P (NIPAm-AETC) / Gly / LDH composite conductive hydrogel and preparation method and application thereof

Abstract

The invention discloses P (NIPAm-AETC) / Gly / LDH composite conductive hydrogel as well as a preparation method and application thereof, and relates to the technical field of flexible sensors. The hydrogel is prepared by the following steps: copolymerizing N-isopropylacrylamide (NIPAm) and acryloyloxyethyl trimethyl ammonium chloride (AETC) to form a matrix, cooperatively introducing glycerol (Gly) and layered double hydroxide (LDH), and initiating a cross-linking reaction through ultraviolet light. The AETC provides a cationic group, so that the conductivity is improved, and the adhesion of the hydrogel is enhanced at the same time. Gly improves the toughness and recovery performance of the hydrogel through dynamic hydrogen-bond interaction, and LDH enhances the conductivity and structural stability. The hydrogel has excellent mechanical properties, good conductivity and adhesion, and can maintain stable and reliable performance in human motion monitoring, flexible sensors, wearable electronic devices and other applications.

Description

Technical Field

[0001] This invention relates to the field of flexible sensor technology, specifically to a P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel, its preparation method, and its application. Background Technology

[0002] Poly(N-isopropylacrylamide) hydrogels are widely used in biomedicine and other fields due to their excellent biocompatibility. The monomer N-isopropylacrylamide (NIPAm) molecule contains both an amide group and a carbon-carbon double bond, providing reaction sites that facilitate chemical modification and laying the foundation for subsequent structural regulation and functional expansion, especially showing application potential in flexible wearable electronic devices.

[0003] However, the PNIPAm bulk hydrogel exhibits low strength and toughness, making it prone to damage under load or dynamic stress environments, which has become a major bottleneck restricting its engineering applications. To address this issue, existing research has attempted to improve mechanical and recovery properties by optimizing molecular chain interactions through comonomer design, introducing reinforcing phases such as nanoclay, or adding glycerol (Gly) to promote dynamic hydrogen bond reconstruction. To achieve conductivity, inorganic conductive fillers such as carbon nanotubes and graphene are often incorporated; however, these strategies often introduce new problems such as decreased biocompatibility and insufficient system homogeneity, making it difficult to meet the safety and long-term stability requirements of flexible sensors.

[0004] Among numerous inorganic components, layered hydrogen hydroxides (LDHs) possess a layered structure, good dispersibility, and relatively good biocompatibility, demonstrating their potential for enhancing toughness and interfacial regulation in polymer composites. Nevertheless, how to significantly improve strength and toughness while simultaneously maintaining ionic conductivity and adhesion, and preserving the homogeneity and stability of the system, remains a key challenge in the design of multifunctional hydrogels.

[0005] Based on the aforementioned status quo and challenges, this invention proposes a method for preparing multifunctional PNIPAm-based hydrogels. A copolymer matrix P(NIPAm-AETC) with cationic sites is constructed through the copolymerization reaction of acryloyloxyethyltrimethylammonium chloride (AETC) and NIPAm, providing potential ion conduction and interfacial adhesion sites for the system. Gly is synergistically introduced to establish a reversible hydrogen bond network, endowing the system with energy dissipation and rapid recovery capabilities. Furthermore, well-dispersed LDH is compounded to achieve network reinforcement and interfacial stability. The coupling of these components at both the intermolecular and multi-scale structural levels promises to simultaneously achieve a combination of high mechanical properties, good conductivity, and excellent adhesion, thereby meeting the application requirements of flexible sensors and wearable devices for multifunctional materials. Summary of the Invention

[0006] The purpose of this invention is to propose a P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel, its preparation method, and its application. The resulting composite conductive hydrogel has excellent mechanical properties, good conductivity, and enhanced adhesion, and can be applied to flexible sensor devices, especially in the field of human motion monitoring, showing high application potential.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel is prepared by UV curing and crosslinking reaction of the following components: N-isopropylacrylamide (NIPAm), acryloyloxyethyltrimethylammonium chloride (AETC), glycerol (Gly), layered double hydroxide (LDH), polyethylene glycol diacrylate (PEGDA), 2-hydroxy-2-methylphenylacetone (HMPP), and solvent;

[0009] In this process, PEGDA is used as a crosslinking agent, HMPP is used as a photoinitiator, NIPAm is copolymerized with AETC to form a hydrogel matrix, AETC provides cationic groups to improve conductivity and enhance adhesion to various substrates, Gly enhances toughness and recovery performance through dynamic hydrogen bonding, and LDH is used as a filler to improve the conductivity and structural stability of the hydrogel.

[0010] As a preferred embodiment of the present invention, the layered double hydroxide (LDH) is nickel cobalt aluminum-layered double hydroxide (NiCoAl-LDH).

[0011] In addition, the present invention also proposes a method for preparing the composite conductive hydrogel, the steps of which are as follows:

[0012] Step 1: Dissolve Gly and NIPAm in ethanol sequentially, add AETC and stir until homogeneous to obtain a clear and transparent precursor solution;

[0013] Step 2: Add LDH dispersion to the precursor solution and obtain a uniform dispersion by ultrasonic treatment;

[0014] Step 3: Add PEGDA and HMPP to the dispersion, stir and sonicate to mix;

[0015] Step 4: Pour the mixed solution into a mold and perform a UV curing crosslinking reaction to obtain P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel.

[0016] As a preferred technical solution of the present invention, in the preparation method:

[0017] In step 1, the mass ratio of NIPAm to AETC is 0.8~1.2:0.8~1.2, and the mass ratio of Gly to (NIPAm+AETC) is 0.01~0.02:1; the stirring and dissolving temperature is 32~35 ℃, and the stirring speed is 300~400 rpm.

[0018] In step 2, the mass ratio of LDH to (NIPAm+AETC) is 0.0002~0.0006:1, the concentration of the LDH dispersion is 2.5~3 mg / mL, and the dispersion medium is ethanol. The ultrasonic dispersion frequency is 80 Hz, and the ultrasonic temperature is 25~28 ℃.

[0019] In step 3, the mass ratio of PEGDA to (NIPAm+AETC) is 0.0005~0.0015:1, and the mass ratio of HMPP to (NIPAm+AETC) is 0.00005~0.00015:1. The ultrasonic dispersion frequency is 80 Hz, and the ultrasonic temperature is 25~28 ℃.

[0020] In step 4, the curing temperature is 25~30 ℃ and the curing time is 20~30 min.

[0021] This invention first dissolves glycerol (Gly) and N-isopropylacrylamide (NIPAm) sequentially in ethanol, then adds acryloyloxyethyltrimethylammonium chloride (AETC) and dissolves it completely to obtain a homogeneous precursor solution; next, a layered double hydroxide (LDH) dispersion is added and ultrasonically treated to ensure uniform dispersion, forming a stable mixed solution; then, a crosslinking agent and a photoinitiator are added, and a P(NIPAm-AETC) / Gly / LDH conductive hydrogel is prepared by UV curing crosslinking reaction. The prepared hydrogel achieves synergistic reinforcement in its structural design. NIPAm and AETC copolymerize to form the hydrogel matrix; AETC provides cationic groups, improving conductivity while enhancing adhesion to various substrates; Gly enhances toughness and recovery performance through dynamic hydrogen bonding; LDH acts as a filler to improve the conductivity and structural stability of the hydrogel. Compared with the prior art, the beneficial effects of this invention are as follows:

[0022] 1. This invention improves the mechanical properties of hydrogels by copolymerizing NIPAm and AETC to form a composite network structure; enhances conductivity and adhesion to the substrate by providing cationic groups through AETC; improves toughness and recovery performance by forming hydrogen bonds through Gly; and improves the conductivity and structural stability of the material through LDH.

[0023] 2. The preparation method proposed in this invention is simple, environmentally friendly, and low in cost. This composite conductive hydrogel, with its excellent comprehensive performance, shows high application potential in flexible sensor devices, especially in human motion monitoring. Attached Figure Description

[0024] Figure 1 Stress-strain curves of the hydrogels prepared in Examples 1-5.

[0025] Figure 2 The relationship between the relative resistance (ΔR / R0) and strain of the P(NIPAm-AETC) / Gly / LDH hydrogel prepared in Example 4.

[0026] Figure 3 The image shows the adhesion performance test results of the P(NIPAm-AETC) / Gly / LDH hydrogel prepared in Example 4 on various substrates. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0028] Example 1

[0029] Dissolve 3.872 g of NIPAm in 1.548 mL of ethanol and stir in a 32 °C water bath until the solution is clear. Then, add 4.84 g of AETC solution (80% by mass) to the solution and continue stirring until completely dissolved. Next, add 8 μL of PEGDA and 15 μL of HMPP (40 μL / mL) to the mixture sequentially, and stir continuously for 30 min to obtain a homogeneous solution.

[0030] The mass ratio of NIPAm to AETC is 1:1; the mass ratio of PEGDA to (NIPAm+AETC) is approximately 0.001:1; and the mass ratio of HMPP to (NIPAm+AETC) is approximately 0.0001:1.

[0031] The resulting mixed solution was poured into a polytetrafluoroethylene mold and heated at 30 °C with a wavelength of 365 nm and a light intensity of 72 mW / cm². 2 The cross-linking reaction was carried out under ultraviolet light irradiation for 30 min, and P(NIPAm-AETC) hydrogel was finally obtained.

[0032] Example 2

[0033] Dissolve 0.155 g Gly and 3.872 g NIPAm in 1.548 mL of ethanol, and stir in a 32 °C water bath until the solution is clear. Then, add 4.84 g of AETC solution (80% by mass) and continue stirring until completely dissolved. Add 8 μL of PEGDA and 15 μL of HMPP (40 μL / mL) to the mixture, and stir for 30 min to obtain a homogeneous solution.

[0034] The mass ratio of NIPAm to AETC is 1:1; the mass ratio of Gly to (NIPAm+AETC) is 0.02:1; the mass ratio of PEGDA to (NIPAm+AETC) is approximately 0.001:1; and the mass ratio of HMPP to (NIPAm+AETC) is approximately 0.0001:1.

[0035] The resulting mixed solution was poured into a polytetrafluoroethylene mold and heated at 30 °C with a wavelength of 365 nm and a light intensity of 72 mW / cm². 2 The cross-linking reaction was carried out under ultraviolet light irradiation for 30 min, and P(NIPAm-AETC) / Gly hydrogel was finally obtained.

[0036] Example 3

[0037] Take 3.872 g of NIPAm and dissolve it in 1.548 mL of ethanol. Stir the solution in a constant temperature water bath at 32 °C until the solution is clear. Then, add 4.84 g of AETC solution (mass percentage concentration of 80%) to the solution and continue stirring until completely dissolved. Next, add NiCoAl-LDH ethanol dispersion (equivalent mass of 4 mg, prepared according to the method disclosed in CN106277072A, the same below) and sonicate to dissolve it. The sonication frequency and temperature are 80 Hz and 25 °C, respectively. Then, add 8 μL of PEGDA and 15 μL of HMPP (concentration of 40 μL / mL) to the above mixed solution in sequence and stir continuously for 30 min to obtain a homogeneous mixed solution.

[0038] The mass ratio of NIPAm to AETC is 1:1; the mass ratio of NiCoAl-LDH to (NIPAm+AETC) is approximately 0.0005:1; the mass ratio of PEGDA to (NIPAm+AETC) is approximately 0.001:1; and the mass ratio of HMPP to (NIPAm+AETC) is approximately 0.0001:1.

[0039] The resulting mixed solution was poured into a polytetrafluoroethylene mold and heated at 30 °C with a wavelength of 365 nm and a light intensity of 72 mW / cm². 2The cross-linking reaction was carried out under ultraviolet light irradiation for 30 min, and P(NIPAm-AETC) / LDH hydrogel was finally obtained.

[0040] Example 4

[0041] 0.155 g Gly and 3.872 g NIPAm were dissolved sequentially in 1.548 mL of ethanol and stirred in a 32 ℃ constant temperature water bath until the solution became clear. Then, 4.84 g of AETC solution (80% by mass) was added to the solution, and stirring continued until completely dissolved. Next, NiCoAl-LDH ethanol dispersion (equivalent to 2 mg) was added, and the solution was sonicated at 80 Hz and 25 ℃. Then, 8 μL of PEGDA and 15 μL of HMPP (40 μL / mL) were added sequentially to the above mixed solution, and stirring was continued for 30 min to obtain a homogeneous mixed solution.

[0042] The mass ratio of NIPAm to AETC is 1:1; the mass ratio of Gly to (NIPAm+AETC) is 0.02:1; the mass ratio of NiCoAl-LDH to (NIPAm+AETC) is approximately 0.00026:1; the mass ratio of PEGDA to (NIPAm+AETC) is approximately 0.001:1; and the mass ratio of HMPP to (NIPAm+AETC) is approximately 0.0001:1.

[0043] The resulting mixed solution was poured into a polytetrafluoroethylene mold and heated at 30 °C with a wavelength of 365 nm and a light intensity of 72 mW / cm². 2 The cross-linking reaction was carried out under ultraviolet light irradiation for 30 min, and P(NIPAm-AETC) / Gly / LDH hydrogel was finally obtained.

[0044] Example 5

[0045] 0.077 g Gly and 3.872 g NIPAm were dissolved sequentially in 1.548 mL of ethanol and stirred in a 32 ℃ constant temperature water bath until the solution became clear. Then, 4.84 g of AETC solution (80% by mass) was added to the solution, and stirring continued until completely dissolved. Next, NiCoAl-LDH ethanol dispersion (equivalent to 4 mg) was added, and the solution was sonicated at 80 Hz and 25 ℃. Then, 8 μL of PEGDA and 15 μL of HMPP (40 μL / mL) were added sequentially to the above mixed solution, and stirring was continued for 30 min to obtain a homogeneous mixed solution.

[0046] The mass ratio of NIPAm to AETC is 1:1; the mass ratio of Gly to (NIPAm+AETC) is approximately 0.01:1; the mass ratio of NiCoAl-LDH to (NIPAm+AETC) is approximately 0.0005:1; the mass ratio of PEGDA to (NIPAm+AETC) is approximately 0.001:1; and the mass ratio of HMPP to (NIPAm+AETC) is approximately 0.0001:1.

[0047] The resulting mixed solution was poured into a polytetrafluoroethylene mold and heated at 30 °C with a wavelength of 365 nm and a light intensity of 72 mW / cm². 2 The cross-linking reaction was carried out under ultraviolet light irradiation for 30 min, and P(NIPAm-AETC) / Gly / LDH hydrogel was finally obtained.

[0048] Figure 1 These are the stress-strain curves of the hydrogels prepared in Examples 1-5. The test results show that the fracture strengths of the hydrogels prepared in Examples 1-5 are 2.60, 3.86, 5.66, 6.30, and 3.83 MPa, respectively; the corresponding elongations at break are 809, 925, 461, 526, and 678%. Among them, the hydrogel prepared in Example 4 exhibits both high fracture strength and good elongation at break, demonstrating the best overall mechanical properties.

[0049] Figure 2 This is the curve showing the relationship between the relative resistance (ΔR / R0) and strain of the hydrogel prepared in Example 4. In the strain range of 0–100%, its sensitivity factor (GF) is 0.72; in the range of 100–400%, GF is 0.88; in the range of 400–500%, GF is 1.32; and in the range of 500–600%, GF is 1.50. The results indicate that this hydrogel exhibits stable and tunable resistance response characteristics over a wide strain range, meeting the conductivity and stability requirements of flexible strain sensing applications.

[0050] Figure 3 The results show the adhesion performance of the hydrogel prepared in Example 4 on different substrates (aluminum, iron, plastic, copper, and glass). It exhibits adhesion strengths of 33.46, 54.73, 90.05, 25.07, and 92.75 kPa on different substrate surfaces, with corresponding peel times of 1.02, 1.28, 3.31, 0.89, and 1.55 s. The test results demonstrate that the hydrogel prepared in this invention maintains high adhesion strength and suitable peel time on various substrates, exhibiting excellent adhesion performance.

Claims

1. A P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel, characterized in that, It is prepared by UV curing and crosslinking reaction of the following components: N-isopropylacrylamide (NIPAm), acryloyloxyethyltrimethylammonium chloride (AETC), glycerol (Gly), layered double hydroxide (LDH), polyethylene glycol diacrylate (PEGDA), 2-hydroxy-2-methylphenylacetone (HMPP) and solvent; In this process, PEGDA is used as a crosslinking agent, HMPP is used as a photoinitiator, NIPAm is copolymerized with AETC to form a hydrogel matrix, AETC provides cationic groups to improve conductivity and enhance adhesion to various substrates, Gly enhances toughness and recovery performance through dynamic hydrogen bonding, and LDH is used as a filler to improve the conductivity and structural stability of the hydrogel.

2. The P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel as described in claim 1, characterized in that, The mass ratio of NIPAm to AETC is 0.8~1.2:0.8~1.2, the mass ratio of Gly to (NIPAm+AETC) is 0.01~0.02:1, the mass ratio of LDH to (NIPAm+AETC) is 0.0002~0.0006:1, the mass ratio of PEGDA to (NIPAm+AETC) is 0.0005~0.0015:1, and the mass ratio of HMPP to (NIPAm+AETC) is 0.00005~0.00015:

1.

3. The P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel as described in claim 1 or 2, characterized in that, The layered double hydroxide (LDH) is nickel cobalt aluminum-layered double hydroxide (NiCoAl-LDH).

4. A method for preparing the P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel as described in claim 1, 2, or 3, characterized in that, The steps are as follows: Step 1: Dissolve Gly and NIPAm in ethanol sequentially, add AETC and stir until homogeneous to obtain a clear and transparent precursor solution; Step 2: Add LDH dispersion to the precursor solution and obtain a uniform dispersion by ultrasonic treatment; Step 3: Add PEGDA and HMPP to the dispersion, stir and sonicate to mix; Step 4: Pour the mixed solution into a mold and perform a UV curing crosslinking reaction to obtain P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel.

5. The preparation method according to claim 4, characterized in that, In step 1, the stirring and dissolving temperature is 32~35 ℃, and the stirring speed is 300~400 rpm.

6. The preparation method according to claim 4, characterized in that, In step 2, the concentration of the LDH dispersion is 2.5~3 mg / mL, and the dispersion medium is ethanol.

7. The preparation method according to claim 4, characterized in that, The ultrasonic dispersion frequency in steps 2 and 3 is 80 Hz, and the ultrasonic temperature is 25~28 ℃.

8. The preparation method according to claim 4, characterized in that, The curing temperature in step 4 is 25~30 ℃, and the curing time is 20~30 min.

9. The application of the P(NIPAm-AETC) / Gly / LDH composite conductive hydrogel as described in claim 1, 2 or 3 in flexible sensors or wearable electronic devices.

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