Anti-swelling hydrogel based on double-crosslinking network and preparation method of anti-swelling hydrogel
By constructing a double-crosslinked network hydrogel based on chitosan and isobornyl acrylate, the problem of easy swelling of hydrogels in liquid environments was solved, achieving a combination of low swelling and high mechanical properties, which is suitable for underwater flexible sensors.
Patent Information
- Application Number
- CN202511625397.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-07
- Publication Date
- 2026-02-17
AI Technical Summary
Existing hydrogels are prone to swelling in liquid environments, which leads to a decrease in mechanical properties and affects the performance of flexible sensors.
An anti-swelling hydrogel was prepared by using a tight microscopic double network structure based on chitosan, isobornyl acrylate, acrylic acid, N-hydroxymethylacrylamide, hydroxyethyl acrylate and deionized water, and double cross-linking through covalent bonds, hydrogen bonds, electrostatic interactions and hydrophobic association, combined with UV light curing.
It achieves low swelling while possessing certain strength and toughness, making it suitable for underwater flexible sensors and ensuring the accuracy of electrochemical signals.
Smart Images
Figure CN121537564A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer hydrogel engineering, specifically including an anti-swelling hydrogel based on a double cross-linked network and its preparation method. Background Technology
[0002] Hydrogels are high molecular polymers with a three-dimensional network cross-linked structure. Due to their high toughness, high elasticity, flexibility, water retention and good biocompatibility, they have been widely used in many fields, such as flexible sensors, biomedicine and soft robotics.
[0003] Currently, hydrogels can be prepared using monomers with specific properties to impart certain functions. For example, adding ionic liquids to the system makes the hydrogel conductive; adding salt ions makes it resistant to freezing at low temperatures; and adding fluorescent agents makes it fluorescently sensitive. However, since hydrogels are hydrophilic polymers, they absorb water and swell in liquid environments. This has a significant impact on their application in flexible sensors. Swelling leads to a decrease in the mechanical properties of the hydrogel, and the formation of a hydration layer reduces the gel adhesion strength. This results in severe delays or even distortions in the electrochemical signals monitored by flexible sensors based on hydrogels.
[0004] Currently, there are many methods to improve the swelling properties of hydrogels, such as introducing hydrophobic monomers into the hydrogel, adjusting the osmotic pressure between the inside and outside of the hydrogel, and increasing the number of crosslinking points to achieve multiple crosslinking. However, directly introducing hydrophobic monomers may make the hydrogel structure brittle; adjusting the internal and external osmotic pressure may make the hydrogel less tough and the crosslinking sparse; increasing the number of crosslinking points may prevent free ions from moving and reduce the conductivity of the hydrogel. Therefore, developing a hydrogel with low swelling but also with certain strength and toughness is one of the problems that researchers in the field of flexible sensing need to solve. Summary of the Invention
[0005] The purpose of this invention is to provide an anti-swelling hydrogel based on a double cross-linked network and its preparation method. While ensuring low swelling, the hydrogel also has certain strength and toughness, providing a new solution to the problems encountered in the field of underwater flexible sensors.
[0006] To achieve the above objectives, this invention provides a method for preparing an anti-swelling hydrogel based on a dual cross-linked network. The hydrogel is a compact microscopic dual-network structure constructed from chitosan, isobornyl acrylate, acrylic acid, N-hydroxymethylacrylamide, hydroxyethyl acrylate, and deionized water, containing covalent bonds, hydrogen bonds, electrostatic interactions, and hydrophobic associations. The method includes the following steps:
[0007] Step 1: Prepare the raw materials, which include chitosan, acrylic acid, isobornyl acrylate, N-hydroxymethylacrylamide, hydroxyethyl acrylate, and 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone.
[0008] Step 2: Add a certain amount of chitosan and acrylic acid to a certain volume of deionized water and stir thoroughly to obtain a mixed solution of the first network.
[0009] Step 3: Take a certain amount of the mixed solution obtained in Step 2, add isobornyl acrylate, N-hydroxymethylacrylamide, and hydroxyethyl acrylate to it, and stir thoroughly.
[0010] Step 4: Add a certain amount of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone to the mixed solution obtained in step 3, and continue stirring until the mixture is homogeneous.
[0011] Step 5: Sonicate the mixed solution obtained in Step 4.
[0012] Step 6: Inject the solution obtained in step 5 into a specific mold and irradiate it with a UV lamp until it gels.
[0013] Step 7: Wash the obtained hydrogel with deionized water to remove unreacted residual monomers on the surface of the hydrogel.
[0014] Preferably, in step 2, 0.35g of chitosan, 3ml of acrylic acid, and 10ml of deionized water are weighed, mixed, and stirred with a mechanical stirrer at 40°C for 1 hour at a speed of 400-600 rpm.
[0015] Preferably, in step 2, 10 ml of the obtained mixed solution is taken.
[0016] Preferably, in step 3, 1.5g of isobornyl acrylate, 0.2g of N-hydroxymethylacrylamide, and 0.9g of hydroxyethyl acrylate are added sequentially to the solution in step 2, and stirred with a magnetic stirrer for 15 minutes at a speed of 1500 rpm.
[0017] Preferably, in step 4, 0.05g of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone photoinitiator is added to the stirred mixture, and the mixture is stirred for 5 minutes at a speed of 1500 rpm using a magnetic stirrer.
[0018] Preferably, in step 5, an ultrasonic cleaner is used to perform ultrasonic degassing treatment on the mixed solution for 5 minutes.
[0019] Preferably, in step 6, ultraviolet light curing involves irradiating the mixed solution with an ultraviolet lamp of a specific wavelength, thereby causing the mixed solution to gel.
[0020] Preferably, in step 6, an ultraviolet lamp with a power of 6W and a wavelength of 365nm is used for irradiation.
[0021] Preferably, in step 6, the ultraviolet lamp is used for 6 minutes of irradiation.
[0022] Preferably, in step 7, the prepared hydrogel is washed with deionized water 3-5 times to remove unreacted residual monomers on the surface of the hydrogel.
[0023] An anti-swelling hydrogel based on a double cross-linked network is prepared by the above-described method for preparing hydrogels with a double cross-linked network. The prepared hydrogel has low swelling properties as well as certain strength and toughness.
[0024] The beneficial effects of this invention are as follows:
[0025] This invention provides a simple method for preparing an anti-swelling hydrogel. The hydrogel is based on a double cross-linked network, ensuring low swelling while maintaining certain strength and toughness. Chitosan and acrylic acid are used as the main framework of the hydrogel. Physical cross-linking is achieved through electrostatic interactions (-COOH in acrylic acid and -NH2 in chitosan) and hydrogen bonding, ensuring the hydrogel's toughness, ion mobility, and biocompatibility. Isoborneol acrylate, as a hydrophobic monomer, exhibits strong hydrophobicity, forming hydrophobic microdomains in the system to resist self-swelling. Furthermore, hydrophobic association between its groups further strengthens the cross-linked network. N-hydroxymethylacrylamide can covalently cross-link with isoborneol acrylate in the system, forming long polymer chains, thereby further strengthening the cross-linked network. Hydroxyethyl acrylate can react with acrylic acid in the first network via free radical polymerization, and also react with N-hydroxymethylacrylamide in the second network to form a strong hydrogen-bonded network. Furthermore, it can further react with the long polymer chains previously formed from isoborneol acrylate and N-hydroxymethylacrylamide to form even longer chains, ensuring the degree of crosslinking between the two networks and preventing phase separation. Moreover, this method cures into a gel under ultraviolet light, requiring very short experimental time.
[0026] The above description is an overview of the present invention. To more fully explain the present invention, the present invention will be further described below with reference to the accompanying drawings and preferred embodiments. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the CS / IBOA hydrogel double crosslinking network principle in this invention;
[0028] Figure 2 The graph shows the swelling rate results of various embodiments of the present invention in an aquatic environment;
[0029] Figure 3 This is a comparison diagram of the swelling of CS / IBOA hydrogel in this invention;
[0030] Figure 4 These are stress-strain curves for various embodiments of the present invention;
[0031] Figure 5 The following are bar charts showing the modulus and toughness of various embodiments of the present invention;
[0032] Figure 6 This is a diagram of the CS / IBOA hydrogel stretching experiment in this invention;
[0033] Figure 7 This is an experimental scenario diagram of the CS / IBOA hydrogel lifting a 400g object in this invention;
[0034] Figure 8 The figures show the water content test results of various embodiments of the present invention;
[0035] Figure 9 These are SEM images of the CS / IBOA hydrogel of the present invention before and after immersion in water;
[0036] Figure 10 The figures show the anti-drying test results of various embodiments of the present invention. Detailed Implementation
[0037] The present application will now be described in further detail with reference to the accompanying drawings. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.
[0038] Example 1
[0039] Preparation of CS-3 / IBOA hydrogel:
[0040] First, add 0.35g chitosan and 3ml acrylic acid to 10ml deionized water and stir at 450rpm for 1h at 40℃ to obtain a CS / PAA mixed solution.
[0041] Then, take 3 ml of the CS / PAA mixed solution and add 0.2 g of N-hydroxymethylacrylamide, 1.5 g of isoborneol acrylate, and 0.9 g of hydroxyethyl acrylate sequentially. Stir with a magnetic stirrer for 15 min at 1500 rpm. Next, add 0.05 g of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and continue stirring for 5 min. After that, sonicate with an ultrasonic cleaner for 5 min. Finally, pour into a polytetrafluoroethylene mold and irradiate with 365 nm ultraviolet light for 6 min to obtain a hydrogel. Finally, wash with deionized water 3-5 times.
[0042] Example 2
[0043] Preparation of CS-10 / IBOA hydrogel:
[0044] First, add 0.35g chitosan and 3ml acrylic acid to 10ml deionized water and stir at 450rpm for 1h at 40℃ to obtain a CS / PAA mixed solution.
[0045] Then, take 10 ml of the CS / PAA mixed solution and add 0.2 g of N-hydroxymethylacrylamide, 1.5 g of isoborneol acrylate, and 0.9 g of hydroxyethyl acrylate sequentially. Stir with a magnetic stirrer for 15 min at 1500 rpm. Next, add 0.05 g of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and continue stirring for 5 min. After that, sonicate with an ultrasonic cleaner for 5 min. Finally, pour into a polytetrafluoroethylene mold and irradiate with a 365 nm UV lamp for 6 min to obtain a hydrogel. Finally, wash with deionized water 3-5 times.
[0046] Example 3
[0047] Preparation of CS-15 / IBOA hydrogel:
[0048] First, add 0.35g chitosan and 3ml acrylic acid to 10ml deionized water and stir at 450rpm for 1h at 40℃ to obtain a CS / PAA mixed solution.
[0049] Then, take 15 ml of the CS / PAA mixed solution and add 0.2 g of N-hydroxymethylacrylamide, 1.5 g of isoborneol acrylate, and 0.9 g of hydroxyethyl acrylate sequentially. Stir with a magnetic stirrer for 15 min at 1500 rpm. Next, add 0.05 g of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and continue stirring for 5 min. After that, sonicate with an ultrasonic cleaner for 5 min. Finally, pour into a polytetrafluoroethylene mold and irradiate with a 365 nm UV lamp for 6 min to obtain a hydrogel. Finally, wash with deionized water 3-5 times.
[0050] Example 4
[0051] Preparation of CS / IBOA-0.5 hydrogel:
[0052] First, add 0.35g chitosan and 3ml acrylic acid to 10ml deionized water and stir at 450rpm for 1h at 40℃ to obtain a CS / PAA mixed solution.
[0053] Then, take 10 ml of the CS / PAA mixed solution and add 0.2 g of N-hydroxymethylacrylamide, 0.5 g of isoborneol acrylate, and 0.9 g of hydroxyethyl acrylate sequentially. Stir with a magnetic stirrer for 15 min at 1500 rpm. Next, add 0.05 g of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and continue stirring for 5 min. After that, sonicate with an ultrasonic cleaner for 5 min. Finally, pour into a polytetrafluoroethylene mold and irradiate with 365 nm ultraviolet light for 6 min to obtain a hydrogel. Finally, wash with deionized water 3-5 times.
[0054] Example 5
[0055] Preparation of CS / IBOA-1.5 hydrogel:
[0056] First, add 0.35g chitosan and 3ml acrylic acid to 10ml deionized water and stir at 450rpm for 1h at 40℃ to obtain a CS / PAA mixed solution.
[0057] Then, take 10 ml of the CS / PAA mixed solution and add 0.2 g of N-hydroxymethylacrylamide, 1.5 g of isoborneol acrylate, and 0.9 g of hydroxyethyl acrylate sequentially. Stir with a magnetic stirrer for 15 min at 1500 rpm. Next, add 0.05 g of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and continue stirring for 5 min. After that, sonicate with an ultrasonic cleaner for 5 min. Finally, pour into a polytetrafluoroethylene mold and irradiate with a 365 nm UV lamp for 6 min to obtain a hydrogel. Finally, wash with deionized water 3-5 times.
[0058] Example 6
[0059] Preparation of CS / IBOA-2.5 hydrogel:
[0060] First, add 0.35g chitosan and 3ml acrylic acid to 10ml deionized water and stir at 450rpm for 1h at 40℃ to obtain a CS / PAA mixed solution.
[0061] Then, take 10 ml of the CS / PAA mixed solution and add 0.2 g of N-hydroxymethylacrylamide, 2.5 g of isobornyl acrylate, and 0.9 g of hydroxyethyl acrylate sequentially. Stir with a magnetic stirrer for 15 min at 1500 rpm. Next, add 0.05 g of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and continue stirring for 5 min. After that, sonicate with an ultrasonic cleaner for 5 min. Finally, pour into a polytetrafluoroethylene mold and irradiate with 365 nm ultraviolet light for 6 min to obtain a hydrogel. Finally, wash with deionized water 3-5 times.
[0062] Test Example 1
[0063] Swelling test:
[0064] The CS / IBOA hydrogels prepared in Examples 1-6 were immersed in water, and the mass of each group was recorded daily, according to SR = (w s -w o ) / w o *100%, of which w s For the quality of the measurement, w o Calculate the swelling ratio based on the initial mass.
[0065] like Figure 1 As shown, the anti-swelling effect is best when the CS / PAA network content is 10 ml and the IBOA monomer content is 1.5 g. Excessive CS / PAA content and excessive IBOA monomer content will cause huge swelling.
[0066] Test Example 2
[0067] Mechanical testing:
[0068] The CS / IBOA hydrogels prepared in Examples 1-6 were subjected to tensile tests using an XL-969S-500 microcomputer tensile strength testing machine. The hydrogel samples were made into cuboid shapes of 50x10mm and 3mm thickness.
[0069] like Figure 3 As shown, the test results indicate that the higher the CS / PAA network content in the system, the better the toughness of the hydrogel; the higher the IBOA content, the higher the strength of the hydrogel, but excessively high content will cause obvious phase separation, which in turn leads to a decrease in strength.
[0070] Test Example 3
[0071] Moisture content test:
[0072] The CS / IBOA hydrogels prepared in Examples 1-6 were placed in an electrically heated drying oven and heated to 60°C until the gels were completely dry, and then dried according to the formula W = (w w -w s ) / w w Where W is the water content, w s The weight after drying, w w Given the original weight, calculate the moisture content.
[0073] like Figure 6 As shown, while ensuring the toughness of the hydrogel, the CS / PAA mixed solution increases the water content in the system and increases swelling. Therefore, an appropriate ratio must be used to ensure both a certain degree of toughness and resistance to swelling.
[0074] Test Example 4 Observe the internal structure of the hydrogel: Figure 9 a shows the original scanning electron microscope images of the hydrogels in Examples 2 and 5. Figure 9 b is a scanning electron microscope image of the hydrogel after soaking in water for 24 hours. Comparing the two images, it can be seen that after soaking, the hydrogel network structure shrinks due to the hydrophobic association in the network, thereby inhibiting the entry of water molecules.
[0077] Test Example 5
[0078] Resistance to drying:
[0079] The CS / IBOA hydrogels prepared in Examples 1-6 were placed in a constant temperature incubator at 25°C, and their weight was recorded daily.
[0080] like Figure 8As shown, at 25°C, the quality of each group decreased the fastest between the first and second days. Groups with excessively high CS / PAA network content or excessively high IBOA monomer content experienced further decreases, while the quality curves of groups 2 and 5 in Examples tended to stabilize.
[0081] In summary, this invention prepares an anti-swelling hydrogel using a strategy based on a double cross-linked network and UV curing, while also exhibiting certain strength and toughness. When the CS / PAA network content and IBOA monomer content are optimal, the swelling rate of the hydrogel remains at approximately 3% after immersion in water for one week. Using the stress-strain curves obtained from tensile tests, the slope of the strain segment from 5% to 15% is used to represent the modulus of each embodiment, and the integral area of the curve is used to represent the toughness of each embodiment. When the CS / PAA network content and IBOA monomer content are optimal, the maximum tensile strength is 162.21 kPa, the maximum elongation at break reaches 665.634%, the modulus reaches 0.64 MPa, and the toughness reaches 0.732 MJ / m³.
[0082] Finally, it should be noted that the above description is only a technical solution of the present invention and not a limitation thereof. For those skilled in the art, modifications or equivalent transformations can still be made to the technical solution of the present invention, and these modifications or equivalent transformations shall not cause the modified technical solution to deviate from the spirit and scope of the present invention.
[0083] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.
Claims
1. A method for the preparation of a dual cross-linked network based anti-swelling hydrogel, characterized in that, The method comprises the following steps: Step 1: preparing raw materials, including chitosan, acrylic acid, isobornyl acrylate, N-methylol acrylamide, hydroxyethyl acrylate and 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy) phenyl]-1-propanone; Step 2: adding a certain amount of chitosan and acrylic acid into a certain volume of deionized water and stirring to obtain a mixed solution of a first network; Step 3: taking a certain amount of the mixed solution obtained in Step 2, adding isobornyl acrylate, N-methylol acrylamide and hydroxyethyl acrylate into the mixed solution and stirring thoroughly; Step 4: adding a certain amount of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy) phenyl]-1-propanone into the mixed solution obtained in Step 3 and continuing to stir until the mixed solution is uniform; Step 5: performing ultrasonic treatment on the mixed solution obtained in Step 4; Step 6: injecting the mixed solution obtained in Step 5 into a specific mold and irradiating with a UV lamp until the mixed solution is gelled; Step 7: washing the hydrogel obtained in Step 6 with deionized water to remove residual monomers on the surface of the hydrogel.
2. A process for the preparation of a double cross-linked network based anti- swelling hydrogel according to claim 1, characterized in that: In Step 2, 0.35 g of chitosan, 3 ml of acrylic acid and 10 ml of deionized water are weighed and mixed, and then stirred at a temperature of 40℃ for 1 h by using a mechanical stirrer at a speed of 400-600 rpm.
3. A process for the preparation of a dual cross-linking network based anti- swelling hydrogel according to claim 1, characterized in that: 10 ml of the mixed solution obtained in Step 2 is taken.
4. A process for the preparation of a dual cross-linking network based anti- swelling hydrogel according to claim 1, characterized in that: In Step 3, 1.5 g of isobornyl acrylate, 0.2 g of N-methylol acrylamide and 0.9 g of hydroxyethyl acrylate are weighed and sequentially added into the mixed solution in Step 2, and then stirred for 15 min by using a magnetic stirrer at a speed of 1500 rpm.
5. A process for the preparation of a dual cross-linking network based anti- swelling hydrogel according to claim 4, characterized in that: 0.05 g of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy) phenyl]-1-propanone photoinitiator is added into the stirred mixed solution, and then stirred for 5 min by using the magnetic stirrer at a speed of 1500 rpm.
6. A process for the preparation of a dual cross-linking network based anti- swelling hydrogel according to claim 1, characterized in that: In Step 5, the mixed solution is subjected to ultrasonic degassing treatment by using an ultrasonic cleaner for 5 min.
7. The method of claim 1, wherein the method is characterized by: In Step 6, the UV light curing is performed by using a UV lamp with a specific wavelength to irradiate the mixed solution so that the mixed solution is gelled, wherein the UV lamp has a power of 6 W and a wavelength of 365 nm.
8. A method of preparing a dual cross-linking network based anti-swelling hydrogel according to claim 7, characterized in that: In Step 6, the UV lamp is irradiated for 6 min.
9. A process for the preparation of a dual cross-linking network based anti- swelling hydrogel according to claim 1, characterized in that: In Step 7, the prepared hydrogel is washed with deionized water for 3-5 times to remove residual monomers on the surface of the hydrogel.
10. A dual cross-linking network based anti-swelling hydrogel, characterized in that: The hydrogel is prepared by using the method of any one of claims 1-9. The hydrogel is prepared by using the method of any one of claims 1-9.