Wood-Inspired Dynamic Covalent Cross-Linking Network for Ultrahigh Adhesion Strength, Desired Weather Resistance, and Closed-Loop Recycling Adhesives

The problems of strength-toughness trade-off and stability-switchability conflict make it a huge challenge to integrate exceptional adhesion and desired recycling performances into a single system. Inspired by wood cellulose molecular chain structure, a parallel-ordered dynamic boronic esters cross-linking network is presented by using 4-dimethylaminopyridine as a countercation stabilizing the boron center to induce boric acid to form ionic spiroborate linkage with linear hydroxyl-decorated epoxy polymer. The ionic spiroborate polymer network has a high cross-linking degree to contribute to structural stability and adhesion strength. Moreover, the unique ionic spiroborate bond cooperates with the parallel-ordered structure, providing a highly effective path and a rapid exchange rate and thus affording excellent closed-loop recycling properties. Given the effects, a superior adhesion strength of 30.86 ± 0.74 MPa is found along with an excellent debonding work of 64929 N m^-1. Also, adhesives show excellent environmental reliability. In addition, the prepared adhesives exhibit good chemical/physical recyclability and display 106.8% conservation of adhesion strength after 3 bonding and debonding tests. This work provides a strategy to construct high-performance adhesives that combine robust adhesion and recyclable properties.