Preparation method of nanocellulose anti-freezing gel based on self-initiation controllable polymerization

Abstract

The invention discloses a preparation method of nanocellulose anti-freezing gel based on self-initiation controllable polymerization, which adopts a eutectic solvent to replace a traditional hydrosolvent, takes cellulose nanofibers as a physical cross-linking agent, and utilizes an oxidation-reduction system constructed by ellagic acid and ferric chloride hexahydrate to realize controllable polymerization of the gel. The anti-freezing performance, mechanical strength and gelling time of the gel can be effectively adjusted by regulating and controlling the proportion of all components in DES, the content of CNF and the concentration of a redox system, so that the high-strength anti-freezing gel with different freezing points and gelling speeds is prepared, and the method has the advantages of low raw material cost, simple and convenient process operation, strong material functionality and the like, and is suitable for industrial production. The prepared gel shows excellent anti-freezing performance, and provides possibility for application of the gel in a low-temperature environment.

Description

Technical Field

[0001] The present invention relates to the field of cellulose-based materials, and in particular to a method for preparing a nano-cellulose antifreeze gel based on self-initiated controlled polymerization. Background Art

[0002] In recent years, with the continuous expansion of the application fields of hydrogels, their demand has also been increasing. The research on hydrogels is moving towards the directions of intelligence, multi-functionality, sustainability, and biomedicine, and these trends will further promote the innovative applications and development of hydrogels in multiple fields. Developing controlled polymerization gels shows important significance in multiple fields. For example, in flexible electronic devices, conductive gels designed by controlled polymerization technology can precisely regulate the network structure and conductive pathways, thereby improving the conductivity, flexibility, and tensile properties of the materials. Such gels can be applied to flexible sensors and wearable electronic devices to achieve high-sensitivity signal detection and transmission.

[0003] However, a large amount of free water is contained inside the hydrogel. When the environmental temperature drops below 0 °C, the free water is prone to freeze, resulting in a change in the gel network structure, making it brittle, significantly decreasing its mechanical properties, and even losing its flexibility. It also hinders the free migration of ions, thus significantly reducing the conductive ability of the hydrogel and affecting its application in flexible sensors and electronic devices. Therefore, developing antifreeze hydrogels, expanding the application range of hydrogels in extremely low-temperature environments, and enhancing their practicability and stability in various fields are of great significance. Summary of the Invention

[0004] The present invention provides a method for preparing a nano-cellulose antifreeze gel based on self-initiated controlled polymerization, and explores a self-initiated polymerization system that can precisely control the initiation time, thereby successfully preparing a nano-cellulose antifreeze gel material with a lower freezing point and excellent low-temperature mechanical properties.

[0005] To achieve the above object, the present invention adopts the following technical means:

[0006] A method for preparing a nano-cellulose antifreeze gel based on self-initiated controlled polymerization, the specific steps are as follows:

[0007] (1) Preparation of a self-initiated redox system

[0008] Weigh 0.05 - 0.1 g of ellagic acid and add it to 10 - 20 mL of a solvent, and then add an equal volume of ferric chloride hexahydrate solution, and continuously stir and react to prepare a redox solution;

[0009] (2) Preparation of a deep eutectic solvent (DES)

[0010] Add 1.35 - 6.75 g of zinc chloride to 11.16 mL of ethylene glycol, and continuously stir under heating conditions until ZnCl₂ is completely dissolved to form a clear solution. After cooling to room temperature, place the obtained solution in a refrigerator for refrigeration, and it can still maintain a clear state, thus obtaining a deep eutectic solvent;

[0011] (3) Disperse cellulose nanofibers (CNF)

[0012] Add 0.025 - 0.075 g of cellulose nanofibers to the deep eutectic solvent in step (2), and perform ultrasonic treatment to obtain a uniformly dispersed DES - CNF solution;

[0013] (4) Preparation of nanocellulose antifreeze gel

[0014] Add 10 - 20 mL of monomer and 0.05 - 0.10 g of initiator to the DES - CNF solution in step (3), mix and stir until all components are completely dissolved, add 20 - 40 μL of cross - linker and stir well to obtain a gel precursor solution. Add 5 - 10 mL of the redox solution in step (1), mix evenly, and then let it stand to obtain the target gel.

[0015] In the above step (1), the solvent is dimethyl sulfoxide.

[0016] In the above step (1), the concentration of the ferric chloride hexahydrate solution is 10 - 60 mg / mL.

[0017] In the above step (1), the stirring speed of the continuous stirring reaction is 400 - 500 r / min, the stirring reaction temperature is 45 - 55 °C, and the time is 5 - 6 hours.

[0018] In the above step (2), the stirring speed of the continuous stirring is 400 - 500 r / min, and the stirring temperature is 75 - 85 °C.

[0019] In the above step (2), the refrigeration temperature is 4 - 6 °C, and the time is 2 - 3 hours.

[0020] In the above step (4), the monomer is acrylic acid; the initiator is ammonium persulfate.

[0021] In the above step (4), the cross - linker is polyethylene glycol diacrylate.

[0022] In the above step (4), the standing time is more than 0.4 minutes.

[0023] In the present invention, by regulating the proportions of the components in the DES, the content of CNF, and the concentration of the redox system, the antifreeze performance, mechanical strength, and gelation time of the gel can be effectively adjusted, thereby preparing high - strength antifreeze gels with different freezing points and gelation speeds.

[0024] The method of the present invention has the advantages of low raw material cost, simple process operation, strong material functionality, etc. The prepared gel exhibits excellent anti-freezing performance, providing broad possibilities for the application of the gel in low-temperature environments.

[0025] The gel prepared by the present invention, as a flexible wearable sensor, can be applied to human motion monitoring and is suitable for human motion at various temperatures. Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the DSC curve of the anti-freezing gel prepared with different ratios of DES;

[0027] Figure 2 It is a schematic diagram of the stress-strain curve of the anti-freezing gel prepared with different contents of CNF;

[0028] Figure 3 It is the ultraviolet-visible spectrum of the anti-freezing gel prepared with different stirring times of the self-initiating system;

[0029] Figure 4 It is a schematic diagram of the application of the nanocellulose-based anti-freezing gel as a flexible sensor in human motion monitoring at low temperature. Detailed Embodiments

[0030] The present invention will be further described below in conjunction with specific embodiments.

[0031] Example 1

[0032] (1) Preparation of the self-initiating redox system:

[0033] Weigh 0.05 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Subsequently, add 10 mL of an aqueous ferric chloride hexahydrate solution with a concentration of 10 mg / mL. Set the stirring speed to 400 r / min by magnetic stirring, the stirring reaction temperature to 45 °C, and the stirring time to 6 hours to prepare a redox solution;

[0034] (2) Preparation of the deep eutectic solvent (DES):

[0035] Weigh 1.35 g of zinc chloride (ZnCl2) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring, set the stirring speed to 400 r / min, and react at 75 °C for 2 hours until ZnCl2 is completely dissolved to form a clear solution. Subsequently, cool it to room temperature and continuously refrigerate it in a 4 °C refrigerator for 3 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared;

[0036] (3) Disperse cellulose nanofibers (CNF):

[0037] Add 0.025 g of cellulose nanofibers to the deep eutectic solvent in step (2), and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0038] (4) Preparation of nanocellulose antifreeze gel:

[0039] Add 10 mL of acrylic acid and 0.05 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 20 μL of crosslinking agent polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 5 mL of the redox solution prepared in step (1). After mixing evenly, let it stand for 76.3 minutes to obtain the target gel, and prepare the antifreeze gel DC-1.

[0040] Example 2

[0041] (1) Preparation of self-initiated redox system:

[0042] Weigh 0.05 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Then add 10 mL of an aqueous solution of ferric chloride hexahydrate with a concentration of 10 mg / mL. Set the stirring speed to 400 r / min by magnetic stirring, the stirring reaction temperature to 45 °C, and the stirring time to 6 hours to prepare a redox solution;

[0043] (2) Preparation of deep eutectic solvent (DES):

[0044] Weigh 2.70 g of zinc chloride (ZnCl2) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring, set the stirring speed to 400 r / min, and react at 75 °C for 2 hours until ZnCl2 is completely dissolved to form a clear solution. Then, cool it to room temperature and continuously refrigerate it in a 4 °C refrigerator for 3 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared;

[0045] (3) Dispersion of cellulose nanofibers (CNF):

[0046] Add 0.025 g of cellulose nanofibers to the deep eutectic solvent in step (2), and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0047] (4) Preparation of nanocellulose antifreeze gel:

[0048] Add 10 mL of acrylic acid and 0.05 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 20 μL of crosslinker polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Then add 5 mL of the redox solution prepared in step (1). After mixing evenly, let it stand for 71.4 minutes to obtain the target gel, and prepare the antifreeze gel DC-2.

[0049] Example 3

[0050] (1) Preparation of self-initiated redox system:

[0051] Weigh 0.05 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Then add 10 mL of an aqueous solution of ferric chloride hexahydrate with a concentration of 10 mg / mL. Set the stirring speed to 400 r / min using magnetic stirring, the stirring reaction temperature to 45 °C, and the stirring time to 6 hours to prepare a redox solution.

[0052] (2) Preparation of deep eutectic solvent (DES):

[0053] Weigh 4.50 g of zinc chloride (ZnCl2) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring and set the stirring speed to 400 r / min. React at 75 °C for 2 hours until ZnCl2 is completely dissolved to form a clear solution. Then, cool to room temperature and continue to refrigerate in a 4 °C refrigerator for 3 hours. If the solution remains clear, the deep eutectic solvent (DES) is successfully prepared.

[0054] (3) Dispersion of cellulose nanofibers (CNF):

[0055] Add 0.025 g of cellulose nanofibers to the deep eutectic solvent in step (2) and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution.

[0056] (4) Preparation of nanocellulose antifreeze gel:

[0057] Add 10 mL of acrylic acid and 0.05 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 20 μL of crosslinker polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Then add 5 mL of the redox solution prepared in step (1). After mixing evenly, let it stand for 67.7 minutes to obtain the target gel, and prepare the antifreeze gel DC-3.

[0058] Example 4

[0059] (1) Preparation of self-initiated redox system:

[0060] Weigh 0.05 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Then add 10 mL of an aqueous ferric chloride hexahydrate solution with a concentration of 10 mg / mL. Set the stirring speed to 400 r / min using magnetic stirring, the stirring reaction temperature to 45 °C, and the stirring time to 6 hours to prepare a redox solution;

[0061] (2) Preparation of deep eutectic solvent (DES):

[0062] Weigh 5.40 g of zinc chloride (ZnCl2) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring, set the stirring speed to 400 r / min, and react at 75 °C for 2 hours until ZnCl2 is completely dissolved to form a clear solution. Then, cool it to room temperature and continue to refrigerate it in a 4 °C refrigerator for 3 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared;

[0063] (3) Dispersion of cellulose nanofibers (CNF):

[0064] Add 0.025 g of cellulose nanofibers to the deep eutectic solvent in step (2) and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0065] (4) Preparation of nanofibrillated cellulose antifreeze gel:

[0066] Add 10 mL of acrylic acid and 0.05 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 20 μL of cross-linking agent polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 5 mL of the redox solution prepared in step (1), mix well, and then let it stand for 66.3 minutes to obtain the target gel, and prepare the antifreeze gel DC-4.

[0067] Example 5

[0068] (1) Preparation of self-initiating redox system:

[0069] Weigh 0.05 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Then add 10 mL of an aqueous ferric chloride hexahydrate solution with a concentration of 10 mg / mL. Set the stirring speed to 400 r / min using magnetic stirring, the stirring reaction temperature to 45 °C, and the stirring time to 6 hours to prepare a redox solution;

[0070] (2) Preparation of deep eutectic solvent (DES):

[0071] Weigh 6.75 g of zinc chloride (ZnCl₂) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring and set the stirring speed to 400 r / min. React at 75 °C for 2 hours until ZnCl₂ is completely dissolved to form a clear solution. Subsequently, cool it to room temperature and continuously refrigerate it in a 4 °C refrigerator for 3 hours. If the solution can still maintain a clear state, a deep eutectic solvent (DES) is successfully prepared;

[0072] (3) Disperse cellulose nanofibers (CNF):

[0073] Add 0.025 g of cellulose nanofibers to the deep eutectic solvent in step (2) and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0074] (4) Preparation of nanocellulose antifreeze gel:

[0075] Add 10 mL of acrylic acid and 0.05 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 20 μL of crosslinking agent polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 5 mL of the redox solution prepared in step (1). After mixing evenly, let it stand for 65.1 minutes to obtain the target gel, and prepare the antifreeze gel DC-5.

[0076] Example 6

[0077] (1) Preparation of self-initiating redox system:

[0078] Weigh 0.075 g of ellagic acid and add it to 20 mL of dimethyl sulfoxide. Subsequently, add 10 mL of an aqueous solution of ferric chloride hexahydrate with a concentration of 20 mg / mL. Use magnetic stirring, set the stirring speed to 450 r / min, the stirring reaction temperature to 50 °C, and the stirring time to 5.5 hours to prepare a redox solution;

[0079] (2) Preparation of deep eutectic solvent (DES):

[0080] Weigh 5.40 g of zinc chloride (ZnCl₂) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring, set the stirring speed to 450 r / min, react at 80 °C for 1.5 hours until ZnCl₂ is completely dissolved to form a clear solution. Subsequently, cool it to room temperature and continuously refrigerate it in a 5 °C refrigerator for 2.5 hours. If the solution can still maintain a clear state, a deep eutectic solvent (DES) is successfully prepared;

[0081] (3) Disperse cellulose nanofibers (CNF):

[0082] Add 0.050 g of cellulose nanofibers to the deep eutectic solvent in step (2), and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0083] (4) Preparation of nanocellulose antifreeze gel:

[0084] Add 15 mL of acrylic acid and 0.05 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 20 μL of crosslinking agent polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 5 mL of the redox solution prepared in step (1), mix well, and then let it stand for 47.2 minutes to obtain the target gel, and prepare the antifreeze gel DC-6.

[0085] Example 7

[0086] (1) Preparation of self-initiating redox system:

[0087] Weigh 0.10 g of ellagic acid and add it to 20 mL of dimethyl sulfoxide. Subsequently, add 10 mL of an aqueous solution of ferric chloride hexahydrate with a concentration of 30 mg / mL. Set the stirring speed to 450 r / min by magnetic stirring, set the stirring reaction temperature to 50 °C, and stir for 5.5 hours to prepare a redox solution;

[0088] (2) Preparation of deep eutectic solvent (DES):

[0089] Weigh 5.40 g of zinc chloride (ZnCl2) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring, set the stirring speed to 450 r / min, and react at 80 °C for 1.5 hours until ZnCl2 is completely dissolved to form a clear solution. Subsequently, cool it to room temperature and continuously refrigerate it in a 5 °C refrigerator for 2.5 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared;

[0090] (3) Dispersion of cellulose nanofibers (CNF):

[0091] Add 0.050 g of cellulose nanofibers to the deep eutectic solvent in step (2), and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0092] (4) Preparation of nanocellulose antifreeze gel:

[0093] Add 20 mL of acrylic acid and 0.075 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 20 μL of crosslinking agent polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 7 mL of the redox solution prepared in step (1). After mixing evenly, let it stand for 25.2 minutes to obtain the target gel, and prepare the antifreeze gel DC-7.

[0094] Example 8

[0095] (1) Preparation of self-initiating redox system:

[0096] Weigh 0.10 g of ellagic acid and add it to 15 mL of dimethyl sulfoxide. Then add 10 mL of an aqueous solution of ferric chloride hexahydrate with a concentration of 40 mg / mL. Set the stirring speed to 450 r / min by magnetic stirring, the stirring reaction temperature to 50 °C, and the stirring time to 5.5 hours to prepare a redox solution.

[0097] (2) Preparation of deep eutectic solvent (DES):

[0098] Weigh 5.40 g of zinc chloride (ZnCl2) and add it to 11.16 mL of ethylene glycol (EG) solvent. Stir magnetically, set the stirring speed to 450 r / min, and react at 80 °C for 1.5 hours until ZnCl2 is completely dissolved to form a clear solution. Then, cool it to room temperature and continuously refrigerate it in a 5 °C refrigerator for 2.5 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared.

[0099] (3) Dispersion of cellulose nanofibers (CNF):

[0100] Add 0.050 g of cellulose nanofibers to the deep eutectic solvent in step (2) and ultrasonically treat it to obtain a uniformly dispersed DES-CNF solution.

[0101] (4) Preparation of nanocellulose antifreeze gel:

[0102] Add 10 mL of acrylic acid and 0.10 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 30 μL of crosslinking agent polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 8 mL of the redox solution prepared in step (1). After mixing evenly, let it stand for 9.3 minutes to obtain the target gel, and prepare the antifreeze gel DC-8.

[0103] Example 9

[0104] (1) Preparation of self-initiating redox system:

[0105] Weigh 0.10 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Subsequently, add 10 mL of an aqueous ferric chloride hexahydrate solution with a concentration of 50 mg / mL. Set the stirring speed to 500 r / min using magnetic stirring, the stirring reaction temperature to 55 °C, and the stirring time to 5 hours to prepare a redox solution;

[0106] (2) Preparation of deep eutectic solvent (DES):

[0107] Weigh 5.40 g of zinc chloride (ZnCl₂) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring and set the stirring speed to 500 r / min. React at 85 °C for 1 hour until ZnCl₂ is completely dissolved to form a clear solution. Subsequently, cool to room temperature and continuously refrigerate in a 6 °C refrigerator for 2 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared;

[0108] (3) Dispersion of cellulose nanofibers (CNF):

[0109] Add 0.050 g of cellulose nanofibers to the deep eutectic solvent in step (2) and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0110] (4) Preparation of nanofibrillated cellulose antifreeze gel:

[0111] Add 10 mL of acrylic acid and 0.75 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 30 μL of crosslinking agent polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 8 mL of the redox solution prepared in step (1), mix well, and then let it stand for 2.5 minutes to obtain the target gel, and prepare the antifreeze gel DC-9.

[0112] Example 10

[0113] (1) Preparation of self-initiating redox system:

[0114] Weigh 0.10 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Subsequently, add 10 mL of an aqueous ferric chloride hexahydrate solution with a concentration of 60 mg / mL. Set the stirring speed to 500 r / min using magnetic stirring, the stirring reaction temperature to 55 °C, and the stirring time to 5 hours to prepare a redox solution;

[0115] (2) Preparation of deep eutectic solvent (DES):

[0116] Weigh 5.40 g of zinc chloride (ZnCl₂) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring and set the stirring speed to 500 r / min. React at 85 °C for 1 hour until ZnCl₂ is completely dissolved to form a clear solution. Subsequently, cool it to room temperature and continuously refrigerate it in a 6 °C refrigerator for 2 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared;

[0117] (3) Disperse cellulose nanofibers (CNF):

[0118] Add 0.050 g of cellulose nanofibers to the deep eutectic solvent in step (2) and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0119] (4) Preparation of nanocellulose antifreeze gel:

[0120] Add 10 mL of acrylic acid and 0.10 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 40 μL of crosslinker polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 10 mL of the redox solution prepared in step (1), mix well, and then let it stand for 0.4 minutes to obtain the target gel, and prepare the antifreeze gel DC-10.

[0121] Example 11

[0122] (1) Preparation of self-initiating redox system:

[0123] Weigh 0.10 g of ellagic acid and add it to 15 mL of dimethyl sulfoxide. Subsequently, add 10 mL of an aqueous solution of ferric chloride hexahydrate with a concentration of 40 mg / mL. Use magnetic stirring, set the stirring speed to 450 r / min, the stirring reaction temperature to 50 °C, and the stirring time to 5.5 hours to prepare a redox solution;

[0124] (2) Preparation of deep eutectic solvent (DES):

[0125] Weigh 5.40 g of zinc chloride (ZnCl₂) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring, set the stirring speed to 450 r / min, react at 80 °C for 1.5 hours until ZnCl₂ is completely dissolved to form a clear solution. Subsequently, cool it to room temperature and continuously refrigerate it in a 5 °C refrigerator for 2.5 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared;

[0126] (3) Disperse cellulose nanofibers (CNF):

[0127] Add 0.025 g of cellulose nanofibers to the deep eutectic solvent in step (2), and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0128] (4) Preparation of nanocellulose antifreeze gel:

[0129] Add 10 mL of acrylic acid and 0.10 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 30 μL of crosslinker polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 7 mL of the redox solution prepared in step (1), mix well, and then let it stand for 13.7 minutes to obtain the target gel, and prepare the antifreeze gel DC-11.

[0130] Example 12

[0131] (1) Preparation of self-initiated redox system:

[0132] Weigh 0.10 g of ellagic acid and add it to 15 mL of dimethyl sulfoxide. Then add 10 mL of an aqueous solution of ferric chloride hexahydrate with a concentration of 40 mg / mL. Set the stirring speed to 450 r / min by magnetic stirring, the stirring reaction temperature to 50 °C, and the stirring time to 5.5 hours to prepare a redox solution;

[0133] (2) Preparation of deep eutectic solvent (DES):

[0134] Weigh 5.40 g of zinc chloride (ZnCl2) and add it to 11.16 mL of ethylene glycol (EG) solvent. Perform magnetic stirring, set the stirring speed to 450 r / min, and react at 80 °C for 1.5 hours until ZnCl2 is completely dissolved to form a clear solution. Then, cool it to room temperature and continuously refrigerate it in a 5 °C refrigerator for 2.5 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared;

[0135] (3) Dispersion of cellulose nanofibers (CNF):

[0136] Add 0.055 g of cellulose nanofibers to the deep eutectic solvent in step (2), and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0137] (4) Preparation of nanocellulose antifreeze gel:

[0138] Add 10 mL of acrylic acid and 0.10 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 30 μL of crosslinker polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Then add 7 mL of the redox solution prepared in step (1). After mixing evenly, let it stand for 12.5 minutes to obtain the target gel, and prepare the antifreeze gel DC-12.

[0139] Example 13

[0140] (1) Preparation of self-initiated redox system:

[0141] Weigh 0.10 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Then add 10 mL of an aqueous solution of ferric chloride hexahydrate with a concentration of 40 mg / mL. Set the stirring speed to 450 r / min using magnetic stirring, the stirring reaction temperature to 50 °C, and the stirring time to 5.5 hours to prepare a redox solution.

[0142] (2) Preparation of deep eutectic solvent (DES):

[0143] Weigh 5.40 g of zinc chloride (ZnCl2) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring, set the stirring speed to 450 r / min, and react at 80 °C for 1.5 hours until ZnCl2 is completely dissolved to form a clear solution. Then, cool it to room temperature and continue to refrigerate it in a 5 °C refrigerator for 2.5 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared.

[0144] (3) Dispersion of cellulose nanofibers (CNF):

[0145] Add 0.060 g of cellulose nanofibers to the deep eutectic solvent in step (2) and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution.

[0146] (4) Preparation of nanocellulose antifreeze gel:

[0147] Add 10 mL of acrylic acid and 0.10 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 30 μL of crosslinker polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Then add 7 mL of the redox solution prepared in step (1). After mixing evenly, let it stand for 11.9 minutes to obtain the target gel, and prepare the antifreeze gel DC-13.

[0148] Example 14

[0149] (1) Preparation of self-initiated redox system:

[0150] Weigh 0.10 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Subsequently, add 10 mL of an aqueous ferric chloride hexahydrate solution with a concentration of 40 mg / mL. Set the stirring speed to 450 r / min using magnetic stirring, the stirring reaction temperature to 50 °C, and the stirring time to 5.5 hours to prepare a redox solution;

[0151] (2) Preparation of deep eutectic solvent (DES):

[0152] Weigh 5.40 g of zinc chloride (ZnCl2) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring, set the stirring speed to 450 r / min, and react at 80 °C for 1.5 hours until ZnCl2 is completely dissolved to form a clear solution. Subsequently, cool it to room temperature and continuously refrigerate it in a 5 °C refrigerator for 2.5 hours. If the solution can still maintain a clear state, the deep eutectic solvent (DES) is successfully prepared;

[0153] (3) Dispersion of cellulose nanofibers (CNF):

[0154] Add 0.065 g of cellulose nanofibers to the deep eutectic solvent in step (2) and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0155] (4) Preparation of nanofibrillated cellulose antifreeze gel:

[0156] Add 10 mL of acrylic acid and 0.10 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 30 μL of crosslinking agent polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 7 mL of the redox solution prepared in step (1), mix well, and then let it stand for 11.2 minutes to obtain the target gel, and prepare the antifreeze gel DC-14.

[0157] Example 15

[0158] (1) Preparation of self-initiating redox system:

[0159] Weigh 0.10 g of ellagic acid and add it to 10 mL of dimethyl sulfoxide. Subsequently, add 10 mL of an aqueous ferric chloride hexahydrate solution with a concentration of 40 mg / mL. Set the stirring speed to 450 r / min using magnetic stirring, the stirring reaction temperature to 50 °C, and the stirring time to 5.5 hours to prepare a redox solution;

[0160] (2) Preparation of deep eutectic solvent (DES):

[0161] Weigh 5.40 g of zinc chloride (ZnCl₂) and add it to 11.16 mL of ethylene glycol (EG) solvent. Use magnetic stirring and set the stirring speed to 450 r / min. React at 80 °C for 1.5 hours until ZnCl₂ is completely dissolved to form a clear solution. Subsequently, cool it to room temperature and continuously refrigerate it in a 5 °C refrigerator for 2.5 hours. If the solution can still maintain a clear state, a deep eutectic solvent (DES) is successfully prepared;

[0162] (3) Disperse cellulose nanofibers (CNF):

[0163] Add 0.075 g of cellulose nanofibers to the deep eutectic solvent in step (2) and perform ultrasonic treatment to obtain a uniformly dispersed DES-CNF solution;

[0164] (4) Preparation of nanocellulose antifreeze gel:

[0165] Add 10 mL of acrylic acid and 0.10 g of initiator ammonium persulfate to the DES-CNF solution in step (3). After mixing, stir until all components are completely dissolved. Add 30 μL of crosslinker polyethylene glycol diacrylate and stir well to obtain a gel precursor solution. Add 7 mL of the redox solution prepared in step (1), mix well, and then let it stand for 7.3 minutes to obtain the target gel, and prepare the antifreeze gel DC-15.

[0166] Figure 1 This is the DSC curve of the nanocellulose-based antifreeze gels DC-1 to 5 synthesized in Examples 1-5 of the present invention. It can be seen from the figure that DC-4 has the best antifreeze performance, and the freezing point reaches -73.03 °C.

[0167] Figure 2 This is the stress-strain curve of the nanocellulose-based antifreeze gels DC-8, DC-11, and DC-11 synthesized in Example 8, Example 11, and Example 15 of the present invention. It can be seen from the figure that DC-8 has the best comprehensive mechanical properties, with a fracture strength of 0.78 MPa at room temperature and still maintaining a fracture strength of 0.76 MPa in a low-temperature environment.

[0168] Figure 3 This is the ultraviolet-visible spectrogram of stirring for 1-9 hours during the preparation of the redox system in Example 8 of the present invention. It can be seen from the figure that when the stirring time reaches 5 hours, the absorption peak of the redox system near 380-390 nm is the most significant. The appearance of this absorption peak is mainly attributed to the characteristic absorption of the carbonyl group (C=O) in the benzene ring structure and the quinone structure.

[0169] Figure 4Schematic diagram of the nanocellulose-based antifreeze gel DC-8 synthesized in Example 8 of the present invention as a flexible sensor at low temperature and applied to human motion monitoring. As can be seen from the figure, as a sensor, this gel not only has good flexibility, but also can achieve wearable motion monitoring work in a low-temperature environment.

[0170] The self-initiated controlled polymerization nanocellulose antifreeze gel prepared in the present invention makes full use of the low freezing point characteristics of the deep eutectic solvent and the role of cellulose nanofibers as physical cross-linking agents, endowing the gel with excellent antifreeze performance and good mechanical properties. Through the redox reaction between Fe3+ and ammonium persulfate, the controlled polymerization of the gel is realized. The prepared antifreeze gel can achieve gelation in as fast as 0.4 minutes, and the lowest freezing point can reach -73.03 °C. The fracture strength at room temperature is 0.78 MPa, while the fracture strength in a low-temperature environment still remains at 0.76 MPa.

[0171] The nanocellulose antifreeze gel prepared in the present invention can be used as a flexible wearable sensor and applied to human motion monitoring, suitable for human motion at various temperatures.

Claims

1. A method for preparing nanocellulose antifreeze gel based on self-initiated controlled polymerization, characterized in that: The specific steps are as follows: (1) Weighing 0.05-0.1 g of ellagic acid and adding it to 10-20 mL of solvent, then adding an equal volume of ferric chloride hexahydrate solution, and continuously stirring the reaction to prepare a redox solution; (2) adding 1.35-6.75 g of zinc chloride to 11.16 mL of ethylene glycol, stirring continuously until ZnCl2 is completely dissolved to form a clear solution, cooling to room temperature, and remaining clear after refrigeration to obtain a low eutectic solvent; (3) adding 0.025-0.075 g of cellulose nanofibers to the low eutectic solvent of step (2), and ultrasonically treating to obtain a uniformly dispersed DES-CNF solution; (4) Add 10-20 mL of monomer and 0.05-0.10 g of initiator to the DES-CNF solution of step (3), mix and stir until all components are completely dissolved, add 20-40 μL of cross-linking agent and stir well to obtain a gel precursor solution, add 5-10 mL of the redox solution of step (1), mix well, and let stand to obtain the target gel.

2. The method for preparing the nanocellulose antifreeze gel based on self-initiated controlled polymerization according to claim 1, characterized in that: In step (1), the solvent is dimethyl sulfoxide.

3. The method for preparing the nanocellulose antifreeze gel based on self-initiated controlled polymerization according to claim 1, characterized in that: In step (1), the concentration of the ferric chloride hexahydrate solution is 10-60 mg / mL.

4. The method for preparing the nanocellulose antifreeze gel based on self-initiated controlled polymerization according to claim 1, characterized in that: In step (1), the reaction is continuously stirred at a speed of 400-500 r / min, a stirring temperature of 45-55° C., and a time of 5-6 hours.

5. According to the method for preparing nanocellulose antifreeze gel based on self-initiated controllable polymerization according to claim 1, in step (2), the speed of continuous stirring is 400-500 r / min, and the stirring temperature is 75-85°C.

6. According to the method for preparing nanocellulose antifreeze gel based on self-initiated controlled polymerization according to claim 1, in step (2), the refrigeration temperature is 4-6°C and the time is 2-3 hours.

7. According to the method for preparing nanocellulose antifreeze gel based on self-initiated controllable polymerization according to claim 1, in step (4), the monomer is acrylic acid; the initiator is ammonium persulfate; and the cross-linking agent is polyethylene glycol diacrylate.

8. According to the method for preparing nanocellulose antifreeze gel based on self-initiated controlled polymerization according to claim 1, in step (4), the standing time is more than 0.4 minutes.

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