A method for preparing a low-hysteresis, high-stretch, self-adhesive double-chemical cross-linked structure hydrogel

Abstract

The present invention belongs to the field of hydrogel preparation and discloses a method for preparing a low hysteresis, high stretchability, self-adhesive double chemical cross-linked structure hydrogel. The present invention utilizes the esterification reaction between 2d resin and carboxyl group in acrylic acid to prepare Al 3+ The coordination of ions and acrylic acid forms a double cross-linked hydrogel. The double cross-linked hydrogel with low hysteresis, high tensile strength and self-adhesion prepared by the present invention has the characteristics of simple preparation method and wide range of raw materials, and has great potential applications in the fields of flexible electronic devices, biosensors, wearable devices, and soft robots.

Description

Technical Field

[0001] The invention belongs to the field of hydrogel preparation, and in particular relates to a method for preparing a low-hysteresis, high-stretching, self-adhesive double chemical cross-linking structure hydrogel. Background Art

[0002] Hydrogels are usually water-soluble polymers with a network cross-linked structure formed by cross-linking of hydrophilic polymer chains in water. They have broad application potential in tissue engineering, drug release, soft electronics and other fields. Electronic skin converts various external stimuli (such as strain, pressure, temperature and humidity) into electrical signals. Strong mechanical properties can make electronic skin have better flexibility, ductility and repeatability, expand the test range and improve accuracy. However, due to its unique mechanical properties and functionality, there are still many challenges in imitating human skin.

[0003] At present, physical (co-mixing, freeze-thaw cycle, Hofmeister effect, etc.) and chemical (metal ion coordination, diene chemical crosslinking, nano-silica modification, etc.) methods are commonly used to modify acrylic hydrogels to improve their mechanical properties. 3+ As a cross-linking point, the mechanical properties of acrylic hydrogels are improved by increasing cross-linking and coordination methods. N, N-dimethylacrylamide, as a commonly used gel cross-linking agent, forms a three-dimensional network structure through free radical polymerization between olefin monomers. In addition, the prior art (CN202111536573.2) causes etherification reaction between 2D resin and alcoholic hydroxyl groups in acryl alcohol under the condition of magnesium chloride as a catalyst and citric acid providing an acidic environment to form a three-dimensional chemical cross-linked structure, thereby enhancing the mechanical properties of acryl alcohol. This method utilizes the reaction of 2D resin with alcoholic hydroxyl groups in acryl alcohol to make the polymer at the hydroxyl end as a cross-linking point, thereby improving the mechanical properties of acryl alcohol. However, in the presence of a poor solvent (water), the chemical cross-linking reaction between 2D resin and acryl alcohol hydrogel requires additional addition of catalysts, environmental regulators, defoamers and other operations, and the reaction is more complicated. Summary of the invention

[0004] In view of the above problems, the present invention proposes a method for preparing a double chemical cross-linked structure hydrogel, so that the obtained acrylic hydrogel has excellent low hysteresis, high stretchability and self-adhesion properties.

[0005] The technical solution of the present invention:

[0006] A method for preparing a low hysteresis, high stretchability, self-adhesive double chemical cross-linked structure hydrogel comprises the following steps:

[0007] (1) dissolving acrylic acid, acrylamide, aluminum chloride hexahydrate and 2d resin in deionized water according to a certain proportion, and mixing them evenly to obtain a mixed solution;

[0008] (2) Adding ammonium persulfate to the above mixed solution, mixing evenly and pouring into a polytetrafluoroethylene mold, then heating in an oven and cooling to room temperature to obtain a double cross-linked hydrogel P(AA-co-AM) / 2d-Al 3+ .

[0009] The molar concentration of the aluminum chloride hexahydrate is 0.25 mol% to 1.0 mol% relative to the amount of the acrylic acid monomer substance.

[0010] The mass ratio of the acrylic acid to acrylamide is 2:1 to 1:3.

[0011] The 2d resin is dihydroxymethyl dihydroxyethylene urea, and the mass concentration of the 2d resin is 16.7wt% to 66.7wt% compared to the mass of the acrylic acid monomer.

[0012] The ammonium persulfate is 2 wt % compared to the total weight of the two monomers of acrylic acid and acrylamide.

[0013] The heating temperature is 50-80° C., and the reaction time is 4-8 hours.

[0014] A low hysteresis, high stretchability, self-adhesive double chemical cross-linked structure hydrogel is used in flexible electronic devices, biosensors, wearable devices, soft robots and other fields.

[0015] Beneficial effects of the present invention:

[0016] (1) The present invention provides a method for preparing a low hysteresis, high stretchability, self-adhesive double chemical cross-linked structure hydrogel, using 2d resin and aluminum chloride hexahydrate as chemical cross-linking points of acrylic hydrogel, and esterifying the carboxyl groups in polyacrylic acid with the 2d resin, and Al 3+ The coordination crosslinking of ions endows the hydrogel with low hysteresis and high tensile properties.

[0017] (2) The present invention proposes a method for preparing a low-hysteresis, high-stretch, self-adhesive double chemical cross-linked structure hydrogel, which uses acrylic acid and acrylamide as the basic skeleton and utilizes the hydrogen bonding effect formed between the carboxyl group of acrylic acid and the amide group of acrylamide and the substrate to improve the self-adhesive properties of the hydrogel.

[0018] (3) The present invention proposes a method for preparing a low hysteresis, high stretchability, self-adhesive double chemical cross-linked structure hydrogel using Al 3+ The coordination between ions and acrylic acid forms dynamic coordination bonds. The existence of dynamic bonds gives the hydrogel good self-repairing properties after damage.

[0019] (4) Compared with the traditional chemically cross-linked acrylic hydrogel, the present invention provides a method for preparing a low hysteresis, high stretchability, self-adhesive double chemical cross-linked structure hydrogel, which has fewer operation steps and is simple and easy to operate. The present invention utilizes the esterification reaction between the 2D resin and the carboxyl group in acrylic acid to play a role in chemical cross-linking. In addition, since the 2D resin contains four hydroxyl structures, the hydrogel can form a bulk polymer during the cross-linking process, thereby reducing the hysteresis performance of the acrylic hydrogel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 P(AA-co-AM), P(AA-co-AM) / Al prepared according to Examples 1, 4 and 5 3+ 、P(AA-co-AM) / 2d-Al 3+ Infrared spectra of hydrogel and 2D resin;

[0021] Figure 2 is the P(AA-co-AM) / 2d-Al with different ratios of acrylic acid and acrylamide monomers prepared according to Example 1 3+ Stress-strain curve of hydrogel;

[0022] Figure 3 is the P(AA-co-AM) / 2d-Al with different 2d resin contents prepared according to Example 2 3+ Stress-strain curve of hydrogel;

[0023] Figure 4 is the P(AA-co-AM) / 2d-Al with different contents of aluminum chloride hexahydrate prepared according to Example 3 3+ Stress-strain curve of hydrogel;

[0024] Figure 5 P(AA-co-AM) / 2d-Al prepared according to Examples 1, 2, and 4 3+ , P(AA-co-AM) / 2d, P(AA-co-AM) hydrogel stress-strain curves

[0025] Figure 6 P(AA-co-AM) / 2d-Al prepared according to Example 1 3+ Stress-strain curves of the hydrogel stretched to 400% for 5 cycles.

[0026] Figure 7 is the P(AA-co-AM) / 2d-Al with different contents of aluminum chloride hexahydrate prepared according to Example 3 3+ Bar graph of adhesion strength of hydrogels to glass.

[0027] Figure 8P(AA-co-AM) / 2d-Al prepared according to Example 1 3+ Stress-strain curves of hydrogel self-healing at different times. Specific implementation plan

[0028] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] The method for preparing a low hysteresis, high stretchability, self-adhesive dual chemical cross-linked structure hydrogel in this embodiment mainly regulates the ratio of different acrylic acid and acrylamide monomers in the hydrogel, and specifically includes the following steps:

[0031] (1) 2.0 g of acrylic acid (AA), 1.0 g of acrylamide (AM), 18.1 mg of aluminum chloride hexahydrate and 1 g of 2d resin were dissolved in 10 ml of deionized water and mixed to obtain a mixed solution.

[0032] (2) Add 60 mg of ammonium persulfate to the mixed solution, mix evenly and pour into a polytetrafluoroethylene mold, then heat in an oven at 60 °C for 4 h. After cooling to room temperature, a double cross-linked hydrogel P(AA-co-AM) / 2d-Al with a mass ratio of acrylic acid to acrylamide of 1:1 was obtained. 3+ ;

[0033] (3) In addition, acrylic acid and acrylamide monomers with a mass ratio of 1:2 and 2:1 were used to prepare double-crosslinked hydrogels with different monomer mass contents according to the above method.

[0034] Example 2

[0035] The method for preparing a low hysteresis, high stretchability, self-adhesive double chemical cross-linked structure hydrogel in this embodiment mainly regulates the content of different 2D resins in the hydrogel, and specifically includes the following steps:

[0036] (1) 2.0 g of acrylic acid (AA), 1.0 g of acrylamide (AM), 18.1 mg of aluminum chloride hexahydrate, and 0.5 g, 0.75 g, 1 g, and 1.25 g of 2d resin were dissolved in 10 ml of deionized water, respectively, and mixed to obtain a mixed solution.

[0037] (2) Add 60 mg of ammonium persulfate to the above mixed solution, mix evenly and pour into a polytetrafluoroethylene mold, then heat in a 60 °C oven for 4 h and cool to room temperature to obtain double cross-linked hydrogels P(AA-co-AM) / 2d-Al with different 2d resin contents. 3+ .

[0038] Example 3

[0039] The method for preparing a low hysteresis, high stretchability, self-adhesive double chemical cross-linked structure hydrogel in this embodiment mainly regulates the different contents of aluminum chloride hexahydrate in the hydrogel, and specifically includes the following steps:

[0040] (1) 2.0 g of acrylic acid (AA), 1.0 g of acrylamide (AM) and 1 g of 2d resin, as well as 6.03 mg (0.25 mol%), 12.06 mg (0.5 mol%), 18.09 mg (0.75 mol%) and 24.12 mg (1.0 mol%) of aluminum chloride hexahydrate were dissolved in 10 ml of deionized water, respectively, and mixed to obtain a mixed solution.

[0041] (2) Add 60 mg of ammonium persulfate to the above mixed solution, mix evenly and pour into a polytetrafluoroethylene mold, then heat in a 60 °C oven for 4 h and cool to room temperature to obtain double cross-linked hydrogels P(AA-co-AM) / 2d-Al with different 2d resin contents. 3+ .

[0042] Example 4 (Comparative Example)

[0043] (1) Dissolve 2.0 g of acrylic acid (AA) and 1.0 g of acrylamide (AM) in 10 ml of deionized water and mix well to obtain a mixed solution.

[0044] (2) Add 60 mg of ammonium persulfate to the above mixed solution, mix evenly and pour into a polytetrafluoroethylene mold, then heat in an oven at 60°C for 4 h and cool to room temperature to obtain double-crosslinked hydrogels P(AA-co-AM) with different 2d resin contents.

[0045] Example 5 (Comparative Example)

[0046] (1) 2.0 g of acrylic acid (AA), 1.0 g of acrylamide (AM) and 18.1 mg of aluminum chloride hexahydrate were dissolved in 10 ml of deionized water and mixed to obtain a mixed solution.

[0047] (2) Add 60 mg of ammonium persulfate to the above mixed solution, mix evenly and pour into a polytetrafluoroethylene mold, then heat in a 60 °C oven for 4 h and cool to room temperature to obtain double cross-linked hydrogels P(AA-co-AM) / Al with different 2d resin contents. 3+ .

[0048] Figure 1 The P(AA-co-AM) and P(AA-co-AM) / Al prepared by the present invention 3+ 、P(AA-co-AM) / 2d-Al 3+Infrared spectra of hydrogel and 2d resin. In the figure, P(AA-co-AM) hydrogel has an infrared spectrum of 1659.5 cm -1 There is a stretching vibration peak of the ester group at the 3+ Form coordination, so that P(AA-co-AM) / Al 3+ and P(AA-co-AM) / 2d-Al 3+ The hydrogel red-shifted. With the introduction of 2d resin, P(AA-co-AM) / 2d-Al 3+ Hydrogel at 1019.6cm -1 There is a COC bond in the ether bond, which fully demonstrates that the introduced 2d resin reacts with the carboxyl group in acrylic acid to form an ether bond.

[0049] The P(AA-co-AM) / 2d-Al2O3 ratios of acrylic acid and acrylamide monomers in Example 1 were measured by a universal testing machine. 3+ The mechanical properties of hydrogels were studied. The sample used in the tensile test was: 6*1*0.2cm 3 The tensile loading rate is 20 mm / min, and the test result is the average of three tests. Figure 2 The results show that the elongation at break and the maximum stress at different ratios of acrylic acid to acrylamide monomers are 598.7% and 73.9 kPa, 256.3% and 41.3 kPa, 416.1% and 67.4 kPa, and 75.7% and 34.4 kPa, respectively, at 2:1, 1:2, 1:3, 2:1, 3:1, 4:1, 6:4, 7:3, 3:3, 3:4 ...

[0050] Figure 3 is the P(AA-co-AM) / 2d-Al with different 2d resin concentrations prepared according to Example 2 3+ The stress-strain curve of the hydrogel shows that when the concentration of 2d resin is 16.7wt%, its elongation at break and maximum stress are 940.5% and 32.1kPa respectively; when it is 33.4wt%, it is 863.5% and 48.1kPa respectively; when it is 50.0wt%, it is 598.7% and 73.9kPa respectively; when it is 66.7wt%, it is 548.5% and 67.5kPa respectively. It is found that with the increase of 2d resin concentration, the stress gradually increases and then decreases. At 50.0wt%, the stress reaches a maximum of 73.9kPa, and the elongation at break gradually decreases. At 16.7wt%, the elongation at break reaches a maximum of 940.5%. This is mainly due to the cross-linking effect of 2d resin, which enhances the stress of the hydrogel but reduces the strain of the hydrogel.

[0051] Figure 4The P(AA-co-AM) / 2d-Al ratio of different aluminum chloride hexahydrate contents prepared according to Example 3 is shown. 3+ Stress-strain curve of hydrogel. When the content of aluminum chloride hexahydrate is 0.25mol%, its elongation at break and maximum stress are 484.1% and 34.0kPa respectively; when it is 0.5mol%, it is 559.8% and 48.9kPa respectively; when it is 0.75mol%, it is 685.2% and 73.9kPa respectively; when it is 1.0mol%, it is 550.3% and 61.1kPa respectively. It is found that with the increase of aluminum chloride hexahydrate content, the stress gradually increases and then decreases, and the stress and strain reach the maximum at 0.75mol%.

[0052] Figure 5 P(AA-co-AM) / 2d-Al prepared according to Example 1 3+ The stress-strain curves of the hydrogel, the P(AA-co-AM) / 2d hydrogel prepared in Example 2, and the P(AA-co-AM) hydrogel prepared in Example 4. It was found that the strain and stress of the P(AA-co-AM) hydrogel without any crosslinking agent were 641% and 5.86 kPa, respectively. After crosslinking with 2d resin, the stress of the P(AA-co-AM) / 2d hydrogel was significantly increased to 60.39 kPa, but the strain was slightly reduced. In addition, the crosslinking of 2d resin and Al 3+ P(AA-co-AM) / 2d-Al cross-linked by two materials 3+ The strain and stress of the hydrogel were further enhanced to 599%, 73.6 kPa. By comparison, it was found that the mechanical tensile properties of the hydrogel cross-linked with the two substances were significantly improved.

[0053] Figure 6 P(AA-co-AM) / 2d-Al prepared according to Example 1 3+ The stress-strain curve of the hydrogel stretched to 400% and cycled 5 times showed that the stress of the hydrogel hardly decreased after 5 consecutive stretchings, and the maximum stress dropped from 43.4 kPa to 42.5 kPa, indicating strong stability.

[0054] Figure 7 is the P(AA-co-AM) / 2d-Al with different contents of aluminum chloride hexahydrate prepared according to Example 3 3+The adhesion strength bar graph of hydrogel adhesion to glass. When the aluminum chloride hexahydrate content is 0.25 mol%, its adhesion strength is: 38.14 kPa; when it is 0.5 mol%, its adhesion strength is: 62.5 kPa; when it is 0.75 mol%, its adhesion strength is: 70.5 kPa; when it is 1.0 mol%, its adhesion strength is: 48.4 kPa. It is found that with the increase of aluminum chloride hexahydrate content, the stress gradually increases and then decreases, and its adhesion strength reaches the maximum at 0.75 mol%.

[0055] Figure 8 P(AA-co-AM) / 2d-Al prepared according to Example 1 3+ Stress-strain curves of hydrogel self-repair at different times. The stress and strain magnitudes after 12 hours of repair are 181.8% and 19.5 kPa; the stress and strain magnitudes after 24 hours of repair are 361.0% and 39.6 kPa; the stress and strain magnitudes after 48 hours of repair are 421.9% and 51.5 kPa; the self-repair efficiencies are 30.3%, 60.2%, and 70.3%, respectively. As time goes by, the self-repair efficiency gradually increases, but due to the long-term dehydration of the hydrogel, the self-repair efficiency only reaches 70.3%.

[0056] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a low hysteresis, high stretchability, self-adhesive double chemical cross-linked structure hydrogel, characterized in that: The following steps are involved: (1) dissolving acrylic acid, acrylamide, aluminum chloride hexahydrate and 2d resin in deionized water according to a certain proportion, and mixing them evenly to obtain a mixed solution; (2) Adding ammonium persulfate to the above mixed solution, mixing evenly and pouring into a polytetrafluoroethylene mold, then heating in an oven and cooling to room temperature to obtain a double cross-linked hydrogel P(AA-co-AM) / 2d-Al 3+ The molar concentration of aluminum chloride hexahydrate is 0.25 of the amount of acrylic acid monomer substance. mol%~1.0mol%; The 2d resin is dihydroxymethyl dihydroxyethylene urea, and the mass concentration of the 2d resin is 16.7wt% to 66.7wt% compared to the mass of the acrylic acid monomer; The mass ratio of the acrylic acid to acrylamide is 2:1 to 1:

3.

2. The preparation method according to claim 1, characterized in that: The ammonium persulfate is 2 wt % compared to the total weight of the two monomers of acrylic acid and acrylamide.

3. The preparation method according to any one of claims 1 to 2, characterized in that: The heating temperature is 50-80° C., and the reaction time is 4-8 hours.

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