A group of researchers led by Specially Appointed Professor HARADA Akira at the Project Research Center for Fundamental Sciences, Graduate School of Science, Osaka University developed hydrogel actuators containing cyclic polysaccharide cyclodextrin and photoresponsive molecule azobenzen (Azo) as molecules functioning as sensors and controllers. These high-toughness gel actuators bend, shrink, and extend according to the irradiation wavelength.

This team focused on host-guest interactions between αCD and Azo and reported about photoresponsive hydrogels reversely exhibiting contraction and expansion behaviors by changing the crosslink density of polymer chains through the suppression of the formation of the inclusion complex of αCD and Azo by photostimulation. In order to build a molecular recognition system, this group chose αCD as a host molecule and photoresponsive azobenzen (Azo) as a guest molecule.

αCD-modifying Azo formed a [c2]daisy chain in water. This group prepared the molecular actuators by crosslinking a CD derivative and TetraPEG through amide bond formation. [c2]AzoCD2 hydrogel showed a stretching property, which was not possessed by conventional materials, due to the sliding motion of the ring and axial molecules. Irradiation with ultraviolet light and visible light caused [c2]Daisy chains to either contract or expand, leading to the production of hydrogel actuators driven by reversible structural change.

(Link) http://resou.osaka-u.ac.jp/en/research/2016/20160513_3