Self-repairing hydrogen bond-lithium bond dual-network intrinsic conductive elastomer and preparation method thereof

Abstract

The invention discloses a self-repairing hydrogen bond-lithium bond dual-network intrinsic conductive elastomer and a preparation method thereof, and belongs to the application field of flexible electronics, intelligent materials and self-adaptive materials. The invention aims to solve the problem that the function of an existing intrinsic conductive elastomer is difficult to quickly and autonomously repair when the intrinsic conductive elastomer is applied to flexible electronics and wearable equipment. The method comprises the following steps: adding choline chloride into acrylic acid, and stirring uniformly and transparently; adding phytic acid, and uniformly stirring; adding lithium trifluoromethanesulfonimide, and uniformly stirring; uniformly stirring a cross-linking agent and an initiator, pouring into a polytetrafluoroethylene mold, and irradiating by using an ultraviolet light source; through molecular structure design, an intrinsic conductive mechanism of the conductive elastomer is established, meanwhile, the room-temperature autonomous self-repairing speed of the conductive elastomer is increased, and the intrinsic conductive elastomer with self-repairing and high repairing efficiency of a hydrogen bond-lithium bond synergetic cross-linked network is obtained. The material can be used as raw materials of flexible electronics, wearable equipment, soft robots and the like.

Description

Technical Field

[0001] The present invention belongs to the application fields of flexible electronics, intelligent materials and adaptive materials. Specifically, it relates to a self-healing hydrogen bond-lithium bond dual-network intrinsically conductive elastomer, and a preparation method thereof for the self-healing hydrogen bond-lithium bond dual-network intrinsically conductive elastomer. Background Art

[0002] Conductive elastomers are a class of polymer materials that combine elasticity and electrical conductivity. Their electrical conductivity stems from the molecular structure or macroscopic design of the material itself. Different from traditional conductive materials (such as metals, carbon materials, etc.) that rely on external rigid conductive fillers, the mechanical properties of elastomers are often damaged after a large amount of conductive fillers are added. Intrinsically conductive elastomers maintain stable electrical conductivity during deformation by reasonably designing the molecular structure of the material. Their electrical conductivity is usually provided by conjugated polymers, conductive polymers or polymer chains containing conductive groups, so the elasticity or mechanical properties of the material will not be damaged due to enhanced electrical conductivity.

[0003] The elastic modulus, electrical conductivity and other mechanical properties of intrinsically conductive elastomers can be optimized by adjusting the molecular structure, crosslinking density, chain segment configuration and external environment (such as temperature, humidity, etc.) to meet specific performance requirements. For example, polar groups on the molecular chain can improve the electrical conductivity of the material, while the crosslinked structure endows the material with excellent elasticity. However, during long-term service, intrinsically conductive elastomers will inevitably suffer mechanical damage due to microcracks or external stresses, resulting in attenuation or even failure of their sensing performance. Therefore, endowing conductive elastomers with self-healing properties, accelerating the self-healing speed and improving the repair efficiency are crucial for enhancing the safety and stability of the material and extending its service life, especially in the application of flexible wearable electronic devices.

[0004] For the application of self-healing intrinsically conductive elastomers in the fields of flexible electronic devices, wearable devices, etc., the restoration of their repair function is particularly important. Although existing self-healing methods can restore the function of the material to a certain extent, their repair time is still relatively long, and the performance of many materials cannot be restored to the original state after self-healing. In addition, how to maintain the stability of the electrical conductivity, elasticity and mechanical properties of intrinsically conductive elastomers during the self-healing process is still a technical problem to be solved urgently. Summary of the Invention

[0005] How to balance conductivity and elasticity during the self-healing process and ensure the stability and reproducibility of both in long-term use remains a major challenge in the design. This is not only of great significance for the research of conductive elastomers themselves but also has a profound impact on the future development of the fields of flexible electronics and intelligent materials. Therefore, delving deeply into the intrinsic conduction mechanism of conductive elastomers and achieving a breakthrough in self-healing efficiency will open up broad prospects for applications in emerging fields such as flexible electronics, wearable devices, and soft robots.

[0006] The present invention aims to solve the problem that existing intrinsic conductive elastomers are difficult to quickly and autonomously repair their functions in the applications of flexible electronics and wearable devices. In order to improve the possibility of self-healing conductive elastomers in the fields of flexible electronics, wearable devices, and soft robots, the present invention obtains a self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomer and its preparation method through molecular structure design.

[0007] The present invention regulates the molecular structure of polyacrylic acid, establishes the intrinsic conduction mechanism of the conductive elastomer while increasing the speed of room-temperature autonomous self-healing of the conductive elastomer, and prepares a self-healing intrinsic conductive elastomer with a hydrogen bond-lithium bond synergistic cross-linked network, namely acrylic acid-choline chloride-phytic acid-lithium bis(trifluoromethanesulfonyl)imide elastomer.

[0008] The highly efficient self-healing property of the self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomer prepared by the present invention extends its service life in applications; the intrinsic conduction mechanism ensures the mechanical properties while increasing the conductivity.

[0009] The present invention endows the conductive elastomer with excellent self-healing properties by introducing multiple hydrogen bonds; at the same time, the introduction of lithium bis(trifluoromethanesulfonyl)imide constructs a complete ionic conductive network inside the material, thus significantly enhancing the conductivity of the conductive elastomer. The hydrogen bond-lithium bond synergistic cross-linked network not only endows the conductive elastomer with excellent stretchability but also provides an effective dynamic energy dissipation mechanism for it. The present invention provides a brand-new idea for the regulation of the self-healing network of subsequent conductive elastomers.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0011] The purpose of the present invention is to provide a preparation method of a self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomer, comprising the following steps:

[0012] Step 1: Add choline chloride to acrylic acid, stir evenly at a certain temperature, add phytic acid, and stir evenly to obtain a mixed solution;

[0013] Step 2: Then add lithium bis(trifluoromethanesulfonyl)imide and stir evenly;

[0014] Step 3: Then add a crosslinking agent and an initiator, stir evenly, pour into a mold, and perform ultraviolet irradiation to obtain the conductive elastomer.

[0015] Further defined, in Step 1, the molar ratio of choline chloride to acrylic acid is (0.1 - 0.5):1.

[0016] Further defined, in Step 1, stir under the condition of 70°C - 90°C.

[0017] Further defined, in Step 1, the mass ratio of phytic acid to acrylic acid is (0.1 - 0.3):1.

[0018] Further defined, in Step 1, stir at a speed of 1000 rpm - 2000 rpm.

[0019] Further defined, in Step 2, the mass ratio of lithium bis(trifluoromethanesulfonyl)imide to the mixed solution is (0.01 - 0.4):1.

[0020] Further defined, in Step 2, stir at a speed of 1000 rpm - 2000 rpm.

[0021] Further defined, in Step 3, the crosslinking agent is one or a combination of polyethylene glycol diacrylate, polyacrylate diacrylate, and polyacrylic acid diacrylate in any ratio, and the molar ratio of the crosslinking agent to acrylic acid is (0.01 - 0.04):1.

[0022] Further defined, in Step 3, the initiator is one or a combination of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2,2'-diphenyl-2-propanone, and 2,4,6-trimethylbenzophenone in any ratio, and the molar ratio of the initiator to acrylic acid is (0.01 - 0.04):1.

[0023] Further defined, in Step 3, the material of the mold is polytetrafluoroethylene.

[0024] Further defined, in Step 3, stir at a speed of 1000 rpm - 2000 rpm.

[0025] Further defined, in Step 3, under the intensity of 5 mW / cm 2 ~50 mW / cm 2 perform ultraviolet irradiation for 10 min - 30 min.

[0026] Another object of the present invention is to provide a self-healing hydrogen bond-lithium bond double network intrinsic conductive elastomer prepared by any of the above methods.

[0027] The conductive elastomer of the present invention uses acrylic acid as the matrix, adds choline chloride and phytic acid to the matrix to increase the number of hydrogen bonds, and introduces lithium bis(trifluoromethanesulfonyl)imide into the matrix to form an ionic conductive network, thereby obtaining a self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomer. It is used in flexible electronics, wearable devices, and soft robots. Its efficient self-healing property extends the service life, and the intrinsic conduction mechanism ensures mechanical properties while improving the conductivity.

[0028] The present invention prepares a self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomer. By virtue of lithium bis(trifluoromethanesulfonyl)imide, a complete ionic conductive network is constructed inside the material, improving the conductive performance of the elastomer, showing a sensitive strain response ability, and the sensitivity coefficient of the composed sensor is as high as 6.37. At the same time, choline chloride and phytic acid provide a dense hydrogen bond network, endowing the elastomer with autonomous self-healing properties, and revealing the self-healing mechanism of the hydrogen bond-lithium bond synergistic crosslinking network.

[0029] The present invention prepares a self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomer. The preparation process is simple, pollution-free, low in energy consumption, low in cost, and high in safety factor, and is suitable for industrial production. It provides a new way to further improve the self-healing regulation mechanism of the intrinsic conductive elastomer.

[0030] In order to further understand the features and technical content of the present invention, please refer to the following detailed description of the present invention and the drawings. However, the attached drawings are only for reference and illustration, and are not used to limit the present invention. Description of the Drawings

[0031] Figure 1 Polarizing microscope images of the self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomers prepared in Examples 1, 2, 3, and 4: a) - d) Polarizing microscope images of the conductive elastomers prepared in different examples;

[0032] Figure 2 Scanning electron microscope surface images of the self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomers prepared in Examples 1, 2, 3, and 4: a) - d) Polarizing microscope images of the conductive elastomers prepared in different examples;

[0033] Figure 3 Conductive properties of the self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomers prepared in Examples 1, 2, 3, and 4: a) is the impedance curve of the conductive elastomer; b) is the bar chart of the conductivity of the conductive elastomer;

[0034] Figure 4(a) is the 25% - 300% tensile-recovery curve of the prepared self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomer;

[0035] Figure 4(b) shows the 325% - 600% tensile - recovery curve of the prepared self - healing hydrogen - bond - lithium - bond double - network intrinsically conductive elastomer;

[0036] Figure 4(c) shows the energy dissipation curve of the prepared self - healing hydrogen - bond - lithium - bond double - network intrinsically conductive elastomer;

[0037] Figure 4(d) shows the yield strain diagram of the prepared self - healing hydrogen - bond - lithium - bond double - network intrinsically conductive elastomer;

[0038] Figure 5 The self - healing process of the prepared self - healing hydrogen - bond - lithium - bond double - network intrinsically conductive elastomer is shown as follows: a) - b) is the self - healing process of the electrical properties of the conductive elastomer; c) is the repair time of the electrical properties of the conductive elastomer; d) is the change in resistance during multiple electrical property repairs of the conductive elastomer. Detailed implementation manners

[0039] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, and do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept of the present invention, several deformations and improvements can be made. These all belong to the protection scope of the present invention.

[0040] For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For those reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0041] Example 1: The preparation method of the self - healing hydrogen - bond - lithium - bond double - network intrinsically conductive elastomer in this example is achieved through the following steps:

[0042] Step 1: Preparation of the conductive elastomer precursor solution:

[0043] 1) Add 16.1 g of choline chloride to a cup containing 16.1 g of acrylic acid, and stir evenly at 80 °C at a speed of 1000 revolutions per minute;

[0044] 2) Add 3.2 g of phytic acid to the mixed solution in step 1) and stir evenly at a speed of 1000 revolutions per minute;

[0045] 3) Add 1.77 g of lithium bis(trifluoromethanesulfonyl)imide to the mixed solution in step 2) and stir evenly at a speed of 1000 revolutions per minute; to obtain the conductive elastomer precursor solution;

[0046] Step 2: Preparation of the conductive elastomer:

[0047] Add 0.391 g of polyethylene glycol diacrylate and 0.518 g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone to the conductive elastomer precursor solution obtained in Step 1, stir evenly at a speed of 1000 revolutions per minute, and then pour it into a polytetrafluoroethylene mold. Use ultraviolet irradiation of 20 mW / cm 2 for 10 minutes to obtain a hydrogen bond-lithium bond double network intrinsic conductive elastomer.

[0048] Example 2: The preparation method of the self-healing hydrogen bond-lithium bond double network intrinsic conductive elastomer in this example is achieved through the following steps:

[0049] Step 1: Preparation of the conductive elastomer precursor solution:

[0050] 1) Add 15.1 g of choline chloride to 16.3 g of acrylic acid in a beaker, and stir evenly at a speed of 1000 revolutions per minute at 85 °C;

[0051] 2) Add 3.2 g of phytic acid to the mixed solution in Step 1, and stir evenly at a speed of 1000 revolutions per minute;

[0052] 3) Add 3.46 g of lithium bis(trifluoromethanesulfonyl)imide to the mixed solution in Step 2, and stir evenly at a speed of 1000 revolutions per minute; to obtain the conductive elastomer precursor solution;

[0053] Step 2: Preparation of the conductive elastomer:

[0054] Add 0.425 g of polyethylene glycol diacrylate and 0.628 g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone to the conductive elastomer precursor solution obtained in Step 1, and stir evenly at a speed of 1000 revolutions per minute. Then pour it into a polytetrafluoroethylene mold. Use ultraviolet irradiation of 30 mW / cm 2 for 20 minutes to obtain a hydrogen bond-lithium bond double network intrinsic conductive elastomer.

[0055] Example 3: The preparation method of the self-healing hydrogen bond-lithium bond double network intrinsic conductive elastomer in this example is achieved through the following steps:

[0056] Step 1: Preparation of the conductive elastomer precursor solution:

[0057] 1) Add 16 g of choline chloride to 21 g of acrylic acid in a beaker, and stir evenly at a speed of 1000 revolutions per minute at 70 °C;

[0058] 2) Add 2.2 g of phytic acid to the mixed solution in Step 1, and stir evenly at a speed of 1000 revolutions per minute;

[0059] 3) Add 5.88 g of lithium bis(trifluoromethanesulfonyl)imide to the mixed solution in step 2), and stir evenly at a speed of 1000 revolutions per minute; obtain a conductive elastomer precursor solution;

[0060] Step 2: Preparation of the conductive elastomer:

[0061] Add 0.633 g of polyethylene glycol diacrylate and 0.917 g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone to the conductive elastomer precursor solution obtained in step 1), and stir evenly at a speed of 1000 revolutions per minute. Subsequently, pour it into a polytetrafluoroethylene mold and irradiate it with ultraviolet light of 45 mW / cm 2 for 17 minutes to obtain a hydrogen bond-lithium bond double network intrinsic conductive elastomer.

[0062] Example 4: In this example, the preparation method of the self-healing hydrogen bond-lithium bond double network intrinsic conductive elastomer is achieved through the following steps:

[0063] Step 1: Preparation of the conductive elastomer precursor solution:

[0064] 1) Add 14 g of choline chloride and 14 g of acrylic acid to a beaker, and stir evenly at 90 °C at a speed of 1000 revolutions per minute;

[0065] 2) Add 1.9 g of phytic acid to the mixed solution in step 1), and stir evenly at a speed of 1000 revolutions per minute;

[0066] 3) Add 5.98 g of lithium bis(trifluoromethanesulfonyl)imide to the mixed solution in step 2), and stir evenly at a speed of 1000 revolutions per minute; obtain a conductive elastomer precursor solution;

[0067] Step 2: Preparation of the conductive elastomer:

[0068] Add 0.457 g of polyethylene glycol diacrylate and 0.711 g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone to the conductive elastomer precursor solution obtained in step 1), and stir evenly at a speed of 1000 revolutions per minute. Subsequently, pour it into a polytetrafluoroethylene mold and irradiate it with ultraviolet light of 50 mW / cm 2 for 30 minutes to obtain a hydrogen bond-lithium bond double network intrinsic conductive elastomer.

[0069] Perform polarized light microscopy observations on the self-healing hydrogen bond-lithium bond double network intrinsic conductive elastomers prepared in Examples 1, 2, 3, and 4 (see Figure 1) The results showed that the addition of lithium bis(trifluoromethanesulfonyl)imide did not cause agglomeration, indicating that the lithium salt was uniformly distributed in the elastomer in ionic form. However, when the content of lithium bis(trifluoromethanesulfonyl)imide was too high, the lithium salt could not dissolve further in the acrylic resin, resulting in precipitation and the appearance of black particles on the surface.

[0070] The self-healing hydrogen bond-lithium bond double-network intrinsic conductive elastomers prepared in Examples 1, 2, 3, and 4 were observed using a scanning electron microscope on the same samples (see Figure 2 ). The results showed that when the addition amount of lithium bis(trifluoromethanesulfonyl)imide was small, the surface of the conductive elastomer was relatively smooth; as the content of the lithium salt increased, a small amount of wrinkles appeared on the surface. The reason is that lithium bis(trifluoromethanesulfonyl)imide exists in the form of lithium bonds, and the relatively high bond energy of the lithium bonds leads to an increase in the number of lithium bonds, increasing the cohesion within the ACPL conductive elastomer, thus resulting in the formation of surface wrinkles.

[0071] The conductive elastomers with different addition amounts of lithium bis(trifluoromethanesulfonyl)imide prepared in Examples 1, 2, 3, and 4 were tested for alternating current impedance between 1 - 10 5 Hz using an impedance meter ( Figure 3 a), and its conductivity at 50 Hz was calculated in detail ( Figure 3 b). It can be seen from the figure that the addition of lithium bis(trifluoromethanesulfonyl)imide has a positive effect on the conductivity of the conductive elastomer. The reason for the increase in conductivity is that the lithium bonds construct an ion transport channel inside the ACPL conductive elastomer, better transporting the movement of ions, increasing the number of effectively transported ions, thus leading to an increase in conductivity;

[0072] The conductive elastomers with different addition amounts of lithium bis(trifluoromethanesulfonyl)imide in Examples 1, 2, 3, and 4 were subjected to a strain continuous tensile test (see Figure 4). The results in Figure 4 showed that as the strain increased, the hysteresis loop of the conductive elastomer also gradually increased, indicating that during the stretching-recovery process, external energy was consumed through the elastomer structure. The stronger the energy dissipation, the better the ductility of the elastomer. The excellent deformation ability of the conductive elastomer stems from the internal dense hydrogen bond and lithium bond synergistic cross-linking network. The two dynamic reversible bonds break and recombine rapidly inside the polymer, helping the polymer dissipate the externally applied energy more effectively. By calculating the ratio of the dissipated energy (U) to the fracture energy (W), it can be seen that at a strain of 250%, the U / W ratio shows an inflection point, indicating that there are two energy dissipation mechanisms in the conductive elastomer, and at this strain, the fracture-recombination mechanisms of hydrogen bonds and lithium bonds reach the limit of energy dissipation.

[0073] The conductive elastomers with different addition amounts of lithium bis(trifluoromethanesulfonyl)imide in Examples 1, 2, 3, and 4 were tested for the conductance self-healing performance ( Figure 5 ). At Figure 5In it, the conductive elastomer is connected in series to the circuit. After being cut off, the circuit is disconnected and the small light bulb goes out. Subsequently, the cut is aligned, the circuit is quickly restored, and the small light bulb lights up, indicating that the conductive path has been repaired. During the experiment, the change in resistance was monitored in real time by a high-precision picoammeter (see Figure 5 c). The results show that when the conductive elastomer is cut off, the resistance increases sharply, and after the cut is aligned, it only takes 116 milliseconds for the resistance to return to its original value. The cut not only contains abundant dynamic hydrogen bonds but also is rich in lithium bonds, and lithium ions can quickly participate in ionic conductance transport. Therefore, the conductive elastomer has excellent conductance repair ability.

[0074] The specific embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A method for preparing a self-repairing hydrogen bond-lithium bond double network intrinsic conductive elastomer, characterized in that: The following steps are involved: Step 1, adding choline chloride to acrylic acid, stirring evenly at a certain temperature, adding phytic acid, stirring evenly, to obtain a mixed solution; Step 2, then add lithium bis(trifluoromethanesulfonyl imide) and stir evenly; Step 3: then add a crosslinking agent and an initiator, stir evenly, pour into a mold, and irradiate with ultraviolet light to obtain the conductive elastomer.

2. The method according to claim 1, characterized in that: The molar ratio of choline chloride to acrylic acid is (0.1-0.5):

1.

3. The method according to claim 1, characterized in that: Stir at 70℃~90℃.

4. The method according to claim 1, characterized in that: The mass ratio of phytic acid to acrylic acid is (0.1-0.3):

1.

5. The method according to claim 1, characterized in that: The mass ratio of lithium bis(trifluoromethanesulfonyl)imide to the mixed solution is (0.01-0.4):

1.

6. The method according to claim 1, characterized in that: The crosslinking agent is one or a combination of polyethylene glycol diacrylate, polyacrylate diacrylate, and polyacrylic acid diacrylate, and the molar ratio of the crosslinking agent to acrylic acid is (0.01-0.04):

1.

7. The method according to claim 1, characterized in that: The initiator is one or a combination of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2,2'-diphenyl-2-propanone, and 2,4,6-trimethylphenylphenone, and the molar ratio of the initiator to acrylic acid is (0.01-0.04):

1.

8. The method according to claim 1, characterized in that: Intensity: 5mW / cm 2 ~50mW / cm 2 Expose to ultraviolet light for 10 to 30 minutes.

9. The method according to claim 1, characterized in that: Stir at a speed of 1000rpm-2000rpm.

10. A self-healing hydrogen bond-lithium bond double network intrinsic conductive elastomer prepared by the method according to any one of claims 1 to 9.

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