阅读说明：本技术 一种聚乙烯醇-单宁酸-硼酸三元交联水凝胶、制备方法及应用 (Polyvinyl alcohol-tannic acid-boric acid ternary crosslinked hydrogel, and preparation method and application thereof ) 是由 袁丛辉 黄俊文 戴李宗 杨杰 柳君 蔡其鹏 杨羽歆 彭超华 刁雪峰 陈国荣 于 2019-08-30 设计创作，主要内容包括：本发明公开了一种聚乙烯醇-单宁酸-硼酸三元交联水凝胶、制备方法及应用。采用聚乙烯醇、单宁酸、硼酸、氢氧化钾、氯化钾为原料,借助硼酸与邻羟基之间的缩合反应,获得交联水凝胶。该合成方法工艺简单,条件温和,易于操作,产物无需后处理。通过改变聚乙烯醇、单宁酸、硼酸、氢氧化钾以及氯化钾的用量可以获得自修复能力、力学强度不同的形状记忆水凝胶。该自修复形状记忆水凝胶在软体机器人、人工韧带,柔性器件,汽车智能感应材料等方面有潜在应用。(The invention discloses a polyvinyl alcohol-tannic acid-boric acid ternary crosslinked hydrogel, a preparation method and application thereof. Polyvinyl alcohol, tannic acid, boric acid, potassium hydroxide and potassium chloride are used as raw materials, and the cross-linked hydrogel is obtained by virtue of condensation reaction between the boric acid and adjacent hydroxyl. The synthesis method has the advantages of simple process, mild conditions, easy operation and no need of post-treatment of the product. The shape memory hydrogel with different self-repairing capabilities and mechanical strengths can be obtained by changing the using amounts of polyvinyl alcohol, tannic acid, boric acid, potassium hydroxide and potassium chloride. The self-repairing shape memory hydrogel has potential application in the aspects of soft robots, artificial ligaments, flexible devices, automobile intelligent sensing materials and the like.)

1. A polyvinyl alcohol-tannic acid-boric acid ternary crosslinked hydrogel is characterized in that: the water-based paint comprises, by mass, 0.5-30% of polyvinyl alcohol, 0.1-15% of tannic acid, 0.0036-10.930% of boric acid, 0.003-12.346% of potassium hydroxide, 0.5-5% of potassium salt and the balance of water; the ternary crosslinked hydrogel has self-repairing and shape memory functions.

2. The ternary crosslinked hydrogel of polyvinyl alcohol-tannic acid-boric acid according to claim 1, characterized in that: the potassium salt comprises at least one of potassium chloride, potassium nitrate, potassium sulfate and potassium acetate.

3. The ternary crosslinked hydrogel of polyvinyl alcohol-tannic acid-boric acid according to claim 1, characterized in that: the potassium salt is potassium chloride, and the mass percentage of the potassium chloride in the system is 0.5-5%.

4. The ternary crosslinked hydrogel of polyvinyl alcohol-tannic acid-boric acid according to claim 1, characterized in that: the ternary crosslinked hydrogel has a dynamic covalent crosslinking structure and a physical crosslinking structure, and has reversible boric acid ester bonds and hydrogen bonds, wherein the hydrogen bonds comprise hydrogen bonds among polyvinyl alcohol molecules and hydrogen bonds between polyvinyl alcohol and tannic acid.

5. A preparation method of polyvinyl alcohol-tannic acid-boric acid ternary crosslinked hydrogel is characterized by comprising the following steps:

(1) dissolving tannic acid, boric acid and potassium hydroxide in deionized water or distilled water, and ultrasonically oscillating to obtain brown solution;

(2) heating the brown solution in the step (1) at 50-100 ℃ for 15-60 min;

(3) slowly adding polyvinyl alcohol and potassium salt into the product of the step (2);

(4) heating the product obtained in the step (3) in an oil bath at the temperature of 80-100 ℃ for 1-5 h, and continuously stirring in the heating process;

(5) and (4) taking out the product obtained in the step (4) and cooling to obtain the ternary crosslinked hydrogel.

6. The method for preparing the ternary crosslinked hydrogel of polyvinyl alcohol-tannin-boric acid according to claim 5, wherein the synthetic route is as follows:

7. the method for preparing the ternary crosslinked hydrogel of polyvinyl alcohol-tannin-boric acid according to claim 5, wherein the method comprises the following steps: in the step (1), the molar ratio of the tannic acid to the boric acid to the potassium hydroxide is 1: 1-20: 1-25 percent, wherein the dosage of the tannic acid accounts for 0.1-15 percent of the mass of the final system.

8. The method for preparing the ternary crosslinked hydrogel of polyvinyl alcohol-tannin-boric acid according to claim 5, wherein the method comprises the following steps: in the step (2), the dosage of the polyvinyl alcohol accounts for 0.5-30% of the mass of the final system.

9. The method for preparing the ternary crosslinked hydrogel of polyvinyl alcohol-tannin-boric acid according to claim 5, wherein the method comprises the following steps: in the step (2), the potassium salt comprises at least one of potassium chloride, potassium nitrate, potassium sulfate and potassium acetate, and the amount of the potassium salt is 0.5-5% of the mass of the final system.

10. The use of the polyvinyl alcohol-tannin-boric acid ternary crosslinked hydrogel as claimed in claim 1 to 4 in a polymer material, wherein: comprises a soft robot, an artificial ligament, a flexible electronic device and a vehicle flexible monitor.

Technical Field

The invention relates to the field of functional polymers, and relates to a polyvinyl alcohol-tannic acid-boric acid ternary crosslinked hydrogel, a preparation method and application thereof.

Background

The mechanical properties of conventional hydrogels tend to be much reduced after trauma. And due to the existence of cracks, the internal structure of the hydrogel can be gradually damaged, so that the function loss and the service life of the hydrogel are reduced. The hydrogel with the self-repairing function can repair internal cracks to restore the structure and the function spontaneously or under external stimulation when being damaged, thereby prolonging the service life of the hydrogel. The self-repairing hydrogel has wide application prospect in the fields of artificial ligaments, flexible electronic devices and the like.

The existing self-repairing conductive hydrogel has some problems which are difficult to ignore, such as insufficient mechanical strength, poor self-repairing performance, inconvenient preparation method and the like. Most of high molecular hydrogel shows poor resilience performance, which is embodied in that the deformation recovery time is long, and a large hysteresis loop exists in a stress-strain curve of cyclic compression, so that the self-repairing performance is poor and the self-repairing time is long. In addition, most self-repairing hydrogels have high toxicity, are not environment-friendly, and are greatly limited in the field of use.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a polyvinyl alcohol-tannic acid-boric acid ternary crosslinked hydrogel, a preparation method and application thereof. Polyvinyl alcohol and tannic acid are used as monomers, boric acid is used as a cross-linking agent, and potassium salt is used as a charge balancing agent to synthesize the hydrogel with the dynamic covalent cross-linking and physical cross-linking structures, and the hydrogel has quick self-repairing and good mechanical properties and also has a shape memory function.

One of the technical schemes adopted by the invention for solving the technical problems is as follows: provides a polyvinyl alcohol-tannic acid-boric acid ternary crosslinked hydrogel, which is characterized in that: the water-based paint consists of 0.5-30% of polyvinyl alcohol (PVA), 0.1-15% of tannic acid, 0.0036-10.930% of boric acid, 0.003-12.346% of potassium hydroxide, 0.5-5% of potassium salt and the balance of water by mass percentage in a system; the ternary crosslinking hydrogel has self-repairing and shape memory functions.

In a preferred embodiment of the present invention, the molar ratio of the tannic acid, the boric acid and the potassium hydroxide is 1: 1-20: 1 to 25.

In a preferred embodiment of the present invention, the potassium salt includes at least one of potassium chloride, potassium nitrate, potassium sulfate, and potassium acetate.

In a preferred embodiment of the present invention, the potassium salt is potassium chloride, and the mass percentage of the potassium chloride in the system is 0.5% -5%.

Boric acid or borates can form borate bonds with hydroxyl groups. The boric acid ester bond has reversibility, can be broken under the action of external stimulation, and can be recovered again after changing the condition. When boric acid or borate is used as a crosslinking agent to form a crosslinked polymer with polyvinyl alcohol and the adjacent hydroxyl of tannic acid, the polymer has good self-repairing performance due to the reversibility of boric acid ester bonds. In addition, the stability of the crosslinked polymer network formed is closely related to the cations present. If potassium hydroxide is used, the alkaline environment is better than that manufactured by using sodium hydroxide, mainly because the potassium ions have large volume and strong capability of stabilizing borate anions, the distance between macromolecular chains is reduced, and the crosslinking degree of the system is higher. The stability of the system can be further improved by additionally adding potassium salt into the system. The invention is based on the condensation reaction of boric acid with tannic acid and hydroxyl groups in polyvinyl alcohol molecules under alkaline conditions to form borate bonds. The boric acid ester bond has reversibility, and a large amount of hydrogen bond actions exist in a crosslinking network, so that the hydrogel has a self-repairing function. The addition of potassium salt improves the stability of the system. Meanwhile, the boric acid ester bond is slightly weaker than the hydrogen bond between PVA high molecular chains, so that the boric acid ester bond can be used as the 'weak crosslinking' of the shape memory system, and the hydrogen bond action between polyvinyl alcohol molecules and the hydrogen bond action between polyvinyl alcohol and tannic acid can be used as the 'strong crosslinking' of the shape memory system, so that the prepared hydrogel has the shape memory function.

The second technical scheme adopted by the invention for solving the technical problems is as follows: the preparation method of the polyvinyl alcohol-tannic acid-boric acid ternary crosslinked hydrogel comprises the following steps:

(1) dissolving tannic acid, boric acid and potassium hydroxide in deionized water or distilled water, and ultrasonically oscillating until the solution becomes brown solution;

(2) heating the brown solution in the step (1) at 50-100 ℃ for 15-60 min;

(3) slowly adding polyvinyl alcohol and potassium salt into the product of the step (2);

(4) heating the product obtained in the step (3) in an oil bath at the temperature of 80-100 ℃ for 1-5 h, and continuously stirring in the heating process;

(5) and (4) taking out the product obtained in the step (4) and cooling to obtain the ternary crosslinked hydrogel with different light brown to dark brown colors.

The synthetic route of the above reaction is as follows:

the third technical scheme adopted by the invention for solving the technical problems is as follows: provides an application of polyvinyl alcohol-tannic acid-boric acid ternary crosslinked hydrogel in high polymer materials, which comprises a soft robot, an artificial ligament and a flexible electronic device. Polyvinyl alcohol is a common medical polymer and has no toxicity; tannin is a natural extract, exists in drinks such as wine and the like, and has no irritation to human bodies; and the main component of the system is water, so that the system has small stimulation to human bodies, and has good biocompatibility.

Compared with the background technology, the technical scheme has the following advantages:

the invention adopts polyvinyl alcohol, tannic acid, boric acid, potassium hydroxide and potassium chloride as raw materials, and obtains the crosslinked hydrogel by virtue of condensation reaction between the boric acid and adjacent hydroxyl. The adjustment of different mechanical properties, self-repairing capability and shape memory capability can be realized by adjusting different proportions of the feeding materials in the preparation process. The whole synthesis process has the advantages of simple process, easy operation, hundreds of percent utilization rate of raw materials, environmental protection, safety and environmental friendliness.

Drawings

FIG. 1 is the synthesis process of ternary crosslinked hydrogel of polyvinyl alcohol-tannic acid-boric acid.

FIG. 2 self-healing efficiency for different tannin (Tannic acid) contents.

FIG. 3 is a stress-strain curve before and after self-healing for different PVA contents.

FIG. 4 is a comparative picture before and after self-healing of example 1.

FIG. 5 is a macroscopic view of the shape memory of example 1, wherein a is the original shape, b is the shape after being fixed for 30 minutes by a mold at room temperature, and c is the shape of the sample which returns to room temperature after being heated in a water bath at 80 ℃.

FIG. 6 is an SEM image of a sample of example 1 after lyophilization, wherein a is 2 μm, b and c are 1 μm, and d is 200 nm.

Detailed Description

The present invention will be further described with reference to the following examples, but the present invention is not limited to the following examples.