Supramolecular polymers

Dynamic Control over Hierarchically Dendritic Architectures of Simple Heterogenous Monomers by Living Supramolecular Assembly

The successful preparation of supramolecular block copolymers (SBCPs) by living supramolecular assembly technology requires two kinetic systems in which both the seed (nucleus) and heterogenous monomer providers are in non-equilibrium. However, employing simple monomers to construct the SBCPs via this technology is almost impossible because the low spontaneous nucleation barrier of simple molecules prevents the formation of kinetic states. Here, with the help of confinement from layered double hydroxide (LDH), various simple monomers successfully form living supramolecular co-assemblies (LSCA). LDH overcomes a considerable energy barrier to obtain living seeds to support the growth of the inactivated second monomer. The ordered LDH topology is sequentially mapped to the seed, second monomer, and binding sites. Thus, the multidirectional binding sites are endowed with the ability to branch, making the branch length of dendritic LSCA reach its maximum value of 3.5 cm so far. The strategy of universality will guide exploration into the development of multi-function and multi-topology advanced supramolecular co-assemblies.

Bracelet-like Complexes of Lithium Fluoride with Aromatic Tetraamides, and Their Potential for LiF-Mediated Self-Assembly: A DFT Study

Geometries and binding energies of complexes between a LiF molecule and a model aromatic tetraamide are obtained using various DFT methods. The tetraamide consists of a benzene ring and four amides positioned so that the LiF molecule can bind via Li⋯O=C or N-H⋯F interactions. The complex with both interactions is the most stable one, followed by the complex with only N-H⋯F interactions. Doubling the size of the former resulted in a complex with a LiF dimer sandwiched between the model tetraamides. In turn, doubling the size of the latter resulted in a more stable tetramer with bracelet-like geometry having the two LiF molecules also sandwiched but far apart from each other. Additionally, all methods show that the energy barrier to transition to the more stable tetramer is small. The self-assembly of the bracelet-like complex mediated by the interactions of adjacent LiF molecules is demonstrated by all computational methods employed.

Multi-chiral materials comprising metallosupramolecular and covalent helical polymers containing five axial motifs within a helix

Supramolecular and covalent polymers share multiple structural effects such as communication mechanisms among monomer repeating units, which are related to their axial helical structure. Herein, a unique multi-helical material combining information from both metallosupramolecular and covalent helical polymers is presented. In this system, the helical structure described by the poly(acetylene) (PA) backbone (cis-cisoidal, cis-transoidal) guides the pendant groups in a fashion where a tilting degree emerges between a pendant and the adjacent ones. As a result, a multi-chiral material is formed comprising four or five axial motifs when the polyene skeleton adopts either a cis-transoidal or cis-cisoidal configuration: the two coaxial helices-internal and external-and the two or three chiral axial motifs described by the bispyridyldichlorido Pt^II complex array. These results show that complex multi-chiral materials can be obtained by polymerizing appropriate monomers that combine both point chirality and the ability to generate chiral supramolecular assemblies.

Role of supramolecular polymers in photo-actuation of spiropyran hydrogels

Supramolecular-covalent hybrid polymers have been shown to be interesting systems to generate robotic functions in soft materials in response to external stimuli. In recent work supramolecular components were found to enhance the speed of reversible bending deformations and locomotion when exposed to light. The role of morphology in the supramolecular phases integrated into these hybrid materials remains unclear. We report here on supramolecular-covalent hybrid materials that incorporate either high-aspect-ratio peptide amphiphile (PA) ribbons and fibers, or low-aspect-ratio spherical peptide amphiphile micelles into photo-active spiropyran polymeric matrices. We found that the high-aspect-ratio morphologies not only play a significant role in providing mechanical reinforcement to the matrix but also enhance photo-actuation for both light driven volumetric contraction and expansion of spiropyran hydrogels. Molecular dynamics simulations indicate that water within the high-aspect-ratio supramolecular polymers exhibits a faster draining rate as compared to those in spherical micelles, which suggests that the high-aspect-ratio supramolecular polymers effectively facilitate the transport of trapped water molecules by functioning as channels and therefore enhancing actuation of the hybrid system. Our simulations provide a useful strategy for the design of new functional hybrid architectures and materials with the aim of accelerating response and enhancing actuation by facilitating water diffusion at the nanoscopic level.

A Comparative XPS, UV PES, NEXAFS, and DFT Study of the Electronic Structure of the Salen Ligand in the H2(Salen) Molecule and the [Ni(Salen)] Complex

A comparative study of the electronic structure of the salen ligand in the H₂(Salen) molecule and the [Ni(Salen)] complex was performed using the experimental methods of XPS, UV PES, and NEXAFS spectroscopy along with DFT calculations. Significant chemical shifts of +1.0 eV (carbon), +1.9 eV (nitrogen), and -0.4 eV (oxygen) were observed in the 1s PE spectra of the salen ligand atoms when passing from a molecule to a complex, unambiguously indicating a substantial redistribution of the valence electron density between these atoms. It is proposed that the electron density transfer to the O atoms in [Ni(Salen)] occurred not only from the Ni atom, but also from the N and C atoms. This process seemed to be realized through the delocalized conjugated π-system of the phenol C 2p electronic states of the ligand molecule. The DFT calculations (total and partial DOS) for the valence band H₂(Salen) and [Ni(Salen)] described well the spectral shape of the UV PE spectra of both compounds and confirmed their experimental identification. An analysis of the N and O 1s NEXAFS spectra clearly indicated that the atomic structure of the ethylenediamine and phenol fragments was retained upon passing from the free salen ligand to the nickel complex.

Distinct seed topologies enable comparison of elongation and secondary nucleation pathways in seeded supramolecular polymerization

The influence of seed topologies on seeded supramolecular polymerization was examined using helicoidal and toroidal supramolecular polymer seeds. The addition of these seeds to a supersaturated solution of monomers led to distinct nucleation-growth kinetics, which were attributed to the significant difference between the elongation from helicoid termini and secondary nucleation catalyzed by the toroid surface.

Design of supramolecular nanosheets for drug delivery applications

Two specific concepts have emerged in the field of materials science over the last several decades: nanosheets and supramolecular polymers. More recently, supramolecular nanosheets, in which these two concepts are integrated, have attracted particular attention, and they exhibit many fascinating characteristics. This review focuses on the design and applications of supramolecular nanosheets consisting of tubulin proteins and phospholipid membranes.

BODIPY as a Multifunctional Theranostic Reagent in Biomedicine: Self-Assembly, Properties, and Applications

The use of boron dipyrromethene (BODIPY) in biomedicine is reviewed. To open, its synthesis and regulatory strategies are summarized, and inspiring cutting-edge work in post-functionalization strategies is highlighted. A brief overview of assembly model of BODIPY is then provided: BODIPY is introduced as a promising building block for the formation of single- and multicomponent self-assembled systems, including nanostructures suitable for aqueous environments, thereby showing the great development potential of supramolecular assembly in biomedicine applications. The frontier progress of BODIPY in biomedical application is thereafter described, supported by examples of the frontiers of biomedical applications of BODIPY-containing smart materials: it mainly involves the application of materials based on BODIPY building blocks and their assemblies in fluorescence bioimaging, photoacoustic imaging, disease treatment including photodynamic therapy, photothermal therapy, and immunotherapy. Lastly, not only the current status of the BODIPY family in the biomedical field but also the challenges worth considering are summarized. At the same time, insights into the future development prospects of biomedically applicable BODIPY are provided.

3D Bioprinting for Tumor Metastasis Research

Tumor metastasis is a multiple cascade process where tumor cells disseminate from the primary site to distant organs and subsequently adapt to the foreign microenvironment. Simulating the physiology of tumor metastatic events in a realistic and three-dimensional (3D) manner is a challenge for in vitro modeling. 3D bioprinting strategies, which can generate well-customized and bionic structures, enable the exploration of dynamic tumor metastasis process in a species-homologous, high-throughput and reproducible way. In this review, we summarize the recent application of 3D bioprinting in constructing in vitro tumor metastatic models and discuss its advantages and current limitations. Further perspectives on how to harness the potential of accessible 3D bioprinting strategies to better model tumor metastasis and guide anti-cancer therapies are also provided.

Pathway-Controlled Aqueous Supramolecular Polymerization via Solvent-Dependent Chain Conformation Effects

Solute-solvent interactions play a critical role in multiple fields, including biology, materials science, and (physical) organic, polymer, and supramolecular chemistry. Within the growing field of supramolecular polymer science, these interactions have been recognized as an important driving force for (entropically driven) intermolecular association, particularly in aqueous media. However, to date, solute-solvent effects remain poorly understood in the context of complex self-assembly energy landscapes and pathway complexity. Herein, we unravel the role of solute-solvent interactions in controlling chain conformation effects, allowing energy landscape modulation and pathway selection in aqueous supramolecular polymerization. To this end, we have designed a series of oligo(phenylene ethynylene) (OPE)-based bolaamphiphilic Pt(II) complexes OPE2-4 bearing solubilizing triethylene glycol (TEG) chains of equal length on both molecule ends, but a different size of the hydrophobic aromatic scaffold. Strikingly, detailed self-assembly studies in aqueous media disclose a different tendency of the TEG chains to fold back and enwrap the hydrophobic molecular component depending on both the size of the core and the volume fraction of the co-solvent (THF). The relatively small hydrophobic component of OPE2 can be readily shielded by the TEG chains, leading to only one aggregation pathway. In contrast, the decreased capability of the TEG chains to effectively shield larger hydrophobic cores (OPE3 and OPE4) enables different types of solvent quality-dependent conformations (extended, partly back-folded and back-folded), which in turn induce various controllable aggregation pathways with distinct morphologies and mechanisms. Our results shed light on previously underappreciated solvent-dependent chain conformation effects and their role in governing pathway complexity in aqueous media.

Chiral Binaphthalene Building Blocks for Self-Assembled Nanoscale CPL Emitters

The introduction of biuret hydrogen-bonding sites onto chiral binaphthalene-based chromophores was investigated as a route to sub-micron-sized, vesicle-like aggregates endowed with chiroptical properties. The synthesis was conducted from the corresponding chiral 4,4'-dibromo-1,1'-bis(2-naphthol) via Suzuki-Miyaura coupling to afford luminescent chromophores whose emission spectrum could be tuned from blue to yellow-green through extension of the conjugation. For all compounds, the spontaneous formation of hollow spheres with a diameter of ca. 200-800 nm was evidenced by scanning electron microscopy, along with strong asymmetry in the circularly polarized absorption spectra. For some compounds, the emission also displayed circular polarization with values of g_lum = ca. 10^-3 which could be increased upon aggregation.

Rational Design of PDI-Based Linear Conjugated Polymers for Highly Effective and Long-Term Photocatalytic Oxygen Evolution

Constructed through relatively weak noncovalent forces, the stability of organic supramolecular materials has shown to be a challenge. Herein, the designing of a linear conjugated polymer is proposed through creating a chain polymer connected via bridging covalent bonds in one direction and retaining π-stacked aromatic columns in its orthogonal direction. Specifically, three analogs of linear conjugated polymers through tuning the aromatic core and its covalently linked moiety (bridging group) within the building block monomer are prepared. Cooperatively supported by strong π-π stacking interactions from the extended aromatic core of perylene and favorable dipole-dipole interactions from the bridging group, the as-expected high crystallinity, wide light absorption, and increased stability are successfully achieved for Oxamide-PDI (perylene diimide) through ordered molecular arrangement, and present a remarkable full-spectrum oxygen evolution rate of 5110.25 µmol g^-1  h^-1 without any cocatalyst. Notably, experimental and theoretical studies reveal that large internal dipole moments within Oxamide-PDI together with its ordered crystalline structure enable a robust built-in electric field for efficient charge carrier migration and separation. Moreover, density functional theory (DFT) calculations also reveal oxidative sites located at carbon atoms next to imide bonds and inner bay positions based on proven spatially separated photogenerated electrons and holes, thus resulting in highly efficient water photolysis into oxygen.

Pathway Complexity in Supramolecular Copolymerization and Blocky Star Copolymers by a Hetero-Seeding Effect

This study unravels the intricate kinetic and thermodynamic pathways involved in the supramolecular copolymerization of the two chiral dipolar naphthalene monoimide (NMI) building blocks (O-NMI and S-NMI), differing merely by a single heteroatom (oxygen vs sulfur). O-NMI exhibits distinct supramolecular polymerization features as compared to S-NMI in terms of its pathway complexity, hierarchical organization, and chiroptical properties. Two distinct self-assembly pathways in O-NMI occur due to the interplay between the competing dipolar interactions among the NMI chromophores and amide-amide hydrogen (H)-bonding that engenders distinct nanotapes and helical fibers, from its antiparallel and parallel stacking modes, respectively. In contrast, the propensity of S-NMI to form only a stable spherical assembly is ascribed to its much stronger amide-amide H-bonding, which outperforms other competing interactions. Under the thermodynamic route, an equimolar mixture of the two monomers generates a temporally controlled chiral statistical supramolecular copolymer that autocatalytically evolves from an initially formed metastable spherical heterostructure. In contrast, the sequence-controlled addition of the two monomers leads to the kinetically driven hetero-seeded block copolymerization. The ability to trap O-NMI in a metastable state allows its secondary nucleation from the surface of the thermodynamically stable S-NMI spherical "seed", which leads to the core-multiarmed "star" copolymer with reversibly and temporally controllable length of the growing O-NMI "arms" from the S-NMI "core". Unlike the one-dimensional self-assembly of O-NMI and its random co-assembly with S-NMI, which are both chiral, unprecedentedly, the preferred helical bias of the nucleating O-NMI fibers is completely inhibited by the absence of stereoregularity of the S-NMI "seed" in the "star" topology.

Two-photon microscopy as a visual tool for polymer compatibilization monitoring: the PE-EVOH case

In this study, we present two-photon microscopy (2PM) as an original technique to investigate the compatibilization between PE-HEMA and EVOH at the sub-micrometer level, both on the surface and in the bulk. 2PM is a nonlinear fluorescence imaging technique commonly exploited for thick biological tissue analysis. Here, we use 2PM to visualize polymer blending through 3D images of the obtained films. Compatibilization was performed in solution, upon functionalization of PE-HEMA with 1.4% molar of ODIN, a fluorescent molecule able to form multiple hydrogen bonds with EVOH and to act as a fluorescent probe. Different blends were synthesized, and the obtained films were analyzed by 2PM. For all compositions, it was demonstrated that ODIN is evenly distributed both on the surface and in the bulk. 2PM analysis of the thermally reprocessed specimen revealed that repeated reprocessing allows the reformation of ODIN dimers as the most stable H-bonding array in the solid state, partially reversing the compatibilization.

Porphyrin-based supramolecular polymers

Porphyrin derivatives are ubiquitous in bio-organisms and are associated with proteins that play important biological roles, such as oxygen transport, photosynthesis, and catalysis. Porphyrins are very fascinating research objects for chemists, physicists, and biologists owing to their versatile chemical and physical properties. Porphyrin derivatives are actively used in various fields, such as molecular recognition, energy conversion, sensors, biomedicine, and catalysts. Porphyrin derivatives can be used as building blocks for supramolecular polymers because their primitive structures have C₄ symmetry, which allows for the symmetrical introduction of self-assembling motifs. This review describes the fabrication of porphyrin-based supramolecular polymers and novel discoveries in supramolecular polymer growth. First, we summarise the (i) design concepts, (ii) growth mechanism and (iii) analytical methods of porphyrin-based supramolecular polymers. Then, the examples of porphyrin-based supramolecular polymers formed by (iv) hydrogen bonding, (v) metal coordination-based interaction, (vi) host-guest complex formation, and (vii) others are summarised. Finally, (viii) applications and perspectives are discussed. Although supramolecular polymers, in a broad sense, can include either two-dimensional (2D) networks or three-dimensional (3D) porous polymer structures; this review mainly focuses on one-dimensional (1D) fibrous supramolecular polymer structures.

Photoresponsive Supramolecular Polymers: From Light-Controlled Small Molecules to Smart Materials

Photoresponsive supramolecular polymers are well-organized assemblies based on highly oriented and reversible noncovalent interactions containing photosensitive molecules as (co-)monomers. They have attracted increasing interest in smart materials and dynamic systems with precisely controllable functions, such as light-driven soft actuators, photoresponsive fluorescent anticounterfeiting and light-triggered electronic devices. The present review discusses light-activated molecules used in photoresponsive supramolecular polymers with their main photo-induced changes, e.g., geometry, dipole moment, and chirality. Based on these distinct changes, supramolecular polymers formed by light-activated molecules exhibit photoresponsive disassembly and reassembly. As a consequence, photo-induced supramolecular polymerization, "depolymerization," and regulation of the lengths and topologies are observed. Moreover, the light-controlled functions of supramolecular polymers, such as actuation, emission, and chirality transfer along length scales, are highlighted. Furthermore, a perspective on challenges and future opportunities is presented. Besides the challenge of moving from harmful UV light to visible/near IR light avoiding fatigue, and enabling biomedical applications, future opportunities include light-controlled supramolecular actuators with helical motion, light-modulated information transmission, optically recyclable materials, and multi-stimuli-responsive supramolecular systems.

Self-Healing, Robust, Liquid-Repellent Coatings Exploiting the Donor-Acceptor Self-Assembly

Liquid-repellent coatings with rapid self-healing and strong substrate adhesion have tremendous potential for industrial applications, but their formulation is challenging. We exploit synergistic chemistry between donor-acceptor self-assembly units of polyurethane and hydrophobic metal-organic framework (MOF) nanoparticles to overcome this challenge. The nanocomposite features a nanohierarchical morphology with excellent liquid repellence. Using polyurethane as a base polymer, the incorporated donor-acceptor self-assembly enables high strength, excellent self-healing property, and strong adhesion strength on multiple substrates. The interaction mechanism of donor-acceptor self-assembly was revealed via density functional theory and infrared spectroscopy. The superhydrophobicity of polyurethane was achieved by introducing alkyl-functionalized MOF nanoparticles and post-application silanization. The combination of the self-healing polymer and nanohierarchical MOF nanoparticles results in self-cleaning capability, resistance to tape peel and high-speed liquid jet impacts, recoverable liquid repellence over a self-healed notch, and low ice adhesion up to 50 icing/deicing cycles. By exploiting the porosity of MOF nanoparticles in our nanocomposites, fluorine-free, slippery liquid-infused porous surfaces with stable, low ice adhesion strengths were also achieved by infusing silicone oil into the coatings.

Simulating Assembly Landscapes for Comprehensive Understanding of Supramolecular Polymer-Solvent Systems

Complexity in supramolecular polymer systems arises from interactions between different components, including solvent molecules. By varying their concentration or temperature in such multicomponent systems, complex phenomena can occur such as thermally bisignate and dilution-induced assembly of supramolecular polymers. Herein, we demonstrate that both these phenomena emerge from the same underlying interaction mechanism between the components. As a model system, amide-decorated supramolecular polymers of porphyrins were investigated in combination with aliphatic alcohols as hydrogen-bond scavengers, and thermodynamic mass-balance models were applied to map the three-dimensional assembly landscapes. These studies unveiled that the interaction between hydrogen-bond scavengers and monomers is temperature-dependent and becomes dominant at high monomer concentrations. With these insights, we could exploit competitive monomer-alcohol interactions to prompt the dilution-induced assembly of various common monomers as well as bisignate assembly events. Moreover, kinetic insights were obtained by navigating through the assembly landscape. Similar to phase diagrams of covalent polymers, these assembly landscapes provide a comprehensive picture of supramolecular polymerizations, which helps to precisely regulate the system properties. The generality of this approach using assembly landscapes makes it relevant for any supramolecular system, and this enhanced control will open the door to build complex and functional supramolecular polymer systems.

Pillararene-Based Supramolecular Polymers for Cancer Therapy

Supramolecular polymers have attracted considerable interest due to their intriguing features and functions. The dynamic reversibility of noncovalent interactions endows supramolecular polymers with tunable physicochemical properties, self-healing, and externally stimulated responses. Among them, pillararene-based supramolecular polymers show great potential for biomedical applications due to their fascinating host-guest interactions and easy modification. Herein, we summarize the state of the art of pillararene-based supramolecular polymers for cancer therapy and illustrate its developmental trend and future perspective.

An Antitumor Dual-Responsive Host-Guest Supramolecular Polymer Based on Hypoxia-Cleavable Azocalix[4]arene

The exploitation of specific guests which can respond to external stimuli is the main approach for the construction of stimuli-responsive supramolecular polymers (SPs) based on host-guest interactions. Most functional guests, however, fail to manifest stimuli-responses. Herein, a hypoxia-responsive dimeric azocalixarene (D-SAC4A) with outstanding hosting properties was used as the macrocyclic building block for the preparation of host stimuli-responsive SPs. Since azocalixarenes can also be compatible with stimuli-responsive guests, an antitumor drug, camptothecin (CPT), was chosen and linked via a disulfide-containing linker to afford a glutathione (GSH)-responsive ditropic guest (D-CPT). A unique dual-responsive SP was obtained by 1 : 1 mixing of D-SAC4A and D-CPT in water, which further assembled into SP nanoparticles (DSPNs). DSPNs displayed outstanding stability against dilution and biological interferants, as well as precise CPT-release under GSH and hypoxia conditions. In vitro and in vivo experiments demonstrated the good biosafety and tumor-suppressive effects of DSPNs.

Introduction of Ferrocene as a Facilitator for the Construction of Supramolecular Polymers

Proper monomer design is the key to enhancing the strength of noncovalent interactions between the molecules toward the efficient formation of supramolecular polymers (SPs). We have designed and synthesized 1,n'-disubstituted ferrocene-azobenzene-long alkyl chains, Fc(CONH-Azo-TDP)₂ , to afford SPs with a high probability. The design exploits the ''molecular ball-bearing'' property of the ferrocene core, which allows two azobenzene arms to rotate in the planes of cyclopentadienyl rings, generating the most suitable molecular conformation required for SP formation. This ferrocene monomer formed a supergel consisting of SPs supported by strong intermolecular (H-bonding and π-π stacking) interactions and higher enthalpy gain than the reference molecules, where the central ferrocene core was replaced by flexible aliphatic as well as rigid benzene linkers. The molecular conformation involved in SPs, the strength of noncovalent interactions, and the process of supramolecular polymerization were investigated through NMR, UV-Vis, XRD and TEM studies. The results demonstrate that ferrocene may act as a good modulator for constructing efficient SPs.

Synthesis and enhanced photocatalytic application of porous nanocomposites of (r)GO/TiO2 embedded HCP (hyper crosslinked polymer)

Nanocomposites (r)GO/TiO₂/hyper crosslinked polymer (HCP) were prepared using ultrasonic-assisted method, and identified by (SEM), (EDS), (TEM), and (XRD) techniques. This study was performed to examine the effect of various operating parameters on photocatalytic degradation of Rhodamine B (Rh.B) over (r)GO/TiO₂ embedded HCP followed by an optimization study using response surface methodology (RSM) based on Box-Behnken design (BBD). The photocatalytic activity of rGO/TiO₂/polycalix[4]resorcinarene ((r)GTP) was evaluated using the cationic dye Rhodamine B as a pollutant model under solar light (intensity = 850 W/m²) between 10 and 12 am, June, Ahvaz, Iran. Response Surface Methodology was adopted for the optimization of degradation parameters viz pH, dye concentration, and nanocomposites dosage and contact time. The optimum values for the maximum Rhodamine B (Rh B) degradation of rGO/TiO₂/polycalix (rGTP) and GTP were obtained, in which the degradation of rGTP was 100% and the degradation efficiency of GO/TiO₂/polycalix (GTP) was 70%. ANOVA analysis results demonstrated that irradiation time and nanocomposite mass were the most significant parameters. It was found that rGO/TiO₂/polycalix[4]resorcinarene (rGTP) nanocomposite displayed the best degradation yield for the dye. The results showed that the rGTP nanocomposite displayed good EIS and CV properties besides being eco-friendly and reusable. It could also show a high capacity for the elimination of the dye in the industrial wastewaters.

Discovery of Y-Shaped Supramolecular Polymers in a Self-Assembling Peptide Amphiphile System

Supramolecular polymers (SPs) formed by self-assembly of peptide-based molecular units assume a variety of interesting one-dimensional (1D) morphologies. While the morphological complexity and phase behavior of self-assembling peptide conjugates bear some resemblance to those of low-molecular-weight and macromolecular surfactants, Y-junctions, or three-way connected constructs, a topological defect observed in traditional surfactants has not been identified, likely due to the intolerance of defective packing by the strong, associative interactions afforded by the peptide segments. Here we report our discovery of branched SPs with Y-junctions and occasionally enlarged spherical end-caps formed by micellization of a ferrocene-based peptide amphiphile in water. Our results suggest that the incorporation of two ferrocenes into the amphiphile design is key to ensure the formation of branched SPs. We hypothesize that the complex interplay of internal interactions limits the effective propagation of hydrogen bonding within the assemblies and, consequently, creates fragmented β-sheets that are more tolerant for supramolecular branching. Given the redox sensitivity of the ferrocene units, sequential addition of reductants and oxidants to the solution led the assemblies to reversibly transform between branched SPs and spherical aggregates.

Self-Assembling Behaviour of Perylene, Perylene Diimide, and Thionated Perylene Diimide Deciphered through Non-Covalent Interactions

The π-conjugated supramolecular polymers (SMP) have gained vast popularity in materials chemistry and biomedicine due to their spectacular self-assembling behaviour. A detailed account of the electronic structure and bonding through quantum theory of atoms-in-molecules, non-covalent interactions, and energy decomposition analysis (EDA) in the oligomers of perylene, perylene diimide (PDI), and thionated-PDI (t-PDI) is presented. The oligomers of all three molecules show a slip angle of θ≈62° thus forming H-aggregates. The stacking pattern in perylene oligomers prefers a slip-stacked brick-layer order, while the bulkier PDI and t-PDI prefer a parallel step-wise pattern in their oligomers. Successive addition of monomers leads to a consequent rise in the association energy, although to a much greater extent in PDI and t-PDI than in perylene. While the major contribution to this association energy comes from the dispersion interactions in all three systems, the steric interactions in t-PDI quench the cooperativity in its SMP formation. A detailed analysis of the non-covalent interactions reveals the presence of π-π, π-hole⋅⋅⋅O=C, and π-hole⋅⋅⋅S=C electrostatic interactions playing a crucial role in the self-assembly process, which can be further implemented on developing force field-based methods for understanding the self-assembling mechanism in higher degree of oligomers.

Growth Rate and Thermal Properties of DNA Origami Filaments

Synthetic DNA filaments exploit the programmability of the individual units and their predictable self-association to mimic the structural and dynamic features of natural protein filaments. Among them, DNA origami filamentous structures are of particular interest, due to the versatility of morphologies, mechanical properties, and functionalities attainable. We here explore the thermodynamic and kinetic properties of linear structures grown from a ditopic DNA origami unit, i.e., a monomer with two distinct interfaces, and employ either base-hybridization or base-stacking interactions to trigger the dimerization and polymerization process. By observing the temporal evolution of the system toward equilibrium, we reveal kinetic aspects of filament growth that cannot be easily captured by postassembly studies. Our work thus provides insights into the thermodynamics and kinetics of hierarchical DNA origami assembly and shows how it can be mastered by the anisotropy of the building unit and its self-association mode.

Density-tunable pathway complexity in a minimalistic self-assembly model

An open challenge in self-assembly is learning how to design systems that can be conditionally guided towards different target structures depending on externally-controlled conditions. Using a theoretical and numerical approach, here we discuss a minimalistic self-assembly model that can be steered towards different types of ordered constructs at the equilibrium by solely tuning a facile selection parameter, namely the density of building blocks. Metadynamics and Langevin dynamics simulations allow us to explore the behavior of the system in and out of equilibrium conditions. We show that the density-driven tunability is encoded in the pathway complexity of the system, and specifically in the competition between two different main self-assembly routes. A comprehensive set of simulations provides insight into key factors allowing to make one self-assembling pathway prevailing on the other (or vice versa), determining the selection of the final self-assembled products. We formulate and validate a practical criterion for checking whether a specific molecular design is predisposed for such density-driven tunability of the products, thus offering a new, broader perspective to realize and harness this facile extrinsic control of conditional self-assembly.

Dexamethasone loaded injectable, self-healing hydrogel microspheresbased on UPy-functionalized Gelatin/ZnHAp physical network promotes bone regeneration

Biopolymer-based injectable hydrogels provide great potential as bone tissue engineering (BTE) scaffolds on account of biocompatibility, and pore interconnectivity that enables delivery of cells and/or signaling molecules for bone repair. Recently, Gelatin hydrogels based on H-bonds were considered in response to concerns around the chemical crosslinking agents. In this study, a self-healing gelatin hydrogel with remarkable compressive and self-healing properties was prepared via formation of quadruple hydrogen bonds between ureidopyrimidinon functional groups, which were substituted on NH₂ groups of gelatin(GelUPy). Degree of substitution controls properties of the resulting hydrogel from a shape- memory hydrogel (100% substitution), to a hydrogel (about 80%), to this self-healing hydrogel (about 40%). We report a strategy that adopts an emulsion synthesis approach to delivery of dexamethasone and Ca/Zn ions from injectable self-healing GelUPy hydrogel (GelUPy-ZnHApUPy-DEX), to induce osteogenic differentiation of adipose-derived stem cells, in vitro, and enhance bone regeneration in a cranial bone defect in a rat model. We show that key properties of the composite hydrogels, including mechanical properties, and release behavior of DEX are a match to the requirements of BTE. Overall, our results demonstrate that this self-healing gelatin approach is a promising strategy to enhance bone regeneration through a minimally invasive procedure.

Bio-Vitrimers for Sustainable Circular Bio-Economy

The aim to achieve sustainable development goals (SDG) and cut CO₂-emission is forcing researchers to develop bio-based materials over conventional polymers. Since most of the established bio-based polymeric materials demonstrate prominent sustainability, however, performance, cost, and durability limit their utilization in real-time applications. Additionally, a sustainable circular bioeconomy (CE) ensures SDGs deliver material production, where it ceases the linear approach from production to waste. Simultaneously, sustainable circular bio-economy promoted materials should exhibit the prominent properties to involve and substitute conventional materials. These interceptions can be resolved through state-of-the-art bio-vitrimeric materials that display durability/mechanical properties such as thermosets and processability/malleability such as thermoplastics. This article emphasizes the current need for vitrimers based on bio-derived chemicals; as well as to summarize the developed bio-based vitrimers (including reprocessing, recycling and self-healing properties) and their requirements for a sustainable circular economy in future prospects.

Self-assembly in systems based on L-cysteine-silver-nitrate aqueous solution: multiscale computer simulation

We use fully atomistic, quantum mechanics and mesoscopic simulations to investigate multiscale structure formation in a supramolecular system based on aqueous solutions of silver nitrate with L-cysteine (CSS). Fully atomistic modeling reveals that silver mercaptide clusters are formed in solution at the stage of aging, which has a pronounced "core-shell" structure. The core is formed due to the bonding of SAg groups of silver mercaptide (SM) zwitterions while the shell consists of NH₃⁺ and C(O)O^- groups. Self-assembly of large-scale aggregates in CSS occurs due to the interaction of SM functional groups located on the surface of the clusters, which allows them to be considered supramonomers. Quantum-mechanical calculations reveal additional insight into the intermolecular interaction of L-cysteine with the components of the system. The data on the structure and properties of supramonomers are used to develop and parameterize a mesoscopic CSS model supplemented with allowance for salt concentration. In the mesoscopic model, supramonomers are presented as "sticky spheres", the interaction between which is determined by short-range and screened Coulomb potentials. Depending on the salt concentration, all structural transitions typical of CSS are observed: the formation of a stabilized colloidal dispersion, the filamentary aggregates of a gel network, the formation of large-scale unbound aggregates, and precipitation. These stages qualitatively reproduce the experimentally observed behavior of a real solution.

Synthesis and Evaluation of a Silver Nanoparticle/Polyurethane Composite That Exhibits Antiviral Activity against SARS-CoV-2

In this proof-of-concept study, we aim to produce a polyurethane (PU)-based composite that can reduce the amount of viable SARS-CoV-2 virus in contact with the surface of the polymeric film without further interventions such as manual cleaning. Current protocols for maintaining the hygiene of commonly used touchpoints (door handles, light switches, shop counters) typically rely on repeated washing with antimicrobial products. Since the start of the SARS-CoV-2 pandemic, frequent and costly surface sanitization by workers has become standard procedure in many public areas. Therefore, materials that can be retrofitted to touchpoints, yet inhibit pathogen growth for extended time periods are an important target. Herein, we design and synthesise the PU using a one-pot synthetic procedure on a multigram scale from commercial starting materials. The PU forms a robust composite thin film when loaded with 10 wt% silver nanoparticles (AgNPs). The addition of AgNPs increases the ultimate tensile strength, modules of toughness and modulus of elasticity at the cost of a reduced elongation at break when compared to the pristine PU. Comparative biological testing was carried out by the addition of pseudotyped virus (PV) bearing the SARS-CoV-2 beta (B.1.351) VOC spike protein onto the film surfaces of either the pristine PU or the PU nanocomposite. After 24 h without further human intervention the nanocomposite reduced the amount of viable virus by 67% (p = 0.0012) compared to the pristine PU treated under the same conditions. The significance of this reduction in viable virus load caused by our nanocomposite is that PUs form the basis of many commercial paints and coatings. Therefore, we envisage that this work will provide the basis for further progress towards producing a retrofittable surface that can be applied to a wide variety of common touchpoints.

Luminescence and Length Control in Nonchelated d 8 ‐Metallosupramolecular Polymers through Metal‐Metal Interactions

Supramolecular polymers (SPs) of d⁸ transition metal complexes have received considerable attention by virtue of their rich photophysical properties arising from metal‐metal interactions. However, thus far, the molecular design is restricted to complexes with chelating ligands due to their advantageous preorganization and strong ligand fields. Herein, we demonstrate unique pathway‐controllable metal‐metal‐interactions and remarkable ³MMLCT luminescence in SPs of a non‐chelated Pt^II complex. Under kinetic control, self‐complementary bisamide H‐bonding motifs induce a rapid self‐assembly into non‐emissive H‐type aggregates (1A). However, under thermodynamic conditions, a more efficient ligand coplanarization leads to superiorly stabilized SP 1B with extended Pt⋅⋅⋅Pt interactions and remarkably long ³MMLCT luminescence (τ^77 K=0.26 ms). The metal‐metal interactions could be subsequently exploited to control the length of the emissive SPs using the seeded‐growth approach.

The Contributions of Supramolecular Kinetics to Dynamics of Supramolecular Polymers

Supramolecular polymers exhibit well-controlled dynamics with fascinating capacity for remodeling, self-healing, and stimuli-responsiveness. Supramolecular kinetics of non-covalent bonds is a dominant control handle among the relevant factors to tailor dynamics of supramolecular polymers. This Review focuses on elucidating how supramolecular kinetics dictates the polymer dynamics in supramolecular polymer systems. The ways to tailor supramolecular kinetics are firstly examined as prerequisites for structure-activity study of supramolecular polymers. We next discuss the role of supramolecular kinetics in supramolecular polymers under different polymer architectures by the combination of both of theoretical and experimental studies. Finally, we conclude by discussing the existing challenges and opportunities in the current studies.