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

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, PTO₂-1/2/3, via a one-pot reaction under three different conditions. The synthesis was achieved through BBr₃ and HBr-mediated oxidation radical polymerization and demethylation using low-cost starting materials. The open-shell character of PTO₂ was systematically confirmed by various characterization techniques, including ¹H NMR, electron spin resonance, and MALDI-TOF mass spectrometry. Notably, PTO₂-2 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), PTO₂-2 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.