A dynamic urea bond-based double-network transparent polyurea hydrogel and a preparation method thereof

Abstract

The application relates to the technical field of functional polymer material design and synthesis, and discloses a double-network transparent polyurea hydrogel based on a dynamic urea bond and a preparation method thereof, which comprises the following components: a first network composed of polyurea high molecular chains containing a dynamic urea bond, and a second network composed of a hydroxyl-containing polymer, an amide-containing polymer or a carboxyl-containing polymer through physical or chemical crosslinking, the first network and the second network form an interpenetrating double-network structure, and the mass ratio of the first network to the second network is 1:0.5-1:3; the preparation method adopts a two-step method: first, a first network gel is constructed, then the first network gel is immersed in a second network component solution to be swelled and balanced, and finally, the second network is formed through ultraviolet light-induced crosslinking or freeze-thaw circulation. The application solves the problems that the mechanical performance and self-repairing performance of the hydrogel are not easy to simultaneously possess and the transparency is insufficient in the prior art.

Description

Technical Field

[0001] This invention relates to the field of functional polymer material design and synthesis technology, specifically to a dual-network transparent polyurea hydrogel based on dynamic urea bonds and its preparation method. Background Technology

[0002] In today's rapidly developing technological landscape, cutting-edge fields such as flexible electronic devices, biomedical implants, and intelligent sensing devices are increasingly demanding high-performance materials. Dynamic urea bond dual-network transparent polyurea hydrogels, with their unique structure and properties, are expected to become key materials for revolutionizing these fields, and their research and application are now imperative.

[0003] Cutting-edge fields such as flexible electronic devices and biomedical implants place higher demands on the comprehensive performance of materials, and hydrogels, as a soft material rich in water, are often used in these fields.

[0004] However, existing hydrogel materials have very low mechanical strength and are prone to tearing or damage under external forces. This structural fragility limits the application of hydrogel materials in load-bearing or durable applications.

[0005] To improve the mechanical properties of hydrogel materials, researchers have developed dual-network hydrogels. The interpenetrating structure of dual-network hydrogels enhances the toughness and strength of the material. However, once this high-strength structure is damaged, the damage is irreversible and permanent because dual-network hydrogels themselves do not have self-healing capabilities.

[0006] To address the lack of self-healing capabilities in dual-network hydrogels, researchers introduced dynamic chemical bonds into the polymer network. These dynamic chemical bonds possess the characteristics of reversible breakage and recombination. When the material is damaged, the chemical bonds dissociate at the fracture surface. When the fracture surfaces re-contact and meet specific conditions, they can reform chemical connections at the interface, thereby restoring the material's structure and properties.

[0007] However, when integrating dual-network hydrogels with dynamic chemical bonds, the mechanical strength of self-healing hydrogels drops to a low level. Although they can repair themselves, the strength and toughness of the material itself are insufficient, making it difficult to meet the mechanical requirements of practical applications. When attempting to introduce dynamic polyurea networks to achieve self-healing, the prepared materials are prone to yellowing, resulting in poor optical transparency, which cannot meet the application requirements of optical devices or transparent sensors. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a dual-network transparent polyurea hydrogel based on dynamic urea bonds and its preparation method, solving the problems of existing technologies where hydrogels are not easy to simultaneously possess mechanical properties and self-healing properties, and where transparency is insufficient.

[0009] To achieve the above objectives, this invention aims to provide a dual-network transparent polyurea hydrogel based on dynamic urea bonds and its preparation method.

[0010] In a first aspect, the present invention provides a dual-network transparent polyurea hydrogel based on dynamic urea bonds, employing the following technical solution: A dual-network transparent polyurea hydrogel based on dynamic urea bonds, comprising the following components: First network: composed of polyurea polymer chains containing dynamic urea bonds; The second network is composed of hydroxyl-containing polymers, amide-containing polymers, or carboxyl-containing polymers through physical or chemical cross-linking. The first network and the second network form an interpenetrating dual network structure, and the quality ratio of the first network to the second network is 1:0.5-1:3.

[0011] Specifically, the first network (polyurea) and the second network (such as polyvinyl alcohol, polyacrylic acid, or polyacrylamide) constructed in this invention interpenetrate each other in space to form an interpenetrating double network structure. When the double-network transparent polyurea hydrogel is subjected to stress, the interpenetrating double network structure allows energy to be effectively dissipated through the combined action of the network chains. The first network acts as a sacrificial network when the dynamic bonds break or the physical or chemical crosslinking points of the second network are destroyed. At the same time, the interpenetrating structure disperses the stress throughout the material, thereby inhibiting the propagation of cracks.

[0012] Specifically, this invention introduces dynamic urea bonds into the polymer chain. Unlike existing covalent bonds, dynamic urea bonds have reversible breakage and recombination characteristics. When the material is damaged, the dynamic urea bonds at the fracture surface dissociate. When the fracture surfaces are re-contacted and repair conditions are applied, the dissociated dynamic urea bonds can reform chemical connections at the interface, thereby restoring the integrity and mechanical strength of the network.

[0013] Furthermore, in terms of raw material selection, the first network of the present invention uses an aliphatic diisocyanate, which is at least one of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate, rather than an aromatic diisocyanate, which is diphenylmethane diisocyanate. The aliphatic diisocyanate raw material does not contain aromatic ring structures that are easily oxidized or form conjugated chromophores, so that the prepared first network polyurea itself is colorless and transparent. When it is compounded with the transparent second network component, due to the good compatibility between the two phases, no macroscopic phase separation that causes light scattering occurs. Therefore, the final dual-network hydrogel as a whole maintains a high optical transmittance.

[0014] Furthermore, the hydrogel has a transmittance of ≥95% in the visible light band (400-800nm).

[0015] Furthermore, the dynamic urea bond is formed by the reaction of an aliphatic diisocyanate monomer with a polyamine compound.

[0016] Furthermore, the aliphatic diisocyanate is selected from at least one of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

[0017] Furthermore, the polyamine compound is selected from at least one of tetraethylenepentamine, triethylenetetramine, and polyethyleneimine.

[0018] Furthermore, the hydroxyl-containing polymer or amide-containing polymer of the second network is at least one of polyvinyl alcohol, polyacrylic acid, and polyacrylamide.

[0019] Furthermore, under a strain of 60%, the hydrogel exhibits a self-healing efficiency ≥90% and a fracture energy ≥4790 J / m. 2 Compressive strength ≥2.88MPa.

[0020] Secondly, the present invention provides a method for preparing a dual-network transparent polyurea hydrogel based on dynamic urea bonds, using the following technical solution: A method for preparing a dual-network transparent polyurea hydrogel based on dynamic urea bonds includes the following steps: S1. Construction of the first network: Diisocyanate and polyamine compound are reacted in the presence of a catalyst to form a prepolymer containing dynamic urea bonds, which is then thermosetting to obtain the first network gel. S2. Introduction of the second network: The first network gel is immersed in the solution of the second network component. After swelling equilibrium, a second cross-linking is performed to obtain a double-network transparent polyurea hydrogel. S3. Purification treatment: Dialyze the double-network gel to remove unreacted monomers and obtain a double-network transparent polyurea hydrogel.

[0021] Specifically, in step S1, thermosetting in the presence of a catalyst ensures efficient and complete reaction between isocyanate and polyamine to form urea bonds. The introduction of the catalyst is key to forming a high-quality dynamic urea bond network. Without a catalyst, the first network will not be sufficiently cross-linked, resulting in a decrease in both self-healing efficiency and mechanical strength. The introduction of the catalyst ensures that the first network has sufficient cross-linking density and number of dynamic bonds, which is the basis for achieving high self-healing efficiency and high mechanical strength.

[0022] Furthermore, this invention separates the preparation processes of the two networks in time and space. The formation of polyurea and the formation of the second network use completely different reaction systems. Step S1 is a polycondensation reaction, and step S2 can be free radical polymerization or physical crosslinking. This two-step process solves the problems of mutual interference, reaction inhibition or side reactions that may exist between different chemical systems.

[0023] Furthermore, step S2, through a process of first swelling equilibrium followed by secondary cross-linking, allows the second network component to uniformly penetrate into the pore structure of the first network. The subsequent secondary cross-linking leaves the second network inside the first network, forming a uniform interpenetrating structure, avoiding macroscopic phase separation, and thus ensuring the high transparency and stability of the material's mechanical properties.

[0024] Furthermore, the catalyst mentioned in step S1 is an organotin compound. In this invention, the organotin compound is dibutyltin dilaurate and stannous octoate, and the amount used accounts for 0.1-1wt% of the total mass of the monomer. The thermosetting temperature is 60-100℃, and the reaction time is 1-5h.

[0025] Specifically, in step S2, the second network component solution is one of polyvinyl alcohol aqueous solution, polyacrylic acid aqueous solution and acrylamide aqueous solution, with a concentration of 10-30 wt% and a swelling time of 12-48 h.

[0026] Furthermore, in step S2, the secondary crosslinking is performed in any of the following ways: UV light-induced crosslinking, with the addition of a photoinitiator, UV intensity 5-20 mW / cm 2 Irradiate for 10-60 minutes; Physical cross-linking is achieved through a freezing-thawing cycle, with freezing temperature of -20 to 40°C, thawing temperature of 25 to 40°C, and ≥3 cycles.

[0027] Furthermore, in step S3, the specific steps of the purification process are as follows: The dual-network gel was placed in deionized water for dialysis for 48-72 hours, with the deionized water being changed every 6-8 hours during the process.

[0028] Specifically, this invention, through the design of an interpenetrating double network structure, combined with the reversible properties of dynamic urea bonds and the stability of hydrophilic polymers, achieves improved light transmittance (≥95%) and fracture energy (≥4790 J / m) of the double-network transparent polyurea hydrogel. 2 It achieves a balance between mechanical properties and self-healing efficiency (≥90%), while also exhibiting strong controllability in the preparation process. It is suitable for multiple fields such as flexible electronic devices, artificial corneas, and strain sensors, solving the problems of insufficient transparency and difficulty in simultaneously possessing mechanical properties and self-healing properties in existing technologies.

[0029] This invention provides a dual-network transparent polyurea hydrogel based on dynamic urea bonds and its preparation method. It has the following beneficial effects: 1. This invention forms an interpenetrating double-network structure by having the first network and the second network interpenetrate and work together in space. When the double-network transparent polyurea hydrogel is subjected to force, the interpenetrating double-network structure can effectively dissipate energy through the joint action of the network chains, thereby inhibiting crack propagation. As a result, the double-network transparent polyurea hydrogel has both high compressive strength and high fracture energy, solving the problem that it is not easy for hydrogels to have both mechanical properties and self-healing properties at the same time in the prior art.

[0030] 2. By selecting aliphatic diisocyanates instead of aromatic diisocyanates, the present invention avoids the problems of yellowing and reduced light transmittance caused by aromatic ring structures. On the other hand, by forming the first network first and then introducing the second network, the process ensures that the first network and the second network form a uniform interpenetrating structure, avoiding macroscopic phase separation, making the double-network transparent polyurea hydrogel colorless and transparent, and improving the light transmittance of the double-network transparent polyurea hydrogel.

[0031] 3. The present invention introduces dynamic urea bonds in the first network, which are different from existing covalent bonds. The dynamic urea bonds introduced in the first network have reversible breakage and recombination characteristics. When the dual-network transparent polyurea hydrogel is damaged, the dynamic urea bonds at the fracture surface can reform chemical connections under heating or room temperature static conditions, restore the network integrity, and improve the self-repair efficiency of the dual-network transparent polyurea hydrogel. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to comparative examples and test cases. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Examples 1-5: Example 1: S1. Weigh hexamethylene diisocyanate and tetraethylenepentamine at a mass ratio of 1:1.2, add 0.3wt% dibutyltin dilaurate, and mix magnetically at 30°C for 30 min to obtain a uniform prepolymer. S2. Place the prepolymer into a polytetrafluoroethylene mold, then heat-cur it in a 60°C oven for 3 hours to obtain the first network polyurea gel, and cool it to room temperature for later use. S3. Weigh 10g of polyvinyl alcohol and dissolve it in 40mL of deionized water. Stir at 80℃ until completely dissolved. After cooling to room temperature, add 0.5wt% of photoinitiator and stir until dissolved to obtain a polyvinyl alcohol aqueous solution. S4. Cut the first network gel into blocks of 2cm×2cm×0.5cm, immerse them in polyvinyl alcohol aqueous solution, and let them stand at 25℃ for 24h to allow the first network gel to fully swell and reach equilibrium, thus obtaining the swollen first network gel. S5. Remove the swollen first network gel, blot the surface liquid with filter paper, and then place it in a UV curing chamber at 10mW / cm². 2 Irradiate with ultraviolet light for 30 minutes to allow the first network gel to complete the chemical cross-linking of the second network, thus obtaining a double-network gel. S6. Place the double-network gel in deionized water and dialyze for 72 hours, changing the deionized water every 6 hours to remove unreacted hexamethylene diisocyanate, tetraethylenepentamine, and polyvinyl alcohol, to obtain a double-network transparent polyurea hydrogel.

[0034] Example 2: S1. Weigh isophorone diisocyanate and triethylenetetramine at a mass ratio of 1:1.0, add dibutyltin dilaurate at a mass of 0.5wt% of the total monomer mass, and stir at 40℃ for 40 min to obtain the prepolymer. S2. Place the prepolymer into a polytetrafluoroethylene mold and heat-cur it at 80°C for 2 hours to obtain the first network gel. Cool it to room temperature for later use. S3. Weigh 15g of acrylamide and dissolve it in 85mL of deionized water. Stir at room temperature until completely dissolved. After cooling to room temperature, add 0.3wt% of photoinitiator and stir until dissolved to obtain an aqueous solution of acrylamide. S4. Cut the first network gel into blocks of 2cm×2cm×0.5cm, immerse them in an acrylamide aqueous solution, and swell them at 30℃ for 36h to allow the first network gel to fully swell and reach equilibrium, thus obtaining the swollen first network gel. S5. Remove the swollen first network gel, blot the surface liquid with filter paper, and then place it in a UV curing chamber at 15mW / cm². 2 Irradiation under ultraviolet light for 20 minutes causes acrylamide to polymerize and form a polyacrylamide network, resulting in a double-network gel. S6. Place the double-network gel in deionized water and dialyze for 60 hours, changing the deionized water every 8 hours to remove unreacted isophorone diisocyanate, triethylenetetramine, and acrylamide, to obtain a double-network transparent polyurea hydrogel.

[0035] Example 3: S1. Weigh dicyclohexylmethane diisocyanate and polyethyleneimine at a mass ratio of 1:0.8, add 0.1wt% stannous octoate, and stir at 25°C for 1 hour to obtain the prepolymer. S2. Place the prepolymer into a polytetrafluoroethylene mold and heat-cur it at 100°C for 1 hour to obtain the first network gel. Cool it to room temperature for later use. S3. Weigh 10g of polyacrylic acid and slowly add it to 90mL of deionized water. Stir at room temperature until the solution is mixed evenly to obtain an aqueous solution of polyacrylic acid. S4. Cut the first network gel into blocks of 2cm×2cm×0.5cm, immerse them in polyacrylic acid aqueous solution, and swell at 25℃ for 48h to allow the first network gel to fully swell and reach equilibrium, thus obtaining the swollen first network gel. S5. Take out the swollen first network gel and freeze it at -20℃ to 40℃ for 12 hours. Then thaw it at 25℃ to 40℃ for 6 hours. Repeat this process 3 times to obtain a double network gel. S6. Place the double-network gel in deionized water and dialyze for 48 hours to remove unreacted dicyclohexylmethane diisocyanate, polyethyleneimine, and stannous octoate, to obtain a double-network transparent polyurea hydrogel.

[0036] Example 4: S1 is the same as step S1 in Example 1; S2, the same as step S2 in Example 1; S3. Weigh 10g of polyvinyl alcohol and dissolve it in 90mL of deionized water. Stir at 80℃ until completely dissolved. After cooling to room temperature, add 0.5wt% of photoinitiator and stir until dissolved to obtain a polyvinyl alcohol aqueous solution. S4, Same as step S4 in Example 1; S5, the same as step S5 in Example 1; S6 is the same as step S6 in Example 1.

[0037] Example 5: S1 is the same as step S1 in Example 1; S2, the same as step S2 in Example 1; S3. Weigh 30g of polyvinyl alcohol and dissolve it in 70mL of deionized water. Stir at 80℃ until completely dissolved. After cooling to room temperature, add 0.5wt% of photoinitiator and stir until dissolved to obtain a polyvinyl alcohol aqueous solution. S4, Same as step S4 in Example 1; S5, the same as step S5 in Example 1; S6 is the same as step S6 in Example 1.

[0038] Comparative Examples 1-7: Comparative Example 1: Compared with Example 1, the difference is that hexamethylene diisocyanate in step S1 is replaced by an equal mass of diphenylmethane diisocyanate, while the other steps are the same.

[0039] Comparative Example 2: Compared with Example 1, the difference is that only steps S1 and S2 were performed, and the product obtained was a polyurea elastomer instead of a hydrogel, which had poor mechanical properties and lower fracture energy and compressive strength than Example 1.

[0040] Comparative Example 3: Compared with Example 1, the difference is that steps S1, S2 and S4 are not performed. Instead, the polyvinyl alcohol aqueous solution prepared in step S3 is directly poured into the polytetrafluoroethylene mold, and step S5 is performed for ultraviolet curing.

[0041] Comparative Example 4: Compared with Example 1, the difference is that the raw materials of step S1 and step S3 were mixed and stirred in a 50 mL three-necked flask, then transferred to a polytetrafluoroethylene mold, heated in an oven at 60 °C and irradiated with ultraviolet light.

[0042] Comparative Example 5: Compared with Example 1, the difference is that dibutyltin dilaurate catalyst is not added in step S1, while the other steps are the same.

[0043] Comparative Example 6: Compared with Example 1, the difference is that the first network was prepared by UV curing using acrylate monomers, crosslinking agents and photoinitiators, and the subsequent steps were the same as steps S4 and S5.

[0044] Comparative Example 7: Compared with Example 3, the difference is that step S5 is changed to the same step as in Example 1, and the remaining steps are the same.

[0045] Test Examples 1-4: Test Example 1: Light Transmittance Test Experimental steps: The hydrogel sample after dialysis was cut into 10mm×10mm×2mm sheets. Deionized water was used as a blank reference. The sample was placed in the optical path, and the transmittance in the wavelength range of 400nm to 800nm ​​was scanned and the average value was recorded.

[0046] Table 1. Optical transmittance test data of hydrogel samples As shown in Table 1, the first network prepared using hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate produces a hydrogel with high transparency. In contrast, Comparative Example 1, which uses diphenylmethane diisocyanate, results in a yellowish final product with reduced light transmittance.

[0047] Test Example 2: Compressive Strength and Fracture Energy Test Experimental procedure: compressive strength The hydrogel sample was prepared as a cylinder with a diameter of 10 mm and a height of 10 mm. Compression was applied to the hydrogel sample at a constant rate of 5 mm / min, and the compressive stress value corresponding to a strain of 60% was recorded.

[0048] Experimental steps: fracture energy The hydrogel sample was prepared into a rectangle of 50mm×20mm×2mm, and a 20mm slit was pre-made on one side. Tensile test was performed using a tensile rate of 50mm / min, and the fracture energy was calculated based on the force-displacement curve.

[0049] Table 2. Compressive strength and fracture energy test data As shown in Table 2, the dual-network hydrogels of Examples 1-5 all exhibit high compressive strength and high fracture energy, while the compressive strength and fracture energy of Comparative Example 2 (only the first network) and Comparative Example 3 (only the second network) are both low, which proves the necessity of the dual-network interpenetrating structure for achieving high compressive strength and high fracture energy of hydrogels.

[0050] Test Example 3: Self-Healing Performance Test Experimental steps: The hydrogel sample was prepared as a standard tensile specimen. The tensile breaking strength of the original specimen was tested. The specimen was completely cut into two pieces with a blade. The cut surfaces were immediately brought back into contact and a slight pressure was applied. Repair was carried out according to the conditions set in different embodiments. The tensile breaking strength of the repaired specimen was tested. The repair efficiency was calculated by dividing the tensile breaking strength by the tensile breaking strength of the original specimen and then multiplying the result by 100%.

[0051] Table 3. Test data on the self-healing efficiency of hydrogel samples As shown in Table 3, Examples 1-3 all exhibited repair efficiencies exceeding 90%, while Comparative Example 6 showed almost no repair capability, and Comparative Example 5 had reduced repair efficiency due to insufficient cross-linking of the first network.

[0052] Test Example 4: Experimental steps: Catalyst comparison: Samples were prepared according to the processes of Example 1 and Comparative Example 5, respectively, with all other steps remaining the same.

[0053] Crosslinking method comparison: Samples were prepared according to the processes of Example 3 and Comparative Example 7, respectively, with all other steps remaining the same.

[0054] Performance characterization: The self-healing efficiency of the samples with different crosslinking methods was tested using the method of Test Example 3, and the compressive strength and fracture energy of the samples with different crosslinking methods were tested using the method of Test Example 2. We also observed whether the samples were successfully cured.

[0055] Table 4. Network quality ratio and key preparation parameters Table 5. Comparison of the Influence of Key Preparation Parameters As can be seen from Tables 4 and 5, the addition of dibutyltin dilaurate is necessary in the preparation of the first network. Although Comparative Example 5 can also form a gel in the absence of a catalyst, the cross-linking of the first network in Comparative Example 5 is insufficient, the number of dynamic urea bonds is insufficient or the network structure is defective, resulting in a self-healing efficiency that is much lower than that of Example 1. At the same time, the compressive strength and fracture energy are also affected.

[0056] In Example 3, the polyacrylic acid can form an effective physical cross-linked second network through freeze-thaw cycles. However, in Comparative Example 7, the freeze-thaw cycle step was replaced with ultraviolet light irradiation. Since the polyacrylic acid does not respond to ultraviolet light, the second network failed to form, and the product did not solidify. It only originated from the swollen first network, which proved the failure of the process mismatch.

Claims

1. A dual-network transparent polyurea hydrogel based on dynamic urea bonds, characterized in that, Including the first network and the second network: The first network is composed of polyurea polymer chains containing dynamic urea bonds formed by the reaction of aliphatic diisocyanate and polyamine compound in the presence of organotin catalyst and thermal curing; it is also called the first network gel. The second network is composed of a polyvinyl alcohol crosslinked network or a polyacrylamide crosslinked network; The second network is formed inside the first network gel by ultraviolet light-induced crosslinking after the first network gel has been immersed in an aqueous solution of polyvinyl alcohol or an aqueous solution of acrylamide and swollen to equilibrium. The first network and the second network form an interpenetrating dual network structure, and the quality ratio of the first network to the second network is 1:1.5-1:2; The dynamic urea bond is formed by the reaction of an aliphatic diisocyanate monomer with a polyamine compound; The polyamine compound is at least one of tetraethylenepentamine, triethylenetetramine, and polyethyleneimine; The amount of the organotin catalyst is 0.1-1 wt% of the total mass of the aliphatic diisocyanate and polyamine compound; The second network component aqueous solution also contains a photoinitiator.

2. The dual-network transparent polyurea hydrogel based on dynamic urea bonds according to claim 1, characterized in that, The aliphatic diisocyanate is at least one of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate.

3. The dual-network transparent polyurea hydrogel based on dynamic urea bonds according to claim 1, characterized in that, The second network is a polyvinyl alcohol crosslinking network, the aliphatic diisocyanate is hexamethylene diisocyanate, the polyamine compound is tetraethylenepentamine, and the mass ratio of the first network to the second network is 1:

2.

4. A method for preparing a dual-network transparent polyurea hydrogel based on dynamic urea bonds, used to prepare the dual-network transparent polyurea hydrogel based on dynamic urea bonds as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Construction of the first network: Aliphatic diisocyanate and polyamine compound are reacted in the presence of organotin catalyst to form a prepolymer containing dynamic urea bonds, which is then thermosetting to obtain the first network gel. S2. Introduction of the second network: Immerse the first network gel in a polyvinyl alcohol aqueous solution or an acrylamide aqueous solution to allow it to swell and reach equilibrium; S3, Secondary cross-linking: The first network gel after swelling equilibrium is subjected to UV light-induced cross-linking, so that the polyvinyl alcohol cross-linking network or polyacrylamide cross-linking network is formed inside the first network gel, forming a uniform interpenetrating network, thereby obtaining a double network gel. S4. Purification treatment: Dialyze the dual-network gel to remove unreacted monomers from the dual-network gel to obtain the dual-network transparent polyurea hydrogel. The quality ratio of the first network to the second network is 1:1.5-1:

2.

5. The method for preparing a dual-network transparent polyurea hydrogel based on dynamic urea bonds according to claim 4, characterized in that, The organotin catalyst is dibutyltin dilaurate or stannous octoate.

6. The method for preparing a dual-network transparent polyurea hydrogel based on dynamic urea bonds according to claim 4, characterized in that, In step S1, the thermosetting temperature is 60-100℃ and the thermosetting time is 1-5h.

7. The method for preparing a dual-network transparent polyurea hydrogel based on dynamic urea bonds according to claim 4, characterized in that, In step S2, the concentration of the second network component aqueous solution is 10-30 wt%, and the swelling equilibrium time is 12-48 h.

8. The method for preparing a dual-network transparent polyurea hydrogel based on dynamic urea bonds according to claim 4, characterized in that, In step S3, the UV intensity of the UV-induced crosslinking is 5-20 mW / cm. 2 The irradiation time is 10-60 minutes; In step S4, the dialysis involves placing the dual-network gel in deionized water for dialysis for 48-72 hours, during which the deionized water is replaced every 6-8 hours.

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