A high-strength and tough shape memory eutectic gel and its preparation method

Abstract

The present invention relates to a high-toughness shape memory eutectic gel and a preparation method thereof, belonging to the technical field of gel materials. The shape memory eutectic gel is obtained by photoinitiated polymerization of a first polymerized monomer and a second polymerized monomer; the molar ratio of the first polymerized monomer to the second polymerized monomer is 1 to 4:1; the first polymerized monomer is prepared by reacting 4-(2-aminoethyl)benzonitrile hydrochloride and acryloyl chloride; and the second polymerized monomer is 1-methyl-3-(4-vinylbenzyl)imidazolium chloride. The eutectic gel provided by the present invention has excellent mechanical strength and shape memory function, and the mechanical strength and electrical conductivity are adjustable to meet different usage requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of gel materials, and in particular to a high-toughness shape memory eutectic gel and a preparation method thereof. Background Art

[0002] The rapid growth of flexible electronic technologies, such as artificial electronic skin, wearable devices, and soft robotics, has created a huge demand for stretchable conductive materials. Hydrogels, advanced polymers with a three-dimensional network structure and water as a dispersion medium, have attracted widespread attention due to their moderate stretchability and excellent ionic conductivity. However, traditional hydrogels suffer from drawbacks such as solvent volatility and poor mechanical properties, which significantly limit their application.

[0003] In recent years, researchers have developed a class of gels using deep eutectic solvents (such as choline chloride-ethylene glycol and choline chloride-glycerol) as dispersion media. These eutectic gels offer advantages such as good biocompatibility, adjustable structure, and low volatility, addressing the issue of poor hydrogel stability. However, the mechanical strength of existing eutectic gels needs to be improved, necessitating the urgent need to develop high-strength and high-toughness eutectic gels. Summary of the Invention

[0004] In response to one or more technical problems existing in the prior art, the present invention provides a high-strength and tough shape-memory eutectic gel and a preparation method thereof. The eutectic gel provided by the present invention has excellent mechanical strength and shape memory function, and its mechanical strength and conductive properties are adjustable to meet different usage requirements.

[0005] In a first aspect, the present invention provides a high-strength and tough shape-memory eutectic gel, which is obtained by photoinitiated polymerization of a first polymer monomer and a second polymer monomer; the molar ratio of the first polymer monomer to the second polymer monomer is 1 to 4:1; the first polymer monomer is obtained by reacting 4-(2-aminoethyl)benzonitrile hydrochloride and acryloyl chloride; and the second polymer monomer is 1-methyl-3-(4-vinylbenzyl)imidazolium chloride.

[0006] Preferably, the molar ratio of the first polymerizable monomer to the second polymerizable monomer is 1.5 to 3.5:1.

[0007] Preferably, the molar ratio of 4-(2-aminoethyl)benzonitrile hydrochloride to acryloyl chloride is 1:1 to 1.2.

[0008] Preferably, the photoinitiator used in the photoinitiated polymerization is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide, and 1-hydroxycyclohexylphenyl ketone, preferably 1-hydroxycyclohexylphenyl ketone.

[0009] Preferably, the amount of the photoinitiator is 0.5-1% of the total mass of the first polymerizable monomer and the second polymerizable monomer.

[0010] In a second aspect, the present invention provides a method for preparing the high-toughness shape memory eutectic gel according to the first aspect, the preparation method comprising:

[0011] Mixing a mixture of 4-(2-aminoethyl)benzonitrile hydrochloride, a base and a solvent with acryloyl chloride, and reacting the mixture to obtain a first polymerizable monomer;

[0012] heating and mixing the first polymerizable monomer and the second polymerizable monomer to obtain a deep eutectic solvent;

[0013] The low eutectic solvent is mixed with a photoinitiator and polymerized by light initiation to obtain a high-strength and tough shape memory low eutectic gel.

[0014] Preferably, the solvent is one or more of ethyl acetate, ethyl ether, dichloromethane and water.

[0015] Preferably, the reaction temperature is 0-25° C.; and the reaction time is 4-6 h.

[0016] Preferably, the reaction further comprises a step of removing the solvent, and the method of removing the solvent is preferably reduced pressure distillation.

[0017] Preferably, the temperature of the heating and mixing is 75-90° C.; and / or

[0018] The photopolymerization is carried out under ultraviolet light irradiation, and the time of the photopolymerization is 30 to 60 minutes.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The present invention discloses a first polymerizable monomer having a phenyl group, an amide group, and a cyano group on the same side chain, and a second polymerizable monomer having a vinyl group and a benzyl group. When the two are mixed, the hydrogen on the amide of the first polymerizable monomer can form hydrogen bonds with the chloride ions of the second polymerizable monomer, thereby obtaining a deep eutectic solvent with excellent temperature sensitivity, thermal stability, and ionic conductivity. After being mixed with a photoinitiator, the deep eutectic solvent undergoes in situ polymerization under the action of light. Based on the dipole-dipole interaction between the cyano groups, the cation-π interaction between the imidazolium cation and the benzene ring, the cation-oxygen interaction between the imidazolium cation and the polymer network, and the hydrogen bonding between the chloride ions and the polymer chains, a supramolecular gel-enhanced structure is formed, resulting in a deep eutectic gel with excellent mechanical strength.

[0021] This invention designs the eutectic gel structure at the molecular level. By introducing non-covalent interactions such as hydrogen bonding, dipole-dipole, and π-cation interactions, it creates a eutectic gel with supramolecular properties, significantly improving its mechanical properties. Furthermore, by adjusting the molar ratio of the first and second monomers, the mechanical strength and electrical conductivity of the eutectic gel can be adjusted to meet diverse application requirements.

[0022] Based on the characteristics of hydrogen bond dissociation at high temperature and hydrogen bond recovery at low temperature, the present invention gives the low-melting eutectic gel temperature stimulus responsiveness and shape memory properties, so that the low-melting eutectic gel has good shape memory function, and its shape memory rate is close to 100%, which can meet the needs of modern society for smart materials to meet different usage requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a diagram characterizing the memory deformation process of the shape memory eutectic gel of Example 1 of the present invention;

[0025] Figure 2 This is a comparison chart of the tensile strength of the shape memory eutectic gels of Examples 1-5 of the present invention;

[0026] Figure 3 This is a comparison chart of the toughness of the shape memory eutectic gels of Examples 1-5 of the present invention;

[0027] Figure 4 is a comparison chart of the adhesion strength of the shape memory eutectic gels of Examples 1-5 of the present invention;

[0028] Figure 5 3 is a comparison chart of the ionic conductivities of the shape memory eutectic gels of Examples 1-5 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] In a first aspect, the present invention provides a high-strength and tough shape-memory eutectic gel, which is obtained by photoinitiated polymerization of a first polymerized monomer and a second polymerized monomer; the molar ratio of the first polymerized monomer to the second polymerized monomer is 1 to 4:1 (for example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1); the first polymerized monomer is obtained by reacting 4-(2-aminoethyl)benzonitrile hydrochloride and acryloyl chloride; and the second polymerized monomer is 1-methyl-3-(4-vinylbenzyl)imidazolium chloride.

[0031] The first polymerizable monomer of the present invention has a phenyl group, an amide group, and a cyano group on the same side chain, and the second polymerizable monomer has a vinyl group and a benzyl group. After the two are mixed, the hydrogen on the amide of the first polymerizable monomer can form a hydrogen bond with the chloride ion of the second polymerizable monomer, thereby obtaining a low eutectic solvent with good temperature sensitivity, thermal stability, and ionic conductivity. After the low eutectic solvent is mixed with a photoinitiator, it undergoes in situ polymerization under the action of light. Based on the dipole-dipole interaction between cyano groups, the cation-π interaction between imidazolium cations and benzene rings, the cation-oxygen interaction between imidazolium cations and polymer networks, and the hydrogen bonding between chloride ions and polymer chains, a supramolecular gel reinforcement structure is formed to obtain a low eutectic gel with excellent mechanical strength. Based on the characteristics of hydrogen bond dissociation at high temperature and hydrogen bond recovery at low temperature, the low eutectic gel has a good shape memory function, and its shape memory rate is close to 100%.

[0032] This invention designs the eutectic gel structure at the molecular level. By introducing non-covalent interactions such as hydrogen bonding, dipole-dipole, and π-cation interactions, it creates a eutectic gel with supramolecular properties, significantly improving its mechanical properties. Furthermore, by adjusting the molar ratio of the first and second monomers, the invention can adjust the mechanical strength (tensile strength, toughness, and adhesion strength) and electrical conductivity (ionic conductivity) of the eutectic gel to meet diverse application requirements.

[0033] Based on the characteristics of hydrogen bond dissociation at high temperature and hydrogen bond recovery at low temperature, the present invention gives the low-melting eutectic gel temperature stimulus responsiveness and shape memory properties, so that the low-melting eutectic gel has good shape memory function, and its shape memory rate is close to 100%, which can meet the needs of modern society for smart materials to meet different usage requirements.

[0034] The first polymerizable monomer of the present invention is represented by the following formula (1), and the second polymerizable monomer is represented by the following formula (2).

[0035]

[0036] According to some preferred embodiments, the molar ratio of the first polymerized monomer to the second polymerized monomer is 1.5 to 3.5:1 (for example, 1.5:1, 2:1, 2.5:1, 3:1 or 3.5:1).

[0037] According to some preferred embodiments, the molar ratio of 4-(2-aminoethyl)benzonitrile hydrochloride to acryloyl chloride is 1:1 to 1.2.

[0038] According to some preferred embodiments, the photoinitiator used in the photoinitiated polymerization is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide, and 1-hydroxycyclohexyl phenyl ketone, preferably 1-hydroxycyclohexyl phenyl ketone.

[0039] According to some preferred embodiments, the amount of the photoinitiator is 0.5-1% (for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%) of the total mass of the first and second polymerized monomers. Controlling the amount of the photoinitiator within this range ensures that the first and second polymerized monomers react to produce a eutectic gel with high tensile strength and good toughness. Within this range, the greater the amount of photoinitiator used, the shorter the time for the photoinitiated polymerization reaction.

[0040] In a second aspect, the present invention provides a method for preparing the high-toughness shape memory eutectic gel according to the first aspect, the preparation method comprising:

[0041] Mixing a mixture of 4-(2-aminoethyl)benzonitrile hydrochloride, a base and a solvent with acryloyl chloride, and reacting the mixture to obtain a first polymerizable monomer;

[0042] heating and mixing the first polymerizable monomer and the second polymerizable monomer to obtain a deep eutectic solvent;

[0043] The low eutectic solvent is mixed with a photoinitiator and polymerized by light initiation to obtain a high-strength and tough shape memory low eutectic gel.

[0044] According to some preferred embodiments, the solvent is one or more of ethyl acetate, ether, dichloromethane, and water, preferably a mixed solvent of ethyl acetate and water.

[0045] According to some preferred embodiments, the reaction temperature is 0-25°C (e.g., 0°C, 5°C, 10°C, 15°C, 20°C, or 25°C); and the reaction time is 4-6 hours (e.g., 4 hours, 5 hours, or 6 hours). The first polymerizable monomer can be obtained by controlling the reaction temperature and time in the preparation process of the first polymerizable monomer of the present invention within the above ranges. Within the above ranges, the reaction temperature increases and the reaction time decreases.

[0046] According to some preferred embodiments, the reaction further comprises a step of removing the solvent, and the method of removing the solvent is preferably reduced pressure distillation.

[0047] According to some preferred embodiments, the heating and mixing temperature is 75 to 90° C. (for example, 75° C., 80° C., 85° C., or 90° C.); the heating and mixing temperature of the first polymerizable monomer and the second polymerizable monomer of the present invention can obtain a low eutectic solvent within the above range, and within the above range, the temperature increases and the time is shortened.

[0048] According to some preferred embodiments, the photopolymerization is carried out under ultraviolet light irradiation, and the photopolymerization time is 30 to 60 minutes (for example, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes).

[0049] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention is further described below with reference to embodiments.

[0050] The present invention does not specifically limit the sources of the reagents used in the examples, and they can be purchased directly or synthesized by themselves. It should be noted that the 1-methyl-3-(4-vinylbenzyl)imidazolium chloride in the examples and comparative examples of the present invention can be purchased directly or prepared by themselves. Among them, the method for preparing 1-methyl-3-(4-vinylbenzyl)imidazolium chloride by themselves comprises: mixing 15.26g of 4-vinylbenzyl chloride and 8.21g of 1-methylimidazole, stirring at 100°C for 24 hours, and obtaining 1-methyl-3-(4-vinylbenzyl)imidazolium chloride.

[0051] The preparation method of the first polymer monomer includes: dissolving 0.27 mol of 4-(2-aminoethyl)benzonitrile hydrochloride and 0.27 mol of sodium hydroxide in a mixed solvent of 200 mL of water and 135 mL of ethyl acetate, and transferring the solution to a round-bottom flask, slowly adding 270 mL of ethyl acetate solution and 0.295 mol of acryloyl chloride thereto, stirring at 0° C. for 6 hours, and removing the solvent by distillation under reduced pressure to obtain the first polymer monomer.

[0052] Example 1

[0053] A method for preparing a high-strength and tough shape memory eutectic gel comprises the following steps:

[0054] The first polymerized monomer was added to the second polymerized monomer (1-methyl-3-(4-vinylbenzyl)imidazolium chloride), wherein the molar ratio of the first polymerized monomer to the second polymerized monomer was 1.5:1, and the mixture was stirred at 75° C. for 15 minutes to form a low eutectic solvent.

[0055] A photoinitiator (1-hydroxycyclohexyl phenyl ketone) was added to the low eutectic solvent and mixed evenly, wherein the amount of the photoinitiator was 1 wt % of the low eutectic solvent. The mixture was placed in a UV crosslinker and irradiated for 30 minutes to obtain a high-strength and tough shape memory low eutectic gel.

[0056] Example 2

[0057] Compared with Example 1, the only difference is that the molar ratio of the first polymerized monomer to the second polymerized monomer is 2:1.

[0058] Example 3

[0059] Compared with Example 1, the only difference is that the molar ratio of the first polymerized monomer to the second polymerized monomer is 2.5:1.

[0060] Example 4

[0061] Compared with Example 1, the only difference is that the molar ratio of the first polymerized monomer to the second polymerized monomer is 3:1.

[0062] Example 5

[0063] Compared with Example 1, the only difference is that the molar ratio of the first polymerized monomer to the second polymerized monomer is 3.5:1.

[0064] The present invention adhered electrodes and wires to the eutectic gel prepared in Example 1 and tested its shape memory properties by electric heating. Figure 1 As shown in the figure, the low-melting eutectic gel is thermally responsive. It deforms at high temperature and its shape is fixed after cooling. After being thermally stimulated again, the shape of the gel can be quickly restored within 8 seconds, and the shape memory rate is close to 100%.

[0065] The present invention uses a tensile testing machine to test the mechanical properties of the eutectic gels prepared in Examples 1-5. The prepared eutectic gel strips are cut into long strips and loaded with a fixture at room temperature. The eutectic gel strips are then stretched at a rate of 5 mm / min to obtain their stress-strain curves. The corresponding tensile strength and toughness are calculated based on the stress-strain curves. The results are shown in FIG. Figure 2 、 Figure 3 As shown. Figure 2It can be seen that with the increase of the molar ratio of the first polymerized monomer to the second polymerized monomer, the tensile strength of the eutectic gel increases from 9.66 MPa to 17.28 MPa; Figure 3 It can be seen that with the increase of the molar ratio of the first polymerized monomer to the second polymerized monomer, the toughness of the eutectic gel increases from 15.7 MPa to 48.2 MPa; it can be seen that by regulating the molar ratio of the first polymerized monomer to the second polymerized monomer, the tensile strength and toughness of the eutectic gel can be adjusted in a large range.

[0066] The adhesion strength of the eutectic gels prepared in Examples 1-5 was tested by a lap shear test. The specific method was as follows: prior to bonding, the substrate (glass plate) was cleaned with deionized water and ethanol and completely dried at room temperature. The eutectic gel was coated on the surface of one substrate and overlapped with another. The bonded substrates were then preloaded for 12 hours to prepare adhesion test samples. The adhesion was measured on a tensile machine at a tensile speed of 50 mm / min. The adhesion strength was obtained by dividing the maximum tension at joint failure by the overlap area. The results are shown in Figure 2. Figure 4 As shown in FIG, the test results show that with the increase of the molar ratio of the first polymerized monomer to the second polymerized monomer, the adhesion strength of the eutectic gel increases from 296.5 kPa to 931.7 kPa. It can be seen that by regulating the molar ratio of the first polymerized monomer to the second polymerized monomer, the adhesion strength of the eutectic gel can be adjusted in a large range.

[0067] The present invention tests the electrical conductivity of the eutectic gels prepared in Examples 1-5 by the AC impedance method. The specific method is as follows: the eutectic gel is sandwiched between two stainless steel electrodes and an AC impedance test is performed on an electrochemical workstation with a frequency range of 1 MHz to 0.01 Hz and an amplitude of 10 mV. The ionic conductivity is calculated and the results are as follows: Figure 5 The test results show that as the molar ratio of the first polymerized monomer to the second polymerized monomer increases, the ionic conductivity of the eutectic gel decreases from 0.31 mS / cm to 0.03 mS / cm. This shows that the ionic conductivity of the eutectic gel can be adjusted over a wide range by regulating the molar ratio of the first polymerized monomer to the second polymerized monomer.

[0068] In summary, the present invention can adjust the tensile strength, toughness, adhesion strength and conductive properties of the eutectic gel within a wide range by regulating the molar ratio of the first polymerized monomer to the second polymerized monomer, which can meet different usage requirements and broaden the application scenarios of the eutectic gel.

[0069] Comparative Example 1

[0070] The method is basically the same as Example 1, except that the molar ratio of the first polymerizable monomer to the second polymerizable monomer is 1:1.

[0071] A eutectic gel can be obtained by reacting the first polymerized monomer and the second polymerized monomer in the above molar ratio, but its adhesion strength is relatively low, only 81.7 kPa.

[0072] Comparative Example 2

[0073] The method is basically the same as Example 1, except that the molar ratio of the first polymerizable monomer to the second polymerizable monomer is 5:1.

[0074] Using the above molar ratio of the first polymerized monomer and the second polymerized monomer cannot form a deep eutectic solvent, and thus cannot obtain a deep eutectic gel.

[0075] Comparative Example 3

[0076] The process is basically the same as Example 2, except that the first polymerizable monomer is N-acrylamidoacetonitrile.

[0077] A eutectic gel can be obtained by reacting N-acrylamidoacetonitrile with a second polymerizable monomer. However, since N-acrylamidoacetonitrile does not have a side chain with a benzene ring, it cannot produce a π-cationic interaction with the imidazolium cation, resulting in a decrease in mechanical properties. The tensile strength of the gel is 6.23 MPa, and the adhesion strength is 270.6 kPa, which are significantly lower than the eutectic gel prepared in the example.

[0078] Comparative Example 4

[0079] The method is basically the same as Example 2, except that the first polymerization monomer is 2-vinylbenzonitrile. It was found that 2-vinylbenzonitrile and the second polymerization monomer (1-methyl-3-(4-vinylbenzyl)imidazolium chloride) are not miscible, and thus a gel cannot be prepared.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A high-toughness shape memory eutectic gel, characterized in that: The shape memory eutectic gel is obtained by photoinitiated polymerization of a first polymerized monomer and a second polymerized monomer; the molar ratio of the first polymerized monomer to the second polymerized monomer is 1 to 4:1; the first polymerized monomer is obtained by reacting 4-(2-aminoethyl)benzonitrile hydrochloride and acryloyl chloride, and the molar ratio of 4-(2-aminoethyl)benzonitrile hydrochloride to acryloyl chloride is 1:1 to 1.2; the second polymerized monomer is 1-methyl-3-(4-vinylbenzyl)imidazolium chloride.

2. The high-toughness shape memory eutectic gel according to claim 1, characterized in that: The molar ratio of the first polymerizable monomer to the second polymerizable monomer is 1.5-3.5:

1.

3. The high-toughness shape memory eutectic gel according to claim 1, characterized in that: The photoinitiator used in the photoinitiated polymerization is one or more of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide, and 1-hydroxycyclohexylphenyl ketone.

4. The high-toughness shape memory eutectic gel according to claim 3, characterized in that: The photoinitiator is 1-hydroxycyclohexyl phenyl ketone.

5. The high-toughness shape memory eutectic gel according to claim 3, characterized in that: The amount of the photoinitiator is 0.5-1% of the total mass of the first polymerizable monomer and the second polymerizable monomer.

6. A method for preparing the high-toughness shape memory eutectic gel according to any one of claims 1 to 5, characterized in that: The preparation method comprises: Mixing a mixture of 4-(2-aminoethyl)benzonitrile hydrochloride, a base and a solvent with acryloyl chloride, and reacting the mixture to obtain a first polymerizable monomer; heating and mixing the first polymerizable monomer and the second polymerizable monomer to obtain a deep eutectic solvent; The low eutectic solvent is mixed with a photoinitiator and polymerized by light initiation to obtain a high-strength and tough shape memory low eutectic gel.

7. The preparation method according to claim 6, characterized in that The solvent is one or more of ethyl acetate, ether, dichloromethane and water.

8. The preparation method according to claim 6, characterized in that The reaction temperature is 0-25° C.; the reaction time is 4-6 h.

9. The preparation method according to claim 6, characterized in that The reaction further comprises the step of removing the solvent.

10. The preparation method according to claim 9, characterized in that The solvent was removed by distillation under reduced pressure.

11. The preparation method according to claim 6, characterized in that The heating and mixing temperature is 75-90° C.; and / or The photopolymerization is carried out under ultraviolet light irradiation, and the photopolymerization time is 30 to 60 minutes.

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