A co-polymerized double network conductive hydrogel and a preparation method and application thereof

Abstract

The purpose of this invention is to address the shortcomings of existing hydrogel material technologies by providing a method for preparing and applying a copolymerized dual-network conductive hydrogel. The dual-network conductive hydrogel provided by this invention combines high toughness and moisture retention. Chemical cross-linking of the raw materials imparts high tensile strength and elasticity to the hydrogel. Furthermore, glycerol is introduced during the hydrogel preparation process, serving as both a reaction solvent and a humectant to enhance the hydrogel's moisture retention properties. In summary, the hydrogel material of this invention exhibits high tensile and load-bearing properties, ultra-fast self-healing properties, and high conductivity. The performance of this hydrogel material is further improved by doping with different media, enabling it to be used in flexible electronic devices and wearable devices. Specifically, doping with conductive media allows for the fabrication of flexible electronic devices such as electrochemical sensors, strain sensors, and supercapacitors.

Description

Technical Field

[0001] This invention belongs to the field of flexible materials technology, and specifically relates to a hydrogel, its preparation method, and its application. Background Technology

[0002] Flexible smart materials, also known as flexible responsive materials, are synthetic materials possessing one or more properties that can be altered by external stimuli, such as stress, temperature, humidity, pH, electric or magnetic fields, light, or chemicals. Due to their stimulus-responsive nature, smart materials have become the foundation for numerous applications, including flexible sensors, actuators, biomimetic materials, molecular self-assembly, smart deformable materials, wearable devices, and biopolysaccharide materials, finding wide application in scientific research and daily life.

[0003] Hydrogels are a type of flexible smart material. They are hydrophilic three-dimensional network polymers that are insoluble in water but can absorb a large amount of water. Currently, hydrogels have the following problems: (1) Low strength: Single network hydrogels or physically cross-linked hydrogels have low extensibility, low mechanical strength, low fatigue resistance, and low aging resistance, which greatly limits their service life; (2) Single function: Some hydrogels have outstanding performance in a certain aspect, such as only having self-healing properties or magnetic field responsiveness, which greatly limits their application areas; (3) Cumbersome preparation methods: Some hydrogels require multi-step chemical synthesis of polymer raw materials, and some hydrogels need to be obtained by direct monomer polymerization at a certain temperature. The polymerization process may require UV light initiation or catalyst initiation, which inevitably introduces small molecule impurities into the hydrogel, making it difficult to put into practical use and the cost of large-scale use is too high; (4) Unsuitable for processing: Hydrogels must have suitable processing methods to be put into practical use. Some hydrogels are too strong or too weak, so they are difficult to process. Some hydrogels will have their function or structure destroyed during processing.

[0004] Therefore, developing a bi-mesh hydrogel that is simple to prepare and has excellent mechanical and electrical properties is of great significance. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing hydrogel material technologies by providing a method for preparing and applying a copolymerized dual-network conductive hydrogel. The dual-network conductive hydrogel provided by this invention combines high toughness and moisturizing ability. Chemical cross-linking of raw materials imparts high tensile strength and elasticity to the hydrogel. The raw material used, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), is an anionic vinyl monomer containing hydrophilic sulfonic acid functional groups and nonionic amide groups. The sulfonic acid groups give the hydrogel ion exchange properties, and the active carbon-carbon double bonds facilitate polymerization. To improve the flexibility of the hydrogel, hydroxyethyl methacrylate is added to construct a dual-network hydrogel. Hydroxyethyl methacrylate contains hydroxyl groups, which form hydrogen bonds in the hydrogel system, further enhancing the flexibility. Simultaneously, the presence of hydrogen bonds can dissipate the energy of external stress, improving the elastic properties of the hydrogel. Glycerin is introduced during the hydrogel preparation process; glycerin acts as both a reaction solvent and a moisturizer, improving the moisturizing properties of the hydrogel. In summary, the hydrogel material of this invention possesses high tensile and load-bearing properties, ultra-fast self-healing properties, and high conductivity. The properties of this hydrogel material are further improved by doping it with different media, making it suitable for use as flexible electronic devices and wearable devices. Specifically, doping with conductive media allows it to be used to fabricate flexible electronic devices such as electrochemical sensors, strain sensors, and supercapacitors.

[0006] To achieve this objective, the present invention employs the following technical solution:

[0007] In a first aspect, the present invention provides a dual-network conductive hydrogel, wherein the structure of the dual-network conductive hydrogel is composed of a first network and a second network;

[0008] The first network is a network formed by chemical crosslinking of any two of the three polymer monomers: methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and hydroxyethyl methacrylate.

[0009] The second network is formed by chemically cross-linking another of the three polymer monomers mentioned above with the first network.

[0010] Furthermore, in the aforementioned dual-network conductive hydrogel, the molar ratio of methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and hydroxyethyl methacrylate is 1–2:1:0.5–2; for example, it can be 1:1:2, 1.5:1:0.5, 1:1:0.5, or 2:1:0.5.

[0011] In this invention, by adjusting the molar ratio of the three polymeric monomers, the cohesive and adhesive forces of the prepared dual-network hydrogel are balanced, resulting in superior flexibility.

[0012] Furthermore, in the aforementioned dual-network conductive hydrogel, the methacrylamide in the polymer monomer can also be other acrylamide derivatives, such as acrylamide, diacetone acrylamide, dimethylaminopropyl acrylamide, N-tert-butylacrylamide, N-ethylacrylamide, N-hydroxymethylacrylamide, etc.

[0013] Furthermore, in the aforementioned dual-network conductive hydrogel, the 2-acrylamido-2-methylpropanesulfonic acid in the polymer monomer can also be other sulfonic acid derivatives, such as 3-sulfopropyl acrylate, sodium methacrylate, etc.

[0014] Furthermore, in the aforementioned dual-network conductive hydrogel, the hydroxyethyl methacrylate in the polymer monomer can also be hydroxypropyl methacrylate or an acrylate derivative, used to form hydrogen bonds and improve the flexibility of the hydrogel.

[0015] Furthermore, the aforementioned dual-network conductive hydrogel can also incorporate glycerin as a humectant.

[0016] Furthermore, the aforementioned dual-network conductive hydrogel can also incorporate a conductive medium.

[0017] Furthermore, the aforementioned dual-network conductive hydrogel uses methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and hydroxyethyl methacrylate as monomers, and is obtained by one-step polymerization.

[0018] In a second aspect, the present invention provides a method for preparing the dual-network conductive hydrogel described in the first aspect:

[0019] The polymeric monomers methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and hydroxyethyl methacrylate were mixed with water, glycerol, a crosslinking agent, and an initiator. Under an inert gas atmosphere, stirring, and heating conditions, a dual-network conductive hydrogel was prepared in one step.

[0020] Preferably, in the above preparation method, the amount of water added is 40%-70% of the total mass of the hydrogel and water, wherein the total mass of the hydrogel is the sum of the masses of the three polymer monomers used to prepare the hydrogel, for example, it can be 40%, 50%, 60%, or 70%.

[0021] Preferably, in the above preparation method, the amount of glycerol added is 6.0%-20% of the total mass of the hydrogel and water, for example, 6.0%, 8.0%, 10%, 15%, or 20%.

[0022] Preferably, in the above preparation method, the crosslinking agent is N,N'-methylenebisacrylamide.

[0023] Preferably, in the above preparation method, the amount of crosslinking agent added is 0.15%-1.6% of the total mass of the hydrogel and water, for example, it can be 0.15%, 0.4%, 0.8%, 1.2%, or 1.6%.

[0024] Preferably, in the above preparation method, the initiator is potassium persulfate.

[0025] Preferably, in the above preparation method, the amount of initiator added is 0.4%-1.8% of the total mass of the hydrogel and water, for example, it can be 0.4%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, or 1.8%.

[0026] Preferably, in the above preparation method, the raw materials further include a conductive medium, wherein the conductive medium is one or more of inorganic salts, carbon materials, metal nanomaterials and ionic liquids.

[0027] Preferably, in the above preparation method, the amount of conductive medium added is 0.01%-4.0% of the total mass of hydrogel and water, for example, it can be 0.01%, 0.05%, 0.1%, 0.5%, 1.0%, 2.0%, 3.0%, or 4.0%.

[0028] Preferably, in the above preparation method, the stirring time of the reaction is 45-90 min, for example, 45 min, 50 min, 55 min, 60 min, 70 min, 80 min, or 90 min.

[0029] Preferably, in the above preparation method, the reaction heating temperature is 60-80℃, for example, 60℃, 70℃, or 80℃.

[0030] Preferably, the above preparation method involves drying the resulting dual-network conductive hydrogel.

[0031] Thirdly, the present invention provides an application of the dual-network conductive hydrogel described in the first aspect, wherein the hydrogel is used as a biosensor and a supercapacitor in flexible electronic devices.

[0032] For example, coating a hydrogel with glucose oxidase allows for the determination of glucose concentration; coating it with uricase allows for the determination of uric acid concentration; and coating it with peroxidase allows for the determination of hydrogen peroxide concentration. Tyrosinase can also be immobilized on the hydrogel to test for phenolic compounds in the environment. Furthermore, by modifying the hydrogel, it can also be used to determine the concentration of heavy metal pollutants in the environment.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. This invention uses a one-pot method to directly react polymer monomers to prepare a dual-network conductive hydrogel, saving many cumbersome and expensive preparation processes and personnel operations.

[0035] 2. The present invention uses hydroxyethyl methacrylate as one of the polymer monomers. Due to the presence of hydroxyl groups, the mechanical properties of the polymer can be effectively improved, and hydrogen bonds can be generated, which can further improve the moisturizing properties of the hydrogel.

[0036] 3. The hydrogel of the present invention has a tensile strength of up to 0.3 MPa, an elongation at break of up to 731%, a self-healing speed of 1-2 seconds, and a healing rate of up to 85%.

[0037] 4. The hydrogel of the present invention, after being doped with various conductive media, can be widely used in the fields of electrochemical sensors and supercapacitors.

[0038] 5. This invention not only improves the preparation efficiency and gelation properties of hydrogels, but also broadens the application fields of hydrogels. Attached Figure Description

[0039] Figure 1 This is the synthesis route of the hydrogel in Example 1.

[0040] Figure 2 The infrared spectra of the monomers used in Example 1 and the hydrogels prepared therefrom are shown.

[0041] Wherein, a is 2-acrylamido-2-methylpropanesulfonic acid, b is methacrylamide, c is hydroxyethyl methacrylate, and d is the prepared hydrogel.

[0042] Figure 3 This is a scanning electron microscope image of the hydrogel prepared in Example 1.

[0043] Figure 4 These are the XRD data of the hydrogel prepared in Example 1.

[0044] Figure 5 This is a standard curve showing the relationship between the response current of the glucose sensor prepared in Example 2 and the glucose concentration.

[0045] Figure 6 This is a standard curve showing the relationship between the sensor response current and diclofenac sodium concentration prepared in Example 3.

[0046] Figure 7 This is the standard curve showing the relationship between the sensor response current and the concentration of olphenamyl prepared in Example 3.

[0047] Figure 8 This is the standard curve showing the relationship between the sensor response current and the paracetamol concentration prepared in Example 3.

[0048] Figure 9This is the standard curve showing the relationship between the sensor response current and hydrogen peroxide concentration prepared in Example 4.

[0049] Figure 10 This is a tensile property test of the hydrogel prepared in Example 5.

[0050] Figure 11 The hydrogel prepared in Example 5 is used as a supercapacitor for specific capacitance testing.

[0051] Figure 12 This is a tensile strength test of the hydrogel prepared in Example 6. Detailed Implementation

[0052] Example 1

[0053] A method for preparing a dual-network conductive hydrogel is as follows:

[0054] Under a nitrogen atmosphere, 2.0724 g of 2-acrylamido-2-methylpropanesulfonic acid (10 mmol), 0.8511 g of methacrylamide (10 mmol), 1.3015 g of hydroxyethyl methacrylate (10 mmol), 5 g of deionized water, and 0.6305 g of glycerol were weighed into a two-necked flask. Then, 0.05 g of potassium persulfate was added as an initiator, 0.02 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.22 g of LiCl was added as a humectant, and the mixture was reacted at 60 °C for 1 hour. Before the reaction reached its endpoint, the hydrogel was injected into a mold and allowed to dry naturally. After 72 hours, it was removed and its performance was tested.

[0055] The hydrogel prepared under these conditions exhibits high tensile strength (up to 700%), load-bearing capacity (0.3 MPa), ultrafast self-healing ability (2 s), and high electrical conductivity (40 Ω). After being cut, the self-healing time is 1 second, and its tensile strength reaches more than 85% of that of the uncut hydrogel.

[0056] Example 2

[0057] A method for preparing a dual-network conductive hydrogel is as follows:

[0058] Under a nitrogen atmosphere, 2.0724 g of 2-acrylamido-2-methylpropanesulfonic acid (10 mmol), 0.8511 g of methacrylamide (10 mmol), 1.3015 g of hydroxyethyl methacrylate (10 mmol), 5 g of deionized water, and 0.6305 g of glycerol were weighed into a two-necked flask. Then, 0.05 g of potassium persulfate was added as an initiator, 0.02 g of N,N'-methylenebisacrylamide as a crosslinking agent, and 0.22 g of LiCl as a conductive medium. The reaction was carried out at 60 °C for 1 hour.

[0059] Once the reaction reaches its endpoint, 1.0 μL of hydrogel is drop-coated onto a clean glassy carbon electrode surface, allowed to dry naturally, and then its performance is tested.

[0060] The evaluation steps for dual-network conductive hydrogels as biosensors are as follows:

[0061] (1) Add 0.05% chitosan acetic acid solution (10 μL) to the glassy carbon surface coated with hydrogel;

[0062] (2) Add 2.0 mg / mL glucose oxidase solution (10 μL) to the surface of chitosan;

[0063] (3) Connect the electrodes and test using an electrochemical workstation.

[0064] Example 3

[0065] A method for preparing a dual-network conductive hydrogel is as follows:

[0066] Under a nitrogen atmosphere, 2.0724 g of 2-acrylamido-2-methylpropanesulfonic acid (10 mmol), 0.8511 g of methacrylamide (10 mmol), 1.3015 g of hydroxyethyl methacrylate (10 mmol), 5 g of deionized water, and 0.6305 g of glycerol were weighed into a two-necked flask. Then, 0.05 g of potassium persulfate was added as an initiator, 0.02 g of N,N'-methylenebisacrylamide as a crosslinking agent, and 2 mg of carbon nanotubes as a conductive ionic medium. The reaction was carried out at 60 °C for 1 hour. Before the reaction reached its endpoint, the hydrogel was injected into a mold and allowed to dry naturally. After 72 hours, it was removed and its performance was tested.

[0067] The evaluation steps for using stretchable dual-network conductive hydrogels as biosensors are as follows:

[0068] (1) 5.0 μL of the hydrogel that has been reacted in this embodiment and has not been dried is dropped onto the clean glassy carbon electrode surface;

[0069] (2) After the hydrogel dries, connect the electrode and test it using an electrochemical workstation.

[0070] Example 4

[0071] Under a nitrogen atmosphere, 2.0724 g of 2-acrylamido-2-methylpropanesulfonic acid (10 mmol), 0.8511 g of methacrylamide (10 mmol), 1.3015 g of hydroxyethyl methacrylate (10 mmol), 5 g of deionized water, and 0.6305 g of glycerol were weighed into a two-necked flask. Then, 0.05 g of potassium persulfate was added as an initiator, 0.02 g of N,N'-methylenebisacrylamide as a crosslinking agent, and 2 mg of carbon black as a conductive ionic medium. The reaction was carried out at 60 °C for 1 hour. Before the reaction reached its endpoint, the hydrogel was injected into a mold and allowed to dry naturally. After 72 hours, it was removed and its performance was tested.

[0072] The evaluation steps for using stretchable dual-network conductive hydrogels as biosensors are as follows:

[0073] (1) 5.0 μL of the hydrogel that has been reacted in this embodiment and has not been dried is dropped onto the clean glassy carbon electrode surface;

[0074] (2) After the hydrogel dries, connect the electrode and test it using an electrochemical workstation.

[0075] Example 5

[0076] Under a nitrogen atmosphere, 2.0724 g of 2-acrylamido-2-methylpropanesulfonic acid (10 mmol), 0.8511 g of methacrylamide (10 mmol), 1.3015 g of hydroxyethyl methacrylate (10 mmol), 5 g of deionized water, and 0.6305 g of glycerol were weighed into a two-necked flask. Then, 0.05 g of potassium persulfate was added as an initiator, 0.02 g of N,N'-methylenebisacrylamide as a crosslinking agent, and 2 mg of graphene oxide as a conductive ionic medium. The reaction was carried out at 60 °C for 1 hour. Before the reaction reached its endpoint, the hydrogel was injected into a mold and allowed to dry naturally. After 72 hours, it was removed and its performance was tested.

[0077] The evaluation steps for using stretchable dual-network conductive hydrogels as supercapacitors are as follows:

[0078] For the specific capacitance test, first weigh 8 mg of graphene oxide-doped hydrogel and place it in an agate mortar. Add 10 μL of ethanol and 10 μL of 5% polytetrafluoroethylene to the mortar and grind it thoroughly in the agate mortar until it becomes a gypsum-like substance. Then transfer it to a 3 cm × 1 cm nickel foam to prepare a nickel foam electrode. Place the electrode on a tablet press and pressurize it at 0.1 MPa for 2 minutes before testing.

[0079] Example 6

[0080] Under a nitrogen atmosphere, 2.0724 g of 2-acrylamido-2-methylpropanesulfonic acid (10 mmol), 0.8511 g of methacrylamide (10 mmol), 1.3015 g of hydroxyethyl methacrylate (10 mmol), 5 g of deionized water, and 0.6305 g of glycerol were weighed into a two-necked flask. Then, 0.05 g of potassium persulfate was added as an initiator, 0.02 g of N,N'-methylenebisacrylamide as a crosslinking agent, and 2 mg of silver nanoparticles were added as a conductive ionic medium. The reaction was carried out at 60 °C for 1 hour. Before the reaction reached its endpoint, the hydrogel was injected into a mold and allowed to dry naturally. After 72 hours, it was removed and its performance was tested.

[0081] Example 7

[0082] Under a nitrogen atmosphere, 4.1448 g of 2-acrylamido-2-methylpropanesulfonic acid (20 mmol), 0.8511 g of methacrylamide (10 mmol), 0.6508 g of hydroxyethyl methacrylate (5 mmol), 3.7645 g of deionized water, and 0.5647 g of glycerol were weighed into a two-necked flask. Then, 0.03764 g of potassium persulfate was added as an initiator, 0.01412 g of N,N'-methylenebisacrylamide as a crosslinking agent, and 0.9411 mg of silver nanoparticles as a conductive ionic medium. The reaction was carried out at 80 °C for 45 min. Before the reaction reached its endpoint, the hydrogel was injected into a mold and dried naturally. After 60 hours, it was removed, yielding the final product.

[0083] Example 8

[0084] Under a nitrogen atmosphere, 2.0724 g of 2-acrylamido-2-methylpropanesulfonic acid (10 mmol), 0.8511 g of methacrylamide (10 mmol), 2.603 g of hydroxyethyl methacrylate (20 mmol), 12.8952 g of deionized water, and 3.6843 g of glycerol were weighed into a two-necked flask. Then, 0.3316 g of potassium persulfate was added as an initiator, 0.2947 g of N,N'-methylenebisacrylamide as a crosslinking agent, and 0.7367 g of silver nanoparticles as a conductive ionic medium. The reaction was carried out at 70 °C for 90 min. Before the reaction reached its endpoint, the hydrogel was injected into a mold and dried naturally. After 60 hours, it was removed, yielding the final product.

[0085] In the above embodiments, the methacrylamide in the polymerizing monomer can also be other acrylamide derivatives, such as acrylamide, diacetone acrylamide, dimethylaminopropyl acrylamide, N-tert-butylacrylamide, N-ethylacrylamide, N-hydroxymethylacrylamide, etc. The 2-acrylamido-2-methylpropanesulfonic acid in the polymerizing monomer can also be other sulfonic acid derivatives, such as 3-sulfopropyl acrylate, sodium methacrylate, etc. The hydroxyethyl methacrylate in the polymerizing monomer can also be hydroxypropyl methacrylate or an acrylate derivative, used to form hydrogen bonds and improve the flexibility of the hydrogel.

Claims

1. A conductive hydrogel, characterized in that, Its preparation method is as follows: The conductive hydrogel was prepared in one step by mixing the polymer monomers methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid and hydroxyethyl methacrylate with water, glycerol, conductive medium, crosslinking agent and initiator under an inert gas atmosphere, stirring and heating. The molar ratio of methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid and hydroxyethyl methacrylate is 1:1:1; The conductive medium is LiCl, carbon nanotubes, carbon black, or graphene oxide. The total mass of the hydrogel is the sum of the masses of the three polymeric monomers used to prepare the hydrogel; The amount of water added is 40%-70% of the total mass of the hydrogel and water; The amount of glycerol added is 6.0%-20% of the total mass of the hydrogel and water; The crosslinking agent is N,N'-methylenebisacrylamide; the amount of crosslinking agent added is 0.15%-1.6% of the total mass of the hydrogel and water. The initiator is potassium persulfate; the amount of initiator added is 0.4%-1.8% of the total mass of the hydrogel and water. The amount of conductive medium added is 0.01%-4.0% of the total mass of hydrogel and water.

2. The conductive hydrogel according to claim 1, characterized in that, The stirring time is 45-90 min; the reaction heating temperature is 60-80 ℃.

3. The application of the conductive hydrogel according to any one of claims 1 to 2, characterized in that, The hydrogel is used as a supercapacitor in flexible electronic devices.

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