High-temperature resins obtained from bismaleamic acids of β,β′-dichloroterephthalyl dimalonitrile

A novel class of bismaleamic acids was synthesized from the reactions of β,β'-dichloroterephtalyl dimalonitrile with a double molar amount of the monomaleamic acid derived from an aromatic diamine utilizing triethylamine as an acid acceptor. Both monomaleamic and bismaleamic acids were characterized by IR and 1H-NMR spectrocscopy as well as elemental analyses. Bismaleamic acids were soluble in various organic solvents. Upon curing at 300°C for 15 h, they yielded insoluble network polymers by dehydration to the corresponding bismaleimides and subsequent crosslinking through their olefinic bonds. It was shown by IR spectroscopy that curing of bismaleamic acids rearranged, at least in part, the enamina nitrile units to 4-aminoquinoline. The cured resins were characterized by DTA and TGA. They showed excellent thermal stability because they were stable up to 355-389°C in N2 and air and afforded an anaerobic char yield of 57-66% at 800°C. In addition, the thermal stability of a typical cured resin was evaluated by isothermal gravimetric analysis.