Light-Triggered Rapid and Reversible Shape Transformation of Polyolefin-like Precision Azo-Homopolymers

Abstract Designing stimuli-responsive homopolymers with a fast and reversible morphology transformation has attracted considerable focus but remains a challenge. Herein, two perfectly regioregular polyolefin-like homopolymers containing azobenzene (azo) pendants on exactly every 11th or 21st carbon atom, along with two regiorandom analogues have been synthesized via acyclic diene metathesis polymerization. The precision azo-homopolymers exhibited relatively shackling photoisomerization transition while the photoisomerization of random azo-copolymers transformed and recovered completely, which led to strikingly different self-assembly behaviors. Notably, two azo-homopolymers initially self-assembled to uniformly dispersed nanospheres, and various morphological changes from one-dimensional to two-dimensional directions were achieved by manipulating UV-light irradiation time based on the synergy of regioregular polyolefin-like backbone and noncovalent aromatic–aromatic interaction of azo pendants, with the initial morphology recovered again under vis-light irradiation. Remarkably, two regiorandom azo-copolymers assemblies presented the coexistence of nanospheres and nanowires, the subsequent light-triggered shape transformation in three-dimensional directions, and the eventual restoration in one-dimensional direction. Overall, this work significantly enriched the family of polymeric assemblies with reversible shape transformation, and the photoresponsive behaviors were extremely sensitive, which provided further guidance for the design of stimuli-responsive self-assembly systems.