Molecular Motions of the Head Group of Sodium 4-(1′-heptylnonyl)benzenesulfonate in Lamellar Liquid Crystals
Deuterium NMR spectra of a specifically deuterated double-tailed surfactant sodium 4-(1′-heptylnonyl)-benzenesulfonate (SHBS) both dry and in liquid crystals formed with water were obtained from -70 to 90°C. The liquid crystalline deuterium powder patterns from the phenyl-ring deuterons can be described by motions characterized as rigid (from -70 to -30°C), 2-fold ring flips (from -40 to -30°C), and rotations in an anisotropic media (-20°C and higher). For the higher temperature spectra (>-20 °C), the inclusion of a single fast rotation, or even anisotropic diffusion alone, did not give the best fits of the experimental spectra. The inclusion of a local ordering potential, or anisotropic viscosity, yielded good fits to the experimental spectra. The local ordering potential required local order parameters from 0.856 to 0.763 for temperatures from 10 to 90°C. The dry surfactant, in contrast to the liquid crystals at the same temperatures, undergoes both fast and slow 2-fold ring flips at 25°C with the fraction of fast flippers increasing with temperature. © 1991 American Chemical Society.
J. R. Duke et al., "Molecular Motions of the Head Group of Sodium 4-(1′-heptylnonyl)benzenesulfonate in Lamellar Liquid Crystals," Langmuir, American Chemical Society (ACS), Jan 1991.
The definitive version is available at https://doi.org/10.1021/la00057a015
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© 1991 American Chemical Society (ACS), All rights reserved.