The preparation and property of photo- and thermo-responsive hydrogels with a blending system

Hydrogels are the attractive biomaterials for biomedical applications. The dual-stimuli-responsive system, which is sensitive to both temperature and UV irradiation, was achieved through the self-assembly of amphiphilic block copolymers in aqueous solution and the cleavage of ο-nitrobenzyl (NB) ester groups under UV irradiation. The copolymer of poly(ε-caprolactone)-b-ο-nitrobenzyl-poly(ethylene glycol)-ο-nitrobenzyl-b-poly(ε-caprolactone) (PCL-NB-PEG-NB-PCL) was prepared by ring-opening polymerization (ROP) and nucleophilic substitution reaction of ε-caprolactone (ε-CL) using photo-sensitized polyethylene glycol as an initiator. After blending with poly(ε-caprolactone)-b-poly(ethylene glycol)-b-poly(ε-caprolactone) (PCL-PEG-PCL), the system exhibited the promising dual sensitivity with wide gel-phase window and controllable sensitive properties. The structures and dual-responsive behaviors were characterized by 1H-NMR, GPC, DMA, UV–Vis, DLS and SEM. The results demonstrated the temperature and photo-sensitivity of the synthesized hydrogel and indicated that the blending of these two copolymers can easily adjust the phase transition temperature and broaden the gel-phase window through the content of NB groups in PCL-NB-PEG-NB-PCL and the hydrophilic/hydrophobic balance of system.