New phosphonated non-fluorinated and partially fluorinated aryl polymers from sulfonated aryl polymers and new polymeric perfluorophosphonic acids from perfluorosulfonic acids, their preparation methods and use in electromembrane applications

Abstract

The present invention relates to a new class of substances of high and low phosphonated aryl polymers and polymeric perfluorophosphonic acids, the starting materials of which are their sulfonated forms, as well as a versatile method for preparing phosphonated polymers from their sulfonic acid forms, and their use in electrical membrane applications.

Description

[Technical Field]

[0001] Novel phosphonated non-fluorinated and partially fluorinated aryl polymers from sulfonated aryl polymers and novel polymeric perfluorophosphonic acids from polymeric perfluorosulfonic acids, methods for their preparation and use in electrical membrane applications. [Background technology]

[0002] The most commonly described phosphonated polymer systems are based on aryl polymers synthesized by nucleophilic substitution (via Michaelis-Arbuzov and Michaelis-Becker rearrangements) of aryl halides with di- or trialkyl phosphites.

[0003] These phosphonated aryl polymers have high thermal and chemical stability. In addition, they have good proton conductivity even in unhumidified conditions. [1-5] The drawback of these phosphonated aryl polymers, such as those from DE102011015212A1, is that they are very brittle in non-hydrated state, that is, in dry state, and therefore cannot be used to make functional membranes.This brittle behavior increases with increasing temperature and decreasing humidity, leading to the mechanical failure of membrane.This makes these polymers impossible to use as membranes for electromembrane processes in the range above 100 ° C.

[0004] US6680346B1 patent by Kyoji Kimoto describes the direct synthesis of phosphonated perfluorophosphonic acids. The patent claims the following structure (Figure 2) (ratio m equals 0 or 1, n equals 2 or 3, X and Y equals -H or -CHSOH, and the ratio A / B equals 1.5 to 15):

[0005] The polymers synthesized in EP2514773A1 and US6680346B1 are likely to undergo cyclization during polymerization, which leads to chain transfer and a decrease in the molecular weight and mechanical strength of the material due to difficult-to-control polymerization conditions. Increasing the molar ratio of short-chain phosphonyl-containing monomer to tetrafluoroethylene monomer further promotes this side reaction, limiting the increase in ion exchange capacity and the material stability.

[0006] The method claimed herein does not have this limitation, as polymeric perfluorosulfonic acids can now be produced with consistent quality (an example of which can be seen in Figure 1). The described phosphonation reaction thus leads to a new, stable class of polymeric perfluorophosphonic acid materials, without the drawbacks of US 6,680,346 B1. The same applies to sulfonated aryl polymers. If the base polymer has good mechanical properties, it will retain these properties in its new form as a phosphonated polymer. Summary of the Invention

[0007] Presentation of the invention The steps of the present invention are based on the discovery and synthesis of new phosphonated polymers that are proton conductive and chemically and mechanically stable even in the dry state. This is achieved by first converting a sulfonated polymer, which already has good mechanical properties and sulfonic acid groups, to the -SOCl form by sulfochlorination with thionyl chloride. Starting from the -SOCl form, it is possible to phosphonate it with a trialkyl phosphite such as tris(trimethylsilyl)phosphite (TTMSP), or convert the -SOCl form to the -SONa (sodium sulfonate) form with sodium sulfite and phosphonate this intermediate product, or further convert the -SONa form to the -SOLi (lithium sulfonate) form and phosphonate this product. Using this process, phosphonated polymers with high mechanical flexibility, chemical stability, and high proton conductivity can be synthesized from any polymer containing sulfonic acid groups. The polymer, which already has good mechanical and chemical properties in the sulfonated form, retains these after phosphonation and, unlike sulfonic acid-containing polymers, also has high proton conductivity above 100°C (Figure 3). The response should be as effective and simple as possible, and that's what we get here.

[0008] The phosphonated polymer should be soluble in common solvents so that membranes can be fabricated therefrom. Using the synthetic routes described herein, phosphonated polymers can in principle be synthesized from any sulfonated polymer.

[0009] The present invention is based on the incorporation of a reactive group -X (-X can be -SO2Cl, -SO2Na, -SO2Li) into a sulfonated polymer and the reaction of that reactive group with a trialkyl phosphite such as TTMSP.

[0010] The phosphonated polymer may still contain free reactive groups -X, depending on the degree of phosphonation. These free groups can then be used to subsequently covalently crosslink the phosphonated polymer, or the unreacted groups can be converted back to the -SO3H form, thus obtaining a polymer containing both sulfonated and phosphonated groups.

[0011] Phosphonation can be carried out in solution. To this end, the polymer bearing the reactive group -X can be dissolved in a solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), or dimethyl sulfoxide (DMSO). TTMSP can optionally be added before, during, or after the dissolution process. Depending on the desired degree of phosphonation, TTMSP is added based on the weight of the polymer, from a low degree of phosphonation of 0.1 wt.% (weight percent) to a high degree of phosphonation of 5000 wt.%.

[0012] The reaction works best and fastest in high boiling point solvents such as NMP, DMAc, and DMSO. Gas evolution can be observed during the reaction, indicating the start of the reaction, and no further gas evolution indicates the end of the reaction.

[0013] The reaction is held at reaction temperature (60°C to 200°C) (depending on the polymer, its molecular weight, and the solvent used) until gas evolution ceases, and then held at reaction temperature for 2 to 8 hours to ensure completion.

[0014] The by-products of the reaction and excess TTMSP are then removed by distillation, leaving the phosphonated polymer in the form of its trimethylsilyl ester in the solvent. The polymer solution is now added to water and, depending on the degree of phosphonation, the polymer will either precipitate as a solid (low degree of phosphonation) or go into solution (high degree of phosphonation). By heating the water / polymer mixture, the phosphonated polymer is hydrolyzed from the trimethylsilyl ester form to the free polymeric phosphonic acid.

[0015] Depending on the degree of phosphonation, the polymer can be washed with water to completely separate the hydrolysis by-products: the water-insoluble polymer components can be washed with water and filtered off, while the water-soluble ones can be purified by dialysis.

[0016] Another variant is where the polymer solution is not precipitated in water; after separating the excess TTMSP, the polymer solution is directly processed into a membrane, which is then hydrolyzed in superheated or boiling water or treated with hot steam.

[0017] A corresponding exemplary reaction scheme of a non-limiting embodiment is shown in FIG. The resulting polymers can be blended with basic polymers, such as polybenzimidazole or anion exchange polymers, to form acid-base blend membranes, covalently crosslinked membranes, and covalently crosslinked acid-base blend membranes.

[0018] The blend ratio between the phosphonated polymer and the basic polymer can be between 99 mol % phosphonated polymer and 1 mol % basic polymer to 1 mol % phosphonated polymer and 99 mol % basic polymer.

[0019] Additional sulfonated polymers may be added to this polymer and blended in any amount. The blend membrane can also be doped with any amount of phosphoric acid, with values ​​between 40 wt.% and 50 wt.% being preferred as the phosphoric acid doping level.

[0020] The obtained polymer can be used in electrochemical cells. Preferably, the obtained polymer can be used in low- or medium-temperature fuel cells in the temperature range of -30°C to 250°C, or low- or medium-temperature electrolytic cells in the temperature range of 0°C to 250°C. Furthermore, the obtained polymer can be used in chemical synthesis reactors in the temperature range of -70°C to 250°C. The obtained polymer can also be used as a separator in primary and secondary batteries, or as a binder in electrodes for primary and secondary batteries. [Brief explanation of the drawings]

[0021] [Figure 1] This is an example of a polymeric perfluorosulfonic acid. [Figure 2] 1 is a structure of a monomer from US 6,680,346 B1 for synthesizing perfluorophosphonic acid. [Figure 3] Conductivity of phosphonated polymers pPEKEKK and Nafion® 212 compared at 50% RH at 30° C. decreasing to 0.2% RH at 180° C. [Figure 4] This is an example of a reaction scheme for PEEK. DETAILED DESCRIPTION OF THE INVENTION

[0022] Examples of non-limiting embodiments: 2 g of sulfonated polyetherketoneetherketoneketone (sPEKEKK) is mixed with 55 g of thionyl chloride and heated to 90°C and refluxed. DMF (dimethylformamide) is then added and heated until no more gas evolution is observed. The reaction is then held at the reaction temperature for an additional 2 hours to ensure completion. Excess thionyl chloride and by-products are now distilled, and the product is slurried with THF (tetrahydrofuran). This solution / suspension can then be precipitated in isopropanol or water. The product is washed to neutrality and then dried. The previously sulfonated polymer is now in the -SO2Cl form. The product is converted to the -SO2Na form in a 2M sodium sulfite solution. The polymer is filtered and washed again with water to remove excess sodium sulfite. 10 wt% LiCl solution is then added to the -SO2Na form of the polymer to convert it to the -SO2Li form. The polymer is then washed again with water to remove excess salt. The polymer is then dried.

[0023] Phosphonation with TTMSP can be carried out in all three forms, -SO2Cl, -SO2Na, and -SO2Li, although the -SO2Li form is preferred. Polymers bearing -SO2Cl, -SO2Na, or -SO2Li groups can be mixed with an organic solvent such as DMAc, NMP, DMSO, and TTMSP and phosphonated.

[0024] In the case of polymeric perfluorosulfonic acids, the reaction can be carried out from polymer granules, powders, etc., as previously described, or by using a membrane of perfluorosulfonic acid directly. To do this, the membrane of perfluorosulfonic acid is pulled through a hot bath of thionyl chloride / DMF, where the sulfochlorination takes place, and then through a water bath for rinsing.

[0025] The -SO2Cl form of the membrane is then pulled through a sodium sulfite bath to form the -SO2Na form, followed by a water rinse. The -SO2Na form of the membrane is then pulled through a LiCl bath to transfer to the -SO2Li form, then washed again in a water bath. All three membrane forms, -SO2Cl, -SO2Na, and -SO2Li, can be pulled through a heated TTMSP bath and finally through a hot / boiling water bath to obtain the phosphonate form by hydrolysis. This can be done in a continuous roll-to-roll process, but batch processes are also possible. The membrane can then be dried and further processed. Phosphonation of the -SO2Li form is preferred.

[0026] Analysis of the experiment: Description of the ion exchange capacity and conductivity up to 180° C. of one of the exemplary phosphonated polymers (FIG. 3).

[0027] Determination of ion exchange capacity 100 mg of the prepared polymer is covered with saturated NaCl solution, stirred for approximately 2 hours, and 2 drops of bromothymol blue are added as an indicator. The protons of the phosphonated polymer exchange with Na ions to form HCl, which can be detected by titration with 0.1 mol of NaOH, and the IEC direct To determine the total IEC, 3 ml of 0.1 M NaOH is added in excess to the solution, stirred again for 2 hours, and back-titrated with HCl.

[0028] In the described experiments, IEC direct = 0.95 mmol / g, and IEC total = 2.2 mmol / g of phosphonated PEKEKK (pPEKEKK). The good proton conductivity even above 100°C can be seen in the conductivity measurements in Figure 3. In addition, the decrease in conductivity can be seen in comparison with Nafion 212 as a reference under the same measurement conditions, where RH is reduced from 50% at 30°C to 0.2% at 180°C (Figure 3).

[0029] The high conductivity at high temperatures can be attributed to the strong withdrawing effect of the SO2 groups on the electrons of the phosphonic acid groups.

[0030] literature [1] Vladimir Atanasov and Jochen Kerres Highly Phosphonated Polypentafluorostyrene; Macromolecules 2011, Volume 44, Issue 16, Pages 6416-6423 [2] VIadimir Atanasov, Dietrich Gudat, Bastian Ruffmann, Jochen Kerres Highly phosphonated polypentafluorostyrene: Characterization and blends with polybenzimidazole, European Polymer Journal, Volume 49, Issue 12, 2013, Pages 3977- 3985 [3] VIadimir Atanasov, Matthias Burger, Sandrine Lyonnard, Lionel Porcar, Jochen Kerres Sulfonated poly (pentafluorostyrene): Synthesis & characterization, Solid State Ionics, Volume 252, 2013, Pages 75-83 [4] Vladimir Atanasov, Jochen Kerres ETFE-g-pentafluorostyrene: Functionalization and proton conductivity, European Polymer Journal, Volume 63, 2015, Pages 168-176 [5] Vladimir Atanasov, Andrey Oleynikov, Jiabing Xia, Sandrine Lyonnard, Jochen Kerres Phosphonic acid functionalized poly (pentafluorostyrene) as polyelectrolyte membrane for fuel cell application, Journal of Power Sources, Volume 343, 2017, Pages 364-372 Specific embodiments of the present invention are as follows. [Aspect 1] 1. A method for preparing a phosphonated polymer from a starting polymer containing sulfonic acid groups, comprising the following method steps: a) The raw polymer is converted to -SO by sulfochlorination with thionyl chloride. 2 Step of converting to Cl form b) reacting this intermediate with tris(trimethylsilyl)phosphite to form the phosphonated polymer, wherein the starting polymer is a member selected from the group consisting of polyimide, polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneetherketoneketone (PEKEKK), polycarbonate, polysulfone, polysulfoxide, polysulfide, non-fluorinated and partially fluorinated polyethersulfone, non-fluorinated and partially fluorinated polyetherethersulfone, polyester, polystyrene, polymeric perfluorosulfonic acid. A method comprising: [Aspect 2] After process step 1a), sodium form -SO 4 is obtained by reaction with sodium sulfite. 2 2. The method of embodiment 1, wherein conversion to Na is carried out first. [Aspect 3] After conversion to the sodium form, the lithium form -SO can be obtained by reaction with lithium chloride or lithium hydroxide or another lithium salt. 2 3. The method of embodiment 2, wherein the conversion to Li is carried out first. [Aspect 4] 4. The method according to any one of aspects 1 to 3, characterized in that process step 1b) is carried out in a solvent, preferably a high-boiling solvent, which is at least one member selected from the group consisting of N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylsulfoxide (DMSO). [Aspect 5] 5. The method according to aspect 4, characterized in that during method step 1b) the solvent is heated to boiling temperature. [Aspect 6] 6. The method according to aspect 5, wherein the reaction mixture is heated to the boiling temperature of the solvent for at least 2 hours, preferably at least 8 hours. [Aspect 7] After process step 1b), the unreacted active group -SO 2 7. The method of any one of aspects 1 to 6, characterized in that Cl, sodium or lithium forms are reacted back to said sulfonic acid groups. [Aspect 8] 8. The method according to any one of aspects 1 to 7, wherein the amount of tris(trimethylsilyl)phosphite is between 0.1 wt.% and 5000 wt.% of the intermediate. [Aspect 9] 9. The method according to any one of aspects 1 to 8, characterized in that the initial polymer is in the form of a membrane, and that process steps 1a) and 1b) are carried out by immersion in the respective reagents, and that after each of said process steps the membrane is rinsed by immersion in water. [Aspect 10] 10. The phosphonated polymer and membrane of any one of embodiments 1 to 9, wherein the polymer contains both sulfonic acid groups and phosphonic acid groups. [Aspect 11] 11. The phosphonated polymer and membrane according to any one of the preceding aspects, characterized in that it is a phosphonated polyetherketoneetherketoneketone (pPEKEKK). [Aspect 12] 12. Use of the polymer and membrane according to any one of embodiments 1 to 11 in an electrochemical cell. [Aspect 13] 13. Use of the membrane according to embodiment 12 in a low temperature or medium temperature fuel cell in the temperature range of -30°C to 250°C. [Aspect 14] 13. Use of the membrane according to embodiment 12 in a low or medium temperature electrolytic cell in the temperature range of 0°C to 250°C. [Aspect 15] 13. Use of the membrane according to embodiment 12 in a chemical synthesis reactor at temperatures between -70°C and 250°C. [Aspect 16] 13. Use of the membrane according to embodiment 12 as a separator in primary and secondary batteries. [Aspect 17] 13. Use of the polymer according to embodiment 12 as a binder for electrodes in primary and secondary batteries.

Claims

1. 1. A method for preparing a phosphonated polymer from a starting polymer containing sulfonic acid groups, comprising the following method steps: a) The raw polymer is converted to -SO by sulfochlorination with thionyl chloride. ２ Converting to Cl form b) reacting the starting polymer converted to the —SO 2 Cl form with tris(trimethylsilyl) phosphite to form the phosphonated polymer, wherein the starting polymer is a member selected from the group consisting of polyimide, polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneetherketoneketone (PEKEKK), polycarbonate, polysulfone, polysulfoxide, polysulfide, non-fluorinated and partially fluorinated polyethersulfone, non-fluorinated and partially fluorinated polyetherethersulfone, polyester, polystyrene, and polymeric perfluorosulfonic acid; A method comprising:

2. After process step 1a), sodium sulfite is reacted with sodium sulfite to give sodium form -SO ２ 2. The method of claim 1, wherein the conversion to Na is carried out first.

3. After conversion to the sodium form, the lithium form -SO can be obtained by reaction with lithium chloride or lithium hydroxide or another lithium salt. ２ 3. The method of claim 2, wherein the conversion to Li is carried out first.

4. 4. The method according to claim 1, wherein process step 1b) is carried out in a solvent.

5. 5. The method according to claim 4, characterized in that during method step 1b) the solvent is heated to boiling temperature.

6. 6. The method of claim 5, wherein the reaction mixture is heated to the boiling temperature of the solvent for at least 2 hours.

7. After process step 1b), the unreacted active groups -SO ２ 2. The method of claim 1, wherein Cl, sodium or lithium forms are back-reacted to the sulfonic acid groups.

8. 2. The method of claim 1, wherein the amount of tris(trimethylsilyl)phosphite is 0.1 wt. % to 5000 wt. % of the starting polymer converted to the —SO 2 Cl form.

9. 2. The method according to claim 1, wherein the initial polymer is in the form of a membrane, and wherein said method steps 1a) and 1b) are carried out by immersion in the respective reagents, and wherein after each of said method steps the membrane is rinsed by immersion in water.

10. 10. A method for preparing a membrane from a phosphonated polymer prepared by the method of claim 1, characterized in that the polymer contains both sulfonic acid groups and phosphonic acid groups.

11. A method for preparing a membrane from a phosphonated polymer prepared by the method of claim 1, characterized in that the phosphonated polymer is phosphonated polyetherketoneetherketoneketone (pPEKEKK).

12. 12. Use of a membrane prepared by the method of claim 10 or 11 in an electrochemical cell.

13. Use of the membrane according to claim 12 in low or medium temperature fuel cells in the temperature range of -30°C to 250°C.

14. Use of the membrane according to claim 12 in low or medium temperature electrolytic cells in the temperature range of 0°C to 250°C.

15. Use of the membrane according to claim 12 in a chemical synthesis reactor at temperatures between -70°C and 250°C.

16. 13. Use of the membrane according to claim 12 as a separator in primary and secondary batteries.

17. 10. Use of the phosphonated polymer prepared by the method of claim 1 as a binder for electrodes for primary and secondary batteries.

Images