Preparation of micron-size monodisperse polymer particles by seeded polymerization utilizing the dynamic monomer swelling method

Utilizing a new type of monomer swelling method, 6.1 μm-size monodisperse polymer particles were prepared by seeded polymerization. 1.8 μm-size monodisperse polystyrene (PS) seed particles (1.8 μm in size) were prepared by dispersion polymerization in ethanol-water (80/20, v/v) medium in the presence of poly(acrylic acid) as stabilizer with 2,2′-azobisisobutyronitrile as initiator. The PS seed dispersion was mixed with ethanol-water (60/40, v/v) solution dissolving styrene (S) monomer, benzoyl peroxide as initiator, and poly(vinyl alcohol) as stabilizer. By slow, continuous, dropwise addition of water with a micro feeder into the mixture, the PS particles absorbed the many S monomers, which were separated from the medium and swelled from 1.8 μm to 8.4 μm while keeping the monodispersity high. We named this procedure the “dynamic swelling method”. Then, the seeded polymerization of the absorbed S monomer was carried out in the presence of NaNO2 as water-solube inhibitor.