As the display industry evolves

the research and development of colorless transparent polyimide (CPI) films for use in flexible display covers have become increasingly prominent. This study leverages commercial anhydrides and diamine monomers to fine-tune the main chain structure

fluorine content

and intermolecular hydrogen bonding

thereby achieving an equilibrium among transparency

dimensional stability

thermal resistance

and mechanical strength of the films. The produced CPI-2-TF film showcases exceptional optical average transmittance (Tav>88%)

along with minimal coefficients of thermal expansion (CTE) (<13 × 10-6 K-1)

elevated glass transition temperatures (Tg) (≥380 ℃)

and superior mechanical properties. These attributes establish a robust foundation for the commercialization and mass production of CPI. Moreover

this study specifically examines the bend-durability of CPI-2-TF. After 200k bending cycles

the film maintained over 99% of their original average transmittance (Tav) and exhibited a mere 4% decrease in mechanical properties. Upon extending the bending to 400k cycles

the films retained virtually unchanged optical performance and over 92% of their mechanical integrity

demonstrating high potential for applications in folding screen smartphones and similar devices.