New patterns of twist-bend liquid crystal phase behaviour: the synthesis and characterisation of the 1-(4-cyanobiphenyl-4'-yl)-10-(4-alkylaniline-benzylidene-4'-oxy)decanes (CB10O·<i>m</i>).
basic_science · Level V
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- Record sourced from PubMed, PMID 35678154.
- Also identified by DOI 10.1039/d2sm00162d.
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Abstract
The synthesis and characterisation of the 1-(4-cyanobiphenyl-4'-yl)-10-(4-alkylanilinebenzylidene-4'-oxy)decanes (CB10O·<i>m</i>) are reported. This series shows a rich liquid crystal polymorphism including twist-bend nematic and smectic phases. All the homologues reported exhibit an enantiotropic conventional nematic phase. For the homologues with <i>m</i> ≤ 10, the local packing in the nematic phases and the layer spacing in the smectic phases indicates an intercalated arrangement of the molecules. An intercalated smectic C<sub>A</sub> phase is observed if <i>m</i>/11 ≈ 0.5. Either side of this condition, the twist-bend nematic phase is observed, a novel pattern of behaviour for a series on increasing a terminal chain length. For longer chain lengths, <i>m</i> = 12, 14, 16 and 18, two twist-bend smectic C (SmC<sub>TB</sub>) phases are observed, and the packing of the molecules is now of a bilayer-type. The higher temperature variant is termed SmC<sub>TB-SH</sub> in which SH (single helix) refers to the presence of a short, distorted clock-type helix. In the lower temperature SmC<sub>TB-DH</sub> phase, an additional longer helix is superimposed on the short one, and DH denotes double helix.