The deuterium Zeeman spin-lattice relaxation times T1Z in 4,4'-di-n-heptylazobenzene (HB), 4,4'-di-n-heptylazoxybenzene (HAB), and 4,4'-di n-octylazoxybenzene (OAB) deuterated on the aromatic rings and on the first methylene group of the chains were measured at 10 and 46.04 MHz by means of the inversion-recovery technique. Measurements were made throughout the mesomorphic range and also in the isotropic phase. The relaxation rates show a discontinuity at the isotropic-nematic transition for all deuterons not ascribable to the onset of orientational order. The trends of lnR are linear within the different phases except near phase transitions, and allow to obtain apparent activation energies for the overall motions of the different C-D bonds.
DEUTERIUM SPIN-LATTICE RELAXATION IN THERMOTROPIC LIQUID-CRYSTALS - STUDY OF 4,4'-DI-NORMAL-HEPTYLAZOBENZENE, 4,4'-DI-NORMAL-HEPTYLAZOXYBENZENE AND 4,4'-DI-NORMAL-OCTYLAZOXYBENZENE
FORTE C
1992
Abstract
The deuterium Zeeman spin-lattice relaxation times T1Z in 4,4'-di-n-heptylazobenzene (HB), 4,4'-di-n-heptylazoxybenzene (HAB), and 4,4'-di n-octylazoxybenzene (OAB) deuterated on the aromatic rings and on the first methylene group of the chains were measured at 10 and 46.04 MHz by means of the inversion-recovery technique. Measurements were made throughout the mesomorphic range and also in the isotropic phase. The relaxation rates show a discontinuity at the isotropic-nematic transition for all deuterons not ascribable to the onset of orientational order. The trends of lnR are linear within the different phases except near phase transitions, and allow to obtain apparent activation energies for the overall motions of the different C-D bonds.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
