Effect of sulfone linkage on chain architecture and structure-property relationships of colorless and transparent polyimides.

Six colorless and transparent polyimide (CPI) films were synthesized using two dianhydrides-4,4'-biphenyl dianhydride (BPA) and 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA)-in combination with three diamines to investigate the effect of backbone structure on material properties. BPA-based CPIs exhibited more linear and densely packed chain structures, resulting in higher glass transition temperatures, enhanced thermal stability, superior mechanical properties, and lower coefficients of thermal expansion. In contrast, DSDA-based CPIs containing polar -SO2- linkages showed slightly reduced glass transition temperatures but improved optical transparency and solubility due to suppressed intermolecular interactions and reduced chain packing density. These results demonstrate that backbone rigidity and polarity play critical roles in balancing thermomechanical stability, optical transparency, and processability in CPI systems. The developed CPI films, which combine high thermal resistance with excellent optical clarity and mechanical robustness, are promising candidates for advanced flexible electronic and optoelectronic systems, including next-generation intelligent and adaptive device platforms.