Synthetic strategies for highly transparent and colorless polyimide film

Abstract Polyimide (PI) is one of the best engineering plastics with excellent thermal, mechanical, dielectric performance and chemical stability. Among various PI products, film is one of the most dominant types. If PI films are to be applied to optical devices and display equipment, it is necessary to improve their optical transparency in the ultraviolet–visible region. However, improving the optical transparency of PI films would affect their thermal performance including thermal and dimensional stability. Therefore, how to balance optical and thermal performance to obtain highly transparent PI films with the best overall performance becomes a focus of current research field. In this review, we categorize transparent PI films into highly transparent PI, transparent PI with high glass transition temperature ( T g ) and transparent PI with low coefficient of thermal expansion (CTE) based on their optical and thermal properties. Then, we review research progress in the field of polymer molecular design including synthesis strategies and properties in recent 5 years, to inspire research ideas and elaborate on the possible ways to develop high‐performance, colorless and transparent PI materials.