Conductive organic hydrogel based on PVA / PEDOT: PSS and preparation method and application thereof

Abstract

The invention discloses conductive organic hydrogel based on PVA / PEDOT: PSS as well as a preparation method and application of the conductive organic hydrogel, and belongs to the technical field of conductive organic hydrogel. The hydrogel is prepared by the following method: freeze-drying a PEDOT: PSS aqueous dispersion, and dispersing the PEDOT: PSS aqueous dispersion in a mixed solvent of DMSO and deionized water to obtain a mixed solution A; adding PVA into a mixed solvent of DMSO and deionized water, and heating in a water bath under a stirring condition to obtain a mixed solution B; uniformly mixing the mixed solution A and the mixed solution B, and further performing ultrasonic dispersion to obtain a mixed solution C; adding calcium chloride into the mixed solution C and stirring to obtain a mixed solution D; and pouring the mixed solution D into a mold, and freezing to obtain the anti-freezing PVA / PEDOT: PSS conductive organic hydrogel. The conductive organic hydrogel disclosed by the invention has excellent conductivity, stretchability and freezing resistance, and can be applied to a low-temperature environment. The preparation method is simple, raw materials are easy to obtain, and the prepared organic hydrogel has good sensing characteristics and has potential application prospects in the field of flexible wearable devices.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive organic hydrogels, and also to bionic materials and self-repairing materials, in particular to a conductive organic hydrogel based on PVA / PEDOT:PSS, and a preparation method and application thereof. Background Art

[0002] Due to their high water content, softness, and stretchability, hydrogels have a modulus and multifunctional responsiveness similar to biological tissues, and have broad application prospects in flexible electronics, biosensors, soft robotics, and other fields. The common method for conductive hydrogels is to introduce conductive nanofillers into the hydrogel matrix, but these conductive nanomaterials have the problem of poor dispersion, which leads to discontinuity of the conductive network and incompatibility at the interface. Poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) is composed of conductive PEDOT and PSS as a dopant / dispersant. Its core advantage lies in the unique combination of high conductivity, solution processability, flexibility, and multifunctionality. These characteristics make it very popular in flexible electronics, biosensors and other fields.

[0003] However, pure PEDOT:PSS conductive hydrogels have limitations such as weak mechanical properties, uncontrollable swelling behavior, and insufficient biocompatibility. Polyvinyl alcohol (PVA) is an ideal choice for hydrogel matrix materials due to its tunable cross-linked network, excellent mechanical properties, and biocompatibility. In recent years, many PVA / PEDOT:PSS dual-network conductive hydrogel materials have been developed. For example, Advanced Materials (Adv. Mater. 2022, 34, 2203650) reported a PEDOT:PSS-PVA hydrogel strain sensor that can continuously monitor physiological signals such as human swallowing and blinking, as well as detect subtle deformations of human skin to recognize gestures. In addition, a PEDOT:PSS / PVA coating reported in Advanced Materials (Adv. Mater. 2023, 35, 2304095) can be used to introduce a robust conductive polymer hydrogel bioelectronic interface onto various device substrates (including metals, glass, and polymers). This coating can be used to monitor various electrophysiological signals in vivo, meeting the high clinical requirements for long-term electrochemical stability of bioelectronics. However, these PEDOT:PSS / PVA conductive hydrogels still suffer from poor environmental stability and insufficient low-temperature resistance, which severely limits their application in winter and even in polar environments. Summary of the Invention

[0004] To solve the above problems, one object of the present invention is to provide a conductive organic hydrogel based on PVA / PEDOT:PSS and a preparation method thereof. The present invention obtains an organic hydrogel with antifreeze properties by dispersing PVA and PEDOT:PSS in a mixed solvent of dimethyl sulfoxide (DMSO) and water, and further forms an ion cross-linked network by introducing calcium ions to prepare a PVA / PEDOT:PSS conductive organic hydrogel with good mechanical properties, antifreeze properties, and sensing properties.

[0005] In order to achieve the above object, the specific technical solutions adopted by the present invention are as follows: A method for preparing a conductive organic hydrogel based on PVA / PEDOT:PSS comprises the following steps: S1. freeze-drying the PEDOT:PSS aqueous dispersion and dispersing it in a mixed solvent of DMSO and deionized water to obtain a mixed solution A; S2. PVA is added to a mixed solvent of DMSO and deionized water, and heated in a water bath under stirring to obtain a mixed solution B; S3, mixing the mixed solution A and the mixed solution B uniformly and then further ultrasonically dispersing them to obtain a mixed solution C; S4, adding calcium chloride to the mixed solution C and stirring to obtain a mixed solution D; S5. Pour the mixed solution D into a mold and freeze it to obtain a freeze-resistant PVA / PEDOT:PSS conductive organic hydrogel.

[0006] As a specific embodiment of the present invention, in the mixed solvent in steps S1 and S2, the mass ratio of DMSO to deionized water is 1:(0.25-1.5).

[0007] In step S1, the PEDOT:PSS aqueous dispersion is freeze-dried and then dispersed in a mixed solvent to control the ratio of DMSO and water in the mixed solvent. The specific stirring conditions can be selected as needed, for example, a planetary stirring speed of 1500-2500 rpm and a stirring time of 3-10 min are used.

[0008] As a specific embodiment of the present invention, the mass percentage of PEDOT:PSS in the mixed solution A is 3-7 wt %. Too high a concentration will make it difficult to disperse evenly, while too low a concentration will significantly reduce the conductive performance.

[0009] In step S2, the dissolution of PVA is accelerated by stirring, and the stirring conditions can be selected as needed, such as stirring at a temperature of 95° C. and a rotation speed of 100-800 rpm for 1-2 h.

[0010] In step S3, ultrasonic treatment is performed to fully mix the mixed solution A and the mixed solution B. Specific operating conditions can be selected as needed, such as ultrasonic dispersion at an ultrasonic power of 600-900 W for 30-60 min.

[0011] As a specific embodiment of the present invention, in the mixed solution C, the mass ratio of PEDOT:PSS to PVA is 1:(2.33~9).

[0012] As a specific embodiment of the present invention, the concentration of calcium ions in the mixed solution D is 0.5-3 wt %.

[0013] As a specific embodiment of the present invention, the freezing temperature in step S5 is -20~-25°C, and the freezing time is 1~12h.

[0014] A conductive organic hydrogel based on PVA / PEDOT:PSS is prepared by the above method.

[0015] Another object of the present invention is to provide an application method of the above-mentioned PVA / PEDOT:PSS-based conductive organic hydrogel, which is prepared into a flexible strain sensor and detects strain in a low-temperature environment.

[0016] The principles of the present invention are as follows: The organic hydrogel of the present invention is an organic hydrogel with a multi-network interpenetrating structure. The hydroxyl group (-OH) and sulfonic acid group (-SO3 - ) forms a hydrogen bond network with the hydroxyl groups of PVA, promoting the uniform dispersion of PEDOT nanoparticles in the hydrogel. 2+ ) can optimize the conductivity, mechanical properties and gelation behavior of hydrogel materials. Among them, DMSO mainly improves the conductivity and processability by regulating the molecular conformation of PEDOT and the structure of PVA gel, and inhibits the formation of ice crystals; while Ca 2+ On the one hand, it forms coordination bonds with the hydroxyl groups in PVA to enhance the mechanical strength and stability of the organic hydrogel. On the other hand, it can improve the dispersion stability of PEDOT:PSS in the composite system through electrostatic interaction with the sulfonic acid groups of PSS.

[0017] Beneficial effect: The conductive organic hydrogel of the present invention utilizes DMSO / Ca 2+ The synergistic effect significantly improves the electrical conductivity, tensile strength and antifreeze properties of the PVA / PEDOT:PSS hydrogel, so that the conductive organic hydrogel of the present invention has excellent electrical conductivity, tensile strength and antifreeze properties, and can be used in low-temperature environments.

[0018] The preparation method of the present invention is simple, the raw materials are easily available, and the prepared organic hydrogel has good sensing properties and has potential application prospects in the field of flexible wearable devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the preparation of the PVA / PEDOT:PSS conductive organic hydrogel of the present invention; Figure 2 This is a physical picture of the conductive organic hydrogel prepared in Example 1; Figure 3 The physical pictures of the organohydrogel prepared in Comparative Example 1 before and after gelation; Figure 4 This is a comparison of the antifreeze properties of the organohydrogels prepared in Example 2 and Comparative Example 2; Figure 5 : The stress-strain curves of the organohydrogels prepared in Comparative Example 1 and Examples 1 to 4; Figure 6 1 is a comparison chart of the electrical conductivity of the organohydrogels prepared in Comparative Example 1 and Examples 1 to 4; Figure 7 is the signal response curve of each strain sensor in Test Example 3. DETAILED DESCRIPTION

[0020] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with specific embodiments. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive and should not be used to limit the scope of protection of the present invention.

[0021] In the following examples and comparative examples, PVA powder was purchased from Sigma-Aldrich with a product number of 363065 and a molecular weight of 146,000 to 186,000. The dried PEDOT:PSS was prepared by the following method: PEDOT:PSS aqueous dispersion was purchased from Zhuhai Kaiwei New Materials Technology Co., Ltd. with a model of KV-ECM-PDD220 and a molecular weight of 70,000 to 90,000.

[0022] Example 1: Preparation of antifreeze PVA / PEDOT:PSS conductive organic hydrogel, the preparation process is as follows Figure 1 As shown, the following steps are included: (1) Pour the PEDOT:PSS aqueous dispersion into a watch glass and place it in a vacuum freeze dryer for freeze drying. Take 5 g of the dried PEDOT:PSS and add it to 95 g of a mixed solvent (DMSO and deionized water in a mass ratio of 6:4). Use a planetary mixer to mix and stir at 2000 rpm for 8 min to obtain dispersion A (5 wt% PEDOT:PSS). (2) 5 g of PVA powder was added to 95 g of mixed solvent and stirred at 200 rpm and 95 °C for 1.5 h to obtain dispersion B (5 wt% PVA). (3) Add 1 g of dispersion A and 9 g of dispersion B to a 20 mL beaker, then place the mixture in an ultrasonic crusher and ultrasonicate for 45 min at an ultrasonic power of 800 W to obtain a dispersion of PVA / PEDOT:PSS in DMSO / H2O, referred to as dispersion C. (4) Add 0.05 g of anhydrous calcium chloride to 10 g of dispersion C to obtain PVA / PEDOT:PSS / Ca 2+ The organic hydrogel precursor is called mixed solution D; (5) Pour the mixed solution D into a polytetrafluoroethylene mold and freeze it in a -20°C refrigerator for 4 h to obtain a freeze-resistant PVA / PEDOT:PSS conductive organic hydrogel.

[0023] The resulting antifreeze PVA / PEDOT:PSS conductive organic hydrogel is Figure 2 shown.

[0024] Comparative Example 1 The PVA / PEDOT:PSS organohydrogel was prepared. The preparation steps thereof were different from those in Example 1 in that: the stirring time in step (1) was 5 min; the stirring speed in step (2) was 300 rpm and the stirring time was 1 h; the continuous ultrasonication time in step (3) was 50 min; and the amount of anhydrous calcium chloride added in step (4) was 0 g, i.e., no anhydrous calcium chloride was added.

[0025] The prepared PVA / PEDOT:PSS conductive organic hydrogel before and after freezing Figure 3 As shown in Figure 3, after freezing at -20°C for 4 h, PVA / PEDOT:PSS transformed from a flowing mixed liquid to an organic hydrogel state.

[0026] Example 2: Preparation of antifreeze PVA / PEDOT:PSS conductive organic hydrogel. The preparation steps are different from those in Example 1 in that: the stirring time in step (1) is 6 minutes, the stirring time in step (2) is 1 hour, the continuous ultrasonic time in step (3) is 55 minutes, the amount of anhydrous calcium chloride added in step (4) is 0.1 g, and the freezing time in the refrigerator in step (5) is 8 hours.

[0027] Comparative Example 2 Prepared without DMSO and Ca 2+The preparation steps of the PVA / PEDOT:PSS conductive organic hydrogel are different from those of Example 2 in that the mixed solvent in steps (1) and (2) is replaced by deionized water, and the amount of anhydrous calcium chloride added in step (4) is 0.

[0028] Prepared without DMSO but with Ca 2+ The preparation steps of the PVA / PEDOT:PSS conductive organic hydrogel are different from those of Example 2 in that the mixed solvent in steps (1) and (2) is replaced by deionized water.

[0029] The morphology of the samples of Comparative Example 2 and Comparative Example 2 before and after freezing at -20°C is as follows: Figure 4 As shown, it was found that the DMSO and Ca 2+ The sample showed obvious freezing after freezing; only Ca 2+ The antifreeze effect of samples with DMSO and Ca 2+ The samples do not freeze and are frost-resistant.

[0030] Example 3: Preparation of antifreeze PVA / PEDOT:PSS conductive organic hydrogel. The preparation steps are different from those in Example 1 in that: the stirring time in step (1) is 10 minutes, the stirring time in step (2) is 1 hour, the continuous ultrasonic time in step (3) is 60 minutes, the amount of anhydrous calcium chloride added in step (4) is 0.2 g, and the freezing time in the refrigerator in step (5) is 8 hours.

[0031] Example 4: Preparation of antifreeze PVA / PEDOT:PSS conductive organic hydrogel. The preparation steps are different from those in Example 1 in that: the stirring time in step (1) is 5 min, the stirring speed in step (2) is 300 rpm, the stirring time is 1 h, the ultrasonic power in step (3) is 900 W, and the continuous ultrasonic time is 50 min, the amount of anhydrous calcium chloride added in step (4) is 0.3 g, and the freezing time in the refrigerator in step (5) is 10 h.

[0032] Test Example 1 The mechanical properties of the organohydrogels of Comparative Example 1 and Examples 1 to 4 were tested by tensile testing using a universal testing machine. Figure 5 shown.

[0033] Test Example 2 Conductivity tests were performed on the organic hydrogels of Comparative Example 1 and Examples 1-4. Mixture D from each Example and Comparative Example was poured into a cubic container with a length, width, and height of 1 cm. The mixture was frozen at -20°C to form a gel to obtain a cubic organic hydrogel. Copper foil was used to connect the two ends of the organic hydrogel, and an LCR digital bridge meter (TH2830) was connected to measure its resistance. The conductivity was calculated using the formula σ = L / RS, where σ is the conductivity, L is the length, R is the measured resistance, and S is the cross-sectional area. The test results are shown in Figure 2. Figure 6 shown.

[0034] Table 1 Mechanical and conductive properties of various conductive organic hydrogels

[0035] Test Example 3 Sensing tests were conducted on the conductive organic hydrogels from Examples 1-3. The PVA / PEDOT:PSS conductive organic hydrogels were sandwiched between two sheets of insulating elastomer (acrylic adhesive tape, model VHB4910, from 3M) to form a sandwich structure. These sandwiches were connected with copper wire to form a strain sensor. The strain sensors were attached to different parts of the human body and connected using an LCR digital bridge to monitor the relative resistance change signal of the bending area in real time.

[0036] The test results are as follows Figure 7 As shown, Figure a is a resistance change signal of the index finger bending when the strain sensor prepared by the hydrogel of Example 1 is attached to the index finger joint, Figure b is a resistance change signal of the finger bending when the strain sensor prepared by the hydrogel of Example 2 is attached to the wrist, and Figure c is a resistance change signal of the knee bending when the strain sensor prepared by the hydrogel of Example 3 is attached to the knee.

[0037] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a conductive organic hydrogel based on PVA / PEDOT:PSS, characterized in that: The steps include: S1. freeze-drying the PEDOT:PSS aqueous dispersion and dispersing it in a mixed solvent of DMSO and deionized water to obtain a mixed solution A; S2. PVA is added to a mixed solvent of DMSO and deionized water, and heated in a water bath under stirring to obtain a mixed solution B; S3, mixing the mixed solution A and the mixed solution B uniformly and then further ultrasonically dispersing them to obtain a mixed solution C; S4, adding calcium chloride to the mixed solution C and stirring to obtain a mixed solution D; S5. Pour the mixed solution D into a mold and freeze it to obtain a freeze-resistant PVA / PEDOT:PSS conductive organic hydrogel.

2. The method for preparing a conductive organic hydrogel based on PVA / PEDOT:PSS according to claim 1, characterized in that: The mass ratio of DMSO to deionized water in the mixed solvent is 1:(0.25~1.5).

3. The method for preparing a conductive organic hydrogel based on PVA / PEDOT:PSS according to claim 1, characterized in that: The mass percentage of PEDOT:PSS in the mixed solution A is 3-7 wt %.

4. The method for preparing a conductive organic hydrogel based on PVA / PEDOT:PSS according to claim 1, characterized in that: The mass ratio of PEDOT:PSS to PVA in the mixed solution C is 1:(2.33~9).

5. The method for preparing a conductive organic hydrogel based on PVA / PEDOT:PSS according to claim 1, characterized in that: The concentration of calcium ions in the mixed solution D is 0.5-3 wt %.

6. The method for preparing a conductive organic hydrogel based on PVA / PEDOT:PSS according to claim 1, characterized in that: In step S5, the freezing temperature is -20 to -25°C, and the freezing time is 1 to 12 hours.

7. A conductive organic hydrogel based on PVA / PEDOT:PSS, characterized in that: The conductive organic hydrogel is prepared by the preparation method of the PVA / PEDOT:PSS-based conductive organic hydrogel according to any one of claims 1 to 6.

8. An application of a conductive organic hydrogel based on PVA / PEDOT:PSS, characterized in that: The PVA / PEDOT:PSS-based conductive organic hydrogel according to claim 7 is prepared as a flexible strain sensor and the strain is detected in a low-temperature environment.

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