Highly phosphonated polypentafluorostyrene: characterization and blends with polybenzimidazole
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In this study we present results of the conductivity and resistance to thermooxidative and condensation reactions of a highly phosphonated poly(pentafluorostyrene) (PWN2010) and of its blends with poly(benzimidazole)s (PBI). This polymer, which combines both: (i) a high degree of phosphonation (above 90%) and (ii) a relatively high acidity (pKa (–PO3- H2M–PO3H ) 0.5) due to the fluorine neighbors, is designed for low humidity operating fuel cell. This was confirmed by the conductivity measurements for PWN2010 reaching r = 5 10 4 S cm 1 at 150 C in dry N2 and r = 1 10 3 S cm 1 at 150 C (k = 0.75). Furthermore, this polymer showed only 48% of anhydride formation when annealing it at T = 250 C for 5 h and only 2% weight loss during a 96 h Fenton test. These properties combined with the ability of the PWN2010 to form homogeneous blends with polybenzimidazoles resulting in stable and flexible polymer films, makes PWN2010 a very promising candidate as a polymer electrolyte for intermediate- and high-temperature fuel cell applications.