Effect of the initial matrix material on the structure of radiation-grafted ion-exchange membranes: Wide-angle and small-angle X-ray scattering studies

Seven different fluoropolymer films were used as matrix materials for radiation-grafted ion-exchange membranes. The crystallinity and preferred orientation of these membranes were studied with wide-angle X-ray scattering, and the lamellar structure of the membranes was examined with small-angle X-ray scattering. The crystallinity of poly(vinylidene fluoride) (PVDF)-based matrix materials varied between 57 and 40%, and the crystallinity of the sulfonated samples varied between 34 and 23%. The lamellar periods of PVDF-based matrix materials were about 115 Angstrom, and the lamellar periods of poly(ethylene-alt-tetrafluoroethylene) and poly(tetrafluoroethyleneco-hexafluoropropylene) were 250 and 212 Angstrom, respectively. When the samples were grafted, the lamellar periods increased. Correlation function analysis showed very clearly that the long-range order decreased because of grafting and sulfonation processes. For those samples that showed good proton conductivity, the lamellar period also increased because of sulfonation. (C) 2002 Wiley Periodicals, Inc.