Self-assembly Behavior Research Articles

C1 symmetric dual-carboxyl-functionalized BODIPY dye: Synthesis, photophysical properties, and self-assembly behavior via hydrogen bonding

A BODIPY derivatives 3 with phenylethynyl bridging two carboxyl groups was synthesized via Sonogashira cross-coupling reaction. The structure was characterized by 1HNMR and HRMS. Its photophysical properties and aggregation behavior in solution were studied by UV–Vis absorption and fluorescence spectroscopy. The compound 3 displays strong absorption and high fluorescence quantum yield. The investigations of UV–Vis and emission also revealed the formation of self-assembled structures in the solid state or liquid/state with translationally slipped π-stacks of BODIPY units driven by hydrogen bonding between the carboxyl groups. The thermodynamic properties of the BODIPY derivative were carried out by DSC and TGA, indicating it possesses high thermal stability. In addition, the self-assembly of the BODIPY derivative functionalized with two carboxyl groups was explicitly investigated by using scanning tunneling microscopy (STM). The highly ordered supramolecular self-assembly monolayers endow the novel carboxyl functionalized BODIPY with good potential for application in organic devices.

Biomimetic and environmentally friendly self-assembly behavior of melamine onto the surface of black phosphorus nanosheets: Constructing advanced P/N-containing nano flame retardants

Herein, inspired by the hierarchical structure within the biological protein, we adjust the temperature of the aqueous solution to control the unfolding and reconstitution of hydrogen bonds among melamine (MA) molecules, thus preparing MA-functionalized black phosphorus (MA@BP) nanosheets. As confirmed by the first-principles calculations, melamine can spontaneously adsorb onto the surface of BP nanosheets and enhance the interfacial interactions between BP nanosheets and thermoplastic polyurethane (TPU) matrix. Compared to pure BP nanosheets, MA@BP nanosheets present more efficient suppression effects in heat release and toxic CO production. Besides, due to the photo-thermal conversion effect of BP nanosheets, TPU-MA@BP-2.0 presents an equilibrium temperature of ∼ 80 °C under simulated sunlight of 1.0 kW/m2 and a significant solar de-icing performance. The solve-free and hydrogen-bond assembly method not only solves the lack problem of functional groups for the functionalization of BP nanosheets, but also develops a flame-retardant and photo-thermal polymer nanocomposite applied in various occasions.

Self-Assembled Materials Based on Fully Aromatic Peptides: The Impact of Tryptophan, Tyrosine, and Dopa Residues.

Peptides are able to self-organize in structural elements including cross-β structures. Taking advantage of this tendency, in the last decades, peptides have been scrutinized as molecular elements for the development of multivalent supramolecular architectures. In this context, different classes of peptides, also with completely aromatic sequences, were proposed. Our previous studies highlighted that the (FY)3 peptide, which alternates hydrophobic phenylalanine and more hydrophilic tyrosine residues, is able to self-assemble, thanks to the formation of both polar and apolar interfaces. It was observed that the replacement of Phe and Tyr residues with other noncoded aromatic amino acids like 2-naphthylalanine (Nal) and Dopa affects the interactions among peptides with consequences on the supramolecular organization. Herein, we have investigated the self-assembling behavior of two novel (FY)3 analogues with Trp and Dopa residues in place of the Phe and Tyr ones, respectively. Additionally, PEGylation of the N-terminus was analyzed too. The supramolecular organization, morphology, and capability to gel were evaluated using complementary techniques, including fluorescence, Fourier transform infrared spectroscopy, and scanning electron microscopy. Structural periodicities along and perpendicular to the fiber axis were detected by grazing incidence wide-angle X-ray scattering. Finally, molecular dynamics studies provided interesting insights into the atomic structure of the cross-β that constitutes the basic motif of the assemblies formed by these novel peptide systems.

Self-Assembly in Curved Space: Ordering, Defect and Entropy

Self-assembly of nanoscale objects is of essential importance in materials science, condensed matter physics, and biophysics. Curvature modifies the principles and sequence of self-assembly in Euclidean space, resulting in unique and more complex structures. Understanding self-assembly behavior in curved space is not only instrumental for designing structural building blocks and assembly processes from a bottom-up perspective but is also critically important for delineating various biological systems. In this review, we summarize efforts made to unveil the physical nature of self-assembly in curved space through experiments and simulations. First, we outline the differences in the physical nature of self-assembly between curved space and Euclidean space by presenting relevant results of experiments and simulations. Second, we explore the principles of self-assembly in curved space at multiple scales and interactions, elucidating important factors that govern the self-assembly process from the perspectives of confinement and structural building blocks. Finally, we enumerate practical applications and control strategies for self-assembly in curved space and outline the challenges and prospects in this field. We hope that this review will encourage further efforts toward fundamental research and broaden the potential applications of designed assemblies in curved space.

Azaylide-based gemini amphiphiles displaying unique self-assembling behavior via an even-odd effect of alkyl linker chain length.

Herein, we report a straightforward synthesis of azaylide-based gemini amphiphiles using bis(diphenylphosphino)alkanes via the Staudinger reaction. The prepared gemini amphiphiles exhibited an even-odd effect in their self-assembly behavior depending on the length of the alkyl linkers. Furthermore, the assembled micelles had high host capability toward hydrophobic guests in water.

Self-assembly of rod-coil-rod block copolymers in a coil-selective solvent: coarse-grained simulation results.

The solution self-assembly of amphiphilic polymers provides a versatile approach to design novel nanostructured materials. Multiblock polymers, particularly those composed of liquid crystalline and coil blocks, are of significant interest due to the potential display of nematic ordering in liquid crystalline domains, offering intriguing optical and mechanical properties. In this study, dissipative particle dynamics is used to investigate the solution self-assembly of rod-coil-rod copolymers in a coil-selective solvent. Extensive molecular simulations were conducted to elucidate the impact of polymer composition, concentration and flexibility on the self-assembly behavior. A quantitative analysis was performed to investigate how polymer conformations varied with changes in composition, concentration, and rigidity. Simulation results show that, at small rod compositions, rod-coil-rod polymers self-assemble into micelles at low concentrations, transitioning to network formation as concentration increases. An increase in rod composition leads to the formation of larger aggregates, resulting in cylindrical micelles and membranes. The results reported here also offer insights into the role of flexibility in shaping the self-assembly behavior of rod-coil-rod triblocks in selective solvents, thus, contributing to a comprehensive understanding of the factors governing the formation of diverse structures in the solution self-assembly of triblock copolymers.

Bridging of poly(acetylene)s and PEG-modified poly(olefin)s through ring-opening metathesis copolymerization (ROMCP)

Amphiphilic copolymers of highly conjugated poly(acetylene)s and PEG–PDI-incorporating poly(olefin)s have been synthesized and analyzed to study their amphiphilic properties, H-type aggregation processes and self-assembling behavior.

Single-bond-linked and vinylene-bridged azulenyl bis(squaraine) dyes: design, synthesis and molecular self-assembly behaviors

Near-Infrared single-bond-linked and vinylene-bridged azulenyl bis(squaraine) dyes were synthesized. Their self-assembly behaviors were investigated under different solvent polarities, compound concentrations and temperatures.

Pnictogen bonding in imide derivatives for chiral folding and self-assembly.

Pnictogen bonding (PnB) is an attraction interaction that originates from the anisotropic distribution of electron density of pnictogen elements, which however has been rarely found in nitrogen atoms. In this work, for the first time, we unveil the general presence of N-involved PnB in aromatic or aliphatic imide groups and reveal its implications in chiral self-assembly of folding. This long-neglected interaction was consolidated by Cambridge structural database (CSD) searching as well as subsequent computational studies. Though the presence of PnB has limited effects on spectroscopic properties in the solution phase, conformation locking effects are sufficiently expressed in the chiral folding and self-assembly behavior. PnB anchors the chiral conformation to control the emergence and inversion of chiroptical signals, while intramolecular PnB induces the formation of supramolecular tilt chirality. It also enables the chiral folding of imide-containing amino acid or peptide derivatives, which induces the formation of unique secondary structural sequences such as β-sheets. Finally, the effects of PnB in directing folded helical structures were revealed. Examples of cysteine and cystine derivatives containing multiple N⋯O and N⋯S PnBs constitute an α-helix like secondary structure with characteristic circular dichroism. This work discloses the comprehensive existence of imide-involved PnB, illustrates its important role in folding and self-assembly, and sheds light on the rational fabrication of conformation-locked compounds and polymers with controllable chiroptical activities.

Effect of the linking bridge type on the self-assembly behaviour of 2',3'-difluoroterphenyl derivatives.

The self-assembly behaviour and the crystallization kinetics of two liquid crystal compounds containing 2',3'-difluorosubstituted terphenyl as the mesogenic core have been described. Calorimetric studies show that the linking bridge type affects the polymorphism of smectic phases. The CH2O.3 compound with the -CH2O- linking bridge connected with a longer methylene spacer possesses the chiral smectic phase with antiferroelectric properties (SmCA* phase), while the COO.6 liquid crystal with the -COO- linking bridge connected with a shorter alkyl chain forms the chiral smectic phase with ferroelectric properties (SmC* phase). Both compounds crystallize upon slow cooling, while fast cooling causes the vitrification of the conformationally disordered crystal phase. Dielectric measurements reveal the complex relaxation dynamics in the identified thermodynamic states. DFT calculations allow us to estimate the nature of relaxation processes.

Self-assembly of amphiphilic asymmetric comb-like copolymers with responsive rigid side chains.

Amphiphilic asymmetric comb-like copolymers (AACCs) exhibit distinct self-assembly behaviours due to their unique architecture. However, the synthetic difficulties of well-defined AACCs have prohibited a systematic understanding of the architecture-morphology relationship. In this work, we conducted dissipative particle dynamics simulations to investigate the self-assembly behaviours of AACCs with responsive rigid side chains in selective solvents. The effects of side chain length, number of branches, and spacers on the morphology of aggregates were investigated by mapping out morphology diagrams. Besides, the numbers and surface areas of aggregates clearly depicted the morphological transitions during the self-assembly process. Moreover, the rod-to-coil conformation transitions were simulated to explore the stimuli-responsive behaviour of the AACCs with responsive rigid side chains by adjusting the bond angle parameter of the rigid chains. The results indicated that without the support of the rigid chains, the assembly structure collapsed, leading to the tube-to-channelized micelles and one-compartment-to-multicompartment vesicle morphology transformations. The simulation results are consistent with earlier experimental results, which can provide theoretical guidance for assembly toward desired nanostructures.

Bioinspired and biomimetic nucleobase-containing polymers: the effect of selective multiple hydrogen bonds.

Bioinspired and biomimetic nucleobase-containing polymers are a series of polydisperse nucleic acid analogs, mainly obtaining through highly efficient and scalable step-growth or chain polymerizations. The combination of pendant nucleobase groups and various backbones endows the polymers/materials with selective multiple H-bonds under distinct conditions, demonstrating the broad applicability of this new family of polymeric materials. In this perspective, we critically summarize recent advances of bioinspired and biomimetic nucleobase-containing polymers and materials in both solution and the bulk. Then, we discuss the effect of multiple H-bonds between complementary nucleobases on the structures and properties of the nucleobase-containing polymers and materials. Selective multiple H-bonds between complementary nucleobases are feasible to modulate the polymer sequence and self-assembly behaviour, achieve templated polymerization, tune nanostructure morphologies and functions, and selectively bind with nucleic acids in various solutions. Meanwhile, bioinspired and biomimetic nucleobase-containing polymers are capable of forming robust polymeric materials such as hydrogels, bioplastics, elastomers, adhesives, and coatings by optimizing the inter- and intramolecular multiple H-bonding interactions. Further, the conclusions and outlook for future development and challenges of bioinspired and biomimetic nucleobase-containing polymers are also presented. This perspective presents useful guidelines for fabricating novel bioinspired and biomimetic polymers and materials through rational design of multiple H-bonds nucleobase interactions.

The mechanism underlying the transitions between stripes, helices, and stacked toroids in the cylindrical shell formed by AB diblock copolymers on a long nanocylinder.

The self-assembly of block copolymers on nanocylinders has attracted a lot of interest due to its potential application in biomedicine and other fields. In this study, the self-assembly phase behavior of AB diblock copolymers on long nanocylinders in soft confinement has been studied by using a simulated annealing method. A square phase diagram of the morphology was constructed by increasing the number of chains of copolymers (cn) and the cylindrical diameter (D). As a result, morphological transitions from striped to helical and axially stacked toroids, as well as reversible transitions, started to appear. By analyzing the chain packing in a fan-shaped region and calculating the mean-square end-to-end distance (DEE2) of the copolymers and number of AB contacts, both types of transitions were found to be driven by the competition between conformational entropy and AB interfacial energy. The number of stripes increased and the helical angle decreased with the increase in cylinder diameter. The chirality of the helix was found to be random.

The effect of water in THF/water mixtures on CMC, aggregation sizes, and fluorescence quenching of a new calix[4]resorcinarene macrocycle.

This study explores how water content modulates the self-assembly and fluorescence behavior of a novel calixarene, C1. C1 forms large, flattened structures in pure THF, but water addition triggers a transition to smaller, unimodal clusters. A critical micellar concentration (CMC) is identified, decreasing with increasing water content. Fluorescence quenching is observed upon water addition, attributed to nonradiative deactivation. These findings highlight water as a key regulator of C1's assembly and fluorescence, paving the way for further development of water-responsive calixarene systems.

2D hexagonal assembly of a dipolar rotor with a close interval of 0.8 nm using a triptycene-based supramolecular scaffold.

Controlling the rotation of carbon-carbon bonds, which is ubiquitous in organic molecules, to create functionality has been a subject of interest for a long time. In this context, it would be interesting to explore whether cooperative and collective rotation could occur if dipolar molecular rotors were aligned close together while leaving adequate space for rotation. However, it is difficult to realize such structures as bulk molecular assemblies, since molecules generally tend to assemble into the closest packing structure to maximize intermolecular forces. To tackle this question, we examined an approach using a supramolecular scaffold composed of a tripodal triptycene, which has been demonstrated to strongly promote the assembly of various molecular and polymer units into regular "2D hexagonal packing + 1D layer" structures. We found that a molecule (1) consisting of a dipolar 1,2-difluorobenzene rotor sandwiched by two 10-ethynyl-1,8,13-tridodecyloxy triptycenes, successfully self-assembles into the desired structure, where the dipolar rotor units align two-dimensionally at a close interval of approximately 0.8 nm while having a degree of freedom for rotational motion. Here we describe the self-assembly behavior of 1 in comparison with the general trend in molecular self-assembly, as well as the motility of the two-dimensionally aligned molecular rotors investigated using solid-state 19F-MAS NMR spectroscopy.

Self-assembly of colloids with competing interactions confined in spheres.

At low temperatures, colloidal particles with short-range attractive and long-range repulsive interactions can form various periodic microphases in bulk. In this paper, we investigate the self-assembly behaviour of colloids with competing interactions under spherical confinement by conducting molecular dynamics simulations. We find that the cluster, mixture, cylindrical, perforated lamellar and lamellar structures can be obtained, but the details of the ordered structures are different from those in bulk systems. Interestingly, the system tends to form more perforated structures when confined in smaller spheres. The mechanism behind this phenomenon is driven by the relationship between the energy of the ordered structures and the bending of the confinement wall, which is different from the mechanism in copolymer systems.

Can Conformational Flexibility Influence the Self-Assembly Behavior and Sensing Efficacy of Fluorogenic Amphiphiles? A Case Study with Bisbenzimidazole based Probes

In this work, we have explored metal ion sensing property of two bisbenzimidazole based fluorescent probes, differed by their conformational flexibility, in the aqueous medium. The compound with flexible methyl...

Fluoranthene imide dimers with strong isomeric effects on the charge transport properties.

To date, the development of high-performance n-type organic semiconductors has remained challenging due to the scarcity of highly electron-deficient π-conjugated structural units and the difficulty of controlling intermolecular packing in the thin-film state. In addition, there have been few reports on the use of dimer design to tune the optoelectronic properties of materials. Herein, we report new cyano-substituted fluoranthene imide-based dimers (F16 and F17) for small-molecule n-type organic semiconductors. It is noteworthy that substituents at different positions lead to different film morphologies and very distinct thermal aggregation behaviors due to different dihedral angles. The self-assembly behavior of F17 improves thermal stability. Therefore, F17, which has a closer cyano groups structure, exhibits better field-effect transistor performance, with a maximum mobility of 6.6 × 10-4 cm2 V-1 s-1, while F16 does not exhibit any transistor performance.

Self-Assembled Aggregated Structures of Natural Products for Oral Drug Delivery.

The self-assembling aggregated structures of natural products have gained significant interest due to their simple synthesis, lack of carrier-related toxicity, and excellent biological efficacy. However, the mechanisms of their assembly and their ability to traverse the gastrointestinal (GI) barrier remain unclear. This review summarizes various intermolecular non-covalent interactions and aggregated structures, drawing on research indexed in Web of Science from 2010 to 2024. Cheminformatics analysis of the self-assembly behaviors of natural small molecules and their supramolecular aggregates reveals assembly-favorable conditions, aiding drug formulation. Additionally, the review explores the self-assembly properties of macromolecules like polysaccharides, proteins, and exosomes, highlighting their role in drug delivery. Strategies to overcome gastrointestinal barriers and enhance drug bioavailability are also discussed. This work underscores the potential of natural products in oral drug delivery and offers insights for designing more effective drug delivery systems.

Interfacial assembly and rheology of multi-responsive glycyrrhizic acid at liquid interfaces.

Glycyrrhizic acid (GA), a naturally derived food-grade saponin molecule, is a promising alternative to synthetic surfactants for stabilizing multiphase systems including emulsions and foams, due to its biological activity and surface-active properties. Understanding the interfacial behavior of GA, particularly in relation to its complex self-assembly behaviors in water induced by multiple environmental stimuli, is crucial to its application in multiphase systems. In this study, we comprehensively investigate the interfacial structure and rheological properties of GA systems, as a function of pH and temperature, through Langmuir-Blodgett films combined with atomic force microscopy, interfacial particle tracking, adsorption kinetics, stress-relaxation behavior and interfacial dilatational rheology. The variation of solution pH provokes pronounced changes in the interfacial properties of GA. At pH 2 and 4, GA fibril aggregates/fibrils adsorb rapidly, followed by rearrangement into large lamellar and rod-like structures, forming a loose and heterogeneous fibrous network at the interface, which exhibit a stretchable gel-like behavior. In contrast, GA at pH 6 and 8, featuring micelles or monomers in solutions, adsorb slowly to the interface and re-assemble partially into small micelle-like or irregular structures, which lead to a dense and homogeneous interfacial layer with stiffer glassy-like responses. With successively elevated temperature, the GA structures (pH 4) at the interface break into smaller fragments and further adsorption is promoted. Upon cooling, the interfacial tension of GA further decreases and a highly elastic interfacial layer may be formed. The diverse GA assemblies in bulk solution impart them with rich and intriguing interfacial behaviors, which may provide valuable mechanistic insights for the development of novel edible soft matter stabilized by GA.