Dynamic mechanical and shape memory properties of copolymers based on o-allylphenol type benzoxazines and diglycidyl ether of bisphenol-A

Three benzoxazines based on o-allylphenol and 1,6-hexamethylenediamine (HDA) or 4,4'-diaminodiphenyl methane (DDM) or 4,4'-diaminodiphenyl ether (DDE) were respectively blended with diglycidyl ether of bisphenol-A (DGEBA) in various weight ratios followed by thermal polymerization to prepare three series of benzoxazine/DGEBA copolymers. With increasing DGEBA content, the peak temperature of the exothermic peaks in the DSC curves shows a systematic increase for the three series of benzoxazine/DGEBA blends. Each copolymer shows a single glass transition temperature (T-9). As the content of DGEBA is increased, T-9 reaches a minimum for the copolymer system based on HDA but a maximum for the two systems based on DDM and DDE. For the same benzoxazine/DGEBA weight ratio, copolymers based on DDM and DDE show high T-9 values over those based on HDA. The three series of benzoxazine/DGEBA copolymers exhibit a one-way dual shape memory effect based on T-9, and the shape memory properties of the copolymers under tensile deformation mode vary with the variation of both diamine bridge structure and DGEBA content. (C) 2018 Society of Chemical Industry