External potential dynamic studies on the formation of interface in polydisperse polymer blends

The formation of interface from an initial sharp interface in polydisperse A/B blends is studied using the external potential dynamic method. The present model is a nonlocal coupling model as we take into account the correlation between segments in a single chain. The correlation is approximately expressed by Debye function and the diffusion dynamics are based on the Rouse chain model. The chain length distribution is described by the continuous Schulz distribution. Our numerical calculation indicates that for a wide range of the Flory-Huggins parameter the broadening of interface with respect to time obeys a power law at early time, and the power indices are the same for both monodisperse and polydisperse blends. The power index is larger than that in the local coupling model. However, there is no unified scaling form of the broadening of the interface width if only the interfacial width at equilibrium is taken into account as the characteristic length of the system, because the correlation makes an extra characteristic length in the system, and the polydispersity is related to this length.