X-ray Absorption and Solid-State NMR Spectroscopy of Fluorinated Proton Conducting Polymers

F-19 and C-13 solid-state nuclear magnetic resonance (SSNMR) spectra and near edge X-ray absorption fine structure (NEXAFS) spectra at the S 2p, C Is, O Is, and F Is edges of three different types of perfluorosulfonic acid (PFSA) proton conducting polymers are reported. The NEXAFS spectra were recorded in a scanning transmission X-ray microscope (STXM). They are reported on quantitative intensity scales, suitable for use as reference standards for analytical spectromicroscopy studies. The NEXAFS spectral features are assigned using comparisons to the corresponding spectra of small molecule and polymer analogues, including C is and F is spectra of polytetrafluoroethylene (PTFE) recorded using STXM. The F-19 and C-13 SSNMR spectra are reported and analyzed. Within each type of spectroscopy, the spectra of the three types of PFSA are very similar. However, small but statistically significant differences were identified which give insights into how minor molecular structure differences are reflected in the SSNMR and NEXAFS spectra. The relative chemical sensitivity of SSNMR and NEXAFS for studies of PFSA materials is compared. Solution-state NMR diffusion profile analyses of two PFSA ionomer dispersions are also reported.