Predictive relation for the a-relaxation time of a coarse-grained polymer melt under steady shear

We examine the influence of steady shear on structural relaxation in a simulated coarse-grained unentangled polymer melt over a wide range of temperature and shear rates. Shear is found to progressively suppress the a-relaxation process observed in the intermediate scattering function, leading ultimately to a purely inertially dominated beta-relaxation at high shear rates, a trend similar to increasing temperature. On the basis of a scaling argument emphasizing dynamic heterogeneity in cooled liquids and its alteration under material deformation, we deduce and validate a parameter-free scaling relation for both the structural relaxation time tau(alpha) from the intermediate scattering function and the "stretching exponent" beta quantifying the extent of dynamic heterogeneity over the entire range of temperatures and shear rates that we can simulate.