Graphene oxide-based hydrogel material as well as room-temperature rapid preparation method and application thereof

Abstract

The invention belongs to the field of high polymer materials, and relates to a preparation method and application of graphene oxide-based conductive hydrogel capable of being rapidly prepared at room temperature. The preparation method comprises the following steps: adding a monomer, an initiator, a reducing agent and a cross-linking agent into a graphene oxide aqueous solution, uniformly mixing, transferring an obtained precursor into a mold, and standing at room temperature to obtain the conductive hydrogel. The graphene oxide-based conductive hydrogel prepared by the invention not only has green and environment-friendly preparation conditions and simple and feasible method, but also has excellent comprehensive properties, such as excellent mechanical strength, good conductivity and strain induced resistance characteristic, and can be widely applied to the fields of flexible strain sensors, bionic electronic skin and the like.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials and relates to a graphene oxide-based hydrogel material and a room temperature rapid preparation method and application thereof. Background Art

[0002] Conductive hydrogel is a new type of material that combines the "soft and wet" properties of hydrogels with the conductivity of conductive materials. Therefore, it has been widely used in high-end fields such as wearable electronic devices, flexible sensors, and electronic skin. However, its traditional preparation method has obvious defects: it usually relies on a high temperature (over 45 degrees Celsius) to trigger the process, which is not only time-consuming (several hours), but also complicated and sometimes requires the use of additional energy sources. This type of preparation method has limitations, which significantly hinders the further development of hydrogel materials and their industrial application in the field of high-precision and cutting-edge technologies. In view of this, developing a method for rapid preparation of hydrogels at room temperature is not only an urgent task in current scientific research work, but also of vital significance for broadening its application fields.

[0003] To address the above problems, researchers have adopted a variety of strategies: constructing redox reaction systems, developing new technologies such as nanoscale autocatalytic mechanisms, and thus achieving rapid preparation of hydrogels at room temperature. 3+ and Al 3+ The formation of coordination bonds with the carboxyl groups on carboxymethyl chitosan achieves rapid gelation of the hydrogel (<10 seconds), and the hydrogel exhibits good self-healing ability, adaptability and temperature responsiveness. Yang et al. used the dynamic redox system of tannic acid-silver to successfully induce the decomposition of ammonium persulfate at room temperature, triggering the free radical polymerization of acrylamide monomers to prepare multifunctional polyacrylamide@cellulose nanocrystals / tannic acid-silver nanocomposite hydrogel. The gel can be formed quickly at room temperature (~30 seconds). Although these methods have overcome the technical difficulties of traditional gel preparation processes to a certain extent, their preparation process is still very complicated, the system is specific, and is accompanied by certain biological toxicity. The above deficiencies and disadvantages limit its development and further application in fields such as electronic skin.

[0004] Therefore, developing a simple, efficient, environmentally friendly hydrogel system that can be quickly prepared at room temperature is one of the technical difficulties that technicians in this field need to solve urgently. Summary of the invention

[0005] In view of this, the purpose of the present invention is to address the problems existing in the prior art and provide a new method for rapidly preparing hydrogel materials at room temperature and its application. Specifically, the present invention cleverly uses a composite system of graphene oxide and a reducing agent to induce graphene oxide to generate free radicals during the reaction process, thereby initiating monomer polymerization without the introduction of energy. This innovation not only overcomes the need for high-temperature reactions in traditional preparation methods, but also achieves rapid preparation of hydrogels at room temperature (5s-600s), greatly improving preparation efficiency.

[0006] Furthermore, the mechanical properties of hydrogel materials can also be improved by introducing graphene oxide.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present invention is as follows: a method for quickly preparing a hydrogel at room temperature, the method specifically comprising: adding acrylamide monomers and acrylic acid monomers to a graphene oxide aqueous solution, stirring and dissolving them to obtain a uniform solution; adding a reducing agent, a cross-linking agent, and an initiator, stirring and dissolving them, pumping bubbles and pouring them into a mold, and standing at room temperature to obtain a graphene oxide-based hydrogel material; wherein the mass of the reducing agent is 1 to 100 times the mass of the graphene oxide; the reducing agent is at least one of sodium borohydride, vitamin C, and vitamin E; the ratio of the mass of graphene oxide to the total mass of the monomers is 1 to 10:1000, and the water content in the reaction system accounts for 65-75wt%.

[0008] In certain embodiments of the present invention, the following scheme is adopted: 1 to 200 parts by weight of ascorbic acid, 0.1 to 30 parts by weight of acrylic acid monomer, 0.1 to 30 parts by weight of acrylamide monomer, 0.001 to 1 parts by weight of hyperbranched polysiloxane and 0.01 to 10 parts by weight of initiator are added to an aqueous solution containing 0.001 to 100 parts by weight of graphene oxide, and the mixture is uniformly mixed and then the reaction is initiated at room temperature for 5 to 600 seconds to obtain a graphene oxide-based hydrogel; In the present invention, the acrylic monomer is acrylic acid, methyl acrylate, lauryl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate or methacrylic acid; the acrylamide monomer is acrylamide, N-isopropyl acrylamide, N-hydroxymethyl acrylamide, N,N-dimethyl acrylamide or methacrylamide.

[0009] In the present invention, the branching degree of the hyperbranched polysiloxane is 0.6-0.8, the vinyl molar content is 12.5-100%, and the alkyl molar content is 0%-87.5%. The double bonds in the structure of the hyperbranched polysiloxane can participate in free radical polymerization, and the characteristics of the multifunctional groups make it a chemical crosslinking point, which has a promoting effect on the rapid formation of a polymer crosslinking network. At the same time, the adjustability of the end group ratio also gives it the ability to flexibly regulate the preparation time of the hydrogel.

[0010] In the present invention, the initiator is one of potassium persulfate, ammonium persulfate and sodium persulfate.

[0011] Another object of the present invention is to provide a hydrogel prepared by the above method, which can optimize its mechanical and electrical properties by regulating the content of graphene oxide and reducing agent, and has great potential application value in the field of flexible sensing (human limb movement) under different conditions.

[0012] It can be seen from the above technical solutions that, compared with the prior art, the present invention provides a hydrogel method and application that is mechanically strong, simple to prepare, and can be quickly prepared at room temperature, and has the following excellent effects: The graphene oxide-based hydrogel prepared by the present invention has fast and controllable room temperature gelation ability (5s-600s), excellent and balanced mechanical properties (tensile strength: 157kPa, elongation at break: 2350%, fracture energy: 2.66MJm -3 ), electrical properties (1.24S / m) and strain sensing performance (maximum GF is 9.48, greater than 2000%).

[0013] In summary, the preparation method of graphene oxide-based hydrogel material proposed in the present invention is green and environmentally friendly, simple and easy, and has low production cost. The prepared hydrogel material has superior mechanical properties and excellent flexible sensing properties, and has great potential application value in the field of human motion monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0015] Figure 1 Digital photos of graphene oxide hydrogels prepared in Example 5 and Comparative Example 2.

[0016] Figure 2 The tensile stress-strain curves of the graphene oxide hydrogels prepared in Example 5, Example 6, Example 9 and Example 11 are shown.

[0017] Figure 3 This is a macroscopic effect diagram of the stretching of the graphene oxide hydrogel prepared in Example 5.

[0018] Figure 4 Infrared thermal imaging of graphene oxide hydrogel prepared in embodiment 5 at room temperature.

[0019] Figure 5 Real-time relative change curve of resistance of the graphene oxide hydrogel prepared in embodiment 5 corresponding to the deformation of the hydrogel induced by joint movement (elbow).

[0020] Figure 6 Demonstration photograph showing that the brightness of the graphene oxide hydrogel-connected LED light prepared in embodiment 5 changes significantly with tensile deformation.

[0021] Figure 7 Digital photographs showing the bonding properties of five prepared graphene oxide hydrogels to different substrates. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The word "embodiment" used here as an "exemplary" does not necessarily mean that any embodiment described is superior to or better than other embodiments. Unless otherwise specified, the performance index tests in the embodiments of this application are performed using conventional test methods in the art. It should be understood that the terms described in this application are only used to describe specific implementation methods and are not used to limit the content disclosed in this application.

[0024] Unless otherwise specified, the technical and scientific terms used in this document have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0025] In order to better illustrate the content of the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0026] Under the premise of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of the present application.

[0027] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0028] Embodiment 1 10 mg of graphene oxide and 19 ml of water were added to a beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 9 g of acrylamide monomer and 1 g of acrylic acid monomer were added to the graphene oxide solution and continued to stir for 30 minutes; then 0.1 ml of cross-linking agent was added to the above solution. 0.15 g of sodium sulfite, a reducing agent, was weighed and added to the above solution and continued to stir for 15 minutes; finally, 0.6 ml of potassium persulfate, an initiator, was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold, and the graphene oxide composite hydrogel was obtained after standing at room temperature for a period of time. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0029] Embodiment 2 20 mg of graphene oxide and 28 ml of water were added to a beaker, and magnetic stirring was performed for 20 minutes to make the graphene oxide solution evenly dispersed; then 8 g of acrylamide monomer and 2 g of methacrylic acid monomer were added to the graphene oxide solution and continued to stir for 30 minutes; then 0.3 ml of cross-linking agent was added to the above solution. 0.3 g of sodium sulfite, a reducing agent, was weighed and added to the above solution and continued to stir for 15 minutes; finally, 1.2 ml of potassium persulfate, an initiator, was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold, and the graphene oxide composite hydrogel was obtained after standing at room temperature for a period of time. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0030] Embodiment 3 10 mg of graphene oxide and 19 ml of water were added to a beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 5 g of methacrylamide monomer and 5 g of methacrylic acid monomer were added to the graphene oxide solution and continued to stir for 30 minutes; then 0.15 ml of cross-linking agent was added to the above solution. 0.15 g of sodium borohydride, a reducing agent, was weighed and added to the above solution and continued to stir for 15 minutes; finally, 0.6 ml of azobisisobutyronitrile, an initiator, was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold, and the graphene oxide composite hydrogel was obtained after standing at room temperature for a period of time. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0031] Embodiment 4 20 mg of graphene oxide and 28 ml of water were added to a beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 4 g of 2-acrylamido-2-methyl-1-propane sulfonic acid monomer and 6 g of 2-furan acrylic acid monomer were added to the graphene oxide solution and continued to stir for 30 minutes; then 0.6 ml of cross-linking agent was added to the above solution. 0.3 g of sodium borohydride, a reducing agent, was weighed and added to the above solution and continued to stir for 15 minutes; finally, 1.2 ml of azobisisobutyronitrile, an initiator, was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold, and the graphene oxide composite hydrogel was obtained after standing at room temperature for a period of time. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0032] Embodiment 5 Add 25 mg of graphene oxide and 27.5 ml of water to a beaker and stir magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then add 10 g of acrylic acid monomer to the graphene oxide solution and continue stirring for 30 minutes; then take 0.15 ml of cross-linking agent and add it to the above solution. Weigh 0.025 g of ascorbic acid as a reducing agent and add it to the above solution and continue stirring for 15 minutes; finally take 0.6 ml of initiator ammonium persulfate and add it to the above solution and stir to dissolve; evacuate the treated solution, pour it into a mold, and stand it at room temperature for a period of time to obtain a graphene oxide composite hydrogel.

[0033] Embodiment 6 30 mg of graphene oxide and 27 ml of water were added to a beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 9 g of acrylamide monomer and 1 g of acrylic acid monomer were added to the graphene oxide solution and continued to stir for 30 minutes; then 0.6 ml of cross-linking agent was added to the above solution. 0.3 g of ascorbic acid as a reducing agent was weighed and added to the above solution and continued to stir for 15 minutes; finally, 0.6 ml of initiator ammonium persulfate was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold. After standing at room temperature for a period of time, a graphene oxide composite hydrogel was obtained. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0034] Embodiment 7 30 mg of graphene oxide and 30 ml of water were added to a beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 1 g of methacrylamide monomer and 9 g of acrylic acid monomer were added to the graphene oxide solution and continued to stir for 30 minutes; then 0.45 ml of cross-linking agent was added to the above solution. 0.15 g of sodium borohydride, a reducing agent, was weighed and added to the above solution and continued to stir for 15 minutes; finally, 0.6 ml of sodium persulfate, an initiator, was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold, and the graphene oxide composite hydrogel was obtained after standing at room temperature for a period of time. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0035] Embodiment 8 10 mg of graphene oxide and 20 ml of water were added to a beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 3 g of NN-dimethylacrylamide monomer and 7 g of 2-acetamidoacrylic acid monomer were added to the graphene oxide solution and continued to stir for 30 minutes; then 0.45 ml of cross-linking agent was added to the above solution. 0.3 g of sodium borohydride, a reducing agent, was weighed and added to the above solution and continued to stir for 15 minutes; finally, 0.6 ml of sodium persulfate, an initiator, was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold, and the graphene oxide composite hydrogel was obtained after standing at room temperature for a period of time. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0036] Embodiment 9 30 mg of graphene oxide and 27 ml of water were added to a beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 5 g of acrylamide monomer and 5 g of acrylic acid monomer were added to the graphene oxide solution and continued to stir for 30 minutes; then 0.6 ml of cross-linking agent was added to the above solution. 0.3 g of ascorbic acid, a reducing agent, was weighed and added to the above solution and continued to stir for 15 minutes; finally, 0.6 ml of initiator ammonium persulfate was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold. After standing at room temperature for a period of time, a graphene oxide composite hydrogel was obtained. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0037] Embodiment 10 Add 0.1g of graphene oxide and 20ml of water to a beaker and stir magnetically for 20min to make the graphene oxide solution evenly dispersed; then add 10g of acrylic acid monomer to the graphene oxide solution and continue stirring for 30min; then take 0.15ml of cross-linking agent and add it to the above solution. Weigh 0.1g of ascorbic acid as a reducing agent and add it to the above solution and continue stirring for 15min; finally take 0.6ml of initiator ammonium persulfate and add it to the above solution and stir to dissolve; evacuate the treated solution, pour it into a mold, and stand it at room temperature for a period of time to obtain a graphene oxide composite hydrogel. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0038] Embodiment 11 25 mg of graphene oxide and 27.5 ml of water were added to a beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 10 g of acrylic acid monomer was added to the graphene oxide solution and continued to stir for 30 minutes; then 0.6 ml of cross-linking agent was added to the above solution. 0.025 g of ascorbic acid, a reducing agent, was weighed and added to the above solution and continued to stir for 15 minutes; finally, 0.6 ml of initiator ammonium persulfate was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold. After standing at room temperature for a period of time, a graphene oxide composite hydrogel was obtained. The reaction process was monitored by infrared thermal imaging, and obvious temperature changes were detected.

[0039] Comparative Example 1 30 ml of water was added to the beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 10 g of acrylic acid monomer was added to the graphene oxide solution and continued to stir for 30 minutes; then 0.15 ml of cross-linking agent was added to the above solution. 0.025 g of ascorbic acid, a reducing agent, was weighed and added to the above solution and continued to stir for 15 minutes; finally 0.6 ml of initiator ammonium persulfate was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold. After standing at room temperature for a period of time, no formed graphene oxide hydrogel could be obtained. The reaction process was monitored by infrared thermal imaging, and no temperature change was detected.

[0040] Comparative Example 2 25 mg of graphene oxide and 27.5 ml of water were added to a beaker and stirred magnetically for 20 minutes to make the graphene oxide solution evenly dispersed; then 10 g of acrylic acid monomer was added to the graphene oxide solution and continued to stir for 30 minutes; then 0.15 ml of cross-linking agent was added to the above solution. Finally, 0.6 ml of initiator ammonium persulfate was added to the above solution and stirred to dissolve; the treated solution was evacuated and poured into a mold. After standing at room temperature for a period of time, no graphene oxide hydrogel could be obtained. The reaction process was monitored by infrared thermal imaging, and no temperature change was detected.

[0041] See attached Figure 1 The significant morphological differences of the graphene oxide hydrogel precursors prepared in Example 5 and Comparative Example 2 in the initial state and after standing at room temperature for a period of time. Example 5 successfully formed a stable graphene oxide hydrogel while Comparative Example 2 remained in a liquid state.

[0042] See attached Figure 2 This is an infrared thermal imaging picture of the graphene oxide hydrogel prepared in Example 5. The image shows that the hydrogel releases heat during the reaction process and reaches the highest temperature of the system at about 551s, indicating the completion of the gelation process.

[0043] See attached Figure 3 The tensile stress-strain curves of the graphene oxide hydrogels prepared in Examples 5, 6, 9 and 11 are shown in FIG. Figure 2 It can be seen that Example 5 has higher tensile strength and better elongation at break, which indicates that it has excellent toughness and ductility when subjected to external force deformation. The above excellent mechanical properties lay a performance foundation for the application of graphene oxide hydrogel in the fields of wearable devices and the like.

[0044] See attached Figure 4 This is a digital photo of the graphene oxide hydrogel prepared in Example 5 of the present invention during mechanical stretching. It can be stretched to 20 times of its original length, further confirming the excellent mechanical properties.

[0045] See attached Figure 5 This is the strain-response resistance change curve of the graphene oxide hydrogel prepared in Example 5 of the present invention. When the joint movement (elbow) induces the hydrogel to deform, its resistance changes rapidly, and when the movement stops, its resistance remains stable. This shows that the graphene oxide hydrogel disclosed in the present invention has good strain responsiveness and can be used for human limb movement monitoring.

[0046] See attached Figure 6This is a demonstration photograph showing that the brightness of the LED lamp connected to the graphene oxide hydrogel prepared in Example 5 of the present invention changes significantly with tensile deformation, indicating that the conductive composite hydrogel has excellent strain conductivity responsiveness and cyclic stability.

[0047] See attached Figure 7 This is a digital photograph of the bonding between the graphene oxide hydrogel prepared in Example 5 of the present invention and different substrates, proving that it has good interface bonding ability with the substrate.

[0048] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for rapidly preparing a hydrogel at room temperature, characterized in that: The method specifically comprises the following: Add acrylamide monomers and acrylic acid monomers to a graphene oxide aqueous solution, stir thoroughly and dissolve to obtain a uniform solution; add a reducing agent, a cross-linking agent and an initiator, stir and dissolve, extract bubbles and pour into a mold, and let stand at room temperature to obtain a graphene oxide-based conductive hydrogel material; wherein the mass of the reducing agent is 1 to 15 times the mass of the graphene oxide; the reducing agent is at least one of sodium borohydride, vitamin C and vitamin E; and the ratio of the mass of graphene oxide to the total mass of the monomers is 1 to 10:1000.

2. The method according to claim 1, characterized in that In the graphene oxide aqueous solution, the amount of graphene oxide used is 10-100 mg, and the amount of solvent water used is 20-30 ml.

3. The method according to claim 1, characterized in that The acrylamide monomer is one of acrylamide, methacrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid, N,N-dimethylacrylamide, and methacrylamide; the acrylic acid monomer is one of acrylic acid, 2-furan acrylic acid, methacrylic acid, and 2-acetamido acrylic acid.

4. The method according to claim 1, characterized in that: The crosslinking agent is a hyperbranched polysiloxane containing both epoxy groups and vinyl groups.

5. The preparation method of the hyperbranched polysiloxane containing both epoxy and vinyl groups is as follows: 0.1-0.5 parts of trialkoxysilane containing epoxy groups, 0.1-0.5 parts of trialkoxysilane containing vinyl groups and 0.3-2 parts of distilled water are mixed uniformly in molar ratio, and 1-10 parts of anhydrous ethanol as a solvent are added, and then a catalyst is slowly added dropwise under stirring; after the addition is completed, the temperature is raised to 20-80° C., the reaction is performed for 1-15 hours, and then vacuum drying is performed to obtain a hyperbranched polysiloxane containing both epoxy and vinyl groups; wherein, The catalyst is one of acetic acid, hydrochloric acid, sulfuric acid or phosphoric acid.

6. The method according to claim 1, characterized in that The initiator is one of potassium persulfate, ammonium persulfate and sodium persulfate; the amount of the initiator is 0.0001-0.01 times the total mass of the monomer.

7. A graphene oxide-based hydrogel material prepared rapidly at room temperature and obtained by the method as described in any one of claims 1 to 5.

8. A graphene oxide-based hydrogel material rapidly prepared at room temperature and obtained by the method as claimed in any one of claims 1 to 5 has a wide range of applications in the field of high-sensitivity strain sensors.

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