Non-amphiphilic mesogen

Formation of the Vi and V2 Mesophases and of the Non-Amphiphilic Cubic Mesophase "Smectic D . In Figures 1 and 5, the formation of the amphiphilic cubic mesophases Vi and V2 is attributed to transitional globular micellar forms which arise intermediate between the indefinitely extended fibrous (M) and lamellar (G) forms which constitute the middle and neat mesophases, respectively. With a few non-amphiphilic mesogens (19, 20, 21, 22) a cubic mesophase "smectic D is found intermediate in the thermal succession of mesophases between smectic A... 

Beside this, in the recent past some investigations on amphotropic materials of non-amphiphilic structure were made as well (see Further Molecular Architectures in this Chapter). Additionally, it is somewhat difficult to draw a sharp separation line between amphiphilic and nonamphiphilic compounds the ability to act as an amphiphile depends mainly on the size and the polarity of the hydrophilic and hydrophobic parts of a molecule. This internal equilibrium can be varied in a broad range. Thus, in this chapter, although mainly directed toward meso-gens of the amphiphilic type, some apolar mesogens will be discussed as well. 

Extensive recent studies has established that liquid crystallinity is not only induced by the presence of mesogenic groups (7). but also induced in certain molecules by the existence of distinct polar and non-polar moieties which segregate forming lamellar structures. These amphiphilic molecules (1.7-1S). both ionic and non-ionic, exhibit liquid crystalline phases in the melt, and form aggregates in solution which generate molecular organizates (19). 

For non-ionic polysoaps the situation is quite different. Whereas in the case of oligoethyleneoxide head groups thermotropic mesophases seem to be absent [87, 121-124, 126, 231, 403, 409], polysoaps with liposaccharide [230,240, 300] surfactant fragments or with lipopeptide [244, 400-402] ones frequently show lamellar mesophases (e.g. of smectic A type) and even nematic ones (Fig. 39). It should be emphasized that the thermotropic mesophases here are not the result of mesogenic groups being present, but are the consequence of the amphiphilic character of the polysoaps and the resulting microphase separation. 

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