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Stiff chain persistence lengths in liquid crystalline copolyesters
Author(s) -
Blackwell John,
Biswas Amit
Publication year - 1986
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19860020104
Subject(s) - chain (unit) , aperiodic graph , monomer , copolymer , crystallography , maxima , work (physics) , sequence (biology) , intensity (physics) , materials science , homologous series , diffraction , series (stratigraphy) , distribution (mathematics) , chemistry , polymer , thermodynamics , mathematics , physics , combinatorics , mathematical analysis , optics , composite material , art , paleontology , biochemistry , astronomy , performance art , biology , art history
This paper describes a continuation of our X‐ray diffraction work on the structure of the mesomorphic copolyesters prepared from p‐hydroxybenzoic acid (HBA) and 2‐hydroxy‐6‐naphthoic acid (HNA). The X‐ray patterns of meltspun fibers of these copolymers show a series of aperiodic meridional maxima, and these are predicted by a model consisting of stiff extended chains of completely random copolymer sequence. The calculated intensity data are independent of the chain length for the model, except that the width of the peak at d≃2.1Å decreases with increasing chain length. For 58/42 copoly(HBA/HNA) the best agreement obtained is for a chain length of 11 monomers, and this corresponds to a correlation or persistence length for the stiff chain conformation in the solid state. This effect has been modeled for an infinite chain by deriving experimental monomer length distribution functions, from a survey of the conformations of models of typical random chain sequences. The distribution function is then incorporated into the intensity calculations and leads to prediction of peak widths that are comparable to those observed.