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Proceedings Paper

Dimerization in trans-4-butyl-cyclohexane carboxylic acid and in its mixture with 12% cis-isomer observed via 1H- and 2H-NMR
Author(s): Sofia I. Torgova; D. Abramic; Alfredo Strigazzi; Slobodan Zumer
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Paper Abstract

In this paper we report the investigation, performed via proton- and deuteron-NMR on samples of trans-4-butyl- cyclohexane carboxylic acid (C4), and via proton-NMR on samples of a cis-trans mixture of the same substance, containing 12 percent cis-isomer (C4.12). The aim of the research was to study the dimerization process at different temperatures via NMR technique. As it is known, only the presence of a conveniently large proportion of closed dimers of trans-isomer allows the nematic mesophase to be established. The results obtained with proton-NMR on C4, approaching on cooling the clearing point, revealed, as expected, the increasing of the amount of closed dimers. Just below the clearing point, in a range of a couple degrees only, the presence of open dimers was detected. On the contrary, down into the nematic phase, only closed dimers turned out to be present. The results obtained via deuteron-NMR on C4, deuterated in the hydroxy position, are consistent with the proton-NMR data. Moreover, the deuteration was found to strongly influence the bonding energy, thus forcing the nematic phase to appear at definitely lower temperature. Furthermore, proton-NMR investigation of C4.12 samples showed a clearing interval instead of a clearing point. These results suggest a phase separation, which is in agreement with our microscopy observations. The presence of open dimers in a small temperature range, just below the clearing interval, is also confirmed. But we didn't succeed to obtain any information about mixed dimers.

Paper Details

Date Published: 1 January 1998
PDF: 7 pages
Proc. SPIE 3319, Liquid Crystals: Chemistry and Structure, (1 January 1998); doi: 10.1117/12.301319
Show Author Affiliations
Sofia I. Torgova, Organic Intermediates and Dyes Institute (Russia)
D. Abramic, Univ. of Ljubljana (Slovenia)
Alfredo Strigazzi, Politecnico di Torino and INFM (Italy)
Slobodan Zumer, Univ. of Ljubljana (Slovenia)

Published in SPIE Proceedings Vol. 3319:
Liquid Crystals: Chemistry and Structure
Marzena Tykarska; Roman S. Dabrowski; Jerzy Zielinski, Editor(s)

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