A method for preparing an underwater adhesive based on natural polysaccharides

Abstract

The application belongs to the technical field of polymer materials and underwater adhesives, and relates to a preparation method of an underwater adhesive based on natural polysaccharides. The specific steps are as follows: S1: dissolving double-bond modified natural polysaccharides in an organic solvent at a certain concentration; S2: adding monomers containing hydrophobic groups and monomers containing double bonds to the solution prepared in S1 at a certain mass ratio, and uniformly mixing; S3: adding an initiator to the solution in S2 at a certain ratio to initiate a free radical copolymerization reaction, and after the reaction is completed, purifying in water, and freeze-drying to obtain a copolymer; and S4: dissolving the copolymer prepared in S3 in an organic solvent at a certain mass ratio to obtain an underwater adhesive. The application has adhesion to hydrophobic, hydrophilic, porous substrates and biological tissues under water; and has underwater adhesion under various liquid environments (blood, urine, physiological saline, body fluid and seawater).

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and underwater adhesives, and particularly relates to a method for preparing an underwater adhesive based on natural polysaccharides. Background Technology

[0002] Since the late 1960s, underwater coatings based on epoxy resins have emerged abroad. Based on this, water-absorbing alkaline earth metal oxides were added as additives, and compounds that react with water to form amines were used as curing agents, resulting in underwater-curing adhesives. In the early 1970s, there were reports of α-cyanoacrylates being used as underwater adhesives. In the late 1970s, polyurethane coatings that could cure in humid atmospheres began to appear abroad, and similar silicone adhesives, acrylate adhesives, and polyurethane adhesives also emerged. In the mid-1980s, scientists in Germany and Belgium conducted research on underwater adhesives from a biomimetic perspective, such as peptide compounds, but this was limited to the laboratory and was very expensive, preventing widespread application. [Wang Xi et al., School of Science, Northwestern Polytechnical University]. In April 2016, the journal *Adhesion* reported that Professor Heberwitt's team at the University of California, Barbara, inspired by the adhesive proteins secreted by marine organisms such as mussels and sandworms, invented a new type of adhesive that can quickly bond underwater. This research was published in the British journal *Nature Materials*. To date, underwater adhesive formulation technology has developed rapidly. Underwater adhesion is playing a crucial role in biomedical engineering fields such as biological tissues, human biomedical devices, and underwater soft robots. In an aquatic environment, the adhesion strength between the substrate and the adhesive is severely weakened due to the presence of the hydration layer, making substrate adhesion in dynamic aquatic environments still challenging. Inspired by the strong underwater adhesion of natural organisms (such as mussels and barnacles), non-covalent interactions (such as electrostatics, hydrogen bonds, and hydrophobic interactions), covalent interactions, and micro / nanostructure modification strategies are often employed to improve the adhesion of adhesives to various underwater substrates. However, most existing polymer adhesives are susceptible to water erosion and may swell and fail, inevitably limiting their development in underwater adhesion applications.

[0003] This invention aims to generate an organic adhesive in an organic solvent based on biomimetic and solvent exchange strategies. The adhesive is primarily composed of natural polysaccharides with hydrophobic and adhesive groups branched onto its side links. In a liquid environment, this adhesive undergoes a solvent exchange process, exposing the hydrophobic groups and repelling interfacial water molecules. This, in turn, allows the adhesive groups to interact with the substrate, achieving superior underwater adhesion. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing an injectable underwater adhesive based on natural polysaccharides. Using natural polysaccharides as the main component, a free radical polymerization reaction is employed to introduce polyphenolic adhesive groups and hydrophobic groups, inducing the aggregation of hydrophobic segments and thereby exposing the adhesive groups, achieving strong and stable underwater adhesion to various materials. The technical solution for achieving this invention is as follows:

[0005] A method for preparing an underwater adhesive based on natural polysaccharides, comprising the following steps:

[0006] S1: Dissolve the double-bonded modified natural polysaccharide in an organic solvent at a certain concentration;

[0007] S2: Add a certain mass ratio of monomers containing hydrophobic groups and polyphenolic monomers containing double bonds to the solution prepared in S1 and mix thoroughly.

[0008] S3: Add a certain proportion of initiator to the solution in S2 to initiate a free radical copolymerization reaction. After the reaction is complete, purify in water and freeze-dry to obtain the copolymer.

[0009] S4: The copolymer obtained in S3 is dissolved in an organic solvent in a certain mass ratio to obtain an underwater adhesive.

[0010] The monomer containing the hydrophobic group is selected from any one or more of the following: methyl acrylate, ethyl acrylate, butyl acrylate, and hexyl acrylate.

[0011] The polyphenol monomer containing double bonds is selected from any one or more of the following: methacrylamide dopamine, caffeic acid, and eugenol.

[0012] The double-bonded modified natural polysaccharide is selected from any one of the following: agarose, sodium alginate, dextran, and fucoidan;

[0013] Furthermore, the preparation method of the double-bonded modified natural polysaccharide in step S1 is as follows: the natural polysaccharide is dissolved in dimethyl sulfoxide, modified by glycidyl methacrylate, dialyzed, and freeze-dried to obtain a methacrylamide polymer.

[0014] Furthermore, in the preparation of the copolymer, the mass ratio of the monomer containing hydrophobic groups to the double-bonded modified natural polysaccharide is 1:3 to 2:1.

[0015] The mass ratio of polyphenol monomers containing double bonds to natural polysaccharides modified with double bonds is 4:1 to 1:5.

[0016] Furthermore, in preparing the copolymer, the initiator is selected from any one of the following: ammonium persulfate, potassium persulfate, and photoinitiator 2959; wherein the mass percentage concentration of the initiator in the organic solvent is 0.2% to 4%.

[0017] Furthermore, in step S4, during the preparation of the adhesive, the mass ratio of the copolymer dissolved in the organic solvent is 1:50 to 1:10. The organic solvent is selected from any one or more of the following: dimethyl sulfoxide, N,N-dimethylformamide, and dioxane;

[0018] Furthermore, the reaction temperature in step S3 is 70–80°C, and the reaction time is 180–270 min.

[0019] The natural polysaccharide-based underwater adhesive prepared by the above method, wherein the pure water is deionized water.

[0020] Preferably, the monomer containing hydrophobic groups in step S2 is butyl acrylate.

[0021] Preferably, the polyphenol monomer containing double bonds in step S2 is methacrylamide.

[0022] More preferably, the methacrylamide is methacrylic anhydride; the mass ratio of the methacrylic anhydride to dopamine is 1:1.1.

[0023] Preferably, the natural polysaccharide modified by double bonding in step S1 is agarose; the double-bonded agarose is prepared by the following method: dissolving agarose in dimethyl sulfoxide solution, modifying it with glycidyl methacrylate, dialysis, and freeze-drying to obtain methacrylamide agarose.

[0024] More preferably, the dissolution temperature is 80°C, the mass ratio of glycidyl methacrylate to agarose is 1:4, and the reaction time is 48 hours.

[0025] Preferably, in step S3, when preparing the copolymer, the mass ratio of butyl acrylate to double-bonded agarose is 1:2; and the mass ratio of methacrylamide to double-bonded agarose is 1:2.

[0026] More preferably, the reaction temperature is 80°C and the reaction time is 240 min.

[0027] Preferably, in step S4, when preparing the adhesive, the mass ratio of the copolymer dissolved in the organic solvent is 1:18.

[0028] More preferably, the initiator is potassium persulfate; the mass percentage concentration of the initiator in the organic solvent is 0.2-4%.

[0029] More preferably, the organic solvent is dimethyl sulfoxide; and the dissolution temperature is 80°C.

[0030] An underwater adhesive based on natural polysaccharides prepared according to the above method

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] (1) Inspired by the underwater adhesion mechanism of mussels, this invention introduces both catechol groups and hydrophobic groups into the natural polysaccharide molecular chain to form a natural polysaccharide copolymer, which is then dissolved in an organic solvent to form an underwater adhesive. Underwater, through solvent exchange, the hydrophobic groups are exposed to the outside, achieving the effect of eliminating the interfacial hydration layer. This facilitates strong non-covalent interactions between the catechol groups and the substrate at the interface, thereby enabling the adhesive to exhibit strong adhesion to various substrates underwater, including hydrophobic substrates, hydrophilic substrates, porous substrates, and biological tissues.

[0033] (2) The adhesive has underwater adhesion in various liquid environments (blood, urine, saline, body fluids and seawater, etc.).

[0034] (3) The underwater adhesive prepared by the present invention is prepared by a "one-pot method", which is simple, does not require complicated conditions, and is suitable for mass production.

[0035] (4) The adhesive prepared by the present invention is injectable underwater, can cover irregular substrate surfaces, and has long-term adhesion stability and degradability.

[0036] (5) The underwater adhesive prepared by the present invention has good biocompatibility and wide applicability. It has been proven in the construction of rat seawater immersion model and in vitro bladder injury model that it can prevent seawater immersion and promote seawater immersion injury and effectively fill the bladder injury site in artificial urine environment. Attached Figure Description

[0037] Figure 1 These are photographs of the underwater adhesive prepared by the method described in the embodiments of the present invention.

[0038] Figure 2 This demonstrates the injectability of the adhesive prepared in this embodiment. As can be seen from the figure, the prepared adhesive can be injected underwater onto a stainless steel substrate.

[0039] Figure 3 This is a comparative schematic diagram showing the underwater overlap-shear adhesion strength of the adhesive product of this invention on various substrates (glass, stainless steel, plastic, wood, and metal, etc.).

[0040] Figure 4 This is a schematic diagram illustrating the adhesion strength of the product of this invention, tested on glass and plastic surfaces respectively through an overlap-shear test, demonstrating its cyclic adhesion.

[0041] Figure 5A photograph of the adhesive product of this invention undergoing an underwater adhesion test with weights.

[0042] Figure 6 The images show actual photos of the product from this invention undergoing underwater injectability and water flow impact resistance tests.

[0043] Figure 7 This is a photograph of the actual product used in the adhesion test of the adhesive prepared in this embodiment to pigskin tissue.

[0044] Figure 8 This demonstrates the injectability of the adhesive prepared in this embodiment onto pigskin underwater. As shown in the figure, after the adhesive is injected underwater onto the surface of the pigskin for a period of time, it adheres well to the surface.

[0045] Figure 9 This is a photograph showing the adhesion of the adhesive prepared in this embodiment to pigskin tissue.

[0046] Figure 10 This embodiment demonstrates the healing effect of the underwater adhesive prepared in this example on seawater-resistant wounds in rats.

[0047] Figure 11 This is a macroscopic diagram of the underwater adhesion of the underwater adhesive prepared in this embodiment onto a sheep bladder.

[0048] Figure 12 This is a schematic diagram illustrating the biodegradability analysis of the underwater adhesive prepared in this embodiment.

[0049] The content of this invention is not limited to any specific embodiment, nor does it represent the best embodiment. Common alternatives known to those skilled in the art are also covered within the scope of protection of this invention. Detailed Implementation

[0050] The following is a detailed description with reference to the accompanying drawings and specific embodiments.

[0051] Reference Figure 1 This is the product prepared according to the method described in this embodiment and above, referred to... Figure 2 This demonstrates the injectability of the adhesive prepared in this embodiment. As shown in the figure, the prepared adhesive can be injected underwater onto a stainless steel substrate. (See reference...) Figure 3 This refers to the underwater lap-shear adhesion strength of the adhesive prepared in this embodiment on various substrate surfaces (glass, stainless steel, plastic, wood, and metal, etc.). (Refer to...) Figure 4 This refers to the underwater overlap-shear adhesion strength of the adhesive prepared in this embodiment in various solutions (blood, urine, saline, body fluids, and seawater, etc.). (Refer to...) Figure 5This is an adhesion strength diagram showing the adhesion of the adhesive to glass and plastic surfaces through an overlap-shear test, respectively. The adhesion strength remained essentially unchanged after three cycles, demonstrating that the hydrogel prepared by this invention possesses repeated adhesion and long-term adhesion stability.

[0052] Reference Figure 6 This is a physical image of the adhesive prepared in this embodiment adhering to a weight underwater. The substrate is a stainless steel sheet. As can be seen from the image, the adhesive prepared in this invention has strong adhesion to the substrate underwater and can support a weight with a mass of 500g.

[0053] Reference Figure 7 This image shows the underwater injectability and water flow impact resistance of the adhesive prepared in this embodiment on a glass substrate. When the sample was placed under running water for 10 seconds, the adhesive and glass remained firmly bonded together. This demonstrates that the underwater adhesive can not only be injected underwater but also adhere rapidly to the substrate surface.

[0054] Reference Figure 8 This demonstrates the injectability of the adhesive prepared in this embodiment onto pigskin underwater. As shown in the figure, after being injected underwater onto the pigskin surface for a period of time, the adhesive adheres well to the surface. (Refer to...) Figure 9 This is a photograph showing the adhesion of the adhesive prepared in this embodiment to pigskin tissue.

[0055] Figure 10 The underwater adhesive prepared in this embodiment has a healing effect on seawater immersion wounds in rats. As can be seen from the figure, the seawater immersion wound area of ​​rats in the underwater adhesive group is significantly smaller than that of rats in the control group. Figure 11 This is a macroscopic image of the underwater adhesion of the underwater adhesive prepared in this embodiment onto a sheep bladder. As can be seen from the image, the adhesive can be injected into the sheep bladder in an artificial urine environment and adhere stably. Figure 12 This is a biodegradability analysis of the underwater adhesive prepared in this embodiment. As can be seen from the figure, the adhesive degrades in the presence of cellulase solution, showing a significant difference compared to its degradation in PBS solution.

[0056] Example 1:

[0057] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0058] Step 1: Preparation of copolymers

[0059] Weigh 0.15 g of double-bonded agarose and dissolve it in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, add 0.1 g of methacrylamide, 0.1 mL of butyl acrylate, and 0.008 g of potassium persulfate sequentially to the solution. After purging with nitrogen, the reaction is carried out in an 80 °C water bath for 4 hours. After the reaction is complete, purify the copolymer in water and freeze-dry it to obtain the copolymer.

[0060] Step 2: Preparation of underwater adhesive

[0061] The obtained copolymer was dissolved in DMSO at a mass ratio of 7:50 under an 80°C water bath to obtain the underwater adhesive. The actual product is shown below. Figure 1 As shown.

[0062] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0063] Example 2:

[0064] Step 1: Preparation of copolymers

[0065] Weigh 0.25 g of double-bonded agarose and dissolve it in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, add 0.05 g of eugenol, 0.15 mL of butyl acrylate, and 0.01 g of ammonium persulfate sequentially to the solution. After purging with nitrogen, react the mixture at 70 °C for 5 hours. After the reaction is complete, purify the mixture in water and freeze-dry it to obtain the copolymer.

[0066] Step 2: Preparation of underwater adhesive

[0067] The obtained copolymer was dissolved in N,N-dimethylformamide at a mass ratio of 9:50 under water bath conditions at 80°C to obtain the underwater adhesive.

[0068] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0069] Example 3:

[0070] Step 1: Preparation of copolymers

[0071] Weigh 0.05 g of double-bonded sodium alginate and dissolve it in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, add 0.15 g of methacrylamide, 0.05 mL of hexyl acrylate, and 0.006 g of potassium persulfate sequentially to the solution. After purging with nitrogen, react the mixture at 80 °C for 3 hours. After the reaction is complete, purify the copolymer in water and freeze-dry it to obtain the copolymer.

[0072] Step 2: Preparation of underwater adhesive

[0073] The obtained copolymer was dissolved in DMSO at a mass ratio of 2:25 under water bath conditions at 80°C to obtain the underwater adhesive.

[0074] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0075] Example 4:

[0076] Step 1: Preparation of copolymers

[0077] Weigh 0.2 g of double-bonded dextran and dissolve it in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, add 0.1 g of caffeic acid, 0.1 mL of butyl acrylate, and 0.008 g of potassium persulfate sequentially to the solution. After purging with nitrogen, the reaction is carried out in an 80 °C water bath for 4 hours. After the reaction is complete, purify the copolymer in water and freeze-dry it to obtain the copolymer.

[0078] Step 2: Preparation of underwater adhesive

[0079] The obtained copolymer was dissolved in dioxane at a mass ratio of 7:50 in an 80°C water bath to obtain an underwater adhesive.

[0080] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0081] Example 5:

[0082] Step 1: Preparation of copolymers

[0083] 0.15 g of double-bonded fucoidan was weighed and dissolved in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, 0.05 mL of urushiol, 0.15 mL of ethyl acrylate, and 0.01 g of sodium persulfate were added sequentially to the solution. Nitrogen gas was introduced, and the reaction was continued at 80 °C for 5 hours. After the reaction was completed, the copolymer was purified in water and lyophilized to obtain the copolymer.

[0084] Step 2: Preparation of underwater adhesive

[0085] The obtained copolymer was dissolved in DMSO at a mass ratio of 7:50 under water bath conditions at 80°C to obtain the underwater adhesive.

[0086] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0087] Example 6:

[0088] Step 1: Preparation of copolymers

[0089] Weigh 0.05 g of double-bonded agarose and dissolve it in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, add 0.05 g of methacrylamide, 0.15 mL of butyl acrylate, and 0.008 g of potassium persulfate sequentially to the solution. After purging with nitrogen, react the mixture at 80 °C for 4 hours. After the reaction is complete, purify the copolymer in water and freeze-dry it to obtain the copolymer.

[0090] Step 2: Preparation of underwater adhesive

[0091] The obtained copolymer was dissolved in DMSO at a mass ratio of 9:50 under water bath conditions at 80°C to obtain the underwater adhesive.

[0092] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0093] Example 7:

[0094] Step 1: Preparation of copolymers

[0095] Weigh 0.15 g of double-bonded agarose and dissolve it in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, add 0.1 g of methacrylamide, 0.1 mL of butyl acrylate, and 0.0125 g of potassium persulfate sequentially to the solution. After purging with nitrogen, react the mixture at 80 °C for 4 hours. After the reaction is complete, purify the mixture in water and freeze-dry it to obtain the copolymer.

[0096] Step 2: Preparation of underwater adhesive

[0097] The obtained copolymer was dissolved in DMSO at a mass ratio of 2:25 under water bath conditions at 80°C to obtain the underwater adhesive.

[0098] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0099] Example 8:

[0100] Step 1: Preparation of copolymers

[0101] 0.25 g of double-bonded fucoidan was weighed and dissolved in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, 0.15 g of caffeic acid, 0.05 mL of octyl acrylate, and 0.006 g of potassium persulfate were added sequentially to the solution. Nitrogen gas was introduced, and the reaction was continued at 80 °C for 3 hours. After the reaction was completed, the copolymer was purified in water and lyophilized to obtain the copolymer.

[0102] Step 2: Preparation of underwater adhesive

[0103] The obtained copolymer was dissolved in N,N-dimethylformamide at a mass ratio of 9:50 under water bath conditions at 80°C to obtain the underwater adhesive.

[0104] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0105] Example 9:

[0106] Step 1: Preparation of copolymers

[0107] 0.2 g of double-bonded sodium alginate was weighed and dissolved in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, 0.1 g of methacrylamide, 0.05 mL of ethyl acrylate, and 0.01 g of sodium persulfate were added sequentially to the solution. Nitrogen gas was introduced, and the reaction was continued at 80 °C for 5 hours. After the reaction was completed, the copolymer was purified in water and lyophilized to obtain the copolymer.

[0108] Step 2: Preparation of underwater adhesive

[0109] The obtained copolymer was dissolved in a dioxane solution at a mass ratio of 2:25 under water bath conditions at 80°C to obtain an underwater adhesive.

[0110] This embodiment provides a method for preparing an underwater adhesive based on natural polysaccharides, the specific steps of which are as follows:

[0111] Example 10:

[0112] Step 1: Preparation of copolymers

[0113] Weigh 0.25 g of double-bonded dextran and dissolve it in 2.5 mL of dimethyl sulfoxide (DMSO) solution at 80 °C. After homogeneous dissolution, add 0.1 mL of urushiol, 0.15 mL of butyl acrylate, and 0.006 g of ammonium persulfate sequentially to the solution. After purging with nitrogen, react the mixture at 80 °C for 3 hours. After the reaction is complete, purify the copolymer in water and freeze-dry it to obtain the copolymer.

[0114] Step 2: Preparation of underwater adhesive

[0115] The obtained copolymer was dissolved in N,N-dimethylformamide at a mass ratio of 9:50 under water bath conditions at 80°C to obtain the underwater adhesive.

[0116] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from the spirit and scope of the claims. These modifications are all protected by the present invention.

Claims

1. A method for preparing an underwater adhesive based on natural polysaccharides, characterized in that, The steps are as follows: S1: The double-bonded modified natural polysaccharide is dissolved in an organic solvent under 80°C water bath conditions; S2: After the solution is dissolved evenly, add the monomer containing hydrophobic groups and the polyphenol monomer containing double bonds to the solution prepared in S1 and mix evenly. The mass ratio of the monomer containing hydrophobic groups to the double-bonded modified natural polysaccharide is 1:3 to 2:1; The monomer containing the hydrophobic group is selected from any one or more of the following: methyl acrylate, ethyl acrylate, butyl acrylate, and hexyl acrylate; The mass ratio of the polyphenol monomer containing double bonds to the double-bonded modified natural polysaccharide is 4:1 to 1:5; The polyphenol monomer containing a double bond is selected from any one or more of the following: methacrylamide dopamine, caffeic acid, and eugenol; S3: Add an initiator to the solution in S2 to initiate a free radical copolymerization reaction. After the reaction is complete, purify in water and freeze-dry to obtain the copolymer. The initiator has a mass percentage concentration of 0.2% to 4% in the organic solvent; S4: Dissolve the copolymer obtained in S3 in an organic solvent at a mass ratio of 1:50 to 1:10 to obtain an underwater adhesive.

2. The method for preparing an underwater adhesive based on natural polysaccharides according to claim 1, characterized in that, The double-bonded modified natural polysaccharide is selected from any one of the following: Agarose, sodium alginate, dextran, fucoidan; The preparation method of the double-bonded modified natural polysaccharide in step S1 is as follows: the natural polysaccharide is dissolved in dimethyl sulfoxide, modified by glycidyl methacrylate, dialyzed, and freeze-dried to obtain a methacrylamide polymer.

3. The method for preparing an underwater adhesive based on natural polysaccharides according to claim 1, characterized in that, When preparing the copolymer, the initiator is selected from any one of the following: ammonium persulfate, potassium persulfate, or sodium persulfate.

4. The method for preparing an underwater adhesive based on natural polysaccharides according to claim 1, characterized in that, The organic solvent is selected from any one or more of the following: dimethyl sulfoxide, N,N-dimethylformamide, and dioxane; In step S3, the reaction temperature is 70–80°C and the reaction time is 180–270 min.

5. The method for preparing an underwater adhesive based on natural polysaccharides according to claim 1, characterized in that, The water used in step S3 is deionized water.

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