Programmable Nanostructural Orientation on Amorphous Phase-Separating Systems

Currently, there remains a lack of broadly applicable strategies for programming the nanostructural orientation in a bottom-up way (e.g., for those widely used amorphous phase-separating systems). This is because, for the systems lacking mesogenic units, the orientation is primarily governed by interfacial energy, which is difficult to modulate spatiotemporally. Herein, we present a strategy to make the orientation of amorphous phase-separating systems photo-programmable. Taking amorphous block copolymers as a clean model system, a persulfurated aromatic modulator that interacts with both domains can be designed, allowing a minimized interfacial energy mismatch between the two domains and the substrate, which favors perpendicular orientation. Upon light irradiation, photoinduced aggregation of the modulator redistributes its partitioning between the domains, amplifying the interfacial energy asymmetry and driving self-assembly to parallel orientation. This orientation switching is resettable through light removal. Such an orientation control strategy is fit for density multiplication of the nanostructures, and can even serve as a template for other material incorporation (e.g., introducing conductive polymers and creating a 25-fold conductivity contrast through orientation), enabling effective function expansion in practical nanotechnology.