A preparation method for 3D printable high-toughness interpenetrating network hydrogel elastomer

Abstract

This invention relates to the field of polymer materials technology, specifically to a 3D-printable high-toughness interpenetrating network hydrogel elastomer, its preparation method, and its applications, aiming to solve the problems of poor mechanical properties and brittleness of traditional hydrogels. The invention mainly consists of methacrylated polyvinyl alcohol (PVA-MA), hydroxypropyl cellulose (HPC), chitosan quaternary ammonium salt (HACC), and carboxylated cellulose nanofibers (CNF). After irradiation under specific ultraviolet light, a hydrogel elastomer is formed, followed by salt solution post-treatment. PVA-MA and HPC are linked by hydrogen bonds, while CNF and HACC generate electrostatic attraction and simultaneously form hydrogen bonds with the carboxyl groups of HPC, thus forming an interpenetrating network. After immersing the formed hydrogel in a salt solution, strong hydrophobic interactions and chain binding are introduced through the Hofmeis ion effect, endowing the hydrogel with excellent toughness, enabling it to withstand an external force of 911.11 ± 13.85 kPa (compressed to 30% of its original height), with an elongation at break exceeding 100% and a tensile strength exceeding 2000 kPa.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to 3D printable high-toughness interpenetrating network hydrogel elastomer hydrogels, their preparation methods, and applications. Background Technology

[0002] Hydrogels are polymeric materials with a three-dimensional network structure that can absorb large amounts of water while maintaining their shape and structure. Due to their good biocompatibility, tunable physicochemical properties, and tissue-like softness, hydrogels have broad application prospects in biomedicine, tissue engineering, drug delivery, and sensors. However, traditional hydrogels often suffer from low mechanical strength and poor toughness, limiting their application in fields requiring high mechanical properties. Summary of the Invention

[0003] 1. In order to solve the problems of low mechanical strength and poor toughness of existing hydrogels, this invention provides a 3D printable high-toughness interpenetrating network hydrogel elastomer, its preparation method and application.

[0004] 2. The 3D printable high-toughness interpenetrating network hydrogel elastomer is composed of the following raw materials in parts by weight:

[0005] Polyvinyl alcohol: 0.5 parts - 5 parts;

[0006] Methacrylic anhydride: 0.5-5 parts;

[0007] Hydroxypropyl cellulose: 0.5-5 parts;

[0008] Chitosan quaternary ammonium salt: 0.05 parts - 0.25 parts;

[0009] Carboxylated cellulose nanofibers: 0.05 parts - 0.25 parts;

[0010] 2-Hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone: 0.01-1 part;

[0011] Sodium citrate: 5-60 parts;

[0012] Sodium chloride: 5-30 parts;

[0013] Deionized water: 20-100 parts.

[0014] 3. The preparation method of the 3D printable high-toughness interpenetrating network hydrogel elastomer includes the following steps:

[0015] (1) Polyvinyl alcohol is heated in a water bath at 90℃ ~ 95℃ and dissolved in 20 ~ 150 ml of deionized water to obtain a polyvinyl alcohol solution with a mass fraction of 1.5% ~ 10%. Methacrylic anhydride with a concentration of 1:1 with polyvinyl alcohol is added to obtain mixed solution A. PVA-MA hydrogel is obtained by photocuring and is denoted as PM hydrogel.

[0016] (2) Add hydroxypropyl cellulose (equivalent to 20% ~ 200% of polyvinyl alcohol) to mixed solution A, heat and stir in a water bath for 12 ~ 48 h, and after it is fully dissolved, mixed solution B is obtained. PVA-MA / HPC hydrogel is obtained by photocuring, and it is denoted as PMH hydrogel.

[0017] (3) Chitosan quaternary ammonium salt and carboxylated cellulose nanofibers were added to mixed solution B in a 1:1 ratio and stirred evenly to obtain mixed solution C. PVA-MA / HPC / HACC / CNF hydrogel was obtained by photocuring and denoted as PMHC hydrogel.

[0018] (4) Add 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone to mixed solution C, stir thoroughly to obtain mixed solution D, and obtain PVA-MA / HPC / HACC / CNF / I2959 hydrogel by photocuring, which is denoted as PMHI hydrogel;

[0019] (5) After immersing the PMHI hydrogel in sodium citrate solutions of different concentrations, it is then immersed in sodium chloride solutions of different concentrations for a certain period of time to obtain a high-toughness interpenetrating network hydrogel elastomer.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) Compared with other hydrogels, the hydrogel elastomer of the present invention has good mechanical strength and can withstand an external force of 911.11±13.85kPa (compressed to 30% of its original height). It can maintain structural integrity when subjected to strong external impact and is not easy to break. This strong mechanical stability provides a solid foundation for its application in various complex and high-strength environments.

[0022] (2) Good toughness: Hydrogel elastomers have good toughness. While having good compressive stress, they can withstand tensile stress of 2251.06±12.35kPa. When deformed by external force, they can quickly return to their original shape after the external force is removed, thanks to their excellent elastic properties, and are not prone to permanent damage.

[0023] (3) The hydrogel elastomer of the present invention has excellent biocompatibility, no toxic side effects on organisms, and can maintain high biosafety and stability, and can be used in the biomedical field.

[0024] (4) The hydrogel elastomer preparation method of the present invention is simple and easy to implement, without the need for high-end and complex instruments and equipment and cumbersome operation steps, and is low in cost and easy to industrialize.

[0025] (5) The hydrogel of the present invention is environmentally friendly and can be reused many times. Its performance will not be greatly reduced due to repeated use, which effectively reduces the generation of waste and reduces resource consumption. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Wherein:

[0027] Figure 1 These are before-and-after comparison images and physical photos of the PVA grafting MA reaction in this invention;

[0028] Figure 2 This is a schematic diagram of the mechanical properties and rebound curve of the PM hydrogel of the present invention under different stresses and strains;

[0029] Figure 3 This is a schematic diagram of the mechanical properties and rebound curve of the PMH hydrogel of the present invention under different stresses and strains;

[0030] Figure 4 This is a schematic diagram of the mechanical properties and rebound curve of the PMHC hydrogel of the present invention under different stresses and strains;

[0031] Figure 5 This diagram shows the mechanical properties and rebound curves of the PMHI hydrogel of the present invention after being immersed in sodium citrate solutions of different concentrations under different stresses and strains.

[0032] Figure 6 These are comparative images of the PMHI hydrogel of the present invention after being soaked in different concentrations for 24 hours.

[0033] Figure 7 This is a comparison image of the PMHI hydrogel of the present invention before and after soaking in sodium citrate solution. Detailed Implementation

[0034] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0036] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0037] The materials obtained in the embodiments of the present invention were subjected to performance testing according to the following method:

[0038] Compression tests were performed on the hydrogel using a texture analyzer (TMS-PRO); tensile tests were performed on the hydrogel using a universal testing machine.

[0039] Example 1

[0040] Add 8.0% PVA (by mass of deionized water) to 25 mL of deionized water, heat in a 95°C water bath to dissolve, and then add MA (m PVA V MA The mixture was stirred magnetically at 500 rpm in the dark (ratio 1:1) until the reaction was complete. Then, HPC (100% of the PVA mass) was added, along with HACC and CNF in a 1:1 ratio (1.6% of the total deionized water mass). I2959 (0.02% of the PVA mass) was added. The mixture was heated in a 35°C water bath and stirred until homogeneous. The solution was extruded into a PTFE mold using a 1ml syringe and irradiated with 365nm UV light for 5 minutes to obtain PMHI hydrogel. Subsequently, it was soaked in a 1.4 mol / L sodium citrate solution for 24 hours to obtain a high-toughness interpenetrating network hydrogel elastomer.

[0041] Example 2

[0042] The difference between this embodiment and Example 1 is that the addition amounts of HPC, CNF, HACC, and I2959 are adjusted to 0%, while the rest of the preparation process is the same as in Example 1, and a hydrogel is obtained.

[0043] Example 3

[0044] The difference between this embodiment and Example 1 is that the addition amounts of CNF, HACC, and I2959 are adjusted to 0%, while the rest of the preparation process is the same as in Example 1, and a hydrogel is obtained.

[0045] Example 4

[0046] The difference between this embodiment and Example 1 is that the amount of I2959 added is adjusted to 0%, while the rest of the preparation process is the same as in Example 1, and a hydrogel is obtained.

[0047] Example 5

[0048] The difference between this embodiment and Embodiment 1 is that the obtained hydrogel is tested directly without post-processing.

[0049] The tensile and compressive properties of the materials obtained in the above embodiments were tested, with the compressive strain set to 70%. The comparison results with those of Example 1 are shown in Table 1.

[0050] Table 1. Stress-strain comparison of the embodiments

[0051]

[0052] As shown in Table 1 above, the addition of HPC significantly increases the compressive and tensile stresses of the hydrogel, demonstrating a substantial impact. This is because the addition of HPC causes hydrogen bonds to form between the hydroxyl groups on the HPC surface and the anhydride groups on the PVA-MA surface, resulting in physical entanglement and increasing the number of cross-linking sites within the hydrogel. This makes the network structure more compact and stable, thereby improving tensile strength, compressive strength, and elastic modulus, enabling it to withstand external forces and rebound quickly. When carboxylated CNF and HACC are added to the system, the carboxyl groups on the surface of the carboxylated CNF will electrostatically attract the positively charged HACC and also form hydrogen bonds with the carboxyl groups of HPC, thus forming an interpenetrating network. The increased number of molecular chain nodes macroscopically manifests as further enhanced toughness. The addition of I2959, as a photoinitiator, can initiate C=C cross-linking at the ends of the PVA-MA molecular chains, resulting in sufficient cross-linking points. This allows the material to initiate polymerization in a short time, improving the bonding force between the internal structures of the hydrogel, thus significantly increasing the compressive and tensile stresses. After the formed hydrogel is immersed in sodium citrate solution, strong hydrophobic interactions and chain binding are introduced through the Hofmeis ion effect, which gives the hydrogel excellent strength and toughness.

[0053] Example 6

[0054] The difference between this embodiment and Example 1 is that the amount of PVA added is adjusted to 2%, 4%, 6%, and 10% of the mass of deionized water, the amount of HPC, CNF, HACC, and I2959 added is 0%, no solution is soaked, and the rest of the preparation process is the same as in Example 1, and a hydrogel is obtained.

[0055] The tensile and compressive properties of the materials obtained in the above embodiments were tested, with the compressive strain set to 70%. The comparison results with those of Example 2 are shown in Table 2.

[0056] Table 2 Comparison of Stress and Strain in Examples

[0057]

[0058] Figure 1The image shows a comparison of the PM hydrogel prepared in Example 6 of this invention before and after the reaction. It can be seen that before the reaction, the methacrylic anhydride appeared as oil droplets in the PVA solution, and during the reaction it was milky white. After the reaction, it became a transparent and clear solution.

[0059] Figure 2 This is a schematic diagram showing the mechanical properties of the PM hydrogel prepared in Example 6 of the present invention under different strains and stresses. Figure 2 (a) is the stress-strain diagram obtained from the compression test. It can be seen that as the PVA content increases, the tensile stress gradually increases, especially when it is 6% to 8%, and the tensile stress is not much different between 8% and 10%. Figure 2 (b) is the stress-strain diagram obtained from the tensile test. When the PVA content is 2%, the sample is too soft and breaks before the tensile test is carried out, so it is directly excluded. In the stress-strain diagrams of the other four samples, it can be seen that as the PVA content increases, the tensile stress gradually increases and the tensile elongation shows a trend of first increasing and then decreasing. The tensile stress increases sharply from 6% to 8%, and the tensile elongation decreases from 8% to 10%. Figure 2 (c) represents the resilience of PM hydrogel. It can be seen that the resilience increases significantly with the increase of PVA content. This is because PVA is the main skeleton structure of the hydrogel network. When its addition amount increases, the hydrogen bonds and C=C photo-induced crosslinking points inside the hydrogel increase, which increases the intermolecular forces and improves the mechanical properties.

[0060] Example 7

[0061] The difference between this embodiment and Example 1 is that the amount of HPC added is adjusted to 40%, 60%, 80%, and 120% of the mass of PVA, while the amounts of CNF, HACC, and I2959 added are 0%. No solution is soaked in the embodiment. The rest of the preparation process is the same as in Example 1, and a hydrogel elastomer is obtained.

[0062] The tensile and compressive properties of the materials obtained in the above embodiments were tested, with the compressive strain set to 70%. The comparison results with those of Example 3 are shown in Table 3.

[0063] Table 3 Stress-Strain Comparison of Examples

[0064]

[0065] Figure 3 The diagram shows the mechanical properties of the PMH hydrogel prepared in Example 7 of this invention under different strains and stresses. It can be seen that the mechanical properties of the hydrogel elastomer are greatly improved after the addition of HPC, but the resilience is reduced compared to before. This may be because the addition of HPC increases the number of nodes in the hydrogel elastomer molecular chain and makes the network connection more dense. Figure 3(a) and (b) are stress-strain diagrams obtained from compression and tension tests. It can be seen that as the amount of HPC added increases, both compressive and tensile stresses gradually increase, but the tensile elongation decreases. This may be because excessive HPC is added, resulting in incomplete dissolution and its presence in powder form, thus exhibiting higher compressive stress. Furthermore, since HPC exists in powder form within the hydrogel elastomer, it causes plastic deformation during tensile testing, leading to a smaller decrease in tensile strain. Conversely, when the amount of HPC added is too low, the distance between molecular chains is larger, making them more prone to movement under external force, resulting in lower compressive and tensile stresses and greater deformation. Figure 3 (c) represents the resilience of PMH hydrogel. It can be seen that the resilience gradually increases with the amount of HPC. However, when the amount of HPC is excessive, the resilience deteriorates and there is an over-stickiness during the preparation process.

[0066] Example 8

[0067] The difference between this embodiment and Example 1 is that the total amount of CNF and HACC added is adjusted to 0.4%, 0.8%, 1.2%, and 2.0% of the mass of deionized water, respectively, and the amount of I2959 added is 0%. No solution is soaked in the hydrogel. The rest of the preparation process is the same as in Example 1.

[0068] The tensile and compressive properties of the materials obtained in the above embodiments were tested, with the compressive strain set to 70%. The comparison results with those of Example 4 are shown in Table 4.

[0069] Table 4 Stress-Strain Comparison of Examples

[0070]

[0071] Figure 4 The diagram shows the mechanical properties of the PMHC hydrogel prepared in Example 8 of this invention under different strains and stresses. It can be seen that after adding CNF and HACC, the compressive stress and tensile stress are both improved compared with the PMH hydrogel elastomer. Figure 4 (a) is the stress-strain diagram obtained from the compression test. It can be seen that when the compressive stress is between 0 and 50 kPa, the deformation curve of the material is close to linear. When the stress is between 50 and 200 kPa, the deformation of the material is similar to the characteristics of a tangent curve. When the stress increases to 200 to 400 kPa, the material reaches its yield limit, and the rate of change of the material's deformation decreases rapidly. At this time, the curve shows a large upward trend. Figure 4 (b) is the stress-strain diagram obtained from the tensile test. It can be seen that the tensile strain of the hydrogel elastomer is mostly around 200%. Compared with PMH, the tensile performance is greatly improved. However, when the amount added is too large, the internal sub-chains of the hydrogel elastomer become dense and the cross-linking is tight, thus reducing the tensile strain. Figure 4 (c) Rebound rate of PMHC hydrogel elastomer. It can be seen that the rebound rate of all samples increased, with the highest rebound rate observed when the total addition of CNF and HACC was 1.6%. This may be because the addition of CNF and HACC disrupted the original structure of HPC, forming an interpenetrating double network structure, which increased the restriction on molecular chain movement, thus requiring greater forces to create relative positions between molecules. At the same time, the abundant hydroxyl groups of CNF have hydrogen bonding with PVA-MA and HPC, and the carboxyl groups on the molecular chain undergo ionic cross-linking with the quaternary ammonium ions on HACC, forming an interpenetrating network with HPC and thus improving the mechanical properties of the hydrogel.

[0072] Example 9

[0073] The difference between this embodiment and Example 1 is that the concentration of sodium citrate was adjusted to 0.2 mol / L, 0.6 mol / L, 1 mol / L, and 1.8 mol / L, while the rest of the preparation process was the same as in Example 1, and a hydrogel was obtained.

[0074] The tensile and compressive properties of the materials obtained in the above embodiments were tested, with the compressive strain set to 70%. The comparison results with those of Example 5 are shown in Table 5.

[0075] Table 5. Stress-strain comparison of the embodiments

[0076]

[0077] Figure 5 The diagram shows the mechanical properties of the PMHI hydrogel prepared in Example 9 of this invention under different strains and stresses. It can be seen that the mechanical properties of the hydrogel elastomer soaked in sodium citrate are greatly improved. Figure 5 (a) is the stress-strain diagram obtained from the compression test. It can be seen that the mechanical properties of the hydrogel elastomer gradually increase with the increase of sodium citrate solution concentration. The mechanical properties increase sharply from 1.4 mol / L to 1.8 mol / L. This may be because the citrate ions in the sodium citrate solution form electrostatic interactions with the quaternary ammonium ions of HACC. At the same time, the salting-out effect enhances the copper ion effect, promotes internal cross-linking, and reduces the electrostatic repulsion between molecular chain segments. Figure 5 (a) is the stress-strain diagram obtained from the compression test. It can be observed that as the sodium citrate solution concentration increased from 0.2 mol / L to 1.8 mol / L, the tensile strength increased from 247.54 ± 7.6 kPa to 4349.20 ± 1.10 kPa, but the elongation at break decreased. This may be because the HPC was not completely dissolved and existed in the system as powder, affecting the tensile elongation. However, soaking in a high concentration of sodium citrate solution increases the crosslinking density, thereby improving the mechanical properties.

[0078] Figure 6The images shown are actual images of the PMHI hydrogel elastomer prepared in Example 9 of this invention after soaking in different concentrations for 24 hours. It can be seen that the hydrogel elastomer expands at lower concentrations and shrinks at higher concentrations. This may be because at low concentrations, the sodium citrate solution has a lower ionic pressure, leading to osmotic pressure inside and outside the hydrogel, which promotes water molecules to enter the hydrogel, thus causing expansion. At higher concentrations, the high concentration of sodium citrate solution has a higher ionic strength, causing a salting-out effect, which leads to the aggregation of molecular chains in the hydrogel elastomer, expelling water molecules. Simultaneously, the high concentration of ions weakens the electrostatic repulsion between chains, resulting in denser hydrogen bonds and hydrophobic interactions, manifesting as hydrogel shrinkage.

[0079] Figure 7 The images shown are comparisons of the PMHI hydrogel elastomer prepared in Example 9 of this invention before and after immersion in sodium citrate solution. It can be seen that before immersion, the hydrogel is opaque milky white, while after immersion, the hydrogel is translucent around the edges and opaque milky white in the center.

[0080] In summary, this invention yields a high-toughness interpenetrating network hydrogel elastomer hydrogel. PVA grafted with MA yields unsaturated carbon-carbon double bonds. Upon excitation with 365nm ultraviolet light, I2959 absorbs light energy, generating highly reactive free radicals that initiate the polymerization of PVA-MA monomers. Furthermore, reversible hydrogen bonding exists between the hydroxyl groups of PVA-MA and HPC, forming the first network layer. The carboxyl groups (-COO) at the ends of the CNF molecular chains are carboxylated. - ) and the quaternary ammonium ion (NH4) at the end of the HACC molecular chain + Hydrogen bonds are formed. HPC molecules, under the influence of certain water molecules, autonomously arrange themselves into a regular cholesteric structure. The addition of CNF and HACC disrupts the original regular layered structure, forming an interpenetrating network. When the gel elastomer is immersed in a sodium citrate solution, the citrate ions react with the NH4+ ions at the ends of the HACC molecular chains. + The salting-out effect further enhances the hydrogen bonding between hydrogel networks.

[0081] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a 3D-printable high-toughness interpenetrating network hydrogel elastomer, characterized in that: (1) Heat polyvinyl alcohol in a water bath at 90℃ ~ 95℃ and dissolve it in 20~150ml of deionized water to obtain a polyvinyl alcohol solution with a mass fraction of 4% ~ 10%. Add methacrylic anhydride, and the mass ratio of polyvinyl alcohol to the volume of methacrylic anhydride is 1:1 to obtain mixed solution A. (2) Add 20% to 200% of the mass of polyvinyl alcohol to mixed solution A, heat and stir in a water bath for 12 to 48 hours, and obtain mixed solution B after it is fully dissolved; (3) Chitosan quaternary ammonium salt and carboxylated cellulose nanofibers were added to mixed solution B at a mass ratio of 1:1, with a total mass of 0.4%, 0.8%, 1.2% or 2.0% of the deionized water, respectively. After stirring evenly, mixed solution C was obtained. (4) Add 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone to mixed solution C, stir thoroughly to obtain mixed solution D, and obtain PVA-MA / HPC / HACC / CNF / I2959 hydrogel by photocuring, which is denoted as PMHI hydrogel; (5) PMHI hydrogel was immersed in sodium citrate solution with a concentration of 0.5mol / L ~ 3mol / L for 24~48h, and then immersed in sodium chloride solution of different concentrations. After a certain period of time, a high-toughness interpenetrating network hydrogel elastomer was obtained.

2. The method for preparing a 3D-printable high-toughness interpenetrating network hydrogel elastomer as described in claim 1, characterized in that: The polyvinyl alcohol is of type 1799, with a molecular weight of 200,000 to 205,000.

3. The method for preparing a 3D-printable high-toughness interpenetrating network hydrogel elastomer as described in claim 1, characterized in that: The molecular weight of the hydroxypropyl cellulose is 100,000 to 500,000.

4. The method for preparing a 3D-printable high-toughness interpenetrating network hydrogel elastomer as described in claim 1, characterized in that: The degree of substitution of the chitosan quaternary ammonium salt is 95% to 99%; the content of the carboxylated cellulose nanofibers is 95% to 99.8%, the diameter is 4 to 10 nm, and the length is 1 to 3 μm.

5. The method for preparing a 3D-printable high-toughness interpenetrating network hydrogel elastomer as described in claim 1, characterized in that: The purity of the 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone is 95% to 99%.

6. The method for preparing a 3D-printable high-toughness interpenetrating network hydrogel elastomer as described in claim 1, characterized in that: The sodium chloride solution concentration is 1~5 mol / L, and the soaking time is 3~48 h.

7. The method for preparing a 3D-printable high-toughness interpenetrating network hydrogel elastomer as described in claim 1, characterized in that: The mixed solution D is extruded under pressure at a speed of 5 to 10 mm / s, and then irradiated under a 254 nm to 405 nm UV lamp for 1 to 30 minutes to form the product.

8. The method for preparing a 3D-printable high-toughness interpenetrating network hydrogel elastomer as described in claim 1, characterized in that: The water bath heating temperature in step (2) is 20 ~ 35℃, and the stirring speed is 30 ~ 500 rmp / s.

9. A 3D printable high-toughness interpenetrating network hydrogel elastomer prepared by the preparation method according to any one of claims 1 to 8.

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