Open‐shell Poly(3,4‐dioxythiophene) Radical for Highly Efficient Photothermal Conversion

Open-shell organic radical semiconductor materials have received increasing attention in recent years due to their distinctive properties compared to the traditional materials with closed-shell singlet ground state. However, their poor chemical and photothermal stability in ambient conditions remains a significant challenge, primarily owing to their high reactivity with oxygen. Herein, a novel open-shell poly(3,4-dioxythiophene) radical PTTO₂ is designed and readily synthesized for the first time using low-cost raw material via a straightforward BBr₃-demethylation of the copolymer PTTOMe₂ precursor. The open-shell character of PTTO₂ is carefully studied and confirmed via the signal-silent ¹H nuclear magnetic resonance spectrum, highly enhanced electron spin resonance signal compared with PTTOMe₂, as well as the ultra-wide ultraviolet-visible-near nfraredUV-vis-NIR absorption and other technologies. Interestingly, the powder of PTTO₂ exhibits an extraordinary absorption range spanning from 300 to 2500 nm and can reach 274 °C under the irradiation of 1.2 W cm^-2, substantially higher than the 108 °C achieved by PTTOMe₂. The low-cost PTTO₂ stands as one of the best photothermal conversion materials among the pure organic photothermal materials and provides a new scaffold for the design of stable non-doped open-shell polymers.