Azobenzene-containing polyimides (azo-PIs) as photodeformable materials have attracted scientific attention in view of combining photoresponse and high performance (such as excellent mechanical and thermal properties). In the previously reported photodeformation of azo-PIs, polarized blue–green light was utilized to produce concerted motion of azobenzene moieties based on the mechanism of photoinduced reorientation. Herein, we explored a designed azo-PI undergoing photodeformation upon unpolarized light irradiation. The azo-PI film aligned by the hot-stretching process exhibited fast and reversible bending behavior under alternate ultraviolet (UV) and visible (vis) light irradiation, indicating the efficient nano-to-macroscopic propagation of molecular deformation of azobenzene. Besides, the aligned azo-PI film even bent in hot water (80 °C) and hot silicone oil (100 and 120 °C) with UV light irradiation.

A series of colorless copolyimide films with high thermal stability and good solubility are synthesized from (trifluoromethyl)biphenyl-4,4’-diamine (TFMB) with different 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) to 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane (6FDA) dianhydride mole ratios through one-pot solution polycondensation. These copolyimide films exhibit excellent optical transparency (T400 > 90% and λ0 ~305–333 nm) with a thickness of 15 μm and good solubility in most organic solvents. The excellent optical properties are mainly attributed to the low inter- and intra-molecular charge transfer interactions due to the alicyclic structure and the strong electronegative CF3 groups. The glass transition temperature increases from 332 to 352 °C with increasing HPMDA content in the copolymers, while the thermal decomposition temperature is improved with increasing 6FDA content. These results indicate that the copolyimide films can be successfully utilized in the development of novel heat-resistant plastic substrates for the optoelectronic engineering applications.

Optically transparent polyimides with excellent thermal stability and shape memory effect have potential applications in optoelectronic devices and aerospace industries. A series of optically transparent shape memory polyimide hybrid films are synthesized from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,2′-bis-(trifluoromethyl)biphenyl-4,4′-diamine (TFMB) with various polyhedral oligomeric silsesquioxane (POSS) contents and then subjected to thermal imidization. The hybrid films show good optical transparency (>80% at 400 nm and >95% at 500 nm) with cutoff wavelengths ranging from 318 to 336 nm. Following the incorporation of the inorganic POSS structure, the hybrid films exhibit excellent thermal stability with glass transition temperature (Tg) ranging from 351 to 372 °C. The hybrid films possess the highest Tg compared with the previously-reported shape memory polymers. These findings show that POSS is successfully utilized to develop transparent polyimides with excellent thermal stability and shape memory effect.