Hydrogen bond modulated photothermal conversion and green-light-induced solid-liquid switching behaviors of azobenzene- and amide-functionalized poly(thioctic acid).

Abstract

Functional materials with photo-triggered solid-liquid phase transition have aroused tremendous research interest for versatile advanced applications. Nevertheless, it remains challenging to precisely tailor their photothermal and adhesive properties via rational molecular design. Herein, a series of azobenzene and amide-functionalized poly(thioctic acid) (Azo-PTA-Am) were synthesized by solvent evaporation induced ring-opening copolymerization of azobenzene-modified TA and various amide-containing TA derivatives. All Azo-PTA-Am samples could undergo reversible solid-liquid transition upon alternating green light irradiation and ambient cooling. Moreover, our results verified that amide structures could modulate hydrogen bonding strength to orderly tune material properties. From tertiary to primary amide, their light-to-heat conversion efficiency rises from 39.1% to 58.4%, accompanied by increased melting temperature and enhanced multi-substrate adhesion. The polymers possess outstanding solvent stability, cycling durability, acid/salt tolerance and recyclable bonding capacity. Consequently, Azo-PTA-Am was exploited for personalized acupoint thermotherapy relying on tunable photothermal output. Our finding provides a new strategy for fabricating photo-responsive materials with tunable performances.