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). Issue 15 (20th March 2019)

• Record Type: Journal Article
• Authors: Walker, Rebecca; Pociecha, Damian; Strachan, Grant J.; Storey, John M. D.; Gorecka, Ewa; Imrie, Corrie T.
• Is Part Of: Soft matter. Volume 15:Issue 15(2019)
• Page Start: 3188
• Page End: 3197
• Publication Date: 2019-03-20
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c9sm00026g
• Languages: English
• ISSNs: 1744-683X

Abstract

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. 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, NTB, 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 T NTB N and T NI show a regular dependence on m . Specifically, T NTB N 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 T NTB N on increasing m such that the ratio T NTB N / 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.O m and CBO5O. m series are compared.