Mesophases of Alkylammonium Salts II. Disorder and Motion in the Low Homologs: [CH3(CH2)n-1]NX,n= 1, 2, 3 and X = Br and I Analyzed by Solid State13C NMR
作者:
Jinlong Cheng,
Alexander Xenopoulos,
Bernhard Wunderlich,
期刊:
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals
(Taylor Available online 1992)
卷期:
Volume 220,
issue 1
页码: 105-125
ISSN:1058-725X
年代: 1992
DOI:10.1080/10587259208033434
出版商: Taylor & Francis Group
关键词: tetra-n-alkylammonium bromides and iodides;disorder and motion;plastic crystal;solid state13C NMR;thermal analysis
数据来源: Taylor
摘要:
Disorder and motion in crystals of tetra-n-alkylammonium halides of short chain length alkyl groups, [CH3(CH2)n-1]4NX, wheren =1, 2, 3 and X = Br and I, have been analyzed based on solid state NMR. The solid-mesophase phase transitions involve orientational motion and disorder of the cation as a whole, so that the mesophases must be identified as plastic crystals. Except for the methyl rotation, the conformational motion,i.e., the rotation about single-bonds, is limited to small-angle librations that do not reach other conformational isomers. The analyzed salts show, thus, a plastic-crystal me-sophase without conformational disorder. The information on the disorder and motion, obtained initially by thermal analysis of the transition, agrees well with the more detailed NMR results.
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