Emulsification and stabilization mechanisms of o/w emulsions in the presence of chitosan.

We study emulsification of paraffin oil in aqueous solutions of chitosan without adding any other surfactant. By monitoring the surface tension of the water-paraffin interface, we show that chitosan itself has only a weak surface activity. Nevertheless, chitosan dissolved in the aqueous phase allows the dispersion of oil by increasing the matrix viscosity and provides stabilization of the oil-water interface by forming a dense polyelectrolitic brush on the water side of this interface. We characterize emulsions with varying oil content, and concentrations of chitosan, and follow their long-term stability. Finally, we show that by precipitating the chitosan the rigid elastic network is formed in the aqueous phase, making a very stable suspension.