A cyclic dimer monomer for preparing an electrochemically corrosion resistant parylene coating and a preparation method and application thereof

Abstract

The application discloses a kind of 4,16 bis (m-methoxyphenyl) -[2,2] -p-xylene ring diatomic for preparing parylene coating resistant to electrochemical corrosion and its preparation method and application, specifically relates to a kind of 4,16 bis (m-methoxyphenyl) -[2,2] -p-xylene ring diatomic, its preparation method includes the following steps: S1, p-xylene ring diatomic is reacted with liquid bromine in the presence of catalyst, first solvent, and intermediate 1 is obtained;S2, intermediate 1 is reacted with 3-hydroxyphenylboronic acid in the presence of base salt, palladium catalyst and second solvent, and intermediate 2 is obtained;S3, intermediate 2 is reacted with methylating agent in the presence of base salt, third solvent, and the ring diatomic monomer is obtained.The phenyl parylene coating prepared from the above monomer shows excellent resistance to electrochemical corrosion, compared with the corrosion-resistant coating formed by the existing parylene monomer, not only the corrosion current density is low, and corrosion potential is high, has good application prospect in electronic product protection or medical instrument protection and the like.

Description

Technical Field

[0001] This invention relates to the fields of organic synthesis and coating preparation, specifically to a cyclodimeric monomer for preparing electrochemically resistant pyrene coatings, its preparation method, and its application. Background Technology

[0002] Metals and their alloys are widely used in critical fields such as industry, marine engineering, electronic devices, and biomedical implants. However, in humid, saline, or other electrolyte environments, metal surfaces are highly susceptible to electrochemical corrosion, leading to material performance degradation, structural failure, and even safety accidents, resulting in significant economic losses. Electrochemical corrosion is essentially a conjugate reaction of anodic dissolution (oxidation) and cathodic reduction (such as oxygen reduction) in an electrolyte solution. Two core electrochemical parameters for evaluating the corrosion resistance of metals are corrosion potential and corrosion current density. Corrosion current density directly characterizes the rate of the corrosion reaction; a lower value indicates a slower corrosion process. Corrosion potential, on the other hand, reflects the thermodynamic tendency of a metal to corrode; generally, a higher corrosion potential means the metal is less susceptible to oxidation. Therefore, developing efficient, stable, and durable surface protection technologies to simultaneously suppress both the thermodynamic tendency and kinetic rate of corrosion is crucial for extending the lifespan of metal components and ensuring equipment reliability.

[0003] Chemical vapor deposition (CVD) of polymer-para-xylene (Parylene, such as Parylene C, N, F, etc.) coatings has become an important choice for high-end protection of precision components, electronic circuits, and medical devices due to its ability to form uniform, pinhole-free, chemically inert films with excellent barrier properties through vapor deposition at room temperature. This process achieves conformal coating by pyrolytic monomers (such as [2,2]-para-cycloaranes) at high temperatures into active monomers, which are then adsorbed and polymerized on the substrate surface at room temperature. The application of Parylene coatings to metal corrosion protection has been reported. Traditional Parylene coatings effectively isolate the metal substrate from direct contact with corrosive media, acting as a physical barrier and typically significantly reducing the corrosion current density of the metal, thereby slowing down the corrosion rate. However, those skilled in the art have discovered a common but often overlooked paradox: while reducing the corrosion current density, these traditional Parylene coatings often lead to a significant negative shift (reduction) in the metal's corrosion potential.

[0004] A negative shift in corrosion potential is an unfavorable signal, indicating that the protected metal has become thermodynamically more reactive and more susceptible to oxidation. While a decrease in corrosion current has a positive effect, the decline in corrosion potential weakens the overall corrosion resistance of the coating system. This is especially true when the coating has defects or is mechanically damaged, potentially accelerating the initiation and development of localized corrosion and reducing the safety margin of protection.

[0005] Therefore, there is an urgent need to develop a new type of phenelin monomer that can not only effectively reduce corrosion current density, but also improve the coating / metal interface characteristics through molecular structure design, thereby avoiding or minimizing the negative impact on corrosion potential. This would provide more durable and reliable protection in harsh electrochemical environments and broaden the application prospects of phenelin coatings in high-end electronic products, medical devices, marine equipment and other fields. Summary of the Invention

[0006] To address the issue that while existing pyrene monomer coatings on metal surfaces can reduce corrosion current density, they often lead to a significant negative shift in the metal's corrosion potential, thus limiting their potential to provide efficient and comprehensive protection in harsh corrosive environments, this invention provides a cyclic dimer monomer for preparing electrochemically resistant pyrene coatings, along with its preparation method and applications. By introducing a specific substituent, m-methoxyphenyl, onto a p-xylene cyclic dimer, 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene cyclic dimer is obtained. Pyrene coatings formed using this monomer exhibit excellent electrochemical corrosion resistance. Compared to existing corrosion-resistant coatings formed with pyrene monomers, they not only have lower corrosion current density but also higher corrosion potential, thus providing more durable and reliable protection in harsh electrochemical environments. This broadens the application prospects of pyrene coatings in high-end electronic products, medical devices, marine equipment, and other fields.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] The first aspect of this invention provides a cyclic dimer monomer for preparing a pyrene coating resistant to electrochemical corrosion, wherein the cyclic dimer monomer is a 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene cyclic dimer, the structure of which is as follows:

[0009] .

[0010] A second aspect of the present invention provides a method for preparing the cyclic dimer monomer for preparing an electrochemically resistant pyrene coating as described in the first aspect, comprising the following steps:

[0011] 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;

[0012] 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.

[0013] 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;

[0014] The structures of intermediates 1 and 2 are shown below:

[0015] .

[0016] Compared to the traditional Grignard route, which involves brominating p-xylene cyclodimers, synthesizing Grignard reagents, and then synthesizing the target product via nucleophilic substitution, the intermediate Grignard reagents synthesized in this method are highly sensitive to water and oxygen, and the reaction conditions are harsh, posing significant safety risks for large-scale production. The synthetic method for preparing the aforementioned cyclodimer monomers provided by this invention primarily obtains the target product through bromination, borosilicate esterification, and transition metal catalytic coupling. This method offers milder reaction conditions, better tolerance to water and oxygen, reduced equipment and operational requirements, higher safety, and simpler operation. Furthermore, the palladium-catalyzed coupling reaction exhibits high chemical selectivity and fewer byproducts, which is beneficial for improving yield and product purity. Moreover, the above synthetic route allows for segmented production, with key intermediates that can be separated, purified, and tested, ensuring quality control at each step and providing reliable process monitoring points for large-scale production, making it more suitable for large-scale, standardized production.

[0017] Further, in step S1, the catalyst is iron powder and / or ferric bromide.

[0018] Further, in step S1, the molar ratio of the p-xylene cyclodimer to liquid bromine and catalyst is 1:(2-4):(0.15-0.21).

[0019] Further, in step S1, the first solvent is selected from one or more of diethyl ether, dichloromethane, and toluene. In some preferred embodiments of the present invention, the first solvent is dichloromethane. More preferably, the mass ratio of the p-xylene cyclodioxide to the first solvent is (0.02-0.04):1.

[0020] Furthermore, in step S1, the reaction temperature is preferably 20-30 °C, and the reaction time is preferably 36-48 h.

[0021] Furthermore, in step S1, the p-xylene cyclodimer and the catalyst are first dissolved in a first solvent, and then liquid bromine is added dropwise to carry out the reaction.

[0022] Furthermore, in step S1, the preparation method further includes the following steps: after the reaction, a supersaturated sulfurous acid solution is added to quench the reaction, followed by extraction and separation of the solid precipitate, and drying of the solid precipitate to obtain the intermediate 1; the solvent for extraction is dichloromethane, and the extracted organic phase is filtered to obtain the solid precipitate.

[0023] Further, in step S2, the alkali salt is selected from one or more of sodium carbonate, potassium acetate, and potassium carbonate; the palladium catalyst is tetratetraphenylphosphine palladium and / or 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride.

[0024] Further, in step S2, the preferred molar ratio of intermediate 1 to 3-hydroxyphenylboronic acid, alkaline salt, and palladium catalyst is 1:(3-6):(5-8):(0.05-0.1).

[0025] 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. In some preferred embodiments of the present invention, the second solvent is a mixed solvent of ethylene glycol dimethyl ether and water. More preferably, the mass ratio of the intermediate 1 to the second solvent is (0.03-0.05):1.

[0026] Furthermore, in step S2, the reaction temperature is preferably 100-120 °C, and the reaction time is preferably 48-60 h.

[0027] Further, in step S2, intermediate 1 is first 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.

[0028] Further, in step S2, the preparation method also 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 intermediate 2 is obtained by extraction, washing, drying, concentration, and column chromatography; the solvent for extraction is ethyl acetate, the solvent for washing is supersaturated sodium chloride aqueous solution, anhydrous sodium sulfate is used for drying, and column chromatography is performed using 300-400 mesh silica gel (the eluent is a mixed solution of petroleum ether / ethyl acetate with a volume ratio of 6:1).

[0029] Further, in step S3, the alkaline 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.

[0030] Further, in step S3, the molar ratio of intermediate 2 to methylating agent and alkali salt is 1:(2.2-3.0):3.

[0031] Further, in step S3, the third solvent is dimethyl sulfoxide and / or N,N-dimethylformamide. In some preferred embodiments of the present invention, the third solvent is dimethyl sulfoxide. More preferably, the mass ratio of the intermediate 2 to the third solvent is (0.03-0.05):1.

[0032] Furthermore, in step S3, the reaction temperature is preferably 50-60 °C, and the reaction time is preferably 36-48 h.

[0033] Furthermore, in step S3, intermediate 2 is first dissolved in a third solvent, and then an alkaline salt and a methylating agent are added to carry out the reaction.

[0034] Further, in step S3, the preparation method also includes the following steps: cooling to 20-40 °C after the reaction, separating the solid precipitate, and obtaining the cyclic dimer monomer by washing, drying, and rotary evaporation; the washing solvent is a 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 refined cyclic dimer monomer is obtained by recrystallization using n-hexane.

[0035] A third aspect of the present invention provides a pyrelin coating, which is prepared from the cyclic dimer monomer described in the first aspect by chemical vapor deposition.

[0036] Furthermore, the cyclic dimer monomer is evaporated and pyrolyzed to deposit on the substrate surface to form the pyrelin coating; the substrate includes, but is not limited to, metals, glass, etc.

[0037] The fourth aspect of this invention provides the application of the paraffin coating described in the third aspect in the protection of electronic products, medical devices, or marine equipment against corrosion.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] 1. This invention provides a cyclic dimer monomer for preparing a pyrene coating resistant to electrochemical corrosion: 4,16 bis(m-methoxyphenyl)-[2,2]-p-xylene cyclic dimer. The coating prepared from this monomer can not only effectively reduce the corrosion current density, but also effectively improve the coating / metal interface characteristics 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 effect of low corrosion current density and high corrosion potential, the metal containing the above-mentioned pyrene coating exhibits excellent salt water corrosion resistance.

[0040] 2. The cyclodimeric monomer provided by the present invention can be prepared from inexpensive and readily available p-xylene cyclodimeric material through bromination, coupling and methylation reaction processes. The preparation method is simple, the conditions are mild and the process is easy to control, and it is suitable for mass production.

[0041] 3. The cyclodimer monomer provided by this invention is used to prepare a pyrene coating on the copper surface through evaporation and pyrolysis. This coating 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 pyrene coatings in high-end electronic products, medical devices, marine equipment and other fields. Attached Figure Description

[0042] Figure 1 Flowchart for the preparation of 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer;

[0043] Figure 2The 1H NMR spectrum of the 4,16-bis(bromo)-[2,2]-p-xylene ring dimer;

[0044] Figure 3 The carbon NMR spectrum of the 4,16-bis(bromo)-[2,2]-p-xylene ring dimer;

[0045] Figure 4 The 1H NMR spectrum of the 4,16-bis(m-hydroxyphenyl)-[2,2]-p-xylene ring dimer;

[0046] Figure 5 The carbon NMR spectrum of 4,16-bis(m-hydroxyphenyl)-[2,2]-p-xylene ring dimer;

[0047] Figure 6 The 1H NMR spectrum of the 4,16bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer;

[0048] Figure 7 The carbon NMR spectrum of the 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer;

[0049] Figure 8 X-ray diffraction (XRD) pattern of 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer;

[0050] Figure 9 The crystal structure diagram of 4,16bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer;

[0051] Figure 10 Electrochemical impedance spectroscopy (EIS)-Bordt plots of pyrelin coatings prepared for different monomers;

[0052] Figure 11 Electrochemical impedance spectroscopy (EIS)-Nyquist plots of pyrelin coatings prepared for different monomers;

[0053] Figure 12 Tafel curves of pyrelin films prepared for different monomers. Detailed Implementation

[0054] 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 invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. The terms “comprising” or “including” as used herein may also be replaced with the closed form “is” or “consisting of”.

[0055] The present invention will be further described below with reference to specific embodiments and accompanying drawings, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0056] Example: This example relates to the preparation of a 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer, the reaction process is as follows: Figure 1 As shown, the details are as follows:

[0057] (1) Preparation of intermediate 1:

[0058] 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%.

[0059] Intermediate 1 was characterized by NMR, such as... Figure 2 , 3 As shown, the details are as follows:

[0060] 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).

[0061] 13 C NMR (101 MHz, CDCl3): δ 141.19, 138.55, 137.35, 134.14, 128.29, 126.76, 32.85.

[0062] The characterization results show that intermediate 1 is a 4,16-bis(bromo)-[2,2]-p-xylene ring dimer.

[0063] (2) Preparation of intermediate 2:

[0064] 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.

[0065] The prepared intermediate 2 was characterized by NMR, such as... Figure 4 , 5 As shown, the details are as follows:

[0066] 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).

[0067] 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.

[0068] The characterization results show that intermediate 2 is a 4,16-bis(m-hydroxyphenyl)-[2,2]-p-xylene ring dimer.

[0069] (3) Preparation of 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene ring dimer:

[0070] 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%.

[0071] The prepared final product was characterized by NMR, such as... Figure 6 , 7 As shown, the details are as follows:

[0072] 1 H 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).

[0073] 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.

[0074] 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.

[0075] 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:

[0076]

[0077] The characterization results show that the final product is 4,16-bis(m-methoxyphenyl)-[2,2]-p-xylene cyclodimer.

[0078] 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:

[0079] 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.

[0080] 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.

[0081] The prepared samples are shown in the table below:

[0082]

[0083] (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:

[0084] 1. Setting up the testing system

[0085] 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.

[0086] 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.

[0087] 2. Open Circuit Potential (OCP) Test

[0088] The working electrode was immersed in the electrolyte for 7200 s to obtain a stable equilibrium potential E. ocp .

[0089] 3. Electrochemical Impedance Spectroscopy (EIS) Test

[0090] At equilibrium potential E ocp The test was conducted with a frequency range of 1-100 kHz and a disturbance amplitude of 5 mV.

[0091] 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.

[0092] 4. Potentiodynamic polarization curve test

[0093] 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.

[0094] 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.

[0095] Table 1

[0096]

[0097] 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.

[0098] 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.

[0099] Figure 11 The diameter of the Nyquist curve corresponds to the charge transfer resistance, which is determined by... Figure 11It 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.

[0100] 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.

[0101] The above-described embodiments are merely preferred embodiments provided to fully illustrate 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.

Images