Bio-Based Transparent Self-Healable Polyimides Enabled by Isosorbide-Derived Dianhydride Design and Aliphatic Chain-Mobility Regulation

Transparent self-healable polyimides are attractive for flexible, wearable, and sustainable electronic devices, but achieving high transparency, rapid healing, and mechanical robustness within a single material remains challenging. Herein, we report a bio-based aliphatic–aromatic polyimide platform that addresses this challenge through the cooperative molecular design of an isosorbide-derived dianhydride (ISSDA), 4,4′-oxydiphthalic anhydride, cystamine, and a bio-based long-chain aliphatic diamine (DDA). Unlike conventional aromatic polyimides, the non-planar and non-conjugated ISSDA structure reduces charge-transfer complex formation and prevents compact chain packing, enabling high optical transparency in a self-healable polyimide network. The DDA segment further introduces controlled chain flexibility, lowers the effective healing barrier, and improves segmental mobility required for dynamic disulfide exchange. As a result, the optimized film achieved over 95% transmittance above 650 nm, thermal healing within 4 min at 150 °C, and only a 7.8% loss in toughness after healing. DFT, TD-DFT, and WAXD analyses confirmed that ISSDA suppresses CTC-related electronic transitions by reducing oscillator strength, enlarging the local interchain distance, and promoting amorphous packing with increased d-spacing. This study provides a bio-derived and structurally tunable route to transparent, tough, and rapidly self-healable engineering polyimides.