Hexagonal-columnar mesophases of acylated azacrowns with enhanced stabilities

A series of discotic liquid crystals based on completely acylated macrocyclic oligoamines (azacrowns) has been synthesized. Discotic mesophases could be very highly stabilized by making use of an increased steric hindrance, caused by supplemental lateral meta-substituents which were introduced into the cinnamic acids used as the acylation agents. Employing this method yields compounds exhibiting hexagonal mesophases over a very broad range of more than 300°. Even if very large macrocycles are used as the core of such disc-shaped compounds, enantiotropic mesophases are achieved. Themeta-substituents as well as the size of the azacrowns were varied and their influence on the mesomorphic behav…

Self-organization of substituted azacrowns based on their discoid and amphiphilic nature

Abstract Cyclame and hexacyclene derivatives, bearing four and six long-chain substituents respectively, were synthesized. They are discussed as monolayer-forming amphiphiles as well as liquid-crystalline-phase-forming thermotropic mesogens. The compounds investigated form ordered monolayers at the gas/water interface. In the monolayer the hydrophilic cyclic head group lies flat on the water surface, whereas the hydrophobic substituents are oriented perpendicularly with respect to the interface. Most derivatives fitted with aromatic substituents exhibit a solid condensed state exclusively. In contrast with this, solid condensed as well as expanded phases can be found when spreading the alip…

Ellipsometric and fluorescence microscopic investigations of a cyclam derivative at the air/water interface

Optical measurements of an acylated azacrown at the air-water interface

In this study, a cyclame derivative bearing four aliphatic chain substituents shows, like many amphiphiles, solid-condensed as well as liquid-expanded phases. In contrast to the classical amphiphiles, the onset of its phase transition is characterized by a bump-like shape whose amplitude is a function of the compression speed. Ellipsometry which is very sensitive to the monolayer physical state changes, and fluorescence microscopy which has contributed significantly to the understanding of the phenomena occurring in the phase transition region have been used to investigate the monolayer behavior of this compound. This study shows that in the liquid-expanded state, the film is homogeneous an…