Temperature response hydrogel constructed by oxime bond and preparation method thereof

Abstract

The invention relates to temperature response hydrogel constructed by oxime bonds and a preparation method of the temperature response hydrogel, the hydrogel is prepared by taking a dendronized phenylacetylene copolymer as a polymer precursor and a hydroxylamine compound as a cross-linking agent through a low-temperature freezing gel forming technology, and the dendronized phenylacetylene copolymer and the cross-linking agent are cross-linked through the oxime bonds. Compared with the prior art, the hydrogel has sensitive temperature responsiveness and response temperature range programmability, and also has a uniform and porous microstructure and excellent compressibility. The invention further provides a temperature response soft robot which is prepared on the basis of the gel precursor obtained by mixing the dendronized phenylacetylene copolymer and the hydroxylamine cross-linking agent, and different basic movement forms can be shown in thermal fields under different conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogel material preparation, in particular to a temperature-responsive hydrogel constructed with oxime bonds and a preparation method thereof. Background Art

[0002] Soft robots are a type of intelligent robot made of flexible materials that mimic the movement mechanisms of living organisms, achieving complex movements through elastic deformation. Unlike traditional rigid robots, their core features are low material modulus (typically 0.1kPa to 10MPa), continuously distributed degrees of freedom, and environmental adaptability. The design of soft robots is inspired by natural organisms (such as octopus tentacles and plant tendrils). Their movement does not rely on rigid joints, but is driven by the intrinsic flexibility of the material and external stimuli (such as air pressure, electric fields, and magnetic fields).

[0003] Bionic smart hydrogels refer to a class of gels that can undergo reversible changes in volume or morphology under external stimuli (such as light, temperature, magnetism, acid and alkali). The modulus of this type of hydrogel is often similar to that of soft tissues found in biological systems. With the growing demand for soft robotics research, hydrogels used in soft robots have experienced rapid development. Among them, temperature-responsive smart hydrogels have the characteristic of undergoing significant volume changes during temperature changes. This is because the thermosensitive polymer used to prepare the hydrogel has a minimum co-solubility temperature (LCST). When the temperature is raised above the LCST, the polymer changes from hydrophilic to hydrophobic and is accompanied by a significant dehydration collapse conformational change. Therefore, temperature-responsive smart hydrogels have development potential in the field of soft robotics and are expected to become one of the commonly used materials for constructing soft robots.

[0004] However, the response temperature range and sensitivity of existing temperature-responsive smart hydrogels remain difficult to implement in practical applications. Intelligent hydrogels with sensitive temperature response and adjustable temperature range are of great significance for the development and application of soft robotics. In recent years, a class of temperature-responsive smart hydrogels has garnered widespread attention. These temperature-responsive smart hydrogels, prepared using alkyloxyether-dendried phenylacetylene copolymers with different hydrophilic end groups, offer a new material option for temperature programming and rapid response due to their tunable chemical structure and dendritic topology. However, these materials suffer from chemical instability and fragility. Summary of the Invention

[0005] The purpose of the present invention is to provide a temperature-responsive hydrogel constructed with oxime bonds and a preparation method thereof, wherein the hydrogel has high temperature response sensitivity and excellent mechanical properties.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] One of the purposes of the present invention is to provide a temperature-responsive hydrogel constructed with oxime bonds, the structural formula of which is shown below:

[0008]

[0009] in,

[0010]

[0011] Wherein, X is methoxy, ethoxy, propoxy or hydroxy, m=200-2000, n=2-2000; j=1-4, k=1-4, l=1-4; i=1-10.

[0012] Preferably, the hydrogel is formed by cross-linking a dendritic phenylacetylene copolymer and a cross-linking agent through oxime bonds, and the structural formula of the dendritic phenylacetylene copolymer is:

[0013]

[0014] in,

[0015]

[0016] wherein X is methoxy, ethoxy, propoxy or hydroxy, m = 200-2000, n = 2-2000; j = 1-4, k = 1-4, l = 1-4;

[0017] The cross-linking agent is a hydroxylamine compound, selected from any one or more of aliphatic hydroxylamine, unsaturated hydroxylamine, and polyhydroxylamine, and its structural formula is as follows:

[0018]

[0019] Wherein, i=1-10.

[0020] Preferably, the cross-linking agent is a dibasic aliphatic hydroxylamine compound.

[0021] Preferably, the dendritic phenylacetylene copolymer is formed by copolymerization of dendritic alkoxy ether-modified phenylacetylene and aldehyde / ketone-substituted phenylacetylene.

[0022] Preferably, the temperature-responsive hydrogel has a porous structure with a pore size of 10-100 microns and a porosity of 40-70%.

[0023] A second object of the present invention is to provide a gel precursor for preparing the temperature-responsive hydrogel constructed with oxime bonds.

[0024] Preferably, the method for preparing the gel precursor comprises the following steps:

[0025] S1: dissolving the dendritic phenylacetylene copolymer in ultrapure water or a buffer solution to prepare a polymer precursor solution;

[0026] S2: dissolving the crosslinker in ultrapure water or a buffer solution to prepare a crosslinker solution;

[0027] S3: adding the crosslinking agent solution dropwise to the polymer precursor solution and mixing them evenly to obtain the gel precursor.

[0028] Preferably, in step S1, the concentration of the dendritic phenylacetylene copolymer in the polymer precursor solution is 0.1-2 wt%.

[0029] Preferably, in step S2, the concentration of the crosslinking agent in the crosslinking agent solution is 0.1-2 wt%.

[0030] Preferably, in steps S1 and S2, the buffer solution is a phosphate buffer solution with a pH of 5.00-9.00 and a concentration of 0.1-1 mol / L.

[0031] Preferably, in step S3, the mixing volume ratio of the polymer precursor solution to the cross-linking agent solution is 1:1-5:1.

[0032] Preferably, in step S3, the cross-linking agent solution is added dropwise to the polymer precursor solution at a rate of 0.1-1 mL / min.

[0033] Preferably, in step S3, the uniform mixing refers to uniform mixing using an oscillator, the rotation speed of the oscillator is 1400-2800 rpm, and the mixing time is 5-10 min.

[0034] A third object of the present invention is to provide a method for preparing a temperature-responsive hydrogel constructed with oxime bonds, which is prepared by subjecting the gel precursor to a low-temperature freezing and standing treatment.

[0035] Preferably, the temperature of the low-temperature freezing and standing treatment is -50-0°C, and the time is 1-7 days.

[0036] A fourth object of the present invention is to provide a temperature-responsive soft robot.

[0037] Preferably, the gel precursor is diluted to obtain a gel precursor dilution liquid, which is then poured into a mold and subjected to a low-temperature freezing molding process. After molding and demolding, the temperature-responsive soft robot is prepared.

[0038] Preferably, the dilution refers to diluting the gel precursor with ultrapure water or a buffer solution.

[0039] Preferably, the dilution ratio is 1-5 times.

[0040] Preferably, the mold includes a polytetrafluoroethylene mold, a polyurethane mold or a polypropylene mold.

[0041] Preferably, the mold comprises a star-shaped, rectangular or claw-shaped mold.

[0042] Further preferably, temperature-responsive soft robots of different shapes can be obtained by using molds of different shapes.

[0043] More preferably, the temperature-responsive soft robot includes a star-shaped soft robot, a rectangular soft robot or a claw-shaped soft robot.

[0044] Further preferably, the thickness of the mold is 0.1-5 cm.

[0045] Further preferably, in the star-shaped mold, the distance from the star-shaped fixed point to the center is 1-10 cm.

[0046] Further preferably, in the rectangular mold, the rectangle is 3-10 cm long and 2.5-9.5 cm wide.

[0047] Preferably, the low-temperature freezing molding treatment is performed at a temperature of -20-0°C and for a period of 1-7 days.

[0048] Preferably, the temperature-responsive soft robot can achieve proportional contraction or directional bending by applying a uniform thermal field or a non-uniform thermal field.

[0049] Preferably, the star-shaped temperature-responsive soft robot can achieve significant geometric contraction when driven by a uniform thermal field.

[0050] Preferably, the rectangular temperature-responsive soft robot (thin-film temperature-responsive soft robot) can achieve significant directional bending when driven by a non-uniform thermal field.

[0051] Further preferably, the uniform heat field is applied in a manner of: immersing the soft robot in ultrapure water and slowly heating it to above the phase change temperature, wherein the initial heating temperature is 0-20°C and the heating rate is 0.1-0.5°C / min.

[0052] Further preferably, the non-uniform thermal field is applied in a manner of: immersing the soft robot in ultrapure water and rapidly heating it to above the phase transition temperature, wherein the initial heating temperature is 60-80°C and the heating rate is 5-10°C / min.

[0053] The present invention first provides a gel precursor of a temperature-responsive hydrogel constructed with an oxime bond, the gel precursor comprising a dendritic phenylacetylene copolymer and a hydroxylamine crosslinking agent, and then undergoes a low-temperature freezing treatment to prepare a temperature-responsive hydrogel. The temperature-responsive hydrogel is formed by crosslinking the dendritic phenylacetylene copolymer and the hydroxylamine crosslinking agent through an oxime bond. Therefore, the prepared temperature-responsive hydrogel has good mechanical properties and stability, and has relatively sensitive temperature responsiveness. By adjusting the chemical structure, its response temperature range can be adjusted. In addition, based on the good mechanical properties and chemical stability of the prepared temperature-responsive hydrogel, the present invention also provides a temperature-responsive soft robot. By applying a uniform thermal field / non-uniform thermal field, the robot body as a whole / partially achieves rapid volume changes, thereby guiding specific forms of movement, such as achieving proportional expansion and contraction through a claw-shaped temperature-responsive soft robot and achieving directional bending through a film-shaped temperature-responsive soft robot.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) The present invention provides a temperature-responsive hydrogel, which is prepared by low-temperature freezing technology using a dendritic phenylacetylene copolymer as a polymer precursor and a hydroxylamine compound as a cross-linking agent. The hydrogel has high sensitivity and excellent mechanical properties.

[0056] (2) The hydrogel of the present invention is prepared based on a gel precursor obtained by mixing a dendritic phenylacetylene copolymer and a hydroxylamine crosslinker. The dendritic phenylacetylene copolymer and the hydroxylamine crosslinker are crosslinked through oxime bonds. The hydrogel obtained based on oxime crosslinking has better chemical stability and better mechanical properties. Its storage modulus can reach more than 4000 Pa, and its compression modulus can reach up to 290,000 Pa.

[0057] (3) The present invention can adjust the response temperature range of the temperature-responsive hydrogel by adjusting the chemical structure, so that the present invention can achieve temperature response within the temperature range of 20-70°C.

[0058] (4) The present invention is also based on the gel precursor. By pouring the diluted gel precursor dilution into a mold and preparing a temperature-responsive soft robot under low-temperature freezing molding treatment, the temperature-responsive soft robot is placed in a uniform or non-uniform thermal field to achieve the movement effect of proportional expansion and contraction or directional bending. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 Schematic diagram of the chemical principle for preparing the temperature-responsive hydrogel in Example 1;

[0060] Figure 2 Schematic diagram of the preparation process of the temperature-responsive hydrogel in Example 1;

[0061] Figure 3 This is a photograph of the temperature-responsive hydrogel in Example 1;

[0062] Figure 4 This is the infrared spectrum of the temperature-responsive hydrogel in Example 1;

[0063] Figure 5 This is a microscopic morphology of the temperature-responsive hydrogel in Example 1;

[0064] Figure 6 is the compressive mechanical properties of the temperature-responsive hydrogel in Example 2;

[0065] Figure 7 This is a design diagram of the motion principle of the temperature-responsive soft robot in Example 3;

[0066] Figure 8 This is a photo of the actual movement of the temperature-responsive soft robot in Example 4. DETAILED DESCRIPTION

[0067] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0068] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0069] Example 1

[0070] A temperature-responsive hydrogel constructed with oxime bonds, the preparation method of which is as follows:

[0071] Step 1, referring to Shen L., et al., Angewandte Chemie International Edition, 2024, 63(34): e202407552. Synthesis of a dendritic phenylacetylene copolymer: Dissolve a phenylacetylene monomer containing a dendritic alkoxy ether substituent and a phenylacetylene monomer containing an aldehyde / ketone substituent in ultra-dry tetrahydrofuran to prepare a mixed solution with a concentration of 10-50 wt%. After freeze-drying, add a rhodium catalyst and a co-catalyst organic base, with a designed catalyst loading ratio of 100:1-1000:1, to obtain the target dendritic phenylacetylene copolymer. The copolymerization ratio is 1:1-100:1.

[0072] Step 2: prepare a dendritic phenylacetylene copolymer solution at room temperature (≤25° C.) with a concentration of 1-20 wt %, and place it at a low temperature of 0-10° C. to fully dissolve.

[0073] Step 3, preparing a crosslinker solution with a concentration of 0.1-2 wt %, and standing until it is fully dissolved;

[0074] Step 4: adding the solution obtained in step 3 dropwise to the solution obtained in step 2, and mixing the mixture on a vortex shaker at a speed of 1400-2800 rpm to obtain a mixed solution;

[0075] Step 5, placing the mixed solution obtained in step 4 in a -50-0°C ambient temperature environment and leaving it for 1-7 days to obtain the target temperature-responsive hydrogel;

[0076] The schematic diagram of the chemical principle of the preparation of temperature-responsive hydrogel is as follows Figure 1 As shown; the preparation process of temperature-responsive hydrogel is as follows Figure 2 As shown; the photo of the temperature-responsive hydrogel is shown Figure 3 Its infrared spectrum and scanning electron microscope are shown in Figure 4 and Figure 5 As shown by Figure 4 and 5 It can be seen that the temperature-responsive hydrogel of the present invention is successfully prepared, and the hydrogel has a porous structure.

[0077] Example 2

[0078] Mechanical properties test of the temperature-responsive hydrogel prepared in Example 1

[0079] To explore the mechanical properties of temperature-responsive hydrogels, a universal testing machine was used to test the compressive strength of the hydrogels when they were compressed to a certain compression deformation. Figure 6 As shown in the figure, its storage modulus can reach more than 4000Pa, and its compression modulus can reach up to 290000Pa.

[0080] Example 3

[0081] A temperature-responsive soft robot comprises the following steps:

[0082] Step 1: further dilute the mixed solution obtained in step 4 of Example 1 with water or buffer solution, with the dilution volume ratio being 1-5 times.

[0083] Step 2: Slowly pour the diluted solution obtained in step 1 into a star-shaped / claw-shaped / rectangular mold made of polytetrafluoroethylene, polyurethane or polypropylene, and shake it slowly at a small angle to allow the liquid to fully flow in the mold. Place it in a -20-0°C freezing environment and wait for it to fully cross-link into gel. The molding time is 1-7 days.

[0084] Example 4

[0085] Basic motion realization of temperature-responsive soft robots

[0086] The basic motion of a soft robot constructed with this hydrogel was investigated near the phase transition temperature. The solution containing the soft robot was heated to near the phase transition temperature using both uniform and non-uniform thermal fields. The uniform thermal field was applied by placing the container containing the soft robot in ultrapure water on a hot plate and slowly heating it from 0-20°C until it reached above the phase transition temperature. The non-uniform thermal field was applied by quickly placing the container containing the soft robot in ultrapure water on a hot plate preheated to 60-80°C for rapid heating.

[0087] Tracking the movement of soft robots with temperature, the design principle is as follows Figure 7 The specific movement process is as shown in Figure 8 As shown, the proportional contraction from each corner to the center of the star-shaped robot is achieved by homogeneous heating, and the upward bending of the film-shaped robot is achieved by heterogeneous heating from bottom to top.

[0088] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A temperature-responsive hydrogel constructed with oxime bonds, characterized in that: Its structural formula is shown below: in, Wherein, X is methoxy, ethoxy, propoxy or hydroxy, m=200-2000, n=2-2000; j=1-4, k=1-4, l=1-4; i=1-10.

2. The temperature-responsive hydrogel constructed with oxime bonds according to claim 1, characterized in that: The hydrogel is formed by cross-linking a dendritic phenylacetylene copolymer and a cross-linking agent through oxime bonds. The structural formula of the dendritic phenylacetylene copolymer is: in, wherein X is methoxy, ethoxy, propoxy or hydroxy, m = 200-2000, n = 2-2000; j = 1-4, k = 1-4, l = 1-4; The cross-linking agent is a hydroxylamine compound, selected from any one or more of aliphatic hydroxylamine, unsaturated hydroxylamine, and polyhydroxylamine, and its structural formula is as follows: Wherein, i=1-10.

3. A gel precursor for preparing the temperature-responsive hydrogel constructed with oxime bonds according to any one of claims 1 to 2, characterized in that: The steps include: S1: dissolving the dendritic phenylacetylene copolymer in ultrapure water or a buffer solution to prepare a polymer precursor solution; S2: dissolving the crosslinker in ultrapure water or a buffer solution to prepare a crosslinker solution; S3: adding the crosslinking agent solution dropwise to the polymer precursor solution and mixing them evenly to obtain the gel precursor.

4. The method for preparing a gel precursor according to claim 3, wherein: In step S1, the concentration of the dendritic phenylacetylene copolymer in the polymer precursor solution is 0.1-2 wt%.

5. The method for preparing a gel precursor according to claim 3, wherein: In step S2, the concentration of the cross-linking agent in the cross-linking agent solution is 0.1-2 wt%.

6. The method for preparing a gel precursor according to claim 3, wherein: In step S3, the mixing volume ratio of the polymer precursor solution to the crosslinker solution is 1:1-5:1, the crosslinker solution is added dropwise to the polymer precursor solution at a rate of 0.1-1 mL / min, and the uniform mixing refers to uniform mixing using an oscillator with a rotation speed of 1400-2800 rpm and a mixing time of 5-10 min.

7. A method for preparing a temperature-responsive hydrogel constructed with oxime bonds, characterized in that: The method is prepared by subjecting the gel precursor as claimed in claim 3 to a low-temperature freezing and standing treatment.

8. The method for preparing the temperature-responsive hydrogel constructed with oxime bonds according to claim 7, wherein: The temperature of the low-temperature freezing and standing treatment is -50-0°C and the time is 1-7 days.

9. A temperature-responsive soft robot, characterized in that: The gel precursor as claimed in claim 3 is diluted to obtain a gel precursor dilution liquid, which is then poured into a mold and subjected to a low-temperature freezing molding process. After molding and demolding, the temperature-responsive soft robot is prepared.

10. The temperature-responsive soft robot according to claim 9, characterized in that: The dilution refers to diluting the gel precursor with ultrapure water or buffer solution, with a dilution ratio of 1-5 times. The mold includes a polytetrafluoroethylene mold, a polyurethane mold or a polypropylene mold. The mold includes a star-shaped, rectangular or claw-shaped mold. The temperature of the low-temperature freezing molding treatment is -20-0°C, and the time is 1-7 days.

Images