Preparation,optimization, and voltammetric characteristics of poly(o‐phenylenediamine) film as a dopamine‐selective polymeric membrane

Poly(o‐phenylenediamine) films were electrochemically prepared on gold electrodes from the corresponding monomer in an aqueous solution at a constant potential. The polymeric films prepared in this one‐step procedure were found to be thin and insoluble in the aqueous solution. Cyclic and differential pulse voltammetric techniques were used to examine the permeation properties of ascorbic acid and dopamine at the resultant polymeric film electrode. Then, the effects of the chemical and electrochemical variables (e.g., film thickness, polymerization potential, concentrations of monomer and electrolyte) on the permselectivity characteristics of the polymeric film were systematically investigated and the optimal values for each parameter were determined. Furthermore, it was found that the optimized polymer electrode was found to be stable for the successive runs. As a result, it is claimed that poly(o‐phenylenediamine) film can be used as a dopamine‐selective polymeric membrane. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 327–332, 2001     

Preparation and properties of polybenzidine film-coated electrode as an H2O2 selective polymeric material

By means of electrochemical polymerization, polybenzidine-modified electrodes were prepared in an aqueous monomer solution at a potential of 0.7 V versus Ag/AgCl. The permselective character of the polybenzidine electrode prepared in a one-step procedure was examined for electroactive (ascorbic acid, oxalic acid, and hydrogen peroxide) and nonelectroactive (lactose, sucrose, and urea) species. Influence of the various parameters on the permselective properties of the polybenzidine membrane was systematically investigated and the optimal values for these parameters were determined. It has been found that polybenzidine membrane showed selective permeation for hydrogen peroxide while blocking the permeation of electroactive and nonelectroactive interferents through film. In brief, it is claimed that this polybenzidine film can be used as a coating material to prevent interferences in electrochemical biosensor applications. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2227–2234, 1998     

Electrochemical preparation of poly(o‐toluidine) film and its application as a permselective membrane

Poly(o‐toluidine) films were electrochemically synthesized on Pt electrodes at a constant potential (0.75 V versus Ag/AgCl) from a deoxygenated aqueous solution of 0.1M toluidine dissolved in 0.1M KCl. To form permselective polymeric film electrodes, poly(o‐toluidine) films at different thicknesses were prepared by varying the amount of charge consumed during electrochemical polymerization. Then, experimental parameters (e.g., concentrations of monomer and electrolyte and pH of the phosphate buffer salt solution) affecting the polymeric film thickness were optimized. Permeation of the various electroactive and nonelectroactive species such as ascorbic acid, oxalic acid, hydrogen peroxide, lactose, sucrose, and urea through the optimized poly(o‐toluidine)‐coated electrodes was investigated using a chronoamperometric technique. From experimental results, it was found that a poly(o‐toluidine)‐coated electrode permitted the oxidation of hydrogen peroxide and prevented the permeation of the mentioned electroactive and nonelectroactive species. In other words, it was seen that this polymeric electrode responded to only hydrogen peroxide selectively. Thus, it has been claimed that a poly(o‐toluidine)‐coated Pt electrode can be used as a permselective polymeric membrane to overcome interference problems occurring in the hydrogen peroxide‐based biosensor applications. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2141–2146, 1999     

Preparation and electrochemical behavior of dopamine-selective polymeric membrane

Summary o-toluidine was polymerized electrochemically using constant-potential electrolysis at a gold electrode surface. Electrochemical behavior of dopamine and ascorbic acid at the polymer electrode prepared in this manner was examined by cyclic and differential pulse voltammetry techniques. The influence of chemical and electrochemical variables on dopamine selectivity of the polymer electrode was systematically investigated and the optimal values for each parameter were determined. Experimental results showed that optimized polymeric membrane exhibited selectivity for dopamine while blocking ascorbic acid. Therefore, it is claimed that poly (o-toluidine) film can be used as a dopamine-selective polymeric membrane in the presence of ascorbic acid. Key Words: poly (o-toluidine); selective membrane; dopamine Received: 22 November 1999/Revised version: 25 January 2000/Accepted: 10 February 2000     

一种引入CO2选择性吸附硅纳米颗粒提高固定载体膜性能的方法（英文）

Fixed carrier membrane exhibits attractive CO2 permeance and selectivity due to its transport mecha-nism of reaction selectivity (facilitated transport). However, its performance needs improvement to meet cost targets for CO2 capture. This study attempts to develop membranes with multiple permselective mechanisms in order to enhance CO2 separation performance of fixed carrier membrane. In this study, a novel membrane with multiple permselective mechanisms of solubility selectivity and reaction selectivity was developed by incorporating CO2-selective adsorptive silica nanoparticles in situ into the tertiary amine containing polyamide membrane formed by interfacial polymerization (IP). Various techniques were employed to characterize the polyamide and polyam-ide-silica composite membranes. The TGA result shows that nanocomposite membranes exhibit superior thermal stability than pure polyamide membranes. In addition, gas permeation experiments show that both nanocomposite membranes have larger CO2 permeance than pure polyamide membranes. The enhanced CO2/N2 separation per-formance for nanocomposite membranes is mainly due to the thin film thickness, and multiple permselective mechanisms of solubility selectivity and reaction selectivity.     

Structure–property relationships for liquid transport in modified polypropylene membranes

In view of the intensifying interest in the application of polymeric membranes in mixture separation processes, the permeation and permselective properties of polypropylene films toward several candidate organic liquids and vapors were investigated. Polymer films were subjected to solvent and thermal treatments, and the effects of these treatments on film morphology and transport properties were studied. Structure–property relationships for membrane permeation were then developed. Polypropylene films were found to be selective toward toluene, relative to isooctane, and p-xylene relative to o-xylene. Liquid flux rates were found to depend primarily upon the solubility of the permeants in the films and the absolute difference in the solubility parameters of the polymer–liquid pair provided a good basis for correlation of this effect. Considering liquids of closely similar solubility parameters, fluxes were found to be dependent upon the apparent molecular cross sections of the permeants. Films annealed in various organic solvents at temperatures of 60–100°C exhibited enhanced permeability, with up to fifteenfold increase relative to untreated membranes, but with reduced selectivity towards the permeants. A mechanism to account for these effects through consideration of the influence of treating solvent type on polymer morphology is proposed. It postulates the formation of more open or coarser spherulitic structures as a result of recrystallization in the presence of solvent during annealing. The enhanced flux rates in the treated films are attributed to the changes in the spherulite textures and to diminished intercrystalline tie chain constrainment within the spherulitic substructure.     

Development of gallic acid sensors based on polyimide-modified platinum electrode

A series aromatic polyimide (PI) membranes in the form of permselective films was synthesised from different dianhydrides with two diamine monomers for gallic acid (GA) measurement. The obtained PI films were examined by Spectroscopic techniques, Scanning Electron Microscopy (SEM) and thermal analysis techniques and then used to fabricate the selective films on the modified electrode. Because of their excellent film properties, as the permselective polymeric membranes were used for determination of GA in the presence of various interferences and real sample. The PI-1-modified Pt electrode showed a very high R-value (0.9935) and reproducibility for GA determination, as well as high selectivity.     

Preparation and separation properties of polyamide nanofiltration membrane

Utilizing an interfacial polymerization technique for the preparation of a polymeric composite nanofiltration membrane, both high permeation flux of water and high salt rejection can be achieved. Synthesis conditions, such as concentration of monomer, reaction time, and swelling agent, significantly affected the separation performance of composite membranes. The composite polyamide membrane had a permeation rate of ～2–5 gallon/ft²/day (gfd) and a salt rejection rate of ～94–99% when 2000 ppm aqueous salt solution was fed at 200 psi and 25°C. Also, a higher performance nanofiltration membrane could be prepared by suitably swelling the support matrix in the period of polymerization. The results of various feed concentrations showed that permeate flux decreased with increasing salt concentration in the feed solution. This result may be due to concentration polarization on the surface of polyamide membranes. The separation performance of polyamide membranes showed an almost independent relationship with operation pressure until it was up to 200 psi. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1112–1118, 2002     

Synthesis and characterization of N-phenylmaleimide-methylvinylisocyanate copolymers with polystyrene side chains

Summary N-Substitued maleimide-methylvinylisocyanate copolymers with high glass transition temperature (T_g) was prepared and reacted with 4-hydroxy TEMPO (4-hydroxy-2,2,6,6-tetramethyl piperidinoxy) to yield polymers possessing stable radical at the side chain. The resulting polymers behaved as polymeric counter radicals for the radical polymerization of styrene. Thus, stable free radical mediated polymerization at the side chain was achieved. The resulting graft copolymers were characterized by spectral and thermal analysis. Received: 6 October 1999/Revised version: 7 March 2000/Accepted: 7 March 2000     

Plasma-polymerized membranes and gas permeability III

Plasma-polymerized films of hexamethyldisiloxane were deposited onto various porous substrates having different pore sizes, and the gas permeability of these composite membranes was studied. In each membrane, permselectivity between oxygen and nitrogen was found, but the oxygen permeation rate was different with each substance tested. The minimum thickness of the plasma-polymerized film needed to plug all pores and show permselectivity is about five times the pore radius of the porous substrate. The maximum oxygen permeation rates of the permselective composite membranes are approximately proportional to the effective areas for the gas permeation and inversely proportional to the pore sizes. The composite membranes show high oxygen permeation rates in cases using porous glass hollow fibers which have small pore sizes and large surface porosity as porous substrates. In cases using polysulfone hollow fibers which have high permselectivity, the composite membranes show much higher permeability ratios of oxygen-to-nitrogen than do those of the porous glass hollow fibers.     

Pervaporation of ethanol-water mixture by plasma films prepared from hexamethyldisiloxane

The plasma polymerization process was investigated to obtain plasma films like poly(dimethylsiloxane), and the formed films were applied as membranes for pervaporation of ethanol-water solution.

A reaction chamber which had the triode electrode structure for initiation of a glow discharge was provided for preparation of films like poly(dimethylsiloxane) by plasma polymerization. Films plasma-polymerized from hexamethyldisiloxane (HMDSO) resembled poly(dimethylsiloxane) in spectroscopic view and were composed of dimethylsiloxane chains with branches of trimethylsilyl groups. The surface energy for the films was 19.6 mN/m. The films deposited from HMDSO on Nuclepore membrane showed good ethanol-selectivity in pervaporation of ethanol-water solution. The separation factor depended on the film thickness as well as the feed composition. The film-thickness effect was maximized at 34 nm thick, and the separation factor reached 4.5. A model for the separation process using our composite membrane was discussed.     

The variation of cholesteric order during polymerization of the solvent in liquid crystalline solutions

Summary Ethyl-cyanoethyl cellulose [(E-CE)C]/acrylic acid (AA) formed a cholesteric liquid crystalline solution with vivid colors when the concentration is 42–52 wt%. (E-CE)C/polyacrylic acid (PAA) composites with cholesteric structure were prepared by polymerization of the AA in the (E-CE)C/AA liquid crystalline solutions. The layers of ordered polymer chains in the cholesteric phase were inclined during polymerization and the degree of the inclination depended on the polymerization temperature and the concentration of the solution before polymerization. Key words: Cholesteric structure, polymerization, and selective reflection. Received: 19 January 2000/Revised version: 13 March 2000/Accepted: 29 March 2000     

Plasma polymerized membranes and gas permeability. I

Gas permeability of composite membrane prepared by plasma polymerization of various organic compounds was studied. In the membrane, a pinhole-free polymeric thin film was formed on a porous substrate. This film below 0.2 μm in thickness had sufficient mechanical strength for gas separation. The composite membranes were recognized to have high permeability and high permselectivity. Especially, the membranes prepared from hexamethyldisiloxane showed high permeation rate for oxygen, and those prepared from 1-hexene or cyclohexane showed high permselectivity between oxygen and nitrogen. chemical structure of plasma-polymerized film prepared from hexamethyldisiloxane was similar to that of dimethylpolysiloxane with a crosslinking of the polymer. The high permeability and high permselectivity of this film is considered to be due to its structure as mentioned above.     

Plasma polymerized electrolyte membranes and electrodes for miniaturized fuel cells

Miniaturized fuel cells for portable systems like cellular phones, laptops, or other conventionally battery-driven devices, as well as long-term stationary monitoring electronics, have a potential market, especially for direct methanol fuel cells. However, design and fabrication technologies have to be adopted that allow the desired miniaturization of such a fuel cell. Thin film technologies like plasma polymerization and sputtering are suitable techniques for realizing membrane electrode assemblies only several microns in thickness that can be deposited on thin substrates (e.g., silicon wafers, porous foils, or others). Furthermore, plasma polymerized films exhibit a high degree of cross-linkage and are pinhole free even for films of only a few hundred nanometer in thickness, in contrast to conventionally polymerized films. In case of an electrolyte membrane these benefits yield a reduction of membrane resistance and a decreased methanol crossover. We have developed plasma polymerized electrolyte membranes using tetrafluoroethylene to generate the polymeric backbone of an ion-conductive membrane and vinylphosphonic acid to incorporate acid groups, which are responsible for the proton conductivity. Depending on the process parameters these films exhibit an ion conductivity in the range of 100 mS/cm to 200 mS/cm (at 80°C), determined by ac-impedance measurements. These films were optimized with respect to their use in direct methanol fuel cells to achieve a high ion conductivity and high thermal resistance. Porous graphite electrodes were fabricated using an acetylene plasma polymerization process. These films are combined with the plasma polymerized electrolyte membrane to form a thin film membrane electrode assembly.     

PLASMA POLYMERIZED ELECTROLYTE MEMBRANES AND ELECTRODES FOR MINIATURIZED FUEL CELLS

Miniaturized fuel cells for portable systems like cellular phones, laptops, or other conventionally battery-driven devices, as well as long-term stationary monitoring electronics, have a potential market, especially for direct methanol fuel cells. However, design and fabrication technologies have to be adopted that allow the desired miniaturization of such a fuel cell. Thin film technologies like plasma polymerization and sputtering are suitable techniques for realizing membrane electrode assemblies only several microns in thickness that can be deposited on thin substrates (e.g., silicon wafers, porous foils, or others). Furthermore, plasma polymerized films exhibit a high degree of cross-linkage and are pinhole free even for films of only a few hundred nanometer in thickness, in contrast to conventionally polymerized films. In case of an electrolyte membrane these benefits yield a reduction of membrane resistance and a decreased methanol crossover. We have developed plasma polymerized electrolyte membranes using tetrafluoroethylene to generate the polymeric backbone of an ion-conductive membrane and vinylphosphonic acid to incorporate acid groups, which are responsible for the proton conductivity. Depending on the process parameters these films exhibit an ion conductivity in the range of 100 mS/cm to 200 mS/cm (at 80°C), determined by ac-impedance measurements. These films were optimized with respect to their use in direct methanol fuel cells to achieve a high ion conductivity and high thermal resistance. Porous graphite electrodes were fabricated using an acetylene plasma polymerization process. These films are combined with the plasma polymerized electrolyte membrane to form a thin film membrane electrode assembly.     

Poly (3-aminophenol) Film as a Uric Acid-Selective Electrode

In order to prepare uric acid-selective polymeric membrane in the presence of electroactive (ascorbic acid, cysteine, oxalic acid) and nonelectroactive (lactose, sucrose and urea) substances, poly (3-aminophenol) films were prepared by means of electropolymerization on Pt electrodes. By systematically investigating the influence of polymerization conditions on sensor performance of the poly (3-aminophenol) film, the optimal parameters were determined. The voltammetric results showed that polymeric films obtained at the optimized conditions were allowed penetration of large amounts of uric acid (UA) while rejecting ascorbic acid, cysteine and oxalic acid in PBS. Therefore, it has been claimed that the polymeric films could be used as uric acid-selective membrane.     

Surface photografting polymerization of vinyl acetate (VAc), maleic anhydride,and their charge transfer complex. I. VAc(1)

Photografting of vinyl acetate (VAc) onto LDPE films was carried out with lamination technology and simultaneous method, using BP as photoinitiator. Some principal factors affecting the grafting polymerization were investigated in detail. The experimental results showed that oxygen dissolved in monomer solution had great influence on grafting polymerization. Compared with other routine monomers (St, MMA, AN, AA, and AAm), VAc exhibited higher photografting reactivity. It was observed that the reaction temperature affected the graft polymerization markedly. To film samples with a given diameter, there exists optimum thickness of monomer solution. Adding a pertinent amount of water to the photografting polymerization system could accelerate the polymerization. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1513–1521, 2000     

Novel polyphosphazenes containing charge-transporting agent and chromophore as pendant groups

Summary Two novel functionalized polyorganophosphazenes containing charge-transporting agent and electro-optical chromophore as side chains for the photorefractive application are synthesized. The structure characterization was carried out by ¹H-NMR, IR and UV-Visble spectra, gel permeation chromatograply and differential scanning calorimetry. Due to the good flexibility of the backbone and the high degree of functionalization, polyphosphazenes are expected to be a good candidate for photorefractive polymeric materials. Received: 13 March 2000/Revised version: 12 July 2000/Accepted: 24 July 2000     

Inorganic Layers on Polymeric Films – Influence of Defects and Morphology on Barrier Properties

Flexible polymeric films are not only widely used in conventional packaging as substitute for glass and aluminum foil packaging but are also proposed as encapsulation for novel products, like flexible solar cells or organic light‐emitting devices. The two essential properties of the polymeric packaging are flexibility and good permeation barrier properties against gases and vapors. This article deals with vacuum web coating as a common way of increasing barrier properties of polymeric films and the problems related to this procedure. Defects caused by particles and surface imperfections are found to dominate the permeation rate for such coated polymeric films. Atomic force microscopy, electron and also optical microscopy was used for analysis of the coating layer. Three‐dimensional numerical simulations were performed for modeling of the influence of defect size, spacing and film thickness. Results of numerical modeling and of many practical experiments show that the permeability is almost independent of the substrate film thickness when a critical thickness is exceeded. In most cases the defects can be treated as independent of each other. The gas permeability of vacuum web‐coated polymeric films can be quantitatively predicted by a simple formula. For gases, like oxygen, it is shown that a statistic analysis of the defect sizes by optical microscopy is sufficient. For water vapor transmission, however, the structure of the coating layer itself has also to be taken into account.     

Preparation of oxygen gas barrier polypropylene films by deposition of SiOx films plasma‐polymerized from mixture of tetramethoxysilane and oxygen

Silicon oxide (SiOx) film deposition on the surface of oriented poly(propylene) (OPP) films was done to form a new oxygen gas barrier material using plasma polymerization of the tetramethoxysilane (TMOS)/O₂ mixture. The SiOx film deposition on OPP films never improved oxygen gas barrier properties. The inefficacy of the SiOx deposition was due to poor adhesion at the interface between the deposited SiOx and OPP films and also to the formation of cracks in the deposited SiOx film. If prior to the SiOx film deposition surface modification of OPP films was done by a combination of the argon plasma treatment and TMOS coupling treatment, this contributed effectively to strong adhesion leading to success in the SiOx deposition on the OPP film surface, and then the oxygen gas barrier ability was improved. The oxygen permeation rate through the SiOx‐deposited OPP film was decreased from 2230 to 37–52 cm³/m²/day/atm, which was comparable to that of poly(vinylidene chloride), 55 cm³/m²/day/atm at a film thickness of 11 μm. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2389–2397, 2000