The size and shape of amylopectin: A study using pulsed‐field gradient nuclear magnetic resonance

Self‐diffusion coefficients have been obtained over a range of concentrations for both polymer and solvent in amylopectin/dimethylsulfoxide and amylopectin/water systems. The measurements were made using pulsed‐field gradient nuclear magnetic resonance (PFG‐nmr). The implications of macromolecule polydispersity to the interpretion of the PFG‐nmr experiment have been considered. Measurements of the self‐diffusion coefficients of solute and solvent are shown to provide an effective probe of polymer size and shape. Such measurements demonstrate that in dimethylsulfoxide, wheat starch amylopectin molecules are highly planar with Mw of order 106. In contrast, amylopectin in water is an aggregate with a more spherical shape and has a volume some 400 times larger than the single molecule.