Shape, molecular weight distribution and viscosity of amylopectin in dilute solution

This paper presents results on the properties of amylopectin in solution using a variety of physical techniques. High-pressure liquid chromatography-multiple angle laser light scattering was used as a direct means to determine not only the number-average and weight-average molecular weights of a series of five amylopectin samples, but also their molecular weight distributions. Small angle X-ray scattering using synchrotron radiation revealed strong evidence to suggest that amylopectin is a manifestly non-spherical macromolecule in aqueous solution or dimethyl sulphoxide. Shear rate-dependent viscosity measurements showed that aqueous amylopectin solutions behave as Newtonian liquids up to a high concentration, with very little evidence for shear thinning at high shear rates. Viscosity data for different concentrations and two different molecular weights were successfully plotted in a reduced form to obtain a master plot, from which estimates for the polymer overlap concentration, c*, were obtained.