Unimolecular Nanoparticles toward More Precise Regulations of Self-Assembled Superlattices in Soft Matter.

The hierarchical self-assembly process opens up great potential for the construction of nanostructural superlattices. Precise regulation of self-assembled superlattices, however, remains a challenge. Even when the primary molecules are precise, the supramolecular motifs (or secondary building blocks) can vary dramatically. In the present work, we propose the concept of unimolecular nanoparticles (UMNPs). The UMNPs act as the supramolecular motif and directly pack into the superlattices. A highly branched giant molecule is presented. We systematically explore its conformations and the superlattice of this giant molecule. Moreover, intriguing complex phases are discovered when blending this UMNP with other conventional giant molecules. These binary mixtures provide direct evidence to support our previously proposed self-sorting process in the self-assembly of "soft alloys". The concept of UMNPs offers a unique approach toward more precise regulation of self-assembled superlattices in soft matter.

Soft Alloys Constructed with Distinct Mesoatoms via Self-Sorting Assembly of Giant Shape Amphiphiles.

The packing structures of spherical motifs affect the properties of resultant condensed materials such as in metal alloys. Inspired by the classic metallurgy, developing complex alloy-like packing phases in soft matter (also called "soft alloys") is promising for the next-generation superlattice engineering. Nevertheless, the formation of many alloy-like phases in single-component soft matter is usually thermodynamically unfavourable and technically challenging. Here, we utilize a novel self-sorting assembly approach to tackle this challenge in binary blends of soft matter. Two types of giant shape amphiphiles self-sort to form their discrete spherical motifs, which further simultaneously pack into alloy-like phases. Three unconventional spherical packing phases have been observed in these binary systems, including MgZn2 , NaZn13 , and CaCu5 phases. It's the first time that the CaCu5 phase is experimentally observed in soft matter. This work demonstrates a general approach to constructing unconventional spherical packing phases and other complex superlattices in soft matter.

Superlattice Engineering with Chemically Precise Molecular Building Blocks.

Correlating nanoscale building blocks with mesoscale superlattices, mimicking metal alloys, a rational engineering strategy becomes critical to generate designed periodicity with emergent properties. For molecule-based superlattices, nevertheless, nonrigid molecular features and multistep self-assembly make the molecule-to-superlattice correlation less straightforward. In addition, single component systems possess intrinsically limited volume asymmetry of self-assembled spherical motifs (also known as "mesoatoms"), further hampering novel superlattices' emergence. In the current work, we demonstrate that properly designed molecular systems could generate a spectrum of unconventional superlattices. Four categories of giant molecules are presented. We systematically explore the lattice-forming principles in unary and binary systems, unveiling how molecular stoichiometry, topology, and size differences impact the mesoatoms and further toward their superlattices. The presence of novel superlattices helps to correlate with Frank-Kasper phases previously discovered in soft matter. We envision the present work offers new insights about how complex superlattices could be rationally fabricated by scalable-preparation and easy-to-process materials.

Ordered Mesoporous Silica Pyrolyzed from Single-Source Self-Assembled Organic-Inorganic Giant Surfactants.

We report the preparation of hexagonal mesoporous silica from single-source giant surfactants constructed via dihydroxyl-functionlized polyhedral oligomeric silsesquioxane (DPOSS) heads and a polystyrene (PS) tail. After thermal annealing, the obtained well-ordered hexagonal hybrid was pyrolyzed to afford well-ordered mesoporous silica. A high porosity (e.g., 581 m2/g) and a uniform and narrow pore size distribution (e.g., 3.3 nm) were achieved. Mesoporous silica in diverse shapes and morphologies were achieved by processing the precursor. When the PS tail length was increased, the pore size expanded accordingly. Moreover, such pyrolyzed, ordered mesoporous silica can help to increase both efficiency and stability of nanocatalysts.

Geometry-Directed Self-Assembly of Polymeric Molecular Frameworks.

Despite the significant advances in creating assembled structures from polymers, engineering the assembly of polymeric materials into framework structures remains an outstanding challenge. In this work, we present a facile strategy to construct polymeric molecular frameworks through the assembly of T-shape polymer-rod-sphere amphiphiles in the bulk state. Various frameworks are yielded as a result of delicate interplays among three components of the T-shape amphiphiles. The internal structure of frameworks was revealed by combining experimental investigations and computational simulations. The frameworks display good solution-processability, thermal stability, and uniform pore-forming capability, which endow the resultant frameworks with great potential in scalable fabrications.

Spherical Supramolecular Structures Constructed via Chemically Symmetric Perylene Bisimides: Beyond Columnar Assembly.

Like other discotic molecules, self-assembled supramolecular structures of perylene bisimides (PBIs) are commonly limited to columnar or lamellar structures due to their distinct π-conjugated scaffolds and unique rectangular shape of perylene cores. The discovery of PBIs with supramolecular structures beyond layers and columns may expand the scope of PBI-based materials. A series of unconventional spherical packing phases in PBIs, including A15 phase, σ phase, dodecagonal quasicrystalline (DQC) phase, and body-centered cubic (BCC) phase, is reported. A strategy involving functionalization of perylene core with several polyhedral oligomeric silsesquioxane (POSS) cages achieved spherical assemblies of PBIs, instead of columnar assemblies, due to the significantly increased steric hindrance at the periphery. This strategy may also be employed for the discovery of unconventional spherical assemblies in other related discotic molecules by the introduction of similar bulky functional groups at their periphery. An unusual inverse phase transition sequence from a BCC phase to a σ phase was observed by increasing annealing temperature.

Supramolecular Self-Assembly of Perylene Bisimide-Based Rigid Giant Tetrahedra.

Recently, ordered structures constructed from rigid three-dimensional (3D) shaped polyhedra have been drawing general interest, with the tetrahedron being the simplest one but showing complicated assembly behaviors. Rigid tetrahedron building blocks have been shown to form quasicrystalline and crystalline phases with high packing fractions by both simulation and experiments. Nevertheless, the study of 3D tetrahedral building blocks is limited, especially in the field of supramolecular self-assembly. Here, we present an experimental study of rigid giant tetrahedral molecules constructed by attaching four bulky polyhedral oligomeric silsesquioxane (POSS) cages to a tetrahedral perylene bisimide (PBI) scaffold. Self-assembly of these giant tetrahedra is mediated by π-π interaction between the tetrahedral PBI-based scaffolds and their overall tetrahedral symmetry. A monolithic nearly centimeter-sized hexagonal supramolecular structure was observed in the giant tetrahedron with short flexible linkers between PBI and POSS cages, while a micrometer-sized crystalline helical structure formed in that with completely rigid aromatic linkers. Their significant difference in electrical conductivity could be explained by two completely different packing models of the giant tetrahedra.

Removal of thallium(I) from aqueous solutions using titanate nanomaterials: The performance and the influence of morphology.

Thallium (Tl) pollution has attracted environmental attention due to its high toxicity, thus the cleanup of Tl from the environment is of significance. Titanate nanomaterials (TNMs) with different morphologies can be synthesized via a hydrothermal reaction under different conditions but the knowledge of the Tl(I) removal by them is limited. Our results indicated that TNM prepared at 130 °C exhibited a nanotubular appearance and a longer reaction time resulted in the formation of perfect nanotube, while that prepared at 180 °C exhibited a nanowire-like arrangement. The nanotubular and nanowire-like TNMs possessed approximately excellent Tl(I) adsorption capacities, wide pH, and temperature application ranges but different adsorption kinetics. Inorganic ions influenced the Tl(I) removal and the inhibiting effect of heavy metal ions followed the sequence Pb(II) > Cu(II) > Cd(II) > Zn(II). The anti-interference ability and selectivity of wire-like TNMs for Tl(I) removal were higher than those of tubular TNMs. High Tl(I) uptakes of tubular and wire-like TNMs were driven by the electrostatic attraction, ion exchange with Na+/H+, and complexation with -ONa functional groups in the interlayers and Ti-OH on the surfaces of TNMs as well as microprecipitation; while their adsorption configurations were different. TNMs are promising for potential applications in Tl(I) elimination from wastewater due to the high adsorption capacity and regenerability. This work indicates that TNMs synthesized under different conditions have the similar Tl(I) adsorption performances and the preparation of TNMs used for Tl(I) removal has an undemanding synthesis condition.

Magnifying the Structural Components of Biomembranes: A Prototype for the Study of the Self-Assembly of Giant Lipids.

How biomembranes are self-organized to perform their functions remains a pivotal issue in biological and chemical science. Understanding the self-assembly principles of lipid-like molecules hence becomes crucial. Herein, we report the mesostructural evolution of amphiphilic sphere-rod conjugates (giant lipids), and study the roles of geometric parameters (head-tail ratio and cross-sectional area) during this course. As a prototype system, giant lipids resemble natural lipidic molecules by capturing their essential features. The self-assembly behavior of two categories of giant lipids (I-shape and T-shape, a total of 8 molecules) is demonstrated. A rich variety of mesostructures is constructed in solution state and their molecular packing models are rationally understood. Giant lipids recast the phase behavior of natural lipids to a certain degree and the abundant self-assembled morphologies reveal distinct physiochemical behaviors when geometric parameters deviate from natural analogues.

Discovery of Structural Complexity through Self-Assembly of Molecules Containing Rodlike Components.

Hierarchical structures are important for transferring and amplifying molecular functions to macroscopic properties of materials. In this regard, rodlike molecules have emerged as one of the most promising molecular building blocks to construct functional materials. Although the self-assembly of conventional molecules containing rodlike components generally results in nematic or layered smectic phases, due to the preferred parallel arrangements of rodlike components, extensive efforts have revealed that rational molecular design provides a versatile platform to engineer rich self-assembled structures. Herein, first successes achieved in polyphilic liquid crystals and rod-coil block systems are summarized. Special attention is paid to recent progress in the conjugation of rodlike building blocks with other molecular building blocks through the molecular Lego approach. Rod-based giant surfactants, sphere-rod conjugates, and dendritic rodlike molecules are covered. Future perspectives of the self-assembly of molecules containing rodlike components are also provided.

Controlling the Periodically Ordered Nanostructures in Ceramics: A Macromolecule-Guided Strategy.

Microscopic structures have a significant influence on the properties of ceramics. The development of macromolecular self-assembly has allowed for control over microscopic structures of ceramics to prepare ceramics with diverse compositions and ordered nanostructures. Herein, recent progress in the preparation of ceramics with periodically ordered nanostructures guided by phase-separated macromolecules are reviewed, which can be summarized as a general strategy termed the "macromolecule-guided strategy." Moreover, two different subcategories, namely, the macromolecule-templated method and the macromolecule-precursor method, are illustrated. In the former method, amphiphilic macromolecules are used as templates to guide the assembly of inorganic species into ordered nanostructures, which are subsequently converted into ceramics; in the latter method, amphiphilic macromolecules containing non-volatile elements are used as the single-source precursors for ordered ceramics. It is believed that the unique diversity and tunable features of macromolecular self-assembly might offer unprecedented opportunities in the development of functional ceramics for various applications.

Identification of a Frank-Kasper Z phase from shape amphiphile self-assembly.

Frank-Kasper phases, a family of ordered structures formed from particles with spherical motifs, are found in a host of materials, such as metal alloys, inorganic colloids and various types of soft matter. All the experimentally observed Frank-Kasper phases can be constructed from the basic units of three fundamental structures called the A15, C15 and Z phases. The Z phase, typically observed in metal alloys, is associated with a relatively large volume ratio between its constituents, and this constraint inhibits its formation in most self-assembled single-component soft-matter systems. We have assembled a series of nanosized shape amphiphiles that comprise a triphenylene core and six polyhedral oligomeric silsesquioxane cages grafted onto it through linkers to give a variety of unconventional structures, which include the Z phase. This structure was obtained through fine tuning of the linker lengths between the core and the peripheral polyhedral oligomeric silsesquioxane cages, and exhibits a relatively large volume asymmetry between its constituent polyhedral particle motifs.

Breaking Parallel Orientation of Rods via a Dendritic Architecture toward Diverse Supramolecular Structures.

Self-assembled nanostructures of rod-like molecules are commonly limited to nematic or layered smectic structures dominated by the parallel arrangement of the rod-like components. Distinct self-assembly behavior of four categories of dendritic rods constructed by placing a tri(hydroxy) group at the apex of dendritic oligo-fluorenes is observed. Designed hydrogen bonding and dendritic architecture break the parallel arrangement of the rods, resulting in molecules with specific (fan-like or cone-like) shapes. While the fan-shaped molecules tend to form hexagonal packing cylindrical phases, the cone-shaped molecules could form spherical motifs to pack into various ordered structures, including the Frank-Kasper A15 phase and dodecagonal quasicrystal. This study provides a model system to engineer diverse supramolecular structures by rod-like molecules and sheds new light into the mechanisms of the formation of unconventional spherical packing structures in soft matter.

Effect of Fullerene Volume Fraction on Two-Dimensional Crystal-Constructed Supramolecular Liquid Crystals.

The volume fraction plays an important role in phase segregated soft matters. We demonstrate here that at high fullerene volume fraction in soft chain-tethered-fullerene dyads, different two-dimensional (2D) crystal-constructed smectic-like lamella liquid crystalline (LC) phases can be formed with triple-layer (ST phase) or quadruple-layer (SQ phase) stacking of fullerenes in 2D crystals. The combination of 2D crystal and LC properties in one system affords these fullerene dyads controlled electron mobility in the range of 10-5 -10-3  cm2 V-1 s-1 at room temperature (ST phase), by regulating the insulated soft layer thickness between 2D crystals via the manipulation of fullerene volume fraction.

Transition Kinetics of Self-Assembled Supramolecular Dodecagonal Quasicrystal and Frank-Kasper σ Phases in ABn Dendron-Like Giant Molecules.

A series of noncrystalline ABn dendron-like giant molecules DPOSS-MPOSSn (n = 2-6, DPOSS: hydrophilic polyhedral oligomeric silsesquioxane (POSS) cage; MPOSS: hydrophobic POSS cage) were synthesized. These samples present a thermodynamically stable phase formation sequence from the hexagonal cylinder phase (plane group of P6mm), to the Frank-Kasper (F-K) A15 phase (space group of Pm3̅n), and further to the F-K σ phase (space group of P42/mnm), with increasing the number of MPOSS in a single molecule (n, from 2 to 6). Moreover, for DPOSS-MPOSS5 and DPOSS-MPOSS6, an intriguing dodecagonal quasicrystal (DQC) structure has been identified and revealed as a kinetic favorable metastable phase at lower temperatures, while the thermodynamically stable phase is the σ phase. The detailed investigation of the transition kinetics between the DQC and σ phase in these samples makes it possible to identify how the self-assembly directs the phase transition in terms of molecular and supramolecular aspects.