Rheology of dextran solutions

Commercial dextran samples of molecular weight up to 2 million and concentr ation up to 30 wt.% in aqueous solutions show Newtonian viscosity behaviour . Plot of shear viscosity as a function of concentration for the 2 million Mw gives a very high critical overlap concentration of approximately 8 wt.% , while the viscosity at 25 wt.% shows a very small molecular weight depend ence, in sharp contrast to findings for flexible polymers in the semi-dilut e region. All these results point to the conclusion that the dextran molecu les are less stiff than most carbohydrates and are highly branched, so that the molecules are in a highly compact configuration in aqueous solution. ( C) 2001 Elsevier Science B.V. All rights reserved.