Effects of Interfacial Interactions and Film Thickness on Nonequilibrium Hierarchical Assemblies of Block Copolymer-Based Supramolecules in Thin Films

The macroscopic alignment of hierarchical assemblies of block copolymer- (BCP-) based supramolecules in thin films is investigated as a function of interfacial interaction and film thickness. We specifically focus on how these two parameters affect the longevity of supramolecular morphology where BCP microdomains are oriented normal to the surface. As the film thickness increases above one equilibrium period of supramolecular assembly, hierarchical assemblies with vertically aligned BCP microdomains can be long-lived metastable state when the volume fraction of the comb block is higher than 0.5. The perpendicular-to-parallel reorientation process strongly depends on the strength of the surface field, the chemical nature of the surface, and the film thickness. The longevity of the vertically aligned assemblies can be attributed to two reasons. One is the spatial distribution of small molecules that mediate the interactions between each BCP block with the underlying substrate and the other is the comb coil architecture of the supramolecule. These studies provide critical guidance to manipulate assemblies of supramolecules in thin films and access transient nanostructures.