Polymer Microspheres Prepared By Continuous Photopolymerization

Polymer microspheres have played an extremely important andspecial role in many areas because of their special size and specialstructure. The commonly used methods to prepared polymermicrospheres, such as emulsion polymerization, suspensionpolymerization and dispersion polymerization have to use a stabilizer oremulsifier which made the complex polymerization process, intractableclean and bad effect to the product. We combined the UV curingtechnology and precipitation polymerization with dynamic productionprocess to prepare polymer microspheres. This continuousphotopolymerization technology has many advantages in preparation ofpolymer microspheres, such as none any stabilizers or emulsifiers used, awide range of solvent to choose, fast heat dissipation, uniformillumination, circulation, continuity, controllability and easy to operate.In the first part, we study the effect of solvent on the preparation ofcross-linked methyl methacrylate microspheres in continuous photopolymerization. First, we selected four solvent systems depended onthe three-dimensional solubility parameter of solvent, and prepared poly(methyl methacrylate) microspheres in the four solvent systems. Theresults showed that the value of the solubility parameter δ of solventsystem, the viscosity of solvent system and the value of polarity δp valuewere all affect the preparation of polymer microspheres. It is difficult toget monodisperse poly (methyl methacrylate) microspheres in ethanol andglycerol solvent system for high viscosity of the solvent system. We gotbetter monodisperse poly (methyl methacrylate) microspheres in acetoneand ethylene glycol solvent system may be for smaller solubilityparameter δ values. In ethanol and water solvent system with high valueof polarity δpalso prepared monodisperse poly (methyl methacrylate)microspheres. We also confirmed that there are C=C residual inpolymethyl methacrylate microspheres surface by infrared spectroscopyabsorption peaks at1640cm–1.In the second part, we prepared crosslinked poly hydroxyethylmethacrylate (PHEMA) microspheres in continuous photopolymerization.First, it confirmed successful preparation of PHEMA microspheres byscanning electron microscopy characterization in continuousphotopolymerization; Secondly, we study the effect of the solvent system,photoinitiator content, monomer content, crosslinker content, anddifferent number of cycle times to preparation of PHEMA microspheres. The results showed that it can get good dispersion of PHEMAmicrospheres both in the solvent system of ethanol and water and thesolvent system of acetone and water; The more monomer andphotoinitiator content, the increase of PHEMA microspheres size andwider the particle size distribution. The increase of crosslinker contentmade it easy to grow into a ball in the polymerization system. PHEMAmicrospheres gradually increased with the increase of the cycle times.Finally, the IR spectrum of PHEMA microsphere verified that PHEMAmicrosphere surface with hydroxyl groups.