Oriented macroporous high-moisture-absorption gel capable of inducing directional crystallization of salt through touch control and preparation method and application of oriented macroporous high-moisture-absorption gel

Abstract

The invention discloses oriented macroporous high-moisture-absorption gel capable of inducing directional crystallization of salt through touch control as well as a preparation method and application of the oriented macroporous high-moisture-absorption gel. The preparation method comprises the following steps: dissolving a polymer monomer, an initiator, a cross-linking agent and a photo-thermal material in molten salt to obtain a gel precursor solution; cooling the gel precursor solution to a temperature below the crystallization temperature of the salt, applying stimulation to the surface of the gel precursor solution to induce crystallization, and performing photopolymerization after crystallization to obtain initial hydrogel; and after removing the unreacted salt template and monomer in the initial hydrogel, soaking the initial hydrogel in a hygroscopic inorganic salt solution for doping and drying to obtain the oriented macroporous high-hygroscopicity gel. According to the invention, the structure and size of the oriented pore channel can be accurately regulated and controlled, and the obtained oriented macroporous high-moisture-absorption gel has the moisture absorption capacity of 1.1-7.19 gg <-1 > and the moisture absorption kinetics of 0.56-1.96 gg <-1 > h <-1 > under the relative humidity of 30%-90%, and has a better application prospect in the fields of water production from air, battery moisture power generation and the like.

Description

Technical Field

[0001] This invention belongs to the field of hygroscopic gel research and development technology, specifically relating to a touch-induced salt-directed crystallization oriented macroporous highly hygroscopic gel, its preparation method, and its application. Background Technology

[0002] Moisture is a key component of the natural water cycle and also an important potential resource. The effective utilization of moisture not only provides a feasible way to obtain freshwater in water-scarce regions but also demonstrates significant value in areas such as spatial humidity control, building energy conservation, thermal management, and moisture-powered electricity generation. However, the efficiency of capturing water vapor in the air is significantly limited by ambient temperature and humidity, making the development of efficient and low-energy-consumption moisture capture and release materials a core focus of related technological development. In recent years, composite hygroscopic gels formed by loading hygroscopic inorganic salts into hydrogel networks have attracted considerable attention due to their combination of the excellent swelling properties and ease of processing of hygroscopic salts and gel matrices. These materials, which store liquid water through the swelling of a polymer network, hold the promise of achieving higher moisture absorption capacity.

[0003] However, because the internal structure of existing hygroscopic gels is usually random porous or dense network, the diffusion and mass transfer resistance of water molecules within the gel is high, resulting in a slow moisture absorption rate, especially at high moisture absorption capacities. Furthermore, to accelerate the desiccation rate, researchers often introduce photothermal components (such as carbon-based materials or metal nanoparticles) to utilize solar energy to drive moisture desorption.

[0004] For example, the invention patent with publication number CN116693928A discloses a photothermal hygroscopic polymer gel and its preparation method and application. The gel is a photothermal hygroscopic polymer gel with random topology structure and has a fast absorption / desorption kinetic mass transfer rate. However, the gel has problems such as disordered network structure, uncontrollable pore size, and difficulty in achieving orientation. Moreover, while this method improves the photothermal conversion efficiency, it often fails to simultaneously optimize the mass transfer channels inside the gel, resulting in a mismatch between the rate of water transport inside the gel and the rate of evaporation on the surface. The overall desorption kinetic improvement is limited, and therefore the moisture absorption capacity is low.

[0005] For example, patent CN118812774A discloses a highly hygroscopic gel with a stable open polymeric network structure and its preparation method. This method uses a co-solvent approach to prepare the hygroscopic gel with a stable open polymeric network structure. The hydrogel's collapse degree can be controlled by adjusting the ratio of water to co-solvent, thus imparting different mass transfer properties. However, it suffers from low hygroscopic capacity and poor mechanical properties, making it difficult to adapt to various complex application environments. Patent CN119684662A discloses a method for preparing oriented porous hydrogels using a salt crystallization template. This invention induces crystal growth by preparing a supersaturated salt water mixed gel solution and then adding a crystal nucleus template. While this method can prepare oriented hierarchical channels, it requires the pre-preparation of scaffolds of different shapes and the application of crystal nuclei during template formation, lacking flexibility and controllability, and also failing to control the channel size.

[0006] Based on the above analysis, how to develop a simple preparation method that can precisely control the orientation pore structure and size, so as to simultaneously endow the hygroscopic gel with rapid absorption / desorption kinetics and high moisture absorption capacity, and realize its wide climate adaptability, is a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a touch-induced salt-directed crystallization oriented macroporous highly hygroscopic gel, its preparation method, and its applications. By using touch-induced salt-directed crystallization, precisely controlling the pore size, and synergistically preparing the hygroscopic gel through the doping of hygroscopic inorganic salts, the process is simple and low-cost. The prepared hygroscopic gel exhibits rapid moisture absorption / desorption kinetics and high moisture absorption capacity, enabling applications with wide climate adaptability.

[0008] A method for preparing a touch-induced salt-oriented crystallization oriented macroporous highly hygroscopic gel includes the following steps: (1) Dissolve polymer monomers, initiators, crosslinking agents and photothermal materials in molten salt to obtain a gel precursor solution; (2) Cool the gel precursor solution to below the crystallization temperature of salt, apply stimulation to the surface of the gel precursor solution to induce crystallization, and then perform photopolymerization after crystallization to obtain the initial hydrogel. (3) After removing the unreacted salt template and monomers from the initial hydrogel, it is then soaked in a hygroscopic inorganic salt solution for doping and drying to obtain an oriented macroporous hygroscopic gel.

[0009] This invention is based on the salt template method. By cooling the gel precursor solution to below the crystallization temperature of the salt, the salt in the gel precursor solution becomes metastable. Considering that molten salt acts as crystal nuclei, exhibiting a lowering of the energy barrier, heterogeneous nucleation, and rapid crystal growth under tactile stimulation, the invention further combines the salt template method with tactile stimulation. Stimulation is applied to the surface of the gel precursor solution, ensuring that each stimulated location provides a low-energy-barrier heterogeneous nucleation site for the metastable salt precursor solution. This induces rapid spontaneous nucleation of the salt at the stimulated location and rapid directional crystal growth perpendicular to the stimulated location. By controlling the synergistic effect of cooling temperature and surface stimulation, precise control over the orientation pore structure and size is achieved, thereby completing crystallization. After crystallization, photopolymerization is performed. The pore structure formed by salt crystallization during polymerization is retained, and the unreacted salt template and monomers are combined to obtain a polymer gel with a controllable directional pore structure. The gel was doped by immersing it in a hygroscopic inorganic salt solution to obtain a hygroscopic gel with an oriented macroporous structure. The presence of the oriented pore structure significantly accelerated the mass transfer of water molecules, resulting in the hygroscopic gel having excellent hygroscopic kinetic properties.

[0010] Preferably, the molten salt in step (1) is obtained by heating sodium acetate trihydrate to 70-90°C.

[0011] Preferably, the polymer monomer mentioned in step (1) is one or more of 2-acrylamide-2-methylpropanesulfonic acid, acrylamide, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, N-isopropylacrylamide, acryloyloxyethyltrimethylammonium chloride, and potassium 3-sulfopropylmethacrylate.

[0012] Since 2-acrylamide-2-methylpropanesulfonic acid and acrylamide have excellent hygroscopic properties, more preferably, the polymer monomer is 2-acrylamide-2-methylpropanesulfonic acid or acrylamide.

[0013] Preferably, the initiator in step (1) is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone.

[0014] Preferably, the crosslinking agent in step (1) is one of N,N-methylenebisacrylamide, ethylene glycol dimethacrylate, divinylbenzene, diisocyanate or triallyl isocyanate.

[0015] More preferably, the crosslinking agent in step (1) is N,N-methylenebisacrylamide.

[0016] Preferably, the photothermal material in step (1) is titanium nitride.

[0017] Preferably, in step (1), the mass percentage of polymer monomer in the gel precursor solution is 15-25 wt.%, the mass percentage of initiator is 0.15-0.25 wt.%, the mass percentage of crosslinking agent is 0.15-0.25 wt.%, and the mass percentage of photothermal material is 0.2-0.35 wt.%.

[0018] More preferably, in step (1), the mass percentage of polymer monomer in the gel precursor solution is 25 wt.%, the mass percentage of initiator is 0.25 wt.%, the mass percentage of crosslinking agent is 0.25 wt.%, and the mass percentage of photothermal material is 0.35 wt.%.

[0019] Preferably, the crystallization temperature of the salt in step (2) is 10-45℃ and the cooling time is 5-15 min.

[0020] Different crystallization temperatures result in different crystal sizes, which in turn lead to different gel pore sizes. The lower the supercooling, the larger the gel pore size and the better the hygroscopic properties. Crystallization temperatures within the aforementioned range can form a gel with a stable network structure and promote the formation of a macroporous structure, thereby improving the gel's hygroscopic properties.

[0021] More preferably, the crystallization temperature of the salt in step (2) is 10-15℃, 20-25℃, 30-35℃, or 40-45℃, and the cooling time is 13-15 min.

[0022] A crystallization temperature of 30-35℃ is the optimal condition for considering both the macroporous structure and network stability, resulting in the best hygroscopic properties. More preferably, the crystallization temperature of the salt is 30-35℃.

[0023] Preferably, the stimulation applied in step (2) is a single-point touch, a multi-point touch, or a linear touch.

[0024] By adjusting the way stimulation is applied to change the direction of touch, the direction and final morphology of crystal growth can be actively guided and controlled, thereby achieving a variety of designable crystallization modes.

[0025] Preferably, in step (2), when the crystallization temperature of the salt is less than 20°C and / or the temperature at which the stimulus is applied is less than 20°C, the pressure at which the stimulus is applied is greater than 0.05 mN; Alternatively, when the crystallization temperature of the salt is greater than or equal to 20℃ but less than 40℃ and the temperature at which the stimulus is applied exceeds 20℃, the pressure of the stimulus applied is greater than 0.1 mN; Alternatively, when the crystallization temperature of the salt is greater than or equal to 40℃ but less than 45℃ and the temperature at which the stimulus is applied is less than 20℃, the pressure of the stimulus applied is greater than 0.5 mN.

[0026] When the crystallization temperature is 30-35℃, crystallization can be controlled by applying a force of not less than 0.1 mN. Because the pressure applied during stimulation works synergistically with the crystallization temperature of the precursor solution, when the crystallization temperature is below 20℃ or the contact temperature during stimulation is below 20℃, the former lowers the nucleation energy barrier, while the latter introduces crystal nuclei by lowering the nucleation energy barrier at the contact site within a small area through low-temperature stimulation. Therefore, a force of not less than 0.05 mN is sufficient to control crystallization. However, if the temperature is increased to 40-45℃, i.e., the supercooling of the precursor solution is reduced, the nucleation energy barrier increases, requiring a force of not less than 0.5 mN to control crystallization.

[0027] Preferably, the photopolymerization time in step (2) is 50-180 min.

[0028] Optionally, the photopolymerization in step (2) is ultraviolet light polymerization, and the polymer is turned over every 20-30 minutes during the polymerization process to ensure uniform polymerization.

[0029] Preferably, in step (3), the initial hydrogel is immersed in deionized water to remove unreacted salt templates and monomers from the initial hydrogel; the immersion temperature is 10-30℃ and the immersion time is 4-24 h.

[0030] Preferably, the hygroscopic inorganic salt solution in step (3) is either a lithium chloride aqueous solution or a calcium chloride aqueous solution; The concentration of the hygroscopic inorganic salt solution is 15-35 wt.%.

[0031] Because lithium chloride has a fast moisture absorption rate, good effect, and a wide applicable humidity range, more preferably, the hygroscopic inorganic salt solution is an aqueous solution of lithium chloride.

[0032] Preferably, the doping temperature in step (3) is 10-40℃ and the doping time is 12-64 h.

[0033] Preferably, the drying temperature in step (3) is 70-130℃ and the drying time is 12-48 h.

[0034] The present invention also provides an oriented macroporous highly hygroscopic gel prepared by the above-described preparation method.

[0035] Preferably, the oriented macroporous hygroscopic gel has a pore size of 10-100 μm.

[0036] The oriented macroporous superhygroscopic gel prepared by this invention has a macroporous structure that provides a high-speed channel for water molecules, allowing water molecules to quickly enter the interior of the polymer and thus increasing the moisture absorption capacity.

[0037] Preferably, the oriented macroporous highly hygroscopic gel has a moisture absorption capacity of 0.96-7.19 g g at a relative humidity of 30%-90%. -1 The hygroscopic kinetics are 0.56-1.96 gg. -1 h -1 .

[0038] This invention also provides the application of the aforementioned oriented macroporous highly hygroscopic gel in the fields of air-to-water conversion and battery-powered humidification.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects: 1. In terms of product structure, the oriented macroporous highly hygroscopic gel prepared by this invention has a highly tunable polymer network structure. By controlling the supercooling and crystal growth direction, the pore direction and pore size can be precisely controlled.

[0040] 2. Considering the product's moisture absorption performance, the oriented macroporous superhygroscopic gel obtained in this invention, through its adjustable pore design, simultaneously achieves excellent moisture absorption capacity, rapid moisture absorption / desorption kinetics, and broad environmental adaptability. Specifically, this oriented macroporous superhygroscopic gel can exhibit a moisture absorption capacity of 0.96-7.19 g / L at 30%RH-90%RH. -1 High moisture absorption capacity and 0.56-1.96 g g -1 h -1 Its ultrafast moisture absorption kinetics exhibit a rapid desorption rate of 96.8% per hour under 1.0 solar intensity and good cycle stability. After 20 cycles in a high humidity environment of 25℃ and 90%RH, it still maintains more than 90.4% of its initial water absorption capacity without any leakage, proving its practicality.

[0041] 3. From the perspective of product preparation process, this invention uses a touch-induced salt template method to prepare oriented macroporous highly hygroscopic gels with adjustable channels. This method does not require an external crystal nucleus mold and is applicable to a variety of monomers. In addition, this method has a simple preparation process, a wide range of raw material sources, a broad range of applications, and high structural tunability. Moreover, it does not require complex operations or expensive equipment during the preparation process, and has good prospects for large-scale application.

[0042] 4. From the perspective of product application performance, the oriented macroporous super hygroscopic gel prepared by this invention has excellent hygroscopic properties and good cycle performance, and has good application prospects in the fields of air-to-water and battery moisture power generation. Attached Figure Description

[0043] Figure 1 The crystallization process is shown in Example 1 for different touch control methods.

[0044] Figure 2The images provided are local structural characterization test diagrams of oriented macroporous hyperhygroscopic gels formed at different overcrystallization temperatures, for the purposes of examples and comparative examples.

[0045] Figure 3 Porosity characterization test diagrams of oriented macroporous hyperhygroscopic gels formed at different crystallization temperatures, provided for the examples.

[0046] Figure 4 This represents the static adsorption capacity result; where, Figure 4 Figure A in the figure is a characterization test diagram of the static adsorption capacity of the oriented macroporous highly hygroscopic gels provided in Examples 1-4 under different humidity conditions. Figure 4 Figure B in the figure shows the static adsorption amounts of Example 1 and the comparative example.

[0047] Figure 5 The time-temperature variation curves of the oriented macroporous highly hygroscopic gels provided in Example 1 and the comparative example are used to characterize the test results.

[0048] Figure 6 The moisture absorption cycle performance test diagram is for the oriented macroporous highly hygroscopic gel provided in Example 1.

[0049] Figure 7 The graph shows a comparison of the desiccant properties of the oriented macroporous hygroscopic gel, the random macroporous hygroscopic gel, and the ordinary hygroscopic gel provided in Example 1, Comparative Example 1, and Comparative Example 2.

[0050] Figure 8 The desorption performance of the oriented macroporous highly hygroscopic gel provided in Example 1 is characterized by different solar radiation intensities.

[0051] Figure 9 The humidity, temperature, moisture absorption / desorption, and solar intensity characterization test charts are obtained by real-time monitoring for 22 hours in the air water intake application of the oriented macroporous super hygroscopic gel provided in Example 1.

[0052] Figure 10 The graph shows the concentration of ions in water obtained from the air-water extraction application of the oriented macroporous superhygroscopic gel provided in Example 1.

[0053] Figure 11 The moisture absorption of the oriented macroporous highly hygroscopic gel formed by polymerization at different monomer solid content ratios provided in Example 6 at 25°C and 30% relative humidity is shown.

[0054] Figure 12 The moisture absorption of the oriented macroporous superhygroscopic gel with the same solid content as that provided in Example 7, formed by polymerization using acrylamide as a monomer, at 25°C and 70% relative humidity.

[0055] Figure 13 The crystal growth process of glass rod touch at different temperatures provided in Example 8. Detailed Implementation

[0056] The present invention will be further illustrated below with reference to the embodiments and accompanying drawings. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0057] Example 1: (1) First, 75 wt.% sodium acetate trihydrate was stirred at 80°C for 40 min until it was completely melted and became transparent. Then, 25 wt.% 2-acrylamide-2-methylpropanesulfonic acid, 0.35 wt.% nano titanium nitride, 0.25 wt.% 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and 0.25 wt.% N,N-methylenebisacrylamide were added and stirred at 80°C until completely dissolved to obtain the gel precursor solution. (2) Next, quickly pour the gel precursor liquid described in step (1) into the mold and let it stand for 15 minutes until the precursor liquid cools to 30-35°C. Apply stimulation by touching it with a glass rod to induce crystallization. During the touching process, the temperature of the glass rod is controlled at 30°C and the touching pressure is 10 mN. The touching process is as follows: Figure 1 As shown, after complete crystallization, it was polymerized under ultraviolet light for 80 minutes, and flipped every 20 minutes to ensure uniform light exposure; (3) After complete polymerization, the sample was soaked in 5000 mL of deionized water for 4 h to completely remove the salt template, unpolymerized monomers, initiators, and crosslinking agents. After removal, the sample was dried in a 100℃ oven for 3 h to obtain the initial hydrogel; (4) The initial hydrogel obtained in step (3) is immersed in a lithium chloride solution with a concentration of 15 wt.% for 6 h at 25 °C, and then dried in an oven at 100 °C for 12 h to obtain an oriented macroporous highly hygroscopic gel.

[0058] Characterization tests: The oriented macroporous highly hygroscopic gel prepared by this strategy exhibits excellent controllability in its dynamic crystallization process. For example... Figure 1 As shown, by simply changing the external touch method (such as tapping or swiping), the direction and final morphology of crystal growth can be actively guided and controlled, thus achieving a variety of designable crystallization modes.

[0059] The oriented macroporous hyperhygroscopic gel prepared by this strategy has the following structure: Figure 2 and Figure 3 As shown, the oriented macroporous hygroscopic gel has pore diameters in the hundreds of micrometers and is uniformly oriented.

[0060] The oriented macroporous highly hygroscopic gel prepared by this strategy can be used for hygroscopic absorption and desorption of water in gases. Figure 4 Figures A and B in the table show the static adsorption capacity of the oriented macroporous highly hygroscopic gel prepared in this embodiment at different humidity levels under 25°C. Its hygroscopic capacity reaches 1.10, 1.91, 2.77, and 7.19 g / L at relative humidity of 30%, 50%, 70%, and 90%, respectively. -1 .

[0061] The oriented macroporous highly hygroscopic gel prepared by this strategy exhibits excellent photothermal conversion performance due to the presence of oriented macropores, such as... Figure 5 As shown, it can rapidly heat from 30℃ to 69.6℃ within 60 minutes.

[0062] A moisture absorption and desorption cycle test was conducted at 90% relative humidity (90%RH). Figure 6 As shown, in 20 cycles of moisture absorption-desorption testing, the oriented macroporous superhygroscopic gel, due to its oriented macroporous structure, has sufficient space to store a large amount of water, ensuring that the absorbed moisture does not leak out, resulting in its moisture absorption performance remaining at 6.4-6.7 g / L under high humidity. -1 In a relatively stable state, it exhibits excellent cyclic moisture absorption stability and can achieve stable cyclic moisture absorption.

[0063] The oriented macroporous highly hygroscopic gel prepared by this strategy exhibits excellent dehumidification properties, such as... Figure 7 As shown, its desorption rate at 1.0 sun is 2.7 g / g. -1 h -1 .

[0064] The oriented macroporous highly hygroscopic gel prepared by this strategy, after being saturated with moisture at 70% relative humidity, underwent photothermal desorption under 0.5, 0.8, 1.0, and 1.5 days of sunlight, respectively. Figure 8 It can be seen that the desorption performance is improved with the increase of light intensity, and the desorption time is shortened for the same amount of desorption.

[0065] The oriented macroporous highly hygroscopic gel prepared by this strategy exhibits excellent outdoor atmospheric water collection performance, such as... Figure 9 As shown, even under low temperature and low humidity conditions, its daily water production remains no less than 3.29 kg / kg. -1 day -1 .

[0066] The oriented macroporous highly hygroscopic gel prepared using this strategy produces water with all ionic properties meeting WHO drinking water standards in outdoor atmospheric water collection applications. Figure 10 As shown, the concentrations of six ions in the prepared water—sodium, potassium, magnesium, calcium, chloride, and sulfur—were 1.44, 0.35, 0.05, 0.61, 4, and 0.21 mg / L, respectively.-1 All of them are below the WHO's drinking water standards.

[0067] Example 2: The preparation method in this embodiment is the same as that in Example 1, except that the gel precursor solution is cooled to 40-45°C before touch-controlled crystallization.

[0068] Characterization tests: The microstructure of the oriented macroporous highly hygroscopic gel prepared by this strategy is as follows: Figure 2 As shown, Figure 3 The figure shows the porosity characterization of the oriented macroporous hygroscopic gel prepared at a crystallization temperature of 45℃, where the crystal size is the largest, and therefore the pore size is the largest.

[0069] Depend on Figure 4 Figure A shows the static adsorption capacity of the oriented macroporous superhygroscopic gel prepared in this embodiment at different humidity levels under 25°C. The oriented macroporous superhygroscopic gel prepared by touch-sensitive salt template at a crystallization temperature of 45°C has a moisture absorption capacity of 1.08, 1.52, 1.88, 2.14, 2.65, 4.41, and 7.14 g / L at relative humidity levels of 30%, 40%, 50%, 60%, 70%, 80%, and 90%, respectively. -1 .

[0070] Example 3: The preparation method in this embodiment is the same as that in Example 1, except that the gel precursor solution is cooled to 20-25°C before touch-controlled crystallization.

[0071] Characterization tests: The microstructure of the oriented macroporous highly hygroscopic gel prepared by this strategy is as follows: Figure 2 As shown, Figure 3 The porosity characterization of the oriented macroporous hygroscopic gel prepared at a crystallization temperature of 25°C is shown. At this temperature, the crystal size is slightly smaller than that of Examples 1 and 2, and therefore the pore size is also slightly smaller than that of Examples 1 and 2.

[0072] Depend on Figure 4 Figure A shows the static adsorption capacity of the oriented macroporous hygroscopic gel prepared in this embodiment at different humidity levels under 25°C. The oriented macroporous hygroscopic gel prepared using a touch-sensitive salt template at a crystallization temperature of 25°C exhibits hygroscopic capacities of 1.07, 1.51, 1.81, 2.05, 2.62, 4.33, and 7.03 g / L at relative humidity levels of 30%, 40%, 50%, 60%, 70%, 80%, and 90%, respectively. -1 .

[0073] Example 4: The preparation method in this embodiment is the same as in Example 1, except that the gel precursor solution is cooled to 10-15°C before touch crystallization.

[0074] Characterization tests: The microstructure of the oriented macroporous highly hygroscopic gel prepared by this strategy is as follows: Figure 2 As shown, Figure 3 The figure shows the porosity characterization of the oriented macroporous hygroscopic gel prepared at a crystallization temperature of 15℃. At this temperature, the crystal size is the smallest, and therefore the pore size is the smallest.

[0075] Depend on Figure 4 Figure A shows the static adsorption capacity of the oriented macroporous superhygroscopic gel prepared in this embodiment at different humidity levels under 25°C. The oriented macroporous superhygroscopic gel prepared by touch-sensitive salt template at a crystallization temperature of 15°C has a moisture absorption capacity of 0.98, 1.48, 1.76, 2.02, 2.52, 4.27, and 6.51 g / L at relative humidity levels of 30%, 40%, 50%, 60%, 70%, 80%, and 90%, respectively. -1 .

[0076] Example 5: The preparation method in this embodiment is the same as in Example 1, except that 15 wt.% of 2-acrylamide-2-methylpropanesulfonic acid is added to prepare a uniform gel precursor solution.

[0077] Characterization tests: The hygroscopic properties of the oriented macroporous highly hygroscopic gel prepared by this strategy were characterized, such as... Figure 11 As shown, the oriented macroporous highly hygroscopic gel prepared in this embodiment has a maximum moisture absorption of 0.96 g g at 30% relative humidity. -1 .

[0078] Example 6: The preparation method in this embodiment is the same as that in Example 1, except that acrylamide is used as a monomer to prepare the gel precursor solution.

[0079] Characterization tests: The hygroscopic properties of the oriented macroporous highly hygroscopic gel prepared by this strategy were characterized, such as... Figure 12 As shown, the oriented macroporous highly hygroscopic gel prepared in this comparative example has a moisture absorption of 1.96 g at 50% relative humidity. -1 .

[0080] Example 7: The preparation method of this embodiment is the same as that of Example 1. The only difference is that, in step (2), glass rods at 10, 20, 30, 40, 50 and 60°C are used for touch crystallization.

[0081] Characterization tests: The crystallization growth rate of the oriented macroporous highly hygroscopic gel prepolymer prepared by this strategy is as follows: Figure 13 As shown, the higher the temperature of the glass rod, the slower the crystal growth. Under the condition that the cooling temperature of the precursor liquid is 30-35℃, crystallization cannot be achieved when the temperature of the glass rod is greater than or equal to 60℃.

[0082] Example 8: The preparation method of this embodiment is the same as that of Example 1. The only difference is that when touching the crystallization in step (2), a force of about 0.1 mN (calculated by a high-precision electronic balance) is used to touch the precursor liquid and the temperature of the glass rod is controlled at 30°C.

[0083] Example 9: The preparation method of this embodiment is the same as that of Example 1. The only difference is that when touching the crystallization in step (2), a force of about 0.45 mN (calculated by a high-precision electronic balance) is used to touch the precursor liquid and the temperature of the glass rod is controlled at 30°C.

[0084] Example 10: The preparation method of this embodiment is the same as that of Example 1. The only difference is that when touching the crystallization in step (2), a force of about 1 mN (calculated by a high-precision electronic balance) is used to touch the precursor liquid and the temperature of the glass rod is controlled at 30°C.

[0085] Example 11: The preparation method of this embodiment is the same as that of Example 1. The only difference is that when touching the crystallization in step (2), a force of about 5 mN (calculated by a high-precision electronic balance) is used to touch the precursor liquid and the temperature of the glass rod is controlled at 30°C.

[0086] Example 12: The preparation method of this embodiment is the same as that of Example 1. The only difference is that when touching the crystallization in step (2), a force of about 15 mN (calculated by a high-precision electronic balance) is used to touch the precursor liquid and the temperature of the glass rod is controlled at 30°C.

[0087] Example 13: The preparation method of this embodiment is the same as that of Example 1. The only difference is that when touching the crystallization in step (2), a force of about 20 mN (calculated by a high-precision electronic balance) is used to touch the precursor liquid and the temperature of the glass rod is controlled at 30°C.

[0088] Example 14: The preparation method of this embodiment is the same as that of Example 1. The only difference is that in step (2), the precursor liquid is cooled to 10°C. When the crystallization is controlled, a force of about 0.05 mN (calculated by a high-precision electronic balance) is used to control the temperature of the glass rod to 30°C.

[0089] Example 15: The preparation method in this embodiment is the same as in Example 1, except that during touch crystallization, a force of about 0.05 mN (calculated by a high-precision electronic balance) of the precursor liquid is used to control the temperature of the glass rod at 10°C.

[0090] Example 16: The preparation method of this embodiment is the same as that of Example 1. The only difference is that in step (2), the precursor liquid is cooled to 40°C. When the crystallization is controlled, a force of about 0.5 mN (calculated by a high-precision electronic balance) is used to control the temperature of the glass rod to 30°C.

[0091] The crystallization conditions of the examples and comparative examples are shown in Table 1. Under the condition that the precursor liquid cooling temperature is 30-35°C, crystallization can be induced when the force is greater than or equal to 0.1 mN. However, if the temperature is lowered to increase the supercooling, or the glass rod temperature is lowered, as in Examples 14 and 15 in Table 1, crystallization can be controlled even under a force of about 0.05 mN. If the temperature is increased, as in Example 16 in Table 1, under the condition that the precursor liquid cooling temperature is 40-45°C, a force of not less than 0.5 mN is required to induce crystallization.

[0092] Table 1

[0093] Comparative Example 1, without touch crystallization: The preparation method of this comparative example is the same as that of Example 1, except that the touch-controlled crystallization is not used. Instead, sodium acetate is supercooled and impurities cause spontaneous random crystallization to be formed, thus preparing a random macroporous gel.

[0094] Characterization tests: The microstructure of the random macroporous hygroscopic gel prepared in this comparative example is as follows: Figure 2 As shown, its internal structure is in a random state; Depend on Figure 4 As shown, the moisture absorption capacities of the random macroporous hygroscopic gel prepared in this comparative example at relative humidity levels of 30%, 50%, 70%, and 90% were 0.92, 1.36, 2.64, and 5.46 g, respectively. -1 The moisture absorption capacity is significantly lower than that of the oriented macroporous highly hygroscopic gel prepared in the example; Depend on Figure 5As shown, the random macroporous hygroscopic gel prepared in this comparative example can only heat up to 63.2℃ within 60 min under 1.0 sun, and its photothermal performance is significantly weaker than that of the oriented macroporous high hygroscopic gel. Depend on Figure 7 As shown, the desorption rate of Comparative Example 1 at 1.0 sun was 2.35 g / g. -1 h -1 Its dehumidification performance is weaker than that of the oriented macroporous highly hygroscopic gel prepared in Example 1.

[0095] Comparative Example 2, without adding molten salt as a crystal nucleus: (1) First, 25 wt.% 2-acrylamide-2-methylpropanesulfonic acid, 0.35 wt.% nano titanium nitride, 0.25 wt.% 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and 0.25 wt.% N,N-methylenebisacrylamide were dissolved in 75 wt.% deionized water and stirred until completely dissolved; (2) Next, pour the gel precursor liquid described in step (1) into the mold and polymerize it under ultraviolet light for 80 min, turning it over every 20 min to ensure uniform light exposure; (3) After complete polymerization, the sample was dried in an oven at 100°C for 3 h to obtain a gel comparison sample; (4) The gel comparison sample obtained in step (3) was immersed in a 15 wt.% lithium chloride solution at 25°C for 6 h, and then dried in an oven at 100°C for 12 h to obtain a common photothermal hygroscopic gel.

[0096] Characterization tests: The microstructure of the hygroscopic gel prepared in this comparative example is as follows: Figure 2 As shown; Depend on Figure 4 As shown, the moisture absorption capacities of this comparative example at relative humidities of 30%, 50%, 70%, and 90% were 0.54, 0.97, 1.67, and 3.72 g, respectively. -1 .

[0097] Figure 5 The time-temperature change curve of this comparative example under 1.0 sun is shown. The results show that it can only heat up to 43°C within 60 minutes, indicating that its photothermal performance is significantly weaker than that of the example and comparative example 1.

[0098] Depend on Figure 7 As shown, the desorption rate of this comparative example at 1.0 sun was 1.82 gg. -1 h -1 Its dehumidification performance is weaker than that of the oriented macroporous highly hygroscopic gel prepared in Example 1.

[0099] Comparative Example 3: The preparation method of this comparative example is the same as that of Example 1, except that during touch crystallization, a force of about 0.05 mN (calculated by a high-precision electronic balance) of the touch precursor liquid is used to control the temperature of the glass rod at 30°C.

[0100] Based on the above embodiments and comparative examples, it is clear that the embodiments of the present invention achieve precise control over the orientation pore structure and size by controlling the synergistic effect of cooling temperature and surface stimulation, resulting in a hygroscopic gel with an orientation macroporous structure. The presence of macropores ensures sufficient pore size to store adsorbed moisture, preventing the loss of hygroscopic components and improving the stability of the hygroscopic component distribution. Due to the confined entanglement polymerization of polymer chains, the mechanical properties and cycle stability of the gel are significantly improved, making it more resistant to harsh natural environments.

[0101] Meanwhile, extensive experiments have verified the influence of different oriented pore sizes on moisture absorption performance. The touch-induced molten salt directional crystallization preparation process is simple and inexpensive, which can meet the needs of industrial production and is in line with the current social requirements for energy and environmental development.

[0102] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a touch-induced salt-directed crystallization oriented macroporous highly hygroscopic gel, characterized in that, Includes the following steps: (1) Dissolve polymer monomers, initiators, crosslinking agents and photothermal materials in molten salt to obtain a gel precursor solution; (2) Cool the gel precursor solution to below the crystallization temperature of salt, apply stimulation to the surface of the gel precursor solution to induce crystallization, and then perform photopolymerization after crystallization to obtain the initial hydrogel. (3) After removing the unreacted salt template and monomers from the initial hydrogel, it is then soaked in a hygroscopic inorganic salt solution for doping and drying to obtain an oriented macroporous hygroscopic gel.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass percentage of polymer monomers in the gel precursor solution is 15-25 wt.%, the mass percentage of initiator is 0.15-0.25 wt.%, the mass percentage of crosslinking agent is 0.15-0.25 wt.%, and the mass percentage of photothermal material is 0.2-0.35 wt.%.

3. The preparation method according to claim 1, characterized in that, In step (2), the crystallization temperature of the salt is 10-45℃ and the cooling time is 5-15 min.

4. The preparation method according to claim 1, characterized in that, In step (2), the stimulation is applied by single-point touch, multi-point touch, or linear touch.

5. The preparation method according to claim 4, characterized in that, In step (2), when the salt crystallization temperature is less than 20°C and / or the temperature at which the stimulus is applied is less than 20°C, the pressure of the stimulus applied is greater than 0.05 mN. Alternatively, when the crystallization temperature of the salt is greater than or equal to 20℃ but less than 40℃ and the temperature at which the stimulus is applied exceeds 20℃, the pressure of the stimulus applied is greater than 0.1 mN; Alternatively, when the crystallization temperature of the salt is greater than or equal to 40℃ but less than 45℃ and the temperature at which the stimulus is applied is less than 20℃, the pressure of the stimulus applied is greater than 0.5 mN.

6. The preparation method according to claim 1, characterized in that, The doping temperature in step (3) is 10-40℃ and the doping time is 12-64 h.

7. The oriented macroporous highly hygroscopic gel prepared by the preparation method according to any one of claims 1-6.

8. The oriented macroporous highly hygroscopic gel according to claim 7, characterized in that, The oriented macroporous hygroscopic gel has a pore size of 10-100 μm.

9. The oriented macroporous highly hygroscopic gel according to claim 7, characterized in that, The oriented macroporous highly hygroscopic gel exhibits a moisture absorption capacity of 0.96-7.19 g g at a relative humidity of 30%-90%. -1 The hygroscopic kinetics are 0.56-1.96 gg. -1 h -1 .

10. The application of the oriented macroporous highly hygroscopic gel according to claim 9 in the fields of air-to-water conversion and battery-powered humidification.

Images