Diffraction by aperiodic polymer chains: the structure of liquid crystalline copolyesters

Blackwell, John; Gutierrez, Genaro A.; Chivers, Robin A.

doi:10.1021/ma00136a019

Cited by 68 publications

(26 citation statements)

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“…The as-extruded B-N thermotropic copolyester fibers exhibit aperiodic meridional reflections, consistent with reports by Blackwell et al and Windle et al [2,10]. Figure 2a shows the corresponding wide-angle X-ray scattering pattern.…”

Section: Resultssupporting

confidence: 88%

Fracture behavior of heat treated liquid crystalline polymers

et al. 2012

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Thermotropic polymers are thermally treated in air at temperatures T a , where T =T a -T s n =40°C, and T s n is the solid-to-nematic transition. Samples are extruded thin films of a series of thermotropic random copolyesters termed B-N, COTBP and RD1000. The thermal treatment produces a second endotherm without changing T s n for B-N and RD1000. However, for COTBP T s n is significantly increased. Regardless of the complex thermal behavior exhibited by the thermotropes, the thermal treatment produces a significant increase in Young's modulus, more than 30% for B-N and over 100% for COTBP. The increase in mechanical modulus is correlated with a thermally-induced fiber-like morphology.

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Section: Resultssupporting

confidence: 88%

Fracture behavior of heat treated liquid crystalline polymers

et al. 2012

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“…Liquid crystalline polyesters are random copolymers, as has been confirmed by X‐ray analysis 16–19. However, the presence of sharp equatorial and off‐equatorial Bragg diffraction maxima indicates some form of three‐dimensional registration of the chains.…”

Section: Introductionmentioning

confidence: 75%

Synthesis and eutectic behavior of liquid crystalline copolyesters

Wang

Luise

2009

J Polym Sci B Polym Phys

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A series of liquid crystalline copolyesters, derived from 1,4‐hydroxy‐benzoic acid (HBA), 6‐hydroxy‐2‐naphthoic acid (HNA), terephthalic acid (TA), and hydroquinone (HQ), were prepared; crystallization, melting and solid‐state structure of the copolyesters were studied by using differential scanning calorimetry (DSC) and wide‐angle x‐ray diffraction (WAXD). It was found that the variation of melting point of the copolyesters with increasing HBA mol % exhibits eutectic melting behavior at a constant mole ratio of HNA, and the extrapolated eutectic temperature decreases linearly with increasing HNA mol %. WAXD analysis of the copolyesters indicates that the d‐spacing related to three‐dimensional order increases first and then decreases with increasing HBA mol %. The increase of the d‐spacing, consistent with looser packing of chains, leads to the reduction of melting point and most likely accounts for the eutectic behavior observed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2171–2177, 2009

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“…A most interesting feature of the data for the Technora copolyamide is the occurrence of nonperiodic layer lines, analogous to those observed for wholly aromatic copolyesters and copolyimides. [8][9][10][11][12][13] The most frequently studied of the latter polymers are the copolyesters prepared from p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA). The X-ray fiber diagrams of copoly(HBA/HNA) contain nonperiodic layer lines that shift progressively along the fiber axis direction with changes in comonomer ratio.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Axial Correlation Lengths and Paracrystalline Distortion for Technora and Kevlar Aromatic Polyamide Fibers

Blackwell

1996

Macromolecules

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X-ray fiber diagrams of the aromatic copolyamide Technora, prepared from terephthaloyl chloride and equimolar proportions of p-phenylenediamine and 3,4′-diaminodiphenyl ether, contain a series of nonperiodic layer lines that point to a structure consisting of parallel chains of random comonomer sequence. The meridional peak positions are predicted accurately for fully extended, infinite chains, and the observed and calculated peak intensities are also in reasonably good agreement. However, there is a less adequate match between the observed and calculated peak profiles, which are predicted to be very much sharper than those observed. The latter agreement is improved by using a model consisting of finite chain segments with a slightly nonlinear (sinuous) conformation. The best agreement for unannealed Technora is obtained with an ordered segment length of 300 ( 15 Å and sinuosity of g ) 1.52 ( 0.05%, where g is analogous to the index of paracrystalline distortion in a homopolymer structure. Very similar results are obtained for fibers that have been thermally annealed. These data are strikingly similar to those for Kevlar fibers (poly(p-phenylene terephthalamide)), for which the crystallite size along the fiber axis direction is 350 ( 10 Å with a paracrystalline distortion of 2.32 ( 0.08% for Kevlar 29, increasing to 400 ( 12 Å with a paracrystalline distortion of 1.71 ( 0.06% for Kevlar 149. Consequently, although Technora is a random copolymer and the presence of the random diaminodiphenyl ether leads to a more distorted lateral packing of the chains than occurs in Kevlar, the fibers produced by the dry-jet wet-spinning process have extended conformations that are very similar in linearity to those for Kevlar, which probably account for the analogous high tensile strengths and moduli.

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Diffraction by aperiodic polymer chains: the structure of liquid crystalline copolyesters

Cited by 68 publications

References 1 publication

Fracture behavior of heat treated liquid crystalline polymers

Fracture behavior of heat treated liquid crystalline polymers

Synthesis and eutectic behavior of liquid crystalline copolyesters

Comparison of the Axial Correlation Lengths and Paracrystalline Distortion for Technora and Kevlar Aromatic Polyamide Fibers

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