Spatial Dependence of Molecular Relaxation in Deformed Polymers

We present a general framework for investigating the spatial and temporal dependence of structural anisotropy relaxation in deformed polymers by combining small-angle neutron scattering and the spherical harmonic expansion technique. Experiments on polymer melts over a wide range of molecular weights reveal that their conformational relaxation at relatively high momentum transfer (Q) and short time can be described by a simple and universal scaling law, with the relaxation rate proportional to Q. This scaling behavior, while further confirmed by coarse-grained molecular dynamics simulations, does not seem to stem from either the Rouse or reptative motions depicted in the classical models, and calls for further development in the theory of polymeric liquids under deformation and flow.