Study On Thermal Polymerization And Photopolymerization To Prepare Microspheres By Stabilizer-Free Dispersion Polymerization

Polymer microspheres are widely applied in daily life. For conventional polymerization methods, emulsion polymerization, suspension polymerization and dispersion polymerization are traditional methods to prepare polymer microspheres. Particles, prepared by emulsion polymerization, have size range from 0.1 to 0.7μm, while those prepared by suspension polymerization have size range from 100 to 1000μm and they are wide dispered. By soap-free or low-emulsion polymerization, the particles size closed to 1μm can be prepared, but it is difficult to prepare polymer microspheres upto 1μm, which is not big enough for many applications. The dispersion polymerization is more effective method to prepared micron polymer microspheres. However, no matter dispersion polymerization, suspension polymerization, emulsion polymerization, dispersant or emulsifier are necessary, which remains on the particle surface after polymerization and may bring some adverse effects to the particle properties. In this paper, polymer microspheres with nice dispersion were prepared without adding any stabilizer or other additives. So the reaction is called stabilizer-free dispersion copolymerization. 1. The polymer microspheres are prepared by conventional thermal stabilizer-free dispersion copolymerization. The mechanism of the existence and stability of microsphere particles are explored, the effects of principal factors such as the initiator and monomer concentrations, molar feed ratio of monomer, the reaction time, reaction temperature, reaction media and cosolvent on the characteristics of the final particles were investigated. The results showed that, homopolymerization of styrene formed in initial polymerization period served as stabilizer and solvent solubility parameter played an important role in the experization, reaction solvent of similar solubility parameter would benefit the stabilizer-free dispersion polymerization. Meanwhile, the results indicated stabilizer-free dispersion copolymerization was a special reaction with its own unique rules.2. Based on profound theoretical research technology and rich experience on UV polymerization in our laboratory, the styrene-maleic anhydride copolymer microspheres and crosslinked polymer microspheres were prepared by photoinitiated stabilizer-free dispersion polymerization and the principal factors which affect the size of the microspheres were studied. Compared with thermal stabilizer-free dispersion copolymerization and photoinitiated stabilizer-free dispersion polymerization, photopolymerization is a fast reaction, but the productions are wide distributed.