Two types of monofunctional benzoxazines with imide functionalities have been synthesized for improved thermal properties. These materials achieve char yields above 55% and exhibit glass transition temperatures above 250 degrees C. The new benzoxazines have maleimide and norbornene functionalities that can further polymerize with mechanisms different from benzoxazine. The multiple polymerization mechanisms of the maleimide based benzoxazine monomer with different free radical initiators are monitored by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The extent and type of polymerization, which affect the final network structure of the benzoxazine polymer, are characterized. (c) 2005 Elsevier Ltd. All rights reserved.