Domain Spacing and Composition Profile Behavior in Salt-Doped Cyclic vs Linear Block Polymer Thin Films: A Joint Experimental and Simulation Study

Abstract

Herein, we leveraged lithium salt doping of linear and cyclic block polymers (BPs) in thin film geometries to demonstrate how BP architecture influences self-assembled nanofeature sizes and interfacial widths in nanostructured thin films as a function of segregation strength. To mitigate potential issues with sample-to-sample variability and time-consuming synthesis, we used a single linear BP specimen that was ring-closed to generate an analogous cyclic BP, and we mixed the cyclic and/or parent linear BP with a lithium salt to modulate effective segregation strength (χeffN). Based on X-ray reflectivity analyses, cyclic polystyrene-block-poly[oligo(ethylene glycol) methacrylate] BP thin film specimens had ∼20% smaller domain spacings than their linear counterparts at all χeffNs and lower absolute sensitivities to changes in χeff at identical molecular weights. We also report the first direct measurements of interfacial widths in cyclic BP assemblies, which quantitatively demonstrated that interfacial mixi...