Viscoelasticity of Dilute Solutions of Semiflexible Polymers

We show using Brownian dynamics simulations and theory how the shear relaxation modulus G(t) of dilute solutions of relatively stiff semiflexible polymers differs qualitatively from that of rigid rods. For chains shorter than their persistence length, G(t) exhibits three time regimes: At very early times, when the longitudinal deformation is affine, G(t) \sim t^{-3/4}. Over a broad intermediate regime, during which the chain length relaxes, G(t) \sim t^{-5/4}. At long times, $G(t) mimics that of rigid rods. A model of the polymer as an effectively extensible rod with a frequency dependent elastic modulus B(\omega) \sim (i \omega)^{3/4} quantitatively describes G(t) throughout the first two regimes.