Novel semi-N-methyl substituted bisbenzimidazole based polyimide films with low coefficient of thermal expansion and high T-g

Herein, novel isomeric diamines containing semi-N-methyl substituted bisbenzimidazole and derived polyimides (PIs) were successfully synthesized. Experimental data showed that the obtained PIs exhibited outstanding heat resistance and dimensional stability, including 5 % thermal weight loss temperature (T-d5 %) of 547 similar to 557 degrees C, high glass transition temperature (T-g) of 407 similar to 423 degrees C, and low coefficient of thermal expansion (CTE) of 2.2 similar to 17.6 ppm/degrees C. The influence of molecular structure of isomeric diamines, including para and ortho substituted N-methyl, on the molecular packing and properties of polymer was discussed. As a result, the novel PIs showed lower CTE than traditional PABZ (5-amino-2-(4-aminobenzene)-benzimidazole) based PIs without bringing high water absorption. These high-performance PI films with matching CTE of copper have potential applications in flexible display substrates and printed circuit boards.

Automated summary

Novel isomeric diamines and derived polyimides with outstanding heat resistance and dimensional stability were successfully synthesized in this study, showing lower CTE compared to traditional PABZ-based PIs. These high-performance PI films with matching CTE of copper have potential applications in flexible display substrates and printed circuit boards.