Open AccessThermal behaviour of cubic phases rich in 1‐monooleoyl‐ rac ‐glycerol in the ternary system
Author(s) -
Persson Gerd,
Edlund Håkan,
Lindblom Göran
Publication year - 2003
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2003.03361.x
Subject(s) - lamellar structure , phase diagram , phase (matter) , materials science , ternary operation , metastability , ternary numeral system , thermal stability , crystallography , analytical chemistry (journal) , thermodynamics , chemistry , chromatography , organic chemistry , physics , computer science , programming language
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)/ 2 H 2 O system with 58 or 45 wt % MO concentration and varying OG/ 2 H 2 O 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 L α 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.