Building block gradient hydrophobic fluorescent ionic gel, its preparation method and application
The modular gradient hydrophobic fluorescent ionogel, designed with a multi-layer gradient structure, solves the problems of stability and sensing performance of ionogels in underwater applications, achieving wide pressure detection and high fluorescence emission, and is suitable for flexible sensors and electronic skin.
Patent Information
- Application Number
- CN202411838803.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2026-06-16
AI Technical Summary
Existing ionogels are prone to absorbing water and swelling or dissolving in underwater wearable devices, resulting in reduced sensor performance, narrow pressure detection range, and insufficient fluorescence, making it difficult to meet the needs of outdoor sports and nighttime search and rescue.
A modular gradient hydrophobic fluorescent ionogel with a multi-layer gradient structure is used to prepare a pressure sensor with long-term water stability and high sensitivity by introducing hydrophobic ionic liquids and cross-linked network polymers to form a multi-layer structure with a gradient distribution of cross-linking degree and combining fluorescent cross-linking agents with different degrees of cross-linking.
It achieves a wide pressure detection range, long-term water stability, and high fluorescence emission intensity, expanding the application of ion gels in flexible sensors and electronic skin, and enhancing the success rate of search and rescue.
Smart Images
Figure CN122213299A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of smart gel materials technology, specifically to a modular gradient hydrophobic fluorescent ion gel, its preparation method, and its application. Background Technology
[0002] Ionogels consist of a polymer cross-linked network and organic salts (ionic liquids) uniformly distributed within the cross-linked structure. Due to their highly tunable mechanical properties, excellent stretchability, and biocompatibility, ionogels have been used to fabricate flexible wearable devices, artificial skin, and pressure sensors. However, the application of ionogels in underwater wearable devices still faces significant challenges. This is because the high concentration of hydrophilic groups in the ionogel causes it to absorb water, swell, and even dissolve. Furthermore, the ionic liquid components can irreversibly diffuse into the water through the solid-liquid interface due to concentration differences, leading to the destruction of the cross-linked structure and a decrease in sensor performance. In addition, the sensitivity and pressure detection range of ionogel-based pressure sensors need further improvement. The pore size of the ionic liquid determines its elastic modulus, flexibility, and mechanical properties, and the tunable internal pore size of the ionogel ensures the design flexibility of the sensitivity of pressure sensors based on it.
[0003] Currently, stable wireless instant communication functions have been developed using the pressure sensing properties of ionogels. However, for outdoor activities, in addition to exchanging information with other people, the passive wilderness search and rescue (WSAR) function is equally important when the wearer is in distress. In low-visibility scenarios such as at night or underwater, the fluorescence properties of ionogels can effectively increase the success rate of search and rescue (SAR).
[0004] Specifically, common methods for preparing ionogels involve completely dissolving and dispersing ionic liquids and polymer monomers, pouring the mixture into a mold, and then performing cross-linking polymerization under ultraviolet light. This method often results in a limited variety of pore morphology and size in the ionogel due to its simple structure, making it impossible to adjust the conductivity and sensing performance of electronic devices based on it. Multilayer gradient gels, on the other hand, can prepare ionogels according to specific needs.
[0005] Therefore, compared with existing ion gel structures and their preparation methods, developing a modular gradient hydrophobic fluorescent ion gel for different application scenarios can effectively expand the application environment of ion gels. Summary of the Invention
[0006] Due to the aforementioned defects in existing technologies, this invention provides a modular gradient hydrophobic fluorescent ion gel, its preparation method, and its applications. By designing a multi-layer gradient structure, it improves upon the problems of poor water stability, narrow pressure detection range, and unsatisfactory mechanical and fluorescence emission performance of existing ion gels, thus expanding the application of ion gels in wearable electronic devices such as flexible pressure sensors, flexible temperature sensors, or flexible electronic skin.
[0007] To achieve the above objectives, the present invention provides the following technical solution:
[0008] In a first aspect, the present invention provides a modular gradient hydrophobic fluorescent ionogel, comprising a multilayer gradient structure ionogel composed of a hydrophobic ionic liquid and a polymeric fluorescent crosslinking network; wherein the degree of crosslinking of the crosslinking network polymer between the layers in the multilayer gradient structure ionogel is gradient distributed.
[0009] Furthermore, the cation of the ionic liquid is an alkyl imidazole cation, and the anion of the ionic liquid is a bis(trifluoromethanesulfonyl)imide anion or a hexafluoroboric acid anion. The ionic liquid includes at least one of the above-mentioned cations and at least one of the above-mentioned anions.
[0010] Furthermore, the crosslinked network polymer is a crosslinked product of 1-vinylimidazole with di(bromomethyl)benzene, tetra(bromomethyl)benzene, or hexa(bromomethyl)benzene.
[0011] Furthermore, the multi-layer gradient structure has 2 to 10 layers.
[0012] Secondly, the present invention provides a method for preparing a modular gradient hydrophobic fluorescent ionogel, comprising the following steps:
[0013] S1. Prepare fluorescent crosslinking agents with different degrees of crosslinking;
[0014] S2. Mix N,N-dimethylacrylamide and tert-butyl acrylate in a molar ratio of 1:1 to 5, and then mix the mixture with a hydrophobic ionic liquid in a mass ratio of 1:1 to 5.
[0015] S3. Add fluorescent crosslinking agents with different degrees of crosslinking (0.1-1% molar fraction) and photoinitiators with a mass fraction of 0.1% to the mixed solution described in S2, and dissolve them completely by ultrasonication at room temperature.
[0016] S4. The mixed solution containing one crosslinking agent described in S3 is polymerized under ultraviolet light to form a first layer of ionic gel. The mixed solution containing another crosslinking agent is dropped onto the surface of the first layer of gel and polymerized under ultraviolet light to form a second layer of ionic gel. Subsequent multilayer gels are formed using a similar method, thereby constructing a modular hydrophobic fluorescent ionic gel.
[0017] Further, the preparation method of the fluorescent crosslinking agent with different degrees of crosslinking in step S1 includes: mixing 1-vinylimidazol with di(bromomethyl)benzene, tetra(bromomethyl)benzene or hexa(bromomethyl)benzene at a molar ratio of 1:2~6 and stirring, reacting completely at room temperature, washing the product with ethyl acetate and drying it; mixing the obtained product with one or more of lithium bis(trifluoromethanesulfonylimide), potassium hexafluorophosphate, and sodium tetrafluoroborate at a molar ratio of 1:2~6, reacting completely at room temperature, washing the product with water and drying it to prepare the fluorescent crosslinking agent.
[0018] Thirdly, the present invention provides a modular gradient hydrophobic fluorescent ionogel prepared by the preparation method described above.
[0019] Furthermore, when the degree of crosslinking of the crosslinking agent used in each layer in step S4 is gradient-distributed, the pore size of the modular gradient hydrophobic fluorescent ionogel is gradient-distributed with each layer, exhibiting a multilayer gradient structure, long-term water stability, pressure sensitivity, and higher fluorescence emission intensity than a single-layer structure. It is understood that the degree of crosslinking of each ionogel layer in step S4 can also be gradient-designed according to the desired function, for example, from low to high and then back to low, or from high to low and then back to high.
[0020] Finally, the present invention provides an application of a modular gradient hydrophobic fluorescent ion gel, which is used in the field of wearable electronic devices such as flexible pressure sensors, flexible temperature sensors, or flexible electronic skin.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] (1) Compared with traditional ion gels, the ion gel of the present invention has extremely strong hydrophobic properties and long-term water stability due to the introduction of hydrophobic ion liquid. At the same time, the modular multilayer gradient ion gel prepared by using fluorescent crosslinking agents with different degrees of crosslinking can achieve a wide pressure detection range, a larger ultimate tensile stress value and fluorescence emission intensity than a single-layer structure.
[0023] (2) In this invention, imidazole ionic liquids and cross-linked products of 1-vinylimidazolium and bromomethyl-substituted benzenes with different degrees of substitution are selected as the main components of the ionic gel. The prepared ionic gel has a uniform texture and strong chemical bonds between layers. Multilayer fluorescent ionic gels with different pore sizes can be designed, and the functional adaptability of the ionic gel can be easily controlled.
[0024] (3) The modular ion gel preparation method of the present invention is simple and easy to industrialize, which broadens the application of ion gel in wearable electronic devices such as flexible pressure sensors, flexible temperature sensors or flexible electronic skin. Attached Figure Description
[0025] The invention, its features, and advantages will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. Like reference numerals denote like parts throughout the drawings. The drawings are not drawn to scale; their purpose is to illustrate the gist of the invention.
[0026] Figure 1 This is a flowchart illustrating the preparation process of the crosslinking agent and ionic liquid in Example 1 of the present invention.
[0027] Figure 2 This is a flowchart illustrating the preparation process of the modular gradient hydrophobic fluorescent ionogel in Example 2 of the present invention.
[0028] Figure 3 This is a cross-sectional microscopic image of the modular gradient hydrophobic fluorescent ionogel of Example 3 of the present invention;
[0029] Figure 4 The water contact angle of the modular gradient hydrophobic fluorescent ionogel in Example 4 of this invention;
[0030] Figure 5 The tensile properties test of the modular gradient hydrophobic fluorescent ionogel in Example 5 of this invention;
[0031] Figure 6 The sensing performance of the modular gradient hydrophobic fluorescent ionogel of Example 5 of the present invention under different pressures;
[0032] Figure 7 This study investigates the fluorescence properties of the modular gradient hydrophobic fluorescent ionogel of Example 5 of the present invention. Detailed Implementation
[0033] The structure of the present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.
[0034] The reaction apparatus, compounds, and solvents involved in the following examples and embodiments are all commercially available. The detection instruments and reagents involved in the following effect examples are all commercially available, the detection methods used are existing technologies that can be found online, and the detection environment is at room temperature. The instruments used to test the sensing performance under different pressures are a universal testing machine and an LCR digital bridge; the test conditions are: gel test size 400 cm². 2 The AC frequency of the LCR digital bridge is 500 MHz.
[0035] Example 1: Synthesis of Crosslinking Agent and Ionic Liquid
[0036] Figure 1 This is a flowchart of the preparation process for crosslinking agents and ionic liquids.
[0037] As an example, the crosslinking agent synthesis method includes the following steps:
[0038] 1.1 Dissolve 10 mmol of 1,4-di(bromomethyl)benzene, 1,2,4,5-tetra(bromomethyl)benzene or 1,2,3,4,5,6-hexa(bromomethyl)benzene in dimethyl sulfoxide, and then add 1-vinylimidazole to the solution in molar ratios of 1:2, 1:4 and 1:6, respectively. Stir at room temperature for 24 h. Wash the three crosslinking agent products three times with ethyl acetate and dry.
[0039] 1.2 Dissolve 10 mmol of the above three crosslinking agents in dimethyl sulfoxide, and add 60, 120, and 180 mmol of LiTFSI to the solution to dissolve. React at room temperature for 48 h. Wash the product three times with water and dry it to obtain the product named [VIm-2]TFSI, [VIm-4]TFSI, and [VIm-6]TFSI.
[0040] Methods for synthesizing ionic liquids:
[0041] 10 mmol N-methylimidazole was mixed with 10 mmol 1-bromoethane and reacted at room temperature for 24 h. The product was washed three times with ethyl acetate and dried.
[0042] 10 mmol of the above product was dissolved in dimethyl sulfoxide, and 10 mmol was added to the solution to dissolve. The reaction was carried out at room temperature for 48 h. The product was washed three times with water and dried to obtain the product named [MIm]TFSI.
[0043] Example 2: Preparation of modular gradient hydrophobic fluorescent ionogels
[0044] 2.1 Preparation of precursor solution
[0045] N,N-dimethylacrylamide (DMAA, 4.36 g, 44 mmol) was mixed with tert-butyl acrylate (t-Ba, 7.05 g, 55 mmol), and then the mixture was mixed with 12.16 g of [MIm]TFSI. A mixture of [VIM-2]TFSI (0.75 g, 1 mmol) and the photoinitiator hydroxycyclohexylphenyl ketone (0.1 wt%) was added to the above mixed solution, and the solution was completely dissolved by sonication at room temperature to obtain a homogeneous and transparent precursor solution, which was used as precursor 1. Precursor solutions 2 and 3 were prepared using [VIM-4]TFSI and [VIM-6]TFSI, respectively.
[0046] 2.2 Preparation of modular ionogels
[0047] See Figure 2Precursor solution 1 was added dropwise to a custom-made soft silicone mold and photoinitiated by a UV lamp (365 nm) for 10 minutes. Similarly, the same volume of precursor solutions 2 and 3 were added dropwise to the previous ionogel and photopolymerized sequentially. The resulting modular gradient ionogel was named t-IG.
[0048] Example 3 Microstructure of Ion Gel
[0049] The microstructure of the ionogel profile in Example 2 was observed using a scanning electron microscope, such as... Figure 3 As shown, in this embodiment, the pores of the ion gel are uniform in size and regular in shape, and the pore size gradually decreases from the first layer of gel to the third layer of gel, showing a clear gradient.
[0050] Example 4 Hydrophobicity test of ionomer gel
[0051] The hydrophobicity of each gel layer in Example 2 was tested, such as... Figure 4 As shown, the water contact angles of the first, second, and third gel layers are 115.0°, 116.8°, and 114.7°, respectively. After soaking in water for 28 days, they become 122.0°, 122.8°, and 122.5°, respectively, indicating that the prepared ionogel has long-term hydrophobic stability.
[0052] Comparative test
[0053] Ion gels of Experimental Examples 1-6 and Comparative Examples 1-4 were prepared using a method similar to that of Example 2. The specific materials and structural characteristics of each ion gel are shown in Table 1.
[0054] Table 1. Material composition and dosage of ionogels in Comparative Examples 1-4 and Experimental Examples 1-6
[0055] Crosslinking agent Crosslinking agent dosage Ionic liquids Mass ratio of mixture to ionic liquid number of floors Experimental Example 1 [VIM-2]TFSI / [VIM-4]TFSI / [VIM-6]TFSI 1 % [MIm]TFSI 1:1 3 Experiment Example 2 [VIM-2]TFSI / [VIM-4]TFSI / [VIM-6]TFSI 0.1 % [MIm]TFSI 1:1 3 Experimental Example 3 <![CDATA[[VIM-2] PF6 / [VIM-4] PF6 / [VIM-6] PF6]]> 1 % <![CDATA[[MIm]PF6]]> 1:1 3 Experiment Example 4 <![CDATA[[VIM-2] BF4 / [VIM-4] BF4 / [VIM-6] BF4]]> 1 % <![CDATA[[MIm]BF4]]> 1:1 3 Experimental Example 5 [VIM-2]TFSI / [VIM-4]TFSI / [VIM-6]TFSI 1 % [MIm]TFSI 1:2 3 Experimental Example 6 [VIM-2]TFSI / [VIM-4]TFSI 1 % [MIm]TFSI 1:1 2 Experimental Example 7 [VIM-2]TFSI / [VIM-4]TFSI / [VIM-6]TFSI 1 % [MIm]TFSI 1:5 5 Experimental Example 8 [VIM-2]TFSI / [VIM-4]TFSI / [VIM-6]TFSI 1 % [MIm]TFSI 1:5 10 Comparative Example 1 [VIM-2]TFSI 1 % [MIm]TFSI 1:1 1 Comparative Example 2 [VIM-3]TFSI 1 % [MIm]TFSI 1:1 1 Comparative Example 3 [VIM-4]TFSI 1 % [MIm]TFSI 1:1 1 Comparative Example 4 [VIM-6]TFSI 1 % [MIm]TFSI 1:1 1
[0056] Evaluation of the mechanical properties of ion gels
[0057] Mechanical performance tests were conducted on comparative examples 1, 3, and 4 and experimental example 1. Figure 5 As shown, the maximum tensile strains of Comparative Examples 1, 3, and 4 were 236%, 98%, and 65%, respectively, and the maximum tensile stresses were 166, 317, and 318 kPa, respectively. In contrast, the maximum tensile strain and stress of the ionogel in Experimental Example 1 were 69% and 340 kPa, respectively. The maximum strain of Experimental Example 1 was between that of Comparative Examples 3 and 4, while its stress was greater than that of all the comparative examples.
[0058] Study on the pressure-sensitive properties of ionogels under different pressures
[0059] The ionogels in Experiment Example 1 have a modular gradient structure, such as... Figure 6As shown, it has a sensitive and accurate ultra-wide detection capability for pressures in the range of 1 Pa to 8 MPa (the two images are magnified views of the sensor at 1 MPa and 8 MPa, respectively), which can meet various application requirements.
[0060] Evaluation of fluorescence properties of ion gel
[0061] The fluorescence properties of comparative groups 1, 3, and 4 were compared with those of experimental group 1. Figure 7 As shown, the ionogels in Comparative Examples 1, 3, and 4, and Experimental Example 1, exhibited maximum emission wavelengths of 437, 446, 455, and 452 nm at an excitation wavelength of 365 nm, with Example 1 showing the strongest fluorescence emission intensity. The fluorescence intensities of Experimental Examples 2-6, from strongest to weakest, are Experimental Example 4, Experimental Example 3, Experimental Example 5, Experimental Example 2, and Experimental Example 6, respectively. The fluorescence intensity of Comparative Examples 1-4 gradually increases.
[0062] Furthermore, the method of Example 2 can be used to prepare modular gradient hydrophobic fluorescent ion gels with different mechanical properties, conductivity, piezoelectric sensing properties, and fluorescence, to meet the needs of different application scenarios.
[0063] From the description of the preparation method above, it can be found that:
[0064] The modular gradient hydrophobic fluorescent ionogel provided by this invention exhibits extremely strong hydrophobic properties and long-term water stability due to the introduction of hydrophobic ionic liquids. Furthermore, by utilizing fluorescent crosslinking agents with different degrees of crosslinking, the modular multilayer gradient ionogel can achieve a wide pressure detection range, a higher ultimate tensile stress value, and a higher fluorescence emission intensity than monolayer structures. The preparation method selects imidazole ionic liquids and crosslinking products of 1-vinylimidazolium with bromomethyl-substituted benzenes of different degrees of substitution as the main components of the ionogel. The resulting ionogel has a uniform texture and strong, tough chemical bonds between layers. This allows for the design of multilayer fluorescent ionogels with different pore sizes, facilitating the control of the ionogel's functional adaptability. Similarly, the preparation method can also select pyridine, quaternary ammonium salt, or pyrrole ionic liquids and fluorescent crosslinking products of different degrees of substitution as the main components of the ionogel to achieve the same technical effects.
[0065] Because the modular gradient hydrophobic fluorescent ion gel of the present invention has long-term water stability, adjustable wide pressure detection range, mechanical strength and fluorescence emission intensity, it can be used in the field of wearable electronic devices such as flexible pressure sensors, flexible temperature sensors or flexible electronic skin.
[0066] In summary, the modular gradient hydrophobic fluorescent ionogel, its preparation method, and its application provided by this invention are highly novel and creative, and have high promotion and application value.
[0067] Those skilled in the art should understand that variations can be implemented by combining existing technology with the above embodiments, which will not be elaborated here. Such variations do not affect the essence of the present invention, and will not be elaborated here either.
[0068] The preferred embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and the devices and structures not described in detail should be understood as being implemented in a conventional manner in the art. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention's technical solutions still fall within the protection scope of the present invention.
Claims
1. A modular gradient hydrophobic fluorescent ionogel, characterized in that: The ionic gel comprises a multilayer gradient structure composed of a hydrophobic ionic liquid and a high-molecular fluorescent crosslinked network polymer; in the multilayer gradient structure ionic gel, the degree of crosslinking of the crosslinked network polymer between layers is gradient distributed.
2. The modular gradient hydrophobic fluorescent ionogel according to claim 1, characterized in that, The cation of the ionic liquid is an alkyl imidazole cation, and the anion of the ionic liquid is a bis(trifluoromethanesulfonyl)imide anion or a hexafluoroboric acid anion. The ionic liquid includes at least one of the above-mentioned cations and at least one of the above-mentioned anions.
3. The modular gradient hydrophobic fluorescent ionogel according to claim 1, characterized in that, The cross-linked network polymer is a cross-linked product of 1-vinylimidazol with di(bromomethyl)benzene, tetra(bromomethyl)benzene, or hexa(bromomethyl)benzene.
4. The modular gradient hydrophobic fluorescent ionogel according to claim 1, characterized in that, The multi-layer gradient structure has 2 to 10 layers.
5. A method for preparing a modular gradient hydrophobic fluorescent ionogel, characterized in that, Includes the following steps: S1. Prepare fluorescent crosslinking agents with different degrees of crosslinking; S2. Mix N,N-dimethylacrylamide and tert-butyl acrylate in a molar ratio of 1:1 to 5, and then mix the mixture with a hydrophobic ionic liquid in a mass ratio of 1:1 to 5. S3. Add fluorescent crosslinking agents with different degrees of crosslinking (0.1-1% molar fraction) and photoinitiators with a mass fraction of 0.1% to the mixed solution described in S2, and dissolve them completely by ultrasonication at room temperature. S4. The mixed solution containing one crosslinking agent described in S3 is polymerized under ultraviolet light to form a first layer of ionic gel. The mixed solution containing another crosslinking agent is dropped onto the surface of the first layer of gel and polymerized under ultraviolet light to form a second layer of ionic gel. Subsequent multilayer gels are formed using a similar method, thereby constructing a modular hydrophobic fluorescent ionic gel.
6. The method for preparing a modular gradient hydrophobic fluorescent ionogel according to claim 5, characterized in that, The preparation method of fluorescent crosslinking agents with different degrees of crosslinking in step S1 includes: mixing 1-vinylimidazol with di(bromomethyl)benzene, tetra(bromomethyl)benzene or hexa(bromomethyl)benzene at a molar ratio of 1:2~6 and stirring, reacting completely at room temperature, and washing the product with ethyl acetate and drying it; mixing the obtained product with one or more of lithium bis(trifluoromethanesulfonylimide), potassium hexafluorophosphate, and sodium tetrafluoroborate at a molar ratio of 1:2~6, reacting completely at room temperature, washing the product with water and drying it to prepare the fluorescent crosslinking agent.
7. A modular gradient hydrophobic fluorescent ionogel, characterized in that, It is prepared using the preparation method described in claim 5 or 6.
8. The modular gradient hydrophobic fluorescent ionogel according to claim 7, characterized in that, The modular gradient hydrophobic fluorescent ionogel has a gradient pore size distribution with each layer, exhibiting a multilayer gradient structure, long-term water stability, pressure sensitivity, and higher fluorescence emission intensity than a single-layer structure.
9. An application of a modular gradient hydrophobic fluorescent ionogel, characterized in that, The modular gradient hydrophobic fluorescent ionogel is used in wearable electronic devices such as flexible pressure sensors, flexible temperature sensors, or flexible electronic skin.