Coordination Crosslinking Research Articles

Engineering plasticization resistant gas separation membranes using metal-organic nanocapsules.

Membrane technologies hold great potential for industrial gas separation. Nevertheless, plasticization, a common phenomenon that is responsible for the loss of gas pair selectivity and the decrease of membrane lifespan, is one of the top challenges withholding the deployment of advanced membrane materials in realistic applications. Here, we report a highly generalizable approach, that utilizes PgC5Cu, a copper metal–organic nanocapsule (MONC) containing 24 open metal sites (OMSs) as a multi-dentate node to coordinatively crosslink polymers. By adding merely 1–3 wt% of PgC5Cu, a wide range of carbonyl group-containing polymers can be effectively crosslinked. Through rigorous dissolution tests, molecular dynamic simulations, and in situ FT-IR spectroscopy, we qualitatively and quantitatively unveiled the coordinative binding nature at the polymer–MONC interface. As a result, we produced a series of composite membranes showing near complete plasticization resistance to CO2, C2H4, and C2H6 under high pressure with no loss of mechanical and gas transport properties.

Correction: A two-dimensional metallosupramolecular framework design based on coordination crosslinking of helical oligoamide nanorods

Correction for ‘A two-dimensional metallosupramolecular framework design based on coordination crosslinking of helical oligoamide nanorods’ by Norton G. West et al., Mater. Adv., 2020, 1, 1134–1141, DOI: 10.1039/D0MA00123F.

A two-dimensional metallosupramolecular framework design based on coordination crosslinking of helical oligoamide nanorods

Coordination crosslinking of oligoamide nanorods yields two dimensional metallosupramolecular framework.

Zn(II)-modified imidazole containing polyimide/ZIF-8 mixed matrix membranes for gas separations

Finely tailoring the interfacial interaction to minimize the defective structure in the hybrid membranes is a key to yield a mixed matrix membrane with enhanced gas separation performance. Here, a highly selective mixed matrix membrane based on imidazole containing polyimides and ZIF-8 fillers is reported. The ZIF-8 with imidazole linker offers a more compatible interface with imidazole containing polyimides. At a MOF loading of 20 wt. %, the membranes have a 2.2-fold increase in the gas permeabilities over unfilled polymers with exceptional H2/CH4 and CO2/CH4 gas selectivities of 224 and 58, respectively. The H2 and CO2 gas permeabilities are 78.5 and 20.3 Barrer, respectively. The Zn2+ post-modification enables the formation of metal coordination crosslinking with enhanced polymer/ZIF-8 interaction, as indicated by increased glass transition temperature, improved thermal stability and insoluble properties in organic solvents. With the proper control of Zn2+ treatment conditions, gas permeabilities of H2 and CO2 can be increased to 110.1 and 27.4 Barrer, respectively, with the constant H2/CH4 and CO2/CH4 gas selectivity. For membranes treated at higher Zn2+ concentration, an enhancement in H2/CH4 gas selectivity was observed with the selectivity increasing from 223.9 to 318.3 and H2 permeability around 72.3 Barrer. The separation performance of H2/CH4 for all Zn2+ modified membranes exceeds the 2008 Robeson upper bound. This facile approach to tune polymer/MOF interaction via metal ion modification promotes the rational design of high-performance gas separation membranes.

Expanding the Toolbox of Metal-Phenolic Networks via Enzyme-Mediated Assembly.

Functional coatings are of considerable interest because of their fundamental implications for interfacial assembly and promise for numerous applications. Universally adherent materials have recently emerged as versatile functional coatings; however, such coatings are generally limited to catechol, (ortho-diphenol)-containing molecules, as building blocks. Here, we report a facile, biofriendly enzyme-mediated strategy for assembling a wide range of molecules (e.g., 14 representative molecules in this study) that do not natively have catechol moieties, including small molecules, peptides, and proteins, on various surfaces, while preserving the molecule's inherent function, such as catalysis (≈80 % retention of enzymatic activity for trypsin). Assembly is achieved by in situ conversion of monophenols into catechols via tyrosinase, where films form on surfaces via covalent and coordination cross-linking. The resulting coatings are robust, functional (e.g., in protective coatings, biological imaging, and enzymatic catalysis), and versatile for diverse secondary surface-confined reactions (e.g., biomineralization, metal ion chelation, and N-hydroxysuccinimide conjugation).

Regulating Cu(II)-benzimidazole coordination structure in rigid-rod aramid fiber and its composites enhancement effects

Coordination crosslinking, as the kind of strongest supramolecular interaction, has been widely introduced into flexible polymer chains, including rubbers and aerogels, while that in rigid-rod polymer is much rare, due to the difficulty in rigid-rod macromolecules' configuration change. Moreover, the exact coordination structure inside those polymers is not clear. Herein, this coordination interaction was incorporated into a traditional rigid-rod polymer, aramid fiber, by Cu2+-benzimidazole coordination reaction, through the careful control of the dynamic reaction conditions, and the structural/performance relationships of fiber and its composites are detailed studied. It is seen that two different coordination structures, S-coordination style (Cu2+ coordination with single benzimidazole unit) and M-coordination style (Cu2+ coordination with multiple benzimidazole units from different macromolecular chains), could be both obtained inside fiber, using different solvents as the reaction medium. Moreover, using reaction kinetics equilibrium, we presented a mathematical method to investigate those two coordination structures in detail, including their average coordination numbers of Cu2+ and reaction equilibrium constant (K). Further, the experimental results show that the fiber with average coordination number of 2 exhibits a comprehensive improved performance in heat/solvent resistance, fluorescence emission as well as fiber's transverse properties, with the corresponding increase of 54.2% and 47.1% for its composites interfacial properties and compressive strength, compared with untreated fiber.

Thermal, mechanical, electrical and thermoelectric properties of Bi–As–Se glasses

The current study focuses on the impact of As addition on the thermal, mechanical, electrical and thermoelectric properties of ternary \({\text{Bi}}_{0.02} {\text{As}}_{\text{x}}\,{\text{Se}}_{{0.98 - {\text{x}}}}\) (\(0.02 \le x \le 0.08\)) glasses. Different elastic moduli such as the micro-hardness (H), Young’s modulus (Y), bulk modulus (K), Poisson’s ratio (Pr) and shear modulus (S) as well as Debye temperature (TD) for the studied glasses were estimated by using the measured values of the ultrasonic speeds (transfer, vl, and shear, vs) and density (ρ). Moreover, the measured values of the dc electrical conductivity (σdc) and thermoelectric power (Sthermo) were used to estimate the activation energies for the electrical (ΔEdc) and for thermoelectric (ΔEthermo) conductions, respectively. It was found that σdc increases, whereas Sthermo, ΔEdc and ΔEthermo decrease with increasing the As content for the \({\text{Bi}}_{0.02} {\text{As}}_{\text{x}}\,{\text{Se}}_{{0.98 - {\text{x}}}}\) (\(0.02 \le x \le 0.08\)) thin films. In addition, replacement of Se with As atoms results in an increase in the average coordination number (CN), cross-linking density (Cd), cohesive energy (CE), ρ, H, Y, K, S and TD, whereas the molar volume (Vm), Pr and the homopolar Se–Se bonds decreased. Both of Y and K as well as ΔEdc are correlated with the glass transition temperature (Tg).

Mussel-Inspired Self-Healing Metallopolymers for Silicon Nanoparticle Anodes.

Polymers with supramolecular functionality are receiving increasing attention for rechargeable battery binders as strong supramolecular interactions can facilitate self-healing effects via bond recovery of the cleaved cross-links. Such self-healing capability is useful for emerging high-capacity battery materials that undergo large volume changes. Benchmarking mussel's sticky byssus cuticle, herein we report a copolymer binder with Fe3+-(tris)catechol coordination cross-links, which can induce a self-healing effect for silicon anodes. The high strength of the Fe3+-(tris)catechol coordination bond can lead to recovery of the dissociated bond that occurs from the large volume expansion of silicon. The given copolymer also contains monomer units with sufficient flexibility to increase the interchain motions for efficient Fe3+-(tris)catechol bond recovery. The superior electrochemical performance of the Si electrodes based on the proposed copolymer binder indicates that metallopolymers which utilize metal-organic ligand coordination for interchain cross-linking are promising binders with self-healing effects for sustainable cycling of high capacity battery electrodes.

Impact of the aluminum sulfate 18‐hydrate particle size on the coordination crosslinking behaviors of acrylonitrile–butadiene rubber–aluminum sulfate 18‐hydrate composites

ABSTRACTIn this study, aluminum sulfate 18‐hydrate [Al2(SO4)3·18H2O] particles of different sizes, which were obtained via high‐energy ball‐milling technology, were successfully compounded with acrylonitrile–butadiene rubber (NBR) to fabricate crosslinked rubber composites. The results suggest that high‐energy ball milling had no significant change on the crystal structure of Al2(SO4)3·18H2O, but it significantly reduced the particle size. The effects of the particles size on the coordination crosslinking behaviors and mechanical properties of the NBR–Al2(SO4)3·18H2O composites were fully explored. The coordination crosslinking reaction was demonstrated to occur between the nitrile group (─CN) and Al(III). Moreover, with the decreasing particle size, the composites achieved a better interfacial adhesion and more crosslinking points, and this led to significant increases in the crosslinking density and the mechanical properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47717.

Ln3+-Induced Diblock Copolymeric Aggregates for Fully Flexible Tunable White-Light Materials.

In this research contribution, nano-aggregates have been fabricated by introducing lanthanide (Ln3+) ions into solutions of amphiphilic diblock copolymers of polystyrene-b-poly (acrylic acid) (PS-b-PAA). The coordination of acrylic acid segments to lanthanide cations induces diblock copolymer (BCPs) self-assembly in order to design stable white luminescent hybrid nanoparticles with fine uniform particle size. The introduction of Ln3+ ions (Eu3+ and Tb3+) bestows the micelles, precisely white light, upon excitation of 342 nm. Lanthanide coordination cross-linking of poly (acrylic acid) segments, or blocks, endows the micelles higher thermal stability than that of BCPs micelles without cross-linking. As the most important key point of this work, the regular and stable nano-particles with high emission quality can make fully flexible electroluminescent devices with self-formation or uncoordinated into polymer hosts. Instead of inorganic luminescent nanoparticles with hard cores, this method can potentially apply for fully flexible white-light emitting diodes (FFWLEDs).

An injectable self-healing coordinative hydrogel with antibacterial and angiogenic properties for diabetic skin wound repair

We report here an injectable, self-healing coordinative hydrogel with antibacterial and angiogenic properties for diabetic wound regeneration. The hydrogel was prepared by coordinative cross-linking of multi-arm thiolated polyethylene glycol (SH-PEG) with silver nitrate (AgNO3). Due to the dynamic nature of Ag-S coordination bond and bacteria-killing activity of Ag+, the resultant coordinative hydrogel featured self-healing, injectable and antibacterial properties. In this study, we synchronously loaded an angiogenic drug, desferrioxamine (DFO), in the coordinative hydrogel during cross-linking. We finally obtained a multifunctional hydrogel that is manageable, resistant to mechanical irritation, antibacterial and angiogenic in vitro. Our in vivo studies further demonstrated that the injectable self-healing hydrogel could efficiently repair diabetic skin wounds with low bacteria-infection and enhance angiogenic activity. In short, besides diabetic skin wound repair, such dynamic multifunctional hydrogel scaffolds would show great promise in the regeneration of different types of exposed wounds, in particular, in situations with disturbed physiological functions, high risk of bacterial infections, and external mechanical irritation.

Disassociation and Reformation Under Strain in Polymer with Dynamic Metal–Ligand Coordination Cross-Linking

Dynamic bonding is a key factor for self-healing and stimuli-response polymeric materials. However, a detailed molecular-level understanding on effects from dynamic bond break and reform from inter...

Anions reversibly responsive luminescent nanocellulose hydrogels for cancer spheroids culture and release

Artificial stimuli-responsive hydrogels that can mimic natural extracellular matrix for growth and release of cancer spheroids (CSs) have attracted much attention. However, such hydrogels still face a challenge in regulating CSs growth and controlled release as well as keeping CSs integrity. Herein, a new class of ClO−/SCN− reversibly responsive nanocellulose hydrogel with fluorescence on-off reporter is developed. Upon addition of ClO−, the gel network of nanocellulose hydrogel was destructed, accompanying by the fluorescent quenching. Notably, when introducing of SCN−, a red fluorescence filamentous hydrogel was recovered by coordination cross-linking. The hydrogel reforms in a completely reversible process through the regulation of ClO−/SCN−. Benefit from the above response features of the hydrogel, the growth of cancer spheroids (CSs) in the hydrogel and on demand release of CSs from the hydrogel could be easily achieved through ClO−/SCN− regulation. Importantly, the growth and release of CSs can be monitored in real time by fluorescence imaging. Overall, such design strategy based on ClO−/SCN−-responsive fluorescent hydrogels provided a new type of multi-responsive hydrogels as main scaffolds for cancer research and cancer drug screening.

Improved tensile strength of acrylonitrile–butadiene rubber/anhydrous copper sulfate composites prepared by coordination cross-linking

Acrylonitrile–butadiene rubber (NBR)/anhydrous copper sulfate (CuSO4) composites were prepared by coordination cross-linking. CuSO4 particles of different sizes are obtained by ball milling in acetone. During heat pressing at 190 °C, a strong cross-linking reaction occurred, which resulted from coordination between cupric ions and nitrile groups. Results showed that the mean size of CuSO4 particles decreased from 7.1 to 0.4 μm after ball milling. Accordingly, the number of coordination cross-linking points increased remarkably, which resulted in an increase in the glass transition temperature and equilibrium torque of the composites. Two models were employed to discuss the cross-link density and demonstrated that both CuSO4 particles and cupric ions contributed to the improvement of cross-linking points. It was noteworthy that this composite exhibited high strength and toughness, with 73.5 MPa tensile strength and 423.7% elongation at break. Moreover, a unique stretching phenomenon, including the features of both rubber and plastic, was observed and explained in detail.

Imidazole-Bearing Polymeric Micelles for Enhanced Cellular Uptake, Rapid Endosomal Escape, and On-demand Cargo Release

The complex design of multifunctional nanomedicine is beneficial to overcome the multiple biological barriers of drug delivery, but it also presents additional hurdles to clinical translation (e.g., scaling-up and quality control). To address this dilemma, we employed a simple imidazole-bearing polymer micelle for enhanced cellular uptake, facilitated endosomal escape, and on-demand release of a model drug, SN-38. The micelles were crosslinked by the reversible imidazole/Zn2+ coordination with a drug loading of ca. 4% (w/w) and a diameter less than 200nm. Under mimicked tumor microenvironment (pH6.8), the surface charge of micelles reversed from negative to positive, leading to enhanced micellesuptake by model 4T1 cells. Such effect was verified by fluorescent labelling of micelles. Compared to imidazole-free nanocarriers, the charge-reversal micelles delivered significantly more SN-38 to 4T1 cells. Due to the proton sponge effect, imidazole-bearing micelles could rapidly escape from endosomes compared to the control micelles, as evidenced by the kinetic analysis of micelle/endosome co-localization. The coordination crosslinking also enabled the acid-triggered drug release. This work provides a "three birds with one stone" approach to achieve the multifunctionality of nanocarriers without complicated particle design, and opens new avenues of advancing nanomedicine translation via simple tailored nanocarriers.

A novel loose-NF membrane based on the phosphorylation and cross-linking of polyethyleneimine layer on porous PAN UF membranes

In this study, a novel loose-NF membrane was fabricated by coating the polyethyleneimine (PEI) layer on a hydrolyzed polyacrylonitrile (HPAN) ultrafiltration membrane, followed by phosphorylation with inositol hexaphosphate (IP6) and cross-linking process. The cross-linked network was constructed by the coordinative cross-linking of Fe (III) ion and phos-(PEI), and the electrostatic attraction of PEI and IP6. At the optimized fabricating conditions, the loose-NF membrane exhibited both high rejection to dyes and transmission to different salts. The rejections of 0.1 g/L methyl blue (MB), congo red (GR), acid fuchsin (AF) and crystal violet (CV) aqueous solutions respectively were 99.92%, 99.53%, 98.99% and 92.86%, and the corresponding fluxes were 11.54, 10.96, 11.40 and 11.76 L m−2 h−1 at operating pressure of 0.2 MPa. Meanwhile, the membrane exhibited low rejections to different salt solutions with the order of MgCl2 (30.51%) > MgSO4 (20.57%) > NaCl (7.46%) > Na2SO4 (5.89%) and fluxes around 19 L m−2 h−1 at 0.2 MPa. Moreover, the prepared membrane possessed high stability for dealing with biologically treated textile effluent (100 h).

A Metal Coordination Crosslinking Novel High Performance Thermoset

N-substituted crosslinking polybenzimidazole pyridine sulfone, as novel high performance functional polymers, was prepared by the coordination of N-substituted polybenzimidazole pyridine sulfone (Py-N-PBIS) ligand with varying content of metallic ion (Co2+, Ni2+, Zn2+). The structures of the polymers were characterized by means of FT-IR and 1H NMR spectroscopy, and the results showed a good agreement with the proposed structures. TGA measurements exhibited that the crosslinking polymers possessed good thermal stability with high thermal decomposition temperatures (thermally stable up to 405-510 °C). Additionally, the thermal stability of the coordination polymers was improved constantly with the increasing of the content of Co2+, Ni2+ or Zn2+. The metal coordination crosslinking N-substituted polybenzimidazole pyridine sulfone could be considered as a novel high performance thermoset.

Thermosensitive behavior of hydrophobically associating anionic guar gum solutions and gels

Herein, we describe the syntheses of novel thermoassociating anionic guar gums (TGGs) with long aliphatic and polyethylene glycol (PEG) segments and characterize these gums by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. Additionally, we explore the properties of TGG solutions and gels by viscometry, dynamic light scattering, fluorescence spectroscopy, and rheometry, revealing the thermoresponsive behavior of these systems. Thus, TGG solution viscosity increases with decreasing PEG segment length below 35°C, with an opposite trend observed at 60°C. Similarly, the critical association concentration increases with increasing PEG segment length at room temperature, with an opposite dependence detected at 50°C. High temperature results in almost complete hydrophobization of PEG segments, endowing TGG solutions with unique thermoassociating behavior. Moreover, TGG gels feature both coordination and physical crosslinking, with the latter enhanced by increased hydrophobic group length, and therefore exhibit viscosities much higher than that of the parent sulfo-hydroxypropyl guar gum (SHG) gel. The storage moduli of TGG gels reach their maxima with increasing temperature. Additionally, the addition of NaCl increases the viscosities of TGG gels to maximum values exceeding that of the SHG gel.

Metal-coordination crosslinked N-polyindoles as recyclable high-performance thermosets and nondestructive detection for their tensile strength and glass transition temperature.

Metal coordination crosslinking between stiff N-polyindole chains was constructed, and the crosslinked films exhibited high tensile strength, high heat resistance and excellent polar solvent resistance. The noncovalent crosslinking can be further removed via external pyrophosphate, which endows the crosslinked polymer with a recyclable behavior. The tensile strength and glass transition temperature of the polymers can be nondestructively detected by taking advantage of the fluorescence quenching effect of metal coordination to the adjacent bipyridine structure.

Mussel-Inspired Self-Healing Double-Cross-Linked Hydrogels by Controlled Combination of Metal Coordination and Covalent Cross-Linking.

Mussel-inspired hydrogels held together by reversible catecholato-metal coordination bonds have recently drawn great attention owing to their attractive self-healing, viscoelastic and adhesive properties together with their pH-responsive nature. A major challenge in these systems is to orchestrate the degree of catechol oxidation that occurs under alkaline conditions in air and has a great impact on the aforementioned properties because it introduces irreversible covalent cross-links to the system, which stiffens the hydrogels but consume catechols needed for self-healing. Herein, we present a catechol-based hydrogel design that allows for the degree of oxidative covalent cross-linking to be controlled. Double cross-linked hydrogels with tunable stiffness are constructed by adding the oxidizable catechol analogue, tannic acid, to an oxidation-resistant hydrogel construct held together by coordination of the dihydroxy functionality of 1-(2'-carboxyethyl)-2-methyl-3-hydroxy-4-pyridinone to trivalent metal ions. By varying the amount of tannic acid, the hydrogel stiffness can be customized to a given application while retaining the self-healing capabilities of the hydrogel's coordination chemical component.