Tough polyurethane ionic gel based on hard segment reinforcement and preparation method thereof

Abstract

The invention relates to the technical field of polyurethane, and particularly discloses tough polyurethane ionic gel based on hard segment reinforcement and a preparation method of the tough polyurethane ionic gel aiming at the problem that the toughness of the existing polyurethane ionic gel is inevitably attenuated due to the fact that the strength of the existing polyurethane ionic gel is enhanced by introducing a rigid group, namely the strength and the toughness are difficult to consider at the same time. The tough polyurethane ionic gel comprises an ionic liquid and modified polyurethane modified by a chain extender; the chain extender comprises one or more of isophthalic acid dihydrazide and the like; the ionic liquid is a 1-alkyl-3-methylimidazolium salt compound, and a pi-pi stacked structure is formed between the ionic liquid and the chain extender; the content of the ionic liquid is 20-110% of the mass of the modified polyurethane. Multiple hydrogen bonds are introduced into the ionic liquid, and the chain extender contains hydrazide groups, so that the ionic gel system contains the multiple hydrogen bonds and a network structure formed by the multiple hydrogen bonds, and not only has high strength, but also can keep good toughness and thermal stability.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane, and in particular to a tough polyurethane ion gel based on hard segment reinforcement and a preparation method thereof. Background Art

[0002] Gel material refers to a special dispersion system in which colloidal particles or polymers in a sol or solution form a spatial network structure under certain conditions through chemical or physical crosslinking, and the structural gaps are filled with liquid or gas as a dispersion medium. Based on the properties of the dispersion medium, gels can be divided into hydrogels, ion gels, and organic gels. Common hydrogel materials refer to gel materials obtained with water as the dispersion medium. Their performance is affected by external conditions such as temperature, humidity, and pH. They lack long-term stability. In high temperature environments, water evaporates and is easy to crystallize at low temperatures. They cannot be used under harsh conditions such as wide temperature ranges and high strength.

[0003] Ionic gels with ionic liquids as dispersion media can effectively overcome the above problems. Specifically, ionic liquids have negligible vapor pressure, good thermal stability and electrochemical stability, non-flammability, adjustable polarity and ionic conductivity, which make ionic gels have good long-term stability and safety in the application environment. Ionic liquids and polymer materials can form stable ionic gels through chemical bonds, hydrogen bonds, electrostatic interactions, etc., and various strengthening and toughening mechanisms can give the gels higher mechanical strength and other properties.

[0004] Polyurethane is a polymer material formed by the continuous polycondensation reaction of polyols and polyisocyanates. Due to the diversity of raw material selection and the designability of synthesis, the performance plasticity of polyurethane is extremely strong. Polyurethane has the advantages of light weight, high strength, thermal insulation, waterproofness, and corrosion resistance, and is an excellent candidate material for preparing ion gel. For example, the patent with publication number CN116693801A discloses a method for preparing zwitterionic polyurethane and zwitterionic polyurethane-based ion gel and its application, and the polyurethane modified by chain extender is compounded with ionic liquid to obtain ion gel with outstanding mechanical properties.

[0005] However, the existing polyurethane ion gels have the following problems in modification design and performance: the strength of the polyurethane ion gel can be enhanced by introducing rigid groups into the polyurethane, but the introduction of a large number of rigid groups will inevitably cause its toughness to decay, that is, it is difficult to take into account both the mechanical strength and toughness of the polyurethane ion gel. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that the existing polyurethane ion gel is enhanced in strength by introducing rigid groups, which inevitably leads to the attenuation of its toughness, that is, it is difficult to take both strength and toughness into consideration at the same time.

[0007] The present invention is achieved through the following technical solutions: The invention provides a tough polyurethane ion gel based on hard segment reinforcement, comprising an ionic liquid and a modified polyurethane modified by a chain extender, wherein the chain extender molecule contains a benzene ring and a hydrazide group, and the ionic liquid is a 1-alkyl-3-methylimidazolium salt compound containing multiple hydrogen bonds.

[0008] Preferably, the chain extender includes one or more of isophthalic acid dihydrazide, phthalic acid dihydrazide, terephthalic acid dihydrazide, 2,5-dibutoxyterephthaloyl dihydrazide, 2,5-dipropoxyterephthaloyl dihydrazide, 2,5-diethoxyterephthaloyl dihydrazide, and 2,5-bis(benzyloxy)terephthaloyl dihydrazide.

[0009] Preferably, the method for preparing the modified polyurethane comprises the following steps: A1: Take a chain extender, add it to the solvent, mix well, and obtain a chain extension reaction solution; A2 Under nitrogen protection, the chain extension reaction liquid is added dropwise to the polyurethane prepolymer, heated and stirred to carry out a chain extension reaction to obtain the modified polyurethane.

[0010] Preferably, the polyurethane prepolymer molecular chain ends contain isocyanate groups. Rigid structures such as isocyanate end-capping groups can be selectively introduced into the polyurethane prepolymer to improve the strength of the material, so those skilled in the art can also choose to introduce other rigid groups besides isocyanate groups according to actual conditions.

[0011] Preferably, the method for preparing the polyurethane prepolymer comprises the following steps: B1 Take diol and diisocyanate in a molar ratio of 1:1.5-3, add them to the solvent, mix them evenly, heat to 20-80°C under nitrogen protection, react, and obtain a polyurethane prepolymer terminated by isocyanate.

[0012] Preferably, the diol includes one or more of poly(1,4-butylene adipate) and polytetrahydrofuran.

[0013] Preferably, the diisocyanate includes one or more of 4,4-diisocyanate dicyclohexylmethane, hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-methylene diisocyanate phenyl.

[0014] Preferably, the ionic liquid includes one or more of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium trifluoroacetate, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate.

[0015] A method for preparing the above-mentioned tough polyurethane ion gel based on hard segment reinforcement comprises the following steps: The ionic liquid is added to the modified polyurethane, dispersed by centrifugation, and then subjected to ultrasonic homogenization treatment. The mixture is then placed in a vacuum for degassing, the solvent is removed, and the mixture is heated and dried to obtain the tough polyurethane ion gel.

[0016] Preferably, the added amount of the ionic liquid is 20-110% of the mass of the modified polyurethane.

[0017] The technical solution of the present invention has the following beneficial effects: In the polyurethane ion gel material system of the present invention, multiple hydrogen bond active sites are introduced into the ionic liquid; and the chain extender and the polyurethane hard segment contain hydrazide groups and benzene ring groups, which can promote the formation of π-π stacking supramolecular effects in the material system under the action of benzene rings in addition to the multiple hydrogen bonds introduced by the ionic liquid itself. In the case of a higher amount of ionic liquid added, not only the mechanical properties are avoided from decreasing, but also the mechanical strength and toughness can be improved simultaneously. Specifically, in the ion gel system, the supramolecular effect can form a network structure, and the supramolecular effect and the network structure formed by it can make the material easier to deform under stress without immediately breaking, thereby improving its toughness; and when fracture or deformation occurs, the reversible sacrificial fracture and re-formation process of the supramolecular effect can absorb a certain amount of energy, thereby slowing down the destruction of the material, that is, showing an excellent toughness effect, and showing good stability in the face of changes in external pressure and temperature; in addition, the supramolecular effect can provide additional interaction forces, making the connection between molecules tighter, and further improving the strength of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the Fourier infrared transform spectrum analysis diagram of various raw materials; Figure 2 Spectral analysis diagrams of polyurethane prepolymer PMI and polyurethane ion gel in Examples 1-5; Figure 3 The thermogravimetric analysis results of the polyurethane prepolymer PMI and the polyurethane ion gel in Examples 1-5 are shown; Figure 4 The figures are the mechanical test results of various polyurethane prepolymers; Figure 5 The figure is a tensile test result diagram of polyurethane ion gel using different types of ionic liquids; Figure 6 The tensile test results of polyurethane ion gel using different amounts of the same ionic liquid are shown in Figure 2. Figure 7 This is a diagram showing the tensile test results of the polyurethane ion gel in Example 1 after undergoing different self-healing times; Figure 8 This is a test result diagram of the tear resistance of the polyurethane ion gel notched specimen in Example 1; Fig. 9 This is a graph showing the puncture resistance test results of the polyurethane ion gel in Example 1. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. Where specific conditions are not specified in the embodiments, they are carried out under conventional conditions or conditions recommended by the manufacturer; where the manufacturers of the instruments, equipment, reagents and raw materials used are not specified, they are all conventional products that can be purchased commercially.

[0020] The present invention provides a tough polyurethane ion gel based on hard segment reinforcement, and the preparation method thereof comprises the following steps: (1) Preparation of polyurethane prepolymer The diol is heated to 80-120°C with stirring at a speed of 200-800rpm, and vacuum dehydration is performed for 0.5-2h. The diisocyanate is taken at a molar ratio of 1:1.5-3, dissolved in a solvent, and evenly mixed with the diol, dispersed by centrifugation, and then a catalyst is added. The catalyst can be dibutyltin dilaurate. Under nitrogen protection, the mixture is heated to 20-80°C and reacted for 0.5-2h to obtain a polyurethane prepolymer solution terminated by isocyanate.

[0021] Among them, the diol can be selected from poly(1,4-butylene adipate) (PBA) or polytetrahydrofuran (PTHF), and the molecular weight of the diol is Mn=1500-2500g / mol; the diisocyanate can be selected from 4,4-diisocyanate dicyclohexylmethane (HDMI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) or 4,4'-methylene diisocyanate phenyl (MDI), etc.; more preferably, poly(1,4-butylene adipate) (PBA) is compounded with 4,4'-methylene diisocyanate phenyl (MDI).

[0022] This process prepares a polyurethane matrix that can be used for ion gel, and rigid bonds can be selectively introduced into the polyurethane matrix to further optimize and improve the rigid strength of the polyurethane matrix. Specifically, the rigid group can adopt the above-mentioned molecular structure terminated by isocyanate, or other conventional rigid structures can be adopted to improve the strength of the material. Therefore, those skilled in the art can also choose to introduce other rigid groups besides isocyanate according to actual conditions.

[0023] (2) Preparation of modified polyurethane Take a chain extender in an equal molar amount to the polyurethane prepolymer, mix the chain extender with DMF, heat to 40-80°C, stir at 200-500rpm for 0.2-1h, and obtain a transparent and clear chain extension reaction liquid; under nitrogen protection, slowly drop the chain extension reaction liquid into the polyurethane prepolymer solution, keep stirring at 20-800rpm, and heat to 20-60°C until all the addition is completed, then maintain the above temperature and stirring conditions, react for 0.2-1h, obtain a transparent modified polyurethane solution, and cool to room temperature for standby use.

[0024] The chain extender molecule contains benzene rings and hydrazide groups, and specifically one or more of isophthalic acid dihydrazide, phthalic acid dihydrazide, terephthalic acid dihydrazide, 2,5-dibutoxy terephthaloyl hydrazide, 2,5-dipropoxy terephthaloyl hydrazide, 2,5-diethoxy terephthaloyl hydrazide, 2,5-bis(benzyloxy) terephthaloyl hydrazide, etc. can be selected. In this process, the chain extender introduces rigid groups into the polyurethane prepolymer molecular chain, and a large number of hard segment structures can make the polyurethane have significant mechanical strength. At the same time, the benzene ring and hydrazide group structure in the chain extender are combined with the subsequent ionic liquid to jointly resist the attenuation of toughness, and jointly act on the material system to form a network structure with multiple hydrogen bonds, which can improve the toughness and thermal stability of the material.

[0025] (3) Preparation of tough polyurethane ion gel based on hard segment reinforcement The ionic liquid is added to the modified polyurethane solution, and the added amount of the ionic liquid is 20-110% of the mass of the modified polyurethane, and the solution is dispersed evenly at 100-300 rpm for 5-15 minutes in an environment of 15-25° C.; then the evenly dispersed solution system is ultrasonically homogenized, and the ultrasonic power is controlled to be 300-500 W, and the ultrasonic frequency is 30-50 kHz, and the solution is placed in a vacuum oven, vacuum degassed for 0.5-2 hours at 60-90° C., and then transferred to a blast drying oven to remove the solvent DMF, and dried at 60-90° C. for 2-6 hours to obtain a polyurethane ion gel product.

[0026] Among them, the ionic liquid includes one or more of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]), 1-butyl-3-methylimidazolium trifluoroacetate ([BMIM][TFA]), 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide ([EMIM][TFSI]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TFO]), etc., and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) is preferred.

[0027] In the present invention, the ionic liquid can be dispersed between the modified polyurethane molecular chains, and while increasing the free volume, the polyurethane ion gel contains a hard segment with multiple supramolecular action sites and a flexible soft segment, wherein the amide bond on the hard segment can form multiple hydrogen bonds with the ionic liquid, thereby improving the compatibility of the two, and stabilizing the ionic liquid to prevent leakage while ensuring the migration ability of the ionic liquid. The molecular chain-ionic liquid hydrogen bond and π-π stacking in the material system are reversible supramolecular effects, which can dissipate a large amount of energy after being subjected to external stress, so that the original bonds are destroyed and rearranged to form new reversible sacrificial bonds, and promote the orientation and crystallization of the molecular chain, so that under the conditions of external force or temperature change, the polyurethane ion gel can show high resistance and self-healing ability.

[0028] Example 1 5 g of poly(1,4-butylene adipate) (PBA) with a molecular weight of Mn=2000 g / mol) was heated to 100°C, stirred, and vacuum-dehydrated; 4,4'-methylene diisocyanate (MDI) with a molar mass twice that of PBA was dissolved in N,N-dimethylformamide (DMF), and PBA and 14 μL of dibutyltin dilaurate were added. Under nitrogen protection, the mixture was heated to 40°C and reacted for 0.5 h to obtain a polyurethane prepolymer terminated with isocyanate.

[0029] Take isophthalic acid dihydrazide (IDHZ) with the same molar mass as PBA, dissolve it in solvent DMF, mix well, and obtain a chain extension reaction liquid; slowly add the chain extension reaction liquid dropwise to the polyurethane prepolymer, and then heat to 40°C and stir under nitrogen protection to carry out a chain extension reaction, and after the dropwise addition is completed, keep stirring and react continuously for 0.5h to obtain a modified polyurethane solution.

[0030] 1-Butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid was added to the modified polyurethane solution, and the addition amount of [BMIM][BF4] was 50% of the mass of PBA. The solution was dispersed by centrifugation at 200 rpm for 10 min in a 20°C environment, and then ultrasonically homogenized at an ultrasonic power of 400 W and an ultrasonic frequency of 40 kHz. The solution was transferred to a vacuum oven and degassed at 80°C for 1 h. The solution was then transferred to a forced air drying oven to remove DMF and dried at 80°C for 4 h to obtain a polyurethane ion gel, which was designated as PMI-[BMIM][BF4]-IL50 group.

[0031] Example 2 The difference between this embodiment and embodiment 1 is that the addition amount of [BMIM][BF4] is 25% of the mass of PBA, and the obtained polyurethane ion gel is recorded as PMI-[BMIM][BF4]-IL25 group.

[0032] Example 3 The difference between this embodiment and embodiment 1 is that the addition amount of [BMIM][BF4] is 75% of the mass of PBA, and the obtained polyurethane ion gel is recorded as PMI-[BMIM][BF4]-IL75 group.

[0033] Example 4 The difference between this embodiment and embodiment 1 is that the addition amount of [BMIM][BF4] is 100% of the mass of PBA, and the obtained polyurethane ion gel is recorded as PMI-[BMIM][BF4]-IL100 group.

[0034] Example 5 The difference between this embodiment and embodiment 1 is that the addition amount of [BMIM][BF4] is 150% of the mass of PBA, and the obtained polyurethane ion gel is recorded as PMI-[BMIM][BF4]-IL150 group.

[0035] Example 6 The difference between this embodiment and embodiment 1 is that the ionic liquid is replaced by 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) with 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), and the obtained polyurethane ion gel is recorded as PMI-[EMIM][BF4]-IL50 group.

[0036] Example 7 The difference between this embodiment and embodiment 1 is that the ionic liquid is replaced by 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) with 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and the obtained polyurethane ion gel is recorded as PMI-[BMIM][PF6]-IL50 group.

[0037] Example 8 The difference between this embodiment and embodiment 1 is that the ionic liquid is replaced by 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) with 1-butyl-3-methylimidazolium chloride ([BMIM][C l ]), the obtained polyurethane ion gel is recorded as PMI-[BMIM][C l ]-IL50 group.

[0038] Example 9 The difference between this embodiment and embodiment 1 is that the ionic liquid is replaced by 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) with 1-butyl-3-methylimidazolium trifluoroacetate ([BMIM][TFA]), and the obtained polyurethane ion gel is recorded as PMI-[BMIM][TFA]-IL50 group.

[0039] Example 10 The difference between this embodiment and embodiment 1 is that the ionic liquid is replaced by 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) with 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]), and the obtained polyurethane ion gel is recorded as PMI-[EMIM][TFSI]-IL50 group.

[0040] Embodiment 11 The difference between this embodiment and embodiment 1 is that the ionic liquid is replaced by 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) with 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TFO]), and the obtained polyurethane ion gel is recorded as PMI-[BMIM][TFO]-IL50 group.

[0041] Example 12 The difference between this example and Example 1 is that 4,4'-methylene diisocyanate (MDI) in the preparation of the polyurethane prepolymer is replaced by 4,4-diisocyanate dicyclohexylmethane (HDMI), and the obtained polyurethane ion gel is recorded as PHMI-[BMIM][BF4]-IL50 group.

[0042] Embodiment 13 The difference between this embodiment and embodiment 1 is that 4,4'-methylene diisocyanate (MDI) in the preparation of the polyurethane prepolymer is replaced by isophorone diisocyanate (IPDI), and the obtained polyurethane ion gel is recorded as PII-[BMIM][BF4]-IL50 group.

[0043] Embodiment 14 The difference between this embodiment and embodiment 1 is that 4,4'-methylene diisocyanate (MDI) in the preparation of the polyurethane prepolymer is replaced by hexamethylene diisocyanate (HDI), and the obtained polyurethane ion gel is recorded as PHI-[BMIM][BF4]-IL50 group.

[0044] Embodiment 15 The difference between this embodiment and embodiment 1 is that poly(1,4-butylene adipate) (PBA) in the preparation of the polyurethane prepolymer is replaced by polytetrahydrofuran (PTHF), and the obtained polyurethane ion gel is recorded as PTMI-[BMIM][BF4]-IL50 group.

[0045] Test example (1) According to GB / T 27843-2011 "Determination of low molecular weight component content of chemical polymers by gel permeation chromatography (GPC)", the molecular weight of the polyurethane prepolymers prepared in Example 1 and Examples 12-15 was measured by gel permeation chromatography. The results are shown in Table 1: Table 1 Molecular weight determination results of different polyurethane prepolymers

[0046] It can be seen from Table 1 above that the number average molecular weights of the polyurethane prepolymers using different diols or diisocyanates in Example 1 and Examples 12-15 are basically in the same range, and the polydispersity coefficients are also relatively close, which means that the subsequent comparison of their performance, etc. has sufficient reference value.

[0047] (2) According to GB / T 7764-2017 "National Standard for Rubber Identification by Infrared Spectroscopy", the raw materials, polyurethane prepolymers and ionic liquids were measured using Fourier transform infrared spectroscopy to characterize their structural characteristics, such as Figure 1 Spectral analysis (FT-IR) of various raw materials including 4,4'-methylene diisocyanate (MDI), poly(1,4-butylene adipate) (PBA), isophthalic acid dihydrazide (IDHZ) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). Figure 2 It is the spectrum analysis diagram of the polyurethane prepolymer PMI and the products in Examples 1-5.

[0048] Depend on Figure 1 and Figure 2 It can be seen that the 2265 cm-1 molecule is not observed in the polyurethane prepolymer PMI. -1 The peak at 3160cm indicates that the isocyanate in the raw material has been completely reacted during the preparation process; while the peak at 3160cm in the polyurethane ion gel -1 and 1055cm -1 The peaks at correspond to the CH bonds and BF bonds in the [BMIM][BF4] ionic liquid, thus proving that the preparation method proposed in the present invention can achieve the successful synthesis of the polyurethane prepolymer and the introduction and compounding of the ionic liquid, thereby successfully obtaining the polyurethane ion gel proposed in the present invention.

[0049] Furthermore, the infrared spectrum curve is subjected to peak fitting, and the degree of hydrogen bond formation of the C=O group can be calculated. The results are shown in Table 2 below: Table 2 Peak fitting results of spectral curves of different polyurethane prepolymers and polyurethane ion gels

[0050] It can be seen from Table 2 above that with the increase in the amount of ionic liquid added, the hydrogen bond formation rate shows a trend of first increasing and then decreasing, and reaches a maximum value of 99.02% at PMI-50.

[0051] (3) According to GB / T 33047.1-2016 "Thermogravimetric analysis (TG) of plastic polymers Part 1: General principles", thermogravimetric analysis of polyurethane prepolymer PMI and polyurethane ion gel with different ionic liquid addition amounts was performed, such as Figure 3 The results of thermogravimetric analysis of polyurethane prepolymer and different polyurethane ion gels are shown in Figure 1. The thermogravimetric analysis can reflect the thermal stability of polyurethane prepolymer PMI and polyurethane ion gels with different ionic liquid addition amounts. The analysis found that after adding ionic liquid, the maximum thermal decomposition temperature increased from 324.6°C to about 409.6°C, that is, the thermal stability of the polyurethane ion gel proposed in the present invention is significantly improved.

[0052] (4) According to GB / T 1040.1-2018 "Determination of tensile properties of plastics Part 1: General principles", mechanical properties tests were conducted on various polyurethane prepolymers, polyurethane ion gels with various ionic liquids, and polyurethane ion gels with various ionic liquid dosages, such as Figure 4 The mechanical test results of different polyurethane prepolymers are shown in Figure 2. Figure 5 The figure shows the mechanical test results of polyurethane ion gel using different types of ionic liquids. Figure 6 This is a graph showing the mechanical test results of polyurethane ion gel using different amounts of the same ionic liquid.

[0053] The polyurethane ion gel proposed in the present invention has high modulus and high strength due to its crystallization and reversible supramolecular action. Under medium and low strains, the original crystal structure is destroyed by stress and the modulus is reduced; under high strain, the molecular chains are oriented to promote the rearrangement of crystals, and new crystal forms are formed, thereby showing the performance effect of tensile strengthening. Specifically, it is measured that its tensile strength can reach 49.22 MPa, the elongation at break is 1721%, and the toughness is 424.09 MJ / m 3 , Young’s modulus 48.66 MPa.

[0054] (5) The polyurethane ion gel prepared in Example 1 was used for self-healing ability test, that is, dumbbell-shaped polyurethane ion gel samples were selected. The sample morphology was referred to GB / T 1040.1-2018 "Determination of tensile properties of plastics Part 1: General". The sample was first cut in the middle, and then the cut surfaces were spliced ​​together. Without applying external force, only the contact state was maintained to allow self-healing. After different self-healing times, tensile tests were performed on it. The results are as follows: Figure 7 As shown. Figure 7 The measurement results shown show that after 12 hours of self-healing process, the tensile strength of the sample can reach more than 90% of the normal uncut sample, indicating that the polyurethane ion gel sample has excellent self-healing ability.

[0055] (6) The polyurethane ion gel prepared in Example 1 was tested for tear resistance. That is, a dumbbell-shaped polyurethane ion gel sample was selected, and a notch with a width of 1 mm was cut out in a test area with a width of 4 mm of the sample. The sample was stretched and torn, and its tear energy Gc was calculated according to the following formula: ; Where W is the tensile fracture energy of a specimen with the same size without a notch, c is the width of the notch (1 mm), and λc is the elongation of the specimen when it breaks with a notch.

[0056] The tearing energy of the notched sample and the unnotched sample used as a control can be obtained by calculation. The results are as follows: Figure 8 As shown in the figure, the larger the tear energy value, the better the tear resistance of the ion gel material. Figure 8 It can be seen that the tear resistance of the notched sample is weaker than that of the non-notched sample, but the tear resistance of the notched polyurethane ion gel sample can still reach a good level, and the tear energy can reach 387.02 kJ / m 2 .

[0057] (7) According to GB / T 31064-2014 “Test method for puncture resistance of rubber or plastic coated fabrics”, the polyurethane ion gel prepared in Example 1 was tested for puncture strength, i.e., the maximum force produced by the puncture needle pressing down on the material was used to determine the maximum puncture force of the material. The maximum puncture force divided by the material thickness can reflect the puncture strength of the material. The results are as follows: Fig. 9 As shown. Through the above test process, it can be concluded that the maximum puncture force of the polyurethane ion gel reaches 165.85N, and its thickness is 1.25mm, that is, the puncture strength is 184.62N / mm, indicating that it has good anti-puncture performance.

[0058] The above experiments show that the polyurethane ion gel proposed in the present invention, relying on the reversible supramolecular effects of hydrogen bonds and π-π stacking, can dissipate a large amount of energy after being subjected to external stress, so that the original bonds are destroyed and rearranged into new reversible sacrificial bonds, while also promoting the orientation and crystallization of molecular chains. Therefore, under various forms of external damage, the polyurethane ion gel shows high resistance, and the energy consumed is also at a high level, which can achieve the performance effect of mechanical strength and toughness coexisting, which is difficult to achieve with existing similar materials.

[0059] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A tough polyurethane ion gel based on hard segment reinforcement, characterized in that: Including ionic liquid and modified polyurethane modified by chain extender; The chain extender includes one or more of isophthalic acid dihydrazide, phthalic acid dihydrazide, terephthalic acid dihydrazide, 2,5-dibutoxy terephthaloyl dihydrazide, 2,5-dipropoxy terephthaloyl dihydrazide, 2,5-diethoxy terephthaloyl dihydrazide, and 2,5-bis(benzyloxy) terephthaloyl dihydrazide; The ionic liquid is a 1-alkyl-3-methylimidazolium salt compound, and a π-π stacking structure is formed between the ionic liquid and the chain extender; The content of the ionic liquid is 20-110% of the mass of the modified polyurethane.

2. The tough polyurethane ion gel based on hard segment reinforcement according to claim 1, characterized in that: The preparation method of the modified polyurethane comprises the following steps: A1: Take a chain extender, add it to the solvent, mix well, and obtain a chain extension reaction solution; A2 Under nitrogen protection, the chain extension reaction liquid is added dropwise to the polyurethane prepolymer, heated and stirred to carry out a chain extension reaction to obtain the modified polyurethane.

3. The tough polyurethane ion gel based on hard segment reinforcement according to claim 2, characterized in that: The molecular chain end of the polyurethane prepolymer contains isocyanate.

4. The tough polyurethane ion gel based on hard segment reinforcement according to claim 3, characterized in that: The preparation method of the polyurethane prepolymer comprises the following steps: B1 Take diol and diisocyanate in a molar ratio of 1:1.5-3, add them to the solvent, mix them evenly, heat to 20-80°C under nitrogen protection, react, and obtain a polyurethane prepolymer terminated by isocyanate.

5. The tough polyurethane ion gel based on hard segment reinforcement according to claim 4, characterized in that: The diol includes one or more of poly(1,4-butylene adipate) and polytetrahydrofuran.

6. The tough polyurethane ion gel based on hard segment reinforcement according to claim 4, characterized in that: The diisocyanate includes one or more of 4,4-diisocyanate dicyclohexylmethane, hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-methylene diisocyanate phenyl.

7. The tough polyurethane ion gel based on hard segment reinforcement according to claim 1, characterized in that: The ionic liquid includes one or more of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium trifluoroacetate, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate.

8. A method for preparing a tough polyurethane ion gel based on hard segment reinforcement according to any one of claims 1 to 7, characterized in that: The steps include: The ionic liquid is added to the modified polyurethane, dispersed by centrifugation, and then subjected to ultrasonic homogenization treatment. The mixture is then placed in a vacuum for degassing, the solvent is removed, and the mixture is heated and dried to obtain the tough polyurethane ion gel.

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