Lyotropic nomenclature

Another problem that exists in notation is the relationship between thermotropic and lyotropic nomenclature. In some cases continuous behavior has been seen between thermotropic and lyotropic mesophases suggesting that they should share the same notation however, at this point in time this has not occurred. 

In their paper the authors follow the nomenclature by Luzzati and indicate the observed me-sophases L or Lp , respectively. Here, however, to separate between lyotropic and thermotropic mesophases the indication was changed into SmA and SmC, respectively. 

The traditional definition of emulsions (1) as consisting of two liquids, of which one is dispersed in the other in the form of macroscopic droplets, was modified by the lUPAC Commission for Nomenclature (2) to include lyotropic liquid crystals. This change was justified by the fact that a large number of commercial emulsions within the areas of foods, pharmaceutics, and personal care contain such structures. Commercial emulsions frequently also contain solid particles, but such systems are usually not called emulsions, but rather emulsions-suspensions to avoid having the term emulsions covering the majority of dispersed systems. 

In general, there are three main types of liquid crystalline phases. All of them appear in thermotropic as well as in lyotropic liquid crystals in one or another variation. Unfortunately, due to historical reasons, the nomenclature of thermotropics [7, 8] and lyotropics [9, 10] is not uniform, making it sometimes complicated to identify analog phases. For the sake of clarity, the notation of thermotropics is sometimes adopted for lyotropics within this thesis. 

The International Union of Pure and Applied Chemistry (lUPAC) recommended in 2001 [10], that every Uquid crystalline phase composed of chiral molecules should be denoted with a superscript asterisk. However, this is not customary in lyotropic liquid crystal nomenclature, except for the chiral nematic phase (N ). Thus, for all other conventional lyotropic liquid crystalline phases the asterisk will be omitted. Whenever the chirality of the molecules seems to be especially important, the according phase will be denoted as chiral . 

In conclusion, this work shows that a lamellar, lilted, fluid phase exists in lyotropic liquid crystals and that it exhibits characteristic chirality effects, namely helicity and spontaneous electrical polarization, known Irom the thermotropic ferroelectric SmC phase. These results contribute significantly to a better understanding of lyotropic liquid crystals and bridge a substantial gap between the two fields of liquid crystal research. In accordance with the established nomenclature of lyotropic and thermotropic liquid crystals, the novel phase is suggested to be denoted as the lamellar L, phase, where the index a denotes a tilted fluid phase and the superscript indicates that molecules are chiral. 

The crystalline phases consist of stacked bilayers of alcohol molecules, which are either in a tilted (y) or perpendicular orientation (a and P) with respect to the plane of the bilayers. A similar stacking of bilayers is found in lamellar liquid crystals but in this case the structure is swollen in a one-dimensional fashion by water and/or oil. Depending on whether the surfactant and cosurfactant chains are in a conformationally disordered molten or an extended rigid state, the lyotropic liquid crystalline phase is called L or phase, respectively. The phase is also known as gel phase. This nomenclature is also used for lipids. Concerning the sur-factant/fatty alcohol/water systans considered here, it must be pointed out that the swelling of a crystals with water results in an Lp phase. 

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