Process for the preparation of polydimethylsiloxane elastomers with an anti-oil penetration coating

Abstract

The application belongs to the technical field of polydimethylsiloxane surface modification, and provides a preparation method of polydimethylsiloxane elastomer with an oil permeation resistant coating, which comprises the following steps: (1) performing surface activation treatment on clean and dry polydimethylsiloxane elastomer by oxygen plasma to obtain an activated polydimethylsiloxane elastomer base material; (2) performing grafting reaction between active end group capped silane and the surface of the activated polydimethylsiloxane elastomer base material to form a flexible molecular brush on the surface of the activated polydimethylsiloxane elastomer base material, and obtain polydimethylsiloxane elastomer with an oil permeation resistant coating; the active end group capped silane is active end group capped silane monomer or active group capped silane polymer. The method can improve the oil permeation resistance and liquid repellency of the polydimethylsiloxane elastomer without damaging the mechanical properties and optical transparency of the polydimethylsiloxane elastomer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polydimethylsiloxane surface modification, and relates to a preparation method of a polydimethylsiloxane elastomer with an oil permeation resistant coating. BACKGROUND

[0002] Polydimethylsiloxane (PDMS) is one of the most important organosilicon polymers in history, and has different applications in many fields. The Si-O-Si bond of the silicon-oxygen main chain of PDMS has a very low torsional barrier, plus the weak intermolecular interaction of the two methyl groups, so that the PDMS molecular chain has high flexibility. The chain PDMS molecule will be converted into an elastomer material with adjustable Young's modulus after chemical crosslinking. Due to excellent optical transparency, temperature resistance, weather resistance and biocompatibility, PDMS elastomers are widely used in various fields. For example, PDMS can be used as a soft lithography stamp resin to prepare microfluidic devices; PDMS elastomers can be used as an insulating layer of wearable electronic products to protect complex circuits from environmental pressure; PDMS elastomers can be used as a biocompatible contact substrate in the food and medical fields, and are used in class II or III medical tubes for extracorporeal circulation in brain shunts, heart surgery and pacemaker leads. For another example, the high dissociation energy (444 KJ / mol) of the Si-O bond in PDMS makes it possible to use it as a sealing material to seal elements used in extreme environments.

[0003] Although PDMS elastomers have a wide range of applications in scientific and industrial fields, when in contact with non-polar liquids, especially hydrocarbons (such as oil), the liquid small molecules can penetrate into the PDMS elastomer due to its internal porous network structure, causing the PDMS elastomer to swell and deform, which seriously affects the performance of the PDMS elastomer assembly. For example, this can make organic synthesis in microchannels infeasible, reduce the sensing accuracy of encapsulated flexible sensors, cause contamination of implanted medical devices, cause elastic failure of mechanical seals, etc. Currently, strategies to improve the anti-permeation performance of PDMS elastomers mainly fall into two categories: bulk modification and surface functionalization. Bulk modification includes vulcanization (see M.M. Kim, Y. Huang, K. Choi et al. Microelectron. Eng. (2014)), compatibilization (see H. Wu, X. Zhang, D. Xu et al. J. Membr. Sci. (2009)), blending (see B. Kaur, S. Kumar, T. Mondal et al. ACS Omega (2020)), etc. Surface functionalization usually involves setting a solvent-resistant solid coating on the surface of the PDMS elastomer (see A.R. Abate, D. Lee, T. Do et al. Lab Chip (2008)). Although these methods can enhance the resistance of PDMS elastomers to non-polar liquids, they inevitably compromise the excellent mechanical properties and optical transparency of PDMS elastomers. PDMS elastomers are used in daily life, scientific research and industry, and if their oil permeation resistance can be improved without compromising their unique properties such as mechanical properties and optical transparency, it will be of great significance to further expand their range of applications. SUMMARY

[0004] In view of the problem that the existing technology uses bulk modification and surface functionalization strategies to improve the anti-permeation performance of PDMS elastomers, which compromises the mechanical properties and optical transparency of PDMS elastomers, the present application provides a method for preparing a polydimethylsiloxane elastomer with an oil permeation-resistant coating, which utilizes the synergistic effect of spatial barriers formed by nano-hole filling of the polydimethylsiloxane elastomer and liquid properties of the molecular brush to impart excellent oil permeation resistance and improve the liquid repellency of the polydimethylsiloxane elastomer without compromising its mechanical properties and optical transparency.

[0005] To achieve the above-mentioned application purposes, the technical solutions adopted by the present application are as follows:

[0006] A method for preparing a polydimethylsiloxane elastomer with an oil permeation-resistant coating, comprising the following steps:

[0007] (1) subjecting clean and dry polydimethylsiloxane elastomer to oxygen plasma surface activation treatment to obtain activated polydimethylsiloxane elastomer substrate;

[0008] (2) grafting reactive end group terminated silane with the surface of the activated polydimethylsiloxane elastomer substrate to form flexible molecular brush on the surface of the activated polydimethylsiloxane elastomer substrate to obtain polydimethylsiloxane elastomer with oil permeation resistant coating;

[0009] The reactive end group terminated silane is either reactive end group terminated silane monomer or reactive group terminated silane polymer; during the grafting reaction, the reactive end group terminated silane monomer polymerizes to form polydimethylsiloxane flexible molecular chain and grafts on the surface of the activated polydimethylsiloxane elastomer substrate, and the silane polymer chain of the reactive group terminated silane polymer directly grafts on the surface of the activated polydimethylsiloxane elastomer substrate.

[0010] In the above technical solution, the reactive end group terminated silane monomer is reactive end group terminated tetramethyldisiloxane, and the reactive group terminated silane polymer is reactive end group terminated polydimethylsiloxane or reactive end group terminated perfluoropolyether silane.

[0011] In the above technical solution, the reactive end group of the reactive end group terminated silane includes at least one of chlorine end group, hydroxyl group, carboxyl group, amino group, alkoxy group, epoxy group and isocyanate group.

[0012] In the above technical solution, the molecular weight of the reactive end group terminated silane is 203-100000 g / mol.

[0013] Further, in the above technical solution, when the molecular weight of the reactive end group terminated silane is less than 10000 g / mol, the grafting reaction in step (2) is performed in a non-contact manner, and when the molecular weight of the reactive end group terminated silane is greater than or equal to 10000 g / mol, the grafting reaction is performed in a contact manner.

[0014] In the above technical solution, the operation of performing the grafting reaction in a non-contact manner in step (2) is as follows: adding the reactive end group terminated silane into a container, fixing the activated polydimethylsiloxane elastomer substrate in the container to avoid direct contact between the activated polydimethylsiloxane elastomer substrate and the liquid reactive end group terminated silane, sealing the container, allowing the reactive end group terminated silane molecules to volatilize and react with the surface of the activated polydimethylsiloxane elastomer substrate, then taking out and rinsing with deionized water, and drying to obtain the polydimethylsiloxane elastomer with oil permeation resistant coating.

[0015] In the above technical solution, the grafting reaction in step (2) is performed in a contact mode, which is performed by smearing the active end group terminated silane on the surface of the activated polydimethylsiloxane elastomer substrate, placing it in a sealed container to allow the active end group terminated silane to react with the surface of the activated polydimethylsiloxane elastomer substrate, then taking it out and rinsing it with deionized water, and drying it to obtain a polydimethylsiloxane elastomer with an oil permeation resistant coating.

[0016] In the above technical solution, when the grafting reaction in step (2) is performed in a non-contact mode, the active end group terminated silane is added to the container in a proportion of 2-50 μL per 1 cm 2 The active end group terminated silane is added to the container in a proportion of 2-50 μL per 1 cm

[0017] In the above technical solution, when the grafting reaction in step (2) is performed in a contact mode, the active end group terminated silane is smeared on the surface of the activated polydimethylsiloxane elastomer substrate, and the area to be formed with an oil permeation resistant coating is completely covered. Generally, the active end group terminated silane can be smeared on the surface of the activated polydimethylsiloxane elastomer substrate in a proportion of 50-500 μL per 1 cm 2 The active end group terminated silane is smeared on the surface of the activated polydimethylsiloxane elastomer substrate in a proportion of 50-500 μL per 1 cm

[0018] In the above technical solution, during the grafting reaction in step (2), the pressure in the container is controlled to be no more than 1013.25 mbar.

[0019] In the above technical solution, during the grafting reaction in step (2), the temperature in the container is preferably controlled to be 10-100°C, and the grafting reaction time is preferably controlled to be 1-720 min.

[0020] In step (1) of the above technical solution, when the clean and dry polydimethylsiloxane elastomer is subjected to surface activation treatment by oxygen plasma, the surface of the clean and dry polydimethylsiloxane elastomer can be subjected to surface activation treatment according to different actual application requirements, and the grafting reaction in step (2) mainly occurs in the treated part.

[0021] In the above technical solution, when the grafting reaction is performed in a non-contact mode, in order to facilitate the active end group terminated silane molecules volatilized from the bottom of the container to fully contact the surface of the activated polydimethylsiloxane elastomer substrate and react, the activated polydimethylsiloxane elastomer substrate is preferably suspended in the container. For example, a support can be placed in the container, or a hook can be provided in the container, and the activated polydimethylsiloxane elastomer substrate is suspended by the support or the hook.

[0022] In step (1) of the above technical solution, the power of the oxygen plasma for surface activation treatment is preferably 10-1500 W, and the time is 10 s-10 min.

[0023] In the above technical solution, the clean and dry PDMS elastomer is obtained by drying the PDMS elastomer after ultrasonic cleaning with an organic solvent (e.g., ethanol) and water to remove surface organic contaminants and solid particles. The drying method can be air blowing, nitrogen blowing, inert gas blowing, or other drying methods. Alternatively, the PDMS elastomer can be dried by baking or natural air drying.

[0024] Compared with the prior art, the technical solution of the present application can produce the following beneficial technical effects:

[0025] 1. The present application provides a method for preparing a PDMS elastomer with an oil-repellent coating. The method first performs surface activation treatment on a clean and dry PDMS elastomer using oxygen plasma to form a large number of active functional groups (e.g., hydroxyl groups) on the surface of the PDMS elastomer, which facilitates subsequent grafting reactions. Then, a non-contact or contact method is used to perform grafting reactions to form a flexible molecular brush on the surface of the activated PDMS elastomer substrate, thereby obtaining a PDMS elastomer with an oil-repellent coating. On the one hand, the flexible molecular brush grafted on the surface of the PDMS elastomer fills the nanopores on the surface of the PDMS elastomer and forms a steric barrier. On the other hand, the flexible molecular brush grafted on the surface of the PDMS elastomer has good dynamic flexibility, making the oil-repellent coating formed by the molecular brush have a liquid-like flowability. These two factors enable the method of the present application to impart excellent oil-repellent properties and improve the liquid-repellent ability of the PDMS elastomer without damaging the mechanical properties and optical transparency of the PDMS elastomer. This solves the problem of the prior art that the bulk modification and surface functionalization strategies will damage the mechanical properties and optical transparency of the PDMS elastomer.

[0026] 2. The method of the present application is simple to operate. By adjusting the molecular structure on the surface of the PDMS elastomer, the method can impart excellent oil-repellent properties and excellent liquid-repellent properties to the PDMS elastomer. The method has low requirements for instruments, reagents, and process conditions, and can be completed under conventional operating conditions. It is easy to promote and apply the method under existing simple process conditions, and is conducive to realizing industrialized production. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1is a flowchart of the preparation of PDMS elastomer with oil permeation resistant coating by the present application using non-contact grafting reaction, in which, 1-PDMS elastomer, 2-activated PDMS elastomer substrate, 3-active end group capped silane molecule, 4-liquid active end group capped silane, 5-vessel, 6-PDMS elastomer grafted with flexible molecular brush.

[0028] Figure 2 is a comparison optical picture of the absorption of hexadecane by blank PDMS elastomer and PDMS elastomer with oil permeation resistant coating prepared in Example 1 at different times.

[0029] Figure 3 is a comparison test result of the absorption rate of hexadecane by blank PDMS elastomer and PDMS elastomer with oil permeation resistant coating prepared in Example 1 at different times.

[0030] Figure 4 is a stress-strain curve of blank PDMS elastomer and PDMS elastomer with oil permeation resistant coating prepared in Example 1.

[0031] Figure 5 is a test result of the transmittance spectrum of blank PDMS elastomer and PDMS elastomer with oil permeation resistant coating prepared in Example 1.

[0032] Figure 6 is a test result of the contact angle hysteresis of water and hexadecane on the surface of blank PDMS elastomer and PDMS elastomer with oil permeation resistant coating prepared in Example 1.

[0033] Figure 7 is a time sequence image of the sliding of 20 μL water droplet and hexadecane droplet on the surface of blank PDMS elastomer and PDMS elastomer with oil permeation resistant coating prepared in Example 1. DETAILED DESCRIPTION

[0034] The preparation method of polydimethylsiloxane elastomer with oil permeation resistant coating provided by the present application is further described by the following examples. It is necessary to point out that the following examples are only used to further describe the present application and cannot be understood as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above description, and such improvements and adjustments still belong to the protection scope of the present application.

[0035] In the following examples, the polydimethylsiloxane (PDMS) elastomer (Sylgard 184) is purchased from Dow Chemical Company, and other reagents are commercially available and can be directly purchased from the market or customized by the manufacturer.

[0036] Example 1

[0037] In this embodiment, a method for preparing a PDMS elastomer with an oil- resistant permeation coating is provided, and the steps are as follows:

[0038] (1) The sheet-shaped PDMS elastomer is sequentially cleaned with ethanol (purity > 99.7%) and deionized water for 60 s to remove organic contaminants and solid particles on the surface of the PDMS elastomer, and then the surface of the PDMS elastomer is blown dry with compressed nitrogen for standby.

[0039] (2) The PDMS elastomer treated in step (1) is placed in a plasma cleaning machine, and the surface of the PDMS elastomer is activated by oxygen plasma. The power of the oxygen plasma treatment is controlled at 50 W, and the treatment time is 30 s. In this step, only one side of the PDMS elastomer is activated to form a large number of active functional groups including hydroxyl groups on the activated surface, and an activated PDMS elastomer substrate is obtained.

[0040] (3) The grafting reaction is carried out in a non-contact manner, and the operation is as follows:

[0041] According to every 1 cm 2 The amount of 4 μL of chloro-terminated polydimethylsiloxane (molecular weight about 3000 g / mol) is added to the glass container, and the activated PDMS elastomer substrate is pasted on the top of the glass container with the activated surface facing down to avoid direct contact between the activated PDMS elastomer substrate and the liquid chloro-terminated polydimethylsiloxane. The glass container is sealed, and the temperature in the glass container is controlled at 60°C and the pressure is controlled at 1.33 mbar. The chloro-terminated polydimethylsiloxane molecules volatilize and contact the surface of the activated PDMS elastomer substrate and undergo grafting reaction. The grafting reaction time is controlled at 60 min, and a flexible molecular brush is formed on the surface of the activated PDMS elastomer substrate, i.e. a flexible molecular brush is formed on the surface of the activated PDMS elastomer substrate by gas phase chemical deposition. Then it is taken out, rinsed with deionized water and blown dry with compressed nitrogen. A PDMS elastomer with an oil-resistant permeation coating is obtained.

[0042] Example 2

[0043] In this embodiment, the performance of the PDMS elastomer with an oil-resistant permeation coating prepared in Example 1 is tested.

[0044] (1) Take the PDMS elastomer used in Example 1 (blank PDMS elastomer) and several PDMS elastomers with oil permeation resistant coating prepared in Example 1, respectively, and drop 5 μL of hexadecane on each blank PDMS elastomer and each PDMS elastomer with oil permeation resistant coating (drop on the oil permeation resistant coating), wipe off the residual hexadecane droplets on the surface every certain time interval, take photos using a digital camera, record the diffusion of hexadecane droplets on the blank PDMS elastomer and the PDMS elastomer with oil permeation resistant coating prepared in Example 1 at different diffusion times, and the results are shown in Figure 2 Figure 2 "before treatment" in the table represents the blank PDMS elastomer, and "after treatment" represents the PDMS elastomer with oil permeation resistant coating prepared in Example 1.

[0045] It can be seen from Figure 2 that the hexadecane droplets will rapidly diffuse into the internal network of the blank PDMS elastomer within the first 10 min, and leave obvious swelling traces on the surface, corresponding to the "before treatment" group of pictures in Figure 2 . After adding the hexadecane on the oil permeation resistant coating, no obvious traces are left on the surface after wiping off the residual hexadecane droplets during the 720 min contact process, corresponding to the "after treatment" group of pictures in Figure 2 , which shows that the oil permeation resistant coating formed on the surface of the PDMS elastomer in Example 1 has excellent oil permeation resistance.

[0046] (2) Take the blank PDMS elastomer and the PDMS elastomer with oil permeation resistant coating prepared in Example 1 as samples, and evaluate their oil permeation resistance by measuring the absorption rate η of the samples to hexadecane droplets. The absorption rate measurement steps are as follows:

[0047] ① Place the sample on the test platform of the contact angle measuring instrument;

[0048] ② Drop 5 μL of hexadecane on the surface of the sample. For the PDMS elastomer with oil permeation resistant coating prepared in Example 1, drop the hexadecane on the oil permeation resistant coating;

[0049] ③ The built-in camera of the contact angle measuring instrument captures the cross-sectional images of the droplets at certain intervals;

[0050] ④ Extract w and θ data from the captured images using analysis software. w is the contact width of the droplet on the surface, and θ is the contact angle of the droplet.

[0051] ⑤ Calculate the absorption rate η using the following formula: η = (V0-V t ) / V0x100%, where V0is the initial volume of the hexadecane droplet on the surface of the sample, and V t ​The residual volume of the hexadecane droplet on the sample surface after absorption time t. The whole hexadecane droplet is regarded as a spherical cap to calculate the volume. The formula of the droplet volume (V) is: V = πw 3 (2 + cosθ)(1 - cosθ) 2 / (24sin 3 θ).

[0052] During the whole measurement process, the positions of the sample and the camera were fixed. In order to avoid the evaporation of hexadecane, all the experiments were carried out at a constant room temperature of 20℃. The measurement was repeated for 3 times, and the average value of the 3 measurements was taken as the measurement result, which is shown in Figure 3 Figure 3 In the figure, "before treatment" represents the blank PDMS elastomer, and "after treatment" represents the PDMS elastomer with the oil permeation resistant coating prepared in Example 1.

[0053] It can be seen from Figure 3 that the PDMS elastomer with the oil permeation resistant coating has obviously better oil permeation resistance than the blank PDMS elastomer. For example, when the hexadecane surface diffusion lasts for 720 min, the absorption rate of hexadecane on the blank PDMS elastomer is as high as 20.8%, while the absorption rate of hexadecane on the PDMS elastomer with the oil permeation resistant coating is only 2.4%, and the absorption rate is reduced by 88.5%.

[0054] (3) The blank PDMS elastomer and the PDMS elastomer with the oil permeation resistant coating prepared in Example 1 were taken as samples, and the samples were subjected to tensile test using a tensile testing machine, and the stress-strain curves were obtained, as shown in Figure 4 Figure 4 In the figure, "before treatment" represents the blank PDMS elastomer, and "after treatment" represents the PDMS elastomer with the oil permeation resistant coating prepared in Example 1.

[0055] It can be seen from Figure 4 that the ultimate tensile strength of the blank PDMS elastomer and the PDMS elastomer with the oil permeation resistant coating prepared in Example 1 is almost the same, which is 4.77 MPa and 4.63 MPa, respectively. Meanwhile, the breaking strain of the two is the same, which is 140%. This indicates that the oil permeation resistant coating formed by grafting flexible molecular brushes on the surface of the PDMS elastomer basically does not cause loss to the mechanical properties of the PDMS elastomer. The elastic modulus of the blank PDMS elastomer and the PDMS elastomer with the oil permeation resistant coating prepared in Example 1 is calculated, which is 1.32 MPa and 1.27 MPa, respectively, and the elastic modulus only changes by 3.8%, which also indicates that the oil permeation resistant coating formed by grafting flexible molecular brushes on the surface of the PDMS elastomer basically does not affect the macroscopic elasticity of the PDMS elastomer.

[0056] ​​(4) Blank PDMS elastomer and the PDMS elastomer with an anti-oil penetration coating prepared in Example 1 were taken as samples, and their transmittance was tested using a spectrophotometer. The test results are as follows: Figure 5 As shown, Figure 5 In this context, "before treatment" refers to the blank PDMS elastomer, and "after treatment" refers to the PDMS elastomer with an anti-oil penetration coating prepared in Example 1.

[0057] Depend on Figure 5 It can be seen that the transmittance of the blank PDMS elastomer and the PDMS elastomer with the anti-oil penetration coating prepared in Example 1 are basically the same. For example, the transmittance of the blank PDMS elastomer at 555 nm is 93.7%, while the transmittance of the PDMS elastomer with the anti-oil penetration coating prepared in Example 1 is 93.6%. This indicates that the anti-oil penetration coating formed by grafting flexible molecular brushes onto the surface of the PDMS elastomer does not affect the light transmittance of the PDMS elastomer.

[0058] (5) Blank PDMS elastomer and the PDMS elastomer with an anti-oil penetration coating prepared in Example 1 were used as samples. Water and hexadecane were used as probe liquids. The contact angle hysteresis of the sample surface was measured using a contact angle meter. For the PDMS elastomer with an anti-oil penetration coating prepared in Example 1, the probe liquid needed to be dropped onto the anti-oil penetration coating for measurement. Three measurements were taken, and the average of the three measurements was taken. The measurement results are as follows: Figure 6 As shown, Figure 6 In this context, "before treatment" refers to the blank PDMS elastomer, and "after treatment" refers to the PDMS elastomer with an anti-oil penetration coating prepared in Example 1.

[0059] Depend on Figure 6 It can be seen that, compared with the blank PDMS elastomer, the contact angle hysteresis values ​​of water and hexadecane on the surface of the PDMS elastomer with anti-oil penetration coating prepared in Example 1 are significantly reduced. The contact angle hysteresis value of water on the surface of the PDMS elastomer with anti-oil penetration coating prepared in Example 1 decreased from 37.9° to 10.5°, and the contact angle hysteresis value of hexadecane on the surface of the PDMS elastomer with anti-oil penetration coating prepared in Example 1 decreased from 15° to 3.1°. This indicates that the anti-oil penetration coating formed by grafting flexible molecular brushes onto the surface of PDMS elastomer can improve the liquid repulsion performance of PDMS elastomer.

[0060] (6) Take the blank PDMS elastomer and the PDMS elastomer with an anti-oil penetration coating prepared in Example 1 as samples. Add 20 μL of water and hexadecane to the sample surface, respectively. For the PDMS elastomer with an anti-oil penetration coating prepared in Example 1, it needs to be added to the anti-oil penetration coating. Use a digital camera to record time-series images of water and hexadecane sliding on the tilted sample surface. The results are as follows.Figure 7 As shown, Figure 7 Figures (a) and (b) represent water and hexadecane, respectively. "Before treatment" represents the blank PDMS elastomer, and "After treatment" represents the PDMS elastomer with an oil-penetration-resistant coating prepared in Example 1.

[0061] Depend on Figure 7 It can be seen that, compared with the blank PDMS elastomer, after grafting a flexible molecular brush onto the surface of the PDMS elastomer to form an anti-oil penetration coating in Example 1, the liquid repulsion performance of the PDMS elastomer is effectively improved, and it can better repel water and hexadecane.

[0062] Example 3

[0063] In this embodiment, a method for preparing a PDMS elastomer with an oil-penetration-resistant coating is provided, comprising the following steps:

[0064] (1) Use ethanol (purity ≥99.7%) and deionized water to ultrasonically clean the PDMS elastomer for 30s in sequence to remove organic contaminants and solid particles on the surface of the PDMS elastomer. Then use compressed nitrogen to dry the surface of the PDMS elastomer for later use.

[0065] (2) The PDMS elastomer treated in step (1) is placed in a plasma cleaner and surface activated by oxygen plasma. The power of the oxygen plasma treatment is controlled at 300W and the treatment time is 10min. A large number of active functional groups, including hydroxyl groups, are formed on the surface of the PDMS elastomer, and the activated PDMS elastomer substrate is obtained.

[0066] (3) The grafting reaction is carried out in a non-contact manner, as follows:

[0067] According to each 1cm 2 Add 10 μL of chlorinated polydimethylsiloxane (molecular weight approximately 425 g / mol) to the bottom area of ​​a glass container. Suspend the activated PDMS elastomer substrate inside the glass container, avoiding direct contact between the activated PDMS elastomer substrate and the liquid chlorinated polydimethylsiloxane. Seal the glass container and control the temperature inside to room temperature (20–25 °C) and the pressure to atmospheric pressure (1013.25 mbar). After the chlorinated polydimethylsiloxane molecules volatilize, they contact the surface of the activated PDMS elastomer substrate and undergo a grafting reaction. Control the grafting reaction time to 5 minutes, forming a flexible molecular brush on the surface of the activated PDMS elastomer substrate. Then remove the substrate, rinse with deionized water, and dry the surface with compressed nitrogen to obtain a PDMS elastomer with an oil-resistant coating.

[0068] Example 4

[0069] In this embodiment, a method for preparing a PDMS elastomer with an oil penetration resistant coating is provided, and the steps are as follows:

[0070] (1) The PDMS elastomer was sequentially cleaned with ethanol (purity ≥ 99.7%) and deionized water for 30 s to remove organic contaminants and solid particles on the surface of the PDMS elastomer, and then the surface of the PDMS elastomer was blown dry with compressed nitrogen for standby.

[0071] (2) The PDMS elastomer treated in step (1) was placed in a plasma cleaning machine, and the surface of the PDMS elastomer was activated by oxygen plasma. The power of the oxygen plasma treatment was controlled at 1500 W, and the treatment time was 10 s. A large number of active functional groups including hydroxyl groups were formed on the surface of the PDMS elastomer, and an activated PDMS elastomer substrate was obtained.

[0072] (3) The grafting reaction was carried out in a contact mode, and the operation was as follows:

[0073] According to the proportion of 50 μL of alkoxy-terminated polydimethylsiloxane (molecular weight 100000 g / mol) per 1 cm 2 The activated PDMS elastomer substrate was coated with 50 μL of alkoxy-terminated polydimethylsiloxane (molecular weight 100000 g / mol) according to the proportion of 50 μL of alkoxy-terminated polydimethylsiloxane (molecular weight 100000 g / mol) per 1 cm

[0074] Example 5

[0075] In this embodiment, a method for preparing a PDMS elastomer with an oil penetration resistant coating is provided, and the steps are as follows:

[0076] (1) The PDMS elastomer was sequentially cleaned with ethanol (purity ≥ 99.7%) and deionized water for 30 s to remove organic contaminants and solid particles on the surface of the PDMS elastomer, and then the surface of the PDMS elastomer was blown dry with compressed nitrogen for standby.

[0077] (2) Put the PDMS elastomer treated in step (1) into a plasma cleaning machine, and perform surface activation treatment on the PDMS elastomer by using oxygen plasma, with the power of oxygen plasma treatment being controlled to be 10 W and the treatment time being controlled to be 60 s, so that a large number of active functional groups including hydroxyl groups are formed on the surface of the PDMS elastomer, thereby obtaining an activated PDMS elastomer substrate.

[0078] (3) Perform the grafting reaction in a non-contact manner, and the operation is as follows:

[0079] According to 1 cm 2 Add 2 μL of chloro-capped 1,3-dichlorotetramethyldisiloxane (molecular weight: 203 g / mol) to the glass container, and then add chloro-capped 1,3-dichlorotetramethyldisiloxane to the glass container, hang the activated PDMS elastomer substrate in the glass container to avoid direct contact between the activated PDMS elastomer substrate and the liquid chloro-capped 1,3-dichlorotetramethyldisiloxane, seal the glass container, control the temperature in the glass container to be room temperature (20-25 °C) and the pressure to be normal pressure (1013.25 mbar), and after the chloro-capped 1,3-dichlorotetramethyldisiloxane molecules volatilize, the chloro-capped 1,3-dichlorotetramethyldisiloxane molecules contact the surface of the activated PDMS elastomer substrate and undergo grafting reaction, and during the grafting reaction, the chloro-capped 1,3-dichlorotetramethyldisiloxane molecules polymerize to form polydimethylsiloxane flexible molecular chains and are grafted on the surface of the activated PDMS elastomer substrate, the grafting reaction time is controlled to be 1 min, and a flexible molecular brush is formed on the surface of the activated PDMS elastomer substrate, and then the activated PDMS elastomer substrate is taken out, rinsed with deionized water, and dried by blowing compressed nitrogen on the surface, thereby obtaining a PDMS elastomer with an oil permeation resistant coating.

[0080] Example 6

[0081] In this embodiment, a method for preparing a PDMS elastomer with an oil permeation resistant coating is provided, and the steps are as follows:

[0082] (1) Ultrasonically clean the PDMS elastomer with ethanol (purity ≥ 99.7%) and deionized water for 30 s in sequence to remove organic contaminants and solid particles on the surface of the PDMS elastomer, and then dry the surface of the PDMS elastomer with compressed nitrogen for standby use.

[0083] (2) Put the PDMS elastomer treated in step (1) into a plasma cleaning machine, and perform surface activation treatment on the PDMS elastomer by using oxygen plasma, with the power of oxygen plasma treatment being controlled to be 300 W and the treatment time being controlled to be 60 s, so that a large number of active functional groups including hydroxyl groups are formed on the surface of the PDMS elastomer, thereby obtaining an activated PDMS elastomer substrate.

[0084] (3) Perform the grafting reaction in a non-contact manner, and the operation is as follows:

[0085] per 1 cm 2 The hydroxyl-terminated perfluoropolyether oxane (molecular weight of about 3000 g / mol) was added into the glass container by adding 10 μL of the hydroxyl-terminated perfluoropolyether oxane per 1 cm2of the bottom area of the glass container, the activated PDMS elastomer substrate was hung in the glass container to avoid direct contact between the activated PDMS elastomer substrate and the liquid hydroxyl-terminated perfluoropolyether oxane, the glass container was sealed, the temperature and pressure in the glass container were controlled at 100 °C and normal pressure (1013.25 mbar) respectively, the hydroxyl-terminated perfluoropolyether oxane molecules volatilized and contacted with the surface of the activated PDMS elastomer substrate to occur grafting reaction, the grafting reaction time was controlled at 20 min, the flexible molecular brush was formed on the surface of the activated PDMS elastomer substrate, then the PDMS elastomer with oil permeation resistant coating was obtained by taking out, rinsing with deionized water and blowing dry the surface with compressed nitrogen.

[0086] Example 7

[0087] In this embodiment, a method for preparing the PDMS elastomer with oil permeation resistant coating was provided, and the steps were as follows:

[0088] (1) The PDMS elastomer was ultrasonically cleaned with ethanol (purity ≥ 99.7%) and deionized water for 30 s in sequence to remove organic contaminants and solid particles on the surface of the PDMS elastomer, and then the surface of the PDMS elastomer was blown dry with compressed nitrogen for standby.

[0089] (2) The PDMS elastomer treated by step (1) was placed in a plasma cleaning machine, and the surface of the PDMS elastomer was activated by oxygen plasma, the power of the oxygen plasma treatment was controlled at 300 W, and the treatment time was controlled at 60 s, a large number of active functional groups including hydroxyl groups were formed on the surface of the PDMS elastomer, and an activated PDMS elastomer substrate was obtained.

[0090] (3) The grafting reaction was performed in a non-contact manner, and the operation was as follows:

[0091] per 1 cm 2The carboxyl-terminated perfluoropolyether oxygen alkane (molecular weight of about 6000 g / mol) is added into the glass container in an amount of 20 μL per 1 cm2of the container bottom area, the activated PDMS elastomer substrate is hung in the glass container to avoid direct contact between the activated PDMS elastomer substrate and the liquid carboxyl-terminated perfluoropolyether oxygen alkane, the glass container is sealed, the temperature in the glass container is controlled at 80°C and the pressure is controlled at normal pressure (1013.25 mbar), the carboxyl-terminated perfluoropolyether oxygen alkane molecules volatilize to contact the surface of the activated PDMS elastomer substrate and grafting reaction occurs, the grafting reaction is controlled for 20 min, a flexible molecular brush is formed on the surface of the activated PDMS elastomer substrate, then the PDMS elastomer is taken out, rinsed with deionized water and dried by blowing compressed nitrogen on the surface, and a PDMS elastomer with an oil permeation resistant coating is obtained.

[0092] Example 8

[0093] In this embodiment, a method for preparing a PDMS elastomer with an oil permeation resistant coating is provided, and the steps are as follows:

[0094] (1) The PDMS elastomer is ultrasonically cleaned with ethanol (purity ≥ 99.7%) and deionized water for 30 s in sequence to remove organic contaminants and solid particles on the surface of the PDMS elastomer, and then the surface of the PDMS elastomer is dried with compressed nitrogen for standby use.

[0095] (2) The PDMS elastomer treated in step (1) is placed in a plasma cleaning machine, and the PDMS elastomer is subjected to surface activation treatment with oxygen plasma, the power of the oxygen plasma treatment is controlled at 50 W, and the treatment time is controlled at 30 s, a large number of active functional groups including hydroxyl groups are formed on the surface of the PDMS elastomer, and an activated PDMS elastomer substrate is obtained.

[0096] (3) The grafting reaction is performed in a non-contact manner, and the operation is as follows:

[0097] According to 20 μL per 1 cm2of the container bottom area, the carboxyl-terminated perfluoropolyether oxygen alkane is added into the glass container, the activated PDMS elastomer substrate is hung in the glass container to avoid direct contact between the activated PDMS elastomer substrate and the liquid carboxyl-terminated perfluoropolyether oxygen alkane, the glass container is sealed, the temperature in the glass container is controlled at 80°C and the pressure is controlled at normal pressure (1013.25 mbar), the carboxyl-terminated perfluoropolyether oxygen alkane molecules volatilize to contact the surface of the activated PDMS elastomer substrate and grafting reaction occurs, the grafting reaction is controlled for 20 min, a flexible molecular brush is formed on the surface of the activated PDMS elastomer substrate, then the PDMS elastomer is taken out, rinsed with deionized water and dried by blowing compressed nitrogen on the surface, and a PDMS elastomer with an oil permeation resistant coating is obtained. 2The amino-terminated polydimethylsiloxane is added into the glass container by adding 10 μL of the amino-terminated polydimethylsiloxane (molecular weight of about 3000 g / mol) to the bottom of the glass container, the activated PDMS elastomer substrate is hung in the glass container to avoid direct contact between the activated PDMS elastomer substrate and the liquid amino-terminated polydimethylsiloxane, the glass container is sealed, the temperature in the glass container is controlled to be room temperature (20-25 °C) and the pressure in the glass container is controlled to be normal pressure (1013.25 mbar), the amino-terminated polydimethylsiloxane molecules volatilize to contact the surface of the activated PDMS elastomer substrate and undergo grafting reaction, the grafting reaction time is controlled to be 5 min, the flexible molecular brush is formed on the surface of the activated PDMS elastomer substrate, then the PDMS elastomer with the anti-oil permeation coating is obtained by taking out, rinsing with deionized water and blowing dry with compressed nitrogen.

[0098] Example 9

[0099] In this embodiment, a preparation method of the PDMS elastomer with the anti-oil permeation coating is provided, and the steps are as follows:

[0100] (1) The PDMS elastomer is ultrasonically cleaned with ethanol (purity ≥ 99.7%) and deionized water for 30 s in sequence to remove organic contaminants and solid particles on the surface of the PDMS elastomer, and then the surface of the PDMS elastomer is blown dry with compressed nitrogen for standby.

[0101] (2) The PDMS elastomer treated in step (1) is placed in a plasma cleaning machine, and the surface of the PDMS elastomer is activated by oxygen plasma, the power of the oxygen plasma treatment is controlled to be 50 W, and the treatment time is controlled to be 30 s, a large number of active functional groups including hydroxyl groups are formed on the surface of the PDMS elastomer, and an activated PDMS elastomer substrate is obtained.

[0102] (3) The grafting reaction is carried out in a non-contact manner, and the operation is as follows:

[0103] According to every 1 cm 2The glass container is sealed, and the temperature and pressure in the glass container are controlled at room temperature (20-25°C) and normal pressure (1013.25 mbar), respectively. The alkoxyl-terminated polydimethylsiloxane molecules volatilize and contact the surface of the activated PDMS elastomer substrate to occur grafting reaction. The grafting reaction time is controlled at 5 min. A flexible molecular brush is formed on the surface of the activated PDMS elastomer substrate. Then, the PDMS elastomer substrate is taken out, rinsed with deionized water, and dried by blowing compressed nitrogen on the surface to obtain a PDMS elastomer with an oil permeation resistant coating.

[0104] Example 10

[0105] In this embodiment, a method for preparing a PDMS elastomer with an oil permeation resistant coating is provided, and the steps are as follows:

[0106] (1) The PDMS elastomer is sequentially cleaned with ethanol (purity ≥ 99.7%) and deionized water for 30 s to remove organic contaminants and solid particles on the surface of the PDMS elastomer. Then, the surface of the PDMS elastomer is dried by blowing compressed nitrogen.

[0107] (2) The PDMS elastomer treated in step (1) is placed in a plasma cleaning machine, and the surface of the PDMS elastomer is activated by oxygen plasma. The power of the oxygen plasma treatment is controlled at 50 W, and the treatment time is controlled at 30 s. A large number of active functional groups including hydroxyl groups are formed on the surface of the PDMS elastomer to obtain an activated PDMS elastomer substrate.

[0108] (3) The grafting reaction is performed in a non-contact manner, and the operation is as follows:

[0109] According to every 1 cm 2The glass container is sealed, and the temperature and pressure in the glass container are controlled at 80°C and normal pressure (1013.25 mbar), respectively. The epoxy-terminated polydimethylsiloxane molecules volatilize and contact the surface of the activated PDMS elastomer substrate to occur grafting reaction. The grafting reaction time is controlled at 5 min. A flexible molecular brush is formed on the surface of the activated PDMS elastomer substrate. Then, the PDMS elastomer is taken out, rinsed with deionized water, and dried by compressed nitrogen. Thus, a PDMS elastomer with an oil permeation resistant coating is obtained.

[0110] Example 11

[0111] In this embodiment, a method for preparing a PDMS elastomer with an oil permeation resistant coating is provided, and the steps are as follows:

[0112] (1) The PDMS elastomer is ultrasonically cleaned with ethanol (purity ≥ 99.7%) and deionized water for 30 s, respectively, to remove organic contaminants and solid particles on the surface of the PDMS elastomer. Then, the surface of the PDMS elastomer is dried by compressed nitrogen for standby.

[0113] (2) The PDMS elastomer treated in step (1) is placed in a plasma cleaning machine, and the surface of the PDMS elastomer is activated by oxygen plasma. The power of the oxygen plasma treatment is controlled at 50 W, and the treatment time is controlled at 30 s. A large number of active functional groups including hydroxyl groups are formed on the surface of the PDMS elastomer, and an activated PDMS elastomer substrate is obtained.

[0114] (3) The grafting reaction is performed in a non-contact manner, and the operation is as follows:

[0115] According to the above method, the amount of epoxy-terminated polydimethylsiloxane added to the glass container is 30 μL per 1 cm 2The isocyanate-terminated polydimethylsiloxane (molecular weight about 3000 g / mol) was added into the glass container by adding 30 μL of isocyanate-terminated polydimethylsiloxane (molecular weight about 3000 g / mol) to the bottom of the container, the activated PDMS elastomer substrate was hung in the glass container to avoid direct contact between the activated PDMS elastomer substrate and the liquid isocyanate-terminated polydimethylsiloxane, the glass container was sealed, the temperature and pressure in the glass container were controlled at 10 °C and normal pressure (1013.25 mbar), respectively, the isocyanate-terminated polydimethylsiloxane molecules volatilized and contacted with the surface of the activated PDMS elastomer substrate to occur grafting reaction, the grafting reaction time was controlled at 5 min, the flexible molecular brush was formed on the surface of the activated PDMS elastomer substrate, then it was taken out, rinsed with deionized water and dried by compressed nitrogen, and the PDMS elastomer with oil permeation resistant coating was obtained.

Claims

1. Process for the preparation of a polydimethylsiloxane elastomer with an anti- oil penetration coating, characterized in that, The method comprises the following steps: (1) performing surface activation treatment on clean and dry polydimethylsiloxane elastomer by oxygen plasma to obtain activated polydimethylsiloxane elastomer substrate; (2) performing grafting reaction between active end group capped silane and the surface of the activated polydimethylsiloxane elastomer substrate to form flexible molecular brush on the surface of the activated polydimethylsiloxane elastomer substrate, and obtaining polydimethylsiloxane elastomer with oil permeation resistant coating; The active end group capped silane is active end group capped silane monomer or active group capped silane polymer; during the grafting reaction, the active end group capped silane monomer is polymerized to form polydimethylsiloxane flexible molecular chain and is grafted on the surface of the activated polydimethylsiloxane elastomer substrate, and the silane polymer chain of the active group capped silane polymer is directly grafted on the surface of the activated polydimethylsiloxane elastomer substrate; The active end group capped silane monomer is active end group capped tetramethyldisiloxane, and the active group capped silane polymer is active end group capped polydimethylsiloxane or active end group capped perfluoropolyether silane; the active end group in the active end group capped silane includes at least one of chlorine end group, hydroxyl group, carboxyl group, amino group, alkoxy group, epoxy group and isocyanate group.

2. The method for preparing the polydimethylsiloxane elastomer with an oil-penetration-resistant coating according to claim 1, characterized in that, The molecular weight of the active end group capped silane is 203-100000 g / mol.

3. The method for preparing the polydimethylsiloxane elastomer with an oil-penetration-resistant coating according to claim 2, characterized in that, When the molecular weight of the active end group capped silane is less than 10000 g / mol, the grafting reaction in step (2) is performed in a non-contact mode; when the molecular weight of the active end group capped silane is greater than or equal to 10000 g / mol, the grafting reaction is performed in a contact mode.

4. The method for preparing the polydimethylsiloxane elastomer with an oil-penetration-resistant coating according to claim 3, characterized in that, When the grafting reaction in step (2) is performed in a non-contact mode, the active end group capped silane is added into a container, the activated polydimethylsiloxane elastomer substrate is fixed in the container to avoid direct contact between the activated polydimethylsiloxane elastomer substrate and the liquid active end group capped silane, the container is sealed, the active end group capped silane molecules are volatilized to perform grafting reaction with the surface of the activated polydimethylsiloxane elastomer substrate, then the product is taken out, washed with deionized water and dried to obtain the polydimethylsiloxane elastomer with oil permeation resistant coating; When the grafting reaction in step (2) is performed in a contact mode, the active end group capped silane is applied on the surface of the activated polydimethylsiloxane elastomer substrate, and the container is sealed to perform grafting reaction between the active end group capped silane and the surface of the activated polydimethylsiloxane elastomer substrate, then the product is taken out, washed with deionized water and dried to obtain the polydimethylsiloxane elastomer with oil permeation resistant coating.

5. The method for preparing the polydimethylsiloxane elastomer with an oil-penetration-resistant coating according to claim 4, characterized in that, When the grafting reaction in step (2) is performed in a non-contact manner, 2 to 50 μL of the active end group-capped silane is added to the container per 1 cm 2 The active end group-capped silane is added to the container in a proportion of 2 to 50 μL per 1 cm2of the bottom area of the container. When the grafting reaction in step (2) is performed in a contact manner, the active end group-capped silane is applied to the surface of the activated polydimethylsiloxane elastomer substrate so as to completely cover the region to be formed with the oil permeation-resistant coating.

6. The method of preparing a polydimethylsiloxane elastomer having an oil- repellent coating according to claim 4 or 5, characterized in that, During the grafting reaction in step (2), the pressure in the container is controlled to be not more than 1013.25 mbar.

7. The method of preparing a polydimethylsiloxane elastomer having an oil- repellent coating according to claim 4 or 5, characterized in that, During the grafting reaction in step (2), the temperature in the container is controlled to be 10-100 ℃, and the grafting reaction time is controlled to be 1-720 min.

8. The method for preparing the polydimethylsiloxane elastomer with an oil-penetration-resistant coating according to claim 1, characterized in that, The power of the oxygen plasma for surface activation treatment is 10-1500 W, and the time is 10 s-10 min.

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