Poly(styrene-co-acrylonitrile) Particles Prepared by Phase Inversion of W/O Emulsions

In this paper, we describe a particle preparation method that combines phase inversion of water in oil (W/O) emulsions with solidification of polymers dissolved in the emulsion droplets, induced by introducing a poor solvent, in order to prepare poly(styrene-co-acrylonitrile) (SAN) particles with a relatively narrow size distribution. W/O emulsions containing SAN are prepared by adding an aqueous solution of polyvinylalcohol (PVA) as a protective colloid into a methylethylketone (MEK) solution of SAN. Sufficient addition of the aqueous solution causes the precipitation of SAN particles from MEK followed by phase inversion from W/O emulsions to oil in water (O/W) emulsions. We also demonstrate that the use of sorbitan fatty acid esters as dispersion agents is effective for controlling size and polydispersity of SAN particles. They depend strongly on the concentrations and kinds of sorbitan fatty acid esters; a low concentration of sorbitan monolaurate resulted in an average particle size of 1.2 μm with a narrow size distribution.