A small molecule ionic liquid monomer adhesive and a preparation method thereof

Abstract

The application discloses a small-molecule ionic liquid monomer adhesive and a preparation method thereof, and belongs to the technical field of adhesives. The small-molecule ionic liquid monomer adhesive has the structural formula shown in the specification. The preparation method comprises the following steps: reacting a halogenated silane reagent with an imidazole containing a functional group alkyl side chain to obtain a small-molecule ionic liquid monomer containing an imidazole cation with a functional group alkane side chain and a silane side chain and a halogen anion; and performing an anion exchange reaction on the small-molecule ionic liquid monomer and a salt containing a target anion to obtain the small-molecule ionic liquid monomer adhesive. The small-molecule ionic liquid is synthesized through a two-step method, the synthesis steps of the ionic liquid adhesive are simplified, the glass transition temperature of the ionic liquid adhesive is reduced, and the wettability of the ionic liquid adhesive on a base material is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives, and in particular relates to a small molecule ionic liquid monomer adhesive and a preparation method thereof. Background Art

[0002] In recent years, ionic liquids have become a research hotspot in the field of adhesives due to their excellent thermal stability, low flammability, wide electrochemical window, and excellent processability, and are considered to be a very promising adhesive material.

[0003] Ionic liquids are composed of anions and cations. By matching different anion and cation types or modifying the substituents on the cations, ionic liquids with varying viscosities can be obtained to meet the needs of various applications. Polyionic liquids (PILs), obtained by polymerizing ionic liquid monomers, possess high cohesion, resulting in excellent adhesive properties. PILs inherit the excellent structural and electrical properties of ionic liquids, such as designability and high conductivity, while also combining the inherent properties of polymers, such as mechanical durability and processability (Patent 201911140763.5). Highly conductive PIL adhesives can also be obtained by adding metal salts (Patent 202311201214.0). However, the high viscosity of PILs limits the transfer of matter and energy during use. Furthermore, the difficulty in precisely controlling the degree of polymerization (DOP) during the polymerization reaction results in low adhesive stability, which is detrimental to their engineering applications. Reducing the DOP of PILs or directly using PIL monomers as adhesives can avoid a number of issues associated with polymerization reactions while simplifying the synthesis process, reducing costs, and improving production efficiency. Therefore, the development and research of small molecule ionic liquid monomers as adhesives is of great significance for promoting the development and application of ionic liquids in the field of adhesives. Summary of the Invention

[0004] To address the problems of polyionic liquids (PILs), such as complex synthesis, high viscosity, and poor wettability on substrates, the present invention proposes a small-molecule ionic liquid monomer adhesive and its preparation method. This invention synthesizes the small-molecule ionic liquid through a two-step process, simplifying the synthesis of the ionic liquid adhesive. The adhesive is liquid at room temperature, lowering its glass transition temperature and improving its wettability on substrates.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the purposes of the present invention is to provide a small molecule ionic liquid monomer adhesive, the structural formula of which is shown below:

[0007]

[0008] R1 is an alkane side chain or an alkene side chain containing a functional group; the functional group is selected from any one of amino, carboxyl, hydroxyl and cyano groups;

[0009] R2 is selected from any one of —OCH2CH3, —OCH3, —OCH(CH3)2, —OSi(CH3)3 and —COCH2CH3;

[0010] X - is an anion;

[0011] The value of n is an integer between 1 and 5.

[0012] Furthermore, the functional group-containing alkane side chain is selected from -CH2CH2NH2, -CH2CH2COOH, -CH2COOH, -CH2CH2OH, -CH=CH2, -CH2C≡N, Any of the following;

[0013] The anion is selected from NO 3- 、SO4 2- 、ClO4 - 、(CF3SO2)2N - 、OTF - 、BF4 - PF6 - 、FSI - and TFSI - Any one of .

[0014] A second object of the present invention is to provide a method for preparing a small molecule ionic liquid monomer adhesive, comprising the following steps:

[0015] The silane halide reagent reacts with an imidazole having an alkyl side chain as a functional group to obtain a small molecule ionic liquid monomer consisting of an imidazole cation having an alkane side chain as a functional group and a silane side chain and a halogen anion;

[0016] The small molecule ionic liquid monomer undergoes anion exchange reaction with a salt containing a target anion to obtain a small molecule ionic liquid monomer adhesive.

[0017] Furthermore, the halosilane reagent is selected from one or more of chlorotriethoxysilane, (3-chloropropyl)trimethoxysilane, (3-bromopropyl)trimethoxysilane, (3-iodopropyl)trimethoxysilane, 3-chloropropyltriethoxysilane, (chloromethyl)trimethoxysilane, (chloromethyl)triethoxysilane, chloromethyltriisopropoxysilane, (3-chloropropyl)tris(trimethylsiloxy)silane and trimethoxychlorosilane.

[0018] Furthermore, the imidazole containing a functional group alkyl side chain is selected from one or more of 1-(2-hydroxyethyl)imidazole, 1-imidazoleacetic acid, 3-imidazol-1-yl-propionic acid, (1-imidazolyl)acetonitrile, 2-(1-imidazolyl)ethylamine dihydrochloride, 1-(4-cyanophenyl)imidazole, 1-vinylimidazole and 4-(1-imidazolyl)benzoic acid.

[0019] Furthermore, the salt containing the target anion is selected from one or more of lithium nitrate, lithium sulfate, lithium perchlorate, lithium trifluoromethylsulfonyl, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethane)sulfonylimide.

[0020] Furthermore, the specific steps of the reaction include: carrying out the reaction in an organic solvent under the protection of an inert atmosphere, the reaction temperature is 70-120° C., and the reaction time is 12-72 hours.

[0021] Furthermore, the organic solvent is selected from one or more of anhydrous ethanol, methanol, acetonitrile, ethyl acetate, dimethyl sulfoxide, toluene, acetone, dichloromethane, chloroform, NN-dimethylformamide and tetrahydrofuran.

[0022] Furthermore, the specific steps of the anion exchange reaction include: dissolving the small molecule ionic liquid monomer and the salt containing the target anion in a solvent respectively and mixing them to complete the anion exchange reaction.

[0023] Furthermore, the solvent is selected from one or more of deionized water, acetone and tetrahydrofuran.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] (1) The small molecule ionic liquid monomer imidazolium cation structure designed and synthesized by the present invention contains a silane side chain with a silicon oxygen group and an alkane side chain with a specific functional group, and the cation structure can be modified in a variety of ways to meet specific application requirements;

[0026] (2) Compared with the prior art, the small molecule ionic liquid monomer adhesive designed and synthesized in the present invention has a lower glass transition temperature, is in liquid or paste state at room temperature, has good wettability for bonding substrate materials, and gradually solidifies under high temperature conditions, thereby exhibiting good bonding performance;

[0027] (3) The preparation method of the small molecule ionic liquid monomer adhesive designed and synthesized by the present invention is simple, easy to operate, green and safe, and only requires two steps to obtain the target small molecule ionic liquid monomer, which is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 After bonding experiments on aluminum, ceramic, epoxy resin, copper, and stainless steel substrates, the shear strength data of the bonded areas were measured at room temperature.

[0030] Figure 2 Figure 1 shows the adhesion test results of IL-1 prepared in Example 1 of the present invention on aluminum, copper, and stainless steel substrates after being soaked in water for 24 hours;

[0031] Figure 3 This is a diagram showing the bonding effect of IL-1 prepared in Example 1 of the present invention and the energetic hydrogel on a stainless steel substrate. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] An embodiment of the present invention provides a small molecule ionic liquid monomer adhesive, the structural formula of which is shown below:

[0038]

[0039] R1 is an alkane side chain or an alkene side chain containing a functional group; the functional group is selected from amino, carboxyl, hydroxyl or cyano;

[0040] R2 is selected from any one of -OCH2CH3, -OCH3, -OCH(CH3)2, -OSi(CH3)3 and -COCH2CH3; three R2 and Si atom form a silane-containing side chain;

[0041] X - is an anion;

[0042] The value of n is an integer between 1 and 5.

[0043] The functional group-containing alkane side chain is selected from -CH2CH2NH2, -CH2CH2COOH, -CH2COOH, -CH2CH2OH, -CH=CH2, -CH2C≡N, Any of the following;

[0044] The anion is selected from NO 3- 、SO4 2- 、ClO4 - 、(CF3SO2)2N - 、OTF - 、BF4 - PF6 - 、FSI - and TFSI - Any one of .

[0045] The present invention also provides a method for preparing a small molecule ionic liquid monomer adhesive, comprising the following steps:

[0046] (1) reacting a halogenated silane reagent with an imidazole containing an alkyl side chain having a functional group to obtain a small molecule ionic liquid monomer consisting of an imidazole cation containing an alkane side chain having a functional group and a silane side chain and a halogen anion;

[0047] (2) The small molecule ionic liquid monomer undergoes anion exchange reaction with a salt containing a target anion to obtain a small molecule ionic liquid monomer adhesive.

[0048] In some embodiments, the halosilane reagent is one or more of chlorotriethoxysilane, (3-chloropropyl)trimethoxysilane, (3-bromopropyl)trimethoxysilane, (3-iodopropyl)trimethoxysilane, 3-chloropropyltriethoxysilane, (chloromethyl)trimethoxysilane, (chloromethyl)triethoxysilane, chloromethyltriisopropoxysilane, (3-chloropropyl)tris(trimethylsiloxy)silane, and trimethoxychlorosilane. As a typical but non-limiting example, in the following preferred embodiments of the present invention, the halosilane reagent can be selected from (3-chloropropyl)trimethoxysilane.

[0049] In some embodiments, the imidazole containing a functional group alkyl side chain is one or more of 1-(2-hydroxyethyl)imidazole, 1-imidazoleacetic acid, 3-imidazole-1-yl-propionic acid, (1-imidazolyl)acetonitrile, 2-(1-imidazolyl)ethylamine dihydrochloride 1-(4-cyanophenyl)imidazole, 1-vinylimidazole and 4-(1-imidazolyl)benzoic acid. As a typical but non-limiting example, in the following preferred embodiments of the present invention, the imidazole containing a functional group alkyl side chain can be selected from 1-imidazoleacetic acid, 1-vinylimidazole, 1-(2-hydroxyethyl)imidazole or (1-imidazolyl)acetonitrile.

[0050] In some embodiments, the salt containing the target anion is one or more of lithium nitrate, lithium sulfate, lithium perchlorate, lithium trifluoromethanesulfonyl, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethane)sulfonyl imide. As a typical but non-limiting example, in the following preferred embodiments of the present invention, the salt containing the target anion can be selected from lithium bis(trifluoromethane)sulfonyl imide.

[0051] In some embodiments, the specific steps of the reaction include: carrying out the reaction in a solvent under the protection of an inert atmosphere, the reaction temperature is 70-120°C, and the reaction time is 12-72h. As a typical but non-limiting example, in the following preferred embodiments of the present invention, the reaction temperature can be selected to be 90°C, the reaction time can be selected to be 48h, and the atmosphere can be selected to be a nitrogen atmosphere. The solvent is one or more of anhydrous ethanol, methanol, acetonitrile, ethyl acetate, dimethyl sulfoxide, toluene, acetone, dichloromethane, chloroform, NN-dimethylformamide and tetrahydrofuran. As a typical but non-limiting example, in the following preferred embodiments of the present invention, the solvent can be selected to be dimethyl sulfoxide.

[0052] In some embodiments, the specific steps of the anion exchange reaction include: dissolving the small molecule ionic liquid monomer and the salt containing the target anion in a solvent and mixing them to complete the anion exchange reaction. The conditions of the anion exchange reaction are: reaction temperature of 30°C and reaction time of 24 hours. The solvent for dissolving the small molecule ionic liquid monomer and the solvent for dissolving the salt containing the target anion can be the same or different. The solvent is one or more of deionized water, acetone and tetrahydrofuran. As a typical but non-limiting example, in the following preferred embodiments of the present invention, the solvent can be deionized water.

[0053] Unless otherwise specified, the "room temperature" in the present invention refers to 20-30°C.

[0054] The raw materials used in the present invention are all purchased from the market.

[0055] The technical solution of the present invention is further illustrated by the following examples.

[0056] Example 1

[0057] A method for preparing a small molecule ionic liquid monomer adhesive comprises the following steps:

[0058] (1) Weigh 19.87 g of (3-chloropropyl)trimethoxysilane and 12.61 g of 1-imidazoleacetic acid and dissolve them in 50 mL of dimethyl sulfoxide respectively. Add the former dropwise to the latter using a dropping funnel under stirring, and protect with nitrogen. Mix, stir, and heat at 90° C. for 48 h. After the reaction is completed and cooled, the reaction solution is precipitated with ethyl acetate, the unreacted raw materials are removed, and the precipitate is collected. The precipitate is washed with ethyl acetate three times and then dried in vacuum at 50° C. to obtain a small molecule ionic liquid monomer with a yield of 83%, which is named IL-1 precursor.

[0059] (2) Weigh 21.15 g of the above-mentioned small molecule ionic liquid monomer IL-1 and dissolve it in 100 mL of deionized water. Weigh 28.71 g of lithium bis(trifluoromethane)sulfonyl imide and dissolve it in 50 mL of deionized water. Mix the two aqueous solutions and stir them at 30°C for 24 hours to perform anion exchange reaction. After the reaction is completed, filter the solution to obtain a precipitate. The precipitate is washed three times with deionized water and then dried in a vacuum drying oven at 40°C for 72 hours to obtain the target small molecule ionic liquid monomer adhesive with a yield of 70%, which is named IL-1.

[0060] Example 2

[0061] The same as Example 1, except that the 1-imidazoleacetic acid in step (1) was replaced by 1-vinylimidazole in equal moles, and the obtained product was named IL-2.

[0062] Example 3

[0063] The same as Example 1, except that the 1-imidazoleacetic acid in step (1) was replaced by 1-(2-hydroxyethyl)imidazole in equal moles, and the obtained product was named IL-3.

[0064] Example 4

[0065] The same as Example 1, except that the 1-imidazoleacetic acid in step (1) was replaced by (1-imidazolyl)acetonitrile in equal moles, and the obtained product was named IL-4.

[0066] Performance testing:

[0067] The bonding performance of the small molecule ionic liquid monomer adhesives obtained in Examples 1-4 above was tested. The substrate materials in the bonding experiments were aluminum, ceramic, epoxy resin, copper, and stainless steel.

[0068] The bonding strength test conditions and methods are: ambient temperature 25°C, lap shear tensile test rate 50mm / min -1 , bonding area is 12*20mm 2 .

[0069] Figure 1 The following table shows the interfacial bonding strength test results of IL-1 on aluminum, ceramic, epoxy resin, copper, and stainless steel substrates in lap shear tests. The results show that, using IL-1 as an interfacial adhesive, the maximum tensile stresses of the interfacial bonding of aluminum, ceramic, epoxy resin, copper, and stainless steel substrates are 356N, 310N, 585N, 67N, and 226N, respectively. The epoxy resin interface exhibits the highest tensile strength of 2.44MPa.

[0070] Figure 2 The interfacial bond strength of metal lap joints bonded to IL-1 after 24 hours of water immersion. The experimental results show that the maximum tensile stress at the bonding interface of aluminum, copper, and stainless steel lap joints after water immersion is 283N, 33N, and 186N, respectively.

[0071] Figure 3 The interface strength test results of IL-1 bonding stainless steel and energetic hydrogel material show that the interface bonding strength is 1.8MPa (using 180° peeling method, the interface bonding effective area is 10*10mm 2 , the maximum tensile strength of the interface should be 180N).

[0072] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. The use of the compound described in the following structure as a small molecule ionic liquid monomer adhesive, characterized in that: The structural formula is: R1 is a side chain containing a functional group, wherein the side chain containing a functional group is -CH2CH2COOH, -CH2COOH, -CH2CH2OH, -CH=CH2, -CH2C≡N, and Any of the following; R2 is selected from any one of —OCH2CH3, —OCH3, —OCH(CH3)2 and —OSi(CH3)3; X - is an anion; the anion is selected from NO 3- 、SO4 2- 、ClO4 - 、(CF3SO2)2N - 、OTF - 、BF4 - PF6 - 、FSI - and TFSI - Any of the following; The value of n is an integer between 1 and 5.

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