KR20210105738A - Sulfonated graft polymer, preparation method thereof and use thereof - Google Patents

Abstract

The present invention relates to a sulfonated graft polymer, a manufacturing method thereof, and a use thereof, and more specifically, to a graft polymer, a polymer electrolyte membrane including the same, and use of the electrolyte membrane, wherein the graft polymer has any one of hydrocarbon-based polymers consisting of a polyimide (PI)-based polymer, a polysulfone (PSU)-based polymer, a polyetherketone (PEK)-based polymer, and a polyarylene ethersulfone (PAES)-based polymer as a main chain, and includes a sulfone group as a single reactive side chain bonded to the main chain.

Description

Sulfonated branched polymer, manufacturing method and use thereof {Sulfonated graft polymer, preparation method thereof and use thereof}

The present invention relates to a sulfonated branched polymer, a method for preparing the same, and a use thereof.

More specifically, polyimide (PI)-based, polysulfone (PSU)-based, polyetherketone (PEK)-based, polyarylene ethersulfone (PAES)-based, polyarylenesulfidesulfone-based, and polyarylene ether A branched polymer containing any one of hydrocarbon-based polymers made of a sulfide-based (polyaryleneethersulfidesulfone) polymer as a main chain and containing a sulfone group as a single reactive side chain bonded to the main chain, a polymer electrolyte membrane containing the same, and the use of the electrolyte membrane it is about

A fuel cell is an energy conversion device that converts chemical energy into electrical energy by an electrochemical reaction between hydrogen or methanol as a fuel and oxygen or air as an oxidizing agent. Basically, an anode, an oxygen electrode, and It includes an electrolyte membrane disposed between two electrodes, and this configuration is called a membrane-electrode assembly. Here, the electrolyte membrane serves to deliver hydrogen ions generated from the fuel electrode to the oxygen electrode (high hydrogen ion conductivity) and as a diaphragm to prevent fuel from mixing with oxygen (high dimensional stability against hydration and low methanol permeability) is responsible for

These polymer electrolyte membranes are largely divided into fluorinated PEM and hydrocarbon-based PEM, among which hydrocarbon-based electrolyte membranes are polyimide (PI), polysulfone (PSU), polyether ketone (PEK), It is manufactured using a polymer such as polyarylene ether sulfone (PAES), and generally has advantages of lower manufacturing cost and excellent thermal stability compared to fluorine-based electrolyte membranes.

On the other hand, the electrolysis (water electrolysis) method of water using a polymer electrolyte membrane, which is one of the hydrogen production methods, is a device that electrochemically decomposes water to produce hydrogen and oxygen. Compared to other hydrogen production methods, operating conditions are simple and small volume. It is a technology attracting attention because it has the advantage of being small and high-purity hydrogen can be obtained. It can also be used for hydrogen fuel cells. Hydrogen fuel cell is a method of producing electricity by electrochemically reacting hydrogen and oxygen as a reverse reaction of water electrolysis.

A polymer electrolyte membrane for water electrolysis is generally a solid polymer electrolyte membrane, which divides oxygen and hydrogen generated during water electrolysis and allows hydrogen ions to pass through, and has a membrane-electrode assembly (MEA) composed of a catalyst and a gas diffusion layer. When a voltage is applied during water electrolysis, an oxidation reaction occurs at the anode. At this time, oxygen and hydrogen ions are generated from water, and these hydrogen ions move to the cathode through the polymer electrolyte membrane and electrons (e) supplied from the outside -) reacts to generate H2.

In the above water electrolysis device, etc., as a polymer electrolyte membrane for exchanging hydrogen, Nafion (product of Dupont Co., Ltd.), which is generally a perfluorine-based membrane, is commercially available. However, the Nafion membrane has a problem in that the manufacturing process is complicated, the price is very expensive, the environmental pollution is large because fluorine is used, and the electrochemical performance such as hydrogen ion conductivity is deteriorated at a high temperature of 80°C or higher.

Accordingly, Japanese Patent Application Laid-Open No. Hei 06-93114 proposes a method for manufacturing an electrolyte membrane based on polyarylene ether sulfone. However, when the degree of sulfonation is increased to increase the exchangeability of hydrogen ions, the mechanical properties of the membrane are reduced due to swelling, and thermal stability is also reduced.

In a fuel cell including a polymer electrolyte membrane, a fluorine-based polymer electrolyte membrane is widely known for its high performance and durability. In particular, in the case of a fluorine-based polymer electrolyte membrane, it can be confirmed that durability is stably shown in the evaluation of mechanical properties through a relative humidity cycle test (RH cycle test). A lot of research on hydrocarbon-based polymer electrolyte membranes is being conducted. In order to increase the ionic conductivity of the hydrocarbon-based polymer electrolyte membrane to the level of the fluorine-based polymer electrolyte membrane, the synthesis of a polymer having a low equivalent weight value is mainly performed, but the hydrocarbon-based polymer having a low equivalent weight value shows a characteristic that mechanical durability is further reduced. In most cases, it is.

Therefore, polymer electrolytes having various molecular structures such as random copolymers, multi-block copolymers, and graft copolymers as specific types of hydrocarbon-based polymer electrolyte membranes to improve the disadvantages of the prior art. Research on membranes is actively underway. As a related prior art, Korean Patent Application Laid-Open No. 10-2015-0143362 describes a poly(arylene ether sulfone) polymer having a graft structure prepared by a cycloaddition reaction between an azidoalkyl group and an ethynyl group and a method for preparing the same. has been However, in the method for preparing a branched polymer, the occurrence of a crosslinking reaction during the grafting reaction causes gelation, destroying the target supply ratio, etc. Although it is very important to suppress the occurrence, there is a disadvantage in that it does not provide a specific solution for avoiding such unnecessary cross-linking reaction.

In addition, Korean Patent Registration No. 10-1229597, which relates to a membrane electrode assembly for a fuel cell and a method for manufacturing the same, discloses a homopolymer, an alternating copolymer, a random copolymer, a block copolymer, a multi-block copolymer, or a graft copolymer. Although it has been described with respect to an electrolyte membrane for a fuel cell containing the electrolyte membrane, specific comparative results have not been presented with respect to the physical properties and effects of the electrolyte membrane according to the polymer structure of the electrolyte membrane.

Japanese Patent Laid-Open No. 06-93114 Korean Patent Publication No. 10-2015-0143362 Korean Patent Registration No. 10-1229597

The present invention was developed to solve the above problems, and an object of the present invention is to provide a sulfonated branched polymer having a single reactive side chain structure.

In addition, in the present invention, it is an object of the present invention to provide a sulfonated branched polymer that can be used as an electrolyte membrane for a fuel cell, a secondary battery, a redox flow battery, or water electrolysis.

In the present invention, in order to solve the above problems, polyimide (PI)-based, polysulfone (PSU)-based, polyetherketone (PEK)-based, polyarylene ethersulfone (PAES)-based, polyarylenesulfidesulfone-based and a branched polymer containing a sulfone group as a single reactive side chain bonded to the main chain and having any one of a hydrocarbon-based polymer consisting of a polyaryleneethersulfidesulfone polymer as a main chain, and a polymer electrolyte membrane comprising the same do.

The method for producing a sulfonated branched polymer according to the present invention has an effect of preventing cross-linking along with the control of IEC by adjusting the molecular weight of the side chain and the molar percentage of the pendant hydroxyl group of the main chain.

The branched polymer having single-terminal reactivity according to the present invention and corresponding to the side chain containing a sulfonic acid group in all benzoyl rings has a high IEC and high acidity of a low equivalent weight value, and is cross-linked during graft reaction due to a single-terminal side chain On the other hand, by excluding a sulfonic acid group from the main chain, excellent hydrous stability, dimensional stability, mechanical properties and durability are improved.

In the sulfonated branched polymer according to the present invention, the interdomain distance between hydrophilic clusters increased as the side chain length increased, and a longer side chain length in a similar IEC showed higher water absorption and proton conductivity.

The sulfonated branched polymer according to the present invention has advantages of low swelling, high ionic conductivity at low humidity, and excellent performance reproducibility compared to multi-block polymers of a similar concept.

The sulfonated branched polymer according to the present invention has excellent performance as an electrolyte membrane for a fuel cell due to current density and excellent chemical and physical durability along with higher proton conductivity than commercial Nafion.

^{1 shows 1} H-NMR spectra of (a) CMSDPS and (b) FMDPS, which are side chain monomers prepared according to an embodiment of the present invention.
^{2 shows (a) 1} H-NMR and (b) ¹⁹ F-NMR spectra of G-sPSS prepared according to an embodiment of the present invention.
^{3 shows 1} H-NMR of G-PES_OH prepared according to an embodiment of the present invention, in which (a) is an -O- group, (b) is a -S- group, and (C) is a -SO _This is the spectrum of G-PES_OH with a 2 - group.
^{4 shows a 1} H-NMR spectrum of Gx/y having an -O- group in the main chain prepared according to an embodiment of the present invention.
^{5 shows a 1} H-NMR spectrum of Gx/y having a -S- group in the main chain prepared according to an embodiment of the present invention.
^{6 shows a 1} H-NMR spectrum of Gx/y _{having a -SO 2} - group in the main chain prepared according to an embodiment of the present invention.
^{7 shows (a) 1} H-NMR and (b) ¹⁹ F-NMR spectra of M_sPSS, which is a hydrophilic block of a multi-block polymer prepared according to an embodiment of the present invention.
^{8 shows a 1} H-NMR spectrum of M_PES, which is a hydrophobic block of a multi-block-type polymer prepared according to an embodiment of the present invention.
^{9 shows a 1} H-NMR spectrum of a multi-block-type polymer prepared according to an embodiment of the present invention.
10 shows (a) a sulfonated cross-linked polymer (when side chains having reactivity at both ends are used for grafting) and (b) a sulfonated branched polymer (side chains having single-terminal reactivity are grafted) according to an embodiment of the present invention; The chemical formula of (when used in ) and the appearance of the reactor during production are shown.
11 shows the results of analysis of water absorption and dimensional expansion of Gx/y having different side chain lengths according to an embodiment of the present invention.
12 shows the proton conductivity analysis results according to the temperature of Gx/y having different side chain lengths according to an embodiment of the present invention.
13 shows the fuel cell performance of G1.64/7500 according to an embodiment of the present invention.
14 shows the OCV test results of G1.64/7500 according to an embodiment of the present invention.
15 shows the OCV test results over time of G1.64/7500 according to an embodiment of the present invention.
16 shows the wet-dry cycle test results of G1.64/7500 according to an embodiment of the present invention.
17 is a comparison of dimensional stability and water absorption of the branched polymer and the multi-block polymer according to an embodiment of the present invention.
18 shows the results of analyzing the proton conductivity with respect to relative humidity for the branched polymer, the multi-block polymer, and the commercial Nafion according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

In the present invention, in order to solve the above problems, polyimide (PI)-based, polysulfone (PSU)-based, polyetherketone (PEK)-based, polyarylene ethersulfone (PAES)-based, polyarylenesulfidesulfone-based and a hydrocarbon-based polymer comprising a polyaryleneethersulfidesulfone-based polymer as a main chain, and provides a branched polymer containing a sulfone group as a single reactive side chain bonded to the main chain.

More specifically, polyimide (PI)-based, polysulfone (PSU)-based, polyetherketone (PEK)-based, polyarylene ethersulfone (PAES)-based, polyarylenesulfidesulfone-based, and polyarylene ether It provides a sulfonated branched polymer, characterized in that it has as a main chain any one of hydrocarbon-based polymers made of a sulfide sulfone-based polymer, and includes a repeating unit represented by the following Chemical Formula 1 as a side chain coupled to the main chain .

<Formula 1>

In Formula 1, L1 and L2 are each independently -O-, -S-, -SO ₂ -, -C=O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any one ego,

R1 and R2 are each independently -SO ₃ M or -SO ₃ H, wherein M is any one of Li, Na or K,

a, and b are each independently 1 to 4,

x is an integer from 1 to 5,000 as a repeating unit,

,

,

중 어느 하나의 비반응성 말단기이고, E is an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group having 6 to 18 carbon atoms, -CN or -NO _{2 a} phenyl group having a substituent,

,

,

Any one of the non-reactive end groups,

,

, 할로겐기, 알콜기, 또는 티올기에서 유래된 연결구조 중 어느 하나의 반응성 말단기이다.R is

,

, a halogen group, an alcohol group, or a reactive end group of any one of a linking structure derived from a thiol group.

In the sulfonated branched polymer according to an embodiment of the present invention, the main chain of the hydrocarbon-based polymer may include a chemical structure of Formula 2 below.

<Formula 2>

In Formula 2, L3 and L4 are each independently -O-, -S-, -SO ₂ -, -C(O)-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any of is one,

R3 to R5 are each independently hydrogen or an alkyl group or an alkylene group containing a linear, branched or CN group having 1 to 10 carbon atoms,

c, and d are each independently 0 to 4, e is 0 to 3,

R6 is a linking group, any one of a chemical structure derived from a thiol group (-SH), an amine group (-NH-), a phenol group (-PhOH) or an alcohol group (-OH),

y is an integer from 1 to 5,000 as a repeating unit.

In the sulfonated branched polymer according to an embodiment of the present invention, the sulfonated branched polymer may further include a repeating unit represented by Formula 2 in the main chain and to which a side chain is not bonded.

In the sulfonated branched polymer according to an embodiment of the present invention, the main chain of the sulfonated branched polymer may have a chemical structure represented by Chemical Formula 3 below.

<Formula 3>

In Formula 3, L3 to L6 are each independently -O-, -S-, -SO ₂ -, -C=O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any one ego,

R3 to R5 and R7, R8 are each independently hydrogen or an alkyl group or an alkylene group containing a straight or branched chain having 1 to 10 carbon atoms or a CN group,

c, d, f, g are each independently 0 to 4, e is 0 to 3,

R6 is a linking group, any one of a chemical structure derived from a thiol group (-SH), an amine group (-NH-), a phenol group (-PhOH) or an alcohol group (-OH),

y and z are repeating units, y + z is an integer from 1 to 5,000,

,

,

중 어느 하나의 비반응성 말단기이다.E is an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group having 6 to 18 carbon atoms, -CN or -NO _{2 a} phenyl group having a substituent,

,

,

any one of the non-reactive end groups.

In addition, in the present invention, polyimide (PI)-based, polysulfone (PSU)-based, polyetherketone (PEK)-based, polyarylene ethersulfone (PAES)-based, polyarylenesulfidesulfone-based and polyarylene Preparing any one of the hydrocarbon-based polymer consisting of an ether sulfide sulfone-based (polyaryleneethersulfidesulfone) polymer as a main chain; It provides a method for producing a sulfonated branched polymer comprising the step of bonding a repeating unit represented by the following formula (1) to the main chain as a side chain.

<Formula 1>

In Formula 1, L1 and L2 are each independently -O-, -S-, -SO ₂ -, -C=O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any one ego,

R1 and R2 are each independently -SO ₃ M or -SO ₃ H, wherein M is any one of Li, Na or K,

a, and b are each independently 1 to 4,

x is an integer from 1 to 5,000 as a repeating unit,

,

,

중 어느 하나의 비반응성 말단기이고, E is an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group having 6 to 18 carbon atoms, -CN or -NO _{2 a} phenyl group having a substituent,

,

,

Any one of the non-reactive end groups,

,

, 할로겐기, 알콜기, 또는 티올기에서 유래된 연결구조 중 어느 하나의 반응성 말단기이다.R is

,

, a halogen group, an alcohol group, or a reactive end group of any one of a linking structure derived from a thiol group.

The main chain of the hydrocarbon-based polymer is a method for producing a sulfonated branched polymer, characterized in that it includes the chemical structure of Formula 2:

<Formula 2>

In Formula 2, L3 and L4 are each independently -O-, -S-, -SO ₂ -, -C(O)-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any of is one,

R3 to R5 are each independently hydrogen or an alkyl group or an alkylene group containing a linear, branched or CN group having 1 to 10 carbon atoms,

c, and d are each independently 0 to 4, e is 0 to 3,

R6 is a linking group, any one of a chemical structure derived from a thiol group (-SH), an amine group (-NH-), a phenol group (-PhOH) or an alcohol group (-OH),

y is an integer from 1 to 5,000 as a repeating unit.

In the method for producing a sulfonated branched polymer according to an embodiment of the present invention, the main chain of the sulfonated branched polymer may include one having a chemical structure of Formula 3 below.

<Formula 3>

In Formula 3, L3 to L6 are each independently -O-, -S-, -SO ₂ -, -C=O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any one ego,

R3 to R5 and R7, R8 are each independently hydrogen or an alkyl group or an alkylene group containing a straight or branched chain having 1 to 10 carbon atoms or a CN group,

c, d, f, g are each independently 0 to 4, e is 0 to 3,

R6 is a linking group, any one of a chemical structure derived from a thiol group (-SH), an amine group (-NH-), a phenol group (-PhOH) or an alcohol group (-OH),

y and z are repeating units, y + z is an integer from 1 to 5,000,

,

,

중 어느 하나의 비반응성 말단기이다.E is an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group having 6 to 18 carbon atoms, -CN or -NO _{2 a} phenyl group having a substituent,

,

,

any one of the non-reactive end groups.

In addition, the present invention provides a sulfonated branched polymer that can be used as an electrolyte membrane for a fuel cell, a secondary battery, a redox flow battery, or water electrolysis.

In addition, the present invention provides a fuel cell, a secondary battery, a redox flow battery, and a water electrolysis device including a sulfonated branched polymer as an electrolyte membrane.

Hereinafter, embodiments and examples of the present invention will be described in detail so that a person with general knowledge in the technical field to which the present application pertains can easily carry out the preferred embodiment of the present invention as shown in the accompanying drawings. In particular, the technical spirit of the present invention and its core configuration and operation are not limited by this. In addition, the content of the present invention may be implemented in various other types of equipment, and is not limited to the implementation examples and embodiments described herein.

<Preparation Example 1> Preparation of side chain monomers (CMDPS, FMDPS)

4-chloro-4'mercaptodiphenylsulfone, which is a side chain monomer of the branched polymer according to an embodiment of the present invention, is denoted as CMDPS, and 4-fluoro-4'mercaptodiphenylsulfone is denoted as FMDPS. CMDPS and FMDPS were prepared by the method of Scheme 1 below.

<Scheme 1>

First, microcrystalline DCDPS (100 g, 0.32 mol) and anhydrous DMSO (42% solids) were added to a 300 mL round bottom flask (RBF) using an argon gas inlet, and the temperature ^{was raised to 60 °} C to dissolve for 1 hour. Then, sodium hydrosulfide hydrate (25.14 g, 0.32 mol), potassium carbonate (21.88 g, 0.16 mol) and anhydrous DMSO were added to the solution to change the color of the solution to green, and then the solution was heated to 80 °C for 4 hours. When the reaction turned the solution orange, the final solution was coagulated in an ice-water bath and filtered. The filtrate was recovered and titrated to pH 3 with hydrochloric acid to form a white precipitate. These precipitates were filtered off, and the filtered solid was dissolved in 5 wt % aqueous potassium carbonate solution. The solution was titrated to pH 3 with hydrochloric acid again with the production of carbon dioxide gas and stirred for 30 minutes, then the solution was filtered, and the filtered solid was dried overnight at 80 °C in a vacuum oven.

FMDPS, which is another side chain monomer according to an embodiment of the present invention, was prepared by using difluorodiphenyl sulfone (DFDPS) using the same method as that of CMDPS.

^{1 shows 1} H-NMR of CMDPS and FMDPS prepared according to an embodiment of the present invention, wherein the ortho proton peaks for the sulfone group of CMDPS are 7.73-7.83 ppm (a) and 7.62-7.72 ppm (b) , the chlorine group and the proton group orthogonal to the thiol group appeared at 7.35-7.44 ppm (c) and 7.22-7.32 ppm (d), respectively, and the proton peak of the thiol group was 3.52-3.64 ppm (e). The production of CMDPS was confirmed based on the appearance, and the chemical structure of FMDPS was confirmed based on the peak shown in FIG. 1 .

<Preparation Example 2> Preparation of sulfonated side chain polymer (G_sPSS)

According to an embodiment of the present invention, the sulfonated side chain polymer is denoted as G-sPSS. G-sPSS was prepared by the following two preparation methods.

<Preparation Example 2-1> Preparation of sulfonated side chain polymer 1

A side chain polymer was prepared according to the reaction route of Scheme 2-1 below using a combination of various kinds of monomers (Monomer: M) and end-capper (E), and the specific preparation method is as follows.

<Reaction Scheme 2-1>

Monomers CMDPS (0.070 mol), 2-naphthalene thiol (0.0046 mol), potassium carbonate (0.045 mol) and anhydrous NMP (17% solids) were first added to synthesize a branched polymer having a target molecular weight of 8000 g/mol. Put in a 250mL RBF with argon gas inlet for 3 hours at 130°C, after which the solution is cooled to room temperature. Additional end capper (0.035 mol) was added at 60 °C for 2 h, and the solution was cooled back to room temperature. Meanwhile, decafluorobiphenyl (0.27 mol) and anhydrous NMP (15% solids) were dissolved in 300 mL RBF at room temperature, and the resulting solution was stored in a refrigerator. After cooling to room temperature or lower, the reaction temperature was maintained at 0 °C using an ice bath, and then the above-mentioned CMDPS solution was added dropwise to the decafluorobiphenyl solution and stirred with an argon gas purge for 2 hours. The final solution was precipitated with methyl alcohol and washed several times with deionized water and methyl alcohol. The product was vacuum dried at 60 °C overnight.

Using the product obtained from the previous step, a sulfonation process was performed to introduce a sulfonic acid group on the side chain. Unsulfonated branched oligomers (0.0030 mol, 1 eq) and fuming sulfuric acid (5 eq) were added to a 250 mL jacketed RFB, which was purged with argon, followed by argon purging beforehand at -10 °C for 5 days. The sulfonated product G_sPSS was then poured into an ice-water bath to dissolve the oligomers. The product was precipitated by saturating the aqueous solution with sodium chloride. After filtration, the filtered solid was dissolved in aqueous solution and titrated to pH 7 with 10 N sodium hydroxide solution. The dissolved solution was re-precipitated by saturation with sodium chloride. After filtration, the filtered solid was vacuum dried at 60 °C overnight. The vacuum dried product was then dissolved in DMSO. Then, the G_sPSS solution was filtered to remove sodium chloride, and the filtrate was precipitated and washed several times in 2-propanol. The final product was vacuum dried at 60 °C overnight.

The same procedures and equivalents were used for the monomeric FMDPS and other end cappers were prepared.

<Preparation Example 2-2> Preparation of sulfonated side chain polymer 2

Another type of side chain polymer according to an embodiment of the present invention uses various types of monomers (Monomer: M) and end-capper (End-capper: E) to form a side chain polymer according to the reaction route of Scheme 2-2 below. was prepared, and the specific manufacturing method is as follows.

<Scheme 2-2>

The monomers CMDPS (0.032 mol), 4-fluorobenzonitrile (0.0021 mol), potassium carbonate (0.020 mol) and anhydrous NMP (17% solids) were first added to synthesize a branched polymer with a target molecular weight of 8000 g/mol. Put in a 250mL RBF with argon gas inlet for 3 hours at 130°C, after which the solution is cooled to room temperature. Additional end capper (0.0010 mol) was added at 60 °C for 2 h, and the solution was cooled back to room temperature. NaSH (0.0027 mol) and potassium carbonate (0.0032 mol) were added to the oligomers at 80 °C for 4 h. On the other hand, at room temperature, decafluorobiphenyl (0.011 mol) and anhydrous NMP (15% solids) were dissolved in 300 mL RBF, and the resulting solution was stored in a refrigerator. After cooling to room temperature or lower, the reaction temperature was maintained at 0 °C using an ice bath, and then the above-mentioned CMDPS solution was added dropwise to the decafluorobiphenyl solution and stirred with an argon gas purge for 2 hours. The final solution was precipitated with methyl alcohol and washed several times with deionized water and methyl alcohol. The product was vacuum dried at 60 °C overnight.

Using the product obtained from the previous step, a sulfonation process was performed to introduce a sulfonic acid group on the side chain. Unsulfonated branched oligomer (0.0022 mol, 1 eq) and fuming sulfuric acid (5 eq) were added to a 250 mL jacketed RFB, which was purged with argon, followed by argon purging beforehand at -10 °C for 5 days. The sulfonated product G_sPSS was then poured into an ice-water bath to dissolve the oligomers. The product was precipitated by saturating the aqueous solution with sodium chloride. After filtration, the filtered solid was dissolved in aqueous solution and titrated to pH 7 with 10 N sodium hydroxide solution. The dissolved solution was re-precipitated by saturation with sodium chloride. After filtration, the filtered solid was vacuum dried at 60 °C overnight. The vacuum dried product was then dissolved in DMSO. Then, the G_sPSS solution was filtered to remove sodium chloride, and the filtrate was precipitated and washed several times in 2-propanol. The final product was vacuum dried at 60 °C overnight.

It was prepared using the same procedure and equivalents for the monomeric FMDPS and other end cappers.

^{2 shows (a) 1} H-NMR and (b) ¹⁹ F-NMR spectra of G-sPSS prepared according to an embodiment of the present invention ^{. In 1} H-NMR, the sulfonate base of the repeating unit is The proton peak ortho for the sulfonate salt group at 8.31-8.38 ppm (a) to 7.73-7.81 ppm (b), and for the sulfone group at 7.26-7.32 ppm (c) the proton peak ortho for the meta-terminal sulfide group is 7.11 appeared at -7.16 ppm (d). ^{In 19} F-NMR, the fluorine peak of the decafluorobiphenyl unit was -170 ppm to -106 ppm. G_sPSS was prepared with various molecular weights (4,994-8,523 g/mol) calculated using the intensity of the terminal peak in ^{1 H-NMR, and these results are summarized in Table 1 below.}

sample code Molecular Weight (g/mol) G_sPSS_7500 7,500 G_sPSS_8500 8,523 G_sPSS_5800 3,503 G_sPSS_5000 4,994

<Preparation Example 3> Preparation of main chain polymer (G_PES_OH)

The main chain polymer according to an embodiment of the present invention is denoted as G-PES_OH, and G-PES_OH was prepared by the method of Scheme 3-1 below.

<Scheme 3-1>

In the preparation of G-PES_OH according to an embodiment of the present invention, G_PES_OH, which is a main chain polymer having an -O- linkage having a molar percentage to pendant methoxy group of 6% and a molecular weight target of 150,000 g/mol, was prepared as follows did.

2-Methoxy hydroquinone (0.19 g, 0.0013 mol), DHDPE (4.19 g, 0.021 mol), DFDPS (5.62 g, 0.22 mol)), potassium carbonate (3.62 g, 0.026 mol), anhydrous using an argon gas inlet. DMAc (40 mL, 20% solids) and anhydrous toluene (40 mL) were refluxed in a 250 mL round bottom flask to raise the temperature to ^{175 °C while azeotropically removing water.} After toluene was completely removed through a Dean-Stark trap, the solution was reacted at 175° C. for 5 hours and cooled to room temperature. 2-Naphthalene thiol (0.11 g, 0.00067 mol), potassium carbonate (0.11 g, 0.00080 mol) and anhydrous DMAc were added to a Schlenk flask with an argon gas inlet and dissolved at a temperature of 130°C. The 2-naphthalene thiol solution catalyzed by potassium carbonate was added to the prepared solution containing 2-methoxyhydroquinone, DHDPE and DFDPS, the temperature was raised to 130 ° C, and the reaction was carried out for 2 hours to synthesize the final solution. The final product G_PES_OCH ₃ was coagulated in deionized water. After thorough washing several times with deionized water and 2-propanol, G_PES_OCH ₃ was filtered, and the filtered solid was vacuum dried at 80 °C overnight.

To decap the methoxy group with the hydroxy group, G_PES_OCH ₃ (10 g, 0.024 mol) was first dissolved in anhydrous chloroform (105.86 mL, 6% solids) at room temperature with an argon gas inlet. After complete dissolution, boron tribromide solution (28.70 mL, 0.029 mol, 20 equiv) was added dropwise to the solution and reacted for 3 h. G_PES_OH was precipitated with methyl alcohol and washed thoroughly with methyl alcohol. The filtered solid was then dried under vacuum at 80 °C overnight.

Next, G_PES_OH, which is a main chain polymer having a -S- or -SO2- linking group, uses 4,4'-thiodiphenol (TDP) instead of 4,4'-dihydroxydiphenyl ether (DHDPE) to the following Reaction Scheme 4 The same method and moles were used as described in The other end cappers were prepared using the same procedure and equivalent weight.

The backbone with an additional sulfone group in the repeating unit was prepared using the same procedure and equivalents for the other end cappers, but after end capping the end groups, an additional oxidation step was performed.

<Scheme 3-2>

^{3 shows 1} H-NMR of G-PES_OH prepared according to an embodiment of the present invention, in which (a) is an -O- group, (b) is a -S- group, and (C) is a -SO _This is the spectrum of G-PES_OH with a 2 - group.

The proton peak ortho to the sulfone group of the repeating unit appeared at 7.83-7.96 ppm (a) and the ortho to the ether group of the repeating unit was at 7.04-7.21 ppm (b). The disappearance of the proton peak of the methoxy group at 3.67 ppm and the appearance of the proton peak of the hydroxyl group at 9.97 ppm (c) confirmed the successful elimination of the pendant group. The molar percentage of hydroxyl groups ^{was calculated by the intensity of the 1} H-NMR peak, and the molecular weight measured by GPC and the intrinsic viscosity of G_PES_OH are as shown in Table 2.

Molecular Weight (g/mol) Polydispersity
index Intrinsic Viscosity (dL/g) G_PES_OH 78,450 1.39 0.59 100,233 1.33 0.7 78,015 1.32 1.18

<Preparation Example 4> Preparation of sulfonated branched polymer (Gx/y)

The sulfonated branched polymer according to an embodiment of the present invention is denoted by Gx/y, x is the experimental IEC, and y is the molecular weight. Gx/y was prepared by the method of Scheme 4 below.

<Scheme 4>

When the G_PES_OH solution was completely dissolved by first adding G_PES_OH (2.15 g, 0.0052 mol) together with anhydrous DMAc (35.87 mL, 6% solids) ^{at 80 o} C in a 100 mL round bottom flask with an argon gas inlet, potassium carbonate ( 0.086 g, 0.00063 mol, 2 equivalents of hydroxyl group mol %) was added to raise the temperature to 110° C. and reacted for 1 hour. Meanwhile, G_sPSS (5 g, 0.00063 mol, mol% of 2 equivalents of hydroxyl groups) was dissolved in anhydrous DMAc (16.01 mL, 25% solids) at 80 °C until completely dissolved. After both the G_PES_OH and G_sPSS solutions were cooled to about 60 °C, the G_sPSS solution was injected into the G_PES_OH solution all at once. The final solution of Gx/y was reacted at 80 °C for 3 days and precipitated with 2-propanol. The filtered Gx/y product was washed several times with deionized water and vacuum dried at 60 °C overnight.

^{Figure 4 shows a 1} H-NMR spectrum of Gx / y having an -O- group in the main chain prepared according to an embodiment of the present invention, Figure 5 is -S in the main chain prepared according to an embodiment of the present invention ¹ H-NMR spectrum of Gx/y having a - group ^{is shown, and FIG. 6 is a 1} H-NMR spectrum of Gx/y _{having a -SO 2} - group in the main chain prepared according to an embodiment of the present invention.

The proton peak of the side chain is shown at 8.29-8.35 ppm for the proton peak orthogonal to the sulfonate salt group at 7.29-7.81 ppm. 7.24-7.32 ppm for the proton peak for the sulfonate salt group, and for the proton peak for the sulfone group of the repeat unit. The proton peak of the backbone is the proton peak ortho to the sulfone group of the repeating unit at 7.83-7.95 ppm, the proton ortho to the terminal sulfide group at 7.24-7.32 ppm, and the ether group of the repeating unit at 7.01-7.19 ppm are identified, and the side chain and the percentage conversion was calculated by comparing the peak intensities of the backbone moieties.

According to an embodiment of the present invention, the branched polymer Gx/y may be prepared by a nucleophilic substitution reaction between a terminal fluorine group of G_sPSS and a pendant hydroxyl group of G_PES_OH. In such a grafting reaction, the occurrence of a crosslinking reaction causes gelation, makes it difficult to an appropriate grafting reaction, such as destroying a target supply ratio, and ultimately makes it difficult to prepare a membrane, so it is very important to suppress the occurrence of a crosslinking reaction. In order to avoid such unnecessary crosslinking reaction, in one embodiment of the present invention, one end is end-capped with 2-naphthalene thiol for monofunctional G_sPSS and both ends are end-capped with 2-naphthalene thiol for G_PES_OH. can The branched polymer finally prepared by controlling the end-capping for the inhibition of this crosslinking reaction was able to compare the properties between Gx/y by controlling the IEC and the length of the side chain, and the molecular weight of G_sPSS and the pendant hide of G_PES_OH It was possible to control the graft rate of G-sPSS reacting with the hydroxy group.

That is, the side chain G_sPSS was constructed with a single functional end to avoid crosslinking when grafting, and G_sPSS is a thio bond of the repeating unit. It was prepared through condensation polymerization with a terminal chlorine group endcapped with 2-naphthalene thiol, and one end of the thiol group is included in the repeating unit of G_sPSS as a thio bond. Since the chloride could react with the pendant hydroxyl group of the main chain G_PES_OH, the chlorine group at the other end was later end-capped with 2-naphthalene thiol. The thiol group at one end of G_sPSS reacts with the fluorine-terminated group, decafluorobiphenyl, to react with the pendant hydroxyl group of G_PES_OH. In the absence of a single functional end, both ends will end with thiol groups, which will react with decafluorobiphenyl at both ends to generate fluorine-terminated end groups, resulting in crosslinking in the grafting. Then, in order to provide hydrophilicity to the side chain, a sulfonic acid group was introduced into G_sPSS by a post-sulfonation method.

On the other hand, the main chain initial pendant methoxy groups G_PES_OCH ₃ is to be de-capped with a pendant hydroxy group of a skeleton G_PES_OH, methoxy group of G_PES_OCH ₃ is a DFDPS fluorine- initially is capped end to avoid the reaction of the terminal end-group . Copolymerization of DHDPE, DFDPS and 2-methoxyhydroquinone was reacted with a target molecular weight terminated with fluorine groups at both ends. Since the fluorine-terminated end group can induce crosslinking by reacting with the hydroxyl group of G_PES_OH in grafting, 2-naphthalene thiol was included in both ends of _{G_PES_OCH 3 in the end cap. G_PES_OCH 3} was synthesized using 2-methoxy hydroquinone at different feed ratios to achieve different molar percentages of pendant methoxy groups. The density of the side chain can be controlled by the molar percentage of the pendant methoxy groups, the methoxy group of G_PES_OCH ₃ will later be dropped into the hydroxy group of G_PES_OH, which will react with the fluorine group of the side chain in the grafting reaction. G_PES_OCH ₃ is changed to G_PES_OH by de-capping the methoxy group to the hydroxy group using boron tribromide solution. The pendant hydroxy groups of G_PES_OH react with the fluorine terminus of G_sPSS later in grafting, and the molar percentage of pendant hydroxy groups is used to control the density of the side chains, which affects the conformation of the ion conduction channel.

<Preparation Example 5> Preparation of hydrophilic block (M_sPSS) of sulfonated multi-block-type polymer

According to an embodiment of the present invention, the hydrophilic block of the multi-block-type polymer was denoted as M-sPSS and prepared by the method of Scheme 5 below.

<Scheme 5>

More specifically, M_sPSS targeting a molecular weight of 8000 g/mol was synthesized by the following method. First, DFDPS (0.067 mol), lithium sulfide (0.065 mol) and anhydrous NMP (20% solids) were added to 300 mL dehydrated RBF through an argon gas inlet. The temperature was gradually raised to 160 °C and reacted for 18 hours. The solution was coagulated and washed several times with deionized water. The filtered solid was then vacuum dried at 80 °C overnight.

To introduce sulfonic acid groups into M_sPSS, by adding a pre-synthesized non-sulfonated hydrophilic block (0.0025 mol, 1 equiv) with fuming sulfuric acid (5 equiv) in 250 mL RBF previously purged with argon at -10 °C for 5 days. The husulfonation process was performed in The sulfonated product was poured into an ice water bath to dissolve the oligomers. Then, the aqueous solution was saturated with sodium chloride to precipitate M_sPSS. After filtration, the filtered solid was dissolved in aqueous solution and titrated to pH 7 with 10 N sodium hydroxide solution. The dissolved solution was re-precipitated by saturation with sodium chloride. After filtration, the filtered solid was dried overnight at 80 °C under vacuum. The vacuum dried product was then dissolved in DMSO. The solution was filtered to remove sodium chloride, the filtrate was precipitated and washed several times in 2-propanol. The final product, M_sPSS, was vacuum dried at 80 °C overnight.

^{7 shows (a) 1} H-NMR and (b) ¹⁹ F-NMR spectra of M_sPSS, which is a hydrophilic block of a multi-block polymer prepared according to an embodiment of the present invention.

<Preparation Example 6> Preparation of hydrophobic block (M_PES) of sulfonated multi-block-type polymer

According to an embodiment of the present invention, the hydrophobic block of the multi-block-type polymer was denoted as M-PES and prepared by the method of Scheme 6 below.

<Scheme 6>

DHDPE (0.063 mol), DCDPS (0.060 mol), potassium carbonate (0.075 mol), anhydrous DMAc (20% solids) and anhydrous toluene were added to 300 to synthesize targeted M_PES with a molecular weight of 9500 g mol-1. While the toluene was refluxed to remove water azeotropically, the temperature was slowly raised to 175 ° C. After completely removing toluene through an RBF mL Dean-Stark trap with an argon gas inlet, the solution was reacted at 175 ° C for 18 hours, cooled to room temperature. The product M_PES was precipitated in deionized water, washed thoroughly with deionized water and 2-propanol, and vacuum dried overnight at 80 °C.

^{8 shows a 1} H-NMR spectrum of M_PES, which is a hydrophobic block of a multi-block-type polymer prepared according to an embodiment of the present invention.

<Preparation Example 7> Preparation of sulfonated multi-block-type polymer

The multi-block polymer according to an embodiment of the present invention is a multi-block copolymer synthesized from M_sPSS, which is a hydrophilic block, and M_PES, which is a hydrophobic block. Mx/y was prepared by the method of Scheme 7 below.

<Scheme 7>

Mx/y was synthesized using anhydrous DMAc (18% solids content) as a solvent by first adding M_PES (0.00059 mol), potassium carbonate (0.00083 mol, 1.4 equiv) and calcium carbonate (0.00071 mol, 1.2 equiv) to 250 . M_sPSS (0.00059 mol) was added to the solution in an mL RBF with an argon gas inlet, and the temperature was raised to 175° C. and reacted for 3 days. The reaction solution was coagulated in 1 M hydrochloric acid to remove calcium carbonate. Mx/y was filtered, and the filtered product was titrated to pH 8 with an aqueous potassium carbonate solution. The product Mx/y was filtered, washed several times with deionized water and 2-propanol, and dried in vacuo at 80° C. overnight.

^{9 shows a 1} H-NMR spectrum of a multi-block-type polymer prepared according to an embodiment of the present invention.

<Preparation Example 8> Preparation of hydrophilic block of sulfonated cross-linked polymer

According to one embodiment of the present invention, the hydrophilic block of the sulfonated cross-linked polymer was prepared by the method of Scheme 8 below.

<Scheme 8>

First, DFDPS (0.067 mol), lithium sulfide (0.065 mol) and anhydrous NMP (20% solids) were added to 300 mL dehydrated RBF through an argon gas inlet. The temperature was gradually raised to 160 °C and reacted for 18 hours, after which the solution was cooled to room temperature. NaSH (0.16 mol) and potassium carbonate (0.19 mol) were added to the oligomer at 80 °C for 5 h. Meanwhile, at room temperature, decafluorobiphenyl (0.8 mol) and anhydrous NMP (15% solids) were dissolved in 500 mL RBF, and the resulting solution was stored in a refrigerator. After cooling to room temperature or lower, the reaction temperature was maintained at 0 °C using an ice bath, and then the above-mentioned oligomer solution was added dropwise to the decafluorobiphenyl solution and stirred with an argon gas purge for 2 hours. The final solution was precipitated with methyl alcohol and washed several times with deionized water and methyl alcohol. The product was vacuum dried at 60 °C overnight.

Using the product obtained from the previous step, a sulfonation process was performed to introduce a sulfonic acid group on the side chain. Unsulfonated branched oligomer (0.0022 mol, 1 eq) and fuming sulfuric acid (5 eq) were added to a 250 mL jacketed RFB, which was purged with argon, followed by argon purging beforehand at -10 °C for 5 days. The sulfonated product was then poured into an ice-water bath to dissolve the oligomers. The product was precipitated by saturating the aqueous solution with sodium chloride. After filtration, the filtered solid was dissolved in aqueous solution and titrated to pH 7 with 10 N sodium hydroxide solution. The dissolved solution was re-precipitated by saturation with sodium chloride. After filtration, the filtered solid was vacuum dried at 60 °C overnight. The vacuum dried product was then dissolved in DMSO. Then, the G_sPSS solution was filtered to remove sodium chloride, and the filtrate was precipitated and washed several times in 2-propanol. The final product was vacuum dried at 60 °C overnight.

<Preparation Example 9> Preparation of hydrophobic main chain of sulfonated cross-linked polymer

Preparation of the hydrophobic main chain of the sulfonated cross-linked polymer according to an embodiment of the present invention is the same as in Preparation Example 3.

<Preparation Example 10> Preparation of sulfonated cross-linked polymer

The chemical structure of the sulfonated cross-linked polymer according to an embodiment of the present invention is as follows.

When the G_PES_OH solution was completely dissolved by first adding G_PES_OH (2.15 g, 0.0052 mol) together with anhydrous DMAc (35.87 mL, 6% solids) ^{at 80 o} C in a 100 mL round bottom flask with an argon gas inlet, potassium carbonate ( 0.086 g, 0.00063 mol, 2 equivalents of hydroxyl group mol %) was added to raise the temperature to 110° C. and reacted for 1 hour. Meanwhile, the sulfonated cross-linked hydrophilic block (10 g, 0.00126 mol, 4 equivalents of mol % of hydroxyl groups) was dissolved in anhydrous DMAc (32.02 mL, 25% solids) at 80 °C until completely dissolved. After cooling both the G_PES_OH and the sulfonated cross-linked hydrophilic block solution to about 60 °C, the sulfonated cross-linked hydrophilic block solution was injected into the G_PES_OH solution all at once. When the sulfonated cross-linked polymer final solution was reacted at 80 °C, it was confirmed that the reaction solution was agglomerated within 30 minutes of the reaction time. A phenomenon in which the polymer was separated by the crosslinking reaction was observed (refer to FIG. 10), and the obtained crosslinked product was not dissolved again in organic solvents including NMP, DMAc, and DMSO.

10 shows (a) a sulfonated cross-linked polymer (when side chains having reactivity at both ends are used for grafting) and (b) a sulfonated branched polymer (side chains having single-terminal reactivity are grafted) according to an embodiment of the present invention; The chemical formula of (when used in ) and the appearance of the reactor during production are shown.

Figure 10 (a) shows that the side chains reactive at both ends are cross-linked with the main chain during graft synthesis using side chains having reactivity at both ends. A phenomenon of heterogeneous separation was confirmed, and as a result, it was impossible to dissolve the graft polymer using side chains having reactivity at both ends, and it was difficult to form a film.

On the other hand, in Fig. 10 (b), it is observed that the graft polymer using a side chain having single-terminal reactivity does not cause excessive viscosity during synthesis and that a homogeneous mixture is maintained during synthesis, as well as a single-terminal end. It was possible to re-dissolve the graft polymer using the reactive side chain, and film formation was easy.

<Preparation Example 8> Preparation of electrolyte membrane

After dissolving the final product of the sulfonated branched polymer (Gx/y) according to an embodiment of the present invention in anhydrous DMAc at a weight volume percentage of 7-21 % w/V (weight/volume) depending on the intrinsic viscosity, the membrane was It was cast through a doctor blade applicator with a target thickness of 20-40 µm. The fabricated membranes were used for analysis of dimensional stability, water absorption, proton conductivity, fuel cell performance, OCV and durability. Table 3 summarizes the physical properties of the sulfonated branched polymer used to prepare the membrane according to an embodiment of the present invention.

theoretical
IEC (meq/g) Experimental IEC
(meq/g) side chain density
(%) graft rate
(%) hydrophobic
of unit
Molecular Weight
(d/mol) intrinsic viscosity
(dL/g) G1.64/7500 1.72 1.64 2.97 68.68 78,450 1.45 G1.48/8500 1.99 1.48 2.43 50.93 78,450 2.88 G1.34/3500 1.78 1.34 4.66 30.41 100,233 1.27 G1.29/5000 1.59 1.29 3.23 49.30 78,015 4.65

However, in Table 3, the side chain density is the ratio of the mole % of the G-sPSS repeating unit to the G_PES_OH repeating unit considering the graft rate.

Calculation of the theoretical IEC of Gx/y according to an embodiment of the present invention was calculated by the following equation.

In the above formula, x represents the percentage of repeating units of the G_PES_OH-containing hydroxy functional group, z represents the repeating units of G_sPSS, and g represents the percentage of conversion.

In addition, the experimental IEC of the graft polymer was measured using a titration method using an automatic titrator (Metrohm 794 Basic Titrino). The membrane was previously _{acidified with 1.5MH 2} SO ₄ , and then completely dried to measure the membrane weight. The dried membrane was then stirred in 100 mL 0.01 M NaCl aqueous solution for 24 h to deprotonate the sulfate group. Using an automatic titrator, the membrane containing aqueous NaCl solution was titrated to pH 7 with 0.01 M NaOH solution. The appropriate IEC value was obtained by the following equation.

In the above formula, C _NaOH represents the concentration of _NaOH, the NaOH volume of V NaOH and the dry weight of the dried membrane.

The intrinsic viscosity was measured using a Cannon-Penske viscometer at 25° C. of a branched polymer dissolved in NMP (0.05 g/dL). In addition, water molecular weight and polydispersity index were analyzed at 40 °C by gel permeation chromatography using a Waters 2414 refractive index detector, a Waters 1515 isocratic HPLC pump, and a Waters 2707 autosampler. The solvent used was 0.05 M LiBr in DMAc.

<Analysis Example 1> Analysis of water absorption rate and dimensional stability of electrolyte membrane

Hydration is very important in PEMS because in general the conduction of protons is facilitated (vehicle mechanism) by sulfonic acid groups interacting with water molecules when hydrated. In addition, water molecules surrounding these sulfonic acid groups aggregate due to hydrophilic-hydrophobic fine phase separation to form ion conductive channels. In general, as the IEC increases, the hydrophilicity increases and the ion conduction channel develops more, resulting in an increase in water absorption and dimensional expansion values. Also, as the length of the side chain increases, more sulfonic acid groups are incorporated into the polymer, resulting in water absorption and dimensional expansion. will increase the expansion. However, excessive dimensional expansion is known to be detrimental to fuel cell performance, since expansion inside the MEA can cause rupture or damage to the membrane entrapped in the frame starting from the edge.

In one embodiment of the present invention, moisture absorption and dimensional expansion were evaluated using the values of thickness, length, and weight of the membrane in dry and wet states. Membrane cut to 2 cm × 2 cm immersed in a deionized water bath at room temperature was gently wiped and the thickness, length and weight were measured. The membrane was then dried under vacuum at 80 °C for 24 h, and the thickness, length and weight were measured. Then, these membranes were reprecipitated in a deionized water bath, gently wiped off after 24 h at room temperature, and the thickness, length and weight were measured again. The water absorption rate was calculated by the following equation.

where W _wet corresponds to the average weight value of the membrane in the wet state and in the _{dry state W dry.}

In addition, the change in the membrane length was calculated by the following equation.

where lwet is equal to the average length value of the membrane in both wet and dry conditions.

In addition, to investigate the morphology (H + morphology) of the membrane, SAXS measurements were performed at the Pohang Accelerator Laboratory (PAL) located in Pohang, Korea using a PAX-II 3C beamline.

According to an embodiment of the present invention, water absorption and dimensional expansion of Gx/y having different side chain lengths were analyzed, and the results are shown in FIG. 11 .

As can be seen from Fig. 11, for G1.64/7500 and G1.48/8500, the membrane showed increased water absorption and dimensional expansion following the general trend of increasing IEC and side chain length, but G1.34/3500 with similar IEC values. and G1.29/5000 show opposite trends for IEC due to differences in side chain lengths. Although the IEC of G1.34/3500 is higher than that of G1.29/5000, the water absorption and dimensional expansion is greater than that of G1.34/3500 of G1.34/5000 (water absorption 44.15%, volume change 41.85%) (water absorption 38.57). %, volume change 35.91%).

According to SAXS analysis, it was confirmed that G1.34/3500 had a shorter interdomain distance between hydrophilic domains than G1.29/5000. According to an embodiment of the present invention, longer side chains can be more flexible and better aggregated, thereby increasing the interdomain distance between the hydrophilic domains. This better aggregation leads to more developed hydrophilic-hydrophobic phase separation, which contributes to higher water absorption and proton conductivity, so the longer side chain G1.29/5000 has water absorption and dimensional expansion compared to the shorter side chain G1.34/3500. It can be seen that this becomes larger.

<Analysis Example 2> Analysis of proton conductivity of electrolyte membrane

Proton conductivity as a function of temperature was measured using a 4-probe conductivity cell and AC impedance analyzer (Solartron-1280 impedance/gain phase analyzer) at ^{25 o} C, 40 ^o C, 60 ^o C and 80 ^{o C.} Oscillation voltages 50-500 mV at 100% RH along the in-plane direction in the frequency range 1-105 Hz. Cells immersed in a water bath were analyzed in a controlled environment in a temperature and humidity chamber (SH-241, ESPEC) and allowed to equilibrate for 1 h before each measurement. The impedance data were used to obtain the proton conductivity (σ) as

proton conductivity (σ) = l/RS

where σ denotes the proton conductivity (S cm-1), the distance between the l electrodes, the impedance of the R membrane, and the surface area for S proton transport.

According to one embodiment of the present invention, proton conductivity is affected by ion conduction channels formed by hydrophilicity and hydrophobic phase separation. As the hydrophilicity of high IEC increases, hydrophilicity-hydrophobic channels are more clearly defined, so that proton conduction is improved it can be seen that

The results of proton conductivity analysis according to the temperature of Gx/y having different side chain lengths according to an embodiment of the present invention are shown in FIG. 12 .

As can be seen in FIG. 12 G1.64 / 7500 (80 ^o C in 0.211S cm-1) and ^{G1.48 / 8500 (80 o 0.189Scm-} 1 in C) is 0.163Scm-1 in Nafion 212 (80 ^o C ), which exhibits higher proton conductivity. At all temperatures, the high hydrophilicity induces a defined ion conduction channel, resulting in increased proton conductivity.

However, G1.34/3500 ( ^{0.103 S cm-1 at 80 o} C) and G1.29/5000 ( ^{0.112 S cm-1 at 80 o} C) are contradictory for IEC values due to the short chain of G1.34. showed results. SAXS analysis revealed that membranes with short hydrophilic side chains not only exhibit shorter interdomain distances between hydrophilic domains, but also could lead to less defined hydrophilic-hydrophobic separation due to the low flexibility of short side chains. This results in low proton conduction, which is the opposite of the trend in IEC values.

<Analysis Example 3> Performance analysis of membrane for fuel cell

Fuel cell performance was measured with a constant supply of fuel, hydrogen at the anode and oxygen at the cathode, and at various relative humidity and temperature conditions, the current density was measured differently from the applied voltage by controlling the load presented as a polarization curve.

MEAs for fuel cell performance testing were prepared via a catalyst-coated membrane decal method of loading 0.4 mgPt cm-1 at a pressure of 14 bar using a vacuum press at 130 °C. Before measuring the voltage, activation of the cell was performed for 48 cycles with various voltages to reach the equilibrium point. Cell performance was performed using a fuel cell test station (Z010-100, SCITHEC KOREA).

For G1.64/7500 according to an embodiment of the present invention, the fuel cell performance was measured by changing the temperature to 65 ℃, 70 ℃ and 80 ℃, and changing the relative humidity to 50% and 100%, and the results are shown in FIG. indicated.

As can be seen from Fig. 13, 65 ^o C at 100% RH displayed the highest current density of 1.2956 A cm-2 at 0.6 V, followed by 70 ^o C (1.258 A cm-2) and 80 ^o C (1.156 A cm-2). 2) was shown. At 50% RH, 65 ^o C exhibited the highest current density at 0.6 V of 0.7934 A cm -2 , followed by 70 ^o C (0.7664 A cm -2 ) and 80 ^o C (0.6424 A cm -2 ). Since the current density is the voltage applied to a real fuel cell vehicle, it was measured as 0.6V, which is also the voltage that can provide the highest power density. The current density at 100% RH is higher than the current density at 50% RH because the ion conduction pathway develops better in hydrated conditions, resulting in increased proton conductivity.

Theoretically, as the temperature increases, the proton conductivity should increase because the activation barrier to proton conduction decreases. Mannafion ionomers can be dehydrated to some extent, with temperature-related consequences for fuel cell performance.

<Analysis Example 4> Chemical durability test of membrane

According to an embodiment of the present invention, MEA for OCV test was prepared through a catalyst-coated gas diffusion layer (GDL) method by loading 0.4 mgPt cm-2 into the anode. To test the chemical stability and degradation of the membrane, the cell was continuously fueled to maintain a current density of 200 mA cm-2 at 90 °C, 30% RH and 150 kPa back pressure, and the OCV was recorded. Back pressure was applied to fill the inside of the cell with gas pressure, allowing water to drain easily and increasing the gas density. Cell performance tests were performed every 100 h at 70 °C, 100% RH and 0 kPa back pressure. Polarization curves were measured with a fuel cell test station (Z010-100, SCITHEC KOREA).

In order to evaluate chemical stability and chemical degradation for G1.64/7500 according to an embodiment of the present invention, hydrogen gas and oxygen gas are continuously supplied to maintain a current density of 200 mA cm-2 while tracking the OCV value and the results are shown in FIG. 14 .

As can be seen from Fig. 14, the OCV of 1.026V at 0 hours gradually decreases on a small scale until about 720 hours. After about 720 h, the OCV decreases below 0.9 V, implying that major chemical degradation by radical formation occurs in the PEM, resulting in additional resistive losses due to loss of proton conductivity and increase in internal resistance. Reduction of OCV is also effected by exhausting the reacted by-products of the catalyst, impairing the equilibrium of the catalyst conditions and contaminating the catalyst bed.

15 shows the results of analyzing the change in OCV with time of G1.64/7500 according to an embodiment of the present invention.

As can be seen from FIG. 15 , the OCV at 100 hours was 0.9586V, 302 hours 0.9489V, and 728 hours 0.9462V. From 100 h to 728 h, only a slight decrease in OCV was observed, indicating that the chemical structure of the membrane remains relatively intact, allowing for efficient protonation. However, after 728 h, the voltage suddenly drops, causing chemical degradation in the membrane, which leads to a decrease in proton conductivity, indicating a decrease in OCV.

<Analysis Example 5> Physical durability test of the membrane

In the physical durability test, the membrane is subjected to a series of wet and dry conditions. The membrane expansion and drying continues at an accelerated rate compared to the practical application of fuel cells, enabling long-term physical durability testing. The membrane is surrounded by a frame of the MEA, the edges weaken first with successive expansions most affected by swelling and drying. After several cycles, defects are formed in the middle of the film. When these defects occur in PEM, fuel can cross the membrane, destroying further measurability of cell performance. Hydrogen crossovers are measured periodically to determine when a critical fault is breaking down the cell.

Long-term durability was measured by a wet-dry cycle test according to an embodiment of the present invention. MEAs were prepared via a catalyst-coated membrane decal method using a vacuum press to load 0.4 mgPt cm-2 at 130 °C and a pressure of 14 bar. For the wet cycle test, 130% RH and 0% RH N2 (1000 sccm) were alternately fed to the MEA at 80 °C for 2 min, respectively. Wet for 2 min and cycle dry for 2 min.

16 shows the wet-dry cycle test results of G1.64/7500 according to an embodiment of the present invention.

As can be seen from FIG. 16 , G1.64/7500 according to one embodiment of the present invention withstood nearly 15000 cycles, which is very useful as a membrane for hydrocarbon-based fuel cells. It can be seen that it is suitable as a PEM for commercial fuel cells.

<Analysis Example 6> Comparative test of branched polymer and multi-block polymer

The branched polymer and the multi-block polymer according to an embodiment of the present invention were compared in comparison with dimensional stability, water absorption, ionic conductivity, and the like.

The physical properties of the samples used for comparison are summarized in Table 4 below.

Experimental IEC
(meq/g) intrinsic viscosity
(dL/g) proton
conductivity
80℃, 50% Dimensional change (%) moisture
absorption △ l △ t △ v Graft1.86/7100 1.86 5.42 34.3 8.03 63.68 91.11 82.67 Graft1.73/11000 1.73 1.21 23.05 5.85 34.75 51.01 55.67 Multiblock1.89/8500 1.89 0.93 33.5 21.58 47.14 117.33 92.34 Multiblock1.72/11000 1.72 1.08 22.2 10.48 38.63 69.19 62.97

17 is a comparison of dimensional stability and water absorption for a branched polymer and a multi-block polymer according to an embodiment of the present invention, and at the same IEC and molecular weight, the branched polymer has lower swelling than the multi-block polymer. phenomenon can be seen.

18 shows the results of analyzing the proton conductivity with respect to relative humidity for the branched polymer, the multi-block polymer, and the commercial Nafion according to an embodiment of the present invention. It can be seen that it exhibits high ionic conductivity.

As described above, a sulfonated branched polymer Gx/y containing a sulfonated branched polymer (G_sPSS) and a main chain polymer (polyarylene ether sulfone) was prepared according to IEC and the length of the side chain, and IEC was the molecular weight and main chain of the side chain. was controlled by adjusting the molar percentage of pendant hydroxyl groups in In the prepared sulfonated branched polymer Gx/y, the interdomain distance between hydrophilic clusters increased as the side chain length increased, and a longer side chain length in a similar IEC showed higher water absorption and proton conductivity. G1.64/7500, a sulfonated branched polymer according to an embodiment, has a higher proton conductivity than commercial Nafion, a current density of 1.2956A cm-2 at 0.6V, and excellent chemical and physical durability as an electrolyte membrane for fuel cells. It can be seen that excellent performance is shown.

Claims (10)

Having any one of the hydrocarbon-based polymers as a main chain,
A sulfonated branched polymer comprising a repeating unit represented by the following formula (1) as a side chain coupled to the main chain:
<Formula 1>

In Formula 1, L1 and L2 are each independently -O-, -S-, -SO ₂ -, -C=O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any one ego,
R1 and R2 are each independently -SO ₃ M or -SO ₃ H, wherein M is any one of Li, Na or K,
a, and b are each independently 1 to 4,
x is an integer from 1 to 5,000 as a repeating unit,
E is an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group having 6 to 18 carbon atoms, -CN or -NO _{2 a} phenyl group having a substituent,

,

,

Any one of the non-reactive end groups,
R is

,

, a halogen group, an alcohol group, or a reactive end group of any one of a linking structure derived from a thiol group. The method according to claim 1,
The main chain of the carbon-hydrogen-based polymer is a sulfonated branched polymer, characterized in that it includes the chemical structure of Formula 2:
<Formula 2>

In Formula 2, L3 and L4 are each independently -O-, -S-, -SO ₂ -, -C(O)-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any of is one,
R3 to R5 are each independently hydrogen or an alkyl group or an alkylene group containing a linear, branched or CN group having 1 to 10 carbon atoms,
c, and d are each independently 0 to 4, e is 0 to 3,
R6 is a linking group, any one of a chemical structure derived from a thiol group (-SH), an amine group (-NH-), a phenol group (-PhOH) or an alcohol group (-OH),
y is an integer from 1 to 5,000 as a repeating unit. 3. The method according to claim 2,
The sulfonated branched polymer is a sulfonated branched polymer, characterized in that it further comprises a repeating unit represented by the formula (2) in the main chain is not bonded to the side chain. 4. The method according to claim 3,
The main chain of the sulfonated branched polymer is a sulfonated branched polymer, characterized in that it has the chemical structure of Formula 3 below:
<Formula 3>

In Formula 3, L3 to L6 are each independently -O-, -S-, -SO ₂ -, -C=O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any one ego,
R3 to R5 and R7, R8 are each independently hydrogen or an alkyl group or an alkylene group containing a straight or branched chain having 1 to 10 carbon atoms or a CN group,
c, d, f, g are each independently 0 to 4, e is 0 to 3,
R6 is a linking group, any one of a chemical structure derived from a thiol group (-SH), an amine group (-NH-), a phenol group (-PhOH) or an alcohol group (-OH),
y and z are repeating units, y + z is an integer from 1 to 5,000,
E is an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group having 6 to 18 carbon atoms, -CN or -NO _{2 a} phenyl group having a substituent,

,

,

any one of the non-reactive end groups. Preparing any one of the hydrocarbon-based polymer as a main chain;
A method for producing a sulfonated branched polymer comprising the step of binding a repeating unit represented by the following Chemical Formula 1 to the main chain as a side chain:
<Formula 1>

In Formula 1, L1 and L2 are each independently -O-, -S-, -SO ₂ -, -C=O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any one ego,
R1 and R2 are each independently -SO ₃ M or -SO ₃ H, wherein M is any one of Li, Na or K,
a, and b are each independently 1 to 4,
x is an integer from 1 to 5,000 as a repeating unit,
E is an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group having 6 to 18 carbon atoms, -CN or -NO _{2 a} phenyl group having a substituent,

,

,

Any one of the non-reactive end groups,
R is

,

, a halogen group, an alcohol group, or a reactive end group of any one of a linking structure derived from a thiol group. 6. The method of claim 5,
The main chain of the hydrocarbon-based polymer is a method for producing a sulfonated branched polymer, characterized in that it includes the chemical structure of Formula 2:
<Formula 2>

In Formula 2, L3 and L4 are each independently -O-, -S-, -SO ₂ -, -C(O)-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any of is one,
R3 to R5 are each independently hydrogen or an alkyl group or an alkylene group containing a linear, branched or CN group having 1 to 10 carbon atoms,
c, and d are each independently 0 to 4, e is 0 to 3,
R6 is a linking group, any one of a chemical structure derived from a thiol group (-SH), an amine group (-NH-), a phenol group (-PhOH) or a hydroxyl group (-OH),
y is an integer from 1 to 5,000 as a repeating unit. 7. The method of claim 6,
The main chain of the sulfonated branched polymer is a method for producing a sulfonated branched polymer, characterized in that it comprises one having a chemical structure of the following formula (3):
<Formula 3>

In Formula 3, L3 to L6 are each independently -O-, -S-, -SO ₂ -, -C=O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - Any one ego,
R3 to R5 and R7, R8 are each independently hydrogen or an alkyl group or an alkylene group containing a straight or branched chain having 1 to 10 carbon atoms or a CN group,
c, d, f, g are each independently 0 to 4, e is 0 to 3,
R6 is a linking group, any one of a chemical structure derived from a thiol group (-SH), an amine group (-NH-), a phenol group (-PhOH) or a hydroxyl group (-OH),
y and z are repeating units, y + z is an integer from 1 to 5,000,
E is an alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted phenyl group having 6 to 18 carbon atoms, -CN or -NO _{2 a} phenyl group having a substituent,

,

,

any one of the non-reactive end groups. A polymer electrolyte membrane comprising the sulfonated branched polymer of any one of claims 1 to 4. 9. The method of claim 8,
The polymer electrolyte membrane is a fuel cell, a secondary battery, a redox flow battery, or a polymer electrolyte membrane, characterized in that the electrolyte membrane for water electrolysis. A device comprising the polymer electrolyte membrane of claim 8,
A device, characterized in that any one of a fuel cell, a secondary cell, a redox flow cell, or a water electrolysis device.

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