Study on preparation and morphology of uniform artificial polystyrene-poly(methyl methacrylate) composite microspheres by employing the SPG (Shirasu Porous Glass) membrane emulsification technique

Fairly uniform polystyrene-poly(methyl methacrylate) (PST-PMMA) composite m icrospheres were prepared by employing the SPG (Shirasu Porous Glass) membr ane emulsification technique. PST, PMMA, and cosurfactant (lauryl alcohol, LOH) dissolved in dichloromethane (DCM) were used as a dispersed phase, and an aqueous phase containing poly(vinyl alcohol) and sodium lauryl sulfate was the continuous phase. The effects of LOH amount on the critical pressur e of emulsification (P-cr), size distribution of droplets, and morphologies of final particles were investigated. Pt was found that P-cr decreased wit h increasing LOH amount because of preferential partition of LOH on the sur face of the droplets in the initial stage of emulsification. When polymer c oncentration or PMMA/PST ratio was low, the size distribution of droplets d ecreased with increasing LOH amount, whereas an inverse trend was observed when both polymer concentration and PMMA/PST ratio were high. When polymer concentration was low, PST-PMMA core-shell particles always were obtained i n the absence of LOH, irrespective of the PMMA/PST ratio. In the presence o f LOH, however, microdomain, hemisphere, and inverted core-shell morphologi es were formed as the PMMA/PST ratio decreased from 5/5 to 1/9 (g/g). When polymer concentration was high, different morphologies such as multiplet an d inverted core-core-shell were observed. Theoretical calculations of morph ologies were carried out, and agreement was obtained between experimental a nd calculated results. (C) 1999 Academic Press.