Dynamic scaling in dilute polymer solutions: The importance of dynamic correlations

The swelling alpha(H) of the hydrodynamic radius of a polymer, obtained using Brownian dynamics simulations of the continuum Edwards model, is found to obey a crossover in the excluded-volume parameter z, which is significantly different from that observed for the swelling alpha(g) of the radius of gyration. It is shown that this difference arises due to contributions from dynamic correlations to the diffusivity, which are ignored in the commonly used definition of hydrodynamic radius based on the Kirkwood expression. Simulated values of alpha(H) are found to be in remarkable agreement with experimental measurements