Light Scattering and Viscosity Behavior of Dextran in Semidilute Solution

Abstract

The solution properties of three dextrans in water with molar masses of 334 000, 506 000 and 2 660 000 g/mol were investigated in a concentration range of 0.1−30%, 0.1−40% and 0.05−65% w/v, respectively. Static and dynamic light scattering, viscometry, and rheological techniques were applied. The forward scattering (at scattering angle θ = 0) could be separated in contributions resulting from repulsive interactions and the true molar mass M w(c) at concentration c. A similar procedure was applied to the apparent radius of gyration to derive the true radius of gyration R g(c). A mean field and a scaling approach were applied, and the difference in the results obtained are discussed. Both molecular parameters remained unchanged up to three times the overlap concentration. At higher concentrations a pronounced increase in M w(c) and R g(c) indicated association. The high M w dextran developed a reversible gel point and critical behavior of percolation theory. The time correlation function of dynamic light scattering displayed fast and slow motions where the slow motion was assigned to clusters. Separating the effect of thermodynamic interactions from the mutual diffusion coefficient allowed the self-diffusion coefficient to be obtained, which is governed by hydrodynamic interactions. The range of this interaction was estimated and compared with the cluster size. The zero shear viscosity showed common behavior with a fairly weak increase in the dilute regime and a steep increase at higher concentrations.

Composition and Heavy Oil Rheology

“…Ioan et al [10] observed this difference in dextran solutions. They showed that C* can be ten times higher than C**.…”

Neutral Polymeric Surfactants Derived from Dextran: A Study of Their Aqueous Solution Behavior

“…½Z that can be considered as a ratio of two overlap concentrations, [17] one involving thermodynamic interactions ½C…”

“…[12] The combination of viscometric measurements and light scattering techniques [static (SLS) and dynamic (DLS)] has been shown to provide useful information concerning the solution behavior of amphiphilic polymers [13][14][15] and particularly that of polysaccharides and polysaccharide derivatives. [16][17][18][19][20] The solution properties of neutral polysaccharides like dextran and pullulan have been characterized by SLS and DLS and compared. [16,17,19,21 -23] Extensive viscometric studies of dextran in various polar solvents have been performed by Güner and coworkers.…”

Optical and Magnetooptical Properties of Clinical Dextrans

“…The c 2 value can be correlated with critical overlap concentration (coc) -c * which is known for dextran and have been evaluated by different methods [14]. However, characteristic concentration c 1 was not observed and evaluated for dextran but tentatively it may be correlated with initial overlap concentration or so-called critical aggregation concentration (cac).…”