Sohn, Joon-Yong, et al. Radiation Physics and Chemistry, 2012, 81(8), 923-926.
Proton exchange membranes (PEMs) based on poly(ethylene-co-tetrafluoroethylene) (ETFE) films can be successfully prepared by graft copolymerization with styrene and VTMS (vinyltrimethoxysilane) or styrene and TMSPM (3-(trimethoxysilyl)propyl methacrylate) binary monomer systems. The results show that silane-crosslinked proton exchange membrane (PEM) not only has lower water absorption and dimensional change rate, but also has higher proton conductivity under low humidity conditions.
Preparation procedure of PEMs based on ETFE film
· After drying and weighing, each dried ETFE film (25 mm thick, 5 cm x 5 cm) was placed in three different mixtures of styrene/acetone, styrene/vinylmethoxysilane(VTMS)/acetone, and styrene/3-(trimethoxy silyl)-propyl methacrylate (TMSPM)/acetone. These mixtures were exposed to g-ray irradiation from a 60Co source at a dose rate of 5 kGy/h. The films were then washed with THF to remove any remaining monomer and homopolymer, followed by a 12-hour drying period in the vacuum oven at 60±1°C.
· Next, the ETFE-g-PS/PVTMS and ETFE-g-PS/PTMSPM films underwent a sol-gel reaction by soaking in a 1 M HCl solution at 80±1°C for 24 hours. The crosslinked films were washed with deionized water and dried in a vacuum oven at 80±1°C overnight. The non-crosslinked and silane-crosslinked films were then treated with a mixture of chlorosulfonic acid/1,2-dichloroethane (2:98 v/v) at room temperature for 12 hours. The sulfonated membranes were washed with dichloromethane and deionized water to remove excess chlorosulfonic acid, followed by hydrolysis in deionized water at 70±1°C for 3 hours.
