Terpyridine-based dual-network conductive hydrogel as well as preparation method and application thereof

Abstract

The invention discloses terpyridyl-based dual-network conductive hydrogel and a preparation method and application thereof, and relates to the field of dual-network hydrogel preparation.The terpyridyl-based dual-network conductive hydrogel is prepared by uniformly mixing a carboxyl-containing terpyridyl derivative, hydrazide and metal salt in water, conducting ionic bond cross-linking reaction on carboxyl and hydrazine under the assistance of the synergistic effect of intermolecular hydrogen bonds, and preparing the terpyridyl-based dual-network conductive hydrogel. And finally, the block polymer network is mixed with the metal salt, so that the hydrogel has good conductivity, and metal ions and a terpyridine ring in the hydrogel form a coordination structure, so that the gel structure is more compact, and the conductivity of the hydrogel is improved. And meanwhile, the comprehensive requirements of sufficient mechanical strength, stable and reliable conductivity, simple and feasible preparation process and excellent flexibility and biocompatibility are met, and good application prospects are shown.

Description

Technical Field

[0001] This invention relates to the field of dual-network hydrogel preparation, and more particularly to a dual-network conductive hydrogel based on terpyridine, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of artificial intelligence and flexible electronics technology, people's demand for flexible electronic devices has become increasingly diversified. To meet this demand, flexible electronic devices are gradually moving towards intelligence, developing intelligent flexible electronic devices with environmental responsiveness and multifunctional integration, which greatly expands their application prospects in wearable devices, intelligent robots, and other fields. Against this backdrop, flexible sensors based on conductive hydrogels have attracted widespread attention from researchers. Hydrogels, due to their bio-tissue-like softness and hydrophilicity, have shown potential application value in flexible sensors, electronic skin, and other devices. However, traditional single-network hydrogels generally suffer from defects such as weak mechanical strength, conductivity easily affected by environmental humidity, and poor structural stability, making it difficult to meet the usage requirements of wearable devices under long-term deformation and complex operating conditions.

[0003] To address the aforementioned issues, the design of dual-network hydrogels has gradually attracted attention. Currently, two main methods are used to construct dual-network hydrogels. One method relies on covalent cross-linking to construct a dual-network conductive hydrogel. Stable dual-network structures are formed through photo-initiated polymerization and high-temperature cross-linking reactions. While this improves mechanical strength, the preparation process is complex and the conductivity is relatively weak. The other method uses conductive fillers to achieve conductivity in dual-network hydrogels. This mainly involves incorporating conductive fillers such as multi-carbon nanotubes, graphene, and polyaniline into the dual network to improve conductivity. However, this method suffers from defects such as uneven dispersion of conductive fillers in the matrix and inconsistent conductivity; it also disrupts the flexible network structure of the hydrogel, leading to decreased flexibility and limiting its application in wearable devices.

[0004] In summary, current dual-network conductive hydrogels cannot simultaneously meet the comprehensive requirements of sufficient mechanical strength, stable and reliable conductivity, simple and easy preparation process, and excellent flexibility and biocompatibility, thus hindering the widespread practical application of flexible electronic devices. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a terpyridine-based dual-network conductive hydrogel, its preparation method, and its application. It simultaneously meets the comprehensive requirements of sufficient mechanical strength, stable and reliable conductivity, simple and easy preparation process, and excellent flexibility and biocompatibility, demonstrating good application prospects.

[0006] This invention is achieved through the following technical solution: A method for preparing a terpyridine-based dual-network conductive hydrogel includes the following steps: A carboxyl-containing terpyridine derivative, acyl hydrazine, and metal salt were mixed evenly in water at a molar ratio of (1~3):(1~2):(1~2). The mixture was then allowed to stand for 60 min to 120 min to obtain a terpyridine-based dual-network conductive hydrogel.

[0007] A further improvement of the present invention is that: The terpyridine derivatives mentioned are 4′-(4-carboxyphenyl)-2,2′,6′,2′′-terpyridine, 2,2':6',2"-terpyridine-4-carboxylic acid, 2,2':6',2"-terpyridine-4,4',4"-tricarboxylic acid, 5'-([4,2':6',4''-terpyridine]-4'-yl)-([1,1':3',1''-terphenyl]-4,4''-dicarboxylic acid or 4'-(4-carboxyphenyl)-[2,2':6',2''-terpyridine]-5,5''-dicarboxylic acid.

[0008] Specifically, the carboxyl-containing terpyridine derivative, deionized water, and 1 mol / L NaOH solution are first mixed evenly to obtain a mixture containing the terpyridine derivative. Then, acyl hydrazine and metal salt are added sequentially and mixed evenly.

[0009] The ratio of deionized water to NaOH solution is 1 mL: 30 μL, and the ratio of the terpyridine derivative to the mixture is (0.5~2.5) g: 100 mL.

[0010] The acylhydrazine is adipic acid diacylhydrazine, sebacylhydrazine, (4-tetrazo-1-yl-phenyl)-acetic acid diacylhydrazine, benzoylhydrazine, isoniazid, succinic acid diacylhydrazine, azelaic acid diacylhydrazine, oxalic acid diacylhydrazine, dodecanedicarboxylic acid diacylhydrazine, terephthalic acid diacylhydrazine, isophthalic acid diacylhydrazine, or maleic anhydride diacylhydrazine.

[0011] The metal salts are AlCl3, Al(NO3)3, FeCl3, Al2(SO4)3, MgSO4, Ba(NO3)2, CaCl2, MgCl2, ZnCl2, FeCl2, CuCl2, AgCl, BaCl2, Na2SO4, CaSO4, ZnSO4, CuSO4, FeSO4, Fe2(SO4)3, BaSO4, Ca CO3, CuCO3, Mg(CO3)2, Fe(NO3)2, Fe(NO3)3, Cu(NO3)2, AgNO3, Li2CO3, CrCl3·6H2O, SnCl2·H2O, K2CO3, NaCl, Cr(NO3)3·9H2O, Cd(NO3)2, Bi(NO3)3, KNO3, KCl or CuSO4·5H2O.

[0012] A dual-network conductive hydrogel obtained by the preparation method of the terpyridine-based dual-network conductive hydrogel described in any one of the above can be used in wearable flexible sensors.

[0013] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for preparing a bipyridine-based dual-network conductive hydrogel. Using a carboxyl-containing bipyridine derivative and an acylhydrazine as raw materials, and a metal salt as a complex, the method utilizes the ionic cross-linking reaction between the carboxyl groups in the bipyridine derivative molecule and the hydrazine groups in the acylhydrazine molecule, supplemented by the synergistic effect of intermolecular hydrogen bonds, to gradually polymerize and form a block polymer network. Finally, this network is mixed with the metal salt. This process not only endows the hydrogel with excellent conductivity but also, through the coordination structure formed between the metal ions and the bipyridine rings in the hydrogel, makes the gel structure more compact, thereby improving its toughness and giving it excellent mechanical properties, conductivity, and strain responsiveness. It also possesses recyclable and reusable properties. These characteristics enable it to function as a flexible sensor for monitoring human movement (large-amplitude movements, small-amplitude movements, micro-expressions, and speech). Pressure can also be applied to it, and it can stably transmit information by recognizing and transmitting Morse code. This invention features mild reaction conditions, a simple synthesis process, low energy consumption, and excellent performance, solving the problems of poor mechanical properties and instability in applications of hydrogels.

[0014] The dual-network conductive hydrogel of this invention differs from traditional hydrogels. The terpyridine derivative and hydrazide form mainly sheet-like or layered aggregates through the synergistic effect of electrostatic attraction (ionic bonds) and hydrogen bonding. After the introduction of the metal salt, the coordination of the metal ions with the terpyridine ring makes the gel network more compact. A continuous fibrous interwoven structure is constructed on the basis of the first-layer network, ultimately forming a dual-network structure of sheet-like or layered basic framework and fibrous coordination crosslinking. It exhibits significant advantages in mechanical properties, thermal stability, conductivity and sensing performance, providing strong support for its wide application in smart wearable devices and other fields. Attached Figure Description

[0015] Figure 1a The FTIR spectra of the hydrogel prepared from BTPA and ADH in Example 1 of this invention.

[0016] Figure 1b The conductive hydrogel in Example 1 of this invention and Figure 1a FTIR spectra of hydrogels.

[0017] Figure 2 This is a SEM image of the terpyridine dual-network conductive hydrogel of Example 1 of the present invention at 5 μm.

[0018] Figure 3aThis is a repeatable test diagram of the terpyridine dual-network conductive hydrogel of Example 2 of the present invention.

[0019] Figure 3b This is another repeatable test diagram of the terpyridine dual-network conductive hydrogel of Example 2 of the present invention. Figure 4 The graph shows the electrical signal test results of the terpyridine dual-network conductive hydrogel of Embodiment 2 of the present invention under human reaction conditions (finger bending).

[0020] Figure 5a This is a schematic diagram of the Morse code-based communication design of the terpyridine dual-network conductive hydrogel in Embodiment 2 of the present invention.

[0021] Figure 5b This is a schematic diagram of the signal waveform of the SOS (distress signal) transmitted by the terpyridine dual-network conductive hydrogel in Embodiment 2 of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] This invention discloses a method for preparing a terpyridine-based dual-network conductive hydrogel, comprising the following steps: Step 1) Select the following terpyridine derivatives containing a carboxyl group: 4′-(4-carboxyphenyl)-2,2′,6′,2′′-terpyridine, 2,2':6',2"-terpyridine-4-carboxylic acid, 2,2':6',2"-terpyridine-4,4',4"-tricarboxylic acid, 5'-([4,2':6',4''-terpyridine]-4'-yl)-([1,1':3',1''-terphenyl]-4,4''-dicarboxylic acid, 4'-(4-carboxyphenyl)-[2,2':6',2''-terpyridine]-5,5''-dicarboxylic acid; Step 2) Dissolve the carboxyl-containing terpyridine derivative in water using a 1 mol / L NaOH solution to prepare a mixed aqueous solution, wherein the mass ratio of the terpyridine derivative to the aqueous solution is (0.5~2.5) g: 100 mL; Step 3) Add acyl hydrazine and different metal salts sequentially to the aqueous solution and mix evenly. The molar ratio of the terpyridine derivative, metal salt and acyl hydrazine is (1~3):(1~2):(1~2). Let stand for 60min~120min to finally obtain a terpyridine-based double network conductive hydrogel. The specific acylhydrazides are: adipic acid diacylhydrazide, sebacylhydrazide, (4-tetrazol-1-yl-phenyl)-acetic acid diacylhydrazide, benzoylhydrazide, isoniazid, succinic acid diacylhydrazide, azelaic acid diacylhydrazide, oxalic acid diacylhydrazide, dodecanedicarboxylic acid diacylhydrazide, terephthalic acid diacylhydrazide, isophthalic acid diacylhydrazide, o-phthalic acid diacylhydrazide, and maleic anhydride diacylhydrazide. The metal salts are: AlCl3, Al(NO3)3, FeCl3, Al2(SO4)3, MgSO4, Ba(NO3)2, CaCl2, MgCl2, ZnCl2, FeCl2, CuCl2, AgCl, BaCl2, Na2SO4, CaSO4, ZnSO4, CuSO4, FeSO4, Fe2(SO4)3, BaSO4, Ca CO3, CuCO3, Mg(CO3)2, Fe(NO3)2, Fe(NO3)3, Cu(NO3)2, AgNO3, Li2CO3, CrCl3·6H2O, SnCl2·H2O, K2CO3, NaCl, Cr(NO3)3·9H2O, Cd(NO3)2, Bi(NO3)3, KNO3, KCl, CuSO4·5H2O; The terpyridine-based dual-network conductive hydrogel sensor prepared in step 4) can be used as a wearable flexible sensor. It can be attached to the skin surface of different joints of the human body to observe whether it can detect the resistance changes generated when different parts of the human body move, so as to test the electrical signals in the reaction state of different parts of the human body.

[0024] Fingers can be bent at different angles (0°, 30°, 60°, 90°); different joints in the body can be used to monitor fist clenching, wrist, elbow, knee, and ankle movements. It can also detect subtle body movements (such as muscle changes in specific areas, like swallowing or smiling). Simple sound recognition (such as saying "hi," "hello," and hydrogel).

[0025] Example 1 0.028 mmol of 4′-(4-carboxyphenyl)-2,2′,6′,2′′-terpyridine (BTPA), 1 mL of H2O, and 30 μL of 1 mol / L NaOH solution were placed in a 2 mL sample vial and stirred until fully dissolved. Then, 0.056 mmol of adipic acid dihydrazide (ADH) and 0.014 mmol of AlCl3 were added sequentially and mixed thoroughly. The mixture was allowed to stand at room temperature for 80 min to obtain a terpyridine-based dual-network conductive hydrogel.

[0026] 0.028 mmol of 4′-(4-carboxyphenyl)-2,2′,6′,2′′-terpyridine (BTPA), 1 mL of H₂O, and 30 μL of 1 mol / L NaOH solution were placed in a 2 mL sample vial and stirred until fully dissolved. Then, 0.056 mmol of adipic acid dihydrazide (ADH) was added and mixed thoroughly. The mixture was allowed to stand at room temperature for 80 min to obtain the final hydrogel. The hydrogel and the aforementioned double-network conductive hydrogel were lyophilized and then subjected to FTIR analysis.

[0027] from Figure 1a It can be seen from 1703 cm -1 The stretching vibration peak of the C=O group of the BTPA carboxylic acid group is present at 3309 cm⁻¹; in the infrared spectrum of the hydrogel, the peak is at 3309 cm⁻¹. -1 The intensity of the -NH2 characteristic peak decreases at 1703 cm⁻¹. -1 The disappearance of the C=O stretching vibration peak of the carboxylic acid group indicates that the carboxyl group in BTPA forms an ionic bond with the amino group in ADH.

[0028] exist Figure 1b In the middle, at 1631, 1596, and 1552 cm -1 The characteristic peaks are attributed to the stretching vibrations of C=C and C=N in the terpyridine ring. The characteristic absorption peaks of BTPA / ADH / AlCl3 dry gel are shifted to 1656, 1620, and 1566 cm⁻¹ compared to BTPA / ADH dry gel. -1 This indicates that Al 3+ It coordinated with the N atom in the pyridine ring.

[0029] See Figure 2 The image shows an SEM image of the conductive hydrogel from Example 1. As can be seen from the image, the terpyridine derivative and the acylhydrazine form mainly sheet-like or layered aggregates through the synergistic effect of electrostatic attraction (ionic bond) and hydrogen bonding. After the introduction of the metal salt, the coordination of the metal ions with the terpyridine ring makes the gel network more compact. A continuous fibrous interpenetrating structure is constructed on the basis of the first layer network, and finally a double network structure of sheet-like or layered basic framework and fibrous coordination crosslinking is formed.

[0030] See Figure 3a and Figure 3bThe figure shows the repeatability test results of the conductive hydrogel in Example 1. When the reagent bottle containing the gel was inverted, the gel briefly remained at the bottom of the bottle. Subsequently, when placed on a shaker, the gel underwent structural disruption due to vibration. After being removed and allowed to stand, it quickly returned to its gel state. Simultaneously, drying the gel at room temperature yielded a white solid. This solid was placed in a sample bottle, and deionized water was added. The mixture was thoroughly stirred and dissolved at a suitable temperature. After cooling to room temperature, it quickly returned to its gel state. These results demonstrate that the gel exhibits excellent reversible recovery capabilities regardless of external forces or solvent removal conditions. This characteristic is of great significance for promoting the green and sustainable development of flexible sensing.

[0031] Example 2 0.028 mmol of 2,2':6',2"-terpyridine-4-carboxylic acid, 1 mL of H2O, and 30 μL of 1 mol / L NaOH solution were placed in a 2 mL sample vial and stirred until fully dissolved. Then, 0.014 mmol of sebacic acid dihydrazide and 0.014 mmol of CrCl3·6H2O were added sequentially and mixed thoroughly. The mixture was allowed to stand at room temperature for 60 min to obtain a terpyridine-based dual-network conductive hydrogel.

[0032] See Figure 4 The graph shows the electrical signal test results of the terpyridine-based dual-network conductive hydrogel prepared in Example 2 under human reactive conditions (finger bending). The prepared hydrogel sensor was used as a wearable device for monitoring human movement.

[0033] As the degree of finger bending increases (0°, 30°, 60°, 90°), a corresponding stable change in relative resistance can be observed, indicating that the strain sensor based on terpyridine dual-network conductive hydrogel has high sensitivity and stability for monitoring subtle changes, such as... Figure 4 As shown. Furthermore, this sensor can also transmit Morse code via pressure to convey desired information, demonstrating potential applications in human-computer interaction. Figure 5a As can be seen, Morse code uses different combinations of dots and short lines to represent English letters. Based on this, symbols corresponding to the English letters (e.g., A, B, C) are used to convey SOS messages (e.g., using a signal representing a change in relative resistance (AR / Ro)). Figure 5bThe signal can be repeated until the response disappears when no pressure is applied to the sensor. This figure is merely an example illustrating the sensitive pressure-sensing capability of the terpyridine-based dual-network conductive hydrogel strain sensor. Therefore, the terpyridine-based dual-network conductive hydrogel strain sensor holds promise for applications in information transmission and encryption. This demonstrates that the terpyridine-based dual-network conductive hydrogel strain sensor is stable, highly sensitive, and has a fast response speed, making it an ideal choice for monitoring human movement.

[0034] Example 3 0.028 mmol of 2,2':6',2"-terpyridine-4,4',4"-tricarboxylic acid, 1 mL of H2O, and 30 μL of 1 mol / L NaOH solution were placed in a 2 mL sample vial and stirred until fully dissolved. Then, 0.028 mmol of azelaic acid dihydrazide and 0.056 mmol of MgSO4 were added sequentially and mixed thoroughly. The mixture was allowed to stand at room temperature for 120 min to obtain a terpyridine-based dual-network conductive hydrogel.

[0035] Example 4 0.042 mmol of 4'-(4-carboxyphenyl)-[2,2':6',2''-terpyridine]-5,5''-dicarboxylic acid, 1 mL of H2O, and 30 μL of 1 mol / L NaOH solution were placed in a 2 mL sample vial and stirred until fully dissolved. Then, 0.014 mmol of dioxalylhydrazide and 0.021 mmol of Ba(NO3)2 were added sequentially and mixed thoroughly. The mixture was allowed to stand at room temperature for 70 min to obtain a terpyridine-based dual-network conductive hydrogel.

[0036] Example 5 0.042 mmol of 5'-([4,2':6',4''-terpyridine]-4'-yl)-([1,1':3',1''-terphenyl]-4,4''-dicarboxylic acid, 1 mL of H2O, and 30 μL of 1 mol / L NaOH solution were placed in a 2 mL sample vial and stirred until fully dissolved. Then, 0.028 mmol of terephthalic acid dihydrazide and 0.014 mmol of Bi(NO3)3 were added sequentially and mixed thoroughly. The mixture was allowed to stand at room temperature for 110 min to obtain a terpyridine-based dual-network conductive hydrogel.

[0037] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a terpyridine-based dual-network conductive hydrogel, characterized in that, A carboxyl-containing terpyridine derivative, acyl hydrazine, and metal salt are mixed evenly in water at a molar ratio of (1~3):(1~2):(1~2). The mixture is then allowed to stand to obtain a terpyridine-based dual-network conductive hydrogel.

2. The method for preparing a terpyridine-based dual-network conductive hydrogel according to claim 1, characterized in that, The terpyridine derivatives mentioned are 4′-(4-carboxyphenyl)-2,2′,6′,2′′-terpyridine, 2,2':6',2"-terpyridine-4-carboxylic acid, 2,2':6',2"-terpyridine-4,4',4"-tricarboxylic acid, 5'-([4,2':6',4''-terpyridine]-4'-yl)-([1,1':3',1''-terphenyl]-4,4''-dicarboxylic acid or 4'-(4-carboxyphenyl)-[2,2':6',2''-terpyridine]-5,5''-dicarboxylic acid.

3. The method for preparing a terpyridine-based dual-network conductive hydrogel according to claim 1, characterized in that, First, the carboxyl-containing terpyridine derivative, deionized water, and 1 mol / L NaOH solution are mixed evenly to obtain a mixture containing the terpyridine derivative. Then, acyl hydrazine and metal salt are added sequentially and mixed evenly.

4. The method for preparing a terpyridine-based dual-network conductive hydrogel according to claim 3, characterized in that, The ratio of deionized water to NaOH solution is 1 mL: 30 μL.

5. The method for preparing a terpyridine-based dual-network conductive hydrogel according to claim 3, characterized in that, The ratio of the terpyridine derivative to the mixture is (0.5~2.5) g: 100 mL.

6. The method for preparing a terpyridine-based dual-network conductive hydrogel according to claim 1, characterized in that, The acylhydrazine is adipic acid diacylhydrazine, sebacylhydrazine, (4-tetrazo-1-yl-phenyl)-acetic acid diacylhydrazine, benzoylhydrazine, isoniazid, succinic acid diacylhydrazine, azelaic acid diacylhydrazine, oxalic acid diacylhydrazine, dodecanedicarboxylic acid diacylhydrazine, terephthalic acid diacylhydrazine, isophthalic acid diacylhydrazine, or maleic anhydride diacylhydrazine.

7. The method for preparing a terpyridine-based dual-network conductive hydrogel according to claim 1, characterized in that, The metal salts are AlCl3, Al(NO3)3, FeCl3, Al2(SO4)3, MgSO4, Ba(NO3)2, CaCl2, MgCl2, ZnCl2, FeCl2, CuCl2, AgCl, BaCl2, Na2SO4, CaSO4, ZnSO4, CuSO4, FeSO4, Fe2(SO4)3, BaSO4, Ca CO3, CuCO3, Mg(CO3)2, Fe(NO3)2, Fe(NO3)3, Cu(NO3)2, AgNO3, Li2CO3, CrCl3·6H2O, SnCl2·H2O, K2CO3, NaCl, Cr(NO3)3·9H2O, Cd(NO3)2, Bi(NO3)3, KNO3, KCl or CuSO4·5H2O.

8. The method for preparing a terpyridine-based dual-network conductive hydrogel according to claim 1, characterized in that, The settling time is 60 min to 120 min.

9. A dual-network conductive hydrogel obtained by the preparation method of the terpyridine-based dual-network conductive hydrogel according to any one of claims 1 to 8.

10. The application of the dual-network conductive hydrogel as described in claim 9 in wearable flexible sensors.

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