Photo-Tuned Solid-Liquid Transition of Azo-Grafted Poly(thioctic acid) with Ultrahigh Photothermal Conversion...

Functional materials with photo-regulated solid-liquid transition have garnered significant attention and found extensive applications across cutting-edge domains. However, previous photo-liquefiable behaviors of azopolymers are usually induced through UV light, which may damage the performances of the materials and is also harmful to human health. Here, a novel azopolymer (Azo-PTA) was fabricated via the ring-opening copolymerization of thioctic acid (TA) and azobenzene-modified thioctic acid (Azo-TA). Interestingly, Azo-PTA could undergo a reversible solid-liquid transition under green light irradiation. The phase transition process of Azo-PTA was investigated systematically through various experimental and measurement methods. The results demonstrated that the solid-liquid transition of Azo-PTA was ascribed to the photothermal effect rather than the photochemical process. The light-to-heat conversion efficiency of Azo-PTA was as high as 84.9%, and the temperature could increase to above 90 °C within 30 s of green light irradiation. Consequently, azopolymers with green light-regulated solid-liquid transition behaviors were successfully achieved. Moreover, several cutting-edge applications of Azo-PTA were explored, including photo-switchable adhesion, self-healing coating, and smart window. Our finding thus opens up a new platform for the fabrication of azopolymers with visible light-regulated solid-liquid transition.