Polyimides with super-high T-g and ultra-low coefficient of thermal expansion from N-substituted bibenzimidazole diamines

Polyimides (PIs) with super heat-resistance and ultralow coefficient of thermal expansion (CTE) are required urgently to employ as plastic substrates in flexible-display devices. To attain the target properties, we designed and synthesized a novel bibenzimidazole diamine characterized in having a N-phenyl group, namely 1-phenyl-2,2 '-bibenzoimidazole-5,5 '-diamine (PhDABZ), and focused on an aromatic poly(benzimidazole imide) series derived from 1,2,4,5-benzenetetracarboxylic (PMDA). Incorporating bibenzimidazole and N-substituent effectively increase the interchain interaction and chance for flexible film formation, which provides the PIs with high glass-transition temperature (T-g > 480 degrees C) and dimensional stability (CTE < 10 ppm K-1). These data provide a feasible method to achieve higher thermal properties of PIs.