Frequency-dependent viscosity of linear polymer chains. Influence of non-Gaussian effects

We have performed Brownian dynamics simulations of Gaussian and semirigid isolated linear chains, with fluctuating hydrodynamic interactions, both with and without intrachain excluded volume interactions. From the simulated dynamic trajectories, we have calculated the stress correlation function. And from this function, after applying a detailed numerical procedure, we have obtained the frequency-dependent complex viscosity. The influence of the rigidity and the excluded volume interactions on this property is discussed as a function of the chain size. While the introduction of semirigid bonds in the chain model creates noticeable differences only in the high frequency region of the viscoelastic moduli, the effect of excluded volume interactions is much more notorious at any frequency, yielding results which are very similar to experimental measurements of dilute polymer solutions in good solvent conditions.