High-performance shape memory aromatic-aliphatic polybenzimidazole copolymers

Abstract

Aromatic-aliphatic polybenzimidazole-based random copolymers (coPBIs) were synthesized by polycondensation of 3,3′-diamonobenzidine and two different dicarboxylic acids, namely 4,4′-oxybis (benzoic acid) and dodecanedioic acid, in Eaton's reagent. Reaction conditions were optimized and the copolymers' composition, determined by 1H NMR spectroscopy, almost completely corresponds to the theoretical value. The resulting coPBIs were comprehensively characterized by different techniques to investigate the influence of the copolymers' composition on their physicochemical properties. It has been found that all the coPBIs demonstrate high mechanical strength, while the thermal stability of the copolymers increases with an increase in the aromatic content. CoPBIs' glass transition temperatures are in good agreement with the calculated from the Gordon-Taylor equation values and varied in the range of 265–301 °C, depending on the aromatic/aliphatic fragments ratio. Moreover, coPBI with 25 mol% of the aromatic content shows an improved shape memory performance (shape fixity ratio and shape recovery ratio are both >95%) in comparison to aliphatic PBI, that could be attributed to the increased content of rigid aromatic segments and a more effective intermolecular interaction. Thus, aromatic-aliphatic copolymerization is an effective tool for target regulation of thermal mechanical properties of the copolymers and could be useful for preparation of high-performance shape memory PBIs.