A diamine monomer containing a bicyclized pendant group structure and a preparation method and application thereof

Abstract

The application discloses a kind of diamine monomer containing bicyclization side group structure and its preparation method and application.The diamine monomer containing bicyclization side group structure has the structure shown in any one of the following formulae:In the application, a series of polyimide films are prepared from the diamine monomer containing bicyclization side group structure, due to the combination of bulky bicyclic substituent and central benzene ring, the rigidity and steric hindrance of the diamine monomer are significantly improved, so that the prepared polyimide film has high specific surface area and gas permeability coefficient, and the gas separation performance is better than that of commercial gas separation membrane and corresponding hexafluorodiamine gas separation membrane, and has good application prospect in industrial hydrogen purification and recovery applications.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field, and relates to a diamine monomer containing a bicyclized pendant group structure and a preparation method and application thereof, in particular to a diamine monomer containing a bicyclized pendant group structure and a preparation method thereof, a polyimide film prepared from the diamine monomer containing a bicyclized pendant group structure and application of the polyimide film in gas separation. BACKGROUND

[0002] Gas membrane separation technology is to use different gas permeation rates of membrane materials in mixed gas, to use the pressure difference of gas on both sides of the membrane as the driving force, to obtain the gas enrichment material with high permeation rate on the permeation side, and to obtain the separation gas with difficult-to-permeate gas enrichment on the non-permeation side, so as to realize the purpose of separating mixed gas. Compared with traditional separation methods such as low-temperature distillation or adsorption, membrane separation technology has many advantages such as simple equipment, small investment, low energy consumption, easy operation, safety and no pollution to the environment, and thus has attracted more and more attention from the scientific research and industrial circles.

[0003] Polyimides generally have high gas permeability and selectivity, and also have excellent heat resistance, mechanical properties and chemical stability. These advantages make polyimides an attractive gas separation membrane material. Since 2002, Air Liquide, Praxair, Parker-Hannifin and Ube companies have applied polyimides to different gas separation fields.

[0004] At present, the commercially available polyimide separation membranes are only and Although they have good mechanical properties, thermodynamic stability and high selectivity coefficient, The permeation coefficient of pure CO2 is 10 barrer and the CO2 / CH4 selectivity is 36 in the prior art, which limits its industrial application due to the low permeation coefficient and separation efficiency. The permeation coefficient P and the ideal selectivity a are two important indicators for evaluating the separation performance of a membrane. A gas separation membrane with high permeation coefficient and high selectivity has been the goal pursued by researchers. However, in fact, the permeation coefficient P and the ideal selectivity a of a polymer membrane often present a trade-off relationship. That is, the polymer membrane with high permeation coefficient has low ideal selectivity, and the polymer membrane with high selectivity has low permeation coefficient. In 1991, Robeson proposed the characteristic limit of high polymer, i.e., the upper limit of Robeson, to describe the trade-off effect of the permeation coefficient and the selectivity. In order to achieve high permeation flux and high separation efficiency, a high polymer membrane should have high permeation coefficient and selectivity at the same time, so that breaking through the upper limit of Robeson and preparing a high-performance separation material will become a main development direction in this field. In addition to high permeation coefficient and selectivity, an ideal gas separation membrane material also needs to have good mechanical properties, thermodynamic stability and film processing properties. SUMMARY

[0005] The main purpose of the present application is to provide a diamine monomer containing a bicyclized pendant group structure and a preparation method and application thereof to overcome the shortcomings of the prior art.

[0006] To achieve the above-mentioned purposes, the technical solutions adopted by the present application comprise:

[0007] The present application provides a diamine monomer containing a bicyclized pendant group structure, which has a structure as shown in any one of formula (I) to formula (V):

[0008]

[0009] The present application also provides a preparation method of the above-mentioned diamine monomer containing a bicyclized pendant group structure, which comprises:

[0010] The diamine monomer containing a bicyclized pendant group structure is prepared by sequentially performing D-A reaction, reduction, substitution, oxidation, esterification, substitution and oximation reaction on benzoquinone and a diene compound.

[0011] The diene compound comprises any one or a combination of two or more of cyclopentadiene, cyclohexadiene, methylcyclopentadiene, tetramethylcyclopentadiene and pentamethylcyclopentadiene.

[0012] The polyimide film is prepared from the aforementioned diamine monomer with bicyclized side group structure, and has a structure as shown in formula (VI):

[0013]

[0014] wherein 1 < n < 1000, and R1 is selected from a structure as shown in any one of the following formulae or a combination of two or more thereof:

[0015]

[0016]

[0017] R2 is selected from a structure as shown in any one of the following formulae:

[0018]

[0019] wherein the dotted line represents a bond connection position.

[0020] The embodiment of the present application also provides a preparation method of the aforementioned polyimide film, which comprises the following steps:

[0021] providing the aforementioned diamine monomer with bicyclized side group structure;

[0022] reacting a mixed reaction system containing the diamine monomer, an aromatic dianhydride, a catalyst and a solvent at 50-100 DEG C for 1-4 hours under a protective atmosphere to prepare a prepolymer;

[0023] continuing to react the prepolymer at 140-200 DEG C for 4-12 hours to prepare the polyimide with bicyclized side group structure;

[0024] and mixing the polyimide with bicyclized side group structure with an organic solvent and performing film spreading treatment to prepare the polyimide film.

[0025] The embodiment of the present application also provides a use of the aforementioned polyimide film in the field of gas separation.

[0026] Compared with the prior art, the embodiment of the present application has the following beneficial effects:

[0027] (1) The polyimide film with bicyclized side group structure provided by the present application introduces the diamine with bicyclized side group structure of rigid twisted structure, which on one hand increases the rigidity of the molecular chain skeleton and reduces the activity of the molecular chain segment, and on the other hand, destroys the ordered packing degree of the polyimide molecular chain segment, weakens the intermolecular force, increases the intermolecular distance, increases the free volume and specific surface area of the polyimide, and the specific surface area is more than 460 m 2g -1 up to 580m 2 g -1 ;

[0028] (2) The polyimide film containing bicyclized pendant group structure provided by the application has permeation coefficients of H2, CO2, O2, N2 and CH4 all exceeding 1000, 1470, 295, 95 and 98 Barrer respectively, which improves the shortcomings of low permeation coefficient and low separation efficiency of commercial polyimide gas separation membrane, and greatly improves the gas separation efficiency;

[0029] (3) The polyimide film containing bicyclized pendant group structure provided by the application has a separation performance of hydrogen / methane and hydrogen / nitrogen close to the upper limit line of 2008 Robeson, which is better than the separation performance of corresponding hexafluorodiamine polyimide, and has great potential in industrial hydrogen purification and recovery applications. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0031] Figures la-d is the nuclear magnetic hydrogen spectrum of the diamine containing bicyclized pendant group structure prepared in the embodiments 1-4 of the application;

[0032] Figures 2a-d is the nuclear magnetic spectrum of the polyimide film containing bicyclized pendant group structure prepared in the embodiment 1 of the application;

[0033] Figure 3 is the ultraviolet-visible light spectrum curve of the polyimide film containing bicyclized pendant group structure prepared in the embodiment 1 of the application;

[0034] Figures 4a-c is the gas separation performance graph of H2 / CH4 of the polyimide film containing bicyclized pendant group structure in the embodiments 1, 2 and 5 of the application and the hexafluorodiamine and seven commercial gas separation membranes in the prior art;

[0035] Figures 5a-c is the gas separation performance graph of H2 / N2 of the polyimide film containing bicyclized pendant group structure in the embodiments 1, 2 and 5 of the application and the hexafluorodiamine and seven commercial gas separation membranes in the prior art. DETAILED DESCRIPTION

[0036] In view of the defects of the prior art, the present inventors have long studied and practiced to propose the technical solution of the present application, which mainly uses p-benzoquinone and a diene compound as initial raw materials, and synthesizes a diamine compound with a large aliphatic cyclic side group through D-A reaction, reduction, oxidation, esterification, substitution, and oximation reaction; and uses the prepared diamine and dianhydride monomer containing a bicyclic side group structure as raw materials to prepare a polyimide film containing a bicyclic side group structure through polymerization reaction and subsequent processing steps, and analysis test data show that the polyimide film containing a bicyclic side group structure prepared by the technical solution of the present application has excellent permeability and selectivity.

[0037] The technical solution of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0038] Specifically, as one aspect of the technical solution of the present application, the diamine monomer containing a bicyclic side group structure has a structure as shown in any one of formula (I) to formula (V):

[0039]

[0040] Another aspect of the embodiments of the present application further provides a preparation method of the aforementioned diamine monomer containing a bicyclic side group structure, which comprises:

[0041] The diene compound includes any one or a combination of two or more of cyclopentadiene, cyclohexadiene, methylcyclopentadiene, tetramethylcyclopentadiene, and pentamethylcyclopentadiene.

[0042] In some preferred embodiments, the diene compound has a structure as shown in any one of the following formulae:

[0043]

[0044] Further, the cyclopentadiene is purchased from the company of Macclin, the cyclohexadiene is purchased from the company of Inokai, and the methylcyclopentadiene, tetramethylcyclopentadiene, and pentamethylcyclopentadiene are purchased from the company of Sigma-Aldrich.

[0045] In some preferred embodiments, the catalyst used in the preparation of the diamine monomer containing a bicyclic side group structure includes methyltrioxorhenium, which is purchased from the company of Sigma-Aldrich.

[0046] In some preferred embodiments, the solvent required for preparing the diamine monomer with bicyclized pendant group structure includes, but is not limited to, ethanol, ethyl acetate, petroleum ether, acetone, chloroform, tetrahydrofuran, N,N-dimethylformamide, diethyl ether, and the like.

[0047] In some preferred embodiments, the method for preparing the diamine monomer with bicyclized pendant group structure further comprises: after the reaction is completed and the reaction system is cooled to room temperature, filtering the obtained mixture, collecting the filtrate, and concentrating to obtain a crude product; and subjecting the crude product to recrystallization and / or column chromatography separation, and vacuum drying to obtain an intermediate product and a final diamine monomer.

[0048] Further, the filtering operation uses a G3 or G4 sand core funnel.

[0049] Further, the column chromatography uses 200-300 mesh silica gel, and the eluent uses ethyl acetate and dichloromethane, with a solvent ratio of 1:10-30 (v / v); ethyl acetate and petroleum ether, with a solvent ratio of 1:1-10 (v / v).

[0050] Further, the product solid obtained by recrystallization and / or column chromatography is vacuum dried at 80-120°C for 6-12 hours.

[0051] Another aspect of the embodiments of the present application also provides a polyimide film prepared from the polyimide with bicyclized pendant group structure, which is prepared from the aforementioned diamine monomer with bicyclized pendant group structure, and the polyimide has a structure as shown in formula (VI):

[0052]

[0053] wherein 1

[0054]

[0055] wherein the dotted line represents the access position of the anhydride.

[0056] R2is selected from any of the structures as shown in the following formula:

[0057]

[0058] wherein the dotted line represents the access position of the amino group.

[0059] In some preferred embodiments, the polyimide film has a thermal decomposition temperature above 400°C at 5 wt% weight loss under a nitrogen atmosphere; and the specific surface area of the polyimide film is above 100 m 2 / g.

[0060] In some preferred embodiments, the polyimide film has a thickness of 50-80 μm.

[0061] Another aspect of the embodiments of the present application also provides a method for preparing the aforementioned polyimide film, which comprises:

[0062] providing the aforementioned diamine monomer with bicyclized pendant group structure;

[0063] reacting a mixed reaction system comprising the diamine monomer, aromatic dianhydride, catalyst and solvent at 50-100 °C for 1-4 h under a protective atmosphere to prepare a prepolymer;

[0064] continuing the reaction of the prepolymer at 140-200 °C for 4-12 h to prepare a polyimide with bicyclized pendant group structure;

[0065] and mixing the polyimide with bicyclized pendant group structure with an organic solvent and performing film casting treatment to prepare a polyimide film.

[0066] In some preferred embodiments, the protective atmosphere is selected from nitrogen and / or inert gas, and the inert gas includes argon.

[0067] In some preferred embodiments, the aromatic dianhydride includes any one of hexafluoroisopropyl phthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyldianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 3,3,4,4-diphenylaluminotetracarboxylic dianhydride, 1,4,5,8- naphthalenetetracarboxylic anhydride, 9,9-bis(triethyl)-2,3,6,7-oxanaphthalene tetracarboxylic dianhydride, pyromellitic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclohexanone-α'-spiro-2'-norbornane-5,5",6,6"-tetracarboxylic dianhydride, 3,3,3',3'-tetramethyl 2,2',3,3'-tetrahydro-1,1-spirobisindene tetracarboxylic dianhydride, 7,7'-spirobisindene[7H-cyclopenta[g]isobenzofuran[5,6-b][1,4]benzodioxin]-1,1',3,3'-tetrahydronaphthalene ketone, 8,8',9,9'-tetrahydro-9,9,9',9'-tetramethyl tetracarboxylic dianhydride, or a combination of two or more thereof, and is not limited thereto.

[0068] In some preferred embodiments, the catalyst includes a basic catalyst and / or an acidic catalyst, wherein the acidic catalyst includes benzoic acid and / or p-hydroxybenzoic acid; and the basic catalyst includes any one of triethylamine, tripropylamine, tributylamine, isoquinoline, or a combination of two or more thereof, and is not limited thereto.

[0069] Further, the basic catalyst includes isoquinoline and / or triethylamine, and is not limited thereto.

[0070] In some preferred embodiments, the solvent includes any one or a combination of two or more of m-cresol, p-chlorophenol, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and is not limited thereto.

[0071] In some preferred embodiments, the molar ratio of the diamine monomer, the aromatic dianhydride, and the catalyst is 1:1:0.5-3.

[0072] In some preferred embodiments, the preparation method further includes, after the prepolymer reaction is completed, adding a precipitant to the obtained mixture, and then performing Soxhlet extraction.

[0073] Further, the precipitant includes any one or a combination of two or more of methanol, ethanol, acetone, petroleum ether, and water, and is not limited thereto.

[0074] In some preferred embodiments, the film formation process includes mixing the polyimide containing a bicyclized pendant group structure with an organic solvent to form a solution having a mass fraction of 1-10%, and then using a casting method to form a film of the solution on a substrate, and then performing a programmed temperature treatment, drying, and demolding.

[0075] Further, the organic solvent includes any one or a combination of two or more of tetrahydrofuran, dichloromethane, trichloromethane, m-cresol, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and is not limited thereto.

[0076] Further, the drying treatment is performed at a temperature of 50-100°C for 6-20h.

[0077] Further, the programmed temperature treatment includes, raising the temperature from room temperature to 60-80°C for 6-10h, then raising the temperature to 80-120°C for 2-5h, then raising the temperature to 120-150°C for 3-6h, and finally raising the temperature to 200-300°C for 2-5h.

[0078] In some more specific embodiments, the preparation method of the polyimide film specifically includes:

[0079] (1) under the protection of a protective atmosphere, a mixed reaction system containing a diamine monomer containing a bicyclized pendant group structure, an aromatic dianhydride, a catalyst, and a solvent is reacted at 50-100°C for 1-4h to obtain a polyamic acid solution (the aforementioned "prepolymer");

[0080] (2) The polyamic acid solution generated in the above step is heated to 140-200°C, and reacted for 4-12 hours to convert the polyamic acid into polyimide;

[0081] (3) The polyimide solution with bicyclic side group structure generated in the above step is poured into a poor solvent to precipitate, and the obtained solid is Soxhlet extracted for 1-2 days;

[0082] The polyimide solid generated in the above step is dried in a sublimation tube, dissolved in a soluble solvent, and configured to have a solid content of 3-15% for film coating treatment to obtain the polyimide film with bicyclic side group structure.

[0083] Another aspect of the embodiment of the present application also provides the use of the aforementioned polyimide film in the field of gas separation.

[0084] Further, the use is the use of the polyimide film in separating hydrogen, methane, carbon dioxide or oxygen.

[0085] For example, the use is the separation of the polyimide film for hydrogen / methane or hydrogen / nitrogen gas pairs.

[0086] For example, the use is the separation of the polyimide film for carbon dioxide / methane or carbon dioxide / nitrogen gas pairs.

[0087] For example, the use is the separation of the polyimide film for oxygen / nitrogen gas pairs.

[0088] The technical solutions of the present application will be further described in detail below in combination with several preferred embodiments and drawings. The embodiments are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0089] The experimental materials used in the following examples are commercially available from conventional biochemical reagent companies, unless otherwise specified.

[0090] Example 1

[0091]

[0092] 1.1 Synthesis of DMNDA monomer

[0093] (1) Freshly distilled cyclopentadiene (2.64 g, 40 mmol) was added dropwise to an ice-cold solution of p-benzoquinone (2.16 g, 20 mmol) in ethanol (20 mL) at 0°C under N2atmosphere. The mixture was stirred at room temperature for 8 hours. The precipitate was collected by filtration, washed with cold ethanol and dried in vacuum to obtain colorless 4.7 g of product I with a yield of 99%.

[0094] (2) A solution of I (1.2 g, 5 mmol) in a mixture of ethyl acetate-ethanol (1 :1) containing 10% Pd / C (20 mg) was hydrogenated in a reaction bomb apparatus under 2.5 MPa of hydrogen. After 8 h, the insoluble catalyst was removed by suction filtration through a G-4 frit funnel and washed with dichloromethane (20 mL) after cooling to room temperature. The filtrate was concentrated under reduced pressure and the solid was dried in vacuo to give II as a colorless crystalline solid in 98% yield (1.9 g).

[0095] (3) A solution of II (2.44 g, 10 mmol) in chloroform (20 mL) was stirred at room temperature and a solution of Br2(1.6 g, 10 mmol) in chloroform (20 mL) was added dropwise slowly over 0.5 h under N2atmosphere. The resulting suspension was stirred at room temperature for 8 h. The resulting suspension was cooled in an ice-acetone bath for 1 h and the precipitate was filtered under vacuum and washed with cold chloroform to give III as a brown solid in 98% yield.

[0096] (4) A three necked round bottom flask was charged with III (8.48 g, 35 mmol), p-toluenesulfonyl chloride (15.650 g, 83 mmol) and dichloromethane (600 mL) and stirred at 0 °C for 1 h under nitrogen atmosphere. Triethylamine (8.938 g, 88.33 mol) was added dropwise slowly under stirring at 0 °C. After the addition was complete, the temperature was raised to 25 °C and stirring was continued for 20 h. The mixture was washed thoroughly with deionized water (3 x 500 mL) and dried over magnesium sulfate. The dichloromethane was removed by rotary evaporation and the crude product was recrystallized from ethanol to give IV as a light yellow crystalline solid in 80% yield (15.4 g).

[0097] (5) A three necked round bottom 500 ml flask equipped with a Dean-Stark apparatus, condenser, magnetic stirrer and gas inlet outlet was charged with IV (27.5 g, 50 mmol), toluene (100 mL) and anhydrous DMF (300 mL). The mixture was heated to 140 °C under nitrogen atmosphere and after 1 h of reaction, toluene and residual water in the reaction solvent were removed from the system as an azeotrope by distillation. After 4 h, potassium o-phenylenediamine (20.50 g, 110 mmol) and 18-crown-6 (2.642 g, 10 mmol) were added and the reaction was continued at 140 °C for 48 h. After cooling to room temperature, the dark brown solution was poured into 800 mL of deionized water. The mixture was extracted with chloroform (3 x 400 mL) and the organic solvent was dried over magnesium sulfate. The chloroform was removed by rotary evaporation to give the crude product which was further purified by washing with ethanol to give V as an off-white solid powder in 30% yield (7.5 g).

[0098] (6) V (26.0 g, 52 mmol) and 6 M HCI in acetic acid (137.5 mL) were placed in a 500 mL three necked round flask equipped with a mechanical stirrer and condenser. The mixture was heated at 140 °C for 45 h, then cooled to room temperature and the precipitate (phthalic acid) was removed by filtration. The filtrate was washed thoroughly with diethyl ether (3 x 200 mL). The aqueous phase was collected and concentrated under reduced pressure. The crude product was further purified by recrystallization from ethanol to give a pale yellow solid (13.75 g) in 85% yield as DMNDA. (NMR spectrum of hydrogen see Figure la ).

[0099] 1.2 Polymerization based on DMNDA diamine monomer

[0100] In this example, the structure of the polyimide based on DMNDA diamine is as follows: (NMR spectrum of hydrogen see Figures 2a-d ).

[0101]

[0102] The polymerization reaction includes the following steps:

[0103] 1.2.1 In this example, the 6FDA-DMNDA polyimide has the following structure:

[0104]

[0105] Under nitrogen protection, hexafluoroisopropyl phthalic anhydride (6FDA) (1.110 g, 2.5 mmol), DMNDA (0.6 g, 2.5 mmol), benzoic acid (0.1527 g, 1.25 mmol) were added into a flask, then m-cresol (6.5 g) was added to control the solid content of the system at 20 wt%. The system was mechanically stirred at 80 °C for 1 h until the reactants were completely dissolved, the temperature was raised to 180 °C, and the reaction was continued for 8 h until the polymer was completely imidized. m-Cresol (24.40 g) was added to dilute the solid content of the system to 5 wt%, and the heating was stopped and the temperature was naturally reduced to room temperature. The reaction solution was poured into a mixed solution of ethanol and water (300 ml, v / v = 1:1) with magnetic stirring, and a white fibrous solid was precipitated, which was filtered. The fibrous solid was placed in a Soxhlet extractor, and ethanol was heated to reflux for 18 h to remove excess m-cresol. After completion, it was dried at 120 °C to obtain a polyimide containing DMNDA structure. (NMR spectrum of hydrogen see Figure 2a .

[0106] The polypyrimidine containing bicyclic pendant group structure was dissolved in chloroform to form a solution with a solid content of 5wt%, and the insoluble substances and impurities were removed by filtration. The polypyrimidine solution was slowly poured onto a flat, smooth and dry glass surface using a casting method. The glass surface was placed in a film coating oven and dried at room temperature for 12h. Then the glass plate was completely immersed in distilled water until the film naturally fell off, and a polypyrimidine film containing a bicyclic pendant group structure (denoted as 6FDA-DMNDA) was obtained.

[0107] The surface area thereof was 469m 2 The permeation coefficient of nitrogen was 95.7 barrer, the permeation coefficient of oxygen was 295 barrer, the permeation coefficient of hydrogen was 1055 barrer, the permeation coefficient of methane was 98.2 barrer, the permeation coefficient of carbon dioxide was 1473 barrer, the permeation selectivity of carbon dioxide / methane was 15.1, the permeation selectivity of carbon dioxide / nitrogen was 15.4, the temperature of 5% thermal weight loss under nitrogen was 454℃, and the glass transition temperature was 419℃.

[0108] 1.2.2 In this embodiment, the Co-CpODA-DMNDA-0.8 polypyrimidine has the following structure:

[0109]

[0110] The preparation of the polypyrimidine gas separation membrane mainly includes the following steps:

[0111] Under the protection of nitrogen atmosphere, 0.2292 g (0.516 mmol) of 6FDA and 0.7933 g (2.064 mmol) of CpODA dianhydride were mixed with 0.6201 g (2.58 mmol) of DMNDA and 0.1578 g (1.29 mmol) of benzoic acid in a three-necked polymerization flask, and then 7.6 g of anhydrous m-cresol solution was added to make the solid content of the whole system 20 wt%, after adjusting the mechanical stirring to a suitable speed, the system was heated to 80 °C for stirring for 1-2 h to make it completely dissolved, forming a relatively transparent light yellow solution, after the solid was completely dissolved, the system was heated to 180 °C for thermal imidization, and the reaction was carried out for 8-10 h to make the polyimide completely thermal imidized, then 10.5 g of m-cresol was added to reduce the solid content of the system to 9 wt%, the heating was turned off, and the temperature was reduced to 80 °C, 300 ml of methanol was stirred on a magnetic stirrer, and the reaction solution was slowly poured into the methanol to obtain a white filamentous fibrous solid, which was continuously stirred on a magnetic stirrer for 2-3 h, and then the filamentous material was filtered and placed in a Soxhlet extractor for 12 h to remove the residual m-cresol solvent in the polymer, and then the filamentous material was dried at 120 °C under vacuum to obtain the polyimide of the above structure.

[0112] The above polymer (0.5 g) was dissolved in chloroform (25 ml) to prepare a solution with a solid content of 10%, and then the solution was filtered through a 0.45 μm filter head to remove insoluble substances, and then the solution was cast on a clean glass dish using a casting method, and then the glass dish was shaken until no bubbles were present, and then a slightly larger glass dish was used to cover the glass dish to prevent impurities from falling into the glass dish, and then the glass dish was placed in a glass box, and the solvent was gradually evaporated at room temperature until the film was dry, and then the film was removed with tweezers to obtain a polyimide film (denoted as Co-CpODA-DMNDA-0.8), and the hydrogen spectrum is shown in Figure 2d .

[0113] The surface area of the polyimide was 497 m 2 / g, and the gas separation test showed that the permeability coefficients of nitrogen, oxygen, hydrogen, methane, carbon dioxide, carbon dioxide / methane, and carbon dioxide / nitrogen were 45.4 barrer, 156 barrer, 727 barrer, 50.6 barrer, 750 barrer, 14.8, and 16.5, respectively, at 1 barrer and 35 °C, the temperature at which 5% of the polyimide was thermally decomposed under nitrogen was 452 °C, and the glass transition temperature of the polyimide was > 450 °C.

[0114] Example 2

[0115]

[0116] 2.1 Synthesis of DENDA monomer

[0117] (1) Freshly distilled cyclohexadiene (3.20 g, 40 mmol) was added dropwise to an ice-cold solution of p-benzoquinone (2.16 g, 20 mmol) in ethanol (20 mL) at 0 °C under N2atmosphere. The mixture was stirred at room temperature for 8 h. The precipitate was collected by filtration, washed with cold ethanol and dried in vacuum to give colorless 5.3 g of product I in 99% yield.

[0118] (2) A solution of I (1.341 g, 5 mmol) in a mixture of ethyl acetate-ethanol (1 : 1) containing 10% Pd / C (20 mg) (20 mL) was hydrogenated in a reaction bomb apparatus under 2.5 MPa of hydrogen. After 8 h, the insoluble catalyst was removed by suction filtration using a G-4 funnel after cooling to room temperature naturally, and washed with dichloromethane (20 mL). The filtrate was concentrated under reduced pressure and the solid was dried in vacuum to give II as a colorless crystalline solid in quantitative yield (1.3 g).

[0119] (3) A solution of II (2.7 g, 10 mmol) in chloroform (20 mL) was stirred at room temperature and a solution of Br2(1.6 g, 10 mmol) in chloroform (20 mL) was added dropwise slowly over 0.5 h under N2atmosphere. The resulting suspension was stirred at room temperature for 8 h. The resulting suspension was cooled in an ice-acetone bath for 1 h, the precipitate was filtered under vacuum and washed with cold chloroform to give III as a brown solid in 98% yield.

[0120] (4) III (9.462 g, 35 mmol), p-toluenesulfonyl chloride (15.650 g, 83 mmol) and dichloromethane (600 mL) were taken in a three necked round bottom flask and stirred at 0 °C under nitrogen atmosphere for 1 h after which triethylamine (8.938 g, 88.33 mol) was added dropwise slowly under stirring at 0 °C. After completion of the addition, the temperature was raised to 25 °C and stirring was continued for 20 h. The mixture was washed thoroughly with deionized water (3 x 500 mL) and dried over magnesium sulfate. Dichloromethane was removed by rotary evaporation and the crude product was recrystallized from ethanol to give IV as a pale yellow crystalline solid in 80% yield (16.18 g).

[0121] (5) IV (28.9 g, 50 mmol), toluene (100 mL) and dry DMF (300 mL) were placed in a three necked round bottomed 500 ml flask fitted with a Dean-Stark apparatus, condenser, magnetic stirrer and gas inlet outlet. The mixture was heated to 140°C under nitrogen atmosphere and after 1 h of reaction, toluene and residual water from the reaction solvent were removed from the system as an azeotrope by distillation. After 4 h, potassium o-phenylenediamine (20.50 g, 110 mmol) and 18-crown-6 (2.642 g, 10 mmol) were added and the reaction was carried out at 140°C for 48 h. After cooling to room temperature, the dark brown solution was poured into 800 mL of deionized water. The mixture was extracted with chloroform (3 x 400 mL) and the organic solvent was dried over magnesium sulfate. The chloroform was removed by rotary evaporation to obtain the crude product which was further purified by washing with ethanol to obtain V as an off-white solid powder in 30% yield (7.9 g).

[0122] (6) V (27.48 g, 52 mmol) and 6 M HCI in acetic acid (137.5 mL) were placed in a 500 ml three necked round bottomed flask fitted with a mechanical stirrer and condenser. The mixture was then heated at 140°C for 45 h after which it was cooled to room temperature and the precipitate (phthalic acid) was removed by filtration. The filtrate was thoroughly washed with diethyl ether (3 x 200 mL). The aqueous phase was collected and concentrated under reduced pressure and the crude product was further purified by recrystallization from ethanol to obtain DENDA as a light yellow solid in 85% yield (14.99 g). (1H NMR spectrum is shown in Figure 2). Figure lb ).

[0123] 2.2 Polymerization based on DENDA diamine monomer

[0124] In this example, the structure of the DENDA diamine based polyimide is as follows:

[0125]

[0126] 2.2.1 In this example, the SBI-DENDA polyimide has the structure of the following formula

[0127]

[0128] Into a flask, under nitrogen protection, was added SBI (1.571 g, 2.5 mmol), DENDA (0.67 g, 2.5 mmol), benzoic acid (0.1527 g, 1.25 mmol), and then m-cresol (6.9 g) was added to control the solid content of the system at 20 wt%. The system was mechanically stirred at 80 °C for 1 h until the reactants were completely dissolved, the temperature was raised to 180 °C, and the reaction was continued for 8 h until the polymer was completely imidized. m-Cresol (24.80 g) was added to dilute the solid content of the system to 5 wt%, and the heating was stopped and the system was allowed to cool to room temperature naturally. The reaction solution was poured into a mixed solution of ethanol and water (300 ml, v / v = 1:1) with magnetic stirring, and a white fibrous solid was precipitated and filtered. The fibrous solid was placed in a Soxhlet extractor, and ethanol was used to reflux for 18 h to remove the excess m-cresol. After the end of the extraction, the product was dried at 120 °C to obtain a polyimide containing DENDA structure.

[0129] The polyimide containing bicyclic pendant group structure was dissolved in chloroform to prepare a solution with a solid content of 5 wt%. The insoluble and impurities were removed by filtration, and the bubbles were removed by vacuum. The polyimide solution was slowly poured onto a flat, smooth and dry glass surface using the casting method. The glass surface was placed in a film coating oven, and after drying at room temperature for 12 h, the glass plate was completely immersed in distilled water, and the film was naturally detached to obtain a polyimide film containing a bicyclic pendant group structure (denoted as SBI-DENDA).

[0130] The gas separation test was performed at 1 barrer and 35 °C, and the permeation coefficients of nitrogen, oxygen, hydrogen, methane, carbon dioxide, and carbon dioxide / methane were 113.5 barrer, 375.4 barrer, 1456 barrer, 156.4 barrer, 1583 barrer, 10.2, and 13.9, respectively. The temperature at which 5% of the weight was lost under nitrogen was 458 °C, and the glass transition temperature was > 450 °C.

[0131] 2.2.2 In this example, the Co-CpODA-DENDA-0.8 polyimide has the following structure

[0132]

[0133] The preparation of the above-mentioned polyimide gas separation membrane mainly includes the following steps:

[0134] Under the protection of nitrogen atmosphere, 0.2292 g (0.516 mmol) of 6FDA and 0.7933 g (2.064 mmol) of CpODA dianhydride were mixed with 0.6924 g (2.58 mmol) of DENDA and 0.1578 g (1.29 mmol) of benzoic acid in a three-necked polymerization flask, and then 7.6 g of anhydrous m-cresol solution was added to make the solid content of the whole system 20 wt%, after the mechanical stirring was adjusted to the appropriate speed, the system was heated to 80°C for stirring for 1-2 h to make it completely dissolved, forming a relatively transparent light yellow solution, after the solid was completely dissolved, the system was heated to 180°C for thermal imidization, and the polyimide was completely thermal imidized after reaction for 8-10 h, 10.5 g of m-cresol was then added to reduce the solid content of the system to 9 wt%, the heating was turned off, and the temperature was reduced to 80°C, 300 ml of methanol was stirred on a magnetic stirrer, and the reaction solution was slowly poured into the methanol to obtain a white fibrous solid, which was continuously stirred on a magnetic stirrer for 2-3 h, the fibrous material was filtered and placed in a Soxhlet extractor for 12 h to remove the residual m-cresol solvent in the polymer, and then the fibrous material was dried at 120°C under vacuum to obtain the polyimide of the above structure.

[0135] The above polymer (0.5 g) was dissolved in chloroform (25 ml) to make a solution with a solid content of 10%, and after being stirred thoroughly to completely dissolve, insoluble substances were filtered out with a filter head of 0.45 μm, and a film was laid by the flow casting method, which was evenly laid on a clean glass dish, shaken until there were no bubbles, then covered with a slightly larger glass dish to prevent impurities from falling in, and placed in a glass box to gradually evaporate the solvent to dryness at room temperature to form a film, which was taken out with tweezers to obtain a polyimide film (denoted as Co-CpODA-DENDA-0.8).

[0136] Through gas separation test, the permeation coefficients of nitrogen, oxygen, hydrogen, methane and carbon dioxide were 53.1 barrer, 178.5 barrer, 1456 barrer, 156.4 barrer and 889.3 barrer respectively at 1 barrer and 35°C, the permeation selectivity of carbon dioxide / methane was 15.76, the permeation selectivity of carbon dioxide / nitrogen was 16.7, the temperature at which 5% of the weight was lost under nitrogen was 458°C, and the glass transition temperature was >450°C.

[0137] Example 3

[0138]

[0139] 3.1 Synthesis of 1-Me-DMNDA monomer

[0140] (1) Freshly distilled methylcyclopentadiene (3.20 g, 40 mmol) was added dropwise to an ice-cold solution of p-benzoquinone (2.16 g, 20 mmol) in ethanol (20 mL) at 0 °C under N2atmosphere. The mixture was stirred at room temperature for 8 h. The precipitate was collected by filtration, washed with cold ethanol and dried in vacuum to give colorless 5.3 g of product I in 99% yield.

[0141] (2) A solution of I (1.341 g, 5 mmol) in a mixture of ethyl acetate-ethanol (1 : 1) containing 10% Pd / C (20 mg) (20 mL) was hydrogenated in a reaction bomb apparatus under 2.5 MPa of hydrogen. After 8 h, the insoluble catalyst was removed by suction filtration with a G-4 funnel after cooling to room temperature naturally, and washed with dichloromethane (20 mL). The filtrate was concentrated under reduced pressure and the solid was dried in vacuum to give II as a colorless crystalline solid in quantitative yield (1.3 g).

[0142] (3) A solution of II (2.72 g, 10 mmol) in chloroform (20 mL) was stirred at room temperature and a solution of Br2(1.6 g, 10 mmol) in chloroform (20 mL) was added dropwise slowly over 0.5 h under N2atmosphere. The resulting suspension was stirred at room temperature for 8 h. The resulting suspension was cooled in an ice-acetone bath for 1 h, the precipitate was filtered under vacuum and washed with cold chloroform to give III as a brown solid in 98% yield (2.7 g).

[0143] (4) III (9.462 g, 35 mmol) was dissolved in acetic acid (300 ml) at 130 °C, and an aqueous solution of potassium bromate (1.3%, 170 ml) was added. The reaction was stirred for 2 min and immediately poured into 100 ml of water. The reaction mixture was stirred for 30 min. The resulting suspension was cooled at room temperature, then filtered and washed with ethanol to give IV as a yellow product in 90% yield (8.45 g).

[0144] (5) A solution of IV (18.785 g, 70 mmol) in ethanol (250 ml, 95%) was added with hydroxylamine hydrochloride (398.1 mg, 5.73 mmol), and the mixture was heated at 78 °C for 2.5 h, then cooled to room temperature and filtered to remove the solid. The filtrate was poured into water (100 mL) and extracted with CH2Cl2(3 x 100 mL). The combined organic extracts were concentrated to give V as a yellow solid in 85% yield (17.75 g).

[0145] (6) V (9.25 g, 31 mmol), Pd / C (1 g, 10% Pd) and ethanol 160 mL were added to a 250 mL flask under nitrogen atmosphere, refluxed at 90 °C, and hydrazine hydrate (90 mL) was added by syringe. After 12 h of reaction, the Pd / C was removed by filtration, the filtrate was concentrated by rotary evaporation, and then poured into water to precipitate the solid, which was collected by filtration, washed with water, and dried at 100 °C under vacuum to give 1-Me-DMNDA (6.6 g) as a white solid in 80% yield. (See Figure 1 for the1H NMR spectrum) Figure lc )

[0146] 3.2 Polymerization based on 1-Me-DMNDA diamine monomer

[0147] In this example, the structure of the polyimide based on 1-Me-DMNDA diamine is as follows:

[0148]

[0149] 3.2.1 In this example, the 6FDA-1-Me-DMNDA polyimide has the following structure:

[0150]

[0151] Under nitrogen protection, hexafluoroisopropyl phthalic anhydride (6FDA) (1.110 g, 2.5 mmol), 1-Me-DENDA (0.671 g, 2.5 mmol), benzoic acid (0.1527 g, 1.25 mmol) were added to a flask, and then m-cresol (6.6 g) was added to control the solid content of the system at 20 wt%. The system was mechanically stirred at 80 °C for 1 h until the reactants were completely dissolved, the temperature was increased to 180 °C, and the reaction was continued for 8 h until the polymer was completely imidized. m-Cresol (24.40 g) was added to dilute the solid content of the system to 5 wt%, and the heating was stopped and the system was naturally cooled to room temperature. The reaction solution was poured into a mixed solution of ethanol and water (300 ml, v / v = 1:1) with magnetic stirring, and a white fibrous solid was precipitated, which was filtered. The fibrous solid was placed in a Soxhlet extractor, and ethanol was heated to reflux for 18 h to remove excess m-cresol. After completion, the polyimide containing 1-Me-DMNDA structure was obtained by drying at 120 °C.

[0152] The polyimide containing bicyclized pendant group structure was dissolved in chloroform to prepare a solution with a solid content of 5 wt%, and insoluble substances and impurities were removed by filtration. The system was vacuumed to eliminate bubbles, and the polyimide solution was slowly poured onto a flat, smooth and dry glass surface dish using the casting method. The glass surface dish was placed in a film coating oven, and after drying at room temperature for 12 h, the glass plate was completely immersed in distilled water until the film naturally fell off, and a polyimide film containing a bicyclized pendant group structure (denoted as 6FDA-1-Me-DENDA) was obtained.

[0153] The surface area thereof was 472 m2 / g by BET test 2 / g, the permeation coefficient of nitrogen was 104.7 barrer, the permeation coefficient of oxygen was 312.5 barrer, the permeation coefficient of hydrogen was 1225 barrer, the permeation coefficient of methane was 115.6 barrer, the permeation coefficient of carbon dioxide was 1705 barrer, the permeation selectivity of carbon dioxide / methane was 14.7, the permeation selectivity of carbon dioxide / nitrogen was 16.2, the temperature of 5% thermal weight loss under nitrogen condition was 421°C, and the glass transition temperature thereof was 408°C.

[0154] 3.2.2 In this example, the Co-BTA-1-Me-DMNDA-0.8 polyimide has the structure of the following formula

[0155]

[0156] Under the protection of nitrogen atmosphere, 0.2292 g (0.516 mmol) of 6FDA and 0.512 g (2.064 mmol) of BTA dianhydride were mixed with 0.6924 g (2.58 mmol) of DENDA and 0.1578 g (1.29 mmol) of benzoic acid in a three-necked polymerization flask, and then 6.6 g of anhydrous m-cresol solution was added to make the solid content of the whole system 20 wt%, after adjusting the mechanical stirring to a proper rotating speed, the system was heated to 80°C for stirring for 1-2 h to make it completely dissolved, forming a relatively transparent light yellow solution, after the solid was completely dissolved, the system was heated to 180°C for thermal imidization, and the reaction was carried out for 8-10 h to make the polyimide completely thermal imidized, then 10.5 g of m-cresol was added to make the solid content of the system 9 wt%, the heating was turned off, and the temperature was lowered to 80°C, 300 ml of methanol was stirred on a magnetic stirrer, and the reaction solution was slowly poured into the methanol to obtain a white fibrous solid, which was continuously stirred on a magnetic stirrer for 2-3 h, and then the fibrous material was filtered and subjected to Soxhlet extraction with methanol for 12 h to remove the residual m-cresol solvent in the polymer, and then the fibrous material was vacuum dried at 120°C to obtain the polyimide with the above structure.

[0157] Dissolve the above polymer (0.5g) in chloroform (25ml) to prepare a 10% solids solution. Stir thoroughly until completely dissolved. Filter out insoluble substances using a 0.45μm filter head. Cast the film using a casting method, spreading it evenly on a clean glass dish. Shake until there are no air bubbles, then cover with a slightly larger glass dish to prevent impurities from falling in. Place in a glass box and allow the solvent to gradually evaporate at room temperature until it dries and forms a film. Remove the film with tweezers to obtain the polyimide film (denoted as Co-BTA-1-Me-DMNDA-0.8).

[0158] Its surface area was determined to be 489 m² according to BET testing. 2 / g, measured by gas separation tests at 1 barrer and 35℃, showed that the permeability coefficients were 78.4 barrer for nitrogen, 258.2 barrer for oxygen, 1189 barrer for hydrogen, 79.2 barrer for methane, and 1473 barrer for carbon dioxide. The permeability selectivity of carbon dioxide / methane was 18.6, and that of carbon dioxide / nitrogen was 18.8. The temperature at which 5% weight loss occurred under nitrogen conditions was 426℃, and its glass transition temperature was 415℃.

[0159] Example 4

[0160]

[0161] 4.1 Synthesis of 4-Me-DMNDA Monomer

[0162] (1) Methylrhenium trioxide (1% mol, 0.023 g) and p-benzoquinone (0.5 g, 4.625 mmol) were dissolved in ice-cold chloroform (10 mL) at 0 °C under a N2 atmosphere. Freshly distilled tetramethylcyclopentadiene (1.74 mL, 11.1 mmol) was slowly added dropwise to the mixture. The mixture was stirred at room temperature for 24 hours until the solution turned dark brown. The catalyst was removed by filtration, washed with chloroform, and the filtrate was concentrated under reduced pressure and filtered. The solid was dried under vacuum to give 0.57 g of colorless product I, with a yield of 70%.

[0163] (2) A solution of I (1.762 g, 5 mmol) in 20 mL of a 1:1 mixture of ethyl acetate and ethanol containing 10% Pd / C (20 mg) was hydrogenated in a reaction vessel under hydrogen gas at 2.5 MPa. After 8 hours, the solution was allowed to cool naturally to room temperature. The insoluble catalyst was removed by filtration through a G-4 funnel and the solution was washed with dichloromethane (20 mL). The filtrate was concentrated under reduced pressure and filtered. The solid was dried under vacuum to give a quantitative yield (1.7 g) of colorless crystalline solid II.

[0164] (3) A solution of II (3.565 g, 10 mmol) in chloroform (20 mL) was stirred at room temperature and a solution of Br2(1.6 g, 10 mmol) in chloroform (20 mL) was added dropwise slowly over 0.5 h under N2atmosphere. The resulting suspension was stirred at room temperature for 8 h. The resulting suspension was cooled in an ice-acetone bath for 1 h, the precipitate was vacuum filtered and washed with cold chloroform to give III as a brown solid in 98% yield (3.4 g).

[0165] (4) III (12.39 g, 35 mmol) was dissolved in acetic acid (300 ml) at 130 °C, and then aqueous potassium bromate (1.3%, 170 ml) was added. The reaction was stirred for 2 min and then poured into 100 ml of water. The reaction mixture was stirred for 30 min. The resulting suspension was cooled at room temperature, then filtered and washed with ethanol to give IV as a yellow product in 90% yield (12.0 g).

[0166] (5) A solution of IV (24.6 g, 70 mmol) in ethanol (250 ml, 95%) was added with hydroxylamine hydrochloride (398.1 mg, 5.73 mmol) and the mixture was heated at 78 °C for 2.5 h, then cooled to room temperature and filtered to remove the solid. The filtrate was poured into water (100 mL) and extracted with CH2Cl2(3 x 100 mL). The combined organic extracts were concentrated to give V as a yellow solid in 85% yield (22.75 g).

[0167] (6) V (11.859 g, 31 mmol), Pd / C (1 g, 10% Pd) and ethanol 160 mL were added to a 250 mL flask under nitrogen atmosphere, and refluxed at 90 °C. Hydrazine hydrate (90 mL) was added with a syringe. After 12 h of reaction, the Pd / C was removed by filtration, the filtrate was concentrated by rotary evaporation, then the solid was precipitated by pouring into water, and the white solid was collected by filtration, then washed with water and dried at 100 °C under vacuum to give 1-Me-DMNDA as a white solid in 70% yield (7.6 g). (See Figure 2 for the1H NMR spectrum) Figure Id )

[0168] 2.2 Polymerization based on 4-Me-DMNDA diamine monomer

[0169] In this example, the structure of the polyimide based on 4-Me-DMNDA diamine is as follows:

[0170]

[0171] 4.2.1 In this example, the 6FDA-4-Me-DMNDA polyimide has the following structure:

[0172]

[0173] Under nitrogen protection, 6FDA (1.110 g, 2.5 mmol), 4-Me-DMNDA (0.881 g, 2.5 mmol), benzoic acid (0.1527 g, 1.25 mmol) were added into a flask, then m-cresol (6.9 g) was added to control the solid content of the system at 20 wt%. The system was mechanically stirred at 80 °C for 1 h until the reactants were completely dissolved, the temperature was raised to 180 °C, and the reaction was continued for 8 h until the polymer was completely imidized. m-Cresol (24.40 g) was added to dilute the solid content of the system to 5 wt%, and the heating was stopped and the system was naturally cooled to room temperature. The reaction solution was poured into a mixed solution of ethanol and water (300 ml, v / v = 1:1) with magnetic stirring, and a white fibrous solid was precipitated and filtered. The fibrous solid was placed in a Soxhlet extractor, and ethanol was heated to reflux for 18 h to remove excess m-cresol. After completion, the product was dried at 120 °C to obtain a polyimide containing 4-Me-DMNDA structure.

[0174] The polyimide containing bicyclic pendant group structure was dissolved in chloroform to prepare a solution with a solid content of 5 wt%, and insoluble substances and impurities were removed by filtration. The solution was degassed by vacuum pumping to remove bubbles. The polyimide solution was slowly poured onto a flat, smooth and dry glass surface using the casting method. The glass surface was placed in a film coating oven, and after drying at room temperature for 12 h, the glass plate was completely immersed in distilled water, and the film was naturally detached to obtain a polyimide film containing a bicyclic pendant group structure (denoted as 6FDA-4-Me-DMNDA).

[0175] The gas separation test was performed at 1 barrer and 35 °C, and the permeation coefficients of nitrogen, oxygen, hydrogen, methane and carbon dioxide were 105.3 barrer, 318.7 barrer, 1308 barrer, 128.5 barrer, 1758 barrer, respectively. The permeation selectivity of carbon dioxide / methane was 13.7, the permeation selectivity of carbon dioxide / nitrogen was 16.7, the temperature at which 5% weight loss occurred under nitrogen was 418 °C, and the glass transition temperature was 425 °C.

[0176] 4.2.2 In this example, the Co-CpODA-4-Me-DMNDA-0.8 polyimide has the following structure

[0177]

[0178] The preparation of the above-mentioned polyimide gas separation membrane mainly includes the following steps:

[0179] Under the protection of nitrogen atmosphere, 0.2292 g (0.516 mmol) of 6FDA and 0.7933 g (2.064 mmol) of CpODA dianhydride were mixed with 0.9096 g (2.58 mmol) of 4-Me-DMNDA and 0.1578 g (1.29 mmol) of benzoic acid in a three-necked polymerization flask, and then 7.6 g of anhydrous m-cresol solution was added to make the solid content of the whole system 20 wt%, after adjusting the mechanical stirring to a suitable speed, the system was heated to 80 °C for stirring for 1-2 h to make it completely dissolved, forming a relatively transparent light yellow solution, after the solid was completely dissolved, the system was heated to 180 °C for thermal imidization, and the polyimide was completely thermal imidized after reaction for 8-10 h, then 10.5 g of m-cresol was added to reduce the solid content of the system to 9 wt%, the heating was turned off, and the temperature was reduced to 80 °C, 300 ml of methanol was stirred on a magnetic stirrer, and the reaction solution was slowly poured into the methanol to obtain a white fibrous solid, which was continuously stirred on a magnetic stirrer for 2-3 h, and then the fibrous material was filtered and placed in a Soxhlet extractor for 12 h to remove the residual m-cresol solvent in the polymer, and then the fibrous material was dried at 120 °C under vacuum to obtain the polyimide with the above structure.

[0180] The above polymer (0.5 g) was dissolved in chloroform (25 ml) to prepare a solution with a solid content of 10%, and the solution was completely dissolved after being stirred well. The insoluble substances were filtered out using a filter head with a pore size of 0.45 μm, and the solution was cast on a clean glass dish using a casting method. The glass dish was shaken until no bubbles were present, and then a larger glass dish was used to cover it to prevent impurities from falling in. The glass box was placed in a glass box, and the solvent was allowed to evaporate gradually at room temperature until the film was dry. The polyimide film (denoted as Co-CpODA-4-Me-DMNDA-0.8) was removed with tweezers.

[0181] Through gas separation test, the permeation coefficient of nitrogen was 54.8 barrer, the permeation coefficient of oxygen was 184.3 barrer, the permeation coefficient of hydrogen was 769.4 barrer, the permeation coefficient of methane was 56.7 barrer, the permeation coefficient of carbon dioxide was 929.7 barrer, the permeation selectivity of carbon dioxide / methane was 16.4, the permeation selectivity of carbon dioxide / nitrogen was 16.9, the temperature at which 5% of the weight was lost under nitrogen was 426 °C, and the glass transition temperature was 408 °C.

[0182] Example 5

[0183]

[0184] 5.1 Synthesis of 5-Me-DMNDA monomer

[0185] (1) Methyltrioxorhenium (1% mol, 0.046 g) was dissolved in ice-cold chloroform (20 mL) solution of p-benzoquinone (1.0 g, 9.25 mmol) at 0 °C under N2atmosphere, freshly distilled tetramethylcyclopentadiene (3.6 mL, 22.2 mmol) was slowly added dropwise to the mixed solution. The mixture was stirred at room temperature for 24 h, the solution turned dark brown, the catalyst was removed by filtration, washed with chloroform and the filtrate was concentrated under reduced pressure, filtered, the solid was dried in vacuum to give colorless 2.6 g of product I with 75% yield.

[0186] (2) A solution of I (1.91 g, 5 mmol) in a mixture of ethyl acetate-ethanol (1 : 1) containing 10% Pd / C (20 mg) (20 mL) was hydrogenated in a reaction bomb apparatus under 2.5 MPa of hydrogen. After 8 h, the insoluble catalyst was removed by suction filtration with a G-4 funnel after cooling to room temperature naturally, and washed with dichloromethane (20 mL). The filtrate was concentrated under reduced pressure, filtered, the solid was dried in vacuum to give colorless crystalline solid II with 90% yield (1.7 g).

[0187] (3) A solution of II (3.846 g, 10 mmol) in chloroform (20 mL) was stirred at room temperature, and a solution of Br2(1.6 g, 10 mmol) in chloroform (20 mL) was slowly added dropwise over 0.5 h under N2atmosphere, the resulting suspension was stirred at room temperature for 8 h. The resulting suspension was cooled in an ice-acetone bath for 1 h, the precipitate was vacuum filtered and washed with cold chloroform to give brown solid III (3.4 g) with 90% yield.

[0188] (4) III (13.39 g, 35 mmol) was dissolved in acetic acid (300 ml) at 130 °C, then aqueous potassium bromate (1.3%, 170 ml) was added, the reaction was 2 min, immediately poured into 100 ml of water. The reaction mixture was stirred for 30 min. The resulting suspension was cooled at room temperature, then filtered and washed with ethanol to give yellow product IV with 80% yield (10.65 g).

[0189] (5) A solution of IV (26.6 g, 70 mmol) in ethanol (250 ml, 95%) was added with hydroxylamine hydrochloride (398.1 mg, 5.73 mmol), the mixture was heated at 78 °C for 2.5 h, then cooled to room temperature, the solid was removed by filtration. The filtrate was poured into water (100 mL), and extracted with CH2Cl2(3 x 100 mL). The combined organic extracts were concentrated to give V (22.9 g) as a tan solid with 80% yield.

[0190] (6) V (12.71 g, 31 mmol), Pd / C (1 g, 10% Pd) and ethanol 160 mL were added to a 250 mL flask under nitrogen atmosphere, refluxed at 90 °C, and hydrazine hydrate (90 mL) was added by syringe. After 12 h of reaction, the Pd / C was removed by filtration, the filtrate was concentrated by rotary evaporation, and then the solid was precipitated by pouring into water. The white solid was collected by filtration, washed with water, and dried under vacuum at 100 °C to give 5-Me-DMNDA (8.83 g) as a white solid in 75% yield.

[0191] 5.2 Polymerization based on 5-Me-DMNDA diamine monomer

[0192] In this example, the structure of the polyimide based on 5-Me-DMNDA diamine is as follows:

[0193]

[0194] 5.2.1 In this example, the 6FDA-5-Me-DMNDA-0.8 polyimide has the following structure:

[0195]

[0196] Under nitrogen protection, hexafluoroisopropyl phthalic anhydride (6FDA) (1.110 g, 2.5 mmol), 5-Me-DENDA (0.951 g, 2.5 mmol), benzoic acid (0.1527 g, 1.25 mmol) were added to a flask, and then m-cresol (7.1 g) was added to control the solid content of the system at 20 wt%. The system was mechanically stirred at 80 °C for 1 h until the reactants were completely dissolved, the temperature was raised to 180 °C, and the reaction was continued for 8 h until the polymer was completely imidized. m-Cresol (24.40 g) was added to dilute the solid content of the system to 5 wt%, and the heating was stopped and the system was naturally cooled to room temperature. The reaction solution was poured into a mixed solution of ethanol and water (300 ml, v / v = 1:1) with magnetic stirring, and a white fibrous solid was precipitated, which was filtered. The fibrous solid was placed in a Soxhlet extractor, and ethanol was heated to reflux for 18 h to remove excess m-cresol. After completion, the polyimide containing 5-Me-DMNDA structure was obtained by drying at 120 °C.

[0197] The polyimide containing bicyclized pendant group structure was dissolved in chloroform to prepare a solution with a solid content of 5 wt%, and insoluble substances and impurities were removed by filtration. The system was vacuumed to eliminate bubbles, and the polyimide solution was slowly poured onto a flat, smooth and dry glass surface dish using the casting method. The glass surface dish was placed in a film coating oven, and after drying at room temperature for 12 h, the glass plate was completely immersed in distilled water until the film naturally fell off, and a polyimide film containing bicyclized pendant group structure (denoted as 6FDA-5-Me-DENDA) was obtained.

[0198] By gas separation test, the permeation coefficient of nitrogen is 116.5 barrer, the permeation coefficient of oxygen is 325 barrer, the permeation coefficient of hydrogen is 1311 barrer, the permeation coefficient of methane is 131 barrer, the permeation coefficient of carbon dioxide is 1764 barrer, the permeation selectivity of hydrogen / methane is 10, the permeation selectivity of hydrogen / nitrogen is 11.2, the temperature of 5% thermal weight loss under nitrogen is 442°C, and the glass transition temperature is >450°C.

[0199] 5.2.2 In this embodiment, the Co-BTA-5-Me-DMNDA-0.8 polyimide has the following structure:

[0200]

[0201] Under the protection of nitrogen atmosphere, 0.2292 g (0.516 mmol) of 6FDA and 0.512 g (2.064 mmol) of BTA dianhydride are mixed with 0.9819 g (2.58 mmol) of DENDA and 0.1578 g (1.29 mmol) of benzoic acid in a three-necked polymerization flask, and then 6.6 g of anhydrous m-cresol solution is added to make the solid content of the whole system 20 wt%, after adjusting the mechanical stirring to a proper speed, the system is heated to 80°C for stirring for 1-2 h to make it completely dissolved, forming a relatively transparent light yellow solution, after the solid is completely dissolved, the system is heated to 180°C for thermal imidization, and the polyimide is completely thermally imidized after reaction for 8-10 h, 10.5 g of m-cresol is then added to reduce the solid content of the system to 9 wt%, the heating is turned off, and the temperature is reduced to 80°C, 300 ml of methanol is stirred on a magnetic stirrer, and the reaction solution is slowly poured into the methanol to obtain a white fibrous solid, which is continuously stirred on the magnetic stirrer for 2-3 h, the fibrous material is filtered and placed in a Soxhlet extractor for 12 h to remove the residual m-cresol solvent in the polymer, and then the fibrous material is vacuum dried at 120°C to obtain the polyimide with the above structure.

[0202] The above polymer (0.5 g) is dissolved in chloroform (25 ml) to make a solution with a solid content of 10%, and the solution is filtered with a 0.45 μm filter head to remove insoluble substances, and then cast film is performed by the casting method, the solution is uniformly spread on a clean glass dish, and then covered with a slightly larger glass dish to prevent impurities from falling into the solution, and then placed in a glass box for gradual evaporation of the solvent at room temperature until the film is dried, and then the film is taken out with tweezers to obtain a polyimide film (denoted as Co-BTA-5-Me-DMNDA-0.8).

[0203] The permeation coefficients of nitrogen, oxygen, hydrogen, methane and carbon dioxide were 82.5 barrer, 264.2 barrer, 1251 barrer, 80.1 barrer and 1651 barrer respectively, the permeation selectivity of hydrogen / methane was 15.6, the permeation selectivity of hydrogen / nitrogen was 15.1, the temperature of 5% weight loss under nitrogen was 432℃, and the glass transition temperature was >450℃.

[0204] The performance test methods involved in the examples are as follows:

[0205] (1) Structure characterization:

[0206] The nuclear magnetic resonance of the polypyrimidine film containing the bicyclized side group structure was tested using a Bruker nuclear magnetic resonance instrument.

[0207] The infrared of the polypyrimidine film containing the bicyclized side group structure was tested using a Fourier transform attenuated total reflection infrared spectrometer.

[0208] (2) Physical property test:

[0209] The specific surface area of the polypyrimidine film containing the bicyclized side group structure was tested using a Micromeritics ASAP 2640 full-automatic specific surface and porosity analyzer, and the polypyrimidine was ground into powder.

[0210] The inter-segment distance d of the polypyrimidine film containing the bicyclized side group structure was tested using an X-ray diffraction analyzer Ultima IV (Rigaku) on the polymer film.

[0211] The density of the polypyrimidine film containing the bicyclized side group structure was tested using an analytical balance Sartorius SQP (with density assembly YDK03) at room temperature, and isooctane was used as a medium solvent.

[0212] (3) Gas separation performance test:

[0213] The permeation coefficients of the polypyrimidine film containing the bicyclized side group structure to five single gases (H2, O2, N2, CH4, CO2) were tested using a gas permeation instrument at 35℃ and 1 Barrer.

[0214] Table 1. Gas permeation coefficient and selectivity coefficient data

[0215]

[0216] Table 2. Solubility performance data of polymers based on DMNDA diamine

[0217]

[0218] Table 3 Thermodynamic properties of DMNDA diamine based polymers

[0219]

[0220] Table 4 Physical properties data of DMNDA diamine based polymers

[0221]

[0222] Performance characterization:

[0223] Figure 3 is a UV-Vis spectrum of the polyimide film containing bicyclized pendent group structure prepared in Example 1 of the present application; Figures 4a-c is a gas separation performance chart of H2 / CH4of the polyimide film containing bicyclized pendent group structure in Examples 1, 2, 5 of the present application and six commercial gas separation membranes of hexafluorodianhydride, seven kinds of the prior art; Figures 5a-cis the gas separation performance chart of the polyimide film containing bicyclized side group structure in embodiments 1, 2, 5 of the present application and the existing technology hexafluorodianhydride, seven kinds of commercial gas separation membranes for H2 / N2. Table 1 lists the gas permeability coefficients and selectivity coefficients of typical embodiments 1, 2 and 5 of the present application, and the reported hexafluorodianhydride, seven kinds of commercial gas separation membranes. From the table, it can be seen that the permeability coefficients of embodiments 1, 2, 5 for five single gases (H2, O2, N2, CH4, CO2) are higher than the permeability coefficients of the corresponding hexafluorodianhydride polyimide polymers (references: Polymer 2019, 161, 16-26; Polymer 2017, 130, 182-190; Macromolecular Rapid Communications 2011, 32(7), 579-86; Chemistry of Materials 2019, 31(5), 1767-1774) and commercial gas separation membranes (references: Journal of Membrane Science 2008, 314(1-2), 123-133; Journal of Applied Polymer Science 2010, 101(6), 3800-3805; Progress in Polymer Science 1988, 13(4), 339-401; Journal of Polymer Science Part B: Polymer Physics 1987, 25(9), 1999-2026; Journal of Membrane Science 1998, 138(2), 143-152), greatly improving the gas separation efficiency. The hydrogen / methane, hydrogen / nitrogen performance of some embodiments is close to the 2008 Robeson upper limit, which has good application prospect in industrial hydrogen purification and recovery applications.

[0224] Table 2 is the solubility of four kinds of polyimides prepared by taking DMNDA diamine monomer as an example. The solubility of 6FDA-DMNDA polyimide is better than that of other polyimides, which may be related to the smaller rigidity of hexafluoroisopropyl unit. All polymers show good solubility. GPC test was carried out with DMF as mobile phase, and the results are shown in Table 3. The measured weight average molecular weight is 62-105 kg mol -1between 48-70 MPa; Young's modulus between 1.48-2.19 GPa; and elongation at break between 3.46-10.89%, which are comparable to the reported mechanical properties of PIM-PIs. The thermal properties of the polymers were determined by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The thermal degradation temperature (T 5％ ) of the synthesized polyimides was between 446-454℃, and the glass transition temperature (Tg) was between 319-423℃, and the presence of bicyclized pendant groups reduced the thermal stability of the polymers.

[0225] Table 4 shows the polymer gas adsorption and microporous properties. The synthesized polymers have a BET specific surface area between 469-631 m 2 g -1 The SBI-DMNDA polymer has the largest specific surface area because the additional introduction of rigid bulky twisted SBI sites can effectively hinder the packing of the polymer molecular chains, thereby making the polymer have a high specific surface area. At the same time, the total pore volume of the polymers at P / P0=0.95 is between 0.276-0.478 cm 3 g -1 The pore size distribution is between 0-2 nm, and there are micropores and ultramicropores. The polymer microporous structure was determined by wide-angle X-ray diffraction (WAXD), and the d value calculated according to the Bragg equation represents the distance between the molecular chains, which is between 0.623-0.777 nm. The free volume fraction (FFV) calculated according to the film density is between 0.193-0.216, and the size order is SBI-DMNDA>6FDA-DMNDA>co-BTA-DMNDA>co-CpODA-DMNDA. This is consistent with the WAXD results. In addition, the present inventors also carried out tests with other raw materials, process operations, and process conditions described in the specification according to the aforementioned embodiments, and all obtained relatively ideal results.

[0226] It should be understood that the technical solutions of the present application are not limited to the specific implementation cases described above, and any technical modification made according to the technical solutions of the present application without departing from the purpose of the present application and the scope protected by the claims falls within the protection scope of the present application.

Claims

1. A diamine monomer containing a bicyclic side group structure, characterized in that, The diamine monomer has a structure shown in any one of Formula (I) - Formula (IV): 。 2. A polyimide film, characterized in that: The polyimide film is prepared from a polyimide with a bicyclic side group structure, and the polyimide with a bicyclic side group structure is prepared from the diamine monomer with a bicyclic side group structure described in Claim 1. The polyimide has a structure shown in Formula (VI): ； where 1 < n < 1000, and R1 is selected from the structures shown in any one of the following formulas or a combination of two or more thereof: ； R2 is selected from the structures shown in any one of the following formulas: ； where the dashed line represents the bond access position.

3. The polyimide film according to claim 2, characterized in that: The polyimide film exhibits a thermal decomposition temperature above 400°C under a nitrogen atmosphere when it loses 5 wt% of its weight; the specific surface area of ​​the polyimide film is over 100 m² / g. 2 / g or more.

4. The polyimide film according to claim 2, characterized in that: The thickness of the polyimide film is 50 - 80 μm.

5. The method for preparing the polyimide film according to any one of claims 2-4, characterized in that... Including: Providing the diamine monomer with a bicyclic side group structure described in Claim 1; Under a protective atmosphere, reacting a mixed reaction system containing the diamine monomer, aromatic dianhydride, catalyst and solvent at 50 - 100 °C for 1 - 4 h to obtain a prepolymer; wherein, the aromatic dianhydride is selected from any one or a combination of two or more of hexafluoroisopropyl phthalic anhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclanone-α'-spiro-2'-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, ​ ​ 6. The preparation method according to claim 5, characterized in that: ​ 7. The preparation method according to claim 6, characterized in that: ​ 8. The preparation method according to claim 5, characterized in that: ​ 9. The preparation method according to claim 5, characterized in that: ​ 10. The preparation method according to claim 5, characterized in that... ​ ​ 11. The preparation method according to claim 5, characterized in that, ​ 12. The preparation method according to claim 11, characterized in that: The organic solvent is selected from tetrahydrofuran, dichloromethane, trichloromethane, m-cresol, etc. ​ -Dimethylformamide, ​ -Dimethylacetamide, N- Any one or a combination of two or more of methylpyrrolidones.

13. The preparation method according to claim 11, characterized in that: ​ 14. The preparation method according to claim 11, characterized in that: The programmed temperature rise process includes: raising the room temperature to 60~80℃ and holding it for 6~10 hours, then raising the temperature to 80~120℃ and holding it for 2-5 hours, then raising the temperature to 120~150℃ and holding it for 3-6 hours, and finally raising the temperature to 200~300℃ and holding it for 2-5 hours.

15. Use of the polyimide film according to any one of claims 2-4 in the field of gas separation.

16. The use according to claim 15, characterized in that: The intended use is the application of the polyimide film in the separation of hydrogen, methane, carbon dioxide, or oxygen.

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