Ultra-stretchable gradient conductive ion gel and its preparation method and application

Abstract

The present invention discloses an ultra-stretchable gradient conductive ion gel, its preparation method, and application. The ion gel is characterized in that it is obtained by in-situ photopolymerization of a polymerizable modified silicone oil and a (meth)acryloyl-containing monomer in an ionic liquid, and the conductivity of the ion gel exhibits a gradient change along the vertical direction of the ion gel. The present invention has the following beneficial effects: (1) an ion gel with a gradient conductivity is obtained through a one-step photopolymerization method; and (2) the synthesized gradient conductive ion gel exhibits outstanding stretchability and sensing properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional polymer conductive materials, and specifically relates to an ultra-stretchable gradient conductive ion gel and its preparation method and application. Background Art

[0002] With the advancement of intelligent lifestyles, demand for flexible sensors is increasing. Flexible sensors have numerous applications in human-machine communication, health monitoring, self-diagnosis, and electronic skin. Ion gels are highly favored by researchers due to their high electrical conductivity, heat resistance, frost resistance, non-flammability, and wide electrochemical window.

[0003] Gradient conductive ion gels have been used to fabricate flexible sensors with high sensitivity and a wide detection range, but there are problems such as complex and time-consuming preparation process and the need for an external electric field. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides an ultra-stretchable gradient conductive ion gel and its preparation method and application. The method is simple and the ultra-stretchable gradient conductive ion gel prepared by this method has excellent comprehensive performance, and has the characteristics of ultra-high stretchability and gradient change of conductivity along the vertical direction.

[0005] Specifically, the present invention includes:

[0006] 1. A method for preparing an ultra-stretchable gradient conductive ion gel, comprising the following steps:

[0007] S1: using a polymerizable modified silicone oil as a crosslinking agent, mixing it with a (meth)acryloyl-containing monomer, an ionic liquid, and a photoinitiator to obtain a precursor solution; wherein the molar ratio of the polymerizable group of the polymerizable modified silicone oil to the (meth)acryloyl-containing monomer is (1-50):1000, the molar ratio of the photoinitiator to the (meth)acryloyl-containing monomer is (1-50):1000, and the molar ratio of the ionic liquid to the (meth)acryloyl-containing monomer is 10:(10-50);

[0008] S2: The precursor solution is solidified through a photo-initiated polymerization reaction to obtain an ultra-stretchable gradient conductive ion gel.

[0009] 2. The method according to item 1, characterized in that the polymerizable modified silicone oil described in step S1 is selected from one or more of (meth)acryloyl-modified silicone oil, vinyl-modified silicone oil, and styrene-modified silicone oil; preferably, the polymerizable modified silicone oil is methacryloyl-modified silicone oil.

[0010] 3. The method according to item 1, characterized in that the (meth)acryloyl-containing monomer described in step S1 is selected from one or more of monofunctional (meth)acryloyl monomers, difunctional (meth)acryloyl monomers, and multifunctional (meth)acryloyl monomers; preferably, the (meth)acryloyl-containing monomer is selected from monofunctional (meth)acryloyl monomers.

[0011] 4. The method according to item 1 is characterized in that the photoinitiator described in step S1 is selected from one or more free radical photoinitiators.

[0012] 5. The method according to item 1 is characterized in that the ionic liquid described in step S1 is one or more of an imidazole ionic liquid, a pyrrole ionic liquid, a quaternary ammonium ionic liquid or a quaternary phosphonium ionic liquid; preferably, the ionic liquid is an imidazole ionic liquid; more preferably, the ionic liquid is 1-ethyl-3-methylimidazolium ethyl sulfate.

[0013] 6. An ultra-stretchable gradient conductive ion gel prepared by the method described in any one of items 1-5.

[0014] 7. An application of an ultra-stretchable gradient conductive ion gel as described in any one of items 1-5, characterized in that the ultra-stretchable gradient conductive ion gel is applied to flexible sensors, supercapacitors, lithium battery solid electrolytes, drivers, gas separation, and optical devices.

[0015] Compared with the background technology, the present invention has the following advantages:

[0016] 1. The preparation method of the present invention is simple and quick, and the conductivity of the ion gel is induced to show a gradient change by the self-floating property of silicone, without the need for complex equipment and a long preparation process.

[0017] 2. The ultra-stretchable gradient conductive ion gel prepared by the present invention has both gradient conductivity change and ultra-high stretchability while also having adhesion.

[0018] 3. The strain sensor composed of the ultra-stretchable gradient conductive ion gel prepared by the present invention and the wire and the testing system has the advantages of wide detection range, high sensitivity and good durability. It can be used to detect human movement and has application potential in wearable devices, medical testing equipment and soft robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the atomic percentage of the bottom and top surfaces of the ultra-stretchable gradient conductive ion gel 3 prepared in Example 3;

[0020] Figure 2 is the conductivity from top to bottom of the ultra-stretchable gradient conductive ion gel 1-4 prepared in Examples 1-4;

[0021] Figure 3 1 is the stress-strain curve of the ultra-stretchable gradient conductive ion gel 1-4 prepared in Examples 1-4;

[0022] Figure 4 is the stress-strain curve of comparative example ion gel 5 prepared in Example 5;

[0023] Figure 5 are photos of the adhesion of the ultra-stretchable gradient conductive ion gel 3 prepared in Example 3 to different substrates;

[0024] Figure 6 is the adhesion strength of the ultra-stretchable gradient conductive ion gel 3 prepared in Example 3 to different substrates;

[0025] Figure 7 is the sensing performance of the flexible strain sensor;

[0026] Figure 8 It is the relative resistance change curve when the flexible strain sensor detects human body movement. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] Example 1:

[0029] Preparation of ultra-stretchable gradient conducting ion gel 1.

[0030] Acrylic acid (4.3236 g, 60 mmol), 1-ethyl-3-methylimidazole ethyl sulfate (4.7200 g, 20 mmol), double-end methacrylate-terminated modified silicone oil (0.3912 g, 0.24 mmol) and photoinitiator 2-hydroxy-2-methylphenylacetone (0.0296 g, 0.18 mmol) were added to a 50 mL round-bottom flask and stirred at room temperature to obtain a precursor solution. The precursor solution was poured into a polytetrafluoroethylene mold and allowed to stand for 30 seconds before being irradiated under a UV lamp (light intensity 50 mW cm -2 , emission wavelength 365 nm) for 5 minutes to obtain the ultra-stretchable gradient conductive ion gel 1.

[0031] Example 2:

[0032] Preparation of ultra-stretchable gradient conducting ion gel 2.

[0033] Acrylic acid (3.6030 g, 50 mmol), 1-ethyl-3-methylimidazole ethyl sulfate (4.7200 g, 20 mmol), double-end methacrylate end-capped modified silicone oil (0.3260 g, 0.20 mmol) and photoinitiator 2-hydroxy-2-methylphenylacetone (0.0246 g, 0.15 mmol) were added to a 50 mL round-bottom flask and stirred at room temperature to obtain a precursor solution. The precursor solution was poured into a polytetrafluoroethylene mold and allowed to stand for 30 seconds before being irradiated under a UV lamp (light intensity 50 mW cm -2 , emission wavelength 365 nm) for 5 minutes to obtain the ultra-stretchable gradient conductive ion gel 2.

[0034] Example 3:

[0035] Preparation of ultra-stretchable gradient conducting ion gel 3.

[0036] Acrylic acid (2.8824 g, 40 mmol), 1-ethyl-3-methylimidazole ethyl sulfate (4.7200 g, 20 mmol), double-end methacrylate end-capped modified silicone oil (0.2608 g, 0.16 mmol) and photoinitiator 2-hydroxy-2-methylphenylacetone (0.0197 g, 0.12 mmol) were added to a 50 mL round-bottom flask and stirred at room temperature to obtain a precursor solution. The precursor solution was poured into a polytetrafluoroethylene mold and allowed to stand for 30 seconds before being irradiated under a UV lamp (light intensity 50 mW cm -2 , emission wavelength 365nm) for 5 minutes to obtain the ultra-stretchable gradient conductive ion gel 3.

[0037] Example 4:

[0038] Preparation of ultra-stretchable gradient conducting ion gel 4.

[0039] Acrylic acid (2.8824 g, 40 mmol), 1-ethyl-3-methylimidazole ethyl sulfate (4.7200 g, 20 mmol), double-terminal methacrylate-modified silicone oil (0.3912 g, 0.24 mmol) and photoinitiator 2-hydroxy-2-methylphenylacetone (0.0197 g, 0.12 mmol) were added to a 50 mL round-bottom flask and stirred at room temperature to obtain a precursor solution. The precursor solution was poured into a polytetrafluoroethylene mold and allowed to stand for 30 seconds before being irradiated under a UV lamp (light intensity 50 mW cm -2 , emission wavelength 365 nm) for 5 minutes to obtain the ultra-stretchable gradient conductive ion gel 4.

[0040] Example 5:

[0041] In this example, N,N'-methylenebisacrylamide was used as a crosslinking agent instead of the double-terminal methacrylate-modified silicone oil to prepare ion gel 5 used as a comparative example.

[0042] Acrylic acid (2.8824 g, 40 mmol), 1-ethyl-3-methylimidazole ethyl sulfate (4.7200 g, 20 mmol), N,N'-methylenebisacrylamide (0.0247 g, 0.16 mmol) and photoinitiator 2-hydroxy-2-methylphenylacetone (0.0197 g, 0.12 mmol) were added to a 50 mL round-bottom flask and stirred at room temperature to obtain a precursor solution. The precursor solution was poured into a polytetrafluoroethylene mold and allowed to stand for 30 seconds before being irradiated under a UV lamp (light intensity 50 mW cm -2 , emission wavelength 365 nm) for 5 minutes to obtain comparative example ion gel 5.

[0043] Example 6:

[0044] The purpose of this example is to illustrate that the double-terminal methacrylate-modified silicone oil in the ion gel 3 prepared in Example 3 has the ability to float itself and form a gradient distribution in the ion gel.

[0045] The element contents on the bottom and top surfaces of the ion gel 3 in Example 3 were tested by scanning electron microscopy-energy dispersive spectrometer. Figure 1 It can be seen that the content of silicon on the top surface of ion gel 3 is 23.60%, which is much higher than the 2.40% on the bottom surface. This indicates that the double-end methacrylate-modified silicone oil component presents a gradient distribution inside ion gel 3. At the same time, due to the gradient distribution of the double-end methacrylate-modified silicone oil component, the content of S element increases from 0.04% on the top surface to 3.64%, indicating that the ionic liquid in ion gel 3 also presents a gradient distribution.

[0046] Example 7:

[0047] The purpose of this example is to illustrate that the ion gel 1-4 prepared in Example 1-4 has a gradient conductivity property, and the conductivity presents a gradient change along the vertical direction within the ion gel 1-4.

[0048] The conductivity of the top, middle and bottom of the ion gels 1-4 prepared in Examples 1-4 was tested by AC impedance method on an electrochemical workstation. Figure 2 It can be seen that the electrical conductivity of ion gels 1-4 all show a gradient change that gradually increases from top to bottom, which indicates that the self-floating property of the silicone oil makes the ion gels 1-4 prepared in Examples 1-4 have gradient conductivity properties.

[0049] Example 8:

[0050] The purpose of this example is to illustrate that the use of an organosilicon crosslinker improves the tensile properties of ion gels 1-4 prepared in Examples 1-4, and to compare them with ion gel 5 in which no organosilicon crosslinker is used.

[0051] The ion gels 1-4 prepared in Examples 1-4 and the ion gel 5 prepared in Example 5 were subjected to uniaxial tensile tests at 25°C at a tensile rate of 100 mm·min -1 , the test results are as follows Figure 3 and Figure 4 The elongation at break of ion gels 1-4 using polymerizable modified silicone oil as a crosslinker all exceeded 8000%, with ion gel 3 in particular achieving a high elongation of 14363%. In contrast, the elongation at break of ion gel 5, prepared in Example 5 using N,N'-methylenebisacrylamide instead of the silicone crosslinker, was only 2850%, demonstrating that the silicone crosslinker imparts ultra-high tensile properties to ion gels 1-4.

[0052] Example 9:

[0053] The purpose of this example is to illustrate that the ion gel 3 prepared in Example 3 has adhesive properties.

[0054] The ion gel 3 prepared in Example 3 was placed in contact with various substrates and then lifted up to test its adhesion. The results are as follows: Figure 5 As shown in FIG, the ion gel 3 has adhesive properties and can adhere to various substrates such as cotton, glass and latex. The adhesion strength of the ion gel 3 prepared in Example 3 was tested by tensile shear test at 25°C. The results are shown in FIG. Figure 6 The ion gel 3 prepared in Example 3 has a high adhesion strength to the glass substrate, reaching 75.1 KPa.

[0055] Example 10:

[0056] The purpose of this embodiment is to illustrate that the flexible strain sensor made of the ion gel 3 prepared in Example 3 has excellent sensing performance and can be used to monitor human body movements.

[0057] The ion gel 3 prepared in Example 3 was combined with a copper wire to form a flexible strain sensor, and the strain sensing performance of the sensor was tested using a universal material testing machine-source meter. Figure 7 (a) It can be seen that the sensor prepared in this embodiment has a wide strain detection range (0-500%) and high sensitivity. The sensitivity factor of the sensor is as high as 2.87 when fitting the data in the strain range of 50-500%. 2 =0.999, indicating that its relative resistance change (△R / R0) has a good linear relationship with the strain. Figure 7(b) shows the change of ΔR / R0 during continuous loading and unloading cycles of the sensor prepared in this example under different strains, indicating that the strain response of the sensor prepared in this example has strong stability and reversibility. Figure 7 (c) It can be seen that the hysteresis of the sensor prepared in this embodiment is small and can be ignored. Figure 7 (d) shows that the sensor prepared in this example has a fast response speed, with a response time of only 177ms. Figure 7 (e) shows the ΔR / R0 curve for the sensor fabricated in this example after 1000 consecutive stretching cycles at a maximum strain of 20%. As can be seen from the figure, the sensor fabricated in this example maintains electrical signal stability and repeatability over 1000 consecutive stretching cycles, demonstrating the excellent durability of the sensor fabricated in this example. Figure 8 This shows that the sensor prepared in this embodiment can accurately respond to human body movements, such as large deformations caused by bending of elbows, fingers and wrists, and small deformations caused by coughing, frowning and smiling.

[0058] The above description is merely 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 conceived by a 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.

Claims

1. A method for preparing an ultra-stretchable gradient conductive ion gel, characterized in that: The following steps are involved: S1: Using a polymerizable modified silicone oil as a crosslinking agent, mixing it with a (meth)acryloyl-containing monomer, an ionic liquid, and a photoinitiator to obtain a precursor solution; wherein the molar ratio of the polymerizable group of the polymerizable modified silicone oil to the (meth)acryloyl-containing monomer is (1-50):1000, the molar ratio of the photoinitiator to the (meth)acryloyl-containing monomer is (1-50):1000, and the molar ratio of the ionic liquid to the (meth)acryloyl-containing monomer is 10:(10-50); The polymerizable modified silicone oil is a double-terminal methacrylate-modified silicone oil, the (meth)acryloyl-containing monomer is acrylic acid, and the ionic liquid is 1-ethyl-3-methylimidazole ethyl sulfate; S2: The precursor solution is solidified through a photo-initiated polymerization reaction to obtain an ultra-stretchable gradient conductive ion gel.

2. The method according to claim 1, characterized in that The photoinitiator in step S1 is selected from one or more free radical photoinitiators.

3. An ultra-stretchable gradient conductive ion gel prepared by the method according to claim 1 or 2.

4. An application of the ultra-stretchable gradient conductive ion gel according to claim 3, characterized in that: The ultra-stretchable gradient conductive ion gel is applied to flexible sensors, supercapacitors, lithium battery solid electrolytes, drivers, gas separation, and optical devices.

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