Anti-freezing, anti-dehydration, anti-adhesion and conductive hydrogel as well as rapid curing preparation method and application thereof

Abstract

The invention discloses anti-freezing, anti-dehydration, adhesion-resistant and conductive hydrogel as well as a rapid curing preparation method and application thereof, and belongs to the technical field of polymer hydrogel. The hydrogel comprises a cross-linked polymer, water, nanofibers, a lithium salt and polyphenol. The preparation method comprises the following steps: dissolving a cross-linked polymer monomer, a lithium salt and polyphenol in a nanofiber suspension, uniformly mixing an auxiliary agent with a nanofiber / cross-linked polymer monomer / lithium salt / polyphenol dispersion liquid under an ice bath condition, adding an initiator and a cross-linking agent, and carrying out rapid curing molding at room temperature through a free radical polymerization reaction. According to the hydrogel disclosed by the invention, due to the existence of inorganic salt ions, the hydrogel is endowed with excellent ionic conductivity, water in a gel network can inhibit the formation of ice crystals in a low-temperature environment due to strong hydration between the hydrogel and water molecules, and meanwhile, water evaporation is effectively reduced at room temperature; therefore, the hydrogel is endowed with freezing resistance and dehydration resistance. In addition, the polyphenol provides abundant free phenolic hydroxyl groups for the hydrogel, so that the hydrogel has good adhesion. The hydrogel can be applied to the fields of flexible wearable sensors and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer hydrogels, and specifically relates to an antifreeze, anti-dehydration, adhesive, conductive hydrogel and a rapid solidification preparation method and application thereof. Background Art

[0002] In recent years, flexible electronic devices have developed rapidly, showing excellent application prospects in the fields of flexible energy storage devices, wearable devices, soft robots, etc. Conductive hydrogel combines the flexible properties of hydrogel and the electrochemical properties of conductive polymers, and is an ideal material for building flexible electronic devices. Although conductive hydrogel has made great progress, there are still problems such as adhesion and narrow applicable temperature range in practical applications. On the one hand, most hydrogels do not have adhesion properties and usually need to rely on other adhesives (such as 3M tape) to achieve adhesion on the surface of the substrate. On the other hand, traditional conductive hydrogels have high water content, which makes them more sensitive to the external environment, and water molecules cannot be firmly locked in the gel network. This part of water inevitably forms ice crystals in a low temperature environment, 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 and unable to work normally, greatly limiting the practical application of hydrogels. In addition, the traditional preparation process of adhesive hydrogels is usually time-consuming, requiring high temperatures or long-term curing, and it is difficult to meet the efficiency requirements of industrial production. Therefore, developing a hydrogel that combines low-temperature tolerance, dehydration tolerance, adhesion and conductivity and can be quickly solidified and formed has important practical significance and broad application prospects. Summary of the invention

[0003] In order to make up for the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a rapid solidification preparation method for antifreeze, anti-dehydration, adhesion, and conductive hydrogel.

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

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

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows.

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

[0008] (1) dissolving a cross-linked polymer monomer, a lithium salt and a polyphenol in a nanofiber suspension, and stirring the mixture to obtain a nanofiber / cross-linked polymer monomer / lithium salt / polyphenol dispersion;

[0009] (2) in an ice bath, mixing the additive and the nanofiber / cross-linked polymer monomer / lithium salt / polyphenol dispersion evenly, then adding an initiator and a cross-linking agent, and performing a free radical polymerization reaction at room temperature to obtain a hydrogel;

[0010] The lithium salt is lithium chloride;

[0011] The polyphenol is 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 cross-linked polymer monomer is acrylamide.

[0015] Preferably, the nanofiber is one of cellulose nanofiber, cellulose nanowhisker, bacterial cellulose, chitosan nanowhisker, sodium alginate nanofiber and starch nanowhisker.

[0016] Preferably, the initiator is ammonium persulfate.

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

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

[0019] Preferably, in the hydrogel, the mass ratio of the cross-linked 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, the cross-linking agent, the auxiliary agent and the cross-linking polymer monomer is (0.05-0.06):(0.001-0.002):(0.01-0.02):1.

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

[0023] An antifreeze, anti-dehydration, adhesive, and conductive hydrogel prepared by any of the preparation methods described above, the hydrogel comprises a cross-linked polymer, water, nanofibers, lithium salts, and polyphenols; the cross-linked polymer is polymerized from acrylamide monomers.

[0024] The above-mentioned antifreeze, anti-dehydration, adhesive, and conductive hydrogel is used in flexible wearable sensors.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The method of preparing antifreeze, anti-dehydration, adhesive, and conductive hydrogels of the present invention does not require additional auxiliary conditions such as light and heat, and can be carried out at room temperature. At the same time, it overcomes the inherent defect that catechol components cannot participate in free radical polymerization in large quantities, and only takes 55-250 seconds to complete the curing and molding. Compared with traditional preparation methods (usually several hours or requiring the assistance of light, heat, etc.), the gel curing time is greatly shortened, the preparation efficiency is significantly improved, and favorable support is provided for large-scale application and rapid on-site preparation.

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

[0028] (3) The antifreeze, anti-dehydration, 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 the fields of flexible wearable sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a differential scanning calorimetry curve of the antifreeze, anti-dehydration, adhesion and conductive hydrogel prepared in Example 1.

[0030] Figure 2 This is a physical picture of the adhesion behavior of the antifreeze, anti-dehydration, adhesion, and conductive hydrogel prepared in Example 1 at -40°C.

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

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

[0033] Figure 5 This is a photograph of the antifreeze, anti-dehydration, adhesive, and conductive hydrogel prepared in Example 1 forming a gel.

[0034] Figure 6 This is a photo of the product prepared in Comparative Example 5. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. For process parameters not specifically noted, conventional techniques may be used.

[0036] The antifreeze property test method of the hydrogel prepared by the present invention is as follows: The antifreeze property of the hydrogel is analyzed using a differential scanning calorimeter (DSC, TAQ200). 5 to 10 mg of the sample is weighed and sealed in a DSC sample pan. In 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, and after keeping warm for 15 minutes, the temperature is heated to 25°C at a heating rate of 5°C / min.

[0037] The adhesion test method of the hydrogel prepared by the present invention is as follows: the hydrogel is placed in a -40°C environment for 2 hours and then quickly taken out to test its adhesion behavior to different substrates (glass, polytetrafluoroethylene, natural rubber, stainless steel).

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

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

[0040] Example 1

[0041] The present embodiment provides an antifreeze, anti-dehydration, adhesive, conductive hydrogel and a preparation method and application thereof.

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

[0043] The curing time of the hydrogel prepared in Example 1 was 219 s, and the phase transition temperature was -125.4 °C (see Figure 1 ), it has good adhesion to glass, polytetrafluoroethylene and silicone substrates after being placed at room temperature for 30 days without drying and stored at -40℃ for 2h (see Figure 2 ), the ionic conductivity at 25℃ and -40℃ is 11.66S / m and 1.25S / m respectively (see Figure 3 ).

[0044] The antifreeze, anti-dehydration, adhesive, and conductive hydrogel prepared in Example 1 is applied to a flexible wearable sensor, which can adhere to a finger and show a corresponding resistance change with the bending degree of the finger. The sensor has good stability, and after multiple bending cycles, the resistance change rate remains basically stable (see Figure 4 ).

[0045] Example 2

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

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

[0048] Example 3

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

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

[0051] Example 4

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

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

[0054] Example 5

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

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

[0057] Example 6

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

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

[0060] Example 7

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

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

[0063] Example 8

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

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

[0066] Example 9

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

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

[0069] Comparative Example 1

[0070] This comparative example provides a hydrogel, and the preparation method of the hydrogel is different from the preparation method of Example 1 in that tannic acid is not added.

[0071] The phase transition temperature of the hydrogel prepared in this comparative example is -124.1°C. It is not dried out when placed at room temperature for 30 days. The ionic conductivity at 25°C and -40°C is 14.94 S / m and 1.01 S / m, respectively, but it does not have adhesion.

[0072] Comparative Example 2

[0073] This comparative example provides a hydrogel, and the preparation method of the hydrogel is different from the preparation method of Example 1 in that lithium chloride is not added.

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

[0075] Comparative Example 3

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

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

[0078] Comparative Example 4

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

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

[0081] It can be seen from Examples 1-3 and Comparative Example 4 that the amount of tannic acid is within a certain range (0.0017:1 to 0.013:1). The more tannic acid is used, 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 slower the polymerization will be or even the failure of polymerization to form a hydrogel will be.

[0082] Comparative Example 5

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

[0084] The curing time of the hydrogel prepared in this comparative example is 300s (see Figure 6 ).

[0085] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing an antifreeze, anti-dehydration, adhesive, conductive hydrogel, characterized in that: The following steps are involved: (1) dissolving a cross-linked polymer monomer, a lithium salt and a polyphenol in a nanofiber suspension, and stirring the mixture to obtain a nanofiber / cross-linked polymer monomer / lithium salt / polyphenol dispersion; (2) in an ice bath, mixing the additive and the nanofiber / cross-linked polymer monomer / lithium salt / polyphenol dispersion evenly, then adding an initiator and a cross-linking agent, and performing a free radical polymerization reaction at room temperature to obtain a hydrogel; The lithium salt is lithium chloride; The polyphenol is tannic acid; The auxiliary agent is N,N,N′,N′-tetramethylethylenediamine, sodium hydroxide or potassium hydroxide; In the hydrogel, the mass ratio of polyphenol to water is 0.0017:1 to 0.013:

1.

2. The method for preparing an antifreeze, anti-dehydration, adhesive, conductive hydrogel according to claim 1, characterized in that: The cross-linked polymer monomer is acrylamide.

3. The method for preparing an antifreeze, anti-dehydration, adhesive, conductive hydrogel according to claim 1, characterized in that: The nanofiber is one of cellulose nanofiber, cellulose nano whisker, bacterial cellulose, chitin nano whisker, sodium alginate nanofiber and starch nano whisker.

4. The method for preparing an antifreeze, anti-dehydration, adhesive, conductive hydrogel according to claim 1, characterized in that: The initiator is ammonium persulfate.

5. The method for preparing an antifreeze, anti-dehydration, adhesive, conductive hydrogel according to claim 1, characterized in that: The cross-linking agent is N,N-methylenebisacrylamide.

6. The method for preparing an antifreeze, anti-dehydration, 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.

7. The method for preparing an antifreeze, anti-dehydration, adhesive, conductive hydrogel according to claim 1, characterized in that: The mass ratio of the initiator, the crosslinking agent, the auxiliary agent and the crosslinking polymer monomer is (0.05-0.06): (0.001-0.002): (0.01-0.02):

1.

8. The method for preparing an antifreeze, anti-dehydration, adhesive, conductive hydrogel according to claim 1, characterized in that: The reaction time is 55-250s.

9. An antifreeze, anti-dehydration, adhesive, conductive hydrogel prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the antifreeze, anti-dehydration, adhesive, conductive hydrogel according to claim 9 in a flexible wearable sensor.

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