Polyimide material based on quaternary copolymerization as well as preparation method and application thereof

Abstract

The invention provides a polyimide material based on quaternary copolymerization as well as a preparation method and application thereof. The preparation method comprises the step of carrying out quaternary copolymerization on different types of fluorine-containing rigid and flexible diamines, a dianhydride monomer containing a hexafluoroisopropyl structure and a flexible ether bond dianhydride monomer to prepare the high-heat-resistance colorless transparent shape memory polyimide material film. The mole number ratio of the dianhydride monomer to the diamine monomer is 1: (0.92-1), the mole number ratio of the two diamine monomers is 1.5: 8.5-8.5: 1.5, and the mole number ratio of the two dianhydride monomers is 2: 8-8: 2. According to the prepared polyimide material based on quaternary copolymerization, through the synergistic effect of the four monomers, finer sequence regulation and control are achieved, the performance is prevented from being changed and changed, and the heat resistance, the optical performance and the shape memory performance are synchronously optimized.

Description

Technical Field

[0001] The present invention belongs to the field of transparent shape memory polymer films, and particularly relates to a polyimide material based on quaternary copolymerization, its preparation method and application. Background Art

[0002] Polyimide (PI) is a kind of high-performance polymer with excellent heat resistance, mechanical properties, chemical stability and electrical insulation properties, and is widely used in fields such as aerospace, microelectronics, and flexible displays. However, due to the large rigidity of its molecular chain, traditional polyimide materials usually show dark yellow or brown, and it is difficult to have both high transparency and shape memory characteristics, which limits their application in high-end fields such as optical devices, smart window films, and transparent flexible electronics. In recent years, with the rapid development of flexible electronics, optoelectronic devices and smart materials, the development of polyimide materials with both high heat resistance, colorless transparency and shape memory function has become a research hotspot.

[0003] The coloring problem of traditional polyimide mainly stems from the formation of charge transfer complexes (CTCs) in the molecular chain, especially polyimide formed by the polymerization of aromatic diamines and aromatic dianhydrides. To inhibit the CTC effect, researchers usually disrupt the conjugated structure of the molecular chain by introducing aliphatic or alicyclic monomers, use fluorine-containing monomers or asymmetric structure monomers to reduce the packing density of the molecular chain, or adopt copolymer modification to adjust the rigid-flexible balance of the molecular chain. However, a single measure cannot make polyimide simultaneously meet the requirements of high heat resistance, colorless transparency and shape memory.

[0004] Shape memory polyimide (SMPI) is a kind of intelligent material that can recover from a temporary shape to an initial shape under external stimuli (such as temperature, light, electricity). Its shape memory performance usually depends on the construction of a crosslinked network or a reversible phase structure. Although these measures enable polyimide to achieve a high-temperature shape memory effect, they lead to a decrease in the transparency of the material. Therefore, how to endow polyimide with reversible shape memory characteristics through molecular design while maintaining high transparency is still a technical problem to be solved urgently.

[0005] In addition, existing research on quaternary copolymer polyimide mostly focuses on improving solubility or dielectric properties, and there is no report on a quaternary copolymer system with high heat resistance, colorless transparency and shape memory function. Traditional ternary copolymer systems often have difficulty in balancing heat resistance and transparency. For example, introducing too many alicyclic monomers can improve transparency, but will significantly reduce T g ; while over-relying on aromatic monomers will lead to an exacerbation of the CTC effect. Therefore, it is urgent to break through the performance bottleneck of existing materials by means of synergistic design of quaternary monomers, constructing rigid segments in the molecular chain to ensure heat resistance, flexible segments to regulate shape memory performance, and structural units to inhibit CTC to achieve high transparency.

[0006] In summary, the development of a new polyimide material based on quaternary copolymerization, through precise regulation of monomer composition and sequence distribution, to achieve the synergistic optimization of high heat resistance, colorless transparency, and shape memory function, not only has important scientific significance but also can meet the urgent needs of high-performance polymers in fields such as high-end optical devices and intelligent sensors. Summary of the Invention

[0007] The purpose of the present invention is to provide a polyimide material based on quaternary copolymerization, its preparation method and application. This preparation method is through the quaternary copolymerization of different types of fluorine-containing rigid and flexible diamines with a dianhydride monomer containing a hexafluoroisopropyl structure and a flexible ether bond dianhydride monomer, and through thermal imidization, a shape memory polyimide material with high heat resistance, excellent mechanical properties, and colorless transparency is prepared, which can be used as the cover plate and substrate material of flexible batteries.

[0008] To achieve the above purpose, the present invention is implemented by adopting the following technical solutions:

[0009] The present invention provides a polyimide material based on quaternary copolymerization, and the polyimide material based on quaternary copolymerization has the following chemical structural formula:

[0010]

[0011] Wherein, R is

[0012] The present invention also provides a preparation method of the above polyimide material based on quaternary copolymerization, including the following steps: 1) Uniformly mix a fluorine-containing rigid diamine monomer and a fluorine-containing flexible diamine monomer, and then add them to a high-boiling polar aprotic solvent to obtain a reaction system; 2) Stir vigorously until the diamine in the reaction system is completely dissolved, and then add a uniformly mixed dianhydride monomer containing a hexafluoroisopropyl structure and a dianhydride monomer containing an ether bond structure, and react for 12 - 24 hours under nitrogen conditions at room temperature to obtain a polyamic acid solution; 3) Let the polyamic acid solution stand to defoam and then coat it on a loading vessel, and use the thermal imidization method to obtain the polyimide material based on quaternary copolymerization.

[0013] Furthermore, the molar ratio of the fluorine-containing rigid diamine monomer to the fluorine-containing flexible diamine monomer is 1.5:8.5 - 8.5:1.5; the molar ratio of the dianhydride monomer containing a hexafluoroisopropyl structure to the dianhydride monomer containing an ether bond structure is 2:8 - 8:2; the molar ratio of the sum of the fluorine-containing rigid diamine monomer and the fluorine-containing flexible diamine monomer to the sum of the dianhydride monomer containing a hexafluoroisopropyl structure and the dianhydride monomer containing an ether bond structure is 1:(0.92 - 1).

[0014] Further, the fluorine-containing rigid diamine monomers include at least one of 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine and 9,9-bis(3-fluoro-4-aminophenyl)fluorene; the fluorine-containing flexible diamine monomers include at least one of 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, and 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene; the dianhydride monomers containing hexafluoroisopropyl structure include at least one of 4,4'-(hexafluoroisopropylidene)phthalic anhydride and bisphenol AF dianhydride; the dianhydride monomers containing ether bond structure include at least one of bisphenol A type diether dianhydride and 2,3,3',4'-diphenylether tetracarboxylic dianhydride.

[0015] Further, the thermal imidization method in step 3) includes performing the following operations in sequence: drying in a vacuum drying oven at 80°C for 2 h; drying at 120°C for 2 h; drying at 150°C for 2 h; drying at 180°C for 2 h; drying at 210°C for 2 h; drying at 240°C for 2 h; the final imidization temperature is 280 - 300°C, and the imidization time is 2 hours.

[0016] Further, the high-boiling polar aprotic solvent in step 1) is selected from one of N-methyl-2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0017] Further, the solid content of polyamic acid in the polyamic acid solution in step 2) is 16 wt% - 25 wt%.

[0018] The present invention also provides an application of the quaternary copolymerization-based polyimide material prepared by the preparation method of the above quaternary copolymerization-based polyimide material in the fields of high-end optical devices and intelligent sensors.

[0019] Further, when the thickness of the quaternary copolymerization-based polyimide material is 50 μm, the light transmittance at 500 nm is between 86% and 88.1%, the glass transition temperature is between 241°C and 284°C, the shape fixation rate is greater than 99.4%, the shape recovery rate is greater than 98.9%, the elongation at break is between 2.6% and 3.5%, and the tensile strength is between 69.2 MPa and 153.5 MPa.

[0020] Further, the quaternary copolymerization-based polyimide material is subjected to shape memory programming to obtain a temporary shape, and the temporary shape is restored to the initial shape by thermal stimulation.

[0021] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0022] The present invention provides a polyimide material based on quaternary copolymerization, its preparation method and applications. In the present invention, different types of fluorine-containing rigid and flexible diamines, a dianhydride monomer containing a hexafluoroisopropyl structure, and a flexible ether bond dianhydride monomer are selected, and a polyimide material based on quaternary copolymerization with a glass transition temperature greater than 241 °C is prepared for the first time by a quaternary copolymerization method. The diamine monomers used in the present invention contain fluorine, which reduces the electron-donating property of the diamine and effectively improves the optical properties of the polyimide. The ether bond and hexafluoroisopropyl structure in the dianhydride monomer increase the intermolecular distance and improve the transparency of the polyimide. In addition, by adjusting the ratio of the rigid and flexible diamine monomers, excellent thermal properties, mechanical properties, and shape memory properties of the polyimide are ensured. Therefore, the polyimide material based on quaternary copolymerization of the present invention not only has excellent heat resistance and mechanical properties of traditional shape memory polyimide, but also has good optical properties that common PIs do not have. The glass transition temperature of the polyimide material based on quaternary copolymerization is greater than 241 °C, the transmittance at 500 nm is higher than 86%, the shape fixing rate and shape recovery rate are both above 98.9%, the elongation at break is between 2.6% and 3.5%, and the tensile strength is between 69.2 MPa and 153.5 MPa. Description of the Drawings

[0023] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute limitations on the embodiments. Unless otherwise stated, the figures in the drawings do not constitute a scale limitation.

[0024] Figure 1 It is a finished product diagram of the polyimide material based on quaternary copolymerization prepared in Example 1;

[0025] Figure 2 It is a finished product diagram of the polyimide material based on quaternary copolymerization prepared in Example 2;

[0026] Figure 3 It is an infrared spectrum diagram of the polyimide material based on quaternary copolymerization prepared in Example 1;

[0027] Figure 4 It is an infrared spectrum diagram of the polyimide material based on quaternary copolymerization prepared in Example 2;

[0028] Figure 5 It is a UV-Vis spectrum diagram of the polyimide material based on quaternary copolymerization prepared in Example 1;

[0029] Figure 6 It is a UV-Vis spectrum diagram of the polyimide material based on quaternary copolymerization prepared in Example 2;

[0030] Figure 7 It is a dynamic thermomechanical property diagram of the polyimide material based on quaternary copolymerization prepared in Example 2;

[0031] Figure 8 Dynamic thermomechanical property diagram of the polyimide material based on quaternary copolymerization prepared in Example 4;

[0032] Figure 9 Shape memory process diagram of the polyimide material based on quaternary copolymerization prepared in Example 1;

[0033] Figure 10 Shape memory process diagram of the polyimide material based on quaternary copolymerization prepared in Example 2. Detailed implementation manners

[0034] The present invention will be described in detail below in conjunction with the specific implementation manners.

[0035] Example 1

[0036] The polyimide material based on quaternary copolymerization in this example is completed according to the following steps:

[0037] I. Add 25 mL of N,N-dimethylacetamide as a solvent into a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlets and outlets, and introduce nitrogen. Add the mixed diamines 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether and 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine into the three-necked flask, and the molar ratio of their amounts is 1.5:8.5; stir in an ice-water bath until completely dissolved to obtain a mixed diamine solution.

[0038] II. Weigh the dried mixed dianhydrides 4,4′-(hexafluoroisopropylidene)phthalic anhydride and bisphenol A type diether dianhydride and add them to the diamine solution in four portions, and the molar ratio of their amounts is 2:8; the molar ratio of the added dianhydrides to the mixed diamines is 1:0.92, and carry out a polymerization reaction for 24 h under ice-water bath and high-speed stirring conditions to obtain a polyamic acid solution.

[0039] III. Filter and let stand the polyamic acid solution to defoam to obtain a uniform solution.

[0040] IV. Coat the defoamed PAA solution on a washed glass plate through a coater, control the wet film thickness to be 313 μm, and the solid content to be 16%. After coating through the coater, cure it by gradient heating to 180 °C.

[0041] V. Put the glass plate with the PAA film into an electrothermal blast drying oven for gradient heating curing. The gradient heating curing program is 80 °C / 2 h, 120 °C / 2 h, 150 °C / 2 h, 180 °C / 2 h, 210 °C / 2 h, 240 °C / 2 h, 280 °C / 2 h.

[0042] VI. After high-temperature treatment, place the glass plate in deionized water and peel off the film. The film is washed, dried, trimmed, and stored in bags. Among them, Figure 1 The figure shows the finished product diagram of the polyimide material based on quaternary copolymerization prepared in this embodiment. Figure 3 The figure shows the infrared spectrum of the polyimide material based on quaternary copolymerization prepared in this embodiment. These characteristic absorption peaks indicate that the polyimide material based on quaternary copolymerization prepared in Example 1 has been completely imidized. Figure 5 The figure shows the ultraviolet-visible spectrum diagram of the polyimide material based on quaternary copolymerization prepared in this embodiment. From Figure 5 it can be seen that the transmittance of the polyimide material based on quaternary copolymerization with a thickness of 50 μm is 88.1% at 500 nm. Figure 7 The figure shows the dynamic thermomechanical properties of the polyimide material based on quaternary copolymerization prepared in this embodiment. From Figure 7 it can be known that the glass transition temperature of the polyimide material based on quaternary copolymerization prepared in Example 1 is 241 °C. Figure 9 The figure shows the shape memory process diagram of the polyimide material based on quaternary copolymerization prepared in this embodiment. It can be seen from the figure that the polyimide material based on quaternary copolymerization prepared in Example 1 has good shape memory effect.

[0043] Example 2

[0044] The polyimide material based on quaternary copolymerization in this embodiment is completed according to the following steps:

[0045] I. Add 25 mL of N,N-dimethylacetamide as a solvent to a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlets and outlets, and introduce nitrogen. Add the mixed diamines 9,9-bis(3-fluoro-4-aminophenyl)fluorene and 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine to the three-necked flask, and their molar ratio is 1.5:8.5; stir in an ice-water bath until completely dissolved to obtain a mixed diamine solution.

[0046] II. Weigh the dried mixed dianhydrides 4,4′-(hexafluoroisopropylidene)phthalic anhydride and bisphenol A type diether dianhydride and add them to the diamine solution in four portions, and their molar ratio is 2:8; the molar ratio of the added dianhydride and the mixed diamine is 1:0.93, and carry out a polymerization reaction for 24 h under ice-water bath and high-speed stirring conditions to obtain a polyamic acid solution.

[0047] III. Filter and let stand to defoam the polyamic acid solution to obtain a uniform solution.

[0048] IV. Coating the defoamed PAA solution onto a cleaned glass plate through a coater, controlling the wet film thickness to be 313 μm and the solid content to be 16%. After coating by the coater, cure it at a gradient temperature up to 180 °C.

[0049] V. Place the glass plate with the PAA film into an electrothermal blast drying oven for gradient temperature curing. The gradient temperature curing program is 80 °C / 2 h, 120 °C / 2 h, 150 °C / 2 h, 180 °C / 2 h, 210 °C / 2 h, 240 °C / 2 h, 280 °C / 2 h.

[0050] VI. After high-temperature treatment, place the glass plate in deionized water and peel off the film. The film is washed, dried, trimmed, and stored in a bag. Among them, Figure 2 The figure shows the finished product diagram of the polyimide material based on quaternary copolymerization prepared in this example. Figure 4 The figure shows the infrared spectrum of the polyimide material based on quaternary copolymerization prepared in this example. These characteristic absorption peaks indicate that the polyimide material based on quaternary copolymerization prepared in Example 2 has been completely imidized. Figure 6 The figure shows the ultraviolet-visible spectrum diagram of the polyimide material based on quaternary copolymerization prepared in this example. From Figure 6 it can be seen that the light transmittance of the polyimide material based on quaternary copolymerization with a thickness of 50 μm is 88.0% at 500 nm. Figure 8 The figure shows the dynamic thermomechanical properties of the polyimide material based on quaternary copolymerization prepared in this example. From Figure 8 it can be known that the glass transition temperature of the polyimide material based on quaternary copolymerization prepared in Example 2 is 284 °C. Figure 10 The figure shows the shape memory process diagram of the polyimide material based on quaternary copolymerization prepared in this example. From the figure, it can be known that the polyimide material based on quaternary copolymerization prepared in Example 2 has a good shape memory effect.

[0051] Example 3

[0052] The polyimide material based on quaternary copolymerization in this example is completed according to the following steps:

[0053] I. Add 25 mL of N,N-dimethylacetamide as a solvent into a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlets and outlets, and introduce nitrogen. Add the mixed diamines 9,9-bis(3-fluoro-4-aminophenyl)fluorene and 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine into the three-necked flask, and their molar ratio is 3:7; stir under an ice-water bath until completely dissolved to obtain a mixed diamine solution.

[0054] II. Weigh the dried mixed dianhydrides 4,4′-(hexafluoroisopropylidene)phthalic anhydride and bisphenol A diether dianhydride, and add them to the diamine solution in four portions. The molar ratio of the substances is 2:8; the molar ratio of the added dianhydride to the mixed diamine is 0.95:1. Under the conditions of an ice-water bath and high-speed stirring, carry out a polymerization reaction for 24 h to obtain a polyamic acid solution.

[0055] III. Filter and let stand to defoam the polyamic acid solution to obtain a homogeneous solution.

[0056] IV. Coat the defoamed PAA solution on a washed glass plate with a coater, controlling the wet film thickness to be 313 μm and the solid content to be 16%. After coating with the coater, cure it by gradient heating to 180 °C.

[0057] V. Put the glass plate with the PAA film into an electrothermal blast drying oven for gradient heating curing. The gradient heating curing program is 80 °C / 2 h, 120 °C / 2 h, 150 °C / 2 h, 180 °C / 2 h, 210 °C / 2 h, 240 °C / 2 h, 280 °C / 2 h.

[0058] VI. After high-temperature treatment, place the glass plate in deionized water and peel off the film. The film is washed, dried, trimmed, and stored in a bag.

[0059] Example 4

[0060] The polyimide material based on quaternary copolymerization in this example is completed according to the following steps:

[0061] I. Add 25 mL of N,N-dimethylacetamide as a solvent to a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlets and outlets, and introduce nitrogen. Add the mixed diamines 9,9-bis(3-fluoro-4-aminophenyl)fluorene and 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine to the three-necked flask. The molar ratio of the substances is 3.5:6.5; stir under ice-water bath conditions until completely dissolved to obtain a mixed diamine solution.

[0062] II. Weigh the dried mixed dianhydrides 2,3,3',4'-diphenylether tetracarboxylic dianhydride and bisphenol A diether dianhydride, and add them to the diamine solution in four portions. The molar ratio of the substances is 3:7; the molar ratio of the added dianhydride to the mixed diamine is 1:1. Under the conditions of an ice-water bath and high-speed stirring, carry out a polymerization reaction for 24 h to obtain a polyamic acid solution.

[0063] III. Filter and let stand to defoam the polyamic acid solution to obtain a homogeneous solution.

[0064] IV. The defoamed PAA solution is coated on a washed glass plate by a coater, controlling the wet film thickness to be 313 μm and the solid content to be 16%. After coating by the coater, it is cured by gradient heating to 180 °C.

[0065] V. The glass plate with the PAA film is placed in an electrothermal blast drying oven for gradient heating curing. The gradient heating curing program is 80 °C / 2 h, 120 °C / 2 h, 150 °C / 2 h, 180 °C / 2 h, 210 °C / 2 h, 240 °C / 2 h, 280 °C / 2 h.

[0066] VI. After high-temperature treatment, the glass plate is placed in deionized water, and the film is peeled off. The film is washed, dried, trimmed, and stored in a bag. Figure 9 The dynamic thermomechanical properties of the polyimide material based on quaternary copolymerization prepared in this example are shown. From Figure 9 it can be seen that the glass transition temperature of the polyimide material based on quaternary copolymerization prepared in Example 4 is 284 °C.

[0067] Example 5

[0068] The polyimide material based on quaternary copolymerization in this example is completed according to the following steps:

[0069] I. Add 25 mL of N,N-dimethylformamide as a solvent into a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlets and outlets, and introduce nitrogen. Add the mixed diamines 9,9-bis(3-fluoro-4-aminophenyl)fluorene and 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine into the three-necked flask, and their molar ratio is 5:5; stir in an ice-water bath until completely dissolved to obtain a mixed diamine solution.

[0070] II. Weigh the dried mixed dianhydrides 2,3,3',4'-diphenylether tetracarboxylic dianhydride and 4,4′-(hexafluoroisopropylidene)phthalic anhydride, and add them to the diamine solution in four portions, and their molar ratio is 2:8; the molar ratio of the added dianhydride to the mixed diamine is 1:1, and carry out a polymerization reaction for 24 h under ice-water bath and high-speed stirring conditions to obtain a polyamic acid solution.

[0071] III. The polyamic acid solution is filtered and allowed to stand to defoam to obtain a uniform solution.

[0072] IV. The defoamed PAA solution is coated on a washed glass plate by a coater, controlling the wet film thickness to be 313 μm and the solid content to be 16%. After coating by the coater, it is cured by gradient heating to 180 °C.

[0073] V. Place the glass plate with the PAA film in an electrothermal blast drying oven for gradient temperature curing. The gradient temperature curing program is 80°C / 2h, 120°C / 2h, 150°C / 2h, 180°C / 2h, 210°C / 2h, 240°C / 2h, 280°C / 2h.

[0074] VI. After high-temperature treatment, place the glass plate in deionized water and peel off the film. The film is washed, dried, trimmed, and stored in a bag.

[0075] Example 6

[0076] The polyimide material based on quaternary copolymerization in this example is completed according to the following steps:

[0077] I. Add 25 mL of N,N-dimethylformamide as a solvent to a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlets and outlets, and introduce nitrogen. Add the mixed diamines 9,9-bis(3-fluoro-4-aminophenyl)fluorene and 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine to the three-necked flask, and their molar ratio is 7:3; stir in an ice-water bath until completely dissolved to obtain a mixed diamine solution.

[0078] II. Weigh the dried mixed dianhydrides bisphenol A diether dianhydride and 4,4′-(hexafluoroisopropylidene)phthalic anhydride and add them to the diamine solution in four portions, and their molar ratio is 2:8; the molar ratio of the added dianhydride to the mixed diamine is 1:1, and carry out a polymerization reaction for 24 h under ice-water bath and high-speed stirring conditions to obtain a polyamic acid solution.

[0079] III. Filter and let stand to defoam the polyamic acid solution to obtain a uniform solution.

[0080] IV. Coat the defoamed PAA solution on a washed glass plate with a coater, control the wet film thickness to be 313 μm, and the solid content to be 16%. After coating with the coater, cure at a gradient temperature to 180°C.

[0081] V. Place the glass plate with the PAA film in an electrothermal blast drying oven for gradient temperature curing. The gradient temperature curing program is 80°C / 2h, 120°C / 2h, 150°C / 2h, 180°C / 2h, 210°C / 2h, 240°C / 2h, 280°C / 2h.

[0082] VI. After high-temperature treatment, place the glass plate in deionized water and peel off the film. The film is washed, dried, trimmed, and stored in a bag.

[0083] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present invention. In actual applications, various changes can be made to it in form and details without departing from the spirit and scope of the present invention. Any person skilled in the art can make their own changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A polyimide material based on quaternary copolymerization, characterized in that: The polyimide material based on quaternary copolymerization has the following chemical structure: Among them, R is 2. A method for preparing a polyimide material based on quaternary copolymerization according to claim 1, characterized in that: The following steps are involved: 1) uniformly mixing a fluorine-containing rigid diamine monomer and a fluorine-containing flexible diamine monomer and adding the mixture into a high-boiling-point polar aprotic solvent to obtain a reaction system; 2) vigorously stirring until the diamine in the reaction system is completely dissolved, then adding a uniformly mixed dianhydride monomer containing a hexafluoroisopropyl structure and a dianhydride monomer containing an ether bond structure, and reacting for 12 to 24 hours under nitrogen conditions at room temperature to obtain a polyamic acid solution; 3) The polyamic acid solution is allowed to stand for defoaming and then coated on a container, and the polyimide material based on quaternary copolymerization is obtained by a thermal imidization method.

3. The method for preparing a polyimide material based on quaternary copolymerization according to claim 2, characterized in that: The molar ratio of the fluorine-containing rigid diamine monomer to the fluorine-containing flexible diamine monomer is 1.5:8.5 to 8.5:1.5; The molar ratio of the dianhydride monomer containing a hexafluoroisopropyl structure to the dianhydride monomer containing an ether bond structure is 2:8 to 8:2; The molar ratio of the sum of the fluorine-containing rigid diamine monomer and the fluorine-containing flexible diamine monomer to the sum of the hexafluoroisopropyl structure-containing dianhydride monomer and the ether bond structure-containing dianhydride monomer is 1:(0.92-1).

4. The method for preparing a polyimide material based on quaternary copolymerization according to claim 2, characterized in that: The fluorine-containing rigid diamine monomer includes at least one of 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine and 9,9-bis(3-fluoro-4-aminophenyl)fluorene; The fluorine-containing flexible diamine monomer includes at least one of 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, and 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene; The dianhydride monomer containing a hexafluoroisopropyl structure includes at least one of 4,4′-(hexafluoroisopropylidene)phthalic anhydride and bisphenol AF dianhydride; The dianhydride monomer containing an ether bond structure includes at least one of bisphenol A type diether dianhydride and 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride.

5. The method for preparing a polyimide material based on quaternary copolymerization according to claim 2, characterized in that: The thermal imidization method in step 3) comprises the following operations in sequence: The heating process in the vacuum drying oven is drying at 80°C for 2h; drying at 120°C for 2h; drying at 150°C for 2h; drying at 180°C for 2h; drying at 210°C for 2h; drying at 240°C for 2h; the final imidization temperature is 280-300°C, and the imidization time is 2 hours.

6. The method for preparing a polyimide material based on quaternary copolymerization according to claim 2, characterized in that: The high boiling point polar aprotic solvent in step 1) is selected from one of N-methyl-2-pyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide.

7. The method for preparing a polyimide material based on quaternary copolymerization according to claim 2, characterized in that: The solid content of the polyamic acid in the polyamic acid solution in step 2) is 16 wt % to 25 wt %.

8. Application of a quaternary copolymer-based polyimide material prepared by the preparation method of a quaternary copolymer-based polyimide material according to any one of claims 2 to 8 in the fields of high-end optical devices and smart sensors.

9. The use according to claim 8, characterized in that: When the thickness of the polyimide material based on quaternary copolymer is 50 μm, the light transmittance at 500 nm is between 86% and 88.1%, the glass transition temperature is between 241° C. and 284° C., the shape fixity is greater than 99.4%, the shape recovery rate is greater than 98.9%, the elongation at break is between 2.6% and 3.5%, and the tensile strength is between 69.2 MPa and 153.5 MPa.

10. The use according to claim 8, characterized in that: The polyimide material based on quaternary copolymer is subjected to shape memory programming to obtain a temporary shape, and the temporary shape is unfolded and restored to the initial shape by thermal stimulation.

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