Polyimides with low coefficient of thermal expansion derived from diamines containing benzimidazole and amide: Synthesis, properties, and the N-substitution effect

Three novel diamines, incorporating benzimidazole and amide moieties, namely 4-amino-N-(5-amino-benzimidazol-2-yl)-benzamide (6a), 4-amino-N-(5-amino-1- methyl-benzimidazol-2-yl)-benzamide (6b), and 4-amino-N-(5-amino-1-phenyl -benzimidazol-2-yl)-benzamide (6c), were designed and synthesized. A series of poly(benzimidazole-amide-imide) (PBIAI) films were prepared from the resulting diamines and 4,4-biphthalic dianhydride (BPDA). These flexible polyimides (PIs) showed high glass transition temperatures (T-g = 353-379 degrees C), low coefficients of thermal expansion (CTE = 3.7-12.3 ppm K-1) and good mechanical properties (sigma = 152-207 MPa and E = 4.5-7.7 GPa), promising candidates for applications in flexible-display substrates. Furthermore, the data guided a feasible method to enhance T-g and reduce CTE by introducing benzimidazole and amide units into PI main chains, and the effect of different N-substituents on performance was revealed.

Automated summary

Three novel diamines were designed and synthesized, leading to the preparation of high-performance poly(benzimidazole-amide-imide) films with high glass transition temperatures and excellent mechanical properties, making them promising candidates for flexible-display substrates.