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Thermally induced fluid reversed hexagonal (H(II)) mesophase
Idit Amar-Yuli1, Ellen Wachtel, Deborah E Shalev
1Casali Institute of Applied Chemistry, The Institute of Chemistry, and Wolfson Centre for Applied Structural Biology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
The Journal of Physical Chemistry. B
|November 9, 2007
Summary
Researchers studied glycerol monooleate (GMO)/tricaprylin (TAG)/water mixtures, finding a low-viscosity hexagonal II (HII) phase forms above 35°C. This fluid HII phase maintains hexagonal symmetry due to reduced domain size and cylinder length.
Area of Science:
- Physical Chemistry
- Materials Science
- Biophysics
Background:
- Glycerol monooleate (GMO) and tricaprylin (TAG) mixtures with water can form various liquid crystalline phases.
- The reverse hexagonal (HII) phase, characterized by water channels within lipid cylinders, is of interest for its unique properties.
Purpose of the Study:
- To characterize the microstructures of the Lc and HII phases in a GMO/TAG/water mixture.
- To investigate factors governing the formation of a low-viscosity HII phase at elevated temperatures (>35°C).
Main Methods:
- Differential scanning calorimetry (DSC)
- Wide- and small-angle X-ray scattering (WAXS and SAXS)
- Nuclear Magnetic Resonance (NMR) spectroscopy (self-diffusion and 2H NMR)
- Fourier transform infrared (FTIR) spectroscopy
Main Results:
- The HII phase exhibits rapid water diffusion within the channels of GMO/TAG cylindrical aggregates.
- Two distinct water diffusion peaks indicate mobile and hydration water at the GMO-water interface.
- Above 35°C, the mixture becomes fluid while maintaining hexagonal symmetry, attributed to reduced domain size and cylinder length.
Conclusions:
- The fluidity of the HII phase above 35°C is linked to decreased domain size and potentially shorter cylinder lengths.
- This fluid HII phase displays increased GMO mobility, decreased water mobility, and a dehydration process.
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