Polyurethane urea elastomer, preparation method and application thereof, and ionic conductive elastomer

Abstract

The invention provides a polyurethane urea elastomer, a preparation method and application thereof, and an ionic conductive elastomer, and belongs to the field of polymer materials. A soft-segment substance, isocyanate and a catalyst are subjected to a prepolymerization reaction to obtain a prepolymer, the prepolymer, a chain extender and an organic solvent are subjected to a chain extension reaction to obtain the PUU elastomer, the soft-segment substance contains hydroxyl, and the chain extender contains phenyl and a bishydrazide substituent. According to the invention, PUU is synthesized by a chain extender simultaneously containing phenyl and a bishydrazide substituent, the phenyl in the PUU can be assembled in situ based on pi-pi interaction to form an aggregate, and the aggregate and multiple hydrogen bonds between amido urea bonds on two sides of the aggregate jointly form a double-lock hard domain which has high binding energy and is cross-linked based on non-covalent interaction in the PUU. The unique structure of PUU improves the mechanical properties, including strength, elasticity and tear resistance, of the material on one hand, and endows the material with a function of repairing mechanical damage on the other hand.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a polyurethane urea elastomer, a preparation method and an application thereof, and an ion conductive elastomer. Background Art

[0002] With the continuous development of intelligent electronic devices, people's demand for conductive elastomer materials with both flexibility and touch sensing functions is increasing day by day. Such materials have broad application potential in various human-computer interaction scenarios, such as smart screens, wearable devices, etc. The core principle is that when the conductive elastomer is subjected to external forces such as stretching or compression, the conductive pathways inside the material will change, resulting in a corresponding change in its resistance value. By monitoring and analyzing this resistance change, the perception of the magnitude or position of the external force can be achieved, and thus functions such as touch and strain sensing can be exerted.

[0003] Existing conductive elastomer materials can be divided into two categories: electronic conductive elastomers and ion conductive elastomers. Electronic conductive elastomers are usually prepared by dispersing electronic conductive media (such as carbon nanotubes, graphene, metal nanoparticles, etc.) in a polymer matrix. Ion conductive elastomers achieve conductivity by introducing freely movable ions or ionic liquids into the polymer matrix. Compared with electronic conductive elastomers, ion conductive elastomers often have better flexibility and lower modulus under large deformations, and their electrical responses are also more sensitive, making them suitable for applications in fields with high sensitivity requirements for tactile or biological signals. However, the polymer matrices (including polyurethane urea PUU) used in related ion conductive materials have problems with poor mechanical properties. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a polyurethane urea elastomer, a preparation method and an application thereof, and an ion conductive elastomer. The polyurethane urea elastomer prepared by the present invention has excellent mechanical properties and excellent reparability.

[0005] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a polyurethane urea elastomer, comprising the following steps:

[0007] Mix a soft segment substance, an isocyanate and a catalyst for prepolymerization reaction to obtain a prepolymer, wherein the soft segment substance contains hydroxyl groups;

[0008] Mix the prepolymer, a chain extender and an organic solvent for chain extension reaction to obtain the polyurethane urea elastomer, wherein the chain extender contains phenyl and bis-acyl hydrazide substituents.

[0009] Preferably, the chain extender comprises an aromatic diacyl hydrazide.

[0010] Preferably, the aromatic dihydrazide includes terephthalic dihydrazide (TDH) and / or isophthalic dihydrazide (IDH).

[0011] Preferably, the mass ratio of the soft segment material to the isocyanate is 5 - 20:1 - 5.

[0012] Preferably, the mass ratio of the soft segment material to the chain extender is 5 - 20:0.5 - 1.5.

[0013] Preferably, the temperature of the chain extension reaction is 20 - 60 °C, and the time is 24 - 48 h.

[0014] The present invention also provides a polyurethaneurea elastomer prepared by the preparation method described in the above technical solution.

[0015] The present invention also provides the application of the polyurethaneurea elastomer described in the above technical solution in the field of ion-conductive elastomers.

[0016] The present invention also provides an ion-conductive elastomer (PUU-ILs), and the raw materials for preparation include the polyurethaneurea elastomer described in the above technical solution and an imidazole-based ionic liquid.

[0017] Preferably, the imidazole-based ionic liquid includes one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), and 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM][PF6]).

[0018] The present invention provides a preparation method of a polyurethaneurea elastomer, including the following steps: mixing a soft segment material, an isocyanate, and a catalyst to carry out a prepolymerization reaction to obtain a prepolymer, wherein the soft segment material contains hydroxyl groups; mixing the prepolymer, a chain extender, and an organic solvent to carry out a chain extension reaction to obtain the polyurethaneurea elastomer, and the chain extender contains phenyl and dihydrazide substituents.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] In the present invention, a chain extender containing both phenyl and bisacylhydrazide substituents is used to synthesize PUU. The phenyl groups in PUU can in-situ assemble into aggregates based on π-π interactions. Together with the multiple hydrogen bonds between the amide ureas on both sides of these aggregates, a "double-lock" hard domain with high binding energy and cross-linked by non-covalent interactions is formed in PUU. On the one hand, the unique structure of PUU improves the mechanical properties of the material, including strength, elasticity and tear resistance. On the other hand, it endows the material with the function of repairing mechanical damage. Moreover, the molecular chains of PUU cross-linked by the hard domain require more energy to slide when subjected to external tensile force. The breakage and recombination of multiple hydrogen bonds more effectively dissipate the energy at the wound, and the stress at the wound is transferred to the entire polymer network, resulting in cracks preferentially expanding gradually along the longitudinal direction, so that the material exhibits excellent tear resistance.

[0021] The data of the examples show that the PUU of the present invention has higher mechanical properties (including tensile strength, compressive strength, toughness, Young's modulus, fracture energy, puncture resistance, impact resistance) and transparency, and PUU-TDH has the best comprehensive performance. The tensile strength of PUU-TDH is 93.1±4.2 MPa, the elongation at break is 997.6±75.6%, and the toughness is 376.6±20.3 MJ·m -3 , the Young's modulus is 16.8±1.5 MPa, the transmittance at 550 nm is 91.1%, the tensile strength after repair is 88.8±2.6 MPa, and the repair efficiency is 95.4±2.8%.

[0022] The present invention also provides an ion-conductive elastomer. The raw materials for preparation include the polyurethane urea elastomer described in the above technical solution and an imidazole-based ionic liquid. The soft segment molecules in the polyurethane urea elastomer have good compatibility with the imidazole-based ionic liquid, ensuring the uniform distribution and high transparency of the conductive medium in the polyurethane urea elastomer, and further endowing the material with excellent electrochemical properties. Moreover, the imidazole-based ionic liquid conducts ions rather than electrons, which is consistent with the signal conduction mechanism in the living body, and is more likely to have good cell compatibility and tissue compatibility. In addition, the movement of the molecular chains in the polyurethane urea elastomer and the dissociation and reconstruction of the non-covalent interactions between the polymer chains endow the ion-conductive elastomer with excellent self-healing properties.

[0023] The data of the examples show that the ion-conductive elastomer provided by the present invention exhibits excellent self-healing properties. The material can be basically completely repaired after 48 h at 60 °C without any solvent assistance, and the repair efficiency is as high as 98%, significantly improving the service life and reliability of the material. The Young's modulus of the material ranges from 12.5 to 20 MPa, and its excellent mechanical properties ensure stability and safety under high load conditions. In addition, the ion-conductive elastomer also has a relatively high fracture energy, ranging from 120 to 150 kJ / m 2, indicating that it can effectively dissipate energy when subjected to external force damage, delay the expansion of the wound along the crack, thus significantly improving its tear resistance, and also has excellent electrical conductivity, with the conductivity range between 6×10 -5 ~2×10 -4 S / cm, which can easily light up a light bulb. At the same time, it also has excellent antibacterial and biocompatibility, can be in direct contact with human skin. Combining with the high elasticity of the material, it can be used as a sensor to sense external force changes and detect human movement, with sensitive and stable feedback signals. It can also be used as an ionic skin to sense pressure, temperature and humidity, and realize the detection of biological signals such as heart rate and electromyogram signals. The ionic conductive elastomer of the present invention has important application prospects in high-end and multi-functional fields such as biomedicine and flexible electronic devices, and is suitable for the functional requirements of various flexible electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the molecular formula of PUU-TDH;

[0025] Figure 2 is the structural schematic diagram of PUU-TDH;

[0026] Figure 3 is the process schematic diagram for preparing the ionic conductive elastomer in the embodiment of the present invention;

[0027] Figure 4 is the tensile stress-strain curve of the polyurethane urea elastomers prepared in the examples and comparative examples;

[0028] Figure 5 is the tear resistance stress-strain curve of PUU-TDH;

[0029] Figure 6 is the puncture resistance force-displacement curve of the polyurethane urea elastomers prepared in the examples and comparative examples;

[0030] Figure 7 is the compression stress-strain curve of the polyurethane urea elastomers prepared in the examples and comparative examples;

[0031] Figure 8 is the impact resistance force-displacement curve of the polyurethane urea elastomers prepared in the examples and comparative examples;

[0032] Figure 9 is the self-healing stress-strain curve of the polyurethane urea elastomers prepared in the examples and comparative examples;

[0033] Figure 10 is the stress-strain curve of multiple reshaping of PUU-TDH;

[0034] Figure 11 is the dynamic thermomechanical curve of the elastomer of PUU-TDH;

[0035] Figure 12 is the rheological curve of PUU-TDH elastomer varying with temperature;

[0036] Figure 13 is the thermogravimetric curve of PUU-TDH elastomer;

[0037] Figure 14 is the GPC spectrogram of PUU-TDH;

[0038] Figure 15 is the X-ray diffraction spectrogram of PUU-TDH;

[0039] Figure 16 is the Fourier transform infrared spectrogram of PUU-TDH-ILs;

[0040] Figure 17 is the ultraviolet-visible transmission spectrum of PUU-TDH-ILs, where the inset is the digital photograph of the PUU-TDH-ILs ion conductive elastomer;

[0041] Figure 18 is the stress-strain curve of PUU-TDH-ILs;

[0042] Figure 19 are the photograph, dimensions and force-displacement curve of PUU-TDH-ILs in the trouser tearing test;

[0043] Figure 20 are the tensile test results of PUU-TDH-ILs in continuous loading-unloading cycles;

[0044] Figure 21 are the stress-strain curves of the original and repaired PUU-TDH-ILs at different repair times at 60 °C;

[0045] Figure 22 are the stress-strain curves of PUU-TDH-ILs after multiple reshaping;

[0046] Figure 23 are the results of the biocompatibility test of the capacitive sensor packaging material;

[0047] Figure 24 Relative capacitance change of the PUU-TDH-ILs sensor fixed on the finger at different bending angles;

[0048] Figure 25 is the relative capacitance change of the sensor with PUU-TDH-ILs under different pressures;

[0049] Figure 26 is the relative capacitance change of the sensor with PUU-TDH-ILs under small strains (3 - 20%);

[0050] Figure 27 It is a schematic diagram showing the states of i in the pre-cut figure and ii in the post-cut figure of a capacitive sensor with PUU-TDH-ILs, and the function of the ionic conductor as the conductor of the LED bulb to light up the small light bulb in iii in the post-healing figure;

[0051] Figure 28 It is for the 1000-cycle stability test of the repaired capacitive sensor with PUU-TDH-ILs under 50% strain. The inset shows the enlarged view of the relative capacitance change from 1 to 100 s and the last 100 s;

[0052] Figure 29 It is the stress-strain curve of PUU-DDH-ILs. Detailed implementation manners

[0053] The present invention provides a preparation method of a polyurethaneurea elastomer, comprising the following steps:

[0054] Mix a soft segment substance, an isocyanate and a catalyst for prepolymerization reaction to obtain a prepolymer, wherein the soft segment substance contains hydroxyl groups;

[0055] Mix the prepolymer, a chain extender and an organic solvent for chain extension reaction to obtain the polyurethaneurea elastomer, wherein the chain extender contains phenyl and bisacylhydrazide substituents.

[0056] In the present invention, unless otherwise specified, the raw materials used are commercially available products in the art.

[0057] The present invention mixes a soft segment substance, an isocyanate and a catalyst for prepolymerization reaction to obtain a prepolymer, wherein the soft segment substance contains hydroxyl groups.

[0058] In the present invention, the soft segment substance preferably includes one or more of polycaprolactone diol (PCL), polytetrahydrofuran (PTMG), polyethylene glycol (PEG), polypropylene glycol (PPG) and polycaprolactone diol-block-polytetrahydrofuran (PCL-b-PTMG).

[0059] In the present invention, the isocyanate preferably includes one or more of isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate (HMDI), hexamethylene diisocyanate (HDI) and diphenylmethane diisocyanate (MDI).

[0060] In the present invention, the organic solvent preferably includes one or more of tetrahydrofuran (THF), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO).

[0061] In the present invention, the catalyst preferably comprises a tin-based catalyst, and the tin-based catalyst preferably comprises one or more of dibutyltin dilaurate (DBTDL), dibutyltin oxide (DBTO), stannous octoate (Sn(Oct)2), dimethyltin dichloride (DMTC), and stannous chloride (SnCl2).

[0062] In the present invention, the mass ratio of the soft segment material to the isocyanate is preferably 5-20:1-5, and specifically can be 10:2.23 or 10:2.62.

[0063] In the present invention, the mass ratio of the soft segment material to the catalyst is preferably 5-20:0.06, and specifically can be 5:0.06, 10:0.06, 15:0.06, or 20:0.06.

[0064] In the present invention, the temperature of the prepolymerization reaction is preferably 60-80°C, and specifically can be 60, 65, 70, 75, or 80°C, and the time is preferably 2-4 h, and specifically can be 2, 3, or 4 h.

[0065] In the present invention, the prepolymerization reaction is preferably carried out in a protective atmosphere, and the protective atmosphere is preferably nitrogen.

[0066] In the present invention, the soft segment material is preferably dehydrated before use. In the present invention, the soft segment material is preferably placed in a three-necked round-bottom flask with a mechanical stirrer, and then heated at 100-130°C and stirred under vacuum conditions for 1-3 h to remove moisture.

[0067] In a specific embodiment of the present invention, preferably after the soft segment material is dehydrated and the temperature of the system is naturally cooled to 60-80°C, the isocyanate and the catalyst are added to the reaction system, and then the prepolymerization reaction is carried out under a nitrogen atmosphere to obtain the prepolymer.

[0068] After the prepolymerization reaction is completed, in the present invention, the obtained prepolymer product is preferably naturally cooled to room temperature - 60°C to obtain the prepolymer.

[0069] After obtaining the prepolymer, in the present invention, the prepolymer, the chain extender, and the organic solvent are mixed to carry out a chain extension reaction to obtain the polyurethane urea elastomer, and the chain extender contains phenyl and bis-acylhydrazide substituents.

[0070] In the present invention, the chain extender preferably includes aromatic dihydrazide. The present invention synthesizes PUU using a chain extender containing both phenyl and bis-hydrazide substituents. The phenyl groups in PUU can form aggregates in situ based on π-π interactions. The aggregates form stable hard domains in the polymer material, which on the one hand improves the mechanical properties of the material, and on the other hand enhances the crosslinking density of the material. The higher crosslinking density between the molecular chains of the polyurethane urea elastomer increases the energy required for the molecular chains to slide when subjected to external force stretching. The breaking and recombination of multiple hydrogen bonds more effectively dissipate the energy at the wound, and the stress at the wound is transmitted to the entire polymer network, resulting in the cracks preferentially expanding gradually along the longitudinal direction, so that the material exhibits excellent tear resistance.

[0071] In the present invention, the aromatic dihydrazide preferably includes terephthalic dihydrazide and / or isophthalic dihydrazide.

[0072] In the present invention, the mass ratio of the soft segment material to the chain extender is preferably 5-20:0.5-1.5, specifically it can be 10:0.97. Limiting the mass ratio of the soft segment material to the chain extender within the above range can obtain an ideal network structure and crosslinking density on the basis of ensuring good processability of the polyurethane elastomer, so as to take into account the high mechanical strength, excellent elasticity and high-efficiency damage repair ability of the material, and avoid the problems of weak intermolecular force caused by insufficient chain extension or hard segment aggregation and decreased flexibility caused by excessive chain extension.

[0073] In the present invention, the temperature of the chain extension reaction is preferably 20-60 °C, specifically it can be 20, 30, 40, 50 or 60 °C, and the time is preferably 24-48 h, specifically it can be 24, 36 or 48 h.

[0074] In the present invention, the chain extension reaction is preferably carried out in a protective atmosphere, and the protective atmosphere is preferably nitrogen.

[0075] In a specific embodiment of the present invention, preferably the chain extender is added to the prepolymer, and then the chain extension reaction is carried out. Before the end of the chain extension reaction, preferably an organic solvent is added to obtain a viscous and transparent polymer solution containing the polyurethane urea elastomer. Removing the solvent in the polymer solution can obtain the polyurethane urea elastomer. The present invention preferably does not remove the solvent in the polymer solution and directly uses the polymer solution to prepare the ion conductive elastomer.

[0076] In the present invention, based on the mass of the soft segment material being 5-20 g, the volume of the added organic solvent is preferably 10-50 mL, specifically it can be 10, 20, 30, 40 or 50 mL.

[0077] After the supplementary organic solvent is added, the system obtained in the present invention is preferably stirred for 1 to 3 h (specifically, it can be 1, 2, or 3 h) to obtain the polymer solution.

[0078] The present invention also provides a polyurethaneurea elastomer prepared by the preparation method described in the above technical solution.

[0079] Taking the polyurethaneurea elastomer PUU-TDH synthesized with PCL-b-PTMG as the soft segment material and IPDI and TDH chain extenders as the hard segment materials as an example, the molecular structure of the polyurethaneurea elastomer is described.

[0080] In the present invention, the polyurethaneurea elastomer is a block copolymer composed of a soft segment material, an isocyanate, and a chain extender. Its unique structure enables it to have both rubber-like elasticity and excellent strength at the same time. The PUU-TDH is composed of three core components: a soft segment material, an isocyanate, and a chain extender. The molecular formula is as Figure 1 shown. PUU-TDH provides a soft "soft segment" by PCL-b-PTMG, IPDI provides the backbone structure of the hard segment, and TDH adjusts the hard segment structure and mechanical properties.

[0081] Figure 2 is a schematic diagram of the PUU-TDH elastomer structure. In the PUU-TDH, phenyl groups can form aggregates in situ based on π-π interactions. These aggregates, together with multiple hydrogen bonds between amide urea bonds on both sides, jointly form "double-lock" hard domains with high binding energy and cross-linked based on non-covalent interactions in the PUU. These nano-hard domains are uniformly dispersed in the PCL-b-PTMG soft segment. On the one hand, they can effectively enhance the mechanical properties of the elastomer, and on the other hand, they can also act as physical cross-linking points, endowing the material with excellent elasticity and shape recovery. In addition, these physical cross-linking points based on supramolecular interactions can be reversibly opened and rebuilt when heated, enabling PUU-TDH to have efficient damage repair performance.

[0082] The present invention also provides the application of the polyurethaneurea elastomer described in the above technical solution in the field of ion-conductive elastomers.

[0083] The present invention has no special limitation on the specific manner of the application, and the manner well-known to those skilled in the art can be adopted.

[0084] The present invention also provides an ion-conductive elastomer, and the raw materials for preparation include the polyurethaneurea elastomer described in the above technical solution and an imidazole-based ionic liquid.

[0085] In the present invention, the imidazole-based ionic liquid preferably includes one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-ethyl-3-methylimidazolium hexafluorophosphate; the imidazole-based ionic liquid can form hydrogen bonds with the soft segment substances of the polyurethane-urea elastomer such as polycaprolactone diol and polyethylene glycol, and the obtained ion-conductive elastomer has better mechanical properties, tear resistance, conductivity, and transparency.

[0086] In the present invention, based on the polyurethane-urea elastomer obtained with the mass of the soft segment substance being 5 - 20 g, the dosage of the imidazole-based ionic liquid is preferably 2 - 10 g, and specifically can be 2, 3, 4, 5, 6, 7, 8, 9, or 10 g.

[0087] In the present invention, the shape of the ion-conductive elastomer is preferably a film, fiber, or block. The present invention has no special limitation on the specific size of the shape of the ion-conductive elastomer, and the sizes well-known to those skilled in the art can be adopted.

[0088] The present invention also provides a preparation method of the ion-conductive elastomer described in the above technical solution, including the following steps:

[0089] Dropwise add and mix the imidazole-based ionic liquid to the polymer solution to obtain the ion-conductive elastomer.

[0090] In the present invention, the temperature of the mixing is preferably room temperature, and the time is preferably 12 - 24 h, and specifically can be 12, 16, 18, 20, 22, or 24 h.

[0091] In the present invention, the mixing is preferably carried out under stirring conditions, and the present invention has no special limitation on the stirring speed.

[0092] Figure 3 It is a schematic flow chart for preparing the ion-conductive elastomer in the examples of the present invention.

[0093] Taking the shape of the ion-conductive elastomer being preferably a film as an example, the present invention preferably pours the mixed solution obtained by mixing the polymer solution and the imidazole-based ionic liquid into a glass petri dish, then removes the bubbles under vacuum at room temperature, then heats the obtained polymer solution overnight on a hot plate at 60 °C, and then dries it in a forced-air oven at 80 °C for 48 h. Finally, the product is placed in a vacuum drying oven at 60 °C to remove the residual solvent under vacuum conditions to obtain the ion-conductive elastomer film.

[0094] The present invention also provides an application of the ionic conductive elastomer described in the above technical solution in flexible electronic devices. The flexible electronic device is preferably used as a sensor to sense external force changes and detect human movements, with sensitive and stable feedback signals. It is also preferably used as an ionic skin to sense pressure, temperature, and humidity, and realize the detection of biological signals such as heart rate and electromyogram signals.

[0095] In the present invention, the sensor is preferably a capacitive sensor.

[0096] Conductive elastomers are usually non-repairable. Once the material is mechanically damaged, its function will decrease sharply or even be completely lost, which not only increases the use and maintenance costs of the material, but also causes a large amount of resource consumption and increases the burden on the environment. In addition, conductive elastomers also have problems such as poor mechanical properties and easy fracture along the notch; the distribution of conductive media in the matrix material is uneven, the conductivity is low, the transparency is poor, and it is difficult to be actually used for flexible stress and strain sensing. The ionic conductive elastomer material designed in the present invention exhibits excellent self-healing properties. The material can be basically completely repaired after 48 hours at 60 °C without any solvent assistance, and the healing efficiency is as high as 98%, significantly improving the service life and reliability of the material. The Young's modulus ranges from 12.5 to 20 MPa, which is significantly higher than that of existing ionic conductive elastomers. The excellent mechanical properties ensure the stability and safety of the material under high load conditions. In addition, it also has a high fracture energy, between 120 and 150 kJ / m 2 , indicating that it can effectively dissipate energy when subjected to external force damage, delay the propagation of the wound along the crack, thereby significantly improving its tear resistance. It also has excellent electrical conductivity, and the conductivity range is between 6×10 -5 ~2×10 -4 S / cm, which can easily light up a light bulb. At the same time, it also has excellent antibacterial and biocompatible properties, can be in direct contact with human skin, and with the high elasticity of the material, it can be used as a sensor to sense external force changes and detect human movements, with sensitive and stable feedback signals, and can also be used as an ionic skin to sense pressure, temperature, and humidity, and realize the detection of biological signals such as heart rate and electromyogram signals. The ionic conductive elastomer of the present invention has important application prospects in high-end and multifunctional fields such as biomedicine and flexible electronic devices, and is suitable for the functional requirements of various flexible electronic devices.

[0097] The main reason for the above advantages of the ionic conductive elastomer of the present invention is:

[0098] 1. Inspired by the fact that an increase in the content of aromatic ring amino acids in the ligament structure of living organisms is beneficial to enhancing the stability of high-density hydrogen bonds, the present invention synthesizes PUU using a molecule containing both an aromatic ring and a diacylhydrazide group as a chain extender. The multiple hydrogen bonds between hydrazides and the π-π stacking of aromatic rings in PUU jointly form the hard domain structure of polyurethane urea. These nano-hard domains are uniformly dispersed in the PCL-b-PTMG soft segment. On the one hand, they can effectively enhance the mechanical properties of the elastomer, and on the other hand, they can also serve as physical cross-linking points, endowing the material with excellent elasticity and shape recovery. In addition, these physical cross-linking points based on supramolecular interactions can be reversibly opened and rebuilt when heated, enabling PUU-TDH to have efficient damage repair performance, which improves the cross-linking density of the material on the one hand and enhances the mechanical properties of the material on the other hand.

[0099] 2. The molecular chains of hard domain cross-linked PUU require more energy to slide when subjected to external tensile force. The breaking and recombination of multiple hydrogen bonds more effectively dissipate the energy at the wound. The stress at the wound is transmitted to the entire polymer network, resulting in cracks preferentially expanding gradually along the longitudinal direction, so that the material exhibits excellent tear resistance.

[0100] 3. During the repair process, increasing the temperature is beneficial to the movement of molecular chains and the dissociation and reconstruction of non-covalent interactions between polymer chains, so it has excellent self-repair performance.

[0101] 4. The good compatibility between the PUU soft segment and the ionic liquid ensures the uniform distribution and high transparency of the ionic liquid in PUU, and further endows the ion-conductive elastomer with excellent electrochemical properties.

[0102] 5. Ionic liquids conduct ions rather than electrons, which is consistent with the signal conduction mechanism in living organisms and is more likely to have good cell compatibility and tissue compatibility.

[0103] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0104] Test standards for mechanical properties and self-repair efficiency:

[0105] The mechanical properties of the elastomer were tested using an Instron5944 universal testing machine at room temperature (25 °C, 40% relative humidity), and the tensile speed was 50 mm / min. The samples used for testing were made into dumbbell shapes with dimensions of 12 mm × 2.0 mm × 0.5 mm. Each sample was subjected to at least five independent tensile tests, and the mechanical property results were the average of these five tests.

[0106] The sample used for the compression test was a circular disk-shaped specimen with a diameter of 20 mm and a thickness of 2 mm, and the test speed was 1 mm / min.

[0107] The puncture resistance test was carried out on a universal testing machine (Instron 5944, maximum load 2 kN) equipped with a sample fixing device and a puncture needle. The thickness of the test sample was 750 μm, the puncture needle moved at a speed of 50 mm / min, and the testing machine synchronously recorded the force and displacement generated during the puncture process.

[0108] The fracture energy test was carried out by a tensile test, using a single-edge notched sample (crack length 1 mm). The notched sample and the unnotched sample had the same dimensions, with a gauge length of 10 mm, a width of 5 mm, and a thickness of 0.8 mm. Both types of samples were tested at a tensile speed of 3 mm / min.

[0109] To evaluate the self-healing efficiency of the material, the following method was adopted: First, the dumbbell-shaped sample was cut with a knife, and after the fracture surfaces were closely fitted, they were kept at different temperatures for a specific time for repair. Subsequently, the repaired samples were subjected to tensile tests, and at least five independent tensile tests were carried out for each sample, and the mechanical property results were the average values of these five tests.

[0110] Example 1

[0111] PCL-b-PTMG was selected as the soft segment material, IPDI and TDH chain extender were selected as the hard segment materials, ultra-dry DMAc was used as the solvent, dibutyltin dilaurate was used as the catalyst, and [EMIM][TFSI] was used as the ionic liquid to synthesize PUU-TDH and PUU-TDH-ILs. Figure 3 This is a schematic flow chart for preparing the ion-conductive elastomer in the embodiment of the present invention.

[0112] Place PCL-b-PTMG (10 g) in a three-necked round-bottom flask equipped with a mechanical stirrer. Immediately heat PCL-b-PTMG at 120 °C and stir under vacuum for 2 h to remove moisture. After the system temperature cools to 70 °C, add IPDI (2.23 g) and 60 mg of dibutyltin dilaurate to the reaction system, and react at 70 °C for 3 h under a nitrogen atmosphere to obtain a prepolymer. Subsequently, add 50 mL of ultra-dry DMAc to the reaction system to dissolve the obtained prepolymer, and lower the temperature to 25 °C. When the reaction system temperature reaches 25 °C, add TDH (0.97 g), and stir at room temperature for 36 h under a nitrogen atmosphere to obtain a viscous transparent polymer solution. Finally, pour the solution into a beaker, add 3 g of [EMIM][TFSI] ionic liquid, and stir at 25 °C for 18 h. Finally, pour the solution into a glass petri dish with a diameter of 150 mm, and remove bubbles at room temperature under vacuum. Then heat the obtained polymer solution on a hot plate at 60 °C overnight, and dry it in a forced-air oven at 80 °C for 48 h. Finally, place the product in a vacuum drying oven at 60 °C to remove residual solvent under vacuum to obtain an ion-conductive elastomer film.

[0113] The conductivity of the obtained ion-conductive elastomer film is 0.2 mS / cm, the Young's modulus is 13.1 MPa, and the fracture energy is 132.5 kJ / m 2 。

[0114] Example 2

[0115] Select PTMG as the soft segment material, HMDI and IDH chain extenders as the hard segment materials, ultra-dry DMF as the solvent, dibutyltin dilaurate as the catalyst, and [EMIM][BF4] as the ionic liquid to synthesize PUU-IDH and PUU-IDH-ILs.

[0116] Place PTMG (10 g) in a three-necked round-bottom flask equipped with a mechanical stirrer. Immediately heat the PTMG at 120 °C and stir it under vacuum for 2 h to remove moisture. After the system temperature cools to 70 °C, add HMDI (2.62 g) and 60 mg of dibutyltin dilaurate to the reaction system, and react at 70 °C for 3 h under a nitrogen atmosphere to obtain a prepolymer. Subsequently, add 50 mL of ultra-dry DMF to the reaction system to dissolve the obtained prepolymer, and lower the temperature to 25 °C. When the reaction system temperature reaches 25 °C, add IDH (0.97 g), and stir at room temperature for 48 h under a nitrogen atmosphere to obtain a viscous transparent polymer solution. Finally, pour the solution into a beaker, add 3 g of [EMIM][BF4] ionic liquid, and stir at 25 °C for 18 h. Finally, pour the solution into a glass petri dish with a diameter of 150 mm, and remove the bubbles at room temperature under vacuum. Then heat the obtained polymer solution on a hot plate at 60 °C overnight, and dry it in a forced-air oven at 80 °C for 48 h. Finally, place the product in a vacuum drying oven at 60 °C to remove the residual solvent under vacuum to obtain an ion-conductive elastomer film.

[0117] The conductivity of the obtained ion-conductive elastomer film is 0.2 S / cm, the Young's modulus is 12.7 MPa, and the fracture energy is 128.2 kJ / m 2 。

[0118] Comparative Example 1

[0119] Select PCL as the soft-segment material, HDI and ODH chain extenders as the hard-segment materials, ultra-dry THF as the solvent, dibutyltin dilaurate as the catalyst, and [EMIM][TFSI] as the ionic liquid to synthesize PUU-ODH and HPUU-ODH-ILs.

[0120] Place PCL (10 g) in a three-necked round-bottom flask equipped with a mechanical stirrer. Immediately heat the PCL at 120 °C and stir it under vacuum for 2 h to remove moisture. After the system temperature cools to 70 °C, add HDI (1.62 g) and 60 mg of dibutyltin dilaurate to the reaction system, and react at 70 °C for 3 h under a nitrogen atmosphere to obtain a prepolymer. Subsequently, add 50 mL of ultra-dry THF to the reaction system to dissolve the obtained prepolymer, and lower the temperature to 25 °C. When the reaction system temperature reaches 25 °C, add ODH (0.59 g), and stir at room temperature for 48 h under a nitrogen atmosphere. Before the end of the reaction, add an additional 20 mL of ultra-dry THF and stir for 3 h to obtain a viscous transparent polymer solution. Finally, pour the solution into a beaker, add 3 g of [EMIM][TFSI] ionic liquid, and stir at 25 °C for 18 h. Finally, pour the solution into a glass Petri dish with a diameter of 150 mm, and remove the bubbles at room temperature under vacuum. Then heat the obtained polymer solution on a hot plate at 60 °C overnight, and dry it in a forced-air oven at 80 °C for 48 h. Finally, place the product in a vacuum drying oven at 60 °C to remove the residual solvent under vacuum to obtain an ion-conductive elastomer film.

[0121] The conductivity of the obtained ion-conductive elastomer film is 0.1 mS / cm, the Young's modulus is 12.2 MPa, and the fracture energy is 112.9 kJ / m 2 。

[0122] Comparative Example 2

[0123] Select PCL-b-PTMG as the soft segment material, HDI and DDH chain extenders as the hard segment materials, ultra-dry DMSO as the solvent, dibutyltin dilaurate as the catalyst, and [EMIM][TFSI] as the ionic liquid to synthesize PUU-DDH and PUU-DDH-ILs.

[0124] Place PCL-b-PTMG (10 g) in a three-necked round-bottom flask equipped with a mechanical stirrer. Subsequently, heat PCL-b-PTMG at 90 °C and stir it under vacuum for 2 h to remove moisture. After the system temperature cools to 80 °C, add HDI (1.62 g) and 60 mg of dibutyltin dilaurate to the reaction system, and react at 80 °C for 3 h under a nitrogen atmosphere to obtain a prepolymer. Then, add 80 mL of ultra-dry DMSO to the reaction system to dissolve the obtained prepolymer, and lower the temperature to 25 °C. When the reaction system temperature reaches 25 °C, add DDH (1.29 g), and stir at 60 °C for 48 h under a nitrogen atmosphere to obtain a viscous and transparent polymer solution. Finally, pour the solution into a beaker, add 5 g of [EMIM][TFSI] ionic liquid, and stir at 25 °C for 18 h. Finally, pour the solution into a glass petri dish with a diameter of 150 mm, and remove the bubbles at room temperature under vacuum. Then, heat the obtained polymer solution on a hot plate at 60 °C overnight, and dry it in a forced-air oven at 80 °C for 48 h. Finally, place the product in a vacuum drying oven at 60 °C to remove the residual solvent under vacuum to obtain an ion-conductive elastomer film.

[0125] The conductivity of the obtained ion-conductive elastomer film is 0.1 mS / cm, the Young's modulus is 12.1 MPa, and the fracture energy is 106.4 kJ / m 2 。

[0126] Table 1 shows the test results of the mechanical properties of the polyurethane-urea elastomers prepared in the examples and comparative examples. Table 2 shows the light transmittance test results of the polyurethane-urea elastomers prepared in the examples and comparative examples. Table 3 shows the test results of the tensile properties and repair efficiency of the polyurethane-urea elastomers prepared in the examples and comparative examples after repair.

[0127] Table 1 Test data of the mechanical properties of the polyurethane-urea elastomers prepared in the examples and comparative examples

[0128]

[0129]

[0130] Table 2 Test data of the light transmittance of the polyurethane-urea elastomers prepared in the examples and comparative examples

[0131] Sample Transmittance at 550 nm (%) PUU-TDH 91.1 PUU-IDH 90.4 PUU-ODH 90.0 PUU-DDH 88.9

[0132] Table 3 Test data of the tensile properties and repair efficiency of the polyurethane-urea elastomers prepared in the examples and comparative examples after repair

[0133] Sample Tensile strength (MPa) Repair efficiency (%) PUU-TDH 88.8±2.6 95.4±2.8 PUU-IDH 79.9±4.3 92.3±5.0 PUU-ODH 75.4±1.6 97.6±2.0 PUU-DDH 66.3±2.1 94.7±3.1

[0134] Figure 4Tensile stress-strain curves of the polyurethane-urea elastomers prepared in the examples and comparative examples Figure 5 Tear stress-strain curve of PUU-TDH Figure 6 Puncture resistance force-displacement curves of the polyurethane-urea elastomers prepared in the examples and comparative examples Figure 7 Compressive stress-strain curves of the polyurethane-urea elastomers prepared in the examples and comparative examples Figure 8 Impact resistance force-displacement curves of the polyurethane-urea elastomers prepared in the examples and comparative examples Figure 9 Self-healing stress-strain curves of the polyurethane-urea elastomers prepared in the examples and comparative examples Figure 10 Stress-strain curves of multiple reshaping of PUU-TDH

[0135] From Tables 1-3 and Figures 4 - 10 it can be seen that the polyurethane-urea elastomers prepared in the examples have higher mechanical properties (including tensile strength, compressive strength, toughness, Young's modulus, fracture energy, puncture resistance, impact resistance) and transparency compared with the comparative examples. In terms of self-healing efficiency and reshaping performance, the examples and comparative examples are very close. In summary, the PUU-TDH prepared in the examples has the best comprehensive performance.

[0136] Figure 11 Dynamic thermomechanical curve of the elastomer of PUU-TDH Figure 12 Rheological curve of the PUU-TDH elastomer varying with temperature Figure 13 Thermogravimetric curve of the PUU-TDH elastomer. It can be seen that the glass transition temperature (T g ) of PUU-TDH is -48 °C, and it has excellent elasticity and flexibility at room temperature, and also has excellent thermal stability. The viscous flow temperature (T f ) is only reached at 203 °C, and only 5% of the mass fraction of the polymer is lost at 281 °C (thermal decomposition temperature T d ).

[0137] Using DMF as the mobile phase and a flow rate of 1 mL / min, the molecular weight of PUU-TDH was characterized. As Figure 14 shown, the molecular weight of PUU-TDH is 78,000, which has a relatively high molecular weight. The large broad peak of XRD proves that PUU-TDH presents an amorphous structure ( Figure 15 ).

[0138] Figure 16 Fourier transform infrared spectrogram of PUU-TDH-ILs. It can be seen that the characteristic absorption peak of isocyanate at 2260 cm -1 is not observed, which proves that the isocyanate groups in the ion-conductive elastomer have completely reacted. At the same time, at 1535 and 3305 cm -1Obvious N-H bending vibration peaks and stretching vibration peaks were detected respectively at this position, further proving the successful synthesis of the elastomer. The strong absorption peak at 867 cm -1 corresponds to the para-phenylene ring structure, indicating that the benzene ring structure has been successfully introduced into the ion-conductive elastomer.

[0139] Figure 17 is the ultraviolet-visible transmission spectrum of PUU-TDH-ILS. Figure 17 The inset in it is the digital photo of the PUU-TDH-ILs ion-conductive elastomer. It can be seen that the ion-conductive elastomer presents a highly transparent and defect-free film. The transmittance of the PUU-TDH-ILs sample at 550 nm is 87.2%.

[0140] Figure 18 is the stress-strain curve of PUU-TDH-ILS. The test process is as follows: Taking PUU-TDH-ILs as an example, the ion-conductive elastomer was cut into dumbbell-shaped specimens with a width of 2 cm and a length of 35 cm with a cutter, and uniaxial tension was carried out on a universal electronic testing machine at a tensile rate of 50 mm / min. As Figure 18 shown, it indicates that the ion-conductive elastomer has excellent comprehensive mechanical properties. With a tensile strength of 15 MPa, an elongation at break of 2680% and a toughness of 177.2 MJ / m 3 were maintained.

[0141] Figure 19 are the photos, dimensions and force-displacement curves of PUU-TDH-ILs in the trouser tear test. The test process is as follows: In the central area of a specimen with a width of 50 mm, a length of 80 mm and a thickness of 0.4 mm, an initial notch of 30 mm was made along the length direction of the specimen. The two edges of the sample were clamped with metal plates to prevent sliding during the tear test. The test was carried out at a speed of 50 mm / min. The fracture energy of the ion conductor was calculated by the trouser tear method, and the value was 132.5 kJ·m -2 , proving the excellent tear resistance of the material.

[0142] Figure 20 are the tensile test results of PUU-TDH-ILs in continuous loading-unloading cycles. The test process is as follows: The dumbbell-shaped specimens were subjected to 10 cycles of tensile with a strain of 800%. The first cycle curve has the largest hysteresis area. As the number of cycles increases, the hysteresis area gradually decreases and tends to be stable. And the residual strain of the material was calculated to be 32% according to the cycle curve, which proves the excellent elasticity and fatigue resistance of the material.

[0143] Figure 21The stress-strain curves of the original and repaired PUU-TDH-ILs at 60 °C with different repair times are shown. It can be seen that the repair efficiency is positively correlated with the repair time. When the repair time is 48 h, the stress-strain curve of the repaired sample basically coincides with that of the original sample, and the repair efficiency is as high as 98%. The repair mechanism is as follows: with the increase in temperature, non-covalent interactions such as hydrogen bonds, van der Waals forces, and π-π interactions in the ion-conductive elastomer gradually dissociate. The two fracture surfaces diffuse into each other due to the increased mobility of the polymer chains. The non-covalent bonds between the molecular chains are in a dynamic equilibrium of dissociation and formation, and high temperature leads to a greater tendency of bond dissociation than formation. Due to the time dependence of the thermal motion of polymer molecules, the above processes all require a certain amount of time to complete. When the temperature drops from the repair temperature to room temperature, the content of non-covalent bonds between the molecular chains at the fracture surface gradually increases until it approaches the original level.

[0144] Figure 22 The stress-strain curves of PUU-TDH-ILs after multiple remolding are shown, indicating that the ion-conductive elastomer can be dissolved in DMAc at room temperature and reprocessed into a transparent and defect-free ion-conductive elastomer by solution casting. Even after multiple cycles of recycling, the stress-strain curve of the reprocessed material almost coincides with that of the original sample. This shows that the mechanical properties of the recycled PUU-TDH-ILs remain basically unchanged.

[0145] To examine whether PUU-TDH-ILs will cause skin irritation or sensitization. The original PUU-TDH-ILs ( Figure 23 i) in it was closely attached to the shaved skin of a mouse ( Figure 23 ii) in it, and fixed with transparent tape for 48 h ( Figure 23 iii) in it. Figure 23 For the biocompatibility test of the capacitive sensor encapsulation material, after removal ( Figure 23 iv) in it, no adverse reactions were observed in the mouse, and there was no inflammation on the skin after contact, thus verifying the good tissue biocompatibility of the material.

[0146] Figure 24 The relative capacitance change of the PUU-TDH-ILs sensor fixed on the finger at different bending angles. When a straight finger is gradually bent, the change in the normalized capacitance of the capacitive sensor with PUU-TDH-ILs is shown. The normalized capacitance increases with the increase in the finger bending angle and stabilizes when the finger is fixed at a certain angle. When the finger is straightened back to the original angle, the signal quickly returns to the baseline.

[0147] Figure 25 The relative capacitance change of the sensor under different pressures is shown. The sensor with PUU-TDH-ILs exhibits obvious and rapid signals when subjected to different pressures;Figure 26 For the relative capacitance change of the sensor with PUU-TDH-ILs under small strain (3 - 20%), it can be seen that in the continuous stretching / releasing cycles of low strain (3 - 20%), a highly reversible and repeatable sharp triangular signal is exhibited.

[0148] The capacitive sensor with PUU-TDH-ILs also has excellent conductivity and self-healing performance. As Figure 27 shown, Figure 27 is the state of the capacitive sensor with PUU-TDH-ILs before cutting Figure 27 in i and after cutting Figure 27 in ii, and its state after healing Figure 27 in iii. The functional ionic conductor as the conductor of the LED bulb can easily light up the small bulb. After cutting and repairing it, the small bulb still has the conductive function. The repaired capacitive sensor was subjected to 1000 consecutive loading-unloading cycles at 50% strain, and the evolution of the electrical signal output was recorded in real time. Figure 28 is the 1000-cycle stability test of the repaired capacitive sensor with PUU-TDH-ILs at 50% strain. The inset shows the enlarged view of the relative capacitance change from 1 - 100 s and the last 100 s. It can be seen that during the cycling process, the highly reproducible output signal can recover to the original value, demonstrating the stability and durability of the sensor.

[0149] The ion-conductive elastomer was uniaxially stretched using a universal electronic testing machine at a stretching speed of 50 mm·min -1 . The samples were made into dumbbell shapes (size: 12 mm × 2.0 mm × 0.5 mm), Figure 29 is the stress-strain curve of PUU-DDH-ILs. It can be seen that the tensile stress of PUU-DDH-ILs is only 1.5 MPa, and the toughness is 17.5 MJ / cm 3 , and the mechanical properties are significantly lower than those of PUU-TDH-ILs. This is because the ion conductor lacks the aggregate hard domains formed by in-situ assembly of π-π interactions, and the energy required for the molecular chains to slide when subjected to external force stretching is lower.

[0150] In summary, the present invention provides a polyurethaneurea elastomer and an ion-conductive elastomer that can repair mechanical damage, have excellent and controllable mechanical properties, and are tear-resistant, with the advantages of high repair efficiency, excellent and adjustable mechanical properties, tear resistance, excellent conductivity, good biocompatibility, high transparency, etc. It can be applied to the preparation of flexible stress sensors, which can be directly attached to the skin surface for monitoring human movement and physiological conditions, and has the advantages of a wide sensing range, high sensitivity, and good stability.

[0151] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a polyurethaneurea elastomer, characterized in that, It includes the following steps: Mix the soft segment material, isocyanate and catalyst to carry out a prepolymerization reaction to obtain a prepolymer, wherein the soft segment material contains hydroxyl groups; Mix the prepolymer, chain extender and organic solvent to carry out a chain extension reaction to obtain the polyurethane-urea elastomer, wherein the chain extender contains phenyl and bis-hydrazide substituents.

2. The preparation method according to claim 1, characterized in that, The chain extender includes aromatic dihydrazide.

3. The preparation method according to claim 2, characterized in that, The aromatic dihydrazide includes terephthalic dihydrazide and / or isophthalic dihydrazide.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the soft segment material to the isocyanate is 5-20:1-5.

5. The preparation method according to claim 1 or 4, characterized in that, The mass ratio of the soft segment material to the chain extender is 5-20:0.5-1.

5.

6. The preparation method according to claim 1, characterized in that, The temperature of the chain extension reaction is 20-60°C, and the time is 24-48h.

7. The polyurethane-urea elastomer prepared by the preparation method according to any one of claims 1-6.

8. The application of the polyurethane-urea elastomer according to claim 7 in the field of ion conductive elastomers.

9. An ion-conductive elastomer, characterized in that, The preparation raw materials include the polyurethane-urea elastomer according to claim 7 and imidazole-based ionic liquids.

10. The ion-conductive elastomer according to claim 9, characterized in that, The imidazole-based ionic liquids include one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium hexafluorophosphate.

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