Thermal programming of triple-shape-memory epoxy with flexible segments and Diels–Alder networks

This study reports the innovative preparation of triple-shape-memory epoxy resin (EP-DA) through thermal programming. Flexible poly(propylene glycol) diglycidyl ether (PEGDE) segments and reversible Diels–Alder (DA) dynamic covalent bonds were introduced into epoxy resin through molecular structural design, controlling glass transition temperature ( T g ) and DA reaction temperature, respectively, which then was used as the two reversible switches of EP-DA. FTIR results verified that PEGDE and DA bond were successfully brought in EP-DA network. DSC and TG tests were used to demonstrate the three stages of EP-DA thermal behavior: T g , DA thermal reversible reaction temperature and thermal degradation temperature. Bending-recovery test verified the dual-shape-memory, and DMA test verified the excellent triple-shape-memory of EP-DA. The general elastic deformation, high elastic deformation and flow deformation of EP-DA molecular segments revealed its shape-memory mechanism. Furthermore, when PEGDE content increased, T g , crosslinking density of EP-DA, fixity ratio and strength decreased, toughness increased, and recovery rate as well as recovery speed were promoted. The thermal reversibility of DA bonds in EP-DA also endues it with retrievability and self-reconstruction. Graphical abstract