Kinetics of polymerization of N,N′-bismaleimide-4,4′-diphenylmethane with barbituric acid

• Kinetics of polymerizations of BMI with BTA in NMP investigated.
• A mechanistic model for competing radical and Michael addition reactions developed.
• The model verified by experiments, and key kinetic parameters determined.

Isothermal kinetics of polymerizations of N,N′-bismaleimide-4,4′-diphenylmethane (BMI) with barbituric acid (BTA) (BMI/BTA = 2/1 (mol/mol)) in N-methyl-2-pyrrolidone in the temperature range 373–403 K were studied. A mechanistic model involving the competing Michael addition and free radical polymerization mechanisms was developed. With the knowledge of the kinetic parameters for Michael addition polymerization obtained from our previous work, this kinetic model in combination with experimental data obtained from DSC and 1H-NMR measurements was used to evaluate the kinetic parameters of free radical polymerization of BMI initiated by BTA. The model adequately predicted the kinetics of polymerization of BMI/BTA at different temperatures. Key kinetic parameters for the free radical polymerization mechanism were then determined. At high temperature, free radical polymerization predominates in the reaction system. By contrast, at low temperature, Michael addition polymerization competes more effectively with free radical polymerization.