Highly phosphonated polypentafluorostyrene: Characterization and blends with polybenzimidazole

Abstract

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 (–PO3H2↔–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 σ=5×10−4Scm−1 at 150°C in dry N2 and σ=1×10−3Scm−1 at 150°C (λ=0.75). Furthermore, this polymer showed only 48% of anhydride formation when annealing it at T=250°C for 5h and only 2% weight loss during a 96h 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.