Uniform microspheres were prepared through precipitation polymerization of 1,1,1-tris(hydro- xymethyl) propane triacrylate (TMPTA)-Styrene styrene (St) with azobisisobutyronitrile (AIBN) as initiator in ethanol and ethanol-water mixture, new solvent systems with low toxicity. Impacts of TMPTA amounts, initiator concentrations and water content in the solvent mixture were studied. Uniform microspheres were obtained within 4 h along with higher monomer conversion. Results demonstrated clearly that increase of initiator amounts and use of water as a cosolvent were indeed very effective to promote the polymerization to high conversions and to get uniform microspheres. With no water under otherwise the same experimental conditions, only about 79% of monomer conversion was detected; while monomer conversion was remarkably increased to 95% when 28 vol% of water was added into ethanol. To reach to this high conversion with no water in the medium, 6 wt% of AIBN was needed. Mechanisms of microsphere formation and methods to promote monomer conversion were also explained.

Key words: precipitation polymerization, 1,1,1-tris(hydroxymethyl) propane triacrylate, uniform microsphere