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We discuss the hydrodynamic radius R-H of polymer chains in good solvent, and show that the leading order correction to the asymptotic law R(H)proportional toN(nu) (N degree of polymerization, nuapproximate to0.59) is an "analytic" term of order N-(1-nu), which is directly related to the discretization of the chain into a finite number of beads. This result is further corroborated by exact calculations for Gaussian chains, and extensive numerical simulations of different models of good-solvent chains, where we find a value of 1.591+/-0.007 for the asymptotic universal ratio R-G/R-H, R-G being the chain's gyration radius. For Theta chains the data apparently extrapolate to R-G/R(H)approximate to1.44, which is different from the Gaussian value 1.5045, but in accordance with previous simulations. We also show that the experimentally observed deviations of the initial decay rate in dynamic light scattering from the asymptotic Benmouna-Akcasu value can partly be understood by similar arguments. (C) 2002 American Institute of Physics.
