Crown ether-based supramolecular elastomers exhibiting reversible and abundant shape programming

Abstract

Crown ether-based polymers are a class of dynamic polymers demonstrating the high strength and stability of covalent polymers as well as the dynamism and stimuli-responsiveness of supramolecular interactions. Previous studies on them mainly focus on physical and mechanical properties, while little attention was paid to their application as functional materials. Shape-changing polymers (SCPs) are engineering materials with great application potential; however, crown ether-based polymer materials have hardly been developed in this aspect. Herein, a series of supramolecular elastomers SE-HG-Z (Z represents the mol% of the host–guest units) were prepared based on benzo-21-crown-7 (B21C7)/secondary dialkylammonium salt (DAAS) host–guest interactions. By adjusting the supramolecular cross-linking degree, SE-HG-Z underwent a transition from soft to tough and finally to brittle. Meanwhile, the thermo-responsiveness of the host–guest interactions endowed the SE-HG-Z with deformability and repeatability. The elastomer showing the best comprehensive performance was selected to obtain U shape, S shape, spiral shape and long strip sequentially by heating, shaping, and cooling the same strip. The reversible shape-programming property of the elastomer was further applied to flexible robotics.