Dual-primer adhesion of polymer networks of dissimilar chemistries

The integration of polymer networks of dissimilar chemistries, such as hydrogels and hydrophobic elastomers, has enabled numerous existing and emerging applications in engineering and medicine. However, it remains a challenge to adhere polymer networks of dissimilar chemistries when neither network contains functional groups for chemical coupling. Here we describe a principle of dual-primer adhesion that meets this challenge. For each preformed network, we formulate a primer with uncrosslinked polymers that (1) match the chemistry of the preformed network, and (2) contain coupling agents for crosslinks and interlinks. We apply the primer on the surface of the preformed network, place two primed networks in contact, and cure. Each primer crosslinks into a network, in topological entanglement with the one preformed network, and the two primer networks form interlinks. The stitch-bond-stitch topology covalently adheres the two preformed networks. We demonstrate the principle by using polydimethylsiloxane elastomer, polyacrylamide hydrogel, and silane coupling agents. Adhesion energy as high as ∼140 J/m² is achieved, comparable to the toughness of the polyacrylamide hydrogel. The principle of dual-primer adhesion opens an enormous design space for general applications.