Maleimide-functionalized benzoxazine is copolymerized with epoxy to improve toughness and processibility without compromising the thermal properties. The incorporation of maleimide functionality into the benzoxazine monomer results in a high performance polymer. All three possible polymerization reactions are confirmed using Fourier transform infrared (FT-IR) spectroscopy. While maleimide-functionalized benzoxazine has a glass transition temperature, T-g, of 252 degrees C, a further 25 degrees C increase of T-g is observed when copolymerized with epoxy. The flexural properties are also measured, and the copolymers exhibit a flexural modulus of 4.2-5.0 GPa. (c) 2006 Wiley Periodicals, Inc.