Cyclic dimer monomer for preparing parylene coating with electrochemical corrosion resistance as well as preparation method and application of cyclic dimer monomer

Abstract

The invention discloses a cyclic dimer monomer for preparing a parylene coating resistant to electrochemical corrosion as well as a preparation method and application of the cyclic dimer monomer, and particularly relates to a 4, 16-bis (m-methoxyphenyl)-[2, 2]-p-xylene cyclic dimer, the preparation method of the cyclic dimer monomer comprises the following steps: S1, reacting the p-xylene cyclic dimer with liquid bromine in the presence of a catalyst and a first solvent to obtain a p-xylene cyclic dimer; an intermediate 1 is obtained; s2, reacting the intermediate 1 with 3-hydroxyphenylboronic acid in the presence of alkali salt, a palladium catalyst and a second solvent to obtain an intermediate 2; and S3, reacting the intermediate 2 with a methylation reagent in the presence of alkali salt and a third solvent to obtain the cyclic dimer monomer. The benzene-substituted parylene coating prepared from the monomer shows excellent electrochemical corrosion resistance, and compared with a corrosion-resistant coating formed by an existing parylene monomer, the benzene-substituted parylene coating is low in corrosion current density and high in corrosion potential and has a good application prospect in the aspects of electronic product protection or medical instrument protection and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of organic synthesis and coating preparation, and particularly relates to a kind of cyclo-dimer monomer for preparing electrochemical corrosion resistant parylene coating and its preparation method and application. BACKGROUND

[0002] Metal and its alloy materials are widely used in key fields such as industry, marine engineering, electronic devices, biomedical implants, etc. However, in humid, salt-containing or other electrolyte environments, metal surfaces are prone to electrochemical corrosion, leading to material performance degradation, structural failure and even safety accidents, causing huge economic losses. The essence of electrochemical corrosion is the conjugate reaction of anodic dissolution (oxidation) and cathodic reduction (such as oxygen reduction) of metal in electrolyte solution. The two core electrochemical parameters for evaluating the corrosion resistance of metal are corrosion potential and corrosion current density. Among them, the corrosion current density directly represents the rate of corrosion reaction, and the lower the value, the slower the corrosion process; while the corrosion potential reflects the thermodynamic tendency of metal corrosion, and a higher corrosion potential generally means that the metal is less likely to be oxidized. Therefore, developing efficient, stable and durable surface protection technology to simultaneously inhibit the thermodynamic tendency and kinetic rate of corrosion is the key to prolonging the service life of metal components and ensuring the reliability of equipment.

[0003] Chemical vapor deposition polymer-p-xylylene (parylene, such as Parylene C, N, F, etc.) coating technology has become an important choice for high-end protection of precision parts, electronic circuits and medical devices, as it can form a uniform, pinhole-free, chemically inert and excellent barrier thin film at room temperature through vapor deposition. This process involves the pyrolysis of a cyclo-dimer monomer (such as [2,2]-p-arylcycloalkane) into active monomers at high temperature, followed by adsorption and polymerization on the surface of the substrate at room temperature, achieving conformal and shape-preserving coating. The application of parylene coating to metal corrosion protection has been reported. Traditional parylene coatings can effectively isolate the metal substrate from direct contact with corrosive media, and as a physical barrier, they can significantly reduce the corrosion current density of the metal, thereby slowing down the corrosion rate. However, practitioners in the field have found a widespread but not fully appreciated paradox: while such traditional parylene coatings reduce the corrosion current density, they often cause a significant negative shift (decrease) in the corrosion potential of the metal.

[0004] The negative shift of corrosion potential is an unfavorable signal, indicating that the protected metal becomes more active and more prone to oxidation in thermodynamics. Although the reduction of corrosion current brings positive effects, the decrease of corrosion potential weakens the overall corrosion resistance of the coating system, especially when the coating has defects or is mechanically damaged, which may accelerate the initiation and development of localized corrosion, reducing the safety margin of protection.

[0005] Therefore, it is urgent to develop a new kind of parylene monomer, so that the prepared coating can not only effectively reduce the corrosion current density, but also improve the coating / metal interface characteristics through molecular structure design, thereby avoiding or minimizing the negative impact on the corrosion potential, providing more durable and reliable protection in harsh electrochemical environments, and broadening the application prospect of parylene coating in high-end electronic products, medical devices, marine equipment and other fields. SUMMARY

[0006] To solve the problem that the coating formed by the existing parylene monomer on the metal surface can reduce the corrosion current density, but often leads to significant negative shift of the metal corrosion potential, thereby limiting its potential to provide efficient and comprehensive protection for metals in harsh corrosion environments, the present application provides a cyclic dimer monomer for preparing an electrochemically corrosion-resistant parylene coating, a preparation method and application thereof. By introducing a specific substituent group, meta-methoxyphenyl, into the p-xylylene cyclic dimer, a 4,16-bis(methoxyphenyl)-[2,2]-p-xylylene cyclic dimer is obtained. The parylene coating formed by the cyclic dimer monomer exhibits excellent electrochemical corrosion resistance. Compared with the corrosion-resistant coating formed by the existing parylene monomer, not only is the corrosion current density lower, but also the corrosion potential is higher, thereby providing more durable and reliable protection in harsh electrochemical environments, and broadening the application prospect of parylene coating in high-end electronic products, medical devices, marine equipment and other fields.

[0007] Specifically, the present application provides the following technical solutions: The first aspect of the present application provides a cyclic dimer monomer for preparing an electrochemically corrosion-resistant parylene coating, the cyclic dimer monomer being 4,16-bis(methoxyphenyl)-[2,2]-p-xylylene cyclic dimer, and the structure thereof being as follows: .

[0008] The second aspect of the present application provides a preparation method of the cyclic dimer monomer for preparing an electrochemically corrosion-resistant parylene coating according to the first aspect, comprising the following steps: S1. reacting p-xylylene cyclic dimer with liquid bromine in the presence of a catalyst, a first solvent to obtain intermediate 1; S2. reacting the intermediate 1 with 3-hydroxyphenylboronic acid in the presence of an alkali salt, a palladium catalyst and a second solvent to obtain intermediate 2; S3. reacting the intermediate 2 with a methylation reagent in the presence of an alkali salt and a third solvent to obtain the cyclic dimer monomer; The structures of the intermediates 1 and 2 are shown as follows: .

[0009] Compared with the traditional synthesis method of the p-xylylene ring diad monomer, the p-xylylene ring diad monomer is synthesized by bromination, borate esterification and transition metal catalytic coupling, and the reaction conditions are mild, the water and oxygen resistance is good, the equipment and operation requirements are reduced, the safety is higher, and the operation is more simple. In addition, through the palladium catalytic coupling reaction, the chemical selectivity is high, the by-products are few, which is beneficial to improve the yield and product purity; and the above synthesis path can realize segmented production, the key intermediates can be separated, purified and tested, the quality of each reaction is controllable, which provides reliable process monitoring points for large-scale production, and is more suitable for large-scale and standardized production.

[0010] Further, in step S1, the catalyst is iron powder and / or iron bromide.

[0011] Further, in step S1, the molar ratio of the p-xylylene ring diad, liquid bromine and catalyst is 1: (2-4): (0.15-0.21).

[0012] Further, in step S1, the first solvent is selected from one or more of diethyl ether, dichloromethane and toluene, and in some preferred embodiments of the present application, the first solvent is dichloromethane, and more preferably, the mass ratio of the p-xylylene ring diad to the first solvent is (0.02-0.04):1.

[0013] Further, in step S1, the reaction temperature is preferably 20-30 ℃, and the reaction time is preferably 36-48 h.

[0014] Further, in step S1, the p-xylylene ring diad and the catalyst are first dissolved in the first solvent, and then liquid bromine is added dropwise for reaction.

[0015] Further, in step S1, the preparation method further comprises the following steps: after the reaction, a supersaturated sulfurous acid solution is added to quench the reaction, the solid precipitate is extracted, separated and dried to obtain the intermediate 1; the extraction solvent is dichloromethane, and the solid precipitate is obtained by filtering the organic phase.

[0016] Further, in step S2, the base salt is selected from one or more of sodium carbonate, potassium acetate and potassium carbonate; and the palladium catalyst is tetraphenylphosphine palladium and / or 1,1'-bis diphenylphosphine ferrocene dichloropalladium.

[0017] Further, in step S2, the molar ratio of the intermediate 1, 3-hydroxyphenylboronic acid, base salt, and palladium catalyst is preferably 1: (3-6): (5-8): (0.05-0.1).

[0018] Further, in step S2, the second solvent is selected from one or more of ethylene glycol dimethyl ether, dimethyl sulfoxide, 1,4-dioxane, and deionized water, and in some preferred embodiments of the present application, the second solvent is a mixture of ethylene glycol dimethyl ether and water, and more preferably, the mass ratio of the intermediate 1 to the second solvent is (0.03-0.05): 1.

[0019] Further, in step S2, the reaction temperature is preferably 100-120 ℃, and the reaction time is preferably 48-60 h.

[0020] Further, in step S2, the intermediate 1 is first dissolved in the second solvent, and then 3-hydroxyphenylboronic acid, base salt, and palladium catalyst are added under a protective atmosphere for reaction.

[0021] Further, in step S2, the preparation method further comprises the following steps: after the reaction, cooling to 20-40 ℃, adding dilute hydrochloric acid to quench the reaction, and then extracting, washing, drying, concentrating, and column chromatography to obtain the intermediate 2; the extraction solvent is ethyl acetate, the washing solvent is supersaturated sodium chloride aqueous solution, anhydrous sodium sulfate is used for drying, and 300-400 mesh silica gel is used for column chromatography (eluent is a mixture of petroleum ether / ethyl acetate in a volume ratio of 6:1).

[0022] Further, in step S3, the base salt is potassium carbonate and / or potassium hydroxide, and the methylating agent is selected from one or more of iodomethane, dimethyl sulfate, and dimethyl carbonate.

[0023] Further, in step S3, the molar ratio of the intermediate 2, methylating agent, and base salt is 1: (2.2-3.0): 3.

[0024] Further, in step S3, the third solvent is dimethyl sulfoxide and / or N,N-dimethylformamide, and in some preferred embodiments of the present application, the third solvent is dimethyl sulfoxide, and more preferably, the mass ratio of the intermediate 2 to the third solvent is (0.03-0.05): 1.

[0025] Further, in step S3, the reaction temperature is preferably 50-60 ℃, and the reaction time is preferably 36-48 h.

[0026] Further, in step S3, the intermediate 2 is first dissolved in the third solvent, and then the base salt and the methylating agent are added for reaction.

[0027] Further, in step S3, the preparation method further comprises the following steps: cooling to 20-40 ℃ after reaction, separating the solid precipitate, washing, drying, and rotary evaporation to obtain the cyclophane monomer; the washing solvent is saturated sodium chloride aqueous solution, and anhydrous sodium sulfate is used for drying; more preferably, the solid obtained by rotary evaporation is dissolved in dichloromethane, and the cyclophane monomer is obtained by recrystallization with n-hexane.

[0028] The third aspect of the present application provides a paryline coating prepared by chemical vapor deposition of the cyclophane monomer of the first aspect.

[0029] Further, the cyclophane monomer is evaporated and cracked to deposit on the surface of a substrate to form the paryline coating; the substrate includes but is not limited to metal, glass, etc.

[0030] The fourth aspect of the present application provides a use of the paryline coating of the third aspect in the protection of electronic products, medical devices, or marine equipment.

[0031] Compared with the prior art, the present application has the following advantages: 1. The present application provides a cyclophane monomer 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylylene cyclophane for preparing a paryline coating resistant to electrochemical corrosion. The coating prepared from the monomer not only effectively reduces the corrosion current density, but also effectively improves the coating / metal interface properties through molecular structure design, thereby reducing the negative impact of the coating on the corrosion potential and maintaining a relatively high corrosion potential. Under the synergistic action of low corrosion current density and high corrosion potential, the metal containing the above-mentioned paryline coating exhibits excellent resistance to salt water corrosion.

[0032] 2. The cyclophane monomer provided by the present application can be prepared from inexpensive and readily available p-xylene cyclophane as a starting material through bromination, coupling, and methylation reaction processes. The preparation method is simple, the conditions are mild, and the process is easy to control, which is suitable for batch production.

[0033] 3. The cyclophane monomer provided by the present application can be used to prepare a paryline coating on the surface of copper by evaporation and cracking, which can effectively reduce the corrosion current density while maintaining a relatively high corrosion potential, thereby providing more durable and reliable protection in harsh electrochemical environments and broadening the application prospects of paryline coatings in high-end electronic products, medical devices, marine equipment, and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The reaction flow chart for preparing 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylylene cyclophane; Figure 2 The nuclear magnetic resonance spectrum of 4,16-bis(bromine)-[2,2]-p-xylylene cyclophane; Figure 3 NMR1H spectrum of 4, 16-bis(m-methoxyphenyl)-[2,2]-paracyclophane; Figure 4 NMR1H spectrum of 4, 16-bis(m-methoxyphenyl)-[2,2]-paracyclophane; Figure 5 NMR1H spectrum of 4, 16-bis(m-methoxyphenyl)-[2,2]-paracyclophane; Figure 6 NMR1H spectrum of 4, 16-bis(m-methoxyphenyl)-[2,2]-paracyclophane; Figure 7 NMR1H spectrum of 4, 16-bis(m-methoxyphenyl)-[2,2]-paracyclophane; Figure 8 X-ray diffraction (XRD) pattern of 4, 16-bis(m-methoxyphenyl)-[2,2]-paracyclophane; Figure 9 Crystal structure of 4, 16-bis(m-methoxyphenyl)-[2,2]-paracyclophane; Figure 10 Electrochemical impedance spectroscopy (EIS) - Bode plot of parylene coatings prepared from different monomers; Figure 11 Electrochemical impedance spectroscopy (EIS) - Nyquist plot of parylene coatings prepared from different monomers; Figure 12 Tafel plot of parylene films prepared from different monomers. DETAILED DESCRIPTION

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", or "includes" and / or "including" when used herein, specify the presence of stated features, integers, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.

[0036] The application will be further described with reference to the following examples and drawings, in which:

[0037] Example: This example relates to the preparation of 4, 16-bis(m-methoxyphenyl)-[2,2]-paracyclophane, reaction scheme as shown in Figure 1 , and specifically as follows: (1) Preparation of intermediate 1: 20 g of p-xylenecyclodione and 1.0 g of iron powder were added to a 500 mL two-necked flask, followed by 300 mL of dichloromethane. Then, 15 mL of liquid bromine was slowly added dropwise at 25 °C, and the mixture was stirred continuously for 36 h. After the reaction, saturated sulfurous acid solution was added to quench the reaction, followed by extraction with dichloromethane. The precipitate was obtained by filtration, and the dried solid precipitate yielded 12 g of intermediate 1, with a yield of 35%.

[0038] The prepared intermediate 1 was characterized by NMR, such as... Figure 2 , 3 As shown, the details are as follows: 1 H NMR (400 MHz, CDCl3): δ 7.14 (dd, J = 7.8, 1.7 Hz, 2H), 6.51 (d, J =1.5 Hz, 2H), 6.44 (d, J = 7.8 Hz, 2H), 3.49 (ddd, J = 13.0, 10.4, 2.2 Hz,2H), 3.15 (ddd,J = 12.7, 10.4, 4.9 Hz, 2H), 2.98 – 2.91 (m, 2H), 2.85 (ddd,J = 13.2, 10.8, 4.9 Hz, 2H).

[0039] 13 C NMR (101 MHz, CDCl3): δ 141.19, 138.55, 137.35, 134.14, 128.29, 126.76, 32.85.

[0040] The characterization results show that intermediate 1 is a 4,16-bis(bromo)-[2,2]-p-xylene ring dimer.

[0041] (2) Preparation of intermediate 2: 3.3 g of intermediate 1 prepared above was placed in a 150 mL two-necked flask, and 90 mL of ethylene glycol dimethyl ether and 9 mL of deionized water were added. The mixture was purged with nitrogen. Under nitrogen atmosphere, 5.6 g of 3-hydroxyphenylboronic acid, 7.2 g of potassium acetate, and 0.924 g of tetrakis(triphenylphosphine)palladium were added. The mixture was then slowly heated to 100 °C, refluxed, and stirred for 48 h. After the reaction, the mixture was cooled to room temperature, and the reaction was quenched with 1 mol / L hydrochloric acid. The mixture was extracted with ethyl acetate, and the organic phase was washed with saturated sodium chloride aqueous solution, dried over anhydrous sodium sulfate, concentrated, and then wet-loaded. The mixture was then subjected to silica gel column chromatography (petroleum ether: ethyl acetate = 6:1) and evaporated to dryness to obtain intermediate 2 in 41% yield.

[0042] The prepared intermediate 2 was characterized by NMR, such as... Figure 4 , 5 As shown, the details are as follows: 1 H NMR (400 MHz, DMSO-d6): δ 9.49 (s, 2H), 7.30 (t, J = 7.8 Hz, 2H), 6.95 – 6.91 (m, 4H), 6.79 (d, J = 1.5 Hz, 2H), 6.69 (d, J = 7.8 Hz, 2H), 6.62(s, 2H), 6.51 – 6.47 (m, 2H), 3.36 (d, J = 6.2 Hz, 2H), 3.00 (ddd, J = 13.4,10.0, 4.3 Hz, 2H), 2.83 (ddd, J = 13.9, 10.1, 4.0 Hz, 2H), 2.65 (dq, J =13.5, 4.3 Hz, 2H).

[0043] 13 C NMR (101 MHz, DMSO-d6): δ 157.94, 142.78, 142.14, 139.79, 136.83,135.21, 132.38, 130.00, 129.32, 120.76, 116.79, 114.30, 34.60, 33.73.

[0044] The characterization results show that intermediate 2 is a 4,16-bis(m-hydroxyphenyl)-[2,2]-p-xylene ring dimer.

[0045] (3) Preparation of 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer: Take 1.1 g of the intermediate 2 prepared above into a 100 mL two-necked flask, add 30 mL of dimethyl sulfoxide, then add 1.24 g of potassium carbonate and 0.6 mL of iodomethane, maintain the reaction temperature at 50 °C, and stir for 48 h. Cool to room temperature, filter to obtain a solid precipitate, wash and dry to obtain the final product, with a yield of 85%.

[0046] The prepared final product was characterized by NMR, such as... Figure 6 , 7 As shown, the details are as follows: 1H NMR (400 MHz, CDCl3): δ 7.41 (t, J = 7.9 Hz, 2H), 7.15 – 7.11 (m,2H), 7.06 (dd, J = 2.7, 1.5 Hz, 2H), 6.93 (ddd, J = 8.2, 2.6, 0.9 Hz, 2H), 6.67 (d, J = 1.5 Hz, 2H), 6.63 (q, J = 2.7, 2.0 Hz, 4H), 3.91 (s, 3H), 3.50 –3.44 (m, 2H), 3.06 – 3.00 (m, 2H), 2.86 – 2.80 (m, 4H).

[0047] 13 C NMR (101 MHz, CDCl3): δ 159.64, 136.86, 134.83, 132.28, 129.48, 129.39, 122.30, 121.95, 116.72, 115.81, 113.86, 111.88, 55.35, 34.75, 33.83.

[0048] The prepared final product was subjected to XRD testing, and the test results are as follows: Figure 8 As shown, sharp diffraction peaks can be observed, indicating that the prepared final product is a crystal.

[0049] A powdered sample of 10 mg of the final product was dissolved in 25 mL of a mixed solvent of dichloromethane and petroleum ether (4:1 ratio). After slow evaporation for two days, a large amount of transparent crystals precipitated. Single-crystal X-ray diffraction analysis of the crystals yielded the following results: Figure 9 The crystal structure shown below has single-crystal parameters as shown in the table below:

[0050] The characterization results show that the final product is 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene cyclodimer.

[0051] Application and performance characterization: (1) The 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer (abbreviated as: benzopyrene OCH3), intermediate 2 (abbreviated as benzopyrene OH) prepared in the examples and commercially available pyrene monomers (pyrene C monomer, pyrene N monomer, pyrene F monomer) were respectively used to prepare the corresponding pyrene coatings on the surface of copper sheets by the following methods. The specific operations are as follows: A 10 mm × 10 mm pure copper sheet was polished with sandpaper of different grits until the surface was smooth, then polished, ultrasonically cleaned in ethanol, and dried in a vacuum drying oven.

[0052] The pyrene monomer is placed in an evaporation chamber and evaporated under a vacuum of 3 Pa (temperature of 200 °C). It is then pyrolyzed in a pyrolysis furnace (temperature of 700 °C) and finally deposited on a copper sheet in the coating chamber to form a transparent pyrene coating.

[0053] The prepared samples are shown in the table below:

[0054] (2) Electrochemical corrosion resistance tests were conducted on the above-mentioned uncoated bare copper and copper sheets containing different pyrene coatings. The specific procedures are as follows: 1. Setting up the testing system Dissolve 3.5 g of sodium chloride in 100 ml of deionized water to prepare a 3.5 wt% NaCl solution, which will be used as the electrolyte solution.

[0055] A copper sheet coated with a film was clamped onto a glassy carbon electrode. A silver chloride electrode was selected as the reference electrode, and a stone rod was used as the counter electrode. Electrochemical corrosion tests were conducted using a three-electrode system in an electrochemical workstation.

[0056] 2. Open Circuit Potential (OCP) Test The working electrode was immersed in the electrolyte for 7200 s to obtain a stable equilibrium potential E. ocp .

[0057] 3. Electrochemical Impedance Spectroscopy (EIS) Test At equilibrium potential E ocp The test was conducted with a frequency range of 1-100 kHz and a disturbance amplitude of 5 mV.

[0058] EIS tests were performed on bare copper and coated copper sheets respectively, and the results were obtained respectively. Figure 10 , 11 The Bode plot and Nyquist plot.

[0059] 4. Potentiodynamic polarization curve test Relative to E ocp The scanning range was -0.30 V to +0.30 V, and the scanning rate was 10 mV / s. Potentiodynamic polarization curves were measured on bare copper and coated copper sheets respectively to obtain... Figure 12 The Tafel curve.

[0060] When evaluating the electrochemical corrosion resistance of materials, since corrosion current density is more important than corrosion potential, the corrosion current density of the materials should be compared first. If the corrosion current density is the same, the corrosion potential should be compared secondly. The lower the corrosion current density and the higher (positive) the corrosion potential, the better the electrochemical corrosion resistance.

[0061] Table 1

[0062] As shown in Table 1, the benzopyrene coating formed on the copper sheet surface using 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer prepared in the embodiments of the present invention as a monomer exhibits excellent electrochemical corrosion resistance. Not only is the corrosion current density significantly lower than that of bare copper (lower than coatings prepared with existing benzopyrene monomers), but the corrosion potential also does not decrease significantly (significantly higher than coatings prepared with existing benzopyrene monomers). In contrast, the benzopyrene coating formed on the copper sheet using intermediate 2 prepared in the embodiments as a monomer, while having a relatively high corrosion potential, exhibits a lower corrosion current density than the benzopyrene N coating and the benzopyrene OCH3 coating.

[0063] Furthermore, in the low-frequency region of the Bode plot, a larger impedance modulus indicates better corrosion resistance of the metal; in the high-frequency region, a larger absolute value of the phase angle peak value indicates better corrosion resistance of the metal. Figure 10 It can be seen that the impedance modulus of the copper sheet coated with benzopyrene OCH3 is 2250 Ω, which is significantly improved compared with other coatings, indicating that the benzopyrene OCH3 coating has the strongest protective performance. The curve showing the change in negative phase angle indicates that the phase angle of the benzopyrene OCH3 coating is the largest in the high-frequency range, approaching -62°, thus greatly improving the corrosion susceptibility of the copper sheet and enhancing its resistance to electrochemical corrosion.

[0064] Figure 11 The diameter of the Nyquist curve corresponds to the charge transfer resistance, which is determined by... Figure 11 It is known that copper sheets coated with benzopyrene OCH3 have a higher charge transfer resistance (significantly better than copper sheets coated with other pyrene coatings), the energy barrier of electrochemical corrosion reaction is increased, and electron gain and loss are suppressed. This is because the dense benzopyrene film provides excellent metal protection properties.

[0065] Therefore, the 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer coating provided by this invention has excellent electrochemical corrosion resistance and has good application prospects in electronic products, medical devices, marine equipment and other fields.

[0066] The embodiments described above are merely preferred embodiments for fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A cyclic dimer monomer for preparing a pyrene coating resistant to electrochemical corrosion, characterized in that, The cyclic dimer monomer is a 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene cyclic dimer, the structure of which is shown below: 。 2. A method for preparing the cyclic dimer monomer as described in claim 1, characterized in that, Includes the following steps: S1. The p-xylene ring dimer was reacted with liquid bromine in the presence of a catalyst and a first solvent to obtain intermediate 1; S2. Intermediate 1 is reacted with 3-hydroxyphenylboronic acid in the presence of an alkaline salt, a palladium catalyst and a second solvent to obtain intermediate 2. S3. The intermediate 2 is reacted with a methylating agent in the presence of an alkaline salt and a third solvent to obtain the cyclic dimer monomer; The structures of intermediates 1 and 2 are shown below: 。 3. The preparation method according to claim 2, characterized in that, Step S1 includes at least one of the following features: (1) The catalyst is iron powder and / or ferric bromide; (2) The molar ratio of the p-xylene ring dimer to liquid bromine and catalyst is 1:(2-4):(0.15-0.21); (3) The first solvent is selected from one or more of diethyl ether, dichloromethane, and toluene; (4) The reaction temperature is 20-30 °C and the time is 36-48 h.

4. The preparation method according to claim 2 or 3, characterized in that, In step S1: First, the p-xylene ring dimer and the catalyst are dissolved in the first solvent, and then liquid bromine is added dropwise to carry out the reaction. The preparation method further includes the following steps: after the reaction, a supersaturated sulfurous acid solution is added to quench the reaction, and the solid precipitate is extracted, separated, and dried to obtain the intermediate 1.

5. The preparation method according to claim 2, characterized in that, Step S2 includes at least one of the following features: (1) The alkaline salt is selected from one or more of sodium carbonate, potassium acetate, and potassium carbonate; (2) The palladium catalyst is tetratriphenylphosphine palladium and / or 1,1'-bisdiphenylphosphine ferrocene palladium dichloride; (3) The molar ratio of intermediate 1 to 3-hydroxyphenylboronic acid, alkaline salt, and palladium catalyst is 1:(3-6):(5-8):(0.05-0.1); (4) The second solvent is selected from one or more of ethylene glycol dimethyl ether, dimethyl sulfoxide, 1,4-dioxane, and deionized water; (5) The reaction temperature is 100-120 °C and the time is 48-60 h.

6. The preparation method according to claim 2 or 5, characterized in that, In step S2: First, intermediate 1 is dissolved in a second solvent, and then 3-hydroxyphenylboronic acid, an alkaline salt, and a palladium catalyst are added under a protective atmosphere to carry out the reaction. The preparation method further includes the following steps: after the reaction, the mixture is cooled to 20-40 °C, dilute hydrochloric acid is added to quench the reaction, and the mixture is then extracted, washed, dried, concentrated, and subjected to column chromatography to obtain the intermediate 2.

7. The preparation method according to claim 2, characterized in that, Step S3 includes at least one of the following features: (1) The methylating agent is selected from one or more of iodomethane, dimethyl sulfate, and dimethyl carbonate; (2) The alkaline salt is potassium carbonate and / or potassium hydroxide; (3) The molar ratio of intermediate 2 to methylating agent and alkali salt is 1:(2.2-3.0):3; (4) The third solvent is dimethyl sulfoxide and / or N,N-dimethylformamide; (5) The reaction temperature is 50-60 °C and the time is 36-48 h.

8. The preparation method according to claim 2 or 7, characterized in that, In step S3: First, intermediate 2 is dissolved in a third solvent, and then an alkaline salt and a methylating agent are added to carry out the reaction. The preparation method further includes the following steps: cooling to 20-40 °C after reaction, separating the solid precipitate, and obtaining the cyclic dimer monomer by washing, drying and rotary evaporation.

9. A Pyrelin coating, characterized in that, The cyclic dimer monomer described in claim 1 is prepared by chemical vapor deposition.

10. The application of the pyrene coating as described in claim 9 in the protection of electronic products, medical devices, or marine equipment.

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