Ultrafast self-healing polyurethane based on disulfide bond as well as preparation method and application of ultrafast self-healing polyurethane

Abstract

The invention provides ultrafast self-healing polyurethane based on disulfide bonds and a preparation method and application thereof, and the preparation method comprises the following steps: (1) under vacuum, mixing polytetrahydrofuran diol, 2, 2 '-(1, 2-ethanedioxy) diethyl mercaptan and 2-hydroxyethyl disulfide, and reacting to obtain a homogeneous soft segment mixture; (2) adding isophorone diisocyanate into the homogeneous soft segment mixture, and carrying out prepolymerization and chain extension reaction to obtain a reacted solution; and (3) adding pentaerythritol tetrakis (3-mercaptopropionic acid) into the reacted solution to carry out cross-linking reaction, and then adding a catalyst to assist polymerization, thereby obtaining the disulfide bond-based ultrafast self-healing polyurethane. According to the present invention, the dynamic disulfide bond is introduced into the polyurethane, such that the high self-healing efficiency and the short polymerization time can be achieved, and the reprocessing and the recycling can be achieved;

Description

Technical Field

[0001] This invention belongs to the field of polyurethane technology, and particularly relates to an ultra-fast self-healing polyurethane based on disulfide bonds, its preparation method, and its application. Background Technology

[0002] Polyurethane (PU) elastomers are widely used in industries such as construction, medical, transportation, and textiles. Due to the complexity and harshness of their operating environments, traditional PU elastomers are highly susceptible to mechanical damage during their service life. If such damage is not repaired in time, it can lead to a rapid decline in performance, ultimately rendering them unusable. Discarded PU elastomers are typically landfilled or incinerated, resulting in resource waste and severe environmental pollution. To contribute to building a sustainable society, next-generation PU elastomers should possess excellent self-healing capabilities, recyclability, and damage tolerance to ensure a longer service life, thereby reducing raw material consumption and carbon emissions.

[0003] In recent years, researchers have focused on developing polyurethane materials with inherent self-healing properties and have successfully developed room-temperature self-healing materials. The prerequisite for achieving ideal self-healing and recyclability is establishing dynamic covalent bonds within the PU material. These covalent bonds are easily broken and reformed, thereby restoring the network structure. *Nature Chemistry* (2016, Vol. 8, pp. 618–624) reported a self-healing polyurethane based on ion interactions, and *Journal of American Chemistry Society* (2020, Vol. 142, pp. 21852–21860) reported a polyurethane based on BO covalent bonds that can achieve self-healing in an aqueous environment. Despite these significant advancements, the long healing time remains one of the core bottlenecks hindering the large-scale practical application of self-healing polyurethanes. Many currently reported high-performance self-healing polyurethanes still require several hours or even longer to fully heal (recovering over 90% of mechanical properties). This time cost is particularly pronounced in scenarios requiring rapid functional recovery, such as electronic skin operating in real time and industrial components produced in continuous production. Healing time is essentially a result of the balance between the dynamic bond exchange rate and the molecular chain migration capability. The pursuit of ultrafast healing at the minute or even second level often requires highly flexible networks. Therefore, how to achieve rapid and efficient self-healing is a fundamental scientific challenge currently facing the field. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an ultra-fast self-healing polyurethane based on disulfide bonds, its preparation method and application, which has high self-healing efficiency and short polymerization time, and can be reprocessed and recycled.

[0005] This invention provides a method for preparing an ultrafast self-healing polyurethane based on disulfide bonds, comprising the following steps:

[0006] (1) Under vacuum, polytetrahydrofuran diol, 2,2'-(1,2-ethylenedioxy)diethylthiol and 2-hydroxyethyl disulfide were mixed and reacted to obtain a homogeneous soft segment mixture;

[0007] (2) The homogeneous soft segment mixture is added to isophorone diisocyanate for prepolymerization and chain extension reaction to obtain the post-reaction solution;

[0008] (3) Add pentaerythritol tetrakis(3-mercaptopropionic acid) to the solution after the reaction to carry out cross-linking reaction, and then add a catalyst to assist polymerization to obtain an ultra-fast self-healing polyurethane based on disulfide bonds.

[0009] Preferably, the molecular weight of the polytetrahydrofuran diol is 500~3000 g / mol.

[0010] Preferably, the reaction temperature in step (1) is 70~125℃ and the reaction time is 0.5~3h.

[0011] Preferably, the antioxidant 3,5-di-tert-butyl-4-hydroxyphenylpropionate isooctyl ester is added in step (2).

[0012] Preferably, in step (2), N,N-dimethylformamide is added to control the viscosity of the reaction system to be 50~200 mPa·s.

[0013] Preferably, the chain extension reaction in step (2) is carried out at a temperature of 10~50℃ for 2~4h.

[0014] In step (3), the cross-linking reaction is carried out at a temperature of 20~60℃ for 0.5~3h.

[0015] Preferably, the catalyst is selected from dibutyltin dilaurate.

[0016] Preferably, the molar ratio of polytetrahydrofuran diol, isophorone diisocyanate, 2,2'-(1,2-ethylenedioxy)diethylthiol, 2-hydroxyethyl disulfide and pentaerythritol tetrakis(3-mercaptopropionic acid) is (1~2):(4~5):(1~1.5):(2~2.5):(1~1.5).

[0017] This invention provides an ultra-fast self-healing polyurethane based on disulfide bonds, which is prepared by the method described in the above technical solution.

[0018] This invention provides an ultrafast self-healing polyurethane film based on disulfide bonds, which is prepared by the following method:

[0019] The solution of ultra-fast self-healing polyurethane based on disulfide bonds prepared by the preparation method described above is cast, vacuum dried and then cured to obtain a film.

[0020] The curing method is a stepped temperature curing: first cure at 75℃ for 12~24h, then raise the temperature to 95℃ and cure for 12~24h.

[0021] This invention provides a method for preparing an ultra-fast self-healing polyurethane based on disulfide bonds, comprising the following steps: (1) under vacuum, mixing polytetrahydrofuran diol, 2,2'-(1,2-ethylenedioxy)diethylthiol and 2-hydroxyethyl disulfide and reacting them to obtain a homogeneous soft segment mixture; (2) adding isophorone diisocyanate to the homogeneous soft segment mixture for prepolymerization and chain extension reaction to obtain a post-reaction solution; (3) adding pentaerythritol tetrakis(3-mercaptopropionic acid) to the post-reaction solution for crosslinking reaction, and then adding a catalyst to assist polymerization to obtain an ultra-fast self-healing polyurethane based on disulfide bonds. This invention introduces 2-hydroxyethyl disulfide (HEDS) containing dynamic disulfide bonds into a polyurethane network. As temperature increases, the mobility of the molecular chains increases, allowing for rapid exchange and rearrangement of the disulfide bonds, thus endowing the material with self-healing capabilities. To further optimize material performance, this invention uses a tetrafunctional pentaerythritol tetra(3-mercaptopropionic acid) ester (PETMP) reacted with a difunctional isocyanate. While generating a cross-linked network, this introduces thermally responsive dynamic thiocarbamate bonds. Under elevated temperature conditions, these dynamic bonds promote reversible exchange and rearrangement through enhanced molecular chain mobility, thereby endowing the material with recyclable properties and synergistically enhancing the self-healing ability of the cross-linked system. Attached Figure Description

[0022] Figure 1 The reaction route diagrams for the ultrafast self-healing polyurethane based on disulfide bonds in Examples 1-3 of this invention are shown below.

[0023] Figure 2 The infrared spectrum of the ultrafast self-healing polyurethane film based on disulfide bonds in an application example of the present invention is shown below.

[0024] Figure 3 This is the Raman spectrum of the ultrafast self-healing polyurethane film based on disulfide bonds in an application example of the present invention;

[0025] Figure 4 Thermogravimetric analysis (TGA) diagram of an ultrafast self-healing polyurethane film based on disulfide bonds in an application example of the present invention;

[0026] Figure 5 This is a DSC curve of an ultrafast self-healing polyurethane film based on disulfide bonds in an application example of the present invention.

[0027] Figure 6This is an optical micrograph of an ultrafast self-healing polyurethane film based on disulfide bonds, used in an application example of the present invention.

[0028] Figure 7 This is a stress-strain curve of an ultrafast self-healing polyurethane film based on disulfide bonds before and after self-healing in an application example of the present invention.

[0029] Figure 8 This is a cyclic tensile curve of an ultra-fast self-healing polyurethane film based on disulfide bonds after self-healing in an application example of the present invention.

[0030] Figure 9 This is a two-dimensional SAXS diagram of a uniaxially stretched ultrafast self-healing polyurethane film based on disulfide bonds in an application example of the present invention.

[0031] Figure 10 These are photos of the ultra-fast self-healing polyurethane film recycling process based on disulfide bonds before and after processing in an application example of this invention.

[0032] Figure 11 This is the stress-strain curve of the finished product obtained after multiple recycling processes of the ultra-fast self-healing polyurethane film based on disulfide bonds in an application example of the present invention. Detailed Implementation

[0033] This invention provides a method for preparing an ultrafast self-healing polyurethane based on disulfide bonds, comprising the following steps:

[0034] (1) Under vacuum, polytetrahydrofuran diol (PTMEG), 2,2'-(1,2-ethylenedioxy)diethylthiol (EDDET) and 2-hydroxyethyl disulfide (HEDS) were mixed and reacted to obtain a homogeneous soft segment mixture;

[0035] (2) The homogeneous soft segment mixture is added to isophorone diisocyanate (IPDI) for prepolymerization and chain extension reaction to obtain the post-reaction solution;

[0036] (3) Add pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP) to the solution after the reaction to carry out cross-linking reaction, and then add a catalyst to assist polymerization to obtain an ultra-fast self-healing polyurethane based on disulfide bonds.

[0037] This invention achieves high self-healing efficiency and extremely short healing time by introducing dynamic disulfide bonds, while also enabling reprocessing and recycling.

[0038] In this invention, polytetrahydrofuran diol (PTMEG), 2,2'-(1,2-ethylenedioxy)diethylthiol (EDDET), and 2-hydroxyethyl disulfide (HEDS) are mixed and reacted under vacuum to obtain a homogeneous soft segment mixture.

[0039] In this invention, the polytetrahydrofuran diol has a molecular weight of 500-3000 g / mol. The polytetrahydrofuran diol is dehydrated before the reaction.

[0040] In this invention, the reaction temperature of the mixture of polytetrahydrofuran diol (PTMEG), 2,2'-(1,2-ethylenedioxy)diethylthiol (EDDET), and 2-hydroxyethyl disulfide (HEDS) is 70~125℃, specifically 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, or 125℃; the reaction time is 0.5~3h, specifically 0.5h, 1h, 1.5h, 2h, 2.5h, or 3h.

[0041] After obtaining the homogeneous soft segment mixture, the present invention adds the homogeneous soft segment mixture to isophorone diisocyanate (IPDI) for prepolymerization and chain extension reaction to obtain the post-reaction solution.

[0042] In this invention, the chain extension reaction temperature is 10~50℃, specifically 10℃, 15℃, 20℃, 25℃, 30℃, 5℃, 40℃, 45℃ or 50℃; the time is 2~4h, specifically 2h, 2.5h, 3h, 3.5h or 4h.

[0043] The synthetic route for the prepolymerization and chain extension reactions of this invention is as follows:

[0044]

[0045]

[0046] The structural formula of the product obtained by prepolymerization and chain extension in this invention is shown in Formula I:

[0047]

[0048] Formula I;

[0049] In the above structural formula I, the value of n ranges from 6.47 to 11.19; the value of x ranges from 0.8 to 2.2; the value of y ranges from 0.8 to 1.7; and the value of z ranges from 1.8 to 3.2. Among these, x, y, and z are statistical averages, and their values ​​are within a continuous interval.

[0050] This invention preferably incorporates an antioxidant to prevent yellowing during prepolymerization and chain extension; the antioxidant is selected from isooctyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate. In a specific embodiment, it is preferred to add 1 drop of isooctyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate.

[0051] In this invention, due to the rapid prepolymerization reaction, the viscosity of the system increases. It is preferable to control the viscosity of the reaction system to be 50~200 mPa·s by adding N,N-dimethylformamide (DMF); specifically, it can be 50 mPa·s, 60 mPa·s, 70 mPa·s, 80 mPa·s, 90 mPa·s, 100 mPa·s, 110 mPa·s, 120 mPa·s, 130 mPa·s, 140 mPa·s, 150 mPa·s, 160 mPa·s, 170 mPa·s, 180 mPa·s, 190 mPa·s, or 200 mPa·s.

[0052] The molar ratio of polytetrahydrofuran diol, isophorone diisocyanate, 2,2'-(1,2-ethylenedioxy)diethylthiol, 2-hydroxyethyl disulfide and pentaerythritol tetrakis(3-mercaptopropionic acid) ester in this invention is (1~2):(4~5):(1~1.5):(2~2.5):(1~1.5).

[0053] In this invention, pentaerythritol tetrakis(3-mercaptopropionic acid) (PETMP) is added to the post-reaction solution to carry out a crosslinking reaction, and then a catalyst is added to assist polymerization to obtain an ultra-fast self-healing polyurethane based on disulfide bonds.

[0054] The crosslinking reaction temperature described in this invention is 20~60℃, specifically 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃; the time is 0.5~3h, specifically 0.5h, 1h, 1.5h, 2h, 2.5h or 3h.

[0055] The synthetic route for the crosslinking reaction in this invention is as follows:

[0056] ;

[0057] In the above structural formula, the value of m ranges from 0.8 to 1.2, which is the statistical average value and the range is a continuous interval; the values ​​of x, y, z and n are the same as the above range.

[0058] In this invention, the catalyst is preferably dibutyltin dilaurate (DBTDL); the amount of dibutyltin dilaurate added is 3~10 μL based on the amount of isophorone diisocyanate IPDI added.

[0059] After obtaining the homogeneous soft segment mixture, the subsequent prepolymerization, chain extension and crosslinking reactions are all carried out under a nitrogen atmosphere to prevent carbon dioxide and water from entering the system.

[0060] This invention also provides an ultrafast self-healing polyurethane film based on disulfide bonds, which is prepared by the following method:

[0061] The solution of ultra-fast self-healing polyurethane based on disulfide bonds prepared by the preparation method described above is cast, vacuum dried and then cured to obtain a film.

[0062] The curing method is a stepped temperature curing: first cure at 75℃ for 12~24h, then raise the temperature to 95℃ and cure for 12~24h.

[0063] The present invention preferably involves casting a solution of ultra-fast self-healing polyurethane based on disulfide bonds into a polytetrafluoroethylene mold.

[0064] Compared with the prior art, the beneficial effects of the present invention are:

[0065] (1) This invention introduces 2-hydroxyethyl disulfide (HEDS) containing dynamic disulfide bonds into a polyurethane network. As the temperature increases, the mobility of the molecular chains increases, allowing the disulfide bonds to rapidly exchange and rearrange, thus endowing the material with self-healing capabilities. To further optimize the material's performance, this invention uses a tetrafunctional pentaerythritol tetra(3-mercaptopropionic acid) ester (PETMP) reacted with a difunctional isocyanate. While generating a cross-linked network, this introduces a thermally responsive dynamic thiocarbamate bond. Under elevated temperature conditions, this dynamic bond promotes reversible exchange and rearrangement through enhanced molecular chain mobility, thereby endowing the material with recyclable properties. It also synergistically enhances the self-healing ability of the cross-linked system.

[0066] (2) Experimental results show that the ultra-fast self-healing polyurethane with dynamic disulfide bonds can achieve self-healing within 5 minutes when placed in the palm of the hand at body temperature. Tensile tests on the healed material show that the polyurethane material still maintains more than 80% of its healing efficiency after multiple healing processes. The material can be recycled by dissolving it in DMF, ultrasonically dissolving it, and then recasting it. The mechanical properties of the samples after multiple recycling processes can also be maintained at more than 80% of their original values.

[0067] (3) The dynamic disulfide bond mechanism proposed in this invention achieves multi-dimensional optimization of material properties by precisely controlling the synergistic effect of dynamic covalent bonds and physical cross-linking networks. It shows broad application prospects and important industrialization value in high-tech fields such as flexible electronic devices, smart response coatings, and advanced packaging materials.

[0068] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides an ultra-fast self-healing polyurethane based on disulfide bonds, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0069] Example 1

[0070] A method for preparing an ultrafast self-healing polyurethane based on disulfide bonds includes the following steps:

[0071] (1) Preparation of prepolymer and chain extension reaction

[0072] First, 20 g of polytetrahydrofuran (PTMEG-2000) with a molecular weight of 2000 g / mol was passed through a 120°C bath. o Dehydration was thoroughly achieved using vacuum drying at C. PTMEG-2000 was added to a three-necked flask equipped with a stirrer, followed by 3.08 g of 2-hydroxyethyl disulfide (HEDS), 1.82 g of 2,2'-(1,2-ethylenedioxy)diethylthiol (EDDET), and 10.37 g of isophorone diisocyanate (IPDI), and the mixture was stirred thoroughly. Then, one drop of the antioxidant 3,5-di-tert-butyl-4-hydroxyphenylpropionate isooctyl ester was added. Nitrogen gas was purged throughout the process, and the reaction was carried out for 2 hours at 25°C. o C.

[0073] (2) Crosslinking reaction

[0074] After the chain extension reaction is complete, a small amount of DMF is added to reduce the reaction viscosity (approximately 50-100 mPa·s). Then, 4.88 g of pentaerythritol tetrakis(3-mercaptopropionic acid) ester (PETMP) is added gradually and slowly. Finally, 0.05 mL of dibutyltin dilaurate (DBTDL) is added. o The polymer solution obtained by reacting at C for 2 h is denoted as SPU. 12 .

[0075] Example 2

[0076] A method for preparing an ultrafast self-healing polyurethane based on disulfide bonds includes the following steps:

[0077] (1) Preparation of prepolymer and chain extension reaction

[0078] First, 20 g of polytetrahydrofuran (PTMEG-2000) with a molecular weight of 2000 g / mol was passed through a 120°C bath. o Dehydration was thoroughly achieved using vacuum drying at C. PTMEG-2000 was added to a stirred three-necked flask, followed by 1.54 g of 2-hydroxyethyl disulfide (HEDS), 3.64 g of 2,2'-(1,2-ethylenedioxy)diethylthiol (EDDET), and 10.37 g of isophorone diisocyanate (IPDI), and the mixture was stirred thoroughly. Then, one drop of the antioxidant 3,5-di-tert-butyl-4-hydroxyphenylpropionate isooctyl ester was added. Nitrogen gas was bubbled through the mixture throughout the process, and the reaction was carried out for 2 hours at 25°C. o C.

[0079] (2) Crosslinking reaction

[0080] After the chain extension reaction is complete, a small amount of DMF is added to reduce the reaction viscosity (approximately 50-100 mPa·s). Then, 4.88 g of pentaerythritol tetrakis(3-mercaptopropionic acid) ester (PETMP) is added gradually and slowly. Finally, 0.05 mL of dibutyltin dilaurate (DBTDL) is added. o The polymer solution obtained by reacting at C for 2 h is denoted as SPU. 21 .

[0081] Example 3

[0082] A method for preparing an ultrafast self-healing polyurethane based on disulfide bonds includes the following steps:

[0083] (1) Preparation of prepolymer and chain extension reaction

[0084] First, 20 g of polytetrahydrofuran (PTMEG-2000) with a molecular weight of 2000 g / mol was passed through a 120°C bath. o Dehydration was thoroughly achieved using vacuum drying at C. PTMEG-2000 was added to a stirred three-necked flask, followed by 5.46 g of 2,2'-(1,2-ethylenedioxy)diethylthiol (EDDET) and 10.37 g of isophorone diisocyanate (IPDI), and the mixture was stirred thoroughly. Then, one drop of the antioxidant 3,5-di-tert-butyl-4-hydroxyphenylpropionate isooctyl ester was added. Nitrogen gas was bubbled through the mixture throughout the process, and the reaction was carried out for 2 hours at 25°C. o C.

[0085] (2) Crosslinking reaction

[0086] After the chain extension reaction is complete, a small amount of DMF is added to reduce the reaction viscosity (approximately 50-100 mPa·s). Then, 4.88 g of pentaerythritol tetrakis(3-mercaptopropionic acid) ester (PETMP) is added gradually and slowly. Finally, 0.05 mL of dibutyltin dilaurate (DBTDL) is added. o The polymer solution obtained by reacting at C for 2 h is denoted as SPU. 30 .

[0087] Application examples

[0088] A method for preparing an ultrafast self-healing polyurethane film based on disulfide bonds includes the following steps:

[0089] The ultra-fast self-healing anhydrous polyurethane polymer solutions based on disulfide bonds prepared in Examples 1-3 were uniformly spread in tetrafluoroethylene molds. First, they were placed in a vacuum oven to remove air bubbles, and then subjected to a stepped heating process within the oven. Specifically, the stepped heating process began at 75°C. o After curing in C for 12-24 hours, the temperature is raised to 95°C. oC curing for 12-24 hours ultimately yielded SPUs. 12 SPU 21 SPU 30 film.

[0090] The performance of the three prepared thin films was tested.

[0091] (1) The SPU was analyzed by reflection using a Fourier transform infrared spectrometer (ATR-FTIR, Nicolai iS 50). 12 SPU 21 SPU 30 The thin film was subjected to infrared spectroscopy testing at room temperature. For example... Figure 2 As shown, at 3307 cm -1 The broad absorption peaks at 1097 and 1037 cm⁻¹ are attributed to the stretching vibration of the NH group in the carbamate. -1 Stretching vibration peaks of CO and CS were observed at 1620 cm⁻¹. -1 The absorption peak at 1717 cm⁻¹ corresponds to the C=O group in the urea group. -1 The peak at 2265 cm⁻¹ is attributed to the C=O group in urethane and thiourethane groups. -1 The complete disappearance of the characteristic absorption peak of the NCO group confirms the complete consumption of isocyanate groups during polymerization; such as Figure 3 As shown, at 500-550 cm -1 The characteristic SS peaks were clearly visible through Raman spectroscopy, confirming the successful modification of the disulfide bond. Based on the stretching vibration peak intensity of the NH group in urethane esters, this application selected the peak intensity of the strongest SPU. 12 Further research will be conducted.

[0092] (2) Thermogravimetric analysis (TGA) was performed on the dried thin film samples using a TGA8000 thermogravimetric analyzer, with temperatures ranging from room temperature to 800°C. o C, the heating rate under nitrogen flow is 10 o C / min. For example... Figure 4 As shown, the temperature at which 10% of the thermal weight loss occurs is 340°C. o Above 665°C, the complete decomposition temperature is 665°C. o The temperature is around 30°C, which proves that it has good thermal stability.

[0093] (3) Differential scanning calorimetry (DSC) measurements were performed on a TA DSC Q2000 thermal analysis system, with a temperature range of -80 to 120°C. o C. The heating and cooling rates are set to 10. o C / min, nitrogen flow rate set to 40 mL / min. Glass transition temperature (T gThe value is determined based on the median point of the transformation recorded during the second heating process. For example... Figure 5 As shown, T g Very low, specifically -47.2℃, indicating that the SPU at room temperature... 12 It has an amorphous structure and a high segment migration rate, which is beneficial for self-healing.

[0094] (4) After cutting the original thin film sample (70 mm × 15 mm × 1 mm) into two pieces, the cut edges are joined together and connected to 37 mm. o A hot plate is placed in contact with the skin for 5 minutes to form a healed sample, such as... Figure 6 As shown, the incision achieved rapid self-healing and was able to withstand a certain degree of tension without breaking.

[0095] (5) Using a universal testing machine (CMT 4104, Nss (Shenzhen) Laboratory Equipment Co., Ltd.), test a 10 mm wide SPU at room temperature. 12 The stress-strain curves obtained by stretching thin film strips under a tensile testing machine are shown below. Figure 7 As shown. Due to the chemical crosslinking and physical hydrogen bonding of the polymer network, stress can be effectively dispersed throughout the entire polymer network during stretching, dissipating stress at the stretching point, effectively increasing strain, and exhibiting excellent tensile strength; after cutting the original film sample into two pieces, the cut edges were spliced ​​together and connected to 37 o The sample was in contact with a hot plate for 5 minutes. Its self-healing performance was then tested by applying a tensile force of 50 mm / min and performing three cut-and-heal tests. After self-healing, the sample did not show significant loss of stress and strain, and the self-healing efficiency reached over 80%.

[0096] (6) For SPU 12 The sample was subjected to cyclic tensile testing, such as Figure 8 As shown, after the first few cycles, the curve has formed a clear hysteresis loop, and the intensity of each decrease is getting smaller and smaller. This is because after the initial stretching, most of the intermolecular hydrogen bonds break, and the remaining hydrogen bonds have a relatively low density and are not easily broken, resulting in a smaller decrease in the intensity and eventually stabilizing. Figure 9 As shown, the two-dimensional SAXS image more intuitively reflects the cyclic stability. When uniaxial tension produces 400% strain, the SAXS image shows obvious orientation, while the SAXS image of the sample after stress release returns to almost the same isotropic as the initial sample.

[0097] (7) Material recycling can be achieved by redissolving the polymerized and cured SPU material in DMF, ultrasonically dissolving it, and then recasting it. Figure 10 As shown, the SPU 12The sample can be shredded, re-dissolved, and cast to form a new recycled SPU. 12 Its recovery rate reached 96.22%, and the mechanical properties of the samples were largely inherited even after multiple recoveries, such as... Figure 11 As shown, the mechanical properties of the sample can be maintained at more than 80% of the original after multiple stretching, proving the feasibility of recycling.

[0098] As can be seen from the above embodiments, the present invention provides a method for preparing an ultra-fast self-healing polyurethane based on disulfide bonds, comprising the following steps: (1) under vacuum, mixing polytetrahydrofuran diol, 2,2'-(1,2-ethylenedioxy)diethylthiol and 2-hydroxyethyl disulfide and reacting them to obtain a homogeneous soft segment mixture; (2) adding isophorone diisocyanate to the homogeneous soft segment mixture for prepolymerization and chain extension reaction to obtain a post-reaction solution; (3) adding pentaerythritol tetrakis(3-mercaptopropionic acid) to the post-reaction solution for crosslinking reaction, and then adding a catalyst to assist polymerization to obtain an ultra-fast self-healing polyurethane based on disulfide bonds. This invention introduces 2-hydroxyethyl disulfide (HEDS) containing dynamic disulfide bonds into a polyurethane network. As temperature increases, the mobility of the molecular chains increases, allowing for rapid exchange and rearrangement of the disulfide bonds, thus endowing the material with self-healing capabilities. To further optimize material performance, this invention uses a tetrafunctional pentaerythritol tetra(3-mercaptopropionic acid) ester (PETMP) reacted with a difunctional isocyanate. While generating a cross-linked network, this introduces thermally responsive dynamic thiocarbamate bonds. Under elevated temperature conditions, these dynamic bonds promote reversible exchange and rearrangement through enhanced molecular chain mobility, thereby endowing the material with recyclable properties and synergistically enhancing the self-healing ability of the cross-linked system.

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an ultrafast self-healing polyurethane based on disulfide bonds, comprising the following steps: (1) Under vacuum, polytetrahydrofuran diol, 2,2'-(1,2-ethylenedioxy)diethylthiol and 2-hydroxyethyl disulfide were mixed and reacted to obtain a homogeneous soft segment mixture; (2) The homogeneous soft segment mixture is added to isophorone diisocyanate for prepolymerization and chain extension reaction to obtain the post-reaction solution; (3) Add pentaerythritol tetrakis(3-mercaptopropionic acid) to the solution after the reaction to carry out cross-linking reaction, and then add a catalyst to assist polymerization to obtain an ultra-fast self-healing polyurethane based on disulfide bonds.

2. The preparation method according to claim 1, characterized in that, The molecular weight of the polytetrahydrofuran diol is 500~3000 g / mol.

3. The preparation method according to claim 1, characterized in that, The reaction temperature in step (1) is 70~125℃ and the time is 0.5~3h.

4. The preparation method according to claim 1, characterized in that, In step (2), the antioxidant 3,5-di-tert-butyl-4-hydroxyphenylpropionate isooctyl ester is added.

5. The preparation method according to claim 1, characterized in that, In step (2), N,N-dimethylformamide is added to control the viscosity of the reaction system to 50~200 mPa·s.

6. The preparation method according to claim 1, characterized in that, In step (2), the chain extension reaction is carried out at a temperature of 10~50℃ for 2~4 hours. In step (3), the cross-linking reaction is carried out at a temperature of 20~60℃ for 0.5~3h.

7. The preparation method according to claim 1, characterized in that, The catalyst is selected from dibutyltin dilaurate.

8. The preparation method according to claim 1, characterized in that, The molar ratio of polytetrahydrofuran diol, isophorone diisocyanate, 2,2'-(1,2-ethylenedioxy)diethylthiol, 2-hydroxyethyl disulfide and pentaerythritol tetrakis(3-mercaptopropionic acid) is (1~2):(4~5):(1~1.5):(2~2.5):(1~1.5).

9. An ultra-fast self-healing polyurethane based on disulfide bonds, prepared by the preparation method according to any one of claims 1 to 8.

10. An ultrafast self-healing polyurethane film based on disulfide bonds, characterized in that, It is prepared by the following method: A solution of ultra-fast self-healing polyurethane based on disulfide bonds, prepared by any one of claims 1 to 8, is cast, vacuum dried, and then cured to obtain a film. The curing method is a stepped temperature curing: first cure at 75℃ for 12~24h, then raise the temperature to 95℃ and cure for 12~24h.

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