SYNTHESIS OF POLYMERIC MICROSPHERES EMPLOYING SPG EMULSIFICATION TECHNIQUE

Relatively uniform polymeric microspheres, the coefficients of variati on being close to 10%, were obtained by the BPO-initiated suspension p olymerization of styrenic monomers. Unlike the conventional stirred-ta nk system, a particular microporous glass membrane (SPG) provided unif orm monomer droplets continuously when monomer was allowed to permeate through the micropores. The monomer droplets were suspended in an aqu eous solution containing the stabilizing agents, transferred to a stir red vessel, and polymerized. Up to 10 mum spheres, of a far narrower s ize distribution than those obtained by conventional microsuspension p olymerization spheres, were obtained. The initial droplet size and dis tribution were retained with the successful suppression of secondary p article nucleation by the addition of hydroquinone in the aueous phase . Crosslinked polystyrene spheres were also synthesized in the presenc e of various low-molecular-weight diluents. While a good solvent, tolu ene, was not so effective; poor solvents, n-hexane and n-heptane, easi ly yielded the microporous structure, the specific surface area being as high as 160 m2/g. (C) 1994 John Wiley & Sons, Inc.