Molecular Motions of the Head Group of SHBS in Lamellar Liquid Crystals
Interim technical rept. Jan 90-Nov 91,
MISSOURI UNIV-ROLLA DEPT OF CHEMISTRY
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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 as from motions characterized as rigid from -70 to -30 C, two fold ring flips from -40 to -30 C, and rotations in an anisotropic media -20 C and higher. For the higher temperature spectra 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 two-fold ring flips at 25 C with the fraction of fast flippers increasing with temperature.