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 PTTO 2 is designed and readily synthesized for the first time using low‐cost raw material via a straightforward BBr 3 ‐demethylation of the copolymer PTTOMe 2 precursor. The open‐shell character of PTTO 2 is carefully studied and confirmed via the signal‐silent 1 H nuclear magnetic resonance spectrum, highly enhanced electron spin resonance signal compared with PTTOMe 2 , as well as the ultra‐wide ultraviolet‐visible‐near nfraredUV–vis–NIR absorption and other technologies. Interestingly, the powder of PTTO 2 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 PTTOMe 2 . The low‐cost PTTO 2 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.