Patent Application
20250163232
The present invention relates to a substance, in particular a functionalized oligomer or polymer, wherein the substance contains oligomeric or polymeric chains to which perfluoroaromatic compounds are coupled or which contain perfluoroaromatic compounds. The invention also relates to a membrane containing such a substance and to the use of a membrane. The invention also relates to a method for the production of such a substance.
Membranes, especially ion exchange membranes, are used in particular in electrochemical processes, for example in electrolysis processes, or in electrochemical systems, for example in a fuel cell or in a battery. High demands are placed on such membranes. On the one hand, they must be sufficiently chemically stable in relation to the surrounding medium for their area of application. In addition, such membranes are often exposed to mechanical stresses. Electrochemical applications also require a certain degree of conductivity combined with a low degree of swelling, i.e. low volume expansion.
Oligomers and polymers from which such membranes are produced can contain perfluoroaromatic compounds. These can be coupled to oligomeric or polymeric chains or be part of the chain backbone. It is also possible to attach such perfluoroaromatic compounds to a base material. In order to improve the properties of such an oligomer/polymer, there are various ways of substituting a fluorine atom of a perfluoroaromatic compound with a functional group. Specifically, it is known to nucleophilically substitute the 4-F fluorine atom in poly(pentafluorostyrene) (PPFSt) with different functional groups, also known as nucleophiles.
By Noy-J.M.; Li, Y.; Smolan, W.; roth, P.J. Azide-para-Fluoro Substitution on Polymers: Multipurpose Precursors for Efficient Sequential Postpoylmerization Modification. Marcomolecules 2019, 52, 3083-3091 is known to replace the 4-F atom of polypentafluorostyrene with an NH2 molecule. A functionalized polymer is produced in two steps starting from polypentafluorostyrene. In the first step, the 4-F atom is replaced by an N3 molecule. In the second step, this N3 molecule is converted into an NH2 molecule. The reaction in the second step is shown in the figure below, where the NH2-functionalized polymer is shown on the left.
Also Chen, J.; Dumas, L.; Duchet-Rumeau, J.; Fleury, E.; Charlot, A.; Portinha, D. Tuning h-bond capability of hydroxylated-poly(2,3,4,5,6-pentaluorostyrene) grafted copolymers prepared by chemeselective and versatile thiol-para-fluoro “click-type” coupling with mercapatoalcohols. J. Polym. Sci. A. Polym. Chem. 2012, 50, 3452-3640 report a simple nucleophilic substitution of the 4-F atom. In this case, a functional group is coupled to the perfluoroaromatic compound in such a way that a fluorine atom is substituted by a mercaptothiol group. The structure of the resulting substance is shown below.
Another simple nucleophilic substitution of a fluorine atom is reported by Sych, G.; Simokaitiene, J.; lygaitis, R.; Jatautiene, E.; Pahsazadeh, R.; Buika, G.; Grazulevicius, J.V. Structure-properties relationship of tetrafluorostyrene-based monomers and polymers containing different donor moieties. Reactive and Functional Polymers 2019, 143, 104323. In this case, a nitrogen atom takes the position of a fluorine atom of the perfluoroaromatic compound. The structure is shown in the figure below.
DE 10 2019 008 024 A1 discloses further nucleophilic substitutions of perfluoroaromatic compounds of oligomers or polymers. Specifically, a nitrogen atom takes the place of the fluorine atom on the perfluoroaromatic compound. The structure finally obtained is shown below.
Further simple nucleophilic substitutions are described in
Sych, G.; Simokaitiene, J.; lygaitis, R.; Jatautiene, E.; Pahsazadeh, R.; Buika, G.; Grazulevicius, J.V. Structure-properties relationship of tetrafluorostyrene-based monomers and polymers containing different donor moieties. Reactive and Functional Polymers 2019, 143, 104323;
Cho, H.; Atanasov, V.; Krieg, H.M.; Kerres, J.A. Novel Anion Exchange Membrane Based on Poly(Pentafluorostyrene) Substituted with Mercaptotetrazole Pendant Groups and its Blend with Polybenzimidazole for Vanadium Redox Flow Battery Applications. Polymers (Basel) 2020, 12;
Atanasov, V.; Burger, M.; Lyonnard, S.; Porcar, L.; Kerres, J. Sulfonated poly(pentafluorostyrene): Synthesis & characterization. Solid State Ionics 2013, 252, 75-83; and
Atanasov, V.; Kerres, J. Highly Phosphonated Polypentafluorostyrene. Macromolecules 2011, 44, 6416-6423.
Such polymers can be provided with a functional group. However, this makes it difficult to achieve certain property profiles. For example, polypentafluorostyrene, whose 4-F atom is substituted with phosphonic acid groups, has a very high brittleness. This makes it impossible to use this material as a membrane in a fuel cell. The mechanical properties can be improved, for example by converting it into an acid-base blend with a mechanically and chemically stable basic polymer such as polybenzimidazole (PBI). However, this conversion reduces the number of free phosphonic acid groups due to ionic cross-linking between the acidic phosphonic acid groups and the basic imidazole groups of the PBI. This leads to a reduction in ionic conductivity, which is undesirable.
The object of the present invention is therefore to provide a substance which has favorable property profiles and can be used in particular in membranes for electrochemical processes. Furthermore, a process for the production of such a substance is to be created.
This object is solved in a substance of the type mentioned at the beginning in that several, in particular two, three, four or five fluorine atoms of the perfluoroaromatic compound are each nucleophilically substituted by a functional group.
Accordingly, the method according to the invention for producing such a substance comprises the following steps:
The invention is thus based on the idea of using the perfluoroaromatic compounds in a starting material to substitute not just one fluorine atom, but several fluorine atoms with functional groups. In other words, functional groups take the place of fluorine atoms. As a result, the property profile can be adapted to the application and different properties can be specifically combined with each other. For example, it is possible to create a polymer with a high ionic conductivity that also has a low brittleness so that it can be used as a membrane in an electrochemical application, for example in a fuel cell, an electrolysis or a redox-flow battery. The material can be an intermediate product, particularly in the manufacture of a membrane.
Specifically, the perfluoroaromatic compound can be or comprise a perfluorophenyl and/or a perfluorobiphenyl unit. A perfluorophenyl unit or a perfluorobiphenyl unit is usually docked to an oligomeric or polymeric backbone and basically comprises several fluorine atoms, in special applications 4 or 8 fluorine atoms. In principle, the perfluoroaromatic compound can also be a perfluoroterphenyl unit or a quaterphenyl unit.
Preferably, the para position and at least one ortho position and/or at least one meta position of the perfluorophenyl unit or the perfluorobiphenyl unit or a perfluoroterphenyl unit or quaterphenyl unit are each substituted by a functional group. It follows from the previously known prior art that a functional group has a tendency to first substitute the para position on the perfluorophenyl unit or the perfluorobiphenyl unit. Therefore, if several functional groups are provided on a perfluoroaromatic compound, the fluorine atom on the para position will certainly be substituted first. A further functional group will then be coupled at an ortho position and/or a meta position. If three fluorine atoms are each substituted by a functional group, an ortho fluorine atom and the meta fluorine atom opposite it can be substituted in addition to the para fluorine atom.
The perfluoroaromatic compound may be contained in the main and/or side chain of the oligomeric or polymeric chain or form a side chain. In other words, a perfluoroaromatic compound may be contained in the backbone or coupled to it. Thus, the incorporation of perfluoroaromatic compounds into the main and/or side chain of the polymer molecule enables subsequent multiple functionalization of the polymer.
In a further embodiment, the oligomeric or polymeric chains may contain cation exchangers and/or anion exchanger groups. Furthermore, the oligomeric or polymeric chains may contain a repeating unit comprising or consisting of pentafluorostyrene.
In a further embodiment, the multiple fluorine atoms of the perfluoroaromatic compound may be substituted with the same functional group or with different functional groups. In other words, the same functional group can replace several fluorine atoms of the perfluoroaromatic compound. Alternatively, different functional groups can also be provided, which can be advantageous in particular for adjusting different material properties.
Specifically, a functional group can be coupled to the perfluoroaromatic compound in such a way that a fluorine atom is substituted via a sulphur atom. In other words, the functional group can be designed in such a way that a sulphur atom takes the place of a fluorine atom of the perfluoroaromatic compound. For example, a molecule with a thiol group can be used for substitution. Such a thiol group, which is also called a sulfhydryl group, is in principle a functional group that is similar in structure to the hydroxyl group (—OH), although the oxygen atom is replaced by a sulfur atom. As the sulphur atom is particularly nucleophilic, it can substitute for the fluorine atom. If a thiol group is introduced into an organic compound, as is the case with the nucleophilic substitution described above, this is referred to as thiolation or thiolation. In this case, the sulphur atom of the thiol group takes the place of a fluorine atom of the perfluoroaromatic compound.
In a further embodiment, a functional group can have a linear and/or branched saturated or unsaturated Cn-body, in particular a C2-, C3-, C6-, C8-, C10-, C12-, C14-, C16- or a C18-body, which carries at one end the sulphur atom which substitutes a fluorine atom of the perfluoroaromatic compound. In other words, the sulphur atom substituting the fluorine atom is followed by a corresponding linear or branched Cn-body, which may also contain double bonds that can potentially be used for further addition or substitution reactions, for example for crosslinking. At the other end of the Cn body, a quinuclidinium group or another quaternary N group, in particular an ammonium, imidazolium, benzimidazolium, piperidinium, piperazinium, guanidinium, pyridinium group, preferably with counterions, can be attached, in particular with a bis(trifluoromethylsulfonyl)amide anion or a mineral acid anion, in particular a halide (F−, Cl−, Br−, I−) or SO42−, HSO4−, PO43−, HPO42−, H2 PO4−, SO32−, SO H3−, phosphonate R—PO H3−, carbonate CO32−, HCO3−, or with an organic carboxylic acid anion, in particular CH3 COO−, HCOO−. In other words, any other quaternary ammonium group NR4+ with R=any alkyl and/or aryl, for example a piperidinium or piperazinium or imidazolium group, benzimidazolium group, pyridinium group, alkylguanidinium group, in particular with a counter anion, can be attached to the other end of the Cn body, in particular mineral acid anions (including halides, sulphates, sulphites, phosphates, carbonates, (per) chlorates, borates), as well as organic counteranions (including bis(sulphonyl)imides, carboxylic acid derivatives, sulphonic acid derivatives, phosphonic acid derivatives). Such Cn-bodies can have a chain-like structure and are then also referred to as Cn-chains.
In addition, the functional group may contain a nitrogen atom as a primary, secondary, tertiary or quaternary amine or ammonium group. Such a nitrogen atom can, for example, be provided within a linear or branched Cn-body which may contain unsaturated groups.
A functional group can be in the form R—SH, R—S−, R—OH, R—NH, R—N− or PO R32, where R is an alkyl radical, aryl radical, alkyl, aryl, a metal, Si(CH)33 or H.
Any form of combination is conceivable. Specifically, the first nucleophile, i.e. the first functional group that substitutes the para-fluorine atom, can have the form R—SH, R—S−, R—OH, R—O−, R—NH2, R—NH, R—N−, or PO R32. Completely independently of this, a second functional group can comprise all forms. The same applies to a third functional group.
It is thus possible that in the case of perfluoroaromatic compounds on which a fluorine atom (for example the 4-F atom in a pentafluorophenyl unit) has already been replaced by one of the aforementioned functional groups, in particular of the form R—SH, by means of a nucleophilic substitution reaction, R—S−, R—OH, R—O−, R—NH2, R—NH, R—N−, or PO R32, subsequently, by means of further nucleophilic substitution reactions, further fluorine atoms are substituted by the same or another functional group, in particular of the form R—SH, R—S−, R—OH, R—O−, R—NH2, R—NH, R—N−, or PO R32.
The remainder R may differ for the various functional groups. It is thus readily possible for the first functional group to have the form R—SH, where R is aryl, and for the second functional group to have the form R—OH, where R is a metal. Furthermore, the third functional group can readily have a further form, for example R—NH, where R is alkyl.
A functional group may also contain a thiol group or be based on a thiol group or have been prepared from a thiol group.
If the functional group has the form S—R, with the sulfur atom taking the position of the substituted fluorine atom, the radical R can be formed as shown in the figure below, but this does not limit the types of possible radicals R.
Furthermore, a functional group may contain SO3 with a counter cation, in particular with a metal counter cation or with an ammonium counter cation in the form NR4+ with R═H, alkyl, aryl or with another N-basic cation, in particular imidazolium, benzimidazolium, guanidinium. A functional group may contain C NH510, where the nitrogen atom substitutes the fluorine atom of the perfluoroaromatic compound. In particular, a residue or counter anion can be coupled via the nitrogen atom. counter anion can be coupled via the nitrogen atom, the radical preferably being a halide (F−, Cl−, Br−, I−) or SO42−, HSO4−, PO43−, HPO42−, H2 PO4−, SO32−, SO H3−, phosphonate R—PO H3−, carbonate CO32−, HCO3− or an organic carboxylic acid anion such as CH3 COO−, HCOO−. The residue or the counter anion may in particular be mineral acid anions (including halides, sulphates, sulphites, phosphates, carbonates, (per) chlorates, borates), or organic counter anions, preferably bis(sulphonyl)imides, carboxylic acid derivatives, sulphonic acid derivatives, phosphonic acid derivatives).
It may be provided that the functional group is coupled to several, in particular to two perfluoroaromatic compounds of two organic oligomeric or polymeric chains, so that the functional group cross-links the chains with one another. This embodiment is based on the idea of not functionalizing the oligomeric or polymeric chains independently of one another, but functionalizing them in such a way that they are additionally crosslinked with one another. This can influence the mechanical properties of the substance in particular.
The chains to be cross-linked can be identical oligomeric or polymeric chains or different chains.
In a specific embodiment, such a functional group can be chain-like and have a sulphur atom at each end, which nucleophilically substitutes a fluorine atom of the perfluoroaromatic compounds. Between the two sulphur atoms, the functional group may contain one or more Cn-bodies and/or a repeating unit.
The problem underlying the invention is further solved by a membrane, in particular a diaphragm membrane, which contains a substance as described above. In a further embodiment, the membrane may be an ion exchange membrane, preferably a cation exchange membrane or an anion exchange membrane.
A further object of the invention is the use of such a membrane in an electrochemical system, in particular in a fuel cell, preferably a hydrogen fuel cell or a direct fuel cell, or in a battery, in particular in a redox flow battery, or in an electrochemical process, in particular in an electrolysis process, in particular in an acidic or alkaline or bipolar membrane electrolysis. Furthermore, such a membrane can be used as an ion-conducting membrane in electrosynthesis applications.
The method according to the invention can be designed in that the perfluoroaromatic compound of the starting material is a perfluorophenyl or a perfluorobiphenyl unit or comprises such a unit. In the nucleophilic substitution, the para and at least one ortho position and/or at least one meta position of the perfluorophenyl unit or the perfluorobiphenyl unit is preferably substituted by a functional group. In principle, the perfluoroaromatic compound can also be a perfluoroterphenyl unit or a quaterphenyl unit.
Examples of raw materials that can be used are shown in the figure below.
Each of the starting materials shown has perfluoroaromatic compounds/assemblies with several fluorine atoms on which nucleophilic substitution reactions can take place. This means that several fluorine atoms can be substituted by functional groups.
The starting material can also be a partially fluorinated polyether or polythioether or polysulfone or a sulfonated, partially fluorinated or a phosphonated partially fluorinated polymer. Furthermore, the starting material can be a polymer of o-, m- or p-terphenyl or o-, m- or p-quaterphenyl and/or perfluoroacetophenone or another (partially) aromatic and partially or perfluorinated ketone.
The starting material may also be characterized in that it contains fluorinated and/or unfluorinated alkaline spacers in the oligomeric or polymeric chains, in particular in the backbone (in the main polymer chain).
Alternatively, the starting material can be a terphenyl polymer or a quaterphenyl polymer, in particular of angled terphenyl and/or quaterphenyl monomers. The chains of the starting material may contain partially fluorinated terphenyl and/or quaterphenyl units. Furthermore, the starting material may contain fluorene-based backbones.
According to one embodiment of the method according to the invention, the starting material can be prepared by coupling perfluoroaromatic compounds to a base material, in particular to a polymer. In other words, a base material can be used to which perfluoroaromatic compounds, in particular perfluorophenyl units or perfluorobiphenyl units, are specifically coupled. The perfluoroaromatic compound, in particular a perfluorophenyl unit or a perfluorobiphenyl unit, can be coupled to the base material by Suzuki-C—C coupling, in particular under the action of a perfluoroaromatic and/or partially fluoroaromatic boronic acid.
For example, a halogenated, aromatic polymer can be used as the base material, which is substituted on the aromatic compound in particular with I and/or Br and/or Cl.
The method according to the invention can be characterized in that the nucleophilic substitution of several fluorine atoms of the perfluoroaromatic compound takes place in one step. The nucleophilic substitution can preferably take place under the action of a base.
Alternatively, the nucleophilic substitution of several fluorine atoms can take place in several successive steps. Preferably, the fluorine atom at the para position is substituted first (in the case of a pentafluorophenyl radical) before at least one, in particular exactly one, fluorine atom is substituted at the ortho position. As a result of the substitution of the fluorine atom at the ortho position, a substitution may subsequently take place at the opposite meta position.
The two steps can take place under the same or different ambient conditions. For example, the first step, in which a para-fluorine atom is substituted, can take place at room temperature. It is also conceivable that the first step takes place at a temperature between 60° C. and 100° C., in particular at a temperature of at least 70° C. and/or at most 85° C. The reaction time can vary considerably between a few minutes and several days. The second step, in which at least one further fluorine atom is substituted by a functional group, can take place at a higher temperature than in the first step. In particular, the temperature may be at least 70° C., preferably at least 80° C. The duration of the substitution reaction can also vary between a few minutes and several days.
Any substitution reaction can take place under the influence of other media. This may be a base. Alternatively or additionally, the reaction can take place under the action of acetone, diazabicycloundecene (DBU), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfate (DMS), CH3 I, dimethyl carbonate or mixtures or dilute solutions of these media.
It is also conceivable that, in particular, a first substitution reaction takes place during the evaporation of a solvent, which preferably takes place at a temperature below 150° C.
A molecule with a linear or branched, saturated or unsaturated Cn-body, in particular with a C2-, C3-, C6-, C8-, C10-, C12-, C14-, C16-, or a C18-body, which carries a thiol group at one end, can be used for substitution. Preferably, an S atom of the thiol group then substitutes an F atom of the perfluoroaromatic compound. In other words, a saturated or unsaturated hydrocarbon with a thiol group can be used as a substituent. If an unsaturated hydrocarbon is used, it can be used for a subsequent reaction, in particular for a thiol-ene click reaction.
At its other end, the molecule used for substitution may contain a quinuclidinium group or another quaternary N group, in particular an ammonium, imidazolium, benzimidazolium, piperidinium, piperazinium, guanidinium or pyridinium group, preferably with counterions, in particular with a bis(trifluoromethylsulfonyl)amide anion or a mineral acid anion, in particular a halide (F−, Cl−, Br−, I−) or SO42−, HSO4−, PO43−, HPO42−, H2 PO, SO4-32−, SO H3−, phosphonate R—PO H3−, carbonate CO32−, HCO3− or with an organic carboxylic acid anion, in particular CH3 COO−, HCOO−. The choice of counterions is not limited to the anions mentioned. Furthermore, the molecule used for substitution may contain a nitrogen atom as a primary, secondary, tertiary or quaternary amine or ammonium group.
For the method according to the invention, a molecule in the form R—SH, R—S−, R—OH, R—NH, R—N− or PO R32 can be used for substitution. Furthermore, a thiol with a terminal sulfonate group can be used for substitution. In addition, a molecule C NH510 may be used for substitution, wherein the nitrogen atom takes the position of a fluorine atom of the perfluoroaromatic compound. In particular, if the nitrogen atom is positively charged, a radical (counterion) can be coupled via the nitrogen atom in a further embodiment, the radical preferably being a halide (F−, Cl−, Br−, I−) or SO42−, HSO4−, PO43−, HPO42, H2 PO4−, SO32−, SO H3−, phosphonate R—PO H3−, carbonate CO32−, HCO3− or an organic carboxylic acid anion, in particular CH3 COO−, HCOO−. In principle, the residue can contain any anion as a counterion, whereby anions such as halide (F−, Cl−, Br−, I−) or SO42−, HSO4−, PO43−, HPO42−, H2 PO4−, SO32−, SO H3−, phosphonate R—PO H3−, carbonate CO32−, HCO3− or an organic carboxylic acid anion such as CH3 COO−, HCOO− are preferred.
If the molecule used for substitution has the form S—R, where the sulphur atom takes or should take the position of the substituted fluorine atom, the radical R can be formed as shown in the figure below.
Furthermore, the molecule used for substitution may contain SO3 with a counter cation, in particular with a metal counter cation or with an ammonium counter cation in the form NR4+ with R═H, alkyl, aryl or with another N-basic cation, in particular imidazolium, benzimidazolium, guanidinium. A functional group may contain C NH510, where the nitrogen atom substitutes the fluorine atom of the perfluoroaromatic compound. In particular, the nitrogen atom can be substituted by a radical or counter anion, where the radical is preferably a halide (F−, Cl−, Br, I−) or SO42−, HSO4−, PO43−, HPO42−, H2 PO4, SO32−, SO H3−, phosphonate R—PO H3−, carbonate CO32−, HCO3− or an organic carboxylic acid anion such as CH3 COO−, HCOO−. The residue or the counter anion may in particular be mineral acid anions (including halides, sulphates, sulphites, phosphates, carbonates, (per) chlorates, borates), or organic counter anions, preferably bis(sulphonyl)imides, carboxylic acid derivatives, sulphonic acid derivatives, phosphonic acid derivatives).
The method according to the invention, in particular the substitution which takes place, can be designed in such a way that the functional group is coupled to several, in particular to two perfluoroaromatic compounds of two organic oligomeric or polymeric chains, so that the functional group cross-links the chains with one another. This embodiment is based on the idea of not functionalizing the oligomeric or polymeric chains independently of one another, but functionalizing them in such a way that they are additionally crosslinked with one another. This can influence the mechanical properties of the substance in particular.
Specifically, the functional group can be chain-like and have a sulphur atom at each end, each of which nucleophilically substitutes a fluorine atom of the perfluoroaromatic compounds. One or more Cn-bodies and/or a repeating unit may be contained between the sulphur atoms.
In a further embodiment of the method according to the invention, subsequent reactions for which the functional groups form a reaction basis can take place following the nucleophilic substitution. The residues of the functional groups, which have been coupled to a perfluoroaromatic compound after the substitution has taken place, can be used as a basis for further subsequent reactions. These include the exchange of the counterions of a positively or negatively charged residue of the functional group, a change in the residues of the functional group or the use of an aromatic/unsaturated residue of the functional group.
Specifically, the counterions of a quaternary ammonium salt or an acid group, which are part of the functional group, can be exchanged. Unsaturated residues of the functional group can be used for downstream functionalization or crosslinking of the polymer/oligomer with the perfluoroaromatic compound.
For further embodiments of the invention, reference is made to the subclaims and to the following description of several embodiments with reference to the figures. The figures show:
The preparation of a functional group, i.e. the preparation of a molecule for functionalization, is shown in detail in
Under the influence of a base, the para-fluorine atom and an ortho-fluorine atom are substituted by the functional group, as can be seen in the perfluorophenyl unit shown on the right in
The substance produced by the reaction is transparent, colorless, flexible and has sufficient film-forming properties for the production of membranes.
The starting point for the second embodiment example are commercially available polymers, e.g. PSU Udel, PPSU Radel R (manufacturer Solvay) or Ultrason E, Ultrason P or Ultrason S (manufacturer BASF) or polyphenylene oxide (PPO)/polyphenylene ether (PPE). These are first lithiated, as shown in
The substance is then reacted with reactive electrophiles such as acid chlorides, sulfonic acid fluorides, ketones, aldehydes or other electrophiles that contain perfluorinated aromatic groups. This process is illustrated in
In a next step, the starting materials obtained in this way, in this case polymers containing perfluoroaromatic compounds, can be reacted with functional groups, for example. As in the first embodiment example, these can be thiols, which means that a sulphur atom takes the place of a fluorine atom.
It is also possible that, in a further step, the modified polymers react with tris-trimethylsilyl (phosphite) to obtain a phosphonated polymer. In a second step, this phosphonated polymer can be further reacted with a thiol, such as that described in embodiment 1.
Alternatively, substitution of the polymer with perfluoroaromatic compounds, which is shown in
It is initially envisaged that a first functional group (Nu1) will substitute a fluorine atom at the para position of the perfluoroaromatic compound. In a subsequent step, a second functional group will then substitute one of the two ortho-fluorine atoms (Nu2). Finally, in a third step, the meta-fluorine atom opposite the substituted ortho-fluorine atom can be substituted.
The nucleophilic substitution of at least two, in this case three, fluorine atoms takes place one after the other. This may involve the same functional group or different functional groups. The functional groups, i.e. the molecules used for substitution, which are also referred to as nucleophiles, can take the form of R—SH, R—S−, R—OH, R—NH, R—N− or PO R32, where R is an alkyl radical, aryl radical, alkyl, aryl, a metal, Si(CH) 33 or H. Any form of combination is conceivable. Specifically, the first nucleotide, i.e. the first functional group which substitutes the para-fluorine atom, can have the form R—SH, R—S−, R—OH, R—O−, R—NH2, R—NH, R—N−, PO R32. Completely independently of this, the second functional group, which is designated NU2, can comprise all forms. The same applies to a third functional group, which is designated Nu3.
The radical R may differ for the various functional groups. It is thus readily possible for the first functional group (Nu1) to have the form R—SH, where R is aryl, and for the second functional group (Nu2) to have the form R—OH, where R is a metal. Furthermore, the third functional group (Nu3) can readily have a further form, for example R—NH, where R is alkyl.
In two further steps, first the para-fluorine atom and then an ortho-fluorine atom can be substituted by a functional group, i.e. a nucleophile. This takes place in each case under the influence of a base, whereby the nucleophile itself can also represent the base, as is the case, for example, when piperidine is used for the nucleophilic substitution of the fluorine atom.
Any functional groups can be used for nucleophilic substitution, in particular the functional groups which are explained in connection with embodiment example 1 and embodiment example 2, as well as embodiment example 4 described below.
First, a polymer to be functionalized is obtained by radical polymerization of pentafluorostyrene. The molar mass is variable between 8,000 and 300,000 g/mol. This starting material is shown schematically on the left in
In a first step, a nucleophilic substitution of the para-fluorine atom of the pentafluorophenyl unit takes place. A degree of substitution of up to 100% can be achieved, based on the fluorine atoms in the para position. The molecules used for functionalization have a thiol group on a saturated hydrocarbon. This means that the sulphur atom of the thiol group takes the position of the substituted para-fluorine atom, as shown in
The substitution of the para-fluorine atom takes place at room temperature over a period of less than 10 minutes, in particular under the influence of triethylamine or triethanolamine or diazabicycloundecene (DBU, exact name 1,8-diazabicyclo [5.4.0]undec-7-ene) and/or acetone. In a second step, an ortho-fluorine atom is substituted. This second step is shown in detail in
The functional groups that substitute the ortho-fluorine atom and the opposite meta-fluorine atom can be identical or different. The sulphur atom substituting the fluorine atom can be followed by a residue, an example of which is shown in
It has been found that the material produced by the reaction described is transparent, colorless and flexible and has sufficient film-forming properties for the production of membranes.
In this embodiment, partially and unsulfonated polyethers are used as starting materials. Examples of starting materials are shown in
After the first substitution on one of the two rings of the perfluorobiphenyl unit, a second substitution occurs in the para position due to the activation of the opposite fluorine atom, as shown in
An adaptation of the thiols used enables the coupling of a large number of functional groups to a fluorinated ionomer. These are then available for further reactions. Examples of such reactions are shown in
In this embodiment, the reaction scheme of which is shown in
During the evaporation of the solvent, a partial nucleophilic substitution of the thiol groups with a fluorine atom of the perfluoroaromatic compound already takes place.
After evaporation of the solvent, the membrane is treated in a strong alkaline solution, e.g. in NaOH, at an elevated temperature. This completes the cross-linking reaction, as the thiol anions are much more nucleophilic than the thiol groups in the H form. The crosslinking leads to the functional groups being coupled to two perfluoroaromatic compounds of two different oligomeric or polymeric chains. As a result, the two chains are crosslinked with each other, as shown in
The functional group used here is a Cn-body, specifically a C6-body, to the two ends of which a thiol group is attached. As can be seen in
A polymer of terphenyl and terfluoroacetophenone is selected as the starting material in the present case. This starting material is shown on the left in
In a first step, the polymer is then reacted with piperidine, i.e. the para-fluorine atom is substituted accordingly. Surprisingly, this results in a 100% substitution of the para-fluorine atom with piperidine, which can be seen in the NMR spectra in
The further modification reaction of the corresponding piperidine-substituted polymer is shown in
Alternatively, after the first step (modification with piperidine), alkylation of the piperidine residue to the piperidinium cation can take place, as shown in
In addition to the use of acylic spacers, the use of ortho- and meta-linked terphenyls is also possible. This is specifically shown in
The nucleophilic substitutions of the fluorine atoms described above can also be carried out on these compounds, as already described in connection with
It is also possible to replace the terphenyl units with biphenyls or partially fluorinated aromatic systems, resulting in novel structures. Such structures can be seen in
By using the partially fluorinated aromatic units, it is possible to make further substitutions on various side chains on the fluorinated units of the backbone in addition to the substitutions on perfluorophenyl units already shown.
In addition, the aromatic portion of the backbone can also be represented by substituted fluorenes. Examples of such structures are shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 105 724.0 | Mar 2022 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/055865 | 3/8/2023 | WO |
