Copolymerized temperature-sensitive hygroscopic gel material as well as preparation method and application thereof

Abstract

The invention belongs to the field of hygroscopic materials, and discloses a copolymerization temperature-sensitive hygroscopic gel material and a preparation method and application thereof. The gel material is prepared by copolymerizing the following raw materials in percentage by mass: 0.5%-15% of a monomer A, 0.5%-15% of a monomer B, 5%-20% of hygroscopic salt and the balance of water, the monomer A is a temperature-sensitive monomer, and the monomer B is a hydrophilic monomer. By adjusting the mass ratio of the monomer to the salt, the critical conversion temperature and the moisture absorption and desorption performance of the material can be flexibly controlled. The material has the temperature-sensitive rapid dehydration characteristic of PNIPAM and the high swelling ratio characteristic of zwitter-ions, and low energy consumption, efficient moisture absorption and rapid water vapor release are achieved. The preparation method comprises the following steps: dissolving the components to prepare a precursor solution, introducing nitrogen to remove oxygen, initiating polymerization and forming at 20-60 DEG C; the obtained gel material shows excellent moisture absorption efficiency and cycling stability in the fields of water taking from air, heat management and heat storage, and has wide application value.

Description

Technical Field

[0001] This invention belongs to the field of hygroscopic materials, and specifically relates to a copolymer thermosensitive hygroscopic gel material, its preparation method, and its applications. This gel material exhibits excellent hygroscopic efficiency and cycling stability in the fields of air water extraction, thermal management, and heat storage. Background Technology

[0002] High humidity environments can negatively impact human health, living comfort, electrical and electronic equipment, and industrial production. Excessive moisture in the air can easily lead to breathing difficulties, especially for people with asthma or chronic obstructive pulmonary disease (COPD). High humidity accelerates food spoilage, causes dampness in clothing and bedding, leading to odors and mold growth, significantly affecting people's comfort. High humidity accelerates the corrosion of internal components in electrical appliances, causing malfunctions and shortening their lifespan. High humidity affects the quality and production processes of products in industries such as pharmaceuticals and electronic components, especially in environments requiring precise temperature and humidity control. Furthermore, high humidity increases energy consumption, as additional energy is needed to maintain suitable indoor temperature and humidity conditions.

[0003] Given the negative impacts of high humidity environments on human health, living comfort, electrical and electronic devices, and industrial production, adopting necessary dehumidification methods is urgent. Compared to commonly used dehumidification equipment such as air conditioners and dehumidifiers, gel polymer dehumidifying materials offer advantages such as portability, recyclability, low production costs, and ease of mass production. Furthermore, polymer gel hygroscopic materials possess a controllable physical structure and chemical properties, enabling them to lock moisture within the gel during the expansion of their three-dimensional network structure, preventing liquid leakage. In recent years, numerous studies have developed various hygroscopic polymer gel materials by combining inorganic salts with excellent hygroscopic properties with highly hydrophilic polymer gels, aiming to efficiently regulate environmental humidity and reduce the various adverse effects caused by high humidity. In recent years, hygroscopic gel materials have shown broad prospects in the fields of air water extraction, thermal management, and thermal storage due to their high hygroscopic capacity, low energy consumption for regeneration, and multifunctionality.

[0004] Patent CN119114021A discloses a method for preparing a solar-driven biomass-based hygroscopic gel and its application. This method uses gluten powder and montmorillonite as raw materials and employs a freeze-drying method to prepare an adsorption polymer material. At 60% humidity, the water absorption capacity reaches approximately 1.11 g / g, significantly improving the material's hygroscopic performance. However, the freeze-drying method is time-consuming, energy-intensive, and requires expensive freeze dryers, vacuum systems, and low-temperature systems, all of which greatly increase the production cost of the material. Furthermore, the gel produced in this patent is difficult to recycle.

[0005] Patent CN115738619A discloses a composite solid desiccant and its preparation method. This desiccant possesses rapid and strong moisture absorption capacity, high moisture absorption volume, and is not easily deliquescent or liquefied, thus avoiding the problem of secondary pollution from brine. Furthermore, it maintains good dehumidification performance even at low ambient humidity, making it suitable for dehumidification needs under varying humidity conditions. However, this patent does not provide details regarding the desorption and regeneration temperature, desorption rate, and desorption and regeneration rate of the composite solid desiccant.

[0006] Patent CN117225363A discloses a method for preparing a hygroscopic gel and an atmospheric water collection device. This hygroscopic gel uses a porous gel as a substrate to support the adsorbent, and lithium chloride-modified Al-Fum as the adsorbent. Carboxylated carbon nanotubes are doped to enhance the material's hygroscopic properties and impart good photothermal performance, enabling hygroscopic absorption and desorption under low humidity. The provided atmospheric water collection device can automatically collect and desorb water under low humidity conditions and solves the problem of leakage of hygroscopic salts during adsorption and desorption. However, the preparation method provided by this technology is cumbersome and complex, which is not conducive to practical production.

[0007] N-Isopropylacrylamide hydrogel is a typical thermosensitive hydrogel, possessing a specific temperature point known as the critical transition temperature (LCST). The NIPAM chain segments contain hydrophilic amide groups (-CONH-) and hydrophobic isopropyl groups (-C3H7). When the gel temperature is below the LCST, the amide groups form numerous hydrogen bonds with water molecules. As the gel temperature rises closer to the LCST, these hydrogen bonds gradually break, causing the amide groups to contract towards the main chain, while the isopropyl groups begin to dominate, reducing the gel's hydrophilicity. When the gel temperature reaches the LCST, the changes in both groups accumulate to a certain extent, causing the gel to change from transparent to opaque. Further increases in temperature cause the gel volume to shrink continuously, eventually squeezing out the liquid.

[0008] The LCST (lowest temperature range) of pure PNIPAM gel is approximately 29–35°C. This means that its direct application in dehumidification and air-to-water extraction requires strict control of the ambient temperature. If a hygroscopic salt is loaded into the PNIPAM gel to increase its water absorption capacity per unit mass, it will be found that the hygroscopic salt competes with the amide groups for water molecules. This causes the hydrogen bonds between the amide groups and water molecules to break at low temperatures, indirectly lowering the LCST. This will make the gel more prone to liquid (salt water) leakage during application, leading to contamination. Therefore, it is of significant practical importance to rationally utilize the temperature sensitivity of PNIPAM and provide a polymer gel hygroscopic material with simple processing, excellent hygroscopic properties, and rapid desorption performance. Summary of the Invention

[0009] In order to overcome the shortcomings and defects of the prior art, the primary objective of this invention is to provide a copolymer thermosensitive hygroscopic gel material that combines the rapid dehydration characteristics of thermosensitive monomers with the high swelling ratio of zwitterions, thereby achieving low energy consumption, high-efficiency moisture absorption and rapid water vapor release.

[0010] Another object of the present invention is to provide a method for preparing a copolymer thermosensitive hygroscopic gel material.

[0011] Another object of the present invention is to provide the application of the above-mentioned gel material in the field of air dehumidification.

[0012] Another objective of this invention is to provide the application of the above-mentioned gel material in the fields of air water intake, thermal management, and thermal storage.

[0013] The objective of this invention is achieved through the following technical solution:

[0014] A copolymer thermosensitive hygroscopic gel material, by weight percentage, is copolymerized from raw materials comprising the following components:

[0015] 0.5%–15% monomer A, 0.5%–15% monomer B, 5%–20% hygroscopic salt, balance being water;

[0016] Monomer A is a thermosensitive monomer, and monomer B is a hydrophilic monomer.

[0017] Preferably, the copolymerized thermosensitive hygroscopic gel material is copolymerized from raw materials comprising the following components:

[0018] 0.5%–15% monomer A, 0.5%–15% monomer B, 5%–20% hygroscopic salt and 65%–95% water.

[0019] Preferably, the copolymerized thermosensitive hygroscopic gel material is copolymerized from raw materials comprising the following components:

[0020] 3%–5% monomer A, 2%–4% monomer B, 5%–15% hygroscopic salt and 80–95% water.

[0021] Preferably, monomer A is one or a mixture of N-isopropylacrylamide (NIPAM), N-vinylcaprolactam (NVCL), N-acryloylpyrrolidine (NAPy), and N,N-diethylacrylamide (DEAAm) in any proportion;

[0022] The monomer B is a hydrophilic zwitterionic monomer selected from one or a mixture of any proportions of 2-methacryloyloxyethyl dimethyl-(3-sulfonylpropyl)ammonium salt (SBMA), 2-methacryloyloxyethyl dimethylammonium acetate (CBMA), and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide (DMAPS).

[0023] The mass ratio of monomer A to monomer B is 1 to 2:1.

[0024] Preferably, the hygroscopic salt is one or a mixture of calcium chloride, lithium chloride, magnesium chloride, zinc chloride, calcium bromide or lithium bromide in any proportion, and the amount of hygroscopic salt added is 100-200% of the total mass of monomer A and monomer B.

[0025] The hygroscopic salt exists in the copolymer thermosensitive hygroscopic gel material through physical loading and / or electrostatic bonding.

[0026] Preferably, the raw material further includes a crosslinking agent, the amount of which is 0.1-10% of the total mass of monomer A and monomer B, more preferably 0.5-5%;

[0027] The crosslinking agent is one of polyethylene glycol diacrylate, N,N'-methylenebisacrylamide, or N,N'-bis(acryloyl)cysteine.

[0028] The copolymer thermosensitive hygroscopic gel material has a swelling ratio of 4 to 5, and its moisture absorption is ≥1g / g when the humidity is ≥60% and the temperature is 30℃ for 12 hours; more preferably, its moisture absorption is ≥2g / g when the humidity is 90% and the temperature is 30℃ for 12 hours.

[0029] A method for preparing a copolymer thermosensitive hygroscopic gel material includes the following steps:

[0030] Step 1: Dissolve monomer A, monomer B, hygroscopic salt, crosslinking agent, and initiator in water in a certain proportion and stir until all solids are dissolved to obtain a preliminary gel precursor solution;

[0031] Step 2: Pass an inert gas through the gel precursor solution for a period of time to remove dissolved oxygen, and obtain an oxygen-free preliminary gel precursor solution.

[0032] Step 3: Add the accelerator to the oxygen-free preliminary gel precursor solution in a certain proportion and stir evenly to obtain the gel precursor solution;

[0033] Step 4: Pour the gel precursor liquid into the mold and obtain the copolymerized thermosensitive hygroscopic gel material through polymerization reaction.

[0034] Preferably, the initiator in step one is one of ammonium persulfate, potassium persulfate, α-ketoglutaric acid, or 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone.

[0035] Preferably, the activator in step three is one of sodium bisulfite, glucose, or N,N,N,N-tetramethylethylenediamine.

[0036] The amount of initiator added is 0.1-10% of the total mass of monomers A and B, more preferably 0.5-5%;

[0037] The amount of the growth promoter added is one to five parts per thousand of the water volume.

[0038] Preferably, the stirring time in step one is 0.1 to 12 hours.

[0039] Preferably, the deoxygenation time in step two is 0.1 to 12 hours.

[0040] Preferably, the stirring time in step three is 0.1 to 5 minutes.

[0041] Preferably, the polymerization reaction conditions in step four are: reaction at 20-60°C in a sealed container for 1-24 hours.

[0042] The above-mentioned copolymer thermosensitive hygroscopic gel material is used in the fields of dehumidification, air water extraction, thermal management and heat storage.

[0043] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0044] (1) This invention allows for flexible control of the critical phase transition temperature (LCST) of materials.

[0045] This invention improves the LCST of NIPAM-based gels by copolymerizing NIPAM with other non-thermosensitive monomers to form a gel. The LCST of the gel can be adjusted by changing the amount of hydrophilic monomers used, allowing for targeted design for different application scenarios.

[0046] (2) The gel has temperature-sensitive properties, which can quickly remove moisture and improve the regeneration rate.

[0047] The gel designed in this invention has a critical transition temperature (LCST) exceeding 100°C. This means that water release during gel regeneration will rely entirely on water evaporation. Unlike traditional thermosensitive gels (such as PNIPAM), no critical transition was observed in this gel within the test temperature range. The gel of this invention not only avoids liquid extrusion (due to salt water corrosion), but also retains its thermosensitive properties due to the high content of amide and isopropyl groups within the gel. The gel of this invention exhibits a faster regeneration rate than other non-thermosensitive gels prepared with the same formulation, achieving complete regeneration within 6 hours.

[0048] (3) Hydrophilic zwitterionic monomers can increase the loading capacity of hygroscopic salts, and the gel has a high swelling ratio.

[0049] Hydrophilic zwitterionic monomers possess both positively and negatively charged groups within their molecular structure, achieving charge balance within the molecule. Hygroscopic salts (e.g., LiCl, CaCl2) consist of both anionic and cationic components. When hydrophilic zwitterionic monomers and hygroscopic salts are stirred simultaneously in an aqueous solution, electrostatic interactions (Coulomb forces) cause the cations and anions of the hygroscopic salts to spontaneously adsorb onto the positively and negatively charged groups within the zwitterionic monomers. Compared to gels without zwitterionic monomers, the gel of this invention can increase the loading capacity for hygroscopic salts, thereby increasing the water absorption capacity of the gel. Due to the stability of electrostatic interactions, the regeneration stability of the gel material of this invention is superior to other non-zwitterionic gels. While achieving charge balance within the gel segments, electrostatic repulsion occurs between polymer segments due to shared charges, resulting in a high swelling ratio. This facilitates increased hygroscopicity and water absorption; the swelling ratio of this invention can reach 4–5 times, exhibiting high water retention and maintaining adsorption stability during hygroscopic processes.

[0050] (4) The gel has excellent hygroscopic properties.

[0051] The polymer gel hygroscopic material of the present invention has a saturated moisture absorption capacity of up to 2.7994 g / g at room temperature and 90% humidity, which is significantly better than commonly used commercial hygroscopic agents such as color-changing silica gel (0.3 g / g) and molecular sieve (0.25 g / g).

[0052] (5) The gel preparation method is simple, the raw materials are readily available, and it has the potential for mass production.

[0053] The raw materials required for the polymer gel hygroscopic material of this invention are produced using mature technologies and are widely available. The preparation of the gel material of this invention can be carried out entirely at room temperature or a low temperature, and all raw materials only require simple stirring. The gel preparation method is simple and easy to implement, and is suitable for mass production. Attached Figure Description

[0054] Figure 1The images show a series of physical images of the in-situ polymerization molding of aluminum sheet in Example 1. a is a physical image of the surface after molding in Example 1; b is a physical image of the side after molding in Example 1; c is a physical image of the surface after drying in Example 1; d is a physical image of the surface of c after absorbing water under certain conditions; e is a physical image of the side of c after absorbing water under certain conditions; f is a physical image of the surface after regeneration in Example 1 (e is dried under certain conditions).

[0055] Figure 2 Fourier transform infrared spectra of Example 1, hygroscopic salt, Comparative Example 1, Comparative Example 2 and Comparative Example 3.

[0056] Figure 3 The XRD curves of Examples 1, 2, 3 and Comparative Example 1, and the XRD standard card of the hygroscopic salt are shown.

[0057] Figure 4 The isothermal adsorption-desorption curve is shown in Example 1.

[0058] Figure 5 The moisture absorption curves of Examples 1, 2, and 3 are shown inside constant temperature and humidity chambers (30°C) at 30%, 60%, and 90% humidity, respectively.

[0059] Figure 6 The desorption curves for Examples 1, 2, and 3 are obtained inside an 80°C constant temperature and humidity chamber.

[0060] Figure 7 The DSC thermograms of Comparative Examples 1, 3, 4, 5 and 6 were obtained by differential scanning calorimetry.

[0061] Figure 8 The DSC thermograms are obtained from differential scanning calorimetry tests of Examples 1, 2, 3 and Comparative Example 1.

[0062] Figure 9 The images show examples 1, 2, 3, 1, 3, 4, 5 and 6, which were heated for 10 minutes on an electric heating table at 80°C.

[0063] Figure 10 The data curves for desorption of Example 1 and Comparative Example 7 on an 80°C electric heating stage are shown. Figure 10 Both samples were prepared by in-situ polymerization on the surface of aluminum sheets, as referenced. Figure 1 )

[0064] Figure 11 These are photographs of Example 1 and Comparative Example 7 being heated on an 80°C electric heating stage.

[0065] Figure 12The image on the left is a graph showing the desorption time per gram of water for Example 1 and Comparative Example 7, while the image on the right is a graph showing the desorption time for Example 1 and Comparative Example 7 as a function of gel mass.

[0066] Figure 13 The swelling ratio test data and test graphs for Examples 1, 2 and 3 are shown. Detailed Implementation

[0067] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0068] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0069] NIPAM: N-isopropylacrylamide; DMAPS: [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide.

[0070] Example 1

[0071] A method for preparing a copolymer thermosensitive hygroscopic gel material includes the following steps:

[0072] (1) Dissolve the thermosensitive monomer NIPAM (8g), the hydrophilic monomer DMAPS (8g), the hygroscopic salt LiCl (16g), the crosslinking agent N,N'-methylenebisacrylamide (160mg), and the initiator ammonium persulfate (300mg) in deionized water (200ml) and stir until all solids are dissolved to obtain the preliminary gel precursor solution, which includes 3.45% thermosensitive monomer NIPAM, 3.45% hydrophilic monomer DMAPS, 6.90% hygroscopic salt LiCl and 86.21% deionized water;

[0073] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0074] (3) Add the accelerator tetramethylethylenediamine (200 μL, the amount of accelerator added is one-thousandth of the volume of deionized water in step (1)) to the oxygen-removed gel precursor solution and mix evenly (30s) to obtain the gel precursor solution.

[0075] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer thermosensitive hygroscopic gel material - Example 1.

[0076] Another copolymer thermosensitive hygroscopic gel material was obtained by room temperature polymerization (without in-situ polymerization on the aluminum sheet surface). This material was used in a continuous heating experiment on an 80°C electric heating platform to observe whether water was squeezed out.

[0077] Example 2

[0078] A method for preparing a copolymer thermosensitive hygroscopic gel material includes the following steps:

[0079] (1) Dissolve the thermosensitive monomer NIPAM (8g), the hydrophilic monomer DMAPS (8g), the hygroscopic salt LiCl (24g), the crosslinking agent N,N'-methylenebisacrylamide (160mg), and the initiator ammonium persulfate (300mg) in deionized water (200ml) and stir until all solids are dissolved to obtain the preliminary gel precursor solution, which includes 3.33% thermosensitive monomer NIPAM, 3.33% hydrophilic monomer DMAPS, 10% hygroscopic salt LiCl and 83.34% deionized water;

[0080] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0081] (3) Add the accelerator tetramethylethylenediamine (200 μL) to the oxygen-free gel precursor solution and mix well (30 s) to obtain the gel precursor solution.

[0082] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer thermosensitive hygroscopic gel material - Example 2.

[0083] Another copolymer thermosensitive hygroscopic gel material was obtained by room temperature polymerization (without in-situ polymerization on the aluminum sheet surface). This material was used in a continuous heating experiment on an 80°C electric heating platform to observe whether water was squeezed out.

[0084] Example 3

[0085] A method for preparing a copolymer thermosensitive hygroscopic gel material includes the following steps:

[0086] (1) Dissolve the thermosensitive monomer NIPAM (8g), the hydrophilic monomer DMAPS (8g), the hygroscopic salt LiCl (32g), the crosslinking agent N,N'-methylenebisacrylamide (160mg), and the initiator ammonium persulfate (300mg) in deionized water (200ml) and stir until all solids are dissolved to obtain the preliminary gel precursor solution, which includes 3.23% thermosensitive monomer NIPAM, 3.23% hydrophilic monomer DMAPS, 12.90% hygroscopic salt LiCl and 80.64% deionized water;

[0087] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0088] (3) Add the accelerator tetramethylethylenediamine (200 μL) to the oxygen-free gel precursor solution and mix well (30 s) to obtain the gel precursor solution.

[0089] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer thermosensitive hygroscopic gel material - Example 3.

[0090] Another copolymer thermosensitive hygroscopic gel material was obtained by room temperature polymerization (without in-situ polymerization on the aluminum sheet surface). This material was used in a continuous heating experiment on an 80°C electric heating platform to observe whether water was squeezed out.

[0091] Example 4

[0092] (1) Dissolve the thermosensitive monomer NIPAM (10.67g), the hydrophilic monomer DMAPS (5.33g), the hygroscopic salt LiCl (16g), the crosslinking agent N,N'-methylenebisacrylamide (160mg), and the initiator ammonium persulfate (300mg) in deionized water (200ml) and stir until all solids are dissolved to obtain the preliminary gel precursor solution, which includes 4.60% thermosensitive monomer NIPAM, 2.30% hydrophilic monomer DMAPS, 6.90% hygroscopic salt LiCl and 86.20% deionized water;

[0093] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0094] (3) Add the accelerator tetramethylethylenediamine (200 μL) to the oxygen-free gel precursor solution and mix well (30 s) to obtain the gel precursor solution.

[0095] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer thermosensitive hygroscopic gel material - Example 4.

[0096] Another copolymer thermosensitive hygroscopic gel material was obtained by room temperature polymerization (without in-situ polymerization on the aluminum sheet surface). This material was used in a continuous heating experiment on an 80°C electric heating platform to observe whether water was squeezed out.

[0097] Comparative Example 1

[0098] (1) Dissolve the thermosensitive monomer NIPAM (8g), the hydrophilic monomer DMAPS (8g), the crosslinking agent N,N'-methylenebisacrylamide (160mg), and the initiator ammonium persulfate (300mg) in deionized water (200ml) and stir until all solids are dissolved to obtain the preliminary gel precursor solution;

[0099] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0100] (3) Add the accelerator tetramethylethylenediamine (200 μL) to the oxygen-free gel precursor solution and mix well (30 s) to obtain the gel precursor solution.

[0101] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer thermosensitive hygroscopic gel material - Comparative Example 1.

[0102] Another copolymer thermosensitive hygroscopic gel material was obtained by room temperature polymerization (without in-situ polymerization on the aluminum sheet surface). This material was used in a continuous heating experiment on an 80°C electric heating platform to observe whether water was squeezed out.

[0103] Comparative Example 2

[0104] (1) Mix the hydrophilic monomer DMAPS (7g) and deionized water (3g) with stirring and purge with nitrogen for 10 minutes.

[0105] (2) When all the powders are dissolved in the solution, ammonium persulfate (APS, 0.06 g) is used as an initiator, and poly(ethylene glycol) diacrylate (PEGDA, 70 μL) is added to the solution as a crosslinking agent and further sonicated for 5 minutes.

[0106] (3) Polymerize at 60°C for 12 hours.

[0107] (4) Immerse the hydrogel in deionized water (12 hours) to remove unreacted material and obtain Comparative Example 2.

[0108] Comparative Example 3

[0109] (1) Dissolve the thermosensitive monomer NIPAM (16g), the crosslinking agent N,N'-methylenebisacrylamide (160mg), and the initiator ammonium persulfate (300mg) in deionized water (200ml) and stir until all solids are dissolved to obtain the preliminary gel precursor solution;

[0110] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0111] (3) Add the accelerator tetramethylethylenediamine (200 μL) to the oxygen-free gel precursor solution and mix well (30 s) to obtain the gel precursor solution.

[0112] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer thermosensitive hygroscopic gel material - Comparative Example 3.

[0113] Another copolymer thermosensitive hygroscopic gel material was obtained by room temperature polymerization (without in-situ polymerization on the aluminum sheet surface). This material was used in a continuous heating experiment on an 80°C electric heating platform to observe whether water was squeezed out.

[0114] Comparative Example 4

[0115] (1) Dissolve the thermosensitive monomer NIPAM (14.4 g), the hydrophilic monomer DMAPS (1.6 g), the crosslinking agent N,N'-methylenebisacrylamide (160 mg), and the initiator ammonium persulfate (300 mg) in deionized water (200 ml) and stir until all solids are dissolved to obtain the preliminary gel precursor solution;

[0116] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0117] (3) Add the accelerator tetramethylethylenediamine (200 μL) to the oxygen-free gel precursor solution and mix well (30 s) to obtain the gel precursor solution.

[0118] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer thermosensitive hygroscopic gel material - Comparative Example 4.

[0119] Comparative Example 5

[0120] (1) Dissolve the thermosensitive monomer NIPAM (12.8g), the hydrophilic monomer DMAPS (3.2g), the crosslinking agent N,N'-methylenebisacrylamide (160mg), and the initiator ammonium persulfate (300mg) in deionized water (200ml) and stir until all solids are dissolved to obtain the preliminary gel precursor solution;

[0121] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0122] (3) Add the accelerator tetramethylethylenediamine (200 μL) to the oxygen-free gel precursor solution and mix well (30 s) to obtain the gel precursor solution.

[0123] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer thermosensitive hygroscopic gel material - Comparative Example 5.

[0124] Another copolymer thermosensitive hygroscopic gel material was obtained by room temperature polymerization (without in-situ polymerization on the aluminum sheet surface). This material was used in a continuous heating experiment on an 80°C electric heating platform to observe whether water was squeezed out.

[0125] Comparative Example 6

[0126] (1) Dissolve the thermosensitive monomer NIPAM (10.67g), the hydrophilic monomer DMAPS (5.33g), the crosslinking agent N,N'-methylenebisacrylamide (160mg), and the initiator ammonium persulfate (300mg) in deionized water (200ml) and stir until all solids are dissolved to obtain the preliminary gel precursor solution;

[0127] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0128] (3) Add the accelerator tetramethylethylenediamine (200 μL) to the oxygen-free gel precursor solution and mix well (30 s) to obtain the gel precursor solution.

[0129] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer thermosensitive hygroscopic gel material - Comparative Example 6.

[0130] Another copolymer thermosensitive hygroscopic gel material was obtained by room temperature polymerization (without in-situ polymerization on the aluminum sheet surface). This material was used in a continuous heating experiment on an 80°C electric heating platform to observe whether water was squeezed out.

[0131] Comparative Example 7

[0132] (1) Dissolve monomer acrylamide (AM8g), hydrophilic monomer DMAPS (8g), hygroscopic salt LiCl (16g), crosslinking agent N,N'-methylenebisacrylamide (160mg), and initiator ammonium persulfate (300mg) in deionized water (200ml) and stir until all solids are dissolved to obtain a preliminary gel precursor solution;

[0133] (2) Nitrogen gas was introduced into the gel precursor solution for a period of time (20 min) to remove dissolved oxygen, and the oxygen-free gel precursor solution was obtained.

[0134] (3) Add the accelerator tetramethylethylenediamine (200 μL) to the oxygen-free gel precursor solution and mix well (30 s) to obtain the gel precursor solution.

[0135] (4) The gel precursor liquid with added tetramethylethylenediamine was poured into a mold and polymerized in situ on the surface of an aluminum sheet in a sealed container at room temperature (12h) to obtain a copolymer hygroscopic gel material - Comparative Example 7.

[0136] Material characterization

[0137] Figure 1 The images show a series of physical images of the in-situ polymerization molding process on the surface of an aluminum sheet in Example 1. a) is a physical image of the surface after molding in Example 1; b) is a side view of the surface after molding in Example 1; c) is a physical image of the surface after drying in Example 1; d) is a physical image of the surface of c after absorbing water for 12 hours at 30°C and 90% RH; e) is a side view of c after absorbing water for 12 hours at 30°C and 90% RH; f) is a physical image of the surface of Example 1 after regeneration (e is dried at 80°C for 6 hours). As can be seen from the images, the gel material of this invention exhibits excellent cycle stability. The gel is polymerized in situ on the surface of the aluminum sheet, and the internal hydrophilic groups such as amide and sulfonic acid groups will form hydrogen bonds with the hydroxyl groups on the aluminum sheet surface, enhancing the stability of the gel and allowing it to maintain structural stability even after regeneration at 80°C.

[0138] Figure 2 Fourier transform infrared (FTIR) spectra of Example 1, hygroscopic salt, Comparative Example 1, Comparative Example 2, and Comparative Example 3. The spectra show that the values ​​corresponding to Example 1, hygroscopic salt, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are observed at 3433 cm⁻¹. -1 Stretching vibration at (-OH) (hydroxyl group). Comparative Example 1 is a copolymer gel of NIPAM and DMAPS, while Comparative Examples 2 and 3 are pure PDMAPS and PNIPAM, respectively. Comparative Examples 1 and 2 were measured at 1037 cm⁻¹. -1 (S=O) and 1192cm -1 Both exhibit characteristic peaks at (CO), which are unique to PDMAPS and not found in PNIPAM. Comparative Examples 1 and 3 show peaks at 1546 cm⁻¹. -1 The presence of a characteristic peak at (-NH) indicates that the -NH peak is unique to PNIPAM. This confirms the successful preparation of the copolymer gel in Comparative Example 1. Loading a certain proportion of hygroscopic salt onto Comparative Example 1 yields Example 1. Example 1 exhibits the three characteristic peaks of Comparative Example 1, with the peak that should be at 1037 cm⁻¹ being the one observed. -1 The characteristic peak of (S=O) shifted due to the Li of the hygroscopic salt. + Compared with SO3 in Comparative Example 1 - This is caused by electrostatic adsorption.

[0139] Figure 3The images show the XRD patterns of Examples 1, 2, 3, and Comparative Example 1, as well as the XRD standard card for the hygroscopic salt. The XRD pattern of Comparative Example 1 shows a broad peak around 18°, indicating that it is a typical amorphous polymer. Examples 1, 2, and 3 are samples obtained by adding different proportions of hygroscopic salt to Comparative Example 1. With the addition of hygroscopic salt, the broad peak disappears, and a series of sharp, high-intensity diffraction peaks appear around 30°, 33°, 35°, and 59°. This indicates that the three examples produced a long-range ordered crystalline structure, meaning that the addition of hygroscopic salt fundamentally changed the polymer structure, transforming it from a predominantly amorphous state to one containing a crystalline phase. Comparing the XRD standard card for the hygroscopic salt, most diffraction peaks are recognizable, with a few showing some shift, presumably due to the Li content of the hygroscopic salt. + Compared with SO3 in Comparative Example 1 - This is caused by electrostatic adsorption.

[0140] Performance testing

[0141] (1) Isothermal adsorption-desorption test

[0142] Figure 4 The isothermal adsorption-desorption curve for Example 1 was tested using a vapor adsorption and specific surface area pore size analyzer (3H-2000PMV) at room temperature. The results show that the saturated moisture absorption capacity of Example 1 at 90% humidity is 2.7994 g / g, which is significantly superior to commonly used commercial desiccants such as silica gel (0.3 g / g) and molecular sieves (0.25 g / g).

[0143] (2) Moisture absorption performance test

[0144] The moisture absorption performance test was conducted in an indoor constant temperature and humidity chamber. The mass of the dried sample to be tested was weighed and recorded as M. d The unit is g. The sample mass is weighed once per hour and recorded as M. w The unit is g. Simultaneously, calculate the unit moisture absorption (water volume) S for each sample. u The unit is g / g. The calculation method is shown in Equation 1.

[0145]

[0146] Figure 5The moisture absorption curves for Examples 1, 2, and 3 are shown below, obtained after absorbing water for 12 hours in a constant temperature and humidity chamber (30°C) at 30%, 60%, and 90% humidity, respectively. Example 2 showed the highest moisture absorption, reaching 2.3281 g / g at 90% humidity and 30°C for 12 hours. Examples 1 and 3 showed slightly lower moisture absorption, at 2.2434 g / g and 2.2298 g / g, respectively. Example 3 experienced liquid leakage after 4 hours at 90% humidity and 30°C, resulting in a sudden drop in moisture absorption. However, at 60% humidity and 30% humidity and 30°C, Example 3 exhibited higher moisture absorption than Examples 1 and 2, reaching 1.0851 g / g and 0.6498 g / g, respectively.

[0147] (3) Regeneration performance test

[0148] Regeneration performance testing was conducted in an indoor constant temperature and humidity chamber. The mass of the completely dried sample was weighed and recorded as M. d The unit is g. The adsorbed sample is placed in a constant temperature and humidity chamber, and the sample mass is weighed every hour, recorded as M. h The unit is g. Simultaneously, calculate the unit water content (water volume) S for each sample. m The unit is g / g.

[0149] The calculation method is shown in Equation 2.

[0150]

[0151] Figure 6 The desorption curves for Examples 1, 2, and 3 are shown inside an 80°C constant temperature and humidity chamber. Examples 1, 2, and 3 can all achieve complete regeneration within 6 hours (unit water content < 0.1 g / g). Example 1 exhibits the fastest desorption rate, achieving almost complete desorption in approximately 4 hours, which is determined by the amount of hygroscopic salt added.

[0152] (4) Differential scanning calorimeter test

[0153] Figure 7 The DSC thermograms are from comparative examples 1, 3, 4, 5, and 6, obtained using differential scanning calorimetry. Figure 7 It can be seen that the copolymerization ratio of thermosensitive monomer A to hydrophilic monomer B has a decisive influence on the LCST of the gel. Comparative Examples 1 and 6, due to the excessively high proportion of hydrophilic monomer B, could not reach the LCST below 100℃. Comparative Example 3, a pure PNIPAM gel, had an LCST of 35.592℃. Comparative Example 4, with a thermosensitive monomer to hydrophilic monomer mass ratio of 9:1, showed a slightly improved LCST of 39.345℃.

[0154] Figure 8The images show the DSC thermograms obtained from differential scanning calorimetry (DSC) tests of Examples 1, 2, 3, and Comparative Example 1. Only Example 3 showed a change in heat flux at around 80°C, which was attributed to the disruption of hydrogen bonds between the amide groups and water caused by the addition of a large amount of hygroscopic salt. Since the regeneration temperature selected in this invention is 80°C, critical transitions did not occur in Examples 1, 2, and 3.

[0155] Figure 9 The images show examples 1, 2, 3, Comparative Examples 1, 3, 4, 5, and 6, heated continuously at 80°C for 10 minutes on an electric heating platform. It can be observed that Comparative Example 3, being a non-copolymer gel, and Comparative Example 4, with a low amount of hydrophilic monomer, have gels with LCSTs far below 80°C, undergoing a critical transition and extruding liquid brine. This indicates that Comparative Examples 3 and 4 are difficult to apply, and their regeneration performance decreases with increasing usage. Comparative Example 5 undergoes a critical transition, but to a low degree; no liquid brine is extruded within 10 minutes, indicating it is still difficult to apply. Examples 1, 2, and 3 do not undergo a critical transition, relying on evaporation to remove moisture, consistent with the design of this invention.

[0156] (5) Desorption rate comparison test

[0157] To further verify that the gel of the present invention has a faster water vapor release capability, we prepared Comparative Example 7 and Example 1 and compared their desorption capabilities on an 80°C electric heating stage. The only difference between Comparative Example 7 and Example 1 is that Example 1 used the thermosensitive monomer NIPAM, while Comparative Example 7 used AM, which is not thermosensitive but has a structure similar to NIPAM.

[0158] Figure 10 The desorption data curves for Example 1 and Comparative Example 7 on an 80°C electric heating stage are shown. Figure 10 Both samples were prepared by in-situ polymerization on the surface of aluminum sheets, as referenced. Figure 1 Example 1 was able to desorb to a relative moisture content of about 2% within 80 minutes, while Comparative Example 7 was only able to desorb to a relative moisture content of about 7%.

[0159] Figure 10 While samples with low moisture content are prone to testing errors, they are more likely to reflect the actual situation. To more intuitively reflect the desorption capacity of the embodiments of the present invention, we prepared two larger samples from Example 1 and Comparative Example 7. For ease of observation, the polymerization of the two larger samples was performed at room temperature (not in situ polymerization on the aluminum sheet surface). Other steps were the same as in Example 1 and Comparative Example 7, see [link to documentation]. Figure 11 . Figure 12The left image is a graph showing the desorption time per gram of water for Example 1 and Comparative Example 7, while the right image is a graph showing the desorption time for Example 1 and Comparative Example 7 as a function of gel mass. It can be seen that the water vapor release capacity of Example 1 is far superior to that of Comparative Example 7. Therefore, the gel material of the present invention has a faster water vapor release capacity, which is of great significance for reducing regeneration energy consumption.

[0160] (6) Gel swelling ratio test

[0161] Figure 13 The swelling ratio test data and graphs for Examples 1, 2, and 3 are shown below. The swelling ratio test requires fixing one end of the gel so that it can only swell in the vertical direction. The measurement conditions are 30°C and 90% RH. Swelling ratio (S) R The calculation method is shown in equation (3).

[0162]

[0163] Where, δ w δ represents the thickness of the hydrogel. d This represents the thickness of the dry gel.

[0164] Depend on Figure 13 It can be seen that Example 1 has the highest swelling ratio, reaching 4.87 times, while the swelling ratios of Examples 2 and 3 are slightly lower, reaching 4.459 times and 4.15 times respectively. The high swelling ratio of the gel means that the gel has high water retention capacity, and Example 1 has the best adsorption stability during the moisture absorption process.

[0165] The above embodiments are merely preferred embodiments of the present invention. The scope of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A copolymer thermosensitive hygroscopic gel material, characterized in that, By weight percentage, the copolymer thermosensitive hygroscopic gel material is copolymerized from raw materials comprising the following components: 0.5%–15% monomer A, 0.5%–15% monomer B, 5%–20% hygroscopic salt, balance being water; Monomer A is a thermosensitive monomer, and monomer B is a hydrophilic monomer.

2. The copolymer thermosensitive hygroscopic gel material according to claim 1, characterized in that, The monomer A is one or a mixture of N-isopropylacrylamide, N-vinylcaprolactam, N-acryloylpyrrolidine, and N,N-diethylacrylamide in any proportion; The monomer B is a hydrophilic zwitterionic monomer selected from one or a mixture of any proportions of 2-methacryloyloxyethyl dimethyl-(3-sulfonylpropyl)ammonium salt, 2-methacryloyloxyethyl dimethylammonium acetate, and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide. The mass ratio of monomer A to monomer B is 1 to 2:

1.

3. The copolymer thermosensitive hygroscopic gel material according to claim 1, characterized in that, The hygroscopic salt is one or a mixture of calcium chloride, lithium chloride, magnesium chloride, zinc chloride, calcium bromide or lithium bromide in any proportion, and the amount of the hygroscopic salt added is 100-200% of the total mass of monomer A and monomer B. The hygroscopic salt exists in the copolymer thermosensitive hygroscopic gel material through physical loading and / or electrostatic bonding.

4. The copolymer thermosensitive hygroscopic gel material according to claim 1, characterized in that the raw materials further include a crosslinking agent, the amount of which is 0.1-10% of the total mass of monomer A and monomer B; The crosslinking agent is one of polyethylene glycol diacrylate, N,N'-methylenebisacrylamide, or N,N'-bis(acryloyl)cysteine; The copolymer thermosensitive hygroscopic gel material has a swelling ratio of 4 to 5, and its moisture absorption is ≥1g / g when the humidity is ≥60% and the temperature is 30℃ for 12 hours.

5. A method for preparing the copolymer thermosensitive hygroscopic gel material according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Dissolve monomer A, monomer B, hygroscopic salt, crosslinking agent, and initiator in water in a certain proportion and stir until all solids are dissolved to obtain a preliminary gel precursor solution; Step 2: Pass an inert gas through the gel precursor solution for a period of time to remove dissolved oxygen, and obtain an oxygen-free preliminary gel precursor solution. Step 3: Add the accelerator to the oxygen-free preliminary gel precursor solution in a certain proportion and stir evenly to obtain the gel precursor solution; Step 4: Pour the gel precursor liquid into the mold and obtain the copolymerized thermosensitive hygroscopic gel material through polymerization reaction.

6. The method for preparing the copolymer thermosensitive hygroscopic gel material according to claim 5, characterized in that, The initiator mentioned in step one is one of ammonium persulfate, potassium persulfate, α-ketoglutaric acid, or 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone.

7. The method for preparing a copolymer thermosensitive hygroscopic gel material according to claim 5, characterized in that, The activator mentioned in step three is one of sodium bisulfite, glucose, or N,N,N,N-tetramethylethylenediamine.

8. The method for preparing the copolymer thermosensitive hygroscopic gel material according to claim 5, characterized in that, The amount of initiator added is 0.1% to 10% of the total mass of monomer A and monomer B; The amount of the growth promoter added is one to five parts per thousand of the water volume.

9. The method for preparing the copolymerized thermosensitive hygroscopic gel material according to claim 5, characterized in that, The polymerization reaction conditions described in step four are: reaction at 20-60°C in a sealed container for 1-24 hours.

10. The application of the copolymer thermosensitive hygroscopic gel material according to any one of claims 1 to 4 in the fields of dehumidification, air water extraction, thermal management and heat storage.

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