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 microspheres were prepared by employing the SPG (Shirasu Porous Glass) membrane 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 pressure of emulsification (Pcr), size distribution of droplets, and morphologies of final particles were investigated. It was found that Pcr decreased with increasing LOH amount because of preferential partition of LOH on the surface of the droplets in the initial stage of emulsification. When polymer concentration or PMMA/PST ratio was low, the size distribution of droplets decreased 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 in the absence of LOH, irrespective of the PMMA/PST ratio. In the presence of LOH, however, microdomain, hemisphere, and inverted core–shell morphologies 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 and inverted core–core–shell were observed. Theoretical calculations of morphologies were carried out, and agreement was obtained between experimental and calculated results.