Abstract
Polar lipids and certain surfactants are known to form thermodynamically stable lyotropic liquid crystals (LLC) when mixed with water. The major phases are lamellar (Lα), normal and reverse hexagonal (HI and HII) and cubic bicontinuous and discontinuous structures (VI, VII and II, III, respectively). Theoretically, the transformation sequence of the phases with increasing water content is III→HII→VII→Lα→VI→HI→II. Lyotropic liquid crystal transformation has been extensively studied and was found to take place also upon surfactant modifications (head or tail), addition of a guest molecule (hydrophilic or hydrophobic), co-surfactant or electrolyte and varying the temperature. The phases are of growing scientific and industrial interest because of their structural resemblance to human membranes through which drug passage of lipophilic compounds (vitamins, fats, oil and cholesterol) occurs and because of their high surface area and solubilization capacities. The variations in the phase formations, the phase behavior and phase transitions are of significant importance when designing a potential application for these systems. This chapter presents studies related to phase behavior and phase transitions as a function of different physical and chemical conditions. The relationship between surfactant geometry that includes tail volume, tail length and area per head group and the corresponding phase formation is stressed. Research demonstrating dependence of the phase behavior on the addition of a third component such as hydrophobic, hydrophilic guest molecule or co-surfactant is summarized. A brief overview of the instruments used in the above is also presented, illustrating their functionality in detecting the phase transitions and the unique information potentially extracted from each instrument. The main findings show successful control of lyotropic liquid crystal structure by altering the surfactant geometry in various respects: unsaturation site or degree, head or tail chain length and by an additional component such as linear or branched oils or alcohols.
Original language | English |
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Title of host publication | Colloid Stability Part II |
Publisher | Wiley-Blackwell |
Pages | 203-245 |
Number of pages | 43 |
Volume | 2 |
ISBN (Electronic) | 9783527631193 |
ISBN (Print) | 9783527314614 |
DOIs | |
State | Published - 9 Aug 2010 |
Bibliographical note
Publisher Copyright:© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. All rights reserved.
Keywords
- Liquid crystal mesophases
- Lyotropic liquid crystals
- Mesophase transformations
- Microstructure identification techniques
- Structural transformation
- Transformation identification techniques