Polycarbonate particles and dye-labeled particles by miniemulsion polymerization

We describe the synthesis of several different polycarbonate particles by miniemulsion polymerization. The monomers were allylmethyl carbonate (AlMeC), di(ethylene glycol) bisallylcarbonate (DBAC), and 4-vinyl-1,3-dioxan-2-one [vinyl ethylene carbonate (VEC)]. For these polymerizations, higher monomer conversions were obtained with oil-soluble initiators (azobisisobutyronitrile and benzoyl peroxide) than with a water-soluble initiator (potassium persulfate). Benzoyl peroxide was particularly effective in yielding particles with a narrow size distribution. Although increasing amounts of a surfactant (sodium dodecyl sulfate) led to smaller particles, the choice of the monomer was the major determinant. For example, in polymerization reactions carried out at 85 degreesC with benzoyl peroxide as the initiator and with otherwise identical recipes, we obtained particle sizes of 181 nm with AlMeC, 296 nm with VEC, and 203 nm with DBAC. Fluorescent particles were synthesized with comonomers based on the benzothioxanthene nucleus. Because the dyes had poor solubility in the monomers, it was necessary to include typically 20 wt % bromobenzene or dichlorobenzene based on the monomer in the miniemulsion reaction mixture. (C) 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1999-2009, 2004.