CO2-responsive self-healing ionic liquid hydrogel and preparation method thereof

Abstract

The invention discloses CO2-responsive self-healing ionic liquid hydrogel and a preparation method thereof.The ionic liquid hydrogel is composed of ionic liquid and water, the mass percentage content of the ionic liquid is 3%-95%, cations in the ionic liquid are one or more of quaternary ammonium cations, imidazole cations and pyridine cations, and the cation in the ionic liquid is one or more of quaternary ammonium cations, imidazole cations and pyridine cations. Anions in the ionic liquid are CO2-responsive anions, the CO2-responsive anions are specifically one or more of phenol anions and amide anions, and CO2 / N2 is alternately introduced into the CO2-responsive self-healing ionic liquid hydrogel, so that reversible transformation of a system between gel and sol can be realized; and meanwhile, the CO2-responsive self-healing ionic liquid hydrogel has a self-healing property. The CO2-responsive self-healing ionic liquid hydrogel prepared by the invention has potential application value in the fields of intelligent soft materials and reaction media.

Description

Technical Field

[0001] The present invention belongs to the technical field of ionic liquid hydrogels, and in particular relates to a CO2-responsive self-healing ionic liquid hydrogel and a preparation method thereof. Background Art

[0002] High-performance soft materials have potential applications in modern environmental and energy technologies, and have attracted widespread attention due to their unique properties, such as stimulus responsiveness and self-healing. In particular, supramolecular hydrogels based on low molecular weight gel factors exhibit excellent properties such as stimulus responsiveness, self-healing and shape memory. However, the design and synthesis of small molecule hydrogel factors are relatively complex, making the preparation of multifunctional supramolecular hydrogels very difficult.

[0003] Ionic liquids are novel environmentally friendly soft functional materials and reaction media due to their excellent properties such as non-volatility, high conductivity, local structural order and designability. In addition, ionic liquids can provide controllable hydrogen bonding, electrostatic and / or hydrophobic interactions, which play a vital role in self-assembly and gel formation. Therefore, ionic liquids can be used as low molecular weight gel factors to construct supramolecular hydrogels. At present, although there are relevant reports on ionic liquid hydrogels in the literature, these disclosed ionic liquid hydrogels do not have self-healing properties.

[0004] CO2 is preferred as a trigger for the "process switch" because of its advantages such as environmental friendliness, biocompatibility, low price, and easy removal. Although CO2-responsive hydrogels have been developed in recent years, such as CO2-switchable cellulose nanocrystal hydrogels and CO2-switchable self-healing hydrogels based on β-cyclodextrin and bile acid. However, in order to make the system CO2-responsive, these hydrogels need to be added with organic compounds, and the addition of these organic compounds may contaminate the system. Therefore, CO2-responsive, self-healing, and organic compound-free ionic liquid hydrogels that integrate multiple functions are in urgent need of development. However, based on existing literature, there are currently no reports on this type of multifunctional ionic liquid hydrogel. Summary of the invention

[0005] The technical problem solved by the present invention is to provide a CO2-responsive self-healing ionic liquid hydrogel and a preparation method thereof. The method uses one or more of quaternary ammonium compounds, imidazole compounds and pyridine compounds as cation donors, and one or more of phenolic compounds and amide compounds having CO2-responsive groups as anion donors, prepares functionalized ionic liquids through acid-base neutralization reaction, and then mixes such ionic liquids with water to prepare ionic liquid hydrogels, and introduces CO2 into the ionic liquid hydrogel system to convert the gel into a sol, and then introduces an N2 system to convert it back into a gel. Alternating the introduction of CO2 / N2 can achieve a reversible gel-sol transition. In addition, such ionic liquid hydrogels have self-healing properties at room temperature. The CO2-responsive self-healing ionic liquid hydrogel prepared by the present invention has potential application value in the field of intelligent soft materials and reaction media.

[0006] In order to solve the above technical problems, the present invention adopts the following technical scheme, a CO2-responsive self-healing ionic liquid hydrogel, characterized in that: the ionic liquid hydrogel is composed of ionic liquid and water, wherein the mass percentage of the ionic liquid is 3%-95%, the cations in the ionic liquid are one or more of quaternary ammonium cations, imidazole cations and pyridinium cations, the anions in the ionic liquid are CO2-responsive anions, and the CO2-responsive anions are specifically one or more of phenol anions and amide anions, and the alternating introduction of CO2 / N2 into the CO2-responsive self-healing ionic liquid hydrogel can realize a reversible transformation of the system between gel and sol, and the CO2-responsive self-healing ionic liquid hydrogel has self-healing properties.

[0007] Furthermore, the quaternary ammonium cation is one or more of a dodecylmethyldiethanolamine cation, a tetradecylmethyldiethanolamine cation and a hexadecylmethyldiethanolamine cation; the imidazolium cation is one or more of a dodecylmethylimidazolium cation, a tetradecylmethylimidazolium cation and a hexadecylmethylimidazolium cation; the pyridinium cation is one or more of a dodecylmethylpyridinium cation, a tetradecylmethylpyridinium cation and a hexadecylpyridinium cation.

[0008] Furthermore, the phenol anion is one or more of 4-methylphenol anion, 4-bromophenol anion, 4-chlorophenol anion, 3-methylphenol anion and 2-methylphenol anion; the amide anion is one or more of succinamide anion, succinamide anion, fumaramide anion and maleimide anion.

[0009] Further, the ionic liquid is one or more of dodecylmethyldiethanolamine 4-methylphenol, tetradecylmethyldiethanolamine 4-methylphenol, hexadecylmethyldiethanolamine 4-methylphenol, dodecylmethyldiethanolamine 3-methylphenol, tetradecylmethyldiethanolamine 3-methylphenol, hexadecylmethyldiethanolamine 3-methylphenol, dodecylmethyldiethanolamine 2-methylphenol, tetradecylmethyldiethanolamine 2-methylphenol, hexadecylmethyldiethanolamine 2-methylphenol, dodecylmethyldiethanolamine 4-bromophenol, tetradecylmethyldiethanolamine 4-bromophenol, hexadecylmethyldiethanolamine 4-bromophenol, dodecylmethyldiethanolamine 4-chlorophenol, tetradecylmethyldiethanolamine 4-chlorophenol and hexadecylmethyldiethanolamine 4-chlorophenol.

[0010] The preparation method of the CO2-responsive self-healing ionic liquid hydrogel described in the present invention has the following specific preparation process: the ionic liquid and water are uniformly mixed to obtain the ionic liquid hydrogel, wherein the mass percentage of the ionic liquid is 3%-95%; at normal temperature and pressure, CO2 is introduced into the obtained ionic liquid hydrogel to transform the ionic liquid hydrogel system from a gel state to a sol state; the obtained sol system is heated and / or nitrogen or air is introduced into the sol system at 25-70°C to transform the sol system back into a gel state.

[0011] Furthermore, the specific preparation process of the CO2-responsive self-healing ionic liquid hydrogel is as follows: the hexadecylmethyldiethanolamine-4-methylphenol ionic liquid and water are mixed and heated to 60°C to mix evenly, and then cooled to room temperature to obtain a hexadecylmethyldiethanolamine-4-methylphenol hydrogel with a mass fraction of 5%; CO2 is introduced into the hexadecylmethyldiethanolamine-4-methylphenol hydrogel at 25°C for 30 minutes to obtain a sol system; the obtained sol system is then heated to 65°C and N2 is introduced, and the sol system is converted back into a gel system.

[0012] Furthermore, the specific preparation process of the ionic liquid is as follows: a CO2-responsive ionic liquid is prepared by an acid-base neutralization reaction using a cation donor and an anion donor as raw materials, wherein the cation donor is one or more of a quaternary ammonium compound, an imidazole compound and a pyridine compound, the quaternary ammonium compound is one or more of dodecylmethyldiethanolamine, tetradecylmethyldiethanolamine and hexadecylmethyldiethanolamine, the imidazole compound is one or more of dodecylmethylimidazole, tetradecylmethylimidazole and hexadecylmethylimidazole, the pyridine compound is one or more of dodecylmethylpyridine, tetradecylmethylpyridine and hexadecylpyridine, the anion donor is one or more of a phenol compound, an amide compound and an amino acid compound, the phenol compound is one or more of 4-methylphenol, 4-bromophenol, 4-chlorophenol, 3-methylphenol and 2-methylphenol, and the amide compound is one or more of succinamide, succinamide, fumaramide and maleimide.

[0013] Application of the CO2 responsive self-healing ionic liquid hydrogel of the present invention in the preparation of intelligent soft functional materials or reaction media.

[0014] Compared with traditional supramolecular hydrogels, the present invention has the following advantages and beneficial effects: (1) The CO2-responsive self-healing ionic liquid hydrogel of the present invention uses CO2 as a simple, green "switch" trigger to make the system stimulus-responsive; (2) The CO2-responsive self-healing ionic liquid hydrogel of the present invention does not require additional additives to enable the ionic liquid hydrogel to have self-healing properties, and will not cause the system to be contaminated by additives; (3) The CO2-responsive self-healing ionic liquid hydrogel of the present invention can reversibly transform the phase behavior of the ionic liquid hydrogel system between a gel state and a sol state by adding or removing CO2; (4) The CO2-responsive self-healing ionic liquid hydrogel of the present invention can simply be aired, nitrogen or heated to return the system to its original state. DETAILED DESCRIPTION

[0015] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0016] Example 1

[0017] Preparation of ionic liquid hydrogels

[0018] Through the conventional heating-cooling method, at room temperature of 25°C, different ionic liquid contents were first dissolved in water of different contents, magnetically stirred and heated to 70°C to mix evenly, and then cooled to room temperature of 25°C to obtain ionic liquid hydrogels of different mass fractions.

[0019] Example 2

[0020] Mechanical properties and viscosity of ionic liquid hydrogels

[0021] At room temperature (25°C), ionic liquids with different chemical structures were formulated into ionic liquid hydrogels with the same molar concentration. A rotational rheometer was used to perform amplitude scanning, frequency scanning in the linear viscoelastic region, and then steady-state shear rate scanning to obtain the storage modulus and viscosity of the ionic liquid hydrogels (Table 1).

[0022] Table 1 Effect of the chemical structure of ionic liquids on the mechanical properties of hydrogels

[0023] Serial number Ionic Liquids Storage modulus / Pa Viscosity / Pa.s 1 <![CDATA[[C 16 MDEA][4-MePhO]]> 38 2811 2 <![CDATA[[C 16 MDEA][4-BrPhO]]]> 24 259 3 <![CDATA[[C 16 MDEA][4-ClPhO]]]> 14 110 4 <![CDATA[[C 16 MDEA][3-MePhO]]]> 28 311 5 <![CDATA[[C 16 MDEA][2-MePhO]]> 23 32 6 <![CDATA[[C 14 MDEA][4-MePhO]]> 28 38 7 <![CDATA[[C 16 me][4-MePhO]]]> 30 1451 8 <![CDATA[[C 16 Py][4-MePhO]]]> 25 925 9 <![CDATA[[C 16 MDEA][Mal]]> 35 182

[0024] Example 3

[0025] Reversible gel-sol transition of ionic liquid hydrogels

[0026] At normal temperature and pressure, 16 CO2 was introduced into the [MDEA][4-MePhO] ionic liquid hydrogel system at a system temperature of 25°C. The changes in mechanical properties and viscosity of the ionic liquid hydrogel before and after the introduction of CO2 are shown in the following table (Table 2).

[0027] Table 2 Before and after CO2 injection [C 16 Changes in storage modulus and viscosity of [MDEA][4-MePhO] hydrogels

[0028] Serial number Storage modulus / Pa Viscosity / Pa.s <![CDATA[Before CO2 passing]]> 38 2811 <![CDATA[After passing CO2]]> 1 2

[0029] Example 4

[0030] Reversibility of the sol-gel transition of ionic liquid hydrogels

[0031] At normal temperature and pressure, 16 When air or nitrogen was introduced into the [MDEA][4-MePhO] ionic liquid hydrogel system, the system was transformed into a gel state. After CO2 was introduced, the gel system was transformed back into a sol system. After six cycles, the conductivity did not change significantly (Table 3), indicating that the system has good reversibility.

[0032] Table 3 Changes in conductivity of the hydrogel system before and after CO2 introduction

[0033]

[0034]

[0035] Example 5

[0036] Self-healing properties of ionic liquid hydrogels

[0037] The rotational rheometer was used to measure [C 16 In the step strain rheological experiment of [MDEA][4-MePhO] hydrogel, 1% and 1000% strain were applied alternately. After 4 cycles, there was no obvious change in the storage modulus (Table 4), indicating that this type of hydrogel system has good self-healing properties.

[0038] Table 4[C 16 Step strain rheological experiments on [MDEA][4-MePhO] hydrogel

[0039] Serial number Cycle times Storage modulus / Pa 1 First cycle 24 2 Second cycle 22 3 Third cycle 22 4 Fourth cycle 22

[0040] The basic principles, main features and advantages of the present invention are shown and described above. Without departing from the spirit and scope of the present invention, the present invention may also be subject to various changes and improvements, which all fall within the scope of the present invention to be protected.

Claims

1. A CO2-responsive self-healing ionic liquid hydrogel, characterized in that: The ionic liquid hydrogel is composed of ionic liquid and water, wherein the mass percentage of the ionic liquid is 3%-95%, the cations in the ionic liquid are one or more of quaternary ammonium cations, imidazole cations and pyridinium cations, the anions in the ionic liquid are CO2-responsive anions, and the CO2-responsive anions are specifically one or more of phenol anions and amide anions. Alternating the introduction of CO2 / N2 into the CO2-responsive self-healing ionic liquid hydrogel can realize a reversible transformation of the system between gel and sol, and the CO2-responsive self-healing ionic liquid hydrogel has self-healing properties.

2. The CO2-responsive self-healing ionic liquid hydrogel according to claim 1, characterized in that: The quaternary ammonium cation is one or more of a dodecylmethyldiethanolamine cation, a tetradecylmethyldiethanolamine cation and a hexadecylmethyldiethanolamine cation; the imidazole cation is one or more of a dodecylmethylimidazolium cation, a tetradecylmethylimidazolium cation and a hexadecylmethylimidazolium cation; the pyridinium cation is one or more of a dodecylmethylpyridinium cation, a tetradecylmethylpyridinium cation and a hexadecylpyridinium cation.

3. The CO2-responsive self-healing ionic liquid hydrogel according to claim 1, characterized in that: The phenol anions are one or more of 4-methylphenol anions, 4-bromophenol anions, 4-chlorophenol anions, 3-methylphenol anions and 2-methylphenol anions; the amide anions are one or more of succinamide anions, succinamide anions, fumaramide anions and maleimide anions.

4. The CO2-responsive self-healing ionic liquid hydrogel according to claim 1, characterized in that: The ionic liquid is one or more of dodecylmethyldiethanolamine 4-methylphenol, tetradecylmethyldiethanolamine 4-methylphenol, hexadecylmethyldiethanolamine 4-methylphenol, dodecylmethyldiethanolamine 3-methylphenol, tetradecylmethyldiethanolamine 3-methylphenol, hexadecylmethyldiethanolamine 3-methylphenol, dodecylmethyldiethanolamine 2-methylphenol, tetradecylmethyldiethanolamine 2-methylphenol, hexadecylmethyldiethanolamine 2-methylphenol, dodecylmethyldiethanolamine 4-bromophenol, tetradecylmethyldiethanolamine 4-bromophenol, hexadecylmethyldiethanolamine 4-bromophenol, dodecylmethyldiethanolamine 4-chlorophenol, tetradecylmethyldiethanolamine 4-chlorophenol and hexadecylmethyldiethanolamine 4-chlorophenol.

5. A method for preparing the CO2-responsive self-healing ionic liquid hydrogel according to claim 1, characterized in that The specific preparation process is: the ionic liquid and water are mixed evenly to obtain an ionic liquid hydrogel, wherein the mass percentage of the ionic liquid is 3%-95%; at normal temperature and pressure, CO2 is introduced into the obtained ionic liquid hydrogel to transform the ionic liquid hydrogel system from a gel state to a sol state; the obtained sol system is heated and / or nitrogen or air is introduced into the sol system at 25-70°C, and the sol system is transformed back into a gel state.

6. The method for preparing the CO2-responsive self-healing ionic liquid hydrogel according to claim 5, characterized in that The specific preparation process is as follows: the hexadecylmethyldiethanolamine 4-methylphenol ionic liquid and water are mixed and heated to 60°C to mix evenly, and then cooled to room temperature to obtain a hexadecylmethyldiethanolamine 4-methylphenol hydrogel with a mass fraction of 5%; CO2 is introduced into the hexadecylmethyldiethanolamine 4-methylphenol hydrogel at 25°C for 30 minutes to obtain a sol system; the obtained sol system is then heated to 65°C and N2 is introduced, and the sol system is converted back into a gel system.

7. The method for preparing the CO2-responsive self-healing ionic liquid hydrogel according to claim 5, characterized in that The specific preparation process of the ionic liquid is as follows: a cation donor and an anion donor are used as raw materials to prepare a CO2-responsive ionic liquid through an acid-base neutralization reaction, wherein the cation donor is one or more of a quaternary ammonium compound, an imidazole compound and a pyridine compound, the quaternary ammonium compound is one or more of dodecylmethyldiethanolamine, tetradecylmethyldiethanolamine and hexadecylmethyldiethanolamine, the imidazole compound is one or more of dodecylmethylimidazole, tetradecylmethylimidazole and hexadecylmethylimidazole, the pyridine compound is one or more of dodecylmethylpyridine, tetradecylmethylpyridine and hexadecylpyridine, the anion donor is one or more of a phenol compound, an amide compound and an amino acid compound, the phenol compound is one or more of 4-methylphenol, 4-bromophenol, 4-chlorophenol, 3-methylphenol and 2-methylphenol, and the amide compound is one or more of succinamide, succinamide, fumaramide and maleimide.

8. Use of the CO2 responsive self-healing ionic liquid hydrogel according to any one of claims 1 to 4 in the preparation of intelligent soft functional materials or reaction media.

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