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Polymer Membrane (polymer + membrane)

Distribution by Scientific Domains

Polymers and Materials Science	57%
Chemistry	42%

Selected Abstracts

Rapid Mass Transport in Mixed Matrix Nanotube/Polymer Membranes,

ADVANCED MATERIALS, Issue 18 2007
A. Gusev
The permeability performance of mixed matrix carbon-nanotube/polymer membranes (see figure) is estimated by using the finite element method. The universal approximation of perfectly permeable nanotubes appears appropriate for predicting the overall rates of single gas solute transport. Based on direct finite element predictions, a set of simple design equations demonstrate that nanotube/polymer membranes can favorably combine the high-flux performance of nanotubes with the intrinsic selectivity of a polymer matrix. [source]

Synthetic Strategies for Controlling the Morphology of Proton Conducting Polymer Membranes,,

FUEL CELLS, Issue 2 2005
Y. Yang
Abstract The nanostructure and morphology of proton conducting polymers is of considerable interest in the search for next generation materials and optimization of existing ones. Synthetic methodologies for tailoring molecular structures that promote nanoscopic phase separation of ionic and non-ionic domains, and the effect of phase separation on parameters such as proton conductivity, are considered. Rather than distinguish proton conducting polymers according to chemical class, they are categorized under sub-headings of random, block, and graft copolymers. The synthetic methodology available to access archetypal polymer structures is dependent on the nature of the monomers and restrictive compared to conventional non-ionic polymer systems. Irrespective of the methodology, ionic aggregation and phase separation are consistently found to play an important role in the proton conductivity of low ion exchange capacity,(IEC) membranes, but less of a role in high IEC membranes. Significant research is required to further develop relationships between polymer architecture, morphology, and electrolytic properties. [source]

Nanotemplating of Biodegradable Polymer Membranes for Constant-Rate Drug Delivery

ADVANCED MATERIALS, Issue 21 2010
Daniel A. Bernards
A nanoporous biodegradable polymer (polycaprolactone) is fabricated utilizing a zinc oxide nanotemplate (see figure). Chemical characterization verifies removal of the template, and preliminary tests on the cytotoxicity demonstrate basic biocompatibility. Diffusion of a model small molecule and a protein are shown to be first and zero order, respectively, indicating these nanoporous membranes may be useful for controlled release of protein-based therapeutics. [source]

The Development of Proton Conducting Polymer Membranes for Fuel Cells Using Sulfonated Carbon Nanofibres

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 3 2008
Fabienne Barroso-Bujans
Abstract This study describes a new strategy to improve the performance of PEMFCs by the addition of S/CNF. The presence of 2.08 vol.-% S/CNF increased the proton conductivity of a S/EPDM by one order of magnitude, which made it comparable to that of Nafion® 117, and without creating an electronic path. Furthermore, the filled membranes showed improved thermal stability and mechanical properties. [source]

Stability Enhancement of All-Solid-State H+ ISEs with Cross-Linked Silicon-Urethane Matrices

ELECTROANALYSIS, Issue 8 2005
Nak-Hyun Kwon
Abstract An all-solid-state hydrogen-ion-selective electrode (ASHISE) was fabricated using the polymer hybrid membrane. Polymer membranes composed of Tecoflex polyurethane (TPU), polyvinyl chloride (PVC), silicon rubber (SR), and additives (KTpClPB, DOA, and TDDA) were cast on a carbon rod. The TPU/SR hybrid membrane exhibited a longer lifetime and a higher sensitivity in the sensing of the H+ ion compared to conventional TPU/PVC and PVC/SR hybrid membranes. Moreover, the addition of SiCl4 to TPU-based matrices enhanced the potentiometric response and ISE stability, due to the chemical bonding between Si and CO in urethane, in which the cross-linking configuration was confirmed by DSC, FT-IR, and XPS experiments. TPU/SR membranes containing SiCl4 were rendered more stable and showed a pH response over a wide range (i.e., pH,2,11.5) with the slope of 60±2,mV/pH for more than four months. The ASHISE exhibited a small interfering potential variation in the wide range of the salt concentration (from 1.0×10,6,M up to 0.1,M). The ASHISE showed a result comparable to a commercial clinical blood analyzer. [source]

Rapid Mass Transport in Mixed Matrix Nanotube/Polymer Membranes,

Quantification of suppression of bitterness using an electronic tongue

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2001
Sou Takagi
Abstract Phospholipids, such as phosphatidic acid, suppress bitter taste without affecting other taste qualities. In the present study, we detected and quantified this suppression effect with an electronic tongue whose transducer is composed of several kinds of lipid/polymer membranes with different characteristics. We measured a phospholipid cocktail and various kinds of taste substances with five basic taste qualities. The responses to quinine hydrochloride and L -tryptophan, which have a bitter taste, were reduced as the phospholipid concentration was increased, and the responses to the other taste substances were not affected by the phospholipids, as with the human sensation test. Furthermore, the change of bitter interisity caused by phospholipid was quantified by principal component analysis and the , scale, which expresses the relationship between taste intensity and taste substance concentration. The results are compared with those of the human sensory test and discussed. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:2042,2048, 2001 [source]

Rapid Mass Transport in Mixed Matrix Nanotube/Polymer Membranes,

Analysis of Simulated Martian Regolith Using an Array of Ion Selective Electrodes

ELECTROANALYSIS, Issue 15-16 2005
Stefan
Abstract A prototype miniature array of polymer membrane and solid state ion selective electrodes was developed for the purpose of performing an in-situ analysis of the soluble ionic species in Martian regolith (soil). The array contains a total of 27 electrodes for K+, Na+, Ca2+, Mg2+, NH, Ba2+, NO, Cl,, and Li+, each in triplicate. Barium electrodes were used to indirectly monitor sulfate through precipitation by the addition of barium chloride while the lithium electrodes served as a reference for the array by having a constant lithium concentration as a background for all solutions. The array was tested with several types of simulants, soils, and sawdust from a Mars meteorite, all with varying salt content, meant to approximate the various hypotheses regarding the ionic composition of the Martian soil. The activities of anions and cations determined with the array were compared to ion chromatography data. [source]

A composite polymer/tricalcium phosphate membrane for guided bone regeneration in maxillofacial surgery

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 5 2001
Anita A. Ignatius
Abstract The aim of the study was the development of a resorbable membrane for guided bone regeneration (GBR) with improved biocompatibility, which should be stiff enough to avoid membrane collapse during bone healing. Combining a bioactive ceramic with a resorbable polymer may improve the biocompatibility and osteoconductivity of resorbable devices. The present article describes the preparation, the mechanical properties, and the in vitro degradation characteristic of a composite membrane made of poly(L, DL-lactide) and ,-tricalcium phosphate in comparison to a membrane made of pure poly(L, DL-lactide). The tensile strength and the elastic modulus as well as the molecular weight of the membranes were measured after in vitro degradation in buffer at 37 °C up to 28 weeks. The initial tensile strength of the composite and the polymer membrane was 37.3 ± 2.4 MPa and 27.7 ± 2.3 MPa and the elastic modulus 3106 ± 108 MPa and 3101 ± 104 MPa, respectively. The mechanical properties remained constant up to 8 weeks and then decreased slowly until week 28. The molecular weight of both membranes decreased steadily from 170,000 D to 30,000 D. It was concluded that the mechanical requirements for a membrane for GBR were fulfilled by the composite membrane. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 564,569, 2001 [source]

Template-Directed Control of Crystal Morphologies

MACROMOLECULAR BIOSCIENCE, Issue 2 2007
Fiona C. Meldrum
Abstract Biominerals are characterised by unique morphologies, and it is a long-term synthetic goal to reproduce these synthetically. We here apply a range of templating routes to investigate whether a fascinating category of biominerals, the single crystals with complex forms, can be produced using simple synthetic methods. Macroporous crystals with sponge-like morphologies identical to that of sea urchin skeletal plates were produced on templating with a sponge-like polymer membrane. Similarly, patterning of individual crystal faces was achieved from the micrometer to nanometer scale through crystallisation on colloidal particle monolayers and patterned polymer thin films. These experiments demonstrate the versatility of a templating approach to producing single crystals with unique morphologies. [source]

Surface Modification of Nafion Membranes Using Atmospheric-Pressure Low-Temperature Plasmas for Electrochemical Applications

PLASMA PROCESSES AND POLYMERS, Issue 4 2008
Jong Hoon Kim
Abstract The surface morphology of a proton-conducting polymer membrane is modified by plasma treatments in view of electrochemical applications. The atmospheric-pressure glow plasmas generated using helium/hydrogen gas mixtures, or helium as the working gas are etching the surfaces very efficiently. The Nafion membranes placed between two dielectric disks undergo morphological, as well as surface chemical structural changes during exposure to the RF powered discharges. The change in the surface morphology depends on the composition of the plasma. The electrochemical cell employing the modified membrane as the electrolyte displays remarkable improvements in registering the current density. [source]

Detecting sub-surface cracking in laminated membranes using infrared imaging

POLYMER COMPOSITES, Issue 6 2001
Thomas J. Mackin
This paper presents a new experimental method that utilizes the thermoelastic effect to detect sub-surface cracks in a laminated polymer membrane. A highly accurate infrared camera is used to measure the thermoelastic and dissipational heat signatures associated with bi-axial fatigue loading of membranes. Changes in these thermal signatures arise whenever cracks form in any layer of the laminate, including fully embedded layers, thereby providing a novel method for experimentally measuring the initiation and growth of damage in sub-surface layers. The proposed method is illustrated using a model 3-layer system of EVOH sandwiched between two polyurethane layers. Bi-axial fatigue loading was used to initiate cracking in the central EVOH layer without damaging the outer polyurethane layers. Cracking in the central layer resulted in a distinct thermal signature that was plainly visible using the proposed method. [source]

Mathematical modeling of reactive transport of anti-tumor drugs through electro-active membranes

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009
Parag Saurabh
Abstract We present a mathematical modeling and design of an implantable polymer membrane-based drug-release device that uses alternate voltage scans across the electro-active membrane for delivery and reactive uptake of anionic anti-tumor drugs. Our mathematical model comprises Poisson,Boltzmann, Nernst,Planck and Diffusion,Reaction equations written for three compartments, namely, the drug reservoir, the polymer membrane and the diseased tissue, with the governing equations for the compartments being linked to each other through the boundary conditions. An analytical solution for the three-compartment model has been obtained using Laplace transforms and residue integration. We use this solution to quantify the various parameters controlling the spatiotemporal dynamics of drug delivery and analyze the efficacy of the reactive transport process for an anionic chemotherapeutic drug, Irinotecan-HCl, commercially also known as CPT-11. We show that a ,smart pill' with optimal drug efficacy may be designed by altering the thickness and the diffusivity of the electro-active membrane, and by tuning the applied voltage and the duration of the positive and the negative voltage scans such that the drug concentration in the tumor tissue is maintained within its therapeutic range. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Poly(vinyl alcohol),polyacrylamide blends with cesium salts of heteropolyacid as a polymer electrolyte for direct methanol fuel cell applications

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
M. Helen
Abstract A class of inorganic,organic hybrid membranes with low methanol permeability characteristics for possible direct methanol fuel cell (DMFC) applications was architected, formulated, and fabricated through the blending of poly(vinyl alcohol) (PVA) and polyacrylamide (PAM) followed by crosslinking with glutaraldehyde (Glu). Cesium salts of different heteropolyacids, including phosphomolybdic acid (PMA), phosphotungstic acid (PWA), and silicotungstic acid (SWA), were incorporated into the polymer network to form corresponding hybrid membrane materials, namely, PVA,PAM,CsPMA,Glu, PVA,PAM,CsPWA,Glu, and PVA,PAM,CsSWA,Glu, respectively (where "Cs" together with a heteropolyacid abbreviation indicates the cesium salt of that acid). All the three hybrid polymer membranes fabricated exhibited excellent swelling, thermal, oxidative, and additive stability properties with desired proton conductivities in the range 10,2 S/cm at 50% relative humidity. A dense network formation was achieved through the blending of PVA and PAM and by crosslinking with Glu, which led to an order of magnitude decrease in the methanol permeability compared to the state-of-the-art commercial Nafion 115 membrane. The hybrid membrane containing CsSWA exhibited a very low methanol permeability (1.4 × 10,8 cm2/s) compared to other membranes containing cesium salt of heteropolyacids such as PMA and PWA. The feasibility of these hybrid membranes as proton-conducting electrolytes in DMFC was investigated, and the preliminary results were compared with those of Nafion 115. The results illustrate the attractive features and suitability of the fabricated hybrid membranes as an electrolyte for DMFC applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Sorption and permeation behavior for CO2 in NH3 -plasma-treated and untreated polystyrene membranes

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007
Y.-S. Yang
Abstract In our preceding work, the simultaneous deviation from the conventional dual-mode sorption and mobility model was observed in a case of CO2 in polystyrene (PS) membrane (glass transition temperature of pure polymer = 95°C) at 60 and 70°C. The plasticization effect of sorbed CO2 on both the sorption and diffusion processes tends to be brought about in glassy polymer membranes near the glass transition temperature. The behavior was simulated based on the concept that only one population of sorbed gas molecules of plasticizing ability to the polymer should exist. In the present work, the sorption and permeation behavior for CO2 in NH3 -plasma-treated and untreated PS membranes at 40°C was investigated, where NH3 -plasma treatment was executed at plasma discharge powers of 40, 80, 120, and 160 W for an exposure time of 2 min. The sorption isotherm could be described by the sorption theory of Mi et al. (Macromolecules 1991, 24, 2361), where the glass transition temperature is depressed by a concentration of sorbed CO2 of plasticizing ability. NH3 -plasma treatment on PS membrane had little influence on the sorption behavior of CO2 at plasma discharge powers up to 160 W. The mean permeability coefficients were somewhat increased only at a discharge power of 160 W. At CO2 pressures below 0.9 MPa, the pressure dependencies of mean permeability coefficients for CO2 in both NH3 -plasma-treated and untreated PS membranes at 40°C could also be simulated on the basis of the concept that only one population of sorbed gas molecules of plasticizing ability should exist. At CO2 pressures above 0.9 MPa, however, a plasticization action of sorbed CO2 had much more influence on the diffusion process rather than on the sorption one, and such a combined concept underestimated the mean permeability coefficient. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1798,1805, 2007 [source]

Solid-supported amphiphilic triblock copolymer membranes grafted from gold surface

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2009
Ekaterina Rakhmatullina
Abstract Gold-supported amphiphilic triblock copolymer brushes composed of two hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) blocks and a hydrophobic poly(n -butyl methacrylate) (PBMA) middle part were synthesized using a surface-initiated ATRP. Attenuated total reflectance Fourier transform infrared spectroscopy, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), ellipsometry, contact angle measurements, and atomic force microscopy were used for the characterization of PHEMA- co -PBMA- co -PHEMA brushes. The PM-IRRAS analysis revealed an increase of the chain tilt toward the gold surface during growth of the individual blocks. We suggest that the orientation of the amphiphilic polymer brushes is influenced by both the chain length and the interchain interactions. Additionally, a detachment of the polymer membranes from the solid support and subsequent gel permeation chromatography analyses allowed us to establish their compositions. We applied block-selective solvents (water and hexane) as well as a good solvent for the whole polymer chain (ethanol) to study the morphology and solvent responsive behavior of the amphiphilic brushes. The presented results could serve as a good starting point for the fabrication of functional solid-supported membranes for biosensing applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1,13, 2009 [source]

Synthesis and Quality Control of Thiol Tagged Compound Libraries for Chemical Microarrays

MOLECULAR INFORMATICS, Issue 11 2006
Sabine Maier
Abstract A method for the synthesis and quality control of compound collections containing reactive thiol functions was developed. Such libraries form the basis for the construction of chemical microarrays to be used in fragment-based screening. Amino-modified polymer membranes fixed into the wells of microtiter plates were used as the solid phase for the nanomole-scale synthesis of a thiol-tagged small molecule library using a spatial one-compound/one-well strategy. A thiolselective Liquid Chromatography-Mass Spectroscopy (LC-MS) protocol of each compound before attachment to the microarray surface was established, allowing an exact determination of compound purity and concentration. The established synthesis and quality control method is an important prerequisite for an accurate read-out of the array compound,target interaction data, and simplifies the usage of small molecule microarrays for low affinity screening. [source]

Permeation of urea through various polyurethane membranes

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2009
Atsushi Watanabe
Abstract BACKGROUND: Controlled-release systems using polymer membranes are very important in agriculture for labour-saving and effective delivery of pesticides and other agents. Polymer-coated granules are one of the most useful formulations, and a study of the factors for polymer design is necessary to achieve various release patterns. A permeation study using plain membranes was carried out in order to clarify parameters, and the results were compared with the release from polymer-coated granules. RESULTS: The permeation coefficient of urea through a plain polyurethane membrane decreased significantly as the urethane and alkyl side chain content increased. The glass transition temperature and crosslink density of the polyurethanes hardly influenced its permeability. The release rate from polyurethane-coated granules was also reduced by alkyl side chains. However, it was faster than that through a plain membrane because of capsule expansion by continuous water penetration and structural changes in the membrane. CONCLUSION: The release rate of urea through a polyurethane plain membrane and from polyurethane-coated granules can be controlled by changing the chemical properties of the membrane. In addition, physical properties such as the glass transition temperature Tg or crosslink density should be considered to assess the release profile from polyurethane-coated granules. Copyright © 2009 Society of Chemical Industry [source]

Generation of Nanopores Down to 10 nm for Use in Deep-Nulling Interferometry

CHEMPHYSCHEM, Issue 2 2008
Axel Wehling Dr.
Abstract Scanning electron microscope images show that it is easy to generate nanopores on polycarbonate membranes with well-defined pore diameters by ion-track perforation and subsequent magnetron sputtering with metal. The size reduction of the nanopores during sputtering with gold is a linear function of time. Images of different angles and from the bottom side of the membrane show that the channels are the smallest very close to the surface of the metal layer, have a conelike shape, and reach about half as much into the polymer membranes as the metal-layer thickness. This topographical pore shape is ideal for use as optically coherent near-field sources in deep-nulling microscopy. We present the first results of significantly improved nulling stabilization in the presence (<2 nm optical pathway difference) and the absence (<0.6 nm optical pathway difference) of the nanoapertures in the focal region of a deep-nulling microscope. [source]