One‐Step Polymerized Stable Open‐Shell Poly(3,4‐dioxythiophene) Radicals for High Photothermal Conversion and Electron Conductivity

ABSTRACT Open‐shell organic radical semiconductors, distinguished by their unique electronic ground states, have attracted growing interest as alternatives to conventional closed‐shell materials. However, their sensitivity to oxygen often leads to limited chemical and photothermal stability, hindering practical application. In previous work, we identified widespread open‐shell diradical character in donor–acceptor semiconductors. In this study, we propose to fully introduce oxygen radicals into the backbone of polythiophene and other donor–acceptor materials, reported three open‐shell poly(3,4‐dioxythiophene radical) polymers, PTO 2 ‐1/2/3, via a one‐pot reaction under three different conditions. The synthesis was achieved through BBr 3 and HBr‐mediated oxidation radical polymerization and demethylation using low‐cost starting materials. The open‐shell character of PTO 2 was systematically confirmed by various characterization techniques, including 1 H NMR, electron spin resonance, and MALDI‐TOF mass spectrometry. Notably, PTO 2 ‐2 exhibited a HOMO energy level of ‐5.42 eV and high electronic conductivity of 2.6 × 10 − 2 S cm − 1 , demonstrating a new design strategy for non‐doped organic semiconductive radical polymers. Furthermore, under 808 nm laser irradiation (1 W cm − 2 ), PTO 2 ‐2 heated from 28°C to 205°C within 60 s, showcasing outstanding photothermal conversion capability. This study provides a new platform for constructing low‐cost, stable, non‐doped open‐shell polymers.