Günter Lattermann

Liquid Crystalline Primary Benzamides

Abstract Several alkoxybenzamides are synthesized and characterized by spectroscopic and chromatographic methods. 3,4,5-Tris(alkoxy)benzamides have been found to exhibit a mesophase of a columnar or stack-like type.

Hydroxy group containing liquid crystals. I. Synthesis and characterization of cis, cis-(3,5-dihydroxycyclohexyl)-3,4,5-tris(decyloxy)benzoate and derivatives

Abstract The first example of a new class of diol mesogens is described. Cis, cis-(3,5-dihydroxycyclohexyl)-3,4,5-tris(decyloxy)benzoate was synthesized starting from cis, cis-phloroglucitol, which had been protected by phenylboronic acid. Polarizing microscopy and calorimetric measurements provide evidence for a broad mesophase range, including room temperature. The existence of a hexagonal columnar structure is probable. Furthermore several derivatives are described.

A liquid-crystalline cyclam derivative

Abstract The first example of a liquid-crystalline tetraacylated cyclam (1,4,8,11-tetraazacyclotetradecane) derivative is described. Its mesomorphic behaviour, presumably discotic, is characterized by means of polarizing microscopy and D.S.C. measurements.

Octahedral metallo-mesogens of chromium, molybdenum and tungsten with 1,4,7-trisubstituted 1,4,7-triazacyclononane and three carbonyl groups as ligands

Abstract Liquid crystalline complexes with chromium, molybdenum and with tungsten as metallic centres are reported. 1,4,7-Trisubstituted 1,4,7-triazacyclononane and three carbonyl groups are coordinated in an octahedral geometry. The observed mesophases are characterized as disordered rectangular columnar of a pyramidic type.

Hydroxy group containing liquid crystals : columnar and cubic phases in two chain diols

Abstract The thermal behaviour of several cis,cis-(3.5-dihydroxycyclohexyl)- 3.4-bis(alkoxy)benzoates is discussed.

Measuring the deformation of a ferrogel sphere in a homogeneous magnetic field

A sphere of a ferrogel is exposed to a homogeneous magnetic field. In accordance to theoretical predictions, it gets elongated along the field lines. The time dependence of the elastic shear modulus causes the elongation to increase with time, similar to mechanic creep experiments, and the rapid excitation causes the sphere to vibrate. Both phenomena can be well described by a damped harmonic oscillator model. By comparing the elongation along the field to the contraction perpendicular to it, we can calculate Poissons ratio of the gel. The magnitude of the elongation is compared to the theoretical predictions for elastic spheres in homogeneous fields.

First examples of a new class of discogen

Abstract Two examples of a new class of discotic liquid crystals are presented. Their molecular architecture consists of a trisubstituted central core (either a benzene or a cyclohexane ring) and three regional cores, with three decyloxy-chains in the 3,4,5-positions of a particular benzene ring. These regional cores are linked to the central core via ester groups. Polarizing microscopy and calorimetric measurements reveal the existence of monotropic and enantiotropic discotic mesophases respectively. The products exhibit a pronounced hindering of crystallization at room temperature.

Synthesis and thermal behaviour of liquid crystalline pyridinium bromides containing a biphenyl core

A range of new pyridinium bromides was synthesized by the quaternization of different substituted pyridines with a group containing a biphenyl core and alkyl chains of differing lengths. The phase behaviour of the pyridinium bromides was studied by differential scanning calorimetry, polarizing optical microscopy and powder X-ray diffraction. It is shown that pyridinium moieties, linked to a rod-like biphenyl core via an alkyl spacer, can form ionic liquid crystals. Unsubstituted pyridinium groups promote mesomorphism. Liquid crystalline phases are formed only from 2- and 4-ethyl substituted pyridinium groups with sufficiently long alkyl terminal chains and spacers; i.e. decyl chains on both sides of the biphenyl core. Both the substitution pattern at the pyridinium group and the alkyl chain length have an influence on the polymorphism of the smectic phases. 3,5-Dimethyl substitution hinders mesophase formation.

Supermolecular self organization via molecular aggregation. Non-discotic three chain diols displaying a hexagonal columnar phase

Abstract A new class of mesogen formed by three chain diols is described. These compounds consist of a central part to which three aliphatic chains of various length (n = 4–14) are attached at one end and two hydroxy groups at the other. X-ray scattering, dilatometric measurements, dielectric and Kerr relaxation studies were carried out. Both X-ray investigations, dielectric and electro-optic studies revealed that the molecules are aggregated in the isotropic fluid state and that hydrogen bonding and dipole correlation contribute to this aggregation. Columnar assemblies of up to several hundred molecules are orientationally correlated in the isotropic fluid phase. Correlated reorientations occur in the presence of external electric fields. The X-ray data show that the aggregates pack in a hexagonal way at lower temperatures giving a structure which strongly resembles that of the hexagonal disordered columnar phase. This anisotropic phase can be quenched to a glassy liquid-crystalline state. It is evident ...

Liquid crystalline derivatives of oligoethylene-amines and -amino ethers with amide, ester, urea or urethane functions

The mesomorphism of diethylenetriamine and triethylenetetramine derivatives, substituted with the 3,4-bis(decyloxy)benzoyl group (‘two chain’ substituent)via amide, ester, urea or urethane moieties, is described. Furthermore, different examples of related linear and cyclic oligoethyleneamino ethers are investigated and compared with the mesomorphism of the first group. Both lamellar smectic A and hexagonal columnar mesophases can be observed in linear compounds, depending on the length of the linear unit. A cyclic derivative displays a cubic phase. The conclusion is emphasized that the mesomorphism of these classes of compounds is caused by microphase separation.