Dimensionally thermally stable biomass-based polyimides for flexible electronic applications

Biomass-based polymers featuring high thermal stability and low water absorption play a vital role in contributing to the environmental sustainability of flexible electronics. In this research, we developed a series of polyimides derived from (3 R,6 S)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) (ISBESA), which can be synthesized from isosorbide bioresources. This study systematically analyzed the effect of ester or amide linkage presence and orientation on the performance of polyimides (PIs). The PI chain configuration and morphology were investigated via experimental results such as d-spacing or film density and theoretical calculations. After introducing the stiff ester linkage, PI-1 with a high chain coplanarity and stacking state exhibits a low water absorption of 0.34 and possesses outstanding thermal/mechanical stability, with a Tg higher than 300 °C, a CTE of 27.8 ppm K–1, and a Young’s modulus of 4.4 GPa, which is superior to those of most reported biopolymers and even Kapton® engineering plastics. In addition, PI-1 exhibits low dielectric properties, with a Dk of 2.84 and a Df of 0.004, due to the low chain polarity and dipole moment. We further demonstrate a flexible transistor based on PI-1 that shows electrical performance comparable to those of traditional silicon-based devices, even after thermal treatment at 150 °C or 1000 bending cycles.