Preparation method of super-stretchable self-healing polysiloxane flexible electrode

Abstract

The invention discloses a preparation method of a super-stretchable self-healing polysiloxane flexible electrode, which comprises the following steps: carrying out surface modification on a carbon nano tube by using catecholamine to obtain a catecholamine modified carbon nano tube marked as CNT-PA; the preparation method comprises the following steps: carrying out surface grafting modification on CNT-PA by adopting an isocyanate dimer to obtain CNT-PA-DI; the preparation method comprises the following steps: respectively dissolving amino polysiloxane and CNT-PA-DI in tetrahydrofuran, and mixing to obtain an amino polysiloxane suspension in which CNT-PA-DI is uniformly dispersed; the preparation method comprises the following steps: respectively dissolving an aldehyde group cross-linking agent and an isocyanate dimer in THF (tetrahydrofuran); adding an amino polysiloxane suspension in which the CNT-PA-DI is uniformly dispersed into the blended solution; and pouring into a polytetrafluoroethylene mold after reaction, and volatilizing the solvent to obtain the flexible electrode. The conductive filler and the polymer matrix in the composite material prepared by the method have excellent compatibility, and the flexible electrode has super stretchability and self-healing performance.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible electrodes, and particularly to a preparation method of a super-stretchable and self-healing polysiloxane flexible electrode. Background Art

[0002] The wide application of flexible electrodes in fields such as electronic skin, medical monitoring devices, and soft robots has greatly promoted the rapid development of flexible electronic technology. However, currently widely used flexible electrodes (such as silver nanowires, PEDOT:PSS) have problems such as reduced conductivity under large strain and inability to self-heal after damage, severely restricting their wide use. Although filling conductive fillers (such as carbon nanotubes, graphene) into a polymer matrix can obtain stretchable flexible electrodes, the poor compatibility between the conductive filler and the polymer matrix and the easy agglomeration of the filler lead to a decrease in the conductive performance of the composite material, and there is no corresponding solution in the prior art. Summary of the Invention

[0003] The object of the present invention is to provide a preparation method of a super-stretchable and self-healing polysiloxane flexible electrode. The method has a simple operation process and mild reaction conditions. In the prepared composite material, the conductive filler and the polymer matrix have excellent compatibility, and the flexible electrode has super-stretchability and can quickly self-heal at room temperature after being mechanically damaged or electrically broken down, still maintaining a high conductivity.

[0004] The object of the present invention is achieved by the following technical solutions: A preparation method of a super-stretchable and self-healing polysiloxane flexible electrode, the method comprising: Step 1: Surface-modify carbon nanotubes CNT with catecholamine to obtain catecholamine-modified carbon nanotubes, denoted as CNT-PA; Step 2: Surface-graft-modify CNT-PA with isocyanate dimer to obtain a conductive filler modified with isocyanate dimer, denoted as CNT-PA-DI; Step 3: Dissolve amino polysiloxane and CNT-PA-DI in tetrahydrofuran THF respectively, and after mixing, obtain an amino polysiloxane suspension with uniformly dispersed CNT-PA-DI; Step 4: Dissolve an aldehyde crosslinking agent and isocyanate dimer in tetrahydrofuran THF respectively, and after mixing, obtain a mixed solution of the aldehyde crosslinking agent and isocyanate dimer in a blend; Step 5: Add the amino polysiloxane suspension with uniformly dispersed CNT-PA-DI obtained in Step 3 into the mixed solution obtained in Step 4 for reaction, and then pour the solution obtained after the reaction into a polytetrafluoroethylene mold, and volatilize the solvent at room temperature to obtain a super-stretchable and self-healing polysiloxane flexible electrode.

[0005] As can be seen from the technical solution provided by the present invention above, the operation process of the above method is simple and the reaction conditions are mild. In the prepared composite material, the conductive filler and the polymer matrix have excellent compatibility, and the flexible electrode has super stretchability and can quickly self-heal at room temperature after being mechanically damaged or electrically broken down, still maintaining a high conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In order 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. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0007] Figure 1 It is a schematic flow chart of the preparation method of the super stretchable self-healing polysiloxane flexible electrode provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0008] 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 a part of the embodiments of the present invention, rather than all the embodiments, which do not constitute a limitation to the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0009] As Figure 1 shown is a schematic flow chart of the preparation method of the super stretchable self-healing polysiloxane flexible electrode provided by the embodiment of the present invention. The method includes: Step 1: Surface-modify carbon nanotubes CNT with catecholamine to obtain catecholamine-modified carbon nanotubes, denoted as CNT-PA; In this step, specifically, 2 - 8 g of CNT is dispersed in 1000 mL of deionized water to form a homogeneous solution; 2 - 4 g of catecholamine is added to the solution, placed in a magnetic stirrer, the stirring speed is set to 300 - 600 r / min, stirred at room temperature for 4 - 10 h, then centrifuged and washed with acetone, and dried at 40 - 60 °C for 12 - 24 h to obtain catecholamine-modified CNT, denoted as CNT-PA.

[0010] Specifically, the catecholamine is one or two of 2-(3,4-dihydroxyphenyl)ethylamine and 1-(3,4-dihydroxyphenyl)-2-aminoethanol.

[0011] Step 2: The CNT-PA is surface graft-modified with isocyanate dimer to obtain a conductive filler modified with isocyanate dimer, denoted as CNT-PA-DI; In this step, specifically, 2 - 8 g of CNT-PA is dispersed in 1000 mL of tetrahydrofuran (THF) to form a homogeneous solution; 0.2 - 1.0 g of isocyanate dimer is added to the solution, placed in a magnetic stirrer, and the stirring speed is set at 300 - 600 r / min, and stirred in a water bath at 40 - 60 °C for 4 - 10 h; Subsequently, centrifugal separation is carried out, washed with acetone, and dried at 40 - 60 °C for 12 - 24 h to obtain CNT-PA modified with isocyanate dimer, denoted as CNT-PA-DI.

[0012] Step 3: The amino polysiloxane and CNT-PA-DI are respectively dissolved in tetrahydrofuran (THF), and after mixing, an amino polysiloxane suspension with uniformly dispersed CNT-PA-DI is obtained; 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; 2 - 8 g of CNT-PA-DI is dissolved in 500 mL of tetrahydrofuran (THF), and ultrasonically dispersed at 50 kHz for 30 - 60 min to form a CNT-PA-DI suspension; The amino polysiloxane solution and the CNT-PA-DI suspension are mixed and stirred at room temperature for 30 - 60 min to obtain an amino polysiloxane suspension with uniformly dispersed CNT-PA-DI.

[0013] In specific implementation, the amino polysiloxane is one or two of polysiloxane with amino groups at both ends or polysiloxane with amino groups in the side chain, and the number average molecular weight is 2000 - 10000.

[0014] Step 4: The aldehyde crosslinking agent and isocyanate dimer are respectively dissolved in tetrahydrofuran (THF), and after mixing, a mixed solution of the aldehyde crosslinking agent and isocyanate dimer is obtained; In this step, specifically, 0.05 - 0.2 g of aldehyde crosslinking agent is dissolved in 20 mL of tetrahydrofuran (THF), and ultrasonically dispersed at 50 kHz for 30 - 60 min to form a uniformly dispersed aldehyde crosslinking agent solution; 0.05 - 0.2 g of isocyanate dimer is dissolved in 20 mL of THF, and ultrasonically dispersed at 50 kHz for 30 - 60 min to form a uniformly dispersed isocyanate dimer solution; Mix the aldehyde group crosslinker solution and the isocyanate dimer solution, and stir at room temperature for 30 - 60 min to obtain a mixed solution of the aldehyde group crosslinker and the isocyanate dimer.

[0015] In specific implementation, the aldehyde group crosslinker is one or more of terephthalaldehyde, isophthalaldehyde, and mellitic aldehyde; The isocyanate dimer is one or more of hexamethylene diisocyanate dimer, isophorone diisocyanate dimer, and dicyclohexylmethane diisocyanate.

[0016] Step 5: Add the uniformly dispersed amino polysiloxane suspension of CNT - PA - DI obtained in Step 3 into the mixed solution obtained in Step 4 for reaction, and then pour the solution obtained after the reaction into a polytetrafluoroethylene mold, and volatilize the solvent at room temperature to obtain a super - stretchable self - healing polysiloxane flexible electrode.

[0017] In this step, specifically, add the amino polysiloxane suspension in Step 3 into the mixed solution of the aldehyde group crosslinker and the isocyanate dimer in Step 4, stir and react at 40 - 60 °C for 1 - 3 h, then pour the solution obtained after the reaction into a polytetrafluoroethylene mold, and volatilize the solvent at room temperature to obtain a super - stretchable self - healing polysiloxane flexible electrode.

[0018] According to the preparation process of this method, catecholamine forms a uniform coating on the surface of CNT, providing abundant phenolic hydroxyl active sites. Further, utilize the reaction between the isocyanate group of the isocyanate dimer and the phenolic hydroxyl group to graft flexible polyurethane chain segments on the surface of CNT; the modified CNT reacts with the amino group of the polysiloxane matrix through the isocyanate group on its surface to form dynamic urea bonds, avoiding the slippage at the filler - matrix interface and solving the problems of poor dispersion and easy agglomeration of CNT in the polymer matrix; the amino group in the amino polysiloxane reacts with the aldehyde group in the aldehyde group crosslinker to generate dynamic imine bonds, and at the same time, the isocyanate dimer introduces urea bonds into the molecular chain to form reversible hydrogen bonds, endowing the polysiloxane with excellent self - healing performance at room temperature.

[0019] 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.

[0020] The following describes the preparation process, mechanical properties, and electrical conductivity of the composite material of the present invention with specific implementation cases: Implementation Case 1 (1) Disperse 4 g of CNT in 1000 mL of deionized water to form Solution 1; (2) Add 2 g of 2 - (3,4 - dihydroxyphenyl)ethylamine into Solution 1, place it in a magnetic stirrer, set the speed to 600 r / min, and stir at room temperature for 6 h to obtain functionalized CNT, generating Solution 2; (3) Centrifuge solution 2, wash it with acetone, and then dry it at 60 °C for 24 h to obtain CNT modified with 2-(3,4-dihydroxyphenyl)ethylamine, denoted as CNT-PA, for standby. (4) Disperse 4 g of CNT-PA in 100 mL of THF to form solution 3. (5) Add 0.8 g of hexamethylene diisocyanate dimer to solution 3, place it in a magnetic stirrer, set the stirring speed to 600 r / min, and stir it in a 60 °C water bath for 8 h to graft isocyanate groups onto the surface of CNT-PA, obtaining the treated mixed solution 4. (6) Centrifuge the mixed solution 4, wash it with acetone, and then dry it at 60 °C for 24 h to obtain CNT-PA modified and modified with hexamethylene diisocyanate dimer, denoted as CNT-PA-DI, for standby. (7) Dissolve 20 g of amino-terminated polysiloxane in 100 mL of THF and ultrasonically disperse it at 50 kHz for 30 min to form a uniform solution 5. (8) Dissolve 4 g of CNT-PA-DI in 60 mL of THF and ultrasonically disperse it at 50 kHz for 30 min to form a uniform suspension 6. (9) Mix solution 5 and suspension 6 and stir at room temperature for 30 min to form solution 7. (10) Dissolve 0.15 g of benzene-1,3,5-tricarbaldehyde in 10 mL of THF and ultrasonically disperse it at 50 kHz for 30 min to form a uniformly dispersed solution 8. (11) Dissolve 0.15 g of hexamethylene diisocyanate dimer in 10 mL of THF and ultrasonically disperse it at 50 kHz for 30 min to form a uniformly dispersed solution 9. (12) Mix solution 8 and solution 9 and stir at room temperature for 30 min to form solution 10. (13) Add solution 10 to solution 7, stir at 60 °C for 3 h, pour it into a polytetrafluoroethylene mold, and volatilize the solvent at room temperature to obtain a super stretchable and self-healing polysiloxane flexible electrode.

[0021] Perform mechanical property tests on the flexible electrode prepared in step (13), and set the tensile rate to 100 mm / min. The mechanical property self-healing test is to cut along the direction perpendicular to the tensile axis in the middle of the test specimen, then closely contact the two fracture surfaces together, repair at room temperature for 30 min, and perform mechanical property tests again. The tensile test results are shown in Table 1 below.

[0022] The flexible electrode prepared in step (13) was subjected to conductivity testing. The specific testing method was as follows: A four-probe resistivity tester was used, with the probes arranged linearly, the distance between adjacent probes being 1.0 ± 0.1 mm, and the probe material being tungsten carbide or gold-plated tungsten needles. The conductivity testing after self-healing was carried out after mechanical damage. After repairing at room temperature for 30 min, the conductivity was tested again. The results of the conductivity testing 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 phloroglucinol in step (10) was 0.05 g. The mechanical properties and conductivity of the prepared flexible electrode before and after self-healing were tested, and 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 phloroglucinol in step (10) was 0.2 g. The mechanical properties and conductivity of the prepared flexible electrode before and after self-healing were tested, and 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 CNT-PA-DI in step (8) was 2 g. The mechanical properties and conductivity of the prepared flexible electrode before and after self-healing were tested, and the test results are shown in Table 1.

[0026] Example 5: The preparation method was the same as that of Example 1, except that the addition amount of CNT-PA-DI in step (8) was 8 g. The mechanical properties and conductivity of the prepared flexible electrode before and after self-healing were tested, and the test results are shown in Table 1.

[0027] Example 6: The preparation method was the same as that of Example 1, except that the addition amount of hexamethylene diisocyanate dimer in step (11) was 0.05 g. The mechanical properties and conductivity of the prepared flexible electrode before and after self-healing were tested, and the test results are shown in Table 1.

[0028] Example 7: The preparation method was the same as that of Example 1, except that the addition amount of hexamethylene diisocyanate dimer in step (11) was 0.2 g. The mechanical properties and conductivity of the prepared flexible electrode before and after self-healing were tested, and the test results are shown in Table 1.

[0029] Example 8: The preparation method was the same as that of Example 1, except that the isocyanate dimer added in step (2) was isophorone diisocyanate dimer. The mechanical properties and electro-driven performance of the prepared flexible electrode before and after self-healing were tested, 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 aldehyde crosslinking agent added in step (10) is 0.15 g of terephthalaldehyde. The mechanical properties and electro-driven performance of the prepared flexible electrode were tested before and after self-healing, 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 catecholamine added in step (2) is 2 g of 1-(3,4-dihydroxyphenyl)-2-aminoethanol. The mechanical properties and conductivity of the prepared flexible electrode were tested before and after self-healing, 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 (7) is 20 g of side-chain amino polysiloxane. The mechanical properties and conductivity of the prepared flexible electrode were tested before and after self-healing, 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 unmodified CNTs are added. The mechanical properties and conductivity of the prepared flexible electrode were tested before and after self-healing, and the comparison results are shown in Table 1.

[0034] Comparative Example 13: The preparation method is the same as that of Example 1, except that no CNTs are added. The mechanical properties and conductivity of the prepared pure silicone rubber were tested before and after self-healing, and the comparison results are shown in Table 1.

[0035] Table 1 Performance comparison of the composites prepared in the examples and comparative examples with the comparative examples Label Tensile strength (original) kPa Tensile strength (after healing) kPa Elongation at break (original) % Elongation at break (after healing) % Conductivity (original) S / cm Conductivity (after healing) S / cm Case 1 47.82 46.95 1265 1245 97.25 88.50 Case 2 38.65 37.88 1430 1401 95.45 86.31 Case 3 60.45 59.24 1054 1033 91.78 83.52 Case 4 35.85 35.13 1490 1460 86.15 77.53 Case 5 67.63 66.28 1010 990 100.34 90.93 Case 6 43.84 42.96 1395 1367 90.48 82.34 Case 7 52.93 51.87 1132 1109 91.26 83.05 Case 8 52.35 51.76 1162 1139 94.37 85.88 Case 9 40.19 39.76 1401 1373 90.74 82.57 Case 10 45.82 45.02 1321 1295 95.35 85.04 Case 11 50.73 48.97 1188 1171 95.31 86.74 Comparative Case 12 48.32 30.51 1055 580 20.51 10.31 Comparative Case 13 20.91 19.64 1632 1503 0 0 It can be seen from the data in Table 1 above that when the CNTs modified with catecholamine and isocyanate dimer are filled to 20 wt%, the elongation at break of the flexible electrode reaches 1265%, the self-healing efficiency of the mechanical properties reaches 98%, the conductivity can reach 97.25 S / cm, and the self-healing efficiency of the conductivity reaches 90%. The self-healing polysiloxane flexible electrode prepared by this method has both super stretchable performance and high conductivity.

[0036] In summary, the super stretchable self-healing polysiloxane flexible electrode prepared by the method described in the embodiments of the present invention can be quickly self-healed at room temperature without any external assistance conditions, and the healing efficiency is as high as over 97% within 30 minutes; the flexible electrode has excellent conductivity and elongation at break, and the preparation process is simple, the reaction conditions are mild, and it is efficient and time-saving.

[0037] As described above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of 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 part 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 this information constitutes the prior art known to those skilled in the art.

Claims

1. A method for preparing an ultra-stretchable self-healing polysiloxane flexible electrode, characterized in that: The method comprises: Step 1, using catecholamine to modify the surface of carbon nanotubes CNT to obtain carbon nanotubes modified with catecholamine, which are denoted as CNT-PA; Step 2, using isocyanate dimer to perform surface graft modification on CNT-PA to obtain an isocyanate dimer-modified conductive filler, which is recorded as CNT-PA-DI; Step 3, dissolving aminopolysiloxane and CNT-PA-DI in tetrahydrofuran (THF) respectively, and mixing to obtain an aminopolysiloxane suspension in which CNT-PA-DI is uniformly dispersed; Step 4, dissolving the aldehyde crosslinking agent and the isocyanate dimer in tetrahydrofuran (THF) respectively, and mixing them to obtain a mixed solution of the aldehyde crosslinking agent and the isocyanate dimer; Step 5: Add the aminopolysiloxane suspension in which CNT-PA-DI is uniformly dispersed obtained in step 3 to the mixed solution obtained in step 4 for reaction, and then pour the solution obtained after the reaction into a polytetrafluoroethylene mold, evaporate the solvent at room temperature, and obtain an ultra-stretchable self-healing polysiloxane flexible electrode.

2. The method for preparing the ultra-stretchable self-healing polysiloxane flexible electrode according to claim 1, characterized in that: The process of step 1 is specifically as follows: Disperse 2-8 g CNT in 1000 mL of deionized water to form a uniform solution; 2-4 g of catecholamines were added to the solution, placed in a magnetic stirrer, the stirring speed was set to 300-600 r / min, stirred at room temperature for 4-10 h, then centrifuged, washed with acetone, and dried at 40-60°C for 12-24 h to obtain catecholamine-modified CNTs, recorded as CNT-PA.

3. The method for preparing the ultra-stretchable self-healing polysiloxane flexible electrode according to claim 1, characterized in that: The process of step 2 is specifically as follows: 2-8 g CNT-PA was dispersed in 1000 mL of tetrahydrofuran (THF) to form a uniform solution; Add 0.2-1.0g of isocyanate dimer to the solution, place in a magnetic stirrer, set the stirring speed to 300-600r / min, and stir in a 40-60℃ water bath for 4-10h; Subsequently, the mixture was centrifuged, washed with acetone, and dried at 40-60° C. for 12-24 h to obtain CNT-PA modified with isocyanate dimer, which was recorded as CNT-PA-DI.

4. The method for preparing the ultra-stretchable self-healing polysiloxane flexible electrode according to claim 1, characterized in that: The process of step 3 is specifically as follows: Dissolve 10-20 g of aminopolysiloxane in 100 mL of THF and disperse by ultrasonic at 50 kHz for 30-60 min to form a uniformly dispersed aminopolysiloxane solution; 2-8 g of CNT-PA-DI was dissolved in 500 mL of tetrahydrofuran (THF) and ultrasonically dispersed at 50 kHz for 30-60 min to form a CNT-PA-DI suspension; The aminopolysiloxane solution and the CNT-PA-DI suspension are mixed and stirred at room temperature for 30-60 minutes to obtain an aminopolysiloxane suspension in which CNT-PA-DI is uniformly dispersed.

5. The method for preparing the ultra-stretchable self-healing polysiloxane flexible electrode according to claim 1, characterized in that: The process of step 4 is specifically as follows: Dissolve 0.05-0.2 g of the aldehyde crosslinking agent in 20 mL of tetrahydrofuran (THF), and disperse by ultrasonic at 50 kHz for 30-60 min to form a uniformly dispersed aldehyde crosslinking agent solution; Dissolve 0.05-0.2 g of isocyanate dimer in 20 mL of THF and disperse by ultrasonic at 50 kHz for 30-60 min to form a uniformly dispersed isocyanate dimer solution; The aldehyde 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 aldehyde crosslinking agent and the isocyanate dimer.

6. The method for preparing the ultra-stretchable self-healing polysiloxane flexible electrode according to claim 1, characterized in that: The process of step 5 is specifically as follows: The aminopolysiloxane suspension in step 3 is added to the mixed solution of the aldehyde crosslinking agent and isocyanate dimer in step 4, and the mixture is stirred and reacted at 40-60°C for 1-3 hours. The resulting solution is then poured into a polytetrafluoroethylene mold, and the solvent is evaporated at room temperature to obtain an ultra-stretchable self-healing polysiloxane flexible electrode.

7. The method for preparing the ultra-stretchable self-healing polysiloxane flexible electrode according to claim 1, characterized in that: In step 3, the aminopolysiloxane is one or both of polysiloxane with amino groups at both ends or polysiloxane with amino groups on the side chains, and the number average molecular weight is 2000-10000.

8. The method for preparing the ultra-stretchable self-healing polysiloxane flexible electrode according to claim 1, characterized in that: In step 4, the aldehyde-based cross-linking agent is one or more of terephthalaldehyde, isophthalaldehyde and trimesaldehyde; The isocyanate dimer is one or more of hexamethylene isocyanate dimer, isophorone isocyanate dimer and dicyclohexylmethane diisocyanate.

9. The method for preparing the ultra-stretchable self-healing polysiloxane flexible electrode according to claim 1, characterized in that: In step 1, the catecholamine is one or both of 2-(3,4-dihydroxyphenyl)ethylamine and 1-(3,4-dihydroxyphenyl)-2-aminoethanol.

Images