Materials comprising porous structures, often in the form of inter-connected concave cavities, are typically assembled from convex molecular building blocks. The use of nanoparticles with a characteristic non-convex shape provides a promising strategy to create new porous materials, an approach that has been recently employed with cage-like molecules to form remarkable liquids with “scrabbled” porous cavities. Nonconvex mesogenic building blocks can be engineered to form unique self-assembled open structures with tunable porosity and long-range order that is intermediate between that of isotropic liquids and crystalline solids.
Research at the University of Manchester proposes the design of highly open liquid-crystalline structures from rigid nanorings with unique classes of geometry. By exploiting the entropic ordering characteristics of athermal colloidal particles, it demonstrates that nonconvex rings of high symmetry with large internal cavities interlock within a two-dimensional layered structure leading to the formation of distinctive liquid crystalline smectic phases. These novel smectic phases possess uniquely high free volumes of up to >95%, a value significantly larger than the 50% that is typically achievable with the smectic phases formed by more conventional convex rod- or disc-like mesogenic particles.