Facile and efficient fabrication of photoresponsive microgels via thiol-Michael addition.

A photoresponsive microgel is designed by the combination of a noncovalent assembly strategy with a covalent cross-linking method. End-functionalized poly(ethylene glycol) with azobenzene [(PEG-(Azo)2)] was mixed with acrylate-modified beta-CD (beta-CD-MAA) to form photoresponsive inclusion complex through hostguest interaction. The above photoresponsive complex was cross-linked by thiol-functionalized PEG (PEG-dithiol) via Michael addition click reaction. The photoreversibility of resulted microgel was studied by TEM, UVVis spectroscopy, and 1H NMR measurements. The characterization results indicated that the reversible size changes of the microgel could be achieved by alternative UVVis irradiations with good repeatability.