A class of monomers containing imide ring dimercapto groups, monomers containing imide ring diacetyl groups and preparation methods thereof, a photoresponsive polyimide material and preparation method thereof

Abstract

The present invention discloses a class of imide ring-containing dimercapto monomers, imide ring-containing diene monomers and preparation methods thereof, a light-responsive polyimide material and preparation method thereof, and relates to the technical field of light-driven materials. The present invention uses a dibasic acid anhydride as the basic monomer unit, and prepares a dimercapto monomer containing an imide structure and a monomer containing an imide ring-containing diene monomer by reacting with a monothiol compound and a monoalkyne compound, respectively. The two monomers are subjected to a thiol-alkyne click reaction to finally obtain a high molecular weight polyimide. The polyimide obtained by the present invention has excellent solubility, high tensile strength, good heat resistance and light transmittance; the polyimide material is placed under an ultraviolet lamp for uneven photocrosslinking to quickly obtain a light driver with excellent reversible driving performance.

Description

Technical Field

[0001] The present invention relates to the technical field of light-driven materials, and in particular to a class of monomers containing imide rings, light-responsive polyimide materials, and preparation methods and applications thereof. Background Art

[0002] Stimuli-responsive materials can deform, change color, or move in response to humidity, light, heat, pH, or magnetic fields. Their potential applications in artificial muscles, flexible robots, and sensors have attracted significant attention. Light is environmentally friendly and can provide energy to remote targets. Modulating the wavelength, intensity, and polarization of light can control the dynamic behavior of soft actuators. Therefore, light has become the preferred energy source for photoresponsive polymer materials. Currently, there are two approaches to preparing photoresponsive polymer materials. One is to introduce azo moieties into the polymer backbone, which induce trans-cis isomerization upon exposure to ultraviolet light to achieve macroscopic deformation. The other is to use a multilayer structure, combining a light-absorbing layer with an expansion / contraction layer to create a photoresponsive material. However, photoresponsive materials based on azo moieties suffer from slow response speeds, the need for visible light irradiation to restore their original shape, and poor thermal and mechanical properties. Furthermore, multilayer structures present issues with interfacial and dynamic fatigue. Furthermore, the preparation of currently reported photoresponsive materials is cumbersome, costly, and limited in functionality.

[0003] Polyimides are a class of specialty engineering materials containing imide units in their molecular backbone. Due to their excellent thermal and mechanical properties, low thermal expansion coefficient, and low dielectric constant, they have been widely used in key fields such as aerospace, microelectronics, and smart materials. There are two general methods for synthesizing polyimides, the most commonly used being the two-step process. However, the formation of high-molecular-weight polyamic acid often requires a reaction time of 24 hours or even several days. Thermal imidization dehydration requires temperatures exceeding 300°C, which is extremely labor-intensive and time-consuming. High-temperature treatment can also degrade the optical properties of the resulting material. Chemical imidization, which involves adding a dehydrating agent and catalyst to a polyamic acid solution, is gentler than thermal imidization. However, due to the limited activity of the monomers, some polymers have lower molecular weights. Furthermore, it is costly and has negative environmental impacts. The one-step process is only suitable for polyimides with ideal solubility. Poor solubility can lead to precipitation during polymerization as a gel or precipitate, resulting in a low molecular weight polymer. Furthermore, the high polymerization temperature and demanding dehydration conditions significantly limit its application. Therefore, considering that polyimide is at the forefront of polymer materials in terms of comprehensive performance and potential market value, it is challenging but of great significance to develop a new mild, efficient, and simple method to prepare photoresponsive polyimide materials with fast response speed and diverse functions. Summary of the Invention

[0004] In view of the deficiencies in the above-mentioned background technology, the present invention provides a simple preparation process and high yield of an imide ring-containing dithiol monomer, a diyne monomer and a preparation method thereof, and then uses the above-mentioned dithiol monomer containing an imide ring and the diyne monomer containing an imide ring to prepare a polyimide material through thiol-alkyne click polymerization. This polymerization can obtain a high molecular weight polyimide at room temperature without any catalyst reaction, and does not require an imidization process. Then, by simply treating the polyimide material with ultraviolet light, a photoresponsive polyimide material with fast response speed, high thermomechanical strength and diverse functionality can be obtained, thereby avoiding the tedious operations and costs in the preparation process of the photoresponsive polymer. The polyimide material is placed under an ultraviolet lamp for uneven photocrosslinking to quickly obtain a light actuator with excellent reversible driving performance.

[0005] The first object of the present invention is to provide a class of monomers containing imide rings, including the following compounds:

[0006] 、 、 ;

[0007] Wherein, R represents an ethynyl group or a thiol group;

[0008] X represents an aromatic ring or an aliphatic ring motif;

[0009] When R represents an ethynyl group, the compound is a diacetylenic monomer containing an imide ring;

[0010] When R represents a mercapto group, the compound is a dithiol monomer containing an imide ring.

[0011] Preferably, X represents any one of the following structural formulas:

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022] .

[0023] The second object of the present invention is to provide a method for preparing a monomer containing an imide ring, comprising the following steps:

[0024] In an inert atmosphere, a dibasic acid anhydride A is added to a carboxylic acid solvent B, and then a monothiol compound C or a monoalkynyl compound E and cyclohexane are added in sequence, and the mixture is heated to reflux for 5 to 10 hours. After post-treatment, the monomer containing the imide ring is obtained.

[0025] Preferably, the monothiol compound C is one or more of 2-mercaptoaniline, 3-aminothiophenol, and p-aminothiophenol; the monoalkynyl compound E is one or more of 2-aminophenylacetylene, 3-aminophenylacetylene, and p-aminophenylacetylene.

[0026] Preferably, the molar ratio of the dibasic acid anhydride A to the monothiol compound C or the monoalkynyl compound E is 1:2-5;

[0027] The molar ratio of the monothiol compound C or the monoalkynyl compound E to the carboxylic acid solvent B is 1:100-150;

[0028] The volume ratio of the cyclohexane to the carboxylic acid solvent B is 1:3-6;

[0029] Wherein, the carboxylic acid solvent B is one or more of formic acid, acetic acid, propionic acid, trifluoroacetic acid, perfluoropropionic acid, and trichloroacetic acid.

[0030] Preferably, the dibasic acid anhydride A is any one or a combination of the following acid anhydrides:

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039] .

[0040] The third object of the present invention is to provide a class of monomers containing imide rings for use in preparing photoresponsive polyimide materials.

[0041] A fourth object of the present invention is to provide a method for preparing a photoresponsive polyimide material, comprising the following steps:

[0042] A dithiol monomer containing an imide ring and a diacetyl monomer containing an imide ring are uniformly dispersed in an organic solvent G, and reacted at 20-80°C for 10-360 min under a nitrogen atmosphere. After the reaction is completed, the reaction solution is drained into methanol to precipitate a fibrous polymer to obtain product H;

[0043] The product H is dissolved in an organic solvent I, filtered through a PTFE filter, and then poured onto or spin-coated on a substrate. The polyimide film J is then dried in a vacuum oven at 60-120°C for 48-72 hours to obtain the polyimide film.

[0044] The polyimide film J was placed under a power density of 5 mW / cm 2 ~5 W / cm 2 , and irradiated under ultraviolet light with a wavelength of 10~450 nm for 1 min~24 h to obtain the photoresponsive polyimide material K.

[0045] The organic solvent G is any one of tetrahydrofuran, dioxane, toluene, chloroform, acetone, ethylene glycol dimethyl ether, acetonitrile, nitrobenzene, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, m-cresol, phenol, p-chlorophenol, o-dichlorobenzene, 1,2,4-trichlorobenzene, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, and ethyl acetate, or a combination thereof;

[0046] The organic solvent I is any one of tetrahydrofuran, dioxane, chloroform, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, m-cresol, phenol, p-chlorophenol, o-dichlorobenzene, 1,2,4-trichlorobenzene, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, and ethyl acetate, or a combination thereof.

[0047] A fifth object of the present invention is to provide a photoresponsive polyimide material.

[0048] A sixth object of the present invention is to provide an application of a photoresponsive polyimide material in a light actuator, a sensor, an artificial muscle or a soft robot.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention provides a class of monomers containing imide rings, photoresponsive polyimide materials, and their preparation methods and applications. The high molecular weight polyimide preparation method proposed by the present invention has high polymerization efficiency. A high molecular weight polyimide can be obtained by a rapid click reaction at room temperature for 15 minutes. The reaction conditions are mild and the process is simple, without the addition of any catalyst. The polymerization reaction has excellent spatial selectivity, and the click reaction of thiol and alkyne only undergoes one anti-Markovnikov addition. The obtained polyimide film has high heat resistance, excellent mechanical strength and good light transmittance. In addition, by adjusting the molecular structure of the dithiol and diyne monomers, the polyimide molecular chain structure can be diversified, giving the film different functionalities. Then, by simply treating the polyimide material with ultraviolet light, the photoresponsive property can be obtained, avoiding the cumbersome operations and costs in the preparation process of the photoresponsive polymer material. Furthermore, the large difference in thermal expansion coefficients between the upper and lower portions of the film after illumination results in a significant deformation in the film upon UV light exposure, which then recovers upon removal of the UV light, enabling the design of models of photocatapults and walking robots. Importantly, the polymer film exhibits a very fast response, with deformation occurring immediately upon UV light exposure and increasing with prolonged exposure. Furthermore, due to the high mechanical strength of polyimide, it can lift objects 30 times its own weight. Furthermore, by introducing aggregation-induced emission (AIE) motifs into the polyimide material, the photoresponsive polyimide material can be endowed with fluorescence emission and fluorescence patterning capabilities. Non-uniform photocrosslinking of this polyimide under UV light rapidly yields a photoactuator with excellent reversible actuation performance.

[0051] The high efficiency and mildness of the polyimide preparation method provided by the present invention benefit from the advantages of the thiol-alkyne click polymerization reaction. Click reaction is a concept proposed in 2001, representing a class of reactions with the advantages of mild conditions, atom economy, modularity, etc., of which the thiol-alkyne click reaction is one of them. Its free radical polymerization mechanism is not only fast and mild, but also does not produce any small molecule substances during the reaction process. We cleverly end-cap the imide moiety with acetylene and thiol at the same time, so that we can take advantage of the click reaction to prepare high molecular weight functional polyimide, which has the advantage of greatly simplified process compared with the traditional polyimide preparation method, that is, through dehydration condensation between dibasic acid anhydride and diamine. In addition, since both monomers contain rigid and highly heat-resistant imide moieties, the thermomechanical properties of the prepared polyimide are very excellent compared to other polymers obtained by thiol click reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of the preparation of photoresponsive polyimide materials

[0053] Figure 2 is the dynamic mechanical curve of polyimide film;

[0054] Figure 3 is the thermogravimetric curve of polyimide film;

[0055] Figure 4 is the stress-strain curve of polyimide film;

[0056] Figure 5 is the light transmittance of polyimide film;

[0057] Figure 6 Schematic diagram of the photoresponse of polyimide material. DETAILED DESCRIPTION

[0058] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0059] The present invention provides a class of imide ring-containing dimercapto monomers, imide ring-containing diene monomers and preparation methods thereof, as well as a photoresponsive polyimide material and preparation method thereof. The present invention uses a dibasic acid anhydride as a basic monomer unit, and prepares a dimercapto monomer containing an imide structure and a monomer containing an imide ring-containing diene monomer by reacting with a monothiol compound and a monoalkyne compound, respectively. The two monomers are subjected to a thiol-alkyne click reaction to ultimately obtain a high-molecular-weight polyimide. The polyimide preparation method proposed in the present invention does not require a complex imidization process and a polymerization time of up to 24-48 hours. It does not require any catalyst and can form a high-molecular-weight polyimide by reacting at room temperature for 15 minutes. The obtained polyimide has excellent solubility and can be prepared into thin films by solution processing, spin coating, etc. Several films have high tensile strength, good heat resistance and light transmittance. By simply treating the polyimide film with ultraviolet light, they created a photoresponsive polyimide material with fast response speed, high thermomechanical strength, and diverse functionality, thus avoiding the tedious steps and costs associated with preparing photoresponsive polymers. Under light induction, the photoresponsive film can rapidly respond to small temperature changes and exhibit large bending amplitudes.

[0060] The present invention uses a dibasic acid anhydride as the basic monomer unit, capped with a thiol group to produce a series of dithiol compounds containing imide rings. A series of diacetylenic monomers containing imide rings are capped with a triple bond, and these two monomers are subjected to thiol-acetylenic click polymerization to prepare a polyimide containing a photosensitive double bond. The resulting polyimide material is then treated with a simple ultraviolet light treatment to crosslink the double bonds in the surface layer of the film, thereby creating a large difference in thermal expansion coefficient with the underlying layer of the film, resulting in a photoresponsive polyimide material.

[0061] The first aspect of the present invention provides a class of monomers containing imide rings, including the following compounds:

[0062] 、 、 ;

[0063] Wherein, R represents an ethynyl group or a thiol group;

[0064] X represents an aromatic ring or an aliphatic ring motif;

[0065] When R represents an ethynyl group, the compound is a diacetylenic monomer containing an imide ring;

[0066] When R represents a mercapto group, the compound is a dithiol monomer containing an imide ring.

[0067] Wherein, X represents any one of the following structural formulas:

[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] .

[0079] A second aspect of the present invention provides a method for preparing a monomer containing an imide ring, comprising the following steps:

[0080] In an inert atmosphere, a dibasic acid anhydride A is added to a carboxylic acid solvent B, and then a monothiol compound C or a monoalkynyl compound E and cyclohexane are added in sequence, and the mixture is heated to reflux for 5 to 10 hours. After post-treatment, the monomer containing the imide ring is obtained.

[0081] Wherein, the monothiol compound C is one or more of 2-mercaptoaniline, 3-aminothiophenol, and p-aminothiophenol; the monoalkynyl compound E is one or more of 2-aminophenylacetylene, 3-aminophenylacetylene, and p-aminophenylacetylene.

[0082] The molar ratio of the dibasic acid anhydride A to the monothiol compound C or the monoalkynyl compound E is 1:2-5;

[0083] The molar ratio of the monothiol compound C or the monoalkynyl compound E to the carboxylic acid solvent B is 1:100-150;

[0084] The volume ratio of the cyclohexane to the carboxylic acid solvent B is 1:3-6;

[0085] Wherein, the carboxylic acid solvent B is one or more of formic acid, acetic acid, propionic acid, trifluoroacetic acid, perfluoropropionic acid, and trichloroacetic acid.

[0086] The dibasic acid anhydride A is any one or a combination of the following acid anhydrides:

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095] .

[0096] In one embodiment, a method for preparing a dithiol monomer containing an imide ring comprises the following steps:

[0097] Dibasic acid anhydride A was added to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, carboxylic acid solvent B was added and mechanical stirring was initiated. Monomercapto compound C and cyclohexane were then added sequentially and the system was heated to reflux. After reflux for 5-10 hours, the mixture was slowly cooled to 25°C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed with distilled water two to three times. The filter cake was dried in a vacuum oven at 80°C for 24 hours to obtain the imide ring-containing dimercapto compound D. The molar ratio of dibasic acid anhydride A to monomercapto compound C was 1:2-5, the molar ratio of monomercapto compound C to carboxylic acid solvent B was 1:100-150, and the volume ratio of cyclohexane to carboxylic acid solvent B was 1:3-6.

[0098] In one embodiment, a dithiol monomer containing an imide ring is prepared by reacting a dibasic acid anhydride with 2-aminothiophenol, 3-aminothiophenol, or p-aminothiophenol. The specific reaction scheme is as follows:

[0099] .

[0100] In one embodiment, a method for preparing a diacetylenic monomer containing an imide ring comprises the following steps:

[0101] Dibasic acid anhydride A was added to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, carboxylic acid solvent B was added and mechanical stirring was initiated. Monoacetylene compound E and cyclohexane were then added sequentially and the system was heated to reflux. After reflux for 5-10 hours, the mixture was slowly cooled to 25°C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed with distilled water two to three times. The filter cake was dried in a vacuum oven at 80°C for 24 hours to obtain the imide ring-containing diacetylene compound F. The molar ratio of dibasic acid anhydride A to monoacetylene compound E was 1:2-5, the molar ratio of monoacetylene compound E to carboxylic acid solvent B was 1:100-150, and the volume ratio of cyclohexane to carboxylic acid solvent B was 1:3-6.

[0102] In one embodiment, a dibasic acetylenic monomer containing an imide ring is prepared by reacting a dibasic acid anhydride with 2-aminophenylacetylene, 3-aminophenylacetylene, or 4-aminophenylacetylene. The specific reaction scheme is as follows:

[0103] .

[0104] A third aspect of the present invention provides the use of a class of monomers containing imide rings in the preparation of photoresponsive polyimide materials.

[0105] A fourth aspect of the present invention provides a method for preparing a photoresponsive polyimide material, comprising the following steps:

[0106] A dithiol monomer containing an imide ring and a diacetyl monomer containing an imide ring are uniformly dispersed in an organic solvent G, and reacted at 20-80°C for 10-360 min under a nitrogen atmosphere. After the reaction is completed, the reaction solution is drained into methanol to precipitate a fibrous polymer to obtain product H;

[0107] The product H is dissolved in an organic solvent I, filtered through a PTFE filter, and then poured onto or spin-coated on a substrate. The polyimide film J is then dried in a vacuum oven at 60-120°C for 48-72 hours to obtain the polyimide film.

[0108] The polyimide film J was placed under a power density of 5 mW / cm 2 ~5 W / cm 2, and irradiated under ultraviolet light with a wavelength of 10~450 nm for 1 min~24 h to obtain the photoresponsive polyimide material K.

[0109] The organic solvent G is any one of tetrahydrofuran, dioxane, toluene, chloroform, acetone, ethylene glycol dimethyl ether, acetonitrile, nitrobenzene, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, m-cresol, phenol, p-chlorophenol, o-dichlorobenzene, 1,2,4-trichlorobenzene, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, and ethyl acetate, or a combination thereof;

[0110] The organic solvent I is any one of tetrahydrofuran, dioxane, chloroform, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, m-cresol, phenol, p-chlorophenol, o-dichlorobenzene, 1,2,4-trichlorobenzene, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, and ethyl acetate, or a combination thereof.

[0111] In one embodiment, a method for preparing a photoresponsive polyimide material includes the following typical steps:

[0112] Step 1. To a mechanically stirred reaction vessel, add dithiol compound D, diacetylenic compound F, and organic solvent G in sequence. Stirring is continued at 20-80°C under a nitrogen atmosphere for 10-360 min. The molar ratio of dithiol compound D to compound F is 1:1-3, and the combined mass fraction of dithiol compound D and compound F is 5 wt%-30 wt%.

[0113] Step 2. After the reaction is completed, the reaction solution is drained into methanol using a glass rod to precipitate a fibrous polymer. After filtration, the filter cake is washed with methanol 2-3 times and dried in a vacuum oven at 60-120 °C for 8-24 h to obtain product H.

[0114] Step 3. Dissolve product H in organic solvent I to a solids content of 0.5 wt% to 40 wt%. Filter through a PTFE filter and cast or spin-coat the solution onto a horizontal glass plate or silicon wafer. Heat the glass plate or silicon wafer in a vacuum oven at 60-120°C for 48-72 hours. After cooling to room temperature, soak the film in deionized water, remove it, and vacuum dry it at 80-150°C for 12-24 hours to obtain a polyimide film J with a thickness of 100 nm to 400 μm.

[0115] Step 4. See Figure 1 As shown, the obtained polyimide film J was placed in a 2 ~5 W / cm 2, and irradiated under ultraviolet light with a wavelength of 10~450 nm for 1 min~24 h to obtain the photoresponsive polyimide material K.

[0116] In one embodiment, a high molecular weight polyimide is obtained by a thiol-alkyne click reaction between a dithiol compound containing an imide ring and a dialkynyl compound containing an imide ring. The reaction does not require any catalyst and can be completed in 2 hours at room temperature. The specific reaction route is as follows:

[0117]

[0118] Wherein, X, X1 and X2 are independently selected from any one of the following structural formulas:

[0119]

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129] .

[0130] A fifth aspect of the present invention provides a photoresponsive polyimide material.

[0131] A sixth aspect of the present invention provides an application of a photoresponsive polyimide material in a light actuator, a sensor, an artificial muscle or a soft robot.

[0132] In the application process, the laser used for the light response is ultraviolet light with a wavelength range below 450 nm.

[0133] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0134] Example 1

[0135] A method for preparing a photoresponsive polyimide film comprises the following steps:

[0136] 4.4424 g of 6FDA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.5038 g of p-aminothiophenol and 25 mL of cyclohexane were added sequentially, and the system was heated to reflux. After reflux for 8 hours, the reaction mixture was slowly cooled to 25 °C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 hours to obtain powdered product D (yield 94%). 4.4424 g of 6FDA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.3430 g of m-aminophenylacetylene and 25 mL of cyclohexane were added sequentially, and the system was heated to reflux. After reflux for 8 hours, the reaction mixture was slowly cooled to 25 °C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 h to obtain powdered product F (yield 91%). To a reaction vessel equipped with a mechanical stirrer, 0.6586 g of product D, 0.6425 g of product F, and 9 mL of tetrahydrofuran were added sequentially and stirred at 25 °C under a nitrogen atmosphere for 15 min. After the reaction, the reaction solution was poured into methanol to precipitate a fibrous solid product. The filter cake was filtered and washed three times with methanol. The filter cake was then dried in a vacuum oven at 80 °C for 20 h to obtain product J. 0.20 g of product J was dissolved in 5 g of N,N-dimethylformamide, filtered through a 220 nm PTFE filter cartridge, and poured onto a pre-leveled glass plate. The glass plate was heated in a vacuum oven at 60 °C for 72 h. After the temperature dropped to 25 °C, the plate was removed, soaked in deionized water for 2.5 h, and then the film was removed and dried in a vacuum oven at 150 °C for 24 h to obtain a polyimide film. The obtained polyimide film was placed under 100 mW / cm 2 The photoresponsive polyimide film was obtained by irradiating the film under a 365 nm ultraviolet lamp for 20 min.

[0137] Example 2

[0138] A method for preparing a photoresponsive polyimide film comprises the following steps:

[0139] 4.4424 g of 6FDA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.5038 g of 3-aminothiophenol and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After reflux for 8 hours, the reaction mixture was slowly cooled to 25 °C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 hours to obtain powdered product D (yield 89%). 4.4424 g of 6FDA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.3430 g of m-aminophenylacetylene and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After 8 hours of reflux, the reaction mixture was slowly cooled to 25°C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80°C for 24 hours to obtain powdered product F (yield 91%). To a reaction vessel equipped with a mechanical stirrer, 0.6586 g of product D, 0.6425 g of product F, and 9 mL of tetrahydrofuran were added sequentially and stirred at 25°C under a nitrogen atmosphere for 20 minutes. After the reaction, the reaction mixture was poured into methanol to precipitate a fibrous solid product. The product was filtered and the filter cake was washed three times with methanol. The filter cake was dried in a vacuum oven at 80°C for 20 hours to obtain product J. 0.40 g of product J was dissolved in 5 g of N,N-dimethylformamide, filtered through a 220 nm pore size tetrafluoroethylene filter cartridge, and poured onto a pre-leveled glass plate. The glass plate was treated in a vacuum oven at 60 °C for 72 h. After the temperature dropped to 25 °C, the glass plate was taken out and soaked in deionized water for 2.5 h. The film was then removed and dried in vacuum at 150 °C for 24 h to obtain a polyimide film. 2 The photoresponsive polyimide film was obtained by irradiating the film under a 365 nm ultraviolet lamp for 30 min.

[0140] Example 3

[0141] A method for preparing a photoresponsive polyimide film comprises the following steps:

[0142] 5.2049 g of BPADA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.5038 g of p-aminothiophenol and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After reflux for 8 hours, the reaction mixture was slowly cooled to 25°C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80°C for 24 hours to obtain powdered product D (yield 89%). 4.4424 g of 6FDA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.3430 g of m-aminophenylacetylene and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After reflux for 8 hours, the reaction mixture was slowly cooled to 25°C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 h to obtain powdered product F (yield 91%). To a reaction vessel equipped with a mechanical stirrer, 0.7348 g of product D, 0.6425 g of product F, and 9 mL of tetrahydrofuran were added sequentially and stirred at 25 °C under a nitrogen atmosphere for 30 min. After completion of the reaction, the reaction solution was poured into methanol to precipitate a fibrous solid product. The filter cake was filtered and washed three times with methanol. The filter cake was then dried in a vacuum oven at 80 °C for 20 h to obtain product J. 0.40 g of product J was dissolved in 5 g of N,N-dimethylformamide, filtered through a 220 nm PTFE filter cartridge, and poured onto a pre-leveled glass plate. The glass plate was heated in a vacuum oven at 60 °C for 72 h. After the temperature dropped to 25 °C, the plate was removed, soaked in deionized water for 2.5 h, and then the film was removed and dried in a vacuum oven at 150 °C for 24 h to obtain a polyimide film. The obtained polyimide film was placed under 200 mW / cm 2 The photoresponsive polyimide film was obtained by irradiating the film under a 365 nm ultraviolet lamp for 20 min.

[0143] Example 4

[0144] A method for preparing a photoresponsive polyimide film comprises the following steps:

[0145] 5.2049 g of BPADA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.5038 g of p-aminothiophenol and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After reflux for 8 hours, the mixture was slowly cooled to 25 °C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 hours to obtain powdered product D (yield 89%). 5.2049 g of BPADA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.3430 g of m-aminophenylacetylene and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After reflux for 8 hours, the mixture was slowly cooled to 25 °C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 h to obtain powdered product F (yield 93%). To a reaction vessel equipped with a mechanical stirrer, 0.7348 g of product D, 0.7188 g of product F, and 9 mL of tetrahydrofuran were added sequentially and stirred at 25 °C under a nitrogen atmosphere for 20 min. After completion of the reaction, the reaction solution was poured into methanol to precipitate a fibrous solid product. The filter cake was filtered and washed three times with methanol. The filter cake was then dried in a vacuum oven at 80 °C for 20 h to obtain product J. 0.40 g of product J was dissolved in 5 g of N,N-dimethylacetamide, filtered through a 220 nm PTFE filter cartridge, and poured onto a pre-leveled glass plate. The glass plate was heated in a vacuum oven at 60 °C for 72 h. After the temperature dropped to 25 °C, the glass plate was removed, soaked in deionized water for 2.5 h, and then the film was removed and dried in a vacuum oven at 150 °C for 24 h to obtain a polyimide film. The obtained polyimide film was placed under 100 mW / cm 2 The photoresponsive polyimide film was obtained by irradiating the film under a 405 nm ultraviolet lamp for 30 min.

[0146] Example 5

[0147] A method for preparing a photoresponsive polyimide film comprises the following steps:

[0148] 5.2049 g of BPADA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.5038 g of p-aminothiophenol and 25 mL of cyclohexane were added sequentially, and the system was heated to reflux. After reflux for 8 hours, the reaction solution was slowly cooled to 25 °C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 hours to obtain powdered product D (yield 89%). 3.1022 g of a-ODPA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.3430 g of m-aminophenylacetylene and 25 mL of cyclohexane were added sequentially, and the system was heated to reflux. After 8 hours of reflux, the mixture was slowly cooled to 25°C. The reaction mixture was poured into distilled water, filtered, and the filter cake washed three times with distilled water. The filter cake was dried in a vacuum oven at 80°C for 24 hours to obtain powdered product F (90% yield). To a reaction vessel equipped with a mechanical stirrer, 0.7348 g of product D, 0.5085 g of product F, and 9 mL of tetrahydrofuran were added sequentially and stirred at 25°C under a nitrogen atmosphere for 15 minutes. After completion of the reaction, the reaction mixture was poured into methanol to precipitate a fibrous solid product. The product was filtered and the filter cake washed three times with methanol. The filter cake was dried in a vacuum oven at 80°C for 20 hours to obtain product J. 0.40 g of product J was dissolved in 5 g of N,N-dimethylacetamide, filtered through a 220 nm pore size tetrafluoroethylene filter cartridge, and poured onto a pre-leveled glass plate. The glass plate was treated in a vacuum oven at 60 °C for 72 h. After the temperature dropped to 25 °C, the glass plate was taken out and soaked in deionized water for 2.5 h. The film was then removed and dried in vacuum at 150 °C for 24 h to obtain a polyimide film. 2 The photoresponsive polyimide film was obtained by irradiating the film under a 365 nm ultraviolet lamp for 20 min.

[0149] Example 6

[0150] A method for preparing a photoresponsive polyimide film comprises the following steps:

[0151] 4.4424 g of 6FDA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.5038 g of p-aminothiophenol and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After reflux for 8 hours, the reaction mixture was slowly cooled to 25 °C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 hours to obtain powdered product D (yield 94%). 3.1022 g of a-ODPA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.3430 g of m-aminophenylacetylene and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After 8 hours of reflux, the reaction mixture was slowly cooled to 25°C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80°C for 24 hours to obtain powdered product F (yield 93%). To a reaction vessel equipped with a mechanical stirrer, 0.6586 g of product D, 0.5085 g of product F, and 9 mL of tetrahydrofuran were added sequentially and stirred at 25°C under a nitrogen atmosphere for 20 minutes. After the reaction, the reaction mixture was poured into methanol to precipitate a fibrous solid product. The product was filtered and the filter cake was washed three times with methanol. The filter cake was dried in a vacuum oven at 80°C for 20 hours to obtain product J. 0.30 g of product J was dissolved in 5 g of N,N-dimethylformamide, filtered through a 220 nm pore size tetrafluoroethylene filter cartridge, and poured onto a pre-leveled glass plate. The glass plate was treated in a vacuum oven at 60 °C for 72 h. After the temperature dropped to 25 °C, the glass plate was taken out and soaked in deionized water for 2.5 h. The film was then removed and dried in vacuum at 150 °C for 24 h to obtain a polyimide film. 2 The photoresponsive polyimide film was obtained by irradiating the film under a 365 nm ultraviolet lamp for 40 min.

[0152] Example 7

[0153] A method for preparing a photoresponsive polyimide film comprises the following steps:

[0154] 4.4424 g of 6FDA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.5038 g of 3-aminothiophenol and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After reflux for 8 hours, the reaction mixture was slowly cooled to 25 °C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 hours to obtain powdered product D (yield 89%). 3.1022 g of a-ODPA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.3430 g of m-aminophenylacetylene and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After 8 hours of reflux, the mixture was slowly cooled to 25°C. The reaction mixture was poured into distilled water, filtered, and the filter cake washed three times with distilled water. The filter cake was dried in a vacuum oven at 80°C for 24 hours to obtain powdered product F (yield 93%). To a reaction vessel equipped with a mechanical stirrer, 0.6586 g of product D, 0.5085 g of product F, and 9 mL of tetrahydrofuran were added sequentially and stirred at 25°C under a nitrogen atmosphere for 20 minutes. After completion of the reaction, the reaction mixture was poured into methanol to precipitate a fibrous solid product. The product was filtered and the filter cake washed three times with methanol. The filter cake was dried in a vacuum oven at 80°C for 20 hours to obtain product J. 0.40 g of product J was dissolved in 5 g of N,N-dimethylformamide, filtered through a 220 nm pore size tetrafluoroethylene filter cartridge, and poured onto a pre-leveled glass plate. The glass plate was treated in a vacuum oven at 60 °C for 72 h. After the temperature dropped to 25 °C, the glass plate was taken out and soaked in deionized water for 2.5 h. The film was then removed and dried in vacuum at 150 °C for 24 h to obtain a polyimide film. 2 The photoresponsive polyimide film was obtained by irradiating the film under a 365 nm ultraviolet lamp for 20 min.

[0155] Example 8

[0156] A method for preparing a photoresponsive polyimide film comprises the following steps:

[0157] 5.2049 g of BPADA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.5038 g of 2-mercaptoaniline and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After reflux for 8 hours, the reaction mixture was slowly cooled to 25 °C. The reaction mixture was poured into distilled water, filtered, and the filter cake was washed three times with distilled water. The filter cake was dried in a vacuum oven at 80 °C for 24 hours to obtain powdered product D (90% yield). 3.1022 g of a-ODPA was added all at once to a three-necked flask equipped with a water separator and a condenser reflux apparatus. Under an argon atmosphere, 121 g of acetic acid was added with mechanical stirring. 2.3430 g of m-aminophenylacetylene and 25 mL of cyclohexane were then added sequentially, and the system was heated to reflux. After 8 hours of reflux, the mixture was slowly cooled to 25°C. The reaction mixture was poured into distilled water, filtered, and the filter cake washed three times with distilled water. The filter cake was dried in a vacuum oven at 80°C for 24 hours to obtain powdered product F (90% yield). To a reaction vessel equipped with a mechanical stirrer, 0.7348 g of product D, 0.5085 g of product F, and 9 mL of tetrahydrofuran were added sequentially and stirred at 25°C under a nitrogen atmosphere for 15 minutes. After completion of the reaction, the reaction mixture was poured into methanol to precipitate a fibrous solid product. The product was filtered and the filter cake washed three times with methanol. The filter cake was dried in a vacuum oven at 80°C for 20 hours to obtain product J. 0.10 g of product J was dissolved in 5 g of N,N-dimethylacetamide, filtered through a 220 nm pore size tetrafluoroethylene filter cartridge, and poured onto a pre-leveled glass plate. The glass plate was treated in a vacuum oven at 60 °C for 72 h. After the temperature dropped to 25 °C, the glass plate was taken out and soaked in deionized water for 2.5 h. The film was then removed and dried in vacuum at 150 °C for 24 h to obtain a polyimide film. 2 The photoresponsive polyimide film was obtained by irradiating the film under a 365 nm ultraviolet lamp for 20 min.

[0158] Reference 1: Yanlei Yu et al., Multiple Shape Manipulation of Azobenzene-Containing Polyimide by Combining Shape Memory Effect, Photofixity, and Photodeformation, ACS Macro Lett. 2023, 12, 921−927, reported the preparation of photoresponsive polyimide actuators using diamines, triamines, and dibasic anhydrides containing azobenzene units in their side chains. Their mechanism of actuation is cis-trans isomerization of the azo moiety under UV and visible light. However, this operation requires dual-wavelength light to drive reversible behavior and is slow, with a bending rate of approximately 88° after 16 seconds of UV irradiation. The PI actuator prepared in this paper can bend 180° after 3 seconds of UV irradiation and returns to its original shape upon removal of the UV light, demonstrating reversibility without the need for visible light irradiation. Reference 2: Loon-Seng Tan et al, PhotomechanicalDeformation of Azobenzene-Functionalized Polyimides Synthesized with BulkySubstituents, ACS Macro Lett. 2017, 6, 1432−1437. The intrinsic PI drivers reported so far also utilize the introduction of azobenzene elements to achieve reversible actuation and suffer from the same drawbacks. Therefore, the present invention has certain advantages.

[0159] In order to illustrate the relevant properties of the photoresponsive polyimide film provided by the present invention, the following description is provided with reference to the accompanying drawings.

[0160] Figure 2 Figure 2 is the dynamic mechanical curve of the polyimide film; 6FDA-6FSH is the film prepared in Example 1, BPADA-6FSH is the film prepared in Example 3, and a-ODPA-6FSH is the film prepared in Example 6. It can be seen that the glass transition temperatures of the three PI films are between 225°C and 250°C.

[0161] Figure 3 Figure 2 is the thermogravimetric curve of polyimide films; 6FDA-6FSH is the film prepared in Example 1, BPADA-6FSH is the film prepared in Example 3, and a-ODPA-6FSH is the film prepared in Example 6. The 5% mass loss temperature for all three polyimide films is above 450°C, with 6FDA-6FSH having the highest mass loss temperature at 482°C.

[0162] Figure 4 Figure 5 is the stress-strain curve of the polyimide films; 6FDA-6FSH is the film prepared in Example 1, BPADA-6FSH is the film prepared in Example 3, and a-ODPA-6FSH is the film prepared in Example 6. The three PI films exhibit high mechanical properties, with tensile strengths ranging from 100 to 120 MPa.

[0163] Figure 5 is the light transmittance of the polyimide film; 6FDA-6FSH is the film prepared in Example 1, BPADA-6FSH is the film prepared in Example 3, and a-ODPA-6FSH is the film prepared in Example 6. The three PI films have excellent light transmittance, exceeding 75% at 450 nm, which is much higher than that of traditional commercial Kapton films.

[0164] Figure 6 The 6FDA-6FSH film prepared in Example 1 was placed under a UV lamp (100 mw / cm 2 ) irradiated for 20 min, a polyimide actuator with responsive movement was obtained. Figure 6 Figure a in the middle shows a photo of the reversible actuator. It can be seen that when placed under UV light, the actuator bends 180° in 3.81 seconds and almost returns to its original shape after the UV light is turned off. Figure 6 Figure b shows the change in the bending angle of the PI film during light switching. Figure 6 Figure c shows the change in the distance between the two ends of the PI film as the light is switched on and off. When placed under ultraviolet light, the length of the two ends of the film is shortened from 1.5 cm to 0.4 cm. When the ultraviolet light is turned off, it almost returns to its original length. Importantly, this process is reversible.

[0165] Table 1 shows the weight average molecular weight and PDI of several polyimides

[0166]

[0167] From Table 1, we can see that several PIs have very high weight-average molecular weights exceeding 10w, and PDIs ranging from 1.38 to 2.68.

[0168] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a photoresponsive polyimide material, characterized in that: The following steps are involved: A dithiol monomer containing an imide ring and a diacetyl monomer containing an imide ring are uniformly dispersed in an organic solvent G, and reacted at 20-80°C for 10-360 minutes under a nitrogen atmosphere. After the reaction is completed, the reaction solution is drained into methanol to precipitate a fibrous polymer to obtain product H; The product H is dissolved in an organic solvent I, filtered through a PTFE filter element, and then poured or spin-coated onto a substrate, and then treated in a vacuum oven at 60-120°C for 48 h-72 h to obtain a polyimide film J; The polyimide film J was placed under a power density of 5 mW / cm 2 ~5 W / cm 2 , irradiated under ultraviolet light with a wavelength of 10-450 nm for 1 min-24 h to obtain the photoresponsive polyimide material K; The organic solvent G is any one of tetrahydrofuran, dioxane, toluene, chloroform, acetone, ethylene glycol dimethyl ether, acetonitrile, nitrobenzene, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, m-cresol, phenol, p-chlorophenol, o-dichlorobenzene, 1,2,4-trichlorobenzene, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, and ethyl acetate, or a combination thereof; The organic solvent I is any one of tetrahydrofuran, dioxane, chloroform, dichloromethane, N,N-dimethylformamide, N,N-dimethylacetamide, m-cresol, phenol, p-chlorophenol, o-dichlorobenzene, 1,2,4-trichlorobenzene, N-methylpyrrolidone, dimethyl sulfoxide, γ-butyrolactone, and ethyl acetate, or a combination thereof; The structures of the dithiol monomer containing an imide ring and the diacetyl monomer containing an imide ring both include the following compounds: 、 、 Wherein, when R represents an ethynyl group, the compound is a diacetylene monomer containing an imide ring; When R represents a mercapto group, the compound is a dithiol monomer containing an imide ring; X represents any one of the following structural formulas: 。 2. The method for preparing a light-responsive polyimide material according to claim 1, wherein: The dithiol monomer containing an imide ring or the diacetyl monomer containing an imide ring is prepared according to the following steps: In an inert atmosphere, a dibasic acid anhydride A is added to a carboxylic acid solvent B, and then a monothiol compound C or a monoalkynyl compound E and cyclohexane are added in sequence. The mixture is heated and refluxed for 5 to 10 hours. After post-treatment, a dithiol monomer containing an imide ring or a dialkynyl monomer containing an imide ring is obtained.

3. The method for preparing the light-responsive polyimide material according to claim 2, wherein: The monothiol compound C is one or more of 2-mercaptoaniline, 3-aminothiophenol, and p-aminothiophenol; the monoalkynyl compound E is one or more of 2-aminophenylacetylene, 3-aminophenylacetylene, and p-aminophenylacetylene.

4. The method for preparing a light-responsive polyimide material according to claim 2, wherein: The molar ratio of the dibasic acid anhydride A to the monothiol compound C or the monoalkynyl compound E is 1:2-5; The molar ratio of the monothiol compound C or the monoalkynyl compound E to the carboxylic acid solvent B is 1:100-150; The volume ratio of the cyclohexane to the carboxylic acid solvent B is 1:3-6; Wherein, the carboxylic acid solvent B is one or more of formic acid, acetic acid, propionic acid, trifluoroacetic acid, perfluoropropionic acid, and trichloroacetic acid.

5. The method for preparing a light-responsive polyimide material according to claim 2, wherein: The dibasic acid anhydride A is any one or a combination of the following acid anhydrides: 。 6. A photoresponsive polyimide material obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the photoresponsive polyimide material according to claim 6 in optical actuators, sensors, artificial muscles or soft robots.

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