Title

31P and 1H NMR as probes of domain alignment in a rigid crystalline surfactant mesophase

Document Type

Article

Date of Original Version

4-26-2005

Abstract

A viscous reverse hexagonal surfactant mesophase containing bis(2-ethylhexyl) sodium sulfosuccinate (AOT) and α-phosphatidylcholine (lecithin), with comparable volume fractions of isooctane and water, was characterized by Fourier transform 31P and 1H NMR spectroscopy. Shear alignment was reflected through both 31P NMR and 1H NMR spectra. A complicated 31P spectrum was observed as a result of superposition of chemical shifts according to the distribution of crystalline domains prior to shear. The initially disordered samples with polydomain structures become macroscopically aligned after Couette shear. 31P NMR chemical shift anisotropy characteristics are used to elucidate orientation of the hexagonal phase. Interestingly, 1H NMR spectra exhibit spectral changes upon shear alignment closely corresponding with that of 31P NMR spectra. These observations complement the findings of mesophase alignment obtained using SANS and imply that 31P and 1H NMR spectroscopy can be used as probes to define microstructure and monitor orientation changes in this binary surfactant system. This is especially beneficial if these mesophases are used as templates for materials synthesis. © 2005 American Chemical Society.

Publication Title

Langmuir

Volume

21

Issue

9

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