Liquid Crystalline Phases and Composition/Temperature
The simplest liquid crystalline phase that is formed by spherical micelles is the 'micellar cubic', denoted by the symbol I1. This is a highly viscous, optically isotropic phase in which the micelles are arranges on a cubic lattice. At higher amphiphile concentrations the micelles fuse to form cylindrical aggregates of indefinite length, and these cylinders are arranged on a long-ranged hexagonal lattice. This lyotropic liquid crystalline phase is known as the 'hexagonal phase', or more specifically the 'normal topology' hexagonal phase and is generally denoted by the symbol HI. At higher concentrations of amphiphile the 'lamellar phase' is formed. This phase is denoted by the symbol Lα. This phase consists of amphiphilic molecules arranged in bilayer sheers separated by layers of water. Each bilayer is a prototype of the arrangement of lipids in cell membranes. For most amphiphiles that consist of a single hydrocarbon chain, one or more phases having complex architectures are formed at concentrations that are intermediate between those required to form a hexagonal phase and those that lead to the formation of a lamellar phase. Often this intermediate phase is a bicontinuous cubic phase.
| Schematic showing the aggregation of amphiphiles into micelles and then into lyotropic liquid crystalline phases as a function of amphiphile concentration and of temperature. |
In principle, increasing the amphiphile concentration beyond the point where lamellar phases are formed would lead to the formation of the inverse topology lyotropic phases, namely the inverse cubic phases, the inverse hexagonal phase (HII) and the inverse micellar cubic phase. In practice inverse topology phases are more readily formed by amphiphiles that have at least two hyrocarbon chains attached to a headgroup. The most abundant phospholipids that are found in cell membranes of mammalian cells are examples of amphiphiles that readily form inverse topology lyotropic phases.
Read more about this topic: Lyotropic Liquid Crystal
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