Chirality-enhanced 2D conductive polymer for flexible electronics and chiral sensing applications

Chiral two-dimensional (2D) conductive polymers, encompassing chiral, 2D, flexible, and conductive properties, constitute a novel class of material that remains largely unexplored. The infusion of chirality into 2D conductive polymers taps into the unique characteristics associated with chirality, presenting opportunities to enhance or tailor the electronic, optical, and structural properties of materials for specific technological applications. In this study, we synthesized a chiral 2D PEDOT:PMo11V nanofilm through interfacial polymerization, effectively integrating a chiral monolayer, conductive polymer, and inorganic cluster. The inclusion of inorganic cluster serves to enhance the conductivity of the resulting chiral nanofilm. Furthermore, we demonstrated the chiral nanofilm as a capable electrochemical sensor for detecting drug enantiomers. The inherent flexibility of the chiral nanofilm also lays the groundwork for the development of chiral flexible/wearable devices.

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/(m2·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/(m2·hr)) > DMF (39.6 L/(m2·hr)) > ethanol (31.2 L/(m2·hr)) > IPA (4.5 L/(m2·hr)) > N-hexane (1.9 L/(m2·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/(m2·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.

Micelles regulated thin film nanocomposite membrane with enhanced nanofiltration performance

The desalination performance of thin film nanocomposite (TFN) membranes is significantly influenced by the nature of nanofillers and the structure of the polyamide (PA) layer. Herein, a micelles regulated interfacial polymerization (MRIP) strategy is reported for the preparation of TFN membranes with enhanced nanofiltration (NF) performance. Specially, stable and ultrafine micelles, synthesized from the poly(ethylene oxide)-b-poly(4-vinyl pyridine)-b-polystyrene (PEO-PVP-PS) triblock copolymers, were utilized as regulators in the aqueous phase during the interfacial polymerization (IP) process. TFN membranes were fabricated with varying concentrations of micelles to improve their properties and performances. The structure of the PA layer was further regulated by modulating the content of trimesoyl chloride (TMC), which significantly enhances the performance of the TFN membrane with micelles. Attributable to the homogeneously dispersed micelles and the modified PA layer, the optimized membrane denoted as TFN-2-0.3 exhibits an improved separation performance of 20.7 L m-2h-1 bar-1 and 99.3 % Na2SO4 rejection, demonstrating nearly twice the permeance and 2.7 % higher rejection than that of the original control membrane, respectively. The mechanism of this MRIP strategy was investigated through the diffusion experiments of piperazine (PIP) and interfacial tension tests. The incorporated micelles effectively lower the interfacial tension, promote the diffusion of PIP and accelerate the IP reaction, resulting in a denser and thinner PA layer. Collectively, these findings demonstrate that TFN membranes with micelles exhibit increased roughness, enhanced hydrophilicity, superior rejection to divalent salts, and better acid-base resistance, highlighting their potential applications in the design of TFN membranes.

Synergistic interfacial polymerization between hydramine/diamine and trimesoyl chloride: A novel reaction for NF membrane preparation

Polyester-amide (PEA) thin film composite (TFC) NF membranes have rapidly evolved towards a competitive performance, benefiting from their remarkable antifouling capability and superior chlorine resistance. In this report, a new concept of synergistic interfacial polymerization is explored, which promptly triggers the reaction between hydramines and trimesoyl chloride (TMC) in the presence of a trace amount of diamines. This rapid-start mode enables the formation of defect-free PEA films without the requirement of catalysis. A comprehensive characterization of physicochemical properties using high-resolution mass spectrometer (HRMS) reveals that the recombination and formation of a "hydramine-diamine" coupling unit plays a decisive role in activating the synergistic interfacial polymerization reaction with TMC molecules. Taking the pair of serinol and piperazine (PIP) as an example, the PEA-NF membrane fabricated with 0.1 w/v% serinol mixed with 0.04 w/v% PIP as water-soluble monomer and 0.1 w/v% TMC as oil phase monomer was found to have a pure water permeability (PWP) of 18.5 L·m-2·h-1·bar-1 and a MgSO4 rejection of 95.5 %, which surpasses almost all the reported PEA NF membranes. Findings of the current research provide more possibilities for the low-cost and rapid synthesis of high-performance PEA membranes aiming for water purification.

Inhibition of biofouling by in-situ grown zwitterionic hydrogel nanolayer on membrane surface in ultralow-pressurized ultrafiltration process

Ultralow-pressurized ultrafiltration membrane process with low energy consumption is promising in surface water purification. However, membrane fouling and low selectivity are significant barriers for the wide application of this process. Herein, an ultrathin zwitterionic hydrogel nanolayer was in-situ grown on polysulfone ultrafiltration membrane surface through interfacially-initiated free radical polymerization. The hydrogel-modified membrane possessed improved biological fouling resistance during the dynamic filtration process (bovine serum albumin, Escherichia coli and Staphylococcus aureus), comparing with commercial polysulfone membrane. The enhanced biofouling resistance ability of zwitterionic hydrogel nanolayer was derived from the foulant repulsion of hydration shell and the bactericidal effect of quaternary ammonium, according to the results of foulant-membrane interaction energy analyses and antibacterial performances. In surface water treatment, the zwitterionic hydrogel layer inhibited biofouling and resulted in the formation of a loose and thin biofilm. In addition, the hydrogel-modified membrane possessed 22% improvement in dissolved organic carbon (DOC) removal and 134% increasement in stable water flux, compared to commercial polysulfone membrane. The in-situ grown zwitterionic hydrogel nanolayer on membrane surface offers a prospectively alternative for biofouling control in ultralow-pressurized membrane process.

Conductive nanofiltration membranes via in situ PEDOT-polymerization for electro-assisted membrane fouling mitigation

Nanofiltration (NF) membranes play a pivotal role in water treatment; however, the persistent challenge of membrane fouling hampers their stable application. This study introduces a novel approach to address this issue through the creation of a poly(3,4-ethylenedioxythiophene) (PEDOT)-based conductive membrane, achieved by synergistically coupling interfacial polymerization (IP) with in situ self-polymerization of EDOT. During the IP reaction, the concurrent generation of HCl triggers the protonation of EDOT, activating its self-polymerization into PEDOT. This interwoven structure integrates with the polyamide network to establish a stable selective layer, yielding a remarkable 90 % increase in permeability to 20.4 L m-2 h-1 bar-1. Leveraging the conductivity conferred by PEDOT doping, an electro-assisted cleaning strategy is devised, rapidly restoring the flux to 98.3 % within 5 min, outperforming the 30-minute pure water cleaning approach. Through simulations in an 8040 spiral-wound module and the utilization of the permeated salt solution for cleaning, the electro-assisted cleaning strategy emerges as an eco-friendly solution, significantly reducing water consumption and incurring only a marginal electricity cost of 0.055 $ per day. This work presents an innovative avenue for constructing conductive membranes and introduces an efficient and cost-effective electro-assisted cleaning strategy to effectively combat membrane fouling.

Polyamide nanofiltration membranes by vacuum-assisted interfacial polymerization: Broad universality of Substrate, wide window of monomer concentration and high reproducibility of performance

Vacuum assistance is used for filtering solid substances onto porous substrates to create composite membranes typically. However, the potential of this approach has rarely been assessed in facilitating the distribution of liquids within those porous substrates to fabricate composite membranes in typical interfacial polymerization. In this work, we demonstrate the advantages of vacuum-assisted interfacial polymerization (VAIP) in terms of substrate universality, monomer concentration range, and performance reproducibility in the fabrication of polyimide nanofiltration membranes. Aqueous solutions of PIP can be homogeneously distributed by vacuum filtration on diverse microfiltration substrates of polyether sulfone (PES), Nylon-66, polyvinylidene fluoride (PVDF), cellulose acetate (CA), and mixed cellulose esters (MCE), respectively. Interfacial polymerization is then performed on these substrates using different concentrations of piperazine (PIP, 0.0075-0.1000 wt%) and trimoyl chloride (TMC, 0.0112-0.1500 wt%). Remarkably, a uniform and ultra-thin polyamide layer with a thickness of 15 nm can be achieved at an exceptionally low PIP concentration of 0.0250 wt%, exhibits a rejection rate of over 98.8 % for Na2SO4 and a water permeance of 25.8 L·m-2·h-1·bar-1. The membranes with a diameter of 30 cm demonstrate reproducibility in nanofiltration performance and satisfactory long-term stability. This method offers a simple yet effective strategy for regulating the liquid distribution and optimizing interfacial polymerization in fabricating polyamide composite membranes.

NaHCO3 addition enhances water permeance and Ca/haloacetic acids selectivity of nanofiltration membranes for drinking water treatment

The existence of disinfection by-products such as haloacetic acids (HAAs) in drinking water severely threatens water safety and public health. Nanofiltration (NF) is a promising strategy to remove HAAs for clean water production. However, NF often possesses overhigh rejection of essential minerals such as calcium. Herein, we developed highly selective NF membranes with tailored surface charge and pore size for efficient rejection of HAAs and high passage of minerals. The NF membranes were fabricated through interfacial polymerization (IP) with NaHCO3 as an additive. The NaHCO3-tailored NF membranes exhibited high water permeance up to ∼24.0 L m - 2 h - 1 bar-1 (more than doubled compared with the control membrane) thanks to the formation of stripe-like features and enlarged pore size. Meanwhile, the tailored membranes showed enhanced negative charge, which benefitted their rejection of HAAs and passage of Ca and Mg. The higher rejection of HAAs (e.g., > 90%) with the lower rejection of minerals (e.g., < 30% for Ca) allowed the NF membranes to achieve higher minerals/HAAs selectivity, which was significantly higher than those of commercially available NF membranes. The simultaneously enhanced membrane performance and higher minerals/HAAs selectivity would greatly boost water production efficiency and water quality. Our findings provide a novel insight to tailor the minerals/micropollutants selectivity of NF membranes for highly selective separation in membrane-based water treatment.

Chlorine resistance property improvement of polyamide reverse osmosis membranes through cross-linking degree increment

Highly permeable polyamide reverse osmosis (RO) membranes are desirable for reducing the energy burden and ensuring future water resources in arid and semiarid regions. One notable drawback of thin film composite (TFC) polyamide RO/NF membranes is the polyamide's sensitivity to degradation by free chlorine, the most used biocide in water purification trains. This investigation demonstrated a significant increase in the crosslinking-degree parameter by the m-phenylenediamine (MPD) chemical structure extending in the thin film nanocomposite (TFN) membrane without adding extra MPD monomers to enhance the chlorine resistance and performance. Membrane modification was carried out according to monomer ratio changes and Nanoparticle embedding into the PA layer approaches. A new class of TFN-RO membranes incorporating novel aromatic amine functionalized (AAF)-MWCNTs embedded into the polyamide (PA) layer was introduced. A purposeful strategy was carried out to use cyanuric chloride (2,4,6-trichloro-1,3,5-triazine) as an intermediate functional group in the AAF-MWCNTs. Thus, amidic nitrogen, connected to benzene rings and carbonyl groups, assembles a structure similar to the standard PA, consisting of MPD and trimesoyl chloride. The resulting AAF-MWCNTs were mixed in the aqueous phase during the interfacial polymerization to increase the susceptible positions to chlorine attack and improve the crosslinking degree in the PA network. The characterization and performance results of the membrane demonstrated an increase in ion selectivity and water flux, impressive stability of salt rejection after chlorine exposure, and improved antifouling performance. This purposeful modification resulted in overthrowing two tradeoffs; i) high crosslink density-water flux and ii) salt rejection-permeability. The modified membrane demonstrated ameliorative chlorine resistance relative to the pristine one, with twice the increase in crosslinking degree, more than four times the enhancement of the oxidation resistance, negligible reduction in the salt rejection (0.83 %), and only 5 L/m2.h flux loss following a rigorous static chlorine exposure of 500 ppm.h under acidic conditions. The excellent performance of new chlorine resistant TNF RO membranes fabricated via AAF-MWCNTs together with the facile membrane manufacturing process offered the possibility of postulating them in the desalination field, which could eventually help the current freshwater supply challenge.

Tailoring properties and performance of thin-film composite membranes by salt additives for water treatment: A critical review

During the fabrication of thin film composite (TFC) membranes by interfacial polymerization (IP), the utilization of salt additives is one of the effective methods to regulate membrane properties and performance. Despite gradually receiving widespread attention for membrane preparation, the strategies, effects and underlying mechanisms of using salt additives have not yet been systematically summarized. This review for the first time provides an overview of various salt additives used to tailor properties and performance of TFC membranes for water treatment. By classifying salt additives into organic and inorganic salts, the roles of added salt additives in the IP process and the induced changes in membrane structure and properties are discussed in detail, and the different mechanisms of salt additives affecting membrane formation are summarized. Based on these mechanisms, the salt-based regulation strategies have shown great potential for improving the performance and application competitiveness of TFC membranes, including overcoming the trade-off relationship between water permeability and salt selectivity, tailoring membrane pore size distribution for precise solute-solute separation, and enhancing membrane antifouling performance. Finally, future research directions are suggested to focus on the long-term stability assessment of salt-modified membranes, the combined use of different salt additives, and the integration of salt regulation with other membrane design or modification strategies.

Unveiling the impact of imidazole derivative with mechanistic insights into neutralize interfacial polymerized membranes for improved solute-solute selectivity

Domestic wastewater (DWW) contains a reservoir of nutrients, such as nitrogen, potassium, and phosphorus; however, emerging micropollutants (EMPs) hinder its applications in resource recovery. In this study, a novel class of nanofiltration (NF) membranes was developed; it enabled the efficient removal of harmful EMP constituents while preserving valuable nutrients in the permeate. Neutral (IM-N) and positively charged (IM-P) imidazole derivative compounds have been used to chemically functionalize pristine polyamide (PA) membranes to synchronously inhibit the hydrolysis of residual acyl chloride and promote their amination. Owing to their distinct properties, these IM modifiers can custom-build the membrane physicochemical properties and structures to benefit the NF process in DWW treatment. The electroneutral NF membrane exhibited ultrahigh solute-solute selectivity by minimizing the Donnan effects on ion penetration (K, N, and P ions rejection < 25%) while imposing remarkable size-sieving obstruction against EMPs (rejection ratio > 91%). Moreover, the hydrophilic IM-modifier synergistically led to enhanced water permeance of 9.2 L m^-2 h^-1 bar^-1, reaching a 2-fold higher magnitude than that of the pristine PA membrane, along with excellent antifouling/antibacterial fouling properties. This study may provide a paradigm shift in membrane technology to convert wastewater streams into valuable water and nutrient resources.

Enhanced high-salinity brines treatment using polyamide nanofiltration membrane with tunable interlayered MXene channel

The introduce of a nanomaterial interlayer between the substrate and polyamide is identified as a promising strategy to construct highly performed membranes. Two-dimensional (2D) materials are potential candidates as interlayer for advanced thin-film nanocomposite interlayer (TFNi) membranes. Nevertheless, low permeability, selectivity and long-term stability are still critical issues in TFNi membrane manufacture. Herein, a scalable approach for constructing TFNi membranes was implemented using stacked MXene nanosheets as interlayer, wherein the Fe₃O₄ nanoparticles worked as the sacrificial template to regulate the interlayer spacing of the 2D channels. SEM, XPS, water contact angle, and zeta potential were used to characterize the physical and chemical properties of prepared TFNi membranes, and the results shows that the presence of MXene interlayer increased the hydrophilicity, thinness and roughness of polyamide layer compared to that of pure TFC membranes. Besides, the enlarged interlayer channel after the sacrifice of the Fe₃O₄ nanoparticles greatly boosted the transport of the water molecules. The resultant membranes exhibited nearly double fold of water flux (66.4 ± 3.45 L·m^-2·h^-1) and higher selective separation factor (48.4) compared with those prepared without interlayer, while the outstanding salt rejection (>97 %) was maintained. This work achieves an innovative strategy for multifunctional polyamide nanofiltration membrane construction.

Efficient capture of endocrine-disrupting compounds by a high-performance nanofiltration membrane for wastewater treatment

Conventional polyamide (PA) nanofiltration (NF) membranes can readily adsorb aromatic compounds, such as endocrine disrupting compounds (EDCs). Therefore, these substances can easily be transported across the membrane by solution-diffusion, resulting in a poor EDC-rejection. In this work, a novel thin film nanocomposite (TFN) membrane was fabricated by incorporating covalent organic frameworks (COFs) into the PA layer via an interfacial polymerization reaction. COFs with functional groups can provide abundant active binding sites for highly efficient EDC-capture. The rejection of the optimal TFN-COF membrane for bisphenol A, bisphenol AF, and sodium 2-biphenylate was 98.3%, 99.1%, and 99.3%, respectively, which was much higher than of the rejection of the pristine NF-membrane (82.4%, 95.5%, and 96.4%, respectively). Additionally, the TFN-COF membrane could be regenerated fast and efficiently by washing with ethanol for some minutes. COF nanofillers with porous structures provide additional water channels, making it possible to overcome the permeability-selectivity trade-off of NF membranes. The water permeance (17.1 L m^-2 h^-1 bar^-1) of the optimal membrane was about two times higher than for the pristine NF-membrane (8.7 L m^-2 h^-1 bar^-1). In addition, the TFN-COF membrane with a COF-loading of 0.05% w/v had an excellent Na₂SO₄ rejection (95.2%) due to size exclusion and strong Donnan effect. This work combines traditional NF membranes and adsorption materials to achieve efficient capture and rapid release of EDCs without sacrificing salt rejections, which opens the door to develop fit-for-purpose adsorptive NF membranes.

Facile monomer interlayered MOF based thin film nanocomposite for efficient arsenic separation

The thin film nanocomposites (TFN) based membranes are sensitive to the synergy between the polymer and nanoparticles. TFN incorporating metal-organic frameworks (MOFs) have shown tremendous enhancement in permeability. This study investigates alternate MOF positioning during TFC fabrication for a highly selective membrane. Co-Zn-based mixed metal-organic framework (mMOF) was interlayered between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) to form a polyamide (PA) selective layer. The practiced method conveniently allowed exact loading of mMOF and thus prevented the loss. Owing to the mMOF's placement between MPD and TMC, an increase in PA cross-linking was observed. The mMOF-MPD monomer compatibility allowed homogeneous distribution and formation of a defect-free PA layer. The surface morphology showed a more pronounced formation of leaves-like features due to interfacial degassing. Neutral solute-based filtration tests determined mean pore size, probability distribution, and MWCO. The incorporation of mMOF led to formation of additional nanochannels in the membrane surface. The perm-selectivity studies performed on a dead-end filtration unit resulted in 94% As⁵⁺ retention with 2.5 times higher permeance than the control. The current study pronounced the viability of the monomer interlayer method to form a highly selective TFN for water separation and related applications.

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.

Low-pressure highly permeable polyester loose nanofiltration membranes tailored by natural carbohydrates for effective dye/salt fractionation

With the continuous pressure of water contamination caused by textile industry, loose nanofiltration (LNF) membranes prepared by green materials with an extraordinary water permeability are highly desirable for the recovery and purification of dyes and salts. In this work, low-pressure LNF membranes with ultrahigh permeability were fabricated via one-step interfacial polymerization (IP), in which inexpensive natural carbohydrate-derived sugars with large size and low reactivity were utilized as aqueous monomers to design selective layer. A systematic characterization by chemical analysis and optical microscopy demonstrated that the formed polyester film features not only loosen the structure, but also results in a hydrophilic and negatively charged surface. The optimized sucrose-based membrane (Su0.6/TMC0.1) with an excellent water permeability of 52.4 LMH bar^-1 was found to have a high rejection of dyes and a high transmission of salts. In addition, the sugar-based membrane manifested an excellent anti-fouling performance and long-term stability. Furthermore, the non-optimized Gl0.6/TMC0.1 and Ra0.6/TMC0.1 membranes also shown a high water permeability, while maintaining a competitive dye/salt separation performance, which confirmed the universal applicability of the membrane design principle. Therefore, the proposed new strategy for preparing next-generation LNF membranes can contribute towards the textile wastewater treatment.

Encapsulation of volatile compounds in liquid media: Fragrances, flavors, and essential oils in commercial formulations

The first marketed example of the application of microcapsules dates back to 1957. Since then, microencapsulation techniques and knowledge have progressed in a plethora of technological fields, and efforts have been directed toward the design of progressively more efficient carriers. The protection of payloads from the exposure to unfavorable environments indeed grants enhanced efficacy, safety, and stability of encapsulated species while allowing for a fine tuning of their release profile and longer lasting beneficial effects. Perfumes or, more generally, active-loaded microcapsules are nowadays present in a very large number of consumer products. Commercial products currently make use of rigid, stable polymer-based microcapsules with excellent release properties. However, this type of microcapsules does not meet certain sustainability requirements such as biocompatibility and biodegradability: the leaking via wastewater contributes to the alarming phenomenon of microplastic pollution with about 4% of total microplastic in the environment. Therefore, there is a need to address new issues which have been emerging in relation to the poor environmental profile of such materials. The progresses in some of the main application fields of microencapsulation, such as household care, toiletries, cosmetics, food, and pesticides are reviewed herein. The main technologies employed in microcapsules production and the mechanisms underlying the release of actives are also discussed. Both the advantages and disadvantages of every technique have been considered to allow a careful choice of the most suitable technique for a specific target application and prepare the ground for novel ideas and approaches for encapsulation strategies that we expect to be proposed within the next years.

Synthesis and characterization of microencapsulated phase change materials with chitosan-based polyurethane shell

In this paper, chitosan-based polyurethane (c-PU) microencapsulated phase change materials (MicroPCMs) were prepared via the interfacial polymerization reaction of hexamethylene diisocyanate and chitosan accompanied by the charge attraction-assisted. The utilization of natural non-toxic chitosan in MicroPCMs expanded the application of chitosan and guided a new approach to preparing green shell. And the morphology of MicroPCMs with different reaction ration, surfactant and the pH value of reaction system were systematically investigated. The MicroPCMs with c-PU shell exhibited outstanding latent thermal performance (ΔH_m = 106.3 J/g, ΔH_c = -105.1 J/g), high energy storage efficiency (E = 71.4%), excellent thermal stability and cyclic durability. The c-PU MicroPCMs with reversible photochromic show promising application in the fields of anti-counterfeiting technology and flexible wearable UV protective clothing.

Relocation and reinforcement of the adhesive/composite interface with spontaneous amine-peroxide interfacial polymerization

OBJECTIVES

This study demonstrates a spontaneous redox polymerization process located at the adhesive-composite interface that precedes photocure of the composite with the intent to improve bonding.

METHODS

An aromatic amine and benzoyl peroxide redox initiator system was partitioned between BAPO-photoinitiated BisGMA/HEMA adhesive and BisGMA/TEGDMA resin-composites. The composite was placed on the photocured adhesive layer with a brief delay before photopolymerization of the composite layer. Micro-tensile bond strength between the adhesive and composite was assessed in comparison with the non-redox active control materials.

RESULTS

The presence of amine or peroxide in these resins without the redox initiation contribution enhanced both the rate and the final conversion of the BAPO-based photopolymerizations. Control formulations using redox-only initiation showed active polymer formation starting at approximately 30 s when physical mixing of the redox components was involved; however, simply by waiting 60 s between composite placement and photocure provided adequate time for passive interfacial diffusion of benzoyl peroxide from the pre-cured adhesive into the overlaid aromatic amine-containing composite such that a sufficient degree of redox initiated interfacial polymerization occurred prior to the composite photocure. The result was a significant increase in the adhesive to composite micro-tensile bond strength with the failure site moved away from the mainly interfacial failure noted for the control.

SIGNIFICANCE

The stress-free autonomous pre-conversion of a redox-initiated thin film of composite that then provides a compositionally homogeneous interface for composite photopolymerization offers a means to enhance at least short-term bond strength between the adhesive and composite phases during restorative placement.

Multi-ionic electrolytes and E.coli removal from wastewater using chitosan-based in-situ mediated thin film composite nanofiltration membrane

This work presents the experimental investigation of flat sheet composite nanofiltration membrane synthesized with chitosan nanoparticles through interfacial polymerization of piperazine with trimesoyl chloride on polyethersulfone/sulfonated polysulfone substrates. The synthesized membrane was tested in wastewater treatment containing inorganic salts and E.Coli. Single binary electrolyte solution of KCl, MgCl₂, MgSO_4, and Na₂SO₄, ternary electrolyte solution, containing a combination of MgCl₂ and MgSO₄, KCl and MgCl₂ and quaternary electrolyte solution of KCl, MgCl_2, and MgSO₄ as feed were treated in crossflow membrane cell for the water flux and species rejection in the permeate under operating pressure up to 0.5 MPa. The rejection of Na¹⁺, K¹⁺, Mg²⁺, Cl^1-, and SO₄^2- was observed to be 81, 28, 87, 96, and 98%, respectively with an average water flux up to 214 ± 10 L m⁻².hr⁻¹ in the permeate for the binary electrolyte solution. Similarly, the rejection for K¹⁺, Mg²⁺, Cl^1- and SO₄^2- was noted to be 33, 94, 97, and 99%, respectively, for ternary electrolyte solution with an average water flux up to 211 ± 10 L m^-2.hr^-1. The quaternary ion system in the feed resulted in an average water flux up to 198 ± 12 L m⁻².hr⁻¹ with the rejection of K⁺, Mg⁺², Cl^- and SO₄^-2 as 35, 87, 96, and 99%, respectively. The model feed solution of E. coli after passing through the membrane achieved an E. coli rejection (99%) with water flux up to 220 L m^-2.hr^-1.

Finely tuned polyamide structure with green plasticizers to construct ultrafast water channels for effective desalination

Highly permeable reverse osmosis (RO) membranes are desirable for alleviating the energy burden and ensuring future water sustainability. Herein, the effectiveness of green plasticizer-assisted interfacial polymerization (GPAIP) for preparing polyamide thin-film composite (TFC) RO membranes with significantly enhanced water permeability was demonstrated. The presence of green citrate plasticizers, namely tributyl citrate (TBC) or acetyl tributyl citrate (ATBC), led to the formation of new hydrogen bonds and inhibited the formation of the initial interchain amide-amide bonding, thus markedly reducing chain rigidity as demonstrated by the decreased elasticity modulus. More flexible polyamide chains resulted in the creation of more ultrafast water channels during filtration. Furthermore, TBC-modified membranes exhibited more elastic polyamide layers and higher water flux than that of ATBC-modified membranes on account of the presence of both hydrogen bond acceptors (OH) and hydrogen bond donors (C=O) in TBC molecules. Specifically, water flux of 0.6 wt% TBC-modified and 0.6 wt% ATBC-modified membranes was 83.6 L m^-2 h^-1 and 49.7 L m^-2 h^-1 respectively, more than 5 times and 3 times that of the pristine membrane. The excellent performance of TFC RO membranes fabricated via GPAIP together with the facile membrane manufacturing process offered the possibility of breaking the predicament in desalination field, which could eventually help ease the current freshwater crisis.

Zwitterionic Copolymer-Regulated Interfacial Polymerization for Highly Permselective Nanofiltration Membrane

A highly permselective nanofiltration membrane was engineered via zwitterionic copolymer assembly regulated interfacial polymerization (IP). The copolymer was molecularly synthesized using single-step free-radical polymerization between 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-aminoethyl methacrylate hydrochloride (AEMA) (P[MPC-co-AEMA]). The dynamic network of P[MPC-co-AEMA] served as a regulator to precisely control the kinetics of the reaction by decelerating the transport of piperazine toward the water/hexane interface, forming a polyamide (PA) membrane with ultralow thickness of 70 nm, compared to that of the pristine PA (230 nm). Concomitantly, manipulating the phosphate moieties of P[MPC-co-AEMA] integrated into the PA matrix enabled the formation of ridge-shaped nanofilms with loose internal architecture exhibiting enhanced inner-pore interconnectivity. The resultant P[MPC-co-AEMA]-incorporated PA membrane exhibited a high water permeance of 15.7 L·m^-2·h^-1·bar^-1 (more than 3-fold higher than that of the pristine PA [4.4 L·m^-2·h^-1·bar^-1]), high divalent salt rejection of 98.3%, and competitive mono-/divalent ion selectivity of 52.9 among the state-of-the-art desalination membranes.

Tailoring the CO2-selectivity of interfacial polymerized thin film nanocomposite membrane via the barrier effect of functionalized boron nitride

Membrane-based separation is an appealing solution to mitigate CO₂ emission sustainably due to its energy efficiency and environmental friendliness. Attributed to its excellent separation endowed by nanomaterial incorporation, nanocomposite membrane is rigorously developed. This study explored the feasibility of boron nitride (BN) embedment and changes to formation mechanism of ultrathin selective layer of thin film nanocomposite (TFN) are investigated. The effects of amine-functionalization on nanosheet-polymer interaction and CO₂ separation performance are also identified. Participation of nanosheets during interfacial polymerization reduced the crosslinking of selective layer, hence, improved TFN permeance while the formation of contorted diffusion paths by the nanosheets favors transport of small gases. Amine-functionalization enhanced the nanosheet-polymer interaction and elevated the membrane affinity towards CO₂ which led to enhanced CO₂ selectivity. The best TFN prepared in this study exhibited 37% and 20% increment in permeability and selectivity, respectively with respect to neat thin film composite (TFC). It is found that the CO₂ separation performance of BN incorporated TFN is on par with many non-porous nanosheet-incorporated TFNs reported in literatures. The transport and barrier effects of BN and functionalized BN are discussed in detail to provide further insights into the development of commercially attractive CO₂ selective TFN membranes.

Wrinkled Fe3O4@C magnetic composite microspheres: Regulation of magnetic content and their microwave absorbing performance

In this work, we develop a novel synthetic strategy for wrinkled magnetic composite microspheres (Fe₃O₄@C). Firstly, hydrophobic oleic acid modified Fe₃O₄ (OA-Fe₃O₄) nanoparticles acted as the magnetic component are prepared by synchronous modification coprecipitation method. The macromolecular emulsifier with initiating activity is obtained by means of soap-free emulsion polymerization under the presence of 1,1-diphenylethylene (DPE). Then, interfacial polymerization is employed to synthesis Fe₃O₄@polymethylglycidyl ester/divinylbenzene composite microspheres (Fe₃O₄@PGMA/DVB). Fe₃O₄@C composite microspheres are obtained by vacuum carbonization of the microspheres. The effect of magnetic content on the microwave absorbing properties of Fe₃O₄@C composite microspheres is explored. The results show that Fe₃O₄@C composite microspheres exhibit the excellent application performance at the Fe₃O₄ content of 0.15 g. The reflection loss can reach -53.7 dB at only thickness of 1.7 mm. The Maximum effective absorption bandwidth is up to 5.26 GHz with a thickness of 1.9 mm. The microwave attenuation mechanism of Fe₃O₄@C composite microspheres is revealed. The excellent absorbing performance is attributed to the enhanced interfacial polarization ability, the surface wrinkled structure and the good synergy between dielectric and magnetic losses. This work provides an effective strategy for the design and preparation of new magnetic composite materials.

Encapsulation, release and insecticidal activity of Pongamia pinnata (L.) seed oil

Pongamia pinnata (L.) seed oil is effective for its insecticidal and larvicidal activities. However, its low aqueous solubility, high photosensitivity, and high volatility restrict its application for the control of agricultural pests. Encapsulation can be an effective technique to overcome such hindrances. Therefore, P. pinnata oil (PO) was extracted from its seeds and analyzed for karanjin content (3.18%) by GC-MS/MS as the marker compound. Micro-encapsulation (MC) of PO was prepared by interfacial polymerization between isocyanates and polyamine and tested for insecticidal and larvicidal activities. Bioassay of the developed formulations was tested in-vitro against 2^nd instar larvae of Bombyx mori (Bivoltine hybrid) and in-vivo insecticidal bio-efficacy was tested against aubergine aphid (Aphis gossypii G.) and whitefly (Bemisia tabaci G.). Various properties of micro-capsules viz., stability, size, oil content and release kinetics were examined. Average diameter of capsules (1 μm) with Zeta potential (-16 mV) was indicated by the Dynamic Light Scattering (DLS) instrument. Existence of PO in the microcapsules was confirmed by an optical microscopic study. Spectroscopic analysis revealed 87.4% of PO was encapsulated in polyurea shell. The shelf-life (T₁₀), half-life (T₅₀), and expiry-life (T₉₀) of polyurea coated capsules were 11.4, 75.3 and 250.0 h, respectively. Polyurea coated PO capsule formulation showed evidence of in-vitro toxicity against 2^nd instar larvae of B. mori (LC₅₀= 1.1%; LC₉₀ = 5.9%). The PO formulation also exhibited 67.0–71.8% and 62.4–74.8% control of aphid and whitefly population in aubergine at 4.0% dose following 7–14 days after application. The study unveiled its significance in developing controlled release herbal formulations of P. pinnata as an alternative to harmful conventional synthetic insecticides for crop protection.

Design and characterization of PANI/starch/Fe2O3 bio composite for wastewater remediation

A new synthesized polyaniline/starch/hematite bio composite (PANI/S/Fe₂O₃ BC) has been studied as an effective material for on-site water remediation. PANI/S/Fe₂O₃ BC was developed by combining the techniques of co-precipitation and interfacial polymerization in the presence of aqueous starch solution in an acidic medium under ultrasonic irradiation. The nano-morphologies and structures of the designed PANI/S/Fe₂O₃ BC were evaluated by various techniques relative to PANI and Fe₂O₃ nanoparticles. In single and multiple systems, PANI/S/Fe₂O₃ BC was evaluated as a possible adsorbent for different heavy metals, including As³⁺, Zn²⁺, and Co²⁺, relative to PANI and Fe₂O₃ nanoparticles. In terms of pH value, operating temperature, initial heavy metal concentration, contact time, adsorbent dose and competitive ions in the solutions, the adsorption process was optimized. For 92% overall adsorption of Co²⁺ and 100% overall adsorption of both As³⁺ and Zn²⁺, the adsorption equilibrium was achieved within 60 and 120 min, respectively. In addition, adsorption thermodynamic analysis shows that the As³⁺ ions adsorption process was not random and the pseudo-second-order fitted with experimental results. Moreover, PANI/S/Fe₂O₃ BC was evaluated as an antibacterial agent against Gram-negative bacteria (Salmonella typhimurium) and Gram-positive bacteria (S. aureus, Methicillin-Resistant Staphylococcus, Aureus Clinical isolate and Bacillus subtilis). The reported performances indicated that the PANI/S/Fe₂O₃ BC is a potent candidate for industrial water bioremediation.

Metal ferrite incorporated polysulfone thin-film nanocomposite membranes for wastewater treatment

Effluents from food, fermentation, and sugar industries contain a large quantity of glucose which has to be removed to limit the chemical oxygen demand (COD) of the water discharged. This work proposes novel thin-film nanocomposite (TFN) membranes incorporated with MgFe₂O₄ and ZnFe₂O₄ nanoparticles to address this concern. The nanoparticles synthesized by the sol-gel method was extensively characterized and then incorporated into the active polyamide layer of the thin-film composite polysulfone membranes. The change in membrane morphology, wettability, chemical structure, and mechanical strength with the incorporation of nanoparticles was studied in detail. Membranes with 0.005 wt.% MgFe₂O₄ nanoparticle exhibited highest glucose rejection (96.52 ± 2.35%) at 10 bar, 25 °C, and sufficiently high pure water flux (50.54 ± 1.92 L/m²h). This membrane also displayed 69.1 ± 5.12% salt rejection when challenged with 2000 ppm synthetic NaCl solution.

Constructing dense and hydrophilic forward osmosis membrane by cross-linking reaction of graphene quantum dots with monomers for enhanced selectivity and stability

This paper reports a novel thin-film nanocomposite (TFN) membrane with a dense, flat, and hydrophilic polyamide (PA) layer. The atypical PA structure was obtained by the cross-linking reaction of graphene oxide quantum dots containing amino groups (NH₂-GOQDs) with triacyl chloride and polyamide oligomers. And the resulting TFN membrane showed a flat (small-scale ridge structure) and smooth surface. Meanwhile, the introduction of oxygen-containing and amino functional groups increased surface hydrophilicity. The reaction of amino groups on the NH₂-GOQDs with acid chloride groups and the carboxyl groups (in the linear part of the polyamide) enhanced the degree of cross-linking of the PA layer, forming a compact surface. Owning to the dense surface structure, excellent hydrophilicity, and small water transmission distance, the optimized TFN membrane exhibited an enhanced water flux of 26.57 L⋅m^-2⋅h^-1 with a low reverse salt flux of 6.0 g⋅m^-2⋅h^-1. Furthermore, nano-indentation/scratch results showed the interface adhesion between substrate and PA layer was improved due to the physical anchoring of NH₂-GOQDs in the substrate. And in the long-term FO test, the TFN membrane showed stable selectivity. This work proves that the targeted structural design of the PA layer at the nanoscale will have a positive impact on desalination field.

Polyurea microencapsulate suspension: An efficient carrier for enhanced herbicidal activity of pretilachlor and reducing its side effects

In this study, Pretilachlor polyurea microencapsulate suspension (PMS) with effective controlled release function was carefully prepared. Under the optimal conditions, wall material PM-200 dosage 4%, emulsifier T-60 dosage 4% with S-20 as solvent, the prepared PMS was demonstrated to have encapsulation efficiency approaching to 95.27 ± 0.57 % and high suspension rates of 97.33 ± 0.49 %. Afterwards, PMS was proved to possess average release rate reached to 85.56 %, 55.46 % and 15.85 % respectively in acidic, basic and natural medium. Subsequently, the herbicidal activity of PMS on barnyard grass and the growth safety of rice were evaluated. PMS showed enhanced herbicidal activity against barnyard grass and had lower toxicity to rice growth compared with technical pretilachlor at dose 270-540 g (a.i.)/hm². In addition, the use safety of PMS was validated to be comparable to that of commercially available pretilachlor emulsifiable concentrate containing additive safener at dose 270-540 g (a.i.)/hm². Moreover, inhibitory effect of PMS on rice growth was demonstrated to completely eliminated by cooperatively treatment with fenclorim. It was concluded that PMS had enhanced herbicidal activity and application safety, meeting the requirements of minimizing adverse effects of the herbicide on the environment, and enjoying a great application potential in agriculture.

Influence of incorporating beta zeolite nanoparticles on water permeability and ion selectivity of polyamide nanofiltration membranes

A novel polyamide (PA) thin film nanocomposite (TFN) membrane modified with Beta (β) zeolite was prepared by interfacial polymerization on a poly (ether sulfone) (PES) ultrafiltration membrane. Compared with the PA thin film composite (TFC) membrane, the introduction of β zeolite with porous structure notably increased the water flux of TFN membrane. Because the β zeolite with tiny-sized and well-defined inner-porous acted as prior flow channels for water molecules and a barrier for the sulfate ions. The successful introduction of β zeolite into the (PA) selective layer and their dispersion in the corresponding layer were verified by scanning electron microscope (SEM) and atomic force microscopy (AFM). Water contact angle, zeta potential measurements were used to characterize the changes of membrane surface properties before and after incorporating the β zeolite. With the β zeolite introducing, the water contact angle of modified TFN membrane was decreased to 47.8°, which was benefited to improve the water flux. Meanwhile, the negative charges of the modified TFN membrane was increased, resulting in an enhancement of separation effect on SO₄^2- and Cl^-. In term of nanofiltration (NF) experiments, the highest pure water flux of the TFN membranes reached up to 81.22 L m^-2 hr^-1 under operating pressure of 0.2 MPa, which was 2.5 times as much as the pristine TFC membrane.

Acetaldehyde gas removal by a nylon film-TiO2 composite sheet prepared on a paper surface using interfacial polymerization and electrostatic interactions

In this study, preparation of a nylon film-TiO₂ composite sheet with both physical durability under UV irradiation and TiO₂ photocatalysis functionality was investigated. First, a nylon film was directly prepared on paper by interfacial polymerization using ethylenediamine and terephthaloyl chloride in a cyclohexane-chloroform mixture (3:1, v/v). Next, the nylon-coated paper was treated with tetraethyl orthosilicate and 3-aminopropyltrimethoxysilane to prepare polysiloxane on its surface. This was followed by fixation of TiO₂ powder via electrostatic interactions with the polysiloxane. Although nylon films on paper usually decompose under TiO₂ photocatalysis, the nylon film-TiO₂ composite sheets prepared using 0.5%-1.0% (w/v) TiO₂ did not decompose under photocatalysis. The residual rate of strength of the sheet remained at almost 100% after 240 h, which could be attributed to protection of the sheet by the polysiloxane layer. The nylon film was fibrous and could effectively adsorb acetaldehyde gas. All of the nylon film-TiO₂ composite sheets prepared using 0.5%-5.0% TiO₂ photocatalytically removed acetaldehyde under UV irradiation and no acetaldehyde gas was detected after 240-300 min. These results show the nylon film-TiO₂ composite sheet can effectively remove acetaldehyde gas by photocatalysis and adsorption and could be applied to removal of volatile organic compounds in indoor air.

Modifying thin film composite membrane with zeolitic imidazolate framework-8@polydopamine for enhanced antifouling property

Biofouling and organic fouling are major obstacles for polymeric membranes during application. In this work, zeolitic imidazolate framework-8@polydopamine (ZIF-8@PDA) nanoparticles were prepared by an aqueous synthesis strategy and incorporated into the polyamide (PA) selective layer to synthesize thin film nanocomposite membrane (TFN) during interfacial polymerization. The permeability and selectivity of the composite membrane were simultaneously improved with the introduction of ZIF-8@PDA. The water permeability of the TFN membrane increased to 3.74 ± 0.19 L/(m2·h·bar), which is 43.8% higher than that of the control membrane. Besides, the rejection of TFN membrane to sodium chloride is 98.68 ± 0.13%, which shows 0.99% increment than the unmodified membrane. Moreover, organic fouling and biofouling of the TFN membrane were also alleviated thanks to the introduction of the hydrophilic ZIF-8@PDA. The short-term filtration results indicate the performance of the TFN membrane is stable during operation.

Emerging thin-film nanocomposite (TFN) membranes for reverse osmosis: A review

Thin-film composite (TFC) membranes are the heart of reverse osmosis (RO) processes for desalination and water reuse. In recent years, nanomaterials with high permeability, selectivity and chemical resistance, and low fouling tendency have begun to emerge and be applied in many other fields. This has stimulated the research on novel RO membranes consisting of nanomaterials (non-porous and porous) in their selective layers. Encouraging results have been demonstrated. Herein, the state-of-the-art developments of polyamide thin-film nanocomposite (TFN) membranes for RO processes are summarized since the concept of TFN was introduced in 2007. While it is obvious that nanomaterials could impart exclusive properties, it should also be noted that significant challenges still exist for research and commercialization of TFN membranes, such as selection of proper nanomaterials, prevention of leaching of nanoparticles, and performance and cost analysis before large-scale RO membrane manufacturing. Future research directions are outlined to offer insights for the fabrication of much advanced TFN membranes with optimal interface morphology and separation performance.

In-situ coating TiO2 surface by plant-inspired tannic acid for fabrication of thin film nanocomposite nanofiltration membranes toward enhanced separation and antibacterial performance

A major issue hindering development of thin film nanocomposite (TFN) nanofiltration (NF) membrane is the interfacial defects induced by nanomaterial aggregation in top layer. Although various nanomaterials surface modification strategies have been developed to eliminate the interfacial defects, they usually involve extra modification steps and complex post-treatments. Inspired by the substrate-independent coating ability of tannic acid (TA) and the fact that the phenolic hydroxyl groups in TA can react with acyl chloride group in trimesoyl chloride, a TA coating solution containing TiO₂ nanoparticles was used as an aqueous phase of interfacial polymerization to prepare interfacial modified TFN NF membranes in this study. Surface modification of TiO₂ nanoparticles and interfacial polymerization can be carried out in a single step without any extra pre-modification step. It was found that the TA coating on TiO₂ nanoparticles surface could decrease TiO₂ aggregations and enhance interfacial compatibility between TiO₂ and polyester matrix. The TFN NF membrane prepared at a TiO₂ loading of 0.020 wt% exhibited a pure water flux of 28.8 L m^-2 h^-1 (284% higher than that of the controlled TFC membrane), and possessed enhanced NaCl and Na₂SO₄ rejections of 57.9% and 94.6%, respectively, breaking through the trade-off between permeability and selectivity.

3D hierarchical graphene/CNT with interfacial polymerized polyaniline nano-fibers

In this work Polyaniline (PANI) fiber has been synthetized by the interfacial polymerization method. The thermal behavior of graphene - multiwall carbon nanotubes (MWCNs) composite material (C-Mix) blended with PANI fiber was investigated. Graphene was prepared by thermal reduction of the fabricated graphene oxide (GO) using modified Hummers' method. SEM measurement reveals that MWCNTs were well organized within 2D large surface area graphene nano-sheets to form 3D carbon-base hierarchical structure, and PANI was mixed as a binder polymer matrix. Structural measurements confirm the formation of wide area graphene sheets with crumples, wrinkles, and folds around the edges. Transmission electron microscopy (TEM) images agreed with the well distribution of CNTs within graphene nano-sheets. Also, the surface morphology of the synthesized composites has a spherical regular agglomeration of PANI granular structure on wide area graphene nano sheets with CNT embedded. The change in the existed phonon modes of the fabricated nano-composite was analyzed using Raman spectroscopy. Moreover, Seebeck coefficient changes from +132.4 μV/K to -10.3 μV/K after adding carbon-based materials which reflects the reverse of predominate carriers by doping PANI with carbon-based material. It has been noticed that there is an enhancement of thermal conductivity of the fabricated composite with respect to neat polymer. Hence, we propose that 3D carbon structure with PANI construct a stable N-Type thermoelectric material.

A star-shaped POSS-containing polymer for cleaner leather processing

A water-based silsesquioxane (POSS)-containing polymer, POSS-PAA, was synthesized by using octavinyl-POSS (V-POSS) and acrylic acid (AA) via interfacial polymerization. The TEM of POSS-PAA showed that the polymer formed a core-shell structure in aqueous solution and was well-dispersed. The star-shaped POSS-PAA and linear PAA were both tanned with 3.5% chromium tanning agent, and leather hide was tanned with 3.5% chromium tanning agent as a control. The results showed that the shrinkage temperature of wet-blue leather treated by POSS-PAA was increased by 3.5 °C than that of the control. The thickening rate of the POSS-PAA treated wet-blue leather samples was increased by 21% and 96% than the linear PAA-treated leather and the control leather, respectively. The EDS results suggested that the POSS-PAA pre-treated leather had a higher chromium content than the others, and the chromium distribution from the leather flesh side to the grain side was uniform. Moreover, the Cr₂O₃ content in both the POSS-PAA and the PAA pre-treated tanning waste water was reduced by about 50%, compared to the control waste. The COD and BOD of the POSS-PAA pre-tanning waste were decreased compared to the others. Therefore, POSS-PAA appeared to be promising for promoting the development of cleaner leather production.

Study of polyamide thin film characteristics impact on permeability/selectivity performance and fouling behavior of forward osmosis membrane

In recent years, forward osmosis (FO) has received considerable attention due to its huge potentials in water desalination. The thin film composite (TFC) membrane used in the FO desalination consists of a bottom support layer covered by an active layer on top. Polyamide (PA) is commonly employed as an active layer forming via interfacial polymerization between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) monomers. In this study, the effects that the MPD and TMC concentrations could have on the performance and anti-fouling behavior of the obtained FO membrane have been investigated. Results showed that there is a trade-off relationship between the water flux and salt rejection, which by increasing MPD concentration, the water flux was reducedو while the salt rejection was enhanced. Also, by increasing the TMC concentration, an opposite trend was observed. Using 0.20 wt.% of TMC monomer, the highest water fluxes of 21.6 LMH and 29.3 LMH were achieved in two different membrane configurations. Furthermore, higher TMC concentration caused better anti-fouling property, when PA active layer of the membrane was in a high fouling potential environment.

Effective Insensitiveness of Melamine Urea-Formaldehyde Resin via Interfacial Polymerization on Nitramine Explosives

To improve the safety of ammonium nitrate explosives, the melamine urea-formaldehyde resin (MUF resin) was selected for the preparation of three typical nitramine explosives (cyclotetramethylenetetranitramine, HMX; cryclo-trimethylenetrinitramine, RDX; and hexanitrohexaazaisowurtzitane, CL-20) based green polymer-bonded explosives (GPBXs) via interfacial polymerization. Meanwhile, the corresponding composite particles prepared by physical mixing and drying bath methods were studied and compared. The particle morphology, crystal structure, thermal stability, and safety performance of the resultant composite particles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, differential scanning calorimeter (DSC), and impact sensitivity test, respectively. SEM results showed that MUF was successfully coated on the surface of the three explosives, and different composite particles prepared by the same method have their own unique characteristics. Such effect is attributed to the resin's ability to isolate and buffer external stimuli. It is obvious that the interfacial polymerization is an effective desensitization technique to prepare core-shell composite particles for explosives.

Cellular interactions with hydrogel microfibers synthesized via interfacial tetrazine ligation

Fibrous proteins found in the natural extracellular matrix (ECM) function as host substrates for migration and growth of endogenous cells during wound healing and tissue repair processes. Although various fibrous scaffolds have been developed to recapitulate the microstructures of the native ECM, facile synthesis of hydrogel microfibers that are mechanically robust and biologically active have been elusive. Described herein is the use of interfacial bioorthogonal polymerization to create hydrogel-based microfibrous scaffolds via tetrazine ligation. Combination of a trifunctional strained trans-cyclooctene monomer and a difunctional s-tetrazine monomer at the oil-water interface led to the formation of microfibers that were stable under cell culture conditions. The bioorthogonal nature of the synthesis allows for direct incorporation of tetrazine-conjugated peptides or proteins with site-selectively, genetically encoded tetrazines. The microfibers provide physical guidance and biochemical signals to promote the attachment, division and migration of fibroblasts. Mechanistic investigations revealed that fiber-guided cell migration was both F-actin and microtubule-dependent, confirming contact guidance by the microfibers. Prolonged culture of fibroblasts in the presence of an isolated microfiber resulted in the formation of a multilayered cell sheet wrapping around the fiber core. A fibrous mesh provided a 3D template to promote cell infiltration and tissue-like growth. Overall, the bioorthogonal approach led to the straightforward synthesis of crosslinked hydrogel microfibers that can potentially be used as instructive materials for tissue repair and regeneration.

Polymerization kinetics of n-butyl cyanoacrylate glues used for vascular embolization

Vascular embolization is a minimally invasive treatment used for the management of vascular malformations and tumors. It is carried out under X-ray by navigating a microcatheter into the targeted blood vessel, through which embolic agents are delivered to occlude the vessels. Cyanoacrylate liquid glues have been widely used for vascular embolization owing to their low viscosity, rapid polymerization/solidification rate, good penetration ability and low tissue toxicity. The objective of this study is to quantitatively investigate the physical properties of two n-butyl cyanoacrylate (nBCA) glues (Glubran 2 and Histoacryl) mixed with an iodized oil (Lipiodol) at various concentrations. We show that an homogeneous solution results from the mixing of the glue and Lipiodol, and that the viscosity, density and interfacial tension of the mixture increase with the proportion in Lipiodol. We have designed a new experimental setup to systemically characterize the polymerization kinetics of a glue mixture upon contact with an ionic solution. We observe that the whole polymerization process includes two phases: an interfacial polymerization that takes place at the interface as soon as the two liquids are in contact with a characteristic time scale of the order of the minute; a volumetric polymerization during which a reaction front propagates within the mixture bulk with a characteristic time scale of the order of tens of minutes. The polymerization rate, front propagation speed and volume reduction increase with the glue concentrations. It is the first time that such comprehensive results are obtained on liquid embolic agents.

Characterization and Evaluation of Reverse Osmosis Membranes Modified with Ag2O Nanoparticles to Improve Performance

The objective of this work was to prepare and characterize a new and highly efficient modified membrane by in situ interfacial polymerization on porous polysulfone supports. The process used m-phenylenediamine and trimesoyl chloride in hexane, incorporating silver oxide Ag2O nanoparticles of varied concentrations from 0.001 to 0.1 wt%. Ag2O nanoparticles were prepared at different sizes varying between 20 and 50 nm. The modified membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle measurement. The results showed a smooth membrane surface and average surface roughness from 31 to 74 nm. Moreover, hydrophilicity improved and the contact angle decreased to 41° at 0.009 wt% silver oxide. The performances of the developed membranes were investigated by measuring permeate fluxes and salt rejection capability by passing NaCl solutions (2000 ppm) through the membranes at 225 psi. The results showed that the flux increased from 26 to 40.5 L/m(2) h, while the salt rejection was high, at 99 %, with 0.003 wt% Ag2O nanoparticles.

Interfacial polymerization of conductive polymers: Generation of polymeric nanostructures in a 2-D space

In the recent advances in the field of conductive polymers, the fibrillar or needle shaped nanostructures of polyaniline and polypyrrole have attracted significant attention due to the potential advantages of organic conductors that exhibit low-dimensionality, uniform size distribution, high crystallinity and improved physical properties compared to their bulk or spherically shaped counterparts. Carrying the polymerization reaction in a restricted two dimensional space, instead of the three dimensional space of the one phase solution is an efficient method for the synthesis of polymeric nanostructures with narrow size distribution and small diameter. Ultra-thin nanowires and nanofibers, single crystal nanoneedles, nanocomposites with noble metals or carbon nanotubes and layered materials can be efficiently synthesized with high yield and display superior performance in sensors and energy storage applications. In this critical review we will focus not only on the interfacial polymerization methods that leads to polymeric nanostructures and composites and their properties, but also on the mechanism and the physico-chemical processes that govern the diffusion and reactivity of molecules and nanomaterials at an interface. Recent advances for the synthesis of conductive polymer composites with an interfacial method for energy storage applications and future perspectives are presented.

Electrical conductivity of poly(3,4-ethylenedioxythiophene):p-toluene sulfonate films hybridized with reduced graphene oxide

Reduced graphene oxide-poly(3,4-ethylenedioxythiophene):p-toluene sulfonate (rGO-PEDOT:PTS) hybrid electrode films were synthesized directly on a substrate by interfacial polymerization between an oxidizing solid layer and liquid droplets of 3,4-ethylenedioxythiophene (EDOT) produced by electrospraying. The EDOT reduced the graphene oxide by donating electrons during its transformation into PEDOT:PTS, and hybrid films consisting of rGO distributed in a matrix of PEDOT:PTS were obtained. These rGO-PEDOT:PTS hybrid films showed excellent electrical conductivities as high as 1,500 S/cm and a sheet resistance of 70 Ω sq(-1). The conductivity values are up to 50% greater than those of films containing conductive PEDOT:PTS alone. These results confirm that highly conductive rGO-PEDOT:PTS hybrid films can potentially be used as organic transparent electrodes.

Facile surface modification of anion-exchange membranes for improvement of diffusion dialysis performance

In this study, a facile membrane modification method by spin-coating of pyrrole (Py) monomers dissolved in a volatile solvent followed by an interfacial polymerization is proposed. The surface of a commercial anion-exchange membrane (i.e., Neosepta-AFX, Astom Corp., Japan) was successfully modified with polypyrrole (Ppy) to improve the acid recovery performance in diffusion dialysis (DD). The result of DD experiments revealed that both the acid and metal ion transports are significantly influenced by the surface modification. The metal crossover through the membranes was largely reduced while mostly maintaining the acid permeability by introducing a thin Ppy layer with excellent repelling property to cations on the membrane surface. As a result, the anion-exchange membrane modified with the optimum content of Py monomer (5 vol.%) exhibited excellent acid dialysis coefficient (KAcid) and selectivity (KAcid/KMetal) which is approximately twice as high as that of the pristine membrane.