Fluorenyl polyimide film with low dielectric constant as well as preparation method and application of fluorenyl polyimide film

Abstract

The invention records a fluorenyl polyimide film with a low dielectric constant and a preparation method and application thereof, and the polyimide is prepared by taking 9, 9-bis (4-(4-aminophenoxy) phenyl) fluorene and 4, 4 '-diaminodiphenyl ether diamine as diamine and aromatic dianhydride as dianhydride, and carrying out thermal imidization on the diamine and the dianhydride to obtain the PI film. The PI film provided by the invention has an asymmetric molecular structure, a fluorine-containing group and a fluorene group. The fluorine group has smaller dipole and lower polarizability, and can increase the free volume, and the free volume of the polymer material is increased, so that the number of polar groups in unit volume can be reduced, and the dielectric constant of the PI film can be reduced. The method can be applied to the high-tech fields of low-dielectric materials, gas separation membranes, fuel cell proton exchange membranes, outer space and the like.

Description

Technical Field

[0001] The present invention belongs to the field of polyimide film materials, and in particular relates to a polyimide film with low dielectric constant and high heat resistance, and a preparation method and application thereof. Background Art

[0002] Solar sails for deep space probes can range in size from tens of meters to several thousand meters. Polyimide exhibits excellent flexibility, mechanical properties, and corrosion resistance under extreme conditions. Its simple production process and large-scale industrial production make it a suitable lightweight material for solar sails. Furthermore, polyimide has a low dielectric constant, low dielectric loss, and high energy storage density, making it a promising material for multi-layer thermal insulation blankets and spacecraft wiring insulation. With the development of the aerospace industry, polyimide is required to be lightweight, easy to process on a large scale, with a low dielectric constant and extremely low dielectric loss.

[0003] The dielectric constant of commercially produced polyimide films currently ranges from 3.2 to 3.8, which cannot meet the requirements of high-end electronics and advanced aerospace materials. Therefore, further reducing the dielectric constant of polyimide while retaining its high performance has become an urgent problem to be solved. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a fluorene-containing polyimide film, a preparation method and application. By designing rigid group polymerization monomers, the thermal stability and corrosion resistance of the polyimide film are improved, and its dielectric constant is reduced, making it suitable for the field of outer space aerospace.

[0005] In order to solve the above problems, the technical solution proposed by the present invention is:

[0006] In a first aspect, the present invention provides a low dielectric constant fluorene-based polyimide film having the following general structural formula (I):

[0007]

[0008] In formula (I), Ar is selected from any one of the following groups:

[0009]

[0010] n is a repeating unit, n=1-100.

[0011] In a second aspect, the present invention provides a method for preparing the low dielectric constant fluorene-based polyimide film according to the first aspect, comprising the following steps:

[0012] 1) reacting diamine and dianhydride at a temperature of -20 to 30° C. for 4 to 10 hours to obtain a polyamic acid prepolymer;

[0013] 2) The polyamic acid solution system obtained in step 1) is evenly spread on a glass plate, and subjected to thermal rearrangement and curing reaction at 120-300° C. in a vacuum drying oven to obtain the film.

[0014] Furthermore, in step 1), the diamine is 9,9-bis(4-(4-aminophenoxy)phenyl)fluorene (BAOFL) and 4,4'-diaminodiphenyl ether (ODA) in a molar ratio of 1:1.

[0015] Furthermore, in step 1), the dianhydride is selected from any one of bisphenol A tetracarboxylic dianhydride (BDAPA), 4,4′-(hexafluoroisopropylene) diphthalic anhydride (6FDA), 4,4′-diphenyl ether dianhydride (ODPA) and pyromellitic anhydride (PMDA).

[0016] Furthermore, in step 1), the solvent of the reaction system is one or more of N-methylpyrrolidone, dichloromethane, chloroform, and 1,4-dioxane.

[0017] Furthermore, in step 1), the molar ratio of diamine to dianhydride is (10:1) to (1:15).

[0018] Furthermore, in step 2), the thermal rearrangement curing reaction time is 9 hours.

[0019] The fluorene-based polyimide film can be applied to high-tech fields such as low dielectric materials, gas separation membranes, fuel cell proton exchange membranes and outer space.

[0020] The advantages and beneficial effects of the present invention are:

[0021] 1) The present invention provides a polyimide film (PI film) with high transparency and low dielectric constant prepared from a series of aromatic diamine monomers. The polyimide is prepared by thermal imidization using 9,9-bis(4-(4-aminophenoxy)phenyl)fluorene (BAOFL), 4,4'-diaminodiphenyl ether (ODA) diamine and a series of aromatic dianhydrides as raw materials.

[0022] 2) The PI film provided by the present invention has an asymmetric molecular structure and contains fluorine-containing groups and fluorene groups. The fluorine groups have a smaller dipole and lower polarizability, and can also increase the free volume. The increased free volume of the polymer material can reduce the number of polar groups per unit volume, thereby reducing the dielectric constant of the PI film.

[0023] 3) The present invention uses ODA, BAOFL, BDAPA, 6FDA, ODPA, and PMDA as reactive monomers. The fluorene-based thermosetting PI film with this chemical structure has good solubility and can be rapidly dissolved in solvents such as NMP, DMF, DMAC, DMSO, m-Cresol, THF, and CHCl3 at room temperature. It also has good temperature stability and is suitable for use in outer space environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 These are the thermogravimetric curves of the PI films prepared in Examples 1 to 4.

[0025] Figure 2 (a) to (d) are the DTG curves of the PI films prepared in Examples 1 to 4, respectively. DETAILED DESCRIPTION

[0026] The present application is further described below with reference to specific embodiments.

[0027] It should be noted that the terms such as "upper", "lower", "left", "right", and "middle" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of this application without substantially changing the technical content.

[0028] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0029] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0030] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement, or value. One skilled in the art can readily determine the degree of flexibility for a particular variable.

[0031] As used herein, the term "at least one of" is intended to be synonymous with "one or more of." For example, "at least one of A, B, and C" explicitly includes only A, only B, only C, and combinations of each thereof.

[0032] This invention optimizes the dielectric properties and thermal stability of polyimide films by introducing rigid groups into the polyimide molecular structure. The large free volume of the fluorene group and the fused ring structure impart excellent overall properties to the polyimide, including excellent solubility in organic solvents, heat resistance and thermal oxidation stability, good mechanical properties, and low dielectric constant and loss.

[0033] Example 1

[0034] Polyimide PI-BDAPA was prepared using BAOFL and ODA as diamine monomers and bisphenol A tetracarboxylic dianhydride (BDAPA) as follows:

[0035] BAOFL and ODA, mixed in a molar ratio of 1:1 as diamine monomers, were added to bisphenol A tetracarboxylic dianhydride (BDAPA) in equal moles in N-methyl-2-pyrrolidone solvent to prepare a 10% (wt / wt) solution. The mixture was stirred and reacted at room temperature for 24 hours under nitrogen flow to obtain a yellow polyamic acid viscous liquid. An appropriate amount of the polyamic acid viscous liquid was cast onto a clean glass plate and dried under reduced pressure at 80°C and 150°C for 4 hours and 2 hours, respectively. A polyamic acid gel film was formed when the solvent was completely removed. The film was then dried at 200°C and 240°C for 2 hours and 1 hour, respectively, and thermally imidized to obtain a polyimide film PI-1, whose structural formula is shown in Formula II and is named bisphenol A tetracarboxylic dianhydride-based polyimide (PI-BDAPA).

[0036]

[0037] 5% weight loss temperature (℃, in nitrogen): 292.20

[0038] Glass transition temperature (℃, DSC): 257.2

[0039] Dielectric constant: 2.3 (1000Hz)

[0040] Dielectric loss: 0.0035 (1000Hz).

[0041] Example 2

[0042] Polyimide PI-6FDA was prepared using BAOFL and ODA as diamine monomers and 4,4′-(hexafluoroisopropylene) diphthalic anhydride (6FDA) as follows:

[0043] BAOFL and ODA, mixed in a molar ratio of 1:1 as diamine monomers, were added with 4,4′-(hexafluoroisopropylene) diphthalic anhydride (6FDA) in equal moles to N-methyl-2-pyrrolidone solvent to prepare a 10% (wt / wt) solution. The solution was stirred and reacted at room temperature for 24 hours under nitrogen flow to obtain a yellow polyamic acid viscous liquid. An appropriate amount of the polyamic acid viscous liquid was cast on a clean glass plate and dried under reduced pressure at 80°C and 150°C for 4 hours and 2 hours, respectively. When the solvent was completely removed, a polyamic acid gel film was formed. The solution was then dried at 200°C and 240°C for 2 hours and 1 hour, and thermal imidization was performed to obtain a polyimide film PI-1, whose structural formula is shown in Formula III and is named hexafluoroisopropylene diphthalic anhydride-based polyimide (PI-6FDA).

[0044]

[0045] 5% weight loss temperature (℃, in nitrogen): 493.93

[0046] Glass transition temperature (℃, DSC): 297.8

[0047] Dielectric constant: 2.8 (1000Hz)

[0048] Dielectric loss: 0.0043 (1000Hz).

[0049] Example 3

[0050] Polyimide PI-ODPA was prepared using BAOFL and ODA as diamine monomers and 4,4′-diphenyl ether dianhydride (ODPA) as follows:

[0051] BAOFL and ODA, mixed in a molar ratio of 1:1 as diamine monomers, were added to N-methyl-2-pyrrolidone solvent in equal moles with 4,4′-diphenyl ether dianhydride (ODPA) to prepare a 10% (wt / wt) solution. Under nitrogen flow, the mixture was stirred and reacted at room temperature for 24 hours to obtain a yellow polyamic acid viscous liquid. An appropriate amount of the polyamic acid viscous liquid was cast on a clean glass plate and dried under reduced pressure at 80°C and 150°C for 4 hours and 2 hours, respectively. When the solvent was completely removed, a polyamic acid gel film was formed. The film was then dried at 200°C and 240°C for 2 hours and 1 hour, and thermal imidization was performed to obtain a polyimide film PI-1, whose structural formula is shown in Formula IV and is named diphenyl ether dianhydride-based polyimide (PI-ODPA).

[0052]

[0053] 5% weight loss temperature (℃, in nitrogen): 195.71

[0054] Glass transition temperature (℃, DSC): 217.8

[0055] Dielectric constant: 3.4 (1000Hz)

[0056] Dielectric loss: 0.0051 (1000Hz).

[0057] Example 4

[0058] Polyimide PI-PMDA was prepared using BAOFL and ODA as diamine monomers and pyromellitic anhydride (PMDA) as follows:

[0059] BAOFL and ODA, mixed in a molar ratio of 1:1 as diamine monomers, were added to N-methyl-2-pyrrolidone solvent in equal moles with pyromellitic anhydride (PMDA) to form a 10% (wt / wt) solution. The solution was stirred and reacted at room temperature for 24 hours under a nitrogen flow to obtain a yellow polyamic acid viscous liquid. An appropriate amount of the polyamic acid viscous liquid was cast on a clean glass plate and dried under reduced pressure at 80°C and 150°C for 4 hours and 2 hours, respectively. When the solvent was completely removed, a polyamic acid gel film was formed. The solution was then dried at 200°C and 240°C for 2 hours and 1 hour, and thermal imidization was performed to obtain a polyimide film PI-1, whose structural formula is shown in Formula V and is named pyromellitic anhydride-based polyimide (PI-PMDA).

[0060]

[0061] 5% weight loss temperature (℃, in nitrogen): 171.27

[0062] Glass transition temperature (℃, DSC): 203.0

[0063] Dielectric constant: 3.7 (1000Hz)

[0064] Dielectric loss: 0.0053 (1000Hz).

[0065] The thermogravimetric curves of the PI films obtained in Examples 1 to 4 are as follows: Figure 1 As shown, the DTG curve is as Figure 2 As shown in a~d in the figure, the dielectric constant and dielectric loss are shown in Table 1~Table 2 respectively.

[0066] Table 1 is the dielectric constant of the PI films prepared in each embodiment

[0067]

[0068] Table 2 is the dielectric loss table of the PI film prepared in Example

[0069]

[0070] 100 mg of the PI films prepared in Examples 1 to 4 were placed in 1 mL of different solvents, including N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), m-cresol (m-Cresol), tetrahydrofuran (THF) and chloroform (CHCl3), respectively. The films were placed at room temperature (25°C) and heated for 2 h to observe the dissolution of the polymers and test the solubility of PI in different solvents. The results are shown in Table 3.

[0071] Table 3 is the dissolution performance table of the PI film prepared in Example

[0072]

[0073] Note: Soluble at room temperature ++, soluble by heating +, insoluble by heating -.

[0074] The above-mentioned implementation cases are only preferred implementation cases in the present invention, but the implementation methods of the present invention are not limited to the above-mentioned implementation cases. For example, various combinations of the schemes in the embodiments and any other changes, modifications, substitutions, and combinations made without departing from the spirit and principles of the present invention should be equivalent replacement methods and are within the scope of protection of the present invention.

Claims

1. A low dielectric constant fluorene-based polyimide film, characterized in that: It has the following general structural formula (I): In formula (I), Ar is selected from any one of the following groups: n is a repeating unit, n=1-100.

2. A method for preparing a low dielectric constant fluorene-based polyimide film, characterized in that: The steps include: 1) reacting diamine and dianhydride at -20 to 30° C. for 4 to 10 hours to obtain a polyamic acid prepolymer; 2) The polyamic acid solution system obtained in step 1) is evenly spread on a glass plate, and subjected to thermal rearrangement and curing reaction at 120-300° C. in a vacuum drying oven to obtain the film.

3. The method according to claim 2, wherein In step 1), the diamine is 9,9-bis(4-(4-aminophenoxy)phenyl)fluorene and 4,4'-diaminodiphenyl ether in a molar ratio of 1:

1.

4. The method according to claim 2, wherein In step 1), the dianhydride is selected from any one of bisphenol A tetracarboxylic dianhydride, 4,4′-(hexafluoroisopropylene) diphthalic anhydride, 4,4′-biphenyl ether dianhydride and pyromellitic anhydride.

5. The method according to claim 2, wherein In step 1), the solvent of the reaction system is one or more of N-methylpyrrolidone, dichloromethane, chloroform, and 1,4-dioxane.

6. The method according to claim 2, wherein In step 1), the molar ratio of diamine to dianhydride is (10:1) to (1:15).

7. The method according to claim 2, wherein In step 2), the thermal rearrangement curing reaction time is 9 hours.

8. Use of the fluorene-based polyimide film according to claim 1 as a low dielectric material, a gas separation membrane, or a proton exchange membrane for a fuel cell.

Images