WO2013146745A1 - Method of producing gel containing ionic liquid - Google Patents

Description

Method for producing gel containing ionic liquid

The present invention relates to a method for producing a polymer crosslinked gel containing an ionic liquid, an ionic liquid mixed solvent suitable for the production method, and an ionic liquid-containing gel obtained by the production method.

In recent years, hydrogel, which is a gel material containing a hydrophilic polymer having a network structure, has attracted attention. Hydrogel has excellent water retention and biocompatibility characteristics, so it can be used not only for medical purposes such as sealing, adhesion prevention, drug delivery and contact lenses, but also for various applications such as sensors and surface coatings. Is an expected material (for example, Patent Documents 1 and 2). However, while it has excellent characteristics, it cannot be used for a wide range of practical purposes, or sufficient strength cannot be obtained, or the moisture contained in the gel evaporates over time and is lost for a long time. There was a problem that could not be done.

Conventionally, since the crosslinking reaction for forming such a hydrogel must be carried out in an aqueous solution, when an organic solvent is to be contained in the gel, the gel is once dehydrated and dried. It has to be immersed and swollen in a desired organic solvent, the process becomes complicated, and it is not easy to produce any shape.

On the other hand, ionic liquids, also called room temperature molten salts, are composed only of ions and are non-volatile and non-flammable despite being liquid in a wide temperature range including room temperature. It is known that it has the property of having From these characteristics, application to various fields including electrochemical devices such as lithium secondary batteries and capacitors, lubricants in machines, etc. is expected and research and development are being performed (for example, Patent Document 3). For such applications, thinning of the ionic liquid is one important key, but no thin film formation reaction in the ionic liquid has been reported so far. In general, in reactions involving the ionization of reactive species, the reaction rate is controlled by controlling the hydrogen ion concentration in the reaction solvent. However, the verification of reaction rate control in an ionic liquid has hardly been performed. Currently.

JP-A-11-189626 JP 2005-60570 A JP 2005-179551 A

It is an object of the present invention to provide a method for producing a polymer crosslinked gel containing an ionic liquid, more specifically, a method for producing a polymer crosslinked gel capable of directly performing a polymer crosslinking reaction in an ionic liquid. And Furthermore, it aims at providing the solvent which enables such a manufacturing method, and the ionic liquid containing gel obtained by the said manufacturing method.

As a result of intensive studies to solve the above problems, the present inventors have used a mixed solvent of a protic ionic liquid and an aprotic ionic liquid as a reaction solvent, so that a specific polymer solution is contained in the ionic liquid. It has been found that a crosslinking reaction (gelation reaction) can proceed only by mixing, whereby a polymer crosslinked gel containing an ionic liquid can be obtained directly. It has also been found that the reaction rate of the gelation reaction can be controlled by changing the ratio of the protic ionic liquid to the aprotic ionic liquid in the mixed solvent. Based on these findings, the present invention has been completed.

That is, in one aspect, the present invention is a method for producing a polymer cross-linked gel containing an ionic liquid, the mixture comprising at least one kind of protic ionic liquid and at least one kind of aprotic ionic liquid. The present invention relates to a production method characterized by crosslinking a polymer in a solvent.

The protonic ionic liquid is preferably an ionic liquid composed of a cation component selected from imidazolium-based, pyridinium-based, or primary ammonium. In particular, the cation component of the protic ionic liquid is preferably 1-ethylimidazolium, and the cation component of the aprotic ionic liquid is preferably 1-ethyl-3-methylimidazolium. More preferably, the combination of the protic ionic liquid and the aprotic ionic liquid is a combination of 1-ethylimidazolium bis (trifluoromethanesulfonyl) amide and 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) amide. The combination is selected from the group consisting of 1-ethylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetrafluoroborate.

The above polymer is preferably a polymer that can form a three-dimensional network structure by cross-linking each other. The polymer comprises a first polymer having f nucleophilic functional groups in the side chain or terminal and a second polymer having g electrophilic functional groups in the side chain or terminal. Here, f + g is preferably 5 or more. More preferably, the polymer structure has a polyethylene glycol skeleton.

（ここで、式（Ｉ）中、ｎ_１１～ｎ_１４は、それぞれ同一又は異なり、２５～２５０の整数を示すものであり、
前記式（Ｉ）中、Ｒ^１１～Ｒ^１４は、それぞれ同一又は異なり、Ｃ_１－Ｃ_７アルキレン基、Ｃ_２－Ｃ_７アルケニレン基、－ＮＨ－Ｒ^１５－、－ＣＯ－Ｒ^１５－、－Ｒ^１６－Ｏ－Ｒ^１７－、－Ｒ^１６－ＮＨ－Ｒ^１７－、－Ｒ^１６－ＣＯ_２－Ｒ^１７－、－Ｒ^１６－ＣＯ_２－ＮＨ－Ｒ^１７－、－Ｒ^１６－ＣＯ－Ｒ^１７－、又は－Ｒ^１６－ＣＯ－ＮＨ－Ｒ^１７－を示し、ここで、Ｒ^１５はＣ_１－Ｃ_７アルキレン基を示し、Ｒ^１６はＣ_１－Ｃ_３アルキレン基を示し、Ｒ^１７はＣ_１－Ｃ_５アルキレン基を示す。）

（ここで、式（ＩＩ）中、ｎ_２１～ｎ_２４は、それぞれ同一又は異なり、２０～２５０の整数を示すものであり、
前記式（ＩＩ）中、Ｒ^２１～Ｒ^２４は、それぞれ同一又は異なり、Ｃ_１－Ｃ_７アルキレン基、Ｃ_２－Ｃ_７アルケニレン基、－ＮＨ－Ｒ^２５－、－ＣＯ－Ｒ^２５－、－Ｒ^２６－Ｏ－Ｒ^２７－、－Ｒ^２６－ＮＨ－Ｒ^２７－、－Ｒ^２６－ＣＯ_２－Ｒ^２７－、－Ｒ^２６－ＣＯ_２－ＮＨ－Ｒ^１７－、－Ｒ^２６－ＣＯ－Ｒ^２７－、又は－Ｒ^２６－ＣＯ－ＮＨ－Ｒ^２７－を示し、ここで、Ｒ^２５はＣ_１－Ｃ_７アルキレン基を示し、Ｒ^２６はＣ_１－Ｃ_３アルキレン基を示し、Ｒ^２７はＣ_１－Ｃ_５アルキレン基を示す。） In one preferred embodiment of the present invention, the polymer contains a compound represented by the following formula (I) and the following formula (II), and has a network structure by crosslinking the ends of the compound with an amide bond. Is.

(Here, in formula (I), n ₁₁ to n ₁₄ are the same or different and each represents an integer of 25 to 250,
In the formula (I), R ¹¹ to R ¹⁴ are the same or different and each represents a C ₁ -C ₇ alkylene group, a C ₂ -C ₇ alkenylene group, —NH—R ¹⁵ —, —CO—R ¹⁵ —, — R ¹⁶ —O—R ¹⁷ —, —R ¹⁶ —NH—R ¹⁷ —, —R ¹⁶ —CO ₂ —R ¹⁷ —, —R ¹⁶ —CO ₂ —NH—R ¹⁷ —, —R ¹⁶ —CO—R ¹⁷ —, or —R ¹⁶ —CO—NH—R ¹⁷ —, wherein R ¹⁵ represents a C ₁ -C ₇ alkylene group, R ¹⁶ represents a C ₁ -C ₃ alkylene group, and R ¹⁷ represents C ₁ -C ₅ alkylene group. )

(In the formula (II), n ₂₁ to n ₂₄ are the same or different and represent an integer of 20 to 250,
In the formula (II), R ²¹ to R ²⁴ are the same or different and each represents a C ₁ -C ₇ alkylene group, a C ₂ -C ₇ alkenylene group, —NH—R ²⁵ —, —CO—R ²⁵ —, — R ²⁶ —O—R ²⁷ —, —R ²⁶ —NH—R ²⁷ —, —R ²⁶ —CO ₂ —R ²⁷ —, —R ²⁶ —CO ₂ —NH—R ¹⁷ —, —R ²⁶ —CO—R ²⁷ —, or —R ²⁶ —CO—NH—R ²⁷ —, wherein R ²⁵ represents a C ₁ -C ₇ alkylene group, R ²⁶ represents a C ₁ -C ₃ alkylene group, and R ²⁷ represents C ₁ -C ₅ alkylene group. )

In another aspect, the present invention relates to a solvent for use in a polymer crosslinking reaction, comprising at least one or more protic ionic liquids and at least one or more aprotic ionic liquids. Here, preferred embodiments of the protic ionic liquid and the aprotic ionic liquid in the solvent of the present invention are the same as described above.

In a further aspect, the present invention relates to a polymer cross-linked gel containing an ionic liquid, wherein the polymer is mixed in a mixed solvent containing at least one protic ionic liquid and at least one aprotic ionic liquid. It relates to a gel obtained by cross-linking. Here, preferred embodiments of the protic ionic liquid and the aprotic ionic liquid are the same as described above. Moreover, the preferable aspect of the polymer seed | species which forms the polymer crosslinked gel of this invention is the same as that of what was described above.

In another aspect, the present invention relates to a thin film comprising a polymer cross-linked gel containing the ionic liquid.

According to the production method of the present invention, by using a mixed solvent of a protic ionic liquid and an aprotic ionic liquid as a reaction solvent, the crosslinking reaction can proceed only by mixing a specific polymer solution in the ionic liquid. It is possible to produce a polymer cross-linked gel containing an ionic liquid. This makes it possible to obtain a gel containing an ionic liquid by a simple process without performing a step of impregnating the ionic liquid after forming the gel once in an aqueous solution or the like.

In addition, by changing the ratio of the protic ionic liquid to the aprotic ionic liquid in the mixed reaction solvent, it is possible to control the reaction rate of the gelation reaction (that is, the gelation time). Therefore, it is very suitable when the gel is formed into a desired shape.

That is, when a device such as a gel thin film containing an ionic liquid is produced, the gel can be formed into an arbitrary shape from a fluid state by a simple process, and depending on the desired final device shape, etc. Since the flow state can be controlled, it is possible to produce a device such as a large amount of a uniform ionic liquid thin film.

The idea of controlling the reaction rate by the ratio of the protic ionic liquid and the aprotic ionic liquid is a novel one that has not been heretofore, and is not limited to the gelation reaction described above, and is a chemical reaction widely involving ionization of reactive species. Therefore, the usefulness of ionic liquids as a reaction solvent in general is demonstrated.

Furthermore, according to the present invention, it is possible to provide a polymer cross-linked gel having the characteristics of an ionic liquid while having the advantages of a conventional hydrogel. Specifically, by using a polymer having a network structure in combination with an ionic liquid, sufficient strength can be obtained even in various applications, and a non-volatile ionic liquid is used as a solvent, so that the gel form is lost. There is an advantage that it can be used in an open system for a long period of time. In addition, since a large amount of ionic liquid can be retained in the gel by using a polymer having a network structure, the gel has the excellent electrical conductivity, CO ₂ absorbability, or flame retardant properties possessed by the ionic liquid. It becomes possible to add. In addition, as described above, since it is not necessary to perform a step of impregnating the ionic liquid after the gel is once formed in an aqueous solution or the like, a highly transparent gel can be obtained.

Moreover, according to the thin film of the present invention, a thin film material having the characteristics of the gel of the present invention can be provided, whereby not only the use of the conventional hydrogel but also the recovery and storage of CO ₂ or lithium Applications can also be expected in the field of electrochemical devices such as ion secondary batteries.

FIG. 1 is a diagram showing a mechanism for controlling gelation time in an ionic liquid according to the present invention. FIG. 2 is a graph showing the measurement results of the time dependency of the storage elastic modulus G ′ and the loss elastic modulus G ″ in the gelation reaction using the ionic liquid mixed solvent of the present invention. FIG. 3 is a graph showing the results of concentration dependence of the protic ionic liquid on the gelation time in the gelation reaction using the ionic liquid mixed solvent of the present invention. FIG. 4 is a graph showing the results of a tensile test performed on the polymer crosslinked gel of the present invention.

Hereinafter, embodiments of the present invention will be described. The scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention can be appropriately changed and implemented without departing from the spirit of the present invention.

(1) Ionic liquid The ionic liquid used as a reaction solvent in the present invention is a mixed solvent containing at least one kind of protic ionic liquid and at least one kind of aprotic ionic liquid.

The term "protic ionic ^{liquid", HA + B → HB + A} - is a ionic liquid synthesized by neutralization of the Bronsted acid represented by the reaction formula (HA) and Bronsted bases (B), Medium It is also called a Japanese ionic liquid. The “aprotic ionic liquid” means something other than these protic ionic liquids.

The type of protic ionic liquid and aprotic ionic liquid used in the present invention is not limited, and known ones can be used. For example, as the cationic species, for example, primary (R ₁₎ NH ₃ ⁺ ), secondary (R ₁ R ₂ NH ₂ ⁺ ), tertiary (R ₁ R ₂ R ₃ NH ⁺ ), quaternary (R ₁ R ₂ R ₃ R ₄ N ⁺ ) chain ammonium Cation (wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently a linear or branched alkyl group having 1 to 15 carbon atoms, or 1 carbon atom having one or more hydroxyl groups in the side chain) -15 linear or branched alkyl groups or phenyl groups) and cyclic ammonium cations. Cyclic ammonium cations include oxazolium, thiazolium, imidazolium, pyrazolium, pyrrolium, furazanium, triazolium, pyrrolidinium, imidazolidinium, pyrazolidinium, pyrrolium, imidazolinium, pyrazolinium, pyrazinium, pyrimidinium, pyridazinium, piperidinium, piperidinium, morpholinium, morpholinium, And lithium and carbazolium. Further, as another cation, a chain phosphonium cation (R ₅ R ₆ R ₇ P ⁺ and R ₅ R ₆ R ₇ R ₈ P ⁺ ), a chain sulfonium cation (R ₉ R ₁₀ R ₁₁ S ⁺ ) (in the formula, , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ are each independently a linear or branched alkyl group having 1 to 12 carbon atoms or a phenyl group) and a cyclic sulfonium cation. Is mentioned. Examples of the cyclic sulfonium cation include thiophenium, thiazolinium, and thiopyranium.

Examples of the anionic species include inorganic acid ions such as phosphoric acid, sulfuric acid, and carboxylic acid, and fluorine ions. Examples of fluorine-based anions include tetrafluoroborate (BF ₄ ⁻ ), hexafluoroborate (BF ₆ ⁻ ), hexafluorophosphate (PF ₆ ⁻ ), hexafluoroarsenate (AsF ₆ ⁻ ), trifluoromethanesulfonate (CF ₃ SO ₃ ⁻ ), bis (fluorosulfonyl) amide ((FSO ₂ ) ₂ N ⁻ ), bis (trifluoromethanesulfonyl) amide ((CF ₃ SO ₂ ) ₂ N ⁻ ), bis (trifluoroethanesulfonyl) amide ( And (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ ) and tris (trifluoromethanesulfonylmethide) ((CF ₃ SO ₂ ) ₃ C ⁻ ).

Among these, in the present invention, the protic ionic liquid can be used as long as proton transfer can occur by the acid-base reaction, and is not particularly limited. For example, an imidazolium-based cation component, Examples thereof include an ionic liquid having a pyridinium-based cation component or a primary ammonium cation component. Preferably, it is an ionic liquid comprising an imidazolium-based or pyridinium-based cation component.

As the aprotic ionic liquid, any combination of the above cationic species and anionic species can be used, but it is preferable to have a skeleton similar to the protic ionic liquid.

For example, the cation component of the protic ionic liquid is 1-alkylimidazolium, and the cation component of the aprotic ionic liquid is 1-alkyl-3-methylimidazolium. Alternatively, the cation component of the protic ionic liquid may be a primary ammonium cation, and the cation component of the aprotic ionic liquid may be a quaternary ammonium cation. Preferably, the cationic component of the protic ionic liquid is 1-ethylimidazolium, and the cationic component of the aprotic ionic liquid is 1-ethyl-3-methylimidazolium.

Specific examples of a combination of a protic ionic liquid and an aprotic ionic liquid include a combination of 1-ethylimidazolium bis (trifluoromethanesulfonyl) amide and 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) amide, Alternatively, a combination of 1-ethylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetrafluoroborate can be given. It is also possible to use a combination of a plurality of types of protic ionic liquids and aprotic ionic liquids.

These ionic liquids can be prepared by methods well known in the art.

(2) Crosslinked polymer The polymer used in the present invention is a polymer that is soluble in an ionic liquid and can contain an ionic liquid by forming a gel by a gelation reaction (crosslinking reaction or the like) in the ionic liquid. Those known in the art can be used according to the final use or shape of the gel. Here, “gel” generally refers to a dispersion having high viscosity and loss of fluidity.

More specifically, a polymer that can form a network structure for containing an ionic liquid by cross-linking each other, particularly a three-dimensional network structure is preferable. Such a polymer typically includes a polymer species having a plurality of polyethylene glycol skeleton branches, and a polymer species having four polyethylene glycol skeleton branches is particularly preferable. However, polymers other than the polyethylene glycol skeleton can be used as long as they can be cross-linked to form a uniform network structure network to form a gel. For example, a polymer having a vinyl skeleton such as methyl methacrylate can also be used.

In order to form such a network structure, the polymer comprises a first polymer having f nucleophilic functional groups at the side chain or terminal and g electrophilic functional groups at the side chain or terminal. A means for reacting and crosslinking two kinds of polymer species of the second polymer having γ is preferable. Here, f + g is preferably 5 or more. These functional groups are more preferably present at the terminal. For example, when the polymer species having four polyethylene glycol skeleton branches is used, an embodiment in which f and g are 4 and f + g is 8 as in the compounds represented by formulas (I) and (II) described later. However, it is preferable in that a uniform network structure network is obtained.

The terminal nucleophilic functional group is preferably an amino group. However, a nucleophilic functional group other than an amino group can be used as the functional group as long as a cross-linking having a high-strength steric structure can be obtained. Examples of such a nucleophilic functional group include —SH or —CO ₂ PhNO ₂ (Ph represents an o-, m-, or p-phenylene group). A nuclear functional group can be used as appropriate.

The terminal electrophilic functional group is preferably an N-hydroxy-succinimidyl (NHS) group. However, other active ester groups having electrophilicity may be used. Examples of such an active ester group include a sulfosuccinimidyl group, a maleimidyl group, a phthalimidyl group, an imidazolyl group, and a nitrophenyl group, and those skilled in the art can appropriately use known active ester groups. . The functional groups may be the same or different, but are preferably the same. By having the same functional group, the reactivity with the nucleophilic functional group becomes uniform, and it becomes easy to obtain a high-strength gel having a uniform three-dimensional structure.

Preferred non-limiting specific examples of the polymer species having a nucleophilic functional group at the terminal are, for example, represented by the following formula (I) having four polyethylene glycol skeleton branches and an amino group at the terminal. Compounds.

In the formula (I), R ¹¹ to R ¹⁴ are the same or different and each represents a C ₁ -C ₇ alkylene group, a C ₂ -C ₇ alkenylene group, —NH—R ¹⁵ —, —CO—R ¹⁵ —, —R ¹⁶ —O—R ¹⁷ —, —R ¹⁶ —NH—R ¹⁷ —, —R ¹⁶ —CO ₂ —R ¹⁷ —, —R ¹⁶ —CO ₂ —NH—R ¹⁷ —, —R ¹⁶ —CO—R ¹⁷ —, Or —R ¹⁶ —CO—NH—R ¹⁷ —, wherein R ¹⁵ represents a C ₁ -C ₇ alkylene group, R ¹⁶ represents a C ₁ -C ₃ alkylene group, and R ¹⁷ represents C It shows the ₁ -C ₅ alkylene group. )

n ₁₁ to n ₁₄ may be the same or different from each other. As the values of n ₁₁ to n ₁₄ are closer, a uniform three-dimensional structure can be obtained and the strength becomes higher. For this reason, in order to obtain a highly strong gel, it is preferable that it is the same. When the value of n ₁₁ to n ₁₄ is too high, the gel strength is weakened, and when the value of n ₁₁ to n ₁₄ is too low, the gel is hardly formed due to steric hindrance of the compound. Therefore, n ₁₁ to n ₁₄ include integer values of 25 to 250, preferably 35 to 180, more preferably 50 to 115, and particularly preferably 50 to 60. The molecular weight is 5 × 10 ³ to 5 × 10 ⁴ Da, preferably 7.5 × 10 ³ to 3 × 10 ⁴ Da, and more preferably 1 × 10 ⁴ to 2 × 10 ⁴ Da.

In the above formula (I), R ¹¹ to R ¹⁴ are linker sites that connect the functional group and the core portion. R ¹¹ to R ¹⁴ may be the same or different, but are preferably the same in order to produce a high-strength gel having a uniform three-dimensional structure. R ¹¹ to R ¹⁴ are a C ₁ -C ₇ alkylene group, a C ₂ -C ₇ alkenylene group, —NH—R ¹⁵ —, —CO—R ¹⁵ —, —R ¹⁶ —O—R ¹⁷ —, —R ¹⁶ —NH—R ¹⁷ —, —R ¹⁶ —CO ₂ —R ¹⁷ —, —R ¹⁶ —CO ₂ —NH—R ¹⁷ —, —R ¹⁶ —CO—R ¹⁷ —, or —R ¹⁶ —CO—NH— R ¹⁷ -is shown. Here, R ¹⁵ represents a C ₁ -C ₇ alkylene group. R ¹⁶ represents a C ₁ -C ₃ alkylene group. R ¹⁷ represents a C ₁ -C ₅ alkylene group.

Here, the “C ₁ -C ₇ alkylene group” means an alkylene group having 1 to 7 carbon atoms which may have a branch, and is a straight chain C ₁ -C ₇ alkylene group or one or two A C ₂ -C ₇ alkylene group having ₂ or more branches (having 2 or more and 7 or less carbon atoms including branches) is meant. Examples of C ₁ -C ₇ alkylene groups are a methylene group, an ethylene group, a propylene group and a butylene group. Examples of C ₁ -C ₇ alkylene groups are —CH ₂ —, — (CH ₂ ) ₂ —, — (CH ₂ ) ₃ —, —CH (CH ₃ ) —, — (CH ₂ ) ₃ —, — ( CH (CH ₃ )) ₂ —, — (CH ₂ ) ₂ —CH (CH ₃ ) —, — (CH ₂ ) ₃ —CH (CH ₃ ) —, — (CH ₂ ) ₂ —CH (C ₂ H ₅ )-,-(CH ₂ ) ₆ -,-(CH ₂ ) ₂ -C (C ₂ H ₅ ) _2- , and-(CH ₂ ) ₃ C (CH ₃ ) ₂ CH _2- .

The “C ₂ -C ₇ alkenylene group” is an alkenylene group having 2 to 7 carbon atoms in the form of a chain having one or two or more double bonds in the chain or having a branched chain. And a divalent group having a double bond formed by removing 2 to 5 hydrogen atoms of adjacent carbon atoms from an alkylene group.

On the other hand, preferred non-limiting specific examples of the polymer species having an electrophilic functional group at the terminal include, for example, four polyethylene glycol skeleton branches and an N-hydroxy-succinimidyl (NHS) group at the terminal. Examples thereof include compounds represented by the following formula (II).

In the above formula (II), n ₂₁ to n ₂₄ may be the same or different. The closer the values of n ₂₁ to n ₂₄ are, the more preferable the hydrogel can have a uniform three-dimensional structure and high strength, and the same is preferable. If the value of n ₂₁ to n ₂₄ is too high, the gel strength is weakened. If the value of n ₂₁ to n ₂₄ is too low, the gel is difficult to be formed due to steric hindrance of the compound. Therefore, n ₂₁ to n ₂₄ may be integer values of 5 to 300, preferably 20 to 250, more preferably 30 to 180, still more preferably 45 to 115, and even more preferably 45 to 55. The molecular weight of the second four-branched compound of the present invention is 5 × 10 ³ to 5 × 10 ⁴ Da, preferably 7.5 × 10 ³ to 3 × 10 ⁴ Da, and 1 × 10 ⁴ to 2 ×. 10 ⁴ Da is more preferable.

In the above formula (II), R ²¹ to R ²⁴ are linker sites that connect the functional group and the core portion. R ²¹ to R ²⁴ may be the same or different, but are preferably the same in order to produce a high-strength gel having a uniform three-dimensional structure. In formula (II), R ²¹ to R ²⁴ are the same or different and each represents a C ₁ -C ₇ alkylene group, a C ₂ -C ₇ alkenylene group, —NH—R ²⁵ —, —CO—R ²⁵ —, —R ²⁶ —O—R ²⁷ —, —R ²⁶ —NH—R ²⁷ —, —R ²⁶ —CO ₂ —R ²⁷ —, —R ²⁶ —CO ₂ —NH—R ¹⁷ —, —R ²⁶ —CO—R ²⁷ —, Or —R ²⁶ —CO—NH—R ²⁷ — is shown. Here, R ²⁵ represents a C ₁ -C ₇ alkylene group. R ²⁶ represents a C ₁ -C ₃ alkylene group. R ²⁷ represents a C ₁ -C ₅ alkylene group.

In the case of the polymer species of the above formulas (I) and (II), they can be cross-linked by an amide bond to form a uniform network structure network.

(3) Gelation reaction Hereinafter, the step of the gelation reaction according to the production method of the present invention will be specifically described.

(3-1) Gelation step As a representative example of the gelation reaction step in the present invention,
a) A desired amount of a protic ionic liquid is added to the aprotic ionic liquid to prepare a mixed solvent of the ionic liquid (here, even when a plurality of aprotic ionic liquids or protic ionic liquids are used, Similarly, a mixed solvent can be prepared),
b) preparing a plurality of polymer solutions in which a desired polymer species is dissolved in the mixed solvent;
c) A step of stirring and mixing the polymer solution.

For example, in the case of using the polymer species of the above formula (I) and formula (II), in step b), a mixed solvent containing the polymer species of formula (I) (“first solution”) and formula (II) A mixed solvent containing the polymer species (“second solution”) is prepared, and these are mixed in step c). Thereby, the formation reaction of an amide bond occurs between the polymer species of the formulas (I) and (II), and a gel having a uniform network structure can be produced.

As the mixing step c), the step of adding and mixing the second solution to the first solution, the step of adding and mixing the first solution to the second solution, the first solution and the second solution And a step of mixing with the above solution. The addition speed, mixing speed, and mixing ratio of the first solution or the second solution are not particularly limited, and can be adjusted as appropriate by those skilled in the art. It will be apparent that even when three or more polymer species are used, corresponding polymer solutions can be prepared in the same manner and mixed as appropriate.

As a means for mixing, for example, a two-component mixing syringe as disclosed in International Publication No. WO2007 / 083522 pamphlet can be used. The temperature of the two liquids at the time of mixing is not particularly limited, and is a temperature range that is equal to or higher than the melting point of the ionic liquid that is the solvent and lower than the temperature at which the cationic species or anionic species constituting the ionic liquid decomposes, May be melted and the temperature of each liquid may be fluid. For example, the temperature of the solution when mixing may be in the range of 1 ° C. to 100 ° C. The temperature of the two liquids may be different, but the same temperature is preferable because the two liquids are easily mixed.

The concentration of the polymer species in the solution can be appropriately changed according to the type of the polymer or ionic liquid. For example, when the polymer species of the formula (I) and the formula (II) are used, the polymer concentration in the mixed solvent is Examples include 10 mg / mL to 500 mg / mL. If the polymer concentration is too low, the gel strength becomes weak, and if the polymer concentration is too high, the gel structure becomes non-uniform and the gel strength becomes weak. Therefore, 20 to 400 mg / mL is preferable, 50 mg / mL to 300 mg / mL is more preferable, and 100 to 200 mg / mL is more preferable.

The polymer species of formula (I) and formula (II) can be mixed in a molar ratio of 0.5: 1 to 1.5: 1. Since the functional groups of the polymer species (ie amino groups and N-hydroxy-succinimidyl groups) can each react 1: 1, the mixing molar ratio is preferably closer to 1: 1, but in order to obtain a high strength gel Is particularly preferably 0.8: 1 to 1.2: 1.

(3-2) Reaction rate control In the mixed solvent of the protic ionic liquid and the aprotic ionic liquid in the present invention, the cross-linking reaction between the polymer species is controlled by adjusting the proton concentration in the solvent system by adding the protic ionic liquid. Can be controlled.

For example, when a cross-linking reaction by forming an amide group between an amino group and an N-hydroxy-succinimidyl group is used as in the polymer species of the above formulas (I) and (II), the amino group is used for the progress of the reaction. Must exist in neutral state (—NH ₂ ). However, the proton component does not exist in the solvent of the aprotic ionic liquid alone, and only —NH ₂ can exist, so that the crosslinking reaction proceeds rapidly. As a result, a uniform and strong desirable gel cannot be obtained. On the other hand, when the protonic ionic liquid is excessive, the amino group is in a cationic state (—NH ³⁺ ) and tends to repel each other, and the cationic amino group reacts with the N-hydroxy-succinimidyl group. This is not preferable because the properties are lowered.

Therefore, by adding an appropriate amount of a protic ionic liquid to the solvent, protons are supplied to the solution and the abundance ratio of -NH ³⁺ groups is adjusted to perform a crosslinking reaction and gelation at a desired reaction rate. Is possible. For example, it is preferable to maintain a non-cationic amino group capable of reacting with an N-hydroxy-succinimidyl group at 5% or less in the solution in order to produce a uniform and strong hydrogel.

Fig. 1 shows the principle of reaction control described above from the viewpoint of chemical reaction kinetics.

Formula (1) in FIG. 1 represents a cross-linking reaction formula of a polymer by taking an amide group formation between an amino group and an N-hydroxy-succinimidyl group as an example. As described above, the neutral amino group (—NH ₂ ) is involved in the reaction, and the cationic amino group (—NH ³⁺ ) is not involved. The abundance ratio of —NH _{2 in} the solution depends on the acid dissociation equilibrium (acid dissociation constant Ka).

On the other hand, the protic ionic liquid in the solution has a self-dissociation equilibrium of the formula (2) (where “C ₂ ImH ⁺ ” represents a 1-ethylimidazolium cation). Here, since “X ⁻ ” that is a constituent anion of the ionic liquid is a strong acid, the concentration [HX] of HX can be regarded as the proton concentration [H ⁺ ]. Therefore, the proton concentration in the solution can be adjusted by the amount of the protonic ionic liquid added.

The abundance ratio of —NH ₂ in the above formula (1) depends on the proton concentration [H ⁺ ] in the solution, as is clear from the equation of the acid dissociation constant Ka, and when [H ⁺ ] increases, ₂ concentration (existence ratio) is in a relationship of increasing. Therefore, the reaction rate of amide bond formation (gelation) can be controlled by adding a protic ionic liquid.

This reaction control is very useful in that the fluid state until the gel solidifies can be appropriately controlled because the fluid state of the gel can be controlled according to the polymer type to be used, the desired final processing shape, and the like. is there

As described above, generally, “X ⁻ ” that is a constituent anion of an ionic liquid is a strong acid, and thus does not become a conjugate base that stabilizes protons. Therefore, it is difficult for the acid (HX) composed of X to coexist with the aprotic ionic liquid. Therefore, the control of the reaction rate is an action obtained only by using a protic ionic liquid.

(4) Processing of gel etc. In this invention, as mentioned above, a gel-like composition of a desired shape can be processed by controlling the gelation reaction. In view of the applicability to various fields, the shape is preferably a thin film. Therefore, as a method for obtaining the gel thin film of the present invention, any method known in the art can be used. For example, in a state having fluidity before the gel is completely solidified, A thin film containing an ionic liquid can be obtained by a technique such as coating on a flat substrate such as glass. In the case of forming into a thin film, the gelation time is preferably 20 to 30 minutes.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Synthesis of branched polymer with polyethylene glycol skeleton:
By amination and succinimidylation of TAPEG (tetraamine-polyethylene glycol) and TNPEG (N-hydroxy-succinimidyl-polyethylene glycol (NHS-PEG)) and THPEG (tetrahydroxyl-polyethylene glycol) having a hydroxyl group at the terminal, respectively. Obtained.

1. Synthesis of THPEG:
Initiator pentaerythritol (0.4572 mmol, 62.3 mg) was dissolved in a mixed solvent of DMSO / THF (v / v = 3: 2) 50 mL, and potassium naphthene (0.4157 mmol, 1.24 mg) was used as a metallizing agent. ), Ethylene oxide (200 mmol, 10.0 mL) was added, and the mixture was heated and stirred at 60 ° C. in the presence of Ar for about 2 days. After completion of the reaction, it was reprecipitated in diethyl ether, and the precipitate was taken out by filtration. Furthermore, it wash | cleaned 3 times with diethyl ether, and 20k THPEG was obtained by drying the obtained white solid under reduced pressure.

2. TAPEG synthesis:
THPEG (0.1935 mmol, 3.87 g, 1.0 equiv) was dissolved in benzene, lyophilized, dissolved in 62 mL of THF, and triethylamine (TEA) (0.1935 mmol, 3.87 g, 1.0 equiv) was added. . To another eggplant flask, 31 mL of THF and methanesulfonyl chloride (MsCl) (0.1935 mmol, 3.87 g, 1.0 equiv) were added and placed in an ice bath. A THF solution of MsCl was added dropwise to a THF solution of THPEG and TEA over about 1 minute, stirred in an ice bath for 30 minutes, and then stirred at room temperature for 1 hour and a half. After completion of the reaction, it was reprecipitated in diethyl ether, and the precipitate was taken out by filtration. Furthermore, it wash | cleaned 3 times with diethyl ether, and the obtained white solid was moved to the eggplant flask, 250 mL of 25% aqueous ammonia was added, and it stirred for 4 days. After completion of the reaction, the solvent was distilled off under reduced pressure using an evaporator, and water was dialyzed twice or three times in an external solution and freeze-dried to obtain TAPEG as a white solid. The chemical formula of the prepared TAPEG is shown in Formula (Ia). In the formula (Ia), n ₁₁ to n ₁₄ were 50 to 60 when the molecular weight of TAPEG was about 10,000 (10 kDa), and 100 to 115 when the molecular weight was about 20,000 (20 kDa).

3. Synthesis of TNPEG:
THPEG (0.2395 mmol, 4.79 g, 1.0 equiv) was dissolved in THF, 0.7 mol / L glutaric acid / THF solution (4.790 mmol, 6.85 mL, 20 equiv) was added, and Ar was present for 6 hours. Stir. After completion of the reaction, it was added dropwise to 2-propanol and centrifuged 3 times. The obtained white solid was transferred to a 300 mL eggplant flask, and the solvent was distilled off under reduced pressure using an evaporator. The residue was dissolved in benzene, and the insoluble material was removed by filtration. The solvent was removed from the obtained filtrate by lyophilization to obtain Tetra-PEG-COOH as a white solid whose terminal was modified with a carboxyl group. This Tetra-PEG-COOH (0.2165 mmol, 4.33 g, 1.0 equiv) was dissolved in THF, and N-hydrosuccinamide (2.589 mmol, 0.299 g, 12 equiv), N, N′-diisopropylsk Cinamide (1.732 mmol, 0.269 mL, 8.0 equiv) was added, and the mixture was stirred with heating at 40 ° C. for 3 hr. After completion of the reaction, the solvent was distilled off under reduced pressure using an evaporator. The resultant was dissolved in chloroform and extracted three times with saturated saline, and the chloroform layer was taken out. Further, after dehydration and filtration with magnesium sulfate, the solvent was distilled off under reduced pressure by an evaporator. The obtained residue was freeze-dried with benzene to obtain TNPEG as a white solid. The chemical formula of the prepared TNPEG is shown in Formula (IIa). In the formula (IIa), n ₂₁ to n ₂₄ were 45 to 55 when the molecular weight of TNPEG was about 10,000 (10 k), and 90 to 115 when the molecular weight was about 20,000 (20 k).

Preparation of mixed solvent of ionic liquid:
1. Synthesis of aprotic ionic liquid:
A synthesis route of 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) amide ([C ₂ mIm ⁺ ] [TFSA ⁻ ]) is shown below.

1-methylimidazole (Wako Pure Chemical Industries) was purified by distillation, and ethyl bromide (Wako Pure Chemical Industries) and lithium bis (trifluoromethanesulfonyl) amide (Wako Pure Chemical Industries) were used unpurified. The produced LiBr and unreacted substances were removed by extraction with water, and a small amount of remaining impurities were removed by activated carbon chromatography. Thereafter, water was removed with a freeze dryer. ^{Using 1} H-NMR, it was confirmed that a high-purity ionic liquid could be synthesized, and the water content was confirmed to be 100 ppm or less by a Karl Fischer moisture meter. In addition, 1-ethyl-3-methylimidazolium tetrafluoroborate ([C ₂ mIm ⁺ ] [BF ₄ ⁻ ]) in which the anion species is changed to BF ₄ is a commercially available product (Wako Pure Chemical Industries), and the water content is curl. It was confirmed to be 150 ppm by a Fisher moisture meter.

2. Synthesis of protic ionic liquid:
A synthesis route of _1- ethylimidazolium bis (trifluoromethanesulfonyl) amide ([C ₂ ImH ⁺ ] [TFSA ⁻ ]) is shown below.

1-Ethylimidazole (C ₂ Im, Wako Pure Chemical Industries, Ltd.) was purified by distillation, and water was removed by molecular sieves. Trifluoromethanesulfonimide (HTFSA, Wako Pure Chemical Industries) was used unpurified. The mixture was mixed in a glove box under an argon atmosphere and stirred for 24 hours to react. After synthesis, moisture was removed with a freeze dryer. ^{Using 1} H-NMR, it was confirmed that a high-purity ionic liquid could be synthesized, and the water content was confirmed to be 115 ppm by a Karl Fischer moisture meter. Further, 1-ethylimidazolium tetrafluoroborate ([C ₂ ImH ⁺ ] [BF ₄ ⁻ ]) in which the anionic species was changed to BF ₄ was synthesized in the same manner using HBF ₄ instead of HTFSA. The water content was confirmed to be 210 ppm by a Karl Fischer moisture meter.

3. Preparation of mixed solvent 4.4. As aprotic ionic liquid 0.01 mL of [C ₂ ImH ⁺ ] [TFSA ⁻ ] as a protic ionic liquid was added to mL [C ₂ mIm ⁺ ] [TFSA ⁻ ] to prepare an 8.0 mM stock solution. The stock solution was further diluted with 1.5 mL of [C ₂ mIm ⁺ ] [TFSA ⁻ ] to obtain 2 mL of a mixed solvent having a concentration of the protic ionic liquid of 2.0 mM. Various mixed solvents with different concentrations of the protic ionic liquid in the range of 1 to 3 mM were prepared by diluting the stock solution.

Aprotic ionic liquid ^{_{[C 2 mIm +] [BF}} 4 -], and _[C 2 ImH ^+] as a protic solvent [BF ₄ ^-] For even mixed solvent used was prepared in the same manner.

Measurement of gelation reaction time:
1. Gelation Procedure First, 1 mL of the ionic liquid mixed solvent obtained in Example 2 was collected in two sample bottles, 50 mg of TAPEG and TNPEG synthesized in Example 1 were added, respectively, and a 2.4 mM solution of TAPEG and TNPEG was added. Was prepared. Thereafter, the two kinds of solutions were mixed with equal amounts (0.9 mL) while stirring, and the progress of the gelation reaction was observed. The reaction temperature was 25 ° C.

2. Measurement of gelation time For the gelation status in the above mixture, dynamic viscoelasticity measurement is performed using a rheometer (Physica MCR501, manufactured by Anton Paar) to calculate storage elastic modulus G ′ and loss elastic modulus G ″. The results of the time dependence of G ′ and G ″ obtained at various protic ionic liquid concentrations are shown in FIG. In FIG. 2, a mixed solvent of [C ₂ mIm ⁺ ] [BF ₄ ⁻ ] and [C ₂ ImH ⁺ ] [BF ₄ ⁻ ] is used.

In FIG. 2, the time at the point where G ′ and G ″ intersect for each protic ionic liquid concentration is defined as the gel time. As a result, the gel time when the concentration of the protic ionic liquid is 1.9 mM is It was 13 minutes, 35 minutes for 2.4 mM and 84 minutes for 2.5 mM.

3. 1. Examination of concentration dependence of protic ionic liquid in gelation time [C ₂ mIm ⁺ ] [TFSA ⁻ ] and [C ₂ ImH ⁺ ] [TFSA ⁻ ], and [C ₂ mIm ⁺ ] [BF ₄ ⁻ ] and [C ₂ ImH The change in gelation time due to the protonic ionic liquid in the reaction solution was calculated for each of the mixed solvents of ⁺ ] [BF ₄ ⁻ ]. The obtained results are shown in FIG.

From the result of FIG. 3, it was found that the gelation time was delayed as the concentration of the protic ionic liquid in the mixed solvent increased. As described above, the reaction time of amide bond formation / crosslinking between TAPEG and TNPEG depends on the concentration of NH ₂ -terminal TAPEG in the solution. Therefore, this result shows that as the proportion of the protic ionic liquid increases, the proton concentration in the solvent increases, and the terminal amino group of TAPEG is cationized (-NH ³⁺ ), thereby forming an amide bond with TNPEG. This suggests that the crosslinking reaction rate has become slow.

On the other hand, it was observed that an aprotic ionic liquid alone solvent containing no protic ionic liquid gelled immediately after mixing of the reaction solution. In such a case, since the gel is solidified before the crosslinking reaction sufficiently proceeds, a sufficient mechanical strength cannot be obtained, which is not preferable.

Moreover, it became clear from the comparison of the ionic liquid kind in FIG. Regarding the anion species to be used, it was found that the protonic ionic liquid concentration required for delaying the gelation was higher in the case of [BF ₄ ⁻ ] than that in [TFSA ⁻ ], that is, the gelation time was shorter.

These results demonstrate that the distribution ratio of NH ₂ / NH ₃ ⁺ in the terminal amino group of TAPEG can be controlled by adjusting the concentration of the protic ionic liquid, and thereby the gelation time can be controlled chemokinetically. It is.

Measurement of elastic modulus:
A tensile test was performed on the gel of the present invention produced from a mixed solvent of [C ₂ mIm ⁺ ] [TFSA ⁻ ] and [C ₂ ImH ⁺ ] [TFSA ⁻ ]. TAPEG and TNPEG having a molecular weight of 10 k and a concentration of 5.0 mM were gelled using two mixed solvents in which the concentration of [C ₂ ImH ⁺ ] [TFSA ⁻ ], which is a protic ionic liquid, was 12 mM and 18 mM. The obtained gel was formed into a 1 × 5 × 20 mm strip shape to obtain a test sample. The tensile tester used was SHIMADZU EZ-L 50N, and the measurement was performed under the condition of a tensile speed of 1 mm · s ⁻¹ . It pulled until it broke from natural length, and the stress was measured.

The results of the tensile test are shown in FIG. From FIG. 4, it was found that the stress monotonously increased with deformation. When the elastic modulus was calculated from the initial slope of the obtained curve, the elastic modulus was 7.7 and 2.4 kPa for gels with the concentration of [C ₂ ImH ⁺ ] [TFSA ⁻ ] being 12 mM and 18 mM, respectively. Met.

Thin film production:
Using a mixed solvent of [C ₂ mIm ⁺ ] [TFSA ⁻ ] and [C ₂ ImH ⁺ ] [TFSA ⁻ ] as a solvent, the concentration of [C ₂ ImH ⁺ ] [TFSA ⁻ ] is 12 mM, the molecular weight is 10 k, the concentration 5.0 mM TAPEG and TNPEG were used. After mixing two liquids of TAPEG and TNPEG solution and stirring sufficiently, the bubbles were removed through a filter having a pore size of 5.0 μm, and then a thin film having a thickness of 200 μm and a length and width of 10 × 10 cm was prepared using a 200 μm spacer. The obtained film could be used as a self-supporting film.

Although specific embodiments of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. In addition, the invention described in the claims may include various modifications of the specific embodiments described above.

Claims (21)

A method for producing a polymer cross-linked gel containing an ionic liquid, wherein the polymer is cross-linked in a mixed solvent containing at least one kind of protic ionic liquid and at least one kind of aprotic ionic liquid. A manufacturing method. The production method according to claim 1, wherein the protic ionic liquid is an ionic liquid composed of a cation component selected from imidazolium-based, pyridinium-based, or primary ammonium. The cation component of the protic ionic liquid is 1-ethylimidazolium, and the cation component of the aprotic ionic liquid is 1-ethyl-3-methylimidazolium. Manufacturing method. The combination of the protic ionic liquid and the aprotic ionic liquid is a combination of 1-ethylimidazolium bis (trifluoromethanesulfonyl) amide and 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) amide, and The production method according to any one of claims 1 to 3, which is selected from the group consisting of a combination of 1-ethylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetrafluoroborate. The production method according to any one of claims 1 to 4, wherein the polymer is a polymer capable of forming a three-dimensional network structure by cross-linking each other. The polymer comprises a first polymer having f nucleophilic functional groups in the side chain or terminal and a second polymer having g electrophilic functional groups in the side chain or terminal, wherein The production method according to any one of claims 1 to 5, wherein f + g is 5 or more. The production method according to any one of claims 1 to 6, wherein the polymer has a polyethylene glycol skeleton. The polymer according to any one of claims 1 to 7, wherein the polymer contains a compound represented by the following formula (I) and the following formula (II), and has a network structure by crosslinking the ends of the compound with an amide bond. The manufacturing method according to one item.

(Here, in formula (I), n ₁₁ to n ₁₄ are the same or different and each represents an integer of 25 to 250,
In the formula (I), R ¹¹ to R ¹⁴ are the same or different and each represents a C ₁ -C ₇ alkylene group, a C ₂ -C ₇ alkenylene group, —NH—R ¹⁵ —, —CO—R ¹⁵ —, — R ¹⁶ —O—R ¹⁷ —, —R ¹⁶ —NH—R ¹⁷ —, —R ¹⁶ —CO ₂ —R ¹⁷ —, —R ¹⁶ —CO ₂ —NH—R ¹⁷ —, —R ¹⁶ —CO—R ¹⁷ —, or —R ¹⁶ —CO—NH—R ¹⁷ —, wherein R ¹⁵ represents a C ₁ -C ₇ alkylene group, R ¹⁶ represents a C ₁ -C ₃ alkylene group, and R ¹⁷ represents C ₁ -C ₅ alkylene group. )

(In the formula (II), n ₂₁ to n ₂₄ are the same or different and represent an integer of 20 to 250,
In the formula (II), R ²¹ to R ²⁴ are the same or different and each represents a C ₁ -C ₇ alkylene group, a C ₂ -C ₇ alkenylene group, —NH—R ²⁵ —, —CO—R ²⁵ —, — R ²⁶ —O—R ²⁷ —, —R ²⁶ —NH—R ²⁷ —, —R ²⁶ —CO ₂ —R ²⁷ —, —R ²⁶ —CO ₂ —NH—R ¹⁷ —, —R ²⁶ —CO—R ²⁷ —, or —R ²⁶ —CO—NH—R ²⁷ —, wherein R ²⁵ represents a C ₁ -C ₇ alkylene group, R ²⁶ represents a C ₁ -C ₃ alkylene group, and R ²⁷ represents C ₁ -C ₅ alkylene group. ) A solvent for use in a crosslinking reaction of a polymer, comprising at least one kind of protic ionic liquid and at least one kind of aprotic ionic liquid. 10. The solvent according to claim 9, wherein the protic ionic liquid is an ionic liquid composed of a cation component selected from imidazolium-based, pyridinium-based, or primary ammonium. The cationic component of the protic ionic liquid is 1-ethylimidazolium, and the cationic component of the aprotic ionic liquid is 1-ethyl-3-methylimidazolium. Solvent. The combination of the protic ionic liquid and the aprotic ionic liquid is a combination of 1-ethylimidazolium bis (trifluoromethanesulfonyl) amide and 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) amide, and The solvent according to any one of claims 9 to 11, which is selected from the group consisting of a combination of 1-ethylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetrafluoroborate. A polymer cross-linked gel containing an ionic liquid, the gel obtained by cross-linking a polymer in a mixed solvent containing at least one kind of protic ionic liquid and at least one kind of aprotic ionic liquid . The gel according to claim 13, wherein the protic ionic liquid is an ionic liquid composed of a cation component selected from imidazolium-based, pyridinium-based, or primary ammonium. 15. The cation component of the protic ionic liquid is 1-ethylimidazolium, and the cation component of the aprotic ionic liquid is 1-ethyl-3-methylimidazolium. Gel. The combination of the protic ionic liquid and the aprotic ionic liquid is a combination of 1-ethylimidazolium bis (trifluoromethanesulfonyl) amide and 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) amide, and The gel according to any one of claims 13 to 15, which is selected from the group consisting of a combination of 1-ethylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetrafluoroborate. The gel according to any one of claims 13 to 16, wherein the polymer is a polymer capable of forming a three-dimensional network structure by crosslinking with each other. The polymer comprises a first polymer having f nucleophilic functional groups in the side chain or terminal and a second polymer having g electrophilic functional groups in the side chain or terminal, wherein The gel according to any one of claims 13 to 17, wherein f + g is 5 or more. The gel according to any one of claims 13 to 18, wherein the polymer has a polyethylene glycol skeleton. The polymer according to any one of claims 13 to 19, wherein the polymer contains a compound represented by the following formula (I) and the following formula (II), and has a network structure by crosslinking the ends of the compound with an amide bond. The gel according to one item.

(Here, in formula (I), n ₁₁ to n ₁₄ are the same or different and each represents an integer of 25 to 250,
In the formula (I), R ¹¹ to R ¹⁴ are the same or different and each represents a C ₁ -C ₇ alkylene group, a C ₂ -C ₇ alkenylene group, —NH—R ¹⁵ —, —CO—R ¹⁵ —, — R ¹⁶ —O—R ¹⁷ —, —R ¹⁶ —NH—R ¹⁷ —, —R ¹⁶ —CO ₂ —R ¹⁷ —, —R ¹⁶ —CO ₂ —NH—R ¹⁷ —, —R ¹⁶ —CO—R ¹⁷ —, or —R ¹⁶ —CO—NH—R ¹⁷ —, wherein R ¹⁵ represents a C ₁ -C ₇ alkylene group, R ¹⁶ represents a C ₁ -C ₃ alkylene group, and R ¹⁷ represents C ₁ -C ₅ alkylene group. )

(In the formula (II), n ₂₁ to n ₂₄ are the same or different and represent an integer of 20 to 250,
In the formula (II), R ²¹ to R ²⁴ are the same or different and each represents a C ₁ -C ₇ alkylene group, a C ₂ -C ₇ alkenylene group, —NH—R ²⁵ —, —CO—R ²⁵ —, — R ²⁶ —O—R ²⁷ —, —R ²⁶ —NH—R ²⁷ —, —R ²⁶ —CO ₂ —R ²⁷ —, —R ²⁶ —CO ₂ —NH—R ¹⁷ —, —R ²⁶ —CO—R ²⁷ —, or —R ²⁶ —CO—NH—R ²⁷ —, wherein R ²⁵ represents a C ₁ -C ₇ alkylene group, R ²⁶ represents a C ₁ -C ₃ alkylene group, and R ²⁷ represents C ₁ -C ₅ alkylene group. ) A thin film comprising a polymer crosslinked gel containing the ionic liquid according to any one of claims 13 to 20.

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