Star Polymer Network Elastomer with Reconfigurable Network Structure via Covalent Bond Exchange through Olefin Metathesis

A covalent adaptable network (CAN) elastomer with a well-defined network structure was fabricated by end-linking monodisperse star polymers via associative dynamic covalent bonds (DCBs). Monodisperse 4-arm star-shaped polyesters with vinyl end groups were synthesized and end-linked by an olefin metathesis reaction, yielding an elastomer with a uniform chain length between cross-links. The well-defined network structure endowed the elastomer with good mechanical properties. The remaining C═C bonds in the network could exchange via olefin metathesis, rendering the network structure reconfigurable. As a result, the elastomer showed stress relaxation and was thermally reprocessable. Moreover, the elastomer was chemically degradable into un-cross-linked polymers under mild conditions through C═C bond exchange. This study demonstrates mechanical robustness and dynamicity in rubbery materials through the combination of a well-defined network structure and associative DCBs.