Phenolic materials have long been known for their use in inks, wood coatings, and leather tanning. However, there has recently been a renewed interest in engineering advanced materials from phenolic ...building blocks. The intrinsic properties of phenolic compounds, such as metal chelation, hydrogen bonding, pH responsiveness, redox potentials, radical scavenging, polymerization, and light absorbance, have made them a distinct class of structural motifs for the synthesis of functional materials. Materials prepared from phenolic compounds often retain many of these useful properties with synergistic effects in applications ranging from catalysis to biomedicine. This Review provides an overview of the diverse functional materials that can be prepared from natural and synthetic phenolic building blocks, as well as their applications.
Phenolics on the rise: Recent advances in the preparation of functional materials, namely thin films, particles, and bulk materials, based on phenolic building blocks and their diverse applications, ranging from biomedicine to catalysis, are highlighted. This Review will help integrate various disciplines that use phenols and serve as a guide for the development of future materials.
The tunable growth of metal–organic materials has implications for engineering particles and surfaces for diverse applications. Specifically, controlling the self‐assembly of metal–phenolic networks ...(MPNs), an emerging class of metal–organic materials, is challenging, as previous studies suggest that growth often terminates through kinetic trapping. Herein, kinetic strategies were used to temporally and spatially control MPN growth by promoting self‐correction of the coordinating building blocks through oxidation‐mediated MPN assembly. The formation and growth mechanisms were investigated and used to engineer films with microporous structures and continuous gradients. Moreover, reactive oxygen species generated by ultrasonication expedite oxidation and result in faster (ca. 30 times) film growth than that achieved by other MPN assembly methods. This study expands our understanding of metal–phenolic chemistry towards engineering metal–phenolic materials for various applications.
Kinetic assembly is an efficient strategy for rapidly and continuously growing metal–phenolic network materials. Using reactive oxygen species, films were grown about 30 times faster than with existing technologies. Furthermore, the films display unique microstructures and continuous film gradients, which are desirable properties for applications in drug delivery and separations.
Abstract
We report a facile strategy for engineering diverse particles based on the supramolecular assembly of natural polyphenols and a self-polymerizable aromatic dithiol. In aqueous conditions, ...uniform and size-tunable supramolecular particles are assembled through π–π interactions as mediated by polyphenols. Owing to the high binding affinity of phenolic motifs present at the surface, these particles allow for the subsequent deposition of various materials (i.e., organic, inorganic, and hybrid components), producing a variety of monodisperse functional particles. Moreover, the solvent-dependent disassembly of the supramolecular networks enables their removal, generating a wide range of corresponding hollow structures including capsules and yolk–shell structures. The versatility of these supramolecular networks, combined with their negligible cytotoxicity provides a pathway for the rational design of a range of particle systems (including core–shell, hollow, and yolk–shell) with potential in biomedical and environmental applications.
Hybrid conformal coatings, such as metal–phenolic networks (MPNs) that are constructed from the coordination-driven assembly of natural phenolic ligands, are of interest in areas including ...biomedicine, separations, and energy. To date, most MPN coatings have been prepared by immersing substrates in solutions containing the phenolic ligands and metal ions, which is a suitable method for coating small or flexible objects. In contrast, more industrially relevant methods for coating and patterning large substrates, such as spray assembly, have been explored to a lesser extent toward the fabrication of MPNs, particularly regarding the effect of process variables on MPN growth. Herein, a spray assembly method was used to fabricate MPN coatings with various phenolic building blocks and metal ions and their formation and patterning were explored for different applications. Different process parameters including solvent, pH, and metal–ligand pair allowed for control over the film properties such as thickness and roughness. On the basis of these investigations, a potential route for the formation of spray-assembled MPN films was proposed. Conditions favoring the formation of bis complexes could produce thicker coatings than those favoring the formation of mono or tris complexes. Finally, the spray-assembled MPNs were used to generate superhydrophilic membranes for oil–water separation and colorless films for UV shielding. The present study provides insights into the chemistry of MPN assembly and holds promise for advancing the fabrication of multifunctional hybrid materials.
The development of fluorescence labeling techniques has attracted widespread interest in various fields, including biomedical science as it can facilitate high‐resolution imaging and the ...spatiotemporal understanding of various biological processes. We report a supramolecular fluorescence labeling strategy using luminescent metal‐phenolic networks (MPNs) constructed from metal ions, phenolic ligands, and common and commercially available dyes. The rapid labeling process (<5 min) produces ultrathin coatings (≈10 nm) on diverse particles (e.g., organic, inorganic, and biological entities) with customized luminescence (e.g., red, blue, multichromatic, and white light) simply through the selection of fluorophores. The fluorescent coatings are stable at pH values from 1 to 8 and in complex biological media owing to the dominant π interactions between the dyes and MPNs. These coatings exhibit negligible cytotoxicity and their strong fluorescence is retained even when internalized into intracellular compartments. This strategy is expected to provide a versatile approach for fluorescence labeling with potential in diverse fields across the physical and life sciences.
A supramolecular fluorescence labeling strategy is established using luminescent metal‐phenolic networks constructed from metal ions, phenolic ligands, and dye molecules. Tunable and customized luminescence (e.g., red, blue, multichromatic, and white light) is achieved on inorganic, organic, and biological particles, with potential applications in the physical and life sciences.
The manipulation of interfacial properties has broad implications for the development of high‐performance coatings. Metal–phenolic networks (MPNs) are an emerging class of responsive, adherent ...materials. Herein, host–guest chemistry is integrated with MPNs to modulate their surface chemistry and interfacial properties. Macrocyclic cyclodextrins (host) are conjugated to catechol or galloyl groups and subsequently used as components for the assembly of functional MPNs. The assembled cyclodextrin‐based MPNs are highly permeable (even to high molecular weight polymers: 250–500 kDa), yet they specifically and noncovalently interact with various functional guests (including small molecules, polymers, and carbon nanomaterials), allowing for modular and reversible control over interfacial properties. Specifically, by using either hydrophobic or hydrophilic guest molecules, the wettability of the MPNs can be readily tuned between superrepellency (>150°) and superwetting (ca. 0°).
Networking: The synthesis of host phenolic building blocks, consisting of macrocyclic host rings and phenolic coordinating functions, enables the rapid assembly of adherent conformal metal–phenolic network coatings on diverse substrates with modular and tunable interfacial properties using host–guest chemistry.
The synthesis of metal nanoparticle (NP)‐coated textiles (nanotextiles) is achieved by a dipping process in water without toxic chemicals or complicated synthetic procedures. By taking advantage of ...the unique nature of tannic acid, metal‐phenolic network‐coated textiles serve as reducing and stabilizing sites for the generation of metal nanoparticles of controllable size. The textiles can be decorated with various metal nanoparticles, including palladium, silver, or gold, and exhibit properties derived from the presence of the metal nanoparticles, for example, catalytic activity in water (>96% over five cycles using palladium nanoparticles) and antibacterial activity against Gram‐negative bacteria (inhibition of Escherichia coli using silver nanoparticles) that outperforms a commercial bandage. The reported strategy offers opportunities for the development of hybrid nanomaterials that may have application in fields outside of catalysis and antimicrobials, such as sensing and smart clothing.
Just dipping produces metal nanoparticle‐coated textiles (nanotextiles) without involving toxic chemicals or complicated synthetic steps. This versatile method enables the incorporation of various metal nanoparticles of controllable size, including palladium, silver, or gold, on the textiles. These nanotextiles show >96% catalytic activity in water over five cycles and superior antibacterial activity when compared against a commercial antibacterial bandage.
Fluorinated motifs are promising for the engineering of repellent coatings, however, a fundamental understanding of how to effectively bind these motifs to various substrates is required to improve ...their stability in different use scenarios. Herein, the binding of fluorinated polyhedral oligomeric silsesquioxanes (POSS) using a cyanoacrylate glue (binder) is computationally and experimentally evaluated. The composite POSS–binder coatings display ultralow surface energy (≈10 mJ m−2), while still having large surface adhesions to substrates (300–400 nN), highlighting that super‐repellent coatings (contact angles >150°) can be readily generated with this composite approach. Importantly, the coatings show super‐repellency to both corrosive liquids (e.g., 98 wt% H2SO4) and ultralow surface tension liquids (e.g., alcohols), with ultralow roll‐off angles (<5°), and tunable resistance to liquid penetration. Additionally, these coatings demonstrate the potential in effective cargo loading and robust self‐cleaning properties, where experimental datasets are correlated with both relevant theoretical predictions and systematic all‐atom molecular dynamics simulations of the repellent coatings. This work not only holds promise for chemical shielding, heat transfer, and liquid manipulations but offers a facile yet robust pathway for engineering advanced coatings by effectively combining components for their mutually desired properties.
Super‐repellent nanocomposite coatings, consisting of low‐energy fluorinated motifs and adherent polymeric binders, can undergo rapid assembly and anchor to various substrate, displaying robust and durable resistance to a wide spectrum of liquids (including corrosive liquids and low surface tension liquids), with the super‐repellency strongly correlating to the physiochemical properties of the interface demonstrated both experimentally and theoretically.
Minimizing the interaction of nanomedicines with the mononuclear phagocytic system (MPS) is a critical challenge for their clinical translation. Conjugating polyethylene glycol (PEG) to nanomedicines ...is regarded as an effective approach to reducing the sequestration of nanomedicines by the MPS. However, recent concerns about the immunogenicity of PEG highlight the demand of alternative low‐fouling polymers as innovative coating materials for nanoparticles. Herein, a highly hydrophilic sulfoxide‐containing polymer—poly(2‐(methylsulfinyl)ethyl acrylate) (PMSEA)—is used for the surface coating of iron oxide nanoparticles (IONPs). It is found that the PMSEA polymer coated IONPs have a more hydrophilic surface than their PEGylated counterparts, and demonstrate remarkably reduced macrophage cellular uptake and much less association with human plasma proteins. In vivo study of biodistribution and pharmacokinetics further reveals a much‐extended blood circulation (≈2.5 times longer in terms of elimination half‐life t1/2) and reduced accumulation (approximately two times less) in the organs such as the liver and spleen for IONPs coated by PMSEA than those by PEG. It is envisaged that the highly hydrophilic sulfoxide‐containing polymers have huge potential to be employed as an advantageous alternative to PEG for the surface functionalization of a variety of nanoparticles for long circulation and improved delivery.
An innovative class of sulfoxide‐containing polymer is used as an exceptional surface functionalization material for nanoparticles. The highly hydrophilic nature of the polymer endows nanoparticles with remarkable low‐fouling property as demonstrated by weak interaction with plasma proteins, prolonged blood circulation, and improved biodistribution profile of conjugated nanoparticles.
Particle‐based pulmonary delivery has great potential for delivering inhalable therapeutics for local or systemic applications. The design of particles with enhanced aerodynamic properties can ...improve lung distribution and deposition, and hence the efficacy of encapsulated inhaled drugs. This study describes the nanoengineering and nebulization of metal–phenolic capsules as pulmonary carriers of small molecule drugs and macromolecular drugs in lung cell lines, a human lung model, and mice. Tuning the aerodynamic diameter by increasing the capsule shell thickness (from ≈100 to 200 nm in increments of ≈50 nm) through repeated film deposition on a sacrificial template allows precise control of capsule deposition in a human lung model, corresponding to a shift from the alveolar region to the bronchi as aerodynamic diameter increases. The capsules are biocompatible and biodegradable, as assessed following intratracheal administration in mice, showing >85% of the capsules in the lung after 20 h, but <4% remaining after 30 days without causing lung inflammation or toxicity. Single‐cell analysis from lung digests using mass cytometry shows association primarily with alveolar macrophages, with >90% of capsules remaining nonassociated with cells. The amenability to nebulization, capacity for loading, tunable aerodynamic properties, high biocompatibility, and biodegradability make these capsules attractive for controlled pulmonary delivery.
The aerodynamic diameters of metal–phenolic capsules are nanoengineered by increasing their shell thickness, which facilitates tailored capsule deposition in a mechanical lung model. The engineered capsules are promising for pulmonary delivery owing to their robustness for nebulization, biocompatibility, biodegradability, and their capacity for cargo loading and surface functionalization.
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