Structure Reconfigurable Mechanochromic Polymer with Shape Memory and Strain-Monitored Function Enabled by a Covalent Adaptable Network
Yuchen Mao, Yuto Kubota, Ruiqi Feng, Jin Gong, Akira Ishigami, Yutaka Kobayashi, Takuma Watabe, Daisuke Aoki, Hideyuki Otsuka, Hiroshi Itô
Abstract
A mechanochromic cross-linker difluorenylsuccinonitrile-containing dimethacrylate (DFMA) was used to build a covalent adaptable network. Owing to the reversible dissociation and reassociation of the central C–C bonds of DFMA, poly(stearyl methacrylate-co-N,N-dimethyl acrylamide) [P(SMA-DMAA)] polymer networks presented mechanical enhancement and strain-monitored function. The impact of the cross-linking design, including full-dynamic, non-dynamic, and half–half hybrid, on dynamic behavior was investigated. In addition, the toughening mechanism and structural reconfiguration were discussed. A non-dynamic network protected the steric configuration and maintained restrictions on segments movement. In a full-dynamic network, the stress concentration was detected, and the effective plastic strain that triggered dynamic covalent bonds to dissociate in a wide range. The reassociation of dynamic covalent bonds led to the structural reconfiguration of molecular segments and improvement in segment orientation for adapting deformation. The covalent adaptable network endowed P(SMA-DMAA) with a self-reinforcing ability and a shape-reprocess performance, showing both shape-memory elasticity and macroscopic solid-state plasticity.