CN110878140B - Novel aromatic polyimide containing imide flexible group and preparation method thereof - Google Patents

Abstract

The invention discloses novel aromatic polyimide containing imide flexible groups and a preparation method thereof, wherein the preparation method comprises the following steps: firstly, 3, 5-diamino-N- (4' -R phenyl) -N- (2 '/4 ' -R benzyl) benzamide compound reacts with dianhydride monomer to generate viscous polyamic acid solution, and then the viscous polyamic acid solution is obtained by dilution, dehydration and drying; the aromatic polyimide of the asymmetric diamine containing the imide flexible group has good thermal stability, excellent light transmission, film forming property and excellent organic solubility, and can be applied to the fields of medicine, microelectronics, aerospace and the like.

Description

Novel aromatic polyimide containing imide flexible group and preparation method thereof

Technical Field

The invention relates to the field of organic synthesis, in particular to novel aromatic polyimide containing imide flexible groups and a preparation method thereof.

Background

Aromatic Polyimide (PI) is a polymer material with excellent comprehensive performance and wide application field, and has been widely applied in various fields of aviation, aerospace, medicine, chemical industry and the like due to a series of excellent performances such as high thermal stability, good mechanical property, low dielectric constant, wide solubility spectrum, good corrosion resistance and the like after the development of more than one hundred years. However, most polyimides have poor solubility, meltability and processability due to the rigid structure of their main chain, and thus the application fields are greatly limited.

The outstanding comprehensive performance of the polyimide material is benefited by the strong interaction between the molecular chains and the molecular chains, and the action can lead the molecular chains of the polyimide to be closely stacked, thereby improving the solvent resistance and the heat resistance of the polyimide. Meanwhile, the mobility of the polyimide is limited due to the close packing of molecular chains, so that the solubility, the processability and the like of the polyimide are not satisfactory, and the application of the polyimide in certain high and new technical fields is limited. If asymmetric groups, large conjugated side groups, flexible links and fluorine atoms are introduced, the solubility of the polyimide material can be improved, the characteristics of poor light transmission in an ultraviolet region and the like can be improved, the light transmission of the material can be improved and the dielectric constant can be reduced by introducing the fluorine atoms, and the absorption loss in a communication band can be reduced by applying the fluorine atoms to an optical waveguide material; and the introduction of large aromatic side groups can reduce the birefringence value of the conventional polyimide material, thereby further reducing the polarization loss of the material in use.

Modification of polyimide was studied as early as the eighties of the twentieth century by yoshio imai of the university of tokyo industries, japan, frankw of the university of Akron, usa, harris, and the like. In 1999, Jianan Ping Chen et al reported several methods for synthesizing carbazole-containing polyimides in Macromolecules, Vol.32,3171-3177, the diamine monomers used have simple synthesis steps but no obvious modification, and the solubility and thermal stability of the polyimide materials synthesized by the diamine monomers are not ideal. There are still significant limitations to the processing and application of polyimide materials. In the same year, David et al have reported a synthesis method for preparing polyimide from a novel tetracarboxylic dianhydride monomer containing phenyl and tert-butyl, m-phenylenediamine, 4' -diaminodiphenyl ether, etc., in Journal of Polymer Science, Vol.37,805-814, and the introduction of the dianhydride monomer into phenyl and tert-butyl has improved solubility, but has not yet reached the ideal level for industrial application. The polyimide obtained by the methods has multiple synthesis steps, complicated post-treatment process and higher cost, and is not beneficial to large-scale industrial production.

Disclosure of Invention

In order to solve the problems, the invention provides novel aromatic polyimide containing imide flexible groups and a preparation method thereof, and the polyimide material synthesized by the method has strong solubility, light transmittance and film-forming property.

The technical scheme of the invention is as follows:

a novel aromatic polyimide containing imide flexible group, the number average molecular weight Mn is 19300-; having a repeating unit represented by the formula (1):

in the formula (1), the R, R' group is one of hydrogen, aliphatic hydrocarbon, aromatic hydrocarbon, alicyclic hydrocarbon, aliphatic group containing heteroatom, aromatic heterocycle, alicyclic heterocycle or mixture group thereof.

In the formula (1), the X group is any one of the following groups,

preferably, in the novel aromatic polyimide containing an imide flexible group of the present invention represented by formula (1), the group R, R' is one of the following groups:

the preparation method of the novel aromatic polyimide containing the imide flexible group specifically comprises the following steps:

(a) under the protection of inert gas, dissolving 3, 5-diamino-N- (4'-R phenyl) -N- (2'/4 '-R benzyl) benzamide compound in an aprotic solvent, then adding dianhydride monomer in 2-3 times, stirring at room temperature for reaction for 12-28 h, wherein the molar ratio of the added 3, 5-diamino-N- (4' -R phenyl) -N- (2 '/4' -R benzyl) benzamide compound to the dianhydride monomer is 1 (1-1.1);

(b) under the protection of inert gas, adding an aprotic solvent into the polyamic acid solution, stirring and reacting for 2-4 h, adding a dehydrating agent, and heating to 100 ℃ to react for 6 h; after the reaction is finished, cooling the reaction liquid to room temperature, then dropwise adding distilled water, filtering, washing with water, and placing the precipitate at 80 ℃ for vacuum drying to obtain powder, namely the novel aromatic polyimide.

Preferably, in the preparation method of the novel aromatic polyimide containing the imide flexible group, the inert gas is nitrogen or argon.

Preferably, the novel aromatic polyimide containing imide flexible group is prepared by the method that the 3, 5-diamino-N- (4' -R phenyl) -N- (2 '/4 ' -R benzyl) benzamide compound is represented by the general formula

The R, R' group in the general formula is preferably

Preferably, in the preparation method of the novel aromatic polyimide containing the imide flexible group, the aprotic solvent is at least one of N-methyl pyrazolidone, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, hexamethylphosphoric triamide or tetrahydrofuran.

Preferably, in the preparation method of the novel aromatic polyimide containing the imide flexible group, the volume ratio of the aprotic solvent added in the step (b) to the aprotic solvent added in the step (a) is 1/5-2/3.

Preferably, the novel aromatic polyimide containing imide flexible groups is prepared by a method in which the dianhydride monomer of step (a) is represented by the general formula

The X group is any one of the following groups,

preferably, the dianhydride monomer is one of pyromellitic dianhydride and 2,2 ', 3, 3' -biphenyl tetracarboxylic dianhydride.

Preferably, the novel aromatic polyimide containing imide flexible groups is prepared by a method in which the dehydrating agent in step (b) is one of an equimolar mixture of pyridine/acetic anhydride, an equimolar mixture of sodium acetate/acetic anhydride, or an equimolar mixture of triethylamine/acetic anhydride.

The basic process of the synthetic reaction of the invention is as follows:

advantageous effects

According to the invention, large aromatic side groups are introduced into asymmetric diamine monomers, including polycyclic aromatic hydrocarbon, alkyl aromatic hydrocarbon, heteroatom-containing aromatic hydrocarbon groups and the like, the regularity of molecular chains of the diamine monomers is destroyed, the molecular chains are twisted and show non-coplanarity, and when the diamine monomers and dianhydride monomers are polymerized to generate polymers, the conjugation effect of a polyimide system can be reduced, and the organic solubility of the polyimide system is improved; in addition, the introduction of the groups also increases the electron donating property of the diamine monomer, and meanwhile, the imide flexible group introduced into the main structure of the diamine monomer has a larger dihedral angle due to the flexible imide bond segment and the methylene group, so that the synthesized polyimide has higher conformation freedom and larger steric hindrance, and the formation and the stability of a charge transfer complex in a polyimide molecule are promoted, thereby being beneficial to the application of a polyimide material in the field of microelectronic storage. In addition, for some fluorine-containing diamine monomers, diamine monomers with different fluorine contents are copolymerized with certain acid anhydride, and the refractive index of the material can be further adjusted by adjusting the fluorine content of the polymer, so that a novel application of the material, namely the material can be applied to optical waveguide materials. Therefore, the polyimide material obtained from the diamine monomer based on the imide flexible group has good thermal stability, solubility and optical properties, and can be applied to the fields of microelectronics, aerospace and the like.

Drawings

FIG. 1 is an XRD diffractogram of polyimide powder of example.

FIG. 2 is an AFM three-dimensional view of a polyimide film of an example.

Detailed Description

The conception, the specific structure, and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below, so that the objects, the features, and the effects of the present invention can be fully understood. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.

Unless otherwise indicated, the starting materials described in the following examples of the present invention are available from Aladdin reagents (Shanghai) Co., Ltd.

The product of the invention needs 3, 5-diamino-N- (4 '-bromophenyl) -N- (4' -bromobenzyl) benzamide as a synthetic raw material, and the synthetic steps are as follows:

(1) adding 3, 5-dinitrobenzoyl chloride (3.44g,20.0mmol) into a 100ml three-neck flask, adding 20ml DMF, stirring to completely dissolve the mixture, adding 12.5ml triethylamine, dropwise adding 4-bromoaniline (5.53g, 24.0mmol) dissolved in 20ml DMF into the reaction system through a constant pressure dropping funnel, after dropwise adding, heating to 60 ℃ and stirring for 5 hours, tracking the reaction progress by TLC until the 3, 5-dinitrobenzoyl chloride is reacted, stopping the reaction, standing and cooling to room temperature. Pouring the reaction liquid into 100ml of mixed liquid of ethanol and water (the volume ratio is 2:1), separating out a large amount of bright yellow crystalline solid, carrying out vacuum filtration, washing the filter cake for 3 times by 100ml of ethanol and water at one time, and drying at the temperature of 60 ℃ in vacuum to obtain the product of 3, 5-dinitro-N- (4' -bromophenyl) benzamide.

(2) Adding 3, 5-dinitro-N- (4' -bromophenyl) benzamide (2.86g,7.80mmol), potassium carbonate (5.38g,39.0mmol) and 60ml of DMF into a 100ml three-necked bottle, stirring at room temperature until the 3, 5-dinitro-N- (4' -bromophenyl) benzamide is completely dissolved, the solution is red, adding p-bromobenzyl bromide/o-bromobenzyl bromide (2.91g,11.7mmol) into 10ml of DMF for dissolving, dropwise adding into the reaction system, after dropwise addition within 30min, heating to 60 ℃, refluxing for 4h, tracking the reaction by TLC until the 3, 5-dinitro-N- (4' -bromophenyl) benzamide is completely reacted, stopping the reaction, standing and cooling to room temperature, slowly pouring the reaction solution into 100ml of a mixed solution of ethanol and ice water (volume ratio of 1.5:1), stirring until a large amount of yellow precipitate is separated out, carrying out vacuum filtration, respectively washing a filter cake for a plurality of times by using ethanol and water, and carrying out vacuum drying for 6h at the temperature of 60 ℃ to obtain the product 3, 5-dinitro-N- (4' -bromophenyl) -N- (2 '/4 ' -bromobenzyl) benzamide.

(3) In N₂Under protection, 3, 5-dinitro-N- (4' -bromophenyl) -N- (2 '/4 ' -bromobenzyl) benzamide (2.78g,5.2mmol) was added to a 100ml three-necked flask, and a mixture of ethanol and water (8.8ml/4.4ml) was added thereto, followed by heating and stirring to obtain 3, 5-bis (tert-butyl) formamideMixing nitro-N- (4 '-bromophenyl) -N- (2'/4 '-bromobenzyl) benzamide with the solution uniformly, adding a mixture of iron powder (2.32g,41.6mmol) and glacial acetic acid (12ml) when the temperature is raised to 50 ℃, continuing to heat to 65 ℃, changing the yellow color of the mixed solution to black, refluxing for 3h, tracking the reaction by TLC until the 3, 5-dinitro-N- (4' -bromophenyl) benzamide is reduced completely, stopping the reaction, standing, cooling to room temperature, performing suction filtration under reduced pressure, adding CH into the filtrate₂Cl₂Until the layers are separated, the organic layer is collected and CH is added₂Cl₂And after 3 times of extraction, adding ammonia water to neutralize the solution until the solution is alkaline, carrying out vacuum filtration, drying the filtrate by using anhydrous sodium sulfate, and carrying out rotary evaporation on the filtrate after the vacuum filtration to obtain the product 3, 5-diamino-N- (4' -bromophenyl) -N- (2 '/4 ' -bromobenzyl) benzamide.

Example 1

(1)N₂To a 50ml three-necked flask were added 3, 5-diamino-N- (4 '-bromophenyl) -N- (4' -bromobenzyl) benzamide (0.3g,0.632mmol), 3, 5-dimethylphenylboronic acid (0.228g,1.52mmol), Pd (PPh) with protection₃)₄(0.0145g,0.0126mmol) and anhydrous potassium carbonate (0.349g,2.53mmol), then respectively adding 15ml of toluene and 7.5ml of distilled water, heating to 110 ℃, refluxing and stirring for about 5 hours, continuously generating bubbles in the reaction, stirring for 5 hours, closing the reaction, standing until the reaction is naturally cooled to room temperature, performing suction filtration under reduced pressure, separating the obtained filtrate, collecting a toluene layer, removing the solvent toluene by rotary evaporation to obtain a white solid, combining the solid with a filter cake, purifying by column chromatography, wherein the used solvents are ethyl acetate and n-hexane, and the polarity ratio of the solvents is ethyl acetate: n-hexane 5:1, and drying the obtained product at 90 ℃ for 12h in vacuum to obtain 3, 5-diamino-N- (4' -3 ", 5 ' -dimethyl biphenyl) -N- (4' -benzyl-3 ', 5 ' -dimethyl phenyl) benzamide, wherein the molecular formula is as follows:

(2) in N₂The product 3, 5-diamino-N- (4 '-3', 5 '-dimethyl biphenyl) -N- (4' -benzyl-3 ', 5' -dimethyl phenyl) benzene was added into a 50mL three-neck flask under protectionFormamide (0.105g,0.2mmol) and an aprotic solvent DMAc (5mL) are stirred at room temperature until the solid is completely dissolved, pyromellitic anhydride (0.0436g,0.2mmol) is slowly added in 3 batches and stirred at room temperature for 24 hours to obtain a light yellow viscous polyamic acid solution;

(3) in N₂Adding 2mL of DMAc into the polyamic acid solution under protection, diluting the solution, continuing stirring for 30min, and then adding 2mL of a pyridine/acetic anhydride mixture (molar ratio is 1:1) of a dehydrating agent; heating to 100 ℃, and continuously stirring for reaction for 5 hours; after the reaction is finished, naturally cooling the reactant to room temperature, slowly dropping the reaction solution into 30mL of distilled water drop by drop, and separating out a large amount of yellow precipitate in the reaction solution; filtering, washing with water, and vacuum drying at 80 deg.C to obtain white polyimide solid powder (PI-1) with molecular formula of

The yield was 92%.

The detection result of the product is as follows: infrared (KBr, cm)^-1)2945 (-C-H stretching vibration of CH 3), 1775 and 1725 (symmetric and asymmetric stretching of C ═ O), 1365(C-N stretching vibration); the molecular weight was measured by GPC, Mn 19400, Mw 34750, Mw/Mn 1.79; elemental analysis: theoretical value C, 79.68%; h, 5.33%; n, 5.16%; actual value C, 79.81%; h, 5.22%; n, 5.05%; TGA thermogravimetric analysis (N)₂):T_5％＝416℃,T_10％The residue rate at 800 ℃ was 50.2% at 452 ℃.

Example 2

(1)N₂To a 50ml three-necked flask were added 3, 5-diamino-N- (4 '-bromophenyl) -N- (4' -bromobenzyl) benzamide (0.3g,0.632mmol), 3, 5-dimethylphenylboronic acid (0.228g,1.52mmol), Pd (PPh) with protection₃)₄(0.0145g,0.0126mmol) and anhydrous potassium carbonate (0.349g,2.53mmol), respectively adding toluene 15ml and distilled water 7.5ml, heating to 110 ℃, refluxing and stirring for about 5h, continuously generating bubbles in the reaction, stirring for 5h, closing the reaction, standing for natural cooling to room temperature, carrying out vacuum filtration, layering the obtained filtrate, collecting the toluene layer, and removing the solvent toluene by rotary evaporation to obtain white solidAnd combining the solid and the filter cake, and purifying by column chromatography, wherein the solvents are ethyl acetate and n-hexane, and the polarity ratio is ethyl acetate: n-hexane 5:1, and drying the obtained product at 90 ℃ for 12h in vacuum to obtain 3, 5-diamino-N- (4' -3 ", 5 ' -dimethyl biphenyl) -N- (4' -benzyl-3 ', 5 ' -dimethyl phenyl) benzamide, wherein the molecular formula is as follows:

(2) in N₂Under protection, the product 3, 5-diamino-N- (4 '-3', 5 '-dimethyl biphenyl) -N- (4' -benzyl-3 ', 5' -dimethyl phenyl) benzamide (0.105g,0.2mmol) and DMAc (5mL) are added into a 50mL three-neck flask, stirred at room temperature until all solids are dissolved, 2 ', 3, 3' -biphenyl tetracarboxylic dianhydride (0.0588g,0.2mmol) is slowly added in 3 batches and stirred at room temperature for 24 hours to obtain a brown polyamic acid solution;

(3) DMAc (3mL) was added to dilute the solution, stirring was continued for 30min, and 2mL of pyridine/acetic anhydride mixture (molar ratio 1:1) was added; then heating to 100 ℃, and continuing stirring for 5 hours; after the reaction is finished, cooling to room temperature, slowly dropping the reaction solution into 30mL of distilled water, separating out a large amount of brown precipitate, filtering the precipitate, washing the precipitate with water, after the solvent is washed away, drying the precipitate at 80 ℃ in vacuum to obtain light yellow solid powder, namely polyimide (PI-2), wherein the molecular formula of the light yellow solid powder is as follows:

the yield was 94%.

The powder was examined for infrared (KBr, cm)^-1)2945(-CH₃C-H stretching vibration) 1770, 1725(C ═ O symmetric and asymmetric stretching), 1371(C-N stretching vibration); molecular weight determination by GPC, Mn 19670, Mw 32300, Mw/Mn 1.64; elemental analysis: theoretical values of C, 79.68%, H, 5.33%, N, 5.16%; found C, 79.49%; h, 5.46%; 5.41 percent of N; TGA thermogravimetric analysis (N)₂):T_5％＝397℃,T_10％The residue ratio at 431 ℃ and 800 ℃ was 49.6％。

Example 3

(1) In a 100mL three-necked flask, under nitrogen atmosphere, 3, 5-diamino-N- (4 '-bromophenyl) -N- (4' -bromobenzyl) benzamide (0.3g,0.632mmol), 4- (dianilino) phenylboronic acid (0.44g,1.52mmol), Pd (PPh)₃)₄(0.0145g,0.0126mmol) and anhydrous potassium carbonate (0.349g,2.53mmol), then respectively adding 15ml of toluene and 7.5ml of distilled water, heating to 110 ℃, refluxing and stirring for about 5 hours, continuously generating bubbles in the reaction, stirring for 5 hours, closing the reaction, standing until the reaction is naturally cooled to room temperature, performing suction filtration under reduced pressure, separating the obtained filtrate, collecting a toluene layer, removing the solvent toluene by rotary evaporation to obtain a white solid, combining the solid with a filter cake, purifying by column chromatography, wherein the used solvents are ethyl acetate and n-hexane, and the polarity ratio of the solvents is ethyl acetate: n-hexane 5:1 and the resulting product was dried under vacuum at 90 ℃ for 12h to give 3, 5-diamino-N- (4 '-phenyl-4 "-triphenylaminyl) -N- (4" -benzyl-4 "' -triphenylaminyl) benzamide. The molecular formula is as follows:

(2) in N₂Under protection, 3, 5-diamino-N- (4 '-phenyl-4' -trianilino) -N- (4 '-benzyl-4' -trianilino) benzamide (0.161g,0.2mmol) and N-methylpyrrolidone (6mL) were added to a 50mL three-necked flask and stirred at room temperature until all the solids were dissolved. Adding pyromellitic anhydride (0.0436g,2mmol) slowly in batches, and stirring at room temperature for 24h to obtain a dark purple amic acid solution;

(3) the solution was diluted with additional N-methylpyrrolidone (3mL) and then 2mL of equimolar pyridine/Ac was added₂Heating the mixture of O to 100 ℃, and continuously stirring for 5 hours; after the reaction is finished, cooling to room temperature, slowly dropping the reaction solution into 30mL of distilled water, separating out a large amount of brown precipitate, filtering, washing off the solvent by using water, and then drying the precipitate at 80 ℃ in vacuum to obtain purple solid powder, namely polyimide (PI-3), wherein the molecular formula of the polyimide is as follows:

the yield was 95%.

Infrared detection result (KBr, cm)^-1)1770, 1725 (symmetric and asymmetric expansion and contraction of C ═ O), 1365(C-N expansion and contraction vibration); the molecular weight is measured by GPC, Mn is 20320, Mw is 36900, and Mw/Mn is 1.82; elemental analysis: theoretical value C, 81.37%; h, 4.89%; n, 6.41%; found C, 81.24%; h, 5.05%; n, 6.56%; TGA thermogravimetric analysis (N)₂):T_5％＝412℃,T_10％The residue rate at 800 ℃ was 59.1% at 432 ℃.

Example 4

(1) In a 100mL three-necked flask, under nitrogen atmosphere, 3, 5-diamino-N- (4 '-bromophenyl) -N- (4' -bromobenzyl) benzamide (0.3g,0.632mmol), 4- (dianilino) phenylboronic acid (0.44g,1.52mmol), Pd (PPh)₃)₄(0.0145g,0.0126mmol) and anhydrous potassium carbonate (0.349g,2.53mmol), then respectively adding 15ml of toluene and 7.5ml of distilled water, heating to 110 ℃, refluxing and stirring for about 5 hours, continuously generating bubbles in the reaction, stirring for 5 hours, closing the reaction, standing until the reaction is naturally cooled to room temperature, performing suction filtration under reduced pressure, separating the obtained filtrate, collecting a toluene layer, removing the solvent toluene by rotary evaporation to obtain a white solid, combining the solid with a filter cake, purifying by column chromatography, wherein the used solvents are ethyl acetate and n-hexane, and the polarity ratio of the solvents is ethyl acetate: and (3) drying the obtained product for 12 hours at the temperature of 90 ℃ in vacuum to obtain 3, 5-diamino-N- (4 '-phenyl-4' -triphenylamine group) -N- (4 '-benzyl-4' -triphenylamine group) benzamide, wherein the molecular formula of the benzamide is as follows:

(2) in N₂Under protection, the product 3, 5-diamino-N- (4 '-phenyl-4' -triphenylamine) -N- (2 '-benzyl-4' -triphenylamine) benzamide (0.161g,0.2mmol) and 6mL of N-methylpyrrolidone are added into a 50mL three-neck flask, the mixture is stirred at room temperature until all solids are dissolved, 2 ', 3, 3' -biphenyl tetracarboxylic dianhydride (0.0588g,0.2mmol) is slowly added in batches, and the mixture is stirred at room temperature for 24 hours to obtain a dark yellow amic acid solution; then, the product is processedThe solution was diluted by addition of N-methylpyrrolidone (3mL) and then equimolar pyridine/Ac was added₂Heating the mixture of O to 100 ℃, and continuously stirring for 5 hours; after the reaction, the reaction mixture was cooled to room temperature, and the reaction mixture was slowly dropped into 50mL of distilled water to precipitate a large amount of yellow precipitate, which was then filtered and washed with water. Vacuum drying at 80 deg.C to obtain yellow solid powder, i.e. polyimide (PI-4) with molecular formula of

The yield was 95%.

Polyimide (PI-4) infrared detection result, (KBr, cm)^-1)1772, 1720 (symmetric and asymmetric expansion and contraction of C ═ O), 1365(C-N expansion and contraction vibration); the molecular weight measured by GPC was Mn 21700, Mw 33250, Mw/Mn 1.53; elemental analysis: theoretical value C, 79.61%; h, 4.29%; n, 6.63%; found C, 79.52%; h, 4.39%; n, 6.61%; TGA thermogravimetric analysis (N)₂):T_5％＝393℃,T_10％The residue rate at 800 ℃ was 57.3%.

Example 5

(1) In N₂To a 50ml three-necked flask were added 3, 5-diamino-N- (4 '-bromophenyl) -N- (4' -bromobenzyl) benzamide (0.3g,0.632mmol), 3,4, 5-trifluorophenylboronic acid (0.227g,1.52mmol), Pd (PPh) with the protection₃)₄(0.0145g,0.0126mmol) and anhydrous potassium carbonate (0.349g,2.53mmol), then respectively adding 15ml of toluene and 7.5ml of distilled water, heating to 110 ℃, refluxing and stirring for about 5 hours, continuously generating bubbles in the reaction, stirring for 5 hours, closing the reaction, standing until the reaction is naturally cooled to room temperature, performing suction filtration under reduced pressure, separating the obtained filtrate, collecting a toluene layer, removing the solvent toluene by rotary evaporation to obtain a white solid, combining the solid with a filter cake, purifying by column chromatography, wherein the used solvents are ethyl acetate and n-hexane, and the polarity ratio of the solvents is ethyl acetate: n-hexane 5:1, and the product obtained is dried for 12h at 90 ℃ in vacuum to obtain 3, 5-diamino-N- (4 '-3 ", 4", 5 "-trifluorobiphenyl) -N- (4" -benzyl-3 "', 4" ', 5 "' -trifluorophenyl) benzamide, the molecular formula of which is:

(2) in N₂Adding 3, 5-diamino-N- (4 '-3', 4', 5' -trifluorobiphenyl) -N- (4 '-benzyl-3', 4', 5' -trifluorophenyl) benzamide (0.111g,0.2mmol) and an aprotic solvent DMAc (5mL) into a 50mL three-neck flask under protection, stirring at room temperature until all solids are dissolved, slowly adding pyromellitic dianhydride (0.0436g,0.2mmol) in 3 batches, and stirring at room temperature for 24 hours to obtain a light yellow viscous polyamic acid solution;

(3) in N₂Adding 2mL of DMAc into the polyamic acid solution under protection, diluting the solution, continuing stirring for 30min, and then adding 2mL of a pyridine/acetic anhydride mixture (molar ratio is 1:1) of a dehydrating agent; heating to 100 ℃, and continuously stirring for reaction for 5 hours; after the reaction is finished, naturally cooling the reactant to room temperature, slowly dropping the reaction liquid into 30mL of distilled water drop by drop, and separating out a large amount of light yellow precipitate in the reaction liquid; filtering, washing with water, and vacuum drying at 80 deg.C to obtain light yellow polyimide solid powder (PI-5) with molecular formula of

The yield was 91%.

The detection result of the product is as follows: infrared (KBr, cm)^-1)1770, 1725 (symmetric and asymmetric expansion and contraction of C ═ O), 1365(C-N expansion and contraction vibration), 1043(C-F expansion and contraction vibration); molecular weight was measured by GPC, Mn is 19750, Mw is 36800, Mw/Mn is 1.86; elemental analysis: theoretical value C, 79.68%; h, 5.33%; n, 5.16%; found C, 79.48%; h, 5.46%; n, 5.38%; TGA thermogravimetric analysis (N)₂):T_5％＝215℃,T_10％The residue rate at 800 ℃ was 55.3% at 411 ℃.

Example 6

(1) In N₂To a 50mL three-necked flask, 3, 5-diamino-N- (4 '-3 ", 4", 5 "-trifluorobiphenyl) -N- (4" -benzyl-3 "', 4" ', 5 "' -trifluorophenyl) benzamide (0.111g,0.2mmol) and 6mL of a mixture (bulk) of N-methylpyrrolidone and DMAc were added under protectionVolume ratio of 2:1), stirring at room temperature until the solid is completely dissolved, slowly adding 2,2 ', 3, 3' -biphenyltetracarboxylic dianhydride (0.0588g,0.2mmol) in 3 batches, and stirring at room temperature for 24 hours to obtain a light yellow viscous polyamic acid solution;

(2) in N₂Adding 3mL of DMAc into the polyamic acid solution under protection, diluting the solution, continuing stirring for 30min, and then adding 2mL of a pyridine/acetic anhydride mixture (molar ratio is 1:1) of a dehydrating agent; heating to 100 ℃, and continuously stirring for reaction for 5 hours; after the reaction is finished, naturally cooling the reactant to room temperature, slowly dropping the reaction solution into 30mL of distilled water drop by drop, and separating out a large amount of white precipitate from the reaction solution; filtering, washing with water, and vacuum drying at 80 deg.C to obtain white polyimide solid powder (PI-6) with molecular formula of

The yield was 92%.

The detection result of the product is as follows: infrared (KBr, cm)^-1)1770, 1725 (symmetric and asymmetric expansion and contraction of C ═ O), 1365(C-N expansion and contraction vibration), 1043(C-F) expansion and contraction vibration; molecular weight measured by GPC, Mn 20480, Mw 36500, Mw/Mn 1.78; elemental analysis: a theoretical value; c, 79.68%; h, 5.33%; n, 5.16%; found C, 79.52%; h, 5.61%; n, 5.38%; TGA thermogravimetric analysis (N)₂):T_5％＝378℃,T_10％The residue rate at 800 ℃ was 51.6% at 396 ℃.

Example 7

(1)N₂To a 50ml three-necked flask were added 3, 5-diamino-N- (4 '-bromophenyl) -N- (2' -bromobenzyl) benzamide (0.3g,0.632mmol), 4- (dianilino) phenylboronic acid (0.44g,1.52mmol), Pd (PPh) with protection₃)₄(0.0145g,0.0126mmol) and anhydrous potassium carbonate (0.349g,2.53mmol), respectively adding toluene 15ml and distilled water 7.5ml, heating to 110 ℃, refluxing and stirring for about 5h, continuously generating bubbles in the reaction, stirring for 5h, closing the reaction, standing for natural cooling to room temperature, carrying out vacuum filtration, layering the obtained filtrate, collecting the toluene layer, removing the solvent toluene by rotary evaporation to obtain a white solid, combining the solid and the filter cake,purifying by column chromatography, wherein the solvents are ethyl acetate and n-hexane, and the polarity ratio is ethyl acetate: and (3) drying the obtained product for 12 hours at the temperature of 90 ℃ in vacuum to obtain 3, 5-diamino-N- (4 '-phenyl-4' -triphenylaminyl) -N- (2 '-benzyl-4' -triphenylaminyl) benzamide, wherein the molecular formula of the benzamide is as follows:

(2) in N₂Adding 3, 5-diamino-N- (4 '-phenyl-4' -triphenylamine) -N- (2 '-benzyl-4' -triphenylamine) benzamide (0.161g and 0.2mmol) and 5mL of aprotic solvent DMAc into a 50mL three-neck flask under protection, stirring at room temperature until all solids are dissolved, slowly adding pyromellitic dianhydride (0.436g and 0.2mmol) in 3 batches, and stirring at room temperature for 24 hours to obtain a yellow viscous polyamic acid solution;

(3) in N₂Adding 2mL of DMAc into the polyamic acid solution under protection, diluting the solution, continuing stirring for 30min, and then adding 2mL of a pyridine/acetic anhydride mixture (molar ratio is 1:1) of a dehydrating agent; heating to 100 ℃, and continuously stirring for reaction for 5 hours; after the reaction is finished, naturally cooling the reactant to room temperature, slowly dropping the reaction solution into 30mL of distilled water drop by drop, and separating out a large amount of yellow precipitate in the reaction solution; filtering, washing with water, and vacuum drying at 80 deg.C to obtain yellow polyimide solid powder (PI-7) with molecular formula of

The yield was 94%.

The detection result of the product is as follows: infrared (KBr, cm)^-1)1775, 1720 (symmetric and asymmetric expansion and contraction of C ═ O), 1363(C — N expansion and contraction vibration); molecular weight was measured by GPC, Mn was 20120, Mw was 35170, and Mw/Mn was 1.75; elemental analysis: theoretical value C, 80.38%; h, 4.86%; n, 6.89%; actually measuring C, 80.05%; h, 5.10%; n, 7.12%; TGA thermogravimetric analysis (N)₂):T_5％＝416℃,T_10％The residue rate at 800 ℃ was 55.1% at 445 ℃.

In summary, the following steps:

(1) the polyimide samples obtained in examples 1 to 7 were tested for solubility and viscosity, and the results are shown in Table 1:

TABLE 1 intrinsic viscosity and solubility test results for PI-1-7

Note: η inh represents the intrinsic viscosity, and polyimide in DMAc (0.5g/dL) solution was tested in a 30 ℃ thermostatted water bath; + + + + indicates room temperature solubility; + dissolving by heating; + means that the heating is slightly soluble; -means that neither is dissolved by heating.

(2) Polyimide (PI-7) powder was taken and characterized using XRD powder diffraction. The XRD diffraction results are shown in FIG. 1. It can be seen that the diffraction peak is "wave packet" and there is no obvious diffraction peak, indicating that the polyimide is in an amorphous state, which is favorable for its good solubility and film-forming property.

(3) Dissolving polyimide (PI-7) powder in DMAc to prepare a solution of 9mg/mL, and filtering the solution for three times by using a 0.22um pinhole filter (organic system); then, spin-coating the polymer solution on ITO conductive glass by using a KW-4A type spin coater under the spin-coating condition of 2800rpm (60 s); followed by drying in a vacuum oven at 80 ℃ for 10 h.

The surface formation state of the polyimide film and the film structure were examined by AFM, and the AFM test results are shown in fig. 2, where the picture scanning area was 0.5 μm × 0.5 μm, the bright area in the figure was a protruded portion, and the dark area was a recessed portion. In the AFM image, although the polymer film is locally more bright, relatively dark areas are few. The thickness of the polymer was 25.6nm and the surface roughness was 1.63 nm. The analysis shows that the surface of the spin-coating film is relatively flat and the roughness is relatively small, and further shows that the polyimide material has relatively good film-forming property.

The above embodiments should not be construed as limiting the present invention, and all the inventions embodied in other forms of modification, replacement or alteration based on the technical idea of the present invention belong to the scope of the present invention. It will be apparent to those skilled in the art that modifications may be made without departing from the invention, such as reacting other 3, 5-diamino-N- (4' -bromophenyl) -N- (2 '/4 ' -bromobenzyl) benzamide compounds as monomers, and the like, and such modifications are within the scope of the claims.

Claims (9)

1. An aromatic polyimide containing an imide flexible group, characterized in that the number average molecular weight Mn is 19300-23500, the weight average molecular weight Mw is 31500-37900, and the molecular weight distribution Mw/Mn is 1.61-1.97; having a repeating unit represented by the formula (1):

in the formula (1), the R, R' group is one of hydrogen, aliphatic hydrocarbon, aromatic hydrocarbon, alicyclic hydrocarbon, aliphatic group containing heteroatom, aromatic heterocycle, alicyclic heterocycle or mixture group thereof,

in the formula (1), the X group is any one of the following groups

2. The aromatic polyimide having an imide flexible group as claimed in claim 1, wherein the group R, R' is one of the following groups:

3. the method for preparing an aromatic polyimide having a flexible imide group according to claim 1 or 2, comprising the steps of:

(a) under the protection of inert gas, dissolving 3, 5-diamino-N- (4'-R phenyl) -N- (2'/4 '-R benzyl) benzamide compound in an aprotic solvent, then adding dianhydride monomer in 2-3 times, stirring at room temperature for reaction for 12-28 h, and adding 3, 5-diamino-N- (4' -R phenyl) -N- (2 '/4' -R benzyl) benzamide compound and dianhydride monomer in a molar ratio of 1: 1-1.1;

(b) under the protection of inert gas, adding an aprotic solvent into the polyamic acid solution, stirring and reacting for 2-4 h, adding a dehydrating agent, and heating to 100 ℃ to react for 6 h; after the reaction is finished, cooling the reaction liquid to room temperature, then dropwise adding into distilled water, filtering, washing with water, and then placing the precipitate in 80C vacuum drying to obtain powder, namely the aromatic polyimide.

4. The method of claim 3, wherein the inert gas is argon.

5. The method of claim 3, wherein the 3, 5-diamino-N- (4' -R-phenyl) -N- (2 '/4 ' -R-benzyl) benzamide compound is represented by the formula

The compound of the general formula (I), wherein the R, R' group is

6. The method according to claim 3, wherein the aprotic solvent is at least one selected from the group consisting of N-methyl pyrazolidinone, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, hexamethylphosphoric triamide and tetrahydrofuran.

7. The method of claim 3, wherein the dianhydride monomer of step (a) is represented by the general formula

The X group is any one of the following groups,

8. the method of claim 7, wherein the dianhydride monomer is selected from pyromellitic dianhydride and 2,2 ', 3, 3' -biphenyltetracarboxylic dianhydride.

9. The method of claim 3, wherein the dehydrating agent in step (b) is one of pyridine/acetic anhydride in equimolar mixture, sodium acetate/acetic anhydride in equimolar mixture, or triethylamine/acetic anhydride in equimolar mixture.

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