Mesogenic Properties of Amphiphilic Liquid Crystals with an Unusual Head-Group Topology

摘要

Liquid crystalline phases may be displayed by unisotropic as well as by amphiphilic molecules. Anisotropic (calarr.itic or dis-cotie) molecules are arranged with their long axes parallel to each other to give thermotropic smectic or columnar liquid-crystalline phases. In contrast, the driving force ot the self-organization ot" amphiphilic molecules is their ability to segregate incompatible (for example, hydrophihc and hydrophobia parts of the individual molecules. This gives rise to large aggregateswhich form the basis of lamellar, columnar, or cubic thermotropic and lyotropic mcsophases. A combination of these two structural principles can provide new liquid-crystalline materials, consisting of rigid units connected with one, two. or even more hydrophihc groups at the termini of their alkyl chains. The segregation of the different parts of the molecules is facilitated by the parallel arrangement of the rigid cores and visa versa. In amphiphilic poiyhydroxy compounds this gives rise to significant mesophase stabilization. The question arose: What happens if a hydrophilic group is not terminally (Fig. 1, A), but laterally (C) attached to a rigid core? The two different organizing forces of liquid-crystalline phases would be perpendicularly directed to each other in these compounds, and the parallel arrangement of the calamitic units would disturb the segregation of hydrophilic and hydrophobic parts of the molecules and visa versa. We have therefore synthesized novel amphiphilic compounds with hvdrophilic groups laterally attached to a rigid 4.4"-didecyloxy-p-terphenyl core.