The Ultrasonic Induced Polymerization of Acrylamide in Aqueous Solution and its Comparison with the Aqueous Polymerization Induced by γ-Ray Irradiation

Polymerization of acrylamide in aqueous solution by the action of ultrasonic (US) irradiation (420kc/s) was investigated and was compared with the reported results of γ-ray induced polymerization of the monomer in aqueous solution. Dependence of polymer yield and molecular weight of the polymer on the irradiation conditions were studied. The polymer yield increases with irradiation time until the yield gets to a saturation value whereas the degree of polymerization decreases with irradiation time. Effect of the temperature on the polymer yield is larger than in the case of radiation induced polymerization, indicating differences in the primary proccesses for γ-ray and US-irradiations. The initiating species have been examined by means of the scavenger method. On the basis of decomposition mechanism of water by US-irradiation, the polymerization is thought to be initiated by the reaction of acrylamide during cavitation with hydroxyl radicals and/or other active intermediates such as excited water molecules which eventually produce hydrogen peroxide. The contribution of hydrogen atoms or solvated electrons after diffused out from the site of cavitation to the initiation step is unlikely since the addition of argentous perchlorate which is non-volatile and is known as a selective scavenger for hydrogen atoms are solvated electrons, does not affect the polymer yield. Other vinyl compounds were also examined for their polymerizability in aqueous solutions under US field. Methacrylamide and methacrylic acid were polymerized well, but methyl methacrylate. acrylonitrile and vinylpyridine were almost inert to US irradiation.