Isopycnic phases and structures in H2O/CO2/ethoxylated alcohol surfactant mixtures

Michael E. Paulaitis, Richard G. Zielinski, Eric W. Kaler

Research output: Contribution to journalConference articlepeer-review


Ternary mixtures of H2O and CO2 with ethoxylated alcohol (CiEj) surfactants can form three coexisting liquid phases at conditions where two of the phases have the same density (isopycnic phases). Isopycnic phase behavior has been observed for mixtures containing the surfactants C8E5, C10E6, and C12E6, but not for those mixtures containing either C4E1 or C8E3. Pressure-temperature (PT) projections for this isopycnic three-phase equilibrium were determined for H2O/CO2/C8E5 and H2O/CO2/C10E6 mixtures at temperatures from approximately 25 to 33°C and pressures between 90 and 350 bar. As a preliminary to measuring the microstructure in isopycnic three component mixtures, phase behavior and small angle neutron scattering (SANS) experiments were performed on mixtures of D2O/CO2/ n-hexaethyleneglycol monododecyl ether (C12E6) as a function of temperature (25-31°C), pressure (63.1-90.7 bar), and CO2 composition (0-3.9 wt%). Parameters extracted from model fits of the SANS spectra indicate that, while micellar structure remains essentially unchanged, critical concentration fluctuations increase as the phase boundary and plait point are approached.

Original languageEnglish (US)
Pages (from-to)41-46
Number of pages6
JournalNASA Conference Publication
Issue number3338
StatePublished - Dec 1 1996
EventProceedings of the 1996 3rd Microgravity Fluid Physics Conference - Cleveland, OH, USA
Duration: Jul 13 1996Jul 15 1996

ASJC Scopus subject areas

  • Aerospace Engineering


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