The relaxation mechanism of an initially straight flexible or stiff polymer chain of length $N$ in a viscous solvent is studied through Brownian dynamics simulations covering a broad range of time scales. After the short-time free diffusion, the chain's longitudinal reduction $R_{\parallel }^2(0)-R_{\parallel }^2\sim N{t}^{1/2}$ at early intermediate times is shown to constitute a universal behavior for any chain stiffness caused by a quasisteady $T\sim N{t}^{-1/2}$ relaxation of tensions associated with the deforming action of the Brownian forces. Stiff chains with a persistence length $E\ge N$ are shown to exhibit a late intermediate-time longitudinal reduction $R_{\parallel }^2(0)-R_{\parallel }^2\sim N^2{E}^{-3/4}{t}^{1/4}$ associated with a $T\sim N^2{E}^{-3/4}{t}^{-3/4}$ relaxation of tensions affected by the deforming Brownian and the restoring bending forces.

• Received 22 April 2004

DOI:https://doi.org/10.1103/PhysRevLett.93.217801