Azobenzene-modified chitosan composites harnessing high-efficiency photosensitive shape memory behaviors

Chitosan-based shape memory polymers (SMPs) represent a promising class of smart materials for biomedical and packaging applications, yet their development is often limited by the reliance on solutions and thermal stimuli. To enable remote and precise control, this study focuses on developing photosensitive SMPs by conferring light responsiveness to chitosan. Azobenzene-modified chitosan (CSM) was synthesized via a three-step process involving maleic anhydride modification of chitosan followed by free radical grafting with 4-acryloyloxyazobenzene. Composite films (CSMCFs) were then prepared by blending the CSM with poly(vinyl alcohol) (PVA) at varying mass ratios. The chemical structures of the intermediates and the final composite were confirmed by ¹H NMR and FTIR spectroscopy. The incorporation of azobenzene groups was verified by UV-vis spectroscopy, and the thermal properties were assessed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The photosensitive shape memory behavior was quantitatively evaluated by measuring the shape fixation rate (R_f) and shape recovery rate (R_r) under 365 nm UV light irradiation. The optimal composites (CSMCF-3), with a CSM/PVA ratio of 3/7 and 0.5 % azobenzene derivative, exhibited a high shape fixation rate of 97.2 % and an exceptional shape recovery rate of 93.3 % within 300 s. These results demonstrate the high potential of these composite films for applications in smart packaging and biomedical devices where remote, light-triggered actuation is desired.