An allyl-containing bifunctional benzoxazine is synthesized from o-allylphenol, 4,4′-diaminodiphenyl ether, and formaldehyde, followed by isomerization in the presence of chlorotris(triphenylphosphine)rhodium(I)/triethylsilane catalytic system yielding a propenyl-containing benzoxazine, and the chemical structures of the two isomers are confirmed. In the thermal activated polymerization, both isomers undergo the oxazine ring-opening polymerization and the radical olefin polymerization with the formation of the corresponding polybenzoxazines, but only one exothermic peak is shown on each of their dynamic differential scanning calorimetry (DSC) curves. After isomerization of allyl into propenyl, the onset and maximum polymerization temperatures decrease, but the temperature range covered by the DSC exothermic peak broadens. Consequently, the structures of the resultant polybenzoxazines are different, and some properties are obviously different, for example, the storage modulus decreases, but the glass transition temperature increases, and the thermal stability is slightly enhanced.

•A copolymer of p-aminobenzonitrile based benzoxazine and epoxy resin was prepared.•The fracture surface of the copolymer shows a homogeneous morphology, and the roughness increases with rising epoxy content.•In the glassy state, the storage modulus of the copolymer initially tends to increase with rising epoxy content, but decreases when epoxy content reaches to 50 wt%.•The glass transition temperature of the copolymer is lower than that of polybenzoxazine, but the onset weight loss temperature is higher.A copolymer of p-aminobenzonitrile type benzoxazine (BA-pabn) and diglycidyl ether of bisphenol-A (DGEBA) was prepared. With rising DGEBA content, the peak temperature of the differential scanning calorimetry curve for polymerization of BA-pabn/DGEBA blend shifts to higher value, and the roughness of the fracture surface of the BA-pabn/DGEBA copolymer increases. In the glassy state, the storage modulus of the copolymer initially tends to increase with rising DGEBA content over pure polybenzoxazine (PBA-pabn), but decreases when DGEBA content reaches to 50 wt%. The copolymer exhibits a single glass transition temperature lower than that of PBA-pabn. The onset weight loss temperature of the copolymer is higher than that of PBA-pabn, but the char yield at 800 °C is lower.