A new benzoxazine-benzoic acid (BBA) was synthesized and the structure was conformed by (1)H-NMR, (13)C-NMR, FTIR, etc. The cure behavior of BBA and cocure behavior of BBA with phenylene bisoxazoline (1,3-PBO) were investigated by differential scanning calorimetry (DSC). It was found that BBA showed a single curing exothermic peak at about 217 degrees C. However, all BBA/1,3-PBO systems exhibited two exothermic peak. One may be attributed to the reaction between carboxyl groups of BBA and 1,3-PBO. And the other was attributed to the ring-opening polymerization of oxazine rings and the reaction between phenolic hydroxyl groups generated by the ring opening of benzoxazine ring and 1,3-PBO. The curing temperature of benzoxazine containing carboxyl groups could be lowered by the copolymerization of 1,3-PBO. Thermogravimetric analysis showed that the incorporation of ester-amide groups had a significant effect on decreasing thermal stability and char yield of the cured resin. SEM results indicated that 1,3-PBO could toughen BBA benzoxazine resin. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 922-928, 2012