Promoting stimuli-responsive motion in soft matter by host-guest interactions

Soft actuators capable of performing complex mechanical motions are highly sought after for the development of next-generation smart materials. Nevertheless, none of the soft actuators reported to date have achieved multiple actuation modes using a single material. To overcome this limitation, we present a responsive composite film that displays distinct actuation modes when exposed to organic vapors. This material is readily prepared and scaled up by incorporating novel urea-cage compounds into a polymer matrix. Through a comprehensive investigation into the actuation mechanism, we demonstrate that the exceptional actuation behavior arises from the polymorphic transformations of the crystalline urea cages, which are triggered by selective host-guest interactions between the cages and solvent guests. It is worth emphasizing that, for the first time, the tool of host-guest chemistry has been harnessed to achieve complex mechanical motion in a soft actuator.