CN114058033B - A method for preparing a temperature-sensitive hydrogel and a temperature-sensitive hydrogel product prepared therefrom - Google Patents

Abstract

The invention relates to the field of new materials, in particular to a preparation method of temperature-sensitive hydrogel and a temperature-sensitive hydrogel product prepared by the same. The preparation method comprises the following steps: and (3) putting the chemically crosslinked polyvinyl alcohol hydrogel into gallic acid solution for dipping treatment, and obtaining the temperature-sensitive polyvinyl alcohol hydrogel after the dipping is finished. According to the invention, the polyvinyl alcohol hydrogel is soaked in gallic acid solution for soaking treatment, so that the hydrogel with temperature sensitivity is obtained, the mechanical strength of the hydrogel can be changed along with the temperature under the stimulation of a certain temperature, and the mechanical strength of the temperature-sensitive hydrogel is obviously higher than that of the common polyvinyl alcohol hydrogel; in addition, when the external temperature reaches the hydrogel phase transition temperature, the transparency of the hydrogel changes suddenly, namely, the hydrogel changes from opaque milky white to transparent state, and the hydrogel can still recover to the initial state after the temperature is reduced, and the change process is reversible.

Description

A method for preparing a temperature-sensitive hydrogel and a temperature-sensitive hydrogel product prepared therefrom

Technical Field

The present invention belongs to the field of intelligent new materials, and in particular relates to a method for preparing a temperature-sensitive hydrogel and a temperature-sensitive hydrogel product prepared therefrom.

Background technique

Hydrogel is a kind of polymer material with a three-dimensional network structure containing a large amount of water. It has important application prospects in the fields of joint lubrication, biological tissue engineering, and drug controlled release carriers. Intelligent hydrogels with temperature-sensitive properties can change their physical state after the external environment temperature reaches the phase transition temperature of the hydrogel, and can return to the original state after the temperature is restored, and the process is completely reversible. Contactless remote control can be achieved by changing the ambient temperature, and it has potential applications in the fields of injectable and biomimetic smart materials. At present, the most common temperature-sensitive hydrogel is chemically cross-linked polyisopropylacrylamide and its copolymer hydrogel. The phase transition temperature of this type of hydrogel can be controlled by changing the molar ratio of polyisopropylacrylamide to the copolymer. When the temperature exceeds the phase transition temperature, dehydration occurs inside the hydrogel, and the hydrogel undergoes a sudden change in volume, swelling and transmittance. When the temperature returns to below the phase transition temperature, the hydrogel returns to its initial state.

Polyvinyl alcohol is a water-soluble polymer with excellent biocompatibility and non-toxicity. Its production and use meet the requirements of today's environmental protection and is a green chemical material. Therefore, polyvinyl alcohol hydrogel is widely used in agriculture, forestry, industry, medicine and health. Common preparation methods for polyvinyl alcohol hydrogels include chemical method, physical method and radiation method. The chemical method requires the introduction of a cross-linking agent, but the cross-linking agent is difficult to eliminate and has cytotoxicity; the freeze-thaw method is the most common physical method for preparing polyvinyl alcohol hydrogels. The hydrogel prepared by this method has the advantage of good elasticity, but it will turn into a solution at a higher temperature, and it has the disadvantages of being time-consuming, having a small swelling degree and being opaque; the radiation method is a green method for synthesizing polyvinyl alcohol hydrogels, with fast synthesis efficiency and good gel transparency, but it has the problems of poor toughness and easy breakage. So far, there are few reports on the development of temperature-sensitive polyvinyl alcohol-based hydrogels with good mechanical properties.

Summary of the invention

In view of the problems existing in the prior art, the object of the present invention is to provide a method for preparing a temperature-sensitive hydrogel and a temperature-sensitive hydrogel product prepared therefrom.

To achieve the purpose of the invention, the technical solution adopted by the present invention is as follows:

A first aspect of the present invention provides a method for preparing a temperature-sensitive hydrogel. The method comprises the following steps: placing a polyvinyl alcohol hydrogel in a gallic acid solution for immersion treatment, and obtaining the temperature-sensitive polyvinyl alcohol hydrogel after the immersion is completed.

According to the above preparation method, preferably, the gallic acid solution is prepared by dissolving gallic acid in water, and the mass fraction of gallic acid in the gallic acid solution is 0.1% to 1.2%.

According to the above preparation method, preferably, the immersion treatment time is 2h to 48h.

According to the above preparation method, preferably, the preparation method of the polyvinyl alcohol hydrogel is: irradiating the polyvinyl alcohol aqueous solution to obtain the polyvinyl alcohol hydrogel.

According to the above preparation method, preferably, the mass fraction of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10% to 15%.

According to the above preparation method, preferably, the irradiation dose of the irradiation treatment is 10 to 30 kGy.

According to the above preparation method, preferably, the irradiation treatment is performed by ⁶⁰ Co γ-ray or electron beam irradiation.

The second aspect of the present invention provides a temperature-sensitive hydrogel product prepared by the preparation method described in the first aspect.

Compared with the prior art, the present invention has the following positive and beneficial effects:

(1) The present invention soaks the polyvinyl alcohol hydrogel in a gallic acid solution for immersion treatment to obtain a temperature-sensitive hydrogel. The mechanical strength of the hydrogel changes with temperature under a certain temperature stimulation. Moreover, the mechanical strength of the temperature-sensitive hydrogel of the present invention is significantly higher than that of ordinary polyvinyl alcohol hydrogel. In addition, when the external temperature reaches the phase transition temperature of the hydrogel, the transparency of the hydrogel will suddenly change, that is, from an opaque milky white to a transparent state. When the temperature is lowered, the hydrogel can still return to its initial state, and the change process is reversible.

(2) The temperature-sensitive hydrogel of the present invention is prepared by directly treating a polyvinyl alcohol aqueous solution with ⁶⁰ Co γ-rays or high-energy electron beam irradiation to obtain a polyvinyl alcohol hydrogel, and then immersing the polyvinyl alcohol hydrogel in a gallic acid solution. The entire preparation process does not use any cross-linking agent or initiator, is environmentally friendly and pollution-free, and the prepared temperature-sensitive hydrogel does not contain harmful components and is non-cytotoxic.

(3) The preparation method of the temperature-sensitive hydrogel of the present invention is simple and easy, does not require expensive equipment, has a wide source of raw materials, and is low in cost, which is conducive to the industrial transformation of technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a photograph of the temperature-sensitive hydrogel transparency changing with temperature according to the present invention;

FIG2 is a graph showing the change in storage modulus (G') and loss modulus (G") of the temperature-sensitive hydrogel of the present invention during the heating process as a function of temperature;

FIG3 is a compressive strength curve of the temperature-sensitive hydrogel of the present invention at the same temperature and different strains.

Detailed ways

Embodiment 1:

A method for preparing a temperature-sensitive hydrogel, the specific steps are as follows:

(1) adding 20 g of polyvinyl alcohol (PVA) to 180 g of water, stirring and heating to 90° C. until a homogeneous and transparent polyvinyl alcohol solution with a mass fraction of 10% is obtained;

(2) transferring the polyvinyl alcohol solution into a mold and irradiating it with ⁶⁰ Co γ-rays at a dose of 30 kGy to obtain a polyvinyl alcohol hydrogel with a thickness of 2 mm;

(3) placing the polyvinyl alcohol hydrogel prepared in step (2) into a gallic acid aqueous solution, soaking for 24 hours, and taking it out after soaking to obtain a temperature-sensitive hydrogel; wherein the mass fraction of gallic acid in the gallic acid aqueous solution is 0.1%.

Embodiment 2:

The content of Example 2 is substantially the same as that of Example 1, except that the mass fraction of gallic acid in the gallic acid aqueous solution in step (3) is 0.2%.

Embodiment 3:

The content of Example 3 is substantially the same as that of Example 1, except that the mass fraction of gallic acid in the gallic acid aqueous solution in step (3) is 0.5%.

Embodiment 4:

The content of Example 4 is substantially the same as that of Example 1, except that the mass fraction of gallic acid in the gallic acid aqueous solution in step (3) is 0.8%.

Embodiment 5:

The content of Example 5 is substantially the same as that of Example 1, except that the mass fraction of gallic acid in the gallic acid aqueous solution in step (3) is 1.0%.

Embodiment 6:

The content of Example 6 is substantially the same as that of Example 1, except that the mass fraction of gallic acid in the gallic acid aqueous solution in step (3) is 1.2%.

Embodiment 7:

A method for preparing a temperature-sensitive hydrogel, the specific steps are as follows:

(1) adding 30 g of polyvinyl alcohol (PVA) to 170 g of water, stirring and heating to 90° C. until a homogeneous and transparent polyvinyl alcohol solution with a mass fraction of 15% is obtained;

(2) transferring the polyvinyl alcohol solution into a mold and irradiating it with ⁶⁰ Co γ-rays at a dose of 30 kGy to obtain a polyvinyl alcohol hydrogel with a thickness of 1 mm;

(3) placing the polyvinyl alcohol hydrogel prepared in step (2) into a gallic acid aqueous solution, soaking for 24 hours, and taking it out after soaking to obtain a temperature-sensitive hydrogel; wherein the mass fraction of gallic acid in the gallic acid aqueous solution is 0.3%.

Embodiment 8:

A method for preparing a temperature-sensitive hydrogel, the specific steps are as follows:

(1) adding 30 g of polyvinyl alcohol (PVA) to 170 g of water, stirring and heating to 90° C. until a homogeneous and transparent polyvinyl alcohol solution with a mass fraction of 15% is obtained;

(2) transferring the polyvinyl alcohol solution into a mold and irradiating it with ⁶⁰ Co γ-rays at a dose of 10 kGy to obtain a polyvinyl alcohol hydrogel with a thickness of 1 mm;

(3) placing the polyvinyl alcohol hydrogel prepared in step (2) into a gallic acid aqueous solution, soaking for 24 hours, and taking it out after soaking to obtain a temperature-sensitive hydrogel; wherein the mass fraction of gallic acid in the gallic acid aqueous solution is 0.3%.

Embodiment 9:

A method for preparing a temperature-sensitive hydrogel, the specific steps are as follows:

(1) adding 30 g of polyvinyl alcohol (PVA) to 170 g of water, stirring and heating to 90° C. until a homogeneous and transparent polyvinyl alcohol solution with a mass fraction of 15% is obtained;

(2) transferring the polyvinyl alcohol solution into a mold and irradiating it with ⁶⁰ Co γ-rays at a dose of 30 kGy to obtain a polyvinyl alcohol hydrogel with a thickness of 2 mm;

(3) placing the polyvinyl alcohol hydrogel prepared in step (2) into a gallic acid aqueous solution, soaking for 4 hours, and taking it out after soaking to obtain a temperature-sensitive hydrogel; wherein the mass fraction of gallic acid in the gallic acid aqueous solution is 0.3%.

Embodiment 10:

A method for preparing a temperature-sensitive hydrogel, the specific steps are as follows:

(1) adding 20 g of polyvinyl alcohol (PVA) to 180 g of water, stirring and heating to 90° C. until a homogeneous and transparent polyvinyl alcohol solution with a mass fraction of 10% is obtained;

(2) transferring the polyvinyl alcohol solution to a mold and irradiating it with an electron beam at a irradiation dose of 30 kGy to obtain a polyvinyl alcohol hydrogel having a thickness of 2 mm;

(3) placing the polyvinyl alcohol hydrogel prepared in step (2) into a gallic acid aqueous solution, soaking for 4 hours, and taking it out after soaking to obtain a temperature-sensitive hydrogel; wherein the mass fraction of gallic acid in the gallic acid aqueous solution is 0.5%.

Embodiment 11:

A method for preparing a temperature-sensitive hydrogel, the specific steps are as follows:

(1) adding 20 g of polyvinyl alcohol (PVA) to 180 g of water, stirring and heating to 90° C. until a homogeneous and transparent polyvinyl alcohol solution with a mass fraction of 10% is obtained;

(2) transferring the polyvinyl alcohol solution to a mold and irradiating it with an electron beam at a irradiation dose of 15 kGy to obtain a polyvinyl alcohol hydrogel having a thickness of 1 mm;

(3) placing the polyvinyl alcohol hydrogel prepared in step (2) into a gallic acid aqueous solution, soaking for 12 hours, and taking it out after soaking to obtain a temperature-sensitive hydrogel; wherein the mass fraction of gallic acid in the gallic acid aqueous solution is 1.0%.

Embodiment 12:

A method for preparing a temperature-sensitive hydrogel, the specific steps are as follows:

(1) adding 20 g of polyvinyl alcohol (PVA) to 180 g of water, stirring and heating to 90° C. until a homogeneous and transparent polyvinyl alcohol solution with a mass fraction of 10% is obtained;

(2) transferring the polyvinyl alcohol solution to a mold and irradiating it with an electron beam at a irradiation dose of 20 kGy to obtain a polyvinyl alcohol hydrogel having a thickness of 1 mm;

(3) placing the polyvinyl alcohol hydrogel prepared in step (2) into a gallic acid aqueous solution, soaking for 12 hours, and taking it out after soaking to obtain a temperature-sensitive hydrogel; wherein the mass fraction of gallic acid in the gallic acid aqueous solution is 0.8%.

Embodiment 13:

The content of Example 13 is basically the same as that of Example 1, except that the irradiation dose in step (2) is 20 kGy.

Comparative Example 1:

A method for preparing a temperature-sensitive hydrogel, the specific steps are as follows:

(1) adding 20 g of polyvinyl alcohol (PVA) to 180 g of water, stirring and heating to 90° C. until a homogeneous and transparent polyvinyl alcohol solution with a mass fraction of 10% is obtained;

(2) transferring the polyvinyl alcohol solution into a mold, irradiating it with an electron beam, and irradiating it with ⁶⁰ Co γ-rays at a irradiation dose of 30 kGy to obtain a polyvinyl alcohol hydrogel with a thickness of 2 mm;

(3) Soak the polyvinyl alcohol hydrogel prepared in step (2) in pure water for 24 hours.

The temperature-sensitive hydrogel prepared by the present invention is tested for its performance:

1. Phase transition temperature detection of hydrogel

The phase transition temperature of the temperature-sensitive hydrogels prepared in Examples 1 to 6 and the hydrogel prepared in Comparative Example 1 was tested, and the test results are shown in Table 1.

Table 1 Phase transition temperature test results of hydrogel

Example No. Gallic acid solution concentration Phase transition temperature Comparative Example 0 none Example 1 0.1% 47±2℃ Example 2 0.2% 53±1℃ Example 3 0.5% 57±2℃ Example 4 0.8% 62±1℃ Example 5 1.0% 65±1℃ Example 6 1.2% 66±1℃

As shown in Table 1, with the increase of gallic acid solution concentration, the phase transition temperature of the temperature-sensitive hydrogel gradually increases. When the concentration of gallic acid solution is 1.0%, the phase transition temperature of the temperature-sensitive hydrogel reaches 65±1°C. When the concentration of gallic acid solution is further increased, the phase transition temperature of the temperature-sensitive hydrogel does not change significantly. The results show that the concentration of gallic acid solution has an important influence on the phase transition temperature of temperature-sensitive hydrogel, and the phase transition temperature of the prepared temperature-sensitive hydrogel can be changed by adjusting the concentration of gallic acid solution.

2. Detection of hydrogel transparency changes with temperature

The temperature-sensitive hydrogel prepared in Example 4 was used as an example to detect the transparency change, and the hydrogel prepared in the comparative example was used as a comparison. The specific operation of the hydrogel transparency change detection experiment is: the prepared hydrogel is placed on a heating table or oven for heating after packaging, and the change in the transparency state of the hydrogel is observed and photographed, and the result is shown in FIG1 .

In FIG1 , A is a photograph recording the initial transparency of the hydrogel when not heated (the left side is the hydrogel prepared in the comparative example, and the right side is the hydrogel prepared in Example 4 of the present invention), B is a photograph recording the transparency of the hydrogel when heated to 61°C (the left side is the hydrogel prepared in the comparative example, and the right side is the hydrogel prepared in Example 4 of the present invention), and C is a photograph recording the transparency of the gel when heated to 65°C (the left side is the hydrogel prepared in the comparative example, and the right side is the hydrogel prepared in Example 4 of the present invention). As can be seen from FIG1 , as the temperature increases, the transparency of the hydrogel prepared in the comparative example hardly changes; as the temperature increases, the temperature-sensitive hydrogel prepared in Example 4 of the present invention gradually changes from an opaque milky white to a transparent state, and when the temperature of the hydrogel returns to the initial temperature, the temperature-sensitive hydrogel can still return to the initial opaque milky white state; and, by repeating the process of initial temperature-heating to the final temperature-cooling to the initial temperature for many times, the transparency of the temperature-sensitive hydrogel of the present invention can change with the temperature as described above.

3. Testing of mechanical properties of hydrogel

(1) Storage modulus and loss modulus testing

The storage modulus (G') and loss modulus (G") of the temperature-sensitive hydrogel prepared in Example 4 were tested, and the hydrogel prepared in the comparative example was used for comparison. The test results of the storage modulus and loss modulus are shown in Figure 2, and the compressive strength test results are shown in Figure 3.

As shown in FIG. 2 , the storage modulus G' of the hydrogel prepared in the comparative example remains almost stable (10 ³ Pa) and does not change significantly when the temperature range increases from room temperature to 75°C; while the storage modulus G' (10 ⁴ Pa) of the hydrogel prepared in Example 4 of the present invention is much higher than that of the comparative example; moreover, in the stage where the temperature is lower than the phase transition temperature, the storage modulus G' and loss modulus G" of the temperature-sensitive hydrogel of the present invention remain basically unchanged, which is consistent with the comparative example, while when the temperature approaches the phase transition temperature, G' and G" drop significantly, indicating that part of the polyvinyl alcohol and hydrogen bond network in the hydrogel system are destroyed, resulting in a sudden change in strength. At the same time, due to the presence of chemical cross-linking bonds, the temperature-sensitive hydrogel prepared in Example 4 of the present invention does not undergo a gel-sol state transition and can maintain its original shape unchanged. This shows that compared with the comparative example, the mechanical strength of the temperature-sensitive hydrogel prepared in the present invention is significantly improved.

(2) Testing of hydrogel compressive strength

The temperature-sensitive hydrogels prepared in Examples 2, 3, 4, 5 and 6 of the present invention were tested for compressive strength, and the hydrogels prepared in the comparative examples were used for comparison. The results of the compressive strength test are shown in FIG3 .

As can be seen from Figure 3, under the same strain (25.6%) conditions, the compressive strength of the hydrogel prepared in the comparative example is 0.055 MPa, and the compressive strengths of the temperature-sensitive hydrogels prepared in Examples 2, 3, 4, 5 and 6 of the present invention are 0.337 MPa, 1.338 MPa, 1.632 MPa, 1.922 MPa and 1.884 MPa, respectively. Among them, the compressive strength of the temperature-sensitive hydrogel prepared in Example 5 is increased by 3391% compared with the comparative example, which shows that the compressive strength of the temperature-sensitive hydrogel prepared in the present invention is significantly higher than that of the ordinary polyvinyl alcohol hydrogel.

Moreover, it can be seen from FIG. 3 that the compressive strength of the temperature-sensitive hydrogel of the present invention increases with the increase of the concentration of the gallic acid solution. Moreover, when the mass fraction of the gallic acid solution is greater than 1%, the compressive strength remains basically unchanged because the absorption of gallic acid by the polyvinyl alcohol hydrogel is close to saturation.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims (6)

1. An application of a hydrogel in the preparation of a temperature-sensitive product, characterized in that the preparation method of the hydrogel is: placing a polyvinyl alcohol hydrogel in a gallic acid solution for immersion treatment, and obtaining the hydrogel after the immersion is completed; the gallic acid solution is prepared by dissolving gallic acid in water, and the mass fraction of gallic acid in the gallic acid solution is 0.2%, 0.3%, 0.5%, 0.8% or 1.2%. 2. The use according to claim 1, characterized in that the immersion treatment time is 2h to 48h. 3. The use according to claim 1, characterized in that the preparation method of the polyvinyl alcohol hydrogel is: irradiating the polyvinyl alcohol aqueous solution to obtain the polyvinyl alcohol hydrogel. 4. The use according to claim 3, characterized in that the mass fraction of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10% to 15%. 5. The use according to claim 4, characterized in that the irradiation dose of the irradiation treatment is 10 to 30 kGy. 6. The use according to claim 5, characterized in that the irradiation treatment is performed by irradiation treatment using ⁶⁰ Co γ rays or electron beams.