Composite hydrogel and preparation method thereof

Abstract

The invention provides composite hydrogel and a preparation method thereof. The composite hydrogel is prepared by the preparation method. The preparation method comprises the following steps: dissolving silk fibroin fibrils in a formic acid-lithium chloride system to obtain a silk fibroin solution with the mass-volume fraction of 5%-10%; uniformly mixing the obtained silk fibroin solution with an inorganic nano filler to obtain a mixed dispersion liquid; the obtained mixed dispersion liquid is subjected to a solvent induction process, and the composite hydrogel is obtained. A surfactant is not needed, a composite functional liquid phase system is converted into the multifunctional composite hydrogel by utilizing a solvent exchange strategy, operation steps are simple, conditions are safe and easy to control, raw materials are cheap and easy to obtain, and large-scale popularization and application are facilitated; the prepared composite hydrogel is stable in structure, and the conductivity and the electromagnetic shielding capability are remarkably enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and in particular relates to a composite hydrogel and a preparation method thereof. Background Art

[0002] Functional hydrogels, due to their unique physical and chemical properties, such as flexibility and strength, hold great promise for applications in a variety of fields, including soft robotics, flexible electronics, electromagnetic radiation protection, and energy conversion. In addition to traditional ionic and conductive polymer hydrogels, researchers are keen to utilize different types of conductive nanomaterials to prepare composite hydrogels. These hydrogels, with their diverse functional properties and adaptability, play an important role in a variety of fields.

[0003] The macroscopic properties of composite hydrogels depend primarily on the type of nanofiller, its distribution within the matrix, and the hydrogel's microstructure. However, interfacial incompatibility between organic and inorganic materials has been a key factor hindering the uniform dispersion and structural control of composite hydrogels. Existing methods still cannot prevent the aggregation of nanomaterials within the hydrogel matrix, which seriously affects the efficient construction of the internal functional network and poses challenges to improving performance.

[0004] Therefore, how to balance the interfacial compatibility between nanofillers and polymer matrices while optimizing the dispersion state of nanomaterials and the microstructure of hydrogels has become an important scientific issue in the research of composite hydrogels.

[0005] Pickering emulsion is widely used as a precursor in the preparation process of functional materials. For example, Chinese patent document CN116179019A discloses a functional slurry and Janus film prepared based on liquid metal Pickering emulsion, and is used in Joule heating and photothermal conversion. Chinese patent document CN119144042A discloses a method and application for preparing aerogel using a cross-linker-free Pickering emulsion template. The Pickering emulsion aerogel has good thermal stability, a large specific surface area and an average pore size, and its preparation process does not require the use of a cross-linking agent. In the field of hydrogels, Chinese patent document CN119552387A discloses a method for preparing a hydrogel with strain sensing properties from a Pickering emulsion stabilized by xylan nanocrystals, which significantly enhances the stability and strength of the three-dimensional skeleton of the hydrogel and gives the hydrogel system a strain-resistance effect.

[0006] However, there are still some problems with the hydrogel materials developed based on emulsion templates, such as: (1) In conventional methods, due to the poor interfacial compatibility between inorganic nanofillers and polymer matrices, there is a lack of effective assembly methods to prepare functional composite emulsions, which are then transformed into hydrogel materials with good self-supporting properties; (2) The current emulsion-type hydrogel materials have not yet established a systematic structure-activity relationship, and there is still a gap in the precise regulation of emulsion structure and macroscopic properties; (3) Due to the limitations of traditional emulsion-based materials, existing research on the functional development of emulsion-type hydrogel materials is still insufficient, which seriously restricts the optimization of their performance characteristics and the expansion of their application range.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The purpose of the present invention is to provide a composite hydrogel and a preparation method thereof to solve the above problems.

[0009] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0010] In one aspect, the present invention provides a method for preparing a composite hydrogel, comprising the following steps:

[0011] S1: Dissolving degummed silk fibroin fibrils in a formic acid-lithium chloride system to obtain a silk fibroin solution with a mass volume fraction of 5%-10%; the mass volume fraction described in this application is a mass volume percentage, which represents the number of grams of solute contained in 100 mL of solution;

[0012] S2: uniformly mixing the silk fibroin solution obtained in S1 with the inorganic nanofiller to obtain a mixed dispersion;

[0013] The inorganic nanofiller includes two-dimensional transition metal carbon / nitride (MXene); or a mixture of two-dimensional transition metal carbon / nitride (MXene) and multi-walled carbon nanotubes (MWCNTs);

[0014] The mixing comprises: uniformly mixing the silk fibroin solution and the dispersion of the two-dimensional transition metal carbon / nitride (MXene);

[0015] Alternatively, the silk fibroin solution is preliminarily mixed with the dispersion of the two-dimensional transition metal carbon / nitride (MXene), and then the multi-walled carbon nanotube (MWCNTs) powder is added to the preliminarily mixed system and further mixed uniformly;

[0016] The preparation of the two-dimensional transition metal carbon / nitride (MXene) dispersion comprises: mixing LiF and HCl solutions, then adding Ti3AlC2 powder and mixing evenly, placing in a 30-45°C water bath and stirring for 36-48 hours, then adding deionized water and centrifuging and washing until neutral, collecting the precipitate and adding water, then sonicating under an inert gas atmosphere, centrifuging and classifying, and concentrating the supernatant.

[0017] Preferably, the concentration of the two-dimensional transition metal carbon / nitride (MXene) dispersion is 30-40 mg / mL;

[0018] Further preferably, the solid mass ratio of the degummed silk fibroin fibrils, the two-dimensional transition metal carbon / nitride (MXene), and the multi-walled carbon nanotubes (MWCNTs) is 1-4:1:4-1;

[0019] The solid mass of the two-dimensional transition metal carbon / nitride (MXene) refers to the mass of the MXene solid dispersed in the dispersion of the two-dimensional transition metal carbon / nitride (MXene), which can be determined by the concentration of the MXene dispersion and the volume of the dispersion used.

[0020] Optionally, the length of the multi-walled carbon nanotubes (MWCNTs) powder is 8-15 nm;

[0021] S3: Placing the mixed dispersion obtained in S2 into a polytetrafluoroethylene mold, and then subjecting it to a solvent induction process. After demolding, the composite hydrogel is obtained. The depth of the mold matches the thickness of the gel to be prepared;

[0022] Preferably, the preparation method further comprises: after obtaining the mixed dispersion liquid described in S2, adding the oil phase dropwise to the mixed dispersion liquid described in S2 at a high shear rate for emulsification to obtain a functional emulsion; then placing the functional emulsion in a polytetrafluoroethylene mold, and then undergoing a solvent induction process, and demolding to obtain the composite hydrogel.

[0023] The solvent induction process specifically includes: immersing the entire polytetrafluoroethylene mold in a solvent to perform solvent exchange;

[0024] Optionally, the preparation method further satisfies one or more of the following conditions:

[0025] a. The high shear rate is 4500-6000rpm / min;

[0026] b. The oil phase comprises toluene and / or cyclohexane;

[0027] c. The emulsification time is 3-5min;

[0028] d. The volume ratio of the oil phase to the functional emulsion is 0.17-0.4:1;

[0029] e. The solvent used in the solvent induction process is a poor solvent for silk fibroin;

[0030] Preferably, the poor solvent is water or methanol;

[0031] f. The duration of the solvent induction process is 12-24h.

[0032] The present invention develops a surfactant-free Pickering emulsion system and transforms it into a multifunctional composite hydrogel using a solvent exchange strategy. Under the shear action of emulsification, the amphiphilic silk fibroin molecular chains and nanofillers assemble to form a functional emulsion with a controllable microstructure through enhanced interfacial interactions; subsequently, solvent exchange is induced to induce a self-crosslinking reaction between the silk fibroin molecular chains accompanied by a microphase separation process, thereby achieving the directional preparation of the functional emulsion into a self-supporting hydrogel. On the one hand, the volume exclusion effect of the emulsion and the rich two-phase interface synergistically improve the structural stability and processability of the hydrogel; on the other hand, by changing the oil phase content in the emulsion, the rational regulation of the emulsion structure is achieved, thereby achieving the precise construction of the internal structure of the composite hydrogel and the optimization of the macroscopic performance.

[0033] Two-dimensional transition metal carbon / nitride (MXene) is an essential component in the formation of functional emulsions. The emulsification mechanism of functional emulsions is primarily based on two aspects: first, physical entanglement and barrier effects exist between the one-dimensional silk fibroin molecular chains and the two-dimensional transition metal carbon / nitride MXene nanosheets, synergistically strengthening and supporting the metastable interface of the silk fibroin emulsion; second, under the action of shear force, the MXene nanosheets can tightly adhere to the two-phase interface, and the polar groups on their surface (such as -OH, -F, etc.) generate strong interactions with the silk fibroin molecular chains, further consolidating and stabilizing the functional emulsion.

[0034] The solvent induction process described in the present invention is a complex process that induces secondary conformational transition, self-crosslinking and microphase separation of silk fibroin molecules through solvent exchange. Specifically, during the preparation of silk fibroin solution, the formic acid-lithium chloride dissolution system causes the silk fibroin fibrils to swell and destroy their original β-pleated crystal structure, thereby obtaining a uniform silk fibroin solution. In this process, the strong polar ions (Li + ) will weaken the original hydrogen bonds and van der Waals forces between silk fibroin molecules; then, in the solvent exchange stage, poor solvents (such as water, alcohol, etc.) will reconstruct the intermolecular forces between silk fibroin chains, causing them to undergo self-crosslinking; at the same time, this process is accompanied by the transformation of amorphous structure to crystalline structure and the occurrence of microphase separation, ultimately forming a self-supporting functional composite hydrogel material.

[0035] The structure of the functional emulsion is primarily influenced by the silk fibroin content and the oil phase ratio, which in turn influences the internal microstructure of the composite hydrogel. On the one hand, as the silk fibroin content increases, the composite hydrogel exhibits a stronger and more stable internal network structure, and its pore wall thickness also increases accordingly. On the other hand, the oil phase ratio in the emulsion is also closely related to the performance of the composite hydrogel. Experimental verification shows that when the oil phase volume fraction is 0.2, the hydrogel exhibits a complete and continuous closed-pore structure. When the oil phase volume fraction increases to 0.4, excessive oil droplets cause the functional emulsion to break and merge. Accordingly, the hydrogel exhibits partial structural fractures and a significant increase in pore size, resulting in an uneven open-pore structure.

[0036] The microstructural characteristics of functional emulsions and composite hydrogels are closely related to their macroscopic properties, directly or indirectly affecting their electrical conductivity, electromagnetic shielding performance, mass transfer, heat transfer, and energy conversion performance.

[0037] Another aspect of the present invention provides a composite hydrogel prepared by the preparation method of the present invention.

[0038] Preferably, the composite hydrogel of the present invention is an emulsion template type composite hydrogel;

[0039] Further preferably, the emulsion template is a Pickering emulsion. Based on the volume exclusion effect, the introduction of a Pickering emulsion template can achieve the directional distribution of fillers in the composite hydrogel and the controllable construction of functional structures. Compared with traditional randomly blended composite hydrogel materials, the emulsion template can induce the directional assembly of nanofillers at the liquid-liquid interface, thereby significantly improving the connection efficiency between fillers in the hydrogel. This assembly method enables the nanomaterial to form a continuous three-dimensional network structure at the interface.

[0040] Beneficial effects of the present invention:

[0041] Compared with the existing technology, the present invention provides a simple and efficient method for preparing multifunctional composite hydrogels based on emulsion templates, which solves the problem of interfacial incompatibility between inorganic functional fillers and polymer matrices in composite materials in conventional technologies. Based on the synergistic effect of silk fibroin and two-dimensional MXene nanosheets, a surfactant-free functional emulsion assembly strategy is proposed, which is converted into a composite hydrogel material with a controllable microstructure through a microphase separation process.

[0042] The percolation threshold of the composite hydrogel provided by the present invention is greatly reduced, and the volume exclusion effect of the emulsion template enables the functional particles such as MXene and MWCNTs to be orderly assembled at the interface between the two phases, significantly shortening the communication path between the nanomaterials. By regulating the oil phase ratio of the emulsion, a reasonable switch between the closed-pore and open-pore structures of the material is achieved, thereby improving the comprehensive performance of the composite hydrogel of the present invention in different application scenarios. The emulsion structure with rich interfaces significantly improves the mechanical stability of the composite hydrogel and efficiently constructs an ordered conductive network inside it, achieving excellent conductive properties (0.58Sm -1 , 1.6 vol%) and electromagnetic shielding capability (62.9 dB); at the same time, the tunable multi-level open-pore structure gives the hydrogel excellent photothermal conversion efficiency and water evaporation performance, and its water evaporation rate can reach up to 3.48 kg m -2 h -1 In addition, the composite hydrogel also exhibits good salt tolerance and can maintain stable and efficient evaporation capabilities even in a high-concentration salt water environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific 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.

[0044] Figure 1 This is a scanning electron micrograph of the composite hydrogel prepared in this application;

[0045] Figure 2 are scanning electron micrographs of the composite hydrogels prepared in Examples 2 and 9;

[0046] Figure 3 (a) is a graph showing the conductivity test results of the composite hydrogel provided in this application;

[0047] Figure 3 (b) is a graph showing the electromagnetic shielding effectiveness of the composite hydrogel provided in this application in the range of 8.2-12.4 GHz;

[0048] Figure 3 (c) is a graph showing the electromagnetic shielding effectiveness of the composite hydrogel provided in this application at 10 GHz;

[0049] Figure 4 A diagram of the photothermal water evaporation rate of the composite hydrogel provided in this application under a simulated solar radiation intensity. DETAILED DESCRIPTION

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0051] It should be noted that the specific preparation method of the silk fibroin solution used in the embodiment of the present invention is as follows: take an appropriate amount of mulberry silk cocoons, cut them into small pieces of 1*1 cm, place them in boiling sodium bicarbonate water for degumming for 20-40 minutes, and repeat this process twice until the excess sericin coating is removed; then, the degummed silk fibroin fibrils dried at room temperature are dissolved in a formic acid-lithium chloride system with a mass volume fraction of lithium chloride of 5% (w / v); silk fibroin solutions with mass volume fractions of 5% (w / v), 6% (w / v), 8% (w / v), and 10% (w / v) are prepared as required.

[0052] It should be noted that the mass volume fraction of silk fibroin is calculated based on the mass of degummed silk fibroin fibrils after drying at room temperature.

[0053] The electromagnetic shielding test method in the embodiment of the present invention adopts a waveguide method to test the electromagnetic shielding effectiveness in the X-band.

[0054] Example 1

[0055] This embodiment provides a composite hydrogel, and the preparation method thereof is as follows:

[0056] S1: 0.24 g of dried degummed silk fibroin fibrils were dissolved in a formic acid-lithium chloride system to prepare a silk fibroin solution with a mass volume fraction of 5%;

[0057] S2: 8 g of LiF powder was added to 100 mL of 9 M hydrochloric acid, and then 5 g of Ti3AlC2 powder was slowly added. The whole was placed in a 40 ° C water bath with magnetic stirring for 40 h, and then deionized water was added and centrifuged and washed until neutral. The precipitate was collected and added with water, and then ultrasonicated under argon atmosphere for 1 h. Centrifugal classification was performed, and the supernatant was taken to obtain a MXene dispersion. After centrifugal concentration, a MXene dispersion with a concentration of 30 mg / mL was obtained;

[0058] S3: The silk fibroin solution prepared in S1 was mixed evenly with 8 mL of the MXene dispersion obtained in S2, and 0.96 g of MWCNTs powder with a length of 8-15 nm was added and mixed again to obtain a mixed dispersion; wherein the mass ratio of the silk fibroin fibrils used in S1, the MXene solid content in the MXene dispersion in S2, and the MWCNTs powder was 1:1:4;

[0059] S4: The mixed dispersion obtained in S3 was transferred to a polytetrafluoroethylene mold with a mold depth of 1.5 mm. The entire mold was then immersed in deionized water for 12 h of solvent exchange. After demolding, a 1.5 mm thick SCM composite hydrogel was obtained, which was recorded as SCM hydrogel.

[0060] Example 2

[0061] This embodiment provides a composite hydrogel, and the preparation method thereof is as follows:

[0062] S1: 0.24 g of dried degummed silk fibroin fibrils were dissolved in a formic acid-lithium chloride system to prepare a silk fibroin solution with a mass volume fraction of 5%;

[0063] S2: 8 g of LiF powder was added to 100 mL of 9 M hydrochloric acid, and then 5 g of Ti3AlC2 powder was slowly added. The whole was placed in a 40 ° C water bath with magnetic stirring for 40 h, and then deionized water was added and centrifuged and washed until neutral. The precipitate was collected and added with water, and then ultrasonicated under argon atmosphere for 1 h. Centrifugal classification was performed, and the supernatant was taken to obtain a MXene dispersion. After centrifugal concentration, a MXene dispersion with a concentration of 30 mg / mL was obtained;

[0064] S3: The silk fibroin solution prepared in S1 was mixed evenly with 8 mL of the MXene dispersion obtained in S2, and 0.96 g of MWCNTs powder with a length of 8-15 nm was added and mixed again to obtain a mixed dispersion. The mass ratio of the silk fibroin fibrils used in S1, the MXene solid content in the MXene dispersion in S2, and the MWCNTs powder was 1:1:4.

[0065] S4: The mixed dispersion obtained in S3 was transferred to a high-speed disperser, and toluene oil droplets were added dropwise at a speed of 4500 rpm / min for emulsification to obtain a functional emulsion. During the process, the volume ratio of the added oil phase toluene to the functional emulsion was controlled to be 0.2:1, and the emulsification time was 3 minutes;

[0066] S5: The functional emulsion obtained in S4 was transferred to a polytetrafluoroethylene mold with a mold depth of 1.5 mm. The entire mold was then immersed in deionized water for 12 h of solvent exchange. After demolding, a composite hydrogel with a thickness of 1.5 mm was obtained, which was recorded as SCM. O / W hydrogel.

[0067] Example 3

[0068] The difference from Example 2 is that the mass volume fraction of the silk fibroin solution prepared in S1 is 6%.

[0069] Example 4

[0070] The difference from Example 2 is that the mass volume fraction of the silk fibroin solution prepared in S1 is 8%.

[0071] Example 5

[0072] The difference from Example 2 is that the mass volume fraction of the silk fibroin solution prepared in S1 is 10%.

[0073] Example 6

[0074] The difference from Example 2 is that in S4, the volume ratio of the oil phase toluene to the functional emulsion is 0.17:1.

[0075] Example 7

[0076] The difference from Example 2 is that in S4, the volume ratio of the oil phase toluene to the functional emulsion is 0.25:1.

[0077] Example 8

[0078] The difference from Example 2 is that in S4, the volume ratio of the oil phase toluene to the functional emulsion is 0.33:1.

[0079] Example 9

[0080] The difference from Example 2 is that in S4, the volume ratio of the oil phase toluene to the functional emulsion is 0.4:1.

[0081] Example 10

[0082] The difference from Example 2 is that the depth of the polytetrafluoroethylene mold used in S5 is 2 mm. Finally, a composite hydrogel with a thickness of 2 mm is obtained.

[0083] Example 11

[0084] The difference from Example 2 is that the depth of the polytetrafluoroethylene mold used in S5 is 3 mm. Finally, a composite hydrogel with a thickness of 3 mm is obtained.

[0085] Example 12

[0086] This embodiment includes the following steps:

[0087] S1-S5: Same as Example 2;

[0088] S6: The composite hydrogel obtained in S5 is SCM O / W The hydrogel was freeze-dried to remove the oil phase inside the hydrogel and obtain the corresponding SCM O / W Aerogel materials;

[0089] S7: Convert S6 to SCM O / W The aerogel material was transferred to deionized water and allowed to stand for 10 minutes to obtain a water-saturated SCM. O / W Hydrogel material.

[0090] Example 13

[0091] The difference from Example 12 is that in S4, the volume ratio of the oil phase toluene to the functional emulsion is 0.17:1.

[0092] Example 14

[0093] The difference from Example 12 is that in S4, the volume ratio of the oil phase toluene to the functional emulsion is 0.25:1.

[0094] Example 15

[0095] The difference from Example 12 is that in S4, the volume ratio of the oil phase toluene to the functional emulsion is 0.33:1.

[0096] Example 16

[0097] The difference from Example 12 is that in S4, the volume ratio of the oil phase toluene to the functional emulsion is 0.4:1.

[0098] Comparative Example 1

[0099] The difference from Example 2 is that no carbon nanotube MWCNTs powder is added to S3.

[0100] Comparative Example 1

[0101] The difference from Example 2 is that the mass ratio of the silk fibroin fibrils used in S1, the MXene solid content in the MXene dispersion in S2, and the MWCNTs powder is 1:2:4.

[0102] Comparative Example 2

[0103] The difference from Example 2 is that the volume ratio of the oil phase toluene to the volume of the functional emulsion is 0.5:1.

[0104] Comparative Example 3

[0105] The difference from Example 2 is that the volume ratio of the oil phase toluene to the volume of the functional emulsion is 0.05:1.

[0106] Comparative Example 4

[0107] The difference from Example 12 is that the volume ratio of the oil phase toluene to the volume of the functional emulsion is 0.5:1.

[0108] Comparative Example 5

[0109] The difference from Example 12 is that the volume ratio of the oil phase toluene to the volume of the functional emulsion is 0.05:1.

[0110] The performance test results of the products obtained in the embodiments, control examples and comparative examples are shown in Table 1 below:

[0111] Table 1 Performance test results of the products obtained in the embodiments, control examples and comparative examples

[0112]

[0113]

[0114] Table 1 shows that the electrical conductivity, electromagnetic shielding properties, and photothermal evaporation performance of the composite hydrogel are closely related to the material's internal microstructure. The introduction of the emulsion template effectively improves the hydrogel's electrical conductivity and electromagnetic shielding properties, primarily due to the volume exclusion effect, which re-optimizes the hydrogel's internal functional network and forms a more efficient and complete electron transport pathway.

[0115] It can be seen from Comparative Example 1 in Table 1 that the addition of carbon nanotube MWCNTs powder can effectively improve the integrity of the conductive network in the hydrogel, thereby enhancing the conductivity and electromagnetic shielding properties of the hydrogel.

[0116] Comparative Example 1 in Table 1 shows that the mass ratio of silk fibroin fibrils, MXene solids content in the MXene dispersion, and MWCNT powder is closely related to the electrical conductivity and electromagnetic shielding properties of the composite hydrogel. Increasing the silk fibroin content enhances the insulation of the composite hydrogel, thickens the pore walls of the internal skeleton, reduces the connection area of the conductive filler, and compromises the integrity of the conductive pathway, ultimately causing a sharp drop in the electrical conductivity and electromagnetic shielding properties of the composite hydrogel.

[0117] Comparative Examples 2-3 in Table 1 show that both excessive and insufficient oil phase can affect the electrical conductivity and electromagnetic shielding properties of the composite hydrogel. Excessive oil phase can lead to demulsification or even failure of emulsification during the emulsification process, preventing the formation of an effective conductive network and significantly reducing the performance of the composite hydrogel. Excessive oil phase content, on the other hand, prevents the optimization of the conductive network within the hydrogel through the oil droplet volume exclusion effect, resulting in the continued presence of agglomeration caused by the mismatch between the filler and the matrix, severely impacting the performance of the composite hydrogel.

[0118] Comparative Examples 4-5 in Table 1 show that both excessive and insufficient oil phase can affect the photothermal evaporation performance of the composite hydrogel. Excessive oil phase can lead to demulsification or even failure of emulsification during the emulsification process, preventing the formation of an effective upward water transfer channel within the hydrogel and limiting the photothermal evaporation process. Excessive oil phase, on the other hand, prevents the formation of an effective porous structure within the hydrogel, severely impacting mass and heat transfer, leading to a decrease in the photothermal evaporation performance of the composite hydrogel.

[0119] Figure 1 The scanning electron micrographs of the composite hydrogels prepared in this application are scanning electron micrographs of the composite hydrogels prepared using different contents of silk fibroin. Figure 1 (a1) and Figure 1 (a2) are scanning electron micrographs of the composite hydrogel prepared in Example 2 at magnifications of 1200 and 2000 times, respectively; Figure 1 (b1) and Figure 1 (b2) are scanning electron micrographs of the composite hydrogel prepared in Example 4 at magnifications of 1200 and 2000 times, respectively; Figure 1 (c1) and Figure 1 (c2) are scanning electron micrographs of the composite hydrogel prepared in Example 5 at magnifications of 1200 and 2000 times, respectively.

[0120] Figure 2 The scanning electron micrographs of the composite hydrogels prepared in Examples 2 and 9, i.e., the scanning electron micrographs of the composite hydrogels under different ratios of the oil phase to the functional emulsion, wherein: Figure 2 (a1) and Figure 2 (a2) are scanning electron micrographs of the composite hydrogel prepared in Example 2 at magnifications of 500 and 2000 times, respectively; Figure 2 (b1) and Figure 2 (b2) are scanning electron micrographs of the composite hydrogel prepared in Example 9 at magnifications of 500 and 2000 times, respectively.

[0121] Figure 3 is the electrical conductivity and electromagnetic shielding effectiveness of the composite hydrogel. Figure 3 (a) is the electrical conductivity of the composite hydrogel; Figure 3 (b) is the electromagnetic shielding effectiveness curve of the composite hydrogel in the range of 8.2-12.4 GHz; Figure 3 (c) The electromagnetic shielding effectiveness of the composite hydrogel at 10 GHz.

[0122] Depend on Figure 3 (a) and (b) show that as the oil phase content increases, the conductivity and electromagnetic shielding properties of the prepared composite hydrogel gradually improve, and reach the optimal value (0.58Sm -1 While an appropriate amount of oil phase helps form an ordered, dense conductive network within the composite hydrogel, an excessive amount of oil phase can easily cause emulsion demulsification and fusion, leading to a partial transformation of the emulsion structure from closed-cell to open-cell, thus destroying the continuous conductive path within the hydrogel. Consequently, as the volume proportion of the oil phase continues to increase, the conductivity and electromagnetic shielding properties of the composite hydrogel also show a trend of decline.

[0123] Depend on Figure 3 c It can be seen that the electromagnetic shielding performance of the composite hydrogel is also related to its thickness. The greater the thickness, the better the electromagnetic shielding performance.

[0124] Figure 4 is the photothermal water evaporation rate of the composite hydrogel under a simulated solar radiation intensity.

[0125] Depend on Figure 4 It can be seen that the photothermal evaporation rate of the composite hydrogel provided by the present invention shows a positive correlation with the oil phase content, that is, the higher the volume proportion of the oil phase, the faster the water evaporation rate of the hydrogel. On the one hand, the large-scale open pore structure can effectively reduce the water content of the hydrogel, reduce the heat loss caused by heating the bulk water, and inhibit the downward transfer of heat, ultimately maintaining an efficient water evaporation interface. On the other hand, the microporous structure within the pore wall promotes the rapid transfer of water within the hydrogel through strong capillary forces. In addition, the interconnected open pore channels of the composite hydrogel provided by this application also enable rapid steam escape and uniform heat distribution.

[0126] Please note that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application. The description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of this application, several variations and improvements can be made, which all fall within the scope of protection of this application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A method for preparing a composite hydrogel, characterized in that: The preparation method comprises the following steps: S1: dissolving degummed silk fibroin fibrils in a formic acid-lithium chloride system to obtain a silk fibroin solution with a mass volume fraction of 5%-10%; S2: uniformly mixing the silk fibroin solution obtained in S1 with the inorganic nanofiller to obtain a mixed dispersion; S3: subjecting the mixed dispersion obtained in S2 to a solvent induction process to obtain the composite hydrogel.

2. The method for preparing the composite hydrogel according to claim 1, wherein: The inorganic nanofiller includes two-dimensional transition metal carbon / nitride (MXene); or a mixture of two-dimensional transition metal carbon / nitride (MXene) and multi-walled carbon nanotubes (MWCNTs).

3. The method for preparing the composite hydrogel according to claim 2, wherein: In step S2, the mixing includes: uniformly mixing the silk fibroin solution and the dispersion of the two-dimensional transition metal carbon / nitride (MXene); Alternatively, the silk fibroin solution is preliminarily mixed with the dispersion of the two-dimensional transition metal carbon / nitride (MXene), and then the multi-walled carbon nanotube (MWCNTs) powder is added to the preliminarily mixed system and further mixed uniformly.

4. The method for preparing the composite hydrogel according to claim 2, wherein: The solid mass ratio of the degummed silk fibroin fibrils, the two-dimensional transition metal carbon / nitride (MXene), and the multi-walled carbon nanotubes (MWCNTs) is 1-4:1:4-1.

5. The method for preparing the composite hydrogel according to claim 3, wherein: The preparation of the two-dimensional transition metal carbon / nitride (MXene) dispersion comprises: mixing LiF and HCl solutions, then adding Ti3AlC2 powder and mixing evenly, placing in a 30-45°C water bath and stirring for 36-48 hours, then adding deionized water and centrifuging and washing until neutral, collecting the precipitate and adding water, then sonicating under an inert gas atmosphere, centrifuging and classifying, and concentrating the supernatant. Preferably, the concentration of the two-dimensional transition metal carbon / nitride (MXene) dispersion is 30-40 mg / mL.

6. The method for preparing the composite hydrogel according to claim 2, wherein: The length of the multi-walled carbon nanotubes (MWCNTs) powder is 8-15 nm.

7. The method for preparing the composite hydrogel according to any one of claims 1 to 6, characterized in that: The preparation method further includes: after obtaining the mixed dispersion described in S2, adding an oil phase dropwise to the mixed dispersion described in S2 at a high shear rate for emulsification to obtain a functional emulsion; and then subjecting the functional emulsion to a solvent induction process to obtain the composite hydrogel.

8. The method for preparing the composite hydrogel according to claim 7, wherein: The preparation method also satisfies one or more of the following conditions: a. The high shear rate is 4500-6000rpm / min; b. The oil phase comprises toluene and / or cyclohexane; c. The emulsification time is 3-5min; d. The volume ratio of the oil phase to the functional emulsion is 0.17-0.4:1; e. The solvent used in the solvent induction process is a poor solvent for silk fibroin; Preferably, the poor solvent is water or methanol; f. The duration of the solvent induction process is 12-24h.

9. A composite hydrogel, characterized in that The method is prepared according to any one of claims 1 to 8.

10. The composite hydrogel according to claim 9, characterized in that The composite hydrogel is an emulsion template type composite hydrogel; Preferably, the emulsion template is a Pickering emulsion.

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