Method for the synthesis of a vinylphenyl imidazole starting monomer for the preparation of a polymer and a membrane

Abstract

The application relates to a process for preparing a starting monomer by imidazolation of an aldehyde group in the para position of a substituted vinylphenyl starting material and to a starting monomer prepared by this method. The application further relates to a method for preparing a polymer from said starting monomer, to a polymer produced in this way, to a membrane consisting of said polymer, and to the use of the membrane for electrolysis, in fuel cells, in redox flow batteries or for dialysis.

Description

[0001]DESCRIPTION Process for producing a starting monomer, starting monomer, process for producing a polymer, polymer. The present invention relates to a process for producing a starting monomer. The invention further relates to a starting monomer. Furthermore, the invention relates to a process for producing a polymer and a polymer, in particular an ion exchange polymer, preferably an anion exchange polymer. As part of the energy transition, alternative ways of generating electricity are increasingly being developed. Fuel cells represent an important area in this regard. These convert the chemical reaction energy of a supplied fuel and an oxidizing agent into electrical energy. There are also other electrochemical applications that are playing an increasing role.This can involve, for example, electrolysis, particularly membrane water electrolysis, or dialysis processes, such as diffusion dialysis, Donnan dialysis, or electrodialysis. Membranes, particularly those made of anion exchange polymers, are used for these processes. These are confronted with aggressive conditions during operation. These usually include an alkaline environment, an existing electrical potential, pressure differences, and possibly elevated temperatures. The nucleophelia of a hydroxide group contained in the polymer can also be problematic. At the same time, the materials used must have high hydroxide conductivity to enable high current densities in the respective applications. For such applications under alkaline conditions, anion exchange polymers or membranes made of such materials are less common, and there is no standard material for these either.Commercially available for alkaline applications are, for example, membranes based on polyaromatics with ether bridges in the polymer backbone (such as those sold by Fumatech under the name Fumasep FAA3) and quaternary ammonium substituents as anion exchange groups. Such membranes can be used reinforced or unreinforced, although the ether bond between the aromatics represents a weak point under alkaline conditions. Aryl ether bonds in the polymer backbone are particularly disadvantageous for such membranes. These can be directly attacked by hydroxide ions in a nucleophilic substitution, which can result in a significant reduction in molecular weight and not only lower conductivity but also a loss of mechanical integrity. Against this background, the object of the present invention is to create an alternative production route for polymers and alternative polymers.Preferably, these polymers should be particularly suitable for use in anion exchange membranes and should be characterized by a correspondingly favorable property profile.This object is initially achieved by a process for producing a starting monomer, comprising the following steps:- Providing a starting material of the form. H, CF3, or aryl, wherein at least one aldehyde group is present on the aromatic compound; -imidazolation of the at least one aldehyde group. The invention is based on the surprising finding that the formation of the imidazole ring at the site of the aldehyde group is possible. Accordingly, it has been shown that, despite a possibly sterically demanding arrangement, the aldehyde group could be imidazolated. In a further embodiment, the starting material can be fluorine-free. R1, R2 = alkyl (C n H 2n-1 , n=1-12), alkoxy (OC n H 2N-1, n=1-12) or aryl, and where R3, R4 = H, alkyl or aryl. In other words, a fluorine-free starting monomer can be produced in this way. It is also possible for the starting material to contain fluorine. For this purpose, it is sufficient that at least one residue (R1, R 2,R3 and / or R4) contains fluorine. Preferably, R1, R2 = F or CF3, and R3, R4 = F, H, CF3 or aryl. In a further embodiment, R1 and R2 can be identical and / or R3 and R4 can be identical in the starting material. A particularly preferred embodiment is one in which R1 and R2 = CH3, R3 and R4 = H. Furthermore, a preferred embodiment is one in which R1 and R2 and R3 and R4 = F. Furthermore, a preferred embodiment is one in which R1 and R2 = CF3 and R3 and R4 = H. At least one, in particular exactly one, aldehyde group can be arranged in a sterically hindered position of the aromatic compound. This aldehyde group is preferably imidazolated. Surprisingly, it has been found that the aldehyde group is imidazolated despite the steric hindrance, as occurred, for example, in the previously described embodiment. In other words, imidazolation occurs despite the steric hindrance of this position.This finding is quite surprising and was not to be expected prior to the experiments conducted. In concrete terms, the imidazolation of the aldehyde group can occur through a chemical reaction with at least one other reactant, in particular with several, preferably two, other reactants. A particularly first further reactant can have the following structure: where R6 = alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy, or CF3, and where R7 = alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy, or CF3, where in particular R6 and R7 are identical. According to a preferred embodiment of the process, the first further reactant is diacetyl and / or benzil. A second reactant can be used, which can preferably be ammonium acetate. The second reactant can have the following structure: The chemical reaction for the production of the starting monomer is shown below. The structures R1, R 2 , R 3,R4, R6, R7 can correspond to the structures mentioned above. In a specific embodiment of the imidazolation, the following mixing ratios of the starting material or the two further reactants are provided. The amount of the first further reactant, in particular biacetyl, is preferably at least 50%, in particular at least 80%, preferably 100%, and / or at most 200%, in particular at most 170%, preferably 150%, particularly preferably about 110% of the amount of the starting material. The amount of the second further reactant, in particular ammonium acetate, is preferably at least 3 times, in particular at least 5 times, preferably at least 7 times, and / or at most 30 times, in particular at most 20 times, preferably at most 10 times, particularly preferably about 10 times the amount of the starting material.Preferably, a further (possibly third) reactant is added to the reaction, for example in the form of butylcatechol, in particular tert-butylcatechol. The mass of the further (third) reactant can be at least 0.5%, in particular at least 1%, preferably at least 1.5%, and / or at most 10%, in particular at most 8%, preferably at most 5%, of the mass of the starting material. This mixture is preferably dissolved in a solvent, in particular in ethanol. The mass can be at least 20 times, in particular at least 30 times, preferably at least 40 times, and / or at most 100 times, in particular at most 80 times, preferably at most 60 times, the mass of the starting material. Furthermore, an acid, in particular acetic acid, can be added during the reaction.The mass of acetic acid can be at least 5 times, in particular at least 10 times, preferably at least 12 times, and / or at most 30 times, in particular at most 25 times, preferably at most 20 times the mass of the starting material. According to a preferred embodiment of the process, the reaction solution thus prepared can be heated to a reaction temperature and maintained at this reaction temperature for a certain period of time. The reaction temperature is preferably at least 30°C, in particular at least 40°C, preferably at least 50°C, and / or at most 120°C, in particular at most 110°C, preferably at most 100°C. The reaction time can be at least two hours, in particular at least 10 hours, and / or at most 48 hours, in particular at most 30 hours. Before the end of the reaction time, the solution can be cooled to room temperature.The solution can then be concentrated before a residue is extracted. Specifically, the residue can be dissolved in chloroform and / or extracted at least once, in particular three times, against NaHCO3 and at least once, in particular exactly once, against H2O. The solvent, in particular ethanol, can then be removed, in particular by means of a rotary evaporator. The crude product obtained can be purified, inter alia, by column chromatography. The yield of imidazolated starting monomer can be at least 2%, in particular at least 5%, preferably at least 10%, 15%, 20%, 40% or 50%, and / or at most 40%, in particular at most 30%, preferably at most 20%, 15% or 7%, based in particular on the amount of starting material used. In a further embodiment of the process according to the invention, the starting material can be prepared by reacting a base material.In other words, the process can also comprise the preparation of the starting material prior to the imidazolation. The starting material preferably contains an aromatic compound bearing two aldehyde groups. The aldehyde groups are preferably located in a para position on the aromatic compound. A possible structure of the base material is shown below: To obtain the starting material, an aldehyde group of the base material is preferably olefinated. This can be achieved by means of a Wittig reaction. The reaction scheme of such a Wittig reaction is shown below. To carry out this reaction, a suspension of at least two excipients can first be prepared. A first excipient can be triphenylphosphonium bromide. A second excipient can be dry tetrahydrofuran (THF). The mass of the second excipient used is preferably at least 5 times, in particular at least 8 times, preferably at least 10 times, and / or at most 30 times, in particular at most 25 times, preferably at most 20 times, particularly preferably about 14 times the mass of the first excipient. This suspension is preferably stirred. The suspension can be cooled to a reaction start temperature. The reaction start temperature can be at least -120°C, in particular at least -100°C, preferably at least -90°C. Furthermore, the reaction start temperature can be at most -20°C, in particular at most -40°C, preferably at most -65°C.According to a particularly preferred embodiment, the reaction start temperature is -78°C. In a subsequent step, a further, third auxiliary substance can be added, in particular dropwise. The third auxiliary substance can be n-butyllithium. The third auxiliary substance can also be butyllithium, in particular n-butyllithium, which is preferably dissolved in a solvent, in particular in hexane. Preferably, a solution of at least 1 M, in particular at least 1.5 M, and / or of at most 5 M, in particular of at most 4 M, in solvent is present. A solution of 2.5 M in hexane is particularly preferred. The molar ratio of the added n-butyllithium to the triphenylmethylphosphonium bromide can be at least 1:5, in particular at least 1:2.5, preferably at least 1:1.5, and / or at most 1:0.25, in particular at most 1:0.5, preferably at most 1:0.7, particularly preferably 1:1.The base material is added to the resulting solution, which is preferably stirred at the reaction start temperature for a period of at least one hour and / or at most 5 hours, preferably for a period of 3 hours. The molar ratio of the base material to the triphenylmethylphosphonium bromide can be at least 1:3, in particular at least 1:2, preferably at least 1:1.5, and / or at most 1:0.3, in particular at most 1:0.5, preferably at most 1:0.7, particularly preferably 1:1. The starting material can preferably be dissolved in tetrahydrofuran (THF) before being added. The solution thus obtained can be warmed to a target temperature, which is in particular at least 10 °C and / or at most 40 °C, preferably room temperature, and stirred for a period of at least 5 hours, in particular at least 10 hours and / or at most 24 hours, in particular at most 18 hours.Individual drops of water can then be added. Finally, the solution is preferably concentrated and purified, in particular by column chromatography, using an auxiliary solution consisting, in particular, of cyclohexane and dichloromethane, preferably in a ratio of 9:1. In a specific embodiment, the yield of the resulting starting material, based on the amount of base material used, can be at least 30%, in particular at least 40%, and / or at most 70%, in particular at most 60%, preferably about 50% or about 48%. In a further embodiment, one of the two aldehyde groups on the base material can be sterically hindered. In this case, the sterically unhindered aldehyde group is preferably olefinated. Surprisingly, it has been found that the Wittig reaction described proceeds only at the sterically unhindered aldehyde group in the 4-position of the phenyl ring.In a further embodiment, the base material can be produced from a base material. In other words, the process according to the invention for producing a starting monomer can also comprise the production of the base material starting from a base material. The production of the base material starting from a base material can take place in several stages, in particular in two stages. For this purpose, a base material can first be provided. This can have the following structure: The designations R1, R2, R3, and R4 can, in principle, be used as previously described. Regarding R3 and R4, an additional variation is that R3 and R4 can be 1. An example reaction sequence for the preparation of the base material starting from the basic material is shown below. First, the base material can be dissolved in dry tetrahydrofuran (THF), particularly under a protective gas atmosphere, preferably under an argon atmosphere. In preparing this solution, the mass of dry THF can be at least 5 times, in particular at least 10 times, particularly preferably at least 15 times and / or at most 50 times, in particular 40 times, preferably at most 30 times, in particular about 21 times the mass of base material used. The solution can be cooled to a reaction start temperature, which is preferably at least -100°C and / or at most -50°C, particularly preferably -78°C. An auxiliary agent, in particular n-butyllithium dissolved in hexane, can be added, particularly under a protective gas atmosphere. The solution in hexane can be present in the same way as described above in connection with the preparation of the starting material starting from the base material.The amount of the added excipient (especially n-butyllithium) is preferably at least 0.5 times, in particular at least 1 times, preferably at least 1.5 times and / or at most 4 times, in particular at most 3 times, preferably at most 2.5 times the amount of the base material used. This solution can be stirred for a defined period after addition of the excipient. This period can be at least 2 minutes, in particular at least 10 minutes and / or at most 120 minutes, in particular at most 60 minutes. Dimethylformamide (DMF) can then be added to the solution.The amount of DMF added can be at least 0.2 times, in particular at least 0.5 times, preferably at most 0.7 times, and / or at most 4 times, in particular at most 3 times, preferably at most 2 times, particularly preferably about 1 times the amount of the base material used. The solution can then be stirred again for a certain period of time. This period can also be at least 2, in particular at least 10 minutes, and / or at most 120 minutes, in particular at most 60 minutes, particularly preferably about 30 minutes. This process can then be repeated, i.e., an auxiliary, in particular n-butyllithium, can be added again.The molar amount of n-butyllithium now added can be at least 1 times, in particular at least 2 times, preferably at least 3 times and / or at most 10 times, in particular at most 8 times, preferably at most 5 times, particularly preferably 4 times the molar amount of the base material used. After further stirring of the solution for a period of at least 20 minutes, in particular at least 60 minutes and / or at most 10 hours, in particular at most 7 hours, DMF can be added again. The molar amount of DMF added can be at least 1 times, in particular at least 2 times, and / or at most 10 times, in particular at most 5 times, preferably about 3 times the amount of the base material used. The solution can be heated during or after the addition of DMF. In particular, the solution can be heated to room temperature.Hydrochloric acid and a solvent, in particular diethyl ether, can then be added to the solution. An organic phase can be separated, and the remaining aqueous phase can be washed at least once, in particular twice, with a solvent, preferably with diethyl ether. The resulting organic extracts can be purified and / or washed with water and / or, in particular, dried over MgSO4 and / or filtered. It is possible to remove the solvent in a vacuum, i.e., under reduced pressure. The residue thus obtained can be recrystallized, in particular from hexane, to preferably yield a white crystalline solid as the base material. The yield of base material can be at least 20%, in particular at least 30%, preferably at least 40%, and / or at most 80%, in particular at most 70%, preferably at most 60%, preferably about 53%, based on the amount of base material used.betragen. The object underlying the invention is further achieved by a starting monomer prepared by a process as described above. Furthermore, the object underlying the invention is achieved by a starting monomer having the following structure: where R1, R2= alkyl (C n H 2n-1 , n=1-12), alkoxy (OC n H 2N-1 , n=1-12), Aryl, F oder CF3, where R3, R4= H, alkyl, aryl, F, H, CF3 or aryl, where R6= alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy, or CF3, and where R7= alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy, oder CF3,where in particular R1 and R2, and / or R3 and R4, and / or R6 and R7 are identical. A particularly preferred embodiment is one in which R1 and R2 = CH3, R3 and R4 = H. Furthermore, a preferred embodiment is one in which R1 and R2 and R3 and R4 = F. Furthermore, a preferred embodiment is one in which R1 and R2 = CF3 and R3 and R4 = H. In a further embodiment, the starting monomer can be fluorine-free. It is also possible for the starting monomer to contain fluorine. In this case, at least one organic radical R1, R2, R3, or R4 contains fluorine. The object underlying the invention is further achieved by a process for producing a polymer, comprising the following steps: - providing a polymer as described above, in particular produced using a process according to the invention for producing a starting monomer as described above; - polymerization, in particular radical polymerization, of the starting monomer.A possible reaction scheme for the preparation of the polymer is shown below. The starting monomer is preferably mixed with an auxiliary, in particular with azobisisobutyronitrile, and dissolved in a solvent. The molar amount of auxiliary is preferably at least 1%, in particular at least 2%, preferably at least 3% and / or at most 20%, in particular at most 10%, preferably at most 8%, particularly preferably 5% of the molar amount of the starting monomer. Ethanol or NMP (N-methyl-2-pyrrolidone), for example, can be used as the solvent. Optionally, degassing can take place. For this purpose, an inert gas, in particular argon, can be passed through the solution. This can be done, for example, for a period of at least 2 minutes, in particular of at least 10 minutes and / or of at most 120 minutes, in particular of at most 60 minutes, preferably of 30 minutes. The solution can be heated to a polymerization temperature.This can be at least 40°C, in particular at least 55°C, preferably at least 65°C, and / or at most 100°C, in particular at most 90°C, preferably at most 80°C, particularly preferably 65°C or 75°C. The solution can be kept at this temperature for a certain reaction time. The reaction time can be at least 4 hours, in particular at least 10 hours, and / or at most 48 hours, in particular at most 36 hours, preferably about 24 hours. During this time, the polymerization can take place, which proceeds in particular as a radical polymerization, preferably as a free radical polymerization. The polymer thus obtained can then be purified by at least one, in particular multiple, preferably four-fold dialysis, for example against ethanol. The polymer thus obtained can have the following structure:. where R1, R2= alkyl (C n H 2n-1 , n=1-12), alkoxy (OC n H2N-1, n=1-12) or aryl, where R3, R4 = H, alkyl, aryl, F, H or CF3, and where R6, R7 = alkyl, aryl or alkoxy or CF3. Particularly preferred is an embodiment in which R1 and R2 = CH3, R3 and R4 = H. Furthermore, preferred is an embodiment in which R1 and R2 and R3 and R4 = F. Furthermore, preferred is an embodiment in which R1 and R2 = CF3 and R3 and R4 = H. The polymer present can be a homopolymer and have the structure described above as a repeating unit. The process according to the invention for producing a polymer can also be characterized in that a further starting monomer is provided and a copolymer is produced. In other words, in addition to the starting monomer produced as described above, a further starting monomer can be provided. In this way, a copolymer can be produced.Preferably, the additional starting monomer, which can also be referred to as a comonomer, is styrene-based. The structure shown above can be contained in the copolymer. Examples of possible comonomers can be found in the figure below: The process according to the invention can be characterized in that it further comprises a subsequent modification of the polymer to create an anion exchange polymer. In other words, a subsequent modification can take place, in particular to provide or increase electrical conductivity. Specifically, the subsequent modification can comprise the alkylation or arylation of imidazole-N (nitrogen). In other words, the nitrogen atoms of the imidazole group can be used for the subsequent modification, for example, by alkylating or arylating them. A possible reaction scheme for the subsequent modification is shown below: R5 can be an aryl or an alkyl. The polymer is preferably dissolved in a solvent, in particular in dry NMP. This can take place at a temperature of at least 30°C, in particular at least 50°C, preferably at least 60°C and / or at most 100°C, in particular at most 90°C, preferably at most 80°C, particularly preferably at 70°C. Specifically, this can take place in a two-necked flask with a reflux condenser. The mass of the solvent can be at least 20 times, in particular 30 times, preferably at least 50 times and / or at most 200 times, in particular at most 150 times, preferably at most 100 times, particularly preferably about 64 times the amount of polymer used. The solution thus obtained can then be cooled. Preferably, the solution is cooled to a temperature of about 40 °C.Subsequently, an excipient, in particular NaH, can be added. The amount of excipient added can be at least 0.5 times, in particular at least 1 times, and / or at most 4 times, in particular at most 3 times, preferably 1.5 times the amount of polymer used. The solution thus obtained can be stirred for a period of time. It is preferably stirred for a period of at least 2 hours and / or at most 24 hours. The temperature can preferably be 70°C. The reaction can further comprise the addition of a further excipient. This can be, for example, 1-bromobutane. The excipient can be added in two stages. The total amount of the auxiliary substance added may be at least 1 time, in particular at least 2 times and / or at most 6 times, in particular at most 5 times the amount of the last polymer.The amount of further excipient added is preferably 3.2 times the amount of polymer used. The same amount of further excipient can be added in each of the two stages. Between the two additions of the further excipient, the resulting solution can be stirred at a temperature of at least 50°C and / or at most 90°C, in particular 70°C, for a period of at least one hour, in particular at least 2 hours, and / or at most 8 hours, in particular at most 6 hours. After the second addition of the further excipient, the further reaction temperature can be increased. The reaction temperature can then be increased to at least 80°C, in particular at least 90°C, and / or at most 120°C, in particular at most 110°C. The solution can then be further stirred at this reaction temperature.In particular, this can take place over a period of at least 2 hours and / or at most 48 hours, preferably over a period of at least 10 and / or at most 18 hours. Finally, the solution can be purified by at least one, in particular multiple, preferably four dialysis, in particular against ethanol. The dialysis can take place for at least 2 hours, in particular at least 8 hours, preferably at least 12 hours and / or at most 72 hours, in particular at most 48, preferably at most 36 hours. The subsequent modification is preferably carried out under the influence of excipients, in particular under the influence of NaH or NMP. Furthermore, an excipient can have the structure R5-BR, R5-CL, R5-CL or R. 5- I, where R5= alkyl, aryl, especially methyl, ethyl, propyl, butyl or pentyl ist.The object underlying the invention is further achieved by a polymer produced by a process for producing a polymer as described above. Furthermore, the object underlying the invention is achieved by a polymer having the following structure: where R1, R2= alkyl (C n H 2n-1 , n=1-12), alkoxy (OC n H 2N-1 , n=1-12) or aryl, where R3, R4= H, alkyl, aryl, F, H or CF3, where R5= alkyl or aryl, and where R6, R7= alkyl, aryl or alkoxy or CF3. In a specific embodiment, the polymer can be characterized in that it is fluorine-free, where R1, R2= alkyl (C n H 2n-1 , n=1-12), alkoxy (OC n H 2N-1, n=1-12) or aryl, where R3, R4 = H, alkyl or aryl, where R5 = alkyl or aryl, in particular methyl, ethyl, propyl, butyl or pentyl, where R6, R7 = alkyl, aryl or alkoxy, in particular methyl, phenyl or methoxy. Alternatively, the polymer can be characterized in that it contains fluorine, where R1, R2 = F or CF3, where R3, R4 = F, H, CF3 or aryl, where R5 = alkyl or aryl, in particular methyl, ethyl, propyl, butyl or pentyl, where R6, R7 = CF3, alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy. In a preferred embodiment, R1 and R2 can be identical and / or R3 and R4 can be identical and / or R6 and R7 can be identical. Particularly preferred is an embodiment in which R1 and R2 = CH3 and R3 and R4 = H. Furthermore, preferred is an embodiment in which R1 and R2 and R3 and R4 = F. Furthermore, preferred is an embodiment in which R1 and R2 = CF3 and R3 and R4 = H.The polymer according to the invention can have the structure shown above as a repeating unit. The polymer can be formed as a homopolymer. The polymer according to the invention can be formed as a copolymer and have the following structure: R1, R2, R3, R4, R5, R6, and R7 can be configured as described above. The copolymer can be a random copolymer, an alternating copolymer, or a block copolymer. The previously displayed structure can represent a repeating unit of the polymer according to the invention. In other words, the polymer according to the invention can have the previously displayed structure as a repeating unit. The object underlying the invention is further achieved by a membrane made from a polymer as described above. The membrane can be configured as a blend membrane, which means that the polymer according to the invention is blended with another polymer to produce the membrane. For example, the other polymer can be POB (poly(oxindolebiphenylene)), O-PBI, or polyvinyl alcohol-co-ethylene. In a further embodiment, the membrane can be an anion exchange membrane.The polymer of the invention may be an anion exchange polymer.The structure of POB is shown below:. The invention relates to such a membrane for alkaline membrane water electrolysis, especially alkaline membrane seawater electrolysis, in alkaline membrane fuel cells, in redox flow batteries, especially vanadium redox flow batteries, for diffusion dialysis, Donnan dialysis, electrodialysis, nanofiltration, and / or reverse osmosis. The polymers according to the invention or membranes produced therefrom are characterized by the use of a polystyrene backbone, a low weight of a repeating unit, and high ion exchange capacities, which leads to high conductivities. Overall, it was surprisingly found that styrene-based polymers containing sterically protected imidazole or imidazolium groups can be produced. For further details of the invention, reference is made to the dependent claims and the following description of several exemplary embodiments with reference to the figures.The starting monomers and polymers, as well as processes, shown in the figures are each preferred embodiments of the present invention. The figures show: Fig. 1 a reaction scheme for the preparation of a polymer according to a first embodiment of the present invention; Fig. 2 1H-NMR spectra during the preparation of the starting material according to the first embodiment; Fig. 3 a 2D-HSQC spectrum of 2,6-dimethyl-4-vinylbenzaldehyde; Fig. 4 a 2D-HMBC spectrum of 2,6-dimethyl-4-vinylbenzaldehyde; Fig. 5 a 1H-NMR spectrum of 2-(2,6-2,6-dimethyl-4-vinylphenyl)-4,5-dimethyl-1H-imidazole); Fig. Figure 6 shows a 1H NMR spectrum of poly(2-(2,6-dimethyl-4-vinylphenyl)-4,5-dimethyl-1H-imidazole) in DMSO-trifluoroacetic acid; Figure 7 shows a GPC curve of poly(2-(2,6-dimethyl-4-vinylphenyl)-4,5-dimethyl-1H-imidazole) in DMSO-trifluoroacetic acid measured in NMP at 70 °C (0.1 M) with polystyrene calibration.Figure 8 shows a reaction scheme for producing a polymer for blending with a polymer according to the invention; Figure 9 shows a reaction scheme for producing a polymer according to the invention according to a second embodiment of the present invention; Figure 10 shows a reaction scheme for producing a polymer according to the invention according to a third embodiment of the present invention; Figure 11 shows a reaction scheme for producing a polymer according to the invention according to a fourth embodiment of the present invention; Figure 12 shows a reaction scheme for producing a polymer according to the invention according to a fifth embodiment of the present invention; Figure 1 shows, in the upper section, a process according to the invention for producing a starting monomer (step 1 - step 4). 2,5-dibromo,1,3-dimethylbenzene is first provided as the starting material (1). Starting from this starting material, a base material is produced (step 1, step 2).This occurs in two steps, ultimately yielding 2,6-dimethylterephalaldehyde (3). Under experimental conditions, this could be accomplished as follows: 2,5-Dibromo-1,3-dimethylbenzene (65.99 g, 250.0 mmol, 1.000 eq.) was dissolved in dry THF (1.563 L) under an Ar atmosphere, and the solution was cooled to -78 °C. Under an Ar atmosphere, n-butyllithium (200 mL, 500.0 mmol, 2.5 M in hexane) was added and stirred for 30 minutes. Subsequently, DMF (19.24 mL, 250.0 mmol, 1.000 eq.) was added to the solution. The solution was stirred for a further 30 minutes before n-butyllithium (400 mL, 1.000 mol, 2.5 M in hexane) was slowly added. The solution was stirred for a further 2 hours, DMF (57.70 mL) was added, and the solution was warmed to room temperature. HCl (1.200 mL, 2 M) and then diethyl ether (600 mL) were added to the mixture. The organic phase was separated, and the aqueous phase was washed twice with diethyl ether (300 mL each).The organic extracts were combined, washed with water, dried over MgSO4, filtered, and the solvent removed in vacuo. The white residue was recrystallized from hexane to give a white crystalline solid. Yield: 21.64 g (133.4 mmol, 53%). 1 H NMR: (500 MHz, CHCl3-d, δ): 10.33 (s, 1H, OC-H), 9.68 (s, 1H, OC-H), 7.58 (s, 2H, H ar), 2.66 (s, 3H, CH3). Starting from this base material, a starting material for the preparation of a starting monomer was generated in step 3. This starting material is 2,6-dimethyl-4-vinylbenzaldehyde (4). This was carried out in experiments. The experiments can be described as follows: A stirred suspension of triphenylmethylphosphonium bromide (47.66 g, 134.42 mmol, 1000 eq.) in dry THF (749.5 mL) was cooled to -78 °C. Subsequently, n-butyllithium (53.37 mL, 134.42 mmol, 2.5 M in hexane, 1000 eq.) was added dropwise at -78 °C, and the solution was stirred for 3 h at -78 °C. Subsequently, 2,6-dimethylterephthalaldehyde (21.64 g, 133.4 mmol, 1.000 eq.) dissolved in THF (85.53 mL) was added. The cooling bath was removed, and the solution was warmed to room temperature and stirred overnight.After a few drops of water were added, the solution was concentrated and purified by column chromatography (cyclohexane / dichloromethane 9:1). Yield: 10.17 g (63.50 mmol, 48%). 1 H NMR: (500 MHz, CHCl3-d, δ, see Figure 7, Figure 8, Figure 9): 10.58 (s, 1H, OC-H), 7.12 (s, 2H, H ar), 6.63 (dd, J = 17.5 Hz, 11 Hz, 1H, CH=CH2), 5.85 (d, J = 17.5 Hz, 1 H, CH=CH2), 5.37 (d, J = 11H z, 1 H, CH=CH2), 2.62 (s, 3H, CH3) Figure 2 shows the different 1H NMR spectra of the symmetrical aldehyde (top) with the corresponding spectrum of the asymmetrical aldehyde (middle) and the corresponding dialdehyde. It can be seen that in the Wittig reaction of the dialdehyde (bottom) with triphenylmethylphosphonium boronide only 2,6-dimethyl-4-vinylbenzaldehyde is formed. This is confirmed by Figures 3 and 4, which show the corresponding 2D-HSQC and HMBC spectra of 2,6-dimethyl-4-vinylbenzaldehyde, respectively. This demonstrated that the asymmetric isomer was formed. In the next step, a starting monomer was prepared from this starting material (4). Biacetyl and ammonium acetate were used as additional reactants. The specific experimental description is explained below: 2,6-dimethyl-4-vinylbenzaldehyde (10.17 g, 63.50 mmol, 1.000 eq.), diacetyl (6.013 g, 69.85 mmol, 1.10 eq.), ammonium acetate (48.95 g, 635.0 mmol, 10.00 eq.), and tert-butylcatechol (200 mg) were dissolved in ethanol (650 mL). Acetic acid (158.8 mL) was then added, and the reaction solution was heated under reflux for 24 h. After the solution was cooled to room temperature, the solution was concentrated, and the residue was dissolved in chloroform and extracted three times against 1 M NaHCO3 (200 mL) and once against H2O (200 mL). The solvent was then removed using a rotary evaporator, and the crude product was purified by column chromatography (cyclohexane / DCM 1:1). Yield: 990.0 mg (4.374 mmol, 7%). 1 H NMR: (500 MHz, CHCl3-d, δ, Figure 10): 7.08 (s, 2H, H ar), 6.63 (dd, J = 17.5 Hz, 11 Hz, 1H, CH=CH2), 5.74 (d, J = 17.5 Hz, 1 H, CH=CH2), 5.24 (d, J = 11 Hz, 1 H, CH=CH2), 2.21 (s, 3H, CH3), 2.12 (s, 3H, CH3). Specifically, an imidazolation of the aldehyde group takes place here. Figure 5 shows the 1H NMR spectrum of the starting monomer (5). In the next step (step 5), polymerization takes place, specifically a free radical polymerization, to yield the polymer (6). The corresponding experimental description is as follows: Azobisisobutyronitrile (18.14 mg, 110.5 µmol, 0.050 eq.) and 2-(2,6-dimethyl-4-vinylphenyl)-4,5-dimethyl-1H-imidazole (500.0 mg, 2.209 mmol, 1.000 eq.) were dissolved in NMP (7 mL). For degassing, argon was bubbled through the solution for 30 minutes. The solution was then heated to 75 °C for 24 h. The polymer was purified by dialysis against ethanol four times (24 h each). 1H NMR: (500 MHz, CHCl3-d, δ, Figure 11): 6.37 (s, 2H, Har), 1.92-2.22 (m, 15H). GPC (0.1 M LiBr in NMP, 70 °C, polystyrene calibration, Figure 12): M. n= 39000 g / mol, Ð = 1.8. Figure 6 shows the 1H NMR spectrum of the resulting polymer (6) in DMSO-trifluoroacetic acid. The signal at 14.5 ppm originates from the trifluoroacetic acid, and the signal at 9.69 ppm is the water peak in an acidic DMSO-trifluoroacetic acid mixture. Finally, Figure 7 shows the GPC curve of the polymer (6) measured in NMP at 70 °C with polystyrene calibration. Following polymerization, a functional modification takes place. According to a preferred embodiment, this is a quaternization. The specific experimental description is as follows: Poly(2-(2,6-dimethyl-4-vinylphenyl)-4,5-dimethyl-1H-imidazole) (0.200 g, 883.7 µmol, 1.000 eq.) is dissolved in dry NMP (12.5 mL) by stirring at 70 °C in a two-neck flask equipped with a reflux condenser. The solution is cooled to 40 °C, then NaH (31.80 mg, 1.326 mmol, 1.500 eq.) is added, and the temperature is raised again to 70 °C.The solution is stirred overnight at 70 °C. 1-Bromobutane (151.0 µL, 1,410 mmol, 1,600 eq.) is then added, and stirring is continued at 70 °C for 4 h. 1-Bromobutane (151.0 µL, 1,410 mmol, 1,600 eq.) is then added again, and the temperature is raised to 100 °C. The solution is stirred overnight at 100 °C and then purified by dialysis against ethanol four times (24 h each). The resulting functionalized polymer can be blended with another polymer to produce a membrane. One possible additional polymer is poly(oxindole biphenylene) (POB). The preparation of this polymer is shown schematically in Figure 8. Membrane production by blending with this polymer can be described as follows.Poly(2-(2,6-dimethylphenyl)-1,3-dibutyl-4,5-dimethyl-1H-imidazol-3-ium bromide) (50 mg) is dissolved in DMSO (200 mg). Subsequently, a POB solution (300 mg, 5 wt.% in DMSO) was added, and after homogenization of the solution, the membrane solution was spread with a doctor blade (height: 400 µm) and dried at 80 °C for 3 h. The membrane thus produced is referred to below as Membrane 1. In addition, two further membranes were prepared: Membrane 2: Poly (2-(2,6-dimethylphenyl)-1,3-dibutyl-4,5-dimethyl-1H-imidazol-3-ium bromide (50 mg) is dissolved in DMSO (298 mg). Subsequently, a poly(2,20-(m-phenylene)-5,5′-bibenzimidazole) (O-PBI) solution (405 mg, 5 wt.% in DMSO) is added and, after homogenization of the solution, the membrane solution is spread with a doctor blade (height: 400 µm) and dried at 80 °C for 3 h. Membrane 3: Poly(2-(2,6-dimethylphenyl)-1,3-dibutyl-4,5-dimethyl-1H-imidazol-3-ium bromide (50 mg) is dissolved in DMSO (298 mg). Subsequently, a polyvi- nyl alcohol-co-ethylene solution (203 mg, 10 wt.% in DMSO) was added and, after homogenization of the solution, the membrane solution was spread with a doctor blade (height: 400 µm) and dried at 80 °C for 3 h. The conductivities of the membranes can be measured with various anions. For this purpose, a BT-710 probe head for conductivity measurements from Scribner was used, with the conductivity measurements being carried out in demineralized water. The conductivity was calculated by varying the voltage from 0 V to 100 mV in 10 mV steps and measuring the corresponding current flow. This was followed by varying the voltage from 0 V to -100 mV in 10 mV steps and measuring the current flowing. Plotting the applied voltage against the measured current produces a straight line whose slope corresponds to the resistance of the membrane.The conductivity σ of membrane 2 in Cl form was determined using the following formula, where L is the distance between the two measuring electrodes, d is the thickness of the membrane and b is the width of the membrane:. For membrane 2, a Cl- conductivity of 2.39 mS / cm was determined at 25 °C. Due to the higher mobility of OH- ions compared to Cl- ions, the corresponding conductivity is expected to be higher. The conductivities can be determined analogously to the procedure described above, whereby care must be taken to work in a CO2-free atmosphere to avoid the formation of HCO3- / CO3. 2-by reacting OH- with CO2. Furthermore, the conductivity can also be increased by reducing the O-PBI content, although care must be taken to ensure that the mechanical stability of the membranes remains sufficient. Embodiment 2: Figure 9 shows a further process for producing a polymer according to the present invention. The same starting material as in the reaction route shown in Figure 1 was used as the starting material for the initial production of a starting monomer (step 1 of Figure 9). However, the imidazolation was not carried out with biacetyl and ammonium acetate, but with the sterically much more demanding benzil and ammonium acetate. Surprisingly, it was found that the imidazolation was successful without attacking the CC double bond. In principle, it is also conceivable to use sterically more hindered alpha-diketones instead of benzil, such asThe two commercially available diketones 1,2-di-O-tolyethane-1,2-dione or 1,2-bis(2,6-dimethylphenyl)ethane-1,2-dione can be used. This allows even greater shielding and thus better chemical stability of the imidazolium cation to be achieved. The resulting starting monomer 8 can be radically polymerized to polymer 9 (step 2). Surprisingly, it has also been shown that the alkylation / quaternization of the imidazole to give the anion exchange polymer (10) is successful. Embodiment 3: Figure 10 shows a further embodiment according to the present invention. The starting material is the commercially available compound 2,5-dibromo-1,3-diiodobenzene (11). Surprisingly, it was possible to convert these with benzeneboronic acid in a Suzuki-Miyaura CC coupling reaction to form a terphenylene compound (2',5'-dibromo-1,1':3',1"-terphenyl)(12).In the following two steps, the bromine residues from compound 12 are exchanged for aldehyde groups to form compound 13, as described in Figure 1 for 2,5-dibromo-1,3-dimethylbenzene. Compound 13, which forms the base material in this case, can then be converted to a modified styrene in a Wittig reaction, whereby, surprisingly, the aldehyde at the sterically protected 4-position is not attacked. In a further step, this starting material (14) is then reacted, for example, with diacetyl and ammonium acetate to form compound 15a or with benzil and ammonium acetate to form compound 15b (starting monomers). These can surprisingly be converted to polymers (16a, 16b) by radical polymerization. In a final step, the imidazole N groups are dialkylated with KOH and CH3I to form the anion exchange polymer (17a, 17b).A further embodiment can consist in dimethylating the starting monomers (15a, 15b) at their imidazole groups and radically polymerizing the quaternized monomer to form the polymers 17a, 17b. In other words, the starting monomer can also be modified so that an anion exchange polymer is obtained immediately after polymerization. Embodiment 4: Figure 11 shows a further embodiment of the process according to the invention. This ultimately results in a fluorinated polymer. 1,2,4,5-tetrafluorobenzene (18) is used as the starting material. This is first lithiated with N-butyllithium and then reacted with ethyl formate. The aldehyde thus formed is then protected with ethylene glycol in a standard procedure to form 1,3-dioxolane (19). The second hydrogen atom in 1,3-dioxolane is also removed by lithiation, and the resulting carbanion is again reacted with ethyl formate to give the compound (20).In the next step, a Wittig olefination takes place to form 2-(2,3,5,6-tetrafluoro-4-vinylphenyl)-1,3-dioxolane (21), which forms the base material. In the next step, this is reacted with TFA to form the starting material (22). Subsequently, the aldehyde group is converted into the corresponding imidazole (23a, 23b) by the Radciszewski synthesis, which is then converted into the polymers (24a, 24b) by radical polymerization in the next step. Finally, the polymer is quaternized to form the fluorine-containing anion exchange polymer (25a, 25b). Such partially fluorinated polystyrene imidazolium salts are of particular interest for acidic electrochemical applications such as redox flow batteries.The results of a 2015 study suggest that partially fluorinated aromatic sulfonated polymer membranes in vanadium redox flow batteries (VRFBs) exhibit better oxidation stability than non-fluorinated aromatic sulfonated polymer membranes. The application of an ionically cross-linked cation exchange blend membrane made of poly(2,3,5,6-tetrafluorostyrene-4-phosphonic acid) and F6PBI in a VRFB also demonstrated excellent chemical stability of this membrane. However, the use of anion exchange membranes (AEMs) is generally preferred over cation exchange membranes (CEMs) in VRFBs. Unlike CEMs, AEMs exclude the highly oxidizing and thus potentially membrane-degrading vanadium cations from the membrane matrix due to the Donnan effect. Embodiment 5: Figure 12 shows a further embodiment of the process according to the invention for producing a starting monomer or a polymer.In this, 2,5-dibromo-1,3 bis (trifluoromethyl)benzene (26) is used as the basic material.

Claims

CLAIMS 1. A process for producing a starting monomer, comprising the following steps: - Providing a starting material of the form wherein at least one, in particular exactly one aldehyde group is present on the aromatic; -imidazolation of at least one aldehyde group.

2. Process according to claim 1, characterized in that the starting material is fluorine-free, wherein R1, R2= alkyl (C n H 2n-1 , n=1-12), alkoxy (OC n H 2N-1 , n=1-12), aryl, and where R3, R4= H, alkyl, aryl. 2 3. The process according to claim 1, characterized in that the starting material contains fluorine, where R1, R2 = F, CF3, and where R3, R4 = F, H, CF3, aryl.

4. The process according to any one of the preceding claims, characterized in that R1 and R2 are identical, and / or that R3 and R4 are identical.

5. The process according to any one of the preceding claims, characterized in that at least one, in particular exactly one, aldehyde group is located at a sterically hindered position of the aromatic compound, and this aldehyde group is imidazolated.

6. The process according to any one of the preceding claims, characterized in that the imidazolation of the aldehyde group takes place by a chemical reaction with at least one further reactant, in particular with several, preferably with two, further reactants.

7. The process according to claim 6, characterized in that a, in particular first, further reactant has the following structure: where R6 = alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy, or CF3, and where R7 = alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy, or CF3, where in particular R6 and R7 are identical. 3 8. The process according to claim 7, characterized in that a particularly first further reactant is biacetyl and / or benzil.

9. The process according to one of claims 6 to 8, characterized in that a particularly second further reactant has the following structure:

10. The process according to one of the preceding claims, characterized in that the starting material is prepared by reacting a base material which has an aromatic compound on which two aldehyde groups are arranged.

11. The process according to claim 10, characterized in that the aldehyde groups are arranged in a para-position on the aromatic compound.

12. The process according to claim 10 or 11, characterized in that an aldehyde group of the base material is olefinated, in particular by means of a Wittig reaction. 13.Process according to one of claims 10 to 12, characterized in that one of the two aldehyde groups on the base material is sterically hindered and the sterically unhindered aldehyde group is olefinated.

14. Starting monomer prepared by a process according to one of the preceding claims. 4 15. Starting monomer, in particular according to claim 14, which has the following structure: where R1, R2= alkyl (C n H 2n-1 , n=1-12), alkoxy (OC n H 2N-1, n=1-12), aryl, F, CF3, where R3, R4=H, alkyl, aryl, F, H, CF3, aryl, where R6=alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy, or CF3, and where R7=alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy, or CF3, where, in particular, R1 and R2, and / or R3 and R4, and / or R6 and R7 are identical.

16. A process for producing a polymer, comprising the following steps: - providing a starting monomer according to claim 14 or claim 15; - polymerization, in particular radical polymerization, of the starting monomer. 5 17. The process according to claim 16, characterized in that a further starting monomer is provided and a copolymer is produced.

18. The process according to claim 17, characterized in that the further starting monomer (comonomer) is styrene-based, and / or that the further starting monomer (comonomer) is selected from the following group: 6 19. The process according to any one of claims 16 to 18, characterized in that the process further comprises a subsequent modification of the polymer to create an anion exchange polymer.

20. The process according to claim 18, characterized in that the subsequent modification comprises the alkylation or arylation of imidazole-N.

21. A polymer prepared by a process according to any one of claims 16 to 20. 7 22. Polymer, in particular according to claim 21, which has the following structure: (O-CnH2N-1, n=1-12), aryl, where R3, R4 = H, alkyl, aryl, F, H, CF3, where R5 = alkyl, aryl, and where R6, R7 = alkyl, aryl or alkoxy or CF3.

23. Polymer according to claim 22, characterized in that it is fluorine-free, where R1, R2 = alkyl (C n H 2n-1 , n=1-12), alkoxy (OC n H 2N-1 , n=1-12), Aryl, F, CF 3,where R3, R4 = H, alkyl, aryl, where R5 = alkyl, aryl, in particular methyl, ethyl, propyl, butyl, pentyl, where R6, R7 = alkyl, aryl, alkoxy, in particular methyl, phenyl, methoxy.

24. Polymer according to claim 22, characterized in that it contains fluorine, where R1, R2 = F, CF3, where R3, R4 = F, H, CF3, aryl, where R5 = alkyl, aryl, in particular methyl, ethyl, propyl, butyl or pentyl, where R6, R7 = CF3, alkyl, aryl or alkoxy, in particular methyl, phenyl, methoxy. 8 25. The polymer according to claim 23 or 24, characterized in that R1 and R2 are identical, and / or that R3 and R4 are identical, and / or that R6 and R7 are identical.

26. The polymer according to any one of claims 22 to 25, characterized in that the polymer is formed as a copolymer and has the following structure:

27. The polymer according to claim 26, characterized in that it is a random copolymer, an alternating copolymer, or a block copolymer.

28. A membrane consisting of a polymer according to any one of claims 21 to 27.

29. Use of the membrane according to claim 28 for electrolysis and / or in fuel cells and / or in redox flow batteries and / or for dialysis, in particular for diffusion dialysis and / or Donnan dialysis and / or for electrodialysis, and / or for filtration and / or for reverse osmosis and / or for pressure-retarded osmosis.

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