In biological systems, molecular recognition on a microscale is integrated to macroscale to achieve reversible motion in our body, as represented by our muscle. We are inspired by such intelligent systems.
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 involvesa 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-Responsive Topological 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. Iwaso, K.; Takashima, Y.; Harada, A. Nat. Chem.2016, 8, 625-632.
