Inverse emulsions stabilized by a hydrophobically modified polysaccharide

Dextran, a neutral bacterial polysaccharide, was chemically modified by the attachment of n-alkyl chains (hydroxy-2 n-dodecyl) through the formation of ether linkages. The extent of hydrophobic modification was high enough to ensure good solubility of the resulting polymer in organic solvents like chloroform. Furthermore, this polymer was shown to lower interfacial tension between water and dichloromethane with similar effect as to a usual oil-soluble molecular surfactant (Span 80). Submicronic water-in-chloroform emulsions were prepared using the modified dextran as the sole stabilizer with volume fractions of disperse phase up to 30%. The initial average droplet size and storage stability of inverse emulsions was discussed as a function of polymer concentration and volume fraction of disperse phase. Ostwald ripening was shown to dominate emulsion ageing for volume fractions up to 10% while another process accelerated emulsion ageing for higher volume fractions. This process was suggested to be coalescence.