کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5413573 | 1506627 | 2008 | 6 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Nonlinear variation of optical absorption and rheological behavior with concentration in dispersed poly(vinyl pyrrolidone) of small molecules in water
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
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چکیده انگلیسی
Interaction of poly(vinyl pyrrolidone) PVP with water molecules is of interest for possible drug applications and other chemical reactions. In this purview, aqueous solutions in 0.1-10 g/dl PVP were studied in terms of the optical absorption spectrum and rheology in this work. The rheology determines a polymer nature of the solutions in the selective concentrations (C). A strong absorption band, which occurs in an asymmetric shape at wavelength maximum λmax = 247 nm (Ï âÏâ electronic transition) in 10 g/dl PVP, shifts nonlinearly to a λmax value as small as 222 nm upon decreasing the C-value. The λmax follows a parabolic path as a function of increasing the C-value in this range. The band narrows down from an average 55 nm bandwidth Îλ in 10 g/dl PVP to a value 15 nm in the 0.1 g/dl PVP in predominant intramolecular interactions in selective conformers in dilute solutions. An opposite effect of red-shift and band broadening occurs in solute-solvent interactions. The viscosity thus increased hardly from a value 10 Ã 10â 4 Pa s in the 0.1 g/dl PVP to as much as 37 Ã 10â 4 Pa s (i.e., as large a factor â¼Â 4) in the 10 g/dl PVP at a shear rate 100 sâ 1. A weak concentration-induced viscosification of dispersed PVP molecules in water is important for the medicinal values.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Liquids - Volume 137, Issues 1â3, 10 January 2008, Pages 58-63
Journal: Journal of Molecular Liquids - Volume 137, Issues 1â3, 10 January 2008, Pages 58-63
نویسندگان
A. Mishra, V.K. Srivastava, S. Ram,