Fabrication of Heterocyclic Polyimide Films With High Thermal Stability and Low Coefficient of Thermal Expansion

ABSTRACT The rapid development of flexible organic light‐emitting diode displays has intensified the demand for polyimide (PI) films with enhanced thermal and mechanical properties. In this study, a dibenzimidazole diamine monomer is synthesized, and a series of PI films are fabricated with the molar ratio of diamine monomer adjusted to optimize film performance. The optimized PI‐1 film exhibits a low coefficient of thermal expansion (5.0 ppm K −1 ), high glass transition temperature (452 °C) and 5% weight loss temperature (550 °C), improved tensile strength (168 MPa) and a modulus of elasticity (5.2 GPa) that meet the requirements for flexible display applications. The findings of this study provide valuable guidance for fabricating advanced PI films based on monomer composition and rational molecular structural design.