A photocured antifog coating based on a zwitterionic copolymer and a method of making the same

Abstract

The application discloses a kind of zwitterionic copolymer-based photocuring anti-fogging coating and preparation method thereof, and the preparation method is: 1) preparation of thiol-modified SiO2 Nanoparticle;2) preparation of zwitterionic copolymer mixed solution;3) thiol-modified SiO2 Nanoparticle is added to second solvent, and preparation is solution 1, adjust pH to 1~3, substrate is immersed in solution 1 for 6~24h modification, and the modified substrate is obtained;Zwitterionic copolymer mixed solution is coated on the surface of modified substrate, and is cured into film under ultraviolet irradiation, and the zwitterionic copolymer-based photocuring anti-fogging coating is obtained.The zwitterionic copolymer-based photocuring anti-fogging coating of the application avoids the interference of light transmittance and fogging, and the light transmittance of the obtained coating is about 80%, and the long-acting anti-fogging test result shows that the coating can be continuously anti-fogging for more than 37 days in 60 DEG C hot fog environment.

Description

Technical Field

[0001] This invention relates to the field of materials technology, specifically to a photocurable antifog coating based on zwitterionic copolymers and its preparation method. Background Technology

[0002] Transparent materials, such as polyolefin films, polycarbonate, high-temperature resistant polyester, and silicate glass, are widely used in diverse and specialized industries, including daily life, medicine, photovoltaics, and the food industry. Due to temperature changes, water molecules inevitably condense into droplets upon contact with the material surface, adhering to it. These irregular droplets cause scattering and refraction of incident light from various directions, severely affecting the material's optical properties and frequently causing aesthetic, hygiene, and safety issues. Therefore, research on anti-fogging properties of transparent materials is of great significance.

[0003] Superhydrophilic and superhydrophobic surfaces have attracted considerable attention from researchers. Compared to the complex processes and energy consumption of hydrophobic coatings, hydrophilic coatings are simpler, more economical, and offer better anti-fogging effects. In recent years, zwitterionic polymers have been widely used in anti-fogging applications due to their extremely strong hydration capabilities. Zwitterionic betaine macromolecules possess both hydrophilic and positively and negatively charged groups, which can form a hydration layer through hydrogen bonding and electrostatic interactions, preventing the formation of water droplets and achieving excellent anti-fogging effects. For example, zwitterionic polymers can form a hydration layer to increase the spatial repulsion effect on the substrate surface, making it difficult for pollutants to penetrate through the hydration layer. This can be used to construct anti-adhesion surfaces or coatings for biomedical applications (Wang L, Li G, Lin Y, Zhang Z, Chen Z, Wu SA strategy for constructing anti-adhesion surfaces based on interfacial thiol-ene photoclick chemistry between DOPA derivatives with a catechol anchor group and zwitterionic betaine macromolecules. PolymerChemistry, 2016, 7(30): 4964-4974.). They also have strong water absorption and hydrophilicity, and have broad application prospects in the field of anti-fog coatings. However, it is still a challenge to construct hydrophilic anti-fog coatings by attaching zwitterionic polymers to various surfaces, especially hydrophobic surfaces, because they have higher solubility and stronger hydration, resulting in less than ideal coating durability.

[0004] Some studies have shown that incorporating inorganic nanomaterials into polymer systems can improve the mechanical strength of coatings, making them less prone to damage and resulting in more durable antifogging effects. For example, Meng et al. combined betaine-modified nanoparticles with hydrophilic polymers, and the resulting hydrophilic cross-linked network gave the coating excellent antifogging performance and stability (Meng F, Xu Y, Wu Z, Chen H. Transparent and superhydrophilic antifogging coatings constructed by poly(N-hydroxyethyl acrylamide)composites. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2022, 642: 128724.). However, inert materials such as polyolefin films have smooth surfaces and poor adhesion, and their compatibility with polar polymers and inorganic fillers is also poor. Therefore, antifogging coatings prepared by physical adhesion are often ineffective.

[0005] Based on the above analysis, developing a durable anti-fog coating on the surface of an inert transparent substrate is an urgent need in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a photocurable antifog coating based on zwitterionic copolymers.

[0007] A second objective of this invention is to provide a method for preparing a photocurable antifog coating based on a zwitterionic copolymer.

[0008] The technical solution of this invention is summarized as follows:

[0009] A method for preparing a photocurable antifog coating based on a zwitterionic copolymer includes the following steps:

[0010] 1) Add nano-silica to an ethanol aqueous solution with a volume concentration of 50%-80% to prepare a dispersion of 1-3 wt%. Adjust the pH of the solution to 2-3, and then add 1-3 times the mass of silane coupling agent to the nano-silica. Stir and reflux the reaction at 80±5℃ for 5-8 hours, and centrifuge. Wash the solid with ethanol and deionized water in sequence, and dry it to obtain mercapto-modified SiO2 nanoparticles.

[0011] 2) Prepare the zwitterionic copolymer mixture, taking the following components by mass percentage:

[0012] Poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate) (III) 5%–10%; crosslinking agent 0.5%–1%; photoinitiator 0.025%–0.2%; thiol-modified SiO2 nanoparticles 0%–2%; balance as first solvent; mix thoroughly to obtain zwitterionic copolymer mixture;

[0013] The structural formula of the poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate)(Ⅲ) is:

[0014]

[0015] Among them, R 1 It can be an H atom or a methyl group;

[0016] R 2 It is an O atom or a secondary amine;

[0017] R 3 for

[0018] m is 2 or 3;

[0019] a is (30~60),

[0020] b is (90~120),

[0021] c is (10~30);

[0022] 3) Add the thiol-modified SiO2 nanoparticles obtained in step 1) to the second solvent to prepare a 2-5 wt% solution 1. Adjust the pH to 1-3. Immerse the oxygen plasma pretreated substrate in solution 1 for 6-24 h for modification. Take it out, wash it with water, and place it at 50-70℃ for 2-6 h to obtain the modified substrate. Coat the zwitterionic copolymer mixture prepared in step 2) onto the surface of the modified substrate and cure it into a film under ultraviolet light to obtain a photocurable antifog coating based on zwitterionic copolymer.

[0023] Preferably, step 1) involves adding nano-silica to an ethanol aqueous solution with a volume concentration of 75% to prepare a 3wt% dispersion, adjusting the pH of the solution to 2.5, adding silane coupling agent at twice the mass of the nano-silica, stirring and refluxing at 80°C for 6 hours, centrifuging, washing the solid sequentially with ethanol and deionized water, and vacuum drying at 50–70°C to obtain thiol-modified SiO2 nanoparticles.

[0024] The particle size of the nano-silica is 30-900 nm.

[0025] The preferred silane coupling agent is (3-mercaptopropyl)trimethoxysilane or γ-mercaptopropyltriethoxysilane.

[0026] The crosslinking agent is preferably N,N-methylenebisacrylamide, ethylene glycol dimethacrylate, or polyethylene glycol diacrylate with a number average molecular weight of 200-600.

[0027] The photoinitiator is preferably: benzoin dimethyl ether, diphenylacetone, or 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone;

[0028] The first solvent is preferably at least one of trifluoroethanol, methanol, and ethanol.

[0029] Step 2) The medium-polymer (betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allylic methacrylate) (III) is prepared by the following method:

[0030] With a molar ratio of (30-60):(90-120):(10-30), raw materials, betaine-type zwitterionic compound, hydroxyethyl acrylate, and allyl methacrylate are dissolved in a 40-60% (v / v) methanol aqueous solution to prepare a 5-20 wt% solution 2. 0.5-1 wt% of the total mass of the raw materials is added as the initiator azobisisobutyronitrile. After removing oxygen from the system, the mixture is heated to 60-80℃ and kept at that temperature for 4-18 hours for free radical polymerization. After dialyzing, the mixture is freeze-dried to obtain poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate) (III).

[0031] Preferred betaine-type zwitterionic compounds are: methacryloylethyl sulfobetaine, acrylamidopropyl sulfobetaine, or methacryloylethyl carboxybetaine.

[0032] Preferably, step 3) is as follows: the thiol-modified SiO2 nanoparticles obtained in step 1) are added to a second solvent to prepare a 5wt% solution 1, the pH is adjusted to 2, the oxygen plasma pretreated substrate is immersed in solution 1 for 12h for modification, taken out, washed with water, and placed at 60°C for 2h to obtain a modified substrate; the zwitterionic copolymer mixture prepared in step 2) is coated on the surface of the modified substrate, and cured under ultraviolet light at 365nm and 8-125W for 15-60min to form a film, thereby obtaining a photocurable antifog coating based on zwitterionic copolymer.

[0033] The second solvent is preferably one or two of deionized water, methanol, and ethanol;

[0034] The substrate is preferably a polyolefin film, a polyethylene film, glass, a high-temperature resistant polyester film, or a polycarbonate film.

[0035] A photocurable antifog coating based on a zwitterionic copolymer prepared by any of the above preparation methods.

[0036] The present invention has the following beneficial effects:

[0037] (1) The modified substrate of the present invention has uniformly distributed thiol-modified SiO2 nanoparticles on its surface. Under ultraviolet light irradiation, the thiol groups at the ends can undergo thiol-olefin photoclick reaction with the carbon-carbon double bonds in zwitterionic copolymers or crosslinking agents to form a dense and stable crosslinked network coating.

[0038] (2) In the zwitterionic copolymer of the present invention, betaine has a strong hydration ability, and together with hydrophilic hydroxyethyl acrylate, it gives the coating excellent wetting properties. Water droplets will form a thin, continuous water film on the surface of the coating, avoiding interference from light transmittance and fogging. Hydrophobic allyl methacrylate can regulate the hydrophilic-hydrophobic balance of the coating, improving the water resistance and stability of the coating. The light transmittance of the resulting coating is about 80%. The results of the long-term anti-fog test show that the coating can continuously prevent fogging for 37 days in a hot fog environment at 60℃.

[0039] (3) The electrostatic interaction and hydrogen bond interaction in the cross-linked network of the present invention are reversible physical interactions, which enhance the adhesion performance of the coating and make the coating have a certain self-healing ability. The cross-linked network structure also makes the coating exhibit excellent mechanical stability. Scratches can be healed in just 4 seconds in an 85°C hot fog environment and can withstand 1000 wear cycles and 100 tape peels.

[0040] (4) The present invention is simple to operate, the raw materials are readily available, economical and safe, and has industrial application prospects. It can meet the anti-fogging requirements of non-polar transparent polyolefin film materials. Attached Figure Description

[0041] Figure 1 This is the 1H NMR spectrum of poly(methacryloylethyl sulfobetaine-co-hydroxyethyl acrylate-co-allylic methacrylate) (Ⅲ-1) synthesized in Example 1 of this invention.

[0042] Figure 2 This is the infrared spectrum of the thiol-modified SiO2 nanoparticles-1 prepared in Example 6 of this invention;

[0043] Figures 3a-3e These are water contact angle test diagrams of the photocurable antifog coatings (prepared on polyolefin films) based on zwitterionic copolymers prepared in Examples 6-10 of the present invention.

[0044] Figure 4 This is a rapid thermal fogging effect diagram of the photocurable antifog coating (prepared on a polyolefin film) based on zwitterionic copolymer prepared in Example 6 of the present invention (left side: untreated; right side: coated).

[0045] Figure 5This is the optical transmittance curve of the photocurable antifog coating based on zwitterionic copolymer prepared in Example 6 of the present invention;

[0046] Figure 6 These are test images of the self-healing performance of the photocurable antifog coating based on zwitterionic copolymer prepared in Example 6 of the present invention (left side: before self-healing; right side: after self-healing);

[0047] Figure 7 This is a 1000-cycle wear cycle test diagram of the photocurable antifog coating based on zwitterionic copolymer prepared in Example 6 of the present invention;

[0048] Figure 8 This is a rapid thermal fogging effect diagram of the photocurable antifog coating based on zwitterionic copolymer prepared in Example 6 of the present invention after 100 tape peeling cycles (left: untreated; right: coated). Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to the implementation examples. The following implementation examples are further illustrations of the present invention and do not limit the scope of application of the present invention. Unless otherwise specified, the raw materials involved in the following specific embodiments are all commercially available, the instruments used are all commercially available, and the processes involved are conventionally selected by those skilled in the art unless otherwise specified.

[0050] This invention uses silane coupling agents carrying thiol groups to modify SiO2 nanoparticles. These nanoparticles can be grafted onto the substrate surface as an intermediate layer or uniformly dispersed in a zwitterionic copolymer mixture. The terminal thiol groups react with carbon-carbon double bonds after UV curing to form a stable semi-interpenetrating polymer network (SIPN) structure, which improves the mechanical properties and adhesion strength of the coating. At the same time, the betaine-type zwitterionic compound and hydrophilic acrylate endow the coating with excellent anti-fogging properties and good self-healing ability.

[0051] Example 1

[0052] Synthesis of poly(methacryloylethyl sulfobetaine-co-hydroxyethyl acrylate-co-allylic methacrylate) (III-1):

[0053] A 10 wt% solution (solution 2) was prepared by dissolving raw materials methacryloyl ethyl sulfobetaine, hydroxyethyl acrylate, and allyl methacrylate in a 50% (v / v) methanol aqueous solution at a molar ratio of 60:90:30. A 1 wt% (v / v) initiator azobisisobutyronitrile (AIBN) was added. After removing oxygen from the system, the mixture was heated to 75°C and kept at that temperature for 6 hours for free radical polymerization. The crude product after the reaction was completed was dialyzed for 3 days, freeze-dried, and pulverized to obtain a white powder, poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate), i.e., poly(methacryloyl ethyl sulfobetaine-co-hydroxyethyl acrylate-co-allyl methacrylate) (Ⅲ-1). The 1H NMR spectrum is shown in [reference needed]. Figure 1 Its structural formula is:

[0054]

[0055] Example 2

[0056] Synthesis of poly(acrylamidopropyl sulfobetaine-co-hydroxyethyl acrylate-co-allylic methacrylate) (Ⅲ-2):

[0057] Acrylamidopropyl sulfobetaine, hydroxyethyl acrylate, and allyl methacrylate were dissolved in a 40% (v / v) methanol aqueous solution at a molar ratio of 60:90:10 to prepare a 20 wt% solution 2. Azobisisobutyronitrile (AIB) initiator (0.5 wt% of the total raw material mass) was added. After removing oxygen from the system, the mixture was heated to 60°C and kept at that temperature for 18 hours for free radical polymerization. The crude product after the reaction was completed was dialyzed for 3 days, freeze-dried, and pulverized to obtain a white powder poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate), namely poly(acrylamidopropyl sulfobetaine-co-hydroxyethyl acrylate-co-allyl methacrylate) (Ⅲ-2), with the following structural formula:

[0058]

[0059] Example 3

[0060] Synthesis of poly(methacryloylethyl carboxybetaine-co-hydroxyethyl acrylate-co-allylic methacrylate) (Ⅲ-3):

[0061] A 5wt% solution (solution 2) was prepared by dissolving raw materials methacryloyl ethyl carboxybetaine, hydroxyethyl acrylate, and allyl methacrylate in a 50% (v / v) methanol aqueous solution at a molar ratio of 45:105:15. Azobisisobutyronitrile (azobisisobutyronitrile) initiator (1wt% of the total raw material mass) was added. After removing oxygen from the system, the mixture was heated to 80°C and kept at that temperature for 4 hours for free radical polymerization. The crude product after the reaction was completed was dialyzed for 3 days, freeze-dried, and pulverized to obtain a white powder, poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate), i.e., poly(methacryloyl ethyl carboxybetaine-co-hydroxyethyl acrylate-co-allyl methacrylate) (Ⅲ-3), with the following structural formula:

[0062]

[0063] Example 4

[0064] Synthesis of poly(methacryloylethyl carboxybetaine-co-hydroxyethyl acrylate-co-allylic methacrylate) (III-4):

[0065] The raw materials methacryloyl ethyl carboxybetaine, hydroxyethyl acrylate, and allyl methacrylate were dissolved in a 60% (v / v) methanol aqueous solution at a molar ratio of 30:120:30 to prepare a 10 wt% solution 2. Azobisisobutyronitrile (AIB) initiator (1 wt% of the total raw material mass) was added. After removing oxygen from the system, the mixture was heated to 65°C and kept at that temperature for 10 hours for free radical polymerization. The crude product after the reaction was completed was dialyzed for 3 days, freeze-dried, and pulverized to obtain a white powder poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate), namely poly(methacryloyl ethyl carboxybetaine-co-hydroxyethyl acrylate-co-allyl methacrylate) (Ⅲ-4), with the following structural formula:

[0066]

[0067] Example 5

[0068] Synthesis of poly(methacryloylethyl sulfobetaine-co-hydroxyethyl acrylate-co-allylic methacrylate) (III-5):

[0069] The raw materials methacryloyl ethyl sulfobetaine, hydroxyethyl acrylate, and allyl methacrylate were dissolved in a 50% (v / v) methanol aqueous solution at a molar ratio of 60:90:20 to prepare a 5 wt% solution 2. Azobisisobutyronitrile (AIB) initiator (0.5 wt% of the total raw material mass) was added. After removing oxygen from the system, the mixture was heated to 75°C and kept at that temperature for 6 hours for free radical polymerization. The crude product after the reaction was completed was dialyzed for 3 days, freeze-dried, and pulverized to obtain a white powder poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate), namely poly(methacryloyl ethyl sulfobetaine-co-hydroxyethyl acrylate-co-allyl methacrylate) (Ⅲ-5), with the following structural formula:

[0070]

[0071] Example 6

[0072] A method for preparing a photocurable antifog coating based on a zwitterionic copolymer includes the following steps:

[0073] 1) Nano-sized silica (particle size: 30–500 nm) was added to a 75% (v / v) ethanol aqueous solution to prepare a 3 wt% dispersion. The pH of the solution was adjusted to 2.5, and then (3-mercaptopropyl)trimethoxysilane (twice the mass of the nano-silica) was added. The mixture was stirred and refluxed at 80 °C for 6 hours. After centrifugation, the solid was washed successively with ethanol and deionized water, and then vacuum dried at 60 °C to obtain mercapto-modified SiO2 nanoparticles-1. Figure 2 The infrared spectrum of thiol-modified SiO2 nanoparticles-1 is shown in the figure.

[0074] 2) The composition of zwitterionic copolymer mixture-1 (hereinafter referred to as mixture-1) is shown in Table 1; mix the components in Table 1 evenly;

[0075] 3) Add the thiol-modified SiO2 nanoparticles-1 obtained in step 1) to the second solvent (ethanol) to prepare a 5wt% solution 1. Adjust the pH to 2. Immerse the oxygen plasma pretreated substrate (polyolefin film) in solution 1 for 12h for modification. Take it out, wash it with water, and place it at 60℃ for 2h to obtain the modified substrate. Coat the zwitterionic copolymer mixture-1 prepared in step 2) onto the surface of the modified substrate and cure it under ultraviolet light at 365nm and 8W for 30min to form a film, thus obtaining a photocurable antifog coating based on zwitterionic copolymer.

[0076] The photocurable antifog coating based on zwitterionic copolymer prepared in this embodiment has a good antifog effect, such as... Figure 4As shown, this is an anti-fogging test conducted using a rapid thermal fogging method. Compared to the original polyolefin film, the bottom lettering is clearly visible on the coated portion. Long-term anti-fogging test results indicate that the coating can maintain anti-fogging for 45 days in a 60℃ thermal fog environment. Figure 5 As shown, the coating has a light transmittance of approximately 80%. Scratches on the coating heal in just 4 seconds under 85°C hot fog conditions. The coating can withstand 1000 abrasion cycles and still maintains good anti-fog performance after 100 tape peels. Figure 6-8 . Figure 3a As shown, the water contact angle after the coating stabilizes is 9.8 ± 0.2°.

[0077] Example 7

[0078] A method for preparing a photocurable antifog coating based on a zwitterionic copolymer includes the following steps:

[0079] 1) Add nano-silica (particle size: 500-600nm) to a 50% ethanol aqueous solution to prepare a 1wt% dispersion. Adjust the pH of the solution to 3, then add γ-mercaptopropyltriethoxysilane at a mass equal to that of nano-silica. Stir and reflux at 85℃ for 5h. Centrifuge, wash the solid with ethanol and deionized water in sequence, and vacuum dry at 70℃ to obtain mercapto-modified SiO2 nanoparticles-2.

[0080] 2) The composition of zwitterionic copolymer mixture-2 (hereinafter referred to as mixture-2) is shown in Table 1;

[0081] 3) Add the thiol-modified SiO2 nanoparticles-2 obtained in step 1) to the second solvent (methanol) to prepare a 2wt% solution 1. Adjust the pH to 3. Immerse the oxygen plasma pretreated substrate (polyolefin film) in solution 1 for 24 hours for modification. Take it out, wash it with water, and place it at 70°C for 2 hours to obtain the modified substrate. Coat the zwitterionic copolymer mixture-2 prepared in step 2) onto the surface of the modified substrate and cure it under ultraviolet light at 365nm and 80W for 30 minutes to form a film, thus obtaining a photocurable antifog coating based on zwitterionic copolymer.

[0082] The photocurable antifog coating based on zwitterionic copolymer prepared in this embodiment exhibits excellent antifog performance. Compared to the original polyolefin film, the bottom lettering is clearly visible on the coated portion. Long-term antifog testing results show that the coating can maintain antifog performance for 44 days in a 60°C hot fog environment. The coating's light transmittance is approximately 79%. The test results for the coating's self-healing and stability are similar to those in Example 6. Figure 3b As shown, the water contact angle after the coating stabilizes is 7.3 ± 0.3°.

[0083] Example 8

[0084] A method for preparing a photocurable antifog coating based on a zwitterionic copolymer includes the following steps:

[0085] 1) Add nano-silica (particle size: 600-900nm) to an 80% ethanol aqueous solution to prepare a 3wt% dispersion. Adjust the pH of the solution to 2, then add γ-mercaptopropyltriethoxysilane in 3 times the mass of nano-silica. Stir and reflux at 75℃ for 8h. Centrifuge, wash the solid with ethanol and deionized water in sequence, and dry it under vacuum at 50℃ to obtain mercapto-modified SiO2 nanoparticles-3.

[0086] 2) The composition of zwitterionic copolymer mixture-3 (hereinafter referred to as mixture-3) is shown in Table 1;

[0087] 3) The thiol-modified SiO2 nanoparticles-3 obtained in step 1) were added to the second solvent (methanol) to prepare a 2wt% solution 1. The pH was adjusted to 1. The substrate (polyolefin film) pretreated with oxygen plasma was immersed in solution 1 for 6 hours for modification. The substrate was then removed, washed with water, and placed at 50°C for 6 hours to obtain the modified substrate. The zwitterionic copolymer mixture-3 prepared in step 2) was coated on the surface of the modified substrate and cured under ultraviolet light at 365nm and 125W for 15 minutes to form a film, thus obtaining a photocurable antifog coating based on zwitterionic copolymer.

[0088] The photocurable antifog coating based on zwitterionic copolymer prepared in this embodiment exhibits excellent antifog performance. Compared to the original polyolefin film, the bottom lettering is clearly visible on the coated portion. Long-term antifog testing results show that the coating can maintain antifog performance for 37 days in a 60°C hot fog environment. The coating's light transmittance is approximately 79%. The test results for the coating's self-healing and stability are similar to those in Example 6. Figure 3c As shown, the water contact angle after the coating stabilizes is 6.4 ± 0.0°.

[0089] Example 9

[0090] A method for preparing a photocurable antifog coating based on a zwitterionic copolymer includes the following steps:

[0091] 1) Same as step 1) in Example 6; thiol-modified SiO2 nanoparticles-1 were obtained;

[0092] 2) The composition of zwitterionic copolymer mixture-4 (hereinafter referred to as mixture-4) is shown in Table 1;

[0093] 3) Add the thiol-modified SiO2 nanoparticles-1 obtained in step 1) to the second solvent (ethanol) to prepare a 5wt% solution 1. Adjust the pH to 1.5. Immerse the oxygen plasma pretreated substrate (polyolefin film) in solution 1 for 12h for modification, take it out, wash it with water, and place it at 60℃ for 4h to obtain the modified substrate. Coat the zwitterionic copolymer mixture-4 prepared in step 2) onto the surface of the modified substrate and cure it under ultraviolet light at 365nm and 8W for 60min to obtain a photocurable antifog coating based on zwitterionic copolymer.

[0094] The photocurable antifog coating based on zwitterionic copolymer prepared in this embodiment exhibits excellent antifog performance. Compared to the original polyolefin film, the bottom lettering is clearly visible on the coated portion. Long-term antifog testing results show that the coating can maintain antifog performance for 37 days in a 60°C hot fog environment. The coating's light transmittance is approximately 81%. The test results for the coating's self-healing and stability are similar to those in Example 6. Figure 3d As shown, the water contact angle after the coating stabilizes is 5.9 ± 0.0°.

[0095] Example 10

[0096] A method for preparing a photocurable antifog coating based on a zwitterionic copolymer includes the following steps:

[0097] 1) Same as step 1) in Example 7; obtain thiol-modified SiO2 nanoparticles-2;

[0098] 2) The composition of zwitterionic copolymer mixture-5 (hereinafter referred to as mixture-5) is shown in Table 1;

[0099] 3) Add the thiol-modified SiO2 nanoparticles-2 obtained in step 1) to the second solvent (80% ethanol aqueous solution by volume) to prepare a 4 wt% solution 1. Adjust the pH to 2. Immerse the oxygen plasma pretreated substrate (polyolefin film) in solution 1 for 12 h for modification. Take it out, wash it with water, and place it at 60°C for 3 h to obtain the modified substrate. Coat the zwitterionic copolymer mixture-5 prepared in step 2) onto the surface of the modified substrate and cure it under ultraviolet light at 365 nm and 80 W for 15 min to obtain a photocurable antifog coating based on zwitterionic copolymer.

[0100] The photocurable antifog coating based on zwitterionic copolymer prepared in this embodiment exhibits excellent antifog performance. Compared to the original polyolefin film, the bottom lettering is clearly visible on the coated portion. Long-term antifog testing results show that the coating can maintain antifog performance for 39 days in a 60°C hot fog environment. The coating's light transmittance is approximately 80%. The test results for the coating's self-healing and stability are similar to those in Example 6. Figure 3eAs shown, the water contact angle after the coating stabilizes is 8.8 ± 0.1°.

[0101] Table 1 (Components by mass percentage)

[0102]

[0103] Experiments have shown that by replacing the polyolefin film in this embodiment with polyethylene film, glass, high-temperature resistant polyester film, or polycarbonate film, while keeping other aspects the same as in this embodiment, a photocurable antifog coating based on zwitterionic copolymer can be obtained.

[0104] The coating performance tests used in this invention include anti-fogging tests, light transmittance tests, and water contact angle tests.

[0105] Anti-fogging test: including rapid hot fogging method and long-term anti-fogging test. For rapid hot fogging method, place the sample 5cm above a beaker containing 85℃ hot water, and place a piece of paper with the word "Antifogging" written on it below the beaker. After 30 seconds, take a picture to record the anti-fogging effect.

[0106] In the long-term anti-fogging test, 400 mL of distilled water was placed in a 500 mL beaker and heated in a 60 °C water bath. The sample was placed above the beaker. The angle between the surface of the photocurable anti-fogging coating based on zwitterionic copolymer prepared in Example 6 and the horizontal plane was 15°. When 1 / 3 of the test area of ​​the photocurable anti-fogging coating based on zwitterionic copolymer was covered by water droplets, it was considered to have failed. The time from the start of anti-fogging to failure was considered the anti-fogging duration. The results of the long-term anti-fogging test showed that the coating prepared in Example 6 could continuously prevent fogging for 45 days in a 60 °C hot fog environment. The long-term anti-fogging test method of the photocurable anti-fogging coating based on zwitterionic copolymer prepared in Examples 7-10 showed that the coating could continuously prevent fogging for 44 days, 37 days, 37 days and 39 days in a 60 °C hot fog environment, respectively.

[0107] Coating transmittance test: The transmittance values ​​of the sample in the 200-800nm ​​wavelength range were read using a visible light spectrophotometer.

[0108] Water contact angle test: Take 6 μL of deionized water, drop it onto the coating surface, and after it stabilizes, use the five-point fitting method to read the value. Measure each coating 5 times and take the average value.

[0109] The applicant declares that this invention illustrates a photocurable antifog coating based on zwitterionic copolymers and its preparation method through the above embodiments. However, this invention is not limited to the above process steps, meaning that this invention does not necessarily rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used in this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A method for preparing a photocurable antifog coating based on a zwitterionic copolymer, characterized in that... Includes the following steps: Step 1: Add nano-silica to an ethanol aqueous solution with a volume concentration of 50%-80% to prepare a 1-3 wt% dispersion. Adjust the pH of the solution to 2-3, then add 1-3 times the mass of the nano-silica silane coupling agent. Stir and reflux at 80±5℃ for 5-8 hours, then centrifuge. Wash the solid sequentially with ethanol and deionized water, and dry to obtain mercapto-modified SiO2 nanoparticles. The silane coupling agent is (3-mercaptopropyl)trimethoxysilane or γ-mercaptopropyltriethoxysilane. Step 2: Prepare the zwitterionic copolymer mixture, taking the following components by mass percentage: Poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate) (III) 5%~10%; crosslinking agent 0.5~1%; photoinitiator 0.025~0.2%; thiol-modified SiO2 nanoparticles: 0~2%; balance is the first solvent; mix evenly to obtain a zwitterionic copolymer mixture; The structural formula of the poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate) (III) is: （Ⅲ）； Among them, R 1 It can be an H atom or a methyl group; R 2 It is an O atom or a secondary amine; R 3 for or ; m is 2 or 3; a is (30~60). b is (90~120). c is (10~30); Step 3: Add the thiol-modified SiO2 nanoparticles obtained in Step 1 to the second solvent to prepare a 2-5 wt% solution 1. Adjust the pH to 1-3. Immerse the oxygen plasma pretreated substrate in solution 1 for 6-24 hours for modification. Remove the substrate, wash it with water, and place it at 50-70℃ for 2-6 hours to obtain the modified substrate. Coat the surface of the modified substrate with the zwitterionic copolymer mixture prepared in Step 2 and cure it into a film under ultraviolet light irradiation to obtain a photocurable antifog coating based on zwitterionic copolymer.

2. The preparation method according to claim 1, characterized in that... Step one involves adding nano-silica to a 75% (v / v) ethanol aqueous solution to prepare a 3 wt% dispersion, adjusting the pH of the solution to 2.5, then adding silane coupling agent at twice the mass of the nano-silica, stirring and refluxing at 80°C for 6 hours, centrifuging, washing the solid sequentially with ethanol and deionized water, and vacuum drying at 50–70°C to obtain thiol-modified SiO2 nanoparticles.

3. The preparation method according to claim 1 or 2, characterized in that... The particle size of the nano-silica is 30-900 nm.

4. The preparation method according to claim 1, characterized in that... In step two: The crosslinking agent is N,N-methylenebisacrylamide, ethylene glycol dimethacrylate, or polyethylene glycol diacrylate with a number average molecular weight of 200-600. The photoinitiator is benzoin dimethyl ether, diphenylacetone, or 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone; The first solvent is at least one of trifluoroethanol, methanol, and ethanol.

5. The preparation method according to claim 1, characterized in that... In step two, poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate) (III) is prepared by the following method: With a molar ratio of (30-60):(90-120):(10-30), raw materials, betaine-type zwitterionic compound, hydroxyethyl acrylate, and allyl methacrylate were dissolved in a methanol aqueous solution with a volume concentration of 40-60% to prepare a 5-20 wt% solution 2. Azobisisobutyronitrile (AIB) initiator was added at a total mass of 0.5-1 wt% of the raw materials. After removing oxygen from the system, the mixture was heated to 60-80℃ and kept at that temperature for 4-18 hours to carry out free radical polymerization. After dialyzing, the mixture was freeze-dried to obtain poly(betaine-type zwitterionic compound-co-hydroxyethyl acrylate-co-allyl methacrylate) (III).

6. The preparation method according to claim 5, characterized in that, The betaine-type zwitterionic compound is methacryloylethyl sulfobetaine, acrylamidopropyl sulfobetaine, or methacryloylethyl carboxybetaine.

7. The preparation method according to claim 1, characterized in that, Step three is as follows: The thiol-modified SiO2 nanoparticles obtained in step one are added to a second solvent to prepare a 5wt% solution 1. The pH is adjusted to 2. The oxygen plasma pretreated substrate is immersed in solution 1 for 12 hours for modification. The substrate is then removed, washed with water, and placed at 60°C for 2 hours to obtain a modified substrate. The zwitterionic copolymer mixture prepared in step two is coated on the surface of the modified substrate and cured under ultraviolet light at 365nm and 8-125W for 15-60 minutes to form a film, thus obtaining a photocurable antifog coating based on zwitterionic copolymer.

8. The preparation method according to claim 1 or 7, characterized in that, The second solvent is one or two of deionized water, methanol, and ethanol; the substrate is a polyolefin film, glass, or a high-temperature resistant polyester film.

9. A photocurable antifog coating based on a zwitterionic copolymer prepared by any one of claims 1-8.

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