A method for preparing a polymer material surface grafted with PDMS brush and application

Abstract

The application relates to a preparation method and application of a polymer material surface grafted PDMS brush, and belongs to the technical field of material surface wettability regulation. The method is as follows: inorganic SiO2 layer is vapor deposited on the polymer surface; the polymer is subjected to plasma treatment and vapor deposition of the inorganic SiO2 layer in sequence, and the vapor deposition sample is taken out; the plasma treatment is carried out again for 5-20 min, and the sample is exposed in air for 10 min; a PDMS brush solution is prepared, 1 wt% concentrated sulfuric acid is added to the whole solution, and mechanical stirring is carried out for 10 min; the PDMS brush solution is dropped on the surface of the vapor deposition sample, and the sample is exposed in air and left for 10-60 min; the sample surface is washed with isopropyl alcohol, toluene and the like, and the ungrafted PDMS brush is washed away; the isopropyl alcohol remaining on the surface is dried, and the super-lubricating surface obtained after the PDMS brush is grafted is introduced, the surface not only has a self-cleaning effect on water, but also has a self-cleaning effect on organic liquids with low surface tension, and the application range is increased.

Description

Technical Field

[0001] This invention belongs to the field of material surface wettability control technology, specifically relating to a method for preparing and applying a PDMS brush grafted onto the surface of a polymer material. Background Technology

[0002] Low liquid adhesion surfaces, such as those with antifouling, drag reduction, and self-cleaning properties, are of great interest in both practical applications and fundamental research. The most common examples are lotus-inspired superhydrophobic surfaces and pitcher plant-inspired smooth liquid-injected porous surfaces (SLIPS). However, superhydrophobic surfaces rely on micro / nano structures, which are easily damaged. SLIPS, on the other hand, require lubricants, which are prone to runoff and cannot be used long-term. Liquid flexible polydimethylsiloxane (PDMS) brush coatings require neither micro / nano structures nor lubricants, while exhibiting low adhesion to droplets across a wide range of surface tensions.

[0003] Many materials in reality are polymers, such as windmill blades. These materials are expensive and difficult to clean. Therefore, grafting a layer of PDMS brushes onto their surfaces is crucial to reduce manual cleaning costs by allowing dust and droplets to easily slide off, and can also significantly improve material utilization. Thus, a brush grafting method suitable for polymer surfaces is needed. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that it is difficult to graft PDMS brushes onto polymer surfaces to achieve a self-cleaning effect. This invention provides a method for preparing and applying PDMS brushes grafted onto polymer material surfaces. This method successfully grafts PDMS brushes onto polymer material surfaces and achieves structural control, which can meet a wider range of application needs.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for preparing a PDMS brush grafted onto the surface of a polymer material, the method comprising:

[0007] Step 1: Vapor deposition of SiO2 inorganic layer on polymer surface: Cut polymer into small pieces, clean the surface with N2, perform plasma treatment for 2 min ~ 10 min, place in a vacuum dryer to perform vapor deposition of SiO2 inorganic layer, and take out vapor deposition sample.

[0008] Step 2: Liquid-phase grafting of PDMS brushes onto the surface of the vapor-deposited sample: The sample from Step 1 is subjected to plasma treatment for 5-20 min, then removed and exposed to air for 5-10 min. A PDMS brush solution is prepared, and concentrated sulfuric acid (0.5 wt%-2 wt% of the total solution) is added. The solution is mechanically stirred for 5-15 min. 0.05 mL-0.2 mL of the PDMS brush solution is added dropwise to a square vapor-deposited sample surface with sides of 0.5-5 cm. The sample is exposed to air and allowed to stand for 10-60 min. After 10-60 min, the sample surface is rinsed with isopropanol and toluene to remove the ungrafted PDMS brushes. Finally, the sample is placed in an oven and heated for 2-10 min to dry any remaining isopropanol and toluene on the surface.

[0009] Further, in step one, the polymer is prepared as follows: epoxy resin and curing agent are mixed at a mass ratio of 1:0.35~0.55, stirred until homogeneous, and then placed in a vacuum oven and evacuated until no bubbles are present; the solution is poured into a mold, and evacuated again until no bubbles are present; then it is placed in an oven for curing at 80~130 ℃ for 1~2 h; the polymer is then removed from the mold to obtain the polymer. Besides polymer substrates, this method is also suitable for substrates such as silicon wafers and glass.

[0010] Further, the epoxy resin is E44 or E51; the curing agent is one or more of polyetheramine D230, polyetheramine D400, pentaethylenehexamine PEHA, toluenedimethylamine MXDA, and diethylenetriamine DETA.

[0011] Furthermore, in step one, the plasma treatment conditions are: the plasma instrument power is 70 W, and the sample surface is bombarded in an oxygen atmosphere to generate hydroxyl groups on the surface.

[0012] Further, in step one, vapor deposition is carried out in a vacuum desiccator: 1-10 mL of concentrated hydrochloric acid and 2-6 mL of tetraethyl silicate are placed in a fixed vacuum desiccator, with the concentrated hydrochloric acid placed in the center, and the samples arranged around the concentrated hydrochloric acid as the center, with square samples having a side length of 0.5-5 cm, and the tetraethyl silicate placed on the outermost edge, and vapor deposition is carried out at 20-30 °C for 0.5-2.5 days.

[0013] Furthermore, in step two, the conditions for plasma treatment are: the plasma instrument power is 70 W, and the sample surface is bombarded in an oxygen atmosphere to generate hydroxyl groups on the surface.

[0014] Furthermore, in step two, the PDMS brushing solution has the following three types:

[0015] (1) Prepare PDMS brush solution using isopropanol and dimethyldimethoxysilane in a mass ratio of 4:1 to 4:4;

[0016] (2) Prepare PDMS brush solution using toluene and dimethyldichlorosilane at a mass ratio of 4:1 to 4:4;

[0017] (3) Prepare PDMS brush solution using isopropanol: monoglycidyl ether-terminated poly(dimethylsiloxane) at a mass ratio of 4:1 to 4:4.

[0018] An application of a polymer of a surface-grafted PDMS brush prepared by the above preparation method in droplet manipulation, wherein the application is as follows:

[0019] Using 3D-printed cuboid, cylindrical, V-shaped, S-shaped, and trapezoidal molds (made of acrylic tube-cured resin), the brushed sample was heated above its glass transition temperature. The mold (with different patterns on the brush surface to demonstrate droplet movement) was pressed onto the sample surface and held in place until the temperature cooled below the glass transition temperature. The groove structure on the sample surface (the cuboid mold has a protruding cuboid section; pressing this cuboid onto the surface leaves the grooved grooves) was preserved, resulting in an anisotropic surface. A 15 μL droplet was used to test the droplet sliding angles in two directions parallel and perpendicular to the grooves on the grooved sample surface. The different sliding angles indicated anisotropy. Furthermore, after obtaining V-shaped and S-shaped grooves on the surface, droplets of a certain volume can slide along these grooves, achieving directional droplet transport and quantitative chemical reactions. Trapezoidal grooves enable droplet self-transportation.

[0020] An application of a polymer of a surface-grafted PDMS brush prepared by the above preparation method in droplet manipulation, wherein the application is as follows:

[0021] A concentric tube mold was prepared by adding a prepared polymer base solution between the inner and outer tubes of the mold and curing it for 3-7 days. The mold was then removed to obtain a polymer tube with a thickness of 0.5-1 mm. The polymer tube was heated above its glass transition temperature, cut open, and flattened. It was then cooled below its glass transition temperature to obtain a rectangular polymer tube. The flattened polymer tube was subjected to vapor deposition and then grafted with a PDMS brush. Finally, the sample was heated above its glass transition temperature to restore the flattened polymer tube to its tubular shape. After heating above its glass transition temperature, one end of the tube was pressed into a rectangular shape, while the other end remained round without being pressed, resulting in an asymmetric tube for droplet self-transport and to reduce evaporation during droplet transport.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. Previously, the substrates for grafted PDMS brushes were glass or silicon wafers. Glass and silicon are inorganic materials with many active groups on their surfaces, making it easy to graft PDMS brushes onto them through plasma treatment. Most materials in daily life are polymer systems; therefore, this invention focuses on grafting PDMS brushes onto polymer surfaces. Polymer surfaces have fewer functional groups, allowing for the introduction of PDMS brushes onto the surface. An inorganic layer increases reactive sites. By adjusting the tetraethyl orthosilicate content, a relatively smooth surface can be obtained. Then, PDMS brush grafting is performed to obtain a sample that meets the requirements. After heating, grooves can be pressed into the surface to achieve droplet manipulation.

[0024] 2. After preparing the polymer substrate, this invention selects a tetraethyl silicate method catalyzed by concentrated hydrochloric acid in a closed environment to obtain the inorganic layer. This method is superior to directly spraying onto the surface. This method has the advantages of simple operation, low cost, and large-area preparation, so as to obtain a super-lubricating surface and enable the polymer surface to acquire self-cleaning properties and anisotropy.

[0025] 3. This invention introduces a smooth inorganic layer, and after grafting PDMS brushes, a super-lubricated surface is obtained. This surface not only has a self-cleaning effect on water but also on low-surface-tension organic liquids, thus expanding its application range. Spraying... The particles produce a superhydrophobic surface, which is easily damaged and only has a self-cleaning effect on water. Attached Figure Description

[0026] Figure 1 This is a 1 kx electron microscope image of the material surface after vapor deposition on the polymer surface;

[0027] Figure 2 This is a 5kx electron microscope image of the material surface after vapor deposition on the polymer surface;

[0028] Figure 3 This is a 1 kx electron microscope image of the material surface after vapor deposition and grafting of PDMS brushes onto the polymer surface.

[0029] Figure 4 This is a 5kx electron microscope image of the material surface after vapor deposition and grafting of PDMS brushes onto the polymer surface.

[0030] Figure 5 This is a photograph showing the sliding angle of 10 μL of water on the surface of a grafted PDMS brush material. The sliding angle is approximately... .

[0031] Figure 6 This is an image of the grooves obtained after pressing the brush surface with a rectangular mold. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0033] Example 1:

[0034] Step 1: Preparation of polymer substrate: Mix E44 and polyetheramine D230 at a mass ratio of 1:0.35, stir until homogeneous, and place in a vacuum oven to evacuate until no bubbles are present; pour the above solution into a mold, and continue to evacuate until no bubbles are present; then place in an oven for curing at 100 ℃ for 2 h and 130 ℃ for 2 h; finally, remove the polymer from the mold to obtain the polymer.

[0035] Step 2: Vapor deposition of SiO2 inorganic layer on polymer surface: The polymer substrate is cut into small pieces, the surface is cleaned with N2, and plasma treated for 10 min: The plasma instrument power is 70 W, and the sample surface is bombarded in an oxygen atmosphere to generate hydroxyl groups. The sample is then removed and placed in a vacuum desiccator for vapor deposition. Vapor deposition is performed in a vacuum desiccator: 3 mL of concentrated hydrochloric acid and 3 mL of tetraethyl silicate are placed in a fixed vacuum desiccator, with the concentrated hydrochloric acid in the center. Four 3 cm × 3 cm blocks of sample are placed around the concentrated hydrochloric acid, with the tetraethyl silicate on the outermost layer. Vapor deposition is performed for 2 days. The vapor-deposited sample is then removed. Figure 1 As shown, a smooth SiO2 inorganic layer was obtained by vapor deposition.

[0036] Step 3: Liquid-phase grafting of PDMS brushes onto the surface of the vapor-deposited sample: The sample from Step 2 was subjected to plasma treatment for 20 min (70 W plasma instrument power; bombardment of the sample surface in an oxygen atmosphere generates hydroxyl groups). It was then removed and exposed to air for 10 min to allow the surface hydroxyl groups to stabilize, facilitating the subsequent brush grafting experiment. A PDMS brush solution was prepared using isopropanol and dimethyldimethoxysilane in a 4:1 mass ratio. Concentrated sulfuric acid (1 wt% of the total solution) was added as a catalyst to catalyze the hydrolysis and dehydration condensation of dimethyldimethoxysilane, followed by mechanical stirring for 10 min. One drop of the PDMS brush solution was added to the surface of a 1 cm × 1 cm vapor-deposited sample and allowed to stand in air for 40 min. After 40 min, the sample surface was rinsed with isopropanol and toluene to remove the ungrafted PDMS brushes. Finally, the sample was placed in an oven and heated for 5 min to dry any remaining isopropanol. The resulting product is shown below. Figure 3 As shown, after the PDMS brushing, the surface cracks of the SiO2 inorganic layer were filled, improving the surface smoothness. Figure 5It is the sliding angle of a 10 μL droplet on the surface after brushing, and the sliding angle is relatively low.

[0037] Using 3D printing V-shaped ( Figure 6 The depth and width of the V-shaped grooves were observed under an electron microscope, along with an S-shaped mold (made of acrylic tube-cured resin). The brushed sample was heated above its glass transition temperature. V-shaped and S-shaped molds (with different patterns on different brush surfaces to demonstrate droplet movement) were pressed onto the sample surface and held in place until the temperature cooled below the glass transition temperature. The groove structure on the sample surface was preserved, resulting in an anisotropic surface. A 20 μL droplet was used to test the droplet sliding angles in two directions parallel and perpendicular to the grooves on the grooved sample surface. The different sliding angles indicated anisotropy. Furthermore, after obtaining V-shaped and S-shaped grooves on the surface, a droplet of a certain volume can slide along the groove shape, achieving directional droplet transport and quantitative chemical reactions. Trapezoidal grooves can enable droplet self-transport.

[0038] Example 2:

[0039] Step 1: Preparation of polymer substrate: Mix E44 and polyetheramine D230 at a mass ratio of 1:0.5, stir until homogeneous, and place in a vacuum oven to evacuate until no air bubbles are present; pour the above solution into a concentric tube mold, and continue to evacuate until no air bubbles are present; then place in an oven for curing at 100 ℃ for 2 h and 130 ℃ for 2 h; finally, remove the polymer from the mold to obtain the polymer.

[0040] Step Two: Vapor Deposition of SiO2 Inorganic Layer on Polymer Surface: Cut the polymer tube into rectangles, clean the surface with N2, and perform plasma treatment for 10 minutes: Use a 70 W plasma instrument to bombard the sample surface in an oxygen atmosphere to generate hydroxyl groups. Remove the sample and place it in a vacuum desiccator for vapor deposition. Vapor deposition is performed in a vacuum desiccator: Place 5 mL of concentrated hydrochloric acid and 5 mL of tetraethyl silicate in a fixed vacuum desiccator, with the concentrated hydrochloric acid in the center. Arrange the samples around the concentrated hydrochloric acid, placing six 2 cm × 1 cm rectangular samples, with the tetraethyl silicate on the outermost edge. Vapor deposition is performed for 2 days. Remove the vapor-deposited samples, as shown below. Figure 2 As shown, a smooth SiO2 inorganic layer was obtained by vapor deposition.

[0041] Step 3: Liquid-phase grafting of PDMS brushes onto the surface of the vapor-deposited sample: The sample from Step 2 is subjected to plasma treatment for 10 min (plasma instrument power 70 W; bombardment of the sample surface in an oxygen atmosphere generates hydroxyl groups). After removal, a PDMS brush solution is prepared using isopropanol:dimethyldimethoxysilane at a mass ratio of 4:1. Concentrated sulfuric acid (1 wt% of the total solution) is added as a catalyst to catalyze the hydrolysis and dehydration condensation of dimethyldimethoxysilane. The mixture is mechanically stirred for 10 min. One drop of the PDMS brush solution is added to the surface of the 2 cm × 1 cm vapor-deposited sample, and the sample is exposed to air and allowed to stand for 30 min. After 30 min, the sample surface is rinsed with isopropanol and toluene to remove ungrafted PDMS brushes. Finally, the sample is placed in an oven and heated for 5 min to dry any residual isopropanol. The resulting product is shown below. Figure 4 As shown, after the PDMS brushing, the surface cracks of the SiO2 inorganic layer were filled, improving the surface smoothness. Figure 5 It is the sliding angle of a 10 μL droplet on the surface after brushing, and the sliding angle is relatively low.

[0042] The PDMS brush grafted sample is heated above the glass transition temperature to restore the flattened polymer tube to its tubular shape. After heating above the glass transition temperature, one end of the tube is pressed into a rectangular shape, while the other end remains round without being pressed, resulting in an asymmetric tube for droplet self-transport and to reduce evaporation during droplet transport.

Claims

1. A method for preparing a PDMS brush grafted onto the surface of a polymer material, characterized in that: The method is as follows: Step 1: Vapor deposition of SiO2 inorganic layer on polymer surface: The polymer is cut into small pieces, the surface is cleaned with N2, subjected to plasma treatment for 2-10 minutes, and then placed in a vacuum desiccator for vapor deposition of SiO2 inorganic layer. The vapor-deposited sample is then removed. The polymer is prepared as follows: epoxy resin and curing agent are mixed at a mass ratio of 1:0.35-0.55, stirred until homogeneous, and then placed in a vacuum oven and evacuated until no bubbles are present. The solution is poured into a mold, and vacuum evacuation is continued until no bubbles are present. Then, it is placed in an oven for curing at 80-130℃. 1~2h; Remove the polymer from the mold to obtain the polymer; The plasma treatment conditions are: plasma instrument power 70W, bombard the sample surface in an oxygen atmosphere to generate hydroxyl groups on the surface; Vapor deposition is carried out in a vacuum desiccator: 1~10mL of concentrated hydrochloric acid and 2~6mL of tetraethyl silicate are placed in a fixed vacuum desiccator, with the concentrated hydrochloric acid placed in the center, and the sample arranged around the concentrated hydrochloric acid as the center, with square samples of 0.5~5cm on the side, and tetraethyl silicate placed on the outermost edge, vapor deposition at 20~30℃ for 0.5~2.5d; Step 2: Liquid-phase grafting of PDMS brushes onto the surface of the vapor-deposited sample: The sample from Step 1 is subjected to plasma treatment for 5-20 min, then removed and exposed to air for 5-10 min. A PDMS brush solution is prepared, and concentrated sulfuric acid (0.5 wt%-2 wt% of the total solution) is added. The solution is mechanically stirred for 5-15 min. 0.05 mL-0.2 mL of the PDMS brush solution is added dropwise to the surface of a square vapor-deposited sample with sides of 0.5-5 cm. The sample is then exposed to air and allowed to stand for 10-60 min. After 10-60 min, the sample surface is rinsed with isopropanol and toluene to remove the ungrafted PDMS brushes. Finally, the sample is placed in an oven and heated for 2-10 min to dry any remaining isopropanol and toluene on the surface.

2. The method for preparing a PDMS brush grafted onto the surface of a polymer material according to claim 1, characterized in that: The epoxy resin is E44 or E51; the curing agent is one or more of polyetheramine D230, polyetheramine D400, pentaethylenehexamine PEHA, toluene dimethylamine MXDA, and diethylenetriamine DETA.

3. The method for preparing a PDMS brush grafted onto the surface of a polymer material according to claim 1, characterized in that: In step two, the plasma treatment conditions are as follows: the plasma instrument power is 70W, and the sample surface is bombarded in an oxygen atmosphere to generate hydroxyl groups on the surface.

4. The method for preparing a PDMS brush grafted onto the surface of a polymer material according to claim 1, characterized in that: In step two, the PDMS brushing solution has the following three types: (1) Prepare PDMS brush solution using isopropanol and dimethyldimethoxysilane in a mass ratio of 4:1 to 4:4; (2) Prepare PDMS brush solution using toluene and dimethyldichlorosilane at a mass ratio of 4:1 to 4:4; (3) Prepare PDMS brush solution using isopropanol: monoglycidyl ether-terminated poly(dimethylsiloxane) at a mass ratio of 4:1 to 4:

4.

5. The application of a polymer of a surface-grafted PDMS brush prepared by the preparation method according to any one of claims 1 to 4 in droplet manipulation, characterized in that: The application is as follows: The brushed sample is heated above the glass transition temperature, and different patterns are made on the brushed surface to demonstrate droplet movement. The sample surface is pressed with a mold and kept pressed. After the temperature cools down to below the glass transition temperature, the groove structure on the sample surface is preserved. The cuboid mold is a cuboid with a protruding cuboid. After pressing this cuboid onto the surface, the surface is left with the cuboid grooves, thus obtaining an anisotropic surface.

6. The application of a polymer of a surface-grafted PDMS brush prepared by the preparation method according to any one of claims 1 to 4 in droplet manipulation, characterized in that: The application is as follows: A concentric tube mold was prepared by adding a prepared polymer base solution between the inner and outer tubes of the mold and curing it for 3-7 days. The mold was then removed to obtain a polymer tube with a thickness of 0.5-1 mm. The polymer tube was heated to above its glass transition temperature, cut open, flattened, and cooled to below its glass transition temperature to obtain a rectangular polymer tube. The flattened polymer tube was subjected to vapor deposition and then grafted with a PDMS brush. Finally, the sample was heated to above its glass transition temperature to restore the flattened polymer tube to its tubular shape. By heating the tube above its glass transition temperature, one end is pressed into a rectangular shape while the other end remains round, resulting in an asymmetrical tube. This allows for droplet self-transportation and reduces evaporation during droplet transport.

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