In situ electron spin resonance study of styrene grafting of electron irradiated fluoropolymer films for fuel cell membranes

Three different electron beam irradiated fluoropolymers (ETFE, FEP, and PVDF) as well as their grafting reactions with styrene in different diluents were investigated by means of electron spin resonance (ESR). Depending on the atmosphere during irradiation, ESR spectra of peroxy and alkyl radicals were observed. Radical decay as a function of time and temperature was investigated in the presence and absence of solvent. Grafting levels and number of monomer units per chain were calculated for both types of radicals. Irradiation atmosphere, grafting temperature, and added solvent affect the morphology of the fluoropolymers, in particular the crystalline versus amorphous fractions and their swelling. They thus influence the rate at which the initial radicals at the polymer backbone are reached during the grafting process. (c) 2006 Wiley Periodicals, Inc.