On the free-radical microemulsion polymerization of butyl acrylate in the presence of Poly(Oxyethylene) macromonomer

The o/w microemulsion polymerizations and copolymerization of butyl acrylate (BA) with methacryloyl-terminated poly(oxyethylene) macromonomer (POE-MA) initiated by both water-soluble (ammonium peroxodisulfate (APS)) and oil-soluble (AIBN) initiators were investigated. The maximum rate of microemulsion polymerization of butyl acrylate was found to increase with increasing APS and AIBN concentration and the increase was more pronounced in runs with APS. The dependence of the rate vs, conversion is described by a curve with a maximum at ca. 20-40 % conversion. The maximum rate of polymerization was found to increase with increasing APS concentration and the increase was proportional to the molecular mass of POE macromonomer. The high radical activity of AIBN was attributed to hoping events. The particle size in the microemulsion polymerization of BA slightly increases with conversion. However, the addition of POE macromonomer influences by a complex way the particle size. The addition of POE changes the electrostatic stabilization mechanism to the electro-steric stabilization mechanism. POE macromonomer or its graft copolymer promotes organized agglomeration and the formation of large number of particles at medium conversion. At low and high conversion larger particles are formed. The rearrangement of reactants and polymer molecules at the beginning and the end of polymerization and the interaction of hydrophilic BA-graft-POE copolymer molecules with polymer particles are assumed to be responsible for the dramatic variations in particle size.