Organized media liquid crystals

From the above examples it is clear that reaction cavity provided by an organized or confining medium has unique features that mimics some of the features of proteins. While crystals and zeolites provide reaction cavities that are inflexible, there is a whole spectrum of organized and confined media (e.g., micelles, host-guest complexes, monolayers and bilayers, liquid crystals etc.,) that allow different degrees of freedom to the reactant molecules. These systems demonstrate clever usage of favorable entropy that is so important in natural systems. One should keep in mind... 

The ability of the amphiphilic molecules to maintain their organization and orientation in aqueous medium at a distinct region of temperatures leads to characteristic features of liquid crystal structures. In this mesogenic state, the molecules keep their order and point to a common direction, not as strictly as in the solid state, nor are they able to move as freely as in liquid state. In most liquid crystal structures more than one state is observed in the range of temperatures that the liquid crystal is present. These states are called mesophases and the phenomenon is called polymorphism . 

This chapter is mainly devoted to organic compounds for which the observed reversible color changes (coloring and fading reactions) are due to the effect of temperature, exclusively. The thermochromic behavior of inorganics, organo-metallics, macromolecular systems (such as polythiophenes), or supramolecular systems (such as liquid crystals) and of molecular systems for which the observed thermochromism is due to external intervention (association with another species like a metal ion or a proton) or to modification of the medium by a thermal effect (thermosolvatochromism, for instance) are not reviewed in this chapter. 

Structured liquids are opaque and usually possess a moderate viscosity. These products are formed when surfactant molecules arrange themselves as liquid crystals [7-9], This form of liquid detergent is largely marketed in Europe and the Asia/Pacific region. Unstructured liquids, on the other hand, are usually thin, clear or translucent, and are formed when all ingredients are solubilized in an aqueous media. Nonaqueous liquids, where the continuous medium consists of an organic solvent, can be either structured or unstructured. 

With time and improved synthetic protocols, larger templates (fuUerenes, dendrimers, nanoparticles, colloids, micelles, lipid bilayers, self-assembled block copolymers, oligonucleotides, DNA and proteins) have been imprinted [14] and the choice of matrices has expanded to liquid crystal polysiloxanes, carbon networks, zeolites, layered aluminophosphates and colloidal crystals, though organic polymer networks remain the dominant imprint casting medium [14]. 

In determining the disjoining pressure of organic liquids, the temperature of the medium is selected so as to eliminate the possibility of liquid crystallization. Therefore, the disjoining pressures reported in [181] for liquids between steel disks were determined at ambient temperatures such that the liquids would not crystallize. The variation of disjoining pressure with thickness of the liquid layer (measurements performed at different temperatures, specific for each liquid) is illustrated by the following data ... 

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