A self-healing antibacterial polyurethane elastomer and its preparation method

Abstract

This invention discloses a self-healing antibacterial polyurethane elastomer and its preparation method. Using polyols as soft segments, isocyanates as hard segments, thiols as chain extenders, and pyrimidines as end-capping agents, a soluble zinc salt is added as a ligand to synthesize a high-performance polyurethane elastomer based on a mercapto-isocyanate click reaction / metal coordination. This elastomer exhibits excellent mechanical properties, remodeling properties, self-healing properties, and antibacterial properties, achieving an antibacterial rate of 99% against Staphylococcus aureus. The metal coordination bonds and the urethane / thiourethane bonds in the main chain constitute a dual dynamic cross-linking network, undergoing a bond exchange reaction at 70°C, promoting self-healing with an efficiency up to 100%. Simultaneously, during hot pressing, the elastomer segments tend to arrange themselves more orderly, resulting in a denser structure. The re-formed metal coordination bonds and intramolecular hydrogen bonds further enhance the cross-linking density of the elastomer, thereby improving its mechanical properties.

Description

Technical Field

[0001] This invention belongs to the field of self-healing technology, specifically, it relates to a self-healing antibacterial polyurethane elastomer and its preparation method. Background Technology

[0002] Materials, especially polymers, often experience internal chemical bond breakage due to various factors during prolonged use, leading to the formation of microcracks that are difficult to detect. If these microcracks are not repaired, they will slowly propagate, causing the material to gradually fail and significantly reducing its lifespan. Polymer self-healing is the process by which polymer materials, after deformation and / or defects, autonomously repair themselves through their inherent structural properties or by adding healing agents and applying external stimuli (light, heat, pH, etc.), thus restoring their structure and function. As a type of smart material, self-healing materials can self-heal after damage, restoring their original structure and function, extending their lifespan, and reducing maintenance costs. They have already shown initial promise in applications such as biomedicine, energy storage devices, anti-corrosion coatings, and smart sensors.

[0003] Thermoplastic polyurethane (TPU) is a material with broad development prospects. It is a polyurethane elastomer that exhibits rubber-like elasticity at room temperature and plasticity at high temperatures. TPU lies between rubber and plastic, possessing both the elasticity of rubber and the rigidity of plastic. Furthermore, TPU demonstrates superior mechanical properties, physical properties, and weather resistance. TPU is widely used in mobile phone cases, shoe soles, artificial leather, automotive parts, gears, and environmentally friendly flooring. Therefore, if it can self-heal, TPU will have an even broader application. Yan et al. prepared a self-healing flexible urea-g-MWCNTs / poly(urethane-sulfide) nanocomposite through a thiol-ene "click" reaction between polyurethane and polysulfide oligomers. The composite material had a maximum tensile strength of 3.29 MPa and a self-healing efficiency of 92%. The fracture strain / ultimate strength recovery rates of the first, second, and third recoveries were 228% / 3.12 MPa, 225% / 2.81 MPa, and 211% / 2.39 MPa, respectively [Yan, Q., et al., A self-healing flexible urea-g-MWCNTs / poly(urethane-sulfide) nanocomposite for sealing electronic devices. Journal of Materials Chemistry C, 2020.8(2):p.607-618.]. Cui Xurui utilized urea-containing hydrogen bonds and Zn 2+Allyl methacrylate self-healing films were prepared by coordination bonds between imidazole groups. These films exhibited a tensile strength of 5.57 ± 1.20 MPa, and after 24 hours of repair at 25°C, the mechanical properties recovered to 4.79 ± 1.97 MPa, achieving a repair efficiency of 86.0% [Cui Xurui, Self-Healing Functional Materials Based on Metal Coordination Bonds. 2021, University of Chinese Academy of Sciences (Institute of Process Engineering, Chinese Academy of Sciences)]. However, the self-healing efficiency of these materials is difficult to achieve 100%, and the performance of the former deteriorates after recycling and remodeling. Considering the multiple reuse of materials, self-healing materials should possess good remodeling properties. Therefore, although self-healing materials show great promise, some problems still need to be solved during their use. Summary of the Invention

[0004] The purpose of this invention is to prepare a polyurethane elastomer with improved mechanical properties and self-healing properties.

[0005] To achieve the above objectives, the present invention provides a method for preparing a self-healing antibacterial polyurethane elastomer, comprising the following steps:

[0006] (1) Mix polyol and isocyanate, dissolve the mixture in an organic solvent, add a catalyst to it, stir, and prepare polyurethane prepolymer;

[0007] (2) Add chain extender and organic solvent to the polyurethane prepolymer obtained in step (1), then add alkaline catalyst and stir to make the polyurethane prepolymer undergo chain extension reaction.

[0008] (3) Add a capping agent to the polyurethane prepolymer after chain extension in step (2), and dry it after reaction to obtain a capped polyurethane prepolymer.

[0009] (4) Dissolve the end-capped polyurethane prepolymer obtained in step (3) in an organic solvent, add soluble zinc salt, sonicate, stir, pour into a mold and place, and dry to obtain a self-healing antibacterial polyurethane elastomer.

[0010] The chain extender mentioned in step (2) includes thiols, and the end-capping agent mentioned in step (3) includes pyrimidine compounds.

[0011] In one embodiment of the present invention, in step (1), the polyol includes at least one of polytetrahydrofuran diol, ethylene oxide-propylene oxide copolymer, polycaprolactone diol, polyethylene glycol, polypropylene glycol, polybutylene glycol, polycaprolactone diol, polyethylene adipate, polypropylene adipate, and polybutylene adipate.

[0012] In one embodiment of the present invention, in step (1), the isocyanate includes at least one of isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecylmethylene diisocyanate, trimethylhexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, and 4,4'-diphenylmethane diisocyanate.

[0013] In one embodiment of the present invention, in step (1), the molar mass ratio of the polyol to the isocyanate is 1:2 to 1:2.05.

[0014] In one embodiment of the present invention, in step (1), the reaction between the polyol and the isocyanate is carried out in an inert environment such as nitrogen, helium, or argon, and the reaction temperature is 40–100°C.

[0015] In one embodiment of the present invention, in step (1), the mass of the organic solvent is 5 to 10 times the mass of the added polyol, and the organic solvent includes at least one of N,N-dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and dichloromethane.

[0016] In one embodiment of the present invention, in step (1), the volume ratio of the catalyst to the mass ratio of the polyol is (0.01-0.03) mL:1 g.

[0017] In one embodiment of the present invention, in step (1), the catalyst comprises an organometallic compound and / or an amine catalyst, wherein the organometallic compound comprises at least one of dibutyltin dilaurate, stannous isooctanoate, zinc isooctanoate, bismuth isooctanoate, bismuth laurate, bismuth neodecanoate, and bismuth naphthenate, and the amine catalyst comprises at least one of N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N',N'-tetramethylalkylene diamine, triethylamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, triethanolamine, and N,N'-dimethylpyridine.

[0018] In one embodiment of the present invention, in step (2), the molar mass ratio of the chain extender to the polyol is 1:0.95 to 1:1.11, and the chain extender includes thiols, which include at least one of 2,2'-(diethoxy)diethylthiol, 1,2-ethanedithiol, butanedithiol, 1,3-propanedithiol, 1,5-pentanedithiol, 2,3-dimercapto-1-propanol, pentaerythritol tetrakis(3-mercaptopropionic acid) ester, and trimethylolpropane tris(3-mercaptopropionate).

[0019] In one embodiment of the present invention, in step (2), the volume ratio of the alkaline catalyst to the mass ratio of the polyol is (0.01-0.03) mL:1g, and the alkaline catalyst includes at least one of N,N-diisopropylethylamine, triethylamine, pyridine, sodium hydroxide, sodium acetate, sodium carbonate, and potassium carbonate.

[0020] In one embodiment of the present invention, in step (2), the mass ratio of the organic solvent to the polyol is 5:1 to 100:1, and the organic solvent includes at least one of N,N-dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and dichloromethane.

[0021] In one embodiment of the present invention, in step (2), the chain extension reaction is carried out in an inert environment such as nitrogen, helium, or argon, and the reaction temperature is 40–100°C.

[0022] In one embodiment of the present invention, in step (3), the mass ratio of the capping agent to the polyol is 1 to 10%, and the capping agent comprises a pyrimidine compound, which includes at least one of 2,4-diamino-6-hydroxypyrimidine, 2-isopropyl-4-methyl-6-hydroxypyrimidine, 2-hydroxypyrimidine, 5-hydroxypyrimidine, 5-fluoro-4-mercapto-2-hydroxypyrimidine, and 5-bromo-2-hydroxypyrimidine.

[0023] In one embodiment of the present invention, in step (3), the reaction temperature is 50-80°C, the reaction time is 6-18h, the room temperature is left to stand for 18-30h, the drying temperature is 50-70°C, and the drying time is 6-18h.

[0024] In one embodiment of the present invention, in step (4), the mass ratio of the organic solvent to the added polyol is 5:1 to 100:1, and the organic solvent includes at least one of N,N-dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and dichloromethane.

[0025] In one embodiment of the present invention, in step (4), the soluble zinc salt includes at least one of zinc chloride, zinc sulfate, zinc nitrate, and zinc lactate, and the molar mass ratio of the amount of the soluble zinc salt added to the amount of the capping agent is 1:(1-6).

[0026] In one embodiment of the present invention, in step (4), the ultrasound is performed in an inert environment such as nitrogen, helium, or argon for 15 to 45 minutes. After stirring at 30 to 50°C for 8 to 16 hours, the mixture is poured into a mold, placed at room temperature for 18 to 30 hours, and then placed in an oven to dry at 50 to 70°C for 18 to 30 hours.

[0027] The present invention also provides a self-healing antibacterial polyurethane elastomer prepared according to the above preparation method.

[0028] The present invention also provides an application of the above-mentioned self-healing antibacterial polyurethane elastomer in the fields of biomedicine, sporting goods, and smart wearables.

[0029] The beneficial effects of this invention are:

[0030] (1) A colorless and transparent self-healing antibacterial polyurethane elastomer was synthesized by using polyol as the soft segment, isocyanate as the hard segment, thiol as the chain extender, pyrimidine as the ligand, and soluble zinc salt as the ligand. The metal coordination bond and the urethane / thiourethane bond in the main chain constitute a double dynamic cross-linking network, which undergoes a bond exchange reaction at 70°C to promote the self-healing of the material. The polyurethane elastomer prepared by the method of this invention can completely self-heal surface scratches within 4 hours at 70°C, with a self-healing efficiency of 100%.

[0031] (2) After the polyurethane elastomer prepared by the method of the present invention is completely sheared and then hot-pressed at 100℃ and 10MPa for 5 minutes, the tensile strength of the elastomer can reach 25.0MPa and the toughness can reach 51.7MJ / m. 3 The results showed improvements of 3.3% and 11.7% respectively compared to the original samples. During the hot pressing process, the elastomer segments tend to be more ordered and the structure is more compact. The re-formed metal coordination bonds and intramolecular hydrogen bonds both contribute to increasing the crosslinking density of the elastomer, thereby improving the mechanical properties of the elastomer.

[0032] (3) The polyurethane elastomer of the present invention exhibits an antibacterial rate of over 99% against both *E. coli* and *S. aureus*, demonstrating good antibacterial properties. The polyurethane elastomer of the present invention also possesses good mechanical properties, with a maximum tensile strength of 24.2 MPa and a toughness of 46.3 MJ / m. 3 .

[0033] (4) The polyurethane elastomer of the present invention has good elasticity. During the stretching process, the coordination bonds inhibit the orientation of the chain segments at small strains; at large strains, the coordination bonds break, the restricted chain segments are released, and the tensile strength and toughness of the elastomer are improved. After 10 stretching cycles, the sample can obtain a curve that almost overlaps with the first cycle when subjected to the 11th cyclic stretching test, indicating that the broken dynamic bonds are reorganized and the mechanical properties are restored. Attached Figure Description

[0034] Figure 1 This is a test graph showing the remodeling performance of the polyurethane elastomer in Example 2;

[0035] Figure 2These are comparison diagrams showing the self-healing properties of polyurethane elastomers from Examples 1-4 and Comparative Example 2;

[0036] Figure 3 This is a graph showing the change in the self-healing mechanical properties of the polyurethane elastomer in Example 2;

[0037] Figure 4 The graphs show the antibacterial properties of the polyurethane elastomers in Comparative Example 1, Comparative Example 2, and Example 2. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be further described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention. The following embodiments are illustrative and not limiting, and cannot be used to limit the protection scope of the present invention.

[0039] Performance testing methods

[0040] Mechanical properties:

[0041] The tensile mechanical properties of the samples were tested using a universal testing machine (Instron, 5967X), with all tests performed at a crosshead rate of 50 mm / min. Tensile tests were conducted at room temperature, and the samples were prepared as dumbbell-shaped strips with a length of 35 mm, a width of 2 mm, and a thickness of 0.15–0.25 mm.

[0042] Reshaping performance:

[0043] The completely shredded sample was hot-pressed at 100℃ and 10MPa for 5 minutes to obtain the reshaped sample. Its tensile mechanical properties were tested again and compared with the initial material mechanical properties to calculate the improvement rate of mechanical properties.

[0044] Mechanical property improvement rate (%) = (Initial mechanical property - Mechanical property after remodeling) / Initial mechanical property * 100%

[0045] Self-healing properties:

[0046] A 0.2 mm deep scratch was created on the sample surface, and the self-healing of the surface scratch was observed under 70°C using an ultra-depth-of-field microscope.

[0047] Mechanical property testing before and after self-healing: The specimens were cut in half and bonded together, then placed at 70℃ for 12 hours before tensile testing. The mechanical properties of the samples were tested using a universal testing machine (Instron, 5967X), with all tests performed at a crosshead rate of 50 mm / min. Tensile tests were conducted at room temperature. Samples were prepared as dumbbell-shaped specimens, 35 mm long, 2 mm wide, and 0.15–0.25 mm thick. The mechanical properties of the material after self-healing were compared with the initial mechanical properties to calculate the self-healing efficiency.

[0048] Self-healing efficiency (%) = (Mechanical strength after self-healing - Initial mechanical strength) / Initial mechanical strength * 100%

[0049] Antibacterial properties:

[0050] Cut the film sample into 2cm diameter discs and sterilize them under UV light. Place the discs into centrifuge tubes and add bacterial solution diluted with PBS buffer to a concentration of 10⁵ CFU / mL. Incubate at 37°C for 12 h in a shaker. Then, place the discs, which have been washed three times with distilled water, into PBS and sonicate for 5 minutes to remove the adhering bacteria and obtain the bacterial solution. Dilute the bacterial solution 100 times with PBS. Spread it onto broth solid medium and incubate at 37°C for 24 h. The photographs were taken with a digital camera. The concentration of adhering colonies C was calculated based on the viable count, as shown in formula (1):

[0051] C=N*n*5 / V (1)

[0052] In the formula, C is in CFU / mL, V refers to the volume (mL) of bacterial solution spread on the fixed culture medium (50 μL for this test), and N and n are the colony count and dilution factor, respectively. The antibacterial rate is then calculated using the formula below.

[0053] Antibacterial rate (%) = (Number of colonies in blank sample - Number of colonies in sample) / Number of colonies in blank sample * 100%

[0054] Example 1

[0055] A method for preparing a self-healing antibacterial polyurethane elastomer includes the following steps:

[0056] (1) Polytetrahydrofuran diol (2.000 g, 2 mmol) and isophorone diisocyanate (0.896 g, 4.03 mmol) were mixed, and the mixture was dissolved in N,N-dimethylacetamide (15 g). Two drops of dibutyltin dilaurate (50 μL) were added to the mixture, and the mixture was stirred and reacted at 70 °C for 2 h under N2 atmosphere to prepare polyurethane prepolymer.

[0057] (2) Add 2,2'-(diethoxy)diethylthiol (0.364 g, 2 mmol) and N,N-dimethylacetamide (15 g) to the polyurethane prepolymer obtained in step (1), and then add two drops of N,N-diisopropylethylamine (50 μL). Stir and let the polyurethane prepolymer react at 60 °C for 8 h.

[0058] (3) Add 2,4-diamino-6-hydroxy-pyrimidine (HPM) (0.015 g, 0.12 mmol) to the polyurethane prepolymer after chain extension in step (2), react for 12 h, pour the obtained product into a mold, place it at room temperature for 24 h, and then put it in an oven at 60 °C to dry and remove the solvent to obtain the end-capped polyurethane prepolymer (PTU-HPM).

[0059] (4) Dissolve the end-capped polyurethane prepolymer obtained in step (3) in N,N-dimethylacetamide (15g), add zinc chloride, and the added HPM:Zn 2+ The molar ratio was 6:1. The mixture was ultrasonicated for 30 min under N2 environment, then stirred at 40℃ for 12 h. The mixture was poured into a mold, left at room temperature for 24 h, and then dried in an oven at 60℃ for another 24 h to remove the solvent, yielding a self-healing antibacterial polyurethane elastomer (PTU-HPM-Zn). 1 / 6 ).

[0060] Example 2

[0061] A method for preparing a self-healing antibacterial polyurethane elastomer includes the following steps:

[0062] (1) Polytetrahydrofuran diol (2.000 g, 2 mmol) and isophorone diisocyanate (0.896 g, 4.03 mmol) were mixed, and the mixture was dissolved in N,N-dimethylacetamide (15 g). Two drops of dibutyltin dilaurate (50 μL) were added to the mixture, and the mixture was stirred and reacted at 70 °C for 2 h under N2 atmosphere to prepare polyurethane prepolymer.

[0063] (2) Add 2,2'-(diethoxy)diethylthiol (0.364 g, 2 mmol) and N,N-dimethylacetamide (15 g) to the polyurethane prepolymer obtained in step (1), and then add two drops of N,N-diisopropylethylamine (50 μL). Stir and let the polyurethane prepolymer react at 70 °C for 8 h.

[0064] (3) Add 2,4-diamino-6-hydroxy-pyrimidine (HPM) (0.015 g, 0.12 mmol) to the polyurethane prepolymer after chain extension in step (2), react for 12 h, pour the obtained product into a mold, place it at room temperature for 24 h, and then put it in an oven at 60 °C to dry and remove the solvent to obtain the end-capped polyurethane prepolymer (PTU-HPM).

[0065] (4) Dissolve the end-capped polyurethane prepolymer obtained in step (3) in N,N-dimethylacetamide (15g), add zinc chloride, and the added HPM:Zn 2+The molar ratio was 4:1. The mixture was ultrasonicated for 30 min under N2 environment, then stirred at 40℃ for 12 h. The mixture was poured into a mold, left at room temperature for 24 h, and then dried in an oven at 60℃ for another 24 h to remove the solvent, yielding a self-healing antibacterial polyurethane elastomer (PTU-HPM-Zn). 1 / 4 ).

[0066] Example 3

[0067] A method for preparing a self-healing antibacterial polyurethane elastomer includes the following steps:

[0068] (1) Polytetrahydrofuran diol (2.000 g, 2 mmol) and isophorone diisocyanate (0.896 g, 4.03 mmol) were mixed, and the mixture was dissolved in N,N-dimethylacetamide (15 g). Two drops of dibutyltin dilaurate (50 μL) were added to the mixture, and the mixture was stirred and reacted at 70 °C for 2 h under N2 atmosphere to prepare polyurethane prepolymer.

[0069] (2) Add 2,2'-(diethoxy)diethylthiol (0.364 g, 2 mmol) and N,N-dimethylacetamide (15 g) to the polyurethane prepolymer obtained in step (1), and then add two drops of N,N-diisopropylethylamine (50 μL). Stir and let the polyurethane prepolymer react at 80 °C for 8 h.

[0070] (3) Add 2,4-diamino-6-hydroxy-pyrimidine (HPM) (0.015 g, 0.12 mmol) to the polyurethane prepolymer after chain extension in step (2), react for 12 h, pour the obtained product into a mold, place it at room temperature for 24 h, and then put it in an oven at 60 °C to dry and remove the solvent to obtain the end-capped polyurethane prepolymer (PTU-HPM).

[0071] (4) Dissolve the end-capped polyurethane prepolymer obtained in step (3) in N,N-dimethylacetamide (15g), add zinc chloride, and the added HPM:Zn 2+ The molar ratio was 2:1. The mixture was ultrasonicated for 30 min under N2 environment, then stirred at 40℃ for 12 h. The mixture was poured into a mold, left at room temperature for 24 h, and then placed in an oven at 60℃ for another 24 h to remove the solvent, yielding a self-healing antibacterial polyurethane elastomer (PTU-HPM-Zn). 1 / 2 ).

[0072] Example 4

[0073] A method for preparing a self-healing antibacterial polyurethane elastomer includes the following steps:

[0074] (1) Polytetrahydrofuran diol (2.000 g, 2 mmol) was mixed with hexamethylene diisocyanate (0.690 g, 4.1 mmol), the mixture was dissolved in N,N-dimethylacetamide (15 g), and two drops of dibutyltin dilaurate (50 μL) were added to it. The mixture was stirred and reacted at 70 °C for 2 h under N2 atmosphere to prepare polyurethane prepolymer.

[0075] (2) Add 1,2-ethanedithiol (0.188 g, 2 mmol) and N,N-dimethylacetamide (15 g) to the polyurethane prepolymer obtained in step (1), and then add two drops of N,N-diisopropylethylamine (50 μL). Stir and let the polyurethane prepolymer react at 80 °C for 8 h.

[0076] (3) Add 2,4-diamino-6-hydroxy-pyrimidine (HPM) (0.001 g, 0.08 mmol) to the polyurethane prepolymer after chain extension in step (2), react for 12 h, pour the obtained product into a mold, place it at room temperature for 24 h, and then put it in an oven at 60 °C to dry and remove the solvent to obtain the end-capped polyurethane prepolymer (PTU-HPM).

[0077] (4) Dissolve the end-capped polyurethane prepolymer obtained in step (3) in N,N-dimethylacetamide (15g), add zinc chloride, and the added HPM:Zn 2+ The molar ratio was 1:1. The mixture was sonicated for 30 min in N2 environment, then stirred at 40℃ for 12 h, poured into a mold, placed at room temperature for 24 h, and then placed in an oven at 60℃ for 24 h to remove the solvent, thus obtaining a self-healing antibacterial polyurethane elastomer (PTU-HPM-Zn1).

[0078] Comparative Example 1

[0079] A method for preparing a polyurethane elastomer includes the following steps:

[0080] (1) Polytetrahydrofuran diol (2.000 g, 2 mmol) and isophorone diisocyanate (0.896 g, 4.03 mmol) were mixed, and the mixture was dissolved in N,N-dimethylacetamide (15 g). Two drops of dibutyltin dilaurate (50 μL) were added to the mixture, and the mixture was stirred and reacted at 70 °C for 2 h under N2 atmosphere to prepare polyurethane prepolymer.

[0081] (2) Add 2,2'-(diethoxy)diethylthiol (0.364 g, 2 mmol) and N,N-dimethylacetamide (15 g) to the polyurethane prepolymer obtained in step (1), and then add two drops of N,N-diisopropylethylamine (50 μL). Stir and let the polyurethane react at 60 °C for 8 h. Continue to react at 60 °C for 12 h, pour into a mold, and dry in an oven at 60 °C to remove the solvent, to obtain polyurethane elastomer (PTU).

[0082] Comparative Example 2

[0083] A method for preparing a polyurethane elastomer includes the following steps:

[0084] (1) Polytetrahydrofuran diol (2.000 g, 2 mmol) and isophorone diisocyanate (0.896 g, 4.03 mmol) were mixed, and the mixture was dissolved in N,N-dimethylacetamide (15 g). Two drops of dibutyltin dilaurate (50 μL) were added to the mixture, and the mixture was stirred and reacted at 70 °C for 2 h under N2 atmosphere to prepare polyurethane prepolymer.

[0085] (2) Add 2,2'-(diethoxy)diethylthiol (0.364 g, 2 mmol) and N,N-dimethylacetamide (15 g) to the polyurethane prepolymer obtained in step (1), and then add two drops of N,N-diisopropylethylamine (50 μL). Stir and let the polyurethane prepolymer react at 60 °C for 8 h.

[0086] (3) Add 2,4-diamino-6-hydroxy-pyrimidine (HPM) (0.030 g, 0.24 mmol) to the polyurethane prepolymer after chain extension in step (2), react for 12 h, pour the obtained product into a mold, place it at room temperature for 24 h, and then put it in an oven at 60 °C to dry and remove the solvent to obtain the end-capped polyurethane prepolymer (PTU-HPM).

[0087] Comparative Example 3

[0088] A method for preparing a self-healing antibacterial polyurethane elastomer includes the following steps:

[0089] (1) Polytetrahydrofuran diol (2.000 g, 2 mmol) and isophorone diisocyanate (0.896 g, 4.03 mmol) were mixed, and the mixture was dissolved in N,N-dimethylacetamide (15 g). Two drops of dibutyltin dilaurate (50 μL) were added to the mixture, and the mixture was stirred and reacted at 70 °C for 2 h under N2 atmosphere to prepare polyurethane prepolymer.

[0090] (2) Add 4,4-dihydroxydiphenyl ether (0.404 g, 2 mmol) and N,N-dimethylacetamide (15 g) to the polyurethane prepolymer obtained in step (1), and then add two drops of N,N-diisopropylethylamine (50 μL). Stir and let the polyurethane prepolymer react at 60 °C for 8 h.

[0091] (3) Add 2,4-diamino-6-hydroxy-pyrimidine (HPM) (0.030 g, 0.24 mmol) to the polyurethane prepolymer after chain extension in step (2), react for 12 h, pour the obtained product into a mold, place it at room temperature for 24 h, and then put it in an oven at 60 °C to dry and remove the solvent to obtain the end-capped polyurethane prepolymer (PU-HPM).

[0092] (4) Dissolve the end-capped polyurethane prepolymer obtained in step (3) in N,N-dimethylacetamide (15g), add zinc chloride, and the added HPM:Zn 2+ The molar ratio was 4:1. The mixture was ultrasonicated for 30 min under N2 atmosphere, then stirred at 40℃ for 12 h. The mixture was poured into a mold, left at room temperature for 24 h, and then placed in an oven at 60℃ for another 24 h to remove the solvent, yielding a polyurethane elastomer (PU-HPM-Zn). 1 / 4 ).

[0093] Comparative Example 4

[0094] A method for preparing a self-healing antibacterial polyurethane elastomer includes the following steps:

[0095] (1) Polytetrahydrofuran diol (2.000 g, 2 mmol) and isophorone diisocyanate (0.896 g, 4.03 mmol) were mixed, and the mixture was dissolved in N,N-dimethylacetamide (15 g). Two drops of dibutyltin dilaurate (50 μL) were added to the mixture, and the mixture was stirred and reacted at 70 °C for 2 h under N2 atmosphere to prepare polyurethane prepolymer.

[0096] (2) Add 2,2'-(diethoxy)diethylthiol (0.364 g, 2 mmol) and N,N-dimethylacetamide (15 g) to the polyurethane prepolymer obtained in step (1), and then add two drops of N,N-diisopropylethylamine (50 μL). Stir and let the polyurethane prepolymer react at 60 °C for 8 h.

[0097] (3) Add 1-(3-aminopropyl)imidazolium (IZ) (0.013 g, 0.1 mmol) to the polyurethane prepolymer after chain extension in step (2), react for 12 h, pour the obtained product into a mold, place it at room temperature for 24 h, and then put it in an oven at 60 °C to dry and remove the solvent to obtain the end-capped polyurethane prepolymer (PTU-IZ).

[0098] (4) Dissolve the end-capped polyurethane prepolymer obtained in step (3) in N,N-dimethylacetamide (15g), add zinc chloride, and the added IZ:Zn 2+ The molar ratio was 4:1. The mixture was ultrasonicated for 30 min under N2 environment, then stirred at 40℃ for 12 h. The mixture was poured into a mold, left at room temperature for 24 h, and then dried in an oven at 60℃ for another 24 h to remove the solvent, yielding a self-healing antibacterial polyurethane elastomer (PTU-IZ-Zn). 1 / 4 ).

[0099] Results analysis:

[0100] Mechanical properties and remodeling properties:

[0101] The self-healing antibacterial polyurethane elastomer PTU-HPM-Zn obtained by adding ZnCl2 1 / 6 PTU-HPM-Zn 1 / 4 PTU-HPM-Zn 1 / 2 The tensile strengths of PTU-HPM-Zn1 (14.2 MPa, 24.2 MPa, 18.2 MPa, and 8.4 MPa, respectively) are all higher than those of the structure without zinc chloride (PTU-HPM, tensile strength 7.2 MPa). The tensile strengths of each elastomer, PTU-HPM and PTU-HPM-Zn1, are higher. 1 / 6 PTU-HPM-Zn 1 / 4 PTU-HPM-Zn 1 / 2 The Young's moduli of PTU-HPM-Zn1 were 3.2 MPa, 5.9 MPa, 11.6 MPa, 7.4 MPa, and 2.9 MPa, respectively; their toughness was 30.0 MJ / m. 3 35.4 MJ / m 3 46.3 MJ / m 3 38.5 MJ / m 3 20.7 MJ / m 3 Among them, the polyurethane prepolymer (PTU-HPM-Zn) prepared in Example 2 1 / 4 Zn has the highest tensile strength and best toughness, and its Young's modulus is 3.6 times that of PTU-HPM. 2+ With increasing Zn content, the elongation at break of the five groups of samples were 1016%, 917%, 773%, 727%, and 678%, respectively, showing a gradual decreasing trend. This may be due to the Zn content. 2+ The coordination structure formed with HPM creates a cross-linked network structure in the system, which to some extent inhibits the movement of molecular chains during stretching. On the one hand, excess ZnCl2 fails to form coordination bonds, instead affecting the continuity of the polyurethane matrix and creating stress concentration points. On the other hand, excess Zn... 2+ The addition of [a substance] hinders the stacking of regular chain segments in polyurethane, resulting in poor mechanical properties.

[0102] Compared with the mechanical properties of the polyurethane elastomers in Examples 1-4, in Comparative Example 3, the thiol chain extender was replaced with 4,4-dihydroxydiphenyl ether, and the resulting polyurethane elastomer had a tensile strength of 26.3 MPa and an elongation at break of 712%. In Comparative Example 4, the pyrimidine end-capping agent was replaced with 1-(3-aminopropyl)imidazolium, and the resulting polyurethane elastomer had a tensile strength of 3.8 MPa and an elongation at break of 1150%.

[0103] Select PTU-HPM-Zn 1 / 4 The sample was completely cut into pieces and then hot-pressed at 100℃ and 10MPa for 5 minutes. After hot pressing, the tensile strength of the sample reached 25.0MPa, and the toughness was 51.7MJ / m. 3 The results showed improvements of 3.3% and 11.7% respectively compared to the original sample (see Table 1). This is because the elastomer segments in the shredded sample can be rapidly reconstructed during the high-temperature hot pressing process. Under pressure, the material structure becomes more compact, and the re-formed metal coordination bonds and intramolecular hydrogen bonds after cooling and shaping help to increase the crosslinking density of the elastomer, thereby further improving the mechanical properties of the reconstructed elastomer. Figure 1 ).

[0104] Table 1 also shows that the amount of zinc ions added, the type and amount of end-capping agent, and the type of chain extender all affect the remodeling properties of the elastomer.

[0105] Self-healing properties:

[0106] The self-healing properties of PTU-HPM and PTU-HPM-Zn were characterized by observing the effects of PTU-HPM (without zinc chloride) and PTU-HPM-Zn using a super-depth-of-field microscope. 1 / 6 PTU-HPM-Zn 1 / 4 PTU-HPM-Zn 1 / 2 Self-healing of surface scratches on PTU-HPM-Zn1 at 70℃ Figure 2 It was observed that when using the same 0.2mm needle for scratch testing, samples with higher ZnCl2 content were more prone to surface scratch damage. Comparing the complete self-healing time of scratches across all samples, PTU-HPM-Zn... 1 / 4 The shortest complete healing time is 4 hours, while PTU-HPM requires 24 hours to fully heal, and PU-HPM-Zn1 scratches require 8 hours to fully heal. This indicates that Zn... 2+ The addition of Zn can promote material healing after forming coordination bonds with HPM, but excessive Zn... 2+ It affects the continuity of polyurethane chain segments, inhibits chain segment movement, weakens the crystallization tendency of the elastomer, and not only slows down the healing rate but also reduces mechanical properties. When Zn2+ When the molar ratio of metal to HPM is 1:4 (optimal ratio), the metal coordination bonds and the thiocarbamate bonds in the main chain form a relatively complete double dynamic cross-linked network. Both the metal coordination bonds and the thiocarbamate bonds are low-bond-energy covalent bonds, which undergo bond exchange reactions at 70℃, promoting the self-healing of the material. The mechanical properties are completely restored after 12 hours, and the self-healing efficiency is 100%. Figure 3 ).

[0107] Comparing the data from Example 2 and Comparative Example 3, it can be seen that when thiols are used as chain extenders, the metal coordination bonds in the elastomer and the thiocarbamate bonds in the main chain can form a relatively complete double dynamic cross-linked network, promoting the self-healing of the material. However, when 4,4-dihydroxydiphenyl ether is used as a chain extender, the above effect is not achieved; although the strength is slightly improved, the self-healing performance of the elastomer is poor. Furthermore, comparing the data from Example 2 and Comparative Example 4, it can be seen that the type of end-capping agent also affects the self-healing efficiency of the elastomer; replacing the pyrimidine end-capping agent with an imidazole end-capping agent significantly reduces the self-healing efficiency of the elastomer.

[0108] Antibacterial properties:

[0109] Figure 4 The results shown are from an experimental test of the antibacterial properties of Staphylococcus aureus. HPM and Zn were introduced into the PTU. 2+ After that, PTU-HPM and PTU-HPM-Zn 1 / 4 The antibacterial efficiencies reached 95% and 99.9%, respectively. Data from the examples and comparative examples show that the antibacterial properties of the polyurethane elastomer are mainly related to the addition of HPM and zinc ions. Preliminary analysis suggests that HPM can interfere with gene expression and related enzyme systems in cells, thereby producing an antibacterial effect. Upon contact with bacteria, zinc ions are slowly released. Due to their redox properties, zinc ions can bind to the bacterial cell membrane and membrane proteins, reacting with the sulfhydryl, carboxyl, and hydroxyl groups of organic matter in their structure, disrupting their structure. After entering the cell, they disrupt the enzymes of the electron transport system and react with DNA, achieving the antibacterial purpose. After killing bacteria, zinc ions can be released from the bacterial cell, repeating the above process.

[0110] Table 1. Self-healing properties, remodeling properties, and antibacterial properties of polyurethane elastomers in Examples 1-4 and Comparative Examples 1-4

[0111]

Claims

1. A method for preparing a self-healing antibacterial polyurethane elastomer, characterized in that, Includes the following steps: (1) Mix polyol and isocyanate, dissolve the mixture in an organic solvent, add a catalyst to it, stir, and prepare polyurethane prepolymer; (2) Add chain extender and organic solvent to the polyurethane prepolymer obtained in step (1), then add alkaline catalyst and stir to make the polyurethane prepolymer undergo chain extension reaction. (3) Add a capping agent to the polyurethane prepolymer after chain extension in step (2), and dry it after reaction to obtain a capped polyurethane prepolymer; (4) Dissolve the end-capped polyurethane prepolymer obtained in step (3) in an organic solvent, add soluble zinc salt, sonicate, stir, pour into a mold and place, and dry to obtain a self-healing antibacterial polyurethane elastomer. The chain extender mentioned in step (2) includes thiols, and the end-capping agent mentioned in step (3) is 2,4-diamino-6-hydroxypyrimidine.

2. The preparation method according to claim 1, characterized in that, In step (1), the polyol includes at least one of polytetrahydrofuran glycol, ethylene oxide-propylene oxide copolymer, polycaprolactone diol, polyethylene glycol, polypropylene glycol, polyethylene adipate, polypropylene adipate, and polybutylene adipate; the isocyanate includes at least one of isophorone diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, toluene diisocyanate, terephthalic diisocyanate, and 4,4'-diphenylmethane diisocyanate; the molar ratio of the polyol to the isocyanate is 1:2 to 1:2.05; the reaction between the polyol and the isocyanate is carried out in an inert environment at a temperature of 40 to 100°C; the inert environment includes any one of nitrogen, helium, or argon.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass of the organic solvent is 5 to 10 times the mass of the added polyol, and the organic solvent includes at least one of N,N-dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and dichloromethane.

4. The preparation method according to claim 1, characterized in that, In step (1), the volume ratio of the catalyst to the mass of the polyol is (0.01~0.03) mL:1g. The catalyst comprises an organometallic compound and / or an amine catalyst. The organometallic compound comprises at least one of dibutyltin dilaurate, stannous isooctanoate, zinc isooctanoate, bismuth isooctanoate, bismuth laurylate, bismuth neodecanoate, and bismuth naphthenate. The amine catalyst comprises at least one of N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N',N'-tetramethylalkylene diamine, triethylamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, triethanolamine, and N,N'-dimethylpyridine.

5. The preparation method according to claim 1, characterized in that, In step (2), the molar mass ratio of the chain extender to the polyol is 1:0.95 to 1:1.

11. The chain extender includes thiols, and the thiols include at least one of 2,2'-(diethoxy)diethylthiol, 1,2-ethanedithiol, butanedithiol, 1,3-propanedithiol, 1,5-pentanedithiol, 2,3-dimercapto-1-propanol, pentaerythritol tetrakis(3-mercaptopropionic acid) ester, and trimethylolpropane tris(3-mercaptopropionate).

6. The preparation method according to claim 1, characterized in that, In step (2), the volume ratio of the alkaline catalyst to the mass ratio of the polyol is (0.01~0.03) mL:1g. The alkaline catalyst includes at least one of N,N-diisopropylethylamine, triethylamine, pyridine, sodium hydroxide, sodium acetate, sodium carbonate, and potassium carbonate. The mass ratio of the organic solvent to the polyol is 5:1~100:

1. The organic solvent includes at least one of N,N-dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and dichloromethane. The chain extension reaction is carried out in an inert environment at a reaction temperature of 40~100℃. The inert environment includes any one of nitrogen, helium, and argon.

7. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of the capping agent to the polyol is 1~10%, the reaction temperature is 50~80℃, the reaction time is 6~18 h, the room temperature is left for 18~30 h, the drying temperature is 50~70℃, and the drying time is 6~18 h.

8. The preparation method according to claim 1, characterized in that, In step (4), the mass ratio of the organic solvent to the added polyol is 5:1 to 100:

1. The organic solvent includes at least one of N,N-dimethylacetamide, dimethylformamide, N-methylpyrrolidone, and dichloromethane. The soluble zinc salt includes at least one of zinc chloride, zinc sulfate, zinc nitrate, and zinc lactate. The molar mass ratio of the amount of the soluble zinc salt added to the amount of the capping agent is 1:1 to 6. The ultrasonication is performed in an inert environment for 15 to 45 minutes. The inert environment includes at least one of nitrogen, helium, and argon. After stirring at 30 to 50 °C for 8 to 16 hours, the mixture is poured into a mold and placed at room temperature for 18 to 30 hours. Then, it is placed in an oven and dried at 50 to 70 °C for 18 to 30 hours.

9. The self-healing antibacterial polyurethane elastomer prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the self-healing antibacterial polyurethane elastomer of claim 9 in the fields of biomedicine, sporting goods, or smart wearables.

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