Polyimides with low coefficient of thermal expansion derived from diamines containing benzimidazole and amide: Synthesis, properties, and the N‐substitution effect
Guangtao Qian, Fengna Dai, Haiquan Chen, Mengxia Wang, Mengjie Hu, Chunhai Chen, Youhai Yu
Abstract
Abstract 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°C), low coefficients of thermal expansion (CTE = 3.7–12.3 ppm K −1 ) and good mechanical properties ( σ = 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.