Abstract: The present invention provides for a process for preparing hollow polymer latexes by a one stage emulsion polymerization. The first step invloves introducing an effective amount of a first charge of a organic phase to an aqueous phase. The first charge of the organic phase comprises monomer which is vertually insoluble in the aqeuous phase and an inert-nonpolymerizable hydrocarbon. The polymer formed from polymerizing the monomer is virtually insoluble in the hydrocarbon, the hydrocarbon is virtually insoluble in the aqueous phase and the monomer is miscible with the hydrocarbon. The monomer is polymerized to produce a low molecular weight polymer such that the low molecular weight polymer will phase separate from the organic phase and conentrates at the surface of the introduced organic phase forming a low molecular weight polymer phase.

Abstract: A latex partice comprising a vinyl aromatic monomer and an vinyl acrylate ester monomer which is modified by a protein binding modifying monomer to facilitate the binding of a protein via coupling techniques. These latex particles are useful in diagnostic test applications. The vinyl acrylate ester monomer and a vinyl aromatic monomer are dispersed in a ratio between 1:3 to 3:1 of vinyl acrylate ester monomer to vinyl aromatic monomer in an aqueous phase containing a protein binding modifying monomer. The protein modifying monomer can be a vinyl carboxylic acid, such as a acrylic acid in a concentration of from about 0.5 percent to about 10 percent of the monomers. The dispersion is subjected to emulsion polymerization to provide a latex particle in a size range from 0.1 to 1 micron. The latex particle is sensitized with an antibody or antigen via coupling techniques.

Abstract: Expandable synthetic resinous microspheres are expanded in a matrix by heating under pressure to at least a foaming temperature and permitting the microspheres to expand at a lower pressure.

Abstract: Uniformity in the polymerization of expandable microspheres disclosed in U.S. Pat. 3,615,972 is improved by replacing a copolymer of adipic acid and diethanol amine with citric acid.