Zusammenfassung
Alginates are naturally occurring biocompatible polysaccharides. They have a broad range of applications, mainly in connection to their ability to control the rheol. of aq. solns. Specifically, addn. of a small amt. of alginate (10% wt) leads to a ~100-fold increase in viscosity. Here we explore whether that pronounced retardation of the long-range correlations is accompanied by mol.-level ...
Zusammenfassung
Alginates are naturally occurring biocompatible polysaccharides. They have a broad range of applications, mainly in connection to their ability to control the rheol. of aq. solns. Specifically, addn. of a small amt. of alginate (10% wt) leads to a ~100-fold increase in viscosity. Here we explore whether that pronounced retardation of the long-range correlations is accompanied by mol.-level changes of the water structure. We employ viscometry, dielec. spectroscopy (DS) and femtosecond IR (fs-IR) pump-probe spectroscopy to study water dynamics in sodium alginate solns. Remarkably, despite the large rheol. effects of alginates in soln., the rotational dynamics of water are remarkably similar to those obsd. in bulk water. Only a small subensemble of water mols. is slowed down significantly, amounting to 6 ± 2 water mols. per saccharide unit. Furthermore, DS measurements reveal an addnl. ~5 water mols. to be slowed down by the counterion (Na+). Our results reveal that the effect of alginate on the dynamics of water is restricted to the first hydration shell. This indicates that the large viscosity increase is detd. by the polysaccharide network, with large water pools present between the polysaccharide chains. [on SciFinder(R)]
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