Effect of Swelling Process on Monodispersity of Porous Polystyrene-Divinylbenzene Microspheres Prepared by Two-step Swelling Polymerization Methods

Porous polystyrene-divinylbenzene (PS-DVB) microspheres of narrow size distribution in the size range of 3.9–4.4 μm were prepared by two-step swelling polymerization methods. Effects of swelling conditions such as swelling activator, temperature, the way of dispersion and dibutyl phthalate (DBP)/seed particle ratio on particle size distribution of the PS-DVB microspheres were investigated in detail. Optimal swelling conditions for the preparation of uniformly sized polystyrene particles have been found as follows: swelling activation agent was dibutyl phthalate (DBP), swelling temperature was 35 °C, dispersion manner was ultrasonic assistant magnetic dispersion, DBP/seed particle ratio was 1–1.5 ml·g ^-1 . It was found that particle size distribution became narrower and swelling time was shortened from more than 24 h to 10 h with the introduction of ultrasonic dispersion, which was attribute to the cavitation effect of ultrasonic and the huge magnetic field action arising therefrom, speeding up the equilibrium of swelling process. Swelling temperature also has significant effect on the monodispersity and particles with the best uniformity could be achieved with the temperature at 35 °C. The possible reason is that process of seed particles absorbing swelling agent through water phase is an equilibrium course of thermodynamics and kinetics.