Macromolecules, Vol.38, No.15, 6598-6609, 2005
The role of environment in structural relaxation of miscible polymer blends
A system of six miscible blends formed from four saturated hydrocarbon polymers is investigated using molecular dynamics simulation. Using this system, we isolate the role of the environment in the dynamic response of each material. Variations due to features inherent to each material are minimized by maintaining the same effective concentration for all components in all blends. This results from the four components having similar self-concentrations arising from chain connectivity and using 50/50 composition for the blends. Variations due to concentration fluctuations are minimized because the chain lengths accessible in simulations are limited. The dynamic response is measured via the self-intermediate scattering function, and its counterpart measuring collective motion, as would be observed in incoherent and coherent quasielastic neutron scattering experiments. For self-motion, significant variations between materials in the environmental effect on dynamic response are observed. These variations are linked to intermolecular packing over the length scale of a Kuhn segment. When collective motion is considered, variations in dynamic response to environment between materials are greatly reduced.