Chemical Compositions and Distributions of Emulsion Copolymers Composed of Styrene and Lower Alkyl Acrylates

Chemical compositions and those distributions of styrene (St)-methyl acrylate (MA) and St-ethyl acrylate (EA) copolymers synthesized by emulsion copolymerization under different polymerization conditions were examined by H-1 NMR and HPLC, respectively, results were compared with those of bulk copolymers. MA or EA fraction at early stage decreased with the increase of emulsifier concentration ([SDS], sodium dodecyl sulfate) and converged to the value calculated using the distribution factor (f(d)) when SDS concentration is extrapolated to zero. In St-MA copolymer, furthermore, MA fraction decreased with the increase of polymerization rates (R-p) and converged to the value from fd when Rp is zero. These results indicate that the MA or EA monomer fraction in micelle decreased compared to the expected value from fd due to the interaction of hydrophilic monomer with emulsifier and/or the diffusion-controlled process. From HPLC studies, it was found that no homopolymer or copolymer with different composition was produced.