X‐ray diffraction by liquid‐crystalline copolymers prepared from 4‐hydroxybenzoic acid and 2‐hydroxy‐6‐naphthoic acid: A one‐dimensional paracrystalline model

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

doi:10.1002/pol.1984.180220716

Cited by 30 publications

(7 citation statements)

References 3 publications

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“…The specimen showed high orientation of the chain axes perpendicular to the fill direction in the mold. X-ray patterns were recorded on film, with the chain axis direction perpendicular to the beam, and then tilted at the appropriate angle (8) for successive meridional maxima. These patterns were scanned by using an Optronics densitometer to record the meridional intensity profiles.…”

Section: Methodsmentioning

confidence: 99%

X-ray analysis of the structure of the thermotropic copolyester XYDAR

Blackwell¹,

Cheng²,

Biswas³

1988

Macromolecules

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Section: Methodsmentioning

confidence: 99%

X-ray analysis of the structure of the thermotropic copolyester XYDAR

Blackwell¹,

Cheng²,

Biswas³

1988

Macromolecules

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“…where Tab(Z) is an element of the matrix T(Z) corresponding to the pair AS and T(Z) is defined as T(Z) = M-X(Z) I -M-X(Z) (7) in which I is the unity matrix.…”

Section: Abmentioning

confidence: 99%

Chain conformation of the Technora copolyamide

Cageao¹,

Schneider²,

Biswas³

et al. 1990

Macromolecules

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This paper describes further X-ray diffraction work on the structure of the copolyamide prepared from terephthaloyl chloride (TPA), phenylenediamine (PDA), and 3,4'-diaminodiphenyl ether (DPE). X-ray fiber diagrams of this material consist of a series of nonperiodic layer lines, and we have shown previously that these are consistent with a structure consisting of parallel chains of completely random comonomer sequence. The meridional peak positions are predicted accurately for a fully extended chain conformation, and the peak intensities are also in reasonably good agreement. However, there is a less than adequate match between the observed and calculated peak profiles, most notably that for the peak at d % 2.15 A, which is predicted to be very much sharper than that observed. The latter peak has been shown to be a measure of the correlation or persistence length for the stiff chain conformation in the solid state and is predicted to be extremely sharp when the chain is modeled by a linear infinite chain of random monomer sequence. A better fit to the broader observed peak is achieved by using a model that incorporates nonlinearity of the chain conformation due to the presence of the ether and 1,3-phenylene linkages, as well as torsional variations. This has been done by defining the nonlinearity in terms of histograms of the axial advance per monomer for each monomer type, based on a survey of models of a large number of chains with sequences selected by Monte Carlo methods. It is clear that the requirements of chain packing imply highly extended conformations, and this probably involves some distortion of the bond and torsion angles in order to align the random sequences.

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“…The fact that the random copolymer chains are aperiodic means the layer lines become more diffuse on moving to higher orders, only to sharpen up again at l = 4 and above. This effect has been analyzed in more detail for this system in ref and for thermotropic liquid crystalline random co-polyester systems in refs and .…”

mentioning

confidence: 99%