Eutectic mixture of two bismaleimide monomers: thermal and mechanistic study in the molten state

Abstract Differential scanning calorimetry analysis of two bismaleimide monomers (N-N-diphenylmethane-4,4′-bismaleimide and m -phenylenebismaleimide) mixed in different proportions has enabled a phase diagram to be constructed. There is a relationship between the melting and solubility of each constituent of the binary system via the different liquid and solid phases. The concept of a eutectic mixture having special thermal properties has thus been demonstrated. The eutectic melting temperatures are very interesting because they are much lower than that of the compound with the lowest melting point, making easier the use of these monomers in the molten state. In addition, the reduction of the temperatures of crosslinking onset becomes maximal in these systems at the eutectic point, at which point there is a unique and perfectly homogeneous melting. In this unique liquid phase, the two monomers can combine to form the network after a copolymerization reaction. Once the network forms, m -phenylenebismaleimide radicals that are more highly stabilized by resonance are more reactive in the initial stages of the copolymerization reaction. © 1997 Elsevier Science Ltd.