A high-strength, high-stretch, and reversibly adhesive ionic gel with multiplexed interactions to suppress microphase separation, methods, and applications thereof

Abstract

This invention relates to ionomers, and more particularly to a high-strength, highly stretchable, and reversibly adhesive ionomer with multiple interactions inhibiting microphase separation, a method thereof, and its applications. The ionomer prepared by this invention exhibits a high tensile strength of 8.4 MPa, a fracture strain of 396%, and excellent toughness of 17.8 MJ m⁻³. This conditioning process also increases the optical transmittance of the ionomer to 87%. Furthermore, the ionomer exhibits strong reversible adhesion (7.46 MPa on glass) through heating-cooling cycles in air and underwater environments. Utilizing these high mechanical properties and reversible underwater adhesion characteristics, this ionomer has been successfully applied to underwater transport monitoring devices, highlighting its great potential in applications requiring both robust mechanical properties and strong adhesion.

Description

Technical Field

[0001] This invention relates to ionic gels, and more particularly to a high-strength, highly stretchable, and reversibly adhesive ionic gel, a method thereof, and applications thereof, which are characterized by multiple interactions inhibiting microphase separation. Background Technology

[0002] Ionogels have been extensively studied in many cutting-edge technology fields, including ionic skin, actuators and sensors, and energy storage devices. However, most reported ionogels cannot simultaneously achieve high tensile strength and excellent tensile properties. These ionogels present a clear trade-off: strong ionogels with high tensile strength tend to be rigid and brittle, while stretchable ionogels with large deformation are soft and have weak mechanical properties. Therefore, developing tough ionogels that combine high tensile strength and large deformation remains crucial for achieving long-term durability in practical applications.

[0003] Currently, researchers have devoted considerable effort to improving the toughness of ionogels, primarily through constructing heterogeneous and homogeneous structures within the ionogel. The former involves in-situ induced phase separation, ionic liquid crystallization, or the incorporation of nanoscale microgels to disperse stress during deformation. For example, a report describes the development of a tough ionogel using the difference in solubility of two hydrophobic monomers in an ionic liquid through in-situ induced phase separation. The resulting ionogel exhibits a tensile strength exceeding 15 MPa, but a strain below 60%. The latter relies on introducing dense and uniform reversible non-covalent bonds—such as hydrogen bonds, electrostatic interactions, and hydrophobic interactions—into the ionogel network to dissipate energy and improve toughness during deformation. Another report describes the design of an ionogel using 2-ureido-4-pyrimidinone as a crosslinking agent. Although the strain of this ionogel reached 800% through π-π stacking effects and hydrogen-bonded supramolecular self-assembly, its tensile strength remained below 0.3 MPa. However, despite significant progress in toughening ionogels, these strategies have focused primarily on improving the fracture strength or tensile properties of ionogels, failing to achieve truly tough ionogels that combine high strength and excellent tensile properties. Recently, a study reported a polyvinyl alcohol / halometalate ion liquid ionogel based on solvent exchange, achieving a limiting fracture stress of 63.1 MPa and a strain of 5248%. However, the uneven diffusion caused by differences in solvent exchange levels may adversely affect the long-term stability of the ionogel's properties. Therefore, how to improve the tensile properties of ionogels while maintaining their strength is a crucial problem that urgently needs to be solved.

[0004] Furthermore, high-strength ionogels typically possess excessively high cohesive energy, resulting in weak interfacial adhesion to substrates. Existing gel adhesives often sacrifice their own mechanical strength to meet adhesion requirements and cannot avoid fatigue damage during use. Therefore, in addition to high strength and excellent tensile properties, reversible adhesive ionogels capable of adhering to various substrates hold significant application potential. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a high-strength, highly stretchable, and reversible adhesive ionogel with multiple interactions that inhibit microphase separation, a method thereof, and its application.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a high-strength, highly stretchable, and reversibly adhesive ionic gel that inhibits microphase separation through multiple interactions. The ionic gel is obtained by introducing a flexible segment that can form dense interactions with multiple components into a macroscopic phase separation system of rigid segments and ionic liquids. The ionic gel has a tensile strength of 8.4 MPa, a tensile strain of 396%, a toughness of 17.8 MJ m⁻³, and an optical transmittance of 87%. The ionic gel exhibits reversible adhesion of 7.46 MPa on glass after undergoing heating-cooling cycles in air and underwater environments.

[0007] Furthermore, the ionic gel is obtained by introducing hydroxyethyl acrylate (HEA) as a flexible segment into a strongly macroscopic phase separation system composed of rigid segment benzyl methacrylate (BzMA) and ionic liquid IL.

[0008] Furthermore, the ionic solution is a 1-butyl-1-methylpiperidine bis(trifluoromethylsulfonyl)imide solution, and the photoinitiator is 1-hydroxycyclohexylphenyl ketone.

[0009] Furthermore, the amount of photoinitiator 1-hydroxycyclohexylphenyl ketone is fixed at 1 wt% of the total mass of the two monomers benzyl methacrylate and hydroxyethyl acrylate.

[0010] Secondly, this invention provides a method for preparing a high-strength, highly stretchable, and reversibly adhesive ionic gel with multiple interactions inhibiting microphase separation. The preparation method is as follows: Step 1: Mix benzyl methacrylate (BzMA), hydroxyethyl acrylate (HEA), ionic liquid, and photoinitiator, and stir to form a homogeneous precursor solution; Step 2: Introduce nitrogen gas into the precursor solution for 10 minutes for degassing. During the gas introduction process, adjust the airflow to make the solution roll evenly without splashing. Step 3: Inject the solution obtained after degassing in Step 2 into a polytetrafluoroethylene (PTFE) mold, and polymerize it under ultraviolet light to obtain an ionogel.

[0011] Furthermore, the amount of HEA used is 50 wt%, and the amount of IL used is 10 wt% IL.

[0012] Furthermore, in step three, the ultraviolet light conditions are 365nm, 1300mW, and irradiation for 1-5 minutes.

[0013] Thirdly, this invention provides the application of high-strength, highly stretchable, and reversibly adhesive ionogels with multiple interactions that inhibit microphase separation in underwater transport monitoring devices. Compared with the prior art, the advantages of the present invention are as follows: This invention proposes a strategy to introduce a flexible segment capable of forming dense interactions with multiple components into a macroscopically phase-separated system dominated by rigid segments. Specifically, hydroxyethyl acrylate is introduced as the flexible segment into a strongly macroscopically phase-separated system composed of the rigid segment benzyl methacrylate (BzMA) and an ionic liquid. Benefiting from the retained micro-entangled regions of BzMA acting as stress-dispersing areas, and the reversible interactions that impart stretchability to the system, the prepared ionogel exhibits a high tensile strength of 8.4 MPa, a fracture strain of 396%, and excellent toughness of 17.8 MJ m⁻³. This modulation process also increases the optical transmittance of the ionogel to 87%. Furthermore, the ionogel exhibits strong reversible adhesion (7.46 MPa on glass) through heating-cooling cycles in air and underwater environments. Utilizing these high mechanical properties and reversible underwater adhesion characteristics, the ionogel has been successfully applied to underwater transport monitoring devices, highlighting its great potential in applications requiring both robust mechanical properties and strong adhesion. Attached Figure Description

[0014] The invention will now be further described with reference to the accompanying drawings.

[0015] Figure 1. Design and preparation of IL-P(BzMA-co-HEA) ionogel constructed by mitigating phase separation and regulating multiple interactions; Figure 2 (a) A photograph of the IL-PBzMA ionogel supporting the weight; (b) SEM image and photograph of the IL-PBzMA ionogel. Figure 3 (a) SEM image and physical image of iontophoresis gel with 50wt% HEA content; (b) Changes in transparency of iontophoresis gel with different HEA contents; (c) Transparency of 50wt% iontophoresis gel; (d) Transparency stability of 50wt% iontophoresis gel. Figure 4 SAXS plot of ion gel Figure 5(a) FTIR spectrum of pure PBzMA; (b) FTIR spectrum of ionogels with different HEA contents; (c) XPS spectrum of ionogels after copolymerization of pure PHEA gel ions and BzMA. Figure 6 (a) FTIR spectra of pure ionic liquids and ionic gels; (b) fluorescence spectra of pure PBzMA, IL-PBzMA, and IL-P (BzMA-co-HEA) ionic gels. Figure 7 (a) Tensile stress-strain curves of ionogels with different HEA contents; (b) Corresponding modulus and toughness bar charts; (c) Tensile stress-strain curves of ionogels with different ionic liquid contents; (d) Corresponding modulus and toughness bar charts. Figure 8 (a) IL-P (BzMA-co-HEA) ion gel can withstand heavy loads, maintain large tensile deformation, and withstand severe torsion and knotting without breaking; (b) A single sheet of IL-P (BzMA-co-HEA) ion gel successfully lifted a 7 kg dumbbell. Figure 9 Nanoindentation testing of IL-P(BzMA-co-HEA) ion gel; Figure 10 Laminated glass devices prepared from IL-P (BzMA-co-HEA) ionogels exhibit superior impact resistance compared to conventional materials; Figure 11 Shape memory function of iontophores; Figure 12 A schematic diagram of the reversible adhesion process; Figure 13 (a) Adhesion strength at room temperature after heating to different temperatures; (b) Tensile curves of ionogels at different temperatures; (c) Corresponding modulus-toughness diagrams; Figure 14 (a) DSC curves with different HEA contents; (b) DMA curves in the temperature range of -40 °C to 100 °C; Figure 15 (a) Schematic diagram of the proposed adhesion mechanism at the ionogel-substrate interface; (b) Adhesion strength on various substrates; (c) Demonstration of strong adhesion: an ionogel adhered to a wooden board successfully lifts a 75 kg adult; (d) Comparison of adhesion performance of this work, other ionogels and commercial adhesives; Figure 16 (a) TG curve of IL-P(BzMA-co-HEA) ionogel; (b) Cyclic adhesion properties of IL-P(BzMA-co-HEA) ionogel, showing the cyclic process of repeated adhesion (at room temperature) and deadhesion (at 80°C); Figure 17 (a) Semi-curing time of ionogel; (b) Repairing a vase with semi-cured ionogel in air; Figure 18 (a) Infrared spectra recorded during the photopolymerization of precursor solution under different UV irradiation times; (b) Water contact angles with different HEA contents; (c) Swelling rates of IL-P(BzMA-co-HEA) ionogel after soaking in water for different times. Figure 19 Images of ionogels immersed in water for different durations; Figure 20 Photo and illustration of a remote-controlled boat equipped with a metal heating device integrating IL-P (BzMA-co-HEA) ion gel; Figure 21 Schematic diagram of the underwater reversible adhesion and transfer process of simulated electronic devices Detailed Implementation

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Example 1

[0018] Preparation: All ionic gels were prepared via free radical polymerization. The simplified steps are as follows: Benzyl methacrylate (BzMA), hydroxyethyl acrylate (HEA), ionic liquid, and photoinitiator were mixed and stirred to form a homogeneous precursor solution. Nitrogen gas was bubbled into the solution for 10 minutes for degassing, with the gas flow adjusted to ensure uniform turbulence without splashing. The solution was then injected into a polytetrafluoroethylene (PTFE) mold and polymerized under ultraviolet light (365nm, 1300mW) for 1-5 minutes. The mass fraction of the monomers used was defined as follows: ωHEA = [mHEA / (mBzMA + mHEA)] × 100%; the content of the ionic liquid (IL) was defined as: ωIL = { mIL / [m(HEA + BzMA) + mIL]} × 100%; the amount of photoinitiator was fixed at 1 wt% of the total mass of the two monomers, benzyl methacrylate and hydroxyethyl acrylate. Taking an IL-P (BzMA-co-HEA) ionogel with 50wt% HEA and 10wt% IL content as an example, the preparation process requires 3g of HEA, 3g of BzMA, 0.67g of ionic liquid, and 0.06g of photoinitiator. Next, the above materials are mixed and stirred in air for 30 minutes, and then the precursor solution is dropped onto a mold, yielding the ionogel after 3 minutes.

[0019] Drugs: Monomers: benzyl methacrylate, hydroxyethyl acrylate; Ionic liquid: 1-butyl-1-methylpiperidine bis(trifluoromethanesulfonyl)imide; Photoinitiator: 1-hydroxycyclohexylphenyl ketone.

[0020] Example 2

[0021] This invention proposes a strategy to achieve high strength and high tensile strength by weakening macroscopic phase separation through multiple interactions. Specifically, in a high-strength heterogeneous system where complete macroscopic phase separation occurs between hard polymer segments and a soft solvent phase, flexible segments capable of interacting with multiple components are introduced to suppress entanglement of hard segments and enhance compatibility, thereby obtaining a microphase-separated homogeneous system with both high strength and high tensile strength. To achieve this goal, benzyl methacrylate (BzMA) is selected as the hard segment monomer. After polymerization in an ionic liquid (IL, 1-butyl-1-methylpiperidinebis(trifluoromethanesulfonyl)imide), due to macroscopic phase separation induced by strong π-π interactions, the IL-PBzMA ionic gel exhibits high strength but almost no tensile strength. Figure 1 b). By introducing hydroxyl-containing hydroxyethyl acrylate (HEA) as a soft-segment monomer, and adjusting the multiple interactions between different components, a microphase separation system can be obtained. Figure 1 c). The resulting IL-P(BzMA-co-HEA) ionogel exhibits excellent optical transparency. By modulating hydrogen bonds, ion-dipole, and cation-π interactions within the system, this invention develops a microphase-separated ionogel with high tensile strength (8.4 MPa), large tensile strain (396%), and significant toughness (17.8 MJ m⁻³). Furthermore, the unique thermal softening behavior and abundant functional groups of this ionogel enable it to achieve strong and reversible adhesion to various substrates in air and underwater.

[0022] Mechanism of ion gels The aggregated PBzMA chains in the IL-PBzMA ionogel effectively disperse stress during deformation, imparting significant rigidity to the ionogel. The mechanical strength of this IL-PBzMA ionogel is sufficient to support a 100-gram weight without significant bending or deformation. Figure 2 a). Furthermore, the internal macroscopic phase separation is reflected in the surface morphology and optical properties of the IL-PBzMA ionogel. Scanning electron microscopy (SEM) reveals that the surface of the IL-PBzMA ionogel is rough and has fine protrusions. The inhomogeneity caused by the π-π stacking of benzene rings within the ionogel also results in its white, opaque appearance. Figure 2 b).

[0023] With the introduction of HEA, the hydroxyl groups on HEA form strong hydrogen bonds with the carbonyl groups on BzMA, allowing the originally stacked PBzMA chains to unfold. Furthermore, by introducing multiple interactions such as ion-dipole, cation-π, and hydrogen bonding into the IL-PBzMA ionogel system, a microphase-separated IL-P(BzMA-co-HEA) ionogel system was ultimately achieved. Figure 3 a). After the introduction of HEA, the SEM images of the IL-P(BzMA-co-HEA) ionogel showed that the rough surface features disappeared, exhibiting a smooth and uniform morphology (3b). The optical transparency of the ionogel also showed a regular change due to the introduction of HEA polymer chains (3c). The highly uniform microphase separation system of the IL-P(BzMA-co-HEA) ionogel exhibits optical transparency due to the absence of obvious light scattering regions, with a transmittance as high as 87% at room temperature, and also demonstrates long-term stability (…). Figure 3 d).

[0024] The transformation from a macroscopically phase-separated heterogeneous system to a micro-phase-separated homogeneous system can also be verified by small-angle X-ray scattering (SAXS). Figure 4 The HEA-free IL-PBzMA ionogel exhibits distinct scattering peaks and high scattering intensity, indicating the presence of a significant two-phase region: a polymer-rich region and a solvent-rich region. With increasing HEA content, the scattering peaks in the IL-P(BzMA-co-HEA) ionogel disappear, and the scattering intensity decreases, suggesting that the multiple interactions introduced by HEA gradually dissolve the aggregated polymer chains. When the HEA content reaches 100% (i.e., no PBzMA polymer is present), the curve shows the lowest intensity and becomes rough, indicating that phase separation has ceased.

[0025] Subsequently, to confirm the role of intermolecular interactions introduced by HEA in alleviating phase separation, Fourier transform infrared spectroscopy (FTIR) analysis was performed. In pure PBzMA, the characteristic peaks at 1190 cm⁻¹ and 1134 cm⁻¹ were attributed to the asymmetric and symmetric stretching vibrations of the COC group, respectively. Figure 5 a). When the HEA content is 10 wt%, the COC stretching vibration peaks are located at 1184 cm⁻¹ and 1134 cm⁻¹ (a). Figure 5 b). With increasing HEA content, the two peaks gradually red-shift, indicating enhanced inter-chain hydrogen bonding. When the HEA content reaches 90 wt%, the two peaks merge into a single broad peak. These results indicate that the introduction of HEA disrupts the π-π stacking of benzyl groups in the PBzMA chain, promoting the formation of inter-chain hydrogen bonds and thus constructing a more ordered polymer network. This network structure establishes an effective energy dissipation pathway, laying the foundation for the excellent mechanical properties of the IL-P(BzMA-co-HEA) ion gel. Furthermore, X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical bonding environment within the IL-P(BzMA-co-HEA) ion gel. Figure 5c). The spectra show that the binding energies of both C=O and CO / C-OH bonds in the P(BzMA-co-HEA) copolymer are significantly increased. Similarly, this shift originates from the hydrogen bonding between the hydroxyl groups on the PHEA chain and the carbonyl groups of PBzMA, as well as the self-association within the PHEA chain, leading to a decrease in the electron cloud density around the relevant atoms.

[0026] Besides the hydrogen bonds between polymer chains, the interaction between polymer chains and ionic liquids is also crucial for promoting microphase separation and enhancing toughness. For example... Figure 6 As shown in Figure a, ion-dipole interactions have been confirmed. The bands at 1355 cm⁻¹ and 1060 cm⁻¹ are attributed to the asymmetric stretching vibrations of the S=O and N / S bonds in the ionic liquid, respectively. In the P(BzMA-co-HEA) ionogel, these bands shift to 1351 cm⁻¹ and 1055 cm⁻¹, respectively, indicating that the ion-dipole interaction between the carbonyl group (C=O) on the polymer chain and the cation in the ionic liquid weakens the inherent electrostatic interaction between the anions and cations within the ionic liquid, thereby increasing the negative charge on the nitrogen atom of the anion. Furthermore, Figure 6 b. The cation-π interaction was characterized by fluorescence spectroscopy. Compared with the pure PBzMA polymer, the fluorescence intensity of the IL-PBzMA ionogel system was significantly reduced. This spectral change originates from the charge transfer process between the benzyl group and the ionic liquid cation, consistent with the formation of the cation-π interaction. In contrast, the emission wavelength of the IL-P(BzMA-co-HEA) ionogel showed a red shift, which may be due to the additional interactions introduced by HEA, such as hydrogen bonding and ion-dipole coupling, affecting the interaction mode between the benzene ring and the cation. In summary, the microphase-separated IL-P(BzMA-co-HEA) ionogel system, constructed from rich dynamic interactions, can achieve chain extension and energy dissipation during deformation, thus endowing it with tunable mechanical properties.

[0027] Mechanical properties of ion gels By adjusting the HEA content, the degree of phase separation and multiple interactions within the IL-P(BzMA-co-HEA) ionogel can be controlled, effectively regulating its mechanical properties to obtain ionogels with brittle-hard, strong-tough, or soft-elastic behaviors. When the HEA mass fraction is 10 wt%, the fracture stress of the IL-P(BzMA-co-HEA) ionogel is 16.69 ± 0.03 MPa (7a), and the modulus reaches 264 MPa. Figure 7(b) but the fracture strain is only 13.14%. In this state, π-π interactions dominate in the network. The stacked benzene rings provide an excessively strong stress distribution mechanism during stretching, and a small amount of HEA is insufficient to dissociate the stacked benzene rings. Therefore, although the fracture strength is high, the network inhomogeneity leads to low tensile strength. When the HEA content increases to 50 wt%, the fracture strength decreases to 8.4 ± 0.06 MPa, but the fracture strain increases significantly to 396% (approximately 30 times that of the 10 wt% sample), and the toughness reaches a peak of 17.8 ± 1.7 MJ m⁻³. Figure 7 b). This indicates that the hydrogen bonds introduced by HEA expose more polymer chains to the ionic liquid, promoting multiple interactions between the polymer chains and the ionic liquid, thereby enhancing tensile strength. The micro-entangled regions of PBzMA retained in the system act as stress-bearing zones during stretching, effectively ensuring the strength of the IL-P(BzMA-co-HEA) ionic gel. When the HEA content further increases, the ionic gel exhibits high ductility, but the tensile strength decreases sharply. This is because the polymer chains are almost completely dissolved, and the ionic gel lacks phase separation regions that provide stress distribution. This invention further investigates the effect of ionic liquid content on the mechanical properties of the ionic gel ( Figure 7 c). It can be concluded that the mechanical properties of ionic gels deteriorate with increasing ionic liquid content. Both modulus and toughness decrease with increasing ionic liquid content, which can be attributed to the plasticizing effect of the ionic liquid on the ionic gel. Figure 7 d). Clearly, by adjusting the content of HEA and ionic liquid, ionic gels can achieve a balance of rigidity and flexibility. An ionic gel containing 50 wt% HEA and 10 wt% ionic liquid was selected as the optimal system for subsequent characterization and mechanistic studies.

[0028] Figure 8 This demonstrates that the IL-P (BzMA-co-HEA) ionogel can withstand loads (such as supporting a 50-gram weight) while also being able to stretch and twist freely. Furthermore, a sample only 6 mm wide and 1 mm thick can easily lift a 7 kg dumbbell and remains intact even when stretched, highlighting the excellent balance between strength and tensile strength. Figure 8 b).

[0029] The high modulus of IL-P(BzMA-co-HEA) ionogel also endows it with a certain degree of rigidity, which can be quantified by nanoindentation testing. Figure 9 The loading-unloading curves show significant stiffness and elastic behavior, as evidenced by the small hysteresis loop.

[0030] Thanks to its excellent energy dissipation capabilities granted by its rich internal interactions, IL-P(BzMA-co-HEA) ionogel can rapidly dissipate stress upon external impact. Laminated glass, made by sandwiching IL-P(BzMA-co-HEA) ionogel between two glass plates, can withstand impact forces up to 2789 N while maintaining structural integrity, whereas the control sample (ordinary glass) shattered under an impact force of only 188 N. Figure 10 This characteristic suggests its potential applications in areas such as windows, high-rise building glass, or electronic device screens, offering both clear visibility and enhanced security.

[0031] Furthermore, thanks to its abundant reversible covalent bonds, the IL-P(BzMA-co-HEA) ionogel not only exhibits good deformability and resilience but also demonstrates shape memory properties. This ionogel can completely recover to its original length after being subjected to 200% strain at room temperature. Figure 11 With a shape fixation rate and recovery rate approaching 100%, it highlights its excellent ductility and elastic recovery ability.

[0032] Adhesion properties of ion gels In addition to its excellent mechanical properties, the IL-P (BzMA-co-HEA) ionogel also exhibits reversible temperature-dependent adhesion characteristics. At room temperature, the ionogel is rigid and non-sticky. Upon heating, it softens and achieves complete contact with the substrate, followed by a sharp increase in adhesion during cooling. Therefore, adhesion and deadhesion can be easily achieved through a simple heating process. Figure 12 ).

[0033] The adhesion strength of the ionogel after heating and cooling at different temperatures was measured using an overlap shear test. The results are as follows: Figure 13 As shown in Figure a. At temperatures equal to or below room temperature, the IL-P(BzMA-co-HEA) ionogel exists in a rigid glassy state and cannot wet the substrate surface; therefore, its adhesion to glass is negligible (unless otherwise stated, adhesion values ​​mentioned below refer to measurements on glass). The adhesion strength of the ionogel increases with increasing heating temperature and upon cooling to room temperature. After heating to 80°C and then cooling, its strength reaches a maximum of 7.46 MPa. This enhancement is attributed to the thermal softening properties of the IL-P(BzMA-co-HEA) ionogel, as shown in the temperature-dependent tensile curve (…). Figure 13 b and Figure 13 c) confirms this.

[0034] As temperature increases, the strength of the IL-P (BzMA-co-HEA) ionogel gradually decreases, making it easier for the softened ionogel to achieve complete contact with the substrate surface. To more clearly elucidate the thermal softening characteristics of the IL-P (BzMA-co-HEA) ionogel, differential scanning calorimetry (DSC) tests were performed. Figure 14 a). With increasing HEA content, the glass transition temperature (Tg) of the ionogel gradually decreases, indicating that the introduction of HEA as a soft segment loosens the internal network structure, making the ionogel more flexible. This observation is consistent with... Figure 3 The mechanical properties exhibited in a and 3b are consistent, demonstrating the rationality of the design. The Tg of the IL-P(BzMA-co-HEA) ionogel containing 50 wt% HEA is approximately 28 °C. This explains why the IL-P(BzMA-co-HEA) ionogel begins to exhibit adhesiveness when the temperature rises above 40 °C. This is further supported by DSC data and dynamic thermomechanical analysis (DMA). curve( Figure 14 (b) This elucidates the mechanism by which thermal softening enhances adhesion: Below Tg, the storage modulus (E′) is higher than the loss modulus (E″), indicating a glassy state where the ionogel cannot adhere to the substrate. Within the range of 40–80 °C, E′ decreases below E″, signifying a transition to a softened state with strong dissipation capabilities, where substrate wetting is optimal. Subsequently, upon cooling to room temperature, the IL-P (BzMA-co-HEA) ionogel transforms into a tough glassy state, thus resisting peeling. Therefore, strong adhesion between the IL-P (BzMA-co-HEA) ionogel and the substrate can be achieved by adjusting the temperature.

[0035] Benefiting from the synergistic effect of multiple interactions between the abundant functional groups on the surface of IL-P (BzMA-co-HEA) ionogel and the substrate—such as hydrogen bonding, cation-π interactions, and ion-dipole and electrostatic interactions—( Figure 15 a) This ionogel can achieve strong adhesion to a variety of substrates, including glass, wood, and metals such as iron sheets. Figure 15 b). Figure 15 c demonstrates an example of high adhesion strength: a wooden board with an adhesion area of ​​only 4 cm² can lift an adult weighing approximately 75 kg. Furthermore, the adhesion strength of IL-P (BzMA-co-HEA) ionomer gel on glass (7.46 MPa) was compared with commercial adhesives and other reported ionomer gels. Figure 15 d). Clearly, the IL-P (BzMA-co-HEA) ionogel adhesive of the present invention exhibits superior adhesive strength compared to these adhesives.

[0036] To prevent damage to the IL-P(BzMA-co-HEA) ionogel from repeated heating, its thermal stability was assessed by thermogravimetric analysis (TG). Figure 16 As shown in figure a, the polymer decomposition of the ionogel occurs in two stages: the first weight loss occurs at approximately 266 °C, corresponding to the decomposition of BzMA; followed by the decomposition of HEA in the range of 327–360 °C. The high decomposition temperatures of each component ensure the stable and effective reversible adhesion of the ionogel. Figure 16 b demonstrates the reversible adhesion cycle stability of the IL-P(BzMA-co-HEA) ionogel, showing no significant fatigue or performance degradation after five heat-cooling cycles.

[0037] Applications of underwater transfer monitors based on the mechanical properties and viscosity of ionogels Underwater adhesives are crucial for sealing and repairing subsea pipelines and cables. In certain applications, such as redeploying installed monitoring equipment or correcting misaligned components during maintenance, adhesives not only need sufficient strength to withstand water pressure but also must possess reversible adhesion properties. Although many commercially available epoxy resins can adhere underwater, their long curing times, low strength, and irreversible bonding severely limit their practical applications. Therefore, a strong and reversible underwater adhesive is urgently needed to meet these application requirements.

[0038] In this study, the present invention can regulate the IL-P(BzMA-co-HEA) ionogel to a semi-solid state by controlling the curing time, and obtains an easily processable semi-solid morphology by curing in only 30 seconds. Figure 17 a). This semi-cured ionogel can be used as an adhesive to repair damaged objects, such as repairing a broken vase ( Figure 17 b). Applying the adhesive to the fracture and further curing it with ultraviolet light can quickly achieve a strong and tough bond.

[0039] For underwater applications, the possibility of component loss during the curing process of the semi-cured ionogel needs to be considered. Therefore, infrared spectroscopy was used to evaluate the monomer conversion rate of IL-P (BzMA-co-HEA) ionogel at different curing times, such as... Figure 18 As shown in Figure a, the characteristic peak of the C=C bond in the 1000–950 cm⁻¹ region disappeared after only 1 minute of UV irradiation, demonstrating the rapid curing capability of this ionogel. Therefore, underwater curing and adhesion can be achieved through rapid UV irradiation. Its underwater adhesion is attributed to the hydrophobic segments of BzMA, which effectively displace the hydration layer on the substrate surface—a key factor for achieving stable and strong adhesion in an aqueous environment. The effect of hydrophobic monomer content on underwater adhesion was evaluated by measuring the contact angle of ionogels with different BzMA contents. Figure 18(b) As the BzMA content increases, the contact angle increases accordingly, indicating an enhanced ability to displace the hydration layer during underwater bonding, thus enabling effective underwater adhesion of the substrate. Anti-swelling behavior is also a key performance characteristic of underwater adhesives. For example... Figure 18 As shown in c, the equilibrium swelling ratio of IL-P(BzMA-co-HEA) ionogel is extremely low, only 3.5%.

[0040] Although the transparency decreased during immersion and stabilized after swelling equilibrium, the volume of the ionogel remained almost unchanged. Figure 19 This characteristic further ensures that the adhesive maintains structural integrity and does not fail during the curing process.

[0041] To further demonstrate its underwater adhesion capability, this invention designed an experimental demonstration simulating the transfer of underwater monitoring equipment. For example... Figure 20 a and Figure 20 As shown in b, this invention assembles a remotely controlled small boat equipped with a metal heater. A semi-cured IL-P (BzMA-co-HEA) ionogel adhesive is applied to the bottom of the heater, enabling it to function as a "grab" to move a starfish-shaped underwater monitoring device.

[0042] Figure 21 The process of transferring the monitor underwater using this adhesive is demonstrated in detail. First, a heater coated with the adhesive is brought into contact with the monitor. Figure 21 I); Subsequently, in-situ curing with ultraviolet irradiation was performed to firmly bond the semi-cured adhesive to the monitor. Figure 21 II); After curing is complete, start the small boat to tow the monitor 30 cm to the target location ( Figure 21 III); After arriving at the destination ( Figure 21 IV) This involves separating the heater from the monitor through heating. Figure 21 V); Finally, guide the small boat back to the starting point to complete the entire transfer process (see appendix). Figure 21 (VI). These results demonstrate the significant potential of this robust IL-P (BzMA-co-HEA) ionogel adhesive for underwater adhesion applications.

[0043] Results and Discussion In summary, the copolymerization of soft HEA segments and rigid BzMA segments effectively reduces phase separation in the IL-P (BzMA-co-HEA) ionogel system, thus preparing an ionogel with high strength, large deformation capacity, and reversible adhesion. The micro-entangled regions of BzMA retained in the system act as stress-bearing zones during stretching, effectively ensuring the strength of the IL-P (BzMA-co-HEA) ionogel; while the abundant reversible interactions within the dissolved regions enable the ionogel to undergo large deformations without being destroyed. Notably, these multiple interactions also endow the ionogel with strong and reversible adhesion in both air and water, paving the way for the development of future robust and reversible adhesion technologies.

Claims

1. A high-strength, highly stretchable, and reversibly adhesive ionic gel with multiple interactions inhibiting microphase separation, characterized in that, The ionogel is obtained by introducing a flexible segment that can form a dense interaction with multiple components into a macroscopic phase separation system of rigid segments and ionic liquids. The ionogel has a tensile strength of 8.4 MPa, a tensile strain of 396%, a toughness of 17.8 MJ m⁻³, and an optical transmittance of 87%. The ionogel exhibits reversible adhesion of 7.46 MPa on glass after heating-cooling cycles in air and underwater environments.

2. The high-strength, highly stretchable, and reversible adhesive ionogel with multiple interactions inhibiting microphase separation according to claim 1, characterized in that, The ion gel is obtained by introducing hydroxyethyl acrylate (HEA) as a flexible segment into a strongly macroscopic phase separation system composed of rigid segment benzyl methacrylate (BzMA) and ionic liquid IL.

3. The high-strength, highly stretchable, and reversible adhesive ionogel with multiple interactions inhibiting microphase separation according to claim 2, characterized in that, The ionic solution is a 1-butyl-1-methylpiperidine bis(trifluoromethylsulfonyl)imide solution, and the photoinitiator is 1-hydroxycyclohexylphenyl ketone.

4. The high-strength, highly stretchable, and reversible adhesive ionogel with multiple interactions inhibiting microphase separation according to claim 2, characterized in that, The amount of photoinitiator 1-hydroxycyclohexylphenyl ketone was fixed at 1 wt% of the total mass of the two monomers benzyl methacrylate and hydroxyethyl acrylate.

5. A method for preparing a high-strength, highly stretchable, and reversible adhesive ionic gel with multiple interactions inhibiting microphase separation as described in any one of claims 1-4, characterized in that, The preparation method is as follows: Step 1: Mix benzyl methacrylate (BzMA), hydroxyethyl acrylate (HEA), ionic liquid, and photoinitiator, and stir to form a homogeneous precursor solution; Step 2: Introduce nitrogen gas into the precursor solution for 10 minutes for degassing. During the gas introduction process, adjust the airflow to make the solution roll evenly without splashing. Step 3: Inject the solution obtained after degassing in Step 2 into a polytetrafluoroethylene (PTFE) mold, and polymerize it under ultraviolet light to obtain an ionogel.

6. The preparation method according to claim 5, characterized in that: The dosage of HEA is 50 wt%, and the dosage of IL is 10 wt% IL.

7. The preparation method according to claim 5, characterized in that: In step three, the ultraviolet light conditions are 365nm, 1300mW, and irradiation for 1-5 minutes.

8. The application of the high-strength, highly stretchable, and reversible adhesive ionogel with multiple interactions inhibiting microphase separation as described in any one of claims 1-4 in an underwater transport monitoring device.

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