Block copolymer self-organization vs. interfacial modification in bilayered thin-film laminates

Abstract

Block copolymers remain one of the most extensively studied and utilized classes of macromolecules due to their extraordinary abilities to (i) self-assemble spontaneously into a wide variety of soft nanostructures and (ii) reduce the interfacial tension between, and thus compatibilize, immiscible polymer pairs. In bilayered thin-film laminates of immiscible homopolymers, block copolymers are similarly envisaged to stabilize such laminates. Contrary to intuition, we demonstrate that highly asymmetric block copolymers can conversely destabilize a laminate, as discerned from macroscopic dewetting behavior, due to dynamic competition between copolymer self-organization away from and enrichment at the bilayer interface. The mechanism of this counterintuitive destabilization is interrogated through complementary analysis of laminates containing mixtures of stabilizing/destabilizing diblock copolymers and time-dependent Ginzburg–Landau computer simulations. This combination of experiments and simulations reveals a systematic progression of supramolecular-level events that establish the relative importance of molecular aggregation and lateral interfacial structuring in a highly nonequilibrium environment.