Tetrafunctional cyclobutanes tune toughness via network strand continuity

Customizing the toughness of polymer networks independently of their chemical composition and topology remains an unsolved challenge. Traditionally, polymer network toughening is achieved by using specialized monomers or solvents or adding secondary networks/fillers that substantially alter the composition and may limit applications. Here we report a class of force-responsive molecules—tetrafunctional cyclobutanes (TCBs)—that enable the synthesis of single-network end-linked gels with...