A high-strength, high-modulus, high-toughness shape memory poly(benzimidazole-benzoxazole) imide material with controllable photodegradability and a preparation method thereof

Abstract

The application discloses a high-strength, high-modulus and high-toughness shape memory poly(benzimidazole-benzoxazole) imide material with controllable photodegradation and a preparation method thereof, and belongs to the technical field of multifunctional polymers. The poly(benzimidazole-benzoxazole) imide polymer with a photodegradation group is obtained by two-step polycondensation and imidization of an imidazole-containing aromatic heterocyclic diamine, a diphenyl dianhydride and a photosensitive group, tosic acid. The tensile strength of the polymer at normal temperature is 262.2 MPa, the Young's modulus is 6.0 GPa, the elongation at break is 27.9%, the energy storage modulus in a shape recovery stage is 100 MPa, the glass transition temperature (T g ) is 380 DEG C, and the polymer has shape memory performance, a shape fixing rate of 99% and a shape recovery rate of 98%. The polymer has the light-controlled degradation characteristics by controlling the proportion of the chemical block photosensitive group, and can be applied in the fields of a light-degradable flexible thin film space cabin and a controllable light-degradable self-adaptive deformation flexible sensor.

Description

Technical Field

[0001] This invention belongs to the field of multifunctional polymer technology, specifically relating to a high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability and its preparation method. Background Technology

[0002] Shape memory polymer (SMP) is a smart material that, when the temperature is above the shape memory transition temperature (T0),... trans When the SMP is given a temporary shape under the action of external force, the temperature is lowered to T. trans The temporary shape is then fixed, and the temperature is raised again to T. trans When subjected to the above conditions, SMP can autonomously return to its initial shape. Compared to shape memory alloys and shape memory ceramics, SMP has the advantages of large deformation and light weight, and has broad application prospects in aerospace, flexible electronics, biomedical engineering and other fields. Shape memory polyimide has advantages such as high mechanical strength, resistance to high and low temperatures, and good thermal stability, but its toughness is poor, and it is prone to breakage after repeated bending, causing material failure. In addition, because shape memory polyimide has rigid structures such as aromatic rings and aromatic heterocycles, it is difficult to degrade after disposal, causing environmental pollution.

[0003] Photodegradation primarily utilizes the effect of light to cause the main chain of polymers to break down, thus initiating the degradation process. Photodegradable materials can be divided into two types: the first is additive-based, where photosensitizers are incorporated into polymer materials. Through the action of light, the photosensitizers become active substances that can induce the degradation of the polymer main chain, thereby achieving the degradation purpose. However, photosensitizers pose a risk of leaching during use, causing pollution to the surrounding environment and limiting their application. The second type is synthetic-based, where photodegradable groups are introduced into the polymer molecule structure to achieve degradation. Photodegradable groups include o-nitrobenzyl ester derivatives, coumarin derivatives, and Truxillic acid derivatives (tuxicosic acid), etc. During photodegradation, o-nitrobenzyl ester derivatives release aldehyde or ketone byproducts. These byproducts can interact with proteins in the body, causing adverse reactions. Compared to nitrobenzyl derivatives, coumarin derivatives have better biocompatibility and human safety because their photodegradation products are alcohol hydroxyl and carboxyl groups, but the photodegradation time is long, ranging from 60 to 600 days. Besides o-nitrobenzyl ester and coumarin derivatives, truxillic acid is also a commonly used photodegrading group. Truxillic acid is a dimer cyclic compound formed by the [2+2] cycloaddition reaction of two cinnamic acids, and can be used at a power of 500W / cm². 2Under 265nm ultraviolet irradiation, the [2+2] cyclic compound is broken down into two monomers. When the polymer chain is connected to the carboxyl groups on both sides, they can be broken down from the middle of the polymer, thereby breaking the main molecular chain, making the material brittle and losing its plasticity. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of poor toughness and difficult degradation of shape memory polyimide, and to provide a high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability and its preparation method. The prepared shape memory polyimide has high strength, high modulus, and high toughness, and can be controlled to degrade under ultraviolet light irradiation.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability, the molecular structure of which is shown below:

[0007]

[0008] The value range of n1+n2+n3 is 116-155.

[0009] Further, the material is prepared from aromatic heterocyclic diamines, biphenyl dianhydride, and Truxillic acid derivatives; the aromatic heterocyclic diamines include imidazole aromatic heterocyclic diamines and oxazole aromatic heterocyclic diamines; the molar ratio of the imidazole aromatic heterocyclic diamines to the oxazole aromatic heterocyclic diamines is 1:1; the Truxillic acid derivatives serve as photo-controlled degradation groups; the molar ratio of the aromatic heterocyclic diamines, biphenyl dianhydride, and Truxillic acid derivatives is 2:1.7-1.88:0.12-0.3.

[0010] Further, the imidazole-based aromatic heterocyclic diamine is one of 2-(4-aminophenyl)-5-aminobenzimidazole (DAPBI) and 2-(3-aminophenyl)-1H-benzimidazole-6-amine; the oxazole-based aromatic heterocyclic diamine is one of 2-(4-aminophenyl)-5-aminobenzoxazole (AAB), 2-(3-aminophenyl)-1,3-benzoxazole-5-amine, and 2-(4-aminophenyl)-1,3-benzoxazole-6-amine; the biphenyl dianhydride is one of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2,3,3',4'-biphenyltetracarboxylic dianhydride; and the Truxillic acid derivative is touxic acid. The synthetic route is as follows: Figure 3 As shown.

[0011] A method for preparing the above-mentioned high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability, the method comprising the following steps:

[0012] Step 1: Dissolve the imidazole-containing aromatic heterocyclic diamine and the oxazole-containing aromatic heterocyclic diamine in a solvent to obtain a mixed solution containing -NH2 groups;

[0013] Step 2: Under a protective atmosphere, biphenyl dianhydride is added to the mixed solution containing -NH2 groups and reacted for 12 hours to obtain a -NH2-terminated polyamic acid solution.

[0014] Step 3: Add tocopheric acid to the -NH2-terminated polyamic acid solution, add a catalyst, and react for 24 hours to obtain a polyamic acid solution containing photosensitive groups;

[0015] Step 4: Pour the polyamic acid solution containing photosensitive groups onto the substrate and place it in a vacuum oven for vacuum drying to remove air bubbles from the polyamic acid solution, thus obtaining a polyamic acid solution substrate without air bubbles.

[0016] Step 5: Place the bubble-free polyamic acid solution substrate in a high-temperature oven and perform thermal imidization by gradient heating to obtain a substrate containing a polyimide film.

[0017] Step 6: Place the substrate containing the polyimide film in water for 1-2 hours to complete demolding. After drying, a high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability is obtained.

[0018] Furthermore, in step one, the solvent includes dimethyl sulfoxide.

[0019] Furthermore, in step two, the protective atmosphere is nitrogen, and the reaction is carried out at room temperature.

[0020] Further, in step three, the concentration of polyamic acid in the polyamic acid solution containing photosensitive groups is 17-22 wt%, and the catalyst is either dihydroxymethylacetone (DCC) or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC), and the content of the catalyst accounts for 5-10 wt% of the mass of tocolytic acid.

[0021] Preferably, biphenyl dianhydride is added to a mixed solution containing -NH2 groups in 3-5 portions according to a specified ratio, and the addition step is completed within 30 minutes. Under a nitrogen protective atmosphere at room temperature, the reaction is carried out at a rotation speed of 300 r / min for 12 hours to obtain a polyamic acid solution. Then, tocopheric acid is added and the reaction continues for 24 hours. The concentration of polyamic acid containing photosensitive groups is 17 wt%. The two reaction times of 12 hours and 24 hours respectively can ensure the performance of the obtained polyimide. If the time is too short, the molecular weight of polyamic acid will be low, and it will fragment in the subsequent thermal imidization step, resulting in many cracks and ultimately film formation failure. If the time is too long, the polyamic acid formed by condensation will hydrolyze, which will also reduce the molecular weight and affect the film formation properties.

[0022] Furthermore, in step four, the vacuum drying process specifically involves controlling the oven temperature to 60°C and maintaining it for 8 hours, then raising the temperature to 100°C and maintaining it for 6 hours; the substrate is a glass plate.

[0023] Further, in step five, the gradient heating for thermal imidization specifically involves: heating at a rate of 3°C / min to 150°C and holding for 2 hours; heating at a rate of 3°C / min to 200°C and holding for 2 hours; heating at a rate of 3°C / min to 250°C and holding for 2 hours; and heating at a rate of 3°C / min to 300°C and holding for 2 hours.

[0024] This invention relates to the application of a high-strength, high-modulus, and high-toughness shape-memory poly(benzimidazole-benzoxazole)imide with controllable photodegradability in fields such as photodegradable deployable flexible thin-film space capsules and controllable photodegradable adaptive deformation flexible sensors. For example, before launch, the flexible thin-film space capsule is in a compressed state, which, compared to a rigid metal space capsule, helps reduce space size and weight, and lowers launch costs. During missions in space, the space capsule can actively deploy its structure when the temperature reaches above the SMPI glass transition temperature, avoiding mechanical impact. After mission completion, the thin-film space capsule undergoes photodegradation under space ultraviolet radiation, thereby protecting the space environment and reducing space debris.

[0025] The advantages of this invention over the prior art are as follows: This invention prepares polyimide by using aromatic heterocyclic diamines containing imidazoles and oxazoles, biphenyl dianhydride, and touxicoic acid. At room temperature, the tensile strength of this polyimide exceeds 250 MPa, the Young's modulus exceeds 5 GPa, the elongation at break is greater than 18%, the storage modulus during shape recovery is not less than 100 MPa, and the glass transition temperature (T0) is... g It exceeds 370℃ and possesses shape memory properties, exhibiting high shape retention and shape recovery rates. Power consumption is 500W / cm. 2After irradiation with 265nm ultraviolet light for 12-20 hours, both the glass transition temperature and tensile strength decreased, indicating photodegradability. Furthermore, the prepared polyimide is an intrinsically photodegradable SMPI, which solves problems such as uneven dispersion, easy precipitation, and stress concentration points associated with physically blended photosensitizers. The resulting polyimide exhibits good photodegradability and has broad application prospects in fields such as photodegradable deployable flexible thin-film space capsules and controllable photodegradable adaptive deformation flexible sensors. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the mechanism of the shape memory effect of the polyimide of the present invention.

[0027] Figure 2 This is a flowchart of the preparation method of the present invention;

[0028] Figure 3 This is a synthetic route diagram of the high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradability of the present invention.

[0029] Figure 4 This is a stress-strain curve of the high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradability in Example 1 of the present invention.

[0030] Figure 5 This is a graph showing the storage modulus and loss factor of the high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradability in Example 1 of the present invention.

[0031] Figure 6 The high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradability in Example 1 of this invention is subjected to a power of 500W / cm 2 Loss factor curve after 12 hours of 265nm ultraviolet irradiation;

[0032] Figure 7 The high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradability in Example 1 of this invention is subjected to a power of 500W / cm 2 Stress-strain curves after 12 hours of 265nm ultraviolet irradiation;

[0033] Figure 8 This is a diagram illustrating the thermally driven shape memory process of high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradability in Example 1 of the present invention.

[0034] Figure 9 This is a schematic diagram illustrating the principle of controlled photodegradation of SMPI. Detailed Implementation

[0035] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0036] It should be noted that, unless otherwise specified, the features in the embodiments of the present invention can be combined with each other. The terms "comprising," "including," "containing," and "having" are non-limiting, meaning that other steps and other components that do not affect the result can be added. The above terms cover the terms "composed of" and "substantially composed of." Unless otherwise specified, the materials, equipment, and reagents are commercially available. Furthermore, it should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of the present invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the present invention described herein can be implemented in sequences other than those illustrated or described herein.

[0037] This invention modulates the molecular structure of polyimide using multiple monomers. An excess of diamine and diacid anhydride monomers generates -NH2-terminated polyamic acid. Then, tocopheric acid containing photosensitive groups is added to the polyamic acid solution. Since the carboxyl group of tocopheric acid is more reactive than that of polyamic acid, it preferentially forms amide bonds with the amine group, equivalent to a chain extension reaction of the polyamic acid molecular chain. After thermal imidization, a multi-block shape memory poly(benzimidazole-benzoxazole)imide (SMPI) with photodegradable groups is obtained. This polymer exhibits high strength, high modulus, and high toughness. Furthermore, by controlling the proportion of chemically block photosensitive groups, it possesses photo-controlled degradation properties, showing broad application prospects in photodegradable deployable flexible thin-film space capsules and controllable photodegradable adaptive deformation flexible sensors.

[0038] To achieve shape memory properties, the polymer molecular chain structure needs both a reversible phase and a stationary phase. Poly(benzimidazole-benzoxazole)imide itself exhibits a significant glass transition, which can act as a shape memory "switch." The stationary phase originates from the interactions between macromolecular chains, including macromolecular chain entanglement and π-π stacking; the reversible phase originates from the asymmetric imidazole ring molecular structure and oxazole ring molecular structure. For example... Figure 1 As shown, when the temperature is below the glass transition temperature (T) of SMPI g When the temperature reaches T, the molecular chain segment motion is in a "frozen" state. g Subsequently, the free volume inside the material increases, and the chain segment motion begins to "thaw," resulting in large deformation under the action of external forces. This external force then lowers the temperature to T. gAt this point, the molecular chain segment motion is "frozen," resulting in a temporary shape, and the elastic strain energy stored during this process is not released but stored in the polymer. When reheated to T... g When the molecular chain segments obtain sufficient energy and free volume, they begin to move violently, and the elastic strain energy stored inside is gradually released. Macroscopically, the material returns from its temporary shape to its original shape.

[0039] Example 1

[0040] (1) Dissolve 2 mmol of 2-(4-aminophenyl)-5-aminobenzimidazole and 2 mmol of 2-(4-aminophenyl)-5-aminobenzoxazole completely in 5.3 mL of dimethyl sulfoxide to obtain a mixed solution containing -NH2 groups.

[0041] (2) 3.76 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added to a mixed solution containing -NH2 groups in four portions, and the feeding step was completed within 30 min; at room temperature, in a nitrogen atmosphere, the reaction was carried out at a speed of 300 r / min for 12 h to obtain a polyamic acid solution with -NH2 end capping.

[0042] (3) Add 0.24 mmol of tocolytic acid to the -NH2-terminated polyamic acid solution, add 0.08 mmol of catalyst dihydroxymethyl acetone, and react for 24 h to obtain a polyamic acid solution containing photosensitive groups.

[0043] (4) Pour the polyamic acid solution containing photosensitive groups onto a glass plate, place it in a vacuum oven at 60°C for 8 hours; then at 100°C for 6 hours, evacuate the vacuum, remove air bubbles, and obtain a polyamic acid glass plate without air bubbles.

[0044] (5) Place the bubble-free polyamic acid glass plate in a high-temperature oven and perform thermal imidization by gradient heating. The thermal imidization steps are as follows: heating rate is 3℃ / min, heating to 150℃ and holding for 2h; heating rate is 3℃ / min, heating to 200℃ and holding for 2h; heating rate is 3℃ / min, heating to 250℃ and holding for 2h; heating rate is 3℃ / min, heating to 300℃ and holding for 2h.

[0045] (6) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 2 hours to complete the demolding.

[0046] (7) Place the demolded film material in an oven at 100°C for 12 hours to evaporate the moisture and obtain a high-strength, high-modulus, high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradation properties.

[0047] in, Figure 4This is a stress-strain curve of the polyimide prepared in this embodiment; Figure 5 This is a graph showing the storage modulus and loss factor of the polyimide prepared in this embodiment; Figure 6 The polyimide prepared in this embodiment was subjected to a power of 500 W / cm. 2 Loss factor curve after 12 hours of 265nm ultraviolet irradiation; Figure 7 The polyimide prepared in this embodiment was subjected to a power of 500 W / cm. 2 Stress-strain curves after 12 hours of 265nm ultraviolet irradiation; Figure 8 This diagram illustrates the shape memory process of the polyimide prepared in this embodiment.

[0048] from Figure 4 It can be seen that the tensile strength of the SMPI prepared in this embodiment at room temperature is 262.2 MPa, the Young's modulus is 6.0 GPa, and the elongation at break is 27.9%; from Figure 5 It can be seen that the storage modulus of the SMPI prepared in this embodiment is 6.7 GPa, T g The temperature is 380℃, meaning the shape memory transition temperature is 380℃, and the minimum energy storage modulus during the shape recovery stage is 100MPa; from Figure 6 It can be seen that the SMPI prepared in this embodiment undergoes a power of 500W / cm². 2 T after 12 hours of 265nm ultraviolet irradiation g It is 352℃, which is higher than the original T. g Lower by 20°C; from Figure 7 It can be seen that the SMPI prepared in this embodiment undergoes a power of 500W / cm². 2 The tensile strength after 12 hours of 265nm ultraviolet irradiation was 204 MPa, a decrease of 58.2 MPa from the original tensile strength, indicating that the SMPI exhibits photodegradability. The decrease in molecular weight leads to a reduction in glass transition temperature and tensile strength. Figure 8 It can be seen that when SMPI is shaped by external force under a thermal environment of 390℃ and then cooled to room temperature, it retains its temporary bent shape after the external force is removed. However, when it is reheated to a thermal environment of 390℃, SMPI can return to its original shape, with a shape fixation rate of 99% and a shape recovery rate of 98%. This polymer, by controlling the proportion of chemically block photosensitive groups, possesses photo-controlled degradation characteristics, and can be applied in fields such as photodegradable unfoldable flexible thin film space capsules and controllable photodegradable adaptive deformation flexible sensors.

[0049] Example 2

[0050] (1) Dissolve 2 mmol of 2-(4-aminophenyl)-5-aminobenzimidazole and 2 mmol of 2-(4-aminophenyl)-5-aminobenzoxazole completely in 5.3 mL of dimethyl sulfoxide to obtain a mixed solution containing -NH2 groups.

[0051] (2) 3.70 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added to a mixed solution containing -NH2 groups in four portions, and the feeding step was completed within 30 min; at room temperature, in a nitrogen atmosphere, the reaction was carried out at a speed of 300 r / min for 12 h to obtain a polyamic acid solution with -NH2 end capping.

[0052] (3) Add 0.3 mmol of tocolytic acid to the -NH2-terminated polyamic acid solution, add 0.1 mmol of catalyst dihydroxymethyl acetone, and react for 24 h to obtain a polyamic acid solution containing photosensitive groups.

[0053] (4) Pour the polyamic acid solution containing photosensitive groups onto a glass plate, place it in a vacuum oven at 60°C for 8 hours; then at 100°C for 6 hours, evacuate the vacuum, remove air bubbles, and obtain a polyamic acid glass plate without air bubbles.

[0054] (5) Place the bubble-free polyamic acid glass plate in a high-temperature oven and perform thermal imidization by gradient heating. The thermal imidization steps are as follows: heating rate is 3℃ / min, heating to 150℃ and holding for 2h; heating rate is 3℃ / min, heating to 200℃ and holding for 2h; heating rate is 3℃ / min, heating to 250℃ and holding for 2h; heating rate is 3℃ / min, heating to 300℃ and holding for 2h.

[0055] (6) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 2 hours to complete the demolding.

[0056] (7) Place the demolded film material in an oven at 100°C for 12 hours to evaporate the moisture and obtain a high-strength, high-modulus, high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradation properties.

[0057] The SMPI prepared in this embodiment has a tensile strength of 260 MPa, a Young's modulus of 5.8 GPa, and an elongation at break of 26.7%; its storage modulus is 6.4 GPa, and its T... g The temperature was 379℃, and the lowest energy storage modulus during the shape recovery stage was 110MPa; the power output was 500W / cm². 2 T after 12 hours of 265nm ultraviolet irradiation g At 348℃, the tensile strength is 196MPa; the shape fixation rate is 99%, and the shape recovery rate is 96%.

[0058] Example 3

[0059] (1) Dissolve 2 mmol of 2-(4-aminophenyl)-5-aminobenzimidazole and 2 mmol of 2-(4-aminophenyl)-5-aminobenzoxazole completely in 5.3 mL of dimethyl sulfoxide to obtain a mixed solution containing -NH2 groups.

[0060] (2) 3.66 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added to a mixed solution containing -NH2 groups in four portions, and the feeding step was completed within 30 min; at room temperature, in a nitrogen atmosphere, the reaction was carried out at a speed of 300 r / min for 12 h to obtain a polyamic acid solution with -NH2 end capping.

[0061] (3) Add 0.34 mmol of tocolytic acid to the -NH2-terminated polyamic acid solution, add 0.11 mmol of catalyst dihydroxymethylacetone, and react for 24 h to obtain a polyamic acid solution containing photosensitive groups.

[0062] (4) Pour the polyamic acid solution containing photosensitive groups onto a glass plate, place it in a vacuum oven at 60°C for 8 hours; then at 100°C for 6 hours, evacuate the vacuum, remove air bubbles, and obtain a polyamic acid glass plate without air bubbles.

[0063] (5) Place the bubble-free polyamic acid glass plate in a high-temperature oven and perform thermal imidization by gradient heating. The thermal imidization steps are as follows: heating rate is 3℃ / min, heating to 150℃ and holding for 2h; heating rate is 3℃ / min, heating to 200℃ and holding for 2h; heating rate is 3℃ / min, heating to 250℃ and holding for 2h; heating rate is 3℃ / min, heating to 300℃ and holding for 2h.

[0064] (6) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 2 hours to complete the demolding.

[0065] (7) Place the demolded film material in an oven at 100°C for 12 hours to evaporate the moisture and obtain a high-strength, high-modulus, high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradation properties.

[0066] The SMPI prepared in this embodiment has a tensile strength of 258 MPa, a Young's modulus of 5.6 GPa, and an elongation at break of 24.8%; its storage modulus is 6.0 GPa, and its T... g The temperature was 374℃, and the lowest energy storage modulus during the shape recovery stage was 108 MPa; the power output was 500 W / cm². 2 T after 12 hours of 265nm ultraviolet irradiation gThe temperature was 343℃, the tensile strength was 186MPa; the shape fixation rate was 97%, and the shape recovery rate was 96%.

[0067] Example 4

[0068] (1) Dissolve 3 mmol of 2-(4-aminophenyl)-5-aminobenzimidazole and 3 mmol of 2-(4-aminophenyl)-5-aminobenzoxazole completely in 7.5 mL of dimethyl sulfoxide to obtain a mixed solution containing -NH2 groups.

[0069] (2) 5.61 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added to a mixed solution containing -NH2 groups in four portions, and the feeding step was completed within 30 min; at room temperature, in a nitrogen atmosphere, the reaction was carried out at a speed of 300 r / min for 12 h to obtain a polyamic acid solution with -NH2 end capping.

[0070] (3) Add 0.39 mmol of tocolytic acid to the -NH2-terminated polyamic acid solution, add 0.13 mmol of catalyst dihydroxymethyl acetone, and react for 24 h to obtain a polyamic acid solution containing photosensitive groups.

[0071] (4) Pour the polyamic acid solution containing photosensitive groups onto a glass plate, place it in a vacuum oven at 60°C for 8 hours; then at 100°C for 6 hours, evacuate the vacuum, remove air bubbles, and obtain a polyamic acid glass plate without air bubbles.

[0072] (5) Place the bubble-free polyamic acid glass plate in a high-temperature oven and perform thermal imidization by gradient heating. The thermal imidization steps are as follows: heating rate is 3℃ / min, heating to 150℃ and holding for 2h; heating rate is 3℃ / min, heating to 200℃ and holding for 2h; heating rate is 3℃ / min, heating to 250℃ and holding for 2h; heating rate is 3℃ / min, heating to 300℃ and holding for 2h.

[0073] (6) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 2 hours to complete the demolding.

[0074] (7) Place the demolded film material in an oven at 100°C for 12 hours to evaporate the moisture and obtain a high-strength, high-modulus, high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradation properties.

[0075] The SMPI prepared in this embodiment has a tensile strength of 261 MPa, a Young's modulus of 5.8 GPa, and an elongation at break of 25.8%; its storage modulus is 6.1 GPa, and its T... g The temperature was 376℃, and the lowest energy storage modulus during the shape recovery stage was 113 MPa; the power output was 500 W / cm².2 T after 12 hours of 265nm ultraviolet irradiation g At 345℃, the tensile strength is 190MPa; the shape fixation rate is 97%, and the shape recovery rate is 98%.

[0076] Example 5

[0077] (1) Dissolve 3 mmol of 2-(4-aminophenyl)-5-aminobenzimidazole and 3 mmol of 2-(4-aminophenyl)-5-aminobenzoxazole completely in 7.5 mL of dimethyl sulfoxide to obtain a mixed solution containing -NH2 groups.

[0078] (2) 5.55 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added to a mixed solution containing -NH2 groups in four portions, and the feeding step was completed within 30 min; at room temperature, in a nitrogen atmosphere, the reaction was carried out at a speed of 300 r / min for 12 h to obtain a polyamic acid solution with -NH2 end capping.

[0079] (3) Add 0.45 mmol of tocolytic acid to the -NH2-terminated polyamic acid solution, add 0.15 mmol of catalyst dihydroxymethyl acetone, and react for 24 h to obtain a polyamic acid solution containing photosensitive groups.

[0080] (4) Pour the polyamic acid containing photosensitive groups onto a glass plate, place it in a vacuum oven at 60°C for 8 hours; then at 100°C for 6 hours, evacuate the vacuum to remove bubbles, and obtain a glass plate of polyamic acid solution without bubbles.

[0081] (5) Place the bubble-free polyamic acid glass plate in a high-temperature oven and perform thermal imidization by gradient heating. The thermal imidization steps are as follows: heating rate is 3℃ / min, heating to 150℃ and holding for 2h; heating rate is 3℃ / min, heating to 200℃ and holding for 2h; heating rate is 3℃ / min, heating to 250℃ and holding for 2h; heating rate is 3℃ / min, heating to 300℃ and holding for 2h.

[0082] (6) Turn off the high-temperature oven and let it cool naturally to room temperature. Take out the glass plate and place it in 100°C deionized water for 2 hours to complete the demolding.

[0083] (7) Place the demolded film material in an oven at 100°C for 12 hours to evaporate the moisture and obtain a high-strength, high-modulus, high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradation properties.

[0084] The SMPI prepared in this embodiment has a tensile strength of 255 MPa, a Young's modulus of 5.4 GPa, and an elongation at break of 23.6%; its storage modulus is 5.7 GPa, and its T... gThe temperature was 372℃, and the lowest energy storage modulus during the shape recovery stage was 103 MPa; the power output was 500 W / cm². 2 T after 12 hours of 265nm ultraviolet irradiation g At 340℃, the tensile strength is 174MPa; the shape fixation rate is 98%, and the shape recovery rate is 97%.

[0085] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications should fall within the protection scope of this invention.

Claims

1. A method for preparing a high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability, characterized in that: The molecular structure of the shape memory poly(benzimidazole-benzoxazole)imide material is shown below: Wherein, the value range of n1+n2+n3 is 116~155; the method includes the following steps: Step 1: Dissolve an imidazole-containing aromatic heterocyclic diamine and an oxazole-containing aromatic heterocyclic diamine in a solvent to obtain a mixed solution containing -NH2 groups; the solvent includes dimethyl sulfoxide; the molar ratio of the imidazole-containing aromatic heterocyclic diamine and the oxazole-containing aromatic heterocyclic diamine is 1:1; the imidazole-containing aromatic heterocyclic diamine is 2-(4-aminophenyl)-5-aminobenzimidazole, and the oxazole-containing aromatic heterocyclic diamine is 2-(4-aminophenyl)-5-aminobenzoxazole; Step 2: Under a protective atmosphere, add biphenyl dianhydride to the mixed solution containing -NH2 groups and react for 12 h to obtain a -NH2-terminated polyamic acid solution; the biphenyl dianhydride is one of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 2,3,3',4'-biphenyltetracarboxylic dianhydride; Step 3: Add tocolytic acid to the -NH2-terminated polyamic acid solution, add a catalyst, and react for 24 h to obtain a polyamic acid solution containing photosensitive groups; the total amount of aromatic heterocyclic diamine, the molar ratio of biphenyl dianhydride and tocolytic acid is 2:1.7~1.88:0.12~0.3; Step 4: Pour the polyamic acid solution containing photosensitive groups onto the substrate and place it in a vacuum oven for vacuum drying to remove air bubbles from the polyamic acid solution, thus obtaining a polyamic acid solution substrate without air bubbles. Step 5: Place the bubble-free polyamic acid solution substrate in a high-temperature oven and perform thermal imidization by gradient heating to obtain a substrate containing a polyimide film. Step 6: Place the substrate containing the polyimide film in water for 1-2 hours to complete demolding. After drying, a high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability is obtained.

2. The method for preparing the high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability according to claim 1, characterized in that: In step two, the protective atmosphere is nitrogen, and the reaction is carried out at room temperature.

3. The method for preparing the high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability according to claim 1, characterized in that: In step three, the concentration of polyamic acid in the polyamic acid solution containing photosensitive groups is 17-22 wt%, and the catalyst is either dihydroxymethylacetone or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, with the catalyst content accounting for 5-10 wt% of the mass of tocolytic acid.

4. The method for preparing the high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability according to claim 1, characterized in that: In step four, the vacuum drying process specifically involves controlling the oven temperature at 60°C for 8 hours, then raising the temperature to 100°C and holding for 6 hours; the substrate is a glass plate.

5. The method for preparing the high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide material with controllable photodegradability according to claim 1, characterized in that: In step five, the gradient heating for thermal imidization specifically involves: heating at a rate of 3 °C / min to 150 °C and holding for 2 h; heating at a rate of 3 °C / min to 200 °C and holding for 2 h; heating at a rate of 3 °C / min to 250 °C and holding for 2 h; and heating at a rate of 3 °C / min to 300 °C and holding for 2 h.

6. The application of a high-strength, high-modulus, and high-toughness shape memory poly(benzimidazole-benzoxazole)imide with controllable photodegradability as described in any one of claims 1 to 5 in the fields of photodegradable deployable flexible thin-film space capsules and controllable photodegradable adaptive deformation flexible sensors.

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