Self-avoiding polymer trapped inside a cylindrical pore: Flory free energy and unexpected dynamics

Abstract

We study the elastic and dynamic behavior of a self-avoiding chain confined inside a cylindrical pore using a Flory-type approach and molecular-dynamics simulations. In the Hookean regime, we find that the effective spring constant of the chain is given by keff approximately N(-1)D(-gamma), where N is the number of monomers and D the diameter of the pore. While the Flory approach reproduces the earlier scaling result gamma=1/3, our simulations confirm a more recent numerical result gamma approximately 0.9 for the computationally accessible regimes. In the absence of hydrodynamic interactions, the relaxation dynamics of a stretched-and-released chain in this regime is characterized by a global relaxation time tauR approximately N2Dgamma with the same exponent gamma for keff. We also discuss how chain relaxation under confinement is influenced by hydrodynamic interactions. In the presence (or absence) of the hydrodynamic interaction, the finite-size effect observed in keff is shown to persist in chain relaxation, resulting in tauR markedly different from previous results.