New insights into the transitional behaviour of methyl-6-O-(n-dodecanoyl)-α-D-glucopyranoside using variable temperature FTIR spectroscopy and X-ray diffraction

A. G. Cook, A. Martinez-Felipe, N. J. Brooks, J. M. Seddon, C. T. Imrie*

*Corresponding author for this work

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

The liquid crystalline behaviour of methyl-6-O-(n-dodecanoyl)--D-glucopyranoside, 1, has been characterised using X-ray diffraction and variable temperature Fourier transform infrared (FTIR spectroscopy). 1 exhibits a monotropic interdigitated smectic A phase consisting of bilayers in which the alkyl chains are overlapped. The crystal-isotropic transition is accompanied by a pronounced decrease in the strength of the hydrogen bonding network involving the sugar groups resulting in a marked change in the environment of the alkyl chains. The isotropic phase consists of disordered smectic-like domains stabilised via hydrogen bonding between the sugar groups. At the transition to the smectic A phase, a subtle change in hydrogen bonding is observed which is manifested by a change in the temperature dependence of the OH stretching peak position in the FTIR spectrum. On crystallisation, the strong hydrogen bonding network is re-established accompanied by a change in the conformational distribution of the alkyl chains. A model is proposed in which a combination of hydrogen bonding (enthalpic effects) and conformational arrangements (entropic effects) promotes initially the formation of smectic-like domains in the isotropic phase and subsequently stabilises the smectic A phase by inhibiting the microphase separation leading to the crystal phase.

Original languageEnglish
Pages (from-to)1817-1827
Number of pages11
JournalLiquid Crystals
Volume40
Issue number12
Early online date1 Nov 2013
DOIs
Publication statusPublished - 1 Dec 2013

Keywords

  • carbohydrate liquid crystal
  • smectic A phase
  • variable temperature FTIR
  • hydrogen bonding
  • transform infrared-spectroscopy
  • liquid-crystalline glycolipids
  • beta-D-glucopyranoside
  • homologous series
  • phase-transitions
  • sugar glasses
  • IR-spectrum
  • D-glucose
  • chain
  • mesomorphism

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