Supramolecular deep eutectic conductive gel with microphase separation structure, preparation method and application thereof

Abstract

The application discloses a supramolecular deep eutectic conductive gel with a micro-phase separation structure and a preparation method and application thereof. The method comprises the following steps: dissolving N-(2-hydroxyethyl) acrylamide monomers and a polyampholyte monomer [3-(methacrylamido) propyl] dimethyl (3-thiopropyl) ammonium hydroxide in a deep eutectic solvent composed of choline chloride and ethylene glycol, and then performing photo-crosslinking; the supramolecular deep eutectic conductive gel is prepared by utilizing the difference in the adsorption capacity of the polyampholyte monomer to the deep eutectic solvent, forming soft and hard two phases rich in and lacking the deep eutectic solvent. The conductive gel has excellent comprehensive mechanical properties and self-recovery, and has the characteristics of good conductivity, environmental stability, biocompatibility and green environmental protection, and can work normally under extreme environments and large strain and stress conditions, and has a wide application prospect in the field of flexible electronics.

Description

Technical Field

[0001] This invention belongs to the field of conductive gel technology, and relates to a supramolecular deep eutectic conductive gel with a microphase separation structure, its preparation method and application. Background Technology

[0002] With the rapid development of network communication and smart terminals, and the continuous iteration of artificial intelligence and virtual reality technologies, people's demand for flexible electronic products that are intelligent, lightweight, and personalized is increasing, and the field of flexible electronics is showing broad application prospects. Compared with traditional electronic technology, flexible electronic devices have excellent stretchability and bendability, overcoming the fundamental defects of rigid devices, and are widely used in wearable electronics, medical and health care, human-computer interaction and other fields.

[0003] Conductive gels are widely used in flexible electronic devices due to their flexibility and conductivity. Hydrogels, containing 70%–80% water, possess excellent flexibility, but water is unstable and prone to evaporation or crystallization. This causes water-based hydrogels to lose flexibility and fail, greatly limiting their applications. To address these issues, ionic liquid conductive gels have been introduced, using chemically stable, non-volatile ionic liquids as dispersion solvents. Because they are water-free, they avoid the failure risks associated with hydrogels and improve the environmental stability of flexible electronic devices. However, ionic liquids are toxic, causing environmental pollution, and their preparation processes are complex and expensive, limiting their market adoption and biocompatible applications. In contrast, deep eutectic solvents, as emerging green solvents, possess physical properties similar to ionic liquids, such as low melting point, low vapor pressure, and high conductivity. Furthermore, their raw materials are green, non-toxic, and inexpensive (Hansen BB, Spittle S, Chen B, et al. Deep Eutectic Solvents: A Review of Fundamentals and Applications. Chem Rev. 2021; 121(3):1232-1285.). However, conductive gels prepared based on deep eutectic solvents currently still cannot meet the needs of the flexible electronics field. For example, Shu Hong et al. polymerized acrylamide in a deep eutectic solvent composed of choline chloride-urea-glycerol and improved the mechanical properties of the gel by adding cellulose slurry to the dispersion system. However, even with the construction of a double network structure composed of polyacrylamide and cellulose, the mechanical properties were not significantly improved due to the single form of intermolecular interaction in the internal network and the lack of covalent / non-covalent interactions (fracture strain was only 250%–450%, and tensile strength was 10 kPa–60 kPa) (S.Hong, Y.Yuan, C.Liu, et al., A stretchable and compressible ion gel based on a deep eutectic solvent applied as a strain sensor and electrolyte for supercapacitors. J.Mater.Chem.C,8(2020),pp.550-560).Ren'ai Li et al. prepared deep eutectic gels by copolymerizing hard segments (poly(acrylamide / choline chloride)) and soft segments (poly(acrylic acid / choline chloride)). Due to the instability of the liquid system leading to irregular phase separation, the increase of soft segments resulted in soft domains being trapped within hard segments, while the increase of hard segments caused soft domains to shrink. Therefore, even with attempts to control the ratio of soft to hard segments, the gel as a whole still exhibited rigid and instretchable characteristics—high strength (65.74–108.13 MPa), but only 5%–10% stretchability. Simultaneously, the densely entangled polymer chains restricted ion migration, resulting in low electrical conductivity (0.37–1.25 × 10⁻⁶). -3S / m). (Ren'ai Li, Kaili Zhang, Guangxue Chen, et al. Stiff, Self-Healable, Transparent Polymers with Synergetic Hydrogen Bonding Interactions. Chem. Mater. 2021, 33, 13, 5189-5196). JiLan et al. used choline chloride / ethylene glycol as a deep eutectic solvent to prepare a dual-network deep eutectic gel composed of physically crosslinked zwitterionic poly(3-dimethyl(methacryloyloxyethyl)propanesulfonate ammonium (PDMAPS)) and chemically crosslinked poly(2-hydroxyethyl methacrylate) (PHEMA). This improved the gel's toughness to some extent (500%–1050%), but due to the predominantly weak physical crosslinking of its internal polymer network, its tensile strength was low (100 kPa–210 kPa) (Lan, J., Zhou, B., Yin, C., Weng, L., Ni, W., & Shi, L. (2021). Zwitterionic dual-network strategy for highly stretchable and transparent ionic conductor.Polymer, 231, 124111.). In summary, the existing gels based on deep eutectic solvents have poor overall mechanical properties and cannot meet the basic requirements for flexible electronic devices. In addition, deep eutectic gels prepared based on conventional polymer monomers have poor conductivity and impedance in the thousands of ohms, which cannot be used in flexible electronic devices (Ge G, Mandal K, Haghniaz R, et al. Deep Eutectic Solvents-based Ionogels with Ultrafast Gelation and High Adhesion in Harsh Environments. Adv Funct Mater. 2023; 33(9):2207388.). Summary of the Invention

[0004] The present invention aims to provide a supramolecular deep eutectic conductive gel with a microphase-separated structure, its preparation method, and its applications. This conductive gel uses N-(2-hydroxyethyl)acrylamide (HEAA) and [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide (SPP) as monomers, and choline chloride and ethylene glycol as deep eutectic solvents (DES), to obtain the supramolecular deep eutectic conductive gel through photopolymerization. The positively and negatively charged groups on the SPP amphoteric monomers within the supramolecular deep eutectic conductive gel can adsorb the polar deep eutectic solvent, thereby forming a soft phase within the conductive gel. The network formed by the crosslinking of HEAA monomers, lacking polar molecules, forms a hard phase, thus preparing a conductive gel with a microphase-separated structure. The deep eutectic solvent used in the conductive gel is formed by the interaction of green and non-toxic choline chloride and ethylene glycol through hydrogen bonding, exhibiting good environmental stability and conductivity. Deep eutectic conductive gels contain abundant reversible non-covalent interactions such as hydrogen bonds, ionic bonds, van der Waals forces, and electrostatic interactions, thus exhibiting excellent self-healing, resilience, and fatigue resistance. The supramolecular deep eutectic conductive gel with a microphase-separated structure of this invention has a simple preparation process, is inexpensive, and environmentally friendly, meeting the various requirements for mechanical properties, environmental stability, and conductivity in flexible electronics applications. This can broaden the application scope of flexible electronic devices and enrich application scenarios.

[0005] The technical solution for achieving the objective of this invention is as follows:

[0006] A method for preparing a supramolecular deep eutectic conductive gel with a microphase-separated structure is described, using N-(2-hydroxyethyl)acrylamide and [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide as monomers, a deep eutectic solvent as a flexible dispersion solvent, and a photoinitiator to initiate free radical supramolecular polymerization crosslinking under ultraviolet light to form the conductive gel. The specific steps are as follows:

[0007] (1) Dissolve choline chloride in ethylene glycol at a molar ratio of 1:2 and heat and stir until clear and transparent, and use it as a deep eutectic solvent.

[0008] (2) Add N-(2-hydroxyethyl)acrylamide monomer and [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide polyamphomonomer to a deep eutectic solvent and stir until clear and transparent as a precursor solution;

[0009] (3) Add photoinitiator to the precursor solution, stir until transparent and clear, and then inject into the mold. Under ultraviolet light irradiation, a polymerization reaction occurs to form a supramolecular deep eutectic conductive gel.

[0010] Preferably, in step (1), the heating temperature is 90-100°C and the stirring speed is 800-1000 rpm.

[0011] Preferably, in step (2), the molar ratio of N-(2-hydroxyethyl)acrylamide to [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide is 8:1 to 10:1, more preferably 9:1.

[0012] Preferably, in step (2), the ratio of the total molar amount of choline chloride and ethylene glycol to the molar amount of [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide is 5:1 to 8:1, more preferably 6:1.

[0013] In step (3), the photoinitiator is a photoinitiator commonly used in the art. In a specific embodiment of the present invention, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone is a representative example.

[0014] Preferably, in step (3), the mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone is 0.1% to 0.2% of the mass of the precursor solution.

[0015] Preferably, in step (2) or (3), the stirring speed is 800 to 1000 rpm.

[0016] Preferably, in step (3), the mold is made of glass and the mold spacing is 900-1100 μm.

[0017] Preferably, in step (3), the wavelength of the ultraviolet light is 254 nm and the ultraviolet light irradiation intensity is 800 μJ / cm. 2 .

[0018] Preferably, in step (3), the polymerization reaction time is 30 minutes.

[0019] Furthermore, the present invention provides a supramolecular deep eutectic conductive gel prepared by the above preparation method.

[0020] Furthermore, the present invention provides the application of the above-mentioned supramolecular deep eutectic conductive gel in the fabrication of flexible electronic devices.

[0021] The flexible electronic devices described in this invention include, but are not limited to, flexible sensors and flexible wearable sensors.

[0022] The flexible sensor and flexible wearable sensor described in this invention are composed of the aforementioned supramolecular deep eutectic conductive gel, copper electrode sheets attached to both sides of the electrolyte, and adhesive tape.

[0023] Preferably, the tape is VHB tape.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) This invention utilizes the hydrogen bond formed between choline chloride and the hydroxyl group in ethylene glycol to produce a eutectic effect, thereby lowering the melting point of choline chloride and preparing a deep eutectic solvent with low vapor pressure, low glass transition temperature, green and pollution-free properties and conductivity. Therefore, the conductive gel prepared has good environmental stability (working temperature range: -64~192℃) and conductivity (ionic conductivity of 0.02S / m).

[0026] (2) In this invention, the polyamplifier [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide adsorbs polar molecules in the deep eutectic solvent to form a soft phase, while N-(2-hydroxyethyl)acrylamide forms a hard phase due to the lack of dispersion solvent. This creates a microphase separation structure inside the conductive gel. The interaction between the soft and hard phases provides an effective energy dissipation mechanism, thereby improving the overall mechanical properties of the conductive gel. It has both high strength and good tensile strength, exhibiting toughened mechanical properties.

[0027] (3) The polyampholy monomer [3-(methacrylamide)propyl]dimethyl(3-thiopropyl)ammonium hydroxide used in this invention has both positively charged and negatively charged groups on one monomer molecule. It can not only adsorb polar molecules in deep eutectic solvents, but also improve the conductivity of conductive gels in conjunction with deep eutectic solvents. The ionic conductivity reaches 0.02 to 0.07 S / m, which is at the same level as expensive and toxic ionic liquid gels.

[0028] (4) The supramolecular deep eutectic conductive gel of the present invention contains a large number of reversible non-covalent physical interactions such as hydrogen bonds, ionic bonds, electrostatic interactions and van der Waals forces. These physical interactions can be rapidly and randomly reconstructed, so that the internal network of the conductive gel has good recovery performance and fatigue resistance: after being stretched to a strain of 500%, unloaded to a strain of 0% and left to stand at room temperature for 5 minutes, 92% of the mechanical properties (energy dissipation) can be recovered. Attached Figure Description

[0029] Figure 1 The stress-strain curves are for the supramolecular deep eutectic conductive gels prepared in Examples 1, 2, and 3.

[0030] Figure 2 The stress-strain curves are for the supramolecular deep eutectic conductive gels prepared in Examples 1, 5, and 6.

[0031] Figure 3 The loading-unloading cyclic tensile stress-strain curve of the supramolecular deep eutectic conductive gel prepared in Example 1;

[0032] Figure 4 The energy dissipation histogram and self-healing efficiency graph are obtained from the loading-unloading cyclic stretching calculation of the supramolecular deep eutectic conductive gel prepared in Example 1.

[0033] Figure 5 The stress-strain curves are those of the supramolecular deep eutectic conductive gel prepared in Example 1 and the deep eutectic gel prepared in Comparative Example 1.

[0034] Figure 6 Scanning electron microscope image of the supramolecular deep eutectic conductive gel prepared in Example 1;

[0035] Figure 7 Impedance spectrum of the supramolecular deep eutectic conductive gel prepared in Example 1;

[0036] Figure 8 Thermogravimetric analysis diagram of the supramolecular deep eutectic conductive gel prepared in Example 1;

[0037] Figure 9 Differential scanning calorimetry (DSC) of the supramolecular deep eutectic conductive gel prepared in Example 1;

[0038] Figure 10 The response of a flexible sensor based on supramolecular deep eutectic conductive gel to tensile stimulation is shown in the figure.

[0039] Figure 11 The response of a flexible sensor based on supramolecular deep eutectic conductive gel to pressure stimulation is shown in the figure.

[0040] Figure 12 The response of a flexible sensor based on supramolecular deep eutectic conductive gel to bending stimulation is shown in the figure.

[0041] Figure 13 The image shows the response signal of a flexible sensor based on supramolecular deep eutectic conductive gel to a 500-cycle tensile test.

[0042] Figure 14 This is a graph showing the response signal of a flexible wearable sensor based on supramolecular deep eutectic conductive gel to human shoulder joint movement.

[0043] Figure 15 This is a graph showing the response signal of a flexible wearable sensor based on supramolecular deep eutectic conductive gel to human elbow joint movement.

[0044] Figure 16 This is a graph showing the response signal of a flexible wearable sensor based on supramolecular deep eutectic conductive gel to human knee joint movement. Detailed Implementation

[0045] The technical solution of the present invention will be further described below with reference to specific embodiments and accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0046] Example 1: Preparation of supramolecular deep eutectic conductive gel with microphase separation structure (monomer molar ratio HEAA:SPP is 9:1, and the molar ratio of polar molecules (cations and anions in choline chloride and ethylene glycol) to SPP is 6:1)

[0047] (1) Weigh 0.3006 g of choline chloride into a 5 mL sample bottle, then add 0.24 mL of ethylene glycol dropwise into the sample bottle, heat and stir at 95 °C for 2 hours until clear and transparent, and let stand at room temperature to obtain a deep eutectic solvent.

[0048] (2) Add 0.3134 g of [3-(methacrylamide)propyl]dimethyl(3-thiopropyl)ammonium hydroxide to the above deep eutectic solvent, then add 1 mL of N-(2-hydroxyethyl)acrylamide dropwise to the sample bottle, and stir at room temperature until clear and transparent to obtain the conductive gel precursor solution.

[0049] (3) Add 20 mg of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone to the above precursor solution, stir until transparent and clear, and then pour into a glass mold. In a UV crosslinker (254 nm), irradiate and polymerize for 30 minutes to obtain a supramolecular deep eutectic conductive gel.

[0050] Example 2: Preparation of supramolecular deep eutectic conductive gel with microphase separation structure (monomer molar ratio HEAA:SPP is 9:1, polar molecule to SPP molar ratio is 5:1)

[0051] (1) Weigh 0.2487 g of choline chloride into a 5 mL sample bottle, then add 0.1986 mL of ethylene glycol dropwise into the sample bottle, heat and stir at 95 °C for 2 hours until clear and transparent, and let stand at room temperature to obtain a deep eutectic solvent.

[0052] (2) Add 0.3134 g of [3-(methacrylamide)propyl]dimethyl(3-thiopropyl)ammonium hydroxide to the above deep eutectic solvent, then add 1 mL of N-(2-hydroxyethyl)acrylamide dropwise to the sample bottle, and stir at room temperature until clear and transparent to obtain the conductive gel precursor solution.

[0053] (3) Add 20 mg of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone to the above precursor solution, stir until transparent and clear, and then pour into a glass mold. In a UV crosslinker (254 nm), irradiate and polymerize for 30 minutes to obtain a supramolecular deep eutectic conductive gel.

[0054] Example 3: Preparation of supramolecular deep eutectic conductive gel with microphase separation structure (monomer molar ratio HEAA:SPP is 9:1, polar molecule to SPP molar ratio is 8:1)

[0055] (1) Weigh 0.3972 g of choline chloride into a 5 mL sample bottle, then add 0.3173 mL of ethylene glycol dropwise into the sample bottle, heat and stir at 95 °C for 2 hours until clear and transparent, and let stand at room temperature to obtain a deep eutectic solvent.

[0056] (2) Add 0.3134 g of [3-(methacrylamide)propyl]dimethyl(3-thiopropyl)ammonium hydroxide to the above deep eutectic solvent, then add 1 mL of N-(2-hydroxyethyl)acrylamide dropwise to the sample bottle, and stir at room temperature until clear and transparent to obtain the conductive gel precursor solution.

[0057] (3) Add 20 mg of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone to the above precursor solution, stir until transparent and clear, and then pour into a glass mold. In a UV crosslinker (254 nm), irradiate and polymerize for 30 minutes to obtain a supramolecular deep eutectic conductive gel.

[0058] Example 4: Mechanical property testing of supramolecular deep eutectic conductive gel with microphase separation structure

[0059] The supramolecular deep eutectic conductive gels prepared in Examples 1-3 were subjected to mechanical property testing. Stress-strain curves of conductive gels with different molar ratios of polar molecules to SPP in the deep eutectic solvent were measured as follows: Figure 1As shown, when the molar ratio of polar molecules to SPP is 5:1, the conductive gel with a microphase-separated structure exhibits high elastic modulus (5.12 MPa) and strength (fracture strength of 5.38 MPa) through the synergistic effect of the soft and hard phases, while maintaining a good elongation at break (824%). When the molar ratio of polar molecules to SPP is 6:1, the ability of SPP to adsorb polar molecules reaches saturation, and the conductive gel exhibits good comprehensive mechanical properties, meeting the requirements of various flexible electronic devices. Its elongation at break is 1097%, and its fracture stress is 936.8 kPa. With further increases in the content of polar molecules, when the molar ratio of polar molecules to SPP reaches 8:1, due to the saturation of SPP adsorption capacity, the excess deep eutectic solvent is uniformly dispersed between the HEAA polymer network, weakening the microphase-separated structure. Therefore, the conductive gel exhibits a softer state, with an elastic modulus of 51 kPa and a fracture strength of 100 kPa, but the elongation at break is significantly improved (2111%). Therefore, the conductive gel prepared in Example 3 is suitable for flexible electronic devices used under high strain conditions. In summary, the conductive gel prepared in Example 1 (with a polar molecule to SPP molar ratio of 6:1) exhibits the best overall mechanical properties.

[0060] Example 5: Preparation of supramolecular deep eutectic conductive gel with microphase separation structure (monomer molar ratio HEAA:SPP is 8:1, polar molecule to SPP molar ratio is 6:1)

[0061] (1) Weigh 0.3368 g of choline chloride into a 5 mL sample bottle, then add 0.2690 mL of ethylene glycol dropwise into the sample bottle, heat and stir at 95 °C for 2 hours until clear and transparent, and let stand at room temperature to obtain a deep eutectic solvent.

[0062] (2) Add 0.3526 g of [3-(methacrylamide)propyl]dimethyl(3-thiopropyl)ammonium hydroxide to the above deep eutectic solvent, then add 1 mL of N-(2-hydroxyethyl)acrylamide dropwise to the sample bottle, and stir at room temperature until clear and transparent to obtain the conductive gel precursor solution.

[0063] (3) Add 20 mg of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone to the above precursor solution, stir until transparent and clear, and then pour into a glass mold. In a UV crosslinker (254 nm), irradiate and polymerize for 30 minutes to obtain a supramolecular deep eutectic conductive gel.

[0064] Example 6: Preparation of supramolecular deep eutectic conductive gel with microphase separation structure (monomer molar ratio HEAA:SPP is 10:1, polar molecule to SPP molar ratio is 6:1)

[0065] (1) Weigh 0.2700g of choline chloride into a 5mL sample bottle, then add 0.2157mL of ethylene glycol dropwise into the sample bottle, heat and stir at 95℃ for 2 hours until clear and transparent, and let stand at room temperature to obtain a deep eutectic solvent.

[0066] (2) Add 0.2821 g of [3-(methacrylamide)propyl]dimethyl(3-thiopropyl)ammonium hydroxide to the above deep eutectic solvent, then add 1 mL of N-(2-hydroxyethyl)acrylamide dropwise to the sample bottle, and stir at room temperature until clear and transparent to obtain the conductive gel precursor solution.

[0067] (3) Add 20 mg of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone to the above precursor solution, stir until transparent and clear, and then pour into a glass mold. In a UV crosslinker (254 nm), irradiate and polymerize for 30 minutes to obtain a supramolecular deep eutectic conductive gel.

[0068] Example 7: Mechanical property testing of supramolecular deep eutectic conductive gel with microphase separation structure

[0069] The supramolecular deep eutectic conductive gels prepared in Examples 1, 5, and 6 were subjected to mechanical property testing. Stress-strain curves of conductive gels with different molar ratios of N-(2-hydroxyethyl)acrylamide (HEAA) and [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide (SPP) were measured as follows: Figure 2 As shown. When the molar ratio of HEAA to SPP monomers is 10:1, compared to Example 1, the increased proportion of HEAA content leads to a higher proportion of the hard phase in the conductive gel, exhibiting an ultra-high elastic modulus of 6.28 MPa. When the molar ratio of HEAA to SPP monomers is 8:1, compared to Example 1, the increased proportion of SPP content leads to a higher proportion of the soft phase in the conductive gel, resulting in a decreased elastic modulus of 0.14 MPa. Due to the lack of effective support from the hard phase, the elongation at break will be 552%. In summary, the conductive gel prepared in Example 2 with a molar ratio of HEAA to SPP monomers of 9:1 exhibits the best overall mechanical properties.

[0070] Example 8: Load-unloading cyclic tensile test of supramolecular deep eutectic conductive gel with microphase separation structure

[0071] The supramolecular deep eutectic conductive gel prepared in Example 1 was subjected to a load-unload cyclic tensile test. First, the conductive gel was stretched to a strain of 500%, then unloaded to a strain of 0%, which was considered the first cyclic tensile test. Immediately afterwards, the same load-unload cyclic tensile test was performed again, followed by repeated load-unload cyclic tensile tests at intervals of 1 minute, 3 minutes, and 5 minutes. The stress-strain curves obtained are shown below. Figure 3As shown in the figure, the loading curve gradually approaches the initial curve as the resting time increases, indicating that the conductive gel has self-recovering resilience in terms of mechanical properties. This is because the conductive gel contains a large number of reversible non-covalent interactions such as hydrogen bonds, ionic bonds, van der Waals forces, and electrostatic interactions. These physical interactions provide an effective energy dissipation mechanism during loading and can be rapidly rebuilt during unloading and resting, which macroscopically manifests as the recovery of the mechanical properties of the conductive gel. Integrating the loading-unloading cycle curve for each cycle yields the energy dissipated during each stretching process (the work done during stretching), as shown in the figure. Figure 4 As shown in the figure, even when immediately reloaded, the conductive gel still dissipates 66% of its initial energy during cyclic stretching. After resting for 5 minutes, this proportion increases to 92%, demonstrating excellent resilience.

[0072] Comparative Example 1: Preparation of N-(2-hydroxyethyl)acrylamide deep eutectic gel (HEAA-DES)

[0073] (1) Weigh 0.3006 g of choline chloride into a 5 mL sample bottle, then add 0.24 mL of ethylene glycol dropwise into the sample bottle, heat and stir at 95 °C for 2 hours until clear and transparent, and let stand at room temperature to obtain a deep eutectic solvent.

[0074] (2) Add 1 mL of N-(2-hydroxyethyl)acrylamide to the above deep eutectic solvent and add it dropwise to the sample bottle. Stir at room temperature until clear and transparent to obtain the conductive gel precursor solution.

[0075] (3) Add 20 mg of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone to the above precursor solution, stir until transparent and clear, and then pour into a glass mold. In a UV crosslinker (254 nm), polymerize under light for 30 minutes to obtain N-(2-hydroxyethyl)acrylamide deep eutectic gel.

[0076] Comparative Example 2: Preparation of deep eutectic gel of [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide (SPP-DES)

[0077] This comparative example is essentially the same as Example 1, except that only [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide is added, and N-(2-hydroxyethyl)acrylamide is not added. Gel formation is impossible under these conditions.

[0078] Example 9: Effectiveness Test of Microphase Separation Structure of Supramolecular Deep Eutectic Conductive Gel

[0079] The supramolecular deep eutectic conductive gel prepared in Example 1 and the deep eutectic gel prepared in Comparative Example 1 were subjected to uniaxial tensile mechanical property tests, and the results are as follows: Figure 5As shown. Example 1 and Comparative Example 1 contain the same amount of deep eutectic solvent. Due to the addition of SPP in Example 1, which induced a microphase separation structure within the conductive gel, the mechanical properties of Example 1 are significantly better than those of Comparative Example 1, proving the existence and effectiveness of the microphase separation structure. Furthermore, the conductive gel prepared in Example 1 was sputtered with gold and observed under a scanning electron microscope at 10,000x magnification. The electron microscope images are shown below. Figure 6 As shown in the figure, a microphase separation structure with clear distinction between light and dark areas can be observed, proving the existence of the microphase separation structure.

[0080] Example 10: Conductivity Testing of Supramolecular Deep Eutectic Conductive Gel with Microphase Separation Structure

[0081] The supramolecular deep eutectic conductive gel prepared in Example 1 was inserted into an electrolyte impedance testing mold, and the impedance spectrum of Example 1 was obtained by scanning in the frequency range of 100 kHz to 1 Hz. Figure 7 As shown, the dimensions of the conductive gel were measured, and the ionic conductivity of the conductive gel was calculated to be 0.02 S / m. This ionic conductivity is on the same order of magnitude as that of ionic liquid gel, which can meet the requirements of most flexible electronic devices.

[0082] Example 11: Environmental stability test of supramolecular deep eutectic conductive gel with microphase separation structure

[0083] The supramolecular deep eutectic conductive gel prepared in Example 1 was subjected to thermogravimetric analysis and differential scanning calorimetry, and the results are as follows: Figure 8 , 9 As shown in the figure, the thermogravimetric analysis (TGA) graph shows that the conductive gel did not experience significant mass loss before 192℃, indicating that the conductive gel hardly underwent any decomposition reaction before 192℃. The differential scanning calorimetry (DSC) graph shows that no glass transition occurred even at temperatures dropping from room temperature to -62℃, and the conductive gel remained flexible throughout.

[0084] Application Example 1: Fabrication of Flexible Sensors and Testing of Their Mechanical Sensing Performance

[0085] Copper wire electrodes were attached to both sides of the supramolecular deep eutectic conductive gel prepared in Example 1, and then encapsulated with VHB elastic tape to assemble a flexible sensor. The response of the flexible sensor to three stimulation signals—stretching, pressing, and bending—was tested, and the test results are as follows: Figure 10 , 11 As shown in Figure 12, the results demonstrate that the flexible sensor produces accurate, sensitive, and stable responses to the three stimulation signals: stretching, pressing, and bending.

[0086] Application Example 2: Fatigue Resistance Testing of Flexible Sensors

[0087] The flexible sensor prepared in Application Example 1 was mounted on a cyclic tensile testing instrument, and 500 cyclic tensile stimuli of the same strain were applied to the flexible sensor. The test results are as follows. Figure 13 As shown in the figure. Because the supramolecular deep eutectic conductive gel constituting the flexible sensor has good resilience, the test results show that the flexible sensor still maintains an accurate and sensitive response after 500 cycles of stretching.

[0088] Application Example 3: Testing of Flexible Wearable Sensors

[0089] The flexible sensor prepared in Application Example 1 was attached to the main joints of the human body, and the response of the flexible wearable sensor to different joint movements was tested. The test results are as follows. Figure 14 , 15 As shown in Figure 16, this resistive strain sensor has a comprehensive and accurate response to the basic movements of human joints, and is expected to expand the application of this wearable sensor in fields such as medical rehabilitation, motion monitoring, and human-computer interaction.

[0090] The above description is merely an embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a supramolecular deep eutectic conductive gel with a microphase-separated structure, characterized in that, The specific steps are as follows: (1) Dissolve choline chloride in ethylene glycol at a molar ratio of 1:2 and heat and stir until clear and transparent, and use it as a deep eutectic solvent; (2) Add N-(2-hydroxyethyl)acrylamide monomer and [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide amphoteric monomer to a deep eutectic solvent and stir until clear and transparent as a precursor solution; (3) Add photoinitiator to the precursor solution, stir until transparent and clear, then inject into the mold and polymerize under ultraviolet light to form supramolecular deep eutectic conductive gel.

2. The preparation method according to claim 1, characterized in that, In step (1), the heating temperature is 90~100℃ and the stirring speed is 800~1000 rpm.

3. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of N-(2-hydroxyethyl)acrylamide to [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide is 8:1 to 10:1; the ratio of the total molar amount of choline chloride and ethylene glycol to the molar amount of [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide is 5:1 to 8:

1.

4. The preparation method according to claim 3, characterized in that, The molar ratio of N-(2-hydroxyethyl)acrylamide to [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide is 9:1; the ratio of the total molar amount of choline chloride and ethylene glycol to the molar amount of [3-(methacryloylamino)propyl]dimethyl(3-thiopropyl)ammonium hydroxide is 6:

1.

5. The preparation method according to claim 1, characterized in that, The photoinitiator is 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, and the mass of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone is 0.1% to 0.2% of the mass of the precursor solution.

6. The preparation method according to claim 1, characterized in that, In step (2) or (3), the stirring speed is 800~1000 rpm; in step (3), the mold is made of glass, the mold spacing is 900~1100 μm, the wavelength of the ultraviolet light is 254nm, and the ultraviolet light irradiation intensity is 800 μJ / cm. 2 The polymerization reaction time is 30 minutes.

7. The supramolecular deep eutectic conductive gel prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the supramolecular deep eutectic conductive gel according to claim 7 in the fabrication of flexible electronic devices.

9. The application according to claim 8, characterized in that, The flexible electronic device is a flexible sensor or a flexible wearable sensor.

10. The application according to claim 9, characterized in that, The flexible sensor or flexible wearable sensor consists of a supramolecular deep eutectic conductive gel and copper electrode sheets and tape attached to both sides of the electrolyte.

11. The application according to claim 10, characterized in that, The tape mentioned is VHB tape.

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