Novel partially fluorinated graft block copolymer ionomer as potential proton exchange membrane material

Abstract

Abstract A novel well-defined graft block copolymer ionomer consisting of poly(2,2,3,3,3-pentafluoropropyl methacrylate)-block-poly(9-anthrylmethyl methacrylate) backbone and partially sulfonated polystyrene side chains, i.e. (PFPMA-b-PMMAnt)-g-SPS was synthesized using double click reactions (Cu catalyzed Huisgen and Diels–Alder reactions) and postsulfonation reaction. The synthesis of this graft ionomer is a three-step procedure including (i) the preparation of maleimide, alkyne and azide end-functional polymers via atom transfer radical polymerization (ATRP), (ii) performing double click reactions in one-pot technique, and (iii) sulfonation reaction of phenyl ring of polystyrene block to yield microphase separated graft block ionomer structure. 1H NMR, FT-IR spectroscopy, SEC (size exclusion chromatography) results present the successful “grafting from” method using ATRP and double click reaction. Both the membranes from graft block ionomer and its sulfonated poly(phenylene oxide) (SPPO) blends were prepared by solution casting method. The produced membranes were characterized in terms of ion exchange capacity (IEC), water uptake, proton conductivity, and thermal properties. Oxidative stabilities of the membranes were also investigated by Fenton test. The morphology of dry membranes was investigated by scanning electron microscopy (SEM). It has been found that the conductivity of the graft block ionomer/SPPO blend membrane measured at 80 °C and relative humidity of 100% is considerably higher than that of the pure SPPO possessing higher ion-exchange capacity.