Bismaleimide polymers (BMI) are known for their good thermal stability and are used in a temperature range of 200-250 degreesC, but they are brittle. New generations of BMIs with added comonomers or elastomers are less fragile. During the polymerization, the main reactions involved are the Michael's reaction (addition of a BMI with an aromatic diamine) and the ene reaction. Because the chemical structure of the network is dependent on the temperature, the reaction kinetics as a function of the thermal cycles of processing are compared using solid-phase C-13-NMR. The morphology of the two-phase structure and the mechanical properties (K-IC) are also studied.