Polystyrene emulsions flocculation

It has been shown that the stability of colloidal suspensions can also be influenced by a pure alcohol-water mixture, without the addition of any surface active agent. In a study of the flocculation of polystyrene emulsions in ethanol-water mixtures (42), the concentration of sodium chloride required to produce rapid flocculation increases with increasing ethanol concentration up to 0.09 molar fraction, beyond this composition, the concentration of sodium chloride required for flocculation decreases rapidly. It will be very informative, therefore, to compare our coagulation rate obtained in the microemulsion media to that in pure IPA + water mixture. The results can be used to further delineate the role of inverted micellar structure on the enhancement of coagulation. 

With emulsions, however, there is some evidence to suggest that the anchor polymer must not only be insoluble in the continuous phase but must also be soluble in the disperse phase to ensure. optimum stability (March and Napper, 1977). March and Napper investigated the preparation of toluene emulsions in water using poly(oxyethylene) of molecular weight 79 000 as the stabilizing moieties. Anchor polymers, such as poly(vinyl acetate), polystyrene and poly(methyl methacrylate) that are soluble in toluene, generated stable emulsions that flocculated only when taken to the thermodynamic limit of stability. Polyacrylonitrile, however, which is insoluble in both water and toluene, was so ineffective as an anchor polymer that the toluene-in-water emulsions prepared with it flocculated almost immediately after preparation. 

A broad range of polymers are produced by polymerization in heterogeneous media, including polyolefins manufactured by slurry (high density polyethylene and isotactic polypropylene) and gas phase (linear low density polyethylene and high density polyethylene) polymerization coatings and adhesives produced by emulsion and miniemulsion polymerization flocculants obtained by inverse emulsion and microemulsion polymerization poly(vinyl chloride) (PVC) and polystyrene produced by suspension polymerization and toners synthesized by dispersion polymerization. As a whole, they represent more than 50% of the polymer produced worldwide [1]. 

Particles that are small relative to emulsion drop size are also expected to have an effect on emulsion properties in systems stabilized by surfactants when present in only small amounts (say a sufficient number of particles to give 10% coverage of droplet surfaces). We reported elsewhere [40] on a preliminary smdy of the ways in which the stability to flocculation and coalescence of water-in-oil emulsions stabilized by the anionic surfactant Aerosol OT are modified by polystyrene latex particles. There is evidence that the particles bridge droplets to give weak floes, which slow down droplet coalescence. 

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