Design of New Mesogenic Block Molecules: Formation of Columnar Mesophases by Calamitic Bolaamphiphiles with Lateral Lipophilic Substituents

Rigid bolaamphiphiles with lateral alkyl chains such as 1 form columnar mesophases of a novel type based on microsegregation of the three incompatible parts of the molecules (shown schematically).     

Combination of Chiral and Achiral Triphenylene Units in a Novel Unsymmetrical Columnar Twin

The synthesis, characterization, and mesomorphic properties of a new type of liquid‐crystalline twin bearing a pentadecyloxytriphenylene subunit tethered via a decyl spacer to a chiral pentakis(3,7‐dimethyloctyloxy)triphenylene are reported. The target compound displays a hexagonal columnar mesophase, which is metastable at room temperature.     

Induced SA phases and reentrant nematic phases in binary systems of homologous terminal-nonpolar compounds

The isobaric phase diagrams of binary systems are presented in which one component is represented by members of the homologous series of swallow tailed compounds. The occurrence of induced S_A phases and reentrant nematic phases was studied in dependence on the length of the alkyl chain of the swallow tailed compound. In some selected binary systems X-ray investigations and calorimetric measurements were performed. An attempt has been made to interprete the results by a simple packing model.     

Studies on Induced Smectic Phases (II) Transition Enthalpies,X-ray Patterns and Layer Spacings of Orthogonal Phases of Binary Mixtures of Nematogens with Contrasting Dielectric Anisotropies

Binary mixtures of two nematogens, 4,4′-di-n-heptyl-azobenzene with 4-n-pentyl-4′ -cyano biphenyl were studied by optical, calorimetric and X-ray measurements. At a given concentration induced phases with a sequence S_A, S_B, S_E were detected, the properties of which were discussed.     

Thermotropic Liquid Crystalline Compounds with Lateral Long Chain Substituents (VII). X-Ray Studies in 1,4-Bis-(4-n-oetyloxybenzyoloxy)-2-n-alkylbenzenes

X-ray studies in substances with the general formula in the nematic states were performed. The results prove the existence of cybotactic groups despite the fact that the branched substances do not show smectogenic properties. We propose a model for the packing of the molecules, which explains the influence of the lengths of the lateral branches on the structure of the cybotactic groups.     

Thermotropic liquid crystalline compounds with lateral long-chain substituents (IV). Physical properties of 1,4-bis-[4-n-octyloxybenzoyloxy]-2-n-alkylbenzenes

In 15 Substances of general formula transition temperatures, transition enthalpies and entropies, densities and phase transition volumina, order parameters of a dissolved dye and optical refractive indices were measured. Additional miscibility and X-ray investigations were performed. The results are discussed on the basis of molecular statistical theories of the nematic state and point to a conformation of the long lateral chains which is nearly parallel to the molecular long axes. The results further show the dominating importance of the steric repulsive forces in stabilizing the nematic state.