Tunable interfacial adhesion based on orthogonal supramolecular forces

Abstract

Inspired by the adhesion phenomena in nature, many synthetic adhesive materials based on supramolecular interactions have been developed. Nevertheless, these materials generally contained a single kind of non-covalent interaction which lacked adjustability in interfacial adhesion strength, restricting their further applications. Herein, adhesive gel AG3 was prepared by mutual adhesion of supramolecular gel G3 self-assembled from polymer P3 through metal coordination between terpyridine (TPY) groups and Zn²⁺ as well as hydrogen bonding of 2-ureido-4-pyrimidone (UPy) groups. In order to realize the tunable interfacial adhesion, distinct competitive molecules were added into adhesive gel AG3. Adhesive gel AG6 was produced after the cyclen solutions were added into adhesive gel AG3. Due to the higher binding ability of cyclen to Zn²⁺, the metal coordination between TPY groups and Zn²⁺ was damaged, causing a decrease in the interfacial adhesion strength. Besides, upon the addition of UPy solutions into adhesive gel AG3, adhesive gel AG7 was generated. Owing to the newly formed hydrogen bonds of the added UPy monomers, the original hydrogen bonds were broken, leading to a decrease in the interfacial adhesion strength. When both two kinds of competitive molecules were added into adhesive gel AG3, then it would distintergrate on account of the destruction of the invovled supramolecular forces.