CN114478923B - A kind of high toughness, antifreeze conductive hydrogel and preparation method - Google Patents

Abstract

The invention relates to a preparation method of hydrogel, in particular to a high-toughness, antifreeze conductive hydrogel and a preparation method, and belongs to the field of polymer preparation. The hydrogel uses polyvinyl alcohol, acrylamide, N-vinyl pyrrolidone, sodium alginate, and glycerol monomer as raw materials, borax as the cross-linking agent of polyvinyl alcohol, and N, N-methylene bisacrylamide As a cross-linking agent for acrylamide, potassium persulfate is used as an initiator and is obtained through a free radical reaction. The final product is then post-processed through a drying-swelling method. The hydrogel prepared by the invention has high toughness and anti-freezing properties, and the cost of the raw materials selected by the invention is low, so it has broad market prospects. The steps are simple, easy to operate and highly practical.

Description

A kind of high toughness, antifreeze conductive hydrogel and preparation method

Technical field

The present invention relates to a preparation method of hydrogel, in particular to a preparation method of high toughness, antifreeze conductive hydrogel, and belongs to the field of polymer preparation.

Background technique

The information in this Background section is disclosed solely for the purpose of increasing understanding of the general background of the invention and is not necessarily considered to be an admission or in any way implying that the information constitutes prior art that is already known to a person of ordinary skill in the art.

Hydrogel is a type of polymer material with a three-dimensional cross-linked network structure and a large amount of water inside. In the gel network, water molecules are tightly combined with the hydrophilic groups of the polymer chain, transforming from a liquid state that is difficult to process at normal temperatures and pressures to a quasi-solid state with limited mobility. Therefore, hydrogel materials have both good solid mechanical properties and fluid thermodynamic properties of traditional bulk materials. As a soft material with water as its main component, hydrogel has strong plasticity, good elasticity and biocompatibility. It has great application prospects in the fields of soft robots, intelligent actuators, tissue engineering and flexible electronic devices.

Flexible electronic devices with significant electrical conductivity and similar sensing functions to human skin are of great significance in advancing human epidermal detection, implantable sensors, and real-time monitoring sensors. Generally speaking, these devices should have appropriate mechanical toughness, an elastic modulus that matches the elastic modulus of the human body, and high sensitivity, and can effectively convert physiological parameters into detectable electrical signals. Among different types of sensing materials, hydrogel, as an extremely hydrophilic three-dimensional network structure gel, deformable and tough conductive hydrogel is one of the most suitable sensor candidate materials. It has a tunable biocompatible elastic modulus with on-demand designed mechanical properties covering all moduli of human tissue to suit sensing applications.

However, traditional hydrogels usually use water as the electronic ionic medium. Although electrical and mechanical properties are obtained, most composite hydrogels cannot withstand extreme environments and do not possess environmental stability. It dries out in hot conditions and freezes at sub-zero temperatures. Even at room temperature, hydrogels inevitably lose water, resulting in mechanical hardening and weak deformability, hindering the environmental stability and operational durability of executable electrical devices. Ionically conductive hydrogels are particularly attractive due to their simple preparation process, low cost, and high electrical conductivity. However, although the abundant water in ionic hydrogels can provide ideal conductivity and efficient ion migration, it often results in mechanical strength. At the same time, the poor frost resistance of ion-conducting hydrogels limits their application in extreme cold environments. This is because the large amount of water in the hydrogel inevitably freezes at subzero temperatures, thus affecting the hydrogel's mechanical elasticity and ion transport capabilities.

Contents of the invention

The purpose of the present invention is to overcome the defects in existing materials and provide a high-toughness, antifreeze conductive hydrogel and a preparation method.

In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

A first aspect of the present invention provides a method for preparing a high-toughness, antifreeze conductive hydrogel, including:

Add polyvinyl alcohol, acrylamide, N-vinylpyrrolidone, acrylamide cross-linking agent, polyvinyl alcohol cross-linking agent, and initiator to the sodium alginate solution in sequence, mix them evenly, and heat to copolymerize to obtain a hydrogel;

The hydrogel is obtained by subjecting it to drying-swelling treatment.

Sodium alginate (SA) is a natural, cheap polysaccharide composed of two substitution units, α-Lguuronic acid and P-D-mannonic acid. It has attracted much attention due to its good biocompatibility and biodegradability. It has a wide range of applications in the fields of chemistry, biology, medicine and food. In addition to its good biocompatibility, sodium alginate also acts as a polyelectrolyte, giving the hydrogel good electrical conductivity. In addition, sodium alginate can also improve the mechanical strength in hydrogel systems. Traditional acrylamide hydrogels often have very low strength, so we introduced N-vinylpyrrolidone into the system to form a copolymer system with acrylamide to enhance the strength of the hydrogel. At the same time, we also induced the formation of PVA microcrystals in the composite hydrogel through the drying-swelling method, which can effectively improve the mechanical properties of the hydrogel.

Research has found that glycerol, as an organic solvent, can form strong hydrogen bonds with water molecules, thereby destroying the ice crystal lattice at sub-zero temperatures to achieve an antifreeze effect while preventing water from evaporating. In addition, one glycerol molecule can provide three hydroxyl groups; therefore, glycerol can also serve as a cross-linking agent for polyvinyl alcohol chains, thereby improving the strength and toughness of polyvinyl alcohol hydrogels. Polyvinyl alcohol can form borate ester bonds with borax solution to give the system a good self-healing effect. At the same time, the abundant hydroxyl groups on the polyvinyl alcohol chain can form dense hydrogen bonds with polyacrylamide and sodium alginate to give the hydrogel excellent toughness.

A second aspect of the present invention provides a high-toughness, antifreeze conductive hydrogel prepared by the above method.

A third aspect of the present invention provides applications of the hydrogel in manufacturing soft robots, intelligent actuators, tissue engineering and flexible electronic devices.

The beneficial effects of the present invention are:

(1) The preparation process of the present invention makes full use of the viscosity characteristics of sodium alginate. The conductive hydrogel mixed with sodium alginate has better mechanical strength and better conductivity.

(2) The introduction of glycerol can not only form strong hydrogen bonds with water molecules, destroy the ice lattice at sub-zero temperatures to achieve an anti-freezing effect, but can also serve as a cross-linking agent for polyvinyl alcohol chains to improve the mechanical strength of the hydrogel.

(3) Further treatment of the hydrogel using the drying-swelling method can induce crystallization of PVA to improve the mechanical properties and stability of the hydrogel.

(4) The preparation method of the present invention is simple, low-priced, highly practical, and easy to promote

Description of the drawings

The description and drawings that constitute a part of the present invention are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

Figure 1 is a stress strain diagram of the hydrogel prepared in each embodiment, in which 5%-9% represents the content of sodium alginate in the system.

Figure 2 is a stress-strain diagram of hydrogels with different glycerol contents, where 0%-30% represents the glycerol content in the system.

Figure 3 is a graph showing the toughness of hydrogels with different glycerol contents.

Figure 4 shows the DSC curves of hydrogels with different glycerol contents.

Figure 5 shows the electrical signal of conductive hydrogel as a strain sensor.

Detailed ways

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings commonly understood by one of ordinary skill in the art to which this invention belongs.

A high-toughness, antifreeze conductive hydrogel and a preparation method include adding different proportions of sodium alginate and glycerin to a polyvinyl alcohol, acrylamide and N-vinylpyrrolidone hydrogel system to prepare a composite hydrogel. This is followed by a drying-swelling process to obtain the final product. In the system, the added amount of sodium alginate is 5%-9%, and the added amount of glycerin is 0%-30%.

In some embodiments, sodium alginate is dissolved in water under heating and stirring, and then cooled to room temperature. Add polyvinyl alcohol, acrylamide, N-vinylpyrrolidone, potassium persulfate, N, N-methylenebisacrylamide, and borax to the above solution, and heat it in a 50-80°C water bath. The acrylamide and N-vinylpyrrolidone is copolymerized to obtain hydrogel. The resulting hydrogel is then completely dried and soaked in water to reswell to the final product.

In some embodiments, after selecting the optimal amount of sodium alginate in the above hydrogel, glycerol is added to the hydrogel system.

The present invention will be further described in detail below with reference to specific embodiments. It should be pointed out that the specific embodiments are for explanation rather than limitation of the present invention.

Example 1:

Dissolve 5% sodium alginate in a certain amount of water and heat it at 90°C until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylene bisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Example 2:

Sodium alginate with a mass content of 6% is dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylene bisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Example 3: Sodium alginate with a mass content of 7% was dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylene bisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Example 4: Sodium alginate with a mass content of 8% was dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylene bisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Example 5: Sodium alginate with a mass content of 9% was dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylene bisacrylamide, 0.04g potassium persulfate and 5g 0.6wt% borax solution Add the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Example 6: As shown in Figure 1, we can see from the stress strain diagram that when the sodium alginate content is 5%, the hydrogel has good mechanical properties. Therefore, this ratio was selected for the following experiments. Sodium alginate with a mass content of 7% is dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, add 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylenebisacrylamide, 0.04g potassium persulfate, and 5g 0.6wt% borax solution. and 5% glycerol were added to the above solution. After stirring thoroughly for one hour, place it in 60°C water and heat it for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Example 7: Sodium alginate with a mass content of 7% was dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, add 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylenebisacrylamide, 0.04g potassium persulfate, and 5g 0.6wt% borax solution. and 5% mass content of glycerol were added to the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Example 8: Sodium alginate with a mass content of 7% was dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, add 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylenebisacrylamide, 0.04g potassium persulfate, and 5g 0.6wt% borax solution. and 10% mass content of glycerol were added to the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Example 9: Sodium alginate with a mass content of 7% was dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, add 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylenebisacrylamide, 0.04g potassium persulfate, and 5g 0.6wt% borax solution. and 20% mass content of glycerol were added to the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Example 10: Sodium alginate with a mass content of 7% was dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylenebisacrylamide, 0.04g potassium persulfate, 5g 0.6wt% borax solution and 30% mass content of glycerol was added to the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Comparative example 1:

Mix 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylenebisacrylamide, 0.04g potassium persulfate, and 5g 0.6wt% borax solution, and stir thoroughly for one hour. Then it was heated in a 60°C water bath for 4-5 hours to obtain a hydrogel. The prepared hydrogel was completely dried in an oven at 50-60°C, and then the dried gel was soaked in water for 2 hours to reswell to obtain the final product.

Comparative example 2:

Sodium alginate with a mass content of 7% is dissolved in a certain amount of water and heated at 90°C until fully dissolved. After cooling to room temperature, add 16g polyvinyl alcohol, 4g acrylamide, 2g N-vinylpyrrolidone, 0.01g N, N-methylenebisacrylamide, 0.04g potassium persulfate, and 5g 0.6wt% borax solution. Add the above solution. Stir thoroughly for one hour and then heat in a 60°C water bath for 4-6 hours to obtain a hydrogel. The prepared hydrogel is completely dried in an oven at 50-60°C, and then the dried gel is soaked in water for 2-4 hours to re-swell to obtain the final product.

As shown in Figures 2 and 3, they are the stress-strain curves and the toughness diagrams of the corresponding proportions of the hydrogel obtained in the examples. It can be seen that as the glycerol content increases, the stress and strain first increase and then decrease. At the same time, it can be seen that the toughness of the hydrogel reaches its maximum when the glycerol content is 10%.

As shown in Figure 4, as the glycerin content increases, the freezing point of the hydrogel gradually decreases and all have good antifreeze effects. Different proportions of glycerin can be selected according to the needs of different applications.

As shown in Figure 5, hydrogel can deliver good electrical signals as a strain sensor.

Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still The technical solutions described in the foregoing embodiments may be modified, or part of them may be replaced by equivalents. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims (8)

1. A method for preparing a high-toughness, antifreeze conductive hydrogel, which is characterized by comprising: Add polyvinyl alcohol, acrylamide, N-vinylpyrrolidone, acrylamide cross-linking agent, polyvinyl alcohol cross-linking agent, and initiator to the sodium alginate solution in sequence, mix them evenly, and heat to copolymerize to obtain a hydrogel; The hydrogel is subjected to drying-swelling treatment to obtain; The content of sodium alginate is 5%-9%; The cross-linking agent of polyvinyl alcohol is borax and glycerin; The content of glycerin is 5~30%; The mass ratio of polyvinyl alcohol, acrylamide, and N-vinylpyrrolidone is 16:4:2. 2. The method for preparing the high-toughness, antifreeze conductive hydrogel according to claim 1, wherein the copolymerization reaction conditions are 50-80°C for 4-6 hours. 3. The method for preparing a high-toughness, antifreeze conductive hydrogel according to claim 1, wherein the cross-linking agent of acrylamide is N,N-methylenebisacrylamide. 4. The preparation method of high toughness, antifreeze conductive hydrogel according to claim 1, characterized in that the initiator is potassium persulfate. 5. The method for preparing high-toughness, antifreeze conductive hydrogel according to claim 1, characterized in that, in the drying-swelling treatment, the drying temperature is 50-60°C. 6. The method for preparing the high-toughness, antifreeze conductive hydrogel according to claim 1, wherein the swelling time is 2-4 hours. 7. High toughness, antifreeze conductive hydrogel prepared by the method of any one of claims 1-6. 8. Application of the hydrogel according to claim 7 in the manufacture of soft robots, intelligent actuators, tissue engineering and flexible electronic devices.