Rosin-induced conductive self-healing dual-network gel and preparation method thereof

Abstract

The preparation method comprises the following steps: by taking epoxy fatty acid methyl ester and sodium lipoate as precursors and utilizing acrylic acid rosin as a ring opening agent and a cross-linking agent at the same time, inducing ring opening polymerization of the epoxy fatty acid methyl ester to form a polyester network; meanwhile, disulfide bonds of the sodium lipoate are promoted to break and polymerize to form a sodium polylipoate network, so that the conductive self-healing dual-network gel is obtained. The preparation method is simple and efficient, and the obtained gel has good conductivity and repeatable self-repairing characteristics.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of double-network self-healing material preparation, and particularly relates to a rosin-induced conductive self-healing double-network gel and a preparation method thereof. BACKGROUND

[0002] Self-healing materials have great potential in prolonging material life, reducing maintenance costs and improving reliability in extreme environments due to their ability to repair damage autonomously. These materials usually rely on dynamic chemical bonds or biomimetic mechanisms to achieve repair function, but for a long time they have faced the core contradiction that mechanical strength and self-healing efficiency are difficult to coordinate. Although the weak interaction of dynamic bonds can promote rapid repair, it often leads to a significant decrease in material mechanical properties, and high-strength materials are difficult to achieve efficient self-healing due to limited molecular chain segment activity. The introduction of double-network structure provides a new way to solve this problem, which can maintain the strength of the material while giving it self-healing ability through the synergistic effect of rigid and flexible networks. However, there are still many challenges in this field, including the need for step-by-step polymerization to build double networks, complex process and poor interface compatibility, the difficulty of existing crosslinking agents to simultaneously control the exchange rate of dynamic bonds in different networks, the lack of environmental friendliness of raw materials, and the poor compatibility of conductive fillers with matrix materials. These problems seriously restrict the development and application of high-performance self-healing materials. Therefore, it is of great scientific significance and application value to develop a new type of self-healing material based on a biomass material-mediated double-network synergistic mechanism, which has excellent mechanical properties, efficient self-healing ability and environmental friendliness. SUMMARY

[0003] The purpose of the present application is to solve the problems existing in the prior art of self-healing gel, and provide a rosin-induced conductive self-healing double-network gel and a preparation method thereof. The gel uses epoxy fatty acid methyl ester and sodium thioctic acid as precursors, and uses the carboxylic acid groups of rosin acrylic acid to promote ring opening of the epoxy groups through protonation, and to polarize the disulfide bond of sodium thioctic acid through coordination with Na⁺, thereby reducing its dissociation energy barrier and achieving the synchronous construction of double networks. At the same time, the obtained double-network gel can realize covalent self-repairing through the reversible disulfide bond exchange of poly-sodium thioctic acid, and the multiple hydrogen bond networks formed by rosin acrylic acid and the double network provide physical crosslinking points, and the synergistic effect of the two can give the material excellent self-healing performance.

[0004] To achieve the above purpose, the technical scheme adopted by the present application is as follows: A rosin-induced conductive self-healing double-network gel, and a preparation method thereof, includes the following steps: (1) Take sodium thioctic acid and add it to anhydrous ethanol, heat in a water bath until completely dissolved, and prepare a sodium thioctic acid solution; (2) adding abietinyl acrylate, epoxy fatty acid methyl ester and silver nanowire solution to the sodium lipoate solution of step (1), and performing reaction under oil bath heating with stirring, wherein abietinyl acrylate, sodium lipoate and epoxy fatty acid methyl ester are simultaneously ring-opening polymerized under the induction of abietinyl acrylate, so as to form the conductive self-healing double network gel.

[0005] Further, the temperature of the water bath heating in step (1) is 40-60 DEG C.

[0006] Further, the concentration of the sodium lipoate solution in step (1) is 0.06-0.5 g / mL.

[0007] Further, the concentration of the silver nanowire solution in step (2) is 0.5-3 mg / mL.

[0008] Further, the mass ratio of the sodium lipoate solution, abietinyl acrylate, epoxy fatty acid methyl ester and silver nanowire solution used in step (2) is 1:1:1:1-5:1:1:1.

[0009] Further, the temperature of the reaction in step (2) is 80-120 DEG C, and the time is 10-25 min.

[0010] The present application uses epoxy fatty acid methyl ester and sodium lipoate as raw materials, and realizes the regulation of double network dynamic balance by a single crosslinking agent, i.e. abietinyl acrylate. On one hand, the carboxyl group of abietinyl acrylate provides an acidic environment to promote the ring-opening polymerization of epoxy fatty acid methyl ester to form the first network; on the other hand, the coordination of abietinyl acrylate and Na+ polarizes the disulfide bond of sodium lipoate, promotes the disulfide bond of sodium lipoate to break and recombine to form the second network; meanwhile, abietinyl acrylate can also crosslink the network structure through hydrogen bonds. In addition, the poly-sodium lipoate network can realize covalent self-repairing through reversible disulfide bond exchange, and the multiple hydrogen bond network constructed by abietinyl acrylate provides reversible physical crosslinking, and the synergistic effect of the two gives the material efficient and repeatable self-healing performance, so that the obtained gel material has great application potential in the field of flexible electronics.

[0011] The significant advantages of the present application are: (1) The gel matrix of the present application is composed of a double network formed by the simultaneous ring-opening polymerization of epoxy fatty acid methyl ester and sodium lipoate, and the double network is "rigid and flexible", and has good mechanical properties and dynamic adjustability.

[0012] (2) The present application adopts the single crosslinking agent of acrylic rosin to realize the regulation of the double network dynamic balance in the process of forming the gel matrix: first, an acidic environment is formed to promote the ring opening of epoxy fatty acid methyl ester and reduce the steric hindrance of the crosslinking between epoxy fatty acid methyl ester molecules, so as to promote the formation of the first network; second, the Na+ of sodium thioctic acid is coordinated to polarize the disulfide bond, reduce the bond energy, promote the disulfide bond of sodium thioctic acid to break to form poly sodium thioctic acid, and prevent the depolymerization of poly sodium thioctic acid, so as to ensure that a stable second network can be constructed. Meanwhile, the acrylic rosin also acts as a crosslinking agent to combine the first and second networks to form a double network structure.

[0013] (4) The conductive self-healing double network gel prepared by the present application has significantly improved mechanical properties, good self-healing ability, high conductivity, and can realize stable human body sensing, and is used for human body dynamic monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The physical map of the conductive self-healing double network gel prepared for Example 4.

[0015] Figure 2 The motion signal sensing map of the elbow of the human body when the conductive self-healing double network gel prepared for Example 4 is adhered to the elbow of the human body as a flexible sensor. DETAILED DESCRIPTION

[0016] A rosin-induced conductive self-healing double network gel, and a preparation method thereof, comprises the following steps: (1) Sodium thioctic acid is taken and added into anhydrous ethanol, and heated in a water bath at 40-60°C until completely dissolved, to prepare a 0.06-0.5g / mL sodium thioctic acid solution; (2) Acrylic rosin, epoxy fatty acid methyl ester and a 0.5-3mg / mL silver nanowire solution are added into the sodium thioctic acid solution of step (1) according to a mass ratio of 1:1:1:1-5:1:1:1, and stirred and reacted under the condition of 80-120°C oil bath heating for 10-25min, to form a conductive self-healing double network gel.

[0017] In order to make the content of the present application more convenient to understand, the technical solutions of the present application are further described below in combination with specific embodiments, but the present application is not limited thereto.

[0018] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0019] Example 1 (1) Take 3g of sodium lipoic acid and add it to 30mL of anhydrous ethanol, heat in a 40°C water bath for 50min until completely dissolved, to obtain a sodium lipoic acid solution with a concentration of 0.1g / mL; (2) Mix the sodium lipoic acid solution prepared in step (1) with 3g of acrylic acid rosin, 3g of epoxy fatty acid methyl ester and 3g of silver nanowire solution with a concentration of 0.5mg / mL, and stir under the condition of 120°C oil bath heating for 10min to form a conductive self-healing double network gel.

[0020] Example 2 (1) Take 5g of sodium lipoic acid and add it to 30mL of anhydrous ethanol, heat in a 40°C water bath for 50min until completely dissolved, to obtain a sodium lipoic acid solution with a concentration of 0.16g / mL; (2) Mix the sodium lipoic acid solution prepared in step (1) with 4g of acrylic acid rosin, 4g of epoxy fatty acid methyl ester and 4g of silver nanowire solution with a concentration of 1mg / mL, and stir under the condition of 120°C oil bath heating for 10min to form a conductive self-healing double network gel.

[0021] Example 3 (1) Take 15g of sodium lipoic acid and add it to 30mL of anhydrous ethanol, heat in a 40°C water bath for 50min until completely dissolved, to obtain a sodium lipoic acid solution with a concentration of 0.5g / mL; (2) Mix the sodium lipoic acid solution prepared in step (1) with 5g of acrylic acid rosin, 5g of epoxy fatty acid methyl ester and 5g of silver nanowire solution with a concentration of 3mg / mL, and stir under the condition of 120°C oil bath heating for 10min to form a conductive self-healing double network gel.

[0022] Example 4 (1) Take 15g of sodium lipoic acid and add it to 30mL of anhydrous ethanol, heat in a 40°C water bath for 50min until completely dissolved, to obtain a sodium lipoic acid solution with a concentration of 0.5g / mL; (2) Mix the sodium lipoic acid solution prepared in step (1) with 6g of acrylic acid rosin, 6g of epoxy fatty acid methyl ester and 6g of silver nanowire solution with a concentration of 3mg / mL, and stir under the condition of 120°C oil bath heating for 10min to form a conductive self-healing double network gel.

[0023] Comparative Example 1 (1) Take 15g of sodium lipoic acid and add it to 30mL of anhydrous ethanol, heat in a 60°C water bath for 20min until completely dissolved, to obtain a sodium lipoic acid solution with a concentration of 0.5g / mL; (2) Mix the sodium lipoic acid solution prepared in step (1) with 6g of epoxy fatty acid methyl ester and 6g of silver nanowire solution with a concentration of 3mg / mL, and stir under the condition of 120°C oil bath heating for 10min to form a gel material.

[0024] Comparative Example 2 (1) 15 g of sodium lipoate was added to 30 mL of anhydrous ethanol, and heated in a 60 °C water bath for 20 min until completely dissolved to form a sodium lipoate solution with a concentration of 0.5 g / mL; (2) The sodium lipoate solution prepared in step (1) was mixed uniformly with 6 g of polymerized rosin, 6 g of epoxy fatty acid methyl ester, and 6 g of silver nanowire solution with a concentration of 3 mg / mL, and stirred under the condition of 120 °C oil bath heating for 10 min to form a gel material.

[0025] The initial samples of the gels prepared in the examples and comparative examples were cut into dumbbell shapes, and then the samples before and after self-repairing were respectively placed on a universal mechanical testing machine, a tensile speed of 100 mm / min was set, and the breaking strength and tensile strength of different gels were tested, and the self-repairing efficiency η was calculated according to formula (1). In addition, the initial samples of the gels prepared in the examples and comparative examples were respectively placed on a TH2830 digital bridge to measure the resistance, and the conductivity of each sample was calculated according to formula (2). The test results are shown in Table 1.

[0026]

[0027] In formula (1), ε original is the tensile strength of the initial sample, and ε healed is the tensile strength of the repaired sample.

[0028] In formula (2), R, L and S respectively represent resistance, length and cross-sectional area.

[0029] Table 1 Performance test of gels

[0030] As can be seen from Table 1, the breaking strength, self-healing efficiency and conductivity of the double network gel obtained in the examples are significantly better than those of the comparative examples, which is mainly due to the fact that the acrylic rosin carboxyl in the examples forms multiple hydrogen bond crosslinking with the epoxy fatty acid methyl ester and sodium lipoate, thereby enhancing the breaking strength and self-healing efficiency of the gel. At the same time, since crosslinking inhibits the depolymerization of poly-sodium lipoate to close the ring, the continuous ion channel is maintained, thereby stabilizing the conductivity of the gel. Among them, the comprehensive performance of the double network gel obtained in Example 4 is the best. In Comparative Example 1, since acrylic rosin is not used, the double network cannot be fully crosslinked, resulting in poor gel breaking strength, low self-healing efficiency and poor conductivity. In Comparative Example 2, although the polymerized rosin contains one carboxyl group, the molecular structure is relatively rigid, and the steric hindrance is increased, resulting in a crosslinking effect with the epoxy fatty acid methyl ester and sodium lipoate that is weaker than that of the acrylic rosin, thereby reducing the breaking strength, self-healing efficiency and conductivity.

[0031] The above description is only the preferred embodiment of the present application, and any equivalent change and modification made according to the scope of the present application should be included in the scope of the present application.

Claims

1. A method for the preparation of rosin-induced electrically conductive self-healing double network gels, characterized by: The method comprises the following steps: (1) taking sodium lipoate and adding it into anhydrous ethanol, heating in a water bath to completely dissolve, and preparing a sodium lipoate solution; (2) adding acrylic rosin, epoxy fatty acid methyl ester and silver nanowire solution into the sodium lipoate solution of step (1), and carrying out reaction under stirring and oil bath heating, thereby forming the conductive self-healing double network gel.

2. A process for the preparation of a rosin-induced conductive self-healing double network gel according to claim 1, characterized in that: The temperature of the water bath heating in step (1) is 40-60℃.

3. A process for the preparation of a rosin-induced conductive self-healing double network gel according to claim 1, characterized in that: The concentration of the sodium lipoate solution in step (1) is 0.06-0.5g / mL.

4. A process for the preparation of a rosin-induced conductive self-healing double network gel according to claim 1, characterized in that: The mass ratio of the sodium lipoate solution, acrylic rosin, epoxy fatty acid methyl ester and silver nanowire solution used in step (2) is 1:1:1:1-5:1:1:

1.

5. A process for the preparation of a rosin-induced electrically conductive self-healing double network gel according to claim 1 or 4, characterized in that: The concentration of the silver nanowire solution is 0.5-3mg / mL.

6. A process for the preparation of a rosin-induced conductive self-healing double network gel according to claim 1, characterized in that: The temperature of the reaction in step (2) is 80-120℃, and the time is 10-25min.

7. A conductive self-healing double network gel prepared by the method of any one of claims 1-6.

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