High-temperature proton-exchange membrane fuel cells (HT-PEMFCs) are mostly based on acid-doped membranes composed of polybenzimidazole (PBI). A severe drawback of acid-doped membranes is the deterioration of mechanical properties upon increasing acid-doping levels. Cross-linking of different polymers is a way to mitigate stability issues. In this study, a new ion-pair-coordinated membrane (IPM) system with quaternary ammonium groups for the application in HT-PEMFCs is introduced. PBI cross-linked with poly­(vinylbenzyl chloride) and quaternized with three amines (DABCO, quinuclidine, and quinuclidinol) are manufactured and compared to the state-of-the-art commercial Dapazol PBI membrane ex situ as well as by evaluating their HT-PEMFC performance. The IPMs show reduced swelling and better mechanical properties upon doping, which enables a reduction in membrane thickness while maintaining a comparably low gas crossover and mechanical stability. The HT-PEMFC based on the best-performing IPM reaches up to 530 mW cm–2 at 180 °C under H2/air conditions at ambient pressure, while Dapazol is limited to less than 430 mW cm–2 at equal parameters. This new IPM system requires less acid doping than conventional PBI membranes while outperforming conventional PBI membranes, which renders these new membranes promising candidates for application in HT-PEMFCs.

In this article, we report the results of high-energy electron beam (e-beam) irradiation of polymer thin films made of poly(semiperfluoroalkyl methacrylate)s (PR F MAs) and propose plausible chemical reactions that may cause their solubility to change in fluorous liquids. It was observed that the polymer films were converted to a more soluble state under low exposure doses of e-beam, possibly due to main-chain scission. However, the films became insoluble with higher doses of e-beam. Three hypotheses were proposed to explain the reduction in solubility, and we used data from Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, mass spectrometry (MS), and nanoindentation to eliminate the less probable hypotheses. The results derived from e-beam-irradiated thin films of three PR F MAs showed that the radical-related Norrish Type I and II pathways may not be the main decomposition routes. The data also suggested that sufficient scission reactions of the perfluorooctyl moieties of PR F MAs do not occur by e-beam. We therefore assumed that the decrease in solubility of the fluorinated polymers results from intermolecular crosslinking reactions between the free radicals and reactive moieties generated on the perfluorooctyl groups by the e-beam. The unique imaging mechanism of PR F MAs may be developed further to synthesize radiationsensitive materials working under e-beam and extreme ultraviolet (λ = 13.5 nm) lithography conditions for advanced patterning applications.Highly fluorinated polymers have gained attention since the 1930s when Schloffer and Scherer discovered poly (chlorotrifluoroethylene) and Plunkett developed high-molecular-weight poly(tetrafluoroethylene) (PTFE). Later, several Additional supporting information may be found in the online version of this article.

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