Polymers for use in alkaline ion conduction

Abstract

The invention relates to a series of novel polymers that are stable in highly alkaline media while at the same time able to conduct ions under such conditions. The present invention further relates to use of such polymers in the preparation of membranes that find use in alkaline water electrolysers.

Description

[0001] Polymers for use in alkaline ion conduction

[0002] Technical field

[0003] The invention relates to a series of novel polymers that are stable in highly alkaline media while at the same time able to conduct ions under such conditions. The present invention further relates to use of such polymers in the preparation of membranes that find use in alkaline water electrolysers.

[0004] Background

[0005] Alkaline water electrolysis (AWE) is a process wherein electrical energy is used to convert, or split, water into hydrogen and oxygen. It is a key technology for large-scale clean fuel (hydrogen) production powdered by renewable energy sources both to reduce cost of needed electricity, but also to obviate the need for fossil fuels. Thus, AWE is a key technology in a green economy transition. However, it is an energy-intensive process which still suffers from challenges for its wide-spread applicability within green energy industry.

[0006] In alkaline water electrolysis, the separator between the anode and the cathode compartments plays a vital role in the overall performance of the electrolysis cell. The separator enables the conduction of hydroxide ions from the cathode to the anode while preventing direct electrical contact between the electrodes and separates the formed gases.

[0007] A number of different materials, generally referred to as separators and / or membranes in the field, include diaphragms, such as current industrial standards under registered trademark Zirfon®, which are usually porous composite materials made from a porous polymer mesh where sufficient hydrophilicity to allow electrolyte uptake is provided by inclusion of Zr-based particles in the porous polymer network. Due to the porous structure of the separator the H2 crossover may reach critical levels during operation at part loads or at unbalanced pressure - which incurs a safety hazard due to highly exothermic reaction between hydrogen and oxygen. Careful tuning of the separator properties is therefore needed to balance the area specific resistance (ASR) versus the gas barrier characteristics. More recently, ion-solvating membranes formed by dense polymer membranes able to conduct hydroxide ions have appeared as an alternative to porous diaphragms. Ionsolvating membranes combine high ion conductivity of aqueous hydroxide solutions with good gas barrier properties. Membranes based on polybenzimidazole (PBI) show remarkably high ion conductivity that far exceeds 100 mS / cm in 20-30 wt.% KOH (M. R. Kraglund et al., D. Aili et al.) which allows for operation at current densities as high as 2000 mA cm-2at <1.9 V when combined with highly active electrodes. However, the stability of the most common PBI derivative, poly(2,2'-(m-phenylene)-5,5'- bibenzimidazole) (m-PBI) membranes is limited due to gradual carbon-backbone degradation, which result in severe structural membrane degradation.

[0008] In light of this, there is a strong unmet need for providing new materials able to function as separators in AWE which also provide for good hydroxide ion conductivity and good gas barrier properties while remaining stable for extended periods of time.

[0009] Summary

[0010] The present invention provides a solution to the above-mentioned limitations by providing polymers made from alkaline stable and / or resistant backbones. These polymers are largely hydrophobic in nature owing to the carbon backbone, but have been functionalized with pendent N-heterocycles, such as tetrazole and triazole groups to increase hydrophilicity and allow for electrode uptake and consequently hydroxide conductivity.

[0011] In one main aspect, the present disclosure provides for the use of a polymer for conduction of ions in an alkaline medium, said polymer comprising a polymer backbone and at least one pendant group, said pendant group having formula -X-R1; wherein X is an optional linker, and

[0012] R1is selected from: any tautomer thereof, or any deprotonated form thereof; wherein,

[0013] R1ais H, or C1-C10 alkyl, aryl or heteroaryl. Another aspect of the present invention relates to a polymer comprising a polymer backbone and at least one pendant group, said pendant group having formula -X-R1; wherein X is an optional linker, R1is selected from: any tautomer thereof, or any deprotonated form thereof; wherein

[0014] R1ais H, or H, or C1-C10 alkyl, aryl or heteroaryl; and the polymer backbone is derived from optionally substituted polyalkylene, polyphenylene, or polyisatin or copolymers thereof.

[0015] The present inventors have synthesized and characterized a diverse range of polymer backbones functionalized tetrazole pending groups. Noticeably, the pendant N- heterocycle groups are functionalized in such as way as to provide a free NH-group on the heterocycle. Importantly, the presence of a free NH group exemplified in the tetrazole or triazole moiety allows formation of anionic charges when submerged in alkaline electrolyte media, which is demonstrated to greatly enhance polarity, hydrophilicity and ion conductivity of the polymers. In addition, the examples demonstrate that tetrazoles and triazoles are unexpectedly very stable under harsh alkaline electrolysis conditions compared to other polar heterocycles.

[0016] By way of the examples, the present inventors illustrate that the polymers herein described can be formed into ion-solvating membranes that take up alkaline electrolytes efficiently and are also ion conducting, such as conducting hydroxide ions. The membranes display high hydroxide conductivity and can therefore support high ionic currents at small voltage losses in AWE cells, while providing a low hydrogen gas crossover. Furthermore, the membranes are able to maintain their performance in alkaline electrolysis cells for extended periods of several hundreds of hours despite the very harsh alkaline pH. The present invention thus overcomes one of the main challenges in the state of the art of ion solvating membranes.

[0017] Thus, other aspects of the present disclosure relates to membranes and electrolysis cells comprising the novel polymers of the present invention (directly, or indirectly in the form of ion-solvating membranes), as well as methods of manufacturing said novel polymers. Description of Drawings

[0018] Figure 1 :1H-NMR spectra of 3FBP, 3FBP-Br, 3FBP-CN and 3FBP-Te.

[0019] Figure 2: Thermogravimetric curves (A) and derivative of weight loss (B) of 3FBP, 3FBP-Br, 3FBP-CN and 3FBP-Te, respectively.

[0020] Figure 3: Electrolyte uptake and swelling of 3FBP-Te as recorded at room temperature in aqueous KOH with concentrations of 0 wt.% (pure water), 5 wt.%, 10 wt.%, 20 wt.% and 30 wt%.

[0021] Figure 4: Corresponding tensile strength and Young’s modulus of 3FBP and 3FBP-Te after equilibration at different KOH concentrations.

[0022] Figure 5: Room temperature through-plane ion conductivity of 3FBP-Te in 5-30 wt.% aqueous KOH.

[0023] Figure 6: Water electrolysis polarization curves for cells equipped with 3FBP-Te and Zirfon in 30 wt% tested at 40 °C (A), 60 °C (B) and 80 °C (C). The potenstiostatic electrochemical impedance spectrum (EIS) of the cell equipped with 3FBP-Te at 40-80 °C is shown in (D).

[0024] Figure 7: H2 in O2 levels and calculated hydrogen permeability at 40 °C (A) and 60 °C (B) during water electrolysis tests in 30 wt.% KOH for cells equipped with 3FBP-Te and Zirfon. For all depicted figures, the x-axis (or abscissa) represents Current density (mA cm-2)

[0025] Figure 8: FTIR spectral evolution of 3FBP-Te membrane after 160 h cell electrolysis tests.

[0026] Figure 9: Overview of preparation of poly(isatin biphenyl) polymers. The letters n and m designate the repeating monomeric units of the polymer.

[0027] Figure 10: (A)1H-NMR spectra of ISBP and ISBP-CNx; (B) representative1H-NMR peak assignment in ISBP-CN47; (C, D) FTIR of ISBP and ISBP-CNx

[0028] Figure 11 :1H-NMR (A) and FTIR (B) spectra of ISBP and the ISBP-Tex series. Thermogravimetric curves and derivative of weight loss (dW / dT) from the neat ISBP, ISBP-CN100 and ISBP-Te series are presented in (C).

[0029] Figure 12: Electrolyte uptake and swelling of the ISBP-Tex series recorded at room temperature in 30 wt.% aqueous KOH. Figure 13: Young’s modulus and tensile strength for tetrazole-containing ISBP polymers before and after equilibration in aqueous KOH with concentration of 30 wt.%.

[0030] Figure 14: Water electrolysis polarization curves of the cell equipped with ISBP-Te100 membrane at 40-80 °C (A), and comparison between ISBP-Te, Zirfon and pristine ISBP at 40 °C (B), 60 °C (C) and 80 °C (D). All testing was done with 30% by weight aqueous KOH as electrolyte.

[0031] Figure 15: H2 in O2 levels (A) and calculated hydrogen permeability (B) at 40 °C, 60 °C and 80 °C for water electrolysis tests in 30 wt.% aqueous KOH for cells equipped with ISBP-Te100 and Zirfon.

[0032] Figure 16: Water electrolysis performance evaluation process including polarization, hydrogen permeability and stability test for the cell equipped with ISBP-Te100. Polarization and EIS evaluation (0-98h), hydrogen permeability evaluation (98-170h) and electrolysis stability evaluation (170-500h).

[0033] Figure 17: FTIR (A) and stress-strain curves (B) of ISBP-Te100 membrane before and after 500 h electrolysis tests in 30 wt.% aqueous KOH.

[0034] Figure 18: FTIR spectra of of pristine SAN25 (A) and SAN30 (B) and the corresponding tetrazole derivatives STZ25 (A) and STZ30 (B)

[0035] Figure 19:1H NMR of pristine SAN25 (a) and SAN30 (b) in DMSO-de.

[0036] Figure 20:1H NMR of tetrazo I ated STZ25 (a) and its methylated version STz2sMe (b) in CDCh.

[0037] Figure 21 :1H NMR of tetrazolated STZ30 (a) and its methylated version STzsoMe (b) in CDCh.

[0038] Figure 22: Thermogravimetric curves (A) and derivative of weight loss (B) of SAN25 / SAN30 polymers and tetrazole derivatives STZ25 / STZ30.

[0039] Figure 23: DSC curves of pristine polymers SAN25 and SAN30 (A) as well as tetrazolated STZ25 and STZ30 (B). solid lines from the legend are drawn as guides for clarity.

[0040] Figure 24: XRD curves of pristine SAN25 / SAN30 and tetrazolated STZ25 / STZ30. X-ray diffraction (XRD) was carried on a powder diffractometer (PanAlytical, Aeris) for 20 angles between 5° and 50° with anode material of Cu Ka (A = 0.154 nm) at a scan rate of 5° min-1.

[0041] Figure 25: KOH electrolyte uptake (line) and area swelling (bars) of STZ25 (a) and STZ30 (b) at room temperature.

[0042] Figure 26: Temperature dependence of conductivity and area specific resistance (ASR) for STZ25 (A) and STZ30 (B) in 15 wt% aqueous KOH. Arrows relate each line to the relevant y-axis for clarity.

[0043] Figure 27: Time evolution of the cell voltage in long term test of cell with STZ25.

[0044] Figure 28: Polarization curves of cells equipped with STZ25 or Zirfon recorded at 60 °C in 15 wt% aqueous KOH after 24, 283 and 479 h for STZ25 and after 21 h for Zirfon (A). Nyquist plots of EIS measurements recorded after 24 h at 1.3V (B). Nitrogen corrected H2 in O2 levels (C) and calculated hydrogen permeability (D) of STz2sand Zirfon at 60 °C in 15 wt% aqueous KOH.

[0045] Figure 29: Scheme showing the stability-tested azole derivatives (a-c) and concentration time dependence (d) derived from the1H-NMR data. More specific details are specified in Example 10. In the plot, the lines for Tr-1 , Tr-2, Tr-3, Tt-1 , Tt-2, Tt-3, Blm-1 , Blm-2 are all following the same line at constant 100%.

[0046] Figure 30. Water electrolysis polarization curves of cells equipped with membranes comprising crosslinked STz25 and STz30, with varying degrees of crosslinking. The term “XL” indicates the degree of crosslinking in %. The “STz25_original” sample had membrane of non-crosslinked STz25. PPS indicates a sample reinforced with a polyphenylene sulfide (PPS) mesh. The tests with STz25 membranes were performed at 80 °C, and the test with the STz30_XL4_PPS membrane was performed at 90 °C.

[0047] Definitions

[0048] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in art to which the subject matter herein belongs. As used herein, the following definitions are supplied to facilitate the understanding of the present invention.

[0049] The term “comprise” is generally used in the sense of include, that is to say permitting the presence of one or more features or components. In addition, as used herein, the language "comprising" can include analogous embodiments described in terms of “consisting of” and / or “consisting essentially of”.

[0050] As used herein, the term "and / or" used in a phrase such as "A and / or B" herein is intended to include "A and B", "A or B", "A", and "B".

[0051] As used herein, the singular forms "a", "an" and "the" include also the plural references unless the context clearly dictates otherwise. Similarly, terms such as “one or more” or “at least one” include both the singular and plural form of the respective feature.

[0052] “A membrane” as described herein refers to a material that forms or is used as a barrier between two compartments that is semi-permeable. “Semi-permeable” means that the membrane allows for certain substances, molecules, ions or particles to pass through the membrane under certain conditions, while preventing other substances, molecules, ions or particles to pass through the membrane. For example, a membrane refers to the separator between cathode and anode compartments in an electrolysis cell which prevents flow of electrical current between the compartments but allows transport of ionic charge carriers, needed to close the circuit. The membrane acting as separator prevents or significantly limits the passage of gas or bubbles. Membranes to act as separators in aqueous electrolysis applications, such as alkaline water electrolysis (AWE), may be made of polymeric materials or composite polymeric materials such commercially available Zirfon®.

[0053] “Electrolyte” as used herein refers to an ionically conductive liquid solution. Electrolytes may be aqueous or non-aqueous, but are preferably aqueous within the present invention. Also preferably the aqueous solutions comprise a significant amount of hydroxide ions such as in the form of KOH.

[0054] Detailed description

[0055] The present disclosure encompasses a set of polymers and membranes specifically engineered for use in alkaline water electrolysis systems. These materials exhibit enhanced chemical stability, improved ion conductivity, and increased resistance to degradation under alkaline conditions. The combination of these features results in superior electrolysis performance, ultimately leading to increased efficiency and longevity of electrolysis cells. An embodiment of the present disclosure is a polymer comprising a polymer backbone and at least one pendant group, said pendant group having formula -X-R1; wherein

[0056] X is an optional linker, and R1is selected from: t polymer backbone does not comprise a base-labile group, such as ester or ether groups.

[0057] In one embodiment of the present disclosure, the polymer comprises or consists of formula (I): formula (I); wherein R1is selected from: any tautomer thereof, or any deprotonated form thereof;

[0058] R1ais H, or C1-C10 alkyl, aryl or heteroaryl;

[0059] A is a C1-C5 alkanediyl group or an aromatic or heteroaromatic group, optionally substituted with one or more, identical or different Ragroups;

[0060] A', B and B’ is each individually selected from a bond, a C1-C5 alkanediyl group, and an aromatic or heteroaromatic group, each of which may optionally be substituted with one or more, identical or different Rbgroups;

[0061] X is an optional linker selected from a C1-C5 alkanediyl group, optionally substituted with one or more identical or different, Rxgroups;

[0062] Ra, Rband Rxare each individually selected from: H, halogen, hydroxy, C1-C10 alkyl and C1-C5 haloalkyl; and n is an integer individually selected from 1 to 60000, and m is an integer selected from 0 to 60000. In one embodiment, the polymer comprises or consists of formula (la): wherein R1is selected from: any tautomer thereof, or any deprotonated form thereof;

[0063] R1ais H, C1-C10 alkyl, aryl or heteroaryl;

[0064] A is a C1-C5 alkanediyl group, or an aromatic or heteroaromatic group, optionally substituted with one or more, identical or different Ragroups;

[0065] B is a bond, a C1-C5 alkanediyl group, or an aromatic or heteroaromatic group, optionally substituted with one or more, identical or different Rbgroups;

[0066] X is an optional linker;

[0067] Ra, Rband Rxare each individually selected from: H, halogen, hydroxy, C1-C10 alkyl and C1-C5 haloalkyl; and n is an integer from 1 to 60000.

[0068] Preferably within the present disclosure, A is selected from the group consisting of: wherein Rb1, Rb1’, Rb2and Rb3are each independently selected from H, halogen, hydroxy, C1-C10 alkyl, and C1-C5 haloalkyl; y2 and y3 are each independently an integer from 0 to 3; and

[0069] * denotes the attachment of -X-R1. Also preferably, wherein A’, B and / or B’ are each individually selected from the group consisting of: wherein Rb1, Rb1’, Rb2and Rb3are each independently selected from H, halogen, hydroxy, C1-C10 alkyl and C1-C5 haloalkyl; y2 and y3 are each independently an integer from 0 to 4.

[0070] In one embodiment, Rb1, Rb1’, Rb2and Rb3are H.

[0071] In one embodiment of the present disclosure, the polymer backbone is a homopolymer or copolymer of an optionally substituted ethylene, phenylene, and / or isatin, In one embodiment the polymer backbone is derived from optionally substituted polyalkylene, polyphenylene, poly(arylene), poly(arylene sulfide), poly(arylene alkylene), or polyisatin or copolymers thereof.

[0072] In one embodiment of the present disclosure, the polymer comprises or consists of any one of formulas Ila, lib, He, lld-1, lld-2, or lld-3: wherein R1and X are as defined for formula (I) and (la) ml, n2, n3, n4, n4’, and n4” are each an integer individually selected from 1 to 60000, n1 and m3 are each an integer individually selected from 0 to 60000; and q, q’, q”, and q’” are in each instance an integer individually selected from 0 to 4. In some embodiments, at least one instance of q, q’, q”, and q’” is not 0.

[0073] In one embodiment, the polymer comprises or consists of formula (Ila), or comprises or consists of formula (lib), or comprises or consists of formula (He), or comprises or consists of formula (lld-1), or comprises or consists of formula (lld-2), or comprises or consists of formula (I Id-3), or any combination of the foregoing.

[0074] In one embodiment, the polymer comprises or consist of formula (Ila) as described herein. In one embodiment, the polymer comprises or consist of formula (lib) as described herein. In one embodiment, the polymer comprises or consist of formula (He) as described herein. In one embodiment, the polymer comprises or consist of formula (I Id-1 ), (lld-2), or (I Id-3), as described herein or any combination of the foregoing.

[0075] In one embodiment of the present disclosure, R1ais H.

[0076] In one embodiment of the present disclosure, X is absent.

[0077] In one embodiment of the present disclosure, X is -(CH2)I-S-, such as -(CH2)-, -(CH2)2- , -(CH2)3-, -(CH2)4-, or -(CH2)S-, wherein one methylene may be replaced with -O- or by an aryl or an heteroaryl group, such as a phenylene group.

[0078] In one embodiment of the present disclosure, R1isHorany tautomer thereof or any deprotonated form thereof. In one embodiment of the present disclosure, R1is or any tautomer thereof or any deprotonated form thereof.

[0079] In some embodiments of the present disclosure, the polymer comprises or consists of formula (Illa): wherein n1 is an integer from 0 to 60000 and ml is an integer from 1 to 60000.

[0080] In one embodiment, n1 is not 0.

[0081] In some further embodiments of the present disclosure, the polymer comprises or consist of formula (111 b) or (lllc): (lllc); wherein n2 or n3 are each independently an integer from 1 to 60000 and m3 is an integer from 0 to 60000. In one embodiment m3 is not 0. In some embodiments of the present disclosure, the polymer comprises or consists of any one of formulas (llld-1), (llld-2), or (llld-3) or a combination thereof; wherein n4, n4’ and n4” are on each instance an integer from 1 to 60000 and q, q’, q”, and q’” are on each instance an integer individually selected from 0 to 4. Preferably, at least one instance of q, q’, q” or q’” is not 0.

[0082] In some embodiments of the present disclosure, (n1+m1) is from 1 to 60000 and / or the ratio of n1 :m1 is from 0.99:0.01 to 0.01 :0.99.

[0083] In one embodiment, n2 is from 1 to 60000.

[0084] In one embodiment (n3 + m3) is from 1 to 60000 and / or the ratio of n3:m3 is from 0.99:0.01 to 0.01 :0.99 and / or n4 is from 1 to 60000.

[0085] In one embodiment of the present disclosure, the average molecular weight (Mw) of the polymer is from 10,000 g / mol to 3,000,000 g / mol. The average molecular weight may be determined using known techniques in the art, such as size exclusion chromatography in comparison with reference standards, or by use of light scattering techniques.

[0086] In one embodiment, when the polymer comprises any one of formulas (llld-1), (llld-2) or (llld-3) or any combination thereof, the polymer may contain azide groups (-N3) in some of the aromatic rings.

[0087] In one embodiment of the present disclosure, the polymer is suitable for use in water electrolysis, such as alkaline water electrolysis.

[0088] In particular embodiments, the suitable for use refers to the polymer, or a membrane comprising said polymer having an in situ operation stability of at least 100 hours. In some embodiments, the polymer of the present disclosure has an in situ stability during operation of more than 100 hours, such as more than 200 hours, such as more than 300 hours, such as more than 400 hours, such as more than 500 hours, such as more than 600 hours, such as more than 700 hours, such as more than 800 hours, such as more than 900 hours, such as more than 1000 hours.

[0089] In one embodiment, the polymer is suitable for water electrolysis such as when performed using a gap cell, or a zero-gap cell, such as using an electrolyte and / or alkaline medium characterized by a hydroxide ion concentration between 1 M and 12 M, such as from KOH. As such, the present disclosure also relates to the use of a polymer for conduction of ions in an alkaline medium, said polymer being as defined herein, more specifically said polymer comprising a polymer backbone and at least one pendant group, said pendant group having formula -X-R1; wherein

[0090] X is an optional linker, and

[0091] R1is selected from: ; any tautomer thereof, or any deprotonated form thereof; wherein,

[0092] R1ais H, or C1-C10 alkyl, aryl or heteroaryl.

[0093] The thermal stability and / or mechanical stability of the polymers of the present disclosure (including membranes comprising said polymers) under AWE operation at elevated temperature (for example at temperatures above 60 °C, e.g. 80 °C or 90 °C), can be increased by introducing crosslinking between the polymer chains. The examples presented herein demonstrate that crosslinking of the polymers of the present disclosure increases the thermal stability and mechanical during in situ operation under AWE conditions at temperatures above 60 °C as compared to noncrosslinked equivalents.

[0094] “Crosslinking”, as known in the art, is a reaction that connects one polymer chain to another. Crosslinking results from the reaction between sites or groups on polymer molecules that forms a region that connects at least two polymer chains to one another, i.e. a region from which at least four chains emanate. The small region connecting the at least two polymer chains is referred to as a crosslink or a crosslinking point and it may be an atom, a group of atoms, or a number of branch points connected by bonds, groups of atoms, or oligomeric chains.

[0095] Thus, in some embodiments, the polymer as defined herein is crosslinked, i.e. the polymer comprises at least one or more crosslinks. In a preferred embodiment, the crosslink is a covalent crosslink formed by a covalent structure.

[0096] Crosslinking of the polymers according to the present disclosure may be performed using crosslinking reagents and conditions known to the skilled person. Multifunctional reactive molecules (e.g. a molecule with two or more reactive sites) able to form covalent bonds between at least two reactive groups in two separate polymer chains can be used for this. For example, in the polymers according to the present disclosure, a crosslink may be formed between two tetrazole groups from separate polymer chains, between two triazole groups from separate polymer chains, or between a tetrazole group of a first polymer chain and a triazole group of a second and separate polymer chain.

[0097] In one embodiment, the polymer comprises a covalent crosslink between two tetrazole groups. In one embodiment, the crosslink comprises or consists of an optionally substituted hydrocarbon chain, such as a Ci-Cs hydrocarbon chain. In some embodiments, the crosslink comprises or consists of an optionally substituted alkanediyl group.

[0098] In one embodiment, the crosslink comprises or consist of -(CH2)t-, wherein t is an integer from 1 to 8, such as 2 to 8, such as 4 to 8.

[0099] In one embodiment, the polymer comprises formula (Illa), wherein n1 is an integer from 0 to 60000 and ml is an integer from 1 to 60000, and the polymer comprises one or more covalent crosslinks between two tetrazole groups of separate polymer chains and the crosslink comprises or consists of -(CH2)t-, wherein t is an integer from 1 to 8, such as 2 to 8, such as 4 to 8.

[0100] In one embodiment, the crosslink is -(CH2)e-. In one embodiment, the degree of crosslinking is 10% or less. In one embodiment, the degree of crosslinking is 2% to 10%, preferably 4% to 10%, more preferably 5% to 10%.

[0101] The degree of crosslinking may be estimated as the amount of possible reactive sites or moieties in the original polymer that have effectively been crosslinked. For example, the degree of crosslinking can be calculated as the percentage of tetrazole and / or triazole groups in the original polymer that have reacted through the crosslinking reaction. Calculation of the degree of crosslinking is elaborated in the examples herein.

[0102] In one embodiment of the present disclosure, the polymer as defined herein is comprised in a membrane, such as a membrane having a thickness of 10 pm to 1 mm.

[0103] Membranes comprising the herein defined polymers are thus also within the scope of the present disclosure.

[0104] In one embodiment, the membranes comprising the novel polymers are characterized by a thickness of such as 10 pm to 20 pm, such as 20 pm to 50 pm, such as 50 pm to 75 pm, such as 75 pm to 100 pm, such as 100 pm to 120 pm, such as 120 pm to 140 pm, such as 140 pm to 160 pm, such as 160 pm to 180 pm, such as 180 pm to 200 pm, such as 200 pm to 250 pm, such as 250 pm to 300 pm, such as 300 pm to 350 pm, such as 350pm to 400 pm, such as 400 pm to 450 pm, such as 450 pm to 500 pm, such as 500 pm to 550 pm, such as 550 pm to 600 pm, such as 600 pm to 650 pm, such as 650 pm to 700 pm, such as 700 pm to 750 pm, such as 750 pm to 800 pm, such as 800 pm to 850 pm, such as 850 pm to 900 pm, such as 1 mm.

[0105] Preferably, the polymer as defined herein is comprised in a membrane having a thickness of 100 pm to 500 pm, such as 100 pm to 250 pm, such as 150 pm.

[0106] The membranes described herein are known in the art as ion-solvating membranes or ISMs. ISMs are polymeric membranes, which when imbibed with an electrolyte such as aqueous KOH, swell and form a homogeneous ternary electrolyte system of polymer / water / KOH. Ion-solvating membranes utilize the uptake and presence of an aqueous alkaline electrolyte to achieve ionic conductivity, and are not necessarily intrinsic hydroxide conductors, but unlike diaphragms they are dense, non-porous and can be prepared as thin as other polymeric membranes.

[0107] In one embodiment of the present disclosure, the membrane is thus a non-porous membrane. Non-porous membranes are defined as not having a pronounced porosity, as otherwise found in commercially available Zirfon®. In the membranes of the present invention, the porosity is from 0.01 to 75% e.g., as measured by, gas pycnometer, mercury intrusion, or by weighing with or without a filing substance.

[0108] In some embodiments, the membrane according to the present disclosure may be combined with inorganic materials deposited within the matrix, as known in the art in the field of electrolysis separators e.g Zirfon®. For example, the membrane according to the present disclosure may in one embodiment be combined with ceramic particles comprising or consisting of ceramic oxides.

[0109] In one embodiment of the present disclosure related to the use in electrolysis, the membrane is in contact with or immersed in an alkaline electrolyte aqueous solution during operation, such as an electrolyte characterized by at least one or more of:

[0110] • hydroxide ion concentration of 0.1 to 12 M,

[0111] • pH of the electrolyte is 12 or higher, such as 13 or higher, such as 14 or higher,

[0112] • hydroxide concentration of 0.5 to 40 % (w / w), and

[0113] • temperature between 10 °C and 150 °C.

[0114] When in contact with the electrolyte, the membranes of the present invention swells by uptake of the electrolyte. The degree of swelling impacts the performance of ion conduction and ultimately in electrolysis.

[0115] In one embodiment of the present disclosure, the membranes as defined herein are characterized by a swelling ratio (SR) of 10 % to 60 %, such as an SR of 10 to 15%, such as of 15 to 20 %, such as of 20 to 25 %, such as of 25 to 30 %, such as of 30 to 35 %, such as of 35 to 40 %, such as of 40 to 50 %, such as of 50 to 60 %.

[0116] In one embodiment, the membrane comprises a crosslinked polymer as defined herein is characterized by swelling ratio (SR) of 10% to 200%, such as 30% to 200%, such as 50% to 200%, such as 70% to 200%, such as a Ell of 100% to 200%.

[0117] Calculation of swelling ratio is elaborated in the examples herein.

[0118] In one embodiment of the present disclosure, the membranes as defined herein are characterized by an electrolyte uptake (Ell) of 1 % to 70 %, such as an Ell of 1 to 5%, such as of 5 to 10 %, such as of 10 to 20 %, such as of 20 to 30 %, such as of 30 to 40 %, such as of 40 to 50 %, such as of 50 to 60 %, such as of 60 to 70 %. In one embodiment of the present disclosure, the membranes as defined herein are characterized by an electrolyte uptake (Ell) of 1 % to 120% by weight, such as an Ell from 70% to 80%, such as of 80% to 90%, such as of 90% to 100%, such as of 100% to 110%, such as of 110% to 120%.

[0119] In one embodiment, the membrane as defined herein has an electrolyte uptake between 30% to 70%.

[0120] In one embodiment, the membrane comprises a crosslinked polymer as defined herein is characterized by an electrolyte uptake (Ell) of 1 % to 200%, such as 30% to 200%, such as 50% to 200%, such as 70% to 200%, such as an Ell of 100% to 200%.

[0121] Calculation of electrolyte uptake is elaborated in the examples herein.

[0122] In one embodiment of the present disclosure, the membrane further comprises a reinforcement layer. The reinforcement layer can add mechanical stability to the membrane when it is swelled by the electrolyte. In one embodiment, the reinforcement layer is a mesh made of a polymeric material. In one embodiment, the reinforcement layer is a mesh comprising of consisting of polyphenylene sulfide (PPS).

[0123] Also within the scope of the present disclosure is an alkaline electrolysis cell comprising: a) an alkaline electrolyte aqueous solution; and b) an ion-solvating membrane as described herein comprising a polymer, wherein the polymer is as defined herein; further wherein said membrane is in contact with or immersed in the alkaline electrolyte aqueous solution.

[0124] During operation of the alkaline electrolysis cell, the electrolyte is characterized by at least one or more selected from:

[0125] • a hydroxide ion concentration between 0.1 M and 12 M,

[0126] • a pH of 12 or higher, such as 13, such as 14, such as 15 or higher,

[0127] • a hydroxide ion concentration between 0.5 wt% and 40 wt% , and

[0128] • a temperature between 10 °C and 150 °C.

[0129] The alkaline electrolysis cell may in some embodiments be an alkaline water electrolysis cell, and may during operation further comprise an anode and a cathode connected to an electrical power source. In some embodiments of the present disclosure, the ionic conductivity of the electrolyte through the membrane is of 10 mS / cm to 200 mS / cm.

[0130] In some embodiments the ionic conductivity of the electrolyte, through the membrane is between 10 mS / cm to 200 mS / cm, such as 10 to 20 mS / cm, such as 20 to 30 mS / cm, such as 30 to 40 mS / cm, such as 40 to 50 mS / cm, such as 50 to 60 mS / cm, such as 60 to 70 mS / cm, such as 70 to 80 mS / cm, such as 80 to 100 mS / cm, such as 100 to 120 mS / cm, such as 120 to 140 mS / cm, such as 140 to 160 mS / cm, such as 160 to 180 mS / cm, such as 180 to 200 mS / cm.

[0131] In one embodiment, the ionic conductivity of the electrolyte, through the membrane is between 60 mS / cm to 200 mS / cm e.g. as measured at room temperature.

[0132] In some embodiments, membrane is in contact with or immersed in an alkaline electrolyte aqueous solution during operation characterized by a concentration of hydroxide ions of 5% to 40% by weight, such as 5% to 30% by weight, such as 5% ,10%, 15%, 20%, 25% or 30%.

[0133] The tetrazole-based polymers of the present invention are manufactured by utilizing well-established organic synthesis, in particular such as [3+2] cycloadditions between nitrile groups and azide groups to synthesize tetrazole functionalized polymers.

[0134] The triazole-based polymers of the present invention may be manufactured by utilizing well-established organic synthesis, in particular such as [3+2] cycloadditions between alkyne groups and azide groups, to synthesize polymers functionalized with 1 ,2,3 triazole moieties.

[0135] One embodiment of the present disclosure is thus a method of manufacturing a tetrazole- functionalized polymer as described herein, comprising the sequential steps of:

[0136] Step A1 : Providing a polymer comprising nitrile groups; and

[0137] Step A2: Reacting said provided polymer with a source of azide anions to conduct a [3+2] cycloaddition with the nitrile groups, thereby forming at least one tetrazole; and

[0138] Step A3: isolating the product obtained in step A2 to obtain a polymer. In one embodiment, the polymer of step A1 comprises or consists of any one of formulas: wherein ml, n2, n3, n4, n4’, and n4” are each an integer individually selected from 1 to

[0139] 60000, n1 and m3 are each an integer individually selected from from 0 to 60000; and q, q’, q”, and q’” are on each instance an integer individually selected from 0 to 4. In one embodiment of the present disclosure, the reaction conditions in step A2 are performed with an alkali metal salt of an azide anion, such as sodium or potassium azide.

[0140] In one embodiment of the present disclosure, step A2 is performed in an organic solvent, such as selected from DMF, N-methylpyrrolidone (NMP), and DMSO, preferably DMF.

[0141] In one embodiment of the present disclosure, step A2 is performed from about 40 °C to about 130 °C.

[0142] In one embodiment of the present disclosure, step A2 is performed in the presence of a base such as a carbonate salt, a hydroxide or an ammonium salt.

[0143] In one embodiment, the method further comprises a step A4, wherein the polymer obtained in step A3 is crosslinked. In one embodiment, step A4 comprises contacting the polymer with an hydrocarbon comprising at least two halogens, preferably two bromine moieties. In a preferred embodiment of the present disclosure, the at least two halogens are positioned at the primary carbon positions of a non-branched or linear hydrocarbon, more preferably one halogen at each distal end of a non-branched or linear hydrocarbon. In one embodiment, step A4 comprises contacting the polymer with a Ci-Cs dibromoalkanediyl, such as 1 ,6-dibromohexane, 1 ,5-dibromopentane or 1 ,4- dibromobutane. In one embodiment, step A4 is performed in a suitable solvent, such as DMF, N-methylpyrrolidone (NMP), or DMSO, or mixtures thereof, preferably DMF. In one embodiment, step A4 is performed in the presence of a base, such as sodium hydride (NaH).

[0144] Items

[0145] 1 . A polymer comprising a polymer backbone and at least one pendant group, said pendant group having formula -X-R1; wherein

[0146] X is an optional linker,

[0147] R1is selected from: any tautomer thereof, or any deprotonated form thereof; wherein,

[0148] R1ais H, C1-C10 alkyl, aryl, or heteroaryl; and the polymer backbone is derived from optionally substituted polyalkylene, polyphenylene, poly(arylene), poly(arylene sulfide), poly(arylene alkylene), or polyisatin or copolymers thereof. The polymer according to item 1 , wherein the polymer backbone is a homopolymer or copolymer of one or more of a group selected from: wherein

[0149] Rb1, Rb1’, Rb2and Rb3are each independently selected from H, halogen, hydroxy, C1-C10 alkyl and C1-C5 haloalkyl; y2 and y3 are each independently an integer from 0 to 4. The polymer according to any one of the preceding items, wherein the polymer comprises or consists of any one of formulas: wherein

[0150] R1ais H, or C1-C10 alkyl, aryl or heteroaryl,

[0151] X is an optional linker, ml , n2, n3, n4, n4’, and n4” are each an integer individually selected from 1 to

[0152] 60000, n1 and m3 are each an integer individually selected from 0 to 60000; and q, q’, q”, and q’” are in each instance an integer individually selected from 0 to 4; and at least one instance of q, q’, q” and q’” is not 0.

[0153] 4. The polymer according to any one of items the preceding items, wherein X is absent or a C1-C5 alkanediyl group.

[0154] 5. The polymer according to any one of the preceding items, wherein R1is

[0155] Hor any tautomer thereof or any deprotonated form thereof.

[0156] 6. The polymer according to any one of items 1 to 4, wherein R1is H or , or any tautomer thereof or any deprotonated form thereof. . The polymer according to any one of items 1 to 5, wherein the polymer comprises or consists of any one of formulas Illa, lllb, lllc, llld-1 , llld-2, or llld-3: wherein ml , n2, n3, n4, n4’, and n4” are each an integer individually selected from 1 to 60000, n1 and m3 are each an integer individually selected from 0 to 60000; and q, q’, q”, and q’” are in each instance an integer individually selected from 0 to 4; and at least one instance of q, q’, q” and q’” is not 0. . A membrane comprising a polymer according to any one of items 1 to 7.. The membrane according to item 8, wherein the membrane further comprises an alkaline electrolyte aqueous solution. 0. The membrane according to any one of items 8 to 9, wherein the alkaline electrolyte aqueous solution is characterized by a hydroxide concentration between 0.5 wt% and 40 wt%. 1. The membrane according to any one of items 8 to 10, wherein the membrane has an electrolyte uptake between 30% and 70% by weight. 2. The membrane according to any one of items 8 to 12, wherein the ionic conductivity through the membrane is from 60 mS / cm to 200 mS / cm at room temperature. 3. Use of a polymer according to any one of items 1 to 7, or a membrane according to any one of items 8 to 12, for conduction of ions in an alkaline medium. 4. An alkaline electrolysis cell comprising: a) an alkaline electrolyte aqueous solution; and b) the membrane according to any one of items 8 to 12; wherein said membrane is in contact with or immersed in the alkaline electrolyte aqueous solution.

[0157] 15. The alkaline electrolysis cell according to item 14, wherein the alkaline electrolyte aqueous solution is as an aqueous alkaline solution characterized by at least one or more selected from: a hydroxide ion concentration between 0.1 M and 12 M, a pH of 12 or higher, such as 13, such as 14, such as 15 or higher, a hydroxide ion concentration between 0.5 wt% and 40 wt% , and a temperature between 10 °C and 120 °C. Examples

[0158] Example 1 : Preparation of poly(arylene-alkylene) polymers

[0159] Materials and Methods

[0160] Materials. 1 ,1 ,1 -Trifluoroacetone (97%), biphenyl (99%), trifluoromethanesulfonic acid (TFSA, 98%), trifluoroacetic acid (TFA, 98%), trifluoroacetic anhydride (TFAA, 99%), copper(l) cyanide (CuCN, 99%), bromine (99%), ammonium chloride (NH4CI, 99%), sodium azide (NalXh, 99%) ethylenediaminetetraacetic acid sodium salt (EDTA-Na2, 99%), sodium hydroxide (NaOH, 97%), dichloromethane (DCM, 99%), THF (tetrahydrofuran), 1-methyl-2-pyrrolidone (NMP, 99%), dimethylformamide (DMF, 99%), deuterated chloroform (CDCI3, 99 atom% D) and deuterated dimethyl sulfoxide (DMSO- d6, 99 atom% D) were obtained from Sigma Aldrich. Potassium hydroxide (KOH, 88%) and methanol (99%) were purchased from VWR Chemicals. Iron powder (99%) was obtained from Fluka. Zirfon Perl UTP 500 was purchased from Agfa. Nickel foam (pore size 450 pm, thickness 1.6 mm) was obtained from Alantum. NMP and DMF were dried over 4 A molecular sieves prior to use. Other chemicals were used as received. The aqueous KOH solutions were prepared by dissolving KOH pellets in milliQ water, and the concentration was determined by density measurements and compared with literature data (W. M. Haynes).

[0161] Synthesis of poly[[1,1'-biphenyl]-4,4'-diyl(1,1,1-trifluoropropan-2-yl)] (3FBP): To a 1000 mL nitrogen purged dry three-neck round-bottom flask, 1 ,1 ,1-trifluroacetone (24.6 g, 0.22 mol) and biphenyl (30.8 g, 0.20 mol) were dissolved in 425 mL DCM and stirred for 30 min in an ice-cooled bath. TFSA (85 mL, 1.06 mol) was thereafter added at the rate of 5 drops per second from an addition funnel. The reaction mixture was stirred at room temperature for 28 h. 8 mL TFAA was added and the viscos mixture was stirred for another 2 h, and thereafter poured into methanol. White fibers formed instantly, which were isolated by filtration and washed thoroughly with methanol. After drying under vacuum for 10 h at 60 °C, 3FBP was obtained as white fibers with a yield of 50.22 g (97%: Yield weight / (Theoretical weight- produced water weight))). Bromination of 3FBP (3FBP-Br): 3FBP (20 g, 80.65 mmol) was dissolved in 500 mL DCM in a double-neck round-bottom flask equipped with a condenser. An aqueous NaOH trap was connected to the top of the condenser top to absorb evolved acidic gas. Iron powder (5.23 g, 93.73 mmol) and bromine (30 mL, 1.17 mol) were then added to the homogenous solution. The reaction mixture was kept stirring at reflux 8h. The solution was poured into methanol, resulting in instant precipitation of gray-white fiber of brominated 3FBP (3FBP-Br). The precipitate was isolated by filtration, thoroughly washed with methanol and water and obtained in 34 g yield after drying. Based on the weight increase, the bromination degree of 3FBP was roughly estimated as 200% for next step reaction calculation.

[0162] Substitution of bromine with nitrile (3FBP-CN): To a 250 mL three-neck round-bottom flask equipped with a magnetic stirrer, condenser and nitrogen inlet, 3FBP-Br (2 g, 4.93 mmol) was dissolved in 50 mL NMP at 80 °C. After the complete dissolution, CuCN (1.4 g, 15.56 mmol) was added and the solution was stirred for 72 h at 166 °C. The solution was cooled to room temperature and poured into water and washed with aqueous EDTA- Na2 solution to remove the copper ions. The nitrile functionalized 3FBP (3FBP-CN) was obtained in 1.26 g as a brownish powder after rinsing in water and drying under vacuum at 80 °C (63% yield).

[0163] Conversion of nitriles to tetrazoles (3FBP-Te): To a 100 mL round-bottom flask equipped with a condenser, 3FBP-CN (1.2 g, 4.03 mmol) was dissolved in 24 mL DMF at 80 °C. NalXh (0.86 g, 13.3 mmol) and NH4CI (0.70 g, 13.3 mmol) were added, and the temperature was increased to 130 °C. After keeping the reaction string for 48 h, the solution was poured into water, and the pH was adjusted to around 4 to precipitate the polymer. The precipitate was washed in water until neutral pH, and the tetrazole functionalized 3FBP (3FBP-Te) was obtained in 1.4 g as a deep brownish powder after filtration and drying at 80 °C.

[0164] Gel permeation chromatography (GPC): The molecular weight ( / Wn) and dispersity (£>) of pristine 3FBP was determined by size exclusion chromatography (SEC) in THF, using an OMNISEC from Malvern Instrument with a refractive index (Rl) detector. A TGuard (Org. Guard Col 10 x 4.6 mm) was used as guard column, two T6000M (General mixed Org. 300 x 8.0 mm) were used as analytical columns. Eight polystyrene standards (Mp= 3,530,000 and 184,000 g / mol from Polymer Standards Service, Mp= 1 ,184,000 g / mol from Polymer Laboratories, Mp= 93,800 and 9,000 g / mol from Sigma-Aldrich, Mp= 35,000 g / mol from Waters and Mp= 17,500 and 3,000 g / mol from Polysciences Inc.) were used for calibration. 3FBP was firstly dissolved in THF for 24 hours before the measurement and was filtered through a 0.2 urn diameter PTFE filter before the injection. The analyses was run at 35 °C with a flow rate of 1 mL / min.

[0165] Inherent viscosity (rjinh): Inherent viscosity (r|inh) values were determined as 0.83 dL / g by using a Ubbelohde suspended level viscometer with polymer concentration 0.5 g / dL in N-methylpyrrolidone (NMP) at 21 °C.

[0166] Infrared spectroscopy: Fourier transform infrared (FTIR) spectra were recorded using a PerkinElmer Spectrum TWO equipped with an attenuated total reflectance accessory in the IR frequency range from 4000 to 500 cm-1.

[0167] NMR:1H NMR spectra were recorded using a Bruker Avance 400 MHz or spectrometer, using deuterated dimethyl sulfoxide (DMSO-cfe) and chloroform (CDCh) as solvent. XPS and XRD: X-ray photoelectron spectroscopy (XPS) was conducted in an ultrahigh vacuum chamber with an ESCALAB 250Xi and a non-monochromatized Al Ka X-ray source (SPECS XR 50). X-ray diffraction (XRD) was carried on a powder diffractometer (PanAlytical, Aeris) for 20 angles between 5° and 50° with anode material of Cu Ka (A = 0.154 nm) at a scan rate of 5° min-1.

[0168] Thermogravi metric analysis (TGA) was carried out using a TA Instruments TGA Q500. The samples were first dried at 60 °C under vacuum overnight. Prior to analysis, the samples were kept at 120 °C during 20 min in the instrument to evaporate traces of water. The measurements were then performed under nitrogen atmosphere from 50 to 600 °C at a heating rate of 10 °C min-1.

[0169] Results

[0170] Base 3FBP polymer was produced with a Mwof 10.9 x 104and PDI of 1.28. The1H NMR spectrum of 3FBP and peak assignments are shown in Figure 1b, with clear peak at 7.4 and 7.6 ppm corresponding the arylene protons and a peak at 2.0 ppm corresponding to the methyl group of the alkylene linkage.

[0171] After bromination to obtain 3FBP-Br, a new peak in the1H NMR appeared with chemical shift 8.1 ppm corresponding to the proton atoms adjacent to bromine. Upon substitution with nitrile to obtain 3FBP-CN, poorly resolved aromatic region in the1H-NMR due to the conjugation involving nitrile groups was observed (Figure 1). Introduction of the tetrazole moiety after reaction of 3FBP-CN with an sodium azide was confirmed by a lower chemical shift of the aromatic protons due to the introduction of electron withdrawing tetrazole and the appearance of a new peak at chemical shift 6.23 ppm corresponding to the proton in the tetrazole ring (Figure 1).

[0172] XPS was used to determine the composition of each of the polymers. In order to determine bromination degree of the 3FBP-Br, fluorine was used as internal standard for normalization. The fractional concentration of the different elements is presented in Table 1 , where the bromination degree was calculated as 166%. The compositions were calculated from the peak deconvoluted spectra. The deconvoluted C1s result of 3FBP- Br in shows a new peak around 268.1 eV, which is due to the presence of C-Br bond. In addition, only one set of spin orbit doublets from Br 3d deconvoluted spectrum was found, which implies the free and ionic bromine have been washed off thoroughly. For 3FBP-CN, new peak around 400 eV was observed, due to the introduction of nitrile. The deconvoluted results for C1s spectrum of 3FBP-CN exhibited new peak around 287.5 eV, which is attributed to binding energy of C=N bond form within the nitrile group. The content of nitrile group in 3FBP-CN was calculated as 150%, which indicates 91% conversion ratio from bromine to nitrile. Moreover, it could be found that 16% of the bromine has not been converted according to the calculation, which shows 166% for total functional degree in 3FBP-CN. This result is in good agreement with the initial bromination degree of 3FBP-Br. After the [3+2] cycloaddition click reaction between the nitrile and the azide, the content of nitrogen in the polymer was found to increased dramatically and the degree of functionalization of 3FBP-Te was calculated as 158%. This corresponds to >100 % conversion, which is due to complete conversion of the nitrile functionalities to tetrazole and substitution of bromine residuals with azide as NalXh was used in excess.

[0173] Table 1 Composition and the group content of 3FBP, 3FBP-Br, 3FBP-CN and 3FBP-Te obtained from XPS. The thermogravimetric curves and corresponding derivative of the weight loss of 3FBP, 3FBP-Br, 3FBP-CN and 3FBP-Te are shown in Figure 2. For 3FBP, the weight remains constants until the temperature reached around 500 °C, corresponding to degradation of the backbone. The onset of major decomposition of 3FBP-Br and 3FBP-CN was around 420 and 430 °C, respectively. For the 3FBP-Te, a major degradation step started at around 200 °C, which could be attributed to ring opening of the tetrazole rings. The subsequent weight losses at 380 and 480 °C are related to the decomposition of the opened tetrazole residuals and backbone, respectively.

[0174] Conclusion

[0175] Tetrazole functionalized 3FBP (3FBP-Te) was successfully prepared and characterized. Example 2: Preparation and testing of poly(arylene-alkylene) ion-solvating membranes

[0176] Materials and Methods

[0177] Membrane casting: 3FBP-Te (0.6 g) was dissolved in 10 mL NMP at 80 °C under ultrasonication overnight. The obtained deep brown viscous solution was cast on cleaned Petri dishes (9 cm diameter) by solvent evaporation at 65 °C for 72 h. The obtained 3FBP-Te membrane was delaminated from the glass substrates after immersing in water overnight, and dried in vacuum oven at 80 °C for another 24 h. The membranes were equilibrated in aqueous KOH at KOH concentration of 5, 10, 20 and 30 wt.% for 24 h before use.

[0178] Scanning electron microscopy (SEM) was carried out using a Zeiss EVO MA10. The cross sections of the membranes were fabricated by cryogenic fracturing in liquid nitrogen, followed by sputter coating with gold.

[0179] Mechanical tests: Stress-strain curves were recorded using a Mecmesin MultiTest-dV Low-force materials tester at a crosshead speed of 20 mm / min, using 5 mm wide specimens.

[0180] Electrolyte uptake and swelling ratio: Before electrolyte uptake and swelling measurement, all the membranes were dried under vacuum at 60 °C overnight. After weighing the dry membranes, the membranes were transferred to different concentration KOH solutions varying from 5 to 30 wt% and kept at room temperature for 24 h. The electrolyte uptake, (EU) (i.e. the sum contributions from water and KOH), was calculated according to Equation 1 , where l / l / wand l / l / d is the weight of the wet and dry membrane, respectively.

[0181] The thickness swelling (swelling ratio, SR) was measured by immersing the samples in the electrolytes of different concentration KOH solutions at room temperature for 24 h, in parallel with the electrolyte uptake test, and calculated according to Equation 2, where Twand 7d is the thickness of the wet and dry membranes, respectively.

[0182] Results

[0183] The electrolyte uptake and swelling of the 3FBP-Te membrane in 0-30 wt.% KOH is presented in Figure 3. The electrolyte uptake was found to peak at 64 wt.% in 5 wt.% KOH, and thereafter declined with increasing KOH concentration. For comparison, the electrolyte uptake of m-PBI membrane peaks at around 25 wt.% KOH (Kraglun et al). The discrepancy is likely due to the significant difference in acidity between the benzimidazole and tetrazole, with pavalues of around is 12.8 and 4.9 respectively. This implies that the 3FBP-Te is readily deprotonated even at relatively low KOH concentration to form negatively charged potassium tetrazolide pendants along the backbone. Without wishing to be bound by theory, this is believed to increase the polarity of the polymer, which could contribute to an increased electrolyte uptake, but may to some extent be counterbalanced by the electrostatic repulsion of hydroxide ions due to Donnan exclusion. The situation may be similar to a perfluorosulfonate membrane equilibrated in KOH, which show decreasing electrolyte uptake with increasing KOH concentration.144451The swelling ratio of the 3FBP-Te membrane followed the same trend as the gravimetric electrolyte uptake, with a peak swelling of 37% in 5 wt% KOH.

[0184] Figure 4 shows the tensile strength and Young’s modulus of 3FBP as well as 3FBP-Te before and after equilibration in aqueous KOH with concentration of 5-30 wt.%. It can be seen that the introduction of tetrazole pendants on the 3FBP backbone had a major impact on the mechanical characteristics at the membrane level. Even though the additional hydrogen bond donor / acceptors potentially could govern intermolecular interaction of the polymer chains, the plasticizing effect by the pendants were dominating. After equilibration in aqueous KOH, the membrane showed a higher degree of plastic deformation. This is a result from the ion-solvation process between KOH and tetrazole, which results in increasing plasticization. The minima in tensile strength and elastic modulus of 2.3 and 24.1 MPa, respectively, were found to coincide with the peak in electrolyte uptake. Conclusion

[0185] Membranes with ion solvating polymer with tetrazole pendant groups were prepared and demonstrated excellent electrolyte uptake. Presence of polar tetrazolide anions in the ion solvating polymer is confirmed.

[0186] Example 3: Ion conductivity and electrolysis testing of poly(arylene-alkylene) ionsolvating membranes

[0187] Materials and Methods

[0188] Ion conductivity and electrolysis testing: The conductivity measurements and electrolysis tests were performed as described in Y. Xia et al. For the conductivity test, the membrane sample was sandwiched between two Ni-mesh electrodes in a two- compartment PTFE cell with agueous KOH in the cell chambers. The through-plane resistance was determined by electrochemical impedance spectroscopy (EIS), using a Gamry Reference 3000 with an AC perturbation of 5.0 mV amplitude in the freguency range from 1000 Hz to 100 kHz. The resistance was taken as the real component of the impedance Zreat 0° phase angle, and the conductivity o was calculated according to Eguation 3, where d and S are the thickness of the membrane and geometric surface area of the Ni electrodes, respectively. The membrane samples were eguilibrated in KOH solutions of different concentrations for at least 24 h before the test. Conductivity is measured at room temperature unless otherwise stated. d

[0189] < = -

[0190] ZKxS

[0191] (3)

[0192] The single cell electrolysis tests were conducted by sandwiching the pre-eguilibrated membrane between two pieces of uncatalyzed Ni-foam electrodes (compressed to 300 pm) with an active geometric area of 10 cm2. Flat sheet polytetrafluoroethylene (PTFE) gaskets with suitable thickness were applied for sealing. The thickness of the gaskets was adjusted to match the thickness of the membrane and electrodes to avoid mechanical damage of the membrane due to compression. During the test, two heating rods and a thermocouple were inserted into the end plates to control the temperature, and 30 wt.% KOH (ag.) was circulated on both sides at a flow of 80 mL / min by two separated gear pumps, in a partially separated electrolyte flow mode. In order to stabilize the cell, a break-in current density of 100 mA cm-2was applied at 40 °C for 1 h. The polarization testing was then followed in sequence with the temperature of 40, 60 and 80 °C. The H2 content in the outlet from the anode compartment was recorded with a hydrogen sensor from Geopal Systems (after drying through a silica gel column). The H2 crossover was determined at current densities of 50, 100, 150, 200 and 400 mA cm-2in sequence at each temperature 40, 60 and 80 °C during continuous nitrogen flush of 56 mL / min. Each current density was maintained for 4 h. The hydrogen content in oxygen and permeability of the selected membrane was calculated according to Y. Xia et al.

[0193] Results

[0194] Features of 3FBP-Te membranes are shown in Table 2. At room temperature, the through plane ion conductivity of 3FBP-Te was found to peak at 19 mS / cm in 5 wt.% KOH and room temperature, and thereafter decreased slightly to 13 mS / cm when the concentration was increased to 30 wt.% KOH, as shown Figure 5. From a conductivity point of view, 5 wt.% KOH appear to be the optimal operating point for the electrolysis tests. However, the cell tests were conducted in 30 wt.% KOH to govern mechanical stability of the membrane. The higher operating concentration was also expected to improve electrode kinetics and reduce hydrogen crossover compared with lower KOH concentration feeds, and facilitate the comparison with the conventional commercially available porous electrode separator (Zirfon).

[0195] Table 2 Overview of key characteristics of the 3FBP-Te in 30 wt.% KOH at room temperature. For cell testing, the 3FBP-Te membranes were sandwiched between a pair of uncatalyzed Ni foams electrodes and mounted in a 10 cm2active area single cell. Initial polarization curves for 3FBP-Te and Zirfon were obtained at 40, 60 and 80 °C as shown in Figure 6a, 6b and 6c, respectively.

[0196] With the increasing temperature, the polarization performance of the cell assembled with 3FBP-Te membrane showed gradual improvement and was found to perform similar to Zirfon at 80 °C. This may be due to an increasing electrolyte uptake of 3FBP-Te with increasing temperature, which leads to a higher conductivity increase than for Zirfon.

[0197] However, the specific conductivity calculated based on the resistance obtained from the linear regression of the polarization curves in the 200-1000 mA cm-2at 40, 60 and 80 °C, was estimated as 12, 13 and 17 mS / cm, respectively.

[0198] The polarization data for 3FBP-Te at 40-80 °C are compared in Figure 6a, 6b and 6c, and the corresponding potentiostatic and galvonostatic EIS are shown in Figure 6d.

[0199] The H2 in O2 level and corresponding H2 permeability at 40 and 60 °C are shown in Figure 7a and 7b, respectively. At 40 °C and at 50 mA cm-2, the H2 crossover of 3FBP- Te corresponded to a specific permeability of 5.2 x 10'10mol s-1cm-1bar1, which is similar to that of Zirfon (7.4 x 10'10mol s-1cm-1bar1). The cell assembled with 3FBP-Te showed a slower increase of permeability than Zirfon with increasing current density and temperature. The cell assembled with 3FBP-Te exhibited three folds lower of the H2 permeability than Zirfon when the current density is above 300 mA cm-2. At 60 °C, both of the cells assembled with 3FBP-Te and Zirfon showed higher H2 permeability than at 40 °C mainly due to the increasing mobility of the hydrogen. Similarly, the cell assembled with 3FBP-Te presented better hydrogen resistance property than Zirfon, likely due to the small amorphous phase within the 3FBP-Te as the XRD results shown.

[0200] After electrolysis, the membranes were analyzed by FTIR and1H-NMR (Figure 8). The FTIR results showed little difference from before an after electrolysis. It can be seen that the partial characteristic tetrazole absorption shifted from 1650 cm-1to 1618 cm-1and 1579 cm-1following the deprotonation of the tetrazole moieties and cation exchange with potassium. Another obvious absorption band is found around 3400 cm-1, which is contributed from the -OH from the absorbed water. The absorption band around 1350 cm-1is due to the potassium carbonate formed from the carbon dioxide from the atmosphere. The1H NMR spectrum, showed the corresponding chemical shifts of the starting materials.

[0201] Conclusion

[0202] The 3FBP-Te membranes showed comparative polarization properties than commercial standard in the industry (Zirfon) with better permeability of H2. At the same time, stability analysis showed no chemical degradation.

[0203] Example 4: Preparation of polyfisatin biphenyl) polymers

[0204] General reagents. Bromoacetonitrile (97%) and 1 / - / -indole-2, 3-dione (isatin, 98%) and were purchased from TCI. Biphenyl (99%), trifluoromethanesulfonic acid (TFSA, 98%), trifluoroacetic acid (TFA, 98%), potassium carbonate (K2CO3, 99%) ammonium chloride (NH4CI, 99%), sodium azide (NaNs, 99%), dimethylacetamide (DMAc, 99%), dimethylformamide (DMF, 99%), hydrochloric acid (HCI, 37%) and deuterated dimethyl sulfoxide (DMSO-cfe, 99 atom% D) were obtained from Sigma-Aldrich. Potassium hydroxide (KOH, 88%) and methanol (99%) were purchased from VWR Chemicals. Zirfon Perl UTP 500 was purchased from Agfa. Ni foam sheet (pore size 450 pm, thickness 1.6 mm) was obtained from Alantum. DMAc and DMF were dried over 4 A molecular sieves prior to use. Other chemicals were used as received. The aqueous KOH solutions were prepared by dissolving KOH pellets in milliQ water, and the concentration was determined by density measurements and compared with literature data (W. M. Haynes).

[0205] Synthesis of poly[(2,3-dihydro-2-oxo-1 H-indole-3,3-diyl)[1,1’-biphenyl]-4,4’-diyl] (ISBP): To a dry 250 mL nitrogen purged three-neck round-bottomed flask equipped with mechanical stirring, a mixture of isatin (7.5 g, 50.98 mmol) and biphenyl (7.48 g, 48.55 mmol) were stirred in 120 mL TFA for 30 min in an ice bath. TFSA (40 mL, 0.5 mol) was thereafter added at the rate of 5 drops per second through an addition funnel. Stirring at the rate of 1200 rpm at room temperature overnight, the mixture was kept under mild stirring for additional 10 h until a highly viscous solution displaying Weissenberg effect was obtained. Weissenberg effect describes a phenomenon that occurs when a spinning rod is inserted in liquid and said liquid is drawn towards the rod and rises up around it. The highly viscous solution was poured into water, which resulted in instant precipitation of a yellow solid. The solid was isolated by filtration, washed thoroughly with water and warm methanol and dried under vacuum at 60 °C overnight (14 g, 99% yield).

[0206] Cyanoalkylation of ISBP (ISBP-CN): ISBP prepared as described above (2 g, 7.07 mmol) was first dissolved in 40 mL NMP, followed by addition of K2CO3 (4 g, 28.99 mmol). After stirring for at least 1 h, bromoacetonitrile (4 mL, 57.40 mmol) was added, and the temperature was allowed to increase to 50 °C. The reaction mixture was stirred for 15 min, 1 h, 5 h or 8 h to control the degree of functionalization. The reaction was quenched by pouring the yellow solution into water. ISBP-CN precipitated as white fibers, which were isolated by filtration, washed by water and dried. The degree of cyanoalkylation was calculated according from1H NMR data. The cyanoalkylated ISBP is hereafter named as ISBP-CNx, where x represents the degree of functionalization (i.e. the mole fraction of cyanoalkylated repeat units).

[0207] Conversion of pendant nitrile groups to tetrazole (ISBP-Te): ISBP-CNx was dissolved in DMF at 80 °C, followed by addition of NaNs (6 eq.) and NH4CI (6 eq.) in sequence. After stirring for 1 h, the temperature was increased to 135 °C, and kept for 72 h. The deep orange solution was poured into 1 mM HCI (aq.). The brown and hard solid precipitated was isolated, washed by water and dried and hereafter referred to as ISBP-Tex, where x represents the degree of functionalization molar content of tetrazole (i.e. the mole fraction of repeat units carrying a tetrazole pendant).

[0208] An overview of the synthesis is shown in Figure 9 (the letters n and m designate the repating monomeric units of the polymer).

[0209] Results

[0210] The structural identity of ISBP was confirmed by1H NMR (Figure 10a), and the intrinsic viscosity of 1.38 dL / g in NMP indicates that a relatively high molecular weight polymer was obtained.

[0211] The1H NMR spectra of ISBP-CN20, ISBP-CN47, ISBP-CN81 , and ISBP-CN100 obtained after 15 min, 1 h, 5 h and 8 h of Cyanoalkylation, respectively are shown in Figure 10a. The degree of functionalization of the ISBP-CN, i.e. the ratio between m and n in the random copolymer structure (see figure 9), was controlled by adjusting the reaction time between 15 min to 8 h. As exemplified in Figure 10b, the new peak at 5.1 ppm in the1H NMR of ISBP-CN47 corresponds to the proton assigned to the -CH2- linkages. The degree of cyanoalkylation x was calculated from the peak integral ratios of 21 to the sum of 21 and e, as defined by Equation 4, where Ai corresponds to the integral of the signals corresponding to the protons on amide, while Aerepresents the peak integral of protons on the methylene linkages.

[0212] The FTIR spectra of ISBP and the ISBP-CNx series are presented in Figure 10c and 10d. Compared with neat ISBP, the ISBP-CNx derivatives showed increasing intensity of the absorption band around 1346 cm-1due to the in plane C-H vibration from of the cyanoalkyl groups. In addition, the absorption band around 3387 cm-1, which corresponded to the N-H bond, was found to decrease with increasing degree of cyanoalkylation. The intensity of the nitrile absorption band around 2285 cm-1was observed.

[0213] The1H-NMR spectra of the ISBP-Tex series are shown in Figure 11a. After the reaction, the peak at 5.1 ppm was shifted to 5.3 ppm, due to the increased de-shielding. The1H- NMR data indicate complete conversion of the cyanoalkyl groups, and the degree of tetrazole functionalization was therefore assumed to equal the degree of cyanoalkylation. As indicated by the FTIR data in Figure 11 b, two increasing absorption bands around 1421 cm-1and 1547 cm-1were found after the conversion to tetrazole, which are attributed to the C-N and C=N vibration from the tetrazole ring, respectively.

[0214] Figure 11c shows the thermogravimetric curves and corresponding derivative of the weight loss of the ISBP-Tex series. Pristine ISBP and the fully cyanoalkylated ISBP are shown for comparison. The first mass loss at around 120 °C is related to the evaporation of the free water. At temperatures above 200 °C, significant mass losses were observed for the ISBP-Tex due to is due to the tetrazole ring decomposition. For the pristine ISBP, a minor mass loss around 250 °C was observed, ascribed to the evaporation of solvent residuals. For ISBP-CN100, no apparent degradation was observed until the temperature reached to 430 °C, which was due to detachment of cyanoalkyl groups. The onset of poly(arylene alkylene) backbone degradation was observed at around 500 °C. Conclusion

[0215] Tetrazole functionalized ISBP-Te was successfully prepared and characterized.

[0216] Example 5: Preparation and testing of polyfisatin biphenyl) ion-solvating membranes

[0217] Materials and methods

[0218] Membrane casting: Approximately 0.6 g of ISBP-Tex was dissolved in 12 mL DMAc under ultrasonication and stirred at 80 °C overnight. The obtained viscous solutions were cast on cleaned petri dishes with the diameter of 11 cm, by solvent evaporation at 80 °C for 36 h. After being submerged in water overnight, the ISBP-Tex membranes were delaminated from the glass substrates and stored in airtight polyethylene bags until used. The membranes were eguilibrated in 30 wt.% KOH solution for 48 h before use.

[0219] Membrane characterization. The1H NMR spectra were acguired on a Magritek Spinsolve 80 MHz spectrometer in DMSO-cfe. The Fourier transform infra-red (FTIR) spectra were detected using a PerkinElmer Spectrum TWO instrument eguipped with an attenuated total reflectance accessory (ATR) within an IR freguency range of 4000 to 400 cm-1. The inherent viscosity of ISBP was determined at 30 °C using an Ubbelohde suspended level viscometer with the polymer dissolved in DMAc. The efflux time was measured at least three times at five different concentrations. The thermogravimetric analysis (TGA) was carried out on a Netzsch STA 409 at a heating rate of 10 °C / min from room temperature to 700 °C under an argon atmosphere. X-ray diffraction (XRD) was carried on a powder diffractometer (Rigaku Minflex 600) for 20 angles between 5° and 50° with anode material of Cu Ka (A = 0.154 nm) at a scan rate of 5° min-1. Stressstrain curves were recorded by a Mecmesin MultiTest-dV Low-force materials tester with a 3 mm wide specimen at a crosshead speed of 20 mm / min.

[0220] Electrolyte uptake. The electrolyte uptake and membrane swelling ratio were measured as described in Example 2.

[0221] Results

[0222] The electrolyte uptake and swelling ratio of the pristine ISBP and the ISBP-Tex series in 30 wt.% KOH are shown in Figure 12. It can be seen that the electrolyte uptake of ISBP- Te20 was similar to that of the pristine ISBP within the experimental error, and that the electrolyte uptake gradually increased with increasing degree of functionalization. For the ISBP-Te100 membrane, the electrolyte uptake reached of 53%, which is about half the electrolyte uptake of m-PBI under similar conditions (D. Aili et al.). As also shown in Figure 4, the swelling ratio decreased with increasing KOH concentration, which indicates that the free volume increased with increasing degree of functionalization.

[0223] Figure 13 shows representative Young’s modulus and tensile strength for ISBP-Tex before and after equilibration in 30 wt% KOH. It can be seen that the introduction the tetrazole pendants resulted in increasing plasticity, and the peak tensile strength gradually decreased from 87 MPa for the pristine ISBP to 60 MPa for ISBP-Te100 series gradually from a to with the increasing tetrazole content. After doping in aqueous KOH, the membranes were further plasticized. However, the minimum tensile strength was 32 MPa, which is higher than that of m-PBI membranes under similar conditions (M. Makrygianni et al.). The Young's modulus of ISBP was around 2.5 and 2.0 GPa before and after doping in aqueous KOH, respectively. The Young's modulus dropped to 1.2 GPa after the introduction of tetrazole pendants, and remained relatively constant as the degree of functionalization was increased. After doping in aqueous KOH, the Young's modulus further decreased and was found to be around 0.5 GPa for the ISBP-Te100 membrane.

[0224] Conclusion

[0225] Membranes comprising ion solvating polymers functionalized with tetrazole pendant groups were prepared and demonstrated excellent electrolyte uptake and mechanical properties. The presence of polar tetrazolide anions in the ion solvating polymer is confirmed.

[0226] Example 6: Ion conductivity and electrolysis testing of polyfisatin biphenyl) ion-solvating membranes

[0227] Materials and methods

[0228] Ion conductivity and electrolysis testing. Was performed as described in Example 3. The H2 crossover was determined at current densities of 50, 100, 150, 200 and 400 mA cm-2in sequence at each temperature 40, 60 and 80 °C. Each current density was maintained for 4 h. Results

[0229] Table 3 summarizes ASR of the ISBP-Tex membranes recorded in 30 wt.% KOH and the corresponding specific conductivity. The trend correlated well with the electrolyte uptake trend showing a conductivity increase with increasing degree of functionalization (Figure 12). The highest conductivity of 10.5 mS / cm was obtained for the ISBP-Te100 membrane. The conventional commercial porous separator Zirfon was listed as the reference. Pristine ISBP was also included as well.

[0230] Table 3 Overview of key properties of the ISBP-Tex membrane in 30 wt.% KOH at room temperature.

[0231] Functional Thickness degree by ASR Conductivity

[0232] (wet) Membrane1H NMR

[0233] (Q (mS / cm)

[0234] (%) (Mm) cm2)

[0235] ISBP 0 60 0.80 7.6

[0236] ISBP-Te20 20 62 1.15 5.4

[0237] ISBP-Te47 47 68 0.93 7.3

[0238] ISBP-Te81 81 72 0.87 8.3

[0239] ISBP-Te100 100 75 0.72 10.5

[0240] Zirfon - 500 0.39 128 The polarization performance of ISBP-Te100 in water electrolysis cell was evaluated at the temperature of 40, 60 and 80 °C as shown in Figure 14a. The comparison between ISBP-Te100, Zirfon and pristine ISBP at 40, 60 and 80 °C are presented in Figure 14b, 14c and 14d respectively. When comparing ISBP-Te100 and pristine ISBP 40 °C, the former showed significantly lower ASR. When the temperature increased to 60 and 80 °C, the polarization performance for the cell assembled with ISBP gradually increased relative to ISBP-Te100.

[0241] The conductivity calculated based on the resistance obtained from the linear regression of the polarization curves (Figure 14) above 200 mA cm-2were apparently lower and estimated to 4.4, 5.5 and 6.7 mS / cm at 40, 60 and 80 °C, respectively. The Nyquist representations of the potentiostatic and galvanostatic EIS recorded at 1 .3 V vs ref. and at 0.01 or 0.1 mA cm-2, were measured for pristine ISBP and ISBP-Te100. For the ISBP-Te100 membrane, the in-situ conductivity calculated according to the high frequency intersection of the potentiostatic EIS were 8.5, 9.2 and 12.5 mS / cm at 40, 60 and 80 °C, respectively.

[0242] According to the EIS results, the tetrazole containing ISBP-Te100, exhibited lower ASR than pristine ISBP, which shows that ISBP-Te100 had better conductivity and cell performance.

[0243] The H2 in O2 level at the anode outlet for the cell equipped with the ISBP-Te100 membrane is shown in Figure 15a as function of current density, with data for Zirfon for comparison. It can be seen that the H2 level in the anode compartment decreased with the decreasing of current density for the cell assembled with ISBP-Te100 due to the dilution of O2.

[0244] As shown in Figure 15b, the cells equipped with ISBP-Te100 and Zirfon exhibited relatively low permeability around of 1.0 x 10'9mol s-1cm-1bar1at 50 mA cm-2. However, Zirfon presented a faster increasing of the H2 permeability with the increasing current density. Especially at 300 mA cm-2, the cell assembled with ISBP-Te100 showed 3 times lower H2 permeability than that of Zirfon from the temperature of 40-80 °C.

[0245] The time evolution of cell voltage of the cell equipped with the ISBP-Te100 membrane is shown in Figure 16. From 0 to 96 h, polarization and EIS test was carried out at 40-80 °C. From 96 to 170 h, the gas permeability was measured by varying the current density from 50 to 300 mA cm-2at 40, 60 and 80 °C, respectively. After 170 h, the cell was kept at 300 mA cm-2at 80 °C to evaluate the membrane durability and water was regularly fed to compensate for the consumption. It can be seen that the cell voltage remained relatively stable around 2.19 V before 420 h during the long term test part, and the hydrogen level fluctuated around 0.1% in the anode. Nevertheless, an increased cell voltage was observed after 420 h, which also coincided with the onset of increased H2 crossover.

[0246] After electrolysis, the membrane was examined by FTIR and tensile testing (Figure 17). The dry and doped pristine membranes are included for comparison. From the FTIR spectra, no significant difference was observed, which implies good stability of ISBP- Te100. The stress-strain curves of the membrane shown in Figure 17b shows >90% of the original strength of the ISBP-Te100 and is therefore unlikely that the fracture was caused by significant backbone degradation.

[0247] 1H-NMR showed only trace degradation of the tetrazole side chain after 500 h and indication that some of the rings corresponding to isatin were opened, but no indication of backbone degradation.

[0248] Conclusion

[0249] The ISBP-Te membranes showed comparative polarization properties than commercial standard in the industry (Zirfon) with better permeability of H2. At the same time, stability analysis showed no chemical degradation.

[0250] Example 7: Preparation of poly(styrene-co-acrylonitirle) polymers

[0251] Materials and Methods

[0252] General reagents. Poly(styrene-co-acrylonitrile) (SAN25, 25 wt% acrylonitrile, Mw= 165,000 g / mol, Sigma-Aldrich), poly(styrene-co-acrylonitrile) (SAN30, 30 wt% acrylonitrile, Mw= 185,000 g / mol, Sigma-Aldrich), NH4CI (99.5%, Sigma-Aldrich), NaNs (99.5%, Sigma-Aldrich), potassium carbonate (99%, Sigma-Aldrich), methyl iodide (99.0%, Sigma-Aldrich), / V, / V-dimethylformamide (DMF, 99.8%, anhydrous, Sigma- Aldrich), methanol (MeOH, 99.8%, Sigma-Aldrich), tetra hydrofuran (THF, >99.9%, Sigma-Aldrich), hydrochloric acid (37%, Sigma-Aldrich) and potassium hydroxide pellets (90%, Sigma-Aldrich) were used as received. The aqueous KOH solutions were prepared by dissolving the KOH in demineralized water, and the concentration was determined by comparing the density with literature data.29Nickel foam was obtained from Alantum.

[0253] Tetrazolation of SAN25 and SAN30: To a solution of SAN25 (1.00 g, 5.7 mmol AN unit) in DMF with a concentration of 5 wt%, NaNs (1.50 g, 23.1 mmol) and NH4CI (1.24 g, 23.1 mmol) were added. The reaction mixture was then stirred at a temperature of 130 °C for 48 h. The crude solution was thereafter poured into 1 M aqueous HCI to precipitate the polymer, which was isolated by filtration, and then redissolved in THF. The solution was again poured into a 1 M aqueous HCI and the precipitated polymer (hereafter referred to as STZ25) was filtered, washed extensively with deionized water, dried in a vacuum oven at 50 °C overnight and obtained in 98% yield. Using the same procedure, STZ30 was synthesized from SAN30 (1 .00 g, 5.5 mmol AN unit), NaNs (1 .45 g, 22.4 mmol) and NH4CI (1.20 g, 22.4 mmol). After work-up and drying, STZ30 was obtained in 97% yield. Methylation of STZ25 and STZ30: STZ25 (1.00 g, 2.2 mmol Tz units) was dissolved in DMF, followed by addition of K2CO3 (0.62 g, 4.4 mmol) and CH3I (0.56 mL, 8.8 mmol). The mixture was stirred overnight at room temperature and thereafter poured into deionized water to precipitate the polymer, which was isolated by filtration. The precipitate was then redissolved in THF and precipitated again. The resulting yellow solid was filtered, washed with deionized water, and dried in a vacuum oven at 50 °C overnight, resulting in a yield of 99%. Similarly, STZ30 (1.00 g, 2.7 mmol Tz units) was methylated using the same procedure: K2CO3 (0.74 g, 5.4 mmol) and Mel (0.67 mL, 10.7 mmol) and obtained in 99% yield.

[0254] Results

[0255] The FT-IR data of the pristine SAN25 and SAN30 copolymers exhibited small bands at approximately 2240 cm-1, indicating the presence of nitrile groups as shown in Figure 18a and 18b, respectively. After the tetrazolation procedure, the absorption bands could no longer be seen, supporting the successful conversion of nitrile groups into tetrazoles. Additionally, the FT-IR spectra of STZ25 and STZ30 showed new bands around 1555 cm-1. These bands are specific to tetrazole groups, further confirming the successful transformation of nitrile groups into tetrazoles.

[0256] The1H NMR spectra of pristine SAN25 / SAN30, as shown in Figure 19a, reveal two distinct regions with overlapping multiplets from about 1.0-3.0 ppm, which correspond to the aliphatic protons of both styrene and acrylonitrile units and a set of multiplets in the region of 6.5-7.6, representing the aromatic protons of the styrene unit. Figure 20 and 21 present the1H NMR spectra of the tetrazolated STZ25 / STZ30 copolymers and their methylated versions in CDCI3. Because STZ25 and STZ30 do not contain protons that can be tracked by1H NMR, full methylation of the tetrazole units was carried out to estimate the degree of conversion. The methylation reaction is well-known to occur in nearly quantitative yield (Henry, R. A et al.), and the degree of tetrazolation could therefore be estimated by comparing the peak integral of the distinctive -CH3 group at 4.07 ppm to the peak integral of the styrene part. The compositions of the pristine SAN25 / SAN30 were also calculated from their1H NMR spectra by comparing the aromatic hydrogens of the styrene unit to the aliphatic hydrogens of the acrylonitrile unit. The estimated compositions are presented in Table 4.

[0257] Table 4 Composition of SAN25 / SAN30 and STZ25 / STZ30 calculated from1H NMR and corresponding glass transition temperatures (Tg) determined by DSC. Polymer Styrene (%) Acrylonitrile (%) Tetrazole (%) Tg(°C)

[0258] SAN25 65.4 34.6 104.9

[0259] SAN30 58.2 41.8 109.9

[0260] STZ2570.6 - 29.4 69.6

[0261] STZ3066.5 - 33.5 109.9

[0262] Conclusion

[0263] Tetrazole functionalized polymers were derived from poly(styrene-co-acrylonitrile) successfully prepared and characterized.

[0264] Example 8: Preparation and testing of poly(styrene-co-acrylonitirle) ion-solvating membranes

[0265] Materials and Methods

[0266] Membrane casting: To prepare the membranes, homogeneous solutions of STZ25 and STZ30 in DMF with a solid content of 10% were prepared. These solutions were then poured onto Petri dishes placed on horizontal glass plate, and the solvent was evaporated at 80 °C with filter paper covering the dishes. After the solvent evaporation, the resulting membranes were carefully delaminated from the glass substrates by immersing in deionized water. The membranes were stored in water until used.

[0267] Characterization. The1H NMR spectra were acguired using a Magritek Spinsolve 80 spectrometer operating at 80 MHz. Deuterated dimethyl sulfoxide (DMSO-cfe) and chloroform (CDCI3) were used as solvents. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra were recorded from 550 cm-1to 4000 cm-1using a PerkinElmer Spectrum Two FT-IR Spectrometer. Thermogravimetric analysis (TGA) was conducted using a Netzsch STA 449 F3 Jupiter instrument under an argon atmosphere, from 25 to 700 °C at a heating rate of 10 °C / min. Differential scanning calorimetry (DSC) was conducted using a Netzsch 200 F3 instrument under a nitrogen atmosphere. The temperature range of 30-190 °C was employed for the pristine polymers, while the functionalized polymers were analyzed in the range of 30-140 °C. The samples underwent a heating-cooling-heating cycle with a heating rate of 10 °C / min. The glass transition temperature (Tg) was determined at the midpoint of the specific heat increment. X-ray diffraction (XRD) patterns of the polymers were obtained using previously described powder diffractometer (Panalytical, Aeris) at room temperature for 20 angles between 5° to 55° using Cu Ka (A = 0.154 nm) at a scan rate of 5° min-1. The membrane cross sections were examined using scanning electron microscopy (SEM) with a Zeiss EVO MA10 instrument. The samples were prepared by cryogenic fracturing in liquid nitrogen and subsequently sputter-coated with gold.

[0268] Electrolyte uptake and swelling. The electrolyte uptake and membrane swelling ratio were measured as described in Example 2.

[0269] Results

[0270] The thermogravimetric curves and derivatives of weight loss of SAN25 / SAN30 and STZ25 / STZ30 are shown in Figure 22a and 22b, respectively. The TGA curves of the pristine SAN25 / SAN30 reveal a major onset of degradation at around 360 °C, following a single-step process. During this step, both the polystyrene and polyacrylonitrile segments of the polymer decompose simultaneously. Interestingly, the thermal stability was not influenced by the compositional differences.

[0271] In contrast, the thermal behavior of STZ25 / STZ30 polymers exhibits three distinct regions of mass loss. The first region, ranging from room temperature up to 140 °C for STZ25 and 160 °C for STZ30, is associated with the release of water molecules bonded to the highly hygroscopic tetrazoles units, and eventual DMF residual from the membrane casting. The next decomposition stage was found to occur between 140 °C and 285 °C for STZ25 and between 165 °C and 290 °C for STZ30. This stage can be attributed to the decomposition of the pendant tetrazole groups.35The final stage involved the decomposition of the polymer backbone, which started at around 310 °C for STZ25 and 330 °C for STZ30.

[0272] The glass transition temperatures (Tg) for the investigated polymers was carried out using differential scanning calorimetry (DSC). For SAN25 / SAN30, the temperature range was set from 30 to 190 °C, while for the STZ25 / STZ30 copolymers, it was from 30 to 140 °C. Figure 23 shows the DSC curves obtained during the final heating cycle, and the obtained Tgvalues are summarized in Table 5. Surprisingly, the difference in Tgbetween STZ25 and STzsowas quite significant, 69.6 °C for STz2s and 109.9 °C for STZ30, which could suggest a strong hydrogen bonding between the tetrazole units of the latter that shifted the Tgtowards higher values.36 Figure 24 displays the X-ray diffraction (XRD) patterns of the pristine SAN25 / SAN30 and the tetrazole-functionalized STZ25 / STZ30 polymers. The XRD patterns of SAN25 and SAN30 exhibit two characteristic amorphous halos at 20 = 13° and 20 = 20°, corresponding to d-spacing values of 6.8 A and 4.4 A, respectively. However, in the XRD patterns of the tetrazole-functionalized STZ25 / STZ30 polymers, which were nearly identical, only the peak at 20 = 20° is observed, which appears broader. This indicates that the introduction of tetrazole units further enhances the amorphous nature of the polymers.

[0273] Table 5 Glass transition temperatures (Tg) determined by DSC of SAN25 / SAN30 and STZ25 / STZ30.

[0274] Figure 25 provides a summary of the electrolyte uptake and area swelling of the STZ25 and STZ30 membranes equilibrated in aqueous KOH with concentration ranging from 5 to 25 wt%. The STZ30 membrane showed excessive swelling in 5 wt% KOH, which made it too soft to handle.

[0275] In general, the general trend observed for electrolyte uptake was a decrease in uptake with a increasing concentration of the surrounding KOH solution. For STZ25, the electrolyte uptake decreased from 110% when equilibrated in 5 wt% KOH decreased to 53% when the KOH concentration was increased to 25 wt%. The electrolyte uptake was slightly lower in 20% KOH, which more likely a result of experimental uncertainty rather than a local minimum.

[0276] The STZ30 membrane exhibited a similar behavior, but with significantly higher uptakes due to the higher tetrazole content. The electrolyte uptake of STZ30 decreased from 362% to 118% as the KOH concentration increased from 10 to 25 wt%. Interestingly, this behavior differs from m-PBI, where the electrolyte uptake typically increases up to a concentration of 25 wt% KOH, where the polymer is nearly completely in the deprotonated polybenzimidazolide form (Konovalova, A et al.). At even higher KOH concentration, the electrolyte uptake of m-PBI start to decrease. The observed electrolyte uptake disparity between STZ25 and STZ30 and m-PBI can be attributed to the difference in acidity between the two azoles. While the paof the benzimidazole units of m-PBI is around 12.8, tetrazoles are considerably more acidic with a pavalue close to that of acetic acid. The relatively strong acidity implies that the ionic potassium tetrazolide form of both STZ25 and STZ30 predominates in the entire KOH concentration range. This makes the polymers highly polar in alkaline environment, which promotes extensive electrolyte uptake.

[0277] The linear swelling followed the same trend as the electrolyte uptake behavior, i.e. decreasing swelling with increasing KOH concentration and decreasing electrolyte uptake. For the STZ25 membranes area swelling in 5 wt% KOH was 20%, which decreased around 7% when the KOH concentration increased to 15 wt% KOH. Interestingly, the geometric area of the membrane remained unchanged in 20 and 25 wt% KOH. The STZ30 membranes showed higher swelling throughout the entire range of KOH concentration range, consistent with the electrolyte uptake trend. The swelling ranged from 56% in a 10 wt% KOH solution to 3% in a 25 wt% KOH solution.

[0278] Conclusion

[0279] Membranes with ion solvating polymer with tetrazole pendant groups were prepared and demonstrated excellent electrolyte uptake and mechanical properties. Presence of polar tetrazolide anions in the ion solvating polymer is confirmed.

[0280] Example 9: Ionic conductivity and electrolysis testing of poly(styrene-co-acrylonitirle) ion-solvating membranes

[0281] Materials and Methods

[0282] Ion conductivity and electrolysis testing. Was performed as described in Example 3.

[0283] Electrolysis testing. A single cell alkaline water electrolysis test was conducted using a 10 cm2flow cell. The membrane samples, pre-doped in a 15 wt% KOH solution for at least 24 h, were placed between two Ni-foam electrodes that were densified by pressing to reduce their thickness from 1600 pm to 250 pm. The cell was sealed using flat sheet PTFE gaskets of suitable thickness. Heating and temperature monitoring were carried out directly within the cell during the experiment. Gear pumps were used to circulate the electrolyte, and a 15 wt% KOH solution (300 mL) was pumped through the electrode compartments at a flow rate of 80 mL / min. The experiments were performed at atmospheric pressure and at a temperature of 60 °C.

[0284] Polarization curves were recorded stepwise with a duration of 60 s at each current density setpoint. Prior to recording the polarization curves, the system was activated for 24 h at a constant current density of 100 mA cm-2. EIS was performed using a VersaStat 4 potentiostat in potentiostatic mode at a potential of 1.3 V. The frequency range for EIS measurements was from 100 kHz to 1 Hz with an amplitude of 10 mV. The cell operated at a constant current density of 100 mA cm-2during the intervals between the polarization experiments and EIS measurements.

[0285] The hydrogen crossover was measured sequentially at current densities of 50, 100, 150, 200, 300, 400, and 500 mA cm-2. At each current density, the setpoint was maintained for 3400 s, and the hydrogen content on the anode side was measured using a hydrogen sensor from Geopal Systems after passing through a silica gel column. To ensure consistent signal quality, a continuous nitrogen flow of 57 mL / min was applied to the system. The hydrogen permeability was calculated using established methods described (Y. Xia et al.).

[0286] Results

[0287] The conductivity dependence on temperature dependence forSTz25 and STzso in 15 wt% KOH is shown in Figure 26a and 26b, respectively. The temperature resolved measurement were carried out on a different batch compared to the room temperature measurement series, which explains the small variations in the low temperature range. For the STZ25 membrane, the conductivity increased from 39 mS / cm at 25 °C to 92 mS / cm at 80 °C. Similarly, for STZ30, a slight temperature increase from 25 to 40 °C resulted in a conductivity increase from 77 mS / cm to 105 mS / cm. When the temperature reached 60 °C, the STZ30 membrane suffered from mechanical failure due to plasticization caused by excessive electrolyte uptake.

[0288] In general, the conductivity values for both STZ25 and STZ30 were significantly higher than that of the poly(arylene alkylene) chemistries with imidazole pendants, which reached 50 mS / cm conductivity in 4 M KOH (approximately 19 wt%) at 80 °C (Chen, Q et al). A single cell electrolysis testing of STZ25 in in 15 wt% KOH at a temperature of 60 °C was performed. After cell assembly, an initial polarization curve and EIS measurement was carried out after equilibrate period of 24 h at a constant current density of 100 mA cm-2. The cell was then operated at a constant current density of 100 mA cm-2for a total duration of 588 h, where the cell suffered from dry-out due to electrolyte imbalance and was stopped. The cell voltage evolution over time is shown in Figure 27.

[0289] Figure 28a shows the polarization curves recorded after 24 h, 283 h and 479 h, which indicating stable performance of the STZ25 membrane and a polarization behavior similar to that of the Zirfon reference material. Additionally, Figure 28b shows that the ASR calculated from EIS for STZ25 was at 0.419 Q cm2, while Zirfon showed an ASR of 0.570 Q cm2. Assuming that the main contribution to the resistance comes from the membrane, this corresponds to an ionic conductivity of 36 mS / cm for STZ25 and 88 mS / cm for Zirfon. It is worth noting that the ionic conductivity value for STZ25 in the single cell test was about half of what was observed in the ex-situ measurements. This discrepancy could be influenced by resistance contributions at the membrane-electrode interface or contributions from K+conductivity to the ex-situ measurements.1

[0290] The hydrogen crossover was also evaluated during the cell test. The data for H2 in O2 levels corrected for nitrogen gas that was used to flush the system is presented in Figure 28c for both STz2s and Zirfon. In the case of Zirfon, the decrease in H2 / O2 level with increasing current density is expected, as it is diluted by the generated O2, and the rate of O2 generation also increases. However, for STZ25, the decrease in H2 level was less pronounced. At 50 mA cm-2, the calculated permeability values, as shown in Figure 28d, were quite similar for both Zirfon and STZ25, with values of 7.71 x 10'9and 8.13 x 10'9mol s'1cm-1bar1, respectively.

[0291] Conclusion

[0292] The ISBP-Te membranes showed comparative polarization properties than commercial standard in the industry (Zirfon) with better hydrogen gas crossover properties. At the same time, stability and performance was maintained for long periods of time.

[0293] Example 10. Stability of small molecule test molecules in alkaline media.

[0294] Materials and Methods

[0295] 25 wt% aqueous KOH solution with internal standard tetramethyl ammonium chloride (25 mM) was prepared by dissolving the commercially available KOH and tetramethyl ammonium chloride in Milli-Q water. The samples were prepared by dissolving the nitrogen heterocycles (see Scheme 2)) (50 mM) in 15 mL of 25 wt % KOH in 50 mL of poly- (tetrafluoroethylene) (PTFE) test tubes. A 0.5 mL of the solution was drawn from the test samples and recorded the1H NMR using a Magritek Spinsolve 80 spectrometer operating at 80 MHz using the 1 D PRESAT method for 0 h concentration. After the first sampling, the tubes were then sealed and heated in an oven set to 80 degrees Celsius. Further sampling was done on a regular basis by taking out 0.5 mL of the liquid from the tubes after it had been cooled to room temperature. The concentration change / degradation of samples over time was calculated by comparing the1H NMR integrals of samples at time t vs the 0 h concentration with reference to the internal standard (TMAC, 5 3.16 ppm). In this1H NMR study we assigned the integral value as one for the proton signal from the internal standard TMAC. The degree of degradation was calculated as the percentage of initial concentration remaining at time t (Equation 5). % Remaining

[0296] °

[0297] Scheme 2 Results

[0298] The results shows that tetrazole small molecules show excellent under alkaline conditions stability in contrast to imidazole moieties (Figure 29).

[0299] Conclusion

[0300] Tetrazoles and triazoles show better stability under alkaline conditions commonly used for alkaline water electrolysis compared to imidazole groups.

[0301] Example 11. Crosslinking of polymers improves stability in alkaline water electrolysis at elevated temperatures.

[0302] Aim

[0303] To study the thermal stability of membranes according to the present disclosure under in situ AWE operation at elevated temperatures, such as above 60 °C.

[0304] It was seen that membranes made of poly(styrene-co-acrylonitrile) polymers (STZ25 and STZ30) at temperatures above 60 °C under AWE operation experienced increased dissolution and thereby reduced longevity as consequence of the electrolyte uptake. To address this potential issue, crosslinking was explored as means to improve the stability of the polymers according to the present disclosure under AWE operation at such temperatures.

[0305] Materials and Methods

[0306] Crosslinking procedure. Poly(styrene-co-acrylonitrile) polymers samples of STZ25 and STZ30, prepared as described in Example 7 were crosslinked. After isolation of the polymer, crosslinking was performed during the casting process of the membrane (as in Example 8), as polymer solubility in organic solvents typically decreases significantly during crosslinking. To prepare the casting solution, 10 wt% of the polymer (1 g, 2.54 mmol of tetrazole for STZ25) was dissolved in DMF. Subsequently, 1.1 equivalents of NaH were added to the solution, which was stirred for 15 minutes. The necessary amount of 1 ,6-dibromohexane to achieve the desired degree of crosslinking (0.076 mmol for 3% crosslinking, 0.127 mmol for 5% crosslinking, and 0.254 mmol for 10% crosslinking) was then added dropwise, and the mixture was stirred for 20 minutes at 80 °C until the solution became clear. The resulting solution was cast onto a petri dish and placed in an oven at 80 °C overnight to allow complete solvent evaporation. The resulting membranes were soaked in deionized water until they could be easily peeled off from the petri dish. The Stzao polymer was crosslinked according to the identical procedure.

[0307] Different samples with varying degrees of crosslinking were prepared. The degree of crosslinking was changed by modifying the amount of the crosslinking agent 1 ,6-dibromohexane. Since the samples became insoluble and could not be analyzed by1H-NMR, the degree of crosslinking was calculated by estimating 100% conversion of the crosslinking reaction.

[0308] Overview of the crosslinked samples: a: The degree of cross inking shall be understood as the percentage of sites available for crosslinking that is occupied by the crosslinker.

[0309] Electrolysis testing. The crosslinked polymer samples were subsequently evaluated in the electrolysis cell to assess the impact of crosslinking on cell performance. The electrolysis set-up was analogous to the described in Example 9, but using temperatures increased temperatures of 80 °C (STZ25 samples) or 90 °C (STZ30 sample). The electrolyte was 15 wt% KOH.

[0310] Results

[0311] As it can be seen in Figure 30, the crosslinked samples demonstrated acceptable polarization curves for AWE. Thus, crosslinked samples demonstrated successful ion conduction in alkaline medium. STz25 with 5% degree of crosslinking performance was comparable to the original pristine STz25 polymer but at a higher temperature (80 °C), which is more beneficial for real-world applications.

[0312] Crosslinking enhanced thermal stability of the polymers, as shown in Table 6. Table 6. a: This sample was reinforced with a polyphenylene sulfide (PPS) mesh to further increase mechanical stability (thickness: 60 ± 7 pm, open area: 70 ± 7%). b: No visible degradation of the membrane was observed upon disassembly of the cell.

[0313] The STz25_XL5 membrane demonstrated stable performance for 142 hours without noticeable degradation upon disassembly. Similarly, for STz25_XL10, the membrane with the highest degree of crosslinking, no degradation was observed after 44 hours of operation at 90 °C, confirming the effectiveness of crosslinking. These results demonstrate that crosslinking significantly increased the thermal and mechanical stability of the membranes at temperatures above 60°C compared to noncrosslinked samples.

[0314] During operation, the membranes became soft, which may leave them more susceptible to mechanical damage. To improve this, one additional sample STz30_XL4_PPS was reinforced with a PPS mesh. The sample was stable and could be operated at 90 °C under AWE conditions. This successfully demonstrated reinforcement to prevent mechanical damage in combination with crosslinking to improve thermal and mechanical stability.

[0315] Conclusion

[0316] Crosslinking increases thermal and mechanical stability under alkaline water electrolysis of membranes comprising polymers with N-pendent heterocycle groups according to the present disclosure. This allows longer operation times at increased temperatures, which are more technically relevant.

[0317] Mechanical stability of the membranes can be improved by using and external reinforcement. References

[0318] W. M. Haynes, Ed., in CRC Handbook of Chemistry and Physics, 93rd Edition (Internet Version 2013), CRC Press / Taylor And Francis , Boca Raton, FL.

[0319] M. R. Kraglund, D. Aili, K. Jankova, E. Christensen, Q. Li, J. O. Jensen, J Electrochem Soc 2016, 163, F3125.

[0320] Y. Xia, S. C. Rajappan, D. Serhiichuk, M. R. Kraglund, J. O. Jensen, D. Aili, J Memb Sci 2023, 680, 121719.

[0321] D. Aili, K. Jankova, J. Han, N.J. Bjerrum, J.O. Jensen, Q. Li, Understanding ternary poly(potassium benzimidazolide)-based polymer electrolytes, Polymer (Guildf). 84 (2016) 304-310. https: / / doi.Org / http: / / dx.doi.org / 10.1016 / j.polymer.2016.01.011

[0322] Henry, R. A. Methylation of 5-Phenyltetrazole. J Am Chem Soc 1951, 73 (9), 4470. https: / / doi.org / 10.1021 / ja01153a517.

[0323] M. Makrygianni, S. Aivali, Y. Xia, M.R. Kraglund, D. Aili, V. Deimede, Polyisatin derived ion-solvating blend membranes for alkaline water electrolysis, J Memb Sci. 669 (2023) 121331. https: / / doi.Org / 10.1016 / j.memsci.2022.121331

[0324] Konovalova, A.; Kim, H.; Kim, S.; Lim, A.; Park, H. S.; Kraglund, M. R.; Aili, D.; Jang, J. H.; Kim, H.-J.; Henkensmeier, D. Blend Membranes of Polybenzimidazole and an Anion Exchange Ionomer (FAA3) for Alkaline Water Electrolysis: Improved Alkaline Stability and Conductivity. J Memb Sci 2018, 564, 653-662. https: / / doi.Org / 10.1016 / j.memsci.2O18.07.074.

[0325] Chen, Q.; Huang, Y.; Hu, X.; Hu, B.; Liu, M.; Bi, J.; Liu, L.; Li, N. A Novel Ion-Solvating Polymer Electrolyte Based on Imidazole-Containing Polymers for Alkaline Water Electrolysis. J Memb Sci 2023, 668, 121186. https: / / doi.Org / 10.1016 / j.memsci.2022.121186.

Claims

Claims1 . Use of a polymer for conduction of ions in an alkaline medium, said polymer comprising a polymer backbone and at least one pendant group, said pendant group having formula -X-R1; whereinX is an optional linker, andR1is selected from:any tautomer thereof, or any deprotonated form thereof; wherein,R1ais H, or C1-C10 alkyl, aryl or heteroaryl.

2. The use according to any one of the preceding claims, wherein the polymer backbone does not comprise a base-labile group, such as ester or ether groups.

3. The use according to any one of the preceding claims, wherein the polymer comprises or consists of formula (I):formula (I); whereinR1is selected from:any tautomer thereof, or any deprotonated form thereof;R1ais H, or C1-C10 alkyl, aryl or heteroaryl;A is a C1-C5 alkanediyl group or an aromatic or heteroaromatic group, optionally substituted with one or more, identical or different Ragroups;A1, B and B’ is each individually selected from: a bond, or a C1-C5 alkanediyl group, an aromatic or heteroaromatic group, each of which may optionally be substituted with one or more, identical or different Rbgroups;X is an optional linker selected from: a C1-C5 alkanediyl group, optionally substituted with one or more identical or different, Rxgroups;Ra, Rband Rxare each individually selected from: H, halogen, hydroxy, C1-C10 alkyl and C1-C5 haloalkyl; n is an integer individually selected from 1 to 60000, m is an integer selected from 0 to 60000.

4. The use according to any one of the preceding claims, wherein the polymer comprises or consists of formula (la):formula (la), wherein:R1is selected from:any tautomer thereof, or any deprotonated form thereof;R1ais H, is H, or C1-C10 alkyl, aryl or heteroaryl;A is a C1-C5 alkanediyl group or an aromatic or heteroaromatic group, optionally substituted with one or more, identical or different Ragroups;B is a bond, or a C1-C5 alkanediyl group or an aromatic or heteroaromatic group, optionally substituted with one or more, identical or different Rbgroups;X is an optional linker;Ra, Rband Rxare each individually selected from: H, halogen, hydroxy, C1-C10 alkyl and C1-C5 haloalkyl; n is an integer from 1 to 60000.

5. The use according to any one of the preceding claims, wherein A is selected from the group consisting of:whereinRb1, Rb1’, Rb2and Rb3are each independently selected from H, halogen, hydroxy, C C10 alkyl and C1-C5 haloalkyl; y2 and y3 are each independently an integer from 0 to 3; and* denotes the attachment of -X-R1.

6. The use according to any one of the preceding claims, wherein A’, B and / or B’ are each individually selected from the group consisting of:whereinRb1, Rb1’, Rb2and Rb3are each independently selected from H, halogen, hydroxy,C1-C10 alkyl and C1-C5 haloalkyl; y2 and y3 are each independently an integer from 0 to 4.

7. The use according to any one of the preceding claims, wherein the polymer backbone is a homopolymer or copolymer of an optionally substituted ethylene, phenylene, and / or isatin.

8. The use according to any one of the preceding claims, wherein the polymer comprises or consists of any one of formulas Ila, lib, He, lld-1 , lld-2, or lld-3:whereinR1is selected from:; any tautomer thereof, or any deprotonated form thereof;R1ais H, or C1-C10 alkyl, aryl or heteroaryl,X is an optional linker, ml , n2, n3, n4, n4’, and n4” are each an integer individually selected from 1 to 60000, n1 and m3 are each an integer individually selected from 0 to 60000; and q, q’, q”, and q’” are in each instance an integer individually selected from 0 to 4.

9. The use according to claim 8, wherein the polymer comprises or consist of formula (Ila).

10. The use according to claim 8, wherein the polymer comprises or consist of formula (Hb).11 . The use according to claim 8, wherein the polymer comprises or consist of formula (He).

12. The use according to claim 8, wherein the polymer comprises or consist of any one of formulas (lld-1), (lld-2), or (lld-3) or any combination thereof.

13. The use according to claim 8 or 12, wherein at least one instance of q, q’, q” or q’” is not 0.

14. The use according to any one of the preceding claims, wherein R1ais H.

15. The use according to any one of the preceding claims, wherein X is absent.

16. The use according to any one of claims 1 to 14 , wherein X is -(CH2)I-S-, such as -(CH2)-, -(CH2)2-, -(CH2)3-, -(CH2)4-, or -(CH2)s-, wherein one methylene may be replaced with -O- or by an aryl or an heteroaryl group, such as a phenylene group.

17. The use according to any one of claims 1 to 16, wherein R1isHor any tautomer thereof or any deprotonated form thereof.

18. The use according to any one of claims 1 to 16, wherein R1is H oror any tautomer thereof or any deprotonated form thereof.

19. The use according to any one of claims 1 to 7, 8 and 14 to 18, wherein the polymer comprises or consists of formula (Illa):wherein n1 is an integer from 0 to 60000 and ml is an integer from 1 to 60000.

20. The use according to claim 19, wherein n1 is not 0.

21. The use according to any one of claims 19 to 20, wherein (n1+m1) is from 1 to 60000.

22. The use according to any one of claims 19 to 21 , wherein the ratio of n1 :m1 is from 0.99:0.01 to 0.01 :0.99.

23. The use according to any one of claims 1 to 7, 10 to 11 , and 14 to 18, wherein the polymer comprises or consist of formula (111 b) or (I I Ic):wherein n2 or n3 are each independently an integer from 1 to 60000 and m3 is an integer from 0 to 60000.

24. The use according to claim 23, wherein n2 is from 1 to 60000.

25. The use according to any one of claims 23 to 24, wherein (n3 + m3) is from 1 to 60000.

26. The use according to any one of claims 23 to 25, wherein the ratio of n3:m3 is from0.99:0.01 to 0.01 :0.99.

27. The use according to any one of claims 1 to 7, 12, and 14 to 18, wherein the polymer comprises or consists of any one of formulas (I I Id-1 ) , (llld-2) or (I I Id-3) or a combination thereof;wherein n4, n4’ and n4” are on each instance an integer from 1 to 60000 and q, q’, q”, and q’” are on each instance an integer individually selected from 0 to 4 .

28. The use according to claim 27, wherein at least one instance of q, q’, q” or q’” is not 0.

29. The use according to any one of claims 27 to 28, wherein n4 is from 1 to 60000.

30. The use according to any one of the preceding claims, wherein the average molecular weight (Mw) of the polymer is from 10,000 g / mol to 3,000,000 g / mol.

31. The use according to any one of the preceding claims, wherein the polymer is crosslinked.

32. The use according to claim 31 , wherein the crosslinking is a covalent crosslinking.

33. The use according to any one claims 31 to 32, wherein the polymer comprises a covalent crosslink between two tetrazole groups.

34. The use according to any one of claims 31 to 33, wherein the crosslink comprises or consists of an optionally substituted hydrocarbon chain, such as a Ci-Cs hydrocarbon chain.

35. The use according to any one of claims 31 to 34, wherein the crosslink comprises or consist of -(CH2)t-, wherein t is an integer from 1 to 8, such as 2 to 8, such as 4 to 8.

36. The use according to any one of claims 31 to 35, the polymer comprises formula (Hla),wherein n1 is an integer from 0 to 60000 and ml is an integer from 1 to 60000, and the polymer comprises one or more covalent crosslinks between two tetrazole groups and the crosslink comprises or consists of -(CH2)t-, wherein t is an integer from 1 to 8, such as 2 to 8, such as 4 to 8.

37. The use according to any one of claims 31 to 36, wherein the crosslink is -(CH2)e-.

38. The use according to any one of claims 31 to 37, wherein the degree of crosslinking is 10% or less, such as the degree of crosslinking is 2% to 10%, preferably 4% to 10%, more preferably 5% to 10%.

39. The use according to any one of the preceding claims, wherein the use is in water electrolysis, such as alkaline water electrolysis.

40. The use according to claim 39, wherein the electrolysis is in a gap cell, or in a zerogap cell.

41. The use according to any one of the preceding claims, wherein the alkaline medium is characterized by a hydroxide ion concentration between 0.1 M and 12 M, such as from KOH.

42. The use according to any one of the preceding claims, wherein the polymer is comprised in a membrane.

43. The use according to claim 42, wherein the membrane has a thickness of 10 pm to 1 mm.

44. The use according to any one of claims 42 to 43, wherein the membrane is in contact with or immersed in an alkaline electrolyte aqueous solution.

45. The use according to claim 44, wherein electrolyte comprises hydroxide ion concentration of 0.1 to 12 M.

46. The use according to claim 44, wherein the pH of the electrolyte 12 or higher, such as 13 or higher, such as 14 or higher.

47. The use according to claim 44, wherein electrolyte comprises an hydroxide concentration of 0.5 to 40 % (w / w).

48. The use according to any one of claims 44 to 47, wherein the electrolyte has a temperature between 10 °C and 150 °C.

49. The use according to any one of claims 42 to 48, wherein the electrolyte uptake in the membrane is between 1% and 70% by weight.

50. The use according to any one of claims 42 to 49, wherein the membrane has a porosity from 0.01 to 75% e.g. as measured by gas pycnometer, mercury intrusion, or by weighing with or without a filing substance.

51. The use according to any one of claims 42 to 50, wherein the membrane further comprises a reinforcement layer.

52. The use according to any one of claims 42 to 50, wherein the reinforcement layer is a mesh made of a polymeric material.

53. The use according to any one of claims 42 to 50, wherein the reinforcement layer is a mesh comprising or consisting of polyphenylene sulfide (PPS).

54. A membrane comprising the polymer as defined in any one of claims 1 to 38, wherein the membrane further comprises an alkaline electrolyte aqueous solution.

55. The membrane according to claim 54, wherein the membrane has a thickness of 10 pm to 1 mm.

56. The membrane according any one of claims 54 to 55, wherein the membrane further comprises an aqueous electrolyte solution.

57. The membrane according any one of claims 54 to 56, wherein the membrane has an electrolyte uptake between 1% and 120% by weight.

58. The membrane according to any one of claims 54 to 57, wherein the membrane is a porous or non-porous membrane.

59. The membrane according to any one of claims 54 to 58, wherein the membrane has a porosity from 0.01 to 75% e.g. as measured by gas pycnometer, mercury intrusion, or by weighing with or without a filing substance.

60. The membrane according to any one of claims 54 to 59, wherein the alkaline electrolyte aqueous solution is characterized by a hydroxide concentration between 0.5 wt% and 40 wt%.

61. The membrane according to any one of claims 54 to 60, wherein the membrane is characterized by an electrolyte uptake between 30% and 70% by weight.

62. The membrane according to any one of claims 54 to 61 , wherein the ionic conductivity through the membrane is from 60 mS / cm to 200 mS / cm at room temperature.

63. An alkaline electrolysis cell comprising: a) an alkaline electrolyte aqueous solution; and b) a membrane comprising a polymer, wherein the polymer is as described in any one of claims 1 to 38; wherein said membrane is in contact with or immersed in the alkaline electrolyte aqueous solution.

64. The alkaline electrolysis cell according to claim 63, wherein the alkaline electrolyte aqueous solution is as an aqueous alkaline solution characterized by at least one or more selected from: a hydroxide ion concentration between 1 M and 12 M, a pH of 12 or higher, such as 13, such as 14, such as 15 or higher, a hydroxide ion concentration between 0.5 wt% and 40 wt% , and a temperature between 10 °C and 120 °C.

65. The alkaline electrolysis cell according to any one of claims 63 to 64, wherein the membrane is as defined in any one of claims 54 to 62.

66. The alkaline electrolysis cell according to any one of claims 63 to 65 , wherein the alkaline electrolysis cell is an alkaline water electrolysis cell.

67. The alkaline electrolysis cell according to any one of claims 63 to 66, wherein the alkaline electrolysis cell comprises an anode and a cathode connected to an electrical power source.

68. The alkaline electrolysis cell according to claim 67, wherein the anode and the cathode are in contact with or immersed in the alkaline electrolyte aqueous solution.

69. The alkaline electrolysis cell according to any one of claims 63 to 68, wherein the ionic conductivity of the electrolyte through the membrane is of 10 mS / cm to 200 mS / cm.

70. The alkaline electrolysis cell according to any one of claims 63 to 68, wherein the conductivity of hydroxide ions through the membrane is of 10 mS / cm to 200 mS / cm.

71. The alkaline electrolysis cell according to any one of claims 63 to 70, wherein the cell is a gap cell, or a zero-gap cell.

72. A polymer comprising a polymer backbone and at least one pendant group, said pendant group having formula -X-R1; whereinX is an optional linker,R1is selected from:any tautomer thereof, or any deprotonated form thereof; wherein,R1ais H, or C1-C10 alkyl, aryl or heteroaryl; and the polymer backbone is derived from optionally substituted polyalkylene, polyphenylene, poly(arylene), poly(arylene sulfide), poly(arylene alkylene), or polyisatin or copolymers thereof.

73. The polymer according to any one of claims 72 , wherein the polymer is as defined in any one of claims 2 to 38.

74. The polymer according to claim 72, wherein the polymer is according to formulawherein n1 is an integer from 0 to 60000 and ml is an integer from 1 to 60000.

75. The polymer according to claim 74, wherein n1 is not 0.

76. The polymer according to any one of claims 74 to 75, wherein (n1+m1) is from 1 to 60000.

77. The polymer according to any one of claims 74 to 76, wherein the ratio of n1 :m1 is from 0.99:0.01 to 0.01 :0.

99.

78. The polymer according to claim 72, wherein the polymer comprises or consist of formula (I I lb) or (lllc):wherein n2 or n3 are each independently an integer from 1 to 60000 and m3 is an integer from 0 to 60000.

79. The polymer according to claim 78, wherein n2 is from 1 to 60000.

80. The polymer according to any one of claims 78 to 79, wherein (n3 + m3) is from 1 to 60000.

81. The polymer according to any one of claims 78 to 80, wherein the ratio of n3:m3 is from 0.99:0.01 to 0.01 :0.99.

82. The polymer according to claim 72, wherein the polymer comprises or consists of any one of formulas (llld-1), (llld-2) or (llld-3) or a combination thereof;wherein n4, n4’ and n4” are on each instance an integer from 1 to 60000 and q, q’, q”, and q’” are on each instance an integer individually selected from 0 to 4 .

83. The polymer according to claim 82, wherein at least one instance of q, q’, q” or q’” is not 0.

84. The polymer according to any one of claims 82 to 83, wherein each of n4, n4’ or n4” is individually selected from is from 1 to 60000.

85. The polymer according to any one of claims 72 to 83, wherein the average molecular weight (Mw) of the polymer is from 10,000 g / mol to 3,000,000 g / mol.

86. The polymer according to any one of claims 72 to 85, wherein the polymer is crosslinked.

87. The polymer according to claim 86, wherein the crosslinking is as defined in any one of claims 31 to 36.

88. A method of manufacturing a tetrazole-functionalized polymer according to any one of claims 72 to 87, the method comprising the sequential steps of:Step A1: Providing a polymer comprising nitrile groups; andStep A2: Reacting said provided polymer with a source of azide anions to conduct a [3+2] cycloaddition with the nitrile groups, thereby forming at least one tetrazole; andStep A3: isolating the product obtained in step A2 to obtain a polymer.

89. The method according to claim 88, wherein the polymer in step A1 comprises or consists of any one of formulas:wherein n1, n2, n3, n4, n4’, and n4” are each an integer individually selected from 1 to60000, ml and m3 are each an integer individually selected from 0 to 60000; and q, q’, q”, and q’” are on each instance an integer individually selected from 0 to 4.

90. The method according to any one of claims 88 to 89, wherein the reaction conditions in step A2 is performed with an alkali metal salt of an azide anion, such as sodium or potassium azide.91 . The method according to any one of claims 88 to 90, wherein step A2 is performed in an organic solvent, such as selected from DMF, N-methylpyrrolidone (NMP), and DMSO, preferably DMF.

92. The method according to claim any one of claims 88 to 91 , wherein step A2 is performed from about 40 °C to about 130 °C.

93. The method according to any one of claims 88 to 92, wherein step A2 is performed in the presence of a base such as a carbonate salt, a hydroxide or an ammonium salt.

94. The method according to any one of claims 88 to 93, further comprising a step A4, wherein the polymer obtained in step A3 is crosslinked.

95. The method according to any one of claims 88 to 94, wherein step A4 comprises contacting the polymer with a hydrocarbon comprising two halogen groups, in the presence of a base, such as sodium hydride (NaH).

96. The method according to any one of claims 88 to 95, wherein step A4 comprises contacting the polymer with a Ci-Cs dibromoalkanediyl, such as 1 ,6- dibromohexane, 1 ,5-dibromopentane, or 1 ,4-dibromobutane, preferably 1 ,6- dibromohexane.

97. The method according to any one of claims 88 to 96, wherein step A4 is performed in a suitable solvent, such as DMF, N-methylpyrrolidone (NMP), or DMSO, preferably DMF.

Images