CN109053470B - Flexible diamine monomer, preparation method thereof and application thereof in preparation of polyimide - Google Patents
Flexible diamine monomer, preparation method thereof and application thereof in preparation of polyimide Download PDFInfo
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- CN109053470B CN109053470B CN201810885144.8A CN201810885144A CN109053470B CN 109053470 B CN109053470 B CN 109053470B CN 201810885144 A CN201810885144 A CN 201810885144A CN 109053470 B CN109053470 B CN 109053470B
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- C07C227/04—Formation of amino groups in compounds containing carboxyl groups
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- C07C213/00—Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton
- C07C213/02—Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton by reactions involving the formation of amino groups from compounds containing hydroxy groups or etherified or esterified hydroxy groups
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- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
- C08G73/1003—Preparatory processes
- C08G73/1007—Preparatory processes from tetracarboxylic acids or derivatives and diamines
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- C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
- C08G73/06—Polycondensates having nitrogen-containing heterocyclic rings in the main chain of the macromolecule
- C08G73/10—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
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Abstract
The invention provides a flexible diamine monomer with a trifluoromethyl substituted dicyclohexylene aliphatic structure and a preparation method and application thereof. The flexible diamine monomer provided by the invention comprises trifluoromethyl, a flexible group and an alicyclic structure, wherein the flexible group is an ether bond or an ester group, and the alicyclic structure is dicyclohexylidene. When the flexible diamine monomer provided by the invention reacts with dianhydride to generate polyimide, the trifluoromethyl and flexible groups in the flexible diamine monomer increase the free volume and flexibility of a polyimide molecular chain, so that a solvent is easy to permeate, and the solubility of the polyimide is improved; the alicyclic structure in the flexible diamine monomer can further improve the solubility and the transparency of polyimide; in addition, the main chain of the flexible diamine monomer provided by the invention has an aromatic ring structure, so that the polyimide prepared by the invention has stronger intermolecular acting force, and further has stronger mechanical property.
Description
Technical Field
The invention belongs to the technical field of organic chemistry, and particularly relates to a flexible diamine monomer, a preparation method thereof and application thereof in preparation of polyimide.
Background
In recent years, with rapid development of high-tech fields such as storage, display, waveguide, solar cell in the field of photovoltaics; the performance requirements of the aerospace and other fields on the material are continuously improved; conventional inorganic materials have been difficult to meet the development requirements of the above advanced technical fields. Therefore, flexible materials made of polymer materials, which can be stretched, folded, and bent at will and can be restored to their original shape, are becoming the development trend of high-tech materials.
Currently, polyimide films are commonly used as flexible substrate materials. However, polyimide has some problems in the process of preparing the polyimide film, for example, the solubility of polyimide is poor, which increases the difficulty of preparing the polyimide film; in addition, the optical transmittance of the polyimide film is low.
In order to improve the solubility of polyimide and the optical transmittance of a polyimide film, researchers mainly adopt physical methods and chemical methods, wherein the physical methods are mainly used for improving the solubility of polyimide and the optical transmittance of the polyimide film by doping inorganic nanoparticles to reduce the crystallinity of the polyimide, but the physical methods can greatly reduce the mechanical properties of the polyimide; the chemical method mainly introduces bulky substituent groups, flexible groups, asymmetric structures, alicyclic structures or non-coplanar structures and the like into polyimide molecular chains through structural modification to improve the solubility of polyimide and the optical transmittance of the polyimide film, but the chemical method cannot simultaneously improve the optical transmittance of the polyimide film and the mechanical property of the polyimide. Therefore, the polyimide has a problem that solubility, optical transmittance and mechanical properties cannot be simultaneously considered when preparing a flexible substrate material.
Disclosure of Invention
The invention provides a flexible diamine monomer with a trifluoromethyl substituted dicyclohexylene aliphatic structure and a preparation method thereof.
The invention provides a flexible diamine monomer with a trifluoromethyl substituted dicyclohexylene aliphatic structure, which has a structure shown in a formula I:
wherein X is
n＝1 or 2.
Preferably, the flexible diamine monomer comprises 1,4- (3-amino-5-trifluoromethylphenoxy) cyclohexane, 4- (3-amino-5-trifluoromethylphenoxy) bicyclohexane, 1,4- (3-amino-5-trifluoromethylester group) cyclohexane or 4,4' - (3-amino-5-trifluoromethylester group) bicyclohexane.
The invention also provides a preparation method of the flexible diamine monomer in the technical scheme, and the preparation method is determined according to X in the structure shown in the formula I:
when the X is
The preparation method of the flexible diamine monomer comprises the following steps:
(1) under the protection of argon, mixing 3-halogen-nitrotrifluorocyclohexane, dimethyl copper lithium, ethylene diamine tetraacetic acid and hydroxyl-cyclohexane in a polar organic solvent, and then carrying out nucleophilic substitution reaction to obtain a dinitro compound with a trifluoromethyl substituted dicyclohexylene aliphatic structure;
(2) carrying out reduction reaction on the dinitro compound obtained in the step (1) by adopting sodium sulfide to obtain X
The flexible diamine monomer of the structure shown in the formula I;
when the X is
The preparation method of the flexible diamine monomer comprises the following steps:
(a) under the protection of argon, 3-nitro-trifluoromethyl cyclohexanecarboxylic acid, hydroxyl-cyclohexane and concentrated sulfuric acid are mixed for esterification reaction to obtain an ester-based dinitro compound with a trifluoromethyl substituted dicyclohexylene aliphatic structure;
(b) reducing the ester-based dinitro compound obtained in the step (a) by adopting hydrogen sulfide and hydrazine hydrate to obtain X
The flexible diamine monomer of formula I.
Preferably, in the step (1), the molar ratio of the 3-halogen-nitrotrifluorocyclohexane to the lithium dimethyl copper to the ethylene diamine tetraacetic acid to the hydroxy-cyclohexane is 4: 0.1-0.4: 0.5-0.6: 1.5-2.
Preferably, the temperature of the nucleophilic substitution reaction in the step (1) is 210-220 ℃.
Preferably, the temperature of the reduction reaction in the step (2) is 105-115 ℃.
Preferably, the molar ratio of the 3-nitro-trifluoromethyl cyclohexanecarboxylic acid to the hydroxy-cyclohexane to the concentrated sulfuric acid in the step (a) is 1: 2-3: 0.4-1.
Preferably, the temperature of the esterification reaction in the step (a) is 115-125 ℃.
Preferably, the temperature of the reduction reaction in the step (b) is 85-110 ℃.
The invention also provides the application of the flexible diamine monomer in the technical scheme or the flexible diamine monomer prepared by the preparation method in the technical scheme in the preparation of polyimide.
The invention provides a flexible diamine monomer with a trifluoromethyl substituted dicyclohexylene aliphatic structure and a preparation method and application thereof. The flexible diamine monomer provided by the invention comprises trifluoromethyl, a flexible group and an alicyclic structure, wherein the flexible group is an ether bond or an ester group, and the alicyclic structure is dicyclohexylidene. When the flexible diamine monomer provided by the invention reacts with dianhydride to generate polyimide, the trifluoromethyl and flexible groups in the flexible diamine monomer increase the free volume and flexibility of a polyimide molecular chain, so that a solvent is easy to permeate, and the solubility of the polyimide is improved; the alicyclic structure in the flexible diamine monomer can further improve the solubility and the transparency of polyimide; in addition, an aromatic ring structure exists in the main chain of the flexible diamine monomer, so that the polyimide prepared by the flexible diamine monomer has stronger intermolecular acting force, and the polyimide prepared by the flexible diamine monomer has stronger mechanical properties. The results of the examples show that it is possible to obtain,the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure provided by the invention has good solubility in common organic solvents, the average light transmittance of the prepared polyimide film in a visible light range exceeds 90%, the tensile modulus E (GPa) of the prepared polyimide is 4.3-4.8 GPa, and the maximum tensile strength sigma ismax(MPa) is 201-210 MPa, and the elongation at break is epsilonmax(%) is 11.5-14.3%.
Drawings
FIG. 1 is a hydrogen nuclear magnetic diagram of 1,4- (3-amino-5-trifluoromethylphenoxy) cyclohexane obtained in example 1;
FIG. 2 is an infrared spectrum of a polyimide prepared in application example 1.
Detailed Description
The invention provides a flexible diamine monomer with a trifluoromethyl substituted dicyclohexylene aliphatic structure, which has a structure shown in a formula I:
wherein X is
n is 1 or 2.
In the present invention, the flexible diamine monomer preferably includes 1,4- (3-amino-5-trifluoromethylcyclohexyloxy) cyclohexane, 4- (3-amino-5-trifluoromethylcyclohexyloxy) bicyclohexane, 1,4- (3-amino-5-trifluoromethylester group) cyclohexane or 4,4' - (3-amino-5-trifluoromethylester group) bicyclohexane.
In the invention, the 1,4- (3-amino-5-trifluoromethyl cyclohexyl oxygen) cyclohexane has a structure shown in a formula II, the 4,4- (3-amino-5-trifluoromethyl cyclohexyl oxygen) bicyclohexane has a structure shown in a formula III, the 1,4- (3-amino-5-trifluoromethyl ester group) cyclohexane has a structure shown in a formula IV, and the 4,4' - (3-amino-5-trifluoromethyl ester group) bicyclohexane has a structure shown in a formula V.
The flexible diamine monomer provided by the invention contains trifluoromethyl, flexible groups (ether bonds and ester groups) and an alicyclic structure (dicyclohexylidene), can react with dianhydride to generate polyimide, and the existence of the trifluoromethyl and the flexible groups (ether bonds and ester groups) increases the free volume and flexibility of a polyimide molecular chain, so that a solvent is easy to permeate, and the solubility of the polyimide is improved; the introduction of the alicyclic structure (dicyclohexylidene) can further improve the solubility and the transparency of the polyimide, because the alicyclic structure (dicyclohexylidene) destroys large pi bonds in the molecular structure of the polyimide, the interaction between molecular chains is reduced, the free volume between the molecular chains is increased, the distance between the molecules is increased, small molecules of a solvent can enter between the molecules to dissolve the small molecules, and the solubility and the transparency of the polyimide are improved to a certain extent; in addition, the main chain of the flexible diamine monomer provided by the invention has an aromatic ring structure, so that the polyimide prepared by the invention has strong linear type and stronger intermolecular force, and further has stronger mechanical property. Therefore, the polyimide prepared from the flexible diamine monomer provided by the invention has excellent light transmittance, mechanical property and solubility.
The invention also provides a preparation method of the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
In the present invention, when said X is
The preparation method of the flexible diamine monomer comprises the following steps:
(1) under the protection of argon, mixing 3-halogen-nitrotrifluorocyclohexane, dimethyl copper lithium, ethylene diamine tetraacetic acid and hydroxyl-cyclohexane in a polar organic solvent, and then carrying out nucleophilic substitution reaction to obtain a dinitro compound with a trifluoromethyl substituted dicyclohexylene aliphatic structure;
(2) reducing the dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure obtained in the step (1) by adopting sodium sulfide to obtain X
The flexible diamine monomer of formula I.
In the present invention, the starting materials for the preparation process are all commercially available products well known to those skilled in the art, unless otherwise specified.
In the invention, under the protection of argon, 3-halogen-nitro-trifluorocyclohexane, dimethyl copper lithium, ethylene diamine tetraacetic acid and hydroxyl-cyclohexane are mixed in a polar organic solvent to obtain a mixed material.
In the invention, the dimethyl copper lithium is used as a catalyst and plays a role in promoting the nucleophilic substitution reaction; the ethylene diamine tetraacetic acid is a ligand and has the functions of adjusting the electrical property of the metal catalyst center and changing the catalytic activity of the metal catalyst center.
In the present invention, the molar ratio of the 3-halo-nitrotrifluorocyclohexane, the lithium dimethyl copper, the ethylenediaminetetraacetic acid and the hydroxy-cyclohexane is preferably 4:0.1 to 0.4:0.5 to 0.6:1.5 to 2, more preferably 4:0.2 to 0.3:0.52 to 0.58:1.5 to 1.8, and even more preferably 4:0.25:0.55: 1.5. In the present invention, the molar ratio of 3-halo-nitrotrifluorocyclohexane, lithium dimethyl copper, ethylenediaminetetraacetic acid and hydroxy-cyclohexane is preferably controlled within the above range, which is advantageous for the sufficient reaction between the raw materials.
The quality of the polar organic solvent is preferably controlled according to the solid content of the mixed material. In the invention, the solid content of the mixed material is preferably 15-20%, and more preferably 16-18%. The invention preferably controls the solid content of the mixed materials within the range, which is beneficial to the full reaction between the reaction raw materials.
The invention mixes the raw materials under the protection of argon, and aims to prevent oxygen, water vapor and the like in the air from influencing the reaction.
After the mixed material is obtained, the mixed material is subjected to nucleophilic substitution reaction to obtain the dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
In the invention, the temperature of the nucleophilic substitution reaction is preferably 210-220 ℃, more preferably 212-218 ℃, and even more preferably 214-216 ℃.
In the present invention, the time of the nucleophilic substitution reaction is preferably determined by the result of TLC real-time detection, and the reaction is stopped when the starting point of the TLC real-time detection disappears.
In the invention, the nucleophilic substitution reaction product is preferably cooled and then mixed with dichloromethane; and sequentially filtering, drying a filter cake and recrystallizing the mixed solution to obtain the dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
The cooling method of the nucleophilic substitution reaction product is not particularly limited in the present invention, and a method commonly used in the art may be employed.
The present invention preferably mixes the cooled nucleophilic substitution reaction product with methylene chloride.
According to the invention, the mixed solution of the nucleophilic substitution reaction product and dichloromethane is preferably subjected to filtration, filter cake drying and recrystallization in sequence to obtain the dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
The present invention is not particularly limited with respect to the specific embodiment of the filtration and cake drying process, and may be carried out in a manner well known to those skilled in the art.
The invention preferably performs recrystallization treatment on the dried reaction product, and the invention preferably performs recrystallization treatment on the crude product to obtain X
The dinitro compound having a trifluoromethyl-substituted dicyclohexylene aliphatic structure of (1).
In the present invention, the recrystallization treatment preferably includes the steps of:
mixing the dried reaction product with cyclohexane, and heating and refluxing to obtain a refluxing reaction solution; to the reflux reactionSlowly adding deionized water into the solution until precipitate is just separated out and is insoluble, and drying the separated precipitate to obtain X
The dinitro compound having a trifluoromethyl-substituted dicyclohexylene aliphatic structure of (1).
In the present invention, it is preferable to sufficiently dissolve the dried reaction product in cyclohexane, which is a benign solvent, by heating and refluxing. In the invention, the temperature of the heating reflux is preferably 95-105 ℃; further preferably 100 ℃.
In the recrystallization treatment, the crude product is preferably mixed with cyclohexane, so that the dried reaction product is fully dissolved in the cyclohexane, and then poor solvent deionized water is gradually added, so that the dinitro compound dissolved in the cyclohexane is gradually precipitated after the solubility is reduced. The invention preferably increases X to X by recrystallization treatment
The purity of the dinitro compound of trifluoromethyl substituted dicyclohexylene aliphatic structure.
After obtaining the dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure, the invention adopts sodium sulfide to carry out reduction reaction on the dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure to obtain the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure, namely X is
The flexible diamine monomer of formula I.
In the invention, preferably, a dinitro compound with a trifluoromethyl substituted dicyclohexylene aliphatic structure is mixed with a solvent for reduction reaction, heated and refluxed, and then mixed with sodium sulfide for reduction reaction.
In the present invention, the solvent for the reduction reaction preferably includes 1, 4-dioxane or absolute ethanol; the mass ratio of the dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure to the reduction reaction solvent is preferably 15-20: 80-85, and more preferably 16-18: 82-84.
In the invention, the mass ratio of the dinitro compound with the trifluoromethyl-substituted dicyclohexylene aliphatic structure to the sodium sulfide is preferably 1: 0.2-1, and more preferably 1: 0.4-0.8. In the present invention, the mass ratio of the dinitro compound to the sodium sulfide is preferably controlled within the above range, which is advantageous for the sodium sulfide to sufficiently reduce the dinitro compound to the diamino compound.
In the invention, the temperature of the reduction reaction is preferably 105-115 ℃, and more preferably 108-112 ℃.
In the present invention, the time of the reduction reaction is preferably determined by TLC detection, and the reaction is stopped when the point of the dinitro compound raw material disappears in the TLC detection.
According to the invention, the reduction reaction product is preferably subjected to filtration, filtrate concentration, drying and recrystallization in sequence to obtain the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
In the invention, the filtering temperature is preferably 105-115 ℃, and the filtering is preferably carried out directly without cooling treatment after the reduction reaction is finished, namely the filtering is carried out while the reaction is hot. According to the invention, the hot filtration is preferably adopted, so that the removal of unreacted sodium sulfide is facilitated, and the precipitation of flexible diamine monomer generated by the reduction reaction is avoided.
The present invention does not require any particular embodiment for filtration, concentration of the filtrate and drying, and may be carried out in a manner commonly used by those skilled in the art.
According to the invention, the dried crude product is preferably subjected to recrystallization treatment to obtain a flexible diamine monomer with a trifluoromethyl substituted dicyclohexylene aliphatic structure; in the present invention, the recrystallization treatment preferably includes the steps of:
mixing the dried crude product with 1, 4-dioxane, and heating and refluxing to obtain a reflux reaction liquid; and slowly adding deionized water into the reflux reaction liquid until a precipitate is just separated out and is insoluble, and drying the separated precipitate to obtain the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
The invention preferably makes the crude product fully dissolved in the benign solvent 1, 4-dioxane by heating reflux treatment. In the invention, the temperature of the heating reflux is preferably 105-115 ℃; further preferably 110 ℃.
In the recrystallization treatment, the crude product is preferably mixed with the 1, 4-dioxane to fully dissolve the crude product in the 1, 4-dioxane, and then the poor solvent deionized water is gradually added to reduce the solubility of the flexible diamine monomer dissolved in the 1, 4-dioxane to gradually separate out. According to the invention, the purity of the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure is improved preferably by recrystallization.
The invention preferably collects the precipitated precipitate by filtration, and then dries the precipitated precipitate to obtain the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure. The present invention is not particularly limited to the specific embodiment of filtration, and may be performed in a manner known to those skilled in the art. In the invention, the temperature of the drying treatment is preferably 95-105 ℃, and more preferably 100 ℃; the drying time is preferably 11 to 13 hours, and more preferably 12 hours.
In the present invention, when said X is
In the case, the preparation process of the flexible diamine monomer is preferably as shown in formula VI:
in the present invention, when said X is
The preparation method of the flexible diamine monomer comprises the following steps:
(a) under the protection of argon, 3-nitro-trifluoromethyl cyclohexanecarboxylic acid, hydroxyl-cyclohexane and concentrated sulfuric acid are mixed for esterification reaction to obtain an ester-based dinitro compound with a trifluoromethyl substituted dicyclohexylene aliphatic structure;
(b) reducing the trifluoromethyl substituted dicyclohexylene aliphatic ester dinitro compound obtained in the step (a) by adopting hydrogen sulfide and hydrazine hydrate to obtain X
The flexible diamine monomer of formula I.
In the present invention, the starting materials for the preparation process are all commercially available products well known to those skilled in the art, unless otherwise specified.
In the invention, under the protection of argon, 3-nitro-trifluoromethyl cyclohexanecarboxylic acid, hydroxy-cyclohexane and concentrated sulfuric acid are mixed to obtain a mixed raw material.
In the present invention, the concentrated sulfuric acid serves as a catalyst and a water absorbent, and plays a role in promoting the esterification reaction. The concentration of the concentrated sulfuric acid is not particularly required, and the method can be realized by adopting the method which is well known by the technical personnel in the field.
In the present invention, the molar ratio of the 3-nitro-trifluoromethylcyclohexanecarboxylic acid to the hydroxy-cyclohexane to the concentrated sulfuric acid is preferably 1:2 to 3:0.4 to 1, and more preferably 1:2.2 to 2.8:0.5 to 0.8. In the present invention, the molar ratio of 3-nitro-trifluoromethylcyclohexanecarboxylic acid, hydroxy-cyclohexane and concentrated sulfuric acid is preferably controlled within the above range, which is advantageous for sufficient reaction between the reaction raw materials.
The mixing method of the 3-nitro-trifluoromethyl cyclohexanecarboxylic acid, the hydroxy-cyclohexane and the concentrated sulfuric acid is not particularly limited, and a mixing method commonly used by those skilled in the art can be adopted.
After the mixed raw material is obtained, the mixed raw material is subjected to esterification reaction to obtain the ester-based dinitro compound with a trifluoromethyl substituted dicyclohexylene aliphatic structure.
In the invention, the temperature of the esterification reaction is preferably 115-125 ℃, and more preferably 120 ℃; the time of the esterification reaction is preferably 0.5 to 1.0 hour, and more preferably 0.6 to 0.8 hour.
After the esterification reaction is finished, the esterification reaction product is preferably subjected to cooling, distillation and concentration, neutralization, standing and layering, washing, rotary evaporation and recrystallization in sequence to obtain the ester-based dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
The esterification reaction product is preferably cooled to obtain a cooled esterification reaction product. The cooling method of the present invention is not particularly limited, and a cooling method known to those skilled in the art may be used.
The invention preferably carries out distillation concentration treatment on the cooled esterification reaction product to obtain a concentrated esterification reaction product. In the invention, the volume ratio of the concentrated esterification reaction product to the cooled esterification reaction product is preferably 0.5-0.6: 1. The method for carrying out the distillation concentration in the present invention is not particularly limited, and a distillation concentration method known to those skilled in the art may be used.
The present invention preferably neutralizes the concentrated esterification reaction product to obtain a neutralized product. In the present invention, the neutralizing agent is preferably a saturated sodium carbonate solution. In the present invention, unreacted 3-nitro-5- (trifluoromethyl) benzoic acid raw material is preferably removed by neutralization treatment. The invention preferably controls the adding amount of the saturated sodium carbonate solution through the pH value of the neutralization product, and stops adding the saturated sodium carbonate solution when the pH value of the neutralization product is neutral.
According to the invention, the neutralization reaction product is preferably subjected to standing layering treatment, the lower layer after standing layering is preferably an aqueous solution, and the upper layer is preferably an organic phase. The present invention preferably collects the upper organic phase. The specific embodiment of the standing layering treatment in the invention is not particularly limited, and a standing layering method commonly used by those skilled in the art can be adopted.
In the present invention, the organic phase is preferably washed with saturated brine, saturated calcium chloride and water in this order. The invention is preferably washed by saturated brine, which is beneficial to removing residual sodium carbonate as a neutralizing agent; according to the invention, the hydroxyl-cyclohexane which is not completely reacted in the reaction raw materials is removed by preferably washing with saturated calcium chloride; the present invention is preferably washed with water to facilitate removal of residual inorganic salts. After the washing treatment is completed, the aqueous phase is preferably removed in the present invention to obtain a washed organic phase.
The invention preferably carries out rotary evaporation treatment on the washed organic phase to obtain a crude product.
The invention removes the organic solvent in the organic phase to obtain the crude product through rotary evaporation treatment.
According to the invention, the crude product is preferably subjected to recrystallization treatment to obtain the ester-based dinitro compound with a trifluoromethyl substituted dicyclohexylene aliphatic structure.
In the present invention, the recrystallization treatment preferably includes the steps of:
mixing the dried crude product with N, N-dimethylformamide, and heating and refluxing to obtain a reflux reaction solution; and slowly adding deionized water into the reflux reaction liquid until a precipitate is just separated out and is insoluble, and drying the separated precipitate to obtain the ester-based dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
The invention preferably makes the crude product fully dissolved in the benign solvent N, N-dimethylformamide by heating and refluxing treatment. In the invention, the temperature of the heating reflux is preferably 155-165 ℃; further preferably 160 ℃.
In the recrystallization treatment, the crude product is preferably mixed with N, N-dimethylformamide firstly, so that the crude product is fully dissolved in the N, N-dimethylformamide, and then poor solvent deionized water is gradually added, so that the ester-based dinitro compound dissolved in the N, N-dimethylformamide is gradually precipitated after the solubility is reduced. The invention preferably improves the purity of the trifluoromethyl substituted dicyclohexylene aliphatic ester dinitro compound by recrystallization.
The present invention preferably collects the precipitated precipitate by filtration. The present invention is not particularly limited to the specific embodiment of filtration, and may be performed in a manner known to those skilled in the art.
In the present invention, the precipitated precipitate is preferably dried. In the invention, the temperature of the drying treatment is preferably 95-105 ℃, and more preferably 100 ℃; the drying time is preferably 11 to 13 hours, and more preferably 12 hours.
After the ester-based dinitro compound with the trifluoromethyl substituted dicyclohexylene aliphatic structure is obtained, the invention adopts hydrogen sulfide and hydrazine hydrate to carry out reduction reaction on the ester-based dinitro compound to obtain the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure, namely X is
The flexible diamine monomer of formula I.
In the invention, the trifluoromethyl substituted dicyclohexylene aliphatic ester-based dinitro compound is preferably mixed with a solvent for reduction reaction, heated to reflux, and then added with a hydrogen sulfide water solution and a hydrazine hydrate solution to carry out reduction reaction.
In the present invention, the solvent for the reduction reaction preferably includes absolute ethanol or 1, 4-dioxane. The mass ratio of the trifluoromethyl substituted dicyclohexylene aliphatic ester-based dinitro compound to the reduction reaction solvent is preferably 10-20: 80-90, and more preferably 12-18: 82-88.
In the present invention, the mass fraction of the aqueous hydrogen sulfide solution is preferably 80% to 90%, and more preferably 85%. In the invention, the mass ratio of the trifluoromethyl-substituted dicyclohexylene aliphatic-structure ester-based dinitro compound to the aqueous hydrogen sulfide solution is preferably 1: 0.2-1, and more preferably 1: 0.4-0.8. In the present invention, the mass ratio of the ester-based dinitro compound to the aqueous hydrogen sulfide solution is preferably controlled within the above range, which is advantageous for the hydrogen sulfide to sufficiently reduce the ester-based dinitro compound to the diamine-based compound.
In the present invention, the mass fraction of the hydrazine hydrate solution is preferably 85%. In the invention, the mass ratio of the trifluoromethyl substituted dicyclohexylene aliphatic ester-based dinitro compound to the hydrazine hydrate solution is preferably 2: 10-20, and more preferably 2: 12-18. In the present invention, the mass ratio of the ester-based dinitro compound to the hydrazine hydrate solution is preferably controlled within the above range, which is advantageous for the hydrazine hydrate to sufficiently reduce the ester-based dinitro compound to the diamine-based compound. The invention preferably adds hydrogen sulfide and hydrazine hydrate at the same time, which is beneficial to promoting the reduction reaction, shortening the reaction time and improving the reaction efficiency.
In the invention, the temperature of the reduction reaction is preferably 85-110 ℃, and more preferably 90-100 ℃.
In the present invention, the time of the reduction reaction is preferably determined by TLC detection, and the reaction is stopped when the TLC detection is carried out until the starting point of the ester-based dinitro compound disappears.
According to the invention, the reduction reaction product is preferably subjected to filtration, filtrate concentration, rotary evaporation and recrystallization in sequence to obtain the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
The present invention does not require any particular embodiment of filtration, and can be carried out in a manner commonly used by those skilled in the art.
The method preferably concentrates the filtered filtrate, wherein the volume of the concentrated filtrate is 1/4-1/3 of the volume of the original filtrate. The present invention is not particularly limited to the specific embodiment of the filtrate concentration, and any filtrate concentration method commonly used by those skilled in the art may be employed.
In the invention, the concentrated filtrate is preferably subjected to rotary evaporation treatment to obtain a crude product. The present invention does not require any particular embodiment of the rotary evaporation treatment, and may be carried out by a rotary evaporation method known to those skilled in the art.
According to the invention, the crude product is preferably subjected to recrystallization treatment to obtain the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure. In the present invention, the recrystallization treatment preferably includes the steps of:
mixing the crude product with absolute ethyl alcohol, and heating and refluxing to obtain a reflux reaction solution; and slowly adding deionized water into the reflux reaction liquid until just precipitate is separated out and is insoluble, cooling and filtering, and drying the separated precipitate to obtain the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure.
The invention preferably makes the crude product fully dissolved in the benign solvent absolute ethyl alcohol by heating reflux treatment. In the invention, the temperature of the heating reflux is preferably 80-90 ℃; further preferably 85 ℃.
In the recrystallization treatment, the crude product is preferably mixed with absolute ethyl alcohol firstly, so that the crude product is fully dissolved in the absolute ethyl alcohol, and then poor solvent deionized water is gradually added, so that the solubility of the flexible diamine monomer dissolved in the absolute ethyl alcohol is reduced and the diamine monomer is gradually separated out. According to the invention, the purity of the flexible diamine monomer with the trifluoromethyl substituted dicyclohexylene aliphatic structure is improved preferably by recrystallization.
In the present invention, it is preferable to cool the reaction mixture to room temperature and then collect the precipitated precipitate by filtration. According to the invention, the flexible diamine monomer is preferably filtered after cooling, so that the flexible diamine monomer can be fully separated out in a precipitation form. The present invention is not particularly limited to the specific embodiment of filtration, and may be performed in a manner known to those skilled in the art.
In the present invention, the precipitated precipitate is preferably dried. In the invention, the temperature of the drying treatment is preferably 55-65 ℃, and more preferably 60 ℃; the drying time is preferably 11 to 13 hours, and more preferably 12 hours.
In the present invention, when said X is
In the preparation process, the flexible diamine monomer is specifically shown as formula VII:
the invention also provides the application of the flexible diamine monomer in the technical scheme or the flexible diamine monomer prepared by the preparation method in the technical scheme in the preparation of polyimide.
In the present invention, the preparation method of the polyimide preferably includes the steps of:
and under the protection of argon, mixing the flexible diamine monomer, the dianhydride monomer, the catalyst and the dehydrating agent, and reacting in a polar organic solvent to obtain the polyimide.
In the present invention, the dianhydride monomer preferably has the structure of formula VIII:
in the present invention, AR in the dianhydride monomer preferably has the following structure:
in the present invention, the dianhydride monomer further preferably includes one or more of pyromellitic dianhydride, 3 ', 4,4' -biphenyltetracarboxylic dianhydride, 3 ', 4,4' -diphenyl ether tetracarboxylic dianhydride, 3 ', 4,4' -benzophenone tetracarboxylic dianhydride, 4,4' - (hexafluoroisopropylidene) diphthalic anhydride and 4,4' - (4, 4' -diphenoloxypropyl) -dibenzoic anhydride.
In the present invention, the molar ratio of the flexible diamine monomer and the dianhydride monomer is preferably 1: 1.
In the present invention, the catalyst preferably comprises pyridine and/or calcium chloride.
In the present invention, the dehydrating agent preferably comprises acetic anhydride and/or phenyl phosphite.
In the invention, the molar ratio of the catalyst, the dehydrating agent and the flexible diamine monomer is preferably 0.5-1.5: 1.5-2.5: 0.5-1.5, more preferably 0.8-1.2: 1.8-2.2: 0.8-1.2, and even more preferably 1:2: 1.
In the present invention, the polar organic solvent preferably includes one or more of N, N-dimethylacetamide, N-dimethylformamide, and N-methylpyrrolidone. In the invention, the mass ratio of the total mass of the flexible diamine monomer and the dianhydride monomer to the polar organic solvent is preferably 10-30: 70-90, and more preferably 15-25: 75-85.
In the present invention, the flexible diamine monomer and the dianhydride monomer are reacted under the protection of argon gas in order to prevent the flexible diamine monomer from being oxidized by oxygen in the air. The invention preferably carries out the reaction under argon, which is beneficial to avoiding the flexible diamine monomer from being oxidized, and further beneficial to ensuring the dianhydride monomer and the flexible diamine monomer to smoothly react to prepare the polyimide.
In the invention, the reaction temperature of the flexible diamine monomer and the dianhydride monomer is preferably 100-120 ℃, and more preferably 110-115 ℃; the reaction time is preferably 2 to 5 hours, and more preferably 3 to 4 hours.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.
Example 1: preparation of 1,4- (3-amino-5-trifluoromethylphenoxy) cyclohexane
The first step of reaction: adding 5.5214g (20mmol) of 3-bromo-5-nitro-trifluorocyclohexane, 11.0428g (0.0378mmol) of dimethyl copper lithium, 6.5164g (20mmol) of cesium carbonate and 3.3128g (0.0113mmol) of ethylene diamine tetraacetic acid into a 250mL three-neck flask with a mechanical stirring device, adding 40 mLN-methyl pyrrolidone as a solvent, adding 1.1616g (10mmol) of 1, 4-dihydroxy-cyclohexane compound under the protection of stirring and fully introducing argon, stirring for 30min at room temperature, heating to the reflux temperature of 210 ℃ under the protection of stirring and argon, and detecting by TLC until a raw material point disappears to finish the reaction; cooling the system, discharging the cooled material into dichloromethane, slowly dripping the solution into methanol, carrying out suction filtration, carrying out vacuum drying to obtain a crude product, dissolving the crude product in a good solvent cyclohexane, heating to the reflux temperature of the reaction solution of 100 ℃, slowly adding poor solvent deionized water into the reflux reaction solution until the crude product is just separated out and insoluble, closing heating, and carrying out cooling suction filtration; vacuum drying at 100 deg.c for 12 hr to obtain dinitro compound with dicyclohexylene aliphatic structure;
the second step of reaction: adding 10.1296g (20mmol) of dinitro compound prepared by the first step of reaction into a 250mL three-neck flask with a mechanical stirring device, adding 132mL of 1, 4-dioxane as a solvent, heating to the reflux temperature of 110 ℃, adding 5.0648g of sodium sulfide Na2S, reacting for 12h under the reflux state, and detecting by TLC (thin layer chromatography) until the raw material point disappears, namely finishing the reaction; the reaction solution was filtered while hot to remove Na2S, the filtrate was collected and distilled under reduced pressure to 60mL, and the concentrate was recrystallized under argon atmosphere to give 6.8g of 1, 4-bis (3-amino-5-trifluoromethylcyclohexyloxy) cyclohexane of which the structure was as follows:
the nuclear magnetic spectrum of 1,4- (3-amino-5-trifluoromethylphenoxy) cyclohexane obtained in example 1 is shown in FIG. 1.
EXAMPLE 2 preparation of 4,4- (3-amino-5-trifluoromethylcyclohexyloxy) bicyclohexane
The first step of reaction: adding 5.5214g (20mmol) of 3-bromo-5-nitrotrifluorocyclohexane, 11.0428g (0.0378mmol) of dimethyl copper lithium, 5.8873g (20mmol) of cesium fluoride and 3.3128g (0.0113mmol) of ethylene diamine tetraacetic acid into a 250mL three-neck flask with a mechanical stirring device, adding 1.9831g (10mmol) of 4,4' -dihydroxy-bicyclohexyl compound under the protection of stirring and full argon gas, stirring for 30min at room temperature, heating to the reflux temperature of 220 ℃ under the protection of stirring and argon gas to perform a melting reaction, and detecting by TLC (thin layer chromatography) until a raw material point disappears to finish the reaction; cooling the system, discharging the cooled product into a 5% sodium hydroxide solution, carrying out suction filtration, washing a filter cake for 2-5 times by using deionized water, drying a crude product in vacuum, dissolving the crude product in a good solvent cyclohexane, heating to the reflux temperature of a reaction solution of 100 ℃, slowly adding poor solvent deionized water into the reflux reaction solution until the crude product is just separated out and insoluble, closing heating, and cooling and carrying out suction filtration; vacuum drying at 100 deg.C for 12h to obtain 4,4' - (3-nitro-5-trifluoromethyl cyclohexyl oxygen) bicyclohexyl compound;
the second step of reaction: 11.7724g (20mmol) of dinitro compound prepared in the first step of reaction is added into a 250mL three-neck flask with a mechanical stirring device, 170mL of 1, 4-dioxane is added as a solvent, the mixture is heated to reflux, 5.8862g of sodium sulfide Na2S is added, 11.6g (197.4mmol) of hydrazine hydrate with the mass fraction of 85 percent is slowly dripped into the reaction system, and the temperature is 110 ℃ at the reflux temperatureReacting for 16h, detecting by TLC until the raw material point disappears, namely finishing the reaction, filtering the reaction solution while the reaction solution is hot to remove Na2S, collecting the filtrate, distilling the filtrate to 60mL under reduced pressure, and recrystallizing the concentrated solution under the argon atmosphere to obtain 8.4g of 4,4' - (3-amino-5-trifluoromethyl cyclohexyl oxygen) bicyclohexyl compound, wherein the obtained product has the following structure:
EXAMPLE 3 preparation of 1,4- (3-amino-5-trifluoromethylcarbonyl) cyclohexane
The first step of reaction: adding 4.8234g (20mmol) of 3-nitro-5- (trifluoromethyl) benzoic acid, 1.16g (10mmol) of 1, 4-cyclohexanediol and 4.5mL of concentrated sulfuric acid into a 250mL three-necked flask with a mechanical stirring device, uniformly mixing, adding zeolite, keeping the slow reflux temperature of 120 ℃ for 0.5h under the protection of stirring, condensing and fully introducing argon, changing the reflux device into a distillation device after reactants in the system are cooled, evaporating the generated dinitro ester-based compound until the volume of distillate is about 1/2 of the total volume of the reactants, slowly adding saturated sodium carbonate solution into the distillate, continuously shaking until the pH test paper is not acidic, transferring the mixed solution into a separating funnel, removing a lower layer aqueous solution, sequentially washing an organic layer with saturated salt solution, saturated calcium chloride and water, removing a lower layer liquid, adding anhydrous magnesium sulfate and drying, carrying out rotary evaporation on an organic layer to obtain a crude product, drying the crude product in vacuum, and carrying out recrystallization treatment on the crude product to obtain a 1,4- (3-amino-5-trifluoromethyl ester group) cyclohexane compound;
the second step of reaction: adding 5.025g (10mmol) of the obtained dinitro ester-based compound into absolute ethyl alcohol, stirring and heating a system to reflux temperature of 85 ℃, adding 12.5625g of H2S aqueous solution, slowly dropwise adding 65mL of hydrazine hydrate solution with the mass fraction of 85%, reacting with the mixture in a reflux state, detecting by TLC until a raw material point disappears to finish the reaction, recrystallizing the concentrated solution under the argon atmosphere, and drying in vacuum at 60 ℃ to obtain 4.1g of 1,4- (3-amino-5-trifluoromethyl ester-based) cyclohexane compound, wherein the obtained product has the following structure:
EXAMPLE 4 preparation of 4,4' - (3-amino-5-trifluoromethylcarbonyl) bicyclohexane
The first step of reaction: adding 4.8234g (20mmol) of 3-nitro-5- (trifluoromethyl) benzoic acid, 1.9831g (10mmol) of 4,4' -dihydroxy-bicyclohexane and 4.5mL of concentrated sulfuric acid into a 250mL three-necked flask provided with a mechanical stirring device, uniformly mixing, adding zeolite, keeping the slow reflux temperature of 120 ℃ for 0.5h under the protection of stirring, condensing and fully introducing argon, cooling reactants in the system, changing the reflux device into a distillation device, distilling off the generated dinitroester-based compound until the volume of distillate is about 1/2 of the total volume of the reactants, slowly adding saturated sodium carbonate solution into the distillate, continuously oscillating until the pH test paper is not acidic, transferring the mixed solution into a separating funnel, separating a lower layer of aqueous solution, washing an organic layer with saturated common salt water, washing with saturated calcium chloride, finally washing with water once, removing lower layer liquid, adding anhydrous magnesium sulfate for drying, carrying out rotary evaporation on an organic layer to obtain a crude product, drying the crude product in vacuum, and carrying out recrystallization on the crude product to obtain a 4,4' - (3-nitro-5-trifluoromethyl ester group) bicyclohexyl compound;
the second step of reaction: adding 6.4664g (10mmol) of the obtained dinitro ester-based compound into 1, 4-dioxane, stirring and heating a system to reflux temperature of 110 ℃, adding 16.166g of H2S aqueous solution, slowly dropwise adding 65mL of hydrazine hydrate solution with the mass fraction of 85%, reacting with reflux, detecting by TLC until a raw material point disappears to obtain the end of the reaction, collecting filtrate, distilling the filtrate under reduced pressure to 1/4 of the volume of the original reaction liquid, finally recrystallizing the concentrated solution under the argon atmosphere, and drying in vacuum at 60 ℃ to obtain 5.2g of 4,4' - (3-amino-5-trifluoromethyl ester group) bicyclohexyl compound, wherein the obtained product has the following structure:
the flexible diamine monomer prepared in the embodiments 1 to 4 is applied to the preparation of polyimide, and the specific implementation method is as shown in application examples 1 to 4:
application example 1:1, 4- (3-amino-5-trifluoromethyl cyclohexyl oxygen) cyclohexane and 4,4' - (hexafluoroisopropylidene) diphthalic anhydride are used for preparing polyimide, and the specific process is as follows:
in a 50mL three-necked flask provided with an argon inlet and outlet, a magnetic stirrer, a thermometer and a condenser, under the protection of argon, 0.8930g (2mmol) of 1,4- (3-amino-5-trifluoromethyl cyclohexyl oxygen) cyclohexane is added, 20mL of N, N-dimethylacetamide is added as a solvent, 0.8885g (2mmol) of 4,4' - (hexafluoroisopropylene) diphthalic anhydride is slowly added, stirring is carried out for 6h at room temperature, 4mL of pyridine and 8mL of acetic anhydride are added, heating is carried out to 100 ℃ for reaction for 2h, cooling is carried out to room temperature after the reaction is finished, discharging materials are put into ethanol, ethanol is refluxed and washed for three times, drying in a vacuum oven at 80 ℃ to obtain 1.4551g of 1, 4-bis (3-amino-5-trifluoromethyl cyclohexyl oxygen) cyclohexane hexafluoro polyimide, marked as PA-1, and obtaining the product with the structure as follows:
the nuclear magnetic spectrum of the polyimide prepared in application example 1 is shown in fig. 2.
Application example 2: the polyimide is prepared from 4,4- (3-amino-5-trifluoromethylcyclohexyloxy) bicyclohexane and 4,4' - (hexafluoroisopropylidene) diphthalic anhydride by the following specific steps:
in a 50mL three-necked flask provided with an argon inlet and outlet, a magnetic stirring bar, a thermometer and a condenser, under the protection of argon, 1.0572g (2mmol) of 4,4 '-bi (3-amino-5-trifluoromethylphenoxy) cyclohexane, 2mL of phenyl phosphite, 1mL of pyridine and 0.2g of CaCl2 and 6mL of NMP are added as solvents, 0.8885g (2mmol) of 4,4' - (hexafluoroisopropyl) dicarboxylic anhydride is slowly added, the mixture is heated to 100 ℃ for reaction for 3 hours, the reaction product is cooled to room temperature after the reaction is finished, the discharging product is put into ethanol for suction filtration, a filter cake is washed by ethanol, water and ethanol for three times under reflux, drying in a vacuum oven at 80 ℃ gave 1.6605g of 4,4' - (3-amino-5-trifluoromethylcyclohexyloxy) dicyclohexyl hexafluoropolyimide, labelled PA-2, giving a product of the formula:
application example 3:1,4- (3-amino-5-trifluoromethyl ester group) cyclohexane and 4,4' - (hexafluoro-isopropyl) diphthalic anhydride are used for preparing polyimide, and the specific process is as follows:
in a 50mL three-necked flask equipped with an argon inlet/outlet, a magnetic stirrer, a thermometer and a condenser, under the protection of argon, 1.005g (2mmol) of 1,4- (3-amino-5-trifluoromethyl ester group) cyclohexane, 2mL of phenyl phosphite and 1mL of pyridine, 0.2g of CaCl2 and 6mL of NMP are added as solvents, 0.8885g (2mmol) of 4,4' - (hexafluoroisopropyl) dicarboxylic anhydride is slowly added, the mixture is heated to 100 ℃ for reaction for 3 hours, the reaction is cooled to room temperature after the reaction is finished, materials are discharged into ethanol and filtered, a filter cake is washed with ethanol, water and ethanol under reflux for three times, the mixture is dried in a vacuum oven at 80 ℃, 1.6905g of 1,4- (3-amino-5-trifluoromethyl ester group) cyclohexane hexafluoropolyimide is obtained, the mark of which is PA-3, and the structure of the obtained product is as follows:
application example 4: the polyimide is prepared from 4,4'- (3-amino-5-trifluoromethyl ester) bicyclohexane and 4,4' - (hexafluoroisopropylene) diphthalic anhydride by the following specific steps:
in a 50mL three-necked flask equipped with an argon inlet/outlet, a magnetic stirrer, a thermometer and a condenser, under the protection of argon, 1.1693g (2mmol) of 4,4' - (3-amino-5-trifluoromethyl ester group) dicyclohexyl, 2mL of phenyl phosphite and 1mL of pyridine and 0.2g of CaCl2 and 5mL of NMP as solvents are added slowly, 0.8885g (2mmol) of 4,4' - (hexafluoroisopropyl) dicarboxylic anhydride is heated to 100 ℃ for reaction for 3 hours, after the reaction is finished, the reaction solution is cooled to room temperature, discharged materials are filtered in ethanol, a filter cake is washed with ethanol, water and ethanol in a refluxing manner for three times, and the filter cake is dried in a vacuum oven at 80 ℃ to obtain 1.7058g of 4,4' - (3-amino-5-trifluoromethyl ester group) dicyclohexyl hexafluoropolyimide, and the obtained product has the following structure:
comparative example
Taking a dihydroxy-phenyl compound as a comparative example, the structural formula of the dihydroxy-phenyl compound is as follows:
the solubility of the polyimides of the examples 1-3 and the comparative examples was tested by the following test methods: the polyimide was dissolved in NMP, DMAC, DMF, DMSO, THF and CHCl, respectively3The concentration of the polyimide in the different solvents was 10 mg/mL. Polyimide was tested for solubility in different solvents, + +: fully dissolving at room temperature; +: heating for complete dissolution; + -: partial dissolution; - -: heating for insolubilization. The test results are shown in table 1.
Table 1: solubility of polyimide in 6 solvents prepared in application examples and comparative examples
| Sample (I) | NMP | DMAC | DMF | DMSO | THF | CHCl3 |
| Application example 1 | ++ | ++ | ++ | ++ | ++ | ++ |
| Application example 2 | ++ | ++ | ++ | ++ | ++ | +- |
| Application example 3 | ++ | ++ | ++ | ++ | ++ | ++ |
| Comparative example | ++ | ++ | +- | ++ | ++ | +- |
As can be seen from the test results in Table 1, the polyimide prepared from the flexible diamine monomer provided by the invention has better solubility.
The polyimide prepared by the application example is prepared into a polyimide film by adopting a method commonly used in the field, and the light transmittance of the polyimide film is tested by adopting the following test method: the method is characterized in that a UV2550 type ultraviolet visible spectrophotometer of Shimadzu Japan is adopted for measurement, and the scanning range is 250-800 nm. The test result shows that the average transmittance of the polyimide film in a visible light range is up to 90 percent, and the average cut-off wavelength is 300 nm.
The mechanical property of the polyimide prepared by the application example is tested, and the test method comprises the following steps: the samples were measured at room temperature using a Shimadzu AG-I model universal tester, with sample sizes of 20mm 3mm 0.02mm and a tensile rate of 8 mm/min. The test results are shown in table 2.
Table 2: mechanical Properties of polyimides prepared in application examples
| Sample (I) | Tensile modulus E (GPa) | Maximum tensile Strength σmax(MPa) | Elongation at break εmax(％) |
| Application example 1 | 4.3 | 210 | 11.5 |
| Application example 2 | 4.8 | 205 | 14.3 |
| Application example 3 | 4.5 | 201 | 13.2 |
The test results in Table 2 show that the polyimide prepared from the flexible diamine monomer provided by the invention has good mechanical properties, wherein E (GPa) is 4.3-4.8 GPa, sigma max (MPa) is 201-210 MPa, and epsilon max (%) is 11.5-14.3%.
As can be seen from the above examples and application examples, the polyimide prepared from the flexible diamine monomer provided by the invention has good solubility and mechanical properties, and the polyimide film has high light transmittance.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (7)
1. A flexible diamine monomer with a trifluoromethyl substituted dicyclohexylene aliphatic structure has a structure shown in formula I:
wherein X is
n is 1 or 2.
2. The flexible diamine monomer of claim 1 wherein the flexible diamine monomer comprises 1,4- (3-amino-5-trifluoromethylester) cyclohexane or 4,4' - (3-amino-5-trifluoromethylester) bicyclohexane.
3. A method for preparing a flexible diamine monomer as claimed in claim 1 or 2, comprising the steps of:
(a) under the protection of argon, 3-nitro-trifluoromethyl cyclohexane formic acid, hydroxyl-cyclohexane and concentrated sulfuric acid are mixed for esterification reaction to obtain an ester dinitro compound with a trifluoromethyl substituted dicyclohexylene aliphatic structure;
(b) reducing the ester-based dinitro compound obtained in the step (a) by adopting hydrogen sulfide and hydrazine hydrate to obtain X
The structurally flexible diamine monomer shown in the formula I.
4. The method according to claim 3, wherein the molar ratio of 3-nitro-trifluoromethylcyclohexanecarboxylic acid, hydroxy-cyclohexane and concentrated sulfuric acid in the step (a) is 1:2 to 3:0.4 to 1.
5. The method according to claim 3 or 4, wherein the temperature of the esterification reaction in the step (a) is 115 to 125 ℃.
6. The method according to claim 3, wherein the temperature of the reduction reaction in the step (b) is 85 to 110 ℃.
7. Use of a flexible diamine monomer as claimed in any one of claims 1 to 2 in the preparation of a polyimide.
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