More Than The Preparation Of Monodisperse Polystyrene Microspheres Particle Size And Its Controlled Assembly

In recent years, monodispersed functional polymer microspheres have become a new area of research in polymer science. Monodispersed microspheres have many advantages, such as large specific area, high surface reaction capability. Due to these advantages, they are widely used in chromatographic separation, standard measurement, analytical chemistry and microelectronics.There are several traditional methods to prepare polystyrene (PS) microspheres, such as emulsion polymerization, dispersion polymerization, suspension polymerization, emulsifier-free emulsion polymerization. Dispersion polymerization and emulsifier-free emulsion polymerization are very popular now as they are simple and reproducible. In this paper, we use dispersion polymerization and emulsifier-free emulsion polymerization to prepare PS microspheres. In order to prepare the PS microspheres with controllable sizes and mono-dispersion, a series of experiments were conducted. The influence factors on PS microspheres’ diameter, size distribution of PS microspheres have been investigated and discussed, such as monomer concentration, initiator reagent and amount of comonomer.1. Preparation and characterization of non-cross-linked PS microspheresWe used dispersion polymerization and emulsifier-free emulsion polymerization to prepare PS microspheres. The composition of dispersion polymerization is that styrene (St) as the monomer,2,2’-zaobis(2-methylpropionitrile)(AIBN) as the initiator, poly(vinyl pyrrolidone)(PVP) as the dispersion stabilizer and a mixture of ethanol and water as the dispersion medium. The emulsifier-free emulsion polymerization were prepared by using St as monomer, Potassium persulfate(KPS) as initiator. The particle size, size distribution and the charge on the surface of the PS microspheres were characterized by transmission electron microscope(TEM), scanning electron microscope (SEM). The results showed that the PS microspheres prepared by dispersion polymerization are completely spherical. The sizes of PS microspheres may change with the changing of the amount of monomer, dispersion stabilizer, initiator and ethanol. The particles size was found to increase with increasing concentration of the monomer and ethanol. It also increased with the decreasing concentration of PVP and initiator. The size of PS microspheres prepared by traditional emulsion polymerization is smaller and with a wide size distribution. The stability of the traditional emulsion polymerization was also investigated. Methacrylic acid is used to improve the stability of emulsifier-free emulsion polymerization.2. Preparation and characterization of cross-linked PS microspheresCross-linked PS microspheres were prepared by emulsifier-free emulsion with using St as monomer, KPS as initiator, Sodium p-Styrene Sulfonate (NaPSS) as comonomers, Divinylbenzene (DVB) as crosslinker, a mixture of water and methanol as dispersion medium. From the results of SEM、TEM、DLS, it is concluded that PS-PVP microspheres has been formed during the emulsifier-free emulsion. A series of experiments were conducted to get the effects of polymerization parameters on particle size and size distribution. The results showed that the size of PS microspheres would be influenced by initiator concentration, monomer concentration and comonomer concentration. The crosslinking degree of PS microspheres were investigated by NMR cross-linked densitometer. The results showed that crosslinking degree of PS microspheres increased with increasing concentration of DVB.3. Investigation of controllable-assembly of PS microspheres with using epoxy resinThe method we used to prepare controllable assembly of PS microspheres is different from traditional ways. Epoxy resin and PS microspheres are dispersed in ethanol, and dropping a small amount of mixture on the surface of glass to achieve controllable assembly of PS microspheres. Epoxy resin is a sticky adhesive that is smeared on the surface of PS microspheres to make them gather and arrange orderly. The sample prepared by this way has excellent heat resistance and chemical resistance. When polystyrene microspheres arranged in order, the surface will give a color.