Synthesis and properties of silicon‐containing bismaleimide resins

Two novel bismaleimide (BMI) monomers containing silicon atom in the structure, i.e., bis[4‐(4‐maleimidophenylcarbonyloxy)phenyl]dimethylsilane (BMI‐SiE1) and bis[4‐(4‐maleimidophenyloxycarbonyl)phenyl]dimethylsilane (BMI‐SiE2), were designed, synthesized, and polymerized with and without the use of diamine as comonomers to yield novel silicon‐containing BMI resins. Both monomers obtained are readily soluble in organic solvents, such as chloroform and N , N ‐dimethylformamide. Differential scanning calorimetry and thermogravimetric analysis investigation of these two monomers indicated a high polymerization temperature ( T p > 240°C) and a good thermal and thermo‐oxidative stability of cured BMI resins. The onset temperature for 5% weight loss was found to be above 450°C in nitrogen and above 400°C in the air. Polymerization of BMI‐SiE1 and BMI‐SiE2 with 4,4′‐diaminodiphenylether (DPE) yielded a series of polyaspartimides that had good solubility and could be thermally cured at 250°C. TGA investigations of the cured diamine‐modified BMI resins showed onset of degradation temperatures ( T d s) in the range of 344–360°C in nitrogen and 332–360°C in the air. Composites based on the cured diamine‐modified BMI resins and glass cloth were prepared and characterized for their dynamic mechanical properties. All the composites showed high glass transition temperatures (e.g., >190°C) and high bending modulus in the range of 1000–2700 MPa.