Amine Monomer Research Articles

Bubble Drainage Assisted Fabrication of Polyamide Membranes with Crater-like Structures for Efficient Desalination.

Bubble drainage (BD) occurs in various natural phenomena and industrial activities, in which bubbles rise toward the water surface and create a progressively thinned two-sided liquid film, called a lamella. Surfactant, as an important regulator in the BD process, not only assembles on both sides of the lamellae, generating a configuration of lamellae sandwiched by monolayers of surfactants (lamellae/MS), but also induces interfacial deformation by lowering interfacial tension. Herein, we developed a strategy of BD assisted interfacial polymerization for the fabrication of polyamide (PA) membranes. The regulated interfacial deformation at the water-oil interface produced a membrane with crater-like structures, which greatly increased the surface area of the PA membrane. Moreover, the lamellae/MS configuration served as a reservoir to spontaneously enrich amine monomers and thus modulate the diffusion-reaction kinetics. The resulting PA membranes exhibited superior separation performance with a water permeance of 44.7 L m-2 h-1 bar-1 and a Na2SO4 rejection of 99.2%.

Ultrafast Water Transport of Reverse Osmosis Membrane Based on Quasi-Vertically Oriented 2D Interlayer.

Interlayered thin-film composite (i-TFC) membranes based on 2D materials have been widely studied due to their high efficiency in mass transfer. However, the randomly stacked 2D nanosheets usually increase the fluid path length to some extent. Herein, in situ-grown quasi-vertically oriented 2D ZIF-L was introduced as an interlayer for preparing high-performance reverse osmosis (RO) membranes. Through the optimization of the crystal growth based on the inert polyethylene substrate, the novel i-TFC RO membrane via interfacial polymerization shows an outstanding water permeance (5.50 L m-2 h-1 bar-1) and good NaCl rejection (96.3%). The membrane also shows promising potential in domestic water purification and organic solvent separation applications. Compared with the randomly stacked ZIF-L interlayer, the advantages of the vertically oriented one were ascribed to the excellent storage capacity of the amine monomers and the intensified gutter effect. This work will encourage more exploration on the interlayer architectures for high-performance i-TFC membranes.

Poly-(aminoethyl piperazine) membranes with ultra-thin selective layers prepared via a rate-retarded interfacial polymerization method

New monomers have been exploring to fabricate interfacial polymerized thin film composite membranes for decades. N-aminoethyl piperazine (AEP), an aliphatic amine with a heterocyclic structure, was used in this work as an amine monomer to synthesize nanofiltration membranes. Due to the high reactivity nature of AEP, a rate-retarded interfacial polymerization method was applied, which was realized by applying ultra-low AEP concentration (0.07 wt%), low reaction temperature (4 °C monomer solutions), and ice-water quench. The resulting AEP membrane had much better performance (3–4 times permeance and closed rejections) compared with the membranes prepared by the hot water post-treatment and the oven heat treatment. At lower monomer concentrations, an NF membrane with a selective layer thickness of only around 20 nm was prepared by the rate-retarded interfacial polymerization method. The membranes had a negatively charged surface with "willow leaf" like morphology. The MWCO was around 200 g mol−1, and the water permeance was up to 22.8 L m−2 h−1 bar−1, which is comparable with the commercial polyamide membrane NF270. Therefore, AEP is a very competitive alternative monomer for NF membrane synthesis.

Poly(β-amino ester) polymer library with monomer variation for mRNA delivery

Non-viral vectors for mRNA delivery primarily include lipid nanoparticles (LNPs) and polymers. While LNPs are known for their high mRNA delivery efficiency, they can induce excessive immune responses and cause off-target effects, potentially leading to side effects. In this study, we aimed to explore polymer-based mRNA delivery systems as a viable alternative to LNPs, focusing on their mRNA delivery efficiency and potential application in mRNA vaccines. We created a library of poly(β-amino ester) (PBAE) polymers by combining various amine monomers and acrylate monomers. Through screening this polymer library, we identified specific polymer nanoparticles (PNPs) that demonstrated high mRNA expression efficiency, with sustained mRNA expression for up to two weeks. Furthermore, the PNPs showed mRNA expression only at the injection site and did not exhibit liver toxicity. Additionally, when assessing immune activation, the PNPs significantly induced T-cell immune activation and were effective in the plaque reduction neutralization test. These results suggest that polymer-based mRNA delivery systems not only hold potential for use in mRNA vaccines but also show promise for therapeutic applications.

Construction of sub-10nm ultra-thin polyamide layer using porous GOQDs-AGQDs interlayer

The application of high-performance polyamide nanofiltration membranes with controllable structures shows promising prospects in fields such as seawater desalination and wastewater treatment. In this study, a high-performance polyamide composite nanofiltration membrane with sub-10nm ultra-thin separation layer was designed and fabricated using a hydrophilic porous GOQDs-AGQDs (graphene oxide quantum dots-amino graphene quantum dots) interlayer to reconstruct the substrate architecture. The GOQDs-AGQDs interlayer not only improved the uniformity and smoothness of the microporous substrate, but also could form hydrogen bond with amine monomers to effectively inhibit its diffusion, thereby effectively slowing down the interfacial polymerization process and facilitating the formation of an ultra-thin, smooth and dense polyamide (PA) layer. The results demonstrate that the optimized PA/GOQDs-AGQDs/PES membrane achieved a PA separation layer thickness as low as 9.4 nm, with a permeation flux of 27.2 L·m−2 ·h−1·bar−1, nearly three times that of the original PA/PES membrane. Simultaneously, it enhanced the Na2SO4 rejection rate to 97.1 %, achieving synchronous improvements in permeability and selectivity. Additionally, the PA/GOQDs-AGQDs/PES composite membrane exhibited relatively low surface roughness and demonstrated excellent long-term stability. This work presents a novel strategy for the controllable fabrication of high-performance nanofiltration membranes.

Synthesis of Quinone‐Amine‐Linked Covalent Organic Frameworks for Boosting the Photocatalytic Removal of Uranium

AbstractCompared to imine covalent organic frameworks (COFs), the superior stability of amine‐linked COFs renders them more suitable for long‐term harsh real‐world environments. Their numerous amine sites can serve as functional groups or be subjected to post‐modification to further enhance the performance of the material. However, the assortment and abundance of amine‐linked COFs via currently lacking due to restricted monomer varieties and synthetic methods. Herein, this study presents an innovative approach for synthesizing quinone‐amine‐linked COFs by directly combining 2,5‐dihydroxy‐1,4‐benzoquinone (DHBQ) with various amine monomers and introduce a novel photocatalyst, DHBQ‐TAPP‐COF, specifically tailored to efficiently reduce uranium in harsh environments. DHBQ‐TAPP‐COF features a unique donor–acceptor structure, with the DHBQ units serving as acceptors because they contain abundant oxygen atoms that facilitate metal ion coordination, thereby enhancing charge carrier separation, carrier utilization, and uranium reduction efficiency. The quinone‐amine linkages offer improved stability, extended π‐conjugation, heightened local polarity, and conductivity, which enable efficient carrier transfer within the material and thus enhance the overall performance of the uranium photocatalyst. The proposed photocatalyst can efficiently reduce U(VI) without sacrificial agents or decomposition to precipitate UO2 at a recovery rate exceeding 98%. This catalyst provides an efficient and convenient strategy for the stable and high‐performance photocatalytic reduction of uranium.

Expanding interfacial polymerization for gas separation beyond water purification

Extending interfacial polymerization (IP) to gas separation is challenging due to microdefects in dry conditions, despite its attractive and straightforward processability. This study presents a systematic defect-tailoring approach for highly reproducible polyamide (PA) thin film composite (TFC) membranes with precise size-sieving ability. The approach combines highly porous polyethylene support, extended IP reaction time (60 min), and post-thermal/solvent treatments, resulting in a homogeneous PA selective layer. Particularly, isopropanol treatment removes less-reacted amine-rich monomers/oligomers and promotes PA network chain relaxation, enhancing molecular-sieving capability. The resulting PA TFC membrane exhibits a remarkable H2/CO2 selectivity of 24.8 (±3.1) and an H2 permeance of 13.6 (±1.8) gas permeation unit, surpassing the polymeric upper bound. It also ensures mechanical stability under high feed pressure and resistance to physical aging, highlighting its robustness. Additionally, universality is validated using different amine monomers. This systematic method provides a valuable framework for producing reproducible PA TFC membranes with exceptional gas separation performance, enabling practical implementation across industrial sectors.

Modulating low-temperature interfacial polymerization with NaHCO3 for high-performance ultrathin nanofiltration membranes

Conventional interfacial polymerization (IP) encounters significant challenges in achieving the desired nanofiltration (NF) membrane structure, owing to uncontrolled diffusion and ultrafast polymerization. Our study introduced carbonates into the low-temperature interfacial polymerization (LTIP) process to precisely regulate the diffusion of amine monomers and polymerization kinetics. Carbonates in the aqueous phase restrict the diffusion of amine monomers while promoting the generation of nanobubbles. Further utilization of the low-temperature oil phase not only retards polymerization but also facilitates the formation of foam nanostructures in the polyamide layer. Density functional theory calculations and molecular dynamics simulations revealed the mechanisms underlying the regulation of amine monomer diffusion and gas-bubble release by carbonates and LTIP. The fabricated membrane has a smoother, ultrathin separation layer while maintaining a high permeability of 35.0 L·m−2·h−1·bar−1 (nearly doubled compared with the pristine membrane) and high Na2SO4 rejection of 99.5 %. This study confirms the practicality of the carbonate-modulated LTIP strategy.

Boosted Intracavity Aperture in Macrocyclic Amines Enabling Finely Regulated Microporous Membranes.

Finely tuning the pore structure of traditional nanofiltration (NF) membranes is challenging but highly effective for achieving efficient separations. Herein, we propose a concept of using macrocyclic amines (1,4,7-triazacyclononane, 3A; 1,4,7,10-tetraazacyclododecane, 4A1; and 1,4,8,11-tetraazacyclotetradecane, 4A2) with different intra-annular apertures to finely modulate the pore structure of microporous membranes via interfacial polymerization (IP). The boost in the intracavity size of the building blocks results in heightened steric hindrance of these amine monomers, leading to a controlled increase in membrane pore size, as demonstrated by both film characterizations and multiscale simulations. In conjunction with the increased intracavity size, the water permeability follows an augmented trend of 3A-TMC, 4A1-TMC, and 4A2-TMC (TMC: trimesoyl chloride) while exhibiting increased molecular weight cut-offs due to larger free-volume elements and stronger pore interconnectivity. Our proposed macrocyclic amine design strategy provides a guideline for finely regulated microporous membranes with high potential in NF-related applications.

Assembly‐Dissociation‐Reconstruction Synthesis of Covalent Organic Framework Membranes with High Continuity for Efficient CO2 Separation

AbstractCovalent organic frameworks (COFs), at the forefront of porous materials, hold tremendous potential in membrane separation; however, achieving high continuity in COF membranes remains crucial for efficient gas separation. Here, we present a unique approach termed assembly‐dissociation‐reconstruction for fabricating COF membranes tailored for CO2/N2 separation. A parent COF is designed from two‐node aldehyde and three‐node amine monomers and dissociated to high‐aspect‐ratio nanosheets. Subsequently, COF nanosheets are orderly reconstructed into a crack‐free membrane by surface reaction under water evaporation. The membrane exhibits high crystallinity, open pores and a strong affinity for CO2 adsorption over N2, resulting in CO2 permeance exceeding 1060 GPU and CO2/N2 selectivity surpassing 30.6. The efficacy of this strategy offers valuable guidance for the precise fabrication of gas‐separation membranes.

Surfactant-interlayer assisted interfacial polymerization for constructing Janus nanofiltration membranes: Enhanced Li+/Mg2+ separation efficiency

Nanofiltration (NF) technology shows significant potential for lithium extraction, but the limited Mg2+ rejection of conventional negatively charged NF membranes constrains Li+/Mg2+ selectivity. This work proposed a surfactant-interlayer assisted interfacial polymerization (SIAIP) methodology to convert a traditional NF membrane into a Janus membrane featuring dual-electrical properties. Sodium dodecyl sulfate (SDS) restricted the IP reaction region and modulated the interfacial diffusion behavior of amine monomers. The hydrophilic and negatively charged hyaluronic acid (HA) interlayer modified the substrate, enhancing membrane permeability. Under the combined influence of SDS and HA, more amine monomers were stored and diffused to the reaction interface, transforming the membrane surface into a positively charged region and forming a Janus structure with the negatively charged interlayer. The optimal SIAIP membranes possessed a homogeneous pore size distribution, with a high selectivity (S Li, Mg) of 42.15 and superb permeability of 11.06 L m−2 h−1 bar−1. This investigation furnishes an innovative approach for developing high-efficiency Li+/Mg2+ separating NF membranes.

Assembly-Dissociation-Reconstruction Synthesis of Covalent Organic Framework Membranes with High Continuity for Efficient CO2 Separation.

Covalent organic frameworks (COFs), at the forefront of porous materials, hold tremendous potential in membrane separation; however, achieving high continuity in COF membranes remains crucial for efficient gas separation. Here, we present a unique approach termed assembly-dissociation-reconstruction for fabricating COF membranes tailored for CO2/N2 separation. A parent COF is designed from two-node aldehyde and three-node amine monomers and dissociated to high-aspect-ratio nanosheets. Subsequently, COF nanosheets are orderly reconstructed into a crack-free membrane by surface reaction under water evaporation. The membrane exhibits high crystallinity, open pores and a strong affinity for CO2 adsorption over N2, resulting in CO2 permeance exceeding 1060 GPU and CO2/N2 selectivity surpassing 30.6. The efficacy of this strategy offers valuable guidance for the precise fabrication of gas-separation membranes.

Effect of surface hydroxyl group density of support membrane on water permeance of polyamide thin-film composite membrane

Polyamide-based thin-film composite (TFC) membranes are widely used in water treatment processes. Recently, the influence of support membranes on the performance of polyamide layers has garnered considerable attention. Regarding the chemical properties of the support membranes, the surface wettability and the interaction between the amine monomer used for interfacial polymerization and the membrane surface are considered to play crucial roles. In this study, we investigated the effect of the wettability of the support membrane surface and its interaction with the amine monomer on the water permeance of TFC membranes. We prepared TFC membranes on polyketone support membranes with varying surface hydroxyl group densities and aqueous solution wettabilities. While no clear correlation was observed between the support membrane's wettability and the water permeance of the TFC membrane, an increase in hydroxyl group density did result in higher water permeance. The hydroxyl groups interact with PIP, inhibiting PIP diffusion and potentially leading to the formation of a thinner polyamide layer, which enhances water permeance. Therefore, the interaction between the amine monomer and support membrane surface strongly affects the formation of the polyamide layer.

Anionic COF nanosheets construct porous and charged interlayer for the preparation of high-performance desalination membranes

Polyamide (PA) membranes prepared by interfacial polymerization (IP) provide an effective solution for efficient desalination. The IP reaction, as a diffusion-controlled polymerization reaction, regulates the storage and diffusion of monomers in the IP process to achieve effective regulation of the PA membrane structure. Higher initial monomer concentration and slower monomer release rate can effectively reduce the membrane thickness and enhance the permeance of the membrane. Herein, ionic covalent organic framework (iCOF) materials with well-developed and ordered pore channels bearing high-density –SO3H groups are used to construct a porous and charged interlayer to regulate the release process of monomers during the IP process. The well-ordered pore structure of iCOF provides sufficient storage space for amine monomers and uniform monomer distribution, accelerating the closure of the incipient film. Moreover, the electrostatic interactions between the high density of negatively charged anionic groups on iCOF and the positively charged amine monomer can reduce the diffusion coefficient of the amine monomer by a factor of two. The above two effects resulted in a nearly 10-fold reduction in the thickness of the PA separation layer and an increase in water permeance up to 24.8 L m−2 h−1 bar−1, nearly three times improvement compared to unmodified PA membrane.

Hyperbranched aromatic poly(amidoamine) mediated interfacial polymerization for high-performance thin film composite membranes

The escalating global demand for clean water has driven a growing interest in developing thin-film composite (TFC) membranes with high permeability and selectivity for wastewater treatment and desalination processes. Engineering polymer materials with precisely tunable properties for selective molecular separation remains a challenging step toward achieving this goal. Herein, we have fabricated a highly permselective asymmetric polyamide nanofilm with a dual-layer structure in which the bottom layer is a porous hyperbranched aromatic polyamide (HBPA) interlayer, and the top layer is a dense polyamide layer with a nanostrip structure. The HBPA porous layer was covalently assembled in situ via oxidative coupling reaction with ammonium persulfate on a polysulfone (PSF) substrate. The hydrophilic porous HBPA interlayer forms nanosized cavities that may enhance the storage and confine amine monomer diffusion, leading to the construction of a striped pattern PA nanofilm. The resulting asymmetric PA membrane exhibits excellent water permeability of 18.39 ± 1 L m−2 h−1 bar−1 (3.98 times that of control membranes) and improved divalent salt (Na2SO4) rejection (≥98 %), surpassing most of the commercial and reported nanofiltration membranes. The HBPA-regulated interfacial polymerization provides a groundbreaking framework for developing high-performance membranes for precisely controlled nanofiltration.

Ultrasonic preparation of fluorinated functionalised magnetic covalent organic frameworks for adsorption and removal of tetrabromobisphenol A

Tetrabromobisphenol A (TBBPA) was a widely used brominated flame retardant, and had attracted widespread attention from researchers due to its potential adverse effects on ecosystems and human health. Therefore, to eliminate the negative effects of TBBPA, methods for the adsorption and removal of TBBPA are urgently needed. In this work, the fluorine-functionalised magnetic covalent organic frameworks (Fe3O4@TFAPT-TFPA@COF) were first prepared through a simple and rapid ultrasound method to efficiently adsorpt and remove TBBPA. Firstly, a pre-modification strategy was used to modify fluorine functional groups onto amine monomers via superacid catalyzed trimerization. Then, amine and aldehyde monomers undergo Schiff base reaction smoothly to form a COF layer coated on the surface of Fe3O4 nanoparticles. The characterisation results indicated that the prepared Fe3O4@TFAPT-TFPA@COF had a high surface area, porosity, crystallinity and abundant F-containing binding sites. Additionally, the adsorption process of prepared Fe3O4@TFAPT-TFPA@COF complied with pseudo-second-order kinetics and the Langmuir adsorption model. It had a large adsorption capacity (107.5 mg g−1), could effectively remove tetrabromobisphenol A within 4 minutes and had excellent regeneration ability within eighth repetitions. Finally, tetrabromobisphenol A was efficiently removed by a small separation column loaded with Fe3O4@TFAPT-TFPA@COF, achieving levels below the detection limit (< 0.05 mg L−1) and providing practical application value for the real-time removal of TBBPA. The main mechanisms promoting the excellent adsorption performance of TBBPA were through halogen bonds, electrostatic interactions, π-π stacking, and hydrogen bonding interactions, providing potential reference value for the adsorption ability and mechanism of TBBPA in other applications.

Preparation and evaluation of Urea‐F amine crosslinkers

AbstractThis study presents the preparation of a long‐chain amine solution, employing the concept of urea‐formaldehyde synthesis. We also investigate the performance shifts in the cured product post‐urea addition. The Urea‐F curing agent is prepared by reacting EDA/DETA/TETA/TEPA, formaldehyde, and urea, and crosslinked with bisphenol A epoxy resin (E51). The crosslinking agent solves the problem of urea not being suitable for curing epoxy resin, and it improves the problem of low mechanical strength of traditional amine crosslinked epoxy resin cured materials. The cured product underwent evaluation through acid and alkali resistance solution measurement and mechanical and thermal tests. The results show enhanced heat resistance in the cured product, with its maximum thermal decomposition rate exceeding 350°C. The cured products have better mechanical properties than the amine monomers, with enhanced bending strength and superior acid–base solution resistance. The scanning electron microscopy micrograph indicates that the cured product fractures have a tight internal structure.

Structure and positive charge regulation in nanofiltration membrane by novel nanomaterial g-C3N5 for efficient Li+/Mg2+ separation

The positively charged nanofiltration (NF) membrane prepared via interfacial polymerization (IP) of polyethyleneimine (PEI) and trimesoyl chloride (TMC) has drawn considerable attention for lithium-magnesium separation, particularly crucial for lithium recovery from salt lakes with high Mg2+/Li+ mass ratios. However, NF membranes prepared solely from amine monomers have not achieved efficient Li+ and Mg2+ separation. In this study, PEI-g-C3N5/TMC composite NF membranes were successfully fabricated by mixing amino-rich graphitic carbon nitride (g-C3N5) with PEI, followed by the IP reaction of the mixed solution with TMC. Molecular dynamics (MD) simulation results showed that g-C3N5 had an attractive effect on PEI, which led to a decrease in the diffusion rate of PEI, thereby resulting in a thinner separation layer. Density functional theory (DFT) revealed that g-C3N5 competed with PEI, leading to a reduction in the crosslinking within the polyamide (PA) layer and subsequently causing an increase in the surface pore size of the membrane. Besides, the hydrophilicity and positive charge of the modified membrane were both improved. MD simulations, transition state theory, and DLVO principles indicated that the modification of the PA layer by g-C3N5 enhanced the repulsion of Mg2+ and the transport of Li+ during the NF process. This breakthrough effectively overcame the trade-off effect between membrane separation and permeability, especially at a g-C3N5 content of 0.06 wt%, where the lithium-magnesium selectivity coefficient (SLi, Mg = 18.18) and pure water flux (Flux = 58.59 L m−2 h−1) reached the optimum values. Meanwhile, the PEI-g-C3N5/TMC membrane demonstrated stable separation performance during prolonged filtration and in solutions with varying Mg2+/Li+ mass ratios. This study not only provides an effective strategy for the design of NF membranes but also expands the application prospects of nanomaterials in the field of membrane separation.

Zr-BTB nanosheets assist in optimizing the structure of forward osmosis membranes to enhance the lithium concentration performance

Recently, low-energy forward osmosis (FO) technology has been employed in the lithium concentration stage during the extraction of lithium from brine sources. The interlayer FO membrane is renowned for its exceptional structural characteristics; however, challenges remain in selecting suitable interlayer materials and exploring their control mechanisms on amine monomers. As interlayer materials, traditional 3D nanomaterials are prone to detachment, while traditional 2D materials without micropores can increase the transmission resistance of water molecules. This study introduces a novel FO membrane utilizing Zr-BTB nanosheets with 5.4 Å micropores as the interlayer material. Based on detection and simulation calculations, it was found that the increase in steric hindrance and interaction forces jointly slowed the diffusion of amine monomers in the presence of the Zr-BTB interlayer. This results in a thinner separation layer, facilitating water transport. The interlayer also plays crucial roles in preventing defective pore formation in the separation layer and assisting in intercepting salt ions. The Zr-BTB interlayer membrane exhibited a water flux of 29.14 L m−2 h−1 and a reverse salt flux of 0.16 g m−2 h−1, which are superior to those of many FO membranes reported in the field. The prepared membrane also has excellent performance in lithium concentration applications, and its separation mechanism was explored by MD simulations.

Controlling amine monomers via UiO-66-NH2 defect sites to enhance forward osmosis membrane performance for lithium recovery

The excessive thickness of the separation layer and the presence of cracks cause low water flux and poor lithium recovery in conventional forward osmosis (FO) membranes. According to the influence of the diffusion behavior of amine monomers in interfacial polymerization, the use of an interlayer optimizes the separation layer structure of traditional thin-film composite FO membrane. However, it is difficult to accurately control the separation layer structure by simply adjusting the amount of the interlayer material loaded. Herein, FO membranes with defect-containing metal–organic framework (MOF) interlayers were constructed. By adjusting the concentrations of competitive ligands, the MOFs showed different degrees of linker loss, which exposed the metal ions in the MOFs to different extents. The defective sites of the constructed MOFs increased the interaction between the interlayer and m-phenylenediamine (MPD), and density functional theory (DFT) simulations also revealed an increase in the binding energy of the two materials. Therefore, MPD attachment and diffusion were controlled by changing the proportion of defects in the MOFs, thereby finely regulating the separation layer structure. Additionally, tannic acid (TA) was predeposited to improve the stability of the interlayer. The prepared membrane exhibited water fluxes of 33.84 and 65.81 LMH and reverse salt fluxes of 0.58 and 2.38 gMH in the active layer facing feed solution (AL-FS) and active layer facing draw solution (AL-DS) modes, respectively. Excellent lithium ion recovery and fouling resistance was also demonstrated in battery wastewater treatment.