Polyimide composite film with photo-thermal repairing and photo-thermal response friction adjusting functions as well as preparation method and application of polyimide composite film

Abstract

The invention provides a polyimide composite film with photo-thermal repair and photo-thermal response friction adjustment as well as a preparation method and application of the polyimide composite film, and belongs to the technical field of self-repair materials. According to the invention, reduced graphene oxide and boxane are introduced into polyimide, boxane is taken as a dynamic cross-linking point, after a polyimide composite film is damaged, under the stimulation of near-infrared light, reduced graphene oxide is taken as a photo-thermal conversion valve, dynamic recombination of boxane can be driven, and by controlling the position of a light source, the dynamic recombination of the boxane can be realized. Accurate and rapid repair of a damaged area can be achieved, and other areas are not affected. Due to the excellent photo-thermal conversion capacity of reduced graphene oxide, breakage and recombination of boron oxygen six rings are stimulated through near-infrared light, so that an energy dissipation channel is adjusted, real-time control over the friction coefficient is achieved, and the polyimide composite film has the characteristic of intelligent friction regulation and control and is suitable for more special complex working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of self-healing materials, and particularly relates to a polyimide composite film with photothermal healing and photothermal-responsive friction regulation, and a preparation method and application thereof. Background Art

[0002] Self-healing materials have the characteristic of stimulus response and can complete crack repair under environmental stimuli such as acid-base stimuli, thermocompression stimuli, light stimuli, etc. According to the classification method, they are divided into two types: external aid type repair and intrinsic type repair. Traditional polyimide (PI) is widely used in flexible electronics, aerospace and other fields due to its excellent thermal stability, mechanical strength and chemical inertness. However, its highly rigid structure makes it lose the self-healing ability. Intrinsic self-healing polyimide realizes damage repair through reversible dynamic bonds. For example, by introducing dynamic imine bonds into the polyimide main chain, etc., the fracture recombination is achieved through temperature stimulation to achieve the healing of microcracks. However, at present, the research on the intrinsic self-healing of rigid polyimide basically focuses on promoting the fracture recombination of dynamic covalent bonds through complex heating and pressurization methods. This complex stimulation method often requires a long time (such as 60-120 min) to achieve repair, and the resulting industrial and time costs limit the scope of use of intrinsic self-healing polyimide in the industry.

[0003] In addition, the friction regulation of traditional polyimide materials often relies on mechanical lubrication or material modification, and it is difficult to achieve real-time response of the friction coefficient. How to combine the repair of polyimide with friction response to construct an intelligent polyimide material with repairability and real-time controllable friction coefficient is of great significance for expanding its application in engineering. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a polyimide composite film with photothermal healing and photothermal-responsive friction regulation, and a preparation method and application thereof. The polyimide composite film provided by the present invention can achieve precise and rapid repair under near-infrared light stimulation, and at the same time has the characteristic of real-time regulation of the friction coefficient under light illumination conditions.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a polyimide composite film with photothermal healing and photothermal-responsive friction regulation, comprising the following steps:

[0007] Provide a reduced graphene oxide dispersion;

[0008] Mix ODA, BPADA, an organic solvent and the reduced graphene oxide dispersion, and carry out a polycondensation reaction to obtain a polyimide precursor solution;

[0009] Mix the polyimide precursor solution with 3-aminophenylboronic acid and carry out a capping reaction to obtain a 3-aminophenylboronic acid-capped polyimide precursor solution;

[0010] Transfer the 3-aminophenylboronic acid-capped polyimide precursor solution to the surface of a substrate and carry out stepwise temperature-raising curing to obtain a polyimide composite film with photothermal repair and photothermal-responsive friction regulation.

[0011] Preferably, the solvent of the reduced graphene oxide dispersion is an organic solvent, and the mass ratio of reduced graphene oxide to the organic solvent is 0.05-0.24:10-21.

[0012] Preferably, the mass ratio of ODA to BPADA is 0.4-1:2-2.5;

[0013] The mass ratio of the reduced graphene oxide to ODA is 0.05-0.24:0.4-1.

[0014] Preferably, the polycondensation reaction is carried out under an ice-water bath condition, and the time of the polycondensation reaction is 2-8 h.

[0015] Preferably, the mass ratio of 3-aminophenylboronic acid to ODA is 0.02-0.1:0.4-1.

[0016] Preferably, the capping reaction is carried out under an ice-water bath condition, the time of the capping reaction is 0-16 h and is not 0.

[0017] Preferably, the theoretical molecular weight of the 3-aminophenylboronic acid-capped polyimide precursor is 10,000-40,000, and the degree of polymerization is 13-80.

[0018] Preferably, the temperature-raising program of the stepwise temperature-raising curing includes:

[0019] First heat preservation at 80 °C for 1-19 h;

[0020] Second heat preservation at 120 °C for 0.5-15 h;

[0021] Third heat preservation at 150 °C for 0.5-15 h;

[0022] Fourth heat preservation at 200 °C for 0.5-20 h;

[0023] Fifth heat preservation at 250 °C for 0.5-25 h.

[0024] The present invention provides a polyimide composite film with photothermal repair and photothermal-responsive friction regulation prepared by the above preparation method.

[0025] The present invention provides an application of the above polyimide composite film with photothermal repair and photothermal-responsive friction regulation in the fields of flexible electronics or precision mechanical transmission.

[0026] The present invention provides a preparation method of a polyimide composite film with photothermal repair and photothermal-responsive friction regulation, comprising the following steps: mixing ODA (4,4'-diaminodiphenyl ether), BPADA (bisphenol A dianhydride), an organic solvent, and a reduced graphene oxide dispersion liquid, and performing a polycondensation reaction to obtain a polyimide precursor solution; mixing the polyimide precursor solution with 3-aminophenylboronic acid (3-ABA) and performing a capping reaction to obtain a 3-aminophenylboronic acid-capped polyimide precursor solution (denoted as rGO@BPAA); transferring the 3-aminophenylboronic acid-capped polyimide precursor solution to the surface of a substrate and performing stepwise temperature-rising curing. During the stepwise temperature-rising curing process, dehydration of polyamic acid and dehydration of borohydric hydroxyl groups to form boroxine are completed to obtain a polyimide composite film with photothermal repair and photothermal-responsive friction regulation (denoted as r-GO@BPI). Among them, the boroxine in the polyimide composite film of the present invention has the structure shown in Formula 1:

[0027]

[0028] The present invention introduces reduced graphene oxide and boroxine into polyimide. Using boroxine as a dynamic crosslinking point, after the polyimide composite film is damaged, under the stimulation of near-infrared light, reduced graphene oxide (r-GO) serves as a photothermal conversion valve, capable of driving the dynamic reorganization of boroxine. The present invention realizes the precise and rapid repair of thermosetting polyimide films under simple near-infrared light stimulation for the first time. The repair time is only 5 minutes, far lower than the reported 60 minutes to 120 minutes, attributed to the fact that reduced graphene oxide rapidly converts near-infrared light into heat and conducts it through a uniform heat conduction network, thereby effectively stimulating the dynamic reorganization of boroxine. By controlling the position of the light source, precise and rapid repair of the damaged area can be achieved without affecting other areas. In addition, due to the excellent photothermal conversion ability of reduced graphene oxide, the polyimide composite film reaches 180-280 °C under near-infrared light stimulation, capable of stimulating the cleavage and reorganization of boroxine and increasing the energy dissipation channels. The present invention adjusts the energy dissipation channels through near-infrared light stimulation, realizes real-time control of the friction coefficient, and endows the polyimide composite film of the present invention with the characteristics of friction intelligent regulation, suitable for more special and complex working conditions.

[0029] In addition, the present invention uses an in-situ polymerization method to prepare a polyimide composite film with photothermal repair and photothermal-responsive friction regulation, which has simple operation and is easy to realize industrial batch production. Description of the Drawings

[0030] Figure 1Schematic diagram of the introduction process of boroxine in the polyimide composite film;

[0031] Figure 2 IR spectra of BPAA and BPI;

[0032] Figure 3 IR spectra of rGO@BPI, rGO and BPI;

[0033] Figure 4 TG diagrams of rGO@BPI and BPI;

[0034] Figure 5 DSC diagrams of rGO@BPI and BPI;

[0035] Figure 6 Photothermal cycling test diagram of rGO@BPI;

[0036] Figure 7 Optical micrograph of precise and rapid photothermal repair of rGO@BPI;

[0037] Figure 8 Photothermal friction regulation results and cycling test results of rGO@BPI. Detailed implementation manners

[0038] The present invention provides a preparation method of a polyimide composite film with photothermal repair and photothermal-responsive friction regulation, comprising the following steps:

[0039] Provide a reduced graphene oxide dispersion;

[0040] Mix ODA, BPADA, an organic solvent and the reduced graphene oxide dispersion, and carry out a polycondensation reaction to obtain a polyimide precursor solution;

[0041] Mix the polyimide precursor solution with 3-aminophenylboronic acid, and carry out a capping reaction to obtain a 3-aminophenylboronic acid-capped polyimide precursor solution;

[0042] Transfer the 3-aminophenylboronic acid-capped polyimide precursor solution to the surface of a substrate, and carry out stepwise temperature-raising curing to obtain a polyimide composite film with photothermal repair and photothermal-responsive friction regulation.

[0043] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0044] The present invention provides a reduced graphene oxide dispersion. In the present invention, the solvent of the reduced graphene oxide dispersion is preferably an organic solvent. In the present invention, the preparation method of the reduced graphene oxide dispersion preferably comprises the following steps:

[0045] Mix reduced graphene oxide with an organic solvent and perform ultrasonic treatment to obtain a reduced graphene oxide dispersion.

[0046] In the present invention, the organic solvent is preferably one or more of N,N'-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF), more preferably N,N'-dimethylacetamide; the mass ratio of the reduced graphene oxide to the organic solvent is preferably 0.05 - 0.24:10 - 21, more preferably 0.12 - 0.2:10 - 20. In the present invention, the power of the ultrasonic treatment is preferably 500 W, and the time is preferably 1 - 12 h, more preferably 5 - 8 h.

[0047] In the present invention, ODA, BPADA, an organic solvent, and the reduced graphene oxide dispersion are mixed to perform a polycondensation reaction to obtain a polyimide precursor solution. In the present invention, the organic solvent is preferably DMAc. There are no special requirements for the amount of the organic solvent used in the present invention, as long as ODA and BPADA can be fully dissolved. As a specific embodiment of the present invention, the amount of the organic solvent used can keep the solid content of the polyimide precursor solution at 13 - 25%.

[0048] In the present invention, the preferred mixing method is as follows:

[0049] Dissolve with the organic solvent BPADA to obtain a BPADA solution;

[0050] Under the condition of an ice-water bath, add ODA to the BPADA solution in batches, and add the reduced graphene oxide dispersion midway. In the present invention, the ODA is preferably added in 2 - 4 batches.

[0051] In the present invention, the mass ratio of the ODA monomer to the BPADA monomer is preferably 0.4 - 1:2 - 2.5, more preferably 0.6 - 0.8:2 - 2.5, and specifically can be 0.8:2.19, 0.8:2.16, or 0.8:2.25. In the present invention, the mass ratio of the reduced graphene oxide (dry weight) to ODA is preferably 0.05 - 0.24:0.4 - 1, more preferably 0.12 - 0.18:0.8. By controlling the reduced graphene oxide within the above dosage in the present invention, the requirements for photothermal stimulation can be ensured, and at the same time, the effect of self-healing is prevented from being affected by excessive reduced graphene oxide.

[0052] In the present invention, the polycondensation reaction is carried out under the condition of an ice-water bath, and the time of the polycondensation reaction is preferably 2 - 8 h, and specifically can be 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, or 8 h. After the polycondensation reaction, no post-treatment is carried out in the present invention, and the polycondensation reaction solution is directly used as the raw material of the polyimide precursor solution to participate in the subsequent reaction.

[0053] After obtaining the polyimide precursor solution, the present invention mixes the polyimide precursor solution with 3-aminophenylboronic acid to carry out a capping reaction, obtaining a 3-aminophenylboronic acid-capped polyimide precursor solution. In the present invention, the mass ratio of the 3-aminophenylboronic acid to ODA is preferably 0.03-0.06:0.4-1, more preferably 0.05-0.06:0.4-1. In the present invention, the capping reaction is carried out under an ice-water bath condition, and the time of the capping reaction is preferably 0-16 h and not 0, specifically it can be 1 h, 3 h, 5 h, 8 h, 10 h, 12 h or 16 h.

[0054] In the present invention, the theoretical molecular weight of the 3-aminophenylboronic acid-capped polyimide precursor is preferably 10,000-40,000, more preferably 20,000-30,000; the degree of polymerization is preferably 13-80, specifically it can be 13, 15, 20, 30, 40, 50, 60, 70 or 80.

[0055] In the present invention, the structure of the 3-aminophenylboronic acid-capped polyimide precursor is shown in Formula 2:

[0056]

[0057] In Formula 2, the degree of polymerization n = 13-80.

[0058] After obtaining the 3-aminophenylboronic acid-capped polyimide precursor solution, the present invention transfers the 3-aminophenylboronic acid-capped polyimide precursor solution to the surface of a substrate and carries out stepwise temperature-raising curing to obtain a polyimide composite film with photothermal repair and photothermal-responsive friction regulation. The present invention has no special requirements for the material of the substrate, as long as it has a planar structure and does not react with the 3-aminophenylboronic acid-capped polyimide precursor during the stepwise temperature-raising curing process, specifically such as a glass plate.

[0059] In the present invention, the temperature-raising program of the stepwise temperature-raising curing preferably includes:

[0060] First heat preservation at 80 °C for 1-19 h, more preferably 3-12 h, further preferably 6-8 h;

[0061] Second heat preservation at 120 °C for 0.5-15 h, more preferably 1-10 h, further preferably 3-8 h;

[0062] Third heat preservation at 150 °C for 0.5-15 h, more preferably 1-10 h, further preferably 3-8 h;

[0063] Fourth heat preservation at 200 °C for 0.5-20 h, more preferably 1-15 h, further preferably 5-10 h;

[0064] The fifth heat preservation is carried out at 250 °C for 0.5 to 25 h, more preferably 2 to 20 h, and further preferably 5 to 10 h.

[0065] In the present invention, the heating rate of the stepwise heating and curing is preferably 1 °C / min; after the stepwise heating and curing, the obtained polyimide composite film is preferably cooled naturally to room temperature in the present invention.

[0066] In the present invention, during the process of stepwise heating and curing, dehydration of polyamic acid is completed at 180-200 °C, and boric hydroxyl groups are dehydrated to form boroxine at 250 °C, thereby introducing boroxine into the polyimide structure.

[0067] In the present invention, the process of introducing boroxine into the polyimide composite film is as Figure 1 shown. Figure 1 In it, ODA, BPADA and 3-aminophenylboronic acid react to obtain a 3-aminophenylboronic acid-terminated polyimide precursor, and then through stepwise heating and curing, dehydration of polyamic acid and dehydration of boric hydroxyl groups to form boroxine are completed.

[0068] The present invention provides a polyimide composite film with photothermal repair and photothermal-responsive friction regulation prepared by the above preparation method. In the present invention, the thickness of the polyimide composite film with photothermal repair and photothermal-responsive friction regulation is preferably 0.18 to 0.3 mm, more preferably 0.2 to 0.25 mm.

[0069] The polyimide composite film provided by the present invention contains reduced graphene oxide and a boroxine structure; the boroxine has the structure shown in Formula 1:

[0070]

[0071] The present invention introduces reduced graphene oxide and boroxine into the polyimide structure. Taking boroxine as a dynamic crosslinking point, after the polyimide composite film is damaged, under the stimulation of near-infrared light, reduced graphene oxide acts as a photothermal conversion valve, which can drive the dynamic recombination of boroxine to achieve photothermal repair of the damaged area. This is attributed to the fact that reduced graphene oxide quickly converts near-infrared light into heat and conducts it through a uniform heat conduction network, thereby effectively stimulating the dynamic recombination of boroxine. By controlling the position of the light source, precise and rapid repair of the damaged area can be achieved without affecting other areas. In the present invention, when the polyimide composite film is subjected to photothermal repair, the wavelength of the near-infrared light is preferably 808 nm, the irradiation time of the near-infrared light is preferably 5 min, and the power of the near-infrared light irradiation is preferably 1.85 W / cm 2 .

[0072] In addition, the polyimide composite film provided by the present invention has the characteristic of real-time regulation of the friction coefficient under light illumination, which is attributed to the excellent photothermal conversion ability of reduced graphene oxide, enabling the polyimide composite film to stimulate the cleavage and recombination of boroxine rings when reaching 210 - 250 °C, increasing the energy dissipation channels, and realizing the real-time control of the friction coefficient by regulating the energy dissipation channels through near-infrared light stimulation. In the present invention, the friction coefficient of the polyimide composite film under normal conditions is preferably 0.2 - 0.4, and the friction coefficient under near-infrared light irradiation is preferably 0.1 - 0.2, and the power of the near-infrared light irradiation is preferably 1.85 - 8 W / cm 2 .

[0073] The present invention provides the application of the above polyimide composite film with photothermal repair and photothermal-responsive friction regulation in the fields of flexible electronics or precision mechanical transmission.

[0074] The following is a detailed description of the polyimide composite film with photothermal repair and photothermal-responsive friction regulation provided by the present invention, its preparation method and application in combination with examples, but they should not be construed as limiting the protection scope of the present invention.

[0075] Example 1

[0076] A preparation method of a polyimide composite film with photothermal repair and photothermal-responsive friction regulation, comprising the following steps:

[0077] (1) Add 0.12 g of r-GO to 10 g of DMAc and ultrasonically treat it for 3 h at 500 W to prepare an r-GO dispersion for later use.

[0078] (2) Slowly add 0.8 g of ODA in three batches under an ice-water bath to the DMAc solution of BPADA (the mass of BPADA is 2.19 g and the mass of DMAc is 10 g), and add the r-GO dispersion in the middle, and react for 5 h to obtain a polyimide precursor solution, denoted as BPAA.

[0079] (3) Add 0.058 g of 3-aminophenylboronic acid to the polyimide precursor solution and react for 10 h to obtain a viscous 3-aminophenylboronic acid-capped polyimide precursor (rGO@BPAA), with a theoretical molecular weight of 15000 and a degree of polymerization n of 21.

[0080] (4) Spread the 3-aminophenylboronic acid-capped polyimide precursor solution on a flat and clean plate, and perform stepwise heating according to the following program with a heating rate of 1 °C / min to obtain a polyimide composite film with photothermal repair and photothermal-responsive friction regulation, denoted as r-GO@BPI, with a thickness of 0.2 mm;

[0081] Keep warm for 12 h at 80 °C;

[0082] The second heat preservation is carried out at 120 °C for 0.5 h;

[0083] The third heat preservation is carried out at 150 °C for 0.5 h;

[0084] The fourth heat preservation is carried out at 200 °C for 1 h;

[0085] The fifth heat preservation is carried out at 250 °C for 2 h.

[0086] Comparative Example 1

[0087] The difference from Example 1 is that the r-GO dispersion liquid is not added and reserved, and polyimide with boroxine ring as the crosslinking point is obtained, denoted as BPI.

[0088] Example 2

[0089] A preparation method of a polyimide composite film with photothermal repair and photothermal response friction regulation, comprising the following steps:

[0090] (1) Add 0.12 g of r-GO to 10 g of DMAc and ultrasonically treat for 3 h under 500 W to prepare an r-GO dispersion liquid for standby.

[0091] (2) Slowly add 0.8 g of ODA in two batches under an ice-water bath to the DMAc solution of BPADA (the mass of BPADA is 2.16 g and the mass of DMAc is 10 g), and add the r-GO dispersion liquid in the middle, and react for 5 h to obtain a polyimide precursor solution.

[0092] (3) Add 0.041 g of 3-aminophenylboronic acid to the polyimide precursor solution and react for 10 h to obtain a viscous 3-aminophenylboronic acid-capped polyimide precursor (rGO@BPAA), with a theoretical molecular weight of 20,000 and a degree of polymerization n of 28.

[0093] (4) Spread the 3-aminophenylboronic acid-capped polyimide precursor solution on a flat and clean plate, and carry out stepwise heating according to the following program, with a heating rate of 1 °C / min, to obtain a polyimide composite film with photothermal repair and photothermal response friction regulation, denoted as r-GO@BPI, with a thickness of 0.2 mm;

[0094] The first heat preservation is carried out at 80 °C for 3 h;

[0095] The second heat preservation is carried out at 120 °C for 1 h;

[0096] The third heat preservation is carried out at 150 °C for 1 h;

[0097] The fourth heat preservation is carried out at 200 °C for 1 h;

[0098] The fifth heat preservation is carried out at 250 °C for 2 h.

[0099] Example 3

[0100] A preparation method of a polyimide composite film with photothermal repair and photothermal response friction regulation, comprising the following steps:

[0101] (1) Add 0.12 g of r-GO to 10 g of DMAc and ultrasonically treat for 3 h under 500 W to prepare an r-GO dispersion for later use.

[0102] (2) Slowly add 0.8 g of ODA in three batches under an ice-water bath to a DMAc solution of BPADA (the mass of BPADA is 2.25 g and the mass of DMAc is 10 g), and add the r-GO dispersion halfway. React for 5 h to obtain a polyimide precursor solution.

[0103] (3) Add 0.09 g of 3-aminophenylboronic acid to the polyimide precursor solution and react for 10 h to obtain a viscous 3-aminophenylboronic acid-capped polyimide precursor (rGO@BPAA), with a theoretical molecular weight of 10,000 and a degree of polymerization n of 14.

[0104] (4) Spread the 3-aminophenylboronic acid-capped polyimide precursor solution on a flat and clean plate, and carry out stepwise heating according to the following program with a heating rate of 1 °C / min to obtain a polyimide composite film with photothermal repair and photothermal response friction regulation, denoted as r-GO@BPI, with a thickness of 0.2 mm;

[0105] First heat preservation at 80 °C for 6 h;

[0106] Second heat preservation at 120 °C for 0.5 h;

[0107] Third heat preservation at 150 °C for 0.5 h;

[0108] Fourth heat preservation at 200 °C for 1 h;

[0109] Fifth heat preservation at 250 °C for 2 h.

[0110] Example 4

[0111] A preparation method of a polyimide composite film with photothermal repair and photothermal response friction regulation, comprising the following steps:

[0112] (1) Add 0.12 g of r-GO to 10 g of DMAc and ultrasonically treat for 3 h under 500 W to prepare an r-GO dispersion for later use.

[0113] (2) 0.8 g of ODA was slowly added in three batches to the DMAc solution of BPADA (the mass of BPADA was 2.13 g and the mass of DMAc was 10 g) under an ice-water bath. The r-GO dispersion was added midway, and the reaction was carried out for 5 h to obtain a polyimide precursor solution.

[0114] (3) 0.027 g of 3-aminophenylboronic acid was added to the polyimide precursor solution and reacted for 10 h to obtain a viscous 3-aminophenylboronic acid-capped polyimide precursor (rGO@BPAA), with a theoretical molecular weight of 30,000 and a degree of polymerization n of 42.

[0115] (4) The 3-aminophenylboronic acid-capped polyimide precursor solution was spread on a flat and clean plate, and the temperature was increased stepwise according to the following procedure at a heating rate of 1 °C / min to obtain a polyimide composite film with photothermal repair and photothermal-responsive friction regulation, denoted as r-GO@BPI, with a thickness of 0.2 mm;

[0116] The first heat preservation was carried out at 80 °C for 10 h;

[0117] The second heat preservation was carried out at 120 °C for 1 h;

[0118] The third heat preservation was carried out at 150 °C for 1 h;

[0119] The fourth heat preservation was carried out at 200 °C for 1 h;

[0120] The fifth heat preservation was carried out at 250 °C for 2 h.

[0121] Structure characterization

[0122] The rGO@BPI obtained in Example 1 and BPI obtained in Comparative Example 1 were subjected to structure characterization as follows:

[0123] The infrared spectra of the polyimide precursor (BPAA) and the polyimide film (BPI) with boroxine rings as dynamic cross-linking points are as Figure 2 shown. Figure 2 Among them, the disappearance of -OH at 3267 cm -1 and the generation of the -B-O- peak at 690 cm -1 proved the final synthesis of the thermosetting polyimide with boroxine rings as dynamic cross-linking points.

[0124] The infrared spectra of rGO@BPI, rGO, and BPI are as Figure 3 shown. It can be seen that after adding reduced graphene oxide, the infrared spectrum of rGO@BPI did not change, indicating that the addition of reduced graphene oxide did not affect its structure.

[0125] The TG diagrams of rGO@BPI and BPI are as Figure 4As shown, it can be seen that the initial decomposition rate of rGO@BPI is relatively fast, which is attributed to the decomposition of functional groups such as -OH and -COOH on reduced graphene oxide. However, its T d The 5% weight loss temperature is still at 536 °C, indicating that it still has high heat resistance.

[0126] The DSC curves of rGO@BPI and BPI are as Figure 5 shown. It can be seen that rGO@BPI and BPI still have high glass transition temperatures, which are 215 °C and 211 °C respectively, indicating that the addition of reduced graphene oxide has little effect on the glass transition temperature.

[0127] Performance Test

[0128] The obtained rGO@BPI in Example 1 was subjected to photothermal cycling test, photothermal repair test and photothermal friction regulation test, as follows:

[0129] The photothermal cycling test diagram of rGO@BPI is as Figure 6 shown. It can be seen that under near-infrared light with a power of 1.85 W / cm 2 , rGO@BPI has a fast photothermal conversion ability and can quickly heat up to about 230 °C, which is sufficient to reach the threshold of the dynamic reorganization of boroxine rings.

[0130] Figure 7 The optical micrograph of the precise and rapid photothermal repair of rGO@BPI is shown. It can be seen that in the area irradiated by near-infrared light with a power of 1.85 W / cm 2 , the scratch can be quickly repaired within 5 minutes, while it is not repaired in the unirradiated area. This shows that when the near-infrared light irradiates the damaged area, reduced graphene oxide transfers the heat energy to the scratch area rapidly through photothermal conversion and heat conduction capabilities, enabling the boroxine rings to break and reorganize, thus repairing the crack. Other areas are not repaired because there is no stimulation of near-infrared light, proving that through the control of near-infrared light, precise repair control of the damaged area can be achieved without interfering with other areas.

[0131] Figure 8 The results of photothermal friction regulation and cycling test of rGO@BPI are shown. Figure 8 In , a is the friction coefficient diagram obtained by performing for 30 min under the conditions of a 3 N load and 2 cm / s and irradiating with a near-infrared lamp with 1.85 - 8 W / cm 2 (the temperature can reach 230 °C) for different times. It can be intuitively seen that the friction coefficient drops from 0.23 - 0.29 to about 0.13 - 0.18; Figure 8 b in is obtained by irradiating with a near-infrared lamp for 5 min and then turning it off for 5 min, and repeating the operation. It can be seen that the polyimide composite film has good cycling performance, proving that real-time regulation of the friction coefficient can be achieved through light irradiation regulation.

[0132] Through the above embodiments, the polyimide composite film prepared by the present invention can be obtained. It has the ability to accurately and quickly repair and adjust friction through near-infrared light, attributed to the excellent photothermal conversion ability of reduced graphene oxide and the dynamic reorganization characteristics of boroxine ring, providing an idea for realizing the preparation of intelligent polyimide films suitable for diverse and complex working conditions.

[0133] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a polyimide composite film with photothermal repair and photothermal response friction adjustment, characterized in that: The following steps are involved: providing a reduced graphene oxide dispersion; Mixing ODA, BPADA, and an organic solvent with the reduced graphene oxide dispersion to perform a polycondensation reaction to obtain a polyimide precursor solution; The polyimide precursor solution is mixed with 3-aminophenylboronic acid to perform a capping reaction to obtain a polyimide precursor solution capped with 3-aminophenylboronic acid; The 3-aminophenylboronic acid-terminated polyimide precursor solution is transferred to the surface of the substrate and subjected to step-wise temperature curing to obtain a polyimide composite film with photothermal repair and photothermal responsive friction regulation.

2. The preparation method according to claim 1, characterized in that: The solvent of the reduced graphene oxide dispersion is an organic solvent, and the mass ratio of the reduced graphene oxide to the organic solvent is 0.05-0.24:10-21.

3. The preparation method according to claim 1, characterized in that: The mass ratio of ODA to BPADA is 0.4-1:2-2.5; The mass ratio of the reduced graphene oxide to ODA is 0.05-0.24:0.4-1.

4. The preparation method according to claim 1 or 3, characterized in that: The polycondensation reaction is carried out in an ice-water bath, and the polycondensation reaction time is 2 to 8 hours.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the 3-aminophenylboronic acid to ODA is 0.02-0.1:0.4-1.

6. The preparation method according to claim 1 or 5, characterized in that: The end-capping reaction is carried out in an ice-water bath, and the end-capping reaction time is 0 to 16 hours, and is not 0.

7. The preparation method according to claim 1 or 5, characterized in that: The theoretical molecular weight of the 3-aminophenylboronic acid-terminated polyimide precursor is 10,000-40,000, and the degree of polymerization is 13-80.

8. The preparation method according to claim 1, characterized in that: The temperature rise procedure of the step-by-step temperature rise curing includes: First insulation at 80°C for 1 to 19 hours; Second insulation at 120°C for 0.5 to 15h; The third heat preservation is carried out at 150°C for 0.5 to 15 hours; The fourth heat preservation is 0.5 to 20 hours at 200°C; The fifth heat preservation is carried out at 250°C for 0.5 to 25 hours.

9. A polyimide composite film having photothermal repair and photothermal responsive friction regulation obtained by the preparation method according to any one of claims 1 to 8.

10. Application of the polyimide composite film with photothermal repair and photothermal responsive friction regulation as claimed in claim 9 in the field of flexible electronics or precision mechanical transmission.

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