Priming Self-Assembly Pathways by Stacking Individual BCP Layers

Block copolymers (BCPs) are a versatile class of macromolecules that spontaneously form well-defined nanostructured arrays that can vary in shape and periodicity. Nonequilibrium assembly strategies hold considerable promise to expand the library of self-assembled nanoscale patterns through exploiting self-assembly’s adaptive nature. We developed a pathway priming strategy where BCP initial configurations (i.e., the initial spatial distribution of chains) are engineered to be structured in nontrivial ways. This is accomplished by sequentially flow coating distinct BCP materials to form layered initial states. Allowing self-assembly to proceed from these non-equilibrium initial states gives rise to a succession of previously inaccessible intermediate states We present a library of exotic motifs non-native to conventional BCP thin-films, including vertical perforated lamellae, aqueduct (lines-on-dots), parapet (dots-on-lines), and criss-cross lamellae networks. Pathway priming leverages self-assembly processes that are manifestly pathway-dependent and expand the accessible range of structures, in turn enabling material properties that surpass their equilibrium analogs.