Thermotropic Ionic Liquid Crystals. II. 1H and 23Na NMR Study of the Smectic Mesophase of Molten Sodium N-Butyrate and Sodium Isovalerate.

摘要

The 1H and 23Na NMR studies of smectic ionic mesophases of molten sodium n-butyrate and sodium isovalerate are reported over the temperature range of the stability of the liquid crystalline phases. The 1H spin-lattice relaxation times for the anions of both the systems are interpreted in terms of diffusion intermolecular with those measured directly by spin-echo technique and indicate that the anion diffuses rapidly. In contrast to the relaxation times 1 relaxation mechanism the results obtained for the proton relaxation times in the rotating coordinate frame indicate that the order-fluctuation relaxation mechanism determined the frequency dispersion of proton relaxation time. The analysis of the proton relaxation times data provides an approximate measure of the order parameter as a function of temperature. Fourier transform spectra of the 23Na transitions show that the electric field gradient (EFG) at the Na(+) ion is nonaveraged and of such a strength as to produce a second order quadrupole effect in the spectra of the central transition.