Characterization of partially sulfonated polyoxadiazoles and oxadiazole–triazole copolymers

Polyoxadiazoles as proton exchange membranes for fuel cell application

The number of researches on the ion exchange membrane has increased considerably in recent years showing interest in fuel cell technology for the automobile and portable applications. The most promising fuel cell technology for low-temperature operation (80 °C < T < 150 °C) uses a polymer membrane separating the anode and cathode compartments in an electrochemical cell. Polyoxadiazoles (PODs) belong to a class of heterocyclic polymers, which possess a number of unique properties, such as thermal, mechanical, and chemical resistance. In the present review, numerous ways of POD synthesis are discussed in relation to their functional properties. In addition, different approaches to the elaboration of POD-based composite membranes are discussed in details in order to reveal the structure/properties relationship.

Hydroxyl functionalized polytriazole-co-polyoxadiazole as substrates for forward osmosis membranes

Hydroxyl functionalized polytriazole-co-polyoxadiazole (PTA-POD) copolymers have been synthesized and cast as promising highly thermally stable, chemically resistant, and antiorganic/biological fouling porous substrates for the fabrication of thin-film composite (TFC) forward osmosis (FO) membranes. The roles of PTA/POD ratios in the membrane substrates, TFC layers, and FO membrane performance have been investigated. This study demonstrates that the substrate fabricated from the copolymer containing 40 mol % PTA is optimal for the TFC membranes. Compared to the POD-TFC membrane, the 40 mol % PTA-TFC membrane exhibits a remarkable decrease in structural parameter (S) of more than 3.3 times. In addition, the 40 mol % PTA-TFC membrane is characterized by high water fluxes of 24.9 LMH and 47.2 LMH using 1 M NaCl as the draw solution and DI water as the feed under FO and pressure retarded osmosis (PRO) modes, respectively. Compared to a polysulfone (PSU) supported TFC-FO membrane under similar fabrication conditions, the 40% mol PTA-TFC membrane shows better FO performance and enhanced antifouling properties on the support (lower protein binding propensity and improved bacterial inhibition). Moreover, the performance of the 40 mol % PTA supported TFC-FO membrane can be improved to 37.5 LMH (FO mode)/78.4 LMH (PRO mode) and potentially higher by optimizing the support morphology, the TFC formation, and the post-treatment process. Hence, the use of newly developed hydroxyl functionalized polytriazole-co-polyoxadiazole copolymers may open up a new class of material for FO processes.

Anhydrous proton motion study by solid state NMR spectroscopy in novel PEMFC blend membranes composed of fluorinated copolymer bearing 1,2,4-triazole functional groups and sPEEK

The proton mobility in a new family of PEMFC blend membranes containing 1,2,4-triazole groups is studied by infrared and solid state NMR spectroscopies.

Cross-linked hybrid nanofiltration membrane with antibiofouling properties and self-assembled layered morphology

A new siloxane monomer, 3-(3-(diethoxy(2-(5-(4-(10-ethoxy-4-hydroxy-2,2-dimethyl-11-oxa-2-ammonio-6-aza-10-silatridecan-10-yl)phenyl)-1,3,4-oxadi azol-2-ylthio)ethyl)silyl)propylamino)-2-hydroxy-N,N,N-trimethylpropan-1-aminium chloride (OA), was synthesized by reported 3-((4-(5-(2-((3-aminopropyl) diethoxysilyl)ethylthio)-1,3,4-oxadiazol-2-yl)phenyl) diethoxysilyl)propan-1-amine (APDSMO) and glycidyltrimethylammonium chloride (GDTMAC) by epoxide ring-opening reaction. OA-poly(vinyl alcohol) (PVA) hybrid antibiofouling nanofilter (NF) membranes were prepared by acid-catalyzed sol-gel followed by formal cross-linking. Membranes showed wormlike arrangement and self-assembled layered morphology with varying OA content. Hybrid NF membrane, especially OA-6, showed low surface roughness, high hydrophilic nature, low biofouling, high cross-linking density, thermal and mechanical stablility, solvent- and chlorine-tolerant nature, along with good permeability and salt rejection. Prepared OA-6 hybrid NF membrane can be used efficiently for desalting and purification of water with about 2.0 g/L salt content (groundwater in major part of India). The described method provides novel route for producing antibiofouling membranes of diversified applications.

Synthesis of Proton-conducting Electrolytes Based on Poly(vinylidene fluoride-co-hexafluoropropylene) via Atom Transfer Radical Polymerization

The preparation of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) grafted poly (styrene sulfonic acid) (PVDF-HFP-g-PSSA) copolymer as proton-conducting electrolytes by atom transfer radical polymerization of styrene sulfonic acid at the secondary halogenated sites of PVDF-HFP was demonstrated. The structure of the PVDF-HFP-g-PSSA copolymers was verified by Fourier transform infrared spectra, proton nuclear magnetic resonance spectra and X-ray photoelectron spectroscopy. The PVDF-HFP-g-PSSA copolymer membranes showed ion exchange capacity values ranging from 0.045 to 0.272 mEq g-1, the water uptake varied from 13.7 to 26.8 wt.% and the proton conductivities varying from 1.85 2 10-4 to 9.8 2 10-4 S cm-1, all of which could be modulated by control of the polymerization time. All the membranes exhibited decomposition temperature up to around 350 °C as revealed by thermogravimetric analysis. The incorporation of poly(styrene sulfonic acid) into PVDF-HFP chains resulted in melting at higher temperatures. The scanning electron microscopy observation indicated that the density of the ionic pathways increased with ionic content, which explained why the ionic conductivity rose to relatively high values as polymerization time increasing.