A freeze-resistant, dehydration-resistant, adhesive, and conductive hydrogel, its rapid curing preparation method and application

Abstract

This invention discloses an antifreeze, dehydration-resistant, adhesive, and conductive hydrogel, along with its rapid curing preparation method and applications, belonging to the field of polymer hydrogel technology. The hydrogel comprises a cross-linked polymer, water, nanofibers, lithium salt, and polyphenols. The preparation process involves first dissolving the cross-linked polymer monomer, lithium salt, and polyphenols in a nanofiber suspension. Then, under ice bath conditions, the additives are uniformly mixed with the nanofiber / cross-linked polymer monomer / lithium salt / polyphenol dispersion. An initiator and cross-linking agent are then added, and the mixture is rapidly cured at room temperature via free radical polymerization. The presence of inorganic salt ions in this invention not only endows the hydrogel with excellent ionic conductivity but also, due to their strong hydration with water molecules, inhibits ice crystal formation in the gel network at low temperatures while effectively reducing water evaporation at room temperature, thus endowing the hydrogel with antifreeze and dehydration-resistant properties. Furthermore, the polyphenols provide abundant free phenolic hydroxyl groups, resulting in good adhesion. The hydrogel of this invention can be applied in fields such as flexible wearable sensors.

Description

Technical Field

[0001] This invention belongs to the field of polymer hydrogel technology, specifically relating to an antifreeze, dehydration-resistant, adhesive, and conductive hydrogel, as well as its rapid curing preparation method and application. Background Technology

[0002] In recent years, flexible electronic devices have developed rapidly, showing excellent application prospects in fields such as flexible energy storage devices, wearable devices, and soft robots. Conductive hydrogels combine the flexibility of hydrogels with the electrochemical properties of conductive polymers, making them ideal materials for constructing flexible electronic devices. Although significant progress has been made in conductive hydrogels, problems such as adhesion and narrow applicable temperature range still exist in practical applications. On the one hand, most hydrogels lack adhesive properties and usually require other adhesives (such as 3M tape) to adhere to the substrate surface. On the other hand, traditional conductive hydrogels have a high water content, making them sensitive to the external environment, and water molecules cannot be firmly locked within the gel network. This water inevitably forms ice crystals at low temperatures, causing the hydrogel to freeze and lose its elasticity. Even at room temperature, water molecules evaporate easily, causing the hydrogel to quickly dehydrate and dry out, rendering it unable to function properly, greatly limiting the practical applications of hydrogels. Furthermore, the traditional preparation process of adhesive hydrogels is usually time-consuming, requiring high temperatures or long curing times, which is difficult to meet the efficiency requirements of industrial production. Therefore, developing a hydrogel that integrates low-temperature resistance, dehydration resistance, adhesion, and conductivity, and can be rapidly solidified, has significant practical implications and broad application prospects. Summary of the Invention

[0003] To overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a rapid curing preparation method for antifreeze, dehydration-resistant, adhesive, and conductive hydrogels.

[0004] Another object of the present invention is to provide the above-described antifreeze, anti-dehydration, adhesive, and conductive hydrogel.

[0005] Another object of the present invention is to provide applications of the above-mentioned antifreeze, dehydration-resistant, adhesive, and conductive hydrogels.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0007] A method for preparing an antifreeze, dehydration-resistant, adhesive, and conductive hydrogel includes the following steps:

[0008] (1) Dissolve cross-linked polymer monomers, lithium salts and polyphenols in nanofiber suspension, and stir evenly to obtain nanofiber / cross-linked polymer monomer / lithium salt / polyphenol dispersion;

[0009] (2) Under ice bath conditions, the additives are mixed evenly with the nanofiber / crosslinking polymer monomer / lithium salt / polyphenol dispersion, and then the initiator and crosslinking agent are added. Free radical polymerization reaction is carried out at room temperature to obtain hydrogel.

[0010] The lithium salt mentioned is lithium chloride;

[0011] The polyphenols mentioned are tannic acid;

[0012] The auxiliary agent is N,N,N′,N′-tetramethylethylenediamine, sodium hydroxide, or potassium hydroxide;

[0013] In the hydrogel, the mass ratio of polyphenol to water is 0.0017:1 to 0.013:1.

[0014] Preferably, the crosslinking polymer monomer is acrylamide.

[0015] Preferably, the nanofibers are one of cellulose nanofibers, cellulose nanocrystals, bacterial cellulose, chitin nanocrystals, sodium alginate nanofibers, and starch nanocrystals.

[0016] Preferably, the initiator is ammonium persulfate.

[0017] Preferably, the crosslinking agent is N,N-methylenebisacrylamide.

[0018] Preferably, the mass ratio of lithium salt to water in the hydrogel is 0.1 to 0.5:1, more preferably 0.5:1.

[0019] Preferably, in the hydrogel, the mass ratio of crosslinked polymer to water is 0.25:1 to 0.5:1.

[0020] Preferably, in the hydrogel, the mass ratio of nanofibers to water is 0.01:1 to 0.1:1.

[0021] Preferably, the mass ratio of the initiator, crosslinking agent, auxiliaries to the crosslinking polymer monomer is (0.05-0.06):(0.001-0.002):(0.01-0.02):1.

[0022] Preferably, the reaction time is 55-250 s.

[0023] An antifreeze, dehydration-resistant, adhesive, and conductive hydrogel prepared by any of the above preparation methods, the hydrogel comprising a crosslinking polymer, water, nanofibers, lithium salt, and polyphenols; wherein the crosslinking polymer is polymerized from acrylamide monomers.

[0024] The above describes the application of an antifreeze, dehydration-resistant, adhesive, and conductive hydrogel in flexible wearable sensors.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] (1) The method of this invention for preparing antifreeze, dehydration-resistant, adhesive, and conductive hydrogels does not require additional light or heat support and can be carried out at room temperature. It also overcomes the inherent limitation of catechol-containing components not participating extensively in free radical polymerization, and curing can be completed in just 55-250 seconds. Compared to traditional preparation methods (which typically take several hours or require light or heat support), this method significantly shortens the gel curing time and greatly improves preparation efficiency, providing favorable support for large-scale applications and rapid on-site preparation.

[0027] (2) The antifreeze, dehydration-resistant, adhesive, and conductive hydrogel prepared by the present invention introduces a large number of inorganic salt ions, which not only gives the hydrogel excellent ionic conductivity, but also the strong hydration between inorganic salt ions and water molecules enables the water in the gel network to inhibit the formation of ice crystals at low temperatures, while effectively reducing water evaporation at room temperature, so that the hydrogel will not freeze at low temperatures and will not dehydrate and dry when stored at room temperature.

[0028] (3) The antifreeze, dehydration-resistant, adhesive, and conductive hydrogel prepared by the present invention can still adhere to various substrate surfaces after being stored in a low-temperature environment, and can be applied to fields such as flexible wearable sensors. Attached Figure Description

[0029] Figure 1 Differential scanning calorimetry curves of the antifreeze, anti-dehydration, adhesive, and conductive hydrogels prepared in Example 1.

[0030] Figure 2 The image shows the adhesion behavior of the antifreeze, anti-dehydration, adhesive, and conductive hydrogel prepared in Example 1 at -40°C.

[0031] Figure 3 The ionic conductivity of the antifreeze, anti-dehydration, adhesive, and conductive hydrogel prepared in Example 1 at different temperatures.

[0032] Figure 4 The graph shows the relative resistance change rate under 50% strain when the antifreeze, dehydration-resistant, adhesive, and conductive hydrogel prepared in Example 1 is applied to a flexible wearable sensor.

[0033] Figure 5 Photographs of the antifreeze, dehydration-resistant, adhesive, and conductive hydrogel prepared in Example 1 during gel formation.

[0034] Figure 6 A photograph of the product prepared for Comparative Example 5. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. For process parameters not specifically specified, conventional techniques can be referred to.

[0036] The method for testing the freeze-thaw resistance of the hydrogel prepared in this invention is as follows: The freeze-thaw resistance of the hydrogel is analyzed using a differential scanning calorimeter (DSC, TAQ200). 5–10 mg of sample is weighed and sealed in a DSC sample pan. Under a nitrogen atmosphere (gas flow rate of 50 mL / min), the temperature is lowered from 25°C to -150°C at a cooling rate of 5°C / min, held at this temperature for 15 min, and then heated back to 25°C at a heating rate of 5°C / min.

[0037] The adhesion test method of the hydrogel prepared in this invention is as follows: after placing the hydrogel in an environment of -40℃ for 2 hours, it is quickly taken out and its adhesion behavior to different matrices (glass, polytetrafluoroethylene, natural rubber, stainless steel) is tested.

[0038] The conductivity testing method for the hydrogel prepared in this invention is as follows: The hydrogel is cut into strips of 10mm × 10mm × 2mm and sandwiched between two titanium sheets to form a sandwich structure. Its conductivity at 1000 nm is scanned using an electrochemical workstation (CHI660e). -2 ~10 5 AC impedance spectrum in the Hz frequency range. Ionic conductivity σ is calculated using the formula: σ = L / (R b ×S), L is the thickness (m) of the hydrogel test, R b S represents the internal resistance (Ω) of the hydrogel electrolyte obtained from impedance data, and S represents the effective contact area (m²) between the hydrogel sample and the platinum sheet. 2 ).

[0039] The application research method of the hydrogel prepared in this invention is as follows: the prepared hydrogel is connected to a wire, and the corresponding resistance change of the hydrogel is recorded using an LCR meter (VC4091C).

[0040] Example 1

[0041] This embodiment provides an antifreeze, anti-dehydration, adhesive, and conductive hydrogel, its preparation method, and its application.

[0042] The preparation method includes the following steps: 1.5 g of lithium chloride, 0.75 g of acrylamide, and 0.04 g of tannic acid are weighed and dissolved in 3 mL of 1 wt% cellulose nanofiber suspension to obtain a cellulose nanofiber / acrylamide / lithium chloride / tannic acid dispersion; then 1.2% (relative to the mass of acrylamide) of N,N,N′,N′-tetramethylethylenediamine is added and stirred thoroughly; then 5.6% (relative to the mass of acrylamide) of ammonium persulfate and 0.1% (relative to the mass of acrylamide) of N,N′-methylenebisacrylamide are added, and free radical polymerization is carried out at room temperature to form a hydrogel (see...). Figure 5 ).

[0043] The hydrogel prepared in Example 1 had a curing time of 219 s and a phase transition temperature of -125.4 °C (see Example 1). Figure 1 It does not dry out after being left at room temperature for 30 days, and still maintains good adhesion to glass, PTFE and silicone substrates after being stored at -40℃ for 2 hours (see...). Figure 2 The ionic conductivity at 25℃ and -40℃ is 11.66 S / m and 1.25 S / m, respectively (see...). Figure 3 ).

[0044] The antifreeze, dehydration-resistant, adhesive, and conductive hydrogel prepared in Example 1 was applied to a flexible wearable sensor. It adhered to the finger and exhibited corresponding resistance changes with the degree of finger bending. The sensor demonstrated good stability, and its resistance change rate remained essentially stable after multiple bending cycles (see Example 1). Figure 4 ).

[0045] Example 2

[0046] This embodiment provides an antifreeze, anti-dehydration, adhesive, and conductive hydrogel. The preparation method of this hydrogel differs from that of Example 1 in that the amount of tannic acid added is 0.005g.

[0047] The hydrogel prepared in this embodiment has a curing time of 55s, a phase transition temperature of -126.4℃, does not dry after being placed at room temperature for 30 days, and still has good adhesion to glass, polytetrafluoroethylene and silicone substrates at low temperatures. The ionic conductivity at 25℃ and -40℃ is 8.11S / m and 0.63S / m, respectively.

[0048] Example 3

[0049] This embodiment provides an antifreeze, dehydration-resistant, adhesive, and conductive hydrogel. The preparation method of this hydrogel differs from that of Example 1 in that the amount of tannic acid added is 0.02g.

[0050] The hydrogel prepared in this embodiment has a curing time of 90s, a phase transition temperature of -125.1℃, does not dry after being placed at room temperature for 30 days, and still has good adhesion to glass, polytetrafluoroethylene and silicone substrates at low temperatures. The ionic conductivity at 25℃ and -40℃ is 9.64S / m and 1.10S / m, respectively.

[0051] Example 4

[0052] This embodiment provides an antifreeze, dehydration-resistant, adhesive, and conductive hydrogel. The preparation method of this hydrogel differs from that of Example 1 in that the added nanofibers are 10wt% cellulose nanofibers.

[0053] The hydrogel prepared in this embodiment has a curing time of 220s, a phase transition temperature of -125.2℃, does not dry out after 30 days at room temperature, still has good adhesion to glass, polytetrafluoroethylene and silicone substrates at low temperatures, and maintains good conductivity at -40℃.

[0054] Example 5

[0055] This embodiment provides an antifreeze, anti-dehydration, adhesive, and conductive hydrogel. The preparation method of this hydrogel differs from that of Example 1 in that the amount of acrylamide added is 1.5g.

[0056] The hydrogel prepared in this embodiment has a curing time of 210s, a phase transition temperature of -126.1℃, does not dry out after being placed at room temperature for 30 days, still has good adhesion to glass, polytetrafluoroethylene and silicone substrates at low temperatures, and maintains good conductivity at -40℃.

[0057] Example 6

[0058] This embodiment provides an antifreeze, anti-dehydration, adhesive, and conductive hydrogel. The preparation method of this hydrogel differs from that of Example 1 in that "1.2% N,N,N′,N′-tetramethylethylenediamine" is replaced with "1% sodium hydroxide".

[0059] The hydrogel prepared in this embodiment has a curing time of 250s, a phase transition temperature of -125.1℃, does not dry out after 30 days at room temperature, still has good adhesion to glass, polytetrafluoroethylene and silicone substrates at low temperatures, and maintains good conductivity at -40℃.

[0060] Example 7

[0061] This embodiment provides an antifreeze, anti-dehydration, adhesive, and conductive hydrogel. The preparation method of this hydrogel differs from that of Example 1 in that the amount of ammonium persulfate added is 6%, and the amount of N,N,N′,N′-tetramethylethylenediamine added is 1%.

[0062] The hydrogel prepared in this embodiment has a curing time of 225s, a phase transition temperature of -126.9℃, does not dry out after 30 days at room temperature, still has good adhesion to glass, polytetrafluoroethylene and silicone substrates at low temperatures, and maintains good conductivity at -40℃.

[0063] Example 8

[0064] This embodiment provides an antifreeze, dehydration-resistant, adhesive, and conductive hydrogel. The preparation method of this hydrogel differs from that of Example 1 in that the amount of ammonium persulfate added is 5%.

[0065] The hydrogel prepared in this embodiment has a curing time of 219s, a phase transition temperature of -124.9℃, does not dry out after 30 days at room temperature, still has good adhesion to glass, polytetrafluoroethylene and silicone substrates at low temperatures, and maintains good conductivity at -40℃.

[0066] Example 9

[0067] This embodiment provides an antifreeze, dehydration-resistant, adhesive, and conductive hydrogel. The preparation method of this hydrogel differs from that of Example 1 in that the amount of N,N′-methylenebisacrylamide added is 0.2%.

[0068] The hydrogel prepared in this embodiment has a curing time of 219s, a phase transition temperature of -125.9℃, does not dry out after 30 days at room temperature, still has good adhesion to glass, polytetrafluoroethylene and silicone substrates at low temperatures, and maintains good conductivity at -40℃.

[0069] Comparative Example 1

[0070] This comparative example provides a hydrogel whose preparation method differs from that of Example 1 in that tannic acid is not added.

[0071] The hydrogel prepared in this comparative example has a phase transition temperature of -124.1℃. It does not dry after being left at room temperature for 30 days. Its ionic conductivity at 25℃ and -40℃ is 14.94 S / m and 1.01 S / m, respectively, but it does not have adhesive properties.

[0072] Comparative Example 2

[0073] This comparative example provides a hydrogel whose preparation method differs from that of Example 1 in that lithium chloride is not added.

[0074] The hydrogel prepared in this comparative example could not form a hydrogel at room temperature.

[0075] Comparative Example 3

[0076] This comparative example provides a hydrogel whose preparation method differs from that of Example 1 in that N,N,N′,N′-tetramethylethylenediamine is not added.

[0077] The hydrogel prepared in this comparative example could not form a hydrogel at room temperature.

[0078] Comparative Example 4

[0079] This comparative example provides a hydrogel whose preparation method differs from that of Example 1 in that the amount of tannic acid added is 0.12g.

[0080] The hydrogel prepared in this comparative example could not form a hydrogel at room temperature.

[0081] As can be seen from Examples 1-3 and Comparative Example 4, within a certain range (0.0017:1 to 0.013:1), the more tannic acid is added, the better the adhesion of the resulting hydrogel will be. However, it will also affect the free radical polymerization of acrylamide. The more tannic acid is added, the more it will delay the polymerization or even prevent the formation of hydrogel.

[0082] Comparative Example 5

[0083] This comparative example provides a hydrogel whose preparation method differs from that of Example 1 in that N,N,N′,N′-tetramethylethylenediamine, ammonium persulfate, and N,N′-methylenebisacrylamide are simultaneously added to the cellulose nanofiber / acrylamide / lithium chloride / tannic acid dispersion.

[0084] The hydrogel prepared in this comparative example cured and solidified in 300 seconds (see...). Figure 6 ).

[0085] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for the preparation of an antifreezing, antidehydrating, adhesive, electrically conductive hydrogel, characterized in that, It comprises the following steps: (1) dissolving the cross-linked polymer monomer, lithium salt and polyphenol in the nanofiber suspension, stirring uniformly to obtain a nanofiber / cross-linked polymer monomer / lithium salt / polyphenol dispersion; (2) mixing the auxiliary with the nanofiber / cross-linked polymer monomer / lithium salt / polyphenol dispersion uniformly under ice bath conditions, then adding the initiator and cross-linking agent, and performing free radical polymerization at room temperature to obtain the hydrogel; The lithium salt is lithium chloride; The polyphenol is tannic acid; The auxiliary is N, N, N', N'-tetramethyl ethylenediamine, sodium hydroxide or potassium hydroxide; In the hydrogel, the mass ratio of polyphenol to water is 0.0017:1~0.013:1; The cross-linked polymer monomer is acrylamide; The nanofiber is one of cellulose nanofiber, cellulose nanowhisker, bacterial cellulose, chitin nanowhisker, sodium alginate nanofiber and starch nanowhisker.

2. A process for the preparation of an anti-freeze, anti-dehydrate, adhesive, conductive hydrogel according to claim 1, characterized in that, The initiator is ammonium persulfate.

3. A process for the preparation of an anti-freeze, anti-dehydrate, adhesive, conductive hydrogel according to claim 1, characterized in that, The cross-linking agent is N, N-methylene bisacrylamide.

4. A process for the preparation of an anti-freeze, anti-dehydrate, adhesive, conductive hydrogel according to claim 1, characterized in that, In the hydrogel, the mass ratio of lithium salt to water is 0.1~0.5:1, the mass ratio of cross-linked polymer to water is 0.25:1~0.5:1, and the mass ratio of nanofiber to water is 0.01:1~0.1:

1.

5. A process for the preparation of an anti-freeze, anti-dehydrate, adhesive, conductive hydrogel according to claim 1, characterized in that, The mass ratio of the initiator, cross-linking agent, auxiliary to cross-linked polymer monomer is (0.05~0.06):(0.001~0.002):(0.01~0.02):

1.

6. A process for the preparation of an anti-freeze, anti-dehydrate, adhesive, conductive hydrogel according to claim 1, characterized in that, The reaction time is 55-250 s.

7. An anti-freezing, anti-dehydrating, adhesive and conductive hydrogel prepared by the preparation method of any one of claims 1-6.

8. The use of the anti-freezing, anti-dehydrating, adhesive and conductive hydrogel of claim 7 in a flexible wearable sensor.

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