Formation of enrichment layers in thin polymer films: The influence of single chain dynamics

Abstract

We study the influence of single-chain dynamics on the collective dynamics during the formation of enrichment layers near walls that attract one species of polymers in a binary blend. This is done by using different dynamic extensions of self-consistent field theory for polymer blends confined between two hard walls. In dynamic self-consistent field theory the densities are evolved in time and the use of an Onsager coefficient proportional to the monomer densities represents the dynamics of pointlike particles. The method of the external potential dynamics makes use of the temporal propagation of the effective external fields. A constant Onsager coefficient in this method implies nonlocal dynamics of polymers. The comparison between the nonlocal dynamics and the local dynamics of pointlike particles shows distinct differences in the density profiles during the formation of enrichment layers: local dynamics leads to a quick process and a narrow depletion layer, whereas the nonlocal dynamics leads to a slower enrichment and wider depletion layers. To validate the self-consistent field results we employ corresponding Monte Carlo simulations using the bond fluctuation model that maps the polymer chains on a coarse-grained lattice. A quantitative comparison of the density profiles reveals better agreement of the simulation results with those achieved with the external potential dynamics method.