Synthesis,characterization, and thermal stability of bismaleimides derived from maleimido benzoic acid

Bismaleimides containing ester, amide, urethane, and imide groups in the backbone were synthesized from maleimido benzoic acid via its acid chloride or isocyanate with 4,4′-dihydroxy-diphenyl-2,2-propane, 3,3′-diamino diphenyl sulfone, and 3,3′,4,4′-benzophenone tetracarboxylic acid anhydride by simple condensation or addition reaction. The new bismaleimides are characterized by IR, ¹H-NMR, and elemental analysis. DSC studies of these bismaleimides indicated a curing exotherm in the temperature range 150–270°C with heat of polymerization 30–50 J/g. Thermogravimetric analysis of the uncured resins showed high thermal stability and char yield for imide containing bismaleimide. The observed char yields of the bismaleimide resins are in accordance with the calculated C/H ratios.