Phenoxy-substituted dextrans as emulsifying agent:: role of the substitution ratio on O/W emulsion stability and interfacial activity

Oil-in-water emulsions were prepared using dextran, a natural polysaccharide, hydrophobically modified with phenoxy groups. Emulsions were prepared by two different processes which were sonication and microfluidization. The average diameter of oil droplets and the stability with time of the resulting emulsions were investigated as a function of polymer concentration (Cp=0.1–1% w/w in water phase) and the degree of polymer grafting (τ=4.2–15.7%). The microfluidization process allowed to realize emulsions with lower initial particle size than the sonication method. For the highest degrees of grafting and for Cp values ≥0.2% w/w, submicronic emulsions were obtained, which were stable for more than 4 months at room temperature. Interfacial measurements at the n-dodecane/water interface clearly showed a better efficiency of the most substituted polymers to lower the surface tension.