Toughening benzoxazine/epoxy thermosets through control of interfacial interactions and morphologies by hyperbranched polymeric ionic liquids

Hyperbranched polymeric ionic liquids (HBPILs) with varying alkyl chain length have been synthesized and used as efficient catalysts for benzoxazine/epoxy thermosets. The values of activation energies for the thermal polymerization of benzoxazine/epoxy thermosets increase with increasing the alkyl chain length of HBPILs. The HBPILs significantly enhance the toughness of benzoxazine/epoxy thermosets. The phase morphologies of the benzoxazine/epoxy thermosets change from a homogeneous structure to a sea-island structure upon increasing the alkyl chain length of HBPILs, while the concentration changes were altered the interface behaviors between HBPILs and benzoxazine/epoxy. As the benzoxazine/epoxy thermosets formed phase separation structure, the toughness is significant improved compared to that of the continuous phase morphology. Moreover, the addition of HBPILs simultaneously improves the glass transition temperature (T g ) and thermal stability of benzoxazine/epoxy thermosets.