AGGREGATION AND SURFACE-PROPERTIES OF SYNTHETIC DOUBLE-CHAIN NONIONICSURFACTANTS IN AQUEOUS-SOLUTION

Double-chain non-ionic surfactants have been synthesized with the gene ral formula 2C(n)MPEG(750), where n is the number of carbons in the al kyl chains and 750 is the molecular weight of the monomethoxypolyoxyet hylene (MPEG) head group. The aggregation and surface properties in di lute aqueous solution (< 1.0% w/w) of surfactants with n=8, 10 and 12 have been determined. Each of the surfactants formed clear, foaming, n on-birefringent solutions. Total-intensity light scattering indicated the presence of micelles with aggregation numbers of 36, 68 and 74 for the 2C(8), 2C(10) and 2C(12) surfactants, respectively, whereas photo n-correlation studies yielded radii, assuming spherical aggregates, of 59-103 Angstrom. Surface-tension measurements gave critical micelle c oncentrations for the surfactants in the range 1.15-7.24 x 10(-6) M; t hese, as expected, decreased when the number of carbon atoms in the al kyl chains was increased. Such studies are important in the design of new surfactants as vehicles for drug delivery because it is imperative to be able to predict the type of aggregate formed by a surfactant.