New insights into the liquid crystal behaviour of hydrogen-bonded mixtures provided by temperature-dependent FTIR spectroscopy

D.A. Paterson, A. Martínez-Felipe, S.M. Jansze, A.T.M. Marcelis, J.M.D. Storey, C.T. Imrie

Research output: Contribution to journalArticleAcademicpeer-review

65 Citations (Scopus)

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 languageEnglish
Pages (from-to)928-939
JournalLiquid Crystals
Volume42
Issue number5-6
DOIs
Publication statusPublished - 2015

Keywords

  • low molar-mass
  • side-chain
  • carboxylic-acids
  • benzoic-acid
  • amorphous polymers
  • pyridyl moieties
  • ir-spectra
  • dimers
  • phase
  • complexes

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