Diamine monomer containing fluorine atoms in main chain, polyimide and preparation method

Abstract

The invention provides a diamine monomer with a main chain containing fluorine atoms, polyimide and a preparation method, and belongs to the technical field of polymer-based functional materials. The diamine monomer containing fluorine atoms in the main chain provided by the invention has a structure as shown in a formula I, in which R1 is selected from H, CH3 or F; r2 is selected from H, CH3 or CF3; and R3 is selected from H or F. According to the invention, fluorine atoms are introduced into a diamine monomer, a class of diamine monomers containing fluorine atoms are designed and synthesized, ether bonds are introduced into the structure and polymerized with commercially available dianhydrides with different structures, and the fluorine atoms introduced into the prepared polyimide enhance the steric hindrance effect, so that the polyimide is of a non-coplanar structure, and the performance of the polyimide is improved. The CTC effect in the structure is weakened, the solubility and the mechanical strength are improved, and a series of polyimide films with relatively good optical properties are obtained; besides introduction of fluorine atoms, other substituent groups are introduced to different positions of a benzene ring to further improve the properties of the PI film.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer-based functional materials, and in particular to a diamine monomer containing fluorine atoms in the main chain, a polyimide and a preparation method thereof. Background Art

[0002] Polyimide (PI) films have excellent properties and play an important role in fields such as foldable mobile phones and flexible wearable devices. With technological advances, polyimide is required to have high optical transmittance, high temperature resistance and good mechanical strength in optical and flexible materials. However, aromatic PI has low transparency and poor mechanical properties, which limits the application of PI. Fluorine atoms have high electronegativity and large steric hindrance, which can effectively weaken the CTC effect, thereby making the PI film colorless. The introduction of ether bonds can also further enhance the flexibility of PI and improve the solubility and mechanical properties of PI. Therefore, compared with ordinary aromatic structures, the introduction of fluorine atoms and ether bonds into PI can significantly improve the thermal stability, solubility, optical properties and mechanical properties of the polymer.

[0003] Currently, literature reports have reported the creation of colorless polyimides by introducing large steric side groups, highly electronegative atoms, or aliphatic fragments, but this can compromise thermal or mechanical properties. Sun's group (Giant, 2023, 14, 100156) proposed a series of heat-resistant, transparent fluorinated polyimide films, but their mechanical properties were compromised, limiting their applications. Zhang's group (Macromolecules, 2022, 55, 18, 7992–8001) proposed polyimide structures containing both norbornene and fluorine atoms. However, due to their low fluorine content, some polyimides exhibit a yellow color and compromise mechanical properties. Lin's group (Macromolecules, 1998, 31, 7, 2080–2086) proposed a series of PI films with excellent optical, thermal, and mechanical properties through monomer structure design. However, the monomer structure synthesis steps are complex and the reaction conditions are harsh. Summary of the Invention

[0004] In view of this, the present invention aims to provide a diamine monomer containing fluorine atoms in the main chain, a polyimide, and a preparation method. The polyimide obtained by polymerizing the diamine monomer provided by the present invention with commercially available dianhydrides of different structures has good thermal stability, solubility, mechanical strength, and optical properties.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is a diamine monomer containing fluorine atoms in the main chain, having the structure shown in Formula I:

[0007]

[0008] wherein R1 is selected from H, CH3 or F; R2 is selected from H, CH3 or CF3; and R3 is selected from H or F.

[0009] The second technical solution of the present invention is a method for preparing the above-mentioned diamine monomer containing fluorine atoms in the main chain, comprising the following steps:

[0010] Step 1. After mixing substituted 4-fluoronitrobenzene, substituted 4-bromophenol, a base and solvent 1, a nucleophilic substitution reaction is carried out under an inert atmosphere to obtain intermediate I;

[0011] Step 2. After mixing the intermediate 1, pinacol diboronate, an alkali metal salt 1, a palladium catalyst, and a solvent 2, a Miyaura borylation reaction is carried out under an inert atmosphere to obtain an intermediate II;

[0012] Step 3. After mixing the intermediate II, Pd / C, hydrazine hydrate and solvent 3, a reduction reaction is carried out under an inert atmosphere to obtain intermediate III;

[0013] Step 4. After mixing the intermediate III, substituted dibromobenzene, alkali metal salt 2, palladium catalyst and solvent 4, a Suzuki reaction is carried out under an inert atmosphere to obtain the diamine monomer containing fluorine atoms in the main chain;

[0014] The structural formula of the substituted 4-fluoronitrobenzene is

[0015] The structural formula of the substituted 4-bromophenol is

[0016] The structural formula of the substituted dibromobenzene is

[0017] wherein R1 is selected from H, CH3 or F, R2 is selected from H, CH3 or CF3, and R3 is selected from H or F.

[0018] The third technical solution of the present invention is a method for preparing polyimide, wherein a dianhydride monomer, the above-mentioned diamine monomer and a solvent 5 are stirred and reacted at room temperature under an inert atmosphere to obtain a polyamic acid solution;

[0019] The polyamic acid solution is thermally imidized to obtain the polyimide.

[0020] A fourth technical solution of the present invention is a polyimide prepared by the above preparation method.

[0021] The present invention discloses the following technical effects:

[0022] The present invention introduces fluorine atoms into diamine monomers, designs and synthesizes a class of diamine monomers containing fluorine atoms, and simultaneously introduces ether bonds into the structure, which are polymerized with commercially available dianhydrides of different structures. Due to the fluorine atoms introduced into the prepared polyimide, the steric hindrance effect is enhanced, the polyimide has a non-coplanar structure, the CTC effect in the structure is weakened, the solubility and mechanical strength are improved, and a series of polyimide films with good optical properties are obtained. In addition to the introduction of fluorine atoms, other substituents are introduced at different positions on the benzene ring to further improve the properties of the PI film. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 is the diamine 1 obtained in Example 1 1 HNMR spectrum;

[0025] Figure 2 is the diamine 2 obtained in Example 2 1 HNMR spectrum;

[0026] Figure 3 is the diamine 3 obtained in Example 3 1 HNMR spectrum;

[0027] Figure 4 is the diamine 4 obtained in Example 4 1 HNMR spectrum;

[0028] Figure 5 is the diamine 5 obtained in Example 5 1 HNMR spectrum;

[0029] Figure 6 is the polyimide PI-1 obtained in Example 6 1 HNMR spectrum;

[0030] Figure 7 is the polyimide PI-2 obtained in Example 7 1 HNMR spectrum;

[0031] Figure 8 is the polyimide PI-3 obtained in Example 8 1 HNMR spectrum;

[0032] Figure 9 is the polyimide PI-4 obtained in Example 9 1 HNMR spectrum;

[0033] Figure 10 is the polyimide PI-5 obtained in Example 10 1 HNMR spectrum. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] In the present invention, the room temperature refers to 20±5°C.

[0040] The first aspect of the present invention provides a diamine monomer containing fluorine atoms in the main chain, having the structure shown in Formula I:

[0041]

[0042] wherein R1 is selected from H, CH3 or F; R2 is selected from H, CH3 or CF3; and R3 is selected from H or F.

[0043] A second aspect of the present invention provides a method for preparing the above-mentioned diamine monomer containing fluorine atoms in the main chain, comprising the following steps:

[0044] Step 1. After mixing substituted 4-fluoronitrobenzene, substituted 4-bromophenol, a base and solvent 1, a nucleophilic substitution reaction is carried out under an inert atmosphere to obtain intermediate I;

[0045] Step 2. After mixing the intermediate 1, pinacol diboronate, an alkali metal salt 1, a palladium catalyst, and a solvent 2, a Miyaura borylation reaction is carried out under an inert atmosphere to obtain an intermediate II;

[0046] Step 3. After mixing the intermediate II, Pd / C, hydrazine hydrate and solvent 3, a reduction reaction is carried out under an inert atmosphere to obtain intermediate III;

[0047] Step 4. After mixing the intermediate III, substituted dibromobenzene, alkali metal salt 2, palladium catalyst and solvent 4, a Suzuki reaction is carried out under an inert atmosphere to obtain the diamine monomer containing fluorine atoms in the main chain;

[0048] The structural formula of the substituted 4-fluoronitrobenzene is

[0049] The structural formula of the substituted 4-bromophenol is

[0050] The structural formula of the substituted dibromobenzene is

[0051] wherein R1 is selected from H, CH3 or F; R2 is selected from H, CH3 or CF3; and R3 is selected from H or F.

[0052] The general reaction formula of the above reaction is:

[0053]

[0054] In a preferred embodiment of the present invention, in step 1, the base is Na2CO3, K2CO3, Cs2CO3 or NaH; the molar ratio of the substituted 4-fluoronitrobenzene, the substituted 4-bromophenol and the base is 1:1-1.2:3-5; the temperature of the nucleophilic substitution reaction is 70-90°C, and the reaction time is 13 hours.

[0055] In a preferred embodiment of the present invention, the solvent 1 is DMSO, DMF or DMAc. The present invention does not impose any particular limitation on the amount of solvent 1, and any amount known to those skilled in the art that can satisfy the nucleophilic substitution reaction can be selected.

[0056] In a preferred embodiment of the present invention, after the nucleophilic substitution reaction is completed, the step of extracting and concentrating the reaction solution and then directly purifying it by flash column chromatography is further included.

[0057] In a preferred embodiment of the present invention, in step 2, the alkali metal salt 1 is Na2CO3, K2CO3, KOAc or NaOAc; the palladium catalyst is PdCl2(dppf), Pd(OAc)2, PdCl2(PPh3)2 or Pd(PPh3)4; the molar ratio of the intermediate 1, bipyralidone borate, alkali metal salt 1 and palladium catalyst is 1:1.2~1.3:3~5:0.03~0.05; the temperature of the Miyaura borylation reaction is 90~110°C and the time is 15h.

[0058] In a preferred embodiment of the present invention, the solvent 2 is 1,4-dioxane, THF, DMSO or DMF. The present invention does not impose any particular limitation on the amount of solvent 2, and any amount known to those skilled in the art that can meet the requirements of the Miyaura borylation reaction can be selected.

[0059] In a preferred embodiment of the present invention, after the Miyaura borylation reaction is completed, the step of purifying the obtained reaction solution by flash column chromatography is further included.

[0060] In a preferred embodiment of the present invention, in step 3, the Pd / C is 10% w / w Pd / C; the amount of the Pd / C is: 0.25-0.3 g Pd / C is added per 1 mmol of intermediate II; the mass fraction of the hydrazine hydrate is 85%; the amount of the hydrazine hydrate is: 0.5-1 mL hydrazine hydrate is added per 1 mmol of intermediate II; the temperature of the reduction reaction is 90° C., and the time is 12 h.

[0061] In a preferred embodiment of the present invention, the solvent 3 is anhydrous ethanol. The amount of the solvent 3 is not particularly limited in the present invention, and can be selected from an amount known to those skilled in the art that satisfies the reduction reaction, for example, 5 to 6 mL of solvent is added per 1 mmol of intermediate II.

[0062] In a preferred embodiment of the present invention, after the reduction reaction is completed, the step of purifying the obtained reaction solution by flash column chromatography is further included.

[0063] In a preferred embodiment of the present invention, in step 4, the alkali metal salt 2 is Na2CO3, K2CO3 or Cs2CO3; the palladium catalyst is the same as the palladium catalyst in step 2; the molar ratio of the intermediate III, substituted dibromobenzene, alkali metal salt 2, and palladium catalyst is 2.2-2.3:1:4-5:0.1-0.2; the temperature of the Suzuki reaction is 80-140°C, and the time is 24 hours.

[0064] In a preferred embodiment of the present invention, the solvent 4 is a mixed solvent of toluene, ethanol and water in a volume ratio of 1:1:1, a mixed solvent of 1,4-dioxane and water in a volume ratio of 1:1, or o-xylene; the present invention does not impose any particular limitation on the amount of solvent 4, and an amount well known to those skilled in the art that can satisfy the Suzuki reaction can be selected, for example:

[0065] When solvent 4 is a mixed solvent of toluene, ethanol, and water in a volume ratio of 1:1:1, the amount used is 4 to 6 mL of the mixed solvent for every 1 mmoL of substituted dibromobenzene;

[0066] When solvent 3 is a mixed solvent of 1,4-dioxane and water in a volume ratio of 1:1, the amount used is 10-12 mL of the mixed solvent for every 1 mmol of substituted dibromobenzene;

[0067] When solvent 3 is o-xylene, the amount used is 6 to 8 mL of solvent per 1 mmol of substituted dibromobenzene.

[0068] In a preferred embodiment of the present invention, after the Suzuki reaction is completed, the step of purifying the obtained reaction solution by flash column chromatography is further included.

[0069] The third aspect of the present invention provides a method for preparing a polyimide, characterized in that, under the protection of an inert atmosphere, a dianhydride monomer, the above-mentioned diamine monomer and a solvent 5 are stirred and reacted at room temperature to obtain a polyamic acid solution;

[0070] The polyamic acid solution is thermally imidized to obtain the polyimide.

[0071] The present invention does not impose any particular limitation on the specific selection of the dianhydride monomer. A dianhydride monomer well known to those skilled in the art can be selected and reacted with a diamine monomer. As an example, when the dianhydride monomer is selected from the following structures, the general reaction formula for synthesizing the polyimide is as follows:

[0072]

[0073] In a preferred embodiment of the present invention, the molar ratio of the dianhydride monomer to the diamine monomer is 1:1; the stirring reaction is carried out at room temperature for 24 to 48 hours.

[0074] In a preferred embodiment of the present invention, the solvent 5 is DMAc.

[0075] The present invention does not impose any particular limitation on the specific preparation steps and parameters of the thermal imidization, and any thermal imidization method well known to those skilled in the art may be used.

[0076] A fourth aspect of the present invention provides a polyimide prepared by the above-mentioned preparation method. The structural formula of the polyimide is as follows:

[0077]

[0078] wherein R1 is selected from H, CH3 or F; R2 is selected from H, CH3 or CF3; R3 is selected from H or F; and 172≤n≤387.

[0079] Unless otherwise specified, the technical solutions described in the present invention are all conventional solutions in the field, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0080] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0081] Example 1

[0082]

[0083] (1) Nucleophilic substitution reaction

[0084] Under a nitrogen atmosphere, 4-fluoronitrobenzene (10.0 mmol, 1.0 equiv), 4-bromophenol (10.0 mmol, 1.0 equiv), K2CO3 (30.0 mmol, 3.0 equiv), and DMSO (10.0 mL) were added to a dry reaction vessel and reacted at 70°C for 13 h. After completion of the reaction, 30 mL of water was added to dilute the system, and 20 mL of EA was used for extraction. The organic phase was concentrated and directly purified by flash column chromatography to obtain intermediate 1-I, 2.35 g, in 80% yield.

[0085] (2) Miyaura borylation reaction

[0086] Under nitrogen atmosphere, intermediate 1-I (10.0 mmol, 1.0 equiv), pinacol diboron (12.0 mmol, 1.2 equiv), KOAc (30.0 mmol, 3.0 equiv), PdCl2(dppf) (0.3 mmol, 0.03 equiv), and 1,4-dioxane (60 mL) were added to a dry reaction vessel and reacted at 110°C for 15 h. After completion of the reaction, the mixture was purified by flash column chromatography to give intermediate 1-II, 2.66 g, in a yield of 78%.

[0087] (3) Reduction reaction

[0088] Under nitrogen atmosphere, intermediate 1-II (10.0 mmol, 1.0 equiv), Pd / C (10% w / w, 0.25 g), 85% hydrazine hydrate (5 mL), and anhydrous ethanol (50 mL) were added to a dry reaction vessel and reacted at 90 ° C for 12 h. After completion of the reaction, the mixture was purified by flash column chromatography to obtain intermediate 1-III, 2.49 g, with a yield of 80%.

[0089] (4) Suzuki reaction

[0090] Under a nitrogen atmosphere, intermediate 1-III (22.0 mmoL, 2.2 equiv), 1,4-dibromotetrafluorobenzene (10.0 mmoL, 1.0 equiv), Cs2CO3 (40.0 mmoL, 4.0 equiv), Pd(PPh3)4 (1.0 mmoL, 0.1 equiv), and o-xylene (66 mL) were added to a dry reaction vessel and reacted at 140°C for 24 h. After completion of the reaction, the mixture was purified by flash column chromatography to obtain Diamine 1, 2.58 g, with a yield of 50%.

[0091] Example 2

[0092]

[0093] (1) Nucleophilic substitution reaction

[0094] The method was the same as the "Nucleophilic Substitution Reaction" step in Example 1, except that 4-bromophenol was replaced with 3-methyl-4-bromophenol, the amount of 3-methyl-4-bromophenol was adjusted to 11.0 mmol (1.1 equiv), and the amount of KCO was adjusted to 40.0 mmol (4.0 equiv). Intermediate 2-1 was obtained, yielding 2.53 g (82%).

[0095] (2) Miyaura borylation reaction

[0096] The method was the same as the "Miyaura borylation reaction" step in Example 1, except that Intermediate 1-I was replaced with Intermediate 2-I, KOAc was replaced with KCO, and the amount of KCO was adjusted to 50 mmol (5 equiv), PdCl(dppf) was replaced with Pd(OAc) to 0.5 mmol (0.05 equiv), and 1,4-dioxane was replaced with THF. Intermediate 2-II was obtained, yielding 1.85 g (52%).

[0097] (3) Reduction reaction

[0098] The method was the same as the "Reduction Reaction" step in Example 1, except that Intermediate 1-II was replaced with Intermediate 2-II, the amount of Pd / C was adjusted to 0.27 g (10% w / w), the amount of 85% hydrazine hydrate was adjusted to 8 mL, and the amount of anhydrous ethanol was adjusted to 60 mL. Intermediate 2-III was obtained, 2.54 g, with a yield of 78%.

[0099] (4) Suzuki reaction

[0100] The method is the same as the "Suzuki reaction" step in Example 1, except that the intermediate 1-III is adjusted to the intermediate 2-III, and the amount of the intermediate 2-III is adjusted to 23 mmol (2.3 equiv), Cs2CO3 is adjusted to K2CO3, Pd (PPh3)4 is adjusted to PdCl2 (dppf), and the amount of PdCl2 (dppf) is adjusted to 2 mmol (0.2 equiv), V 甲苯 :V 乙醇 :V 水 =1:1:1 (50 mL), and the reaction temperature was adjusted to 80° C. Diamine 2 was obtained, 2.01 g, with a yield of 37%.

[0101] Example 3

[0102]

[0103] (1) Nucleophilic substitution reaction

[0104] The method was the same as the "nucleophilic substitution reaction" step in Example 1, except that p-fluoronitrobenzene was replaced with m-fluoronitrobenzene, 4-bromophenol was replaced with 3-fluoro-4-bromophenol, and the amount of 3-fluoro-4-bromophenol was adjusted to 12.0 mmol / L (1.2 equiv), K2CO3 was replaced with Cs2CO3, and the amount of Cs2CO3 was adjusted to 50.0 mmol / L (5.0 equiv), and DMSO was replaced with DMF. Intermediate 3-I was directly purified by flash column chromatography to obtain 2.19 g of the intermediate in a 70% yield.

[0105] (2) Miyaura borylation reaction

[0106] The method was the same as the "Miyaura borylation reaction" step in Example 1, except that Intermediate 1-I was replaced with Intermediate 3-I, the amount of pinacol diboron was adjusted to 13 mmol (1.3 equiv), KOAc was replaced with NaCO, and the amount of NaCO was adjusted to 40 mmol (4.0 equiv), PdCl(dppf) was replaced with Pd(PPh), and 1,4-dioxane was replaced with DMF. Intermediate 3-II was obtained, 1.80 g, in a 50% yield.

[0107] (3) Reduction reaction

[0108] The method was the same as the "Reduction Reaction" step in Example 1, except that Intermediate 1-II was replaced with Intermediate 3-II, the amount of Pd / C was adjusted to 0.3 g (10% w / w), and the amount of 85% hydrazine hydrate was adjusted to 10 mL. Intermediate 3-III was obtained, 2.63 g, with a yield of 80%.

[0109] (4) Suzuki reaction

[0110] The method is the same as the "Suzuki reaction" step in Example 1, except that the intermediate 1-III is adjusted to the intermediate 3-III, 1,4-dibromotetrafluorobenzene is adjusted to 1,4-dibromo-2,5-difluorobenzene, Cs2CO3 is adjusted to Na2CO3, and the amount of Na2CO3 is adjusted to 50mmoL (5.0equiv), Pd(PPh3)4 is adjusted to PdCl2(PPh3)2, V 1,4-二氧六环 :V 水 =1:1 (100 mL), and the reaction temperature was adjusted to 110° C. Diamine 3 was obtained, 0.93 g, with a yield of 18%.

[0111] Example 4

[0112]

[0113] (1) Nucleophilic substitution reaction

[0114] The method was the same as the "Nucleophilic Substitution Reaction" step in Example 1, except that p-fluoronitrobenzene was replaced with 3-methyl-4-fluoronitrobenzene, 4-bromophenol was replaced with 3-fluoro-4-bromophenol, and KCO was replaced with NaCO. Intermediate 4-I was obtained, 2.02 g, in a 62% yield.

[0115] (2) Miyaura borylation reaction

[0116] The method was the same as the "Miyaura borylation reaction" step in Example 1, except that Intermediate 1-I was replaced with Intermediate 4-I, KOAc was replaced with NaOAc, PdCl2(dppf) was replaced with PdCl2(PPh3)2, the amount of Pd(OAc)2 was adjusted to 0.4 mmol (0.04 equiv), and 1,4-dioxane was replaced with DMSO. Intermediate 4-II was obtained, yielding 1.04 g (28%).

[0117] (3) Reduction reaction

[0118] The method was the same as the "reduction reaction" step in Example 1, except that intermediate 1-II was replaced with intermediate 4-II to obtain intermediate 4-III, 2.78 g, with a yield of 81%.

[0119] (4) Suzuki reaction

[0120] The method was the same as the "Suzuki reaction" step in Example 1, except that Intermediate 1-III was replaced with Intermediate 4-III, 1,4-dibromotetrafluorobenzene was replaced with 1,4-dibromo-2,5-difluorobenzene, and Pd(PPh3)4 was replaced with Pd(OAc)2. Diamine 4 was obtained, 1.96 g, in a 36% yield.

[0121] Example 5

[0122]

[0123] (1) Nucleophilic substitution reaction

[0124] The method was the same as the "Nucleophilic Substitution Reaction" step in Example 1, except that p-fluoronitrobenzene was replaced with 3-trifluoromethyl-4-fluoronitrobenzene, 4-bromophenol was replaced with 3-methyl-4-bromophenol, K2CO3 was replaced with NaH, and DMSO was replaced with DMAc. Intermediate 5-1 was obtained, 1.90 g, in a 50% yield.

[0125] (2) Miyaura borylation reaction

[0126] The method was the same as the "Miyaura borylation reaction" step in Example 1, except that intermediate 1-I was replaced by intermediate 5-I to obtain intermediate 5-II, 3.37 g, with a yield of 79%.

[0127] (3) Reduction reaction

[0128] The method was the same as the "reduction reaction" step in Example 1, except that intermediate 1-II was replaced with intermediate 5-II to obtain intermediate 5-III, 3.38 g, with a yield of 85%.

[0129] (4) Suzuki reaction

[0130] The method was the same as the "Suzuki reaction" step in Example 1, except that intermediate 1-III was replaced with intermediate 5-III and 1,4-dibromotetrafluorobenzene was replaced with 1,4-dibromo-2,5-difluorobenzene. Diamine 5 was obtained in a yield of 68%, 4.38 g.

[0131] Example 6

[0132]

[0133] Diamine 1 and PMDA were polymerized by thermal imidization. The specific steps were as follows: under N2 atmosphere, dried diamine Diamine 1 (1 mmoL, 1.0 equiv) was weighed into a 50 mL dry round-bottom flask, and anhydrous DMAc solvent was added via syringe. After the diamine was completely dissolved, an anhydrous DMAc solution of dianhydride PMDA (1 mmoL, 1.0 equiv) was added dropwise via syringe, and the solid content was controlled at 15% (a total of 4.1973 g of anhydrous DMAc solvent was added to the system). The reaction was carried out at room temperature for 24 h to obtain a polyamic acid solution PAA-1. The polyamic acid solution was then poured onto a clean glass plate and scraped with a spatula. , control the film thickness at 50 μm, program the temperature in the imide furnace to remove the solvent in vacuum and perform thermal imidization (program temperature rising process: heat up to 100°C at a rate of 80°C / h and keep warm for 1 hour, then heat up to 150°C at a rate of 100°C / h and keep warm for 1 hour, then heat up to 200°C at a rate of 150°C / h and keep warm for 1 hour, heat up to 230°C at a rate of 200°C / h and keep warm for 1 hour). After the thermal imidization is completed, wait for the temperature of the tube furnace to drop to room temperature, take out the glass plate, and immerse the obtained polyimide film in deionized water, wait for it to fall off naturally, and place the obtained polyimide film in a 100°C oven to dry the residual solvent and moisture to obtain the polyimide film PI-1.

[0134] Example 7

[0135]

[0136]

[0137] The method is the same as Example 6, except that Diamine 1 is replaced by Diamine 2, PMDA is replaced by 6-FDA, the amount of 6-FDA is adjusted to 0.4531 g (1.02 mmol, 1.02 equiv), and the amount of anhydrous DMAc is adjusted to 5.6536 g to obtain the corresponding polyimide film PI-2.

[0138] Example 8

[0139]

[0140] The method was the same as Example 6, except that Diamine 1 was replaced with Diamine 3, PMDA was replaced with HBPDA, the amount of HBPDA was adjusted to 0.3094 g (1.01 mmol, 1.01 equiv), and the amount of anhydrous DMAc was adjusted to 4.6801 g to obtain the corresponding polyimide film PI-3.

[0141] Example 9

[0142]

[0143] The method was the same as that in Example 6, except that Diamine 1 was replaced with Diamine 4, PMDA was replaced with ODPA, and the amount of anhydrous DMAc was replaced with 4.8439 g to obtain the corresponding polyimide film PI-4.

[0144] Example 10

[0145]

[0146] The method was the same as that in Example 6, except that Diamine 1 was replaced with Diamine 5, PMDA was replaced with BPDA, and the amount of anhydrous DMAc was replaced with 5.3199 g to obtain the corresponding polyimide film PI-5.

[0147] Structural characterization:

[0148] Figure 1 is the diamine Diamine1 in Example 1 1 HNMR spectrum;

[0149] Depend on Figure 1 It can be seen that 1 H NMR (400 MHz, CDCl3) δ7.57 (d, J = 7.5 Hz, 4H), 7.21 (d, J = 6.0 Hz, 4H), 6.69 (d, J = 7.5 Hz, 4H), 6.61 (d, J = 7.5 Hz, 4H), 4.21 (s, 4H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of diamine 1.

[0150] Figure 2 is the diamine Diamine2 in Example 2 1 HNMR spectrum;

[0151] Depend on Figure 2 It can be seen that 1HNMR (400 MHz, CDCl3) δ7.43 (d, J = 7.5 Hz, 2H), 7.03 (s, 2H), 6.96 (dt, J = 7.5 Hz, J = 2.3 Hz, 2H), 6.68 (d, J = 7.0 Hz, 4H), 6.60 (d, J = 7.2 Hz, 4H), 4.20 (d, J = 2.6 Hz, 4H), 2.37 (s, 6H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of diamine 2.

[0152] Figure 3 is the diamine 3 in Example 3 1 HNMR spectrum;

[0153] Depend on Figure 3 It can be seen that 1 H NMR (400 MHz, CDCl3) δ7.63–7.53 (m, 4H), 7.03–6.92 (m, 4H), 6.90–6.83 (m, 2H), 6.33–6.24 (m, 4H), 6.22 (t, J = 2.0 Hz, 2H), 4.14 (d, J = 4.8 Hz, 4H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of diamine 3.

[0154] Figure 4 is the diamine Diamine4 in Example 4 1 HNMR spectrum;

[0155] Depend on Figure 4 It can be seen that 1 H NMR (400 MHz, CDCl3) δ7.61–7.53 (m, 4H), 6.95–6.80 (m, 4H), 6.62 (d, J = 7.5 Hz, 2H), 6.53 (s, 2H), 6.48 (dd, J = 7.5 Hz, J = 1.8 Hz, 2H), 4.09 (s, 4H), 2.33 (s, 6H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of diamine 4.

[0156] Figure 5 is the diamine Diamine5 in Example 5 1 HNMR spectrum;

[0157] Depend on Figure 5 It can be seen that 1H NMR (400 MHz, CDCl3) δ7.54–7.43 (m, 4H), 7.06 (dd, J = 7.5 Hz, J = 2.0 Hz, 1H), 6.97 (d, J = 6.1 Hz, 2H), 6.92 (s, 1H), 6.78–6.70 (m, 2H), 6.40–6.33 (m, 2H), 6.15 (dd, J = 8.9 Hz, J = 1.7 Hz, 2H), 4.09 (d, J = 2.8 Hz, 4H), 2.33 (d, J = 8.1 Hz, 6H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of diamine 5.

[0158] Figure 6 is the polyimide PI-1 in Example 6 1 HNMR spectrum;

[0159] Depend on Figure 6 It can be seen that 1 H NMR (400 MHz, CDCl3) δ8.45 (d, J=1.6 Hz, 2H), 8.15 (d, J=7.5 Hz, 2H), 7.58 (dd, J=7.4 Hz, J=4.9 Hz, 4H), 7.49 (d, J=7.5 Hz, 2H), 7.23 (dd, J=11.6 Hz, J=7.5 Hz, 4H), 7.15 (d, J=7.5 Hz, 2H), 7.03 (d, J=7.5 Hz, 2H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of polyimide PI-1.

[0160] Figure 7 is the polyimide PI-2 in Example 7 1 HNMR spectrum;

[0161] Depend on Figure 7 It can be seen that 1 H NMR (400 MHz, CDCl3) δ8.17–8.07 (m, 5H), 8.00 (d, J = 7.5 Hz, 1H), 7.90–7.81 (m, 2H), 7.52–7.43 (m, 4H), 7.15 (d, J = 7.5 Hz, 2H), 7.07 (dd, J = 7.5 Hz, J = 2.0 Hz, 1H), 7.04–6.98 (m, 4H), 6.97 (s, 1H), 2.36 (d, J = 7.0 Hz, 6H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of polyimide PI-2.

[0162] Figure 8 is the polyimide PI-3 in Example 8 1 HNMR spectrum;

[0163] Depend on Figure 8 It can be seen that 1 H NMR (400MHz, CDCl3) δ7.62–7.51(m,4H),7.43–7.31(m,4H),7.16(s,1H),7.07–7.00(m, 3H),6.95(dd,J=7.5Hz,J=1.8Hz,1H),6.91–6.83(m,3H),3.53(q,J=7.0Hz,1H),3.33(q , J = 7.0 Hz, 1H), 3.19 (q, J = 7.0 Hz, 1H), 2.80 (q, J = 7.0 Hz, 1H), 2.45–2.31 (m, 2H), 2.24–2.15 (m, 1H), 2.15–2.06 (m, 1H), 1.86–1.71 (m, 2H), 1.47–1.35 (m, 4H), 1.35–1.18 (m, 4H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of polyimide PI-3.

[0164] Figure 9 is the polyimide PI-4 in Example 9 1 HNMR spectrum;

[0165] Depend on Figure 9 It can be seen that 1 H NMR (400 MHz, CDCl3) δ8.21 (dd, J = 7.5 Hz, 1.9 Hz, 1H), 8.09–7.98 (m, 3H), 7.61 (d, J = 6.7 Hz, 1H), 7.57 (dt, J = 8.2 Hz, J = 4.1 Hz, 5H), 7.51 (d, J = 2.0 Hz, 1H), 7.44 (dd, J = 7.5 Hz, J = 2.0 Hz, 1H), 7.29–7.24 (m, 2H), 7.00–6.93 (m, 3H), 6.85–6.78 (m, 3H), 2.39 (s, 3H), 2.34 (s, 3H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of polyimide PI-4.

[0166] Figure 10 is the polyimide PI-5 in Example 10 1 HNMR spectrum;

[0167] Depend on Figure 10 It can be seen that 1H NMR (400MHz, CDCl3) δ8.43 (s, 1H), 8.34 (d, J = 1.9Hz, 1H), 8.15 (dd, J = 9.3Hz, J = 7.6Hz, 2 H),7.99(dd,J=8.9Hz,J=1.9Hz,1H),7.93–7.86(m,2H),7.75(dd,J=7.5Hz,J=2.0Hz,1H) ,7.55–7.44 (m, 4H),7.26 (dd, J = 8.9 Hz, J = 1.9 Hz, 1H),7.15 (dd, J = 7.5 Hz, J = 1.9 Hz, 1H),7.10–7.03 (m, 2H),7.00 (d, J = 7.2 Hz, 3H),6.89 (dd, J = 7.5 Hz, J = 5.7 Hz, 1H),2.35 (s, 6H). The peak positions and integrated peak areas were consistent with the structure, indicating the successful synthesis of polyimide PI-5.

[0168] Performance testing:

[0169] Thermal properties (DSC) test procedure for polyimide films PI-1 to PI-5: Weigh 3 to 5 mg of polyimide films PI-1 to PI-5 into a peeled solid crucible. Under a nitrogen atmosphere, the glass transition temperature of the PI-1 to PI-5 polymers was measured at a heating rate of 10°C / min and a temperature range of 40-400°C. The glass transition temperature was obtained from the second test curve after sample annealing. The test results are shown in Table 1.

[0170] Thermal stability (TGA) testing procedure for polyimides PI-1 to PI-5: 5-10 mg of solid polyimides PI-1 to PI-5 were weighed into a clean, peeled crucible and tested under a nitrogen atmosphere at a heating rate of 20°C / min over a temperature range of 100-820°C. The thermal stability of polyimides PI-1 to PI-5 was examined under a nitrogen atmosphere. The test results are shown in Table 1.

[0171] Solubility testing of polyimides PI-1 to PI-5: A certain amount of polyimide was dissolved in different solvents to prepare solutions with a concentration of 10 mg / mL. The solubility of the solutions was then tested accordingly. The test results are shown in Table 2.

[0172] Mechanical property testing procedures for polyimides PI-1 to PI-5: Films (approximately 50 μm thick, 6 mm wide, and 25 mm long) were tested at room temperature at a tensile rate of 5 mm / min. The test results were averaged across five test samples. The test results are shown in Table 3.

[0173] Transmittance test procedure for polyimides PI-1 to PI-5: The transmittance of the polyimide film was tested in the transmission mode at 25°C. The test results are shown in Table 4.

[0174] Table 1 DSC and TGA test data of polyimide prepared in Examples 6 to 10

[0175]

[0176]

[0177] Table 2 Solubility of polyimides prepared in Examples 6 to 10 in six common solvents

[0178]

[0179] (Note: -: insoluble upon heating, +-: partially soluble, +: soluble upon heating, ++: easily soluble at room temperature) Table 3 Tensile strength, tensile modulus, and elongation at break of the polyimides prepared in Examples 6 to 10

[0180] Polyimides <![CDATA[T S (MPa)]]> <![CDATA[T M (GPa)]]> <![CDATA[E B (%)]]> Example 6 57±1.3 1.36±0.08 7.2±2.3 Example 7 68±1.7 1.51±0.13 6.8±1.5 Example 8 51±2.3 1.25±0.16 8.2±1.2 Example 9 62±1.9 1.33±0.03 7.8±2.1 Example 10 72±1.4 1.65±0.10 8.5±1.2

[0181] Table 4 Transmittance of polyimides prepared in Examples 6 to 10

[0182] Polyimides <![CDATA[T 450nm (%)]]> Example 6 52 Example 7 70 Example 8 75 Example 9 80 Example 10 76

[0183] As can be seen from Table 1, the Tg of the five synthesized polyimides are between 246 and 283°C, all of which have high glass transition temperatures; from the TGA data, it can be seen that the 5% thermal weight loss range of the polyimide in a nitrogen atmosphere is 410 to 468°C, indicating that the polyimide has good thermal stability in a nitrogen atmosphere.

[0184] It can be seen from Table 2 that the concentration of the solutions of polyimides with different structures formed in different solvents is all 10 mg / mL. The results show that Examples 6 to 10 have good solubility in some common solvents.

[0185] As can be seen from Table 3, the tensile strength, tensile modulus and elongation at break of polyimide are 51-72 MPa, 1.25-1.65 GPa and 6.8-8.5%, respectively. The introduction of fluorine atoms gives polyimide better mechanical properties.

[0186] It can be seen from Table 4 that the five synthesized polyimides all have high transmittance. The fluorine atoms introduced into the structure increase the steric hindrance, causing the polyimide chains to form a non-coplanar structure, hindering the formation of CTC, and helping to further improve the transmittance of the polyimide.

[0187] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A diamine monomer containing fluorine atoms in the main chain, characterized in that: It has the structure shown in formula I: wherein R1 is selected from H, CH3 or F; R2 is selected from H, CH3 or CF3; and R3 is selected from H or F.

2. A method for preparing a diamine monomer containing fluorine atoms in the main chain according to claim 1, characterized in that: The following steps are involved: Step 1. After mixing substituted 4-fluoronitrobenzene, substituted 4-bromophenol, a base and solvent 1, a nucleophilic substitution reaction is carried out under an inert atmosphere to obtain intermediate I; Step 2. After mixing the intermediate 1, pinacol diboronate, an alkali metal salt 1, a palladium catalyst, and a solvent 2, a Miyaura borylation reaction is carried out under an inert atmosphere to obtain an intermediate II; Step 3. After mixing the intermediate II, Pd / C, hydrazine hydrate and solvent 3, a reduction reaction is carried out under an inert atmosphere to obtain intermediate III; Step 4. After mixing the intermediate III, substituted dibromobenzene, alkali metal salt 2, palladium catalyst and solvent 4, a Suzuki reaction is carried out under an inert atmosphere to obtain the diamine monomer containing fluorine atoms in the main chain; The structural formula of the substituted 4-fluoronitrobenzene is The structural formula of the substituted 4-bromophenol is The structural formula of the substituted dibromobenzene is wherein R1 is selected from H, CH3 or F; R2 is selected from H, CH3 or CF3; and R3 is selected from H or F.

3. The preparation method according to claim 2, characterized in that In step 1, the base is Na2CO3, K2CO3, Cs2CO3 or NaH; the molar ratio of the substituted 4-fluoronitrobenzene, substituted 4-bromophenol and the base is 1:1-1.2:3-5; the temperature of the nucleophilic substitution reaction is 70-90°C and the time is 13 hours.

4. The preparation method according to claim 2, characterized in that In step 2, the alkali metal salt 1 is Na2CO3, K2CO3, KOAc or NaOAc; the palladium catalyst is PdCl2(dppf), Pd(OAc)2, PdCl2(PPh3)2 or Pd(PPh3)4; the molar ratio of the intermediate 1, bipyralidone borate, alkali metal salt 1 and palladium catalyst is 1:1.2~1.3:3~5:0.03~0.05; the temperature of the Miyaura borylation reaction is 90~110°C and the time is 15h.

5. The preparation method according to claim 2, characterized in that In step 3, the amount of Pd / C is: 0.25-0.3 mg Pd / C is added per 1 mmol of intermediate II; the mass fraction of hydrazine hydrate is 85%; the amount of hydrazine hydrate is: 0.5-1 mL hydrazine hydrate is added per 1 mmol of intermediate II; the temperature of the reduction reaction is 90° C., and the time is 12 h.

6. The preparation method according to claim 2, characterized in that In step 4, the alkali metal salt 2 is Na2CO3, K2CO3 or Cs2CO3; the palladium catalyst is the same as the palladium catalyst in step 2; the molar ratio of the intermediate III, substituted dibromobenzene, alkali metal salt 2, and palladium catalyst is 2.2-2.3:1:4-5:0.1-0.2; the temperature of the Suzuki reaction is 80-140°C, and the time is 24h.

7. A method for preparing polyimide, characterized in that: Under inert atmosphere, the dianhydride monomer, the diamine monomer according to claim 1 and the solvent 5 are stirred and reacted at room temperature to obtain a polyamic acid solution; The polyamic acid solution is thermally imidized to obtain the polyimide.

8. The preparation method according to claim 7, characterized in that The molar ratio of the dianhydride monomer to the diamine monomer is 1:1; the stirring reaction temperature is room temperature, and the time is 24 to 48 hours.

9. A polyimide prepared by the preparation method according to claim 7 or 8.

Images