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Abstract: A novel salt-responsive thin-film composite (TFC) reverse osmosis (RO) membrane was prepared by tethering a zwitterionic polymer poly (4-(2-sulfoethyl)-1-(4-vinylbenzyl) pyridinium betaine) (PSVBP) onto a commercial RO membrane. The graft polymerization was conducted by surface-initiated free radical polymerization of SVBP initiated by a K2S2O8–NaHSO3 redox system. The membrane surface before and after graft polymerization was investigated in detail using ATR-FTIR, XPS, zeta potential, water contact angle and SEM. The change on surface chemical composition demonstrated successful grafting of PSVBP onto the RO membrane surface. The PSVBP grafting added negative charge onto the membrane surface and significantly improved membrane surface hydrophilicity. The RO test indicates that PSVBP grafting can increase the rejection from 98.0% to 99.7% with the trade-off 20% of the permeation flux. A cross-flow protein fouling test as long as 100h indicates that the resulted PA-g-PSVBP membrane had superior antifouling property in the short term but lost the advantage for long-term operation. In spite of the long-term fouling, the PA-g-PSVBP membrane can restore 90% of the initial flux by rinsing with brine. The salt-responsive property of the PSVBP brush is believed to provide a driving force for the release of protein foulants. [Copyright &y& Elsevier]

Abstract: A novel random terpolymer poly(methylacryloxyethyldimethyl benzyl ammonium chloride-r-acrylamide-r-2-hydroxyethyl methacrylate) (P(MDBAC-r-Am-r-HEMA)) was synthesized via free radical polymerization and used as the coating material on the polyamide thin film composite (TFC) reverse osmosis (RO) membrane to improve its chlorine resistance and antifouling performance. The chlorine resistance of the membranes was evaluated by cross-flow filtration of the NaClO solution. Antifouling performance was evaluated by cross-flow filtration of the protein solution and cell-culture experiments. The membrane surface was analyzed via ATR-FTIR, XPS, SEM and streaming potential measurements. The coated membrane can tolerate chlorine exposure over 16,000ppmh, which is 7–10 times the pristine membrane. The bacteria growth can be significantly depressed on the coated membrane surface. The coated membrane can retain its flux very well under protein filtration. It is believed that the surface coating layer works as a protective and sacrificial layer, preventing the attack of chlorine on the underlying polyamide film. The PMDBAC and PAm components are essential to the antimicrobial property and the improved surface hydrophilicity is beneficial to the antifouling performance of the membrane. The coated membrane offers potential use as a novel RO membrane with improved antifouling performance and chlorine resistance. [Copyright &y& Elsevier]

Abstract: Thio-ene chemistry was used to modulate pore size and surface properties of regenerated cellulose membranes (RCM). A series of thiol PEGs (PEG-SH) (Mn, ca. 2000, 6000 and 10,000g/mol) were tethered onto vinylated RCM surface. The membrane surface was analyzed by ATR–FTIR, XPS and SEM. The thio-ene reaction conditions, including the UV irritation time, the 2,2-dimethoxy-2-phenylacetophenone (DMPA) concentration and the PEG-SH concentration, were optimized to achieve high graft yields. The highest graft densities for PEG2000, PEG6000 and PEG10,000 are 1.37nm−2, 0.32nm−2 and 0.10nm−2, respectively. Membrane pore size was determined using the Guerout–Elford–Ferry method. The antifouling performance was evaluated by the protein filtration experiment. Effects of graft chain length and graft density on membrane morphology, pore size, permeation and antifouling properties were systematically studied. The results indicate that the change of membrane morphology, pore size and permeation properties with PEG grafting is more closely related to graft density than the chain length. The attainment of high graft density is more important than long chain length to achieve excellent antifouling performance. A series of membranes with pore size ranging from 70 to 140nm were obtained. [Copyright &y& Elsevier]

Graphical abstract Highlights • Amino acid grafted AO-PAN@OHec membrans were fabricated and used for hemoperfusion. • The mechanical properties of PAN membranes were significantly improved by adding OHec. • The hydrophilic surface of the Lys-PAN@OHec membranes reduced protein absorption. • The modified membranes enhanced anti-fouling ability and blood compatibility. Abstract By blending the modified laponite (OHec) and polyacrylonitrile (PAN), we prepared polyacrylonitrile nanofiber membranes (PAN@OHec) using the electrospinning technique. Then, the amidoxime modification was carried on using the hydroxylamine hydrochloride, yielding NH 2 contained amidoximated polyacrylonitrile nanofiber membranes (AO-PAN@OHec). Amino acids were grafted onto AO-PAN@OHec by a hydrothermal method to prepare materials with a good hemocompatibility. The morphology, structure, wettability, and chargeability of the modified Lys-PAN@OHec nanofiber membranes were characterized by Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), Energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), WCA and Solid zeta potential measurements. We investigated the anti-protein contamination ability of the modified PAN nanofiber membranes. Hemocompatibility of the modified PAN nanofiber membranes were evaluated by the adhesion property of the platelet and erythrocyte. As a result, the hydrophilicity of the modified PAN nanofiber membranes were significantly improved. The protein adsorption was decreased. Besides, the modified membranes were proved to suppress the adhesion of platelet and erythrocyte compared with original PAN membranes. [ABSTRACT FROM AUTHOR]

A fast and facile protocol is reported aiming at improving the antifouling property and hemocompatibility of poly(vinylidene fluoride) (PVDF) membranes by tethering PEG hydrogel and zwitterion immobilization. The coated PEG hydrogel was first prepared by interfacial polymerization and tethered on an alkali treated PVDF membrane (PVDFA) surface via a simultaneous thio-ene and thiol-epoxy reaction. Then, the thiol groups of cysteine reacted with the epoxy groups in PEG hydrogel to fabricate the PVDFA-g-Cys membrane. The membrane fabrication was complete within less than 20 min and was conducted in mild conditions. The successful preparation of PVDFA-g-Cys membrane was confirmed by ATR-FTIR and XPS. Raman spectroscopy showed that the hydrogels covalently bonded to the PVDF membrane surface. The membrane retained its mechanical strength after modification. The SEM measurements suggested that the membrane became denser after hydrogel coating, meanwhile, the EDX test verified that the functional species uniformly distributed in the membrane matrix. Water contact angle (WCA), protein adsorption and protein filtration tests showed significant improvements in hydrophilicity and antifouling properties for the modified membrane. The negativity of the membrane surface measured by the streaming potential method provides a basis for protein resistance and hemocompatibility. Moreover, the suppressed platelet adhesion and prolonged plasma coagulant time show that the PVDFA-g-Cys membrane has ultralow thrombotic potential and better hemocompatibility. The reported surface modification method combing thio-ene and thio-epoxy chemistry not only facilitates fabrication of hemocompatible PVDF membrane but also provide an universal chemical platform for multifunctionalization of porous membranes. [ABSTRACT FROM AUTHOR]

Antifouling PVDF membranes were prepared by grafting hyperbranched polyols on the membrane surface via a three-step modification method. The membrane was first prepared by alkaline treatment to introduce alkenyl groups, then chemically immobilizing hyperbranched poly(ethyleneimine) (HPEI) on membrane surface through Michael reaction followed by ring opening reaction of the glycidol with amine groups. Chemical compositions, surface morphology and physicochemical properties of the original and modified membranes were characterized via attenuated total refection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), water contact angle (WCA) and zeta potential measurements. The antifouling property of the modified membrane was assessed by the static bovine serum albumin (BSA) and lysozyme (LZM) adsorption as well as cross-flow filtration of BSA aqueous solution. The results explicate that surface modification using hyperbranched polymers can alter membrane chemistry and morphology significantly. In contrast to the original PVDF membrane, the modified membrane shows superhydrophilic property and relatively high capability to resist nonspecific protein adsorption. Three HPEIs were used for modification and the obtained PVDFA-g-PG 60,000 membrane has a static BSA protein adsorption of 45 μg/cm 2 and shows the highest protein resistance. However, the PVDF-g-PG membrane is positively charged due to the unreacted amine groups. As a result, the PVDF-g-PG membranes also show high flux decline during the filtration of BSA aqueous solution due to the electrostatic interaction. In spite of that, the PVDF-g-PG membranes still maintain high flux recovery ratio and good washing properties. [ABSTRACT FROM AUTHOR]

A series of stimuli-responsive reverse (RO) membranes were prepared by tethering three stimuli-responsive polymers, poly (sulfobetaine methacrylate) (PSBMA), poly (4-(2-Sulfoethyl)-1-(4-vinyl-benzyl) pyridinium betain) (PSVBP) and poly (N-isopropylacrylamide) (PNIPAM) onto the surface of a commercial thin-film (TFC) RO membrane via surface-initiated graft polymerization. The membrane surface was characterized by ATR-FTIR, XPS, zeta potential, water contact angle (WCA), FESEM and AFM. Membrane characterization indicates successful grafting of these polymers, with more negatively-charged, smoother and more hydrophilic surfaces as a result. Long-term fouling-rinsing cycled experiments were conducted to evaluate fouling resistance and cleaning efficiency. With CaCO 3 as the foulant, the modified membranes showed better fouling resistance in the whole testing as long as 320 h; with BSA as the foulant, they only showed better antifouling performance in short term. However, the modified membranes showed much higher cleaning efficiency in both cases, with the PA-g-PSVBP membrane as the best one. [ABSTRACT FROM AUTHOR]