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Herein, we are reporting improved process for chloromethylation of polysulfone (PS) by in situ Friedel–Craft reaction without the use of chloromethyl methyl ether (CME). Further, in situ amination (Menshutkin reaction) was carried out to prepare quaternized ammonium polysulfone (QAPS). QAPS of varied degree of chloromethylation (DCM) (44.01–65.67%) was used for preparing anion-exchange membranes (AEMs) and it was observed that their pore morphology was highly dependent on membrane drying conditions (temperature and RH). As representative case, QAPS membrane (DCM: 44.01% and named as AEM-1(NF) x : x indicates drying temperature) dried at low temperature (30 °C (RH: 75%); 45 °C (RH: 54%) and 60 °C (RH: 12%)) showed nano-porous nature with 5.28–1.89 L m −2 h −1 bar −1 permeability corresponding to 59.31–80.23% salt rejection. Further, permeability of AEM–1(NF) x followed the trend: AEM–1(NF) 30 >AEM-1(NF) 45 >AEM-1(NF) 60 . Formation of porous structure of these membranes was attributed to the phase inversion of the QAPS polymer due to presence of atmospheric water at low temperature (high RH). In addition, QAPS membranes (different DCM values) dried at 80 °C (RH:<5%), exhibited completely dense nature with negligible permeability and named as AEM-1, AEM-2 and AEM-3 (DCM; 44.01; 53.87 and 65.67, respectively). Especially, AEM-3 (DCM: 65.67%) was designed to possess all the required properties such as high water uptake (22.20%), ion-exchange capacity (1.597 mequiv g −1 ), and counter-ion transport number (0.96), along with reasonable conductivity (8.45 mS cm −1 ) due to quaternary ammonium group functionality. Chronopotentiometric and i – v studies of AEMs revealed excellent electro-transport property for AEM-3, while its electrodialysis (ED) performance confirmed the suitability for electro-membrane applications. Reported method is novel for preparing stable alkaline membrane with tuneable permeability and charged nature for separations of molecules/ions by pressure and/or electro-driven technologies. [ABSTRACT FROM AUTHOR]

We prepared highly charged bi-functionalized copolymer (BFC) and sulphonated mesoporous silica embedded with aprotic ionic liquid (IL) (1-ethyl-3-methylimidazolium ethyl sulfate) based anhydrous conducting cross-linked polymer electrolyte membrane (PEM) by sol–gel. Composite PEMs with 0–10 wt% sulphonated silica and 20 wt% IL content (BFC/Si- x /IL) were characterized by their morphology, stability, IEC, water retention ability and temperature dependent anhydrous conductivity. Conductivity of pristine BFC membrane (1.57 mS cm −1 ) was increased with incorporation of sulphonated-SiO 2 (10 wt%) in the membrane matrix (BFC/Si-10) (3.56 mS cm −1 ), may be due to formation of interconnected network or channels in the membrane matrix. After embedding of aprotic IL (20 wt%; ~80 µS/cm conductivity) in highly acidic polymer (BFC/Si-10), conductivity of BFC/Si-10/IL composite PEM was about 8.79 mS cm −1 at 30 °C. High anhydrous conductivity for BFC/Si-10/IL PEM was attributed to the exchanged protons from highly acidic membrane matrix by IL cation, and accordingly a mechanism was proposed. Further, enhanced bound water content and thus slow dehydration of BFC/Si- x /IL composite PEMs, make them a promising candidate for fuel cell application under low humidification. [ABSTRACT FROM AUTHOR]

Anion exchange membranes (AEMs) have found numerous electrochemical applications because of their good conductivity and permselectivity. Herein, we are reporting a method to prepare silica modified poly(ethyleneimine) (SMPEI) with 3-Glycidoxypropyl-trimethoxysilan (GPTMS) by epoxide ring opening reaction. Stable AEMs of different compositions were prepared with SMPEI and a plasticizer poly(vinyl alcohol) (PVA) by acid catalyzed sol–gel followed by formal cross-linking. The reported method is simple and a green alternative for the preparation of AEM without the use of hazardous chemicals. Suitability of prepared AEMs for electrodialytic application was assessed by analyzing their physicochemical properties, stabilities under operating conditions, conductivity, electro-osmotic and chronopotentiometry studies. A highly suitable membrane, SMPEI/PVA-40, exhibited 55.32 mS cm −1 conductivity (in equilibration with 0.04 N NaCl solution at 30 °C), ion-exchange capacity (1.31 meq g −1 ) and permselectivity (0.79) with good electrodialytic performance. Preparation protocols and properties of the reported composite AEM represent a promising starting point for architecting highly conducting and stable AEMs, but we have to study the trade-off between properties, stabilities and electro-osmotic mass drag before its commercial exploitation. [ABSTRACT FROM AUTHOR]

Laser-induced graphene (LIG) is a three-dimensional porous carbon material prepared by direct laser writing with a CO 2 laser on various polymers in an ambient atmosphere, leading to electrically conductive, low fouling coatings. Recently, LIG has been synthesized on porous supports, which led to highly permeable and porous separation filters and LIG composites have greatly improved the stability. On the other hand, graphene oxide (GO) has emerged as a promising 2D nanomaterial to coat porous or non-porous polymer membrane supports resulting in separation membranes with enhanced separation and surface properties. Here, we report a robust, hybrid LIG-GO membrane fabricated by filtration and crosslinking of GO onto the LIG membrane support, generating ultrafiltration membranes with tailored performance. Increasing the amount of crosslinked GO on the LIG surface resulted in increased rejection of bovine serum albumin (BSA) up to 69%, and bacterial rejection was increased from 20 to 99.9%, which agreed with the measured molecular weight cut-off determination that approached ~ 90 kDa as the GO content increased. Higher flux recovery ratios and lower BSA adsorption were seen with LIG-GO membranes, and the hybrid membranes showed comparatively good antifouling. These composite membranes showed 83% less biofilm growth compared to a typical polymer ultrafiltration membrane under non-filtration condition. Noteworthy is that the LIG supporting layer maintained its electrical conductivity and the LIG-GO membrane used as electrodes showed complete elimination of bacterial viability with potent antimicrobial killing effects when treated with mixed bacterial culture. In cross-flow filtration, LIG-GO membranes with 3V anodic electric field showed 11% improvement of flux as compared to typical polymer ultrafiltration membrane. The LIG-GO membranes expand possibilities for the use of LIG in membrane separation applications, especially ultrafiltration. Carbon-based antifouling, electrically conductive ultrafiltration membranes were fabricated using laser-induced graphene membrane supports and crosslinked graphene oxide. Image 1 • laser-induced graphene (LIG) integrated into composite membranes. • LIG composites with crosslinked graphene oxide(GO) show ultrafiltration properties. • LIG-GO composite membranes stable under extended sonication at low and high pH. • Membranes electrically active, showing low fouling and bacterial killing effects. • LIG-GO more biofouling resistant than commercial UF membrane in cross-flow testing. [ABSTRACT FROM AUTHOR]