Grafting of nitrogen containing monomers onto poly(ethylene-alt-tetrafluoroethylene) films by bulk polymerization for proton exchange membranes

Bulk polymerization is suggested as an alternative to solution polymerization to graft N-containing monomers onto poly(ethylene-alt-tetrafluoroethylene) films to produce highly conductive membranes. Among the tested monomers, 4-vinyl pyridine was found as the most reactive monomer giving grafting levels (%GL) >120 % compared with %GL <45 % previously reported under similar conditions. Doping grafted films with H3PO4 converted them to membranes with enhanced water swellability but their conductivity values were at the same order of magnitude of membranes prepared by solution polymerization. These results demonstrate the importance of having both high grafting levels and homogeneous distribution of grafting throughout the base polymer.