Dynamic birefringence and molecular rigidity of poly-p-benzamide in solution

Tsvetkov, V.N.; Kudryavtsev, G. I.; Shtennikova, I.N.; Peker, T.V.; Zakharova, E.N.; Kalmykova, V.D.; Volokhina, A. V.

doi:10.1016/0032-3950(76)90177-5

Cited by 7 publications

(2 citation statements)

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“…5 The average molecular weights (M W ) of these PPTA batches were controlled by varying the temperature at which polymerizations were carried out and were estimated from viscosity measurements in 96% H 2 SO 4 using calibration curves described in the literature. 19 According to these measurements, the molecular weights of the samples that were here analyzed are approximately half as large as those reported in the literature for commercial PPTA fibers. 7 The solutions to be studied by NMR were prepared by dissolving in the 5 mm NMR tubes on which the measurements were carried out various quantities of synthetic PPTA in 99.8 ( 0.1% H 2 SO 4 aliquots.…”

Section: Methodsmentioning

confidence: 59%

“…(Scheme 1) . The average molecular weights ( M W ) of these PPTA batches were controlled by varying the temperature at which polymerizations were carried out and were estimated from viscosity measurements in 96% H 2 SO 4 using calibration curves described in the literature . According to these measurements, the molecular weights of the samples that were here analyzed are approximately half as large as those reported in the literature for commercial PPTA fibers…”

Section: Methodsmentioning

confidence: 98%

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Molecular Organization of Poly(p-phenyleneterephthalamide) in Sulfuric Acid: An NMR Study

Zhou

Frydman

1996

J. Phys. Chem.

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Solutions prepared by dissolving synthetic poly(p-phenyleneterephthalamide) (PPTA) in 99.8% H2SO4 were analyzed using natural abundance NMR methods as a function of the polymer concentration, molecular weight, and temperature. Concentration and molecular weight-driven transitions between isotropic, nematic, and solid-like phases could be clearly distinguished from the 13C NMR spectra of the solute and from 1H NMR spectra of the solvent. The 13C solute NMR spectra point toward a distribution in the order parameter of the liquid crystalline director and could be quantitatively reproduced using 13C shielding tensor elements measured by solid NMR in polycrystalline PPTA. Thermodynamic parameters for the nematic ⇄ isotropic equilibrium were obtained from the temperature dependence of the liquid crystalline 13C NMR spectra, and 2D NMR methods were employed to retrieve information about the kinetics of PPTA and H2SO4 migration between isotropic and nematic domains. The results obtained from these spectroscopic studies compare well with previous observations obtained using non-NMR methods; the significance of the new NMR measurements is briefly discussed.

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Section: Methodsmentioning

confidence: 59%

Section: Methodsmentioning

confidence: 98%