Liquid Crystalline 1,3,4‐Thiadiazoles. I. Biphenyl‐ and Terphenyl Analogous 1,3,4‐Thiadiazoles
The synthesis of disubstituted 1,3,4‐ and 1,2,4‐thiadiazoles and 1,3,4‐oxadiazoles is described and their melting and clearing points are investigated. The influence of the heterocyclic ring system on the formation of crystalline liquid phases is discussed.
Systematic investigations have allowed us to formulate a structural model representing the relationship between vitrification and mesogenity in low-molecular-weight liquid-crystalline compounds. The tendency to transform the highly viscous mesophases into glass phases is caused mainly by the bulkiness of the molecules. The freezing of such mesophases, oriented by external influences at high temperatures, can be used for information storage.
The cholesteric twist inversion by temperature variation of a single component thennotropic liquid crystalline system was experimentally investigated and is explained by the partial twistmg power model, evaluating the temperature dependent pilch of five different configurations of a benzoic acid biphenyl ester with two chiral centers. The temperature dependence of the twisting power and the cholesteric pitch for several stereoisomeric compounds can In first appro;timation be predicted by the partial twisting powers of the individual chiral centers determined from the panially racemic configurations.
Liquid‐crystalline Heterocycloalkanes. I. Synthesis and Properties of Substituted 1,3‐Dioxanes
The synthesis of 2,5‐disubstituted 1,3‐dioxanes is described, their melting and clearing points and their physical properties (dielectric anisotropy, viscosity, transition enthalpies, optical birefringence) are investigated. The cyano substituted 1,3‐dioxans 5 and 7 are valuable materials for application in displays.
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