Rapid decomposition of a cationic azo-initiator under microwave irradiation

摘要

Microwave-assisted decomposition of 2,2' - azobis(2-methylpropionamidine) dihydrochloride (or V50), a cationic azo-initiator, and emulsion polymerizations were performed and compared to reactions with conventional heating. Higher decomposition rate constants were found in microwave reactions. This was ascribed to the development of hot spots inside the reaction mixture, promoted by microwave irradiation. In polymerization reactions, microwave-promoted acceleration of the reactions. The effect of high power irradiation was also studied, using a pulsed method in which samples were repeatedly heated at constant power (500 or 1400 W), and cooled down by immersing in an ice bath. Rapid reactions were obtained, because a great amount of energy could be applied within short time intervals. The power level had no effect on the decomposed percentages and on the monomer conversion, and only affected the irradiation time.