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Thermal behaviour of cubic phases rich in 1-monooleoyl-rac-glycerol in the ternary system: 1-monooleoyl-rac-glycerol/n-octyl-β-d-glucoside/water
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2003 (English)In: The FEBS Journal, ISSN 1742-464X, E-ISSN 1742-4658, Vol. 270, no 1, 56-65 p.Article in journal (Refereed) Published
Abstract [en]

Using synchrotron X-ray diffraction the thermal behaviour was studied of the cubic phases in the 1-monooleoyl-rac-glycerol (MO)/n-octyl-β-d-glucopyranoside (OG)/2H2O system with 58 or 45 wt % MO concentration and varying OG/2H2O contents. These MO contents correspond to a Pn3m cubic single-phase or a Pn3m cubic phase in excess water on the binary MO/water axis of the ternary phase diagram. The cubic liquid crystalline phases are stable with small fractions of OG, while higher OG concentrations trigger a cubic-to-lamellar phase transition. Moreover, with increasing OG concentration the initial Pn3m structure is completely converted to an Ia3d structure prior to the Lα phase being formed. Upon heating this effect is reversed, resulting in an Ia3d-to-Pn3m phase transition. For some samples additional peaks were observed in the diffractograms upon heating, resulting from the metastability notoriously shown by bicontinuous cubic phases. This judgement is supported by the fact that upon cooling these peaks were absent. Remarkably, both the Ia3d and the Pn3m cubic structures could be in equilibrium with excess water in this ternary system. A comparison is made with previous results on n-dodecyl-β-d-maltoside (DM), showing that cubic phases with OG have higher thermal and compositional stability than with DM.

Place, publisher, year, edition, pages
2003. Vol. 270, no 1, 56-65 p.
National Category
Chemical Sciences
URN: urn:nbn:se:umu:diva-8741DOI: 10.1046/j.1432-1033.2003.03361.xOAI: diva2:148412
Available from: 2008-02-08 Created: 2008-02-08 Last updated: 2012-06-26Bibliographically approved
In thesis
1. Amphiphilic Molecules in Aqueous Solution
Open this publication in new window or tab >>Amphiphilic Molecules in Aqueous Solution
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to investigate amphiphilic molecules in aqueous solution. The work was divided into two parts. In the first part the effects of different counterions on phase behavior was investigated, while the second part concerns the 1-monooleoyl-rac-glycerol (MO)/n-octyl-β-D-glucoside (OG)/2H2O-system.

The effects of mixing monovalent and divalent counterions were studied for two surfactant systems, sodium/calcium octyl sulfate, and piperidine/piperazine octanesulfonate. It was found that mixing monovalent and divalent counterions resulted in a large decrease in cmc already at very low fractions of the divalent counterion. Moreover, the degree of counterion binding for piperidine in the piperidine/piperazine octanesulfonate system was much higher than predicted, probably due to the larger hydrophobic moiety of piperidine.

The effects of hydrophobic counterions were studied for eight alkylpyridinium octanesulfonates (APOS). The results were discussed in terms of packing constraints. The anomalous behavior of the 2H2O quadrupolar splittings in the lamellar phases was explained by the presence of two or more binding sites at the lamellae surface.

The MO/OG/water system was studied in general and the MO-rich cubic phases in particular. When mixing MO and OG it was found that OG-rich structures (micelles, hexagonal and cubic phase of space group Ia3d) could solubilize quite large amounts of MO, while the MO-rich cubic structures where considerable less tolerant towards the addition of OG. The micelles in the OG-rich L1 phase were found to remain rather small and discrete in the larger part of the L1 phase area, but at low water concentration and high MO content a bicontinuous structure was indicated. Only small fractions of OG was necessary to convert the MO-rich cubic Pn3m structure to an Ia3d structure, and upon further addition of OG a lamellar (La) phase formed. Since the larger part of the phase diagram contains a lamellar structure (present either as a single La phase or as a dispersion of lamellar particles together with other phases), the conclusion was that introducing OG in the MO structures, forces the MO bilayer to become more flat. Upon heating the cubic phases, structures with more negative curvature were formed. The transformation between the cubic structures required very little energy, and this resulted in the appearance of additional peaks in the diffractograms.

46 p.
Physical chemistry, liquid crystal, phase diagrams, counterions, alkylpyridinium octanesulfonates, 1-monooleoyl-rac-glycerol, n-octyl-β-D-glucoside, cubic phases, Fysikalisk kemi
National Category
Physical Chemistry
Research subject
Physical Chemistry
urn:nbn:se:umu:diva-90 (URN)91-7305-501-8 (ISBN)
Public defence
2003-10-03, O 102, Kornboden, Sundsvall, 13:00
Available from: 2003-10-03 Created: 2003-10-03 Last updated: 2012-06-26Bibliographically approved

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