(272a) Diblock Polymer Network Phases Confined to a Thin Film

Ordered block polymer phases confined to a thin film are of practical interest for various applications, from nanolithography to optical metamaterials to filtration membranes. Thin-film confinement is also a way to alter the phase behavior of the polymer system, providing a set of tunable parameters that can be used to drive formation of new materials without the need for increasingly complex polymer architectures. However, the effect of thin-film confinement on many block polymer phases is still quite poorly understood, particularly for the three-dimensionally bicontinuous network phases. In this study, we use self-consistent field theory to model the equilibrium thermodynamics of thin films containing AB diblock polymers that form the double-gyroid network phase in the bulk. We first describe the distortions and symmetry breaking that occur due to the presence of the film boundaries. These distortions determine the most stable orientation of the double-gyroid phase and the relative stability of other network phases. Phase diagrams are then presented, revealing that the double-gyroid phase remains stable down to very small film thicknesses, and that preferential wetting can change the preferred gyroid orientation. These results demonstrate that thin-film network phases in various orientations can be obtained through block polymer self-assembly, and provide clarity into the effect of confinement on these types of phases.