Rational design and size regulation of unimolecular nanoparticles for constructing diverse superlattices in soft matter

Abstract

Different from the classical self-assembly process in soft matter, we have proposed the concept of unimolecular nanoparticles (UMNPs), which act as spherical motifs and can directly pack into ordered structures (superlattices) in a single step. However, the design principles of UMNPs have been so far vague and qualitative. Here we have developed a series of giant molecules synthesized from β-cyclodextrin (βCD) and polyhedral oligomeric silsesquioxane (POSS). These samples all present spherical packing superlattices and further prove to be UMNPs. By changing the linkages between βCD and OPOSS, the volume of these UMNPs can be adjusted between 44 and 96 nm³, which is very much enlarged compared with our previous studies. We outline the rules for constructing UMNPs: a highly branched core, rigid ligands and short linkers between the core and the ligands are needed. Binary blending of these UMNPs also offers us various unusual superlattices (NaZn₁₃, AlB₂, and C14). Among them, the binary blends of two different βCD-type UMNPs lead to the first unimolecular-level binary superlattice, which can more precisely mimic the phase behaviour of nanocrystal superlattices natured with one-step self-assembly. In general, our study of βCD-type UMNPs enables customization in both size and softness, offering a valuable tool for investigating more intricate nanostructures and advanced functional materials.