Short- and intermediate-time behavior of the linear stress relaxation in semiflexible polymers

The linear viscoelasticity of semiflexible polymers is studied through Brownian Dynamics simulations covering a broad range of chain stiffness and time scales. Our results agree with existing theoretical predictions in the flexible and stiff limits; however, we find that over a wide intermediate-time window spanning several decades, the stress relaxation is described by a single power law $t^{-\alpha },$ with the exponent $\alpha$ apparently varying continuously from $1/2$ for flexible chains, to $5/4$ for stiff ones. Our study identifies the limits of validity of the $t^{-3/4}$ power law at short times predicted by recent theories. An additional regime is identified, the “ultrastiff” chains, where this behavior disappears. In the absence of Brownian motion, the purely mechanical stress relaxation produces a $t^{-3/4}$ power law for both short and intermediate times.