the study of surfactant adsorption at the air-liquid interface. Neutron reflection and surface tension have been used to study It provides a direct and absolute method for the determinathe adsorption of the nonionic surfactant monododecyl hexaethyltion of adsorbed amounts for one component (5) and multiene glycol (C 12 E 6 ) and the mixed nonionic-anionic surfactants ncomponent (6) surfactant systems. Furthermore, it enables dodecyl triethylene glycol (C 12 E 3 ) and Sodium dodecyl sulfate the structure of the adsorbed layer to be determined in greater (SDS) at the air-liquid interface. Water and a sorbitol ( d-glucitol, detail than has previously been possible (7) by other tech-CH 2 OH(HCOH) 4 CH 2 OH)/water mixture were selected as the solniques. It has most recently been exploited in the determinavents. The addition of 300 g/liter of sorbitol to an aqueous solution tion of the conformation of the alkyl (7) and ethylene oxide of C 12 E 6 reduces the critical micellar concentration, cmc, from Ç7 chains (8) and the effects of temperature on the nonionic 1 10 05 to Ç3 1 10 05 M, and increases the surface pressure at the cmc; the effect on the C 12 E 3 /SDS mixture is less. Despite these surfactants C 12 E 3 , C 12 E 6 and C 12 E 8 (9, 10).
changes, the pattern of adsorption at the air-liquid interface is
Neutron reflection and surface tension were used to deteressentially unaltered by the addition of sorbitol, and the surface mine the adsorption of C 12 E 6 at the air-solution interface tension and neutron reflectivity data are in good agreement. The for water and water-sorbitol mixed solvents at surfactant consequences of the sorbitol addition are however seen directly in concentrations below the cmc of C 12 E 6 in water. The role the structure of the C 12 E 6 monolayer. The ethylene oxide (EO) of sorbitol in altering the surface partitioning of the mixed chain is more extended than in water, and more displaced from nonionic-anionic surfactants, C 12 E 3 /SDS, was investigated the solvent, consistent with dehydration of the ethylene oxide using neutron reflection, and was compared with earlier regroup.