Parametric investigations on proton conducting membrane by radiation induced grafting of 4-vinylpyridine onto poly(vinylidene fluoride) and phosphoric acid doping

Abstract

Abstract Proton conducting membrane composed of grafted basic moiety doped with phosphoric acid (PA) was studied. The membrane denoted as PVDF-g-4-VP/PA was prepared by radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(vinylidene fluoride) (PVDF) films followed by doping with PA. The effect of grafting conditions on the degree of grafting (G%) was investigated. The acid doping conditions (G%, time and PA concentration) were also investigated with respect to doping level. The grafted precursors and the acid doped membranes were characterized by means of Fourier transform infrared (FTIR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). The membranes showed a thermal stability up to a temperature of ∼ 160 ℃, above which they undergo a multi-step degradation pattern due to decomposition of the protonated functions, poly(4VP) grafts and PVDF matrix, respectively. The proton conductivities of the membranes were found to increase with the increase in G% ( doping level) and the temperature with a maximum proton conductivity of 62 mS cm−1 achieved at 100 ℃ without any humidification. The results of the present study show that the prepared membrane has a potential to be proposed for operating polymer electrolyte membrane fuel cell above 80 ℃.