Walter Mächtle

Block copolymer micelles as seed in emulsion polymerization

The size of aggregates formed by poly(acrylic acid)-block-poly(methyl methacrylate) block copolymers was determined and the applicability of these block copolymers as stabilizers in emulsion polymerization was investigated. The analytical methods included transmission electron microscopy, light scattering, and analytical ultracentrifugation. Polymers with a hydrophilic poly(acrylic acid) block of equal or larger size than the hydrophobic poly(methyl methacrylate) block are efficient as stabilizers down to block copolymer-to-monomer ratios of less than 1 wt.-%. From the influence of the block copolymer-to-monomer ratio on the latex particle size, from the relation between the number of block copolymer molecules per latex particle and the aggregation number of the block copolymer micelles, and from fluorescence studies we conclude that micelles consisting of block copolymers with 35 or more hydrophobic MMA units act as a seed in the emulsion polymerization of acrylic and methacrylic monomers.