Gas Transport Properties of Polybenzimidazoles with Bulky Substituents

This work deals with the gas transport characteristics at 35 °C of two new polybenzimidazoles (PBIs) previously synthesized at INEOS RAS for use in high-temperature fuel cells: PBIs with bulky phosphonethylated substituents (PBI-O-PhT-P) and PBIs with bulky substituents and a hexafluoroisopropylidene group in the main chain (PBI-4MeO-6F). It is shown that both of these polymers are moderately permeable polymers and, in terms of hydrogen permeability, are at the level of previously studied PBIs with bulky or fluorinated substituents. PBI-O-PhT-P exhibits irregular transport parameters for CO2, indicating specific interactions of CO2 with the polymer. Despite the low selectivity values, taking into account an increase in the selectivity of H2/CO2 with temperature, there is every reason to assume that the studied PBIs are promising for the processes of high-temperature hydrogen separation.