Rudolf Eidenschink

Physical properties of nematic phenylcyclohexanes, a new class of low melting liquid crystals with positive dielectric anisotropy

Abstract Those isotropic and anisotropic molecular properties of p-disubstituted phenylcyclohexane which govern the electrooptical behaviour of these molecules are described and compared to the properties of known liquid crystals.

Low Viscous Compounds of Highly Nematic Character

Abstract Mixtures of broad nematic temperature ranges that permit acceptably short switching times of electro-optical displays at −40°C can be composed of compounds of relatively low polarity and high transition temperatures from the nematic to the isotropic state (T NI. Structures combining 1,4-phenylene and trans-1,4-cyclohexylene rings are particularly suited for this purpose.

New Developments in Liquid Crystal Materials

Abstract A summary of some new developments in liquid crystal compounds which are of practical interest and at the same time contribute towards understanding the connection between chemical structure and the occurrence of liquid crystal phases is given. Of major importance are combinations of saturated and aromatic ring systems, as well as the effects of substitution in these systems on the transition point from the nematic to the isotropic phase and on other physical properties required for practical use in liquid crystal displays.

Low‐(Delta)n‐twisted nematic cell with improved optical properties

It is demonstrated by model calculations and experimental results, that the range of viewing angles of a twisted nematic (TN) display can be considerably improved by using a liquid‐crystal material with a low refractive index anisotropy Dn<0.1.

Nematic liquid crystals with positive dielectric and negative diamagnetic anisotropy

Abstract p -Alkyl- p ′-cyanocyclohexylcyclohexanes CCH represent a new class of thermotropic nematic liquid crystals which no longer exhibit UV absorption abobe 200 nm, are distinguised by an optical anisotropy of less than 0.1, and in contrast to all previously known “dielectric positive”, thermotropic nematic liquid crystals possess a negative diamagnetic anisotropy.

The Crystal and Molecular Structures of Four Homologous, Mesogenic trans,trans- 4,4'-dial kyl-( 1 OC, 1 '-bicyclohexyl)-4P- carbon i t ri I (CCN 's)

Abstract The crystal and molecular structures of four homologous (R′(CN)-C6H9-C6H10-R, CCNs) were determined using single crystal x-ray diffraction data. In all four structures the cyano groups occupy axial positions whereas the alkyl groups occupy equatorial ones. The cyclohexane rings are approximately perpendicular to each other in CCN33 (R˭R′˭C 3 H7), in CCN35 (R˭C 3 H7, R′˭C 5 H11) and in CCN38 (R˭C 3 H7, R′˭C 8 H17) leading to a room filling of the free space produced by the cyano groups. More than that, the hydrogen-hydrogen contacts between the cyclohexane rings are minimal in such an arrangement. However, in CCN46 (R˭C 4 H9, R′˭C 6 H13) the molecules contain nearly coplanar bicyclohexyl moieties. These and some other structural features are discussed with regard to the question of the extent to which the crystalline state can be interpreted as a precursor of liquid crystalline states.

1,3‐Anionische Cycloadditionen, XV. Reaktionen von trans,trans‐1,3‐Diphenyl‐2‐azaallyllithium mit Heterokumulenen

trans,trans-1,3-Diphenyl-2-azaallyllithium (1) cycloaddiert sich regiospezifisch an die CN-Doppel-bindung des Phenylisocyanats sowie Phenyl- und Methylisothiocyanats unter Bildung eines Imidazolidin-4-ons (2a) bzw. -4-thions (2b, c). Bei entsprechenden Umsetzungen mit den symmetrischen Heterokumulenen Schwefelkohlenstoff und Dicyclohexylcarbodiimid folgt der Cycloaddition jeweils eine schnelle Sekundarreaktion (4, 7). 1,3-Anionic Cycloadditions, XV. Reactions of trans,trans-1,3-Diphenyl-2-azaallyllithium with Heterocumulenes trans,trans-1,3-Diphenyl-2-azaallyllithium (1) reacts with phenylisocyanate, phenylisothiocyanate, and methylisothiocyanate to give an imidazolidine-4-one (2a) or imidazolidine-4-thione (2b, c), respectively. When reacting with carbon disulfide or dicyclohexylcarbodiimide (symmetrical heterocumulenes) the cycloaddition is followed by a fast secondary reaction ( 4, 7).

Unusual lift by shearing mesogenic fluids

Abstract The compounds hexakis- and pentakis[octylthio]benzene showing discotic phases below room temperature were sheared in an oscillation mode under load between a cylinder and a disk of chromium steel at temperatures between 60 and 120[ddot]C. Surprisingly, after some initial wear friction coefficients f decreased to values between 0.005 and 0.001. Under these conditions known lubrication oils cause boundary friction with values some 100 times higher. The nonmesogenic compounds hexakis[2-ethylhexylthio]benzene and hexakis[2-octylthio]benzene behave like known oils. Possible reasons for this promising behaviour of the mesogenic compounds are discussed.

The Liquid Crystal Properties of 1 -(4-Cyanophenyl)–trans-4-n-dodecylcyclohexane (PCH-12)

Abstract 1-(4-Cyanophenyl)-trans-4-n-dodecylcyclohexane, a long chain member of the PCH series of liquid crystal materials has been prepared and its phase behavior established by optical microscopy and DSC. In comparison with the purely smectic (SA) biphenyl analogue (K36), PCH-12 maintains an enantiotropic nematic phase range of about 9°C above its monotropic smectic A phase, allowing a clearer comparison to be made between the smectic tendencies of the PCH and the K series.

Principle of Maximum Flow Energy, a Useful Working Hypothesis to Approach Ordering Phenomena in Fluids

The hypothesis that the variation of energy with time and volume for real and/or imaginary exchange processes leads to a maximum is applied to various phenomena found with fluids, especially with liquid crystals. Reference is made to some qualitative regularities in the correlation of chemical structure and the thermodynamic stability of the thermotropic nematic phase, the enthalpy of the phase transition between fluid phases, the heuristically important finding of an exothermic transition from the nematic to the isotropic phase, a very distinct deuterium isotopic effect on the optical nonlinearity of a dye-doped nematic phase, and the additional hydrodynamic lifting force observed in technical slide bearings lubricated with isotropic oils containing mesogenic compounds. The relation of the suggested variation to the universally valid principle of least action and its applicability to irreversible processes are discussed.