Preparation method of an organic-inorganic hybrid double conductive network polyvinyl alcohol composite hydrogel

Abstract

The present invention relates to the field of hydrogel synthesis, and discloses a method for preparing an organic-inorganic hybrid double conductive network polyvinyl alcohol composite hydrogel, wherein an organic conductive material, an inorganic conductive material, and polyvinyl alcohol are used as raw materials, and a polyvinyl alcohol composite hydrogel with a double conductive network is prepared under the action of a crosslinking agent through physical ball milling and in-situ polymerization. The method proposed by the present invention is simple to operate, and the intermediate product does not produce toxic substances. The prepared composite hydrogel has the characteristics of being non-toxic, environmentally friendly, having excellent stretchability, high conductivity, strong adhesion performance, and rapid self-healing, and shows great potential in the field of wearable flexible sensing.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogels, and particularly relates to a preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel. Background Art

[0002] Hydrogels are soft materials formed by chemical and physical cross-linking with water retention ability and a three-dimensional (3D) porous network structure. They have properties such as stretchability, self-healing ability, and biocompatibility, and are highly favored by researchers in fields such as biomedicine, health monitoring, and flexible wearable devices.

[0003] Polyvinyl alcohol (PVA) is a widely used water-soluble polymer material. PVA-based hydrogels not only have the properties of general hydrogels but also have advantages such as low toxicity and degradability, and have been widely used in the biomedical field. However, the mechanical properties and electrical conductivity of PVA hydrogels are poor, which limits their further applications. The common practice is to add carbon materials, conductive polymers, metal nanomaterials, etc. to the 3D porous network of hydrogels to synthesize functional hydrogels with excellent electrical conductivity. Such conductive hydrogels have extensive applications in fields such as health detection, human-computer interaction, and supercapacitors.

[0004] Common conductive materials are divided into organic materials and inorganic materials. Among them, polypyrrole (PPy) is a common organic conductive polymer, usually prepared by chemical polymerization or electrochemical oxidation of pyrrole monomers. It has good air stability and excellent electrical conductivity and can be used in biomaterials, electrocatalysis, conductive composites, etc. Inorganic conductive materials include graphene, carbon nanotubes, graphite, carbon black, etc.

[0005] However, directly adding conductive fillers to hydrogels often leads to uneven distribution and even destroys the hydrogel network, affecting the performance of the composite hydrogel. In addition, the complex synthesis process of the composite hydrogel also causes certain limitations. Therefore, a simple experimental scheme is needed to prepare multifunctional composite hydrogels that can simultaneously possess electrical conductivity, excellent mechanical properties, adhesiveness, and self-healing ability. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems of complex preparation process, strict synthesis conditions, poor mechanical properties, poor electrical conductivity, and low sensitivity of existing composite hydrogels, and provide a preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel with high stretchability and self-healing ability. And the hydrogel is assembled into a flexible wearable sensor, which can be used to monitor human movement.

[0007] In order to achieve the purpose of the present invention, the present invention now uses the following technical solutions:

[0008] A preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel, comprising the following specific steps:

[0009] (1) Under the conditions of heating and stirring, dissolve PVA in deionized water to prepare a PVA aqueous solution;

[0010] (2) Add an inorganic conductive material to the PVA aqueous solution and make it uniformly dispersed by means of physical ball milling to prepare a conductive PVA aqueous solution;

[0011] (3) Add a ferric chloride solution to the conductive PVA aqueous solution, stir evenly, then add pyrrole monomer, and under certain temperature and continuous stirring conditions, make the monomer pyrrole in-situ polymerize in PVA to form polypyrrole, so as to prepare a double-conductive network PVA aqueous solution;

[0012] (4) Under certain temperature and continuous stirring conditions, add a certain amount of cross-linking agent to the double-conductive network PVA aqueous solution and react for a period of time to prepare the organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel.

[0013] The PVA raw material used in step (1) includes granular, flaky and flocculent raw materials, and the molecular weight ranges from 10,000 to 300,000.

[0014] The mass fraction of the PVA aqueous solution prepared in step (1) is 1-15 wt%, and the heating temperature is 50-100 °C.

[0015] The inorganic conductive material described in step (2) includes carbon nanotubes, graphene and its derivatives, carbon black, expanded graphite, conductive two-dimensional transition metal carbides, nitrides or carbonitrides (MXene), wherein the inorganic conductive material can be used alone or in combination of one or more, and its addition amount is 1-100 wt% of the absolute dry weight of PVA.

[0016] The physical ball milling speed described in step (2) is 150-360 r / min, and the ball milling time is 20-480 min.

[0017] The ferric chloride solution described in step (3) is prepared by mixing ferric chloride powder, sodium p-toluenesulfonate powder and deionized water, and the ferric chloride concentration is 1-20 wt%.

[0018] The purity of the pyrrole monomer described in step (3) is 98%, the weight of the added pyrrole monomer is 10-100 wt% of the absolute dry weight of PVA, and the volume ratio of the added ferric chloride solution to the pyrrole monomer is 1:1.

[0019] The stirring temperature described in step (3) is 10-60 °C, and the in-situ polymerization time is 10-120 min.

[0020] The crosslinking agent described in step (4) is an aqueous borax solution, which is prepared from borax and deionized water at room temperature, and has a mass fraction of 3-6 wt%.

[0021] The stirring temperature in step (4) is 10-60 °C, the addition amount of the crosslinking agent is 1-20 wt% of the absolute dry weight of PVA, and the reaction time is 1-10 min.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] (1) The synthesis method uses a simple one-pot method to prepare an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel, which is easy to operate and has low requirements for synthesis conditions;

[0024] (2) The prepared polyvinyl alcohol composite hydrogel has good conductivity, stretchability, adhesiveness and self-healing ability at the same time;

[0025] (3) The present invention uses MXene as a hydrogel filling material. There are a large number of hydrophilic groups on the surface of MXene, such as -O, -OH and -F, which makes it easy for MXene nanosheets to crosslink with the hydrogel and can be used as a multifunctional crosslinking agent and stress transfer center to better improve the mechanical properties of the hydrogel. Brief Description of the Drawings

[0026] In order to more intuitively illustrate the technical solutions implemented in the present invention, the following briefly introduces the drawings required to describe the specific solutions. Figure 2-10 The composite hydrogel in is the sample prepared in Example 1:

[0027] Figure 1 is the preparation flow chart of the polyvinyl alcohol composite hydrogel;

[0028] Figure 2 is the macroscopic photograph of the composite hydrogel;

[0029] Figure 3 is the scanning electron micrograph of the composite hydrogel;

[0030] Figure 4 is the infrared spectrum of the composite hydrogel;

[0031] Figure 5 is the conductivity test chart of the composite hydrogel;

[0032] Figure 6 is the mechanical test chart of the composite hydrogel;

[0033] Figure 7 is the self-healing property of the composite hydrogel;

[0034] Figure 8 is the adhesiveness of the composite hydrogel;

[0035] Figure 9 is the cyclic tensile test diagram of the composite hydrogel sensor;

[0036] Figure 10 is the sensing application test diagram of the composite hydrogel sensor. Detailed implementation manner

[0037] In order to make the objectives, advantages and technical solutions of the present invention easier to understand, the following will be described in conjunction with specific examples, but the present invention is not limited thereto.

[0038] Example 1:

[0039] Prepare 25 mL of a 10 wt% PVA aqueous solution, heat and stir it in an oil bath at 96 °C for 30 min to obtain a transparent PVA aqueous solution. Take 0.2 g of MXene (Ti 3 C 2 ) powder and add it to the PVA aqueous solution, mix and load it into a ball milling tank, and ball mill it in a ball mill at a rotation speed of 360 r / min for 30 min to obtain a PVA and MXene mixed solution. Then, weigh 4.75 g of ferric chloride powder and 6.78 g of p-toluenesulfonate powder, add them to 50 mL of deionized water, and continuously stir until the powder is completely dissolved to obtain a ferric chloride solution. Take 1 mL of the ferric chloride solution and add it to the PVA and MXene mixed solution, and stir it at 20 °C for 30 min. Add 1 mL of pyrrole monomer to the mixed solution obtained in the above step, and stir it at 20 °C for 60 min to prepare a double conductive network PVA aqueous solution. Finally, weigh 0.4 g of borax and add it to deionized water, and continuously stir until the borax is completely dissolved to obtain a 4 wt% borax aqueous solution. Under the conditions of 30 °C and vigorous stirring, take 10 mL of the borax aqueous solution and add it to the above solution to prepare a double conductive network polyvinyl alcohol composite hydrogel hybridized by MXene and PPy.

[0040] The conductivity of the prepared hydrogel is 2.0 S m -1 , the tensile strain is 4350%, the stress is 26.78 kPa, the self-healing time of the hydrogel is 120 s, and the adhesion strength to wood is 18.75 kPa.

[0041] Comparative Example 1:

[0042] Prepare 25 mL of a 10 wt% PVA aqueous solution, heat and stir it in an oil bath at 96 °C for 30 min to obtain a transparent PVA aqueous solution. Take 0.2 g of MXene (Ti 3 C 2The powder was added to the PVA aqueous solution, and after magnetic stirring, a mixed solution of PVA and MXene was obtained. Then, 4.75 g of ferric chloride powder and 6.78 g of sodium p-toluenesulfonate powder were weighed and added to 50 mL of deionized water, and stirred continuously until the powder was completely dissolved to obtain a ferric chloride solution. 1 mL of the ferric chloride solution was added to the mixed solution of PVA and MXene, and stirred at 20 °C for 30 min. 1 mL of pyrrole monomer was added to the mixed solution obtained in the above step, and stirred at 20 °C for 60 min to prepare a double conductive network PVA aqueous solution. Finally, 0.4 g of borax was weighed and added to deionized water, and stirred continuously until the borax was completely dissolved to obtain a 4 wt% borax aqueous solution. Under the conditions of 30 °C and vigorous stirring, 10 mL of the borax aqueous solution was added to the above solution to prepare a double conductive network polyvinyl alcohol composite hydrogel hybridized with unball-milled MXene and PPy.

[0043] The tensile strain of the prepared hydrogel was 2312%, and the stress was 21.52 kPa. Compared with the PVA composite hydrogel prepared by the ball milling method in Example 1, its mechanical properties were weakened.

[0044] Example 2:

[0045] 25 mL of a 10 wt% PVA aqueous solution was prepared, heated and stirred in an oil bath at 96 °C for 30 min to obtain a transparent PVA aqueous solution. 0.2 g of graphene powder was added to the PVA aqueous solution, and the mixture was placed in a ball milling tank and ball milled in a ball mill at a rotation speed of 300 r / min for 90 min to obtain a mixed solution of PVA and graphene. Then, 4.75 g of ferric chloride powder and 6.78 g of sodium p-toluenesulfonate powder were weighed and added to 50 mL of deionized water, and stirred continuously until the powder was completely dissolved to obtain a ferric chloride solution. 1 mL of the ferric chloride solution was added to the mixed solution of PVA and graphene, and stirred at 30 °C for 30 min. 1 mL of pyrrole monomer was added to the mixed solution obtained in the above step, and stirred at 30 °C for 30 min to prepare a double conductive network PVA aqueous solution. Finally, 0.4 g of borax was weighed and added to deionized water, and stirred continuously until the borax was completely dissolved to obtain a 4 wt% borax aqueous solution. Under the conditions of 60 °C and vigorous stirring, 10 mL of the borax aqueous solution was added to the above solution to prepare a double conductive network polyvinyl alcohol composite hydrogel hybridized with graphene and PPy.

[0046] The conductivity of the prepared hydrogel was 1.4 S m -1 , the tensile strain was 3325%, the stress was 32.60 kPa, the self-healing time of the hydrogel was 150 s, and the adhesion strength to wood was 14.18 kPa.

[0047] Example 3:

[0048] Prepare 25 mL of an aqueous PVA solution with a concentration of 10 wt%, heat and stir it in an oil bath at 96 °C for 30 min to obtain a transparent aqueous PVA solution. Take 0.3 g of carbon nanotubes and add them to the aqueous PVA solution, mix and load them into a ball milling tank, and ball mill them in a ball mill at a rotation speed of 360 r / min for 20 min to obtain a mixed solution of PVA and carbon nanotubes. Then, weigh 4.75 g of ferric chloride powder and 6.78 g of sodium p-toluenesulfonate powder, add them to 50 mL of deionized water, and continuously stir until the powder is completely dissolved to obtain a ferric chloride solution. Take 1 mL of the ferric chloride solution and add it to the mixed solution of PVA and carbon nanotubes, and stir at 20 °C for 20 min. Add 1 mL of pyrrole monomer to the mixed solution obtained in the above step, and stir at 20 °C for 240 min to prepare a double conductive network aqueous PVA solution. Finally, weigh 0.4 g of borax and add it to deionized water, and continuously stir until the borax is completely dissolved to obtain a borax aqueous solution with a concentration of 4 wt%. Under the conditions of 60 °C and vigorous stirring, take 5 mL of the borax aqueous solution and add it to the above solution to prepare a double conductive network polyvinyl alcohol composite hydrogel hybridized with carbon nanotubes and PPy.

[0049] The conductivity of the prepared hydrogel is 2.5 S m -1 , the tensile strain is 3615%, the stress is 24.36 kPa, the self-healing time of the hydrogel is 130 s, and the adhesion strength to wood is 16.30 kPa.

[0050] Figure 2 It is proved that the prepared hydrogel has good plasticity and ductility.

[0051] Figure 3 It is the SEM image of the PVA composite hydrogel, from which the 3D network structure of the PVA hydrogel can be clearly seen.

[0052] Figure 4 It is proved that both MXene and PPy have been filled into the PVA hydrogel.

[0053] Figure 5 It is proved that the hydrogel has good electrical conductivity and can be used as a wire to transmit current.

[0054] Figure 6 It is proved that the hydrogel prepared by this method can have good mechanical properties. Compared with the pure PVA hydrogel, the maximum strain and maximum stress of the prepared PVA composite hydrogel are both significantly improved.

[0055] Figure 7It is shown that the prepared PVA composite hydrogel has good self-healing performance and can still be stretched to multiple lengths without breaking after being cut and self-healed.

[0056] Figure 8 It is shown that the prepared PVA composite hydrogel can exhibit good adhesion to different materials (skin, wood, plastic, and glass).

[0057] Figure 9 It is proved that the capacitive sensor based on this hydrogel has good sensing performance and can work normally under different strains and frequencies.

[0058] Figure 10 It is proved that the capacitive sensor based on this hydrogel can be used for human sensing and monitoring.

[0059] The present invention provides a simple method to prepare an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel by filling inorganic conductive materials and organic conductive materials into a PVA matrix, which has conductivity, excellent tensile properties, self-healing properties, and adhesion properties.

[0060] It should be noted that the above examples are only listed as the implementation schemes of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle scope of the present invention shall be included within the protection scope of the present invention.

Claims

1. Preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel, characterized in that: It includes the following steps: (1) Under the conditions of heating and stirring, dissolve PVA in deionized water to prepare a PVA aqueous solution; (2) Add an inorganic conductive material to the PVA aqueous solution and use physical ball milling to disperse it evenly to prepare a conductive PVA aqueous solution; (3) Add a ferric chloride solution to the conductive PVA aqueous solution, stir evenly, then add pyrrole monomer, and under certain temperature and continuous stirring conditions, in-situ polymerize the monomer pyrrole in PVA to form polypyrrole to prepare a double-conductive network PVA aqueous solution; (4) Under certain temperature and continuous stirring conditions, add a certain amount of cross-linking agent to the double-conductive network PVA aqueous solution and react for a period of time to prepare the organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel; The inorganic conductive material described in step (2) is MXene-Ti 3 C 2 .

2. The preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel according to claim 1, characterized in that: The PVA raw material used in step (1) includes granular, flaky and flocculent raw materials, and the molecular weight ranges from 10,000 to 300,000.

3. The preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel according to claim 1, characterized in that: The mass fraction of the PVA aqueous solution prepared in step (1) is 1-15 wt%, and the heating temperature is 50~100°C.

4. The preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel according to claim 1, characterized in that: The addition amount of the inorganic conductive material in step (2) is 1-100 wt% of the absolute dry weight of PVA.

5. The preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel according to claim 1, characterized in that: The physical ball milling speed in step (2) is 150-360 r / min, and the ball milling time is 20-480 min.

6. The preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel according to claim 1, characterized in that: The ferric chloride solution in step (3) is prepared by mixing ferric chloride powder, sodium p-toluenesulfonate powder and deionized water, and the ferric chloride concentration is 1-20 wt%.

7. The preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel according to claim 1, characterized in that: The purity of the pyrrole monomer in step (3) is 98%, the added weight of the pyrrole monomer is 10-100 wt% of the absolute dry weight of PVA, and the volume ratio of the ferric chloride solution to the pyrrole monomer is 1:

1.

8. The preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel according to claim 1, characterized in that: The stirring temperature in step (3) is 10~60°C, and the in-situ polymerization time is 10~120 min.

9. The preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel according to claim 1, characterized in that: The crosslinking agent described in step (4) is an aqueous borax solution, which is prepared from borax and deionized water at room temperature, and has a mass fraction of 3-6 wt%.

10. According to the preparation method of an organic-inorganic hybrid double-conductive network polyvinyl alcohol composite hydrogel described in claim 1, characterized in that: the stirring temperature in step (4) is 10-60 °C, the addition amount of the crosslinking agent is 1-20 wt% of the absolute dry weight of PVA, and the reaction time is 1-10 min.

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