Reducing active layer thickness of polyamide composite membranes using a covalent organic framework interlayer in interfacial polymerization

Polyamide(PA)-based thin-film composite membranes exhibit enormous potential in water purification,owing to their facile fabrication,decent performance and desirable stability.However,the thick PA active layer with high transport resistance from the conventional interfacial polymerization hampers their applications.The controllable fabrication of a thin PA active layer is essential for high separation efficiency but still challenging.Herein,a covalent organic framework TpPa-1 interlayer was firstly deposited on a polyethersulfone(PES)substrate to reduce the thickness of PA active layer in interfacial polymerization.The abundant pores of TpPa-1 increase the local concentration of amine monomers by adsorbing piperazine molecules,while hydrogen bonds between hydrophilic groups of TpPa-1 and piperazine molecules slow down their diffusion rate.Arising from those synergetic effects,the PA active layer is effectively reduced from 200 nm to 120 nm.By optimizing TpPa-1 interlayer and PA active layer,the water flux of resultant membranes can reach 171.35 L·m^-2·h^-1·MPa^-1,which increased by 125.4%compared with PA/PES membranes,while the rejection rates of sodium sulfate and dyes solution remained more than 90%and 99%,respectively.Our strategy may stimulate rational design of ultrathin PA-based nanofiltration membranes with high performances.

Preparation of Composite Charge-mosaic Hollow Fiber Membrane by Interfacial Polymerization

The preparation of composite charge-mosaic membrane included spinning of hollow fiber as the supporting membrane, preparing a selective layer on the inside surface of the fiber by interfacial polymerization. The charge-mosaic membranes show a high salt permeability while retaining sucrose. The charge-mosaic membrane can be effectively used to separate multivalent salts with organic matter of molecular weight great than 300 g/mol in industry.

Covalent organic frameworks-incorporated thin film composite membranes prepared by interfacial polymerization for efficient CO_(2) separation

Thin film composite(TFC)membranes with nanofillers additives for CO_(2)separation show promising applications in energy and environment-related fields.However,the poor compatibility between nanofillers and polymers in TFC membranes is the main problem.In this work,covalent organic frameworks(COFs,TpPa-1)with rich ANHA groups were incorporated into polyamide(PA)segment via in situ interfacial polymerization to prepare defect-free TFC membranes for CO_(2)/N_(2)separation.The formed covalent bonds between TpPa-1 and PA strengthen the interaction between nanofillers and polymers,thereby enhancing compatibility.Besides,the incorporated COFs disturb the rigid structure of the PA layer,and provide fast CO_(2)transfer channels.The incorporated COFs also increase the content of effective carriers,which enhances the CO_(2)facilitated transport.Consequently,in CO_(2)/N_(2)mixed gas separation test,the optimal TFC(TpPa_(0.025)-PIP-TMC/m PSf)membrane exhibits high CO_(2)permeance of 854 GPU and high CO_(2)/N_(2)selectivity of 148 at 0.15 MPa,CO_(2)permeance of 456 GPU(gas permeation unit)and CO_(2)/N_(2)selectivity of 92 at 0.5 MPa.In addition,the Tp Pa_(0.025)-PIP-TMC/m PSf membrane also achieves high permselectivty in CO_(2)/CH_(4)mixed gas separation test.Finally,the optimal TFC membrane showes good stability in the simulated flue gas test,revealing the application potential for CO_(2)capture from flue gas.

Highly permeable reverse osmosis membranes incorporated with hydrophilic polymers of intrinsic microporosity via interfacial polymerization

Enhancing the water permeation while maintaining high salt rejection of existing reverse osmosis(RO)membranes remains a considerable challenge.Herein,we proposed to introduce polymer of intrinsic microporosity,PIM-1,into the selective layer of reverse osmosis membranes to break the trade-off effect between permeability and selectivity.A water-soluble a-LPIM-1 of low-molecular-weight and hydroxyl terminals was synthesized.These designed characteristics endowed it with high solubility and reactivity.Then it was mixed with m-phenylenediamine and together served as aqueous monomer to react with organic monomer of trimesoyl chloride via interfacial polymerization.The characterization results exhibited that more“nodule”rather than“leaf”structure formed on RO membrane surface,which indicated that the introduction of the high free-volume of a-LPIM-1 with three dimensional twisted and folded structure into the selective layer effectively caused the frustrated packing between polymer chains.In virtue of this effect,even with reduced surface roughness and unchanged layer thickness,the water permeability of prepared reverse osmosis membranes increased 2.1 times to 62.8 L·m^(-2)·h^(-1) with acceptable Na Cl rejection of 97.6%.This attempt developed a new strategy to break the trade-off effect faced by traditional polyamide reverse osmosis membranes.

Ultrathin Nanofilms Prepared by Interfacial Polymerization

Recently,Livingston and his colleagues published two articles in Nature and Science,respectively,to tackle the challenges of accurate molecular sieving and crude oil separation in the field of membrane separation by preparing ultrathin nanofilms through interfacial polymerization.One is that the nanofilms with ordered sub-nanopores achieve accurate molecular sieving atångström precision,and the other is that the permeability of hydrophobic polyamide nanofilms to hydrophobic liquid is significantly enhanced by an order of magnitude.The thoughtful design and excellent performance provide a feasible strategy for the development of membrane separation,and show great potential in industrial applications(drug separation and crude oil fractionation).

Epoxy microcapsules for high-performance self-healing materials using a novel method via integrating electrospraying and interfacial polymerization

The high-efficiency fabrication of high-quality microcapsules containing epoxy is crucial to the further development of the potential practical self-healing epoxy systems based on microencapsulated two-part epoxy-amine chemistry.Herein,a novel microencapsulation technique based on non-equilibrium droplets via integrating electrospraying and interfacial polymerization(ES-IP)was established to efficiently microencapsulate epoxy monomers.The ES-IP technique,consisting of three continuous steps,i.e.electrospraying to massively generate droplets,enwrapping every single droplet through instant interfacial polymerization,and thickening shell at an elevated temperature,has great flexibility to regulate the microencapsulation process and the microcapsule quality.The fabricated core-shell structured epoxy microcapsules(Ep-MCs)were comprehensively characterized for their properties,showing that they have high cleanness with rare impurities,controllable and tunable size,good thermal stability and tightness,and high effective core fraction.The high-quality Ep-MCs were adopted to formulate a self-healing epoxy based on the microencapsulated epoxy-amine chemistry.The highest healing efficiency,in terms of the recovered mode I fracture toughness,of 110±17%was achieved after being healed at room temperature(~25℃)for 48 h.While the developed ES-IP technique facilitates the microencapsulation technique based on non-equilibrium droplets,the fabricated high-quality Ep-MCs greatly promote the further developments of the practical self-healing materials.

Emulsion interfacial polymerization of anticancer peptides:fabricating polypeptide nanospheres with high drug-loading efficiency and enhanced anticancer activity

The development of drug delivery systems with high drug-loading efficiency, kinetic stability against dilution, as well as enhanced anticancer activity is of crucial importance to the fields of self-assembly and nanomedicine. Herein, we propose a strategy where the anticancer peptide acts as water-soluble monomer to directly participate in emulsion interfacial polymerization for fabricating polypeptide nanospheres. The constructed polypeptide nanospheres hold a high drug loading efficiency of 77%, and can be stably dispersed in highly diluted aqueous solutions. The acid-labile amide linkage in polypeptide nanospheres can be hydrolyzed in tumor acidic environments, thus releasing anticancer peptides selectively. The polypeptide nanospheres achieve significantly enhanced anticancer activity against HCT116 cells in vitro and in vivo through improved mitochondrial and membrane disruption. In addition, its side effects on normal cells can be reduced significantly. It is highly anticipated that more kinds of anticancer drug candidates or anticancer drugs can be applied to fabricate polymeric nanomedicines with improved anticancer activity through this strategy.

Polyamide Nanofiltration Membrane from Surfactant-assembly Regulated Interfacial Polymerization of 2-Methylpiperazine for Divalent Cations Removal

Removal of metal ions from water can not only alleviate the scaling problem of domestic and industrial water,but also solve the water safety problem caused by heavy metal ion pollution.Here,we fabricate a positively charged nanofiltration membrane via surfactant-assembly regulated interfacial polymerization(SARIP)of 2-methylpiperazine(MPIP)and trimesoyl chloride(TMC).Due to the existence of methyl substituent,MPIP has lower reactive activity than piperazine(PIP)but stronger affinity to hexane,resulting in a nanofiltration(NF)membrane with an opposite surface charge and a loose polyamide active layer.Interestingly,with the help of sodium dodecyl sulfate(SDS)assembly at the water/hexane,the reactivity between MPIP and TMC was obviously increased and caused in turn the formation of a positively charged polyamide active layer with a smaller pore size,as well as with a narrower pore size distribution.The resulting membrane shows a highly efficient removal of divalent cations from water,of which the rejections of MgCl_(2),CoCl_(2)and NiCl_(2)are higher than 98.8%,98.0%and 98.0%,respectively,which are better than those of most of other positively charged NF membranes reported in literatures.

Preparation of Poly-α-Olefin Microcapsule Particles Coated with Polyurethane as a Drag Reducer Based on Interface Polymerization

The molecular behavior of polyurethane(PU)coating materials during the surface adsorption of poly-α-olefin as a drag reducing polymer was explored by a molecular dynamics simulation.Three different PU capsule wall materials were synthesized using two reaction monomers,and a poly-α-olefin/PU drag reducer microcapsule was prepared based on interface polymerization.The structure,morphology,thermal stability,compressive strength,and drag reduction performance of the microcapsules were characterized and compared.The results showed that a non-bonding interaction induced the adsorption of the PU coating material,poly-α-olefin and PU then fused at the interface,and the PU coating material was embedded into the inner grooves of poly-α-olefin in the form of a local mosaic,thereby forming a stable core–shell structure.The morphological characterization indicated that PU and poly-α-olefin could form microcapsule structures.The thermal decomposition temperature of the microcapsule was dependent on the type of capsule wall material.The microcapsule structure had a slight effect on poly-α-olefin drag reduction.The system enabled poly-α-olefin to exist in powdered particles through microcapsulation,and had a good dispersion effect that facilitated storage and transport processes.The method effectively inhibited the accumulation and bonding of poly-α-olefin at room temperature.

Aqueous Two-Phase Interfacial Assembly of COF Membranes for Water Desalination

Aqueous two-phase system features with ultralow interfacial tension and thick interfacial region,affording unique confined space for membrane assembly.Here,for the first time,an aqueous two-phase interfacial assembly method is proposed to fabricate covalent organic framework(COF)membranes.The aqueous solution containing polyethylene glycol and dextran undergoes segregated phase separation into two water-rich phases.By respectively distributing aldehyde and amine monomers into two aqueous phases,a series of COF membranes are fabricated at water-water interface.The resultant membranes exhibit high NaCl rejection of 93.0-93.6% and water permeance reaching 1.7-3.7 L m^(−2) h^(−1) bar^(−1),superior to most water desalination membranes.Interestingly,the interfacial tension is found to have pronounced effect on membrane structures.The appropriate interfacial tension range(0.1-1.0 mN m^(−1))leads to the tight and intact COF membranes.Furthermore,the method is extended to the fabrication of other COF and metal-organic polymer membranes.This work is the first exploitation of fabricating membranes in all-aqueous system,confering a green and generic method for advanced membrane manufacturing.

Tannic acid/Fe^(3+)interlayer for preparation of high-permeability polyetherimide organic solvent nanofiltration membranes for organic solvent separation

Organic solvent nanofiltration(OSN)membranes have a great application prospect in organic solvent separation,but the development of OSN membranes is mainly restricted by trade-off between permeability and rejection rate.In this work,a TA/Fe^(3+)polymer was introduced into polyetherimide(PEI)ultrafiltration membranes crosslinked with hexamethylene diamine as the intermediate layer,and OSN membranes with high separation performance and solvent permeability were obtained through interfacial polymerization and solvent activation.The interlayer with high surface hydrophilicity and a fixed pore structure controlled the adsorption/diffusion of the amine monomer during interfacial polymerization,forming a smooth(average surface roughness<5.5 nm),ultra-thin(separation layer thickness reduced from 150 to 16 nm)and dense surface structure polyamide(PA)layer.The PA-Fe^(3+)_3-HDA/PEI membrane retained more than 94%of methyl blue(BS)in 0.1 g·L^(-1)BS ethanol solution at 0.6 MPa,and the ethanol permeation reached 28.56 L^(-1)·m^(-2)·h^(-1).The average flux recovery ratio(FRR)of PA-Fe^(3+)_(3)-HDA/PEI membrane was found to be 84%,which has better fouling resistance than PA-HDA/PEI membrane,and it was found to have better stability performance through different solvent immersion experiments and continuous operation in 0.1 g·L^(-1)BS ethanol solution.Compared with thin-film composite nanofiltration membranes,the PA-Fe^(3+)_(3)-HDA/PEI membrane can be manufactured from an economical and environment-friendly method and overcomes the trade-off between permeability and rejection rate,showing great application potential in organic solvent separation systems.

Ultrathin polyamide nanofiltration membrane prepared by triazine-based porous organic polymer as interlayer for dye removal

Separation membrane with high flux is generally encouraged in industrial application,because of the tremendous needs for decreasing membrane areas,usage costs and space requirements.The most effective and direct method for obtaining the high flux is to decrease membrane thickness.Polyamide(PA)nanofiltration membrane is conventionally prepared by the direct interfacial polymerization(IP)on substrate surface,and results in a thick PA layer.In this work,we proposed a strategy that constructing triazine-based porous organic polymer(TRZ-POP)as the interlayer to prepare the ultrathin PA nanofiltration membranes.TRZ-POP is firstly deposited on the polyethersulfone substrate,and then the formed TRZ-POP provides more adhesion sites towards PA based on its high specific surface areas.The chemical bonding between terminal amine group of TRZ-POP and the amide group of PA further improves the binding force,and strengthens the stability of PA layer.More importantly,the high porosity of TRZPOP layer causes the higher polymerization of initial PA owning to the stored sufficient amino monomer;and H-bonding interaction between amine groups of TRZ-POP and piperazine(PIP)can astrict the release of PIP.Thus,IP process is controlled,and the thinnest thickness of prepared PA layer is only<15 nm.As expected,PA/TRZ-POP membrane shows a more excellent water flux of 1414 L·m^(-2)·h^(-1)·MPa^(-1)than that of the state-of-the-art nanofiltration membranes,and without sacrificing dye rejection.The build of TRZPOP interlayer develops a new method for obtaining a high-flux nanofiltration membrane.

Effects of Processing Conditions on the Properties of Epoxy Resin Microcapsule

In order to improve the healing performance and increase the service life of the polymer matrix composites, microcapsules were prepared by interracial polymerization process with urea formaldehyde resin and epoxy resin E-51 as the wall material and core material separately. The effects of core/shell mass ratio and emulsifier on the distribution, topography and encapsulation rate of microcapsules were investigated. By optimizing the conditions, microcapsules with little particle size, well dispersion and compact surface were prepared. The distribution, topography, stability and compositions of the microcapsules were characterized using Nano-2s, optical microscope, scanning electron microscopy, thermal analysis and Fourier transform infrared spectroscopy. The osmosis performance of the microcapsules was evaluated. The experimental results showed that the ratio of core/shell materials （1：1） and 1% DBS as emulsifier were optimum preparation conditions and the encapsulation rate was 62.5%. The microcapsules can be synthesized successfully with mean diameter 548.6 nm and exhibit a good chemical stability below 225 ℃. The FTIR result indicated that urea-formaldehyde resin was formed and the core materials were successfully encapsulated in urea-formaldehyde shell. Osmosis performance evaluation showed that the microcapsules were well coated and slowly osmosed.

SYNTHESES AND CHARACTERIZATION OF A NEW TYPE OF LIQUID CRYSTALLINE POLYESTERS

A new type of liquid crystalline polyesters with resorcin as one part of the mesogenic unitconnected together by polymethylene, or phenylene group, and lateral groups consisting of arigid azobenzene as another part of the mesogenic unit were synthesized by interfacialpolymerization of diacyl chlorides in 1, 2-dichloroethane and 2, 4-dihydroxy-4'-nitroazobenzen inaqueous alkaline solution. The polyester structures were confirmed by proton NMR and IRspectra. Their phase transition behavior and texture were studied by polarizing microscopy andDSC.

Ferric acetylacetonate/covalent organic framework composite for high performance photocatalytic oxidation

Ferric acetylacetonate/covalent organic framework(Fe(acac)_(3)/COF)composite was synthesized by interfacial polymerization method at room temperature.The crystal structure,morphology and porosity property of the composite were characterized by X-ray diffraction,scanning electron microscope,transmission electron microscope and nitrogen adsorption.The interaction between Fe(acac)_(3) and COF was investigated by Fourier transform infrared spectra and X-ray photoelectron spectroscopy.The Fe(acac)_(3)/COF composite was used as a photocatalyst for the oxidation of benzyl alcohol under mild conditions.It exhibits high activity and selectivity for the reaction,of which the mechanism was investigated by determining its photoelectric properties.The Fe(acac)_(3)/COF catalyst developed in this work has application potential in other photocatalytic reactions.

A combined interfacial and in-situ polymerization strategy to construct well-defined core-shell epoxy-containing SiO_(2) - based microcapsules with high encapsulation loading, super thermal stability and nonpolar solvent tolerance

SiO_(2)-based microcapsules containing hydrophobic molecules exhib-ited potential applications such as extrinsic self-healing,drug delivery,due to outstanding thermal and chemical stability of SiO_(2).However,to construct SiO_(2)-based microcapsules with both high encapsulation loading and long-term structural stability is still a troublesome issue,limiting their further utilization.We herein design asingle-batch route,a combined interfacial and in-situ polymerization strategy,to fabricate epoxy-containing SiO_(2)-based microcapsules with both high encapsu-lation loading and long-term structural stability.The final SiO_(2)-based microcapsules preserve high encapsulation loading of 85.7 wt% by controlling exclusively hydrolysis and condensed polymerization at oil/water interface in the initial interfacial polymerization step.In the subsequent in-situ polymerization step,the initial SiO_(2)-based microcapsules as seeds could efficiently harvest SiO_(2) precursors and primary SiO 2 particles to finely tune the SiO_(2) wall thickness,thereby enhancing long-term structural stability of the final SiO_(2)-based microcapsules including high thermal stability with almost no any weight loss until 250℃,and strong tolerance against nonpolar solvents such as CCl_(4) with almost unchanged core-shell structure and unchanged core weight after immersing into strong solvents for up to 5 days.These SiO_(2)-based microcapsules are extremely suited for processing them into anticorrosive coating in the presence of nonpolar solvents for self-healing application.

Effects of Surface Modifi cation on the Properties of Microcapsules for Self-healing

Poly（urea-formaldehyde）（UF） microcapsules with epoxy resin E-51 as core material used as self-healing materials were prepared by interfacial polymerization method. The surface of UF microcapsules was modifi ed by γ-（2,3-epoxypropoxy） propytrimethoxysilane（KH-560）. The interfacial interactions between UF microcapsules and KH-560 were studied by Fourier transform infrared spectroscopy（FTIR） and X-ray photoelectron spectrometric analysis（XPS） of microcapsules. The surface topography of microcapsules was characterized by scanning electron microscopy（SEM）. The thermal stability and mechanical properties were evaluated. FTIR and XPS results showed that there were physical and chemical combinations between the silicon coupling agent and the microcapsules surface. The thermal stability and mechanical property analysis showed that the addition of KH-560 could greatly improve the thermal stability, tensile property and elastic property. SEM results indicated that the addition of KH-560 could improve the bonding between the surface of microcapsules and resin matrix and improve the ability of self-healing.

Ultrathin organic solvent nanofiltration membrane with polydopamine-HKUST-1 interlayer for organic solvent separation

Polydopamine(PDA)and metal-organic skeleton HKUST-1 were co-deposited on the base membrane of hexamethylenediamine(HDA)-crosslinked polyetherimide(PEI)ultrafiltration membrane as the interlayer,and high-throughput organic solvent nanofiltration membrane(OSN)was prepared by interfacial polymerization and solvent activation reaction.The polyamide(PA)layer surface roughness from 28.4 nm in PA/PEI to 78.3 nm in PA/PDA-HKUST-10.6/PEI membrane,reduced the thickness of the separation layer from 79 to 14 nm,and significantly improved the hydrophilic,thermal and mechanical properties.The flux of the PA/PDA-HKUST-10.6/PEI membrane in a 0.1 g/L Congo Red(CR)ethanol solution at 0.6 MPa test pressure reached 21.8 L/(m^(2)·hr)and the rejection of CR was 92.8%.Solvent adsorption test,N,N-dimethylformamide(DMF)immersion experiment,and long-term operation test in ethanol showed that the membranes had high solvent tolerance.The solvent flux test demonstrated that,under the test pressure of 0.6 MPa,the flux of different solvents ranked as follows:methanol(56.9 L/(m^(2)·hr))>DMF(39.6 L/(m^(2)·hr))>ethanol(31.2 L/(m^(2)·hr))>IPA(4.5 L/(m^(2)·hr))>N-hexane(1.9 L/(m^(2)·hr)).The ability of the membranes to retain dyes in IPA/water dyes solution was also evaluated.The flux of the membrane was 30.4 L/(m^(2)·hr)and the rejection of CR was 91.6%when the IPA concentration reached 50%.This OSN membrane-making strategy is economical,environment-friendly and efficient,and has a great application prospect in organic solvent separation systems.

Study on the morphological regulation mechanism of hollow silica microsphere prepared via emulsion droplet template

The morphology regulation of hollow silica microspheres is significant for their properties and applications. In this paper, hollow silica microspheres were formed through the hydrolysis and condensation reaction of tetraethyl orthosilicate(TEOS) at the interface of the emulsion droplet templates composed of liquid paraffin and TEOS, followed by dissolving paraffin with ethanol. The effects of various factors including the emulsifier structure and content, TEOS content, catalyst type, and the ethanol content in the continuous water phase on the particle size, shell thickness and morphology of the prepared hollow silica microspheres were studied in detail. The results show that the diffusion and contact of TEOS and water molecules as well as the hydrolysis condensation reaction of TEOS at the oil-water interface are two critical processes for the synthesis and morphological regulation of hollow silica microspheres. Cationic emulsifier with a hydrophobic chain of appropriate length is the prerequisite for the successful synthesis of hollow silica microspheres. The ethanol content in water phase is the dominant factor to determine the average diameter of hollow microspheres, which can vary from 96 nm to 660 nm with the increase of the volume ratio of alcohol-water from 0 to 0.7. The silica wall thickness varies with the content and the hydrophobic chain length of the emulsifier, TEOS content, and the activity of the catalyst. The component of the soft template will affect the morphology of the silica wall. When the liquid paraffin is replaced by cyclohexane, hollow microspheres with fibrous mesoporous silica wall are fabricated. This work not only enriches the basic theory of interfacial polymerization in the emulsion system, but also provides ideas and methods for expanding the morphology and application of hollow silica microspheres.

Microencapsulation of n-Eicosane as Energy Storage Material

For heat energy storage application, polyurea microcapsules containing phase change material, n-eicosane, were synthesized by using interfacial polymerization method with toluene-2,4-diisocyanate (TDI) and diethylenetriamine (DETA) as monomers in an emulsion system. Poly(ethylene glycol)octyl-phenyl ether (OP), a nonionic surfactant, was the emulsifier for the system. The experimental result indicates that TDI was reacted with DETA in a mass ratio of 3 to 1. FT-IR spectra confirm the formation of wall material, polyurea, from the two monomers, TDI and DETA. Encapsulation efficiency of n-eicosane is about 75%. Microcapsule of n-eicosane melts at a temperature close to that of n-eicosane, while its stored heat energy varies with core material n-eicosane when wall material fixed. Thermo-gravimetric analysis shows that core material n-eicosane, micro-n-eicosane and wall material polyurea can withstand temperatures up to 130, 170 and 250 ℃, respectively.