New mesogenic 1,3,4-oxadiazole derivatives |
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Authors: | Dalia Girdziunaite Carsten Tschierske Eva Novotna Horst Kresse Annemarie Hetzheim |
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Abstract: | The synthesis of novel liquid-crystalline heteroaromatic compounds incorporating the five membered 1,3,4-oxadiazole ring is described. Due to the bent molecular structure of the oxadiazole ring their mesophase stability is low if the heterocyclic ring occupies a central position, but it is increased if this ring is shifted to a terminal position. Dielectric measurements indicate that the 2-n-alkylthio substitutes 1,3,4-oxadiazole derivatives change the sign of the dielectric anisotropy at the phase transition from the nematic to the smectic A phase. This effect is explained by the increase of the antiparallel correlation of the molecules on formation of the smectic layers. |
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