CN113150316B

CN113150316B - High-strength stretchable PAA-Fe3+Preparation method of AG ion conductive hydrogel

Info

Publication number: CN113150316B
Application number: CN202110293419.0A
Authority: CN
Inventors: 李巧玲; 张雨; 韩昕; 范泽文
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2021-03-19
Filing date: 2021-03-19
Publication date: 2022-06-14
Anticipated expiration: 2041-03-19
Also published as: CN113150316A

Abstract

The invention discloses a high-strength stretchable PAA-Fe³⁺Preparation method of AG ion-conductive hydrogel, PAA-Fe³⁺the/AG is polyacrylic acid-ferric iron ion/agar ion conductive hydrogel. The invention can also effectively control PAA-Fe by changing the soaking time³⁺Mechanical strength and conductivity of AG ion-conducting hydrogels. The hydrogel has adjustable high mechanical property, stretchability and high conductivity, and has great application potential in wearable sensors, soft robots and other aspects.

Description

High-strength stretchable PAA-Fe3+Preparation method of AG ion conductive hydrogel

Technical Field

The invention relates to a stretchable PAA-Fe with high strength³⁺A preparation method of AG ion conductive hydrogel belongs to the field of functional polymers and conductive materials.

Background

The conductive hydrogel is a special intelligent hydrogel, overcomes the inherent high rigidity of a conductive polymer conjugate system, can cooperatively exert the electronic characteristics of a conductor and the flexibility of the hydrogel, can be used for manufacturing flexible electronic devices, and has wide application prospects in the aspects of soft robots, human motion monitoring sensors, human-computer interaction and the like.

A common method for preparing electrically conductive hydrogels today is to introduce electrically conductive fillers (e.g., carbon nanotubes, etc.) or electrically conductive polymers (e.g., polyaniline, etc.) into the polymer network. However, the conductive properties and mechanical properties of hydrogels are degraded due to the tendency of conductive fillers to accumulate in most hydrogels, as well as the self-polymerizing nature of the conductive monomers. Recently, ion-conductive hydrogels have received much attention from researchers due to their simple preparation process and higher conductivity.

It is worth noting that the ion conductive hydrogel still has the restriction factors that the high mechanical property and the high conductivity cannot be compatible at present. For example, in the related applications of bioelectronics, the conductive materials need not only to have good biocompatibility so that they can be used with the human body (such as skin, muscle, heart or brain) for a long period of time, but more importantly, they need to have both high electrical conductivity and good mechanical properties, which can ensure that the related system can still maintain high electrical conductivity for signal transmission under the condition of large mechanical load and large strain, and also avoid the problems of system breakdown due to accidental breakage. Therefore, the development of hydrogels having both high mechanical strength and electrical conductivity has become a hot research topic in recent years.

Disclosure of Invention

The invention aims to provide a stretchable PAA-Fe with high strength³⁺The preparation method of the AG ion conductive hydrogel solves the problem that the high mechanical strength and the high conductivity of the hydrogel in the prior art can not be simultaneously considered

The invention provides a stretchable PAA-Fe with high strength³⁺A preparation method of/AG (polyacrylic acid-ferric ion/agar) ion conductive hydrogel comprises the following steps:

step one, preparing agar water solution

Dissolving agar in 90 deg.C water completely, and cooling to 40-50 deg.C to obtain 1-3 wt% agar water solution;

step two, different Fe³⁺Preparation of content hydrogel

Potassium persulfate (0.5-1.5 wt% of acrylic acid) is used as an initiator, and Fe³⁺（FeCl₃.6H₂O mass fraction is 1-5% of acrylic acid) as a cross-linking agent, and adding the cross-linking agentAnd (3) carrying out free radical polymerization on the obtained agar aqueous solution to prepare hydrogel, wherein the mass ratio of acrylic acid to agar is (6-25) to (1-3).

Step three, soaking the prepared hydrogel in a saturated sodium chloride solution for 0-24 h to obtain PAA-Fe with different mechanical strengths and conductivities³⁺AG ion conductive hydrogel. Properties of the resulting hydrogel: the optimal hydrogel has the highest tensile strength of 1.9 MPa, the optimal elongation at break of 600 percent and the highest electrical conductivity of 5.5S m^-1。

And the forming condition of the hydrogel in the second step is polymerization for 1-2 h at 50-60 ℃.

The dosage of the deionized water in the whole reaction is controlled to be 4-6 times of the mass of the acrylic acid.

PAA-Fe prepared by the invention³⁺The AG ion conductive hydrogel performance detection method comprises the following steps:

1）PAA-Fe³⁺detection of mechanical properties of AG ion conductive hydrogel

The mechanical properties were tested by a universal tester (INSTRON LEGEND 2345). The prepared PAA-Fe³⁺The AG ion conductive hydrogel is cut into long strips, the length is 10 mm, the width is 8 mm, and the thickness is 2 mm. The tensile rate was 20 mm/min and the maximum tensile stress and elongation at break were recorded. Toughness is defined as the area under the stress-strain curve.

2）PAA-Fe³⁺Conductivity testing of AG ion-conductive hydrogel

The measurement of the conductivity was done at an electrochemical workstation and the conductivity of the hydrogel was calculated by measuring the Electrochemical Impedance Spectroscopy (EIS) of the sample. Prepared PAA-Fe³⁺The AG ionic conductive hydrogel is sandwiched between two platinum sheets, and the area (S) of the hydrogel is 0.5 cm²The thickness (l) was 0.3 cm. The ion conductivity (σ) is calculated as: σ = l/(R)_bXS), wherein R is_bIs the bulk resistance, determined by the intersection of the impedance curve with the real axis.

The invention has the beneficial effects that:

(1) the method of the invention prepares different Fe³⁺A content of hydrogel and byOptimizing the soaking strategy results in a stretchable PAA-Fe with high strength³⁺AG ion high-conductivity hydrogel. PAA-Fe³⁺The AG ion conductive hydrogel has a great amount of ionic bonds, hydrogen bonds and chain entanglement caused by salting-out effect, so that the hydrogel has good mechanical strength; na entering the system by soaking⁺、Cl^-And Fe contained in the system itself³⁺Providing high conductivity to the hydrogel. Meanwhile, PAA-Fe can be effectively controlled by controlling the soaking time³⁺The AG ion conductive hydrogel has mechanical strength and conductivity to meet different application requirements.

(2) The PAA-Fe prepared by the method³⁺The AG ion conductive hydrogel has high strength, stretchability and high conductivity, can play an important role in the fields of wearable electronic equipment, human-computer interaction and the like, and has wide application prospects.

Drawings

FIG. 1 shows PAA-Fe³⁺The AG ion conductive hydrogel is used for detecting the mechanical property. Wherein a is PAA-Fe with different soaking time in example 2³⁺The tensile stress-strain curve of the AG ion conductive hydrogel, and b is a toughness graph corresponding to a tensile test.

FIG. 2 shows PAA-Fe³⁺and/AG ion conductive hydrogel conductivity detection images. Wherein a is PAA-Fe of different soaking time in example 2³⁺The Nyquist curve of the/AG ion-conducting hydrogel, b is a specific conductivity map calculated from the Nyquist curve.

Detailed Description

The present invention is further illustrated by, but is not limited to, the following examples.

Example 1:

high-strength stretchable PAA-Fe³⁺The preparation method of the AG ion high-conductivity hydrogel comprises the following steps:

step one) 0.3 g of agar was completely dissolved in water at 90 ℃ and then cooled to 50 ℃.

Step two) different Fe³⁺Preparation of content hydrogel

By persulfuric acidPotassium (0.025 g) as initiator, Fe³⁺（FeCl₃.6H₂The mass fraction of O is 1 percent of that of acrylic acid) is taken as a cross-linking agent, the agar aqueous solution prepared in the step one) is added, and 5 g of acrylic acid is polymerized by free radicals to prepare the hydrogel.

Step three), soaking the prepared hydrogel in a saturated sodium chloride solution for 10 hours to obtain PAA-Fe with different mechanical strengths and conductivities³⁺AG ion conductive hydrogel.

And the forming condition of the hydrogel in the second step is polymerization for 2 hours at 60 ℃.

The amount of deionized water used for the whole reaction was controlled to 20 mL.

Example 2:

step one) 0.6 g of agar was completely dissolved in water at 90 ℃ and then cooled to 50 ℃.

Step two) different Fe³⁺Preparation of content hydrogel

Potassium persulfate (0.075 g) as initiator, Fe³⁺（FeCl₃.6H₂The mass fraction of O is 3 percent of that of acrylic acid) is taken as a cross-linking agent, the agar aqueous solution prepared in the step one) is added, and 7.5 g of acrylic acid is polymerized by free radicals to prepare the hydrogel.

And the forming condition of the hydrogel in the second step is polymerization for 1.5 hours at 60 ℃.

The amount of deionized water used for the whole reaction was controlled to 30 mL.

Example 3:

step one) 0.9 g of agar was completely dissolved in water at 90 ℃ and then cooled to 50 ℃.

Step two) different Fe³⁺Preparation of content hydrogel

0.15 g of potassium persulfate as initiator and Fe³⁺（FeCl₃.6H₂The mass fraction of O is 5 percent of that of acrylic acid) is taken as a cross-linking agent, the agar aqueous solution prepared in the step one) is added, and 10 g of acrylic acid is polymerized by free radicals to prepare the hydrogel.

And the forming condition of the hydrogel in the second step is polymerization for 1 h at 60 ℃.

The amount of deionized water used in the whole reaction was controlled at 40 mL.

PAA-Fe³⁺Detection of AG ion-conductive hydrogel:

1）PAA-Fe³⁺the AG ion conductive hydrogel has the following mechanical property detection:

the mechanical properties were tested by a universal tester (INSTRON LEGEND 2345). Prepared PAA-Fe³⁺The AG ion conductive hydrogel is cut into long strips, the length is 10 mm, the width is 8 mm, and the thickness is 2 mm. The tensile rate was 20 mm/min and the maximum tensile stress and elongation at break were recorded. Toughness is defined as the area under the stress-strain curve. The detection results are shown in FIG. 1, in which: FIG. a is PAA-Fe for different soaking times in example 2³⁺The tensile stress-strain curve of the/AG ion conductive hydrogel is shown in the figure b, and the figure b is a toughness figure corresponding to a tensile test. As can be seen from the figure, the tensile stress of the hydrogel gradually increased with the increase of the soaking time until reaching the maximum value when the soaking time was 10 hours, the tensile strength was 2.0 MPa, which was 7 times more (0.28 MPa) than that of the hydrogel without soaking, and the toughness also reached the maximum value, which was 7.1 MJ/m³Thus showing that the hydrogel has excellent mechanical properties.

2）PAA-Fe³⁺Conductivity testing of AG ion-conductive hydrogel

The measurement of the conductivity is carried out at an electrochemical workstation by measuring the electrochemical resistance of the sampleThe conductivity of the hydrogel was calculated by anti-spectroscopy (EIS). PAA-Fe of example 2 with different soaking time³⁺The AG ionic conductive hydrogel is sandwiched between two platinum sheets, and the area (S) of the hydrogel is 0.5 cm²The thickness (l) was 0.3 cm. The ion conductivity (σ) is calculated as: σ = l/(R)_bXS), wherein R is_bIs the bulk resistance, determined by the intersection of the impedance curve with the real axis. The results are shown in FIG. 2, where a is PAA-Fe of example 2 with different soaking time³⁺The Nyquist curve of the/AG ion-conducting hydrogel, b is a specific conductivity map calculated from the Nyquist curve. As can be seen from the figure, the conductivity of the hydrogel gradually increased with the increase of the soaking time until reaching a maximum value of 5.5S/m at 10 h, which is higher than that of the hydrogel without soaking (2.3S/m), indicating that soaking can improve the mechanical and electrical conductivity properties of the hydrogel at the same time.

Claims

1. High-strength stretchable PAA-Fe³⁺The preparation method of the AG ion conductive hydrogel is characterized by comprising the following steps:

the method comprises the following steps: dissolving agar in water at 90 deg.C, and cooling to 40-50 deg.C; preparing agar water solution with 1-3 wt%;

step two: different Fe³⁺Preparation of content hydrogel

Potassium persulfate as initiator, Fe³⁺In the presence of the agar obtained in the step one, the free radical polymerization of acrylic acid is used as a cross-linking agent to prepare hydrogel; the mass ratio of the acrylic acid to the agar is (6-25) to (1-3), and the using amount of the potassium persulfate is 0.5-1.5wt% of the acrylic acid;

said Fe³⁺Is derived from FeCl₃▪6H₂O，FeCl₃▪6H₂The using amount of O is 1-5% of the mass of acrylic acid;

step three: soaking the obtained hydrogel in saturated sodium chloride solution for 2-24 hr to obtain PAA-Fe with different mechanical strength and conductivity³⁺AG ion conductive hydrogel.

2. According to the rightThe high strength, stretchable PAA-Fe of claim 1³⁺The preparation method of the AG ion conductive hydrogel is characterized by comprising the following steps: in the second step, the hydrogel is polymerized for 1-2 h under the forming condition of 50-60 ℃.

3. Stretchable PAA-Fe with high strength according to claim 1³⁺The preparation method of the AG ion conductive hydrogel is characterized by comprising the following steps: in the first step and the second step, the water consumption of the whole reaction is controlled to be 4-6 times of the mass of the acrylic acid.

4. A high strength, stretchable PAA-Fe prepared by the method of any one of claims 1 to 3³⁺The AG ion conductive hydrogel is characterized in that: the maximum tensile strength of the hydrogel can reach 1.9 MPa, the elongation at break can reach 600%, and the conductivity can reach 5.5S m^-1。