Mainchain Alternating Azopolymers with Fast Photo-Induced Reversible Transition Behavior

The trans-to-cis rate and ratio are key factors to azopolymers for many valuable photoresponsive applications. In this work, we designed and synthesized a series of mainchain azopolymers (P(EGx-alt-Azo)n) composed of alternatingly connected rigid azobenzene (Azo) units and flexible oligo ethylene glycol (EGx) units to accomplish a fast photo-induced reversible transition. Herein, the flexible EGx units submerge the individual Azo units to adapt to the isomerization of the Azo units. The rigid Azo units can pile up through interchain π–π stacking and isomerize adequately upon UV irradiation to accomplish swift photo-induced reversible transitions. Therefore, P(EG6-alt-Azo)19 features very fast and effective trans-to-cis isomerization and exhibits distinct a photo-switchable glass-transition temperature (Tg) and rapid solid-to-liquid transition, which is promising for applications such as healable coatings, switchable adhesives, and athermal nanopatterning. This study gives an unusual insight into designing smart polymer materials with certain topology structures.