Crystal structures of sodium dimethyl sulfosuccinate and sodium diethyl sulfosuccinate

Nagasoe, Yasuyuki; Hattori, Norikatsu; Masuda, Hideki; Okabayashi, Hirofumi; O’Connor, Charmian J.

doi:10.1016/s0022-2860(98)00378-0

Cited by 5 publications

(2 citation statements)

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“…Binary, ternary, or quaternary systems using AOT display rich lyotropic polymorphism that includes monolayers, bilayers, and hexagonal and cubic phases. − At higher AOT concentrations, the lyotropic systems are often hexagonal. ,,, However, neat AOT is itself liquid crystalline, a fact that had received relatively little attention. No full crystal structure has been given so far for pure solid AOT, and only structures of some simpler nonbranched AOT analogues have been determined. − The mesophase of neat AOT is described as most probably hexagonal. ,− Not much progress has been made since 1970 when it was proposed that six AOT molecules radiate out from the column center, polar heads pointing inward and the molecular plane lying parallel to the column axis . In a more recent work on AOT−urea complexes, the structural model of the mesophase of pure AOT was left unchanged, assuming 6 radiating molecules .…”

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confidence: 99%

Structure of Liquid Crystalline Aerosol-OT and Its Alkylammonium Salts

et al. 2009

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Aerosol-OT is a widely used anionic surfactant, and its lyotropic properties have been studied extensively. However, neat AOT is itself liquid crystalline. We carried out an X-ray study of neat AOT sodium salt, as well as of AOT-n-decyl-, n-dodecyl-, n-tetradecyl-, and n-hexadecylammonium salts. We confirm an earlier report that pure AOT forms a hexagonal columnar phase but propose a different packing model. This involves a relatively highly ordered structure with each column cross-section containing three tessellated molecules in the plane normal to the column axis. The structure is trigonal locally but hexagonal over the long-range. This mode of assembly is supported by electron density reconstruction and molecular modeling. At subambient temperatures, the AOT-alkylammonium complexes Cn-AOT, with n=10-16, also display a hexagonal columnar phase, but this is more disordered, and each column cross-section contains only two ion pairs. Unusually, molar enthalpy and entropy of the columnar-isotropic transition in Cn-AOT salts decrease with increasing n. This is attributed to a disproportionally high conformational disorder of the radial chains in the columnar phase, which is required for efficient space filling.

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Section: Introductionmentioning

confidence: 99%

Structure of Liquid Crystalline Aerosol-OT and Its Alkylammonium Salts

et al. 2009

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“…The small angle X-ray scattering (SAXS) technique has then been used to examine the difference in aggregational behavior between the freshly prepared and aged samples for SDOleSdecanewater system. The dynamic molecular models of AOT-reversed micelles 1619 and the crystal structures of the AOT-homologs 4,20 are used to explain the aggregational behavior of the SDOleSdecane water system at the molecular level.…”

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Effect of Hydration on the Very Slow Droplet–Lamellar Transition in Dioleylsulfosuccinate/Decane/Water System: A Small Angle X-ray Scattering Study

Ghosh¹,

Ichiyanagi²,

Okabayashi³

et al. 2009

Bulletin of the Chemical Society of Japan

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Time-and temperature-dependence of the small angle X-ray scattering (SAXS) profiles for homogeneous and transparent solutions of the sodium dioleylsulfosuccinate (SDOleS)decanewater system with various molar ratios of [H 2 O]/ [SDOleS] have been examined. The time-dependence of the SAXS profiles has provided evidence that the droplet lamellar transition occurs spontaneously but very slowly at 298 K. This behavior depends upon the quantity of water solubilized into the SDOleS microemulsions. Some microstructural models have been proposed to explain this very slow transition.It is well known that dynamic surface phenomena occur in the self-assembled systems formed on the airwater or oil water interface within the time scale 1,2 ranging from 10 ¹3 to 10 3 s. Extensive studies of these phenomena have been carried out for more than seventy years.In self-assembled systems of surfactants with low molecular weight, change in surface-tension occurs rapidly (usually in less than 1 s).2 Germasheva and Panaeva 3 observed a slow surface-tension equilibration in micellar solutions of sulfosuccinates, which could not be interpreted solely on the basis of diffusion to the surface. For very pure samples of sodium diheptylsulfosuccinate (SDHpS), Lucassen and Drew 4 reported a similar slow surface-tension variation and a simultaneous increase in the surface dilational modulus. They suggested that knowledge of the detailed crystal structure should provide useful information about ordering in a membrane. van den Tempel and Lucassen-Reynders 2 suggested that slow changes in surface-tension and an increase in elastic modulus might be caused by the cooperative ordering in the surface. The effect of such surface properties on the formation of a three-dimensional (crystalline) structure, similar to that of a lamellar liquid crystal, was studied by Franses et al. 5 Their results imply that the observed variation in surface-tension is a reflection of the change in aggregational structure on the surface.The reversed micelle of sodium 1,2-bis(2-ethylhexyl)sulfosuccinate (AOT) (Scheme 1) incorporates a relatively large number of water molecules in its polar core, thereby forming a water droplet 69 and providing a water/oil interface. In a freshly prepared AOT-reversed micelle, cooperative ordering in the membrane structure at this oil/water interface should occur until the membrane reaches its final ordered state. This concept implies that a difference in the aggregational structure of the interface exists between freshly prepared and aged interfaces. Previous studies on phase behaviors of the AOToilwater systems 715 have been focused on the final ordered structures, a limitation imposed by the fast rate of attainment of the final ordered state. However, interpretation of such an ordering process at the molecular level is rare, in spite of the paramount importance of the practical applications of surfactants.In this present study, an AOT-homolog with longer hydrocarbon chains, sodium dioleylsulfosuccinate (SDOleS) (Scheme 1) has been synth...

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