Poly(acetylene azobenzene oligoethylene glycol) with Concurrently Reversible Photomechanical and Photoelectric Responsiveness upon Ultraviolet Irradiation

Abstract

Most multiple-responsive materials are limited to a single response mode to a stimulus. Herein, we present a unique conjugate azopolymer, poly(acetylene azobenzene oligoethylene glycol) (P(AAzo-OEG₄)), that concurrently exhibits both reversible photomechanical and photoelectric responsiveness upon ultraviolet (UV) light stimulus. This azopolymer features a polyacetylene backbone adorned with azobenzene pendants and terminated with oligoethylene glycol (OEG) tails. The integration of a conjugated skeleton with azobenzene pendants endows the polymer with specific phototunable mechanical and electrical responsiveness, along with a photothermal effect that enhances its photomobile and photoelectric performance. The OEG tails promote the solubility and film-forming capabilities of the polymer. When doped with iodine, P(AAzo-OEG₄) demonstrates a repeatable doubling of conductivity upon UV irradiation, owing to the photoelectric and photothermal effect. Remarkably, P(AAzo-OEG₄) exhibits reversible three-state conductivity in response to cyclic irradiation with UV light, blue light, and natural light, making it a promising candidate for photocontrolled logical sensors. Furthermore, P(AAzo-OEG₄)/polyethylene (PE) and P(AAzo-OEG₄)/polyimide (PI) composite films show amphotropic bending due to the isomerization-induced volume expansion. These two types of composite films could be configured as a photodriven gripper and a photocontrolled switch, respectively. This study provides a straightforward strategy for fabricating photoactuators and photoelectric devices by using a single material, opening up promising avenues in the design of multifunctional photosensitive polymers.