Structural Modification of Anhydride-Cured Epoxy Resins by Diol-Induced Longer Segments

Anhydride-cured epoxy resins are widely used in diverse applications due to their excellent thermal stability and mechanical strength. In this study, we found that introducing a small amount of a diol compound (bisphenol A, BPA) into the mixture of an epoxide compound (bisphenol A diglycidyl ether, DGEBA) and an anhydride compound (methyl tetrahydrophthalic anhydride, MeTHPA) increased the cross-linking density of the resulting anhydride-cured epoxy resin. The resulting network architecture led to an overall increase in the glass transition temperature, thermal stability, mechanical strength, and toughness of the anhydride-cured epoxy resins. However, excessive BPA addition decreased the cross-linking density, which in turn deteriorated these properties. The effect of incorporating BPA into the cross-linked network structure was further analyzed by molecular dynamics simulations. The simulation revealed that the longer network segment generated by the addition of BPA can facilitate the formation of a dense cross-linked network with increased connectivity and reduced number of structural defects. This integrated experimental and computational study provides insight into structure–property relationships and design principles in anhydride-cured epoxy networks.