Zwitterionic copolymeric hydrogel with high pore connectivity and its preparation method and application

Abstract

The application belongs to the technical field of seawater desalination, and more particularly relates to a zwitterionic copolymer hydrogel with high pore connectivity and a preparation method and application thereof. The preparation method comprises the following steps: (1) adding a crosslinking agent and a photoinitiator into a mixed aqueous solution containing methacryloyloxyethyl trimethyl ammonium chloride, 2-acrylamido-2-methyl propane-1-sodium sulfonate and Na2SO4, mixing uniformly, and performing polymerization under ultraviolet light to form a polymer; and (2) forming a photothermal layer on the surface of the polymer, and post-treating to obtain the zwitterionic copolymer hydrogel with high pore connectivity. The hydrogel prepared by the application has the characteristics of high pore connectivity, and can still maintain excellent evaporation rate in the process of continuous operation; and has excellent salt shrinkage resistance. The hydrogel prepared by the application has wide application in the fields of water treatment, seawater desalination and fresh water recovery.

Description

Technical Field

[0001] This invention belongs to the technical field of seawater desalination, and more specifically, relates to a zwitterionic copolymer hydrogel with high pore connectivity, its preparation method, and its application. Background Technology

[0002] Freshwater scarcity is a major global challenge, and its solution is urgently needed. Solar-driven interfacial evaporation technology, with its advantages of low energy consumption and environmental friendliness, is considered a sustainable route for brine desalination. The core of this technology lies in the design of the interfacial material, whose water transport performance directly determines the efficiency and stability of the evaporation process. Among them, hydrogel evaporators have attracted much attention due to their high water content, tunable structure, and hydrophilic properties.

[0003] Currently, while constructing highly porous hydrogel evaporators using zwitterionic monomers is an effective approach, traditional methods for improving pore connectivity often involve the use of organic reagents, which may pose potential ecotoxicity and environmental pollution. Furthermore, the limited variety of zwitterionic monomers makes it difficult to optimize salt-out resistance for specific applications with varying salinity and salt ion compositions. In contrast, monoionic hydrogel monomers are abundant in the market, allowing for free selection and combination, and are also less expensive.

[0004] However, the aforementioned hydrogels suffer from two major bottlenecks: first, the lack of interconnected pore structures restricts capillary-driven water transport, leading to localized dehydration and performance degradation; second, they are prone to volume shrinkage in saline environments, hindering the function of the evaporation interface and reducing the light absorption area. To address these challenges, it is crucial to construct a hydrogel that possesses both continuous water supply and adaptive swelling capabilities in saline environments, along with high pore connectivity and an excellent evaporation rate. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the primary objective of this invention is to provide a method for preparing zwitterionic copolymer hydrogels with high pore connectivity.

[0006] A second objective of this invention is to provide a zwitterionic copolymer hydrogel with high pore connectivity prepared by the aforementioned preparation method.

[0007] A third objective of this invention is to provide the application of the zwitterionic copolymer hydrogel with high pore connectivity in the fields of water treatment, seawater desalination, and freshwater recycling.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] This invention claims protection for a method for preparing a zwitterionic copolymer hydrogel with high pore connectivity, comprising the following steps:

[0010] (1) A crosslinking agent and a photoinitiator were added to a mixed aqueous solution containing methacryloyloxyethyltrimethylammonium chloride, sodium 2-acrylamido-2-methylpropane-1-sulfonate and Na2SO4 and mixed evenly. The mixture was then polymerized under ultraviolet light to form a polymer.

[0011] (2) The polymer surface is polymerized to form a photothermal layer, and then post-processed to prepare a zwitterionic copolymer hydrogel with high pore connectivity;

[0012] The molar ratio of methacryloyloxyethyltrimethylammonium chloride and sodium 2-acrylamido-2-methylpropane-1-sulfonate is 1:0.5-2;

[0013] In the mixed aqueous solution, the concentration of Na2SO4 is 1.3-1.7 mol / L.

[0014] This invention successfully prepared a zwitterionic copolymer hydrogel with high pore connectivity, which can maintain an excellent evaporation rate during continuous operation and has excellent and long-lasting water transport capacity. In addition, the zwitterionic copolymer hydrogel also has excellent salt shrinkage resistance, avoiding the problem of volume shrinkage, thus enabling the hydrogel to operate stably in salt water.

[0015] This invention, by selecting specific cationic and anionic monomers and controlling their molar ratio within a specific range, prepares a hydrogel with an open-pore structure exhibiting high pore connectivity. In contrast, hydrogels prepared using other anionic monomers exhibit a closed-pore structure and lack high pore connectivity. When only cationic or anionic monomers are used, or when the molar ratio of cationic and anionic monomers is outside the specific range, uncounted net charges exist in the polymer network. External salt ions rapidly shield the electrostatic repulsion between chains and reduce osmotic pressure, causing the network to shrink drastically and making it impossible to maintain a highly swollen state in practical brine environments.

[0016] Furthermore, the inventors discovered through research that using Na2SO4 as the salt ion and controlling the concentration of Na2SO4 in the solution within a specific range can, on the one hand, enable the prepared zwitterionic copolymer hydrogel to have high pore connectivity; on the other hand, it can shield the electrostatic effect between anionic and cationic monomers, thereby regulating the polymerization between anionic and cationic monomers. The resulting zwitterionic network has a typical salt-dissolution effect due to the uniform distribution of chain segments, and can maintain a swollen state in the salt solution, thereby avoiding volume shrinkage.

[0017] Preferably, the concentration of methacryloxyethyltrimethylammonium chloride in the mixed aqueous solution is 0.25-1 mol / L; and / or the concentration of sodium 2-acrylamido-2-methylpropane-1-sulfonate in the mixed aqueous solution is 0.25-1 mol / L. More preferably, the concentration of methacryloxyethyltrimethylammonium chloride in the mixed aqueous solution is 0.5-0.8 mol / L; and / or the concentration of sodium 2-acrylamido-2-methylpropane-1-sulfonate in the mixed aqueous solution is 0.5-0.8 mol / L.

[0018] Preferably, the photothermal layer is at least one of polypyrrole, polydopamine, and polyaniline. More preferably, the photothermal layer is polypyrrole.

[0019] Preferably, in step (2), the photothermal layer is prepared by coating the polymer surface with an initiator solution and a pyrrole aqueous solution in step (1), and then polymerizing the polymer surface through an in-situ polymerization reaction to form a photothermal layer.

[0020] Preferably, the initiator is a persulfate, including but not limited to ammonium persulfate.

[0021] Preferably, the concentration of the initiator in the initiator solution is 1-3 mol / L.

[0022] Preferably, after coating the initiator solution for 10-20 hours, the pyrrole aqueous solution is coated and left to stand for 10-20 hours.

[0023] Preferably, the concentration of pyrrole in the pyrrole aqueous solution is 3-8 vol%.

[0024] Preferably, the crosslinking agent is at least one of N,N'-methylenebisacrylamide, polyethylene glycol diacrylate, and bis-tert-butylperoxyisopropylbenzene; and / or the photoinitiator is at least one of 4-phenylbenzophenone, 4-acryloyloxybenzophenone, and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0025] Preferably, the concentration ratio of the crosslinking agent to the monomer is 1:50-200. More preferably, the concentration ratio of the crosslinking agent to the monomer is 1:80-120.

[0026] Preferably, in step (1), the ultraviolet light wavelength is 254-365 nm, and the polymerization time is 10-30 min. More preferably, in step (1), the ultraviolet light wavelength is 365 nm, and the polymerization time is 15 min.

[0027] Preferably, the molar ratio of methacryloyloxyethyltrimethylammonium chloride to sodium 2-acrylamido-2-methylpropane-1-sulfonate is 1:0.8-1.2. More preferably, the molar ratio of methacryloyloxyethyltrimethylammonium chloride to sodium 2-acrylamido-2-methylpropane-1-sulfonate is 1:1. Within this preferred range, the prepared zwitterionic copolymer hydrogel exhibits a superior evaporation rate and a higher equilibrium swelling ratio.

[0028] Preferably, the concentration of Na₂SO₄ in the mixed aqueous solution is 1.4-1.6 mol / L. The inventors have discovered that when the concentration of Na₂SO₄ is controlled within this range, the prepared zwitterionic copolymer hydrogel exhibits excellent evaporation rate and equilibrium swelling ratio. However, when the concentration of Na₂SO₄ exceeds this range, the hydrogel precursor solution becomes difficult to dissolve.

[0029] Preferably, in step (2), the post-treatment is: repeated washing with pure water. In some more specific embodiments, the post-treatment is: immersing the prepared product in pure water, changing the pure water every 24 hours, and continuing for 5-8 days to completely remove unreacted monomers and salts.

[0030] Furthermore, this invention claims protection for zwitterionic copolymer hydrogels with high pore connectivity prepared by the aforementioned preparation method.

[0031] Furthermore, the present invention claims protection for a solar thermal interface evaporation device, comprising the above-mentioned zwitterionic copolymer hydrogel with high pore connectivity.

[0032] Preferably, the solar thermal interface evaporation device includes a substrate, a support layer disposed within the substrate, and the zwitterionic copolymer hydrogel with high pore connectivity disposed within the support layer.

[0033] Preferably, the matrix can be a matrix conventionally used in the art, including but not limited to polystyrene foam. Preferably, the support layer can be a support layer conventionally used in the art, including but not limited to melamine resin sponge.

[0034] Furthermore, this invention seeks to protect the application of the zwitterionic copolymer hydrogel with high pore connectivity and the solar photothermal interface evaporation device in the fields of water treatment, seawater desalination, or freshwater recycling.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention provides a method for preparing zwitterionic copolymer hydrogels. The prepared hydrogels have high pore connectivity and can maintain an excellent evaporation rate during continuous operation, exhibiting excellent and long-lasting water transport capabilities. In addition, the zwitterionic copolymer hydrogels also have excellent resistance to salt shrinkage, avoiding the problem of volume shrinkage and hindering the evaporation interface function, thereby enabling the hydrogels to operate stably in salt water. Attached Figure Description

[0037] Figure 1 Scanning electron microscope images of the hydrogels prepared in Example 1 and Comparative Examples 1-3.

[0038] Figure 2 Scanning electron microscope images of the hydrogels prepared for comparative examples 4-7.

[0039] Figure 3 Scanning electron microscope images of the hydrogels prepared for comparative examples 8-11.

[0040] Figure 4 Scanning electron microscope images of the hydrogels prepared for comparative examples 12-13.

[0041] Figure 5 The swelling of the hydrogels prepared in Example 1 and Comparative Examples 1-13 in a 3.5wt% NaCl aqueous solution.

[0042] Figure 6 Evaporation rate curves of the hydrogels prepared in Example 1 and Comparative Examples 1-13 in a 3.5wt% NaCl aqueous solution.

[0043] Figure 7 Evaporation rate test of PDAppy-4 prepared for Example 1 in real seawater for up to 7 days. Detailed Implementation

[0044] The present invention will be further described below with reference to the specification and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0045] Example 1: Zwitterionic copolymer hydrogel with high pore connectivity

[0046] (1) A hydrogel precursor solution was prepared by dissolving methacryloyloxyethyltrimethylammonium chloride and sodium 2-acrylamido-2-methylpropane-1-sulfonate in a 1:1 molar ratio with crosslinking agent N,N'-methylenebisacrylamide in a 1.5 mol / L Na2SO4 aqueous solution. The volume of water in the hydrogel precursor solution was 5 mL, the concentrations of methacryloyloxyethyltrimethylammonium chloride and sodium 2-acrylamido-2-methylpropane-1-sulfonate were both 0.75 mol / L, and the concentration of N,N'-methylenebisacrylamide was 0.0075 mol / L.

[0047] (2) Add 20 μL of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone to the hydrogel precursor solution, mix well and inject into a culture dish mold with a diameter of 35 mm. Cover it with a quartz glass plate and initiate the polymerization reaction under ultraviolet light with a wavelength of 365 nm for 15 min to form a zwitterionic hydrogel with an interconnected porous structure, denoted as PDA-4.

[0048] (3) Spread 1 mL of 2.00 mol / L ammonium persulfate aqueous solution evenly on the surface of the obtained hydrogel and let it stand for 12 h; then coat it with 1 mL of 5.00 vol% pyrrole aqueous solution and let it stand for another 12 h. A polypyrrole photothermal layer is loaded on the surface of the hydrogel through in-situ polymerization reaction; the hydrogel loaded with the polypyrrole photothermal layer is washed in pure water, and the pure water is replaced every 24 h. The treatment is continued for 7 days, and finally zwitterionic copolymer hydrogel with high pore connectivity is obtained, which is denoted as PDAppy-4.

[0049] Example 2: Zwitterionic copolymer hydrogel with high pore connectivity

[0050] The difference between this embodiment and Example 1 is that in step (1), the concentration of methacryloyloxyethyltrimethylammonium chloride is 0.75 mol / L and the concentration of sodium 2-acrylamido-2-methylpropane-1-sulfonate is 0.9 mol / L.

[0051] Example 3: Zwitterionic copolymer hydrogel with high pore connectivity

[0052] The difference between this embodiment and Example 1 is that in step (1), the concentration of methacryloyloxyethyltrimethylammonium chloride is 0.75 mol / L and the concentration of sodium 2-acrylamido-2-methylpropane-1-sulfonate is 0.6 mol / L.

[0053] Comparative Example 1

[0054] The difference between this comparative example and Example 1 is that in step (1), the concentration of Na2SO4 in the Na2SO4 aqueous solution is 0 mol / L, that is, no Na2SO4 is added; the hydrogel prepared in step (2) is denoted as PDA-1; the hydrogel prepared in step (3) is denoted as PDAppy-1.

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 1 is that: in step (1), the concentration of Na2SO4 in the Na2SO4 aqueous solution is 0.5 mol / L; the hydrogel prepared in step (2) is denoted as PDA-2; and the hydrogel prepared in step (3) is denoted as PDAppy-2.

[0057] Comparative Example 3

[0058] The difference between this comparative example and Example 1 is that: in step (1), the concentration of Na2SO4 in the Na2SO4 aqueous solution is 1.0 mol / L; the hydrogel prepared in step (2) is denoted as PDA-3; and the hydrogel prepared in step (3) is denoted as PDAppy-3.

[0059] Comparative Example 4

[0060] The difference between this comparative example and Example 1 is that in step (1), while keeping the total concentration of the two monomers unchanged, only methacryloyloxyethyltrimethylammonium chloride was added, and sodium 2-acrylamido-2-methylpropane-1-sulfonate was not added; the hydrogel prepared in step (2) is denoted as PDA-5; the hydrogel prepared in step (3) is denoted as PDAppy-5.

[0061] Comparative Example 5

[0062] The difference between this comparative example and Example 1 is that in step (1), while keeping the total concentration of the two monomers constant, the molar ratio of methacryloyloxyethyltrimethylammonium chloride and sodium 2-acrylamido-2-methylpropane-1-sulfonate is 1:3; the hydrogel prepared in step (2) is denoted as PDA-6; the hydrogel prepared in step (3) is denoted as PDAppy-6.

[0063] Comparative Example 6

[0064] The difference between this comparative example and Example 1 is that in step (1), while keeping the total concentration of the two monomers unchanged, the molar ratio of methacryloyloxyethyltrimethylammonium chloride and sodium 2-acrylamido-2-methylpropane-1-sulfonate is 3:1; the hydrogel prepared in step (2) is denoted as PDA-7; the hydrogel prepared in step (3) is denoted as PDAppy-7.

[0065] Comparative Example 7

[0066] The difference between this comparative example and Example 1 is that in step (1), while keeping the total concentration of the two monomers unchanged, only sodium 2-acrylamido-2-methylpropane-1-sulfonate was added, and no methacryloyloxyethyltrimethylammonium chloride was added; the hydrogel prepared in step (2) is denoted as PDA-8; the hydrogel prepared in step (3) is denoted as PDAppy-8.

[0067] Comparative Example 8

[0068] The difference between this comparative example and Example 1 is that in step (1), Na2SO4 is replaced with NaCl; the hydrogel prepared in step (2) is denoted as PDA-9; and the hydrogel prepared in step (3) is denoted as PDAppy-9.

[0069] Comparative Example 9

[0070] The difference between this comparative example and Example 1 is that: in step (1), Na2SO4 is replaced with NaBr; the hydrogel prepared in step (2) is denoted as PDA-10; and the hydrogel prepared in step (3) is denoted as PDAppy-10.

[0071] Comparative Example 10

[0072] The difference between this comparative example and Example 1 is that in step (1), Na2SO4 is replaced with Na2CO3; the hydrogel prepared in step (2) is denoted as PDA-11; and the hydrogel prepared in step (3) is denoted as PDAppy-11.

[0073] Comparative Example 11

[0074] The difference between this comparative example and Example 1 is that in step (1), Na2SO4 is replaced with (NH4)2SO4; the hydrogel prepared in step (2) is denoted as PDA-12; and the hydrogel prepared in step (3) is denoted as PDAppy-12.

[0075] Comparative Example 12

[0076] The difference between this comparative example and Example 1 is that in step (1), sodium 2-acrylamido-2-methylpropane-1-sulfonate is replaced with methacrylic acid; the hydrogel prepared in step (2) is denoted as PDA-13; and the hydrogel prepared in step (3) is denoted as PDAppy-13.

[0077] Comparative Example 13

[0078] The difference between this comparative example and Example 1 is that in step (1), sodium 2-acrylamido-2-methylpropane-1-sulfonate is replaced with acrylic acid; the hydrogel prepared in step (2) is denoted as PDA-14; and the hydrogel prepared in step (3) is denoted as PDAppy-14.

[0079] Test Example 1

[0080] The morphology of hydrogels PDA-4, PDA-1, PDA-2, and PDA-3 prepared in Example 1 and Comparative Examples 1-3 was characterized by scanning electron microscopy.

[0081] Figure 1 Scanning electron microscope (SEM) images of the hydrogels prepared in Examples 1-3 of this invention, which are examples of Example 1 of this invention. Figure 1 It can be seen that PDA-1, PDA-2, and PDA-3 prepared in Comparative Examples 1-3 formed closed-pore structures with poor connectivity, while a specific concentration of Na2SO4 could promote the aggregation of polymer chains to form micron-sized microsphere clusters (PDA-4). At the same time, the gaps between the microspheres naturally formed interconnected three-dimensional channels, significantly improving the connectivity of the channels. The pore structure of the hydrogels prepared in Examples 2 and 3 is similar to that of the hydrogel PDA-4 in Example 1.

[0082] Test Example 2

[0083] The morphology of hydrogels PDA-5, PDA-6, PDA-7, and PDA-8 prepared in Comparative Examples 4-7 was characterized by scanning electron microscopy.

[0084] Figure 2 These are scanning electron microscope (SEM) images of the hydrogels prepared in comparative examples 4-7 of this invention. Figure 2 It is known that only when the molar ratio of methacryloyloxyethyltrimethylammonium chloride and sodium 2-acrylamido-2-methylpropane-1-sulfonate is within a specific range, the prepared hydrogel (PDA-4) possesses an open-pore structure with high pore connectivity (e.g., Figure 1 and Figure 2 (As shown). In contrast, the hydrogels PDA-5, PDA-6, PDA-7, and PDA-8 prepared in Comparative Examples 4-7, although their SEM images show partial aggregation, still have closed-pore structures and do not possess high pore connectivity.

[0085] Test Example 3

[0086] The morphology of hydrogels PDA-9, PDA-10, PDA-11, and PDA-12 prepared in Comparative Examples 8-11 was characterized by scanning electron microscopy.

[0087] Figure 3 These are scanning electron microscope (SEM) images of the hydrogels prepared in Comparative Examples 8-11 of this invention. Figure 3It can be seen that the hydrogels prepared using aqueous solutions of different types of inorganic salts (NaCl, NaBr, Na2CO3, (NH4)2SO4) all exhibit a closed-cell structure with low pore connectivity. Although some samples show local aggregation in SEM images, this does not change their overall closed-cell structure.

[0088] Test Example 4

[0089] The morphology of hydrogels PDA-13 and PDA-14 prepared in Comparative Examples 12-13 was characterized by scanning electron microscopy.

[0090] Figure 4 These are scanning electron microscope (SEM) images of the hydrogels prepared in Comparative Examples 12-13 of this invention. Figure 4 It can be seen that the PDA-13 and PDA-14 hydrogels prepared by replacing sodium 2-acrylamido-2-methylpropane-1-sulfonate with other types of monomers both exhibit closed-pore structures with low pore connectivity, as shown by SEM characterization. Although local aggregation was observed in the SEM images of PDA-14, its overall structure remained unchanged and still belongs to the closed-pore type.

[0091] Test Example 5

[0092] Hydrogels PDA-4, PDA-1, PDA-2, PDA-3, PDA-5, PDA-6, PDA-7, PDA-8, PDA-9, PDA-10, PDA-11, PDA-12, PDA-13, and PDA-14 prepared in Examples 1 and Comparative Examples 1-13 were washed and cut into standard cylindrical samples with known wet weight. These samples were then immersed in a sufficient amount of 3.5 wt% NaCl solution (simulating seawater concentration) and swelled at a constant temperature of 25°C. Samples were removed at preset time points (10 min, 30 min, 1 h, 2 h, 6 h, 12 h…), and the surface droplets were quickly blotted dry with filter paper before being weighed immediately. The swelling equilibrium was determined by the mass change rate being less than 2% after three consecutive weighings. The swelling behavior and salt tolerance of the hydrogels in a saline environment were systematically evaluated by measuring the equilibrium swelling rate.

[0093] Figure 5 The swelling of the hydrogels prepared in Example 1 and Comparative Examples 1-13 in a 3.5 wt% NaCl aqueous solution is shown. Figure 5 As shown, the equilibrium swelling rates of PDA-2 to PDA-4 and PDA-9 to PDA-14 are all ≥1g / g, proving that their network structure will not shrink due to the penetration of salt ions, and can endow the hydrogel with stable anti-salt shrinkage properties.

[0094] In Comparative Example 1, no inorganic salt was added, and the equilibrium swelling rate of the prepared PDA-1 was approximately 0.4 g / g. This is because without the addition of Na2SO4, the electrostatic effect between anionic and cationic monomers cannot be shielded, leading to uneven polymerization. This results in the product being microscopically closer to a physical blend of polyelectrolyte segments with net charge, forming a hybrid network with local enrichment of cationic and anionic segments. This structure fails to form the complete salt-soluble effect characteristic of zwitterionic copolymers, and therefore cannot achieve effective swelling in salt solutions, ultimately exhibiting shrinkage.

[0095] In Comparative Examples 4-7, the addition of one or two ionic monomers, or the addition of two ionic monomers outside the specific molar ratio range, resulted in a low equilibrium swelling rate. This is because an imbalance in the ratio of anionic and cationic monomers leads to an uncounted net charge in the polymer network. The introduced salt ions quickly shield the electrostatic repulsion between chains and reduce the osmotic pressure, causing the network to shrink rapidly. In practical applications, this network cannot maintain a high swelling state in the brine environment and is therefore unsuitable for practical use.

[0096] Test Example 6

[0097] The PDAppy hydrogels prepared in Example 1 and Comparative Examples 1-13 were cut into cylindrical samples with a diameter of 30.0 mm and a height of 5.0 mm. A piece of fully impregnated melamine resin sponge (slightly larger than the hydrogel) was used as a support layer, and the hydrogel sample was placed on it. The composite was then placed together in a polystyrene foam float frame with an opening in the center, ensuring that the lower surface of the hydrogel was in full contact with the water through the sponge, while the upper surface was completely exposed to air and light.

[0098] The external environment for the evaporation test was maintained at constant temperature and humidity. Simulated vertical sunlight exposure was used, with the light intensity maintained at 1.0 kW / m². 2 The ambient temperature and humidity were stabilized at approximately 26°C and 40%, respectively. The assembly was floated in an evaporating dish containing 500 mL of 3.5 wt% NaCl solution (simulating seawater concentration), and its mass change was continuously recorded in real time using an analytical balance with an accuracy of 0.1 mg, with a data acquisition frequency of 5 minutes per cycle.

[0099] Evaporation rate calculation: The evaporation rate of all samples was uniformly calculated using their initial projected area (based on a diameter of 30.0 mm). The evaporation rate was calculated based on the change in mass over time using Formula 1:

[0100]

[0101] Where v is the evaporation rate (unit: kg / m³) 2 ·h), dm is the mass change of water (unit: kg), and S is the initial top surface area of ​​the hydrogel evaporator (unit: m²).2 ), dt is the duration of the test (unit: h).

[0102] Figure 6 Evaporation rate curves of PDAppy-1 to PDAppy-14 prepared in Example 1 and Comparative Examples 1-13 in 3.5 wt% NaCl aqueous solution. Figure 6 It can be seen that in a 3.5 wt% NaCl solution, except for PDAppy-4, PDAppy-1 to PDAppy-3 and PDAppy-5 to PDAppy-13 all contracted due to water supply bottlenecks (or the combined effect of water supply bottlenecks and salting-out effect), resulting in a gradual decrease in evaporation rate over time. Only PDAppy-4, with its excellent pore connectivity, ensured a sufficient water supply. This indicates that the PDAppy-4 prepared in this invention exhibits a strong salt-dissolution effect, causing the hydrogel to swell and increase in size, thereby effectively increasing the light-absorbing area and improving evaporation performance.

[0103] Test Example 7

[0104] The PDAppy-4 prepared in Example 1 was placed in seawater from the East China Sea at a concentration of 1.0 kW / m 2 A continuous 7-day test was conducted under simulated sunlight. By monitoring mass changes and salt crystallization in real time, the long-term evaporation stability, structural durability, and resistance to salt crystallization in a real seawater environment were systematically examined.

[0105] Figure 7 Evaporation rate testing of PDAppy-4 prepared in Example 1 in real seawater for up to 7 days. Figure 7 It can be seen that the PDAppy-4 prepared by this invention can operate stably for 7 days in a simulated real seawater environment without significant performance degradation, demonstrating its excellent stability.

[0106] The foregoing examples are merely illustrative, used to explain some features of the method described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are demonstrated by the applicant's actual experimental results. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A method for preparing a zwitterionic copolymer hydrogel with high pore connectivity, characterized in that, Includes the following steps: (1) A crosslinking agent and a photoinitiator were added to a mixed aqueous solution containing methacryloyloxyethyltrimethylammonium chloride, sodium 2-acrylamido-2-methylpropane-1-sulfonate and Na2SO4 and mixed evenly. The mixture was then polymerized under ultraviolet light to form a polymer. (2) The polymer surface is polymerized to form a photothermal layer, and then post-processed to prepare a zwitterionic copolymer hydrogel with high pore connectivity; The molar ratio of methacryloyloxyethyltrimethylammonium chloride and sodium 2-acrylamido-2-methylpropane-1-sulfonate is 1:0.5-2; In the mixed aqueous solution, the concentration of Na2SO4 is 1.3-1.7 mol / L.

2. The preparation method according to claim 1, characterized in that, In the mixed aqueous solution, the concentration of methacryloyloxyethyltrimethylammonium chloride is 0.25-1 mol / L; and / or in the mixed aqueous solution, the concentration of sodium 2-acrylamido-2-methylpropane-1-sulfonate is 0.25-1 mol / L.

3. The preparation method according to claim 1, characterized in that, The photothermal layer is at least one of polypyrrole, polydopamine, and polyaniline.

4. The preparation method according to claim 1, characterized in that, The crosslinking agent is at least one of N,N'-methylenebisacrylamide and polyethylene glycol diacrylate; and / or The photoinitiator is at least one of 4-phenylbenzophenone, 4-acryloyloxybenzophenone, and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

5. The preparation method according to claim 1, characterized in that, In step (1), the wavelength of the ultraviolet light is 254-365 nm, and the polymerization reaction time is 10-30 min.

6. The preparation method according to claim 1, characterized in that, The molar ratio of methacryloyloxyethyltrimethylammonium chloride and sodium 2-acrylamido-2-methylpropane-1-sulfonate is 1:0.8-1.

2.

7. The preparation method according to claim 1, characterized in that, In the mixed aqueous solution, the concentration of Na2SO4 is 1.4-1.6 mol / L.

8. The zwitterionic copolymer hydrogel with high pore connectivity prepared by the preparation method according to any one of claims 1-7.

9. The application of the zwitterionic copolymer hydrogel with high pore connectivity as described in claim 8 in the field of seawater desalination or freshwater recycling.

10. A solar thermal interface evaporation device, characterized in that, Includes the zwitterionic copolymer hydrogel with high pore connectivity as described in claim 8.

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