A new type of bismaleimide (BMT) resin was synthesized and confirmed by IR spectroscopy, elemental analysis, H-1-NMR spectroscopy, and C-13-NMR spectroscopy. The reactivity was measured by differential scanning calorimetry. In addition, compositions of the synthesized BMI with three conventional BMIs (4,4'-bismaleimidodiphenylmethane, 4,4'-bismaleimidodiphenylether, 4,4'-bismaleimidodiphenylsulfone) were used for making a comparison of their reactivity and thermal properties. Through the evaluation of thermogravimetric analyses, the polymers obtained through the reactions between the newly synthesized BMI containing biphenylphosphine oxide and other BMIs also demonstrated excellent thermal properties in the high temperature region and a high char yield of up to 30-45%. (c) 2005 Wiley Periodicals, Inc.