Molecular Nanoparticles Are Unique Elements for Macromolecular Science

摘要

In this talk, we present a unique approach to the design and synthesis of "giant molecules" based on "nano-atoms" for engineering structures across different length scales and controlling their macroscopic properties. Herein, "nano-atoms" refer to shape-persistent molecular nanoparticles (MNPs) with precisely-defined chemical structures and surface functionalities that can serve as elemental building blocks for the precision synthesis of "giant molecules" by methods such as a sequential click approach. Typical "nano-atoms" include those based on fullerenes, polyhedral oligomeric silsesquioxanes, polyoxometalates, and folded globular proteins. The resulting "giant molecules" are precisely-defined macromolecules. They include, but are not limited to, giant surfactants, giant shape amphiphiles, and giant polyhedra. Giant surfactants are composed of "nano-atoms" tethered with flexible polymer tails of various compositions and architectures at specific sites that have drastic chemical differences such as amphiphilicity. Giant shape amphiphiles are built up by covalently-bonded molecular segments with distinct shapes where the self-assembly is driven by the shape of the molecular segment as well as the chemical interaction. Giant polyhedra are either made of a large MNP or by deliberately placing "nano-atoms" at the vertices of a polyhedron. Giant molecules capture the essential structural features of their small-molecule counterparts in many ways but possess much larger sizes; therefore, they are recognized in some cases as size-amplified versions of those counterparts and often, they bridge the gap between small-molecules and traditional macromolecules. Highly diverse, thermodynamically stable and metastable hierarchal structures are commonly observed in the bulk, thin-film, and solution states of these giant molecules. Controlled structural variations by precision synthesis further reveal a remarkable sensitivity of their self-assembled structures to the primary chemical structures. Unconventional nanostructures can be obtained in confined environments or through directed self-assembly. All the results demonstrate that MNPs are unique elements for macromolecular science, providing a versatile platform for engineering nanostructures that are not only scientifically intriguing, but also technologically relevant.