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Physicochemical properties of aqueous xanthan solutions: Static light scattering
Author(s) -
Gamini Amelia,
Mandel Michel
Publication year - 1994
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360340610
Subject(s) - chemistry , molar mass , radius of gyration , dispersity , ionic strength , aqueous solution , static light scattering , scattering , analytical chemistry (journal) , light scattering , dissociation (chemistry) , gel permeation chromatography , hydrodynamic radius , chromatography , polymer , polymer chemistry , organic chemistry , optics , physics , micelle
The secondary structure of xanthan in solutions of relatively low salt concentration and at room temperature has been investigated using static light scattering experiments. Additional evidence has been found for a dimeric structure at 25°C in 0.01 M NaCl. From the experimental z ‐average mean square (ms) radius of gyration, a value for the persistence length p has been estimated, taking explicitly into account the polydispersity of the three samples used, which has been established by gel permeation chromatography (GPC) measurements. The experimental particle scattering functions of the three samples are consistent with theoretical estimates for polydisperse systems with the same value of p = 65 ± 10 nm and the molar mass per unit length for a dimeric structure. This secondary structure remains unaffected by the ionic strength in the 0.005–0.0lM range. Partial aggregation seems to occur at higher NaCl concentrations. Light scattering and GPC data show that heating the xanthan 0.01 M NaCl solutions to about 70°C considerably reduces the M w of the low molar mass sample (2.3 × 10 5 ‐g·mol −1 ), contrary to what is observed for the high molar mass sample (1.8 × 10 6 ‐g·mol −1 ). These experimental findings can be accounted for by a partial temperature‐induced dissociation of the xanthan dimers according to an all‐or‐none mechanism. © 1994 John Wiley & Sons, Inc.