most promising low-cost alternatives for renewable energy production with devices now reaching power conversion efficiencies (PCEs) above the milestone value of 10%. These enhanced performances were achieved by developing new electron-donor (ED) and electron-acceptor (EA) materials as well as finding the adequate morphologies in either bulk heterojunction or sequentially deposited active layers. In particular, producing adequate vertical concentration gradients with higher concentrations of ED and EA close to the anode and cathode, respectively, results in an improved charge collection and consequently higher photovoltaic parameters such as the fill factor. In this review, we relate processes to generate active layers with ED–EA vertical concentration gradients. After summarizing the formation of such concentration gradients in single layer active layers through processes such as annealing or additives, we will verify that sequential deposition of multilayered active layers can be an efficient approach to remarkably increase the fill factor and PCE of PSCs. In fact, applying this challenging approach to fabricate inverted architecture PSCs has the potential to generate low-cost, high efficiency and stable devices, which may revolutionize worldwide energy demand and/or help develop next generation devices such as semi-transparent photovoltaic windows. PMID:28772878

Fabrication Processes to Generate Concentration Gradients in Polymer Solar Cell Active Layers.

PubMed

Inaba, Shusei; Vohra, Varun

2017-05-09

Polymer solar cells (PSCs) are considered as one of the most promising low-cost alternatives for renewable energy production with devices now reaching power conversion efficiencies (PCEs) above the milestone value of 10%. These enhanced performances were achieved by developing new electron-donor (ED) and electron-acceptor (EA) materials as well as finding the adequate morphologies in either bulk heterojunction or sequentially deposited active layers. In particular, producing adequate vertical concentration gradients with higher concentrations of ED and EA close to the anode and cathode, respectively, results in an improved charge collection and consequently higher photovoltaic parameters such as the fill factor. In this review, we relate processes to generate active layers with ED-EA vertical concentration gradients. After summarizing the formation of such concentration gradients in single layer active layers through processes such as annealing or additives, we will verify that sequential deposition of multilayered active layers can be an efficient approach to remarkably increase the fill factor and PCE of PSCs. In fact, applying this challenging approach to fabricate inverted architecture PSCs has the potential to generate low-cost, high efficiency and stable devices, which may revolutionize worldwide energy demand and/or help develop next generation devices such as semi-transparent photovoltaic windows.

Gradient polymer-disposed liquid crystal single layer of large nematic droplets for modulation of laser light.

PubMed

Hadjichristov, Georgi B; Marinov, Yordan G; Petrov, Alexander G

2011-06-01

The light modulating ability of gradient polymer-disposed liquid crystal (PDLC) single layer of large droplets formed by nematic E7 in UV-cured polymer NOA65 is studied. Operating at relatively low voltages, such PDLC film with a of thickness 10-25 μm and droplet size up to 50 μm exhibits a good contrast ratio and is capable of producing a large phase shift for the propagating coherent light. For a linearly polarized He-Ne laser (λ=633 nm), an electrically commanded phase shift as large as π/2 can be obtained by the large-droplet region of the film. The electrically produced phase shift and its spatial profile controlled by the thickness of the gradient PDLC single layers of large nematic droplets can be useful for tunable spatial light modulators and other devices for active control of laser light.

Fabrication and independent control of patterned polymer gate for a few-layer WSe{sub 2} field-effect transistor

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

Hong, Sung Ju; Park, Min; Kang, Hojin

We report the fabrication of a patterned polymer electrolyte for a two-dimensional (2D) semiconductor, few-layer tungsten diselenide (WSe{sub 2}) field-effect transistor (FET). We expose an electron-beam in a desirable region to form the patterned structure. The WSe{sub 2} FET acts as a p-type semiconductor in both bare and polymer-covered devices. We observe a highly efficient gating effect in the polymer-patterned device with independent gate control. The patterned polymer gate operates successfully in a molybdenum disulfide (MoS{sub 2}) FET, indicating the potential for general applications to 2D semiconductors. The results of this study can contribute to large-scale integration and better flexibilitymore » in transition metal dichalcogenide (TMD)-based electronics.« less

Shellac Films as a Natural Dielectric Layer for Enhanced Electron Transport in Polymer Field-Effect Transistors.

PubMed

Baek, Seung Woon; Ha, Jong-Woon; Yoon, Minho; Hwang, Do-Hoon; Lee, Jiyoul

2018-06-06

Shellac, a natural polymer resin obtained from the secretions of lac bugs, was evaluated as a dielectric layer in organic field-effect transistors (OFETs) on the basis of donor (D)-acceptor (A)-type conjugated semiconducting copolymers. The measured dielectric constant and breakdown field of the shellac layer were ∼3.4 and 3.0 MV/cm, respectively, comparable with those of a poly(4-vinylphenol) (PVP) film, a commonly used dielectric material. Bottom-gate/top-contact OFETs were fabricated with shellac or PVP as the dielectric layer and one of three different D-A-type semiconducting copolymers as the active layer: poly(cyclopentadithiophene- alt-benzothiadiazole) with p-type characteristics, poly(naphthalene-bis(dicarboximide)- alt-bithiophene) [P(NDI2OD-T2)] with n-type characteristics, and poly(dithienyl-diketopyrrolopyrrole- alt-thienothiophene) [P(DPP2T-TT)] with ambipolar characteristics. The electrical characteristics of the fabricated OFETs were then measured. For all active layers, OFETs with a shellac film as the dielectric layer exhibited a better mobility than those with PVP. For example, the mobility of the OFET with a shellac dielectric and n-type P(NDI2OD-T2) active layer was approximately 2 orders of magnitude greater than that of the corresponding OFET with a PVP insulating layer. When P(DPP2T-TT) served as the active layer, the OFET with shellac as the dielectric exhibited ambipolar characteristics, whereas the corresponding OFET with the PVP dielectric operated only in hole-accumulation mode. The total density of states was analyzed using technology computer-aided design simulations. The results revealed that compared with the OFETs with PVP as the dielectric, the OFETs with shellac as the dielectric had a lower trap-site density at the polymer semiconductor/dielectric interface and much fewer acceptor-like trap sites acting as electron traps. These results demonstrate that shellac is a suitable dielectric material for D-A-type semiconducting

Detection Of Uric Acid Based On Multi-Walled Carbon Nanotubes Polymerized With A Layer Of Molecularly Imprinted PMAA

NASA Astrophysics Data System (ADS)

Chen, Po-Yen; Lin, Chia-Yu; Ho, Kuo-Chuan

2009-05-01

A molecularly imprinted poly-metharylic acid (PMAA), polymerizing on the surface of multi-walled carbon nanotube (MWCNT), was synthesized. The MWCNT was modified by a layer of carboxylic acid and reacted with EDC and NHS to activate the carboxylic acid, which was prepared for the purpose of bonding allyl amine and getting an unsaturated side chain (-C=C). The resultant structure is abbreviated as MWCNTs-CH=CH2. It is well known that the vinyl group side chain provides good attachment between the MWCNTs and the molecularly imprinted polymer (MIP). The MIP based on PMAA was polymerized on the surface of MWCNTs-CH=CH2 with the addition of uric acid (UA). The non-imprinted polymer (NIP) was polymerized without adding UA. The adsorbed amount of UA approached the equilibrium value upon 60 min adsorption. The adsorption isotherm was obtained by immersing 10 mg of MIP or NIP in 5 mL aqueous solution containing different concentrations of UA. The adsorbed amounts were measured via a UV-Vis spectrometer at a wavelength of 292 nm. From the adsorption isotherm, it is seen that the MIP particles possess a good imprinting efficiency of about 4.41.

Deuterium-Tritium Beta-Layering Within a National Ignition Facility Scale Polymer Target in the LANL Cryogenic Pressure Loader

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

Ebey, Peter S.; Dole, James M.; Geller, Drew A.

2005-11-15

Beta-layering, the process of beta-decay heat-driven mass redistribution, has been demonstrated in a deuterium-tritium (D-T)-filled polymer sphere of the type required for fusion ignition experiments at the National Ignition Facility. This is the first report, to the best of the authors' knowledge, of a D-T layer formed in a permeation-filled sphere. The 2-mm-diam sphere was filled with D-T by permeation; cooled to cryogenic temperatures while in the high-pressure permeation vessel; and, while cold, removed to an optical axis where the D-T was frozen, melted, and beta-layered in a series of experiments over several weeks' time. This work was performed inmore » the Los Alamos National Laboratory cryogenic pressure loader system. The beta-layering time constant was 24.0 {+-} 2.5 min, less than the theoretical value of 26.8 min, and not showing the significant increase due to build-up of {sup 3}He often observed in beta-layered samples. Supercooling of the liquid D-T was observed. Neither the polymer target nor its tenting material showed visual signs of degradation after 5 weeks of exposure to D-T. Small external thermal gradients were used to shift the D-T material back and forth within the sphere.« less

Hollow mesoporous structured molecularly imprinted polymer as adsorbent in pipette-tip solid-phase extraction for the determination of antiretrovirals from plasma of HIV-infected patients.

PubMed

Simões, Nathália Soares; de Oliveira, Hanna Leijoto; da Silva, Ricky Cássio Santos; Teixeira, Leila Suleimara; Sales, Thaís Lorenna Souza; de Castro, Whocely Victor; de Paiva, Maria José Nunes; Sanches, Cristina; Borges, Keyller Bastos

2018-05-17

In this work a hollow mesoporous structured molecularly imprinted polymer was synthetized and used as adsorbent in pipette-tip solid-phase extraction for the determination of lamivudine (3TC), zidovudine (AZT) and efavirenz (EFZ) from plasma of human immunodeficiency virus (HIV) infected patients by high-performance liquid chromatography (HPLC). All parameters that influence the recovery of the pipette tip based on hollow mesoporous molecularly imprinted polymer solid-phase extraction (PT-HM-MIP-SPE) method were systematically studied and discussed in detail. The adsorbent material was prepared using methacrylic acid and 4-vinylpyridine as functional monomers, ethylene glycol dimethacrylate as crosslinker, acetonitrile as solvent, 4,4'-azobis(4-cyanovaleric acid) as radical initiator, benzalkonium chloride as surfactant), 3TC, and AZT as templates. The simultaneous separation of 3TC, AZT and EFZ by HPLC-UV was performed using a Gemini C18 Phenomenexࣨ column (250 mm × 4.6 mm, 5 μm) and mobile phase consisting of acetonitrile: water pH 3.2 (68:32, v/v), flow rate of 1.0 mL min -1 and λ = 260 nm. The method was linear over the concentration range from 0.25 to 10 μg mL -1 for 3TC and EFZ, and 0.05 to 2.0 μg mL -1 for AZT, with correlation coefficients larger than 0.99 for all analytes. Recovery ± relative standard deviations (RSDs %) were 41.99±2.38 %, 82.29±1.63 %, and 83.72±7.52 % for 3TC, AZT, and EFZ, respectively. The RSDs and relative errors (REs) were lower than 15 % for intra and interday assays. The method has been successfully applied for monitoring HIV-infected patients outside the therapeutic dosage.2 This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Incorporating an Electrode Modification Layer with a Vertical Phase Separated Photoactive Layer for Efficient and Stable Inverted Nonfullerene Polymer Solar Cells.

PubMed

Shi, Zhenzhen; Liu, Hao; Wang, Yaping; Li, Jinyan; Bai, Yiming; Wang, Fuzhi; Bian, Xingming; Hayat, Tasawar; Alsaedi, Ahmed; Tan, Zhan'ao

2017-12-20

For bulk heterojunction polymer solar cells (PSCs), the donors and acceptors featuring specific phase separation and concentration distribution within the electron donor/acceptor blends crucially affect the exciton dissociation and charge transportation. Herein, efficient and stable nonfullerene inverted PSCs incorporating a phase separated photoactive layer and a titanium chelate electrode modification layer are demonstrated. Water contact angle (WCA), scanning kelvin probe microscopy (SKPM), and atomic force microscopy (AFM) techniques are implemented to characterize the morphology of photoactive layers. Compared with the control conventional device, the short-circuit current density (J sc ) is enhanced from 14.74 to 17.45 mAcm -2 . The power conversion efficiency (PCE) for the inverted PSCs with a titanium (diisopropoxide)-bis-(2,4-pentanedionate) (TIPD) layer increases from 9.67% to 11.69% benefiting from the declined exciton recombination and fairly enhanced charge transportation. Furthermore, the nonencapsulated inverted device with a TIPD layer demonstrates the best long-term stability, 85% of initial PCE remaining and an almost undecayed open-circuit voltage (V oc ) after 1440 h. Our results reveal that the titanium chelate is an excellent electrode modification layer to incorporate with a vertical phase separated photoactive layer for producing high-efficiency and high-stability inverted nonfullerene PSCs.

Design of latex-layered double hydroxide composites by tuning the aggregation in suspensions.

PubMed

Pavlovic, Marko; Rouster, Paul; Bourgeat-Lami, Elodie; Prevot, Vanessa; Szilagyi, Istvan

2017-01-25

Colloidal stability of polymeric latex particles was studied in the presence of oppositely charged layered double hydroxide (LDH) platelets of different interlayer anions. Adsorption of the LDH particles led to charge neutralization and to overcharging of the latex at appropriate concentrations. Mixing stable colloidal suspensions of individual particles results in rapid aggregation once the LDH adsorption neutralizes the negative charges of the polymer spheres, while stable suspensions were observed at high and low LDH doses. The governing interparticle interactions included repulsive electrical double layer forces as well as van der Waals and patch-charge attractions, whose strength depended on the amount of LDH particles adsorbed on the latex surface. The type of the LDH interlayer anions did not affect the colloidal stability of the samples. Structural investigation of the obtained latex-LDH composites revealed that the polymer spheres were completely coated with the inorganic platelets once their concentration was sufficiently high. These results are especially important for designing synthetic routes for hybrid systems in suspensions, where stable colloids are required for uniform film-formation and for the homogeneous distribution of the inorganic filler within the composite materials.

A paradigm for peptide vaccine delivery using viral epitopes encapsulated in degradable polymer hydrogel capsules.

PubMed

Chong, Siow-Feng; Sexton, Amy; De Rose, Robert; Kent, Stephen J; Zelikin, Alexander N; Caruso, Frank

2009-10-01

We report on the use of degradable polymer capsules as carriers for the delivery of oligopeptide antigens to professional antigen presenting cells (APCs). To achieve encapsulation, oligopeptide sequences were covalently linked to a negatively charged carrier polymer via biodegradable linkages and the resulting conjugate was then adsorbed onto amine-functionalized silica particles. These peptide-coated particles were then used as templates for the layer-by-layer (LbL) deposition of thiolated poly(methacrylic acid) (PMA(SH)) and poly(vinylpyrrolidone) (PVPON) multilayers. Removal of the silica core and disruption of the hydrogen bonding between PMA(SH) and PVPON by altering the solution pH yielded disulfide-stabilized PMA capsules that retain the encapsulated cargo in an oxidative environment. In the presence of a natural reducing agent, glutathione, cleavage of the disulfide bonds causes release of the peptide from the capsules. The developed strategy provides control over peptide loading into polymer capsules and yields colloidally stable micron- and submicron-sized carriers with uniform size and peptide loading. The conjugation and encapsulation procedures were proven to be non-degrading to the peptide vaccines. The peptide-loaded capsules were successfully used to deliver their cargo to APCs and activate CD8 T lymphocytes in a non-human primate model of SIV infection ex vivo. The reported approach represents a novel paradigm in the delivery of peptide vaccines and other therapeutic agents.

Simulations of noble gases adsorbed on graphene

NASA Astrophysics Data System (ADS)

Maiga, Sidi; Gatica, Silvina

2014-03-01

We present results of Grand Canonical Monte Carlo simulations of adsorption of Kr, Ar and Xe on a suspended graphene sheet. We compute the adsorbate-adsorbate interaction by a Lennard-Jones potential. We adopt a hybrid model for the graphene-adsorbate force; in the hybrid model, the potential interaction with the nearest carbon atoms (within a distance rnn) is computed with an atomistic pair potential Ua; for the atoms at r>rnn, we compute the interaction energy as a continuous integration over a carbon uniform sheet with the density of graphene. For the atomistic potential Ua, we assume the anisotropic LJ potential adapted from the graphite-He interaction proposed by Cole et.al. This interaction includes the anisotropy of the C atoms on graphene, which originates in the anisotropic π-bonds. The adsorption isotherms, energy and structure of the layer are obtained and compared with experimental results. We also compare with the adsorption on graphite and carbon nanotubes. This research was supported by NSF/PRDM (Howard University) and NSF (DMR 1006010).

Behavior of adsorbed Poly-A onto sodium montmorillonite

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

Palomino-Aquino, Nayeli; Negrón-Mendoza, Alicia, E-mail: negron@nucleares.unam.mx

2015-07-23

The adsorption of Poly-A (a polynucleotide consisting of adenine, ribose and a phosphate group), onto a clay mineral, was studied to investigate the extent of adsorption, the site of binding, and the capacity of the clay to protect Poly-A, while it is adsorbed onto the clay, from external sources of energy. The results showed that Poly-A presented a high percentage of adsorption at the edges of the clay and that the survival of the polynucleotide was superior to irradiating the polymer in the absence of the clay.

Modeling adsorption: Investigating adsorbate and adsorbent properties

NASA Astrophysics Data System (ADS)

Webster, Charles Edwin

1999-12-01

Surface catalyzed reactions play a major role in current chemical production technology. Currently, 90% of all chemicals are produced by heterogeneously catalyzed reactions. Most of these catalyzed reactions involve adsorption, concentrating the substrate(s) (the adsorbate) on the surface of the solid (the adsorbent). Pore volumes, accessible surface areas, and the thermodynamics of adsorption are essential in the understanding of solid surface characteristics fundamental to catalyst and adsorbent screening and selection. Molecular properties such as molecular volumes and projected molecular areas are needed in order to convert moles adsorbed to surface volumes and areas. Generally, these molecular properties have been estimated from bulk properties, but many assumptions are required. As a result, different literature values are employed for these essential molecular properties. Calculated molar volumes and excluded molecular areas are determined and tabulated for a variety of molecules. Molecular dimensions of molecules are important in the understanding of molecular exclusion as well as size and shape selectivity, diffusion, and adsorbent selection. Molecular dimensions can also be used in the determination of the effective catalytic pore size of a catalyst. Adsorption isotherms, on zeolites, (crystalline mineral oxides) and amorphous solids, can be analyzed with the Multiple Equilibrium Analysis (MEA) description of adsorption. The MEA produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, ΔHi, and entropies, ΔSi) of adsorption for each process. Pore volumes and accessible surface areas are calculated from the process capacities. Adsorption isotherms can also be predicted for existing and new adsorbate-adsorbent systems with the MEA. The results show that MEA has the potential of becoming a standard characterization method for microporous solids that will lead to an increased understanding of their behavior in gas

Adsorption of poly(ethylene oxide) on smectite: Effect of layer charge.

PubMed

Su, Chia-Chi; Shen, Yun-Hwei

2009-04-01

The adsorption of polymers on clay is important in many applications. However the mechanisms of poly(ethylene oxide) (PEO) adsorption on smectite is not well elucidated at present. The aim of this study was to investigate the effect of layer charge density on the adsorption of PEO by smectite. The results indicated that both the hydrophobic interaction (between CH(2)CH(2) groups and siloxane surface) and the hydrogen bonding (between ether oxygen of PEO and structure OH of smectite) lead to PEO preferential adsorption on the surface of low-charge smectite. In addition, the delamination of low-charge smectite in water is enhanced upon PEO adsorption presumably due to the hydrophilic ether oxygen of adsorbed PEO.

Enhanced Lifetime of Polymer Solar Cells by Surface Passivation of Metal Oxide Buffer Layers.

PubMed

Venkatesan, Swaminathan; Ngo, Evan; Khatiwada, Devendra; Zhang, Cheng; Qiao, Qiquan

2015-07-29

The role of electron selective interfaces on the performance and lifetime of polymer solar cells were compared and analyzed. Bilayer interfaces consisting of metal oxide films with cationic polymer modification namely poly ethylenimine ethoxylated (PEIE) were found to enhance device lifetime compared to bare metal oxide films when used as an electron selective cathode interface. Devices utilizing surface-modified metal oxide layers showed enhanced lifetimes, retaining up to 85% of their original efficiency when stored in ambient atmosphere for 180 days without any encapsulation. The work function and surface potential of zinc oxide (ZnO) and ZnO/PEIE interlayers were evaluated using Kelvin probe and Kelvin probe force microscopy (KPFM) respectively. Kelvin probe measurements showed a smaller reduction in work function of ZnO/PEIE films compared to bare ZnO films when aged in atmospheric conditions. KPFM measurements showed that the surface potential of the ZnO surface drastically reduces when stored in ambient air for 7 days because of surface oxidation. Surface oxidation of the interface led to a substantial decrease in the performance in aged devices. The enhancement in the lifetime of devices with a bilayer interface was correlated to the suppressed surface oxidation of the metal oxide layers. The PEIE passivated surface retained a lower Fermi level when aged, which led to lower trap-assisted recombination at the polymer-cathode interface. Further photocharge extraction by linearly increasing voltage (Photo-CELIV) measurements were performed on fresh and aged samples to evaluate the field required to extract maximum charges. Fresh devices with a bare ZnO cathode interlayer required a lower field than devices with ZnO/PEIE cathode interface. However, aged devices with ZnO required a much higher field to extract charges while aged devices with ZnO/PEIE showed a minor increase compared to the fresh devices. Results indicate that surface modification can act as a

First-principles study of pollutant molecules absorbed on polymeric adsorbents using the vdW-DF2 functional

NASA Astrophysics Data System (ADS)

Zhu, Jinguo; Wang, Yapeng; Tian, Ting; Zhang, Qianfan

2018-03-01

Polymeric adsorbents have been attracting increasing attention because of their favorable structrual properties and effectiveness of solving small molecules contaminants. However, due to the absence of deep insight into the adsorption mechanism of polymeric adsorbents, researches on new polymeric adsorbents can only be carried out by repeated experiments and tests, which is extremely inefficient. Therefore, investigating the adsorption process of polymeric adsorbents, especially the mechanism of adsorbing various air pollutant molecules by materials modelling and simulation, is of great significance. Here in this work, we systematically studied the adsorption mechanism by first-principles computation with van der Waals interaction. It demonstrates that the adsorption between them was pure physisorption originating from the hydrogen bond and intermolecular forces consisting of Keesom force, Debye force and London dispersion force. The proportions of these forces varied according to different adsorption systems. The adsorption effects were determined by the polymers’ dipole moment and polarizability. The adsorption performance of some polymers with special structures was also investigated to explore their possibility as potential adsorbents. The results of our simulation can provide some guidance for developing new polymeric adsorbents with better performance.

Removal of cyanotoxins from surface water resources using reusable molecularly imprinted polymer adsorbents.

PubMed

Krupadam, Reddithota J; Patel, Govind P; Balasubramanian, Rajasekhar

2012-06-01

Microcystins (MCs; cyclic heptapeptides) are produced by freshwater cyanobacteria and cause public health concern in potable water supplies. There are more than 60 types of MCs identified to date, of which MC-LR is the most common found worldwide. For MC-LR, the WHO has established a threshold value of 1 μg L(-1) for drinking water. The present MCs removal methods such as coagulation, flocculation, adsorption, and filtration showed low efficiency for removing dissolved MC fraction from surface waters to the stipulated limit prescribed by WHO based on MC health impacts. The search for cost-effective and efficient removal method is still warranted for remediation of dissolved MC-LR-contaminated water resources. Molecularly imprinted polymer (MIP) adsorbent has been prepared using non-covalent imprinting approach. Using MC-LR as a template, itaconic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linking monomer, a MIP has been synthesized. Computer simulations were used to design effective binding sites for MC-LR binding in aqueous solutions. Batch binding adsorption assay was followed to determine binding capacity of MIP under the influence of environmental parameters such as total dissolved solids and pH. The adsorptive removal of MC-LR from lake water has been investigated using MIPs. The MIP showed excellent adsorption potential toward MC-LR in aqueous solutions with a binding capacity of 3.64 μg mg(-1) which is about 60% and 70% more than the commercially used powdered activated carbon (PAC) and resin XAD, respectively. Environmental parameters such as total organic carbon (represented as chemical oxygen demand (COD)) and total dissolved solids (TDS) showed no significant interference up to 300 mg L(-1) for MC-LR removal from lake water samples. It was found that the binding sites on PAC and XAD have more affinity toward COD and TDS than the MC-LR. Further, the adsorption capacity of the MIP was evaluated rigorously by its repeated

Multiple dynamic regimes in colloid-polymer dispersions: New insight using X-ray photon correlation spectroscopy

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

Srivastava, Sunita; Kishore, Suhasini; Narayanan, Suresh

We present an X-ray photon correlation spectros- copy (XPCS) study of dynamic transitions in an anisotropic colloid-polymer dispersion with multiple arrested states. The results provide insight into the mechanism for formation of repulsive glasses, attractive glasses, and networked gels of col- loids with weakly adsorbing polymer chains. In the presence of adsorbing polymer chains, we observe three distinct regimes: a state with slow dynamics consisting of finite particles and clusters, for which interparticle interactions are predominantly repulsive; a second dynamic regime occurring above the satu- ration concentration of added polymer, in which small clusters of nanoparticles form via a short-rangemore » depletion attraction; and a third regime above the overlap concentration in which dynamics of clusters are independent of polymer chain length. The observed complex dynamic state diagram is primarily gov- erned by the structural reorganization of a nanoparticle cluster and polymer chains at the nanoparticle-polymer surface and in the concentrated medium, which in turn controls the dynamics of the dispersion« less

Osmotic pellet system comprising osmotic core and in-process amorphized drug in polymer-surfactant layer for controlled delivery of poorly water-soluble drug.

PubMed

Saindane, Nilesh; Vavia, Pradeep

2012-09-01

The aim of the present investigation was to develop controlled porosity osmotic system for poorly water-soluble drug based on drug in polymer-surfactant layer technology. A poorly water-soluble drug, glipizide (GZ), was selected as the model drug. The technology involved core of the pellets containing osmotic agent coated with drug dispersed in polymer and surfactant layer, finally coated with release-retardant layer with pore former. The optimized drug-layer-coated pellets were evaluated for solubility of GZ at different pH conditions and characterized for amorphous nature of the drug by differential scanning calorimetry and X-ray powder diffractometry. The optimized release-retardant layer pellets were evaluated for in vitro drug release at different pH, hydrodynamic, and osmolality conditions. The optimized drug layer showed improvement in solubility (10 times in pH 1.2, 11 times in pH 4.5, and 21 times in pH 6.8), whereas pellets coated with cellulose acetate (15.0%, w/w, weight gain) with pore former triethyl citrate (10.0%, w/w, of polymer) demonstrated zero-order drug release for 24 h at different pH conditions; moreover, retardation of drug release was observed with increment of osmolality. This system could be a platform technology for controlled delivery of poorly water-soluble drugs. Copyright © 2012 Wiley Periodicals, Inc.

Electrophoretic mobilities of counterions and a polymer in cylindrical pores

PubMed Central

Singh, Sunil P.; Muthukumar, M.

2014-01-01

We have simulated the transport properties of a uniformly charged flexible polymer chain and its counterions confined inside cylindrical nanopores under an external electric field. The hydrodynamic interaction is treated by describing the solvent molecules explicitly with the multiparticle collision dynamics method. The chain consisting of charged monomers and the counterions interact electrostatically with themselves and with the external electric field. We find rich behavior of the counterions around the polymer under confinement in the presence of the external electric field. The mobility of the counterions is heterogeneous depending on their location relative to the polymer. The adsorption isotherm of the counterions on the polymer depends nonlinearly on the electric field. As a result, the effective charge of the polymer exhibits a sigmoidal dependence on the electric field. This in turn leads to a nascent nonlinearity in the chain stretching and electrophoretic mobility of the polymer in terms of their dependence on the electric field. The product of the electric field and the effective polymer charge is found to be the key variable to unify our simulation data for various polymer lengths. Chain extension and the electrophoretic mobility show sigmoidal dependence on the electric field, with crossovers from the linear response regime to the nonlinear regime and then to the saturation regime. The mobility of adsorbed counterions is nonmonotonic with the electric field. For weaker and moderate fields, the adsorbed counterions move with the polymer and at higher fields they move opposite to the polymer's direction. We find that the effective charge and the mobility of the polymer decrease with a decrease in the pore radius. PMID:25240366

The effect of adsorbates on the electrical stability of graphene studied by transient photocurrent spectroscopy

NASA Astrophysics Data System (ADS)

Kalkan, S. B.; Aydın, H.; Özkendir, D.; ćelebi, C.

2018-01-01

Adsorbate induced variations in the electrical conductivity of graphene layers with two different types of charge carriers are investigated by using the Transient Photocurrent Spectroscopy (TPS) measurement technique. In-vacuum TPS measurements taken for a duration of 5 ks revealed that the adsorption/desorption of atmospheric adsorbates leads to more than a 110% increment and a 45% decrement in the conductivity of epitaxial graphene (n-type) and chemical vapor deposition graphene (p-type) layers on semi-insulating silicon carbide (SiC) substrates, respectively. The graphene layers on SiC are encapsulated and passivated with a thin SiO2 film grown by the Pulsed Electron Deposition method. The measurements conducted for short periods and a few cycles showed that the encapsulation process completely suppresses the time dependent conductivity instability of graphene independent of its charge carrier type. The obtained results are used to construct an experimental model for identifying adsorbate related conductivity variations in graphene and also in other 2D materials with an inherently high surface-to-volume ratio.

The Structures of Fibronectin Adsorbed on Polyelectrolyte Thin Films

NASA Astrophysics Data System (ADS)

Shin, Kwanwoo; Satija, Sushil; Fang, Xiao-Hua; Li, Bin-Quan; Nadine, Pernodet; Miriam, Rafailovich; Sokolov, Jonathan; Arach, Goldar; Roser, Steve

2002-03-01

We have shown that it is possible to form a fibrilar network of fibronectin on a polyelectrolyte polymer film whose dimensions are similar to those reported on the extra cellular matrix. The fibronectin network was observed to form only when the charge density of the polymer was in excess of the natural charge density of the cell wall. Furthermore, the self-organized fibronectin layer was much thicker than the polymer film, indicating that long ranged interaction may play a key role in the assembly process. It is therefore important to understand the structure of the polymer layer/protein interface. Here we report on a neutron reflectivity study where we explore the structure of the polyelectrolyte layer, in this case sulfonated polystyrene (PSS_x.), with varying degree of sulfonation (x<30%), as a function of sulfur content and counter ion concentration. These results are then correlated with systemic study of the adsorption and the multilayer formation of fibronectin as a function of incubation time for various sulfonation levels of PSS_x. Furthermore, the surface charge on the substrates can be strongly influenced by the presence of salt ions, it is important to understand changes due to electrostatic interactions occurring in the various salt conditions. Complementary X-ray reflection was used to determine the salt density profile associating with the internal ionic polymer matrix. This work was funded in part of the NSF-MRSEC program.

Organimetallic Fluorescent Complex Polymers For Light Emitting Applications

DOEpatents

Shi, Song Q.; So, Franky

1997-10-28

A fluorescent complex polymer with fluorescent organometallic complexes connected by organic chain spacers is utilized in the fabrication of light emitting devices on a substantially transparent planar substrate by depositing a first conductive layer having p-type conductivity on the planar surface of the substrate, depositing a layer of a hole transporting and electron blocking material on the first conductive layer, depositing a layer of the fluorescent complex polymer on the layer of hole transporting and electron blocking material as an electron transporting emissive layer and depositing a second conductive layer having n-type conductivity on the layer of fluorescent complex polymer.

Facile Approach to Preparing a Vanadium Oxide Hydrate Layer as a Hole-Transport Layer for High-Performance Polymer Solar Cells.

PubMed

Cong, Hailin; Han, Dongwei; Sun, Bingbing; Zhou, Dongying; Wang, Chen; Liu, Ping; Feng, Lai

2017-05-31

We demonstrate a facile and green approach to preparing a vanadium oxide hydrate (VO x ·nH 2 O) layer to serve as the hole-transport layer (HTL) in high-performance polymer solar cells (PSCs). The VO x ·nH 2 O layer was in situ prepared by a combined H 2 O 2 and ultraviolet-ozone (UVO) processing on a VO x layer. The as-prepared VO x ·nH 2 O layer featured a work function of 5.0 ± 0.1 eV, high transmittance, and better interface properties compared to those of the generally prepared VO x (UVO or thermal annealing) layers. PSCs based on poly[(ethylhexyl-thiophenyl)-benzodithiophene-(ethylhexyl)-thienothiophene]/[6,6]-phenyl-C 71 -butyric acid methyl ester using the VO x ·nH 2 O layer as the HTL yielded high power conversion efficiencies (PCEs) up to 8.11%, outperforming the devices with VO x layers (PCE of 6.79% for the UVO-processed VO x layer and 6.10% for the thermally annealed VO x layer) and conventional polyethylenedioxythiophene-polystyrenesulfonate (PEDOT:PSS) layers (PCE of 7.67%). The improved PCE was attributed to the enhanced J SC and/or fill factor, which mainly correlate to the improved interfacial contact between the photoactive layer and the indium tin oxide/HTL or cathode when using the VO x ·nH 2 O layer as the HTL. A similar improvement in the PCE was also observed for the PSCs based on poly(3-hexylthiophene)/[6,6]-phenyl-C 61 -butyric acid methyl ester. In addition, PSCs with a VO x ·nH 2 O layer as the HTL showed a higher stability than that of those with a PEDOT:PSS layer. Hence, it would be possible to use this simply and in situ prepared VO x ·nH 2 O layer as an inexpensive HTL for high-performance PSCs.

Surface area of vermiculite with nitrogen and carbon dioxide as adsorbates

USGS Publications Warehouse

Thomas, Josephus; Bohor, Bruce F.

1969-01-01

Surface-area studies were made on several homoionic vermiculites with both nitrogen and carbon dioxide as adsorbates. These studies show that only very slight penetration occurs between individual vermiculite platelets. This is in contrast to an earlier investigation of montmorillonite where it was found that the degree of penetration between layers is quite high, particularly for carbon dioxide, and is governed by the size and charge of the interlayer cation. The inability of these adsorbates to penetrate substantially between vermiculite platelets is due primarily to this mineral's high surface-charge density.The extent of penetration of nitrogen and carbon dioxide at the edges of vermiculite platelets, though slight, is influenced by the coordinated water retained within the sample at a given degassing temperature. Forces between layers are weakened with increasing water content, which permits slightly greater penetration by adsorbate gases. Thus, the surface area of vermiculite, as determined by gas adsorption, is larger than the calculated external surface area based upon particle size and shape considerations. In addition, "extra" surface is provided by the lifting and scrolling of terminal platelets. These morphological features are shown in scanning electron micrographs of a naturally occuring vermiculite.

Phase diagram and transformations of iron pentacarbonyl to nm layered hematite and carbon-oxygen polymer under pressure

DOE PAGES

Ryu, Young Jay; Kim, Minseob; Yoo, Choong -Shik

2015-10-12

In this study, we present the phase diagram of Fe(CO) 5, consisting of three molecular polymorphs (phase I, II and III) and an extended polymeric phase that can be recovered at ambient condition. The phase diagram indicates a limited stability of Fe(CO) 5 within a pressure-temperature dome formed below the liquid- phase II- polymer triple point at 4.2 GPa and 580 K. The limited stability, in turn, signifies the temperature-induced weakening of Fe-CO back bonds, which eventually leads to the dissociation of Fe-CO at the onset of the polymerization of CO. The recovered polymer is a composite of novel nm-lamellarmore » layers of crystalline hematite Fe 2O 3 and amorphous carbon-oxygen polymers. These results, therefore, demonstrate the synthesis of carbon-oxygen polymer by compressing Fe(CO) 5, which advocates a novel synthetic route to develop atomistic composite materials by compressing organometallic compounds.« less

Two-step adsorption on jungle-gym-type porous coordination polymers: dependence on hydrogen-bonding capability of adsorbates, ligand-substituent effect, and temperature.

PubMed

Uemura, Kazuhiro; Yamasaki, Yukari; Onishi, Fumiaki; Kita, Hidetoshi; Ebihara, Masahiro

2010-11-01

A preliminary study of isopropanol (IPA) adsorption/desorption isotherms on a jungle-gym-type porous coordination polymer, [Zn(2)(bdc)(2)(dabco)](n) (1, H(2)bdc = 1,4-benzenedicarboxylic acid, dabco =1,4-diazabicyclo[2.2.2]octane), showed unambiguous two-step profiles via a highly shrunk intermediate framework. The results of adsorption measurements on 1, using probing gas molecules of alcohol (MeOH and EtOH) for the size effect and Me(2)CO for the influence of hydrogen bonding, show that alcohol adsorption isotherms are gradual two-step profiles, whereas the Me(2)CO isotherm is a typical type-I isotherm, indicating that a two-step adsorption/desorption is involved with hydrogen bonds. To further clarify these characteristic adsorption/desorption behaviors, selecting nitroterephthalate (bdc-NO(2)), bromoterephthalate (bdc-Br), and 2,5-dichloroterephthalate (bdc-Cl(2)) as substituted dicarboxylate ligands, isomorphous jungle-gym-type porous coordination polymers, {[Zn(2)(bdc-NO(2))(2)(dabco)]·solvents}(n) (2 ⊃ solvents), {[Zn(2)(bdc-Br)(2)(dabco)]·solvents}(n) (3 ⊃ solvents), and {[Zn(2)(bdc-Cl(2))(2)(dabco)]·solvents}(n) (4 ⊃ solvents), were synthesized and characterized by single-crystal X-ray analyses. Thermal gravimetry, X-ray powder diffraction, and N(2) adsorption at 77 K measurements reveal that [Zn(2)(bdc-NO(2))(2)(dabco)](n) (2), [Zn(2)(bdc-Br)(2)(dabco)](n) (3), and [Zn(2)(bdc-Cl(2))(2)(dabco)](n) (4) maintain their frameworks without guest molecules with Brunauer-Emmett-Teller (BET) surface areas of 1568 (2), 1292 (3), and 1216 (4) m(2) g(-1). As found in results of MeOH, EtOH, IPA, and Me(2)CO adsorption/desorption on 2-4, only MeOH adsorption on 2 shows an obvious two-step profile. Considering the substituent effects and adsorbate sizes, the hydrogen bonds, which are triggers for two-step adsorption, are formed between adsorbates and carboxylate groups at the corners in the pores, inducing wide pores to become narrow pores. Interestingly, such

Rapid removal of aniline from contaminated water by a novel polymeric adsorbent.

PubMed

Huang, Yunhong; Xu, Yang; He, Qinghua; Cao, Yusheng; Du, Bibai

2014-01-01

Dummy molecularly imprinted polymers (DMIPs) for aniline were synthesized by a thermal polymerization method using acrylamide as a functional monomer, ethylene dimethacrylate as a crosslinker, 2,2-azobisisobutyronitrile as a free radical initiator, acetonitrile as a porogenic solvent, and analogues of aniline, namely sulfadiazine, as the template. The DMIPs that were obtained showed a high affinity to aniline compared to non-imprinted polymers. It was proven that the DMIPs obtained using sulfadiazine as the template were much better than the molecularly imprinted polymers using aniline as the template. The results indicated that the Freundlich model was fit for the adsorption model of DMIP for aniline and the adsorption model of the DMIP for aniline was multilayer adsorption. Furthermore, the results showed that the DMIP synthesized by bulk polymerization could be used as a novel adsorbent for removal of aniline from contaminated water.

Polymer coated CaAl-layered double hydroxide nanomaterials for potential calcium supplement.

PubMed

Kim, Tae-Hyun; Lee, Jeong-A; Choi, Soo-Jin; Oh, Jae-Min

2014-12-05

We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement.

Adsorption of polyethyleneimine and polymethacrylic acid onto synthesized hematite.

PubMed

Chibowski, S; Patkowski, J; Grzadka, E

2009-01-01

An influence of different functional groups of polymer, its molecular weight, polydispersity ratio (M(w)/M(n)) and presence of impurities on its adsorption in different pH values (3, 6 and 9) onto synthesized hematite (Fe(2)O(3)) was measured. A structure of adsorbed macromolecules of PMA and PEI was obtained according to S-F theory. Two polymers were used: polymethacrylic acid (PMA) of 6500 and 75,100 molecular weight as well as polyethyleneimine (PEI) 25,000 commercial and fractionated. Electrokinetic properties of the interface oxide-polymer solution (surface charge density and zeta potential) were also measured as well as adsorption layer thicknesses (with use of viscosimetric measurements). Obtained data show, that all above-mentioned factors do influence not only the adsorption process itself but also a surface charge, zeta potential and structure of adsorbed polymer layers on polymer/hematite interface.

Development of porous structured polyvinyl alcohol/zeolite/carbon composites as adsorbent

NASA Astrophysics Data System (ADS)

Laksmono, J. A.; Sudibandriyo, M.; Saputra, A. H.; Haryono, A.

2017-05-01

Adsorption is a separation process that has higher energy efficiency than others. Analyzing the nature of the adsorbate and the selection of suitable adsorbent are key success in adsorption. The performance of the adsorbent can be modified either physically or chemically to obtain the efficiency and effectiveness of the adsorption, this can be facilitated by using a composite adsorbent. In this study, we have conducted the preparation process of a polyvinyl alcohol (PVA)/zeolite/carbon composites. The resulting adsorbent composites are dedicated for ethanol - water dehydration proposes. The composites were prepared using cross-linked polymerization method followed by supercritical fluid extraction (SFE) to obtain the porous structured upon drying process. The characterization of the functional groups and morphology were performed by using Fourier Transform Infra-Red (FTIR) and Scanning Electron Microscopy (SEM), respectively. The FTIR analysis showed that composite prepared by SFE method formed hydrogen bonding confirmed by the appearance of peaks at 2950 - 3000 cm-1 compared to composite without SFE method, whereas, the results of SEM study showed the formation of three layered structures. On basis of the obtained results, it can be shown that PVA/zeolite/carbon has high potential to be develop further as an adsorbent composite.

Adsorption of four perfluorinated acids on non ion exchange polymer sorbents.

PubMed

Senevirathna, S T M L D; Tanaka, S; Fujii, S; Kunacheva, C; Harada, H; Shivakoti, B R; Dinh, H; Ariyadasa, T

2011-01-01

Perfluorinated compounds (PFCs) have attracted global concern due to their ubiquitous distribution and properties of persistence, bio accumulation and toxicity. The process of adsorption has been identified as an effective technique to remove PFCs in water. Different non ion-exchange polymeric adsorbents were tested with regard to their sorption kinetics and isotherms at low PFCs concentrations. Selected PFCs were perfluorobutanoic acid (PFBA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA) and the tested polymers were three types of Dowex optopores (V-493, V503, and L493), Amberlite XAD-4, and Filtrasorb 400 (Granular Activated Carbon-GAC). We observed the selective adsorption of PFCs on synthetic polymers. For PFDA, Amberlite XAD-4 gave the Freundlich adsorption constant of 2,965 (microg PFCs/g sorbent)(microg PFCs/L)(-n), which was higher than that of GAC (121.89 (microg PFCs/g sorbent) (microg PFCS/L)(-n)). In the case of PFBA, GAC showed better performance (13.36) (microg PFCs/g sorbent) microg PFCS/L)(-n) than synthetic polymers (0.62-5.23) (microg PFCs/g sorbent) (microg PFCS/L)(-n). Adsorption kinetics of all adsorbents were well described (R2 = 0.85-1) by pseudo-second order kinetic model. Sorption capacity was influenced by initial PFCs concentration for all adsorbents. GAC reached the equilibrium concentration within 4 hours, Amberlite XAD 4 reached it within 10 hours and other polymers took more than 70 hours.

Multilayer Electroactive Polymer Composite Material

NASA Technical Reports Server (NTRS)

Harrison, Joycelyn S. (Inventor); Holloway, Nancy M. (Inventor); Park, Cheol (Inventor); Draughon, Gregory K. (Inventor); Ounaies, Zoubeida (Inventor)

2011-01-01

An electroactive material comprises multiple layers of electroactive composite with each layer having unique dielectric, electrical and mechanical properties that define an electromechanical operation thereof when affected by an external stimulus. For example, each layer can be (i) a 2-phase composite made from a polymer with polarizable moieties and an effective amount of carbon nanotubes incorporated in the polymer for a predetermined electromechanical operation, or (ii) a 3-phase composite having the elements of the 2-phase composite and further including a third component of micro-sized to nano-sized particles of an electroactive ceramic incorporated in the polymer matrix.

Thickness Dependent Effective Viscosity of a Polymer Solution near an Interface Probed by a Quartz Crystal Microbalance with Dissipation Method

PubMed Central

Fang, Jiajie; Zhu, Tao; Sheng, Jie; Jiang, Zhongying; Ma, Yuqiang

2015-01-01

The solution viscosity near an interface, which affects the solution behavior and the molecular dynamics in the solution, differs from the bulk. This paper measured the effective viscosity of a dilute poly (ethylene glycol) (PEG) solution adjacent to a Au electrode using the quartz crystal microbalance with dissipation (QCM-D) technique. We evidenced that the effect of an adsorbed PEG layer can be ignored, and calculated the zero shear rate effective viscosity to remove attenuation of high shear frequency oscillations. By increasing the overtone n from 3 to 13, the thickness of the sensed polymer solution decreased from ~70 to 30 nm. The zero shear rate effective viscosity of the polymer solution and longest relaxation time of PEG chains within it decrease with increasing solution thickness. The change trends are independent of the relation between the apparent viscosity and shear frequency and the values of the involved parameter, suggesting that the polymer solution and polymer chains closer to a solid substrate have a greater effective viscosity and slower relaxation mode, respectively. This method can study the effect of an interface presence on behavior and phenomena relating to the effective viscosity of polymer solutions, including the dynamics of discrete polymer chains. PMID:25684747

Forces between Two Glass Surfaces with Adsorbed Hexadecyltrimethylammonium Salicylate.

PubMed

Imae, T; Kato, M; Rutland, M

2000-02-22

Forces have been measured for hexadecyltrimethylammonium salicylate (C(16)TASal) layers on glass beads. During the inward process, hydrophobic attraction occurred at lower adsorption of C(16)TASal and electrostatic repulsion interactions happened at higher adsorption. While the jump-in phenomenon was observed for solutions of concentrations below the critical micelle concentration (cmc = 0.15 mM), the step-in phenomenon was characteristic for solutions at the cmc and above the cmc, suggesting the push-out of adsorbed C(16)TASal layers and/or inserted micelles. The remarkable pull-off phenomenon on the outward process occurred for all solutions, indicating a strong interaction between C(16)TASal molecules. For aqueous 0.15 mM C(16)TASal solutions of various NaSal concentrations, on the inward process, the electrostatic repulsive interaction decreased with adding NaSal. This is due to the electrostatic shielding by salt excess. The height of the force wall on the inward process reached a maximum at 0.01 M NaSal, but the interlocking between molecules on two surfaces during the outward process was minimized at 0.1 M NaSal. These tendencies, which are different from that of the electrostatic repulsion interaction, imply the strong cohesion between adsorbed C(16)TASal layers.

Learning from Natural Nacre: Constructing Layered Polymer Composites with High Thermal Conductivity.

PubMed

Pan, Guiran; Yao, Yimin; Zeng, Xiaoliang; Sun, Jiajia; Hu, Jiantao; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

2017-09-27

Inspired by the microstructures of naturally layered and highly oriented materials, such as natural nacre, we report a thermally conductive polymer composite that consists of epoxy resin and Al 2 O 3 platelets deposited with silver nanoparticles (AgNPs). Owing to their unique two-dimensional structure, Al 2 O 3 platelets are stacked together via a hot-pressing technique, resulting in a brick-and-mortar structure, which is similar to the one of natural nacre. Moreover, the AgNPs deposited on the surfaces of the Al 2 O 3 platelets act as bridges that link the adjacent Al 2 O 3 platelets due to the reduced melting point of the AgNPs. As a result, the polymer composite with 50 wt % filler achieves a maximum thermal conductivity of 6.71 W m -1 K -1 . In addition, the small addition of AgNPs (0.6 wt %) minimally affects the electrical insulation of the composites. Our bioinspired approach will find uses in the design and fabrication of thermally conductive materials for thermal management in modern electronics.

Amine-tethered solid adsorbents coupling high adsorption capacity and regenerability for CO2 capture from ambient air.

PubMed

Choi, Sunho; Gray, McMahan L; Jones, Christopher W

2011-05-23

Silica supported poly(ethyleneimine) (PEI) materials are prepared via impregnation and demonstrated to be promising adsorbents for CO(2) capture from ultra-dilute gas streams such as ambient air. A prototypical class 1 adsorbent, containing 45 wt% PEI (PEI/silica), and two new modified PEI-based aminosilica adsorbents, derived from PEI modified with 3-aminopropyltrimethoxysilane (A-PEI/silica) or tetraethyl orthotitanate (T-PEI/silica), are prepared and characterized by using thermogravimetric analysis and FTIR spectroscopy. The modifiers are shown to enhance the thermal stability of the polymer-oxide composites, leading to higher PEI decomposition temperatures. The modified adsorbents present extremely high CO(2) adsorption capacities under conditions simulating ambient air (400 ppm CO(2) in inert gas), exceeding 2 mol(CO (2)) kg(sorbent)(-1), as well as enhanced adsorption kinetics compared to conventional class 1 sorbents. The new adsorbents show excellent stability in cyclic adsorption-desorption operations, even under dry conditions in which aminosilica adsorbents are known to lose capacity due to urea formation. Thus, the adsorbents of this type can be considered promising materials for the direct capture of CO(2) from ultra-dilute gas streams such as ambient air. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thickness dependence of curvature, strain, and response time in ionic electroactive polymer actuators fabricated via layer-by-layer assembly

NASA Astrophysics Data System (ADS)

Montazami, Reza; Liu, Sheng; Liu, Yang; Wang, Dong; Zhang, Qiming; Heflin, James R.

2011-05-01

Ionic electroactive polymer (IEAP) actuators containing porous conductive network composites (CNCs) and ionic liquids can result in high strain and fast response times. Incorporation of spherical gold nanoparticles in the CNC enhances conductivity and porosity, while maintaining relatively small thickness. This leads to improved mechanical strain and bending curvature of the actuators. We have employed the layer-by-layer self-assembly technique to fabricate a CNC with enhanced curvature (0.43 mm-1) and large net intrinsic strain (6.1%). The results demonstrate that curvature and net strain of IEAP actuators due to motion of the anions increase linearly with the thickness of the CNC as a result of the increased volume in which the anions can be stored. In addition, after subtracting the curvature of a bare Nafion actuator without a CNC, it is found that the net intrinsic strain of the CNC layer is independent of thickness for the range of 20-80 nm, indicating that the entire CNC volume contributes equivalently to the actuator motion. Furthermore, the response time of the actuator due to anion motion is independent of CNC thickness, suggesting that traversal through the Nafion membrane is the limiting factor in the anion motion.

From 1D Polymers to 2D Polymers: Preparation of Free-Standing Single-Monomer-Thick Two-Dimensional Conjugated Polymers in Water.

PubMed

Zhang, Na; Wang, Taisheng; Wu, Xing; Jiang, Chen; Zhang, Taiming; Jin, Bangkun; Ji, Hengxing; Bai, Wei; Bai, Ruke

2017-07-25

Recently, investigation on two-dimensional (2D) organic polymers has made great progress, and conjugated 2D polymers already play a dynamic role in both academic and practical applications. However, a convenient, noninterfacial approach to obtain single-layer 2D polymers in solution, especially in aqueous media, remains challenging. Herein, we present a facile, highly efficient, and versatile "1D to 2D" strategy for preparation of free-standing single-monomer-thick conjugated 2D polymers in water without any aid. The 2D structure was achieved by taking advantage of the side-by-side self-assembly of a rigid amphiphilic 1D polymer and following topochemical photopolymerization in water. The spontaneous formation of single-layer polymer sheets was driven by synergetic association of the hydrophobic interactions, π-π stacking interactions, and electrostatic repulsion. Both the supramolecular sheets and the covalent sheets were confirmed by spectroscopic analyses and electron microscope techniques. Moreover, in comparison of the supramolecular 2D polymer, the covalent 2D polymer sheets exhibited not only higher mechanical strength but also higher conductivity, which can be ascribed to the conjugated network within the covalent 2D polymer sheets.

Polymer based tunneling sensor

NASA Technical Reports Server (NTRS)

Wang, Jing (Inventor); Zhao, Yongjun (Inventor); Cui, Tianhong (Inventor)

2006-01-01

A process for fabricating a polymer based circuit by the following steps. A mold of a design is formed through a lithography process. The design is transferred to a polymer substrate through a hot embossing process. A metal layer is then deposited over at least part of said design and at least one electrical lead is connected to said metal layer.

Slippery self-lubricating polymer surfaces

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

Aizenberg, Joanna; Aizenberg, Michael; Cui, Jiaxi

The present disclosure describes a strategy to create self-healing, slippery self-lubricating polymers. Lubricating liquids with affinities to polymers can be utilized to get absorbed within the polymer and form a lubricant layer (of the lubricating liquid) on the polymer. The lubricant layer can repel a wide range of materials, including simple and complex fluids (water, hydrocarbons, crude oil and bodily fluids), restore liquid-repellency after physical damage, and resist ice, microorganisms and insects adhesion. Some exemplary applications where self-lubricating polymers will be useful include energy-efficient, friction-reduction fluid handling and transportation, medical devices, anti-icing, optical sensing, and as self-cleaning, and anti-fouling materialsmore » operating in extreme environments.« less

Graphene: Polymer composites as moisture barrier and charge transport layer toward solar cell applications

NASA Astrophysics Data System (ADS)

Sakorikar, Tushar; Kavitha, M. K.; Tong, Shi Wun; Vayalamkuzhi, Pramitha; Loh, Kian Ping; Jaiswal, Manu

2018-05-01

Graphene: polymer composite based electrically conducting films are realized by a facile solution processable method. Ultraviolet Photoelectron Spectroscopy (UPS) measurements on the composite films, reveal a low work function of reduced graphene oxide (rGO) obtained from hydrazine hydrate reduction of graphene oxide (GO). We suggest that the low work function could potentially make rGO: PMMA composite suitable for electron conducting layer in perovskite solar cells in place of traditionally used expensive PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) layer. Further, we demonstrate from the gravimetric experiments conducted on rGO: PMMA films, that the same coating is also resistant to moisture permeation. This latter property can be used to realize a protective coating layer for perovskite films, which are prone to moisture induced degradation. Thus, dual functionality of rGO-PMMA films is demonstrated towards integration with perovskite solar cells. Architecture of perovskite solar cell based on these concepts is proposed.

Reflective article having a sacrificial cathodic layer

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

Kabagambe, Benjamin; Buchanan, Michael J.; Scott, Matthew S.

The present invention relates to reflective articles, such as solar mirrors, that include a sacrificial cathodic layer. The reflective article, more particularly includes a substrate, such as glass, having a multi-layered coating thereon that includes a lead-free sacrificial cathodic layer. The sacrificial cathodic layer includes at least one transition metal, such as a particulate transition metal, which can be in the form of flakes (e.g., zinc flakes). The sacrificial cathodic layer can include an inorganic matrix formed from one or more organo-titanates. Alternatively, the sacrificial cathodic layer can include an organic polymer matrix (e.g., a crosslinked organic polymer matrix formedmore » from an organic polymer and an aminoplast crosslinking agent). The reflective article also includes an outer organic polymer coating, that can be electrodeposited over the sacrificial cathodic layer.« less

Molecular Adsorber Coating

NASA Technical Reports Server (NTRS)

Straka, Sharon; Peters, Wanda; Hasegawa, Mark; Hedgeland, Randy; Petro, John; Novo-Gradac, Kevin; Wong, Alfred; Triolo, Jack; Miller, Cory

2011-01-01

A document discusses a zeolite-based sprayable molecular adsorber coating that has been developed to alleviate the size and weight issues of current ceramic puck-based technology, while providing a configuration that more projects can use to protect against degradation from outgassed materials within a spacecraft, particularly contamination-sensitive instruments. This coating system demonstrates five times the adsorption capacity of previously developed adsorber coating slurries. The molecular adsorber formulation was developed and refined, and a procedure for spray application was developed. Samples were spray-coated and tested for capacity, thermal optical/radiative properties, coating adhesion, and thermal cycling. Work performed during this study indicates that the molecular adsorber formulation can be applied to aluminum, stainless steel, or other metal substrates that can accept silicate-based coatings. The coating can also function as a thermal- control coating. This adsorber will dramatically reduce the mass and volume restrictions, and is less expensive than the currently used molecular adsorber puck design.

Fabrication and Characterization of Hybrid Organic-Inorganic Electron Extraction Layers for Polymer Solar Cells toward Improved Processing Robustness and Air Stability.

PubMed

Fredj, Donia; Pourcin, Florent; Alkarsifi, Riva; Kilinc, Volkan; Liu, Xianjie; Ben Dkhil, Sadok; Boudjada, Nassira Chniba; Fahlman, Mats; Videlot-Ackermann, Christine; Margeat, Olivier; Ackermann, Jörg; Boujelbene, Mohamed

2018-05-23

Organic-inorganic hybrid materials composed of bismuth and diaminopyridine are studied as novel materials for electron extraction layers in polymer solar cells using regular device structures. The hybrid materials are solution processed on top of two different low band gap polymers (PTB7 or PTB7-Th) as donor materials mixed with fullerene PC 70 BM as the acceptor. The intercalation of the hybrid layer between the photoactive layer and the aluminum cathode leads to solar cells with a power conversion efficiency of 7.8% because of significant improvements in all photovoltaic parameters, that is, short-circuit current density, fill factor, and open-circuit voltage, similar to the reference devices using ZnO as the interfacial layer. However when using thick layers of such hybrid materials for electron extraction, only small losses in photocurrent density are observed in contrast to the reference material ZnO of pronounced losses because of optical spacer effects. Importantly, these hybrid electron extraction layers also strongly improve the device stability in air compared with solar cells processed with ZnO interlayers. Both results underline the high potential of this new class of hybrid materials as electron extraction materials toward robust processing of air stable organic solar cells.

Durable metallized polymer mirror

DOEpatents

Schissel, Paul O.; Kennedy, Cheryl E.; Jorgensen, Gary J.; Shinton, Yvonne D.; Goggin, Rita M.

1994-01-01

A metallized polymer mirror construction having improved durability against delamination and tunneling, comprising: an outer layer of polymeric material; a metal oxide layer underlying the outer layer of polymeric material; a silver reflective layer underneath the metal oxide layer; and a layer of adhesive attaching the silver layer to a substrate.

Interface-engineering additives of poly(oxyethylene tridecyl ether) for low-band gap polymer solar cells consisting of PCDTBT:PCBM₇₀ bulk-heterojunction layers.

PubMed

Huh, Yoon Ho; Park, Byoungchoo

2013-01-14

We herein report on the improved photovoltaic (PV) effects of using a polymer bulk-heterojunction (BHJ) layer that consists of a low-band gap electron donor polymer of poly(N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)) (PCDTBT) and an acceptor of [6,6]-phenyl C₇₁ butyric acid methyl ester (PCBM₇₀), doped with an interface-engineering surfactant additive of poly(oxyethylene tridecyl ether) (PTE). The presence of an interface-engineering additive in the PV layer results in excellent performance; the addition of PTE to a PCDTBT:PCBM₇₀ system produces a power conversion efficiency (PCE) of 6.0%, which is much higher than that of a reference device without the additive (4.9%). We attribute this improvement to an increased charge carrier lifetime, which is likely to be the result of the presence of PTE molecules oriented at the interfaces between the BHJ PV layer and the anode and cathode, as well as at the interfaces between the phase-separated BHJ domains. Our results suggest that the incorporation of the PTE interface-engineering additive in the PCDTBT:PCBM₇₀ PV layer results in a functional composite system that shows considerable promise for use in efficient polymer BHJ PV cells.

Nanostructured biosensors built by layer-by-layer electrostatic assembly of enzyme-coated single-walled carbon nanotubes and redox polymers.

PubMed

Wang, Youdan; Joshi, Pratixa P; Hobbs, Kevin L; Johnson, Matthew B; Schmidtke, David W

2006-11-07

In this study, we describe the construction of glucose biosensors based on an electrostatic layer-by-layer (LBL) technique. Gold electrodes were initially functionalized with negatively charged 11-mercaptoundecanoic acid followed by alternate immersion in solutions of a positively charged redox polymer, poly[(vinylpyridine)Os(bipyridyl)2Cl(2+/3+)], and a negatively charged enzyme, glucose oxidase (GOX), or a GOX solution containing single-walled carbon nanotubes (SWNTs). The LBL assembly of the multilayer films were characterized by UV-vis spectroscopy, ellipsometry, and cyclic voltammetry, while characterization of the single-walled nanotubes was performed with transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. When the GOX solution contained single-walled carbon nanotubes (GOX-SWNTs), the oxidation peak currents during cyclic voltammetry increased 1.4-4.0 times, as compared to films without SWNTs. Similarly the glucose electro-oxidation current also increased (6-17 times) when SWNTs were present. By varying the number of multilayers, the sensitivity of the sensors could be controlled.

Probing adsorption of polyacrylamide-based polymers on anisotropic Basal planes of kaolinite using quartz crystal microbalance.

PubMed

Alagha, Lana; Wang, Shengqun; Yan, Lujie; Xu, Zhenghe; Masliyah, Jacob

2013-03-26

Quartz crystal microbalance with dissipation (QCM-D) was applied to investigate the adsorption characteristics of polyacrylamide-based polymers (PAMs) on anisotropic basal planes of kaolinite. Kaolinite basal planes were differentiated by depositing kaolinite nanoparticles (KNPs) on silica and alumina sensors in solutions of controlled pH values. Adsorption of an in-house synthesized organic-inorganic Al(OH)3-PAM (Al-PAM) as an example of cationic hybrid PAM and a commercially available partially hydrolyzed polyacrylamide (MF1011) as an example of anionic PAM was studied. Cationic Al-PAM was found to adsorb irreversibly and preferentially on tetrahedral silica basal planes of kaolinite. In contrast, anionic MF1011 adsorbed strongly on aluminum-hydroxy basal planes, while its adsorption on tetrahedral silica basal planes was weak and reversible. Adsorption study revealed that both electrostatic attraction and hydrogen-bonding mechanisms contribute to adsorption of PAMs on kaolinite. The adsorbed Al-PAM layer was able to release trapped water overtime and became more compact, while MF1011 film became more dissipative as backbones stretched out from kaolinite surface with minimal overlapping. Experimental results obtained from this study provide clear insights into the phenomenon that governs flocculation-based solid-liquid separation processes using multicomponent flocculants of anionic and cationic nature.

Polymer-Based Surfaces Designed to Reduce Biofilm Formation: From Antimicrobial Polymers to Strategies for Long-Term Applications.

PubMed

Riga, Esther K; Vöhringer, Maria; Widyaya, Vania Tanda; Lienkamp, Karen

2017-10-01

Contact-active antimicrobial polymer surfaces bear cationic charges and kill or deactivate bacteria by interaction with the negatively charged parts of their cell envelope (lipopolysaccharides, peptidoglycan, and membrane lipids). The exact mechanism of this interaction is still under debate. While cationic antimicrobial polymer surfaces can be very useful for short-term applications, they lose their activity once they are contaminated by a sufficiently thick layer of adhering biomolecules or bacterial cell debris. This layer shields incoming bacteria from the antimicrobially active cationic surface moieties. Besides discussing antimicrobial surfaces, this feature article focuses on recent strategies that were developed to overcome the contamination problem. This includes bifunctional materials with simultaneously presented antimicrobial and protein-repellent moieties; polymer surfaces that can be switched from an antimicrobial, cell-attractive to a cell-repellent state; polymer surfaces that can be regenerated by enzyme action; degradable antimicrobial polymers; and antimicrobial polymer surfaces with removable top layers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multi-Layer Coating of Ultrathin Polymer Films on Nanoparticles of Alumina by a Plasma Treatment

DTIC Science & Technology

2001-01-01

Proc. Vol. 635 © 2001 Materials Research Society Multi-Layer Coating of Ultrathin Polymer Films on Nanoparticles of Alumina by a Plasma Treatment Donglu...interconnected organic and inorganic networks results in coatings with a very low permeability for gases and liquids. Hybrid materials are very suitable for... materials consist of a clear alcoholic solution that can easily be processed by classical application techniques such as dipping, spraying, or spin coating

C,N-bipyrazole receptor grafted onto a porous silica surface as a novel adsorbent based polymer hybrid.

PubMed

Radi, Smaail; Attayibat, Ahmed; El-Massaoudi, Mohamed; Bacquet, Maryse; Jodeh, Shehdeh; Warad, Ismail; Al-Showiman, Salim S; Mabkhot, Yahia N

2015-10-01

A simple heterogeneous synthesis of pure adsorbent based polymer hybrid made by condensing a functionalized C,N-bipyrazole with a 3-glycidoxypropyl-trimethoxysilane silylant agent, previously anchored on a silica surface was developed. The formed material (SG2P) was characterized through elemental analysis, FT-IR spectroscopy, (13)C NMR of solid state, scanning electron microscope (SEM), and was studied and evaluated by determination of the surface area using the BET equation, the adsorption and desorption capability using the isotherm of nitrogen and B.J.H. pore sizes. The new material exhibits good thermal stability determined by thermogravimetry curves and good chemical stability was examined in various acidic and buffer solutions (pH 1-7). The binding and adsorption abilities of SG2P were investigated for Hg(2+), Cd(2+), Pb(2+), Zn(2+), K(+), Na(+) and Li(+) cations and compared to the results of classical liquid-liquid extraction with the unbound C,N-bipyrazole compound. The grafting at the surface of silica does not affect complexing properties of the ligand and the SG2P exhibits a high selectivity toward Hg(2+) ion with no complexation being observed towards zinc and alkali metals. The extracted and the complexing cation percentages were determined by atomic absorption measurements. Copyright © 2015 Elsevier B.V. All rights reserved.

Single-layer electroluminescent devices based on fluorene-1H-pyrazolo[3,4-b]quinoxaline co-polymers

NASA Astrophysics Data System (ADS)

Pokladko-Kowar, Monika; Danel, Andrzej; Chacaga, Łukasz

2013-11-01

A fluorene based copolymer was synthesized for electroluminescent application. To the main chain of polymer the nitrogen heterocyclic, 1H-pyrazolo[3,4-b]quinoxaline, unit was introduced. The incorporation of this derivative tuned the emission from the blue to yellow-green one. A simple, single layered device was fabricated with the configuration ITO/PEDOT/co-poly-FLU-PQX/Ca/Mg.

Quantitative fabrication of functional polymer surfaces

NASA Astrophysics Data System (ADS)

Rengifo, Hernan R.

areal density. The approach is based upon synthesis of an alkyne-end-functional diblock copolymer alpha-alkyne-o-Br-poly(tBA- b-MMA). The block copolymer self-assembles to form a bilayer on the substrate and directs alkyne groups to the surface. Azido-functionalized DNA is immobilized on alkyne functionalized substrates by a "click" reaction. The density of immobilized DNA can be quantitatively controlled by varying the parameters used for spin-coating the polymer film or by adjusting the hydrophilicity of the polymer surface underlying the reactive alkyne functional groups. In Chapter 5, Layer by layer (LbL) assembly techniques construct multilayer thin films by sequential deposition of monomolecular layers of organic molecules. One of the drawbacks associated with their use is that monomolecular layers are usually held together by relatively weak forces such as Van der Waals, electrostatic and hydrogen bonding interactions, and can therefore be lacking in mechanical integrity. In this chapter, it is demonstrated that heterobifunctional polymers, functionalized with one azide chain terminus and a protected alkyne group as the other chain terminus, constitute a powerful and versatile means for the covalent layer-by-layer (CLbL) assembly of thin polymer films. Each monomolecular polymer layer is covalently bound to both the preceding and following layers to produce a robust multilayer structure. Because the coupling chemistry used, "click" chemistry, is highly chemoselective, the layering process is virtually independent of the chemical nature of the polymer so that the constitution of each layer can be selected at will. Unlike other layer-by-layer deposition techniques, the layer thickness in CLbL is not equivalent to the diameter of the polymer chain, but is related to the polymer chain length and can be controlled by adjustment of either the polymer molecular weight or the areal density of surface alkyne groups.

Atomic layer deposited oxide films as protective interface layers for integrated graphene transfer

NASA Astrophysics Data System (ADS)

Cabrero-Vilatela, A.; Alexander-Webber, J. A.; Sagade, A. A.; Aria, A. I.; Braeuninger-Weimer, P.; Martin, M.-B.; Weatherup, R. S.; Hofmann, S.

2017-12-01

The transfer of chemical vapour deposited graphene from its parent growth catalyst has become a bottleneck for many of its emerging applications. The sacrificial polymer layers that are typically deposited onto graphene for mechanical support during transfer are challenging to remove completely and hence leave graphene and subsequent device interfaces contaminated. Here, we report on the use of atomic layer deposited (ALD) oxide films as protective interface and support layers during graphene transfer. The method avoids any direct contact of the graphene with polymers and through the use of thicker ALD layers (≥100 nm), polymers can be eliminated from the transfer-process altogether. The ALD film can be kept as a functional device layer, facilitating integrated device manufacturing. We demonstrate back-gated field effect devices based on single-layer graphene transferred with a protective Al2O3 film onto SiO2 that show significantly reduced charge trap and residual carrier densities. We critically discuss the advantages and challenges of processing graphene/ALD bilayer structures.

Dual phase polymer gel electrolyte based on non-woven poly(vinylidenefluoride-co-hexafluoropropylene)–layered clay nanocomposite fibrous membranes for lithium ion batteries

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

Shubha, Nageswaran; Prasanth, Raghavan; Energy Research Institute - NTU

2013-02-15

Graphical abstract: Display Omitted Highlights: ► P(VdF-co-HFP)–clay nanocomposite based electrospun membranes are prepared. ► The membranes are used as polymer gel electrolyte (PGE) in lithium ion batteries. ► The composite PGE shows ionic conductivity of 5.5 mS cm{sup −1} at room temperature. ► Li/PGE/LiFePO{sub 4} cell delivers initial discharge capacity of 160 mAh g{sup −1}. ► The use of prepared electrolyte significantly improved the cell performance. -- Abstract: A new approach for fabricating polymer gel electrolytes (PGEs) based on electrospun poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) incorporated with layered nanoclay has been employed to enhance the ionic conductivity and electrochemical properties of P(VdF-co-HFP) withoutmore » compromising its mechanical strength. The effect of layered nanoclay on properties of membranes has been evaluated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Surface morphology of the membranes has been studied using field-emission scanning electron microscopy (FE-SEM). Polymer gel electrolytes are prepared by soaking the fibrous membrane into 1 M LiPF{sub 6} in EC/DEC. The electrochemical studies show that incorporation of layered nanoclay into the polymer matrix greatly enhanced the ionic conductivity and compatibility with lithium electrodes. The charge–discharge properties and cycling performance of Li/LiFePO{sub 4} cells comprising nanocomposite polymer gel electrolytes have been evaluated at room temperature.« less

Poly(ethylene oxide) surfactant polymers.

PubMed

Vacheethasanee, Katanchalee; Wang, Shuwu; Qiu, Yongxing; Marchant, Roger E

2004-01-01

We report on a series of structurally well-defined surfactant polymers that undergo surface-induced self-assembly on hydrophobic biomaterial surfaces. The surfactant polymers consist of a poly(vinyl amine) backbone with poly(ethylene oxide) and hexanal pendant groups. The poly(vinyl amine) (PVAm) was synthesized by hydrolysis of poly(N-vinyl formamide) following free radical polymerization of N-vinyl formamide. Hexanal and aldehyde-terminated poly(ethylene oxide) (PEO) were simultaneously attached to PVAm via reductive amination. Surfactant polymers with different PEO:hexanal ratios and hydrophilic/hydrophobic balances were prepared, and characterized by FT-IR, 1H-NMR and XPS spectroscopies. Surface active properties at the air/water interface were determined by surface tension measurements. Surface activity at a solid surface/water interface was demonstrated by atomic force microscopy, showing epitaxially molecular alignment for surfactant polymers adsorbed on highly oriented pyrolytic graphite. The surfactant polymers described in this report can be adapted for simple non-covalent surface modification of biomaterials and hydrophobic surfaces to provide highly hydrated interfaces.

Copper and zinc removal from roof runoff: from research to full-scale adsorber systems.

PubMed

Steiner, M; Boller, M

2006-01-01

Large, uncoated copper and zinc roofs cause environmental problems if their runoff is infiltrated into the underground or discharged into receiving waters. Since source control is not always feasible, barrier systems for efficient copper and zinc removal are recommended in Switzerland. During the last few years, research carried out in order to test the performance of GIH-calcite adsorber filters as a barrier system. Adsorption and mass transport processes were assessed and described in a mathematical model. However, this model is not suitable for practical design, because it does not give explicit access to design parameters such as adsorber diameter and adsorber bed depth. Therefore, for e.g. engineers, an easy to use design guideline for GIH-calcite adsorber systems was developed, mainly based on the mathematical model. The core of this guideline is the design of the depth of the GIH-calcite adsorber layer. The depth is calculated by adding up the GIH depth for sorption equilibrium and the depth for the mass transfer zone (MTZ). Additionally, the arrangement of other adsorber system components such as particle separation and retention volume was considered in the guideline. Investigations of a full-scale adsorber confirm the successful application of this newly developed design guideline for the application of GIH-calcite adsorber systems in practice.

Fullerene surfactants and their use in polymer solar cells

DOEpatents

Jen, Kwan-Yue; Yip, Hin-Lap; Li, Chang-Zhi

2015-12-15

Fullerene surfactant compounds useful as interfacial layer in polymer solar cells to enhance solar cell efficiency. Polymer solar cell including a fullerene surfactant-containing interfacial layer intermediate cathode and active layer.

Durable metallized polymer mirror

DOEpatents

Schissel, P.O.; Kennedy, C.E.; Jorgensen, G.J.; Shinton, Y.D.; Goggin, R.M.

1994-11-01

A metallized polymer mirror construction is disclosed having improved durability against delamination and tunneling, comprising: an outer layer of polymeric material; a metal oxide layer underlying the outer layer of polymeric material; a silver reflective layer underneath the metal oxide layer; and a layer of adhesive attaching the silver layer to a substrate. 6 figs.

Evidence of Near Surface Layer Stabilization by Liquid Multilayer Adsorbed Films

NASA Astrophysics Data System (ADS)

Strange, Nicholas; Larese, J. Z.

Molecular adsorption on surfaces is fundamentally important in a variety of scientific and technological processes. Surface adsorption plays a key role in catalysis/catalytic supports, optoelectronic devices, lubrication and adhesion, wetting phenomena, and separations. We present the results of a comprehensive investigation of the first ten members of the homologous series of n-alkanes (methane-decane) adsorbed on the basal plane of hexagonal boron nitride using high-resolution, volumetric adsorption isotherm measurements (more than 30 separate temperatures per molecule). The experimentally determined heats of adsorption vs. carbon chain length follow the well-known ``odd-even'' behavior of the n-alkanes. While this may not be surprising we will illustrate additional potential surface configurations that can lead to an increase in entropy. Potential phase transitions are identified using changes in the 2D-compressibility. In addition, we describe the results of companion molecular dynamics modeling to provide microscopic insight to the wetting behavior as a function of alkane chain length and film thickness. A comparison with the behavior of the same n-alkane set on MgO and graphite will also be included. These studies can serve as the basis for developing accurate, robust models of the potential energy surfaces and can be used for future investigations of the microscopic structure and dynamics of these adsorbed films using neutron/xray diffraction and neutron spectroscopy.

The uranium from seawater program at PNNL: Overview of marine testing, adsorbent characterization, adsorbent durability, adsorbent toxicity, and deployment studies

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

Gill, Gary A.; Kuo, Li -Jung; Janke, Christopher James

The Pacific Northwest National Laboratory's (PNNL) Marine Science Laboratory (MSL) located along the coast of Washington State is evaluating the performance of uranium adsorption materials being developed for seawater extraction under realistic marine conditions with natural seawater. Two types of exposure systems were employed in this program: flow-through columns for testing of fixed beds of individual fibers and pellets and a recirculating water flume for testing of braided adsorbent material. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time, typically 42 to 56 day exposures, to determine the adsorbent capacitymore » and adsorption rate (kinetics). Analysis of uranium and other trace elements collected by the adsorbents was conducted following strong acid digestion of the adsorbent with 50% aqua regia using either Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The ORNL 38H adsorbent had a 56 day adsorption capacity of 3.30 ± 0.68 g U/ kg adsorbent (normalized to a salinity of 35 psu), a saturation adsorption capacity of 4.89 ± 0.83 g U/kg of adsorbent material (normalized to a salinity of 35 psu) and a half-saturation time of 28 10 days. The AF1 adsorbent material had a 56 day adsorption capacity of 3.9 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu), a saturation capacity of 5.4 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu) and a half saturation time of 23 2 days. The ORNL amidoxime-based adsorbent materials are not specific for uranium, but also adsorb other elements from seawater. The major doubly charged cations in seawater (Ca and Mg) account for a majority of the cations adsorbed (61% by mass and 74% by molar percent). For the ORNL AF1 adsorbent material, U is the 4th most abundant element adsorbed by mass and 7th most abundant by molar percentage. Marine testing

The uranium from seawater program at PNNL: Overview of marine testing, adsorbent characterization, adsorbent durability, adsorbent toxicity, and deployment studies

DOE PAGES

Gill, Gary A.; Kuo, Li -Jung; Janke, Christopher James; ...

2016-02-07

The Pacific Northwest National Laboratory's (PNNL) Marine Science Laboratory (MSL) located along the coast of Washington State is evaluating the performance of uranium adsorption materials being developed for seawater extraction under realistic marine conditions with natural seawater. Two types of exposure systems were employed in this program: flow-through columns for testing of fixed beds of individual fibers and pellets and a recirculating water flume for testing of braided adsorbent material. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time, typically 42 to 56 day exposures, to determine the adsorbent capacitymore » and adsorption rate (kinetics). Analysis of uranium and other trace elements collected by the adsorbents was conducted following strong acid digestion of the adsorbent with 50% aqua regia using either Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The ORNL 38H adsorbent had a 56 day adsorption capacity of 3.30 ± 0.68 g U/ kg adsorbent (normalized to a salinity of 35 psu), a saturation adsorption capacity of 4.89 ± 0.83 g U/kg of adsorbent material (normalized to a salinity of 35 psu) and a half-saturation time of 28 10 days. The AF1 adsorbent material had a 56 day adsorption capacity of 3.9 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu), a saturation capacity of 5.4 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu) and a half saturation time of 23 2 days. The ORNL amidoxime-based adsorbent materials are not specific for uranium, but also adsorb other elements from seawater. The major doubly charged cations in seawater (Ca and Mg) account for a majority of the cations adsorbed (61% by mass and 74% by molar percent). For the ORNL AF1 adsorbent material, U is the 4th most abundant element adsorbed by mass and 7th most abundant by molar percentage. Marine testing

Polymer bulk heterojunction solar cells with PEDOT:PSS bilayer structure as hole extraction layer.

PubMed

Kim, Wanjung; Kim, Namhun; Kim, Jung Kyu; Park, Insun; Choi, Yeong Suk; Wang, Dong Hwan; Chae, Heeyeop; Park, Jong Hyeok

2013-06-01

A high current density obtained in a limited, nanometer-thick region is important for high efficiency polymer solar cells (PSCs). The conversion of incident photons to charge carriers only occurs in confined active layers; therefore, charge-carrier extraction from the active layer within the device by using solar light has an important impact on the current density and the related to power conversion efficiency. In this study, we observed a surprising result, that is, extracting the charge carrier generated in the active layer of a PSC device, with a thickness-controlled PEDOT:PSS bilayer that acted as a hole extraction layer (HEL), yielded a dramatically improved power conversion efficiency in two different model systems (P3HT:PC₆₀BM and PCDTBT:PC₇₀BM). To understand this phenomenon, we conducted optical strength simulation, photocurrent-voltage measurements, incident photon to charge carrier efficiency measurements, ultraviolet photoelectron spectroscopy, and AFM studies. The results revealed that approximately 60 nm was the optimum PEDOT:PSS bilayer HEL thickness in PSCs for producing the maximum power conversion efficiency. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymer as an Additive in the Emitting Layer for High-Performance Quantum Dot Light-Emitting Diodes.

PubMed

Liang, Feng; Liu, Yuan; Hu, Yun; Shi, Ying-Li; Liu, Yu-Qiang; Wang, Zhao-Kui; Wang, Xue-Dong; Sun, Bao-Quan; Liao, Liang-Sheng

2017-06-14

A facile but effective method is proposed to improve the performance of quantum dot light-emitting diodes (QLEDs) by incorporating a polymer, poly(9-vinlycarbazole) (PVK), as an additive into the CdSe/CdS/ZnS quantum dot (QD) emitting layer (EML). It is found that the charge balance of the device with the PVK-added EML was greatly improved. In addition, the film morphology of the hole-transporting layer (HTL) which is adjacent to the EML, is substantially improved. The surface roughness of the HTL is reduced from 5.87 to 1.38 nm, which promises a good contact between the HTL and the EML, resulting in low leakage current. With the improved charge balance and morphology, a maximum external quantum efficiency (EQE) of 16.8% corresponding to the current efficiency of 19.0 cd/A is achievable in the red QLEDs. The EQE is 1.6 times as high as that (10.5%) of the reference QLED, comprising a pure QD EML. This work demonstrates that incorporating some polymer molecules into the QD EML as additives could be a facile route toward high-performance QLEDs.

Application of a molecularly imprinted polymer for the extraction of kukoamine a from potato peels.

PubMed

Piletska, Elena V; Burns, Rosemary; Terry, Leon A; Piletsky, Sergey A

2012-01-11

A molecularly imprinted polymer (MIP) for the purification of N(1),N(12)-bis(dihydrocaffeoyl)spermine (kukoamine A) was computationally designed and tested. The properties of the polymer were characterized. The protocol of the solid phase extraction (SPE) of kukoamine A from potato peels was optimized. A HPLC-MS method for the quantification of kukoamine A was developed and used for all optimization studies. The capacity of the MIP in relation to kukoamine A from the potato peels extract was estimated at 54 mg/g of the polymer. The kukoamine A purified from potato extract using MIP was exceptionally pure (≈ 90%). Although the corresponding blank polymer was less selective than the MIP for the extraction of kukoamine A from the potato extract, it was shown that the blank polymer could be effectively used for the purification of the crude synthetic kukoamine (polymer capacity = 80 mg of kukoamine A/g of the adsorbent, kukoamine A purity ≈ 86%). Therefore, selective adsorbents could be computationally designed for other plant products, allowing their purification in quantities that would be sufficient for more detailed studies and potential practical applications.

A report on emergent uranyl binding phenomena by an amidoxime phosphonic acid co-polymer

DOE PAGES

Abney, C. W.; Das, S.; Mayes, R. T.; ...

2016-08-01

Development of technology to harvest the uranium dissolved in seawater would enable access to vast quantities of this critical metal for nuclear power generation. Amidoxime polymers are the most promising platform for achieving this separation, yet design of advanced adsorbents is hindered by uncertainty regarding the uranium binding mode. In this work we use XAFS to investigate the uranium coordination environment in an amidoxime-phosphonic acid copolymer adsorbent. In contrast to the binding mode predicted computationally and from small molecule studies, a cooperative chelating model is favoured, attributable to emergent behavior resulting from inclusion of amidoxime in a polymer. Samples exposedmore » to seawater also display a feature consistent with a 2-oxo-bridged transition metal, suggesting formation of an in situ specific binding site. As a result, these findings challenge long held assumptions and provide new opportunities for the design of advanced adsorbent materials.« less

Interplay of Interfacial Layers and Blend Composition To Reduce Thermal Degradation of Polymer Solar Cells at High Temperature.

PubMed

Ben Dkhil, Sadok; Pfannmöller, Martin; Schröder, Rasmus R; Alkarsifi, Riva; Gaceur, Meriem; Köntges, Wolfgang; Heidari, Hamed; Bals, Sara; Margeat, Olivier; Ackermann, Jörg; Videlot-Ackermann, Christine

2018-01-31

The thermal stability of printed polymer solar cells at elevated temperatures needs to be improved to achieve high-throughput fabrication including annealing steps as well as long-term stability. During device processing, thermal annealing impacts both the organic photoactive layer, and the two interfacial layers make detailed studies of degradation mechanism delicate. A recently identified thermally stable poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl

Dispersing nanoparticles in a polymer film via solvent evaporation

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

Cheng, Shengfeng; Grest, Gary S.

Large-scale molecular dynamics simulations are used to study the dispersion of nanoparticles (NPs) in a polymer film during solvent evaporation. As the solvent evaporates, a dense polymer-rich skin layer forms at the liquid/vapor interface, which is either NP rich or poor depending on the strength of the NP/polymer interaction. When the NPs are strongly wet by the polymer, the NPs accumulate at the interface and form layers. However, when the NPs are only partially wet by the polymer, most NPs are uniformly distributed in the bulk of the polymer film, with the dense skin layer serving as a barrier tomore » prevent the NPs from moving to the interface. Furthermore, our results point to a possible route to employ less favorable NP/polymer interactions and fast solvent evaporation to uniformly disperse NPs in a polymer film, contrary to the common belief that strong NP/polymer attractions are needed to make NPs well dispersed in polymer nanocomposites.« less

Dispersing nanoparticles in a polymer film via solvent evaporation

DOE PAGES

Cheng, Shengfeng; Grest, Gary S.

2016-05-19

Large-scale molecular dynamics simulations are used to study the dispersion of nanoparticles (NPs) in a polymer film during solvent evaporation. As the solvent evaporates, a dense polymer-rich skin layer forms at the liquid/vapor interface, which is either NP rich or poor depending on the strength of the NP/polymer interaction. When the NPs are strongly wet by the polymer, the NPs accumulate at the interface and form layers. However, when the NPs are only partially wet by the polymer, most NPs are uniformly distributed in the bulk of the polymer film, with the dense skin layer serving as a barrier tomore » prevent the NPs from moving to the interface. Furthermore, our results point to a possible route to employ less favorable NP/polymer interactions and fast solvent evaporation to uniformly disperse NPs in a polymer film, contrary to the common belief that strong NP/polymer attractions are needed to make NPs well dispersed in polymer nanocomposites.« less

π-Electron-system-layered polymer: through-space conjugation and properties as a single molecular wire.

PubMed

Morisaki, Yasuhiro; Ueno, Shizue; Saeki, Akinori; Asano, Atsushi; Seki, Shu; Chujo, Yoshiki

2012-04-02

[2.2]Paracyclophane-based through-space conjugated oligomers and polymers were prepared, in which poly(p-arylene-ethynylene) (PAE) units were partially π-stacked and layered, and their properties in the ground state and excited state were investigated in detail. Electronic interactions among PAE units were effective through at least ten units in the ground state. Photoexcited energy transfer occurred from the stacked PAE units to the end-capping PAE moieties. The electrical conductivity of the polymers was estimated using the flash-photolysis time-resolved microwave conductivity (FP-TRMC) method and investigated together with time-dependent density functional theory (TD-DFT) calculations, showing that intramolecular charge carrier mobility through the stacked PAE units was a few tens of percentage larger than through the twisted PAE units. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural properties of buried conducting layers formed by very low energy ion implantation of gold into polymer

NASA Astrophysics Data System (ADS)

Teixeira, F. S.; Salvadori, M. C.; Cattani, M.; Brown, I. G.

2009-09-01

We have investigated the fundamental structural properties of conducting thin films formed by implanting gold ions into polymethylmethacrylate (PMMA) polymer at 49 eV using a repetitively pulsed cathodic arc plasma gun. Transmission electron microscopy images of these composites show that the implanted ions form gold clusters of diameter ˜2-12 nm distributed throughout a shallow, buried layer of average thickness 7 nm, and small angle x-ray scattering (SAXS) reveals the structural properties of the PMMA-gold buried layer. The SAXS data have been interpreted using a theoretical model that accounts for peculiarities of disordered systems.

Unexpected behavior of ultra-thin films of blends of polystyrene/poly(vinyl methyl ether) studied by specific heat spectroscopy

NASA Astrophysics Data System (ADS)

Madkour, Sherif; Szymoniak, Paulina; Schick, Christoph; Schönhals, Andreas

2017-05-01

Specific heat spectroscopy (SHS) employing AC nanochip calorimetry was used to investigate the glassy dynamics of ultra-thin films (thicknesses: 10 nm-340 nm) of a polymer blend, which is miscible in the bulk. In detail, a Poly(vinyl methyl ether) (PVME)/Polystyrene (PS) blend with the composition of 25/75 wt. % was studied. The film thickness was controlled by ellipsometry while the film topography was checked by atomic force microscopy. The results are discussed in the framework of the balance between an adsorbed and a free surface layer on the glassy dynamics. By a self-assembling process, a layer with a reduced mobility is irreversibly adsorbed at the polymer/substrate interface. This layer is discussed employing two different scenarios. In the first approach, it is assumed that a PS-rich layer is adsorbed at the substrate. Whereas in the second approach, a PVME-rich layer is suggested to be formed at the SiO2 substrate. Further, due to the lower surface tension of PVME, with respect to air, a nanometer thick PVME-rich surface layer, with higher molecular mobility, is formed at the polymer/air interface. By measuring the glassy dynamics of the thin films of PVME/PS in dependence on the film thickness, it was shown that down to 30 nm thicknesses, the dynamic Tg of the whole film was strongly influenced by the adsorbed layer yielding a systematic increase in the dynamic Tg with decreasing the film thickness. However, at a thickness of ca. 30 nm, the influence of the mobile surface layer becomes more pronounced. This results in a systematic decrease in Tg with the further decrease of the film thickness, below 30 nm. These results were discussed with respect to thin films of PVME/PS blend with a composition of 50/50 wt. % as well as literature results.

Biomimetic piezoelectric quartz crystal sensor with chloramphenicol-imprinted polymer sensing layer.

PubMed

Ebarvia, Benilda S; Ubando, Isaiah E; Sevilla, Fortunato B

2015-11-01

The measurement of banned antibiotic like chloramphenicol is significant for customer protection and safety. The presence of residual antibiotics in foods and food products of animal origin could pose as health hazards and affect food quality for global acceptance. In this study, the potential of a chloramphenicol sensor based on molecularly imprinted polymer (MIP) coupled with a piezoelectric quartz crystal was explored. The MIP was prepared by precipitation polymerization at 60 °C. Methacrylic acid was used as monomer, trimethylolpropane trimethacrylate (TRIM) as crosslinker, and chloramphenicol as the template. Template removal on the resulting polymer was done by extraction using methanol-acetic acid. Characterization of the MIP and NIP were conducted by spectroscopic and microscopic methods. These further supported the imprinting and rebinding process of chloramphenicol to the polymer matrix. The chloramphenicol sensor was devised by spin-coating onto one side of the 10 MHz AT-cut quartz crystal the MIP suspension in polyvinylchloride-tetrahydrofuran (6:2:1 w/w/v) solution. Optimization of sensor response was performed by varying the type of cross-linker, amount of MIP sensing layer, curing time, and pH. The sensor exhibited good sensitivity of about 73 Hz/log (conc., µg mL(-1)) and good repeatability (rsd<10%). A linear relationship (r(2)=0.9901) between frequency shift and chloramphenicol concentration in the range of 1×10(-6) up to 1×10(-1) µg/mL was obtained. The sensor response was highly selective to chloramphenicol than with other compounds of similar chemical structures. Acceptable percent recovery was obtained for real sample analysis using the sensor. The proposed sensor could be a promising low cost and highly sensitive approach for residual chloramphenicol quantification in food products. Copyright © 2015 Elsevier B.V. All rights reserved.

Layered conductive polymer on nylon membrane templates for high performance, thin-film supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Shi, HaoTian Harvey; Naguib, Hani E.

2016-04-01

Flexible Thin-film Electrochemical Capacitors (ECs) are emerging technology that plays an important role as energy supply for various electronics system for both present era and the future. Intrinsically conductive polymers (ICPs) are promising pseudo-capacitive materials as they feature both good electrical conductivity and high specific capacitance. This study focuses on the construction and characterization of ultra-high surface area porous electrodes based on coating of nano-sized conductive polymer materials on nylon membrane templates. Herein, a novel nano-engineered electrode material based on nylon membranes was presented, which allows the creation of super-capacitor devices that is capable of delivering competitive performance, while maintaining desirable mechanical characteristics. With the formation of a highly conductive network with the polyaniline nano-layer, the electrical conductivity was also increased dramatically to facilitate the charge transfer process. Cyclic voltammetry and specific capacitance results showed promising application of this type of composite materials for future smart textile applications.

Enhancing the performance of green solid-state electric double-layer capacitor incorporated with fumed silica nanoparticles

NASA Astrophysics Data System (ADS)

Chong, Mee Yoke; Numan, Arshid; Liew, Chiam-Wen; Ng, H. M.; Ramesh, K.; Ramesh, S.

2018-06-01

Solid polymer electrolyte (SPE) based on fumed silica nanoparticles as nanofillers, hydroxylethyl cellulose (HEC) as host polymer, magnesium trifluoromethanesulfonate salt and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid is prepared by solution casting technique. The ionic conductivity, interactions of adsorbed ions on the host polymer, structural crystallinity and thermal stability are evaluated by electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Ionic conductivity studies at room temperature reveals that the SPE with 2 wt. % of fumed silica nanoparticles gives the highest conductivity compared to its counterpart. The XRD and FTIR studies confirm the dissolution of salt, ionic liquid and successful incorporation of fumed silica nanoparticles with host polymer. In order to examine the performance of SPEs, electric double-layer capacitor (EDLC) are fabricated by using activated carbon electrodes. EDLC studies demonstrate that SPE incorporated with 2 wt. % fumed silica nanoparticles gives high specific capacitance (25.0 F/g) at a scan rate of 5 mV/s compared to SPE without fumed silica. Additionally, it is able to withstand 71.3% of capacitance from its initial capacitance value over 1600 cycles at a current density of 0.4 A/g.

Epitaxial Growth of Thin Ferroelectric Polymer Films on Graphene Layer for Fully Transparent and Flexible Nonvolatile Memory.

PubMed

Kim, Kang Lib; Lee, Wonho; Hwang, Sun Kak; Joo, Se Hun; Cho, Suk Man; Song, Giyoung; Cho, Sung Hwan; Jeong, Beomjin; Hwang, Ihn; Ahn, Jong-Hyun; Yu, Young-Jun; Shin, Tae Joo; Kwak, Sang Kyu; Kang, Seok Ju; Park, Cheolmin

2016-01-13

Enhancing the device performance of organic memory devices while providing high optical transparency and mechanical flexibility requires an optimized combination of functional materials and smart device architecture design. However, it remains a great challenge to realize fully functional transparent and mechanically durable nonvolatile memory because of the limitations of conventional rigid, opaque metal electrodes. Here, we demonstrate ferroelectric nonvolatile memory devices that use graphene electrodes as the epitaxial growth substrate for crystalline poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) polymer. The strong crystallographic interaction between PVDF-TrFE and graphene results in the orientation of the crystals with distinct symmetry, which is favorable for polarization switching upon the electric field. The epitaxial growth of PVDF-TrFE on a graphene layer thus provides excellent ferroelectric performance with high remnant polarization in metal/ferroelectric polymer/metal devices. Furthermore, a fully transparent and flexible array of ferroelectric field effect transistors was successfully realized by adopting transparent poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] semiconducting polymer.

Optimization of the Energy Level Alignment between the Photoactive Layer and the Cathode Contact Utilizing Solution-Processed Hafnium Acetylacetonate as Buffer Layer for Efficient Polymer Solar Cells.

PubMed

Yu, Lu; Li, Qiuxiang; Shi, Zhenzhen; Liu, Hao; Wang, Yaping; Wang, Fuzhi; Zhang, Bing; Dai, Songyuan; Lin, Jun; Tan, Zhan'ao

2016-01-13

The insertion of an appropriate interfacial buffer layer between the photoactive layer and the contact electrodes makes a great impact on the performance of polymer solar cells (PSCs). Ideal interfacial buffer layers could minimize the interfacial traps and the interfacial barriers caused by the incompatibility between the photoactive layer and the electrodes. In this work, we utilized solution-processed hafnium(IV) acetylacetonate (Hf(acac)4) as an effective cathode buffer layer (CBL) in PSCs to optimize the energy level alignment between the photoactive layer and the cathode contact, with the short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) all simultaneously improved with Hf(acac)4 CBL, leading to enhanced power conversion efficiencies (PCEs). Ultraviolet photoemission spectroscopy (UPS) and scanning Kelvin probe microscopy (SKPM) were performed to confirm that the interfacial dipoles were formed with the same orientation direction as the built-in potential between the photoactive layer and Hf(acac)4 CBL, benefiting the exciton separation and electron transport/extraction. In addition, the optical characteristics and surface morphology of the Hf(acac)4 CBL were also investigated.

Preparation of lysine-decorated polymer-brush-grafted magnetic nanocomposite for the efficient and selective adsorption of organic dye

NASA Astrophysics Data System (ADS)

Jing, Shiyao; Wang, Xin; Tan, Yebang

2018-05-01

A novel magnetic nanocomposite (Lys-PGMA@Fe3O4) containing amphoteric polymer brushes was synthesized by combining surface-initiated atom-transfer radical polymerization and lysine modification. The chemical structure of Lys-PGMA@Fe3O4 was confirmed by multiple methods, such as FT-IR, TGA, elemental analysis. The core-brush morphology was clearly observed by transmission electron microscopy. Lys-PGMA@Fe3O4 was then used to selectively and efficiently adsorb hazardous dyes. Adsorption results showed that Lys-PGMA@Fe3O4 had considerable adsorption capacity (0.54 and 0.85 mmol·g-1 for LY and MEB, respectively) and rapid adsorption rate (within 10 min), which can be attributed to the nanosize and abundant adsorptive polymer brushes. The selective adsorption of a mixture of lemon yellow (pH = 4.0) and methylene blue (pH = 10.0) was achieved through the amphoteric polymer brushes. Similar to traditional adsorbent materials, Lys-PGMA@Fe3O4 also showed easy magnet-assisted separation property. Lys-PGMA@Fe3O4 adsorbent can also be regenerated to reduce application cost. Overall, results demonstrated that Lys-PGMA@Fe3O4 nanocomposite was an excellent adsorbent material for removing dye pollutants from wastewater.

Performance enhancement of polymer electrolyte membrane fuel cells by dual-layered membrane electrode assembly structures with carbon nanotubes.

PubMed

Jung, Dong-Won; Kim, Jun-Ho; Kim, Se-Hoon; Kim, Jun-Bom; Oh, Eun-Suok

2013-05-01

The effect of dual-layered membrane electrode assemblies (d-MEAs) on the performance of a polymer electrolyte membrane fuel cell (PEMFC) was investigated using the following characterization techniques: single cell performance test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). It has been shown that the PEMFC with d-MEAs has better cell performance than that with typical mono-layered MEAs (m-MEAs). In particular, the d-MEA whose inner layer is composed of multi-walled carbon nanotubes (MWCNTs) showed the best fuel cell performance. This is due to the fact that the d-MEAs with MWCNTs have the highest electrochemical surface area and the lowest activation polarization, as observed from the CV and EIS test.

Efficiency enhancement of polymer solar cells by applying poly(vinylpyrrolidone) as a cathode buffer layer via spin coating or self-assembly.

PubMed

Wang, Haitao; Zhang, Wenfeng; Xu, Chenhui; Bi, Xianghong; Chen, Boxue; Yang, Shangfeng

2013-01-01

A non-conjugated polymer poly(vinylpyrrolidone) (PVP) was applied as a new cathode buffer layer in P3HT:PCBM bulk heterojunction polymer solar cells (BHJ-PSCs), by means of either spin coating or self-assembly, resulting in significant efficiency enhancement. For the case of incorporation of PVP by spin coating, power conversion efficiency (PCE) of the ITO/PEDOT:PSS/P3HT:PCBM/PVP/Al BHJ-PSC device (3.90%) is enhanced by 29% under the optimum PVP spin-coating speed of 3000 rpm, which leads to the optimum thickness of PVP layer of ~3 nm. Such an efficiency enhancement is found to be primarily due to the increase of the short-circuit current (J(sc)) (31% enhancement), suggesting that the charge collection increases upon the incorporation of a PVP cathode buffer layer, which originates from the conjunct effects of the formation of a dipole layer between P3HT:PCBM active layer and Al electrodes, the chemical reactions of PVP molecules with Al atoms, and the increase of the roughness of the top Al film. Incorporation of PVP layer by doping PVP directly into the P3HT:PCBM active layer leads to an enhancement of PCE by 13% under the optimum PVP doping ratio of 3%, and this is interpreted by the migration of PVP molecules to the surface of the active layer via self-assembly, resulting in the formation of the PVP cathode buffer layer. While the formation of the PVP cathode buffer layer is fulfilled by both fabrication methods (spin coating and self-assembly), the dependence of the enhancement of the device performance on the thickness of the PVP cathode buffer layer formed by self-assembly or spin coating is different, because of the different aggregation microstructures of the PVP interlayer.

Soy-based Polymers for Surface Modification and Interactions with Lignocellulosic Materials

NASA Astrophysics Data System (ADS)

Salas Araujo, Carlos Luis

-conglycinin was reduced (by 25 and 57 % on silica and cellulose, respectively). Similarly, the addition of 10 mM of 2-mercaptoethanol (a denaturing agent) reduced the mass adsorbed for both proteins. The amounts of 11S and 7S adsorbed on lignin and self-assembled 1-dodecanethiol monolayers were higher when the protein was in the native state if compared to that after chemical denaturation (by using urea and 2-mercaptoethanol). Urea-denatured proteins adsorbed more extensively onto the hydrophobic SAM monolayes. The reduction in water contact angle after protein adsorption (≈40° and 35° for native 11S and 7S, respectively) suggests strong nonspecific interactions between the protein and the substrates, favoring conformational changes at the interface that contribute to exposure and rearrangement of hydrophobic and hydrophilic amino acid residues. The adsorption on polypropylene thin films and nonwovens of different grades of soy proteins in their native as well as thermally-denatured states, including purified glycinin and beta-conglycinin as well as commercial soy flour and isolate was investigated at 25 °C in PBS buffer (pH 7.4). It was found that application of a primer layer of a cationic surfactant, dioctadecyldimethylammonium bromide (DODA) dramatically enhanced protein adsorption, which resulted in fully wettable systems. Fluorescence imaging experiments with tagged proteins confirmed the contribution of a fully-covering layer facilitated by the cationic surfactant pre-treatment. Furthermore, complementary wicking tests indicated that the nonwoven fabrics absorbed a significant amount of water (≈25 times their weight) when the fibers carried pre-adsorbed proteins.

Temperature-responsive polymer-brush constructed on a glass substrate by atom transfer radical polymerization.

PubMed

Kitano, Hiromi; Kondo, Takuya; Suzuki, Hisatomo; Ohno, Kohji

2010-05-15

A polymer brush of 2-(2-methoxyethoxy)ethyl methacrylate (MDM) was prepared by atom transfer radical polymerization (ATRP) using a 11-(2-bromoisobutyroyloxy)undecyl moiety-carrying initiator covalently fixed to a glass substrate. An aqueous solution of the MDM polymer (E-PMDM), which had been prepared for comparison, turned to be opaque above certain temperature (26.2 °C for E-PMDM (M(n,GPC)=1.84×10(4))), which was corresponding to the lower critical solution temperature (LCST) of the polymer. The PMDM polymer brush accumulated on the glass surface also indicated temperature-responsive changes in contact angle of air bubble in the air-in-water system. Furthermore, non-specific adsorption of various proteins (bovine serum albumin (BSA), human immunoglobulin G (IgG) and bovine plasma fibrinogen (BPF)) to the surface of polymer brush on the glass plate was examined by the bicinchoninic acid method. The PMDM brush did not adsorb IgG and BPF significantly below the LCST of the polymer chain, whereas adsorbed a larger amount of the proteins above the LCST. A similar but less significant temperature-responsive adsorption was observed in the case of BSA. These results suggest usability of the temperature-responsive polymer-brushes with pendent ω-methoxy oligo(ethylene glycol) groups to coat various materials for bio-medical applications. Copyright © 2010. Published by Elsevier Inc.

Imaging Fourier transform spectroscopy of the boundary layer plume from laser irradiated polymers and carbon materials

NASA Astrophysics Data System (ADS)

Acosta, Roberto I.

The high-energy laser (HEL) lethality community needs for enhanced laser weapons systems requires a better understanding of a wide variety of emerging threats. In order to reduce the dimensionality of laser-materials interaction it is necessary to develop novel predictive capabilities of these events. The objective is to better understand the fundamentals of laser lethality testing by developing empirical models from hyperspectral imagery, enabling a robust library of experiments for vulnerability assessments. Emissive plumes from laser irradiated fiberglass reinforced polymers (FRP), poly(methyl methacrylate) (PMMA) and porous graphite targets were investigated primarily using a mid-wave infrared (MWIR) imaging Fourier transform spectrometer (FTS). Polymer and graphite targets were irradiated with a continuous wave (cw) fiber lasers. Data was acquired with a spectral resolution of 2 cm-1 and spatial resolution as high as 0.52 mm2 per pixel. Strong emission from H2O, CO, CO2 and hydrocarbons were observed in the MWIR between 1900-4000 cm-1. A single-layer radiative transfer model was developed to estimate spatial maps of temperature and column densities of CO and CO2 from the hyperspectral imagery of the boundary layer plume. The spectral model was used to compute the absorption cross sections of CO and CO2, using spectral line parameters from the high temperature extension of the HITRAN. Also, spatial maps of gas-phase temperature and methyl methacrylate (MMA) concentration were developed from laser irradiated carbon black-pigmented PMMA at irradiances of 4-22 W/cm2. Global kinetics interplay between heterogeneous and homogeneous combustion kinetics are shown from experimental observations at high spatial resolutions. Overall the boundary layer profile at steady-state is consistent with CO being mainly produced at the surface by heterogeneous reactions followed by a rapid homogeneous combustion in the boundary layer towards buoyancy.

Detection of Nisin and Fibrinogen Adsorption on Poly(ethylene Oxide) Coated Polyurethane Surfaces by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)

PubMed Central

Schilke, Karl F.; McGuire, Joseph

2011-01-01

Stable, pendant polyethylene oxide (PEO) layers were formed on medical-grade Pellethane® and Tygon® polyurethane surfaces, by adsorption and gamma-irradiation of PEO-polybutadiene-PEO triblock surfactants. Coated and uncoated polyurethanes were challenged individually or sequentially with nisin (a small polypeptide with antimicrobial activity) and/or fibrinogen, and then analyzed with time-of-flight secondary ion mass spectrometry (TOF-SIMS). Data reduction by robust principal components analysis (PCA) allowed detection of outliers, and distinguished adsorbed nisin and fibrinogen. Fibrinogen-contacted surfaces, with or without nisin, were very similar on uncoated polymer surfaces, consistent with nearly complete displacement or coverage of previously-adsorbed nisin by fibrinogen. In contrast, nisin-loaded PEO layers remained essentially unchanged upon challenge with fibrinogen, suggesting that the adsorbed nisin is stabilized within the pendant PEO layer, while the peptide-loaded PEO layer retains its ability to repel large proteins. Coatings of PEO loaded with therapeutic polypeptides on medical polymers have the potential to be used to produce anti-fouling and biofunctional surfaces for implantable or blood-contacting devices. PMID:21440897

Potassium Niobate Nanolamina: A Promising Adsorbent for Entrapment of Radioactive Cations from Water

PubMed Central

Sun, Jin; Yang, Dongjiang; Sun, Cuihua; Liu, Long; Yang, Shuanglei; (Alec) Jia, Yi; Cai, Rongsheng; Yao, Xiangdong

2014-01-01

Processing and managing radioactive waste is a great challenge worldwide as it is extremely difficult and costly; the radioactive species, cations or anions, leaked into the environment are a serious threat to the health of present and future generations. We report layered potassium niobate (K4Nb6O17) nanolamina as adsorbent to remove toxic Sr2+, Ba2+ and Cs+ cations from wastewater. The results show that K4Nb6O17 nanolamina can permanently confine the toxic cations within the interlayer spacing via a considerable deformation of the metastable layered structure during the ion exchange process. At the same time, the nanolaminar adsorbent exhibits prompt adsorption kinetics, high adsorption capacity and selectivity, and superior acid resistance. These merits make it be a promising material as ion exchanger for the removal of radioactive cations from wastewater. PMID:25472721

Potassium niobate nanolamina: a promising adsorbent for entrapment of radioactive cations from water.

PubMed

Sun, Jin; Yang, Dongjiang; Sun, Cuihua; Liu, Long; Yang, Shuanglei; Alec Jia, Yi; Cai, Rongsheng; Yao, Xiangdong

2014-12-04

Processing and managing radioactive waste is a great challenge worldwide as it is extremely difficult and costly; the radioactive species, cations or anions, leaked into the environment are a serious threat to the health of present and future generations. We report layered potassium niobate (K4Nb6O17) nanolamina as adsorbent to remove toxic Sr(2+), Ba(2+) and Cs(+) cations from wastewater. The results show that K4Nb6O17 nanolamina can permanently confine the toxic cations within the interlayer spacing via a considerable deformation of the metastable layered structure during the ion exchange process. At the same time, the nanolaminar adsorbent exhibits prompt adsorption kinetics, high adsorption capacity and selectivity, and superior acid resistance. These merits make it be a promising material as ion exchanger for the removal of radioactive cations from wastewater.

Hybrid polymer networks as ultra low `k` dielectric layers

DOEpatents

Lewicki, James; Worsley, Marcus A.

2016-02-16

According to one embodiment, a polymeric material includes at least one polydimethylsiloxane (PDMS) polymer, and at least one polyhedral oligomericsilsequioxane (POSS) molecule. According to another embodiment, a method includes providing at least one polydimethylsiloxane (PDMS) polymer, providing at least one polyhedral oligomericsilsequioxane (POSS) molecule, and coupling the at least one PDSM polymer to the at least one POSS molecule to form a hybrid polymeric material.

Structural features of the adsorption layer of pentacene on the graphite surface and the PMMA/graphite hybrid surface

NASA Astrophysics Data System (ADS)

Fadeeva, A. I.; Gorbunov, V. A.; Litunenko, T. A.

2017-08-01

Using the molecular dynamics and the Monte Carlo methods, we have studied the structural features and growth mechanism of the pentacene film on graphite and polymethylmethacrylate /graphite surfaces. Monolayer capacity and molecular area, optimal angles between the pentacene molecules and graphite and PMMA/graphite surfaces as well as the characteristic angles between the neighboring pentacene molecules in the adsorption layer were estimated. It is shown that the orientation of the pentacene molecules in the film is determined by a number of factors, including the surface concentration of the molecules, relief of the surface, presence or absence of the polymer layer and its thickness. The pentacene molecules adsorbed on the graphite surface keep a horizontal position relative to the long axis at any surface coverage/thickness of the film. In the presence of the PMMA layer on the graphite, the increase of the number of pentacene molecules as well as the thickness of the PMMA layer induce the change of molecular orientation from predominantly horizontal to vertical one. The reason for such behavior is supposed to be the roughness of the PMMA surface.

Flexible Strain Sensor Based on Layer-by-Layer Self-Assembled Graphene/Polymer Nanocomposite Membrane and Its Sensing Properties

NASA Astrophysics Data System (ADS)

Zhang, Dongzhi; Jiang, Chuanxing; Tong, Jun; Zong, Xiaoqi; Hu, Wei

2018-04-01

Graphene is a potential building block for next generation electronic devices including field-effect transistors, chemical sensors, and radio frequency switches. Investigations of strain application of graphene-based films have emerged in recent years, but the challenges in synthesis and processing achieving control over its fabrication constitute the main obstacles towards device applications. This work presents an alternative approach, layer-by-layer self-assembly, allowing a controllable fabrication of graphene/polymer film strain sensor on flexible substrates of polyimide with interdigital electrodes. Carboxylated graphene and poly (diallyldimethylammonium chloride) (PDDA) were exploited to form hierarchical nanostructure due to electrostatic action. The morphology and structure of the film were inspected by using scanning electron microscopy, x-ray diffraction and Fourier transform infrared spectroscopy. The strain-sensing properties of the graphene/PDDA film sensor were investigated through tuning micrometer caliper exertion and a PC-assisted piezoresistive measurement system. Experimental result shows that the sensor exhibited not only excellent response and reversibility behavior as a function of deflection, but also good repeatability and acceptable linearity. The strain-sensing mechanism of the proposed sensor was attributed to the electrical resistance change resulted from piezoresistive effect.

Monolayers and multilayers of conjugated polymers as nanosized electronic components.

PubMed

Zotti, Gianni; Vercelli, Barbara; Berlin, Anna

2008-09-01

Conjugated polymers (CPs) are interesting materials for preparing devices based on nanoscopic molecular architectures because they exhibit electrical, electronic, magnetic, and optical properties similar to those of metals or semiconductors while maintaining the flexibility and ease of processing of polymers. The production of well-defined mono- and multilayers of CPs on electrodes with nanometer-scale, one-dimensional resolution remains, however, an important challenge. In this Account, we describe the preparation and conductive properties of nanometer-sized CP molecular structures formed on electrode surfaces--namely, self-assembled monolayer (SAM), brush-type, and self-assembled multilayer CPs--and in combination with gold nanoparticles (AuNPs). We have electrochemically polymerized SAMs of carboxyalkyl-functionalized terthiophenes aligned either perpendicular or parallel to the electrode surface. Anodic coupling of various pyrrole- and thiophene-based monomers in solution with the oligothiophene-based SAMs produced brush-like films. Microcontact printing of these SAMs produced patterns that, after heterocoupling, exhibited large height enhancements, as measured using atomic force microscopy (AFM). We have employed layer-by-layer self-assembly of water-soluble polythiophene-based polyelectrolytes to form self-assembled multilayers. The combination of isostructural polycationic and polyanionic polythiophenes produced layers of chains aligned parallel to the substrate plane. These stable, robust, and dense layers formed with high regularity on the preformed monolayers, with minimal interchain penetration. Infrared reflection/adsorption spectroscopy and X-ray diffraction analyses revealed unprecedented degrees of order. Deposition of soluble polypyrroles produced molecular layers that, when analyzed using a gold-coated AFM tip, formed gold-polymer-gold junctions that were either ohmic or rectifying, depending of the layer sequence. We also describe the electronic

BET, thermal degradation, and FTIR spectras of triazine polyamine polymers.

PubMed

Can, Mustafa

2017-04-01

Here we show effect of the polyamine polymer chain length to BET isotherms. According to IUPAC classification [1], all three polymers are fitting type 1 physical adsorption isotherm with H3 hysteresis (except for EDA having H2 hysteresis). Moreover, TG and TGA analysis of polymers triazine-ethylenediamine (EDA) and triazine-triethylenetetramine (TETA) are provided. Due to the similarities of the structure, main decomposition temperatures are close to each other (between 593 K and 873 K). In order to understand change of FTIR spectra with adsorption and stripping Au(III), fresh, Au(III) adsorbed and recycled spectras of polymers measured. For further discussions about the effect of chain length to adsorption of Au(III) onto triazine polyamine polymer particles "Au (III) Uptake by Triazine Polyamine Polymers: Mechanism, Kinetic and Equilibrium Studies" Can et al. [2] (article in press).

The Uranium from Seawater Program at the Pacific Northwest National Laboratory: Overview of Marine Testing, Adsorbent Characterization, Adsorbent Durability, Adsorbent Toxicity, and Deployment Studies

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

Gill, Gary A.; Kuo, Li-Jung; Janke, Chris J.

The Pacific Northwest National Laboratory’s (PNNL) Marine Science Laboratory (MSL) located along the coast of Washington State is evaluating the performance of uranium adsorption materials being developed for seawater extraction under realistic marine conditions with natural seawater. Two types of exposure systems were employed in this program: flow-through columns for testing of fixed beds of individual fibers and pellets and a recirculating water flume for testing of braided adsorbent material. Testing consists of measurements of the adsorption of uranium and other elements from seawater as a function of time, typically 42 to 56 day exposures, to determine the adsorbent capacitymore » and adsorption rate (kinetics). Analysis of uranium and other trace elements collected by the adsorbents was conducted following strong acid digestion of the adsorbent with 50% aqua regia using either Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) or Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The ORNL 38H adsorbent had a 56 day adsorption capacity of 3.30 ± 0.68 g U/ kg adsorbent (normalized to a salinity of 35 psu), a saturation adsorption capacity of 4.89 ± 0.83 g U/kg of adsorbent material (normalized to a salinity of 35 psu) and a half-saturation time of 28 ± 10 days. The AF1 adsorbent material had a 56 day adsorption capacity of 3.9 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu), a saturation capacity of 5.4 ± 0.2 g U/kg adsorbent material (normalized to a salinity of 35 psu) and a half saturation time of 23 ± 2 days. The ORNL amidoxime-based adsorbent materials are not specific for uranium, but also adsorb other elements from seawater. The major doubly charged cations in seawater (Ca and Mg) account for a majority of the cations adsorbed (61% by mass and 74% by molar percent). For the ORNL AF1 adsorbent material, U is the 4th most abundant element adsorbed by mass and 7th most abundant by molar percentage« less

Water Vapor Permeation of Metal Oxide/Polymer Coated Plastic Films

NASA Astrophysics Data System (ADS)

Numata, Yukihiro; Oya, Toshiyuki; Kuwahara, Mitsuru; Ito, Katsuya

Barrier performance to water vapor permeation of ceramic coated layers deposited on flexible polymer films is of great interest to food packaging, medical device packaging and flat panel display industries. In this study, a new type film in which a ceramic layer is deposited on a polymer coated film was proposed for lower water vapor permeation. It is important how to control interfacial properties between each layer and film for good barrier performance. Several kinds of polymer coated materials were prepared for changing surface free energy of the films before and after depositing the ceramic layer. The ceramic layer, which is composed of mixed material of SiO2 and Al2O3, was adopted under the same conditions. The following results were obtained; 1) Water vapor permeation is not related to the surface energy of polymer coated films, 2) After depositing the ceramic layer, however, a strong correlation is observed between the water vapor permeation and surface free energy. 3) The phenomenon is considered that the polarity of the polymer layers plays a key role in changing the structure of ceramic coated layers.

Structure and rheology of star polymers in confined geometries: a mesoscopic simulation study.

PubMed

Zheng, Feiwo; Goujon, Florent; Mendonça, Ana C F; Malfreyt, Patrice; Tildesley, Dominic J

2015-11-28

Mesoscopic simulations of star polymer melts adsorbed onto solid surfaces are performed using the dissipative particle dynamics (DPD) method. A set of parameters is developed to study the low functionality star polymers under shear. The use of a new bond-angle potential between the arms of the star creates more rigid chains and discriminates between different functionalities at equilibrium, but still allows the polymers to deform appropriately under shear. The rheology of the polymer melts is studied by calculating the kinetic friction and viscosity and there is good agreement with experimental properties of these systems. The study is completed with predictive simulations of star polymer solutions in an athermal solvent.

Atomic layer deposition on polymer fibers and fabrics for multifunctional and electronic textiles

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

Brozena, Alexandra H.; Oldham, Christopher J.; Parsons, Gregory N., E-mail: gnp@ncsu.edu

Textile materials, including woven cotton, polymer knit fabrics, and synthetic nonwoven fiber mats, are being explored as low-cost, flexible, and light-weight platforms for wearable electronic sensing, communication, energy generation, and storage. The natural porosity and high surface area in textiles is also useful for new applications in environmental protection, chemical decontamination, pharmaceutical and chemical manufacturing, catalytic support, tissue regeneration, and others. These applications raise opportunities for new chemistries, chemical processes, biological coupling, and nanodevice systems that can readily combine with textile manufacturing to create new “multifunctional” fabrics. Atomic layer deposition (ALD) has a unique ability to form highly uniform andmore » conformal thin films at low processing temperature on nonuniform high aspect ratio surfaces. Recent research shows how ALD can coat, modify, and otherwise improve polymer fibers and textiles by incorporating new materials for viable electronic and other multifunctional capabilities. This article provides a current overview of the understanding of ALD coating and modification of textiles, including current capabilities and outstanding problems, with the goal of providing a starting point for further research and advances in this field. After a brief introduction to textile materials and current textile treatment methods, the authors discuss unique properties of ALD-coated textiles, followed by a review of recent electronic and multifunctional textiles that use ALD coatings either as direct functional components or as critical nucleation layers for active materials integration. The article concludes with possible future directions for ALD on textiles, including the challenges in materials, manufacturing, and manufacturing integration that must be overcome for ALD to reach its full potential in electronic and other emerging multifunctional textile systems.« less

Polymer brush covalently attached to OH-functionalized mica surface via surface-initiated ATRP: control of grafting density and polymer chain length.

PubMed

Lego, Béatrice; François, Marion; Skene, W G; Giasson, Suzanne

2009-05-05

The controlled grafting density of poly(tert-butyl acrylate) was studied on OH-activated mica substrates via surface-initiated atom-transfer radical polymerization (ATRP). By properly adjusting parameters such as the immobilization reaction time and the concentration of an ATRP initiator, a wide range of initiator surface coverages and hence polymer densities on mica were possible. The covalently immobilized initiator successfully promoted the polymerization of tert-butyl acrylate on mica surfaces. The resulting polymer layer thickness was measured by AFM using a step-height method. Linear relationships of the polymer thickness with respect to the molecular weight of the free polymer and with respect to the monomer conversion were observed, suggesting that ATRP is well controlled and relatively densely end-grafted layers were obtained. The polymer grafting density controlled by adjusting the initiator surface coverage was confirmed by the polymer layer swelling capacity and film thickness measurements.

Insight into the adsorption of PPCPs by porous adsorbents: Effect of the properties of adsorbents and adsorbates.

PubMed

Zhu, Zengyin; Xie, Jiawen; Zhang, Mancheng; Zhou, Qing; Liu, Fuqiang

2016-07-01

Adsorption is an efficient method for removal of pharmaceuticals and personal care products (PPCPs). Magnetic resins are efficient adsorbents for water treatment and exhibit potential for PPCP removal. In this study, the magnetic hypercrosslinked resin Q100 was used for adsorption of PPCPs. The adsorption behavior of this resin was compared with those of two activated carbons, namely, Norit and F400D. Norit exhibited the fastest adsorption kinetics, followed by Q100. Norit featured a honeycomb shape and long-range ordered pore channels, which facilitated the diffusion of PPCPs. Moreover, the large average pore size of Q100 reduced diffusion resistance. The adsorbed amounts of 11 PPCPs on the three adsorbents increased with increasing adsorbate hydrophobicity. For Q100, a significant linear correlation was observed between the adsorption performance for PPCPs and hydrophobicity (logD value) of adsorbates (R(2) = 0.8951); as such, PPCPs with high logD values (>1.69) could be efficiently removed. Compared with those of Norit and F400D, the adsorption performance of Q100 was less affected by humic acid because of the dominant hydrophobic interaction. Furthermore, Q100 showed improved regeneration performance, which renders it promising for PPCP removal in practical applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Mechanical reinforcement and segmental dynamics of polymer nanocomposites

NASA Astrophysics Data System (ADS)

Gong, Shushan

The addition of nanofiller into a polymer matrix will dramatically change the physical properties of polymer. The introduction of nanofiller makes the polymer more applicable in many industries, such as automobile tires, coatings, semiconductors, and packaging. The altered properties are not the simple combination of the characters from the two components. The interactions in polymer nanocomposites play an important role in determining the physical properties. This dissertation focuses on the mechanical properties of polymer nanocomposites (silica/poly-2-vinylpyridine) above their glass transition temperature Tg, as a model for automobile tires, which utilize small silica particles in crosslinked rubber far above Tg. We also investigate the impacts of the interaction between particle filler and polymer matrix on the altered mechanical properties. Dielectric relaxation spectroscopy (DRS) is used to study the glassy bound polymer layers formed around the particles. The results show evidence of the existence of immobilized polymer layers at the surface of each nanoparticle. At the same time, the thickness of the immobilized polymer layers is quantified and formed to be around 2 nm. Then we consider particles with glassy bound polymer layers are bridged together (either rubbery bridge or glassy bridge) by polymer chains and form small clusters. Clusters finally percolate to form a particle-polymer network as loading fraction increases. Rheology is used to study the network formation, and to predict the boundary of rubbery bridge and glassy bridge regimes. The distance between particles determines the type of polymer bridging. The particle spacing larger than Kuhn length makes flexible (rubbery) bridge with rheology described by a flexible Rouse model for percolation. When the spacing is shorter than the Kuhn length (~ 1nm), stiffer bridge forms instead, which is called glassy bridge. The mechanical differences between rubbery bridge and glassy bridge, and the effect of

Normal and frictional interactions of purified human statherin adsorbed on molecularly-smooth solid substrata.

PubMed

Harvey, Neale M; Carpenter, Guy H; Proctor, Gordon B; Klein, Jacob

2011-09-01

Human salivary statherin was purified from parotid saliva and adsorbed to bare hydrophilic (HP) mica and STAI-coated hydrophobic (HB) mica in a series of Surface Force Balance experiments that measured the normal (F(n)) and friction forces (F(s)*) between statherin-coated mica substrata. Readings were taken both in the presence of statherin solution (HP and HB mica) and after rinsing (HP mica). F(n) measurements showed, for both substrata, monotonic steric repulsion that set on at a surface separation D ~20 nm, indicating an adsorbed layer whose unperturbed thickness was ca 10 nm. An additional longer-ranged repulsion, probably of electrostatic double-layer origin, was observed for rinsed surfaces under pure water. Under applied pressures of ~1 MPa, each surface layer was compressed to a thickness of ca 2 nm on both types of substratum, comparable with earlier estimates of the size of the statherin molecule. Friction measurements, in contrast with F(n) observations, were markedly different on the two different substrata: friction coefficients, μ ≡ ∂F(s)*/∂F(n), on the HB substratum (μ ≈ 0.88) were almost an order of magnitude higher than on the HP substratum (μ ≈ 0.09 and 0.12 for unrinsed and rinsed, respectively), and on the HB mica there was a lower dependence of friction on sliding speed than on the HP mica. The observations were attributed to statherin adsorbing to the mica in multimer aggregates, with internal re-arrangement of the protein molecules within the aggregate dependent on the substratum to which the aggregate adsorbed. This internal re-arrangement permitted aggregates to be of similar size on HP and HB mica but to have different internal molecular orientations, thus exposing different moieties to the solution in each case and accounting for the very different friction behaviour.

Epoxy resin reinforced with nanothin polydopamine-coated carbon nanotubes: a study of the interfacial polymer layer thickness

DOE PAGES

Ling, Yang; Li, Weizhen; Wang, Baoyu; ...

2016-03-29

Carbon nanotubes (CNTs) functionalized by a nanothin poly(dopamine) (PDA) layer were produced by a one-pot, nondestructive approach, with direct polymerization of dopamine on the CNT surface. The thickness of the PDA layer can be well-controlled by the reaction time and the proportion of dopamine, and this thickness is found to be the key factor in controlling the dispersion of CNTs and the extent of the interfacial interactions between the CNT@PDA and epoxy resin. SEM results indicated that the dispersion of CNTs in epoxy was improved significantly by coating a nanothin PDA layer onto the CNT surface. In agreeme nt withmore » this finding, the CNTs functionalized with the thinnest PDA layer provided the best mechanical and thermal properties. This result confirmed that a thinner PDA layer could provide optimized interfacial interactions between the CNT@PDA and epoxy matrix and weaken the self-agglomeration of CNTs, which led to an improved effective stress and heat transfer between the CNTs and the polymer matrix.« less

Research on the Changes to the Lipid/Polymer Membrane Used in the Acidic Bitterness Sensor Caused by Preconditioning

PubMed Central

Harada, Yuhei; Noda, Junpei; Yatabe, Rui; Ikezaki, Hidekazu; Toko, Kiyoshi

2016-01-01

A taste sensor that uses lipid/polymer membranes can evaluate aftertastes felt by humans using Change in membrane Potential caused by Adsorption (CPA) measurements. The sensor membrane for evaluating bitterness, which is caused by acidic bitter substances such as iso-alpha acid contained in beer, needs an immersion process in monosodium glutamate (MSG) solution, called “MSG preconditioning”. However, what happens to the lipid/polymer membrane during MSG preconditioning is not clear. Therefore, we carried out three experiments to investigate the changes in the lipid/polymer membrane caused by the MSG preconditioning, i.e., measurements of the taste sensor, measurements of the amount of the bitterness substance adsorbed onto the membrane and measurements of the contact angle of the membrane surface. The CPA values increased as the preconditioning process progressed, and became stable after 3 d of preconditioning. The response potentials to the reference solution showed the same tendency of the CPA value change during the preconditioning period. The contact angle of the lipid/polymer membrane surface decreased after 7 d of MSG preconditioning; in short, the surface of the lipid/polymer membrane became hydrophilic during MSG preconditioning. The amount of adsorbed iso-alpha acid was increased until 5 d preconditioning, and then it decreased. In this study, we revealed that the CPA values increased with the progress of MSG preconditioning in spite of the decrease of the amount of iso-alpha acid adsorbed onto the lipid/polymer membrane, and it was indicated that the CPA values increase because the sensor sensitivity was improved by the MSG preconditioning. PMID:26891299

A two-dimensional layered Cd(II) coordination polymer with a three-dimensional supramolecular architecture incorporating mixed multidentate N- and O-donor ligands.

PubMed

Huang, Qiu-Ying; Su, Ming-Yang; Meng, Xiang-Ru

2015-06-01

The combination of N-heterocyclic and multicarboxylate ligands is a good choice for the construction of metal-organic frameworks. In the title coordination polymer, poly[bis{μ2-1-[(1H-benzimidazol-2-yl)methyl]-1H-tetrazole-κ(2)N(3):N(4)}(μ4-butanedioato-κ(4)O(1):O(1'):O(4):O(4'))(μ2-butanedioato-κ(2)O(1):O(4))dicadmium], [Cd(C4H4O4)(C9H8N6)]n, each Cd(II) ion exhibits an irregular octahedral CdO4N2 coordination geometry and is coordinated by four O atoms from three carboxylate groups of three succinate (butanedioate) ligands and two N atoms from two 1-[(1H-benzimidazol-2-yl)methyl]-1H-tetrazole (bimt) ligands. Cd(II) ions are connected by two kinds of crystallographically independent succinate ligands to generate a two-dimensional layered structure with bimt ligands located on each side of the layer. Adjacent layers are further connected by hydrogen bonding, leading to a three-dimensional supramolecular architecture in the solid state. Thermogravimetric analysis of the title polymer shows that it is stable up to 529 K and then loses weight from 529 to 918 K, corresponding to the decomposition of the bimt ligands and succinate groups. The polymer exhibits a strong fluorescence emission in the solid state at room temperature.

Deformation sensor based on polymer-supported discontinuous graphene multi-layer coatings

NASA Astrophysics Data System (ADS)

Carotenuto, G.; Schiavo, L.; Romeo, V.; Nicolais, L.

2014-05-01

Graphene can be conveniently used in the modification of polymer surfaces. Graphene macromolecules are perfectly transparent to the visible light and electrically conductive, consequently these two properties can be simultaneously provided to polymeric substrates by surface coating with thin graphene layers. In addition, such coating process provides the substrates of: water-repellence, higher surface hardness, low-friction, self-lubrication, gas-barrier properties, and many other functionalities. Polyolefins have a non-polar nature and therefore graphene strongly sticks on their surface. Nano-crystalline graphite can be used as graphene precursor in some chemical processes (e.g., graphite oxide synthesis by the Hummer method), in addition it can be directly applied to the surface of a polyolefin substrate (e.g., polyethylene) to cover it by a thin graphene multilayer. In particular, the nano-crystalline graphite perfectly exfoliate under the application of a combination of shear and friction forces and the produced graphene single-layers perfectly spread and adhere on the polyethylene substrate surface. Such polymeric materials can be used as ITO (indium-tin oxide) substitute and in the fabrication of different electronic devices. Here the fabrication of transparent resistive deformation sensors based on low-density polyethylene films coated by graphene multilayers is described. Such devices are very sensible and show a high reversible and reproducible behavior.

Adsorptive detoxification of fermentation inhibitors in acid pretreated liquor using functionalized polymer designed by molecular simulation.

PubMed

Devendra, Leena P; Pandey, Ashok

2017-11-01

Acid pretreatment is the most common method employed in the lignocellulosic biorefinery leading to the separation of pentose and hexose sugar. The liquor obtained after pretreatment (acid pretreatment liquor or APL) needs to be detoxified prior to fermentation. The aim of this study was to design functional groups on a polymer matrix which are selective in their interaction to inhibitors with little or no specificity to sugars. Molecular modeling was used as a tool to design a suitable adsorbent for selective adsorption of inhibitors from a complex mixture of APL. Phenyl glycine-p-sulfonic acid loaded on chloromethylated polystyrene polymer was designed as an adsorbent for selective interaction with inhibitors. Experimental verification of the selectivity was successfully achieved. The current study provides insights on the adsorptive separation processes at the molecular level by design of specific adsorbent which can be tailor made for the better selectivity of the desired component.

Development and characterization of high refractive index and high scattering acrylate polymer layers

NASA Astrophysics Data System (ADS)

Eiselt, Thomas; Gomard, Guillaume; Preinfalk, Jan; Gleissner, Uwe; Lemmer, Uli; Hanemann, Thomas

2016-04-01

The aim is to develop a polymer layer which has the ability to diffuse light homogeneously and exhibit a high refractive index. The mixtures are containing an acrylate casting resin, benzylmethacrylate, phenanthrene and other additives. Phenanthrene is employed to increase the refractive index. The mixtures are first rheologically characterized and then polymerized with heat and UV radiation. For the refractive index measurements the polymerized samples require a planar surface without air bubbles. To produce flat samples a special construction consisting of a glass plate, a teflon sheet, a silicone ring (PDMS mold), another teflon sheet and another glass plate is developed. Glue clamps are used to fix this construction together. Selected samples have a refractive index of 1.585 at 20°C at a wavelength of 589nm. A master mixture with a high refractive index is taken for further experiments. Nano scaled titanium dioxide is added and dispersed into the master mixture and then spin coated on a glass substrate. These layers are optically characterized. The specular transmission and the overall transmission are measured to investigate the degree of scattering, which is defined as the haze. Most of the presented layers express the expected haze of over 50%.

Uniform Deposition of Protein Incorporated Mineral Layer on Three-Dimensional Porous Polymer Scaffolds

PubMed Central

Segvich, Sharon; Smith, Hayes C.; Luong, Linh N.; Kohn, David H.

2009-01-01

Inorganic–organic hybrid materials designed to facilitate bone tissue regeneration use a calcium phosphate mineral layer to encourage cell adhesion, proliferation, and osteogenic differentiation. Mineral formed on porous materials is often discontinuous through the thickness of the scaffold. This study aimed to uniformly coat the pores of three-dimensional (3D) porous, polymer scaffolds with a bone-like mineral layer in addition to uniformly incorporating a model protein within this mineral layer. A filtration system designed to induce simulated body fluid flow through the interstices of 3D polylactic-co-glycolic acid scaffolds (10-mm diameter × 2-mm thickness) illustrated that a uniform, continuous mineral layer can be precipitated on the pore surfaces of a 3D porous structure within 5 days. MicroCT analysis showed increased mineral volume percent (MV%) (7.86 ± 3.25 MV%, p = 0.029) and continuous mineralization of filtered scaffolds compared with two static control groups (floating, 0.16 ± 0.26 MV% and submerged, 0.20 ± 0.01 MV%). Furthermore, the system was effective in coprecipitating a model protein, bone sialoprotein (BSA), within the mineral layer. A 10-fold increase in BSA incorporation was seen when coprecipitated filtered scaffolds (1308 ± 464 μg) were compared to a submerged static control group (139 ± 45 μg), p < 0.001. Confocal microscopy visually confirmed uniform coprecipitation of BSA throughout the thickness of the filtration scaffolds. The designed system enables 3D mineralization through the thickness of porous materials, and provides the option of including coprecipitated biomolecular cues within the mineral layer. This approach of providing a 3D conductive and osteoinductive environment could be conducive to bone tissue regeneration. PMID:17618505

Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

NASA Astrophysics Data System (ADS)

Qian, L.; Xu, Z.; Teng, F.; Duan, X.-X.; Jin, Z.-S.; Du, Z.-L.; Li, F.-S.; Zheng, M.-J.; Wang, Y.-S.

2007-06-01

Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)- p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

Complete braided adsorbent for marine testing to demonstrate 3g-U/kg-adsorbent

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

Janke, Chris; Yatsandra, Oyola; Mayes, Richard

ORNL has manufactured four braided adsorbents that successfully demonstrated uranium adsorption capacities ranging from 3.0-3.6 g-U/kg-adsorbent in marine testing at PNNL. Four new braided and leno woven fabric adsorbents have also been prepared by ORNL and are currently undergoing marine testing at PNNL.

Nanoclay-Based Solid-Amine Adsorbents for Carbon Dioxide Capture

NASA Astrophysics Data System (ADS)

Roth, Elliot A.

The objective of this research was to develop an efficient, low cost, recyclable solid sorbent for carbon dioxide adsorption from large point sources, such as coal-fired power plants. The current commercial way to adsorb CO 2 is to use a liquid amine or ammonia process. These processes are used in industry in the "sweetening" of natural gas, but liquid based technologies are not economically viable in the adsorption of CO2 from power plants due to the extremely large volume of CO2 and the inherent high regeneration costs of cycling the sorbent. Therefore, one of the main objectives of this research was to develop a novel sorbent that can be cycled and uses very little energy for regeneration. The sorbent developed here is composed of a nanoclay (montmorillonite), commonly used in the production of polymer nanocomposites, grafted with commercially available amines. (3-aminopropyl) trimethoxysilane (APTMS) was chemically grafted to the edge hydroxyl groups of the clay. While another amine, polyethylenimine (PEI), was attached to the surface of the clay by electrostatic interactions. To confirm the attachment of amines to the clay, the samples were characterized using FTIR and the corresponding peaks for amines were observed. The amount of amine loaded onto the support was determined by TGA techniques. The treated clay was initially analyzed for CO2 adsorption in a pure CO 2 stream. The adsorption temperatures that had the highest adsorption capacity were determined to be between 75°C and 100°C for all of the samples tested at atmospheric pressure. The maximum CO2 adsorption capacity observed was with nanoclay treated with both APTMS and PEI at 85°C. In a more realistic flue gas of 10% CO2 and 90% N2, the adsorbents had essentially the same overall CO2 adsorption capacity indicating that the presence of nitrogen did not hinder the adsorption of CO2. Adsorption studies in pure CO2 at room temperature under pressure from 40-300 PSI were also conducted. The average

Thermodynamics of the adsorption of flexible polymers on nanowires

NASA Astrophysics Data System (ADS)

Vogel, Thomas; Gross, Jonathan; Bachmann, Michael

2015-03-01

Generalized-ensemble simulations enable the study of complex adsorption scenarios of a coarse-grained model polymer near an attractive nanostring, representing an ultrathin nanowire. We perform canonical and microcanonical statistical analyses to investigate structural transitions of the polymer and discuss their dependence on the temperature and on model parameters such as effective wire thickness and attraction strength. The result is a complete hyperphase diagram of the polymer phases, whose locations and stability are influenced by the effective material properties of the nanowire and the strength of the thermal fluctuations. Major structural polymer phases in the adsorbed state include compact droplets attached to or wrapping around the wire, and tubelike conformations with triangular pattern that resemble ideal boron nanotubes. The classification of the transitions is performed by microcanonical inflection-point analysis.

Thermodynamics of the adsorption of flexible polymers on nanowires.

PubMed

Vogel, Thomas; Gross, Jonathan; Bachmann, Michael

2015-03-14

Generalized-ensemble simulations enable the study of complex adsorption scenarios of a coarse-grained model polymer near an attractive nanostring, representing an ultrathin nanowire. We perform canonical and microcanonical statistical analyses to investigate structural transitions of the polymer and discuss their dependence on the temperature and on model parameters such as effective wire thickness and attraction strength. The result is a complete hyperphase diagram of the polymer phases, whose locations and stability are influenced by the effective material properties of the nanowire and the strength of the thermal fluctuations. Major structural polymer phases in the adsorbed state include compact droplets attached to or wrapping around the wire, and tubelike conformations with triangular pattern that resemble ideal boron nanotubes. The classification of the transitions is performed by microcanonical inflection-point analysis.

Influence of temperature and molecular structure on ionic liquid solvation layers.

PubMed

Wakeham, Deborah; Hayes, Robert; Warr, Gregory G; Atkin, Rob

2009-04-30

Atomic force microscopy (AFM) force profiling is used to investigate the structure of adsorbed and solvation layers formed on a mica surface by various room temperature ionic liquids (ILs) ethylammonium nitrate (EAN), ethanolammonium nitrate (EtAN), ethylammonium formate (EAF), propylammonium formate (PAF), ethylmethylammonium formate (EMAF), and dimethylethylammonium formate (DMEAF). At least seven layers are observed for EAN at 14 degrees C (melting point 13 degrees C), decreasing as the temperature is increased to 30 degrees C due to thermal energy disrupting solvophobic forces that lead to segregation of cation alkyl tails from the charged ammonium and nitrate moieties. The number and properties of the solvation layers can also be controlled by introducing an alcohol moiety to the cation's alkyl tail (EtAN), or by replacing the nitrate anion with formate (EAF and PAF), even leading to the detection of distinct cation and anion sublayers. Substitution of primary by secondary or tertiary ammonium cations reduces the number of solvation layers formed, and also weakens the cation layer adsorbed onto mica. The observed solvation and adsorbed layer structures are discussed in terms of the intermolecular cohesive forces within the ILs.

In-syringe extraction using dissolvable layered double hydroxide-polymer sponges templated from hierarchically porous coordination polymers.

PubMed

Ghani, Milad; Frizzarin, Rejane M; Maya, Fernando; Cerdà, Víctor

2016-07-01

Herein we report the use of cobalt porous coordination polymers (PCP) as intermediates to prepare advanced extraction media based on layered double hydroxides (LDH) supported on melamine polymer foam. The obtained dissolvable Ni-Co LDH composite sponges can be molded and used as sorbent for the in-syringe solid-phase extraction (SPE) of phenolic acids from fruit juices. The proposed sorbent is obtained due to the surfactant-assisted self-assembly of Co(II)/imidazolate PCPs on commercially available melamine foam, followed by the in situ conversion of the PCP into the final dissolvable LDH coating. Advantageous features for SPE are obtained by using PCPs with hierarchical porosity (HPCPs). The LDH-sponge prepared using intermediate HPCPs (HLDH-sponge) is placed in the headspace of a glass syringe, enabling flow-through extraction followed by analyte elution by the dissolution of the LDH coating in acidic conditions. Three phenolic acids (gallic acid, p-hydroxybenzoic acid and caffeic acid) were extracted and quantified using high performance liquid chromatography. Using a 5mL sample volume, the obtained detection limits were 0.15-0.35μgL(-1). The proposed method for the preparation of HLDH-sponges showed a good reproducibility as observed from the intra- and inter-day RSD's, which were <10% for all analytes. The batch-to-batch reproducibility for three different batches of HLDH-sponges was 10.6-11.2%. Enrichment factors of 15-21 were obtained. The HLDH-sponges were applied satisfactorily to the determination of phenolic acids in natural and commercial fruit juices, obtaining relative recoveries among 89.7-95.3%. Copyright © 2016 Elsevier B.V. All rights reserved.

Transverse thermal depinning and nonlinear sliding friction of an adsorbed monolayer.

PubMed

Granato, E; Ying, S C

2000-12-18

We study the response of an adsorbed monolayer under a driving force as a model of sliding friction phenomena between two crystalline surfaces with a boundary lubrication layer. Using Langevin-dynamics simulation, we determine the nonlinear response in the direction transverse to a high symmetry direction along which the layer is already sliding. We find that below a finite transition temperature there exist a critical depinning force and hysteresis effects in the transverse response in the dynamical state when the adlayer is sliding smoothly along the longitudinal direction.

Rotary adsorbers for continuous bulk separations

DOEpatents

Baker, Frederick S [Oak Ridge, TN

2011-11-08

A rotary adsorber for continuous bulk separations is disclosed. The rotary adsorber includes an adsorption zone in fluid communication with an influent adsorption fluid stream, and a desorption zone in fluid communication with a desorption fluid stream. The fluid streams may be gas streams or liquid streams. The rotary adsorber includes one or more adsorption blocks including adsorbent structure(s). The adsorbent structure adsorbs the target species that is to be separated from the influent fluid stream. The apparatus includes a rotary wheel for moving each adsorption block through the adsorption zone and the desorption zone. A desorption circuit passes an electrical current through the adsorbent structure in the desorption zone to desorb the species from the adsorbent structure. The adsorbent structure may include porous activated carbon fibers aligned with their longitudinal axis essentially parallel to the flow direction of the desorption fluid stream. The adsorbent structure may be an inherently electrically-conductive honeycomb structure.

Planar conjugated polymers containing 9,10-disubstituted phenanthrene units for efficient polymer solar cells.