Cyclodextrin cross-linked supramolecular hydrogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of environmental restoration, and particularly relates to cyclodextrin cross-linked supramolecular hydrogel as well as a preparation method and application thereof. A construction unit of the supramolecular hydrogel comprises double-bond modified beta-cyclodextrin and acrylic acid interacting with the double-bond modified beta-cyclodextrin through a covalent bond; plant hormones are included in a cavity of the double-bond modified beta-cyclodextrin. The supramolecular hydrogel adhesive tape is provided with charges and cavities, can include plant hormones, and can be used together with soil improvement plants such as green manure to enhance the saline-alkali soil improvement effect by regulating and controlling the salinity of plant rhizosphere soil, improving the emergence rate, promoting plant growth and improving the environmental stress resistance of the plants. Cavities of the double-bond modified beta-cyclodextrin can effectively include plant hormones, and the supramolecular hydrogel is formed through covalent interaction between the acrylic acid and the double-bond modified beta-cyclodextrin. Based on multi-covalent and non-covalent interaction, the supramolecular hydrogel has the advantage of controllably releasing plant hormones, and realizes sustainable environmental remediation by cooperating with plant remediation.

Description

Technical Field

[0001] This invention belongs to the field of environmental remediation technology, specifically relating to a cyclodextrin crosslinked supramolecular hydrogel, its preparation method, and its application. Background Technology

[0002] In the remediation and improvement of saline-alkali land, existing chemical amendments are easily washed away by water flow, and the activity of biological agents drops sharply in high-salt and highly alkaline environments. Although hydrogels are environmentally friendly, conventional products lack salt tolerance and are prone to disassembly under high ionic strength, making it difficult to effectively regulate soil physicochemical properties in the long term. Therefore, developing supramolecular hydrogels with highly efficient salt-alkali regulation capabilities and the ability to synergistically promote plant growth in saline-alkali environments has become a key direction for overcoming the bottlenecks in saline-alkali land remediation. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a cyclodextrin crosslinked supramolecular hydrogel, its preparation method, and its application. The cyclodextrin crosslinked supramolecular hydrogel provided by this invention has a good promoting effect on plant growth in saline-alkali soil.

[0004] This invention provides a cyclodextrin crosslinked supramolecular hydrogel, wherein the building units of the cyclodextrin crosslinked supramolecular hydrogel include double-bond modified β-cyclodextrin and acrylic acid that covalently interacts with the double-bond modified β-cyclodextrin; wherein the double-bond modified β-cyclodextrin is N-(hydroxymethyl)acrylamide modified β-cyclodextrin. The cavity of the double-bond modified β-cyclodextrin contains plant hormones.

[0005] Preferably, the mass ratio of the double-bond modified β-cyclodextrin to acrylic acid is 1:(1~15).

[0006] Preferably, the plant hormone includes one or more of ascorbic acid, strigolactone 2-naphthaleneacetic acid, and 6-benzyladenine.

[0007] Preferably, the molar ratio of the double-bond modified β-cyclodextrin to the plant hormone is 1:(10~60).

[0008] This invention also provides a method for preparing the cyclodextrin crosslinked supramolecular hydrogel described above, comprising the following steps: β-Cyclodextrin, N-(hydroxymethyl)acrylamide, and organic solvent were mixed and modified to obtain double-bond modified β-cyclodextrin; The double-bond modified β-cyclodextrin, acrylic acid and first water were mixed and subjected to a pre-crosslinking reaction to obtain AA&β-CD gel; The AA&β-CD gel, plant hormone, and second water were mixed and encapsulated to form a gel, resulting in the cyclodextrin crosslinked supramolecular hydrogel.

[0009] Preferably, the molar ratio of the double-bond modified β-cyclodextrin to the volume of the first water is 3 mmol:(19~21) mL; and the volume ratio of the acrylic acid to the first water is 1:(5~10).

[0010] Preferably, the AA&β-CD gel, plant hormone, and second water are mixed as follows: first, the plant hormone and second water are mixed to prepare a plant hormone aqueous solution, and then the AA&β-CD gel is added; the concentration of the plant hormone aqueous solution is 2 mg / mL.

[0011] Preferably, the process after coating the synthetic adhesive further includes freeze drying, which includes a pre-cooling stage and a drying stage in sequence; the temperature of the pre-cooling stage is not higher than -40°C and the holding time is 1~1.5h; the temperature of the drying stage is -70~-50°C and the holding time is 48~72h.

[0012] The present invention also provides the application of the cyclodextrin crosslinked supramolecular hydrogel described in the above technical solution or the cyclodextrin crosslinked supramolecular hydrogel obtained by the above preparation method in saline-alkali soil.

[0013] Preferably, the application includes the following steps: Cyclodextrin-crosslinked supramolecular hydrogels were added to saline-alkali soil, and then plants were transplanted into the resulting mixed soil for cultivation. On a dry weight basis, the amount of the cyclodextrin crosslinked supramolecular hydrogel added is 10-50g per square meter of saline-alkali soil.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a cyclodextrin crosslinked supramolecular hydrogel, wherein the building units of the cyclodextrin crosslinked supramolecular hydrogel include double-bond modified β-cyclodextrin and acrylic acid that covalently interacts with the double-bond modified β-cyclodextrin; the double-bond modified β-cyclodextrin is N-(hydroxymethyl)acrylamide modified β-cyclodextrin; and plant hormones are encapsulated within the cavity of the double-bond modified β-cyclodextrin.

[0015] The cyclodextrin crosslinked supramolecular hydrogel (denoted as AA&β-CD) provided by this invention Plant hormones (SA) have cavities that can encapsulate plant hormones, thus synergistically promoting plant growth in saline-alkali soils with phytoremediation, resulting in high environmental remediation efficiency. The supramolecular hydrogel provided by this invention is a supported supramolecular hydrogel composed of acrylic acid and acrylamide-modified β-cyclodextrin. β-cyclodextrin serves as a site for covalent cross-linking reactions, forming a multi-layered network structure that increases the hydrogel's stability and strength, and improves its water content. There is a covalent interaction between acrylic acid (AA) and double-bond modified β-cyclodextrin (β-CD), and the cavities of the double-bond modified β-cyclodextrin can effectively encapsulate plant hormones (SA), demonstrating good compatibility between the two. Based on covalent interactions (double-bond modified β-cyclodextrin as the host and plant hormones as the guest), the supramolecular hydrogel provided by this invention possesses the advantage of controllable release of plant hormones, potentially making it a highly efficient platform for reducing soil salinization.

[0016] The cyclodextrin crosslinked supramolecular hydrogel of this invention is formed through a crosslinking reaction, exhibiting high structural controllability. The network pore size and crosslinking density can be precisely controlled by adjusting the amount of crosslinking agent and reaction conditions, thereby regulating the swelling rate, degradation rate, and mechanical properties. Simultaneously, biocompatibility can be optimized by adjusting the degree of crosslinking, reducing salt and alkali stress on plants and cells.

[0017] This invention also provides a method for preparing the cyclodextrin crosslinked supramolecular hydrogel described above, which is simple in steps, convenient in operation, highly feasible, and suitable for industrial production.

[0018] This invention also provides the application of the cyclodextrin cross-linked supramolecular hydrogel described in the above-described technical solutions, or the cyclodextrin cross-linked supramolecular hydrogel obtained by the preparation method described in the above-described technical solutions, in saline-alkali soils. The supramolecular hydrogel provided by this invention has a cavity structure, synergistically promoting plant growth in saline-alkali soils through combined phytoremediation, resulting in high environmental remediation efficiency and strong practicality. The cyclodextrin cross-linked supramolecular hydrogel provided by this invention synergistically with phytoremediation, achieving high remediation efficiency and a short remediation cycle. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a scanning electron microscope image of the AA & β-CD gel in Example 1; Figure 2 This is a scanning electron microscope image of the supramolecular hydrogel in Example 1; Figure 3The image shows the FT-IR spectrum of the supramolecular hydrogel in Example 1. Figure 4 The scan images show the rheological properties and strain amplitude of the supramolecular hydrogel in Example 1. Figure 5 The changes in maize biomass under the addition of different materials in a hydroponic experiment; Figure 6 The changes in sesame biomass when different materials were added during hydroponic experiments; Figure 7 The changes in maize biomass under the addition of different materials in the soil culture experiment; Figure 8 The changes in sesame biomass under the addition of different materials in the soil culture experiment. Detailed Implementation

[0021] This invention provides a cyclodextrin crosslinked supramolecular hydrogel, wherein the building units of the cyclodextrin crosslinked supramolecular hydrogel include double-bond modified β-cyclodextrin and acrylic acid that covalently interacts with the double-bond modified β-cyclodextrin; the double-bond modified β-cyclodextrin is β-cyclodextrin modified with N-(hydroxymethyl)acrylamide; The cavity of the double-bond modified β-cyclodextrin contains plant hormones.

[0022] In this invention, the structural formula of the double-bond modified β-cyclodextrin is shown in Formula I: Formula I, In formula I, R is H or The degree of substitution is 14.2% to 50%.

[0023] The building blocks of the supramolecular hydrogel provided by this invention include acrylic acid that covalently interacts with the double-bond modified β-cyclodextrin. The mass ratio of the double-bond modified β-cyclodextrin to acrylic acid is preferably 1:(1~15), specifically 1:1, 1:5, 1:6, or 1:10.

[0024] In this invention, the plant hormone preferably includes one or more of ascorbic acid, strigolactone, 2-naphthaleneacetic acid, and 6-benzyladenine; the structural formula of the ascorbic acid is shown in Formula II: Formula II.

[0025] In this invention, the molar ratio of the double-bond modified β-cyclodextrin to the plant hormone is preferably 1:(10~60), specifically 1:20, 1:30, or 1:60. This molar ratio provides a good loading rate for the plant hormone.

[0026] In this invention, the double-bond modified β-cyclodextrin is a macrocyclic host obtained by replacing the hydroxyl groups on the β-cyclodextrin with N-(hydroxymethyl)acrylamide. Plant hormones are encapsulated through host-guest interactions, and supramolecular hydrogels containing plant hormones are constructed through covalent interactions.

[0027] This invention also provides a method for preparing the cyclodextrin crosslinked supramolecular hydrogel described above, comprising the following steps: β-Cyclodextrin, N-(hydroxymethyl)acrylamide, and organic solvent were mixed and modified to obtain double-bond modified β-cyclodextrin; The double-bond modified β-cyclodextrin, acrylic acid and first water were mixed and subjected to a pre-crosslinking reaction to obtain AA&β-CD gel; The AA&β-CD gel, plant hormone, and second water were mixed and encapsulated to form a gel, resulting in the cyclodextrin crosslinked supramolecular hydrogel.

[0028] Unless otherwise specified, all materials and equipment used in this invention are commercially available products in the field.

[0029] This invention modifies β-cyclodextrin, N-(hydroxymethyl)acrylamide and organic solvent by mixing them (etherification reaction) to obtain double-bond modified β-cyclodextrin.

[0030] In this invention, when the β-cyclodextrin, N-(hydroxymethyl)acrylamide and organic solvent are mixed, a catalyst is preferably added, the catalyst being p-toluenesulfonic acid hydrate, and the ratio of the catalyst to the organic solvent is preferably 2.6 mmol:100 mL.

[0031] In this invention, the organic solvent preferably includes N,N-dimethylformamide (DMF).

[0032] In this invention, the preferred ratio of β-cyclodextrin, N-(hydroxymethyl)acrylamide and organic solvent is 13 mmol: 20 mmol: 100 mL.

[0033] In this invention, the modification is preferably carried out under oil bath and stirring conditions, the oil bath temperature is preferably 80°C, and the stirring time is preferably 30 min. The modified mixture preferably further includes: mixing the obtained reaction solution with acetone, washing the resulting precipitate with acetone, and then drying it; the volume ratio of the reaction solution to acetone during mixing is preferably 1:5, and the washing is preferably performed 3 times.

[0034] After obtaining the double-bond modified β-cyclodextrin, the present invention mixes the double-bond modified β-cyclodextrin, acrylic acid and first water to carry out a pre-crosslinking reaction to obtain AA&β-CD gel.

[0035] In this invention, the first mixing is preferably: stirring acrylic acid and water (referred to as stirring A) until the solution is clear to obtain an aqueous solution of acrylic acid, and then stirring and mixing the double bond modified β-cyclodextrin and the aqueous solution of acrylic acid (referred to as stirring B).

[0036] In this invention, the volume ratio of acrylic acid to water is preferably 1:(5~10), specifically 1:5, 1:8, or 1:10. This volume ratio of acrylic acid to water ensures the gel's mechanical properties.

[0037] In this invention, the stirring speed of the stirring A is preferably 480~960 rpm, specifically 480 rpm, 600 rpm, 720 rpm, 840 rpm or 960 rpm, and the stirring time is preferably 20~40 min, specifically 25 min, 30 min or 35 min.

[0038] In this invention, the stirring speed of the stirring B is preferably 480~960 rpm, specifically 480 rpm, 600 rpm, 720 rpm, 840 rpm or 960 rpm, and the stirring time is preferably 10~12 min, specifically 11 min.

[0039] In this invention, the mixing of the double-bond modified β-cyclodextrin, acrylic acid, and first water is preferably carried out at room temperature and under stirring conditions, and the stirring time is preferably 30 min. Preferably, an initiator is also added to the mixing of the double-bond modified β-cyclodextrin, acrylic acid, and first water. The initiator is preferably ammonium persulfate, and the molar ratio of ammonium persulfate to acrylic acid is 1:(11~22), specifically 1:22. The molar ratio of the double-bond modified β-cyclodextrin to the volume of the first water is preferably 3 mmol:(19~21) mL; the volume ratio of the acrylic acid to the first water is preferably 1:(5~10).

[0040] In this invention, the temperature of the pre-crosslinking reaction is preferably 60°C and the time is preferably 3 hours; the pre-crosslinking reaction is preferably followed by standing and washing with water, and the standing time is preferably 12 hours.

[0041] After obtaining the AA&β-CD gel, the present invention mixes the AA&β-CD gel, plant hormone, and second water to form a composite gel, thereby obtaining the cyclodextrin crosslinked supramolecular hydrogel.

[0042] In this invention, the preferred method for mixing the AA&β-CD gel, plant hormone, and second water is to first prepare a plant hormone aqueous solution by mixing the plant hormone and the second water, and then add the AA&β-CD gel. The concentration of the plant hormone aqueous solution is preferably 2 mg / mL.

[0043] In this invention, the temperature of the coating adhesive is preferably 15~40℃, specifically 20℃ or 25℃.

[0044] In this invention, the process of forming the synthetic gel preferably further includes allowing the resulting product to stand before washing with water and freeze-drying. The standing time is preferably 4-32 hours, specifically 12 hours or 24 hours; the water washing removes free monomers and oligomers that have not formed a hydrogel. The freeze-drying preferably includes a pre-cooling stage and a drying stage sequentially; the temperature of the pre-cooling stage is preferably not higher than -40°C, specifically -40°C, -45°C, -50°C, -55°C, or -60°C, and the holding time of the pre-cooling stage is preferably 1-1.5 hours, specifically 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, or 1.5 hours. The temperature of the drying stage is preferably -70~-50℃, specifically -70℃, -65℃, -60℃, -55℃ or -50℃, and the holding time of the drying stage is preferably 48~72h, specifically 48h, 54h, 60h, 66h or 72h; the equipment for freeze drying is preferably a freeze dryer.

[0045] In this invention, the AA&β-CD gel, plant hormone, and second water are preferably mixed by stirring and ultrasonication in sequence; the stirring speed is preferably 900~1300 rpm, specifically 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, or 1300 rpm, and the mixing time is preferably 1~2 h, specifically 1.5 h; the ultrasonic mixing time is preferably 0.5~1.5 h, specifically 1 h.

[0046] The present invention also provides the application of the cyclodextrin crosslinked supramolecular hydrogel described in the above technical solution or the cyclodextrin crosslinked supramolecular hydrogel obtained by the preparation method described in the above technical solution in saline-alkali soil.

[0047] In this invention, the application of the cyclodextrin-crosslinked supramolecular hydrogel in saline-alkali soil preferably includes the following steps: adding the cyclodextrin-crosslinked supramolecular hydrogel to the saline-alkali soil, and then transplanting plants into the resulting mixed soil for cultivation; the amount of the cyclodextrin-crosslinked supramolecular hydrogel added is 10-50g per square meter of saline-alkali soil, based on dry weight. The cyclodextrin-crosslinked supramolecular hydrogel forms a remediation system with the plants, thereby reducing the degree of soil salinization.

[0048] In this invention, the process of transplanting the plant preferably includes adding a nutrient solution to the mixed soil; the nutrient solution is preferably Hoagland nutrient solution or a prepared Hoagland nutrient solution. The preferred nutrient composition of the Hoagland nutrient solution includes: potassium sulfate 607 mg / L, ammonium dihydrogen phosphate 115 mg / L, magnesium sulfate 493 mg / L, EDTA iron sodium salt 20 mg / L, ferrous sulfate 2.86 mg / L, borax 4.5 mg / L, manganese sulfate 2.13 mg / L, copper sulfate 0.05 mg / L, zinc sulfate 0.22 mg / L, and ammonium sulfate 0.02 mg / L. The preferred method for preparing the Hoagland nutrient solution is as follows: mixing Hoagland nutrient solution, calcium salt, and water; the calcium salt is preferably calcium nitrate tetrahydrate; and the water is preferably distilled water. The preferred mass ratio of Hoagland nutrient solution to calcium salt is 1260:945; the preferred mass ratio of the total Hoagland content in the Hoagland nutrient solution to water is 1.26:1000~4000, specifically 1.26:1000, 1.26:2000, 1.26:3000, or 1.26:4000. The mixing of Hoagland nutrient solution, calcium salt, and water is preferably performed by heating; the preferred heating temperature is based on the dissolution of the Hoagland nutrient solution and calcium salt in the water.

[0049] In this invention, the plant is preferably one or more of economic crops or landscape plants; the economic crop is preferably one or two of corn and sesbania; the landscape plant preferably includes one or more of reed, arundinaria and water lily.

[0050] In this invention, the plant transplantation is preferably carried out by transplanting the plant into a mixed soil, thereby dispersing the cyclodextrin-crosslinked supramolecular hydrogel in the rhizosphere. Through the above operation, this invention ensures that the cyclodextrin-crosslinked supramolecular hydrogel aggregates near the plant rhizosphere, thus enhancing the effective promotion of plant growth by the sustained-release plant hormones from the cyclodextrin-crosslinked supramolecular hydrogel.

[0051] In this invention, the density of plant transplantation can be 45-55 plants / m². 2 Specifically, it can be 50 plants / m². 2 .

[0052] In this invention, the process preferably includes daily watering of the mixed soil after plant transplantation. The mass ratio of water to cyclodextrin-crosslinked supramolecular hydrogel can be 50-150:0.2770-0.7354, specifically 75:0.3, 75:0.6, 100:0.6, 100:0.7, 100:0.7354, or 125:0.7. This invention, through water replenishment, helps restore and maintain the structure of the cyclodextrin-crosslinked supramolecular hydrogel, thus enhancing its effectiveness.

[0053] To further illustrate the present invention, the cyclodextrin crosslinked supramolecular hydrogels, their preparation methods, and applications provided by the present invention are described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0054] Example 1 The supramolecular hydrogel prepared in this embodiment uses β-cyclodextrin modified with double bonds as the host and ascorbic acid (ASA) as the guest.

[0055] The preparation method of supramolecular hydrogel in this embodiment includes the following steps: 1. Preparation of double-bond modified β-cyclodextrin: β-cyclodextrin (β-CD, 15 g, 13 mmol) and N-(hydroxymethyl)acrylamide (2 g, 20 mmol) were dissolved in 100 mL of DMF. The catalyst p-toluenesulfonic acid hydrate (500 mg, 2.6 mmol) was added to the solution, and the mixture was stirred in an oil bath at 80 °C for 30 min. The solution was poured into 500 mL of acetone, the precipitate was filtered, and the product was washed three times with 30 mL of acetone. The residue was dried in a vacuum oven to obtain the target product (double-bond modified β-cyclodextrin). 2. Preparation of AA&β-CD gel: Double bond modified β-cyclodextrin (0.0507 g), acrylic acid (300 μL) and 2 mL water were stirred at room temperature for 30 min. After mixing evenly, 0.2 mmol of ammonium persulfate was added as an initiator, sealed and crosslinked in a constant temperature water bath at 60℃ for 3 h. After standing for 12 h, it was washed with deionized water to obtain AA&β-CD gel (denoted as AA&β-CD).

[0056] 3. Preparation of supramolecular hydrogel: The AA&β-CD gel prepared above was mixed with plant hormones in a certain proportion to prepare a supramolecular hydrogel containing plant hormones. First, a plant hormone (ascorbic acid, ASA) solution was prepared. ASA was dissolved in 150 mL of deionized water to prepare a 2 mg / mL ascorbic acid solution. 0.5 mL of the prepared AA&β-CD gel was added to the ascorbic acid solution and allowed to stand for 12 h to obtain a jelly-like gel. The gel was washed with deionized water to remove free monomers and oligomers that did not form a hydrogel, thus obtaining the supramolecular hydrogel (denoted as AA&β-CD). ASA).

[0057] The properties of the supramolecular hydrogel were detected using a rheometer and scanning electron microscope, and its structure was observed using infrared spectroscopy and XRD. The results are as follows: Figures 1-4 As shown.

[0058] Figure 1 and Figure 2The images shown are scanning electron microscope (SEM) images of the AA&β-CD gel and the supramolecular hydrogel containing plant hormones in this embodiment. It can be seen that the gel has a porous structure and can contain plant hormones.

[0059] Figure 3 The FT-IR spectra of the AA&β-CD gel and the supramolecular hydrogel containing plant hormones in this embodiment show that the structure of acrylic acid remained essentially unchanged during the gel formation process.

[0060] Figure 4 The image shows the rheological properties and strain amplitude test scans of the supramolecular hydrogel in this embodiment. It can be seen that G′ is much larger than G′′ throughout the entire test strain range, indicating that the gel is always dominated by elasticity and has a low viscosity. It belongs to a rigid gel system with "strong elasticity and weak fluidity" and can withstand large deformations without significant structural collapse.

[0061] Application Example 1: Hydroponic Experiment Seedlings were raised in a greenhouse environment with day and night temperatures of 30 ℃ / 25 ℃ and day and night relative humidity of 70% / 90%, with a photoperiod of 12 h. Corn and green manure plant sesbania were selected and sown in seedling trays containing nutrient soil and vermiculite (3:1 v / v) substrate, respectively. After germination, the seedlings were allowed to develop two pairs of leaves.

[0062] Select seedlings that are uniform in size and growing well, and remove the soil attached to the roots of each plant; rinse the roots three times with deionized water, culture the plants in deionized water for 1 day, change the water, and continue to culture in deionized water until the plants grow white aquatic roots.

[0063] Transfer the solution to a glass culture bottle containing 150 mL of 1 / 2 strength Hoagland nutrient solution. Cover the bottle with a black bag to simulate a dark soil environment. Use planting cotton and a planting basket to plant the plants at the bottle opening. Refill the bottle with nutrient solution daily until it reaches the mark. When the plants grow to about 10 cm in height, select uniform plants, replace the nutrient solution, and continue the experiment.

[0064] A typical stress environment was simulated by mixing NaCl and Na₂SO₄ at a ratio of 9 mol:1 mol, and 150 mL of a 1 / 2 Hoagland nutrient solution with a salt concentration of 200 mmol / L was prepared. The nutrient solution was added to each hydroponic bottle, and the bottles were aerated and stirred once a day for 1 min each time, with deionized water added to maintain the solution volume.

[0065] Add the frozen dry gel to the dialysis bag and seal it in a hydroponic bottle. After 5 days of hydroponics, the plants are rinsed, blanched, and dried to constant weight according to ASTM E1620-2016, "Standard Guide for the Determination of Biomass in Biological Samples". The remaining biomass is then quantified by weighing.

[0066] Table 1. Experimental Design of Supramolecular Hydrogel-Plant Hydroponics

[0067] The changes in biomass of corn and sesbania under different material additions in hydroponic experiments are as follows: Figure 5 , 6 As shown.

[0068] In the hydroponic experiment, the biomass of both maize and sesbania in the SS group was significantly reduced compared to the CK group. This indicates that plant growth is inhibited under salt-alkali stress, and the different degrees of inhibition between maize and sesbania may be due to differences in the ability of plant species to resist salt-alkali stress. Compared to the SS group, the biomass of the aboveground parts, roots, and whole plants of both maize and sesbania in different material addition groups was significantly increased.

[0069] For maize, compared to the SS group, the ASA, AC, and ACA groups showed increases in whole plant biomass of 152%, 13%, and 99%, respectively; root biomass of 127%, 5%, and 53%, respectively; and aboveground biomass of 167%, 17%, and 126%, respectively. For sesbania, compared to the SS group, the ASA, AC, and ACA groups showed increases in whole plant biomass of 46%, 56%, and 112%, respectively; root biomass of 35%, 46%, and 77%, respectively; and aboveground biomass of 52%, 53%, and 127%, respectively. The reason why the ACA group was not as effective as the ASA group may be that maize seedlings have a higher demand for ASA, and the added ASA is directly and quickly absorbed by the maize, thus promoting rapid seedling growth. AA & β-CD... The presence of cyclodextrin in ASA regulates the release rate of ASA, resulting in a lower concentration of ASA in the hydroponic solution and less ASA being absorbed by corn, thus slowing down its growth-promoting effect compared to the ASA group; however, the long-term effect is better in the ACA group.

[0070] Application Example 2: Soil Cultivation Experiment Soil cultivation experiments were conducted in a greenhouse environment with day / night temperatures of 25 / 30℃ and day / night relative humidity of 70% / 90%, with a photoperiod of 12 hours. Corn and green manure plant sesbania were selected for pot experiments. Polyethylene pots were used, with each pot containing 0.6 kg (dry weight) of mixed soil. The soil used in the experiment was taken from uncontaminated topsoil from Nankai University's Jinan Campus (E117°21′47.27″, N38°59′26.99″); Ninghe, Tianjin, with a soil salinity of 3.15‰ and a pH of 8.56. After natural air drying, stones, impurities, and plant and animal remains were removed, the soil was crushed with a small wooden mallet, and sieved through a 2 mm sieve. Three experimental groups were set up, with ordinary farmland soil without added materials serving as a control. The specific experimental design is as follows: Table 2 Experimental Design of Supramolecular Hydrogel-Phytoremediation

[0071] The changes in biomass of corn and sesame under different material additions in the soil culture experiment are as follows: Figure 7 , 8 As shown.

[0072] Compared to the control group, the biomass of maize and sesbania in the pot experiment was significantly reduced, indicating that maize and sesbania suffered severe damage and growth inhibition during cultivation in high-salt-alkali soil; however, in AA&β-CD... The growth of both organisms improved under the influence of ASA.

[0073] For maize, compared to the SS group, the biomass of the aboveground parts, roots, and whole plants in the ACA group increased significantly, by 55%, 145%, and 67%, respectively. For sesbania, compared to the SS group, the biomass of the aboveground parts, roots, and whole plants in the ACA group increased by 96%, 109%, and 98%, respectively. This indicates that ASA was released from the hydrogel, promoting plant growth. In maize growth, AA & β-CD... The addition of ASA has a more pronounced effect on the roots, possibly because the released ASA is mostly absorbed by the roots at a faster rate, and the plant's demand for ASA is relatively high, resulting in less utilization by the above-ground parts and a weaker growth-promoting effect compared to the underground parts. During the growth of sesbania, the demand for ASA is less than that of corn, and the ASA released by the controlled-release system is slowly and evenly utilized by the entire plant, thus the increase in biomass in the above-ground and underground parts is relatively even.

[0074] In the examples, plant growth was inhibited under salt-alkali stress. However, the differences in the ability of sesbania and maize to resist salt-alkali stress resulted in varying degrees of inhibition. AA & β-CD The addition of ASA alleviated the hindrance to plant growth and cell damage caused by salt and alkali stress. The release of ASA promoted plant growth and significantly increased the biomass of the aboveground parts, roots and whole plants of sesbania and maize, thereby improving the rhizosphere soil environment. It can be used as an enhanced means of improving saline-alkali soil with plants.

[0075] As can be seen from the above embodiments and test examples, the supramolecular hydrogel provided by the present invention has the function of promoting plant growth in saline-alkali soil, has a promoting effect on the improvement of saline-alkali soil by plants, and has high environmental remediation efficiency.

[0076] The supramolecular hydrogel (AA&β-CD) developed in this invention In saline-alkali stress environments, the slow-release system of guest molecules in the ASA (autoclave-associated saline-alkali hydrogel) can promote plant growth. The adsorption system of this gel can alleviate the saline-alkali stress pressure on plant roots and prolong the action time of guest molecules, thereby enhancing the soil-improving effect of plants, especially green manure, on saline-alkali soil. Compared with the saline-alkali stress group, plant biomass increased. Furthermore, the addition of supramolecular hydrogels changes the traditional method of foliar spraying of plant hormones, adopting a root-addition method, which is not only simple to operate but also improves the utilization rate of plant roots and has a more significant promoting effect on soil microorganisms.

[0077] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on the present invention without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A cyclodextrin crosslinked supramolecular hydrogel, characterized in that, The building blocks of the cyclodextrin crosslinked supramolecular hydrogel include double-bond modified β-cyclodextrin and acrylic acid that covalently interacts with the double-bond modified β-cyclodextrin; the double-bond modified β-cyclodextrin is N-(hydroxymethyl)acrylamide modified β-cyclodextrin. The cavity of the double-bond modified β-cyclodextrin contains plant hormones.

2. The cyclodextrin crosslinked supramolecular hydrogel according to claim 1, characterized in that, The mass ratio of the double-bond modified β-cyclodextrin to acrylic acid is 1:(1~15).

3. The cyclodextrin crosslinked supramolecular hydrogel according to claim 1, characterized in that, The plant hormones include one or more of ascorbic acid, strigolactone, 2-naphthaleneacetic acid, and 6-benzyladenine.

4. The cyclodextrin crosslinked supramolecular hydrogel according to claim 1 or 3, characterized in that, The molar ratio of the double-bond modified β-cyclodextrin to the plant hormone is 1:(10~60).

5. The method for preparing the cyclodextrin crosslinked supramolecular hydrogel according to any one of claims 1 to 4, characterized in that, Includes the following steps: β-Cyclodextrin, N-(hydroxymethyl)acrylamide, and organic solvent were mixed and modified to obtain double-bond modified β-cyclodextrin; The double-bond modified β-cyclodextrin, acrylic acid and first water were mixed and subjected to a pre-crosslinking reaction to obtain AA&β-CD gel; The AA&β-CD gel, plant hormone, and second water were mixed and encapsulated to form a gel, resulting in the cyclodextrin crosslinked supramolecular hydrogel.

6. The preparation method according to claim 5, characterized in that, The molar ratio of the double-bond modified β-cyclodextrin to the volume of the first water is 3 mmol:(19~21) mL; the volume ratio of the acrylic acid to the first water is 1:(5~10).

7. The preparation method according to claim 5, characterized in that, The AA&β-CD gel, plant hormone, and second water are mixed as follows: first, the plant hormone and second water are mixed to prepare an aqueous solution of plant hormone, and then the AA&β-CD gel is added; the concentration of the aqueous solution of plant hormone is 2 mg / mL.

8. The preparation method according to claim 5, characterized in that, The process of coating the synthetic adhesive further includes freeze drying, which includes a pre-cooling stage and a drying stage in sequence; the temperature of the pre-cooling stage is not higher than -40℃, and the holding time is 1~1.5h; the temperature of the drying stage is -70~-50℃, and the holding time is 48~72h.

9. The application of the cyclodextrin crosslinked supramolecular hydrogel according to any one of claims 1 to 4 or the cyclodextrin crosslinked supramolecular hydrogel obtained by the preparation method according to any one of claims 5 to 8 in saline-alkali soil.

10. The application according to claim 9, characterized in that, The application includes the following steps: Cyclodextrin-crosslinked supramolecular hydrogels were added to saline-alkali soil, and then plants were transplanted into the resulting mixed soil for cultivation. On a dry weight basis, the amount of the cyclodextrin crosslinked supramolecular hydrogel added is 10-50g per square meter of saline-alkali soil.

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