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Thermotropic Liquid Crystals of Main‐Chain Polyesters having a Mesogenic 4,4′‐Biphenyldicarboxylate Unit, 14
Author(s) -
Osada Kensuke,
Koike Masao,
Tagawa Hirotaka,
Tokita Masatoshi,
Watanabe Junji
Publication year - 2004
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200300258
Subject(s) - perpendicular , thermotropic crystal , liquid crystal , polymer , anisotropy , materials science , fiber , polyester , mesogen , composite material , crystallography , chemistry , condensed matter physics , optics , liquid crystalline , geometry , physics , optoelectronics , mathematics
Summary: Anisotropy in molecular motions of a glassy smectic CA (SmCA) liquid crystal of a main‐chain BB‐5(3‐Me) polyester was examined by dynamic mechanical analysis (DMA) for fibrous monodomain samples with two distinct orientations of smectic layers perpendicular and parallel to the fiber axis. The α ‐process attributed to micro‐Brownian motion of the polymer on the glass transition shows clear anisotropy explainable by the nature of the smectic layer structure. Time‐temperature superposition is applicable to the α ‐process, so that the frequency of the micro‐Brownian motion in the SmCA phase can be estimated despite the narrow frequency range in DMA. The results suggest that the decoupling of the molecular motions in two characteristic directions are parallel and perpendicular to the layer. The amplitude of the micro‐Brownian motion in the layer normal direction is 3 times smaller than that in the layer direction, and the frequency in the layer normal direction is 2.5 times higher than that in the layer direction.Illustration of molecular packing structures: fiber A (left side) and fiber B (right side) with the orientations of polymers parallel and perpendicular to the fiber, respectively.