Photopolymerization of butyl acrylate microemulsion. Effect of reaction conditions and additives on fates of desorbed radicals

Oil/water microemulsion polymerizations of butyl acrylate photoinitiated by a UV light were investigated. The rate-conversion curve shows two rate intervals with the maximum rate ca. at 10-30% conversion and final conversion below 100%. The rate of polymerization, particle size, final conversion and molecular weight were found to decrease with the addition of naphthalene, anthracene and benzophenone. The addition of acrylonitrile (a partly water-soluble monomer) increases the final conversion. The number of particles was found to increase in the presence of additives. The direct photolysis of the monomer swollen emulsifier micelles generates the initiating radicals. The retardation effects of additives are attributed to the transfer of energy and/or reactions of growing radicals with reaction intermediates.