KR101912459B1 - Polyimide nanocomposite, preparing method thereof, and composite membrane including the composite - Google Patents

Abstract

Disclosed are a polyimide nanocomposite having a polyimide and a product wherein a defect of a reduced graphene oxide functionalized with at least one selected from a ring compound containing a hetero ring and a hetero atom is healed, a manufacturing method thereof, and a composite membrane having the polyimide nanocomposite. The polyimide nanocomposite of the present invention and a composite film having the same may contain a polyimide and a healed product of the surface of the functionalized reduced graphene oxide to improve dispersibility and improve thermal stability and mechanical properties.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyimide nanocomposite, a method for producing the same, and a composite membrane comprising the same.

The present invention relates to a polyimide nanocomposite, a process for producing the same, and a composite membrane comprising the same, more particularly, to a polyimide nanocomposite containing a polyimide and a product obtained by healing defects of functionalized graphene, And a composite membrane comprising the same.

With the rapid development of science and technology and industry, there is a demand for better quality, higher performance products, materials and composites. Particularly, the field of research on composite materials is being actively developed, in which the original properties of materials having excellent properties are maximized through interaction with the properties of the filler to develop more improved properties. Accordingly, it is necessary to develop a composite material which can be easily mass-produced and used in various fields. In particular, polyimide is a polymer having an imide bond in its main chain and has heat resistance and chemical resistance derived from the chemical stability of the imide. Aromatic polyimides are used in high strength and high temperature applications such as automobile materials and aerospace materials as well as daily necessities due to their excellent mechanical properties and electrical insulating properties due to their rigid backbone structure and widely applied in various electronic materials fields . However, since polyimide itself is limited in its low electrical conductivity and mechanical properties, it can be used only in some industrial fields, and its application is limited in industrial fields such as semiconductors.

SUMMARY OF THE INVENTION The present invention provides a polyimide nanocomposite having improved mechanical strength and electric conductivity by healing defects of functionalized reduced graphene oxide, and a method for producing the same.

Another object of the present invention is to provide a composite membrane containing the above-mentioned polyimide nanocomposite.

In order to solve the above problems, the present invention provides a polyimide nanocomposite comprising a product wherein a defect of reduced graphene oxide functionalized with at least one selected from a ring compound containing a hetero ring and a hetero atom is healed, and a polyimide.

Another object of the present invention is to provide a process for producing graphene oxide by reacting graphene oxide with at least one member selected from ring compounds including heterocyclic and heteroatoms to form reduced graphene oxide functionalized with at least one ring compound selected from ring compounds containing hetero ring and hetero atom A first step of obtaining;

An intramolecular cross-dehydrogenative coupling (ICDC) of reduced graphene oxide functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom-containing ring compound is performed to form a ring containing a hetero ring and a hetero atom A second step of obtaining a defect healing product of reduced graphene oxide functionalized with at least one selected from the compounds; And

And a third step of performing a polymerization reaction of a defect healing product of reduced graphene oxide functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom and a polyamic acid precursor and then conducting an imidation reaction, There is provided a process for producing a polyimide nanocomposite which obtains the above-mentioned polyimide nanocomposite.

Another aspect of the present invention provides a composite membrane comprising the polyimide nanocomposite.

The polyimide nanocomposite of the present invention and the composite film containing the same may contain a polyimide and a healed product of the surface of the functionalized reduced graphene oxide to improve the dispersibility and improve the thermal stability and the mechanical properties.

FIG. 1 is a schematic view for explaining a process for producing a polyimide nanocomposite according to Example 1. FIG.
Fig. 2 is a graph showing the results of the measurement of graphene oxide (GO) obtained according to Preparation Example 1, pyridine functionalized reduced grapheme oxide (Py-RGO) functionalized with pyridine group obtained according to Production Example 2, The results of Raman spectroscopic analysis of the chemical defect-healing of pyridine functionalized reduced grapheme oxide (H-Py-RGO) of pin oxide are shown.
3 shows the thermogravimetric analysis results of GO obtained according to Preparation Example 1 and Py-RGO and H-Py-RGO obtained according to Production Example 2. FIG.
4 shows the results of measurement of powder resistance against GO obtained according to Preparation Example 1 and Py-RGO and H-Py-RGO obtained according to Production Example 2. Fig.
5A and 5B are transmission electron microscope images of Py-RGO and H-Py-RGO prepared according to Production Example 2, respectively.
Fig. 6 shows the tensile strength test results of the composite membrane containing the polyimide nanocomposite prepared in Example 1, the composite membrane containing the polyimide composite of Comparative Example 1, and the polyimide membrane prepared in Comparative Example 2. Fig.
7A is an SEM photograph of the polyimide film of Comparative Example 2. Fig.
7B is an SEM photograph of a composite membrane containing the polyimide nanocomposite prepared according to Example 1. FIG.
8 is a graph showing the results of measurement of the thermal expansion coefficient of the polyimide nanocomposite obtained according to Example 1. FIG.

Hereinafter, the polyimide nanocomposite of the present invention, the production method thereof, and the composite membrane containing the polyimide nanocomposite will be described in more detail.

There is provided a polyimide nanocomposite comprising a polyimide and a product wherein a defect of reduced graphene oxide functionalized with at least one selected from a ring compound containing a hetero ring and a hetero atom is healed.

The term " heterocycle " in at least one selected from the group consisting of " heterocyclic " and " cyclic compound containing heteroatom " means a heteroatom containing ring such as nitrogen (N), oxygen (O), phosphorus (P) For example, pyridine.

As used herein, the term " functionalization " means that physical and chemical treatments are applied to the surface of a material to form a new functional group, thereby deforming the inherent characteristics of the material. And the defect of reduced graphene oxide refers to at least one selected from sp ³ carbon and carbon vacancy. The defect healing in reduced graphene oxide can be confirmed from the mixing ratio of sp ² C and sp ³ C through X-ray photoelectron spectroscopy (XPS) C1s spectrum.

The sp ² C / sp ³ C ratio in the XPS C ^{1 s} spectrum of the product wherein the defects of the reduced graphene oxide functionalized with at least one selected from the above-mentioned heterocyclic ring and the heteroatom-containing ring compound is healed includes a hetero ring and a hetero atom It is increased as compared to the sp ² C / C sp ³ ratio in the XPS C1s spectra of the reduced graphene oxide functionalized with at least one selected from a cyclic compound.

The C / O ratio can be 11.1 to 15.6% through XPS analysis of the product wherein the defect of the reduced graphene oxide functionalized with at least one selected from the group consisting of heterocyclic and heteroatom-containing rings is healed. Where% represents atomic%.

The term "ring compound containing a hetero atom" means a carbon ring compound substituted with a group containing a hetero atom such as nitrogen (N), oxygen (O), phosphorus (P) and sulfur (S) For example, pyridine.

The reduced graphene oxide functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom is a reaction product of graphene oxide and at least one selected from the amine compounds represented by the following general formula (1).

[Chemical Formula 1]

Grafting functionalized with at least one selected from among a ring compound containing a hetero ring and a hetero atom is a compound in which a group derived from at least one selected from ring compounds having a hetero ring and a hetero atom at the terminal of graphene is bonded via a covalent bond . The product wherein the defect of the reduced graphene oxide functionalized with at least one selected from the group consisting of a heterocyclic ring and a cyclic compound containing a heteroatom is healed can be obtained from reduced graphene oxide functionalized with at least one selected from ring compounds including a heterocyclic ring and a hetero atom Defects indicate healed products, for example, products in which defects have healed through intermolecular cross-link dehydrogenation coupling reactions using iron chloride. And the products healed from the reduced graphene oxide functionalized in the polyimide nanocomposite can serve as fillers.

The term " Py-RGO " as used throughout this specification should be understood to mean reduced graphene oxide functionalized with an amine group (e.g., pyridine group) derived from the amine compound described above, -RGO " should be understood as a product in which defects of the reduced graphene oxide functionalized with the above-mentioned amine groups (e.g., pyridine groups) are cured.

In the polyimide nanocomposite of the present invention, the pyridine group present on the surface of the reduced graphene oxide acts as a catalyst to improve the mechanical properties and oxygen gas barrier properties of the polyimide nanocomposite. The mechanical properties and the oxygen gas barrier properties are improved as described above because the functionalized reduced graphene oxide defective products and polyimide are bonded to each other through hydrogen bonding or the like in the polyimide nanocomposite so that the reduced graphene oxide is efficiently dispersed and distributed . Reduced graphene oxide can have, for example, a sheet form.

The defects existing in the reduced graphene oxide constituting the polyimide nanocomposite of the present invention are healed, thereby improving the mechanical properties and the properties such as conductivity of the reduced graphene oxide. The reaction of graphene oxide with at least one selected from the group represented by the formula (1) is carried out by dispersing graphene oxide in a solvent, mixing a selected one of the compounds represented by the formula (1) and heat- Process. When this reaction is completed, a reduced graphene oxide functionalized with a compound represented by the formula (1) can be obtained through a work-up process.

As used herein, the term " graphene oxide " refers to a material in which graphene oxide forming a polycyclic aromatic molecule in which a plurality of carbon atoms are covalently linked to one another and arranged in one plane forms a sheet structure of a single atomic layer, A plurality of in-plate graphene oxides are interconnected to form a network structure arranged in one plane, and combinations thereof are also possible. The carbon atoms linked by the covalent bond may form a 6-membered ring as a basic repeating unit, but may further include a 5-membered ring and / or a 7-membered ring. The graphene oxide may have a plurality of layers in which a plurality of sheet structures are stacked and have an average thickness of about 100 nm or less, for example, about 10 nm or less, specifically 0.01 to 10 nm.

In the present specification, "graphen oxide" is interpreted as a term including graphene oxide in which a functional group such as a hydroxyl group, a carboxyl group, a carbonyl group, or an epoxy group is introduced with functional groups such as an ester group, an ether group, an amide group and an amino group.

In the present specification, the content of oxygen in graphene oxide may be, for example, 0.1 to 40 atomic%.

Examples of the solvent for dispersing the graphene oxide include water, ethanol, methanol, methanol, isopropanol, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dichloroethane, dichlorobenzene, dimethylsulfoxide , Aniline, propylene glycol, propylene glycol diacetate, methoxypropanediol, diethylene glycol, acetylacetone, cyclohexanone, propylene glycol monomethyl ether acetate,? -Butyrolactone, nitromethane, tetrahydrofuran, Butyl nitrite, methyl cellosolve, ethyl cellosolve, diethyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, dipropylene glycol methyl ether, toluene, xylene, hexane, methyl ethyl ketone , Methyl iso ketone, hydroxymethyl cellulose, propylene glycol methyl ether acetate, and heptane. . The content of the solvent is in the range of 1000 to 9000 parts by weight based on 100 parts by weight of the graphene oxide.

The content of the healing product of the reduced graphene oxide functionalized in the polyimide nanocomposite of the present invention is 0.1 to 30 wt%, for example, 0.5 to 20 wt%, for example, 0.5 to 5 wt%.

The functionalized reduced graphene oxide covalently bonded to graphene oxide by chemical method and introducing an amine group to the surface of the graphene oxide by a chemical method is used as a precursor of polyamic acid (PAA) precursor of polyimide (PI) To improve the dispersibility and mutual bonding through the chemical bonding between the polyamic acid precursor and the functionalized reduced graphene oxide and to improve the electrical conductivity and mechanical strength as a polymer composite material by improving the defects and improving the properties of graphene . ≪ / RTI >

An intramolecular cross-dehydrogenative coupling (ICDC) reaction of the reduced graphene oxide functionalized with the compound represented by the formula (1) is carried out to carry out a chemical defect healing process to perform amine group functionalization and defect This healed reduced graphene oxide is obtained.

The intermolecular cross-linked dehydrogenation coupling reaction can be carried out by adding iron chloride and heat-treating at 25 to 60 ° C.

The group represented by the formula (1) is, for example, 4-hydrazinopyridine represented by the following formula (1a).

[Formula 1a]

The product wherein the defect of graphene functionalized with at least one selected from the heterocyclic ring and the heteroatom-containing ring compound is healed can be selected from the compounds represented by the following formulas (2) to (5).

(2)

 (3)

[Chemical Formula 4]

[Chemical Formula 5]

In addition to the hydroxyl group and the carboxyl group present in the graphene oxide of the above-mentioned formula, at least one selected from a carbonyl group, an epoxy group, an ester group, an ether group and an amide group may be further present.

Groups derived from at least one selected from carboxyl groups, hydroxyl groups, heterocyclic rings and heteroatoms bonded to graphene oxide in the above formula are shown briefly for convenience and can be combined with numbers and positions other than those shown in the formula Do.

In the above formula (2), the red line represents the area where the defect is healed, and the sp ² Carbon has been converted to sp ³ carbon.

Hereinafter, the polyimide nanocomposite of the present invention and the method for producing the composite membrane including the same will be described.

First, a first step of reacting graphene oxide with at least one member selected from a heterocyclic ring and a ring compound containing a hetero atom to obtain a reduced graphene oxide functionalized with at least one selected from ring compounds including a heterocyclic ring and a hetero atom . Thus, the reduced graphene oxide is obtained through the reduction and functionalization of graphene oxide through the first step.

The graphene oxide is not particularly limited as long as it is functionalized with an amine group derived from the compound represented by the formula (1) to produce a polyimide nanocomposite by reacting the polyamic acid precursor with the functional group upon polyamic acid and polyimide polymerization Do not.

In one embodiment, the graphene oxide may be reacted with at least one compound selected from the group consisting of compounds represented by formula (1) to reduce and functionalize the graphene oxide, thereby reducing the functionality of the graphene oxide.
An intramolecular cross-dehydrogenative coupling of a reduced graphene oxide functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom-containing ring compound is performed to form a heterocyclic ring and a heteroatom-containing ring compound A second step of obtaining a defect healing product of reduced graphene oxide functionalized with at least one selected. In the second step, the reduced graphene oxide may be cured by intermolecular cross-linking dehydrogenation reaction by adding iron chloride to the functionalized reduced graphene oxide and conducting the reaction at 25 to 60 ° C.

delete

The defective healing product of the functionalized reduced graphene oxide is added to the polymerization process of the polyamic acid using the polyamic acid precursor to carry out the polymerization reaction to perform the third step to obtain the defective healing product of functionalized reduced graphene oxide and the polyamic acid To obtain a nanocomposite. The defect healing product of the functionalized reduced graphene oxide can be uniformly dispersed in the polyamic acid.

The content of the defect healing product of the functionalized reduced graphene oxide is 0.1 to 30% by weight, for example 0.5 to 20% by weight, based on the total weight of the defect healing product of the functionalized reduced graphene oxide and the polyamic acid precursor, , For example 0.5 to 5% by weight.

A mixture of diamine, acid dianhydride and solvent described above is used during the polymerization of the polyamic acid precursor. The polymerization reaction is carried out in an inert gas atmosphere. As the solvent, for example, N-methyl-2-pyrrolidone, tetrahydrofuran and the like are used. The inert gas atmosphere is formed using argon, nitrogen, or the like.

The above-mentioned polymerization reaction may vary depending on the type of the diamine compound and acid dihydrate to be used, the kind of the functional group bonded to the reduced graphene oxide, and the like. For example, the polymerization reaction may be carried out at a temperature in the range of, for example, 25 to 150 ° C. In the present invention, defective healing products of functionalized reduced graphene oxide are used as catalysts for the polymerization of polyamic acid, so that they can be polymerized at lower temperatures than those of conventional polyamic acids.

Defect healing products of functionalized reduced graphene oxide can either form chemical bonds directly with the polyamic acid precursor or increase the dispersibility of the polyamic acid and reduced graphene oxide in the solvent.

Then, a desired polyimide nanocomposite can be obtained through an imidization reaction of a nanocomposite containing a defective healing product of functionalized reduced graphene oxide and a polyamic acid.

The imidization reaction includes a method of dehydrating cyclization by heating and a method of dehydrating cyclization by using a dehydrating agent. The dehydrating cyclization by heating is carried out, for example, at a high temperature of 300 to 400 캜 to carry out imidization. The method of dehydrating cyclization using a dehydrating agent is carried out at a temperature of 200 ° C or lower to carry out imidation. It is also possible to use a catalyst such as an acid or base together with a dehydrating agent. For example, an organic acid such as p-hydroxyphenylacetic acid is used as the acid catalyst and isoquinoline, triethylamine, pyridine, 1,4-diazabicyclo [2.2.2] octane or the like is used as the base catalyst .

According to one embodiment, the imidization reaction is carried out through heat treatment.

Polyamic acid precursors are diamines and acid dianhydrides for the production of polyamic acids. The diamine and the acid dianhydride can be used as long as they are commonly usable in the production of polyimide.

The diamine compound may be at least one selected from, for example, aromatic diamines, alicyclic diamines and aliphatic diamines.

The aromatic diamines include, for example, 3,3'-dihydroxybenzidine, p-phenylenediamine, m-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminotoluene, 1,3-bis 4,4'-diaminophenoxy) benzene, 4,4'-diamino-1,5-phenoxypentane, 4,4'-diaminobiphenyl, 3,3'-dimethyl- Aminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2'- (4-aminophenoxy) benzene, diaminodiphenylsulfone, diaminobenzophenone, diaminonaphthalene, 1,4-bis (4-aminophenoxy) Bis (4-aminophenyl) benzene, 4,4'-bis (4-aminophenyl) benzene, Phenoxy) diphenylsulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-trifluoromethyl-4,4'-diaminobiphenyl and mixtures thereof Can be selected from the group consisting of.

The alicyclic diamine is, for example, 1,4-diaminocyclohexane, 1,4-cyclohexanebis (methylamine), 4,4'-diaminodicycohexylmethane (MCA), 4,4'-methylenebis (2-methylcyclohexylamine) (MMCA), and mixtures thereof.

The aliphatic diamines include, for example, ethylenediamine (EN), 1,3-diaminopropane (13DAP), tetramethylenediamine, 1,6-hexamethylenediamine (16DAH), 1,12-diaminododecane (112DAD) And an aliphatic diamine selected from the group consisting of mixtures thereof.

The acid dihydrate may be, for example, a compound represented by the following formula (6).

[Chemical Formula 6]

In the formula (6), R ₅ is a group selected from the group represented by the formula (7).

(7)

In the formula (7), * represents a bonding position.

The acid dianhydride may be, for example, pyromellitic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanediamine hydride (6FDA), 4- (2,5- Dioxotetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), pyromellitic acid dianhydride , 5-benzenetetracarboxylic dianhydride, PMDA), benzophenone tetracarboxylic dianhydride (BTDA), biphenyltetracarboxylic dianhydride (BPDA), oxydiphthalic dianhydride (ODPA) , Biscarboxyphenyldimethylsilanediamine hydride (SiDA), bisdicarboxyphenoxy diphenylsulfide dianhydride (BDSDA), sulfonyldiphthalic anhydride (SO ₂ DPA), cyclobutane tetracarboxylic dianhydride (CBDA), isopropylidene is phenoxybisphthalic anhydride (6HBDA), bicyclo [2.2.2] -7-octene-2,3,5,6-tetracarboxylic acid dianhydride (BTA).

The polyimide of the polyimide nanocomposite according to one embodiment has a number average molecular weight of 10,000 to 500,000 g / mol.

The polyimide nanocomposite and the composite membrane comprising the polyimide nanocomposite prepared according to the present invention have improved mechanical strength and electrical characteristics as compared with the conventional polyimide or polyimide composite. In addition, the composite thus produced can be used in various fields such as semiconductor, conductive film, fiber, automobile material, aerospace material, and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are only for illustrating the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

Manufacturing example  One: Grapina Of graphene oxide  Produce

And oxidized by the Brodie's method described later to obtain graphene oxide (GO).

1 g of natural graphite and 8.5 g of NaClO ₃ were mixed and stirred at room temperature. The mixture was added dropwise through a dropping funnel to 9 ml of fuming nitric acid in an ice bath and then stirred at room temperature for 24 hours. Then, 5 ml of fuming sulfuric acid was further added to the reaction mixture, and then the reaction mixture was heated to 60 ° C and stirred for 24 hours. Then, when the reaction was completed, 200 ml of deionized water was added to the reaction mixture and washed with 100 ml of 3M HCl. The resultant was filtered and the neutralized mixture was dried in a vacuum oven controlled at 50 DEG C for 24 hours to obtain the desired graphene oxide.

Manufacturing example  2: Amine  Functionalized Grapina Oxide  The defect healing product (H- Py - RGO )

25 g of 4-chloropyridine hydrochloride was added to 30.3 g of the hydrazine monohydrate solution. Thereafter, the temperature of the reaction tank was set at 80 DEG C and the magnet was stirred for 24 hours. After the reaction was completed, the reaction mixture was extracted with 50% sodium hydroxide solution and ethyl acetate solution. After the extraction, distilled water remaining as magnesium sulfate was removed and filtration was performed. And then dried in a vacuum oven at 40 DEG C for 2 hours to obtain 16.8 g of 4-hydrazinopyridine of formula (I).

[Formula 1a]

3.0 g of graphene oxide (GO) obtained according to Preparation Example 1 was dispersed in 100 ml of ethanol by sonication for 1 hour. To a dispersin of graphene oxide, 16.8 g of 4-hydra After the addition of the ginopyridine, the temperature of the reactor was set to 80 DEG C and the mixture was stirred for about 48 hours.

When the reaction mixture was stirred and the reaction was complete, the reaction mixture was filtered and washed with distilled water. The resultant washed with distilled water was dried in a vacuum oven at about 60 ° C. for 24 hours to obtain reduced graphene oxide (Py-RGO) functionalized with pyridine group derived from 4-hydrazinopyridine.

0.2 g of Py-RGO was added to 100 ml of dichloromethane (CH ₂ Cl ₂ ) and dispersed by ultrasonication. Then, 5 equivalents of iron (III) chloride in nitromethane was slowly added to the reaction mixture over 2 hours under a nitrogen atmosphere. After that, the mixture was stirred at room temperature (25 ° C) for 24 hours, and 100 ml of methanol was added to terminate the reaction.

After the reaction was completed, the reaction mixture was filtered and washed with methanol. The washed product was then dried in a vacuum oven at about 60 DEG C to produce a healing product (H-Py-RGO) of reduced graphene oxide functionalized with pyridine groups.

[Reaction Scheme 1]

Example  1: polyimide composite containing Composite membrane  Produce

(H-Py-RGO) of reduced graphene oxide functionalized with the pyridine group obtained according to Production Example 2 was added to N-methyl 2-pyrrolidone (NMP), and the resultant was subjected to homogenization and ultrasonic treatment Lt; / RTI > The weight ratio of the healing product (H-Py-RGO) of reduced graphene oxide functionalized with pyridine group to NMP was 13:87.

0.8650 g of 3,3'-dihydroxybenzidine (DHB) as a polyamic acid precursor of Formula 8 was added to the dispersion, and the mixture was stirred at room temperature (25 ° C) for 1 hour. Then, a polyamic acid precursor And 0.8725 g of pyromellitic dianhydride (PMDA) represented by the following general formula (9) was added thereto, followed by magnetic stirring at room temperature for 24 hours to prepare a polyamic acid filled with a healing product of reduced graphene oxide functionalized with a pyridine group Respectively. Here, the content of the defect repair product of the polyamic acid precursor and the amine-functionalized graphene oxide was adjusted so that the weight ratio of the polyamic acid (PAA) and the defect-healing product of the amine-functionalized graphene oxide was 99.5: 0.5.

[Chemical Formula 8]

Thereafter, the resultant was bubbled in a vacuum oven at room temperature (25 ° C) for 2 hours, and then spin-coated on a glass substrate. The glass substrate coated with the polyamic acid prepared through the above process was dried in a vacuum oven at 90 ° C. for 1 hour and then heat-treated at 90 ° C. for about 1 hour at 150 ° C. for about 1 hour , About 200 ° C for about 1 hour, 250 ° C for about 30 minutes, and 300 ° C for about 30 minutes) to prepare a composite membrane containing the polyimide nanocomposite.

The process for producing the composite membrane containing the polyimide nanocomposite as described above is as shown in FIG.

In the polyimide nanocomposite prepared according to Example 1, the weight ratio of the healing product of the reduced graphene oxide functionalized with the polyimide to the pyridine group is 99.5: 0.5.

Example  2-4: polyimide nanocomposite containing Composite membrane  Produce

The polyamic acid precursor and graphene functionalized with a pyridine group, such that the weight ratio of the healing product of the reduced graphene oxide functionalized with polyamic acid (PAA) to the pyridine group is 99: 1, 97: 3, 95: A composite membrane containing the polyimide nanocomposite was prepared in the same manner as in Example 1, except that the content of the defect repair product of the oxide was controlled.

Comparative Example  1: Reduction functionalized with pyridine group Grapina Oxide Filled  Containing polyimide composite Composite membrane  Produce

(Py-RGO) functionalized with a pyridine group derived from 4-hydrazinopyridine obtained in Production Example 2 were mixed at a weight ratio of 99.5: 0.5, NMP was added to the mixture, Each was dispersed by homogenizer and ultrasonic treatment. The blend weight ratio of the mixture of polyamic acid and reduced graphene oxide (Py-RGO) functionalized with pyridine group derived from 4-hydrazinopyridine obtained in Preparation Example 2 and NMP was 13:87.

0.8650 g of 3,3'-dihydroxybenzidine represented by the formula (8), which is a polyamic acid precursor, was added to the dispersion and stirred at room temperature for 1 hour. Then, pyromellitic acid dianhydride (PMDA) of formula (9) as a polyamic acid precursor g, and the mixture was magnetically stirred at room temperature (25 ° C) for 24 hours to prepare polyamic acid having amine group-functionalized reduced graphene oxide.

Thereafter, the resultant was bubbled in a vacuum oven at room temperature for 2 hours, and then spin-coated on the glass substrate. The glass substrate coated with the polyamic acid prepared above was dried in a vacuum oven at 90 ° C for 1 hour and then heat-treated at 90 ° C for 1 hour, 150 ° C for 1 hour, 200 ° C 30 minutes at 250 < 0 > C, 30 minutes at 300 < 0 > C).

Comparative Example  2: Polyimide film  Produce

0.8650 g of 3,3'-dihydroxybenzidine (DHB) was added to NMP, stirred at room temperature for 1 hour, and 0.8725 g of pyromellitic dianhydride (PMDA) was added. The weight ratio of NMP and DHB was 87:13.

The resultant was then magnetically stirred at room temperature (25 DEG C) for 24 hours to prepare a polyamic acid. Thereafter, the resultant was bubbled in a vacuum oven at room temperature for 2 hours, and then spin-coated on a glass substrate. The glass substrate coated with the polyamic acid prepared through the above process was dried in a vacuum oven at 90 ° C. for 1 hour and then subjected to heat treatment (90 ° C. for 1 hour, 150 ° C. for 1 hour, 200 Lt; 0 > C for 1 hour, 250 < 0 > C for 30 minutes and 300 < 0 > C for 30 minutes) to prepare a composite membrane containing the polyimide composite.

Comparative Example  3: Reduction functionalized with pyridine group Grapina Oxide Filled  Containing polyimide composite Composite membrane  Produce

Except that the mixed weight ratio of polyamic acid and reduced graphene oxide (Py-RGO) functionalized with a pyridine group derived from 4-hydrazinopyridine obtained in Production Example 2 was changed to 99: 1. To prepare a composite membrane containing a polyimide composite filled with reduced graphene oxide functionalized with a pyridine group.

Evaluation example  1: Raman spectroscopy

The GO obtained according to Preparation Example 1 and the Py-RGO and H-Py-RGO obtained according to Production Example 2

Raman analysis was performed. Raman analysis was performed using a Raman spectroscopic analyzer (LabRAM HR, Horiba, Japan), and the results of the Raman analysis are shown in Fig.

Referring to FIG. 2, the D and G peaks of graphene oxides can be identified.

In FIG. 2, the I _G / I _D ratio of each graphene oxide was 1.26 for GO and 1.17 for Py-RGO, and the D peak was increased while the amine group was functionalized. It was confirmed that functionalization of amine group on the surface of graphene and reduction of hydroxyl group, carboxyl group and the like.

I _G / I _D ratio in the H-Py-RGO is increased significantly to 1.56. This means that the defects are reduced by increasing the SP ² bond on the graphene surface.

Evaluation example 2: Thermal weight  analysis ( Thermogravimetric  analysis: TGA )]

The thermogravimetric analysis of Py-RGO and H-Py-RGO obtained according to Preparation Example 1 and GO according to Preparation Example 2 was carried out using a thermogravimetric analyzer (TA 50, TA Instruments, USA) Is shown in Fig.

Referring to FIG. 3, it can be seen that GO has a large weight reduction at 150 ° C. as a function of oxygen is removed, while Py-RGO is reduced at the same time by performing amine group functionalization and reduction of GO . In addition, H-Py-RGO can be confirmed that the thermal stability is improved by reducing defects on the graphene surface.

Evaluation example  3: Powder resistance  Powder resistivity measurement]

Powder resistance of the GO obtained according to Preparation Example 1 and the Py-RGO and H-Py-RGO obtained according to Preparation Example 2 was measured using a powder resistance measuring device (FPP-RS8, Dasol Eng, Korea) The measurement results of the conductivity are shown in Fig.

Referring to FIG. 4, it can be confirmed that the GO has a very low electrical conductivity due to the oxygen function. Py-RGO has been reduced 97 Scm ^{- 1} was determined by. H-Py-RGO was measured to have 313Scm ^-1 , which is three times higher than that of Py-RGO. It was confirmed that the carbon atoms on the surface of the graphene having the sp ³ bond structure formed the sp ² covalent bond by reducing the defects.

Evaluation example  3: Transmission electron microscopy: TEM )]

Transmission electron micrographs of Py-RGO and H-Py-RGO prepared according to Preparation Example 2 are shown in FIGS. 5A and 5B, respectively. As a result of the SAED pattern analysis, the SAED pattern of H-Py-RGO compared to Py-RGO shows a clearer hexagonal shape, It is possible to confirm that the defects are healed by forming networking between the carbon atoms on the surface of the graphene.

Evaluation example  4: Tensile strength test

The tensile strength of the composite membrane containing the polyimide nanocomposite according to Example 1-2, the composite membrane containing the polyimide composite of Comparative Example 1 and the polyimide membrane prepared in Comparative Example 2 was measured using a universal testing machine (UTM) (5567A, Instron, USA) and the tensile strength test results are shown in Table 1 and FIG. 6, respectively.

division Sample name Mixing weight ratio Tensile Strength (MPa) Modulus of elasticity (GPa) Example 1 PI / H-Py-RGO 99.5: 0.5 661.0 ± 75.9 25.21 ± 1.3 Example 2 PI / H-Py-RGO 99: 1 883.5 ± 77.7 39.4 ± 3.7 Comparative Example 1 PI / Py-RGO 99.5: 0.5 527.2 ± 11.62 58.6 ± 1.2 Comparative Example 3 PI / Py-RGO 99: 1 488.0 + - 11.81 62.8 ± 2.4 Comparative Example 2 Pristine PI - 126.5 ± 7.1 6.2 ± 0.7

Referring to Table 1 and FIG. 6, it was confirmed that the physical properties of the composite membrane containing the polyimide nanocomposite were greatly improved when the healing product of the reduced graphene oxide functionalized with the pyridine group was added as a filler in the preparation of the polyimide nanocomposite .

When the graphene oxide functionalized with the pyridine groups of Comparative Examples 1 and 3 was used as the filler, the tensile strength of the composite film was increased to about 4 times as compared with that of the polyimide film of Comparative Example 2. [ This is because the reduced graphene oxide functionalized with the pyridine group in the polyimide is uniformly dispersed and interaction and chemical bonding with the polyimide are formed.

The tensile strength of the composite membrane containing the polyimide nanocomposite of Example 1 was increased to 7 times or more as compared with that of the polyimide membrane of Comparative Example 2 and was found to be about 1.8 times higher than that of the composite membrane of Comparative Example 1 Could. This is a result obtained by improving the mechanical strength of the reduced graphene oxide having a large surface area that can interact with the polyimide as the defect of the surface is healed.

Evaluation example  5: Scanning electron microscope: SEM )

The composite membrane containing the polyimide nanocomposite of Example 1 and the polyimide membrane of Comparative Example 2 were subjected to scanning electron microscopic analysis. SEM analysis was performed using a SEM analyzer (Nova Nano SEM, FEI, USA).

Images of the SEM analysis results are shown in FIGS. 7A and 7B, respectively. FIG. 7A is an SEM image of the polyimide film of Comparative Example 2, and FIG. 7B is an SEM image of the polyimide nanocomposite of Example 1. FIG.

Referring to Fig. 7A, the polyimide film of Comparative Example 2 showed a clean surface without impurities. Referring to FIG. 7B, the polymer mattress and the filler interact with each other to show that the strength of the composite is enhanced due to graphene oxide.

Evaluation example  6: Measurement of thermal expansion coefficient ( Thermomechanical  analyzer: TMA )

The thermal expansion coefficients of the polyimide nanocomposite of Example 1-4 and the polyimide of Comparative Example 2 were measured to determine the thermal stability, and the results are shown in FIG. The thermal expansion coefficient was measured according to ASTM E931 Standard using a thermomechanical analyzer (TMA 402 F3, Netzsch, USA).

Referring to FIG. 8, when the content of the filler was increased in the order of 0 wt%, 0.5 wt%, 1.0 wt% and 3 wt%, the coefficient of thermal expansion (CTE) decreased. From these results, it is understood that the defective healing product of graphene oxide functionalized with pyridine group increases the chain orientation in the polyimide and plays a role in suppressing thermal expansion.

Evaluation example  7: XPS  analysis

Py-RGO obtained according to Preparation Example 2 and H-Py-RGO obtained according to Example 1 were subjected to XPS analysis. XPS analysis was performed using an XPS analyzer (AXIS-NOVA, Kratos Inc., USA) and the results are shown in Table 2 below.

Referring to Table 2, the H-Py-RGO obtained according to Example 1 showed an increase in sp2C / sp3C as compared with Py-RGO obtained according to Production Example 2. [ From this, it can be seen that defects of the reduced graphene oxide functionalized with the pyridine group were healed. The GO obtained according to Production Example 1, the Py-RGO obtained according to Production Example 2, and the H-Py- RGO was analyzed by elemental composition using XPS analyzer. The analysis results are shown in Table 3 below.

As shown in Table 3, when the C / O ratio of Py-RGO was increased as compared with the C / O ratio of GO, the reduction of GO was observed, and the nitrogen content of H-Py-RGO and Py- , It was confirmed that a compound having a pyridine group in H-Py-RGO and Py-RGO was introduced.

The embodiments of the present invention described above should not be construed as limiting the technical idea of the present invention. The scope of protection of the present invention is limited only by the matters described in the claims, and those skilled in the art will be able to modify the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the scope of protection of the present invention as long as it is obvious to those skilled in the art.

Claims (10)

A product in which defects of reduced graphene oxide functionalized with at least one selected from ring compounds including a hetero ring and a hetero atom are healed; And
A polyimide nanocomposite comprising polyimide. The method according to claim 1,
Wherein the reduced graphene oxide functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom-
A polyimide nanocomposite which is a reaction product of graphene oxide and at least one selected from amine compounds represented by the following formula (1)
[Chemical Formula 1]

. The method according to claim 1,
A product obtained by healing a defect of reduced graphene oxide functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom,
Wherein the polyimide nanocomposite is a product obtained by an intermolecular cross-linking dehydrogenation reaction of reduced graphene oxide functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom-containing ring compound. The method according to claim 1,
A product obtained by healing a defect of reduced graphene oxide functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom,
A polyimide nanocomposite comprising at least one compound selected from compounds represented by the following formulas (2) to (5):
(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

The method according to claim 1,
The content of the healed product of the reduced graphene oxide functionalized with at least one selected from the heterocyclic ring and the cyclic compound containing a hetero atom is 0.1 to 30% by weight based on the total weight of the polyimide nanocomposite, . A first step of reacting graphene oxide with at least one member selected from the group consisting of a heterocyclic ring and a ring compound containing a hetero atom to obtain a reduced graphene oxide functionalized with at least one selected from ring compounds including a hetero ring and a hetero atom;
An intramolecular cross-dehydrogenative coupling of a reduced graphene oxide functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom-containing ring compound is performed to form a heterocyclic ring and a heteroatom-containing ring compound A second step of obtaining a defect healing product of reduced graphene oxide functionalized with at least one selected; And
And a third step of performing a polymerization reaction of a defect healing product of graphene functionalized with at least one selected from the group consisting of the heterocyclic ring and the heteroatom and a polyamic acid precursor and then carrying out an imidation reaction, To obtain a polyimide nanocomposite according to any one of claims 1 to 5. The method according to claim 6,
The intermolecular cross-linking dehydrogenation coupling of the reduced graphene oxide functionalized with at least one selected from among the ring compounds containing the heterocyclic ring and the hetero atom is carried out by adding iron chloride to the functionalized reduced graphene oxide and carrying out the reaction at 25 to 60 ° C A method for producing a polyimide nanocomposite. The method according to claim 6,
And a cyclic compound containing at least one ring selected from the group consisting of a heterocyclic ring and a heterocyclic ring containing heteroatom is a reaction product of graphene oxide and one selected from amine compounds represented by the following formula 1:
[Chemical Formula 1]

. The method according to claim 6,
Wherein said first step is a reaction of graphene oxide with at least one compound selected from the group consisting of compounds represented by the following general formula (1)
Wherein the reaction is carried out according to a process of dispersing graphene oxide in a solvent and then mixing at least one selected from compounds represented by the following general formula (1) and heat-treating the mixture at 35 to 100 캜.
[Chemical Formula 1]

. A composite membrane comprising the polyimide nanocomposite of any one of claims 1 to 5.

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