KR101841692B1 - Semi-fluorinated Poly(ether sulfone) block copolymers and Anion Exchange Polymer Electrolyte Membrane using the same - Google Patents

Abstract

The present invention relates to a semi-fluorinated polyether sulfone block copolymer and an anion exchange polymer electrolyte membrane using the same. More particularly, the block copolymer has repeating units, wherein a repeating unit is formed by connecting a hydrophilic region formed by a pendent polyether sulfone backbone with at least one of quaternary ammonium salt or imidazolium salt and a hydrophobic region formed by a fluorinated polyether sulfone backbone while decafluorobiphenyl or hexafluorobenzene is used as a medium. The anion exchange polymer electrolyte membrane using the copolymer according to the present invention not only enhances conductivity, but also exhibits excellent water absorption, thermal stability, aqueous alkaline stability and anion conductivity.

Description

Technical Field The present invention relates to a semi-fluorinated polyether sulfone block copolymer and an anion exchange polymer electrolyte membrane using the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-fluorinated polyether sulfone block copolymer and an anion exchange polyelectrolyte membrane using the same. More particularly, the present invention relates to an anion exchange polymer electrolyte membrane using decafluorobiphenyl or hexafluorobenzene, Wherein the quaternary ammonium salt or imidazolium salt is contained in one repeating unit by linking a hydrophilic region composed of a pendant polyethersulfone backbone and a hydrophobic region composed of a fluorinated polyethersulfone backbone, And an anion exchange polymer electrolyte membrane using the same.

Recently, anion exchange membrane fuel cell (AEMFC) has attracted considerable interest, showing great advantages such as high power and high energy density compared with polymer electrolyte membrane fuel cell (PEMFC). The AEMFC is a non-noble metal catalyst (nickel, cobalt, etc.) that exhibits low oxygen overvoltage and easy reaction kinetics of the anode with fuel flexibility (such as methanol, ethanol, ethylene glycol, etc.) The fuel cell cost can be greatly reduced through improved durability.

However, anion exchange membranes (AEMs) as membrane electrolytes in AEMFCs are generally more stable compared to acidic proton exchange membranes (PEM) (conduction ratio of H ⁺ / OH ^- in highly diluted solutions is approximately 1.76) It is generally known to have low ionic conductivity. Since the ion conductivity of the ion exchange membrane is closely related to the ion exchange capacity (IEC) and the water uptake, the method of improving the ion conductivity by increasing the IEC of the ion exchange membrane has a large amount of water absorption and low mechanical properties .

Therefore, in developing AEMFC AEM, research and development are needed to satisfy the comprehensive conditions of high hydroxide conductivity, excellent dimensional stability and chemical stability in a basic environment.

Korean Patent Publication No. 2012-0082007

As a result of intensive studies in order to solve the above problems in the block copolymer of the present invention and the anion exchange polyelectrolyte membrane using the block copolymer,

Through the synthesis of a semi-fluorinated polyether sulfone block copolymer comprising a pendant quaternary ammonium salt group and an imidazolium base, the hydrophilic / hydrophobic phase separation structure resulting from the block copolymer structure enhances the conductivity of the membrane It has been found that the electrolyte membrane using the block copolymer can exhibit excellent properties such as water absorption, thermal stability, aqueous alkaline stability and anionic conductivity.

Accordingly, it is an object of the present invention to provide a polyvinyl alcohol copolymer which exhibits a hydrophilic / hydrophobic phase-separated structure in one repeating unit constituting a block copolymer, so that not only the conductivity of the membrane is improved but also excellent water absorption, thermal stability, aqueous alkali stability and anion conductivity And an anion-exchange polymer electrolyte membrane using the block copolymer.

One embodiment of the present invention relates to a semi-fluorinated poly (ether sulfone) (FPES), wherein the block copolymer according to the present invention comprises

A hydrophilic region comprising at least one quaternary ammonium salt and hydrogen, or at least one imidazolium salt and a hydrogen pendant polyethersulfone backbone; And

A hydrophobic region comprised of a fluorinated polyethersulfone backbone,

The hydrophilic region and the hydrophobic region include a repeating unit represented by the following Formula 1, which is linked via decafluorobiphenyl or hexafluorobenzene.

 [Chemical Formula 1]

In this formula,

R is decafluorobiphenyl or hexafluorobenzene,

,

또는 수소이되, 상기

와

는 동시에 포함되지 않으며,R "

,

Or hydrogen,

Wow

Are not simultaneously included,

x and y are integers from 5 to 25,

n is an integer of 2 to 10;

In one embodiment of the present invention, when the quaternary ammonium salt is pendant with the R "group, about 55 to 75% of the total R" is selectively substituted from bromine (Br) with a quaternary ammonium salt, .

Further, when the imidazolium salt is pendant with the R 'group, about 55 to 75% of the total R' 'can be selected from bromine (Br) to imidazolium salt, and the remainder can be pendant with hydrogen.

The imidazolium salt may be an alkyl imidazolium salt.

An embodiment of the present invention relates to an anion exchange polyelectrolyte membrane characterized by comprising the semi-fluorinated polyether sulfone block copolymer.

The polymer electrolyte membrane may be formed of at least one selected from the group consisting of silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), inorganic phosphoric acid, sulfonated SiO ₂ , sulfonated ZrO 2 and sulfonated ZrP ). ≪ / RTI >

The polymer electrolyte membrane may further include a porous support.

One embodiment of the present invention relates to a fuel cell employing the anion-exchange polymer electrolyte membrane.

One embodiment of the present invention relates to a process for the preparation of a compound of formula (2)

(i) reacting a compound of formula (4) and a compound of formula (5) in the presence of K ₂ CO ₃ to produce a compound of formula (6);

(ii) endcapping a compound of formula (6) with hexafluorobenzene (HFB) in the presence of K ₂ CO ₃ to produce a compound of formula (10);

(iii) reacting a compound of formula (VII) with a compound of formula (VIII) in the presence of K ₂ CO ₃ to produce a compound of formula (9);

(iv) reacting a compound of formula (9) and a compound of formula (10) in the presence of K ₂ CO ₃ to prepare a compound of formula (11);

(v) reacting a compound of the following formula (11) with N-bromosuccinimide (NBS) and benzoyl peroxide (BPO) to prepare a compound of the following formula (12); And

(vi) reacting a compound of the following formula (12) with trimethylamine or ethylimidazole to prepare a compound of the following formula (2).

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

(11)

[Chemical Formula 12]

(2)

In this formula,

R 'is Br or hydrogen,

,

또는 수소이며,R "

,

Or hydrogen,

x and y are integers from 5 to 25,

n is an integer of 2 to 10;

Hereinafter, the production method of the present invention will be described in more detail with reference to Reaction Scheme 1 below. The method described in the following Reaction Scheme 1 exemplifies the representative method, but the reaction reagent, the reaction conditions, and the like may be changed as required.

[Reaction Scheme 1]

Step 1: To a solution of the compound of formula 6 ( FPES - 2) of  Produce

The compound (FPES-2) of formula (6) is prepared by reacting the compound of formula (4,4'-Hexafluoroisopropylidene, 6FBPA) with the compound of formula (5) (4,4'-dichlorodiphenylsulfone, DCDPS) in the presence of K ₂ CO ₃ can do.

As the reaction solvent, N-methyl-2-pyrrolidone (NMP) is preferably used, but it is not limited thereto.

The reaction temperature is preferably about 180 to 200 DEG C, and the reaction time is preferably about 20 to 24 hours.

Step 2: To a solution of the compound of formula 10 ( FPES - 3) of  Produce

The F-terminated oligomer, FPES-3, can be prepared by end capping a compound of formula 6 (FPES-2 oligomer) in the presence of K ₂ CO ₃ with hexafluorobenzene (HFB) .

End capping of the compound of formula (6) with HFB requires that the compound of formula (10) to be prepared is reacted with OH-terminated 2,2-bis (4-hydroxy-3,5-dimethylphenyl) (PES-1), which is an oligomer based on bis (4-hydroxy-3,5-dimethylphenyl) propane, TMBPA) (see Step 4 below).

In consideration of the volatility of the HFB, the end-capping reaction was carried out in the presence of K ₂ CO ₃ at a reaction temperature of about 80 to 90 ° C without nitrogen purge.

The reaction solvent is preferably, but not limited to, dimethylacetamide (DMAc).

The reaction time is preferably about 20 to 24 hours.

Since the HFB is multifunctional and highly reactive, it can be used in an excess amount (compound of Formula 6: HFB = 1: 10) in order to avoid oligomer bonding.

In one embodiment of the present invention, a block copolymer according to the present invention can be prepared by using decafluorophenyl instead of hexafluorobenzene (see the following formula (3)).

Step 3: To a solution of the compound of formula 9 ( PES - 1) of  Produce

The compound of formula 9 (PES-1) can be prepared by reacting the compound of formula 7 (TMBPA) with the compound of formula 8 (4,4'-difluorodiphenylsulfone, DFDPS) in the presence of K ₂ CO ₃ .

As the reaction solvent, NMP is preferably used, but it is not limited thereto.

The reaction temperature is suitably about 170 to 180 DEG C, and the reaction time is preferably about 20 to 24 hours.

Step 4: Compound of formula 11 ( FPES )

The compound of formula 11 (FPES) can be prepared by reacting a compound (poly (ether sulfone) oligomer, PES-1) with the compound of formula 10 (FPES-3) in the presence of K ₂ CO ₃ .

As the reaction solvent, DMAc is preferable, and cyclohexane is preferably used to azeotropically remove water from the reaction, but it is not limited thereto.

The reaction temperature is preferably about 100 to 110 DEG C, and the reaction time is preferably about 20 to 24 hours.

The compound of Formula 6 and the compound of Formula 7 are preferably reacted in a 1: 1 stoichiometry.

Step 5: To a solution of the compound of formula 12 ( FPES - Br )

The brominated multiblock copolymer (FPES-Br) is prepared by reacting a compound of formula 11 (FPES) with a radical (N-bromosuccinimide, NBS) and benzoyl peroxide Followed by reaction.

As the reaction solvent, 1,1,2,2-tetrachloroethane is preferable, but it is not limited thereto.

The reaction temperature is preferably about 80 to 90 占 폚, and the reaction time is preferably about 5 to 6 hours.

The method of preparing the multiblock copolymer containing pendent quaternary ammonium (FPES-QA) according to the present invention will be described in more detail with reference to Reaction Scheme 2 below. The method described in the following Reaction Scheme 2 exemplifies the representative method, but the reaction reagent, the reaction conditions, and the like may be changed as required.

[Reaction Scheme 2]

Step 6: FPES - QA  Produce

FPES-QA can be prepared by reacting the compound of formula 12 (FPES-Br) with trimethylamine (TMA).

The reaction solvent is preferably, but not limited to, dimethylformamide (DMF).

The reaction temperature is suitably room temperature, and the reaction time is preferably about 24 to 48 hours.

The method of preparing FPES-IM (the multiblock copolymer containing pendent imidazolium) will be described in more detail with reference to Reaction Scheme 3 below. The method described in the following Reaction Scheme 3 exemplifies the representative method, but the reaction reagent, the reaction conditions, and the like may be changed as required.

[Reaction Scheme 3]

Step 7: FPES - IM  Produce

FPES-IM can be prepared by reacting a compound of formula 12 (FPES-Br) with ethylimidazole.

The reaction solvent is preferably, but not limited to, DMF.

The reaction temperature is preferably from 80 to 90 캜, and the reaction time is preferably from about 24 to 48 hours.

The synthesis of the ionomer involves benzyl bromination of the precursor block copolymer followed by quaternization and anion exchange with the hydroxide ion. Prior to that, there was a relatively low temperature (e.g., 105 < 0 > C) between the oligomer blocks based on 2,2-bis (4-hydroxy- The precursor block copolymer containing a benzylmethyl group was synthesized by using hexafluorobenzene having high reactivity as a linking group for the coupling reaction at a temperature of 60 ° C.

In order to avoid the use of carcinogenic chloromethylation reagents for halomethylation, monomers containing benzylmethyl groups are used in the synthesis of precursor hydrophilic blocks, while partially fluorinated hydrophobic blocks promote phase separation with hydrophilic moieties, thereby improving anion transport properties It is expected to be.

In halomethylation with commonly used carcinogenic chloromethyl methyl ether (or in situ generated) reagents, the high reactivity of the reagent is frequently caused only to functionalize only once on the skeletal aromatic ring prior to side reactions and cross-linking, Limit ionic function of polymer.

On the other hand, N-bromosuccinimide (NBS) can be handled much more safely, and the introduction of the benzyl bromide moiety into the benzyl moiety along the polymer backbone can provide an opportunity to synthesize multifunctional aromatic rings within the PES.

The block copolymer according to the present invention and the anion exchange polyelectrolyte membrane using the block copolymer exhibit a phase separation structure in one repeating unit constituting the block copolymer to thereby improve the conductivity of the hydrophilic / hydrophobic membrane and to provide excellent water absorption, thermal stability, Alkali stability and anion conductivity characteristics.

1 is a ¹ H NMR spectrum of FPES (a) and FPES-Br (b) according to the present invention measured in CDCl ₃ .
2 is a ¹ H NMR spectrum of FPES-QA (a) FPES-IM (b) according to the present invention measured in DMSO-d ₆ .
Figure 3 is an FTIR spectrum of FPES, FPES-Br, FPES-QA and RPES-IM block copolymers according to the present invention.
Figure 4 is a graph showing TGA thermal analysis of FPES, FPES-QA and FPES-IM block copolymers according to the present invention.
5 is a photograph showing the FPES-QA (a) and FPES-IM (b) films according to the present invention after treatment with 1M NaOH at 60 ° C for 168 hours.
6 is an SEM image of the appearance (a and d), the surfaces (b and e), and the cross sections (c and f) of the FPES-QA film and the FPES-IM film according to the present invention.
7 is an AFM image of the FPES-QA (a) film and the FPES-IM (b) film according to the present invention. The inserted picture represents a 3D image.
8 is a graph showing the Arrhenius-type temperature dependence of the hydroxyl conductivity () of the FPES-QA (a) film and the FPES-IM (b) film according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are for illustrative purpose only and that the scope of the present invention is not limited to these embodiments.

(DFDPS), 4,4'-dichlorodiphenylsulfone (DCDPS), hexafluorobenzene (HFB), hexafluorobenzene (HFB ) Was obtained from Alfa Aesar and used as such. 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane (TMBPA) was purchased from TCI and used as such. DCDPS, DFDPS, 6FBPA and TMBPA were dried at 60 ° C and vacuum for 24 hours prior to polymerization. Anhydrous potassium carbonate (Merck) was dried in a vacuum oven at 100 占 폚 for 10 hours. NMP (Daejung) was stirred and refined using NaOH, and distilled using P ₂ O ₅ under reduced pressure. DMAc (Daejung) was also distilled using P ₂ O ₅ under reduced pressure. Toluene (Merck) was refluxed over sodium metal to remove water and distilled just before use. All other chemicals were obtained from commercial sources and were used without further purification.

¹ H NMR spectra were recorded on a Varian Unity Inova 500 spectrometer (400) using CDCl ₃ (internal reference (δ (1 H) = 7.26 ppm) or DMSO-d 6 (internal reference (δ (1 H) = 2.50 ppm; The number average molecular weight (Mn) and the PDI (Mw / Mn) were measured using a Polystyrene standard calibrated to polystyrene standards (5 μm, 10 ⁵ , 10 ³ , 10 ² A 300 X 8.0 mm) columns were installed for the SEC. For the SEC, an Agilent 1100 pump, a refractive index detector and a PSS SDV TGA (thermogravimetry) was measured at a heating rate of 10 DEG C / min using a TGA Q5000 (TA Instruments) and the decomposition temperature under nitrogen was measured. For TGA, the sample was vacuumed for at least 6 hours and at 100 DEG C . the pre-heating to remove water was pre-hydrated (pre-hydrated) membrane OH ^- A state was investigated alkali stable membrane soaked in a 1M KOH solution saturated with N ₂ eseo 60 ℃. By measuring the change in weight and appearance were evaluated for degradation of the polymer membrane.

Non-contact (tapping mode) atomic force microscopy (AFM) was performed using n-Tracer SPM (Nanofocus). The cantilever is made of silicon and has a resonance frequency of about 320 kHz and a nominal radius of curvature of less than 8 nm. Membrane samples were equilibrated to ~ 50% RH at least 24 hours prior to the experiment. Scanning electron microscopy (SEM) images were taken with a Philips XL 30 FEG microscope and an accelerating voltage of 10 kV.

The OH ^- form of the membrane was dried in vacuo and at 90 DEG C for 24 hours, then the water uptake, rate of expansion, weight, length and thickness of the membrane (about 5 cm x 1 cm) were recorded. The dried membrane was then equilibrated by immersing in deionized water for 24 hours at various temperatures. Then, the membrane was taken out, the excess water on the surface was wiped off with a blowing paper, and the weight, length and thickness were measured in a hurry. The water absorption amount (WUW) is calculated by the following equation (1).

[Equation 1]

Where W _wet and W _dry are the weight of the wet film and the weight of the dried film, respectively.

The expansion ratio is calculated by the following equations (2) and (3).

&Quot; (2) "

&Quot; (3) "

Where l and t are the film length and film thickness, respectively.

The hydration number is calculated from the following equation (4).

&Quot; (4) "

Here, M _{W, H 2 O} is the molecular weight of water. IEC _W is an ion exchange capacity based on weight.

The IEC _W is measured as the number of moles of the ionic groups per gram of dried polymer (mmol / g or mequiv / g) through the Mohr's method. Approximately 0.1 g of the dried membrane (-Br form) was poured into 50 mL of 0.2 M NaNO ₃ aqueous solution for 48 hours to permit exchange of nitrate ions in the solution with bromine in the membrane. The concentration of bromine released into the solution was measured by titration with 0.01 M AgNO ₃ solution using K ₂ CrO ₄ as a colorimetric indicator. IEC _W is calculated according to the following equation (5).

&Quot; (5) "

Wherein W _dry is the weight of dry film, ΔV is the volume of the consumed _AgNO3 AgNO ₃ solution, _AgNO3 C is the concentration of AgNO ₃ solution.

The in-plane hydroxyl ion (OH ^- ) conductivity of the polymer membrane was measured using a direct-produced 2-probe conductivity cell using the electrochemical impedance spectroscopy (GAMRY Reference 3000 ™) in the frequency range of 100 Hz to 1 MHz ) Values were measured. Conductivity Measurements All membranes were equilibrated in deionized water saturated with N ₂ for at least 24 hours. Experiments were carried out with the fixed membrane being equilibrated in deionized water saturated with N ₂ in a way across a pair of platinum conductance cells. The ionic conductivity (sigma, S / cm) was calculated as:

&Quot; (6) "

Where A is the cross-sectional area calculated through the thickness (t) and width (w) of the film and R (Ω) is the resistance resulting from the intersection with the Re (Z) axis on the complex impedance plane.

Example  One: OH - terminal oligomer PES Synthesis of -1

The OH-terminal oligomer PES-1 was synthesized to have a target number average molecular weight of 5 kDa through a typical process as follows.

A mixture of DFDPS (5.537 g, 21.7 mmol), TMBPA (6.844 g, 24.0 mmol), potassium carbonate (7.5 g, 54.4 mmol), NMP (80 mL) and toluene (40 mL) were placed in a Deanstock trap, condenser, magnetic stirrer, Was placed in a 250 mL 2 neck round bottom flask equipped with an outlet. The mixture was heated to 150 < 0 > C in a nitrogen atmosphere. Toluene and residual water of the reaction mixture was azeotropically removed from the system through distillation for 3 to 4 hours. Thereafter, the temperature was raised to 170 DEG C, and the reaction was continued for another 20 hours. After cooling to room temperature, the mixture was poured into acidified methanol. Filtration, sufficient washing with deionized water and drying in vacuo and 100 < 0 > C for 24 hours gave 11.3 g (94% yield) of oligomer in the form of a white powder.

Example  2: F-terminal oligomer FPES Synthesis of -3

First, FPES-2, an OH-terminal oligomer having a target number average molecular weight of 8 kDa, was synthesized as follows.

A solution of DCDPS (7.304 g, 25.4 mmol), 6FBPA (9.162 g, 27.2 mmol), potassium carbonate (9.4 g, 68.1 mmol), NMP (110 mL) and toluene (60 mL) was placed in a Deanstock trap, condenser, magnetic stirrer, Was placed in a 250 mL 2 neck round bottom flask equipped with an outlet. The mixture was first heated at 160 占 폚 for 4 hours and then at 185 占 폚 for 24 hours. Finally, the mixture was precipitated in acidified methanol. The product was filtered, washed several times with deionized water, and dried in vacuo and 100 < 0 > C for 24 hours (13.8 g, 92% yield).

The reactive F-termini were obtained by endcapping the synthesized FPES-2 via hexafluorobenzene in DMAc at 80 < 0 > C through a nucleophilic aromatic substitution reaction. The end capping reaction is as follows.

FPES-2 (12 g, 1.5 mmol) and potassium carbonate (0.62 g, 4.5 mmol) were placed in a 250 mL 3 neck round bottom flask equipped with a Deanstock trap, condenser, magnetic stirrer, nitrogen inlet and outlet. Distilled DMAc (120 mL) and cyclohexane (40 mL) were charged to the flask. The solution was refluxed at < RTI ID = 0.0 > 110 C < / RTI > to azeotropically remove water from the system using cyclohexane over 3 hours. The reaction temperature was lowered to 80 ° C and nitrogen purge was stopped. HFB (2.79 g, 15 mmol) was then added and the reaction was allowed to proceed for 12 hours. The solution was cooled and precipitated in methanol containing several drops of HCl. Filtration, sufficient washing with deionized water, vacuum and drying at 60 < 0 > C for 24 hours gave the product.

Multiblock copolymers are generally synthesized via high temperature reactions (above 180 ° C) between halogen-terminated oligomers and hydroxyl-terminated oligomers, and this reaction condition causes randomization of the moieties due to the trans etherification reaction.

On the other hand, another promising method for preventing the randomization of the polymer structure through trans etherification has been to use a variety of high molecular weight sulfonated multi-block PEM materials with a very low chain reaction temperature About 105 ° C), DFB and HFB are successfully used as chain extenders or linking groups.

Thus, here, for the first time in the manufacture of the AEM material, a precursor block copolymer was synthesized using HFB for bonding as shown in Scheme 1 above. For this, OH-terminated oligomers (PES-1 & FPES-2) based on TMBPA and 6FBPA with controlled molecular weights (for example 5 kDa and 8 kDa, respectively) were dissolved in dried N-methyl-2-pyrrolidone In the presence of potassium carbonate. The target molecular weight and end group functionality of the oligomers were ascertained by offsetting stoichiometry. Since phenoxy end groups were required, the over-calculated molar amounts of TMBPA and 6FBPA were used to synthesize the respective blocks. The chemical structure and molecular weight of oligomers based on TMBPA and 6FBPA were determined by ¹ H NMR spectroscopy and GPC measurement. The integral of the proton of the phenyl group at the end of the ¹ H NMR spectrum of a number average molecular weight of the oligomer 1 integral (PES- of protons in the repeating unit (in the case of a PES-1, 7, 16 for FPES-2) 1 in case of FPES-2, 14 in case of FPES-2).

It was confirmed that the end capping of the original oligomer was successful as the phenoxy end group peak completely disappeared at 7.80 ppm and 6.92 ppm in the ¹ H NMR spectrum (see FIG. 1) of the obtained oligomer. End capping was also confirmed in ¹⁹ F NMR, where the integration ratios show three peaks consistent with their chemical structure.

Example  3: block copolymer FPES  synthesis

The block copolymer was synthesized through the linkage between FPES-3, a polyether sulphone oligomer based on 6FBPA end-capped with HFB, and PES-1, a polyethersulfon oligomer based on OH-terminal TMBPA. A typical binding reaction is as follows.

PES-1 (8g, 1.18mmol), potassium carbonate (0.65g, 4.72mmol), DMAc (145mL) and cyclohexane (50mL) were added to a 250mL three necked round tube equipped with a Deanstock trap, condenser, magnetic stirrer, nitrogen inlet, Bottom flask. The reaction mixture was heated at 100 < 0 > C for 4 hours to azeotropically remove water from the system using cyclohexane. After the cyclohexane was removed, the vacuum dried FPES-3 oligomer (9.583 g, 1.18 mmol) was added. The coupling reaction proceeded at 105 to 110 DEG C for up to 48 hours. The viscous reaction solution was precipitated in a mixture of methanol and water in a 1: 1 ratio. The copolymer was filtered, dried in vacuum and at 120 < 0 > C for 24 hours.

As measured in GPC, the precursor block copolymer The molecular weight of FPES was Mn ~ 36 kDa (PDI ~ 3.71) several times the molecular weight of the starting oligomer (see Table 1 and Figure 2), indicating that a multi-block copolymer was successfully formed. The resultant precursor block copolymer is obtained by reacting the precursor block copolymer with some organic solvent such as chloroform, dichloromethane, 1,1,2,2-tetrachloroethane, N, N-dimethylformamide (DMF), DMAc, dimethylsulfoxide (DMSO) .

[Table 1]

a: polydispersity index (PDI)

The chemical structure and molecular weight of the precursor block copolymer were determined by ¹ H NMR and FTIR spectra. Referring to the spectrum of the starting oligomer (Fig. 1 (a)), the ¹ H NMR spectrum of the precursor block copolymer FPES was well assigned to the estimated chemical structure. The composition of the copolymer was in good agreement with the oligomer feed ratio, which further supports the block structure. In Figure 1 (a), the phenoxy end group peak (9) at 7.09 ppm of the PES-1 oligomer disappeared at 6.88 ppm due to coupling through the HFB coupler in the FPES. In addition, the terminal peaks (6 and 8) located at the end of the PES-1 oligomer within the alkyl zones (located at 2.01 ppm and 1.62 ppm, respectively) completely disappeared from the spectrum of the FPES block copolymer, Indicating that it was completely done.

Example  4: Bromomethylated  Block copolymer FPES - Br  synthesis

The FPES block, which is a polyethersulphone containing benzylmethyl in 1,1,2,2-tetrachloroethane by initiating a radical reaction with N-bromosuccinimide (NBS) brominating agent and benzoyl peroxide (BPO) Bromination of the coalescent was carried out. A typical procedure is as follows.

16 g (14.5 mmol) of FPES and 320 mL of 1,1,2,2-tetrachloroethane were placed in a 500 mL three-neck round bottom flask equipped with a condenser, magnetic stirrer, nitrogen gas inlet and outlet. After the polymer was completely dissolved at 85 캜, the nitrogen purge was stopped and NBS (11.432 g, 64.2 mmol) and BPO (0.777 g, 3.2 mmol) were added. The reaction was continued at 85 < 0 > C for 5 hours. After cooling to room temperature, the mixture was poured into ethanol. The product was filtered, dried in vacuo and at 60 < 0 > C for 24 hours.

Example  5: FPES - QA  And FPES - IM  synthesis

The general procedure for manufacturing FPES-IM is as follows.

The brominated multiblock copolymer FPES-Br (14 g) was dissolved in dried DMF (140 mL) and ethyl imidazole (14.735 g) was added dropwise. The reaction mixture was heated to 85 < 0 > C over 24 h under nitrogen. After cooling to room temperature, the reaction mixture was poured into ethyl acetate. The resulting polymer was filtered off and dried in vacuo and at 85 캜 to obtain FPES-IM as a brown solid.

In the case of FPES-QA, a trimethylamine solution (dissolved in water at a concentration of 50% by weight) in place of ethyl imidazole was added to the polymer solution of DMF. The mixture was stirred under a sealed condition and at room temperature for 24 hours using a magnet. In addition, the FPES-QA product was isolated by precipitation in ethyl acetate, which was filtered and vacuum dried at 85 < 0 > C.

By using NBS (1.1 eq. ₃ ArCH contrast) was performed tetrachloroethane brominated at the benzylic methyl groups of the precursor block copolymer FPES 5 times within and 85 ℃. As the reaction progressed, the reaction solution showed a significant viscosity increase in only 1 hour, but then the viscosity decreased until 2 hours later and a clear reddish brown solution was formed. The brominated product was precipitated in ethanol, followed by filtration and drying to give the product as a yellow product. The 1 H NMR spectra of the block copolymer (FPES, FIG. 1 (a)) and the brominated block copolymer (FPES-Br, FIG. 1 (b)) were compared to show that the new peaks 19 ', 26', 25 ' 21 'appeared in the aromatic region of the spectrum of FPES-Br, a brominated polymer. However, a noticeable difference is that with the emergence of a number of new peaks at ~ 4.29-4.20 ppm (and 4.47 ppm), corresponding to the bromobenzyl protons 17 '(and 27') of the brominated polymer, (And 2.19 ppm) corresponding to benzyl methyl (1 '(and 22')) of the copolymer. This indicated selective bromination at the benzyl position. The degree of bromination calculated from the relative integral ratios of these two peaks (bromobenzyl protons and benzylmethyl protons) was 82%. The bromination yield was also calculated from the molar amount of NBS used in the reaction and the amount of bromine detected in the brominated multiblock copolymer (Table 2). The bromination reaction over a period of 5 hours is generally associated with chloromethylation (or in situ generated) which would require a larger amount of reagent (20-50 equivalents of chloromethyl methyl ether) and a longer reaction time (2-6 days) Yield of 74.5%, which is higher than the general yield, and almost quantitative. Bromomethylation via NBS, compared with chloromethylation, which requires many optimizations to reproduce the yield repeatedly due to frequent side reactions due to the concentration of the reaction solution, the amount of chloromethylating reagent, the amount of catalyst, and the reaction temperature, Provides a more convenient path to control.

[Table 2]

a: Calculated from bromine detected from FPES-Br in ¹ H NMR spectrum and bromine added to NBS.

b: degree of bromination calculated from ¹ H NMR spectrum using the following equation: DBM (%) = 3x (H17 '+ H27') x100 / [3x (H17 '+ H27') + 2x (H1 '+ H22 ').

c: Calculated from the degree of bromination and block copolymer composition as determined via ¹ H NMR spectrum.

d: Calculated using aggregate titration method.

The uniform quaternary ammonium and imidazolium functionalization of the brominated block copolymer (FPES-Br) was achieved in DMF solution at temperatures depending on the nature of the reagents, namely, trimethylamine or 1-ethylimidazole. In the ¹ H NMR spectrum of FPES-QA (Fig. 2 (a)), peaks near 3.08-3.17 ppm were assigned to protons (28 ") of the methyl group of the quaternary ammonium moiety. From the ratio of the integral of the peaks to the aromatic peaks, it can be seen that the degree of amination is close to 100%. In the ¹ H NMR spectrum of FPES-IM (Fig. 2 (b)), peaks at 9.3 ppm and 5.3 ppm were observed in the imidazolium protons 29 '''of ethyl imidazole and in benzyl protons 17' , Which means that the imidazolium group has been successfully coupled. The peaks of the brominated benzyl protons (17 ') were completely replaced by peaks of the benzyl protons (30''') functionalized with imidazolium, and thus the degree of quaternization of the brominated multiblock copolymer was found to be 100% lost.

The chemical structures of FPES, FPES-Br, FPES-QA and FPES-IM were further confirmed by FT-IR analysis (FIG. 3). In the figure, peaks at 1320 cm ^-1 and 1150 cm ^-1 confirm the presence of sulfone (SO ₂ ) while peaks at 1245 cm ^-1 are characteristic peaks of aryl ether. The peak at 3080 cm ^-1 is due to the stretching of the aromatic CH bonds and the sharp peak at 1585 cm ^-1 is due to the aromatic C = C stretch. Peak at 2870-2965cm ^-1 are due to -CH2- and -CH ₃ height. The broad band of this spectrum at ~ 3400 cm <" ¹ > is due to the extensional vibration of OH (due to moisture) or NH bond. Unlike the spectrum of FPES and FPES-Br, the peak at 1663 cm ^-1 corresponds to the CN bond of the quaternary ammonium group or imidazolium group of FPES-QA or FPES-IM. These observations confirmed that the quaternized block copolymer was successfully synthesized.

(NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), tetrahydrofuran (THF), chloroform, 1,2 dichloroethane, The solubility (as 10% (w / v)) of the ionomer block copolymer in various solvents such as 2,2-tetrachloroethane, methanol, ethanol, (n- or 2-) propanol, water was tested. While the quaternized multi-block copolymers are insoluble in THF, the halogenated solvents, alcohols and water are well soluble in bipolar aprotic solvents such as NMP, DMAc, DMF and DMSO and are clear when stirred with a magnetic stir bar A uniform solution was formed. FPES-QA showed slightly higher solubility than FPES-IM block copolymer. The overall high solubility of the resulting quaternized block copolymer for strong polar aprotic solvents enabled the preparation of membranes via solution casting. This high solubility is important because ionomers in solution can form ionic aggregates, the main driving force for phase separation in solution cast films. This well-developed phase separation is known to decisively promote high ionic conductivity.

Example  6: Manufacture of membranes

FPES-QA and FPES-IM membranes were prepared from each DMF solution using a solution-casting method. The general procedure is as follows.

FPES-QA (0.5 g) was dissolved in 10.0 mL of dried DMF by stirring at room temperature for 1 to 2 hours. The solution was then filtered over a Petri dish through a twisted cotton pad and dried in an oven at 55 ° C for 12 hours. The membrane was soaked in deionized water and peeled off. For OH-type membranes, the resulting membranes were soaked in 1 M KOH in a closed vessel at ambient temperature for 48 hours. Finally, the resulting membrane was washed thoroughly and stored in deionized water saturated with N ₂ for further measurement.

Experimental Example  One: Thermal stability  And alkali stability

For use in fuel cells, anion exchange membranes must have high thermal stability because high temperature operation is required to control thermodynamic voltage loss. Thus, as shown in FIG. 4, thermogravimetric analysis (TGA) was performed in a nitrogen environment to investigate the thermal stability of the Br ^- form of FPES-QA and FPES-IM. The initial weight loss (about 4 wt%) at about 50-190 [deg.] C is due to the evaporation of moisture that has been absorbed into the film. As temperature increased, FPES-QA was decomposed in two stages, corresponding to the loss of quaternary ammonium groups at 190-390 ° C followed by polymer backbone decomposition at about 400 ° C. On the other hand, FPES-IM was gradually pyrolyzed in the range of 210-550 ° C, indicating that the block polymer functionalized with imidazolium was thermally more stable than the block polymer functionalized with ammonium. These results confirm that the two ionomer membranes exhibit high thermal stability over the range of requirements for application to AEMFCs.

The chemical stability of AEM is of great interest because most AEMs have low stability at high pH conditions for practical use in fuel cells. Therefore, the FPES-QA film and the FPES-IM film were examined for their chemical stability in terms of their residual weight by immersing them in 1 M NaOH at 60 DEG C for 168 hours. Figure 5 shows digital photographs of the membranes after 168 hours of experiments in 1M NaOH. After 5 days, FPES-QA did not retain its shape and was split into several pieces (Fig. 5 (a)). On the other hand, the FPES-IM membrane retained more than 95% of its initial weight after 7 days, while maintaining its shape and appearance (Fig. 5 (b)). Possible explanation for the loss of mechanical properties is that quaternary ammonium quaternary groups initiate ether hydrolysis of the skeleton. Thus, the FPES-IM membrane exhibits higher chemical stability than multi-block FPES-QA and various other AEM analogues reported elsewhere. Unlike quaternary alkylammonium cationic groups, the imidazolium cationic groups will not undergo high pH conditions and nucleophilic substitution or Hophman degradation at relatively high temperatures. There is no? -Hydrogen in the imidazolium cation group substituted with 1,3-alkyl, which has a large? -Conjugated conjugated system. Therefore, imidazolium cation groups could be stable at high pH conditions.

6 shows the appearance, surface and cross-sectional SEM image of the FPES-QA film and the FPES-IM film. In Fig. 6 (a), a transparent and flexible film is observed. The as-fabricated films are homogeneous and dense without any visible significant defects (Fig. 6 (b) and (c)). The FPES-IM membrane (IECw = 1.95 mequiv / g) is structurally relatively smoother and more dense. On the other hand, QA-PES membranes (IECw = 2.11 mequiv / g) expand to form a relatively coarse structure. We also observed the morphology of AEM with AFM to investigate hydrophilic / hydrophobic phase separation. In Fig. 7, dark regions represent hydrophilic (ionic) domains, and lighter regions represent hydrophobic domains. The surface image shows pronounced hydrophilic / hydrophobic phase separation with interconnected hydrophilic networks of small ionic domains of 5-10 nm in size, which is the result of a hydrophilic / hydrophobic block structure. In addition, ionic domains with well-connected networks of up to tens of nanometers were observed, which could provide a good ion transport pathway.

Experimental Example  2: IEC, water absorption, swelling and hydrolysis rate

One of the main objectives of the preparation of ionomer membranes prepared from the same backbone skeleton but functionalized in different ways was to investigate the effect of various functionalization by keeping IECw similar. The IECw of the FPES-QA and FPES-IM membranes was theoretically calculated from the block copolymer composition and the degree of bromination, assuming that the benzyl bromide is converted to a fully quaternized form. The theoretical IECw of the FPES-QA and FPES-IM membranes were 2.11 and 1.95 mequiv / g, respectively. This difference in IECw values is due to the different masses of quaternary ammonium cations and imidazolium. IECw of the membrane was also measured by titration and titration of Br ^- using silver nitrate, which is shown in Table 2. The measured values exceeded 95% of the theoretical values, which may be due to polymer mass calculations.

The water absorption amount, the expansion ratio (longitudinal direction,? 1 and thickness,? T) and the hydroxyl conductivity of AEM are shown in Table 3. The multi-block copolymers comprising hydrophilic blocks and hydrophobic blocks can form phase-separated copolymers, and for certain IECw values, there is a clear phase separation (well-connected hydrophilic Domain). ≪ / RTI > Tanaka et al. Also reported that large hydrophobic domains self-organizing from hydrophobic blocks specifically inhibit excessive water uptake and swelling. Thus, the ideal designed FPES-QA and FPES-IM membranes absorbed more water than the random polymer QPAE-a ⁵ membrane, and the QPE-bl-5 (X5Y11) membrane, the F- QPES membranes, as compared to the various ionomers. This may be due to the strong field effect of tightly clustered ionic groups that self-organize from the hydrophilic blocks in the membrane. As expected, the water absorption of the membrane increases with increasing IECw and temperature. The number of water molecules absorbed per QA or imidazolium group (denoted by?) As a means for evaluating the water absorption properties of membranes with different IECw values was also calculated using the theoretical IECw. FPES-QA membranes with similar functional densities (similar IECw values) to FPES-IM membranes absorb larger amounts (higher λ values) of water than FPES-IM membranes.

We have found that the lower λ value of the imidazolium-based polymer is relatively low compared to the strong Coulomb (or ion dipole) interaction between the delocalized imidazolium cation and the water molecule and the quaternary ammonium material It is presumed that it is caused by a weak steric hindrance. The expansion rates of FPES-QA and FPES-IM membranes increased with increasing IECs and water uptake. The membranes exhibit good dimensional stability with an expansion rate of about 20% at about 20%, which is about or less than that of many other AEMs. The FPES-QA and FPES-IM membranes exhibit similar in-plane expansion, but FPES-QA exhibits expansion anisotropy in the thickness direction rather than in the plane direction, as opposed to FEPS-IM. The degree of expansion anisotropy (Δt / Δl) of the FPES-IM membrane was about 0.9 while the degree of expansion anisotropy of the FPES-QA membrane was about 1.85. The expansion anisotropy of the FPES-QA corresponds to a high λ value.

However, it is well known that the dimensional stability of membranes with similar IECw values is strongly dependent on the water uptake, and the over-bounding water uptake mainly results in relatively low dimensional stability. More water uptake and greater through-plane expansion in the case of FPES-QA may suggest that a more orderly hydrophilic domain is formed within the membrane structure. In addition, a smaller dimensional change in the plane direction of the FPES-QA film is expected to be advantageous for the production of high-quality membrane electrode assemblies for application to humidity conditions of fuel cells.

[Table 3]

Hydroxide high conductivity is an important factor to realize a high-performance AEMFC, conductivity of hydroxide at 60-90 ℃ operating temperature is 10 mScm ^- should be larger than ^one. Therefore, the in-plane hydroxyl conductivity () of FPES-QA and FPES-IM membranes was measured as a function of temperature (30-80 ° C) in deionized water by AC impedance spectroscopy. Prior to the start of the experiment, the deionized water used in the experiment was purged with nitrogen gas to limit exposure of the OH ^- form film to CO ₂ . However, as Hickner's study showed that AEM rapidly converted from hydroxyl form to bicarbonate form over several hours and consequently reduced ionic conductivity, experimental limitations suggest that the possibility of partial conversion from OH ^- form to bicarbonate form I can not exclude it. Hydroxy conductivity at the stated temperature range was 21-63 mS / cm for FPES-QA and 22-56 mS / cm for FPES-IM. The values were much higher or similar to those of many other random AEMs and block AEMs and met the appropriate requirements for fuel cell applications. The high hydroxide conductivity in AEM is achieved by the phase separation of hydrophilic / hydrophobic domains, with an interconnected network of hydrophilic channels by the block structure of the ionomer. The dependence of hydroxide conductivity on IECw values shows a linear trend similar to that of water uptake. The hydroxyl conductivity of the ionomer membrane also increased dramatically with increasing temperature. In FIG. 8, the FPES-QA film and the FPES-IM film showed a temperature-dependent hydroxylation behavior in the Arrhenius equation. The activation energy (Ea) of hydroxyl conductivity was calculated based on the Arrhenius equation of the following Equation (7) by applying a linear least square fit to the data shown in Fig.

&Quot; (7) "

In this case, σ is the hydroxide conductivity (mS / cm), R is the universal gas constant (8.314 J / mol K), A is the exponential factor and T is the absolute temperature (K).

The calculated activation energy of hydroxyl transport, Ea, was 19.36 kJ / mol for the FPES-QA membrane and 16.18 kJ / mol for the FPES-IM membrane. The values were much higher than the activation energy of hydroxyl transport of Nafion ^ⓡ 117 (13.63 kJ / mol) and were similar to those of quaternized polyarylene ether with tetraphenylmethane moiety. These results indicate that the mobility of the hydroxide ion in the ionomer membrane is more dependent on temperature as compared to the proton in Nafion ^ⓡ 117. The difference in Ea value is due to the polymer chain structure and water absorption of the ionomer membrane.

Therefore, there is a direct correlation between conductivity and morphology because Ea of FPES-QA film is larger than Ea of FPES-IM film. Since FPES-IM shows increased degree of phase separation (apparent in the AFM image recorded in partially hydrated state), the hydroxide ion can move and pass well in comparison to the hydroxide ion in the FPES-QA membrane . Increasing the degree of phase separation decreased the structural barrier of water transport and increased the hydroxyl conductivity and the water diffusion coefficient according to the water content of the membrane. This fact is evident in the fact that the hydroxyl conductivity at low temperatures is higher in FPES-IM than in FPES-QA. However, in the case of FPES-QA in which the hydrophilic domains are not well connected in the low-temperature phase-separated structure, a rise in temperature has resulted in the absorption of excess large water molecules, which causes the channels of more open structure to swell, And to increase the conductivity.

In summary, we succeeded in synthesizing AEM, a partially fluorinated polyethersulfone block copolymer based on the novel quaternary ammonium- and imidazolium, to have the same degree of functionalization as the same skeleton structure. The block structure of the polyethersulfone AEM with HFB as a linker enables a flexible, tough membrane with a distinct phase separation structure for easier ion transport.

The FPES-QA membrane exhibited larger water uptake and larger expansion anisotropy than the FPES-IM membrane. At all temperatures after 40 ° C, the FPES-QA membrane exhibited a higher hydroxyl conductivity than FPES-IM. Although the FPES-QA film has higher IECw (FPES-QA, IECw = 2.07 mequiv / g; FPES-IM, IECw = 1.93 mequiv / g) at atmospheric conditions, it has a denser structure . The hydroxyl conductivity in the longitudinal direction was 21-63 mS / cm for FPES-QA and 22-56 mS / cm for FPES-IM.

Thus, according to the present invention, it has been found that FPES-IM with high hydroxide conductivity, better thermal stability, dimensional stability and chemical stability can provide better AEM for alkaline fuel cell applications.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

Claims (5)

A hydrophilic region comprising at least one quaternary ammonium salt and hydrogen, or at least one imidazolium salt and a hydrogen pendant polyethersulfone backbone; And
A hydrophobic region comprised of a fluorinated polyethersulfone backbone,
Wherein the hydrophilic region and the hydrophobic region are linked via a decafluorobiphenyl or hexafluorobenzene, wherein the semi-fluorinated polyether sulfone block comprises a repeating unit represented by the following formula (1) Copolymer:
[Chemical Formula 1]

In this formula,
R is decafluorobiphenyl or hexafluorobenzene,
R "

,

Or hydrogen,

Wow

Are not simultaneously included,
x and y are integers from 5 to 25,
n is an integer of 2 to 10; The semi-fluorinated polyether sulfone block copolymer according to claim 1, wherein the repeating unit is represented by the following formula (2) or (3):
(2)

(3)

In this formula,
R "

,

Or hydrogen,

Wow

Are not simultaneously included,
x and y are integers from 5 to 25,
n is an integer of 2 to 10; An anion exchange polyelectrolyte membrane characterized by comprising a semi-fluorinated polyether sulfone block copolymer according to claim 1. A fuel cell employing the anion-exchange polymer electrolyte membrane according to claim 3. (i) reacting a compound of formula (4) and a compound of formula (5) in the presence of K ₂ CO ₃ to produce a compound of formula (6);
(ii) endcapping the compound of formula (6) with hexafluorobenzene in the presence of K ₂ CO ₃ to produce a compound of formula (10);
(iii) reacting a compound of formula (VII) with a compound of formula (VIII) in the presence of K ₂ CO ₃ to produce a compound of formula (9);
(iv) reacting a compound of formula (9) and a compound of formula (10) in the presence of K ₂ CO ₃ to prepare a compound of formula (11);
(v) reacting a compound of the following formula (11) with N-bromosuccinimide (NBS) and benzoyl peroxide (BPO) to prepare a compound of the following formula (12); And
(vi) reacting a compound represented by the following formula (12) with trimethylamine or ethylimidazole to obtain a semi-fluorinated polyether sulfone block copolymer having a repeating unit represented by the following formula Manufacturing method:
[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

(11)

[Chemical Formula 12]

(2)

In this formula,
R 'is Br or hydrogen,
R "

,

Or hydrogen,
x and y are integers from 5 to 25,
n is an integer of 2 to 10;

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