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

Blackwell, John; Cheng, H. M.; Biswas, Arpita

doi:10.1021/ma00179a009

Cited by 55 publications

(14 citation statements)

References 5 publications

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“…In particular, the peak in the 2.11 Å (2 ϭ 42.9°) region has shifted to d ϭ 2.07 Å (2 ϭ 43.7°), in good agreement with the observed value of 2.06 Å (2 ϭ 44.0°), and is significantly broadened. As before, the intensity match is not good, but our previous work for copoly(HBA/biphenol/terephthalic acid) 5 showed that chain-packing effects are likely to reduce the relative intensities of the inner reflections due to monomer staggering, which would effectively increase the relative intensity of the peak at d ϭ 2.07 Å (2 ϭ 43.7°). The most important point is that the simulation for the random copolymer reproduces all the observed peaks, including that at d ϭ 5.40 Ϯ 0.05 Å (2 Ϸ 16.4°), which is the crucial test for nonperiodicity.…”

Section: Resultsmentioning

confidence: 77%

“…It will be seen that this copolymer gives rise to nonperiodic diffraction effects similar to those reported previously for other random copolymers, notably the wholly aromatic copolyesters prepared from p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid, copoly(HBA/ HNA). [1][2][3][4][5] The X-ray fiber diffraction patterns of the latter copolymers contain nonperiodic layer lines, i.e., the layers do not occur at orders of a simple repeat. They are also shifted systematically with the monomer ratio, and thus cannot be explained by a block copolymer structure.…”

Section: Introductionmentioning

confidence: 99%

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X-ray analysis of the structure of a copoly(ester-imide)

Cho

Blackwell

Чвалун

et al. 1998

J. Polym. Sci. B Polym. Phys.

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The structure of a thermotropic liquid crystalline copoly(ester‐imide) prepared from p‐hydroxybenzoic acid (48 mol %), 4,4′‐dihydroxybenzophenone (26 mol %), and N,N′‐bis(trimellitimide)hexane (26 mol %) has been investigated by X‐ray diffraction. X‐ray fiber diagrams of as‐spun and annealed fibers contain a series of aperiodic layer lines reminiscent of those seen for fibers of other copolymers that have extended chain conformations and completely random monomer sequences. The positions of these layer lines were reproduced approximately in simulation of the X‐ray scattering by a fully extended chain of completely random sequence, and the match was improved to within experimental error when we considered a stereochemically acceptable sinuous chain. This agreement was lost when the sequence statistics deviated were completely random. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3137–3145, 1998

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Section: Resultsmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

X-ray analysis of the structure of a copoly(ester-imide)

Cho

Blackwell

Чвалун

et al. 1998

J. Polym. Sci. B Polym. Phys.

Self Cite

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“…Both show a high degree of axial orientation of the molecules and a three‐dimensional order. The most interesting feature of the data for both copolyesters is the occurrence of a series of nonperiodic layer lines, analogous to those observed for wholly aromatic copolyesters, copolyamides, and copolyimides 2–12. The HBA/HNA copolyesters are the most frequently studied, and their X‐ray fiber diagrams contain nonperiodic layer lines across the entire composition range that shift progressively along the fiber axis direction with changes in the comonomer ratio.…”

Section: Introductionmentioning

confidence: 64%

Axial correlation lengths for aromatic copolyesters

2001

J Polym Sci B Polym Phys

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X-ray methods were used to investigate the structure of Vectra(R) and Xydar(R) polyesters. Xydar(R) is based on the aromatic polyester prepared from p-hydroxy-benzoic acid (HBA), terephthalic acid, and biphenol. Vectra(R) consists of HBA and 2-hydroxy-6-naphthoic acid. X-ray fiber diagrams of these materials consist of a series of nonperiodic layer lines, which are consistent with a structure consisting of parallel chains of a random comonomer sequence. The meridional peak positions are predicted accurately for fully extended, infinite chains, and the observed and calculated 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 much sharper than those observed. The latter agreement is improved with a model consisting of finite chain segments with a slightly nonlinear (sinuous) conformation. The best agreement for the observed peak profiles is obtained with an ordered segment length of 90 +/-6 Angstrom and a sinuosity of g = 3.67 +/-0.08% for Vectra(R) fibers and with an ordered segment length of 104 +/-6 Angstrom and a sinuosity of g = 3.33 +/-0.08% for Xydar(R) fibers. (C) 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1839-1847, 2001

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“…2 Consequently, the polymer must encounter elevated temperatures at almost every stage in preparing, melt blending, and processing (such as spinning) stages, as well as in service and during repair. 2,3 It is necessary to assess and predict the thermostability under these conditions. 4 A few reports have dealt with the synthesis, 2,5-9 phase transition, 2 X-ray fiber diagram, 2,3 three-dimensional diffractogram in the temperature range from room temperature to 380°C, 2 tensile property, 1 and thermal degradation 4 of the copolyester and its fiber.…”

Section: Introductionmentioning

confidence: 99%

Thermal degradation kinetics of thermotropic poly(p-oxybenzoate-co-p,p?-biphenylene terephthalate) fiber

Huang

1999

J. Appl. Polym. Sci.

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An advanced heat-resistant fiber (trade name Ekonol) spun from a nematic liquid crystalline melt of thermotropic wholly aromatic poly(p-oxybenzoate-p,pЈ-biphenylene terephthalate) has been subjected to a dynamic thermogravimetry in nitrogen and air. The thermostability of the Ekonol fiber has been studied in detail. The thermal degradation kinetics have been analyzed using six calculating methods including five single heating rate methods and one multiple heating rate method. The multiple heating-rate method gives activation energy (E), order (n), frequency factor (Z) for the thermal degradation of 314 kJ mol Ϫ1 , 4.1, 7.02 ϫ 10 20 min Ϫ1 in nitrogen, and 290 kJ mol Ϫ1 , 3.0, 1.29 ϫ 10 19 min Ϫ1 in air, respectively. According to the five single heating rate methods, the average E, n, and Z values for the degradation were 178 kJ mol Ϫ1 , 2.1, and 1.25 ϫ 10 10 min Ϫ1 in nitrogen and 138 kJ mol Ϫ1 , 1.0, and 6.04 ϫ 10 7 min Ϫ1 in air, respectively. The three kinetic parameters are higher in nitrogen than in air from any of the calculating techniques used. The thermostability of the Ekonol fiber is substantially higher in nitrogen than in air, and the decomposition rate in air is higher because oxidation process is occurring and accelerates thermal degradation. The isothermal weight-loss results predicted based on the nonisothermal kinetic data are in good agreement with those observed experimentally in the literature.

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

Cited by 55 publications

References 5 publications

X-ray analysis of the structure of a copoly(ester-imide)

X-ray analysis of the structure of a copoly(ester-imide)

Axial correlation lengths for aromatic copolyesters

Thermal degradation kinetics of thermotropic poly(p-oxybenzoate-co-p,p?-biphenylene terephthalate) fiber

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