Supramolecularly Directed Area-Selective Photo-Cross-Linking of Block Copolymers for Robust Nanostructures

Abstract This study introduces a versatile method for fabricating cross-linked, hierarchically ordered multilayer nanostructures from PS-b-P4VP block copolymer (BCP) films. The approach combines supramolecular hydrogen bonding of cinnamic acid selective to the P4VP block, followed by UV-induced photocycloaddition to form truxillic acid cross-links. Efficient cross-linking was achieved under low UV-irradiance that resulted in densified films with excellent film retention (∼99%). Swelling studies showed that the BCP film is solvent-stable and exhibits limited swelling despite domain-selective cross-linking. Interestingly, the non-cross-linked domains remain available for solvent uptake, leading to morphological reconstruction. These solvent-stable films were further used to fabricate layer-by-layer multilayer architectures while preserving the laterally ordered nanoscale morphologies generated by BCP microphase separation. The combined findings establish a versatile platform that integrates block copolymer self-assembly with layer-by-layer nanofabrication, providing tunable multilayer nanostructures for applications in grayscale lithography, membranes, directed self-assembly, and multifunctional coatings.