THE INFLUENCE OF CHAIN-LENGTH ON THE HYDRODYNAMIC BEHAVIOR OF AMYLOSE

Dilute aqueous solutions of amylose (< 1.5 mg/mL) have been studied by static and dynamic light-scattering techniques. The samples used were monodisperse fractions which covered molecular weights in the range 2 x 10(4) - 1 x 10(6). The hydrodynamic radii (R(H)) were computed from the translational diffusion coefficient at infinite dilution. The characteristic exponents for the dependence of the molecular weight on the dimensions of the polymer chain in good solvents, determined as nu(G) for R(G) values and nu(H) for R(H) values, respectively, were close to the value predicted for a theta solvent in 0.1M KCl (nu(H) 0.47, nu(G) 0.51) and for a good solvent in 0.1M KOH (nu(H) 0.57, nu(G) 0.67). The ratio zeta = R(H)/R(G) is discussed, as is the stiffness of the polymer in those solvents on the basis of the persistence length.