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Surface tension and small-angle neutron scattering have been used to study the nature of surfactant adsorption on silica sols. This paper presents results on the characterization of the ludox silica sol and adsorbed layers of hexaethylene glycol monododecyl ether (C12E6). Preliminary results are presented that demonstrate the presence of a lower consolute boundary for the composite system.

Small-angle neutron scattering (SANS) has been used to investigate the geometry of micelles of the poly(oxyethylene) nonionic surfactants C16E6 and C16E8 aligned in situ in a shear flow, in the presence of "salting in" or "salting out" electrolyte. With increasing temperature, a growth of rodlike micelles and a subsequent reduction in effective rod length are observed. This evolution of micelle rod length, accompanied by subtle changes in rod flexibility, is attributed to changes in intramicelle ethylene oxide (EO)-ethylene oxide interactions.

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Small angle neutron scattering has been used to investigate the nature of the adsorption of the alkyl polyoxyethylene ether (C n EO m ) nonionic surfactants on Ludox silica sols. Variations in the adsorbed layer thickness and volume fraction of surfactant in the adsorbed layer with sol type, concentration, temperature, and surfactant type are observed. In particular, the structure of the adsorbed layer of the C16EO6 and C16EO8 surfactants (for which the bulk micellar phase is rodlike micelles) is similar to that found for the C12EO6 and C12EO5 surfactants.