Hydrophobic siloxane shielded alkali-resistant self-healing polyurethane hybrid elastomer with dynamic disulfide bonds, and preparation method and application thereof

Abstract

The application belongs to the technical field of polymer self-repairing elastomer materials, and specifically discloses an alkali-resistant self-repairing polyurethane hybrid elastomer and a preparation method and application thereof. The elastomer realizes the synergistic improvement of mechanical properties, self-repairing capability and environmental tolerance by synergistically introducing dynamic disulfide bonds, hydrophobic siloxane segments and rigid aromatic crosslinking structures in the same polyurethane network. The preparation method uses polyurethane precursors as raw materials, dissolves the precursors in N,N-dimethylformamide (DMF), and then casts into a film and dries, so that the process flow is simple and easy to operate. The surface scratch of the elastomer can be closed and repaired within 120 min at 60 DEG C, and the tensile property remains stable after multiple damage-repair cycles. Meanwhile, the hydrophobic siloxane-rich phase acts as a micro diffusion barrier, so that the material can still maintain the stability of chemical structure and mechanical properties under the condition of soaking in strong alkaline medium with pH = 12.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to self-healing elastomer materials, specifically to an alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond, its preparation method, and its application. Background Technology

[0002] In contemporary polymer science and engineering applications, elastomer materials that simultaneously meet the requirements of high mechanical properties, chemical stability, and self-healing are considered one of the key bottlenecks for further development in fields such as flexible electronics, soft robotics, and sealing systems for harsh environments. Flexible electronics (such as foldable displays and electronic skin) require substrate materials to maintain structural and functional stability under cyclic loading; soft actuators and sensors are susceptible to mechanical damage and chemical corrosion during dynamic environmental interactions; and sealing components of electric vehicle battery packs and deep-sea exploration equipment require materials to maintain mechanical integrity over long periods in hot, humid, or saline environments. These requirements collectively point to a core objective: to simultaneously achieve synergistic optimization of high strength, high toughness, fatigue resistance, hydrolysis resistance, and intrinsic self-healing capabilities at the molecular scale.

[0003] Currently, dynamic covalent chemistry (especially in polyurethane systems containing disulfide bonds) is frequently used to endow elastomers with self-healing capabilities. However, dynamic networks often face unavoidable inherent contradictions: flexible segments and easily exchangeable bonds that facilitate rapid repair often reduce the material's modulus, tensile strength, and creep resistance; while increasing the density of physical or chemical crosslinks can enhance mechanical stability, it inhibits segment movement and hinders dynamic bond exchange, leading to incomplete damage closure. Furthermore, in actual service environments, polar linkages such as polyurethane / urea bonds are prone to hydrolytic fracture under hot, humid, or alkaline conditions, causing irreversible network degradation and resulting in permanent loss of mechanical properties and repairability. Therefore, how to maintain high strength and toughness while achieving tolerance to harsh environments such as alkalinity, and simultaneously ensuring efficient self-healing, remains a crucial problem to be solved in the design of dynamic elastomers. Summary of the Invention

[0004] The purpose of this invention is to provide an alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond, its preparation method and application. By synergistically introducing dynamic disulfide bonds, hydrophobic siloxane segments and rigid aromatic crosslinking structures into a single polyurethane network, it achieves repeatable self-healing while taking into account mechanical strength and toughness, and improves the chemical and mechanical stability of the material in harsh environments such as alkaline media.

[0005] This invention is achieved through the following technical solution: A method for preparing an alkali-resistant, self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond formation includes the following steps: Step 1: Dissolve 1,3-bis(3-aminopropyl)tetramethyldisiloxane and L-cysteine ​​dimethyl ester in anhydrous N,N-dimethylformamide at a molar ratio of (1~2):(1~2). Under nitrogen protection, slowly add anhydrous N,N-dimethylformamide solution of 4,4′,4″-triphenylmethane triisocyanate at 0~5℃ until the molar ratio of isocyanate to amino group in the solution is (0.95~1.05):1. After the addition is complete, heat the mixture to 60~80℃ and react for 6~12 h. After the reaction is complete, slowly pour the reaction solution into deionized water to precipitate. Collect the solid, wash and dry to obtain polyurethane precursor PUST. Step 2: Dissolve the polyurethane precursor prepared in Step 1 in an organic solvent at a mass-volume ratio of 0.05-0.2 g / mL at 60-80 °C to form a homogeneous solution; Step 3: Pour the solution obtained in Step 2 into a polytetrafluoroethylene mold, and evaporate the solvent at 40~60 ℃ to obtain a thin film, thus obtaining an alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding synergistic dynamic disulfide bonds.

[0006] The present invention also has the following technical features: Preferably, in step one, during the dissolution of 1,3-bis(3-aminopropyl)tetramethyldisiloxane and L-cysteine ​​dimethyl ester in anhydrous N,N-dimethylformamide, the mass-to-volume ratio of solute to solvent is 0.05~0.3 g / mL, and the dissolution process is carried out using a magnetic stirrer at a rate of 200~500 r / min.

[0007] Preferably, the concentration of the anhydrous N,N-dimethylformamide solution of 4,4′,4″-triphenylmethane triisocyanate in step one is 0.05~0.2 g / mL.

[0008] Preferably, in step one, the dropping rate of the anhydrous N,N-dimethylformamide solution of 4,4′,4″-triphenylmethane triisocyanate is 0.5~3.0 mL / min; during the dropping process, a magnetic stirrer is used to stir at a rate of 300~800 r / min.

[0009] Preferably, in step one, the mixture is stirred at a rate of 200-600 r / min using a magnetic stirrer during the reaction process.

[0010] Preferably, the washing in step one involves washing with ethanol 3 to 5 times.

[0011] Preferably, the drying in step one is performed by drying in a vacuum oven at 40~70℃ until constant weight.

[0012] This invention also protects an alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond prepared according to the above method, and its application in a strongly alkaline environment.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The elastomer of this invention achieves a performance balance by leveraging the synergistic effect of dynamic disulfide bond exchange, physical shielding of hydrophobic siloxane phase, and phase structure regulation of stepwise polymerization reaction of rigid aromatic crosslinking, relying on the bonding and microphase separation characteristics of polyurethane molecular network, thus achieving chemical and mechanical stability in a balanced manner while taking into account mechanical toughness, repeatable self-healing and alkaline media environment. This invention utilizes L-cysteine ​​dimethyl ester to introduce disulfide bonds (-SS-), which can undergo a reversible sulfur-sulfide bond exchange reaction under mild thermal stimulation (60°C). When scratches are generated on the material surface, the disulfide bonds at the breakage points undergo homolytic / heterolytic cleavage under thermal action, forming sulfur free radicals or sulfide anions. The sulfur active groups at different fracture sites come into contact with each other and re-bond, achieving scratch closure and molecular chain reconstruction; simultaneously, with 4,4′,4″- Triphenylmethane triisocyanate (TTI), as a rigid aromatic crosslinking agent, undergoes an addition reaction with the amino groups provided by L-cysteine ​​dimethyl ester (Cys-OMe) and 1,3-bis(3-aminopropyl)tetramethyldisiloxane (SiDA) to form a polyurethane crosslinking network, constructing a rigid physical scaffold to ensure the initial mechanical strength of the material and prevent material softening caused by excessive disulfide bond exchange. On the other hand, by controlling the crosslinking density, it provides suitable space for chain segment movement for disulfide bond exchange—neither too dense crosslinking inhibits chain segment migration (leading to repair failure) nor too sparse crosslinking causes disordered chain segment movement. The disulfide bond exchange reaction is a reversible dynamic covalent reaction, and no chemical degradation occurs during multiple repair cycles. At the same time, the rigid crosslinking network maintains the overall structural integrity of the material. The hydrophobic siloxane segments (SiDA-introduced) of this invention exhibit significant differences in hydrophilicity and hydrophobicity compared to the polar framework and dynamic disulfide segments of polyurethane. During molecular self-assembly, the siloxane segments spontaneously accumulate to form hydrophobic microregions, constituting a microphase-separated structure with the polar and crosslinked phases of polyurethane. The siloxane-enriched phase is a chemically inert hydrophobic region; on the one hand, its hydrophobic properties can repel the wetting of alkaline aqueous solutions and reduce OH-. - On the one hand, it contacts the active sites inside the material; on the other hand, the enriched phase forms a continuous microscopic diffusion barrier, significantly reducing OH... - The mass transfer rate within the material, blocking OH from the mass transfer process. - Nucleophilic attack on the polyurethane backbone (urethane bonds) and dynamic disulfide bonds to form OH groups. -The diffusion is effectively shielded; the urethane bonds and dynamic disulfide bonds in polyurethane are nucleophilic reactive sites under alkaline conditions. The presence of the siloxane barrier encapsulates these reactive bonds within nonpolar microregions or polar phases, preventing them from reacting with OH groups. - It acts directly, thereby inhibiting bond hydrolysis and breakage reactions under alkaline conditions, stabilizing the chemical structure and mechanical properties of the material, and forming a protective mechanism of active bonds; The preparation process of this invention is simple, and the microphase structure and chain segment mobility of the material can be controlled, giving it outstanding potential for industrial applications. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the design and synthesis of the polyurethane hybrid elastomer (PSCT) of the present invention; Figure 2 Tensile stress-strain curves of the samples prepared in Examples 1-3; Figure 3 Cyclic tensile strain curves of the samples prepared in Examples 1-3; Figure 4 Comparison of tensile stress-strain curves of the sample prepared in Example 1 before and after alkaline solution treatment; Figure 5 The contact angle of the sample prepared in Example 1; Figure 6 The graph shows the change in storage modulus of the samples prepared in Examples 1-3 as a function of temperature. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0016] Example 1 This embodiment presents an alkali-resistant, self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond synthesis, the synthesis route of which is as follows: Figure 1 As shown, its preparation method includes the following steps: 1) Preparation of polyurethane precursor: 1,3-bis(3-aminopropyl)tetramethyldisiloxane and L-cysteine ​​dimethyl ester were dissolved in anhydrous N,N-dimethylformamide at a molar ratio of 1:1, wherein the mass-volume ratio of solute to solvent was 0.051 g / mL, and the dissolution process was carried out by stirring with a magnetic stirrer at a rate of 2001 r / min. Under nitrogen protection, an anhydrous N,N-dimethylformamide solution of 4,4′,4″-triphenylmethane triisocyanate with a concentration of 0.051 g / mL was slowly added dropwise at 0.51 mL / min at 01 °C until the molar ratio of isocyanate to amino groups in the solution was 0.95:1. During the dropwise addition, the mixture was stirred at 300 r / min using a magnetic stirrer. After the dropwise addition was completed, the mixture was heated to 60 °C and reacted for 12 h. During the reaction, the mixture was stirred at 200 r / min using a magnetic stirrer. After the reaction was completed, the reaction solution was slowly poured into deionized water to precipitate the solid. The solid was collected, washed three times with ethanol, and dried to constant weight in a vacuum oven at 40 °C to obtain the polyurethane precursor PUST. 2) Dissolving the film-forming precursor solution: Weigh 0.5g of the PUST and add it to 5 mL of N,N-dimethylformamide (DMF), and dissolve it at 70 °C to form a homogeneous solution; 3) Film formation: Pour the solution obtained in step 2) into a PTFE mold and evaporate the solvent at 50 °C to obtain an elastomer film, which is the polyurethane hybrid elastomer.

[0017] Alkali-resistant environment stability evaluation: The sample was immersed in an alkaline solution with pH=12, and the mass change was monitored within 24 h; the sample after immersion for 6 h was subjected to Fourier transform infrared spectroscopy and tensile testing to evaluate the retention of the chemical structure and mechanical properties of the sample.

[0018] Self-healing performance evaluation: A scratch of about 1 mm depth was prepared on the sample surface with a scalpel. The sample was placed at 60℃ and the morphology of the scratch was monitored within 120 min. Multiple damage-repair cycles were performed, and a tensile test was conducted after each repair.

[0019] like Figure 1 The diagram illustrates the design concept and properties of the polyurethane hybrid elastomer (PSCT) of this invention. This invention ingeniously integrates 1,3-bis(3-aminopropyl)tetramethyldisiloxane (providing hydrophobicity and flexibility), dimethyl cysteine ​​(providing dynamic disulfide bonds), and 4,4′,4″-triphenylmethane triisocyanate (providing rigid support nodes) into the same polymer network. In this structure, the hydrophobic siloxane segments spontaneously accumulate, forming a microphase separation structure with the polar and crosslinked phases of the polyurethane, laying the molecular structural foundation for subsequent alkali resistance and mechanical strength.

[0020] Example 2 This embodiment provides an alkali-resistant, self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond formation. Its preparation method includes the following steps: 1) Preparation of polyurethane precursor: 1,3-bis(3-aminopropyl)tetramethyldisiloxane and L-cysteine ​​dimethyl ester were dissolved in anhydrous N,N-dimethylformamide at a molar ratio of 1:2, wherein the mass-volume ratio of solute to solvent was 0.3 g / mL, and the dissolution process was carried out by stirring with a magnetic stirrer at a rate of 500 r / min. Under nitrogen protection, an anhydrous N,N-dimethylformamide solution of 0.2 g / mL 4,4′,4″-triphenylmethane triisocyanate was slowly added dropwise at 5 °C at a rate of 3.0 mL / min until the molar ratio of isocyanate to amino groups in the solution reached 1.05:1. During the dropwise addition, the mixture was stirred at 800 r / min using a magnetic stirrer. After the dropwise addition was completed, the mixture was heated to 80 °C and reacted for 6 h. During the reaction, the mixture was stirred at 600 r / min using a magnetic stirrer. After the reaction was completed, the reaction solution was slowly poured into deionized water to precipitate the solid. The solid was collected, washed five times with ethanol, and dried to constant weight in a vacuum oven at 70 °C to obtain the polyurethane precursor PUST. 2) Dissolving the film-forming precursor solution: Weigh 0.4 g of the PUST and add it to 5 mL of DMF, then dissolve it at 65 °C to form a homogeneous solution; 3) Film formation: Pour the solution obtained in step 2) into a PTFE mold and evaporate the solvent at 45 °C to obtain an elastomer film. The elastomer prepared above was used to evaluate its stability in alkaline environments: the sample was immersed in an alkaline solution with pH=12 and the mass change was monitored within 24 h; the sample immersed for 6 h was used for FT-IR and tensile stress-strain tests.

[0021] The elastomer prepared above was used to evaluate its self-healing performance: a scratch of about 1 mm depth was prepared on the sample surface, the sample was placed at 55 ℃, the change in scratch morphology was monitored within 120 min, and a tensile test was performed after repair to evaluate mechanical retention.

[0022] Example 3 This embodiment provides an alkali-resistant, self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond formation. Its preparation method includes the following steps: 1) Preparation of polyurethane precursor: 1,3-bis(3-aminopropyl)tetramethyldisiloxane and L-cysteine ​​dimethyl ester were dissolved in anhydrous N,N-dimethylformamide at a molar ratio of 2:1, wherein the mass-volume ratio of solute to solvent was 0.2 g / mL, and the dissolution process was carried out by stirring with a magnetic stirrer at a speed of 300 r / min. Under nitrogen protection, an anhydrous N,N-dimethylformamide solution of 0.1 g / mL 4,4′,4″-triphenylmethane triisocyanate was slowly added dropwise at 3℃ at a rate of 2.0 mL / min until the molar ratio of isocyanate to amino groups in the solution was 1:1. During the dropwise addition, the mixture was stirred at a rate of 500 r / min using a magnetic stirrer. After the dropwise addition was completed, the mixture was heated to 70℃ and reacted for 8 h. During the reaction, the mixture was stirred at a rate of 400 r / min using a magnetic stirrer. After the reaction was completed, the reaction solution was slowly poured into deionized water to precipitate the solid. The solid was collected, washed four times with ethanol, and dried to constant weight in a vacuum oven at 60℃ to obtain the polyurethane precursor PUST. 2) Dissolving the film-forming precursor solution: Weigh 0.8 g of the PUST and add it to 4 mL of DMF, then dissolve it at 80 °C to form a homogeneous solution; 3) Film formation: Pour the solution obtained in step 2) into a PTFE mold and evaporate the solvent at 60 °C to obtain an elastomer film.

[0023] The elastomer prepared above was used to evaluate its stability in alkaline environments: the sample was immersed in an alkaline solution with pH=12 and the mass change was monitored within 48 h; the sample immersed for 12 h was subjected to FT-IR and tensile stress-strain tests.

[0024] The elastomer prepared above was used to evaluate its self-healing performance: a scratch of about 1 mm depth was prepared on the sample surface, the sample was placed at 65 ℃, and the change in scratch morphology was monitored within 120 min; and tensile tests were performed on the samples before and after repair for comparison.

[0025] Figure 2 The tensile stress-strain curves of the samples prepared in Examples 1-3 of this invention show that a perfect balance between the rigid physical support and the flexible siloxane chain segments is achieved, with a toughness of up to 107.1 MJ / m³. Before fracture, a large amount of energy can be dissipated through chain segment rearrangement and disulfide bond exchange.

[0026] Figure 3 Cyclic tensile strain curves of the samples prepared in Examples 1-3; from Figure 3 The cyclic tensile test showed that, compared with the sample with low crosslinking (which is prone to irreversible plastic deformation), the moderately crosslinked elastomer prepared in Example 1 showed extremely fast strain recovery and high overlap under multiple cyclic stresses, exhibiting excellent fatigue resistance and dimensional stability.

[0027] Figure 4The image shows a comparison of the tensile stress-strain curves of the sample prepared in Example 1 before and after treatment with an alkaline solution. After the elastomer containing hydrophobic siloxane was soaked in a strong alkali for 6 hours or even longer, its tensile curve almost completely overlapped with the initial state before soaking, and its strength and toughness did not decrease significantly.

[0028] Figure 5 The contact angle of the sample prepared in Example 1; such as Figure 5 As shown, the elastomer prepared in this embodiment of the invention exhibits a large water contact angle (e.g., 95.4°), confirming that the siloxane segments introduced into the system can spontaneously migrate and accumulate on the material surface and subsurface, forming a dense, low-surface-energy hydrophobic layer. This siloxane-enriched phase, as a key "physical shielding layer," effectively repels the wetting of external water molecules and hydrated ions, providing the first line of defense for improving tolerance to harsh environments.

[0029] Figure 6 The storage modulus of the polyurethane hybrid elastomers (PSCTs) prepared in Examples 1-3 is shown as a function of temperature. The curves show that the preferred sample in Example 1 exhibits a high storage modulus plateau in the room temperature range, ensuring the mechanical strength required for use as an engineering material or electronic substrate. However, when the temperature rises to approximately 54°C, the storage modulus decreases significantly, indicating localized network relaxation and opening a sufficient "kinetic window" for dynamic disulfide bond exchange. Therefore, under the conditions described in the examples (60°C), the material achieves complete scratch closure and efficient recovery of mechanical properties within 120 minutes.

[0030] Example 4 This embodiment provides an alkali-resistant, self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond formation. Its preparation method includes the following steps: 1) Preparation of polyurethane precursor: 1,3-bis(3-aminopropyl)tetramethyldisiloxane and L-cysteine ​​dimethyl ester were dissolved in anhydrous N,N-dimethylformamide at a molar ratio of 2:1.5, wherein the mass-volume ratio of solute to solvent was 0.1 g / mL, and the dissolution process was carried out by stirring with a magnetic stirrer at a rate of 300 r / min. Under nitrogen protection, an anhydrous N,N-dimethylformamide solution of 0.1 g / mL 4,4′,4″-triphenylmethane triisocyanate was slowly added dropwise at 4 °C at a rate of 1.0 mL / min until the molar ratio of isocyanate to amino groups in the solution reached 0.95:1. During the dropwise addition, the mixture was stirred at 800 r / min using a magnetic stirrer. After the dropwise addition was completed, the mixture was heated to 80 °C and reacted for 8 h. During the reaction, the mixture was stirred at 300 r / min using a magnetic stirrer. After the reaction was completed, the reaction solution was slowly poured into deionized water to precipitate the solid. The solid was collected, washed three times with ethanol, and dried to constant weight in a vacuum oven at 40 °C to obtain the polyurethane precursor PUST. 2) Dissolving the film-forming precursor solution: Weigh 0.5 g of the PUST and add it to 10 mL of DMF, then dissolve it at 60 °C to form a homogeneous solution; 3) Film formation and post-treatment: Pour the solution obtained in step 2) into a PTFE mold and evaporate the solvent at 40 ℃ to obtain a film; after the film is demolded, it is further dried at 60 ℃ for 2 h to obtain an elastomer film.

[0031] The elastomer prepared above was used to evaluate its stability in alkaline environments: the sample was immersed in an alkaline solution with pH=12 and the mass change was monitored within 24 h; the sample immersed for 6 h was subjected to FT-IR and tensile stress-strain tests.

[0032] The elastomer prepared above was used to evaluate its self-healing performance: a scratch of about 1 mm depth was prepared on the sample surface, the sample was placed at 60 ℃, and the change in scratch morphology was monitored within 120 min; and 3 damage-repair cycles were performed, with tensile tests performed after each repair.

[0033] Comparative Example 1 A method for preparing a self-healing polyurethane elastomer without hydrophobic siloxanes, comprising the following steps: (Comparative sample without hydrophobic siloxanes) 1) Preparation of polyurethane precursor: The preparation process is basically the same as in Example 1, except that 1,6-hexanediamine is used instead of 1,3-bis(3-aminopropyl)tetramethyldisiloxane in Example 1 to synthesize a polyurethane precursor control sample; 2) Dissolving the film-forming precursor solution: Weigh 0.5 g of the polyurethane precursor control sample and add it to 5 mL of N,N-dimethylformamide (DMF), and dissolve it at 70 °C to form a homogeneous solution; 3) Film formation: Pour the solution obtained in step 2) into a PTFE mold and evaporate the solvent at 50 °C to obtain an elastomer film.

[0034] Performance Testing and Result Analysis: The prepared films were immersed in an alkaline solution at pH 12 for tolerance evaluation. The results showed that after immersion for 6 hours, the samples exhibited significant macroscopic swelling and microcracks; further tensile testing revealed that the samples were extremely prone to fracture, with severe strength loss. FT-IR results showed that some urethane bonds underwent hydrolytic breakage; due to the lack of a microscopic diffusion barrier constructed by hydrophobic siloxanes, hydroxide ions (OH-) in the alkaline solution... - The diffusion barrier mechanism directly attacks polar urethane and disulfide bonds, causing rapid macroscopic swelling and degradation in strong alkali environments. The superior alkali resistance data compared to Example 1 clearly and powerfully demonstrates that the diffusion barrier mechanism of this invention successfully addresses the industry pain point of dynamic polyurethane's susceptibility to failure in alkaline environments.

[0035] Comparative Example 2 A comparative sample without dynamic disulfide bonds; a method for preparing an alkali-resistant polyurethane elastomer without dynamic disulfide bonds, comprising the following steps: 1) Preparation of polyurethane precursor: The preparation process is basically the same as in Example 1, except that 1,4-butanediol is used as a sulfur-free common chain extender to replace cystine dimethyl ester in Example 1 to synthesize a polyurethane precursor comparative sample. 2) Dissolving the film-forming precursor solution: Weigh 0.5 g of the polyurethane precursor control sample and add it to 5 mL of N,N-dimethylformamide (DMF), and dissolve it at 70 °C to form a homogeneous solution; 3) Film formation: Pour the solution obtained in step 2) into a PTFE mold and evaporate the solvent at 50°C to obtain an elastomer film.

[0036] Performance Testing and Result Analysis: Scratches approximately 1 mm deep were created on the surface of the samples using a scalpel, and the samples were placed at 60 °C. Results showed that the scratch morphology did not change significantly within 120 min of monitoring, failing to achieve closure and repair. Subsequent tensile testing indicated that its mechanical properties could not be restored. Dynamic thermomechanical analysis (DMA) also showed that its network, lacking dynamic covalent bond exchange, could not undergo effective network relaxation and reconstruction under heating conditions. Although the material prepared in Comparative Example 2 possessed certain mechanical strength, it completely lost its self-healing ability even after heating due to the lack of a reversible covalent bond exchange mechanism after mechanical damage.

[0037] The elastomer of this invention achieves a performance balance by leveraging the synergistic effect of dynamic disulfide bond exchange, physical shielding of the hydrophobic siloxane phase, and phase structure regulation of the stepwise polymerization reaction of rigid aromatic crosslinking, relying on the bonding and microphase separation characteristics of the polyurethane molecular network. This results in a balance of mechanical strength and toughness, repeatable self-healing, and chemical and mechanical stability in alkaline media environments.

Claims

1. A method for preparing an alkali-resistant, self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond, characterized in that, Includes the following steps: Step 1: Dissolve 1,3-bis(3-aminopropyl)tetramethyldisiloxane and L-cysteine ​​dimethyl ester in anhydrous N,N-dimethylformamide at a molar ratio of (1~2):(1~2). Under nitrogen protection, slowly add anhydrous N,N-dimethylformamide solution of 4,4′,4″-triphenylmethane triisocyanate at 0~5℃ until the molar ratio of isocyanate to amino group in the solution is (0.95~1.05):

1. After the addition is complete, heat the mixture to 60~80℃ and react for 6~12 h. After the reaction is complete, slowly pour the reaction solution into deionized water to precipitate. Collect the solid, wash and dry to obtain polyurethane precursor PUST. Step 2: Dissolve the polyurethane precursor prepared in Step 1 in an organic solvent at a mass-volume ratio of 0.05-0.2 g / mL at 60-80 °C to form a homogeneous solution; Step 3: Pour the solution obtained in Step 2 into a polytetrafluoroethylene mold, and evaporate the solvent at 40~60 ℃ to obtain a thin film, thus obtaining an alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding synergistic dynamic disulfide bonds.

2. The method for preparing the hydrophobic siloxane-shielded synergistic dynamic disulfide bond alkali-resistant self-healing polyurethane hybrid elastomer according to claim 1, characterized in that, In step one, during the dissolution of 1,3-bis(3-aminopropyl)tetramethyldisiloxane and L-cysteine ​​dimethyl ester in anhydrous N,N-dimethylformamide, the mass-to-volume ratio of solute to solvent is 0.05~0.3 g / mL, and a magnetic stirrer is used to stir at a rate of 200~500 r / min during the dissolution process.

3. The method for preparing the alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond according to claim 1, characterized in that, In step one, the concentration of the anhydrous N,N-dimethylformamide solution of 4,4′,4″-triphenylmethane triisocyanate is 0.05~0.2 g / mL.

4. The method for preparing the alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond according to claim 1, characterized in that, In step one, the dropping rate of the anhydrous N,N-dimethylformamide solution of 4,4′,4″-triphenylmethane triisocyanate is 0.5~3.0 mL / min; during the dropping process, a magnetic stirrer is used to stir at a rate of 300~800 r / min.

5. The method for preparing the alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond according to claim 1, characterized in that, In step one, the mixture is stirred at a rate of 200-600 r / min using a magnetic stirrer during the reaction process.

6. The method for preparing the alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond according to claim 1, characterized in that, The washing described in step one involves washing with ethanol 3 to 5 times.

7. The method for preparing the alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond according to claim 1, characterized in that, The drying process described in step one involves drying the product in a vacuum oven at 40-70°C until it reaches a constant weight.

8. An alkali-resistant self-healing polyurethane hybrid elastomer with hydrophobic siloxane shielding and synergistic dynamic disulfide bond prepared by the method according to any one of claims 1-7.

9. The application of the hydrophobic siloxane-shielded synergistic dynamic disulfide bond alkali-resistant self-healing polyurethane hybrid elastomer according to claim 8 in a strongly alkaline environment with pH=12.

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