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Introduction and General Theory of Lyotropic Liquid Crystals

1992; Springer Nature; Linguagem: Inglês

10.1007/978-1-4684-9151-7_26

0258-1221

D. Roux,

Molecular spectroscopy and chirality

Amphilic molecules incorporate two antagonistic chemical functions. One part of the molecule is very soluble in water (hydrophilic) and another part is very soluble in an organic solvent (hydrophobic). Due to these opposite effects the molecules in solution aggregate spontaneously into objects of very different size and shape, among which one principally observes spheres, cylinders and twodimensional objects (membranes). Many of the phases observed in a typical phase diagram are liquid crystals. For example, the lamellar phase, which consists of a stack of membranes with a long range order in the direction perpendicular to the plane, is a smectic A phase. At first these phases appeared relatively uninteresting, but now they have been extensively studied and they exhibit extremely interesting and peculiar behavior. In certain cases, close to a transition toward nematic or hexagonal phases, the lamellar phase cannot be described as a stack of flat membranes but exhibits many defects that can be observed experimentally.In principle, the lyotropic nature of the phase allows the repeating distance d between the membranes to vary. In many systems this variation remains small (typically ranging from 30 to 60 Å), however in certain cases it is possible to prepare lamellar phases with extremely large repeating distances (up to several 1000 Å). These systems are especially interesting because, as we will see, they permit us to study the interactions between membranes over a wide range of conditions. They are also a unique example of a colloidal smectic A phase.