Stabilization of oil-in-water emulsions by non-ionic detergents: the effect of polyoxyethylene chain length

Abstract

The stability of emulsions of anisole and chlorobenzene in water has been estimated by following microscopically the size distribution of emulsions as a function of time. The effect of increasing the length of the polyoxyethylene glycol chain of the hexadecyl ether non-ionic stabilizers from three units to nine units was determined. Electrophoretic measurements indicated that the higher stability obtained on increasing the glycol chain length is not due to an increasing surface potential: it is ascribed to an entropic effect. Stability data are tabulated as rates of coalescence (s−1) and results are presented relating these rates to zeta-potential, surface concentration and polyoxyethylene chain length. The results are discussed qualitatively and compared with the results obtained with cetomacrogol 1000 (Elworthy & Florence, J. Pharm. Pharmac., 1967, 19, 140S).