Abstract
The phase behaviour of equimolar mixtures of 6-(4'-cyanobiphenyl-4-yl)hexyloxybenzoic acid (CB6OBA) with either 1-(4-butylazobenzene-4'-oxy)-5-(4-oxypyridine)pentane (BuABO5OPyr) or 1-(4-butylazobenzene-4'-oxy)-6-(4-oxypyridine)hexane (BuABO6OPyr) is reported. CB6OBA shows a monotropic twist-bend nematic phase and an enantiotropic nematic phase whereas the two pyridyl-based components do not exhibit liquid crystallinity. Both equimolar mixtures (CB6OBA/BuABOnOPyr) show enantiotropic nematic phases. The nematic-isotropic transition temperature and associated entropy change are higher for the CB6OBA/BuABO6OPyr mixture than for the CB6OBA/BuABO5OPyr mixture. This may be accounted for in terms of the average shapes of the hydrogen-bonded 1:1 complexes formed between the two differing components in the mixtures. However, Fourier transform infrared spectroscopy reveals that this complex is not formed quantitatively, but instead a complex mixture exists over the complete temperature range studied, involving the 1:1 complex, both cyclic and open acid dimers, free acid and hence, free BuABOnOPyr molecules.
Original language | English |
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Pages (from-to) | 928-939 |
Number of pages | 12 |
Journal | Liquid Crystals |
Volume | 42 |
Issue number | 5-6 |
Early online date | 25 Jun 2015 |
DOIs | |
Publication status | Published - 2015 |
Bibliographical note
Disclosure statementNo potential conflict of interest was reported by the authors.
Keywords
- liquid crystal dimers
- variable temperature FTIR
- hydrogen bonding
- twist-bend nematic
- low molar-mass
- side-chain
- carboxylic-acids
- benzoic acids
- amorphous polymers
- pyridyl moieties
- IR-spectra
- dimers
- phase
- complexes