PREPARATION OF MONODISPERSE, MICRON-SIZED POLYSTYRENE PARTICLES WITH SINGLE-STAGE POLYMERIZATION IN AQUEOUS-MEDIA

A single-stage polymerization technique, proposed for producing micron -sized polymer particles in aqueous media by Gu and Konno, was examine d. Styrene was used for the monomer, potassium persulfate for the init iator, and cetyltrimethylammonium bromide and sodium dodecyl sulfate w ere used for the ionic surfactants to control the aggregation of the p articles during the reaction. Particle-size distributions and monomer- to-polymer conversions were measured over a range of initiator concent ration (2-8 mmol/dm(3) H2O), stirring speed (200-400 rpm), surfactant addition time and monomer concentration (1.1-2.2 mol/dm(3) H2O). Chang es in the initiator concentration and stirring speed did not bring abo ut significant effect on the particle-size distributions. On the other hand, the addition of time affected the coefficient of variation of t he particle-size distribution, but it had no significant effect on the average diameter of the particles. An increase in the monomer concent ration enlarged the average size without lowering the coefficient of v ariation of particle-size distribution. Monodisperse polystyrene parti cles with an average diameter of 3.3 mu m and a coefficient of variati on of particle size distribution 7% could be prepared with the present technique. (C) 1998 Academic Press.