HYDROCARBON DISPERSIONS OF ACRYLIC MICROSPHERES WITH POLAR SURFACE FUNCTIONALITY

Submicron and micron sized particles containing a crosslinked core and a polar shell were prepared by 3-stage nonaqueous dispersion [NAD] po lymerization in an aliphatic hydrocarbon medium. When a poly(12-hydrox ystearic acid) [PHS] comb stabilizer was used in all three stages, the particles produced were spherical, submicron in size, and had a relat ively broad size distribution. If the monomer mixture in the third sta ge contained relatively large amounts of butyl acrylate, stable disper sions of sponge-like aggregates, 3-5 mum in size, were obtained. When butyl rubber was employed as a stabilizer precursor in the seed format ion step, the shape of the final particles depended upon whether a cro sslinker was employed in the second stage polymerization. When a cross linker was present, the second-stage particles and the subsequent thir d-stage particles had a shrunken, raisin-like appearance. When no cros slinker was present, spherical particles were obtained. In both cases, the resulting third-stage particles were easily dispersed in water co ntaining a small amount of amine base, indicating that -COOH and -OH g roups are located at the surface (or in a shell at the surface) in the se NAD particles. (C) 1994 John Wiley & Sons, Inc.