Cooper G, Grieser F, Biggs S
The Advanced Mineral Products Research Centre, The University of Melbourne, Parkville, Vic. 3052, Australia
J Colloid Interface Sci. 1996 Dec 1;184(1):52-63. doi: 10.1006/jcis.1996.0596.
The polymerization of oil-in-water (o/w) emulsions of monomeric species has been performed at 30°C (±5°C) under ultrasonic irradiation, in the absence of any added chemical initiators. Emulsions of butyl acrylate and vinyl acetate as well as emulsified mixtures of the two monomers have been reacted in this way. In all cases, the radicals formed as a result of the ultrasonic cavitation were sufficient to cause polymerization. Stable blue-white or white dispersions of polymer latex particles were obtained. The kinetics of the copolymerization process were monitored. The data obtained here show that the polymerization rate depends strongly upon the monomer concentration dissolved in the aqueous phase and on its vapor pressure. The more volatile of the monomers examined, vinyl acetate, was seen to have a markedly lower polymerization rate at equivalent monomer concentrations when compared to the butyl acrylate. This was attributed to monomer evaporation into the cavities formed by the ultrasound, causing a dampening of the cavitation process and hence a lower radical density. Data of particle sizes and polymer molecular weights for the latex samples support this hypothesis.
在无任何添加化学引发剂的情况下，单体种类的水包油（o/w）乳液的聚合反应于30℃（±5℃）在超声辐照下进行。丙烯酸丁酯和醋酸乙烯酯乳液以及两种单体的乳化混合物均以这种方式进行反应。在所有情况下，超声空化产生的自由基足以引发聚合反应。得到了聚合物胶乳颗粒稳定的蓝白色或白色分散体。监测了共聚过程的动力学。此处获得的数据表明，聚合速率强烈依赖于溶解在水相中的单体浓度及其蒸气压。在所研究的单体中，挥发性更强的醋酸乙烯酯在等效单体浓度下的聚合速率明显低于丙烯酸丁酯。这归因于单体蒸发到超声形成的空穴中，导致空化过程受到抑制，从而自由基密度降低。胶乳样品的粒径和聚合物分子量数据支持这一假设。
