Characterization of radiation‐grafted polymer films using CP/MAS NMR spectroscopy and confocal Raman microscopy

Preirradiated poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) base film were grafted with different amounts of an α-methylstyrene (AMS) and methacrylonitrile (MAN) copolymer. The molar ratio of AMS and MAN in the grafted polymer was determined using 13C- CP/MAS NMR spectroscopy and compared with the molar ratio determined with FTIR spectroscopy. The distribution of the components across the thickness of the grafted films was determined using confocal Raman microscopy. The validation of the confocal Raman microscopy was performed with FEP films grafted with MAN only, where pronounced grafting fronts were observed. The local degree of grafting for AMS/MAN co-grafted FEP films was calculated for each sample based on the intensity profiles, taking the mass of the grafted polymer and its molar ratio into account. The grafting of the AMS/MAN co-grafted films was found to be homogeneous over the thickness, even in case of small amounts of the copolymer (15 mass%). The homogeneity of the grafting across the film thickness is a prerequisite to obtain sufficient proton conductivity after sulfonation of the radiation-grafted films. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012