Synthesis and characterizations of cross-linked polystyrene microspheres with quarternary ammonium on the surface and studies on their swelling behavior

Cross-linked polystyrene microspheres with quarternary ammonium have been prepared via surfactant-free emulsion polymerization. It was confirmed that the sizes of the microspheres decreased at a certain extent when the contents of the initiator, cross-linked reagent or functional monomer were increased. TEM observation indicated that the size of polymer microspheres ranged from tens of nanometer to hundreds of nanometer. The XPS results showed that the hydrophilic quarternary ammonium groups tended to be rich on the surface of the microspheres during the polymerization. In addition, their swelling ratio can be investigated by using the "in-situ" swelling measurement of polymer microspheres.