Molecular Nanoparticles Are Unique Elements for Macromolecular Science: From “Nanoatoms” to Giant Molecules

Abstract

In this Perspective, we present a unique approach to the design and synthesis of giant molecules based on “nanoatoms” for engineering structures across multiple length scales and controlling their macroscopic properties. Herein, “nanoatoms” 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 sequential “click” approach. Typical “nanoatoms” include those MNPs 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 polymer tail-tethered “nanoatoms” where the two components have drastic chemical differences to impart amphiphilicity. Giant shape amphiphiles not only are built up by covalently bonded MNPs of distinct shapes where the self-assembly is driven by chemical interactions but also are largely influenced by the packing constraints of each individual shape. Giant polyhedra are either made of a large MNP or by deliberately placing “nanoatoms” at the vertices of a polyhedron. In general, giant molecules capture the essential structural features of their small-molecule counterparts in many ways but possess much larger sizes. They are recognized in certain 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.

Rational design of nanomaterials from assembly and reconfigurability of polymer-tethered nanoparticles

“…With powerful tools in hand both to synthesize TNP-building blocks of arbitrary complexity, [30] and to simulate their assembly behavior, [17] it is tempting to begin exploring complex assemblies that could lead to new applications and devices. [91][92][93][94] A pressing challenge is unifying these tools before moving into application.…”

“…[21,27] This technique has recently been used to interchange nearly every portion of the building block. [21,[30][31][32] Examples include the ability to interchange head groups from polyhedral oligomeric silsesquioxane (POSS) cages to gold NPs, as well as to exchange polymer types such as polystyrene or poly(methyl methacrylate) (PMMA); additionally, the size, number, and placement of these chemically distinct domains can be controlled, such as tethering a single corner of a POSS molecule with one or more polymer tethers. [21,27,[30][31][32] Related methods have been used to create additional types of polymer-NP composite blocks.…”

“…As mentioned previously, direct realizations of TNP assembly have come from the use of "click chemistry" to attach tethers to NPs directly, creating gram quantities of material. [21,27,30] TNPs created with this method have been used to self-assemble many of the same structures observed in block copolymers, but with the additional benefit of controlling the specific material composition of each domain of the material. By tuning various portions of the block geometry, different types of structures are accessible.…”

Understanding the Regioselective Hydrolysis of Human Serum Albumin by Zr(IV)-Substituted Polyoxotungstates Using Tryptophan Fluorescence Spectroscopy

“…These molecules are an assemblage of oxo-bridged early transition metals (mostly Mo, W, and V) in their highest oxidation state [13,14]. Their chemical and physical properties can be tuned, giving rise to a large number of possible applications in the fields of catalysis [15][16][17], material science [18][19][20] and medicine [21][22][23][24]. Moreover, the removal of one or more of the addenda atoms from the POM framework results in the formation of a lacunary species, which can coordinate different metal ions, resulting in the formation of metal-substituted POMs [11,25].…”

Janus colloidal copolymers

“…Unconventional new superstructures based on JCCPs are anticipated. As an example, large molecules like polyhedral oligomeric silsesquioxane, buckminsterfullerene and polyoxometalate can self-organize into new superstructures after conjugation of polymer chains onto one side by sequential "click" steps [5]. This approach relies on precise control of the number of clickable sites on the large molecules.…”