Self-Healable Acrylic-Based Covalently Adaptable Networks

Combining autonomous self-healing and reprocessing in one material offers an extended life span and enables shape configuration changes. We developed commodity poly((2-acetoacetoxy)ethyl methacrylate/methyl methacrylate/n-butyl acrylate) [p(AAEMA/MMA/nBA)] copolymer networks that are capable of both self-healing without intervention as well as reprocessing. The thermoplastic p(AAEMA/MMA/nBA) was obtained by copolymerizing (2-acetoacetoxy)ethyl methacrylate (AAEMA), methyl methacrylate (MMA), and n-butyl acrylate (nBA), followed by cross-linking with tristriaminoethyl amine (TREN) to form covalently adaptable networks (CANs). This copolymer network exhibits self-healability under ambient conditions and reprocessibility by compression molding at 120 °C. Using an array of thermo-mechanical and spectroscopic tools, these studies show that reprocessibility is achieved by the exchange reactions of dynamic cross-links, whereas self-healing is facilitated by the recovery of energetically favorable inter-chain van der Waals interactions accompanied by the reversible E ⇌ Z isomerization of the C═C bonds in vinylogous urethane moieties of the network.