Synthesis and characterization of phenylsiloxane‐modified bismaleimide/barbituric acid‐based polymers with 3‐aminopropyltriethoxysilane as the coupling agent

The preparation and characterization of phenylsiloxane ( PhSLX )‐modified N , N ′‐bismaleimide‐4,4′‐diphenylmethane ( BMI )/barbituric acid ( BTA ) (10/1 mol/mol) oligomers are described. 3‐Aminopropyltriethoxysilane ( APTES ) was used as the coupling agent. The resultant hybrid BMI / BTA‐APTES‐PhSLX polymers were characterized primarily using thermogravimetric analysis in combination with differential scanning calorimetry and Fourier transform infrared measurements. The thermal stability of the BMI / BTA oligomer was improved significantly by incorporation of a small amount (20–30 wt%) of the copolymer of PhSLX and APTES ( PASi ). After adequate post‐curing reactions, the PASi ‐modified BMI / BTA oligomers ( HYBRID20 and HYBRID30 containing 20 and 30 wt% PASi , respectively) exhibited greatly reduced thermal degradation rates in the temperature range 300–800 °C and an increased level of residues at 800 °C as compared to the native BMI / BTA oligomer. This was further confirmed by thermal degradation kinetic studies, in which the activation energies for the thermal degradation reactions of the cured PASi ‐modified BMI / BTA oligomers were shown to be higher than that of the pristine BMI / BTA oligomer. © 2012 Society of Chemical Industry