Stabilization of Water-In-Water Emulsions by Linear Homo-Polyelectrolytes.

The effect of adding a small quantity of linear polymers on the stability of water-in-water (W/W) emulsions was studied for emulsions of dextran-rich droplets in a continuous poly(ethylene oxide) (PEO) phase (D/P) and vice versa (P/D). It was found that out of 16 different polymers that were tested, three had a significant effect: chitosan (Chit), diethyl aminoethyl dextran (DEAED), and propylene glycol alginate (PGA). In the presence of Chit or PGA, P/D emulsions were much less stable than D/P emulsions, but DEAED stabilized both types of emulsion. Interactions of these polymers with PEO or dextran were investigated with light scattering, and the microstructure of the emulsions was studied with confocal laser scanning microscopy. The effect of pH, polymer concentration, interfacial tension, and ionic strength on the stability was investigated and was found to be different for the three polymer types. The results suggest that stabilization of W/W emulsions by linear polymers requires that they contain both charged and hydrophobic units.