Synthetic strategies for highly transparent and colorless polyimide film

• Published in: Journal of applied polymer science 2022-07, Vol.139 (28), p.n/a
• Main Authors: Liu, Yuan‐Yuan, Wang, Ya‐Kun, Wu, Da‐Yong
• Format: Article
• Language: English
• Subjects: Chemical synthesis; coefficient of thermal expansion; colorless polyimides; Dimensional stability; Display devices; Glass transition temperature; high transparency; Materials science; Optical properties; Polyimide resins; Polymers; synthetic strategies; Thermal expansion; thermal stability; Thermodynamic properties
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.52604

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 (Tg) 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. Building high‐performance colorless and transparent polyimide (PI) films at the molecular level requires balancing the light transmittance, thermal stability, dimensional stability and other properties of PIs. The main strategy is to inhibit the formation of charge transfer complexes intermolecularly and intramolecularly, and to improve the rigidity of the molecule. This review focuses on how to achieve this goal.