Miniemulsion polymerization of styrene with polymeric costabilizers

The polymeric costabilizers poly(stearyl methacrylate-co-2-hydroxyethylmethacrylate) (PSH) and poly(lauryl methacrylate-co-2-hydroxyethylmethacrylate) (PLH), composed of a hydrophilic backbone and several hydrophobic alkyl (stearyl or lauryl) side chains, were prepared by the free-radical copolymerization of stearyl methacrylate (SMA) or lauryl methacrylate (LMA) with 2-hydroxyethylmethacrylate and evaluated in the miniemulsion polymerization of styrene (ST). For comparison, the reactive costabilizers SMA and LMA were also included in this work. The hydrophobicity of costabilizers in increasing order was PLH < PSH < LMA < SMA. Only a small amount of these comb-like copolymers was capable of producing kinetically stable ST emulsion droplets. The more hydrophobic the costabilizer was, the more effective was the costabilizer in the retardation of Ostwald ripening. About 30-40% of the monomer droplets were successfully converted into latex particles during the polymerization. The degree of monomer droplet nucleation increased with increasing hydrophobicity of the costabilizer. The formation of particle nuclei in the continuous aqueous phase played a crucial role in the polymerization kinetics. © 2004 Wiley Periodicals, Inc.