Phase transitions in block copolymer thin films: from self-consistent field theory to field theoretical simulations

Abstract

Nowadays block copolymer thin film became a standard material providing templates for nanoscience, but there still remain many fundamental questions regarding its phase transition and nanostructure alignment. In this study, we utilize three theoretical tools to investigate the formation of heterogeneous nanostructures and the effect of fluctuation. The first one is the discrete chain self-consistent field theory (DCSCFT) which provides the mean field theory of discrete bead model with the addition of finite-range interaction. We are especially interested in the effect of preferential and/or neutral interfaces on the shift of order-to-disorder transition (ODT) temperature, and the theoretical results are compared with experiments. The second one is the single chain in mean field (SCMF) simulation which allows polymer chains to make Monte Carlo moves under quasi-instantaneously updated self-consistent fields. By comparing free energy and natural period of the block copolymer phases, we systematically show that DCSCFT serves as an intermediate step between SCMF simulation and SCFT. In addition, we adopted angle dependent bond potential to simulate semiflexible polymers using bead-spring and freely-jointed chain models. It turns out that the lamellar domain has a tendency to align perpendicular to the surfaces when the chain stiffness is high. The last one is the Langevin field theoretical simulation (L-FTS). It is supposed to include the full compositional fluctuation of incompressible polymer melts, and its results are compared with the thin film ODT shifts predicted by the mean field theories.