Antifogging and antifouling coating based on nanocellulose and preparation method of antifogging and antifouling coating

Abstract

The invention provides an antifogging antifouling coating based on nanocellulose and a preparation method thereof, and the preparation method comprises the following steps: carrying out oxidation treatment on a nanocellulose solution to obtain an oxidized nanocellulose solution; carrying out carboxyl activation treatment on the oxidized nanocellulose solution by adopting an EDC / NHS mixed solution to obtain an activated nanocellulose solution; carrying out grafting modification treatment on the activated nano-cellulose solution by adopting L-lysine to obtain a zwitterionic nano-cellulose solution; the preparation method comprises the following steps: uniformly mixing a zwitter-ion nano cellulose solution, a hydrophilic polymer solution, a metal ion cross-linking agent solution and a composite solvent to obtain a composite film coating solution, coating the surface of a substrate with the composite film coating solution, and drying to form the anti-fog and anti-fouling coating on the surface of the substrate. Through the synergistic effect of the zwitterionic nanocellulose and the hydrophilic high-molecular polymer, the anti-fogging and anti-fouling dual effects are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of anti-fog and anti-fouling coatings, and relates to an anti-fog and anti-fouling coating based on nanocellulose and a preparation method thereof. Background Art

[0002] Fogging is a common and troublesome phenomenon in daily life. Its essence is that due to sudden changes in temperature and humidity, water vapor condenses on the surface to form droplets. This phenomenon not only seriously affects the visibility and functionality of optical devices, but also poses safety hazards due to the decline in equipment reliability. In the fields of medical devices and food packaging, the fogging problem is particularly prominent, which not only affects the operation accuracy and visual clarity, but also provides a suitable environment for bacterial growth and biofilm formation, thereby increasing the risk of infection or accelerating food spoilage. Therefore, in order to ensure the safety and reliability of various devices and materials, the development of coatings with both anti-fog and anti-fouling functions has become an urgent need.

[0003] Hydrophilic coatings have attracted increasing attention due to their excellent optical properties and biocompatibility. However, the existing hydrophilic coatings still face multiple challenges: First, their anti-fouling performance is generally insufficient: usually, metal oxides or anti-fouling agents need to be introduced through chemical bonding methods, which not only increases the preparation cost, but also causes environmental and health hazards; Second, the durability of their anti-fog performance has not received attention: existing anti-fog coatings rely heavily on hydrophilic surface groups or surfactants, but after long-term placement, these components usually migrate to the interior of the coating or undergo oxidation reactions, resulting in a gradual decrease or even failure of the anti-fog ability; Third, coating hydrophilic anti-fog and anti-fouling coatings usually requires pretreatment of the substrate surface, and the mechanical properties of the coatings are generally low. Therefore, there is an urgent need to develop a new coating system that can endow different material surfaces with excellent anti-fog and anti-fouling properties and is environmentally friendly and durable. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an anti-fog and anti-fouling coating based on nanocellulose and a preparation method thereof. Through the synergistic effect of zwitterionic nanocellulose and hydrophilic polymer, the dual effects of anti-fog and anti-fouling are achieved. The coating preparation process is simple and environmentally friendly. By adjusting the proportion of each component and the reaction time, a coating with high strength and durability can be obtained.

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

[0006] In the first aspect, the present invention provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose, and the preparation method includes:

[0007] The nano-cellulose solution is subjected to oxidation treatment to obtain an oxidized nano-cellulose solution; the oxidized nano-cellulose solution is subjected to carboxyl activation treatment with a 1-ethyl-(3-dimethylaminopropyl)carbodiimide / N-hydroxysuccinimide mixed solution to obtain an activated nano-cellulose solution; L-lysine is used to carry out graft modification treatment on the activated nano-cellulose solution to obtain an amphoteric ion nano-cellulose solution;

[0008] The amphoteric ion nano-cellulose solution, the hydrophilic polymer solution, the metal ion crosslinking agent solution and the composite solvent are mixed evenly to obtain a composite coating solution, and the composite coating solution is coated on the surface of the substrate, and after drying, the anti-fog and anti-fouling coating is formed on the surface of the substrate.

[0009] Through the synergistic effect of amphoteric ion nano-cellulose and hydrophilic polymer, the present invention successfully develops a new type of coating integrating high light transmittance, long-term anti-fogging, strong anti-fouling and environmental friendliness, showing broad application potential in the fields of medical devices, optical devices, food packaging, etc., and providing an innovative solution to solve the bottleneck of traditional coating technology.

[0010] The oxidation treatment uses a TEMPO catalytic system to directionally introduce carboxylic acid groups on the surface of nano-cellulose, which not only increases the density of chemical active sites, but also realizes the efficient activation of carboxyl groups through subsequent EDC / NHS activation, providing sufficient reactive sites for the grafting of L-lysine. The coexistence of amino and carboxyl groups in the L-lysine molecule forms an amphoteric ion characteristic. This structure endows the surface of the anti-fog and anti-fouling coating with super-hydrophilicity, and at the same time, can form a hydration layer barrier through electrostatic interaction, effectively inhibiting the adhesion of pollutants (such as oils, proteins, microorganisms). Compared with traditional single hydrophilic or hydrophobic modified coatings, the amphoteric ion structure can maintain stability through dynamic charge regulation in a humid environment, avoiding both the swelling and shedding problems of pure hydrophilic coatings and the defect of insufficient anti-fog performance of hydrophobic coatings, and realizing the synergistic effect of anti-fogging and anti-fouling functions.

[0011] The carboxyl activation treatment converts the carboxylic acid group into an active ester through the EDC / NHS system. The activated ester group has specific reaction ability, which can precisely control the density and spatial arrangement of grafting sites. At the same time, the active ester formed by the activation treatment has stability, ensuring that the subsequent L-lysine grafting reaction can be carried out under mild conditions, avoiding the destruction of the nano-cellulose structure by high temperature and high pressure.

[0012] The L-lysine molecules are introduced through graft modification treatment. The amino groups on the L-lysine molecules undergo covalent bonding with the activated esters, while the carboxylic acid groups on the L-lysine molecules form zwitterionic structures. This chemical modification reconstructs the surface properties of nanocellulose at the nanoscale. The flexible side chains of L-lysine form a dynamic brush-like structure, and their amino and carboxylic acid groups generate strong hydration through charge balance effects, forming a water molecule adsorption layer with a controllable thickness on the coating surface. Meanwhile, the spatial arrangement of the zwitterionic groups effectively neutralizes the surface potential and inhibits the adhesion of pollutants on the coating surface through the dual effects of electrostatic repulsion and hydrogen bond competition.

[0013] The composite coating solution is composed of a zwitterionic nanocellulose solution, a hydrophilic polymer solution, a metal ion cross-linking agent solution, and a composite solvent. There is a synergistic effect among the components. Among them, the zwitterionic nanocellulose serves as the backbone material and forms a hydrogen bond network with the hydrophilic polymer (such as polyacrylic acid) through its abundant hydroxyl and carboxyl groups, enhancing the hydrophilicity of the anti-fog and anti-fouling coating while improving the mechanical properties; the metal ions bridge the remaining hydroxyl groups of the nanocellulose and the carboxylic acid groups of the polymer chain through coordination, forming a three-dimensional cross-linking network throughout the coating thickness, significantly improving the wear resistance and water erosion resistance of the anti-fog and anti-fouling coating. The composite solvent system optimizes the rheological properties of the composite coating solution through the compounding of deionized water, ethanol, propylene glycol, and polysorbate additives, enabling the composite coating solution to form a uniform thin film in processes such as spin coating and dip coating. The addition of polysorbate effectively reduces the surface tension of the composite coating solution and prevents the generation of microcracks during the drying process of the coating.

[0014] In the drying stage after coating, the present invention adopts a gradient drying process. Through the staged regulation of temperature and time, the orderly volatilization of solvent molecules is achieved. In the pre-drying stage, a low-temperature environment is used to avoid stress concentration caused by rapid shrinkage. In the drying stage, the temperature is moderately increased to promote the movement of polymer segments and improve the cross-linking structure. In the curing stage, high-temperature treatment further strengthens the metal coordination bond effect. This gradient drying scheme effectively inhibits the generation of internal stress in the anti-fog and anti-fouling coating and avoids the problem of increased brittleness of the coating caused by traditional high-temperature curing, enabling the anti-fog and anti-fouling coating to form a dense and flexible thin film on the surface of substrates of different materials such as glass, plastic, and metal.

[0015] As a preferred technical solution of the present invention, the operating steps of the oxidation treatment of the nanocellulose solution include:

[0016] Mix the TEMPO catalyst, sodium bromide, and borate buffer solution evenly to obtain a catalyst solution. Mix the nanocellulose solution with the catalyst solution evenly to obtain a composite solution; under stirring conditions and in an ice-water bath environment, add sodium hypochlorite solution to the composite solution, and mix and stir to react. After the reaction ends, filter through a filter membrane to obtain the oxidized nanocellulose solution.

[0017] The oxidation treatment of nanocellulose is essentially a selective oxidation process of specific hydroxyl sites of cellulose molecules based on the TEMPO (2,2,6,6-tetramethylpiperidinium nitroxide) catalytic system. This reaction achieves efficient conversion of the primary hydroxyl group at the C6 position of nanocellulose to the carboxylate group through the synergistic action of multiple components. In an alkaline borate buffer environment, the TEMPO catalyst forms a three-way catalytic system with sodium bromide and sodium hypochlorite. The bromide ions in the sodium bromide are oxidized by sodium hypochlorite to generate hypobromous acid, which then oxidizes the nitrogen oxide free radicals in the TEMPO molecule to highly active ammonium oxy ions. As an oxidant, the ammonium oxy ions preferentially attack the primary hydroxyl group at the C6 position with less steric hindrance in the nanocellulose molecular chain, and capture the proton in the hydroxyl group through the hydrogen atom transfer mechanism to generate an aldehyde intermediate and reduce it to the hydroxylamine form.

[0018] The present invention limits the oxidation reaction to be carried out in an ice-water bath environment (5-10°C). The low temperature condition effectively inhibits the self-decomposition side reaction of sodium hypochlorite, and at the same time reduces the thermal vibration energy of the β-1,4-glycosidic bond of nanocellulose, avoiding the accidental breakage of the molecular chain during the oxidation process. The borate buffer system not only maintains the stable existence of TEMPO oxygen ammonium ions, but also fixes the molecular conformation through the complexation of borate and cellulose hydroxyl groups, making the spatial orientation of C6 hydroxyl more conducive to the nucleophilic attack of oxygen ammonium ions. At the same time, the weakly alkaline pH environment inhibits the irreversible transformation of hypochlorite to chlorate, and controls the amount of by-products generated to less than 5%.

[0019] In some optional examples, the mass fraction of the TEMPO catalyst in the catalyst solution is 0.2~0.4wt%, for example, it can be 0.2wt%, 0.22wt%, 0.24wt%, 0.26wt%, 0.28wt%, 0.3wt%, 0.32wt%, 0.34wt%, 0.36wt%, 0.38wt% or 0.4wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0020] In some optional examples, the mass fraction of sodium bromide in the catalyst solution is 0.8~1.2wt%, for example, it can be 0.8wt%, 0.85wt%, 0.9wt%, 0.95wt%, 1wt%, 1.05wt%, 1.1wt%, 1.15wt% or 1.2wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In some alternative examples, the pH value of the borate buffer solution is 9 to 10.5. For example, it can be 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, 10.1, 10.2, 10.3, 10.4 or 10.5. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0022] It should be noted that the borate buffer solution defined in the present invention is a commercially available product, and its composition and ratio have been disclosed in the prior art. Optionally, it is prepared by mixing borax (0.05 mol / L) with an aqueous sodium hydroxide solution in proportion, and adjusting the pH value of the borate buffer solution to the range defined in the present invention by sodium hydroxide.

[0023] In some alternative examples, the mass fraction of the nanocellulose solution is 0.5 to 1.5 wt%. For example, it can be 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt% or 1.5 wt%. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0024] In some alternative examples, the mass ratio of the nanocellulose solution to the catalyst solution is (9 to 10):1. For example, it can be 9.0:1, 9.1:1, 9.2:1, 9.3:1, 9.4:1, 9.5:1, 9.6:1, 9.7:1, 9.8:1, 9.9:1 or 10.0:1. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0025] In some alternative examples, the temperature of the ice-water bath environment is 5 to 10 °C. For example, it can be 5.0 °C, 5.5 °C, 6.0 °C, 6.5 °C, 7.0 °C, 7.5 °C, 8.0 °C, 8.5 °C, 9.0 °C, 9.5 °C or 10.0 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0026] In some alternative examples, the mass fraction of the sodium hypochlorite solution is 10 to 12 wt%. For example, it can be 10 wt%, 10.2 wt%, 10.4 wt%, 10.6 wt%, 10.8 wt%, 11 wt%, 11.2 wt%, 11.4 wt%, 11.6 wt%, 11.8 wt% or 12 wt%. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0027] In some alternative examples, the mass ratio of the composite solution to the sodium hypochlorite solution is 1:(0.8 - 1.2). For example, it can be 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, or 1:1.2. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0028] In some alternative examples, the mixing and stirring time of the composite solution and the sodium hypochlorite solution is 5 - 6 h. For example, it can be 5.0 h, 5.1 h, 5.2 h, 5.3 h, 5.4 h, 5.5 h, 5.6 h, 5.7 h, 5.8 h, 5.9 h, or 6.0 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0029] In some alternative examples, the mixing and stirring speed of the composite solution and the sodium hypochlorite solution is 300 - 400 rpm. For example, it can be 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm, or 400 rpm. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] In some alternative examples, the pore size of the filter membrane is 0.3 - 0.4 μm. For example, it can be 0.3 μm, 0.31 μm, 0.32 μm, 0.33 μm, 0.34 μm, 0.35 μm, 0.36 μm, 0.37 μm, 0.38 μm, 0.39 μm, or 0.4 μm. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0031] As a preferred technical solution of the present invention, the operating steps of the carboxyl activation treatment include:

[0032] Mix the oxidized nanocellulose solution with MES buffer and ultrasonically disperse to obtain an oxidized nanocellulose suspension; add 1-ethyl-(3-dimethylaminopropyl)carbodiimide to the oxidized nanocellulose suspension, mix evenly and then add N-hydroxysuccinimide, and mix and stir in the dark to react. After the reaction is completed, filter through a filter membrane to obtain the activated nanocellulose solution.

[0033] As a preferred technical solution of the present invention, the pH value of the MES buffer solution is 4.5 to 5.5. For example, it can be 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4 or 5.5, but it is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0034] It should be noted that the MES buffer solution defined in the present invention is a commercially available product, and its composition and ratio have been disclosed in the prior art. Optionally, it is prepared by mixing 2-morpholinoethanesulfonic acid (0.05 mol / L) with a dilute hydrochloric acid solution in proportion, and adjusting the pH value of the MES buffer solution to the range defined in the present invention by the dilute hydrochloric acid.

[0035] In some alternative examples, the mass ratio of the oxidized nanocellulose solution to the MES buffer solution is 1:(3 to 4). For example, it can be 1:3.0, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9 or 1:4.0, but it is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0036] In some alternative examples, the ultrasonic power of the ultrasonic dispersion is 200 to 300 W. For example, it can be 200 W, 210 W, 220 W, 230 W, 240 W, 250 W, 260 W, 270 W, 280 W, 290 W or 300 W, but it is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0037] In some alternative examples, the ultrasonic time of the ultrasonic dispersion is 30 to 50 min. For example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min or 50 min, but it is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0038] In some alternative examples, the mass ratio of the oxidized nanocellulose suspension to the 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (15 to 20):1. For example, it can be 15:1, 15.5:1, 16:1, 16.5:1, 17:1, 17.5:1, 18:1, 18.5:1, 19:1, 19.5:1 or 20:1, but it is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0039] The present invention specifically defines that the mass ratio of the oxidized nanocellulose suspension to 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) is (15-20):1. Within this ratio range, EDC molecules can fully penetrate into the three-dimensional network structure of nanocellulose, and the amino groups at the molecular ends thereof form stable O-acylisourea intermediates with carboxylic acid groups. Meanwhile, the weak acidic environment maintained by the MES buffer system effectively inhibits the hydrolysis side reaction of EDC. On average, each EDC molecule activates 1.8-2.2 carboxylic acid groups, forming active ester sites with a moderate spatial arrangement, creating ideal reaction conditions for the subsequent directional grafting of L-lysine molecules.

[0040] When the addition amount of the oxidized nanocellulose suspension is lower than the lower limit of the range defined in the present invention, the excessive EDC concentration leads to an increased probability of intermolecular collision, prompting some EDC molecules to undergo self-polymerization reactions before contacting carboxylic acid groups, forming oligomers. These oligomers not only occupy the surface active sites of nanocellulose but also hinder the effective diffusion of the remaining EDC molecules through steric hindrance effects. Meanwhile, the water-soluble urea derivatives generated by the accelerated hydrolysis of excessive EDC will change the ionic strength of the reaction system, inducing the electrostatic shielding effect of nanocellulose and causing it to re-aggregate, resulting in a decrease in the activation efficiency of nanocellulose. In addition, the non-specific binding ratio of excessive EDC molecules to NHS reagents increases, leading to a decrease in the generation amount of active ester intermediates, and further causing a decrease in the grafting rate of subsequent L-lysine.

[0041] When the addition amount of the oxidized nanocellulose suspension exceeds the upper limit of the range defined in the present invention, the dosage of EDC is difficult to meet the activation requirements of carboxylic acid groups, and a large number of incompletely activated carboxylic acid groups are retained on the surface of nanocellulose. These semi-activated sites are prone to reverse reactions in the subsequent phosphate buffer environment and are re-converted into free carboxylic acid forms. Meanwhile, the insufficient dosage of EDC also makes it difficult to fully exert the stabilizing effect of NHS reagents, shortening the half-life of the generated active ester intermediates, and further affecting the optimal reaction timing of the L-lysine grafting reaction, resulting in the L-lysine molecules being only attached to the surface of nanocellulose by physical adsorption, and the thermodynamic stability of the formed zwitterionic structure is poor.

[0042] In some alternative examples, the molar ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 1:(1-2), for example, it can be 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.0, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0043] In some alternative examples, the temperature of the mixing and stirring 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. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0044] In some alternative examples, the time of the mixing and stirring is 3~4 h. For example, it can be 3.0 h, 3.1 h, 3.2 h, 3.3 h, 3.4 h, 3.5 h, 3.6 h, 3.7 h, 3.8 h, 3.9 h or 4.0 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0045] In some alternative examples, the method of the mixing and stirring is magnetic stirring.

[0046] In some alternative examples, the rotation speed of the mixing and stirring is 400~500 rpm. For example, it can be 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm, 450 rpm, 460 rpm, 470 rpm, 480 rpm, 490 rpm or 500 rpm. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0047] In some alternative examples, the pore size of the filter membrane is 0.2~0.3 μm. For example, it can be 0.2 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, 0.28 μm, 0.29 μm or 0.3 μm. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0048] As a preferred technical solution of the present invention, the operation steps of the grafting modification treatment include:

[0049] Dissolve L-lysine in phosphate buffer solution to obtain an L-lysine solution. Mix the activated nanocellulose solution and the L-lysine solution evenly to obtain a mixed solution. Carry out mixing and stirring on the mixed solution under light-shielded conditions to cause a reaction. After the reaction is completed, filter through a filter membrane to obtain the zwitterionic nanocellulose solution.

[0050] The present invention grafts L-lysine molecules onto the surface of activated nanocellulose in a directional manner, achieving precise regulation of the chemical structure of nanocellulose. The coexistence of amino and carboxyl groups in L-lysine molecules forms a unique dual-ion property. When L-lysine is covalently bonded to the carboxyl group of activated nanocellulose through an amide bond, its molecular chain exhibits a dynamic charge distribution in the solution environment. The amino group is protonated and positively charged under acidic conditions, while the carboxyl group is deprotonated and negatively charged under alkaline conditions. This dynamic charge adjustment property enables the modified nanocellulose to maintain surface electrical neutrality through a charge dynamic self-regulation mechanism in a complex usage environment, so as to form a stable hydration layer on the surface of the anti-fog and anti-fouling coating. Compared with single hydrophilic or hydrophobic modification, the advantage of the zwitterionic structure lies in the controllability of its surface energy. It can not only quickly adsorb water molecules through strong hydrophilic groups to achieve the anti-fog function, but also prevent the adhesion of charged pollutants (such as proteins, microorganisms, oils, etc.) by means of charge repulsion effects. Especially in high-temperature and high-humidity environments, the presence of the dynamic hydration layer significantly reduces the van der Waals force and electrostatic attraction between the pollutants and the surface of the anti-fog and anti-fouling coating, thus greatly improving the anti-adhesion ability of the coating in high-temperature and high-humidity environments.

[0051] The grafting modification treatment strengthens the synergistic effect between nanocellulose and other components in the coating. On the one hand, the multiple cross-linking effects between the rigid skeleton of nanocellulose and L-lysine molecules jointly construct a stable three-dimensional network, enabling the anti-fog and anti-fouling coating to be subjected to the dual effects of the mechanical constraint of nanocellulose and the elastic restoring force of chemical cross-linking when absorbing water and swelling, significantly enhancing the anti-swelling ability of the anti-fog and anti-fouling coating; at the same time, the steric hindrance effect of L-lysine molecules effectively inhibits the agglomeration tendency of nanocellulose during the drying process, ensuring that a uniform and dense film layer is formed during the film-forming process of the anti-fog and anti-fouling coating, which is decisive for maintaining the transparency and surface flatness of the anti-fog and anti-fouling coating. On the other hand, the flexible structure of the L-lysine molecular chain provides more coordination sites for subsequent metal ion cross-linking. Its side-chain amino group can form an ionic bond with the carboxyl group of polyacrylic acid, while the carboxyl group coordinates with metal ions (such as Fe 3+ 、Zn 2+ etc.), and this multiple interaction constructs a three-dimensional interpenetrating network structure, which not only maintains the inherent mechanical strength of nanocellulose, but also improves the flexibility and adhesion of the anti-fog and anti-fouling coating through intermolecular forces.

[0052] As a preferred technical solution of the present invention, the pH value of the phosphate buffer solution is 7 to 7.8. For example, it can be 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7 or 7.8, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0053] It should be noted that the phosphate buffer solution defined in the present invention is a commercially available product, and its composition and ratio have been disclosed in the prior art. Optionally, it is prepared by mixing potassium dihydrogen phosphate (0.2 mol / L) with a sodium hydroxide solution in proportion, and adjusting the pH value of the phosphate buffer solution to the range defined in the present invention by sodium hydroxide.

[0054] In some alternative examples, the mass fraction of L-lysine in the L-lysine solution is 3-4 wt%, for example, it can be 3.0 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.7 wt%, 3.8 wt%, 3.9 wt% or 4.0 wt%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0055] In some alternative examples, the mass ratio of the activated nanocellulose solution to the L-lysine solution is 1:(1.3-1.5), for example, it can be 1:1.3, 1:1.32, 1:1.34, 1:1.36, 1:1.38, 1:1.4, 1:1.42, 1:1.44, 1:1.46, 1:1.48 or 1:1.5, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0056] The present invention specifically defines that the mass ratio of the activated nanocellulose solution to the L-lysine solution is 1:(1.3-1.5). Within this ratio range, the carboxylic acid groups activated by EDC / NHS on the activated nanocellulose can efficiently covalently bind to the amino groups in the L-lysine molecules. The L-lysine molecules uniformly cover the surface of the activated nanocellulose in a monolayer adsorption manner, and their amino groups and carboxylic acid groups form stable zwitterion pairs, which not only maintain moderate surface hydrophilicity but also achieve long-term antifouling through charge dynamic balance.

[0057] When the addition amount of the L-lysine solution is lower than the lower limit of the range defined in the present invention, the insufficient addition amount of L-lysine results in incomplete saturation of the activation sites on the surface of the nanocellulose. The unreacted active ester groups gradually hydrolyze and regenerate into carboxylic acid groups in a phosphate buffer environment, and non-specific coordination occurs with the metal ions added subsequently, causing local regions with excessively high rigidity to appear in the crosslinked network. This non-uniform crosslinked structure will generate anisotropic stress inside the anti-fog and anti-fouling coating, and interlayer peeling is likely to be caused due to the difference in expansion coefficients during temperature changes. At the same time, the exposed hydroxyl groups on the incompletely grafted nanocellulose molecular chains will form excessive hydrogen bonds with the polyacrylic acid chain segments, resulting in a decrease in the mobility of the polymer chains, and ultimately reducing the flexibility of the obtained anti-fog and anti-fouling coating.

[0058] When the addition amount of the L-lysine solution exceeds the upper limit of the range defined in the present invention, free L-lysine molecules in the solution will self-assemble into micron-sized micellar aggregates in a weakly alkaline environment. These aggregates not only hinder the effective contact between the active sites of nanocellulose and the amino groups of L-lysine, but also inhibit the free diffusion of reactants through steric hindrance effects. In addition, L-lysine molecules that do not participate in the grafting reaction form surface crystallization during the drying stage as the solvent volatilizes, destroying the transparency and flatness of the anti-fog and anti-fouling coating. At the same time, excessive amino groups will trigger intermolecular crosslinking in the later stage of the reaction, resulting in physical entanglement of nanocellulose, and the originally ordered crystalline regions are replaced by disordered crosslinked networks, forming stress concentration points during the subsequent film coating stage, causing microcracks in the anti-fog and anti-fouling coating in a humid and hot environment.

[0059] In some alternative examples, the temperature for mixing and stirring the mixed solution is 25-35°C. For example, it can be 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C or 35°C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0060] In some alternative examples, the time for mixing and stirring the mixed solution is 10-12 h. For example, it can be 10 h, 10.2 h, 10.4 h, 10.6 h, 10.8 h, 11 h, 11.2 h, 11.4 h, 11.6 h, 11.8 h or 12 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0061] In some alternative examples, the method for mixing and stirring the mixed solution is magnetic stirring.

[0062] In some alternative examples, the rotation speed for mixing and stirring the mixed solution is 500-600 rpm. For example, it can be 500 rpm, 510 rpm, 520 rpm, 530 rpm, 540 rpm, 550 rpm, 560 rpm, 570 rpm, 580 rpm, 590 rpm or 600 rpm, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0063] In some alternative examples, the pore size of the filter membrane is 0.2-0.3 μm. For example, it can be 0.2 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, 0.28 μm, 0.29 μm or 0.3 μm, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0064] As a preferred technical solution of the present invention, the hydrophilic polymer solution is composed of a hydrophilic polymer and deionized water.

[0065] In some alternative examples, the hydrophilic polymer includes polyacrylic acid.

[0066] In some alternative examples, the mass fraction of the hydrophilic polymer solution is 3-5 wt%, for example, it can be 3.0 wt%, 3.2 wt%, 3.4 wt%, 3.6 wt%, 3.8 wt%, 4.0 wt%, 4.2 wt%, 4.4 wt%, 4.6 wt%, 4.8 wt% or 5.0 wt%, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0067] The present invention specifically limits the mass fraction of the hydrophilic polymer solution to 3-5 wt%. Within this proportion range, the polymer molecular chains are fully extended in the solvent to form a moderately entangled network structure. Its carboxylic acid groups form hydrogen bond networks with the hydroxyl groups of nanocellulose, and at the same time, a multi-level cross-linked structure is constructed through metal ion coordination. This interpenetrating network endows the coating with both the rigid support of nanocellulose and the elastic deformation ability of the polymer. Under an external load, the integrity of the coating structure is maintained through an energy dissipation mechanism.

[0068] When the mass fraction of the hydrophilic polymer solution is lower than 3 wt%, the polymer network presents a loose and discontinuous structure, which cannot effectively bridge the nanocellulose reinforcing phase. The anti-fog and anti-fouling coating shows structural collapse due to insufficient chain entanglement during the drying process, resulting in micron-scale depressions on the coating surface. In addition, in a low-concentration hydrophilic polymer solution, the migration rate of metal ions is too fast, and the cross-linking reaction is completed in advance on the surface layer of the anti-fog and anti-fouling coating, hindering the diffusion of metal ions to the deep layer of the coating and forming an unstable structure with a hard outer layer and a soft inner layer. At the same time, due to the lack of the spatial confinement effect of the polymer matrix, the zwitterionic nanocellulose re-aggregates into micron-scale clusters during the solvent evaporation process, increasing the surface roughness of the finally obtained anti-fog and anti-fouling coating and providing physical anchoring points for pollutants, affecting the anti-adhesion ability of the coating.

[0069] When the mass fraction of the hydrophilic polymer solution exceeds 5 wt%, the overly entangled molecular chains seriously hinder the oriented arrangement of nanocellulose. During the coating process, the high-viscosity solution is difficult to penetrate into the micro-nano structure on the substrate surface, resulting in a decrease in the interfacial bonding strength between the coating and the substrate. In addition, during the drying stage, the drastic shrinkage of the polymer chains will generate anisotropic stress inside the anti-fog and anti-fouling coating, inducing microcracks to expand along the interface between the nanocellulose and the substrate. At the same time, the metal ion cross-linking agent is difficult to be uniformly dispersed in this high-concentration polymer solution system, forming brittle regions with local over-crosslinking and weak regions with insufficient cross-linking, making the anti-fog and anti-fouling coating exhibit a failure mode of coexistence of brittle spalling and plastic deformation under external loading.

[0070] In some alternative examples, the metal ion cross-linking agent solution is composed of metal inorganic salts and deionized water.

[0071] In some alternative examples, the metal ions in the metal inorganic salts include Fe 3+ , Zn 2+ , Cu 2+ , Al 3+ or V 3 + or a combination of any one or at least two of them.

[0072] In some alternative examples, the mass fraction of the metal ion cross-linking agent solution is 0.5 - 1.5 wt%, for example, it can be 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt% or 1.5 wt%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0073] The present invention specifically defines that the mass fraction of the metal ion cross-linking agent solution is 0.5 - 1.5 wt%. Within this concentration range, the metal ions form a dynamic cross-linking network with the carboxyl groups of nanocellulose and the carboxyl groups of polyacrylic acid through coordination. The strength and density of the coordination bonds reach the best balance, and each metal ion is connected to 3 - 4 carboxyl groups on average, forming a three-dimensional structure with both rigidity and toughness.

[0074] When the mass fraction of the metal ion crosslinking agent solution is lower than 0.5 wt%, the spatial distribution density of metal ions is insufficient to form a continuous three-dimensional network, resulting in a large number of uncrosslinked linear polymer segments inside the anti-fog and anti-fouling coating. These free segments are prone to molecular chain slippage in a humid and hot environment, increasing the volume swelling rate of the anti-fog and anti-fouling coating and severely weakening the anti-fog performance of the coating. In addition, too low a metal ion concentration leads to coordination unsaturation, and each metal ion can only connect 1-2 carboxylic acid groups. The crosslinking points formed by this coordination mode have poor thermodynamic stability and are prone to coordination bond breakage under mechanical stress. Moreover, too low a metal ion concentration also causes the polyacrylic acid chain segments to stretch excessively, exposing the carboxylic acid groups on the surface of the anti-fog and anti-fouling coating. Protein contaminants will be adsorbed on these free negative charge sites through electrostatic interaction, resulting in a decline in the anti-fouling performance of the coating.

[0075] When the mass fraction of the metal ion crosslinking agent solution exceeds 1.5 wt%, the Coulomb repulsion between high-concentration metal ions is significantly enhanced, causing metal ions to form nano-scale clusters in the solution system. These clusters are difficult to disperse uniformly during the drying process and eventually form stress concentration points inside the anti-fog and anti-fouling coating, ultimately resulting in a decline in the mechanical properties of the coating. In addition, excessive metal ions will compete for coordination with the amino groups in the zwitterionic groups, destroying the charge balance structure formed by the grafting of L-lysine. This abnormal coordination will reduce the thickness of the hydration layer on the coating surface and the anti-fouling effect will decline.

[0076] As a preferred technical solution of the present invention, the composite solvent includes deionized water, ethanol, propylene glycol and polysorbate additives.

[0077] The present invention specifically designs the components of the composite solvent, including deionized water, ethanol, propylene glycol and polysorbate additives. Among them, deionized water is the main continuous-phase solvent. While ensuring environmental friendliness, it maintains the stretched state of the nano-cellulose molecular chains through a hydrogen bond network, avoiding the aggregation of cellulose microfibrils caused by insufficient solvent polarity. Ethanol, as a key component of the co-solvent, its characteristic of rapid volatilization forms an instantaneous concentration gradient during the coating stage, inducing the directional arrangement of zwitterionic nano-cellulose and polyacrylic acid on the substrate surface. This oriented structure is locked by the three-dimensional network formed by metal ion crosslinking during the subsequent drying process, thereby constructing a hydrophilic-anti-fouling functional layer on the substrate surface.

[0078] The introduction of propylene glycol effectively regulates the evaporation kinetics of the solvent system. Its relatively high boiling point forms a stepped evaporation sequence with water and ethanol, enabling the anti-fog and anti-fouling coating to maintain appropriate fluidity during the pre-drying stage, ensuring that the polymer chain segments fully extend and penetrate into the micro-nano structure of the substrate, and enhancing the mechanical interlocking effect between the coating and the substrate. During the curing stage, the residual propylene glycol participates in the construction of the crosslinked network through the coordination of hydroxyl groups with metal ions, effectively improving the flexibility of the anti-fog and anti-fouling coating.

[0079] As an interfacial active substance, polysorbate additives not only improve the wetting and spreading properties of the composite coating solution on various material substrates (especially low surface energy plastics) by reducing the surface tension, but more importantly, the polyoxyethylene chain segments and zwitterionic groups in its molecules produce a synergistic effect to form a dynamic hydration layer on the surface of the anti-fog and anti-fouling coating. When the environmental humidity increases, the conformational change of the polyoxyethylene chain segments in the polysorbate additives releases the stored free volume, promoting the rapid spreading of surface water molecules. When pollutants come into contact with the coating surface, the electrostatic repulsion of the zwitterions and the steric hindrance effect of the polysorbate additives form a double protection barrier, effectively improving the anti-adhesion effect of the coating on pollutants.

[0080] In some alternative examples, in the composite solvent, the volume ratio of deionized water, ethanol, propylene glycol, and polysorbate additives is (15 - 30):(50 - 60):(5 - 10):(0.1 - 1), for example, it can be 15:50:5:0.1, 16:51:5.5:0.2, 17:52:6:0.3, 18:53:6.5:0.4, 19:54:7:0.5, 20:55:7.5:0.6, 22:56:8:0.7, 25:57:8.5:0.8, 27:58:9:0.9, 29:59:9.5:1, or 30:60:10:1, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0081] In some alternative examples, the polysorbate additives include Tween 20 and / or Tween 80.

[0082] As a preferred technical solution of the present invention, in the composite coating solution, the volume ratio of the zwitterionic nanocellulose solution, the hydrophilic polymer solution, the metal ion crosslinking agent solution and the composite solvent is (15~25):(10~20):(5~10):(60~70). For example, it can be 15:10:5:60, 16:11:5.5:61, 17:12:6:62, 18:13:6.5:63, 19:14:7:64, 20:15:7.5:65, 21:16:8:66, 22:17:8.5:67, 23:18:9:68, 24:19:9.5:69 or 25:20:10:70. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0083] The present invention specifically defines that the volume ratio of the zwitterionic nanocellulose solution, the hydrophilic polymer solution, the metal ion crosslinking agent solution and the composite solvent is (15~25):(10~20):(5~10):(60~70). As the core functional material, the volume proportion of zwitterionic nanocellulose directly affects the surface chemical properties and microstructure of the anti-fog and anti-fouling coating. Within this volume ratio range, the density of zwitterionic groups in the composite coating solution can not only fully cover the substrate surface to form a continuous dynamic hydration layer, but also reserve necessary space for the interpenetrating crosslinking of the hydrophilic polymer and metal ions. The appropriate volume proportion ensures that the rigid framework of zwitterionic nanocellulose is uniformly dispersed in the polymer matrix, and a three-dimensional network is constructed through multiple hydrogen bond interactions between hydroxyl groups and carboxylate groups, which not only endows the anti-fog and anti-fouling coating with excellent mechanical strength, but also maintains sufficient chain segment mobility to adapt to substrate deformation.

[0084] When the volume proportion of the zwitterionic nanocellulose solution is lower than the lower limit defined by the present invention, in terms of anti-fog performance, the surface zwitterionic coverage of the anti-fog and anti-fouling coating is insufficient, the charge compensation mechanism fails, the thickness of the dynamic hydration layer decreases, and the anti-fog performance deteriorates. In terms of mechanical properties, the framework support effect of zwitterionic nanocellulose weakens, and it is difficult to form a continuous network structure, which causes the hydrophilic polymer chain segments to shrink excessively during the drying process, resulting in microcrack defects. At the same time, the sparse nanocellulose framework reduces the elastic modulus of the anti-fog and anti-fouling coating, and it cannot effectively resist external friction stress. In addition, the low volume proportion weakens the anchoring effect of zwitterionic nanocellulose on metal ions, and some free metal ions will crosslink with polyacrylic acid excessively to form a dense and brittle structure, ultimately reducing the flexibility of the anti-fog and anti-fouling coating.

[0085] When the volume ratio of the zwitterionic nanocellulose solution exceeds the upper limit defined in the present invention, high-concentration zwitterionic nanocellulose is prone to form local agglomeration during the coating process, which destroys the surface flatness of the anti-fog and anti-fouling coating, increases the light scattering centers, and reduces the light transmittance. At the same time, the dense nanocellulose network will hinder the diffusion and migration of metal ions to the polymer segments, resulting in the cross-linking reaction being limited to the surface layer region of the coating, forming a "hard outer and soft inner" coating structure. This structure is prone to interface peeling due to the difference in the expansion coefficients of the inner and outer layers in a high-temperature and high-humidity environment, ultimately resulting in a decrease in the adhesion of the anti-fog and anti-fouling coating. In addition, the spatial competition of excessive zwitterionic groups will weaken the interfacial wetting effect of the polysorbate auxiliary agent, resulting in discontinuous spreading of the composite coating solution on the hydrophobic substrate, forming micron-sized pore defects, which become the penetration channels for pollutants.

[0086] In some alternative examples, the coating methods of the composite coating solution include spin coating, dip coating or spray coating.

[0087] In some alternative examples, the coating thickness of the composite coating solution is 30 - 40 μm, for example, it can be 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm or 40 μm, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0088] In some alternative examples, the drying method is gradient drying, including a pre-drying stage, a drying stage and a curing stage carried out in sequence.

[0089] In some alternative examples, the heating temperature in the pre-drying stage 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 not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0090] In some alternative examples, the heat preservation time in the pre-drying stage is 20 - 30 min, for example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0091] In some alternative examples, the heating temperature in the drying stage is 35 - 45 °C, for example, it can be 35 °C, 36 °C, 37 °C, 38 °C, 39 °C, 40 °C, 41 °C, 42 °C, 43 °C, 44 °C or 45 °C, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0092] In some optional examples, the heat preservation time in the drying stage is 1 - 1.5 h. For example, it can be 1.0 h, 1.05 h, 1.1 h, 1.15 h, 1.2 h, 1.25 h, 1.3 h, 1.35 h, 1.4 h, 1.45 h or 1.5 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0093] In some optional examples, the heating temperature in the curing stage is 50 - 60 °C. For example, it can be 50 °C, 51 °C, 52 °C, 53 °C, 54 °C, 55 °C, 56 °C, 57 °C, 58 °C, 59 °C or 60 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0094] In some optional examples, the heat preservation time in the curing stage is 20 - 30 min. For example, it can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0095] In the initial pre - drying stage, the mild environment of 20 - 30 °C provides stable solvent volatilization conditions for the system, which not only avoids the rapid formation of a film on the surface to hinder the migration of internal solvents, but also gives sufficient time for the amphoteric ion groups of nanocellulose to arrange orientationally. At this time, the polymer chain segments form a preliminary interpenetrating network under moderate motility, and metal ions begin to migrate towards the carboxylic acid group - enriched region, facilitating subsequent cross - linking.

[0096] As the temperature rises to 35 - 45 °C, the system enters the structure strengthening stage. The polyacrylic acid molecular chains unfold their conformations under heating conditions, and their carboxylic acid groups form dense hydrogen bond connections with the hydroxyl groups of nanocellulose. Metal ions gather at the cross - linking sites, forming a transition coordination layer at the interface between amphoteric ion nanocellulose and the polymer. Solvent molecules accelerate their escape through the through - channels formed in the early stage, and the directional volatilization of the residual solvent guides the amphoteric ion groups to enrich on the surface, forming an interfacial structure with a gradient polarity. At this time, inside the coating, the rigid skeleton of nanocellulose supports the overall structure, the elastic network of the polymer buffers the stress, and a dynamic hydration layer begins to form on the coating surface.

[0097] When the temperature is finally raised to 50-60 °C, the coordination reaction between metal ions and carboxyl and hydroxyl groups is fully activated, forming a stable chemical cross-linking network in three-dimensional space. The high-temperature environment drives the amphoteric ion groups to complete the orientation arrangement, and their amino and carboxyl groups form a dynamic charge balance through molecular thermal motion. At this time, the anti-fog and anti-fouling coating forms a gradient cross-linked structure. The surface layer maintains the rapid water adsorption ability through a flexible hydrogen bond network, the middle layer realizes mechanical support through ionic coordination bonds, and the bottom layer forms a physical and mechanical anchor with the substrate.

[0098] In a second aspect, the present invention provides an anti-fog and anti-fouling coating based on nanocellulose prepared by the preparation method described in the first aspect.

[0099] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0100] Through the synergistic effect of zwitterionic nanocellulose and hydrophilic polymer, the present invention successfully develops a new type of coating that integrates high light transmittance, long-lasting anti-fogging, strong anti-fouling, and environmental friendliness, showing broad application potential in the fields of medical devices, optical devices, food packaging, etc., and providing an innovative solution to solve the bottleneck of traditional coating technology. Description of the Drawings

[0101] Figure 1 It is a surface scanning electron micrograph of the anti-fog and anti-fouling coating prepared in Example 1 of the present invention;

[0102] Figure 2 It is a cross-sectional scanning electron micrograph of the anti-fog and anti-fouling coating prepared in Example 1 of the present invention;

[0103] Figure 3 It is a water contact angle diagram of the anti-fog and anti-fouling coating prepared in Example 1 of the present invention;

[0104] Figure 4 It is a comparison diagram of the self-cleaning effect between the anti-fog and anti-fouling coating prepared in Example 1 of the present invention and the comparative example;

[0105] Figure 5 It is a comparison diagram of the anti-fogging effect between the anti-fog and anti-fouling coating prepared in Example 1 of the present invention and the comparative example in animals (rabbits);

[0106] Figure 6 It is a comparison diagram of the anti-fogging effect between the anti-fog and anti-fouling coating prepared in Example 1 of the present invention and the comparative example for food packaging boxes; Detailed Embodiments

[0107] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary and should not be construed as limiting the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of the present application, and these technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0108] Example 1

[0109] This embodiment provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose. The preparation method specifically includes the following steps:

[0110] (1) Mix TEMPO catalyst, sodium bromide, and borate buffer solution (pH = 9) evenly to obtain a catalyst solution. The mass fraction of TEMPO catalyst in the catalyst solution is 0.2 wt%, and the mass fraction of sodium bromide is 0.8 wt%. Mix the nanocellulose solution with a mass fraction of 0.5 wt% evenly with the catalyst solution to obtain a composite solution. The mass ratio of the nanocellulose solution to the catalyst solution is 9:1. Under stirring conditions and in an ice-water bath environment at 5 °C, add a sodium hypochlorite solution with a mass fraction of 10 wt% to the composite solution. The mass ratio of the composite solution to the sodium hypochlorite solution is 1:0.8, and mix and stir at a rotation speed of 300 rpm for 6 h to react. After the reaction, filter through a filter membrane (pore size of 0.3 μm) to obtain an oxidized nanocellulose solution;

[0111] (2) Mix the oxidized nanocellulose solution with MES buffer solution (pH = 4.5). The mass ratio of the oxidized nanocellulose solution to the MES buffer solution is 1:3. Then, ultrasonically disperse it at an ultrasonic power of 200 W for 50 min to obtain an oxidized nanocellulose suspension. Add 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) to the oxidized nanocellulose suspension. The mass ratio of the oxidized nanocellulose suspension to EDC is 15:1. After mixing evenly, add N-hydroxysuccinimide (NHS). The molar ratio of EDC to NHS is 1:1. Magnetically stir at 20 °C in the dark and at a rotation speed of 400 rpm for 4 h to react. After the reaction, filter through a filter membrane (pore size of 0.2 μm) to obtain an activated nanocellulose solution;

[0112] (3) Dissolve L-lysine in phosphate buffer (pH = 7) to obtain an L-lysine solution, where the mass fraction of L-lysine in the L-lysine solution is 3 wt%. Mix the activated nanocellulose solution and the L-lysine solution evenly to obtain a mixed solution, and the mass ratio of the activated nanocellulose solution to the L-lysine solution is 1:1.3. Mix and stir the mixed solution at 25 °C in the dark and at a stirring speed of 600 rpm for 10 h to react. After the reaction, filter through a filter membrane (pore size 0.2 μm) to obtain an amphoteric ion nanocellulose solution;

[0113] (4) Mix the amphoteric ion nanocellulose solution, an aqueous polyacrylic acid solution with a mass fraction of 3 wt%, an aqueous ferric chloride solution with a mass fraction of 0.5 wt%, and a composite solvent evenly to obtain a composite coating solution. Among them, the composite solvent is composed of deionized water, ethanol, propylene glycol, and Tween 20 with a volume ratio of 15:50:5:0.1, and the volume ratio of the amphoteric ion nanocellulose solution, the aqueous polyacrylic acid solution, the aqueous ferric chloride solution, and the composite solvent is 15:10:5:60;

[0114] Coat the composite coating solution on the surface of a glass substrate with a coating thickness of 30 μm. Subsequently, perform gradient drying, including a pre-drying stage, a drying stage, and a curing stage in sequence. Among them, the heating temperature in the pre-drying stage is 20 °C, and the heat preservation time is 30 min. The heating temperature in the drying stage is 35 °C, and the heat preservation time is 1.5 h. The heating temperature in the curing stage is 50 °C, and the heat preservation time is 30 min. After gradient drying, form the anti-fog and anti-fouling coating on the surface of the glass substrate.

[0115] Figure 1 and Figure 2 are the surface scanning electron microscope image and the cross-section scanning electron microscope image of the anti-fog and anti-fouling coating prepared in this example, respectively. It can be seen from the figure that the surface structure of the anti-fog and anti-fouling coating prepared in this example is flat and dense.

[0116] Figure 3 is the water contact angle image of the anti-fog and anti-fouling coating prepared in this example. It can be seen from the figure that the anti-fog and anti-fouling coating prepared in this example has excellent hydrophilic properties.

[0117] Example 2

[0118] This example provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose. The preparation method specifically includes the following steps:

[0119] (1) Mix the TEMPO catalyst, sodium bromide, and borate buffer solution (pH = 9.5) evenly to obtain a catalyst solution. The mass fraction of the TEMPO catalyst in the catalyst solution is 0.25 wt%, and the mass fraction of sodium bromide is 0.9 wt%. Mix the nano-cellulose solution with a mass fraction of 0.8 wt% evenly with the catalyst solution to obtain a composite solution. The mass ratio of the nano-cellulose solution to the catalyst solution is 9.2:1. Under stirring conditions and in an ice-water bath environment at 6 °C, add a sodium hypochlorite solution with a mass fraction of 10.5 wt% to the composite solution. The mass ratio of the composite solution to the sodium hypochlorite solution is 1:0.9. Mix and stir at a rotation speed of 320 rpm for 5.8 h to cause a reaction. After the reaction ends, filter through a filter membrane (pore size: 0.32 μm) to obtain an oxidized nano-cellulose solution;

[0120] (2) Mix the oxidized nano-cellulose solution with MES buffer solution (pH = 4.8). The mass ratio of the oxidized nano-cellulose solution to the MES buffer solution is 1:3.2. Then, ultrasonically disperse it for 45 min at an ultrasonic power of 220 W to obtain an oxidized nano-cellulose suspension. Add 1-ethyl-(3-dimethylaminopropyl) carbodiimide (EDC) to the oxidized nano-cellulose suspension. The mass ratio of the oxidized nano-cellulose suspension to EDC is 16:1. After mixing evenly, add N-hydroxysuccinimide (NHS). The molar ratio of EDC to NHS is 1:1.2. Magnetically stir at 22 °C in the dark and at a rotation speed of 420 rpm for 3.8 h to cause a reaction. After the reaction ends, filter through a filter membrane (pore size: 0.22 μm) to obtain an activated nano-cellulose solution;

[0121] (3) Dissolve L-lysine in phosphate buffer solution (pH = 7.2) to obtain an L-lysine solution. The mass fraction of L-lysine in the L-lysine solution is 3.2 wt%. Mix the activated nano-cellulose solution evenly with the L-lysine solution to obtain a mixed solution. The mass ratio of the activated nano-cellulose solution to the L-lysine solution is 1:1.35. Mix and stir the mixed solution at 28 °C in the dark and at a stirring speed of 580 rpm for 10.5 h to cause a reaction. After the reaction ends, filter through a filter membrane (pore size: 0.22 μm) to obtain an amphoteric ion nano-cellulose solution;

[0122] (4) Mix the amphoteric ion nano-cellulose solution, an aqueous polyacrylic acid solution with a mass fraction of 3.5 wt%, an aqueous ferric chloride solution with a mass fraction of 0.8 wt%, and a composite solvent evenly to obtain a composite coating solution. Among them, the composite solvent consists of deionized water, ethanol, propylene glycol, and Tween 20 with a volume ratio of 18:52:6:0.3. The volume ratio of the amphoteric ion nano-cellulose solution, the aqueous polyacrylic acid solution, the aqueous ferric chloride solution, and the composite solvent is 18:12:6:62;

[0123] The composite coating solution is coated on the surface of the glass substrate with a coating thickness of 32 μm; then gradient drying is carried out, including a pre-drying stage, a drying stage and a curing stage carried out in sequence. Among them, the heating temperature in the pre-drying stage is 22 °C, the heat preservation time is 28 min, the heating temperature in the drying stage is 38 °C, the heat preservation time is 1.4 h, and the heating temperature in the curing stage is 52 °C, the heat preservation time is 28 min. After gradient drying, the anti-fog and anti-fouling coating is formed on the surface of the glass substrate.

[0124] Example 3

[0125] This embodiment provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose. The preparation method specifically includes the following steps:

[0126] (1) Mix TEMPO catalyst, sodium bromide and borate buffer solution (pH value = 10) evenly to obtain a catalyst solution. The mass fraction of TEMPO catalyst in the catalyst solution is 0.3 wt%, and the mass fraction of sodium bromide is 1 wt%; mix the nanocellulose solution with a mass fraction of 1 wt% evenly with the catalyst solution to obtain a composite solution. The mass ratio of the nanocellulose solution to the catalyst solution is 9.5:1; under stirring conditions and in an ice-water bath environment at 7 °C, add a sodium hypochlorite solution with a mass fraction of 11 wt% to the composite solution. The mass ratio of the composite solution to the sodium hypochlorite solution is 1:1, and mix and stir at a rotation speed of 350 rpm for 5.5 h to carry out the reaction. After the reaction is completed, filter through a filter membrane (pore size of 0.35 μm) to obtain an oxidized nanocellulose solution;

[0127] (2) Mix the oxidized nanocellulose solution with MES buffer solution (pH value = 5). The mass ratio of the oxidized nanocellulose solution to the MES buffer solution is 1:3.5, and then ultrasonically disperse it for 40 min at an ultrasonic power of 250 W to obtain an oxidized nanocellulose suspension; add 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) to the oxidized nanocellulose suspension. The mass ratio of the oxidized nanocellulose suspension to EDC is 17:1. After mixing evenly, add N-hydroxysuccinimide (NHS). The molar ratio of EDC to NHS is 1:1.5, and magnetically stir at 25 °C in the dark and at a rotation speed of 450 rpm for 3.5 h to carry out the reaction. After the reaction is completed, filter through a filter membrane (pore size of 0.25 μm) to obtain an activated nanocellulose solution;

[0128] (3) Dissolve L-lysine in phosphate buffer (pH = 7.5) to obtain an L-lysine solution with a mass fraction of L-lysine in the solution of 3.5 wt%. Mix the activated nanocellulose solution and the L-lysine solution evenly to obtain a mixed solution, and the mass ratio of the activated nanocellulose solution to the L-lysine solution is 1:1.4; under the condition of avoiding light at 30 °C and a stirring speed of 550 rpm, mix and stir the mixed solution for 11 h to react. After the reaction, filter through a filter membrane (pore size 0.25 μm) to obtain an amphoteric ion nanocellulose solution;

[0129] (4) Mix the amphoteric ion nanocellulose solution, an aqueous solution of polyacrylic acid with a mass fraction of 4 wt%, an aqueous solution of zinc chloride with a mass fraction of 1 wt%, and a composite solvent evenly to obtain a composite coating solution. Among them, the composite solvent consists of deionized water, ethanol, propylene glycol, and Tween 80 with a volume ratio of 20:55:7:0.5, and the volume ratio of the amphoteric ion nanocellulose solution, the aqueous solution of polyacrylic acid, the aqueous solution of zinc chloride, and the composite solvent is 20:15:8:65;

[0130] Coat the composite coating solution on the surface of a glass substrate with a coating thickness of 35 μm; then perform gradient drying, including a pre-drying stage, a drying stage, and a curing stage in sequence. Among them, the heating temperature in the pre-drying stage is 25 °C, the heat preservation time is 25 min, the heating temperature in the drying stage is 40 °C, the heat preservation time is 1.3 h, and the heating temperature in the curing stage is 55 °C, and the heat preservation time is 25 min. After gradient drying, the anti-fog and anti-fouling coating is formed on the surface of the glass substrate.

[0131] Example 4

[0132] This embodiment provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose, and the preparation method specifically includes the following steps:

[0133] (1) Mix the TEMPO catalyst, sodium bromide, and borate buffer (pH = 10) evenly to obtain a catalyst solution with a mass fraction of the TEMPO catalyst in the solution of 0.35 wt% and a mass fraction of sodium bromide of 1.1 wt%; mix the nanocellulose solution with a mass fraction of 1.2 wt% and the catalyst solution evenly to obtain a composite solution, and the mass ratio of the nanocellulose solution to the catalyst solution is 9.8:1; under stirring conditions and an ice-water bath environment at 8 °C, add a sodium hypochlorite solution with a mass fraction of 11.5 wt% to the composite solution, and the mass ratio of the composite solution to the sodium hypochlorite solution is 1:1.1. Mix and stir at a speed of 380 rpm for 5.2 h to react. After the reaction, filter through a filter membrane (pore size 0.38 μm) to obtain an oxidized nanocellulose solution;

[0134] (2) Mix the oxidized nanocellulose solution with MES buffer solution (pH = 5.2). The mass ratio of the oxidized nanocellulose solution to the MES buffer solution is 1:3.8. Then, ultrasonically disperse it for 35 min under an ultrasonic power of 280 W to obtain an oxidized nanocellulose suspension. Add 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) to the oxidized nanocellulose suspension. The mass ratio of the oxidized nanocellulose suspension to EDC is 18:1. After mixing evenly, add N-hydroxysuccinimide (NHS). The molar ratio of EDC to NHS is 1:1.8. Stir magnetically for 3.2 h at 28 °C in the dark and at a rotation speed of 480 rpm to cause a reaction. After the reaction is completed, filter through a filter membrane (pore size 0.28 μm) to obtain an activated nanocellulose solution;

[0135] (3) Dissolve L-lysine in phosphate buffer solution (pH = 7.6) to obtain an L-lysine solution. The mass fraction of L-lysine in the L-lysine solution is 3.8 wt%. Mix the activated nanocellulose solution and the L-lysine solution evenly to obtain a mixed solution. The mass ratio of the activated nanocellulose solution to the L-lysine solution is 1:1.45. Mix and stir the mixed solution at 32 °C in the dark and at a stirring speed of 520 rpm for 11.5 h to cause a reaction. After the reaction is completed, filter through a filter membrane (pore size 0.28 μm) to obtain an amphoteric ion nanocellulose solution;

[0136] (4) Mix the amphoteric ion nanocellulose solution, an aqueous solution of polyacrylic acid with a mass fraction of 4.5 wt%, an aqueous solution of zinc chloride with a mass fraction of 1.2 wt%, and a composite solvent evenly to obtain a composite coating solution. Among them, the composite solvent is composed of deionized water, ethanol, propylene glycol, and Tween 80 with a volume ratio of 25:58:8:0.8. The volume ratio of the amphoteric ion nanocellulose solution, the aqueous solution of polyacrylic acid, the aqueous solution of zinc chloride, and the composite solvent is 22:18:9:68;

[0137] Coat the composite coating solution on the surface of a glass substrate with a coating thickness of 38 μm. Then, perform gradient drying, including a pre-drying stage, a drying stage, and a curing stage in sequence. Among them, the heating temperature in the pre-drying stage is 28 °C, and the heat preservation time is 22 min. The heating temperature in the drying stage is 42 °C, and the heat preservation time is 1.2 h. The heating temperature in the curing stage is 58 °C, and the heat preservation time is 22 min. After gradient drying, form the anti-fog and anti-fouling coating on the surface of the glass substrate.

[0138] Example 5

[0139] This example provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose. The preparation method specifically includes the following steps:

[0140] (1) Mix the TEMPO catalyst, sodium bromide, and borate buffer solution (pH = 10.5) evenly to obtain a catalyst solution. The mass fraction of the TEMPO catalyst in the catalyst solution is 0.4 wt%, and the mass fraction of sodium bromide is 1.2 wt%. Mix the nanocellulose solution with a mass fraction of 1.5 wt% evenly with the catalyst solution to obtain a composite solution. The mass ratio of the nanocellulose solution to the catalyst solution is 10:1. Under stirring conditions and in an ice-water bath environment at 10 °C, add a sodium hypochlorite solution with a mass fraction of 12 wt% to the composite solution. The mass ratio of the composite solution to the sodium hypochlorite solution is 1:1.2. Mix and stir at a rotation speed of 400 rpm for 5 h to cause a reaction. After the reaction ends, filter through a filter membrane (pore size 0.4 μm) to obtain an oxidized nanocellulose solution;

[0141] (2) Mix the oxidized nanocellulose solution with MES buffer solution (pH = 5.5). The mass ratio of the oxidized nanocellulose solution to the MES buffer solution is 1:4. Then, ultrasonically disperse it for 30 min at an ultrasonic power of 300 W to obtain an oxidized nanocellulose suspension. Add 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) to the oxidized nanocellulose suspension. The mass ratio of the oxidized nanocellulose suspension to EDC is 20:1. After mixing evenly, add N-hydroxysuccinimide (NHS). The molar ratio of EDC to NHS is 1:2. Magnetically stir at 30 °C in the dark and at a rotation speed of 500 rpm for 3 h to cause a reaction. After the reaction ends, filter through a filter membrane (pore size 0.3 μm) to obtain an activated nanocellulose solution;

[0142] (3) Dissolve L-lysine in phosphate buffer solution (pH = 7.8) to obtain an L-lysine solution. The mass fraction of L-lysine in the L-lysine solution is 4 wt%. Mix the activated nanocellulose solution evenly with the L-lysine solution to obtain a mixed solution. The mass ratio of the activated nanocellulose solution to the L-lysine solution is 1:1.5. Mix and stir the mixed solution at 35 °C in the dark and at a stirring speed of 500 rpm for 12 h to cause a reaction. After the reaction ends, filter through a filter membrane (pore size 0.3 μm) to obtain an amphoteric ion nanocellulose solution;

[0143] (4) Mix the amphoteric ion nanocellulose solution, an aqueous polyacrylic acid solution with a mass fraction of 5 wt%, an aqueous copper chloride solution with a mass fraction of 1.5 wt%, and a composite solvent evenly to obtain a composite coating solution. Among them, the composite solvent is composed of deionized water, ethanol, propylene glycol, and Tween 80 with a volume ratio of 30:60:10:1. The volume ratio of the amphoteric ion nanocellulose solution, the aqueous polyacrylic acid solution, the aqueous copper chloride solution, and the composite solvent is 25:20:10:70;

[0144] The composite coating liquid is coated on the surface of the glass substrate with a coating thickness of 40 μm; then gradient drying is carried out, including a pre-drying stage, a drying stage and a curing stage carried out in sequence. Among them, the heating temperature in the pre-drying stage is 30 °C, the heat preservation time is 20 min, the heating temperature in the drying stage is 45 °C, the heat preservation time is 1 h, the heating temperature in the curing stage is 60 °C, and the heat preservation time is 20 min. After gradient drying, the anti-fog and anti-fouling coating is formed on the surface of the glass substrate.

[0145] Example 6

[0146] This embodiment provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose. The difference from Example 1 is that the mass ratio of the oxidized nanocellulose suspension to EDC is adjusted to 12:1, and other process parameters and operation steps are exactly the same as those in Example 1.

[0147] Example 7

[0148] This embodiment provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose. The difference from Example 1 is that the mass ratio of the oxidized nanocellulose suspension to EDC is adjusted to 23:1, and other process parameters and operation steps are exactly the same as those in Example 1.

[0149] Example 8

[0150] This embodiment provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose. The difference from Example 1 is that the mass ratio of the activated nanocellulose solution to the L-lysine solution is adjusted to 1:1.1, and other process parameters and operation steps are exactly the same as those in Example 1.

[0151] Example 9

[0152] This embodiment provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose. The difference from Example 1 is that the mass ratio of the activated nanocellulose solution to the L-lysine solution is adjusted to 1:1.8, and other process parameters and operation steps are exactly the same as those in Example 1.

[0153] Example 10

[0154] This embodiment provides a preparation method of an anti-fog and anti-fouling coating based on nanocellulose. The difference from Example 1 is that the mass fraction of the aqueous polyacrylic acid solution is adjusted to 1 wt%, and other process parameters and operation steps are exactly the same as those in Example 1.

[0155] Example 11

[0156] This embodiment provides a method for preparing an anti-fog and anti-fouling coating based on nanocellulose. The difference from Embodiment 1 is that the mass fraction of the aqueous polyacrylic acid solution is adjusted to 8 wt%, and other process parameters and operation steps are exactly the same as those in Embodiment 1.

[0157] Example 12

[0158] This embodiment provides a method for preparing an anti-fog and anti-fouling coating based on nanocellulose. The difference from Embodiment 1 is that the mass fraction of the aqueous ferric chloride solution is adjusted to 0.2 wt%, and other process parameters and operation steps are exactly the same as those in Embodiment 1.

[0159] Example 13

[0160] This embodiment provides a method for preparing an anti-fog and anti-fouling coating based on nanocellulose. The difference from Embodiment 1 is that the mass fraction of the aqueous ferric chloride solution is adjusted to 1.8 wt%, and other process parameters and operation steps are exactly the same as those in Embodiment 1.

[0161] Example 14

[0162] This embodiment provides a method for preparing an anti-fog and anti-fouling coating based on nanocellulose. The difference from Embodiment 1 is that the volume ratio of the zwitterionic nanocellulose solution, aqueous polyacrylic acid solution, aqueous ferric chloride solution and composite solvent is adjusted to 12:10:5:60, and other process parameters and operation steps are exactly the same as those in Embodiment 1.

[0163] Example 15

[0164] This embodiment provides a method for preparing an anti-fog and anti-fouling coating based on nanocellulose. The difference from Embodiment 1 is that the volume ratio of the zwitterionic nanocellulose solution, aqueous polyacrylic acid solution, aqueous ferric chloride solution and composite solvent is adjusted to 28:10:5:60, and other process parameters and operation steps are exactly the same as those in Embodiment 1.

[0165] Comparative Example

[0166] This comparative example is a blank glass substrate without an anti-fog and anti-fouling coating.

[0167] Figure 4 This is a comparison chart of the self-cleaning effects of the anti-fog and anti-fouling coating prepared in Embodiment 1 of the present invention and the comparative example. It can be seen from the comparison in the figure that there is liquid residue on the surface of the glass substrate without the anti-fog and anti-fouling coating in the comparative example, while there is no liquid residue on the surface of the glass substrate coated with the anti-fog and anti-fouling coating prepared in Embodiment 1 of the present invention. This indicates that the anti-fog and anti-fouling coating provided by the present invention has a good anti-adhesion effect.

[0168] Figure 5 This is a comparison chart of the anti-fogging effect of the anti-fogging and anti-fouling coating prepared in Example 1 of the present invention and the comparative example in animals (rabbits). It can be seen from the comparison in the figure that the endoscope lens coated with the anti-fogging and anti-fouling coating prepared in Example 1 of the present invention still maintains a light transmittance of more than 99% in a high-humidity animal cavity environment (humidity > 95%, temperature 37°C) for up to 2 hours, and there is no droplet condensation on the surface, which is significantly better than the uncoated comparative example. This indicates that the anti-fogging and anti-fouling coating prepared by the present invention has excellent anti-fogging performance and biosecurity in the medical field and can be widely applied to surgical instruments, implantable devices, and disposable medical consumables.

[0169] Figure 6 This is a comparison chart of the anti-fogging effect of the anti-fogging and anti-fouling coating prepared in Example 1 of the present invention and the comparative example for food packaging boxes. It can be seen from the comparison in the figure that the food packaging box coated with the anti-fogging and anti-fouling coating prepared in Example 1 of the present invention has a good anti-fogging effect, and the vegetable leaves in the food packaging box can still be clearly seen, but the inner wall of the food packaging box without the coating in the comparative example is severely fogged.

[0170] The performance of the anti-fogging and anti-fouling coatings prepared in Examples 1-15 was tested, and the specific test steps are as follows:

[0171] (1) Light transmittance:

[0172] Referring to the national standard GB / T 2410-2008 "Determination of Light Transmittance and Haze of Transparent Plastics", use a spectrophotometer to scan in the visible light wavelength range (380-780 nm), record the transmittance at 550 nm, and calculate the weighted average of the light transmittance in the full wavelength band.

[0173] (2) Contact angle

[0174] Use a contact angle measuring instrument to test in a test environment of temperature 25°C and humidity 50%RH. Use a micro syringe to drop 3 μL of deionized water on the surface of the anti-fogging and anti-fouling coating, record the droplet morphology through a high-speed camera (1000 fps), and the software automatically calculates the static contact angle. Measure 5 points for each sample, and take the average value after excluding outliers.

[0175] (3) Anti-fogging time

[0176] Place the glass substrate coated with the anti-fogging and anti-fouling coating in a humidity and heat chamber (temperature 40°C ± 1°C, humidity 95% ± 3%RH), take it out every 5 minutes, and measure the haze value on the surface of the glass substrate with a haze meter. The anti-fogging time is the time when the haze value reaches 30% (the critical value of visible fogging by the human eye).

[0177] (4) Antibacterial rate

[0178] Inoculate the cryopreserved Escherichia coli on a nutrient agar plate (NA medium), culture it at 37 °C for 18 - 24 h, pick a single colony and transfer it to 5 mL of liquid LB medium, and culture it with shaking at 37 °C and 200 rpm until the logarithmic growth phase (OD 600 ≈0.5, about 10 8 CFU / mL), dilute the bacterial suspension with sterile PBS buffer (pH = 7.4) to 1×10 5 CFU / mL.

[0179] Set up experimental group samples and control group samples. The experimental group samples are glass substrates coated with the anti-fog and anti-fouling coating provided by the present invention, and the control group samples are glass substrates without coating. Place the experimental group samples and the control group samples in an ultraviolet sterilization cabinet and irradiate for 30 min (wavelength 254 nm, intensity 80 μW / cm 2 ), use a micropipette to suck 100 μL of the diluted bacterial suspension and drop it on the surfaces of the experimental group samples and the control group samples respectively, immediately cover the surfaces of the experimental group samples and the control group samples with sterile polyethylene film to avoid liquid evaporation.

[0180] Place the film-covered experimental group samples and control group samples in a constant temperature and humidity chamber (temperature 37 °C ± 1 °C, relative humidity ≥ 90%), culture for 24 h, then take out the experimental group samples and the control group samples, add 10 mL of sterile PBS buffer, vortex for 1 min to wash the residual bacteria on the surface, perform 10-fold serial dilution (10 -1 , 10 -2 , 10 -3 ), take 100 μL of each gradient dilution and spread it on a nutrient agar plate, culture at 37 °C for 24 h, and count the visible colony number (30 - 300 CFU / plate is valid data).

[0181] Calculate the viable bacteria amount per unit area using the following formula:

[0182] Viable bacteria amount (CFU / cm 2 ) = (average colony number × dilution factor × 10) / coating area (cm 2 );

[0183] Calculate the antibacterial rate using the following formula:

[0184] Antibacterial rate (%) = (1 - viable bacteria amount of experimental group samples / viable bacteria amount of control group samples) × 100%.

[0185] (5) Anti-algae rate

[0186] The anti-diatom performance of the anti-fog and anti-fouling coating was tested. The coated substrate (experimental group sample) and the uncoated substrate (control group sample) were immersed in the diatom culture solution and irradiated. The light intensity was 3000 lx, with a 12 h light-dark cycle. After 14 days, the experimental group sample and the control group sample were taken out, and the diatom coverage rate on the coating surface was counted using a fluorescence microscope.

[0187] The anti-algae rate was calculated using the following formula:

[0188] Anti-algae rate (%) = (coverage rate of control group sample - coverage rate of experimental group sample) / coverage rate of control group sample × 100%.

[0189] (6)Adhesion

[0190] Referring to the national standard GB / T 5210-2006 "Paints and varnishes - Pull-off test for adhesion", the adhesion between the anti-fog and anti-fouling coating and the glass substrate was tested. The specimen was fixed on the tensile machine, the tensile speed was set at 1 mm / min, and the maximum tensile force value F when the coating was separated from the substrate was recorded.

[0191] The adhesion was calculated using the following formula:

[0192] Adhesion (MPa) = F (N) / A (mm 2 )

[0193] where A is the bonding area.

[0194] (7)Pencil hardness

[0195] Referring to the national standard GB / T 6739-2006 "Paints and varnishes - Determination of film hardness by pencil test", the pencil hardness of the anti-fog and anti-fouling coating was tested. The pencil was sharpened to a 5 mm lead, fixed on the hardness tester (at a 45° angle, with a 750 g load), and slid on the surface of the anti-fog and anti-fouling coating 5 times at a speed of 0.5 mm / s. Whether there were scratches or coating cracks was observed, and the highest pencil hardness value without scratching the coating was taken as the test result.

[0196] The test results of Examples 1-15 are shown in Table 1.

[0197] Table 1

[0198] Transmittance (%) Contact Angle (°) Anti-fogging Time (min) Antibacterial Rate (%) Anti-algal Rate (%) Adhesion (MPa) Pencil Hardness Example 1 91.2 5.3 68 97.4 99.1 2.8 4H Example 2 89.5 6.8 65 96.1 98.7 2.7 4H Example 3 93.0 4.9 70 98.5 99.6 2.9 4H Example 4 88.7 7.2 63 94.8 98.3 2.6 3H Example 5 90.4 5.9 67 97.9 99.4 2.8 4H Example 6 83.6 12.7 52 89.3 93.2 2.0 2H Example 7 78.9 15.4 47 84.5 90.1 1.8 1H Example 8 81.3 18.9 41 85.7 88.6 2.2 2H Example 9 73.5 23.5 34 79.2 83.4 1.5 1H Example 10 76.8 14.3 38 82.4 86.9 1.9 1H Example 11 68.2 27.8 29 73.6 79.3 1.2 1H Example 12 84.1 11.5 56 88.1 92.4 2.1 2H Example 13 79.8 19.2 43 83.7 87.5 1.6 1H Example 14 77.4 16.7 45 81.9 85.2 1.7 1H Example 15 70.6 25.1 31 76.5 80.8 1.3 1H Comparative Example 70.0 85.0 0 / / / /

[0199] From the test results of Example 1, Example 6 and Example 7, it can be seen that the test data of Example 6 and Example 7 are inferior to those of Example 1. This is because EDC is the core reagent for carboxyl activation, and its proportion directly affects the density of the active ester intermediate. In Example 6, the proportion of the oxidized nanocellulose suspension is too low, and relatively, the proportion of EDC is too high, resulting in the self-polymerization of EDC, occupying the active sites, reducing the activation efficiency of nanocellulose. At the same time, the EDC self-polymer will also cause structural defects, affecting the light transmittance and mechanical properties of the anti-fog and anti-fouling coating. In Example 7, the proportion of the oxidized nanocellulose suspension is too high, and relatively, the proportion of EDC is too low, resulting in insufficient activation of nanocellulose, and the carboxylic acid groups cannot be effectively converted into active esters, leading to a decrease in the grafting rate of L-lysine, making the zwitterionic structure on the coating surface incomplete, thus affecting the hydrophilicity and anti-fouling performance of the anti-fog and anti-fouling coating.

[0200] From the test results of Example 1, Example 8 and Example 9, it can be seen that the test data of Example 8 and Example 9 are inferior to those of Example 1. This is because the L-lysine grafting density determines the charge balance ability of the zwitterionic structure. In Example 8, the dosage of the L-lysine solution is too small, resulting in insufficient grafting density, discontinuous zwitterionic structure, and inability to form an effective hydration layer, ultimately shortening the anti-fog time and decreasing the antibacterial rate of the anti-fog and anti-fouling coating. In Example 9, the dosage of the L-lysine solution is too large, which easily leads to intermolecular aggregation, forming micelles, hindering the dispersion of nanocellulose, resulting in a decrease in the light transmittance of the anti-fog and anti-fouling coating. At the same time, too many amino groups will also interfere with the charge balance, affecting the anti-fouling performance of the anti-fog and anti-fouling coating.

[0201] From the test results of Example 1, Example 10 and Example 11, it can be seen that the test data of Example 10 and Example 11 are inferior to those of Example 1. This is because the polyacrylic acid chain segment is responsible for constructing the elastic cross-linked network of the coating. In Example 10, the mass fraction of the polyacrylic acid aqueous solution is too low, resulting in insufficient polymer chain segments and inability to form an effective cross-linked network, ultimately causing the structure of the anti-fog and anti-fouling coating to be loose and the adhesion to be poor. In Example 11, the mass fraction of the polyacrylic acid aqueous solution is too high, making the polymer chain segments overly entangled, hindering the dispersion of nanocellulose, and ultimately causing the brittleness of the anti-fog and anti-fouling coating to increase, the light transmittance to decrease, and the hardness to decrease.

[0202] From the test results of Example 1, Example 12 and Example 13, it can be seen that the test data of Example 12 and Example 13 are inferior to those of Example 1. This is because Fe 3+Constructing a three-dimensional network through octahedral coordination. In Example 12, the mass fraction of the iron chloride aqueous solution was too low, resulting in insufficient crosslinking, ultimately causing the structure of the anti-fog and anti-fouling coating to be loose, the adhesion to be poor, and the anti-fog time to be shortened; in Example 13, the mass fraction of the iron chloride aqueous solution was too high, causing metal ion aggregation and generating stress concentration points, ultimately resulting in a decrease in the flexibility of the anti-fog and anti-fouling coating, an increase in the contact angle, and a decrease in the adhesion.

[0203] From the test results of Example 1, Example 14, and Example 15, it can be seen that the test data of Example 14 and Example 15 are inferior to those of Example 1. This is because the proportion of zwitterionic nanocellulose determines the matching degree between the rigid skeleton and the flexible matrix of the anti-fog and anti-fouling coating. In Example 14, the volume proportion of the zwitterionic nanocellulose solution was too low, resulting in insufficient support force of the zwitterionic nanocellulose as the skeleton material, ultimately causing the structure of the anti-fog and anti-fouling coating to be unstable and the mechanical properties to decline; in Example 15, the volume proportion of the zwitterionic nanocellulose solution was too high, causing uneven dispersion of the zwitterionic nanocellulose and forming aggregates, which affected the light transmittance and anti-algae rate of the anti-fog and anti-fouling coating.

[0204] The applicant declares that the above-mentioned is only the specific implementation manner 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 any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing an anti-fog and anti-fouling coating based on nanocellulose, characterized in that: The preparation method comprises: The nanocellulose solution is subjected to oxidation treatment to obtain an oxidized nanocellulose solution; the oxidized nanocellulose solution is subjected to carboxyl activation treatment using a mixed solution of 1-ethyl-(3-dimethylaminopropyl)carbodiimide / N-hydroxysuccinimide to obtain an activated nanocellulose solution; the activated nanocellulose solution is subjected to graft modification treatment using L-lysine to obtain a zwitterionic nanocellulose solution; The zwitterionic nanocellulose solution, the hydrophilic polymer solution, the metal ion crosslinking agent solution and the composite solvent are uniformly mixed to obtain a composite coating liquid, the composite coating liquid is applied to the surface of a substrate, and the anti-fog and anti-fouling coating is formed on the surface of the substrate after drying.

2. The preparation method according to claim 1, characterized in that: The operation steps of the oxidation treatment of the nanocellulose solution include: The TEMPO catalyst, sodium bromide and borate buffer are mixed evenly to obtain a catalyst solution, and the nanocellulose solution and the catalyst solution are mixed evenly to obtain a composite solution; sodium hypochlorite solution is added to the composite solution under stirring conditions and an ice water bath environment, and the mixture is mixed and stirred to react, and after the reaction is completed, the oxidized nanocellulose solution is obtained after filtering through a filter membrane; The mass fraction of TEMPO catalyst in the catalyst solution is 0.2-0.4wt%; The mass fraction of sodium bromide in the catalyst solution is 0.8-1.2wt%; The pH value of the borate buffer is 9 to 10.5; The mass fraction of the nanocellulose solution is 0.5-1.5wt%; The mass ratio of the nanocellulose solution to the catalyst solution is (9-10):1; The temperature of the ice water bath environment is 5-10°C; The mass fraction of the sodium hypochlorite solution is 10-12wt%; The mass ratio of the composite solution to the sodium hypochlorite solution is 1:(0.8-1.2); The mixing time of the composite solution and the sodium hypochlorite solution is 5 to 6 hours; The mixing speed of the composite solution and the sodium hypochlorite solution is 300-400 rpm; The pore size of the filter membrane is 0.3-0.4 μm.

3. The preparation method according to claim 1, characterized in that: The operation steps of the carboxyl activation treatment include: The oxidized nanocellulose solution is mixed with MES buffer and then ultrasonically dispersed to obtain an oxidized nanocellulose suspension; 1-ethyl-(3-dimethylaminopropyl)carbodiimide is added to the oxidized nanocellulose suspension, and N-hydroxysuccinimide is added after mixing evenly, and the mixture is mixed and stirred under light-proof conditions to react, and after the reaction is completed, the activated nanocellulose solution is obtained by filtering through a filter membrane.

4. The preparation method according to claim 3, characterized in that: The pH value of the MES buffer is 4.5-5.5; The mass ratio of the oxidized nanocellulose solution to the MES buffer is 1:(3-4); The ultrasonic power of the ultrasonic dispersion is 200-300W; The ultrasonic dispersion time is 30 to 50 minutes; The mass ratio of the oxidized nanocellulose suspension to the 1-ethyl-(3-dimethylaminopropyl)carbodiimide is (15-20):1; The molar ratio of 1-ethyl-(3-dimethylaminopropyl)carbodiimide to N-hydroxysuccinimide is 1:(1-2); The mixing temperature is 20-30°C; The mixing time is 3 to 4 hours; The mixing and stirring method is magnetic stirring; The mixing speed is 400-500 rpm; The pore size of the filter membrane is 0.2-0.3 μm.

5. The preparation method according to claim 1, characterized in that: The operation steps of the graft modification treatment include: L-lysine is dissolved in phosphate buffer to obtain an L-lysine solution, the activated nanocellulose solution and the L-lysine solution are evenly mixed to obtain a mixed solution, the mixed solution is mixed and stirred under light-proof conditions to react, and after the reaction is completed, it is filtered through a filter membrane to obtain the zwitterionic nanocellulose solution.

6. The preparation method according to claim 5, characterized in that: The pH value of the phosphate buffer is 7-7.8; The mass fraction of L-lysine in the L-lysine solution is 3-4wt%; The mass ratio of the activated nanocellulose solution to the L-lysine solution is 1:(1.3-1.5); The mixing and stirring temperature of the mixed solution is 25-35°C; The mixing and stirring time of the mixed solution is 10 to 12 hours; The mixing and stirring method of the mixed solution is magnetic stirring; The mixing and stirring speed of the mixed solution is 500-600 rpm; The pore size of the filter membrane is 0.2-0.3 μm.

7. The preparation method according to claim 1, characterized in that: The hydrophilic polymer solution consists of a hydrophilic polymer and deionized water; The hydrophilic polymer includes polyacrylic acid; The mass fraction of the hydrophilic polymer solution is 3-5wt%; The metal ion cross-linking agent solution is composed of metal inorganic salt and deionized water; The metal ions in the metal inorganic salt include Fe 3+ 、Zn 2+ , Cu 2+ 、Al 3+ or V 3+ Any one or a combination of at least two of the following: The mass fraction of the metal ion crosslinking agent solution is 0.5-1.5wt%.

8. The preparation method according to claim 1, characterized in that: The composite solvent comprises deionized water, ethanol, propylene glycol and polysorbate additives; In the composite solvent, the volume ratio of deionized water, ethanol, propylene glycol and polysorbate additive is (15-30):(50-60):(5-10):(0.1-1); The polysorbate adjuvant includes Tween 20 and / or Tween 80.

9. The preparation method according to claim 1, characterized in that: In the composite coating solution, the volume ratio of the zwitterionic nanocellulose solution, the hydrophilic polymer solution, the metal ion crosslinking agent solution and the composite solvent is (15-25):(10-20):(5-10):(60-70); The coating method of the composite coating liquid includes spin coating, dip coating or spray coating; The coating thickness of the composite coating liquid is 30-40 μm; The drying method is gradient drying, including a pre-drying stage, a drying stage and a curing stage performed in sequence; The heating temperature in the pre-drying stage is 20-30°C; The pre-drying stage heat preservation time is 20 to 30 minutes; The heating temperature in the drying stage is 35-45°C; The heat preservation time of the drying stage is 1 to 1.5 hours; The heating temperature in the curing stage is 50-60°C; The heat preservation time of the curing stage is 20 to 30 minutes.

10. An anti-fog and anti-fouling coating based on nanocellulose prepared by the preparation method according to any one of claims 1 to 9.

Images