Preparation method and application of antifreeze pectin-based conductive hydrogel based on synergistic effect of conductive polymer and multivalent salt ions

Abstract

The present invention discloses a preparation method and application of an antifreeze pectin-based conductive hydrogel based on the synergistic effect of a conductive polymer and multivalent salt ions. Pectin, carboxymethyl chitosan, methylenebisacrylamide, and ammonium persulfate are successively dissolved in an acrylamide solution to obtain an acrylamide / pectin-carboxymethyl chitosan solution; CaCl2 is dissolved in the above solution; it is polymerized into a pectin / carboxymethyl chitosan-CaCl2 / polyacrylamide hydrogel in a blast drying oven as a basic skeleton, and then placed in a CaCl2 solution containing pyrrole and dopamine hydrochloride for in-situ synthesis of polypyrrole to obtain an antifreeze pectin-based conductive hydrogel. The present invention effectively solves the problems of poor mechanical properties, poor conductivity, and lack of antifreeze properties of existing conductive hydrogel electrodes.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation and application of conductive hydrogels, and specifically relates to a preparation method and application of antifreeze pectin-based conductive hydrogel based on the synergistic effect of conductive polymers and multivalent salt ions. Background Art

[0002] Wearable electronic devices have been widely used in the fields of medical monitoring, electronic skin, flexible touch displays and human-computer interaction. By converting mechanical deformation into electrical signals, this signal conversion method connects human biology with traditional electronic devices, greatly changing people's lives. In recent years, hydrogels have been regarded as new materials for wearable sensors due to their ideal biocompatibility and softness. So far, hydrogel-based sensors mainly include two types: the first is ion-conductive hydrogels immersed in polyelectrolytes or salt ions containing a large number of free ions, such as by simply immersing double network hydrogels in sodium chloride solution, a multifunctional ion-conductive sensor has been successfully prepared. However, the conductivity, sensitivity and environmental stability of these hydrogels are limited, which restricts their practical applications. The other is electronic conductive hydrogels introduced by conductive fillers (such as polyaniline (PANI), graphene / graphene oxide, carbon nanotubes or MXene). For example, by in situ polymerization of polyaniline on chitosan, an electronic conductive hydrogel was designed, which is sensitive to strain changes and can be used as a strain hydrogel-based sensor. The TENG based on triboelectric charging and electrostatic induction proposed by Academician Wang Zhonglin in 2012 provides a feasible and promising solution to the above problems for sensors used to monitor human body movements. However, the poor solubility and dispersibility of conductive fillers may weaken the mechanical properties and compatibility of hydrogels. Generally, ideal hydrogel sensors need to integrate various functions, such as conductivity, good mechanical properties, stretchability, and biocompatibility. However, meeting all requirements in a single electronic device remains a challenge. Summary of the invention

[0003] The technical problem solved by the present invention is to provide a method for preparing an antifreeze pectin-based conductive hydrogel based on the synergistic effect of conductive polymers and multivalent salt ions, so as to solve the problems of poor mechanical properties, poor conductivity and lack of antifreeze properties of existing conductive hydrogel electrodes. The antifreeze pectin-based conductive hydrogel prepared by this method can be used to prepare friction nanogenerator electrodes.

[0004] The present invention starts from the design of an antifreeze pectin-based conductive hydrogel based on the synergistic effect of conductive polymers and multivalent salt ions: acrylamide monomers are used to form polyacrylamide chains through spontaneous addition polymerization, and the polyacrylamide chains and the cross-linking agent methylene bisacrylamide form a three-dimensional network through addition reaction, and CaCl 2 Ca2+ As a cross-linking point, it forms an eggshell structure with the unesterified carboxyl groups in the galacturonic acid in pectin, thereby forming Ca 2+ -COO- coordination complex network; form a physical cross-linked network with the carboxyl groups on carboxymethyl chitosan, and multiple networks are interlaced with each other, thereby effectively improving its mechanical properties. The formed multi-network hydrogel is the basic framework, placed in a CaCl 2 The in-situ polymerization of polypyrrole in solution makes the hydrogel have better electrical conductivity; high concentration of Ca 2+ The presence of makes the hydrogel have a certain antifreeze property. The prepared pectin-based high-performance antifreeze and anti-drying hydrogel is used as an electrode in a flexible friction nanogenerator to test its electrical output performance and investigate its practical application value.

[0005] The present invention adopts the following technical solution to solve the above technical problems, which is a method for preparing an antifreeze pectin-based conductive hydrogel based on the synergistic effect of a conductive polymer and multivalent salt ions, characterized in that the specific steps are:

[0006] Step S1: dissolving 9.94 g acrylamide in 40 mL deionized water to prepare an acrylamide solution, and then sequentially adding 0.005 g methylenebisacrylamide, 0.2 g pectin, 0.3 g carboxymethyl chitosan and 0.24 g ammonium persulfate to fully dissolve them to obtain an acrylamide / chitosan-pectin solution;

[0007] Step S2: 0.5 g CaCl 2 Place it in the acrylamide / chitosan-pectin solution obtained in step S1, perform ultrasonic treatment after it is fully dissolved, then drop it into a glass container with a syringe, and place it in a forced air drying oven at 60°C to obtain pectin / carboxymethyl chitosan-CaCl 2 / polyacrylamide hydrogel;

[0008] Step S3: Dissolve 0.048-0.193 g of pyrrole monomer and 0.05-0.2 g of dopamine hydrochloride in 10 mL of deionized water at 4 °C and stir to mix well. Then add the pectin / carboxymethyl chitosan-CaCl prepared in step S2. 2 / polyacrylamide hydrogel, soaked at 4°C, then the hydrogel was taken out and stored in a sealed empty container at 4°C to allow polypyrrole (Ppy) to evenly penetrate into the pectin-based hydrogel;

[0009] Step S4: Soak the hydrogel obtained in step S3 in FeCl 3 and CaCl 2 In aqueous solution, FeCl 3 The molar concentration of CaCl is 0.089 mol / L. 2The mass percentage of pectin is 60wt%, and the antifreeze pectin-based conductive hydrogel is obtained by immersing at 4°C.

[0010] The application of the antifreeze pectin-based conductive hydrogel as a friction nanogenerator electrode of the present invention is characterized by the specific process of placing the friction nanogenerator electrode prepared by the antifreeze pectin-based conductive hydrogel on the surface of the friction layer, connecting the wire between the hydrogel and the friction layer, and then taking the same friction layer to cover the opposite side to form a sandwich structure, and closing the ports at the four ends with flexible double-sided tape to obtain a friction nanogenerator based on the antifreeze pectin-based conductive hydrogel.

[0011] It is further defined that the friction layer is polydimethylsiloxane, which is prepared by mixing Sylgard 184 monomer and Sylgard 184 curing agent in a mass ratio of 10:1, and the flexible double-sided adhesive is VHB tape.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. The acrylamide used in the present invention forms polyacrylamide chains through spontaneous addition polymerization, and the polyacrylamide chains and the cross-linking agent methylene bisacrylamide form a three-dimensional network through addition reaction. 2 The unesterified carboxyl groups in galacturonic acid in pectin form an eggshell structure to form Ca 2+ -COO- coordination complex network forms a physical cross-linked network with the carboxyl groups on carboxymethyl chitosan. Multiple networks are interspersed with each other, thereby effectively improving the mechanical properties of the hydrogel, and the tensile properties can reach about 2800%.

[0014] 2. The present invention adopts the method of in-situ polymerization of polypyrrole, and the conductive polymer and multivalent salt ions work synergistically to further improve the conductivity of the hydrogel electrode, from 5.417m / s to 8.085m / s, and the tensile performance can also reach 800%; high concentration Ca 2+ The presence of makes the hydrogel have good antifreeze properties and can be used normally at low temperatures of -24°C.

[0015] 3. The present invention adopts a closed sandwich structure, through the friction layer-hydrogel electrode-friction layer sandwich structure, and the port is sealed with a flexible double-sided tape, which improves the anti-drying property of the hydrogel. Within 30 days, the water loss rate of the hydrogel is controlled within 3.98%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the overall structure of the high-performance antifreeze and anti-drying hydrogel friction nanogenerator in Example 6;

[0017] Description of the drawings: 1 - polydimethylsiloxane film, 2 - antifreeze pectin-based conductive hydrogel, 3 - wire;

[0018] Figure 2 This is the stress-strain test curve of the prepared antifreeze pectin-based conductive hydrogel with pure salt ions;

[0019] Figure 3 is a stress-strain test curve of the antifreeze pectin-based conductive hydrogel prepared in Example 3;

[0020] Figure 4 is the conductivity graph of the antifreeze pectin-based conductive hydrogel prepared in Examples 1-5;

[0021] Figure 5 is a graph showing the water loss resistance of the antifreeze pectin-based conductive hydrogel prepared in Example 6;

[0022] Figure 6 is a voltage output signal diagram of the antifreeze pectin-based conductive hydrogel friction nanogenerator prepared in Example 6;

[0023] Figure 7 is a current output signal diagram of the antifreeze pectin-based conductive hydrogel friction nanogenerator prepared in Example 6;

[0024] Figure 8 is a transfer charge signal diagram of the antifreeze pectin-based conductive hydrogel friction nanogenerator prepared in Example 6;

[0025] Fig. 9 is a conductivity diagram of the antifreeze pectin-based conductive hydrogel prepared in Example 6 before and after freezing;

[0026] Fig.10 This is a voltage output signal diagram of the antifreeze pectin-based conductive hydrogel friction nanogenerator prepared in Example 6 before and after freezing. DETAILED DESCRIPTION

[0027] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0028] Example 1

[0029] Step S1: dissolving 9.94 g acrylamide in 40 mL deionized water, and then adding 0.2 g pectin, 0.3 g carboxymethyl chitosan, 0.005 g methylene bisacrylamide and 0.24 g ammonium persulfate to fully dissolve the acrylamide / pectin-carboxymethyl chitosan solution at a rotation speed of 1500 r / min;

[0030] Step S2: 0.5 g CaCl2 Add the solution to the acrylamide / pectin-carboxymethyl chitosan solution obtained in step S1 at a speed of 600 r / min. After sufficient dissolution, place it in an ultrasonic treatment for 30 min. Then, drop it into a glass container with a needle and place it in a forced air drying oven at 60 ° C for 1 h to obtain pectin / carboxymethyl chitosan-CaCl 2 / polyacrylamide hydrogel;

[0031] Step S3: Dissolve 0.048 g of pyrrole monomer in 10 mL of deionized water at 4 °C and stir evenly, then add the pectin / carboxymethyl chitosan-CaCl obtained in step S2 2 / polyacrylamide hydrogel was immersed at 4 °C for 12 h, and then the hydrogel was taken out and stored in a sealed empty container at 4 °C for 3 h to allow PPy to evenly penetrate into the pectin-based hydrogel;

[0032] Step S4: Soak the hydrogel obtained in step S3 in FeCl 3 (0.089 mol / L) and CaCl 2 The antifreeze pectin-based conductive hydrogel was obtained by immersing it in a (60wt%) aqueous solution at 4°C, and its conductivity was 5.417m / s.

[0033] Example 2

[0034] Step S1: 9.94 g acrylamide was dissolved in 40 mL deionized water, and then 0.2 g pectin, 0.3 g carboxymethyl chitosan, 0.005 g methylene bisacrylamide and 0.24 g ammonium persulfate were added to fully dissolve the acrylamide / pectin-carboxymethyl chitosan solution at a rotation speed of 1500 r / min;

[0035] Step S2: 0.5 g CaCl 2 Add the solution to the acrylamide / pectin-carboxymethyl chitosan solution obtained in step S1 at a speed of 600 r / min. After sufficient dissolution, place it in an ultrasonic treatment for 30 min. Then, drop it into a glass container with a needle and place it in a forced air drying oven at 60 ° C for 1 h to obtain pectin / carboxymethyl chitosan-CaCl 2 / polyacrylamide hydrogel;

[0036] Step S3: Dissolve 0.048 g of pyrrole monomer and 0.05 g of dopamine hydrochloride in 10 mL of deionized water at 4 °C and stir evenly, then add the pectin / carboxymethyl chitosan-CaCl obtained in step S2. 2 / polyacrylamide hydrogel was immersed at 4 °C for 12 h, and then the hydrogel was taken out and stored in a sealed empty container at 4 °C for 3 h to allow PPy to evenly penetrate into the pectin-based hydrogel;

[0037] Step S4: Soak the hydrogel obtained in step S3 in FeCl 3 (0.089 mol / L) and CaCl 2 The antifreeze pectin-based conductive hydrogel was obtained by immersing it in a (60wt%) aqueous solution at 4°C, and the conductivity was 6.678m / s.

[0038] Example 3

[0039] Step S1: dissolving 9.94 g acrylamide in 40 mL deionized water, and then adding 0.2 g pectin, 0.3 g carboxymethyl chitosan, 0.005 g methylene bisacrylamide and 0.24 g ammonium persulfate to fully dissolve the acrylamide / pectin-carboxymethyl chitosan solution at a rotation speed of 1500 r / min;

[0040] Step S2: 0.5 g CaCl 2 Add the solution to the acrylamide / pectin-carboxymethyl chitosan solution obtained in step S1 at a speed of 600 r / min. After sufficient dissolution, place it in an ultrasonic treatment for 30 min. Then, drop it into a glass container with a needle and place it in a forced air drying oven at 60 ° C for 1 h to obtain pectin / carboxymethyl chitosan-CaCl 2 / polyacrylamide hydrogel;

[0041] Step S3: Dissolve 0.097 g of pyrrole monomer and 0.1 g of dopamine hydrochloride in 10 mL of deionized water at 4 °C and stir to mix well. Then add the pectin / carboxymethyl chitosan-CaCl obtained in step S2. 2 / polyacrylamide hydrogel was immersed at 4 °C for 12 h, and then the hydrogel was taken out and stored in a sealed empty container at 4 °C for 3 h to allow PPy to evenly penetrate into the pectin-based hydrogel;

[0042] Step S4: Soak the hydrogel obtained in step S3 in FeCl 3 (0.089 mol / L) and CaCl 2 The antifreeze pectin-based conductive hydrogel was obtained by immersing it in a (60wt%) aqueous solution at 4°C, and the conductivity was 8.085m / s.

[0043] Example 4

[0044] Step S1: dissolving 9.94 g acrylamide in 40 mL deionized water, and then adding 0.2 g pectin, 0.3 g carboxymethyl chitosan, 0.005 g methylene bisacrylamide and 0.24 g ammonium persulfate to fully dissolve the acrylamide / pectin-carboxymethyl chitosan solution at a rotation speed of 1500 r / min;

[0045] Step S2: 0.5 g CaCl 2Add the solution to the acrylamide / pectin-carboxymethyl chitosan solution obtained in step S1 at a speed of 600 r / min. After sufficient dissolution, place it in an ultrasonic treatment for 30 min. Then, drop it into a glass container with a needle and place it in a forced air drying oven at 60 ° C for 1 h to obtain pectin / carboxymethyl chitosan-CaCl 2 / polyacrylamide hydrogel;

[0046] Step S3: Dissolve 0.145 g of pyrrole monomer and 0.15 g of dopamine hydrochloride in 10 mL of deionized water at 4 °C and stir to mix well. Then add the pectin / carboxymethyl chitosan-CaCl obtained in step S2. 2 / polyacrylamide hydrogel was immersed at 4 °C for 12 h, and then the hydrogel was taken out and stored in a sealed empty container at 4 °C for 3 h to allow PPy to evenly penetrate into the pectin-based hydrogel;

[0047] Step S4: Soak the hydrogel obtained in step S3 in FeCl 3 (0.089 mol / L) and CaCl 2 The antifreeze pectin-based conductive hydrogel was obtained by immersing it in a (60wt%) aqueous solution at 4°C, and the conductivity was 7.568m / s.

[0048] Example 5

[0049] Step S1: dissolving 9.94 g acrylamide in 40 mL deionized water, and then adding 0.2 g pectin, 0.3 g carboxymethyl chitosan, 0.005 g methylene bisacrylamide and 0.24 g ammonium persulfate to fully dissolve the acrylamide / pectin-carboxymethyl chitosan solution at a rotation speed of 1500 r / min;

[0050] Step S2: 0.5 g CaCl 2 Add the acrylamide / pectin-carboxymethyl chitosan solution obtained in step S1 at a speed of 600 r / min. After sufficient dissolution, place it in an ultrasonic treatment for 30 min, then drop it into a glass container with a needle, place it in a forced air drying oven at 60 ° C for 1 h to obtain pectin / carboxymethyl chitosan-CaCl 2 / polyacrylamide hydrogel;

[0051] Step S3: Dissolve 0.193 g of pyrrole monomer and 0.2 g of dopamine hydrochloride in 10 mL of deionized water at 4 °C and stir to mix well. Then add the pectin / carboxymethyl chitosan-CaCl obtained in step S2. 2 / polyacrylamide hydrogel was immersed at 4 °C for 12 h, and then the hydrogel was taken out and stored in a sealed empty container at 4 °C for 3 h to allow PPy to evenly penetrate into the pectin-based hydrogel;

[0052] Step S4: Immerse the hydrogel obtained in Step S3 in an aqueous solution of FeCl 3 (0.089 mol / L) and CaCl 2 (60 wt%) to obtain an antifreeze pectin-based conductive hydrogel by soaking at 4°C, with a conductivity of 7.079 m / s.

[0053] Example 6

[0054] The flexible triboelectric nanogenerator is composed of an antifreeze pectin-based conductive hydrogel 2 as the electrode, and PDMS (polydimethylsiloxane film 1) is a mixture of Sylgard 184 monomer and Sylgard 184 curing agent in a mass ratio of 10:1 as the friction layer. Specifically, the above-prepared antifreeze pectin-based conductive hydrogel (Example 4) is placed on the surface of the friction layer, and a wire 3 is connected between the hydrogel and the friction layer. Then, the same friction layer is taken and covered on the opposite side to form a sandwich structure, and the four ends are sealed with flexible double-sided tape to obtain a triboelectric nanogenerator based on pectin-based antifreeze and dry-resistant hydrogel. The thickness of the friction layer is 1 mm, and the thickness of the hydrogel electrode is 3 mm. The open-circuit voltage of the flexible triboelectric nanogenerator based on pectin-based antifreeze and dry-resistant hydrogel as the electrode is measured to be 320 V, the short-circuit current is 9 μA, and the transferred charge is 70 nC using a 6514 system electrometer.

[0055] The above examples describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above examples. What is described in the above examples and the specification only illustrates the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. Preparation method of antifreeze pectin-based conductive hydrogel based on the synergistic effect of conductive polymer and multivalent salt ions, Features The specific steps are: Step S1: dissolving 9.94 g acrylamide in 40 mL deionized water to prepare an acrylamide solution, and then sequentially adding 0.005 g methylenebisacrylamide, 0.2 g pectin, 0.3 g carboxymethyl chitosan and 0.24 g ammonium persulfate to fully dissolve them to obtain an acrylamide / chitosan-pectin solution; Step S2: 0.5 g CaCl 2 Place it in the acrylamide / chitosan-pectin solution obtained in step S1, perform ultrasonic treatment after it is fully dissolved, then drop it into a glass container with a syringe, and place it in a forced air drying oven at 60°C to obtain pectin / carboxymethyl chitosan-CaCl 2 / polyacrylamide hydrogel; Step S3: Dissolve 0.048-0.193 g of pyrrole monomer and 0.05-0.2 g of dopamine hydrochloride in 10 mL of deionized water at 4 °C and stir to mix well. Then add the pectin / carboxymethyl chitosan-CaCl prepared in step S2. 2 / polyacrylamide hydrogel, soaked at 4°C, then the hydrogel was taken out and stored in a sealed empty container at 4°C to allow polypyrrole to evenly penetrate into the pectin-based hydrogel; Step S4: Soak the hydrogel obtained in step S3 in FeCl 3 and CaCl 2 In aqueous solution, FeCl 3 The molar concentration of CaCl is 0.089 mol / L. 2 The mass percentage of pectin is 60wt%, and the antifreeze pectin-based conductive hydrogel is obtained by immersing at 4°C.

2. Application of the antifreeze pectin-based conductive hydrogel prepared according to the method of claim 1 as a triboelectric nanogenerator electrode, Features The specific process is: place the friction nanogenerator electrode prepared from the above-mentioned antifreeze pectin-based conductive hydrogel on the surface of the friction layer, connect the wire between the hydrogel and the friction layer, and then take the same friction layer to cover the opposite side to make it a sandwich structure, and close the ports at the four ends with flexible double-sided tape to obtain a friction nanogenerator based on antifreeze pectin-based conductive hydrogel.

3. The use according to claim 2, Features: The friction layer is polydimethylsiloxane, which is prepared by mixing Sylgard 184 monomer and Sylgard 184 curing agent in a mass ratio of 10:

1. The flexible double-sided adhesive tape is VHB tape.

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