Disclosure of Invention
In order to overcome the defects and shortcomings of the prior art, the invention mainly aims to provide a high-strength lignin/polyvinyl alcohol composite conductive hydrogel.
The invention also aims to provide a preparation method of the high-strength lignin/polyvinyl alcohol composite conductive hydrogel.
The purpose of the invention is realized by the following scheme:
a high-strength lignin/polyvinyl alcohol composite conductive hydrogel is a lignin-enhanced PVA hydrogel, and specifically is prepared by mixing lignin with PVA to prepare a gel A, sequentially soaking in a water-soluble silver salt solution, and reducing by a reducing agent to obtain the high-strength lignin/polyvinyl alcohol composite conductive hydrogel.
The mass ratio of PVA to lignin is preferably 2:1 to 10: 1.
The mass concentration of PVA in the gel A is preferably 4.5 to 30%.
The gel prepared by mixing the lignin and the PVA can be prepared by mixing and dispersing the lignin and the PVA in a solvent, stirring for 1-6h at 70-140 ℃, casting and molding, and then obtaining the composite hydrogel by a freezing-thawing method or a solvent exchange method. More preferably at 80-120 deg.C for 1-6 h. The stirring rate is preferably 100-. The solvent is preferably a mixed solvent of water and dimethyl sulfoxide, and the volume ratio of the mixed solvent to the dimethyl sulfoxide is 4:1-1: 4.
The casting molding process conditions may be conventional casting molding process conditions in the art, and are well known to those skilled in the art. The freeze-thaw method or the solvent exchange method is a conventional method for preparing a hydrogel and is well known to those skilled in the art.
The soaking time is preferably 1-6 h.
The concentration of the water-soluble silver salt solution can be 0.01-1 mol/L. The water soluble silver salt may be selected from silver nitrate and the like.
The reduction by the reducing agent can be realized by soaking the soaked hydrogel in a reducing agent solution, and more specifically, the soaked hydrogel can be soaked in a reducing agent solution for 1-5 hours.
The reducing agent can be sodium citrate, sodium borohydride, dopamine, ascorbic acid and the like.
The concentration of the reducing agent solution is preferably 0.1 to 2 mol/L.
The PVA used in the present invention is an alcoholysis product of polyvinyl acetate known in the art, preferably having an alcoholysis degree of 85% or more and a molecular weight of 3000 or more.
The lignin used in the present invention can be, but is not limited to, at least one of alkali lignin obtained by alkali pulping in paper industry, enzymatic lignin extracted from ethanol prepared by fermenting lignocellulose, organosolv lignin extracted from lignocellulose by organosolv method, or lignosulfonate (including calcium lignosulfonate, sodium lignosulfonate, and lignosulfonic acid) as a byproduct in sulfite pulping.
According to the invention, lignin is added into the polyvinyl alcohol hydrogel, the amphiphilic lignin forms a nano microphase separation structure in the polyvinyl alcohol hydrogel through self-assembly, and simultaneously the lignin promotes the polyvinyl alcohol hydrogel to carry out Ag+Adsorption of (3); further introducing a reducing agent to adsorb Ag on the outer surface of the hydrogel+Reducing to form compact nano silver particle clusters on the surface of the hydrogel. The compact external structure and the loose internal structure enable the hydrogel to have ultrahigh mechanical strength and toughness, and meanwhile, the shell formed by the nano silver particle clusters also endows the hydrogel with excellent conductivity and antibacterial performance.
The invention can obtain hydrogel with different mechanical properties and conductive properties by adjusting the dosage of lignin in the hydrogel and the concentration of the water-soluble silver salt and the reducing agent solution, and the tensile strength of the hydrogel can reach 0.1-13.0MPa, and can reach 13.0MPa at most; the elongation at break can reach 461-1500 percent, and the highest elongation at break can reach 1500 percent; the conductivity can reach 0.009-10.126S/m.
The invention also provides a preparation method of the high-strength lignin/polyvinyl alcohol composite conductive hydrogel, which comprises the following steps:
(1) mixing PVA and lignin, adding the mixture into a solvent, uniformly dispersing, stirring for 1-6h at 70-140 ℃, casting and molding, and obtaining the composite hydrogel by a freezing-thawing method or a solvent exchange method;
(2) soaking the composite hydrogel obtained in the step (1) in a water-soluble silver salt solution for 1-6 h;
(3) and (3) soaking the soaked hydrogel in a reducing agent solution for 1-5 hours to obtain the high-strength lignin/polyvinyl alcohol composite conductive hydrogel.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the lignin used in the invention is alkali lignin obtained by alkali pulping in the paper industry or enzymolysis lignin extracted from ethanol prepared by fermenting lignocellulose or lignin or lignosulfonate byproduct extracted from lignocellulose by an organic solvent method in pulping by lignin or sulfite, the raw material of the lignosulfonate is derived from biomass resources, and the lignosulfonate composite hydrogel has environmental friendliness and biodegradability.
2. According to the invention, amphipathic lignin is added to form a nano microphase separation structure through hydrophobic self-assembly in a polyvinyl alcohol hydrogel matrix; meanwhile, the chelation of lignin promotes the polyvinyl alcohol composite hydrogel to Ag+Adsorption of (3); reducing Ag adsorbed on the outer surface of the hydrogel by further introducing a reducing agent+And forming compact nano silver particle clusters on the surface of the hydrogel. The compact external structure and the loose internal structure of the hydrogel impart it with ultra-high mechanical strength and toughness.
3. The lignin/polyvinyl alcohol composite hydrogel prepared by the invention also has excellent conductivity and antibacterial activity.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
The materials referred to in the following examples are commercially available. The using amount of each component is g and mL in parts by mass.
Example 1
Taking 4.5 parts by mass of polyvinyl alcohol and 0.5 part by mass of lignin, and adding 72.4 parts by volume of water; 18.1 volume parts of DMSO solution, heating at 70 ℃, mechanically stirring at 100rpm for 1h, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12h, thawing for 2h, soaking the thawed composite hydrogel in deionized water for 24h for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.01mol/L silver nitrate solution for 1h, and then soaking in 0.1mol/L sodium citrate for 1h to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 2
Adding 66.15 parts by volume of water into 5 parts by mass of polyvinyl alcohol and 0.5 part by mass of lignin; 28.35 volume parts of DMSO solution, heating at 80 ℃, mechanically stirring at 120rpm for 2 hours, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.02mol/L silver nitrate solution for 2 hours, and then soaking in 0.2mol/L dopamine for 2 hours, thus finally obtaining the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 3
Adding 55.8 parts by volume of water into 5.5 parts by mass of polyvinyl alcohol and 1.5 parts by mass of lignin; and (2) heating the DMSO solution by 37.2 volume parts at 90 ℃, mechanically stirring at 300rpm for 3 hours, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.03mol/L silver nitrate solution for 3 hours, and then soaking in 0.3mol/L sodium citrate for 3 hours to finally obtain a finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 4
Taking 6 parts by mass of polyvinyl alcohol and 2 parts by mass of lignin, and adding 46 parts by volume of water; and (2) mechanically stirring 46 parts by volume of DMSO solution at the heating temperature of 100 ℃ for 4h at 400rpm, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12h, thawing for 2h, soaking the thawed composite hydrogel in deionized water for 24h for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.04mol/L silver nitrate solution for 3h, and then soaking in 0.4mol/L sodium borohydride for 4h to finally obtain a finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 5
Taking 6.5 parts by mass of polyvinyl alcohol and 2.5 parts by mass of lignin, and adding 36.4 parts by volume of water; 54.6 parts by volume of DMSO solution, heating at 110 ℃, mechanically stirring at 500rpm for 5 hours, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.05mol/L silver nitrate solution for 5 hours, and then soaking in 0.5mol/L sodium citrate for 5 hours to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 6
Taking 7 parts by mass of polyvinyl alcohol and 5 parts by mass of lignin, and adding 26.4 parts by volume of water; 61.6 volume parts of DMSO solution, heating at 120 ℃, mechanically stirring at 600rpm for 6 hours, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the exchanged composite hydrogel in 0.06mol/L silver nitrate solution for 6 hours, and then soaking in 0.5mol/L ascorbic acid for 5 hours to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is byproduct sodium lignosulfonate produced in sulfite pulping.
Example 7
Taking 8 parts by mass of polyvinyl alcohol and 3.5 parts by mass of lignin, and adding 17.7 parts by volume of water; 70.8 volume parts of DMSO solution, mechanically stirring at 800rpm for 2 hours at the heating temperature of 140 ℃, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.07mol/L silver nitrate solution for 2 hours, and then soaking in 0.6mol/L sodium citrate for 2 hours to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 8
Adding 69.6 parts by volume of water into 9 parts by mass of polyvinyl alcohol and 4 parts by mass of lignin; and (2) heating 17.4 parts by volume of DMSO solution at 140 ℃, mechanically stirring at 800rpm for 2 hours, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, soaking the composite hydrogel after solvent exchange in 0.08mol/L silver nitrate solution for 1 hour, and soaking in 0.7mol/L dopamine for 2 hours to finally obtain a finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 9
Adding 59.85 parts by volume of water into 10 parts by mass of polyvinyl alcohol and 4.5 parts by mass of lignin; 25.65 parts by volume of DMSO solution, heating at 70 ℃, mechanically stirring at 300rpm for 1h, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12h, thawing for 2h, soaking the thawed composite hydrogel in deionized water for 24h for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.09mol/L silver nitrate solution for 2h, and then soaking in 0.8mol/L sodium citrate for 2h to finally obtain the finished product of the lignin/polyvinyl alcohol composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 10
Taking 11 parts by mass of polyvinyl alcohol and 5 parts by mass of lignin, and adding 50.4 parts by volume of water; and (2) mechanically stirring 33.6 parts by volume of DMSO solution at the heating temperature of 120 ℃ for 3 hours at 900rpm, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.10mol/L silver nitrate solution for 5 hours, and then soaking in 0.9mol/L sodium borohydride for 5 hours to finally obtain a finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 11
Taking 12 parts by mass of polyvinyl alcohol and 5.5 parts by mass of lignin, and adding 41.25 parts by volume of water; 41.25 parts by volume of DMSO solution, heating at 130 ℃, mechanically stirring at 1000rpm for 6 hours, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.2mol/L silver nitrate solution for 6 hours, and then soaking in 1.0mol/L sodium citrate for 2 hours to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 12
Taking 13 parts by mass of polyvinyl alcohol and 6 parts by mass of lignin, and adding 32.4 parts by volume of water; 48.6 parts by volume of DMSO solution, heating at 140 ℃, mechanically stirring at 500rpm for 4 hours, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.3mol/L silver nitrate solution for 1 hour, and then soaking in 1.1mol/L ascorbic acid for 2 hours to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 13
Taking 14 parts by mass of polyvinyl alcohol and 6.5 parts by mass of lignin, and adding 23.85 parts by volume of water; 55.65 volume parts of DMSO solution, heating at 70 ℃, mechanically stirring at 300rpm for 6h, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12h, thawing for 2h, soaking the thawed composite hydrogel in deionized water for 24h for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.04mol/L silver nitrate solution for 2h, and then soaking in 1.5mol/L sodium citrate for 5h to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is lignosulfonic acid, a by-product of sulfite pulping.
Example 14
Taking 15 parts by mass of polyvinyl alcohol and 7 parts by mass of lignin, and adding 15.6 parts by volume of water; 62.4 volume parts of DMSO solution, heating at 110 ℃, mechanically stirring at 100rpm for 2h, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12h, thawing for 2h, soaking the thawed composite hydrogel in deionized water for 24h for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.03mol/L silver nitrate solution for 6h, and then soaking in 1.8mol/L dopamine for 4h to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is alkali lignin obtained by alkali pulping in the paper industry.
Example 15
Taking 17 parts by mass of polyvinyl alcohol and 7.5 parts by mass of lignin, and adding 60.4 parts by volume of water; 15.1 volume parts of DMSO solution, heating at 70 ℃, mechanically stirring at 200rpm for 3 hours, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then placing the composite hydrogel after solvent exchange in 0.50mol/L silver nitrate solution for soaking for 5 hours, and then placing in 1.8mol/L sodium citrate for soaking for 2 hours, thus finally obtaining the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is alkali lignin obtained by alkali pulping in the paper industry.
Example 16
Taking 18 parts by mass of polyvinyl alcohol and 8 parts by mass of lignin, and adding 51.8 parts by volume of water; 22.2 volume parts of DMSO solution, mechanically stirring at 500rpm for 5 hours at the heating temperature of 130 ℃, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.70mol/L silver nitrate solution for 5 hours, and then soaking in 2.0mol/L sodium citrate for 3 hours to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is a byproduct calcium lignosulfonate produced in sulfite pulping.
Example 17
Taking 19 parts by mass of polyvinyl alcohol and 9 parts by mass of lignin, and adding 43.2 parts by volume of water; 28.8 volume parts of DMSO solution, heating at 80 ℃, mechanically stirring at 1000rpm for 2h, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12h, thawing for 2h, soaking the thawed composite hydrogel in deionized water for 24h for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.9mol/L silver nitrate solution for 6h, and then soaking in 1.5mol/L sodium borohydride for 4h to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is byproduct sodium lignosulfonate produced in sulfite pulping.
Example 18
Taking 20 parts by mass of polyvinyl alcohol and 5 parts by mass of lignin, and adding 37.5 parts by volume of water; and (2) heating 37.5 parts by volume of DMSO solution at 140 ℃, mechanically stirring at 150rpm for 3 hours, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 1mol/L silver nitrate solution for 5 hours, and then soaking in 0.5mol/L sodium citrate for 4 hours to finally obtain a finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is a byproduct calcium lignosulfonate produced in sulfite pulping.
Example 19
Taking 23 parts by mass of polyvinyl alcohol and 10 parts by mass of lignin, and adding 26.8 parts by volume of water; 40.2 volume parts of DMSO solution, heating at 100 ℃, mechanically stirring at 200rpm for 2h, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12h, thawing for 2h, soaking the thawed composite hydrogel in deionized water for 24h for solvent exchange, then soaking the composite hydrogel after solvent exchange in 1.0mol/L silver nitrate solution for 6h, and then soaking in 2.0mol/L ascorbic acid for 5h to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is byproduct sodium lignosulfonate produced in sulfite pulping.
Example 20
Taking 20 parts by mass of polyvinyl alcohol and 15 parts by mass of lignin, and adding 19.5 parts by volume of water; and (2) mechanically stirring 45.5 parts by volume of DMSO solution at the heating temperature of 110 ℃ for 1h at 800rpm, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12h, thawing for 2h, soaking the thawed composite hydrogel in deionized water for 24h for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.5mol/L silver nitrate solution for 3h, and then soaking in 0.5mol/L sodium citrate for 5h to finally obtain the finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is a byproduct calcium lignosulfonate produced in sulfite pulping.
Example 21
Taking 30 parts by mass of polyvinyl alcohol and 5 parts by mass of lignin, and adding 13 parts by volume of water; and (2) mechanically stirring 52 parts by volume of DMSO solution at the heating temperature of 120 ℃ for 6h at 600rpm, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12h, thawing for 2h, soaking the thawed composite hydrogel in deionized water for 24h for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.60mol/L silver nitrate solution for 6h, and then soaking in 1.9mol/L sodium citrate for 4h to finally obtain a finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is alkali lignin obtained by alkali pulping in the paper industry.
Example 22
Taking 30 parts by mass of polyvinyl alcohol and 10 parts by mass of lignin, and adding 48 parts by volume of water; and (2) mechanically stirring 12 parts by volume of DMSO solution at the heating temperature of 120 ℃ for 4 hours at 500rpm, pouring the fully dissolved mixed solution into a mold, naturally cooling at room temperature, freezing for 12 hours, thawing for 2 hours, soaking the thawed composite hydrogel in deionized water for 24 hours for solvent exchange, then soaking the composite hydrogel after solvent exchange in 0.60mol/L silver nitrate solution for 5 hours, and then soaking in 1.7mol/L sodium borohydride for 3 hours to finally obtain a finished product of the lignin/polyvinyl alcohol/silver composite hydrogel. Wherein the selected lignin is a byproduct calcium lignosulfonate produced in sulfite pulping.
The products of the examples are prepared into sample strips meeting the GBT 1040.3-2006 standard, an MTS universal tester is adopted to test mechanical property data such as tensile strength, compressive strength, breaking tensile rate and the like, a dumbbell-shaped hydrogel sample strip is adopted in the tensile property test, and a cylindrical hydrogel sample is adopted in the compressive property test. The hydrogel conductivity σ was calculated according to the formula σ ═ d/(R · a), where the R value is the resistance of the hydrogel measured by a four-probe detector, a is the cross-sectional area of the hydrogel, and d is the distance between the two probes. The performance results of the lignin/polyvinyl alcohol/silver composite hydrogel are summarized in table 1.
The mechanical property test of the lignin/polyvinyl alcohol/silver composite hydrogel is carried out according to the GB/T1040.3-2006 standard, the thicknesses of 10 random positions among the middle sections of the composite hydrogel are measured by using an electronic digital display caliper, then the average value is taken, and then the tensile strength of the hydrogel is measured by using a universal tester at the tensile speed of 100 mm/min; compression performance test the compression performance of the hydrogel was tested at a compression speed of 50mm/min, 90% compressive strain.
TABLE 1 Properties of Lignin/polyvinyl alcohol/silver composite hydrogels
As can be seen from table 1, examples 1, 6, 18 and 21, to which 5 wt% of lignosulfonic acid, sodium lignosulfonate, calcium lignosulfonate and lignin were added, respectively, have significantly improved elongation at break and tensile strength and toughness, relative to the pure PVA blank control; the addition of lignin can obviously improve the tensile strength, the elongation at break and the absorption energy at break of the hydrogel; the results of the embodiment show that the hydrogel can be effectively reinforced and toughened by adding the lignin and sequentially soaking the silver nitrate solution and the sodium citrate solution; and the electrical conductivity of the hydrogel can be obviously improved by soaking the silver nitrate solution and the sodium citrate solution.
Since the raw materials and blending process used in other examples are similar to those of example 1, the performance of the hydrogels prepared in other examples are similar to the above results, and thus are not repeated.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.