Preparation and shape memory behavior of novel heat-resistance epoxy networks containing phthalide cardo structure

Heat-resistance epoxy shape memory (SM) materials were prepared based on diglycidylether of bisphenol A (DGEBA) epoxy resin with the mixture of 4,4'-diaminodiphenylether (DDM) and phthalide-containing aromatic amine (PBMI-DDM), which was synthesized by Michael addition of 3,3-bis[4-(4-maleimido phenoxy)phenyl]-phthalide (PBMI) and DDM, in different molar ratios as curing agents. The chemical structure of PBMI-DDM was confirmed by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectra. The dynamical mechanical behavior and high-temperature tensile properties, and the influence of PBMI-DDM content and number of cycles on SM performance were investigated in detail. With increasing PBMI-DDM content, the glass transition temperatures (T-g) decreased, damping loss factors increased, and shape recovery ratio (R-r) and shape fixity ratio (R-f) were improved significantly. R-r and R-f of the pure PBMI-DDM cured epoxy resins are both lager than 90% with a deformation strain above 15%. The T-g and activation energies (Delta E) of alpha-relaxation for the epoxy system with unstable SM performance are constantly increased with SM cycles due to the adjustment and rearrangement of network chains.