Reversible Semicrystalline Polymer as Actuators Driven by Organic Solvent Vapor.

A semicrystalline polymer actuator, which is responsive to solvent vapor with fast and large scale locomotion, is described. The thermoset semicrystalline polymer can be easily synthesized from crystallizable polyester segment poly (ε-caprolactone) and isophorone diisocyanate trimer. Organic solvent vapor is used to induce the reversible swelling-crystallization conversion of the crystallizable polyester segment, resulting in its expansion/shrinkage. The contraction of the polymer actuator (1 mm thick) needs only ≈4 s in room temperature. When exposed to air the polymer actuator can exhibit a fast self-oscillation. Then, a soft crawler based on this polymer is demonstrated. Driven by organic solvent it walks rapidly and steadily. The microscope images show the fast swelling-crystallization conversion that gives rise to reversible shape changes of the polymer.