Conductive composite hydrogel with bidirectional porous structure and pH response and preparation method thereof

Abstract

The invention relates to a conductive composite hydrogel with a bidirectional porous structure and pH response, and belongs to the field of organic polymer materials. The conductive composite hydrogel is formed by polymerizing polypyrrole, acrylic acid and poly (N-isopropylacrylamide) by adopting a two-step method. The preparation method comprises the following steps: firstly, preparing hydrogel sensitive to pH change through free radical copolymerization; then, the influence of different dopants on the morphology and conductivity of polypyrrole is researched, and the optimal dopant is selected; and finally, polymerizing pyrrole in the hydrogel prepared in advance by adopting a chemical oxidation method to obtain the conductive composite hydrogel which has a bidirectional pore structure and is sensitive to pH change. The composite hydrogel not only has a biphase porous structure and high-sensitivity pH responsiveness, but also can remarkably change along with the change of the pH value, the conductivity can be improved by 20 times under the alkaline condition, and the conductivity can be improved by nearly 200 times under the acidic condition. In addition, the composite hydrogel also shows excellent capacitive performance and electrochemical stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and relates to a conductive composite hydrogel with a bidirectional porous structure and pH response and its preparation method, especially a method for preparing a conductive composite hydrogel based on the combined use of polypyrrole with acrylic acid and N-isopropylacrylamide. Background Technology

[0002] Hydrogels are soft materials composed of cross-linked hydrophilic polymer chains and a three-dimensional polymer network with high water-holding capacity. They have a media composition similar to that of biological organisms and good flexibility, with unique properties and broad application prospects.

[0003] Poly(N-isopropylacrylamide) (PNIPAM) is one of the most commonly used polymers in hydrogel synthesis and a typical temperature-responsive hydrogel. Below the lower critical transition temperature (LCST), the hydrophilic amide groups dominate, interacting with water molecules through hydrogen bonds, thus absorbing water and swelling. Above the LCST, the hydrophobic groups (isopropyl groups) in the structure become more dominant than the hydrogen bonds between the amide groups and water, leading to water loss and shrinkage of the hydrogel. Based on this property, poly(N-isopropylacrylamide) hydrogels can be used as temperature-sensitive smart responsive materials.

[0004] The pH response of a material originates from the ionization of functional groups on the polymer backbone. When side functional groups are ionized, the charge density of the hydrogel is redistributed. Two hydrogel backbones with the same charge will separate due to electrostatic repulsion, making the polymer network looser and causing the hydrogel to absorb water and swell. Generally, based on the nature of the functional side groups, pH-responsive hydrogels can be classified into cationic hydrogels and anionic hydrogels. For cationic hydrogels, when the pH value is less than the ionization constant of an acid, the side groups of the cationic hydrogel are protonated. The protonated hydrogel becomes positively charged, the gaps between the polymer chains increase, and the pressure inside decreases. Due to the pressure difference between the external and internal environments, water from the outside enters the hydrogel, causing it to swell. Typical examples of pH-responsive materials include polyacrylic acid, polyacrylamide, and polymethacrylic acid.

[0005] Conductive polymers (CPs), also known as conductive high-molecular materials, are synthetic polymers characterized by their flexibility, applicability, and electron delocalization. CPs can be used in complex systems that communicate electrically with physiological tissues such as nerves, brain, muscles, and heart tissues, such as polyaniline, polythiophene, polyacetylene, and polypyrrole (PPy). Among these conductive polymers, polypyrrole (PPy) is considered the most important due to its environmental stability, high conductivity, ease of chemical or electrochemical preparation, and high efficiency in redox processes. Its conductivity mechanism is as follows: its structure consists of a conjugated structure with alternating carbon-carbon single and double bonds. The double bonds are composed of σ electrons and π electrons. The σ electrons are fixed and cannot move freely, forming covalent bonds between carbon atoms. The two π electrons in the conjugated double bonds are not fixed to any one carbon atom; they can translocate from one carbon atom to another, exhibiting a tendency to extend along the entire molecular chain. The overlap of the π electron clouds within the molecule creates a common energy band for the entire molecule, and π electrons are similar to free electrons in metallic conductors. When an electric field is present, electrons that make up π bonds can move along the molecular chain. Therefore, PPy can conduct electricity.

[0006] Because PPy is a polymer with an ultralong conjugated structure composed of numerous alternating carbon-carbon single and double bonds, its macromolecular chains lack defects, resulting in poor conductivity, even non-conductivity, and poor dispersibility. To increase its conductivity, certain defects must be introduced into its conjugated structure, either by removing electrons from the polymer chain (oxidation) or inserting electrons (reduction). This process is called doping. After doping, electrons that can move within a certain delocalized range on the polymer chain significantly improve its conductivity. Therefore, the key to its conductivity lies in doping. The essence of doping is the charge transfer or redox reaction between the conjugated polymer chain and the dopant.

[0007] These properties make polypyrrole (PPy) a widely applicable functional material in electrochemical processes and biotechnology. However, its low solubility limits its practical use, necessitating the exploration of various composite forms to overcome this limitation. Therefore, using it in combination with hydrogels as a newly formed composite material is a suitable option. Summary of the Invention

[0008] This invention relates to a simple and controllable conductive composite hydrogel with a bidirectional porous structure and pH responsiveness, and its preparation method. The method utilizes readily available raw materials, is simple to operate, and is easily scalable for industrial production. The conductive composite hydrogel with a bidirectional porous structure and pH responsiveness obtained by this method is a novel material never before reported. This composite hydrogel not only possesses a biphasic porous structure and highly sensitive pH responsiveness, but its conductivity also changes significantly with pH value, increasing by 20 times under alkaline conditions and nearly 200 times under acidic conditions. Furthermore, this composite hydrogel exhibits excellent capacitance and electrochemical stability. This conductive composite hydrogel with a bidirectional porous structure and pH responsiveness has broad positive applications in the biomedical field for drug delivery, control, and release.

[0009] To achieve the above objectives, the present invention employs the following technical solutions: Step 1: Synthesizing the pH-sensitive hydrogel (P(NIPAM / AA)) from the first step; Step 2: Selection of dopant; Step 3: Synthesizing a conductive composite hydrogel (PPy-P(NIPAM / AA)) with a bidirectional porous structure and pH response.

[0010] Step 1: P(NIPAM / AA) hydrogel, prepared from the following components:

[0011]

[0012] Step 2: Selection of dopant in the synthesis of polypyrrole (PPy):

[0013] 5 parts of pyrrole

[0014] 5 parts oxidant

[0015] 1 part dopant

[0016] Step 3: The PPy-P(NIPAM / AA) hydrogel is prepared from the following components: After freeze-drying the P(NIPAM / AA) hydrogel prepared in Step 1, polypyrrole (PPy) is loaded onto it in a pyrrole solution. The solution components, expressed as molar fractions, are as follows:

[0017] 5 parts of pyrrole

[0018] 5 parts oxidant

[0019] 1 part dopant

[0020] Preferably, P(NIPAM / AA) hydrogels belong to free radical polymerization, and it is simple and easy to initiate free radical polymerization using photoinitiators.

[0021] Preferably, the P(NIPAM / AA) hydrogel is a free radical polymer, the initiator is benzophenone, and the polymerization is carried out under ultraviolet light irradiation.

[0022] Preferably, the oxidant in step two is ferric chloride hexahydrate (FeCl3·6H2O).

[0023] Preferably, the P(NIPAM / AA) hydrogel is synthesized by free radical copolymerization of N-isopropylacrylamide (NIPAM), acrylic acid (AA), and N,N'-methylenebisacrylamide (MBA) in dimethyl sulfoxide (DMSO).

[0024] Preferably, the conductive polymer is polypyrrole (PPy). PPy has a conjugated structure consisting of alternating carbon-carbon single and double bonds. The double bonds are composed of σ electrons and π electrons. The σ electrons are fixed and cannot move freely, forming covalent bonds between carbon atoms. The two π electrons in the conjugated double bonds are not fixed to any one carbon atom; they can translocate from one carbon atom to another, exhibiting a tendency to extend along the entire molecular chain. This overlap of π electron clouds within the molecule creates a shared energy band, and π electrons are similar to free electrons in metallic conductors. When an electric field is present, the electrons forming the π bonds can move along the molecular chain. Therefore, PPy is conductive.

[0025] Preferably, PPy is a polymer with an ultralong conjugated structure composed of a large number of alternating carbon-carbon single and double bonds. Its macromolecular chains lack defects, resulting in poor conductivity, or even no conductivity, and poor dispersibility. Dopants can be used to remove electrons from the PPy polymer chains or insert electrons into the macromolecular chains, disrupting the conjugated structure and thus enabling PPy molecules to exhibit good conductivity.

[0026] Preferably, polypyrrole is obtained by chemical oxidation, and the dopants are: acid dopants are p-toluenesulfonic acid (TSA), hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3), and surfactant dopants are sodium dodecylbenzenesulfonate (SDBS), hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfonate (SDS1), and sodium dodecyl sulfate (SDS2). Dopants with high polypyrrole conductivity are selected for subsequent doping.

[0027] Preferably, step one: the P(NIPAM / AA) hydrogel is prepared from the following components:

[0028]

[0029]

[0030] Step 2: The PPy-P(NIPAM / AA) hydrogel was prepared from the following components: the freeze-dried P(NIPAM / AA) hydrogel was loaded with polypyrrole (PPy) in 75 mL of pyrrole solution. The solution components, by mole fraction, are as follows:

[0031] 5 parts of pyrrole

[0032] 5 parts oxidant

[0033] 1 part dopant

[0034] Preferably, the dopant in step two is one of sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfonate (SDS1), and sodium dodecyl sulfate (SDS2).

[0035] To achieve the above objectives, the present invention employs the following technical solution: The preparation method of the conductive composite hydrogel (PPy-P(NIPAM / AA)) with bidirectional porous structure and pH response includes the following steps:

[0036] (1) Take 200mg N-isopropylacrylamide, 30mg acrylic acid, 10mg initiator benzophenone, 10mg crosslinking agent N,N'-methylenebisacrylamide, and 2mL dimethyl sulfoxide;

[0037] (2) Dissolve N-isopropylacrylamide, acrylic acid and crosslinking agent in dimethyl sulfoxide. After adding the initiator, quickly transfer the solution into a 5.0×1.5cm polytetrafluoroethylene reaction tank.

[0038] (3) After the reaction was irradiated with ultraviolet light for 10 hours and polymerized, the prepared hydrogel was soaked in deionized water for solvent exchange. Then the water in the hydrogel was changed every 12 hours. After 3 days, a P(NIPAM / AA) hydrogel with a thickness of 1.0±0.1 mm was obtained.

[0039] (4) The obtained P(NIPAM / AA) hydrogel was frozen in a -20℃ freezer for 12 hours and then placed in a 50℃ freeze dryer for vacuum freeze drying for 24 hours.

[0040] (5) Selection of dopant: Take a certain amount of pyrrole monomer, dopant and 75 mL of deionized water and add them to a three-necked flask and mix them evenly. Take a certain amount of oxidant and add it to 25 mL of deionized water. Use a constant pressure dropping funnel to slowly add it to the flask (control the addition within 30 min). After stirring the reaction at 0℃ for 6 h, wash the obtained product with ethanol and deionized water respectively to obtain polypyrrole monomer (where the molar ratio of dopant, pyrrole and oxidant is 1:5:5). Measure its conductivity and select the dopant with higher conductivity for subsequent doping steps.

[0041] (6) A certain amount of pyrrole monomer, 75 mL of deionized water, and the PPy dopant with high conductivity synthesized in (5) were added to a three-necked flask and mixed evenly. The freeze-dried P(NIPAM / AA) hydrogel was placed into the flask and stirred at 0°C for 5 h to ensure that the hydrogel was fully filled with pyrrole solution. A certain amount of oxidant was added to 25 mL of deionized water and slowly added to the flask using a constant pressure dropping funnel (the addition was completed within 30 min). After stirring at 0°C for 6 h, the resulting product was washed with ethanol and deionized water to obtain a conductive composite hydrogel with a bidirectional porous structure and pH response. (The molar ratio of dopant, pyrrole, and oxidant was 1:5:5.)

[0042] Preferably, the preparation method is simple, the reaction does not require heating, and the risk factor is low.

[0043] The solvent is dimethyl sulfoxide, a colorless and odorless transparent liquid at room temperature. It is a hygroscopic and flammable liquid with high polarity, high boiling point, aprotic properties, and water miscibility. It has extremely low toxicity, good thermal stability, is immiscible with alkanes, and is soluble in most organic compounds such as water, ethanol, propanol, diethyl ether, benzene, and chloroform. It is known as a "universal solvent" and is one of the most powerful dissolving agents among commonly used organic solvents.

[0044] This invention also discloses a method for preparing the aforementioned conductive composite hydrogel (PPy-P(NIPAM / AA)) with a bidirectional porous structure and pH responsiveness. By in-situ implanting a polypyrrole conductive polymer network into a porous hydrogel (P(NIPAM / AA)) that is sensitive to pH changes, a conductive composite hydrogel with a bidirectional porous structure and pH responsiveness is designed. This composite hydrogel not only possesses a biphase porous structure and highly sensitive pH response, but its conductivity also changes significantly with pH value, increasing by 20 times under alkaline conditions and nearly 200 times under acidic conditions. Furthermore, in the composite hydrogel, the PNIPAM hydrogel bulk acts as an internal electrolyte reservoir accommodating mobile ions, the biphase porous structure provides channels for electrolyte ion transport, and the polypyrrole network is responsible for electrochemical performance. Therefore, this composite hydrogel also exhibits excellent capacitive performance and electrochemical stability.

[0045] Beneficial effects:

[0046] 1. The conductive composite hydrogel with a bidirectional porous structure and pH response disclosed in this invention is obtained through a two-step method, and the conductive composite hydrogel prepared by this method perfectly solves the problem of low polypyrrole solubility. This invention provides a new direction for the design and manufacture of conductive hydrogel materials with pH sensitivity and capacitive properties, and shows great application potential in fields such as biomedicine and smart wearable devices.

[0047] 2. The conductive composite hydrogel with bidirectional porous structure and pH response disclosed in this invention is a novel material that has never been reported before, and has a biphase porous structure and highly sensitive pH response.

[0048] 3. The conductivity of the conductive composite hydrogel with bidirectional porous structure and pH response disclosed in this invention can change significantly with pH value. The conductivity can be increased by 20 times under alkaline conditions and by nearly 200 times under acidic conditions.

[0049] 4. The conductive composite hydrogel with a bidirectional porous structure and pH response disclosed in this invention exhibits excellent capacitive performance and electrochemical stability. This conductive composite hydrogel with a bidirectional porous structure and pH response has broad and positive applications in flexible sensors, flexible electronic products, and supercapacitors.

[0050] 5. Using acrylic acid as a pH-responsive material to introduce carboxyl groups into the hydrogel, under acidic conditions, due to the hydrogen bonding between carboxyl groups, the intersegments in the network are relatively close, resulting in a lower swelling ratio of the hydrogel. As the pH increases, the carboxyl group (-COOH) ionizes into a carboxyl anion (-COO). - This causes the hydrogen bonds between the macromolecular chains in the gel network to dissociate, increases the electrostatic repulsion between ions, makes the network structure looser, increases the volume, and thus exhibits an increased swelling rate.

[0051] 6. The P(NIPAM / AA) hydrogel uses benzophenone as the initiator, and the polymerization is carried out under ultraviolet light irradiation, which is simple, safe and reliable. Furthermore, pyrrole is polymerized in the freeze-dried P(NIPAM / AA) hydrogel via chemical oxidation to form a conductive composite hydrogel with a bidirectional porous structure and pH responsiveness, thus achieving good conductivity that responds to pH.

[0052] 7. We used cyclic voltammetry (CV) to analyze the electrochemical properties of PPy-P (NIPAM / AA) hydrogels with different pyrrole contents (Examples 1, 4, 5, and 6) in a 0.5 M H₂SO₄ electrolyte. Figure 8 a. At a scanning potential of 0-0.8V and a scanning rate of 50mV / s, all CV curves are approximately symmetrical and rectangular, indicating that PPy-P(NIPAM / AA) hydrogels possess typical capacitive properties. 0.75 -P(NIPAM / AA) hydrogel (Example 5) exhibits a high current response and the largest area of ​​integration of the CV curve, indicating that it has the strongest charge storage capacity and the best capacitance performance. Attached Figure Description

[0053] Figure 1ai are SEM images of undoped and polypyrrole polymerized with dopants CTAB, SDBS, SDS1, SDS2, TSA, HCl, H2SO4, and HNO3, respectively.

[0054] Figure 2 The conductivity diagrams are for undoped and polypyrrole polymerized with dopants CTAB, SDBS, SDS1, SDS2, TSA, HCl, H2SO4, and HNO3.

[0055] Figure 3 Conductivity of conductive composite hydrogels with bidirectional porous structure and pH response synthesized with different dopants (Examples 1, 2, 3);

[0056] Figure 4 a and b are conductive composite hydrogels with bidirectional porous structure and pH response prepared in this invention (Example 1, PPy). 0.25 SEM diagram of the network structure of -P(NIPAM / AA));

[0057] Figure 5 The hydrogels are polypyrrole (PPy), pH-sensitive hydrogels (P(NIPAM / AA)), and conductive composite hydrogels with bidirectional porous structures and pH responsiveness (Example 1, PPy). 0.25 Infrared absorption spectrum of -P(NIPAM / AA));

[0058] Figure 6 A conductive composite hydrogel with a bidirectional porous structure and pH response (Example 4, PPy) 0.50 -P(NIPAM / AA) (a) Conductivity changes in different acid and base solutions; (b) Conductivity changes after five cycles in 0.1M NaOH and 0.1M HCl solutions; (c) Conductivity changes after five cycles in 0.1M NH3·H2O and 0.1M HCl solutions.

[0059] Figure 7 The conductivity changes of (a) polypyrrole (PPy) and (b) a pH-sensitive hydrogel (P(NIPAM / AA)) in acidic and alkaline solutions.

[0060] Figure 8 (a) Cyclic voltammetry curves of conductive composite hydrogels with different pyrrole contents and bidirectional porous structure and pH response (Examples 1, 4, 5, 6); (b) Conductive composite hydrogels with bidirectional porous structure and pH response (Example 5, PPy 0.50Electrochemical stability of P(NIPAM / AA); (cf) Cyclic voltammetry curves of conductive composite hydrogels with bidirectional porous structure and pH response at different scan rates (Examples 1, 4, 5, 6).

[0061] Figure 9 Nyquist curves for conductive composite hydrogels with bidirectional porous structure and pH response with different pyrrole contents (Examples 1, 4, 5, and 6).

[0062] Example 1

[0063] A conductive composite hydrogel (PPy) with a bidirectional porous structure and pH response 0.25 A method for preparing -P(NIPAM / AA) hydrogel, characterized by comprising the following steps:

[0064] (1) Take 200mg N-isopropylacrylamide, 30mg acrylic acid, 10mg benzophenone as initiator, 10mg N,N'-methylenebisacrylamide as crosslinking agent, and 2mL dimethyl sulfoxide;

[0065] (2) Dissolve N-isopropylacrylamide, acrylic acid and crosslinking agent in dimethyl sulfoxide, mix the solution quickly, add benzophenone as an initiator, stir thoroughly and then quickly transfer the solution to a 5.0×1.5cm polytetrafluoroethylene reaction tank;

[0066] (3) After the reaction was irradiated with ultraviolet light for 10 hours and polymerized, the prepared hydrogel was soaked in deionized water for solvent exchange. Then the water in the hydrogel was changed every 12 hours. After 3 days, a PNIPAM hydrogel with a thickness of 1.0±0.1 mm was obtained.

[0067] (4) The obtained hydrogel was pre-frozen in a -20℃ freezer for 12 hours and then placed in a 50℃ freeze dryer for vacuum freeze drying for 24 hours;

[0068] (5) Take 0.25 mL of pyrrole monomer, 75 mL of deionized water and 0.197 g of sodium dodecyl sulfonate (SDS1) and add them to a three-necked flask. Mix them evenly. Take the P(NIPAM / AA) hydrogel prepared in step (3), freeze-dry it and put it into the flask. Mix and stir at 0℃ for 5 h to make the P(NIPAM / AA) hydrogel fully filled with pyrrole solution. Take 0.977 g of FeCl3·6H2O and add it to 25 mL of deionized water. Add it slowly to the flask using a constant pressure dropping funnel (controlling the addition within 30 min). After stirring the reaction at 0℃ for 6 h, wash the obtained product with ethanol and deionized water respectively to obtain a conductive composite hydrogel (PPy) with bidirectional porous structure and pH response. 0.25-P(NIPAM / AA)). (The molar ratio of dopant, pyrrole, and oxidant is 1:5:5)

[0069] Example 2

[0070] A method for preparing a conductive composite hydrogel with a bidirectional porous structure and pH response, characterized by comprising the following steps:

[0071] (1) Take 200mg N-isopropylacrylamide, 30mg acrylic acid, 10mg benzophenone as initiator, 10mg N,N'-methylenebisacrylamide as crosslinking agent, and 2mL dimethyl sulfoxide;

[0072] (2) Dissolve N-isopropylacrylamide, acrylic acid and crosslinking agent in dimethyl sulfoxide, mix the solution quickly, add benzophenone as an initiator, stir thoroughly and then quickly transfer the solution to a 5.0×1.5cm polytetrafluoroethylene reaction tank;

[0073] (3) After the reaction was irradiated with ultraviolet light for 10 hours and polymerized, the prepared hydrogel was soaked in deionized water for solvent exchange. Then the water in the hydrogel was changed every 12 hours. After 3 days, a PNIPAM hydrogel with a thickness of 1.0±0.1 mm was obtained.

[0074] (4) The obtained hydrogel was pre-frozen in a -20℃ freezer for 12 hours and then placed in a 50℃ freeze dryer for vacuum freeze drying for 24 hours.

[0075] (5) Add 0.25 mL of pyrrole monomer, 75 mL of deionized water, and 0.209 g of sodium dodecyl sulfate (SDS2) to a three-necked flask and mix thoroughly. Take the P(NIPAM / AA) hydrogel prepared in step (3), freeze-dry it, and place it in the flask. Mix and stir at 0°C for 5 h to ensure that the P(NIPAM / AA) hydrogel is fully filled with pyrrole solution. Add 0.977 g of FeCl3·6H2O to 25 mL of deionized water and slowly add it to the flask using a constant pressure dropping funnel (controlling the addition within 30 min). After stirring the reaction at 0°C for 6 h, wash the resulting product with ethanol and deionized water respectively to obtain a conductive composite hydrogel with a bidirectional porous structure and pH response. (The molar ratio of dopant, pyrrole, and oxidant is 1:5:5.)

[0076] Example 3

[0077] A method for preparing a conductive composite hydrogel with a bidirectional porous structure and pH response, characterized by comprising the following steps:

[0078] (1) Take 200mg N-isopropylacrylamide, 30mg acrylic acid, 10mg benzophenone as initiator, 10mg N,N'-methylenebisacrylamide as crosslinking agent, and 2mL dimethyl sulfoxide;

[0079] (2) Dissolve N-isopropylacrylamide, acrylic acid and crosslinking agent in dimethyl sulfoxide, mix the solution quickly, add benzophenone as an initiator, stir thoroughly and then quickly transfer the solution to a 5.0×1.5cm polytetrafluoroethylene reaction tank;

[0080] (3) After the reaction was irradiated with ultraviolet light for 10 hours and polymerized, the prepared hydrogel was soaked in deionized water for solvent exchange. Then the water in the hydrogel was changed every 12 hours. After 3 days, a PNIPAM hydrogel with a thickness of 1.0±0.1 mm was obtained.

[0081] (4) The obtained hydrogel was pre-frozen in a -20℃ freezer for 12 hours and then placed in a 50℃ freeze dryer for vacuum freeze drying for 24 hours.

[0082] (5) Add 0.25 mL of pyrrole monomer, 75 mL of deionized water, and 0.252 g of sodium dodecylbenzenesulfonate (SDBS) to a three-necked flask and mix thoroughly. Take the P(NIPAM / AA) hydrogel prepared in step (3), freeze-dry it, and place it in the flask. Mix and stir at 0°C for 5 h to ensure that the P(NIPAM / AA) hydrogel is fully filled with pyrrole solution. Add 0.977 g of FeCl3·6H2O to 25 mL of deionized water and slowly add it to the flask using a constant pressure dropping funnel (controlling the addition within 30 min). After stirring the reaction at 0°C for 6 h, wash the obtained product with ethanol and deionized water respectively to obtain a conductive composite hydrogel with a bidirectional porous structure and pH response. (The molar ratio of dopant, pyrrole, and oxidant is 1:5:5.)

[0083] Example 4

[0084] A conductive composite hydrogel (PPy) with a bidirectional porous structure and pH response 0.50 A method for preparing -P(NIPAM / AA) hydrogel, characterized by comprising the following steps:

[0085] (1) Take 200mg N-isopropylacrylamide, 30mg acrylic acid, 10mg benzophenone as initiator, 10mg N,N'-methylenebisacrylamide as crosslinking agent, and 2mL dimethyl sulfoxide;

[0086] (2) Dissolve N-isopropylacrylamide, acrylic acid and crosslinking agent in dimethyl sulfoxide, mix the solution quickly, add benzophenone as an initiator, stir thoroughly and then quickly transfer the solution to a 5.0×1.5cm polytetrafluoroethylene reaction tank;

[0087] (3) After the reaction was irradiated with ultraviolet light for 10 hours and polymerized, the prepared hydrogel was soaked in deionized water for solvent exchange. Then the water in the hydrogel was changed every 12 hours. After 3 days, a PNIPAM hydrogel with a thickness of 1.0±0.1 mm was obtained.

[0088] (4) The obtained hydrogel was pre-frozen in a -20℃ freezer for 12 hours and then placed in a 50℃ freeze dryer for vacuum freeze drying for 24 hours;

[0089] (5) Take 0.50 mL of pyrrole monomer, 75 mL of deionized water and 0.394 g of sodium dodecyl sulfonate (SDS1) and add them to a three-necked flask and mix well. Take the P(NIPAM / AA) hydrogel prepared in step (3), freeze-dry it and put it into the flask and mix and stir at 0℃ for 5 h to make the P(NIPAM / AA) hydrogel fully saturated with pyrrole solution. Take 1.953 g of FeCl3·6H2O and add it to 25 mL of deionized water. Add it slowly to the flask using a constant pressure dropping funnel (controlling the addition within 30 min). After stirring the reaction at 0℃ for 6 h, wash the obtained product with ethanol and deionized water respectively to obtain a conductive composite hydrogel (PPy) with bidirectional porous structure and pH response. 0.50 -P(NIPAM / AA)). (The molar ratio of dopant, pyrrole, and oxidant is 1:5:5)

[0090] Example 5

[0091] A conductive composite hydrogel (PPy) with a bidirectional porous structure and pH response 0.75 A method for preparing -P(NIPAM / AA) hydrogel, characterized by comprising the following steps:

[0092] (1) Take 200mg N-isopropylacrylamide, 30mg acrylic acid, 10mg benzophenone as initiator, 10mg N,N'-methylenebisacrylamide as crosslinking agent, and 2mL dimethyl sulfoxide;

[0093] (2) Dissolve N-isopropylacrylamide, acrylic acid and crosslinking agent in dimethyl sulfoxide, mix the solution quickly, add benzophenone as an initiator, stir thoroughly and then quickly transfer the solution to a 5.0×1.5cm polytetrafluoroethylene reaction tank;

[0094] (3) After the reaction was irradiated with ultraviolet light for 10 hours and polymerized, the prepared hydrogel was soaked in deionized water for solvent exchange. Then the water in the hydrogel was changed every 12 hours. After 3 days, a PNIPAM hydrogel with a thickness of 1.0±0.1 mm was obtained.

[0095] (4) The obtained hydrogel was pre-frozen in a -20℃ freezer for 12 hours and then placed in a 50℃ freeze dryer for vacuum freeze drying for 24 hours;

[0096] (5) Take 0.75 mL of pyrrole monomer, 75 mL of deionized water and 0.590 g of sodium dodecyl sulfonate (SDS1) and add them to a three-necked flask and mix well. Take the P(NIPAM / AA) hydrogel prepared in step (3), freeze-dry it and put it into the flask and mix and stir at 0℃ for 5 h to make the P(NIPAM / AA) hydrogel fully filled with pyrrole solution. Take 2.930 g of FeCl3·6H2O and add it to 25 mL of deionized water. Add it slowly to the flask using a constant pressure dropping funnel (controlling the addition within 30 min). After stirring the reaction at 0℃ for 6 h, wash the obtained product with ethanol and deionized water respectively to obtain a conductive composite hydrogel (PPy) with bidirectional porous structure and pH response. 0.75 -P(NIPAM / AA)). (The molar ratio of dopant, pyrrole, and oxidant is 1:5:5)

[0097] Example 6

[0098] A conductive composite hydrogel (PPy) with a bidirectional porous structure and pH response 1.00 A method for preparing -P(NIPAM / AA) hydrogel, characterized by comprising the following steps:

[0099] (1) Take 200mg N-isopropylacrylamide, 30mg acrylic acid, 10mg benzophenone as initiator, 10mg N,N'-methylenebisacrylamide as crosslinking agent, and 2mL dimethyl sulfoxide;

[0100] (2) Dissolve N-isopropylacrylamide, acrylic acid and crosslinking agent in dimethyl sulfoxide, mix the solution quickly, add benzophenone as an initiator, stir thoroughly and then quickly transfer the solution to a 5.0×1.5cm polytetrafluoroethylene reaction tank;

[0101] (3) After the reaction was irradiated with ultraviolet light for 10 hours and polymerized, the prepared hydrogel was soaked in deionized water for solvent exchange. Then the water in the hydrogel was changed every 12 hours. After 3 days, a PNIPAM hydrogel with a thickness of 1.0±0.1 mm was obtained.

[0102] (4) The obtained hydrogel was pre-frozen in a -20℃ freezer for 12 hours and then placed in a 50℃ freeze dryer for vacuum freeze drying for 24 hours;

[0103] (5) Take 1.00 mL of pyrrole monomer, 75 mL of deionized water and 0.788 g of sodium dodecyl sulfonate (SDS1) and add them to a three-necked flask and mix well. Take the P(NIPAM / AA) hydrogel prepared in step (3), freeze-dry it and put it into the flask and mix and stir at 0℃ for 5 h to make the P(NIPAM / AA) hydrogel fully filled with pyrrole solution. Take 3.906 g of FeCl3·6H2O and add it to 25 mL of deionized water. Add it slowly to the flask using a constant pressure dropping funnel (controlling the addition within 30 min). After stirring the reaction at 0℃ for 6 h, wash the obtained product with ethanol and deionized water respectively to obtain a conductive composite hydrogel (PPy) with bidirectional porous structure and pH response. 1.00 -P(NIPAM / AA)). (The molar ratio of dopant, pyrrole, and oxidant is 1:5:5)

[0104] See Figure 1 The image shows scanning electron microscope images of polypyrrole (PPy) synthesized with different dopants, in which the molar ratio of dopant, pyrrole and oxidant is 1:5:5. Figure 1 'a' is a dopant-free synthesized PPy, which generally presents as a regularly wrinkled thin film. Adding a surfactant results in slightly different morphologies of the synthesized polypyrrole. Figure 1 While CTAB is used as a dopant, it reduces the aggregation degree of PPy. Simultaneously, the presence of aromatic rings and other structures in the surfactant increases the crystallinity of PPy. When CTAB is used as a dopant, the PPy polymer exhibits a linear structure and forms an array structure (…). Figure 1 c); When SDBS is used as a dopant, the PPy polymer exhibits an irregular particle shape. Figure 1 b); When SDS1 and SDS2 are dopants, the prepared PPy particles are unevenly distributed. Figure 1 (d, e) This may be because after SDS1 and SDS2 are doped into the polymer chain segments, the long alkyl chains of the surfactants enhance the intermolecular forces, leading to increased particle interactions. The particles are thus constrained during dispersion, resulting in a specific dispersion state. Using protic acids as dopants has been found to affect the morphology of PPy polymers. Figure 1As shown in figure 1, when TSA is added to the synthesis solution, the resulting PPy polymer exhibits a regular particle morphology. The HCl-doped PPy polymer material has a dense cluster-like particle structure on its surface. The H2SO4-doped PPy material is covered with large nodules formed by particle aggregation, and its overall structure is somewhat similar to that of a cauliflower. The HNO3-doped PPy exhibits a loose and porous coral-like structure, indicating that HNO3-doped PPy exhibits less aggregation and is more orderly and loose compared to HCl and H2SO4-doped PPy. Overall, the PPy particles prepared by protonic acid doping are more uniformly distributed, and there is relatively less aggregation between particles. This indicates that the protonic acid dopant weakens the interaction forces between PPy particles, resulting in a more ordered PPy morphology.

[0105] See Figure 2 Dopant not only affects the morphology of PPy polymers but also their conductivity. Among several anionic surfactants (sulfonic acid-based dopants), SDS1-doped PPy exhibited the highest conductivity (32 S / cm), demonstrating that different dopants have varying effects at the same doping level. The size, nucleophilicity, and electronegativity of the dopant ions directly influence the polymerization morphology and charge transport of PPy, thus affecting the material's conductivity. Figure 2 Data shows that the conductivity of SDS1-doped PPy is significantly higher than that of SDBS-doped PPy, meaning that the larger the volume of the dopant anion, the lower the conductivity of PPy. This is because large-volume ions occupy more space, reducing electron transport paths, increasing electron transport distance and resistance, and may also disrupt the conjugated structure of the molecular chain, reducing the number of π bonds involved in electron transport, thus lowering conductivity. In contrast, small-volume ions can interact better with the polypyrrole molecular chain, maintaining or enhancing its conjugated structure and electron transport paths, thereby improving conductivity. The cationic surfactant CTAB only alters the morphology of the PPy polymer; its conductivity compared to undoped PPy does not change significantly. This may be due to the large volume of the dopant cation, leading to greater separation of the polymer molecular chains.

[0106] Among several proton acid dopants, HCl-doped polypyrrole (PPy) exhibits the lowest electrical conductivity. This is likely because HCl is a strong acid that affects the polymerization process of PPy, increasing the risk of peroxidation during polymerization and disrupting the conjugated structure of PPy, thus leading to decreased conductivity. In contrast, PPy synthesized with HNO3 doping shows superior conductivity compared to other proton acid dopants. This is likely due to the strong oxidizing properties of HNO3, which allows it to more effectively remove electrons from the polypyrrole chains during doping, forming more hole carriers and thus improving conductivity. Furthermore, HNO3 doping may promote the ordered arrangement of polypyrrole molecular chains, enhance electron delocalization, and provide more electron flow channels, facilitating electron flow and further improving the material's conductivity.

[0107] See Figure 3 The polypyrrole composite hydrogel synthesized with SDS1 as a dopant (Example 1) exhibited the highest conductivity, followed by SDS2 (Example 2) and SDBS (Example 3). This aligns with the above findings. Figure 2 The conductivity trends of polypyrrole synthesized with different dopants are similar to those of pure polypyrrole. This means that the conductivity change trend caused by the dopants is still maintained in the hydrogel. This may indicate that the dopants are still effective in the composite hydrogel, and the interaction between the dopants and polypyrrole is not significantly affected in the hydrogel system.

[0108] See Figure 4 PPy 0.25 Scanning electron microscope image of -P(NIPAM / AA) hydrogel (Example 1) is shown below. Figure 4 As shown, due to the conductivity of PPy, we can clearly observe the morphology of the composite. PPy is uniformly embedded in the network framework of the hydrogel, and the composite clearly maintains the network structure of the hydrogel. The biphase porous structure of the conductive composite hydrogel can be seen, which indicates that polypyrrole has been successfully integrated into the network structure of the hydrogel.

[0109] See Figure 5 By comparing PPy, P(NIPAM / AA) hydrogel and PPy 0.25 The infrared characteristic spectrum of PPy hydrogel (Example 1) was observed at 1540 cm⁻¹. -1 The stretching vibrations attributed to the C-rings in the pyrrole ring, 1460 cm -1 The stretching vibrations belong to the =CN group. The plane vibrations of CH and NH are located at 1035 cm⁻¹. -1 Location, 900cm -1 and 60cm -1The absorption at this point corresponds to the out-of-plane deformation vibration of CH, 1162 cm⁻¹. -1 The absorption peak at 2970 cm⁻¹ corresponds to the in-plane deformation vibration. In the FTIR spectrum of the P(NIPAM / AA) hydrogel, the peak at 2970 cm⁻¹ corresponds to the in-plane deformation vibration. -1 The absorption peak at 1540 cm⁻¹ corresponds to the stretching vibration of CH₄. -1 The absorption peak at 1460 cm⁻¹ corresponds to the bending vibration of NH₄⁺. -1 The absorption peak corresponds to the stretching vibration of CN, at 1384 cm⁻¹. -1 The point exhibits asymmetric bending vibration at 3080 cm. -1 The absorption peak is for the amide group, at 2934 cm⁻¹. -1 and 2970cm -1 The peaks at 1540 cm⁻¹ belong to the asymmetric stretching vibrations of -CH₂ and -CH₃, respectively; at 1540 cm⁻¹... -1 This is a stretching vibration of the C=C double bond, at 1723 cm⁻¹. -1 The peak at 1162 cm⁻¹ represents the stretching vibration of the C=O double bond. -1 The absorption peak at that point corresponds to deformation vibrations within the CN plane. In PPy 0.25 In the infrared spectrum of the -P(NIPAM / AA) hydrogel, the characteristic peaks of both PPy and P(NIPAM / AA) hydrogels are present and overlap, but no new peaks appear. Figure 5 (The bottom one) indicates that no chemical reaction occurred between PPy and P(NIPAM / AA) hydrogel, and PPy was loaded onto P(NIPAM / AA) hydrogel through physical adsorption or intermolecular forces.

[0110] See Figure 6 , Figure 6 a shows PPy in Example 4 0.50 The change in conductivity of -P(NIPAM / AA) hydrogel in acidic and alkaline solutions, when PPy 0.50 When the -P(NIPAM / AA) hydrogel was immersed in 0.1M NaOH solution, its conductivity increased from 7.53E-05 S / cm to 1.75E-03 S / cm, approximately 20 times that of its initial state. Further immersion in 0.1M HCl solution resulted in a rapid increase in conductivity to 1.42E-02 S / cm, nearly 200 times that of its initial state. We hypothesize that the biphase porous structure of the hydrogel provides channels for the movement of electrons and ions. In alkaline solution, the carboxyl groups (-COOH) on the polymer backbone are ionized into carboxyl anions (-COO₂). - In hydrogels, the charge density is redistributed. Due to electrostatic repulsion, two polymer backbones with the same charge will separate from each other, making the polymer network looser. Macroscopically, this manifests as the hydrogel absorbing water and swelling. 0.50The increased size of the -P(NIPAM / AA) hydrogel allows for faster electron movement along the polymer backbone in PPy, thereby improving its conductivity. 0.50 The conductivity of the -P(NIPAM / AA) hydrogel increases rapidly in 0.1M HCl solution, possibly due to a redistribution of the charge density in the hydrogel and the presence of H+ in the solution. + With -COO - The combination causes two polymer backbones with opposite charges to approach each other, resulting in a denser polymer network. Macroscopically, this manifests as the hydrogel shrinking due to dehydration and becoming smaller in size. However, protons in the solution attach to the carbon atoms on the polymer backbone, and the charges carried by these protons extend along a segment of the conjugated polymer chain, changing the charge distribution on the polymer chain and thus further improving the conductivity.

[0111] Figure 6 b shows PPy in Example 4 0.50 The conductivity changes of the -P(NIPAM / AA) hydrogel after five cycles in acid and alkali solutions were observed. We found that the conductivity of the composite hydrogel increased from alkali to acid and decreased back to its initial state from acid to alkali. After five cycles, its conductivity remained stable. This indicates that PPy 0.50 The conductivity of -P(NIPAM / AA) hydrogel exhibits cyclic behavior with pH; theoretically, as long as the composite hydrogel is not damaged during cycling, the conductivity can continue to change in a controllable manner. Replacing the strong alkaline solution with a weak base (0.1M NH3·H2O), such as... Figure 6 As shown in c, PPy 0.50 The -P(NIPAM / AA) hydrogel still exhibited conductivity changes over five cycles, demonstrating its sensitive response to pH stimulation. Compared to strong alkaline solutions, the composite hydrogel showed lower conductivity in ammonia water. This is because the ionization of NaOH solution is complete, while the ionization of NH3·H2O solution is incomplete, but this still fully demonstrates the effectiveness of PPy. 0.50 The conductivity of -P(NIPAM / AA) hydrogel exhibits cyclical changes with pH.

[0112] See Figure 7 We further investigated the pH response mechanism of PPy-P(NIPAM / AA) hydrogel. When PPy was immersed in 0.1M NH3·H2O and 0.1M HCl solutions, its conductivity remained unchanged, indicating that PPy itself does not possess pH-responsive properties (7a). When P(NIPAM / AA) hydrogel was immersed in acid and alkaline solutions, we found a slight increase in conductivity from alkaline to acidic solutions. Figure 7(b) This is because the P(NIPAM / AA) polymer hydrogel itself is non-conductive. In HCl, the entry or adsorption of protons leads to an increase in conductivity. However, neither polymer alone can achieve a highly sensitive response to pH stimulation. Therefore, we hypothesize that the introduction of PPy enhances the conductivity of the P(NIPAM / AA) hydrogel. Furthermore, the three-dimensional porous network structure of the hydrogel allows PPy to be uniformly dispersed within the hollow structure, which provides ion transport channels, thus enhancing the conductivity of the composite. Therefore, the highly sensitive change in conductivity at different pH values ​​is due to the synergistic effect of PPy and the P(NIPAM / AA) hydrogel.

[0113] See Figure 8 We further investigated the electrochemical properties of the composite hydrogel. Because the P(NIPAM / AA) hydrogel has a three-dimensional porous structure, it is beneficial for water absorption and storage. Using it as an electrolyte reservoir provides rapid ion transport and significant ion conductivity for the PPy-P(NIPAM / AA) composite hydrogel electrode. We used cyclic voltammetry (CV) to analyze the electrochemical properties of PPy-P(NIPAM / AA) hydrogels with different pyrrole contents (Examples 1, 4, 5, and 6) in a 0.5 M H₂SO₄ electrolyte. Figure 8 a. At a scanning potential of 0-0.8V and a scanning rate of 50mV / s, all CV curves are approximately symmetrical and rectangular, indicating that PPy-P(NIPAM / AA) hydrogels possess typical capacitive properties. 0.75 The -P(NIPAM / AA) hydrogel (Example 5) exhibited a high current response and the largest area under the cross-sectional area (CV) curve, indicating its strongest charge storage capacity and optimal capacitance performance. This may be because PPy itself possesses capacitive properties, and increasing its content is beneficial for improving the capacitance of the composite hydrogel. However, PPy... 1.00 The capacitance performance of the PPy-P(NIPAM / AA) hydrogel (Example 6) decreased because the high pyrrole content blocked the ion transport channels inside the hydrogel, resulting in a smaller response current. We further tested the electrochemical response of the PPy-P(NIPAM / AA) hydrogel at different scan rates. Figure 8 cf), the study found that PPy 0.75 -P(NIPAM / AA) hydrogel (Example 5) and PPy 1.00 -P(NIPAM / AA) hydrogel (Example 6) exhibits a symmetrical rectangular shape at different scan rates, such as Figure 8 As shown in d and e, the composite hydrogel exhibits sensitive and reversible capacitive behavior.

[0114] Furthermore, PPy-P(NIPAM / AA) hydrogels exhibit electrochemical stability. For example... Figure 8 b, PPy 0.75 The CV curve of the PPy-P(NIPAM / AA) hydrogel (Example 5) remained basically stable after 100 cycles, indicating that the composite hydrogel maintained excellent current response and repeatability, thus demonstrating that the PPy-P(NIPAM / AA) hydrogel has good electrochemical stability. We speculate that this is because SDS1-doped PPy has good stability, and the relatively uniform distribution of PPy in the hydrogel helps to maintain the stability of its electrical properties.

[0115] See Figure 9 We further investigated the electrochemical activity of PPy-P(NIPAM / AA) hydrogels with different pyrrole contents using electrochemical impedance spectroscopy (EIS). Figure 9 The Nyquist curves for PPy-P(NIPAM / AA) composite hydrogels with different pyrrole contents (Examples 1, 4, 5, and 6) show a distinct semi-circular shape at high frequencies and a straight line at low frequencies. The diameter of the Nyquist curve can be used to evaluate interfacial impedance, and the first intersection of the semi-circle with the X-axis represents the internal resistance of the material. The figure shows that each PPy-P(NIPAM / AA) hydrogel exhibits a straight line with a large slope in the low-frequency region. The slopes of these lines are calculated to be 2.86, 2.01, 3.22, and 2.60, respectively, indicating that PPy... 0.75 The slope of the -P(NIPAM / AA) hydrogel (Example 5) is larger than that of other hydrogels, which suggests that the ion diffusion and transfer rate of this composite hydrogel is faster than that of other hydrogels. On the other hand, the diameter of the semicircle of this composite hydrogel in the high-frequency region is smaller, which indicates that the interfacial impedance value is relatively low and the charge is more easily migrated on its surface, showing that it has good electrochemical properties, which is consistent with the results of cyclic voltammetry.

Claims

1. A method for preparing a conductive composite hydrogel (PPy-P(NIPAM / AA)) with a bidirectional porous structure and pH response, characterized in that... The specific steps are as follows: Step 1: A pH-sensitive hydrogel (P(NIPAM / AA)) was prepared by mass fraction from the following components: Step 2: The PPy-P(NIPAM / AA) hydrogel was prepared from the following components. The P(NIPAM / AA) hydrogel synthesized in Step 1 was taken, freeze-dried, and then loaded with polypyrrole (PPy) in a pyrrole solution. The solution components, expressed as molar fractions, are as follows: 5 parts of pyrrole 5 parts oxidant One part of dopant.

2. The method for preparing the conductive composite hydrogel (PPy-P(NIPAM / AA)) with bidirectional porous structure and pH response according to claim 1, characterized in that, The P(NIPAM / AA) hydrogel described above belongs to free radical polymerization. Free radical polymerization initiated by an initiator is simple and easy to carry out. The synthesis conditions are polymerization under ultraviolet light irradiation.

3. The method for preparing the conductive composite hydrogel (PPy-P(NIPAM / AA)) with bidirectional porous structure and pH response according to claim 1, characterized in that, The P(NIPAM / AA) hydrogel is synthesized by free radical copolymerization of N-isopropylacrylamide (NIPAM), acrylic acid (AA), and N,N'-methylenebisacrylamide (MBA) in dimethyl sulfoxide (DMSO).

4. The method for preparing the conductive composite hydrogel (PPy-P(NIPAM / AA)) with bidirectional porous structure and pH response according to claim 1, characterized in that, In step two, pyrrole is chemically oxidized to obtain polypyrrole.

5. The method for preparing the conductive composite hydrogel (PPy-P(NIPAM / AA)) with bidirectional porous structure and pH response according to claim 1, characterized in that, In step two, the oxidant is ferric chloride hexahydrate (FeCl3·6H2O).

6. The method for preparing the conductive composite hydrogel (PPy-P(NIPAM / AA)) with bidirectional porous structure and pH response according to claim 1, characterized in that, In step two, the dopant is either an acid or a surfactant.

7. The method for preparing the conductive composite hydrogel (PPy-P(NIPAM / AA)) with bidirectional porous structure and pH response according to claim 1, characterized in that, In step two, the dopant is one of sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfonate (SDS1), or sodium dodecyl sulfate (SDS2).

8. The method for preparing the conductive composite hydrogel (PPy-P(NIPAM / AA)) with bidirectional porous structure and pH response according to claim 1, characterized in that, Includes the following steps: (1) Take 200mg N-isopropylacrylamide, 30mg acrylic acid, 10mg benzophenone, 10mg N,N'-methylenebisacrylamide, and 2mL dimethyl sulfoxide; (2) Dissolve N-isopropylacrylamide, acrylic acid and crosslinking agent in dimethyl sulfoxide. After adding the initiator, quickly transfer the solution into a 5.0×1.5cm polytetrafluoroethylene reaction tank. (3) After the reaction was irradiated with ultraviolet light for 10 hours and polymerized, the prepared hydrogel was soaked in deionized water for solvent exchange. Then the water in the hydrogel was changed every 12 hours. After 3 days, a P(NIPAM / AA) hydrogel with a thickness of 1.0±0.1 mm was obtained. (4) The obtained P(NIPAM / AA) hydrogel was frozen in a -20℃ freezer for 12 hours and then placed in a 50℃ freeze dryer for vacuum freeze drying for 24 hours. (5) Take a certain amount of pyrrole monomer, 75 mL of deionized water and one of the dopant: sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfonate (SDS1), sodium dodecyl sulfate (SDS2) into a three-necked flask and mix them evenly. Put the P(NIPAM / AA) hydrogel prepared in step 3 after freeze drying into the flask and stir at 0°C for 5 h to fully saturate the hydrogel with pyrrole solution. Take a certain amount of oxidant FeCl3·6H2O and add it to 25 mL of deionized water. Slowly add it to the flask using a constant pressure dropping funnel (controlling the addition within 30 min). After stirring the reaction at 0°C for 6 h, wash the obtained product with ethanol and deionized water respectively to obtain a conductive composite hydrogel with bidirectional porous structure and pH response (where the molar ratio of dopant, pyrrole and oxidant is 1:5:5).

9. A conductive composite hydrogel with a bidirectional porous structure and pH response prepared by any one of claims 1-8.

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