Thermoplastic polyurethane elastomer, ionic gel and preparation method thereof

Abstract

The invention discloses a thermoplastic polyurethane elastomer and ionic gel and a preparation method thereof. A simple and efficient Michael addition reaction and an ammonolysis reaction of ester are carried out. And the diamino chain extender containing amide and tertiary amine groups is prepared. The thermoplastic polyurethane elastomer material prepared by using the chain extender provides additional hydrogen bond binding sites due to the amide group, so that the thermoplastic polyurethane elastomer material has excellent mechanical properties. In addition, after the side chain of the polyurethane elastomer is subjected to quaternization modification, the obtained quaternary ammonium salt group can be used as a binding site of electrostatic acting force. After the ionic liquid [EMIM] [HSO4] is doped into a polyurethane elastomer, the ionic gel with excellent mechanical properties can be obtained, and the ionic gel can also be used for a strain sensor. The method provides a thought for the preparation of the thermoplastic polyurethane elastomer and the preparation of the ionic gel.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a method for preparing an ion gel based on a thermoplastic polyurethane elastomer. Background Art

[0002] Ion gel is a new type of gel material, which is characterized by the use of ionic liquid as its dispersion medium. This material combines many advantages of ionic liquids, including excellent ionic conductivity, electrochemical stability, low volatility and excellent flame retardant properties. Inheriting the excellent conductive properties of ionic liquids, ion gels show great application potential in the field of electronic devices, such as ion skin and flexible electronic devices. Although ion gels have broad application prospects in the above fields, due to the plasticizing effect of ionic liquids, polymers tend to be more viscous rather than elastic, and their mechanical properties are usually poor, such as low fracture strength, toughness and modulus, which limits their application in a wider range of fields. Existing reported ion gel materials usually do not have high strength and elongation at break, so it is necessary to design ion gel materials with high strength and elongation at break. Summary of the invention

[0003] The object of the present invention is to provide a thermoplastic polyurethane elastomer and an ion gel, including methods for preparing the same, and the application of the ion gel in a strain sensor. The thermoplastic polyurethane elastomer provided by the present invention is based on a brand-new diamino chain extender. The chain extender contains an amide group and a tertiary amine group, the amide group can be used as a hydrogen bond binding site, and the tertiary amine group can be converted into a quaternary ammonium salt group through a quaternization reaction as a binding site for electrostatic forces. The polyurethane elastomer thus obtained has good mechanical properties, self-healing ability and recyclability. By introducing an ionic liquid containing a hydrogen bond binding site through hydrogen bonding forces and electrostatic forces, the obtained ion gel material exhibits excellent mechanical properties, strain sensing performance and high conductivity. The present invention successfully prepares a diamino chain extender through a simple reaction process, and further synthesizes a thermoplastic polyurethane elastomer using the chain extender. Through a simple doping step, an ion gel material with excellent performance can also be prepared.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A diamino chain extender contains both an amide group and a tertiary amine group; the amide group can provide a hydrogen bonding site for a polymer; and the tertiary amine group can be quaternized to form a quaternary ammonium salt.

[0005] The structural formula of the above-mentioned diamino chain extender of the present invention is as follows:

[0006] Among them, n is 1 to 10.

[0007] The invention discloses a preparation method of the diamino chain extender, comprising the following steps: using methyl acrylate and N,N-dimethylethylenediamine as raw materials to prepare a chain extender precursor; and then using the chain extender precursor and ethylenediamine as raw materials to prepare the diamino chain extender.

[0008] As an example, the present invention provides a method for preparing a diamino chain extender, comprising the following steps: (1) Methyl acrylate and N,N-dimethylethylenediamine are reacted at room temperature for 8 to 15 hours to obtain a chain extender precursor; preferably, after the reaction is completed, methanol and methyl acrylate are removed by reduced pressure distillation to obtain a chain extender precursor, the chemical structure of which is as follows: ; (2) reacting a chain extender precursor and ethylenediamine at room temperature to 50° C. for 18 to 30 hours to obtain a diamino chain extender; preferably, after the reaction is completed, methanol and ethylenediamine are removed by vacuum distillation to obtain a diamino chain extender 3,3'-((2-(dimethylamino)ethyl)imino)bis(N-(2-aminoethyl)propionamide) (DEAAP), the chemical structure of which is as follows: .

[0009] The invention discloses a thermoplastic polyurethane elastomer. The raw materials for preparing the thermoplastic polyurethane elastomer include diisocyanate, the above-mentioned diamino chain extender, diol and halogenated alkane.

[0010] In the present invention, the diol is a macromolecular diol, and the halogenated alkane includes a brominated alkane; the diisocyanate includes but is not limited to one or more of isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

[0011] In the present invention, the molar ratio of the diisocyanate to the diol is (5-2):1; the molar ratio of the halogenated alkane to the diamino chain extender is (1.8-2.2):1.

[0012] The present invention provides a method for preparing the above-mentioned thermoplastic polyurethane elastomer, comprising the following steps: Preparation of prepolymer: reacting macromolecular diol and diisocyanate at 75-90°C for 0.5-2 h in the presence of a catalyst to obtain an isocyanate-terminated polyurethane prepolymer; Preparation of polymer: The polyurethane prepolymer terminated with isocyanate of diamino chain extender is continuously reacted at room temperature for 10 to 15 hours to obtain a polymer; Quaternization reaction of thermoplastic polyurethane elastomer: react bromoalkane with polymer at 40°C to 60°C for 10 to 15 hours to obtain thermoplastic polyurethane elastomer; preferably, precipitate and wash the obtained polymer solution in ether, and then dry to obtain thermoplastic polyurethane elastomer material.

[0013] In the above technical solution, the weight average molecular weight of the macromolecular diol is 1000 g mol -1 ~3000 g mol -1 , preferably 2000 g mol -1 ; The molar ratio of the diisocyanate to the macromolecular diol is (4-3):1; the R value, i.e. the molar ratio of isocyanate to (hydroxyl + amine), is 1.2:1.

[0014] In the above technical solution, the molar ratio of the brominated alkane to the diamino chain extender is 2:1.

[0015] In the above technical scheme, the selected macromolecular diol includes, but is not limited to, one or more of polycaprolactone diol, polytetrahydrofuran, polycarbonate diol, and polyethylene glycol.

[0016] In the above technical solution, the selected diisocyanate includes but is not limited to one or more of isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

[0017] Preferably, the macromolecular diol is polycaprolactone diol (PCL).

[0018] Preferably, the diisocyanate is isophorone diisocyanate (IPDI), and its chemical structure is as follows:

[0019] The invention discloses a thermoplastic polyurethane elastomer-based ion gel material, the raw materials for preparing the material include the thermoplastic polyurethane elastomer and an ionic liquid; preferably, the ionic liquid includes 1-ethyl-3-methylimidazole hydrogen sulfate The thermoplastic polyurethane elastomer-based ion gel material is prepared by blending the thermoplastic polyurethane elastomer and the ionic liquid.

[0020] Preferably, the mass ratio of the thermoplastic polyurethane elastomer to the ionic liquid is 1:(0.1-0.4).

[0021] The present invention discloses the use of the above-mentioned diamino chain extender in the preparation of polyurethane materials; or the use of the above-mentioned thermoplastic polyurethane elastomer-based ion gel material in the preparation of functional materials; preferably, the functional materials include ion skins and flexible electronic devices, strain sensors, etc.

[0022] The invention discloses a strain sensor, the raw materials for preparing the strain sensor include the above-mentioned thermoplastic polyurethane elastomer-based ion gel material.

[0023] As an example, the present invention also provides a preparation method of a thermoplastic polyurethane-based ion gel material: the thermoplastic polyurethane elastomer obtained above and the ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate are heated and stirred at 70 to 90°C for 3 to 5 hours to obtain a thermoplastic polyurethane-based ion gel material; further, the obtained ion gel solution is coated on a mold and dried to obtain an ion gel material; for example, the ion gel solution is dried at 80°C for 12 hours, and then vacuum dried at 60°C for 24 hours to obtain the ion gel material.

[0024] The chemical formula of ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate is as follows:

[0025] Due to the adoption of the above technical solution, the present invention has the following advantages: The present invention successfully prepares a novel thermoplastic polyurethane elastomer by introducing an amide group as a hydrogen bonding site into a thermoplastic polyurethane elastomer and introducing a quaternary ammonium salt group as a bonding site for electrostatic forces on the side chain. Furthermore, an ion gel with excellent mechanical properties is prepared by doping with an ionic liquid. In the synthesis of the diamine chain extender, a simple and efficient Michael addition reaction and an ester aminolysis reaction are selected. These two reactions have the advantages of high atomic utilization and fast reaction rate, and are relatively simple to purify. The prepared thermoplastic polyurethane elastomer material exhibits good mechanical properties, self-healing properties and recyclability due to the hydrogen bonding forces between the amide groups. The ion gel material prepared by the thermoplastic polyurethane elastomer also exhibits good mechanical properties, mainly manifested in high tensile strength, excellent elongation at break and excellent toughness. In addition, the ion gel material has also successfully realized the application of strain sensing. The present invention provides a new idea for preparing thermoplastic polyurethane elastomers and high-toughness ion gels. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the appearance of the ion gel prepared in Example 4 of the present invention.

[0027] Figure 2 The hydrogen nuclear magnetic resonance spectrum of the diamino chain extender DEAAP prepared in Example 2 of the present invention ( 1 1H NMR) schematic.

[0028] Figure 3 Schematic diagram of electrospray ionization mass spectrometry (ESI-MS) of the diamino chain extender DEAAP prepared in Example 2 of the present invention.

[0029] Figure 4 This is a schematic diagram of the Fourier transform infrared spectrum (FT-IR) of the diamino chain extender DEAAP prepared in Example 2 of the present invention.

[0030] Figure 5 Thermoplastic polyurethane elastomer prepared in Example 4 of the present invention (a) before quaternization modification (b) after quaternization modification 1 Schematic diagram of H NMR.

[0031] Figure 6 This is a schematic diagram of high-resolution X-ray electron spectroscopy (XPS) of the thermoplastic polyurethane elastomer prepared in Example 4 of the present invention.

[0032] Figure 7 FT-IR schematic diagram of IPDI and PCL prepared in Example 2 of the present invention and the thermoplastic polyurethane elastomer prepared in Example 8.

[0033] Figure 8 This is a schematic diagram of FT-IR of the thermoplastic polyurethane elastomer prepared in Example 4 of the present invention.

[0034] Fig. 9 This is a schematic diagram of X-ray diffraction (XRD) of the thermoplastic polyurethane elastomer prepared in Example 4 of the present invention.

[0035] Fig.10 These are stress-strain curves of the thermoplastic polyurethane elastomers prepared in Examples 3 to 5 of the present invention.

[0036] Fig.11 This is the stress-strain curve of the fracture energy test of the thermoplastic polyurethane elastomer prepared in Example 4 of the present invention.

[0037] Fig.12 The stress-strain curves of the thermoplastic polyurethane elastomer prepared in Example 4 of the present invention under cyclic stretching at different strains.

[0038] Fig.13 This is the stress-strain curve of the thermoplastic polyurethane elastomer prepared in Example 4 of the present invention after three cycles of recycling and uniaxial stretching.

[0039] Fig.14 The stress-strain curves of the thermoplastic polyurethane elastomer prepared in Example 4 of the present invention under uniaxial tension at different repair times.

[0040] Fig.15 The ionic gel prepared by [EMIM] [HSO4] and Example 8 of the present invention is 1 Schematic diagram of H NMR.

[0041] Fig.16FT-IR schematic diagram of [EMIM][HSO4] of the present invention, the thermoplastic polyurethane elastomer prepared in Example 4, and the ion gel prepared in Example 8.

[0042] Fig.17 Schematic diagram of ultraviolet spectra (Uv-vis) of the thermoplastic polyurethane elastomer prepared in Example 4 and the ion gel prepared in Example 8 of the present invention.

[0043] Fig.18 The uniaxial tensile stress-strain curves of the ion gels prepared in Examples 7 to 9 of the present invention.

[0044] Fig.19 The stress-strain curves of the ion gel prepared in Example 8 of the present invention under cyclic stretching at different strains.

[0045] Fig. 20 (a) Schematic diagram of electrochemical impedance spectroscopy (EIS) and (b) ionic conductivity bar graph of the ion gel prepared in Examples 7 to 9 of the present invention.

[0046] Fig.21 Schematic diagram of the sensitivity factor (GF) of the ion gel prepared in Example 8 of the present invention.

[0047] Fig. 22 Schematic diagram of the relative resistance change of the ion gel prepared in Example 8 of the present invention under (a) 5 different strains and (b) 100 cyclic stretching times of 50% strain.

[0048] Fig.23 Schematic diagram of the sensing performance of the ion gel prepared in Example 8 of the present invention.

[0049] Fig.24 The mechanical properties of the ion gel prepared in Example 8 of the present invention are compared with those of the same type of polyurethane-based ion gel. DETAILED DESCRIPTION

[0050] The present invention develops a new diamino chain extender DEAAP. The polyurethane elastomer prepared using the chain extender contains an amide group and a tertiary amine group. The polyurethane elastomer containing a quaternary ammonium salt on the side chain can be obtained by a one-step quaternization reaction. The polyurethane elastomer exhibits excellent mechanical properties, including high tensile strength, excellent elongation at break and good toughness. The material exhibits high fracture energy in terms of damage resistance. In addition, an ion gel material is prepared using the polyurethane elastomer as a substrate. In this process, the amide group serves as a hydrogen bond binding site, while the quaternary ammonium salt group serves as a binding site for electrostatic forces. By adding an ionic liquid [EMIM][HSO4], the prepared ion gel exhibits high tensile strength and elongation at break, providing an innovative solution for the preparation of ion gel materials.

[0051] In the present invention, the thermoplastic polyurethane elastomer is prepared from the following raw materials: Chain extender: the above diamino chain extender; Diisocyanate: one or more of isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate; Macromolecular diol: one or more of polycaprolactone diol, polytetrahydrofuran, polycarbonate diol, polyethylene glycol; Bromoalkane: one of 1-bromohexane, 1-bromopropane, and 1-bromododecane.

[0052] As is common knowledge, thermoplastic polyurethane elastomers are prepared in the presence of solvents and catalysts (such as dibutyltin dilaurate).

[0053] In the thermoplastic polyurethane elastomer of the present invention, the polymer main chain contains amide groups as hydrogen bond binding sites; and the side chain contains quaternary ammonium salt groups as electrostatic force binding sites.

[0054] In the thermoplastic polyurethane elastomer-based ion gel material of the present invention, the ionic liquid 1-ethyl-3-methylimidazole hydrogen sulfate is combined with the polymer through hydrogen bonding force and electrostatic force.

[0055] As an example, the present invention provides a method for preparing a diamino chain extender, comprising the following steps: (1) Methyl acrylate is dissolved in methanol solvent, and then a methanol solution of N,N-dimethylethylenediamine is added dropwise at room temperature. After the addition is completed, the reaction is continued at room temperature for 12 h. After the reaction is completed, methanol and methyl acrylate are removed by vacuum distillation to obtain a chain extender precursor, the chemical structure of which is as follows:

[0056] (2) The precursor of the chain extender is dissolved in a methanol solvent, and then the methanol solution of ethylenediamine is slowly added dropwise at 40°C. After the addition is completed, the temperature is maintained at 40°C to allow the reaction to proceed for 24 hours. After the reaction is completed, methanol and ethylenediamine are removed by vacuum distillation to obtain a diamine-based chain extender 3,3'-((2-(dimethylamino)ethyl)imino)bis(N-(2-aminoethyl)propionamide) (DEAAP), the chemical structure of which is as follows:

[0057] The present invention provides a method for preparing a thermoplastic polyurethane elastomer, comprising the following steps: Preparation of prepolymer: The macromolecular diol is stirred under vacuum at 120°C to remove moisture, and then a solution of diisocyanate and dibutyltin dilaurate in N,N-dimethylformamide (DMF) is added, and the reaction is carried out at 85°C for 1 hour. The isocyanate-terminated polyurethane prepolymer can be obtained; Preparation of thermoplastic polyurethane elastomer: Add the DMF solution of diamino chain extender to the prepolymer solution at room temperature and continue the reaction at room temperature for 12 h; Quaternization reaction of thermoplastic polyurethane elastomer: add bromoalkane to the obtained polymer solution and react at 50° C. for 12 hours. Then, the obtained polymer solution is precipitated and washed in ether, and then dried to obtain a thermoplastic polyurethane elastomer material.

[0058] In order to better understand the content of the present invention, the content of the present invention is further described below in conjunction with a specific implementation method, but the protection content of the present invention is not limited to the following embodiments; the reagents used in the present invention are existing products, and the specific preparation operations and performance tests are conventional techniques, such as the dripping of raw materials is a conventional operation in the art.

[0059] Example 1 Methyl acrylate (8.610 g) was dissolved in 10 ml methanol in a round-bottom flask; at the same time, N,N-dimethylethylenediamine (3.472 g) was dissolved in 20 ml methanol in a constant pressure funnel. The methanol solution of N,N-dimethylethylenediamine was added dropwise at room temperature; after the addition was completed, the reaction was allowed to continue at room temperature for 24 h. After the reaction was completed, methanol and methyl acrylate were removed by vacuum distillation (60°C), and heating was continued until no bubbles were generated, at which time the chain extender precursor was obtained.

[0060] Example 2 Dissolve anhydrous ethylenediamine (19.232 g) in 20 ml methanol in a round-bottom flask; at the same time, dissolve 10.406 g of chain extender precursor in 30 ml methanol and place in a constant pressure funnel. Add the methanol solution of chain extender precursor dropwise at room temperature; after the addition is complete, allow the reaction to continue at 40°C for 24 h. After the reaction is completed, remove methanol and ethylenediamine by vacuum distillation (80°C), and continue heating until no bubbles are generated, at which point the diamino chain extender DEAAP is obtained.

[0061] Example 3 Prepolymerization: PCL (8.0 g, 2000 g mol -1) was placed in a three-necked flask, heated at 120 °C, and stirred under vacuum for 1 h to remove moisture. Next, the reaction temperature was set to 85 °C. At the same time, IPDI (2.7 g) and two drops of DBTDL were dissolved in 30 ml of dry DMF, and then the solution was added to the three-necked flask. The reaction was continued at 85 °C for 1 hour, during which nitrogen was continuously introduced; Chain extension reaction: After the prepolymerization reaction, the temperature was set to 25°C, DEAAP (1.9 g) was dissolved in 100 ml of dry DMF and then added to a three-necked flask. The reaction was carried out at 25°C for 12 h, and nitrogen was continuously injected during the reaction; Quaternization reaction: Raise the temperature to 50°C, add 1-bromohexane (2.0 g), and keep the reaction for 12 hours. After the reaction is completed, drop the sample into ether for precipitation, and then wash it 3 times. After drying, a thermoplastic polyurethane elastomer product can be obtained; Molding: Thermoplastic polyurethane elastomer (0.5 g) sample was dissolved in 1.5 ml DMF, and then the polymer solution was coated in a PTFE mold with a mold size of 4 cm × 2 cm × 0.1 cm (length × width × thickness). The thermoplastic polyurethane elastomer film was obtained by drying at 80 °C for 12 h and then vacuum drying at 60 °C for 24 h.

[0062] Embodiment 4-5 The molar ratio of IPDI to PCL was changed, and the R value was kept at 1.2. The remaining steps and conditions were the same as those in Example 3, and different thermoplastic polyurethane elastomers were obtained. The numbers, components and contents of all prepared thermoplastic polyurethane elastomers are shown in Table 1.

[0063] Table 1 Raw material amounts of different polyurethane elastomer examples

[0064] After the thermoplastic polyurethane elastomer evaporates and forms a film, Figure 1 As shown, it is APU 3.5 Physical picture of thermoplastic polyurethane elastomer.

[0065] Example 6 0.5 g of thermoplastic polyurethane elastomer was dissolved in 1.5 ml of DMF, and 0.05 g of ionic liquid [EMIM][HSO4] was added. The mixture was heated and stirred at 80°C for 4 h, and then the solution was coated on a PTFE mold with a size of 4 cm × 2 cm × 0.1 cm (length × width × thickness). The ion gel membrane was obtained by drying at 80°C for 12 h and vacuum drying at 60°C for 24 h.

[0066] Embodiments 7 to 9 The amount of ionic liquid added was changed, and the remaining steps and conditions were the same as those in Example 6 to obtain different ionic gels. The numbers, components and contents of all prepared ionic gels are shown in Table 2.

[0067] Table 2 Raw material dosage of different ion gel examples

[0068] After the thermoplastic polyurethane elastomer evaporates and forms a film, Figure 1 As shown, it is APU 3.5 / 30 Actual picture of ion gel.

[0069] Example 10 The structure of the diamino chain extender DEAAP was characterized by the following method: like Figure 2 As shown, DEAAP was characterized by H NMR spectrum, and all characteristic peaks of DEAAP were assigned and integrated, which proved that it was successfully synthesized. Figure 3 As shown in Figure 1, DEAAP was subjected to electrospray ionization mass spectrometry analysis. The analysis results showed that the mass-to-charge ratio of the most abundant peak was 317.27, which was exactly one proton different from the predicted molecular weight of 316.26, which also proved the successful preparation of DEAAP. Figure 4 As shown, DEAAP was analyzed by Fourier transform infrared spectroscopy at 3284 cm -1 The NH stretching vibration peak of DEAAP can be found at 1639 cm -1 The peak belongs to the stretching vibration absorption peak of C=O in amide, 1546 cm -1 The absorption peak at 40° belongs to the characteristic spectrum of amide II band of CN and NH. The above analysis proves the successful preparation of chain extender DEAAP.

[0070] Embodiment 11 Thermoplastic polyurethane elastomer (APU 3.5 The specific method is as follows: like Figure 5 As shown, the thermoplastic polyurethane elastomer was analyzed by nuclear magnetic resonance hydrogen spectrum. 3.5 In addition, by comparing with the unquaternized sample, it can be found that the chemical shift of the methyl H connected to the N atom on the quaternary ammonium salt group has changed, which can prove the successful modification of the quaternary ammonium salt. Figure 6 As shown, the APU was analyzed using high-resolution X-ray electron spectroscopy. 3.5 The quaternization degree Q was calculated to be 23.6%. Figure 7 As shown, the raw materials and APU were characterized by Fourier transform infrared spectroscopy.3.5 By comparing the products, it can be found that the product has a wavelength of 2250 cm -1 The absence of the characteristic peak of isocyanate at can indicate the successful preparation of the material. Figure 8 As shown, at 3300 cm -1 The characteristic peak of NH stretching vibration of amide is 1552 cm -1 The characteristic peak of NH bending vibration is at 1730 cm -1 and 1645 cm -1 The above analysis shows that thermoplastic polyurethane elastomer APU 3.5 On the other hand, Fig. 9 As shown, X-ray diffraction was used to characterize APU 3.5 When the sample was analyzed, no crystallization peak of PCL was observed, but a representative amorphous diffraction peak appeared at about 20°, indicating that the chain extender DEAAP inhibited the crystallization tendency of PCL.

[0071] Example 12 The mechanical properties of thermoplastic polyurethane elastomer are characterized by the following methods: Take the above thermoplastic polyurethane elastomer, place both ends of the material on the clamp of the tensile machine, and -1 The stretching speed is 2000mm and the stretching properties are observed. Fig.10 As shown in the figure, with the increase of hard segment content, the tensile strength of thermoplastic polyurethane elastomer increases from 12.6 MPa to 43.1 MPa. In this system design, the chain extender introduces additional amide groups, which can provide a large number of hydrogen bond donors and acceptors together with urethane bonds and urea bonds. The hard segments are combined due to strong intermolecular hydrogen bonds. During the stretching process, these hydrogen bonds will act as sacrificial bonds and dissipate energy through breaking and reorganization. 3.5 The best toughness was therefore further analyzed. In order to evaluate the tolerance of the elastomer to defects and damage, notched tensile tests were performed. Fig.11 As shown, the Greensmith method is used for calculation, and the results show that APU 3.5 Even with a 1 mm notch, the fracture energy of the elastomer is as high as 110.5 kJ m -2 To characterize the APU 3.5 The fatigue resistance of the samples was further tested by cyclic tensile test. -1 The specimens were subjected to cyclic tensile tests at different strains. Fig.12As shown in Figure 3, the hysteresis loop gradually increases with the increase of tensile strain, which indicates that the higher the strain, the greater the energy dissipation. This indicates that during the stretching process, hydrogen bonds are broken and sacrificed to dissipate energy. The mechanical parameters of thermoplastic polyurethane elastomers with different hard segment ratios are shown in Table 3.

[0072] Table 3 Comparison of uniaxial tensile data of thermoplastic polyurethane elastomers

[0073] Thermoplastic polyurethane elastomer (APU 3.5 For example, the recyclability test The crosslinking of the thermoplastic polyurethane elastomer sample is achieved through hydrogen bonding rather than covalent bonding, which means that the sample still has a linear structure and can be dissolved or melted. Therefore, the elastomer sample was recycled. 3.5 After being chopped up, it was dissolved in ethanol and then re-coated on a polytetrafluoroethylene mold to prepare a transparent film by solvent evaporation. After each recycling, a uniaxial tensile test was performed again to obtain a stress-strain curve. Fig.13 As shown in Figure 2, even after three cycles of recycling, the stress recovery rate can still reach 80%. 3.5 It shows good recycling ability.

[0074] Thermoplastic polyurethane elastomer (APU 3.5 For example, self-healing performance test Due to the dynamic effect of hydrogen bonds in the hard domain, thermoplastic polyurethane elastomers have the ability to self-heal. However, hydrogen bonds can only achieve the dynamic process of breaking and reorganization at high temperatures, so higher temperatures are required to achieve the self-healing process of the elastomer. First, the spline is cut evenly in the center, and then the cuts are aligned. Then, it is heated at 80°C for different times, and a uniaxial tensile test is performed to obtain the corresponding stress-strain curve. Fig.14 As shown in the figure, after the sample was heated at 80℃ for 36 h, its stress-strain curve has basically returned to its initial state, indicating that the sample has completed the self-healing process. When the strain reaches 1000%, it still does not break, so APU 3.5 The samples showed excellent self-healing ability.

[0075] Example 13 Thermoplastic polyurethane-based ion gel (APU 3.5 / 30 sample as an example) for structural characterization, the specific method is as follows: Using nuclear magnetic resonance hydrogen spectroscopy to compare ionic liquid [EMIM][HSO4] with ion gel APU 3.5 / 30 compared and found that [EMIM]+ The active hydrogen on the surface of the polymer matrix was significantly shifted, which was due to the formation of hydrogen bonding forces between the carbonyl groups of the polymer matrix, proving that there was a hydrogen bonding force between the cations of the ionic liquid [EMIM][HSO4] and the polymer. The ionic liquid and ion gel were further characterized by FT-IR. Fig.16 As shown, 3152 cm -1 The CH stretching vibration on the imidazole ring shifts to a lower wavenumber of 3151 cm -1 , which also proves that there is a hydrogen bond between the active hydrogen on the imidazole ring and the polymer. -1 The stretching vibration peak of S=O at 1653 cm-1 shifts to a higher wave number. -1 , indicating that S=O forms a hydrogen bond with the polymer as a hydrogen bond acceptor. Finally, the -1 and 1646 cm -1 The C=O stretching vibration peaks of the ester bond and amide bond at the -1 and 1653 cm -1 This indicates that there is hydrogen bonding between the carbonyl group on the polymer and the ionic liquid as a hydrogen bond acceptor. -1 The peak at [EMIM][HSO4] belongs to the stretching vibration peak of SO, but in APU 3.5 / 30, the peak shifts to a higher wave number of 857 cm -1 , which indicates that [HSO4] - Electrostatic interaction occurs with the quaternary ammonium salt on the polymer molecule. The above characterization proves that the ionic liquid [EMIM][HSO4] and the polymer APU 3.5 There are hydrogen bonds and electrostatic interactions between them. Fig.17 As shown, by characterizing the transparency of the ion gel, it can be seen that its transparency in the visible light range is not much different from that of the thermoplastic polyurethane elastomer, which indicates that the ionic liquid has good compatibility with the polymer.

[0076] Embodiment 14 The mechanical properties of thermoplastic polyurethane-based ion gel were characterized by the following method: Take the above ion gel, place both ends of the material on the clamp of the tensile machine, and test at a speed of 50 mm min. -1 The stretching speed is 2000mm and the stretching properties are observed. Fig.18 As shown in Figure 2, with the increase of the content of ionic liquid [EMIM][HSO4], the strength of the ion gel showed a trend of gradual decrease, and the toughness also showed a trend of gradual decrease. From the addition amount of 0 to 40 wt%, the toughness increased from 187.1 MJ m-3 Gradually decreased to 68.5 MJ m -3 This is because the addition of ionic liquids will destroy the original hard domain crosslinking due to hydrogen bonding with the polymer main chain. In addition, the addition of ionic liquids will also have a plasticizing effect on the polymer, further reducing its strength and toughness. Therefore, the fluidity between polymer chains is enhanced, which is manifested as a gradual increase in elongation at break. However, when the ionic liquid is increased to 40 wt%, it cannot be increased further. This is because when the content of ionic liquid reaches a certain level, the material's ability to dissipate energy will also decrease. When the amount of ionic liquid added reaches 30 wt%, its toughness can reach 78.6 MJ m -3 In order to gain a deeper understanding of the mechanical properties of the ion gel, cyclic tensile measurements at different cyclic strains were performed. 3.5 / 30 as an example, Fig.19 As shown in the figure, at the first strain of 100%, since the dynamic cross-linking network remains intact, all samples only undergo elastic deformation, and the ion gel can be restored to its initial state driven by entropy. As the strain gradually increases, the hysteresis area of ​​these curves increases significantly. The reason is that large deformation destroys dynamic interactions such as hydrogen bonds and electrostatic forces, and there is not enough time to rebuild these dynamic bonds. It can also be seen from the figure that the hysteresis area is proportional to the strain, indicating that more energy is dissipated at higher strains, so damage to the ion gel material can be avoided. The mechanical parameters of ion gels with different ionic liquid contents are shown in Table 4.

[0077] Table 4 Comparison of uniaxial tensile data of thermoplastic polyurethane elastomers

[0078] Embodiment 15 The electrical properties and sensing characteristics of thermoplastic polyurethane-based ion gels were characterized as follows: Electrochemical impedance spectroscopy was performed using an electrochemical workstation (CS350, corrtest) by assembling an ion gel membrane and two symmetrical stainless steel electrodes (Φ = 14 mm) in a test frequency range of 1 Hz to 100 kHz. Fig. 20 As shown in the electrochemical impedance spectra of ion gels at different ionic liquid contents, the bulk impedance shows a trend of gradually decreasing with the increase of ionic liquid content. On the other hand, when the amount of ionic liquid added increases from 10 wt% to 40 wt%, the conductivity increases from 1.15×10 -3 S m -1 Increased to 47.29×10 -3 S m -1 Considering the dual effects of mechanical and electrical properties, APU will be used in the future. 3.5 / 30 for sensor characterization.

[0079] Thermoplastic polyurethane-based ion gel (APU 3.5 / 30 samples as an example) to test the sensor performance The sensing performance of the ion gel was tested using an LCR digital bridge tester (TH2830, Changzhou Tonghui Electronics). The ion gel of the present invention was taken, and copper wires were connected to its two ends respectively. The other end of the copper wire was connected to the test instrument. The ion gel was assembled into a wearable sensor to detect the change in resistance value. In order to characterize the sensitivity of the sensor device, Fig.21 As shown in the figure, the change value of the resistance signal is monitored in the strain range of 0-100%, and a linear fit is performed. The calculated sensitivity coefficient is 0.64, which shows that the strain sensor has good sensing sensitivity and is suitable for signal monitoring and transmission. Under different strain conditions, the strain sensor is subjected to cyclic tensile tests and its resistance signal is detected. Fig. 22 As shown in Figure a, with the increase of strain, the resistance signal shows a slight decay phenomenon, which is consistent with the hysteresis phenomenon in the cyclic tensile test results in the previous article, indicating that the fatigue resistance of the material will affect the application of strain sensors to a certain extent. At a strain of 50%, the material was subjected to more than 100 cyclic tensile tests and its resistance signal was monitored. Fig. 22 As shown in Figure b, the signal value decays in the early stage of cyclic stretching. However, as the number of stretching increases, the resistance signal change value generally shows a stable trend, indicating the stability of signal transmission. Fig.23 As shown, the strain sensor was fixed to the wrist, finger, elbow and knee joints of the human body, and all of them transmitted signals with high recognition. This shows that the ion gel can monitor the motion signals of the human body in real time in the application field of strain sensors. The above shows that the ion gel material invented in this article has good stability and sensitivity as a strain sensor.

[0080] The present invention has developed a new diamino chain extender DEAAP. The polyurethane elastomer prepared using this chain extender contains amide groups and tertiary amine groups. The polyurethane elastomer containing quaternary ammonium salts on the side chain can be obtained through a one-step quaternization reaction. This polyurethane elastomer exhibits excellent mechanical properties, including high tensile strength, excellent elongation at break and good toughness. The material exhibits high fracture energy in terms of damage resistance. Fig.24 (See references below) as shown in the figure, APU 3.5The / 30 sample showed higher values ​​in strength and elongation at break than other polyurethane-based ion gel materials reported in the literature. Further, ion gel materials were prepared using this polyurethane elastomer as a substrate. In this process, the amide groups acted as hydrogen bonding sites, while the quaternary ammonium salt groups acted as electrostatic bonding sites. By adding ionic liquid [EMIM][HSO4], the prepared ion gel showed high tensile strength and elongation at break, providing an innovative solution for the preparation of ion gel materials.

[0081] [1] T. L. Chen, G. Ye, H. W. Wu, S. Y. Qi, G. R. Ma, Y. Zhang, Y. Zhao, J. Zhu, X. D. Gu, N. Liu Adv. Funct. Mater. 2022, 32 , 2206424. [2] BC Zhao, JQ Yan, F. Long, W. Qiu, GQ Meng, ZC Zeng, H. Huang, H. Wang, NB Lin, XY Liu Adv. Sci. 2023, 10 , e2300857. [3] X. Wen, JH Xu, HB Wang, ZL Du, S. Wang, X. Cheng Polym. Eng. Sci. 2022, 62 , 3132-3143. [4] JH Xu, H. Wang, X. Wen, S. Wang, HB Wang ACS Appl. Mater. Interfaces 2022, 14 , 54203-54214. [5] JH Xu, H. Wang, XS Du, X. Cheng, ZL Du, HB Wang ACS Appl. Mater. Interfaces 2021, 13 , 20427-20434. [6] YL Fang, HL Cheng, H. He, S. Wang, JM Li, SZ Yue, L. Zhang, ZL Du, JY Ouyang Adv. Funct. Mater. 2020, 30 , 2004699. [7] YL Zhao, HL Cheng, YX Li, JC Rao, SZ Yue, QJ Le, Q. Qian, Z. Liu, JY Ouyang J. Mater. Chem. A 2022, 10 , 4222-4229. [8] YP Li, Y. Jin, WH Zeng, HY Jin, X. Shang, R. Zhou ACS Appl. Mater. Interfaces 2023, 15 , 35469-35482. [9] FY Ou, T. Xie, XZ Li, ZC Zhang, C. Ning, L. Tuo, WY Pan, CS Wang, XY Duan, QH Liang, W. Gao, ZQ Li, SL Zhao Mater. Horiz. 2024, 11 , 2191-2205.

[10] HB Wang, JH Xu, KJ Li, Y. Dong, ZL Du, S. Wang J. Mater. Chem. B 2022, 10 , 1301-1307. The above examples are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above examples. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention are still regarded as the protection scope of the solution of the present invention.

Claims

1. A diamino chain extender, characterized in that The diamino chain extender contains an amide group and a tertiary amine group.

2. The diamino chain extender according to claim 1, characterized in that: The general structural formula of the diamino chain extender is as follows: ； Among them, n is 1 to 10.

3. The method for preparing the diamino chain extender according to claim 1, characterized in that: A chain extender precursor is prepared by taking methyl acrylate and N,N-dimethylethylenediamine as raw materials; and then a diamino chain extender is prepared by taking the chain extender precursor and ethylenediamine as raw materials.

4. A thermoplastic polyurethane elastomer, characterized in that: The raw materials for preparing the thermoplastic polyurethane elastomer include diisocyanate, the diamino chain extender according to claim 1, diol, and halogenated alkane.

5. The thermoplastic polyurethane elastomer according to claim 4, characterized in that: The diol is a macromolecular diol, and the halogenated alkane includes a brominated alkane; the diisocyanate includes but is not limited to one or more of isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.

6. The thermoplastic polyurethane elastomer according to claim 4, characterized in that: The molar ratio of the diisocyanate to the diol is (5-2):1; the molar ratio of the halogenated alkane to the diamino chain extender is (1.8-2.2):

1.

7. A thermoplastic polyurethane elastomer-based ion gel material, characterized in that: The raw materials for preparing the thermoplastic polyurethane elastomer-based ion gel material include the thermoplastic polyurethane elastomer described in claim 4 and an ionic liquid.

8. The thermoplastic polyurethane elastomer-based ion gel material according to claim 7, characterized in that: The mass ratio of thermoplastic polyurethane elastomer to ionic liquid is 1:(0.1-0.4).

9. Use of the diamino chain extender according to claim 1 in the preparation of polyurethane materials; or use of the thermoplastic polyurethane elastomer-based ion gel material according to claim 7 in the preparation of functional materials.

10. A strain sensor, wherein the raw materials for preparing the strain sensor include the thermoplastic polyurethane elastomer-based ion gel material according to claim 7.

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