Deuterium NMR Study of Uniaxial-Biaxial Phase Transitions in a Smectogen
作者:
X. Shen,
RonaldY. Dong,
期刊:
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals
(Taylor Available online 1995)
卷期:
Volume 262,
issue 1
页码: 293-303
ISSN:1058-725X
年代: 1995
DOI:10.1080/10587259508033534
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
The effects of uniaxial-biaxial phase transition on the spectral densities measured from the deuteron Zeeman (T1Z)and quadrupolar (T1Q) spin-lattice relaxation times are examined in two partially deuterated samples of 4-n-pentyloxybenzylidene-4‘-heptylaniline(50.7): one deuterated at the methine site (50.7-d1) and one with the aniline ring deuterated (50.7-d4). The deuterated sites are chosen so that their relaxation behaviours are not complicated by internal chain dynamics. It is found that the spectral densities show discontinuities at theSc- SBphase transition, but show no discontinuity at theSA- SCandSB- SGphase transitions. Both the smectic C and G phases are biaxial. The results are discussed in terms of molecular reorientation and director fluctuations. Preliminary data for the sample director oriented at 90° with the external magnetic field are reported in the B and G phases of 50.7-d1.
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