Molecular curvature, specific intermolecular interactions and the twist-bend nematic phase: the synthesis and characterisation of the 1-(4-cyanobiphenyl-4-yl)-6-(4-alkylanilinebenzylidene-4-oxy)hexanes (CB6O.m)

Rebecca Walker, Damian Pociecha, Grant J Strachan, John M D Storey, Ewa Gorecka, Corrie T Imrie (Corresponding Author)

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Abstract

The syntheses and characterisation of the first ten homologues of the 1-(4-cyanobiphenyl-4-yl)-6-(4-alkylanilinebenzylidene-4-oxy)hexanes (CB6O.m) are reported. All ten members of the series exhibit an enantiotropic nematic, N, phase, and a monotropic twist-bend nematic, N-TB, phase. Only CB6O.10 shows a smectic phase. The assignment of both nematic phases was confirmed using X-ray diffraction. For short chain lengths (m = 1-6) the local packing in both nematic phases is an intercalated arrangement, for intermediate chain lengths a frustrated local structure is seen and for the longest chain length, a bilayer arrangement is observed. This change in the local structure on increasing m has no apparent effect on the stability of either nematic phase, and TNTBN and T-NI show a regular dependence on m. Specifically, TNTBN and T-NI decrease on increasing m and superimposed upon this is a weak odd-even effect in which the odd members show the higher values. T-NI decreases more rapidly than TNTBN on increasing m such that the ratio TNTBN/T-NI increases. The lower temperature liquid crystal phase shown by 1-(4-cyanobiphenyl-4-yloxy)-5-(4-butylanilinebenzylidene-4-oxy)pentane (CBO5O.4) is reassigned as a twist-bend nematic phase. The transitional properties of the CB6O.m, CB6O.Om and CBO5O.m series are compared.

Original languageEnglish
Pages (from-to)3188-3197
Number of pages10
JournalSoft matter
Volume15
Early online date11 Mar 2019
DOIs
Publication statusPublished - 21 Apr 2019

Keywords

  • LIQUID-CRYSTAL DIMERS
  • TRANSITIONAL PROPERTIES
  • MESOMORPHIC BEHAVIOR
  • MESOPHASE
  • OLIGOMERS
  • DEPENDENCE
  • COMPOUND
  • MIXTURES
  • GEOMETRY
  • TRIMERS

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