| Abstract: | Submicron and micron sized particles containing a crosslinked core and a polar shell were prepared by 3-stage nonaqueous dispersion NAD] polymerization in an aliphatic hydrocarbon medium. When a poly (12-hydroxystearic acid) PHS] comb stabilizer was used in all three stages, the particles produced were spherical, submicron in size, and had a relatively broad size distribution. If the monomer mixture in the third stage contained relatively large amounts of butyl acrylate, stable dispersions of sponge-like aggregates, 3–5 μm in size, were obtained. When butyl rubber was employed as a stabilizer precursor in the seed formation step, the shape of the final particles depended upon whether a crosslinker was employed in the second stage polymerization. When a crosslinker was present, the second-stage particles and the subsequent third-stage particles had a shrunken, raisin-like appearance. When no crosslinker was present, spherical particles were obtained. In both cases, the resulting third-stage particles were easily dispersed in water containing a small amount of amine base, indicating that ? COOH and ? OH groups are located at the surface (or in a shell at the surface) in these NAD particles. © 1994 John Wiley & Sons, Inc. |
