Synthesis of Monodisperse Low‐Crosslinked Polymer Microspheres With Sulfonic Acid by Precipitation Polymerization

ABSTRACT Monodisperse crosslinked polymer microspheres with phenylsulfonate were successfully synthesized via precipitation polymerization of divinylbenzene, styrene, and a styrene dimer with two phenyl sulfonate groups ( M ). The use of M in polymerization allowed us to obtain monodisperse microspheres even though the molar ratio of total crosslinker was less than 20 mol%. The effects of various polymerization conditions, including the molar ratio of total crosslinker, monomer concentration, initiator concentration, solvent composition, and comonomers, on yield, particle size, and sulfonic acid content were systematically investigated. The number‐averaged diameters of the polymer microspheres ( D n ) were in the range of 0.59 to 2.30 μm. Small particles were obtained at a high molar ratio of total crosslinker, whereas larger particles were obtained at higher monomer or initiator concentrations. In addition, the yield of microspheres increased with increasing the molar ratio of total crosslinker and monomer concentration. The solvent ratio and comonomer type also markedly influenced the size of the resulting microspheres. After the deprotection of the phenyl sulfonate moieties of the polymer microspheres, followed by acid treatment, monodisperse low‐crosslinked polymer microspheres with sulfonic acid were successfully obtained. The synthetic approach is a reliable method for preparing monodisperse low‐crosslinked polymer microspheres with sulfonic acid.