A tough polyurethane ion gel based on hard segment reinforcement and its preparation method

Abstract

The present invention relates to the technical field of polyurethanes. Aiming at the problem that the existing polyurethane ion gels inevitably lead to the attenuation of their toughness when enhancing their strength by introducing rigid groups, that is, it is difficult to take into account both strength and toughness at the same time, a tough and strong polyurethane ion gel based on hard segment enhancement and its preparation method are specifically disclosed. The tough and strong polyurethane ion gel includes an ionic liquid and a modified polyurethane modified by a chain extender; the chain extender includes one or more of isophthalic dihydrazide, etc.; 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; and the content of the ionic liquid is 20-110% of the mass of the modified polyurethane. By introducing multiple hydrogen bonds into the ionic liquid and the chain extender containing hydrazide groups, the ionic gel system contains multiple hydrogen bonds and the network structure formed by them, not only has high strength, but also can maintain good toughness and thermal stability.

Description

Technical Field

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

[0002] A gel material refers to a special dispersion system in which colloidal particles or macromolecules in a sol or solution form a three-dimensional network structure through chemical cross-linking or physical cross-linking under certain conditions, and the structural voids are filled with a liquid or gas as a dispersion medium. Based on the properties of the dispersion medium, gels can be classified into hydrogels, ion gels, organic gels, etc. Common hydrogel materials refer to gel materials obtained by using water as the dispersion medium. Their properties are affected by external conditions such as temperature, humidity, and pH, lacking long-term stability. In a high-temperature environment, water volatilizes and it is easy to crystallize at low temperatures, and it cannot be used under harsh conditions such as a wide temperature range and high strength.

[0003] Ion gels with ionic liquids as the dispersion medium 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, making ion gels have good long-term stability and safety in the application environment. Ionic liquids and polymer materials can be combined through chemical bonds, hydrogen bonds, electrostatic interactions, etc. to form stable ion gels, and various strengthening and toughening mechanisms can endow the gels with 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 properties of polyurethane are highly plastic. Polyurethane has the advantages of light weight, high strength, heat insulation, waterproof, corrosion resistance, etc., and is an excellent candidate material for preparing ion gels. For example, the patent with the publication number CN116693801A discloses a preparation method and application of zwitterionic polyurethane and zwitterionic polyurethane-based ion gels. After the polyurethane modified by a chain extender is compounded with an ionic liquid, an ion gel with outstanding mechanical properties is prepared.

[0005] However, the existing polyurethane ion gels have the following problems in modification design and performance: By introducing rigid groups into polyurethane, the strength of the polyurethane ion gel can be enhanced, but introducing a large number of rigid groups will inevitably cause the attenuation of its toughness, that is, it is difficult to balance 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 gels inevitably lead to the attenuation of their toughness by introducing rigid groups to enhance their strength, that is, it is difficult to balance strength and toughness simultaneously.

[0007] The present invention is achieved through the following technical solutions:

[0008] The present invention provides a tough polyurethane ion gel based on hard segment enhancement, which comprises an ionic liquid and a modified polyurethane modified by a chain extender. 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.

[0009] Preferably, the chain extender includes one or more of isophthalic dihydrazide, phthalic dihydrazide, terephthalic dihydrazide, 2,5-dibutoxyterephthalic dihydrazide, 2,5-dipropoxyterephthalic dihydrazide, 2,5-diethoxyterephthalic dihydrazide, 2,5-bis(benzyloxy)terephthalic dihydrazide.

[0010] Preferably, the preparation method of the modified polyurethane comprises the following steps:

[0011] A1 Take the chain extender, add it to a solvent, and mix well to obtain a chain extension reaction solution;

[0012] A2 Under nitrogen protection, drop the chain extension reaction solution into the polyurethane prepolymer, heat and stir to carry out a chain extension reaction to obtain the modified polyurethane.

[0013] Preferably, the molecular chain ends of the polyurethane prepolymer contain isocyanate groups. Rigid structures such as isocyanate end-capping groups can be selectively introduced into the polyurethane prepolymer to enhance the strength of the material. Therefore, those skilled in the art can also select other rigid groups other than isocyanate groups according to the actual situation.

[0014] Preferably, the preparation method of the polyurethane prepolymer comprises the following steps:

[0015] B1 Take a diol and a diisocyanate in a molar ratio of 1:1.5-3, add them to a solvent, mix evenly, and under nitrogen protection, heat to 20-80 °C for reaction to obtain a polyurethane prepolymer capped with isocyanate groups.

[0016] Preferably, the diol includes one or more of poly(1,4-butylene adipate) and polytetrahydrofuran.

[0017] Preferably, the diisocyanate includes one or more of 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and 4,4'-methylenebis(phenyl isocyanate).

[0018] 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 bis(trifluoromethylsulfonyl)imide, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate.

[0019] A preparation method of a tough polyurethane ionic gel based on hard segment enhancement as described above includes the following steps:

[0020] Take the ionic liquid, add it to the modified polyurethane, disperse it by centrifugation, then perform ultrasonic homogenization treatment, then place it under vacuum degassing, remove the solvent, and heat and dry it to obtain the tough polyurethane ionic gel.

[0021] Preferably, the addition amount of the ionic liquid is 20-110% of the mass of the modified polyurethane.

[0022] The technical solution of the present invention has the following beneficial effects:

[0023] In the polyurethane ionic 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. In addition to the multiple hydrogen bonds introduced by the ionic liquid itself, it can also promote the formation of π-π stacking supramolecular interactions in the material system under the action of the benzene ring. In the case of a relatively high addition amount of the ionic liquid, not only can the mechanical properties be prevented from decreasing, but also the mechanical strength and toughness can be improved simultaneously. Specifically, in this ionic gel system, the above-mentioned supramolecular interactions can form a network structure. The supramolecular interactions and the network structure formed by them can make the material more easily deformed under stress and will not break immediately, thus improving its toughness; and when fracture or deformation occurs, the reversible sacrificial bond breaking and reformation process of the supramolecular interactions can absorb a certain amount of energy, thereby slowing down the destruction of the material, that is, showing excellent toughness effects, and showing good stability in the face of external pressure and temperature changes; in addition, the supramolecular interactions can provide additional interaction forces, making the connection between molecules closer and further improving the material strength. Description of the Drawings

[0024] Figure 1 It is the Fourier transform infrared spectroscopy analysis diagram of various raw materials;

[0025] Figure 2 It is the spectroscopy analysis diagram of the polyurethane prepolymer PMI and the polyurethane ionic gels in Examples 1-5;

[0026] Figure 3 It is the thermogravimetric analysis result diagram of the polyurethane prepolymer PMI and the polyurethane ionic gels in Examples 1-5;

[0027] Figure 4 Graph of the mechanical test results of various polyurethane prepolymers;

[0028] Figure 5 Graph of the tensile test results of polyurethane ion gels with different types of ionic liquids;

[0029] Figure 6 Graph of the tensile test results of polyurethane ion gels with different dosages of the same ionic liquid

[0030] Figure 7 Graph of the tensile test results of the polyurethane ion gel in Example 1 after different self-healing times;

[0031] Figure 8 Graph of the tear resistance test results of the notched specimen of the polyurethane ion gel in Example 1;

[0032] Figure 9 Graph of the puncture resistance test results of the polyurethane ion gel in Example 1. Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Among them, for those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer; for those instrument devices, reagent raw materials, etc. whose manufacturers are not specified, they are all conventional products that can be obtained by purchasing in the market.

[0034] The present invention provides a tough polyurethane ion gel based on hard segment reinforcement, and its preparation method includes the following steps:

[0035] (1) Prepare a polyurethane prepolymer

[0036] Stir and heat the diol to 80 - 120 °C, with a stirring speed of 200 - 800 rpm, and perform vacuum dehydration for 0.5 - 2 h; take the diisocyanate according to a molar ratio of 1:1.5 - 3, dissolve it in a solvent, mix it evenly with the diol, disperse it by centrifugation, then add a catalyst. The catalyst can be dibutyltin dilaurate. Under nitrogen protection, heat it to 20 - 80 °C and react for 0.5 - 2 h to obtain a polyurethane prepolymer solution capped with isocyanate groups.

[0037] Among them, the diol can be selected from poly(1,4-butylene adipate) (PBA), polytetrahydrofuran (PTHF), etc., and the molecular weight of the diol Mn = 1500 - 2500 g / mol; the diisocyanate can be selected from 4,4'-dicyclohexylmethane diisocyanate (HDMI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4'-methylenebis(phenyl isocyanate) (MDI), etc.; more preferably, poly(1,4-butylene adipate) (PBA) is compounded with 4,4'-methylenebis(phenyl isocyanate) (MDI).

[0038] This process prepares a polyurethane matrix that can be used for ion gels. Rigid bonds can be selectively introduced into the polyurethane matrix to further optimize and enhance the rigid strength of the polyurethane matrix. Specifically, the rigid group can adopt the above-mentioned molecular structure capped with isocyanate groups, or other conventional rigid structures can also be used to enhance the strength of the material. Therefore, those skilled in the art can also select other rigid groups other than isocyanate groups according to the actual situation.

[0039] (2)Preparation of modified polyurethane

[0040] Take a chain extender in an equimolar amount to the polyurethane prepolymer, mix the chain extender with DMF, heat to 40 - 80 °C, stir at 200 - 500 rpm for 0.2 - 1 h to obtain a transparent and clear chain extension reaction solution; under nitrogen protection, slowly drop the chain extension reaction solution into the polyurethane prepolymer solution, while maintaining stirring at 20 - 800 rpm and heating to 20 - 60 °C until all the dropping is completed. Then, maintain the above temperature and stirring conditions and react for 0.2 - 1 h to obtain a transparent modified polyurethane solution, and cool it to room temperature for standby.

[0041] Among them, the chain extender molecule contains a benzene ring and a hydrazide group. Specifically, it can be selected from one or more of isophthalic dihydrazide, phthalic dihydrazide, terephthalic dihydrazide, 2,5-dibutoxyterephthalic dihydrazide, 2,5-dipropoxyterephthalic dihydrazide, 2,5-diethoxyterephthalic dihydrazide, 2,5-bis(benzyloxy)terephthalic dihydrazide, etc. In this process, rigid groups are introduced into the polyurethane prepolymer molecular chain through the chain extender. A large number of hard segment structures can endow the polyurethane with significant mechanical strength. At the same time, the benzene ring and hydrazide group structures in the chain extender combine with the subsequent ionic liquid to jointly resist the attenuation of toughness, and act together on the material system to form a network structure of multiple hydrogen bonds, which can improve the toughness and thermal stability of the material, etc.

[0042] (3)Preparation of tough polyurethane ion gel based on hard segment reinforcement

[0043] An ionic liquid is added to the above-mentioned modified polyurethane solution, and the addition amount of the ionic liquid is 20-110% of the mass of the modified polyurethane. Then, it is centrifugally dispersed at 100-300 rpm for 5-15 min in an environment of 15-25 °C to make it uniformly dispersed. Then, the uniformly dispersed solution system is ultrasonically homogenized, with the ultrasonic power controlled at 300-500 W and the ultrasonic frequency at 30-50 kHz. It is placed in a vacuum oven and vacuum degassed at 60-90 °C for 0.5-2 h, and then transferred to a forced-air drying oven to remove the solvent DMF, and dried at 60-90 °C for 2-6 h to obtain a polyurethane ion gel product.

[0044] 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 bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TFO]), etc. Preferably, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) is used.

[0045] In the present invention, the ionic liquid can be dispersed between the molecular chains of the modified polyurethane. While increasing the free volume, the polyurethane ion gel contains hard segments with multiple supramolecular interaction sites and flexible soft segments. Among them, the amide bonds on the hard segments can form multiple hydrogen bonds with the ionic liquid, improving the compatibility between the two. On the premise of ensuring the migration ability of the ionic liquid, the ionic liquid is stabilized to prevent leakage. The molecular chain-ionic liquid hydrogen bonds and π-π stacking in the material system belong to reversible supramolecular interactions. After being subjected to external stress, a large amount of energy can be dissipated, the original bonds are broken and rearranged to form new reversible sacrificial bonds, and the orientation and crystallization of the molecular chains are promoted. Therefore, under the conditions of external force or temperature change, etc., the polyurethane ion gel can exhibit high resistance and self-healing ability.

[0046] Example 1

[0047] 5 g of poly(butylene adipate) (PBA) with a molecular weight Mn = 2000 g / mol is heated to 100 °C, stirred, and vacuum dehydrated. 4,4'-methylenebis(phenyl isocyanate) (MDI) with twice the molar mass of PBA is dissolved in N,N-dimethylformamide (DMF), and then PBA and 14 μL of dibutyltin dilaurate are added. Under nitrogen protection, it is heated to 40 °C and reacted for 0.5 h to obtain a polyurethane prepolymer capped with isocyanate groups.

[0048] Take isophthalic dihydrazide (IDHZ) with the same molar mass as PBA, dissolve it in the solvent DMF, mix well to obtain a chain extension reaction solution; slowly drop the chain extension reaction solution into the polyurethane prepolymer, and under nitrogen protection, heat it to 40 °C and stir to carry out the chain extension reaction. After the dropping is completed, keep stirring and react continuously for 0.5 h to obtain a modified polyurethane solution.

[0049] Add 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid to the modified polyurethane solution, and the addition amount of [BMIM][BF4] is 50% of the mass of PBA. In an environment of 20 °C, centrifuge and disperse it at 200 rpm for 10 min, then carry out ultrasonic homogenization treatment under the conditions of ultrasonic power of 400 W and ultrasonic frequency of 40 kHz. Transfer it to a vacuum oven, under the condition of 80 °C, carry out vacuum degassing for 1 h, then transfer it to a forced-air drying oven to remove DMF, and dry it at 80 °C for 4 h to obtain a polyurethane ion gel, denoted as the PMI-[BMIM][BF4]-IL50 group.

[0050] Example 2

[0051] The difference between this example and Example 1 is that the addition amount of [BMIM][BF4] is 25% of the mass of PBA, and the obtained polyurethane ion gel is denoted as the PMI-[BMIM][BF4]-IL25 group.

[0052] Example 3

[0053] The difference between this example and Example 1 is that the addition amount of [BMIM][BF4] is 75% of the mass of PBA, and the obtained polyurethane ion gel is denoted as the PMI-[BMIM][BF4]-IL75 group.

[0054] Example 4

[0055] The difference between this example and Example 1 is that the addition amount of [BMIM][BF4] is 100% of the mass of PBA, and the obtained polyurethane ion gel is denoted as the PMI-[BMIM][BF4]-IL100 group.

[0056] Example 5

[0057] The difference between this example and Example 1 is that the addition amount of [BMIM][BF4] is 150% of the mass of PBA, and the obtained polyurethane ion gel is denoted as the PMI-[BMIM][BF4]-IL150 group.

[0058] Example 6

[0059] The difference between this example and Example 1 is that the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) is replaced by 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), and the resulting polyurethane ion gel is denoted as the PMI-[EMIM][BF4]-IL50 group.

[0060] Example 7

[0061] The difference between this example and Example 1 is that the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) is replaced by 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and the resulting polyurethane ion gel is denoted as the PMI-[BMIM][PF6]-IL50 group.

[0062] Example 8

[0063] The difference between this example and Example 1 is that the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) is replaced by 1-butyl-3-methylimidazolium chloride ([BMIM][C l ), and the resulting polyurethane ion gel is denoted as the PMI-[BMIM][C l -IL50 group.

[0064] Example 9

[0065] The difference between this example and Example 1 is that the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) is replaced by 1-butyl-3-methylimidazolium trifluoroacetate ([BMIM][TFA]), and the resulting polyurethane ion gel is denoted as the PMI-[BMIM][TFA]-IL50 group.

[0066] Example 10

[0067] The difference between this example and Example 1 is that the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) is replaced by 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]), and the resulting polyurethane ion gel is denoted as the PMI-[EMIM][TFSI]-IL50 group.

[0068] Example 11

[0069] The difference between this example and Example 1 is that the ionic liquid is replaced from 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) with 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TFO]), and the obtained polyurethane ion gel is denoted as the PMI-[BMIM][TFO]-IL50 group.

[0070] Example 12

[0071] The difference between this example and Example 1 is that 4,4'-methylenebis(phenyl isocyanate) (MDI) in the preparation of the polyurethane prepolymer is replaced with 4,4'-dicyclohexylmethane diisocyanate (HDMI), and the obtained polyurethane ion gel is denoted as the PHMI-[BMIM][BF4]-IL50 group.

[0072] Example 13

[0073] The difference between this example and Example 1 is that 4,4'-methylenebis(phenyl isocyanate) (MDI) in the preparation of the polyurethane prepolymer is replaced with isophorone diisocyanate (IPDI), and the obtained polyurethane ion gel is denoted as the PII-[BMIM][BF4]-IL50 group.

[0074] Example 14

[0075] The difference between this example and Example 1 is that 4,4'-methylenebis(phenyl isocyanate) (MDI) in the preparation of the polyurethane prepolymer is replaced with hexamethylene diisocyanate (HDI), and the obtained polyurethane ion gel is denoted as the PHI-[BMIM][BF4]-IL50 group.

[0076] Example 15

[0077] The difference between this example and Example 1 is that poly(1,4-butylene adipate) (PBA) in the preparation of the polyurethane prepolymer is replaced with polytetrahydrofuran (PTHF), and the obtained polyurethane ion gel is denoted as the PTMI-[BMIM][BF4]-IL50 group.

[0078] Test Example

[0079] (1) According to GB / T 27843-2011 "Chemicals - Determination of low molecular weight components in polymers - Gel permeation chromatography (GPC)", the molecular weights of the polyurethane prepolymers prepared in Example 1 and Examples 12 - 15 were determined by gel permeation chromatography, and the results are shown in Table 1 below:

[0080] Table 1 Molecular weight determination results of different polyurethane prepolymers

[0081]

[0082] As can be seen from Table 1 above, for the polyurethane prepolymers using different diols or diisocyanates in Example 1 and Examples 12 - 15, their number-average molecular weights are basically in the same range and the polydispersity coefficients are also relatively close, indicating that subsequent comparison of their properties has sufficient reference value.

[0083] (2)According to GB / T 7764-2017 "National Standard for Rubber Identification - Infrared Spectroscopy Method", Fourier transform infrared spectroscopy was used to measure the raw materials, polyurethane prepolymers and ionic liquids to characterize their structural features, such as Figure 1 Spectral analysis diagrams (FT-IR) of various raw materials including 4,4'-methylenebis(phenyl isocyanate) (MDI), poly(butylene adipate) (PBA), isophthalic dihydrazide (IDHZ) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]). Figure 2 Spectral analysis diagrams of polyurethane prepolymer PMI and the products in Examples 1 - 5.

[0084] From Figure 1 and Figure 2 it can be seen that no peak at 2265 cm -1 was observed in the polyurethane prepolymer PMI, indicating that the isocyanate in the raw materials has been completely reacted during the preparation process; while the peaks at 3160 cm -1 and 1055 cm -1 in the polyurethane ion gel correspond to the C-H bond and B-F bond in the [BMIM][BF4] ionic liquid. Therefore, it can be confirmed that the preparation method proposed in the present invention can successfully synthesize the polyurethane prepolymer and introduce and compound the ionic liquid, thus successfully obtaining the polyurethane ion gel proposed in the present invention.

[0085] Furthermore, by performing peak fitting on the infrared spectral curves, the degree of hydrogen bond formation of the C=O group can be calculated, and the results are shown in Table 2 below:

[0086] Table 2 Peak fitting results of spectral curves of different polyurethane prepolymers and polyurethane ion gels

[0087]

[0088] As can be seen from Table 2 above, with the increase of the ionic liquid addition amount, 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.

[0089] (3)According to GB / T 33047.1-2016 "Plastics - Polymer Thermogravimetry (TG) - Part 1: General Principles", thermogravimetric analysis was carried out on the polyurethane prepolymer PMI and polyurethane ion gels with different ionic liquid addition amounts, such as Figure 3It is a thermogravimetric analysis result diagram of polyurethane prepolymer and different polyurethane ion gels. Through thermogravimetric analysis, the thermal stability of polyurethane prepolymer PMI and polyurethane ion gels with different ionic liquid addition amounts can be reflected. And through analysis, it is found that after adding ionic liquid, the maximum thermal decomposition temperature is increased from 324.6 °C to about 409.6 °C. That is, for the polyurethane ion gel proposed by the present invention, its thermal stability is significantly improved.

[0090] (4)According to GB / T 1040.1-2018 "Plastics - Determination of tensile properties - Part 1: General principles", the mechanical properties of various polyurethane prepolymers, polyurethane ion gels with various ionic liquids, and polyurethane ion gels with various ionic liquid dosages are respectively tested, such as Figure 4 It is a mechanical test result diagram of different polyurethane prepolymers. Figure 5 It is a mechanical test result diagram of polyurethane ion gels with different ionic liquid types. Figure 6 It is a mechanical test result diagram of polyurethane ion gels with different dosages of the same ionic liquid.

[0091] For the polyurethane ion gel proposed by the present invention, its crystallization and reversible supramolecular interaction endow the material with high modulus and high strength. At medium and low strains, the original crystal structure is damaged by stress and the modulus decreases; while at high strains, the molecular chains are oriented to promote the rearrangement of crystallization, and a new crystal form is formed, thus showing the performance effect of tensile strengthening. Specifically, its tensile strength can reach 49.22 MPa, the elongation at break is 1721%, the toughness is 424.09 MJ / m 3 , and the Young's modulus is 48.66 MPa.

[0092] (5)Take the polyurethane ion gel prepared in Example 1 for self-healing ability test. That is, select dumbbell-shaped polyurethane ion gel samples, and the sample morphology refers to GB / T 1040.1-2018 "Plastics - Determination of tensile properties - Part 1: General principles". First, cut the sample in the middle, then splice the cut surfaces together, and under the condition of not applying external force, only keep the contact state to make it self-heal. After different self-healing times, conduct tensile tests on it, and the results are as Figure 7 shown. From Figure 7 the measured results shown, after 12 h of self-healing process, the tensile strength of the sample can reach more than 90% of that of the normal uncut sample, indicating that the self-healing ability of this polyurethane ion gel sample is excellent.

[0093] (6) Take the polyurethane ion gel prepared in Example 1 and conduct a tear resistance test. That is, select a dumbbell-shaped polyurethane ion gel sample, cut a 1-mm-wide notch in the 4-mm-wide test area of the sample, stretch the sample and cause it to tear, and then calculate its tear energy Gc according to the following formula:

[0094] ;

[0095] where W is the tensile fracture energy of a specimen without a notch of the same size, c is the width of the notch (1 mm), and λc is the elongation of the specimen at the time of fracture with a notch.

[0096] By calculation, the tear energies of the notched sample and the unnotched sample for comparison can be obtained. The results are as Figure 8 shown. The larger the tear energy value, the better the tear resistance of the ion gel material. It can be seen from Figure 8 that the tear resistance of the notched sample is weaker than that of the unnotched sample, but the tear resistance of the notched sample of this polyurethane ion gel can still reach a good level, and the tear energy can reach 387.02 kJ / m 2 .

[0097] (7) According to GB / T 31064-2014 "Test Method for Puncture Resistance of Rubber or Plastic Coated Fabrics", take the polyurethane ion gel prepared in Example 1 and conduct a puncture strength test. That is, measure the maximum puncture force of the material by the maximum force exerted by the puncture needle pressing down on the material, and divide the maximum puncture force by the material thickness to reflect the puncture strength of the material. The results are as Figure 9 shown. Through the above test process, it can be obtained that the maximum puncture force of this polyurethane ion gel reaches 165.85 N, and its thickness is 1.25 mm, that is, the puncture strength is 184.62 N / mm, indicating that it has good puncture resistance.

[0098] Through the above experiments, it can be shown that the polyurethane ion gel proposed in the present invention relies on the reversible supramolecular actions such as hydrogen bonds and π-π stacking therein. After being subjected to external stress, it can dissipate a large amount of energy, causing the original bonds to be broken and rearranged into new reversible sacrificial bonds, and at the same time promoting the orientation and crystallization of molecular chains. Therefore, under various external damage forms, this polyurethane ion gel shows a high resistance ability, and the energy consumed is also at a high level, that is, it can achieve the performance effect of coexistence of mechanical strength and toughness that is difficult to achieve by existing similar materials.

[0099] The above are only the 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 within the protection scope of the present invention.

Claims

1. A tough polyurethane ion gel based on hard segment enhancement, characterized in that, It includes an ionic liquid and a modified polyurethane modified by a chain extender; The chain extender includes one or more of isophthalic dihydrazide, phthalic dihydrazide, terephthalic dihydrazide, 2,5-dibutoxyterephthalic dihydrazide, 2,5-dipropoxyterephthalic dihydrazide, 2,5-diethoxyterephthalic dihydrazide, 2,5-bis(benzyloxy)terephthalic 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; And 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 enhancement according to claim 1, wherein The preparation method of the modified polyurethane includes the following steps: A1 Take the chain extender, add it to a solvent, and mix evenly to obtain a chain extension reaction solution; A2 Under nitrogen protection, drop the chain extension reaction solution into the polyurethane prepolymer, heat and stir to carry out a chain extension reaction to obtain the modified polyurethane.

3. The tough polyurethane ion gel based on hard segment enhancement according to claim 2, characterized in that, The molecular chain ends of the polyurethane prepolymer contain isocyanate groups.

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 includes the following steps: B1 Take a diol and a diisocyanate in a molar ratio of 1:1.5-3, add them to a solvent, mix evenly, and under nitrogen protection, heat to 20-80 °C to carry out a reaction to obtain a polyurethane prepolymer capped with isocyanate groups.

5. The tough polyurethane ion gel based on hard segment enhancement according to claim 4, wherein 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, wherein The diisocyanate includes one or more of 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-methylenebis(phenyl isocyanate).

7. The tough polyurethane ion gel based on hard segment enhancement according to claim 1, wherein The ionic liquid is 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 bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium trifluoromethanesulfonate; 8. A preparation method of a tough polyurethane ion gel based on hard segment enhancement as described in any one of claims 1 to 7, characterized in that, It includes the following steps: Take the ionic liquid, add it to the modified polyurethane, centrifuge and disperse it, then carry out ultrasonic homogenization treatment, then place it under vacuum degassing, remove the solvent, and heat and dry it to obtain the tough polyurethane ion gel.

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