Crosslinked Monodisperse Polystyrene Microspheres Synthesis And Characterization

The monodisperse polymer microspheres with large size are a kind of macromolecular particles which have been developed in recent 20 years. They are of wide prospects for using in many fields such as standard measurement, information, medicine, immunity, biochemistry etc. This paper was aimed at preparing the micro-size mono-disperse PS particles and mono-size crosslinked polystyrene microspheres (CPS) by dispersion polymerization. Firstly, some pretty polymerization systems was chosen, and then, the influences of polymerization parameters on particle size and size distribution were investigated to find out the reasonable polymerization way of PS mono-disperse particles.A series of experiments were conducted to get the effects of polymerization parameters on particle size and size distribution. The results show that the size of polystyrene microspheres decreases with increasing amount of stabilizer, increasing initiator concentration and initial monomer concentration could increase particle size and broaden the size distribution. While, introducing the monomer in a lump administers to obtaining monodisperse polystyrene microspheres.The stability mechanism of the dispersion system was also investigated by means of IR. The existence of adsorption-stabilization mechanism is proved. In the beginning, monomer, dispersant and initiator all dissolve in the dispersed media, the reaction system is homogeneous prior to dispersion polymerization. As soon as the polymerization begins, primary radicals, generated by decomposition of the initiator, grow in the continuous phase by the addition of monomer units until they reach their critical chain length where they precipitate to form nuclei. These nuclei are unstable and aggregate with each other; concurrently, they adsorb the stabilizer and finally become stable particles. The existing particles continue to grow by capturing the nuclei and oligo-radicals which will either continue to grow inside the particles or terminate with other radicals. At the end of the polymerization nuclei formation stops owing to the exhaustion of the monomer.The standard recipes for preparing 1.8μm, 2.2μm PS particles have been gotten.