Zwitterionic Polyelectrolyte Research Articles

Sulfocontaining polyelectrolyte cryogels as metamaterials for energy storage devices

AbstractA set of ionic cryogels based on the biocompatible zwitterionic polyelectrolyte N‐(3‐sulfopropyl)‐N‐(methacryloxyethyl)‐N,N‐dimethylammonium betaine and a second comonomer of a different nature (from the class of acrylates, acetates or sulfonic acids) is successfully synthesized. The variation of the nature of the comonomer used allows a material to be obtained with controlled pore sizes and hierarchical porosity as proved by SEM, optical microscopy and N2 adsorption–desorption experiments. The compositions of cryogels with good adhesive properties to the electrode, as well as effective ion exchange during an electrochemical reaction inside the cryogels, which is shown by reversible copper recharge processes after doping a cryogel with copper ions, are determined. Thus, cryogels that meet the primary requirements for a material for use as polymer electrolytes for batteries are synthesized and characterized. © 2024 Society of Chemical Industry.

Zwitterionic Polyelectrolyte Complex Vesicles Assembled from Homopoly(2-Oxazoline)s as Enzyme Catalytic Nanoreactors for Potent Anti-Tumor Efficiency.

Enzymes are known for their remarkable catalytic efficiency across a wide range of applications. Here, we present a novel and convenient nanoreactor platform based on zwitterionic polyelectrolyte complex vesicles (PCVs), assembled from oppositely charged homopoly(2-oxazoline)s, facilitating enzyme immobilization. We show remarkable enhancements in catalytic activity and stability by encapsulation of lipase as a model enzyme. Even as the temperature rises, the performance of the lipase remains robust. Further, the structural characteristics of PCVs, including hollow architecture and semipermeable membranes, endow them with unique advantages for enzyme cascade reactions involving glucose oxidase (GOx) and horseradish peroxidase (HRP). A decline in catalytic efficiency is shown when the enzymes are individually loaded and subsequently mixed, in contrast to the coloaded GOx-HRP-PCV group. We demonstrate that the vesicle structures establish confined environments where precise enzyme-substrate interactions facilitate enhanced catalytic efficiency. In addition, the nanoreactors exhibit excellent biocompatibility and efficient anti-tumor activity, which hold significant promise for biomedical applications within enzyme-based technologies.

Non-monotonic variation in the streaming potential in polyelectrolyte grafted nanochannels mediated by ion partitioning effects

BackgroundPolyelectrolyte grafted ‘soft’ nanochannels are known to enhance electrokinetic energy conversion efficiency, paving the way for a sustainable energy harvesting mechanism. However, the true potential of their efficacy remains to be tapped, as attributed to a deficit in accounting for the interplay between solution pH and ion partitioning effect arising due to permittivity contrast between the coated layer and the bulk media, leading to predictions of an erroneous ionic distribution and a wrongly estimated electrokinetic response. ResultsWe unravel the electrokinetic behavior of a pH-regulated zwitterionic polyelectrolyte layer grafted nanofluidic system. To this end, we derive a detailed theoretical formulation that considers the nuanced interplay between solution pH and the ion partitioning effect through a thermodynamically consistent ionic distribution. Here, for the first time, we demonstrate a non-monotonic trend in the streaming potential with an increase in the ion partitioning effect, in contrast to a monotonic increase as reported previously. Additionally, we identify a critical permittivity ratio specific to the solution pH at which maximum streaming potential can be obtained. SignificanceWe shed light on the counterintuitive effect borne from the increased ion partitioning effect, unveiling a hitherto hidden facet of electrokinetics. By elucidating the delicate balance between solution pH, ion partitioning effect, and polyelectrolyte charge, our findings offer a comprehensive understanding of the multifaceted interplay shaping soft-electrokinetic systems, thereby paving the way for transformative advancements in energy conversion technologies.

Nanofibrous membranes modified by zwitterionic polyelectrolyte brushes for effective adsorption of ciprofloxacin hydrochloride

In this study, zwitterionic polyelectrolyte brushes poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) were grafted on poly (vinyl alcohol)/graphene oxide (PVA/GO) nanofibrous membranes by surface-initiated activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP). The obtained PVA/GO@PMPC nanofibrous membranes were used as adsorbents for removal of ciprofloxacin hydrochloride. The membrane prepared with the most amount of GO in the electrospinning solution and the highest MPC concentration during grafting polymerization displayed the largest adsorption amount of ciprofloxacin hydrochloride (245.6 mg/g). Within 15 h, the adsorption achieved equilibrium, and the removal process agreed well with pseudo-second-order kinetic model. At pH = 7.0, the maximum adsorption capacity was attained, and the adsorption capacity increased gradually with temperature. Study on adsorption mechanism revealed that π-π interactions, hydrogen bonding interactions and electrostatic interactions might be involved for removal of ciprofloxacin hydrochloride. After being repeatedly used for six times, binding affinity of the membrane did not change significantly. This study provided a general method for creating nanofibrous membranes with superior adsorption performance for removal of organic pollutants.

Recombinant Multi-l-Arginyl-Poly-l-Aspartate (Cyanophycin) as an Emerging Biomaterial.

Multi-l-arginyl-poly-l-aspartate (MAPA) is a non-ribosomal polypeptide which synthesis is directed by cyanophycin synthetase, and its production can be achieved using recombinant microorganisms carrying the cphA gene. Along its poly-aspartate backbone, arginine or lysine links to each aspartate via an isopeptide bond. MAPA is a zwitterionic polyelectrolyte full of charged carboxylic, amine, and guanidino groups. In aqueous solution, MAPA exhibits dual thermal and pH responses similar to those stimuli-responsive polymers. Being biocompatible, the films containing MAPA can support cell proliferation and elicits minimal immune response in macrophages. Dipeptides from MAPA after enzymatic treatments can provide nutritional benefits. In light of the increasing interest in MAPA, this article focuses on the recent discovery of the function of cyanophycin synthetase and the potentials of MAPA as a biomaterial.

Freestanding two-dimensional nanofluidic membranes modulated by zwitterionic polyelectrolyte for mono-/di-valent ions selectivity transport

Effective separation of mono-/di-valent metal ions based on membrane technology is highly desirable in the energy storage and environmental protection field, but requires membranes capable of selective recognition of ions with similar nano-scale size. In this work, we designed and synthesized the sulfonate polyethylenimine (PEI-SO3H), as a zwitterionic polyelectrolyte, and integrated it into two-dimensional (2D) graphene oxide (GO) confined channels. Stable and sub-nanometer ion-selective transport channels enable fast transport of monovalent metal ions with high mono-/di-valent ion selectivity for K+/Mg2+ (12.2), Na+/Mg2+ (11.4) and Li+/Mg2+ (10.1) under electric field. Notably, the hydration compensation-promoting diffusion (HCPD) mechanism based on the synergistic effect of amino groups as compensation sites and sulfonic acid groups as recognition sites was proposed to understand the high-efficiency ion-selective transport process. In addition, instructed by abovementioned theory, the 2D vermiculite membrane was also designed to well realize the mono-/di-valent ions separation. This study provides a new strategy to construct freestanding 2D membranes with efficient ion-selective transport channels instructed by HCPD theory, which is expected to expand the potential for using membranes in the lithium extraction.

Zwitterionic polyelectrolyte brush modified chitosan nanoparticles as functional biolubricant with good friction-reduction effect

Osteoarthritis (OA) caused by the articular cartilage degeneration is closely related to the lubrication dysfunction of joint. At present, injecting biolubricants into the joint cavity is regarded as an effective strategy for the treatment of arthritis. Herein, a biocompatible chitosan (CS)-based nanoparticles (NPs) biolubricant (CS-PMPC@DS NPs) with dual function of lubrication and anti-inflammatory was fabricated. Zwitterionic polyelectrolyte brush poly(2-methacryloyloxyethyl phosphorylcholine, PMPC) was grafted onto the NPs via atom transfer radical polymerization (ATRP) strategy, while the anti-inflammatory drug (diclofenac sodium, DS) was encapsulated within them. Under the synergistic effect rolling lubrication and hydration lubrication mechanisms, the obtained biolubricant exhibited superior lubrication performance in either artificial joint materials or cartilage contacts, which presents great potential for OA treatment.

Synergistic foam stabilization and transport improvement in simulated fractures with polyelectrolyte complex nanoparticles: Microscale observation using laser etched glass micromodels

Inaccessibility to direct pore scale observation in hydrocarbon recovery of tight shale formations poses a great challenge to water-energy nexus initiatives and necessitates the use of high throughput technologies to emulate environmentally friendly processes. Herein, we employ a precise glass micromodel fabrication and visualization method to isolate the supercritical CO2 bubbles surrounded by CO2-water lamella prepared in saline produced water stabilized with molecular complexation of zwitterionic surfactants (ZS) and polyelectrolyte complex nanoparticles (PECNP).The Selective Laser Enhanced Etching (SLE) technique was selected for micromodel simulation of high-pressure flow. Two representative designs, (1) fracture/micro-crack network and (2) fracture/matrix were etched on fused silica glass with a laser printing machine and scCO2 foam was injected to study the foamability, propagation, stability, and fluid loss properties.The highly monodispersed and uniformly distributed array of scCO2 bubbles were detected in flow of scCO2 foam in highly saline brine containing ionic complexes of positively charged PECNPs and ZS, whereas foam flow with the lamella containing ZS in fractures offered a noticeably large and polydisperse array of scCO2 bubbles. scCO2 bubble motion and deformation were traced, and local description of foam flow was visually examined. The confined array of scCO2 bubbles stabilized by ZS in microcracks was affected by bubble growth and coalescence, whereas the super-populated array of monodispersed scCO2 bubbles with lamella containing complexes of PECNP and ZS were able to fill the channels with stable configurations within the timeframe of comparative stability measurements. The ability of complex fluid to prevent the formation damage was evaluated through fluid loss visualization in micromodels. Probing scCO2 foam transport in homogenous porous media revealed smaller volume leak-off for scCO2 foam containing PECNP-ZS ionic complexes.

Charge Properties and Electric Field Energy Density of Functional Group-Modified Nanoparticle Interacting with a Flat Substrate.

Functionalized nanofluidics devices have recently emerged as a powerful platform for applications of energy conversion. Inspired by biological cells, we theoretically studied the effect of the interaction between the nanoparticle and the plate which formed the brush layer modified by functional zwitterionic polyelectrolyte (PE) on the bulk charge density of the nanoparticle brush layer, and the charge/discharge effect when the distance between the particle and the plate was changed. In this paper, The Poisson–Nernst–Planck equation system is used to build the theoretical model to study the interaction between the nanoparticle and the plate modified by the PE brush layer, considering brush layer charge regulation in the presence of multiple ionic species. The results show that the bulk charge density of the brush layer decreases with the decrease of the distance between the nanoparticle and the flat substrate when the interaction occurs between the nanoparticle and the plate. When the distance between the particle and the plate is about 2 nm, the charge density of the brush layer at the bottom of the particle is about 69% of that at the top, and the electric field energy density reaches the maximum value when the concentration of the background salt solution is 10 mm.

Antibacterial Zwitterionic Polyelectrolyte Hydrogel Adhesives with Adhesion Strength Mediated by Electrostatic Mismatch.

Biotissue adhesives and antibacterial materials have great potential applications in wound dressing, implantable devices, and bioelectronics. In this study, stretchable tissue adhesive hydrogels with intrinsic antibacterial properties have been demonstrated by copolymerizing zwitterionic monomers with ionic monomers. The hydrogels are stretchable to about 900% strain and show a modulus of 4-9 kPa. The zwitterionic moieties provide strong dipole-dipole interaction, electrostatic interaction, and hydrogen bonding with the skin surface, and thus show adhesion strength values of 1-4 kPa to skin. Meanwhile, the copolymerized cationic or anionic monomers break the intrinsic electrostatic stoichiometry of the zwitterionic units and thus mediate the electrostatic interactions and the adhesion strength with the surface. The stretchable hydrogels form a robust and compliant (due to low modulus and stretchability) adhesive to skin, rubber, glass, and plastics, and could be repeatedly peeled-off and readhered to the skin. Moreover, the abundant quaternary ammonium (QA) groups in the zwitterionic moieties and the added QA groups endow it outstanding antibacterial properties (>99%). These stretchable tissue adhesive antibacterial hydrogels are promising for wound dressings and implantable devices.

Application of Nanoscale Zwitterionic Polyelectrolytes Brush with High Stability and Quantum Yield in Aqueous Solution for Cell Imaging

Cationic and zwitterionic polyelectrolytes are synthesized through atom transfer radical polymerization (ATRP), comprising a polyfluorene backbone with a small fraction of 2,1,3-benzothiadiazole and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) side chains. Due to higher charge density generated from grafted side chains, two polymers show higher water solubility and higher quantum yield. In comparison with cationic polyelectrolytes, zwitterionic polyelectrolytes are stable over a broad pH range from 1 to 13, even in 1 M NaCl solution. The absence of FRET between zwitterionic polymers and dye-labeled ssDNA indicates their ultralow nonspecific adsorption, while cationic polymer shows much stronger nonspecific interactions. The MTT assay of zwitterionic polymers exhibits their minimal cytotoxicity and potential in long-term clinical application. Most importantly, zwitterionic polymer could be efficiently taken up by cells, whereas cationic polymer stains the surface of cell due to membrane disruption generated from positive charges. The results illustrate that conjugated zwitterionic polymer could serve as a novel type of highly efficient ultralow fouling material with low cytotoxicity for labelling cell or potential biomedical applications.

Reversibly highly stretchable and self‐healable zwitterion‐containing polyelectrolyte hydrogel with high ionic conductivity for high‐performance flexible and cold‐resistant supercapacitor

AbstractIt remains challenging to develop stretchable and self‐healable polymer electrolytes with improved ion‐conductive nature for high‐performance multifunctional flexible supercapacitors. Herein, a P(AM‐SBMA‐AMPS)‐SiO2 zwitterion‐containing polyelectrolyte hydrogel is fabricated via copolymerization of acrylamide (AM), sulfobetaine methacrylate (SBMA) zwitterionic monomer, and 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) anionic monomer grafted from the surface of vinyl silica nanoparticles (VSNPs). The hydrogen bonding among polymer chains and the high‐density dynamic ionic interactions between SBMA and AMPS work as reversible “sacrificial bonds” to toughen hydrogel, while the VSNPs function as multifunctional crosslinkers and stress transfer centers, which makes these hydrogels tough (fracture energy 2.7 MJ m−3), stretchable (fracture strain 4,016%), and self‐healable (fracture strain of healable sample 775%). More importantly, this zwitterion‐containing polyelectrolyte hydrogel exhibits high ionic conductivities (3.4 S m−1) owing to the highly hydration capacity of the zwitterionic polyelectrolyte copolymer which produced efficient ion migration channels for ion transport. Accordingly, a flexible supercapacitor based on this multifunctional hydrogel as electrolyte demonstrates a high electric double‐layer capacitive capacitance of 60.6 F g−1 at 0.5 A g−1 and excellent capacitance retention of ~98% over 1,000 cycles as well as encouraging electrochemical properties at subzero temperature. This work provides new insights into the synthesis of highly conductive and multifunctional polyelectrolyte hydrogels for high‐performance flexible supercapacitors. © 2020 Wiley Periodicals, Inc.

Novel Fe3O4 based superhydrophilic core-shell microspheres for breaking asphaltenes-stabilized water-in-oil emulsion

Stabilization and destabilization of emulsions play an important role in a wide range of engineering and environmental processes (e.g., oil-water separation, waste water treatment). The destabilization of water-in-oil (W/O) emulsions in the presence of asphaltenes, which form a protective interfacial layer to prevent the coalescence of emulsions, is a well-known challenging issue in oil production. In this study, a novel type of core-shell microspheres with magnetic core functionalized with a superhydrophilic zwitterionic polyelectrolyte shell has been developed and characterized, which shows excellent capability in breaking asphaltene-stabilized W/O emulsions and releasing considerable amount of water with the assistance of an external magnetic field. Surface force measurements using drop probe atomic force microscope (AFM) demonstrated the strong attraction between zwitterionic polyelectrolytes and emulsion droplets. The water-oil interfacial tension was found to increase with the addition of the microspheres, contributing to the coalescence of emulsions. Quartz crystal microbalance with dissipation monitoring (QCM-D) tests demonstrated that asphaltenes could be adsorbed on the polyelectrolyte surface, suggesting that the polyelectrolyte could interact and disrupt the protective asphaltene layer at oil-water interfaces to facilitate the demulsification. The adsorbed asphaltenes on the polyelectrolyte shell can be released when the microsphere was treated in water, showing a reversable asphaltene adsorption/desorption behavior, which has great potential for cyclic reuse. Our results provide useful insights into the fundamental interactions between emulsions in the presence of polyelectrolytes, with implications for the development of new demulsification methods in water-oil separation and other environment related processes.

Enhancing antifogging/frost-resisting performances of amphiphilic coatings via cationic, zwitterionic or anionic polyelectrolytes

Polymeric antifogging and frost-resisting coatings were successfully prepared, but the performances of amphiphilic coatings containing different kinds of cationic, zwitterionic and anionic polyelectrolytes are still needed to investigate systematically. In this work, antifogging/frost-resisting coatings with high transparence were developed from amphiphilic copolymers of cationic, zwitterionic or anionic poly(2-(dimethylamino)ethyl methacrylate (DMAEMA)-co-2,2,2-trifluoroethyl methacrylate (FMA))-b-polyelectrolytes with a small amount of ethylene glycol dimethacrylate via UV-curing. Studies on the prepared amphiphilic coatings suggested that the cationic and zwitterionic coatings exhibited superior antifogging properties, whereas the anionic polyelectrolyte-based coating demonstrated a better frost-resisting behavior. Water molecule activities in the amphiphilic coatings were analyzed by differential scanning calorimetry, Raman spectroscopy and low field nuclear magnetic resonance. It was found that the cationic and zwitterionic coatings containing 2-(methacryloyloxy)-ethyltrimethyl ammonium chloride and sulfobetaine methacrylate, respectively, exhibited stronger polymer-water interactions dominated by strong hydrogen bonds, and held more nonfreezable water content with shorter transverse spin-spin relaxation time T2 than the anionic coating containing 3-sulfopropyl methacrylate potassium (SPMA). Electrostatic interactions between anionic SPMA and DMAEMA units in the copolymer could weaken the polymer-water interaction, leading to a compromise in the antifogging performance and an enhancement of frost-resisting ability of the coating. The results of this study would be applicable for exploring the advanced antifogging/frost-resisting coatings.

Biomimetic Lubrication and Surface Interactions of Dopamine-Assisted Zwitterionic Polyelectrolyte Coatings.

A bioinspired zwitterionic polyelectrolyte coating with excellent hydration ability has been regarded as a promising lubricating candidate for modifying artificial joint cartilage surface. In physiological fluids, the ubiquitous proteins play an important role in achieving outstanding boundary lubrication; however, a comprehensive understanding of the hydration lubrication between polyelectrolyte coatings and proteins still remains unclear. In this work, a facile fabrication of ultrasmooth polyelectrolyte coatings was developed via codeposition of synthesized poly(dopamine methacrylamide- co-2-methacryloyloxyethyl phosphorylcholine) (P(DMA- co-MPC)) and dopamine (DA) in a mild condition. Upon optimization of the feeding ratio of P(DMA- co-MPC) and DA, the as-fabricated PDA/P(DMA- co-MPC) coatings exhibit excellent lubricating properties when sliding with each other (friction coefficient μ = 0.036 ± 0.002, ∼2.8 MPa), as well as sliding with a model protein (bovine serum albumin (BSA)) layer (μ = 0.041 ± 0.005, ∼4.8 MPa) in phosphate-buffered saline (PBS, pH 7.4). Intriguingly, the lubrication in both systems shows Amontons-like behaviors: the friction is directly proportional to the applied load but independent of the shear velocity. Moreover, the PDA/P(DMA- co-MPC) coatings could resist the protein fouling (i.e., BSA) in PBS, which is crucial to prevent the surfaces from being contaminated when applied in biological media, thus maintaining their lubricating properties. Our results provide a versatile approach for facilely fabricating polyelectrolyte coatings with superior lubrication properties to both polyelectrolyte coatings and protein surfaces, with useful implications into the development of novel lubricating coatings for bioengineering applications (e.g., artificial joints).

Improved antifouling ability of thin film composite polyamide membrane modified by a pH-sensitive imidazole-based zwitterionic polyelectrolyte

In this work, poly[1-vinyl-3(2-carboxyethyl) imidazolium betaine] (PVCIB), as a zwitterionic polyelectrolyte, was tethered onto a commercial thin film composite polyamide (TFC PA) membrane. First, polyvinyl imidazole (PVI) was grafted onto the TFC PA membrane surface by free radical graft polymerization method at various grafting times. Afterwards, one of PVI-modified membranes was betainized using 3-bromopropionic acid to obtain PVCIB brushes on the membrane surface. Evaluation of membrane performance through desalination process indicated that despite decrease of salt rejection, water flux increased from 73.4 L/m2 h in the PA membrane to 91.6 L/m2 h in the PA-PVCIB membrane. Antimicrobial assessment using Escherichia coli showed that the PVCIB-modified membrane was able to inhibit bacterial growth by about 98.8%. Antifouling and cleaning abilities of membranes were investigated using BSA and lysozyme at various pH values. It was revealed that hydrophilic PVCIB brushes considerably improved protein-resistant property of the TFC PA membrane. However, by considering pH-dependent behavior of PVCIB (zwitterionic at alkaline pH or polyelectrolyte at acidic pH), it was found that hydration repulsion or electrostatic repulsive forces also made a major contribution to the fouling mitigation. Accordingly, the PA-PVCIB membrane exhibited remarkable antifouling ability to resist non-specific protein adsorption at neutral and alkaline pHs, whereas both PA-PVI and PA-PVCIB membranes exhibited high resistance to the positively charged lysozyme adhesion at acidic pH.

Stimuli‐responsive amphiphilic PDMAEMA‐b‐PLMA copolymers and their cationic and zwitterionic analogs

ABSTRACTIn this work, the synthesis and characterization of novel amphiphilic diblock copolymers of poly(2‐dimethylamino ethyl methacrylate)‐b‐poly(lauryl methacrylate), PDMAEMA‐b‐PLMA, using the reversible addition‐fragmentation chain transfer (RAFT) polymerization technique, are reported. The diblocks were successfully derivatized to cationic and zwitterionic block polyelectrolytes by quaternization and sulfobetainization of the PDMAEMA block, respectively. Furthermore, their molecular and physicochemical characterization was performed by using characterization techniques such as NMR and FTIR, size exclusion chromatography, light scattering techniques, and transmission electron microscopy. The structure of the diblock micelles, their behavior, and properties in aqueous solution were investigated under the effect of pH, temperature, and ionic strength, as PDMAEMA and its derivatives are stimuli‐responsive polymers and exhibit responses to variations of at least one of these physicochemical parameters. These new families of stimuli‐responsive block copolymers respond to changes of their environment giving interesting nanostructures, behavioral motifs, and properties, rendering them useful as nanocarriers for drug delivery and gene therapy. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 598–610

Antibacterial activity, thermal stability and ab initio study of copolymer containing sulfobetaine and carboxybetaine groups

Here, we have explored the antibacterial activity, thermal stability and theoretical study of two copolymers that contain sulfobetaine and carboetaine moiety. Copolymers were synthesized based on Schiff base chemistry with generation of zwitterionic centres by nucleophilic addition of sultone/lactone. To predict and confirm the molecular structure of zwitterionic polyelectrolyte molecule, the theoretical study of structural features and other thermodynamic characteristics of copolymer constituents was obtained by ab initio calculations. Various parameters such as geometry optimization, energy calculations, frequency calculations and intrinsic reaction coefficient (IRC) are simulated using Hartree Fock (HF) method. The geometry optimizations are analyzed at HF/3-21 G default level of theory. The vibrational frequency is calculated via density functional theory (DFT)/B3LYP 6-31G*(d) level whose values are in accord with the experimental observed frequency. Both copolymers have been successfully assessed for antibacterial activity against Staphylococcus aureus and Pseudomonas aeuroginosa bacterial strains by disc diffusion method. The antibacterial study helped in evaluating zone of inhibition, minimum inhibitory concentration and minimum bactericidal concentration. Sulfobetaine copolymer is found to be more effective in curtailing the infection caused by bacteria as compared to carbobetaine.

Anti-Fouling Double-Skinned Forward Osmosis Membrane with Zwitterionic Brush for Oily Wastewater Treatment

Despite its attractive features for energy saving separation, the performance of forward osmosis (FO) has been restricted by internal concentration polarization and fast fouling propensity that occur in the membrane sublayer. These problems have significantly affected the membrane performance when treating highly contaminated oily wastewater. In this study, a novel double-skinned FO membrane with excellent anti-fouling properties has been developed for emulsified oil-water treatment. The double-skinned FO membrane comprises a fully porous sublayer sandwiched between a highly dense polyamide (PA) layer for salt rejection and a fairly loose dense bottom zwitterionic layer for emulsified oil particle removal. The top dense PA layer was synthesized via interfacial polymerization meanwhile the bottom layer was made up of a zwitterionic polyelectrolyte brush - (poly(3-(N-2-methacryloxyethyl-N,N-dimethyl) ammonatopropanesultone), abbreviated as PMAPS layer. The resultant double-skinned membrane exhibited a high water flux of 13.7 ± 0.3 L/m2.h and reverse salt transport of 1.6 ± 0.2 g/m2.h under FO mode using 2 M NaCl as the draw solution and emulsified oily solution as the feed. The double-skinned membrane outperforms the single-skinned membrane with much lower fouling propensity for emulsified oil-water separation.

Gated ion transport in a soft nanochannel with biomimetic polyelectrolyte brush layers

Functionalized nanofluidics has recently emerged as a powerful platform for applications of energy conversion as well as ionic diodes. Inspired by biological cells, we theoretically investigate for the first time the gate modulation of ion transport and selectivity in the soft nanochannel functionalized with biomimetic, pH-tunable, zwitterionic polyelectrolyte (PE) brush layers. The gate effect on the modulation of Donnan potential, ionic conductance, and ion selectivity in the biomimetic soft nanochannel is remarkable when the background salt concentration is low, pH is close to the isoelectric point of PE brush layers (slightly acidic), and the grafting density of PE brushes on the channel wall is small. Under those conditions, the biomimetic gated soft nanochannel is capable of being highly cation-selective when a negative gate voltage is applied. The findings provide a novel way for designing nanofluidic devices used in osmotic energy conversion and ion current rectification.