Sulfonated Poly Ether Ether Ketone Research Articles

Antimicrobial Peptide Conjugated on Graphene Oxide-Containing Sulfonated Polyetheretherketone Substrate for Effective Antibacterial Activities against Staphylococcus aureus.

In the present study, the antimicrobial peptide nisin was successfully conjugated onto the surface of sulfonated polyetheretherketone (SPEEK), which was decorated with graphene oxide (GO) to investigate its biofilm resistance and antibacterial properties. The PEEK was activated with sulfuric acid, resulting in a porous structure. The GO deposition fully covered the porous SPEEK specimen. The nisin conjugation was accomplished using the crosslinker 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) through a dip-coating method. The surface micrographs of the SPEEK-GO-nisin sample indicated that nisin formed discrete islets on the flat GO surface, allowing both the GO and nisin to perform a bactericidal effect. The developed materials were tested for bactericidal efficacy against Staphylococcus aureus (S. aureus). The SPEEK-GO-nisin sample had the highest antibacterial activity with an inhibition zone diameter of 27 mm, which was larger than those of the SPEEK-nisin (19 mm) and SPEEK-GO (10 mm) samples. Conversely, no inhibitory zone was observed for the PEEK and SPEEK samples. The surface micrographs of the bacteria-loaded SPEEK-GO-nisin sample demonstrated no bacterial adhesion and no biofilm formation. The SPEEK-nisin and SPEEK-GO samples showed some bacterial attachment, whereas the pure PEEK and SPEEK samples had abundant bacterial colonies and thick biofilm formation. These results confirmed the good biofilm resistance and antibacterial efficacy of the SPEEK-GO-nisin sample, which is promising for implantable orthopedic applications.

Regulation of respiratory rate and storage quality of postharvest cauliflower based on gas permeability modification using gas barrier (GB) - gas conductor (GC) blending packaging

The aim of this work is to explore a method to develop equilibrium modified atmosphere packaging (EMAP) via density of available active site (AAS). Sulfonated poly etheretherketone (SPEEK) was prepared as a component to promote gas permeation, i.e. gas conductor (GC). It was mixed with polysulfone (PSF) as gas barrier (GB). With varying GC and GB concentrations, the prepared EMAP provided internal equilibrium atmospheres with 1.8% - 7.2% CO2 and 3.1% - 4.4% O2, in which respiratory rate of preserved cauliflower was inhibited and thereby the storage quality was maintained. Final sensory score of the cauliflower samples preserved in EMAP for 30 days was better than that of control samples (3.5 vs. 1.6), while the texture properties were maintained compared to those in the control samples. Additionally, the inhibitory effects were also shown in color parameters and chemical indicators. The findings in this work would promote the development of modified atmosphere packaging technology.

Construction of continuous proton transport channels in SPEEK using porous titanium dioxide nanotubes

Due to its adaptable performance and industrial manufacturing, sulfonated poly ether ether ketone (SPEEK) is suitable for proton exchange membrane (PEM). Organica-inorganic composite membrane was suggested as a way to further enhance its performance. By combining different weights of titanium (IV) oxide acetylacetonate (TiOacac) with polyacrylonitrile (PAN), a PAN/TiOacac solution was created that could then be used to create PAN/TiOacac nanofiber. After the nanofiber has been calcined, TNT-10, TNT-30, and TNT-50 can be produced. Following the incorporation of these three types of TNT into the SPEEK matrix, the solution-casting approach allowed for the simple development of the TNT/SPEEK membrane. The composite membrane of 1%TNT-10/SPEEK and 1%TNT-50/SPEEK was discontinuous and inefficient due to the loose and abundant titanium dioxide in TNT-10 and TNT-50, respectively. While it was compact for TNT-30 with premium performance, so 1%TNT-30/SPEEK would form continuous proton transport channels in PEM and have an interaction between TNT-30 and SPEEK matrix, which was confirmed by FTIR, TEM and XPS. To create a high-performance PEM, it is necessary to develop a continuous proton transport channel.

Effects of the Applied Potential on the Performance of Polysulfone Membranes Functionalized with Sulfonated Polyether Ether Ketone Polymers.

The global water crisis growth has led to a tremendous increase in membrane technology research. Membranes are favored over many other technologies for water treatment because, in principle, they require no chemical additives and can be used isothermally at low temperatures. Membranes that can reject contaminants and salts, produce adequate permeate flux values, and require minimal cleaning are highly demanded. However, most synthesized membranes on the market have associated problems, such as membrane fouling; inverse relationships between flux and solute rejection; and the high cost of synthesis, operation, and maintenance. Therefore, there is a continuied need to produce membranes with properties that make them able to sustain flux and selectivity over time. This research study focused on increasing the surface charge and hydrophilicity of polysulfone (PSf) membranes by incorporating sulfonate-functionalized poly-ether-ether-ketone (SPEEK) into PSf/N-Methyl-2-pyrrolidone (PSf/NMP) membranes. The sulfonation of the PEEK provided a net increase in negative charge on the surface of the membranes that enabled charge repulsion to take place, thus increasing the rejection of ions. In this project, the effect of the applied potential on the performance of SPEEK: PSf/NMP membranes was evaluated. The characterization of the as-synthesized membranes was carried out using the surface's structure and morphology, contact angle, and zeta potential. Furthermore, a voltage of 1.5 V was applied to the membranes in the presence of various salts (sodium chloride, calcium chloride, and potassium chloride salts) to evaluate the effects of the applied potential on solute rejection. It was found that both the permeability and the selectivity of the membranes increased when the voltage was applied. The obtained results indicate that incorporating SPEEK into PSf/NMP membranes increased the hydrophilicity of the membranes, and under the applied voltage, the incorporation allowed it to function as an electrodialysis process that is capable of removing ions from water bodies by utilizing the charge repulsion of ions.

Optimization through response surface methodology of 3D printed membrane preparation conditions for use in vanadium redox flow battery: A vanadium/proton selectivity study

AbstractSPEEK membrane applicable in Vanadium Redox Flow Battery (VRFB) have been 3D printed via Fused Deposition Modeling (FDM). Response Surface Methodology (RSM) has been used to optimize conditions for 3D printing membrane. Good membranes characteristics were obtained by manipulating three parameters, namely the printing temperature, the orientation of the printing layer and the sulfonation time. We evaluated the effects of these three variables on the permeability of membranes to protons and vanadium ions. Results have shown that sulfonation is the most significant variable influencing vanadium and proton permeability. The optimal printing conditions were found at 408°C temperature with a horizontal layer orientation, while the best sulfonation is obtained at 6 min. The optimal membrane has an ion exchange capacity of 0.86 mmolg−1, a water uptake ratio of 22%, a VO2+ permeability of 6.1 × 10−8 cm2 min−1, a H+ permeability of 7.0 × 10−6 cm2 min−1, excellent mechanical stability and better H+/VO2+ perm selectivity than conventional sulfonated polyether ether ketone (SPEEK), Fap450 and Nafion211 membranes. The above results show that the 3D‐SPEEK membrane has great advantages and broad prospects for VRFB applications.

Polydopamine-coated polyimide nanofiber to anchor HPW and construct the pocket-like composite membrane with excellent proton conductivity and stability

Solid heteropolyacids with high intrinsic proton conductivity, like phosphotungstic acid (HPW), were added to further enhance the proton conductivity of sulfonated poly ether ketone (SPEEK). The great solubility of solid acid within water, however, would produce a dramatic decline in stability and durability. In this study, we utilized polydopamine (PDA) coated polyimide (PI) nanofiber to form the acid-base pair between PDA@PI nanofiber and HPW/SPEEK to anchor the HPW. Additionally, a pocket was constructed in the sandwich-structure PDA@PI/SPEEK + HPW membrane to help better anchor the HPW. After 6 weeks of durability treatment during 60 °C and 100% RH, proton conductivity of PDA@PI/SPEEK + HPW-20 was 163.5 mS cm−1, which was only 23.0% lower than that of the initial state. By sharp contrast, it was 55.2% lower than the initial state for pristine SPEEK. And its swelling ratio is only 54% compared with 128% of pristine SPEEK under the same condition. We first revealed and investigated the acid-base pair created by PDA@PI and HPW/SPEEK, which was beneficial for proton conductivity and durability. This pocket-like PDA@PI/SPEEK + HPW membrane would inspire a wide application in PEM among excellent proton conductivity, better stability, with endurance.

Size exclusion chromatography characterization of poly (ether ether ketone), PEEK, after chemical modification

AbstractCharacterization of the molar mass distribution (MMD) of poly (ether ether ketone) (PEEK) is very troublesome due to the insolubility of PEEK in common solvents. The solubility of PEEK may be substantially improved after its sulfonation. Sulfonated PEEK (SPEEK) was prepared by sulfonation of PEEK with 98% concentrated H2SO4 at room temperature. The presence of sulfonic acid group (‐SO3H) in PEEK matrix was confirmed by nuclear magnetic resonance and Fourier transform infrared spectroscopy. The degree of sulfonation (DS ~ 95%) was determined by proton nuclear magnetic resonance in deuterated dimethyl sulfoxide and by thermal analysis methods. The equivalent molar mass and MMD of sulfonated PEEK was determined at 30°C in three polar solvents (N,N‐dimethylacetamide, N,N‐dimethylformamide N‐methyl‐2‐pyrollidone) in PS/DVB column using calibration with PMMA standards. A salt (LiBr) was added to the solvents for suppression of undesired interactions of analytes with the column packing. Moreover, the sulphonated PEEK was separated with size exclusion chromatography (SEC) coupled to a multi‐angle light scattering (MALS) detector. It was found that the absolute average molar mass of SPEEK from the MALS detection is much closer to the value measured by SEC in N,N‐dimethylacetamide +LiBr than the values determined in N,N‐dimethylformamide and N‐methyl‐2‐pyrollidone.

In Situ-Doped Sulfonated Schiff-Base Networks in SPEEK Composite Membranes with Enhanced Proton Conductivity.

Sulfonated polyether ether ketone (SPEEK) has been widely investigated in proton exchange membrane fuel cells (PEMFCs) due to its excellent thermal stability, chemical stability, and low cost compared with Nafion. However, excessive degree of sulfonation will easily lead to the decrease in thermal stabilities and mechanical properties of SPEEK membranes, which limits the enhancement of proton conductivity. In this work, a series of Schiff-base networks (SNWs) with different contents are in situ synthesized in the SPEEK membrane by a Schiff-base co-condensation reaction, and then, the composite membranes are soaked in sulfonic acid for further improvement of proton conductivity. The highest doping amount of the SNW filler in SPEEK can reach 20 wt %. High loading and low leaching rate of H2SO4 are easily achieved owing to the similar size between sulfuric acid molecules and micropores in SNW. Moreover, abundant amino and imine groups in SNW networks contribute to the anchoring of H2SO4 into the pores by acid-base interactions. The proton conductivity of the SPEEK/S-SNW-15 composite membrane can reach 115.53 mS cm-1 at 80 °C and 100% RH. Meanwhile, the composite membrane also exhibits satisfied stability and mechanical property.

Surface modification, counter-ion exchange effect on thermally annealed sulfonated poly (ether ether ketone) membranes for vanadium redox flow battery

In this work, we report new approaches to sulfonated poly ether ether ketone (SPEEK) membranes to improve its inhibition to vanadium ions along with polymer reinforcement. First approach includes facile thermal annealing of SPEEK membrane (SPEEK-T) which could reinforce the polymer matrix. Second approach was to exchange the labile proton of SPEEK with benzimidazole to protect the hydrolytic decomposition of sulfonic acid followed by thermal annealing (SPEEK-Benz), and third approach focused on creating barrier layer for vanadium ions by coating polyethyleneimine on SPEEK membrane followed by thermal treatment (SPEEK-PEI). The chemical stability study of the membranes revealed acceptable dimension change and VO2+ electrolyte sorption for all the membranes with least dimension change and weight gain of 5 % and 12 %, respectively, for SPEEK-PEI. Amongst four prepared membranes, SPEEK-PEI membrane displayed least diffusion coefficient of 8.04 × 10−7, 8.94 × 10−7, 4.20 × 10−7 cm2 min−1 for V3+, VO2+, and VO2+ ions respectively. VRFB assembled with SPEEK-PEI resulted highest Coulombic efficiency (CE) of 97 % and energy efficiency (EE) of 66 % over 50 charge/discharge cycles at 100 mA cm−2. Peak power density of 255, 248, 240 and 235 mW cm−2 at current density of 300 mA cm−2 was observed for SPEEK-PEI, SPEEK-Benz, SPEEK-T, and SPEEK-48, respectively; these values were higher than 225 mW cm−2 for Nafion®117 in identical experimental conditions. The excellent VRFB performance suggest that the developed new approaches have pronounced effect on the membrane properties and can be further improved to obtain an ideal VRFB separator. Furthermore, the surface modification approaches adopted in this work is facile, reproducible and scalable and can be further designed to develop high performance ion exchange membranes for separation/purification and energy.

Antibacterial properties of antimicrobial peptide HHC36 modified polyetheretherketone.

Polyetheretherketone (PEEK) is considered to be a new type of orthopedic implant material due to its mechanical properties and biocompatibility. It is becoming a replacement for titanium (Ti) due to its near-human-cortical transmission and modulus of elasticity. However, its clinical application is limited because of its biological inertia and susceptibility to bacterial infection during implantation. To solve this problem, there is an urgent need to improve the antibacterial properties of PEEK implants. In this work, we fixed antimicrobial peptide HHC36 on the 3D porous structure of sulfonated PEEK (SPEEK) by a simple solvent evaporation method (HSPEEK), and carried out characterization tests. We evaluated the antibacterial properties and cytocompatibility of the samples in vitro. In addition, we evaluated the anti-infection property and biocompatibility of the samples in vivo by establishing a rat subcutaneous infection model. The characterization test results showed that HHC36 was successfully fixed on the surface of SPEEK and released slowly for 10 days. The results of antibacterial experiments in vitro showed that HSPEEK could reduce the survival rate of free bacteria, inhibit the growth of bacteria around the sample, and inhibit the formation of biofilm on the sample surface. The cytocompatibility test in vitro showed that the sample had no significant effect on the proliferation and viability of L929 cells and had no hemolytic activity on rabbit erythrocytes. In vivo experiments, HSPEEK can significantly reduce the bacterial survival rate on the sample surface and the inflammatory reaction in the soft tissue around the sample. We successfully loaded HHC36 onto the surface of SPEEK through a simple solvent evaporation method. The sample has excellent antibacterial properties and good cell compatibility, which can significantly reduce the bacterial survival rate and inflammatory reaction in vivo. The above results indicated that we successfully improved the antibacterial property of PEEK by a simple modification strategy, making it a promising material for anti-infection orthopedic implants.

Effect of Surface Modification of PEEK Artificial Phalanx by 3D Printing on its Biological Activity

Objective: Polyetheretherketone (PEEK) is widely used as an orthopedic implant material owing to its good biocompatibility and mechanical strength; however, PEEK implants are biologically inert, resulting in suboptimal cellular responses after implantation. The aim of this study was to enhance the biological activity of PEEK through sulfonation treatment. Methods: In this study, distal phalangeal implants of PEEK were customized by fused deposition modeling (FDM) printing technology and soaked in concentrated sulfuric acid at different times to obtain sulfonated PEEK (SPEEK). The groups were divided into five groups according to the sulfonation time as follows: 0 min (control group), 1 min (group SPEEK1), 2 min (group SPEEK2), 4 min (group SPEEK4), and 8 min (group SPEEK8). Then the physicochemical characteristics of implants were determined by SEM, XRD, EDS, etc. The implants were co-cultured with stem cells from human exfoliated deciduous teeth (SHED), and then the cell proliferation, adhesion, alkaline phosphatase (ALP) activity, and alizarin red staining were performed to detect the biological activity, biocompatibility, and osteogenic activity of the SPEEK implants. Results: The sulfonation time range of 1 to 8 min could promote the formation of micropores on the surface of PEEK implants, while slightly affecting the composition and compression performance of the implants. Compared with the control group, the hydrophilicity of PEEK materials was not improved after sulfonation treatment. Tests for adhesion and proliferation of SHED indicated that SPEEK2 showed superior biocompatibility. Furthermore, ALP activity and semi-quantitative analysis of Alizarin red staining showed that the osteogenic activity of SPEEK2 phalanges exhibited significantly stronger osteogenic activity than the other groups. Conclusions: The method presented here provides a promising approach to improve the surface bioactivity of PEEK implants prepared by FDM, providing a shred of primary evidence to support the application of SPEEK in orthopedics.

Positive role of sulfonated PEEK coating for PEEK membrane in mass transfer of lithium extraction

Membrane extraction (ME) is a promising technology for efficiently separating lithium from salt-lake brine with high Mg/Li ratio. By utilizing a solvent resistant semicrystalline poly(ether ether ketone) (PEEK), an extraction-stripping loop is envisioned, but significant improvement in the lithium extraction flux is required. We report in this paper a new finding of strong interaction of the extractant, Tributyl phosphate (TBP), to PEEK, leading to reduction in Li extraction flux. Phosphorous element inside PEEK substrate supported the finding; significantly higher Li flux was observed when the top surface faces the organic extractant than that when the bottom surface faces the organic. Mass transfer model detailed the consequence of infiltration by TBP to the ion flux due to the low diffusion coefficient of the bulky ion-extractant complex. We further coated a sulfonated PEEK (SPEEK) layer to effectively improve the lithium extraction flux by 154 %. This new finding provides a coherent understanding for previous results that morphology optimization did not show significant changes in ME performance. With current findings, membrane extraction is one step further to practical applications.

Interfacial enhancement of CF/PEEK composites by coating sulfonated PEEK sizing agent

Because of the inert surface and low wettability of carbon fibers (CF), the interfacial binding between CF and polyetheretherketone (PEEK) matrix is poor. The surface of CF was modified by preparing sulfonated polyetheretherketone (SPEEK)/carboxylated carbon nanotubes (MWCNTS) sizing agent, which contributed to the developed physical and chemical compatibility of reinforcing fibers and the matrix. After sizing by the sulfonated polyether ether ketone with a sulfonation degree of 16.67% and 0.5wt% carboxylated carbon nanotubes, the flexural strength and interlaminar shear strength of the modified composites were significantly improved by 74.2% and 84.2% by comparison to CF/PEEK composites without sizing agent. The coating method by SPEEK-MWCNTS is confirmed to be an essential approach to constructing excellent interface between the enhancement phase and thermoplastic matrix.

Surface modification of polyether ether ketone implant with a novel nanocomposite coating containing poly (vinylidene fluoride) toward improving piezoelectric and bioactivity performance

Polyether ether ketone (PEEK) is an appropriate biomaterial for orthopedic implant applications due to its superior mechanical properties, chemical resistance, nontoxicity, and Magnetic resonance imaging (MRI) compatibility. Unfortunately, the inherent bio-inertness of PEEK restricted its application and required some modification to provide better bioactivity. Besides it, the generated electrical signals in the bone due to its piezoelectricity features have a vital role in regulating bone repair and regeneration. We aimed to modify the surface of PEEK with a dual-functionality nanocomposite that provides surface bioactivity and simulates the piezoelectricity of bone. So, we introduced a novel piezoelectric-bioactive nanocomposite of dispersed poly (vinylidene fluoride) (PVDF) in a sulfonated PEEK (SPEEK) matrix containing Nanohydroxyapatite (nHA) and Carbon nanofiber (CNF) fillers for coating on PEEK substrate to improve its biological activity and simulate the electrical microenvironment for bone tissue. Furthermore, sulfonation of the PEEK surface was conducted as an intermediate layer to prepare better adhesion between the coating nanocomposite and the PEEK sublayer. Surface and cross-section morphology, apatite formation, and cell attachment were investigated on the different treated PEEK surfaces using field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray analysis (EDX). Also, piezoelectric performance, electrical conductivity, contact angle, and mechanical properties were examined on the prepared samples. Moreover, cell viability and cell morphology were investigated for biological evaluation with human osteoblast-like MG-63 cells. Collectively, the hydrophilicity of modified PEEK (mPEEK) coated with nanocomposite was improved due to the synergistic effects of SPEEK functional groups and nHA. Also, comprehensive investigation on the mPEEK treated with nanocomposite indicated a noticeably better bone-like apatite formation, cell proliferation, and cell attachments in the presence of nHA. The transfer of induced piezoelectric charges from dispersed PVDF in the matrix to the surface of nanocomposite containing 2 wt% of CNF increased output voltage to 1893 mV. On the other hand, the presence of CNF in nanocomposites enhanced tensile strength and Young's modulus by 92% and 117%, respectively.

Efficiency Analysis of Fuel Cell Components with Ionic Poly-Arylether Composite Membrane.

We use polyethylene glycol as an additive to explore how the hydrogen bonding of this additive changes the properties of SA8 blended sulfonated polyetheretherketone (SPEEK) composite films. We mixed a 5%wt polyethylene glycol solution into a 12.5%wt SA8 solution, and then prepared a film with a total weight of 40 g at a ratio of 1:99. The SA8 (PEG) solution was prepared and then mixed with 5%wt SPEEK solution, and a film-forming solution with a total weight of 8g in different mixing ratios was created. Polyethylene glycol (PEG) was mixed into the sulfonated polyarylether polymer SA8 to form physical cross-linking. Therefore, the sulfonated polyether ether ketone SPEEK was mixed in, and it exhibited good thermal stability and dimensional stability. However, there was some decrease in proton conductivity as the proportion of SPEEK increased. Although SPEEK mixed with sulfonated polymer reduces the proton conductivity, the physical cross-linking of PEG can improve the proton conductivity of the composite membrane, and adding SPEEK can not only solve the problem of the high sulfonation film swelling phenomenon, it can also improve the dimensional stability of the film through the hydrogen bonding force of PEG and obtain a composite film with excellent properties.

Fabrication of a Cation Exchange Membrane with Largely Reduced Anion Permeability for Advanced Aqueous K-ion Battery in an Alkaline-Neutral Electrolyte Decoupling System.

Herein, an efficient method to prepare sulfonated polyether ether ketone (SPEEK) based cation exchange membranes (CEMs) is developed, where polyethersulfone (PES) is used as an additive. The optimized membrane of 30wt.%PES/SPEEK-M exhibits a rather low anion permeability and a high ionic conductivity of 9.52mScm-1 together with low volume swelling in water. Meanwhile, tensile strength of the membrane is as high as 31.4MPa with a tensile strain of 162%. As separators for aqueous K-ion batteries (AKIBs) with decoupled gel electrolytes (Zn anode in alkaline and Prussian blue (FeHCF) cathode in neutral). Discharge voltage of the AKIB can reach 2.3V. Meanwhile, Zn dendrites can be effectively suppressed in the gel anolyte. Specific capacities of the FeHCF cathode are 116.7mAhg-1 at 0.3Ag-1 (close to its theoretical value), and 95.0mAhg-1 at 1.0Ag-1 , indicating good rate performance. Capacity retention of the cathode is as high as 91.2% after 1000 cycles' cycling owing to the well remained neutral environment of the catholyte. There is almost no pH change for the catholyte after cycling, indicating good anion-blocking or cation-selecting ability of the 30wt.%PES/SPEEK-M, much better than other membranes.

Sulfonated polyether ether ketone composite proton exchange membranes incorporated with a novel hierarchical‐structure hybrid nanofiller consisting solid superacid zirconium phosphate and CNTs

AbstractHow to simultaneously improved the proton conductivity and mechanical strength is a key problem facing currently used proton exchange membranes (PEMs). Herein, a solid inorganic superacid‐zirconium phosphate (ZrP) with a two‐dimensional layer structure was combined with one‐dimensional carbon nanotubes (CNTs) to prepare hybrid nanofiller ZrP‐CNTs by an in situ chemical deposition method. The new hybrid nanofiller was then applied to modify sulfonated polyether ether ketone (SPEEK), a widely used PEM matrix, to obtain a series of composite membranes. The structure and properties of the membranes were fully characterized by SEM, XRD, FTIR, TG, tensile properties, and proton conductivity. The results showed that the proton conductivities of the membranes were significantly improved due to the addition of super solid acid‐ZrP that has abundant proton sources or proton sites. Moreover, the composite membranes exhibited better mechanical properties and thermal stability than those of pure SPEEK membrane, owing to the great interface interaction and good compatibility between ZrP‐CNTs and SPEEK. The composite membrane (2 wt% ZrP‐CNTs) demonstrated the optimal comprehensive performance. Its proton conductivity was 36.63 mS cm−1 and its tensile strength was 37.56 MPa, which was 70% and 10%, respectively, higher than those of the pure SPEEK membrane under the same condition.

Ultrasonic-Assisted Rapid Preparation of Sulfonated Polyether Ether Ketone (PEEK) and Its Testing in Adsorption of Cationic Species from Aqueous Solutions.

Herein, we report a new approach for the sulfonation of polyether ether ketone (PEEK) following a shorter path of reaction undertaken at 60 °C under ultrasonication. The application of this method enabled the reduction of the reaction time from several hours to less than one hour, achieving a relevant sulfonation degree. The sulfonated-PEEK (SPEEK) was characterized by advanced chemical and physical instrumental methods. According to 1H-NMR analysis, the degree of sulfonation of the polymer was equal to 70.3%. Advanced microscopy (SEM) showed that the fabricated SPEEK beads (2-4 mm) were porous inside with a log-normal distribution of pore sizes within the range 1.13-151.44 μm. As an application, the SPEEK polymer was tested for the adsorption of a cationic organic pollutant (Methylene blue, MB) from aqueous solutions. The equilibrium studies (isotherms) disclosed maximum adsorption capacities of 217 mg/g, 119 mg/g, and 68 mg/g at temperatures of 323 K, 313 K, and 300 K, respectively. The thermodynamic calculations indicated an endothermic effect (ΔHad = +11.81 kJ/mol) of the investigated adsorption process. The maximum removal efficiency of 99.14% was established by process optimization using the design of experiments strategy and data-driven modeling. Additionally, molecular docking simulations were performed to disclose the mechanism of interaction at the molecular level between the adsorbent (SPEEK) and pollutant.

“SPEEK-COF” Composite Cation Exchange Membrane for Zn-I2 Redox Flow Battery

Zinc-based energy storage is increasingly getting attention owing to its outstanding characteristics over to the other systems. Their high abundance, user-friendliness, environmental benignity, and low reduction potential which can avoid unwanted hydrogen evolution are some of the attractive features. Appropriate membrane selection for the zinc-based redox flow battery is challenging. Herein we report the composite of SPEEK (sulfonated polyether ether ketones) with covalent organic frameworks (COF) as a potential membrane for zinc-based redox flow battery. Biphenyl-based knitting type COF was prepared, post sulfonated and blended with SPEEK. In a Zn/I2 redox flow battery system, the discharge capacity was found to be 19.8 AhL−1, 17.4 AhL−1, 15.1 AhL−1 for 20%, 15%, 10% SCOF loading respectively against 14.5 AhL−1 for pristine SPEEK at 20 mAcm−2 current density. The capacity was improved by about 36% higher than the neat SPEEK membrane. This improvement in the battery performance might be due to the higher ionic conductivity and hydrophilicity after SCOF loading. We found that the 15% loading was the maximum limit for the battery performance, beyond which the energy efficiency was found to be fading, which is due to the excessive dendrite growth on the membrane surface.

Consecutive and reliable proton transfer channels construction based on the compatible interface between nanofiber and SPEEK

It is indispensable to balance the proton conductivity and dimensional stability, as well as maintain the high long-term durability of proton exchange membranes (PEMs). Herein, we proposed the sandwich structure composite membrane containing a middle layer of sulfonated polyetheretherketone (SPEEK) sandwiched by two layers of hybrid polyimide (PI) nanofiber. The hybrid nanofibers were fabricated via in situ loading different contents of NH2-UiO-66 (NU6) onto PI nanofiber as proton acceptors for amino-functionalization, resulting in NU6@PI nanofibers (NP) with different forms of assembly. By incorporating three-dimensional nanofibers into SPEEK, the dimensional stability of the composite membrane was dramatically boosted. The –SO3H groups on SPEEK interact with –NH2 groups on NP to form long-range acid-base pairs and acid-rich layer along the NP-SPEEK interface, which can provide abundant proton-conducting sites for proton transfer. Significantly, the continuous and uniform assembly of NU6 on PI nanofiber can form a compatible interface with SPEEK, ensuring the reliability of the proton pathways and robust mechanical properties. Insufficient or excessive loads of NU6 will lead to an imperfect NP-SPEEK interface, resulting in discontinuous proton channels or forming numerous defects that hinder continuous proton transport. The composite membrane of 4NP-SPEEK-4NP (40%NU6@PI-SPEEK-40%NU6@PI) with consecutive and reliable proton transfer channels displays enhanced stress, optimal proton conductivity, and excellent H2/O2 fuel cell performance. The durability test at 60 °C and 100% RH for 32 days reveals that the proton conductivity retention and tensile strength of the composite membrane are 89.8% and 47.8 MPa, which are 33.8% and 52.7% higher than those of SPEEK, respectively. The prepared membranes not only can be potential candidates for fuel cells but also provides a useful strategy for the longtime effective construction and regulation of proton transport channels in PEMs.