Photopatternable and Stretchable Random Polymer Semiconductor via Oxetane Side-Chain Engineering

Flexible electronic devices demand semiconducting materials that combine high charge transport performance, mechanical resilience, and compatibility with advanced patterning techniques. Conventional photolithography is incompatible with polymer semiconductors, and existing photo-crosslinking strategies often compromise mobility due to backbone side reactions. Here we report an oxetane side‑chain engineering strategy that enables a diketopyrrolopyrrole (DPP)‑based random terpolymer, PDPPSe‑oxe17, to form robust crosslinked networks under mild UV irradiation with iodonium salt photoinitiators. Controlled incorporation of oxetane groups (17 mol%) preserves the electronic structure of the conjugated backbone while enabling rapid ring‑opening polymerization for high‑resolution photopatterning. The polymer exhibits a high hole mobility of 2.19 ± 0.28 cm² V^{- 1} s^{- 1}, which slightly increases to 2.27 ± 0.19 cm² V^{- 1} s^{- 1} after crosslinking-representing one of the highest mobilities reported for photopatterned OFETs. The resulting 3D polyoxetane network imparts good mechanical robustness, allowing films to withstand 108% strain and retain ∼85% and ∼76% mobility at 30% and 50% strain. Even at 100% strain, the mobility remains ∼1.4 ± 0.12 cm² V^{- 1} s^{- 1}, whereas non‑crosslinked counterparts retain only ∼3% of their initial mobility. This work establishes a generalizable molecular design principle for intrinsically photopatternable and stretchable polymer semiconductors.