Preparation method and application of near-infrared photothermal self-repairing film

Abstract

The application is suitable for the technical field of seawater desalination membranes, and provides a preparation method and application of a near-infrared photothermal self-repairing membrane.The application uses thioacet hydrazide (TAH) with a disulfide bond as a main material, and dopes Keggin-type polyoxometalate (POMs) of protonated TAH as an additive (TAH@PW) to prepare a seawater desalination membrane with near-infrared (NIR) photothermal self-healing capability.The dynamic covalent bond in TAH supports the self-healing behavior of the membrane, and the introduction of TAH@PW improves the mechanical strength and photothermal performance of the membrane.When the molar ratio of TAH@PW to TAH is 1 / 100, the Young's modulus increases from 7 MPa to 195 MPa;the membrane evaporation efficiency reaches 2.75 kg m ‑2 h ‑1 <2> / m2·h, and the photothermal conversion efficiency is 94.4%.In addition, the damaged seawater desalination membrane can maintain almost unchanged mechanical strength and evaporation efficiency after healing.

Description

Technical Field

[0001] This invention belongs to the field of seawater desalination membrane technology, and particularly relates to a method for preparing a near-infrared photothermal self-healing membrane and its application. Background Technology

[0002] Compared to limited freshwater resources, the ocean is abundant in water. However, seawater has a high salinity and is contaminated with pollutants, making it unsuitable for direct drinking or use in production and daily life. To date, seawater desalination methods include multi-effect distillation, multi-stage flash evaporation, and electrodialysis, but most suffer from high costs, high energy consumption, and low efficiency. Therefore, exploring new seawater desalination technologies is imperative. Solar energy has been applied in various fields such as photocatalysis, energy conversion, and biomass materials, and it can be used as a renewable energy source for seawater desalination. However, the low photothermal conversion efficiency of materials, their non-recyclability, and damage during use affect the rate of water vapor generation, hindering the development of this technology. Therefore, developing novel solar-powered seawater desalination membranes with high strength, easy healing, and high evaporation efficiency is of great significance.

[0003] Disulfide bonds, a type of dynamic covalent bond with high bond energy, are an ideal choice for constructing self-healing materials and have been widely applied in various fields. However, self-healing materials based on purely organic components often suffer from insufficient mechanical strength and lack of functionality. Therefore, introducing inorganic components to enhance the strength and endow the material with special functions is an effective design strategy. In the process of introducing inorganic components into organic polymers, achieving uniform dispersion of the inorganic components and obtaining products with uniform performance is an important research topic. One possible method to solve this problem is to use large-sized, uniformly structured discrete inorganic units to composite with organic components, and then dope them into the polymer. This can effectively improve the dispersion uniformity of the inorganic components.

[0004] Polyoxometalates (POMs) are inorganic clusters formed by high-valence early transition metal ions sharing oxygen atoms. They are characterized by simple synthesis, tunable composition, uniform size, clear structure, and rich functionality, leading to their wide application in catalysis, separation, and biology. POMs are covered with oxygen atoms and carry multiple negative charges. Through electrostatic interactions or hydrogen bonding, organic components can replace the original cations in the cluster, forming organic-inorganic hybrid materials. Depending on different structural and functional requirements, the organic components on the surface of the inorganic clusters can be hydrophobic alkyl chains, hydrophilic polyethylene glycol, or other functional groups. Introducing such POM-containing organic-inorganic hybrid composites into organic polymers can not only improve the mechanical strength of the system but also provide certain functional properties as needed. Furthermore, the structural characteristics of POMs give them a good affinity for water molecules, showing potential in constructing hydrophilic photothermal evaporation sites. Based on this background, we propose a method for preparing a near-infrared photothermal self-healing film and its application. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a near-infrared photothermal self-healing film and its application, aiming to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a near-infrared photothermal self-healing film includes the following steps:

[0008] Step 1, Preparation of TAH:

[0009] Lipoic acid (TA) was dissolved in acetonitrile. N,N′-succinimide carbonate and triethylamine (Et3N) were added to the solution, and the mixture was stirred at room temperature for 2 hours. The solution was then concentrated under reduced pressure at room temperature, and a 5% NaHCO3 aqueous solution was added to form a yellow precipitate. The precipitate was filtered, washed with water, and then dissolved in CH3CN. 80% hydrazine monohydrate was added dropwise to the solution, and the mixture was stirred at room temperature for 3 hours. The filtrate was then concentrated under reduced pressure after filtration. A 5% NaHCO3 aqueous solution was added, and the mixture was extracted with CHCl3. The yellow organic layer was washed three times with a 5% NaHCO3 aqueous solution, dried on MgSO4, and the solvent was evaporated under reduced pressure to obtain a yellow solid monomer.

[0010] Step 2, Preparation of POMs hybrid polymers:

[0011] TAH dissolves and protonates in acidic solution, and then combines with PW through hydrogen bonding and electrostatic attraction to obtain TAH@PW;

[0012] Step 3: Preparation of the target copolymer:

[0013] TAH was heated at 130°C in a constant temperature oil bath for 2.5 hours to generate a liquid. TAH@PW was then added and heated for another 0.5 hours. The resulting liquid was poured into a silicone mold to generate the target copolymer.

[0014] Furthermore, the specific process of step S1 is as follows:

[0015] 4.8 g of 0.023 mol lipoic acid (TA) was dissolved in 200 mL of acetonitrile. 7.2 g of 0.028 mol N,N′-succinimide carbonate and 3 eq of 10 mL triethylamine (Et3N) were added to the solution. The mixture was stirred at room temperature for 2 h, concentrated under reduced pressure at room temperature, and 5% NaHCO3 aqueous solution was added to form a yellow precipitate. The precipitate was filtered, washed with water, and then dissolved in 200 mL of CH3CN. 15 mL of 80% hydrazine monohydrate was added dropwise to the solution, stirred at room temperature for 3 h, filtered, and the filtrate was concentrated under reduced pressure. 5% NaHCO3 aqueous solution was added, and the mixture was extracted with 200 mL of CHCl3. The yellow organic layer was washed three times with 5% NaHCO3 aqueous solution, dried on MgSO4, and the solvent was evaporated under reduced pressure to obtain a yellow solid monomer.

[0016] Furthermore, in step 2, the pH value of the acidic solution is 2-3.

[0017] Furthermore, in step 3, the molar ratio of TAH@PW to TAH is 1 / 100.

[0018] Application of a near-infrared photothermal self-healing membrane prepared according to the above-described method in seawater desalination.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. This invention not only proposes a general method for constructing a near-infrared photothermal self-healing membrane for use in seawater desalination, but also realizes photothermal self-healing of POMs hybrid materials.

[0021] 2. When the molar ratio of TAH@PW to TAH is 1 / 100, the Young's modulus increases from 7 MPa to 195 MPa; the evaporation efficiency of the prepared membrane reaches 2.75 kg m³ / s. -2 h -1 The photothermal conversion efficiency is 94.4%. Furthermore, after the damaged seawater desalination membrane heals, it can maintain almost unchanged mechanical strength and evaporation efficiency. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the preparation method and application of near-infrared photothermal self-healing films.

[0023] Figure 2Infrared spectra of PW (black line), TAH (red line), TAH@PW (purple line), and CP-1 / 100 (green line).

[0024] Figure 3 Thermogravimetric curves for P-TAH and CP-1 / 100 are shown.

[0025] Figure 4 NMR spectra (DMSO-d6) of TAH, TAH@PW, and CP-1 / 100.

[0026] Figure 5 In the figure, (a) is the tensile stress-strain curve; (b) is the Young's modulus of the copolymer. (a) from bottom to top, (b) from left to right: P-TAH, CP-1 / 18000, CP-1 / 10000, CP-1 / 5000, CP-1 / 1000, CP-1 / 500, CP-1 / 300, CP-1 / 100.

[0027] Figure 6 The NMR spectrum of TAD (DMSO-d6).

[0028] Figure 7 NMR spectra of TAD and TAD@PW (DMSO-d6).

[0029] Figure 8 The infrared spectra are for PW (black line), TAD@PW (red line), and TAD (blue line).

[0030] Figure 9 Optical images of copolymers containing different TAD@PW.

[0031] Figure 10 Optical images and color-changing mechanisms of the copolymer.

[0032] Figure 11 In the figures, (a) shows the UV spectra of PW, TAH, TAH@PW, and CP-1 / 100; (b) shows the UV spectra of PW, TAH, TAH@PW, and CP-1 / 100 after heating.

[0033] Figure 12 In the figure, (a) is the XPS spectrum of W element in TAH@PW and CP-1 / 100; (b) is the XPS spectrum of N element in TAH, TAH@PW and CP-1 / 100; and (c) is the XPS spectrum of S element in TAH, TAH@PW and CP-1 / 100.

[0034] Figure 13In the figures, (a) represents P-TAH, (b) represents CP-1 / 18000, (c) represents CP-1 / 10000, (d) represents CP-1 / 5000, (e) represents CP-1 / 1000, (f) represents CP-1 / 500, (g) represents CP-1 / 300, and (h) represents the infrared thermal image of CP-1 / 100 under 808nm near-infrared laser irradiation for 60s. (i) shows the temperature-time curves of the copolymers; from bottom to top, they are: P-TAH, CP-1 / 18000, CP-1 / 10000, CP-1 / 5000, CP-1 / 1000, CP-1 / 500, CP-1 / 300, and CP-1 / 100; (j) shows the real-time temperature change of CP-1 / 100 during 5 near-infrared laser on / off cycles. All data were obtained under illumination by an 808nm near-infrared laser with a spot size of 2*5mm.

[0035] Figure 14 In the image, (a)-(c) are optical images of CP-1 / 100 after healing under 808nm near-infrared laser irradiation at (a)0, (b)20, and (c)40s (spot size 2*5mm); (d) is an optical image of CP-1 / 100 before and after healing; (e) is the tensile stress-strain curve of CP-1 / 100 at different times; and (f) is the tensile period of the CP-1 / 100 sample after healing under 808nm near-infrared laser irradiation (spot size 4*5mm).

[0036] Figure 15 Optical images of P-TAH, CP-1 / 18000, CP-1 / 10000, and CP-1 / 5000 after healing under 808nm near-infrared laser irradiation at 0, 20, and 40 seconds (spot size 2*5mm).

[0037] Figure 16 Optical images of CP-1 / 1000, CP-1 / 500, and CP-1 / 300 after healing for 0, 20, and 40 seconds under 808nm near-infrared laser irradiation (spot size 2*5mm).

[0038] Figure 17 In the images, (a) is P-TAH, (b) is CP-1 / 18000, (c) is CP-1 / 10000, (d) is CP-1 / 5000, (e) is CP-1 / 1000, (f) is CP-1 / 500, (g) is CP-1 / 300, and (h) is CP-1 / 100, all infrared thermal images taken for 60 seconds under 808nm near-infrared laser irradiation (spot size 4*5mm).

[0039] Figure 18 The bar graph shows the healing efficiency of CP-1 / 100 under 808nm laser irradiation (spot size is 4*5mm).

[0040] Figure 19 This represents the self-healing mechanism of copolymers driven by near-infrared radiation.

[0041] Figure 20 Optical images of P-TAH, CP-1 / 18000, CP-1 / 10000, CP-1 / 5000, CP-1 / 1000, CP-1 / 500, CP-1 / 300, and CP-1 / 100 in various solvents after 12 hours.

[0042] Figure 21 For CP-1 / 100 in different H + Optical images after soaking in an aqueous solution of a certain concentration for 12 hours.

[0043] Figure 22 Optical images of CP-1 / 100 before and after immersion in seawater for 12 hours.

[0044] Figure 23 The contact angles are for P-TAH (left) and CP-1 / 100 (right).

[0045] Figure 24 In the diagram, (a) shows the optical absorption spectrum of CP-1 / 100; (b) shows the mass change of seawater with and without CP-1 / 100 added over 1 hour under one solar irradiation; (c) shows the change in seawater surface temperature with and without CP-1 / 100 under one solar irradiation; and (d) shows the mass change under 0.5, 1, 2, and 3 solar irradiations (intensities of 0.5, 1, 2, and 3 kW m², respectively). -2 (e) represents the change in seawater mass under CP-1 / 100 conditions; (f) represents the seawater evaporation rate over 10 cycles under CP-1 / 100 conditions; and (c) represents the ion concentration in seawater before and after evaporation.

[0046] Figure 25 In the figure, (a) represents the mass change of the container under dark conditions after 24 hours with and without CP-1 / 100; (b) represents the equivalent enthalpy with and without CP-1 / 100.

[0047] Figure 26 DSC for water with and without CP-1 / 100.

[0048] Figure 27 In the figure, (a)-(d) represent the surface temperatures of CP-1 / 100 under sunlight at working conditions (a) 0.5, (b) 1, (c) 2, and (d) 3, respectively.

[0049] Figure 28 In the image, (a) shows the optical images before and after CP-1 / 100 healing; (b) shows the seawater evaporation rate after three cutting and healing cycles in the presence of CP-1 / 100. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0051] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0052] This invention uses disulfide-bonded thioacetylhydrazine (TAH) as the main material to prepare a hybrid film with near-infrared (NIR) photothermal self-healing capability, and uses protonated TAH-doped Keggin-type POMs (TAH@PW) to improve the mechanical strength of the material, applying it to solar-driven seawater desalination (e.g. Figure 1 (As shown).

[0053] An embodiment of the present invention provides a method for preparing a near-infrared photothermal self-healing film, comprising the following steps:

[0054] Step 1, Preparation of thioacetylhydrazine (TAH): Lipoic acid (TA, 4.8 g, 0.023 mol) was dissolved in acetonitrile (200 mL). N,N′-succinimide carbonate (7.2 g, 0.028 mol) and triethylamine (Et3N, 3 eq, 10 mL) were added to the solution. The mixture was stirred at room temperature for 2 h, concentrated under reduced pressure at room temperature, and 5% NaHCO3 aqueous solution was added to form a yellow precipitate. The precipitate was filtered, washed with water, and then dissolved in CH3CN (200 mL). 80% hydrazine monohydrate (15 mL) was added dropwise to the solution, stirred at room temperature for 3 h, filtered, and the filtrate was concentrated under reduced pressure. 5% NaHCO3 aqueous solution was added, and the mixture was extracted with CHCl3 (200 mL). The yellow organic layer was washed three times with 5% NaHCO3 aqueous solution, dried on MgSO4, and the solvent was evaporated under reduced pressure to obtain a yellow solid monomer (4.5 g, 87.8%). 1 HNMR(500MHz,DMSO-d6)δ8.90(s,1H),4.12(s,2H),3.57(m,1H),3.10(m,2H), 2.37(m,1H),1.98(m,2H),1.84(m,1H),1.62(m,1H),1.48(m,3H),1.30(m,2H).

[0055] The synthetic route for TAH is as follows:

[0056]

[0057]

[0058] Step 2, Preparation of POMs hybrid polymer (synthesized via a two-step method): TAH is dissolved and protonated in an acidic solution (pH = 2-3), and then reacted with Keggin POMs Na3PW. 12 O 40 (PW) is combined via hydrogen bonding and electrostatic attraction to obtain TAH@PW.

[0059] Fourier transform infrared (FT-IR) spectroscopy shows that the characteristic vibrational band of PW in TAH@PW appears at 1083 cm⁻¹. -1 (PO a ) and 985cm -1 (W=O) d ), 887cm -1 (WO b -W) and 795cm -1 (WO c -W) indicates the stability of the cluster structure ( Figure 2 ).

[0060] Thermogravimetric analysis (TGA) curves show that at 700℃, the weight loss of CP-1 / 100 reaches 89.6%, which comes from the loss of the organic portion. The remaining 10.4% is the oxide formed after the calcination of inorganic anions. Figure 3 ).

[0061] The results of nuclear magnetic resonance spectroscopy (NMR) show that ( Figure 4 The hydrogen proton peaks of the amino and amide bonds in TAH@PW shifted to a higher field and broadened, indicating that the head movement of the quaternary ammonium salt was restricted. The test results show that TAH was successfully coated on the PW surface.

[0062] Infrared, nuclear magnetic resonance and elemental analysis results (Table 1) confirmed that the anion PW successfully combined with protonated TAH to form TAH@PW.

[0063] Table 1 Elemental Analysis of TAH@PW

[0064]

[0065] Organic elemental analysis (Table 2) showed that the molar ratio of PW in the final CP-1 / 100 reached 1%, indicating that there was no mass loss during the polymerization process.

[0066] Table 2 Elemental Analysis of CP-1 / 100

[0067]

[0068]

[0069] Step 3: Preparation of the target copolymer:

[0070] TAH was heated at 130°C for 2.5 hours in a constant-temperature oil bath to generate a liquid. TAH@PW was then added to the liquid, and the mixture was heated for another 0.5 hours. The resulting liquid was poured into a silicone mold with low surface energy and good non-adhesion properties, which had almost no effect on the solidification of the liquid (P-TAH), thus generating the target copolymer.

[0071] Based on the molar ratio of TAH@PW in the polymer, the resulting copolymers were named CP-1 / 18000, CP-1 / 10000, CP-1 / 5000, CP-1 / 1000, CP-1 / 1500, CP-1 / 300, and CP-1 / 100, respectively. Taking CP-1 / 100 as an example... Figure 4 As shown, it is compared with TAH@PW. 1 The H NMR spectra were compared. The results showed that the chemical shifts of TAH were almost the same in both states, except that the peak of the active H atom broadened and shifted, indicating that the hybrid copolymer was successfully prepared.

[0072] Example 1: Mechanical strength of the copolymer;

[0073] Mechanical strength is an important factor in evaluating material properties, and this invention has verified it. For example... Figure 5 As shown, without the addition of TAH@PW, the tensile stress of the copolymer exhibits a steady increasing trend, reaching a maximum of 2.5 MPa at a strain of 240%. With the addition of TAH@PW, the tensile stress of the copolymer increases from 5 MPa to 22.5 MPa, and the molar content of TAH@PW increases from 1 / 18000 to 1 / 100, resulting in a significant improvement in mechanical strength. The Young's modulus of the copolymer also changes significantly with the addition of TAH@PW; when the molar ratio of TAH@PW to TAH increases from 0 to 1 / 100, the Young's modulus of the copolymer increases from 7 MPa to 195 MPa.

[0074] To pinpoint the source of mechanical strength, a detailed structural analysis of the polymer was conducted. Clearly, disulfide ring-opening polymerization provides the basic structure of the polymer chain, playing a crucial role in its mechanical strength properties. Besides the SS bond, hydrogen bonds between the terminal -NH-NH2 groups also facilitate polymer network formation. To better evaluate the influence of hydrogen bonds on the mechanical properties of disulfide polymers, N-(2-(dimethylamino)ethyl)-5-(1,2-dithiamine-3-yl)pentanamide (TAD), with a molecular structure similar to TAH, was synthesized based on literature. The synthetic route for TAD is as follows:

[0075]

[0076] In TAH, the terminal molecule is modified with a -NH-NH2 group, which is believed to form strong hydrogen bonds between molecules, enhancing their bonding strength. In TAD, however, two methyl groups replace the -NH-NH2 group, failing to provide additional hydrogen bonds. Following a similar synthetic procedure to TAH@PW, TAD@PW was prepared, and its structure was confirmed by NMR and FT-IR spectroscopy. Figure 6-8 ).

[0077] The prepared TAD@PW is used as an additive to hybridize the polymer formed from pure TAD into a solvent-free state. For example... Figure 9 As shown, when the molar ratio of TAD@PW increases from 0 to 1 / 100, the polymer remains in a viscous state with poor mechanical strength. Therefore, hydrogen bonding plays an important role in improving the degree of crosslinking and enhancing the robustness of the polymer.

[0078] Example 2: Near-infrared photothermal properties of the copolymer;

[0079] With the addition of TAH@PW, the transparency of the copolymer decreased, and the color changed from yellow to dark blue. Figure 10 To investigate the source of the color, we tested the UV-Vis-NIR spectra of PW, TAH, TAH@PW, and CP-1 / 100, such as... Figure 11 As shown in (a), the characteristic band of O→W ligand-to-metal charge transfer (LMCT) of PW at approximately 270 nm can be clearly seen in the UV spectra of TAH@PW and CP-1 / 100, indicating that the structure of PW is well preserved during the color change process. The absorption peak of TAH, TAH@PW, and CP-1 / 100 at 330 nm belongs to disulfide bonds, which also proves the successful complexation of PW with TAH. During the preparation of the copolymer, after heating, CP-1 / 100 shows a new broad absorption band at approximately 753 nm. Figure 11 (b) can be clearly attributed to W. 5+ →W 6+ Intervalence charge transfer (IVCT), the characteristic absorption band of heteropolyblue, indicates the formation of reduced polyblue (PW). X-ray photoelectron spectroscopy (XPS) analysis also confirmed the formation of PW after the thermochromic process. 5+ The existence of. For example... Figure 12 As shown in (a), the valence of W atoms was detected as +6 in TAH@PW, and no W atoms were found. 5+ Signal, from W 6+ and W 5+ The peak area ratio shows that W appears after the thermal discoloration occurs. 5+ The concentration of W ions reached approximately 22%, indicating that some W... 6+ The ions are reduced to W during the color change process. 5+The stability of this thermochromic behavior of CP-1 / 100 should be attributed to the special structure of TAH. Of the two signal peaks corresponding to N1s, the peak at 401.6 eV originates from the amino group, and the peak at 399.9 eV originates from the amide bond. Figure 12 (b) Compared to TAH, the amino peak of TAH@PW shifted by 0.1 eV towards lower electron binding energies, which is attributed to the protonation of the amino group in TAH. A new peak appeared in the N1s spectrum of CP-1 / 100 at 404 eV, which is attributed to the loss of electrons on nitrogen during electron transfer. After peak separation at S2p, the signals at 163.4 eV and 164.7 eV in TAH, TAH@PW, and CP-1 / 100 remained unchanged, indicating that the electron transfer process was independent of sulfur. Figure 12 (c)

[0080] like Figure 10 As shown, the thermochromic process of the O→W LMCT band in PW causes the ammonium active proton of TAH to transfer to the bridging O atom at the WO6 octahedral thermochromic site. Then the d of the bridging O... 1 The process of electrons combining with protons provided by TAH and the interaction between the O→WLMCT transition and the non-bonding electrons of the amino N atom, leaving a hole on another O atom to form a charge transfer complex, implies the separation of electron and hole charges. The tight binding of TAH and PW in CP-1 / 100 keeps the colored charge transfer complex stable and enables the thermochromic process.

[0081] The formation of heteropolyblue endows the material with excellent near-infrared absorption capabilities and enables it to effectively convert near-infrared light into heat. The photothermal effect of the copolymer was evaluated under near-infrared laser irradiation and monitored using an infrared thermal imager. Figure 13 As shown in (a)-(h), under 808nm near-infrared laser (power density of 1W cm⁻¹), -2 Under irradiation with a spot size of 2*5mm, as the molar ratio of TAH@PW changed from 1 / 18000 to 1 / 100, the plateau temperature of the copolymer increased from 30℃ to 138℃, indicating that POMs play a decisive role in the photothermal properties. Temperature-time curve ( Figure 13 (i) indicates that all copolymers exhibit similar photothermal behavior, with the surface temperature of the copolymer rapidly increasing and reaching a steady state. In contrast, under the same conditions, the control sample (without TAH@PW) showed a smaller temperature increase (less than 7 °C), attributed to the inherent thermal effect in the near-infrared. The steady-state temperature was significantly dependent on the TAH@PW content, suggesting that the photothermal effect of the copolymer can be tailored by the amount of TAH@PW. Furthermore, by exposing the material to a power of 1 W cm⁻¹… -2The photothermal stability of the copolymer was investigated under repeated laser irradiation. After repeated laser irradiation, the temperature change within a fixed irradiation time was negligible, indicating that the copolymer possesses high photostability. Figure 13 (j)

[0082] Example 3: Photothermal self-healing of the copolymer;

[0083] Generally, self-healing materials require heating to high temperatures to activate a dynamic exchange reaction, thereby initiating the repair mechanism. In certain specific cases, self-healing needs to be achieved in designated areas to prevent excess heat from unnecessarily affecting other areas of the material. Direct heating makes it impossible to achieve accurate, rapid, and controlled material healing. In contrast, near-infrared light exposure can be used for remote stimulation, rapidly turning on and off as needed to achieve self-healing properties.

[0084] As mentioned above, the heteropolyblue in the copolymer can convert near-infrared light into heat in situ, thus enabling precise self-healing and control based on the location and extent of mechanical damage. Taking the CP-1 / 100 sample as an example... Figure 14 As shown, in near-infrared light (power density of 1W cm⁻¹) -2 Under irradiation with a spot size of 2*5mm, a crack with a width of 80μm can be rapidly repaired within 40 seconds. This means that the self-healing process of the copolymer can be successfully activated by near-infrared laser. To demonstrate the role of heteropolyblue in the photoinduced self-healing of the copolymer, we conducted control experiments using samples of pure polyTAH or low-content TAH@PW. The near-infrared self-healing process of the copolymer was directly observed using an optical microscope. Figure 15 As shown, for polymers without POM, the scratched surface appears unchanged under near-infrared laser irradiation, and photothermal conversion is negligible. With increasing heteropolyblue content in the copolymer, the scratch width gradually decreases. Figure 15 and Figure 16 This indicates that heteropolyblue is the key component of the copolymer's photoinduced self-healing.

[0085] The self-healing properties of CP-1 / 100 were evaluated through a complete fracture process. Increasing crack size requires a larger laser spot; therefore, an 808nm laser with a spot area of ​​4*5mm was used. With increasing spot area, the plateau temperature of copolymers containing different POM contents all increased to some extent. Figure 17 Taking CP-1 / 100 as an example, under near-infrared laser irradiation with a 4*5mm spot, the surface temperature reached 162℃, showing a significant increase.

[0086] like Figure 14 As shown in (d), a CP-1 / 100 block is completely cut and then subjected to an 808nm laser (power density of 1W cm⁻¹). -2After irradiation with a light spot size of 4*5mm for 70 seconds, the two broken parts could be reassembled. To further evaluate the repair effect, the following formula was used to quantitatively evaluate the repair capacity, and the repair efficiency of the material was calculated by comparing the tensile strength before and after the damage:

[0087]

[0088] in, and These represent the healed and original tensile stresses of the material, respectively. For example... Figure 14 As shown in (e), taking CP-1 / 100 as an example, when the near-infrared light irradiation time is 40s, the tensile stress is 10.7MPa, approximately 50% of the maximum value, and the strain is 52.6%. With increasing irradiation time, both tensile stress and strain increase. After 70s of irradiation, CP-1 / 100 exhibits good recovery toughness, with a healing rate of 91.71%. The stress-strain curve of the healed CP-1 / 100 essentially coincides with the stress-strain curve of the original sample. This self-healing behavior is recyclable; after three cycles, the repair efficiency can reach over 90%. Figure 14 (f) and Figure 18 ).

[0089] Based on the structure and self-healing process of copolymers, this invention proposes a simplified repair mechanism, such as... Figure 19 As shown, when near-infrared light irradiates a crack, the heteropolyblue within the beam spot efficiently and rapidly converts light energy into heat. The accumulated heat causes a sudden increase in local temperature, sufficient to dissociate or exchange dynamic interactions (disulfide bonds, multiple hydrogen bonds, and ion aggregation), and accelerate chain diffusion at the damaged interface, thus successfully healing the crack. Once the near-infrared light is removed, the local temperature drops to room temperature. Ultimately, the dynamic interactions change, constraints are re-established, chain dynamics slow down, and the elastomer recovers its mechanical properties.

[0090] Example 4: Application of copolymers in solar-driven seawater desalination membranes;

[0091] This copolymer possesses good processability, high photothermal performance, and rapid near-infrared self-healing properties, making it an ideal candidate material for solar-driven seawater desalination. Here, the copolymer's good processability supports the fabrication of customized membranes, including various shapes, sizes, and thicknesses. The high photothermal conversion efficiency derived from heteropolyblue allows the copolymer to absorb solar energy and convert it into heat energy, transferring it to seawater to form steam, which is then cooled to produce fresh water. If the seawater desalination membrane is damaged, it can be rapidly repaired under near-infrared light irradiation. These factors hold promise for overcoming the current bottlenecks in solar-driven seawater desalination technology. Before using this copolymer for seawater desalination, its stability was verified. First, its solubility was tested with different solvents. Figure 20As shown in Table 3, the copolymer is insoluble in water, ethyl acetate (C2H5COOC2H5), tetrahydrofuran (THF), ethanol (CH3CH2OH), and chloroform (CHCl3), but soluble in dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF). Furthermore, the copolymer exhibits slight swelling in methanol (CH3OH), but remains insoluble.

[0092] Table 3 Solvent stability of the copolymers in organic solvents

[0093]

[0094] Taking CP-1 / 100 as an example, the stability of the copolymer under different pH conditions was evaluated. Figure 21 As shown, CP-1 / 100 in different H + After being immersed in a solution of a certain concentration for 12 hours, the appearance of the copolymer remained unchanged, indicating that the copolymer has high stability in these environments.

[0095] The stability of the copolymer in seawater was tested. For example... Figure 22 As shown, after immersion in simulated seawater for 12 hours, the surface of CP-1 / 100 showed no significant changes. The experiment demonstrates that this copolymer exhibits high stability under various harsh conditions, ensuring its application as a seawater desalination membrane.

[0096] Since seawater evaporates through a membrane, the membrane's permeation significantly impacts evaporation efficiency. This invention evaluates the membrane's hydrophilicity / hydrophobicity using contact angle testing. Figure 23 As shown, the water contact angle (WCA) of pure P-TAH without POM is 109±2°, indicating hydrophobicity. However, for CP-1 / 100, the introduction of hydrophilic POM effectively reduces the WCA to 82±2°, demonstrating enhanced hydrophilicity. Therefore, the polyacids in the copolymer not only contribute to near-infrared photothermal properties but also increase the membrane's affinity for water, which is beneficial for seawater desalination.

[0097] From optical images of copolymers ( Figure 10 As can be seen, with the insertion of TAH@PW, the color of the copolymer changes from yellow to black, indicating that the copolymer has broad optical absorption of sunlight. Detailed absorbance characterization was performed using UV-Vis-NIR spectroscopy with ~2 mm thin films (…). Figure 24 (a)). Due to the presence of heteropolyblue in the copolymer, CP-1 / 100 exhibits excellent light absorption performance in the 200-2500 nm spectral range, effectively absorbing most of the solar energy.

[0098] Hot CP-1 / 100 was poured into a circular silicone mold with a diameter of 3.5 cm. After 0.5 h, nine circular holes were evenly punched into the material using a 1 mm diameter iron needle. After cooling, the material could be perfectly removed from the silicone mold, yielding a seawater desalination membrane. The prepared membrane was transferred to a sponge for solar water evaporation testing. When the membrane was placed in simulated seawater, the sponge served as a floating thermal barrier to support it. The sponge not only supported the photothermal membrane but also provided water permeability and insulation. Solar evaporation measurements were conducted under air conditioning and humidification control at approximately 25°C and 45% humidity. A xenon lamp (CEL-HXUV300W) equipped with a standard AM1.5 spectral filter was used as the light source. Solar flux was measured using a power meter. The membrane temperature was recorded using an infrared thermal imager. Changes in water mass were monitored using a laboratory balance. Containers containing the test aqueous solution were surrounded by polystyrene foam to reduce heat loss. A purification experiment was conducted on a seawater solution (containing NaCl, KCl, CaCl2, and MgCl2) prepared using CP-1 / 100 under one sun. The ion concentration in the collected water after evaporation was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). Solar vapor generation performance was monitored over time, and the mass reduction of water with or without CP-1 / 100 was recorded after the temperature reached steady state.

[0099] like Figure 24 As shown in (b), under the same light conditions, the vaporization rate of water in CP-1 / 100 is significantly faster than that of pure water. Based on the slope of the mass change curve, the water evaporation rate was calculated. Under one solar irradiation, CP-1 / 100 exhibited the highest evaporation rate, reaching 2.75 kg m³. -2 h -1 .

[0100] According to theoretical thermodynamics, the evaporation rate should be 1.47 kg m³ / s. -2 h -1 The solar vaporization performance of CP-1 / 100, exceeding the theoretical limit, is at its maximum. Therefore, the superior solar vaporization performance of CP-1 / 100, surpassing the theoretical limit, is attributed to the active intermediate states of water molecules within the polymer network. The equivalent enthalpy of vaporization of water in CP-1 / 100 is as follows: Figure 25 As shown, the enthalpy of vaporization is lower than that of pure water, confirming the active intermediate state of water molecules in the CP-1 / 100 polymer network.

[0101] To obtain the true enthalpy of vaporization of water in the CP-1 / 100 polymer network, samples with and without CP-1 / 100 were placed in sealed containers at ambient temperature (25°C) and dark pressure to ensure identical energy input. The relative humidity inside the containers was stabilized (~45%) using a supersaturated potassium carbonate solution. The equivalent enthalpy of vaporization of water in CP-1 / 100 (h⁻¹) was calculated. LV) can be based on the same power input (U in ) Calculated by the change in the mass of the wastewater sample:

[0102] U in =h vap ×m0=h LV ×m g

[0103] Among them, h vap m and m0 are the enthalpy of vaporization and mass change of pure water, respectively. g The change in water mass in CP-1 / 100. The change in mass mass and the calculated h. LV like Figure 25 As shown. The h of water in the obtained CP-1 / 100 sample. LV (~1236J g) -1 ) compared to pure water (2028 Jg) -1 )reduce.

[0104] Due to changes in experimental equipment, the enthalpy of water evaporation needs to be recalculated. The mass change of pure water over 24 hours was 0.1836 g, and the mass change of water in CP-1 / 100 was 0.3012 g. Since the enthalpy of water evaporation is 2028 J / g... -1 The enthalpy of evaporation of water in CP-1 / 100 is:

[0105] hLV=(h vap m0) / m g =(2028×0.1836) / 0.3012≈1236J g -1

[0106] Intermediate water is generally considered to be active water, an intermediate state between bound water and free water. The interactions between these water molecules and polymer chains and adjacent water molecules are relatively subtle. Therefore, active water consumes less energy during evaporation than pure water. Calculations show that the evolution energy of water of crystallization in CP-1 / 100 (1236 J g) -1 The evolution energy is lower than that of pure water (2028 J g). -1 This confirms the intermediate state of active water molecules within the CP-1 / 100 structure. Figure 26 In the differential scanning calorimetry (DSC) analysis, the water in CP-1 / 100 also underwent low-energy evaporation, indicating the activation process of water in the hydrophilic region of POM. The equivalent dark evaporation measurement results are in good agreement with the DSC experimental results, supporting this low-energy evaporation process.

[0107] In summary, this material possesses advantages such as adjustable hydrophilicity, enhanced solar absorptivity, and reduced enthalpy of evaporation, making it an ideal choice for solar evaporators. The energy efficiency (η) of CP-1 / 100 in this system can be calculated using the following formula:

[0108] η=mh LV / P0 (2)

[0109] Where m is the net evaporation rate calculated by subtracting the evaporation rate under darkness from the evaporation rate under one sun, and h LV P0 is the equivalent enthalpy of vaporization of water in CP-1 / 100, and P0 is the solar irradiance of one solar mass (1 kWm). -2 According to this formula, the energy efficiency of CP-1 / 100 is calculated to be ~94.4%, making it an ideal photothermal material.

[0110] To evaluate the photothermal conversion capability, infrared imaging cameras were used to record the real-time temperature changes of seawater and CP-1 / 100 material under operating conditions. For example... Figure 24 As shown in (c), the surface temperatures of seawater and CP-1 / 100 material increased to 27.2℃ and 50.6℃, respectively, indicating that CP-1 / 100 material possesses excellent photothermal conversion performance. The above experiments demonstrate that CP-1 / 100 can effectively convert sunlight into heat through localized evaporation. The effect of light intensity was investigated by adjusting the distance between the light source and the CP-1 / 100 surface. Figure 24 As shown in (d), the evaporation rate undoubtedly increases with increasing light intensity, reaching 6.03 kg m³ under three solar radiations. -2 h -1 The increase in evaporation can be attributed to the rise in material surface temperature. After 30 minutes of irradiation, the surface temperature of CP-1 / 100 increased from 32.8℃ to 70.9℃, and the light intensity increased from 0.5 solar irradiance to 3 solar irradiance. Figure 27 ).

[0111] The stability of gas production performance of simulated seawater under a single solar irradiation was determined through photothermal desalination experiments. Figure 24 As shown in (e), CP-1 / 100 maintained high seawater evaporation performance over 10 cycles, with evaporation rates ranging from 2.69 to 2.75 kgm³. -2 h -1 Within the specified range, this demonstrates that CP-1 / 100 exhibits stable continuous seawater desalination photothermal performance. Using simulated seawater as the water source, inductively coupled plasma mass spectrometry (ICP-MS) was employed to evaluate the quality of the treated water. After desalination via the solar water evaporation system, the concentrations of various ions (Na+, Na+, and Sodium) were... + K + Ca 2+ Mg 2+ All of them decreased significantly by 3 orders of magnitude. Figure 24(f) The experimental results meet the World Health Organization's drinking water standards. Therefore, the recommended CP-1 / 100 evaporation system has a significant efficiency in removing salt ions and can produce high-purity drinking water.

[0112] To investigate the ability of the CP-1 / 100 membrane evaporator to repair its structural integrity and moisture evaporation after physical damage, the two sides of the CP-1 / 100 membrane on the evaporator were cut open with a scalpel. Figure 28 (a) Subsequently, the separated portions of the CP-1 / 100 membrane were gently pressed together and reattached under an 808nm near-infrared laser (1Wcm). -2 After irradiation for 8 minutes under conditions of 4*5mm light spot size, the damaged CP-1 / 100 membrane healed, with the healed portion supporting its weight. Although a shallow groove can be observed in the optical image, the seawater evaporation rate of the repaired CP-1 / 100 membrane evaporator recovered to 2.61 kgm³. -2 h -1 ( Figure 28 (b) This value is similar to that of the prepared CP-1 / 100 membrane, indicating that the damage can be completely recovered due to the self-healing ability of the CP-1 / 100 membrane.

[0113] In summary, a series of organic-inorganic hybrids were synthesized by doping TAH polymers with protonated TAH-modified Keggin POMs. The introduction of inorganic clusters improved the mechanical strength of the hybrid materials; as the molar ratio of TAH@PW increased from 0 to 1 / 100, its Young's modulus increased from 7 MPa to 195 MPa. This increase in mechanical strength is attributed to the increased crosslinking density between the organic and inorganic parts, resulting in more supramolecular forces. The tungsten ions in the inorganic clusters were partially reduced from +6 to +5 valence, exhibiting strong absorption in the near-infrared region, thus giving the hybrid materials excellent photothermal properties. Combining the photothermal properties of POMs with the abundant dynamic covalent bonds in TAH, the prepared materials exhibited rapid self-healing behavior under near-infrared irradiation. The improved mechanical strength and photothermal properties make them an ideal choice for seawater desalination membranes. Experimental results show that, under one solar irradiation, the seawater desalination membrane prepared with this material achieved an evaporation efficiency as high as 2.75 kg m³. -2 h -1 The photothermal conversion efficiency was 94.4%. After 10 cycles, the evaporation efficiency showed no significant change, indicating high stability of the seawater desalination membrane. Self-healing experiments showed that the membrane could rapidly repair itself under 808nm light irradiation, and after 3 cycles, the evaporation efficiency of the repaired membrane was similar to that of the original membrane. This invention provides a modular strategy for constructing POM-based seawater desalination membranes, allowing the use of various inorganic and organic components to adjust evaporation and photothermal conversion efficiencies. The results of this invention also pave the way for research on the photothermal self-healing properties of POM-based materials, which can be applied in multiple fields.

[0114] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for preparing a near-infrared photothermal self-healing film, characterized in that, Includes the following steps: Step 1, Preparation of TAH: Lipoic acid was dissolved in acetonitrile. N,N′-succinimide carbonate and triethylamine were added to the solution, and the mixture was stirred at room temperature for 2 h. The solution was then concentrated under reduced pressure at room temperature, and 5% NaHCO3 aqueous solution was added to form a yellow precipitate. The precipitate was filtered, washed with water, and then dissolved in CH3CN. 80% hydrazine monohydrate was added dropwise to the solution, and the mixture was stirred at room temperature for 3 h. The filtrate was then concentrated under reduced pressure after filtration. 5% NaHCO3 aqueous solution was added, and the solution was extracted with CHCl3. The yellow organic layer was washed three times with 5% NaHCO3 aqueous solution, dried on MgSO4, and the solvent was evaporated under reduced pressure to obtain a yellow solid monomer. Step 2, Preparation of POMs hybrid polymers: TAH dissolves and protonates in an acidic solution, then combines with PW via hydrogen bonding and electrostatic attraction to obtain TAH@PW, where PW is Keggin-type phosphotungstic acid with the chemical formula Na3PW. 12 O 40 ; Step 3: Preparation of the target copolymer: TAH was heated at 130°C in a constant temperature oil bath for 2.5 h to generate a liquid. TAH@PW was then added and heated for another 0.5 h. The resulting liquid was poured into a silicone mold to generate the target copolymer.

2. The method for preparing the near-infrared photothermal self-healing film according to claim 1, characterized in that, The specific process of step 1 is as follows: 4.8 g of 0.023 mol lipoic acid was dissolved in 200 mL of acetonitrile. 7.2 g of 0.028 mol N,N′-succinimide carbonate and 3 eq of 10 mL triethylamine were added to the solution. The mixture was stirred at room temperature for 2 h, concentrated under reduced pressure at room temperature, and 5% NaHCO3 aqueous solution was added to form a yellow precipitate. The precipitate was filtered, washed with water, and then dissolved in 200 mL of CH3CN. 15 mL of 80% hydrazine monohydrate was added dropwise to the solution, stirred at room temperature for 3 h, filtered, and the filtrate was concentrated under reduced pressure. 5% NaHCO3 aqueous solution was added, and the mixture was extracted with 200 mL of CHCl3. The yellow organic layer was washed three times with 5% NaHCO3 aqueous solution, dried on MgSO4, and the solvent was evaporated under reduced pressure to obtain a yellow solid monomer.

3. The method for preparing the near-infrared photothermal self-healing film according to claim 1, characterized in that, In step 2, the pH value of the acidic solution is 2-3.

4. The method for preparing the near-infrared photothermal self-healing film according to claim 1, characterized in that, In step 3, the molar ratio of TAH@PW to TAH is 1 / 100.

5. The application of a near-infrared photothermal self-healing membrane prepared by any one of claims 1-4 in seawater desalination.

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