Fig. 2: Non-native structures.
From: Priming self-assembly pathways by stacking block copolymers
Three examples of non-native structures that appear as a result of pathway-primed self-assembly. For each, top-view and cross-sectional SEM are shown (scale bars 100 nm) on top, and corresponding molecular dynamics (MD) simulations below. a Local phase separation can occur on a faster timescale than chain interdiffusion, giving rise to layered configurations such as parapet, formed by annealing a C/L bilayer (L75 bottom layer was preannealed 1200 s at 250 °C, second layer C67, bilayer annealed 15 s at 250 °C). b The existence of two chain types allows otherwise defective structures to be stabilized, such as perforations in an HPL (L36/C67 bilayer annealed 300 s at 270 °C). A map of the local chain composition (fC,local) highlights how C chains concentrate around high-curvature perforations, stabilizing them. c Interfacial energetics can drive towards non-uniform distribution of chains, which leads to the formation of the aqueduct morphology (bilayer where each layer is a blend of C67:L75, annealed 1200 s at 250 °C). (right) The fraction of C chains (fC) through the film depth (normalized height z/h) highlights how the different morphologies have distinct underlying chain spatial distributions.
