Preparation method of transparent antifouling hyperbranched self-cleaning coating

Abstract

The invention discloses a preparation method of a transparent antifouling hyperbranched self-cleaning coating. The preparation method comprises the following steps: firstly, carrying out transesterification on vinyltriethoxysilane and diethylene glycol to prepare hyperbranched polysiloxane; then, 2-(perfluorooctyl) ethyl methacrylate, a free radical initiator azodiisobutyronitrile and double-bond-end hyperbranched polysiloxane are subjected to a free radical copolymerization reaction to obtain a hyperbranched fluorosilicone copolymer, the polymer is sprayed to the surfaces of different base materials, and the transparent hyperbranched fully-hydrophobic solid lubricating coating can be obtained by heating and curing. The coating constructed by the invention has ultra-low surface energy and low viscosity, can effectively repel liquids with different surface tensions and viscosities, maintains clear optical transparency, can realize integration of antifouling and anti-adhesion functions of a vehicle windshield coating, and has a wide application prospect. And a feasible path is opened up for the design of outdoor optical surface high-performance protective coatings for traffic, new energy, building glass, electronic equipment and the like.

Description

Technical Field

[0001] This invention belongs to the field of functional coating preparation / construction, and specifically relates to a method for preparing a transparent, anti-fouling, hyperbranched, self-cleaning coating. Background Technology

[0002] As the direct interface between a vehicle and the external environment, the windshield is a core component ensuring driving safety. Most windshields are made of soda-lime laminated glass, whose surface is both hydrophilic and oleophilic, exhibiting high adhesion to liquids. During driving, they are susceptible to various contaminants such as rainwater, oil droplets, dust, and bird droppings. These sticky substances, when long-term adhered to the glass, significantly reduce light transmittance and interfere with the driver's vision, impacting driving safety. To ensure clear visibility and long-term use, developing multifunctional, highly transparent surfaces with excellent self-cleaning and anti-fouling properties is a highly attractive solution. An ideal surface not only effectively repels liquids and solids with varying surface tensions and viscosities but also integrates multiple functional properties, showing broad application prospects in fields such as architecture, biotechnology, marine engineering, electronics, and solar power generation.

[0003] Polymer coatings can be functionally controlled through molecular and structural design, offering customizability and multifunctionality. They are also a preferred technological approach for preparing materials that combine high optical transparency with surface antifouling properties. Current antifouling coating designs primarily draw inspiration from nature and introduce functional groups to impart desired properties. For example, Chinese patent CN119060347A proposes a supramolecular self-assembled hydrophobic surfactant with lotus leaf-like structure and hydrophobic wax properties, applicable to hydrophobic coatings. Other strategies lean towards molecular design; CN120484176A introduces aromatic acid compounds with antifouling functions into linear resins, inventing an antifouling-self-polishing coating. Furthermore, patent CN120574399A uses a POSS structure as the molecular matrix, grafting flexible polymer brushes onto active sites to disclose an organic-inorganic hybrid antifouling self-cleaning resin. However, the above coating research struggles to simultaneously achieve high light transmittance, durability, omnidirectional repellency, and synergistic multifunctionality, failing to meet the practical needs of multifunctional protective coatings for outdoor optical surfaces. Therefore, it is necessary to develop fully hydrophobic coatings with mechanical stability as potential materials for practical applications. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a simple and highly transparent method for preparing an anti-fouling hyperbranched self-cleaning coating. This method can achieve long-term self-cleaning and anti-fouling properties at the interface, maintain clear optical transparency, and provide multi-dimensional protection for vehicle windshields, thus having broad application prospects.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: A method for preparing a transparent, anti-fouling, hyperbranched, self-cleaning coating, characterized by comprising the following steps: S1. Vinyltriethoxysilane and diethylene glycol are blended and heated under nitrogen protection to undergo transesterification reaction to obtain a hyperbranched polysiloxane solution. S2. Wash the hyperbranched polysiloxane solution prepared in step S1 with n-hexane to remove unreacted monomers. After washing, allow it to stand and separate into layers. Remove the upper layer of n-hexane containing impurities and collect the bottom precipitate. Then dissolve the precipitate with dichloromethane. Place the solution in a rotary evaporator and remove the dichloromethane solvent under reduced pressure to finally obtain a light yellow transparent viscous liquid. S3. The initiator azobisisobutyronitrile and the fluorinated monomer ethyl 2-(perfluoropropyl)methacrylate were added to the solvent 1H, 1H, 5H-perfluoropentyl-1, 1, 2, 2-tetrafluoroethyl ether and stirred at room temperature until completely dissolved to form a stable homogeneous solution. S4. Dissolve the hyperbranched polysiloxane viscous in step S2 in tetrahydrofuran, add the solution in step S3 dropwise under nitrogen protection, heat up to undergo free radical copolymerization to obtain a hyperbranched fluorosilicone copolymer solution, remove the high-boiling-point solvent by rotary evaporation, and add ethyl acetate to prepare the coating. S5. Using a one-step spraying method, the coating prepared in step S4 is applied to the surface of different substrates and cured to obtain a transparent, anti-fouling, hyperbranched, self-cleaning coating.

[0006] Preferably, the solvents n-hexane, dichloromethane, tetrahydrofuran, or ethyl acetate are all of analytical grade.

[0007] Preferably, the molar ratio of diethylene glycol to vinyltriethoxysilane in step S1 is 1.5-2.5:1, no other solvent is required, the reaction temperature is 130-170°C, and the reaction time is 8-10 hours.

[0008] Preferably, the hexane washing in step S2 is performed 3 times, and the volume ratio of dichloromethane to hyperbranched polysiloxane precipitate is 15:1.

[0009] Preferably, the initiator in step S3 has a mass fraction of 0.3%-0.5%, and the volume of the 1H, 1H, 5H-perfluoropentyl-1, 1, 2, 2-tetrafluoroethyl ether solvent is 10 times the mass of the added 2-(perfluoropropyl)methacrylate ethyl ester monomer.

[0010] Preferably, the mass ratio of hyperbranched polysiloxane to ethyl 2-(perfluoropropyl)methacrylate in step S4 is 1:3.5, the reaction temperature is 60-70℃, and the reaction time is 6-8 hours.

[0011] Preferably, the curing temperature in step S5 is 70-80℃, and the curing time is 3-5 hours.

[0012] Compared with the prior art, the beneficial effects of the present invention are: (1) The samples after spraying the self-cleaning coating of the present invention have fully hydrophobic properties, with contact angles (CA) of 118° / 85.1° / 65.4° for water / oil / ethanol and sliding angles (SA) of 15° / 5.2° / 6.2°; (2) The transmittance of the sample coating after spraying the self-cleaning coating of the present invention can reach 91.8% (wavelength of 550nm), with excellent flexibility (bending radius of curvature of 1 mm) and stable mechanical strength, and has broad substrate applicability (glass, plastic, sponge, fiber, metal); (3) The samples after spraying the self-cleaning coating of the present invention have low viscosity and excellent anti-fouling / self-cleaning properties, with a sample surface energy as low as 8.89 mN·m -1 It can repel a wide range of liquids with varying surface tensions (18.4-72.8 mN·m). -1 (4) The samples after the self-cleaning coating of the present invention has excellent chemical stability. The WCA of the coating after immersion in different acid, alkali, salt and organic solvent (ethanol, toluene, n-hexane) media is maintained at 116°, and the SA of other liquids does not change significantly. (5) The samples after the self-cleaning coating of the present invention has comprehensive performance of UV resistance and high / low temperature resistance. In a one-month UV, low temperature and high temperature environment, the sliding performance of its surface does not change, and the water contact angle is about 115°. (6) In the vehicle windshield protection test, the samples after the self-cleaning coating of the present invention can resist stubborn stains such as bird droppings and insect protein (coverage rate is only 2%), proving that it has excellent self-cleaning and anti-fouling properties. Attached Figure Description

[0013] Figure 1 SEM image of polymer coating surface (a), water / oil wetting behavior of polymer coating surface (b), large-area preparation and optical transparency of polymer coating (c), movement of blue ink, ethanol and paraffin oil contaminant on tilted coating surface (d), anti-graffiti performance, anti-fouling and self-cleaning behavior of polymer coating surface (e). Figure 2 Images of water droplet wetting on different substrate coating surfaces (a), images of water droplet wetting on polymer coating surfaces with sliding angles of liquids with different surface tensions (b), coating flexibility test and sliding angles of different liquids (c), coating mechanical strength and sliding angles of different liquids (d). Figure 3 Optical images (a) of a brand new windshield and a coated windshield after being contaminated by common environmental pollutants, and (b) of the application of the protective performance of the polymer coating on the windshield. Detailed Implementation

[0014] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0015] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0016] Example 1: A method for preparing a transparent, anti-fouling, hyperbranched, self-cleaning coating (1) 7.61 g (0.04 mol) vinyltriethoxysilane and 9.29 g (0.09 mol) diethylene glycol were mixed in a 200 mL three-necked flask (equipped with magnetic stirring and reflux condenser), stirred under nitrogen protection, and reacted at 130°C to 170°C for 10 hours until no distillate was formed, to obtain a pale yellow liquid.

[0017] (2) Transfer the crude solution obtained in step (1) to a 250 mL beaker, add 100 mL of analytical grade n-hexane, and stir with a magnetic stirrer for 10 min to fully dissolve the impurities in the n-hexane. After standing for 20 min, slowly pour off the supernatant, retaining the bottom precipitate. Repeat this process twice. Then add 60 mL of dichloromethane to obtain a clear, pale yellow solution. Transfer this solution to a rotary evaporator and remove the solvent by vacuum distillation to finally obtain a light yellow, viscous, hyperbranched polysiloxane (HBPSi).

[0018] (3) Dissolve 1.16 g of ethyl 2-(perfluoropropyl)methacrylate (CAS No.: 1996-88-9, purity ≥97%) and 0.004 g of initiator azobisisobutyronitrile (AIBN) in 12 mL of 1H,1H,5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether (HFO) solvent.

[0019] (4) Dissolve 0.33 g of HBPSi in 3.5 mL of tetrahydrofuran (THF) solvent, place in a three-necked flask, and set the temperature to 65 °C. Then, add the solution from step (3) dropwise over 2 hours through a constant pressure dropping funnel. After the addition is complete, continue the reaction for 6 hours. A milky white hyperbranched fluorosilicone copolymer (LHFO) is obtained. Finally, HFO is removed by a rotary evaporator, and LHFO is dissolved in ethyl acetate to prepare a coating.

[0020] (5) The mixed coating obtained in step (4) is drop-coated onto a glass substrate and cured by heating to obtain a transparent, anti-fouling, hyperbranched, self-cleaning coating. The coating surface has micro- and nano-scale protrusions. Figure 1 a) The water static contact angle (WCA) is 118°, and the oil contact angle is 85.1°. Figure 1 b). The coating was prepared on a 100×100 cm bare glass surface, and observation revealed that it exhibited excellent optical transparency, making it suitable for applications such as vehicle windshields that maintain their original optical characteristics. Quantitative characterization using UV-Vis testing showed that its transmittance at 550 nm was approximately 91.8%. Figure 1 c). Evaluation of the slip behavior of the coated surface at a 25° inclination under different surface tensions and viscous fouling media (water, ethanol, paraffin oil, etc.). Figure 1 d) It was observed that the coating surface exhibited ultra-low viscosity to various water-based contaminants, organic solvents, and alkyl oils. Liquids of 15-30 μL could rapidly slide / remove from the surface within 0.1-10 s, leaving no residue. Anti-graffiti, anti-sludge, and self-cleaning tests, as shown in optical images, revealed that brush ink, mud, and grit adhered to the glass substrate, while the coated surface remained clean, demonstrating the coating's significant anti-fouling and self-cleaning properties. Figure 1 e).

[0021] Example 2: A method for preparing a transparent, anti-fouling, hyperbranched, self-cleaning coating (1) 7.61 g (0.04 mol) vinyltriethoxysilane and 9.29 g (0.09 mol) diethylene glycol were mixed in a 200 mL three-necked flask (equipped with magnetic stirring and reflux condenser), stirred under nitrogen protection, and reacted at 130°C to 170°C for 10 hours until no distillate was formed, to obtain a pale yellow liquid.

[0022] (2) Transfer the crude solution obtained in step (1) to a 250 mL beaker, add 100 mL of analytical grade n-hexane, and stir with a magnetic stirrer for 10 min to fully dissolve the impurities in the n-hexane. After standing for 20 min, slowly pour off the supernatant, retaining the bottom precipitate. Repeat this process twice. Then add 60 mL of dichloromethane to obtain a clear, pale yellow solution. Transfer this solution to a rotary evaporator and remove the solvent by vacuum distillation to finally obtain a light yellow, viscous, hyperbranched polysiloxane (HBPSi).

[0023] (3) Dissolve 1.16 g of ethyl 2-(perfluoropropyl)methacrylate (CAS No.: 1996-88-9, purity ≥97%) and 0.004 g of initiator azobisisobutyronitrile (AIBN) in 12 mL of 1H,1H,5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether (HFO) solvent.

[0024] (4) Dissolve 0.33 g of HBPSi in 3.5 mL of tetrahydrofuran (THF) solvent, place in a three-necked flask, and set the temperature to 65 °C. Then, add the solution from step (3) dropwise over 2 hours through a constant pressure dropping funnel. After the addition is complete, continue the reaction for 6 hours. A milky white hyperbranched fluorosilicone copolymer (LHFO) is obtained. Finally, HFO is removed by a rotary evaporator, and LHFO is dissolved in ethyl acetate to prepare a coating.

[0025] (5) The mixed coating obtained in step (4) is dripped onto a glass substrate and cured by heating to obtain a transparent, anti-fouling, hyperbranched, self-cleaning coating. The sprayed coating shows good adaptability to different substrates. Figure 2 a) On smooth substrates such as glass, PET, PI, and plastics, the WCA values ​​are 118°, 112°, 116°, and 111°, respectively. On rough substrates such as sponge and fabric, the WCA values ​​are higher, at 155° and 142°, respectively. This indicates that the coating can be widely applied to various common substrates in daily life. The practical application requirements for surface liquid repellency cover a wide range of surface tensions. Various liquids with surface tensions between 18.4 and 72.8 mN / m can easily slide off the sprayed coating surface with a small sliding angle. Figure 2 b). The PET substrate coated with this coating can be easily bent into a U-shape with a radius of curvature of 0.5 cm. After 1000 such repeated bending and releasing cycles, the sliding behavior of the liquid on the LHFO coating surface did not change significantly. Figure 2 c). In continuous water jet impact tests ( Figure 2 d) A water jet was continuously sprayed at a speed of 1.5 L / min onto a coating placed at a 45° tilt angle. After being impacted by 5 L of water jet, the surface of the coating remained unaffected by the liquid, and no watermarks were left on the glass coating surface during the water jet impact. This demonstrates its impeccable flexibility and stable mechanical properties.

[0026] Example 3: A method for preparing a transparent, anti-fouling, hyperbranched, self-cleaning coating (1) 7.61 g (0.04 mol) vinyltriethoxysilane and 9.29 g (0.09 mol) diethylene glycol were mixed in a 200 mL three-necked flask (equipped with magnetic stirring and reflux condenser), stirred under nitrogen protection, and reacted at 130°C to 170°C for 10 hours until no distillate was formed, to obtain a pale yellow liquid.

[0027] (2) Transfer the crude solution obtained in step (1) to a 250 mL beaker, add 100 mL of analytical grade n-hexane, and stir with a magnetic stirrer for 10 min to fully dissolve the impurities in the n-hexane. After standing for 20 min, slowly pour off the supernatant, retaining the bottom precipitate. Repeat this process twice. Then add 60 mL of dichloromethane to obtain a clear, pale yellow solution. Transfer this solution to a rotary evaporator and remove the solvent by vacuum distillation to finally obtain a light yellow, viscous, hyperbranched polysiloxane (HBPSi).

[0028] (3) Dissolve 1.16 g of ethyl 2-(perfluoropropyl)methacrylate (CAS No.: 1996-88-9, purity ≥97%) and 0.004 g of initiator azobisisobutyronitrile (AIBN) in 12 mL of 1H,1H,5H-perfluoropentyl-1,1,2,2-tetrafluoroethyl ether (HFO) solvent.

[0029] (4) Dissolve 0.33 g of HBPSi in 3.5 mL of tetrahydrofuran (THF) solvent, place in a three-necked flask, and set the temperature to 65 °C. Then, add the solution from step (3) dropwise over 2 hours through a constant pressure dropping funnel. After the addition is complete, continue the reaction for 6 hours. A milky white hyperbranched fluorosilicone copolymer (LHFO) is obtained. Finally, HFO is removed by a rotary evaporator, and LHFO is dissolved in ethyl acetate to prepare a coating.

[0030] (5) The mixed coating obtained in step (4) is dripped onto a glass substrate and cured by heating to obtain a transparent, anti-fouling, hyperbranched, self-cleaning coating. This coating is applied to a vehicle windshield. Various pollutants marked with dyes (water, acid rain, sludge water, honey water, bird droppings, insect protein suspension) are poured onto the windshield using a spray bottle. All pollutants are firmly adsorbed by the uncoated windshield, with a wide pollution coverage area that is difficult to fall off naturally. The coated area remains transparent and clean, effectively resisting the invasion of pollutants (coverage area < 2%). The coating's broad resistance to single-component liquids and multi-component complex fluids is directly verified. After the windshield is exposed to the natural environment (outdoor parking, road driving) for one month, the original windshield is contaminated by a mixture of dust, rain streaks, etc., and raindrops adhere to the surface after rain. However, in the coated area, raindrops do not adhere to the surface, and most of the raindrops and pollutants can be washed away by rainwater or by natural wind during riding, maintaining high light transmittance. This fully demonstrates its excellent anti-fouling performance in actual vehicle windshield protection, providing anti-fouling solutions for transportation, new energy, construction and other fields.

Claims

1. A method for preparing a transparent, anti-fouling, hyperbranched, self-cleaning coating, characterized in that, Includes the following steps: S1. Vinyltriethoxysilane and diethylene glycol are blended and heated under nitrogen protection to undergo transesterification reaction to obtain a hyperbranched polysiloxane solution. S2. Wash the hyperbranched polysiloxane solution prepared in step S1 with n-hexane to remove unreacted monomers. After washing, allow it to stand and separate into layers. Remove the upper layer of n-hexane containing impurities and collect the bottom precipitate. Then dissolve the precipitate with dichloromethane. Place the solution in a rotary evaporator and remove the dichloromethane solvent under reduced pressure to finally obtain a light yellow transparent viscous liquid. S3. The initiator azobisisobutyronitrile and the fluorinated monomer ethyl 2-(perfluoropropyl)methacrylate were added to the solvent 1H, 1H, 5H-perfluoropentyl-1, 1, 2, 2-tetrafluoroethyl ether and stirred at room temperature until completely dissolved to form a stable homogeneous solution. S4. Dissolve the hyperbranched polysiloxane viscous in step S2 in tetrahydrofuran, add the solution in step S3 dropwise under nitrogen protection, heat up to undergo free radical copolymerization to obtain a hyperbranched fluorosilicone copolymer solution, remove the high-boiling-point solvent by rotary evaporation, and add ethyl acetate to prepare the coating. S5. Using a one-step spraying method, the coating prepared in step S4 is applied to the surface of different substrates and cured to obtain a transparent, anti-fouling, hyperbranched, self-cleaning coating.

2. The method for preparing the transparent, anti-fouling, hyperbranched, self-cleaning coating according to claim 1, characterized in that, The solvents n-hexane, dichloromethane, tetrahydrofuran, or ethyl acetate are all of analytical grade.

3. The method for preparing the transparent, anti-fouling, hyperbranched, self-cleaning coating according to claim 1, characterized in that, The molar ratio of diethylene glycol to vinyltriethoxysilane in step S1 is 1.5-2.5:1, the reaction temperature is 130-170℃, and the reaction time is 8-10 hours.

4. The method for preparing the transparent, anti-fouling, hyperbranched, self-cleaning coating according to claim 1, characterized in that, The hexane washing in step S2 is performed 3 times, and the volume ratio of dichloromethane to hyperbranched polysiloxane precipitate is 15:

1.

5. The method for preparing the transparent anti-fouling hyperbranched self-cleaning coating according to claim 1, characterized in that, The initiator in step S3 has a mass fraction of 0.3%-0.5%, and the volume of the 1H, 1H, 5H-perfluoropentyl-1, 1, 2, 2-tetrafluoroethyl ether solvent is 10 times the mass of the added 2-(perfluoropropyl)methacrylate ethyl ester monomer.

6. The method for preparing the transparent anti-fouling hyperbranched self-cleaning coating according to claim 1, characterized in that, The mass ratio of hyperbranched polysiloxane to ethyl 2-(perfluoropropyl)methacrylate in step S4 is 1:3.5, the reaction temperature is 60-70℃, and the reaction time is 6-8 hours.

7. The method for preparing the transparent, anti-fouling, hyperbranched, self-cleaning coating according to claim 1, characterized in that, The curing temperature in step S5 is 70-80℃, and the curing time is 3-5 hours.

8. A transparent, antifouling, hyperbranched, self-cleaning coating prepared by the preparation method according to any one of claims 1-7.

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