Self-assembling nanocomposite tectons: Making ordered nanomaterials from soft building blocks

The synthesis of colloidal crystals is often analogized to atomic crystallization because the two types of materials possess similar unit cell geometries, defect structures, and crystallization kinetics. However, colloids have several potential impediments that can obstruct their crystallization, making it difficult to achieve crystals with equivalent amounts of long-range order. Their weak interparticle forces result in a much shallower energy minimum than that of atomic bonds, and their dispersity in size as compared to perfectly uniform atoms makes adopting a well-ordered arrangement more challenging. Determining the extent to which these barriers can frustrate colloidal assembly and designing systems that can overcome them is necessary to develop functional materials based on colloidal components. In this work we discuss how Nanocomposite Tectons (NCTs) can be used to explore the similarity between colloidal and atomic matter, and how their design allows them to crystallize even when they stray significantly from perfect uniformity. NCTs consist of an inorganic nanoparticle core and a polymeric shell, with each chain terminating in a supramolecular binding group at the periphery of the NCT. Unlike many colloidal crystallization schemes that rely on entropy maximization via dense packing, NCTs have an enthalpic driving force derived from the hydrogen bonds that form between complementary particles. Here we demonstrate that colloidal crystallization dictated by enthalpically favored binding allows for significant tunability of NCT crystal quality as a result of the chosen thermal processing profile. Additionally, we show that the flexibility of NCT polymer chains allows them to circumvent challenges associated with dispersity in building block size, as nanoparticle core dispersities as high as 23% are still able to form highly ordered arrays. We conclude that NCTs’ enthalpically driven attraction and deformable polymer shell can make the NCTs resilient against poor dispersity, enabling their use as synthons for complex materials.