Study on the partially cross-linked poly(styrene-b-(ethylene-co-butylene)-b-styrene) anion exchange membrane remotely (spaced hexyl) grafted double cation separated by different alkyl groups

In order to improve the alkali stability and OH⁻ conductivity of Poly (styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS)-based anion exchange membranes (AEMs), double cations with different alkyl intervals are remotely grafted onto the SEBS skeleton with hexyl as a linker through reactions such as acylation and ketone reduction. Then, SEBS-0.8Cn-0.2C6 cross-linked membranes were prepared to study the effect of the length of the alkyl chain between the dications on the ion transport and other properties. The OH⁻ conductivity of SEBS-0.8C4-0.2C6 cross-linked membrane can reach 85.27 mS cm⁻¹ at 80 °C, and the peak power density can reach 225 mW cm⁻² at a current density of 450 mA cm⁻². As the dicationic spacer alkyl chains became longer, the swelling rate and water uptake of the membranes increased, resulting in significant improvements in mechanical properties and chemical stability. After soaking in 2 M NaOH solution at 80 °C for 1200 h, the conductivity of SEBS-0.8C6-0.2C6 decreased by only 5.76%. Optimizing the side chain structure of SEBS skeleton can effectively improve the comprehensive performance of AEM.     

Quaternary ammonium-functionalized hexyl bis(quaternary ammonium)-mediated partially crosslinked SEBSs as highly conductive and stable anion exchange membranes

We chemically modify a commercially available elastomeric triblock copolymer, poly(styrene-b-ethylene-co-butylene-b-styrene) SEBS, to produce quaternary ammonium-functionalized hexyl bis(quaternary ammonium)-mediated partially-crosslinked SEBSs with different grafting degree of the conducting head groups as highly conductive and stable anion exchange membranes (AEMs). In an attempt to achieve a high ion exchange capacity and hence conductivity of the corresponding membranes without causing ‘gelation’, which these types of SEBS polymers typically experience, we use a SEBS with a high content (57%) of styrene, and graft the quaternary ammonium (QA) as both a crosslinker and the conducting head group on the side chain of the SEBS. The partial crosslinking approach, in combination with introducing these QA-conducting head groups as the side chain of the SEBS, helps to form larger ion clusters, and also to form a nano-phase morphology with long-range connecting channels. This induced the highest ion conductivity, 174.8 mS cm⁻¹ at 80 °C, reported to date among these types of SEBS series. In addition, we obtain excellent cell performance with a current density of 450 mA cm⁻² at 0.6 V and a peak power density of 315 mW cm⁻² at 95% RH and 60 °C using the corresponding AEM.     

Poly(isatin-piperidinium-terphenyl) anion exchange membranes with improved performance for direct borohydride fuel cells

In this work, an effective design strategy for anion exchange membranes (AEMs) incorporating ether-bond free and piperidinium cationic groups promote chemical stability. A series of poly (isatin-piperidium-terphenyl) based AEMs were synthesized by superacid catalyzed polymerization reaction, followed by quaternization. The effect of functionalization on the performance of poly (isatin-N-dimethyl piperidinium triphenyl) (PIDPT-x) AEMs was investigated. Highly reactive N-propargylisatin was introduced into the backbone to achieve high molecular weight polymers (η_a = 2.06–3.02 dL g⁻¹) leading to robust mechanical properties, as well as modulating 1.78–2.00 mmol g⁻¹ of the ion exchange capacity (IEC) of the AEMs by feeding. Apart from that, the rigid non-ionized isatin-terphenyl segment provides AEMs improved dimensional stability with a swelling ratio of less than 12% at 80 °C. Among them, PIDPT-90 exhibited a higher OH⁻ conductivity of 105.6 mS cm⁻¹ at 80 °C. The alkali-stabilized PIDPT-85 AEM was presented, in which OH⁻ conductivity retention maintained 85.6% in a 2 M NaOH at 80 °C after 1632 h. Afterward, the direct borohydride fuel cells (DBFC) with PIDPT-90 membrane as a separator showed an open-circuit voltage of 1.63 V and a peak power density of 75.5 mWcm⁻² at 20 °C. This work demonstrates the potential of poly (isatin- N-dimethyl piperidinium triphenyl) as AEM for fuel cells.     

Development of crosslinked SEBS-based anion exchange membranes for water electrolysis: Investigation of the crosslinker effect

SEBS (styrene-b-(ethylene-co-butylene)-b-styrene)) is a non-aryl-ether-type tri-block copolymer widely used as an anion exchange membrane (AEM) material due to its excellent alkaline stability and phase separation properties. However, low tensile strength due to the aliphatic chains and the poor physical properties of the SEBS-based membranes limit their practical application for AEM water electrolysis (AEMWE) or AEM fuel cell (AEMFC). In this study, three types of crosslinked AEMs were prepared using bromohexyl pentafluorobenzyl SEBS as a polymer backbone, and three different crosslinkers, dimethyl amine (DMA), tetramethyl diaminohexane (TMHA), and tris(dimethyl aminomethyl) phenol (TDMAP). Once introduced, these crosslinking agents were converted into the corresponding conducting head groups. The thermal, chemical, physical, and electrical properties of the obtained crosslinked membranes were then investigated for use in AEMWE. In particular, the TDMAP-50x-SEBS membrane with 50% degree of crosslinking experienced hydrogen bonding with water and OH⁻ due to the presence of OH groups in the structure of the crosslinking agent (TDMAP). Because of this, the membrane showed an improved morphology and high conductivity (20 °C: 31.8 mS cm⁻¹, 80 °C: 109.9 mS cm⁻¹). In addition, TDMAP induced physical crosslinking by hydrogen bonding between molecules so that the corresponding membrane (TDMAP-50x-SEBS) exhibited high alkaline and oxidative stability and good mechanical properties. This SEBS-based membrane has a tensile strength of 18.0 MPa and Young's modulus of 165.14 MPa. The WE single-cell test (1 M KOH solution at 70 °C) using TDMAP-50x-SEBS also showed a cell performance of 1190 mA cm⁻² at 2.0 V. This is 126% higher than the cell performance measured for FAA-3-50, a commercialized AEM material, under the same conditions.     

Highly conductive partially cross-linked poly(2,6-dimethyl-1,4-phenylene oxide) as anion exchange membrane and ionomer for water electrolysis

Cross-linked quaternised Poly(2,6-dimethyl-1,4-Phenylene Oxide) (QPPO)-based membranes were prepared via Friedel-Crafts reactions using SnCl₄ catalyst, 1,3,5-trioxane and chlorotrimethylsilane as environmentally-friendly chloromethylating reagents. New equations to calculate the degree of chloromethylation (DC) and cross-linking degree (CLD) were proposed. Ionic conductivity of 133 mS cm⁻¹ at 80 °C was obtained, one of the highest reported for QPPO based membranes. We have compared QPPO to chloromethylated polystyrene-b-poly(ethylene/butylene)-b-polystyrene (SEBS) ionomer and report on the importance of ionomer-membrane interaction as well as the trade-off between swelling ratio and conductivity on performance and mechanical stability of AEM water electrolyser. Exsitu stability testing after 500 h in 1 M KOH showed membranes retained up to 94% of their original IEC. QPPO was employed as both membranes and ionomers in electrolyser tests. QPPO membranes exhibited area specific resistance of 104 mΩ cm⁻² and electrolyser current density of 814 mA cm⁻² at 2.0 V in 0.1 M NaOH solution at 40 °C.     

Enhancement in proton conductivity by blending poly(polyoxometalate)-b-poly(hexanoic acid) block copolymers with sulfonated polysulfone

Designing polymer chains which contain building blocks with well-defined dimension is an efficient method to induce microphase separation and regulate the ionic channels of polymer electrolyte membranes (PEMs). In this study, a Wells-Dawson-type polyoxometalate (POM) is synthesized and chemically bonded to a norbornene derivative to prepare poly (POM) blocks. Then the block copolymer poly (POM)₁₀-b-poly (COOH)₃₀₀ is fabricated using poly (POM) and poly (COOH) blocks. Finally, the block copolymer is blended with sulfonated polysulfone (SPS). The electrostatic interactions between the block copolymer and SPS confer the blend membrane with enhanced mechanical and dimensional stabilities. Due to the homogenous distribution of POM clusters and the hydrophilic-hydrophobic interactions between POMs and polymer backbones, the adjacent hydrophilic domains are connected and continuous proton-transfer channels are induced. As a result, the blend membrane displays proton conductivity of 0.053 S cm⁻¹ (25 °C, 100% RH) and 1.5 × 10⁻² S cm⁻¹ (80 °C, 40% RH), which are 2.52 and 6.25 times higher than those of the plain SPS membrane. Furthermore, SPS/POM-BC-30 shows a maximum power density of 164.9 mW cm⁻², which is 54.7% higher than SPS.     

Preparation and characterization of a polyvinyl alcohol grafted bis-crown ether anion exchange membrane with high conductivity and strong alkali stability

A new type of symmetrical bis-crown ether is prepared by connecting dibenzo-18-crown-6 ether on both sides of the chromotropic acid, and then grafting the aforementioned bis-crown ether onto polyvinyl alcohol matrix to prepare a series of anion exchange membranes (AEMs), which their have high conductivity and strong alkali stability. These synthesized membranes were named B-C_X%-P AEMs (x is the mass percentage of the symmetrical bis-crown ether (B–C)). Then, the chemical structure of aforementioned AEMs were verified by means of ¹H NMR, FT-IR and UV. Meanwhile, the OH⁻ conductivity, alkaline stability and single cell performance of the synthesized membrane were also investigated. The results revealed that the conductivity of B–C_30%-P membrane is the highest at 80 °C (235 mS cm⁻¹), and the power density is also the highest (197 mW cm⁻²), and the alkali stability of the membrane synthesized in this paper was also improved. The conductivity at 80 °C was only reduced by 4%, which was obtained by immersing the B–C_30%-P membrane immersed in 6 mol L⁻¹ KOH solution for 168 h, which the aforementioned results proved that the synthesized membrane in this research had excellent OH⁻ conductivity and alkaline stability.     

Macromolecule sulfonated Poly(ether ether ketone) crosslinked poly(4,4′-diphenylether-5,5′-bibenzimidazole) proton exchange membranes: Broaden the temperature application range and enhanced mechanical properties

Proton exchange membranes with a wide application temperature range were fabricated to start high-temperature fuel cells under room temperature. The volume swelling stability, oxidative stability as well as mechanical properties of crosslinked membranes have been improved for covalently crosslinking poly(4,4′-diphenylether-5,5′-bibenzimidazole) (OPBI) with fluorine-terminated sulfonated poly(ether ether ketone) (F-SPEEK) via N-substitution reactions. High proton conductivity was simultaneously realized at both high (80–160 °C) and low (40–80 °C) temperatures by crosslinking and jointly constructing hydrophilic-hydrophobic channels. The crosslinked membranes exhibited the highest proton conductivity of 191 mS cm⁻¹ at 80 °C under 98% relative humidity (RH) and 38 mS cm⁻¹ at 160 °C under anhydrous, respectively. Compared with OPBI membrane, the fuel cell performance of the crosslinked membranes showed higher peak power density at full temperature range (40–160 °C).     

Poly (aryl piperidinium) membranes with dipolar alkyl nitrile sidechains for fuel cells

Several poly (biphenyl piperidine-trifluoroacetophenone) based polymers with different grafting ratios of polar alkyl nitrile side chains are synthesized, named PBPAp-PN-x. The relationship between structure and performance is studied, including conductivity, swelling ratio (SR), morphology, single-cell performance, etc. The SR and conductivity at 80 °C of PBPAp-PN30% are 41.0% and 142.3 mS cm⁻¹, whereas those of PBPAp-PN0% are 77.8% and 155.3 mS cm⁻¹, respectively. Further, molecular dynamics (MD) simulations are carried out to microcosmically reveal the mechanism of structure-property relationship, which simulate the number of water molecules (N_H2O) and the diffusion coefficients (D). The simulations also indicate polar cyanide groups can form close contacts, which is similar to physical crosslinking to inhibit the swelling of backbone. As a result, the advantage of grafting dipolar molecules in AEMs not only effectively resolves the “trade-off” problem between ionic conductivity and dimensional stability, but also might be a promising application in fuel cells.     

Highly durable and conductive poly(arylene piperidine) with a long heterocyclic ammonium side-chain for hydroxide exchange membranes

Recently, the preparation of hydroxide exchange membranes (HEMs) without ether bonds have attracted much attention because of their high chemical stability. Hence, ether-bond free, highly durable, and conductive poly(arylene piperidine)s (PAPips) tethered with heterocyclic ammonium via hexyl spacer chains were prepared successfully for HEMs via a facile synthetic procedure. The effect of the cationic groups (quaternary ammonium, piperidinium, and morpholinium) on the properties of the corresponding PAPip-based HEMs, including the morphology, hydroxide conductivity, and alkaline and chemical stability were systematically investigated. The as-designed PAPip-based membranes exhibited excellent overall performance. The membranes attached with piperidinium (IEC = 1.64 mmol g⁻¹) exhibited a hydroxide conductivity of 0.082 S cm⁻¹ at 80 °C and exhibited significant alkaline stability which maintained 80.1% of its conductivity after immersion in 1 M NaOH at 80 °C for 1500 h. The as-prepared membrane also presented a peak power density of 76 mW cm⁻² at 80 °C in a H₂/O₂ HEMFC. The resulting HEMs also showed excellent mechanical properties, thermal stability, and well-defined phase separation.     

High chemical stability anion exchange membrane based on poly(aryl piperidinium): Effect of monomer configuration on membrane properties

In recent years, ether-free polyaryl polymers prepared by superacid-catalyzed Friedel-Crafts polymerization have attracted great research interest in the development of anion exchange membranes(AEMs) due to their high alkali resistance and simple synthesis methods. However, the selection of monomers for high-performance polymer backbone and the relationship between polymer structure construction and properties need further investigated. Herein, a series of free-ether poly(aryl piperidinium) (PAP) with different polymer backbone steric construction were synthesized as stable anion exchange membranes. Meta-terphenyl, p-terphenyl and diphenyl-terphenyl copolymer were chosen as monomers to regulate the spatial arrangement of the polymer backbone, which tethered with stable piperidinium cation to improve the chemical stability. In addition, a multi-cation crosslinking strategy has been applied to improve ion conductivity and mechanical stability of AEMs, and further compared with the performance of uncrosslinked AEMs. The properties of the resulting AEMs were investigated and correlated with their polymer structure. In particular, m-terphenyl based AEMs exhibited better dimensional stability and the highest hydroxide conductivity of 144.2 mS/cm at 80 °C than other membranes, which can be attributed to their advantages of polymer backbone arrangement. Furthermore, the hydroxide conductivity of the prepared AEMs remains 80%–90% after treated by 2 M NaOH for 1600 h, exhibiting excellent alkaline stability. The single cell test of m-PTP-20Q4 exhibits a maximum power density of 239 mW/cm² at 80 °C. Hence, the results may guide the selection of polymer monomers to improve performance and alkaline durability for anion exchange membranes.     

End-group crosslinked hexafluorobenzene contained anion exchange membranes

A kind of anion exchange membranes (AEMs) with CC bond end-group crosslinked structure was synthesized successfully. Unlike the traditional aliphatic AEMs, the AEMs were prepared in this work by a strategy to realize the CC bond thermal end-group crosslinking reaction, exhibiting an obvious microphase separation structure and a suitable dimensional stability. The well-defined ion channels constructed in the AEMs guarantee the fast OH⁻ conduction, as confirmed via physical and chemical characterization. The conductivity was dramatically enhanced due to the effective ion channels and increased ion exchange capacity. Among the as-prepared AEMs, the PHFB-VBC-DQ-80% AEM has a conductivity of 135.80 mS cm⁻¹ at 80 °C. The single cell based on PHFB-VBC-DQ-80% can achieve a power density of 141.7 mW cm⁻² at a current density of 260 mA cm⁻² at 80 °C. The AEMs show good thermal stability verified by a thermogravimetric analyzer (TGA). Furthermore, the ionic conductivity of PHFB-VBC-DQ-80% only decreased by 7.1% after being soaked in a 2 M NaOH solution at 80 °C for 500 h.     

Facile self-crosslinking to improve mechanical and durability of polynorbornene for alkaline anion exchange membranes

Crosslinking is a valid approach to enhance the mechanical and durability performance of anion exchange membranes (AEMs). Herein, a facile and effective self-crosslinking strategy, with no need for an additional crosslinker or a catalyzer, is proposed. A series of tunable self-crosslinking and ion conduction polynorbornene membranes are designed. The 5-norbornene-2-methylene glycidyl ether (NB-MGE) component which affords self-crosslinking enhances dimensional stability, while the flexible 5-norbornene-2-alkoxy-1-hexyl-3-methyl imidazolium chloride (NB-O-Im⁺Cl⁻) hydrophilic unit contributes high conductivity. The crosslinking significantly decreases the water uptake, and water swelling ratio provides excellent solvent-resistance and enhances the thermal and mechanical properties. Additionally, crosslinked rPNB-O-Im-x AEMs exhibit desirable alkaline stability. Impressively, the rPNB-O-Im-30 (IEC = 1.377) shows a moderate ion conductivity (61.8 m S cm⁻¹, 80 °C), with a suppressed water absorption and 88.17% initial OH⁻ conductivity is maintained after treated for 240 h with a 1.0 M NaOH solution at 60 °C. Suitably assessed of rPNB-O-Im-30 AEM reveals a 98.4 mW cm⁻² peak power density reached at a current density of about 208 mA cm⁻². The report offers a facile and effectual preparative technique for preparing dimensional and alkaline stable AEMs for fuel cells applications.     

Facile construction of poly(arylene ether)s-based anion exchange membranes bearing pendent N-spirocyclic quaternary ammonium for fuel cells

Anion exchange membrane (AEM) fuel cells have received significant attention due to their low fuel permeability and the use of non-platinum catalysts. However, the development of AEMs with robust chemical stability and high conductivity is still a great challenge. Herein, we prepare a new type of partially fluorinated backbone bearing pendent N-spirocyclic quaternary ammonium (QA) cations via a facile Williamson reaction, which displays great potential for fuel cells. The integration of the two substructures (a fluorinated moiety into a polymer backbone and a pendent cation structure) is beneficial for the fabrication of a well-defined micro-phase separation structure, thereby facilitating the construction of a highly-efficient ion transporting pathway. Correspondingly, the resulting AEM (PAENQA-1.0), despite its a relatively low ionic exchange capacity (0.93 meq g⁻¹) demonstrates a conductivity of 63.1 mS cm⁻¹ (80 °C). Meanwhile, the constrained ring conformation of N-spirocyclic QA results in improved stability of the AEMs.     

Novel quaternized carbon dots modified polysulfone-based anion exchange membranes with improved performance

At present, low conductivity and poor chemical stability are still the biggest challenges in the research on anion exchange membranes (AEMs). Herein, novel nanocomposite AEMs were first constructed by introducing quaternized carbon dots (QCDs) into the imidized polysulfone matrix (Im-PSU). QCDs were synthesized by quaternization of CDs derived from citric acid and ethylenediamine. The physicochemical properties and electrochemical properties of the nanocomposite AEMs were significantly improved due to the introduction of QCDs. It was found that the QCDs can improve the ion transport channel of the nanocomposite AEMs. Compared with pure Im-PSU AEM, the OH⁻ conductivity and physicochemical properties of the nanocomposite membranes were enhanced, and the OH⁻ conductivity of ImPSU-1.0%-QCDs composite membrane can reach 109.3 mS cm⁻¹ at 80 °C, and 61.2% initial OH⁻ conductivity was maintained in 1.0 M NaOH solution for 500 h at 60 °C. Our research proves that the nanofiller with a small size can better improve the performance of composite AEMs, and provide an efficient strategy for future research work in the design and preparation of AEMs.     

Novel poly(carbazole-butanedione) anion exchange membranes constructed by obvious microphase separation for fuel cells

To develop anion exchange membranes with excellent chemical stability and high performance. A series of quaternary ammonium functionalized (hydrophilic) hydrophobic rigid poly (carbazole-butanedione) (HOCB-TMA-x) anion exchange membranes were prepared, where x represents the percentage content of hydrophobic unit octylcarbazole (OCB). Due to the introduction of hydrophobic rigid unit octylcarbazole and hexyl flexible side chain, the hydrophilic-hydrophobic microstructure of AEMs was developed. The AEMs exhibit excellent overall performance, specifically the low swelling ratio HOCB-TMA-30 membrane exhibits the highest OH^? conductivity of 152.9 mS/cm at 80 °C. Furthermore, the ionic conductivity of AEM decreased by only 9.5% after 2250 h of immersion in 1 M NaOH. The maximum peak power density of a single cell with a current density of 4.38 A/cm² at 80 °C was 1.85 W/cm².     

4-Aminopyridine grafted sulfonated poly(arylene ether ketone sulfone) proton exchange membrane with high relative selectivity for fuel cells

A series of sulfonated poly(arylene ether ketone sulfone)s polymer having a degree of sulfonation of 80% and a carboxyl group in the side chain (C-SPAEKS) were prepared by polycondensation. The 4-aminopyridine grafted sulfonated poly(arylene ether ketone sulfone)s polymer membranes (SPPs) were prepared by amidation reaction with the carboxyl group to immobilize 4-aminopyridine on the side chain. The ¹H NMR results and Fourier transform infrared of SPP membranes demonstrated the successful grafting of the 4-aminopyridine. Proton conductivity, water absorption, swelling ratio, and thermal stability of different proportions of SPP membranes were investigated under the different conditions. With the increase of pyridine grafting content, the methanol permeability coefficient of the membrane decreased significantly from 8.17 × 10⁻⁷ cm²s⁻¹ to 8.92 × 10⁻⁸ cm²s⁻¹ at 25 °C. And, the proton conductivity and relative selectivity of the membrane were positively correlated with the grafted pyridine content. Among them, the SPP-4 membrane exhibited the highest proton conductivity of 0.088 Scm⁻¹ at 100 °C. The relative selectivity increased from 4.73 × 10⁴ S scm⁻³ to 9.84 × 10⁴ S scm⁻³.     

Flexibly crosslinked and post-morpholinium-functionalized poly(2,6-dimethyl-1,4-phenylene oxide) anion exchange membranes

Morpholinium-functionalized cross-linked poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) anion exchange membranes were prepared using a crosslinking/post-functionalization method. 4,4'-(oxybis(ethane-2,1-diyl)) dimorpholine (OEDM) having a flexible long chain and hydrophilic ether bond was for the first time used as the crosslinker. The brominated PPO reacted with OEDM, forming a crosslinked structure and accomplishing partial functionalization. Further functionalization was carried out by immersion in N-methylmorpholine aqueous solution. The degree of crosslinking was controlled by varying the proportion of brominated PPO to OEDM because excessive bromomethyl groups ensured the occurrence of crosslinking reaction. The cross-linked structure promoted the formation of micro-phase separation and effectively limited swelling. The crosslinked membrane shows much higher conductivity and lower swelling ratio compared to non-crosslinked one at similar IEC. The highest hydroxide conductivity that the crosslinked membrane achieves is 35 mS cm⁻¹ at 20 °C. The power density for the H₂/O₂ single cell assembled with this membrane is up to 193 mW cm⁻². In addition, the crosslinked PPO-MmOH-Cr membrane exhibits good alkaline stability with conductivity loss of less than 15% after soaking in 1 M KOH for 96 h.     

In-situ molecular-level hybridization enabling high-sulfonation-degree sulfonated poly(ether ether ketone) membrane with excellent anti-swelling ability and proton conduction

Sulfonated poly(ether ether ketone) (SPEEK) membrane with high sulfonation degree (SD) is a promising substitute of Nafion as proton exchange membrane (PEM), due to the excellent proton conductivity and low cost. However, its widespread application is limited by the inferior structural stability. Here, we report the fabrication of high SD SPEEK membrane with outstanding structural stability through an in-situ molecular-level hybridization method. Concretely, the ionic nanophase of SPEEK membrane is filled with precursors, which are then in-situ converted into polymer quantum dots (PQDs) by a microwave-assisted polycondensation process. In this manner, the micro-phase separation structure of SPEEK membrane is well maintained. PQDs with abundant hydrophilic functional groups together with the inherent –SO₃H groups impart hybrid membrane highly enhanced proton conductivity of 138.2 mS cm⁻¹ at 80 °C, which is comparable to Nafion. This then offers a 116.3% enhancement in device output power. Meanwhile, PQDs act as cross-linkers via generated electrostatic interactions with SPEEK, affording hybrid membrane with SD of 94.1% an ultralow swelling ratio of 1.35% at 25 °C, about 35 times lower than control membrane. More importantly, the in-situ molecular-level hybridization method is versatile, which can also boost the performances of chitosan (CS)-based membranes.     

A facile,effective thermal crosslinking to balance stability and proton conduction for proton exchange membranes based on blend sulfonated poly(ether ether ketone)/sulfonated poly(arylene ether sulfone)

The development of hydrocarbon polymer electrolyte membranes with high proton conductivities and good stability as alternatives to perfluorosulfonic acid membranes is an ongoing research effort. A facile and effective thermal crosslinking method was carried out on the blended sulfonated poly (ether ether ketone)/poly (aryl ether sulfone) (SPEEK/SPAES) system. Two SPEEK polymers with ion exchange capacities (IECs) of 1.6 and 2.0 mmol g^?1 and one SPAES polymer (2.0 mmol g^?1) were selected to create different blends. The effect of thermal crosslinking on the fundamental properties of the membranes, especially their physicochemical stability and electrochemical performance, were investigated in detail. The homogeneous and flexible thermally-crosslinked SPEEK/SPAES membranes displayed excellent mechanical toughness (27–46 Mpa), suitable water uptake (<60%), high dimensional stability (swelling ratio < 15%) and large proton conductivity (>120 mS cm^?1) at 80 °C. The thermal crosslinking membranes also show significantly enhanced hydrolytic (<2.5%) and oxidative stability (<2%). Fuel cell with t-SPEEK/SPAES (1:2:2) membrane achieves a power density of 665 mW cm^?2 at 80 °C.