Dynamic birefringence and conformation of poly-p-phenylene terephthalamide molecules in solution

Tsvetkov, V.N.; Shtennikova, I.N.; Peker, T.V.; Kudriavtsev, G.I.; Volokhina, A. V.; Kalmykova, V.D.

doi:10.1016/0014-3057(77)90125-2

Cited by 20 publications

(4 citation statements)

References 2 publications

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“…The latter are hereafter reported in terms of inherent viscosities, i.e., true experimental values, instead of MW data calculated from still controversial [qj-M relationships (7,8).…”

Section: Resultsmentioning

confidence: 99%

Role of the reaction parameters in the direct synthesis of aromatic polyamides

Mariani¹,

Mazzanti²,

Russo³

1995

Can. J. Chem.

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A thorough study, devoted to analyzing the role of various reaction parameters in the direct synthesis of poly@-phenylene terephthalamide) and poly@-benzamide), activated by triphenyl phosphite, is described. The effects of temperature, salt type and concentration, amount of triphenyl phosphite and its stepwise introduction, as well as monomer and reagent concentrations, are considered. The inherent viscosity values of the above aromatic polyamides are higher than those reported in the literature for analogous syntheses and are comparable to the values of typical samples obtained by the acyl chloride routes.

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“…The latter are hereafter reported in terms of inherent viscosities, i.e., true experimental values, instead of MW data calculated from still controversial [qj-M relationships (7,8).…”

Section: Resultsmentioning

confidence: 99%

Role of the reaction parameters in the direct synthesis of aromatic polyamides

Mariani¹,

Mazzanti²,

Russo³

1995

Can. J. Chem.

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“…[5][6][7][8][9][10][11][12][13][14][15][16] The q values are tabulated in Table I. Diffusion and sedimentation experiments appear not to be suffi- Table I Persistence Length (q) in Á, Measured in 96% Sulfuric Acid technique (ref) p-BA p-PT light scattering, Rg (5) 400 200 light-scattering depolarization ratio (6) 150 flow birefringence (7) 185 light scattering (8) 600 200 viscosity (8) 400 150 flow birefringence (9) 325 light-scattering depolarization (10) 287 electric birefringence, Kerr effect (11) 300 light scattering (12) >450 flow birefringence (13) 1000 flow birefringence (14) 650 flow birefringence (15) 1050 650 flow birefringence (16) 435 275 ciently sensitive to yield even a rough estimate of g. 15,17,18 Changes in the nature and strength of the solvent acid, manifested by variations in the protonation level of the amide groups along the chain and in the consequential changes in chain extension and rigidity, were also reported to affect the exponent o,19,20 the persistence length q,18 and the radius of gyration Bg. 19 Plots by Arpin and Strazielle5,8 of intrinsic viscosity and radius of gyration against weight-average molecular weight (Mw) show the same dependencies and the same data scatter for unfractionated as for fractionated p-PT.…”

Section: Introductionmentioning

confidence: 99%

Depolarization ratios and rigidity of aromatic polyamides

Zero¹,

Aharoni²

1987

Macromolecules

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Monodisperse oligomers and several unfractionated polymers of poly(p-benzanilide-terephthalamide) (p-BT) were prepared and characterized. Their depolarization ratios were measured in concentrated (96%) sulfuric acid and they produced optical anisotropy values essentially the same as those of poly(p-phenylene terephthalamide) (p-PT) of comparable Mw. A numerical fit to our p-BT data and literature data for fractionated p-PT yielded a persistence length of 113 Á. The unfractionated p-PT, particularly at high molecular weights, tended to yield higher depolarization ratios and, consequently, higher persistence lengths than equivalent fractionated material, possibly due to high polydispersity.

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“…Hence orientation during processing is of practical interest and is the subject of several previous studies. [1][2][3][4][5][6][7][8] Orientation of the molecules may play an important role during the polymerization process as well. All previous investigations of the kinetics of solution polycondensation of RRL molecules show that after an initial period, during which the polymerization is relatively rapid, the rate constant decreases by an order of magnitude and the molecular weight increases very slowly with time.…”

Section: Introductionmentioning

confidence: 99%

“…Figure5, Variation of DPW of PPTA in reactor I and reactor II with time at different shear rates. The full lines are plots of the fitted polynomials (eqs 4.1 and 4.2), and the dashed line indicates the time range during which uniform shear flow could not be maintained.…”

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confidence: 99%

Shear flow induced orientation development during homogeneous solution polymerization of rigid rodlike molecules

Agarwal¹,

Khakhar²

1993

Macromolecules

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The dynamic variation of optical birefringence during solution polycondensation of rigid rodlike molecules in a simple shear flow is obtained. At relatively high shear rates (413 s-1) and late stages of the polymerization the orientation of the molecules is found to be significant. Molecular orientation is important in such reactions since it increases the polymerization rate and alters the molecular weight distribution (Agarwal, U. S.; Khakhar, D. V. Nature 1992, 360, 53). The birefringence at different shear rates (7) over the course of the polymerization is found to depend only on y/D" where D, is the rotational diffusivity. The predictions of the theory of Marrucci and Grizzuti («7. Polym. Sci., Polym. Lett. Ed. 1983,21, 83), however, show large deviations in comparison to the experimental birefringence measurements. The experiments are carried out using terephthaloyl chloride and p-phenylenediamine to produce poly(p-phenyleneterephthalamide) in a mixed solvent at low temperatures. A two-reactor system is used in which the second reactor is designed to give a uniform simple shear flow and to allow for measurement of birefringence during polymerization.

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Dynamic birefringence and conformation of poly-p-phenylene terephthalamide molecules in solution

Cited by 20 publications

References 2 publications

Role of the reaction parameters in the direct synthesis of aromatic polyamides

Role of the reaction parameters in the direct synthesis of aromatic polyamides

Depolarization ratios and rigidity of aromatic polyamides

Shear flow induced orientation development during homogeneous solution polymerization of rigid rodlike molecules

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