Preparation of Hydrophilic Polystyrene Microspheres with Casein Molecules on the Surface

In this study, suspension polymerization is described to prepare hydrophilic polystyrene microspheres with casein macromolecules on the surface. In the suspension polymerization, casein w as used as an emulsifier and stabilizer instead of synthetic surfactants. The microspheres had spherical shape and the size distribution was narrow, the average size was about 3.5 µm. The microspheres were characterized with a Fourier transform infrared spectroscopy, revealing the existence of hydroxyl, carboxyl and amino groups. XPS analysis was carried out to study the surface composition, it revealed that the nitrogen concentration was 5.04% on the surface of the particles and it remained almost unchanged after the particles were washed by 2% SDS. The microspheres were confirmed to be hydrophilic due to the casein molecules on the surface.