CN110681324B - Graphene oxide hybrid multi-wall self-lubricating micro-nano capsule and preparation method thereof - Google Patents
Graphene oxide hybrid multi-wall self-lubricating micro-nano capsule and preparation method thereof Download PDFInfo
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- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/02—Making microcapsules or microballoons
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- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
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- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
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Abstract
The invention relates to a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule and a preparation method thereof. The micro-nano capsule takes ionic liquid as a core material, and the structure of a wall material is as follows from inside to outside: polyurea/graphene oxide/(polyethyleneimine/graphene oxide)n. The preparation method comprises the following steps: (1) forming a mixture comprising: graphene oxide; an ionic liquid; and water; (2) adding a chain extender into the mixture and an isocyanate monomer, and heating to react to obtain the polyurea/graphene oxide double-wall micro-nano capsule coated with the ionic liquid; (3) forming a mixed system comprising: a polyethyleneimine; dopamine hydrochloride; and a buffer solution; (4) mixing the micro-nano capsule prepared in the step (2) with a mixed system, and reacting at room temperature to obtain a dopamine-polyethyleneimine modified polyurea/graphene oxide double-wall micro-nano capsule; (5) and (4) mixing the micro-nano capsule obtained in the step (4) with a graphene oxide aqueous solution, and reacting under stirring.
Description
Technical Field
The invention relates to the technical field of self-lubricating materials, in particular to a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule and a preparation method thereof.
Background
The problems of friction and abrasion inevitably exist in key parts in the fields of petrochemical industry, aerospace, mechanical engineering and the like, such as gears, bearings, pistons and the like, so that the problems of shortened service life of equipment, poor safety of the equipment, lowered production capacity and the like are caused, and serious environmental pollution and major accidents are caused. Therefore, the research on the friction-reducing and wear-resisting material has important significance. The polymer-based composite material has excellent properties of light weight, high strength, corrosion resistance, easy forming and processing and the like, so that the polymer-based composite material is widely used for replacing a plurality of metal materials and becomes the antifriction and wear-resistant material with the greatest development prospect. However, the polymer material has the defects of poor heat transfer and wear resistance and the like, so that the application of the polymer material in the field of tribology is limited. With the development of high and new technologies, instruments and equipment develop towards high temperature, high load and light weight, the requirements on high-performance resin matrix composite materials are increased day by day, particularly higher requirements on the comprehensive properties of the resin matrix composite materials such as self-lubrication, wear resistance and the like are provided, and the common resin matrix self-lubricating materials no longer meet the use requirements. Therefore, the research on the resin-based self-lubricating composite material with excellent self-lubricating and wear-resisting properties is of great significance.
The currently used polymer-based self-lubricating composite materials mainly comprise the following three types: self-lubricating composite materials filled with solid nano-particles, porous self-lubricating composite materials filled with lubricants and self-lubricating composite materials filled with self-lubricating microcapsules (also called microcapsule type self-lubricating composite materials). The microcapsule type self-lubricating composite material is prepared by microencapsulating liquid lubricant with specific microcapsule wall material, and then filling the microcapsule wall material into a polymer matrix to form a polymer matrix composite material or coating with self-lubricating function. The composite material or the coating can cause the microcapsule to break and release the lubricant under the action of friction force in the friction process, so that a self-lubricating transfer film is formed between the friction surface and the mating surface of the composite material, the direct contact between the friction surface and the mating surface is prevented, in addition, a microcapsule cavity left on the friction surface of the composite material can capture abrasive dust generated in the friction process, and the friction effect of abrasive particles is reduced, so that the friction and wear performance of the self-lubricating composite material is obviously improved. The problems of large friction coefficient of solid lubrication and lubrication failure of a porous lubricating material in a long-time friction application process are solved to a certain extent.
In recent years, research on microcapsule type self-lubricating composite materials mainly focuses on the preparation of self-lubricating microcapsules and the research on tribological properties of the self-lubricating microcapsules and the composite materials. The commonly used microencapsulated lubricants are mainly paraffin wax, lubricant base oil, silicone oil, siloxane, isocyanate, oleamide, and the like. The wall materials of the common microcapsules mainly comprise organic wall materials represented by Polysulfone (PSF), Polystyrene (PS), Polyurea (PU), urea resin (PUF), melamine resin (PMF) and the like, and the organic wall materials have good encapsulation property, but the organic wall materials are generally poor in mechanical property, so that the microcapsules are easy to break in the using process; or with SiO2Inorganic materials represented by the above general formula are used as wall materials, and generally have good thermal stability, but inorganic wall materials are generally poor in encapsulation property, and have porous structures.
At present, there is a document that self-lubricating microcapsules are added to polymer matrixes such as epoxy resin, polyurethane, polytetrafluoroethylene and the like to prepare self-lubricating composite materials or coatings, and the tribological performance research on the composite materials or the coatings finds that the addition of the microcapsules can obviously improve the frictional wear performance of the composite materials, so that some progress has been made in the research field of microcapsule type self-lubricating composite materials, and the field has a wide application prospect, however, the following key problems need to be solved at present:
(1) the particle size of the self-lubricating microcapsule reported in the existing literature is mostly in the range of dozens to hundreds of micrometers, the larger particle size of the microcapsule can influence the mechanical property of the composite material, and although the mechanical property and the tribological property of the composite material can be improved by adding a nano reinforcing material into a matrix of the composite material, the problem that a nano additive is difficult to disperse is still not effectively solved.
(2) Reported mechanical properties of microcapsule wall materials such as urea-formaldehyde resin (PUF), melamine resin (PMF), Polyurea (PU) and the like are poor, and capsules are easy to break in the preparation process of a resin-based composite material, so that the self-lubricating effect of the composite material is seriously influenced; although the wall materials such as Polysulfone (PSF), Polystyrene (PS) and the like have good mechanical properties, the softening temperature of the wall materials is low (generally lower than 170 ℃), and the wall materials are limited in the high-temperature molding of resin matrixes or the application in high-temperature environments. The organic/inorganic hybrid wall material can improve the thermal stability of the microcapsule, but the proportion of the inorganic component in the wall material structure in the organic/inorganic hybrid wall material reported in the existing literature is small, and the content of the inorganic component can not be effectively regulated and controlled, so that the ideal effect can not be achieved. Therefore, the existing microcapsule type self-lubricating system cannot meet the purposes of friction reduction and wear resistance under the conditions of high temperature, high speed, high load and the like.
(3) Because of weak interfacial adhesion between the capsule and the resin matrix, the mechanical property of the composite material added with the capsule is remarkably reduced, so that the improvement of the friction and wear properties of the composite material is influenced, and few reports exist at present on the research of modifying the wall material of the capsule so as to improve the interfacial bonding strength between the wall material of the capsule and the resin matrix.
Disclosure of Invention
In view of the above prior art, the inventors of the present invention have conducted extensive and intensive studies in the field of self-lubricating capsule materials, and according to the results of the studies, a first object of the present invention is to provide a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule, and a second object of the present invention is to provide a method for preparing a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule.
In order to achieve the purpose, the invention provides the following technical scheme:
a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule takes ionic liquid as a core material and a multilayer graphene oxide hybrid system as a wall material;
the multilayer graphene oxide hybrid system has the following structure from inside to outside:
polyurea/graphene oxide/(polyethyleneimine/graphene oxide)nN represents the number of layers of polyethyleneimine/graphene oxide, and n is a natural number not less than 1.
Optionally, the structure of the multilayer graphene oxide hybrid system is, from inside to outside: polyurea/graphene oxide/polyethyleneimine/graphene oxide.
Optionally, the structure of the multilayer graphene oxide hybrid system is, from inside to outside: polyurea/graphene oxide/(polyethyleneimine/graphene oxide)n，n≥2。
Preferably, the micro-nano capsule has one or more of the following properties:
the content of the core material is 40-85%;
the thermal decomposition temperature is higher than 250 ℃.
A preparation method of a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule comprises the following steps:
(1) forming a mixture comprising:
graphene oxide;
an ionic liquid; and
water;
(2) mixing the mixture obtained in the step (1) with an isocyanate monomer, adding a chain extender, and heating for reaction to obtain a polyurea/graphene oxide double-wall micro-nano capsule coated with ionic liquid;
(3) forming a mixed system comprising:
a polyethyleneimine;
dopamine hydrochloride; and
a buffer solution;
(4) mixing the micro-nano capsule prepared in the step (2) with the mixed system obtained in the step (3), and reacting at room temperature to obtain a dopamine-polyethyleneimine modified polyurea/graphene oxide double-wall micro-nano capsule;
(5) and (3) mixing the micro-nano capsule obtained in the step (4) with a graphene oxide aqueous solution, and reacting under stirring to obtain a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule with a core material of ionic liquid and a wall material of polyurea/graphene oxide/polyethyleneimine/graphene oxide from inside to outside.
Preferably, in step (1), the concentration of graphene oxide in water is 0.01-0.5 wt%, preferably 0.05-0.2 wt%; the mass ratio of the ionic liquid to the water is 1: (5-50), preferably 1: (20-30);
preferably, in forming the mixture obtained in step (1), the pH of the mixture is adjusted to 2 to 5, preferably 2 to 3;
preferably, in the formation of the mixture obtained in step (1), the mixture obtained by mixing the graphene oxide, the ionic liquid and the water is dispersed at 0-25 ℃ by means of ultrasonic or mechanical stirring;
more preferably, the ultrasound time is 5-30 min; or
The rotating speed of the mechanical stirring is 1000-30000r/min, and the stirring time is 5-30 min.
Preferably, in the step (2), the isocyanate monomer is fluoroketone isocyanate and/or toluene diisocyanate, and the chain extender is triethylene tetramine and/or 1, 4-butanediol;
preferably, the mass ratio of the isocyanate monomer to the chain extender is (1-1.5): 1;
preferably, water is used as a solvent, and the chain extender is prepared into a solution with the concentration of 10-30wt% for use;
preferably, the mass ratio of the isocyanate monomer to the ionic liquid is 1: (1-5).
Preferably, the mixture obtained in the step (1) and the isocyanate monomer are mechanically stirred at the speed of 300-800r/min to be uniformly mixed, and then the chain extender is added; and/or
Preferably, the polyurea/graphene oxide double-wall micro-nano capsule coated with the ionic liquid is obtained by reacting at 40-70 ℃, and the reaction time is preferably 2-4 h.
Preferably, in step (3), the buffer solution is a tris (hydroxymethyl) aminomethane aqueous solution having a concentration of 0.1 to 0.5wt%, and the pH is adjusted to 8 to 9 with hydrochloric acid;
the concentration of the polyethyleneimine in the buffer solution is 0.1-0.5 wt%;
the concentration of the dopamine hydrochloride in the buffer solution is 0.1-0.5 wt%; and/or
The concentration of the micro-nano capsule in the buffer solution is 1-10 wt%.
Preferably, in the step (4), the reaction is carried out for 3-6h at room temperature;
in the step (5), the concentration of the graphene oxide aqueous solution is 0.1-1 wt%;
the concentration of the micro-nano capsule obtained in the step (4) in the graphene oxide aqueous solution is 1-10 wt%;
the stirring speed is controlled at 200-500 r/min; and/or
The reaction time is controlled to be 0.5-12 h.
Preferably, the preparation method further comprises the following steps:
(6) mixing the micro-nano capsule obtained in the step (5) with the mixed system obtained in the step (3), reacting at room temperature, filtering, washing and drying a reactant, mixing with a graphene oxide aqueous solution, and reacting under stirring;
repeating the steps m times, wherein m is n-2, n is more than or equal to 2, each micro-nano capsule used in each repetition is the micro-nano capsule obtained in the previous step, the obtained core material is ionic liquid, and the wall material is polyurea/graphene oxide/(polyethyleneimine/graphene oxide) from inside to outsidenThe graphene oxide hybrid multi-wall self-lubricating micro-nano capsule.
Advantageous effects
The technical scheme of the invention has the following advantages:
the multi-wall self-lubricating micro-nano capsule with the particle size ranging from hundreds of nanometers to microns is synthesized by taking ionic liquid as a core material and taking a multi-layer GO (graphene oxide) hybrid system as a wall material. The ionic liquid has the properties of high thermal oxidation stability, difficult volatility, nonflammability, bipolarity and the like, and is a green efficient lubricant with great prospect. Especially for some machine equipment operating above 250 ℃, conventional hydrocarbon lubricating oils may start to decompose, but the ionic liquid may remain stable. The unique two-dimensional crystal structure, high thermal conductivity, high strength and hardness, high wear resistance, etc. make GO an effective solid lubricant. The invention combines the two through the same carrier and the capsule, realizes the ultralow tribology performance of the self-lubricating composite material through liquid-solid synergistic lubrication, and simultaneously solves the problem of poor wear resistance of the ionic liquid under high load.
The invention finally prepares the PU/GO/(PEI/GO) n multi-wall micro-nano capsule with controllable wall thickness by a layer-by-layer self-assembly technology of interaction between negative charges on GO and positive charges on PEI.
Drawings
FIG. 1 is PU/GO/(PEI/GO)nA schematic diagram of a multi-wall micro-nano capsule synthesis principle.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention provides a preparation method of a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule in a first aspect. The preparation method comprises the following steps:
the invention provides a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule in a first aspect, wherein the micro-nano capsule takes ionic liquid as a core material and takes a multilayer graphene oxide hybrid system as a wall material; the multilayer graphene oxide hybrid system has the following structure from inside to outside: polyurea/graphene oxide/(polyethyleneimine/graphene oxide)nN represents the number of layers of polyethyleneimine/graphene oxide, and n is a natural number not less than 1. The value of n can be 1, and at this time, the structure of the multilayer graphene oxide hybrid system is as follows from inside to outside: polyurea/graphene oxide/polyethyleneimine/graphene oxide. The value of n can be more than or equal to 2, and at the moment, the structure of the multilayer graphene oxide hybrid system is as follows from inside to outside: polyurea/graphene oxide/(polyethyleneimine/graphene oxide)n，n≥2。
The multi-wall self-lubricating micro-nano capsule with the particle size ranging from hundreds of nanometers to microns is synthesized by taking ionic liquid (the type of the ionic liquid is not specifically limited by the invention) as a core material and taking a multi-layer GO (graphene oxide) hybrid system as a wall material. The ionic liquid has the properties of high thermal oxidation stability, difficult volatility, nonflammability, bipolarity and the like, and is a green efficient lubricant with great prospect. Especially for some machine equipment operating above 250 ℃, conventional hydrocarbon lubricating oils may start to decompose, but the ionic liquid may remain stable. The unique two-dimensional crystal structure, high thermal conductivity, high strength and hardness, high wear resistance, etc. make GO an effective solid lubricant. The invention combines the two through the same carrier and the capsule, realizes the ultralow tribology performance of the self-lubricating composite material through liquid-solid synergistic lubrication, and simultaneously solves the problem of poor wear resistance of the ionic liquid under high load.
However, the self-lubricating capsules provided by the invention can not only play a role of introducing GO but also can not only make use of the excellent friction resistance of GO to enable the GO to have a synergistic effect with ionic liquid. Firstly, the introduction of GO endows the capsule with high thermal stability and good mechanical property, thereby expanding the application of the capsule under the conditions of high temperature, high load and the like. Secondly, the number of layers of GO, namely the wall thickness of the capsule can be regulated and controlled by a layer-by-layer self-assembly technology, so that the controllability of the performance of the capsule and the composite material can be realized; thirdly, due to the introduction of GO in the structure of the micro-nano capsule wall material, a large number of active functional groups on the surface of GO can form chemical bonds with the resin matrix, so that the interface bonding strength between the capsule and the resin matrix is remarkably improved, and the mechanical property and the tribological property of the resin-based self-lubricating composite material can be effectively improved; finally, the multilayer GO is hybridized on the capsule wall material, so that the problem that the nano-scale GO is difficult to disperse in a resin matrix is effectively solved, and more importantly, the excellent friction resistance of the GO can be cooperated with the ionic liquid, so that the ultralow tribological performance of the capsule type self-lubricating composite material is realized.
Through detection, the micro-nano capsule provided by the invention has one or more of the following properties:
the content of the core material is 40-85%;
the thermal decomposition temperature is higher than 250 ℃.
The micro-nano capsule provided by the invention can be applied to the preparation of self-lubricating polymer materials or self-lubricating polymer coatings in various polymer resin matrixes such as epoxy resin, polyamide, polyimide, polytetrafluoroethylene, polyether ether ketone, polypropylene, polyethylene and the like, and the prepared self-lubricating polymer materials or coatings have excellent friction and wear resistance and can be applied to wear-resistant parts of equipment such as important machinery, chemical engineering and the like.
The invention provides a preparation method of a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule in a second aspect, and the graphene oxide hybrid multi-wall self-lubricating micro-nano capsule provided by the invention in the first aspect can be prepared by the method. The preparation method comprises the following steps:
(1) forming a mixture comprising:
graphene oxide;
an ionic liquid; and
water;
(2) mixing the mixture obtained in the step (1) with an isocyanate monomer, adding a chain extender, and heating for reaction to obtain a polyurea/graphene oxide double-wall micro-nano capsule coated with ionic liquid;
(3) forming a mixed system comprising:
a polyethyleneimine;
dopamine hydrochloride; and
a buffer solution;
(4) mixing the micro-nano capsule prepared in the step (2) with the mixed system obtained in the step (3), and reacting at room temperature to obtain a dopamine-polyethyleneimine modified polyurea/graphene oxide double-wall micro-nano capsule;
(5) and (3) mixing the micro-nano capsule obtained in the step (4) with a graphene oxide aqueous solution, and reacting under stirring to obtain a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule with a core material of ionic liquid and a wall material of polyurea/graphene oxide/polyethyleneimine/graphene oxide from inside to outside.
The ionic liquid and GO are respectively used as a core material and a wall material of the capsule through the same carrier-capsule, and no relevant report is found at present in the research on the ultralow tribological performance of the self-lubricating composite material through liquid-solid synergistic lubrication. The inventor of the invention explores a feasible preparation process of the self-lubricating micro-nano capsule taking the ionic liquid as the core material and the multilayer GO hybrid system as the wall material. In the process of research, the inventor finds that the ionic liquid is a green efficient lubricant, the friction and wear performance of the ionic liquid is far higher than that of the conventional lubricating oil, but the encapsulation is difficult due to the high viscosity and the bipolar property of the ionic liquid, and particularly the preparation of nano-scale capsules is difficult. Therefore, the prepared ionic liquid capsule with high core material content has the particle size in the micro-nano range, and the application of the self-lubricating capsule can be greatly expanded. The preparation method used in the present invention overcomes this problem. According to the invention, the graphene oxide is used to enable the ionic liquid to form a stable O/W type Pickering emulsion in water, and compared with the O/W type Pickering emulsion formed by the traditional surfactant, the Pickering emulsion formed by the graphene oxide is more stable, so that the ionic liquid has a better dispersion effect. The formation of a Pickering emulsion system requires that solid particles have the optimal hydrophilic-lipophilic balance value at an oil-water interface, graphene oxide has a two-dimensional crystal structure, and the surface of the graphene oxide contains a large number of active functional groups to enable the graphene oxide to have the amphiphilic property, so that the graphene oxide can be used as a Pickering emulsion dispersant; in a stable oil-in-water system, the energy required for removing the nanosheet layered GO dispersing agent from the oil-water interface is far greater than that for removing surfactants such as small molecules or spherical particles, so that GO serving as a Pickering dispersing agent of the oil-water interface has more excellent dispersing performance, and micro-nano-scale dispersion of a high-viscosity ionic liquid lubricant in a water phase can be realized.
The reaction principle of the preparation method provided by the invention is as follows:
referring to fig. 1, prior to reaction, GO may act as a stabilizer, stabilizing a mixture comprising an ionic liquid and water. After the reaction is finished, GO is coated on the outer side (possibly hybridized together) of the polymerized PU to form a self-lubricating double-wall micro-nano capsule with the core material of ionic liquid and the wall material of PU/GO.
The polyethyleneimine and dopamine hydrochloride form polyethyleneimine crosslinked polydopamine with positive charges on the surface, as GO on the surface of the PU/GO double-wall micro-nano capsule has negative charges, the polyethyleneimine crosslinked polydopamine is automatically coated on the surface of the PU/GO double-wall micro-nano capsule, and the PU/GO/(PEI/GO) n multi-wall micro-nano capsule with controllable wall thickness is finally prepared by a layer-by-layer self-assembly technology of interaction of the negative charges on GO and the positive charges on PEI.
In some preferred embodiments, in step (1), the concentration of graphene oxide in water is 0.01 to 0.5wt%, for example, may be 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5wt%, preferably 0.05 to 0.2 wt%. In some preferred embodiments, the mass ratio of ionic liquid to water is 1: (5-50) may be, for example, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, preferably 1: (20-30). By controlling the dosage of the graphene oxide, the ionic liquid and the water, the mixture prepared in the step (1) forms a Pickering emulsion with stable graphene oxide. The inventor finds in research that when the proportion of the graphene oxide is too low, the graphene oxide cannot play a good stabilizing role. When the proportion of the graphene oxide is too high, more graphene oxide cannot play a better stabilizing role, and the redundant part can independently exist in the system, so that the capsule preparation is influenced. Meanwhile, the ratio of graphene oxide can affect the size of emulsion droplets, generally, the higher the ratio of graphene oxide is, the smaller the particle size of the emulsion is, but the particle size does not change any more when the concentration of graphene oxide reaches a certain value. The oil-water ratio imbalance condition occurs when the proportion of the ionic liquid is too low or too high, and the stability of the mixture (namely Pickering emulsion) is reduced.
In some preferred embodiments, in forming the mixture obtained in step (1), the pH of the mixture is adjusted to 2 to 5 to ensure the stability of the mixture, which may be, for example, 2, 3, 4, 5, preferably 2 to 3. The amphiphilic property of graphene oxide is determined by the pH value, and the pH value can change the wettability of GO on an oil-water interface, so that the stability of the Pickering emulsion is influenced. When the pH value is lower, the hydrophilicity of GO is weaker, and when the pH value is within the range of 2-5, the hydrophilic and lipophilic performance of GO can realize the stable dispersion of Pickering of GO to ionic liquid. When the pH is higher, the ionization degree of carboxyl (-COOH) on GO is increased, the hydrophilicity of GO is enhanced, the GO is not easy to be adsorbed on an oil-water interface, and the GO is not easy to form a stable emulsion.
The inventors have also found in their studies that mixing process conditions are also an important factor affecting the stability of the mixture formed in step (1). For research reasons, it is preferable in the present invention that, in forming the mixture obtained in step (1), the mixture obtained by mixing graphene oxide, an ionic liquid and water is dispersed by ultrasonic or mechanical stirring at 0 to 25 ℃ (e.g., 0 ℃, 1 ℃, 2 ℃, 3 ℃,4 ℃, 5 ℃, 6 ℃, 7 ℃, 8 ℃, 9 ℃, 10 ℃, 11 ℃, 12 ℃, 13 ℃, 14 ℃, 15 ℃, 16 ℃, 17 ℃, 18 ℃, 19 ℃, 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃). More preferably, when the dispersion is carried out by ultrasonic means, the ultrasonic time is 5-30min and is preferably carried out at 0 ℃, and the temperature condition of 0 ℃ can be provided by using an ice bath; when the dispersion is carried out by mechanical stirring, the rotation speed of the mechanical stirring is 1000-30000r/min, for example, 1000r/min, 2000r/min, 3000r/min, 4000r/min, 5000r/min, 6000r/min, 7000r/min, 8000r/min, 9000r/min, 10000r/min, 20000r/min, 30000r/min, and the stirring time is 5-30min, for example, 5min, 10min, 15min, 20min, 25min, 30 min.
In some preferred embodiments, in step (2), the isocyanate-based monomer is fluorone isocyanate and/or toluene diisocyanate. In some preferred embodiments, the chain extender is triethylene tetramine and/or 1, 4-butanediol. More preferably, the mass ratio of the isocyanate-based monomer to the chain extender is (1-1.5): 1. more preferably, the chain extender is formulated to be used in a solution having a concentration of 10 to 30wt% (e.g., may be 10wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%) using water as a solvent. More preferably, the mass ratio of the isocyanate monomer to the ionic liquid is 1 (1-5) to ensure the content of the core material in the capsule, and may be 1:1, 1:2, 1:3, 1:4, 1:5, for example.
In some preferred embodiments, the mixture obtained in step (1) is mechanically stirred with the isocyanate monomer at 300-800r/min (for example, 300r/min, 400r/min, 500r/min, 600r/min, 700r/min, 800r/min) to mix uniformly, and then the chain extender is added.
In some preferred embodiments, the polyurea/graphene oxide double-wall micro-nano capsule coated with the ionic liquid is obtained by reacting at 40-70 ℃ (for example, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 56 ℃, 60 ℃, 65 ℃, 70 ℃), and the reaction time is preferably 2-4h, for example, 2h, 3h, 4 h.
In some preferred embodiments, in step (3), the buffer solution is an aqueous solution of tris (hydroxymethyl) aminomethane at a concentration of 0.1 to 0.5wt% (e.g., can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%), and is adjusted to a pH of 8 to 9 with hydrochloric acid.
In some preferred embodiments, the concentration of the polyethyleneimine in the buffer solution is 0.1 to 0.5wt%, and for example, may be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%.
In some preferred embodiments, the concentration of dopamine hydrochloride in the buffer solution is 0.1 to 0.5wt%, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%. In some preferred embodiments, the concentration of the micro-nano capsule in the buffer solution is 1 to 10wt%, for example, 1wt%, 2 wt%, 3 wt%, 4 wt%, 5wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%.
In some preferred embodiments, the micro-nano capsule prepared in step (2) is mixed with the mixed system obtained in step (3), the mixture is reacted at room temperature for 3 to 6 hours (for example, 3 hours, 4 hours, 5 hours and 6 hours), the reactant is washed (with deionized water, ethanol and acetone), filtered and dried, and the dopamine-polyethyleneimine modified polyurea/graphene oxide double-wall micro-nano capsule is obtained.
In some preferred embodiments, in step (5), the concentration of the graphene oxide aqueous solution is 0.1 to 1wt%, for example, may be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%. In some preferred embodiments, the concentration of the micro-nano capsule obtained in step (4) in the graphene oxide aqueous solution is 1-10wt%, for example, 1wt%, 2 wt%, 3 wt%, 4 wt%, 5wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%. In addition, the stirring speed is preferably controlled at 200-500r/min, for example, 200r/min, 300r/min, 400r/min, 500 r/min; preferably, the reaction time is controlled to be 0.5 to 12 hours, for example, 0.5 hour, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours.
In some preferred embodiments, the preparation method further comprises the steps of:
(6) mixing the micro-nano capsule obtained in the step (5) with the mixed system obtained in the step (3), reacting at room temperature for 3-6h, filtering, washing and drying a reactant, mixing with a graphene oxide aqueous solution, wherein the concentration of the graphene oxide aqueous solution used in the step is 0.1-1wt%, the concentration of the micro-nano capsule in the graphene oxide aqueous solution is 1-10wt%, and reacting under stirring, wherein the reaction time is controlled to be 0.5-12 h;
repeating the steps m times, wherein m is n-2, n is more than or equal to 2, the micro-nano capsule used in each repetition is the micro-nano capsule obtained in the previous step, the core material obtained by the layer-by-layer self-assembly technology is ionic liquid, and the wall material is polyurea/graphene oxide/(polyethyleneimine/graphene oxide) from inside to outsidenThe graphene oxide hybrid multi-wall self-lubricating micro-nano capsule.
More comprehensively, the preparation method provided by the invention comprises the following steps:
(1) forming a mixture comprising: graphene oxide; an ionic liquid; and water, the pH of the mixture is adjusted to 2-5, preferably 2-3; the concentration of the graphene oxide in water is 0.01-0.5 wt%, preferably 0.05-0.2 wt%; the mass ratio of the ionic liquid to the water is 1: (5-50), preferably 1: (20-30); dispersing a mixture obtained by mixing graphene oxide, ionic liquid and water at 0-25 ℃ by means of ultrasonic or mechanical stirring; more preferably, the ultrasonic treatment is carried out for 5-30min under the ice bath condition; or the rotating speed of the mechanical stirring is 1000-;
(2) mixing the mixture obtained in the step (1) with an isocyanate monomer, adding a chain extender, and heating for reaction to obtain a polyurea/graphene oxide double-wall micro-nano capsule coated with ionic liquid; the isocyanate monomer is fluorine ketone isocyanate and/or toluene diisocyanate, and the chain extender is triethylene tetramine and/or 1, 4-butanediol; the mass ratio of the isocyanate monomer to the chain extender is (1-1.5): 1; using water as a solvent, and preparing the chain extender into a solution with the concentration of 10-30wt% for use; the mass ratio of the isocyanate monomer to the ionic liquid is 1: (1-5); mechanically stirring the mixture obtained in the step (1) and the isocyanate monomer at the speed of 300-800r/min to be uniformly mixed, then adding the chain extender, heating to 40-70 ℃ to react for 2-4 h;
(3) forming a mixed system comprising: a polyethyleneimine; dopamine hydrochloride; and a buffer solution; the buffer solution is a tris (hydroxymethyl) aminomethane aqueous solution with the concentration of 1-0.5wt%, and the pH value is adjusted to 8-9 by hydrochloric acid; the concentration of the polyethyleneimine in the buffer solution is 0.1-0.5 wt%; the concentration of the dopamine hydrochloride in the buffer solution is 0.1-0.5 wt%;
(4) mixing the micro-nano capsule prepared in the step (2) with the mixed system obtained in the step (3), and reacting for 3-6h at room temperature to obtain a dopamine-polyethyleneimine modified polyurea/graphene oxide double-wall micro-nano capsule; the concentration of the micro-nano capsule in the buffer solution in the step (3) is 1-10 wt%;
(5) mixing the micro-nano capsule obtained in the step (4) with a graphene oxide aqueous solution, and reacting under stirring to obtain a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule with a core material of ionic liquid and a wall material of polyurea/graphene oxide/polyethyleneimine/graphene oxide from inside to outside; the concentration of the graphene oxide aqueous solution is 0.1-1 wt%; the concentration of the micro-nano capsule obtained in the step (4) in the graphene oxide aqueous solution is 1-10 wt%; the stirring speed is controlled at 200-500r/min, and the reaction time is controlled at 0.5-12 h.
On the basis of the preparation method, the preparation method also comprises the following steps:
(6) mixing the micro-nano capsule obtained in the step (5) with the mixed system obtained in the step (3), reacting at room temperature for 3-6h, filtering, washing and drying a reactant, mixing with a graphene oxide aqueous solution, wherein the concentration of the graphene oxide aqueous solution used in the step is 0.1-1wt%, the concentration of the micro-nano capsule in the graphene oxide aqueous solution is 1-10wt%, and reacting under stirring, wherein the reaction time is controlled to be 0.5-12 h;
repeating the steps m times, wherein m is n-2, n is more than or equal to 2, each micro-nano capsule used in each repetition is the micro-nano capsule obtained in the previous step, the obtained core material is ionic liquid, and the wall material is polyurea/graphene oxide/(polyethyleneimine/graphene oxide) from inside to outsidenThe graphene oxide hybrid multi-wall self-lubricating micro-nano capsule.
The following are examples of the present invention.
Example 1
(1) Adding ionic liquid into the graphene oxide aqueous solution, adjusting the pH of the system to 3, wherein the concentration of the graphene oxide aqueous solution is 0.05 wt%, and the mass ratio of the ionic liquid to water is 1: 10. And ultrasonically dispersing the mixed solution for 5min, and ultrasonically treating the mixed solution in an ice bath to prepare the Pickering emulsion A with stable GO.
(2) Adding isophorone isocyanate into the solution A, wherein the mass ratio of isocyanate to ionic liquid is 1:1, mechanically stirring for 5min (the rotating speed is 300r/min), adding 10wt% of triethylene tetramine aqueous solution, wherein the mass ratio of isocyanate to triethylene tetramine is 1:1, heating the system to 40 ℃, and reacting for 4h to prepare the polyurea/graphene oxide (PU/GO) double-wall micro-nano capsule coated with the ionic liquid.
(3) Preparing a Tris (hydroxymethyl) aminomethane (Tris) aqueous solution with the concentration of 0.1 wt%, adjusting the pH of the aqueous solution to 8-9 with diluted hydrochloric acid, adding Polyethyleneimine (PEI), wherein the concentration of polyethyleneimine in the Tris solution is 0.1 wt%, manually shaking for 5s, adding dopamine hydrochloride (DA-HCL), wherein the concentration of dopamine hydrochloride in the Tris solution is 0.1 wt%, manually shaking for 5s, adding 1wt% (referring to the mass percentage content in the Tris solution) of the micro-nano capsule prepared in the step (2), reacting for 3h at room temperature, filtering, washing and drying to obtain the dopamine-polyethyleneimine modified micro-nano capsule with positive charges on the surface.
(4) And (3) mixing the micro-nano capsule obtained in the step (3) with a GO aqueous solution with the concentration of 0.1 wt%, wherein the mass fraction of the micro-nano capsule in the GO aqueous solution is 1wt%, mechanically stirring at normal temperature for 200r/min, and reacting for 1h to prepare the PU/GO/PEI/GO multi-wall micro-nano capsule.
(5) And (3) repeating the step (3) and the step (4) to obtain a multi-wall structure, wherein the PU/GO/PEI/GO micro/nano capsules in the step (3) are required to be replaced by the PU/GO/PEI/GO micro/nano capsules, and by analogy, the PU/GO/(PEI/GO) n multi-wall micro/nano capsules with controllable wall thickness are finally prepared by a layer-by-layer self-assembly technology of interaction of negative charges on GO and positive charges on PEI.
Example 2
(1) Adding ionic liquid into the graphene oxide aqueous solution, adjusting the pH of the system to 3, wherein the concentration of the graphene oxide aqueous solution is 0.01 wt%, and the mass ratio of the ionic liquid to water is 1: 20. And ultrasonically dispersing the mixed solution for 10min, and ultrasonically treating the mixed solution in an ice bath to prepare the Pickering emulsion A with stable GO.
(2) Adding toluene diisocyanate into the solution A, wherein the mass ratio of the toluene diisocyanate to the ionic liquid is 1:2, mechanically stirring for 5min (the rotating speed is 400r/min), adding 15 wt% of triethylene tetramine aqueous solution, wherein the mass ratio of the toluene diisocyanate to the triethylene tetramine is 1:1, heating the system to 50 ℃, and reacting for 3h to prepare the polyurea/graphene oxide (PU/GO) double-wall micro-nano capsule coated with the ionic liquid.
(3) Preparing a Tris (hydroxymethyl) aminomethane (Tris) aqueous solution with the concentration of 0.3 wt%, adjusting the pH of the aqueous solution to 8-9 with diluted hydrochloric acid, adding Polyethyleneimine (PEI), wherein the concentration of polyethyleneimine in the Tris solution is 0.2 wt%, manually shaking for 10s, adding dopamine hydrochloride (DA-HCL), wherein the concentration of dopamine hydrochloride in the Tris solution is 0.3 wt%, manually shaking for 10s, adding 5wt% (referring to the mass percentage content in the Tris solution) of the micro-nano capsule prepared in the step (2), reacting for 4h at room temperature, filtering, washing and drying to obtain the dopamine-polyethyleneimine modified micro-nano capsule with positive charges on the surface.
(4) And (3) mixing the micro-nano capsule obtained in the step (3) with a GO aqueous solution with the concentration of 0.3 wt%, wherein the mass fraction of the micro-nano capsule in the GO aqueous solution is 3 wt%, mechanically stirring at normal temperature for 300r/min, and reacting for 4h to prepare the PU/GO/PEI/GO multi-wall micro-nano capsule.
(5) And (3) repeating the step (3) and the step (4) to obtain a multi-wall structure, wherein the PU/GO/PEI/GO micro/nano capsules in the step (3) are required to be replaced by the PU/GO/PEI/GO micro/nano capsules, and by analogy, the PU/GO/(PEI/GO) n multi-wall micro/nano capsules with controllable wall thickness are finally prepared by a layer-by-layer self-assembly technology of interaction of negative charges on GO and positive charges on PEI.
Example 3
(1) Adding ionic liquid into the graphene oxide aqueous solution, adjusting the pH of the system to 3, wherein the concentration of the graphene oxide aqueous solution is 0.1 wt%, and the mass ratio of the ionic liquid to water is 1: 30. And (3) emulsifying the mixed solution at a high speed for 20min, wherein the emulsifying speed is 10000r/min, and the temperature is 5 ℃, so as to prepare the Pickering emulsion A with stable GO.
(2) Adding isophorone isocyanate into the solution A, wherein the mass ratio of isocyanate to ionic liquid is 1:4, mechanically stirring for 10min (the rotating speed is 500r/min), adding 20 wt% of 1, 4-butanediol aqueous solution, wherein the mass ratio of isocyanate to 1, 4-butanediol is 1.5:1, heating the system to 60 ℃, and reacting for 3h to prepare the polyurea/graphene oxide (PU/GO) double-wall micro-nano capsule coated with the ionic liquid.
(3) Preparing a Tris (hydroxymethyl) aminomethane (Tris) aqueous solution with the concentration of 0.4 wt%, adjusting the pH of the aqueous solution to 8-9 with diluted hydrochloric acid, adding Polyethyleneimine (PEI), wherein the concentration of polyethyleneimine in the Tris solution is 0.4 wt%, manually shaking for 30s, adding dopamine hydrochloride (DA-HCL), wherein the concentration of dopamine hydrochloride in the Tris solution is 0.3 wt%, manually shaking for 30s, adding 6 wt% (referring to the mass percentage content in the Tris solution) of the micro-nano capsule prepared in the step (2), reacting for 5h at room temperature, filtering, washing and drying to obtain the dopamine-polyethyleneimine modified micro-nano capsule with positive charges on the surface.
(4) And (3) mixing the micro-nano capsule obtained in the step (3) with a GO aqueous solution with the concentration of 0.5wt%, wherein the mass fraction of the micro-nano capsule in the GO aqueous solution is 5wt%, mechanically stirring at normal temperature for 400r/min, and reacting for 6h to prepare the PU/GO/PEI/GO multi-wall micro-nano capsule.
(5) And (3) repeating the step (3) and the step (4) to obtain a multi-wall structure, wherein the PU/GO/PEI/GO micro/nano capsules in the step (3) are required to be replaced by the PU/GO/PEI/GO micro/nano capsules, and by analogy, the PU/GO/(PEI/GO) n multi-wall micro/nano capsules with controllable wall thickness are finally prepared by a layer-by-layer self-assembly technology of interaction of negative charges on GO and positive charges on PEI.
Example 4
(1) Adding ionic liquid into the graphene oxide aqueous solution, adjusting the pH of the system to 3, wherein the concentration of the graphene oxide aqueous solution is 0.2 wt%, and the mass ratio of the ionic liquid to water is 1: 50. And (3) emulsifying the mixed solution at a high speed for 20min, wherein the emulsifying speed is 20000r/min, and the temperature is 0 ℃, so as to prepare the Pickering emulsion A with stable GO.
(2) Adding toluene diisocyanate into the solution A, wherein the mass ratio of the toluene diisocyanate to the ionic liquid is 1:5, mechanically stirring for 10min (the rotating speed is 700r/min), adding a 30wt% aqueous solution of 1, 4-butanediol, wherein the mass ratio of the toluene diisocyanate to the 1, 4-butanediol is 1.5:1, heating the system to 70 ℃, and reacting for 2h to prepare the polyurea/graphene oxide (PU/GO) double-wall micro-nano capsule coated with the ionic liquid.
(3) Preparing a Tris (hydroxymethyl) aminomethane (Tris) aqueous solution with the concentration of 0.5wt%, adjusting the pH of the aqueous solution to 8-9 with diluted hydrochloric acid, adding Polyethyleneimine (PEI), wherein the concentration of polyethyleneimine in the Tris solution is 0.4 wt%, manually shaking for 30s, adding dopamine hydrochloride (DA-HCL), wherein the concentration of dopamine hydrochloride in the Tris solution is 0.5wt%, manually shaking for 30s, adding 9 wt% (referring to the mass percentage content in the Tris solution) of the micro-nano capsule prepared in the step (2), reacting for 5h at room temperature, filtering, washing and drying to obtain the dopamine-polyethyleneimine modified micro-nano capsule with positive charges on the surface.
(4) And (3) mixing the micro-nano capsule obtained in the step (3) with a GO aqueous solution with the concentration of 0.8 wt%, wherein the mass fraction of the micro-nano capsule in the GO aqueous solution is 8 wt%, mechanically stirring at normal temperature for 500r/min, and reacting for 10h to prepare the PU/GO/PEI/GO multi-wall micro-nano capsule.
(5) And (3) repeating the step (3) and the step (4) to obtain a multi-wall structure, wherein the PU/GO/PEI/GO micro/nano capsules in the step (3) are required to be replaced by the PU/GO/PEI/GO micro/nano capsules, and by analogy, the PU/GO/(PEI/GO) n multi-wall micro/nano capsules with controllable wall thickness are finally prepared by a layer-by-layer self-assembly technology of interaction of negative charges on GO and positive charges on PEI.
Example 5
(1) Adding ionic liquid into the graphene oxide aqueous solution, adjusting the pH of the system to 3, wherein the concentration of the graphene oxide aqueous solution is 0.5wt%, and the mass ratio of the ionic liquid to water is 1: 50. And emulsifying the mixed solution at a high speed for 30min, wherein the emulsifying speed is 30000r/min, and the temperature is 0 ℃, so as to prepare the Pickering emulsion A with stable GO.
(2) Adding isophorone isocyanate into the solution A, wherein the mass ratio of isocyanate to ionic liquid is 1:5, mechanically stirring for 10min (the rotating speed is 800r/min), adding 30wt% of triethylene tetramine aqueous solution, wherein the mass ratio of isocyanate to triethylene tetramine is 1.5:1, heating the system to 70 ℃, and reacting for 2h to prepare the polyurea/graphene oxide (PU/GO) double-wall micro-nano capsule coated with the ionic liquid.
(3) Preparing a Tris (hydroxymethyl) aminomethane (Tris) aqueous solution with the concentration of 0.5wt%, adjusting the pH of the aqueous solution to 8-9 with diluted hydrochloric acid, adding Polyethyleneimine (PEI), wherein the concentration of polyethyleneimine in the Tris solution is 0.5wt%, manually shaking for 30s, adding dopamine hydrochloride (DA-HCL), wherein the concentration of dopamine hydrochloride in the Tris solution is 0.5wt%, manually shaking for 30s, adding 10wt% (referring to the mass percentage content in the Tris solution) of the micro-nano capsule prepared in the step (2), reacting for 6h at room temperature, filtering, washing and drying to obtain the dopamine-polyethyleneimine modified micro-nano capsule with positive charges on the surface.
(4) And (3) mixing the micro-nano capsule obtained in the step (3) with a GO aqueous solution with the concentration of 1wt%, wherein the mass fraction of the micro-nano capsule in the GO aqueous solution is 10wt%, mechanically stirring at normal temperature for 500r/min, and reacting for 12h to prepare the PU/GO/PEI/GO multi-wall micro-nano capsule.
(5) And (3) repeating the step (3) and the step (4) to obtain a multi-wall structure, wherein the PU/GO/PEI/GO micro/nano capsules in the step (3) are required to be replaced by the PU/GO/PEI/GO micro/nano capsules, and by analogy, the PU/GO/(PEI/GO) n multi-wall micro/nano capsules with controllable wall thickness are finally prepared by a layer-by-layer self-assembly technology of interaction of negative charges on GO and positive charges on PEI.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. The graphene oxide hybrid multi-wall self-lubricating micro-nano capsule is characterized in that the micro-nano capsule takes ionic liquid as a core material and takes a multi-layer graphene oxide hybrid system as a wall material;
the multilayer graphene oxide hybrid system has the following structure from inside to outside:
polyurea/graphene oxide/(polyethyleneimine/graphene oxide)nN represents the number of layers of polyethyleneimine/graphene oxide, and n is a natural number not less than 2.
2. A micro-nano capsule according to claim 1, wherein the multilayer graphene oxide hybrid system has a structure from inside to outside: polyurea/graphene oxide/polyethyleneimine/graphene oxide.
3. A micro-nano capsule according to any one of claims 1 to 2,
the micro-nano capsule has one or more of the following properties:
the content of the core material is 40-85%;
the thermal decomposition temperature is higher than 250 ℃.
4. A preparation method of the graphene oxide hybrid multi-wall self-lubricating micro-nano capsule according to any one of claims 1 to 3, wherein the preparation method comprises the following steps:
(1) forming a mixture comprising:
graphene oxide;
an ionic liquid; and
water;
wherein the concentration of the graphene oxide in water is 0.07-0.5 wt%;
adjusting the pH of the mixture to 2-5 when forming the mixture obtained in the step (1);
(2) mixing the mixture obtained in the step (1) with an isocyanate monomer, adding a chain extender, and heating for reaction to obtain a polyurea/graphene oxide double-wall micro-nano capsule coated with ionic liquid;
(3) forming a mixed system comprising:
a polyethyleneimine;
dopamine hydrochloride; and
a buffer solution;
wherein the buffer solution is a tris (hydroxymethyl) aminomethane aqueous solution with a concentration of 0.1-0.5wt%, and the pH is adjusted to 8-9 with hydrochloric acid;
the concentration of the polyethyleneimine in the buffer solution is 0.2-0.5 wt%;
(4) mixing the micro-nano capsule prepared in the step (2) with the mixed system obtained in the step (3), and reacting at room temperature to obtain a dopamine-polyethyleneimine modified polyurea/graphene oxide double-wall micro-nano capsule;
(5) and (3) mixing the micro-nano capsule obtained in the step (4) with a graphene oxide aqueous solution, and reacting under stirring to obtain a graphene oxide hybrid multi-wall self-lubricating micro-nano capsule with a core material of ionic liquid and a wall material of polyurea/graphene oxide/polyethyleneimine/graphene oxide from inside to outside.
5. The production method according to claim 4,
in the step (1), the mass ratio of the ionic liquid to the water is 1: (5-50);
adjusting the pH of the mixture to 2-3 when forming the mixture obtained in step (1);
in the formation of the mixture obtained in the step (1), the mixture obtained by mixing the graphene oxide, the ionic liquid and the water is dispersed at 0-25 ℃ by means of ultrasonic or mechanical stirring.
6. The production method according to claim 5,
in the step (1), the mass ratio of the ionic liquid to the water is 1: (20-30);
when the mixture obtained in the step (1) is formed, the ultrasonic time is 5-30 min; or
The rotating speed of the mechanical stirring is 1000-30000r/min, and the stirring time is 5-30 min.
7. The production method according to claim 4,
in the step (2), the isocyanate monomer is fluoroketone isocyanate and/or toluene diisocyanate, and the chain extender is triethylene tetramine and/or 1, 4-butanediol;
the mass ratio of the isocyanate monomer to the chain extender is (1-1.5): 1;
using water as a solvent, and preparing the chain extender into a solution with the concentration of 10-30wt% for use;
the mass ratio of the isocyanate monomer to the ionic liquid is 1: (1-5);
mechanically stirring the mixture obtained in the step (1) and the isocyanate monomer at the speed of 300-800r/min to be uniformly mixed, and then adding the chain extender; and/or
The polyurea/graphene oxide double-wall micro-nano capsule coated with the ionic liquid is obtained by reacting at 40-70 ℃, and the reaction time is 2-4 h.
8. The production method according to claim 4,
in the step (3), the concentration of the dopamine hydrochloride in the buffer solution is 0.1-0.5 wt%.
9. The production method according to claim 4,
in the step (4), the concentration of the micro-nano capsule in the buffer solution in the step (3) is 1-10 wt%; reacting for 3-6h at room temperature;
in the step (5), the concentration of the graphene oxide aqueous solution is 0.1-1 wt%;
the concentration of the micro-nano capsule obtained in the step (4) in the graphene oxide aqueous solution is 1-10 wt%;
the stirring speed is controlled at 200-500 r/min; and/or
The reaction time is controlled to be 0.5-12 h.
10. The production method according to any one of claims 4 to 9,
the preparation method also comprises the following steps:
(6) mixing the micro-nano capsule obtained in the step (5) with the mixed system obtained in the step (3), reacting at room temperature, filtering, washing and drying a reactant, mixing with a graphene oxide aqueous solution, and reacting under stirring;
repeating the steps for m times, wherein m = n-2, n is not less than 2, each micro-nano capsule used in each repetition is the micro-nano capsule obtained in the previous step, the obtained core material is ionic liquid, and the wall material is polyurea/graphene oxide/(polyethyleneimine/graphene oxide) from inside to outsidenThe graphene oxide hybrid multi-wall self-lubricating micro-nano capsule.
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