An ionic gel having a microscale hydrophobic domain, and a method of making and using the same

Abstract

The present application relates to an ionic gel with micron-sized hydrophobic domains and its preparation method and application, the ionic gel is obtained by polymerization reaction with raw materials containing hydrophilic monomer, hydrophobic monomer, crosslinking agent, initiator and ionic liquid.The ionic gel realizes the combination of high ductility, crack resistance, fatigue resistance and temperature switch adhesion ability, and is a high-performance ionic gel material with comprehensive performance upgrade.The preparation process of the present application is simple, and the performance is superior, and has wide application prospect in the fields of soft robot, wearable electronics and artificial intelligence interactive interface.

Description

Technical Field

[0001] This invention belongs to the field of ionogel materials, and specifically relates to an ionogel with micron-sized hydrophobic water, its preparation method and application. Background Technology

[0002] Ionic gels are advanced functional materials composed of three-dimensional polymer networks and ionic liquids. Due to their combination of the structural rigidity of polymers and the functional versatility of ionic liquids, they have become core candidate materials in fields such as flexible electronics, artificial intelligence, health monitoring, human-computer interaction, and soft robotics. Ionic liquids, as quasi-solid-state electrolytes, possess extremely low thermal volatility, a wide electrochemical window, high thermal stability, and excellent ionic conductivity, enabling them to exhibit superior stability compared to traditional hydrogels or organic gels under extreme environments (such as extreme cold or vacuum). In AI skin applications, ionic gels can mimic the tactile sensing capabilities of biological tissues, efficiently converting mechanical deformation into electrical signals to achieve highly sensitive pressure and strain monitoring. In the field of soft robotics, these materials are used to manufacture durable actuators and sensors, requiring materials to possess not only good electrical properties but also excellent mechanical integrity to withstand complex motion loads.

[0003] However, traditional homogeneous ionogels, while maintaining high ionic conductivity, inevitably suffer from a significant decrease in mechanical strength (such as modulus and toughness), thus limiting their long-term usability in load-bearing or high-mechanical-demand environments. Furthermore, traditional ionogels prepared through chemical crosslinking typically have limited tensile strength (usually <1000%) due to the restriction of polymer chain movement caused by covalent crosslinking, and lack stress dissipation mechanisms during crack propagation, resulting in poor tear resistance. Therefore, designing ionogels that simultaneously resist crack propagation and withstand large deformations remains a key challenge.

[0004] In recent years, inspired by the multi-level ordered structures in nature (such as collagen fibers in sea cucumber dermis and microphase separation in jellyfish skin), researchers have introduced microphase separation structures and dynamic sacrificial bonds in hopes of achieving a synergistic improvement in mechanical properties and functionality. This strategy is typically achieved by injecting ionic liquids into hydrophobic polymer networks or synthesizing microphase-separated copolymers. Existing research has shown that nanoscale phase separation can effectively enhance mechanical properties and may introduce additional functions such as self-healing and stimulus response. For example, Lu et al. synthesized a toughened ionic gel by copolymerizing two polymerizable ionic liquids in a non-polymerizable ionic liquid matrix. The hydrophobic microdomains significantly improved the mechanical properties, achieving a tensile stress of 4.5 MPa and a strain of approximately 800% (Chemical Engineering Journal, 2022, 439). Hu et al. employed a simpler copolymerization method to achieve nanoscale in-situ phase separation of acrylic acid and acrylamide in ionic liquids. The resulting ionic gel exhibited a high tensile strength of 12.6 MPa, a Young's modulus of 46.5 MPa, and 600% strain and self-healing / shape memory properties (Nature Materials, 2022, 21(3): 359-65). Wu et al. prepared a dynamically phase-separated, highly damped, self-healing ionic elastomer using two different fluorinated monomers, achieving an ultra-high elongation of 2168% at room temperature (Advanced Materials, 2023, 35(10)). These ionic gels exhibit superior performance, but the phase-separated structures achieved to date are mainly limited to the nanoscale, resulting in limited improvement in their elongation, remaining below 1000% and failing to achieve a leapfrog improvement. Currently, a promising but not yet fully explored direction is the construction and precise control of micron-scale hydrophobic domains in ionic gels.

[0005] Switchable adhesion is another important requirement for ionic gels in fields such as flexible sensors, intelligent grasping, and human-computer interaction. Common adhesion control methods include constructing surface microstructures such as biomimetic micropillar arrays, or introducing stimuli-responsive functional groups such as temperature, light, and humidity. These responsive adhesives mainly rely on the physical state switching of the polymer network under stimulation (such as glass-to-rubber transition or crystallization-to-melt transition), and achieve the "on" and "off" of adhesion by adjusting the interfacial contact area or the energy dissipation capacity inside the material. However, traditional adhesion modification methods often face the problems of limited adhesion switching rate and poor durability in complex environments. One study proposed a control process based on phase separation-induced "lubricating layer" formation: using polymers with low critical solution temperature (LCST) characteristics (such as polyN,N-dimethylacrylamide or polybutyl acrylate) to construct a network, when the temperature rises and triggers phase separation, the ionic liquid droplets that were originally uniformly distributed in the network are squeezed out and enriched on the material surface, forming a micron-sized liquid lubricating film. This lubricating film effectively blocks direct contact between the polymer chains and the substrate, causing the adhesion strength to decrease rapidly and achieving "on-demand desorption" (Soft Matter, 2022, 18, 5934-5938). This high-temperature debonding and low-temperature adhesion characteristic is consistent with most adhesives; however, the use of phase change materials and network structures to construct patch materials with low-temperature debonding and high-temperature adhesion is still relatively rare.

[0006] Currently, research on microphase-separated ionogels has mainly focused on the formation of nanoscale microphases and the achievement of high strength and toughness. In summary, traditional ionogels struggle to simultaneously possess ultra-high ductility, fatigue resistance, crack propagation resistance, and switchable adhesion capabilities (high-temperature adhesion and low-temperature debonding). There is an urgent need in this field for a novel ionogel material with ultra-high ductility, excellent crack propagation resistance, fatigue resistance, and temperature-switched adhesion in a micrometer-scale microphase. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an ionic gel with micron-sized hydrophobic water, its preparation method and application.

[0008] This invention provides an ionic gel with micron-sized hydrophobic water, wherein the ionic gel is obtained by polymerization reaction using raw materials containing hydrophilic monomers, hydrophobic monomers, crosslinking agents, initiators and ionic liquids;

[0009] The hydrophobic monomer is an acrylate or methacrylate containing an alkyl chain with more than 12 carbon atoms; the crosslinking agent is a long-chain alkyl diol ester; the hydrophobic monomer accounts for 2.5-20% of the total molar amount of the monomer; and the ion gel contains micron-sized hydrophobic water areas.

[0010] The crosslinking agent is a covalent crosslinking agent.

[0011] The long carbon chain structure of the hydrophobic monomer and the covalent crosslinking agent simultaneously provides hydrophobic interaction, synergistically constructing hydrophobic water areas, providing energy dissipation capabilities, and achieving comprehensive performance improvement.

[0012] Preferably, the hydrophilic monomer is methacrylic acid (MAA).

[0013] Preferably, the hydrophobic monomer comprises octadecyl methacrylate (OMA); the crosslinking agent is 1,12-dodecyl diol ester, wherein the 1,12-dodecyl diol ester comprises 1,12-dodecanediol dimethacrylate.

[0014] Preferably, the initiator is a hydrophilic ultraviolet initiator; wherein the hydrophilic ultraviolet initiator includes 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (I2959).

[0015] Preferably, the ionic liquid is a hydrophilic ionic liquid, wherein the hydrophilic ionic liquid includes ethyl 1-ethyl-3-methylimidazolium sulfate [EMIM] [EtSO4].

[0016] Preferably, the hydrophobic monomer is 10-20% of the total molar amount of the monomer.

[0017] Preferably, the crosslinking agent is 0.5-2% of the total molar amount of the monomers, the initiator is 0.05-0.2% of the total molar amount of the monomers, and the ionic liquid accounts for 50-60% of the total gel mass.

[0018] The ion gel contains micron-sized hydrophobic water areas, i.e., hydrophobic microdomains.

[0019] Furthermore, the micron-scale hydrophobic water region is a hydrophobic microdomain with a diameter of 10 μm to 30 μm.

[0020] This invention provides a method for preparing any of the described ionic gels with micron-scale hydrophobic water, comprising:

[0021] Hydrophilic monomers, hydrophobic monomers, crosslinking agents, initiators, and ionic liquids are mixed and polymerized to obtain ionic gels.

[0022] The mixture is then pulverized using a cell disruptor for 1-5 minutes; the polymerization reaction is cured under 365 nm ultraviolet light for 0.5-1 minutes.

[0023] Furthermore, a method for preparing ionogels with micron-sized hydrophobic water includes:

[0024] Hydrophilic monomers and initiators are dissolved in ionic liquid solvents to obtain a solution. Then, hydrophobic monomers and crosslinking agents are added to obtain a mixture. The mixture is then pulverized using a cell disruptor at high power and injected into a mold for UV curing.

[0025] When the hydrophobic monomer is solid, after adding the hydrophobic monomer and crosslinking agent, the solid is turned into a liquid by heat treatment at a temperature above the melting point of the hydrophobic monomer, thus obtaining a mixture.

[0026] Temperatures above the melting point should be controlled to be 2-5℃ higher than the melting point.

[0027] This invention provides an application of any of the described ionogels with micron-scale hydrophobic water in the fields of soft robotics, wearable electronics, and artificial intelligence interactive interfaces.

[0028] The ion gel described in this invention employs a multi-scale microphase synergistic enhancement architecture, as described below:

[0029] 1. Dual Dynamic Dissipation Mechanism: Unlike the single covalent crosslinking of traditional single-network ionic gels, this invention introduces octadecyl methacrylate for copolymerization on the basis of a hydrophilic covalent network, constructing micron-scale hydrophobic domains composed of long carbon alkyl chains. Furthermore, the long carbon chain crosslinking agents exhibit hydrophobic interactions, interacting not only with each other within the network but also with the hydrophobic monomers, forming dual hydrophobic domains throughout the network. During stress, the covalent crosslinking points provide the basic elastic recovery force (elastic modulus U). elastic The micron-sized hydrophobic regions act as "sacrificial bonds." The long alkyl chains within these hydrophobic regions are tightly bound together by van der Waals forces and hydrophobic interactions. Under extreme stretching, these physical interaction domains undergo deformation, chain sliding, recombination, and internal dissociation. This process generates significant energy dissipation (dissipation energy term U). diss Its total energy absorption formula follows U total =U elastic +U diss U diss Much larger than U elastic This fundamentally inhibits the rapid propagation of cracks.

[0030] 2. Micrometer-scale effect: Compared to nanometer-scale phase separation, the micrometer-scale (10-30 μm) hydrophobic water bodies constructed in this invention have a larger specific surface area and a higher volume fraction (e.g., ...). Figure 2 (As shown). These micron-scale structures effectively passivate crack tips and disperse concentrated stress throughout the network. By controlling the distribution density of the hydrophobic water areas through a high-power pulverization process, the isotropy of the ionogel in three-dimensional space is ensured.

[0031] 3. Temperature-responsive adhesion switching interface: A temperature-switching interface is designed using the phase transition properties of hydrophobic monomers and the hydrophobic interactions of long carbon chains. When the temperature is below its melting point, the alkyl chains are in a crystalline state, exhibiting a hard and low-energy surface, resulting in a non-adhesive state. When the temperature rises above the phase transition point, the alkyl chains transform from a highly ordered state to a highly disordered molten state. The highly mobile chain segments on the substrate surface achieve extremely high instantaneous adhesion through van der Waals forces and hydrophobic interactions.

[0032] Molecular construction pathway

[0033] The synthetic route of the ion gel described in this invention includes the following ideas:

[0034] 1. Thermodynamic mismatch-driven self-assembly: The core technology lies in utilizing the solubility threshold between polar ionic liquids and nonpolar long-chain monomers. In the precursor liquid stage, hydrophilic monomers, hydrophobic monomers, and ionic liquids maintain a metastable homogeneous state. The hydrophobic interaction between the long alkyl chain segments of the hydrophobic monomers and the hydrophilic ionic liquid promotes the self-assembly of the hydrophobic segments, forming discrete hydrophobic water areas.

[0035] 2. Kinetic-constrained growth control: By precisely adjusting the monomer ratio, the power of the oscillating precursor solution, and the initiator content, the microphase separation rate and the overall network gelation rate are competitively balanced. Before the overall network locks in, the hydrophobic water regions are ensured to grow to the ideal micron-scale size, thereby obtaining a spatially highly uniform heterogeneous structure.

[0036] 3. Precise selection of multifunctional components: During the preparation process, the covalent crosslinking agent possesses a hydrophobic structure, which can chemically "stitch" the main hydrophilic framework with the hydrophobic area, ensuring effective stress transfer at the multiphase interface. Simultaneously, some hydrophobic monomers that do not participate in the formation of the hydrophobic area exist on the gel surface, forming temperature-sensitive functional components.

[0037] Beneficial effects

[0038] (1) Ultra-high ductility: The elongation at break can be continuously adjusted between 400% and 12050% depending on the monomer ratio, and it has excellent fatigue resistance. Under ultra-high cyclic strain of 1500%, its mechanical property recovery rate remains above 90%, and it has a large energy dissipation rate. Through multi-scale dissipation structure, the material achieves high ductility.

[0039] (2) Temperature-switching adhesion capability: Achieve significant difference in adhesion performance between room temperature (20℃) and high temperature (50℃) environments. The adhesion strength to substrates such as paper at high temperature needs to reach 400 kPa (far exceeding the 141 kPa of traditional thermally responsive hydrogels), while after cooling, it can achieve rapid peeling with no residue, and the adhesion switching ratio is not less than 50.

[0040] (3) Excellent environmental stability: The ion gel material of the present invention will not undergo morphological changes or component loss under high temperature environment.

[0041] Compared with existing technologies, the ion gel of this invention achieves a combination of high ductility, crack propagation resistance, fatigue resistance, and temperature-switching adhesion capabilities, making it a high-performance ion gel material with comprehensively upgraded performance. Attached Figure Description

[0042] Figure 1 Fourier transform infrared (FTIR) spectra of the ionogels prepared in Example 1 and Comparative Example 1 (a); optical micrographs of the ionogel prepared in Example 1 with hydrophobic monomers accounting for 20% of the total molar amount of monomers around the phase transition point (b).

[0043] Figure 2 AFM phase diagram of the ion gel prepared in Example 1 with hydrophobic monomers accounting for 10% of the total molar amount of monomers;

[0044] Figure 3 Stress-strain curves (a) of ionomers with different ratios prepared in Example 1; tensile cycle diagrams (b) of ionomers with different ratios prepared in Example 1 under 100% strain.

[0045] Figure 4 The images show the crack propagation characteristics of Example 1 and Comparative Example 1; (a) shows the crack propagation resistance of the ion gel with a notch in Example 1, where the hydrophobic monomer accounts for 10% of the total molar amount of the monomer; (b) shows the crack propagation resistance of the ion gel with a notch in Comparative Example 1.

[0046] Figure 5 The stress-strain curves of the ionogels prepared in Comparative Examples 2 and 3 are shown; where (a) represents hydrophobic monomers with different numbers of alkyl chain carbons; and (b) represents crosslinking agents with different structures.

[0047] Figure 6 Fourier transform infrared (FTIR) spectra of ion gels with different ratios prepared in Example 1 (a), and Fourier transform infrared (FTIR) spectra of P(MAA-co-OMA-20%) under different strains (b).

[0048] Figure 7 The images show atomic force microscopy images of Example P(MAA-co-OMA-20%) under no strain (left) and under 10000% strain (right).

[0049] Figure 8 This is a schematic diagram showing the adhesion ability of the ion gel prepared in Example 1, in which the hydrophobic monomer accounts for 10% of the total molar amount of the monomer, under different temperature conditions.

[0050] Figure 9 The adhesion results of the ion gel prepared in Example 1 with 10% hydrophobic monomer as the total molar amount of the monomer to different substrate materials are shown in (a), the adhesion results under multiple adhesion experiments are shown in (b), and the adhesion results are shown in (c) when switching between the OMA phase transition temperature and the substrate temperature are shown in (c). Detailed Implementation

[0051] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0052] I. Materials and Reagents

[0053] Octadecyl methacrylate (OMA) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; methacrylic acid (MA) was purchased from Thermo Fisher Scientific (China) Co., Ltd.; 1,12-dodecanediol dimethacrylate was purchased from Shanghai Merrill Biochemical Technology Co., Ltd.; the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (I2959) was purchased from Shanghai Ruineng Technology Development Co., Ltd.; and the ionic liquid 1-ethyl-3-methylimidazolium sulfate ethyl salt [EMIM] [EtSO4] was purchased from Lanzhou Zhongke Kaitai Green Chemistry Technology Development Co., Ltd. (Note: The original text Lanzhou Greenchem Research Institutes Co., Ltd. is "Lanzhou Green Chemistry Research Institute", but it is often translated as the company name, so it is treated as the common translation here).

[0054] II. Performance Testing Methods

[0055] Mechanical properties: Compression and tensile tests were performed using a UH 6502 electronic universal testing machine. The mechanical properties of the ionogel were tested at room temperature (20–25°C, relative humidity 20%–40%) without any special measures to prevent moisture absorption. The energy dissipation rate at each stage was calculated by integrating the area of ​​the linear region of the stress-strain curve.

[0056] Unless otherwise specified, the displacement rate for both tensile and shear tests is 10 mm·min. -1 In the cyclic tensile test, when the specimen is stretched to an elongation ratio λ = 1, 2, 4, 6, 8, the testing machine beam will return to its initial position as soon as possible, and no recovery interval is set between each cycle of the test.

[0057] In the tear test, samples with initial cracks were prepared. The samples were held by their two arms and then moved at different displacement rates (2–300 mm·min). -1 A tear test is performed, and the force sensor records the corresponding stress.

[0058] Adhesion performance: A sandwich structure of substrate-material-substrate is adopted. The upper and lower ends of the two substrates are fixed by a universal testing machine to obtain the force required for the material to separate from the substrate. The adhesion stress is calculated by recording the adhesion area.

[0059] Characterization of hydrophobic water structure and stress changes: Fourier transform infrared spectroscopy (FT-IR) was performed using a PerkinElmer Spectrum Two spectrometer. During measurement, the gel was stretched to different strain states using a graduated ruler before testing.

[0060] The microstructural changes of hydrophobic microspheres in ionogels around the phase transition temperature were observed using an optical microscope (ECLIPSE 80i, Nikon, Japan).

[0061] Atomic force microscopy (AFM) observations were performed on samples of P(MAA-co-OMA-x%) (i.e., methacrylic acid-octadecyl methacrylate copolymer, where x% is the molar percentage of OMA).

[0062] Small-angle X-ray scattering (SAXS) tests were performed on a Xeuss 2.0 SAXS / WAXS system (Bruker Nanostar).

[0063] Thermal properties: The thermal properties of the samples were measured using a differential scanning calorimeter (DSC, model 204 F1, NETZSCH GmbH, Germany) under a nitrogen atmosphere, with a heating rate of 20 °C / min. -1 The scanning range is from 0 ℃ to 90 ℃.

[0064] Example 1

[0065] Preparation of ionogels in micron-sized hydrophobic waters:

[0066] In this embodiment, a series of ionic gels were synthesized by one-step photopolymerization. The gel network was constructed in the ionic liquid 1-ethyl-3-methylimidazolium sulfate ethyl salt [EMIM][EtSO4] using methacrylic acid (MAA, accounting for 40% of the total gel mass) and octadecyl methacrylate (OMA, with molar fractions x of 2.5%, 5%, 6%, 7%, 8%, 9%, 10%, 14%, 17%, and 20%, respectively) as comonomers and 1,12-dodecanediol dimethacrylic acid as a crosslinking agent.

[0067] The specific preparation process (one-pot method) is as follows: At 25 ℃, MAA and photoinitiator I2959, accounting for 0.1% of the total molar amount of monomers, are first dissolved in an ionic liquid. Then, x% of OMA and 1% of crosslinking agent, accounting for 1% of the total molar amount of monomers, are added. The mixture is heated to 40 ℃ to melt OMA into a liquid (the melting point of OMA is around 38 ℃). The mixture is then pulverized in a cell disruptor for 3 min, injected into a polytetrafluoroethylene mold, and cured under 365 nm ultraviolet light for 1 min to obtain an ionic gel with a solid content of 40 wt%.

[0068] The molar percentage of different octadecyl methacrylates in the monomer is represented by x, denoted as P(MAA-co-OMA-x%).

[0069] like Figure 2 The image shows the AFM phase diagram of the ionogel prepared in Example 1 with 10% hydrophobic monomer by total molar amount. The hydrophobic water regions are stable in size at 10-30 μm. Optical micrographs of the ionogel prepared in Example 1 with 20% hydrophobic monomer by total molar amount around the phase transition point are shown below. Figure 1 As shown in (b) of the diagram.

[0070] Due to the interaction of the components within the ionogel, the hydrophobic water area eventually stabilizes at a size of 10-30 μm. This size remains consistent regardless of the molar ratio of different hydrophobic monomers. Although the size changes with the OMA phase transition caused by temperature variations, the size of the hydrophobic water area remains at 10-30 μm when placed at room temperature (25°C) or when the temperature is switched back to the phase transition point below 38°C.

[0071] Comparative Example 1

[0072] The preparation method of this comparative ionogel differs from that of Example 1 only in that octadecyl methacrylate is completely omitted, while other raw materials and reaction conditions remain the same, and the final ionogel is a colorless and transparent film.

[0073] Comparative Example 2

[0074] The preparation method of this comparative ionogel differs from that of Example 1 (preparation method of ionogel with hydrophobic monomer accounting for 5% of the total molar amount of monomer) only in that octadecyl methacrylate is replaced with polyalkyl methacrylate with different alkyl groups. The final ionogel is a colorless and transparent film.

[0075] By replacing octadecyl methacrylate with butyl methacrylate and lauryl methacrylate, which have shorter carbon chains, compared with Example 1 under the same testing conditions, a dual decrease in tensile strength and ductility was observed. Figure 5As shown in (a) above. It can be seen that the realization of super-ductility requires precise control of the intensity of hydrophobic interaction forces, and the formed hydrophobic microdomains need to strictly follow the process of deformation and destruction under stress.

[0076] Comparative Example 3

[0077] The preparation method of this comparative ionogel differs from that of Example 1 (preparation method of ionogel with hydrophobic monomer accounting for 5% of the total molar amount of monomer) only in that N,N'-methylenebisacrylamide (MBA) and ethylene glycol dimethacrylate (EGDMA) are used to replace the original crosslinking agent, respectively. The content of the crosslinking agent is 1% of the total molar amount of monomer in both cases, and the final ionogel is a transparent film.

[0078] according to Figure 5 As shown in (b), the ion gels obtained by using crosslinking agents MBA and EGDMA without long alkyl chains respectively showed an improvement in Young's modulus, but the overall mechanical properties shifted towards brittleness, and the extensibility of the ion gels decreased significantly.

[0079] The preparation and testing results of Examples 1 and Comparative Examples 1-3 above show that only hydrophobic monomers with sufficiently long alkyl chains (such as OMA) can form strong hydrophobic association. These associated structures, as efficient energy dissipation units, are key to the material's excellent mechanical properties. Furthermore, the long alkyl chains of the crosslinking agent itself also play a synergistic role in the toughening process, further enhancing the stability and dynamic reversibility of the hydrophobic microregions. By selecting appropriate crosslinking agents and hydrophobic monomer carbon chain lengths, and controlling the ratio of the two comonomers, P(MAA-co-OMA-20%) was determined to be the optimal formulation for ductility, with a breaking elongation of 12050%. P(MAA-co-OMA-10%) was determined to be the optimal formulation for adhesion, achieving an adhesion force of 400 kPa to paper and further improving adhesion force after more than ten cycles of adhesion, thus realizing a temperature-sensitive switchable adhesion function.

[0080] Performance characterization and results analysis

[0081] Infrared analysis: Fourier transform infrared spectroscopy (FTIR) analysis was performed, first at 1217 cm⁻¹. -1 The observation of characteristic C–O stretching vibration peaks of OMA confirms that OMA has been successfully copolymerized into the polymer network. Figure 1 As shown in (a) of the diagram.

[0082] Further in-situ infrared spectroscopy was used to monitor the micro-changes in the ionogel network during the stretching process: such as Figure 6 As shown in (a), with increasing OMA content, the stretching vibration peak of methylene (-CH2-) increases from 2940 cm⁻¹. -1Redshifted to 2926 cm -1 This indicates the enhancement of hydrophobic interactions and the formation of microdomain structures; while... Figure 6 As shown in (b), under ultra-high strain tension (over 5000% strain), the peak of P(MAA-co-OMA-20%) increases from 2926 cm⁻¹. -1 Blue shifted to 2942 cm -1 This directly proves that the hydrophobic microdomains were forcibly stretched apart and the internal hydrophobic interactions were significantly weakened. Two-dimensional correlation spectroscopy (2DCOS) provides evidence of dynamic molecular evolution: in the small strain stage, the 2924 cm⁻¹ in the synchronous spectrum... -1 The strong self-peak (Φ≈7.6) at the position indicates that the methylene vibration in the hydrophobic microdomain is the most sensitive and fastest responding unit, and the asynchronous spectrum (Ψ≈+1.09, 2950–3200 cm⁻¹) shows that the methylene vibration is the most sensitive and fastest responding unit. -1 This further reveals that conformational changes of the methylene group in the hydrophobic microdomain take precedence over the responses of functional groups such as carbonyl or hydroxyl groups on the MAA chain, exhibiting a sequence response mechanism of "hydrophobic region priority, followed by hydrophilic network". After entering the hyperstretched state, 2924 cm -1 The sharp decrease in peak intensity (Φ≈2.3) and the significant expansion of the positive correlation region indicate that the previously isolated preferential response hydrophobic microdomains were disrupted, the homogeneity of the methylene conformation was lost, and the stress was distributed to a more widely homogenized molecular network. The asynchronous spectrum signal intensity decreased by an order of magnitude (Ψ≈±0.1), the response mode was reorganized, the molecular motion sequence became blurred, and the motion of hydrophobic fragments and hydrophilic network components tended to be consistent. In summary, during small strain processes, micron-sized hydrophobic microdomains act as the main energy dissipation centers; under ultra-large strain, the microdomains irreversibly break down, and the hydrophobic fragments integrate with the surrounding hydrophilic chains, causing the entire network to deform synchronously as a unified whole and dissipate energy, realizing the transformation from "local sequential response" to "global coordinated response".

[0083] Hydrophobic microdomain related tests: Atomic force microscopy (AFM) observations provide the most direct morphological evidence for this mechanism. For example... Figure 7 As shown, in the unstretched state, the phase transition microdomains exhibit homogeneity; when the strain reaches 10000%, the originally homogeneous phase is disrupted from the inside, and the homogeneous structure of the microdomains is completely disintegrated. In summary, this invention reveals a layered energy dissipation mechanism dominated by micron-scale hydrophobic structural domains: energy is dissipated through reversible deformation under small strain, while irreversible fracture imparts extreme ductility to the material under large strain. This mechanism, synergistic with the strength of the covalent network, endows ionogels with ultra-high ductility, crack propagation resistance, and excellent fatigue resistance, laying a theoretical foundation for their application under extreme conditions.

[0084] Mechanical properties: according to Figure 3The stress-strain curve in (a) shows that when the OMA content is low (< 5%), the strength and modulus of the gel are improved, but the elongation at break is limited. This is attributed to the enhanced network chain entanglement caused by the introduction of a small amount of OMA. When the OMA content is further increased to ≥ 10%, the mechanical response of the material undergoes a fundamental change: the elongation at break increases sharply to over 1000%, exhibiting super-stretchability while maintaining considerable strength. When the OMA content is increased to 20%, the material exhibits extremely high ductility, reaching 12050%. Figure 3 As shown in (b), energy dissipation capability was evaluated through cyclic tensile testing. As the OMA content increased from 2.5% to 20%, the energy dissipation ratio increased from 38% to 57%. This high energy dissipation rate indicates that the material can effectively dissipate stress at the crack tip through a microdomain sacrificial mechanism, thereby endowing the gel with significant resistance to crack propagation. Figure 4 As shown in (a), the ionogel prepared in Example 1, even with a notch, remained intact when stretched to four times its original length; as Figure 4 As shown in (b) of the paper, the ionogel prepared in Comparative Example 1 breaks down when stretched to only 1.5 times its original length in the presence of a notch.

[0085] Temperature-switched adhesion properties: Based on a systematic study of the adhesion properties of ionogels, the material exhibits significant thermo-switched adhesion behavior, which is closely related to the phase transition process of OMA. For example... Figure 8-9 As shown, taking P(MAA-co-OMA-10%) as an example, the gel could not adhere to a 100 g weight at 20℃, while the gel at 40℃ could firmly adhere to and easily lift the weight, directly demonstrating the effective control of adhesion behavior by temperature. Further quantification of adhesion strength through overlap shear tests revealed that, due to the abundance of functional groups such as hydroxyl and carboxyl groups in the system, the ionogel could effectively adhere to the surfaces of various materials, including glass, non-woven fabrics, iron, nitrile gloves, paper, and plastics. The highest adhesion strength (450 kPa) was observed on paper, mainly attributed to the strong hydrogen bonding between the ionogel and the hydroxyl groups on the paper surface. Furthermore, this adhesion performance is reusable; after at least ten repeated adhesion tests on a glass substrate, the adhesion strength did not weaken. The adhesion strength of this ionogel material can reversibly switch multiple times with temperature changes: when the temperature cycles between 20℃ and 30℃, the adhesion force of the ionogel responds synchronously and maintains stable switching performance. In summary, below the phase transition point, OMA regional crystallization leads to an ordered arrangement of molecular chains, hindering close contact between long alkyl chains and the substrate surface. Above the phase transition point, however, OMA is distributed on the gel surface, and its hydrophobic properties interact strongly with the substrate interface, forming a robust interfacial adhesion. This switchable adhesion behavior is achieved through both OMA component phase transition-induced chain migration and changes in surface hydrophobicity.

[0086] In summary, this invention, through network design and component optimization, achieves an ionic gel with superior extensibility, crack propagation resistance, fatigue resistance, and temperature-switching adhesion properties, and its preparation method is simple and environmentally friendly.

Claims

1. An ionic gel with micron-sized hydrophobic water, characterized in that, The ionic gel is obtained by polymerization reaction using raw materials containing hydrophilic monomers, hydrophobic monomers, crosslinking agents, initiators and ionic liquids. The hydrophobic monomer is an acrylate or methacrylate containing an alkyl chain with more than 12 carbon atoms; the crosslinking agent is a long-chain alkyl diol ester; the hydrophobic monomer accounts for 2.5-20% of the total molar amount of the monomer; and the ion gel contains micron-sized hydrophobic water areas.

2. The ionogel according to claim 1, characterized in that, The hydrophilic monomer is methacrylic acid (MAA).

3. The ionogel according to claim 1, characterized in that, The hydrophobic monomer includes octadecyl methacrylate (OMA); the crosslinking agent is 1,12-dodecyl diol ester, wherein the 1,12-dodecyl diol ester includes 1,12-dodecanediol dimethacrylate.

4. The ionogel according to claim 1, characterized in that, The initiator is a hydrophilic ultraviolet initiator; wherein the hydrophilic ultraviolet initiator includes 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone; The ionic liquid is a hydrophilic ionic liquid, wherein the hydrophilic ionic liquid includes ethyl 1-ethyl-3-methylimidazolium sulfate [EMIM] [EtSO4].

5. The ionogel according to claim 1, characterized in that, The hydrophobic monomer is 10-20% of the total molar amount of the monomer.

6. The ionogel according to claim 1, characterized in that, The crosslinking agent is 0.5-2% of the total molar amount of the monomers, the initiator is 0.05-0.2% of the total molar amount of the monomers, and the ionic liquid accounts for 50-60% of the total gel mass.

7. The ionogel according to claim 1, characterized in that, The diameter of the micron-sized hydrophobic water area is 10-30 μm.

8. A method for preparing an ionic gel with micron-scale hydrophobic water as described in any one of claims 1-7, characterized in that, include: Hydrophilic monomers, hydrophobic monomers, crosslinking agents, initiators, and ionic liquids are mixed and polymerized to obtain ionic gels.

9. The preparation method according to claim 8, characterized in that, The mixture is then pulverized using a cell disruptor for 1-5 minutes; the polymerization reaction is cured under ultraviolet light for 0.5-1 minutes.

10. The application of an ion gel with micron-scale hydrophobic water as described in any one of claims 1-7 in the fields of soft robotics, wearable electronics, and artificial intelligence interactive interfaces.

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