{{unreferenced, date=April 2017
A micellar cubic phase is a
lyotropic liquid crystal phase formed when the concentration of
micelles
A micelle () or micella () (plural micelles or micellae, respectively) is an aggregate (or supramolecular assembly) of surfactant amphipathic lipid molecules dispersed in a liquid, forming a colloidal suspension (also known as associated colloi ...
dispersed in a solvent (usually water) is sufficiently high that they are forced to pack into a structure having long-ranged positional (translational) order. For example, spherical micelles a subic packing of a body-centred cubic lattice.
Normal topology micellar cubic phases, denoted by the symbol I
1, are the first lyotropic liquid crystalline phases that are formed by
type I amphiphiles
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. The amphiphiles' hydrocarbon tails are contained on the inside of the micelle and hence the polar-apolar interface of the aggregates has a positive
mean curvature In mathematics, the mean curvature H of a surface S is an ''extrinsic'' measure of curvature that comes from differential geometry and that locally describes the curvature of an embedded surface in some ambient space such as Euclidean space.
T ...
, by definition (it curves away from the polar phase).
Inverse topology micellar cubic phases (such as the Fd3m phase) are observed for some
type II amphiphiles
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at very high amphiphile concentrations. These aggregates, in which water is the minority phase, have a polar-apolar interface with a negative
mean curvature In mathematics, the mean curvature H of a surface S is an ''extrinsic'' measure of curvature that comes from differential geometry and that locally describes the curvature of an embedded surface in some ambient space such as Euclidean space.
T ...
. The structures of the normal topology micellar cubic phases that are formed by some types of amphiphiles (e.g. the oligoethyleneoxide monoalkyl ether series of
non-ionic surfactants are the subject of debate. Micellar cubic phases are isotropic phases, but are distinguished from
micellar solutions
A micellar solution consists of a dispersion of micelles in a solvent (most usually water). Micelles consist of aggregated amphiphile
An amphiphile (from the Greek αμφις amphis, both, and φιλíα philia, love, friendship), or amphipat ...
by their very high viscosity. When thin film samples of micellar cubic phases are viewed under a polarising microscope they appear dark and featureless. Small air bubbles trapped in these preparations tend to appear highly distorted and occasionally have faceted surfaces.
Phases of matter
Liquid crystals