Mussel-inspired chemistry based on polydopamine (PDA) deposition has been developed as a facile and universal method for the surface modification of various materials. However, the inherent ...shortcomings of PDA coatings still impede their practical applications in the development of functional materials. In this review, we introduce the recent progress in the emerging dopamine-assisted co-deposition as a one-step strategy for functionalizing PDA-based coatings, and improving them in the aspects of deposition rate, morphology uniformity, surface wettability and chemical stability. The co-deposition mechanisms are categorized and discussed according to the interactions of dopamine or PDA with the introduced co-component. We also emphasize the influence of these interactions on the properties of the resultant PDA-based coatings. Meanwhile, we conclude the representative potential applications of those dopamine-assisted co-deposited coatings in material science, especially including separation membranes and biomaterials. Finally, some important issues and perspectives for theoretical study and applications are briefly discussed.
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•Mussel-inspired polydopamine deposition has been developed as a facile and universal method for surface modification.•Dopamine-assisted co-deposition has emerged to overcome the short-comings of polydopamine based deposition.•Co-deposition mechanisms are categorized according to the interactions of dopamine with the introduced co-component.•Representative potential applications of co-deposited coatings are reviewed based on their physicochemical properties.
The demand for highly efficient and multifunctional membranes in various separation processes is increasing. Recently, mussel-inspired polydopamine (PDA) has provided a promising way to meet these ...requirements because of its surface-adhesive property and film-forming ability. However, traditional PDA coatings usually suffer from the disadvantages of nonuniformity, incompactness, and instability, leading to poor molecular separation and service performance. Herein, uniform, compact, and robust PDA coatings were fabricated on an ultrafiltration substrate via a reasonable screening of oxidants for the oxidized self-polymerization of dopamine. The as-prepared PDA coatings were nanoporous (0.56 ± 0.04 and 0.93 ± 0.04 nm) with a thickness of ∼75 nm, which endows the composite membranes with a high solute rejection and solvent permeability during molecular separation. They are useful in organic solvent nanofiltration because of their superior structural stability. Moreover, the composite membranes can be used for recycling the nanometer catalyst from organic solvents for the first time, which has significantly broadened the potential applications of these mussel-inspired coatings for versatile separation processes.
A defect-free and stable selective layer is of critical significance for thin film composite membrane with excellent separation performance and service durability. We report a facial strategy for ...fabricating thin film nanocomposite (TFN) nanofltration membranes (NFMs) based on the codeposition of polydopamine, polyetheylenimine, and silica nanoparticles. Tripled water flux can be obtained from the TFN NFMs as compared with those NFMs without silica nanoparticles. This is ascribed to the improved wettability of the membrane surfaces and the enlarged pore sizes of the selective layer. The interfacial compatibility of the inorganic fillers and the polymer matrices can be enhanced by the electrostatic interactions of silica nanoparticles with polyethylenimine and the adhesive characteristics of polydopamine, resulting in a defect-free selective layer and then good rejection for both bivalent cations and neutral solutes. The rigid silica nanoparticles also improve the surface mechanical strength of the TFN NFMs effectively and lead to structural stability and compaction resistance during the long-term filtration process.
Engineering coatings with precise physicochemical properties allows for control over the interface of a material and its interactions with the surrounding environment. However, assembling coatings ...with well‐defined properties on different material classes remains a challenge. Herein, we report a co‐assembly strategy to precisely control the structure and properties (e.g., thickness, adhesion, wettability, and zeta potential) of coatings on various materials (27 substrates examined) using quinone and polyamine building blocks. By increasing the length of the amine building blocks from small molecule diamines to branched amine polymers, we tune the properties of the films, including the thickness (from ca. 5 to ca. 50 nm), interfacial adhesion (0.05 to 5.54 nN), water contact angle (130 to 40°), and zeta potential (−42 to 28 mV). The films can be post‐functionalized through the in situ formation of diverse nanostructures, including nanoparticles, nanorods, and nanocrystals. Our approach provides a platform for the rational design of engineered, substrate‐independent coatings for various applications.
Coatings and thin films of amino‐quinone networks are prepared on various materials by a co‐assembly strategy using quinones and polyamines. Using different building blocks affords precise control over the structures and properties of the coatings, which can serve as multifunctional reaction platforms to synthesize nanoparticles on surfaces.
Bioinspired polyphenol/polyamine codeposition has been demonstrated by the competence for surface modification; however, the reaction processes including mechanism and kinetics remain superficially ...understood. In this work, the catechol (CA)–amine reaction has been thoroughly investigated by using CA and two amines m-phenylenediamine and piperazine. We verify that both primary and secondary amines are prone to link with CA through Michael addition to form polyphenol/polyamine oligomers under aerobic and mild-alkaline conditions. Molecular simulations indicate that the Michael addition products are dominant for both aromatic and aliphatic amines with CA, which supports the durable chem- and phystability of the codeposited coatings. The aggregation kinetics of polyphenol/polyamine is provided for the first time, and the formed aggregates show high-adhesive properties, which can be deposited as the skin layers for high-performance nanofiltration membranes.
We propose a novel strategy for narrowing down the pore size distribution of ready-made nanofiltration membranes (NFMs) via pore wall modification. NFMs were subjected to the filtration of a highly ...reactive molecule solution, during which large pores were selectively reduced in size. The as-treated NFMs have high monovalent ion/divalent ion selectivity.
Mussel-inspired chemistry has been broadly exploited for multifunctional coatings in the surface modification of applied materials. Polyphenols are ubiquitous in plant tissues and far less expensive ...than polydopamine for mussel-inspired chemistry. Herein, we report a facile and effective method to modify porous membranes viathe co-deposition of catechol (CCh) and polyethyleneimine (PEI). The membrane structures and properties were investigated by ATR/FTIR, XPS, FESEM, zeta potential, water contact angle and pure water flux measurements. The results reveal that the membranes deposited with a CCh-PEI mass ratio of 1 : 0.25 show excellent hydrophilicity, ultrahigh water permeation flux and distinguished surface charges. These membranes were used to decolorize anionic dye solutions during filtration with superior removal efficiencies of over 99%. Moreover, they have good reusability over repeated operations with a simple regeneration process.
Nanofiltration membranes (NFMs) are widely used in saline water desalination, wastewater treatment, and chemical product purification. However, conventional NFMs suffer from broad pore size ...distribution, which limits their applications for fine separation, especially in complete separation of molecules with slight differences in molecular size. Herein, defect-free composite NFMs with narrow pore size distribution are fabricated using a contra-diffusion method, with dopamine/polyethylenimine solution on the skin side and ammonium persulfate solution on the other side of the ultrafiltration substrate. Persulfate ions can diffuse through the ultrafiltration substrate into the other side and in situ trigger dopamine to form a codeposited coating with polyethylenimine. The codeposition is hindered on those sites completely covered by the polydopamine/polyethylenimine coating, although it is promoted at the defects or highly permeable regions because it is induced by the diffused persulfate ions. Such a “self-completion” process results in NFMs with highly uniform structures and narrow pore size distribution, as determined by their rejection of neutral solutes. These near electrically neutral NFMs show a high rejection of divalent ions with a low rejection of monovalent ions (MgCl2 rejection = 96%, NaCl rejection = 23%), majorly based on a steric hindrance effect. The as-prepared NFMs can be applied in molecular separation such as isolating cellulose hydrogenation products.
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