Interface repulsion and arrest of coarsening in thin films of homopolymer blends due to thermal oscillations*

In equilibrium the interface potential that describes the interaction between two AB interfaces in a binary blend of A and B homopolymers is attractive, and this interface attraction gives rise to a coarsening of the blend morphology even in the absence of interface curvature. Using continuum models we demonstrate that the time-periodic variation of the Flory-Huggins parameter (or temperature or solvent concentration) qualitatively alters this behavior, i.e., for suitable parameter we find that AB interfaces repel each other and adopt a well-defined distance. We explore for which oscillation periods and amplitudes this interface repulsion occurs and how the preferred interface distance depends on these parameters. Using particle-based simulations we explicitly demonstrate that this dissipative self-assembly of a homopolymer blend results in a lamellar structure with multiple planar interfaces in a thin film geometry.