Super-hydrophobic material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of oily sewage treatment, and discloses a super-hydrophobic material and a preparation method and application thereof.The super-hydrophobic material comprises a substrate and a composite coating coated on the surface of the substrate, and the composite coating is a polymer network formed by a chain polymer and a polyphenol polymer modified by a hydrophobic unit through hydrogen bonds; the polyphenol polymer is a polymer of a catechol compound and / or a pyrogallol compound. The super-hydrophobic material has excellent mechanical stability and self-repairing capability, and has excellent and stable oil-water separation efficiency when being used for oil-water separation.

Description

Superhydrophobic materials, their preparation methods and applications Technical Field

[0001] This invention relates to the field of oily wastewater treatment technology, specifically to a superhydrophobic material, its preparation method, and its application. Background Technology

[0002] Oily wastewater treatment has long been a major technological challenge in the field of industrial and domestic wastewater treatment. Traditional oil-water separation technologies, such as gravity sedimentation, flotation, adsorption, and electrochemical methods, generally suffer from high energy consumption, low efficiency, secondary pollution, and poor treatment effects on emulsified and dissolved oils. Superhydrophobic / superoleophilic materials possess unique surface wettability (water contact angle > 150°, oil contact angle ≈ 0°), offering significant advantages over traditional methods, including ease of operation and low energy consumption, demonstrating great potential in the field of oil-water separation.

[0003] Currently, the mainstream method for preparing superhydrophobic materials involves loading perfluorinated compounds or polysiloxanes onto a substrate using methods such as physical spraying, spin coating, or impregnation to form a hydrophobic coating on the substrate surface. However, the adhesion between the coating and the substrate in superhydrophobic materials prepared by these methods is relatively weak. In practical use, the coating can wear down or even detach due to water erosion, mechanical friction, and pressure, causing a rapid decline in the oil-water separation capability of the superhydrophobic material. Therefore, providing a superhydrophobic material with stable mechanical properties and oil-water separation capability is of great significance. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low mechanical stability and unstable oil-water separation ability of existing superhydrophobic materials, and to provide a superhydrophobic material, its preparation method and application. This superhydrophobic material has excellent mechanical stability and self-healing ability, and has excellent and stable oil-water separation efficiency when used for oil-water separation.

[0005] To achieve the above objectives, the first aspect of the present invention provides a superhydrophobic material, comprising a substrate and a composite coating coated on the surface of the substrate, wherein the composite coating is a polymer network formed by a chain polymer and a polyphenol polymer modified with hydrophobic units through hydrogen bonds, and the polyphenol polymer is a polymer of catechol compounds and / or pyrogallol compounds.

[0006] The second aspect of the present invention provides a method for preparing a superhydrophobic material, comprising the following steps: (1) contacting a substrate with an alkaline solution containing catechol compounds and / or pyrogallol compounds, wherein the catechol compounds and / or pyrogallol compounds undergo oxidative self-polymerization to obtain a material coated with a first coating, wherein the pH of the alkaline solution is ≥8; (2) contacting the chain polymer with the material coated with the first coating in a liquid medium and performing a first heat treatment to obtain a material coated with a second coating; (3) immersing the material coated with the second coating in a solution containing a hydrophobic modifier and performing a second heat treatment to obtain a superhydrophobic material.

[0007] A third aspect of the present invention provides a superhydrophobic material prepared by the preparation method described in the second aspect of the present invention.

[0008] The fourth aspect of this invention provides an application of the superhydrophobic material described in the first or third aspect of this invention in oil-water separation.

[0009] The composite coating of the superhydrophobic material of this invention is a polymer network composed of chain polymers and polyphenol polymers modified with hydrophobic units. On the one hand, the polyphenol polymers contain abundant phenolic hydroxyl groups, which simultaneously form hydrogen bonds with multiple chain polymers, increasing the crosslinking density of the polymer network and enhancing the mechanical stability of the superhydrophobic material. Simultaneously, the chain polymers and the substrate exhibit non-covalent interactions such as hydrogen bonding and van der Waals forces, further enhancing the adhesion between the composite coating and the substrate and strengthening the mechanical stability of the superhydrophobic material. On the other hand, when the composite coating suffers mechanical damage leading to localized hydrogen bond breakage, the chain polymers migrate and rearrange towards the damaged area under the drive of molecular thermal motion, causing the broken functional groups to re-form hydrogen bonds, thereby endowing the superhydrophobic material with self-healing capabilities, extending its service life, and enabling it to exhibit stable and high oil-water separation efficiency when used for oil-water separation.

[0010] The superhydrophobic material of this invention exhibits an initial water contact angle higher than 155°, demonstrating excellent hydrophobic properties. After 100 cycles of mechanical friction, the water contact angle remains above 150°; after 5000 cycles of mechanical extrusion, the water contact angle remains above 150°; and after 10000 cycles of mechanical extrusion, the water contact angle remains above 140°, indicating good mechanical stability. Furthermore, the superhydrophobic material of this invention possesses excellent self-healing capabilities, with a self-healing efficiency exceeding 90%. This superhydrophobic material can be used for oil-water separation, achieving an initial oil-water separation efficiency exceeding 99%. Even after 100 cycles of mechanical friction and subsequent self-healing, the oil-water separation efficiency remains above 95%, demonstrating that the superhydrophobic material of this invention exhibits excellent and stable oil-water separation efficiency. Detailed Implementation

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0012] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0013] In this invention, room temperature refers to 25°C. In the structural formula, " "As a whole, it indicates the binding site of the group, not the methyl group."

[0014] Chain polymers include linear polymers and branched polymers, but exclude three-dimensional polymers.

[0015] Catechols are a class of organic compounds with 1,2-dihydroxybenzene as their basic structural skeleton, and include their various substituted derivatives. Pyrogallols are a class of organic compounds with 1,2,3-trihydroxybenzene as their basic structural skeleton, and include their various substituted derivatives.

[0016] The first aspect of the present invention provides a superhydrophobic material, comprising a substrate and a composite coating coated on the surface of the substrate, wherein the composite coating is a polymer network formed by a chain polymer and a polyphenol polymer modified with hydrophobic units through hydrogen bonds, and the polyphenol polymer is a polymer of catechol compounds and / or pyrogallol compounds.

[0017] Polyphenol polymers contain abundant phenolic hydroxyl groups, which on the one hand have various non-covalent interactions with the substrate, thus adhering tightly to the substrate surface; on the other hand, they readily react with amines, thiols, isocyanates, and silanes, thereby achieving hydrophobic modification of the material.

[0018] Polyphenol polymers, through their abundant phenolic hydroxyl groups, simultaneously form hydrogen bonds with multiple chain polymers, increasing the crosslinking density of the polymer network and enhancing the mechanical stability of the superhydrophobic material. Simultaneously, the chain polymers and the substrate exhibit non-covalent interactions such as hydrogen bonding and van der Waals forces, further strengthening the adhesion between the composite coating and the substrate and enhancing the mechanical stability of the superhydrophobic material. When the composite coating suffers mechanical damage leading to localized hydrogen bond breakage, the chain polymers migrate and rearrange towards the damaged area under the drive of molecular thermal motion, causing the broken functional groups to re-form hydrogen bonds, thus endowing the superhydrophobic material with self-healing capabilities and extending its service life.

[0019] In some embodiments, preferably, the thickness of the composite coating is 200-500 nm. When the thickness of the composite coating is within the above range, the superhydrophobic material exhibits both high oil-water separation efficiency and oil phase flux. The thickness of the composite coating can be any value between any two of the following: 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, and 500 nm.

[0020] In some embodiments, preferably, based on the total mass of the composite coating, the content of the chain polymer is 34-90 wt%, the content of the polyphenol polymer is 8-47 wt%, and the content of the hydrophobic unit is 1-33 wt%.

[0021] By adjusting the content of chain polymers, polyphenol polymers, and hydrophobic units, superhydrophobic materials can possess excellent hydrophobic properties, mechanical stability, and self-healing properties. Based on the total mass of the composite coating, the content of the chain polymer can be any value between any two of the following: 34 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 69 wt%, 75 wt%, 84 wt%, 90 wt%. The content of the polyphenol polymer can be any value between any two of the following: 8 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 47 wt%. The content of the hydrophobic units can be any value between any two of the following: 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 28 wt%, 33 wt%.

[0022] In some embodiments, preferably, the chain polymer is selected from at least one of chain polyhydroxy polymers, chain polycarboxylic polymers, chain polyamino polymers, and chain polyester polymers.

[0023] Chain-like polyhydroxy polymers, chain-like polycarboxyl polymers, chain-like polyamino polymers, and chain-like polyester polymers provide abundant hydroxyl, carboxyl, amino, or ester groups, which can form strong hydrogen bonds with the phenolic hydroxyl groups of polyphenol polymers, giving superhydrophobic materials excellent mechanical stability and self-healing ability.

[0024] In some embodiments, preferably, the chain-like polyhydroxy polymer is selected from at least one of polyvinyl alcohol, agarose, polyethylene glycol, and chitosan.

[0025] In some embodiments, preferably, the number-average molecular weight of the polyvinyl alcohol is 10,000-100,000 g / mol. The number-average molecular weight of the polyvinyl alcohol can be any value between any two of the following: 10,000 g / mol, 20,000 g / mol, 40,000 g / mol, 60,000 g / mol, 80,000 g / mol, and 100,000 g / mol.

[0026] In some embodiments, preferably, the number-average molecular weight of the polyethylene glycol is 2000-20000 g / mol. The number-average molecular weight of the polyethylene glycol can be any value between any two of the following: 2000 g / mol, 4000 g / mol, 8000 g / mol, 12000 g / mol, 16000 g / mol, and 20000 g / mol.

[0027] In some embodiments, preferably, the degree of deacetylation of the chitosan is not less than 85%. A higher degree of deacetylation of chitosan results in more free amino groups on the chitosan molecular chain, which can form hydrogen bonds with polyphenol polymers, further enhancing the mechanical stability and self-healing properties of the superhydrophobic material. The degree of deacetylation of chitosan can be any value between any two of 85%, 90%, 95%, and 100%.

[0028] In some embodiments, preferably, the chain-like polycarboxylic polymer is selected from at least one of polyacrylic acid, polymethacrylic acid, and polymaleic acid.

[0029] In some embodiments, preferably, the chain polyamino polymer is selected from polyethyleneamine and / or polyethyleneimine.

[0030] In some embodiments, preferably, the chain-like polyester polymer is selected from polylactic acid and / or polycaprolactone.

[0031] Polymers of pyrogallol compounds have more phenolic hydroxyl groups, resulting in stronger hydrogen bonding with chain polymers and a greater number of hydrophobic units that can be connected. Consequently, the superhydrophobic materials exhibit better hydrophobic properties, mechanical stability, and self-healing capabilities.

[0032] In some embodiments, preferably, the catechol compound is selected from catechol, , , , , , At least one of them.

[0033] In some embodiments, preferably, the pyrogallol compound is selected from pyrogallol, tannic acid, and... At least one of them.

[0034] and , and As a chiral isomer, this invention has no special requirements for molecular configuration; R configuration, S configuration, or a mixture of both configurations are acceptable.

[0035] In some embodiments, preferably, the hydrophobic unit is selected from... At least one of -NH-R3, -S-R4, -OC(=O)-NH-R5, wherein R2 is selected from C 10 -C 20 Alkyl or C6-C 20 Perfluoroalkyl groups, R3, R4, and R5 are each independently selected from C10. 10 -C 20 Alkyl groups. Hydrophobic units with long alkyl chains significantly improve the hydrophobic properties of materials.

[0036] The superhydrophobic material of the present invention does not limit the type of substrate. In some embodiments, the substrate is preferably a porous substrate.

[0037] In some embodiments, preferably, the substrate is one of melamine sponge, polypropylene nonwoven fabric, stainless steel screen, and nylon filter membrane.

[0038] In some embodiments, preferably, the melamine sponge has an average pore size of 100-300 μm.

[0039] In some embodiments, preferably, the stainless steel screen has a mesh size of 100-300.

[0040] In some embodiments, preferably, the polyphenol polymer further includes transition metal ions, which are connected to catechol compounds and / or pyrogallol compounds through coordination bonds to enhance the crosslinking strength of the polymer network and improve the mechanical stability of the composite coating.

[0041] In some embodiments, preferably, the transition metal ion is selected from Fe. 3+ Fe2+ Cu 2+ Cu + Mn 2+ Mn 3+ Mn 4+ Ni 3+ Ni 2+ Co 3+ Co 2+ Zn 2+ At least one of them.

[0042] In some embodiments, preferably, the content of the transition metal ions is 0.00001-0.001 wt% based on the mass of the composite coating. Based on the mass of the composite coating, the content of the transition metal ions can be any value between any two of the following: 0.00001 wt%, 0.00005 wt%, 0.0001 wt%, 0.0003 wt%, 0.0005 wt%, 0.0007 wt%, and 0.001 wt%.

[0043] The second aspect of the present invention provides a method for preparing a superhydrophobic material, comprising the following steps: (1) contacting a substrate with an alkaline solution containing catechol compounds and / or pyrogallol compounds, wherein the catechol compounds and / or pyrogallol compounds undergo oxidative self-polymerization to obtain a material coated with a first coating, wherein the pH of the alkaline solution is ≥8; (2) contacting the chain polymer with the material coated with the first coating in a liquid medium and performing a first heat treatment to obtain a material coated with a second coating; (3) immersing the material coated with the second coating in a solution containing a hydrophobic modifier and performing a second heat treatment to obtain a superhydrophobic material.

[0044] Catechols and / or pyrogallols undergo oxidative self-polymerization under pH ≥ 8 conditions, generating polyphenol polymers in situ on the substrate surface. Compared with traditional methods such as spraying and spin coating, they exhibit stronger adhesion to the substrate.

[0045] This invention successfully constructs a polymer network dynamically cross-linked by hydrogen bonds by contacting a chain polymer with the material coated with a first coating and subjecting it to a first heat treatment. This not only enhances the mechanical stability of the superhydrophobic material but also endows it with self-healing capabilities, thereby extending its service life. Bulk polymers, with their network structure, are difficult to dissolve and fully contact with polyphenol polymers, and have fewer functional groups capable of forming hydrogen bonds with polyphenol polymers, making them unsuitable for constructing the polymer network of this invention.

[0046] The hydrophobic properties of the material are further significantly improved through hydrophobic modification to obtain the superhydrophobic material of the present invention.

[0047] The present invention does not have any particular limitation on the type of substrate. It can be a porous substrate such as melamine sponge, or a non-porous substrate such as stainless steel plate.

[0048] In some embodiments, preferably, the substrate is one of melamine sponge, polypropylene nonwoven fabric, stainless steel screen, and nylon filter membrane.

[0049] In some embodiments, preferably, the melamine sponge has an average pore size of 100-300 μm.

[0050] In some embodiments, preferably, the stainless steel screen has a mesh size of 100-300.

[0051] Before the substrate is brought into contact with an alkaline solution containing catechol compounds and / or pyrogallol compounds, it needs to be pretreated. The pretreatment method is a conventional method in the art, such as placing the substrate in acetone, anhydrous ethanol and deionized water in sequence for ultrasonic treatment to remove surface contaminants, and then drying it in an oven.

[0052] In some embodiments, preferably, the alkaline solution also contains transition metal ions. Transition metal ions can act as catalysts to accelerate the oxidative self-polymerization of catechols and / or pyrogallols.

[0053] In some embodiments, preferably, the transition metal ion is selected from Fe. 3+ Fe 2+ Cu 2+ Cu + Mn 2+ Mn 3+ Mn 4+ Ni 3+ Ni 2+ Co 3+ Co 2+ Zn 2+ At least one of the following. High-valence metal ions can rapidly oxidize the catechol structure and / or pyrogallol structure, while being reduced to a low-valence state themselves, and then rapidly oxidized to a high-valence state by oxygen. This valence state conversion increases the oxidation rate of the catechol structure, thereby increasing the oxidative self-polymerization rate.

[0054] In some embodiments, preferably, the mass ratio of the transition metal ion to the catechol compound and / or pyrogallol compound is 1:50,000-500,000. Within this range, the transition metal ion effectively catalyzes the oxidative self-polymerization reaction of the catechol compound and / or pyrogallol compound, while avoiding excessive coordination of the transition metal ion with its intermediate, which would hinder further polymerization of the intermediate. The mass ratio of the transition metal ion to the catechol compound and / or pyrogallol compound can be any value between any two numbers selected from 1:50,000, 1:100,000, 1:150,000, 1:200,000, 1:250,000, 1:300,000, 1:350,000, 1:400,000, 1:450,000, and 1:500,000.

[0055] In some embodiments, preferably, the catechol compound is selected from catechol, , , , , , At least one of them.

[0056] In some embodiments, preferably, the pyrogallol compound is selected from pyrogallol, tannic acid, and... At least one of them.

[0057] and , and As a chiral isomer, this invention has no special requirements for molecular configuration; R configuration, S configuration, or a mixture of both configurations are acceptable.

[0058] In some embodiments, preferably, the concentration of the catechol compound and / or pyrogallol compound in the alkaline solution is 0.5-10 g / L. The concentration of the catechol compound and / or pyrogallol compound in the alkaline solution can be any value between any two of the following: 0.5 g / L, 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 8 g / L, and 10 g / L.

[0059] In some embodiments, preferably, the concentration of the catechol compound and / or pyrogallol compound in the alkaline solution is 3-6 g / L.

[0060] In some embodiments, preferably, the volume of the alkaline solution is 100-400 mL.

[0061] In some embodiments, preferably, the volume (mL) of the alkaline solution is proportional to the surface area (mm) of the substrate.2 The ratio is 0.1-3:1.

[0062] By adjusting the concentrations of catechol compounds and / or pyrogallol compounds in the alkaline solution, and the volume (mL) of the alkaline solution relative to the surface area (mm) of the substrate... 2 The ratio of polyphenols to the content of polyphenols in the composite coating is adjusted to ensure uniform adhesion of the polyphenol polymer to the substrate and thus affect the hydrophobic properties, mechanical stability and self-healing properties of the superhydrophobic material.

[0063] In some embodiments, preferably, the pH of the alkaline solution is 8.5-10. When the pH of the alkaline solution is within this range, catechol compounds and / or pyrogallol compounds exhibit suitable polymerization rates, which is beneficial for forming a uniform polyphenol polymer coating on the substrate surface. This results in a superhydrophobic material with excellent mechanical stability and stable hydrophobic properties, thus extending the service life of the superhydrophobic material. The pH of the alkaline solution can be any value between any two numbers from 8.5, 8.7, 9, 9.2, 9.5, 9.7, and 10.

[0064] In some embodiments, preferably, the reaction temperature for oxidative self-polymerization is 20-80 °C. Oxidative self-polymerization can be carried out under mild reaction conditions, and increasing the temperature can accelerate the reaction rate. The reaction temperature for oxidative self-polymerization can be any value between any two of the following: 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C.

[0065] In some embodiments, preferably, the reaction temperature of the oxidative self-polymerization is 20-30 °C. A reaction temperature within this range is beneficial for forming a uniform polyphenol polymer coating on the substrate surface, thereby obtaining a superhydrophobic material with excellent mechanical stability and stable hydrophobic properties.

[0066] In some embodiments, preferably, the reaction time for the oxidative self-polymerization is 6-48 h. The oxidative self-polymerization time can be any value between any two of the following: 6 h, 12 h, 18 h, 24 h, 30 h, 36 h, 42 h, and 48 h.

[0067] In some embodiments, preferably, after oxidative self-polymerization, loosely attached oligomers or unreacted small molecules on the first coating are removed using conventional methods in the art, such as rinsing with deionized water for 10-20 minutes. This is followed by further drying using conventional methods in the art, such as drying in an oven at 50-80 °C for at least 2 hours.

[0068] In some embodiments, preferably, the chain polymer is selected from at least one of chain polyhydroxy polymers, chain polycarboxylic polymers, chain polyamino polymers, and chain polyester polymers.

[0069] Chain-like polyhydroxy polymers, chain-like polycarboxyl polymers, chain-like polyamino polymers, and chain-like polyester polymers provide abundant hydroxyl, carboxyl, amino, or ester groups, which can form strong hydrogen bonds with the phenolic hydroxyl groups of polyphenol polymers, giving superhydrophobic materials excellent mechanical stability and self-healing ability.

[0070] In some embodiments, preferably, the chain-like polyhydroxy polymer is selected from at least one of polyvinyl alcohol, agarose, polyethylene glycol, and chitosan.

[0071] When the number average molecular weight of polyvinyl alcohol and polyethylene glycol is too low, they are not easy to form a network structure. When it is too high, their solubility is poor, which is not conducive to sufficient contact with polyphenol polymers to form hydrogen bonds. Selecting a suitable number average molecular weight of polyvinyl alcohol and polyethylene glycol is beneficial to obtaining superhydrophobic materials with excellent mechanical stability and self-healing properties.

[0072] In some embodiments, preferably, the number-average molecular weight of the polyvinyl alcohol is 10,000-100,000 g / mol. The number-average molecular weight of the polyvinyl alcohol can be any value between any two of the following: 10,000 g / mol, 20,000 g / mol, 40,000 g / mol, 60,000 g / mol, 80,000 g / mol, and 100,000 g / mol.

[0073] In some embodiments, preferably, the number-average molecular weight of the polyethylene glycol is 2000-20000 g / mol. The number-average molecular weight of the polyethylene glycol can be any value between any two of the following: 2000 g / mol, 4000 g / mol, 8000 g / mol, 12000 g / mol, 16000 g / mol, and 20000 g / mol.

[0074] In some embodiments, preferably, the degree of deacetylation of the chitosan is not less than 85%. A higher degree of deacetylation of chitosan results in a greater number of free amino groups in the chitosan molecular chain, which improves the solubility of chitosan, facilitates sufficient contact between chitosan and polyphenol polymers, and allows the free amino groups to form hydrogen bonds with the polyphenol polymers, further enhancing the mechanical stability and self-healing properties of the superhydrophobic material. The degree of deacetylation of chitosan can be any value between any two of 85%, 90%, 95%, and 100%.

[0075] In some embodiments, preferably, the chain-like polycarboxylic polymer is selected from at least one of polyacrylic acid, polymethacrylic acid, and polymaleic acid.

[0076] In some embodiments, preferably, the chain polyamino polymer is selected from polyethyleneamine and / or polyethyleneimine.

[0077] In some embodiments, preferably, the chain-like polyester polymer is selected from polylactic acid and / or polycaprolactone.

[0078] In some embodiments, preferably, the mass ratio of the chain polymer to the catechol compound and / or pyrogallol compound is 1-10:1. When the mass ratio of the chain polymer to the catechol compound and / or pyrogallol compound is within the above range, a high-crosslink density hydrogen bond network is formed, which improves the mechanical stability and self-healing properties of the superhydrophobic material, while reserving connection sites and space for hydrophobic units, thus balancing hydrophobic properties with mechanical stability and self-healing properties. The mass ratio of the chain polymer to the catechol compound and / or pyrogallol compound can be any value between any two numbers from 1:1, 2:1, 3:1, 4:1, 5:1, 8:1, and 10:1.

[0079] In some embodiments, preferably, the mass ratio of the chain polymer to the catechol compound and / or pyrogallol compound is 2-5:1.

[0080] The method of contacting the chain polymer with the material coated by the first coating in a liquid medium includes: adding the material coated by the first coating to a chain polymer solution, wherein the liquid medium is the solvent of the chain polymer solution.

[0081] In some embodiments, preferably, the free chain polymers adsorbed on the material surface are removed before the first heat treatment. The removal method is a conventional method in the art, such as rinsing with deionized water for 10-20 minutes.

[0082] In some embodiments, preferably, the temperature of the first heat treatment is 40-150 °C.

[0083] The first heat treatment removes water molecules from the coating, releasing hydrogen bond sites occupied by water molecules. Simultaneously, it promotes the movement of the chain polymer molecules, enabling the chain polymer to form hydrogen bonds with the phenolic hydroxyl groups on multiple polyphenol polymers. This increases the hydrogen bond crosslinking density and improves the mechanical stability of the superhydrophobic material. The temperature of the first heat treatment should not be too high to avoid carbonization of the chain polymer and polyphenol polymer. The temperature of the first heat treatment can be any value between any two of the following: 40℃, 60℃, 80℃, 100℃, 120℃, 130℃, and 150℃.

[0084] In some embodiments, preferably, the temperature of the first heat treatment is 60-120 °C.

[0085] In some embodiments, preferably, the first heat treatment time is 2-16 hours. The first heat treatment time can be any value between any two of the following: 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, and 16 hours.

[0086] In some embodiments, preferably, the first heat treatment time is 6-14 h.

[0087] In some embodiments, preferably, the mass ratio of the hydrophobic modifier to the catechol compound and / or pyrogallol compound is 0.1-1:1. When the mass ratio of the hydrophobic modifier to the catechol compound and / or pyrogallol compound is within the above range, the hydrophobic units in the composite coating have a suitable content, thereby enabling the superhydrophobic material to possess excellent hydrophobic properties, mechanical stability, and self-healing properties. The mass ratio of the hydrophobic modifier to the catechol compound and / or pyrogallol compound can be any value between any two numbers from 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.8:1, and 1:1.

[0088] In some embodiments, preferably, the hydrophobic modifier is selected from... At least one of R1-NH2, R4-SH, and R5-N=C=O, wherein R1 is selected from C1-C5 alkyl groups and R2 is selected from C 10 -C 20 Alkyl or C6-C 20 Perfluoroalkyl groups, R3, R4, and R5 are each independently selected from C10. 10 -C 20 alkyl.

[0089] When the hydrophobic modifier is R3-NH2, R4-SH, or R5-N=C=O, the hydrophobic modifier undergoes an addition reaction with the phenolic hydroxyl groups of the polyphenol polymer. When hydrolyzed into silanol, it further undergoes a condensation reaction with phenolic hydroxyl groups, thereby achieving hydrophobic modification of the material.

[0090] Before the second heat treatment, remove the unreacted hydrophobic modifier. The removal method is a conventional method in the art, such as rinsing with ethanol for 10-30 min in a constant temperature shaker at a frequency of 100-200 r / min at 20-30 ℃.

[0091] In some embodiments, preferably, the temperature of the second heat treatment is 60-180 °C. When the temperature of the second heat treatment is within the above range, the reaction is more likely to occur, which is beneficial for hydrophobic modification and thus obtaining a superhydrophobic material with excellent hydrophobic properties. The temperature of the second heat treatment can be any value between any two numbers selected from 60 °C, 80 °C, 100 °C, 120 °C, 130 °C, 150 °C, and 180 °C.

[0092] In some embodiments, preferably, the temperature of the second heat treatment is 120-160°C.

[0093] In some embodiments, preferably, the second heat treatment time is 6-24 hours. The second heat treatment time can be any value between any two of the following: 6 hours, 8 hours, 12 hours, 16 hours, 20 hours, and 24 hours.

[0094] A third aspect of the present invention provides a superhydrophobic material prepared by the preparation method described in the second aspect of the present invention.

[0095] The fourth aspect of this invention provides an application of the superhydrophobic material described in the first or third aspect of this invention in oil-water separation.

[0096] The present invention will be described in detail below through embodiments. In the following embodiments, surface SEM images and cross-sectional SEM images of the superhydrophobic material were obtained using a ZEISS Sigma 300 scanning electron microscope. The coating thickness of the superhydrophobic material was obtained by analyzing the cross-sectional SEM images. The water contact angle of the superhydrophobic material was measured using a Dataphysics OCA20 contact angle measuring instrument; mechanical friction testing was performed using a Taber 5135 abrasion tester, and mechanical extrusion testing was performed using a Shimadzu AG-Xplus universal testing machine.

[0097] The mass of the composite coating and the mass of each component in the composite coating are obtained by weighing the substrate, the material coated with the first coating, the material coated with the second coating, and the superhydrophobic material separately, and then using the difference weighing method. The ratio of the mass of each component to the mass of the composite coating is the content of each component in the composite coating. When the composite coating also includes transition metal ions, the mass of the transition metal ions is obtained by weighing the remaining ash mass after the composite coating is completely burned and then converting it. The mass of the polyphenol polymer is obtained by subtracting the mass of the substrate and the mass of the transition metal ions from the mass of the material coated with the first coating in sequence. The ratio of the mass of the transition metal ions or the mass of the polyphenol polymer to the mass of the composite coating is the content of the transition metal ions or polyphenol polymer based on the composite coating.

[0098] All reagents used in this invention are commercially available products.

[0099] Example 1 (1) A 16.2 mg / L ferric chloride solution was prepared by dissolving ferric chloride in water. 1.0 g of tannic acid was weighed and dissolved in water. 1 mL of the ferric chloride solution was added, and the pH was adjusted to 10 by adding borate buffer to prepare a 200 mL alkaline solution. A white circular melamine sponge with an average pore size of 200 μm and a diameter of Ф10 mm × 10 mm was placed in acetone, anhydrous ethanol, and deionized water in sequence, and ultrasonically cleaned for 15 min in each solution. It was then dried in a 60 ℃ oven for 5 h, and then completely immersed in the above alkaline solution and shaken at 25 ℃ for 48 h. The sponge was then removed, rinsed with deionized water for 15 min, and dried in a 60 ℃ oven for 5 h to obtain the material coated with the first coating.

[0100] (2) Dissolve 3.0 g of polyvinyl alcohol with a number average molecular weight of 50,000 g / mol in water to prepare a 200 mL polyvinyl alcohol solution. Place the material coated with the first coating in the polyvinyl alcohol solution and shake at 40 °C for 12 h. Take it out and rinse it with deionized water for 15 min. Perform the first heat treatment at 100 °C for 12 h to obtain the material coated with the second coating.

[0101] (3) Dissolve 0.5 g of octadecyltrimethoxysilane in ethanol to prepare a 100 mL solution. Immerse the material coated with the second coating in the solution and let it stand at room temperature for 8 h. Take it out and rinse it with ethanol for 20 min in a constant temperature shaker at 25 ℃ with an oscillation frequency of 150 r / min. Take it out and perform a second heat treatment at a temperature of 120 ℃ for 6 h to obtain a superhydrophobic material with a composite coating thickness of 282 nm. Based on the total mass of the composite coating, the content of the chain polymer is 66.70630 wt%, the content of the polyphenol polymer is 22.21025 wt%, the content of the hydrophobic unit is 11.08333 wt%, and the content of the transition metal ion is 0.00012 wt%.

[0102] Example 2 (1) Weigh 1.1 g of catechol and dissolve it in water. Add borate buffer to adjust the pH to 9 and prepare 200 mL of alkaline solution. Place a 200 mesh, Ф10 mm × 0.05 mm stainless steel sieve in acetone, anhydrous ethanol and deionized water in sequence, sonicate each for 10 min, blow dry with nitrogen gas, and then completely immerse it in the above alkaline catechol solution. Shake at 30 °C for 48 h, take it out and rinse with deionized water for 15 min, and place it in a 60 °C oven to dry for 5 h to obtain the material coated with the first coating.

[0103] (2) Dissolve 3g of chitosan with a degree of deacetylation of 90% in water to prepare a chitosan solution of 200 mL. Place the material coated with the first coating in the chitosan solution and shake at 40 °C for 5 h. Then take it out, rinse it with deionized water for 15 min, and perform the first heat treatment at 70 °C for 8 h to obtain the material coated with the second coating.

[0104] (3) Dissolve 0.3 g of perfluorooctyltriethoxysilane in ethanol to prepare a 100 mL solution. Immerse the material coated with the second coating in the solution and let it stand at room temperature for 4 h. Take it out and rinse it with ethanol for 20 min in a constant temperature shaker at 25 ℃ with an oscillation frequency of 150 r / min. Take it out and perform a second heat treatment at a temperature of 150 ℃ for 6 h to obtain a superhydrophobic material with a composite coating thickness of 250 nm. Based on the total mass of the composite coating, the content of the chain polymer is 68.2 wt%, the content of the polyphenol polymer is 25 wt%, and the content of the hydrophobic unit is 6.8 wt%.

[0105] Example 3 was carried out according to the method of Example 1, except that the amount of polyvinyl alcohol powder added was 0.5 g, so that the mass ratio of the chain polymer to catechol and / or pyrogallol compounds was 0.5:1. The composite coating of the superhydrophobic material prepared in Example 3 had a thickness of 210 nm. Based on the total mass of the composite coating, the content of the chain polymer was 24.99993 wt%, the content of the polyphenol polymer was 49.99986 wt%, the content of the hydrophobic unit was 24.99993 wt%, and the content of the transition metal ion was 0.00028 wt%.

[0106] Example 4 was carried out according to the method of Example 1, except that the amount of polyvinyl alcohol powder added was 8 g, so that the mass ratio of the chain polymer to catechol and / or pyrogallol compounds was 8:1. The composite coating of the superhydrophobic material prepared in Example 4 had a thickness of 486 nm. Based on the total mass of the composite coating, the content of the chain polymer was 84.21048 wt%, the content of the polyphenol polymer was 10.52631 wt%, the content of the hydrophobic unit was 5.26315 wt%, and the content of the transition metal ion was 0.00006 wt%.

[0107] Example 5 was performed according to the method of Example 1, except that the temperature of the first heat treatment was 40°C. The composite coating of the superhydrophobic material prepared in Example 5 had a thickness of 263 nm. Based on the total mass of the composite coating, the content of the chain polymer was 58.48267 wt%, the content of the polyphenol polymer was 20.08654 wt%, the content of the hydrophobic unit was 21.43068 wt%, and the content of the transition metal ion was 0.00011 wt%.

[0108] Example 6 was performed according to the method of Example 1, except that the temperature of the first heat treatment was 200°C. The composite coating of the superhydrophobic material prepared in Example 6 had a thickness of 254 nm. Based on the total mass of the composite coating, the content of the chain polymer was 55.24157 wt%, the content of the polyphenol polymer was 18.35279 wt%, the content of the hydrophobic unit was 26.40551 wt%, and the content of the transition metal ion was 0.00013 wt%.

[0109] Comparative Example 1 (1) Ferric chloride was dissolved in water to prepare a 16.2 mg / L ferric chloride solution. 1.0 g of tannic acid was weighed and dissolved in water. 1 mL of ferric chloride solution was added, and borate buffer was added to adjust the pH to 10 to prepare a 200 mL alkaline tannic acid solution. A white circular melamine sponge with an average pore size of 200 μm and a diameter of Ф10 mm × 10 mm was placed in acetone, anhydrous ethanol, and deionized water in sequence. Each sponge was ultrasonically cleaned for 15 min, dried in a 60 ℃ oven for 5 h, and then completely immersed in the above alkaline tannic acid solution. The sponge was shaken at 25 ℃ for 48 h, rinsed with deionized water for 15 min, and dried in a 60 ℃ oven for 5 h to obtain the material coated with the first coating.

[0110] (2) Dissolve 0.5 g of octadecyltrimethoxysilane in ethanol to prepare a 100 mL solution. Immerse the material coated with the first coating in the solution and let it stand at room temperature for 8 h. Take it out and rinse it with ethanol for 20 min in a constant temperature shaker at 25 ℃ with an oscillation frequency of 150 r / min. Take it out and perform a second heat treatment at a temperature of 120 ℃ for 6 h to obtain a superhydrophobic material.

[0111] Comparative Example 2 was carried out according to the method of Example 1, except that the first heat treatment was not performed.

[0112] Comparative Example 3 (1) 3.0 g of polyvinyl alcohol with a number average molecular weight of 50,000 g / mol was dissolved in 200 mL of water to prepare a polyvinyl alcohol solution. White circular melamine sponges with an average pore size of 200 μm and a diameter of Ф10 mm × 10 mm were placed in acetone, anhydrous ethanol and deionized water in sequence, and ultrasonically cleaned for 15 min each. They were then dried in an oven at 60 ℃ for 5 h. After that, they were completely immersed in the above polyvinyl alcohol solution and shaken at 40 ℃ for 12 h. They were then taken out, rinsed with deionized water for 15 min, and placed in an oven at 60 ℃ for 5 h.

[0113] (2) Prepare a 16.2 mg / L ferric chloride solution by dissolving ferric chloride in water. Weigh 1.0 g of tannic acid and dissolve it in water. Add 1 mL of the ferric chloride solution and adjust the pH to 10 with borate buffer to prepare a 200 mL alkaline solution. Completely immerse the sponge with the polyvinyl alcohol coating from step (1) in the alkaline solution and shake it at 25 °C for 48 h. Remove it and rinse it with deionized water for 15 min. Perform the first heat treatment at 100 °C for 12 h to obtain the material coated with the second coating.

[0114] (3) Dissolve 0.5 g of octadecyltrimethoxysilane in ethanol to prepare a 100 mL solution. Immerse the material coated with the second coating in the solution and let it stand at room temperature for 8 h. Take it out and rinse it with ethanol for 20 min in a constant temperature shaker at 25 ℃ with an oscillation frequency of 150 r / min. Take it out and perform a second heat treatment at a temperature of 120 ℃ for 6 h to obtain the superhydrophobic material.

[0115] Test Example: Mechanical Friction Test. The superhydrophobic material was fixed on an abrasion tester, and its surface was rubbed 100 times in one direction with 240-grit sandpaper under a 100 g load. The water contact angle after friction was measured.

[0116] Self-healing performance test. After the above mechanical friction test was performed on the superhydrophobic material, it was placed in an 80 ℃ oven for 2 h and the water contact angle was measured again. The self-healing efficiency of the superhydrophobic material was calculated according to the following formula (1):

[0117] Where θ0 is the initial water contact angle, θ1 is the water contact angle after friction, and θ2 is the water contact angle after self-healing.

[0118] Mechanical extrusion test. The superhydrophobic material was subjected to 10,000 mechanical extrusions using a universal testing machine at a compression speed of 5 mm / min and a compressive stress of 50 N. The water contact angle after extrusion was measured.

[0119] Oil-water separation test. The oil-water mixture has a volume ratio of 1:1, an initial mass of m1, and a separated oil phase mass of m2. The separation efficiency of the superhydrophobic material for the oil-water mixture is:

[0120] For a superhydrophobic material with a melamine sponge substrate, first weigh the sponge and record its initial mass as m3. Then soak it in an oil-water mixture for 20 minutes to saturate the sponge with oil. Remove the sponge and weigh it after the adsorbed oil droplets stop dripping. Record the weight as m4. Then the mass of the separated oil phase m2 is m4-m3.

[0121] For superhydrophobic materials with a stainless steel mesh substrate, the separated oil phase can be obtained by filtration.

[0122] The properties of the superhydrophobic materials prepared in Examples 1-6 and Comparative Examples 1-3 are summarized in Table 1.

[0123] Table 1 Properties of superhydrophobic materials

[0124] As shown in Table 1, the hydrophobic materials prepared in Examples 1-6 not only possess excellent hydrophobic properties and mechanical stability, but also excellent self-healing properties. After 100 mechanical friction cycles, they exhibit self-healing properties and maintain an oil-water separation efficiency of over 95%, significantly extending their service life. Comparative Example 1, which did not include the chain polymer, lacked self-healing properties in its hydrophobic material. Comparative Example 2, which did not undergo a first heat treatment, had a low density of hydrogen-bonded crosslinking networks formed between the chain polymer and the polyphenol polymer, resulting in poor mechanical stability and self-healing properties in its hydrophobic material. Compared to Example 1, Comparative Example 3 altered the reaction sequence, first forming a chain polymer coating on the substrate surface, followed by oxidative self-polymerization of catechols and / or pyrogallols. Since the polyphenol polymer mainly deposited on the surface of the chain polymer, a high-density hydrogen-bonded crosslinking network was not formed, resulting in poor mechanical stability and self-healing properties in the prepared hydrophobic material. Furthermore, the bonding force between the chain polymer and the substrate was weaker than that between the polyphenol polymer and the substrate, further reducing the mechanical stability of the hydrophobic material.

[0125] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A superhydrophobic material, characterized in that, The invention includes a substrate and a composite coating applied to the surface of the substrate. The composite coating is a polymer network formed by hydrogen bonds between a chain polymer and a polyphenol polymer modified with hydrophobic units. The polyphenol polymer is a polymer of catechol compounds and / or pyrogallol compounds.

2. The superhydrophobic material according to claim 1, wherein, The thickness of the composite coating is 200-500 nm; and / or, based on the total mass of the composite coating, the content of the chain polymer is 34-90 wt%, the content of the polyphenol polymer is 8-47 wt%, and the content of the hydrophobic unit is 1-33 wt%.

3. The superhydrophobic material according to claim 1 or 2, wherein, The chain polymer is selected from at least one of chain polyhydroxy polymers, chain polycarboxyl polymers, chain polyamino polymers, and chain polyester polymers; preferably, the chain polyhydroxy polymer is selected from at least one of polyvinyl alcohol, agarose, polyethylene glycol, and chitosan; more preferably, the number average molecular weight of the polyvinyl alcohol is 10,000-100,000 g / mol; more preferably, the number average molecular weight of the polyethylene glycol is 2,000-20,000 g / mol; more preferably, the degree of deacetylation of the chitosan is not less than 85%; preferably, the chain polycarboxyl polymer is selected from at least one of polyacrylic acid, polymethacrylic acid, and polymaleic acid; preferably, the chain polyamino polymer is selected from polyvinylamine and / or polyethyleneimine; preferably, the chain polyester polymer is selected from polylactic acid and / or polycaprolactone.

4. The superhydrophobic material according to any one of claims 1-3, wherein, The catechol compounds are selected from catechol, 、 、 、 、 、 At least one of the following; and / or, the pyrogallol compound is selected from pyrogallol, tannic acid, At least one of the following; and / or, the hydrophobic unit is selected from... At least one of -NH-R3, -S-R4, -OC(=O)-NH-R5, wherein R2 is selected from C 10 -C 20 Alkyl or C6-C 20 Perfluoroalkyl groups, R3, R4, and R5 are each independently selected from C10. 10 -C 20 Alkyl group; and / or, the substrate is a porous substrate, preferably one of melamine sponge, polypropylene nonwoven fabric, stainless steel screen, and nylon filter membrane.

5. The superhydrophobic material according to any one of claims 1-4, wherein, The polyphenol polymer further includes transition metal ions, which are linked to catechol compounds and / or pyrogallol compounds via coordination bonds; preferably, the transition metal ions are selected from Fe. 3+ Fe 2+ Cu 2+ Cu + Mn 2+ Mn 3+ Mn 4+ Ni 3+ Ni 2+ Co 3+ Co 2 + Zn 2+ At least one of the following; preferably, the content of the transition metal ions is 0.00001-0.001 wt% based on the mass of the composite coating.

6. A method for preparing a superhydrophobic material, characterized in that, The process includes the following steps: (1) contacting the substrate with an alkaline solution containing catechol compounds and / or pyrogallol compounds, wherein the catechol compounds and / or pyrogallol compounds undergo oxidative self-polymerization to obtain a material coated with a first coating, wherein the pH of the alkaline solution is ≥8; (2) contacting the chain polymer with the material coated with the first coating in a liquid medium and performing a first heat treatment to obtain a material coated with a second coating; (3) immersing the material coated with the second coating in a solution containing a hydrophobic modifier and performing a second heat treatment to obtain a superhydrophobic material.

7. The preparation method according to claim 6, wherein, The alkaline solution further contains transition metal ions; preferably, the transition metal ions are selected from Fe. 3+ Fe 2+ Cu 2+ Cu + Mn 2+ Mn 3+ Mn 4+ Ni 3+ Ni 2+ Co 3+ Co 2 + Zn 2+ At least one of the following; preferably, the mass ratio of the transition metal ion to catechol compounds and / or pyrogallol compounds is 1:50000-500000.

8. The preparation method according to claim 6 or 7, wherein, The catechol compounds are selected from catechol, 、 、 、 、 、 At least one of the following; and / or, the pyrogallol compound is selected from pyrogallol, tannic acid, At least one of the following: and / or, the concentration of the catechol compound and / or pyrogallol compound in the alkaline solution is 0.5-10 g / L, preferably 3-6 g / L; and / or, the volume of the alkaline solution is 100-400 mL; and / or, the pH of the alkaline solution is 8.5-10; and / or, the reaction temperature of the oxidative self-polymerization is 20-80 ℃, preferably 20-30 ℃; and / or, the reaction time of the oxidative self-polymerization is 6-48 h; and / or, the substrate is a porous substrate, preferably one of melamine sponge, polypropylene nonwoven fabric, stainless steel screen, and nylon filter membrane.

9. The preparation method according to any one of claims 6-8, wherein, The chain polymer is selected from at least one of chain polyhydroxy polymers, chain polycarboxyl polymers, chain polyamino polymers, and chain polyester polymers; preferably, the chain polyhydroxy polymer is selected from at least one of polyvinyl alcohol, agarose, polyethylene glycol, and chitosan; more preferably, the number average molecular weight of the polyvinyl alcohol is 10,000-100,000 g / mol; even more preferably, the number average molecular weight of the polyethylene glycol is 2,000-20,000 g / mol. g / mol; more preferably, the degree of deacetylation of the chitosan is 85%-100%; preferably, the chain polycarboxylic acid polymer is selected from at least one of polyacrylic acid, polymethacrylic acid, and polymaleic acid; preferably, the chain polyamino polymer is selected from polyethyleneimine and / or polyethyleneimine; preferably, the chain polyester polymer is selected from polylactic acid and / or polycaprolactone; and / or, the mass ratio of the chain polymer to the catechol compound and / or pyrogallol compound is 1-10:1, preferably 2-5:1; and / or, the temperature of the first heat treatment is 40-150 °C, preferably 60-120 °C; and / or, the time of the first heat treatment is 2-16 h, preferably 6-14 h.

10. The preparation method according to any one of claims 6-9, wherein, The mass ratio of the hydrophobic modifier to the catechol compound and / or pyrogallol compound is 0.1-1:1; and / or, the hydrophobic modifier is selected from... At least one of R1-NH2, R4-SH, and R5-N=C=O, wherein R1 is selected from C1-C5 alkyl groups and R2 is selected from C 10 -C 20 Alkyl or C6-C 20 Perfluoroalkyl groups, R3, R4, and R5 are each independently selected from C10. 10 -C 20 Alkyl group; and / or, the temperature of the second heat treatment is 60-180 °C, preferably 120-160 °C; and / or, the time of the second heat treatment is 6-24 h.

11. A superhydrophobic material prepared by the preparation method according to any one of claims 6-10.

12. The application of the superhydrophobic material according to any one of claims 1-5 or 11 in oil-water separation.

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