A dynamically cross-linked self-healing PMMA, and a preparation method and application thereof

Abstract

The application provides a kind of dynamic crosslinking self-repairing PMMA and its preparation method and application, the application can realize molecular self-guiding accurate repair by introducing double coordination octacyclic ring borate dynamic crosslinking structure, the dynamic crosslinking self-repairing PMMA of the application can quickly repair scratch at room temperature without external addition of repair agent after being damaged by external damage, is not dependent on extreme conditions, automatically realizes the repair of damage site, and the repair condition is mild, and the effective self-repairing temperature can reach 15 DEG C at least;And can carry out multiple repair cycles, has long cycle repair life, and has little influence on the optical performance of PMMA, widens the application field of PMMA material.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to a dynamically cross-linked self-healing PMMA, its preparation method, and its application. Background Technology

[0002] Polymethyl methacrylate (PMMA) is widely used in optical devices, automotive glass, electronic screens, medical devices, aerospace, and other fields due to its light transmittance (>92%), strong weather resistance, and ease of processing. However, traditional PMMA has some inherent defects, such as susceptibility to scratches and cracks during use. Cracks can propagate over time, leading to structural failure. Once damaged, its performance deteriorates significantly and is difficult to self-repair. This not only affects the material's lifespan and performance stability but also increases the cost of repair and replacement.

[0003] In recent years, with the development of materials science, the demand for smart materials has been increasing. Self-healing materials, as a new type of smart material, can automatically recover some or all of their properties after being damaged, and have attracted widespread attention. Research on the self-healing properties of PMMA materials has also gradually become a hot topic.

[0004] Currently, there are various methods to achieve self-healing in PMMA. For example, microcapsules can be added to the polymer matrix. When the material is damaged, the microcapsules rupture and release a repair agent, thereby filling and repairing the cracks. However, this method has problems such as poor compatibility between the microcapsules and the matrix, uneven dispersion of the microcapsules in the matrix, and limited repair cycles. Alternatively, reversible physical crosslinking or chemical bonding can be used to construct a dynamic structure, enabling the material to undergo reversible changes when subjected to external stimuli (such as temperature, light, pH, etc.) to achieve self-healing. For example, CN116082672A discloses a high-performance PMMA that can self-heal at 130℃ and 10kPa pressure based on hindered urea dynamic crosslinking. However, it requires high-temperature triggering and is not suitable for low-temperature scenarios. Traditional borate ester dynamic covalent bonds rapidly hydrolyze and fail when humidity is >60%, and the repair efficiency decreases by >70% after 7 days.

[0005] Nitrogen-coordinated boron diester bonds (NCB bonds) are a new generation of dynamic covalent bonds, achieved through boron-nitrogen coordination (…). This elevates the stability and dynamics of traditional borate ester bonds to a revolutionary level; boron-nitrogen coordination allows the boron atom to move from sp... 2 Planar structure converted to sp 3 With its tetrahedral structure, electrophilicity is reduced, and the energy barrier for water molecule attack is increased from 65 KJ / mol to 120 KJ / mol. The hydrolysis rate constant is 360 times lower than that of traditional borate ester bonds. Furthermore, the bond exchange activation energy of NCB bonds is low, which can be triggered at around 25-40℃. The minimum repair temperature can reach 15℃, resulting in mild self-repair conditions and high environmental tolerance.

[0006] Therefore, in this field, the further development of materials that can exhibit efficient self-healing properties under mild conditions is a key research focus. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a dynamically cross-linked self-healing PMMA, its preparation method, and its applications. The dynamically cross-linked self-healing PMMA of the present invention can automatically repair damaged areas without the need for external repair agents after being subjected to external damage. The repair conditions are mild, and multiple repair cycles can be performed, thereby significantly improving the service life and application value of PMMA materials.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] On one hand, the present invention provides a dynamically cross-linked self-healing PMMA, wherein the dynamically cross-linked self-healing PMMA has the following structure:

[0010] .

[0011] in The PMMA backbone contains bis(2-hydroxyethyl)amino in its side chain moiety, and the structure of the PMMA containing bis(2-hydroxyethyl)amino in its side chain moiety is as follows:

[0012]

[0013] R1 is a C1-C4 alkyl, cyclohexyl, phenyl, or benzyl group, and the molar ratio of m to n is 5-30:95-70 (e.g., 5:95, 7:93, 10:90, 15:85, 20:80, 22:78, 25:75, or 30:70). R2, R3, R4, and R5 are hydrogen, methyl, ethyl, methoxy, hydroxyl, amino, tert-butyl, fluorine, or chlorine.

[0014] In this invention, the dynamically cross-linked self-healing PMMA structure has a nitrogen-coordinated cycloborone diester bond dynamic cross-linking structure, which can have efficient self-healing performance under mild conditions. This allows the PMMA material to automatically repair the damaged area without the need for external repair agents after being damaged by external factors, and it can undergo multiple repair cycles.

[0015] On the other hand, the present invention provides a method for preparing dynamically cross-linked self-healing PMMA as described above, the method comprising the following steps:

[0016] (1) The acryloyl chloride compound shown in Formula I reacts with triethanolamine to obtain the acrylate monomer containing bis(2-hydroxyethyl)amino group shown in Formula II, as shown in the following reaction formula:

[0017] ;

[0018] (2) The acrylate monomer containing bis(2-hydroxyethyl)amino obtained in step (1) is polymerized with MMA monomer (methyl methacrylate) under the initiation of an initiator to obtain PMMA with bis(2-hydroxyethyl)amino in the side chain portion as shown in Formula III. The reaction formula is as follows:

[0019] ;

[0020] (3) The PMMA with bis(2-hydroxyethyl)amino side chain obtained in step (2) is reacted with the 1,4-phenylenediboronic acid crosslinking agent shown in Formula IV to obtain the dynamically crosslinked self-healing PMMA. The reaction formula is as follows:

[0021]

[0022] .

[0023] In this invention, the molar ratio of the acryloyl chloride compound shown in Formula I in step (1) to triethanolamine is 1:1.00 to 1:1.05, for example 1:1.00, 1:1.01, 1:1.02, 1:1.03, 1:1.04 or 1:1.05.

[0024] Preferably, the acryloyl chloride compound of Formula I in step (1) is selected from any one or a combination of at least two of methacryloyl chloride, ethylacryloyl chloride, propylacryloyl chloride, isopropylacryloyl chloride, n-butylacryloyl chloride, sec-butylacryloyl chloride, isobutylacryloyl chloride, tert-butylacryloyl chloride, methoxymethacryloyl chloride, cyclohexylacryloyl chloride, phenylacryloyl chloride or benzylacryloyl chloride.

[0025] Preferably, the reaction in step (1) is carried out in the presence of an acid-binding agent.

[0026] Preferably, the acid-binding agent is selected from any one or a combination of at least two of triethylamine, diisopropylethylamine, 4-dimethylaminopyridine, pyridine, or piperidine.

[0027] Preferably, the molar ratio of the acid-binding agent to triethanolamine is 1.1-1.3:1, for example, 1.1:1, 1.2:1 or 1.3:1.

[0028] Preferably, the acryloyl chloride compound of formula I in step (1) is added dropwise to the reaction system containing triethanolamine at -13 to -7°C (e.g., -13°C, -10°C, -9°C, -8°C, -7°C).

[0029] Preferably, the reaction in step (1) is carried out in an organic solvent selected from any one or a combination of at least two of dichloromethane (CH2Cl2), chloroform, tetrahydrofuran, dimethyl sulfoxide, N,N-dimethylformamide, methanol, ethanol, isopropanol or acetone.

[0030] Preferably, the reaction in step (1) is carried out under nitrogen protection.

[0031] Preferably, the reaction in step (1) is carried out under stirring.

[0032] Preferably, the temperature of the reaction in step (1) is -13 to -7℃ (e.g., -13℃, -10℃, -9℃, -8℃, -7℃), and the reaction time is 0.5-2h (e.g., 0.5h, 0.8h, 1h, 1.5h or 2h).

[0033] In this invention, after the reaction in step (1) is completed, the post-processing purification operation includes filtration, washing with 5% hydrochloric acid solution, washing with saturated NaHCO3 solution, washing with saturated saline solution, drying with anhydrous MgSO4, filtration, rotary evaporation, and column chromatography purification.

[0034] Preferably, the molar ratio of the acrylate monomer containing bis(2-hydroxyethyl)amino to the MMA monomer in step (2) is 5-30:95-70, for example 5:95, 7:93, 10:90, 15:85, 20:80, 22:78, 25:75 or 30:70, etc.

[0035] Preferably, the initiator is used in an amount of 20 to 200 ppm of the total monomer mass, for example, 20 ppm, 50 ppm, 80 ppm, 100 ppm, 120 ppm, 150 ppm, 180 ppm or 200 ppm.

[0036] Preferably, the initiator is selected from any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, or dodecyl peroxide.

[0037] Preferably, the polymerization reaction in step (2) is carried out in the presence of a chain transfer agent.

[0038] Preferably, the chain transfer agent is selected from any one or a combination of at least two of n-butanethiol, tert-butanethiol, n-octanethiol, isooctanethiol, n-dodecylthiol, tert-dodecylthiol, or methyl 3-mercaptopropionate.

[0039] Preferably, the chain transfer agent is used in an amount of 500 to 3000 ppm of the total mass of the monomer, for example, 500 ppm, 800 ppm, 1000 ppm, 1300 ppm, 1500 ppm, 2000 ppm, 2500 ppm or 3000 ppm.

[0040] Preferably, the polymerization reaction in step (2) is carried out in a solvent selected from any one or a combination of at least two of chloroform, benzene, toluene, ethylbenzene, N,N-dimethylformamide, tetrahydrofuran or acetonitrile.

[0041] Preferably, the polymerization reaction in step (2) is carried out under stirring.

[0042] Preferably, the polymerization reaction in step (2) is carried out at a temperature of 40-90°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, and the reaction time is 2-8h, such as 2h, 3h, 4h, 5h, 6h, 7h or 8h.

[0043] Preferably, the 1,4-phenylenediboronic acid-based crosslinking agent (BDBA) in step (3) is any one or a combination of at least two of the following: 1,4-phenylenediboronic acid, 2,5-difluoro-1,4-phenylenediboronic acid, 2,5-dichloro-1,4-phenylenediboronic acid, 2,5-di-tert-butyl-1,4-phenylenediboronic acid, perfluoro-1,4-phenylenediboronic acid, 2,5-diethyl-1,4-phenylenediboronic acid, 2,5-dihydroxy-1,4-phenylenediboronic acid, 2,5-dimethyl-1,4-phenylenediboronic acid, 2,5-dimethoxy-1,4-phenylenediboronic acid, 2,3-difluoro-1,4-phenylenediboronic acid, 2,6-difluoro-1,4-phenylenediboronic acid, 2-methoxy-1,4-phenylenediboronic acid, and 2-amino-1,4-phenylenediboronic acid.

[0044] Preferably, the amount of the 1,4-phenylenediboronic acid crosslinking agent in step (3) is 0.3-0.6 times the molar equivalent of the acrylate monomer containing bis(2-hydroxyethyl)amino in the PMMA containing bis(2-hydroxyethyl)amino in the side chain portion; for example, 0.3, 0.4, 0.5 or 0.6 times.

[0045] Preferably, before the reaction in step (3), the PMMA containing bis(2-hydroxyethyl)amino in the side chain is dehydrated using a 4Å molecular sieve. In this invention, dehydration of the raw materials is necessary. The borate esterification reaction is reversible; if a large amount of water is present at the initial stage of the reaction, it will inhibit the formation of borate ester bonds (kinetic barrier). Furthermore, 1,4-phenylenediboronic acid-based crosslinking agents are prone to hydrolysis and self-condensation under aqueous conditions, forming byproducts with unintended structures such as borooxanes (-BOB-). These byproducts consume valuable boric acid functional groups, leading to a reduction in crosslinking points and an uneven network.

[0046] Preferably, the 4Å molecular sieve is an activated molecular sieve, and the activation temperature is 500-600℃ (e.g., 500℃, 530℃, 550℃, 580℃ or 600℃), and the treatment time is 3-6h (e.g., 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h).

[0047] Preferably, the reaction in step (3) is carried out in the presence of an organic base catalyst, wherein the organic base catalyst is selected from any one or a combination of at least two of triethylamine, diisopropylethylamine, pyridine, dimethylaminopyridine or piperidine.

[0048] Preferably, the reaction temperature in step (3) is 38-42℃, for example 38℃, 40℃, 41℃ or 42℃, and the reaction time is 4-12h, for example 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h.

[0049] Preferably, the reaction in step (3) is carried out under nitrogen protection and at a humidity of 58-62%. Reaction under nitrogen and the aforementioned humidity conditions allows for "pre-equilibrium" and "stability enhancement" of the dynamic cross-linked network (around 60% humidity is a typical optimized value); trace amounts of water vapor allow for temporary bond breakage and recombination, enabling the molecular chains to relax to a more stable state, thereby reducing internal defects. Coordination increases the electron density of the boron atom, reducing its electrophilicity and thus enhancing the hydrolytic stability of boronic esters; those that cannot form effective... Coordinated, unstable boronic ester bonds are selectively hydrolyzed and no longer formed in this controlled, humid environment; while strong boronic ester bonds can be formed. The coordinated boron diester structure can persist resiliently. After this process, the vast majority of the crosslinking points retained in the material are structurally correct. Coordinated and stable dynamic covalent bonds. This makes the resulting material exhibit extremely high stability in air (typically with humidity <60%), with almost no hydrolysis; and when self-repair is required, these bonds can undergo reversible breakage and recombination at the interface.

[0050] On the other hand, the present invention provides a dynamically cross-linked self-healing PMMA film, wherein the dynamically cross-linked self-healing PMMA film is formed from dynamically cross-linked self-healing PMMA as described above.

[0051] In this invention, the dynamically cross-linked self-healing PMMA film is obtained by dissolving the dynamically cross-linked self-healing PMMA in a solvent, casting it onto a substrate, evaporating the solvent, drying it, immersing it in water, peeling it off from the substrate, and drying it.

[0052] Preferably, the solvent is DMF (N,N-dimethylformamide).

[0053] In this invention, dynamically cross-linked self-healing PMMA is dissolved in a solvent to prepare a 20-50% (e.g., 20%, 25%, 30%, 35%, 40%, 45%, or 50%) solution.

[0054] Preferably, the solvent evaporation process involves drying at 25-35°C (e.g., 25°C, 30°C, or 35°C) and 45-55% (e.g., 45%, 48%, 50%, or 55%) humidity for 2-4 hours (e.g., 2 hours, 3 hours, or 4 hours), under which the solvent evaporates slowly to prevent the formation of pores.

[0055] Preferably, the drying is performed at 60-70°C (e.g., 60°C, 63°C, 65°C, 68°C, or 70°C) and 25-35% (e.g., 25%, 28%, 30%, or 35%) humidity for 6-8 hours (e.g., 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours) to form a homogeneous network; finally, drying is performed at 80-90°C (e.g., 80°C, 83°C, 85°C, 88°C, or 90°C) and 5-15% (e.g., 5%, 8%, 10%, 12%, or 15%) humidity for 2-4 hours (e.g., 2 hours, 3 hours, or 4 hours) to enhance nitrogen coordination stability.

[0056] Preferably, the immersion time in water is 5-15 seconds, for example, 5 seconds, 8 seconds, 10 seconds, 12 seconds or 15 seconds.

[0057] Preferably, the drying process involves treating the product in a hot air oven at 90-120°C (e.g., 90°C, 95°C, 100°C, 110°C, or 120°C) for 20-40 minutes (e.g., 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes) to release internal stress.

[0058] In this invention, a glass plate is selected as the substrate. Before use, the glass plate is plasma cleaned (O2 plasma, cleaning power of 80-120W, cleaning time of 5-10min) to enhance wettability.

[0059] On the other hand, the present invention provides the application of dynamically cross-linked self-healing PMMA or dynamically cross-linked self-healing PMMA films as described above in optical devices, automotive glass, electronic screens, medical devices, and aerospace materials.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] This invention introduces a double The dynamically cross-linked structure of the octetral borate ester enables precise molecular self-guided repair. The dynamically cross-linked self-healing PMMA of this invention can rapidly repair scratches at room temperature without the need for external repair agents after being damaged. It does not rely on extreme conditions and automatically repairs the damaged area under mild conditions, with an effective self-healing temperature as low as 15°C. Furthermore, it can undergo multiple repair cycles, exhibiting a long cycle repair life, and has minimal impact on the optical properties of PMMA, thus broadening the application areas of PMMA materials.

[0062] The preparation method of the present invention is based on the construction of a dynamic covalent network, which can be extended to other polymer materials, such as polyurethane, epoxy resin, polystyrene, hydrogel, etc. Detailed Implementation

[0063] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0064] Example 1

[0065] This embodiment provides a dynamically cross-linked self-healing PMMA and a self-healing PMMA film prepared therefrom, the preparation method of which is as follows:

[0066] (1) Preparation of monomer R1-CON(OH)2 (R1 is -CH3)

[0067]

[0068] First, 14.92 g of TEOA (triethanolamine) was dissolved in 80 mL of anhydrous CH2Cl2, and the solution was cooled to -10 ± 3 °C in an ice-salt bath. Methacrylamide solution (10.45 g methacryloyl chloride + 20 mL anhydrous CH2Cl2) and triethylamine solution (12.14 g triethylamine + 20 mL anhydrous CH2Cl2) were simultaneously and slowly added dropwise using a double constant-pressure dropping funnel at rates of 1.0 mL / min and 1.2 mL / min, respectively. The reaction was stirred for 1.5 h under nitrogen protection. Subsequently, the solution was filtered, washed with 5% hydrochloric acid solution until the aqueous phase pH reached 2-3, washed with saturated NaHCO3 solution until no CO2 was produced, washed with saturated brine, dried over anhydrous MgSO4 for 30 min, filtered, concentrated by rotary evaporation, and purified by column chromatography to obtain the monomer CH3-CON(OH)2.

[0069] (2) Preparation of prepolymer P(MMA-co-CH3-CON(OH)2)

[0070]

[0071] 8.5 g MMA (0.085 mol), 3.255 g CH3-CON(OH)2 (0.015 mol), 0.0242 g BPO and 0.0235 g n-dodecyl mercaptan were dissolved sequentially in 20 mL toluene. The mixture was purged with nitrogen for 30 min to remove oxygen, and then stirred at 80 °C for 6 h under a nitrogen atmosphere. After the reaction was completed, the reaction solution was dropped into methanol to precipitate the polymer. The polymer was filtered, washed three times with methanol, and then dried in a vacuum drying oven at 80 °C for 8 h to obtain the prepolymer.

[0072] (3) Preparation of self-healing PMMA powder

[0073]

[0074]

[0075] It is a PMMA backbone with bis(2-hydroxyethyl)amino in the side chain.

[0076] Dissolve 3g of prepolymer in 30mL of anhydrous DMF, add 6g of activated 4Å molecular sieve, stir at room temperature for 8h under nitrogen atmosphere, filter out the prepolymer solution, and seal for later use; then dissolve 0.3172g (1.914mmol, 0.5 times the molar equivalent of CH3-CON(OH)2) of 1,4-phenylenediboric acid in 2mL of anhydrous DMF, and add 9.7mg (9.6×10⁻⁶) of the solution. -5 Anhydrous triethylamine (mol, 5% mol / L 1,4-phenylenediboronic acid molar equivalent) was used to prepare a crosslinking agent solution for later use. The crosslinking agent solution was slowly added dropwise to the prepolymer solution. The reaction temperature was 40℃, and nitrogen gas with 60% humidity was continuously introduced during the reaction. The mixture was stirred for 8 hours. After the reaction was completed, the product was precipitated with ice-cold ether, washed 3 times, and then dried in a vacuum drying oven at 40℃ for 24 hours to obtain self-healing PMMA powder based on dynamic crosslinking of dinitrogen-coordinated boron diester.

[0077] (4) Preparation of self-healing colorless and transparent PMMA film

[0078] 2g of PMMA powder was dissolved in 10mL of DMF and cast onto a clean glass plate to a thickness of 0.2mm. The mixture was then dried at 25℃ and 50% humidity for 3 hours, followed by drying at 60℃ and 30% humidity for 6 hours, and finally drying at 80℃ and 10% humidity for 3 hours. After cooling to room temperature, the mixture was immersed in deionized water and peeled off after 10 seconds. Finally, it was treated in a 100℃ hot air oven for 30 minutes to obtain a dynamically cross-linked, self-healing, colorless, and transparent PMMA film.

[0079] Example 2

[0080] The preparation method of Example 1 was followed, except that in the preparation of the prepolymer, the feed amounts were 7.0 g MMA (0.07 mol) and 6.51 g CH3-CON(OH)2 (0.03 mol), and in the preparation of the self-healing PMMA powder, the feed amounts of 1,4-phenylenediboric acid and anhydrous triethylamine were 0.5519 g (3.33 mmol, 0.5 times the molar equivalent of CH3-CON(OH)2) and 16.8 mg (1.66 × 10⁻⁶) respectively. -4 mol, 5% of the molar equivalent of 1,4-phenylenediboronic acid.

[0081] Example 3

[0082] The preparation method of Example 1 was followed, except that in the preparation of the prepolymer, the feed amounts were 9.2 g MMA (0.092 mol) and 1.736 g CH3-CON(OH)2 (0.008 mol), and in the preparation of the self-healing PMMA powder, the feed amounts of 1,4-phenylenediboric acid and anhydrous triethylamine were 0.1819 g (1.097 mmol, 0.5 times the molar equivalent of CH3-CON(OH)2) and 5.6 mg (5.49 × 10⁻⁶) respectively. -5 mol, 5% of the molar equivalent of 1,4-phenylenediboronic acid.

[0083] Example 4

[0084] The preparation method of Example 1 was followed, except that in the preparation of the prepolymer, the feed amounts were 8.0 g MMA (0.08 mol) and 4.34 g CH3-CON(OH)2 (0.02 mol), and in the preparation of the self-healing PMMA powder, the feed amounts of 1,4-phenylenediboric acid and anhydrous triethylamine were 0.4030 g (2.431 mmol, 0.5 times the molar equivalent of CH3-CON(OH)2) and 12.3 mg (1.21 × 10⁻⁶) respectively. -4 mol, 5% of the molar equivalent of 1,4-phenylenediboronic acid.

[0085] Example 5

[0086] The self-healing PMMA powder was prepared according to the method described in Example 1, except that the amounts of 1,4-phenylenediboric acid and anhydrous triethylamine added were 0.1903 g (1.15 mmol, 0.3 times the molar equivalent of CH3-CON(OH)2) and 5.8 mg (5.74 × 10⁻⁶) respectively. -5 mol, 5% of the molar equivalent of 1,4-phenylenediboronic acid.

[0087] Example 6

[0088] The self-healing PMMA powder was prepared according to the method described in Example 2, except that the amounts of 1,4-phenylenediboric acid and anhydrous triethylamine added were 0.3312 g (2.0 mmol, 0.3 times the molar equivalent of CH3-CON(OH)2) and 10.1 mg (1 × 10⁻⁶) respectively. -5 mol, 5% of the molar equivalent of 1,4-phenylenediboronic acid.

[0089] Comparative Example 1

[0090] The preparation method of Example 1 was followed, except that in the preparation of the prepolymer, the feed amounts were 9.6 g MMA (0.096 mol) and 0.868 g CH3-CON(OH)2 (0.004 mol), and in the preparation of the self-healing PMMA powder, the feed amounts of 1,4-phenylenediboric acid and anhydrous triethylamine were 0.095 g (5.73 × 10⁻⁶ mol) and 0.868 g CH3-CON(OH)2 (0.004 mol), respectively. -4 mol, 0.5 times the molar equivalent of CH3-CON(OH)2 feed), 2.9 mg (2.86 × 10 -5 mol, 5% of the molar equivalent of 1,4-phenylenediboronic acid.

[0091] Comparative Example 2

[0092] The self-healing PMMA powder was prepared according to the method of Comparative Example 1, except that the amounts of 1,4-phenylenediboric acid and anhydrous triethylamine added were 0.057 g (3.44 × 10⁻⁶ g) and 0.44 × 10⁻⁶ g, respectively. -4 mol, 0.3 times the molar equivalent of CH3-CON(OH)2 feed), 1.7 mg (1.72 × 10⁻⁶) -5 mol, 5% of the molar equivalent of 1,4-phenylenediboronic acid.

[0093] Comparative Example 3

[0094] The preparation method of Example 1 was followed, except that in the preparation of the prepolymer, the feed amounts were 6g MMA (0.06mol) and 8.68g CH3-CON(OH)2 (0.04mol), and in the preparation of the self-healing PMMA powder, the feed amounts of 1,4-phenylenediboric acid and anhydrous triethylamine were 0.6674g (4.09×10⁻⁶) and 0.6674g (4.09×10⁻⁶) respectively. -3 mol, 0.5 times the molar equivalent of CH3-CON(OH)2 feed, 20.7 mg (2.04 × 10⁻⁶) -4 mol, 5% of the molar equivalent of 1,4-phenylenediboronic acid.

[0095] Comparative Example 4

[0096] Commercially available PMMA, Mitsubishi Rayon VH001, was used. 3g of VH001 particles were dissolved in 30mL of anhydrous DMF, then precipitated with ice-cold ether, washed three times, and finally dried in a vacuum drying oven at 80℃ for 12h to obtain VH001 powder after removing the additives. The film-forming steps were carried out according to step four in Example 1 to obtain a non-crosslinked colorless and transparent VH001 film.

[0097] The self-healing performance of the prepared self-healing PMMA film was tested according to the Chinese Society for Corrosion and Protection standard T / CSCP 0003-2023 "Evaluation Method for Self-Healing Performance of Organic Coatings";

[0098] The tensile properties test film strips were prepared according to the national standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets"; the tensile strength change of the prepared self-healing PMMA film was tested according to the national standard GB / T 1040.1-2006 "Determination of tensile properties of plastics - Part 1: General".

[0099] The optical properties of the self-healing PMMA film were tested according to the national standard GB / T 2410-2008 "Determination of light transmittance and haze of transparent plastics".

[0100] The test results are shown in Table 1 below:

[0101] Table 1

[0102]

[0103] Among them, "healing effect" is evaluated by the degree of morphological restoration (observed by optical microscope). A healing status of less than 80% is "poor", 80-90% is "good", and more than 90% is "excellent".

[0104] The "minimum effective repair temperature" was determined by a step-by-step heating experiment combined with a repair efficiency threshold, with an M value of ≤-171 for scratch repair in 24 hours as the standard for effective repair.

[0105] The “M value” indicates the degree of corrosion spread at the scratch. M = (CW) / 2, where “W” is the original width of the scratch (0.38 mm) and “C” is the maximum width of the corroded area of ​​the scratch.

[0106] "Maximum number of repair cycles" refers to the cumulative number of repair cycles performed on the same location for 12 hours at 40°C until the tensile strength is less than 80% of the initial strength.

[0107] "N / A" indicates that even with increased temperature, the scratch repair M value after 24 hours will not reach the minimum effective repair standard.

[0108] In the data table, except for the maximum number of cycles for repair, all other parameters were measured on the original PMMA membrane.

[0109] The data in the table above shows that:

[0110] The PMMA dynamically crosslinked by dinitrogen-coordinated boron diester according to the present invention has excellent self-healing properties. It can quickly repair scratches at room temperature, with mild self-healing conditions. The maximum number of cycles for repair can even reach 16, greatly improving the lifespan. Moreover, within a certain composition range, it has little impact on light transmittance and haze, and can still maintain the high optical performance of PMMA.

[0111] The applicant declares that this invention illustrates the dynamically cross-linked self-healing PMMA, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A dynamically cross-linked self-healing PMMA, characterized in that, The dynamically cross-linked self-healing PMMA has the following structure: ； in The PMMA backbone contains bis(2-hydroxyethyl)amino in its side chain moiety, and the structure of the PMMA containing bis(2-hydroxyethyl)amino in its side chain moiety is as follows: R1 is C1-C4 alkyl, cyclohexyl, phenyl, benzyl, m to n is 5-30:95-70, and R2, R3, R4, R5 are hydrogen, methyl, ethyl, methoxy, hydroxyl, amino, tert-butyl, fluorine or chlorine. The dynamically cross-linked self-healing PMMA is obtained by reacting PMMA with bis(2-hydroxyethyl)amino in the side chain portion as described above with a 1,4-phenylenediboronic acid cross-linking agent as shown in Formula IV. ； The amount of the 1,4-phenylenediboronic acid-based crosslinking agent is 0.3-0.6 times the molar equivalent of the acrylate monomer containing bis(2-hydroxyethyl)amino in the PMMA containing bis(2-hydroxyethyl)amino in the side chain.

2. The method for preparing dynamically cross-linked self-healing PMMA according to claim 1, characterized in that, The preparation method includes the following steps: (1) The acryloyl chloride compound shown in Formula I reacts with triethanolamine to obtain the acrylate monomer containing bis(2-hydroxyethyl)amino group shown in Formula II, as shown in the following reaction formula: ； (2) The acrylate monomer containing bis(2-hydroxyethyl)amino obtained in step (1) is polymerized with the MMA monomer under the initiation of an initiator to obtain PMMA with bis(2-hydroxyethyl)amino in the side chain portion as shown in Formula III. The reaction formula is as follows: ； (3) The PMMA with bis(2-hydroxyethyl)amino side chain obtained in step (2) is reacted with the 1,4-phenylenediboronic acid crosslinking agent shown in Formula IV to obtain the dynamically crosslinked self-healing PMMA. The reaction formula is as follows: 。 3. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of the acryloyl chloride compound shown in Formula I to triethanolamine is 1:1.00 to 1:1.05; The acryloyl chloride compound represented by Formula I in step (1) is selected from any one or a combination of at least two of the following: methacryloyl chloride, ethylacryloyl chloride, propylacryloyl chloride, isopropylacryloyl chloride, n-butylacryloyl chloride, sec-butylacryloyl chloride, isobutylacryloyl chloride, tert-butylacryloyl chloride, methoxymethacryloyl chloride, cyclohexylacryloyl chloride, phenylacryloyl chloride, or benzylacryloyl chloride.

4. The preparation method according to claim 2, characterized in that, The reaction in step (1) is carried out in the presence of an acid-binding agent; the acid-binding agent is selected from any one or a combination of at least two of triethylamine, diisopropylethylamine, 4-dimethylaminopyridine, pyridine or piperidine; The molar ratio of the acid-binding agent to triethanolamine is 1.1-1.3:

1.

5. The preparation method according to claim 2, characterized in that, In step (1), the acryloyl chloride compound shown in Formula I is added dropwise to a reaction system containing triethanolamine at -13 to -7°C; The reaction in step (1) is carried out in an organic solvent selected from any one or a combination of at least two of the following: dichloromethane, chloroform, tetrahydrofuran, dimethyl sulfoxide, N,N-dimethylformamide, methanol, ethanol, isopropanol or acetone; The reaction described in step (1) is carried out under nitrogen protection; The reaction described in step (1) is carried out under stirring; The reaction temperature in step (1) is -13 to -7℃, and the reaction time is 0.5 to 2h.

6. The preparation method according to claim 2, characterized in that, In step (2), the molar ratio of the acrylate monomer containing bis(2-hydroxyethyl)amino to the MMA monomer is 5-30:95-70; The initiator accounts for 20-200 ppm of the total monomer mass; The initiator is selected from any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide or dodecyl peroxide; The polymerization reaction described in step (2) is carried out in the presence of a chain transfer agent; The chain transfer agent is selected from any one or a combination of at least two of n-butanethiol, tert-butanethiol, n-octanethiol, isooctanethiol, n-dodecylthiol, tert-dodecylthiol, or methyl 3-mercaptopropionate; The chain transfer agent is used in an amount of 500-3000 ppm of the total mass of the monomer; The polymerization reaction in step (2) is carried out in a solvent selected from any one or a combination of at least two of the following: chloroform, benzene, toluene, ethylbenzene, N,N-dimethylformamide, tetrahydrofuran, or acetonitrile. The polymerization reaction in step (2) is carried out under stirring; The polymerization reaction in step (2) is carried out at a temperature of 40-90℃ and for a reaction time of 2-8h.

7. The preparation method according to claim 2, characterized in that, The 1,4-phenylenediboronic acid crosslinking agent in step (3) is any one or a combination of at least two of the following: 1,4-phenylenediboronic acid, 2,5-difluoro-1,4-phenylenediboronic acid, 2,5-dichloro-1,4-phenylenediboronic acid, 2,5-di-tert-butyl-1,4-phenylenediboronic acid, perfluoro-1,4-phenylenediboronic acid, 2,5-diethyl-1,4-phenylenediboronic acid, 2,5-dihydroxy-1,4-phenylenediboronic acid, 2,5-dimethyl-1,4-phenylenediboronic acid, 2,5-dimethoxy-1,4-phenylenediboronic acid, 2,3-difluoro-1,4-phenylenediboronic acid, 2,6-difluoro-1,4-phenylenediboronic acid, 2-methoxy-1,4-phenylenediboronic acid, and 2-amino-1,4-phenylenediboronic acid. The amount of 1,4-phenylenediboronic acid crosslinking agent used in step (3) is 0.3-0.6 times the molar equivalent of the acrylate monomer containing bis(2-hydroxyethyl)amino in PMMA containing bis(2-hydroxyethyl)amino in the side chain portion; Before the reaction described in step (3), PMMA containing bis(2-hydroxyethyl)amino in the side chain is dehydrated; The water removal treatment was carried out using a 4Å molecular sieve. The 4Å molecular sieve is an activated molecular sieve, and the activation temperature is 500-600℃, and the treatment time is 3-6h. The reaction in step (3) is carried out in the presence of an organic base catalyst, wherein the organic base catalyst is selected from any one or a combination of at least two of triethylamine, diisopropylethylamine, pyridine, dimethylaminopyridine or piperidine; The reaction temperature in step (3) is 38-42℃, and the reaction time is 4-12h; The reaction described in step (3) is carried out under nitrogen protection and at a humidity of 58-62%.

8. A dynamically cross-linked self-healing PMMA membrane, characterized in that, The dynamically cross-linked self-healing PMMA film is formed from the dynamically cross-linked self-healing PMMA as described in claim 1.

9. The dynamically cross-linked self-healing PMMA membrane according to claim 8, characterized in that, The dynamically cross-linked self-healing PMMA film is prepared by the following method: the dynamically cross-linked self-healing PMMA is dissolved in a solvent, then cast onto a substrate, the solvent is evaporated, then dried, immersed in water, then peeled off from the substrate, and dried to obtain the dynamically cross-linked self-healing PMMA film. The solvent is N,N-dimethylformamide; The dynamically cross-linked self-healing PMMA was dissolved in a solvent to prepare a 20-50% solution. The process of evaporating the solvent involves drying at 25-35°C and 45-55% humidity for 2-4 hours. The drying process involves drying at 60-70℃ and 25-35% humidity for 6-8 hours to form a homogeneous network; finally, drying at 80-90℃ and 5-15% humidity for 2-4 hours. The immersion time in water is 5-15 seconds; The drying process involves processing the product in a hot air oven at 90-120℃ for 20-40 minutes.

10. The application of the dynamically cross-linked self-healing PMMA film according to claim 1 or the dynamically cross-linked self-healing PMMA film according to claim 8 or 9 in optical devices, automotive glass, electronic screens, medical devices, and aerospace materials.

Images