Double-layer hydrogel capable of enhancing moisture absorption and circulating heat dissipation as well as preparation and application of double-layer hydrogel

Abstract

The invention discloses a double-layer hydrogel capable of enhancing moisture absorption and circulating heat dissipation and preparation and application thereof.The method comprises the steps that 1, after CaCl2. 6H2O and deionized water are mixed, polyvinyl alcohol and borax are added under the condition of water bath heating and stirring, and polyvinyl alcohol phase change hydrogel is obtained; 2) uniformly mixing a polymeric monomer, a cross-linking agent, a catalyst and the modified aloe extract, then adding a photoinitiator, and further uniformly mixing; 3, after the surface of the phase change layer is activated through oxygen plasmas, the moisture absorption layer monomer solution is coated and subjected to ultraviolet polymerization, and finally the double-layer hydrogel is obtained.The hydrogel prepared through the method has excellent heat dissipation performance and interface stability and can be used for electronic equipment cooling, building energy saving and functional special clothes.

Description

Technical Field

[0001] This invention belongs to the field of hydrogel materials, and relates to a double-layer hydrogel with enhanced moisture absorption and heat dissipation, its preparation and application. Background Technology

[0002] As electronic devices develop towards high performance and miniaturization, their power density is increasing, leading to a sharp rise in heat flux density. Effective thermal management has become crucial to ensuring equipment performance, reliability, and service life.

[0003] Hydrogels, containing a large amount of water, can achieve efficient and rapid heat dissipation through water evaporation, making them a highly promising passive cooling technology. However, a significant limitation of single hydrogel materials is that when exposed to air, the internal water will irreversibly and continuously evaporate and dissipate. Once the water is depleted, its heat dissipation function will immediately cease.

[0004] Therefore, there is an urgent need in this field for a new material structure that can combine efficient evaporative heat dissipation with sustainable moisture replenishment, so as to achieve strong and long-lasting heat dissipation while ensuring the stability of the material interface and the overall mechanical properties, in order to meet the application requirements of electronic devices, buildings and clothing. Summary of the Invention

[0005] To address the aforementioned shortcomings, this invention effectively solves the technical bottlenecks through interfacial polymerization self-assembly technology and Schiff base-modified aloe vera extract. This invention aims to develop a self-hygroscopic bilayer phase change hydrogel as a novel heat dissipation material based on the natural transpiration cooling mechanism of leaves.

[0006] This invention provides a double-layer hydrogel with enhanced moisture absorption and cyclic heat dissipation, its preparation, and its application. The double-layer hydrogel of this invention consists of a phase change layer and a moisture-absorbing layer. The phase change layer is composed of polyvinyl alcohol, borax, and CaCl2, while the moisture-absorbing layer is composed of acrylamide, sodium methacrylate, and modified aloe vera extract. The double-layer hydrogel exhibits excellent tensile and moisture-absorbing properties, and while removing heat, it also possesses moisture-absorbing and regenerating characteristics.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing a double-layer hydrogel with enhanced moisture absorption and heat dissipation, characterized by comprising the following steps: (1) Polyvinyl alcohol was added to CaCl2 solution and reacted, followed by the addition of borax and reaction, and then solidified to obtain phase change hydrogel; (2) Disperse the polymer monomer and crosslinking agent in water, add the modified aloe vera extract and catalyst to react, and add the photoinitiator to obtain a mixture; (3) After surface activation of the phase change hydrogel in step (1), the mixture in step (2) is coated on the surface and cured by ultraviolet light to obtain the double-layer hydrogel.

[0008] Preferably, in step (1), the mass ratio of the solute in the CaCl2 solution to polyvinyl alcohol is 4:1 to 10:1; and the mass ratio of polyvinyl alcohol to borax is 1:1 to 9:1.

[0009] Preferably, in step (1), after adding polyvinyl alcohol, it is stirred at 60℃~100℃ for 2~5 hours until no particulate polyvinyl alcohol is observed; after adding borax, it is reacted for 20~40 minutes until a viscous gel liquid is formed; then it is poured into a mold and kept in a vacuum drying oven at 50~80℃ for 1~5 hours to remove air bubbles, and then cured at room temperature and pressure.

[0010] Preferably, in step (2), the polymerizing monomer is a mixture of sodium methacrylate and acrylamide in a mass ratio of 1:1 to 6:1; The crosslinking agent is N,N′-methylenebisacrylamide; The catalyst is N,N,N,N-tetramethylethylenediamine; The photoinitiator is at least one of photoinitiator I2959, photoinitiator LAP, and photoinitiator VA-086.

[0011] Preferably, in step (2), the amount of crosslinking agent added is 1 to 5 wt% of the polymer monomer; the amount of catalyst added is 0.5 to 3 wt% of the polymer monomer; the amount of modified aloe vera extract added is 5 to 15 wt% of the polymer monomer; and the amount of photoinitiator added is 2 to 10 wt% of the polymer monomer.

[0012] Preferably, in step (2), the modified aloe extract refers to an aloe extract modified by the Schiff base reaction. The specific method is as follows: chitosan is added to the aloe polysaccharide solution to react, so that the mass ratio of aloe polysaccharide to chitosan containing amino compounds in the system is (2:1) ~ (4:1); the reaction is carried out in the dark at pH 5.0 ± 0.2 and 60 ± 2℃ for 16-18 hours; after the reaction is completed, the cooled reaction solution is poured into anhydrous ethanol, and after standing, the precipitate is washed with ethanol and water, dried, and pulverized to obtain the modified aloe extract.

[0013] Preferably, in step (3), the surface activation refers to: placing the phase change hydrogel in a plasma treatment instrument and treating it for 2 to 10 minutes under a power of 50 to 70 W.

[0014] Preferably, in step (3), the thickness of the mixed liquid coating is controlled to be 0.5~3mm; the conditions for ultraviolet curing are: under N2 protection, using a wavelength of 365 nm and a power density of 4.0 mW / cm². 2 Treat with ultraviolet light at 30~35℃ for 2~3 hours.

[0015] The enhanced moisture-absorbing and heat-dissipating bilayer hydrogel prepared by the method described in this invention.

[0016] The present invention relates to the application of the enhanced moisture-absorbing and heat-dissipating double-layer hydrogel in electronic devices, building energy conservation, and functional special clothing.

[0017] This invention has the following advantages over current mainstream thermal management materials: (1) Flexible phase change hydrogel. Currently, the main thermal management materials are difficult to fit tightly with the equipment at low temperatures, which can easily generate large contact thermal resistance and further affect their heat dissipation effect.

[0018] (2) Bionic blades, water evaporation removes heat. Traditional solid-liquid phase change materials have low phase change enthalpy, making them difficult to apply in high energy density heat dissipation scenarios. Water, on the other hand, has a high liquid-gas phase change enthalpy (about 2.2 kJ / g), which can quickly remove heat and achieve rapid cooling of the equipment.

[0019] (3) Phase change hydrogel combined with hygroscopic hydrogel to achieve regenerative cycle of water adsorption and desorption. The phase change hydrogel is attached to the equipment. During operation, it carries away heat by evaporating water. The hygroscopic hydrogel adsorbs water vapor from the environment and transports it to the phase change hydrogel through osmotic pressure, forming an adsorption-desorption cycle of water vapor. This can greatly extend the maximum working time of the phase change hydrogel. When idle, the hydrogel can be placed in a high humidity environment to achieve the recycling of the hydrogel. Attached Figure Description

[0020] Figure 1 This is a diagram showing the cooling effect of the hydrogel in Example 1.

[0021] Figure 2 This is a diagram showing the cooling effect of the hydrogel in Example 1 applied to the back of a mobile phone.

[0022] Figure 3 The mass loss of the hydrogel in Example 1 over time is shown on different temperature heating platforms.

[0023] Figure 4 This is a comparison chart of the mass changes between Example 1 and Comparative Example 1.

[0024] Figure 5 This is a photograph of the hydrogel in Example 5 in its fully water-saturated state.

[0025] Figure 6 This is a photograph of the hydrogel after water desorption in Example 5. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to examples, but the implementation of the present invention is not limited thereto.

[0027] The Schiff base-modified aloe vera extract used in the following examples was prepared by the following method: a) Reaction system configuration: Aloe vera polysaccharide powder (supplier: Changshengqing Biotechnology) was dissolved in deionized water to prepare a solution with a mass-volume concentration of 2%-5%. While stirring, an equal volume of a 1% (w / w) aqueous solution of chitosan in acetic acid was added to this solution, controlling the mass ratio of aloe vera polysaccharide to chitosan to be (2:1) ~ (4:1). The pH of the reaction system was then monitored using a pH meter and adjusted to 5.0 ± 0.2 using dilute hydrochloric acid or dilute sodium hydroxide solution.

[0028] b) Schiff base reaction: The above mixed solution is transferred to a round-bottom flask or reaction vessel and reacted in a constant temperature oil bath at 60 ± 2℃ with a mechanical stirring rate of 200-400 rpm for 16-18 hours in the dark to form a dynamic covalent cross-linked network through the Schiff base reaction.

[0029] c) Post-reaction treatment: After the reaction is complete, cool the reaction solution to room temperature.

[0030] 1. Precipitation and Washing: Under vigorous stirring, the reaction solution is slowly poured into 3 times its volume of anhydrous ethanol. The modified product will form a fibrous or flocculent precipitate. After standing, the supernatant is discarded, and the precipitate is washed twice with a 75% (v / v) ethanol aqueous solution to remove unreacted small molecule impurities.

[0031] 2. Drying: Transfer the washed precipitate to a petri dish and place it in a vacuum drying oven at 50°C for 24 hours.

[0032] 3. Grinding: After grinding the dried block product, pass it through an 80-mesh sieve to obtain a brownish-yellow Schiff base modified aloe extract powder, which is then placed in a desiccator and sealed for storage. Example 1

[0033] Step (1): Weigh 10 g of CaCl2•6H2O and 10 mL of deionized water and place them in a three-necked flask. Dissolve them in a 60°C water bath and mechanically stir at 600 r / min. Add 1 g of polyvinyl alcohol (degree of hydrolysis: 95%, average molecular weight: 8.9 × 10⁻⁶). 4 ~9.8×10 4(i.e., 89,000 ~ 98,000 g / mol) Supplier: Shanghai Macklin Biochemical Technology Co., Ltd.; Stir continuously at 85℃ for 3 hours until the system is a homogeneous milky white solution with no visible particles. Then, add 0.4 g of borax and continue stirring for 0.5 hours until a viscous gel liquid is formed. Pour the obtained gel liquid into a mold and place it in a vacuum drying oven at 65℃ for 2.5 hours to remove air bubbles. Subsequently, solidify at room temperature and pressure to obtain a transparent polyvinyl alcohol phase change hydrogel.

[0034] Step (2): Weigh 2 g of sodium methacrylate, 1.2 g of acrylamide and 0.05 g of N,N′-methylenebisacrylamide respectively, disperse them in a beaker containing 20 mL of deionized water, and stir magnetically at room temperature for 1 hour until the solution is clear. Then weigh 0.25 g of Schiff base modified aloe vera extract and 0.03 g of N,N,N,N-tetramethylethylenediamine (TEMED) and slowly pour them into the above solution. Stir for 1 hour. Then add 0.15 g of photoinitiator I2959 and continue to stir in the dark for 0.5 hours to ensure complete dissolution, to obtain a mixed solution of moisture-absorbing layer monomers.

[0035] Step (3): Cut the phase change hydrogel prepared in step (1) into the required size and place one surface of it in an oxygen plasma treatment instrument. Treat for 2 minutes at a power of 50 W to complete surface activation. Uniformly coat the hygroscopic layer monomer mixture from step (2) onto the activated phase change hydrogel surface, controlling the coating thickness to 2 mm. Then, place it in an ultraviolet curing chamber under N2 protection, using a wavelength of 365 nm and a power density of 4.0 mW / cm². 2 Irradiation with ultraviolet light at 30°C for 2.5 hours causes the moisture-absorbing layer to complete interfacial polymerization on the surface of the phase change layer. After polymerization, the resulting bilayer structure material is removed, yielding a bilayer hydrogel with enhanced moisture absorption and heat dissipation. The two layers of this product are bonded together at the molecular level, resulting in a strong interfacial bond. Example 2

[0036] Step (1): Weigh 6.0 g of CaCl2•6H2O and 40 mL of deionized water and place them in a beaker. Stir magnetically in a water bath at 60°C for 0.5 hours until CaCl2•6H2O is completely dissolved to obtain a CaCl2 solution. Separately, weigh 1.5 g of polyvinyl alcohol (degree of hydrolysis: 95%, molecular weight: 89,000–98,000) and 18.5 mL of deionized water and place them in a three-necked flask. Stir mechanically at 500 r / min in a water bath at 80°C for 4 hours. Then add 0.3 g of borax and continue stirring for half an hour. Pour the mixture into a mold to obtain a colorless polyvinyl alcohol gel. Pour the resulting gel liquid into the mold and place it in a vacuum drying oven at 65°C for 2.5 hours to remove air bubbles. Then solidify at room temperature and pressure to obtain a transparent polyvinyl alcohol phase change hydrogel.

[0037] Step (2): Weigh 2.8 g of sodium methacrylate, 1.5 g of acrylamide, and 0.08 g of N,N′-methylenebisacrylamide, and disperse them in a beaker containing 25 mL of deionized water. Stir magnetically at room temperature for 1 hour until the solution is clear. Then weigh 0.34 g of Schiff base-modified aloe vera extract and 0.03 g of N,N,N,N-tetramethylethylenediamine (TEMED) and stir magnetically for 1 hour to mix them evenly. Subsequently, add 0.20 g of photoinitiator I2959 and continue stirring in the dark for 0.5 hours to ensure complete dissolution, obtaining a mixed solution of hygroscopic layer monomers.

[0038] Step (3): Cut the phase change hydrogel prepared in step (1) into the required size and place one surface of it in an oxygen plasma treatment instrument. Treat for 2 minutes at a power of 50 W to complete surface activation. Uniformly coat the hygroscopic layer monomer mixture from step (2) onto the activated phase change hydrogel surface, controlling the coating thickness to approximately 1.0 mm. Then, place it in an ultraviolet curing chamber under N2 protection, using a wavelength of 365 nm and a power density of 4.0 mW / cm². 2 Irradiation with ultraviolet light at 30°C for 2.5 hours causes the moisture-absorbing layer to complete interfacial polymerization on the surface of the phase change layer. After polymerization, the resulting bilayer structure material is removed, yielding a bilayer hydrogel with enhanced moisture absorption and heat dissipation. Example 3

[0039] Step (1): Weigh 10 g of CaCl2•6H2O and 35 mL of deionized water and place them in a beaker. Stir magnetically in a water bath at 55°C for 0.5 hours until CaCl2•6H2O is completely dissolved to obtain a CaCl2 solution. Separately, weigh 1.8 g of polyvinyl alcohol (specification: hydrolysis degree 95%, average molecular weight 89,000–98,000 g / mol) and 15 mL of deionized water and place them in a three-necked flask. Stir mechanically at 400 r / min in an 80°C water bath for 4 hours. Then add 0.3 g of borax and continue stirring for half an hour. Pour the mixture into a mold to obtain a colorless polyvinyl alcohol gel. Pour the obtained gel liquid into the mold and place it in a vacuum drying oven at 65°C for 2.5 hours to remove air bubbles. Then solidify at room temperature and pressure to obtain a transparent polyvinyl alcohol phase change hydrogel.

[0040] Step (2): Weigh 2.8 g of sodium methacrylate, 1.5 g of acrylamide, and 0.08 g of N,N′-methylenebisacrylamide, and disperse them in a beaker containing 25 mL of deionized water. Stir magnetically at room temperature for 1 hour until the solution is clear. Then, weigh 0.44 g of Schiff base-modified aloe vera extract and 0.03 g of N,N,N,N-tetramethylethylenediamine (TEMED) and slowly pour them into the above solution, stirring for 1 hour. Subsequently, add 0.18 g of photoinitiator I2959 and continue stirring in the dark for 0.5 hours to ensure complete dissolution, obtaining a mixed solution of hygroscopic layer monomers.

[0041] Step (3): Cut the phase change hydrogel prepared in step (1) into the required size and place one surface of it in an oxygen plasma treatment instrument. Treat for 2 minutes at a power of 50 W to complete surface activation, controlling the coating thickness to approximately 1.0 mm. Uniformly coat the activated phase change hydrogel surface with the hygroscopic layer monomer mixture solution from step (2). Then, place it in an ultraviolet curing chamber under N2 protection, using a wavelength of 365 nm and a power density of 4.0 mW / cm². 2 Irradiation with ultraviolet light at 30°C for 2.5 hours causes the moisture-absorbing layer to complete interfacial polymerization on the surface of the phase change layer. After polymerization, the resulting bilayer structure material is removed, yielding a bilayer hydrogel with enhanced moisture absorption and heat dissipation. Example 4

[0042] Step (1): Weigh 10 g of CaCl2•6H2O and 10 mL of deionized water and place them in a beaker. Stir magnetically in a 55°C water bath for 0.5 hours until CaCl2•6H2O is completely dissolved to obtain a CaCl2 solution. Separately, weigh 2.4 g of polyvinyl alcohol (degree of hydrolysis: 95%, molecular weight: 89,000–98,000) and 18.2 mL of deionized water and place them in a three-necked flask. Stir mechanically in a 70°C water bath at 500 r / min for 4 hours. Then add 0.4 g of borax and continue stirring for half an hour. Pour the mixture into a mold to obtain a colorless polyvinyl alcohol gel. Place the gel in a 90°C oven for 2 hours until the mass no longer changes. Finally, immerse the dried gel in the above CaCl2 solution for 3 hours. After complete swelling, remove the gel to obtain a phase change hydrogel.

[0043] Step (2): Weigh 2.4 g of sodium methacrylate, 1.6 g of acrylamide, and 0.08 g of N,N′-methylenebisacrylamide, and disperse them in a beaker containing 30 mL of deionized water. Stir magnetically at room temperature for 1 hour until the solution is clear. Then, weigh 0.5 g of Schiff base-modified aloe vera extract and 0.03 g of N,N,N,N-tetramethylethylenediamine (TEMED) and slowly pour them into the above solution, stirring for 1 hour. Subsequently, add 0.18 g of photoinitiator I2959 and continue stirring in the dark for 0.5 hours to ensure complete dissolution, obtaining a mixed solution of hygroscopic layer monomers.

[0044] Step (3): Cut the phase change hydrogel prepared in step (1) into the required size and place one surface of it in an oxygen plasma treatment instrument. Treat for 2 minutes at a power of 50 W to complete surface activation. Uniformly coat the hygroscopic layer monomer mixture from step (2) onto the activated phase change hydrogel surface, controlling the coating thickness to approximately 1.0 mm. Then, place it in an ultraviolet curing chamber under N2 protection, using a wavelength of 365 nm and a power density of 4.0 mW / cm². 2 Irradiation with ultraviolet light at 30°C for 2.5 hours causes the moisture-absorbing layer to complete interfacial polymerization on the surface of the phase change layer. After polymerization, the resulting bilayer structure material is removed, yielding a bilayer hydrogel with enhanced moisture absorption and heat dissipation. Example 5

[0045] Step (1): Same as in Example 1, weigh 10 g of CaCl2•6H2O and 10 mL of deionized water and place them in a three-necked flask. Melt them in a 60°C water bath and mechanically stir at 600 r / min. Add 1 g of polyvinyl alcohol (degree of hydrolysis: 95%; average molecular weight: 8.9 × 10⁻⁶). 4 ~9.8×10 4(i.e., 89,000 ~ 98,000 g / mol) Supplier: Shanghai Macklin Biochemical Technology Co., Ltd.) and stirred at 85°C for 3 hours until no particulate polyvinyl alcohol was observed. Then, 0.4 g of borax was added, and after reacting for half an hour, it was poured into a mold and placed in a vacuum drying oven at 60°C for 2 hours to remove air bubbles. It was then cured at room temperature to obtain a phase change hydrogel. Step (2): Weigh 2 g of sodium methacrylate, 1.2 g of acrylamide, and 0.05 g of N,N′-methylenebisacrylamide, and disperse them in a beaker containing 20 mL of deionized water. Stir magnetically at room temperature for 1 hour until the solution is clear. Then, weigh 0.3 g of Schiff base-modified aloe vera extract and 0.03 g of N,N,N,N-tetramethylethylenediamine (TEMED) and slowly pour them into the above solution, stirring for 1 hour. Subsequently, add 0.15 g of photoinitiator I2959 and continue stirring in the dark for 0.5 hours to ensure complete dissolution, obtaining a mixed solution of hygroscopic layer monomers.

[0046] Step (3): Cut the phase change hydrogel prepared in step (1) into standard sizes and activate one surface of it using an oxygen plasma treatment instrument. The treatment parameters are: power 50 W, time 2 minutes. The moisture-absorbing layer monomer mixture solution from step (2) is uniformly coated on the activated phase change hydrogel surface, and the coating thickness is controlled to be about 1.0 mm.

[0047] Subsequently, it was placed in an ultraviolet curing chamber under N2 protection, using a wavelength of 365 nm and a power density of 4.0 mW / cm². 2 Ultraviolet light is passed through a quartz glass plate and irradiated at 30°C for 2.5 hours, causing the moisture-absorbing layer monomers to polymerize in situ on the surface of the phase change layer and form strong chemical bonds.

[0048] After polymerization, the resulting material is removed, yielding a bilayer phase change hydrogel with high interfacial bonding strength and moisture absorption-regeneration cycle function. Example 6

[0049] Step (1): Weigh 12 g of CaCl2•6H2O and 15 mL of deionized water into a beaker and stir magnetically in a 60°C water bath for 0.5 hours until completely dissolved to obtain a homogeneous CaCl2 solution. Separately weigh 2.0 g of polyvinyl alcohol (hydrolysis degree: 95%, molecular weight: 89,000–98,000) and 20 mL of deionized water into a three-necked flask and stir mechanically at 500 r / min for 4 hours in an 85°C water bath until completely dissolved. Then add 0.35 g of borax and continue stirring for 0.5 hours until a homogeneous viscous liquid is formed. Pour the mixture into a mold and place it in a 60°C vacuum drying oven for 2 hours to remove air bubbles. After curing at room temperature, a transparent polyvinyl alcohol phase change hydrogel is obtained.

[0050] Step (2): Weigh 3.0 g of sodium methacrylate, 1.8 g of acrylamide, and 0.1 g of N,N′-methylenebisacrylamide, disperse them in 30 mL of deionized water, and stir magnetically for 1 hour at room temperature until completely dissolved. Then add 0.4 g of Schiff base-modified aloe vera extract and 0.03 g of N,N,N,N-tetramethylethylenediamine (TEMED) and stir magnetically for 1 hour to mix thoroughly. Then add 0.20 g of photoinitiator I2959 and continue stirring in the dark for 0.5 hours to ensure complete dissolution, obtaining a mixed solution of hygroscopic layer monomers.

[0051] Step (3): The surface of the phase change hydrogel obtained in step (1) is subjected to oxygen plasma treatment (power 55 W, time 2.5 minutes) to increase surface activity and reaction sites.

[0052] The moisture-absorbing layer monomer mixture solution from step (2) is uniformly coated onto the surface of the activated phase change hydrogel, and the coating thickness is controlled to be approximately 1.2 mm.

[0053] Subsequently, it was placed in an ultraviolet curing chamber under N2 protection, using a wavelength of 365 nm and a power density of 4.0 mW / cm². 2 Irradiation with ultraviolet light at 30°C for 3.0 hours causes the moisture-absorbing layer to polymerize in situ at the interface and form a strong chemical bond with the phase change layer.

[0054] After polymerization, the resulting material is removed, yielding a bilayer hydrogel with excellent interfacial stability and high moisture absorption and heat dissipation properties.

[0055] Comparative Example 1 The only difference between the preparation method of the hydrogel in this example and that in Example 1 is that the monomer mixture solution without a moisture-absorbing layer is not coated in this example; it is a single-layer polyvinyl alcohol phase change hydrogel.

[0056] See attached document Figure 1As shown, under natural cooling conditions, it takes approximately 2900 s for the water temperature to drop to room temperature of 25°C; however, with the bilayer hydrogel prepared in Example 1, the cooling time is significantly shortened to 850 s. Once the water temperature reaches the ambient temperature, the moisture concentration gradient between the surface of the bilayer hydrogel and the surrounding air continues to drive the cooling process, and ultimately, the water temperature can be further reduced to 19°C, which is 6°C lower than the ambient temperature.

[0057] See attached document Figure 2 As shown, the dimensions are 0.05 × 0.05 × 0.005 m. 3 The bilayer hydrogel prepared in Example 1 was attached to the back of a Xiaomi 10 Pro phone. Temperature changes during charging and gaming were monitored in real time using thermocouples and compared with those under natural cooling conditions. During charging, the peak temperature of the phone using the bilayer hydrogel prepared in Example 1 was 29.3℃, 7.8℃ lower than the naturally cooled phone (37.1℃). During gaming, the peak temperature of the phone using the bilayer hydrogel prepared in Example 1 was 31.6℃, 6.5℃ lower than the naturally cooled phone (38.1℃). After 2 hours of testing, the temperature of the phone using the bilayer hydrogel prepared in Example 1 stabilized at 25.2℃, 2℃ lower than the ambient temperature.

[0058] See attached document Figure 3 As shown, the mass loss of the bilayer hydrogel prepared in Example 1 was measured over time on heating platforms at different temperatures (50°C, 60°C, and 70°C). The results show that even under high temperature conditions of 70°C, the hydrogel can still maintain a continuous cooling effect for nearly 5 hours.

[0059] See attached document Figure 4 The moisture absorption and regeneration time of the bilayer phase change hydrogel in Example 1 and the hydrogel without a moisture-absorbing layer in Comparative Example 1 were compared after heating for 1 hour. The saturated bilayer phase change hydrogel in Example 1 and the hydrogel without a moisture-absorbing layer in Comparative Example 1 were placed in a 50°C oven and heated for 1 hour, then quickly placed in a constant temperature and humidity chamber at 25°C and 90% RH for static standing. The hydrogels were periodically removed and weighed. The results showed that after heating for 1 hour, the bilayer phase change hydrogel in Example 1 still retained a higher percentage of its mass. During the moisture absorption stage, the bilayer phase change hydrogel in Example 1 (0.01 × 0.01 × 0.005 m...) 3 At 25℃ and 90% RH, it takes nearly 10 hours to recover its initial mass, exhibiting a shorter regeneration time than the hydrogel without the hygroscopic layer in Comparative Example 1. These results demonstrate that the bilayer phase change hydrogel with the hygroscopic layer possesses superior moisture absorption and regeneration capabilities. The hydrogel's heat dissipation performance primarily relies on water evaporation, and its mass recovery ability during dehydration and rehydration indicates that the rehydrated hydrogel retains its heat dissipation function.

[0060] See attached document Figure 5 Example image of a saturated bilayer hydrogel prepared in Example 5 (after absorbing water for 24 hours in a constant temperature and humidity chamber with a humidity of 90% and a temperature of 25°C).

[0061] See attached document Figure 6 Example image: The bilayer hydrogel prepared in Example 5 after drying in an oven at 50°C for 24 hours.

[0062] The preferred embodiments of the present invention have been described in detail above. These are the results of numerous experiments conducted by the inventors with considerable human, financial, and time investment. It should be understood that those skilled in the art can make many modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by these claims.

Claims

1. A method for preparing a double-layer hydrogel with enhanced moisture absorption and heat dissipation, characterized in that, Includes the following steps: (1) Polyvinyl alcohol was added to CaCl2 solution and reacted, followed by the addition of borax and reaction, and then solidified to obtain phase change hydrogel; (2) Disperse the polymer monomer and crosslinking agent in water, add the modified aloe vera extract and catalyst to react, and add the photoinitiator to obtain a mixture; (3) After surface activation of the phase change hydrogel in step (1), the mixture in step (2) is coated on the surface and cured by ultraviolet light to obtain the double-layer hydrogel.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of the solute in the CaCl2 solution to polyvinyl alcohol is 4:1 to 10:1; the mass ratio of polyvinyl alcohol to borax is 1:1 to 9:

1.

3. The preparation method according to claim 2, characterized in that, In step (1), after adding polyvinyl alcohol, stir at 60℃~100℃ for 2~5 hours until no particulate polyvinyl alcohol is observed; after adding borax, react for 20~40 minutes until a viscous gel liquid is formed. It is then poured into a mold and kept in a vacuum drying oven at 50~80℃ for 1~5 hours to remove air bubbles, and then cured at room temperature and pressure.

4. The preparation method according to claim 1, characterized in that, In step (2), the polymerizing monomer is a mixture of sodium methacrylate and acrylamide in a mass ratio of 1:1 to 6:1; The crosslinking agent is N,N′-methylenebisacrylamide; The catalyst is N,N,N,N-tetramethylethylenediamine; The photoinitiator is at least one of photoinitiator I2959, photoinitiator LAP, and photoinitiator VA-086.

5. The preparation method according to claim 4, characterized in that, In step (2), the amount of crosslinking agent added is 1 to 5 wt% of the polymer monomer; the amount of catalyst added is 0.5 to 3 wt% of the polymer monomer; the amount of modified aloe vera extract added is 5 to 15 wt% of the polymer monomer; and the amount of photoinitiator added is 2 to 10 wt% of the polymer monomer.

6. The preparation method according to claim 4, characterized in that, In step (2), the modified aloe extract refers to the aloe extract modified by the Schiff base reaction. The specific method is as follows: add an aqueous solution of chitosan in acetic acid to the aloe polysaccharide solution and react so that the mass ratio of aloe polysaccharide to chitosan in the system is (2:1) ~ (4:1); react in the dark at pH 5.0 ± 0.2 and 60 ± 2℃ for 16-18 hours; after the reaction is completed, pour the cooled reaction solution into anhydrous ethanol, let it stand, take the precipitate, wash it with an aqueous ethanol solution, dry it, pulverize it and obtain the modified aloe extract.

7. The preparation method according to claim 1, characterized in that, In step (3), the surface activation refers to: placing the phase change hydrogel in a plasma treatment instrument and treating it for 2 to 10 minutes at a power of 50 to 70 W.

8. The preparation method according to claim 6, characterized in that, In step (3), the thickness of the mixed liquid coating is controlled to be 0.5~3mm; the conditions for ultraviolet curing are: under N2 protection, using a wavelength of 365 nm and a power density of 4.0 mW / cm². 2 Treat with ultraviolet light at 30~35℃ for 2~3 hours.

9. The enhanced moisture-absorbing and heat-dissipating bilayer hydrogel prepared by the method according to any one of claims 1 to 8.

10. The application of the enhanced moisture-absorbing and heat-dissipating double-layer hydrogel of claim 9 in electronic devices, building energy conservation, and functional special clothing.

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