High-temperature colorless shape memory polyimide film as well as preparation method and application thereof

Abstract

The invention relates to a high-temperature colorless shape memory polyimide film as well as a preparation method and application thereof. The structural formula of the high-temperature colorless shape memory polyimide film is as follows: different types of diamine monomers containing trifluoromethyl structures, dianhydride monomers containing hexafluoroisopropyl structures and flexible ether bond dianhydride monomers are copolymerized to prepare the high-temperature colorless shape memory polyimide film. The mole number ratio of the dianhydride monomer to the diamine monomer is 1: (0.92-0.95). The shape memory polyimide film prepared by the invention has good optical and thermal properties, and also ensures the shape memory property. The preparation method is simple, few in technological process and low in production cost.

Description

Technical Field

[0001] The invention belongs to the field of shape memory polymer films, and in particular relates to a high-temperature colorless shape memory polyimide film and a preparation method and application thereof. Background Art

[0002] As one of the most heat-resistant polymer materials, polyimide (PI) has excellent mechanical properties, dielectric properties and flexibility, and has a wide range of applications in many fields such as aerospace, biomedicine and optoelectronics. Shape memory polyimide has good shape memory properties due to its special structure and can be used in the fields of optoelectronic materials, biology and space self-deployment structures.

[0003] The charge-transfer complex (CTC) effect within and between polyimide molecules makes polyimide have high temperature resistance and excellent mechanical properties that other polymer materials do not have. At the same time, the polyimide film absorbs blue-violet light in visible light and often appears brown-yellow, which is the main reason for the color development of aromatic polyimide. This characteristic seriously hinders the application of polyimide in the optoelectronic field. The preparation of colorless and transparent polyimide film can solve this problem. Colorless and transparent polyimide (Colorless The synthesis strategy of polyimide (CPI) is mainly achieved by suppressing the CTC effect, including the introduction of strong electronegative substituents, twisted structures, alicyclic structures, asymmetric structures, flexible structural units, inorganic nanoparticles and copolymerization. Among them, the copolymerization method is usually lower than the corresponding homopolymerization method in the regularity of polyimide molecules, which will lead to a reduction in intermolecular interactions and produce new features, such as changed optical properties and thermal properties. In addition, the performance can be changed by changing the ratio of diamine and dianhydride monomers to prepare colorless and transparent polyimide films.

[0004] In recent years, with the rapid development of smart phones, smart homes, aerospace and other fields, optoelectronic devices tend to be lightweight and flexible. Traditional commonly used glass, paper and metal substrates are gradually being eliminated. Optical polymer films are gradually gaining more and more attention in the fields of optoelectronic devices such as flexible printed circuit boards, folding screen mobile phones, flexible solar cells and touch tablets due to their excellent optical properties, bendability, high temperature resistance, impact resistance and light weight. The processing of optoelectronic devices cannot be separated from high temperature treatment, so optical polymer films must have a certain degree of heat resistance. Optical polyimide film stands out from many materials with its excellent high temperature resistance and becomes a promising material for flexible optoelectronic device substrates. After solving the problem of realizing high temperature resistant flexible optoelectronic device substrate materials, optoelectronic devices are expected to achieve more functions. When an optical polymer film with shape memory effect is used as a flexible substrate for optoelectronic devices, the shape memory function of flexible optoelectronic devices can be realized.

[0005] Therefore, preparing a high-temperature colorless shape memory polyimide film to endow flexible optoelectronic devices with shape memory properties has become a key technical issue studied by scientific researchers. Summary of the invention

[0006] The purpose of the present invention is to provide a high-temperature colorless shape memory polyimide film and a preparation method and application thereof. The present invention prepares a colorless and transparent shape memory polyimide film material with good temperature resistance by copolymerizing a diamine monomer containing a trifluoromethyl structure with a dianhydride monomer containing a hexafluoroisopropyl structure or a flexible ether bond dianhydride monomer through thermal imidization. The shape memory polyimide film material can be used as a flexible optical material for optoelectronic devices.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a high temperature colorless shape memory polyimide film, wherein the high temperature colorless shape memory polyimide film has the following chemical structure:

[0009]

[0010] Wherein, a, b, c, d, e, m, n, and k are all positive integers between 0 and 1, and c and d must be 0 or 1 at the same time;

[0011] R 1 for

[0012] R 2 , R 5 for

[0013] R 3 for

[0014] R 4 for

[0015] When a, c, and d are all 1 at the same time, R 2 and R 5 Need to be the same;

[0016] When a is 1, but c and d are not 1, then m is 0, n is 2, and the two R 2 different:

[0017] When c and d are 1, but a is not 1, then n is 0, m is 2, and the two R 5 different.

[0018] Furthermore, when the thickness of the high-temperature colorless shape-memory polyimide film is 50 μm, the light transmittance of the high-temperature colorless shape-memory polyimide film at 500 nm is between 87% and 90%, the glass transition temperature is between 240° C., the shape fixation rate is greater than 98.9%, and the shape recovery rate is greater than 99.4%.

[0019] The second aspect of the present invention provides a method for preparing the above-mentioned high-temperature colorless shape memory polyimide film, which comprises the following steps: 1) first adding a diamine monomer containing a trifluoromethyl structure into a high-boiling point polar aprotic solvent; 2) vigorously stirring until the diamine is completely dissolved, and then adding a dianhydride monomer containing a hexafluoroisopropyl structure or a dianhydride monomer containing an ether bond structure, and reacting for 10 to 24 hours under nitrogen conditions at room temperature to obtain a polyamic acid solution with a certain solid content; 3) coating the polyamic acid solution after standing and defoaming on a clean and dry glass plate, and using a thermal imidization method to obtain a high-temperature colorless shape memory polyimide film.

[0020] Furthermore, the diamine monomer containing a trifluoromethyl structure includes at least one of 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)benzene]hexafluoropropane, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl, and 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene; the dianhydride monomer containing a hexafluoroisopropyl structure includes 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 4,4'-oxydiphthalic anhydride.

[0021] Furthermore, the thermal imidization method in step 3) includes: heating process in a vacuum drying oven 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 270°C to 300°C, and the imidization time is 2 hours.

[0022] Furthermore, in the step 1), the high boiling point polar aprotic solvent is selected from one of N-methyl-2-pyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide.

[0023] Furthermore, in the step 2), the solid content of the polyamic acid in the polyamic acid solution is 16 wt % to 20 wt %.

[0024] Furthermore, the molar ratio of the diamine monomer containing a trifluoromethyl structure to the dianhydride monomer containing a hexafluoroisopropyl structure or the dianhydride monomer containing an ether bond structure is 1:(0.92-0.95).

[0025] The third aspect of the present invention provides the application of the above-mentioned high-temperature colorless shape memory polyimide film in the field of flexible optoelectronic devices.

[0026] Furthermore, the temporary shape obtained by shape memory knitting the high temperature colorless shape memory polyimide film material can be expanded and restored to the initial shape by thermal stimulation.

[0027] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0028] The present invention provides a high-temperature colorless shape memory polyimide film and a preparation method and application thereof. The present invention selects a diamine monomer with a trifluoromethyl structure and a dianhydride monomer containing a hexafluoroisopropyl structure or an dianhydride monomer containing an ether bond structure, and adopts a ternary copolymerization method to prepare a high-temperature colorless shape memory polyimide film with a glass transition temperature greater than 240°C for the first time. The diamine monomer used in the present invention contains a trifluoromethyl structure, which reduces the electron donating property of the diamine, thereby reducing the charge transfer complexation effect between molecules and within molecules, and effectively increases the optical properties of the polyimide. The flexible dianhydride containing an ether bond structure and a hexafluoroisopropyl structure increases the intermolecular distance and improves the transparency of the polyimide. In addition, the selection of aromatic diamine and dianhydride monomers ensures that the polyimide has excellent thermal properties, mechanical properties and shape memory properties. Therefore, the high-temperature colorless shape memory polyimide film of the present invention has both the excellent heat resistance of traditional shape memory polyimide and the good optical properties that common PI does not have. The glass transition temperature of the high-temperature colorless shape memory polyimide film is greater than 240° C., the transmittance at 500 nm is higher than 88%, and the shape fixation and shape recovery rates are both above 98.9%. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention, in which:

[0030] Figure 1 This is a finished product picture of the high temperature colorless shape memory polyimide film prepared in Example 2;

[0031] Figure 2 This is a finished product picture of the high temperature colorless shape memory polyimide film prepared in Example 3;

[0032] Figure 3 This is an infrared spectrum of the high temperature colorless shape memory polyimide film prepared in Example 2;

[0033] Figure 4 This is an infrared spectrum of the high temperature colorless shape memory polyimide film prepared in Example 3;

[0034] Figure 5 This is a UV-visible spectrum of the high-temperature colorless shape memory polyimide film prepared in Example 2;

[0035] Figure 6 This is a UV-visible spectrum of the high-temperature colorless shape memory polyimide film prepared in Example 3;

[0036] Figure 7 This is a dynamic thermomechanical performance diagram of the high-temperature colorless shape memory polyimide film prepared in Example 2;

[0037] Figure 8 This is a dynamic thermomechanical performance diagram of the high temperature colorless shape memory polyimide film prepared in Example 3;

[0038] Fig. 9 This is a shape memory process diagram of a high temperature colorless shape memory polyimide film prepared in Example 2;

[0039] Fig.10 This is a diagram of the shape memory process of the high-temperature colorless shape memory polyimide film prepared in Example 3. DETAILED DESCRIPTION

[0040] The present invention is described in detail below in conjunction with specific implementation modes.

[0041] Example 1

[0042] The high temperature colorless shape memory polyimide film of this embodiment is prepared according to the following steps:

[0043] 1. Add 25 mL of N,N-dimethylacetamide as solvent to a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlet and outlet, and introduce nitrogen. Add the mixed diamine 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether and 2,2'-bis(trifluoromethyl)diaminobiphenyl to the three-necked flask, with the molar ratio of the substances being 8:2; stir in an ice-water bath until completely dissolved to obtain a mixed diamine solution.

[0044] 2. Weigh the dried dianhydride monomer 4,4′-(hexafluoroisopropylidene)phthalic anhydride and add it to the diamine solution four times. The molar ratio of the added dianhydride to the mixed diamine is 1:0.97. Perform the polymerization reaction in an ice-water bath with high-speed stirring for 24 hours to obtain a polyamic acid solution.

[0045] 3. The polyamic acid solution is filtered and allowed to stand to defoam to obtain a uniform solution.

[0046] 4. The PAA solution after defoaming is coated on the cleaned glass plate by a coating machine, and the wet film thickness is controlled to be 313 μm and the solid content is 16%. After coating by the coating machine, the temperature is gradually increased to 180°C for curing.

[0047] 5. Put the glass plate with PAA film into an electric heating blast drying oven for gradient temperature curing. The gradient temperature curing program is 80℃ / 2h, 120℃ / 2h, 150℃ / 2h, 180℃ / 2h, 210℃ / 2h, 240℃ / 2h, 280℃ / 2h.

[0048] 6. 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 bagged for storage to obtain a high temperature colorless shape memory polyimide film.

[0049] Example 2

[0050] The high temperature colorless shape memory polyimide film of this embodiment is prepared according to the following steps:

[0051] 1. Add 25 mL of N,N-dimethylacetamide as solvent to a 100 mL three-necked flask equipped with a mechanical stirrer and a nitrogen inlet and outlet, and introduce nitrogen. Add diamine 2,2'-bis(trifluoromethyl)diaminobiphenyl to the three-necked flask; stir in an ice-water bath until completely dissolved to obtain a diamine solution.

[0052] 2. Weigh the dried dianhydride monomer 4,4′-(hexafluoroisopropylidene)phthalic anhydride and bisphenol A diether dianhydride and mix them evenly, with the molar ratio of the substance amount being 2:8. Add the mixed dianhydride to the diamine solution in four times, with the molar ratio of the added mixed dianhydride to the diamine being 1:0.95, and polymerize for 24 hours in an ice water bath with high-speed stirring to obtain a polyamic acid solution.

[0053] 3. The polyamic acid solution is filtered and allowed to stand to defoam to obtain a uniform solution.

[0054] 4. Apply the defoamed PAA solution on the cleaned glass plate through a coating machine, control the wet film thickness to 250μm, and the solid content to 20%. Apply through the coating machine and gradually heat up to 180℃ for curing.

[0055] 5. Put the glass plate with PAA film into an electric heating blast drying oven for gradient temperature curing. The gradient temperature curing program is 80℃ / 2h, 120℃ / 2h, 150℃ / 2h, 180℃ / 2h, 210℃ / 2h, 240℃ / 2h, 280℃ / 2h.

[0056] 6. After high temperature treatment, the glass plate is placed in deionized water and the film is peeled off. The film is washed, dried, cut and tested to obtain a high temperature colorless shape memory polyimide film.

[0057] in, Figure 1 Shown is a finished product image of the high-temperature colorless shape memory polyimide film prepared in this embodiment. Figure 3 The infrared spectrum of the high-temperature colorless shape memory polyimide film prepared in this example is shown. These characteristic absorption peaks indicate that the high-temperature colorless shape memory polyimide film prepared in Example 2 has been completely imidized. Figure 5 The UV-Vis spectrum of the high temperature colorless shape memory polyimide film prepared in this embodiment is shown in FIG. Figure 5 It can be seen that the colorless and transparent polyimide film with a thickness of 50 μm has a light transmittance of 88.9% at 500 nm. Figure 7 The following are the dynamic thermomechanical properties of the high temperature colorless shape memory polyimide film prepared in this embodiment. Figure 7 It can be seen that the glass transition temperature of the high-temperature colorless shape memory polyimide film prepared in Example 2 is 251°C. Fig. 9 The diagram shows the shape memory process of the high-temperature colorless shape memory polyimide film prepared in this embodiment. It can be seen from the diagram that the high-temperature colorless shape memory polyimide film prepared in Example 2 has a good shape memory effect.

[0058] Example 3

[0059] The high temperature colorless shape memory polyimide film of this embodiment is prepared according to the following steps:

[0060] 1. Add 25 mL of N,N-dimethylacetamide as solvent to a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlet and outlet, and introduce nitrogen. Add diamine 2,2′-bis(trifluoromethyl)-4,4′-diaminophenyl ether to the three-necked flask; stir in an ice-water bath until completely dissolved to obtain a diamine solution.

[0061] 2. Weigh the dried dianhydride monomer 4,4′-(hexafluoroisopropylidene)phthalic anhydride and bisphenol A diether dianhydride and mix them evenly, with the molar ratio of the substance amount being 4:6. Add the mixed dianhydride to the diamine solution in four times, with the molar ratio of the added mixed dianhydride to the diamine being 1:0.93, and polymerize for 24 hours in an ice water bath with high-speed stirring to obtain a polyamic acid solution.

[0062] 3. The polyamic acid solution is filtered and allowed to stand to defoam to obtain a uniform solution.

[0063] 4. Apply the defoamed PAA solution on the cleaned glass plate through a coating machine, control the wet film thickness to 250μm, and the solid content to 20%. Apply through the coating machine and gradually heat up to 180℃ for curing.

[0064] 5. Put the glass plate with PAA film into an electric heating blast drying oven for gradient temperature curing. The gradient temperature curing program is 80℃ / 2h, 120℃ / 2h, 150℃ / 2h, 180℃ / 2h, 210℃ / 2h, 240℃ / 2h, 280℃ / 2h.

[0065] 6. After high temperature treatment, the glass plate is placed in deionized water and the film is peeled off. The film is washed, dried, cut and tested to obtain a high temperature colorless shape memory polyimide film.

[0066] in, Figure 2 Shown is a finished product image of the high-temperature colorless shape memory polyimide film prepared in this embodiment. Figure 4 The infrared spectrum of the high-temperature colorless shape memory polyimide film prepared in this example is shown. These characteristic absorption peaks indicate that the high-temperature colorless shape memory polyimide film prepared in Example 3 has been completely imidized. Figure 6 The UV-Vis spectrum of the high temperature colorless shape memory polyimide film prepared in this embodiment is shown in FIG. Figure 6 It can be seen that the colorless and transparent polyimide film with a thickness of 50 μm has a light transmittance of 89.5% at 500 nm. Figure 8 The following are the dynamic thermomechanical properties of the high temperature colorless shape memory polyimide film prepared in this embodiment. Figure 8 It can be seen that the glass transition temperature of the high-temperature colorless shape memory polyimide film prepared in Example 3 is 245°C. Fig.10 The figure shows the shape memory process diagram of the high-temperature colorless shape memory polyimide film prepared in this embodiment. It can be seen from the figure that the high-temperature colorless shape memory polyimide film prepared in Example 3 has a good shape memory effect.

[0067] Example 4

[0068] The high temperature colorless shape memory polyimide film of this embodiment is prepared according to the following steps:

[0069] 1. Add 25 mL of N,N-dimethylacetamide as solvent to a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlet and outlet, and introduce nitrogen. Add the mixed diamine 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl and 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)benzene]hexafluoropropane to the three-necked flask, with the molar ratio of the substances being 5:5; stir in an ice-water bath until completely dissolved to obtain a mixed diamine solution.

[0070] 2. Weigh the dried dianhydride monomer bisphenol AF dianhydride and add it to the diamine solution four times, the molar ratio of the added dianhydride to the mixed diamine is 1:0.97, and carry out polymerization reaction for 24 hours in an ice water bath with high-speed stirring to obtain a polyamic acid solution.

[0071] 3. The polyamic acid solution is filtered and allowed to stand to defoam to obtain a uniform solution.

[0072] 4. Apply the defoamed PAA solution on the cleaned glass plate through a coating machine, control the wet film thickness to 250μm, and the solid content to 20%. Apply through the coating machine and gradually heat up to 180℃ for curing.

[0073] 5. Put the glass plate with PAA film into an electric heating blast drying oven for gradient temperature curing. The gradient temperature curing program is 80℃ / 2h, 120℃ / 2h, 150℃ / 2h, 180℃ / 2h, 210℃ / 2h, 240℃ / 2h, 280℃ / 2h.

[0074] 6. 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 bagged for storage to obtain a high temperature colorless shape memory polyimide film.

[0075] Example 5

[0076] The high temperature colorless shape memory polyimide film of this embodiment is prepared according to the following steps:

[0077] 1. Add 25 mL of N,N-dimethylacetamide as solvent to a 100 mL three-necked flask equipped with a mechanical stirrer and a nitrogen inlet and outlet, and introduce nitrogen. Add diamine 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene to the three-necked flask; stir in an ice-water bath until completely dissolved to obtain a diamine solution.

[0078] 2. Weigh the dried dianhydride monomers bisphenol AF dianhydride and 4,4'-oxydiphthalic anhydride and mix them evenly, with the molar ratio of the substance amount being 7:3. Add the mixed dianhydride to the diamine solution four times, with the molar ratio of the added mixed dianhydride to the diamine being 1:0.97, and polymerize for 24 hours in an ice water bath with high-speed stirring to obtain a polyamic acid solution.

[0079] 3. The polyamic acid solution is filtered and allowed to stand to defoam to obtain a uniform solution.

[0080] 4. Apply the defoamed PAA solution on the cleaned glass plate through a coating machine, control the wet film thickness to 250μm, and the solid content to 20%. Apply through the coating machine and gradually heat up to 180℃ for curing.

[0081] 5. Put the glass plate with PAA film into an electric heating blast drying oven for gradient temperature curing. The gradient temperature curing program is 80℃ / 2h, 120℃ / 2h, 150℃ / 2h, 180℃ / 2h, 210℃ / 2h, 240℃ / 2h, 280℃ / 2h.

[0082] 6. 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 bagged for storage to obtain a high temperature colorless shape memory polyimide film.

[0083] Example 6

[0084] The high temperature colorless shape memory polyimide film of this embodiment is prepared according to the following steps:

[0085] 1. Add 25 mL of N,N-dimethylacetamide as solvent to a 100 mL three-necked flask equipped with mechanical stirring and nitrogen inlet and outlet, and introduce nitrogen. Add the mixed diamine 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl and 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether to the three-necked flask, with the molar ratio of the substances being 2:8; stir in an ice-water bath until completely dissolved to obtain a mixed diamine solution.

[0086] 2. Weigh the dried dianhydride monomer bisphenol AF dianhydride and add it to the diamine solution four times, the molar ratio of the added dianhydride to the mixed diamine is 1:0.95, and carry out polymerization reaction for 24 hours in an ice water bath with high-speed stirring to obtain a polyamic acid solution.

[0087] 3. The polyamic acid solution is filtered and allowed to stand to defoam to obtain a uniform solution.

[0088] 4. Apply the defoamed PAA solution on the cleaned glass plate through a coating machine, control the wet film thickness to 250μm, and the solid content to 20%. Apply through the coating machine and gradually heat up to 180℃ for curing.

[0089] 5. Put the glass plate with PAA film into an electric heating blast drying oven for gradient temperature curing. The gradient temperature curing program is 80℃ / 2h, 120℃ / 2h, 150℃ / 2h, 180℃ / 2h, 210℃ / 2h, 240℃ / 2h, 280℃ / 2h.

[0090] 6. 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 bagged for storage to obtain a high temperature colorless shape memory polyimide film.

[0091] Those skilled in the art can understand that the above-mentioned embodiments are specific examples for implementing the present application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the present application. Any person skilled in the art can make their own changes and modifications without departing from the spirit and scope of the present application, so the scope of protection of the present application shall be based on the scope defined in the claims.

Claims

1. A high temperature colorless shape memory polyimide film, characterized in that: The high temperature colorless shape memory polyimide film has the following chemical structure: Wherein, a, b, c, d, e, m, n, and k are all positive integers between 0 and 1, and c and d must be 0 or 1 at the same time; R1 is R2, R5 are R3 is R4 is When a, c, and d are all 1, R2 and R5 must be the same; When a is 1, but c and d are not 1, then m is 0, n is 2, and the two R2 in the repeating unit are different: When c and d are 1, but a is not 1, n is 0, m is 2, and the two R5 in the repeating unit are different.

2. The high temperature colorless shape memory polyimide film according to claim 1, characterized in that: When the thickness of the high-temperature colorless shape memory polyimide film is 50 μm, the light transmittance of the high-temperature colorless shape memory polyimide film at 500 nm is between 87% and 90%, the glass transition temperature is between 240° C., the shape fixation rate is greater than 98.9%, and the shape recovery rate is greater than 99.4%.

3. The method for preparing a high temperature colorless shape memory polyimide film according to claim 1 or 2, characterized in that: The method comprises the following steps: 1) firstly adding a diamine monomer containing a trifluoromethyl structure into a high boiling point polar aprotic solvent; 2) Stir vigorously until the diamine is completely dissolved, then add a dianhydride monomer containing a hexafluoroisopropyl structure or a dianhydride monomer containing an ether bond structure, and react for 10 to 24 hours under nitrogen conditions at room temperature to obtain a polyamic acid solution with a certain solid content; 3) coating the polyamic acid solution after standing and defoaming on a clean and dry glass plate, and preparing a high-temperature colorless shape memory polyimide film by a thermal imidization method.

4. The method for preparing a high-temperature colorless shape memory polyimide film according to claim 3, characterized in that: The diamine monomer containing a trifluoromethyl structure includes at least one of: 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)benzene]hexafluoropropane, 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether, 2,2'-bis(trifluoromethyl)diaminobiphenyl, and 1,4-bis(2-trifluoromethyl-4-aminophenoxy)benzene; The dianhydride monomers containing a hexafluoroisopropyl structure include: 4,4′-(hexafluoroisopropylidene)phthalic anhydride, bisphenol AF dianhydride; The dianhydride monomer containing an ether bond structure includes at least one of bisphenol A type diether dianhydride and 4,4'-oxydiphthalic anhydride.

5. The method for preparing a high temperature colorless shape memory polyimide film according to claim 3, characterized in that: The thermal imidization method in step 3) comprises: 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 270°C to 300°C, and the imidization time is 2 hours.

6. The method for preparing a high-temperature colorless shape memory polyimide film according to claim 3, characterized in that: In the step 1), the high boiling point polar aprotic solvent is selected from one of N-methyl-2-pyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide.

7. The method for preparing a high temperature colorless shape memory polyimide film according to claim 3, characterized in that: The solid content of the polyamic acid in the polyamic acid solution in step 2) is 16 wt % to 20 wt %.

8. The method for preparing a high-temperature colorless shape memory polyimide film according to claim 3, characterized in that: The molar ratio of the diamine monomer containing a trifluoromethyl structure to the dianhydride monomer containing a hexafluoroisopropyl structure or the dianhydride monomer containing an ether bond structure is 1:(0.92-0.95).

9. Use of the high-temperature colorless shape memory polyimide film as claimed in claim 1 or 2 in the field of flexible optoelectronic devices.

10. The use according to claim 9, characterized in that: A temporary shape is obtained by shape memory weaving a high-temperature colorless shape memory polyimide film material, and the temporary shape can be expanded and restored to an initial shape by thermal stimulation.

Images