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Home  >  Journal list  >  Polymer Journal  >  Vol.36  No.10 (2004)  >  pp.830-840

Polymer Journal
<<Previous article Vol.36  No.10 (2004)   pp.830 - 840 Next article>>

Solid-State 13C NMR Analysis of the Crystalline–Noncrystalline Structure and Chain Conformation of Thermotropic Liquid Crystalline Polyester

Miwa Murakami1), Hiroyuki Ishida1), Hironori Kaji1), Fumitaka Horii1), Masatoshi Tokita2) and Junji Watanabe2)
1) Institute for Chemical Research, Kyoto University
2) Department of Organic and Polymer Materials Chemistry, Tokyo Institute of Technology

ABSTRACT:  The crystalline–noncrystalline structure and chain conformation of thermotropic liquid crystalline polyester (BB-8), composed of mesogenic biphenyl and spacer CH2 sequence units, have been characterized by high-resolution solid-state 13C NMR spectroscopy. The sample was crystallized by cooling from the melt through the smectic A phase. 13C spin–lattice relaxation measurements reveal that all resonance lines contain three components with different T1C values of 200–430, 9–38, and 0.4–5.5 s, which correspond to the crystalline, medium, and noncrystalline components, respectively. The high-resolution 13C NMR spectrum for each component is selectively recorded by utilizing the difference in T1C and conformation of the spacer CH2 sequences of each component is evaluated by considering the γ-gauche effect on 13C chemical shift values. The noncrystalline component is found to adopt a characteristic conformation xttttttx in which the trans–gauche exchange conformations (x) are introduced at both ends of the CH2 sequence, whereas the all-trans conformation tttttttt is allowable for the crystalline and medium components. 13C chemical shift anisotropy spectra of the respective carbons are obtained by the two-dimensional magic angle turning method to examine molecular motion of the mesogen and spacer units. The mesogenic phenylene units undergo rapid fluctuation around the bond axis of the units in the medium and noncrystalline components while the crystalline component is highly restricted in such molecular motion. On the basis of these results, a molecular motion model is proposed for the noncrystalline component, which corresponds to the supercooled smectic A phase, for the BB-8 sample.

Liquid Crystalline Polymer/ Polyester/ Solid-State 13C NMR/ Conformation/ Co-planarity/ Molecular Motion

Published online: October 14, 2004
© Copyright, 2004 by The Society of Polymer Science, Japan



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