CN114395145A - Preparation method of tannic acid modified GO/polyvinyl alcohol nanocomposite hydrogel - Google Patents

Abstract

The invention discloses a preparation method of tannic acid-modified GO/polyvinyl alcohol nanocomposite hydrogel. The specific steps include: first, using tannic acid to modify graphene oxide to prepare tannic acid-functionalized reduced graphene oxide Powder, tannic acid-functionalized reduced graphene oxide powder is doped into polyvinyl alcohol by a blending method, and then a tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel is obtained by a freeze-thaw method. The hydrogel prepared by the method of the invention enhances the dispersibility of the conductive filler in the gel matrix, and simultaneously improves the electrical conductivity and mechanical properties of the hydrogel. In addition, the modified material used in the method is green and natural, and the preparation process Simple and easy to implement in the production environment, achieving a low-cost, high-efficiency production mode.

Description

Preparation method of tannic acid modified GO/polyvinyl alcohol nanocomposite hydrogel

technical field

The invention belongs to the technical field of polymer composite material preparation, and particularly relates to a preparation method of a tannic acid-modified GO/polyvinyl alcohol nanocomposite hydrogel.

Background technique

Hydrogel is a flexible material with a three-dimensional network structure formed by the cross-linking of polymer materials containing hydrophilic groups through intermolecular covalent bonds and hydrogen bonds. Nanocomposite hydrogels are usually prepared by adding nanoscale fillers to immiscible soft or rigid components by physical blending or in situ growth. Compared with pure polymer hydrogels, nanocomposite hydrogels have richer properties.

Graphene oxide (GO) is an effective filler, which is produced by the oxidation exfoliation of graphite, and has a large specific surface area, which can improve the electrical properties, mechanical properties and thermal properties of composite materials. However, in the currently prepared graphene oxide nanocomposite hydrogels, due to the poor electrical conductivity of graphene oxide and its lack of compatibility and interfacial bonding strength with the hydrogels, the electrical and mechanical properties of the composites are still poor. cannot meet demand. Therefore, it is an urgent problem to modify graphene oxide to improve its electrical conductivity, its compatibility with hydrogels, and its interfacial bonding strength.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of tannic acid-modified GO/polyvinyl alcohol nanocomposite hydrogel, which enhances the dispersibility of graphene oxide in the gel matrix, and simultaneously improves the electrical conductivity and mechanical properties of the hydrogel. performance.

The technical solution adopted in the present invention is, the preparation method of tannic acid modified GO/polyvinyl alcohol nanocomposite hydrogel is specifically implemented according to the following steps:

Step 1, preparing tannic acid functionalized reduced graphene oxide;

Step 2, adding polyvinyl alcohol into deionized water, stirring to obtain a suspension, pouring the suspension into a round-bottomed flask, and placing it in an oil bath for stirring reaction to obtain solution b;

Step 3, adding the tannic acid functionalized reduced graphene oxide prepared in step 1 to solution b, placing it in an oil bath and stirring to obtain mixed solution a, pouring mixed solution a into a polytetrafluoroethylene mold, freeze-thaw cycle to obtain tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogels.

The present invention is also characterized in that,

In step 1, the details are:

The graphene oxide is added to the tris(hydroxymethyl)aminomethane solution, stirred evenly, and subjected to ultrasonic treatment to obtain solution a; then tannic acid is added, and the pH of solution a is adjusted to 8-10 with HCl, and after stirring the reaction, Washing with deionized water, suction filtration, and freeze drying to obtain black powdery tannic acid functionalized reduced graphene oxide.

The concentration of the tris(hydroxymethyl)aminomethane solution is 0.1-0.15moL/L; the mass ratio of tannic acid to graphene oxide is 2-4:1; the concentration of HCl is 0.1-0.3moL/L.

The ultrasonic power is 120~150W, the ultrasonic time is 20~30min; the stirring reaction time is 8~10h; when lyophilized, first freeze in a cold trap at -55~-65℃ for 3~6h, and then dry for 24~48h.

In step 2, the mass fraction of the polyvinyl alcohol suspension is 6-9%; the oil-bath reaction temperature is 95°C, and the oil-bath reaction time is 3-5h.

In step 3, the concentration of tannic acid functionalized reduced graphene oxide added in solution b is 0.5-5 moL/L; the temperature of the oil bath is 90°C, and the time of the oil bath is 1-3 h.

In step 3, during freeze-thaw cycles, the freezing temperature is -20--30°C, the freezing time is 10-15h, the thawing time is 3-6h, and the number of freeze-thaw cycles is 2-5 times.

The beneficial effects of the present invention are:

The tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel enhances the dispersibility of the conductive filler in the gel matrix, and simultaneously improves the electrical conductivity and mechanical properties of the hydrogel. Composite hydrogels can be used for strain sensors. In addition, the modified material used in the method is green and natural, meets the requirements of green environmental protection, the preparation process is simple, the production environment is easy to realize, and a low-cost and high-efficiency production mode is achieved.

Description of drawings

Fig. 1 is the infrared spectrogram of tannic acid modified graphene oxide of the present invention and unmodified graphene oxide;

FIG. 2 is a tensile stress-strain curve diagram of unmodified hydrogel and tannic acid-modified GO/polyvinyl alcohol hydrogel of the present invention.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

The present invention is a preparation method of tannic acid-modified GO/polyvinyl alcohol nanocomposite hydrogel. The natural polyphenolic compound tannic acid is used to modify graphene oxide, and the tannic acid is modified by a blending method. The graphene oxide is doped into polyvinyl alcohol to prepare a nanocomposite hydrogel; specifically, it is implemented according to the following steps:

Step 1, preparing tannic acid functionalized reduced graphene oxide;

The graphene oxide is added to the tris (Tris) solution, stirred evenly, and subjected to ultrasonic treatment to obtain solution a; then tannic acid is added, and the pH of solution a is adjusted to 8-10 with HCl, and stirred at room temperature After the reaction, washing with deionized water, suction filtration, and lyophilization to obtain black powdery tannic acid-functionalized reduced graphene oxide;

Among them, the concentration of tris(hydroxymethyl)aminomethane solution is 0.1～0.15moL/L; the mass ratio of tannic acid and graphene oxide is 2～4:1; the ultrasonic power is 120～150W, and the ultrasonic time is 20～30min; The concentration of HCl is 0.1～0.3moL/L; the stirring reaction time is 8～10h; when lyophilized, first freeze in a cold trap at -55～-65℃ for 3～6h, and then dry for 24～48h;

Step 2, prepare polyvinyl alcohol solution;

Add polyvinyl alcohol into deionized water, stir magnetically to obtain a suspension, pour the suspension into a round-bottomed flask and place it in an oil bath for stirring reaction to obtain solution b;

The mass fraction of the polyvinyl alcohol suspension is 6-9%; the oil-bath reaction temperature is 95°C, and the oil-bath reaction time is 3-5h;

Step 3, adding the tannic acid functionalized reduced graphene oxide prepared in step 1 into solution b, placing it in an oil bath and stirring to obtain mixed solution a, and pouring mixed solution a into a polytetrafluoroethylene (PTFE) mold , freeze-thaw cycles to obtain tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogels with high electrical conductivity and excellent mechanical properties;

The concentration of tannic acid functionalized reduced graphene oxide added in solution b is 0.5-5moL/L; the temperature of the oil bath is 90°C, and the time of the oil bath is 1-3h;

When performing freeze-thaw cycles, the freezing temperature is -20--30°C, the freezing time is 10-15h, the thawing time is 3-6h, and the number of freeze-thaw cycles is 2-5 times.

The infrared spectra of the tannic acid modified graphene oxide and the unmodified graphene oxide of the present invention are shown in Figure 1. It can be seen that after GO is reduced by TA, the epoxy functional groups, epoxy and alkane in the graphene sample The oxygen stretching vibration peak was significantly weakened or even disappeared, indicating that GO was successfully modified and reduced.

Figure 2 is the tensile stress-strain curves of unmodified polyvinyl alcohol hydrogel and TA-GO/PVA conductive hydrogels with different conductive filler concentrations. It can be seen from Figure 2 that the hydrogels (PVAHydrogels) without tannic acid modified GO fillers have a tensile strength of only 76.27kPa, while the nanocomposite water with 2 mg/ml and 5 mg/ml tannic acid modified GO fillers The tensile strengths of the gels (TA-GO _2mg/ml PVA Hydrogels, TA-GO _5mg/ml PVA Hydrogels) are 228.84kPa and 574.79kPa respectively. Compared with the unmodified hydrogels, the tensile strength of the hydrogels prepared by the present invention is 228.84kPa and 574.79kPa respectively. The strength is increased by 3-7.5 times. Compared with the unmodified hydrogel, the tensile strength of the tannic acid modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel of the present invention is obviously improved. That is, the nanocomposite hydrogel of the present invention has more excellent mechanical properties than the unmodified one.

Example 1

A preparation method of a tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel of the present invention is specifically implemented according to the following steps:

Step 1: Weigh 1.2114g Tris (Tris), add it to 100mL deionized water to prepare Tris buffer; Weigh 1g graphene oxide and add it to 100mL Tris solution , after stirring evenly, 135W ultrasonic for 30min to obtain solution a; add 4g tannic acid to solution a, then adjust pH to about 8.5 with 0.1moL/L hydrochloric acid, stir and react at room temperature for 10h, and then wash with deionized water until neutral. After vacuum filtration, the obtained solid was put into a freeze dryer, frozen in a cold trap for 12 hours, and then freeze-dried for 48 hours. After grinding, black powdery tannic acid-functionalized reduced graphene oxide was obtained.

Step 2, add 5.4 g of polyvinyl alcohol to 60 mL of deionized water, stir magnetically for 1 h, and foam to obtain a suspension, pour the suspension into a round-bottomed flask, and mechanically stir the suspension at a speed of 1000 r/min. Placed in a 95°C oil bath for 3h to obtain solution b.

Step 3, take 60 mg of tannic acid-functionalized reduced graphene oxide prepared in step 1, add it to solution b, stir at a speed of 1500 r/min and place it in a 90°C oil bath for 2 hours to obtain mixed solution a, and inject mixed solution a into The polytetrafluoroethylene (PTFE) mold was placed in the refrigerator, frozen at -24 °C for 12 hours, and then thawed at room temperature for 3 hours. After 3 freeze-thaw cycles, the tannic acid modification with high electrical conductivity and excellent mechanical properties was obtained. Graphene oxide/polyvinyl alcohol nanocomposite hydrogels.

Example 2

A preparation method of a tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel of the present invention is specifically implemented according to the following steps:

Step 1: Weigh 1.2114g Tris (Tris), add it to 100mL deionized water to prepare Tris buffer; Weigh 1g graphene oxide and add it to 100mL Tris solution , after stirring evenly, 135W ultrasonic for 30min to obtain solution a; add 4g tannic acid to solution a, then adjust pH to about 8.5 with 0.1moL/L hydrochloric acid, stir and react at room temperature for 10h, and then wash with deionized water until neutral. After vacuum filtration, the obtained solid was put into a freeze dryer, frozen in a cold trap for 12 hours, and then freeze-dried for 48 hours. After grinding, black powdery tannic acid-functionalized reduced graphene oxide was obtained.

Step 2, add 5.4 g of polyvinyl alcohol to 60 mL of deionized water, stir magnetically for 1 h, and foam to obtain a suspension, pour the suspension into a round-bottomed flask, and mechanically stir the suspension at a speed of 1000 r/min. Placed in a 95°C oil bath for 3h to obtain solution b.

Step 3, take 120 mg of tannic acid-functionalized reduced graphene oxide prepared in step 1 and add it to solution b, stir at a speed of 1500 r/min and place it in an oil bath at 90 °C for 2 hours to obtain mixed solution a, and inject mixed solution a into The polytetrafluoroethylene (PTFE) mold was placed in the refrigerator, frozen at -24 °C for 12 hours, and then thawed at room temperature for 3 hours. After 3 freeze-thaw cycles, the tannic acid modification with high electrical conductivity and excellent mechanical properties was obtained. Graphene oxide/polyvinyl alcohol nanocomposite hydrogels.

Example 3

A preparation method of a tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel of the present invention is specifically implemented according to the following steps:

Step 1: Weigh 1.2114g Tris (Tris), add it to 100mL deionized water to prepare Tris buffer; Weigh 1g graphene oxide and add it to 100mL Tris solution , after stirring evenly, 135W ultrasonic for 30min to obtain solution a; add 4g tannic acid to solution a, then adjust pH to about 8.5 with 0.1moL/L hydrochloric acid, stir and react at room temperature for 10h, and then wash with deionized water until neutral. After vacuum filtration, the obtained solid was put into a freeze dryer, frozen in a cold trap for 12 hours, and then freeze-dried for 48 hours. After grinding, black powdery tannic acid-functionalized reduced graphene oxide was obtained.

Step 2, add 5.4 g of polyvinyl alcohol to 60 mL of deionized water, stir magnetically for 1 h, and foam to obtain a suspension, pour the suspension into a round-bottomed flask, and mechanically stir the suspension at a speed of 1000 r/min. Placed in a 95°C oil bath for 3h to obtain solution b.

Step 3, take 180 mg of tannic acid-functionalized reduced graphene oxide prepared in step 1 and add it to solution b, stir at a speed of 1500 r/min and place it in an oil bath at 90 °C for 2 h to obtain mixed solution a, and inject mixed solution a into The polytetrafluoroethylene (PTFE) mold was placed in the refrigerator, frozen at -24 °C for 12 hours, and then thawed at room temperature for 3 hours. After 3 freeze-thaw cycles, the tannic acid modification with high electrical conductivity and excellent mechanical properties was obtained. Graphene oxide/polyvinyl alcohol nanocomposite hydrogels.

Example 4

A preparation method of a tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel of the present invention is specifically implemented according to the following steps:

Step 1: Weigh 1.2114g Tris (Tris), add it to 100mL deionized water to prepare Tris buffer; Weigh 1g graphene oxide and add it to 100mL Tris solution , after stirring evenly, 135W ultrasonic for 30min to obtain solution a; add 4g tannic acid to solution a, then adjust pH to about 8.5 with 0.1moL/L hydrochloric acid, stir and react at room temperature for 10h, and then wash with deionized water until neutral. After vacuum filtration, the obtained solid was put into a freeze dryer, frozen in a cold trap for 12 hours, and then freeze-dried for 48 hours. After grinding, black powdery tannic acid-functionalized reduced graphene oxide was obtained.

Step 2, add 5.4 g of polyvinyl alcohol to 60 mL of deionized water, stir magnetically for 1 h, and foam to obtain a suspension, pour the suspension into a round-bottomed flask, and mechanically stir the suspension at a speed of 1000 r/min. Placed in a 95°C oil bath for 3h to obtain solution b.

Step 3, take 240 mg of tannic acid-functionalized reduced graphene oxide prepared in step 1, add it to solution b, stir at a speed of 1500 r/min and place it in an oil bath at 90 °C for 2 h to obtain mixed solution a, and inject mixed solution a into The polytetrafluoroethylene (PTFE) mold was placed in the refrigerator, frozen at -24 °C for 12 hours, and then thawed at room temperature for 3 hours. After 3 freeze-thaw cycles, the tannic acid modification with high electrical conductivity and excellent mechanical properties was obtained. Graphene oxide/polyvinyl alcohol nanocomposite hydrogels.

Example 5

A preparation method of a tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel of the present invention is specifically implemented according to the following steps:

Step 1: Weigh 1.2114g Tris (Tris), add it to 100mL deionized water to prepare Tris buffer; Weigh 1g graphene oxide and add it to 100mL Tris solution , after stirring evenly, 135W ultrasonic for 30min to obtain solution a; add 4g tannic acid to solution a, then adjust pH to about 8.5 with 0.1moL/L hydrochloric acid, stir and react at room temperature for 10h, and then wash with deionized water until neutral. After vacuum filtration, the obtained solid was put into a freeze dryer, frozen in a cold trap for 12 hours, and then freeze-dried for 48 hours. After grinding, black powdery tannic acid-functionalized reduced graphene oxide was obtained.

Step 2, add 5.4 g of polyvinyl alcohol to 60 mL of deionized water, stir magnetically for 1 h, and foam to obtain a suspension, pour the suspension into a round-bottomed flask, and mechanically stir the suspension at a speed of 1000 r/min. Placed in a 95°C oil bath for 3h to obtain solution b.

Step 3, take 300 mg of tannic acid-functionalized reduced graphene oxide prepared in step 1 and add it to solution b, stir at a speed of 1500 r/min and place it in an oil bath at 90 °C for 2 hours to obtain mixed solution a, and inject mixed solution a into The polytetrafluoroethylene (PTFE) mold was placed in the refrigerator, frozen at -24 °C for 12 hours, and then thawed at room temperature for 3 hours. After 3 freeze-thaw cycles, the tannic acid modification with high electrical conductivity and excellent mechanical properties was obtained. Graphene oxide/polyvinyl alcohol nanocomposite hydrogels.

The performance of the tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel prepared in the embodiment of the present invention is detected, and the results are shown in Table 1 and Table 2:

Table 1 Comparison of electrical performance test results

sample name Resistance (kΩ) Example 1 376.00 Example 2 110.00 Example 3 86.20 Example 4 68.55 Example 5 55.00 Unmodified polyvinyl alcohol hydrogel 1570

Table 2 Comparison of compressive strength test results

sample name Compressive strength (kPa) Example 1 897.762 Example 2 1213.940 Example 3 1352.830 Example 4 1523.451 Example 5 1730.766 Unmodified polyvinyl alcohol hydrogel 800.712

It can be seen from the resistance test of the hydrogel in Table 1 that with the doping of the conductive filler tannic acid modified graphene oxide, the resistance of the hydrogel gradually decreases, that is, with the conductive filler tannic acid modified graphene oxide With the doping of alkene, the prepared hydrogels showed increasingly excellent electrical conductivity. Therefore, it can be seen that the tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel prepared by the present invention exhibits excellent electrical properties compared with the unmodified one.

From the compressive performance test of the hydrogel in Table 2, it can be seen that with the increase of the doping concentration of the conductive filler tannic acid modified graphene oxide, the compressive strength of the hydrogel gradually increases. Compared with the unmodified one, the tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogel prepared by the present invention exhibits more excellent mechanical properties.

Non-covalent modification of graphene oxide with tannic acid (TA), which acts as a reducing agent and a stabilizer, promotes the uniform distribution of reduced graphene oxide (rGO) in the polyvinyl alcohol polymer network. The tannic acid-modified GO acts as both a conductive component and a nano-enhancer in the hydrogel, thereby endowing the hydrogel with excellent electrical conductivity and increasing its mechanical properties.

In the present invention, the performance of the hydrogel is changed by adding conductive filler tannic acid to modify the graphene oxide. elimination, leading to the formation of catechol and reduced graphene oxide in TA. Tannic acid has a benzene ring structure, it also interacts with the conjugated Π bond on the graphene sheet while reducing graphene oxide, and can be inserted between the graphene sheets, thereby effectively hindering the graphene sheet. of stacking. The TA-modified GO can be uniformly distributed in the polyvinyl alcohol polymer network, which increases the electrical conductivity of the hydrogel. ②The tannic acid (TA) modified GO and the hydroxyl groups on the polyvinyl alcohol (PVA) molecular chain formed various hydrogen bond combinations, which increased the interfacial bonding force between TA-GO and PVA, thereby improving the composite water Mechanical properties of gels.

Claims (7)

1. the preparation method of tannic acid modified GO/polyvinyl alcohol nanocomposite hydrogel, is characterized in that, is specifically implemented according to the following steps: Step 1, preparing tannic acid functionalized reduced graphene oxide; Step 2, adding polyvinyl alcohol into deionized water, stirring to obtain a suspension, pouring the suspension into a round-bottomed flask, and placing it in an oil bath for stirring reaction to obtain solution b; Step 3, adding the tannic acid functionalized reduced graphene oxide prepared in step 1 to solution b, placing it in an oil bath and stirring to obtain mixed solution a, pouring mixed solution a into a polytetrafluoroethylene mold, freeze-thaw cycle to obtain tannic acid-modified graphene oxide/polyvinyl alcohol nanocomposite hydrogels. 2. the preparation method of tannic acid modified GO/polyvinyl alcohol nanocomposite hydrogel according to claim 1, is characterized in that, in described step 1, is specifically: The graphene oxide is added to the tris(hydroxymethyl)aminomethane solution, stirred evenly, and subjected to ultrasonic treatment to obtain solution a; then tannic acid is added, and the pH of solution a is adjusted to 8-10 with HCl, and after stirring the reaction, Washing with deionized water, suction filtration, and freeze drying to obtain black powdery tannic acid functionalized reduced graphene oxide. 3. The preparation method of tannic acid-modified GO/polyvinyl alcohol nanocomposite hydrogel according to claim 2, wherein the concentration of the tris(hydroxymethyl)aminomethane solution is 0.1～0.15moL/L; The mass ratio of nitric acid to graphene oxide is 2 to 4:1; the concentration of HCl is 0.1 to 0.3 moL/L. 4. The preparation method of tannic acid-modified GO/polyvinyl alcohol nanocomposite hydrogel according to claim 2, wherein the ultrasonic power is 120-150W, the ultrasonic time is 20-30min; the stirring reaction time is 8～10h; when lyophilized, first freeze in a cold trap at -55～-65℃ for 3～6h, and then dry for 24～48h. 5. The preparation method of tannic acid-modified GO/polyvinyl alcohol nanocomposite hydrogel according to claim 1, wherein in the step 2, the mass fraction of the polyvinyl alcohol suspension is 6-9 %; the oil bath reaction temperature is 95℃, and the oil bath reaction time is 3～5h. 6. The preparation method of tannic acid-modified GO/polyvinyl alcohol nanocomposite hydrogel according to claim 1, wherein in the step 3, adding the tannic acid functionalized reduction oxidation in solution b The graphene concentration is 0.5-5 moL/L; the oil bath temperature is 90 °C, and the oil bath time is 1-3 h. 7. The preparation method of tannic acid-modified GO/polyvinyl alcohol nanocomposite hydrogel according to claim 1, wherein in the step 3, during freeze-thaw cycle, the freezing temperature is -20～ -30℃, the freezing time is 10-15h, the thawing time is 3-6h, and the number of freeze-thaw cycles is 2-5 times.

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