Diffusion NMR for determining the homogeneous length-scale in lamellar phases.

Ingrid Aslund, Celia Cabaleiro-Lago, Olle Söderman, Daniel Topgaard

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

The size of the anisotropic domains in a lyotropic liquid crystal is estimated using a new protocol for diffusion NMR. Echo attenuation decays are recorded for different durations of the displacement-encoding gradient pulses, while keeping the effective diffusion time and the range of the wave vectors constant. Deviations between the sets of data appear if there are non-Gaussian diffusion processes occurring on the time-scale defined by the gradient pulse duration and the length-scale defined by the wave vector. The homogeneous length-scale is defined as the minimum length-scale for which the diffusion appears to be Gaussian. Simulations are performed to show that spatial variation of the director orientation in an otherwise homogeneous system is sufficient to induce non-Gaussian diffusion. The method is demonstrated by numerical solutions of the Bloch-Torrey equation and experiments on a range of lamellar liquid crystals with different domain sizes.

Original languageEnglish
Pages (from-to)2782-2794
Number of pages12
JournalJournal of Physical Chemistry B
Volume112
Issue number10
DOIs
Publication statusPublished - 2008
Externally publishedYes

Swedish Standard Keywords

  • Physical Chemistry (10402)

Keywords

  • Gradient spin-echo
  • diffraction
  • field-gradient
  • matrix
  • model
  • nuclear-magnetic-resonance
  • pore
  • porous systems
  • restricted self-diffusion
  • water

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