Preparation of monodisperse polystyrene microspheres with different functional groups using soap-free emulsion polymerization

Monodisperse polystyrene microspheres with different functional groups have important applications in both the medical and analytical fields. In this study, we prepared monodisperse microspheres with sulfonic acid or carboxyl groups using soap-free emulsion polymerization (SFEP) with potassium persulfate as the initiator. A series of monodisperse polystyrene microspheres with sizes between 100 and 500 nm were successfully prepared by copolymerizing different types of ionic monomers at different concentrations. The microspheres were characterized by using dynamic light scattering (DLS), Zeta potential measurements (ZP), FT-IR spectroscopy, and transmission electron microscopy (TEM). The mechanism of the particle nucleation and growth were studied by combining the changes in particle size and the number of particles. The results showed that the addition of hydrophilic comonomers like sodium p-styrene sulfonate, acrylic acid, and methacrylic acid significantly improved the stability of the polystyrene microspheres and promoted particle nucleation, resulting in less particle aggregation and microspheres with smaller sizes.