The dielectric and conductometric properties of aqueous solutions of xanthan, an ionic polysaccharide consisting of a linear cellulosic backbone with three-sugar side chains, have been extensively investigated over two frequency ranges, from 1 kHz to 10 MHz and from 1 MHz to 1 GHz by means of frequency domain dielectric spectroscopy, at different polyion concentrations and at two different temperatures, above room temperature, in the range where an order-disorder transition occurs. The dielectric spectra have been analyzed on the basis of two contiguous dielectric dispersions described by a Cole-Cole relaxation function, and the parameters have been discussed on the basis of currently accepted dielectric relaxation theories of polyelectrolyte solutions. For the majority of the polyion concentrations employed, a semidilute regime occurs and the two observed dielectric relaxation are ascribed to counterion fluctuations on two different scale lengths, the first associated to the polymer contour length and the second one to an average distance between charged groups of adjacent polyions. Moreover, these measurements suggests that a conformational transition occurs at temperatures above 40 degrees C with the consequent formation of an extended three-dimensional network. This transition results in a particular behavior of the dielectric relaxation on the polymer concentration.

Bordi, F., Cametti, C., Paradossi, G. (1995). Radiowave dielectric properties of xanthan in aqueous solutions. THE JOURNAL OF PHYSICAL CHEMISTRY, 99(1), 274-284 [10.1021/j100001a043].

Radiowave dielectric properties of xanthan in aqueous solutions

PARADOSSI, GAIO
1995-01-01

Abstract

The dielectric and conductometric properties of aqueous solutions of xanthan, an ionic polysaccharide consisting of a linear cellulosic backbone with three-sugar side chains, have been extensively investigated over two frequency ranges, from 1 kHz to 10 MHz and from 1 MHz to 1 GHz by means of frequency domain dielectric spectroscopy, at different polyion concentrations and at two different temperatures, above room temperature, in the range where an order-disorder transition occurs. The dielectric spectra have been analyzed on the basis of two contiguous dielectric dispersions described by a Cole-Cole relaxation function, and the parameters have been discussed on the basis of currently accepted dielectric relaxation theories of polyelectrolyte solutions. For the majority of the polyion concentrations employed, a semidilute regime occurs and the two observed dielectric relaxation are ascribed to counterion fluctuations on two different scale lengths, the first associated to the polymer contour length and the second one to an average distance between charged groups of adjacent polyions. Moreover, these measurements suggests that a conformational transition occurs at temperatures above 40 degrees C with the consequent formation of an extended three-dimensional network. This transition results in a particular behavior of the dielectric relaxation on the polymer concentration.
1995
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore CHIM/02 - CHIMICA FISICA
English
Con Impact Factor ISI
CHARGED LINEAR MACROMOLECULES; INDUCED CONFORMATIONAL TRANSITION; POLY-ELECTROLYTE SOLUTIONS; DOUBLE-STRANDED HELIX; LOW IONIC-STRENGTH; XANTHOMONAS-CAMPESTRIS; EXTRACELLULAR POLYSACCHARIDE; LIGHT-SCATTERING; COUNTERION CONDENSATION; POLY(L-GLUTAMIC ACID)
Bordi, F., Cametti, C., Paradossi, G. (1995). Radiowave dielectric properties of xanthan in aqueous solutions. THE JOURNAL OF PHYSICAL CHEMISTRY, 99(1), 274-284 [10.1021/j100001a043].
Bordi, F; Cametti, C; Paradossi, G
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/44561
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