Gradient ionic gel composition for flexible sensor and preparation thereof

Abstract

This invention discloses a gradient ion gel composition for flexible sensors and its preparation. The gradient ion gel, which can be used in flexible sensors, contains a hyperbranched organosilicon crosslinking agent with self-floating properties and imparting gradient conductivity to the ion gel, a second free radical polymerizable monomer, an ionic liquid, and a photoinitiator. The beneficial effects of this invention are: the prepared gradient conductive ion gel exhibits good tensile properties and fatigue resistance; the prepared gradient conductive ion gel possesses multiple sensing properties.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer conductive materials technology, specifically relating to a gradient ion gel composition for flexible sensors and its preparation. Background Technology

[0002] Flexible electronic devices, especially flexible sensors, have been widely used in fields such as human-computer interaction, wireless communication, and health monitoring. Due to their unique flexibility and stability, ionogels, as an emerging soft conductor material, have begun to show promise in the field of flexible electronic devices. Ionogels not only possess high conductivity but also can withstand extreme temperatures and chemical environments, providing strong support for the operation of flexible electronic devices in harsh environments.

[0003] Gradient-conductive ionogels have been used to fabricate flexible sensors with high sensitivity and wide detection range. However, their complex fabrication process, demanding operation, and requirement for additional equipment have limited their application and development in flexible sensors. Therefore, simplifying the fabrication process and reducing equipment hardware requirements are pressing issues that need to be addressed for gradient-conductive ionogels. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a gradient ion gel composition, its preparation, and its application. This composition exhibits gradient conductivity, excellent fatigue resistance, and the ability to convert various stimuli into electrical signals. Through extensive and in-depth research, this invention prepares a series of gradient ion gel compositions by compounding a self-floating, free-radical polymerizable hyperbranched organosilicon crosslinking agent, other free-radical polymerizable monomers, ionic liquids, and photoinitiators.

[0005] Specifically, the present invention includes:

[0006] A gradient ionogel composition comprising a polymerizable hyperbranched organosilicon crosslinking agent, a second free radical polymerizable monomer, an ionic liquid, and a photoinitiator;

[0007] The structural formula of the hyperbranched organosilicon crosslinking agent is shown in formula a:

[0008]

[0009] Where R1 is n1 and n2 are taken from 1 to 10, and R2 is methoxy, ethoxy, or hydroxyl.

[0010] In this invention, the second free radical polymerizable monomer refers to other free radical polymerizable monomers in the ion gel composition besides hyperbranched organosilicon crosslinking agents.

[0011] Preferably, the polymerizable free radical monomer is selected from one or more combinations of methacrylate monomers and acrylate monomers; the methacrylate monomer is selected from one or more combinations of monofunctional, difunctional, or polyfunctional methacrylate monomers; and the acrylate monomer is selected from one or more combinations of monofunctional, difunctional, or polyfunctional acrylate monomers.

[0012] The ionic liquid is selected from one or more of imidazole ionic liquids, pyrrole ionic liquids, quaternary ammonium ionic liquids, or quaternary phosphonium ionic liquids; preferably, the ionic liquid is an imidazole ionic liquid.

[0013] Preferably, the photoinitiator is selected from one or more free radical photoinitiators.

[0014] This invention provides a method for preparing the gradient ion gel composition described above, comprising the following steps:

[0015] A precursor solution is obtained by mixing a polymerizable hyperbranched organosilicon crosslinking agent with a monomer containing (meth)acryloyl groups, an ionic liquid, and a photoinitiator; wherein the molar ratio of the polymerizable hyperbranched organosilicon crosslinking agent to the monomer containing (meth)acryloyl groups is (1-50):1000, the molar ratio of the photoinitiator to the monomer containing (meth)acryloyl groups is (1-50):1000, and the molar ratio of the ionic liquid to the monomer containing (meth)acryloyl groups is 10:(10-50).

[0016] In another aspect, this invention provides the application of the above-described gradient ion gel composition in flexible sensors. The beneficial effects of this invention are as follows:

[0017] 1. The gradient ion gel composition prepared by the present invention has gradient conductivity and good fatigue resistance due to the introduction of a free radical polymerizable hyperbranched organosilicon crosslinking agent;

[0018] 2. The gradient ion gel composition prepared in this invention can improve the sensitivity of sensors to strain and pressure responses, and this gradient ion gel composition has broad application prospects in the field of multi-response flexible electronics. Attached Figure Description

[0019] Figure 1 The stress-strain curve of the gradient ionogel composition prepared in Example 5 is shown.

[0020] Figure 2 The stress-compressive strain curves of the gradient ionogel composition prepared in Example 5 are shown.

[0021] Figure 3 The gradient ionogel composition IG prepared in Example 6 20 -b0.25 Stress-strain curves during continuous tensile cycles;

[0022] Figure 4 The gradient ionogel composition IG prepared in Example 6 10 -b 0.25 Stress-strain curves during continuous compression cycles;

[0023] Figure 5 The gradient ionogel composition IG prepared in Example 7 20 -b 0.25 The ΔR / R0 strain curve;

[0024] Figure 6 The gradient ionogel composition IG prepared in Example 7 10 -b 0.25 The ΔR / R0 pressure curve;

[0025] Figure 7 The gradient ionogel composition IG prepared in Example 7 10 -b 0.25 The ΔR / R0-time curve for temperature increase from 20℃ to 50℃; Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0027]

Example 1

[0028] Preparation of hyperbranched organosilicon crosslinking agent A

[0029] At 25°C, γ-methacryloxypropyltrimethoxysilane (24.8 g, 10 mmol) and deionized water (2.0 g, 110 mmol) were added to a 100 mL round-bottom flask. Dilute hydrochloric acid (1 mol / L) was added dropwise with stirring to adjust the pH of the reaction solution to 1–2. The reaction solution was then heated to 50°C and maintained for 5 h. Afterward, methanol was removed by rotary evaporation under reduced pressure to obtain a colorless, transparent liquid hyperbranched organosilicon crosslinking agent A, whose M... w The concentration was 1371 g / mol, and the degree of branching was 0.49.

[0030]

Example 2

[0031] Preparation of hyperbranched organosilicon crosslinking agent B

[0032] At 25°C, γ-methacryloyloxypropyltrimethoxysilane (24.8 g, 10 mmol) and deionized water (2.3 g, 130 mmol) were added to a 100 mL round-bottom flask. Dilute hydrochloric acid (1 mol / L) was added dropwise with stirring to adjust the pH of the reaction solution to 1–2. The reaction solution was then heated to 50°C and maintained for 5 h. Afterward, methanol was removed by rotary evaporation under reduced pressure to obtain a colorless, transparent liquid hyperbranched organosilicon crosslinking agent B, whose M... w The concentration was 1606 g / mol, and the degree of branching was 0.41.

[0033]

Example 3

[0034] Preparation of hyperbranched organosilicon crosslinking agent C

[0035] At 25°C, γ-methacryloxypropyltrimethoxysilane (24.8 g, 10 mmol) and deionized water (2.3 g, 130 mmol) were added to a 100 mL round-bottom flask. Dilute hydrochloric acid (1 mol / L) was added dropwise with stirring to adjust the pH of the reaction solution to 1–2. The reaction solution was then heated to 60°C and maintained for 7 h. Afterward, methanol was removed by rotary evaporation under reduced pressure to obtain a colorless, transparent liquid hyperbranched organosilicon crosslinking agent C, whose M... w The concentration was 1912 g / mol, and the degree of branching was 0.59.

[0036]

Example 4

[0037] This embodiment illustrates that a gradient ionogel composition of hyperbranched organosilicon crosslinking agents A, B, and C has gradient conductivity.

[0038] A gradient ionogel composition was prepared according to the formulation in Table 1, consisting of photoinitiator (TPO-L), monomer acrylic acid (AA), ionic liquid ethyl 1-ethyl-3-methylimidazolium sulfate (EMIMES), and hyperbranched organosilicon crosslinking agent A, B, or C. After thorough mixing, the gradient ionogel composition was poured into a polytetrafluoroethylene mold (10×10×10mm) and allowed to stand for 1 hour. The mixture was then subjected to oxygen-barrier conditions and a light intensity of 100 mW / cm². -2 The gradient ionogel was obtained by irradiating the sample with a UV lamp with an emission wavelength of 365 nm for 5 minutes. The conductivity σ of the gradient ionogel was then tested by AC impedance spectroscopy, and the results are shown in Table 1. The conductivity of the gradient ionogel compositions of hyperbranched organosilicon crosslinking agents A, B, and C decreased from top to bottom, indicating that the gradient ionogel compositions of hyperbranched organosilicon crosslinking agents A, B, and C exhibit gradient conductivity.

[0039] Table 1. Gradient ionogel compositions and their conductivity

[0040] formula <![CDATA[IG 20 -a 0.25 ]]> <![CDATA[IG 20 -b 0.25 ]]> <![CDATA[IG 20 -c 0.25 ]]> AA (mmol) 20 20 20 EMIMES (mmol) 10 10 10 n(TPO-L):n(AA) 3:1000 3:1000 3:1000 n(A):n(AA) 2.5:1000 0:1000 0:1000 n(B):n(AA) 0:1000 2.5:1000 0:1000 n(C):n(AA) 0:1000 0:1000 2.5:1000 <![CDATA[σ 上 (mS cm -1 )]]> 0.0076 0.0064 0.0041 <![CDATA[σ 下 (mS cm -1 )]]> 0.0199 0.0157 0.0150

[0041]

Example 5

[0042] The purpose of this embodiment is to illustrate that the gradient ion gel composition has good stretchability and compressibility.

[0043] The formulation of the gradient ionogel composition is shown in Table 2. The cured gradient ionogel composition was subjected to uniaxial tensile and compression tests at 25°C using a universal testing machine. The test results are shown in [Table 2]. Figure 1 and Figure 2 With the increase of hyperbranched silicone crosslinking agent B content, the fracture stress of the cured gradient ionogel composition increased and the fracture strain decreased, but the minimum fracture strain was still close to 900%. When the compressive strain reached 80%, the cured gradient ionogel composition did not break, and its stress also increased with the increase of hyperbranched silicone crosslinking agent B content, with the highest stress reaching 1.35 MPa.

[0044] Table 2 Formulation of Gradient Ion Gel Compositions

[0045]

[0046]

Example 6

[0047] The purpose of this embodiment is to illustrate that the gradient ion gel composition has excellent fatigue resistance.

[0048] The formulation of the gradient ionogel composition is shown in Table 3. The cured gradient ionogel composition was subjected to continuous cyclic tensile and cyclic compression tests at 25°C using a universal testing machine, with 20 cycles in each test. The test results are shown in [Table 3]. Figure 3 and Figure 4 The load-unload curves of the cured gradient ionogel composition overlapped in the 2nd to 20th cycles, and the stress corresponding to the maximum strain remained almost unchanged in the 1st to 20th cycles, indicating that the gradient ionogel composition has excellent fatigue resistance.

[0049] Table 3 Gradient Ion Gel Composition Formulation

[0050]

[0051]

Example 7

[0052] This embodiment is intended to illustrate that the gradient ion gel composition has multiple sensing properties.

[0053] The formulation of the gradient ionomer gel composition is shown in Table 3. The strain, pressure, and temperature sensing properties of the cured gradient ionomer gel composition were tested using a universal testing machine coupled with a source meter. The results are as follows: Figure 5-7 As shown. From Figure 5It can be seen that the relative resistance change ΔR / R0 of the gradient ionogel composition gradually increases with increasing applied strain, with a sensitivity of 2.50. Fitting the experimental data reveals an excellent linear correlation between ΔR / R0 and the applied strain, with a linear correlation coefficient exceeding 0.999. Figure 6 It can be seen that the gradient ion gel composition exhibits different pressure sensing characteristics in the low-pressure and high-pressure regions: when the applied pressure is in the low-pressure region (0–1 kPa), the relative resistance change ΔR / R0 of the gradient ion gel composition increases rapidly with pressure, exhibiting high sensitivity, reaching a maximum of 19.33 kPa. -1 When the applied pressure is in the high-pressure range (1–200 kPa), the relative resistance change ΔR / R0 of the gradient ionogel composition increases slowly with pressure, with a sensitivity of 0.09 MPa. -1 .from Figure 7 It can be seen that the resistance of the gradient ion gel composition is negatively correlated with temperature; the higher the temperature, the lower the resistance of the gradient ion gel composition, and the larger the absolute value of ΔR / R0. This indicates that the gradient ion gel composition has multiple sensing properties.

[0054] 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 variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A gradient ionogel composition comprising a polymerizable hyperbranched organosilicon crosslinking agent, a second free radical polymerizable monomer, an ionic liquid, and a photoinitiator; The structural formula of the hyperbranched organosilicon crosslinking agent is shown in formula a: Where R1 is n1 and n2 are taken from 1 to 10, and R2 is methoxy, ethoxy, or hydroxyl.

2. The gradient ionogel composition according to claim 1, characterized in that, The second free radical polymerizable monomer refers to other free radical polymerizable monomers in the ionogel composition besides hyperbranched organosilicon crosslinking agents.

3. The gradient ionogel composition according to claim 2, characterized in that, The second free radical polymerizable monomer is selected from one or more combinations of methacrylate monomers and acrylate monomers; the methacrylate monomer is selected from one or more combinations of monofunctional, difunctional or polyfunctional methacrylate monomers; the acrylate monomer is selected from one or more combinations of monofunctional, difunctional or polyfunctional acrylate monomers.

4. The gradient ionogel composition according to claim 1, characterized in that, The ionic liquid is selected from one or more of imidazole ionic liquids, pyrrole ionic liquids, quaternary ammonium ionic liquids, or quaternary phosphonium ionic liquids.

5. The gradient ionogel composition according to claim 4, characterized in that, The ionic liquid is an imidazole-based ionic liquid.

6. The gradient ionogel composition according to claim 1, characterized in that, The photoinitiator is selected from one or more free radical photoinitiators.

7. A method for preparing the gradient ionogel composition according to any one of claims 1-6, characterized in that, Includes the following steps: A precursor solution is obtained by mixing a polymerizable hyperbranched organosilicon crosslinking agent with a monomer containing (meth)acryloyl groups, an ionic liquid, and a photoinitiator; wherein the molar ratio of the polymerizable hyperbranched organosilicon crosslinking agent to the monomer containing (meth)acryloyl groups is (1-50):1000, the molar ratio of the photoinitiator to the monomer containing (meth)acryloyl groups is (1-50):1000, and the molar ratio of the ionic liquid to the monomer containing (meth)acryloyl groups is 10:(10-50).

8. The gradient ion gel composition according to any one of claims 1-6 is applied to a flexible sensor.

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