Self-Assembly of Hierarchical Silicon-Containing Block Copolymers with Cross-Linkable 3 nm Smectic Motifs for Nanopatterning and Osmotic Energy Conversion Membranes

Highly-dense small-feature-size nanopatterns and nanoporous membranes are important in advanced microelectronics, nanofiltration, and biomimic device manufacturing. Here, we report the synthesis and self-assembly of a series of high-interaction-parameter (high-chi) silicon-containing hierarchical block copolymers (BCPs) with cross-linkable subordering chalcone motifs, which possess both an intrinsic native etching contrast for nanofabrication and cross-linkability under ultraviolet light for generating free-standing membranes. BCPs with a volume fraction of chalcone block of 55-74% form ordered primary nanostructures with period 15-22 nm including lamellae, double gyroid, hexagonally packed cylinders, and body-centered cubic spheres of the minority Si-containing block. The majority PChMA block self-assembles into a highly ordered 3 nm smectic sublattice, and cross-linking after self-assembly enables the formation of free-standing isoporous membranes. Both silicon oxide nanopatterns and free-standing nanoporous osmotic energy conversion membranes are generated by etching films of these BCPs. This work demonstrates that the combination of hierarchical ordering and cross-linkable motifs in a high-interaction parameter BCP enables applications in both nanofabrication and free-standing functional porous membranes.