Novel intercrosslinked networks of siliconized epoxy-1,2-bis(maleimido)ethane matrix systems are developed. The siliconization of epoxy resin is carried out by using 5-15% hydroxyl-terminated poly(dimethylsiloxane) with gamma-aminopropyltriethoxysilane as a crosslinking agent and dibutyltin dilaurate as a catalyst. The siliconized epoxy systems are further modified with 5-15% 1,2-bis(maleimido)ethane and cured by using diaminodiphenylmethane. The prepared neat resin castings are characterized for their mechanical properties. Mechanical studies indicate that the introduction of siloxane into these epoxy resins improves the toughness with a reduction in the stress-strain values, whereas incorporation of bismaleimide (BMI) into the epoxy resin improves the stress-strain properties with a lowering of the toughness. The introduction of both siloxane and BMI into the epoxy resin influences the mechanical properties according to their content percentages. Differential scanning calorimetry (DSC), thermogravimetry, and heat distortion temperature analyses are also carried out to assess the thermal behavior of the matrix materials that are developed. DSC thermograms of the BMI modified epoxy systems show unimodal reaction exotherms. The glass-transition temperature, thermal degradation temperature, and heat distortion temperature of the cured BMI modified epoxy and siliconized epoxy systems increase with increasing BMI content. The water absorption behavior of the matrix materials is also studied. (C) 2003 Wiley Periodicals, Inc.