Poly(arylene ether ketone) Copolymer Grafted with Amine Groups

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Poly(arylene ether ketone) Copolymer Grafted with Amine Groups Containing Long Alkyl Chain by Chloroacetylation for Improved Alkaline Stability and Conductivity of Anion Exchange Membrane Geetanjali Shukla, and Vinod Kumar Shahi ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.7b00282 • Publication Date (Web): 20 Feb 2018 Downloaded from http://pubs.acs.org on February 21, 2018

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ACS Applied Energy Materials

Poly(arylene ether ketone) Copolymer Grafted with Amine Groups Containing Long Alkyl Chain by Chloroacetylation for Improved Alkaline Stability and Conductivity of Anion Exchange Membrane a,b

a,b,

Geetanjali Shukla , and Vinod K. Shahi * a b Electro-Membrane Processes Division and Academy of Scientific and Innovative Research, CSIR-Central Salt and Marine Chemicals Research Institute, Council of Scientific & Industrial Research, Gijubhai Badheka Marg, Bhavnagar 364 002, Gujarat, India Fax: +91-0278-2566970; Tel: +91-278-2569445; E-mail: [email protected]; [email protected]

ABSTRACT: We report simple and controllable acetylation of poly (arylene ether ketone) (PK) followed by Menshutkin reaction (quaternization), to prepare highly alkaline stable and conductive (phase separated) anion exchange membrane (AEM). Long side alkyl chain grafted with ammonium groups facilitates decent hydrophilic/hydrophobic micro-phase separation. Prepared AEMs exhibited improved conductivity, alkaline stability, and water resistivity, because of well-designed membrane architecture. Under alkaline conditions, nucleophilic substitution reaction and/or Hofmann elimination reaction (β-hydrogen) are expected to protected by grafting of large volumetric alkyl chain (C=16) with amine groups responsible for steric hindrance. Suitably assessed PK-QD-48 AEM reveals 0.81 V open circuit voltage (OCV) corresponding to 25.53 mW cm-2 power density at 65 oC in alkaline direct methanol fuel cell (ADMFC) operation. Reported synthetic strategy offers a novel route for preparing highly conducting, and alkaline stable AEM for fuel cells and diversified electrochemical applications. KEYWORDS: anion exchange membrane, poly (arylene ether ketone), improved conductivity, high alkaline stable, alkaline fuel cell.

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1. INTRODUCTION There is technological requirement of stable and ion conducting polymers for energy related devices such as chemical/biological fuel cells, battery etc.1-4 Traditionally, ion (cation and anion) exchange membranes have been widely utilized to solve the diversified industrial problems including desalination of sea/brackish water by electrodialysis, purification of pharmaceuticals

and

biomaterials,

electro-deionization,

energy-less

separation

and

purification by diffusion dialysis or donnan dialysis, ion separation, and electrolysis, etc.5-9 Recently, anion exchange membrane fuel cells (AEMFCs) were considered as promising than proton exchange membrane fuel cells (PEMFCs) because of improved O2 reduction, fuel oxidation kinetics (essential for high efficiency), and use of non-precious metal catalysts.10-14 Anion exchange membrane (AEM) is a key AEMFC component that acts as selective OHconductor and electrical insulator between electrodes. AEM should possess stable polymer matrix containing nano-channels essential for good OH- mobility (conductivity), stable structural integrity under adverse operating conditions (high temperature and alkalinity).15,16 A variety AEMs based on poly(arylene ether)s and their analogues, polyimides, poly(phenylene oxide)s etc. main polymer back displaying wide-range conductivity, were reported.17-22 High ionic conductivity of AEM was achieved by grafting of different functional groups, such as quaternary ammonium,23-26 guanidinium,27,28 imidazolium,29,30 sulfonium,31 or phosphonium32 with main polymer back bone. Generally, AEMs possess quaternary ammonium groups grafted with aromatic polymer chain, which is achieved by either: (i) chloromethylation using chloromethyl ether (CME); or (ii) bromination (Br2 water). Both recations are complicated and hazardous in nature.33 Further, these membranes, with high ionic content, are generally suffering due to huge water uptake (WU) and thus dimensional instability.18,16 Thus, complete understanding between controlled polymer


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structure, ionic content (ion exchange capacity), phase separated morphology, and trade-off between conductivity and WU, is necessary to architect high performance AEM. AEMs based on phase separated block copolymers such as PK or poly (arylene ether sulfone) showed high stabilities (thermal, and mechanical) due to proper sequencing of hydrophobic and hydrophilic units.34-36,37(added) But, dimensional instability of these membranes (due to high degree of functionalization) is a serious problem for their practical exploitation. To prepare comb shaped AEMs, bromination of poly(phenylene oxide) (PPO) (degree of bromination: 70-85%) was reported for introducing quaternary ammonium groups.18 Reported AEM showed polymer degradation, intra-polymer crosslinking, and restricted conductivity, due to high degree of bromination.38 Alkaline stability is a serious problem for the commercialization of AEM.37,39,40 Under strong alkaline environment cationic functional groups attached with the polymer backbone such as, benzyl-trimethyl ammonium,24,25 imidazolium,29 phosphonium,32 and guanidinium,28 showed degradation mechanism either by: Hofmann elimination (presence of β-hydrogen),37 or direct nucleophilic substitution,21,41. Recently, long alkyl chain tethered quaternary ammonium groups reported as alkaline stable AEMs due to comb-shaped structure had the best alkaline stability.42 In addition, for comb shaped AEM, alkaline instability via Hofmann elimination reaction may be avoided by steric hindrance of large volumetric alkyl chain (C=16) with amine group.42,43 Well hydrophilic-hydrophobic units sequenced copolymer (such as PK), provides effective membrane architecting strategy. Hydrophilic unit contributes towards high conductivity, while hydrophobic unit maintains WU and thus dimensional stability.44,16 To avoid the use of hazardous materials (such as CME or bromine water) during preparation of AEM, we report controllable acetylation of phase separated PK, while long alkyl chain was grafted with quaternary ammonium groups to achive good



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alkaline stability and OH- conductivity. Herein, we report a comb-shaped choloroacetylated PK (PK-CAL) with different degree of acetylation. Reported procedure is simple and avoids the unwanted cross-linking. 2. MATERIALS AND METHODS Materials. 4,4’-Difluorobenzophenone (DFBP) (99%), 4,4’-Dihydroxybiphenyl (DBP) and N,N-dimethyl-1-hexadecylamine (DHDA) were obtained from SigmaAldrich Chemicals. 2,2-Bis(4-hydroxy-3,5-dimethylphenyl)propane (BHDMP) (98%), were received from TCI Chemicals. Toluene, dry dimethylacetamide (DMAc), Nmethyl-2-pyrrolidinone (NMP), dimethyl sulfoxide (DMSO), trimethylamine (TMA), K2CO3, N,N-dimethylformamide (DMF), chloroform, chloroacetyl chloride (CAL), anhydrous aluminum chloride of analytical grade were obtained from commercial sources and used as received. Deionized (DI) water was used for all experiments. Synthesis of PK copolymer. The PKs, composing tetra methane moieties, were synthesized by nucleophilic substitution and polycondensation reaction (Scheme 1). In this typical polymerization method, to a 100 mL three neck round bottom flask equipped with a magnetic stirrer, a Dean−Stark trap, a condenser with N2 gas inlet and outlet, DFBP (2.0 g), DBP (1.0 g), BHDMP (1.0 g), K2CO3 (2.7 g), DMAc (40 mL), and toluene (15 mL) were added. The polymerization reaction was carried out at 140-155 oC (oil bath) under N2 environment under constant stirring for 3 h, afterward temperature was increased to 175-180 °C and reaction was continued for 20 h. Simultaneously, toluene and produced water mixture was distilled out from the reaction mixture. Obtained liquid mixture was transferred into hot water to precipitate the PKs. Obtained crude product was successively washed with DI water, methanol several times, and dried under vacuum oven at 80 oC for 24 h. Yield: 98%. Chloroacetylation of PKs by Friedel–Crafts Reaction. In a 100 mL three-neck round bottom flask which was fitted out with a CaCl2 tube and a magnetic stirrer, PKs (2.4 g) was


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dissolved in 30 mL of chloroform and anhydrous AlCl3 (1.62 g) was added under vigorous stirring. After complete dissolution of the AlCl3, desired amount of CAL was added dropwise and stirred at 45 oC for 4 h. Chloroacetylated PK (PK-CAL) was precipitated in methanol and dried at 60 oC for 48 h, Yield: ~ 80%. Synthesis of PK-QD, PK-QT and Membrane Preparation. The PK-CAL was quaternized by Menshutkin reaction, using N,N-dimethyl-1-hexadecyamine (DHDA) and trimethyamine (TMA) as a quaternizing agents, to prepare PK-QD and PK-QT, respectively.3,45 To prepare PK-QD, PK-CAL (1.5 g) was dissolved in 20 mL of NMP, and DHDA (2.6 g) was added under continuous stirring for 48 h at room temperature (RT). Reaction mixture was precipitated in excess of toluene, product was filtered, washed with toluene and hexane many times, and dried under vacuum oven for 24 h. To prepare the membrane, obtained comb-shaped PK-QD was dissolved in NMP (8.0 wt %), transformed as thin film on a cleaned glass plate, and dried under vacuum oven at 70 °C for 24 h. The resultant PK-QD membrane was peeled off and conditioned by equilibrating in 1.0 M NaOH solution for 24 h to convert in OH− form (designated as PK-QD-x, where x denotes degree of chloroacetylation (41-54%)). Similar procedure was adopted to prepare non-comb shaped PK-QT membrane. PK-CAL (1.5 g) was dissolved in 20 mL NMP in a glass vial under stirring, thin film was cast onto a glass plate and dried under vacuum oven at 70 °C for 24 h. Resultant membrane was immersed in a 45 wt% trimethylamine aqueous solution for 48 h and washed with DI water several times. Dried membrane conditioned by equilibrating in 1.0 M NaOH solution for 24 h to convert in OH− form (designated as PK-QT- x, where x denotes degree of chloroacetylation). Instrumental Analysis and Membrane Characterizations. Detailed instrumental analysis for the

1

H NMR spectra (500 MHz), FT-IR spectra, transmission electron



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microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), gas permeation chromatography (GPC), and mechanical strength are included in the Section S1 of the Supporting Information. Detailed methods adopted for the measurements of water uptake (WU), ion exchange capacity (IEC), swelling ratio (SR), hydroxide conductivity (κm), and ionic mobility are included in Section S2 of the Supporting Information. Preparation of Membrane Electrode Assembly (MEA) and Measurement. Membrane electrode assembly (MEA) was prepared by layer-by-layer coating of three different layers (AEM, anode/cathode catalyst layer (ratio of Pt/C: 40 wt%) and diffusion layer) using carbon paper (Toray) with 12 wt.% PTFE solution by the brush painting method.22 The gas diffusion layer (GDL) (25 cm2) was prepared by coating of catalyst ink of carbon black (Vulcan XC72R) with 0.50 mg/cm2 coating density dispersed in PTFE solution. In case of both catalyst, anode and cathode, Pt loading was 0.4 mg/cm2. Prepared MEA was pressured (1.2 MPa) and heated at 65 oC for 12 h to achieve the better curing. Thus, obtained MEA (composite structure of elelctrode/AEM/electrode) was assembled into a single cell (FC25-01 DM fuel cell). In the anode compartment, fuel (2.0 M methanol in 2.0 M NaOH) was fed with 5 ml min-1 flow rate, while air was fed in the cathode compartment with 100 ml min-1 flow rate. Current-voltage polarization curves were recorded using MTS-150 manual fuel cell test station (ElectroChem Inc., USA). 3.

RESULTS AND DISCUSSION

Synthesis and Characterization of PK Copolymers and Their Derivative. Functional derivatives of PK copolymer (PK-CAL, PK-QD and PK-QT) were synthesized via polycondensation reaction (Scheme 1). Chemical structures of pristine PK, PK-CAL, PK-QD and PK-QT were validated by 1H NMR (Figure 1) and FTIR spectra (Figure S1). Phenylene protons were confirmed by peaks between 6.6-8.6 ppm (c-h), whereas protons of aliphatic


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region exhibited peaks ~1.6-2.5 ppm (a, b) (Figure 1A). Absorption band around 1651, 1577, 1101 and 2931 cm-1 also confirmed the presence of C=O, C=C, C-O-C and C-H groups (Figure S1A). Molecular weights (Mn and Mw) and poly-dispersity index (PDI) for pristine PK were measured by GPC and found to be 68.6 kDa, 135.8 kDa, and 1.88, respectively. Controlled chloroacetylation (41-54%) of PK was achieved by varying reaction temperature, time, and catalyst (AlCl3) content and degree of chloroacetylation was obtained by integration of 1H NMR peaks at ~ 4.5 ppm (Figure S2) and data arranged in Table 1. In the 1

H NMR spectra of PK-CAL, peaks at ~ 4.5 ppm (c) was attributed to chloroacetyl proton

(Figure 1B) occupied adjacent position to the methyl group (BHDMP) due to its high reactivity towards fridel craft acetylation. Successful chloroacetylation was also confirmed by absorption band 766 cm-1 of C-Cl groups,46 and significant reduction in molecular weights (Mn: 66.6 kDa and Mw: 132.8 kDa) and PDI (1.90). The PK-QD and PK-QT, both showed broad peak around 4.5-4.8 ppm (c) (Figure 1C,D) and FTIR bands at 1360 and 1370 cm-1 (CN bond) (Figure S1C,D). Further, chemical shift between 3.5-1.1 ppm (d-i) confirms the successful grafting of DHDA groups (C=16) with PK-CAL main chain (Figure 1D). After successful synthesis of PK-QT and PK-QD, membranes (thickness: ~ 150 µm) were prepared by solution casting in NMP and converted into hydroxyl form after suitable conditioning in 1.0 M NaOH solution for 24 h. Resultant membranes were designated as PK-QT and PK-QD. Morphological Result of Anion Exchange Membranes. The PK-QD AEMs were prepared by amination using DHDA with long alkyl chain (C=16) followed by quaternization, are expected to show comb-shaped morphology, while in PK-QT, amine groups were attached with PK via one carbon atom and showed non-comb shaped morphology. Surface and cross-sectional images of both AEMs showed smooth, dense and homogeneous morphology without any cracks and holes (Figure 2(A-D)). The AFM images of quaternary amine group and long alkyl chain quaternary amine group embedded AEMs



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endorse the hydrophilic (dark region) and hydrophobic (light region) phase separation. Further, AFM images PK-QT-41 and PK-QD-41 membranes, showed dark region (hydrophilic) and light region (hydrophobic). The PK-QD-41 membrane grafted long alkyl chain possessed inter-connected and larger ionic domains in compare with PK-QT-41 AEM (Figure 3(C,D)). In comb-shaped membrane (PK-QD-41), inter-connected ionic domains were responsible for the ion conducting pathway.3 The TEM image of PK-QD-41 also showed the better hydrophilic/hydrophobic phase separation with large ionic domains (nanochannels for ion conduction) in compare with PK-QT-41 AEM. (Figure 3 A,B). Mechanical and Thermal Stabilities. Mechanical stability of dry membrane samples (OH-) was studied at 30 oC by stress-strain curve (Figure S3). The PK-QD-41 AEM showed relatively good tensile strength and strain in compare with PK-QT-41 (Figure 4). Further, about 35-28 MPa tensile strength and ~ 9-7% strain values of comb-shaped PK-QD AEM are comparable with the strain values (4.8-9.2%) of different AEMs reported in the litreture.47-49 For both membranes (PK-QT-41 and PK-QD-41) with nearly equal IEC values, showed approximate similar TGA spectra (Figure S4). The three step weight loss was observed, and first step weight loss (100-150 oC) was aroused due to the evaporation of trap water in AEM. The second weight loss (150-400 oC) was assigned to the decomposition of quaternary groups, while third step weight loss ( > 400 oC) was attributed to the decomposition of polymer backbone. Further, about ~ 40 and 50% remained weight (%) was observed for PKQT-41 and PK-QD-41 AEMs, respectively. This confirmed the stable nature of PK-QD membrane with long alkyl chain. These informations also supports good mechanical and thermal stability of comb-shaped PK-QD AEMs, because grafting of long alkyl chain (C = 16) with amine groups. Anion Exchange Membrane and Their Physicochemical Properties. An ideal architecting strategy for AEM depends on trade-off behaviour between membrane


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conductivity, density of functional groups, balance between hydrophilic-hydrophobic phase separation and water uptake (WU). Presence of water molecules in the membrane phase is necessary for ion conduction, while its excessive value adversely effects mechanical properties. Comb-shaped (PK-QD-41) membrane showed comparatively low WU than noncomb shaped AEM (PK-QT-41), inspite of similar degree of acetylation and thus extent of functionalization. The relatively low WU values (6.82-8.40%) played important role for good dimensional stability of PK-QD membranes. These membranes with different degree of acetylation (41-54%) exhibited 1.34-1.98 meq./g ion exchange capacity (IEC) (Table 2). The PK-QT-41 membrane showed relatively high IEC in compare with PK-QD-41 membrane, inspite of same degree of acetylation. These observations also support the earlier reports that low WU was induced by comb-shaped morphology, while PK-QT-41 showed high WU value and thus high swelling ratio (SR: (λ > 10)).38,50,51,3 In both cases (comb and non-comb shaped), functional groups (quaternary amine) were attached with main polymer chain via methylene groups, but different trend of WU may be attributed to the carbon chain (C=16) grafted with functional groups for comb-shaped membranes. Thus, hydrophobic nature of grafted carbon chain restricted the water adsorption in the membrane matrix. Generally, membrane conductivity (κm) depends on IEC, density of exchangeable functional groups and κm value, for comb-shaped AEM these parameter varied with degree of acetylation (Table 2). Under similar preparative conditions, comb-shaped AEM exhibited improved conductivity in compare with non-comb shaped (PK-QT). As reference, PK-QD-41 showed 2.25×10-2 S cm-1 hydroxide conductivity in compare with 1.86×10-2 S cm-1 for PK-QT-41 AEM, in spite of low IEC and WU for the previous case. The conductivity of different PK-QD AEMs followed Arrhenius type nature between 30-80 oC at 100% RH (Figure 5). In this case, phase separation was pronounced due to two reasons: hydrophobic and hydrophilic segments in the main



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polymer chain (PK), and hydrophilic and hydrophobic aggregates formed by functional group grafted with long alkyl chain (C=16), thereon. Phase separation between hydrophobic and hydrophilic domains is necessary for formation of nanoscale ion conducting channels and improved conductivity,52,3 while grafting of long hydrophobic alkyl chain with functional groups was responsible for comb-shaped structure. These observations were further validated by ionic mobility (µOH-) data included in Table 2. Thus, PK-QD-54 AEM exhibited high desnity functional groups and interconnected ion-conducting channels, responsible for high conductivity (3.66×10-2 S cm-1) in compare with other AEMs (either well-phase separated or combshape structured) reported in the literature (Table 3).16,53,18,17,54 Alkaline Stability. The alkaline stability of prepared membrane was assessed by conductivity remained after equilibrating the AEM in 2.0 M NaOH at 60 oC for 720 h (Figure 6). Initially, conductivity declines (upto 300 h) and retained its values as constant beyond 300-400 h). In case of PK-QT-41 membrane about 57% (1.06 x 10-2) membrane conductivity was remained up to 720 h. Whereas, PK-QD-54 and PK-QD48 retained about 76% and 82 % ionic conductivity after alkaline test for 720 h. The 1

H NMR spectra of PK-QD-54 membrane showed small reduction in the intensity of

peaks around 3.0, 3.5, and 4.6 ppm, after alkaline stability test (Figure S5). PK-QD54 and PK-QD-48 AEM showed the better alkaline stability in compare of PK-QT-41 (without β-hydrogen). Under strong alkaline conditions, stability of AEMs is an important issue. This includes

either drgradation of polymer back bone due to

hydroxide ion attack on ether and/or ketone linkage, or degaradtion of trimethyl ammonium groups by direct nucleophilic substitution. Detailed mechanisms for both types of degradation have been included in Figure S6. The excellent stability of PKQD-54 and 48 AEM probably results due to the grafting of long alkyl chain, which


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reduced the possibility of Hofmann elimination reaction and OH- attack by nucleophilic substitution reaction, due to steric hinderence.39,40,38 Single cell performance. For single cell alkaline DMFC performance, PK-QD-48 was picked cause contained good balance between ionic conductivity, mechanical stability as well as alkaline stability. AEM was evaluated and polarization curve (current-voltage) along power density curve have been included in Figure 7. PK-QD48 AEM showed 0.81V OCV and 25.53 mW cm-2 maximum power density at 75.1 mA cm-2 current density. High OCV of the assessed AEM was attributed to the less fuel loss (reverse electro-osmosis), high membrane conductivity and better kinetics in alkaline medium. After alkaline treatment (2.0 M NaOH solution at 70 oC for about 720 hours), single cell performance of reported AEM was also assessed and negligible loss in OCV/ power density (~3%) was recorded. These information also ruled out any significant deterioration in membrane performance after sever alkaline treatment. Single cell performance of PK-QD-48 AEM, may be effected by several experimental conditions including MEA fabrication, temperature, and procedure of catalyst loading. Further at 60 oC, conductivity of PK-QD-48 AEM (4.3 × 10-2 S cm-1) is moderate, and may effects the single-cell performance. Previously reported AEMs also exhibited 0.69-0.95 V OCV, 2.1-23.0 mW/cm2 peak power density, and reported as potential candidate.28,55,56 Comparable electrochemical properties of PK-QD-48 AEM revealed its suitability for AEMFC applications. 4. CONCLUSION We synthesised well-phase separated PK copolymer via polycondensation reaction with controllable degree of acetylation, while comb shaped structure was architected by grafting of long alkyl chain containing DHDA. Nano-scale organised hydrophilichydrophobic domains results OH- conducting channels responsible for improved OH-



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mobility/conductivity along with good mechanical properties. In addition, combshaped structure was mitigating dimensional (low WU) and alkaline stability of the AEMs. Single cell AEMFC performance of PK-QD-48 AEM (0.81 V) OCV and 25.53 mW cm-2 maximum power density at 75.1 mA cm-2 current density) revealed its potential suitability for fuel cell applications. Improved performance and stability of the reported AEM has been attributed to the grafted alkyl chain length with well-phase separated polymer back bone. ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at www.acs.org. The supporting information provides instrumental details for 1

H NMR, FTIR spectra, Stress-strain curve, TGA, SEM, AFM and TEM (Section S1),

Water uptake, Ion exchange capacity, Swelling ratio, Hydroxide conductivity and ionic mobility included in Section S2, FT-IR spectra for different AEM (Figure. S1), Different degree of chloroacetylation (Figure. S2), Stress strain curve (Figure S3), TGA spectra (Figure. S4), 1H NMR spectra before and after alkaline stability test (Figure S5), and Degradation step involved in AEM (Figure S6). AUTHOR INFORMATION Corresponding Authors ∗E-mail: [email protected] Notes The authors declare no competing financial interest ACKNOWLEDGEMENTS Manuscript registration number: CSIR-CSMCRI – . The authors are grateful for financial support from Department of Science and Technology, Govt. of India, (project


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Table of Contents graphic

Comb shaped poly(arylene ether ketone) based anion exchange membrane with improved OHconductivity and alkaline stability.


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Scheme 1. Synthesis of PK-QD and PK-QT AEMs.



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Figure 1. 1H NMR spectra of (A) PK, (B) PK-CAL, (C) PK-QT-41 and (D) PK-QD54.


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Figure 2. SEM images: (A & C) surface and (B & D) cross-section of PK-QD-41 and PK-QT-41 respectively.

Figure 3. TEM (A & B) and AFM (C & D) images of PK-QT-41 and PK-QD-41 AEMs respectively.



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Figure 4. Tensile strength and elongation at break (%) for PK-QD-X (X= 41, 48, 54) and PK-QT-41 AEMs AEMs.


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Figure 5. Conductivity of PK-QD-X (X= 41, 48, 54) and PK-QT-41 AEMs at different temperatures.



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Figure 6. Deterioration in membrane conductivity (25 oC); of different AEMs, after treatment in 2.0 M NaOH at 70 oC for different time periods.

Figure 7. Fuel cell performance of developed PK-QD-48 AEM.


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Table 1. Degree of Chloroacetylation (DCAL) and Molecular Weights (Mn, and Mw) for PK and Different PK-CAL with Varied Composition. Code PK PK-CAL-41 PK-CAL-48 PK-CAL-54

PK-CAL-AlCl3 T (oC) Pristine 1.00:1.00:1.00 1.00:1.00:1.15 1.00:1.00:1.20

DCAL (%)

-40 45 50

-41 48 54

Mn (kDa) 68.6 66.6 64.2 63.6

Mw (kDa) 135.8 132.8 130.6 128.4

PDI 1.88 1.90 2.03 2.01

Table 2. Physicochemical Properties of PK-QD-X (X = 41, 48, 54) and PK-QT-1 AEMs.

IEC (meq/g) WU SR κm × 10-2c λ µOH- ×10-3 (%) (S cm-1) (cm2 s-1 V-1) Measureda Calculatedb PK-QD-41 1.38 1.34 10.21 6.82 2.25 4.23 0.56 PK-QD-48 1.66 1.64 16.32 7.64 2.94 5.52 0.64 PK-QD-54 2.02 1.98 21.57 8.40 3.66 6.05 0.68 PK-QT-41 1.44 1.40 26.42 10.60 1.86 11.11 0.46 b c a Calculated IEC by 1H NMR spectra; Measured IEC by back titration at 30 oC; Calculated at 30 oC. Code

Table 3. Comparison of Membrane Conductivity of Reported Membrane with Other Similar Membrane Reported in the Literature. Membrane reported AI-PES-16 PP-DMHDA-20 PPO-DMHDA-55 QA-FEKS IM-PFEKS PPO-TQA-1 PK-QD-54

κm (mS/cm) 32 19.2 35 22.3 17.1 13.4 36.6

Reference 16 53 18 17 17 54 Reported in this manuscript



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Comb shaped poly(arylene ether ketone) based anion exchange membrane with improved OHconductivity and alkaline stability.

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Poly(arylene ether ketone) Copolymer Grafted with Amine Groups

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