Arylene Ether Sulfone Research Articles

Preparation of sulfonated polysulfone/sulfonated titanium dioxide hybrid membranes for DMFC applications

ABSTRACTSulfonated titanium dioxide (STiO2) was prepared by the reaction of TiO2 with 1,3‐propanesultone. Novel STiO2 incorporated sulfonated poly(aryl ether sulfone) (SPAES) nanocomposite proton exchange membranes (PEMs) were made by solution casting. Fourier transform infrared, X‐ray photoelectron spectroscopy, and proton nuclear magnetic resonance indicated the successful preparation of STiO2 and SPAES. The thermogravimetric analysis and oxidative stability testing results implied that SPAES/STiO2 membranes had better stability than pristine SPAES membrane. Meanwhile, the scanning electron microscopy spectra exhibited that the introduction of sulfonated groups on the surface of TiO2 significantly improved its dispersibility in SPAES matrix. More specifically, SPAES membrane incorporated with 2%STiO2 exhibited higher proton conductivity (60 mS cm−1), lower methanol permeability (2.1 × 10−7 cm2 s−1) and better proton selectivity (28.0 × 104 S s cm−3) than that of pure SPAES and SPAES/1%TiO2 membrane. The SPAES‐1%STiO2 membrane showed better performance in direct methanol fuel cell (DMFC) test than SPAES and Nafion 117 due to the reduction of methanol crossover. From these results, it is evident that SPAES/STiO2 nanocomposite PEMs have great potential for applications in DMFCs. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48938.

Micro-block versus random quaternized poly(arylene ether sulfones) with highly dense quaternization units for anion exchange membranes

A systematic study was carried out to investigate the effect of different distributions of conducting groups in segments for poly(arylene ether sulfone)s.

Synthesis and characterization of a novel crosslinkable side-chain sulfonated poly(arylene ether sulfone) copolymer proton exchange membranes.

A series of novel crosslinkable side-chain sulfonated poly(arylene ether sulfone) copolymers (S-SPAES(x/y)) was prepared from 4,4′-biphenol, 4,4′-difluorodiphenyl sulfone, and a new difluoro aromatic monomer 1-(2,6-difluorophenyl)-2-(3,5-dimethoxyphenyl)-1,2-ethanedione (DFDMED) via co-polycondensation, demethylation, and further nucleophilic substitution of 1,4-butane sultone. Meanwhile, quinoxaline-based crosslinked copolymers (CS-SPAES(x/y)) were obtained via cyclo-condensation between S-SPAES(x/y) and 3,3′-diaminobenzidine. Both the crosslinkable and crosslinked copolymer membranes exhibit good mechanical properties and high anisotropic membrane swelling. Crosslinkable S-SPAES(1/2) with an ion exchange capacity (IEC) of 2.01 mequiv. g−1 displays a relatively high proton conductivity of 180 mS cm−1 and acceptable single-cell performance, which is attributed to its good microphase separation resulting from the side-chain sulfonated copolymer structures. Compared with S-SPAES(1/1) (IEC of 1.68 mequiv. g−1), crosslinked CS-SPAES(1/2) with a comparable IEC exhibits a larger conductivity of 157 mS cm−1, and significantly higher oxidative stability and lower membrane swelling, suggesting a distinct performance improvement due to the quinoxaline-based crosslinking.

Poly(arylene ether sulfone) crosslinked networks with pillar[5]arene units grafted by multiple long-chain quaternary ammonium salts for anion exchange membranes.

Several high-molecular-weight pillar[5]arene-containing poly(arylene ether sulfone) polymers were synthesized for the first time. Through grafting and crosslinking approaches, networks consisting of the molecular chains bearing multiple long-chain quaternary amine salts were fabricated. For the crosslinked membranes, high conductivity and low swelling were achieved even at low ion exchange capacity.

Blends of highly branched and linear poly(arylene ether sulfone)s: Multiscale effect of the degree of branching on the morphology and mechanical properties

This study reports the synthesis of highly branched poly(arylene ether sulfone)s (HBPAES) and their incorporation into linear poly(arylene ether sulfone) (LPAES) to investigate the effect of branched topology on the morphological and mechanical properties of final polymer blends. The A2 + B3 polymerization was utilized to synthesize HBPAESs with varying distance between branch points by reacting monomeric 4,4′-dichlorodiphenyl sulfone (DCDPS) or pre-synthesized chlorine terminated linear oligomers with various degrees of polymerization as the A₂ species with 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) as the B₃ monomer. The chemical structure and the degree of branching of synthesized HBPAESs were characterized by 1H Nuclear Magnetic Resonance (NMR) spectroscopy, while Size Exclusion Chromatography (SEC) and Differential Scanning Calorimetry (DSC) were used for the determination of their molecular weight and glass transition temperatures. Polymer blends of HBPAES and LPAES (10/90 w/w) were solution cast into free-standing, dry films and characterized by tensile tests, Dynamic Mechanical Analysis (DMA), Atomic Force (AFM) and Scanning Electron (SEM) Microscopies. Complementary to experimental studies, these blends were modeled with dissipative particle dynamics (DPD) simulations to explain their microphase behavior, miscibility, and morphology. The experimental and computational studies together revealed that understanding the effect of the degree of branching on the intermolecular interactions of highly branched polymers with their linear analogues is critical to obtain final polymer blends with tunable mechanical properties and enhanced fracture behavior.

Polydopamine-modified sulfonated polyhedral oligomeric silsesquioxane: An appealing nanofiller to address the trade-off between conductivity and stabilities for proton exchange membrane

To address the trade-off between conductivity and stabilities for proton exchange membrane (PEM), polydopamine-modified sulfonated polyhedral oligomeric silsesquioxane (D-sPOSS) is facilely prepared and introduced into sulfonated poly(arylene ether sulfone) (SPAES) polymer matrix. The interaction between sulfonic acid groups of POSS (or of polymer chain) and basic groups of polydopamine not only can avoid the excessive swelling and maintain a high-level mechanical strength of the membrane, but also can enhance the proton hopping diffusion with uninterrupted trajectory. While the resulting D-sPOSS doped hybrid membranes exhibit prominent dimensional stability, oxidative stability and thermal stability in comparison with the sulfonated POSS (sPOSS) doped hybrid membranes and the plain SPAES membrane, the D-sPOSS doped hybrid membranes also possess superior proton conductivity, low methanol permeability and excellent single cell performance. Particularly, the proton conductivity of the hybrid membrane with 2 wt% content of D-sPOSS at 80 °C and 100% RH achieves 0.243 S cm−1, which is approximately 2 times higher than that of Nafion-117 membrane, 2.4 times higher than that of the pristine SPAES membrane and 1.5 times higher than that of the sPOSS doped hybrid membrane with 2 wt% loading under the same condition.

Enhanced ionic conductivity of anion exchange membranes by grafting flexible ionic strings on multiblock copolymers

A new strategy to prepare high-conductivity anion exchange membranes (AEMs) is presented here. A series of phenolphthalein-based poly(arylene ether sulfone nitrile) multiblock AEMs has been synthesized by selectively grafting flexible ionic strings on hydrophilic segments to form ionic regions. Moreover, the phenolphthalein groups are introduced to force chains apart and create additional interchain spacing. In addition, the nitrile groups suspended on main chains are aimed at enhancing the anti-swelling behavior of as-prepared AEMs. Along these processes, well-defined phase separation has been attained, forming excellent ion-transport channels. The effective phase separation has been confirmed by atomic force microscopy. Finally, as-prepared AEMs exhibit a high hydroxide conductivity, ranging from 40.1 to 121.6 mS cm−1 in the temperature range of 30–80 °C, and superior ionic conductivity to IEC ratio at 80 °C. Furthermore, excellent thermal stability and desirable mechanical strength have been rendered by as-prepared AEMs. However, the alkaline stability of as-prepared AEMs requires further optimization.

Polysulfone-polyvinylpyrrolidone blend membranes as electrolytes in alkaline water electrolysis

Development of thin, dense and robust alkaline polymer membranes with high hydroxide ion conductivity is key to advanced alkaline electrolysis as it can enable operation at higher current density and/or efficiency, while improving the dynamic response of the electrolyzer. In this work, a homogeneous blend membrane system based on poly(arylene ether sulfone) (PSU) and poly(vinylpyrrolidone) (PVP) is explored as an alkaline ion-solvating polymer matrix. Increasing PVP content in the blend drastically increases electrolyte uptake, and at PVP contents higher than 45 wt%, the membrane can support ion conductivity in a technologically relevant range of 10–100 mS cm-1 or even higher when equilibrated in 20 wt% aqueous KOH. The membrane system is extensively characterized throughout the full composition range and the down-selected composition composed of 25% PSU and 75% PVP is employed in a single cell lab-scale water electrolyzer, showing excellent performance and stability during the course of one week at 500 mA cm-2 at 60 °C in 20 wt% KOH. Good performance stability was demonstrated for more than 700 h at 80 °C, but the gradually increasing KOH concentration due to evaporative loss of water resulted in membrane degradation.

Synthesis and Properties of Novel Side‐Chain Sulfonated Poly(Arylene Ether Sulfone)s for Proton Exchange Membranes

ABSTRACTA series of novel side‐chain sulfonated poly(arylene ether sulfone) (SPAES) multiblock and random copolymers were synthesized by condensation polymerization from a new disulfonated aryl sulfone monomer, 4,4′‐difluoro‐2,2′‐bis(3‐sulfobenzoyl)diphenyl sulfone disodium salt (DFBSPS). The chemical structures of DFBSPS and the SPAESs were characterized by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FTIR) spectra. The SPAES membranes prepared by solution cast method exhibited high tensile strength (50–71 MPa) and high radical oxidative stability. They could keep their morphology and maintain proton conductivities after hydrolysis test in 95 °C water for 1000 h. They also showed smaller swelling ratio in in‐plane direction than in through‐plane direction and such an anisotropic effect was more significant for the multiblock copolymers than for the random ones. The multiblock copolymer membranes exhibited higher proton conductivity than the random ones with similar ion exchange capacities (IECs). Preliminary hydrogen‐oxygen fuel cell tests were performed at 60 °C and 80% relative humidity (RH). The results showed that the single cell equipped with the multibiock copolymer membrane SB3 exhibited 0.12 W cm−2 higher maximum output power density than the one equipped with the random copolymer membrane SR3 (with the same IEC), indicating much better performance of the former. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2304–2313

A high-performance membrane electrode assembly for polymer electrolyte membrane fuel cell with poly(arylene ether sulfone) nanofibers as effective membrane reinforcements

Direct membrane deposition was recently introduced as a novel polymer electrolyte membrane fabrication method. This method is extended to fabricate a high-performance membrane electrode assembly for polymer electrolyte membrane fuel cell with poly(arylene ether sulfone) nanofibers as effective membrane reinforcements. The nanofibers are directly electrospun onto gas diffusion electrodes. By spray-coating ionomer dispersion into the pore space of nanofiber mats, composite membranes of 15 μm thickness are fabricated. The introduction of the electrically and ionically insulating nanofibers do not hamper the cell performance. At 80 °C and 75% relative humidity, the power density of the fuel cell employing direct membrane deposition, 2.85 W cm−2, is about 1.36 times higher than that of the reference fuel cell (2.09 W cm−2) with Nafion® 211 membrane and identical catalyst. Its cell resistance (28 mΩ cm2) is much lower than that of the membrane electrode assembly fabricated by the catalyst coating membrane method (46 mΩ cm2). The performance differences between two fabrication methods are systematically analyzed by electrochemical impedance spectroscopy. Most notably, even though the thickness of the polymer electrolyte is much lower than that of Nafion® 211 (25 μm), it shows much higher internal short resistance and better durability because of the existence of reinforcement.

High refractive and low birefringent materials based on Poly(arylene ether phosphine oxide)s and Poly(arylene ether phosphine sulfide)s

Poly(arylene ether phosphine oxide)s and poly(arylene ether phosphine sulfide)s with high refractive indices and low birefringences have been developed. The poly(arylene ether phosphine oxide)s were synthesized by the polycondensation of bis(4-fluorophenyl)phenylphosphine oxide with various bisphenols. Subsequently, the poly(arylene ether phosphine sulfide)s were synthesized by the sulfurization reaction of the poly(arylene ether phosphine oxide)s with Lawesson's reagent. These polymers have excellent thermal stabilities (Td5 > 490 °C), high glass transition temperatures (Tg = 198–281 °C), and no absorption in the visible light region. In addition, they achieve high refractive indices of 1.649–1.675 for the poly(arylene ether phosphine oxide)s and 1.671–1.691 for the poly(arylene ether phosphine sulfide)s owing to the highly polarizable P X (X = O, S) groups in their backbones. Their orientational birefringences (CR values) are in the range from +0.7 × 10−9 to +3.0 × 10−9 Pa−1, which are lower than those of the conventional poly(arylene ether ketone) and poly(arylene ether sulfone) (+7.8 × 10−9 and +4.0 × 10−9 Pa−1, respectively).

Well-defined poly(ether sulfone)-b-polylactide: synthesis and microphase separation behavior

We investigated the microphase separation behavior of well-defined poly(arylene ether sulfone)-b-polylactide (PES-b-PLA) diblock copolymers. PES was synthesized by the nucleophilic aromatic substitution polymerization of 4-fluoro-4′-hydroxydiphenyl sulfone potassium salt in the presence of an allyl-functionalized initiator, which follows a chain growth condensation polymerization mechanism. A hydroxyl group installed via a thiol-ene reaction was utilized as the initiating site for the ring opening polymerization of d,l-lactide, producing the target polymer. The polymers were further purified by preparative size-exclusion chromatography and analyzed by small-angle X-ray scattering with temperature variations from room temperature to 150 °C. The PES block was glassy in the employed temperature range, but the PLA chains provided sufficient mobility for ordering of the block copolymer when PES was the minor fraction. An order-disorder transition (ODT) with changing temperature could not be located because PLA was not stable above 170 °C. From the degree of polymerization values of the polymers near the ODT, the Flory–Huggins interaction parameter, χ, could be roughly estimated as 0.12 at 150 °C. This high χ value suggests that engineering plastic-containing block copolymers could be useful in advanced lithographic and filtration applications. Well-defined poly(arylene ether sulfone)-b-polylactides (PES-b-PLAs) were successfully synthesized and their microphase separation behavior was investigated. PES was obtained via chain growth condensation polymerization, and subsequent end group modification followed by ring opening polymerization of d,l-lactide produced the diblock copolymers. By small-angle X-ray scattering experiments in bulk, the formation of ordered morphologies including spherical, cylindrical, gyroidal, and lamellar was observed. An effective interaction parameter at 150 °C was roughly estimated as 0.12 for the first time in engineering plastic-containing block copolymers.

Synthesis and properties of long-chain-branched poly(aryl ether sulfone)-poly(tetrahydrofuran) multiblock copolymers

Long-chain-branched poly(aryl ether sulfone)-poly(tetrahydrofuran) multiblock copolymers (PES-BPTHF) composed of hard linear and soft branching segments were synthesized from bromo-terminated poly(tetrahydrofuran) and hydroxy-terminated poly(aryl ether sulfone). A study on the effect of concentration on polymerization behavior revealed that soluble powder was obtained at the optimized reaction concentration of 7 wt%. Gelation and intramolecular cyclization were observed at high and low concentrations, respectively. The microphase-separated morphology of PES-BPTHF was confirmed by atomic force microscopy, small-angle X-ray scattering (SAXS), and dynamic mechanical analysis (DMA) measurements. Fewer entangled poly(tetrahydrofuran) segments were detected in PES-BPTHF than in PES-PTHF by SAXS, DMA and tensile measurements. Rheological measurements suggested high chain entanglement of PES-BPTHF in its melt phase. It is interesting to note that the polymer chains in the soft domains become less entangled and more reminiscent of hyperbranched architectures, whereas the overall chain entanglements are increased due to the long-chain-branched structure. Long-chain-branched poly(aryl ether sulfone)-poly(tetrahydrofuran) multiblock copolymers composed of hard linear and soft branching segments were synthesized from bromo-terminated poly(tetrahydrofuran) and hydroxy-terminated poly(aryl ether sulfone). Optimization of the polymerization conditions afforded soluble powder at a reaction concentration of 7 wt%. Microphase-separated morphology was observed for the branched multiblock copolymers. Compared with the corresponding linear multiblock copolymer, the branched polymer chains in the soft domains become less entangled and more reminiscent of hyperbranched architectures, whereas the overall chain entanglements are increased due to the long-chain-branched structure.

A High-Performance Membrane Electrode Assembly for PEM Fuel Cell with Poly (ether sulfone) Nanofibers As Effective Membrane Reinforcements

Direct membrane deposition is introduced as a novel polymer electrolyte membrane fabrication method. This method is extended to fabricate a high-performance membrane electrode assembly for polymer electrolyte membrane fuel cell with poly (arylene ether sulfone) nanofibers as effective membrane reinforcements. The nanofibers are directly electrospun onto gas diffusion electrodes. By spray-coating ionomer dispersion into the pore space of nanofiber mats, composite membranes of 15 μm thickness are fabricated. The introduction of the electrically and ionically insulating nanofibers do not hamper the cell performance. At 80 ℃ and 75% relative humidity, the power density of the fuel cell employing direct membrane deposition, 2.85 W/cm2, is about 1.36 times higher than that of the reference fuel cell (2.09 W/cm2) with Nafion® 211. Its cell resistance (28 mΩ·cm2) is much lower than that of the membrane electrode assembly fabricated by the catalyst coating membrane method (46 mΩ·cm2). The performance differences between two fabrication methods are systematically analyzed by electrochemical impedance spectroscopy. Even though the thickness of the polymer electrolyte (15 μm) is much lower than that of Nafion® 211, it shows much higher internal short resistance because of the existence of nanofibers.

Synthesis and characterization of hydrophilicity-controlled poly(arylene ether sulfone) copolymers with phenolphthalein-based carboxylic acid groups for separation membrane applications

Hydrophilicity-controlled poly(arylene ether sulfone) copolymers with phenolphthalein-based carboxylic acid groups (PES-COOH-X) were synthesized via direct copolymerization by adjusting the feed molar ratio. The chemical structures of the obtained copolymers were confirmed by 1H nuclear magnetic resonance (NMR) spectroscopy. The copolymers showed good solubility in common aprotic solvents and exhibited excellent mechanical properties. The water contact angles of the obtained copolymers could be reduced by approximately 52% from 92.1° to 44.2° with increasing content of phenolphthalein-derived monomer, 2-[bis(4-hydroxyphenyl)methyl] benzoic acid (PPH-COOH), in the feed molar ratio. A series of PES-COOH-X membranes was prepared via a conventional immersion precipitation phase inversion method. The effects of the monomer feed molar ratio on the morphology, hydrophilicity, pure water flux, and water uptake of the prepared membranes were investigated. The results showed that the pure water flux of the PES-COOH-X membranes was significantly enhanced by almost a factor of two as compared to the pristine PES membrane. From the water contact angle data, it was identified that the hydrophilicity of the membranes was increased rapidly with increasing PPH-COOH content in the membranes. These hydrophilicity-controlled poly(arylene ether sulfone) copolymers may be considered as good candidates for separation membrane materials.

Fluorene-containing poly(arylene ether sulfone nitrile)s multiblock copolymers as anion exchange membranes

A series of novel fluorene-containing poly(arylene ether sulfone nitrile)s (FPESN-m/n) multiblock copolymers bearing 1,2-dimethylimidazole groups (ImFPESN-m/n) were synthesized for preparing anion exchange membranes (AEMs). Bromination rather than chloromethylation was used in this work. The bulky and rigid fluorene groups were introduced to force each chain apart to create large interchain spacing. Strong polar nitrile groups were introduced into the hydrophobic segments with the intention of enhancing the anti-swelling property of the AEMs. The length of fluorene–containing hydrophobic segment was varied to study the structure–property of the AEMs. With the ion groups anchored selectively and densely on the hydrophilic segments, all the AEMs exhibited well-defined hydrophilic/hydrophobic microphase-separated structures. As a result, the AEMs showed high hydroxide conductivities in the range of 35.2–118.3 mS cm−1 from 30 to 80 °C and superb ratios of ionic conductivity to swelling at 80 °C. Furthermore, the AEMs also exhibited good mechanical properties, thermal and alkaline stabilities.

Preparation of Graft Poly(Arylene Ether Sulfone)s-Based Copolymer with Enhanced Phase-Separated Morphology as Proton Exchange Membranes via Atom Transfer Radical Polymerization.

Novel proton exchange membranes (PEMs) based on graft copoly(arylene ether sulfone)s with enhanced phase-separated morphology were prepared using atom transfer radical polymerization (ATRP). A series of PEMs with different graft lengths and sulfonation degrees were prepared. The phase-separated morphologies were confirmed by transmission electron microscopy. Among the membranes prepared and evaluated, PAESPS18S2 exhibited considerably high proton conductivity (0.151 S/cm, 85 °C), benefitting from the graft polymer architecture and phase-separated morphology. The membranes also possessed excellent thermal and chemical stabilities. Highly conductive and stable copoly(arylene ether sulfone)-based membranes would be promising candidates as polymer electrolytes for fuel cell applications.

Synthesis and property of novel anion exchange membrane based on poly(aryl ether sulfone)s bearing piperidinium moieties

A novel bisphenol monomer bearing a cyclic tertiary amine was prepared in good yields by the acid-catalyzed reaction of N-methyl-4-piperidone and phenol. Tertiary amine poly(aryl ether sulfone) (TAPES) with high molecular weights of up to 95.3 kg mmol−1 and good thermal stability was synthesized by nucleophilic substitution of the bisphenol monomer with 4,4′-dichlorodiphenyl sulfone. The spatial separation between the cyclic tertiary amine groups and the hydroxyl ortho-position improves the stability of the intermediate and was the key to the polymerization. The anion exchange membranes (AEMs) QPES or DQPES are obtained by quaternization of TAPES with methyl iodide or (3-bromopropyl)trimethylammonium bromide, respectively. DQPES (ion exchange capacity = 3.12 mmol g−1) shows a higher ion conductivity of 59.8 mS cm−1 and reasonable dimensional stability in water at 80 °C. DQPES membrane revealed that the high conductivity might be due to its phase-separated structure in small-angle X-ray scattering test. The alkaline stability of QPES and the methoxy-capped QPES was compared, end-capping was found to improve the stability of piperidinium cations. This method offers a versatile platform for cost-effective synthesis of piperidinium-based AEMs with poly (aryl ether) backbones, and may provide a strategy to improve alkaline stability.

A high-performance anion exchange membrane based on poly(arylene ether sulfone) with a high concentration of quaternization units

To achieve a balance between the dimensional stability and ionic conductivity coordination of anion exchange membranes (AEMs), a novel quaternized poly(arylene ether sulfone) (QPAES) with multiple phenyl units was prepared. A bis-tetraphenyl (BTP) bisphenol monomer was designed to synthesize a series of polymers through the polycondensation reaction. The as-prepared QAPES-BTP-30% showed an ion exchange capacity (IEC) of 2.46 meq g−1 and a good hydroxide conductivity (66.2 mS cm−1). The swelling behavior was also suppressed by the high-density hydrophilic groups and hydrophobic regions, thereby further improving the dimensional stability of the series of AEMs with high IECs. Small-angle X-ray scattering measurements were performed to demonstrate the distinct nanosized hydrophilic/hydrophobic phase separation. All the prepared membranes retained more than 85% of the original hydroxide conductivity and almost 90% of the IEC value after immersion in 4 M KOH aqueous solution at room temperature for 35 days. Moreover, these membranes were used for single-cell performance tests and were shown to be suitable for practical application (QAPES-BTP-30%: an open-circuit voltage (OCV) of 1.01 V and a maximum power density of 151 mW cm−2 at 60 °C under full humidification). These results suggest that QAPAES-BTP-AEMs containing concentrated quaternary ammonium show good comprehensive performance.

Side-chain effects on the properties of highly branched imidazolium-functionalized copolymer anion exchange membranes

A set of highly branched imidazolium-functionalized poly(arylene ether sulfone)s copolymer bearing with flexible alkyl side chains of different lengths are designed and synthesized. The ion exchange capacity (IEC), ionic conductivity, water uptake, thermal stability, mechanical property and alkaline resistance of the anion exchange membranes (AEMs) were evaluated in detail. Atomic force microscopy and small-angle X-ray scattering are used to study morphology which reveals that the branched membrane with an alkyl side chain (6 carbons) achieves the highest conductivity (up to 115.8 mS cm−1 at 80 °C) due to the well-developed hydrophilic/hydrophobic phase separation. In addition, the branched co-polymer AEM with a longer alkyl side chain (12 carbons) exhibit the best robust alkaline stability, it decreases only 27% of ionic conductivity after 550 h in 1 M KOH. Therefore, this study provides a comprehensive insight into the tuneable membrane properties of highly branched copolymers as a change in the length of flexible alkyl side chains.