The diffusion and sedimentation of poly-p-benzamide in sulphuric acid and dimethyl acetamide

Vitovskaya, M.G.; Lavrenko, P. N.; Okatova, O. V.; Astapenko, E. P.; Nikolayev, V.Ya.; Kalmykova, V.D.; Volokhina, A. V.; Kudryavtsev, G. I.; Tsvetkov, V.N.

doi:10.1016/0032-3950(77)90006-5

Cited by 11 publications

(3 citation statements)

References 4 publications

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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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Section: Introductionmentioning

confidence: 99%

Depolarization ratios and rigidity of aromatic polyamides

Zero¹,

Aharoni²

1987

Macromolecules

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“…Assuming a high value of the Kuhn segment of PABI and the stretched state of the macromolecules in LC sulfuric acid solution due to solvation, it is nevertheless not possible to exclude the possibility of conformational rearrangement of the macromolecules into a more twisted form during desolvation and precipitation of the polymer from a jet of LC solution in the spinning bath in spinning of fibres. The benzimidazole ring in PABI introduces breaks in the chain at m~ angle of approximately 30 ~ and thus perturbs the parallelism of chain transfer bonds [8], primarily causing the less rigid-chain character of the PABt macromolecules in comparison to PPTA.…”

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confidence: 99%

“…The information on the rigidity of the molecular chains of PABI based on determination of the Kuhn segment is ambiguous and differs significantly as a function of the solvent selected and the temperature [6]. It is equal to 25+5 nm, determined in sulfuric acid at 20~ and in N,N-dimethylacetamide [6][7][8], which is lower than the Kuhn segment for PPTA (30_+5 nm) [7,8]. Moreover, a Kuhn segment of 40+5 nm is obtained for PABI in sulfuric acid at 80~ which is more correct in the opinion of the investigators in [9] due to the change in the solvating power of sulfuric acid with respect to the amide and imidazole groups of PABI on heating, so important at 20~ that it distorts the results of determining the molecular characteristics by light scattering.…”

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confidence: 99%

Fabrication of fibres from sulfuric acid solutions of copolyamides containing polyamide—Benzimidazole units and their heat treatment

Sugak¹,

Kiya-Oglu²,

Goloburdina³

1999

Fibre Chem

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It was interesting to study in detail heat treatment of fibres made of this copolymuide and a copolymnide consisting of PABI and PPTA-C1 units (p-phenylenediamine with monochloro substitution in the aromatic nucleus and terephthaloyl chloride) [2] for which facilitation of structural rearrangement during heat treatment can be expected due to the chlorine substitution.The copolyamides were synthesized by low-temperature polycondensation in N,N-dimethylacetmnide meditun with LiC1 using a-picoline as HCI acceptor, as described in [3].The composition and specific viscosity of the copolyamides (q_) are reported in Table 1, including the 11 of samples ~p sp of fleshly spun fibres differing due to degradation of the polymers during preparation mid preparation of the LC solutions lor spinning the fibres. We used 22% LC solutions of tile copolyamides in 99.8% sulfuric acid at 70~ for spinning tile fibres. The high viscosity of the LC solutions --on the level of 2000-5000 Pa-sec (in conditions of shear stress of 800 Pa and at a temperature of 70~ --makes it difficult to process them aud is perhaps the cause of the appearance of small breaks in individual fibres during spinning. Spinning through an air gap was conducted according to the data in [4]. The LC solutions were extruded through the channels of the spinneret (I00 channels 0.08 mm in diameter) into a 4-6 mm air gap and then into an aqueous spinning bath cooled to 10~ The jets of LC solution underwent 3.5-7-fold orientational drawing, calculated as the ratio of the rate of taking the fibre up on a perforated bobbin to the flow rate of the LC solution from the channels without consideration of spinneret expansion of the jet. The fibre formed in the spinning bath passed a bath layer 100 mm deep from the Termotex, Terlon, Mytishchi.

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