Functional Supramolecular Materials Formed by Non-covalent Bonds

Abstract

Molecular recognition is essential for realizing functional supramolecular materials. Non-covalent host-guest interactions are effective tools to introduce various functions and properties into materials. This review focuses on the functions such as selective molecular adhesions, self-healing, toughness, and actuation properties of the supramolecular polymeric materials. These functions have been achieved by using reversible bond formations between cyclodextrins (CDs) and guest molecules. The host-guest interactions involving CDs can be used to achieve efficient stimuli-responsive behaviors and self-healing properties. Furthermore, the supramolecular materials have been found to exhibit macroscopic rapid expanding and contracting driven by external stimuli under semidry conditions. Supramolecular actuator using host-guest complexations can be prepared by two approaches. The first is the functionalization of a supramolecular gel, which changes the cross-linking density between the polymers. The second is the utilization of a topological gel to change length of the polymer chain between cross-linked points. Both types of the actuators exhibit bending behaviors by external stimuli. This review summarizes the advancements within the past 10 years in supramolecular materials that utilize the host-guest interactions and the sliding motion of ring molecules functionalized by chemical or physical processes.