Dispersion Polymerization of Styrene Employing Lyophilic Comonomer in the Absence of Stabilizer: Synthesis of Impurity-free Microspheres

Abstract: We investigated the feasibility of dispersion polymerization without any stabilizer, which has been con-sidered essential for ensuring colloidal stability. By employing small amounts of a lyophilic comonomer, 4-vinyl pyridine, styrene was successfully polymerized by dispersion polymerization in aqueous alcohol without stabilizer to afford stable poly(styrene-co-4-vinyl pyridine) copolymer microspheres. The stable microspheres were produced in the 4-vinyl pyridine range of 2-15 wt % to styrene. Without 4-vinyl pyridine, severely coagulated particles were obtained, implying that the poly(4-vinyl pyridine) moiety endowed colloidal stability. The polymerization kinetics, behavior, and properties of the ultimate particles showed general features of dispersion polymerization. The study results suggest that stabilizer-free dispersion polymerization is possible, thereby facilitating the synthesis of impurity (stabilizer)-free polymer particles