Force-induced discoloration and self-repairing multi-network elastomer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of intelligent materials and polymer composite materials, and relates to a force-induced discoloration and self-repairing multi-network elastomer as well as a preparation method and application thereof. The elastomer is formed by interpenetrating three layers of networks, the first network comprises a force-sensitive cross-linking agent which can be broken under stress and release active groups, the second network comprises a force-induced color-changing cross-linking agent which can be subjected to ring opening and color changing under stress, and the third network is a common cross-linked network. The force-sensitive groups of the first network and the second network are activated under the action of mechanical force, stress early warning is realized through color change, and cross-linking among networks or self-repairing in the networks is realized through in-situ chemical reaction or thermal induction dimerization, so that the toughness and the stability of the material are improved, and the service life of the material is prolonged. According to the invention, the problem that the mechanical property of the traditional dual / multi-network material is reduced due to the fracture of a sacrificial network in the use process is solved.

Description

Technical Field

[0001] This invention belongs to the field of intelligent polymer materials and composite materials technology, specifically relating to a mechanochromic and self-healing multi-network elastomer, its preparation method, and its application. Background Technology

[0002] Dual-network / multi-network structures are an effective strategy for improving the mechanical properties of soft materials (such as hydrogels and elastomers). In these structures, the highly cross-linked first network acts as a "sacrificial network," breaking first under stress to dissipate energy, while the less cross-linked second and third networks maintain the overall material structure, resulting in high toughness and strength. However, the breakage of the "sacrificial bonds" in traditional dual-network materials is irreversible, leading to a continuous decline in mechanical properties during use, lack of damage warning, and absence of self-repair capabilities.

[0003] Methocortical materials can convert mechanical signals into visible optical signals, providing early warning of material damage. Self-healing materials can automatically repair damage and extend service life. Currently, integrating methocortical and self-healing functions into multi-network elastomers and achieving synergistic enhancement between network layers remains a challenge. Existing dual-network materials often have limited functionality, making it difficult to simultaneously achieve real-time stress warning, efficient performance repair, and methocortical enhancement between networks.

[0004] Some studies have used Schiff base reactions to construct gelatin-polyacrylamide dual-network hydrogels, which simultaneously contain Schiff base bonds, hydrogen bonds, and metal coordination interactions, resulting in high tensile strength and high tensile strength. These hydrogels have been used in wearable sensors, but their repair efficiency is low, only around 82%.

[0005] Most studies have only achieved a simple superposition of a single function such as "self-healing" or "mechanical color change" with a dual-network structure. For example, while self-healing networks can restore integrity, the repaired "sacrificial bonds" are difficult to dissipate energy efficiently as before; mechanochromism is also mostly an independent optical response and fails to actively participate in the mechanical enhancement process of the network structure. Ideal "inter-network mechanical enhancement" requires functional units to actively optimize the mechanical behavior of the network, which is currently very rare. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a force-induced color-changing and self-healing multi-network elastomer, its preparation method, and its applications. This material provides a clear warning through color changes when subjected to stress, and can achieve self-healing or performance enhancement through various subsequent treatments (such as static treatment, heating, or light exposure), significantly extending the material's service life and reliability.

[0007] To achieve the above objectives, the present invention provides a method for preparing a force-induced color-changing and self-healing multi-network elastomer, comprising the following steps: S1. Under a protective atmosphere, anthracene-maleimide diacrylate monomer and n-butyl methacrylate monomer are mixed and dissolved in the first solvent, and then added to the reaction system simultaneously with the first initiator through a multi-channel metering feeder at a preset rate, and the first stage copolymerization reaction is carried out under ultraviolet light. S2. Under a protective atmosphere, n-butyl acrylate and spirothiazine diacrylate derivative are mixed and dissolved in a second solvent, and then added to the reaction system simultaneously with the second initiator at a preset rate through a multi-channel metering feeder, and the second stage copolymerization reaction is carried out at 80°C. S3. Under a protective atmosphere, acrylonitrile, n-butyl acrylate, and n-butyl methacrylate are mixed and dissolved in a third solvent, and then added to the reaction system simultaneously with a third initiator at a preset rate through a multi-channel metering feeder, and the third stage copolymerization reaction is carried out at 80°C. S4. After the reaction is complete, remove the reactants and dry them, remove the solvent, or heat them.

[0008] Furthermore, the first solvent is dimethylacetamide.

[0009] Furthermore, the molar ratio of the anthracene-maleimide diacrylate monomer to the n-butyl methacrylate monomer is 1:5 to 5:1.

[0010] Furthermore, the concentration of the anthracene-maleimide diacrylate monomer mixture is 0.1~2.5 mol / L.

[0011] Furthermore, the structural formula of the claimed anthracene-maleimide diacrylate is as follows: .

[0012] Furthermore, the first initiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0013] Furthermore, the addition rate of the first initiator is 0.1~2 mL / min, and the amount used is 0.8%~1% of the total mass of anthracene-maleimide diacrylate monomer and n-butyl methacrylate monomer.

[0014] Furthermore, ultraviolet light was applied perpendicularly to the surface of the reaction liquid at an intensity of 5–20 mW / cm². 2 .

[0015] Furthermore, the reaction temperature was 25.0±0.5℃, and the reaction time was 0.5~2h.

[0016] Furthermore, the second solvent is dimethylacetamide.

[0017] Furthermore, the molar ratio of n-butyl acrylate to metronidazole crosslinking agent is 1:5 to 5:1.

[0018] Furthermore, the concentration of the spirothiran diacrylate derivative mixture is 0.1~2.5 mol / L.

[0019] Furthermore, the structural formula of the claimed spirothiran diacrylate derivative is as follows: Where R1 is ; R2 is selected from any one of nitro, methyl, ethyl, bromo, and chloro groups.

[0020] Furthermore, the second initiator is azobisisobutyronitrile.

[0021] Furthermore, the addition rate of the second initiator is 0.1~2 mL / min, and the amount is 0.8%-1% of the total mass of n-butyl acrylate and spirothian diacrylate derivative.

[0022] Furthermore, before the reaction, the temperature was increased from 25℃ to 80.0±0.2℃ at a linear heating rate of 1-2℃ / min, and the reaction time was 5-7 hours.

[0023] Furthermore, the third solvent is dimethylacetamide.

[0024] Furthermore, the molar ratio of acrylonitrile, n-butyl acrylate, and n-butyl methacrylate is 1~5:1:1.

[0025] Furthermore, the concentration of the mixed acrylonitrile is 0.1~2.5 mol / L.

[0026] Furthermore, the third initiator is azobisisobutyronitrile.

[0027] Furthermore, the addition rate of the third initiator is 0.1~2 mL / min, and the amount used is 0.8%~1.0% of the total mass of acrylonitrile, n-butyl acrylate, and n-butyl methacrylate monomers.

[0028] Furthermore, after the feeding is completed at 80.0±0.2℃, the reaction continues for 2~4 hours.

[0029] A second aspect of the present invention provides a force-sensitive color-changing and self-healing multi-network elastomer, prepared by the preparation method described in the present invention. The elastomer is composed of a first network, a second network, and a third network that interpenetrate and interweave with each other. The first network contains a force-sensitive crosslinking structure that breaks under stress and releases maleimide active groups. The second network contains a force-sensitive crosslinking structure that changes color upon ring-opening under stress and generates sulfur anions after ring-opening. The third network is a common crosslinking structure that provides basic mechanical support. Furthermore, the force-sensitive ring-opening response threshold of the second network is higher than the force-sensitive breaking response threshold of the first network.

[0030] Furthermore, the maleimide active groups released after the first network breaks down undergo addition or condensation reactions with the sulfide anions generated after the second network opens its ring.

[0031] A third aspect of the present invention provides an application of the elastomer described in the present invention in stress early warning, wherein the application realizes stress early warning by monitoring the color change of the elastomer during the stress process; wherein, the color of the elastomer gradually changes from light yellow to white, indicating that the internal stress of the material has reached the level that triggers the opening of the second network; and changes from white to green, indicating that the second network inside the material has opened.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects: 1. Multifunctional integration: A single material simultaneously achieves stress visualization and early warning, self-healing, and performance enhancement.

[0033] 2. Excellent performance: The material has high toughness (tensile strength > 800%, strength > 5 MPa) and stable performance within a certain high temperature range (such as 100℃).

[0034] 3. Sustainability: Through self-healing and toughening mechanisms, the service life of the material is greatly extended, which is in line with the development concept of green materials. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments are further described below. It should be understood that the accompanying drawings only show some embodiments of the present invention. For those skilled in the art, other forms of drawings or equivalent content can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the force-induced color change of the three-network elastomer in multiple embodiments of the present invention during the stretching process; Figure 2 This is a diagram showing the material color change caused by the action of force clusters during the stretching process in multiple three-network elastomers according to embodiments of the present invention. Figure 3This is a comparison of the color changes of the elastic rings after stretching in Comparative Example 1 and Example 1; Figure 4 The 1H NMR spectrum of the anthracene-maleimide diacrylate monomer: 1 H NMR (400 MHz, DMSO-d6) δ 7.51 (dd, J = 5.6, 3.0 Hz, 1H), 7.35 (dd, J = 5.7, 3.1 Hz, 1H), 7.27(dd, J = 6.0, 2.3 Hz, 1H), 7.23 – 7.18 (m, 2H), 7.16 – 7.07 (m, 3H), 6.35 (s,1H), 6.25 (d, J = 17.3 Hz, 2H), 6.01 (s, 2H), 5.96 (s, 1H), 5.43 (s, 2H),4.81 (s, 1H), 3.40 (s, 2H), 3.35 (s, 2H), 3.28 (t, J = 5.4 Hz, 2H). Figure 5 The 1H NMR spectrum of the spirothiran diacrylate derivative: 1 H NMR (500 MHz, Chloroform-d) δ 6.53 (ddd, J = 5.8, 1.8, 0.8 Hz, 1H), 6.44 – 6.39 (m, 2H), 6.34 (dd, J =17.3, 1.4 Hz, 1H), 6.08 (ddd, J = 45.2, 17.3, 10.5 Hz, 2H), 5.82 (ddd, J =18.9, 10.4, 1.4 Hz, 2H), 5.24 (d, J = 1.7 Hz, 1H), 4.99 (d, J = 12.9 Hz, 1H), 4.48 (dd, J = 12.9, 0.8 Hz, 1H), 4.32 – 4.22 (m, 2H), 3.82 – 3.73 (m, 2H), 3.00 – 2.90 (m, 2H). Detailed Implementation

[0037] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0038] According to one aspect of the present invention, a method for preparing a force-sensitive color-changing and self-healing multi-network elastomer is provided, comprising the following steps: S1. Under a protective atmosphere, anthracene-maleimide diacrylate monomer and n-butyl methacrylate monomer are mixed and dissolved in the first solvent, and then added to the reaction system simultaneously with the first initiator through a multi-channel metering feeder at a preset rate, and the first stage copolymerization reaction is carried out under ultraviolet light. S2. Under a protective atmosphere, n-butyl acrylate and spirothiazine diacrylate derivative are mixed and dissolved in a second solvent, and then added to the reaction system simultaneously with the second initiator at a preset rate through a multi-channel metering feeder, and the second stage copolymerization reaction is carried out at 80°C. S3. Under a protective atmosphere, acrylonitrile, n-butyl acrylate, and n-butyl methacrylate are mixed and dissolved in a third solvent, and then added to the reaction system simultaneously with a third initiator at a preset rate through a multi-channel metering feeder, and the third stage copolymerization reaction is carried out at 80°C. S4. After the reaction is complete, remove the reactants and dry them, remove the solvent, or heat them.

[0039] In this invention, the protective atmosphere is nitrogen, argon, or other inert gas that does not affect the experimental results of this invention.

[0040] In this invention, the monomer and solvent are mixed and dissolved in each step using magnetic stirring (e.g., 500 rpm) to ensure complete dissolution.

[0041] In this invention, the mixing and dissolution, along with the initiator, are simultaneously added to the reaction system at a preset rate via a multi-channel metering feed device. Preferably, the reaction system is stirred at a certain rate (e.g., 600 rpm) to conduct a semi-continuous reaction. The preset rate ensures that the mixed monomers and initiator are added simultaneously within a certain time, and the concentration of monomers is controlled by the rate to avoid explosive polymerization. Generally, the multi-channel metering feed device is preferably a three-necked flask with a constant-pressure dropping funnel or a similar instrument. A certain volume of solvent (generally roughly equivalent to the volume of the monomer-mixed solvent in each step) is added to the reaction system as a base liquid. The solvent is preferably dimethylacetamide (DMAC, water content ≤50 ppm).

[0042] In this invention, the elastomer consists of three interconnected networks. The first network is an anthracene-maleimide diacrylate network. The second network is a spirothian diacrylate derivative network. The third network is a polyacrylate network. The first, second, and third networks are formed simultaneously and interwoven to produce a mechanical capability warning / self-healing multi-network elastomer. Stress warning is achieved through color changes in the second network. Simultaneously, the active groups released from the first network react in situ with the active sites exposed by the ring opening of the second network, or cross-linking between networks or self-healing within the network is achieved through thermally induced dimerization. The third network provides basic mechanical support for the elastomer and prevents structural collapse during the repair process, achieving a synergistic function of warning, repair, and structural support.

[0043] In some embodiments, the first solvent is dimethylacetamide.

[0044] In some embodiments, the molar ratio of the anthracene-maleimide diacrylate monomer to the n-butyl methacrylate monomer is 1:5 to 5:1.

[0045] In some embodiments, the concentration of the anthracene-maleimide diacrylate monomer mixture is 0.1~2.5 mol / L.

[0046] In some embodiments, the structural formula of the claimed anthracene-maleimide diacrylate is as follows: .

[0047] In some embodiments, the first initiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0048] In some embodiments, the first initiator is added at a rate of 0.1 to 2 mL / min, and the amount added is 0.8% to 1% of the total mass of anthracene-maleimide diacrylate monomer and n-butyl methacrylate monomer.

[0049] In some embodiments, ultraviolet light is used to vertically irradiate the surface of the reaction liquid at an intensity of 5~20 mW / cm². 2 .

[0050] In some embodiments, the reaction temperature is 25.0±0.5℃ and the reaction time is 0.5~2h.

[0051] In some embodiments, the second solvent is dimethylacetamide.

[0052] In some embodiments, the molar ratio of n-butyl acrylate to metronidazole crosslinking agent is 1:5 to 5:1.

[0053] In some embodiments, the concentration of the spirothiran diacrylate derivative mixture is 0.1~2.5 mol / L.

[0054] In some embodiments, the structural formula of the claimed spirothiran diacrylate derivative is as follows: Where R1 is ; R2 is selected from any one of nitro, methyl, ethyl, bromo, and chloro groups.

[0055] In some embodiments, the second initiator is azobisisobutyronitrile (AIBN).

[0056] In some embodiments, the addition rate of the second initiator is 0.1~2 mL / min, and the amount used is 0.8%-1% of the total mass of n-butyl acrylate and spirothian diacrylate derivative.

[0057] In some embodiments, the temperature is increased from 25°C to 80.0±0.2°C at a linear heating rate of 1-2°C / min before the reaction, and the reaction time is 5-7 hours.

[0058] In some embodiments, the third solvent is dimethylacetamide.

[0059] In some embodiments, the molar ratio of acrylonitrile, n-butyl acrylate, and n-butyl methacrylate is 1 to 5:1:1.

[0060] In some embodiments, the concentration of the acrylonitrile mixture is 0.1~2.5 mol / L.

[0061] In some embodiments, the third initiator is azobisisobutyronitrile (AIBN).

[0062] In some embodiments, the third initiator is added at a rate of 0.1 to 2 mL / min, and the amount is 0.8% to 1.0% of the total mass of acrylonitrile, n-butyl acrylate, and n-butyl methacrylate monomers.

[0063] In some embodiments, the reaction continues for 2 to 4 hours after the feeding is completed at 80.0±0.2°C.

[0064] According to a second aspect of the present invention, a force-sensitive color-changing and self-healing multi-network elastomer is provided, which is prepared by the preparation method described in the present invention. The elastomer is composed of a first network, a second network, and a third network that interpenetrate and interweave with each other. The first network contains a force-sensitive crosslinking structure that breaks under stress and releases maleimide active groups. The second network contains a force-sensitive crosslinking structure that changes color upon ring-opening under stress and generates sulfur anions after ring-opening. The third network is a common crosslinking structure that provides basic mechanical support. Furthermore, the force-sensitive ring-opening response threshold of the second network is higher than the force-sensitive fracture response threshold of the first network, thereby achieving orderly triggering of warning and repair.

[0065] In some embodiments, the maleimide active groups released after the first network breaks down undergo addition or condensation reactions with the sulfur anions generated after the second network opens its ring, forming covalent crosslinks between the networks to achieve toughening.

[0066] In this invention, the following preferred embodiment provides a method for stress warning and performance recovery using this elastomer. Stress levels can be warned by observing color changes; simple static placement, heating, or ultraviolet irradiation can trigger dimerization or click chemistry reactions of the released active groups, achieving self-healing or toughening of the material. The method for the elastomer to perform self-healing or toughening includes: After applying mechanical force to the elastomer until it changes color, it is left to stand in a dark environment, causing the cyclopentadiene structure released by the first network to dimerize, thus achieving self-repair; or, After applying mechanical force to the elastomer until it changes color, rapid self-repair is achieved by accelerating the dimerization of the cyclopentadiene structure through heating. When mechanical force is applied to the elastomer to simultaneously activate the first and second network force-sensitive groups, the maleimide structure released by the first network undergoes a click chemical reaction with the sulfur anions generated by the ring opening of the second network, forming covalent crosslinks between the networks and achieving toughening.

[0067] In this invention, the maximum deformation of the elastomer is adjusted by using a suitable proportion of acrylate monomers so that the material itself can achieve a certain deformation.

[0068] According to a third aspect of the present invention, an application of the elastomer described herein in stress early warning is provided, wherein the application realizes stress early warning by monitoring the color change of the elastomer during the stress process; wherein, the color of the elastomer gradually changes from light yellow to white, indicating that the internal stress of the material has reached the level that triggers the opening of the second network; and changes from white to green, indicating that the second network inside the material has already opened.

[0069] This invention provides applications of the aforementioned elastomer, including as a flexible stress sensor, an early warning patch for structural health monitoring, and an engineered elastomer component with self-healing capabilities.

[0070] The embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the invention. For those skilled in the art, other equivalent embodiments based on the content of the present invention can be obtained without creative effort, and all such embodiments should be considered to fall within the protection scope of the present invention.

[0071] Unless otherwise specified, the raw materials used in the following examples are all publicly available in the prior art, such as those that can be directly purchased or prepared according to publicly available preparation methods. The following ingredients in the examples—n-butyl acrylate, n-butyl acrylate, n-butyl methacrylate, acrylbenzene, maleic anhydride, furan, ethanolamine, 9-anthrayl alcohol, acryloyl chloride, 2,3,3-trimethylindole, 2-iodoethanol, methacrylic acid, 3-chloromethyl-5-nitrosalicylic acid, N,N-dimethylthiocarbamoyl chloride, 2-hydroxy-2-methyl-1-phenyl-1-propanone, azobisisobutyronitrile, dimethylacetamide, dichloromethane, ethyl acetate, petroleum ether, isopropanol, toluene, and N,N-dimethylformamide—were all purchased from Anaiji Company.

[0072] Preparation Example 1 Preparation of anthracene-maleimide diacrylate monomer: A round-bottom flask was filled with 25 mL of dichloromethane, followed by the addition of maleic anhydride (50 mmol). Stirring was initiated, and furan (50 mmol) was slowly added dropwise to the flask via a constant-pressure funnel. Nitrogen gas was applied under ice bath conditions for 10 minutes. Ethanolamine (50 mmol) was then added, and the reaction was allowed to proceed for 2 hours. After the reaction was complete, the mixture was cooled to room temperature, filtered under reduced pressure, and washed three times with ethyl acetate. This solution was then added to a clean, dry 100 mL round-bottom flask containing 9-anthrayl alcohol (50 mmol). A mixture of 28 mL isopropanol and 27 mL toluene was dissolved in the solution, and the mixture was refluxed for 12 hours. Acryloyl chloride (100 mmol) was dissolved in 30 mL of dichloromethane, and the mixture was added dropwise via a constant-pressure dropping funnel under ice bath conditions. After the reaction was complete, the solvent was removed under reduced pressure using a rotary evaporator, followed by separation using a chromatography column (ethyl acetate: petroleum ether = 3:1). The product was then evaporated to dryness. The 1H NMR spectrum of the product is shown below. Figure 4 As shown.

[0073] Preparation Example 2 Preparation of spirothian diacrylate derivative: Take a clean and dry 100 mL round-bottom flask, add 2,3,3-trimethylindole (50 mmol), dissolve it completely in 20 mL of chloroform, seal the flask, freeze, evacuate the gas, and thaw it to remove oxygen from the system. Then add 2-iodoethanol (50 mmol) and react for 48 hours. Then add sodium hydroxide (50 mmol) to obtain product A. Take a clean, dry 100 mL flask, add 100 mmol of methacrylic acid and 100 mmol of 3-chloromethyl-5-nitrosalicylic acid, dissolve the reactants in 100 mL of toluene, seal the system, evacuate and then purge with nitrogen, repeat three times, and reflux for 4 hours. Dissolve 100 mmol of N,N-dimethylthiocarbamoyl chloride in 10 mL of N,N-dimethylformamide, and slowly add it dropwise in an ice bath in a constant pressure dropping funnel for about 15 minutes. Then add 4 mL of 0.7 mol / L sodium hydroxide dropwise, react at room temperature for 15 minutes, add product A (51 mmol), and react in an ice bath for 2 hours. Separate by silica gel column chromatography (petroleum ether: ethyl acetate = 4:1), and obtain the spirothiran diacrylate derivative by rotary evaporation under reduced pressure. The 1H NMR spectrum is shown below. Figure 5 As shown.

[0074] Example 1 S1. Inject 20 mL of distilled and purified dimethylacetamide (DMAC, water content ≤50 ppm) into a three-necked reaction flask that has undergone three nitrogen purging cycles. Under continuous high-purity nitrogen (≥99.999%) protection, accurately weigh 15 mmol of anthracene-maleimide diacrylate monomer and 5 mmol of n-butyl methacrylate are mixed with DMAC to prepare 30 mL of monomer solution A. The reaction system is kept at a constant temperature of 25.0 ± 0.5 °C. Using a light-proof precision syringe pump, 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP) is placed in a brown reservoir. Turn on the ultraviolet light source (dominant wavelength 365 nm, light intensity 15 mW / cm²). 2 (After calibrating with an irradiometer), ultraviolet light was applied perpendicularly to the surface of the reaction liquid. Under continuous illumination and stirring, monomer solution A and HMPP were simultaneously and slowly added dropwise to a three-necked reaction flask at a rate of 1 mL / min. The addition process lasted for 30 minutes.

[0075] S2. In a glove box, precisely weigh 5 mmol of n-butyl acrylate and 15 mmol of spirothiazine diacrylate derivative were mixed with DMAC to prepare 25 mL of solution B. Under nitrogen protection, this solution was added to the system treated in S1 at a constant rate over 30 minutes via a constant-pressure dropping funnel, while maintaining stirring at 600 rpm. Simultaneously, azobisisobutyronitrile (0.8% of the total monomer mass in the first stage) was dissolved in a trace amount of DMAC and added dropwise to the system, controlling the dropping rate to complete the addition within 1 hour. Simultaneously, the temperature was programmed to increase from 25 °C to 80 °C at a linear heating rate of 1.5 °C / min (temperature control accuracy ±0.2 °C). The second-stage copolymerization reaction was carried out at this temperature for 6 hours.

[0076] S3. Dissolve acrylate (containing 10 mmol acrylonitrile, 10 mmol n-butyl acrylate, and 10 mmol n-butyl methacrylate) in dimethylacetamide, and dissolve azobisisobutyronitrile (1.0% of the monomer mass in the second stage feed) in a trace amount of dimethylacetamide to prepare monomer solution C (30 mL) and azobisisobutyronitrile solution. Maintain the reaction system at 80.0 ± 0.2 °C, start the feeding system, and add monomer solution C and azobisisobutyronitrile solution dropwise at a completely synchronized and independently controllable flow rate for a total dropping time of 3 hours. After the dropping is completed, continue the reaction at 80 °C for 3 hours to complete the third stage polymerization reaction, which lasts for a total of 6 hours.

[0077] S4. Place the reactants in a vacuum oven at 70°C and -0.1 MPa for 8 hours.

[0078] Example 2 S1. Inject 20 mL of distilled and purified dimethylacetamide (DMAC, water content ≤50 ppm) into a three-necked reaction flask that has undergone three nitrogen purging cycles. Under continuous high-purity nitrogen (≥99.999%) protection, accurately weigh 10 mmol of anthracene-maleimide diacrylate monomer and 10 mmol of n-butyl methacrylate are mixed with DMAC to prepare 30 mL of monomer solution A. The reaction system is kept at a constant temperature of 25.0 ± 0.5 °C. Using a light-proof precision syringe pump, 2-hydroxy-2-methyl-1-phenyl-1-propanone is placed in a brown reservoir. The ultraviolet light source (dominant wavelength 365 nm, light intensity 15 mW / cm²) is turned on. 2 (After calibrating with an irradiometer), ultraviolet light was applied perpendicularly to the surface of the reaction liquid. Under continuous illumination and stirring, monomer solution A and HMPP were simultaneously and slowly added dropwise to a three-necked reaction flask at a rate of 0.5 mL / min. The addition process lasted for 60 minutes.

[0079] S2. In a glove box, precisely weigh 10 mmol of n-butyl acrylate and 10 mmol of spirothiazine diacrylate derivative were mixed with DMAC to prepare a 25 mL solution B. Under nitrogen protection, this solution was added to the system treated in S1 at a constant rate over 30 minutes via a constant-pressure dropping funnel, while maintaining stirring at 600 rpm. Simultaneously, azobisisobutyronitrile (0.8% of the total monomer mass in the first stage) was dissolved in a trace amount of DMAC and added dropwise to the system, controlling the dropping rate to complete the addition within 1 hour. Simultaneously, the temperature was programmed to increase from 25 °C to 80 °C at a linear heating rate of 1.5 °C / min (temperature control accuracy ±0.2 °C). The second-stage copolymerization reaction was carried out at this temperature for 6 hours.

[0080] S3. Dissolve acrylate (containing 20 mmol acrylonitrile, 10 mmol n-butyl acrylate, and 10 mmol n-butyl methacrylate) in dimethylacetamide, and dissolve azobisisobutyronitrile (1.0% of the monomer mass in the second stage feed) in a trace amount of dimethylacetamide to prepare monomer solution C (30 mL) and azobisisobutyronitrile solution. Maintain the reaction system at 80.0 ± 0.2 °C, start the feeding system, and add monomer solution C and azobisisobutyronitrile solution dropwise at a completely synchronized and independently controllable flow rate for a total dropping time of 3 hours. After the dropping is completed, continue the reaction at 80 °C for 3 hours to complete the second stage polymerization reaction, which lasts for a total of 6 hours.

[0081] S4. Place the reactants in a vacuum oven at 70°C and -0.1 MPa for 8 hours.

[0082] Example 3 S1. Inject 20 mL of distilled and purified dimethylacetamide (DMAC, water content ≤50 ppm) into a three-necked reaction flask that has undergone three nitrogen purging cycles. Under continuous high-purity nitrogen (≥99.999%) protection, accurately weigh 5 mmol of anthracene-maleimide diacrylate monomer and 15 mmol of n-butyl methacrylate are mixed with DMAC to prepare 30 mL of monomer solution A. The reaction system is kept at a constant temperature of 25.0 ± 0.5 °C. Using a light-proof precision syringe pump, 2-hydroxy-2-methyl-1-phenyl-1-propanone is placed in a brown reservoir. The ultraviolet light source (dominant wavelength 365 nm, light intensity 15 mW / cm²) is turned on. 2 (After calibrating with an irradiometer), ultraviolet light was applied perpendicularly to the surface of the reaction liquid. Under continuous illumination and stirring, monomer solution A and HMPP were simultaneously and slowly added dropwise to a three-necked reaction flask at a rate of 1 mL / min. The addition process lasted for 30 minutes.

[0083] S2. In a glove box, precisely weighed 15 mmol of n-butyl acrylate and 5 mmol of spirothiazine diacrylate derivative were mixed with DMAC to prepare 25 mL of solution B. Under nitrogen protection, this solution was added to the system treated in S1 at a constant rate over 30 minutes via a constant-pressure dropping funnel, while maintaining stirring at 600 rpm. Simultaneously, azobisisobutyronitrile (0.8% of the total monomer mass in the first stage) was dissolved in a trace amount of DMAC and added dropwise to the system, controlling the dropping rate to complete the addition within 1 hour. Simultaneously, the temperature was programmed to increase from 25 °C to 80 °C at a linear heating rate of 1.5 °C / min (temperature control accuracy ±0.2 °C). The second-stage copolymerization reaction was carried out at this temperature for 6 hours.

[0084] S3. Dissolve acrylate (containing 30 mmol acrylonitrile, 10 mmol n-butyl acrylate, and 10 mmol n-butyl methacrylate) in dimethylacetamide, and dissolve azobisisobutyronitrile (1.0% of the monomer mass in the second stage feed) in a trace amount of dimethylacetamide to prepare monomer solution C (30 mL) and azobisisobutyronitrile solution. Maintain the reaction system at 80.0 ± 0.2 °C, start the feeding system, and add monomer solution C and azobisisobutyronitrile solution dropwise at a completely synchronized and independently controllable flow rate for a total dropping time of 3 hours. After the dropping is completed, continue the reaction at 80 °C for 3 hours to complete the third stage polymerization reaction, which lasts for a total of 6 hours.

[0085] S4. Place the reactants in a vacuum oven at 70°C and -0.1 MPa for 8 hours.

[0086] Comparative Example 1 S1. Inject 20 mL of distilled and purified dimethylacetamide (DMAC, water content ≤50 ppm) into a three-necked reaction flask that has undergone three nitrogen purging cycles. Under continuous high-purity nitrogen (≥99.999%) protection, accurately weigh 5 mmol of anthracene-maleimide diacrylate and 5 mmol of n-butyl methacrylate monomers into the DMAC, and stir magnetically (500 rpm) until completely dissolved to prepare a 60 mL mixed solution. Maintain the reaction system at 25.0 ± 0.5 °C, and using a light-protected precision syringe pump, place 2-hydroxy-2-methyl-1-phenyl-1-propanone into a brown reservoir. Turn on the ultraviolet light source (dominant wavelength 365 nm, light intensity 15 mW / cm²). 2 (After being calibrated by an irradiometer), ultraviolet light was applied perpendicularly to the surface of the reaction liquid. Under continuous illumination and stirring, HMPP was slowly added dropwise to the mixed solution at a constant rate of 0.5 mL / min using a syringe pump. The addition process lasted for 120 minutes.

[0087] S2. A mixed solution of acrylates (containing acrylonitrile, n-butyl acrylate, and n-butyl methacrylate, each 10 mmol) and azobisisobutyronitrile (1.0% of the monomer mass in the second stage feed) were dissolved in dimethylacetamide to prepare a monomer solution (30 mL) and an azobisisobutyronitrile solution. The reaction system was maintained at 80.0 ± 0.2 °C. The feeding system was started, and the monomer solution and the azobisisobutyronitrile solution were added dropwise at a completely synchronized and independently controllable flow rate for a total dropping time of 3 hours. After the dropping was completed, the reaction was continued at 80 °C for another 3 hours to complete the second stage polymerization reaction, which lasted a total of 6 hours.

[0088] S3. Place the reactants in a vacuum oven at 70°C and -0.1 MPa for 8 hours.

[0089] Performance testing Force-induced color change warning test and repair test: Samples from each embodiment were cut into dumbbell shapes and stretched at a speed of 10 mm / min. For example... Figures 1-2 As shown, the sample in the examples changed from light yellow to white and then to green as the stretching rate increased. Initially, the sample was pale yellow. As the stretching process continued, the first network was destroyed, while the second network was not activated. Therefore, at low stretching rates (0-400%), the material was stretched, and the color gradually lightened. As the stretching rate continued to increase (500%-700%), the second network began to activate, and the spirothian diacrylate derivative underwent ring-opening under stress, turning into green thioisocyanate (TMC). Example 3 showed a weaker color change due to the lowest content of methanophores. Figure 3 As shown, in the comparative example, stretching did not cause the material to change color because no chromophores were added.

[0090] The results are shown in Table 1. Because Example 1 has the lowest acrylonitrile content and Example 3 has the highest acrylonitrile content and the greatest rigidity, the maximum fracture deformation value of the material is affected by the acrylonitrile content in the following order: Example 1 > Example 2 > Example 3. Comparative Example 1 does not contain spirothiophene chromophores (which have a certain degree of rigidity) and therefore does not have a color-changing function. Furthermore, it has the lowest acrylonitrile content, so the maximum fracture deformation value of this material can reach 1200%. During the heat repair experiment, Diels-Alder dimerization occurred inside the materials of Examples 1, 2, and 3, reforming the cross-linked network. This allowed the toughened materials to complete the subsequent cyclic tensile test. Example 1 maintained more than 90% of its original strength. Example 3 had a lower recovery strength due to fewer anthracene-maleimide diacrylate groups. Comparative Example 1, lacking repair groups, could not be repaired due to fracture.

[0091] Table 1 Cyclic tensile testing: The samples were subjected to 10 cycles of 600% strain tensile testing to assess their stress strength and repair effect. As shown in Table 2, the cyclic tensile test revealed that in Examples 1, 2, and 3, the spirothiophene diacrylate derivative underwent ring-opening under stress after deformation, increasing the crosslinking strength of the supporting material for 10 cycles of tensile testing. In contrast, Comparative Example 1, lacking spirothiophene, fractured on the second cycle of tensile testing.

[0092] Table 2 The embodiments of the present invention have been described above with reference to the accompanying drawings. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the core idea of ​​the present invention. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing a force-induced color-changing and self-healing multi-network elastomer, characterized in that, Includes the following steps: S1. Under a protective atmosphere, anthracene-maleimide diacrylate monomer and n-butyl methacrylate monomer are mixed and dissolved in the first solvent, and then added to the reaction system simultaneously with the first initiator through a multi-channel metering feeder at a preset rate, and the first stage copolymerization reaction is carried out under ultraviolet light. S2. Under a protective atmosphere, n-butyl acrylate and spirothiazine diacrylate derivative are mixed and dissolved in a second solvent, and then added to the reaction system simultaneously with the second initiator at a preset rate through a multi-channel metering feeder, and the second stage copolymerization reaction is carried out at 80°C. S3. Under a protective atmosphere, acrylonitrile, n-butyl acrylate, and n-butyl methacrylate are mixed and dissolved in a third solvent, and then added to the reaction system simultaneously with a third initiator at a preset rate through a multi-channel metering feeder, and the third stage copolymerization reaction is carried out at 80°C. S4. After the reaction is complete, remove the reactants and dry them, remove the solvent, or heat them.

2. The preparation method according to claim 1, characterized in that, In step S1, The first solvent is dimethylacetamide; and / or The molar ratio of the anthracene-maleimide diacrylate monomer to the n-butyl methacrylate monomer is 1:5 to 5:1; and / or The concentration of the anthracene-maleimide diacrylate monomer mixture is 0.1~2.5 mol / L; and / or The structural formula of the anthracene-maleimide diacrylate is as follows: 。 3. The preparation method according to claim 1, characterized in that, In step S1, The first initiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone; and / or The first initiator is added at a rate of 0.1~2 mL / min, and the amount added is 0.8%~1% of the total mass of anthracene-maleimide diacrylate monomer and n-butyl methacrylate monomer; and / or Ultraviolet light is applied perpendicularly to the surface of the reaction liquid at an intensity of 5–20 mW / cm². 2 ; and / or The reaction temperature was 25.0±0.5℃, and the reaction time was 0.5~2h.

4. The preparation method according to claim 1, characterized in that, In step S2, The second solvent is dimethylacetamide; and / or The molar ratio of n-butyl acrylate to the metronic crosslinking agent is 1:5 to 5:1; and / or The concentration of the spirothiran diacrylate derivative mixture is 0.1~2.5 mol / L; and / or The structural formula of the claimed spirothiran diacrylate derivative is as follows: Where R1 is ; R2 is selected from any one of nitro, methyl, ethyl, bromo, and chloro groups.

5. The preparation method according to claim 1, characterized in that, In step S2, The second initiator is azobisisobutyronitrile; and / or The second initiator is added at a rate of 0.1~2 mL / min, and the amount added is 0.8%-1% of the total mass of n-butyl acrylate and spirothian diacrylate derivative; and / or Before the reaction, the temperature was increased from 25℃ to 80.0±0.2℃ at a linear heating rate of 1-2℃ / min, and the reaction time was 5-7 hours.

6. The preparation method according to claim 1, characterized in that, In step S3, The third solvent is dimethylacetamide; and / or The molar ratio of acrylonitrile, n-butyl acrylate, and n-butyl methacrylate is 1~5:1:1; and / or The concentration of the mixed acrylonitrile is 0.1~2.5 mol / L.

7. The preparation method according to claim 1, characterized in that, In step S3, The third initiator is azobisisobutyronitrile; and / or The third initiator is added at a rate of 0.1~2 mL / min, and the amount used is 0.8%~1.0% of the total mass of acrylonitrile, n-butyl acrylate, and n-butyl methacrylate monomers; and / or After feeding is completed at 80.0±0.2℃, continue the reaction for 2~4 hours.

8. A force-induced color-changing and self-healing multi-network elastomer, characterized in that, The elastomer is prepared by any one of the preparation methods described in claims 1 to 7, wherein the elastomer is composed of a first network, a second network, and a third network that interpenetrate and interweave with each other; the first network contains a force-sensitive crosslinking structure that breaks under stress and releases maleimide active groups, the second network contains a force-sensitive crosslinking structure that changes color upon ring opening under stress and generates sulfur anions after ring opening, and the third network is a common crosslinking structure that provides basic mechanical support; and the force-sensitive ring-opening response threshold of the second network is higher than the force-sensitive breaking response threshold of the first network.

9. The elastomer according to claim 8, characterized in that, The maleimide active groups released after the first network breaks down undergo addition or condensation reactions with the sulfide anions generated after the second network opens its ring.

10. The application of the elastomer according to claim 8 or 9 in stress early warning, characterized in that, The application achieves stress early warning by monitoring the color change of the elastomer during the stress process; wherein, the color of the elastomer gradually changes from light yellow to white, indicating that the internal stress of the material has reached the level that triggers the opening of the second network; and changes from white to green, indicating that the second network inside the material has already opened.

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