Preparation method of transparent self-healing polysiloxane dielectric elastomer composite material

Abstract

The present invention discloses a method for preparing a transparent self-healing polysiloxane dielectric elastomer composite material. First, aminopolysiloxane and ionic liquid are dissolved in tetrahydrofuran (THF) respectively, and after mixing, an aminopolysiloxane solution in which the ionic liquid is uniformly dispersed is obtained; an epoxy crosslinker and an isocyanate dimer are dissolved in THF respectively, and after mixing, a mixed solution of the epoxy crosslinker and the isocyanate dimer is obtained; the mixed solution of the epoxy crosslinker and the isocyanate dimer is added to the aminopolysiloxane solution in which the ionic liquid is uniformly dispersed and fully reacted, and then the reacted solution is poured into a polytetrafluoroethylene mold and cured under vacuum to obtain a transparent self-healing polysiloxane dielectric elastomer composite material. The above method can prepare a dielectric elastomer with high transmittance, high dielectric constant, low modulus, and the ability to quickly self-heal under mild conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric elastomers, and in particular to a method for preparing a transparent self-healing polysiloxane dielectric elastomer composite material. Background Art

[0002] Dielectric elastomers are electroactive polymers with advantages such as fast response, high strain output, and high energy density. A dielectric elastomer actuator, consisting of a dielectric elastomer film and flexible electrodes coated on either side, can produce muscle-like contraction and relaxation in response to external electrical stimulation. This has broad application prospects in artificial muscles, energy harvesting, and flexible electronics.

[0003] Silicone rubber has become the main raw material for preparing dielectric elastomer actuators due to its excellent chemical stability, flexibility, electrical insulation, and biocompatibility. However, the low dielectric constant of silicone rubber requires a high driving voltage to achieve a large driving strain, which seriously limits its practical application. Although filling a silicone rubber matrix with a high dielectric constant filler can effectively increase the dielectric constant of the composite material, it often comes at the cost of an increase in the material's elastic modulus and a decrease in transparency, which is not conducive to its application in soft robotics, tunable optics, and other aspects. In addition, silicone rubber does not have self-healing properties. Once mechanical damage or electrical breakdown occurs, it cannot be reused and must be discarded, which is not conducive to its long-term stable use. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a transparent self-healing polysiloxane dielectric elastomer composite material. This method achieves the compatibility of high transmittance, excellent self-healing performance, high dielectric constant, and low elastic modulus of the dielectric elastomer through molecular structure design and regulation. The synthesis process is mild and the operation is simple.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a transparent self-healing polysiloxane dielectric elastomer composite material, the method comprising:

[0007] Step 1, dissolving the aminopolysiloxane and the ionic liquid in tetrahydrofuran (THF) respectively, and mixing them to obtain an aminopolysiloxane solution in which the ionic liquid is uniformly dispersed;

[0008] Step 2, dissolving the epoxy crosslinking agent and the isocyanate dimer in THF respectively, and mixing them to obtain a mixed solution of the epoxy crosslinking agent and the isocyanate dimer;

[0009] Step 3: Add the mixed solution in step 2 to the aminopolysiloxane solution in which the ionic liquid is uniformly dispersed in step 1. After sufficient reaction, pour the prepolymer obtained by the reaction into a polytetrafluoroethylene mold and cure it under vacuum to obtain a transparent self-healing polysiloxane dielectric elastomer composite material.

[0010] It can be seen from the technical solution provided by the present invention that the above method achieves the compatibility of high transmittance, excellent self-healing performance, high dielectric constant and low elastic modulus of the dielectric elastomer through molecular structure design and regulation, and the synthesis process is mild and simple to operate, demonstrating the great potential of this elastomer in the field of emerging flexible electronics and optical electronic equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0012] Figure 1 A schematic flow chart of a method for preparing a transparent self-healing polysiloxane dielectric elastomer composite material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0013] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments, and do not constitute a limitation of the present invention. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0014] like Figure 1 FIG2 is a flow chart of a method for preparing a transparent self-healing polysiloxane dielectric elastomer composite material provided by an embodiment of the present invention, wherein the method comprises:

[0015] Step 1, dissolving the aminopolysiloxane and the ionic liquid in tetrahydrofuran (THF) respectively, and mixing them to obtain an aminopolysiloxane solution in which the ionic liquid is uniformly dispersed;

[0016] In this step, 10-20 g of aminopolysiloxane is dissolved in 100 mL of THF and ultrasonically dispersed at 50 kHz for 30-60 min to form a uniformly dispersed aminopolysiloxane solution;

[0017] Dissolve 1-5 g of ionic liquid in 50 mL of THF and disperse ultrasonically at 50 kHz for 30-60 min to form an ionic liquid solution;

[0018] The ionic liquid solution and the aminopolysiloxane solution are mixed and stirred at room temperature for 30-60 minutes to obtain an aminopolysiloxane solution in which the ionic liquid is uniformly dispersed.

[0019] In a specific implementation, the aminopolysiloxane is one or both of a polysiloxane with amino groups at both ends and a polysiloxane with amino groups on the side chain, and the number average molecular weight is 2000-10000;

[0020] The ionic liquid is one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-1-methylpyrrolidine dicyanamide, trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide, and 1-ethyl-3-methylimidazolium acetate.

[0021] Step 2, dissolving the epoxy crosslinking agent and the isocyanate dimer in THF respectively, and mixing them to obtain a mixed solution of the epoxy crosslinking agent and the isocyanate dimer;

[0022] In this step, 0.05-0.5 g of epoxy crosslinker was dissolved in 10 mL of THF and ultrasonically dispersed at 50 kHz for 30-60 min to form a uniformly dispersed epoxy crosslinker solution;

[0023] Dissolve 0.05-0.5 g of isocyanate dimer in 10 mL of THF and disperse by ultrasonication at 50 kHz for 30-60 min to form a uniformly dispersed isocyanate dimer solution;

[0024] The epoxy crosslinking agent solution and the isocyanate dimer solution are mixed and stirred at room temperature for 30-60 minutes to obtain a mixed solution of the epoxy crosslinking agent and the isocyanate dimer.

[0025] In a specific implementation, the epoxy crosslinking agent is one or more of 1,4-butanediol diglycidyl ether, tris(2,3-epoxypropyl)isocyanurate, dioxirane and dibutylene oxide;

[0026] The isocyanate dimer is one or more of hexamethylene isocyanate dimer, isophorone isocyanate dimer and dicyclohexylmethane diisocyanate.

[0027] Step 3: Add the mixed solution in step 2 to the aminopolysiloxane solution in which the ionic liquid is uniformly dispersed in step 1. After sufficient reaction, pour the prepolymer obtained by the reaction into a polytetrafluoroethylene mold and cure it under vacuum to obtain a transparent self-healing polysiloxane dielectric elastomer composite material.

[0028] In this step, the mixed solution in step 2 is added to the aminopolysiloxane solution in which the ionic liquid is uniformly dispersed in step 1, and the mixture is stirred and reacted at 40-60°C for 1-3 hours. The prepolymer obtained by the reaction is then poured into a polytetrafluoroethylene mold and cured in a vacuum at 40-60°C to obtain a transparent self-healing polysiloxane dielectric elastomer composite material.

[0029] It can be seen from the above process scheme that during the preparation process, the amino group in the aminopolysiloxane reacts with the epoxy group in the epoxy crosslinker to generate a hydroxyl group, and at the same time, the isocyanate dimer introduces a urea bond into the molecular chain. The multiple hydrogen bonds formed between the molecular chains give the polysiloxane good self-healing properties; the anions in the ionic liquid have strong polarity and can form dipole-dipole interactions with the Si-O-Si segments in the aminopolysiloxane, and the cationic flexible alkyl chains in the ionic liquid have good compatibility with the aliphatic segments of the elastomer, which can achieve molecular-level dispersion of the ionic liquid in the aminopolysiloxane, thereby giving the elastomer composite material a high dielectric constant, and at the same time significantly reducing its elastomer modulus, ultimately obtaining a high-driving strain dielectric elastomer composite material with excellent self-healing properties.

[0030] It should be noted that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0031] The following describes the preparation process, mechanical properties, and electric drive performance of the composite material using a specific implementation case:

[0032] Implementation Case 1

[0033] (1) Dissolve 20 g of amino-terminated polysiloxane in 100 mL of THF and disperse under ultrasonication at 50 kHz for 30 min to form a homogeneous solution 1;

[0034] (2) 2 g of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt was dissolved in 10 mL of THF and ultrasonically dispersed at 50 kHz for 30 min to form a homogeneous solution 2;

[0035] (3) Solution 1 and solution 2 were mixed and stirred at room temperature for 30 min to form a homogeneous solution 3;

[0036] (4) 0.2 g of 1,4-butanediol diglycidyl ether was dissolved in 5 mL of THF and ultrasonically dispersed at 50 kHz for 30 min to form a homogeneous solution 4;

[0037] (5) 0.2 g of hexamethylene isocyanate dimer was dissolved in 5 mL of THF and ultrasonically dispersed at 50 kHz for 30 min to form a uniformly dispersed solution 5;

[0038] (6) Solution 4 and Solution 5 were mixed and stirred at room temperature for 1 h to form Solution 6;

[0039] (7) Solution 6 was added to solution 3, stirred at 60 °C for 3 h, poured into a polytetrafluoroethylene mold, and the solvent was evaporated at 60 °C in vacuum to obtain a transparent self-healing polysiloxane dielectric elastomer composite material.

[0040] The dielectric elastomer composite material prepared in step (7) was subjected to mechanical property testing at a tensile rate of 100 mm / min. The mechanical property self-healing test was performed by cutting the test specimen in the middle perpendicular to the tensile axis. The two fractured surfaces were then brought into close contact and repaired at room temperature for 1 hour. The mechanical property test was then repeated. The tensile test results are shown in Table 1 below.

[0041] The dielectric elastomer composite material prepared in step (7) was subjected to an electric drive performance test. The specific test method is: a circular flexible electrode with a diameter of 10 mm was sprayed on both sides of the dielectric elastomer film using a spray gun, and cured in a 60°C oven to form a dielectric elastomer actuator. A DC voltage was applied to the electrode, and a camera was used to record the change in the electrode area under electric field stimulation in real time. The planar electric drive strain of the dielectric elastomer was calculated by the formula S = (A-A0) / A0×100%, where A0 is the area of the electrode area when no electric field is applied, and A is the area under a certain electric field strength. The electric drive self-healing performance test was performed after the dielectric elastomer actuator was electrically broken down, repaired at room temperature for 1 hour, and then the electric drive performance test was performed again. The results of the electric drive performance test are shown in Table 1 below.

[0042] The dielectric elastomer composite material prepared in step (7) was subjected to a transmittance test. The transmittance was tested on a UV-visible spectrophotometer. The test sample thickness was 1 mm and the test was carried out at room temperature. The transmittance test results are shown in Table 1 below.

[0043] Implementation Case 2: The preparation method is the same as Implementation Case 1, except that the amount of 1,4-butanediol diglycidyl ether added in step (4) is 0.05 g. The prepared dielectric elastomer composite material is subjected to mechanical property tests, electric drive performance tests, and transmittance tests before and after self-healing. The test results are shown in Table 1.

[0044] Implementation Case 3: The preparation method is the same as Implementation Case 1, except that the amount of 1,4-butanediol diglycidyl ether added in step (4) is 0.5 g. The prepared dielectric elastomer composite material is subjected to mechanical property tests, electric drive performance tests, and transmittance tests before and after self-healing. The test results are shown in Table 1.

[0045] Implementation Case 4: The preparation method is the same as that of Implementation Case 1, except that the amount of 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt added in step (2) is 0.05 g. The prepared dielectric elastomer composite material was subjected to mechanical property tests, electric drive performance tests, and transmittance tests before and after self-healing. The test results are shown in Table 1.

[0046] Implementation Case 5. The preparation method is the same as Implementation Case 1, except that the amount of 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt added in step (2) is 0.5 g. The prepared dielectric elastomer composite material was subjected to mechanical property tests, electric drive performance tests, and transmittance tests before and after self-healing. The test results are shown in Table 1.

[0047] Implementation Case 6: The preparation method is the same as Implementation Case 1, except that the amount of hexamethylene isocyanate dimer added in step (5) is 0.05 g. The prepared dielectric elastomer composite material is subjected to mechanical property tests, electric drive performance tests, and transmittance tests before and after self-healing. The test results are shown in Table 1.

[0048] Implementation Case 7. The preparation method is the same as Implementation Case 1, except that the amount of hexamethylene isocyanate dimer added in step (5) is 0.5 g. The prepared dielectric elastomer composite material is subjected to mechanical property tests, electric drive performance tests, and transmittance tests before and after self-healing. The test results are shown in Table 1.

[0049] Example 8: The preparation method was the same as Example 1, except that the ionic liquid added in step (2) was 2 g of lithium bis(trifluoromethanesulfonylimide). The prepared dielectric elastomer composite was tested for mechanical properties and electrical drive performance before and after self-healing. The test results are shown in Table 1.

[0050] Example 9: The preparation method was the same as Example 1, except that 0.2 g of tris(2,3-epoxypropyl)isocyanurate was used as the epoxy crosslinking agent in step (4). The prepared dielectric elastomer composite was tested for mechanical properties, electrical drive performance, and transmittance before and after self-healing. The test results are shown in Table 1.

[0051] Implementation Case 10. The preparation method is the same as Implementation Case 1, except that the isocyanate dimer added in step (5) is 0.2 g of isophorone isocyanate dimer. The prepared dielectric elastomer composite material was subjected to mechanical property tests, electric drive performance tests, and transmittance tests before and after self-healing. The test results are shown in Table 1.

[0052] Example 11: The preparation method is the same as Example 1, except that 20 g of side-chain aminopolysiloxane is added in step (1). The mechanical properties and conductivity of the prepared flexible electrode were tested before and after self-healing. The test results are shown in Table 1.

[0053] Comparative Example 12: The preparation method was the same as in Example 1, except that 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt was not added. Mechanical properties, electrical drive performance, and transmittance tests were performed on the pure aminopolysiloxane elastomer before and after self-healing. The comparative results are shown in Table 1.

[0054] Table 1 Performance comparison of composite materials prepared in implementation case and comparison case

[0055] Label Tensile strength (original) MPa Tensile strength (after healing) MPa Breakdown strength (original) kV / mm Breakdown strength (after healing) kV / mm Electrodeformation (original)% Electrodeformation (after healing)% Transmittance (%) Case 1 0.045 0.041 12.34 11.73 106.41 99.45 95 Case 2 0.032 0.029 10.52 9.57 90.15 85.46 91 Case 3 0.068 0.061 13.36 12.34 85.79 78.93 94 Case 4 0.064 0.059 15.96 14.52 84.94 78.26 95 Case 5 0.036 0.024 10.16 9.25 85.48 80.06 92 Case 6 0.033 0.030 10.34 9.41 86.49 80.57 92 Case 7 0.052 0.048 13.48 11.95 90.61 84.31 93 Case 8 0.056 0.050 12.02 11.03 84.47 79.43 91 Case 9 0.051 0.041 12.48 11.36 90.31 83.77 92 Case 10 0.049 0.047 12.76 11.61 99.45 97.15 93 Case 11 0.050 0.047 12.55 11.86 96.21 92.75 95 Comparative Case 12 0.151 0.065 40.34 20.15 20.64 15.68 95

[0056] From the data in Table 1 above, it can be seen that when the filling amount of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is 10wt%, the tensile strength of the polysiloxane dielectric elastomer composite material reaches 0.045MPa, the transmittance reaches 95%, and under the action of an electric field of 12.34kV / mm, the electrodeformation can reach 106.41%, the self-healing efficiency reaches 93%, and excellent electrical breakdown strength is maintained.

[0057] In summary, the transparent self-healing polysiloxane dielectric elastomer composite material prepared by this method has a transmittance of more than 90%, and can self-heal for 1 hour at room temperature with a healing efficiency of more than 90%. The composite material has excellent electrical driving performance and mechanical properties, and the preparation process is simple and the reaction conditions are mild.

[0058] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art.

Claims

1. A method for preparing a transparent self-healing polysiloxane dielectric elastomer composite material, characterized in that: The method comprises: Step 1, dissolving the aminopolysiloxane and the ionic liquid in tetrahydrofuran (THF) respectively, and mixing them to obtain an aminopolysiloxane solution in which the ionic liquid is uniformly dispersed; Wherein, the ionic liquid is one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, lithium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, 1-butyl-1-methylpyrrolidine dicyanamide salt, trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide salt, and 1-ethyl-3-methylimidazolium acetate; Step 2, dissolving the epoxy crosslinking agent and the isocyanate dimer in THF respectively, and mixing them to obtain a mixed solution of the epoxy crosslinking agent and the isocyanate dimer; Step 3: Add the mixed solution in step 2 to the aminopolysiloxane solution in which the ionic liquid is uniformly dispersed in step 1. After sufficient reaction, pour the prepolymer obtained by the reaction into a polytetrafluoroethylene mold and cure it under vacuum to obtain a transparent self-healing polysiloxane dielectric elastomer composite material.

2. The method for preparing the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, characterized in that: The process of step 1 is specifically as follows: Dissolve 10-20 g of aminopolysiloxane in 100 mL of THF and disperse it ultrasonically at 50 kHz for 30-60 min to form a uniformly dispersed aminopolysiloxane solution; Dissolve 1-5 g of ionic liquid in 50 mL of THF and disperse ultrasonically at 50 kHz for 30-60 min to form an ionic liquid solution; The ionic liquid solution and the aminopolysiloxane solution are mixed and stirred at room temperature for 30-60 minutes to obtain an aminopolysiloxane solution in which the ionic liquid is uniformly dispersed.

3. The method for preparing the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, characterized in that: The process of step 2 is specifically as follows: Dissolve 0.05-0.5 g of epoxy crosslinker in 10 mL of THF and disperse by ultrasonic at 50 kHz for 30-60 min to form a uniformly dispersed epoxy crosslinker solution; Dissolve 0.05-0.5 g of isocyanate dimer in 10 mL of THF and disperse by ultrasonication at 50 kHz for 30-60 min to form a uniformly dispersed isocyanate dimer solution; The epoxy crosslinking agent solution and the isocyanate dimer solution are mixed and stirred at room temperature for 30-60 minutes to obtain a mixed solution of the epoxy crosslinking agent and the isocyanate dimer.

4. The method for preparing the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, characterized in that: The process of step 3 is specifically as follows: The mixed solution in step 2 is added to the aminopolysiloxane solution in which the ionic liquid is uniformly dispersed in step 1, and the mixture is stirred and reacted at 40-60° C. for 1-3 hours. The prepolymer obtained by the reaction is then poured into a polytetrafluoroethylene mold and cured in a vacuum at 40-60° C. to obtain a transparent self-healing polysiloxane dielectric elastomer composite material.

5. The method for preparing the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, characterized in that: In step 1, the aminopolysiloxane is one or both of polysiloxane with amino groups at both ends and polysiloxane with amino groups on the side chains, and has a number average molecular weight of 2,000-10,000.

6. The method for preparing the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, characterized in that: In step 2, the epoxy crosslinking agent is one or more of 1,4-butanediol diglycidyl ether, tris(2,3-epoxypropyl)isocyanurate, dioxirane and dibutylene oxide; The isocyanate dimer is one or more of hexamethylene isocyanate dimer, isophorone isocyanate dimer and dicyclohexylmethane diisocyanate.

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