Preparation method of high-strength supramolecular lignin / polyvinyl alcohol hydrogel

Abstract

The invention discloses a preparation method of high-strength supramolecular lignin / polyvinyl alcohol hydrogel. The high-strength supramolecular lignin / polyvinyl alcohol hydrogel is prepared by gradually diffusing a lignosulfonate solution into a polyvinyl alcohol (PVA) solution and self-assembling. The supramolecular hydrogel prepared by the method disclosed by the invention has good mechanical properties, freezing resistance, ultraviolet resistance and the like, so that the supramolecular hydrogel has huge application potential in the fields of tissue engineering, rubber, plastic substitution, wearable electronics and the like.

Description

Technical Field

[0001] The invention belongs to the field of functional polymer materials, and in particular relates to a method for preparing a high-strength supramolecular lignin / polyvinyl alcohol hydrogel. Background Art

[0002] Hydrogel is a polymer compound composed of a three-dimensional polymer network. It has the advantages of high water content, adjustable mechanical properties and good biocompatibility, and is therefore widely used in the fields of tissue engineering, drug sustained release and sensing. However, the mechanical properties of traditional hydrogels are relatively low, which greatly limits their application in actual production and life. In addition, chemically cross-linked hydrogels usually use complex, expensive, time-consuming and environmentally unfriendly methods, which increases their production costs. Therefore, it is of great significance to design a green and environmentally friendly method to prepare high-strength hydrogels.

[0003] Polyvinyl alcohol (PVA) hydrogel has good biocompatibility and degradability, and is widely used in tissue engineering, drug delivery, cell culture and other fields. PVA hydrogel can be cross-linked physically (freeze-thaw) or chemically. Physical cross-linking requires multiple freeze-thaw cycles at low temperatures, which is time-consuming and energy-consuming, and the strength of the gel is low. Chemically cross-linked hydrogels are potentially toxic, which greatly limits the application of hydrogels.

[0004] Lignin is an aromatic polymer second only to cellulose in plant fiber raw materials. It has the advantages of wide sources, green environmental protection, biocompatibility, sustainability and low cost. Lignin contains a large number of phenolic hydroxyl groups, methoxy groups, etc., which can form hydrogen bonds with PVA. However, after the simple lignin and PVA are blended, there are only weak hydrogen bonds and entanglement, which cannot give the hydrogel strong mechanical properties. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a high-strength supramolecular lignin / polyvinyl alcohol hydrogel to solve the problems of time-consuming, energy-consuming and insufficient mechanical strength of the existing polyvinyl alcohol hydrogel preparation process. The supramolecular hydrogel prepared by the method of the present invention has good mechanical properties, antifreeze and UV resistance, etc., so that it has great application potential in the fields of tissue engineering, rubber, plastic replacement and wearable electronics.

[0006] The preparation method of the high-strength supramolecular lignin / polyvinyl alcohol hydrogel of the present invention comprises the following steps:

[0007] Prepare a PVA solution, dissolve it completely at 95°C, cool it to room temperature, then transfer the PVA solution to a mold, slowly add lignin sulfonate solution on the top of the PVA solution, and infiltrate it at room temperature for more than 60 minutes to obtain a high-strength supramolecular hydrogel.

[0008] The concentration of the lignin sulfonate solution is from 10 wt % to saturation, preferably 40 wt %.

[0009] The lignin sulfonate is selected from any one of sodium lignin sulfonate and calcium lignin sulfonate or a mixture of the two.

[0010] The solvent of the lignin sulfonate solution is one of water, ethanol, ethylene glycol, and glycerol, or a mixture of one of ethanol, ethylene glycol, and glycerol and water. In the latter case, the mass ratio of one of ethanol, ethylene glycol, and glycerol to water is 0:1 to 1:0.

[0011] The concentration of the PVA solution is 15-30wt%, preferably 20wt%.

[0012] The volume ratio of the lignin sulfonate solution to the PVA solution is 1:2 to 2:1.

[0013] The penetration time is preferably 2-12 h.

[0014] The present invention induces PVA to crystallize and gel by gradually infiltrating lignin sulfonate into PVA solution. By adjusting the concentration of lignin sulfonate, immersion time and PVA concentration, supramolecular lignin / polyvinyl alcohol hydrogels with different mechanical properties are obtained, and the tensile strength can reach up to 20 MPa, the Young's modulus can reach up to 14 MPa, and the toughness can reach up to 50 MJ / m 3 .

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. The lignin used in the present invention is lignin sulfonate, a byproduct obtained by the sulfite process in the pulp and paper industry, which has the advantages of wide sources, green environmental protection, biocompatibility, sustainability, etc. Compared with the existing polyvinyl alcohol hydrogel, the lignin composite hydrogel prepared by the present invention has lower cost and is a fully biodegradable material, and is a green and environmentally friendly polymer material.

[0017] 2. The present invention utilizes lignin sulfonate to soak PVA solution to obtain high-strength supramolecular lignin / polyvinyl alcohol hydrogel. This is different from the traditional method of PVA hydrogel through freeze-thaw or chemical crosslinking agent. In the present invention, due to the osmotic effect, lignin sulfonate gradually penetrates into the PVA solution and induces PVA crystallization. In addition, lignin sulfonate can also form hydrogen bonds with PVA to enhance the mechanical properties of the hydrogel.

[0018] 3. The supramolecular lignin / polyvinyl alcohol hydrogel prepared by the present invention has excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a photo of the actual object of the lignin / polyvinyl alcohol hydrogel obtained in Example 6.

[0020] Figure 2 The mechanical properties of the lignin / polyvinyl alcohol hydrogel obtained in Example 6 are shown in Figure (a) as the tensile stress-strain diagram after soaking in saturated LS for different time periods, and Figure (b) as the toughness and Young's modulus after soaking in saturated LS for different time periods.

[0021] Figure 3 The antifreeze properties of the lignin / polyvinyl alcohol hydrogel obtained in Example 6. (a) shows the DSC curves of the hydrogels soaked for different times during cooling from 20 to -80 °C, (b) the tensile stress-strain curves of the hydrogels soaked for 12 hours at -60 °C. The inset shows the appearance photos of different hydrogels at -60 °C, (c) the photos of the hydrogels soaked for 12 hours at -60 °C at 0 and ~375% strain.

[0022] Figure 4 This is the anti-ultraviolet performance of the lignin / polyvinyl alcohol hydrogel obtained in Example 6. DETAILED DESCRIPTION

[0023] The method of the present invention is further described in detail below in conjunction with the embodiments. It should be particularly noted that the protection scope of the present invention should include but is not limited to the technical content disclosed in this embodiment.

[0024] Embodiment 1:

[0025] 1. Take 40 g of sodium lignin sulfonate, dissolve it in 60 g of deionized water solution, stir evenly at room temperature, and ultrasonicate it for 30 min.

[0026] 2. Take 2.5 g PVA and dissolve it in 7.5 g deionized water. Dissolve it completely at 95 °C and cool it to room temperature. Move it into a mold and slowly pour the solution in step 1 on the surface of the PVA solution. Place it at room temperature for 2 h to obtain a high-strength supramolecular hydrogel.

[0027] Embodiment 2:

[0028] 1. Take 20 g of sodium lignin sulfonate, dissolve it in 60 g of glycerol, stir evenly at room temperature, and ultrasonicate it for 30 minutes.

[0029] 2. Take 15g PVA and dissolve it in 35g deionized water. Dissolve it completely at 95°C, cool it to room temperature, move it into a mold and slowly pour the solution in step 1 on the surface of the PVA solution. Leave it at room temperature for 3h to obtain a high-strength supramolecular hydrogel.

[0030] Embodiment 3:

[0031] 1. Take 20 g of glycerol and add it to 50 g of deionized water. After mixing evenly, add 30 g of sodium lignin sulfonate, stir evenly at room temperature, and ultrasonicate it for 60 min.

[0032] 2. Take 12 g of PVA and dissolve it in 38 g of deionized water. Dissolve it completely at 95 °C, cool it to room temperature, move it into a mold and slowly pour the solution in step 1 on the surface of the PVA solution. Leave it at room temperature for 6 hours to obtain a high-strength supramolecular hydrogel.

[0033] Embodiment 4:

[0034] 1. Take 30 g of sodium lignin sulfonate and dissolve it in a mixed solution of 70 g of ethylene glycol and glycerol (mass ratio is 1:1), stir evenly at room temperature, then add 10 g of glycerol and ultrasonicate it for 30 min.

[0035] 2. Take 8 g of PVA and dissolve it in 32 g of deionized water. Dissolve it completely at 95 °C, cool it to room temperature, transfer it to a mold and slowly pour the solution in step 1 on the surface of the PVA solution. Leave it at room temperature for 4 h to obtain a high-strength supramolecular hydrogel.

[0036] Embodiment 5:

[0037] 1. Take 10 g of sodium lignin sulfonate and dissolve it in 50 g of deionized water solution. Stir evenly at room temperature, then add 10 g of glycerol and ultrasonicate it for 30 min.

[0038] 2. Take 10 g of PVA and dissolve it in 40 g of deionized water. Dissolve it completely at 95 °C, cool it to room temperature, move it into a mold and slowly pour the solution in step 1 on the surface of the PVA solution. Leave it at room temperature for 2 h to obtain a high-strength supramolecular hydrogel.

[0039] Embodiment 6:

[0040] 1. Take 8 g of sodium lignin sulfonate, dissolve it in 16 g of deionized water solution, stir evenly at room temperature, and ultrasonicate it for 30 min.

[0041] 2. Take 2 g of PVA and dissolve it in 7.5 g of deionized water. Dissolve it completely at 95 °C, cool it to room temperature, transfer it to a mold and slowly pour the solution in step 1 on the surface of the PVA solution. Place it at room temperature for 2, 6, 12, 24, and 48 h to obtain a high-strength supramolecular hydrogel.

[0042] Figure 2 are the mechanical properties of the lignin / polyvinyl alcohol hydrogel obtained in Example 6. Figure 2It can be seen that as the immersion time increases, the tensile strength and fracture strain of the hydrogel also increase. After immersion for 48 h, the mechanical strength and elongation at break of the lignin / polyvinyl alcohol hydrogel are as high as 20 MPa and 500%, respectively. The Young's modulus of the hydrogel is as high as 14 MPa, and the toughness can reach 50 MJ / m 3 It is worth noting that PVA cannot form gel without being soaked in lignin sulfonic acid. After being soaked in sodium lignin sulfonate, the strength, elongation at break, toughness and Young's modulus of the hydrogel are rapidly improved.

[0043] Since the raw materials and blending processes used in other embodiments have similar characteristics to those of Embodiment 1, after testing, the properties of the hydrogels prepared in other embodiments have similar characteristics to the above results, and therefore they are not repeated one by one.

[0044] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a high-strength supramolecular lignin / polyvinyl alcohol hydrogel, characterized in that The steps include: Prepare a PVA solution, heat it to completely dissolve it, then cool it to room temperature, then transfer the PVA solution to a mold, slowly add a lignin sulfonate solution to the upper surface of the PVA solution, and let it stand and penetrate at room temperature to obtain a high-strength supramolecular hydrogel.

2. The preparation method according to claim 1, characterized in that: The lignin sulfonate is selected from any one of sodium lignin sulfonate and calcium lignin sulfonate or a mixture of the two.

3. The preparation method according to claim 2, characterized in that: The concentration of the lignin sulfonate solution is from 10 wt % to saturation.

4. The preparation method according to claim 3, characterized in that: The concentration of the lignin sulfonate solution is 40 wt %.

5. The preparation method according to claim 2, characterized in that: The solvent of the lignin sulfonate solution is one of water, ethanol, ethylene glycol, and glycerol, or a mixture of one of ethanol, ethylene glycol, and glycerol and water.

6. The preparation method according to claim 1, characterized in that: The concentration of the PVA solution is 15-30wt%.

7. The preparation method according to claim 6, characterized in that: The concentration of the PVA solution is 20 wt %.

8. The preparation method according to claim 3 or 6, characterized in that: The volume ratio of the lignin sulfonate solution to the PVA solution is 1:2 to 3:

1.

9. The preparation method according to claim 1, characterized in that: Penetration time ≥60min.

10. The preparation method according to claim 1, characterized in that: The penetration time is 2-12 h.

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