Research Theme
Supramolecular Actuator
Two structural approaches may realize supramolecular actuators through host?guest interactions: a method with a linear main chain and one with a side chain in the polymer structure. Our research employs the polymer side chain method because various functions are relatively easy to be introduced into materials. Supramolecular gel are based on integrating host?guest interactions on the polymer side chains. The association and dissociation of inclusion complexes as crosslinking units on the polymer side chains demonstrate contraction and expansion motions due to changes in the crosslinking density. Topological gel is mechanically crosslinked by molecules. The drive mechanism, which involves a sliding motion in the [c2]daisy chain, is completely different from previously reported stimuli-responsive actuators, such as polymer gels, liquid crystalline elastomers, conjugated polymers, and carbon nanotubes.
Light Stimuli-Responsive Polyurethane
In this study, we developed a photoresponsive polyurethane (CD-Azo-PU) based on the control of hard segment crystallization of polyurethane (PU) by the formation of inclusion complexes of azobenzene (Azo) and cyclodextrin (CD), CD-Azo-PU consists of a polyurethane main chain and a 1:2 inclusion complex of Azo and γ-cyclodextrin (γCD) as a movable cross-linking point. Under ultraviolet (UV, λ = 365 nm) irradiation, CD-Azo-PU bent toward the light source direction (defined as forward direction). On the other hand, linear azopolyurethane (Azo-LPU) without peracetylated γ-cyclodextrin diol (TAcγCD-diOH) as a mobile cross-linker bent in the direction opposite to the light source. The bending velocity was measured to be 0.25°/s for CD-Azo-PU and 0.083°/s for Azo-LPU, with CD-Azo-PU showing faster response. These results indicate that fast and specific photoresponsive driving of CD-Azo-PU was achieved by introducing a movable cross-linking point into CD-Azo-PU.
Zhou, X.; Ikura, R.; Jin, C; Yamaoka, K.; Park, J.; Takashima, Y.,Aggregate 2023, e457.
Light-ResponsiveTopological Gel
The mechanically cross-linked hydrogel([c2]AzoCD2 hydrogel) build with four-arm poly(ethylene glycol)(tetraPEG) and [c2]daisy chains consisting of alfa-cyclodextrin(αCD) and azobenzene (Azo) showed the photo-responsive contraction and expansion behaviors. These behaviors were caused by the decrease of distance between crosslinked points related to the sliding motion of [c2]daisy chains. As a further result, the [c2]AzoCD2 xerogel lyophilized from the hydrogel have more ability to response to light than the hydrogel.
