| Autor: |
Gruger, Alain, Romain, François, Calvé, Nicole Le |
| Zdroj: |
Molecular Crystals and Liquid Crystals; March 1985, Vol. 116 Issue: 1 p85-109, 25p |
| Abstrakt: |
A study of the infrared and Raman spectroscopic changes occurring in the frequency range 200-1600 cm-1 at the solid-solid or solid-liquid crystal transitions of the homologous series of 4,4'-di-n-alkoxyazoxybenzenes (n - 1 to 1) has enabled us to determine their molecular configurations in the solid phases and the liquid crystal state. In the low temperature solid phase, the alkoxy tails of the n = 2,3, 5,7 compounds have an all-trans configuration whereas those of the n = 4 and 6 compounds show g± or g± tg± defects. Some kind of configurational change appears at the crystal polymorphic transition for n = 3, 4, 5 and at the mesomorphic transition for n = 6 and 7 according to the relative importance of the enthalpic and entropic variations of the crystal-crystal or crystal-liquid crystal transition. As to the n = 1 and 2 compounds, it seems that the perturbations observed are related to a statistical disorder of the azoxy group rather than the two possible orientations of the methoxy or ethoxy groups around the ring-to-oxygen bond. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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