Twist-Bend Nematogenic Supramolecular Dimers and Trimers Formed by Hydrogen Bonding

Rebecca Walker* (Corresponding Author), Damian Pociecha, Alfonso Martinez-Felipe, John MD Storey, Ewa Gorecka, Corrie T Imrie

*Corresponding author for this work

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Abstract

A selection of novel non-symmetric supramolecular liquid crystal dimers and trimers formed by hydrogen-bonding have been prepared and their phase behaviour characterised by polarised optical microscopy, X-ray diffraction and temperature-dependent Fourier-transform infrared spectroscopy. We mix the bent twist-bend nematogen 4-[6-(4’-cyanobiphenyl-4-yl) hexyloxy]-benzoic acid (CB6OBA) with a series of small stilbazole-based compounds 4-[(E)-2-(n-alkoxyphenyl)ethenyl]pyridines (nOS) of varying terminal chain length (n) to obtain the CB6OBA:nOS complexes. Complexes with n ≤ 7 exhibit nematic and twist-bend nematic behaviour, followed on cooling by a smectic C phase for n = 4–7, and finally, a hexatic-type smectic X phase for n = 3–7. Mixtures with n = 8–10 exhibit a smectic A phase below the conventional nematic phase, and on further cooling, a biaxial smectic Ab phase and the same hexatic-type SmX phase. Supramolecular trimers, CB6OBA:CB6OS and CB6OBA:1OB6OS, formed between CB6OBA and dimeric stilbazoles [(E)-2-(4-[6-(4’-methoxy[1,1’-biphenyl]-4-yl)hexyl]oxyphenyl)ethenyl]pyridine (1OB6OS) or 4-[(E)-4’-(6-4-[(E)-2-(pyridin-4-yl)ethenyl]phenoxyhexyl)[1,1’-biphenyl]-4- carbonitrile (CB6OS), exhibit nematic and twist-bend nematic phases, and are the first hydrogen-bonded trimers consisting of unlike donor and acceptor fragments to do so.
Original languageEnglish
Article number175
Number of pages16
JournalCrystals
Volume10
Issue number3
Early online date6 Mar 2020
DOIs
Publication statusPublished - Mar 2020

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Keywords

  • liquid crystals
  • twist-bend nematic phase
  • hydrogen-bonding
  • supramolecular dimers
  • supramolecular trimers
  • spontaneous symmetry breaking
  • ACIDS
  • BEHAVIOR
  • OLIGOMERS
  • PHASE
  • supramolecular liquid crystals
  • LIQUID-CRYSTAL DIMERS
  • INSIGHTS

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