Preparation Of Monodisperse Polymer Microspheres And Their Self-assembly

Microspheres with high monodispersity and the suprastructure formed by self-assembly of the polymer microspheres showed great value in many fields. A great number of researches on the preparation of the microspheres and their self-assembly have been reported. Since the1990 s, precipitation polymerization has been used for the preparation of monodisperse microspheres. In this work, monodisperse microspheres of crosslinked poly(methyl methacrylate)(PMMA) are prepared by precipitation polymerization in ethanol and/or its mixture with water. A third organic solvent, which is not fully dissolved in the mixture of water and ethanol, is added into the mixture to provide droplet templates.First, monodisperse microspheres are prepared with trihydroxymethyl propane triacrylate(TMPTA) and methyl methacrylate(MMA) in the water-ethanol mixture by precipitation polymerization. And azobisisobutyronitrile(AIBN) is used as initiator. The result show that when TMPTA amount is between 50~70 wt% of the whole amount of the monomers,microspheres are highly monodisperse. Changing the content of water in the system could adjust the diameter of microspheres. The diameter of the microspheres increased with decreased amount of water in the solvent.The third solvent was added to a mixed solvent of water-ethanol as the droplet templates.Monodieperse P(TMPTA-MMA) microspheres were put into the mixed system for self-assembly. The effects of the third solvent and its amount, the assembly temperature, the amounts of water, microspheres and that of TMPTA, the shaking frequency during self-assembly and the size of microspheres are studied. Suprastructures of colloidosomes with Golfball-like structure are achieved by assembly of P(TMPTA-MMA) microspheres when benzene was used as the third solvent. The amount of TMPTA in microspheres preparation was 60 wt%; the amount of water was 27.5 vol% in the mixed solvent of ethanol-water; the amount of benzene was 12.7 mL and microspheres were 0.187 g for a system of 50 mL; the microsphere’s diameter was not larger than 1.1 μm; the assemble temperature was 30 °C and the shaking frequency was 120 osc/min.Pentaerythritol triacrylate(PETA) was used in microsphere preparation instead ofTMPTA. When the amount of PETA was 50~85 wt%, monodisperse microspheres were prepared in ethanol. The diameter of the microspheres could be adjusted by adding water in to the system. Microspheres of high monodispersity were obtained only when the amount of water was below 17 vol% in the ethanol-water mixture..The factors, such as the nature of the third solvent, the assembly temperature, the amount of water, the amount of the third solvent and the amount of microspheres, were also studied in self-assembly of P(PETA-MMA) microspheres. Suprastructures of colloidosomes with Golfball-like structure are achieved when benzene or toluene was used as the third solvent.The optimized experiment condition were: the amount of PETA in microspheres preparation was 60 wt%; the amount of water was 27.5 vol%; the amount of microspheres was 0.187 g and benzene was 13.7 mL when the whole system was 50 mL; if toluene was used as the third solvent its amount was 8.7 mL for a same system of 50 mL; the assemble temperature was30 °C and the shaking frequency was 120 osc/min.