Complex 2D Square Nanopatterns via Intrinsic Anisotropic Confinement

Square patterns are integral to industry-standard rectilinear coordinate systems, yet fabricating complex two-dimensional (2D) square patterns remains a formidable challenge. Herein, we report the emergence of complex 2D nanopatterned morphologies with p4mm and p4gm plane group symmetries and ultrasmall feature sizes (∼3 nm) in three-component bolaform giant surfactants which consist of a central polystyrene chain flanked by a perfluoroalkyl-functionalized polyhedral oligomeric silsesquioxane (FPOSS) at one terminus and a size-tunable oligosiloxane-functionalized POSS (Si_xPOSS) at the other. The structural evolution proceeds through a hierarchical phase-separation mechanism: an initial primary segregation between the highly immiscible FPOSS and mixed PS/Si_xPOSS domain is followed by secondary phase separation between the weakly incompatible PS and Si_xPOSS within their shared nanoconfined region. Successful formation of these unconventional structures relies on a hierarchy of interaction strengths to direct self-assembly at different length scales and on the intrinsic anisotropic confinement formed in situ. The final morphology is sensitive to molecular parameters such as size, shape, and volume asymmetry of the terminal nanoparticles. This work establishes a versatile molecular platform for engineering complex 2D superlattices, offering a promising avenue for advanced nanolithography and integrated circuit fabrication in industry.