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

1977; Elsevier BV; Volume: 13; Issue: 6 Linguagem: Inglês

10.1016/0014-3057(77)90125-2

1873-1945

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

Analytical Chemistry and Chromatography

Flow birefringence (FB) for samples of poly-p-phenylene terephthalamide (PPPhTPhA) dissolved in sulphuric acid has been investigated; intrinsic viscosities [η] of the solutions have been measured. Characteristic values of FB [n] and orientation angles [χ/g] of the solutions were determined. Coefficients of rotatory diffusion Dr and molecular weights M of all the samples of PPPhTPhA were calculated using the values of [χ/g] and [η]. Dependences of [η] and Dr on M show that the conformation of the PPPhTPhA molecules in solution resembles a slightly bending rod. Quantitative data on the equilibrium rigidity of the PPPhTPhA molecules were obtained from comparison of characteristic values of [n] and [χ/g] at different M and from the dependence of [n]/[η] on M, using the theory of optical anisotropy of persistent chains and also from the dependence of [η] on M. It was shown that the number of monomer units in a statistical segment of the PPPhTPhA chain is S = 200 ± 20; this corresponds to a segment length of (1300 ± 130) Å. The equilibrium rigidity of the PPPhTPhA chain is slightly lower than that of the PPBA molecules. Possible reasons for this difference are discussed.