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

Abstract

The invention discloses a transparent self-healing polysiloxane dielectric elastomer composite material preparation method, which comprises: respectively dissolving amino polysiloxane and an ionic liquid in tetrahydrofuran THF, and mixing to obtain an amino polysiloxane solution in which the ionic liquid is uniformly dispersed; the preparation method comprises the following steps: respectively dissolving an epoxy cross-linking agent and an isocyanate dimer in THF (tetrahydrofuran), and mixing to obtain a mixed solution of the epoxy cross-linking agent and the isocyanate dimer; the preparation method comprises the following steps: adding a mixed solution of an epoxy cross-linking agent and an isocyanate dimer into an amino polysiloxane solution in which ionic liquid is uniformly dispersed, fully reacting, pouring the reacted solution into a polytetrafluoroethylene mold, and curing in vacuum to obtain the transparent self-healing polysiloxane dielectric elastomer composite material. The method can be used for preparing the dielectric elastomer which is high in transmissivity, high in dielectric, low in modulus and capable of quickly self-healing under mild conditions.

Description

Technical Field

[0001] The 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 elastomer is an electroactive polymer with the advantages of fast response speed, large strain output, and high energy density. The dielectric elastomer actuator, which is composed of a dielectric elastomer film and flexible electrodes coated on both sides, can produce muscle-like contraction-relaxation deformation under external electrical stimulation, and has broad application prospects in artificial muscles, energy harvesting, flexible electronics and other fields.

[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 dielectric constant of silicone rubber is low, which requires a higher driving voltage to obtain a larger driving strain, which seriously limits its practical application. Although filling a silicone rubber matrix with a high dielectric filler can effectively improve the dielectric constant of the composite material, it often comes at the cost of an increase in the elastic modulus of the material and a decrease in transparency, which is not conducive to its application in soft robots, tunable optics, etc. In addition, silicone rubber does not have self-healing properties. Once it is mechanically damaged or an electrical breakdown occurs, it cannot be used again and can only 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. The 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 the operation is simple.

[0005] The objective of the present invention is achieved through the following technical solutions: A method for preparing a transparent self-healing polysiloxane dielectric elastomer composite material, the method comprising: 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; 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: adding the mixed solution in step 2 to the aminopolysiloxane solution in which the ionic liquid is uniformly dispersed in step 1, and after sufficient reaction, pouring the prepolymer obtained by the reaction into a polytetrafluoroethylene mold and curing it under vacuum to obtain a transparent self-healing polysiloxane dielectric elastomer composite material.

[0006] As can be seen from the technical solutions provided by the present invention above, through molecular structure design and regulation, the above method realizes the compatibility of high transmittance, excellent self-healing performance, high dielectric constant, and low elastic modulus of the dielectric elastomer, and the synthesis process is mild and the operation is simple, demonstrating the great potential of this elastomer in the fields of emerging flexible electronics and optoelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings without creative efforts based on these drawings.

[0008] Figure 1 It is a schematic flowchart of the preparation method of the transparent self-healing polysiloxane dielectric elastomer composite provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0009] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments, which do not constitute a limitation to the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.

[0010] As Figure 1 shown is a schematic flowchart of the preparation method of the transparent self-healing polysiloxane dielectric elastomer composite provided by the embodiment of the present invention, and the method includes: Step 1: Dissolve amino polysiloxane and ionic liquid in tetrahydrofuran (THF) respectively, and after mixing, obtain an amino polysiloxane solution with uniformly dispersed ionic liquid; In this step, specifically, 10 - 20 g of amino polysiloxane is dissolved in 100 mL of THF, and ultrasonically dispersed at 50 kHz for 30 - 60 min to form a uniformly dispersed amino polysiloxane solution; Dissolve 1 - 5 g of ionic liquid in 50 mL of THF, and ultrasonically disperse at 50 kHz for 30 - 60 min to form an ionic liquid solution;

[0011] Mix the ionic liquid solution and the amino polysiloxane solution, and stir at room temperature for 30 - 60 min to obtain an amino polysiloxane solution with uniformly dispersed ionic liquid.

[0012] In specific implementation, the amino polysiloxane is one or both of polysiloxanes with amino groups at both ends and polysiloxanes with amino groups in the side chains, and the number-average molecular weight is 2000-10000; The ionic liquid is one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium dicyanamide, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, and 1-ethyl-3-methylimidazolium acetate.

[0013] Step 2: Dissolve the epoxy crosslinker and the isocyanate dimer in THF respectively, and after mixing, obtain a mixed solution of the epoxy crosslinker and the isocyanate dimer; In this step, 0.05-0.5 g of the epoxy crosslinker is dissolved in 10 mL of THF, and ultrasonic dispersion is carried out at 50 kHz for 30-60 min to form a uniformly dispersed epoxy crosslinker solution; Dissolve 0.05-0.5 g of the isocyanate dimer in 10 mL of THF, and ultrasonic disperse it at 50 kHz for 30-60 min to form a uniformly dispersed isocyanate dimer solution; Mix the epoxy crosslinker solution and the isocyanate dimer solution, and stir at room temperature for 30-60 min to obtain a mixed solution of the epoxy crosslinker and the isocyanate dimer.

[0014] In specific implementation, the epoxy crosslinker is one or more of 1,4-butanediol diglycidyl ether, tris(2,3-epoxypropyl) isocyanurate, diepoxyethane, and diepoxybutane; The isocyanate dimer is one or more of hexamethylene diisocyanate dimer, isophorone diisocyanate dimer, and dicyclohexylmethane diisocyanate.

[0015] Step 3: Add the mixed solution in Step 2 to the amino polysiloxane solution in which the ionic liquid is uniformly dispersed in Step 1. After sufficient reaction, pour the obtained prepolymer into a polytetrafluoroethylene mold and cure it under vacuum to obtain a transparent self-healing polysiloxane dielectric elastomer composite material.

[0016] In this step, specifically, add the mixed solution in Step 2 to the amino polysiloxane solution in which the ionic liquid is uniformly dispersed in Step 1, stir and react at 40-60 °C for 1-3 h, then pour the obtained prepolymer into a polytetrafluoroethylene mold, and cure it at 40-60 °C under vacuum to obtain a transparent self-healing polysiloxane dielectric elastomer composite material.

[0017] As can be seen from the above process scheme, during the preparation process, the amino group in the amino polysiloxane reacts with the epoxy group in the epoxy crosslinking agent to generate hydroxyl groups. At the same time, the isocyanate dimer introduces urea bonds into the molecular chain, and the multiple hydrogen bonds formed between the molecular chains endow the polysiloxane with 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 amino polysiloxane, while the flexible alkyl chains of the cations in the ionic liquid have good compatibility with the aliphatic segments of the elastomer, enabling the molecular-level dispersion of the ionic liquid in the amino polysiloxane, thereby endowing the elastomer composite with a high dielectric constant and significantly reducing its elastomer modulus, ultimately obtaining a high-driving-strain dielectric elastomer composite with excellent self-healing properties.

[0018] It should be noted that the content not described in detail in the embodiments of the present invention belongs to the prior art well-known to those skilled in the art.

[0019] The following describes the preparation process, mechanical properties, and electro-driving properties of the composite material with specific implementation cases: Implementation Case 1 (1) Dissolve 20 g of amino-terminated polysiloxane in 100 mL of THF and ultrasonically disperse it for 30 min at 50 kHz to form a uniform solution 1. (2) Dissolve 2 g of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide in 10 mL of THF and ultrasonically disperse it for 30 min at 50 kHz to form a uniform solution 2. (3) Mix solution 1 and solution 2 and stir at room temperature for 30 min to form a uniform solution 3. (4) Dissolve 0.2 g of 1,4-butanediol diglycidyl ether in 5 mL of THF and ultrasonically disperse it for 30 min at 50 kHz to form a uniform solution 4. (5) Dissolve 0.2 g of hexamethylene diisocyanate dimer in 5 mL of THF and ultrasonically disperse it for 30 min at 50 kHz to form a uniformly dispersed solution 5. (6) Mix solution 4 and solution 5 and stir at room temperature for 1 h to form solution 6. (7) Add solution 6 to solution 3, stir at 60 °C for 3 h, pour it into a polytetrafluoroethylene mold, and evaporate the solvent under vacuum at 60 °C to obtain a transparent self-healing polysiloxane dielectric elastomer composite.

[0020] The dielectric elastomer composite prepared in step (7) was subjected to mechanical property testing, and the tensile rate was set at 100 mm / min. The mechanical property self-healing test was carried out by cutting the middle part of the test specimen perpendicular to the tensile axis, then closely contacting the two fracture surfaces together, repairing at room temperature for 1 hour, and then carrying out mechanical property testing again. The tensile test results are shown in Table 1 below.

[0021] The dielectric elastomer composite prepared in step (7) was subjected to electro-driven performance testing. The specific testing method was as follows: circular flexible electrodes with a diameter of 10 mm were sprayed on both sides of the dielectric elastomer film using a spray gun, and then cured in an oven at 60 °C to form a dielectric elastomer actuator. A DC voltage was applied to the electrodes, and at the same time, a camera was used to record the change process of the electrode area under the electric field stimulation in real time. The planar electro-driven strain of the dielectric elastomer was calculated by the formula S = (A - A0) / A0 × 100%, where A0 is the area of the electrode region without applying an electric field, and A is the area at a certain electric field strength. The electro-driven self-healing performance test was carried out after the dielectric elastomer actuator was electrically broken down, repaired at room temperature for 1 hour, and then the electro-driven performance test was carried out again. The electro-driven performance test results are shown in Table 1 below.

[0022] The dielectric elastomer composite prepared in step (7) was subjected to transmittance testing. The transmittance was tested on an ultraviolet-visible spectrophotometer. The thickness of the test sample was 1 mm, and the test was carried out at room temperature. The transmittance test results are shown in Table 1 below.

[0023] Example 2: The preparation method was the same as that of Example 1, except that the addition amount of 1,4-butanediol diglycidyl ether in step (4) was 0.05 g. The dielectric elastomer composite prepared was subjected to mechanical property testing, electro-driven performance testing, and transmittance testing before and after self-healing. The test results are shown in Table 1.

[0024] Example 3: The preparation method was the same as that of Example 1, except that the addition amount of 1,4-butanediol diglycidyl ether in step (4) was 0.5 g. The dielectric elastomer composite prepared was subjected to mechanical property testing, electro-driven performance testing, and transmittance testing before and after self-healing. The test results are shown in Table 1.

[0025] Example 4: The preparation method was the same as that of Example 1, except that the addition amount of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide in step (2) was 0.05 g. The dielectric elastomer composite prepared was subjected to mechanical property testing, electro-driven performance testing, and transmittance testing before and after self-healing. The test results are shown in Table 1.

[0026] Example 5: The preparation method is the same as that of Example 1, except that the addition amount of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide in step (2) is 0.5 g. The mechanical property test, electro-driven property test and transmittance test of the prepared dielectric elastomer composite material before and after self-healing are carried out, and the test results are shown in Table 1.

[0027] Example 6: The preparation method is the same as that of Example 1, except that the addition amount of hexamethylene diisocyanate dimer in step (5) is 0.05 g. The mechanical property test, electro-driven property test and transmittance test of the prepared dielectric elastomer composite material before and after self-healing are carried out, and the test results are shown in Table 1.

[0028] Example 7: The preparation method is the same as that of Example 1, except that the addition amount of hexamethylene diisocyanate dimer in step (5) is 0.5 g. The mechanical property test, electro-driven property test and transmittance test of the prepared dielectric elastomer composite material before and after self-healing are carried out, and the test results are shown in Table 1.

[0029] Example 8: The preparation method is the same as that of Example 1, except that the ionic liquid added in step (2) is 2 g of lithium bis(trifluoromethylsulfonyl)imide. The mechanical property test and electro-driven property test of the prepared dielectric elastomer composite material before and after self-healing are carried out, and the test results are shown in Table 1.

[0030] Example 9: The preparation method is the same as that of Example 1, except that the epoxy cross-linking agent added in step (4) is 0.2 g of tris(2,3-epoxypropyl)isocyanurate. The mechanical property test, electro-driven property test and transmittance test of the prepared dielectric elastomer composite material before and after self-healing are carried out, and the test results are shown in Table 1.

[0031] Example 10: The preparation method is the same as that of Example 1, except that the isocyanate dimer added in step (5) is 0.2 g of isophorone diisocyanate dimer. The mechanical property test, electro-driven property test and transmittance test of the prepared dielectric elastomer composite material before and after self-healing are carried out, and the test results are shown in Table 1.

[0032] Example 11: The preparation method is the same as that of Example 1, except that the amino polysiloxane added in step (1) is 20 g of side-chain amino polysiloxane. The mechanical property test and conductivity test of the prepared flexible electrode before and after self-healing are carried out, and the test results are shown in Table 1.

[0033] Comparative Example 12: The preparation method is the same as that of Example 1, except that 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide is not added. The mechanical property test, electro-driven property test and transmittance test of the pure amino polysiloxane elastomer before and after self-healing are carried out, and the comparison results are shown in Table 1.

[0034] Table 1 Performance Comparison of Composites Prepared by Implementation Cases and Comparative Cases with Comparative Cases Label Tensile strength (original) MPa Tensile strength (after healing) MPa Breakdown strength (original) kV / mm Breakdown strength (after healing) kV / mm Electrostrictive deformation (original) % Electrostrictive deformation (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 It can be seen from the data in Table 1 above that when the filling amount of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt is 10 wt%, the tensile strength of the polysiloxane dielectric elastomer composite reaches 0.045 MPa, the transmittance reaches 95%, under the action of an electric field of 12.34 kV / mm, the electrostrictive deformation can reach 106.41%, the self-healing efficiency reaches 93%, and excellent electric breakdown strength is maintained.

[0035] In summary, the transparent self-healing polysiloxane dielectric elastomer composite prepared by this method has a transmittance of over 90%, self-heals at room temperature for 1 hour with a healing efficiency of over 90%, and this composite has excellent electro-driven performance and mechanical properties, and the preparation process is simple and the reaction conditions are mild.

[0036] As mentioned above, only the specific preferred embodiments of the present invention are described, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims. The information disclosed in the background art section of this article is only intended to deepen the understanding of the overall background art of the present invention, and should not be regarded as an admission or any form of implication that this information constitutes the prior art known to those skilled in the art.

Claims

1. A preparation method of a transparent self-healing polysiloxane dielectric elastomer composite material, characterized in that, The method includes the following steps: Step 1: Dissolve the amino polysiloxane and the ionic liquid in tetrahydrofuran (THF) respectively, and after mixing, an amino polysiloxane solution with uniformly dispersed ionic liquid is obtained. Step 2: Dissolve the epoxy crosslinking agent and the isocyanate dimer in THF respectively, and after mixing, a mixed solution of the epoxy crosslinking agent and the isocyanate dimer is obtained. Step 3: Add the mixed solution in Step 2 to the amino polysiloxane solution with uniformly dispersed ionic liquid in Step 1. After sufficient reaction, pour the resulting prepolymer into a polytetrafluoroethylene mold and cure it under vacuum to obtain a transparent self-healing polysiloxane dielectric elastomer composite.

2. The preparation method of the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, wherein The specific process of Step 1 is as follows: Dissolve 10 - 20 g of amino polysiloxane in 100 mL of THF, and ultrasonically disperse it at 50 kHz for 30 - 60 min to form a uniformly dispersed amino polysiloxane solution. Dissolve 1 - 5 g of ionic liquid in 50 mL of THF, and ultrasonically disperse it at 50 kHz for 30 - 60 min to form an ionic liquid solution. Mix the ionic liquid solution and the amino polysiloxane solution, and stir at room temperature for 30 - 60 min to obtain an amino polysiloxane solution with uniformly dispersed ionic liquid.

3. The preparation method of the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, characterized in that The specific process of Step 2 is as follows: Dissolve 0.05 - 0.5 g of epoxy crosslinking agent in 10 mL of THF, and ultrasonically disperse it at 50 kHz for 30 - 60 min to form a uniformly dispersed epoxy crosslinking agent solution. Dissolve 0.05 - 0.5 g of isocyanate dimer in 10 mL of THF, and ultrasonically disperse it at 50 kHz for 30 - 60 min to form a uniformly dispersed isocyanate dimer solution. Mix the epoxy crosslinking agent solution and the isocyanate dimer solution, and stir at room temperature for 30 - 60 min to obtain a mixed solution of the epoxy crosslinking agent and the isocyanate dimer.

4. The preparation method of the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, characterized in that The specific process of Step 3 is as follows: Add the mixed solution in Step 2 to the amino polysiloxane solution with uniformly dispersed ionic liquid in Step 1, stir and react at 40 - 60 °C for 1 - 3 h, then pour the resulting prepolymer into a polytetrafluoroethylene mold and cure it under vacuum at 40 - 60 °C to obtain a transparent self-healing polysiloxane dielectric elastomer composite.

5. The preparation method of the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, wherein, In Step 1, the amino polysiloxane is one or both of the polysiloxane with amino groups at both ends and the polysiloxane with amino groups in the side chain, and the number-average molecular weight is 2000 - 10000. The ionic liquid is one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium dicyanamide, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium acetate.

6. The preparation method of the transparent self-healing polysiloxane dielectric elastomer composite material according to claim 1, wherein, In Step 2, the epoxy crosslinking agent is one or more of 1,4-butanediol diglycidyl ether, tris(2,3-epoxypropyl) isocyanurate, diepoxyethane and diepoxybutane. The isocyanate dimer is one or more of hexamethylene diisocyanate dimer, isophorone diisocyanate dimer and dicyclohexylmethane diisocyanate.

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