Dilational rheology of air/water interfaces covered by nonionic amphiphilic polysaccharides. Correlation with stability of oil-in-water emulsions

Biodegradable polymeric emulsifiers were prepared by covalent attachment of aliphatic hydrocarbon groups onto dextran macromolecules (a bacterial nonionic polysaccharide), varying the number of attached hydrocarbon tails. Submicronic oil-in-water emulsions were prepared by sonication using previous polymeric stabilizers with oil volume fractions between 10 and 50% and two oils (hexadecane and nujol). An optimal range of dextran hydrophobic modification was evidenced conciliating a strong anchoring of polymer to oil/water interface and sufficient steric repulsions between droplets. These results were correlated to dilational rheology of air/water interfaces covered by amphiphilic dextrans. The storage stability of these emulsions was of several weeks.