Influence of terminal substituent on non-linear S-shaped oligomers consisting of azobenzene moieties at the peripheral arm: Synthesis, characterisation and phase transition behaviour

Guan Yeow Yeap*, Faridah Osman, Keisuke Ito, Daisuke Takeuchi, Chien Min Lin, Hong-Cheu Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

A series of symmetrical S-shaped mesogens based on 4,4′-bis-(6-bromohexyloxy)biphenyl as a central unit containing two 2-{6-[4-(4-substitutedphenylazo)phenoxy]hexyloxy}phenol as side-chain groups has been successfully synthesised. The terminal substituent was varied from halogen (X = F, Cl, Br and I) to non-halogen (X = C2H5 and OC2H5). The oligomers with C2H5 and OC2H5 substituents exhibit predominantly the monotropic nematic (N) phase. The OC2H5-containing derivatives possess long-range stability of N phase than its C2H5-containing analogue in which it has small range of N phase stability. As for halogen-containing analogues, oligomer with F exhibits monotropic N phase whilst oligomers with Cl and Br exhibit monotropic N and smectic A (SmA) phases. In addition, homologue with Br shows additional phase which is smectic B (SmB) phase upon further cooling. However, the oligomers in which F, Cl and Br were substituted by I exhibits purely monotropic SmA and SmB phases. X-ray diffraction measurements reveal that the smectic phase is inclined to the monolayer structure.

Original languageEnglish
Pages (from-to)809-821
Number of pages13
JournalLiquid Crystals
Volume44
Issue number5
DOIs
StatePublished - 9 Apr 2017

Keywords

  • monolayer
  • monotropic
  • nematic
  • S-shaped mesogen
  • smectic A
  • smectic B

Fingerprint Dive into the research topics of 'Influence of terminal substituent on non-linear S-shaped oligomers consisting of azobenzene moieties at the peripheral arm: Synthesis, characterisation and phase transition behaviour'. Together they form a unique fingerprint.

Cite this