Covalent adaptive polymer networks for switchable adhesives

Adhesives that can switch their total adhesion strength on-demand are a new class of materials and can have a broad utility in biomedicine and microelectronics, among others. Total adhesion strength can be modulated by the physical or chemical changes of materials induced by external stimuli, such as light, heat, or chemical species. A covalent adaptive network is a crosslinked polymer network whose topology or covalent connectivity changes in response to a stimulus (usually heat) and thus can alter its adhesive properties. In this review, we highlight recent developments in covalent adaptive networks utilized in switchable adhesives. Furthermore, we discuss the mechanisms of covalent bond exchange (associative or dissociative), focusing on molecular design to affect the total adhesion strength and reversibility, as well as unique features that can be leveraged for future adhesives.