A fully bio-based amphoteric polyelectrolyte antifouling coating, preparation method and use thereof

Abstract

The present invention provides a fully bio-based amphoteric polyelectrolyte antifouling coating, a preparation method and use thereof, comprising: (I) soaking a substrate in a mixed solution of concentrated sulfuric acid and hydrogen peroxide, taking out and washing after soaking for a period of time; (II) soaking the washed substrate in a Tris-hydrochloric acid buffer of dopamine, reacting under light-proof conditions, and taking out and washing after the reaction is completed; (III) soaking the substrate in a deacetylated nano-chitin solution, taking out and washing after soaking for a period of time; (IV) soaking the substrate in a nano-cellulose solution, taking out and rinsing after soaking for a period of time; (V) alternately repeating step (III) and step (IV) at least 2 times to form the fully bio-based amphoteric polyelectrolyte antifouling coating on the surface of the substrate. The present invention uses nano-cellulose and deacetylated chitin as raw materials to prepare a fully bio-based amphoteric polyelectrolyte antifouling coating, which has a simple preparation process, is environmentally friendly and has strong controllability.

Description

Technical Field

[0001] The invention belongs to the technical field of antifouling coatings, and relates to a fully bio-based amphoteric polyelectrolyte antifouling coating, a preparation method and use thereof. Background Art

[0002] The ocean contains abundant new energy, biological and mineral resources. In recent years, the focus of people's development activities has gradually shifted to the ocean. For the current marine industry, the formation of biofouling is an inevitable problem. Marine biofouling is caused by the continuous sedimentation, attachment and poor reproduction of microorganisms, plants and animals in the ocean on the solid surface of the underwater substrate. It has many adverse effects on marine shipping and the development and utilization of marine resources, and seriously affects the normal operation of ships and underwater facilities. Marine bacteria, algae, shellfish and other polluting organisms deposit and grow on the surface of the ship to form a layer of biofilm, resulting in a significant increase in the roughness of the hull surface. The increase in roughness will increase the friction resistance of the ship during navigation, which will not only increase fuel consumption and the emission of harmful gases, but also reduce the navigation speed of the ship and shorten the service life of the hull. Subsequent cleaning and maintenance requires a lot of manpower, material resources and time costs, resulting in huge economic losses.

[0003] As the global green safety standards for marine application materials gradually increase, the development of new environmentally friendly antifouling alternative materials has important practical significance. After a lot of research, new environmentally friendly antifouling materials have developed rapidly. At present, new antifouling materials mainly include self-polishing antifouling materials, bionic antifouling materials, biodegradable polymer antifouling materials and fouling desorption antifouling materials. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a fully bio-based amphoteric polyelectrolyte antifouling coating, a preparation method and use thereof. A fully bio-based amphoteric polyelectrolyte antifouling coating is prepared using nanocellulose and deacetylated chitin as raw materials through layer-by-layer deposition self-assembly technology. The preparation process is simple, environmentally friendly and highly controllable. The surface charge, thickness, mechanical strength, hydrophilicity and other properties of the antifouling coating can be regulated by changing the degree of oxidation of nanocellulose, the degree of deacetylation of deacetylated nanochitin and the number of alternating immersions.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, the preparation method comprising:

[0007] (I) The substrate is immersed in a mixture of concentrated sulfuric acid and hydrogen peroxide, and then taken out for cleaning after immersion for a period of time;

[0008] (II) Soaking the cleaned substrate in a dopamine-containing Tris-HCl buffer solution and reacting the substrate in a dark environment. After the reaction is complete, the substrate is taken out and washed.

[0009] (III) soaking the substrate in the deacetylated nano-chitin solution for a period of time and then taking it out for cleaning;

[0010] (IV) soaking the substrate in the nanocellulose solution for a period of time and then taking it out and rinsing it;

[0011] (V) alternately repeating step (III) and step (IV) at least twice to form the all-biobased amphoteric polyelectrolyte antifouling coating on the surface of the substrate.

[0012] The present invention alternately soaks the substrate in a deacetylated nano-chitin solution and a nano-cellulose solution for multiple times. The nano-cellulose, due to its preparation method, carries a large number of hydroxyl groups, sulfate groups and carboxyl groups on its surface, and is an anionic polymer; while the deacetylated nano-chitin carries amino groups on its surface, and is a cationic polymer. During the alternating soaking process, the electrostatic interaction between the anionic polymer and the cationic polymer is used to realize the layer-by-layer self-assembly of the nano-cellulose and the deacetylated nano-chitin, thereby depositing a layer of a fully bio-based amphoteric polyelectrolyte antifouling coating with controllable thickness and high hydration on the surface of the substrate.

[0013] The wettability and adhesion of the substrate surface have an important influence on the formation of biological fouling on the antifouling coating. The all-biobased amphoteric polyelectrolyte antifouling coating prepared by the present invention is electrically neutral, has strong hydration ability and hydrophilicity, and can tightly bind water molecules under the action of electrostatic interaction and hydrogen bonding to form a dense hydration layer on the surface of the all-biobased amphoteric polyelectrolyte antifouling coating. The formation of the hydration layer avoids the adsorption of charged and uncharged pollutants, increases the difficulty of attachment of biological fouling in the water environment, thereby further reducing the interaction between the barrier pollutants and the surface bonds of the antifouling coating, alleviating the occurrence of pollution, and improving the anti-pollution ability of the antifouling coating.

[0014] The deacetylated nano-chitosan obtained by partial deacetylation of chitosan is a biomaterial with antibacterial activity. It can be adsorbed on the surface of bacterial cells to form a polymer film, which prevents nutrients from being transported into the bacterial cells, thereby playing an antibacterial and sterilizing role. The larger the molecular weight of the deacetylated nano-chitosan, the denser the polymer film formed, the more nutrients can be prevented from entering the bacterial cells, and the more significant the antibacterial effect. At the same time, the deacetylated nano-chitosan can also penetrate into the bacterial cells. Since the deacetylated nano-chitosan carries a positive charge, it can interact with acidic substances such as lipopolysaccharide, teichoic acid, glycosylated teichoic acid, and capsular polysaccharides produced on the surface of bacteria, causing physiological dysfunction; at the same time, it can also adsorb the cytoplasm with anions in the bacterial cells to cause flocculation, disrupting the normal physiological activities of bacteria, thereby achieving antibacterial and antibacterial effects. The smaller the molecular weight of the deacetylated nano-chitosan, the easier it is to enter the interstitial structure of the bacterial cell wall and interfere with the metabolism of the cells.

[0015] The present invention generates a polydopamine layer with strong adhesion on the surface of the substrate by means of the oxidative self-polymerization of dopamine. The hydroxyl and amine groups on the polydopamine layer can be used as hydrophilic groups to improve the hydrophilicity of the antifouling coating. Compared with other modification methods, the method of modifying the surface of the substrate using dopamine is simpler and more convenient. The oxidative self-polymerization reaction of dopamine can be carried out in an aqueous solution under mild reaction conditions, without the use of catalysts and organic solvents, thus avoiding the pollution problem caused by the use of chemical reagents to the environment; no harsh reaction conditions such as heating and pressurization are required, and the reaction can be carried out at room temperature and pressure; no complicated pretreatment of the substrate surface is required, the operation is simple, and the reaction process is easy to control.

[0016] In the preparation process, the present invention first soaks the substrate in the Tris-hydrochloric acid buffer of dopamine, and dopamine can form a polydopamine layer on the substrate surface of any type of material by self-polymerization in the Tris-HCl buffer solution environment, and produces stronger adhesion to the substrate surface. Simultaneously, the polydopamine layer can also be used as a connecting bridge between the antifouling coating and the substrate, and the antifouling coating is firmly connected to the substrate surface, effectively preventing the antifouling coating from falling off from the substrate surface, improving the service life of the antifouling coating, and effectively reducing the specific adhesion of fouling organisms or making the adhered pollutants fall off. Subsequently, the present invention soaks the substrate formed with the polydopamine layer in a deacetylated nano-chitin solution, and reacts the carboxyl group in the deacetylated nano-chitin molecular chain with the amino group in the polydopamine molecular chain to realize the chemical bonding of the deacetylated nano-chitin and dopamine, and firmly adheres to the substrate surface by itself through the deposition of dopamine, effectively enhancing the mechanical strength of the antifouling coating, and ensuring the wear resistance and service life of the antifouling coating during service. Finally, the present invention uses negatively charged nanocellulose and positively charged deacetylated nanochitin to alternately soak the substrate for multiple times, and deposits the nanocellulose / deacetylated nanochitin composite antifouling coating on the surface of the polydopamine layer through layer-by-layer deposition self-assembly technology. Since the deacetylated nanochitin has certain antibacterial properties, combined with the hydration ability and hydrophilicity of the composite antifouling coating, it is difficult for algae and other plankton in the ocean to attach to the surface of the antifouling coating. A small amount of bacteria and microorganisms partially attached to the surface of the antifouling coating will also be removed under the antibacterial effect of the deacetylated nanochitin, thereby preventing bacteria and microorganisms from forming a biofilm on the surface of the antifouling coating due to massive reproduction.

[0017] During the alternating immersion process, there is both chemical adsorption and physical adsorption between nanocellulose and deacetylated nanochitin. On the one hand, the molecular chain of deacetylated nanochitin contains a large number of amino groups, which contain lone pairs of electrons and can form coordination bonds NH3 with hydrogen ions in the solution. + , while the carboxyl groups on the surface of nanocellulose can react with NH3 + The reaction forms new chemical bonds, thus achieving chemical adsorption. On the other hand, the surface of deacetylated nano-chitin carries a positive charge, while the surface of nanocellulose carries a negative charge. The two can achieve physical adsorption through electrostatic attraction, thus achieving in-situ layer-by-layer self-assembly. During the layer-by-layer self-assembly process, the nanocellulose molecular chains and the deacetylated nano-chitin molecular chains will also become entangled at the stacking interface, thus forming a complex topological structure, which makes the antifouling coating composed of nanocellulose / deacetylated nano-chitin have a strong interface bonding strength between the layers, and finally improves the overall mechanical strength of the all-bio-based amphoteric polyelectrolyte antifouling coating.

[0018] As a preferred technical solution of the present invention, in step (I), the mixed solution of concentrated sulfuric acid and hydrogen peroxide is obtained by compounding concentrated sulfuric acid and hydrogen peroxide solution.

[0019] In some preferred embodiments, the volume ratio of the concentrated sulfuric acid to the hydrogen peroxide solution is 1:(1-4), for example, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] In some preferred embodiments, the mass fraction of the hydrogen peroxide solution is 10-30wt%, for example, it can be 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt% or 30wt%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In some preferred embodiments, the soaking time is 20-80 min, for example, it can be 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min or 80 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] In some preferred embodiments, the immersion temperature is 25-85°C, for example, it can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or 85°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] As a preferred technical solution of the present invention, in step (II), the reaction temperature is 20-30°C, for example, it can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] In some preferred embodiments, the reaction time is 0.5-5h, for example, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] In some preferred embodiments, the concentration of dopamine in the Tris-HCl buffer of dopamine is 1-5 mg / mL, for example, 1.0 mg / mL, 1.5 mg / mL, 2.0 mg / mL, 2.5 mg / mL, 3.0 mg / mL, 3.5 mg / mL, 4.0 mg / mL, 4.5 mg / mL or 5.0 mg / mL, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] In some preferred embodiments, the reaction process is carried out in a shaker to shake the substrate.

[0027] The concentration of dopamine in the Tris-hydrochloric acid buffer of dopamine directly affects the growth rate of the polydopamine layer. The present invention specifically limits the concentration of dopamine in the Tris-hydrochloric acid buffer of dopamine to 1-5 mg / mL. When the concentration of dopamine is lower than 1 mg / mL, it is not conducive to the self-polymerization of dopamine, and a uniform and stable polydopamine layer cannot be formed. In addition, the growth rate of the polydopamine layer is too slow and the thickness is too thin, and a chemical interface bridge between the substrate and the composite coating cannot be effectively formed. When the concentration of dopamine is higher than 5 mg / mL, the self-polymerization rate of dopamine is too fast, and the formed polydopamine layer is too thick. Since the polymerization process of dopamine cannot be controlled, it is easy to cause uneven thickness distribution of the polydopamine layer, affecting the surface flatness of the antifouling coating.

[0028] It should be noted that the preparation process of the Tris-hydrochloric acid buffer provided by the present invention is disclosed in the prior art, and the present invention does not make specific requirements and special limitations thereto. Exemplarily, the present invention provides the following preparation process of the Tris-hydrochloric acid buffer for reference by those skilled in the art:

[0029] Dissolve 12.14 g of tris(hydroxymethyl)aminomethane in 2 L of ultrapure water, adjust the pH of the solution to 8.5 with 1 M hydrochloric acid, and mix thoroughly to obtain Tris-hydrochloric acid buffer (50 mM, pH = 8.5).

[0030] It should be noted that since the pH value of Tris-HCl buffer is extremely sensitive to temperature, care should be taken to maintain the solution temperature at 25°C during the pH adjustment process.

[0031] Of course, it can be understood that the preparation process of the Tris-hydrochloric acid buffer defined above does not constitute a further limitation on the technical solution of the present invention, and the Tris-hydrochloric acid buffer obtained by other preparation methods can also be used in the present invention.

[0032] As a preferred technical solution of the present invention, in step (III), the deacetylated nano-chitosan in the deacetylated nano-chitosan solution is prepared by the following method:

[0033] Chitosan is mixed with sodium hydroxide solution and heated, and chitosan is subjected to a deacetylation reaction to obtain a reaction product. The reaction product is cooled and repeatedly washed until it is neutral; and then the reaction product is nanosized to obtain the deacetylated nano-chitosan.

[0034] It should be noted that the deacetylated nano-chitosan defined in the present invention is prepared by sequentially deacetylation and high-pressure homogenization of chitosan, and the deacetylated nano-chitosan finally obtained can be deacetylated chitosan nanocrystals or deacetylated chitosan nanofibers.

[0035] The present invention does not impose any specific requirements or restrictions on the nano-sizing method of the reaction product. Currently, commonly used nano-sizing methods include hydrochloric acid hydrolysis, mechanical treatment, TEMPO oxidation, dissolution regeneration and electrostatic spinning.

[0036] The hydrochloric acid hydrolysis method is mainly used to prepare chitin nanocrystals. Chitosan is a semi-crystalline polymer with crystalline and amorphous regions. Since the crystalline and amorphous parts of chitosan have different kinetics during acid hydrolysis, the swelling and acid hydrolysis of the amorphous part are faster than those of the crystalline part. Therefore, the amorphous part is acid-hydrolyzed first, and the remaining highly crystalline area is subjected to 3 mol / L HCl, and the C2 amino cation of the aminoglucose unit is subjected to electrostatic repulsion, ultrasound or other shear forces to obtain chitosan nanocrystals.

[0037] Mechanical treatment is mainly used to prepare chitosan nanofibers. Under acidic or neutral conditions, wet or dry chitosan is treated with ultrasound, crushing, grinding, high-pressure homogenization, high-pressure water jet treatment, or a combination of these methods to make chitosan nanofibers. Under acidic conditions, a small amount of amine groups on C2 in the wet chitosan structural unit are protonated into cations, generating electrostatic repulsion to destroy the hydrogen bonds between chitosan molecules, and the chitosan is nanofibered through mechanical treatment.

[0038] The TEMPO oxidation method can prepare both chitin nanocrystals and chitin nanofibers. The TEMPO system refers to the oxidation of chitin using a 2,2,6,6-tetramethylpiperidin-1-oxyl free radical (TEMPO) / NaBr / NaClO system, wherein NaClO is the main oxidant in the system, which first reacts with NaBr to generate NaBrO, and the generated NaBrO oxidizes TEMPO to generate nitrosium ions. In an aqueous solution with a pH of 10, by controlling the amount of NaClO, the amorphous part of the chitin is oxidized by the nitrosium ions to form polysaccharide uronic acid soluble in water, while the C6 hydroxyl group on the surface of the crystalline part is oxidized to carboxylic acid or carboxylate, obtaining anionic chitin on the surface that is insoluble in water, and forming a stable nano-chitin suspension by relying on electrostatic repulsion or osmotic action under the action of mechanical force.

[0039] As a preferred technical solution of the present invention, the mass fraction of the sodium hydroxide solution is 25-35wt%, for example, it can be 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt% or 35wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In some preferred embodiments, the heating temperature is 80-95°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C or 95°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In some preferred embodiments, the heating time is 6-12 h, for example, it can be 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h or 12 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] From the perspective of the molecular structure of chitin, chitin is mainly a linear polysaccharide composed of 2-acetamido-2-deoxy-β-D-pyranose glucan (acetylglucosamine) units connected by β-(1-4) glycosidic bond units, which makes chitin stable and rigid. Chitin molecules are rich in hydroxyl and amino groups, which promote the formation of intermolecular and intramolecular hydrogen bonds, making chitin molecules into linear aggregates with a wide range of crystallinity.

[0043] The invention performs deacetylation treatment on chitosan in a sodium hydroxide solution, removes the acetylamino group at the C2 position in the chitosan molecular chain and converts it into an amino group, and converts the acetylamino group on the structural unit of the obtained deacetylated chitosan into an active amino group through the deacetylation treatment.

[0044] The deacetylation process of chitin is a typical heterogeneous reaction, which is mainly divided into two stages: the deacetylation reaction of the outermost layer of chitin and the reaction after the outermost layer is completely deacetylated. The initial stage of the deacetylation reaction is approximately a first-order reaction. The heterogeneous deacetylation reaction rate of chitin in sodium hydroxide solution is mainly affected by the hydrolysis resistance of the amide on the surface of chitin and the OH - Due to the influence of ion diffusion resistance, the acetylamino group is connected to the chitin molecular chain through a CN single bond. The present invention preferably uses microwave heating to carry out the deacetylation reaction. Ultrasonic treatment can also be applied during the deacetylation process to promote the OH in the solution. - The diffusion of ions accelerates the initial reaction rate.

[0045] The concentration of sodium hydroxide solution and the reaction temperature will affect the deacetylation degree of chitin, which is an important factor affecting the performance, solubility, flexibility, polymer conformation and viscosity of chitin, and ultimately affects the surface charge, hydrophilicity and antibacterial properties of the antifouling coating.

[0046] The present invention particularly limits the mass fraction of the sodium hydroxide solution used in the deacetylation treatment to 25-35wt%. The intrinsic viscosity of the deacetylated nano-chitin prepared within this range is the highest. When the mass fraction of the sodium hydroxide solution is lower than 25wt%, the deacetylation reaction of the chitin is not complete. On the contrary, when the mass fraction of the sodium hydroxide solution is higher than 35wt%, the molecular chain of the generated deacetylated nano-chitin is broken and degraded, the yield of the deacetylated nano-chitin is reduced, and the intrinsic viscosity of the solution is reduced. In addition, due to the limited solubility of sodium hydroxide, when the amount of sodium hydroxide added is too high, the chitin cannot be completely dissolved.

[0047] The present invention specifically limits the reaction time of the deacetylation treatment to 6-12 hours. As the reaction time increases, the deacetylation degree of chitin increases, the output of deacetylated nano-chitin increases, and the intrinsic viscosity of the solution increases. When the reaction is carried out for 12 hours, the content of the deacetylated nano-chitin reaches a maximum value, and the intrinsic viscosity of the solution also reaches a maximum value. If the reaction time is further extended, the molecular chain of the deacetylated nano-chitin is affected by OH. - The attack probability also gradually increases, resulting in the breakage and degradation of the generated deacetylated nano-chitin molecular chains, a decrease in the yield of deacetylated nano-chitin, and a decrease in the intrinsic viscosity of the solution.

[0048] The present invention particularly limits the heating temperature of the deacetylation process to 80-95°C. As the reaction temperature increases, the intrinsic viscosity of the deacetylated nano-chitin gradually increases. When the reaction temperature reaches 95°C, the intrinsic viscosity of the solution reaches a maximum value. When the temperature continues to rise, the intrinsic viscosity instead shows a downward trend. This is because the reaction temperature is too high, resulting in the breakage and degradation of the deacetylated nano-chitin molecular chain, the reduction of the output of the deacetylated nano-chitin, and the reduction of the intrinsic viscosity of the solution. However, when the reaction temperature is lower than 80°C, the deacetylation reaction of the nano-chitin is not sufficient, and the output of the deacetylated nano-chitin is reduced.

[0049] As a preferred technical solution of the present invention, in step (III), the mass fraction of the deacetylated nano-chitosan solution is 0.1-0.5wt%, for example, it can be 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt% or 0.5wt%, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] The present invention particularly limits the mass fraction of the deacetylated nano-chitosan solution to 0.1-0.5wt%. When the mass fraction of the deacetylated nano-chitosan solution is lower than 0.1wt%, the deacetylated nano-chitosan solution adheres firmly to the substrate surface through the reaction of the carboxyl group and the amino group and the dopamine self-polymerization, and forms a complex winding topological structure, which gives the antifouling coating higher mechanical properties. Therefore, when the mass fraction of the deacetylated nano-chitosan solution is too low, the content of the deacetylated nano-chitosan deposited on the substrate surface is reduced, resulting in a significant deterioration of the adhesion of the antifouling coating on the substrate, and the antifouling coating is difficult to form a film, and is very easy to separate from the substrate during seawater immersion; at the same time, the antibacterial ability of the antifouling coating is also derived from the deacetylated nano-chitosan, and when the deposition amount of the deacetylated nano-chitosan is too low, the antibacterial effect of the antifouling coating will also decrease.

[0051] When the mass fraction of the deacetylated nano-chitosan solution is higher than 0.5wt%, small solid particles formed by the agglomeration of deacetylated nano-chitosan begin to appear on the surface of the antibacterial non-woven fabric. This is because the deacetylated nano-chitosan is small in size and has a large specific surface area, with more active groups. At the same time, due to the strong hydrogen bonding and adsorption effect between the deacetylated nano-chitosan molecules, the deacetylated nano-chitosan is prone to agglomeration, resulting in a decrease in the interfacial bonding strength between the nanocellulose deposition layer and the deacetylated nano-chitosan deposition layer, affecting the interlayer chemical compatibility of the antifouling coating. At the same time, as the agglomeration of deacetylated nano-chitosan intensifies, the surface flatness of the antifouling coating decreases and the roughness increases, providing biological fouling attachment points for bacteria, algae and microorganisms.

[0052] In some preferred embodiments, the immersion time of the substrate in the deacetylated nano-chitin solution is 30-90 min, for example, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min or 90 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] As a preferred technical solution of the present invention, in step (IV), the nanocellulose in the nanocellulose solution includes any one of cellulose nanofibers, cellulose nanocrystals, phosphorylated cellulose nanofibers, phosphorylated cellulose nanocrystals, carboxylated cellulose nanofibers or carboxylated cellulose nanocrystals, or a combination of at least two of them.

[0054] Nanocellulose has chemically active hydroxyl groups on its surface, which are easy to modify and surface-modify. Through chemical modification, a series of modified nanocellulose, nanocellulose derivatives and copolymers thereof can be obtained, such as phosphorylated cellulose nanofibers, phosphorylated nanofiber crystals, carboxylated cellulose nanofibers, carboxylated nanofiber crystals, carboxymethyl cellulose nanofibers and carboxymethyl nanofiber crystals. Chemical modification can greatly improve the physical properties of nanocellulose, such as solubility, dispersibility, rheology and stability. In addition, by introducing polar functional groups such as carboxyl groups on the surface of nanocellulose through chemical modification, the negative charge content of nanocellulose can be increased, which is more conducive to the formation of a tightly connected binding interface between nanocellulose and deacetylated nanochitin through electrostatic interaction and hydrogen bonding.

[0055] In order to help those skilled in the art to better and fully implement the technical solution provided by the present invention, the present invention provides the following optional modification and preparation method of cellulose nanofibers:

[0056] For example, phosphorylated cellulose nanofibers can be prepared by the following method:

[0057] (1) weighing cellulose raw material, phosphate and urea in a molar ratio of 1:(0.5-2):(3-7), dissolving phosphate and urea in deionized water by ultrasonication, and adjusting the pH of the solution to an acidic range of 3-4.5, wherein the deionized water is weighed in a mass ratio of cellulose raw material to deionized water of 1:(2.5-8);

[0058] (2) Fully soaking the cellulose raw material in the phosphorylation reagent solution, using an air compressor pump to apply a pressure of 0.1-0.4 MPa to fully soak the cellulose raw material and effectively compact the cellulose raw material; and performing a heat soaking pretreatment at 60-95°C for 10-180 min; drying the cellulose raw material after the heat soaking pretreatment at 70-110°C to constant weight, and further heating to 140-165°C for curing for 10-90 min to complete the phosphorylation modification chemical reaction;

[0059] (3) After washing and purifying the phosphorylated cellulose slurry with water, the slurry is homogenized 5-15 times at a pressure of 70-100 MPa using a mechanical processing device such as a high-pressure homogenizer to obtain phosphorylated cellulose nanofibers with high charge density.

[0060] Exemplarily, carboxylated cellulose nanofibers can be prepared by the following method:

[0061] (1) mixing pulp, 2,2,6,6-tetramethylpiperidinium-N-oxyl radical, sodium bromide and sodium hypochlorite to obtain a reaction solution, wherein the concentration of pulp in the reaction solution is 10-30 g / L, the concentration of 2,2,6,6-tetramethylpiperidinium-N-oxyl radical is 0.2-0.4 g / L, the concentration of sodium bromide is 1-3 g / L, and the concentration of sodium hypochlorite is 100-130 g / L;

[0062] (2) adjusting the pH value of the reaction solution to 9-11, carrying out an oxidation reaction at 28-35° C. for 1-2 hours, and washing the reaction product after the reaction to obtain carboxylated cellulose;

[0063] (3) The carboxylated cellulose is homogenized at a high pressure of 200-1000 bar for 2-10 times to achieve fiber nanofiberization and obtain carboxylated nanocellulose.

[0064] Exemplarily, carboxymethyl cellulose nanofibers can be prepared by the following method:

[0065] (1) soaking the cellulose raw material in a reaction solvent, adding 40-60 wt% of alkali solution to the raw material, and performing a first alkalization reaction at 15-78° C. for 1-4 hours; then adjusting the temperature to 20-37° C. and adding 10-60 wt% of chloroacetic acid solution, and performing a first etherification reaction at 60-82° C. for 1-4 hours to obtain a reaction solution;

[0066] (2) After an interval of 0.5-1 hour, 40-60 wt% of alkali solution is added to the reaction solution, and a second alkalization reaction is carried out at 15-78° C. for 1-4 hours. Subsequently, the temperature is adjusted to 20-37° C. and 10-60 wt% of chloroacetic acid solution is added, and a second etherification reaction is carried out at 60-82° C. for 1-4 hours to obtain carboxymethyl cellulose;

[0067] (3) dispersing carboxymethyl cellulose in deionized water to form a 0.5-4% carboxymethyl cellulose suspension, and homogenizing the carboxymethyl cellulose suspension under high pressure at 200-1000 bar for 2-10 times to achieve fiber nanofiberization and obtain carboxymethyl cellulose nanofibers.

[0068] Of course, it can be understood that the preparation methods of the various types of cellulose nanofibers defined above are all optional schemes and do not constitute further limitation of the technical scheme of the present invention. The cellulose nanofibers prepared by other disclosed prior arts or undisclosed new technologies used in the present invention also fall within the protection scope and disclosure scope of the present invention.

[0069] As a preferred technical solution of the present invention, in step (IV), the mass fraction of the nanocellulose solution is 0.1-0.5wt%, for example, it can be 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt% or 0.5wt%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0070] The present invention particularly limits the mass fraction of nanocellulose solution to 0.1-0.5wt%. When the mass fraction of nanocellulose solution is lower than 0.1wt%, since the antifouling coating is realized by the stronger water-binding ability of nanocellulose to resist the biofouling attachment effect, therefore, when the deposition amount of nanocellulose is too low, it will cause the coating surface to be unable to form a dense hydration layer to realize the fouling resistance, which ultimately leads to the weakening of the antifouling effect of the antifouling coating, and the effect of resisting the attachment of non-specific proteins and diatoms is significantly reduced; when the mass fraction of nanocellulose solution is higher than 0.5wt%, accordingly, the proportion of deacetylated nano-chitin in the antifouling coating is reduced, resulting in a reduction in the connection points between the antifouling coating and the polydopamine layer, which ultimately affects the mechanical properties of the antifouling coating, so that the interfacial bonding strength between the antifouling coating and the substrate is reduced, and the service life of the antifouling coating is shortened. In addition, nanocellulose also has agglomeration problems, resulting in a reduction in the interfacial bonding strength between the nanocellulose deposition layer and the deacetylated nano-chitin deposition layer, affecting the interlayer chemical compatibility of the antifouling coating. At the same time, as the agglomeration of nanocellulose intensifies, the surface flatness of the antifouling coating decreases and the roughness increases, providing biofouling attachment points for bacteria, algae and microorganisms.

[0071] In some preferred embodiments, the immersion time of the substrate in the nanocellulose solution is 30-90 min, for example, it can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min or 90 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0072] In the present invention, after multiple alternating soakings, the soaked substrate needs to be heated and dried. The surface of the antifouling coating formed after drying is flat and dense. This is because the nanocellulose and deacetylated nanochitin have different charges, so that in the process of forming the antifouling coating, there is not only entanglement force between fibers, but also electrostatic effect, which makes the antifouling coating formed flat and dense.

[0073] Exemplarily, the present invention provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, the preparation method comprising the following steps:

[0074] (1) The substrate is immersed in a mixture of concentrated sulfuric acid and hydrogen peroxide at 25-85°C, wherein the volume ratio of concentrated sulfuric acid to hydrogen peroxide solution is 1:(1-4), and the mass fraction of hydrogen peroxide solution is 10-30wt%. The substrate is immersed for 20-80 minutes and then taken out for cleaning;

[0075] (2) Soaking the cleaned substrate in a dopamine Tris-HCl buffer solution, wherein the concentration of dopamine in the dopamine Tris-HCl buffer solution is 1-5 mg / mL, and reacting for 0.5-5 h at 20-30° C. in a dark environment. The reaction process is carried out in a shaker and the substrate is shaken. After the reaction is completed, the substrate is taken out and washed;

[0076] (3) mixing chitosan with 25-35wt% sodium hydroxide solution and heating to 80-95°C, keeping the temperature for 6-12 hours, and deacetylating the chitosan to obtain a reaction product; cooling the reaction product and repeatedly washing it until it is neutral, and then high-pressure homogenizing it at 200-1000 bar for 2-10 times to obtain deacetylated nano-chitosan;

[0077] (4) Soaking the substrate in a 0.1-0.5 wt% deacetylated nano-chitin aqueous solution for 30-90 min and then taking it out for cleaning;

[0078] (5) Soaking the substrate in a 0.1-0.5 wt% nanocellulose solution for 30-90 min and then taking it out and rinsing it;

[0079] (6) Repeating step (4) and step (5) alternately at least twice to form the all-biobased amphoteric polyelectrolyte antifouling coating on the surface of the substrate.

[0080] In a second aspect, the present invention provides an all-biobased amphoteric polyelectrolyte antifouling coating, wherein the all-biobased amphoteric polyelectrolyte antifouling coating is prepared by the preparation method described in the first aspect.

[0081] In a third aspect, the present invention provides a use of the all-biobased amphoteric polyelectrolyte antifouling coating described in the second aspect, wherein the all-biobased amphoteric polyelectrolyte antifouling coating is used in food, cosmetics, biomedicine, marine vessels and wearable electronic devices.

[0082] Compared with the prior art, the present invention has the following beneficial effects:

[0083] The present invention adopts layer-by-layer deposition self-assembly technology, uses nanocellulose and deacetylated chitin as raw materials, and prepares a fully bio-based amphoteric polyelectrolyte antifouling coating. The preparation process is simple, environmentally friendly and highly controllable. The surface charge, thickness, mechanical strength, hydrophilicity and other properties of the antifouling coating can be regulated by changing the oxidation degree of nanocellulose, the deacetylation degree of deacetylated nanochitin and the number of alternating immersion times.

[0084] The nano cellulose and deacetylated chitosan used in the present invention are both rigid materials, and the antifouling coating prepared with the two as raw materials has good mechanical properties and can be applied to more complex and harsh environmental systems. The prepared antifouling coating has the characteristics of electrical neutrality, high hydration, biocompatibility, non-toxicity, and antibacterial antifouling, and can reach an antifouling efficiency of more than 95% for bacteria and diatoms. At the same time, since rice cellulose and deacetylated chitosan are both biomass materials, they are effective utilization of sustainable resources, fully meet the current requirements of green chemistry and sustainable development theory, and are expected to be applied to technical fields such as food preservation, cosmetics, biomedicine, marine ships, and wearable electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 A process flow chart of the preparation of the antifouling coating provided in Examples 1-11 of the present invention;

[0086] Figure 2 This is a water contact angle diagram of the antifouling coating prepared in Example 1 of the present invention;

[0087] Figure 3 This is a water contact angle diagram of the antifouling coating prepared in the comparative example of the present invention;

[0088] Figure 4 This is a picture of surface protein adsorption of the antifouling coating prepared in Example 1 of the present invention;

[0089] Figure 5 This is a picture of surface protein adsorption of the antifouling coating prepared in the comparative example of the present invention;

[0090] Figure 6 These are photos of the steel plate surface after the antifouling coating prepared in Example 1 was placed in the actual marine environment for the 10th, 15th, 30th and 60th days;

[0091] Figure 7 The following are photos of the steel plate surface after the antifouling coating prepared in the comparative example was placed in the actual marine environment for the 10th, 15th, 30th and 60th days. DETAILED DESCRIPTION

[0092] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limitations on the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments recorded herein.

[0093] Example 1

[0094] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, such as Figure 1 As shown, the preparation method comprises the following steps:

[0095] (1) The steel plate was immersed in a mixture of concentrated sulfuric acid and hydrogen peroxide at 25°C, wherein the volume ratio of concentrated sulfuric acid to hydrogen peroxide solution was 1:1, and the mass fraction of hydrogen peroxide solution was 10wt%. The steel plate was immersed for 80 min and then taken out for cleaning;

[0096] (2) Soak the cleaned steel plate in a dopamine Tris-HCl buffer solution, where the concentration of dopamine in the dopamine Tris-HCl buffer solution is 1 mg / mL, and react for 5 h at 20°C in the dark. Shake the steel plate on a shaker during the reaction. After the reaction is complete, remove the steel plate and wash it.

[0097] (3) mixing chitosan with a 25 wt % sodium hydroxide solution and heating it to 80° C. for 12 h to deacetylate the chitosan to obtain a reaction product; cooling the reaction product and repeatedly washing it until it is neutral, and then high-pressure homogenizing it at 600 bar for 8 times to obtain deacetylated nano-chitosan;

[0098] (4) Soak the steel plate in a 0.1 wt% deacetylated nano-chitosan aqueous solution for 90 min and then take it out for cleaning;

[0099] (5) Soaking the steel plate in a 0.1 wt% aqueous solution of phosphorylated cellulose nanofibers for 90 min and then taking it out and rinsing it;

[0100] (6) Repeating step (4) and step (5) alternately for two times to form the all-biobased amphoteric polyelectrolyte antifouling coating on the surface of the steel plate.

[0101] Example 2

[0102] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, such as Figure 1 As shown, the preparation method comprises the following steps:

[0103] (1) The steel plate was immersed in a mixture of concentrated sulfuric acid and hydrogen peroxide at 40°C, where the volume ratio of concentrated sulfuric acid to hydrogen peroxide solution was 1:2 and the mass fraction of hydrogen peroxide solution was 15wt%. The steel plate was immersed for 60 min and then taken out for cleaning;

[0104] (2) Soak the cleaned steel plate in a dopamine Tris-HCl buffer solution, where the concentration of dopamine in the dopamine Tris-HCl buffer solution is 2 mg / mL, and react for 3 h at 22°C in the dark. Shake the steel plate on a shaker during the reaction. After the reaction is completed, take it out and wash it.

[0105] (3) mixing chitosan with a 28 wt % sodium hydroxide solution and heating it to 85° C. for 10 h to deacetylate the chitosan to obtain a reaction product; cooling the reaction product and repeatedly washing it until it is neutral, and then high-pressure homogenizing it at 600 bar for 8 times to obtain deacetylated nano-chitosan;

[0106] (4) Soak the steel plate in a 0.2 wt% deacetylated nano-chitosan aqueous solution for 80 min and then take it out for cleaning;

[0107] (5) Soaking the steel plate in a 0.2 wt% cellulose nanofiber aqueous solution for 80 min and then taking it out and rinsing it;

[0108] (6) Repeating step (4) and step (5) alternately for 4 times to form the all-biobased amphoteric polyelectrolyte antifouling coating on the surface of the steel plate.

[0109] Example 3

[0110] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, such as Figure 1 As shown, the preparation method comprises the following steps:

[0111] (1) The steel plate was immersed in a mixture of concentrated sulfuric acid and hydrogen peroxide at 50°C, wherein the volume ratio of concentrated sulfuric acid to hydrogen peroxide solution was 1:3, and the mass fraction of hydrogen peroxide solution was 20wt%. The steel plate was immersed for 50 min and then taken out for cleaning;

[0112] (2) Soak the cleaned steel plate in a dopamine Tris-HCl buffer solution, where the concentration of dopamine in the dopamine Tris-HCl buffer solution is 3 mg / mL, and react for 2 h at 25°C in the dark. Shake the steel plate on a shaker during the reaction. After the reaction is completed, take it out and wash it.

[0113] (3) mixing chitosan with a 30 wt % sodium hydroxide solution and heating to 90° C. for 10 h to deacetylate the chitosan to obtain a reaction product; cooling the reaction product and repeatedly washing it until it is neutral, and then high-pressure homogenizing it at 600 bar for 8 times to obtain deacetylated nano-chitosan;

[0114] (4) Soak the steel plate in a 0.3 wt% deacetylated nano-chitosan aqueous solution for 60 min and then take it out for cleaning;

[0115] (5) Soaking the steel plate in a 0.3 wt% carboxylated cellulose nanofiber aqueous solution for 60 min and then taking it out and rinsing it;

[0116] (6) Step (4) and step (5) are repeated alternately for 6 times to form the all-biobased amphoteric polyelectrolyte antifouling coating on the surface of the steel plate.

[0117] Example 4

[0118] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, such as Figure 1 As shown, the preparation method comprises the following steps:

[0119] (1) The steel plate was immersed in a mixture of concentrated sulfuric acid and hydrogen peroxide at 60°C, where the volume ratio of concentrated sulfuric acid to hydrogen peroxide solution was 1:3 and the mass fraction of hydrogen peroxide solution was 25wt%. The steel plate was immersed for 40 min and then taken out for cleaning;

[0120] (2) Soak the cleaned steel plate in a dopamine Tris-HCl buffer solution, where the concentration of dopamine in the dopamine Tris-HCl buffer solution is 4 mg / mL, and react for 1 h at 28°C in the dark. Shake the steel plate on a shaker during the reaction. After the reaction is completed, take it out and wash it.

[0121] (3) mixing chitosan with a 32 wt % sodium hydroxide solution and heating it to 90° C. for 8 h to deacetylate the chitosan to obtain a reaction product; cooling the reaction product and repeatedly washing it until it is neutral, and then high-pressure homogenizing it at 600 bar for 8 times to obtain deacetylated nano-chitosan;

[0122] (4) Soak the steel plate in a 0.4 wt% deacetylated nano-chitosan aqueous solution for 40 min and then take it out for cleaning;

[0123] (5) Soak the steel plate in a 0.4 wt% aqueous solution of cellulose nanocrystals for 40 min and then rinse it;

[0124] (6) Step (4) and step (5) are repeated alternately for 8 times to form the all-biobased amphoteric polyelectrolyte antifouling coating on the surface of the steel plate.

[0125] Example 5

[0126] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, such as Figure 1 As shown, the preparation method comprises the following steps:

[0127] (1) The steel plate was immersed in a mixture of concentrated sulfuric acid and hydrogen peroxide at 85°C, where the volume ratio of concentrated sulfuric acid to hydrogen peroxide solution was 1:4 and the mass fraction of hydrogen peroxide solution was 30wt%. The steel plate was immersed for 20 min and then taken out for cleaning;

[0128] (2) Soak the cleaned steel plate in a dopamine Tris-HCl buffer solution, where the concentration of dopamine in the dopamine Tris-HCl buffer solution is 5 mg / mL, and react for 0.5 h at 30°C in the dark. Shake the steel plate on a shaker during the reaction. After the reaction is completed, take it out and wash it;

[0129] (3) mixing chitosan with a 35 wt % sodium hydroxide solution and heating it to 95° C. for 6 h to deacetylate the chitosan to obtain a reaction product; cooling the reaction product and repeatedly washing it until it is neutral, and then high-pressure homogenizing it at 600 bar for 8 times to obtain deacetylated nano-chitosan;

[0130] (4) Soak the steel plate in a 0.5 wt% deacetylated nano-chitosan aqueous solution for 30 min and then take it out for cleaning;

[0131] (5) Soak the steel plate in a 0.5 wt% aqueous solution of phosphorylated cellulose nanocrystals for 30 min and then rinse it;

[0132] (6) Step (4) and step (5) are repeated alternately 10 times to form the all-biobased amphoteric polyelectrolyte antifouling coating on the surface of the steel plate.

[0133] Example 6

[0134] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, which differs from Embodiment 1 in that, in step (2), the mass fraction of dopamine in the Tris-hydrochloric acid buffer of dopamine is adjusted to 0.5 mg / mL, and other operating parameters and process steps are the same as those in Embodiment 1.

[0135] Example 7

[0136] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, which differs from Embodiment 1 in that, in step (2), the dopamine mass fraction of the dopamine Tris-hydrochloric acid buffer is adjusted to 8 mg / mL, and the other operating parameters and process steps are the same as those in Embodiment 1.

[0137] Example 8

[0138] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating. The difference from Embodiment 1 is that in step (4), the mass fraction of the deacetylated nano-chitin aqueous solution is adjusted to 0.05 wt %, and the other operating parameters and process steps are the same as those in Embodiment 1.

[0139] Example 9

[0140] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating. The difference from Embodiment 1 is that in step (4), the mass fraction of the deacetylated nano-chitin aqueous solution is adjusted to 0.8 wt %, and the other operating parameters and process steps are the same as those in Embodiment 1.

[0141] Example 10

[0142] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating. The difference from Embodiment 1 is that in step (5), the mass fraction of the phosphorylated cellulose nanofiber aqueous solution is adjusted to 0.05 wt %, and the other operating parameters and process steps are the same as those in Embodiment 1.

[0143] Embodiment 11

[0144] This embodiment provides a method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating. The difference from Embodiment 1 is that in step (5), the mass fraction of the phosphorylated cellulose nanofiber aqueous solution is adjusted to 0.8 wt %, and the other operating parameters and process steps are the same as those in Embodiment 1.

[0145] Comparative Example

[0146] This comparative example is a steel plate without any coating.

[0147] The antifouling principle of the hydrophilic antifouling coating is to form a dense hydration layer on the surface by combining nanocellulose with water molecules, thereby achieving the purpose of hindering the attachment of fouling organisms. The static water contact angle is an important indicator to characterize the wettability of the sample surface. The water contact angles of the antifouling coatings prepared in Example 1 and the comparative example are shown in FIG. Figure 2 and Figure 3As shown, by comparison, it can be seen that the water contact angle of the all-biobased amphoteric polyelectrolyte antifouling coating prepared in Example 1 is significantly smaller than that of the comparative example, which indicates that the all-biobased amphoteric polyelectrolyte antifouling coating prepared in Example 1 has better wetting properties and is more conducive to forming a dense hydration layer on the surface of the all-biobased amphoteric polyelectrolyte antifouling coating.

[0148] The coatings prepared in Example 1 and the comparative example were subjected to a protein anti-adhesion performance test and a real sea hanging board test to comprehensively evaluate the anti-fouling effect of the all-biobased amphoteric polyelectrolyte antifouling coating prepared in the present invention.

[0149] (1) Protein anti-adhesion performance test:

[0150] In the process of marine fouling organisms attaching, the first thing to approach the hull surface is protein, and the aggregation of protein provides the basis for the formation of biofilm. Therefore, in order to fundamentally prevent the attachment of fouling organisms, the first thing to examine is the protein anti-attachment ability of the coating. The present invention uses bovine serum albumin labeled with fluorescein isothiocyanate to apply to the coating surface, and detects the adsorption behavior of bovine serum albumin on the coating surface by laser confocal microscopy, so as to evaluate the coating's anti-attachment ability to protein.

[0151] The specific testing process is as follows:

[0152] In a dim light environment, use a pipette to transfer 50 μL of bovine serum albumin solution labeled with fluorescein isothiocyanate, drop it on the coating surface, cover it with a coverslip to spread the bovine serum albumin solution evenly, remove the coverslip after 24 hours, and wash the coating surface with PBS buffer.

[0153] The coating surface was photographed and observed using a confocal microscope. The parameters of the confocal microscope were set as follows: the emission light wavelength range was 500-550 nm, the excitation light wavelength was 488 nm, and the following images were obtained: Figure 4 and Figure 5 The protein adsorption images shown in Figure 4 and Figure 5 The protein adsorption on the surface of the all-biobased amphoteric polyelectrolyte antifouling coating of Example 1 and the surface of the steel plate of the comparative example respectively shows that the amount of protein adsorbed on the surface of the all-biobased amphoteric polyelectrolyte antifouling coating prepared in Example 1 is significantly less than that of the comparative example.

[0154] (2) Actual sea hanging board test:

[0155] In order to better evaluate the anti-fouling and anti-corrosion capabilities of the all-biobased amphoteric polyelectrolyte anti-fouling coating prepared by the present invention in actual application scenarios, the present invention conducted a real sea hanging test on the steel plate coated with the anti-fouling coating provided in Example 1 and the steel plate provided in the comparative example, and tested the attachment of fouling organisms in the sea area to the coating surface in a real marine environment.

[0156] The hanging plate experiment was carried out on a floating raft in the Bohai Sea area of ​​Tianjin. The steel plates were sampled and photographed on the 10th, 15th, 30th and 60th days to observe the fouling organisms attached to the steel plate surface. The actual photos of the steel plates in Example 1 and the comparative example are shown in Figure 1. Figure 6 and Figure 7 shown.

[0157] Depend on Figure 6 It can be seen that at the beginning of the hanging board test, the surface of the steel plate coated with the antifouling coating did not show obvious changes. As the hanging board test time prolonged, a small amount of bacteria and organic molecules attached to the surface of the steel plate. When the test lasted for 60 days, a small amount of biofilm appeared in some areas of the steel plate surface. Figure 7 It can be seen that in the early stage of the hanging board test, the bacteria and organic molecules in the seawater gathered on the surface of the coated steel plate and released extracellular secretions, thereby forming a thicker biofilm on the surface of the steel plate. As the hanging board test time prolonged, the biofilm attached to the surface of the steel plate increased and thickened, and a large number of bacteria, microorganisms and algae were attached to the surface of the biofilm.

[0158] The contact angle test was performed on the antifouling coatings prepared in Examples 1-11 and the steel plates provided in the comparative examples. The antifouling coatings were abraded 50 times with 600-grit sandpaper and the contact angles were measured again. The original contact angles and the contact angles after abrasion were obtained as shown in Table 1.

[0159] The zeta potential of the antifouling coatings prepared in Examples 1-11 was measured, and the test results are shown in Table 1.

[0160] The anti-algae rate and anti-bacterial rate of the anti-fouling coating prepared in Examples 1-11 were tested, and the testing process specifically included the following steps:

[0161] (1) Test relative bioadhesion density:

[0162] Diatom adhesion density: Nitzschia closterium (a typical benthic marine fouling organism) was cultured in F / 2 medium in a light incubator at 20°C with a light: dark cycle of 12:12 hours. The steel plates coated with the antifouling coating were immersed in the diatom suspension (~108 cells / mL). After one week of cultivation, the antifouling coating was rinsed with seawater to remove the unstable attached diatoms. Then, the diatoms deposited on the antifouling coating were observed by optical microscopy (CX-23, Olympus), and ten areas were randomly recorded to obtain the average diatom density on the antifouling coating.

[0163] Bacterial adhesion density: The coatings were immersed in an E. coli suspension (~106 CFU) and incubated at 37 °C for 12 h. After incubation, the coatings were rinsed with phosphate buffer to remove unstable attached bacteria. Subsequently, the bacteria attached to the surface of the antifouling coatings were observed under a microscope (CX-23, Olympus), and ten areas were randomly recorded to obtain the average bacterial density on the coatings.

[0164] (2) The anti-algae rate is calculated using the following formula:

[0165]

[0166] Wherein, N1 is the diatom adhesion density of the comparative example, and N2 is the diatom adhesion density of each embodiment.

[0167] The antibacterial rate was calculated using the following formula:

[0168]

[0169] M1 is the bacterial adhesion density of the comparative example, and M2 is the bacterial adhesion density of each embodiment.

[0170] The anti-algae rate and anti-bacterial rate of the antifouling coating are shown in Table 1.

[0171] Table 1

[0172] Original water contact angle / ° Water contact angle after wear / ° Zeta potential / mV Anti-algae rate / % Antibacterial rate / % Example 1 22.5 23.8 -34.5 82.5 87.3 Example 2 17.4 18.5 -26.3 83.4 90.4 Example 3 13.6 14.1 -22.8 89.9 92.5 Example 4 12.9 13.2 -19.0 93.5 99.9 Example 5 11.3 12.7 -18.8 92.1 98.0 Example 6 23.4 35.6 -35.6 72.4 82.5 Example 7 29.5 30.4 -33.4 76.8 85.7 Example 8 25.8 26.7 -45.3 62.3 58.6 Example 9 28.2 30.3 -38.9 70.6 76.5 Example 10 23.5 24.8 -52.1 65.8 73.2 Embodiment 11 30.7 33.5 -43.4 72.0 80.1 Comparative Example 62.0 / / / /

[0173] It can be seen from the data in Table 1 that the antifouling coatings prepared in Examples 1-5 have excellent hydrophilicity and antibacterial properties, and the anti-algae rate and antibacterial rate are both above 80%.

[0174] It can be seen from the test data provided by Example 1, Example 6 and Example 7 that the contact angle of the antifouling coating prepared in Example 6 attenuates much more after wear than Example 1, which indicates that the interface performance between the antifouling coating and the steel plate in Example 6 is poor, which further leads to a decrease in the anti-algae rate and antibacterial rate of the antifouling coating. This is because the concentration of dopamine in Example 6 is too low, which is not conducive to the self-polymerization of dopamine, and cannot effectively form a chemical interface bridge between the substrate and the composite coating, which ultimately leads to a decrease in the interfacial bonding strength between the antifouling coating and the substrate, and the antifouling coating is easy to peel off the substrate. The water contact angle of the antifouling coating prepared in Example 7 is higher than that in Example 1. At the same time, the anti-algae rate and antibacterial rate of the antifouling coating are lower than those in Example 1. This is because the concentration of dopamine in Example 7 is too high, resulting in an uneven thickness distribution of the polydopamine layer, affecting the surface flatness of the antifouling coating, and then affecting the formation of a hydration layer on the surface of the antifouling coating, which ultimately leads to the antibacterial effect of the antifouling coating.

[0175] It can be seen from the test data provided by Examples 1, 8 and 9 that the anti-algae rate and antibacterial rate of the antifouling coating prepared in Example 8 are lower than those in Example 1, especially the antibacterial rate is much lower than that in Example 1. This is because the mass fraction of the deacetylated nano-chitin aqueous solution in Example 8 is too low. On the one hand, the charge of the deacetylated nano-chitin and the phosphorylated cellulose nanofibers do not match, and an electrically neutral antifouling coating cannot be formed; on the other hand, the antibacterial effect of the antifouling coating mainly comes from the deacetylated nano-chitin. Due to the low amount of deacetylated nano-chitin added, the antibacterial performance of the antifouling coating is significantly reduced. The water contact angle of the antifouling coating prepared in Example 9 is higher than that in Example 1. At the same time, the anti-algae rate and antibacterial rate of the antifouling coating are lower than those in Example 1. This is because the mass fraction of the deacetylated nano-chitosan aqueous solution in Example 9 is too high. On the one hand, the charge of the deacetylated nano-chitosan and the phosphorylated cellulose nanofibers does not match, and an electrically neutral antifouling coating cannot be formed; on the other hand, the deacetylated nano-chitosan agglomerates, resulting in a decrease in the surface flatness of the antifouling coating, an increase in roughness, a decrease in hydrophilicity, and an increase in hydrophobicity, providing biological fouling attachment points for bacteria, algae, and microorganisms.

[0176] It can be seen from the test data provided by Examples 1, 10 and 11 that the anti-algae rate and antibacterial rate of the anti-fouling coating prepared in Example 10 are lower than those in Example 1. This is because the mass fraction of the phosphorylated cellulose nanofiber aqueous solution in Example 10 is too low. On the one hand, the charge of the phosphorylated cellulose nanofibers and the deacetylated nano-chitin do not match, and an electrically neutral anti-fouling coating cannot be formed; on the other hand, the water binding capacity of the anti-fouling coating is reduced, making it impossible to form a dense hydration layer on the surface of the anti-fouling coating to achieve fouling resistance, ultimately resulting in a decrease in the anti-algae rate and antibacterial rate. The water contact angle of the antifouling coating prepared in Example 11 is higher than that in Example 1. At the same time, the anti-algae rate and antibacterial rate of the antifouling coating are lower than those in Example 1. This is because the mass fraction of the phosphorylated cellulose nanofiber aqueous solution in Example 11 is too high. On the one hand, the charge of the phosphorylated cellulose nanofibers and the deacetylated nanochitin do not match, and an electrically neutral antifouling coating cannot be formed; on the other hand, the phosphorylated cellulose nanofibers agglomerate, resulting in a decrease in the surface flatness of the antifouling coating, an increase in roughness, a decrease in hydrophilicity, and an increase in hydrophobicity, providing biological fouling attachment points for bacteria, algae, and microorganisms.

[0177] It can be seen from the test data provided by Example 1 and the comparative example that the contact angle of the antifouling coating prepared in the comparative example is much higher than that in Example 1. This is because the steel plate is not coated with a coating in the comparative example, while Example 1 uses hydrophilic phosphorylated cellulose nanofibers and deacetylated nanochitin to alternately immerse and deposit the steel plate, thereby forming a hydrophilic antifouling coating on the surface of the steel plate.

[0178] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a fully bio-based amphoteric polyelectrolyte antifouling coating, characterized in that: The preparation method comprises: (I) The substrate is immersed in a mixture of concentrated sulfuric acid and hydrogen peroxide, and then taken out for cleaning after immersion for a period of time; (II) Soaking the cleaned substrate in a dopamine-containing Tris-HCl buffer solution and reacting the substrate in a dark environment. After the reaction is complete, the substrate is taken out and washed. (III) soaking the substrate in the deacetylated nano-chitin solution for a period of time and then taking it out for cleaning; (IV) soaking the substrate in the nanocellulose solution for a period of time and then taking it out and rinsing it; (V) alternately repeating step (III) and step (IV) at least twice to form the all-biobased amphoteric polyelectrolyte antifouling coating on the surface of the substrate; In step (II), the concentration of dopamine in the dopamine Tris-HCl buffer is 1-5 mg / mL; In step (III), the deacetylated nano-chitosan in the deacetylated nano-chitosan solution is prepared by the following method: The chitosan is mixed with a sodium hydroxide solution and heated to perform a deacetylation reaction on the chitosan to obtain a reaction product, the reaction product is cooled and repeatedly washed until it is neutral; and then the reaction product is nanosized to obtain the deacetylated nano-chitosan; The mass fraction of the sodium hydroxide solution is 25-35wt%; The heating temperature is 80-95°C; The heating time is 6-12h; The mass fraction of the deacetylated nano-chitosan solution is 0.1-0.5wt%; In step (IV), the mass fraction of the nanocellulose solution is 0.1-0.5wt%.

2. The preparation method according to claim 1, characterized in that: In step (I), the mixed solution of concentrated sulfuric acid and hydrogen peroxide is obtained by compounding concentrated sulfuric acid and hydrogen peroxide solution; The volume ratio of the concentrated sulfuric acid to the hydrogen peroxide solution is 1:(1-4); The mass fraction of the hydrogen peroxide solution is 10-30wt%; The soaking time is 20-80min; The soaking temperature is 25-85°C.

3. The preparation method according to claim 1, characterized in that: In step (II), the reaction temperature is 20-30°C; The reaction time is 0.5-5h; The reaction process is carried out in a shaker to shake the substrate.

4. The preparation method according to claim 1, characterized in that: In step (III), the substrate is immersed in the deacetylated nano-chitosan solution for 30-90 minutes.

5. The preparation method according to claim 1, characterized in that: In step (IV), the nanocellulose in the nanocellulose solution includes any one of cellulose nanofibers, cellulose nanocrystals, phosphorylated cellulose nanofibers, phosphorylated cellulose nanocrystals, carboxylated cellulose nanofibers or carboxylated cellulose nanocrystals, or a combination of at least two of them.

6. The preparation method according to claim 1, characterized in that: In step (IV), the substrate is immersed in the nanocellulose solution for 30-90 minutes.

7. A fully bio-based amphoteric polyelectrolyte antifouling coating, characterized in that: The all-biobased amphoteric polyelectrolyte antifouling coating is prepared by the preparation method described in any one of claims 1 to 6.

8. Use of the all-biobased amphoteric polyelectrolyte antifouling coating according to claim 7, characterized in that: The all-biobased amphoteric polyelectrolyte antifouling coating is used in food, cosmetics, biomedicine, marine vessels and wearable electronic devices.

Images