A hydrogel constructed based on a mechanical interlocking principle and a preparation method thereof

Abstract

The application discloses a hydrogel based on a mechanical interlocking principle, and a preparation method and application thereof. The hydrogel is composed of a flexible high polymer main chain and a rigid short side chain. The flexible high polymer main chain is used as the main body, and the rigid short side chain is added into the flexible high polymer chain as a mechanical interlocking unit. The super-strong, super-tough and crack growth resistant hydrogel material based on the mechanical interlocking structure can be applied to soft robots, artificial skin, flexible electronic devices, artificial tendons, cartilage repair and regeneration. The rigid polypeptide in the application has a single end connected with acrylic acid to provide an unsaturated carbon-carbon double bond for participating in copolymerization.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new materials, in particular to a super-strong, super-tough and anti-crack growth hydrogel material and a preparation method and application thereof. BACKGROUND

[0002] The crosslinking methods of conventional hydrogels are mainly divided into physical crosslinking and chemical crosslinking. Physical crosslinking mainly includes protein specific interaction, hydrogen bond, ion interaction, hydrophobic interaction, metal coordination, etc. These crosslinking methods are mainly used for preparing injectable hydrogels or increasing the dissipation of hydrogels. On the other hand, compared with physical crosslinking, due to the higher bond energy of covalent bond, the chemical crosslinking hydrogel usually has higher elasticity and toughness, but due to the irreversibility of covalent bond destruction, most of the chemical crosslinking hydrogels are difficult to withstand large-scale deformation, and this shortcoming limits its application in flexible electronic devices and other materials requiring large-scale deformation.

[0003] The present application proposes a hydrogel based on the mechanical interlocking structure of polymer chains. Unlike physical crosslinking or chemical crosslinking, the mechanical interlocking hydrogel does not have strictly defined crosslinking points, but is the result of the competition and balance between mechanical interlocking and swelling force. Since the mechanical interlocking hydrogel is integrally crosslinked, it is very insensitive to defects and has almost the same breaking strain as the hydrogel without cracks when the original width of the crack is 30%. The Young's modulus reaches 23 kPa, the breaking strength reaches 3.1 MPa, the toughness reaches 28 MJ / m 3 , the breaking toughness reaches 57 kJ / m 2 , and the breaking toughness is about 4 times that of rubber. The design of the mechanical interlocking hydrogel provides a new idea different from the traditional crosslinking methods of hydrogels. Due to its unique structure and excellent mechanical properties, this kind of hydrogel can be applied to soft robots, artificial skin, artificial tendons and cartilage repair, etc. SUMMARY

[0004] The problem to be solved by the present application is to provide an innovative solution to the lack of anti-crack growth in the existing hydrogel materials.

[0005] To solve the above problems, the present application adopts the following scheme:

[0006] A hydrogel constructed based on the principle of mechanical interlocking, characterized in that the hydrogel network is mainly composed of flexible polymer main chains, and rigid short side chains are added to the flexible polymer main chains as mechanical interlocking units. During the swelling process of the hydrogel, the flexible main chains gradually unfold under the action of the swelling force, and the mechanical interlocking structure is formed between the rigid short side chains and hinders the further sliding of the flexible main chains, and finally the swelling balance under the competition of the swelling force and the mechanical interlocking is reached.

[0007] Further, the hydrogel constructed based on the mechanical interlocking principle is characterized in that the flexible high-molecular main chain is a high-molecular chain generated by polyaddition of unsaturated small-molecule monomers, and the rigid short side chain is a polypeptide or a protein biological macromolecule with a single-end modified unsaturated bond.

[0008] Further, the hydrogel constructed based on the mechanical interlocking principle is characterized in that the flexible high-molecular main chain is polyacrylamide, poly-N-methylol acrylamide or polyhydroxyethyl methacrylate polymer, and the rigid short side chain is (KA) 3 (the sequence is acrylate-tryptophan-glycine-glycine-lysine-alanine-lysine-alanine-lysine-alanine-lysine), K3A3 (the sequence is acrylate-tryptophan-glycine-glycine-lysine-lysine-lysine-alanine-alanine-alanine), A3K3 (the sequence is acrylate-tryptophan-glycine-glycine-alanine-alanine-alanine-lysine-lysine-lysine) or (KG) 3 (the sequence is acrylate-tryptophan-glycine-glycine-lysine-glycine-lysine-glycine-lysine-glycine).

[0009] A preparation method of a hydrogel constructed based on the mechanical interlocking principle is characterized in that the unsaturated small-molecule monomer constituting the flexible high-molecular main chain is acrylamide, and the rigid short side chain is (KA) 3. The steps for preparing the super-strong, super-tough and crack growth resistant hydrogel are as follows: the unsaturated small-molecule monomer and the polypeptide or protein biological macromolecule with a single-end modified unsaturated bond are mixed and dissolved in a PBS buffer solution; the mixed solution is ultrasonically treated for 15 minutes to remove dissolved oxygen therein; a lithium phenyl (2,4,6-trimethylbenzoyl) phosphate salt with a final concentration of 0.0001 ml / ml is added to the solution after ultrasonic treatment as a photoinitiator; then the solution is placed under irradiation of a 405 nm blue light for 2 hours; the unsaturated small-molecule monomers generate high-molecular chains through polyaddition, and the polypeptide or protein biological macromolecule with a single-end modified unsaturated bond also randomly participates in the reaction and is connected to the high-molecular chains to obtain a primary hydrogel material; the obtained primary hydrogel material is immersed in 50 times the volume of a PBS buffer solution for more than 24 hours to complete the stability balance of the mechanical interlocking structure and the swelling of the hydrogel, thereby obtaining the super-strong, super-tough and crack growth resistant hydrogel material.

[0010] Preferably, the acrylamide is a flexible main chain monomer small molecule, and the (KA) 3 is a rigid short side chain, so that the hydrogel with super strength, super toughness and crack growth resistance is prepared; the acrylamide monomer and the (KA) 3 polypeptide are mixed and dissolved in a PBS buffer (the concentration is 0.01 M, and the pH is 7.4) at a concentration of 600 mg / ml and 200 ml / ml; the mixed solution is ultrasonically treated for 15 minutes to remove dissolved oxygen therein; the lithium phenyl (2, 4, 6-trimethylbenzoyl) phosphate salt with a final concentration of 0.0001 ml / ml is added to the solution after ultrasonic treatment as a photoinitiator; then the solution is placed under the irradiation of blue light with a wavelength of 405 nm for 2 hours; the acrylamide monomers generate polymer chains through polyaddition reaction, and the single-end acrylate-modified polypeptide (KA) 3 also randomly participates in the reaction and is connected to the polymer chains, so that the primary hydrogel material is obtained; the obtained primary hydrogel material is immersed in 50 times the volume of the PBS buffer for more than 24 hours, so that the stability balance of the mechanical interlocking structure and the swelling of the hydrogel are completed, and the hydrogel material with super strength, super toughness and crack growth resistance is obtained.

[0011] Further, the preparation method is characterized in that the PBS buffer has a concentration of 0.01 M and a pH of 7.4.

[0012] The super strong, super tough and crack growth resistant hydrogel material is applied to various flexible electronic devices.

[0013] The super strong, super tough and crack growth resistant hydrogel material is applied to soft robots.

[0014] The super strong, super tough and crack growth resistant hydrogel material is applied to biological medicine, medical devices or tissue engineering.

[0015] The technical effects of the present application are as follows: 1. Compared with traditional hydrogels, the hydrogel material in the present application does not contain traditional chemical crosslinking points or physical crosslinking points, but a mechanical interlocking structure between rigid chains, and a brand-new crosslinking mechanism realizes excellent mechanical properties in non-covalent hydrogels, the Young's modulus reaches 23 kPa, the breaking strength reaches 3.1 MPa, the toughness reaches 28 MJ / m 3 , the breaking toughness reaches 57 kJ / m 2 , and the breaking toughness reaches 4 times that of rubber.

[0016] 2. Compared with the crack growth resistance of traditional hydrogels, the hydrogel material in the present application has almost the same breaking strain as the hydrogel without cracks when the original width of the crack is 30%, and the crack insensitivity reaches 96%.

[0017] 5. Compared with traditional hydrogel materials, the hydrogel adhesive material in the application has high toughness, high strength and crack growth resistance, while traditional hydrogel materials can only achieve relatively high properties in one of the above aspects, and it is difficult to balance all aspects. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Network diagram of super-strong, super-tough and crack growth resistant hydrogel material.

[0019] Figure 2 Comparison diagram of missing rigid polypeptide side chain in super-strong, super-tough and crack growth resistant hydrogel material.

[0020] Figure 3 Mechanical property characterization of super-strong, super-tough and crack growth resistant hydrogel material.

[0021] Figure 4 Crack growth resistant photo of super-strong, super-tough and crack growth resistant hydrogel material.

[0022] Figure 5 Wear resistance test of super-strong, super-tough and crack growth resistant hydrogel material.

[0023] Figure 6 Recovery mechanical property characterization of super-strong, super-tough and crack growth resistant hydrogel material. DETAILED DESCRIPTION

[0024] The application will be further described in detail below with reference to the accompanying drawings.

[0025] A super-strong, super-tough and crack growth resistant hydrogel material based on the principle of mechanical interlocking, the hydrogel network is mainly composed of flexible polymer main chains, and rigid short side chains are added to the flexible polymer chains as mechanical interlocking units. During the swelling process of the hydrogel, the flexible main chain gradually unfolds under the action of swelling force, while the mechanical interlocking structure is formed between the rigid short side chains and hinders the further sliding of the flexible main chain, and finally reaches the swelling balance under the competition of swelling force and mechanical interlocking. Figure 1 ).

[0026] The flexible polymer main chain is a polymer chain generated by the polyaddition reaction of unsaturated small molecule monomers, and the material is preferably polyacrylamide, poly-N-methylol acrylamide, polyhydroxyethyl methacrylate and the like.

[0027] The acrylamide is used as a monomer small molecule for generating a flexible polymer main chain, and (KA) 3 is used as a typical example of a rigid short side chain to prepare a hydrogel with super strength, super toughness and crack growth resistance. The acrylamide monomer and (KA) 3 polypeptide are mixed and dissolved in a PBS buffer (concentration: 0.01 M, pH: 7.4) at a concentration of 600 mg / ml and 200 ml / ml. The mixed solution is ultrasonically treated for 15 minutes to remove dissolved oxygen therefrom. A lithium phenyl (2,4,6-trimethylbenzoyl) phosphate salt is added to the solution after ultrasonic treatment as a photoinitiator at a final concentration of 0.0001 ml / ml. Then, the solution is placed under irradiation of blue light at 405 nm for 2 hours. The acrylamide monomer generates a polymer chain through an addition polymerization reaction to form polyacrylamide (PAM), and the single-end acrylate-modified polypeptide (KA) 3 also randomly participates in the reaction and is connected to the polymer chain to obtain a primary hydrogel material. The obtained primary hydrogel material is immersed in 50 times the volume of the PBS buffer for more than 24 hours to complete the stability balance of the mechanical interlocking structure and the swelling of the hydrogel to obtain a hydrogel material with super strength, super toughness and crack growth resistance. The PBS buffer has a concentration of 0.01 M and a pH of 7.4.

[0028] The following tests the performance of the present application through examples.

[0029] Example 1. Stability verification of the hydrogel with a mechanical interlocking structure in the present application

[0030] In the present application, in order to verify the influence of the rigid short side chain on the stability of the mechanical interlocking structure, a control group experiment is designed: the (KA) 3 polypeptide in the raw materials of the experimental group hydrogel is replaced by an equal molar amount of acrylamide as the control group, and the rest of the method for preparing the hydrogel remains unchanged. The results show that after swelling for 24 hours, the control group hydrogel cannot support a fixed shape and is in the form of a viscous droplet, while the experimental group hydrogel maintains a stable circular shape and is transparent and elastic (as shown in Figure 2 ).

[0031] Example 2. Strength and toughness mechanical test of the hydrogel material in the present application

[0032] In order to verify the strength and toughness of the hydrogel material in the present application, standard mechanical property tests are performed on the material, and different flexible main chain monomers and rigid short side chains are used as control groups. As shown in Figure 3 a, the monomers constituting the flexible polymer main chain are selected from acrylamide, N-hydroxymethyl acrylamide and hydroxyethyl methacrylate, and the rigid short side chain polypeptides are selected from (KA) 3, K3A3, A3K3 and (KG) 3. Among them, the PAM-(KA) 3 combination has the most outstanding mechanical properties, with a tensile strain at break of 26 mm / mm, a Young's modulus of 23 kPa, a breaking strength of 3.1 MPa and a toughness of 28 MJ / m 3The fracture toughness reaches 57 kJ / m 2 Its fracture toughness is four times that of rubber. For example... Figure 3 As shown in b, the mechanical properties of this hydrogel material vary with the peptide content in the hydrogel network. The optimal mechanical properties are obtained when the molar ratio of peptide to acrylamide monomer is 0.032. Figure 3 As shown in Figure c, in the tensile test comparison between hydrogels with and without cracks, the two exhibit almost the same fracture strain. Figure 4 Photographs of two hydrogels with the same tensile fracture strain are shown, demonstrating the excellent crack growth resistance of the hydrogel material of the present invention.

[0033] Example 3: Test of the abrasion resistance properties of the hydrogel material of the present invention.

[0034] To further verify the crack growth resistance of the hydrogel material in this invention, the hydrogel material in this invention was subjected to the same abrasion resistance test as other experimental groups. Figure 5 The test method is shown in Figure 1, which uses the CS mode of the rheometer with a torque of 2525 μNm, a normal force of 5 N, and an angular velocity of 1 rad / s. Figure 5 In type a, a sudden strain change was observed in the PAM-K3A3 hydrogel at 0.5 hours, indicating that microcracks within the hydrogel were rapidly growing under cyclic shear force. The abrupt change in the ordinary BIS hydrogel occurred at 5.58 hours, indicating that its abrasion resistance was slightly better than that of the PAM-K3A3 hydrogel. The strain of the PAM-(KA)3 hydrogel remained stable over 6 hours, demonstrating its excellent abrasion resistance. Commercial Teflon was used as a control group in the test. Figure 5 b shows a photograph of the hydrogels after the friction test. The PAM-(KA)3 hydrogel remained largely intact, while the PAM-K3A3 hydrogel and the ordinary BIS hydrogel were damaged.

[0035] Example 4: Rapid mechanical property recovery test of the hydrogel material of the present invention.

[0036] To further verify the crack growth resistance of the hydrogel material in this invention, continuous tensile mechanical tests were conducted on the hydrogel material. The maximum strain under continuous tensile stress was 8 mm / mm, and the tensile rate was 10 mm / min. Figure 6 The results show that after 1000 continuous tensile cycles, its maximum stress remains at 96.2%, demonstrating its excellent resistance to crack growth within the hydrogel.

Claims

1. A hydrogel constructed on the principle of mechanical interlocking, characterized in that, The hydrogel is composed of a flexible high molecular main chain and a rigid short side chain; wherein the flexible high molecular main chain is taken as the main body, and the rigid short side chain is added in the flexible high molecular chain as a mechanical interlocking unit; the rigid short side chain is (KA) 3, K3A3, A3K3 or (KG) 3, wherein (KA) 3 is a single-end modified unsaturated bond polypeptide with the sequence of acrylate-tryptophan-glycine-glycine-lysine-alanine-lysine-alanine-lysine-alanine, K3A3 is a single-end modified unsaturated bond polypeptide with the sequence of acrylate-tryptophan-glycine-glycine-lysine-lysine-lysine-alanine-alanine-alanine, A3K3 is a single-end modified unsaturated bond polypeptide with the sequence of acrylate-tryptophan-glycine-glycine-alanine-alanine-alanine-lysine-lysine-lysine, and (KG) 3 is a single-end modified unsaturated bond polypeptide with the sequence of acrylate-tryptophan-glycine-glycine-lysine-glycine-lysine-glycine-lysine-glycine; the flexible high molecular main chain is a polyacrylamide, a poly-N-methylol acrylamide or a polyhydroxyethyl methacrylate polymer.

2. A method for preparing the hydrogel according to claim 1, based on the principle of mechanical interlocking, characterized in that, The unsaturated small molecule monomer constituting the flexible high molecular main chain is acrylamide, and the rigid short side chain is (KA) 3; the super-strong, super-tough and crack growth resistant hydrogel is prepared by the following steps: the unsaturated small molecule monomer and (KA) 3 are mixed and dissolved in a PBS buffer solution; the mixed solution is ultrasonically treated for 15 minutes to remove dissolved oxygen therein; a lithium salt of phenyl (2, 4, 6-trimethylbenzoyl) phosphate with a final concentration of 0.0001 ml / ml is added to the solution after ultrasonic treatment as a photoinitiator; then the solution is placed under blue light irradiation at 405 nm for 2 hours; the unsaturated small molecule monomer generates a polymer chain through a polyaddition reaction, and (KA) 3 also randomly participates in the reaction and is connected to the polymer chain to obtain a primary hydrogel material; the obtained primary hydrogel material is immersed in 50 times the volume of a PBS buffer solution for more than 24 hours to complete the stability balance of the mechanical interlocking structure and the swelling of the hydrogel, thereby obtaining the super-strong, super-tough and crack growth resistant hydrogel.

3. The production method according to claim 2, characterized by, The PBS buffer solution has a concentration of 0.01M and a pH of 7.

4.

4. Application of the hydrogel constructed based on the mechanical interlocking principle in claim 1 to various flexible electronic devices.

5. Application of the hydrogel constructed based on the mechanical interlocking principle in claim 1 to soft robots.

6. Application of the hydrogel constructed based on the mechanical interlocking principle in claim 1 to the preparation of medical devices.

Images