Preparation method of high-sensitivity anti-freezing composite hydrogel based on multiple synergistic effects

Abstract

The invention relates to the technical field of polymer nano composite materials, and particularly discloses a preparation method of high-sensitivity anti-freezing composite hydrogel based on multiple synergistic effects and application of the high-sensitivity anti-freezing composite hydrogel in the field of flexible sensing. According to the method, a blending system of cellulose nanofibers (CNF) and 3, 4-ethylenedioxythiophene-polystyrene sulfonate (EDOT: PSS) is innovatively adopted as a conductive reinforcement phase, in-situ polymerization reaction is induced through a redox initiation system, and nanocellulose / PEDOT: PSS composite dispersion liquid is constructed; and further carrying out free radical copolymerization reaction with an acrylamide (AM) monomer and a lithium chloride (LiCl) antifreeze agent to form the composite hydrogel with an interpenetrating network structure. Wherein a multi-hydrogen bond cross-linked network is formed between the CNF and a polymer matrix through rich hydroxyl groups on the surface of the CNF, so that the mechanical strength of the hydrogel is macroscopically improved; a PEDOT conductive chain constructs a continuous conductive path in a three-dimensional network, so that the conductivity of the hydrogel is enhanced; liCl destroys ice crystal growth kinetics through hydration, the freezing point of the system is reduced to-40 DEG C or below, and meanwhile, the LiCl and a CNF-PAM matrix generate ion-dipole interaction to synergistically inhibit the phase separation phenomenon in a low-temperature environment. The hydrogel has excellent mechanical adaptability, wide temperature range stability and rapid strain response characteristics, and can be widely applied to flexible electronic devices, biomedical sensing and intelligent wearable equipment in extreme environments.

Description

Technical Field

[0001] The present invention belongs to the field of polymer nanocomposites, and particularly relates to a method for preparing a composite hydrogel with toughness, conductivity, high sensitivity and freeze resistance, and a composite hydrogel prepared by this method and its applications. Background Art

[0002] With the continuous and rapid development of the world economy, the pressure on energy and the environment is increasing continuously. Since fossil fuel resources are limited, energy has become a huge crisis gradually faced by mankind. The transformation and development of renewable energy conversion technologies is the engine for the green transformation of the global economy. Cellulose is one of the most abundant natural renewable resources in nature, with the advantages of being renewable, inexpensive, environmentally friendly, and biodegradable, and has been widely used in the fields of papermaking, biology, and energy storage. With the rapid development of nanotechnology in the direction of biomass refining, researchers have found that nanocellulose prepared from cellulose not only has the properties of cellulose, but also has characteristics such as a large aspect ratio, a high specific surface area, a low density, and a three-dimensional cross-linked structure, and has become a good precursor for preparing hydrogels. Constructing multifunctional composite hydrogel materials with excellent mechanical properties using nanocellulose is of dual significance for reducing environmental pollution and slowing down energy consumption.

[0003] In 1987, researchers Skotheim et al. first reported a method for converting 3,4-ethylenedioxythiophene (abbreviated as EDOT) into a polymer with conductive properties. They used an oxidant (such as iron peroxide) for chemical oxidation to polymerize EDOT into PEDOT. PEDOT, poly(ethylene glycol)dithiophene, is an organic conductive polymer with high electrical conductivity, excellent mechanical and thermal stability, and adjustable optical and electrochemical properties. Therefore, it has a wide range of applications in the fields of electronics, optoelectronics, and energy. The composite material of PEDOT and cellulose hydrogel can be used to prepare a flexible sensor. This sensor can be used to monitor physical quantities such as bending, stretching, and pressure. Due to the conductive properties of PEDOT, the sensor can achieve highly sensitive signal detection and has good flexibility, and can adapt to a variety of complex environments. The negatively charged property of PSS can interact with the positively charged PEDOT to form a stable PEDOT:PSS complex. This interaction helps to prevent the aggregation of PEDOT particles and improve the stability and mechanical strength of the composite material. By adjusting the concentration and molecular weight of PSS, the dispersion state of PEDOT particles can be controlled to make them evenly distributed on the substrate.

[0004] The prior art, such as CN202011474226.7, discloses a preparation method of an antifreeze self-healing conductive hydrogel. The conductive nanofiller / nanocellulose / polyacrylamide hydrogel is immersed in an aqueous solution of a composite modifier containing an antifreeze agent and a metal salt. The metal salt synergistically with the antifreeze agent component displaces water molecules in the hydrogel network system, reduces the freezing point of water in the composite hydrogel network structure, and improves its antifreeze performance; the metal cations form reversible ionic bonds with cellulose in the composite hydrogel, and cellulose forms reversible hydrogen bond interactions with polyacrylamide, and the formed multiple reversible networks endow the prepared hydrogel with excellent mechanical strength; and the metal salt synergistically with the conductive nanofiller endows the prepared hydrogel with excellent electrical conductivity, sensitive sensing performance and mechanical flexibility to meet the requirements of corresponding application scenarios.

[0005] The prior art, such as CN202311171051.6, discloses a self-adhesive antifreeze moisturizing multifunctional conductive hydrogel and a preparation method thereof. A deep eutectic solvent prepared from a hydrogen bond acceptor and a hydrogen bond donor is mixed with an alkali solution as a polymerization medium, a conductive component and an antifreeze component of a polyacrylamide hydrogel, nano-cellulose is used as a toughening material, and polydopamine is used as an adhesive component, and a self-adhesive antifreeze hydrogel is obtained through a polymerization reaction.

[0006] There is no research on cellulose nanofibers / PEDOT:PSS as a functional additive to enhance the mechanical properties and electrical conductivity of hydrogels in the above prior art. Cellulose can provide more hydrogen bond sites to construct multiple reversible networks for the hydrogel to enhance the mechanical properties of the hydrogel. PEDOT, as a conductive material, further enhances the electrical conductivity of the hydrogel.

[0007] Therefore, it is necessary to improve and expand the existing methods for preparing hydrogels so that the prepared hydrogels have richer functionality. Summary of the Invention

[0008] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a highly sensitive, antifreeze composite hydrogel, a preparation method and an application thereof. The present invention improves the existing method for preparing hydrogels. The composite hydrogel prepared by the present invention has good mechanical properties and sensitivity, and has stable mechanical properties and sensing properties at -40°C.

[0009] Based on the above purpose, the technical solution adopted by the present invention is as follows:

[0010] In the first aspect, the present invention provides a preparation method of a highly sensitive, antifreeze composite hydrogel, comprising the following steps:

[0011] S1: Disperse cellulose nanofibers in water to form a cellulose nanofiber suspension. Add EDOT and PSS to the cellulose nanofiber suspension and mix evenly to obtain a cellulose nanofiber / EDOT:PSS dispersion. Then add sodium persulfate and FeCl3 to the cellulose nanofiber / EDOT:PSS dispersion to initiate the polymerization of EDOT to prepare a cellulose nanofiber / PEDOT:PSS dispersion.

[0012] S2: Add LiCl and acrylamide to the prepared cellulose nanofiber / PEDOT:PSS dispersion in step S1, and mix evenly to obtain a cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion.

[0013] S3: Pour the dispersion in S2 into a glass bottle, and add N,N'-methylenebisacrylamide, N,N,N',N'-tetramethylethylenediamine, and ammonium persulfate to initiate the polymerization of acrylamide to prepare a cellulose nanocellulose / PEDOT:PSS / polyacrylamide / LiCl composite hydrogel.

[0014] The present invention uses cellulose nanofibers, PEDOT:PSS, acrylamide, and LiCl as raw materials. First, the cellulose nanofibers and EDOT:PSS are dispersed in water and then mixed evenly to undergo a polymerization reaction to prepare a cellulose nanofiber / PEDOT:PSS dispersion, and the cellulose nanofibers are used to effectively inhibit the aggregation of PEDOT. Then, acrylamide and LiCl are mixed with the cellulose nanofiber / PEDOT:PSS dispersion to prepare a cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl composite hydrogel. The addition of cellulose nanofibers in the composite hydrogel increases the hydrogen bond sites of the molecular chains microscopically, thereby improving the mechanical strength of the hydrogel macroscopically. PEDOT enhances the conductivity of the hydrogel, and LiCl, as a metal salt, reduces the freezing point of water in the hydrogel, effectively inhibiting the freezing of the hydrogel in a cold environment, making the hydrogel have outstanding flexibility, conductivity, and antifreeze properties, and playing an important role in the design and manufacture of wearable sensors.

[0015] Preferably, in the cellulose nanofiber / EDOT:PSS dispersion, the mass ratio of cellulose nanofibers, EDOT, and PSS is 1:0.9:0.8. In addition, the concentration of the cellulose nanofibers is 1 wt%.

[0016] Preferably, the mass ratio of acrylamide to cellulose nanofibers is 10:1. The mass ratios of LiCl to acrylamide are 3:10, 3:5, and 9:10, respectively.

[0017] It was found through experiments that if the proportion of LiCl is higher than the above range, the flexibility of the hydrogel after mixing becomes weaker, and it is not easy to deform, resulting in poor sensing performance of the hydrogel;

[0018] Preferably, the cellulose nanofiber suspension is mixed with EDOT:PSS under stirring, and ultrasonically dispersed evenly to form a cellulose nanofiber / EDOT:PSS dispersion. Then, sodium persulfate and FeCl3 are added to the cellulose nanofiber / EDOT:PSS dispersion under stirring to obtain a cellulose nanofiber / PEDOT:PSS dispersion.

[0019] Preferably, the polymerization reaction time of EDOT is 24 hours.

[0020] Preferably, the cellulose nanofiber / PEDOT:PSS is washed twice with a methanol / water mixture, then washed three times repeatedly with deionized water, and finally a cellulose nanofiber / PEDOT:PSS suspension is obtained after ultrasonication.

[0021] Preferably, the centrifugation speed is 10000 r / min and the centrifugation time is 15 min; the ultrasonic frequency is 60 - 100 KHz and the ultrasonic time is 20 - 30 min.

[0022] Preferably, the concentrations of N,N′-methylenebisacrylamide, N,N,N′,N′-tetramethylethylenediamine, and ammonium persulfate are 0.08%, 0.2%, and 0.8% (relative to the mass of acrylamide).

[0023] Preferably, in step S3, the process needs to be carried out in an ice-water bath.

[0024] In a second aspect, the present invention provides a highly sensitive and freeze-resistant composite hydrogel prepared by the above preparation method.

[0025] Preferably, the highly sensitive and freeze-resistant composite hydrogel prepared by the present invention has a compressive strength of 0.8 - 0.91 MPa under 75% compressive strain and has stable mechanical properties at -40°C. The hydrogel undergoes a high compressive strain of 50% without significant geometric deformation and exhibits a high stress retention rate of 90.1% after 100 cycles.

[0026] In a third aspect, the present invention provides the application of the above highly sensitive and freeze-resistant composite hydrogel in a flexible sensor.

[0027] The composite hydrogel prepared by the present invention has good mechanical strength, flexibility, freeze resistance, and high sensitivity, so that it has high application prospects in the field of flexible sensors.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. The present invention prepares a highly sensitive, highly conductive and antifreeze composite hydrogel by adjusting the mixing method of cellulose nanofibers, PEDOT:PSS, acrylamide, and LiCl. The cellulose nanofibers not only play a role in skeleton support, but also the intertwined cellulose nanofibers provide more sites for forming hydrogen bonds in the composite hydrogel, thereby enhancing the mechanical properties of the hydrogel. With the addition of the conductive polymer PEDOT:PSS, the conductivity of the hydrogel is increased. The doping of LiCl enhances the water interaction and mechanical strength of the hydrogel, not only reducing the freezing point of the hydrogel, but also regulating the interaction between PAM chains, and establishing a denser cross-linked network for the hydrogel. This further broadens the application fields of the composite hydrogel and also conforms to the concept of sustainable development of contemporary new energy.

[0030] 2. The highly sensitive and antifreeze composite hydrogel prepared by the preparation method of the present invention does not produce significant geometric deformation under 50% compressive strain and exhibits a high stress retention rate of not less than 90% after 100 cycles. In addition, it also has excellent antifreeze performance and still maintains good flexibility at -40°C.

[0031] 3. The highly sensitive and antifreeze composite hydrogel prepared by the preparation method of the present invention has high application prospects in the field of flexible sensors and is expected to provide a new multifunctional platform for devices such as wearable electronic devices, electronic skin, and human motion monitoring.

[0032] In summary, based on the abundant oxygen-containing functional groups on the surface of cellulose nanofibers, hydrogen bond interaction is formed with the surface of polyacrylamide. The cellulose nanofibers provide a double cross-linked network structure for the polyacrylamide hydrogel. PEDOT:PSS provides conductive substances for the composite hydrogel, improves its conductivity, and enhances the sensitivity of the composite hydrogel. LiCl strengthens the hydration between water molecules, reduces the freezing point of the hydrogel, prevents the formation of ice, and enables the hydrogel to have stability and antifreeze performance in a cold environment. The cellulose nanofiber / PEDOT:PSS / polyacrylamide / LiCl composite hydrogel prepared by the present invention not only has good mechanical properties and antifreeze performance, but also has excellent conductivity and great application prospects in the field of flexible sensors. Description of the Drawings

[0033] Figure 1 It is the compression diagram of the composite hydrogel in Example 1;

[0034] Figure 2 It is the compression curve of the composite hydrogel in Example 1 under 75% strain;

[0035] Figure 3 It is the compression curve of the composite aerogel in Example 2 under 75% strain;

[0036] Figure 4 It is the compression curve of the composite aerogel at 75% strain in Example 3. Figure 5 It is the mechanism diagram of the preparation process of the composite aerogel in the example. Detailed implementation manners

[0037] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The test methods used in the examples are all conventional methods unless otherwise specified; the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0038] Example 1

[0039] A highly sensitive and antifreeze composite hydrogel and its preparation method and application, comprising the following steps:

[0040] (1) Preparation of cellulose nanofiber / PEDOT:PSS dispersion

[0041] Add 206 μL of EDOT and 218 μL of PSS to 0.3 g of cellulose nanofibers (mass fraction of 1 wt%). Stir with a magnetic stirrer at room temperature for 15 minutes. Then, add 5 g of sodium persulfate and 1 mg of FeCl3 to the cellulose nanofiber / EDOT:PSS dispersion, and stir at 500 rpm for 30 min. After reacting for 24 h, cellulose nanofiber / PEDOT:PSS is obtained. Wash the cellulose nanofiber / PEDOT:PSS with a methanol / water mixture (mass ratio of 1:1) twice, and centrifuge to remove impurities. Then wash repeatedly with deionized water three times. Finally, ultrasonicate to obtain a cellulose nanofiber / PEDOT:PSS dispersion with a concentration of 1 wt%.

[0042] (2) Preparation of cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion

[0043] Add 3 g of acrylamide to 3 ml of the cellulose nanofiber / PEDOT:PSS suspension (1 wt%) (i.e., the dispersion obtained in step (1) of Example 1), and stir for 30 min to ensure uniform mixing. Then add 0.9 g of LiCl to the mixed solution and stir for 30 min to ensure complete dissolution of LiCl. A cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion is obtained.

[0044] (3) Preparation of cellulose nanofiber / PEDOT:PSS / polyacrylamide composite hydrogel

[0045] Pour the cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion (i.e., the dispersion obtained in step (2) of Example 1) into a glass bottle, continuously stir it in an ice-water bath for 3 min, and simultaneously add 2.4 mg of MBA, 30 μL of TEMED, and 24 mg of APS to initiate the polymerization reaction of acrylamide to form polyacrylamide, obtaining a cellulose nanofiber / PEDOT:PSS / polyacrylamide composite hydrogel. The polymerization reaction is carried out at room temperature.

[0046] The compressive strength of the cellulose nanofiber / PEDOT:PSS / polyacrylamide composite hydrogel prepared in this example is as Figure 1-2 shown. At a compressive strain of 75%, the pressure is 0.56 MPa, and the dissipated energy is 32.84 KJ / m3. According to DSC testing, the composite hydrogel shows a heat absorption peak at -25.4 °C. The hydrogel still maintains its original shape at -20 °C without freezing.

[0047] Example 2

[0048] A highly sensitive and freeze-resistant composite hydrogel, its preparation method and application, including the following steps:

[0049] (1) Preparation of cellulose nanofiber / PEDOT:PSS dispersion

[0050] Add 206 μL of EDOT and 218 μL of PSS to 0.3 g of cellulose nanofibers (mass fraction 1 wt%). Stir with a magnetic stirrer at room temperature for 15 minutes. Then, add 5 g of sodium persulfate and 1 mg of FeCl3 to the cellulose nanofiber / EDOT:PSS dispersion and stir at 500 rpm for 30 min. After reacting for 24 h, cellulose nanofiber / PEDOT:PSS is obtained. Wash the cellulose nanofiber / PEDOT:PSS twice with a methanol / water mixture (1:1 mass ratio) and centrifuge to remove impurities. Then wash it repeatedly with deionized water three times. Finally, ultrasonicate to obtain a 1 wt% cellulose nanofiber / PEDOT:PSS dispersion.

[0051] (2) Preparation of cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion

[0052] Add 3 g of acrylamide to 3 ml of the cellulose nanofiber / PEDOT:PSS suspension (1 wt%) (i.e., the dispersion obtained in step (1) of Example 2), stir for 30 min to ensure uniform mixing. Then add 1.8 g of LiCl to the mixed solution and stir for 30 min to ensure complete dissolution of LiCl. Obtain a cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion.

[0053] (3) Preparation of Cellulose Nanofiber / PEDOT:PSS / Polyacrylamide Composite Hydrogel

[0054] Pour the cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion (i.e., the dispersion obtained in step (2) of Example 2) into a glass bottle, continuously stir it in an ice-water bath for 3 min, and simultaneously add 2.4 mg of MBA, 30 μL of TEMED, and 24 mg of APS to initiate the polymerization reaction of acrylamide to generate polyacrylamide, thus obtaining the cellulose nanofiber / PEDOT:PSS / polyacrylamide composite hydrogel. The polymerization reaction is carried out at room temperature.

[0055] The compressive strength of the cellulose nanofiber / PEDOT:PSS / polyacrylamide composite hydrogel prepared in this example is as Figure 3 shown. At a compressive strain of 75%, the pressure is 0.76 MPa and the dissipated energy is 37.94 KJ / m3. According to the DSC test, a heat absorption peak appears in the composite hydrogel at -41.0 °C. The hydrogel still maintains its original shape at -40 °C and no freezing phenomenon occurs.

[0056] Example 3

[0057] A highly sensitive and freeze-resistant composite hydrogel, its preparation method and application, comprising the following steps:

[0058] (1) Preparation of Cellulose Nanofiber / PEDOT:PSS Dispersion

[0059] Add 206 μL of EDOT and 218 μL of PSS to 0.3 g of cellulose nanofibers (mass fraction 1 wt%). Stir with a magnetic stirrer at room temperature for 15 minutes. Then, add 5 g of sodium persulfate and 1 mg of FeCl3 to the cellulose nanofiber / EDOT:PSS dispersion and stir at 500 rpm for 30 min. After reacting for 24 h, cellulose nanofiber / PEDOT:PSS is obtained. Wash the cellulose nanofiber / PEDOT:PSS twice with a methanol / water mixture (mass ratio 1:1) and centrifuge to remove impurities. Then wash it repeatedly with deionized water three times. Finally, ultrasonicate to obtain a 1 wt% cellulose nanofiber / PEDOT:PSS dispersion.

[0060] (2) Preparation of Cellulose Nanofiber / PEDOT:PSS / Acrylamide / LiCl Dispersion

[0061] Add 3 g of acrylamide to 3 ml of cellulose nanofiber / PEDOT:PSS suspension (1 wt%) (i.e., the dispersion obtained in step (1) of Example 3), and stir for 30 min to ensure uniform mixing. Then add 2.7 g of LiCl to the mixed solution and stir for 30 min to ensure complete dissolution of LiCl. A cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion is obtained.

[0062] (3) Preparation of cellulose nanofiber / PEDOT:PSS / polyacrylamide composite hydrogel

[0063] Pour the cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion (i.e., the dispersion obtained in step (2) of Example 3) into a glass bottle, continuously stir in an ice-water bath for 3 min, and simultaneously add 2.4 mg of MBA, 30 μL of TEMED, and 24 mg of APS to initiate the polymerization reaction of acrylamide to form polyacrylamide, obtaining a cellulose nanofiber / PEDOT:PSS / polyacrylamide composite hydrogel. The polymerization reaction is carried out at room temperature.

[0064] The compressive strength of the cellulose nanofiber / PEDOT:PSS / polyacrylamide composite hydrogel prepared in this example is as Figure 4 shown. At a compressive strain of 75%, the pressure is 0.91 MPa and the dissipated energy is 41.94 KJ / m3. According to DSC testing, no heat absorption peak appears in the composite hydrogel at -60.0 °C.

[0065] In summary, based on the abundant oxygen-containing functional groups on the surface of cellulose nanofibers, hydrogen bond interactions are formed with the surface of polyacrylamide. The cellulose nanofibers provide a double-crosslinked network structure for the polyacrylamide hydrogel. PEDOT:PSS provides conductive substances for the composite hydrogel, improving its conductivity and enhancing the sensitivity of the composite hydrogel. LiCl strengthens the hydration between water molecules, lowers the freezing point of the hydrogel, prevents the formation of ice, and enables the hydrogel to have stability and freeze resistance in a cold environment. The cellulose nanofiber / PEDOT:PSS / polyacrylamide / LiCl composite hydrogel prepared by the present invention not only has good mechanical properties and freeze resistance, but also has excellent conductivity, and has great application prospects in the field of flexible sensors.

Claims

1. A preparation method of a high-sensitivity and freeze-resistant composite hydrogel, characterized in that, The preparation method comprises the following steps: S1: Dispersing cellulose nanofibers in water to form a cellulose nanofiber suspension, adding EDOT and PSS to the cellulose nanofiber suspension, and uniformly mixing to obtain a cellulose nanofiber / EDOT:PSS dispersion; then adding sodium persulfate and FeCl3 to the cellulose nanofiber / EDOT:PSS dispersion to initiate the polymerization of EDOT to prepare a cellulose nanofiber / PEDOT:PSS dispersion; S2: Adding LiCl and acrylamide to the cellulose nanofiber / PEDOT:PSS dispersion prepared in step S1, and uniformly mixing to obtain a cellulose nanofiber / PEDOT:PSS / acrylamide / LiCl dispersion; S3: Pouring the dispersion in S2 into a glass bottle, adding N,N′-methylenebisacrylamide, N,N,N′,N′-tetramethylethylenediamine, and ammonium persulfate to initiate the polymerization of acrylamide to prepare a cellulose nanocellulose / PEDOT:PSS / polyacrylamide / LiCl composite hydrogel.

2. The preparation method of the highly sensitive and freeze-resistant composite hydrogel according to claim 1, wherein, In the cellulose nanofiber / EDOT:PSS dispersion, the mass ratio of cellulose nanofibers, EDOT, and PSS is 1:0.9:0.

8. In addition, the concentration of the cellulose nanofibers is adjusted to 1 wt%.

3. The preparation method of the highly sensitive and freeze-resistant composite hydrogel according to claim 1, characterized in that, The mass ratio of acrylamide to cellulose nanofibers is 10:1; the mass ratio of LiCl is 0.3 - 0.9 (w / v, based on the volume of cellulose nanofiber / PEDOT:PSS).

4. The preparation method of the highly sensitive and freeze-resistant composite hydrogel according to claim 1, wherein Mixing the cellulose nanofiber suspension with EDOT:PSS under stirring, and ultrasonically dispersing uniformly to form a cellulose nanofiber / EDOT:PSS dispersion, and then adding sodium persulfate and FeCl3 to the cellulose nanofiber / EDOT:PSS dispersion under stirring to obtain a cellulose nanofiber / PEDOT:PSS dispersion.

5. The preparation method of the highly sensitive and freeze-resistant composite hydrogel according to claim 1, characterized in that The polymerization reaction time of EDOT is 24 hours.

6. The preparation method of the highly sensitive and freeze-resistant composite hydrogel according to claim 1, characterized in that Washing the nanocellulose fiber / PEDOT:PSS twice with a methanol / water mixture. Then repeating the washing three times with deionized water. Finally, obtaining a cellulose nanofiber / PEDOT:PSS suspension after ultrasonic treatment.

7. The preparation method of the highly sensitive and freeze-resistant composite hydrogel according to claim 6, characterized in that, The rotation speed of the centrifugation is 10000 r / min, and the centrifugation time is 15 min; the ultrasonic frequency is 60 - 100 KHz, and the ultrasonic time is 20 - 30 min.

8. The preparation method of the highly sensitive and freeze-resistant composite hydrogel according to claim 1, wherein In step S3, the concentrations of N,N′-methylenebisacrylamide, N,N,N′,N′-tetramethylethylenediamine, and ammonium persulfate are 0.08%, 0.2%, and 0.8% (relative to the mass of acrylamide).

9. The preparation method of the highly sensitive and antifreeze composite hydrogel according to claim 1, characterized in that, In step S3, the process needs to be carried out in an ice-water bath.

10. A high-sensitivity and freeze-resistant composite hydrogel, characterized in that, The high-sensitivity and antifreeze composite hydrogel is prepared by the preparation method according to any one of claims 1 - 9.

11. The highly sensitive and freeze-resistant composite hydrogel according to claim 10, wherein The compressive strength of the high-sensitivity and freeze-resistant composite hydrogel is 0.8 to 0.91 MPa, and it has a high sensitivity of 7.7 to 10.3 MPa. -1 Moreover, it has stable mechanical properties and sensing properties at -40°C.

12. Application of the high-sensitivity and antifreeze composite hydrogel according to claim 10 or 11 in a flexible sensor.

Images