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 nonplanar and nonconjugated 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 analyses confirmed that ISSDA suppresses and blueshifts the near-UV electronic transitions relevant to visible transparency, while WAXD analysis revealed enlarged interchain d-spacing and increased amorphous packing. This study provides a bio-derived and structurally tunable route to transparent, tough, and rapidly self-healable engineering polyimides.