Thermostable Polymers: Spectroscopies and Thermal Studies of Bismaleimide Systems in the Solid State

Abstract

The study by DSC of two bismaleimide monomers (binary system BMI/BMI) mixed in different proportions led us to propose a phase diagram. 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, facilitating the use of these monomers in the molten state. In the eutectic mixture, the two monomers were copolymerized and the resulting cross-linked networks characterized by 13C-NMR and FT-IR analysis. Another study by FT-IR of binary BMI/diamine systems has shown the importance of steric hindrance caused by the diamine or the BMI in the context of the two principal reactions of copolymerization and homopolymerization expected in these systems. In each mixture studied, the addition of diamine changed the melting points, with a general decrease, the first in all cases remaining lower than that of the diamine alone (the most meltable compound) and the second much lower than that of the pure bismaleimide monomer considered. It was noted that increasing hindrance on the diamine reduced the extent of the copolymerization reaction and favoured the homopolymerization reaction in the molten state.