Conductive elastomer and preparation method and application thereof

Abstract

The invention discloses a preparation method of a conductive elastomer. The preparation method comprises the following steps: (1) mixing N-hydroxyethyl acrylamide, glycerol and choline chloride, heating and stirring to obtain a clear and transparent solution A; (2) adding furfuryl methacrylate and N, N '-(4, 4'-methylene diphenyl) bismaleimide into the solution A prepared in the step (1), heating and stirring to obtain a clear and transparent solution B; (3) adding a photoinitiator into the solution B prepared in the step (2), and stirring in a dark place to obtain a clear and transparent solution C; and (4) pouring the solution C prepared in the step (3) into a mold, and performing in-situ polymerization under ultraviolet irradiation to obtain the conductive elastomer. The conductive elastomer has excellent mechanical strength and toughness.

Description

Technical Field

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

[0002] With the wide application of flexible electronic devices in multiple fields, the demand for flexible conductive materials is increasing day by day. The application range of hydrogels is limited due to their poor stability at high or low temperatures, while most of the ionic liquids required for the preparation of ion gels are costly and potentially toxic, which limits their large-scale application. Therefore, it is particularly important to develop a new type of flexible conductive material with low cost, low toxicity, and high performance.

[0003] As an emerging flexible conductive material, polymerizable deep eutectic solvent-based ionic conductive elastomers not only have the characteristics of strong thermal stability and low toxicity, but also show great potential in conductivity, transparency, etc. However, their mechanical strength and toughness are poor and cannot meet the needs of some high-strength scenarios. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a conductive elastomer, a preparation method thereof, and an application thereof, and the conductive elastomer has excellent mechanical strength and toughness.

[0005] The above technical object of the present invention is achieved by the following technical solutions:

[0006] A preparation method of a conductive elastomer, comprising the following steps:

[0007] (1) Mix N-hydroxyethyl acrylamide, glycerol, and choline chloride, and then heat and stir to obtain a clear and transparent solution A;

[0008] (2) Add furfuryl methacrylate and N,N'-(4,4'-methylenediphenyl) bismaleimide to the solution A prepared in step (1), and heat and stir to obtain a clear and transparent solution B;

[0009] (3) Add a photoinitiator to the solution B prepared in step (2), and stir in the dark to obtain a clear and transparent solution C;

[0010] (4) Pour the solution C prepared in step (3) into a mold, and carry out in-situ polymerization under ultraviolet light irradiation to obtain a conductive elastomer.

[0011] Preferably, in step (1), the N-hydroxyethyl acrylamide, the glycerol, and the choline chloride are mixed according to a molar ratio of (2.5-3.5):(0.3-0.8):1.

[0012] Preferably, in step (1), the temperature of the heating and stirring is 60-90°C, and the time of the heating and stirring is 0.5-1 h.

[0013] Preferably, in step (2), the molar ratio of the addition amounts of furfuryl methacrylate and N,N'-(4,4'-methylenediphenyl)bismaleimide is (2-5):1, and the addition amount of furfuryl methacrylate is 0.1-1.5 mol% of N-hydroxyethylacrylamide in solution A.

[0014] Preferably, in step (2), the temperature of the heating and stirring is 70-80°C, and the time of the heating and stirring is 6-8 h.

[0015] Preferably, in step (3), the photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone.

[0016] Preferably, in step (3), the addition amount of the photoinitiator is 0.1-0.5 mol% of N-hydroxyethylacrylamide in solution B.

[0017] Preferably, in step (4), the power of the ultraviolet light is 100-300 W, the height of the ultraviolet light source from the mold is 10-15 cm, and the irradiation time is 1-2 min.

[0018] Preferably, in step (4), the mold is a silicone gasket, and its specifications are: length 20-100 mm, width 5-30 mm, and thickness 0.5-5 mm.

[0019] A conductive elastomer is prepared by the preparation method as described above.

[0020] Application of the conductive elastomer as described above in a flexible strain sensor.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) The first aspect of the present invention starts from the "one-pot method" design principle, utilizes the solvent property of the polymerizable deep eutectic solvent, and prepares a crosslinking agent containing Diels-Alder bonds therein. The crosslinking agent can be uniformly dissolved in the polymerizable deep eutectic solvent and can be directly crosslinked into the polymer network by in-situ ultraviolet light polymerization. It overcomes the disadvantage that most current flexible conductive materials need to introduce and remove additional solvents (such as tetrahydrofuran, N,N-dimethylformamide) when introducing Diels-Alder bond crosslinking.

[0023] (2) The second aspect of the present invention is the preparation of a Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomer. The inventor creatively proposed to enhance the mechanical properties and mechanical toughness of the polymerizable deep eutectic solvent-based ionic conductive elastomer through Diels-Alder bonds, getting rid of the dilemma that the mechanical properties of the polymerizable deep eutectic solvent-based ionic conductive elastomer enhanced by hydrogen bonds have not been improved much. The preparation process of this ionic conductive elastomer is simple, and it exhibits high mechanical strength, high transparency, good electrical conductivity and thermal stability.

[0024] (3) The third aspect of the present invention is that all experimental materials used are common chemical industrial raw materials and do not require further chemical treatment; the preparation process of the Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomer uses in-situ ultraviolet photopolymerization, which is environmentally friendly and efficient.

[0025] (4) The fourth aspect of the present invention is that the Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomer can be used for timely monitoring and response to different human motion conditions. Description of the Drawings

[0026] Figure 1 Stress-strain curves of the Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomers DA-ICE0, DA-ICE 0.25 、DA-ICE 0.50 、DA-ICE 0.75 and DA-ICE 1.00 ;

[0027] Figure 2 Optical property diagrams of the Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomers DA-ICE0, DA-ICE 0.25 、DA-ICE 0.50 、DA-ICE 0.75 and DA-ICE 1.00 ;

[0028] Figure 3 Electrical conductivity diagrams of the Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomer;

[0029] Figure 4 Infrared spectra of the polymerizable deep eutectic solvent and the mixed solution;

[0030] Figure 5 Thermal stability diagrams of the Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomer;

[0031] Figure 6Figure a in shows the relative resistance change diagram of a wearable strain sensor assembled with a Diels-Alder bond-crosslinked polymerizable deep eutectic solvent-based ion conductive elastomer for monitoring and responding to regular finger bending and stretching. Figure b shows the relative resistance change diagram of a wearable strain sensor assembled with a Diels-Alder bond-crosslinked polymerizable deep eutectic solvent-based ion conductive elastomer for monitoring and responding to the movement of the elbow. Detailed implementation mode

[0032] The present invention will be further described below in conjunction with specific embodiments.

[0033] Example 1:

[0034] A preparation method of a conductive elastomer includes the following steps:

[0035] (1) Preparation of polymerizable deep eutectic solvents (PDESs): Mix N-hydroxyethyl acrylamide (HEAA), glycerol (Gly), and choline chloride (ChCl) in a molar ratio of 3:0.5:1 and add them to a flat-bottomed flask. Stir at 75 °C for 30 min to obtain a clear and transparent solution of PDESs. Keep the prepared PDESs in a vacuum desiccator for later use.

[0036] (2) Preparation of a prepolymer solution: Add furfuryl methacrylate (FMA) and N,N'-(4,4'-methylenediphenyl) bismaleimide (BIM) to the obtained clear and transparent solution of PDESs. Stir at 75 °C for 6 h to obtain a clear and transparent prepolymer solution. The addition amount of FMA is 0.375 mol% of HEAA, and the addition amount of BIM is 0.250 mol% of HEAA.

[0037] (3) Preparation of a Diels-Alder bond-crosslinked polymerizable deep eutectic solvent-based ion conductive elastomer: Add a photoinitiator, 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone, to the obtained clear and transparent prepolymer solution. After stirring evenly in the dark at room temperature of 25 °C, inject the solution into a silicone mold clamped by double-layer glass plates and carry out in-situ polymerization under ultraviolet light irradiation to obtain a Diels-Alder bond-crosslinked polymerizable deep eutectic solvent-based ion conductive elastomer, denoted as DA-ICE 0.25 . The addition amount of the photoinitiator is 0.1 mol% of HEAA, the ultraviolet light irradiation time is 2 min, the model of the ultraviolet light source device is RW-UVA-Φ200U type, the power is 200 W, and the height of the ultraviolet lamp from the silicone mold is 15 cm.

[0038] Example 2:

[0039] A preparation method of a conductive elastomer includes the following steps:

[0040] (1) Preparation of polymerizable deep eutectic solvents (PDESs): N - hydroxyethyl acrylamide (HEAA), glycerol (Gly), and choline chloride (ChCl) were mixed in a molar ratio of 3:0.5:1 and added to a flat - bottom flask. The mixture was stirred at 75 °C for 30 min to obtain a clear and transparent solution of PDESs. The prepared PDESs were stored in a vacuum desiccator for subsequent use.

[0041] (2) Preparation of prepolymer solution: Furfuryl methacrylate (FMA) and N,N' - (4,4' - methylenediphenyl) bismaleimide (BIM) were added to the obtained clear and transparent solution of PDESs. The mixture was stirred at 75 °C for 6 h to obtain a clear and transparent prepolymer solution. The addition amount of FMA was 0.750 mol% of HEAA, and the addition amount of BIM was 0.500 mol% of HEAA.

[0042] (3) Preparation of Diels - Alder cross - linked polymerizable deep - eutectic - solvent - based ionic conductive elastomer: Photoinitiator 2 - hydroxy - 4′ - (2 - hydroxyethoxy) - 2 - methylpropiophenone was added to the obtained clear and transparent prepolymer solution. After stirring evenly in the dark at room temperature (25 °C), the solution was injected into a silicone mold clamped by double - layer glass plates and subjected to in - situ polymerization under ultraviolet light irradiation to obtain a Diels - Alder cross - linked polymerizable deep - eutectic - solvent - based ionic conductive elastomer, denoted as DA - ICE 0.50 . The addition amount of the photoinitiator was 0.1 mol% of HEAA, the ultraviolet light irradiation time was 2 min, the model of the ultraviolet light source device was RW - UVA - Φ200U, the power was 200 W, and the height of the ultraviolet lamp from the silicone mold was 15 cm.

[0043] Example 3:

[0044] A preparation method of a conductive elastomer, comprising the following steps:

[0045] (1) Preparation of polymerizable deep eutectic solvents (PDESs): N - hydroxyethyl acrylamide (HEAA), glycerol (Gly), and choline chloride (ChCl) were mixed in a molar ratio of 3:0.5:1 and added to a flat - bottom flask. The mixture was stirred at 75 °C for 30 min to obtain a clear and transparent solution of PDESs. The prepared PDESs were stored in a vacuum desiccator for subsequent use.

[0046] (2) Preparation of the prepolymer solution: Furfuryl methacrylate (FMA) and N,N'-(4,4'-methylenediphenyl) bismaleimide (BIM) were added to the prepared clear and transparent solution PDESs, and stirred at 75 °C for 6 h to obtain a clear and transparent prepolymer solution. The addition amount of FMA was 1.125 mol% of HEAA, and the addition amount of BIM was 0.750 mol% of HEAA.

[0047] (3) Preparation of the Diels-Alder bond-crosslinked polymerizable deep eutectic solvent-based ion conductive elastomer: Photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone was added to the prepared clear and transparent prepolymer solution. After stirring evenly in the dark at room temperature of 25 °C, the solution was injected into a silicone mold clamped by double-layer glass plates and in-situ polymerized under ultraviolet light irradiation to obtain the Diels-Alder bond-crosslinked polymerizable deep eutectic solvent-based ion conductive elastomer, denoted as DA-ICE 0.75 . The addition amount of the photoinitiator was 0.1 mol% of HEAA, the ultraviolet light irradiation time was 2 min, the model of the ultraviolet light source device was RW-UVA-Φ200U type, the power was 200 W, and the height of the ultraviolet lamp from the silicone mold was 15 cm.

[0048] Example 4:

[0049] A preparation method of a conductive elastomer, comprising the following steps:

[0050] (1) Preparation of the polymerizable deep eutectic solvent (PDESs): N-Hydroxyethyl acrylamide (HEAA), glycerol (Gly), and choline chloride (ChCl) were mixed in a molar ratio of 3:0.5:1 and added to a flat-bottomed flask, and stirred at 75 °C for 30 min to obtain a clear and transparent solution PDESs. The prepared PDESs was stored in a vacuum desiccator for subsequent use.

[0051] ((2) Preparation of the prepolymer solution: Furfuryl methacrylate (FMA) and N,N'-(4,4'-methylenediphenyl) bismaleimide (BIM) were added to the prepared clear and transparent solution PDESs, and stirred at 75 °C for 6 h to obtain a clear and transparent prepolymer solution. The addition amount of FMA was 0.150 mol% of HEAA, and the addition amount of BIM was 1.000 mol% of HEAA.

[0052] (3) Preparation of Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomer: Add photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone to the prepared clear and transparent prepolymer solution. After stirring evenly in the dark at room temperature (25 °C), inject the solution into a silicone mold clamped by double-layer glass plates and carry out in-situ polymerization under ultraviolet light irradiation to obtain a Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomer, denoted as DA-ICE. 1.00 The addition amount of the photoinitiator is 0.1 mol% of HEAA, the ultraviolet light irradiation time is 2 min, the model of the ultraviolet light source device is RW-UVA-Φ200U type, the power is 200 W, and the height of the ultraviolet lamp from the silicone mold is 15 cm.

[0053] Comparative Example 1:

[0054] A preparation method of a conductive elastomer includes the following steps:

[0055] (1) Preparation of polymerizable deep eutectic solvents (PDESs): Mix N-hydroxyethyl acrylamide (HEAA), glycerol (Gly), and choline chloride (ChCl) in a molar ratio of 3:0.5:1 and add them to a flat-bottomed flask. Stir at 75 °C for 30 min to obtain a clear and transparent solution of PDESs. Store the prepared PDESs in a vacuum desiccator for subsequent use.

[0056] (2) Preparation of prepolymer solution: Add furfuryl methacrylate (FMA) and N,N'-(4,4'-methylenediphenyl) bismaleimide (BIM) to the prepared clear and transparent solution of PDESs. Stir at 75 °C for 6 h to obtain a clear and transparent prepolymer solution. The addition amount of FMA is 0 mol% of HEAA, and the addition amount of BIM is 0 mol% of HEAA.

[0057] (3) Preparation of Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomer: Add photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone to the prepared clear and transparent prepolymer solution. After stirring evenly in the dark at room temperature (25 °C), inject the solution into a silicone mold clamped by double-layer glass plates and carry out in-situ polymerization under ultraviolet light irradiation to obtain a Diels-Alder crosslinked polymerizable deep eutectic solvent-based ionic conductive elastomer, denoted as DA-ICE0. The addition amount of the photoinitiator is 0.1 mol% of HEAA, the ultraviolet light irradiation time is 2 min, the model of the ultraviolet light source device is RW-UVA-Φ200U type, the power is 200 W, and the height of the ultraviolet lamp from the silicone mold is 15 cm.

[0058] Test Example:

[0059] Performance Testing of Diels-Alder Bond Crosslinked Polymerizable Deep Eutectic Solvent-Based Ionic Conductive Elastomers:

[0060] (1) Mechanical Property Characterization: At room temperature, a stress-strain tensile curve test was carried out using an INSTRON 5565 material testing machine (500N sensor). The tensile speed was set at 10 mm / min. The samples were cut into long strip shapes: 50 mm in length, 10 mm in width, and 1 mm in thickness. The toughness of the material was calculated by integrating the stress-strain curve.

[0061] (2) Optical Property Characterization: Optical pictures were taken by a camera; optical property curves were obtained by testing with a UV-2600i ultraviolet-visible spectrophotometer. The scanning wavelength range was 200 - 800 nm, the scanning speed was fast, air was used as the reference, and the temperature condition was 25°C.

[0062] (3) Conductive Property Pictures: Pictures of the conductive elastomer were taken by a camera when the circuit was connected.

[0063] (4) Infrared Spectroscopy (FTIR) Test: Fourier transform infrared spectra were measured by an ATR-FTIR spectrometer. The scanning range was 400 - 4000 cm -1 , the resolution was 0.09 cm -1 , the number of scans was 64 times, and the temperature condition was 25°C.

[0064] (5) Thermal Stability Test: A ceramic crucible was weighed at room temperature, and 5 - 10 mg of the sample was placed in a thermogravimetric analyzer (TG209F3). The test temperature was 40 - 600°C; the heating rate was 10°C / min; the test environment was nitrogen.

[0065] (6) Sensing Property Test: The elastomer has intrinsic conductivity and intrinsic stretchability. It was fixed on different parts of the human body, and the elastomer was connected to a digital source meter (Keithley DMM7510) through a wire to assemble a flexible strain sensor. The digital source meter was used to measure the relative resistance (ΔR / R0) change of the elastomer in real time under different stretching ratios and different human movements. The test temperature was 25°C, and the humidity was 30 - 35%.

[0066] In the present invention, Diels-Alder bonds are used to crosslink polymerizable deep eutectic solvent-based ionic conductive elastomers, significantly enhancing the mechanical properties of the elastomers, such as Figure 1As shown, with the introduction of the Diels-Alder bond crosslinker, the mechanical properties of the ion-conductive elastomer are significantly improved. In particular, the maximum stress increases by more than twofold, and the mechanical toughness is also significantly enhanced. In addition, as the amount of the crosslinker added increases, the maximum stress and maximum strain of the material decrease, which is due to excessive crosslinking inside the material. The specific mechanical property parameters are shown in Table 1.

[0067] Table 1:

[0068] Test Item Maximum Stress (MPa) Maximum Strain (%) <![CDATA[Toughness (MJ m -3 )]]> Comparative Example 1 6.61 567 20.77 Example 1 15.31 572 52.24 Example 2 15.56 509 40.48 Example 3 14.59 362 27.78 Example 4 14.82 341 26.25

[0069] The Diels-Alder bond-crosslinked polymerizable deep eutectic solvent-based ion-conductive elastomer of the present invention has good optical properties. As shown in Figure 2 (a), the prepared ion-conductive elastomers all show good light transmittance outdoors. As can be seen from Figure 2 (b), the Diels-Alder bond-crosslinked polymerizable deep eutectic solvent-based ion-conductive elastomer exhibits a high transparency of more than 92% within the visible light range.

[0070] The Diels-Alder bond-crosslinked polymerizable deep eutectic solvent-based ion-conductive elastomer of the present invention has intrinsic conductivity and can keep the circuit in a conductive state in a circuit connected in series with a small light bulb. After the power is turned on, the small light bulb can emit light stably, as shown in Figure 3 .

[0071] In order to verify the successful preparation of the polymerizable deep eutectic solvent and the successful synthesis of the Diels-Alder bond crosslinker in the prepolymer solution, an ATR-FTIR spectrometer was used to measure the corresponding test samples. Figure 4 (a) is the infrared spectrum of HEAA, ChCl, Gly, and the mixed solution after heating and stirring. It can be seen that HEAA has an obvious carbonyl characteristic peak at 1654 cm -1 , the characteristic peak of the carbon-carbon double bond is at 1625 cm -1 , and the characteristic peak of the hydroxyl group is near 3300 cm -1 . In the FTIR curve of the mixed solution of the three components, the corresponding infrared characteristic peaks of each component can be found, and no new functional group characteristic peaks are generated, indicating that no chemical reaction occurs between the components during the preparation process. In Figure 4 (b), the absorption peak at 2964 cm -1 of the FMA curve corresponds to the C―H stretching vibration on the furan ring, and 1503 cm -1 is the characteristic absorption peak of the C=C stretching vibration on the furan ring; in the infrared spectrum of BMI, 1708 cm -1 is the stretching vibration peak of C=O on the imide; in the infrared spectrum of the prepolymer solution, 1714 cm -1An obvious characteristic absorption peak of the DA adduct appears, while other characteristic absorption peaks of FMA and BMI still exist, indicating the successful synthesis of the Diels-Alder crosslinking agent.

[0072] The polymerizable deep eutectic solvent-based ionic conductive elastomer crosslinked by the Diels-Alder bond of the present invention has good thermal stability. As Figure 5 shown, the mass loss is very small in the range of 0-150 °C. The mass loss during this period is mainly due to the small amount of moisture absorbed by the elastomer in the air. The material shows good thermal stability and can meet the use requirements of conventional flexible conductive materials.

[0073] In addition, when the polymerizable deep eutectic solvent-based ionic conductive elastomer crosslinked by the Diels-Alder bond is assembled into a wearable strain sensor, it can monitor and respond to different human movements in a timely manner. As Figure 6 shown, where Figure 6 (a) When the finger bends and stretches regularly, the sensor can regularly show a relative resistance change of about 20%. Figure 6 (b) When it is applied to the motion monitoring of the elbow, it can also output a stable signal, indicating that the sensor has excellent sensing performance.

[0074] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a conductive elastomer, characterized in that: The following steps are involved: (1) N-hydroxyethyl acrylamide, glycerol, and choline chloride are mixed, heated, and stirred to obtain a clear and transparent solution A; (2) adding furfuryl methacrylate and N,N'-(4,4'-methylenediphenyl)bismaleimide to the solution A prepared in step (1), heating and stirring to obtain a clear and transparent solution B; (3) adding a photoinitiator to the solution B obtained in step (2), stirring in the dark to obtain a clear and transparent solution C; (4) Pour the solution C obtained in step (3) into a mold and perform in-situ polymerization under ultraviolet light to obtain a conductive elastomer.

2. The preparation method of a conductive elastomer according to claim 1, wherein: In step (1), the N-hydroxyethyl acrylamide, the glycerol and the choline chloride are mixed in a molar ratio of (2.5-3.5):(0.3-0.8):

1.

3. The preparation method of a conductive elastomer according to claim 1, characterized in that: In step (1), the temperature of the heating and stirring is 60-90° C., and the time of the heating and stirring is 0.5-1 h.

4. The preparation method of a conductive elastomer according to claim 1, wherein: In step (2), the molar ratio of furfuryl methacrylate to N,N'-(4,4'-methylenediphenyl)bismaleimide is (2-5):1, and the amount of furfuryl methacrylate added is 0.1-1.5 mol% of N-hydroxyethyl acrylamide in solution A.

5. The preparation method of a conductive elastomer according to claim 1, wherein: In step (2), the temperature of the heating and stirring is 70-80° C., and the time of the heating and stirring is 6-8 h.

6. The preparation method of a conductive elastomer according to claim 1, characterized in that: In step (3), the photoinitiator is 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone.

7. The preparation method of a conductive elastomer according to claim 1, characterized in that: In step (3), the amount of the photoinitiator added is 0.1-0.5 mol% of the N-hydroxyethyl acrylamide in the solution B.

8. The preparation method of a conductive elastomer according to claim 1, characterized in that: In step (4), the power of the ultraviolet light is 100-300W, the height of the ultraviolet light source from the mold is 10-15 cm, and the irradiation time is 1-2 min.

9. A conductive elastomer, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the conductive elastomer according to claim 9 in a flexible strain sensor.

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