Photo-responsive self-healing antibacterial nylon material and preparation method thereof

Abstract

The application discloses a kind of photoresponsive self-repair antibacterial nylon materials and preparation method thereof.The material is modified nylon 6 polymer, aromatic Schiff base dynamic imine bond generated by condensation reaction of carboxyl benzaldehyde and p-phenylenediamine is embedded in its molecular main chain, which gives the material the ability of light-triggered self-repair without external heat source, and unexpectedly improves the mechanical properties and thermal stability of the material, the molecular chain end is bonded with antibacterial organic acid through amide bond, and the antibacterial organic acid is 2-methyl-4-(trifluoromethyl) thiazole-5-carboxylic acid.The preparation method adopts one-pot two-stage polymerization, after pressure opening ring prepolymerization, pressure relief vacuum is carried out to carry out deep condensation and end-capping, and the product is obtained by extrusion granulation and drying.The material can realize room temperature self-repair under natural light, and the antibacterial component is non-dissolution fixed.The application process is simple, the performance is adjustable, and can be used in the field of intelligent packaging, repairable antibacterial coating and biomedical materials.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a photoresponsive self-healing antibacterial nylon material and its preparation method. Background Technology

[0002] Nylon 6, due to its excellent mechanical strength, wear resistance, and processing fluidity, has become a widely used engineering plastic in the automotive, electronics, and packaging industries. However, in practical applications, nylon 6 materials face two inherent challenges: First, under cyclic stress or external force damage, microcracks are easily generated inside the material, and these cracks continue to expand, eventually leading to a sharp drop in mechanical properties and premature product failure; second, in humid or confined environments, the material surface is extremely prone to becoming a breeding ground for bacteria and other microorganisms, posing health and safety risks.

[0003] To address the aforementioned issues, existing technologies have attempted to functionalize nylon 6. For example, Chinese patent CN109251311A discloses a self-healing nylon material that incorporates quadruple hydrogen bonds (such as ureidopyrimidinone units) and mechanochromic units into the polymer matrix, enabling the material to possess damage warning and repair capabilities. However, the self-healing process of this approach essentially relies on external heating to drive the reversible recombination of hydrogen bonds, rather than spontaneously occurring under more gentle and convenient conditions such as room temperature or natural light. This severely limits its application in outdoor or energy-saving scenarios.

[0004] On the other hand, for the antibacterial modification of nylon materials, technical solutions represented by Chinese patent CN120365554A typically employ physical blending or chemical grafting to introduce antibacterial agents. While physical blending is simple to operate, the antibacterial components easily migrate and dissolve from the matrix, leading to a significant decrease in antibacterial effect over time and potentially posing environmental and health risks. Chemical grafting, although it can improve the stability of antibacterial components, often faces problems such as complex processes, low grafting efficiency, or significant impact on the activity of antibacterial components. More importantly, these solutions do not consider the self-repairing ability of the material after damage.

[0005] Therefore, how to develop a novel nylon 6 material that can synergistically solve the problems of material durability and hygiene safety at the molecular level and has a simple preparation process is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a photoresponsive self-healing antibacterial nylon material and its preparation method, solving the technical problems that "existing self-healing nylon requires an external heat source to trigger and has harsh repair conditions, while existing antibacterial nylon has antibacterial components that are easy to migrate and dissolve, have poor long-term effects, and it is difficult to obtain both types of functions at the same time".

[0007] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a photoresponsive self-healing antibacterial nylon material, wherein the material is a modified nylon 6 polymer, the main chain of which contains an aromatic Schiff base dynamic imine bond, and the ends of the molecular chain are bonded with an antibacterial organic acid through an amide bond. The aromatic Schiff base dynamic imine bond originates from an aromatic imine monomer, which is embedded in the polymer backbone through the active groups at both ends of its end in the polymerization reaction of nylon 6. The aromatic imine monomer is a compound generated by the condensation reaction of p-carboxybenzaldehyde and p-phenylenediamine. The antibacterial organic acid is 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid; The modified nylon 6 polymer is prepared by two-stage polymerization: the first stage polymerization is pressure ring-opening prepolymerization, and the second stage polymerization is normal compression polymerization followed by vacuum polymerization.

[0008] The structural formula of the modified nylon 6 polymer is as follows:

[0009] Where x is between 0.9 and 0.99, y is between 0.01 and 0.1, and x + y = 1; n is a natural number between 50 and 160.

[0010] Secondly, this invention provides a method for preparing a photoresponsive self-healing antibacterial nylon material, comprising the following steps: (1) Using p-carboxybenzaldehyde and p-phenylenediamine as raw materials, the reaction was carried out in anhydrous ethanol under nitrogen protection and heated. The resulting aromatic imine monomer was purified, washed and dried under vacuum. (2) Add caprolactam, the above aromatic imine monomer, antibacterial organic acid, 1,6-hexanediamine and deionized water to a high-pressure polymerization reactor, replace with nitrogen, and then heat and pressurize to carry out the first stage of polymerization. (3) Depressurize to atmospheric pressure and heat up, then evacuate to carry out the second stage of polymerization; (4) After polymerization, nitrogen gas is introduced at normal pressure, followed by melt extrusion, water bath cooling, granulation, and vacuum drying to obtain nylon material.

[0011] Specifically, the amount of p-carboxybenzaldehyde and p-phenylenediamine fed is 0.05-0.15 mol, and the molar ratio between them is 1:1.

[0012] Specifically, the polymerization temperature in the first stage is 220~250℃, the pressure is 0.8~1.2MPa, and the reaction time is 1.5~3h.

[0013] Specifically, the polymerization temperature in the second stage is 240~260℃, the vacuum degree is -0.09~-0.1MPa, and the reaction time is 0.5~2h.

[0014] Specifically, the amount of the aromatic imine monomer added is 5-15% of the molar amount of caprolactam.

[0015] Specifically, the amount of antibacterial organic acid added is 1 to 3% of the total mass of caprolactam, aromatic imine monomer, 1,6-hexanediamine, antibacterial organic acid and deionized water.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) This invention realizes the self-healing of materials under natural light irradiation. By embedding aromatic Schiff base dynamic imine bonds in the nylon main chain, the dynamic bonds undergo a reversible imine exchange reaction under natural light irradiation, which closes and repairs the microcracks on the material surface at room temperature. The repair efficiency can reach up to 99%. The repair process does not require an external heat source or external repair agent, and it also improves the mechanical properties and thermal stability of the material.

[0017] (2) This invention provides a non-leaching, long-lasting, and stable antibacterial material. By linking 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid to the end of the polymer chain via covalent amide bonds, the antibacterial functional groups are firmly fixed in the material and are not easily migrated or dissolved. Test results show that the material has an antibacterial rate of up to 99.9% against Escherichia coli and Staphylococcus aureus, and its antibacterial properties remain good after washing with water.

[0018] (3) The present invention adopts a one-pot two-stage polymerization process, which simultaneously completes the insertion of dynamic imine bonds and the end-capping of antibacterial organic acids. The process is simple, and the resulting material maintains good mechanical properties while having both photo-responsive self-healing and long-lasting antibacterial functions. Moreover, the self-healing efficiency and antibacterial activity can be controlled by adjusting the feeding ratio of functional monomers. Attached Figure Description

[0019] Figure 1 This is the reaction equation for the synthesis of aromatic imine monomers in this invention.

[0020] Figure 2 The 1H NMR spectrum of the aromatic imine monomer of this invention ( 1 H NMR).

[0021] Figure 3 This is the reaction equation for the synthesis of the nylon material of this invention.

[0022] Figure 4 This is a comparison diagram of the antibacterial effects of the nylon material in Example 4 and the nylon material in Comparative Example 1.

[0023] Figure 5 This is a comparison image of the nylon material before and after scratch repair in Comparative Example 1 of this invention.

[0024] Figure 6 This is a comparison image of the nylon material before and after scratch repair in Example 4 of the present invention.

[0025] Figure 7 The thermogravimetric curve of the nylon material in Example 4 of this invention is shown.

[0026] Figure 8 The thermogravimetric curve of the nylon material in Comparative Example 4 of this invention is shown. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] The implementation scheme of the present invention is as follows: First, p-carboxybenzaldehyde and p-phenylenediamine are added to 250 mL of anhydrous ethanol, stirred and heated under nitrogen protection, and reacted at 75-85 °C for 10-12 h. After cooling, the mixture is filtered, and the collected solid is purified by column chromatography. It is washed successively with 50 mL of anhydrous ethanol and 30 mL of diethyl ether, and dried under vacuum at 60-80 °C for 12-24 h to obtain an aromatic imine monomer. Through the condensation reaction of p-carboxybenzaldehyde and p-phenylenediamine, an aromatic imine monomer containing carboxyl and amino groups at both ends is prepared. This monomer has the ability to participate in the nylon polycondensation reaction and embeds an aromatic Schiff base dynamic imine bond into the nylon backbone. This aromatic Schiff base dynamic imine bond can undergo a reversible imine exchange reaction under natural light irradiation, so that the molecular chains at the damaged site can be rearranged and connected, thereby realizing the self-repair of microcracks at room temperature under light irradiation without any external heat source or repair agent.

[0029] In the following preferred embodiments, the amount of p-carboxybenzaldehyde and p-phenylenediamine fed is 0.05-0.15 mol, and the molar ratio between them is 1:1.

[0030] In this invention, the first-stage polymerization process is as follows: 1399.2–1751.3 g of caprolactam, 178.9–445.8 g of the above-mentioned aromatic imine monomer, 20.7–62.1 g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 12.7–38.1 g of 1,6-hexanediamine, and 100.0 g of deionized water are added to a high-pressure polymerization reactor in proportion. The air inside the reactor is replaced three times with nitrogen, and the temperature is increased at a rate of 1–2 °C / min. In the first-stage polymerization, caprolactam undergoes ring-opening under the initiation of water and copolymerizes with the aromatic imine monomer, antibacterial organic acid, and 1,6-hexanediamine to form a prepolymer containing dynamic imine bonds of aromatic Schiff bases. At the same time, the antibacterial organic acid is bonded to the polymer chain end in the form of covalent amide bonds, permanently fixing the antibacterial functional group to the end of the material, preventing it from migrating and dissolving from the matrix, thereby endowing the material with long-lasting, stable, non-dissolving broad-spectrum antibacterial properties.

[0031] In the following preferred embodiments, the amount of the aromatic imine monomer added is 5-15% of the molar amount of caprolactam, for example, it can be 5%, 10%, 12%, or 15%. Within this feeding ratio range, the material can take into account both excellent photoresponsive self-healing properties and mechanical strength.

[0032] In the following preferred embodiments, the polymerization temperature in the first stage is 220~250℃, the pressure is 0.8~1.2MPa, and the reaction time is 1.5~3h.

[0033] In this invention, the second-stage polymerization process is as follows: the vapor in the system is slowly released, the pressure is reduced to atmospheric pressure within 0.5 to 2 hours, and then the temperature is increased to carry out the reaction under vacuum; free water and some small molecule byproducts in the system are removed by depressurization, so that the polymerization reaction proceeds in the direction of generating high molecular weight polymers; then, residual moisture and volatile small molecules are further removed by vacuuming, which promotes the full progress of the amidation reaction. On the one hand, it promotes the continuous growth of polymer molecular chains to obtain high molecular weight nylon materials with practical mechanical properties, and on the other hand, it promotes the full reaction of antibacterial organic acids with amino groups at the ends of polymer chains to achieve efficient end-capping of antibacterial functional groups.

[0034] In the following preferred embodiments, the polymerization temperature in the second stage is 240~260℃, the vacuum degree is -0.09~-0.1MPa, and the reaction time is 0.5~2h.

[0035] After the two-stage polymerization reaction is completed, nitrogen gas is introduced to atmospheric pressure, the molten polymer is extruded into a water bath for cooling and drawing into strips, and then granulated using a pelletizer. The resulting slices are then vacuum dried at 80~100℃ for 10~12h to obtain nylon material.

[0036] Example 1; (1) 0.05 mol of p-carboxybenzaldehyde and 0.05 mol of p-phenylenediamine were added to 250 mL of anhydrous ethanol, stirred and heated under nitrogen protection, and reacted at 75 °C for 10 h. After cooling, the mixture was filtered, and the collected solid was purified by column chromatography. It was washed successively with 50 mL of anhydrous ethanol and 30 mL of diethyl ether, and dried under vacuum at 60 °C for 12 h to obtain an aromatic imine monomer. (2) 1751.3g of caprolactam, 185.7g of the above aromatic imine monomer, 20.7g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 12.7g of 1,6-hexanediamine and 100.0g of deionized water were added to a high-pressure polymerization reactor. The air inside the reactor was replaced with nitrogen three times. The temperature was increased to 240℃ at a rate of 1.5℃ / min. The pressure inside the reactor was maintained at 1.0MPa. The reaction was carried out for 2h to carry out the first stage of polymerization. (3) Slowly release the vapor in the system, reduce the pressure to atmospheric pressure within 0.5h, and raise the temperature to 240℃ at the same time; turn on the vacuum system, reduce the pressure of the reaction system to -0.09MPa, and continue the reaction at 240℃ for 0.5h to carry out the second stage of polymerization; (4) After the reaction is complete, nitrogen gas is introduced to atmospheric pressure, the molten polymer is extruded into a water bath to cool and be drawn into strips, and then granulated by a pelletizer. The resulting slices are vacuum dried at 80°C for 10 hours to obtain nylon material.

[0037] Example 2; (1) 0.1 mol of p-carboxybenzaldehyde and 0.1 mol of p-phenylenediamine were added to 250 mL of anhydrous ethanol, stirred and heated under nitrogen protection, and reacted at 80 °C for 11 h. After cooling, the mixture was filtered, and the collected solid was purified by column chromatography. It was washed successively with 50 mL of anhydrous ethanol and 30 mL of diethyl ether, and dried under vacuum at 70 °C for 18 h to obtain an aromatic imine monomer. (2) 1719.6g of caprolactam, 182.3g of the above aromatic imine monomer, 41.4g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 25.4g of 1,6-hexanediamine and 100.0g of deionized water were added to a high-pressure polymerization reactor. The air inside the reactor was replaced with nitrogen three times. The temperature was increased to 240℃ at a rate of 1.5℃ / min. The pressure inside the reactor was maintained at 1.0MPa. The reaction was carried out for 2h to carry out the first stage of polymerization. (3) Slowly release the vapor in the system, reduce the pressure to normal pressure within 1 hour, and raise the temperature to 250°C at the same time; turn on the vacuum system, reduce the pressure of the reaction system to -0.1MPa, and continue the reaction at 250°C for 1 hour to carry out the second stage of polymerization; (4) After the reaction is complete, nitrogen gas is introduced to atmospheric pressure, the molten polymer is extruded into a water bath to cool and draw into strips, and then granulated by a pelletizer. The resulting slices are vacuum dried at 90°C for 11 hours to obtain nylon material.

[0038] Example 3; (1) 0.1 mol of p-carboxybenzaldehyde and 0.1 mol of p-phenylenediamine were added to 250 mL of anhydrous ethanol, stirred and heated under nitrogen protection, and reacted at 80 °C for 11 h. After cooling, the mixture was filtered, and the collected solid was purified by column chromatography. It was washed successively with 50 mL of anhydrous ethanol and 30 mL of diethyl ether, and dried under vacuum at 70 °C for 18 h to obtain an aromatic imine monomer. (2) 1687.9g of caprolactam, 178.9g of the above aromatic imine monomer, 62.1g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 38.1g of 1,6-hexanediamine and 100.0g of deionized water were added to a high-pressure polymerization reactor. The air inside the reactor was replaced with nitrogen three times. The temperature was increased to 240℃ at a rate of 1.5℃ / min. The pressure inside the reactor was maintained at 1.0MPa. The reaction was carried out for 2h to carry out the first stage of polymerization. (3) Slowly release the vapor in the system, reduce the pressure to normal pressure within 1 hour, and raise the temperature to 250°C at the same time; turn on the vacuum system, reduce the pressure of the reaction system to -0.1MPa, and continue the reaction at 250°C for 1 hour to carry out the second stage of polymerization; (4) After the reaction is complete, nitrogen gas is introduced to atmospheric pressure, the molten polymer is extruded into a water bath to cool and draw into strips, and then granulated by a pelletizer. The resulting slices are vacuum dried at 90°C for 11 hours to obtain nylon material.

[0039] Example 4; (1) 0.1 mol of p-carboxybenzaldehyde and 0.1 mol of p-phenylenediamine were added to 250 mL of anhydrous ethanol, stirred and heated under nitrogen protection, and reacted at 80 °C for 11 h. After cooling, the mixture was filtered, and the collected solid was purified by column chromatography. It was washed successively with 50 mL of anhydrous ethanol and 30 mL of diethyl ether, and dried under vacuum at 70 °C for 18 h to obtain an aromatic imine monomer. (2) 1537.0g of caprolactam, 308.0g of the above aromatic imine monomer, 61.3g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 38.1g of 1,6-hexanediamine and 100.0g of deionized water were added to a high-pressure polymerization reactor. The air inside the reactor was replaced with nitrogen three times. The temperature was increased to 220°C at a rate of 1°C / min. The pressure inside the reactor was maintained at 0.8MPa. The reaction was carried out for 1.5h to carry out the first stage of polymerization. (3) Slowly release the vapor in the system, reduce the pressure to normal pressure within 1 hour, and raise the temperature to 250°C at the same time; turn on the vacuum system, reduce the pressure of the reaction system to -0.1MPa, and continue the reaction at 250°C for 1 hour to carry out the second stage of polymerization; (4) After the reaction is complete, nitrogen gas is introduced to atmospheric pressure, the molten polymer is extruded into a water bath to cool and draw into strips, and then granulated by a pelletizer. The resulting slices are vacuum dried at 90°C for 11 hours to obtain nylon material.

[0040] Example 5; (1) 0.15 mol of p-carboxybenzaldehyde and 0.15 mol of p-phenylenediamine were added to 250 mL of anhydrous ethanol, stirred and heated under nitrogen protection, and reacted at 85 °C for 12 h. After cooling, the mixture was filtered, and the collected solid was purified by column chromatography. It was washed successively with 50 mL of anhydrous ethanol and 30 mL of diethyl ether, and dried under vacuum at 80 °C for 24 h to obtain an aromatic imine monomer. (2) 1480.8g of caprolactam, 364.2g of the above aromatic imine monomer, 61.3g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 38.1g of 1,6-hexanediamine and 100.0g of deionized water were added to a high-pressure polymerization reactor. The air inside the reactor was replaced with nitrogen three times. The temperature was increased to 250℃ at a rate of 2℃ / min. The pressure inside the reactor was maintained at 1.2MPa. The reaction was carried out for 3h to carry out the first stage of polymerization. (3) Slowly release the vapor in the system, reduce the pressure to normal pressure within 2 hours, and raise the temperature to 260°C at the same time; turn on the vacuum system, reduce the pressure of the reaction system to -0.1MPa, and continue the reaction at 260°C for 2 hours to carry out the second stage of polymerization; (4) After the reaction is complete, nitrogen gas is introduced to atmospheric pressure, the molten polymer is extruded into a water bath to cool and draw into strips, and then granulated by a pelletizer. The resulting slices are vacuum dried at 100°C for 12 hours to obtain nylon material.

[0041] Example 6; (1) 0.15 mol of p-carboxybenzaldehyde and 0.15 mol of p-phenylenediamine were added to 250 mL of anhydrous ethanol, stirred and heated under nitrogen protection, and reacted at 85 °C for 12 h. After cooling, the mixture was filtered, and the collected solid was purified by column chromatography. It was washed successively with 50 mL of anhydrous ethanol and 30 mL of diethyl ether, and dried under vacuum at 80 °C for 24 h to obtain an aromatic imine monomer. (2) 1399.2g of caprolactam, 445.8g of the above aromatic imine monomer, 61.3g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 38.1g of 1,6-hexanediamine and 100.0g of deionized water were added to a high-pressure polymerization reactor. The air inside the reactor was replaced with nitrogen three times. The temperature was increased to 250℃ at a rate of 2℃ / min. The pressure inside the reactor was maintained at 1.2MPa. The reaction was carried out for 3h to carry out the first stage of polymerization. (3) Slowly release the vapor in the system, reduce the pressure to normal pressure within 2 hours, and raise the temperature to 260°C at the same time; turn on the vacuum system, reduce the pressure of the reaction system to -0.1MPa, and continue the reaction at 260°C for 2 hours to carry out the second stage of polymerization; (4) After the reaction is complete, nitrogen gas is introduced to atmospheric pressure, the molten polymer is extruded into a water bath to cool and draw into strips, and then granulated by a pelletizer. The resulting slices are vacuum dried at 100°C for 12 hours to obtain nylon material.

[0042] Comparative Example 1; The difference between Comparative Example 1 and Example 4 is that step (1) is omitted, and step (2) is changed to: 1537.0g of caprolactam and 100.0g of deionized water are added to a high-pressure polymerization reactor, the air inside the reactor is replaced with nitrogen three times, the temperature is raised to 220°C at a rate of 1°C / min, the pressure inside the reactor is maintained at 0.8MPa, and the reaction is carried out for 1.5h to carry out the first stage of polymerization; the remaining steps are the same as in Example 4.

[0043] Comparative Example 2; The difference between Comparative Example 2 and Example 4 lies in step (2). Step (2) is changed as follows: 1925.0g of caprolactam, 40.9g of the above-mentioned aromatic imine monomer, 21.0g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 12.7g of 1,6-hexanediamine and 100.0g of deionized water are added to a high-pressure polymerization reactor. The air inside the reactor is replaced with nitrogen three times. The temperature is increased to 220°C at a rate of 1°C / min. The pressure inside the reactor is maintained at 0.8MPa. The reaction is carried out for 1.5h to carry out the first stage of polymerization. The remaining steps are the same as in Example 4.

[0044] Comparative Example 3; The difference between Comparative Example 3 and Example 4 lies in step (2). Step (2) is changed to: 1537.0g of caprolactam, 308.0g of the above-mentioned aromatic imine monomer, 38.1g of 1,6-hexanediamine and 100.0g of deionized water are added to a high-pressure polymerization reactor, the air inside the reactor is replaced with nitrogen three times, the temperature is raised to 220°C at a rate of 1°C / min, the pressure inside the reactor is maintained at 0.8MPa, and the reaction is carried out for 1.5h to carry out the first stage of polymerization; the remaining steps are the same as in Example 4.

[0045] Comparative Example 4; The difference between Comparative Example 4 and Example 4 lies in step (2). Step (2) is changed as follows: 1537.0g of caprolactam, 308.0g of 4-aminobenzoic acid, 61.3g of 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid, 38.1g of 1,6-hexanediamine and 100.0g of deionized water are added to a high-pressure polymerization reactor. The air inside the reactor is replaced with nitrogen three times. The temperature is increased to 220°C at a rate of 1°C / min. The pressure inside the reactor is maintained at 0.8MPa. The reaction is carried out for 1.5h to carry out the first stage of polymerization. The remaining steps are the same as in Example 4.

[0046] Test and Results Analysis Tensile property testing: The samples of each embodiment and comparative example were tested according to GB / T1040.2-2022 standard.

[0047] Thermodynamic stability testing: Performed by thermogravimetric analysis. Test conditions were as follows: Samples from each embodiment and comparative example were first molded into test specimens using a standard injection molding process, and then vacuum-dried at 80°C for 4 hours before testing to ensure the removal of moisture interference. Then, under the same atmosphere, the temperature was increased from room temperature to 800°C at a rate of 20°C / min. The temperature corresponding to a 5% mass loss in each test specimen (denoted as T5%) was recorded to characterize the thermal stability of the material.

[0048] Self-healing performance test: The sample was formed into a film of approximately 0.2 mm thickness at 240℃ using a hot-pressing method. Standardized scratches were made on the surface of the film using a scalpel blade. The sample was then placed under a xenon lamp (simulating sunlight, light intensity 100 mW / cm²). 2 Irradiate for 5 minutes, and measure the width of the scratch at the same location using a digital microscope. Self-repair rate = (initial scratch width - final scratch width) / initial scratch width × 100%.

[0049] Antibacterial performance test: Refer to Chinese National Standard GB / T31402 The antibacterial effect was tested using the method described in 2023. Samples were pressed into thin sheets, sprayed with 75% alcohol, air-dried, and then sterilized by irradiation under a UV lamp for 30 minutes. Finally, a solution of 6×10⁻⁶ alcohol was dropped onto the sheet. 5 0.4 mL of CFU / mL bacterial suspension was incubated at 37°C for 24 h. The suspension was then washed and diluted with 10 mL of LCDLP liquid medium, serially diluted, and mixed with PCA medium. The solutions were incubated at 37°C for 48 h, and colonies were counted using an automated colony counter to estimate the bacterial concentration after incubation. A blank control group without any added materials was used. The bacteria used for testing were Staphylococcus aureus and Escherichia coli. The antibacterial rate was calculated as follows: (CFU / mL control group bacterial concentration) / (CFU / mL control group bacterial concentration). The concentration of the test sample bacterial solution was calculated as (concentration of the test sample) / concentration of the control group solution × 100%. The specific results are shown in Table 1.

[0050] Table 1

[0051] As shown in Table 1, Examples 1-5 demonstrate that the materials prepared by embedding aromatic imine monomers into the nylon backbone using the one-pot method described in this invention, and covalently capping 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid at the chain ends, all possess self-healing and antibacterial properties. Specifically, Examples 4-6 exhibit a self-healing rate as high as 99%, and antibacterial rates against both test bacteria are greater than 99.9%; Examples 1-3 show self-healing rates between 89% and 91%, and antibacterial rates between 85.8% and 99.9%, proving that the technical solution of this invention can effectively endow nylon 6 materials with photoresponsive self-healing capabilities and broad-spectrum antibacterial properties.

[0052] Comparative Example 1 shows that when aromatic imine monomers and antibacterial organic acids are lacking, the resulting pure nylon material has almost no self-healing ability and antibacterial properties.

[0053] In Comparative Example 2, the addition of aromatic imine monomers accounted for 1% of the molar amount of caprolactam, and the self-healing rate of the nylon material was only 62%. This indicates that when the amount of monomers added is below the range specified in this invention, the self-healing rate decreases significantly. Therefore, this invention can effectively regulate the self-healing rate of materials by controlling the content of aromatic imine monomers.

[0054] Comparative Example 3 shows that when only aromatic imine monomers are added without the addition of antibacterial organic acids, the material maintains a high self-healing rate, but the antibacterial rate is extremely low.

[0055] Comparative Example 4 shows that if only antibacterial organic acids are added without the addition of dynamic aromatic imine monomers, the material exhibits excellent antibacterial properties, but the self-healing rate is less than 5%, indicating that the material cannot obtain photo-triggered self-healing ability when lacking the dynamic imine bond of the aromatic Schiff base.

[0056] like Figure 1 As shown, Figure 1 This is the reaction equation for the synthesis of aromatic imine monomers of the present invention. This reaction can be used to prepare photoresponsive functional monomers for nylon modification.

[0057] like Figure 2 As shown, the aromatic imine monomer prepared in this invention... 1 The HNMR spectrum shows clear characteristic peak distribution with no obvious impurity peak interference, indicating that the aromatic imine monomer has an accurate structure and high purity, providing a key raw material with stable quality for the subsequent preparation of modified nylon polymers.

[0058] like Figure 3 As shown, Figure 3 The reaction equation for the synthesis of nylon materials in this invention involves copolymerizing functional monomers with raw materials such as caprolactam to achieve a stable combination of photoresponsive self-healing and antibacterial functions on the molecular chain.

[0059] Figure 4 This is a comparison diagram of the antibacterial effects of the nylon material in Example 4 and the nylon material in Comparative Example 1 of the present invention. Figure 4 (a) is a comparison diagram of Staphylococcus aureus. Figure 4 (b) is a comparison diagram of Escherichia coli, such as Figure 4 As shown, almost no bacteria survived on the surface of the sample in Example 4, and the antibacterial effect was significantly better than that of the ordinary nylon material in Comparative Example 1.

[0060] Figure 5 This is a comparison image of the nylon material before and after scratch repair in Comparative Example 1 of this invention. Figure 5 It is known that conventional nylon materials do not have effective self-healing ability for scratches.

[0061] Figure 6 These are before-and-after comparison images of scratch repair on nylon material in Embodiment 4 of the present invention. Figure 6 (a) is the image before restoration. Figure 6 (b) is the restored image, such as Figure 6 As shown, scratches on the material surface can quickly close and disappear after being exposed to light, demonstrating excellent light-responsive self-healing effect.

[0062] Combination Figure 7 and Figure 8 It can be seen that the thermal degradation temperature of the nylon material in Example 4 of this invention is 397.96℃, which is higher than the thermal degradation temperature of the nylon material without added aromatic imine monomers (393.66℃). The aromatic imine monomers contain dynamic rigid units, which enhance the interaction between polymer chains and improve the thermodynamic stability of the material; combined with Table 1 and... Figures 6-7 It can be seen that the introduction of aromatic imine monomers unexpectedly enhances the mechanical properties and thermal stability of the material. However, when the molar addition of aromatic imine monomers exceeds 10%, the mechanical properties gradually decrease as the content of aromatic imine monomers continues to increase, indicating that the addition of excessive rigid molecules affects the arrangement of molecular chains.

[0063] Based on the performance data of various embodiments, it can be seen that the material prepared by this invention has excellent performance adjustability and wide application adaptability, and the component ratio can be flexibly adjusted according to the functional requirements of actual use scenarios. Among them, the material with a molar addition of 10% aromatic imine monomer can achieve a self-healing efficiency of 99% while maintaining a tensile strength of 75.1 MPa, which can meet the application scenarios with extreme requirements for self-healing ability; the material with a molar addition of 5% aromatic imine monomer can achieve a self-healing rate of about 90% and complete antibacterial performance, and has stable mechanical properties. It can achieve a good synergistic match between photoresponsive self-healing, long-lasting antibacterial effect and structural mechanical properties, and is suitable for use scenarios that require both intelligent functions and structural reliability.

[0064] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A photoresponsive self-healing antibacterial nylon material, characterized in that, The material is a modified nylon 6 polymer, whose main molecular chain contains aromatic Schiff base dynamic imine bonds, and whose molecular chain ends are bonded with antibacterial organic acids through amide bonds. The aromatic Schiff base dynamic imine bond originates from an aromatic imine monomer, which is embedded in the polymer backbone through the active groups at both ends of its end in the polymerization reaction of nylon 6. The modified nylon 6 polymer is prepared by two-stage polymerization: the first stage polymerization is pressure ring-opening prepolymerization, and the second stage polymerization is normal compression polymerization followed by vacuum polymerization.

2. The material according to claim 1, characterized in that, The aromatic imine monomer is a compound generated by the condensation reaction of p-carboxybenzaldehyde and p-phenylenediamine.

3. The material according to claim 1, characterized in that, The antibacterial organic acid is 2-methyl-4-(trifluoromethyl)thiazole-5-carboxylic acid.

4. A method for preparing the material as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Using p-carboxybenzaldehyde and p-phenylenediamine as raw materials, the reaction was carried out in anhydrous ethanol under nitrogen protection and heated. The resulting aromatic imine monomer was purified, washed and dried under vacuum. (2) Add caprolactam, the above aromatic imine monomer, antibacterial organic acid, 1,6-hexanediamine and deionized water to a high-pressure polymerization reactor, replace with nitrogen, and then heat and pressurize to carry out the first stage of polymerization. (3) Depressurize to atmospheric pressure and heat up, then evacuate to carry out the second stage of polymerization; (4) After polymerization, nitrogen gas is introduced at normal pressure, followed by melt extrusion, water bath cooling, granulation, and vacuum drying to obtain nylon material.

5. The method according to claim 4, characterized in that, The amount of p-carboxybenzaldehyde and p-phenylenediamine fed is 0.05-0.15 mol each, and the molar ratio between them is 1:

1.

6. The method according to claim 4, characterized in that, The polymerization temperature in the first stage is 220~250℃, the pressure is 0.8~1.2MPa, and the reaction time is 1.5~3h.

7. The method according to claim 4, characterized in that, The polymerization temperature in the second stage is 240~260℃, the vacuum degree is -0.09~-0.1MPa, and the reaction time is 0.5~2h.

8. The method according to claim 4, characterized in that, The amount of the aromatic imine monomer added is 5-15% of the molar amount of caprolactam.

9. The method according to claim 4, characterized in that, The amount of antibacterial organic acid added is 1 to 3% of the total mass of caprolactam, aromatic imine monomer, 1,6-hexanediamine, antibacterial organic acid and deionized water.

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