Tough hydrogel based on polymerization-induced hydrophilic and hydrophobic microphase separation and preparation method thereof

Abstract

The invention discloses tough hydrogel based on polymerization-induced hydrophilic and hydrophobic microphase separation and a preparation method thereof.The preparation method comprises the steps that firstly, a hydrophobic high-molecular polymer is dissolved in acrylic acid, then other hydrophilic polymer monomers can be added according to needs, and uniform and transparent liquid is formed; adding a small amount of initiator and cross-linking agent to obtain a bulk polymerization reaction system; initiating bulk polymerization, and performing microphase separation on a polymerization induction system to obtain a hydrogel precursor; and immersing the hydrogel precursor in water to remove residual chemicals and swell the hydrogel precursor to balance, and promoting further microphase separation of hydrophilic and hydrophobic macromolecules by water to obtain the tough hydrogel for polymerization-induced hydrophilic and hydrophobic microphase separation. Compared with the traditional hydrophilic hydrogel with a single network, the hydrogel has the advantages that the mechanical strength is obviously improved, the strength and the toughness can be comparable with the mechanical properties of biological tissues and are kept stable, and the hydrogel has huge potential in the directions of artificial heart valves, artificial cartilages, artificial blood vessels and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of hydrogel materials, and relates to a flexible material hydrogel preparation technology, in particular to a tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation and a preparation method thereof. BACKGROUND

[0002] Hydrogels are cross-linked polymer networks of solid and liquid components, similar to soft tissues of the human body, due to their soft and water-containing characteristics, they are promising materials for applications in many fields such as biomedical engineering, soft robots and environmental research. Many applications require hydrogels to bear mechanical load under static or cyclic load conditions. In general, biological tissues have high toughness. However, traditional synthetic hydrogels are composed of inhomogeneous hydrophilic polymer networks, and their mechanical strength (<1 MPa) and toughness are usually very weak, which greatly limits the application of such hydrogels. For a simple polymer network, the increase of elastic modulus and strength is often accompanied by the decrease of deformation ability, fracture energy and fatigue threshold, so for most materials, strength and toughness are in conflict, and the improvement of material strength often accompanies the sacrifice of toughness, so it is a challenge to design and develop hydrogels with high toughness while giving high modulus and strength.

[0003] The reason for the poor mechanical properties of traditional hydrogels is due to several inherent characteristics: first, the inhomogeneity of polymer density distribution and the length of polymer chains between crosslinking points. Therefore, the hydrogel is prone to stress concentration when loaded, thereby causing fracture. Second, the lack of energy dissipation mechanism makes the hydrogel have low toughness. Third, traditional hydrogels usually contain a large amount of water, and the low solid phase content further leads to weak and brittle mechanical properties.

[0004] Although hydrogels have many advantages, the above mechanical performance deficiencies have greatly limited their applications, so improving the mechanical properties of hydrogels can greatly expand their application fields and application scenarios. The main strategies for improving the mechanical properties of hydrogels through structural components can be divided into three categories: 1) design topological structures, such as slip ring gels, uniform four-arm gels and highly entangled gels, to make the stress more evenly distributed in the single network system; 2) introduce energy dissipation mechanisms through sacrificial bonds, such as double network hydrogels; 3) introduction of high-order structures, such as microphase separation, microcrystals, and fibers or fabrics. The present application combines the characteristics of the above three strategies, uses monomer bulk polymerization to obtain a super-high entangled hydrogel, and at the same time introduces hydrophobic interactions to make the gel form a micromicrophase separation structure, effectively dissipate energy, and obtain a polymerization-induced hydrophilic-hydrophobic microphase separation hydrogel. Compared with traditional hydrophilic hydrogels, the mechanical strength of the obtained polymerization-induced hydrophilic-hydrophobic microphase separation hydrogel is significantly improved, especially its high strength (0.1-10 MPa) and toughness 1-20 MJ m -3The mechanical strength and toughness of the hydrogel can be comparable to the mechanical properties of biological tissues, and the hydrogel can be stable in a physiological saline or PBS buffer environment, which makes the hydrogel have great application potential in the fields of artificial heart valves, artificial cartilage, artificial blood vessels and other biomedical fields. SUMMARY

[0005] In order to solve the problem that the conventional hydrogel has low mechanical strength and toughness and is limited in application, the application provides a strong and tough hydrogel based on polymer-induced hydrophobic microphase separation and a preparation method thereof, so as to effectively solve the above technical problems.

[0006] In order to solve the above technical problems, the technical scheme adopted by the application is as follows: A preparation method of a strong and tough hydrogel based on polymer-induced hydrophobic microphase separation, comprising the following steps: S1, dissolving a hydrophobic polymer in liquid acrylic acid to configure a liquid phase system; S2, continuously adding a crosslinking agent and an initiator to obtain a bulk polymerization reaction system; S3, polymerizing the bulk polymerization reaction system under the initiation condition of the initiator, and when the polymerization reaches a certain degree, the hydrophobic polymer gradually precipitates from the solution, and the bulk polymerization reaction system gradually undergoes microphase separation, and after the reaction is completed, a hydrogel precursor is obtained; S4, swelling the hydrogel precursor to obtain a strong and tough hydrogel.

[0007] The principle of preparing the strong and tough hydrogel is as follows: Through solvent-free bulk polymerization, the entanglement between the polymer chains is the strongest, and the stress is more uniformly distributed in the network system; by introducing a hydrophobic polymer, the hydrophobic interaction is used as a sacrificial bond, and the introduction of the sacrificial bond can effectively dissipate energy during the stress process of the gel; in the initial state, the hydrophobic polymer is dissolved in acrylic acid to form a uniform bulk polymerization reaction system, then the monomer solution is subjected to bulk polymerization, and when the monomer solution is polymerized to a certain degree, the hydrophobic polymer (which does not participate in polymerization) gradually precipitates from the solution, at this time the homogeneous system gradually undergoes microphase separation, and the hydrophobic polymer is highly entangled in the polymer; when swelling, the polyacrylic acid absorbs water and swells, and the hydrophobic polymer is forcibly stretched, and the tensile stress is concentrated in the more tough hydrophobic region, while the hydrophilic region (carboxyl group on the polyacrylic acid) ensures its ductility, so that the gel still has good deformation ability on the basis of improved modulus and strength; after swelling equilibrium, water promotes further microphase separation of the hydrophobic polymer, and a strong and tough hydrogel based on polymer-induced hydrophobic microphase separation is obtained, so that the polymer-induced hydrophobic microphase separation hydrogel has good toughness.

[0008] Further, according to the above principle, the hydrophobic polymer does not need to participate in the reaction, but needs to be dissolved in the liquid acrylic acid, so any hydrophobic polymer that can be dissolved in the acrylic acid can meet the requirements of the present application; for example, the hydrophobic polymer includes but is not limited to one or more of cellulose acetate, polylactic acid, ethyl cellulose, polycaprolactone, polymethyl methacrylate, polybutylene adipate, and polyacrylic acid.

[0009] Further, in step S1, the dissolution temperature of the hydrophobic polymer is 25-90°C.

[0010] Further, in S2, before adding the crosslinking agent and the initiator, a hydrophilic polymer monomer can also be added and dissolved in the liquid phase system as a functional monomer, and copolymerized with the acrylic acid to obtain unique functions such as special material adhesion ability, drug loading ability, etc.

[0011] It should be noted that the hydrophilic polymer monomer is used as a functional monomer, so the content can be 0 or any content required by the actual function, and those skilled in the art can adjust it according to the required function.

[0012] Further, according to the above principle, the hydrophilic polymer monomer only needs to meet the requirements of participating in the polymerization of acrylic acid copolymerization and being able to be dissolved in acrylic acid, without other special requirements, and the hydrophilicity only needs to meet the requirement of having a hydrophilic group, for example, the hydrophilic polymer monomer is a hydrophilic monomer that can be copolymerized with acrylic acid, and the hydrophilic monomer includes but is not limited to one or a combination of hydroxyethyl acrylate, acrylamide, N,N-dimethyl acrylamide, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide, N-(3-dimethylaminopropyl) methacrylamide, and N-hydroxyethyl acrylamide.

[0013] Furthermore, the crosslinking agent can be any conventional crosslinking agent, exemplary of which are polyisocyanates (such as JQ-1, JQ-1E, JQ-2E, JQ-3E, JQ-4, JQ-5, JQ-6, PAPI, emulsifiable MDI, tetraisocyanate), polyamines (such as propylenediamine, MOCA), polyols (such as polyethylene glycol, polypropylene glycol, trimethylolpropane, trimethylolethane), glycidyl ethers (such as polypropylene glycol glycidyl ether), inorganic crosslinking agents (such as zinc oxide, aluminum chloride, aluminum sulfate, sulfur, boric acid, borax, chromium nitrate), and organic crosslinking agents (such as styrene, α-methylstyrene, acrylonitrile, acrylic acid, methyl methacrylate). The following are crosslinking agents: acrylic acid, glyoxal, aziridine, organosilicon (e.g., tetraethyl orthosilicate, methyl orthosilicate, trimethoxysilane), benzenesulfonic acid (e.g., p-toluenesulfonic acid, p-toluenesulfonyl chloride), acrylate (e.g., 1,4-butanediol diacrylate, ethylene glycol dimethacrylate, TAC, butyl acrylate, HEA, HPA, HEMA, HPMA, MMA), organic peroxide (e.g., dicumyl peroxide, bis(2,4-dichlorobenzoyl peroxide), organometallic compounds (e.g., aluminum isopropoxide, zinc acetate, titanium acetylacetone), aziridine, multifunctional polycarbodiimide crosslinking agents, blocked crosslinking agents, and isocyanate crosslinking agents.

[0014] Furthermore, the initiator includes a photoinitiator and a thermal initiator.

[0015] Furthermore, the photoinitiator is an ultraviolet photoinitiator, specifically including the following major categories: 1. Benzoin and its derivatives (benzoin, benzoin dimethyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether).

[0016] 2. Benzoyl derivatives (diphenyl ethyl ketone, α,α-dimethoxy-α-phenyl acetophenone).

[0017] 3. Alkyl phenyl ketones (α,α-diethoxyacetophenone, α-hydroxyalkylphenyl ketone, α-aminealkylphenyl ketone).

[0018] 4. Acylphosphine oxides (aromatic phosphine oxides, bisbenzoylphenylphosphine oxides).

[0019] 5. Benzophenones (benzophenone, 2,4-dihydroxybenzophenone, michalcone).

[0020] 6. Thioxanthones (thiopropoxythioanthones, isopropylthioanthones).

[0021] Cationic photoinitiators are also important photoinitiators, including diaryliodonium salts, triaryliodonium salts, alkyliodonium salts, and cumeneferrocene hexafluorophosphate.

[0022] The thermal initiator includes any one of organic peroxide initiators, inorganic peroxide initiators, azo initiators, and redox initiators.

[0023] Organic peroxides are classified into the following 6 categories: 1. Acyl peroxides (benzoyl peroxide, lauroyl peroxide).

[0024] 2. Hydrogen peroxides (cumene hydrogen peroxide, tert-butyl hydrogen peroxide).

[0025] 3. Dialkyl peroxides (di-tert-butyl peroxide, dicumyl peroxide).

[0026] 4. Ester peroxides (tert-butyl peroxide, tert-butyl peroxyvalerate). 5. Ketone peroxides (methyl ethyl ketone peroxide, cyclohexanone peroxide).

[0027] 6. Dicarbonate peroxides (diisopropyl peroxide dicarbonate, dicyclohexyl peroxide dicarbonate).

[0028] Azo initiators include azobisisobutyronitrile (AIBN) and azobisisoheptanenitrile (AIHH).

[0029] Inorganic peroxides are soluble in water and are often used in emulsion and aqueous solution polymerization reactions. They are mainly persulfates, such as potassium persulfate, sodium persulfate, and ammonium persulfate.

[0030] Redox initiation systems utilize free radicals generated from electron transfer between oxidants and reductants to initiate polymerization reactions. Therefore, compared to thermally decomposing initiators, redox initiators can initiate polymerization reactions at lower temperatures (0–50°C), which increases the reaction rate and reduces energy consumption. Examples of redox initiators that can form redox systems include benzoyl peroxide / sucrose, tert-butyl hydroperoxide / sodium thiosulfate, tert-butyl hydroperoxide / sodium metabisulfite, and benzoyl peroxide / N,N-dimethylaniline. Ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / sodium formaldehyde sulfoxylate, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, benzoyl peroxide / N,N-diethylaniline, benzoyl peroxide / ferrous pyrophosphate, potassium persulfate / silver nitrate, persulfate / thiol, cumene hydrogen peroxide / ferrous chloride, potassium persulfate / ferrous chloride, hydrogen peroxide / ferrous chloride, cumene hydrogen peroxide / tetraethyleneimine, etc. Among them, tert-butyl hydrogen peroxide / sodium metabisulfite has the most suitable reaction rate.

[0031] Furthermore, in step S3, the hydrophobic polymer content in the hydrogel precursor is 0-60% (in the dry state, excluding endpoint 0).

[0032] It should be noted that the mass content of the hydrophobic polymer of the present invention is related to its molecular weight or molecular length. Those skilled in the art can determine a suitable mass content based on a certain type of hydrophobic polymer by conducting a limited number of experiments.

[0033] It should be noted that the bulk polymerization of this invention is a common polymerization, so the amount of crosslinking agent and initiator added can be the conventional amount according to their respective types.

[0034] Furthermore, in step S4, the solvent for the swelling hydrogel precursor is any one of pure water, physiological saline, or PBS buffer. During the swelling process, residual chemicals are washed away by changing the solvent or by using a flowing solvent. After swelling equilibrium, a strong and tough hydrogel is obtained.

[0035] On the other hand, the present invention also provides a strong hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation, which is prepared by the above preparation method.

[0036] On the other hand, the present invention also provides a method for preparing a hydrogel precursor for 3D printing, characterized by comprising the following steps: S1. Dissolve the hydrophobic polymer in liquid acrylic acid to prepare a liquid phase system; S2. Continue to add crosslinking agent and photoinitiator to obtain the bulk polymerization reaction system; S3. Continue to add light absorber to obtain precursor gel solution, which can be 3D printed using projection micro-stereolithography technology.

[0037] Furthermore, the light absorber is curcumin.

[0038] It should be noted that the hydrogel precursor of the present invention can be any shape, and can be made into the corresponding product form as needed. For specific shape design, a corresponding shape mold can be used as a reaction container, or 3D printing can be used, and appropriate crosslinking agents and initiators can be selected for 3D printing.

[0039] The beneficial effects of this invention are as follows: The polymerization-induced hydrophilic-hydrophobic microphase separation hydrogel obtained in this invention exhibits significantly improved mechanical strength compared to traditional single-network hydrophilic hydrogels, particularly its high strength (0.1~10 MPa) and toughness (1~20 MJ / m). −3 It can match the mechanical properties of biological tissues and can remain stable in physiological saline and PBS buffer environments. These advantages make it have great potential for application in artificial heart valves, artificial cartilage, artificial blood vessels and other fields. Attached Figure Description

[0040] Figure 1The present invention provides a flowchart of a method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation.

[0041] Figure 2 An acrylic acid and acrylamide copolymer hydrogel with added cellulose acetate, wherein cellulose acetate accounts for 10% of the mass of the hydrogel precursor, and the hydrogel is about 5 mm wide and about 0.6 mm thick, can suspend a weight of 2 kg.

[0042] Figure 3 The stress-strain curves for tensile tests of acrylic acid and acrylamide copolymer hydrogels containing cellulose acetate are shown below (the curves from low strength to high strength are for conventional acrylic acid and acrylamide copolymer hydrogels (aqueous solution polymerization system, water content of 50%), and acrylic acid and acrylamide copolymer hydrogels with cellulose acetate content of 0 wt%, 5 wt%, 10 wt%, and 15 wt% respectively (water content of not less than 50% after expansion).

[0043] Figure 4 Transmission electron microscopy (TEM) images of a cellulose acetate-acrylic acid-acrylamide copolymer hydrogel (cellulose acetate comprising 15% of the hydrogel precursor by mass) were obtained by cutting the precursor bulk material using a cryostat and observing at room temperature. Dark and light-colored regions constitute two phases of the material, with a phase spacing of approximately 120 nm.

[0044] Figure 5 The cellulose acetate hydrogel with a 3D-printed three-dimensional scaffold structure mentioned in Example 4 is an example of this. Detailed Implementation

[0045] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0046] like Figure 1 As shown, this invention provides a method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation, comprising the following steps: S1. Dissolve the hydrophobic polymer in liquid acrylic acid to prepare a liquid phase system; S2. Add and dissolve the hydrophilic polymer monomer into the liquid phase system; S3. Continue to add crosslinking agent and initiator to obtain the bulk polymerization reaction system; S4. The bulk polymerization reaction system is subjected to polymerization under the initiation conditions of an initiator. When the polymerization reaches a certain extent, the hydrophobic polymer gradually precipitates out of the solution, and the bulk polymerization reaction system gradually separates into microphases. After the reaction is complete, the hydrogel precursor is obtained. S5. Swell the hydrogel precursor to obtain a strong and tough hydrogel.

[0047] Example 1: (1) Add 4 g of ethyl cellulose (hydrophobic polymer) to 17 mL of acrylic acid solution and dissolve at 60 °C to prepare a liquid phase system.

[0048] (2) 18 g of acrylamide was added to and dissolved in the liquid phase system as a hydrophilic second monomer. 0.036 g of Irgacure 2959 was added to the liquid phase system as an initiator and 0.25 g of ethylene glycol dimethacrylate was added as a crosslinking agent to obtain the bulk polymerization reaction system.

[0049] (3) The bulk polymerization system is poured into a mold consisting of two glass plates separated by a silicone rubber spacer with a thickness of 1 mm, and the mixture is subjected to a strength of 0.3 W / m. -2 A hydrogel precursor with a mass fraction of 10% ethyl cellulose was obtained by polymerization under a 365 nm UV lamp for 2 hours.

[0050] (4) Subsequently, the hydrogel precursor was immersed in water to remove residual chemicals and swell to equilibrium to obtain a strong hydrogel with polymer-induced hydrophilic and hydrophobic microphase separation of sheet ethyl cellulose.

[0051] Example 2: (1) Add 4 g of polymethyl methacrylate (hydrophobic polymer) to 17 mL of acrylic acid solution and dissolve at 70 °C to prepare a liquid phase system.

[0052] (2) 18 g of acrylamide was added to and dissolved in the liquid phase system as a hydrophilic second monomer. 0.036 g of Irgacure 2959 was added to the liquid phase system as an initiator and 0.25 g of ethylene glycol dimethacrylate was added as a crosslinking agent to obtain the bulk polymerization reaction system.

[0053] (3) The bulk polymerization system is poured into a mold consisting of two glass plates separated by silicone rubber spacers with a thickness of 0.5 mm, and the mixture is subjected to a strength of 0.3 W / m. -2 A hydrogel precursor containing 10% polymethyl methacrylate was obtained by polymerization under a 365 nm UV lamp for 2 hours.

[0054] (4) Subsequently, the hydrogel precursor was immersed in water to remove residual chemicals and swell to equilibrium to obtain a strong hydrogel with sheet-like polymethyl methacrylate polymerization-induced hydrophilic and hydrophobic microphase separation.

[0055] Example 3: (1) 3 g of cellulose acetate (hydrophobic polymer) was prepared and added to 12.72 mL of acrylic acid solution and dissolved at 70 °C.

[0056] (2) 13.48 g of hydroxyethyl methacrylate was added to and dissolved in the liquid phase system as a hydrophilic second monomer. 0.017 g of Irgacure 2959 was added to the liquid phase system as an initiator and 0.12 g of ethylene glycol dimethacrylate was added as a crosslinking agent to obtain the bulk polymerization reaction system.

[0057] (3) The bulk polymerization system is poured into a mold consisting of two glass plates separated by silicone rubber spacers with a thickness of 0.5 mm, and the mixture is subjected to a strength of 0.2 W / m. -2 A hydrogel precursor of acrylic acid and hydroxyethyl methacrylate copolymer with a mass fraction of 10% cellulose acetate was obtained by polymerization under a 365 nm UV lamp for 2 hours (dry state).

[0058] (4) Subsequently, the hydrogel precursor was immersed in water to remove residual chemicals and swell to equilibrium to obtain a strong hydrogel with polymerization-induced hydrophilic and hydrophobic microphase separation.

[0059] Example 4: (1) Add 4 g of polylactic acid (hydrophobic polymer) to 17 mL of acrylic acid solution and dissolve at 70 °C to prepare a liquid phase system.

[0060] (2) 18 g of acrylamide was added to and dissolved in the liquid phase system as a hydrophilic second monomer. 0.036 g of Irgacure 2959 was added to the liquid phase system as an initiator and 0.25 g of ethylene glycol dimethacrylate was added as a crosslinking agent to obtain the bulk polymerization reaction system.

[0061] (3) The bulk polymerization system is poured into a mold consisting of two glass plates separated by silicone rubber spacers with a thickness of 0.5 mm, and the mixture is subjected to a strength of 0.2 W / m. -2 The hydrogel precursor was obtained by polymerization under a 365 nm UV lamp for 2 hours.

[0062] (4) Subsequently, the hydrogel precursor was immersed in water to remove residual chemicals and swell to equilibrium to obtain a strong hydrogel with polylactic acid polymerization-induced hydrophilic and hydrophobic microphase separation.

[0063] Example 5: (1) Add 4 g of cellulose acetate (hydrophobic polymer) to 22 mL of acrylic acid solution and dissolve at 80 °C to prepare a liquid phase system.

[0064] (2) 23 g of acrylamide was added to and dissolved in the liquid phase system as a hydrophilic second monomer. 0.1 wt% (2,4,6(trimethylbenzoyl)diphenylphosphine oxide) was added to the liquid phase system as an initiator and 0.32 g of ethylene glycol dimethacrylate was added as a crosslinking agent to obtain the bulk polymerization reaction system.

[0065] (3) The hydrogel was manufactured using a 3D printer (microArch S140, BMF, China) with a printing resolution of 10 µm. Before printing, curcumin (0.03 wt%), a light absorber, was added to the bulk polymerization reaction system to obtain a precursor gel solution. Projection micro-stereolithography was used, and the printing layer thickness was set to 20 µm. The overall 3D network structure of the target was formed layer by layer based on the imported slice model data. The light intensity used during printing was 90 mW cm⁻¹. -2 The exposure time was 15 seconds. After printing, the printed structure was cleaned with N,N-dimethylformamide to remove the precursor gel solution, yielding a hydrogel precursor with a cellulose acetate content of 8%.

[0066] (4) Subsequently, the hydrogel precursor was immersed in water to remove residual chemicals and swell to equilibrium to obtain a strong hydrogel with a three-dimensional network structure induced by cellulose acetate polymerization to separate hydrophilic and hydrophobic microphases (e.g., Figure 5 (As shown).

[0067] Example 6: (1) Add 4 g of cellulose acetate (hydrophobic polymer) to 17 mL of acrylic acid solution and dissolve at 65 °C to prepare a liquid phase system.

[0068] (2) 18 g of acrylamide was added to and dissolved in the liquid phase system as a hydrophilic second monomer. 0.036 g of Irgacure 2959 was added to the liquid phase system as an initiator and 0.25 g of ethylene glycol dimethacrylate was added as a crosslinking agent to obtain the bulk polymerization reaction system.

[0069] (3) The bulk polymerization system is poured into a mold consisting of two glass plates separated by silicone rubber spacers with a thickness of 0.5 mm, and the mixture is subjected to a strength of 0.2 W / m. -2 A hydrogel precursor with a cellulose acetate mass fraction of 10% was obtained by polymerization under a 365 nm UV lamp for 2 hours.

[0070] (4) Subsequently, the hydrogel precursor was immersed in water to remove residual chemicals and swell to equilibrium to obtain a strong hydrogel with cellulose acetate polymerization-induced hydrophilic and hydrophobic microphase separation.

[0071] Example 7: (1) Add 1.9 g of cellulose acetate (hydrophobic polymer) to 17 mL of acrylic acid solution and dissolve at 70 °C to prepare a liquid phase system.

[0072] (2) 18 g of acrylamide was added to and dissolved in the liquid phase system as a hydrophilic second monomer. 0.036 g of Irgacure 2959 was added to the liquid phase system as an initiator and 0.25 g of ethylene glycol dimethacrylate was added as a crosslinking agent to obtain the bulk polymerization reaction system.

[0073] (3) The bulk polymerization system is poured into a mold consisting of two glass plates separated by silicone rubber spacers with a thickness of 0.5 mm, and the mixture is subjected to a strength of 0.2 W / m. -2 A hydrogel precursor with a cellulose acetate mass fraction of 5% was obtained by polymerization under a 365 nm UV lamp for 2 hours.

[0074] (4) Subsequently, the hydrogel precursor was immersed in water to remove residual chemicals and swell to equilibrium to obtain a strong hydrogel with cellulose acetate polymerization-induced hydrophilic and hydrophobic microphase separation.

[0075] Example 8: (1) Add 6.36 g of cellulose acetate (hydrophobic polymer) to 17 mL of acrylic acid solution and dissolve at 70 °C to prepare a liquid phase system.

[0076] (2) 18 g of acrylamide was added to and dissolved in the liquid phase system as a hydrophilic second monomer. 0.036 g of Irgacure 2959 was added to the liquid phase system as an initiator and 0.25 g of ethylene glycol dimethacrylate was added as a crosslinking agent to obtain the bulk polymerization reaction system.

[0077] (3) The bulk polymerization system is poured into a mold consisting of two glass plates separated by silicone rubber spacers with a thickness of 0.5 mm, and the mixture is subjected to a strength of 0.2 W / m. -2 A hydrogel precursor with a cellulose acetate mass fraction of 15% was obtained by polymerization under a 365 nm UV lamp for 2 hours.

[0078] (4) Subsequently, the hydrogel precursor was immersed in water to remove residual chemicals and swell to equilibrium to obtain a strong hydrogel with cellulose acetate polymerization-induced hydrophilic and hydrophobic microphase separation.

[0079] Comparative Example 1: Copolymer hydrogel obtained by bulk polymerization in the absence of hydrophobic polymers.

[0080] (1) Add 18 g of acrylamide as a hydrophilic monomer to 17 mL of acrylic acid and dissolve to form a transparent mixture.

[0081] (2) 0.036 g Irgacure 2959 as an initiator and 0.25 g ethylene glycol dimethacrylate as a crosslinking agent were added to the liquid phase system to obtain the bulk polymerization reaction system.

[0082] (3) The bulk polymerization system is poured into a mold consisting of two glass plates separated by silicone rubber spacers with a thickness of 0.5 mm, and the mixture is subjected to a strength of 0.2 W / m. -2 The hydrogel precursor was obtained by polymerization under a 365 nm UV lamp for 2 hours.

[0083] (4) Subsequently, the hydrogel precursor is immersed in water to remove residual chemicals and swell to equilibrium to obtain the copolymer hydrogel obtained by bulk polymerization.

[0084] Comparative Example 2: Copolymer hydrogel obtained by conventional aqueous solution polymerization.

[0085] (1) Dissolve 17 mL of acrylic acid and 18 g of acrylamide as a hydrophilic monomer in 38 mL of water to form a transparent mixture.

[0086] (2) 0.036 g Irgacure 2959 as an initiator and 0.25 g ethylene glycol dimethacrylate as a crosslinking agent were added to the liquid phase system to obtain a solution copolymerization reaction system.

[0087] (3) Pour the solution copolymerization system into a mold consisting of two glass plates separated by a silicone rubber spacer with a thickness of 0.5 mm, and then place it in a mold with a strength of 0.2 W / m. -2 The hydrogel precursor was obtained by polymerization under a 365 nm UV lamp for 2 hours.

[0088] (4) Subsequently, the hydrogel precursor is immersed in water to remove residual chemicals and swell to equilibrium to obtain a copolymer hydrogel obtained by conventional aqueous solution polymerization.

[0089] Performance testing: like Figure 2 As shown, the strong hydrogel in Example 6 was prepared into a hydrogel with a width of about 5 mm and a thickness of about 0.6 mm, which can suspend a weight of 2 kg.

[0090] like Figure 3 As shown, the stress-strain curves of the strong and tough hydrogels prepared in Examples 6-8 and the hydrogels prepared in Comparative Examples 1 and 2 were tested in a tensile test of the copolymer hydrogels, as shown in the figure. Figure 3 As shown, the addition of hydrophobic polymers effectively improves the mechanical strength of hydrogels. Within the test range, the higher the cellulose acetate content, the higher the strength of the hydrogel.

[0091] The mechanical properties of the hydrogels obtained in Examples 1-4, 6, and Comparative Examples 1 and 2 are shown in Table 1.

[0092] Using a cryostat, the precursor of the strong hydrogel in Example 6 was obtained, sectioned, and sliced ​​to a thickness of approximately 100 nm. The slices were then observed at room temperature, and the results are as follows. Figure 4 As shown, after polymerization, the dark and light regions constitute two phases of the material, indicating that the polymerization process induces microphase separation in the material, with a phase spacing of approximately 120 nm.

[0093] The overall structure of the three-dimensional network printed in Example 5 is as follows: Figure 5 As shown, from Figure 5 It can be seen that the overall structure of the three-dimensional network is clear and complete, indicating that any structure can be created as needed.

[0094] Table 1 shows the mechanical properties of the hydrogels obtained in the various embodiments and comparative examples of this invention.

[0095] As shown in Table 1, the modulus, strength, and toughness of the hydrogels with the introduction of hydrophobic polymers are simultaneously improved, all of which far exceed those of the bulk polymerized hydrogels or conventional hydrogels in Comparative Examples 1 and 2. This indicates that the preparation strategy of polymerization-induced hydrophilic-hydrophobic microphase separation hydrogels provided by the present invention simultaneously improves the strength and toughness of the hydrogel, improves the weak mechanical properties of conventional hydrogels, and has universal applicability.

[0096] A comparison of Examples 3 and 6 in Table 1 shows that the functional monomers also affect the strength and toughness of the hydrogel. In Example 3, hydroxyethyl methacrylate was used as the second monomer in the copolymerization, and the hydrogel strength was 1.71 MPa and the fracture energy was 3.52 MJ / m. −3 The mechanical properties already meet the requirements comparable to those of biological tissues. In Example 6, the comonomer was replaced with acrylamide, and the resulting hydrogel had a strength of 4.54 MPa and a fracture energy of 19.11 MJ / m². −3 The results show a significant improvement, indicating that different hydrogel copolymer monomers also affect the strength and toughness of the hydrogel system proposed in this invention.

[0097] The above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Although the invention has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications, or equivalent substitutions of the technical solutions of the invention do not depart from the spirit and scope of the invention and should be covered within the scope of the claims of the invention.

Claims

1. A method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation, characterized in that, Includes the following steps: A hydrophobic polymer was dissolved in liquid acrylic acid to prepare a liquid phase system; Continue adding crosslinking agents and initiators to obtain the bulk polymerization reaction system; The bulk polymerization system is subjected to polymerization under the initiation conditions of an initiator. When the polymerization reaches a certain extent, the hydrophobic polymer gradually precipitates out of the solution, and the bulk polymerization system gradually undergoes microphase separation. After the reaction is complete, the hydrogel precursor is obtained. The hydrogel precursor was swollen to obtain a strong and tough hydrogel.

2. The method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation according to claim 1, characterized in that, The hydrogel precursor contains 0-60% hydrophobic polymer by mass.

3. The method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation according to claim 1, characterized in that, The hydrophobic polymer is any hydrophobic polymer that can be dissolved in acrylic acid, including one or more of cellulose acetate, polylactic acid, ethyl cellulose, methyl cellulose, polycaprolactone, polymethyl methacrylate, polyethyl methacrylate, polybutylene adipate, and polyethyl acrylate.

4. The method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation according to claim 1, characterized in that, It also includes adding hydrophilic polymer monomers as functional monomers to the bulk polymerization reaction system.

5. The method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation according to claim 3, characterized in that, The hydrophilic polymer monomer is a hydrophilic monomer that can copolymerize with acrylic acid, including one or a combination of hydroxyethyl acrylate, acrylamide, N,N-dimethylacrylamide, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide, N-(3-dimethylaminopropyl)methacrylamide, and N-hydroxyethylacrylamide.

6. The method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation according to claim 1, characterized in that, The crosslinking agent is any one or more of the following: polyisocyanates, polyamines, polyols, glycidyl ethers, inorganic crosslinking agents, organic crosslinking agents, organosilicones, benzenesulfonic acids, acrylates, organic peroxides, organometallic compounds, aziridines, multifunctional polycarbodiimide crosslinking agents, blocked crosslinking agents, and isocyanate crosslinking agents.

7. The method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation according to claim 1, characterized in that, The initiator includes photoinitiators and thermal initiators.

8. The method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation according to claim 1, characterized in that, The photoinitiator is an ultraviolet photoinitiator, and the thermal initiator includes any one of organic peroxide initiators, inorganic peroxide initiators, azo initiators, and redox initiators.

9. The method for preparing a strong and tough hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation according to claim 1, characterized in that, The solvent for the swelling hydrogel precursor is any one of pure water, physiological saline, or PBS buffer. During the swelling process, residual chemicals are washed away by changing the solvent or by using a flowing solvent. After swelling equilibrium, a strong and tough hydrogel is obtained.

10. A robust hydrogel based on polymerization-induced hydrophilic-hydrophobic microphase separation, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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