S. Hietala et al., STRUCTURAL INVESTIGATION OF RADIATION GRAFTED AND SULFONATED POLY(VINYLIDENE FLUORIDE), PVDF, MEMBRANES, Journal of materials chemistry, 7(5), 1997, pp. 721-726
Radiation grafted and sulfonated poly(vinylidene fluoride), PVDF, memb
ranes have been studied by thermal analysis and X-ray diffraction to d
etermine the changes in membrane crystallinity and structure during pr
eparation. Commercial PVDF films were irradiated with an electron beam
, grafted with styrene and finally sulfonated. Both the crystallinity
and the size of the crystallites of PVDF decrease in the grafting reac
tion. A further decrease in crystallinity is observed in the sulfonati
on reaction. The residual crystallinity of PVDF was considerable (10-2
0%) even in membranes which had been subjected to severe reaction cond
itions. These results can be explained by assuming that the grafting t
akes place mainly in the amorphous region of the PVDF, and close to th
e surfaces of the crystals, but that grafts do not penetrate into the
crystals. The proton conductivity of the grafted and sulfonated PVDF m
embranes reached values comparable to those of Nafion membranes.