Preparation and characterization of bismaleimide-diamine prepolymers and their thermal-curing behavior

Various bismaleimide-diamine Michael addition type prepolymers were prepared through melt condensation and using acetone, dimethylformamide, and m-cresol as solvents in a molar ratio of 1 : 1. Structures of the prepolymers, such as terminal moieties and molecular weight of main chain, depended strongly an the preparation conditions used. More terminal double bonds were observed in the molecule of the prepolymer (sample 3) prepared in dimethylformamide solution without a catalyst. In contrast, the prepolymer produced in m-cresol solution had a polyaspartimide structure with a higher molecular weight. The differential scanning calorimetry and Fourier transform infrared spectra results demonstrated that the molecular structure of the prepolymer had a noticeable effect on their thermal-curing behavior. Thermal properties (T-g and T-d) of cured polymers were evaluated. The polyimide (sample 3b) from sample 3 exhibited the highest T-g and T-d1, but still retained very good processing properties for film casting. (C) 1998 John Wiley & Sons, Inc.