KR101509316B1 - Polyimide, method for preparion of the same and film including the same - Google Patents

Abstract

The present invention relates to a polyimide, a process for producing the same, and a film comprising the polyimide.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyimide, a method for producing the same, and a film comprising the polyimide. BACKGROUND ART [0002]

The present invention relates to a polyimide, a process for producing the same, and a film comprising the polyimide.

Aromatic polyimides have been extensively studied as high-performance polymers because of their excellent thermal stability, thermal oxidation stability, chemical resistance, mechanical properties and electrical properties. These aromatic polyimides are widely used in the fields of gas separation, microelectronics, aerospace devices, integrated electronic circuits, passivation coatings, substrate materials, adhesives, composites, and the like. However, since aromatic polyimides have poor solubility, high processing temperatures, and strong interaction between chains, the available fields have been limited. In addition, the aromatic polyimide had low light transmittance and was impossible to change directly to polyimide in imidized form. In order to overcome such disadvantages, recent studies have focused on the development of novel polyimides which not only have excellent processability but also maintain excellent properties.

Particularly, various studies have focused on π-conjugated polyimide. Due to the luminescence and electronic properties of polyimide, such studies are likely to be applied to optoelectronics and photonics. Partially, pyridine and its derivatives are of more interest because pyridine is an electron-poor aromatic heterocyclic substituent with a local, non-covalent electron pair in the SP ² orbital at the nitrogen atom. Accordingly, the pyridine-containing polyimide can increase the electron affinity to improve the electron-transporting property and provide the possibility of proton doping of the unshared electron pair as a method of changing the luminescence property. Many conjugated polymers containing pyridine in the main chain have been synthesized. Because materials have excellent optical properties, they are also being applied to the development of polymer optoelectronic and organic photoluminescent materials. However, these materials have disadvantages such as low solubility and glass transition temperature, and thus their application is limited.

The coloration of the aromatic polyimide is mainly caused by the charge transfer between the molecules between the diamine, the electron donor, and the dianhydride, the electron acceptor. In recent years, efforts have been made to synthesize fluorinated aromatic polyimides, particularly trifluoromethyl-containing polyimides. By introducing bulky-CF ₃ to the polyimide main chain, not only the solubility but also the light transmittance can be improved, the water absorption rate can be lowered, the polarizability of the CF bond can be lowered, and the free volume can be also increased .

Multifunctional comonomers have been used to include branched segments in polyimide structures, making the material more suitable for processing and application. Most polymers are of increasing interest due to their unique structural properties, excellent physical and chemical properties, and wide application range. Recently, some researchers have produced hyperbranched polyimide (hyperbranched polyimide). Such polyimide not only has excellent properties of polyimide such as high heat resistance, high strength and low dielectric constant, but also has high solubility, low viscosity and hardness.

An object of the present invention is to provide a polyimide film excellent in thermal and mechanical properties and excellent in dielectric constant and optical characteristics.

It is also an object of the present invention to provide a polyimide for use in the production of the film and a process for producing the same.

In order to accomplish the above object, the present invention provides a polyimide represented by the following general formula (1) or (2).

[Chemical Formula 1]

(2)

In the above formulas (1) and (2)

Ar ₁ is a C ₆ to C ₃₆ aryl group, and the aryl group may be substituted or unsubstituted with a C ₁ to C ₁₂ alkyl group or a C ₁ to C ₁₂ haloalkyl group,

and n is an integer of 50 to 200. [

The present invention also provides a process for producing the polyimide represented by the above formula (1).

The present invention also provides a process for producing the polyimide represented by the above formula (2).

In addition, the present invention provides a film comprising the polyimide copolymer.

The polyimide of the present invention is excellent in solubility in an organic solvent. The polyimide film containing the polyimide copolymer has high transparency, flexibility and strength, excellent thermal and mechanical properties, and high permittivity and optical properties.

1 is a graph showing the results of ¹ H-NMR analysis of the monomers synthesized in Synthesis Examples 1 to 3, respectively.
2 is a graph showing the results of ¹ H-NMR analysis of the polyimide synthesized in Examples 1 and 2 and Comparative Example 1, respectively.
3 is a graph showing FTIR analysis results of the polyimide synthesized in Example 1. FIG.
4 is a graph showing the results of differential scanning calorimetry of polyimide synthesized in Examples 1 to 4 and Comparative Examples 1 and 2, respectively.
5 is a graph showing the results of thermogravimetric analysis of the polyimides synthesized in Examples 1 and 2 and Comparative Example 1, respectively.
6 is a graph showing the results of thermogravimetric analysis of the polyimides synthesized in Examples 3 and 4 and Comparative Example 2, respectively.
7 is a graph showing UV-Vis spectra of the copolymers synthesized in Examples 1 and 2, respectively.

Hereinafter, the present invention will be described.

The present invention provides a polyimide represented by the following general formula (1) or (2).

In the above Formulas 1 and 2,

Ar ₁ is a C ₆ to C ₃₆ aryl group, and the aryl group may be substituted or unsubstituted with a C ₁ to C ₁₂ alkyl group or a C ₁ to C ₁₂ haloalkyl group,

and n is an integer of 50 to 200. [

,

에서 선택된다.The Ar < ₁ >

,

.

The polyimide represented by the above formula (1) or (2) can be prepared by various methods.

According to an embodiment of the present invention, the polyimide of Formula 1 may be prepared by mixing a dianhydride of Formula 3, an aromatic diamine of Formula 4, and a diamine monomer of Formula 5, Synthesizing an intermediate to be displayed, and curing the intermediate of formula (6).

[Reaction Scheme 1]

In Formulas (5) and (6), Ar ₁ and n are the same as defined in Formula (1).

The polyimide represented by Formula 1 according to Reaction Scheme 1 may be prepared by the following process, but is not limited thereto.

First, the intermediate (linear polyamic acid) represented by Formula 6 is synthesized by reacting the dianhydride of Formula 3, the aromatic diamine of Formula 4, and the diamine of Formula 5.

An intermediate represented by the formula (6) is synthesized by a polycondensation reaction, the solvent used is not specifically limited, but is preferable to use the N- methyl-2-pyrrolidone (N -methyl-2-pyrrolidinone, NMP) And stirring at room temperature for 24 hours.

The mixing ratio of the dianhydride, the aromatic diamine and the diamine is not particularly limited, but is preferably a molar ratio of dianhydride: aromatic diamine: diamine = 2: 1: 1.

Wherein the diamine monomer is prepared by mixing a 4-nitroacetophenone and a benzaldehyde derivative (Ar ₁ -CHO) to form a polymer and mixing the polymer with hydrazine and reducing .

In the benzaldehyde derivative (Ar ₁ -CHO), Ar ₁ is a C ₆ to C ₃₆ aryl group, and the aryl group is a C ₁ to C ₁₂ alkyl group, a C ₁ to C ₁₂ haloalkyl group, or a C ₁ to C ₁₂ ≪ / RTI > arylamine group of formula < RTI ID = 0.0 >

,

에서 선택되며, 상기 벤즈알데하이드 유도체는 벤즈알데하이드, 4-트리플루오로메틸 벤즈알데하이드인 것이 바람직하다.The Ar < ₁ >

,

, And the benzaldehyde derivative is preferably benzaldehyde, 4-trifluoromethylbenzaldehyde.

Specifically, a benzaldehyde derivative and a nitroacetophenone are synthesized as a dinitro or trinitro compound through the Chichibabin reaction in the presence of ammonium acetate and acetic acid.

The synthesized dinitro or trinitro compound forms a diamine monomer by reduction in the presence of hydrazine

[Reaction Scheme 3]

Next, a linear polyimide of the above formula (1) is formed by curing for intermediate thermal imidization represented by the above formula (6).

The curing temperature and time are not particularly limited, but the temperature is preferably in the range of 80 to 250 ° C, and the curing time is preferably 1 to 8 hours.

According to another embodiment of the present invention, the polyimide of Formula 2 may be prepared by reacting the dianhydride of Formula 3, the aromatic diamine of Formula 4, the diamine of Formula 5, and the triamine monomer of Formula 7, And synthesizing an intermediate represented by the following formula (8) and curing the intermediate of the following formula (8).

[Reaction Scheme 2]

In the formula (8), Ar ₁ and n are the same as defined in the above formula (2).

The polyimide represented by Formula 2 according to Reaction Scheme 2 may be prepared by the following process, but is not limited thereto.

First, the intermediate (branched polyamic acid) represented by Formula 8 is synthesized by reacting the dianhydride of Formula 3, the aromatic diamine of Formula 4, the diamine of Formula 5, and the triamine of Formula 7.

An intermediate represented by the formula (8) is synthesized by a polycondensation reaction, the solvent used is not specifically limited, but is preferable to use the N- methyl-2-pyrrolidone (N -methyl-2-pyrrolidinone, NMP) And stirring at room temperature for 24 hours.

The mixing ratio of the dianhydride, the aromatic diamine, the diamine, and the triamine is not particularly limited, but is preferably a molar ratio of dianhydride: aromatic diamine: diamine: triamine = 0.5: 2: 1:

Next, the intermediate represented by the formula (8) is cured for thermal imidization to form the branched polyimide of the formula (2).

The curing temperature and time are not particularly limited, but the temperature is preferably in the range of 80 to 250 ° C, and the curing time is preferably 1 to 8 hours.

The linear polyimide represented by the formula (1) and the branched polyimide represented by the formula (2) of the present invention may be used in the form of a mixture of m-cresol, NMP, N, N-dimethylformamide (DMF), dimethylsulfoxide, N, N-dimethylacetamide And the like. In addition, the film comprising the polyimide of the present invention is transparent, flexible, and excellent in strength. It also exhibits excellent thermal and mechanical properties and exhibits excellent dielectric constant and optical properties.

Specifically, the film comprising the polyimide of the present invention has a glass transition temperature of 264 to 331 DEG C and exhibits excellent thermal stability at a 10% mass change temperature of 580 to 620 DEG C in a nitrogen atmosphere. It also exhibits UV absorption in the region of 200 to 400 nm, has a blocking wavelength of 372 to 392 nm and exhibits a low dielectric constant in the range of 3.897 to 4.276 at 1 MHz.

Further, the fluoro group-containing polyimide of the present invention exhibits superior permeability and flexibility than non-fluorinated polyimide due to the insertion of the branched moiety. Such a fluoride-introduced polyimide is more suitable as an engineering material.

Hereinafter, the present invention will be described in detail with reference to examples. However, these examples are for illustrating the present invention specifically, and the scope of the present invention is not limited to these examples.

[material]

4- (Trifluoromethyl) benzaldehyde, 4-nitrobenzaldehyde, benzaldehyde and 4-nitroacetophenone are commercially available under the trade name of Tokyo Chemical Co., Tokyo Chemical Co., LTD.). 5,5'-biisobenzofuran-1,1 ', 3,3'-tetraone, BPDA), 4,4'- (4,4'-oxydianiline, ODA), glacial acetic acid, ammonium acetate, ferric chloride hexahydrate, anhydrous ethanol and hydrazine monohydrate. monohydrate, 80 vol .-%) was purchased from Aldrich Chemical Co. and used without further purification. Carbon powder (200 mesh) was activated at 110 ° C for 4 hours. N- methyl-2-pyrrolidone (N -methyl-2-pyrrolidinone, NMP) was used and dried with calcium hydride (calcium hydride), distilled.

[ Synthetic example  1] 4,4 '-( 4- Phenylpyridine -2,6- Dill ) Dibenzylamine ( DAPP )

Benzaldehyde (3.18 g, 0.03 mol), 4-nitroacetophenone (9.91 g, 0.06 mol), ammonium acetate (30 g) and glacial acetic acid (50 ml) were mixed and refluxed for 3 hours. The resulting mixture was cooled and the monomers were precipitated. Collected by filtration, and then washed with acetic acid and cold ethanol. The monomers collected by filtration were recrystallized using N, N-dimethylformamide, and the obtained monomers were dried under a vacuum of 80 캜. After drying, the resulting monomer (5 g), ferric chloride hexahydrate (0.20 g), carbon powder (0.7 g) and ethanol (100 ml) were mixed and refluxed. Thereafter, a mixture of ethanol (14 ml) and hydrazine hydrate (14 ml) was added dropwise over 2 hours. After the addition, the final mixture was refluxed for at least 12 hours. Then, it was filtered and poured into deionized water, then the precipitate was collected, recrystallized in ethanol, and dried under a vacuum of 60 ° C.

Yield: 63 wt.%, Melting point: 225 占 폚. FTIR (KBr): 3400, 3334, and 3210 (-NH2), 1595 and 1540 (pyridine) cm ^-1 . _{^{1 H NMR (DMSO- d 6)}} δ (ppm): 8.01-8.03 (d, 4H), 7.93-7.95 (d, 2H), 7.80-7.81 (d, 2H), 7.45-7.56 (m, 3H), 6.68-6.70 (d, 4H), 5.45 (s, 4H).

[ Synthetic example  2] 4,4 '- (4- (4- ( Trifluoromethyl ) Phenyl ) Pyridine-2,6- Dill ) Dibenzylamine ( FDAPP )

4-Trifluoromethylbenzaldehyde (3.0 g, 0.016 ml), 4-nitroacetophenone (5.55 g, 0.03 ml), ammonium acetate (20 g) and glacial acetic acid (50 ml) were mixed and refluxed for 4 hours. The resulting mixture was cooled and the monomers were precipitated. Collected by filtration, and then washed with acetic acid and cold ethanol. The monomers collected by filtration were recrystallized using N, N-dimethylformamide, and the obtained monomers were dried under a vacuum of 80 ?. After drying, the resulting monomer (5 g), ferric chloride hexahydrate (0.20 g), carbon powder (0.7 g) and ethanol (100 ml) were mixed and refluxed. Thereafter, a mixture of ethanol (14 ml) and hydrazine hydrate (14 ml) was added dropwise over 2 hours. After the addition, the final mixture was refluxed for at least 12 hours. Then, it was filtered and poured into deionized water, and then the precipitate was collected, recrystallized in ethanol, and dried under a vacuum of 60 ° C.

Yield: 62 wt.%. melting point: 240 캜. FTIR (KBr): 3400, 3334, and 3210 (NH 2), 1595 and 1540 (pyridine) cm ^-1 . ≪ ¹ > H NMR (DMSO- _{d 6) δ (ppm):} 8.02-8.04 (d, 4H), 7.94-7.96 (d, 2H), 7.80-7.81 (d, 2H), 7.48-7.56 (m, 4H), 6.68-6.72 (m, 6H), 5.42 (s, 6H).

[ Synthetic example  3] 4,4 ', 4 "- (pyridine-2,4,6-triyl) Tribenzeneamine ( TAPP )

4-Nitrobenzaldehyde (4.53 g, 0.03 mol), 4-nitroacetophenone (9.91 g, 0.06 mol), ammonium acetate (30 g) and glacial acetic acid (50 ml) were mixed and refluxed for 3 hours. The resulting mixture was allowed to cool, and the precipitated red monomer was collected by filtration and washed with acetic acid and cold ethanol. The monomers collected by filtration were recrystallized using N, N-dimethylformamide, and the obtained monomers were dried under a vacuum of 80 캜. After drying, the obtained monomer (7.5 g), ferric chloride hexahydrate (0.30 g), carbon powder (0.7 g) and ethanol (100 ml) were mixed and refluxed. Thereafter, a mixture of ethanol (20 ml) and hydrazine hydrate (20 ml) was added dropwise for 2 hours. After the addition, the final mixture was refluxed for at least 12 hours. Then, it was filtered and poured into deionized water, and then the precipitate was collected, recrystallized in ethanol, and dried under a vacuum of 60 ° C.

Yield: 72 wt.%. melting point: 249.8 캜. FTIR (KBr): 3400, 3334, and 3210 (NH 2), 1595 and 1540 (pyridine) cm ^-1 . _{^{1 H NMR (DMSO- d 6)}} δ (ppm): 7.96-7.98 (d, 4H), 7.67-7.69 (d, 2H), 7.66 (s, 2H), 6.68-6.70 (d, 2H), 6.65- 6.67 (d, 4H), 5.45 (s, 2H), 5.38 (s, 4H).

[ Example  One] DAPP - PI Manufacturing

N- methyl-2-pyrrolidinone (12 ml), DAPP (0.35 g, 1.0 mmol) synthesized in Synthesis Example 1 and ODA (0.20 g, 1.0 mmol) were added to a 50 ml three-necked round flask and stirred. , 2.0 mmol) was slowly added and the mixture was stirred at room temperature for 24 hours. The mixture was then poured onto a glass plate. The glass plate on which the mixture was poured was dried in an oven at 80 DEG C for 8 hours and dried at 120, 150, 200 and 250 DEG C for 1 hour, respectively. The dried glass plate was immersed in warm water, and the resulting DAPP-PI film was peeled from the glass plate.

[ Example  2] FDAPP - PI Manufacturing

Was prepared in the same manner as in Example 1 except that FDAPP synthesized in Synthesis Example 2 was used instead of DAPP.

[ Example  3] Br - DAPP - PI Manufacturing

N- methyl-2-pyrrolidinone (12 ml), DAPP (0.35 g, 1.0 mmol) synthesized in Synthesis Example 1, TAPP and ODA (0.20 g, 1.0 mmol) synthesized in Synthesis Example 3 were added to a 50 ml three- After stirring, BPDA (0.59 g, 2.0 mmol) was slowly added and the mixture was stirred at room temperature for 24 hours. The mixture was then poured onto a glass plate. The glass plate on which the mixture was poured was dried in an oven at 80 DEG C for 8 hours and dried at 120, 150, 200 and 250 DEG C for 1 hour, respectively. The dried glass plate was immersed in warm water, and the resulting Br-DAPP-PI film was peeled from the glass plate.

[ Example  4] Br - FDAPP - PI Manufacturing

Was prepared in the same manner as in Example 3, except that FDAPP synthesized in Synthesis Example 2 was used instead of DAPP.

[ Comparative Example  One] ROOM - BPDA - PI Manufacturing

Was prepared in the same manner as in Example 1, except that DAPP was not used.

[ Comparative Example  2] Br - ROOM - BPDA - PI Manufacturing

Was prepared in the same manner as in Example 3, except that DAPP was not used.

[ Experimental Example  One] PI Check the structure of

1) ¹ H-NMR analysis

The structures of DAPP, FDAPP, TAPP, and linear polyimide synthesized in Synthesis Examples 1 to 3, Examples 1 and 2, and Comparative Example 1 were confirmed by ¹ H-NMR spectroscopy. The results are shown in FIGS. 1 and 2 . At this time, ¹ H-NMR spectroscopy was performed using a Bruker DRX (400 MHz) spectrometer, and DMSO-d ₆ and tetramethylsilane (TMS) were used as solvents and internal standards, respectively.

2) FTIR analysis

In addition, FTIR analysis of DAPP-PI synthesized in Example 1 was performed using a SCINCO FTIR analyzer, and the results are shown in FIG.

3) Results

Referring to the results of DAPP, FDAPP and TAPP in Fig. 1, peaks of aromatic rings appeared at 6.68 to 8.14 ppm, and -NH ₂ peaks at 5.46 ppm.

As can be seen from Fig. 2, in the case of the linear polyimide, the peaks of the aromatic rings appeared at 7.00 to 7.04, 7.47 to 7.55 and 8.10 to 8.37 ppm, respectively, and the peaks of the dianhydride and non-pyridinediamine phenyl ring 7.80 ~ 8.04 and 7.58 ~ 7.65ppm, respectively. The integration ratio of peaks of these aromatic rings was verified by the molar ratio of each component of the copolymer.

[ Experimental Example  2] PI Of solubility

The solubility of the polyimide prepared in each of Examples 1 to 4 and Comparative Examples 1 and 2 was confirmed by dissolving 100 mg of polyimide in each of the solvents (900 mg) listed in Table 1 below at room temperature and high temperature, Table 1 shows the results.

Polyimide was excellent in solubility in organic solvents such as NMP and m-cresol at room temperature and dissolved in solvents such as DMSO, DMAc and DMF at high temperatures. Because of the limited flexibility of the ether linkages, the polyimides produced exhibit marginal solubility, but the introduction of bulky, external trifluoromethylphenyl and pyridine moieties on the polymer backbone reduces the interaction between the polymer chains, The solubility can be improved by bonding.

The solubility of the polyimide varies depending on the dianhydride used. Fluorinated polyimides, FDAPP-PI and Br-FDAPP-PI, were more soluble than non-fluorinated polyimides in strong polar solvents such as m-cresol, NMP, DMAc and DMF at room temperature. In addition, the branched polyimides exhibited similar solubilities and better solubility than the linear polyimides. As a result, it can be seen that the introduction of the trifluoromethyl group can improve the solubility of the polyimide.

Organic solvent m -Cresol NMP DMAc DMF DMSO THF Comparative Example 1 ++ ++ + + + Example 1 ++ ++ + + + Example 2 ++ ++ + + + Comparative Example 2 ++ ++ + + + Example 3 ++ ++ + + + Example 4 ++ ++ + + +

++: Soluble at room temperature, + -: partly soluble, +: soluble upon heating, -: insoluble even upon heating.

[ Experimental Example  3] PI Differential scanning calorimetry

Differential scanning calorimetry of the polyimides prepared in Examples 1 to 4 and Comparative Examples 1 and 2 was performed using Perkin-Elmer DSC 7 at a heating rate of 20 ° C / min under nitrogen. The results are shown in FIG. 4 .

As shown in Fig. 4, none of the polyimides of the Examples exhibited crystallization or fusing transaction temperatures.

[ Experimental Example  4] PI Of glass transition temperature

The glass transition temperatures of the polyimides prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were measured by refraction of the midpoint in the graph of the heat capacity versus temperature shown in FIG. 4, and the results are shown in Table 2 below.

As shown in Table 2, the glass transition temperature was in the range of 264 to 343 DEG C and increased with the insertion of pyridine and fluorine groups. In particular, FDAPP-PI and Br-FDAPP-PI derived from FDAPP have the highest glass transition temperature due to the influence of the trifluoromethylphenyl group enhancing the chain strength. In addition, the branched polyimide had a lower glass transition temperature than the linear polyimide, and thus the strength was lower than that of the linear polyimide. This was thought to be due to the influence of the bifurcated moieties to make the chain flexible.

Polymer Yield (%) ηinh ^a
(dL / g) Film quality ^b T _g (° C) T ₅ (캜) T ₁₀ (캜) Comparative Example 1 96 0.68 C, F and T 290 530 571 Example 1 94 0.71 C, F and T 331 573 608 Example 2 95 0.73 C, F and T 343 592 620 Comparative Example 2 96 0.67 C, F and T 284 520 559 Example 3 97 0.69 C, F and T 264 560 580 Example 4 95 0.68 C, F and T 270 578 597

^a Measured on 0.5% polymer solution in NMP at 25 ℃. ^b C: clear, F: flexible, T: tough.

[ Experimental Example  5] Confirmation of Thermal Stability of Copolymer

The thermal stability of the polyimide films prepared in each of Examples 1 to 4 and Comparative Examples 1 and 2 was measured with a Perkin-Elmer TGA 7 analyzer. The results are shown in FIGS. 5, 6 and Table 2.

The polymer film does not exhibit weight loss before the scanning temperature reaches 530 캜, indicating that pyrolysis does not occur. The 5% and 10% weight loss temperatures (T ₅ and T ₁₀ ), which are the criteria for determining the thermal stability of the high temperature polymer, were in the range of 520-593 ° C and 559-620 ° C, respectively. This indicated that the polyimide film was excellent in thermal stability. According to Table 2, the pyridine-containing polyimide was found to have better thermal stability than the pyridine-free polyimide. This is the result obtained by introducing a pyridine ring into the polymer main chain. In addition, both the linear and branched polyimides containing trifluoromethyl (FDAPP-PI and BR-FDAPP-PI) had higher 5% and 10% weight loss temperatures than non-fluorinated polyimides. It is believed that the introduction of the strong negative affinity of the -CF ₃ group limits the movement of the polymer-link and improves the thermal stability. In addition, the branched polyimide is more susceptible to pyrolysis because of its more flexible structure than the linear polyimide.

[ Experimental Example  6] PI Optical properties of

The optical properties of the polyimide prepared in each of Examples 1 and 2 were measured using a Perkin-Elmer 1-17 UV spectrophotometer at 200-450 nm in an NMP solution protonated with 10 ^-4 g / ml NMP solution and HCl, The results are shown in FIG.

DAPP-PI and FDAPP-PI have absorption bands in the region of 200 to 400 nm and absorption maxima at 265 nm due to the transfer of n-π ^{* of the} imide group and the transfer of the π-π ^* of phenyl and pyridine groups. When protonated with different concentrations of HCl, the intensity of the pyridine chromophore decreases, and the shift of this spectrum is believed to be due to the low n-π ^* transition energy of the positively charged polymer.

The cut-off wavelengths (λ ₀ ) of these polymers are shown in Table 3 below, ranging from 372 to 392 nm. The linear and branched fluoropolyimides FDPPA-PI and Br-FDPPA-PI had low blocking wavelength and high optical transmittance. This is believed to be due to the reduction of the charge transfer complex between molecules between the diamine, an alternating electron donor, and the dianhydride moiety, an electron acceptor. Bulk and electron-withdrawing -CF ₃ groups in diamine moieties reduce the formation of intermolecular charge transfer complexes between polymer chains through steric hindrance and inducing effects. Also, because of the low polarizability of the CF bond, the secondary effect of the -CF ₃ group on film permeability is weaker in the cohesive force between the molecules. Because of the effect of the branching unit, the branched polyimide can overcome steric hindrances more easily than the linear polyimide, has a relatively higher cutting wavelength (? ₀ ) and low optical transmission.

Polymer Film thickness (탆) λ ₀ ^a (nm) ε ^b (1 MHz) Comparative Example 1 61 439 3.991 Example 1 68 381 4.189 Example 2 71 372 3.897 Comparative Example 2 67 446 4.192 Example 3 65 392 4.276 Example 4 69 385 4.015

^a ? ₀ , the cut-off wavelength. ^b ?, dielectric constant at 1 MHz.

[ Experimental Example  7] Permittivity of Copolymer

The permittivities of the polyimides prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were measured using an impedance analyzer (HP-4194A, Hewlett-Packard), and the results are shown in Table 3.

As can be seen from Table 3, the dielectric constant of the polyimide at 1 MHz ranges from 3.897 to 4.276. Compared to -CF ₃ free analogs, the fluorinated polyimide film had a lower dielectric constant. This is thought to be due to an increase in free volume and a decrease in polarizability. Binding of the bulky trifluoromethylphenyl groups blocked the polymer chains and reduced the interchain charge transfer of the highly polar dianhydride groups. In addition, large fluorine atoms increase the free volume fraction in the polymer, thereby reducing the number of polar functional groups in the unit volume. Also, the large electronegativity of the CF bond has lowered the electron polarization in the polymer. As a result, the fluorinated polyimide, FDAPP-PI film, had a lower dielectric constant of 3.897 at 1 MHz than the non-fluorinated polyimides ODA-BPDA-PI and DAPP-PI. Because of the branching effect, the branched polyimide contained a low free volume in the polymer and was more strongly affected by the polar functional group, causing electron polarization in the polymer and affecting the dielectric constant. As a result, the dielectric constant of the branched polyimide was higher than that of the linear polyimide.

Claims (5)

A polyimide represented by the following formula (1) or (2)
[Chemical Formula 1]

(2)

In the above formulas (1) and (2)
Ar ₁ is a C ₆ to C ₃₆ aryl group, and the aryl group may be substituted or unsubstituted with a C ₁ to C ₁₂ alkyl group or a C ₁ to C ₁₂ haloalkyl group,
and n is an integer of 50 to 200. [ Synthesizing an intermediate represented by Formula 6 by polymerizing a dianhydride of Formula 3, an aromatic diamine of Formula 4, and a diamine monomer of Formula 5 below; And
A step of curing the intermediate represented by the following formula 6
A process for producing a polyimide represented by the following formula (1)
(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

[Chemical Formula 1]

In the above formulas (1), (5) and (6)
Ar ₁ is a C ₆ to C ₃₆ aryl group, and the aryl group may be substituted or unsubstituted with a C ₁ to C ₁₂ alkyl group or a C ₁ to C ₁₂ haloalkyl group,
and n is an integer of 50 to 200. [ Synthesizing an intermediate represented by the following formula (8) by polymerizing a dianhydride represented by the following formula (3), an aromatic diamine represented by the following formula (4), a diamine represented by the following formula (5) and a triamine monomer represented by the following formula (7) And
A step of curing the intermediate represented by the following formula (8)
A process for producing a polyimide represented by the following formula (2)
(3)

[Chemical Formula 4]

[Chemical Formula 5]

(7)

[Chemical Formula 8]

(2)

In the above Formulas 2, 5 and 8,
Ar ₁ is a C ₆ to C ₃₆ aryl group, and the aryl group may be substituted or unsubstituted with a C ₁ to C ₁₂ alkyl group or a C ₁ to C ₁₂ haloalkyl group,
and n is an integer of 50 to 200. [ The method according to claim 2 or 3,
The diamine monomer of Formula 5 may be prepared by mixing 4-nitroacetophenone and a benzaldehyde derivative (Ar ₁ -CHO) to form an intermediate; And
Mixing said intermediate with hydrazine and reducing said intermediate,
Wherein Ar ₁ is a C ₆ to C ₃₆ aryl group and the aryl group is substituted or unsubstituted with a C ₁ to C ₁₂ alkyl group, a C ₁ to C ₁₂ haloalkyl group, or a C ₁ to C ₁₂ arylamine group A process for producing polyimide. A film comprising the polyimide of claim 1.

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