A method for preparing magnetically deformable high-solid content hydrogel

Abstract

The invention discloses a method for preparing a magnetically deformable high-solid content hydrogel, the method comprising the following steps: step one: adding polyvinyl alcohol to deionized water, heating and dissolving, and obtaining a polyvinyl alcohol aqueous solution; step two: sequentially adding acrylamide, N,N'-methylenebisacrylamide and potassium persulfate to the polyvinyl alcohol aqueous solution, and stirring to obtain a uniform solution; step three: dropping a boric acid aqueous solution into the uniform mixed solution to obtain a dynamic cross-linked hydrogel; step four: adding ferrosoferric oxide solid powder to the dynamic cross-linked hydrogel, stirring evenly and placing in a vacuum environment to remove bubbles, to obtain a dynamic reversible network hydrogel; step five: transferring the dynamic reversible network hydrogel to a polytetrafluoroethylene mold for thermally initiated polymerization to obtain a magnetically deformable high-solid content hydrogel. The method is simple and easy, and the prepared double network hydrogel has good mechanical properties and stability and a certain magnetic response deformation ability.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material preparation, and relates to a method for preparing a hydrogel, in particular to a method for preparing a high-solid-content magnetically deformable hydrogel. Background Art

[0002] Hydrogels are polymers with three-dimensional networks formed by cross-linking hydrophilic groups. They swell in water without dissolving, are soft, and have adjustable properties. They can be equipped with various functions, such as magnetic, optical, electrical, thermal, humidity, and pH stimuli, and can also load various materials and transport drugs, making them an ideal substrate for flexible actuators. Currently, magnetically responsive hydrogels, with their unique properties of tissue penetration, contactless remote spatiotemporal control, and rapid reversible response, have attracted extensive research and application in areas such as microscopic robotics, tissue engineering, drug or cell transport and release, biomimetic actuators, and environmental management. However, most existing magnetically responsive hydrogels suffer from common problems such as high brittleness and low toughness, high strength but low elongation at break, and limited solid loading capacity. These issues result in slow magnetic response and low shape-shifting efficiency in magnetic hydrogel-based flexible actuators. Therefore, developing new sensitive, low-strength, high-load magnetically responsive hydrogels, both in terms of materials and structure, has become a key focus in the development of flexible intelligent magnetically responsive actuators.

[0003] At present, there are two main ways to improve the mechanical properties of magnetic hydrogels. One is to establish the interaction between magnetic particles and hydrogel substrate by modifying functional groups on the surface of magnetic particles; the other is to introduce another cross-linking system into the magnetic hydrogel to form a double-network magnetic hydrogel. Based on the Hoffmeister effect and the toughening method of double-network hydrogels, researchers have prepared a Fe3O4 / CS (chitosan)-PAAm double-network electromagnetically conductive hydrogel with ultra-high toughness through ionic crosslinking, molecular entanglement, and hydrogen bond enhancement between nanoparticles and polymer networks. The magnetic particle content can reach 43wt% (43% is relative to the total weight of polymer and water, which is converted to 30.07% of the total mass). The modulus of the prepared hydrogel is 1.3MPa and the toughness exceeds 54KJ / m 2The deformation of the gel can be adjusted by applying an external magnetic field, thus giving the gel the function of a soft magnetic response actuator (MEI L, CONG J, LI S, et al. Polyacrylamide-Chitosanbased magnetic hydrogels with high stiffness and ultra-toughness[J]. Composites Part A: Applied Science and Manufacturing, 2023, 168: 107478.). In addition, the researchers compounded 3-(trimethoxysilyl)propyl methacrylate-coated Fe3O4 nanoparticles with polyacrylamide hydrogel to produce a magnetically responsive hydrogel with a magnetic powder content of up to 60 wt% (37.5% of the total mass, relative to the total weight of the polymer and water) and uniform distribution, relatively high modulus and toughness, and rapid response to magnetic fields. The hydrogel can adhere to hard and soft surfaces rich in hydroxyl groups. By coating the surface with polydimethylsiloxane, it can not only prevent the leakage of magnetic particles and dehydration, but also exhibit excellent performance underwater (HU X, NIAN G, LIANG X, et al. Adhesive Tough Magnetic Hydrogels with High Fe3O4 Content[J].).

[0004] Although significant progress has been made in the development of magnetically responsive hydrogel flexible brakes, there are still some difficulties and challenges in improving their performance. For example, the goals of achieving high solid content and good dispersion of solid particles in hydrogels are often contradictory, and the mechanical properties of hydrogels gradually deteriorate with increasing solid content. Summary of the Invention

[0005] To address the common issues of existing magnetic hydrogels, such as high brittleness but low toughness, high strength but low elongation at break, and limited solid loading, this invention provides a method for preparing magnetically deformable, high-solids hydrogels. This simple and easy method uses magnetic particles to impart magnetic responsiveness to the gel. Hydrogels of any shape can be constructed using different molds. The resulting double-network hydrogel exhibits excellent mechanical properties and stability, and possesses a certain degree of magnetically responsive deformation capability.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a magnetically deformable high-solid content hydrogel comprises the following steps:

[0008] Step 1: Add polyvinyl alcohol to deionized water, heat and dissolve, and obtain a polyvinyl alcohol aqueous solution with a mass concentration of 3 to 15%;

[0009] Step 2: adding acrylamide, N,N'-methylenebisacrylamide and potassium persulfate in sequence to the polyvinyl alcohol aqueous solution obtained in step 1, and stirring to obtain a uniform solution, wherein: the amount of acrylamide added is 40-100% of the molar amount of the polyvinyl alcohol repeating unit, the amount of N,N'-methylenebisacrylamide added is 0.4-1% of the molar amount of acrylamide, and the amount of potassium persulfate added is 1-2% of the molar amount of acrylamide;

[0010] Step 3: Adding boric acid aqueous solution dropwise to the uniformly mixed solution obtained in step 2 while stirring to obtain a uniform dynamically cross-linked hydrogel, wherein the concentration of the boric acid aqueous solution is 0.01 to 0.02 g / mL, the amount added is 0.4 to 2% of the molar amount of the polyvinyl alcohol repeating unit, and the stirring speed is 150 to 250 rpm;

[0011] Step 4: adding ferrosoferric oxide solid powder in small amounts and batches to the dynamically cross-linked hydrogel obtained in step 3, stirring evenly, and then placing in a vacuum environment to remove bubbles to obtain a dynamic reversible network hydrogel loaded with a high content of magnetic particles, wherein: the mechanical stirring speed is 100-200 rpm, the particle size of ferrosoferric oxide is 50-500 nm, and the amount of ferrosoferric oxide added is 10-64 wt% of the dynamically cross-linked hydrogel obtained in step 3;

[0012] Step 5: The dynamic reversible network hydrogel obtained in step 4 is transferred to a polytetrafluoroethylene mold and placed in an oven at 50-70°C for thermal polymerization for 2-6 hours to obtain a magnetically deformable high-solid content hydrogel with good mechanical properties and stability.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. The hydrogel constructed by the present invention has a magnetic particle loading capacity of up to 64%, and the structural stability of the hydrogel is good.

[0015] 2. The hydrogel constructed by the present invention has certain strength and toughness, and at the same time has excellent magnetic response deformation ability.

[0016] 3. The hydrogel constructed by the present invention has a wide adjustable range of properties. By rationally designing the ratio between the double networks and the content of each substance, the overall mechanical properties of the gel can be adjusted.

[0017] 4. The preparation method of the present invention is simple and easy to scale up for preparation. The operation process has strong stability and has practical application prospects and sustainability.

[0018] 5. The present invention is expected to develop hydrogel materials with high practical value in many fields, including but not limited to high-solid content gel propellants, high-solid content conductive hydrogels, high-solid content magnetron gels, etc., showing important application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 These are optical images of magnetic hydrogels with solid contents of approximately 20%, 55%, and 64%, respectively.

[0020] Figure 2 This is an infrared image of the magnetic hydrogel.

[0021] Figure 3 This is the SEM image of the hydrogel with a solid content of 64%.

[0022] Figure 4 This is the rotational rheometer oscillation amplitude sweep curve of a hydrogel precursor mixture with a solid content of 64%.

[0023] Figure 5 This is the rotational rheometer oscillation amplitude sweep curve of hydrogel with a solid content of 64%.

[0024] Figure 6 This is the thermogravimetric curve of the double network hydrogel with a solid content of about 55%.

[0025] Figure 7 This is the thermogravimetric curve of the double network hydrogel with a solid content of about 64%. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0027] The present invention provides a method for preparing a magnetically deformable high-solid content hydrogel. The method uses polyvinyl alcohol as a raw material, first heating it in deionized water to dissolve it, then adding acrylamide, N,N'-methylenebisacrylamide, and an initiator, potassium persulfate, to the polyvinyl alcohol aqueous solution. After all of the polyvinyl alcohol is dissolved, an aqueous boric acid solution is added dropwise while mechanically stirring. Then, solid particles of ferrosoferric oxide are added and stirred evenly to obtain a dynamic reversible network hydrogel loaded with a high content of solid particles. The hydrogel is then transferred to a polytetrafluoroethylene mold and placed in a 60°C environment for thermal initiation, thereby constructing a double-network hydrogel with excellent mechanical properties and a high content of magnetic particles. The specific steps are as follows:

[0028] Step 1: Add polyvinyl alcohol to deionized water, heat and dissolve, and obtain a polyvinyl alcohol aqueous solution with a mass concentration of 3 to 15%;

[0029] Step 2: adding acrylamide, N,N'-methylenebisacrylamide and potassium persulfate in sequence to the polyvinyl alcohol aqueous solution obtained in step 1, and stirring to obtain a uniform solution, wherein: the amount of acrylamide added is 40-100% of the molar amount of the polyvinyl alcohol repeating unit, the amount of N,N'-methylenebisacrylamide added is 0.4-1% of the molar amount of acrylamide, and the amount of potassium persulfate added is 1-2% of the molar amount of acrylamide;

[0030] Step 3: Adding a boric acid aqueous solution dropwise to the uniformly mixed solution obtained in step 2 while stirring to obtain a stable, fluid dynamic cross-linked hydrogel, wherein the boric acid aqueous solution has a concentration of 0.01 to 0.02 g / mL, an amount of the boric acid aqueous solution added is 0.4 to 2% of the molar amount of the polyvinyl alcohol repeating unit, and the stirring speed is 150 to 250 rpm;

[0031] Step 4: adding ferrosoferric oxide solid powder in small amounts and batches to the dynamically cross-linked hydrogel obtained in step 3, stirring evenly, and then placing in a vacuum environment to remove bubbles to obtain a dynamic reversible network hydrogel loaded with a high content of magnetic particles, wherein: the mechanical stirring speed is 100-200 rpm, the particle size of ferrosoferric oxide is 50-500 nm, and the amount of ferrosoferric oxide added is 10-64 wt% of the dynamically cross-linked hydrogel obtained in step 3;

[0032] Step 5: The dynamic reversible network hydrogel obtained in step 4 is transferred to a polytetrafluoroethylene mold and placed in an oven at 50-70°C for thermal polymerization for 2-6 hours to obtain a magnetically deformable high-solid content hydrogel with good mechanical properties and stability.

[0033] Example 1:

[0034] At room temperature and pressure, 1g of polyvinyl alcohol was added to 12ml of deionized water, and the mixture was heated and stirred in an oil bath at 80°C to dissolve the polyvinyl alcohol aqueous solution; 2g of the polyvinyl alcohol aqueous solution was added, 0.3554g of acrylamide, 0.0039g of N,N'-methylenebisacrylamide, and 0.0135g of potassium persulfate were added in sequence, and stirred to obtain a uniform solution; mechanical stirring was turned on, and 50μl of a 0.01g / ml boric acid aqueous solution was added, and the addition was divided into five times, 10μl was taken out at a time using a pipette, and each time was 2.5 minutes apart, and the mixture was stirred until the state of the mixture was uniform; 4.21g of 500nm ferrosoferric oxide was added in small amounts and multiple times, and mechanical stirring was stopped after mixing evenly, and then the mixture was placed in a vacuum environment to remove bubbles; the uniform mixture was then transferred to a polytetrafluoroethylene mold sprayed with a release agent, placed in a 60°C oven for thermal initiation polymerization for 4h, and removed from the mold to obtain a hydrogel with a specific shape, good mechanical properties, good stability, and a solid content of approximately 64%.

[0035] Example 2:

[0036] At room temperature and pressure, 1g of polyvinyl alcohol is added to 10ml of deionized water, and the mixture is heated and stirred in an oil bath at 80°C to dissolve the polyvinyl alcohol aqueous solution; 2g of the polyvinyl alcohol aqueous solution is added, 0.3909g of acrylamide, 0.0042g of N,N'-methylenebisacrylamide, and 0.0149g of potassium persulfate are added in sequence, and stirred to obtain a uniform solution; mechanical stirring is turned on, and 70μl of a 0.01g / ml boric acid aqueous solution is added, and the addition is divided into seven times, 10μl is taken out at a time using a pipette, and each time is 2.5 minutes apart, and the mixture is stirred until the state of the mixture is uniform; 2.95g of 50nm ferrosoferric oxide is added in small amounts and multiple times, and mechanical stirring is stopped after mixing evenly, and then the mixture is placed in a vacuum environment to remove bubbles; the uniform mixture is then transferred to a polytetrafluoroethylene mold sprayed with a release agent, placed in a 60°C oven for thermal initiation polymerization for 4h, and removed from the mold to obtain a hydrogel with a specific shape, good mechanical properties, good stability, and a solid content of approximately 55%.

[0037] Example 3:

[0038] At room temperature and pressure, 1g of polyvinyl alcohol was added to 10ml of deionized water, and the mixture was heated and stirred in an oil bath at 80°C to dissolve the polyvinyl alcohol aqueous solution; 3g of the polyvinyl alcohol aqueous solution was added to 0.5864g of acrylamide, 0.0050g of N,N'-methylenebisacrylamide, and 0.0279g of potassium persulfate in sequence, and stirred to obtain a uniform solution; mechanical stirring was turned on, and 90μl of a 0.01g / ml boric acid aqueous solution was added, and the addition was divided into nine times. 10μl was taken out at a time using a pipette and dropped in, with an interval of 2.5 minutes each time, and the mixture was stirred until the state of the mixture was uniform; 2.17g of 50nm ferrosoferric oxide was added in small amounts several times, and mechanical stirring was stopped after mixing evenly, and the mixture was placed in a vacuum environment to remove bubbles; the uniform mixture was then transferred to a polytetrafluoroethylene mold sprayed with a release agent, placed in a 60°C oven for thermal initiation polymerization for 4h, and then removed from the mold to obtain a hydrogel with a specific shape, good mechanical properties, good stability, and a solid content of approximately 37.5%.

[0039] Example 4:

[0040] At room temperature and pressure, 1g of polyvinyl alcohol was added to 12ml of deionized water, and the mixture was heated and stirred in an oil bath at 80°C to dissolve the polyvinyl alcohol aqueous solution; 2.5g of the polyvinyl alcohol aqueous solution was taken, and 0.3554g of acrylamide, 0.0058g of N,N'-methylenebisacrylamide, and 0.0135g of potassium persulfate were added thereto in sequence, and stirred to obtain a uniform solution; mechanical stirring was turned on, and 100μl of a 0.01g / ml boric acid aqueous solution was added, and the addition was divided into 10 additions, and 10μl was taken out at a time using a pipette, with an interval of 2.5 minutes each time, and the mixture was stirred until the state of the mixture was uniform; 0.7190g of 500nm ferrosoferric oxide was added thereto in small amounts and multiple times, and mechanical stirring was stopped after mixing evenly, and the mixture was placed in a vacuum environment to remove bubbles; the uniform mixture was then transferred to a polytetrafluoroethylene mold sprayed with a release agent, placed in a 55°C oven for thermal initiation polymerization for 4h, and removed from the mold to obtain a hydrogel with a specific shape, good mechanical properties, good stability, and a solid content of approximately 20%.

[0041] Depend on Figure 1 It can be seen that the magnetic hydrogels with solid contents of 20%, 55% and 64% respectively have stable and complete structures.

[0042] Depend on Figure 2 Visible, 1667cm -1 At 3450cm -1 There is a broad absorption band at 1351cm, which is caused by the stretching vibration of the -OH group on the polyvinyl alcohol. The full width at half maximum (FWHM) of this peak clearly shows the extensive hydrogen bonding between adjacent hydroxyl groups. The red shift of the hydroxyl peak indicates that hydrogen bonding is formed between the double network hydrogel and the magnetic particles. -1 The peak at 584 cm is the borate ester bond peak after adding boric acid. -1 The peaks at (A) and (B) are the Fe-O stretching vibration peaks after the addition of Fe3O4. This demonstrates the successful preparation of DN hydrogels and the introduction of magnetic particles into them.

[0043] Depend on Figure 3 It can be seen that the magnetic solid particles are densely loaded in the gel network, and no obvious hydrogel network structure can be seen. At the same time, no obvious stratification phenomenon is found, indicating that the solid particles are evenly dispersed.

[0044] Depend on Figure 4 As can be seen, the loss modulus is greater than the storage modulus, so the loss factor is greater than 1, and the mixed system exhibits partial fluid behavior, lacking a stable structure and a certain degree of integrity. With increasing shear stress, the modulus values ​​increase because the dynamic cross-linked network has a certain elasticity, and with increasing shear stress, a climbing phenomenon occurs.

[0045] Depend on Figure 5It can be seen that after the chemical cross-linking network is formed, the storage modulus of the composite system is greater than the loss modulus, and is increased by about two orders of magnitude compared with the value before curing. The mixed system exhibits a solid-like behavior and has a certain stable structure and integrity.

[0046] Depend on Figure 6 、 Figure 7 It can be seen that as the temperature gradually increases, the gel composite first undergoes desolvation and volatilization of small molecular components. At nearly 250°C, the polymer gradually begins to thermally degrade. At around 400°C, ferrosoferric oxide can be oxidized to iron oxide by oxygen in the air. At 800°C, the residue is mainly red iron oxide.

Claims

1. A method for preparing a magnetically deformable high-solid content hydrogel, characterized in that The method comprises the following steps: Step 1: Add polyvinyl alcohol to deionized water, heat and dissolve, and obtain a polyvinyl alcohol aqueous solution with a mass concentration of 3 to 15%; Step 2: adding acrylamide, N,N'-methylenebisacrylamide and potassium persulfate in sequence to the polyvinyl alcohol aqueous solution obtained in step 1, and stirring to obtain a uniform solution, wherein: the amount of acrylamide added is 40-100% of the molar amount of the polyvinyl alcohol repeating unit, the amount of N,N'-methylenebisacrylamide added is 0.4-1% of the molar amount of acrylamide, and the amount of potassium persulfate added is 1-2% of the molar amount of acrylamide; Step 3: Adding boric acid aqueous solution dropwise to the uniformly mixed solution obtained in step 2 while stirring to obtain a uniform dynamically cross-linked hydrogel, wherein the amount of boric acid aqueous solution added is 0.4 to 2% of the molar amount of the polyvinyl alcohol repeating unit; Step 4: adding ferrosoferric oxide solid powder to the dynamically cross-linked hydrogel obtained in step 3, stirring evenly, and then placing in a vacuum environment to remove bubbles, thereby obtaining a dynamic reversible network hydrogel loaded with a high content of magnetic particles, wherein the amount of ferrosoferric oxide added is 10 to 64 wt% of the dynamically cross-linked hydrogel obtained in step 3; Step 5: The dynamic reversible network hydrogel obtained in step 4 is transferred to a polytetrafluoroethylene mold and placed in an oven for thermally initiated polymerization for 2 to 6 hours to obtain a magnetically deformable high-solid content hydrogel with good mechanical properties and stability.

2. The method for preparing a magnetically deformable high-solid content hydrogel according to claim 1, characterized in that In the step 3, the concentration of the boric acid aqueous solution is 0.01 to 0.02 g / mL.

3. The method for preparing a magnetically deformable high-solid content hydrogel according to claim 1, characterized in that In the step 3, the stirring speed is 150-250 rpm.

4. The method for preparing a magnetically deformable high-solid content hydrogel according to claim 1, characterized in that In the step 4, the rotation speed of the mechanical stirring is 100-200 rpm.

5. The method for preparing a magnetically deformable high-solid content hydrogel according to claim 1, characterized in that In the step 4, the particle size of ferrosoferric oxide is 50 to 500 nm.

6. The method for preparing a magnetically deformable high-solid content hydrogel according to claim 1, characterized in that In the step 5, the oven temperature is 50-70°C.

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