Longitudinal relaxation of initially straight flexible and stiff polymers

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 to(2)(0)-R(parallel to)(2)similar toNt(1/2) at early intermediate times is shown to constitute a universal behavior for any chain stiffness caused by a quasisteady Tsimilar toNt(-1/2) relaxation of tensions associated with the deforming action of the Brownian forces. Stiff chains with a persistence length Egreater than or equal toN are shown to exhibit a late intermediate-time longitudinal reduction R-parallel to(2)(0)-R(parallel to)(2)similar toN(2)E(-3/4)t(1/4) associated with a Tsimilar toN(2)E(-3/4)t(-3/4) relaxation of tensions affected by the deforming Brownian and the restoring bending forces.