A soluble dynamic photo-induced deformation polyimide-polyurea and a preparation method and application thereof

Abstract

This invention relates to a soluble, dynamically photodeformable polyimide-polyurea, its preparation method, and its applications. Isocyanate monomers are placed in a reactor, and a polar aprotic solvent is added to dissolve the isocyanate monomers. A diamine monomer containing an azophenyl group and flexible groups is dissolved in the polar aprotic solvent. The solution containing the diamine monomer is then introduced into the reactor for reaction. After the reaction is complete, a dianhydride monomer is added, and a polyamic acid solution is obtained through a condensation polymerization reaction. The polyamic acid solution is coated onto a substrate, and thermal imidization is completed by programmed temperature rise on a hot stage to obtain a soluble, dynamically photodeformable polyimide-polyurea thin film material. This invention introduces isocyanate groups into the material system to form strong hydrogen bonds, preparing an azophenyl polyimide-polyurea structure with dynamically reversible properties. The material of this invention can maintain basic properties while also exhibiting excellent photodeformation properties.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and in particular relates to a soluble dynamic photodeformable polyimide-polyurea, its preparation method and application. Background Technology

[0002] Polyimide materials, due to their rigid backbone structure, possess excellent mechanical properties, thermal stability, chemical stability, and dielectric properties, making them widely used as high-performance engineering materials in aerospace, chemical, and electronic information fields. With the advent of the intelligent era, polyimide materials with stimulus-responsive deformation capabilities have attracted increasing attention. Among them, polyimide materials with photo-induced deformation capabilities have become a hot topic due to the advantages of light, such as its cleanliness, long-range capability, and precision.

[0003] Photodeformable materials containing photosensitive groups can convert light energy into mechanical energy output, and the magnitude of the generated mechanical energy is directly related to the material's stiffness (modulus). Photodeformable polyimides combine excellent thermal stability, mechanical properties, and remotely driven deformation characteristics, and are expected to be gradually applied to high-temperature actuators, space-deployable structures, and soft robots operating in special environments. Introducing photoresponsive azophenyl groups into the polyimide molecular structure is the most direct method for preparing photodeformable polyimides. However, polyimide materials have a stable molecular structure with strong cross-linking networks and intermolecular interactions between molecular chains, making rapid movement difficult. Therefore, photodeformation behavior of polyimide films only occurs at relatively low thicknesses, making it difficult to fabricate photo-controlled actuators with load-bearing capacity and more functions. Currently, there are two main strategies reported to improve the photodeformability of azophenyl polyimide materials: one is to introduce flexible segments on both sides of the azophenyl unit in the main chain; the other is to attach azophenyl groups as side chains to the polyimide. However, these methods reduce the rigidity of the polyimide molecular chain and the inter-chain interactions, thus sacrificing the excellent heat resistance and mechanical properties of polyimide. Furthermore, during use, polyimide will develop defects of varying degrees due to prolonged thermal and mechanical stress. These defects will continue to grow, reducing the stability of the material and causing damage to the equipment.

[0004] Chinese patent CN114163637B discloses an azophenyl polyimide film material with reversible photodeformation properties, its preparation and application. The preparation method of the material includes the following steps: 1) dissolving a diamine monomer containing an azophenyl group and a dianhydride monomer containing X in a polar aprotic solvent and carrying out a condensation polymerization reaction to obtain a polyamic acid solution; 2) coating the polyamic acid solution onto a substrate and carrying out thermal imidization to obtain a polyimide film material; 3) thermally stretching the polyimide film material; in application, ultraviolet light and visible light are used as the driving source for photodeformation.

[0005] Chinese patent CN115197420B discloses a photodeformable azophenyl polyimide thin film material that requires no orientation and is not controlled by polarized light, and its preparation method. First, a diamine monomer containing azophenyl side chains is synthesized. Then, the monomer is placed in a reactor, deoxygenated, and a polar aprotic solvent is added to dissolve the diamine monomer containing azophenyl side chains. Next, a dianhydride monomer is dissolved in the polar aprotic solvent. After the dianhydride monomer is completely dissolved, the solution containing the dianhydride monomer is added to the reactor, and a polyamic acid solution is generated through condensation polymerization. After the reaction is complete, the polyamic acid solution is coated onto a substrate, and thermal imidization is completed by programmed temperature rise to obtain the photodeformable azophenyl polyimide thin film material that requires no orientation and is not controlled by polarized light.

[0006] However, the thermal and mechanical properties of the polyimide film materials in the aforementioned existing patents need to be improved. They cannot simultaneously achieve excellent heat resistance, mechanical properties, and photodeformation properties, and the materials also lack self-healing properties. Summary of the Invention

[0007] Given that existing technologies cannot simultaneously achieve heat resistance, mechanical properties, and photodeformation properties in polyimides, this invention provides a soluble, dynamically photodeformable polyimide-polyurea, its preparation method, and its applications.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] This invention first provides a soluble, dynamically photodeformable polyimide-polyurea, which is an azobenzene polyimide-polyurea, and its molecular structure contains the following units:

[0010]

[0011]

[0012] Where m and n represent the degree of polymerization.

[0013] X is a tetravalent aromatic hydrocarbon group or an aliphatic hydrocarbon group.

[0014] Z represents the isocyanate group that provides hydrogen bonding.

[0015] W is a diamine monomer with a flexible group.

[0016] Y is a diamine residue containing an azophenyl group.

[0017] In one embodiment of the present invention, X is selected from one of the following tetravalent aromatic hydrocarbon group or aliphatic hydrocarbon group structural formulas:

[0018]

[0019]

[0020] In one embodiment of the present invention, Z is selected from one of the following structural formulas:

[0021] In one embodiment of the present invention, W is selected from one of the following structural formulas:

[0022]

[0023] In one embodiment of the present invention, the general structural formula of Y is as follows:

[0024]

[0025] Where R is chosen from C2, C3, C4, C5, C6, C7, C8, C9, C 10 C 11 C 12 Hydrocarbon group.

[0026] The present invention further provides a soluble dynamic photodeformable polyimide-polyurea thin film material prepared based on the aforementioned soluble dynamic photodeformable polyimide-polyurea.

[0027] The present invention further provides a method for preparing a soluble dynamic photodeformable polyimide-polyurea thin film material, comprising the following steps:

[0028] The isocyanate monomer is placed in a reactor, and a polar aprotic solvent is added to dissolve the isocyanate monomer.

[0029] The diamine monomer containing azophenyl and a flexible group is dissolved in a polar aprotic solvent, and the solution containing the diamine monomer is fed into a reactor to carry out the reaction.

[0030] After the reaction is complete, dianhydride monomer is added, and polyamic acid (PAA) solution is obtained through condensation polymerization.

[0031] A polyamic acid solution was coated onto a substrate and placed on a hot stage for programmed temperature rise to complete thermal imidization, resulting in a soluble dynamic photodeformable polyimide-polyurea film material.

[0032] The structures of the isocyanate monomer, diamine monomer, and dianhydride monomer satisfy the molecular structure of the final soluble dynamic photodeformable polyimide-polyurea as defined above.

[0033] In one embodiment of the present invention, the molar ratio of dianhydride monomer to diamine monomer is 1:1 to 1:1.01, and the molar ratio of isocyanate monomer to dianhydride monomer is 1:15 to 1:6.

[0034] In one embodiment of the present invention, the polar aprotic solvent is any one of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF) or N-methylpyrrolidone (NMP).

[0035] In one embodiment of the present invention, the solid content of the polyamic acid solution is 10% to 15%.

[0036] In one embodiment of the present invention, the reaction temperature is 25°C-90°C, and the condensation polymerization reaction time is 12h-24h, preferably 12-16h.

[0037] In one embodiment of the present invention, the thermal imidization process temperature is as follows: heating to 80°C and reacting for 1 hour, then heating to 100°C and reacting for 1 hour, then heating to 150°C and reacting for 1 hour, then heating to 200°C and reacting for 1 hour, and finally heating to 250°C and reacting for 1 hour.

[0038] In one embodiment of the present invention, the temperature for dissolving the isocyanate monomer is 25°C-90°C.

[0039] In one embodiment of the invention, a polar aprotic solvent is added to the reactor containing the isocyanate monomer using a syringe.

[0040] In one embodiment of the invention, a syringe is used to inject a solution containing a diamine monomer into a reactor.

[0041] The present invention also provides the application of soluble dynamic photodeformable polyimide-polyurea thin film materials for the preparation of photodeformable materials or photodeformable devices.

[0042] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0043] This invention starts with molecular structure design, introducing isocyanate groups into the material system to form strong hydrogen bonds, thus preparing an azophenyl polyimide-polyurea structure with dynamic reversible properties. Previously, most azophenyl polyimides required the addition of crosslinking agents to prepare films, making them difficult to dissolve and recycle, and also limiting their photodeformation capabilities to some extent. This invention simplifies the process and reduces costs by introducing dynamic hydrogen bonds into the polyimide backbone to form a physical crosslinking network.

[0044] Hydrogen bonding generated by urea bonds enhances the intermolecular forces of the material, improving its heat resistance and mechanical properties. More importantly, the reversible dissociation of hydrogen bonds under light can modulate intermolecular interactions. During dissociation, the intermolecular interactions weaken, the modulus of azophenyl polyimide decreases, and this facilitates deformation. Therefore, the introduction of hydrogen bonds makes azophenyl polyimide a photosensitive stiffness material, enabling it to maintain its basic properties while exhibiting excellent photosensitive deformation performance. Simultaneously, dynamic hydrogen bonding endows the material with good solubility and self-healing properties, allowing for repeated recycling.

[0045] This application innovates on the molecular structure of the material by introducing polyurea segments into azophenyl polyimide, thus preparing an azophenyl polyimide-polyurea structure with dynamic reversible properties. Its advantages are mainly reflected in the fact that the hydrogen bonding generated by the urea bonds not only enhances the intermolecular interactions of the material, improving its heat resistance and mechanical properties, but also significantly enhances the system's photodeformation capability due to the mechanism of hydrogen bond dissociation under light irradiation. Furthermore, as a physical cross-linking structure, hydrogen bonds also endow the material with excellent solubility and self-healing properties, improving its recyclability. For example, the glass transition temperature of the material system in this application is 320°C, while the materials in the prior art patents CN114163637B and CN115197420B have glass transition temperatures of 147°C and 195°C, respectively; the elastic modulus of the azobenzene polyimide-polyurea material in this application is 2.4 GPa, while the materials in the prior art patents CN114163637B and CN115197420B have elastic moduli of 1.2 GPa and 1.35 GPa, respectively. Attached Figure Description

[0046] Figure 1 Synthetic pathway diagram of azobenzene polyimide-polyurea;

[0047] Figure 2 Comparison of the energy storage modulus of azobenzene polyimide and azobenzene polyimide-polyurea before and after ultraviolet irradiation;

[0048] Among them, (a) compares the storage modulus of hydrogen-free azobenzene polyimide before and after ultraviolet irradiation; (b) compares the storage modulus of hydrogen-bonded azobenzene polyimide-polyurea before and after ultraviolet irradiation.

[0049] Figure 3 The photoinduced deformation results of thin films;

[0050] Figure 4 The self-healing results of the thin film;

[0051] Among them, (a) the self-healing ability of the film and (b) the stress-strain curves of the film before and after damage self-healing. Detailed Implementation

[0052] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0053] Example 1

[0054] This embodiment provides a method for synthesizing azobenzene polyimide-polyurea. The synthetic route is referenced below. Figure 1 .

[0055] In this embodiment, the monomers used are 4,4-diphenylmethane diisocyanate (MDI), p-diaminoazobenzene (DAAB), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and hexafluoroisopropylphthalic anhydride (6FDA).

[0056] MDI (0.14 g, 0.563 mmol) was added to a 100 mL round-bottom flask, followed by 26.70 mL of N-methylpyrrolidone to dissolve it. After the MDI was completely dissolved, BAPP (0.69 g, 1.69 mmol) and DAAB (1.08 g, 5.07 mmol) were added to the solution and stirred until dissolved. Finally, 6 FDA (3.00 g, 6.76 mmol) was added, and the reaction was carried out for 12 h to prepare a polyamic acid (PAA) solution.

[0057] After filtration, polyamic acid was uniformly drop-coated onto a clean glass plate. The temperature was increased according to the following procedure: 80°C for 1 hour, then 100°C for 1 hour, then 150°C for 1 hour, then 200°C for 1 hour, and finally 250°C for 1 hour. The heating was then turned off, and the plate was allowed to cool naturally to room temperature. The glass plate containing the film was then placed in water. After the film separated from the glass plate, it was washed and dried to obtain a soluble, dynamically photodeformable polyimide-polyurea film material, referred to simply as the film material.

[0058] Comparative Example 1

[0059] This comparative example provides a method for synthesizing hydrogen-bonded azobenzene polyimide.

[0060] In a 100 mL round-bottom flask, add BAPP (0.69 g, 1.69 mmol) and DAAB (1.08 g, 5.07 mmol), then add 26.00 mL of N-methylpyrrolidone and stir until completely dissolved. Finally, add 6 FDA (3.00 g, 6.76 mmol) and react for 12 h to prepare a polyamic acid (PAA) solution.

[0061] After filtration, polyamic acid was evenly drop-coated onto a clean glass plate. The temperature was increased according to the following procedure: 80°C for 1 hour, then 100°C for 1 hour, then 150°C for 1 hour, then 200°C for 1 hour, and finally 250°C for 1 hour. The heating was then turned off, and the mixture was allowed to cool naturally to room temperature. The glass plate containing the film was then placed in water. After the film separated from the glass plate, it was washed and dried to obtain the film material.

[0062] Example 2

[0063] This embodiment provides a method for synthesizing azobenzene polyimide-polyurea containing dicyclohexylmethane diisocyanate (HMDI).

[0064] HMDI (0.147 g, 0.563 mmol) was added to a 100 mL round-bottom flask, followed by 26.70 mL of N-methylpyrrolidone for dissolution. After the HMDI was completely dissolved, BAPP (0.69 g, 1.69 mmol) and DAAB (1.08 g, 5.07 mmol) were added to the solution at 45 °C and stirred until dissolved. Finally, 6 FDA (3.00 g, 6.76 mmol) was added, and the reaction was carried out for 12 h to prepare a polyamic acid (PAA) solution.

[0065] After filtration, polyamic acid was evenly drop-coated onto a clean glass plate. The temperature was increased according to the following procedure: 80°C for 1 hour, then 100°C for 1 hour, then 150°C for 1 hour, then 200°C for 1 hour, and finally 250°C for 1 hour. The heating was then turned off, and the mixture was allowed to cool naturally to room temperature. The glass plate containing the film was then placed in water. After the film separated from the glass plate, it was washed and dried to obtain the film material.

[0066] Example 3

[0067] This embodiment provides the photo-variable stiffness properties of azobenzene polyimide-polyurea.

[0068] Both sets of films prepared in Example 1 and Comparative Example 1 were cut into strips of 20 mm × 5 mm × 100 μm and subjected to a temperature of 70 mW / cm². 2 The modulus change was measured after 10 minutes of exposure to 365nm ultraviolet light.

[0069] refer to Figure 2The modulus of hydrogen-free azophenyl polyimide (Comparative Example 1) before and after light irradiation was 3.0 GPa and 2.8 GPa, respectively, a decrease of approximately 7%. The modulus of azophenyl polyimide containing dynamic hydrogen bonds (Example 1) before and after light irradiation was 3.2 GPa and 1.8 GPa, respectively, a decrease of approximately 44%. The initial moduli of the two materials were almost the same, but the modulus of azophenyl polyimide-polyurea decreased significantly under light irradiation, indicating that its molecular chain structure changed, while the structure of hydrogen-free azophenyl polyimide remained stable.

[0070] Example 4

[0071] This example illustrates the photodeformation properties of azobenzene polyimide-polyurea.

[0072] refer to Figure 3 The film prepared in Example 1 was cut into strips of 5 mm × 1 mm × 15 μm and subjected to a temperature of 70 mW / cm². 2 Under 365nm ultraviolet light, the sample bent towards the light source, reaching a maximum bending angle of 65° within 10 seconds. Then, using 50mW / cm² light... 2 When the film is irradiated with 530nm green light, it returns to its initial state within 5 seconds. Furthermore, the photoinduced deformation behavior of the film exhibits good repeatability.

[0073] Example 5

[0074] This example illustrates the self-healing properties of azobenzene polyimide-polyurea.

[0075] refer to Figure 4 The film prepared in Example 1 was cut into strips of 20 mm × 5 mm × 100 μm and then imprinted. The imprinted film developed a 30 μm crack. The damaged film was placed on a hot stage and observed using a super-depth-of-field microscope. Above 200°C, the crack began to shrink continuously. At 250°C, the crack completely disappeared within 3 minutes. The mechanical properties of the self-healed film were characterized, and its stress-strain curve showed a consistent trend with the previously intact film.

[0076] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A soluble dynamic photo-morphing polyimide-polyurea, characterized in that, It is an azobenzene polyimide-polyurea, and its molecular structure contains the following units: Where m and n represent the degree of polymerization. X is a tetravalent aromatic hydrocarbon group or an aliphatic hydrocarbon group. Z represents the isocyanate group that provides hydrogen bonding. W is a diamine monomer with a flexible group. Y is a diamine residue containing an azophenyl group.

2. The soluble dynamic photo-morphing polyimide-polyurea of claim 1, wherein, X is selected from one of the following tetravalent aromatic or aliphatic hydrocarbon structural formulas:

3. The soluble dynamic photo-morphing polyimide-polyurea of claim 1, wherein, The Z is selected from one of the following structural formulas:

4. The soluble dynamic photo-morphing polyimide-polyurea of claim 1, wherein, The W is selected from one of the following structural formulas:

5. The soluble dynamic photo-morphing polyimide-polyurea of claim 1, wherein, The general structural formula for Y is as follows: wherein R is a hydrocarbon group selected from C2, C3, C4, C5, C6, C7, C8, C9, C 10 , C 11 , C 12 .

6. A soluble dynamic photodeformable polyimide-polyurea thin film material prepared based on any one of claims 1-5.

7. A method of producing a soluble dynamic photo-morphing polyimide- polyurea film material as claimed in claim 6, characterized in that, Includes the following steps: The isocyanate monomer is placed in a reactor, and a polar aprotic solvent is added to dissolve the isocyanate monomer. The diamine monomer containing azophenyl and a flexible group is dissolved in a polar aprotic solvent, and the solution containing the diamine monomer is fed into a reactor to carry out the reaction. After the reaction is complete, dianhydride monomer is added, and polyamic acid solution is obtained through condensation polymerization. A polyamic acid solution was coated onto a substrate and placed on a hot stage for programmed temperature rise to complete thermal imidization, resulting in a soluble dynamic photodeformable polyimide-polyurea film material. The structures of the isocyanate monomer, diamine monomer, and dianhydride monomer satisfy the molecular structure of the final soluble dynamic photodeformable polyimide-polyurea as defined in any one of claims 1-5.

8. The method of claim 7, wherein the dynamic photo-morphing polyimide- polyurea film material is soluble. The molar ratio of dianhydride monomer to diamine monomer is 1:1 to 1:1.01, and the molar ratio of isocyanate monomer to dianhydride monomer is 1:15 to 1:

6. The polar aprotic solvent is any one of N,N-dimethylacetamide, N,N-dimethylformamide or N-methylpyrrolidone; The solid content of the polyamic acid solution is 10% to 15%.

9. The method of claim 7, wherein the dynamic photo-morphing polyimide- polyurea film material is soluble. The reaction temperature is 25℃-90℃, and the condensation polymerization reaction time is 12h-24h. The temperature program for thermal imidization is as follows: heat to 80°C and react for 1 hour, then heat to 100°C and react for 1 hour, then heat to 150°C and react for 1 hour, then heat to 200°C and react for 1 hour, and finally heat to 250°C and react for 1 hour.

10. The application of the soluble dynamic photodeformable polyimide-polyurea film material according to claim 6, characterized in that, Used to prepare photodeformable materials or photodeformable devices.

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