A porous absorbent hydrogel and its preparation method and application

Abstract

The present application relates to the field of atmospheric water harvesting, and specifically relates to a porous hygroscopic gel, a preparation method and application thereof. The present application first modifies the structure of traditional binary eutectic solvent to prepare ternary eutectic solvent with hygroscopicity and polymerizability, uses the ternary eutectic solvent as an external phase, uses an organic solvent which is easy to dry and remove as an internal phase, and prepares a high internal phase emulsion under the assistance of a suitable proportion and a stabilizer; continues to add an initiator and a crosslinking agent to form a template prepolymer liquid, and prepares the porous hygroscopic gel through subsequent polymerization and vacuum drying process. Using the high internal phase emulsion as a template can introduce a highly interpenetrating porous structure to the gel, thereby accelerating the mass transfer process of water molecules and realizing atmospheric water harvesting.

Description

Technical Field

[0001] This invention relates to the field of atmospheric environmental water collection, specifically to a porous hygroscopic gel, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The atmosphere contains a significant amount of freshwater, estimated at 12,900 cubic kilometers, representing approximately 10% of the Earth's total freshwater resources, and this water can be continuously replenished through the water cycle. Therefore, adsorption-based atmospheric water harvesting systems are considered a promising method for alleviating water scarcity. These systems can produce freshwater across a wide range of relative humidity (RH), particularly in low RH (RH < 60%) environments, by directly capturing water molecules from the air using adsorbents with high water affinity. In adsorption-based atmospheric water harvesting, the hygroscopic agent is a key factor determining the overall performance of the adsorbent material and its suitability for various environmental conditions.

[0004] Desiccant is a material with a high affinity for water molecules, capable of capturing atmospheric water molecules and enriching them on its surface or within its internal structure. Its moisture absorption mechanism can be categorized based on the type of desiccant: surface water adsorption, micropore filling, and capillary condensation / absorption. Commonly used desiccant materials include nanoporous materials (MOF, COF, and microporous aluminum phosphate, etc.), hygroscopic salts (lithium chloride, lithium bromide, and calcium chloride, etc.), highly hydrophilic polymers, and liquid desiccant. Among these, gel materials, due to their unique hydrophilicity and swelling properties, have gradually become an ideal atmospheric desiccant. For example, Wang et al. (ACS Materials Lett. 2020, 2, 471.) further doped lithium chloride desiccant into a hydrogel formed from sodium alginate and calcium chloride to achieve low-energy collection of atmospheric water. Furthermore, the introduction of lithium chloride can increase the degree of cross-linking, thereby improving the mechanical properties of the gel and thus enhancing its cycling stability. T. Chen et al. (Angew. Chem. Int. Ed. 2020, 59, 19237.) prepared a superhygroscopic organic hydrogel by immersing a hydrogel formed by polymethacrylic acid and polyacrylamide in glycerol and using solvent displacement.

[0005] Most current hygroscopic gels are hydrogels or organic hydrogels. Research on eutectic solvent gels, which are constructed using eutectic solvents as dispersion media and have lower saturated vapor pressures and thus higher hygroscopic efficiency, is limited. Summary of the Invention

[0006] To overcome the above problems, this invention provides a porous hygroscopic gel, its preparation method, and its applications. First, the structure of a traditional binary eutectic solvent is modified to prepare a ternary eutectic solvent that combines hygroscopicity and polymerizability. This ternary solvent is used as the external phase, and an easily dryable organic solvent is used as the internal phase. A high internal phase emulsion is prepared with the aid of a suitable ratio and a stabilizer. An initiator and a crosslinking agent are then added to form a template prepolymer. Subsequent polymerization and vacuum drying processes yield the porous hygroscopic gel. Using the high internal phase emulsion as a template introduces a highly interpenetrating porous structure into the gel, thereby accelerating the mass transfer process of water molecules and achieving atmospheric water collection.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0008] A first aspect of the present invention provides a porous hygroscopic gel composition comprising the following components:

[0009] Ternary polymerizable eutectic solvent, composed of monomer, hydrogen bond acceptor and hydrogen bond donor;

[0010] Stabilizer;

[0011] internal phase;

[0012] Initiator;

[0013] Crosslinking agent;

[0014] Accelerator.

[0015] In a second aspect, the present invention provides a porous hygroscopic gel, wherein the above-mentioned porous hygroscopic gel composition is used to form a high internal phase emulsion gel, and the internal phase is removed to form a porous structure with high porosity.

[0016] A third aspect of the present invention provides a method for preparing the above-mentioned porous hygroscopic gel, comprising the following steps:

[0017] (1) Mixing monomers, hydrogen bond acceptors and hydrogen bond donors and heating them together forms a ternary polymerizable eutectic solvent;

[0018] (2) Add stabilizer and internal phase to the ternary polymerizable eutectic solvent in (1), and obtain a high internal phase emulsion after homogenization;

[0019] (3) Add initiator, crosslinking agent and accelerator to the high internal phase emulsion in (2), mix homogeneously to form template prepolymer liquid, initiate external phase polymerization, and obtain high internal phase emulsion gel.

[0020] (4) Remove the internal phase from the high internal phase emulsion gel to obtain a porous hygroscopic gel.

[0021] A fourth aspect of the present invention provides the application of the above-mentioned porous hygroscopic gel as a self-hygroscopic material in atmospheric water collection.

[0022] A fifth aspect of the present invention provides the application of the above-described porous hygroscopic gel as a self-hygroscopic material in humidity monitoring.

[0023] A sixth aspect of the present invention provides the application of the above-mentioned porous hygroscopic gel as a self-hygroscopic material in soil improvement.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) Traditional high internal phase emulsions often require the addition of large amounts of stabilizers to ensure their emulsification effect during preparation, and the amount of polymerizable monomers added in the external phase is limited, which severely restricts the universality of gel preparation methods and is not conducive to improving mechanical properties and hygroscopic capacity. The ternary polymerizable eutectic solvent proposed in this invention can simultaneously play the roles of reactant monomer, reaction medium, and hygroscopic component in the preparation of porous hygroscopic materials. Biocompatible amphiphilic proteins are used as stabilizers, reducing the amount of stabilizers used and being environmentally friendly. The preparation process only requires simple homogenization to form a stable high internal phase emulsion, with low energy consumption and simple operation.

[0026] (2) Compared with the traditional high internal phase emulsion template method, this invention utilizes a ternary eutectic solvent with both hygroscopicity and polymerizability as the external phase and an easily dryable organic solvent as the internal phase. A porous hygroscopic gel can be prepared through a simple mixing, heating, and vacuum drying process. A highly interpenetrating porous structure can be formed without a complex internal phase removal process, and the structure and properties of the porous gel can be changed by adjusting the template parameters.

[0027] (3) The porous hygroscopic gel prepared by this invention has high porosity (59.5%) and low density (0.7 g / cm³). 3 Large specific surface area (37.5m²) 2 / g), which is beneficial to the mass transfer process, thus exhibiting high hygroscopic capacity, and is expected to play a role in atmospheric water collection, soil improvement and humidity monitoring.

[0028] (4) The porous hygroscopic gel of the present invention has a simple, economical and practical preparation process, requires no special equipment or harsh conditions, has practical value, and is easy to scale up. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 Infrared spectra of the ternary eutectic solvents prepared in Examples 1-4;

[0031] Figure 2 Differential scanning calorimetry (DSC) was performed on the ternary eutectic solvents prepared in Examples 1-4.

[0032] Figure 3 Photographs showing the contact angles of the ternary eutectic solvent prepared in Example 3 on the surface of soy protein isolate;

[0033] Figure 4 a to f are optical microscope images of the high internal phase emulsions prepared in Examples 1-5 and 7, respectively.

[0034] Figure 5 The images show scanning electron microscope (SEM) images of the gels prepared in Example 3 and Comparative Example 1, where a is Example 3 and b is Comparative Example 1.

[0035] Figure 6 Mercury intrusion porosimetry curves of the gels prepared in Example 3 and Comparative Example 1;

[0036] Figure 7 The pore size distribution curves are for the gels prepared in Example 3 and Comparative Example 1.

[0037] Figure 8 The water absorption properties of the gels prepared in Example 3 and Comparative Example 1 under different humidity conditions are shown; a is 100% humidity, b is 75% humidity.

[0038] Figure 9 Raman spectra of the eutectic solvent (a) and gel (b) in Example 3; in-situ Raman mapping images of the gel surface (c) and cross section (d);

[0039] Figure 10 The moisture absorption (Fig. a) and water retention (Fig. b) properties of the modified soil and the real soil in Experiment Example 1 are shown. Detailed Implementation

[0040] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] A first typical embodiment of the present invention provides a porous hygroscopic gel composition comprising the following components:

[0043] Ternary polymerizable eutectic solvent, composed of monomer, hydrogen bond acceptor and hydrogen bond donor;

[0044] Stabilizer;

[0045] internal phase;

[0046] Initiator;

[0047] Crosslinking agent;

[0048] Accelerator.

[0049] In one or more embodiments, the hydrogen bond acceptor includes choline chloride.

[0050] In one or more embodiments, the hydrogen bond donor includes urea, ethylene glycol or glycerol, preferably urea.

[0051] In one or more embodiments, the monomer includes acrylamide, acrylic acid, or methacrylic acid, preferably acrylamide. In this invention, the monomer acts as a hydrogen bond donor, combining with other hydrogen bond donors and hydrogen bond acceptors to form a ternary polymerizable eutectic solvent. The ternary eutectic solvent provided in this invention possesses both polymerizability and hygroscopicity, enabling in-situ gel formation without the need for external polymerizable monomers; it improves the hygroscopicity of existing polymerizable eutectic solvents, overcoming the lack of flexibility in existing eutectic solvent polymers, thus providing a new approach for selecting hygroscopic gel dispersion media.

[0052] In one or more embodiments, the molar ratio of the monomer, hydrogen bond acceptor, and hydrogen bond donor is 0.5 to 2:1:2.

[0053] In one or more embodiments, the internal phase comprises n-hexane.

[0054] In one or more embodiments, the volume ratio of the internal phase in the high internal phase emulsion is greater than 74%, preferably 75%.

[0055] In one or more embodiments, the stabilizer is an amphiphilic polymer, including soy protein isolate. The soy protein isolate content is 10–40 mg / mL. To ensure that the emulsion does not demulsify during polymerization and maintains a complete template structure, a stabilizer needs to be added during the preparation of the high internal phase emulsion. If the stabilizer content is too low, a stable high internal phase emulsion cannot be obtained, and demulsification is likely to occur during polymerization, thus losing the template function of the emulsion. If the stabilizer content is too high, the excess stabilizer will dissolve in the eutectic solvent of the external phase, resulting in excessively high external phase viscosity, which is detrimental to the formation of the high internal phase emulsion.

[0056] In one or more embodiments, the initiator comprises ammonium persulfate; the crosslinking agent comprises N,Nˊ-methylenebisacrylamide; and the accelerator comprises N,N,Nˊ,Nˊ-tetramethylethylenediamine.

[0057] A second typical embodiment of the present invention provides a porous hygroscopic gel, wherein the above-mentioned porous hygroscopic gel composition forms a high internal phase emulsion gel, and the internal phase is removed to form a porous structure with high porosity.

[0058] A third typical embodiment of the present invention provides a method for preparing the above-mentioned porous hygroscopic gel, comprising the following steps:

[0059] (1) Mixing monomers, hydrogen bond acceptors and hydrogen bond donors and heating them together forms a ternary polymerizable eutectic solvent;

[0060] (2) Add stabilizer and internal phase to the ternary polymerizable eutectic solvent in (1), and obtain a high internal phase emulsion after homogenization;

[0061] (3) Add initiator, crosslinking agent and accelerator to the high internal phase emulsion in (2), mix homogeneously to form template prepolymer liquid, initiate external phase polymerization, and obtain high internal phase emulsion gel.

[0062] (4) Remove the internal phase from the high internal phase emulsion gel to obtain a porous hygroscopic gel.

[0063] In one or more embodiments, in step (1), the heating temperature is 75-85°C, preferably 80°C; the heating time is 1.5-3 hours, preferably 2 hours.

[0064] In one or more embodiments, in step (2), the homogenization rate is 1800-2500 rpm, preferably 2000 rpm, and the homogenization time is 4-8 min, preferably 5 min.

[0065] In one or more embodiments, in step (3), when homogenizing and mixing evenly, the homogenization rate is 1800-2500 rpm, preferably 2000 rpm, and the homogenization time is 1-4 min, preferably 2 min.

[0066] In one or more embodiments, in step (3), the external phase polymerization is initiated by thermal initiation at a temperature of 65-80°C, preferably 70°C, and the reaction time is 0.5-2h, preferably 1h.

[0067] In one or more embodiments, in step (4), the internal phase in the high internal phase emulsion gel is removed by heating. The heating temperature is 50-60°C, preferably 55°C, and the heating time is 10-15 hours, preferably 12 hours. Under this environment, the internal phase n-hexane will evaporate from the inside of the gel. During the evaporation process, n-hexane will break through the droplet barrier to form a highly interpenetrating porous structure.

[0068] A fourth typical embodiment of the present invention provides the application of the above-mentioned porous hygroscopic gel as a self-hygroscopic material in atmospheric water collection.

[0069] The fifth typical embodiment of the present invention provides the application of the above-mentioned porous hygroscopic gel as a self-hygroscopic material in humidity monitoring.

[0070] The sixth typical embodiment of the present invention provides the application of the above-mentioned porous hygroscopic gel as a self-hygroscopic material in soil improvement.

[0071] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0072] In the following examples, the soy protein isolate (SPI) was purchased from Shanghai Maclean Biotechnology Co., Ltd., CAS No. 9010-10-0.

[0073] Example 1

[0074] (1) Synthesize a ternary polymerizable eutectic solvent. Weigh 7g of choline chloride (ChCl), 6g of urea, and 1.8g of acrylamide (AM) into a round-bottom flask, place it in an oil bath at 80℃, and heat it for 2 hours under magnetic stirring to obtain a transparent eutectic solvent with a certain viscosity.

[0075] (2) Take 200 μL of the above eutectic solvent and mix it with 50 μL of ultrapure water, 20 mg of soy protein isolate and 750 μL of n-hexane. Mix them at 2000 rpm for 5 min to obtain a high internal phase emulsion with the eutectic solvent as the external phase.

[0076] (3) Add 1.2 mg of ammonium persulfate, 0.6 mg of N,Nˊ-methylenebisacrylamide and 2 μL of N,N,Nˊ,Nˊ-tetramethylethylenediamine to the prepared high internal phase emulsion. Mix at 2000 rpm for 2 min and then heat in an oil bath at 70 °C for 1 h. Thermally initiates the free radical polymerization of acrylamide to form a high internal phase emulsion gel.

[0077] (4) Finally, the above-mentioned high internal phase emulsion gel was placed in a vacuum drying oven at 55°C and vacuum dried for 12 hours to allow the internal phase n-hexane to completely evaporate, thereby forming a porous gel with high porosity.

[0078] Example 2

[0079] (1) Synthesize a ternary polymerizable eutectic solvent. Weigh 7g of choline chloride, 6g of urea and 3.6g of acrylamide into a round-bottom flask, place it in an oil bath at 80℃, and heat it for 2h under magnetic stirring to prepare a transparent eutectic solvent with a certain viscosity.

[0080] (2) Take 200 μL of the above eutectic solvent and mix it with 50 μL of ultrapure water, 20 mg of soy protein isolate and 750 μL of n-hexane. Mix them at 2000 rpm for 5 min to obtain a high internal phase emulsion with the eutectic solvent as the external phase.

[0081] (3) Add 1.2 mg of ammonium persulfate, 0.6 mg of N,Nˊ-methylenebisacrylamide and 2 μL of N,N,Nˊ,Nˊ-tetramethylethylenediamine to the prepared high internal phase emulsion. Mix at 2000 rpm for 2 min and then heat in an oil bath at 70 °C for 1 h. Thermally initiates the free radical polymerization of acrylamide to form a high internal phase emulsion gel.

[0082] (4) Finally, the above-mentioned high internal phase emulsion gel was placed in a vacuum drying oven at 55°C and vacuum dried for 12 hours to allow the internal phase n-hexane to completely evaporate, thereby forming a porous gel with high porosity.

[0083] Example 3

[0084] (1) Synthesize a ternary polymerizable eutectic solvent. Weigh 7g of choline chloride, 6g of urea and 5.3g of acrylamide into a round-bottom flask, place it in an oil bath at 80℃, and heat it for 2h under magnetic stirring to obtain a transparent eutectic solvent with a certain viscosity.

[0085] (2) Take 200 μL of the above eutectic solvent and mix it with 50 μL of ultrapure water, 20 mg of soy protein isolate and 750 μL of n-hexane. Mix them at 2000 rpm for 5 min to obtain a high internal phase emulsion with the eutectic solvent as the external phase.

[0086] (3) Add 1.2 mg of ammonium persulfate, 0.6 mg of N,Nˊ-methylenebisacrylamide and 2 μL of N,N,Nˊ,Nˊ-tetramethylethylenediamine to the prepared high internal phase emulsion. Mix at 2000 rpm for 2 min and then heat in an oil bath at 70 °C for 1 h. Thermally initiates the free radical polymerization of acrylamide to form a high internal phase emulsion gel.

[0087] (4) Finally, the above-mentioned high internal phase emulsion gel was placed in a vacuum drying oven at 55°C and vacuum dried for 12 hours to allow the internal phase n-hexane to completely evaporate, thereby forming a porous gel with high porosity.

[0088] Example 4

[0089] (1) Synthesize a ternary polymerizable eutectic solvent. Weigh 7g of choline chloride, 6g of urea and 7.1g of acrylamide into a round-bottom flask, place it in an oil bath at 80℃, and heat it for 2h under magnetic stirring to obtain a transparent eutectic solvent with a certain viscosity.

[0090] (2) Take 200 μL of the above eutectic solvent and mix it with 50 μL of ultrapure water, 20 mg of soy protein isolate and 750 μL of n-hexane. Mix them at 2000 rpm for 5 min to obtain a high internal phase emulsion with the eutectic solvent as the external phase.

[0091] (3) Add 1.2 mg of ammonium persulfate, 0.6 mg of N,Nˊ-methylenebisacrylamide and 2 μL of N,N,Nˊ,Nˊ-tetramethylethylenediamine to the prepared high internal phase emulsion. Mix at 2000 rpm for 2 min and then heat in an oil bath at 70 °C for 1 h. Thermally initiates the free radical polymerization of acrylamide to form a high internal phase emulsion gel.

[0092] (4) Finally, the above-mentioned high internal phase emulsion gel was placed in a vacuum drying oven at 55°C and vacuum dried for 12 hours to allow the internal phase n-hexane to completely evaporate, thereby forming a porous gel with high porosity.

[0093] Example 5

[0094] (1) Synthesize a ternary polymerizable eutectic solvent. Weigh 7g of choline chloride, 6g of urea and 5.3g of acrylamide into a round-bottom flask, place it in an oil bath at 80℃, and heat it for 2h under magnetic stirring to obtain a transparent eutectic solvent with a certain viscosity.

[0095] (2) Take 200 μL of the above eutectic solvent, mix it with 50 μL of ultrapure water, 10 mg of soy protein isolate and 750 μL of n-hexane, and vortex at 2000 rpm for 5 min to obtain a high internal phase emulsion with the eutectic solvent as the external phase.

[0096] (3) Add 1.2 mg of ammonium persulfate, 0.6 mg of N,Nˊ-methylenebisacrylamide and 2 μL of N,N,Nˊ,Nˊ-tetramethylethylenediamine to the prepared high internal phase emulsion. Mix at 2000 rpm for 2 min and then heat in an oil bath at 70 °C for 1 h. Thermally initiates the free radical polymerization of acrylamide to form a high internal phase emulsion gel.

[0097] (4) Finally, the above-mentioned high internal phase emulsion gel was placed in a vacuum drying oven at 55°C and vacuum dried for 12 hours to allow the internal phase n-hexane to completely evaporate, thereby forming a porous gel with high porosity.

[0098] Example 6

[0099] (1) Synthesize a ternary polymerizable eutectic solvent. Weigh 7g of choline chloride, 6g of urea and 5.3g of acrylamide into a round-bottom flask, place it in an oil bath at 80℃, and heat it for 2h under magnetic stirring to obtain a transparent eutectic solvent with a certain viscosity.

[0100] (2) Take 200 μL of the above eutectic solvent, mix it with 50 μL of ultrapure water, 30 mg of soy protein isolate and 750 μL of n-hexane, and vortex at 2000 rpm for 5 min to obtain a high internal phase emulsion with the eutectic solvent as the external phase.

[0101] (3) Add 1.2 mg of ammonium persulfate, 0.6 mg of N,Nˊ-methylenebisacrylamide and 2 μL of N,N,Nˊ,Nˊ-tetramethylethylenediamine to the prepared high internal phase emulsion. Mix at 2000 rpm for 2 min and then heat in an oil bath at 70 °C for 1 h. Thermally initiates the free radical polymerization of acrylamide to form a high internal phase emulsion gel.

[0102] (4) Finally, the above high internal phase emulsion gel was placed in a vacuum drying oven at 55°C and vacuum dried for 12 hours to allow the internal phase hexane to completely evaporate, thereby forming a porous gel with high porosity.

[0103] Example 7

[0104] (1) Synthesize a ternary polymerizable eutectic solvent. Weigh 7g of choline chloride, 6g of urea and 5.3g of acrylamide into a round-bottom flask, place it in an oil bath at 80℃, and heat it for 2h under magnetic stirring to obtain a transparent eutectic solvent with a certain viscosity.

[0105] (2) Take 200 μL of the above eutectic solvent, mix it with 50 μL of ultrapure water, 40 mg of soy protein isolate and 750 μL of n-hexane, and vortex at 2000 rpm for 5 min to obtain a high internal phase emulsion with the eutectic solvent as the external phase.

[0106] (3) Add 1.2 mg of ammonium persulfate, 0.6 mg of N,Nˊ-methylenebisacrylamide and 2 μL of N,N,Nˊ,Nˊ-tetramethylethylenediamine to the prepared high internal phase emulsion. Mix at 2000 rpm for 2 min and then heat in an oil bath at 70 °C for 1 h. Thermally initiates the free radical polymerization of acrylamide to form a high internal phase emulsion gel.

[0107] (4) Finally, the above-mentioned high internal phase emulsion gel was placed in a vacuum drying oven at 55°C and vacuum dried for 12 hours to allow the internal phase n-hexane to completely evaporate, thereby forming a porous gel with high porosity.

[0108] Comparative Example 1

[0109] Take 200 μL of the ternary polymerizable eutectic solvent prepared in Example 3, 20 mg of soy protein isolate, 1.2 mg of ammonium persulfate, 0.6 mg of N,N′-methylenebisacrylamide, and 2 μL of N,N,N′,N′-tetramethylethylenediamine, mix them at 2000 rpm for 2 min, and then heat them in an oil bath at 70 °C for 1 h. Thermal initiation of acrylamide completes free radical polymerization to form a eutectic solvent gel without high porosity.

[0110] Comparative Example 2

[0111] (1) Synthesize a binary polymerizable eutectic solvent. Weigh 7g of choline chloride and 5.3g of acrylamide into a round-bottom flask, place it in an oil bath at 80℃, and heat it for 2h under magnetic stirring to prepare a transparent eutectic solvent with a certain viscosity.

[0112] (2) Take 200 μL of the above eutectic solvent, mix it with 50 μL of ultrapure water, 20 mg of soy protein isolate and 750 μL of n-hexane, and swirl it at 2000 rpm for 5 min. A stable high internal phase emulsion cannot be formed.

[0113] (3) Add 1.2 mg of ammonium persulfate, 0.6 mg of N,Nˊ-methylenebisacrylamide and 2 μL of N,N,Nˊ,Nˊ-tetramethylethylenediamine to the above unstable emulsion. Mix at 2000 rpm for 2 min and then heat in an oil bath at 70 °C. Thermal initiation of acrylamide to complete free radical polymerization to form emulsion gel. During the polymerization process, the emulsion demulsifies and separates into phases, and cannot be used as a template to introduce a highly interconnected porous structure for the gel.

[0114] The structure and performance are characterized as follows:

[0115] (1) Characterization of ternary polymerizable eutectic solvents:

[0116] The ternary eutectic solvents prepared in Examples 1-7 are transparent liquids with a certain viscosity. The successful preparation of this DES was confirmed by infrared spectroscopy, differential scanning calorimetry (DSC), and contact angle testing.

[0117] Figure 1 The infrared spectra of the ternary eutectic solvents prepared in Examples 1-4 are shown below. Figure 1 As can be seen from this, when acrylamide is added to choline chloride and urea, 3033cm -1 The characteristic peak of acrylamide appears at 1625 cm⁻¹, namely the CH stretching vibration peak connected to the double bond. -1 CN bond and 1440cm -1 The CH stretching vibration peak at that point shifts to lower wavenumbers due to the formation of more hydrogen bonds, thus proving the hydrogen bonding interaction among the three.

[0118] Figure 2 Differential scanning calorimetry (DSC) analysis of the ternary eutectic solvents prepared in Examples 1-4, from... Figure 2 As can be seen, the melting point of the eutectic solvent formed by choline chloride and urea is around 12℃. With the addition of acrylamide, the melting point of the eutectic solvent gradually increases, which further confirms the successful preparation of the ternary eutectic solvent.

[0119] Figure 3 These are contact angle photographs of the ternary eutectic solvent prepared in Example 3 on the surface of soy protein isolate. Figure 3 It can be seen that soy protein isolate has a higher affinity for eutectic solvents, and the addition of acrylamide further enhances its wettability to soy protein isolate, which is beneficial for forming a high internal phase emulsion with the eutectic solvent as the external phase.

[0120] (2) Characterization of high internal phase emulsion template:

[0121] The high internal phase emulsions prepared in Examples 1-7 are opaque emulsions and do not flow when inverted. This was verified by optical microscopy (…). Figure 4 It can be observed that the emulsion consists of a large number of densely packed droplets, exhibiting the typical structural characteristics of a high internal phase emulsion.

[0122] The influence of the eutectic solvent component on emulsion formation was further investigated. Figure 4 (ad) As the amount of acrylamide increases, the emulsion droplets gradually decrease in size, which may be related to changes in its contact angle and interfacial tension.

[0123] The effect of stabilizer content on emulsion formation was then investigated. Figure 4 (e, c, f) It was found that as the content of the stabilizer soy protein isolate increased, the emulsion droplets gradually decreased in size. This is because with the increase of stabilizer content, more stabilizer can be adsorbed at the interface to stabilize the emulsion. Therefore, the emulsion structure can be adjusted by regulating the composition of the eutectic solvent and the content of the stabilizer, thereby using this as a template to prepare emulsion gels with different pore sizes to regulate the gel structure.

[0124] If a traditional binary polymerizable eutectic solvent is used as the external phase, even with an increased stabilizer content, a stable high internal phase emulsion cannot be formed. The emulsion will break down and undergo complete phase separation after standing at room temperature for 3 hours. Due to its instability, the emulsion formed in Comparative Example 2 will also undergo complete phase separation during gel polymerization, and the emulsion droplets cannot be stably dispersed in the dispersion medium to serve as a template for introducing a porous structure into the gel.

[0125] Finally, a porous gel (Example 3) prepared using a eutectic solvent with a molar ratio of choline chloride, urea, and acrylamide of 1:2:1.5 and a high internal phase emulsion containing 20 mg / mL of stabilizer was selected as a template for comparison with the original gel (Comparative Example 1). This is because at this ratio, a relatively small amount of stabilizer is needed to achieve the preparation of an emulsion with uniform and stable droplet size, thus reducing costs.

[0126] (3) Characterization of porous hygroscopic gel (AWHG):

[0127] The porous hygroscopic gels prepared in Examples 1-7 are opaque, lightweight porous gels with good viscoelasticity.

[0128] Figure 5 The images show scanning electron microscope (SEM) images of the gels prepared in Example 3 and Comparative Example 1. The SEM results show that the porous gel prepared using the emulsion as a template has a highly interconnected porous structure with macropores around 40 μm in size. These macropores are formed after the volatilization of the inner phase of the emulsion template, consistent with the size observed under the emulsion microscope. In contrast, the templateless gel has an average pore size of around 3 μm and lacks a highly interpenetrating hierarchical pore structure. The small pores on the macropore walls in the AWHG are caused by volume shrinkage during monomer polymerization. Mercury porosimetry (MPA) is also shown. Figure 6 and 7 This also indicates that the porous hygroscopic gel prepared using the emulsion as a template has a porosity (59.5%) and a specific surface area (37.5 m²). 2 Both the porosity ( / g) and specific surface area (22.9m²) of the template-free gel were significantly higher than those of the gel without a template (porosity: 26.3%; specific surface area: 22.9m²). 2 / g), this interconnected porous high porosity is conducive to the mass transfer process, thereby improving the atmospheric water collection capacity of the gel.

[0129] (4) Hygroscopicity of the gel:

[0130] Firstly, under conditions of 100% humidity, the high porosity of the porous hygroscopic gel gives it more efficient water absorption, achieving swelling equilibrium within 10 minutes, and its total water absorption is 4 times that of the control sample. Figure 8 a). The same porous hygroscopic gel also exhibited higher hygroscopicity than the control sample under 70% humidity conditions. Figure 8 b). This demonstrates the effectiveness of the porous structure.

[0131] (5) The hygroscopic mechanism of the gel:

[0132] From Raman spectra ( Figure 9 a) shows that the characteristic peak of water molecules, namely the hydroxyl absorption peak, is at 3300 cm⁻¹. -1 At this location, the eutectic solvent, except at 3300 cm⁻¹ -1 In addition to the hydroxyl absorption peak at 2900 cm⁻¹, there is also an absorption peak at 29-1 There is also an absorption peak at the CH bond, and even after it is polymerized to form a porous hygroscopic gel, these two characteristic absorption peaks are still retained. Figure 9 b). Therefore, the ratio of the peak areas of the two peaks can be used to examine the process of gel hygroscopicity, from the surface of the gel ( Figure 9 c) and cross-section ( Figure 9 d) The mapping spectrum shows that as time goes on, due to the presence of hydrophilic groups such as hydroxyl and amino groups on the gel surface, water molecules are gradually adsorbed on the gel surface, and due to the presence of osmotic pressure, water molecules gradually permeate into the gel interior, thereby achieving the collection of atmospheric water.

[0133] Experimental Example 1

[0134] Soil improvement application: The porous hygroscopic gel of the present invention is mixed with soil, and the hygroscopic and water-retaining capacity of the gel soil is investigated by mass change.

[0135] Figure 10 The results show that, under conditions of room temperature and 70% humidity, the moisture absorption capacity of soil modified with porous hygroscopic gel is 8 times that of the original soil. Furthermore, after one month of environmental storage (…),… Figure 10 b) Its moisture retention capacity is also significantly higher than that of the original soil, which is beneficial to the growth of plants and crops and is expected to play a role in the field of soil moisture retention and soil improvement.

[0136] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A porous hygroscopic gel composition, characterized in that, Includes the following components: Ternary polymerizable eutectic solvent, composed of monomer, hydrogen bond acceptor and hydrogen bond donor; Stabilizer; internal phase; Initiator; Crosslinking agent; Accelerator; The hydrogen bond donor is urea, ethylene glycol, or glycerol; The internal phase is n-hexane; The stabilizer is an amphiphilic polymer, specifically soy protein isolate; The molar ratio of the monomer, hydrogen bond acceptor, and hydrogen bond donor is 0.5~2:1:2; The volume ratio of the internal phase in a high internal phase emulsion is greater than 74%; The content of the soy protein isolate is 10~40 mg / mL; The preparation method of porous hygroscopic gel includes the following steps: (1) Mixing monomers, hydrogen bond acceptors and hydrogen bond donors and heating them together forms a ternary polymerizable eutectic solvent; (2) Add stabilizer and internal phase to the ternary polymerizable eutectic solvent in (1), and obtain a high internal phase emulsion after homogenization; (3) Add initiator, crosslinking agent and accelerator to the high internal phase emulsion in (2), mix homogeneously to form template prepolymer liquid, initiate external phase polymerization, and obtain high internal phase emulsion gel; (4) Remove the internal phase from the high internal phase emulsion gel to obtain a porous hygroscopic gel; In step (4), the internal phase in the high internal phase emulsion gel is removed by heating. The heating temperature is 50~60 ℃ and the heating time is 10~15 h.

2. The porous hygroscopic gel composition according to claim 1, characterized in that, The hydrogen bond acceptor is choline chloride; Alternatively, the hydrogen bond donor may be urea; Alternatively, the monomer may be acrylamide, acrylic acid, or methacrylic acid; Alternatively, the initiator is ammonium persulfate; the crosslinking agent is N,N'-methylenebisacrylamide; and the accelerator is N,N,N',N'-tetramethylethylenediamine.

3. The porous hygroscopic gel composition according to claim 1, characterized in that, The monomer is acrylamide; the volume ratio of the internal phase in the high internal phase emulsion is 75%.

4. A porous hygroscopic gel, characterized in that, The porous hygroscopic gel composition of claim 1 forms a high internal phase emulsion gel, removing the internal phase to form a porous structure with high porosity.

5. The porous hygroscopic gel composition according to claim 1, characterized in that, In step (1), the heating temperature is 75~85 ℃; the heating time is 1.5~3 h; Alternatively, in step (2), the homogenization rate is 1800~2500 rpm and the homogenization time is 4~8 min.

6. The porous hygroscopic gel composition according to claim 5, characterized in that, In step (1), the heating temperature is 80℃; the heating time is 2 hours. Alternatively, in step (2), the homogenization rate is 2000 rpm and the homogenization time is 5 min.

7. The porous hygroscopic gel composition according to claim 1, characterized in that, In step (3), the homogenization rate is 1800~2500 rpm and the homogenization time is 1~4 min; Alternatively, in step (3), the external phase polymerization is initiated by thermal initiation at a temperature of 65-80 °C and a reaction time of 0.5-2 h.

8. The porous hygroscopic gel composition according to claim 7, characterized in that, In step (3), the homogenization rate is 2000 rpm and the homogenization time is 2 min; Alternatively, in step (3), the external phase polymerization is initiated by thermal initiation at a temperature of 70 °C and a reaction time of 1 h.

9. The porous hygroscopic gel composition according to claim 1, characterized in that, In step (4), the internal phase in the high internal phase emulsion gel is removed by heating at a temperature of 55 °C for 12 h.

10. The application of the porous hygroscopic gel according to claim 4 as a self-hygroscopic material in atmospheric water collection.

11. The application of the porous hygroscopic gel according to claim 4 as a self-hygroscopic material in humidity monitoring.

12. The application of the porous hygroscopic gel according to claim 4 as a self-hygroscopic material in soil improvement.

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