CN109731752B

CN109731752B - Method for preparing high-molecular coating with self-cleaning function on surface of article

Info

Publication number: CN109731752B
Application number: CN201910041155.2A
Authority: CN
Inventors: 汪大洋; 陶琦
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2019-01-16
Filing date: 2019-01-16
Publication date: 2020-11-03
Anticipated expiration: 2039-01-16
Also published as: CN109731752A

Abstract

A method for preparing a polymer coating with a self-cleaning function on the surface of an article comprises the following steps: step 1, cleaning pollutants on the surface of an article to be coated to obtain an article with a clean surface; step 2, preparing a poly dimethyl diallyl ammonium chloride (PDADMAC) aqueous solution containing NaCl; step 3, coating the article with the clean surface obtained in the step 1 with the PDADMAC aqueous solution containing NaCl prepared in the step 2 to obtain an article containing a PDADMAC film; step 4, preparing inorganic or organic salt water solution; and 5, soaking the article containing the PDADMAC film obtained in the step 3 in the saline solution obtained in the step 4 to obtain a PDADMAC coating for coating the surface of the article with self-cleaning property. Any oily pollutant on the surface of the prepared coating can be completely, quickly and effectively cleaned by water without the aid of detergents and washing equipment. The PDADMAC coating is modified on the surfaces of various filter membranes or screens, so that simple and efficient oil/water separation filter membranes and screens can be manufactured.

Description

Method for preparing high-molecular coating with self-cleaning function on surface of article

Technical Field

The invention relates to a preparation method of a high polymer coating, and particularly provides a method for preparing a high polymer coating with a self-cleaning function on the surface of an article and the article with the high polymer coating

Background

In human production and life, oil pollution is visible everywhere, and the removal of the oil pollution on the surface of a material is always an urgent problem to be solved. The conventional oil removing method requires a detergent and a large amount of water, which is not only a waste of water resources but also causes environmental pollution. Therefore, the preparation of the coating of the self-cleaning material in water has great significance for removing oil stains on the surface of the material.

At present, a micro-nano structure can be constructed on the surface of a material by some technologies, the surface of the material containing the micro-nano structure can basically realize self-cleaning in water, but once the surface is polluted, the oil is accumulated in the micro-nano structure on the surface and is difficult to clean.

The hydrophilic material can be made into a self-cleaning coating due to the strong hydration capability of surface groups, but the surface of the hydrophilic material is exposed in the air, and particularly after the hydrophilic material is polluted by oil, the surface hydrophilic groups automatically generate surface reconstruction so as to reduce the surface energy, thereby weakening or even completely losing the surface hydrophilicity.

Disclosure of Invention

The present inventors have recently found that the phosphorylcholine ion polymer coating layer can maintain stable and strong hydrophilicity in air or oil due to the strong hydrophilicity of specific diionic groups, thereby exhibiting a highly effective self-cleaning effect. However, the surface coating of the diionic polymer requires severe experimental conditions and is essentially impossible to apply on a large scale in practice.

The inventors of the present invention prepared a surface coating with a highly efficient self-cleaning function by a layer-by-layer assembly coating method using a nanocellulose coating. However, the preparation of the required nanocellulose requires a very complicated chemical synthesis process, and basically, the cheap large-scale preparation cannot be realized at present, which greatly restricts the practical application of the nanocellulose coating.

The inventors of the present invention have also found that the hydrophilicity of the surface of a polymer having a self-cleaning function is very stable, and the contact angle of water on the surface of the polymer is not changed by the change of the surrounding environment. Our studies show that only on self-cleaning surfaces the contact angle (expw/o) experimentally measured for water in an oil-phase medium is almost equal to the value (calw/o) calculated by means of the experimentally measured contact angle (expw/a) in an air environment, i.e. w/o expw/o-calw/o is smaller than the contact angle experimental measurement error (3 °).

The inventors of the present invention believe that PDADMAC is a positively charged polymer polyelectrolyte, and the counter ion thereof is chloride (Cl-), and the current research results demonstrate that PDADMAC can effectively adhere to the surfaces of various articles having different surface chemistries, thereby easily forming a dense surface coating. Because of the electrostatic interaction of the quaternary ammonium salt groups on the surface and water molecules, the surface of the prepared PDADMAC film shows good hydrophilicity. Our recent research results show that because the quaternary ammonium salt group on the surface of PDADMAC has a rigid and isotropic molecular structure, the surface hydrophilicity is affected little by the surface reconstruction caused by the exposure to air or oil pollution, i.e. the surface of PDADMAC shows very stable hydrophilicity. However, although the expw/a and expw/o values of the surface of the PDADMAC film are both between 25 DEG and 40 DEG, the w/o value thereof is more than 5 DEG, i.e., the surface of the PDADMAC film with Cl-ion as a counter ion does not have a self-cleaning function (FIG. 2).

Therefore, based on these researches, the inventors of the present invention selected PDADMAC as a surface coating material, and replaced Cl "ions on the surface of PDADMAC film with other anions having stronger interaction with water molecules by ion exchange, thereby enhancing the hydrophilicity of the surface and realizing a highly effective self-cleaning function. In order to break through these prior art barriers, the present invention aims to develop a simple and feasible method for applying a self-cleaning surface polymer to the surface of any object.

Specifically, the method for preparing a polymer coating with a self-cleaning function on the surface of an article, which is developed by the present invention, has very stable hydrophilicity, and is placed in water or washed with water after being polluted by an oily medium, wherein the oily medium can be automatically separated from the surface of the coating without any residue, comprises the following steps:

step 1, cleaning organic pollutants on the surface of an article to be coated to obtain an article with a clean surface;

step 2: preparing a poly dimethyl diallyl ammonium chloride (PDADMAC) solution containing sodium chloride (NaCl), wherein the concentration of PDADMAC is 0.1-5mg/mL, and the concentration of NaCl is 0-5M;

and step 3: coating the article with the clean surface obtained in the step 1 by using a prepared PDADMAC aqueous solution containing NaCl to obtain an article containing a PDADMAC film;

and 4, step 4: preparing an inorganic salt aqueous solution containing inorganic anions;

and 5: soaking the article containing the PDADMAC film obtained in the step (3) in the inorganic salt aqueous solution obtained in the step (4) for 5-100 minutes to realize the sufficient replacement of counter anions on the surface of the PDADMAC film and inorganic anions in the solution, taking out the article, washing the article modifying the PDADMAC film with water, and obtaining a high-efficiency self-cleaning polymer coating coated on the surface of the article by replacing the optimized inorganic anions; or after step 3, performing the following steps;

step 6, preparing an organic salt water solution containing organic anions;

and 7, soaking the article containing the PDADMAC film obtained in the step 3 in the organic salt water solution obtained in the step 6 for 5-100 minutes to realize the sufficient replacement of counter anions on the surface of the PDADMAC film and inorganic anions in the solution, taking out the article, washing the article modifying the PDADMAC film with water, and obtaining the high-efficiency self-cleaning polymer coating coated on the surface of the article by replacing the optimized organic anions.

In the method of the invention, PDADMAC can be effectively adhered to the surfaces of various articles with different surface chemistries, so that a compact surface coating can be easily formed, meanwhile, the surface of the PDADMAC film shows good hydrophilicity and stability, and Cl & lt- & gt ions on the surface of the PDADMAC film are replaced by other anions with stronger interaction with water molecules through ion exchange, so that the hydrophilicity of the surface of the PDADMAC film is enhanced, and the efficient self-cleaning function is realized. However, the concentration of the prepared PDADMAC solution is too high, which is not favorable for uniform coating of PDADMAC, while the concentration of the PDADMAC solution is too low, which results in too thin PDADMAC film, and the concentration of PDADMAC is usually selected to be 0.1-5 mg/mL. In addition, NaCl was added to adjust the concentration of Cl-ions.

Preferably, the oily medium comprises: oils and fats such as crude oil, engine oil, diesel oil, animal oil or vegetable oil, alcohols such as butanol or pentanol, alkanes such as hexane or hexadecane, and organic solvents such as chloroform or toluene.

Preferably, the concentration of PDADMAC in the PDADMAC aqueous solution prepared in the step 2 is 0.5mg/mL-2mg/mL, and the concentration of NaCl is 0.001-1M.

Preferably, the coating method of step 3 includes: layer-by-layer assembly, solution spin coating, electrospinning or solution casting.

Preferably, the inorganic anion of step 4 comprises F^1-、HCO₃ ^1-、SO₄ ^2-、PO₄ ^3-、HPO₄ ^2-、H₂PO₄ ^1-、BrO^3-、IO^3-Or SO₃ ^2-Ions. Preferably, the organic anion described in step 6The ions include: citrate ion, oxalate ion, or tartrate ion.

Preferably, the concentration of said inorganic or organic anion used to replace the counter anion on the surface of the PDADMAC film is from 0.003 to 5M.

Preferably, the method for drying the PDADMAC film-coated article having the self-cleaning function includes: naturally drying in air, drying at high temperature or blowing with inert gas.

Preferably, the blowing with an inert gas includes blowing with nitrogen.

In the above-described method of the present invention, a dense, uniform PDADMAC film may optionally be applied to the surface of any article by any conventional method. However, the following methods are generally adopted to facilitate industrial production:

the method comprises the following steps: layer-by-layer assembly method

A pair of oppositely charged groups of the polymer needs to be selected. Alternative positively charged group containing polymers include PDADMAC (polydimethyldiallylammonium chloride), PAH (polyallylammonium chloride), PEI (polyetherimide). Alternative negatively charged group containing polymers include PSS (sodium polystyrene sulfonate), PAA (polyacrylic acid). The article to be coated is alternately soaked in the two polymer water solutions and cleaned, so that the two polymer films are deposited on the surface of the article layer by layer, and the polymer film with controllable film thickness and uniform and smooth surface is prepared. PDADMAC is selected as the most layer of the obtained polymer film by controlling the layer-by-layer assembly process.

The second method comprises the following steps: solution spin coating method

Fixing an article to be coated on a spin coater, dripping a PDADMAC aqueous solution on the surface of the article to be coated, spreading the liquid drop of the PDADMAC aqueous solution to form a uniform liquid film by means of high-speed rotation of the spin coater, and coating the surface of the article with a uniform PDADMAC film after water in the liquid film is completely volatilized in the spin coating process.

The third method comprises the following steps: electrostatic spinning process

Fixing an article to be coated on an electrospinning device, using a PDADMAC aqueous solution as electrospinning liquid, and coating a PDADMAC fiber film on the surface of the article by an electrospinning method by adjusting the distance between the surface of the article and a spinning nozzle.

The method four comprises the following steps: method of solution casting

Uniformly spreading the PDADMAC aqueous solution on the surface of an article to be coated at normal temperature and normal pressure, and preparing a PDADMAC film on the surface of the article by controlling the volatilization speed of water in a drying (including drying or naturally airing) process.

Preferably, the material of the article includes wood, metal, inorganic nonmetal, synthetic polymer plastic, natural polymer and other materials, wherein:

the metal material comprises metal materials such as iron, titanium, nickel, copper, aluminum and the like and alloys thereof;

the inorganic non-metallic material comprises silicon, silicon carbide, aluminum oxide, silicon oxide and the like;

the synthetic polymer material comprises polyethylene, polypropylene, polystyrene, polydimethylsiloxane, polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, polysulfone polymers, polyamide polymers, polyethylene terephthalate and the like;

the natural polymer material comprises chitin, cellulose acetate and the like.

When counter ions on the surface of the PDADMAC film, i.e. Cl-ions, are coated by F^1-、HCO₃ ^1-、SO₄ ^2-、PO₄ ^3-、HPO₄ ^2-、H₂PO₄ ^1-、BrO^3-、IO^3-Or SO₃ ^2-After inorganic anions are replaced, the surface of the PDADMAC film shows excellent self-cleaning function.

For example: SO (SO)₄ ^2-Substituted PDADMAC (SO)₄ ^2-PDADMAC) film surface is almost 0 DEG, less than the contact angle experimental measurement error (3 deg). If the edible oil is dropped in SO₄ ^2-After the PDADMAC film is placed on the surface of the film, the film is put into water, edible oil can automatically and rapidly shrink into oil drops within 3-5 seconds, and the oil drops float on the surface of the film and are completely desorbed. Namely SO₄ ^2-The PDADMAC film has a self-cleaning function.

When counter ions, namely Cl < - > ions, on the surface of the PDADMAC film are replaced by organic anions such as citrate ions, oxalate ions, tartrate ions and the like, the surface of the PDADMAC film shows excellent self-cleaning function.

For example: citrate ion (Ct)^3-) Permuted PDADMAC (Ct)^3-PDADMAC) film surface w/o value of about 1 DEG less than the experimental measurement error of the contact angle (3 deg.). If edible oil is dropped on Ct^3-After the PDADMAC film is placed on the surface of the film, the film is put into water, edible oil can automatically and rapidly shrink into oil drops within 3-5 seconds, and the oil drops float and are completely desorbed from the surface of the film. I.e. Ct^3-The PDADMAC film has a self-cleaning function.

By adopting the technology of the invention, the prepared PDADMAC film with the self-cleaning function allows various oil stains including alcohols such as crude oil, engine oil, diesel oil, animal oil, vegetable oil, butanol and amyl alcohol, hexane, alkanes such as hexadecane, common organic solvents such as chloroform and toluene to be simply cleaned by water. If the self-cleaning coating is put into water or washed by water after being polluted by the oily medium, the oily pollutant can automatically and completely separate from the surface of the PDADMAC film without any residue, so as to achieve the self-cleaning effect.

Drawings

FIG. 1 is a schematic diagram of the ion exchange process on the surface of the membrane.

FIG. 2 is a series of optical photographs recording the dewetting process of an oil on a surface of PDADMAC (Cl- -PDADMAC) with Cl-ions as the surface counter-ion in water.

FIG. 3 is a graph of oil in SO recorded in water₄ ^2-PDADMAC (SO) with surface counter ion₄ ^2-PDADMAC) surface dewetting procedure a series of optical photographs. Fig. 3A shows a layer-by-layer assembly method, fig. 3B shows a solution spin coating method, fig. 3C shows an electrospinning method, and fig. 3D shows a solution casting method.

Figure 4 is a series of optical photographs recording the extraction of oil slick from water using a stainless steel screen coated with PDADMAC film.

Fig. 5 is a series of optical photographs recording the extraction of oil slick from water using a polyethylene nonwoven fabric coated with PDADMAC film.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

The technical solution of the present invention will be described in detail below with specific examples.

Example 1 a PDADMAC film was prepared on the surface of a single crystal silicon wafer by means of a layer-by-layer assembly process.

Step 1, boiling a monocrystalline silicon wafer in a sulfuric acid/hydrogen peroxide mixed solution (volume ratio is 7: 3) at 90 ℃ for 4 hours to remove organic impurities on the surface, and then ultrasonically cleaning the monocrystalline silicon wafer for multiple times by using deionized water;

step 2, diluting a commercial PDADMAC aqueous solution with 20-35% of NaCl aqueous solution by mass and 20-35 ten thousand of molecular weight, wherein the concentration of NaCl in the final macromolecule aqueous solution is 0.5M and the concentration of PDADMAC is 1 mg/mL;

and step 3: dissolving sodium polystyrene sulfonate (PSS) solid powder with the molecular weight of 7 ten thousand in water to prepare uniform aqueous solution, and diluting the prepared PSS aqueous solution with NaCl aqueous solution to prepare macromolecular aqueous solution with the PSS concentration of 1mg/mL and the NaCl concentration of 0.5M;

and 4, step 4: soaking the cleaned silicon wafer prepared in the step 1 in the PDADMAC aqueous solution prepared in the step 2 for 20 minutes, washing the silicon wafer with deionized water, and drying the silicon wafer with nitrogen;

and 5: soaking the silicon wafer obtained in the step 4 in the PSS aqueous solution prepared in the step 3 for 20 minutes, washing with deionized water, and drying with nitrogen;

step 6, repeating the step 4 and the step 5 for 4 times, depositing 4 (PDADMAC/PSS) double-layer films on the surface of the silicon wafer, and finally repeating the step 4 once, and depositing a layer of PDADMAC film on the outermost surface of the obtained double-layer film;

and 7: respectively soaking the silicon wafer coated with PDADMAC on the outermost layer prepared in the step 6 in NaF, NaCl, NaBr, NaI and Na with the concentration of 0.1M₂SO₄、NaHCO₃、Na₃PO₄、Na₂HPO₄、NaH₂PO₄、NaBrO₃、NaIO₃、Na₂SO₃Sodium formate, sodium acetate, sodium oxalate, sodium malonate, sodium tartrate and ascorbic acidSoaking in water solution of sodium or sodium citrate for 1 hr, washing with deionized water, blowing with nitrogen gas, and drying overnight. The self-cleaning effect of the surface of the PDADMAC film thus prepared is shown in fig. 3 and table 1.

Example 2 PDADMAC film was prepared on the surface of a single crystal silicon wafer by solution spin coating.

Step 1, boiling a monocrystalline silicon wafer in a sulfuric acid/hydrogen peroxide mixed solution (volume ratio is 7: 3) at 90 ℃ for 4 hours to remove organic impurities on the surface, then ultrasonically cleaning the monocrystalline silicon wafer for multiple times by using deionized water, and drying the monocrystalline silicon wafer by using nitrogen;

step 2, diluting a commercial PDADMAC aqueous solution with 20-35% of NaCl aqueous solution and 20-35 ten thousand of molecular weight, wherein the concentration of NaCl in the final macromolecule aqueous solution is 1M and the concentration of PDADMAC is 2 mg/mL;

step 3, spin-coating to form a film by using a table type spin coater, connecting the spin coater with a mechanical pump to fix the monocrystalline silicon substrate, rotating at a high speed to remove dust, dripping the PDADMAC aqueous solution prepared in the step 2 on the newly cleaned silicon wafer prepared in the step 1, completely covering the surface of the silicon wafer by using the PDADMAC aqueous solution, and then spin-coating at the rotating speed of 3000r/min for 10 min;

step 4, after the spin coating is finished, the prepared silicon wafer coated with the PDADMAC film is placed into a vacuum oven to be dried at 60 ℃;

step 5, soaking the silicon chip coated with the PDADMAC film prepared in the step 4 in NaF, NaCl, NaBr, NaI and Na with the concentration of 0.1M respectively₂SO₄、NaHCO₃、Na₃PO₄、Na₂HPO₄、NaH₂PO₄、NaBrO₃、NaIO₃、Na₂SO₃Soaking in water solution of sodium formate, sodium acetate, sodium oxalate, sodium malonate, sodium tartrate, sodium ascorbate or sodium citrate for 1 hr, washing with deionized water, blowing with nitrogen gas, and drying overnight. The self-cleaning effect of the surface of the PDADMAC film thus prepared is shown in fig. 3 and table 1.

Example 3 PDADMAC films were prepared on the surface of monocrystalline silicon wafers by means of solution casting.

step 2, diluting a commercial PDADMAC aqueous solution with the NaCl aqueous solution, wherein the mass fraction of the commercial PDADMAC aqueous solution is 20-35%, and the molecular weight of the commercial PDADMAC aqueous solution is 20-35 ten thousand, so that an aqueous solution with the NaCl concentration of 0.005M and the PDADMAC concentration of 0.1mg/mL is prepared;

step 3, directly dripping the PDADMAC aqueous solution prepared in the step 2 on the newly cleaned silicon wafer prepared in the step 1, after the PDADMAC aqueous solution is leveled on the surface of the silicon wafer and the surface of the silicon wafer is completely and uniformly covered, placing the silicon wafer in a dryer for natural drying; or after the step 2, or after the step,

step 4, soaking the newly cleaned silicon wafer prepared in the step 1 in the PDADMAC aqueous solution prepared in the step 2 for 1 hour, taking out the silicon wafer, then washing the silicon wafer for multiple times by using deionized water, and placing the silicon wafer in a dryer for natural drying;

step 5; soaking the silicon wafer coated with the PDADMAC film prepared in the

step

3 or 4 in NaF, NaCl, NaBr, NaI and Na with the concentration of 0.1M respectively₂SO₄、NaHCO₃、Na₃PO₄、Na₂HPO₄、NaH₂PO₄、NaBrO₃、NaIO₃、Na₂SO₃Soaking in water solution of sodium formate, sodium acetate, sodium oxalate, sodium malonate, sodium tartrate, sodium ascorbate or sodium citrate for 1 hr, washing with deionized water, blowing with nitrogen gas, and drying overnight. The self-cleaning effect of the surface of the PDADMAC film thus prepared is shown in fig. 3 and table 1.

Example 4 PDADMAC film was prepared on the surface of a monocrystalline silicon wafer by means of electrospinning.

step 2, diluting a commercial PDADMAC aqueous solution with the mass fraction of 20-35% and the molecular weight of 20-35 ten thousand by using deionized water to prepare the PDADMAC aqueous solution with the concentration of 5 mg/mL;

step 3, injecting the PDADMAC aqueous solution prepared in the step 2 into an injector of an electrospinning device, fixing the newly cleaned silicon wafer prepared in the step 1 on a receiving device, wherein the feeding speed is 0.2mL/h, the electrospinning voltage is 15kV, the curing distance is 15cm, the receiving device is of a flat plate type, and the rotating speed of a roller is 400 rmp;

step 4, when the electrostatic spinning film fully spreads the surfaces of the silicon wafers, taking down the silicon wafers, and drying the silicon wafers in a vacuum oven at 60 ℃;

The article coated with the PADAMAC film with Cl "ions as counter ions obtained in examples 1 to 4 was immersed in an inorganic or organic salt aqueous solution containing an inorganic or organic anion having a self-cleaning function, immersed for 60 minutes, taken out, and washed with water to impart a self-cleaning function to the surface of the PDADMAC film (fig. 1).

After edible rapeseed oil was dropped in the air on the surface of the Cl-PDADMAC coating prepared in examples 1-4 to form a uniform oil film, the oil film was put in water and the oil film contracted into oil droplets on the surface of the Cl-PDADMAC coating, but the oil droplets remained stably adsorbed on the coating surface all the time (fig. 2). For easy observation, the edible rapeseed oil was stained with nile red dye. And the second figure shows that PDADMAC film is coated on the surface of a silicon chip by a layer-by-layer assembly method, and the corresponding surface under the picture is dripped with oil, namely the time of the Cl-PDADMAC coating in water.

When edible rapeseed oil is in the airIn drops of SO prepared in examples 1-4₄ ^2-After a layer of uniform oil film is formed on the surface of the PDADMAC coating, putting the PDADMAC coating into water, and keeping the oil film in SO within 3-5 seconds₄ ^2-The PDADMAC coating surface shrinks into oil droplets which quickly and completely float off the coating surface (fig. 3). For easy observation, the edible rapeseed oil was stained with nile red dye. The PDADMAC film is coated on the surface of the silicon wafer by four methods of layer-by-layer assembly, solution spin coating, electrostatic spinning and solution casting.

To record the oil in water in SO₄ ^2-PDADMAC (SO) with surface counter ion₄ ^2-PDADMAC) surface dewetting procedure a series of optical photographs. When edible rapeseed oil was dropped in the air in the SO prepared in examples 1-4₄ ^2-After a layer of uniform oil film is formed on the surface of the PDADMAC coating, putting the PDADMAC coating into water, and keeping the oil film in SO within 3-5 seconds₄ ^2-The surface of the PDADMAC coating shrinks into oil droplets which quickly and completely float off the surface of the coating. For easy observation, the edible rapeseed oil was stained with nile red dye. The PDADMAC film is coated on the surface of the silicon wafer by four methods of layer-by-layer assembly, solution spin coating, electrostatic spinning and solution casting. Four SO after oil is dripped on the corresponding surface under the picture₄ ^2-The time elapsed for the PDADMAC coating in water (fig. 3).

Example 5 PDADMAC film prepared on the surface of polypropylene plastic lunch box by solution casting method.

Step 1, placing a commercial polypropylene plastic lunch box in ethanol and deionized water respectively, carrying out ultrasonic cleaning for multiple times, removing organic impurities on the surface, and airing in the air;

step 2, diluting a commercial PDADMAC aqueous solution with the NaCl aqueous solution, wherein the mass fraction of the commercial PDADMAC aqueous solution is 20-35%, and the molecular weight of the commercial PDADMAC aqueous solution is 20-35 ten thousand, so as to prepare an aqueous solution with the NaCl concentration of 1M and the PDADMAC concentration of 2 mg/mL;

step 3, soaking the newly cleaned polypropylene lunch box prepared in the step 1 in the PDADMAC aqueous solution prepared in the step 2 for 1 hour, taking out the lunch box, then cleaning the lunch box for multiple times by using deionized water, and placing the lunch box in the air for natural drying;

step 4; respectively soaking the PDADMAC film-coated polypropylene lunch box prepared in the step 3 in NaF, NaCl, NaBr, NaI and Na with the concentration of 0.1M₂SO₄、NaHCO₃、Na₃PO₄、Na₂HPO₄、NaH₂PO₄、NaBrO₃、NaIO₃、Na₂SO₃Soaking in water solution of sodium formate, sodium acetate, sodium oxalate, sodium malonate, sodium tartrate, sodium ascorbate or sodium citrate for 1 hr, washing with deionized water, blowing with nitrogen gas, and drying overnight. The self-cleaning effect of the PDADMAC film coated on the surface of the polypropylene lunch box is summarized in the table I.

Example 6 PDADMAC film coated on stainless steel screen surface by layer-by-layer assembly method

Step 1: placing the stainless steel mesh with the average gap size of 25 micrometers in ethanol and deionized water respectively, performing ultrasonic cleaning for multiple times to remove organic impurities on the surface, and airing in the air;

and 4, step 4: soaking the newly cleaned stainless steel screen mesh prepared in the step 1 in the PDADMAC aqueous solution prepared in the step 2 for 20 minutes, then washing the stainless steel screen mesh with deionized water, and drying the stainless steel screen mesh with nitrogen;

and 5: soaking the stainless steel screen mesh obtained in the step 4 in the PSS aqueous solution prepared in the step 3 for 20 minutes, washing with deionized water, and drying with nitrogen;

step 6, repeating the step 4 and the step 5 for 4 times, depositing 4 (PDADMAC/PSS) double-layer films on the surface of the stainless steel screen, and finally repeating the step 4 once, and depositing a PDADMAC film on the outermost surface of the obtained double-layer film;

and 7: prepared concentration of 0.5M Na₂SO₄An aqueous solution;

step 8, soaking the stainless steel screen coated with the PDADMAC film on the outermost layer prepared in the step 6 in the Na prepared in the step 7₂SO₄Soaking in water solution for 0.5 hr, taking out the sieve, washing with deionized water, blowing with nitrogen gas, and drying overnight.

And step 9: a stainless steel net coated with a PDADMAC (Cl- -PDADMAC) film with Cl-ion as counter ion prepared in step 6 and SO prepared in step 8₄ ^2-PDADMAC (SO) with ion as counter ion₄ ^2-PDADMAC) film coated stainless steel mesh was fixed to one end of the plastic tube to make an oil extractor.

As shown in FIG. 4, the prepared oil extractor was inserted into edible rapeseed oil/water two-phase mixture, and SO4 was obtained when the oil extractor was pulled out of the oil/water two-phase mixture^2-The stainless steel screen coated with PDADMAC film only allows water to flow out freely, and the edible rapeseed oil is intercepted in the plastic pipe, so that the floating oil is extracted from water. In contrast, both water and oil were free to flow through the Cl- -PDADMAC film coated stainless steel mesh, and floating oil could not be pulled up from the water. The stainless steel screen is fixed at one end of the plastic, the stainless steel screen on the left plastic tube is coated with PDADMAC (Cl-PDADMAC) film with Cl-ion as counter ion, and the stainless steel screen on the right plastic tube is coated with SO₄ ^2-PDADMAC (SO) with ion as counter ion₄ ^2--PDADMAC) film. The average size of the openings in the screen was 25 microns. As shown, the dry stainless steel mesh was immersed from air into the upper oil phase, then into water, and finally lifted out of the oil/water two-phase mixture. SO with self-cleaning function₄ ^2-the-PDADMAC film coated screen can effectively extract oil from the oil/water two-phase mixture, while the Cl-PDADMAC film coated screen, which does not have a self-cleaning function, cannot extract oil from the oil/water two-phase mixture. For the convenience of observation, the oil phase is edible rapeseed oil dyed by Nile red dye.

Example 7 PDADMAC film coated on the surface of polyethylene nonwoven fabric by solution casting method

Step 1, carrying out ultrasonic cleaning on commercial polyethylene non-woven fabrics with the average gap size of 10 microns in ethanol and deionized water for multiple times respectively to remove organic impurities on the surfaces, and airing in the air;

step 2, diluting a commercial PDADMAC aqueous solution with the NaCl aqueous solution, wherein the mass fraction of the commercial PDADMAC aqueous solution is 20-35%, and the molecular weight of the commercial PDADMAC aqueous solution is 20-35 ten thousand, so as to prepare an aqueous solution with the NaCl concentration of 0.5M and the PDADMAC concentration of 1 mg/mL;

step 3, soaking the newly cleaned polyethylene non-woven fabric prepared in the step 1 in the PDADMAC aqueous solution prepared in the step 2 for 1 hour, taking out the newly cleaned polyethylene non-woven fabric, then cleaning the newly cleaned polyethylene non-woven fabric with deionized water for multiple times, and placing the newly cleaned polyethylene non-woven fabric in the air for natural drying;

step 4, preparing 0.1M sodium citrate aqueous solution

Step 5; and (3) soaking the polyethylene non-woven fabric coated with the PDADMAC film prepared in the step (3) in the sodium citrate aqueous solution prepared in the step (4) for 1 hour, taking out and washing the polyethylene non-woven fabric with deionized water, standing overnight in the air, and naturally airing.

Step 6: coating the polyethylene non-woven fabric with the PDADMAC (Cl-PDADMAC) film with Cl-ion as the counter ion prepared in the step 3 and the PDADMAC (Ct) film with citrate ion as the counter ion prepared in the step 5^3-PDADMAC) film coated polyethylene nonwoven fabric was fixed to one end of the plastic tube to make an oil extractor.

As shown in FIG. 5, the prepared oil extractor was inserted into a hexadecane/water two-phase mixture, and after the oil extractor was pulled out of the oil/water two-phase mixture, Ct was measured^3-The PDADMAC film coated non-woven fabric allows only free outflow of water, intercepting hexadecane in the plastic tube, achieving the oil slick extraction from water. On the contrary, water and oil can freely flow out of the Cl-PDADMAC film coated non-woven fabric, and floating oil can not be extracted from water. The polyethylene nonwoven cloth is fixed at one end of the plastic, the nonwoven cloth on the left plastic tube is coated with PDADMAC (Cl-PDADMAC) film with Cl-ion as counter ion, and the nonwoven cloth on the right plastic tube is coated with PDADMAC filmNon-woven fabric is coated with SO₄ ^2-PDADMAC (SO) with ion as counter ion₄ ^2--PDADMAC) film. The average size of the voids in the nonwoven fabric was 10 microns. As shown, the dried nonwoven fabric is first immersed in the upper oil phase from air, then in water, and finally lifted out of the oil/water two-phase mixture. SO with self-cleaning function₄ ^2-the-PDADMAC film coated nonwoven can effectively extract oil from the oil/water two-phase mixture, while the Cl-PDADMAC film coated nonwoven without self-cleaning function cannot extract oil from the oil/water two-phase mixture. For ease of observation, the oil phase was hexadecane stained with sudan red dye.

A series of optical photographs were recorded of the oil slick extracted from the water using a stainless steel screen coated with PDADMAC film. The stainless steel mesh used was fixed to one end of a plastic tube, the stainless steel mesh on the left plastic tube in the figure was coated with a PDADMAC (Cl-PDADMAC) film with Cl-ion as a counter ion, and the stainless steel mesh on the right plastic tube was coated with PDADMAC (SO 42-ion as a counter ion)₄ ^2--PDADMAC) film. The average size of the openings in the screen was 25 microns. As shown, the dried stainless steel mesh was immersed from air into the upper oil phase, then into water, and finally lifted out of the oil/water two-phase mixture. SO with self-cleaning function₄ ^2-the-PDADMAC film coated screen can effectively extract oil from the oil/water two-phase mixture, while the Cl-PDADMAC film coated screen, which does not have a self-cleaning function, cannot extract oil from the oil/water two-phase mixture. For ease of observation, the oil phase was canola oil stained with nile red dye (fig. 4).

A series of optical photographs were recorded of the oil slick extraction from water using a polyethylene nonwoven coated with PDADMAC film. The polyethylene nonwoven fabric used was fixed to one end of a plastic tube, the nonwoven fabric on the left plastic tube in the figure was coated with a PDADMAC (Cl-PDADMAC) film with Cl-ions as counter ions, and the nonwoven fabric on the right plastic tube was coated with SO₄ ^2-PDADMAC (SO) with ion as counter ion₄ ^2--PDADMAC) film. The nonwoven fabric has an average size of voids of10 microns. As shown, the dried nonwoven fabric was first immersed in the upper oil phase from air, then in water, and finally lifted out of the oil/water two-phase mixture. SO with self-cleaning function₄ ^2-the-PDADMAC film coated nonwoven can effectively extract oil from the oil/water two-phase mixture, while the Cl-PDADMAC film coated nonwoven without self-cleaning function cannot extract oil from the oil/water two-phase mixture. For ease of observation, the oil phase was sudan dye dyed hexadecane (fig. 5).

TABLE 1

Table one summarizes the dewetting behavior of edible rapeseed oil on PDADMAC film surfaces with different surface counter anions in water. In table one, √ represents a coating that can realize self-cleaning when oil is desorbed on the surface of the film in water, and x represents a coating that can not realize self-cleaning when oil is still adhered on the surface of the film in water. As can be seen from the results shown in Table I, the inorganic anions F-, HCO₃ ^1-、SO₄ ^2-、PO₄ ^3-、HPO₄ ^2-、H₂PO₄ ^1-、BrO^3-、IO^3-Or SO₃ ^2-Ions and organic anions, namely citrate ions, oxalate ions or tartrate ions can be used as effective counter ions to realize the self-cleaning function.

Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

1. Use of a polymer coating with self-cleaning function on the surface of an article, wherein the hydrophilicity of the surface of the polymer coating with self-cleaning function is very stable, the polymer coating with self-cleaning function is polluted by an oily medium, and the oily medium can be automatically separated from the surface of the coating without any residue after being put into water or washed by water, and the step of preparing the polymer coating with self-cleaning function comprises the following steps:

step 2, preparing a PDADMAC aqueous solution containing NaCl, wherein the PDADMAC concentration of the prepared PDADMAC aqueous solution containing NaCl is 0.1-5mg/mL, the NaCl concentration is 0.001-5M, and the PDADMAC is poly-dimethyl diallyl ammonium chloride;

step 3, coating the article with the clean surface obtained in the step 1 with the PDADMAC aqueous solution containing NaCl prepared in the step 2 to obtain an article containing a PDADMAC film;

step 4, preparing an inorganic salt aqueous solution with the inorganic anion concentration of 0.001-5M, wherein the inorganic anions are as follows: f^1-、HCO₃ ^1-、SO₄ ^2-、BrO^3-、IO^3-Or SO₃ ^2-Ions;

step 5, soaking the article containing the PDADMAC film obtained in the step 3 in the inorganic salt water solution obtained in the step 4 for 5-100 minutes to obtain an article of the PDADMAC film replacing inorganic anions, and washing the obtained article with water to obtain a self-cleaning polymer coating coated on the surface of the article;

or after step 3, performing the following steps:

step 6: preparing an aqueous solution of an organic salt having an organic anion concentration of 0.001-5M, wherein the organic anion is: citrate, oxalate or tartrate ions;

and 7: and (3) soaking the article containing the PDADMAC film obtained in the step (3) in the organic salt water solution obtained in the step (6) for 5-100 minutes to obtain an article of the PDADMAC film replacing organic anions, and washing the obtained article with water to obtain a self-cleaning polymer coating coated on the surface of the article.

2. The use of claim 1, the PDADMAC concentration of the formulated PDADMAC aqueous solution containing NaCl in step 2 is from 0.5mg/mL to 2 mg/mL.

3. The use according to claim 1, wherein the PDADMAC aqueous solution containing NaCl is formulated at a NaCl concentration of 0.001-1M in step 2.

4. Use according to claim 1, the coating comprising: layer-by-layer assembly, solution spin coating, electrospinning or solution casting.

5. Use according to any one of claims 1 to 4, wherein the concentration of the salt solution of the inorganic anion for replacing the counter anion of the surface of the PDADMAC film is between 0.003 and 5M.

6. Use according to any one of claims 1 to 4, wherein the concentration of the salt solution of the organic anion for replacing the counter anion of the surface of the PDADMAC film is between 0.003 and 5M.

7. Use according to any one of claims 1 to 4, the article modifying PDADMAC comprising: synthetic polymer material, natural polymer material, wood material, metal material or inorganic non-metal material.

8. Use according to any one of claims 1 to 4, the oily medium comprising crude oil, motor oil, diesel oil, animal oil, vegetable oil, butanol, pentanol, hexane, hexadecane, chloroform or toluene.