Solvent-Mediated Self-Assembly in Thin Films of Block Copolymer-Based Supramolecules

Block copolymer-based supramolecules offer a versatile platform to generate hierarchical assemblies. However, the system is complex and there is a limited understanding of the self-assembly process which is critical for precise control of the nanostructure. Here, we investigate the effects of small molecule loading and the solvent annealing condition on thin films of supramolecules on flat and patterned substrates. The studies show that small molecule loading and the solvent annealing condition greatly affect the assembly rate, grain size, and feature size. On the line-patterned surface, the microdomains can be macroscopically aligned with an order parameter as high as 0.9 without sacrificing commensurability between the pattern feature size and periodicity. Rather, the supramolecule self-assembles into structures with two distinct periodicities. The feature sizes are 0.9 and 1.33 times of that on a flat surface in the trench and on the mesa, respectively. The observed heterogeneous nanostructures are attributed to the redistribution of the small molecule and self-adaptation of the supramolecule to release energy costs that arise from incommensurability. The present study opens a new path to enrich the diversity of morphologies afforded by a single self-assembly system