Eutectic conductive gel and method of preparation and use

Abstract

The application relates to the technical field of conductive gels, and particularly discloses a eutectic conductive gel, a preparation method and application. The eutectic conductive gel comprises 24-36 parts of lithium salt, 48-70 parts of glycerol, 3-6 parts of polyvinyl alcohol modified carbon nanotubes, 20-25 parts of methyl methacrylate, 0.8-2.0 parts of sodium carboxymethyl cellulose, 0.1-0.2 parts of a crosslinking agent, 0.5-1.0 parts of an initiator and 1-3 parts of deionized water. The eutectic conductive gel has excellent electronic conductivity, the electronic conductivity can reach 1.8*10 ‑3 S / cm, and has good mechanical properties, the tensile strength can reach more than 90 KPa, the elongation at break can reach more than 550%, and the eutectic conductive gel can still maintain stable electrical functions under compression, stretching and bending, and has wide application prospects in the field of flexible electronic devices.

Description

Technical Field

[0001] This invention relates to the field of conductive gel technology, and in particular to a eutectic conductive gel, its preparation method, and its application. Background Technology

[0002] With the continuous progress of society, the booming development of the information age, and the advancements in big data, the Internet of Things, and 5G technologies, flexible wearable electronic devices, as one of the core components for information collection and processing, have gained popularity among researchers. Flexible wearable electronic devices refer to flexible electronic devices that can be directly or indirectly closely fitted to the skin and maintain stable electrical functions under compression, stretching, and bending conditions. They can be applied in personalized healthcare, human-computer interaction, smart fabrics, energy storage, and other fields.

[0003] In recent years, electronic devices based on hydrogels have been extensively researched and developed. Hydrogels possess excellent properties such as flexibility, biocompatibility, and biotissue similarity, leading to their widespread application in numerous fields including artificial skin, drug delivery, tissue engineering, contact lenses, and wearable electronic devices. However, hydrogels suffer from poor stability, easily freezing at low temperatures and volatilizing at high temperatures. Currently, the antifreeze properties of hydrogels are mainly improved by adding inorganic salts and glycerol; however, due to the essential high salt content in water, hydrogels rapidly corrode metal electrodes. To overcome the shortcomings of hydrogels, researchers have developed ionomers. However, the high cost and certain toxicity of ionomers have limited their development. Eutectic solvents are a class of green ionic liquids, non-toxic or low-toxic, inexpensive and readily available, and possess excellent properties such as non-flammability, low vapor pressure, and good conductivity. Therefore, ionomers designed based on eutectic solvents have attracted widespread attention. However, most current ionomers based on eutectic solvents have low strength and cannot maintain stable electrical functions under compression, tension, and bending conditions. Therefore, how to obtain ionogels with high strength and high tensile properties is an urgent problem to be solved. Summary of the Invention

[0004] To address the problems of low strength and inability to maintain stable electrical properties under compression, stretching, and bending conditions in existing ionogels, this invention provides a eutectic conductive gel, its preparation method, and its applications.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] A eutectic conductive gel comprises the following raw material components in parts by weight: 24-36 parts lithium salt, 48-70 parts glycerol, 3-6 parts polyvinyl alcohol modified carbon nanotubes, 20-25 parts methyl methacrylate, 0.8-2.0 parts sodium carboxymethyl cellulose, 0.1-0.2 parts crosslinking agent, 0.5-1.0 parts initiator, and 1-3 parts deionized water.

[0007] Compared to existing technologies, the eutectic conductive gel provided by this invention uses a eutectic solvent formed by lithium salt and glycerol as the solvent and methyl methacrylate as the monomer. Under the action of an initiator and a crosslinking agent, the eutectic conductive gel is polymerized. The eutectic solvent is anchored in the polymethyl methacrylate matrix through the formation of non-covalent bonds, thereby forming a porous conductive gel. This effectively improves the compressibility, stretchability, and bendability of the conductive gel. Simultaneously, the presence of lithium salt also contributes to improving the conductivity of the gel. The conductivity of the gel is further enhanced by adding polyvinyl alcohol-modified carbon nanotubes. The eutectic solvent formed by lithium salt and glycerol increases the dispersion of polyvinyl alcohol-modified carbon nanotubes in the polymethyl methacrylate matrix, and the polyvinyl alcohol-modified carbon nanotubes have better compatibility with polymethyl methacrylate, which also helps improve the dispersibility of carbon nanotubes in the gel. Furthermore, this invention selects sodium carboxymethyl cellulose as a reinforcing agent, effectively improving the mechanical properties of the gel.

[0008] The eutectic conductive gel provided by this invention has good conductivity and mechanical strength, and can maintain stable electrical functions under compression, stretching, bending and other conditions. It solves the bottleneck problem of traditional hydrogels being prone to freezing at low temperatures and water loss at high temperatures, which can easily lead to loss of function. It has broad application prospects in the field of flexible electronic devices.

[0009] Furthermore, the preparation method of the polyvinyl alcohol modified carbon nanotubes includes the following steps:

[0010] Carbon nanotubes were added to xylene and dispersed evenly to obtain a carbon nanotube dispersion.

[0011] Polyvinyl alcohol was added to the carbon nanotube dispersion, mixed evenly, and reacted at 150℃-170℃. After cooling, solid-liquid separation and drying were performed to obtain the polyvinyl alcohol-modified carbon nanotubes.

[0012] Based on the above, the mass-to-volume ratio of the carbon nanotubes to xylene is 0.1 g:(8-12) mL.

[0013] Based on the above, the mass ratio of polyvinyl alcohol to carbon nanotubes is 1.5:1 to 2.5:1.

[0014] Based on the above, the reaction time is 2-3 hours.

[0015] Modifying carbon nanotubes with polyvinyl alcohol can effectively improve their conductivity and compatibility with polymethyl methacrylate (PMMA), thereby improving the uniformity of carbon nanotube dispersion in the conductive gel system and further enhancing the conductivity of the gel. In addition, polyvinyl alcohol-modified carbon nanotubes can also improve the thermal stability of the gel to a certain extent.

[0016] Furthermore, the lithium salt is lithium chloride.

[0017] Furthermore, the mass ratio of the lithium salt to glycerol is 1:2.0-1:2.5.

[0018] The preferred lithium salt, and the mass ratio of lithium salt to glycerol, are beneficial to improving the stability and strength of the conductive gel.

[0019] Furthermore, the mass ratio of sodium carboxymethyl cellulose to methyl methacrylate is 0.03:1-0.05:1.

[0020] Choosing sodium carboxycellulose as a reinforcing agent can effectively improve the tensile strength of conductive gels, and at the same time, it is also beneficial to improve the conductivity of the gels.

[0021] Furthermore, the crosslinking agent is potassium persulfate.

[0022] Furthermore, the initiator is N,N'-methylenebisacrylamide.

[0023] This invention also provides a method for preparing a eutectic conductive gel, comprising the following steps:

[0024] S1. Weigh each component according to the design ratio, mix the weighed lithium salt and glycerol evenly, heat to 50℃-60℃, and keep the temperature constant until the system is homogeneous and transparent to obtain a eutectic solvent.

[0025] S2, the weighed polyvinyl alcohol modified carbon nanotubes, sodium carboxymethyl cellulose, methyl methacrylate and crosslinking agent are added sequentially to the eutectic solvent and mixed evenly to obtain a gel precursor;

[0026] Dissolve the weighed initiator in deionized water to obtain an initiator solution;

[0027] S3, after adding the gel precursor to the mold, add the initiator solution and polymerize to obtain a eutectic conductive gel.

[0028] The method for preparing eutectic conductive gel provided by this invention uses readily available raw materials, has a simple process, is highly operable, is environmentally friendly, and is suitable for large-scale production applications.

[0029] Furthermore, in S3, the polymerization temperature is 85℃-95℃, and the polymerization reaction time is 5min-10min.

[0030] The present invention also provides the application of the above-mentioned eutectic conductive gel in flexible sensors.

[0031] The eutectic conductive gel provided by this invention exhibits excellent electronic conductivity, with an electronic conductivity reaching 1.8 × 10⁻⁶. -3 With a tensile strength of over 90 kPa and an elongation at break of over 550%, it can maintain stable electrical functions under compression, tension, and bending conditions, fully meeting the requirements of future wearable and soft robot applications, and has broad application prospects in the field of flexible electronic devices. Attached Figure Description

[0032] Figure 1 SEM images of the eutectic conductive gel prepared in Example 2 of this invention at different magnifications. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Example 1

[0035] This embodiment provides a method for preparing polyvinyl alcohol modified carbon nanotubes, specifically including the following steps:

[0036] Weigh 1g of carbon nanotubes and add them to 100mL of xylene. Disperse the carbon nanotubes by ultrasonication at 40W for 10min to obtain a carbon nanotube dispersion.

[0037] Weigh 2g of polyvinyl alcohol and add it to the above carbon nanotube dispersion. Stir and disperse at 350r / min for 15min, then heat to 160℃ and keep warm for 2h. Cool to room temperature, filter, dry, and grind to obtain polyvinyl alcohol modified carbon nanotubes.

[0038] This embodiment can also use other raw material ratios and reaction conditions specified in this invention to prepare polyvinyl alcohol modified carbon nanotubes. As long as the polyvinyl alcohol modified carbon nanotubes prepared are within the scope specified in this invention, they can achieve the same technical effect.

[0039] Example 2

[0040] This embodiment provides a eutectic conductive gel, comprising the following raw material components in parts by weight:

[0041] 30 parts lithium chloride, 70 parts glycerol, 4 parts polyvinyl alcohol modified carbon nanotubes, 24 parts methyl methacrylate, 1.0 part sodium carboxymethyl cellulose, 0.15 parts N,N'-methylenebisacrylamide, 0.7 parts potassium persulfate, and 2 parts deionized water.

[0042] The preparation method of the above-mentioned eutectic conductive gel includes the following steps:

[0043] S1. Weigh each component according to the design ratio, mix the weighed lithium salt and glycerol evenly, heat to 50℃-60℃, and keep the temperature constant until the system is homogeneous and transparent to obtain a eutectic solvent.

[0044] S2, add the weighed polyvinyl alcohol modified carbon nanotubes to the eutectic solvent, disperse by ultrasonication, then add sodium carboxymethyl cellulose, heat to 60°C, stir magnetically at 200 r / min for 20 min, cool to room temperature, add methyl methacrylate and N,N'-methylenebisacrylamide, heat to 40°C, stir magnetically at 300 r / min for 15 min, cool to room temperature to obtain the gel precursor;

[0045] Dissolve the weighed initiator in deionized water to obtain an initiator solution;

[0046] S3. The gel precursor is added into a cylindrical mold with a diameter of 20 mm and a thickness of 30 mm. Then, the initiator solution is poured into the mold, polymerized at 90 °C for 8 min, and dried to obtain a eutectic conductive gel.

[0047] The SEM image of the eutectic conductive gel prepared in this embodiment is shown below. Figure 1 As shown in the figure, the conductive gel has a relatively stable three-dimensional structure.

[0048] Example 3

[0049] This embodiment provides a eutectic conductive gel, comprising the following raw material components in parts by weight:

[0050] 24 parts lithium chloride, 48 parts glycerol, 3 parts polyvinyl alcohol modified carbon nanotubes, 25 parts methyl methacrylate, 0.8 parts sodium carboxymethyl cellulose, 0.1 parts N,N'-methylenebisacrylamide, 0.5 parts potassium persulfate, and 1 part deionized water.

[0051] The preparation method of the above-mentioned eutectic conductive gel includes the following steps:

[0052] S1. Weigh each component according to the design ratio, mix the weighed lithium salt and glycerol evenly, heat to 50℃-60℃, and keep the temperature constant until the system is homogeneous and transparent to obtain a eutectic solvent.

[0053] S2, add the weighed polyvinyl alcohol modified carbon nanotubes to the eutectic solvent, disperse by ultrasonication, then add sodium carboxymethyl cellulose, heat to 60°C, stir magnetically at 200 r / min for 15 min, cool to room temperature, add methyl methacrylate and N,N'-methylenebisacrylamide, heat to 40°C, stir magnetically at 300 r / min for 20 min, cool to room temperature to obtain the gel precursor;

[0054] Dissolve the weighed initiator in deionized water to obtain an initiator solution;

[0055] S3. The gel precursor is added into a cylindrical mold with a diameter of 20 mm and a thickness of 30 mm. Then, the initiator solution is poured into the mold, polymerized at 85°C for 10 min, and dried to obtain a eutectic conductive gel.

[0056] Example 4

[0057] This embodiment provides a eutectic conductive gel, comprising the following raw material components in parts by weight:

[0058] The ingredients are: 36 parts lithium chloride, 54 parts glycerol, 6 parts polyvinyl alcohol modified carbon nanotubes, 20 parts methyl methacrylate, 1.2 parts sodium carboxymethyl cellulose, 0.2 parts N,N'-methylenebisacrylamide, 1.0 part potassium persulfate, and 3 parts deionized water.

[0059] The preparation method of the above-mentioned eutectic conductive gel includes the following steps:

[0060] S1. Weigh each component according to the design ratio, mix the weighed lithium salt and glycerol evenly, heat to 50℃-60℃, and keep the temperature constant until the system is homogeneous and transparent to obtain a eutectic solvent.

[0061] S2, add the weighed polyvinyl alcohol modified carbon nanotubes to the eutectic solvent, disperse by ultrasonication, then add sodium carboxymethyl cellulose, heat to 60°C, stir magnetically at 200 r / min for 20 min, cool to room temperature, add methyl methacrylate and N,N'-methylenebisacrylamide, heat to 40°C, stir magnetically at 300 r / min for 20 min, cool to room temperature to obtain the gel precursor;

[0062] Dissolve the weighed initiator in deionized water to obtain an initiator solution;

[0063] S3. The gel precursor is added into a cylindrical mold with a diameter of 20 mm and a thickness of 30 mm. Then, the initiator solution is poured into the mold, polymerized at 95°C for 5 min, and dried to obtain a eutectic conductive gel.

[0064] Comparative Example 1

[0065] This comparative example provides a conductive hydrogel comprising the following raw material components in parts by weight:

[0066] 102 parts deionized water, 4 parts polyvinyl alcohol modified carbon nanotubes, 24 parts methyl methacrylate, 1.0 part sodium carboxymethyl cellulose, 0.15 parts N,N'-methylenebisacrylamide, and 0.7 parts potassium persulfate.

[0067] The preparation method of the above-mentioned eutectic conductive gel includes the following steps:

[0068] S1. Weigh each component according to the design ratio. Add the weighed polyvinyl alcohol modified carbon nanotubes to 80wt% deionized water and disperse by ultrasonication. Then add sodium carboxymethyl cellulose, heat to 60℃, and mix by magnetic stirring at 200r / min for 20min. Cool to room temperature, add methyl methacrylate and N,N'-methylenebisacrylamide, heat to 40℃, and mix by magnetic stirring at 300r / min for 15min. Cool to room temperature to obtain the gel precursor.

[0069] Dissolve the weighed initiator in the remaining deionized water to obtain an initiator solution;

[0070] S3. The gel precursor is added into a cylindrical mold with a diameter of 20 mm and a thickness of 30 mm. Then, the initiator solution is poured into the mold, polymerized at 90°C for 8 min, and dried to obtain a conductive hydrogel.

[0071] Comparative Example 2

[0072] This comparative example provides a eutectic conductive gel, which differs from Example 1 only in that sodium carboxymethyl cellulose is replaced with an equal amount of corn starch. The specific formulation is as follows:

[0073] 30 parts lithium chloride, 70 parts glycerol, 4 parts polyvinyl alcohol modified carbon nanotubes, 24 parts methyl methacrylate, 1.0 part corn starch, 0.15 parts N,N'-methylenebisacrylamide, 0.7 parts potassium persulfate, and 2 parts deionized water.

[0074] The preparation method of the above-mentioned eutectic conductive gel is exactly the same as that in Example 1, and will not be repeated here.

[0075] Comparative Example 3

[0076] This comparative example provides a eutectic conductive gel, which differs from Example 1 only in that methyl methacrylate is replaced with an equal amount of acrylamide. The specific formulation is as follows:

[0077] 30 parts lithium chloride, 70 parts glycerol, 4 parts polyvinyl alcohol modified carbon nanotubes, 24 parts acrylamide, 1.0 part sodium carboxymethyl cellulose, 0.15 parts N,N'-methylenebisacrylamide, 0.7 parts potassium persulfate, and 2 parts deionized water.

[0078] The preparation method of the above-mentioned eutectic conductive gel is exactly the same as that in Example 1, and will not be repeated here.

[0079] Comparative Example 4

[0080] This comparative example provides a eutectic conductive gel, which differs from Example 1 only in that the polyvinyl alcohol modified carbon nanotubes are replaced with an equal amount of unmodified carbon nanotubes. The specific formulation is as follows:

[0081] 30 parts lithium chloride, 70 parts glycerol, 4 parts carbon nanotubes, 24 parts methyl methacrylate, 1.0 part sodium carboxymethyl cellulose, 0.15 parts N,N'-methylenebisacrylamide, 0.7 parts potassium persulfate, and 2 parts deionized water.

[0082] The preparation method of the above-mentioned eutectic conductive gel is exactly the same as that in Example 1, and will not be repeated here.

[0083] conductivity test

[0084] The conductivity of the gels prepared in Examples 1-3 and Comparative Examples 1-4 was tested, and the steps were as follows:

[0085] The two ends of the gel sample were connected to the corresponding electrodes of the conductivity meter. After waiting for 3 minutes at 25°C, the data stabilized and the measurement data were recorded. The results are shown in Table 1.

[0086] Table 1. Conductivity test results

[0087] sample <![CDATA[Conductivity (×10 -3 S / cm)]]> Example 1 1.86 Example 2 1.82 Example 3 1.81 Comparative Example 1 1.15 Comparative Example 2 1.74 Comparative Example 3 1.68 Comparative Example 4 1.66

[0088] As shown in the table above, the conductivity of the gel sample prepared in Example 1 is significantly better than that of Comparative Example 1, proving that lithium chloride not only contributes to the synergistic effect of hydrogen bonding in ionomer gels but also acts as a conductive ion in the polymer. Glycerol, as a solvent, increases the contact between conductive particles. Therefore, lithium chloride and glycerol play important roles in the conductivity of the gel. The conductivity of Example 1 is significantly better than that of Comparative Example 4, proving that polyvinyl alcohol modification of carbon nanotubes results in more functional groups on the surface of the carbon nanotubes, increasing the carrier concentration and carrier migration ability. Furthermore, the conductivity of Example 1 is superior to that of Comparative Examples 1-3, demonstrating that the crosslinking system prepared in the embodiments of this invention has superior conductivity.

[0089] Mechanical performance testing

[0090] The gel samples prepared in Examples 1-3 and Comparative Examples 2-4 were subjected to tensile testing using a universal testing machine (100N) at room temperature (25℃) at a tensile rate of 50 mm / min. The tensile strength and elongation at break were calculated according to the following formulas. The test results are shown in Table 2.

[0091] Table 2 Mechanical Performance Test Results

[0092] sample Tensile strength Elongation at break Example 1 94 kPa 567％ Example 2 93 kPa 565％ Example 3 92 kPa 563％ Comparative Example 2 89 kPa 557％ Comparative Example 3 86 kPa 553％ Comparative Example 4 84 kPa 552％

[0093] As shown in the table above, Examples 1-3 all exhibit good mechanical properties. The mechanical properties of the gel sample prepared in Example 1 are significantly better than those in Comparative Example 3, indicating that the gel prepared using methyl methacrylate as a monomer has a more compact structure than the gel prepared using acrylamide as a monomer, thus resulting in superior mechanical properties. Compared to Comparative Example 4, Example 1 demonstrates that polyvinyl alcohol-modified carbon nanotubes have better dispersibility in the gel system, enhancing the interaction between the polyvinyl alcohol-modified carbon nanotubes and the gel matrix, thereby improving the mechanical properties of the gel. Therefore, the addition of methyl methacrylate and polyvinyl alcohol-modified carbon nanotubes can impart good mechanical properties to the prepared eutectic conductive gel, which is beneficial for expanding the application range of the gel.

[0094] Stability test

[0095] The stability properties of the gel samples prepared in Example 1 and Comparative Example 1 were tested.

[0096] The mass loss of the gel samples prepared in Example 1 and Comparative Example 1 at 100°C every 4 hours was tested using a thermogravimetric analyzer (TG). The results are shown in Table 3.

[0097] Table 3 Stability Test Results

[0098]

[0099] As can be seen from the table above, the eutectic conductive gel prepared in Example 1 lost only 8% of its initial mass after being kept at 100°C for 24 hours, while the hydrogel prepared in Comparative Example 1 lost about 70% of its mass after 24 hours. This shows that the stability of the eutectic conductive gel prepared in this example is significantly better than that of the hydrogel, which can effectively solve the problem of poor stability of existing hydrogels.

[0100] In summary, the eutectic conductive gel provided by this invention has a dense three-dimensional network structure, excellent mechanical properties, superior conductivity, and good long-term stability. It has broad application prospects in the field of flexible electronic devices, and the raw materials are widely available. The preparation method is simple and suitable for large-scale production and application, thus having high practical value.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a eutectic conductive gel in a flexible sensor, characterized in that, The eutectic conductive gel is made from the following raw material components in parts by weight: 24-36 parts lithium salt, 48-70 parts glycerol, 3-6 parts polyvinyl alcohol modified carbon nanotubes, 20-25 parts methyl methacrylate, 0.8-2.0 parts sodium carboxymethyl cellulose, 0.1-0.2 parts crosslinking agent, 0.5-1.0 parts initiator, and 1-3 parts deionized water; The eutectic solvent formed by the lithium salt and glycerol is used as the solvent for preparing the eutectic conductive gel.

2. The application as described in claim 1, characterized in that, The preparation method of the polyvinyl alcohol modified carbon nanotubes includes the following steps: Carbon nanotubes were added to xylene and dispersed evenly to obtain a carbon nanotube dispersion. Polyvinyl alcohol was added to the carbon nanotube dispersion, mixed evenly, and reacted at 150℃-170℃. After cooling, solid-liquid separation and drying were performed to obtain the polyvinyl alcohol-modified carbon nanotubes.

3. The application as described in claim 2, characterized in that, The mass-to-volume ratio of the carbon nanotubes to xylene is 0.1 g: (8-12) mL; and / or The mass ratio of polyvinyl alcohol to carbon nanotubes is 1.5:1 to 2.5:1; and / or The reaction time is 2-3 hours.

4. The application as described in claim 1, characterized in that, The lithium salt is lithium chloride.

5. The application as described in claim 1 or 4, characterized in that, The mass ratio of the lithium salt to glycerol is 1:2.0-1:2.

5.

6. The application as described in claim 1, characterized in that, The mass ratio of sodium carboxymethyl cellulose to methyl methacrylate is 0.03:1-0.05:

1.

7. The application as described in claim 1, characterized in that, The crosslinking agent is N,N'-methylenebisacrylamide; and / or The initiator is potassium persulfate.

8. The application according to any one of claims 1-7, characterized in that, The preparation method of the eutectic conductive gel includes the following steps: S1. Weigh each component according to the design ratio, mix the weighed lithium salt and glycerol evenly, heat to 50℃-60℃, and keep the temperature constant until the system is homogeneous and transparent to obtain a eutectic solvent. S2, the weighed polyvinyl alcohol modified carbon nanotubes, sodium carboxymethyl cellulose, methyl methacrylate and crosslinking agent are added sequentially to the eutectic solvent and mixed evenly to obtain a gel precursor; Dissolve the weighed initiator in deionized water to obtain an initiator solution; S3, after adding the gel precursor to the mold, add the initiator solution and polymerize to obtain a eutectic conductive gel.

9. The application as described in claim 8, characterized in that, In S3, the polymerization temperature is 85℃-95℃, and the polymerization reaction time is 5min-10min.

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