Synthesis of microphase‐separated poly(styrene‐co‐sodium styrene sulfonate) membranes using amphiphilic urethane acrylate nonionomers as an reactive compatibilizer

Microphase‐separated poly(styrene‐co‐sodium styrene sulfonate) random copolymer (PSSU) membranes were fabricated through a new copolymerization process. Two immiscible monomers, styrene and sodium styrene sulfonate were dissolved in a single solvent and formed homogeneous solutions, which were directly converted to wall‐to‐wall membranes via radical copolymerization process with microphase separation. Since urethane acrylate nonionomer (UAN) chain has amphiphilicity as well as reactivity with vinyl monomers, UAN chain could act not only as compatibilizer for polystyrene and poly(sodium styrene sulfonate), but also as macrocrosslinker, which makes it possible for the formation of crosslinked copolymer of two immiscible polymers without macrophase separation. TEM image of the PSSU membranes showed that nanosized hydrophilic domains formed by hydrophilic/hydrophobic microphase separation were dispersed at hydrophobic matrix phase. PSSU membranes fabricated using UAN chain having longer chain length of polyethylene oxide showed bigger size of hydrophilic domains, which was also confirmed by TEM images. Fabricated PSSU membranes showed proton conductivity higher than 10^?2 S/cm and methanol permeability lower than 10^?7 cm²/s of Nafion® 117 membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Temperature‐induced volume change and glucose sensitivity of poly[(N‐isopropylacry‐ lamide)‐co‐acrylamide‐co‐(phenylboronic acid)] microgels

Nearly monodisperse glucose‐sensitive poly[(N‐isopropylacrylamide)‐co‐acrylamide‐co‐(phenylboronic acid)] microgels were synthesized in aqueous media by the functionalization of poly[(N‐isopropylacrylamide)‐co‐acrylamide‐co‐(acrylic acid)] microgels with 3‐aminophenylboronic acid via carbodiimide coupling. The glucose‐sensitive and thermosensitive behaviour of the microgels was investigated using a dynamic light scattering technique. The introduction of the hydrophobic phenylboronic acid (PBA) group significantly decreases the temperature at which maximum volume change of the resultant microgel particles is observed. The glucose sensitivity of the PBA‐containing microgels relies on the stabilization of the charged phenylborate ions by binding with glucose, which can convert more hydrophobic PBA groups to the hydrophilic phenylborate ions. The effect of pH, ionic strength and PBA content on temperature‐induced volume change and glucose sensitivity was systemically studied. The effect of NaCl on the glucose sensitivity was also investigated at physiological pH and ionic strength. Copyright © 2011 Society of Chemical Industry     

Self-assembly of cationic rod-like poly(2,5-pyridine) by acidic bis(trifluoromethane)sulfonimide in the hydrated state: A highly-ordered self-assembled protonic conductor

We show that acid-base complexation of rod-like poly(2,5-pyridine) (PPY) by bis(trifluoromethane)sulfonimide (TFSI) leads to highly-ordered lamellar self-assemblies in the hydrated films and shows relatively high room temperature conductivity of ca. 10⁻⁴ S/cm. Thin films with different nominal degrees of complexation were studied using X-ray diffraction, Fourier transform infrared spectroscopy, contact angle measurements, conductivity measurements, and polarised optical microscopy. We propose that the self-assembly is promoted by the amphiphilicity of TFSI and the interplay between the hydrophilic and hydrophobic sites within the complexes. The hydrophilic sites allow confinement of water molecules within the hydrated self-assemblies for low loading of TFSI to promote proton conductivity. For high loading of TFSI in the hydrated state, another coincident self-assembled structure is additionally observed, which we suggest to form due to phase separated water/TFSI domains, as resembling lamellar water/surfactant liquid crystalline phases. The new type of self-assembled acid-base material combining rod-like polymeric cations and ionic liquid anions suggests new routes for ionic and protonic transport and functional materials.     

Sulfonated poly(bis‐A)‐sulfones as proton exchange membranes for direct methanol fuel cell application

Sulfonated poly(bis‐A)‐sulfone (SPSF) samples were prepared by a mild postsulfonation method using trimethylsilyl chlorosulfonate as sulfonation agent, and their thermal and mechanical properties were evaluated. The serials of SPSF membranes are thermally stable up to 450°C in air. When compared with the poly(bis‐A)‐sulfone membrane, the hydrophilicity and water uptake of the SPSF membranes are enhanced. A microphase‐separated structure comprised of hydrophilic and hydrophobic polymer backbone was observed from atomic force microscopy phase images. The hydrophilic ionic clusters become continuous to form channels when ion exchange capacity (IEC) reached 1.47 mequiv/g. Moreover, the membranes showed very good proton conductivities (20°C, 0.01–0.11 S/cm) and low‐methanol permeability (0.09–3.06 × 10^?6 cm²/s), and the methanol diffusion coefficients were lower than that of Nafion112 (1.35 × 10^?6 cm²/s) with IEC values from 0.70 to 1.47 mequiv/g. However, the Fenton's reagent test revealed that the membranes exhibited very poor oxidation stability, which is the main defect limiting the application of SPSF for proton exchange membranes. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Synthesis and properties of sulfonated poly(phosphazene)‐graft‐poly(styrene‐co‐N‐benzylmaleimide) copolymers via atom transfer radical polymerization for proton exchange membrane

A series of sulfonated poly(phosphazene)‐graft‐poly(styrene‐co‐N‐benzylmaleimide) (PP‐g‐PSN) copolymers were prepared via atom transfer radical polymerization (ATRP), followed by regioselective sulfonation which occurred preferentially at the poly(styrene‐co‐N‐benzylmaleimide) sites. The structures of these copolymers were confirmed by Fourier transform infrared (FTIR) spectroscopy, ¹H‐NMR, and ³¹P‐NMR, respectively. The resulting sulfonated PP‐g‐PSN membranes showed high water uptakes (WUs), low water swelling ratios (SWs), low methanol permeability coefficients, and proper proton conductivities. In comparison with non‐grafting sulfonated poly(bis(phenoxy)phosphazene) (SPBPP) membrane previously reported, the present membranes displayed higher proton conductivity, significantly improved the thermal and oxidative stabilities. Transmission electron microscopy (TEM) observation showed clear phase‐separated structures resulting from the difference in polarity between the hydrophobic polyphosphazene backbone and hydrophilic sulfonated poly(styrene‐co‐N‐benzylmaleimide) side chains, indicating effective ionic pathway in these membranes. The results showed that these materials were promising candidate materials for proton exchange membrane (PEM) in direct methanol fuel cell (DMFC) applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42251.     

Molecular modeling studies of polymer electrolytes for power sources

Density functional theory and classical molecular dynamics simulations permit us to elucidate details of ionic and molecular transport useful for the design of polymer electrolyte membranes. We consider two systems of current interest: (a) ionic transport in polyethylene-oxide compared to that in a polyphosphazene membrane targeted to be a good ionic carrier but a bad water carrier and (b) transport of oxygen and protons through hydrated nafion in the vicinity of a catalyst phase.It is shown that in polyphosphazene membranes, nitrogen atoms interact more strongly with lithium ions than ether oxygens do. As a result of the different complexation of Li⁺ with the polymer sites, Li⁺ has a much higher diffusion coefficient in polyphosphazene than in polyethylene oxide electrolyte membranes, with the consequent relevance to lithium-water battery technology.For the hydrated membrane/catalyst interface, our simulations show that the Nafion membrane used in low-temperature fuel cells interacts strongly with the catalytic metal nanoparticles directing the side chain towards the catalyst surface. Results at various degrees of hydration of the membrane illustrate the formation of water clusters surrounding the polymer hydrophilic sites, and reveal how the connectivity of these clusters may determine the transport mechanism of protons and molecular species.     

Influence of chemical compositions on the properties of random and multiblock sulfonated poly(arylene ether sulfone)‐based proton‐exchange membranes

The influence of chemical compositions on the properties of sulfonated poly(arylene ether sulfone)‐based proton‐exchange membranes was studied. First, we synthesized three different series of random SPAES copolymers using three kinds of hydrophobic monomers, including 4,4′‐dihydroxyldiphenylether, 2,6‐dihydroxynaphthalene (DHN), and 4,4′‐hexafluoroisopropylidenediphenol (6F‐BPA) to investigate effects of hydrophobic components on the properties of SPAES membranes as proton‐exchange membranes. Random SPAES copolymers with 6F‐BPA showed the highest proton conductivity while random SPAES copolymers with DHN displayed the lowest methanol permeability among the three random copolymers. Subsequently, we synthesized multiblock SPAES using the DHN as a hydrophobic monomer and studied the effect of the length of hydrophilic segments in the multiblock SPAES copolymers on membrane performance. The results indicated that longer hydrophilic segments in the copolymers led to higher water uptake, proton conductivity, and proton/methanol selectivity of membranes even at low humidity. In addition, the morphology studies (AFM and SAXS measurements) of membranes suggested that multiblock copolymers with long hydrophilic segments resulted in developed phase separation in membranes, and ionic clusters formed more easily, thus improving the membrane performance. Therefore, both the kinds of hydrophobic monomers and the length of hydrophilic segments in SPAES copolymers would influence the membranes performance as proton‐exchange membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Ionically Cross‐Linked Proton Conducting Membranes for Fuel Cells

For improving stability without sacrificing ionic conductivity, ionically cross‐linked proton conducting membranes are fabricated from Na⁺‐form sulfonated poly(phthalazinone ether sulfone kentone) (SPPESK) and H⁺‐formed sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO). Ionically acid‐base cross‐linking between sulfonic acid groups in SPPO and phthalazone groups in SPPESK impart the composite membranes the good miscibility and electrochemical performance. In particular, the composite membranes possess proton conductivity of 60–110 mS cm⁻¹ at 30 °C. By controlling the protonation degree of SPPO within 40–100 %, the composite membranes with favorable cross‐linking degree are qualified for application in fuel cells. The maximum power density of the composite membrane reaches approximately 1100 mW cm⁻² at the current density of 2800 mA cm⁻² at 70 °C.     

A new inhibitor of P(AM‐DMDAAC)/PVA intermacromolecular complex for shale in drilling fluids

A new poly(acrylamide‐dimethyldiallyammonium chloride)/poly(vinyl alcohol) [P(AM‐DMDAAC)/PVA, ADVA] intermacromolecular complex inhibitor of shale‐hydrated swelling was studied for its ability to counter well instability. ADVA exhibited excellent inhibitory performance, and the probable inhibition mechanism was determined. The hydrophilic groups in ADVA adsorbed to montmorillonite (MMT) through hydrogen bonding and cation exchange, and the hydrophobic groups isolated water from MMT. ADVA adhered to the MMT and entered the interlayer instead of water due to the PVA structure. ADVA could also form a thin film and reduce the hydrophilic property of the shale core to prevent water from contacting the shale formation. With the structure of poly(acrylamide‐dimethyldiallyammonium chloride) (AD), the complex adsorbed and bridged MMT to reduce the filtration loss of the basic mud after hot‐rolling. This prevented contact of free water from drilling fluids with the shale formation during the drilling process. With these properties, ADVA demonstrated potential application as an inhibitor for use in drilling fluids. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45584.     

Hydrogels based on poly(ethylene oxide) and poly(tetramethylene oxide) or poly(dimethyl siloxane). II. Physical properties and bacterial adhesion

To investigate the effects of polymer chemistry and topology on physical properties and bacterial adhesion, various hydrogels composed of short hydrophilic [poly(ethylene oxide) (PEO)] and hydrophobic blocks were synthesized by polycondensation reactions. Differential scanning calorimetry and X‐ray diffraction analysis confirmed that all of the hydrogels were strongly phase‐separated due to incompatibility between PEO and hydrophobic blocks such as poly(tetramethylene oxide) (PTMO) and poly(dimethyl siloxane) (PDMS). The crystallization of PEO in the hydrogels was enhanced by the incorporation of longer PEO chains, the adoption of PDMS as a hydrophobic block, and the grafting of monomethoxy poly(ethylene oxide) (MPEO). Compared to Pellethane, the control polymer, the hydrogels exhibited higher Young's moduli and elongations at break, which was attributed to the crystalline domains of PEO and the flexible characteristics of the hydrophobic blocks. The mechanical properties of the hydrogels, however, significantly deteriorated when they were hydrated in distilled water; this was primarily ascribed to the disappearance of PEO crystallity. The water capacity of hydrogels at 37°C in phosphate‐buffered saline (PBS) (pH = 7.4) was dominantly dependant on PEO content, which also influenced the thermonegative swelling behavior. From the bacterial adhesion tests, it was evident that both S. epidermidis and E. coli adhered to Pellethane much greater than to the hydrogels, regardless of the preadsorption of albumin. Better resistance to bacterial adhesion was observed in hydrogels with longer PEO chains, with PTMO as a hydrophobic block, and with MPEO grafts. The least bacterial adhesion for both species was achieved on MPEO_2k–PTMO, a hydrogel with MPEO grafts. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1505–1514, 2003     

Vesicular and micellar self‐assembly of stimuli‐responsive poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) amphiphilic diblock copolymers

Dually responsive amphiphilic diblock copolymers consisting of hydrophilic poly(N‐isopropyl acrylamide) [poly(NIPAAm)] and hydrophobic poly(9‐anthracene methyl methacrylate) were synthesized by reversible addition fragmentation chain‐transfer (RAFT) polymerization with 3‐(benzyl sulfanyl thiocarbonyl sulfanyl) propionic acid as a chain‐transfer agent. In the first step, the poly(NIPAAm) chain was grown to make a macro‐RAFT agent, and in the second step, the chain was extended by hydrophobic 9‐anthryl methyl methacrylate to yield amphiphilic poly(N‐isopropyl acrylamide‐b‐9‐anthracene methyl methacrylate) block copolymers. The formation of copolymers with three different hydrophobic block lengths and a fixed hydrophilic block was confirmed from their molecular weights. The self‐assembly of these copolymers was studied through the determination of the lower critical solution temperature and critical micelle concentration of the copolymers in aqueous solution. The self‐assembled block copolymers displayed vesicular morphology in the case of the small hydrophobic chain, but the morphology gradually turned into a micellar type when the hydrophobic chain length was increased. The variations in the length and chemical composition of the blocks allowed the tuning of the block copolymer responsiveness toward both the pH and temperature. The resulting self‐assembled structures underwent thermally induced and pH‐induced morphological transitions from vesicles to micelles and vice versa in aqueous solution. These dually responsive amphiphilic diblock copolymers have potential applications in the encapsulation of both hydrophobic and hydrophilic drug molecules, as evidenced from the dye encapsulation studies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46474.     

Control of morphology of sulfonated syndio‐polystyrene membranes through constraints imposed by siloxane networks

The incorporation of siloxane networks in sulfonated polystyrene membranes by the sol‐gel process was used to explore the possibility of developing low cost membrane for direct methanol fuel cells. A precursor solution of a hydrophobic siloxane network was allowed to diffuse and react into sulfonated syndio‐polystyrene ionomeric membranes. The organic‐inorganic hybrid domains so produced were able to reduce considerably the swelling of the ionomeric polymer in water, thereby increasing the dimensional stability of membranes. The physical and chemical properties of the sulfonated and hybrids membranes were examined by thermogravimetric analysis (TGA), infrared spectroscopy (FTIR) and small angle X‐ray scattering (SAXS) analysis. The water uptake and the ionic conductivity were also evaluated at temperatures up to 60° C. It was found that both the unmodified sulfonated membranes and the corresponding hybrid exhibited a two‐phase morphology, consisting of crystalline lamellar domains embedded in the amorphous ionomeric polymer, featuring segregated hydrophobic/hydrophilic domains with characteristic separation lengths ranging between 3.9 and 1.7 nm. The presence of inorganic domains not only increased the dimensional stability of the membrane, by reducing the water uptake, but also decreased the rate of methanol crossover. Furthermore it was found that the inorganic network stabilizes the membrane morphology, enhancing the retention of proton conductivity after aging in water. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Controlled co‐delivery of hydrophilic and hydrophobic drugs from thermosensitive and crystallizable copolymer nanoparticles

Functionalized amphiphilic block copolymers poly(N‐isopropyl acrylamide)‐b‐poly(stearyl methacrylate) (PNIPAM‐PSMA) are synthesized. Their self‐assembled core‐shell nanoparticles have the hydrophilic thermosensitive shell and hydrophobic crystallizable core. Nanoparticles exhibit volume phase transition at temperature of 38 °C and its poly(stearyl methacrylate) (PSMA) moiety could form nano size crystals to retain drugs, making them good carriers for drug co‐delivery system. Thermosensitivity and crystallinity of nanoparticles are characterized with dynamic light scattering (DLS), differential scanning calorimetry (DSC), small‐angle X‐ray scattering (SAXS), and atomic force microscopy (AFM). The interactions and relationship between chemical structures of copolymer nanoparticles and loading drugs are discussed. Different loading techniques and combined loading of hydrophobic/hydrophilic drugs are studied. Nanoparticles show a good and controllable drug loading capacity (DL) of hydrophilic/hydrophobic drugs. The drugs release kinetics is analyzed with Fick's law and Weibull model. A general method for analyzing drug release kinetics from nanoparticles is proposed. Weibull model is well fitted and the parameters with definite physical meaning are analyzed. PNIPAM‐PSMA nanoparticles show a quite different thermal response, temporal regulation, and sustained release effect of hydrophilic and hydrophobic drugs, suggesting a promising application in extended and controlled co‐delivery system of multi‐drug. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44132.     

Permeation of urea and water through sulfonated poly(styrene-isobutylene-styrene) membranes with counterion substitution

This study describes the influence of counterion substitution on the transport of urea and water through sulfonated poly(styrene-isobutylene-styrene) (SIBS) membranes. SIBS was sulfonated to 66.4% to allow for enough ionic domains to transport urea and water through the membrane. Counterions, including alkyl-substituted ammonium ions, influenced the ionic domains creating a selective barrier that hindered the transport of urea and water through SIBS. Permeability measurements demonstrated that counterion substitution significantly affected the transport of urea. Membranes with higher charge counterions exhibited a more pronounced reduction in permeability due to the formation of crosslinks and increased restriction on molecular diffusion. Membranes substituted with ammonium salts showed reduced permeability due to the alkyl chains' hydrophobic nature, which created a physical barrier against the passage of urea molecules. Pure water flux tests indicated that counterion substitution also reduced the water flux of the membranes. Membranes with +1 counterions showed a small reduction in the water flux, while membranes with higher charge counterions and alkyl chain substitutions exhibited larger reductions, highlighting the influence of crosslinking and hydrophobicity on water transport.     

Biocomposite proton‐exchange membrane electrolytes for direct methanol fuel cells

Poly(vinyl alcohol) (PVA)‐amino acid (AA) biocomposite membranes are prepared by blending PVA with AAs such as glycine, lysine (LY), and phenyl alanine followed by in situ crosslinking with citric acid (CA) and explored as a new class of biocomposite membrane electrolytes for direct methanol fuel cells (DMFCs). CA crosslinks with PVA through esterification offers adequate chemical, thermal, and morphological stability thereby produces methanol‐obstructing close‐packed polymeric network. These biocomposite membranes are characterized in terms of mechanical, thermal, sorption, and proton‐conducting properties. Hydrophilic nature of AA zwitterions significantly facilitates proton conduction and CA crosslinking mitigates methanol crossover through establishing appropriate balance between hydrophilic/hydrophobic domains. The rational design of membrane microstructure with proper arrangement of hydrophobic/hydrophilic domains is a key to enhance electrochemical selectivity of PVA‐AA/CA biocomposite membranes. Biocomposite membrane comprising LY exhibits nearly threefold higher electrochemical selectivity in relation to PVA/CA blend membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43514.     

Partial crosslinking method for poly(2,6‐dimethyl‐1,4‐phenylene oxide)–poly(vinyl alcohol) membranes to obtain optimized stability and permeability

A partial crosslinking method was developed to modify hydrophilic membranes. The membrane was sandwiched between two porous plates to protect part of the areas, then immersed into a crosslinking solution such as glutaraldehyde, and finally, set free from the plates. The protected and unprotected areas were alternatively distributed to form a heterogeneous membrane. The unprotected areas were crosslinked to enhance the membrane stability, whereas the protected areas retained their original permeability. Three types of hydrophilic base membranes were selected and prepared from poly(2,6‐dimethyl‐1,4‐phenylene oxide) and poly(vinyl alcohol). The base membranes were partially crosslinked (5.56% of the direct area with enlarged areas) to investigate their stability and diffusion dialysis (DD) performances. The partially crosslinked membranes had remarkably reduced water uptake and swelling degrees compared with the base membranes (72.4–250.4 vs 178.2%–544.4% and 94.0%–408.0% vs. 163.8%–814.8%). Meanwhile, the membranes still retained high DD performances for separating HCl–FeCl₂ or NaOH–NaAlO₂ solutions. The dialysis coefficients of HCl and NaOH were much higher than those of the fully crosslinked membranes (0.0209 vs. 0.0109 m/h and 0.0059–0.0085 vs. 0.0017–0.0022 m/h). Hence, partial crosslinking was effective in optimizing the membrane hydrophilicity and permeability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45305.     

Morphology of sulfonated polyarylenethioethersulfone random copolymer series as proton exchange fuel cells membranes by small angle neutron scattering

Sulfonated polyarylenethioethersulfone (SPTES) copolymers with high proton conductivity (100-215 mS/cm at 65 °C, 85% relative humidity) are promising potential proton exchange membrane (PEM) for fuel cells. Small angle neutron scattering (SANS) of the hydrated SPTES copolymer membranes at 25 °C exhibit a nanostructure which can be approximated by correlated polydisperse spherical aggregates containing water molecules with liquid-like ordering (Percus Yevick approximation) and large scale water pockets. The ionic domain radius and the volume packing density of the aggregates present in the hydrated SPTES copolymer membranes at 25 °C increased with increasing degree of sulfonation. SPTES-80 with highest degree of sulfonation (71.6%) showed a Guinier plateau at the very low q range (q < 1 × 10⁻⁴ 1/Å) indicating presence of isolated large scale morphology (R_g = 1.3 ± 0.18 micron). The radius of spherical ionic aggregates present in the hydrated SPTES-50 and SPTES-60 copolymer membranes increased with increasing temperature to 55 °C, but the large scale morphology changed to a fractal network. Further increase of the sulfonation degree to 63.3% and 71.6% (SPTES-70 and SPTES-80) resulted in a substantial morphology change of the spherical aggregates to an irregular bicontinuous hydrophobic/hydrophilic morphology for the hydrated SPTES-70 and SPTES-80 copolymer membranes at 55 °C. Presence of ionic maxima followed by a power law decay of −4 for SPTES-70 and SPTES-80 copolymer membranes was attributed to the bicontinuous phase morphology at high degree of sulfonation and elevated temperature (55 °C). The disruption of the larger scale fractal morphology was characterized by significant decrease in the intermediate scattering intensity. Hydrophobic and hydrophilic domains were separated distinctly by sulfonic groups at the interface showing as power law decay of −4 for all hydrated SPTES copolymers.     

Antifouling enhancement of PVDF membrane tethered with polyampholyte hydrogel layers

The preparation and property of antifouling poly(vinylidene fluoride) (PVDF) membrane tethered with polyampholyte hydrogel layers were described in this work. In fabricating these membranes, the [2‐(methacryloyloxy)ethyl] trimethylammonium chloride and 2‐acrylamide‐2‐methyl propane sulfonic acid monomers were grafted onto the alkali‐treated PVDF membrane to yield polyampholyte hydrogel layers via radical copolymerization with N,N′‐methylenebisacrylamide as crosslinking agent. The analyses of fourier transform infrared attenuated total reflection spectroscopy and X‐ray photoelectron spectroscopy confirm the covalent immobilization of polyampholyte hydrogel layer on PVDF membrane surface. The grafting density of polyampholyte hydrogel layer increases with the crosslinking agent growing. Especially for the membrane with a high grafting density, a hydrogel layer can be observed obviously, which results in the complete coverage of membrane pores. Because of the hydrophilic characteristic of grafted layer, the modified membranes show much lower protein adsorption than pristine PVDF membrane. Cycle filtration tests indicate that both the reversible and irreversible membrane fouling is alleviated after the incorporation of polyampholyte hydrogel layer into the PVDF membrane. This work provides an effective pathway of covalently tethering hydrogel onto the hydrophobic membrane surface to achieve fouling resistance. POLYM. ENG. SCI., 55:1367–1373, 2015. © 2015 Society of Plastics Engineers     

Characterization of graft polymerization of fluoroalkyl methacrylate onto PDMS hollow‐fiber membranes and their permselectivity for volatile organic compounds

Polydimethylsiloxane (PDMS) hollow‐fiber membranes grafted with 1H,1H,9H‐hexadecafluorononyl methacrylate (HDFNMA), which is a fluoroalkyl methacrylate, using a ⁶⁰Co irradiation source, were characterized and applied to pervaporation. The PDMS hollow‐fiber membranes were filled with N₂ gas and sealed. The membranes and the HDFNMA solution were then irradiated simultaneously. In the HDFNMA solution, graft polymerization was performed. The degree of grafting of the outside surface of the hollow fiber was greater than that in the inside surface of the hollow fiber. In the grafted PDMS hollow‐fiber membranes, the best separation performance was shown due to the introduced hydrophobic polymer, poly(HDFNMA). The grafted membrane had a microphase‐separated structure, that is, a separated structure of PDMS and graft‐polymerized HDFNMA. The permeability of molecules in the poly(HDFNMA) phase was so low that the diffusion of molecules was prevented in the active layer with many poly(HDFNMA) domains, as the feed solution was introduced through the inside of the hollow fibers and the outside was vacuumed. As the feed solution was introduced through the outside of the hollow fibers and the inside was vacuumed, the diffusion of molecules was not prevented in the active layer with few poly(HDFNMA) domains. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1573–1580, 2003     

Proton exchange composite membranes from blends of brominated and sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide)

New composite proton exchange membrane was prepared by mixing a 1‐methyl‐2‐pyrrolidone (NMP) solution of sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) in sodium form and brominated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (BPPO) for hydrophilic‐hydrophobic balance, then casting the solution as a thin film, evaporating the solvent, and treating the membrane with aqueous hydrochloric acid. The resulting membranes were subsequently characterized using FTIR‐ATR, SEM‐EDXA, and TGA instrumentation as well as measurements of basic properties such as ion exchange capacity (IEC), water uptake, proton conductivity, methanol permeability, and single cell performance. Water uptake, IEC, proton conductivity, and methanol permeability all increased with a corresponding increase of SPPO content. By properly compromising the conductivity and methanol permeability, membranes with 60–80 wt % SPPO content exhibited comparable proton conductivity to that of Nafion^® 117, with only half the methanol permeability, thereby demonstrating higher single cell performance. The membranes developed in this study could thus be a suitable candidate electrolyte for proton exchange membrane fuel cells (PEMFCs). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012