MICROSTRUCTURE IN D2O N-HEXAETHYLENE GLYCOL MONODODECYL ETHER (C(12)E(6))/CO2 MIXTURES DETERMINED BY SMALL-ANGLE NEUTRON-SCATTERING/

Phase behavior and small-angle neutron scattering (SANS) experiments w ere performed on mixtures of D2O/CO2/n-hexaethylene glycol monododecyl ether (C(12)E(6)) as a function of temperature (25-31 degrees C), pre ssure (63.1-90.7 bar), and CO2 composition (0-3.9 wt %). The addition of carbon dioxide shifts the liquid-liquid miscibility gap present in C(12)E(6)D(2)O mixtures to lower temperatures. Parameters extracted fr om model fits of the SANS spectra. indicate that, while micellar struc ture remains essentially unchanged, critical concentration fluctuation s increase as the phase boundary and plait point are-approached. The v ariations of micelle structure, scattering contrast, and particle volu me fraction with pressure, temperature, and carbon dioxide concentrati on are consistent with only a minimal amount of carbon dioxide enterin g the micelles under all conditions.