Surface functionalization of poly(vinylidene fluoride) membrane by radiation-induced emulsion polymerization of hydroxyethyl acrylates in an aqueous medium

Decades ago, surface modification of poly(vinylidene fluoride) (PVDF) membrane became an essential subject. The change is mainly to enhance the hydrophilicity properties of the membrane in order to increase the adsorption capacity, thus making as a novel adsorbent. This study aims to used radiation-induced polymerization and compares the final properties of PVDF grafted hydroxyethyl acrylates (HEA) prepare by two different approaches. The PVDF-grafted-HEA has achieved either direct polymerization or emulsion polymerization. Tween-20 has been used as a surfactant in emulsion polymerization. The final PVDF-grafted poly-HEA was analyzed using several different instruments to observe the changes in terms of morphological structure, topography properties, thermal stability, mechanical strength, and hydrophilicity. Significant differences were seen in morphology and contact angles properties. By emulsion polymerization, poly-HEA grafted in the shape of micelles compare to by direct polymerization shown a thin homogenous layer. Thus, the surface roughness of PVDF by emulsion is higher lead to higher contact angles. Even though both approaches demonstrate significant changes in the physicochemical properties of the PVDF membrane, it is revealed that radiation-induced direct polymerization approaches could achieve a hydrophilic PVDF-grafted HEA.     

Soil polymer conditioner based on montmorillonite‐poly(acrylic acid) composites

The constant deterioration of the soil as a result of natural and anthropogenic processes produces decrease of soil fertility and agricultural production, increase in the cost of food, desertification, and loss of water resources. The objective of this work was to develop a hybrid composite that structural and functionally mimics the humified structure of soils for the development of remediation strategies based on geotransformation of degraded soils. For that, two different strategies for the modification of clay surface were evaluated: (i) covalent linking using trichlorovinylsilane and (ii) electrostatic interaction using N‐vinylbenzyl‐N‐triethyl ammonium chloride. Later, modified clay was characterized and used as crosslinking agent during the free‐radical polymerization of acrylic acid. Particulate nanostructured polymers were characterized and their water absorption capacity, cationic exchange capacity, and ionic retention capacity were determined. Results showed that clay‐poly(acrylic acid) composites can be obtained by described methodology. In addition, materials with 60 and 80% w/w of modified MMT were obtained with particulate shape, high water absorption capacity (273%–568%), high cationic exchange capacity (124–666 meq+/100 g) and high ionic retention capacity (108–194 and 263–313 meq/100 g for major and minor elements, respectively). Finally, it was concluded that synthesized materials mimic structural and functionally the humified structure of soils. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46211.     

Preparation and characterization of poly(vinyl chloride)‐graft‐acrylic acid membrane by electron beam

Poly(vinyl chloride) (PVC) was irradiated by electron beam in vacuum at 20 KGy to produce living free radicals, and then reacted with acrylic acid (AA) in solution to obtain the PVC‐g‐AA copolymers. The copolymers were characterized by Fourier transform infrared spectroscopy. Porous membranes were prepared from copolymers by the phase inversion technique. The morphology of PVC‐g‐AA membranes was studied by field emission scanning electron microscopy. The mean pore size and pore size distribution were determined by a mercury porosimeter. The mean pore size was 0.19 μm, and the bulk porosity was 56.02%. The apparent static water contact angle was 89.0°. The water drop penetration rate was 2.35 times to the original membrane. The maximum stress was 4.10 MPa. Filtration experiments were carried out to evaluate the fouling resistance of the PVC‐g‐AA membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation and microstructural analysis of poly(ethylene oxide) comb‐type grafted poly(N‐isopropyl acrylamide) hydrogels crosslinked by poly(ϵ‐caprolactone)

Poly(N‐isopropyl acrylamide) (PNIPAAm)‐graft‐poly(ethylene oxide) (PEO) hydrogels crosslinked by poly(?‐caprolactone) diacrylate were prepared, and their microstructures were investigated. The swelling/deswelling kinetics and compression strength were measured. The relationship between the structure and properties of hydrogel are discussed. It was found that the PEO comb‐type grafted structure reduced the thermosensitivity and increased the compression strength. The addition of poly(?‐caprolactone) (PCL) accelerated the deswelling rate of the hydrogels. Meanwhile, the entanglement of PCL chains restrained the further swelling of the network of gels. The PCL crosslinking agent and PEO comb‐type grafted structure made the behavior of the hydrogels deviate from the rubber elasticity equations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Cotton‐fabric‐grafted poly(N‐isopropyl acrylamide) initiated by ammonium peroxydisulfate

In this article, we report that thermoresponsive poly(N‐isopropyl acrylamide) (PNIPAAm) was successfully grafted onto a cotton fabric (CF) surface by free‐radical solution grafting polymerization; we obtained a thermoresponsive CF‐grafted PNIPAAm. This reaction system only contained four constituents: the monomer, solvent, initiator, and CFs. Ammonium peroxydisulfate was chosen as the initiator, and water was chosen as the solvent. A series of initiator concentrations and grafting polymerization temperatures were used in the experiments, and their effects on the grafting ratio (G) were also studied. Also, the effects of the G of CF‐g‐PNIPAAm on their corresponding thermoresponses was studied further. The structure of CF‐g‐PNIPAAm was characterized by Fourier transform infrared spectroscopy–attenuated total reflectance analysis and scanning electron microscopy analysis. The G of CF‐g‐PNIPAAm was measured by a gravimetric method. The thermoresponse of CF‐g‐PNIPAAm was characterized by modulated differential scanning calorimetry, water contact angle measurements, and wetting time measurements. The experiments manifested the following results: (1) the initiator concentration and grafting polymerization temperature both influenced G, (2) the grafted PNIPAAm covered the CF surface, (3) the CF‐g‐PNIPAAm showed thermoresponsive hydrophilicity/hydrophobicity, and (4) a relationship existed between the thermoresponse of CF‐g‐PNIPAAm and the corresponding G. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41193.     

Preparation of poly(methyl methacrylate)‐grafted attapulgite by surface‐Initiated radical polymerization

Poly(methyl methacrylate) (PMMA) was bonded on the surface of attapulgite (ATP) by using an ammonium persulfate amine redox initiation system via grafting from approach. ATP was modified with (3‐aminopropyl)triethoxysilane to anchor amine groups on the surface, and then the amine‐functionalized ATP was further treated with methacryloyl chloride and 4,4′‐azobis(4‐cyanovaleric acid) to give methacryl‐ and azo‐functionalized ATP, respectively. Subsequently, surface‐initiated graft polymerization of MMA in a soap‐free emulsion was performed to afford ATP/PMMA hybrids. Meanwhile, graft polymerizations on the surface of methacryl‐ and azo‐functionalized ATP were carried out for comparison. The grafting of PMMA on the surface of ATP was characterized by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and thermogravimetric analysis (TGA). The crystal structure of hybrids was characterized by X‐ray diffraction analysis. The morphology of hybrids was observed by scanning electron microscopy and transmission electron microscopy. The degree of grafting obtained from surface‐initiated graft polymerization in a soap‐free emulsion was found to be the greatest (29.4%) estimated from TGA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41062.     

Formation of multilayer poly(acrylic acid)/poly(vinylidene fluoride) composite membranes for pervaporation

Dual‐ and multilayer composite membranes, consisting of poly(acrylic acid) (PAA) and poly(vinylidene fluoride) (PVDF), were synthesized by the plasma‐induced polymerization technique. The dual‐layer membrane had a dense PAA layer grafted onto a microporous PVDF substrate, whereas in the multilayer membranes, the grafted PAA and the PVDF layers were arranged in an alternating sequence (e.g., PAA/PVDF/PAA and PAA/PVDF/PAA/PVDF/PAA). These membranes were used in a pervaporation process to separate ethanol–water solutions. For the dual‐layer membranes, the results indicated that the separation factor increased and the permeation flux decreased with increasing amounts of grafted PAA. For the case of grafting yield < 0.6 mg/cm², the composite membrane demonstrated poor separation. As the grafting yield reached 0.85 mg/cm², a sharp increase of the separation factor was observed. For the multilayer membranes, the pervaporation performances were very good, with high separation factors (on the order of 100) and reasonable permeation fluxes over a wide ethanol concentration range. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2266–2274, 2004     

Thermosensitive copolymer synthesized by controlled living radical polymerization: Phase behavior of diblock copolymers of poly(N‐isopropyl acrylamide) families

In this study, we prepared a series of thermosensitive polymers with low polydispersity index (PDI) values by nitroxide‐mediated controlled radical polymerization (NMRP) with 2,2,6,6‐tetramethyl‐1‐piperdinyloxy nitroxide (TEMPO) as a stable nitroxide‐free radical. Poly(N‐isopropyl acrylamide) (PNIPAAm)‐block‐poly(N‐tert‐butyl acrylamide) (PNTBA) was successfully synthesized, first, through polymerization with N‐isopropyl acrylamide to obtain the reactive polymer PNIPAAm‐TEMPO and, second, through polymerization by the addition of N‐tert‐butyl acrylamide (NTBA). The added molar fraction of NTBA during the second polymerization was adjusted accordingly to obtain the final polymerization product, a thermosensitive polymer (PNIPAAm‐block‐PNTBA), which had a targeted lower critical solution temperature (LCST). The result shows that the synthesis method used in this study effectively controlled the formation of the polymer to obtain a low PDI. The thermosensitive block copolymer, PNIPAAm‐b‐PNTBA (molar ratio = 9:1), with LCSTs in the range 27.7–39.8°C, was obtained through controlled living radical polymerization with PNIPAAm–TEMPO. Specifically, the 5 wt % aqueous solution of PNIPAAm‐b‐PNTBA (molar ratio = 9:1) had an LCST of 37.4°C; this was close to body temperature, 37°C. The 5 wt % aqueous solution of PNIPAAm‐b‐PNTBA (molar ratio = 9:1) showed potential for use in biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43224.     

Preparation and characterization of polyaniline N‐grafted with poly(ethyl acrylate) synthesized via atom transfer radical polymerization

Polyaniline (PANI) N‐grafted with poly(ethyl acrylate) (PEA) was synthesized by the grafting of bromo‐terminated poly (ethyl acrylate) (PEA‐Br) onto the leucoemeraldine form of PANI. PEA‐Br was synthesized by the atom transfer radical polymerization of ethyl acrylate in the presence of methyl‐2‐bromopropionate and copper(I) chloride/bipyridine as the initiator and catalyst systems, respectively. The leucoemeraldine form of PANI was deprotonated by butyl lithium and then reacted with PEA‐Br to prepare PEA‐g‐PANI graft copolymers containing different amounts of PEA via an N‐grafting reaction. The graft copolymers were characterized by Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. Solubility testing showed that the solubility of PANI in chloroform was increased by the grafting of PEA onto PANI. The morphology of the PEA‐g‐PANI graft copolymer films was observed by scanning electron microscopy to be homogeneous. The electrical conductivity of the graft copolymers was measured by the four‐probe method. The results show that the conductivity of the PANI decreased significantly with increasing grafting density of PEA onto the PANI backbone up to 7 wt % and then remained almost constant with further increases in the grafting percentage of PEA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Amphiphilic ABA‐type triblock copolymers for the development of high‐performance poly(vinylidene fluoride)/poly(vinyl pyrrolidone) blend ultrafiltration membranes for oil separation

ABA‐type amphiphilic triblock copolymers (TBCs) were synthesized by a reversible addition fragmentation chain transfer (RAFT) process with a telechelic polystyrene macro‐RAFT agent and 4‐[n‐(acryloyloxy)alkyloxy]benzoic acid monomers. Ultrafiltration (UF) membranes were fabricated by a phase‐inversion process with blends of the TBC, poly(vinylidene fluoride) (PVDF), and poly(vinyl pyrrolidone) (PVP) in dimethylformamide. The UF‐fabricated membranes were characterized by scanning electron microscopy, atomic force microscopy, water contact angle measurement, thermogravimetric analysis, and differential scanning calorimetry. Pure water permeation, molecular weight cutoff values obtained by the permeation of different molecular weight polymers as probe solutes, bovine serum albumin (BSA) solution permeate flux, and oil–water emulsion filtration tests were used to evaluate the separation characteristics of the fabricated membranes. The tripolymer blend membranes exhibited a higher flux recovery ratio (FRR) after the membrane was washed with sodium lauryl sulfate (0.05 wt %) solution for a BSA solution (FRR = 88%) and oil–water emulsion (FRR = 95%) feeds when than the PVDF–PVP blend membrane (57 and 80% FRR values for the BSA solution and oil–water emulsion, respectively). The pendant carboxylic acid functional moieties in this ABA‐type TBC have potential advantages in the fabrication of high‐performance membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45132.     

Improved swelling–deswelling behavior of poly(N‐isopropyl acrylamide) gels with poly(N,N′‐dimethyl aminoethyl methacrylate) grafts

Thermoresponsive and pH‐responsive gels were synthesized from N‐isopropyl acrylamide (NIPA) and N,N′‐dimethyl aminoethyl methacrylate (DMAEMA) monomers. Gelation reactions were carried out with both conventional free‐radical polymerization (CFRP) and controlled free‐radical polymerization [reversible addition fragmentation transfer (RAFT)] techniques. The CFRP gels were prepared by polymerizing mixtures of NIPA and DMAEMA in 1,4‐dioxane in presence of N,N'‐methylene bisacrylamide (BIS) as cross‐linker. The RAFT gels were prepared by a the polymerization of NIPA via a similar process in the presence of different amounts of poly(N,N′‐dimethyl aminoethyl methacrylate) macro chain‐transfer agent and the crosslinker. These gels were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry. SEM analysis revealed a macroporous network structure for the RAFT gels, whereas their volume phase‐transition temperatures (VPTTs) were found to be in the range 32–34°C, close to that of poly(N‐isopropyl acrylamide) gels. However, the CFRP copolymer gels exhibited a higher VPTT; this increased with increasing DMAEMA content. The RAFT gels exhibited higher swelling capabilities than the corresponding CFRP gels and also showed faster shrinking–reswelling behavior in response to changes in temperature. All of the gels showed interesting pH‐responsive behavior as well. The unique structural attributes exhibited by the RAFT gels can potentially open up opportunities for developing new materials for various applications, for example, as adsorbents or carrier of drugs or biomolecules. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42749.     

Thermoresponsive and biocompatible poly(vinyl alcohol)‐graft‐poly(N,N‐diethylacrylamide) copolymer: Microwave‐assisted synthesis,characterization, and swelling behavior

Novel thermoresponsive poly(vinyl alcohol)‐graft‐poly(N,N‐diethylacrylamide) (PVA‐g‐PDEAAm) copolymers were prepared by microwave‐assisted graft copolymerization using a potassium persulfate/N,N,N′,N′‐tetramethylethylenediamine (KPS/TEMED) initiator system. The structures of PVA‐g‐PDEAAm copolymers were characterized by ¹H‐NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry/thermogravimetric analysis, gel permeation chromatography, X‐ray diffraction, and scanning electron microscopy. The effects of various process parameters on grafting were systematically studied: microwave power, KPS, monomer and PVA concentrations, and ultraviolet irradiation. Under optimal conditions, the maximum grafting percent and graft efficiency were 101% and 93%, respectively. Furthermore, a lower critical temperature of copolymers was measured in the range 29–31 °C by ultraviolet spectroscopy. The swelling behavior of graft membranes was carried out at various temperatures, and the results showed that the swelling behavior of membranes was dependent on the temperature. In vitro cell culture studies using L929 fibroblast cells confirmed cell compatibility with the PVA‐g‐PDEAAm copolymer and its membrane, making them an attractive candidate for drug delivery systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45969.     

Facile UV‐curing technique to establish a 3D‐grafted poly(ethylene glycol) layer on an epoxy resin base for underwater applications

Construction of a highly hydrophilic polymer surface with excellent long‐term stability underwater is a great challenge. In this paper, a facile ultraviolet (UV) curing technique was employed to realize the three‐dimensional (3D) grafting of poly(ethylene glycol) diacrylate (PEGDA, molecular weight: 400, 600, and 1000 g/mol) on a bisphenol A epoxy acrylate (BEA) sheet. The cross section morphology, surface chemical composition, and wettability of the sheets were monitored using an optical microscope, an attenuated total reflectance Fourier transform infrared spectroscope, and a water contact angle analyzer, respectively. The PEGDA‐grafted epoxy sheets displayed a highly hydrophilic surface and meanwhile possessed excellent stability underwater, despite the molecular weight of PEGDA. In contrast, the PEGDA/BEA blend sheets are easily damaged underwater, due to strong swelling. In addition, the PEGDA1000‐grafted BEA sheet demonstrated good antifouling performance in a natural marine environment. Nevertheless, its long‐term antifouling is not satisfactory, being presumably due to hydrolysis or biodegradation of the PEG segments. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43972.     

Preparation of temperature sensitive poly(vinylidene fluoride) hollow fiber membranes grafted with N‐isopropylacrylamide by a novel approach

In the present study, the temperature sensitive PVDF‐g‐NIPAAm HFM was prepared by grafting N‐isopropylacrylamide (NIPAAm) on poly(vinylidene fluoride) (PVDF) hollow fiber membrane (HFM) using a novel approach, alkaline treatment method. The structures of PVDF‐g‐NIPAAm HFM were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The effects of alkaline treatment time and grafting yield on the mechanical properties of PVDF HFM were measured and analyzed. In addition, the temperature sensitive behavior of PVDF‐g‐NIPAAm HFM and the effect of grafting yield on the temperature sensitive behavior were investigated by the flux of pure water and the rejection of ovalbumin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 833–837, 2006     

Antifouling poly(vinylidene fluoride) hollow fiber membrane with hydrophilic surfaces by ultrasonic wave‐assisted graft polymerization

Acrylic acid (AA)‐grafted poly(vinylidene fluoride) (PVDF) hollow fiber membrane was obtained by ultrasonic wave‐assisted graft polymerization. The grafting density (GD) of AA on the PVDF membrane surface could be controlled by altering the reaction conditions, such as ultrasonic time, ultrasonic power, monomer concentration and initiator concentration. The attenuated total reflectant Fourier transform infrared spectra (FITR‐ATR) and X‐ray photoelectron spectroscopy were used to investigate the chemical composition of modified membranes. The changes of surface morphology and roughness were characterized by field emission scanning electron microscope and atomic force microscopy. Results show that AA was successfully grafted on the membrane surface. With increasing GD, the static water contact angle was decreased from 95.7 to 41.4°, indicating that hydrophilicity of modified membrane was significantly enhanced. Pure water flux before and after bovine serum albumin (BSA) contamination was measured. The modified membrane with the GD of 0.76 mg/cm² has the highest water flux as high as 350 L/m²·h. When compared with the pristine membrane(M0), the flux recovered ratio was improved from 52.75 to 96.29% at the GD 2.76 mg/cm² (M3), which suggested the protein fouling could be effectively prevented for the modified membrane. POLYM. ENG. SCI., 2018. © 2018 Society of Plastics Engineers POLYM. ENG. SCI., 59:E446–E454, 2019. © 2018 Society of Plastics Engineers     

Hydrolyzed collagen‐grafted‐poly[(acrylic acid)‐co‐(methacrylic acid)] hydrogel for drug delivery

Hydrolyzed collagen‐grafted‐poly[(acrylic acid)‐co‐(methacrylic acid)] hydrogels were synthesized by solution polymerization and confirmed by infrared spectroscopy. From sequential univariate analysis, the optimal molar ratio of acrylic acid: methacrylic acid was 92:8 in the presence of N,N′‐methylenebisacrylamide, ammonium persulfate, and N,N,N′,N′‐tetramethylethylenediamine at 0.12, 0.015, and 0.2% mol of the monomers, respectively. The water absorbency of this hydrogel was both pH‐ and temperature‐dependent, but was higher in nonbuffered water than in boric acid/citric acid/phosphate buffer under the same conditions. The optimal hydrogel could swiftly swell and deswell in neutral and acid solutions, respectively. Its potential application in drug delivery was examined using insulin and methylene blue as model payload drugs. Loading in a 50% (v v^?1) ethanol solution gave a higher insulin loading level than in the buffer water. Insulin and methylene blue were both released at pH 6.8 but not at pH 1.2, but followed first order kinetics and the Higuchi equation, respectively. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45654.     

Acid‐synergized grafting of sodium styrene sulfonate onto electron beam irradiated‐poly(vinylidene fluoride) films for preparation of fuel cell membrane

The role of acid addition in synergizing radiation induced grafting of sodium styrene sulfonate (SSS) onto electron beam‐irradiated poly(vinylidene fluoride) (PVDF) films as a single‐step route for preparation of proton exchange membranes containing sulfonic acid groups was systematically investigated. The grafting reaction, known for its poor kinetics, was studied using SSS diluted in various solvents and solvent/acid solutions of different concentrations and volumes. The addition of acid solution was found to marvelously synergize the grafting reaction from very low values (e.g., 0.5%) to achieve high degrees (e.g., 65%) of grafting and such synergetic effect depends on the type, concentration and volume of the added acid. The degree of grafting was also found to be function of the monomer concentration and the irradiation dose at constant acid concentration and volume. The obtained membranes were investigated with Fourier transform infrared spectroscopy (FTIR), scanning transmission electron microscopy (STEM), and X‐ray diffractometry (XRD). The results of present study reveal that grafting of SSS to levels suitable for fuel cell application onto PVDF film is only possible by adding aqueous acids solution. Moreover, the addition of acid makes this shorter single‐step method more economical route for preparation of proton exchange membranes for fuel cells. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of cationic exchange membranes based on organo‐montmorillonite/poly(vinylidene fluoride) by two‐step chemically induced grafting method

In this research, OMMT/PVDF‐based cationic exchange membranes were prepared by two‐step chemically induced grafting method. The various preparation conditions, such as alkaline treatment, initiation, and grafting conditions, and the relationship between the preparation conditions and the cationic exchange membrane performance, such as area resistance and cationic permselectivity, were investigated. The chemical and crystal changes on the membrane surface were characterized by Fourier transform infrared spectroscopy (FTIR), energy dispersive spectrum (EDS), and X‐ray diffraction (XRD), respectively. Surface morphological changes were also characterized by scanning electron microscopy (SEM). The results reveal that the OMMT/PVDF‐based cationic exchange membrane was successfully prepared by this method. The OMMT/PVDF‐based cationic exchange membrane doped 8.5% OMMT prepared using optimum preparation parameters showed excellent basic properties. The area resistance was measured as low as 1.8 Ω cm², while the cationic permselectivity was as high as 93.4%. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2753–2763, 2013     

Sulfonation of styrene‐grafted poly(vinylidene fluoride) films

Electron‐beam irradiated and styrene‐grafted poly(vinylidene fluoride) films are sulfonated with chlorosulfonic acid in dichloroethane under various conditions. The impact of the reaction time, the concentration of the sulfonating agent, and the reaction temperature on the properties of the sulfonated film is examined. Sulfonation proceeds via a reaction front mechanism. Sulfonation of surface‐grafted films is incomplete at room temperature. The number of side reactions taking place appears to be linearly dependent on the concentration of the sulfonation solution. Dimensional changes suggest that sulfone crosslinking is significant at higher concentrations. This reduces the ion‐exchange capacity and proton conductivity of the films but increases the resistance to oxidation in a H₂O₂ solution. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1572–1580, 2001     

Fabrication of antifouling membranes by blending poly(vinylidene fluoride) with cationic polyionic liquid

Membrane fouling problem is now limiting the rapid development of membrane technology. A newly synthesized cationic polyionic liquid (PIL) [P(PEGMA-co-BVIm-Br)] was blended with poly(vinylidene fluoride) (PVDF) to prepare antifouling PVDF membranes. The PVDF/P(PEGMA-co-BVIm-Br) exhibited an increased surface hydrophilicity, the water contact angle was reduced from 77.8° (pristine PVDF) to 57.9°. More porous membrane structure was obtained by adding PIL into the blending polymers, as high as 478.0 L/m²·h of pure water flux was detected for the blend PVDF membrane in comparison with pristine PVDF (17.2 L/m²·h). Blending of the cationic PIL with PVDF gave a more positive surface charge than pristine PVDF membrane. Blend membranes showed very high rejection rate (99.1%) and flux recovery rate (FRR, 83.0%) to the positive bovine serum albumin (BSA), due to the electrostatic repulsion between the membrane surface and proteins. After three repeated filtration cycles of positive BSA, the blend PVDF membranes demonstrated excellent antifouling performance, the permeation flux of the membranes was recovered very well after a simple deionized water washing, and as high as 70% of FRR was obtained, the water flux was maintained at above 350 L/m²·h. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48878.