Monosize polystyrene microbeads by dispersion polymerization

Abstract Monosize Polystyrene microbeads were prepared by dispersion polymerization in different alcohol/ water media. Azobisisobutyronitrile and polyacrylic acid were utilized as initiator and steric stabilizer, respectively. The polymerizations were performed in three kinds of dispersion media having different polarities: isopropanol/water, 1‐butanol/water, and 2‐butanol/water. The effects of initiator and stabilizer concentrations, alcohol/water ratio, and monomer/dispersion medium ratio on the size and monodispersity of the polymeric microbeads were investigated. By dispersion polymerization, polystyrene (PS) microbeads were obtained in the size range of 1.0–4.0 μm with narrow size distribution or in the monosize form. The average size and size distribution of microbeads with increasing polarity of the dispersion medium. The average size and size distribution increased with increasing initiator concentration in all dispersion media. The increase in the stabilizer concentration in homogeneous dispersion media resulted in a decrease in average size and size distribution of the microbeads. A clear increase was observed in the average size with increasing monomer/dispersion medium ratio. Isopropanol/water dispersion medium provided monosize microbeads with higher values of monomer/dispersion medium ratio. © 1993 John Wiley & Sons, Inc.