Polyimide adhesive based on cooperation of double dynamic bonds and preparation method thereof

Abstract

The invention discloses a polyimide adhesive based on cooperation of double dynamic bonds and a preparation method thereof, hydrogen bonds, dynamic disulfide bonds and flexible molecular chain segments are introduced into polyimide through copolymerization of fluorinated dianhydride and two different diamines, and the obtained high-molecular-weight dynamic polyimide adhesive is adjustable in rigidity and flexibility, and has the advantages of high-molecular-weight dynamic polyimide, high-molecular-weight polyimide, high-molecular-weight polyimide, high-molecular-weight polyimide, high-molecular-weight polyimide, high-molecular-weight polyimide, high-molecular-weight polyimide, high-molecular-weight polyimide and the like. Meanwhile, the glass transition temperature is high (the maximum Tg is 265.4 DEG C), and the self-repairing capacity and the low-boiling-point organic solvent rapid dissolving and recycling capacity are achieved. In addition, the adhesive has excellent tensile shear strength (as high as 12.54 MPa). Preferably, graphene (GNP) is added into the double-dynamic polyimide matrix for ultrasonic mixing, and the polyimide-based heat-conducting adhesive is prepared through thermal imidization. When the content of GNP is 7.5 wt%, the in-plane heat conductivity coefficient of the material is 3.32 W / (mK), and the tensile shear strength of the heat-conducting adhesive can reach 8.49 MPa, so that the heat-conducting adhesive can be comparable with a high-performance commercial heat-conducting adhesive, and can be used as a reusable adhesive between heat management material interfaces.

Description

Technical Field

[0001] The present invention relates to the technical field of polyimide materials, and in particular to a polyimide adhesive based on double dynamic bond collaboration and a preparation method thereof. Background Art

[0002] With the rapid development of electronic devices towards miniaturization, high integration and high frequency, high-performance adhesives are urgently needed to meet the needs of reliable heat dissipation and mechanical support under high-temperature conditions. Polyimide (PI) is regarded as an ideal matrix material for high-temperature adhesives due to its excellent high and low temperature resistance, thermal stability, mechanical strength and chemical corrosion resistance. However, traditional polyimide has poor solubility and is difficult to melt and reprocess due to its rigid main chain. It needs to be processed in a strong polar solvent (such as NMP) or under high temperature and high pressure, resulting in complex process, low environmental protection and limited application. It is even more difficult to compound with other fillers. In addition, the intrinsic thermal conductivity of pure PI is only 0.1-0.3W / (m·K), which is difficult to meet the heat dissipation requirements of high-power devices. Although thermal conductivity can be improved by blending high thermal conductivity fillers, it is easy to cause interface defects due to filler agglomeration, and thermal conductivity and bonding strength cannot be balanced.

[0003] Existing technologies typically improve recyclability and processability by introducing dynamic covalent bonds (such as Diels-Alder bonds and disulfide bonds) to impart self-healing and recyclability to materials. However, the reversibility of a single dynamic bond at high temperatures can cause structural instability, and the temperature window for dynamic covalent bond reconstruction is narrow, making it difficult to balance mechanical properties, heat resistance, and processability. These shortcomings severely restrict the application prospects of polyimide adhesives in high-end electronic packaging, aerospace, and other fields. A breakthrough is urgently needed through the coordinated design of the "rigid-flexible-dynamic" molecular structure of the material. Summary of the Invention

[0004] Based on the above problems in the prior art, the present invention provides a high T g The present invention introduces hydrogen bonds, dynamic disulfide bonds, and flexible molecular chains to copolymerize two different diamines with dianhydride to obtain a polyamic acid solution. The resulting soluble, fusible, and recyclable intrinsic polyimide adhesive is prepared through thermal imidization. The adhesive has good solubility in organic solvents, is easy to process, has high bonding strength, and is recyclable. It is suitable for high-temperature and high-frequency electronic device packaging and aerospace thermal protection.

[0005] The present invention also provides a high T gA soluble, recyclable composite polyimide-based thermally conductive adhesive is prepared using the polyimide adhesive described in this invention as a matrix, mixed with graphene to create a thermally conductive adhesive that combines high thermal conductivity with high bonding strength. This thermally conductive adhesive exhibits stability and durability in high-temperature environments and is recyclable after bonding. Overall, it is suitable for heat dissipation bonding in high-power semiconductor modules, ensuring structural stability and thermal management under extreme operating conditions.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention provides a high T g , a soluble polyimide adhesive, wherein the polyimide adhesive has the structural formula:

[0008]

[0009] The present invention also provides a method for preparing the polyimide adhesive, which comprises the following steps:

[0010] Step 1: Weigh different molar ratios of 4,4'-diaminodiphenyl disulfide (4APD) and aminopropyl-terminated polydimethylsiloxane (PDMS) and dissolve them in a solvent. Add the diamine mixed solution to a two-necked flask equipped with a stirrer. Use a three-way valve to fill the flask with nitrogen and keep it sealed. Dissolve the dianhydride TA-TFMB in the solvent in three batches. Use a syringe to inject the dianhydride solution into the flask every 5-10 minutes. The mixed solution is observed to gradually become viscous. After reacting overnight for 12 hours, a polyamic acid solution is obtained.

[0011] Step 2: Spin-coat the polyamic acid solution evenly onto a polytetrafluoroethylene mold and heat on a 60-100°C hotplate for 5-12 hours. Then, heat the mold in a muffle furnace at a rate of 5-10°C / min to 100, 150, and 200°C, maintaining each temperature for two hours. Finally, heat treat at 250°C for one hour to form a film-like polyimide adhesive. Due to its dual-dynamic structural properties, the maximum thermal imidization temperature is set at 250°C.

[0012] In step 1, the solvent is selected from a mixture of one or more of N,N'-dimethylformamide (DMF), N,N'-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP), preferably NMP. The solid content of the system is controlled to be 18-25%.

[0013] In step 1, the molar ratio of dianhydride to total diamine content is (1.05-1):1, and the molar ratio of diaminodiphenyl disulfide (4APD) to aminopropyl-terminated polydimethylsiloxane (PDMS) is 2:8, 3:7, 4:6, 5:5, or 7:3. The preferred ratio is 2:8, as it exhibits the best fracture toughness while maintaining a low self-healing temperature.

[0014] In step 1, the number average molecular weight of aminopropyl-terminated polydimethylsiloxane (PDMS) is preferably 1000 g / mol. A lower molecular weight results in poor self-healing properties, while a higher molecular weight hinders the glass transition temperature. The total molar ratio of dianhydride TA-TFMB to diamine is (1.01-1.1):1. Considering the reaction of the anhydride groups in the dianhydride with moisture in the air to form carboxylic acid and the loss during the dosing process, a slight excess of dianhydride is required relative to the diamine.

[0015] The number average molecular weight of the polyimide adhesive prepared in step 2 is in the range of 30,000 g / mol to 75,000 g / mol, and the glass transition temperature can reach up to 265.4°C.

[0016] The present invention also provides a method for preparing the polyimide-based thermally conductive adhesive, which comprises the following steps:

[0017] The thermally conductive adhesive is based on a polyimide film with a diamine molar ratio of 2:8. The polyimide film is dissolved in an organic solvent, and 2.5%-10% by mass of a thermally conductive filler is weighed and ultrasonically dispersed in the organic solvent. The filler dispersion and the polyimide solution are then mixed and ultrasonically stirred for 5-24 hours. The evenly dispersed mixed solution is spin-coated on a Teflon high-temperature resistant cloth and dried to obtain a polyimide-based thermally conductive adhesive based on double dynamic bond collaboration.

[0018] The organic solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran, dichloromethane, chloroform, or a combination thereof, preferably tetrahydrofuran.

[0019] The thermally conductive filler is any one of two-dimensional carbides and nitrides (MXene), boron nitride, graphene, carbon nanotubes, and graphite, or a combination thereof, preferably graphene.

[0020] Furthermore, the prepared high molecular weight polyimide-based thermally conductive adhesive is hot-melted at a temperature of 250° C. and a pressure of 2 MPa for 30 minutes, or quickly dissolved in a solvent at room temperature for less than 15 minutes and recycled.

[0021] The beneficial effects of the present invention are embodied in:

[0022] The present invention prepares a polyimide adhesive with adjustable glass transition temperature by regulating the ratio of 4,4'-diaminodiphenyl disulfide (4APD) and aminopropyl-terminated polydimethylsiloxane (PDMS) and copolymerizing them with dianhydride (TA-TFMB) containing amide bonds. On the one hand, disulfide bonds and flexible PDMS molecular chains are introduced to give the polyimide adhesive solubility and processability. The fluidity of the flexible molecular chains promotes the exchange reaction of the disulfide bonds, allowing the polyimide adhesive to be hot-pressed to repair cracks at 120°C and 5MPa. On the other hand, by copolymerizing the dianhydride TA-TFMB, amide groups are introduced into the polymer backbone, and hydrogen bonds can be formed between the amide groups and the molecular chains, which not only improves thermal stability but also compensates for the loss of molecular chain rigidity caused by the introduction of flexible groups, thereby increasing the glass transition temperature (T g >150℃). In addition, the polarity of the amide group is utilized to enhance the interfacial compatibility, interfacial adhesion and cohesive energy between the adhesive and the surface of the bonded material, thereby achieving an improvement in tensile shear strength (the tensile shear strength between copper substrates reaches 12.54MPa). In addition, the thermal conductivity of commercial high-performance thermal conductive adhesives used for CPU heat dissipation ranges from 2.0 to 5.0W / mk, and the tensile shear strength of thermal conductive adhesives for general industrial applications ranges from 5 to 15MPa. When the filler content of the polyimide thermal conductive adhesive composited with graphene of the present invention is 7.5wt%, the in-plane thermal conductivity of the material is 3.32W / (m · K), the tensile shear strength of the thermal conductive adhesive reaches 8.49MPa, which meets the standards of commercial high-performance thermal conductive adhesives. At the same time, it can be quickly dissolved multiple times (dissolution time at room temperature is less than 15min) and multi-dimensionally recycled, effectively solving the limitations of polyimide adhesives and their thermal conductive glues that are non-degradable and difficult to reuse, and has significant characteristics and substantial progress. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the synthesis route of a dual dynamic synergistic polyimide adhesive provided in Examples 1, 2, 3, 4, and 5 of the present invention.

[0024] Figure 2 These are GPC charts of the polyimide adhesives obtained in Examples 1, 2, 3, 4, and 5 of the present invention.

[0025] Figure 3 DMA curves of the polyimide adhesives obtained in Examples 1, 2, 3, 4, and 5 of the present invention.

[0026] Figure 4 Graphs showing the mechanical properties of the self-healing polyimide adhesive films with different molar ratios of diamine obtained in Examples 1, 2, 3, 4, and 5 of the present invention, and the polyimide-based thermally conductive adhesive films with different filler contents obtained in Examples 6, 7, 8, and 9.

[0027] Figure 5 Graph showing thermal conductivity of polyimide-based thermally conductive adhesive films obtained in Examples 6, 7, 8, and 9 of the present invention and Comparative Example 2.

[0028] Figure 6 The bonding sample is prepared from the polyimide adhesive and the copper substrate according to Example 1 of the present invention.

[0029] Figure 7 Graph showing the tensile shear strength performance of the polyimide-based thermally conductive adhesives obtained in Examples 6, 7, and 8 of the present invention and Comparative Example 3.

[0030] Figure 8 This is a graph showing the tensile shear strength performance of the polyimide adhesive obtained in Example 1 of the present invention after four cycles.

[0031] Figure 9 This is an optical image of the crack repair of the polyimide adhesive obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0033] In the following examples, thermal conductivity was measured using a thermal conductivity meter (Hot Disk, Kegonas Instruments Trading Shanghai Co., Ltd.). The crack repair test method involved using a scalpel to create a crack of uniform depth in the composite film. The film was then placed in a hot press and heated and pressurized for repair. The repaired film was observed for scratches using a polarizing microscope, and mechanical properties were retested after repair. The repair efficiency for tensile strength and elongation at break was calculated using formula (1):

[0034]

[0035] Among them, σ0 and σ h are the tensile strength and elongation at break of the original and repaired specimens, respectively.

[0036] Adhesive performance testing: The strength of the polyimide adhesives prepared in the above examples was tested with reference to the method in GB / T 7124-2022 “Determination of tensile shear strength of adhesives (rigid material to rigid material)”.

[0037] Example 1:

[0038] In this embodiment, high T based on dual dynamic bond cooperation is prepared according to the following steps. g , soluble polyimide adhesive:

[0039] Step 1: Weigh 0.062 g (0.250 mmol) of 4,4'-diaminodiphenyl disulfide (4APD) and 1 g (1 mmol) of aminopropyl-terminated polydimethylsiloxane (PDMS) and dissolve them in a solvent. Add the diamine mixed solution to a two-necked flask equipped with a stirrer. Use a three-way valve to fill the flask with nitrogen and keep it sealed. Dissolve 0.844 g (1.263 mmol) of TA-TFMB in the solvent in three batches. Inject the dianhydride solution into the flask every 5 minutes using a syringe. The mixed solution is observed to gradually become viscous. After reacting overnight for 12 hours, a polyamic acid solution is obtained.

[0040] Step 2: Spin-coat the polyamic acid solution evenly on a polytetrafluoroethylene mold, heat it on a 60°C hot plate for 10 hours, then place it in a muffle furnace and heat it to 100, 150, and 200°C at a rate of 5°C / min, and keep it at each temperature for two hours. Finally, heat treat it at 250°C for 1 hour to obtain a film-like polyimide adhesive.

[0041] The two sides of the polyimide film were laminated with a metal copper sheet, and a strong bonding sample was obtained after hot pressing at 250°C and a pressure of 2 MPa for 30 minutes.

[0042] The gel permeation chromatography (GPC) analysis of the polyimide adhesive obtained in this embodiment is shown in FIG. Figure 2 As shown, its molecular weight M n =56112, and the polymer dispersibility index is 1.79.

[0043] Example 2:

[0044] In this embodiment, high T based on dual dynamic bond cooperation is prepared according to the following steps. g , soluble polyimide adhesive:

[0045] Step 1: Weigh 0.093 g (0.375 mmol) of 4,4'-diaminodiphenyl disulfide (4APD) and 0.875 g (0.875 mmol) of aminopropyl-terminated polydimethylsiloxane (PDMS) and dissolve them in a solvent. Add the diamine mixed solution to a two-necked flask equipped with a stirrer. Use a three-way valve to fill the flask with nitrogen and keep it sealed. Dissolve 0.844 g (1.263 mmol) of TA-TFMB in the solvent in three batches. Use a syringe to inject the dianhydride solution into the flask every 5 minutes. The mixed solution is observed to gradually become viscous. After reacting overnight for 12 hours, a polyamic acid solution is obtained.

[0046] Step 2: Spin-coat the polyamic acid solution evenly on a polytetrafluoroethylene mold, heat it on a 60°C hot plate for 10 hours, then place it in a muffle furnace and heat it to 100, 150, and 200°C at a rate of 5°C / min, and keep it at each temperature for two hours. Finally, heat treat it at 250°C for 1 hour to obtain a film-like polyimide adhesive.

[0047] The gel permeation chromatography (GPC) analysis of the polyimide adhesive obtained in this embodiment is shown in FIG. Figure 2 As shown, its molecular weight M n =50454, and the polymer dispersibility index is 2.05.

[0048] Example 3:

[0049] Step 1: Weigh 0.124 g (0.5 mmol) of 4,4'-diaminodiphenyl disulfide (4APD) and 0.75 g (0.75 mmol) of aminopropyl-terminated polydimethylsiloxane (PDMS) and dissolve them in a solvent. Add the diamine mixed solution to a two-necked flask equipped with a stirrer. Use a three-way valve to fill the flask with nitrogen and keep it sealed. Dissolve 0.844 g (1.263 mmol) of TA-TFMB in the solvent in three batches. Use a syringe to inject the dianhydride solution into the flask every 5 minutes. The mixed solution is observed to gradually become viscous. After reacting overnight for 12 hours, a polyamic acid solution is obtained.

[0050] Step 2: Spin-coat the polyamic acid solution evenly on a polytetrafluoroethylene mold, heat it on a 60°C hot plate for 10 hours, then place it in a muffle furnace and heat it to 100, 150, and 200°C at a rate of 5°C / min, and keep it at each temperature for two hours. Finally, heat treat it at 250°C for 1 hour to obtain a film-like polyimide adhesive.

[0051] The gel permeation chromatography (GPC) analysis of the polyimide adhesive obtained in this embodiment is shown in FIG. Figure 2 As shown, its molecular weight M n =44870, and the polymer dispersibility index is 1.97.

[0052] Example 4:

[0053] In this embodiment, high T based on dual dynamic bond cooperation is prepared according to the following steps. g , soluble polyimide adhesive:

[0054] Step 1: Weigh 0.155 g (0.625 mmol) of 4,4'-diaminodiphenyl disulfide (4APD) and 0.625 g (0.625 mmol) of aminopropyl-terminated polydimethylsiloxane (PDMS) and dissolve them in a solvent. Add the diamine mixed solution to a two-necked flask equipped with a stirrer. Use a three-way valve to fill the flask with nitrogen and keep it sealed. Dissolve 0.844 g (1.263 mmol) of TA-TFMB in the solvent in three batches. Use a syringe to inject the dianhydride solution into the flask every 5 minutes. The mixed solution is observed to gradually become viscous. After reacting overnight for 12 hours, a polyamic acid solution is obtained.

[0055] Step 2: Spin-coat the polyamic acid solution evenly on a polytetrafluoroethylene mold, heat it on a 60°C hot plate for 10 hours, then place it in a muffle furnace and heat it to 100, 150, and 200°C at a rate of 5°C / min, and keep it at each temperature for two hours. Finally, heat treat it at 250°C for 1 hour to obtain a film-like polyimide adhesive.

[0056] The gel permeation chromatography (GPC) analysis of the polyimide adhesive obtained in this embodiment is shown in FIG. Figure 2 As shown, its molecular weight M n =46419, and the polymer dispersibility index is 1.99.

[0057] Example 5:

[0058] In this embodiment, high T based on dual dynamic bond cooperation is prepared according to the following steps. g , soluble polyimide adhesive:

[0059] Step 1: Weigh 0.217 g (0.875 mmol) of 4,4'-diaminodiphenyl disulfide (4APD) and 0.375 g (0.375 mmol) of aminopropyl-terminated polydimethylsiloxane (PDMS) and dissolve them in a solvent. Add the diamine mixed solution to a two-necked flask equipped with a stirrer. Use a three-way valve to fill the flask with nitrogen and keep it sealed. Dissolve 0.844 g (1.263 mmol) of TA-TFMB in the solvent in three batches. Inject the dianhydride solution into the flask every 5 minutes using a syringe. The mixed solution gradually becomes viscous. After reacting overnight for 12 hours, a polyamic acid solution is obtained.

[0060] Step 2: Spin-coat the polyamic acid solution evenly on a polytetrafluoroethylene mold, heat it on a 60°C hot plate for 10 hours, then place it in a muffle furnace and heat it to 100, 150, and 200°C at a rate of 5°C / min, and keep it at each temperature for two hours. Finally, heat treat it at 250°C for 1 hour to obtain a film-like polyimide adhesive.

[0061] The gel permeation chromatography (GPC) analysis of the polyimide adhesive obtained in this embodiment is shown in FIG. Figure 2 As shown, its molecular weight M n =60739, and the polymer dispersibility index is 1.87.

[0062] Example 6:

[0063] In this embodiment, high T based on dual dynamic bond cooperation is prepared according to the following steps. g , Soluble polyimide-based thermally conductive adhesive:

[0064] A polyimide film with a diamine molar ratio of 2:8 was used as the matrix. The polyimide film was dissolved in an organic solvent, and 2.5% by mass of a thermal conductive filler was weighed and ultrasonically dispersed in the organic solvent. Then, the filler dispersion and the polyimide solution were mixed and stirred ultrasonically for 24 hours. The evenly dispersed mixed solution was spin-coated on a Teflon high-temperature resistant cloth and dried to obtain a polyimide-based thermal conductive adhesive based on double dynamic bond collaboration.

[0065] The polyimide-based thermal conductive adhesive film was laminated on both sides with a metal copper sheet, and a firm bonding sample was obtained after hot pressing at 250° C. and applying a pressure of 2 MPa for 30 minutes.

[0066] Example 7:

[0067] In this embodiment, high T based on dual dynamic bond cooperation is prepared according to the following steps. g , Soluble polyimide-based thermally conductive adhesive:

[0068] A polyimide film with a diamine molar ratio of 2:8 was used as the matrix. The polyimide film was dissolved in an organic solvent, and 5% mass fraction of thermal conductive filler was weighed and ultrasonically dispersed in the organic solvent. Then, the filler dispersion and the polyimide solution were mixed and stirred ultrasonically for 24 hours. The evenly dispersed mixed solution was spin-coated on a Teflon high-temperature resistant cloth and dried to obtain a polyimide-based thermal conductive adhesive based on double dynamic bond collaboration.

[0069] The polyimide-based thermal conductive adhesive film was laminated on both sides with a metal copper sheet, and a firm bonding sample was obtained after hot pressing at 250° C. and applying a pressure of 2 MPa for 30 minutes.

[0070] Example 8:

[0071] In this embodiment, high T based on dual dynamic bond cooperation is prepared according to the following steps. g , Soluble polyimide-based thermally conductive adhesive:

[0072] A polyimide film with a diamine molar ratio of 2:8 was used as the matrix. The polyimide film was dissolved in an organic solvent, and 7.5% by mass of a thermal conductive filler was weighed and ultrasonically dispersed in the organic solvent. Then, the filler dispersion and the polyimide solution were mixed and stirred ultrasonically for 24 hours. The evenly dispersed mixed solution was spin-coated on a Teflon high-temperature resistant cloth and dried to obtain a polyimide-based thermal conductive adhesive based on double dynamic bond collaboration.

[0073] The polyimide-based thermal conductive adhesive film was laminated on both sides with a metal copper sheet, and a firm bonding sample was obtained after hot pressing at 250° C. and applying a pressure of 2 MPa for 30 minutes.

[0074] Example 9:

[0075] In this embodiment, high T based on dual dynamic bond cooperation is prepared according to the following steps. g , Soluble polyimide-based thermally conductive adhesive:

[0076] A polyimide film with a diamine molar ratio of 2:8 was used as the matrix. The polyimide film was dissolved in an organic solvent, and 10% by mass of a thermal conductive filler was ultrasonically dispersed in the organic solvent. The filler dispersion and the polyimide solution were then mixed and stirred ultrasonically for 24 hours. The evenly dispersed mixed solution was spin-coated on a Teflon high-temperature resistant cloth and dried to obtain a polyimide-based thermal conductive adhesive based on double dynamic bond collaboration.

[0077] The polyimide-based thermal conductive adhesive film was laminated on both sides with a metal copper sheet, and a firm bonding sample was obtained after hot pressing at 250° C. and applying a pressure of 2 MPa for 30 minutes.

[0078] Comparative Example 1:

[0079] In this comparative example, high T based on dual dynamic bond cooperation was prepared according to the following steps. g , soluble polyimide adhesive:

[0080] Step 1: Weigh 0.062 g (0.250 mmol) of 4,4'-diaminodiphenyl disulfide (4APD) and 1 g (1 mmol) of aminopropyl-terminated polydimethylsiloxane (PDMS) and dissolve them in a solvent. Add the diamine mixed solution to a two-necked flask equipped with a stirrer. Use a three-way valve to fill the flask with nitrogen and keep it sealed. Dissolve 0.844 g (1.263 mmol) of TA-TFMB in the solvent in three batches. Inject the dianhydride solution into the flask every 5 minutes using a syringe. The mixed solution is observed to gradually become viscous. After reacting overnight for 12 hours, a polyamic acid solution is obtained.

[0081] Step 2: Spin-coat the polyamic acid solution evenly on a polytetrafluoroethylene mold, heat it on a 60°C hot plate for 10 hours, then place it in a muffle furnace and heat it to 100, 150, and 200°C at a rate of 5°C / min, and keep it at each temperature for two hours. Finally, heat treat it at 300°C for 1 hour to obtain a film-like polyimide adhesive.

[0082] Comparative Example 2:

[0083] This comparative example provides a high T unfilled GNP based on double dynamic bond cooperation. g , Soluble polyimide-based thermally conductive adhesive:

[0084] A polyimide film with a diamine molar ratio of 2:8 was used as the matrix. The polyimide film was dissolved in an organic solvent, and 0% mass fraction of thermal conductive filler was weighed and ultrasonically dispersed in the organic solvent. Then, the filler dispersion and the polyimide solution were mixed and stirred ultrasonically for 24 hours. The evenly dispersed mixed solution was spin-coated on a Teflon high-temperature resistant cloth and dried to obtain a polyimide-based thermal conductive adhesive based on double dynamic bond collaboration.

[0085] The polyimide-based thermal conductive adhesive film was laminated on both sides with a metal copper sheet, and a firm bonding sample was obtained after hot pressing at 250° C. and applying a pressure of 2 MPa for 30 minutes.

[0086] Comparative Example 3:

[0087] In this comparative example, high T based on dual dynamic bond cooperation was prepared according to the following steps. g , Soluble polyimide-based thermally conductive adhesive:

[0088] A polyimide film with a diamine molar ratio of 2:8 was used as the matrix. The polyimide film was dissolved in an organic solvent, and 8% mass fraction of thermal conductive filler was weighed and ultrasonically dispersed in the organic solvent. Then, the filler dispersion and the polyimide solution were mixed and stirred ultrasonically for 24 hours. The evenly dispersed mixed solution was spin-coated on a Teflon high-temperature resistant cloth and dried to obtain a polyimide-based thermal conductive adhesive based on double dynamic bond collaboration.

[0089] The polyimide-based thermal conductive adhesive film was laminated on both sides with a metal copper sheet, and a firm bonding sample was obtained after hot pressing at 250° C. and applying a pressure of 2 MPa for 30 minutes.

[0090] Figure 1 Schematic diagram of the synthesis route of a dual dynamic synergistic polyimide adhesive provided in Examples 1, 2, 3, 4, and 5 of the present invention.

[0091] Figure 2The following are GPC charts of the polyimide adhesives obtained in Examples 1, 2, 3, 4, and 5 of the present invention. It can be seen that all polyimides exhibit solubility and high molecular weight. The polyimides obtained in Examples 1, 2, 3, 4, and 5 of the present invention have number average molecular weights of 56,112 g / mol, 50,454 g / mol, 44,870 g / mol, 46,419 g / mol, and 60,739 g / mol, respectively. Their molecular weight polydispersity coefficients are 1.79, 2.05, 1.97, 1.99, and 1.87, respectively.

[0092] Figure 3 The DMA curves of the polyimide adhesives obtained in Examples 1, 2, 3, 4, and 5 of the present invention are shown. It can be seen that as the PDMS content decreases, the glass transition temperature of the polyimide gradually increases, reaching a maximum of 265.4°C.

[0093] Figure 4 Figures show the mechanical properties of polyimide adhesive films containing different diamine molar ratios obtained in Examples 1, 2, 3, 4, and 5, as well as polyimide-based thermally conductive adhesive films containing different filler contents obtained in Examples 6, 7, 8, and 9. As can be seen, as the PDMS content decreases, the tensile strength of the polyimide increases, while the elongation at break decreases. As the filler content increases, the tensile strength of the thermally conductive polyimide composite film first increases and then decreases.

[0094] Figure 5 The thermal conductivity of the polyimide-based thermally conductive adhesive film obtained in Examples 6, 7, 8, and 9 of the present invention and Comparative Example 2 is shown in the figure. When the GNP content is 10 wt%, the thermal conductivity of the material is improved by 484%, and the thermal conductivity is 3.91 W / (m · K).

[0095] Figure 6 The bonding sample is prepared from the polyimide adhesive and the copper substrate according to Example 1 of the present invention. After the polyimide adhesive is peeled off from the copper substrate, it can be re-bonded by hot pressing.

[0096] Figure 7 The tensile shear strength performance graph of the polyimide-based thermally conductive adhesive obtained in Examples 6, 7, and 8 of the present invention and Comparative Example 3. When the GNP content is 7.5 wt%, the material still has a tensile shear strength of 8.49 MPa.

[0097] Figure 8 This is a graph showing the tensile shear strength performance of the polyimide adhesive obtained in Example 1 of the present invention after four cycles of bonding. It can be seen that after four cycles of bonding, the tensile shear strength is still 10.63 MPa, and the recovery rate is 85%.

[0098] Figure 9This is an optical image of the crack repair of the polyimide adhesive obtained in Example 1 of the present invention. It can be seen that the crack is effectively repaired under hot pressing conditions.

[0099] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A polyimide adhesive based on dual dynamic bond collaboration, characterized in that: First, 4,4'-diaminodiphenyl disulfide (4APD), aminopropyl-terminated polydimethylsiloxane (PDMS), and fluorine- and amide-containing dianhydride (TA-TFMB) were copolymerized at different molar ratios to obtain dynamic polyamic acid. Then, a fluorinated polyimide adhesive with synergistic effects of dynamic hydrogen bonds and disulfide bonds was prepared by thermal imidization. The structural formula of the fluorinated dual dynamic polyimide adhesive is: 。 2. A method for preparing a polyimide adhesive based on double dynamic bond collaboration, characterized in that: The method comprises the following steps: Step 1: Weigh different molar ratios of 4,4'-diaminodiphenyl disulfide (4APD) and aminopropyl-terminated polydimethylsiloxane (PDMS) and dissolve them in a solvent. Add the diamine mixed solution to a mechanically stirred flask, fill the flask with nitrogen using a three-way valve and keep it sealed. Dissolve the dianhydride TA-TFMB in the solvent in three batches. Inject the dianhydride solution into the flask using a syringe every 5-10 minutes. The mixed solution gradually becomes viscous. After reacting overnight for 12 hours, a polyamic acid solution is obtained. Step 2: Spin-coat the polyamic acid solution evenly on a polytetrafluoroethylene mold, heat it on a 60-100°C hot plate for 5-12 hours, then place it in a muffle furnace and heat it to 100, 150, and 200°C at a rate of 5-10°C / min, respectively, and keep it at each temperature for two hours. Finally, heat treat it at 250°C for 1 hour to obtain a film-like polyimide adhesive.

3. The preparation method according to claim 2, wherein: In step 1, the number average molecular weight of aminopropyl-terminated polydimethylsiloxane (PDMS) is preferably 1000 g / mol, and the molar ratio of 4,4'-diaminodiphenyl disulfide (4APD) to PDMS is 1:9-9:

1.

4. The preparation method according to claim 2, wherein: The number average molecular weight of the prepared dual dynamic polyimide adhesive ranges from 30,000 g / mol to 75,000 g / mol, and the glass transition temperature can reach up to 265.4°C.

5. The polyimide adhesive based on double dynamic bond collaboration according to claim 1, characterized in that: The thermally conductive adhesive is based on a polyimide film with a diamine molar ratio of 2:

8. The polyimide film is dissolved in an organic solvent, and 2.5%-10% by mass of a thermally conductive filler is weighed and ultrasonically dispersed in the organic solvent. The filler dispersion and the polyimide solution are then mixed and ultrasonically stirred for 5-24 hours. The evenly dispersed mixed solution is spin-coated on a Teflon high-temperature resistant cloth and dried to obtain a polyimide-based thermally conductive adhesive based on double dynamic bond collaboration.

6. The polyimide adhesive based on dual dynamic bond collaboration according to claim 5, characterized in that: The organic solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, tetrahydrofuran, dichloromethane, and chloroform, or a combination thereof.

7. The polyimide adhesive based on dual dynamic bond collaboration according to claim 5, characterized in that: The thermally conductive filler is any one of two-dimensional carbide and nitride MXene, boron nitride, graphene, carbon nanotubes, graphite, or a combination thereof.

8. The polyimide adhesive based on dual dynamic bond collaboration according to claim 5, characterized in that: The prepared high molecular weight polyimide-based thermal conductive adhesive is hot-melted at a temperature of 250° C. and a pressure of 2 MPa for 30 minutes, or is quickly dissolved in a solvent at room temperature for less than 15 minutes and recycled.

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