Grafted polybenzimidazole copolymers bearing polyhedral oligosilsesquioxane pendant moieties

A series of N-POSS-substituted polybenzimidazole (POSS-g-PBI) bearing polyhedral oligomeric silsesquioxane (POSS) pendant moieties were synthesized. X-ray powder diffraction analyses and Scanning electron microscope characterization revealed that POSS was dispersed well in the polybenzimidazole matrix. The grafted POSS pendant moieties can break the PBI intermolecular face-to-face packing and hydrogen bonding. As a result, POSS-g-PBIs showed better solubility than the pure polybenzimidazole because of less tight molecular chain packings. The intrinsic viscosity of POSS-g-PBI in a DMSO solution decreased with increasing amounts of grafted POSS in the polybenzimidazole molecular chains. The mechanical properties, including Young's modulus, breaking strength and elongation at break, increased by introducing POSS into the polybenzimidazole backbone. Contact angle tests showed that the surface of POSS-g-PBI became hydrophobic with increasing amounts of grafted POSS. POSS-g-PBIs also exhibited good thermal stability.