A para-xylene ring dimer derivative for preparing parylene film and its preparation method and application

Abstract

The invention discloses a para-xylene ring dimer derivative for preparing a parylene film, and a preparation method and application thereof, and specifically relates to a 4,16-bis(trifluoromethyl)-[2,2]-para-xylene ring dimer, wherein the preparation method comprises the following steps: S1, reacting 4-methyl-2-(trifluoromethyl)benzoic acid with a reducing agent in the presence of a solvent to obtain an intermediate 1; S2, reacting the intermediate 1 with a chlorinating agent in the presence of a solvent to obtain an intermediate 2; S3, reacting the intermediate 2 with an organic amine in the presence of a solvent to obtain an intermediate 3; S4, reacting the intermediate 3 with an alkaline agent in the presence of an inhibitor and a solvent to obtain 4,16-bis(trifluoromethyl)-[2,2]-para-xylene ring dimer. The parylene film prepared from the compound as a monomer exhibits high hydrophobicity, is superior to the currently best commercially available waterproof parylene AF4, and has a low preparation cost, and has good application prospects in terms of protective materials.

Description

Technical Field

[0001] The invention relates to the field of organic synthesis, and in particular to a p-xylene ring dimer derivative for preparing a parylene film, and a preparation method and application thereof. Background Art

[0002] The poly(p-xylene) family prepared from p-xylene dimers and their derivatives is a class of protective materials with extremely excellent performance. This type of material is of great importance in the three-proof materials because it does not require solvents and initiators, has high purity, good flexibility, is smooth and pinhole-free, and has good conformality. Different p-xylene derivatives can also bring new characteristics based on the original excellent performance, making poly(p-xylene) materials have a very wide range of applications (see: CP Tan, HG Craighead, Materials, 2010, 3, 1803-1832), and has excellent performance in micro-electromechanical systems, electronic components, biomedicine, protection and other application scenarios.

[0003] This type of para-xylene cyclodimer and its derivatives can be deposited conformally and pinhole-free on any material and any complex geometry to form parylene films, providing an excellent barrier to prevent water diffusion and corrosion resistance. Therefore, parylene series films open up a wide range of applications in any technical field requiring a clear dielectric, hydrophobic and chemical barrier (see: C. Desai, N. Laube, J. Coat. Technol. Res., 2019, 16(1), 103-111). For example, in the biomedical field where it shines, surface wettability is one of the key properties of parylene films, which affects the biological reactions of the microdevice biological interface, such as cell adhesion, protein adsorption and blood coagulation (see: XP Bi, BP Crum, W. Li, J. Microelectromech. Systems, 2014, 23(3), 628-635). Currently, hydrophobic parylene includes parylene C, parylene D, parylene AF4, etc., and their untreated water contact angles are 87°, 97°, and 100°, respectively (see: BJ Raos, MC Simpson, CS Doyle, ESGraham, CP Unsworth, PLoS One, 2019, 14(6), e0218850). The hydrophobic angle of this type of parylene film is usually not higher than 100°, and the monomer cost of parylene AF4, which has relatively better hydrophobic properties, is expensive, up to 20,000 US dollars / 1 kg (see: G. Lee, HJ Lee, J. Lee, KJ Lee, Thin Solid Films, 2024,797, 140333), which seriously limits its practical application in different fields.

[0004] Based on this, there is an urgent need for a monomer that has low preparation cost and can be used to prepare a parylene film with good hydrophobicity, so as to promote the use of the parylene film in different fields. Summary of the invention

[0005] The invention provides a para-xylene ring dimer derivative for preparing a parylene film, and a preparation method and application thereof. The parylene film prepared from 4,16-bis(trifluoromethyl)-[2,2]-para-xylene ring dimer as a monomer exhibits high hydrophobicity, which is superior to parylene AF4. The compound can be prepared from 4-methyl-2-(trifluoromethyl)benzoic acid as a starting material through reduction, chlorination, salt formation and cyclization reaction processes. The operation is simple and the preparation cost is low, and the compound has good application prospects in protective materials.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] The first aspect of the present invention provides a p-xylene ring dimer derivative for preparing a parylene film, and the structure of the p-xylene ring dimer derivative is as follows:

[0008] .

[0009] The second aspect of the present invention provides a method for preparing the p-xylene ring dimer derivative for preparing the parylene film according to the first aspect, comprising the following steps:

[0010] S1, reacting 4-methyl-2-(trifluoromethyl)benzoic acid with a reducing agent in the presence of a first solvent to obtain an intermediate 1;

[0011] S2, reacting the intermediate 1 with a chlorinating agent in the presence of a second solvent to obtain an intermediate 2;

[0012] S3, reacting the intermediate 2 with an organic amine in the presence of a third solvent to obtain an intermediate 3;

[0013] S4, reacting the intermediate 3 with an alkaline reagent in the presence of a polymerization inhibitor and a fourth solvent to obtain the p-xylene ring dimer derivative;

[0014] The structures of the intermediates 1-3 are shown below:

[0015] ,

[0016] Wherein, R is methyl, ethyl or propyl.

[0017] Further, in S1, the reducing agent is preferably lithium aluminum hydride and / or sodium borohydride; more preferably, the molar ratio of the 4-methyl-2-(trifluoromethyl)benzoic acid to the reducing agent is (0.5-3):1, for example 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, etc., including but not limited to the molar ratios listed above.

[0018] Further, in S1, the first solvent is selected from one or more of diethyl ether, tetrahydrofuran, dichloromethane, and toluene. In some preferred embodiments, the first solvent is diethyl ether; more preferably, the mass ratio of the 4-methyl-2-(trifluoromethyl)benzoic acid to the first solvent is (0.01-0.2):1.

[0019] Furthermore, in S1, the reaction temperature is preferably 30-60°C, and the reaction time is preferably 6-24 h.

[0020] Furthermore, in S1, 4-methyl-2-(trifluoromethyl)benzoic acid is first dissolved in a first solvent, and then a reducing agent is added at 0-30°C, and then the temperature is raised to 30-60°C to react for 6-24 hours.

[0021] Furthermore, in S1, the preparation method further comprises the following steps: after the reaction, cooling to 0-5°C, adding water and / or aqueous sodium hydroxide solution to quench the reaction, filtering to remove the precipitate, and drying the organic phase to obtain the intermediate 1.

[0022] Furthermore, in S2, the chlorinating agent is preferably one or more of phosphorus chloride, thionyl chloride, concentrated hydrochloric acid, and Lucas reagent; more preferably, the molar ratio of the intermediate 1 to the chlorinating agent is (0.5-3):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, etc., including but not limited to the molar ratios listed above.

[0023] Further, in S2, the second solvent is selected from one or more of dichloromethane, ether, tetrahydrofuran, and toluene. In some preferred embodiments, the second solvent is dichloromethane; more preferably, the mass ratio of the intermediate 1 to the second solvent is (0.01-0.4):1.

[0024] Furthermore, in S2, the reaction temperature is preferably 30-60° C., and the reaction time is preferably 1-3 h.

[0025] Further, in S2, the intermediate 1 is first dissolved in a second solvent, and then a chlorinating agent is added at 0-30°C, and then the temperature is raised to 30-60°C to react for 1-3 h.

[0026] Furthermore, in S2, the preparation method further comprises the following steps: after the reaction, cooling to 0-20°C, adding a saturated sodium bicarbonate solution to quench the reaction, and obtaining the intermediate 2 through extraction and evaporation.

[0027] Furthermore, in S3, the organic amine is preferably trimethylamine, triethylamine or tripropylamine; more preferably, the molar ratio of the intermediate 2 to the organic amine is (0.5-2.5):1, for example 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, etc., including but not limited to the molar ratios listed above.

[0028] Furthermore, in S3, the third solvent is toluene; more preferably, the mass ratio of the intermediate 2 to the third solvent is (0.2-0.5):1.

[0029] Furthermore, in S3, the reaction temperature is preferably 40-80° C., and the reaction time is preferably 3-8 h.

[0030] Furthermore, in S3, the intermediate 2 is first dissolved in a third solvent, and then an organic amine is added, and then the temperature is raised to 40-80° C. and reacted for 3-8 h.

[0031] Furthermore, in S3, the preparation method further comprises the following steps: after the reaction, the water layer is allowed to stand, and the intermediate 3 is obtained by washing and drying.

[0032] Further, in S4, the alkaline reagent is preferably one or more of sodium hydroxide, potassium hydroxide, sodium ethoxide, potassium ethoxide, and the inhibitor is preferably one or more of p-phenol monobutyl ether, tert-butyl catechol, and p-tert-butylphenol; more preferably, the molar ratio of the intermediate 3 to the alkaline reagent and the inhibitor is (20-50): (150-200): 1.

[0033] Furthermore, in S4, the fourth solvent is preferably one or more of water, toluene, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, benzene, and xylene.

[0034] Furthermore, in S4, the reaction temperature is preferably 80-120° C., and the reaction time is preferably 2-24 h.

[0035] Furthermore, in S4, the intermediate 3 is first dissolved in water to obtain an aqueous solution of the intermediate 3, and then the aqueous solution of the intermediate 3 is added dropwise to a mixed solution containing an alkali reagent, an inhibitor and a fourth solvent at 80-100 °C. After the addition is complete, the temperature is raised to 100-120 °C and the reaction is carried out for 2-24 h; preferably, the mass ratio of the intermediate 3 to water is (0.1-0.8):1.

[0036] Furthermore, in S4, the preparation method further comprises the following steps: after the reaction, adding water to separate the organic phase, washing the organic phase with water and / or an acid solution, then adding activated carbon to the washed organic phase, heating to 40-100°C and stirring for 0.5-3 h, filtering and cooling and crystallizing to obtain the p-xylene cyclodimer derivative; preferably, dissolving the solid obtained by cooling and crystallizing in n-hexane, and recrystallizing to obtain a fine p-xylene cyclodimer derivative.

[0037] The present invention also provides a parylene film, which is prepared by chemical vapor deposition using the p-xylene ring dimer derivative described in the first aspect as a monomer.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The present invention provides a para-xylene ring dimer derivative for preparing parylene film: 4,16-bis(trifluoromethyl)-[2,2]-para-xylene ring dimer. The hydrophobic angle of the parylene film prepared with the compound as a monomer can reach 105°, which is significantly better than the commonly used hydrophobic parylene on the market, and better than the best waterproof parylene AF4 currently available on the market.

[0040] 2. The present invention also provides a method for synthesizing 4,16-bis(trifluoromethyl)-[2,2]-p-xylene cyclodimer, which uses 4-methyl-2-(trifluoromethyl)benzoic acid, which is easily available and inexpensive, as a starting material, and is prepared by reduction, chlorination, salt formation, and cyclization. The synthesis method is simple to operate, has mild reaction conditions, a high product yield, and a low preparation cost. The cost of a laboratory test is only 20 yuan / g (mass production can further reduce its cost), and it is suitable for mass preparation. Compared with the expensive hydrophobic parylene AF4 monomer, the 4,16-bis(trifluoromethyl)-[2,2]-p-xylene cyclodimer that can be prepared at a low cost has good application prospects in protective materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A reaction flow chart for preparing 4,16-bis(trifluoromethyl)-[2,2]-p-xylene cyclodimer;

[0042] Figure 2 is the H NMR spectrum of 4-methyl-2-(trifluoromethyl)benzyl alcohol;

[0043] Figure 3 It is the NMR carbon spectrum of 4-methyl-2-(trifluoromethyl)benzyl alcohol;

[0044] Figure 4 This is the H NMR spectrum of 4-methyl-2-(trifluoromethyl)benzyl chloride;

[0045] Figure 5 This is the NMR carbon spectrum of 4-methyl-2-(trifluoromethyl)benzyl chloride;

[0046] Figure 6 This is the H NMR spectrum of 4-methyl-2-(trifluoromethyl)benzyltrimethylammonium chloride;

[0047] Figure 7 This is the NMR carbon spectrum of 4-methyl-2-(trifluoromethyl)benzyltrimethylammonium chloride;

[0048] Figure 8 It is the H NMR spectrum of 4,16-bis(trifluoromethyl)-[2,2]-p-xylene ring dimer;

[0049] Fig. 9 It is the NMR carbon spectrum of 4,16-bis(trifluoromethyl)-[2,2]-p-xylene ring dimer;

[0050] Fig.10 The contact angle test results of the parylene film prepared with 4,16-bis(trifluoromethyl)-[2,2]-p-xylene cyclodimer as monomer;

[0051] Fig.11 Comparison of water contact angles of parylene films prepared with different monomers. DETAILED DESCRIPTION

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. The "include" or "comprising" described in the present invention means that in addition to the components described, other components may also be included or contained. The "include" or "comprising" described in the present invention may also be replaced by the closed "for" or "consisting of...".

[0053] The present invention is further described below in conjunction with specific embodiments and drawings so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Example 1

[0054] This embodiment relates to the preparation of a 4,16-bis(trifluoromethyl)-[2,2]-p-xylene ring dimer. The reaction process is as follows: Figure 1 As shown, the details are as follows:

[0055] Preparation of intermediate 1:

[0056] In a 500 mL three-necked flask, 15.31 g of 4-methyl-2-(trifluoromethyl)benzoic acid and 300 mL of ether solvent were added, stirred for 30 min under a nitrogen atmosphere, cooled to 0 °C, and then 45 mL of lithium aluminum hydride (2.5 mol / L) tetrahydrofuran solution was added. The temperature was slowly raised to 40 °C, heated to reflux, and stirred for 24 h. After the reaction was completed, the temperature was lowered to 0 °C, and 4.3 mL of water, 4.3 mL of 15% sodium hydroxide solution, and 12.9 mL of water were added in sequence to quench the reaction. The precipitate was removed by filtration, the organic phase was dried, and the solvent was removed to obtain 13.05 g of intermediate 1 with a yield of 97.90%;

[0057] The prepared intermediate 1 was characterized by NMR. Figure 2 , 3 As shown, the details are as follows:

[0058] 1 H NMR (400 MHz, CDCl3): δ 7.57 (d, J = 7.8 Hz, 1H) 7.45 (s, 1H), 7.38 (d, J = 1.6 Hz, 1H), 4.84 (s, 2H), 2.40 (s, 3H).

[0059] 13 C NMR (75 MHz, CDCl3): δ 137.57, 136.15, 132.74, 129.22, 126.45, 126.37, 122.69, 61.44, 21.01.

[0060] The characterization results show that intermediate 1 is 4-methyl-2-(trifluoromethyl)benzyl alcohol.

[0061] Preparation of Intermediate 2:

[0062] 12 g of the intermediate 1 prepared above was placed in a 250 mL three-necked flask, and 120 mL of ether solvent was added. The mixture was stirred for 30 min under a nitrogen atmosphere and cooled to 0 °C. 8 mL of thionyl chloride was added, and the temperature was slowly raised to 40 °C. The mixture was heated to reflux and stirred for 3 h. After cooling, the mixture was quenched with a saturated sodium bicarbonate solution, the layers were separated, and the organic phase was taken and evaporated to obtain 9.68 g of intermediate 2 with a yield of 73.54%.

[0063] The prepared intermediate 2 was characterized by NMR. Figure 4 , 5 As shown, the details are as follows:

[0064] 1 H NMR (400 MHz, CDCl3): δ 7.47(d, J = 7.7 Hz, 1H), 7.44 (s, 1H), 7.33(d, J = 7.7 Hz, 1H), 4.69 (s, 2H), 2.37 (s, 3H).

[0065] 13 C NMR (100 MHz, CDCl3): δ 138.90, 132.97, 132.71, 131.92, 130.92, 126.72, 126.67, 42.07, 21.04.

[0066] The characterization results show that intermediate 2 is 4-methyl-2-(trifluoromethyl)benzyl chloride.

[0067] Preparation of intermediate 3:

[0068] In a 250 mL three-necked flask, add 20 g of intermediate 2, 65 mL of toluene and 20 g of 30% trimethylamine, keep the temperature at 35 °C, stir continuously for 4 h, let stand for stratification, take the water layer, wash the obtained water layer with tert-butyl methyl ether. Filter the water layer through diatomaceous earth, remove the solvent, and obtain 18.6 g of intermediate 3 with a yield of 76.76%.

[0069] The prepared intermediate 3 was characterized by NMR. Figure 6 , 7 As shown, the details are as follows:

[0070] 1 H NMR (400 MHz, CDCl3): δ 7.96 (d, J = 7.9 Hz, 1H), 7.56 (d, J = 1.8Hz, 1H), 7.49 (d, J = 1.7 Hz, 1H), 5.07 (s, 2H), 3.43 (s, 9H), 2.44 (s, 3H).

[0071] 13 C NMR (100 MHz, CDCl3): δ 142.02, 136.39, 133.33, 128.32, 128.27,125.30, 122.31, 64.88, 53.49, 21.26.

[0072] The characterization results show that intermediate 3 is 4-methyl-2-(trifluoromethyl)benzyltrimethylammonium chloride.

[0073] Preparation of 4,16-bis(trifluoromethyl)-[2,2]-p-xylene ring dimer:

[0074] Dissolve 20 g of intermediate 3 in 30 g of water to obtain a quaternary ammonium salt solution for use. Add 20 g of solid sodium hydroxide and 50 g of water to a three-necked flask to prepare a solution, then add 100 mL of toluene and 0.8 g of tert-butylphenol, heat to 95 °C, and then slowly drop the quaternary ammonium salt solution, and the addition is completed in about 2 hours. After slowly heating to 110 °C, keep warm for 8 h, and separate about 20 mL of water throughout the process. After the reaction is completed, cool to room temperature, add 20 mL of water, let stand, and separate the alkali solution. Wash with 20 mL of water, 20 mL of dilute sulfuric acid, and 20 mL of ice water respectively. Add 10 g of activated carbon to the treated toluene layer and heat to 80 °C. After stirring for 0.5 h, filter while hot and cool to crystallize. Recrystallize with 220 g of n-hexane and dry to obtain 12.4 g of the final product with a yield of 36.1% and a purity of 99.5%.

[0075] The final product was characterized by NMR. Figure 8 , 9 As shown, the details are as follows:

[0076] 1 H NMR (400 MHz, CDCl3): δ 6.85 (d, J = 1.9 Hz, 1H), 6.79 (d, J = 7.9Hz, 1H), 6.44 (d, J = 7.9 Hz, 1H), 3.41 – 3.52 (m, 1H), 3.24 (dd, J = 10.4,8.7 Hz, 1H)3.04 – 3.15 (m, 2H).

[0077] 13 C NMR (100 MHz, CDCl3): δ 140.00, 138.14, 135.67, 135.29, 129.12,129.07, 34.79, 32.88.

[0078] The characterization results show that the final product is 4,16-bis(trifluoromethyl)-[2,2]-p-xylene ring dimer. Comparative Example 1

[0079] 4,16-dibromo-[2,2]-p-xylene cyclodimer was dissolved in N,N-dimethylacetamide, methyl fluorosulfonyl difluoroacetate was added, cuprous iodide was used as a catalyst, and the reaction was carried out at 80°C for 8 hours. After filtration and washing, the crude product was obtained. After mass spectrometry test, it was found that about 30% of the product was produced and about 40% of the monosubstituted by-product was produced. Column chromatography was used for separation. Since the polarity of the raw material, product and by-product was very small and very close, they could not be separated and purified. Comparative Example 2

[0080] Dissolve 4,16-dibromo-[2,2]-p-xylene cyclodimer in methylpyrrolidone, add sodium trifluoroacetate, and use cuprous iodide as a catalyst. React at 140 °C for 72 hours, filter and wash to obtain a crude product. After mass spectrometry, it can be seen that only 10% of the product is produced, and about 20% of the monosubstituted by-product is produced. A large amount of unreacted raw materials are separated by column chromatography. Since the polarity of the raw materials, products, and by-products is very small and very close, they cannot be separated and purified.

[0081] Application and performance characterization

[0082] The 4,16-bis(trifluoromethyl)-[2,2]-p-xylene ring dimer (abbreviated as: parylene DCF3) prepared in Example 1 and commercially available parylene monomers (parylene C monomer, parylene D monomer, parylene AF4 monomer) were respectively used to prepare the corresponding parylene films by the following methods. The specific operations are as follows:

[0083] The parylene monomer is placed in an evaporation chamber, evaporated in the evaporation chamber (the temperature of the evaporation chamber is 180°C) under a vacuum degree of 4 Pa, and cracked in a cracking furnace (the temperature of the cracking furnace is 680°C), and finally deposited on a glass sheet in a coating chamber to form a transparent film. After the film is formed, it is peeled off from the glass plate to obtain a parylene film.

[0084] The structure of Parylene DCF3 monomer: , the structure of the prepared Parylene DCF3 film: The water contact angle test results of the film are as follows: Fig.10 As shown, the hydrophobic angle can reach 105°.

[0085] The structure of Parylene C monomer: , the structure of the prepared Parylene C film: ;

[0086] The structure of Parylene D monomer: , the structure of the prepared Parylene D film: ;

[0087] The structure of Parylene AF4 monomer: , the structure of the prepared Parylene AF4 film: .

[0088] The test results of water contact angles of films prepared from different parylene monomers and the hydrophobic angles of parylene CCF3 films reported in the literature (G. Lee, HJ Lee, J. Lee, KJ Lee, Thin Solid Films. 2024, 797, 140333) are shown in Table 1. The structure of parylene CCF3 monomer is The film structure is .

[0089] Table 1

[0090]

[0091] From Table 1 and Fig.11 It can be seen that the hydrophobic angle of the parylene film prepared by using the 4,16-bis(trifluoromethyl)-[2,2]-p-xylene cyclic dimer provided by the present invention as a monomer is significantly higher than that of the above-mentioned hydrophobic parylene material, and is even better than the hydrophobicity of the film prepared from parylene AF4, and the preparation cost is much lower than that of parylene AF4, which has good application prospects in hydrophobic protective materials.

[0092] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A para-xylene ring dimer derivative for preparing parylene film, characterized in that: The structure of the p-xylene ring dimer derivative is shown below: 。 2. A method for preparing the p-xylene ring dimer derivative according to claim 1, characterized in that: The following steps are involved: S1, reacting 4-methyl-2-(trifluoromethyl)benzoic acid with a reducing agent in the presence of a first solvent to obtain an intermediate 1; S2, reacting the intermediate 1 with a chlorinating agent in the presence of a second solvent to obtain an intermediate 2; S3, reacting the intermediate 2 with an organic amine in the presence of a third solvent to obtain an intermediate 3; S4, reacting the intermediate 3 with an alkaline reagent in the presence of a polymerization inhibitor and a fourth solvent to obtain the p-xylene ring dimer derivative; The structures of the intermediates 1-3 are shown below: ， Wherein, R is methyl, ethyl or propyl.

3. The preparation method according to claim 2, characterized in that: S1 contains at least one of the following features: (1) The reducing agent is lithium aluminum hydride and / or sodium borohydride; (2) The molar ratio of 4-methyl-2-(trifluoromethyl)benzoic acid to the reducing agent is (0.5-3):1; (3) The first solvent is selected from one or more of diethyl ether, tetrahydrofuran, dichloromethane, and toluene; (4) The reaction temperature is 30-60 °C and the reaction time is 6-24 h.

4. The preparation method according to claim 2 or 3, characterized in that: In S1: First, 4-methyl-2-(trifluoromethyl)benzoic acid is dissolved in a first solvent, and then a reducing agent is added at 0-30°C, and then the temperature is raised to 30-60°C to react for 6-24 hours; The preparation method also The method comprises the following steps: cooling the temperature to 0-5°C after the reaction, adding water and / or sodium hydroxide aqueous solution to quench the reaction, filtering to remove the precipitate, and drying the organic phase to obtain the intermediate 1.

5. The preparation method according to claim 2, characterized in that: S2 contains at least one of the following features: (1) The chlorinating agent is selected from one or more of phosphorus chloride, thionyl chloride, concentrated hydrochloric acid, and Lucas reagent; (2) The molar ratio of the intermediate 1 to the chlorinating agent is (0.5-3):1; (3) The second solvent is selected from one or more of dichloromethane, ether, tetrahydrofuran, and toluene; (4) The reaction temperature is 30-60 °C and the reaction time is 1-3 h.

6. The preparation method according to claim 2 or 5, characterized in that: In S2: First, the intermediate 1 is dissolved in the second solvent, and then a chlorinating agent is added at 0-30 °C, and then the temperature is raised to 30-60 °C to react for 1-3 h; The preparation method also The method comprises the following steps: cooling to 0-20° C. after the reaction, adding a saturated sodium bicarbonate solution to quench the reaction, standing the mixture to collect an organic layer, and evaporating the organic layer to obtain the intermediate 2.

7. The preparation method according to claim 2, characterized in that: S3 contains at least one of the following characteristics: (1) The organic amine is trimethylamine, triethylamine or tripropylamine; (2) The molar ratio of the intermediate 2 to the organic amine is (0.5-2.5):1; (3) The third solvent is toluene; (4) The reaction temperature is 40-80 °C and the reaction time is 3-8 h.

8. The preparation method according to claim 2 or 7, characterized in that: In S3: Firstly, the intermediate 2 is dissolved in the third solvent, and then the organic amine is added, and then the temperature is raised to 40-80 °C and reacted for 3-8 hours; The preparation method also The method comprises the following steps: after the reaction, the organic layer is allowed to stand, and the organic layer is washed and dried to obtain the intermediate 3.

9. The preparation method according to claim 2, characterized in that: S4 contains at least one of the following features: (1) The alkaline reagent is selected from one or more of sodium hydroxide, potassium hydroxide, sodium ethoxide, and potassium ethoxide; (2) The polymerization inhibitor is selected from one or more of p-phenol monobutyl ether, tert-butyl catechol, and p-tert-butylphenol; (3) The molar ratio of the intermediate 3 to the alkaline reagent and the polymerization inhibitor is (20-50): (150-200): 1; (4) The fourth solvent is selected from one or more of water, toluene, N,N-dimethylformamide, N,N-dimethylacetamide, sulfolane, benzene, and xylene; (5) The reaction temperature is 80-120 °C and the reaction time is 2-24 h.

10. The preparation method according to claim 2 or 9, characterized in that: In S4, First, the intermediate 3 is dissolved in water to obtain an aqueous solution of the intermediate 3, and then the aqueous solution of the intermediate 3 is added dropwise to a mixed solution containing an alkali reagent, an inhibitor and a fourth solvent at 80-100° C. After the addition is complete, the temperature is raised to 100-120° C. and the reaction is carried out for 2-24 hours; The preparation method further comprises the following steps: adding water to separate the organic phase after the reaction, washing the organic phase with water and / or an acid solution, then adding activated carbon to the washed organic phase, heating to 40-100°C and stirring for 0.5-3 h, filtering, cooling and crystallizing to obtain the p-xylene ring dimer derivative.

11. A parylene film, characterized in that: The parylene film is prepared by chemical vapor deposition using the p-xylene dimer derivative described in claim 1 as a monomer.

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