Flow birefringence and optical anisotropy of poly(N-vinylpyrrolidone) molecules |
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Authors: | A I Kononov M A Sibileva N A Mikhailova A E Grishchenko |
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Institution: | 19556. Department of Physics, St. Petersburg State University, Ul’yanovskaya ul. 1, Petrodvorets, St. Petersburg, 198504, Russia
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Abstract: | Concentration dependences of flow birefringence and viscosity of poly(N-vinylpyrrolidone) solutions in water and benzyl alcohol are investigated. The intrinsic anisotropy for a poly(N-vinylpyrrolidone) macromolecular segment, (α1 ? α2) = ?(82 ± 8) × 10?25 cm3, is determined from the results of birefringence measurements in benzyl alcohol. For aqueous solutions, a strong concentration dependence of the specific anisotropy of solution is obtained, a result that may be explained by the heterogeneity of coils. A model allowing for this heterogeneity is suggested. It makes it possible to fit the concentration dependence to a hyperbolic function, to separate contributions of heterogeneity anisotropy and form anisotropy to the birefringence of a solution, and to estimate the segment asymmetry parameter as p = 3.0 ± 0.5. |
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