Zwitterionic‐polymer‐functionalized poly(vinyl alcohol‐co‐ethylene) nanofiber membrane for resistance to the adsorption of bacteria and protein

A zwitterionic poly(vinyl alcohol‐co‐ethylene) (PVA‐co‐PE) nanofiber membrane for resistance to bacteria and protein adsorption was fabricated by the atom transfer radical polymerization of sulfobetaine methacrylate (SBMA). The PVA‐co‐PE nanofiber membrane was first surface‐activated by α‐bromoisobutyryl bromide, and then, zwitterionic SBMA was initiated to polymerize onto the surface of nanofiber membrane. The chemical structures of the functionalized PVA‐co‐PE nanofiber membranes were confirmed by attenuated total reflectance–Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. The morphologies of the PVA‐co‐PE nanofiber membranes were characterized by scanning electron microscopy. The results show that the poly(sulfobetaine methacrylate) (PSBMA) was successfully grafted onto the PVA‐co‐PE nanofiber membrane, and the surface of the nanofiber membrane was more hydrophilic than that of the pristine membrane. Furthermore, the antibacterial adsorption properties and resistance to protein adsorption of the surface were investigated. This indicated that the PSBMA‐functionalized surface possessed good antibacterial adsorption activity and resistance to nonspecific protein adsorption. Therefore, this study afforded a convenient and promising method for preparing a new kind of soft and nonwoven dressing material with antibacterial adsorption and antifouling properties that has potential use in the medical field. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44169.     

Electrospun nanofiber‐coated separator membranes for lithium‐ion rechargeable batteries

Nanofiber‐coated composite membranes were prepared by electrospinning polyvinylidene fluoride‐co‐chlorotrifluoroethylene (PVDF‐co‐CTFE) and PVDF‐co‐CTFE/polyvinylidene fluoride‐co‐hexafluoropropylene (PVDF‐co‐HFP) onto six different Celgard® microporous battery separator membranes. Application of a PVDF‐based copolymer nanofiber coating onto the surface of the battery separator membrane provides a method for improving the electrolyte absorption of the separator and the separator‐electrode adhesion. Peel tests showed that both PVDF‐co‐CTFE and PVDF‐co‐CTFE/PVDF‐co‐HFP nanofiber coatings have comparable adhesion to the membrane substrates. Electrolyte uptake capacity was investigated by soaking the nanofiber‐coated membranes in a liquid electrolyte solution. PVDF‐co‐CTFE and PVDF‐co‐CTFE/PVDF‐co‐HFP nanofiber‐coated membranes exhibited higher electrolyte uptake capacities than uncoated membranes. It was also found that PVDF‐co‐CTFE nanofiber‐coated membranes have higher electrolyte uptakes than PVDF‐co‐CTFE/PVDF‐co‐HFP nanofiber‐coated membranes due to the smaller diameters of PVDF‐co‐CTFE nanofibers and higher polarity of PVDF‐co‐CTFE. The separator–electrode adhesion properties were also investigated. Results showed PVDF‐co‐CTFE and PVDF‐co‐CTFE/PVDF‐co‐HFP nanofiber coatings improved the adhesion of all six membrane substrates to the electrode. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thin film composite forward osmosis membranes with poly(2‐hydroxyethyl methacrylate) grafted nano‐TiO2 as additive in substrate

The poly(2‐hydroxyethyl methacrylate) grafted titanium dioxide nanoparticles were synthesized and added to the substrate of flat‐sheet thin film composite forward osmosis (TFC‐FO) membranes. The hydrophilicity of substrate was improved, which was advantageous to enhance the water flux of TFC‐FO membranes. The membranes containing a 3 wt % TiO₂‐PHEMA in the substrate exhibited a finger‐like structure combined with sponge‐like structure, while those with lower or without TiO₂‐PHEMA content showed fully finger‐like structures. As for FO performance, the TFC‐FO membranes with 3 wt % TiO₂‐PHEMA content achieved the highest water flux of 42.8 LMH and 24.2 LMH against the DI water using 2M NaCl as the draw solution tested under the active layer against draw solution (AL‐DS) mode and active layer against feed solution (AL‐FS) mode, respectively. It was proven that the hydrophilic property of membrane substrates was a strong factor influencing the water flux in FO tests. Furthermore, the structural parameter was remarkably decreased with an increase of TiO₂‐PHEMA content in membrane substrate, indicating the reducing of internal concentration polarization. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43719.     

Tris(hydroxymethyl)aminomethane polyamide thin‐film‐composite antifouling reverse osmosis membrane

For the applications of reverse osmosis (RO) process, membrane fouling caused by organic molecule adsorption is still a serious problem which significantly decreases membrane lifespan and increases operation costs. In this present article, we report the thin film composite (TFC) RO membrane functionalized with tris(hydroxymethyl)aminomethane (THAM) using one‐step method for improved antifouling property. The results of surface characterization indicated that THAM was successfully grafted onto the active layer of membrane by covalent linkage. Mult‐hydroxyl‐layer was generated and remained steadily on TFC membrane surface after modification. The contact angle decreased from 75.9 ± 3.0° to 46.9 ± 2.3°, which showed a distinct improvement of membrane surface hydrophilicity after modification. The grafted THAM improved water flux by 28.3%, while salt rejection was almost unchanged in membrane property tests. The modified membranes presented preferable antifouling property to foulants of bovine serum albumin, sodium alginate, and dodecyl trimethyl ammonium bromide than that of pristine membranes during dynamic fouling experiments. The method in this study provided an effective way to improve antifouling property of the polyamide thin‐film‐composite RO membrane. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45891.     

Alkyl amine functional dextran macromonomer‐based thin film composite loose nanofiltration membranes for separation of charged and neutral solutes

Thin film composite (TFC) nanofiltration membranes with defined porous structure of the separation layer are desirable for the concentration of neutral solute and separation of salts from a mixture. Herein, we report the formation of TFC membranes composed of polyamide (PA) separation layer by the interfacial polymerization between new dextran‐butyl amine (Dex‐NH₂) macromonomer and trimesoyl chloride on polysulfone support membrane. The membranes prepared with 1%–1.5% (wt/vol) of Dex‐NH₂ exhibited water permeance of 110–116 L m^?2 h^?1 MPa^?1 with 62%–71% rejection of Na₂SO₄ and 12%–14% rejection of MgCl₂. The membranes also showed about 91% rejection of poly(ethylene glycol) of molecular weight 2000 g/mol and about 11% rejection of NaCl. A decrease in permeance and ions selectivity was observed with increasing concentration of Dex‐NH₂. The dextran chains attached to the PA network restrict the diffusion of Dex‐NH₂ toward the interfacial zone and thereby assist the formation of porous and thin PA layer compared to that when free amine (alkyl diamine) was used. These membranes are applicable for the separation of small molecular weight neutral solutes from mixture containing monovalent salts. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45301.     

Preparation and characterization of a composite nanofiltration membrane interfacially polymerized from cis,cis‐1,3,5‐triaminocyclohexane and trimesoyl chloride

cis,cis‐1,3,5‐Triaminocyclohexane (TAC) was synthesized and used to prepare composite nanofiltration (NF) membranes by interfacial polymerization with trimesoyl chloride (TMC). The surface elemental composition, morphology, and hydrophilicity of the prepared NF membranes were characterized. The separation performances were examined with various salts and polyethylene glycol (PEG400, PEG600) solutions. The effects of preparation conditions were also systematically studied. The NF membrane was negatively charged and exhibited a salt rejection in the order Na₂SO₄ (98.2%) > MgSO₄ (90.8%) > MgCl₂ (84.5%) > NaCl (54.6%). The water permeability was 1.56 L m^?2 h^?1 bar^?1, and the molecular weight cutoff was 600 Da. The TAC/TMC membrane exhibited some characteristics that were different from the ones made from common diamines such as m‐phenylenediamine: (1) the surface was smoother, without a ridge‐and‐valley structure; (2) there were two kinds of crosslinking points in the polyamide chains; (3) the active layer was formed faster (only 5 seconds was required to reach a Na₂SO₄ rejection of 98%). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43511.     

Engineering silver-zwitterionic composite nanofiber membrane for bacterial fouling resistance

Bacterial attachment and fouling compromise material performance in applications ranging from marine equipment and biomedical devices to water treatment systems. For membrane-based water treatment systems, bacterial attachment and biofilm formation decrease water purification efficiency and reduces mechanical durability of the membranes. In this work, we present a concurrent electrospinning and copolymerization approach to engineer composite nanofiber membranes comprising of silver nanoparticle containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP-Ag) nanofibers and [copolymerized zwitterionic sulfobetaine methacrylate-methacryl polyhedral oligomeric silsesquioxane]-poly(methyl methacrylate) nanofibers. We characterized the surface morphology, topography, material chemistry, and wettability of the nanofiber membranes with scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and contact angle measurements. We then challenged these nonwoven membranes with two model microbes, Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus, and found that the silver-zwitterionic composite nanofiber membrane exhibited superior bacterial fouling resistance by reducing >90% of bacterial attachment when compared to neat PVDF-HFP and PVDF-HFP-Ag nanofiber membranes. This study demonstrates that concurrent electrospinning enables free-standing nanofiber membranes with sustained bacterial fouling resistance, with potential in applications in filtration and water treatment technologies for which antifouling strategies are imperative. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47580.     

Influences of the chain structure of PE‐b‐PEG on the properties of PE/PE‐b‐PEG blend membranes prepared by TIPS

In this article, a series of diblock copolymer polyethylene‐b‐ poly(ethylene glycol)s (PE‐b‐PEGs) with various molecular weight of polyethylene segment was blended with linear low‐density PE. The PE/PE‐b‐PEG blend porous membranes with high porosity were obtained by thermally induced phase separation (TIPS) process. The isothermal crystallization kinetics of PE/LP/PE‐b‐PEG blends indicated that the introduction of PE‐b‐PEG could inhibit the growth rate of polyethylene crystals which could increase the pore size and porosity of the membranes. The PE/PE‐b‐PEG blend membranes with PE₁₃₀₀‐b‐PEG₂₂₀₀ showed the largest pore size and porosity due to its crystallization behavior during TIPS. The surface of the membranes became smoother and the morphology of the membranes could be effectively tuned by introducing PE‐b‐PEG. Compared with the PE membrane, the PE/PE‐b‐PEG blend membranes exhibited higher hydrophilicity (the water contact angle decreased from 112° to 84°), water permeability (the permeation flux increased from 80 to 440 L/m² h under 0.1 MPa), rejection performance (completely reject carbon particles in the filtration of carbon ink solution), and fouling resistance (the value of protein adsorption dropped from 0.25 to 0.05 mg/cm²). The hydrophilicity and fouling resistance of PE/PE‐b‐PEG blend membranes increased as the length of PE segment in PE‐b‐PEGs decreased. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46499.     

Potential of DMSO as greener solvent for PES ultra‐ and nanofiltration membrane preparation

In this article, the performance of polyethersulfone (PES) ultra‐ and nanofiltration membranes, prepared with the non‐toxic solvent dimethyl sulfoxide (DMSO), was investigated. The membranes were prepared by immersion precipitation via phase inversion. Experimental results proved that DMSO is a better alternative to N‐methyl‐2‐pyrrolidone (NMP) as solvent for PES ultrafiltration membranes as the membranes had a higher permeability and rejection of bovine serum albumin (BSA). An explanation was found based on experimental cloud point data and scanning electron microscopy images showing the morphology. The rejection of BSA and rose Bengal (RB) was proportional to the polymer concentration. On the contrary, the permeability decreased with increasing polymer concentration. For a casting thickness of 250 µm, an optimal balance between permeability and rejection of macromolecules for ultrafiltration was found at 24 wt % PES. The permeability was inversely proportional to the casting thickness, but a small decrease in rejection was observed when lowering the thickness. A good balance between permeability and rejection of RB was found, using a reference nanofiltration membrane of 28.5 wt % PES with 150 µm casting thickness. This membrane achieved a RB rejection of 95.3% and a pure water flux of 2.03 L m^?2 h^?1 bar^?1. The membrane thickness and polymer concentration did not have a clear influence on the hydrophilicity of the membranes. It can be concluded that DMSO is a benign alternative as compared to traditional solvents such as NMP and also results in better PES membrane performances. DMSO is a perfectly suitable solvent for ultrafiltration applications and has potential to be used for nanofiltration applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46494.     

Novel thin-film composite nanofiltration membranes fabricated via the incorporation of ssDNA for highly efficient desalination

In this work, the biomacromolecule, single-stranded deoxyribonucleic acid (ssDNA) was innovatively incorporated into the polyamide layer to tailor the permeate flux and antifouling performance of the nanofiltration (NF) membranes. With active amines groups, the ssDNA was as the aqueous phase monomers along with piperazine (PIP), and reacted with trimesoyl chloride on polyethersulfone substrate to fabricate thin-film composite (TFC) NF membranes. The NF membrane prepared under optimal ratio of ssDNA/PIP had a pure water permeability of 75.8 L m⁻² h⁻¹ (improved 58% compared to PIP NF membrane) and Na₂SO₄ rejection of 98.0% at 6.0 bar. The rejections for different inorganic salts were the order: Na₂SO₄ (98.0%) > MgSO₄ (89.2%) > MgCl₂ (72.8%) > NaCl (23.0%). Furthermore, the TFC NF membranes showed good antifouling performance in long-term running with 300 ppm bovine serum albumin and humic acid solution. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 47102.     

Positively charged composite nanofiltration membrane prepared by poly(N,N‐dimethylaminoethyl methacrylate)/polysulfone

Poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) can be crosslinked by quaternization to develop a positively charged dense network structure. According to this mechanism, PDMAEMA/polysulfone (PSF) positively charged nanofiltration membrane was developed by interfacial crosslinking polymerization using PSF plate microfiltration membrane as support layer, PDMAEMA aqueous solution as coating solution, and p‐xylylene dichloride/n‐heptane as crosslinking agent. Technique and condition of developing membrane such as concentration of coating solution, coating time, pH value of coating solution, content of low molecular weight additive in coating solution, concentration of crosslinking agent, crosslinking time, and number of coatings were studied. FTIR, SEM, and X‐ray photoelectron spectroscopy were used to characterize the structure of membranes. This membrane had rejection to inorganic salts in water solution, the rejection rate to MgSO₄ (1 g/L water solution at 0.8 MPa and 30°C) was about 90%, and permeation flux was about 10–20 L m^?2 h^?1. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2721–2728, 2004     

Fabrication of efficient pervaporation desalination membrane by reinforcement of poly(vinyl alcohol)–silica film on porous polysulfone hollow fiber

Pervaporation membrane technology is commercially successful in the dehydration of organic solvents, and the technology has potential for seawater desalination with high recovery because of its capability to treat highly saline water. But to make the technology advantageous over the other available membrane desalination technologies in terms of productivity flux without additional energy cost, the selective barrier layer is required to be extremely thin, defect‐free, hydrophilic, and selective to water. In this work, we prepared an efficient membrane by reinforcing a highly water‐permeable but continuous barrier layer of poly(vinyl alcohol)–silica (PVA‐SiO₂) hybrid material on porous polysulfone hollow fibers. The PVA‐SiO₂ in acidified and hydrated ethanol was aged at room temperature for a period to allow solvent evaporation to obtain the solution concentration desired for the reinforcement. The reinforced hollow fiber membrane with optimal PVA‐SiO₂ barrier layer thickness exhibited a performance with a flux of 20.6 L m^?2 h^?1 and 99.9% salt rejection from a saline feed of 2000 ppm NaCl at 333 K. The effects of PVA‐SiO₂, temperature, and feed salinity on the pervaporation performance of the membrane were also studied. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45718.     

High‐performance composite nanofiltration membranes fabricated via ternary mixture: Complementary preponderance of the fluorine‐containing monomer 2,2′‐bis(1‐hydroxyl‐1‐trifluoromethyl‐2,2,2‐triflutoethyl)‐4,4′‐methylene dianiline and the rigid monomer bisphenol F

In a previous study, we proved that tailoring the polyamide backbone stiffness is an effective way to fabricate high‐performance polyamide nanofiltration (NF) membranes. However, in the previous study, we mainly focused on the flat membrane and did not consider its chlorine tolerance. In this study, by regulating the aqueous‐phase compositions in the interfacial polymerization process, chlorine tolerance on NF hollow‐fiber membranes was endowed while the membrane performance stayed high. The experimental results show that when the ratio of Piperazine (PIP)–bisphenol F (BPF)/2,2′‐bis(1‐hydroxyl‐1‐trifluoromethyl‐2,2,2‐triflutoethyl)‐4,4′‐methylene dianiline (BHTTM) was 5:1:4, the NF membrane possessed a permeate flux of 21.0 L m^?2 h^?1 bar^?1 and an Na₂SO₄ rejection up to 90.0%. X‐ray photoelectron spectroscopy analysis also confirmed that the polymerization degree of the PIP–BPF–BHTTM NF membrane was the highest. Moreover, the NF membrane could tolerate active chlorine to over 10,000 ppm h Cl. After the active chlorine treatment, the permeate flux increased over 30.0 L m^?2 h^?1 bar^?1, and the Na₂SO₄ rejection was about 90.0%. Although the PIP–BHTTM NF membrane also possessed good chlorine tolerance, its permeate flux (after active chlorine treatment) was only 60% of that of the PIP–BPF–BHTTM NF membrane. Therefore, the PIP–BPF–BHTTM NF membrane possessed a combination of high flux and high chlorine tolerance and showed good potential in water treatment in rigorous environments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46482.     

TFC reverse osmosis polyamide membranes—Effect of increasing sulfonic group concentration on water flux and salt rejection performance

Thin film composite ( TFC ) membranes for reverse osmosis were prepared with a polyamide top layer with an increasing concentration of sulfonic groups obtained with mixtures of m‐phenylenediamine (MPD), and the sulfonated diamine, 4‐diaminobenzensulfonic acid (DABS) crosslinked with trimesoyl chloride via interfacial polymerization. The presence of sulfonic groups in the top layer diminishes the roughness of the surface of the membrane as observed by scanning electron microscopy and atomic force microscopy. It was also found that the best curing temperature for stabilization of the top polyamide layer in the TFC membrane was 90 °C. Increased hydrophilicity with an increasing concentration of DABS in the top layer of the membrane was confirmed by contact angle measurements. The results show that concentrations above 5 wt % DABS were detrimental for the membrane flux and salt rejection, R(%). The incorporation of sulfonic groups up to 5 wt % DABS improves the flux and R(%) as compared to a TFC membrane without ionic groups. Constant salt rejection was observed in the TFC membrane with 5 wt % DABS which at least maintain a nearly constant water flux after three cycles and improve R(%) after repeated testing of the same membrane in a RO high pressure cell. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46500.     

Hydrophilic PVA-co-PE nanofiber membrane functionalized with iminodiacetic acid by solid-phase synthesis for heavy metal ions removal

A novel hydrophilic poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofiber membrane for heavy metal ions removal was fabricated by the solid phase synthesis of iminodiacetic acid (IDA) on nanofiber membrane surfaces. The hydrophilic PVA-co-PE nanofiber membranes were activated with cyanuric chloride. The IDA was then covalently linked to the activated PVA-co-PE nanofiber membranes. The chemical structures of activated and functionalized PVA-co-PE nanofiber membranes were confirmed with FTIR–ATR. The morphology of PVA-co-PE nanofiber membranes were characterized with SEM. The increase in the amount of IDA on functionalized PVA-co-PE nanofiber membranes significantly improved the adsorption amount of Cu²⁺. The IDA functionalized PVA-co-PE nanofiber membranes demonstrated excellent adsorption capability of Cu²⁺, Co²⁺, Zn²⁺ and Ni²⁺. The adsorption of above heavy metal ions could be repeatedly regenerated by desorbing the ions adsorbed on nanofiber membranes. The novel IDA functionalized PVA-co-PE nanofiber membranes have great potential in the application of industry and drinking water treatment.     

Amphiphilic poly(acrylonitrile‐co‐acrylic acid)/silver nanocomposite additives for the preparation of antibiofouling membranes with improved properties

This work focuses the preparation of polymer‐silver nanocomposite (Ag‐Nc) dense free standing films and nonwoven fabric supported porous ultrafiltration membranes with improved membrane performance and long‐term antibiofouling properties. New polyacrylonitrle‐based Ag‐Ncs, poly(acrylonitrle‐co‐acrylic acid)‐silver (PAN‐co‐PAA‐Ag) containing 35 wt% of PAA and 0.35–0.65 wt% of Ag‐nanoparticles (Nps) were synthesized and used as additives for the fabrication of PAN‐based (PAN/PAN‐co‐PAA‐Ag) Ag‐Nc porous membranes and dense‐free standing films. The Ag‐Nps were homogeneously dispersed into the PAN‐co‐PAA random copolymer matrix. The prepared membranes (PAN/PAN‐co‐PAA‐Ag) showed combination of properties such as excellent antimicrobial activity towards both Gram Negative and Gram Positive bacteria (prevent biofilm formation), improved protein antifouling properties, and enhanced water flux when compared to neat PAN‐based membrane. The antimicrobial properties, hydrophilicity, and the water flux of various membranes follow the following order for the membranes PAN < PAN/PAN‐co‐PAA < PAN/PAN‐co‐PAA‐Ag. Extraneous addition of small amount of polyethylene glycol (PEG) during preparation of additive i.e. [PEG + PAN‐co‐PAA]‐Ag further improved the protein antifouling properties of the PAN‐based membranes (PAN/[PEG+PAN‐co‐PAA‐Ag]). The dispersed Ag‐Nps were stable on the surface of phase inverted membranes for long period of time and PAN/PAN‐co‐PAA‐Ag membranes are therefore suitable for long‐term water treatment under bacterial environment. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Development of stable and active PVA‐PSSA/SA‐PVA catalytic composite membrane for esterification enhancement

An active and stable catalytic composite membrane (CCM), poly(vinyl alcohol)–poly(styrene sulfonic acid)/sodium alginate–poly(vinyl alcohol) (PVA‐PSSA/SA‐PVA), was prepared to enhance the esterification of ethanol and propionic acid. The morphologies and crystal structures of the CCMs were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray diffraction. The effects of catalytic layer thickness, mass ratio of PVA to PSSA, concentration of catalytic layer solution, ratio of reaction volume to membrane area, and molar ratio of propionic acid to ethanol were discussed. The pervaporation results showed that the flux of CCM increased from 118 to 320 g m^?2 h^?1 compared with the SA‐PVA membrane because of the close affinity and low resistance of PSSA to water. After crosslinking with 3‐aminopropylmethyldiethoxysilane, the CCMs had good catalytic activities. The acid conversion reached 92.8% at 75 °C in 12 h, and the stabilization of the CCM was greatly improved. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46514.     

Preparation of PFSA‐PVA/PSf hollow fiber membrane for IPA/H2O pervaporation process

Using Na⁺ form of perfluorosulfonic acid (PFSA) and poly(vinyl alcohol) (PVA) as coating materials, polysulfone (PSf) hollow fiber ultrafiltration membrane as a substrate membrane, PFSA‐PVA/PSf hollow fiber composite membrane was fabricated by dip‐coating method. The membranes were post‐treated by two methods of heat treatment and by both heat treatment and chemical crosslinking. Maleic anhydride (MAC) aqueous solution was used as chemical crosslinking agent using 0.5 wt % H₂SO₄ as a catalyst. PFSA‐PVA/PSf hollow fiber composite membranes were used for the pervaporation (PV) separation of isopropanol (IPA)/H₂O mixture. Based on the experimental results, PFSA‐PVA/PSf hollow fiber composite membrane is suitable for the PV dehydration of IPA/H₂O solution. With the increment of heat treatment temperature, the separation factor increased and the total permeation flux decreased. The addition of PVA in PFSA‐PVA coating solution was favorable for the improvement of the separation factor of the composite membranes post‐treated by heat treatment. Compared with the membranes by heat treatment, the separation factors of the composite membranes post‐treated by both heat treatment and chemical crosslinking were evidently improved and reached to be about 520 for 95/5 IPA/water. The membranes post‐treated by heat had some cracks which disappeared after chemical crosslinking for a proper time. Effects of feed temperature on PV performance had some differences for the membranes with different composition of coating layer. The composite membranes with the higher mass fraction of PVA in PFSA‐PVA coating solution were more sensitive to temperature. It was concluded that the proper preparation conditions for the composite membranes were as follows: firstly, heated at 160°C for 1 h, then chemical crosslinking at 40°C for 3 h in 4% MAC aqueous solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Development of thin‐film composite membranes for carbon dioxide and methane separation using sulfonated poly(phenylene oxide)

Novel membranes based on sulfonated poly (phenylene oxide) (SPPO) was developed. SPPO membranes in the hydrogen form were converted to metal ion forms. The effect of exchange with metal ions including monovalent (Li⁺, Na⁺, K⁺), divalent (Mg²⁺, Ba²⁺, Ca²⁺) and trivalent (Al³⁺) ions was investigated in terms of permeation rate and permeation rate ratios for CO₂ and CH₄ gases. Both dense homogeneous membranes and thin‐film composite (TFC) membranes were studied for their gas separation characteristics. The effect of membrane preparation conditions and operating parameters on the membrane performance were also investigated. The selectivity of the TFC membrane increased as the cationic charge density increased as a result of electrostatic cross‐linking. TFC membrane of very high selectivity was achieved by coating a thin layer of SPPO‐Mg on a PES substrate. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 735–742, 2000     

Electrospinning preparation,characterization, and enhanced photocatalytic activity of an Silicotungstic acid (H4SiW12O40)/poly(vinyl alcohol)/poly(methyl methacrylate) composite nanofiber membrane

Silicotungstic acid (H₄SiW₁₂O₄₀)/poly(vinyl alcohol) (PVA)/poly(methyl methacrylate) (PMMA) composite nanofiber membranes were prepared by an electrospinning technique. A PMMA emulsion was mixed with PVA and H₄SiW₁₂O₄₀ evenly in water (electrospinning solvent). The configuration and elemental composition of the membranes were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy. The results indicate that H₄SiW₁₂O₄₀ with an intact Keggin structure existed in the composite membrane. The as‐prepared H₄SiW₁₂O₄₀/PVA/PMMA membranes exhibited enhanced photocatalytic efficiency (>84%) in the degradation of methyl orange (MO); it outperformed H₄SiW₁₂O₄₀ powder (4.6%) and the H₄SiW₁₂O₄₀/PVA nanofiber membrane (75.2%) under UV irradiation. More importantly, the H₄SiW₁₂O₄₀/PVA/PMMA membranes could be easily separated from the aqueous MO solution, and the photocatalytic efficiency of the membranes decreased inappreciably after three photocatalytic cycles. This may have been due to the enhanced water tolerance of the membranes and the stability of H₄SiW₁₂O₄₀ in the membranes. The photocatalytic process was driven by the reductive pathway with a much faster degradation rate because of the presence of PVA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43193.