9301711 Ruckenstein Porous polymer particles are useful in applications such as chromatography, ion exchange, reactive polymer matrixes, and for controlled release of drugs. The synthesis of these macroreticular particles is, in general, based on the suspension polymerization of a dispersed phase that consists of monomer, crosslinking agent, initiator, and a suitable inert liquid which does not polymerize and that functions as a porogen. The size of the particles obtained depends upon the suspending medium as well as the dispersant it contains. The porosity of the particles is controlled by varying the volume fraction of the porogen and adjusting the concentration of the crosslinking agent. This project has two goals: (1) to develop new methods for the preparation of porous micron-size particles and to learn to control their internal surface area and their pore size distribution, and (2) to suggest some applications in the area of the heterogenization of homogeneous catalysts. The development of a new method for the preparation of porous polymer particles based on the concentrated emulsion polymerization method is planned. The concentrated emulsion is obtained by dispersing a hydrophobic (hydrophilic) liquid into a surfactant-containing hydrophilic (hydrophobic) liquid with mechanical stirring. The volume fraction of the dispersed phase should be larger than 0.74, which represents the volume fraction of the most compact arrangement of spheres of equal radii, and can be as large as 0.99. The concentrated emulsions have the appearance and behavior of gels and therefore can be handled easily. The concentrated emulsion is stabilized by the adsorption of the surfactant on the surface of dispersed droplets. This concentrated emulsion method employs a small volume fraction of continuous phase thus a small amount of the hydrophobic phase is employed to prepare hydrophilic particles. Three kinds of porous particles will be prepared: (1) porous crosslinke d hydrophobic particles, (2) sparse poly(vinylbenzylchloride) matrices encapsulated by porous nutshells of crosslinked polystyrene, and (3) porous crosslinked hydrophilic particles of polyacrylamide or other hydrophilic polymers. Some applications that will be studied include using the second category of materials synthesized to entrap cobalt carbonyl anions and materials synthesized under the third category to immobilize enzymes that are compatible with the hydrophilic pores. ***
