Murat Barsbay

Functionalization of cellulose with epoxy groups via γ-initiated RAFT-mediated grafting of glycidyl methacrylate

Glycidyl methacrylate (GMA), was grafted from cellulose by the combination of radiation-induced initiation and the reversible addition-fragmentation chain transfer (RAFT) polymerization technique, leading to epoxy functionalized surfaces that enable further modifications. Cumyl dithiobenzoate and 2-cyanoprop-2-yl dithiobenzoate were employed as the RAFT agents. The effects of absorbed dose, monomer and RAFT agent concentrations and solvent choice on grafting yield were investigated. Characterization of the synthesized copolymers by ATR-FTIR spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, thermal analysis and contact angle measurements revealed the grafting of poly(glycidyl methacrylate) (PGMA) from cellulose. Size-exclusion chromatography analysis indicated the difficulty of controlling the polymerization of GMA due to branching and/or crosslinking reactions that might occur in PGMA structure under γ-radiation.

Towards new proton exchange membrane materials with enhanced performance via RAFT polymerization

This study focuses on the synthesis of well-defined proton exchange membranes (PEM) for fuel cell applications using reversible addition–fragmentation chain transfer (RAFT) polymerization in the radiation-induced grafting part of the overall process. Novel PEMs were prepared via grafting of polystyrene (PS) from a poly(ethylene-alt-tetrafluoroethylene) (ETFE) film as a model system. The membranes with various grafting degrees were characterised by ATR-FTIR, Raman, X-ray photoelectron and positron annihilation lifetime spectroscopy, as well as SEM-EDX, AFM, TGA, DSC and DMA techniques. This extensive characterization confirmed the existence of grafted PS chains in copolymer compositions and the success of subsequent sulfonation. The number-average molecular weight and polydispersity of the non-grafted PS determined by size-exclusion chromatography (SEC) indicated a controlled polymerization in solution. SEM-EDX and AFM results implied that polymerizations were controlled also within the ETFE matrix and on its surface. The introduction of RAFT polymerization in the PEM fuel cell preparation process enhanced the structural uniformity and performance in terms of proton conductivity compared to a conventional method.