High-performance and robust high-temperature polymer electrolyte membranes with moderate microphase separation by implementation of terphenyl-based polymers

Acid loss and plasticization of phosphoric acid(PA)-doped high-temperature polymer electrolyte membranes(HT-PEMs)are critical limitations to their practical application in fuel cells.To overcome these barriers,poly(terphenyl piperidinium)s constructed from the m-and p-isomers of terphenyl were synthesized to regulate the microstructure of the membrane.Highly rigid p-terphenyl units prompt the formation of moderate PA aggregates,where the ion-pair interaction between piperidinium and biphosphate is reinforced,leading to a reduction in the plasticizing effect.As a result,there are trade-offs between the proton conductivity,mechanical strength,and PA retention of the membranes with varied m/p-isomer ratios.The designed PA-doped PTP-20m membrane exhibits superior ionic conductivity,good mechanical strength,and excellent PA retention over a wide range of temperature(80–160°C)as well as satisfactory resistance to harsh accelerated aging tests.As a result,the membrane presents a desirable combination of performance(1.462 W cm^(-2) under the H_(2)/O_(2)condition,which is 1.5 times higher than that of PBI-based membrane)and durability(300 h at 160°C and 0.2 A cm^(-2))in the fuel cell.The results of this study provide new insights that will guide molecular design from the perspective of microstructure to improve the performance and robustness of HT-PEMs.

High performance photodegradation resistant PVA@TiO_(2)/carboxyl-PES self-healing reactive ultrafiltration membrane

The occurrence of ultrafiltration(UF)membrane fouling frequently hampers the sustainable advancement of UF technology.Reactive self-cleaning UF membranes can effectively alleviate the problem of membrane fouling.Nevertheless,the self-cleaning process may accelerate membrane aging.Addressing these concerns,we present an innovative design concept for composite self-healing materials based on self-cleaning UF membranes.To begin,TiO_(2)nanoparticles were incorporated into the polymer molecular structure via molecular design,resulting in the synthesis of TiO_(2)/carboxyl-polyether sulfone(PES)hybrid materials.Subsequently,the nonsolvent-induced phase inversion technique was employed to prepare a novel of UF membrane.Lastly,a polyvinyl alcohol(PVA)hydrogel coating was applied to the hybrid UF membrane surface to create PVA@TiO_(2)/carboxyl-PES self-healing reactive UF membranes.By establishing a covalent bond,the TiO_(2)nanoparticles were effectively and uniformly dispersed within the UF membrane,leading to exceptional self-cleaning properties.Furthermore,the water-absorbing and swelling properties of PVA hydrogel,along with its capacity to form hydrogen bonds with water molecules,resulted in UF membranes with improved hydrophilicity and active self-healing abilities.The results demonstrated that the water contact angle of PVA@5%TiO_(2)/carboxyl-PES UF membrane was 43.1°.Following a 1-h exposure to simulated solar exposure,the water flux recovery ratio increased from 48.16%to 81.03%.Moreover,even after undergoing five cycles of 12-h simulated sunlight exposure,the UF membranes exhibited a consistent retention rate of over 97%,thus fully demonstrating their exceptional self-cleaning,antifouling,and selfhealing capabilities.We anticipate that the self-healing reactive UF membrane system will serve as a pioneering and comprehensive solution for the self-cleaning antifouling challenges encountered in UF membranes while also effectively mitigating the aging effects of reactive UF membranes.

Electrospinning organic solvent resistant preoxidized poly(acrylonitrile)nanofiber membrane and its properties

A high performance preoxidized poly(acrylonitrile)(O-PAN)nanofiber membrane with excellent solvent resistance,thermal stability and flexibility was fabricated by the preoxidation of electrospun PAN nanofiber membrane.The performance of resultant O-PAN nanofiber membrane was optimized by altering the PAN concentration and preoxidation temperature.The results showed that the O-PAN nanofiber membrane which made from PAN concentration of 14%(mass)and preoxidation temperature of 250.0
℃ have a more optimal comprehensive performance.In the long-term separation test of SiO2 particle(1 μm)in DMAc suspension,the permeate flux of O-PAN nanofiber membrane stabilized at 227.91 L·m^(-2)·h^(-1)(25
℃,0.05 MPa)while the SiO2 rejection above 99.6%,which showed excellent solvent resistance and separation performance.In order to further explore the application of the O-PAN nanofiber membrane,the OPAN nanofiber membrane was treated with fluoride and used in oil/water separation process.The O-PAN nanofiber membrane after hydrophobic treatment showed excellent hydrophobicity and good oil/water separation performance with the permeate flux about 969.59 L·m^(-2)·h^(-1)while the separation efficiency above 96.1%.The O-PAN nanofiber membrane exhibited a potential application prospect in harsh environment separation.

Graphene quantum dots doped poly(vinyl alcohol)hybrid membranes for desalination via pervaporation

Pervaporation desalination by highly hydrophilic materials such as poly(vinyl alcohol)(PVA)based separation membrane is a burgeoning technology of late years.However,the improvement of membrane flux in pervaporation desalination has been a difficult task.Here,a novel hybrid membrane with doped graphene oxide quantum dots(GOQDs)which is rich in hydrophilic groups and small size into the matrix of PVA was prepared to improve the membrane flux.The membranes structures were described by field emission scanning electron microscopy(FESEM),atomic force microscopy(AFM),Fourier transform infrared(FT-IR),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA)and X-ray diffraction(XRD).And more,Water contact angle,swelling degree,and pervaporation properties were carried out to explore the effect of GOQDs in PVA matrix.In addition,GOQDs content in the hybrid membrane,NaCl concentration,and feed temperature were investigated accordingly.Moreover,the hydrogen bonds between PVA chains were weakened by the interaction between GOQDs and PVA chains.Significantly,the hybrid membrane with optimized doped GOQDs content,200 mg·L^(-1),displays a high membrane flux of 17.09 kg·m^(-2)·h^(-1)and the salt rejection is consistently greater than 99.6%.

Poly(Ionic Liquid) as an Anion Exchange Membrane for a 3.3 V Copper–Lithium Battery

Metal–metal battery bears great potential for next-generation large-scale energy storage system because of its simple manufacture process and low production cost.However,the cross-over of metal cations from the cathode to the anode causes a loss in capacity and influences battery stability.Herein,a coating of poly(ionic liquid)(PIL)with poly(diallyldimethylammonium bis(trifluoromethanesulfonyl)imide)(PDADMA^(+)TFSI^(−))on a commercial polypropylene(PP)separator serves as an anion exchange membrane for a 3.3 V copper–lithium battery.The PIL has a positively charged polymer backbone that can block the migration of copper ions,thus improving Coulombic efficiency,long-term cycling stability and inhibiting self-discharge of the battery.It can also facilitate the conduction of anions through the membrane and reduce polarization,especially for fast charging/discharging.Bruce-Vincent method gives the transport number in the electrolyte to be 0.25 and 0.04 for PP separator without and with PIL coating,respectively.This suggests that the PIL layer reduces the contribution of the internal current due to cation transport.The use of PIL as a coating layer for commercial PP separator is a cost-effective way to improve overall electrochemical performance of copper–lithium batteries.Compared to PP and polyacrylic acid(PAA)/PP separators,the PIL/PP membrane raises the Coulombic efficiency to 99%and decreases the average discharge voltage drop to about 0.09 V when the current density is increased from 0.1 to 1 mA cm^(−2).

Synthesis and characterization of quaternized poly(phthalazinone ether sulfone ketone)for anion-exchange membrane

Chloromethylated poly（phthalazinone ether sulfone ketone） （CMPPESK） was prepared from poly（phthalazinone ether sulfone ketone） （PPESK） using chloromethyl octyl ethers （CMOE） with lower toxicity as chloromethylated regent. CMPPESK was soluble in N-methyl-2-pyrrolidone （NMP）, N,N-dimethylacetamide （DMAc） and chloroform. Quaternized poly（phthalazinone ether sulfone ketone） （QAPPESK） was prepared from CMPPESK by quaternization. QAPPESK had excellent solvent resistance, which was only partly soluble in sulfuric acid （98%） and swollen in N,N-dimethylformamide （DMF）. The vanadium redox flow battery （V-RFB） using QAPPESK anion-exchange membrane had better performance with 88.3% of overall energy efficiency.

Tetra-alkylsulfonate functionalized poly(aryl ether) membranes with nanosized hydrophilic channels for efficient proton conduction

The microstructure of polymer electrolyte membranes plays a key role in ion conductivity and water transport.Herein,fluorinated poly(aryl ether)s with tetra-alkylsulfonate side chains(SFPAEs)have been successfully synthesized from the copolymerization of a newly developed tetra-allyl-containing bisphenol(TABP)monomer,followed by the thiol-ene addition with sodium 3-mercapto-1-propanesulfonate to attach the ionic groups at the end of the flexible chains.Being the first of its kind,the densely distributed and lengthy alkylsulfonate group possesses the benefit of ease to self-assemble into hydrophilic domains during membrane preparation via solution casting.Indeed,the TEM characterizations revealed that distinct hydrophilic channels of 1-2 nm width had been formed,much larger than those of a home-made control sample where only di-alkylsulfonate side chains were attached.The SFPAE-4-45 with an IECw of 2.0 mmol g^-1 exhibited an enhanced proton conductivity of 143.7 m S cm^-1 at room temperature,which was superior to that of Nafion 212(91.0 m S cm^-1).Furthermore,the oxidative stabilities of SFPAEs were significantly higher than those of non-fluorinated analogs in literature.This study offered a new route to engineering the pendent structure of ionomers for well-defined microscopic morphologies.

A Hybrid Membrane of Poly(vinyl alcohol) and Phosphotungstic Acid for Fuel Cells

Proton conducting membranes composed of phosphotungstic acid (PWA) and poly(vinyl alcohol) (PVA)were prepared. Conductivity and Fourier transform infrared spectrometer(FTIR) measurements show that most ofthe acid embedded are stable in the PVA matrix when the membrane is immerged in water or methanol solution atroom temperature. Conductivity of the composite membranes scatters around 10-3 S.cm-1 at room temperature.The methanol crossover through the membranes is about an order of magnitude lower than that through Nafion117 membrane.

Effect of Graft Yield on the Thermo-Responsive Permeability Through Porous Membranes with Plasma-Grafted Poly(N-isopropylacrylamide)Gates

The effect of graft yield on both the thermo-responsive hydraulicpermeability and the therrno-responsive diffusional permeability through porous membranes withplasma-grafted poly(N-isopropylacrylamide) (PNIPAM) gates was investigated. Both thermo-responsiveflat membranes and core-shell microcapsule membranes with a wide range of graft yield of PNIPAM wereprepared using a plasma-graft pore-filling polymerization method. The grafted PNIPAM was formedhomogeneously throughout the entire thickness of both the flat polyethylene membranes and themicrocapsule polyamide membranes. Both the hydraulic permeability and the diffusional permeabilitywere heavily dependent on the PNIPAM graft yield. With increasing the graft yield, the hydraulicpermeability (water flux) decreases rapidly at 25℃ because of the decrease of the pore size;however, the water flux at 40℃ increases firstly to a peak because of the increase ofhydrophobicity of the pore surface, and then decreases and finally tends to zero because of the poresize becoming smaller and smaller. For the diffusional permeability, the temperature showsdifferent effects on the diffusional permeability coefficients of solutes across the membranes. Whenthe graft yield was low, the diffusional coefficient of solute across the membrane was higher attemperature above the lower critical solution temperature (LCST) than that below the LCST; however,when the graft yield was high, the diffusional coefficient was lower at temperature above the LCSTthan that below the LCST. It is very important to choose or design a proper graft yield of PNIPAMfor obtaining a desired thermo-responsive 'on/off' hydraulic or diffusional permeability.

Photochemical surface modification of poly(arylsulfone) ultrafiltration membrane and covalent immobilization of enzyme

The sensitivity of poly(arylsulfone)(PSf) for UV irradiation in different solvents(water and ethanol) was investigated. It is confirmed that acrylic acid(AA) and acrylamide(AAm) are grafted only onto the surface of the membrane instead of the interior by FTIR and scanning electron microscope(SEM). The membrane performance(Δ J/J 0 and contact angle θ ) after photografting was studied. In the range of conditions used, the grafting yield increases with irradiation time and monomer concentration growing. After photografting and N 3 dimethyl aminopropyl N' ethycarbodiimide hydrochloride(EDC) activation, PSf membrane was immobilized with hydrogen peroxide oxidoreductase, and showed a higher activity than the control membrane.

MORPHOLOGIES AND GAS SEPARATION PROPERTIES OF MELT-SPUN ASYMMETRIC POLY(4-METHYL-1-PENTENE)HOLLOW FIBER MEMBRANES

Poly(4-methyl-1-pentene) (PMP) hollow fiber membranes were prepared by the melt-spun and cold-stretch(MSCS) method. Scanning electronic microscopy (SEM) was used to characterize the section and surface structures of themembranes with special asymmetric structure. The preliminary results of gas permeation measurements indicated that the resultant hollow fiber membranes have the potential ability for oxygen/nitrogen separation.

MICROPOROUS PVDF-HFP-BASED POLYMER MEMBRANES FORMED FROM SUPERCRITICAL CO_2 INDUCED PHASE SEPARATION

Microporous poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)membranes following supercritical CO_2 induced phase separation process were prepared using four solvents.The solid electrolytes of PVDF-HFP were formed by microporous PVDF-HFP membranes filled and swollen by a liquid electrolyte.The effect of the solvents on the morphology and structure,electrolyte absorptions and lithium ionic conductivity of the activated membranes were investigated.It was approved that all the membrane had the similar...

Proton-Exchange Sulfonated Poly （ether ether ketone） （SPEEK）/SiOx-S Composite Membranes in Direct Methanol Fuel Cells

A sulfonated poly（ether ether ketone） （SPEEK） membrane with a fairly high degree of sulfonation （DS） can swell excessively and even dissolve at high temperature. To solve these problems, insolvable functionalized silica powder with sulfonic acid groups （SiOx-S） was added into the SPEEK matrix （DS = 55.1%） to prepare SPEEK/ SiOx-S composite membranes. The decrease in both the swelling degree and the methanol permeability of the membranes was a dose-dependent result of addition of the SiOx-S powder. Pure SPEEK membrane swelled 52.6% at 80℃, whereas the SPEEK/SiOx-S （15%, by mass） membrane swelled only 27.3% at the same temperature. From room temperature to 80℃, all SPEEK/SPEEK/SiOx-S composite membranes had methanol permeability of about one order of magnitude lower than that ofNafion115. Compared with pure SPEEK membranes, the addition of the SiOx-S powder not only leads to higher proton conductivity, but also increases the dimensional stability at higher temperatures, and greater proton conductivity can be achieved at higher temperature. The SPEEK/SiO4-S （20%, by mass） membrane could withstand temperature up to 145℃, at which in 100% relative humidity （RH） its proton conductivity exceeded slightly that of Nafion 1 15 membrane and reached 0.17 S·cm^-1, while pure SPEEK membrane dissolved at 90℃. The SPEEK/SiOx-S composite membranes are promising for use in direct methanol fuel cells because of their good dimensional stability, high proton conductivity, and low methanol permeability.

Fabrication of poly(vinylidene fluoride) membrane via thermally induced phase separation using ionic liquid as green diluent

Ionic liquid(IL),1-butyl-3-methylimidazolium hexafluorophosphate([BMIM]PF6)as a new and environmentally friendly diluent was introduced to prepare poly(vinylidene fluoride)(PVDF)membranes via thermally induced phase separation(TIPS).Phase diagram of PVDF/[BMIM]PF6 was measured.The effects of polymer concentration and quenching temperature on the morphologies,properties,and performances of the PVDF membranes were investigated.When the polymer concentration was 15 wt%,the pure water flux of the fabricated membrane was up to nearly 2000 L·m-2·h-1,along with adequate mechanical strength.With the increasing of PVDF concentration and quenching temperature,mean pore size and water permeability of the membrane decreased.SEM results showed that PVDF membranes manufactured by ionic liquid(BMIm PF6)presented spherulite structure.And the PVDF membranes were represented asβphase by XRD and FTIR characterization.It provides a new way to prepare PVDF membranes with piezoelectric properties.

Proton-exchange Sulfonated Poly（ether ether ketone）/Sulfonated Phenolphthalein Poly（ether sulfone） Blend Membranes in DMFCs

A sulfonated poly（ether ether ketone） （SPEEK） membrane with fairly high degree of sulfonation （DS） swells excessively and even dissolves at high temperature. To solve these problems, sulfonated phenolphthalein poly（ether sulfone） （SPES-C, DS= 53.7%） is blended with the SPEEK matrix （DS= 55.1%, 61.7%） to prepare SPEEKJSPES-C blend membrane. The decrease in swelling degree and methanol permeability of the membrane is dose-dependent. Pure SPEEK （DS = 61.7%） membrane dissolves completely in water at 70℃, whereas the swelling degree of the SPEEK （DS = 61.7%）/SPES-C （40%, by mass） membrane is 29.7% at 80℃. From room temperature to 80℃, the methanol permeability of all SPEEK （DS = 55.1%）/SPES-C blend membranes is about one order of magnitude lower than that of Nafion 115. At higher temperature, the addition of SPES-C polymer increases the dimensional stability and greater proton conductivity can be achieved. The SPEEK （DS = 55.1%）/SPES-C （40%, by mass） membrane can withstand temperatures up to 150℃. The proton conductivity of SPEEK （DS = 55.1%）/SPES-C （30%, by mass） membrane approaches 0.16 S·cm^-1, matching that of Nafion 115 at 140℃ and 100% RH, while pure SPEEK （DS = 55.1%） membrane dissolves at 90℃. The SPEEK/SPES-C blend membranes are promising for use in direct methanol fuel cells because of their good dimensional stability, high proton conductivity, and low methanol permeability.

Molecular Imprinting Fibrous Membranes of Poly(acrylonitrile-co-acrylic acid) Prepared by Electrospinning

IntroductionOver the past few decades, molecular imprinting has been described as a technology for preparing ＂molecular doors＂ which can be matched to ＂template keys＂. It has been found to be a simple and effective approach to introduce specific recognition sites into synthetic polymers, namely, to create molecular imprinting polymers Remarkable features such as stability, ease of preparation and low cost, have made molecular imprinting polymers particularly attractive in chemical sensors, catalysis, drug delivery, and dedicated separations. Practical applications of molecular imprinting polymers require accessible sites, fast mass transfer, and quick binding. However, present techniques used to prepare molecular imprinting polymers most often result in materials exhibiting a high affinity and selectivity but a low capacity and poor site accessibility for the target molecules. It is also very difficult to remove the imprinted molecules located in these molecular imprinting polymers because the highly cross-linked structures do not allow the templates to move freely. To some extent, combining molecular imprinting technology with membrane separation and surface imprinting can overcome the shortcomings, such as mass transfer limitations and non-quantitative recovery of the template molecules seen for imprinted materials fabricated by conventional bulk methods. In that ease, it appears to us that molecular imprinting polymers with high surface area to volume ratios are particularly desirable for largescale applications. Eleetrospun nano and ultrafine fibrous membranes are the most suitable materials due to advantages such as： （1） large specific surfaces, providing relatively high imprinting sites per unit mass; （2） fine porous structures, resulting in the accessibility of imprinting sites and low diffusion resistance necessary for high efficiency; and （3） easy recoverability from practical operation or applicability for continuous usages. Therefore, in this work, we prepared a unique kind of imprinted material--molecularly imprinted fibrous membranes of poly （ acrylonitrile-co-acrylic acid） fabricated by means of an electrospinning process.

Two dimensional MoS_(2) finding its way towards constructing high-performance alkaline recovery membranes

The available alkaline recovery membranes are currently dominated by polymeric materials,but they suffer from a permeation-selectivity trade-off and inferior chemical resistance.Robust two dimensional(2D) lamellar membranes with sub-nanometer wide channels are promising candidates for discerning OH^(-)and other anions.Here,we report the development of alkaline recycling membranes through stacking MoS_(2) nanosheets.Benefiting from the ordered and narrow 2D channels,MoS_(2) membranes show excellent alkaline recovery performances.The OH^(-)dialysis coefficient (U_(OH)-) and separation factor (S)towards simulated OH^(-) and WO_(4)^(2-) across the 500 nm thick MoS_(2) laminates reach 6.9×10^(-3)m·h^(-1)and 34.3 respectively.Furthermore,the chemical environments of MoS_(2) laminates were modulated by intercalating ionic poly(sodium 4-styrene sulfonate)(PSS@MoS_(2)).The U_(OH)-and S values of PSS@MoS_(2) membrane further improve to 11.7×10^(-3)m·h^(-1)and 49.8 respectively.Besides,both MoS_(2) and PSS@MoS_(2) membranes exhibit promising stability.

HYDROPHILIC MODIFICATION OF PPESK POROUS MEMBRANES VIA AQUEOUS SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

Hydrophilic surface modification of poly(phthalazinone ether sulfone ketone)(PPESK) porous membranes was achieved via surface-initiated atom transfer radical polymerization(ATRP) in aqueous medium.Prior to ATRP.chloromethyl groups were introduced onto PPESK main chains by chloromethylation.Chloromethvlated PPESK(CMPPESK) was fabricated into porous membrane through phase inversion technique.Hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate)(P(PEGMA)) brushes were grafted from CMPPESK membrane ...

Polyvinyl acetate/poly(amide-12-b-ethylene oxide) blend membranes for carbon dioxide separation

In this paper,blend membranes from polyvinyl acetate(PVAc)and block copolymer poly(amide-12-b-ethylene oxide)(Pebax1074)are prepared by solution casting and solvent evaporation method.Although they are homogeneous on a macro-scale,the observations from DSC and SEM indicate micro-phase separation for PVAc/Pebax1074 blend membranes.With the increase of Pebax1074 content,gas permeabilities of CO2,H2,N2and CH4all increase greatly.PVAc/Pebax1074 blend membranes with high PVAc content are appropriate for CO2/CH4separation.The temperature dependence of gas permeability is divided into rubbery region and glassy region.The activation energies of permeation in rubbery region are smaller than those in glassy region,and they all decrease with increasing Pebax1074 content.For N2,H2and CH4,their gas permeation properties are mainly influenced by the dual-mode sorption and hydrostatic pressure effect.But for CO2,its permeability increases with the increase of pressure due to CO2-induced plasticization effect,which is more obvious for PVAc/Pebax1074 blend membranes with high PVAc content.

Preparation of PVDF/SiO₂Composite Nanofiber Membrane Using Electrospinning for Polymer Electrolyte Analysis

Superhydrophobic poly(vinylidene fluoride) PVDF-SiO2 composite membranes with different % of SiO2 contents were prepared by electrospinning. The surface morphologies of the membranes are characterized by using scanning electron microscopy. The nanofibers in the membranes were stacked in layers to produce fully interconnected pores that resulted in high porosity. The incorporation of SiO2 into the nanofiber membrane improved the ionic conductivity from 0.2428 × 10-4Scm-1 to 7.731 × 10-4Scm-1 at room temperature. The surface roughness of the membranes increased with increasing the SiO2 content, while the average diameter of nanofibers was rarely affected. Superhydrophobic PVDF membrane with a contact angle larger than 136° was prepared by the electrospinning of the SiO2 functionalized PVDF. The surface composition of the membranes is analyzed by using FTIR and the contact angles and water drops on the surface of the membrane are measured. The contact angle experimental results of PVDF-SiO2 composite membranes showed an improvement of hydrophobicity with % of nano SiO2.