Dual-seeded dispersion polymerization: formation mechanism of novel and unique ring-like and almond-shell-like polystyrene particles

In the present work, time course analysis of dual-seeded dispersion polymerization (DSDP) of 2-ethylhexyl methacrylate (EHMA) with polystyrene (PS) and poly(methyl methacrylate) (PMMA) seed beads in the presence of decane droplets and evaporation of decane after the polymerization was carried out in order to investigate the formation mechanism of almond-shell-like PS particles. It was observed that most of the PMMA seed beads becomes unstable and coagulate in the beginning of the polymerization, whereas shape of PS seed particles changes from golf-ball-like to novel and unique ring-like, and then almond-shell-like one by developing the polymerization. In addition, the effect of the hydrocarbon and PEHMA content on the shape of the obtained particles was studied. The experimental results revealed that shape of PS particles is very sensitive to little changes in decane content. As a matter of fact, decreasing the solvent concentration acts in a way that monomer conversion does. On the other hand, it was observed that asymmetric almond-shell-like particles are produced using different concentrations of PEHMA.