CN111748106B - Chitosan gel material prepared from chitosan solution with pH value of 6-8 and preparation method thereof - Google Patents

Chitosan gel material prepared from chitosan solution with pH value of 6-8 and preparation method thereof Download PDF

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CN111748106B
CN111748106B CN201910248354.0A CN201910248354A CN111748106B CN 111748106 B CN111748106 B CN 111748106B CN 201910248354 A CN201910248354 A CN 201910248354A CN 111748106 B CN111748106 B CN 111748106B
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蔡杰
钟奕
张俐娜
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Wuhan University WHU
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Abstract

The invention provides a method for preparing a chitosan gel material by using a chitosan solution with a pH value of 6-8, which comprises the following steps: (1) preparing a dispersion liquid; (2) adding chitosan into the dispersion liquid, controlling the temperature to be between the freezing point and 35 ℃, introducing carbon dioxide into the solution, stirring the solution to dissolve the chitosan, and defoaming the solution to obtain a transparent chitosan solution with the pH value of 6-8; (3) heating or adding a chemical cross-linking agent into the chitosan solution to perform chemical reaction or directly immersing the chitosan solution into a coagulating bath to regenerate chitosan gel; (4) and drying the chitosan hydrogel and the organic gel to obtain the chitosan aerogel. The invention has the beneficial effects that: the provided dissolving method is carried out in an environment with the pH value of 6-8, so that the degradation of chitosan molecular chains can be effectively weakened, and the stability of the chitosan solution is high; the chitosan dissolution process is efficient, energy-saving, green and environment-friendly. The method for preparing the chitosan gel is easy to realize large-scale production and has no residue of strong acidic and strong alkaline substances.

Description

Chitosan gel material prepared from chitosan solution with pH value of 6-8 and preparation method thereof
Technical Field
The invention belongs to the field of natural polymer synthesis, and particularly relates to a chitosan gel material prepared by using a chitosan solution with a pH value of 6-8 and a preparation method thereof.
Background
The chitosan is a deacetylated product of chitin, and when the deacetylation degree of the chitin is more than 55%, the chitin is converted into chitosan which can be dissolved in an acidic aqueous solution. The chitosan has good biocompatibility and biodegradability, can promote wound healing, and has hemostatic effect. The chitosan solution obtained by dissolving the chitosan can be used for preparing new materials such as chitosan fiber, chitosan film, chitosan hydrogel, chitosan aerogel, chitosan microspheres and the like, and has good application prospect in the fields of separation and adsorption, biomedical materials, flexible electronic devices, heat insulation materials and the like.
Chitosan has a large number of hydrogen bonds both intra-and intermolecular, and is therefore difficult to dissolve in water and common organic solvents. The traditional method is to use low-concentration acetic acid or hydrochloric acid aqueous solution to dissolve chitosan, but chitosan is easy to degrade molecular chains of chitosan in acidic aqueous solution. Recently, some alkaline aqueous solvents have been developed to dissolve chitosan. The current alkaline aqueous solvents used to dissolve chitosan include lithium hydroxide-sodium hydroxide-urea combination (patent 201110099176.3), lithium hydroxide-potassium hydroxide-urea combination (patent 201310405191.5), sodium hydroxide-urea combination (Zhang W, Xia W.Disolution and stability of lithium hydroxide/urea aqueous solution [ J ]. Journal of Applied Polymer Science,2014,131(3): 1082. alpha. 1090.) and lithium hydroxide-urea combination (Li C, Han Q, Guan Y, et al. Michael reaction of chitosan with acrylic acid in aqueous solution of alkali-urea solution [ J ]. Polymer Bulletin,2015,72(8): 2087. alpha. 5.). The specific dissolving method is that firstly the chitosan is added into the alkaline hydrosolvents for soaking, then the mixture is frozen and frozen, finally the mixture is unfrozen and stirred at room temperature, and the chitosan is completely dissolved after one or more times of freezing-unfreezing. The freezing-thawing process consumes a large amount of energy, which is very disadvantageous for industrial applications, and thus, the efficiency of preparing the chitosan alkaline aqueous solution is to be improved.
The pH value of the pure water changes along with the temperature change, and the range of the pH value is 6-8. Besides acid and alkaline water solvents, the report about the water solvent dissolution of chitosan with the pH value of 6-8 is blank. Compared with a strong alkaline aqueous solvent and an acidic aqueous solvent, the chitosan is more stable in the aqueous solvent with the pH value of 6-8, and the degradation of chitosan molecular chains is not easy to occur. The chitosan is dissolved in a strong acid or strong alkaline environment, the problem of further degradation of the chitosan possibly exists in the process of processing or further processing the solution into hydrogel and aerogel, the performance of the gel is further influenced, meanwhile, the pH value of a reaction system is influenced to a certain extent, and certain limitation can be generated on the selection of other reagents.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for preparing a chitosan gel material based on a chitosan solution obtained by dissolving chitosan at a pH value of 6-8.
The method provided by the invention enables the chitosan to be dissolved in the environment with the pH value of 6-8, can effectively reduce the degradation of chitosan molecules, enables the formed chitosan solution to be more stable, further prepares the chitosan gel material, and fills the gap of preparing the chitosan gel material from the chitosan solution with the pH value of 6-8. On one hand, the chitosan hydrogel and the aerogel can be widely applied to the fields of wound dressings, skin care products, cosmetics, heat insulation materials, sound insulation materials and the like as substitutes of the traditional hydrogel; on the other hand, the chitosan material as a gel has potential application in the fields of catalysis, cell culture and the like as a carrier, and in addition, functional groups or materials can be introduced for modification in the process of preparing the chitosan membrane, so that the functionality is increased, and the application range is expanded.
The scheme provided by the invention is as follows:
in a first aspect, a hydrogel prepared by using a chitosan solution with a pH value of 6-8 and a preparation method thereof are provided.
The preparation method comprises the following steps:
(1) preparing a dispersion liquid;
(2) adding chitosan into the dispersion liquid, controlling the temperature to be between the freezing point and 35 ℃, introducing carbon dioxide into the solution, simultaneously stirring to dissolve the chitosan, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and defoaming to obtain a transparent chitosan solution with the pH value of 6-8;
(3) preparing the chitosan hydrogel: and (3) heating the chitosan aqueous solution obtained in the step (2) to form gel, or adding a chemical cross-linking agent to perform chemical cross-linking reaction to form gel, or immersing the gel in a coagulating bath to perform physical cross-linking to obtain the chitosan gel.
Specifically, the dispersion is one or a mixture of two of a urea aqueous solution and a thiourea aqueous solution.
Further, the concentration of the urea aqueous solution is 6-60 wt%. Preferably, the concentration of the urea aqueous solution is 18 to 60 wt%.
Further, the concentration of the thiourea aqueous solution is 3-14 wt%. Specifically, the concentration of the thiourea aqueous solution is 7-14 wt%.
Specifically, the mass ratio of the chitosan to the dispersion liquid in the step (2) is 1: 7-1: 1000. Preferably, the mass ratio of the chitosan to the dispersion liquid is 1: 7-1: 100.
Specifically, the heating temperature for preparing the gel by heating is 40-130 ℃; the coagulant is one or more of alcohols, salts, amides, dimethyl sulfoxide, ethyl acetate and acetone. Preferably, the salt is selected from ammonium salt, sodium salt, potassium salt, magnesium salt, calcium salt and aluminum salt, and the concentration of the salt solution is 5-40 wt%. Preferably, the alcohol is selected from methanol and ethanol, and the concentration of the alcohol is 10-100 wt%. The chemical cross-linking agent is a common cross-linking agent which is equivalent to the chitosan monomer with the molar ratio of 0.1-10, and comprises aldehyde cross-linking agents, glycidyl ether cross-linking agents, epoxy compounds, iridoids and polyphenols, preferably glutaraldehyde, epoxy chloropropane, genipin and procyanidine.
In a second aspect, an organic chitosan gel material and a preparation method thereof are provided.
The preparation method comprises the following steps: and (3) replacing the organic solvent with the prepared chitosan hydrogel to obtain the organogel.
Wherein the organic solvent used for replacing the chitosan hydrogel is low-boiling point and volatile alkanes, halogenated hydrocarbons, alcohols, phenols, ethers and acetals, ketones, acids and anhydrides, esters, nitrogen-containing organic compounds, sulfur-containing organic compounds, or a mixture of the above liquids.
In a third aspect, chitosan aerogels and methods of making the same are provided.
The preparation method comprises the following steps: drying the chitosan hydrogel or the organic gel prepared by the method to remove liquid to obtain the chitosan aerogel. The drying step is to remove the liquid medium by supercritical drying, normal pressure drying or freeze drying.
In a fourth aspect, a method for preparing a hydrophobic chitosan aerogel is provided.
The preparation method comprises the following steps: and (3) carrying out hydrophobic modification on the prepared aerogel to obtain the hydrophobic chitosan aerogel.
Specifically, the method of the hydrophobic modification is by chemical vapor deposition or chemical grafting or physical coating. Depositing or grafting or coating a hydrophobic compound with lower surface chemical energy on the surface of the chitosan rich in hydroxyl and amino.
Further, the compounds having a low surface chemical energy include inorganic oxides, silanes, long-chain alkane acid chlorides, and fluorides.
In a fifth aspect, a method of preparing a carbon aerogel is provided.
The preparation method comprises the following steps: and under the protection of inert atmosphere, carrying out heat treatment on the prepared aerogel at the temperature of more than 150 ℃ to obtain the carbon aerogel.
In a sixth aspect, a method for preparing a functional chitosan gel material is provided.
The preparation method comprises the following steps: functional organic or inorganic additives and low-dimensional nano materials are introduced into the prepared chitosan hydrogel or aerogel, or natural macromolecules or synthetic macromolecules are introduced and blended to prepare the hydrogel or aerogel material.
Specifically, the functional organic or inorganic additive is one or more selected from a plasticizer, a reinforcing agent, a refractory additive, a dye, an optical stabilizer, an antibacterial bacteriostatic agent, a conductive material and a surfactant.
Specifically, the low-dimensional nanomaterial is selected from graphene and derivatives thereof, carbon nanotubes and derivatives thereof, metal or metal oxide nanoparticles, organic framework compounds, and layered nanomaterials. The natural polymer or synthetic polymer is selected from polymer nanofiber, cellulose and its derivatives, animal protein, vegetable protein, collagen, alginate, conductive polymer, polyvinyl alcohol or polyethylene glycol.
The invention has the beneficial effects that:
(1) the dissolving method provided by the invention is carried out in an environment with a pH value of 6-8, so that the degradation of chitosan molecules can be effectively reduced, and the stability of chitosan in the dissolving process is high;
(2) the chitosan dissolution process is efficient, energy-saving, green and environment-friendly, is beneficial to improving the production efficiency and reducing the production cost, and can be used for large-scale production;
(3) the pH value of the prepared chitosan solution is 6-8, the stability of the raw material as a gel material is high, the environment of a reaction system is not influenced, and the selection of other raw materials is more free and flexible;
(4) compared with the chitosan gel prepared by the traditional acid dissolving method, the gel prepared by the method provided by the invention has better toughness (the compression fracture strain is more than 80%) and higher strength, and has wide application prospect as a biomedical gel material.
Detailed Description
The invention will be further illustrated with reference to specific examples, to which the present invention is not at all restricted.
The chitosan used in the following examples is extracted from natural organisms such as shrimp shell, crab shell, squid parietal bone, diatom, insects and the like containing chitin, and the specific extraction steps are soaking with alkali liquor to remove protein, soaking with acid liquor to remove inorganic salt, decoloring with oxidant, washing with water and drying to obtain purified chitin. The chitosan is prepared by deacetylation reaction of chitin in sodium hydroxide or potassium hydroxide aqueous solution.
Example 1
Soaking shrimp shell in alkali solution to remove protein, soaking in acid solution to remove inorganic salt, and decolorizing with hydrogen peroxide water solution to obtain purified chitin. Heating chitin in 50 wt% sodium hydroxide water solution for 1h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 70%.
An aqueous urea solution having a concentration of 6 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:7, introducing carbon dioxide into the mixture at 35 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, obtaining a transparent chitosan solution after centrifugal deaeration, and enabling part of chitosan insoluble substances to be arranged at the bottom of a centrifugal tube. The chitosan gel was prepared using the chitosan solution after removing insoluble matter.
Pouring the chitosan stock solution into a pore plate mold with the diameter of 10mm and the height of 10mm, heating at 40 ℃ to form chitosan gel, washing with deionized water to obtain chitosan hydrogel, and measuring the compressive fracture strain to be 85% and the fracture stress to be 3.2MPa by using a universal tester.
Example 2
Soaking crab shell with alkali solution to remove protein, soaking with acid solution to remove inorganic salt, and decolorizing with hydrogen peroxide solution to obtain purified chitin. Heating chitin in 55 wt% potassium hydroxide water solution for 2h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 60%.
An aqueous urea solution having a concentration of 18 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:1000, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube. The chitosan gel was prepared using the chitosan solution after removing insoluble matter.
Pouring the chitosan stock solution into a pore plate mold with the diameter of 10mm and the height of 10mm, heating at 130 ℃ to form chitosan gel, washing with deionized water to obtain chitosan hydrogel, and measuring the compressive fracture strain by using a universal tester to be 82% and the fracture stress to be 0.8 MPa.
Example 3
Soaking squid bones in alkali liquor to remove proteins, and soaking in acid liquor to remove inorganic salts to obtain purified chitin. Heating chitin in 58 wt% potassium hydroxide water solution for 2h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 60%.
An aqueous urea solution having a concentration of 60wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:100, introducing carbon dioxide into the mixture at 0 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifuge tube. The chitosan solution was used to prepare chitosan gel.
Adding epichlorohydrin which is 10 times of the molar ratio of the chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mould with the diameter of 10mm and the height of 10mm, soaking in a potassium chloride aqueous solution with the salt concentration of 20 wt%, taking out the chitosan gel after soaking for 6h, washing with deionized water to obtain the chitosan hydrogel, and measuring the compression fracture strain to be 84% and the fracture stress to be 3.4MPa by using a universal tester.
Example 4
Soaking shrimp shell in alkali solution to remove protein, soaking in acid solution to remove inorganic salt, and decolorizing with hydrogen peroxide water solution to obtain purified chitin. Heating chitin in 50 wt% sodium hydroxide water solution for 2h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 70%.
An aqueous solution of thiourea having a concentration of 3% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:7, introducing carbon dioxide into the mixture at 35 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifuge tube. The chitosan solution was used to prepare chitosan gel.
Adding epoxy chloropropane with the molar ratio of 0.1 time of that of the chitosan monomer, stirring, centrifugally defoaming, pouring into a pore plate mold with the diameter of 10mm and the height of 10mm, soaking in a sodium sulfate aqueous solution with the salt concentration of 5wt%, taking out the chitosan gel after soaking for 6h, washing with deionized water to obtain the chitosan hydrogel, and measuring the compressive fracture strain to be 85% and the fracture stress to be 3.7MPa by using a universal tester.
Example 5
Soaking crab shell with alkali solution to remove protein, soaking with acid solution to remove inorganic salt, and decolorizing with hydrogen peroxide water solution to obtain purified chitin. Heating chitin in 45 wt% sodium hydroxide water solution for 2h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 60%.
An aqueous solution of thiourea having a concentration of 7% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:1000, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube. The chitosan gel was prepared using the chitosan solution after removing insoluble matter.
Adding glutaraldehyde with the molar ratio of 10 times of that of the chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mold with the diameter of 10mm and the height of 10mm, soaking in an ammonium sulfate aqueous solution with the salt concentration of 30 wt%, taking out the chitosan gel after soaking for 6h, washing with deionized water to obtain the chitosan hydrogel, and measuring the compression fracture strain to be 81% and the fracture stress to be 0.9MPa by using a universal testing machine.
Example 6
Soaking the top bone of the squid in alkali liquor to remove protein, and soaking in acid liquor to remove inorganic salt to obtain purified chitin. Heating chitin in 45 wt% sodium hydroxide water solution for 2h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 70%.
An aqueous thiourea solution having a concentration of 14% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:100, introducing carbon dioxide into the mixture at 0 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifuge tube. The chitosan solution was used to prepare chitosan gel.
Adding genipin with a molar ratio 10 times that of a chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mold with a diameter of 10mm and a height of 10mm, soaking in a magnesium chloride aqueous solution with a salt concentration of 40wt%, taking out the chitosan gel after soaking for 6h, washing with deionized water to obtain chitosan hydrogel, and measuring the compression fracture strain to be 85% and the fracture stress to be 4.9MPa by using a universal tester.
Example 7
An aqueous solution of 10wt% urea to 7 wt% thiourea was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:100, introducing carbon dioxide into the mixture at 35 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifuge tube. The chitosan solution was used to prepare chitosan gel.
Adding procyanidin with a molar ratio 10 times that of chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mold with a diameter of 10mm and a height of 10mm, soaking in 10wt% calcium chloride aqueous solution, soaking for 6h, taking out chitosan gel, washing with deionized water to obtain chitosan hydrogel, and measuring the compressive fracture strain of 85% and the fracture stress of 5.2MPa by using a universal tester.
Example 8
An aqueous urea solution having a concentration of 25 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:10, introducing carbon dioxide into the mixture at 25 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Pouring the chitosan stock solution into a pore plate die with the diameter of 10mm and the height of 10mm, heating at 60 ℃ to form chitosan gel, washing with deionized water to obtain chitosan hydrogel, and measuring the compressive fracture strain to be 85% and the fracture stress to be 3.3MPa by using a universal tester.
Example 9
An aqueous urea solution having a concentration of 30 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:10, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding procyanidin with a molar ratio of 0.1 time of that of chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mold with a diameter of 10mm and a height of 10mm, soaking in a potassium chloride aqueous solution with a salt concentration of 10wt%, taking out chitosan gel after soaking for 6h, washing with deionized water to obtain chitosan hydrogel, and measuring a compressive fracture strain of 85% and a fracture stress of 4.2MPa by using a universal tester.
Example 10
An aqueous 12 wt% thiourea solution was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:10, introducing carbon dioxide into the mixture at 10 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding genipin with a molar ratio of 0.1 time of that of a chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mold with a diameter of 10mm and a height of 10mm, soaking in a calcium chloride aqueous solution with a salt concentration of 10wt%, soaking for 6h, taking out the chitosan gel, washing with deionized water to obtain a chitosan hydrogel, and measuring the compressive fracture strain to be 82% and the fracture stress to be 5.0MPa by using a universal tester.
Example 11
An aqueous 12 wt% thiourea solution was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 10 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding glutaraldehyde with the molar ratio of 0.1 time of that of the chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mold with the diameter of 10mm and the height of 10mm, soaking in an ethanol aqueous solution with the ethanol concentration of 10wt%, taking out the chitosan gel after soaking for 6h, washing with deionized water to obtain chitosan hydrogel, and measuring the compression fracture strain to be 85% and the fracture stress to be 5.4MPa by using a universal tester.
Example 12
An aqueous urea solution having a concentration of 25 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 5 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding procyanidin with a molar ratio of 1.0 time of chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mold with a diameter of 10mm and a height of 10mm, soaking in a magnesium chloride aqueous solution with a salt concentration of 40wt%, soaking for 6h, taking out chitosan gel, washing with deionized water to obtain chitosan hydrogel, and measuring a compressive fracture strain of 83% and a fracture stress of 5.1MPa by using a universal tester.
Example 13
An aqueous urea solution having a concentration of 30 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 2 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding genipin with a molar ratio 1.0 time that of a chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mold with a diameter of 10mm and a height of 10mm, soaking in an aluminum chloride aqueous solution with a salt concentration of 40wt%, soaking for 6h, taking out the chitosan gel, washing with deionized water to obtain a chitosan hydrogel, and measuring a compressive fracture strain of 83% and a fracture stress of 5.4MPa by using a universal testing machine.
Example 14
An aqueous urea solution having a concentration of 27 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 35 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding glutaraldehyde with the molar ratio of 1.0 time of that of the chitosan monomer, stirring, centrifuging, defoaming, pouring into a pore plate mold with the diameter of 10mm and the height of 10mm, soaking in an ethanol solution with the ethanol concentration of 100wt%, taking out the chitosan gel after soaking for 6h, washing with deionized water to obtain chitosan hydrogel, and measuring the compression fracture strain to be 89% and the fracture stress to be 5.8MPa by using a universal tester.
Example 15
An aqueous urea solution having a concentration of 24 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding epoxy chloropropane with the molar ratio of 1.0 time of that of the chitosan monomer, stirring, centrifugally defoaming, pouring into a pore plate mould with the diameter of 10mm and the height of 10mm, soaking in an ethanol aqueous solution with the ethanol concentration of 50 wt%, taking out the chitosan gel after soaking for 6h, washing with deionized water to obtain the chitosan hydrogel, and measuring the compression fracture strain to be 90% and the fracture stress to be 6.8MPa by using a universal tester.
Example 16
An aqueous urea solution having a concentration of 16 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding epoxy chloropropane with the molar ratio of 1.0 time of that of the chitosan monomer, stirring, centrifugally defoaming, pouring into a pore plate mold with the diameter of 10mm and the height of 10mm, soaking in a methanol aqueous solution with the methanol concentration of 50 wt%, taking out the chitosan gel after soaking for 6h, washing with deionized water to obtain the chitosan hydrogel, and measuring the compression fracture strain to be 90% and the fracture stress to be 6.7MPa by using a universal tester.
Example 17
An aqueous urea solution having a concentration of 18 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Pouring the chitosan stock solution into a pore plate die with the diameter of 10mm and the height of 10mm, heating at 60 ℃ to form chitosan gel, soaking in a methanol aqueous solution with the methanol concentration of 100wt% for 6h, washing with deionized water to obtain the chitosan hydrogel, and measuring the compressive fracture strain to be 85% and the fracture stress to be 3.6MPa by using a universal tester.
Example 18
An aqueous 10wt% thiourea solution was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Pouring the chitosan stock solution into a pore plate die with the diameter of 10mm and the height of 10mm, heating at 60 ℃ to form chitosan gel, soaking in a sulfuric acid aqueous solution with the acid concentration of 20 wt% for 1min, washing with deionized water to obtain chitosan hydrogel, and measuring the compressive fracture strain to be 85% and the fracture stress to be 3.2MPa by using a universal tester.
Example 19
An aqueous 12 wt% thiourea solution was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Pouring the chitosan stock solution into a pore plate die with the diameter of 10mm and the height of 10mm, heating at 60 ℃ to form chitosan gel, soaking in a sulfuric acid aqueous solution with the acid concentration of 5wt% for 2min, washing with deionized water to obtain chitosan hydrogel, and measuring the compressive fracture strain to be 85% and the fracture stress to be 3.1MPa by using a universal tester.
Example 20
An aqueous 12 wt% thiourea solution was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Pouring the chitosan stock solution into a pore plate die with the diameter of 10mm and the height of 10mm, heating at 80 ℃ to form chitosan gel, soaking in 5-20 wt% potassium sulfate-ethanol aqueous solution for 10min, washing with deionized water to obtain chitosan hydrogel, and measuring the compressive fracture strain to be 85% and the fracture stress to be 4.2MPa by using a universal tester.
Example 21
An aqueous thiourea solution having a concentration of 14% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Pouring the chitosan stock solution into a pore plate die with the diameter of 10mm and the height of 10mm, heating at 80 ℃ to form chitosan gel, soaking in a magnesium chloride-ethanol aqueous solution with the concentration of 5-20 wt% for 30min, washing with deionized water to obtain the chitosan hydrogel, and measuring the compressive fracture strain to be 85% and the fracture stress to be 4.1MPa by using a universal tester.
Example 22
The chitosan hydrogel prepared in example 1 was placed in ethylene glycol for displacement to obtain an ethylene glycol-containing chitosan organogel which did not freeze at-5 ℃ and still had elasticity, and the compressive strain at break was 80% and the stress at break was 7.3MPa as measured by a universal tester.
Example 23
The chitosan hydrogel prepared in example 3 was placed in an ethylene glycol aqueous solution with a mass fraction of 95 wt% for replacement to obtain an ethylene glycol-containing chitosan organogel which did not freeze at-5 ℃ and still had elasticity, and the compressive strain at break was 85% and the stress at break was 5.6MPa as measured by a universal tester.
Example 24
The chitosan hydrogel prepared in example 7 was placed in an ethylene glycol aqueous solution with a mass fraction of 90 wt% for replacement to obtain an ethylene glycol-containing chitosan organogel, which did not freeze at-5 ℃ and still had elasticity, and the compressive strain at break was 89% and the stress at break was 6.2MPa as measured by a universal tester.
Example 25
The chitosan hydrogel prepared in example 5 was placed in ethanol for displacement to obtain a chitosan ethanol gel, and the gel was dried by carbon dioxide critical point to prepare a chitosan aerogel. The specific surface area of the aerogel is measured by nitrogen adsorption, and the BET specific surface area of the aerogel is 360m2(g), the aerogel compression strain of 80% measured by the universal tester of the compressive stress of 60MPa, and no fracture.
Example 26
The chitosan hydrogel prepared in example 10 was placed in ethanol for displacement to obtain a chitosan ethanol gel, and the gel was dried by carbon dioxide critical point to prepare a chitosan aerogel. The specific surface area of the aerogel is measured by nitrogen adsorption, and the BET specific surface area of the aerogel is 400m2(g), the aerogel compression strain of 80% measured by the universal tester of the compressive stress of 80MPa, and no fracture.
Example 27
The chitosan hydrogel prepared in example 15 was placed in tert-butanol for substitution to obtain chitosan tert-butanol gel, which was dried at-50 ℃ by a freeze dryer to prepare chitosan aerogel. The specific surface area of the aerogel is measured by nitrogen adsorption, and the BET specific surface area of the aerogel is 430m2(g), the aerogel compression strain of 80% measured by the universal tester of the compressive stress of 75MPa, and no fracture.
Example 28
The chitosan hydrogel prepared in example 20 was dried at-50 ℃ by a freeze dryer to prepare a chitosan aerogel. Placing the chitosan aerogel in a dryer in different humidity environments, adding 1mL of trichlorosilane and 1mL of water, placing at 50 ℃ for 12 hours for Chemical Vapor Deposition (CVD), and then vacuum-drying the chitosan aerogel grafted with polysiloxane compounds by the CVD method at 50 ℃ for 1 hour. Obtaining the hydrophobic chitosan aerogel.
Example 29
The chitosan hydrogel prepared in example 15 was placed in ethanol for substitution to obtain a chitosan ethanol gel. The ethanol gel is placed in a toluene solution, and then picoline (catalyst) and silanes (in an equimolar ratio to the chitosan monomer) are added into the toluene solution to react for 3 hours. And after full reaction, finally obtaining hydrophobic chitosan organogel, washing with ethanol, replacing with a tert-butyl alcohol solvent, and finally drying the chitosan tert-butyl alcohol gel at-50 ℃ by a freeze dryer to prepare the hydrophobic chitosan aerogel.
Example 30
The chitosan hydrogel prepared in example 20 was placed in ethanol for displacement to obtain a chitosan ethanol gel, and the gel was dried by carbon dioxide critical point to prepare a chitosan aerogel. And heating the obtained chitosan aerogel to 1000 ℃ from room temperature at a speed of 10 ℃/min, and taking nitrogen as protective gas to obtain the nitrogen-doped porous carbon aerogel. The specific surface area of the carbon aerogel obtained by the nitrogen adsorption-desorption experiment is 1110m2/g。
Example 31
The chitosan hydrogel prepared in example 16 was placed in ethanol for substitution to obtain a chitosan ethanol gel, and the gel was dried by carbon dioxide critical point to prepare a chitosan aerogel. And heating the obtained chitosan aerogel to 800 ℃ from room temperature at a speed of 10 ℃/min, and taking nitrogen as protective gas to obtain the nitrogen-doped porous carbon aerogel. The specific surface area of the carbon aerogel obtained by the nitrogen adsorption-desorption experiment is 900m2/g。
Example 32
Heating chitin in 50 wt% sodium hydroxide water solution for 1 hr for deacetylation reaction to obtain chitosan with deacetylation degree of about 70%. Preparing 97g of urea aqueous solution with the concentration of 25 wt% in advance as dispersion liquid, adding 0.1g of graphene oxide, performing ultrasonic dispersion, adding 3g of chitosan, stirring at 10 ℃ and introducing carbon dioxide, stopping introducing the carbon dioxide and stirring after the chitosan is completely dissolved, and performing centrifugal deaeration to obtain a transparent chitosan/graphene oxide solution. Pouring the chitosan/graphene oxide solution stock solution into a pore plate mold with the diameter of 10mm and the height of 10mm, soaking the pore plate mold in an ethanol water solution with the water content of 90 wt%, taking out the chitosan/graphene oxide gel after soaking for 12h, washing the chitosan/graphene oxide gel with deionized water to obtain the chitosan/graphene oxide composite hydrogel, and measuring the compression fracture strain to be 85% and the fracture stress to be 6.2MPa by using a universal testing machine.
Example 33
Heating chitin in 50 wt% sodium hydroxide water solution for 1 hr for deacetylation reaction to obtain chitosan with deacetylation degree of about 70%. 97g of thiourea aqueous solution with the concentration of 9 wt% was prepared in advance as a dispersion, 3g of chitosan was added, stirring was carried out at 10 ℃ and carbon dioxide was introduced until the chitosan was dissolved, and a transparent chitosan solution was obtained after centrifugal deaeration. Adding 0.1g of modified carbon nano tube into 100g of chitosan solution, stirring and dispersing, pouring the chitosan/modified carbon nano tube stock solution into a pore plate die with the diameter of 10mm and the height of 10mm, soaking in an ethanol aqueous solution with the water content of 90 wt%, soaking for 12h, taking out the chitosan/modified carbon nano tube gel, washing with deionized water to obtain the chitosan/modified carbon nano tube hydrogel, and measuring the compression fracture strain to be 89% and the fracture stress to be 6.6MPa by using a universal tester.
Example 34
Heating chitin in 50 wt% sodium hydroxide water solution for 1 hr for deacetylation reaction to obtain chitosan with deacetylation degree of about 70%. 97g of urea aqueous solution with the concentration of 18 wt% is prepared in advance as dispersion, 3g of chitosan is added, stirring is carried out at the temperature of 10 ℃, carbon dioxide is introduced until the chitosan is dissolved, and transparent chitosan solution is obtained after centrifugal deaeration. Adding 0.8g of glass fiber into 100g of chitosan solution, stirring and dispersing, pouring the chitosan/glass fiber stock solution into a pore plate die with the diameter of 10mm and the height of 10mm, soaking in an ethanol water solution with the water content of 90 wt%, taking out the chitosan/glass fiber gel after soaking for 12h, washing with deionized water to obtain the chitosan/glass fiber hydrogel, and measuring the compression fracture strain to be 85% and the fracture stress to be 6.7MPa by using a universal tester.
Example 35
Heating chitin in 50 wt% sodium hydroxide water solution for 1 hr for deacetylation reaction to obtain chitosan with deacetylation degree of about 70%. 97g of a urea aqueous solution with the concentration of 6 wt% to 7 wt% was prepared in advance as a dispersion, 3g of chitosan was added, stirring was performed at 10 ℃ and carbon dioxide was introduced until the chitosan was dissolved, and a transparent chitosan solution was obtained after centrifugal deaeration. Adding 1g of sodium carboxymethylcellulose into 100g of chitosan solution, stirring and dispersing, pouring the chitosan/sodium carboxymethylcellulose stock solution into a pore plate die with the diameter of 10mm and the height of 10mm, soaking in an ethanol water solution with the water content of 90 wt%, soaking for 12h, taking out the chitosan/sodium carboxymethylcellulose gel, washing with deionized water to obtain the chitosan/sodium carboxymethylcellulose hydrogel, and measuring the compression fracture strain of 89% and the fracture stress of 6.7MPa by using a universal tester.
Example 36
Heating chitin in 50 wt% sodium hydroxide water solution for 1 hr for deacetylation reaction to obtain chitosan with deacetylation degree of about 70%. 97g of urea aqueous solution with the concentration of 24 wt% is prepared in advance as dispersion, 3g of chitosan is added, stirring is carried out at the temperature of 10 ℃, carbon dioxide is introduced until the chitosan is completely dissolved, and a transparent chitosan solution is obtained after centrifugal deaeration. Pouring the chitosan/sodium carboxymethylcellulose stock solution into a pore plate mold with the diameter of 10mm and the height of 10mm, soaking in an ethanol aqueous solution with the water content of 90 wt%, taking out the chitosan gel after soaking for 12h, washing with deionized water, soaking the chitosan hydrogel in an aqueous solution with the concentration of 0.04 mol/kg-1Soaking in silver nitrate water solution for 24 hr, taking out, performing hydrothermal reaction at 125 deg.C in a hydrothermal reaction kettle, and reducing silver ions to silver nanoAnd (4) rice grains to obtain the silver nanoparticle composite chitosan hydrogel.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention.

Claims (13)

1. A method for preparing a chitosan gel material by using a chitosan solution with a pH value of 6-8 is characterized by comprising the following steps:
(1) preparing a dispersion liquid;
the dispersion is one or a mixture of two of a urea aqueous solution and a thiourea aqueous solution; the concentration of the urea aqueous solution is 6-60 wt%; the concentration of the thiourea aqueous solution is 3-14 wt%;
(2) adding chitosan into the dispersion liquid, controlling the temperature to be between the freezing point and 35 ℃, introducing carbon dioxide into the solution, simultaneously stirring to dissolve the chitosan, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and defoaming to obtain a transparent chitosan solution with the pH value of 6-8; the mass ratio of the chitosan to the dispersion liquid is 1: 7-1: 1000;
(3) preparing the chitosan hydrogel: preparing hydrogel from the chitosan solution obtained in the step (2) by heating, chemically crosslinking or immersing in a coagulating bath; the coagulant used in the coagulation bath is one or more of alcohols, salts, amides, dimethyl sulfoxide, ethyl acetate and acetone.
2. The method of claim 1, wherein: the concentration of the urea aqueous solution is 18-60 wt%; the concentration of the thiourea aqueous solution is 7-14 wt%.
3. The method of claim 1, wherein: the heating temperature for heating and preparing the gel in the step (3) is 40-130 ℃; the chemical cross-linking agent is one or more of aldehyde cross-linking agents, glycidyl ether cross-linking agents, epoxy compounds, iridoid and polyphenol.
4. The method of claim 1, wherein: the alcohol is selected from methanol and ethanol, and the concentration of the alcohol is 10-100 wt%; the salt is selected from ammonium salt, sodium salt, potassium salt, magnesium salt, calcium salt and aluminum salt, and the concentration of the salt solution is 5-40 wt%.
5. A method for preparing a chitosan organogel, comprising the method for preparing a chitosan gel material according to claim 1, and further placing the chitosan hydrogel prepared according to claim 1 in an organic solvent for replacement to obtain a chitosan organogel; wherein the organic solvent used for replacing the chitosan hydrogel is low-boiling point and volatile alkanes, halogenated hydrocarbons, alcohols, phenols, ethers and acetals, ketones, acids and anhydrides, esters, nitrogen-containing organic compounds, sulfur-containing organic compounds or a mixture of the former.
6. A method for preparing chitosan aerogel, which comprises the method for preparing chitosan gel material of claim 1 or the method for preparing chitosan organogel of claim 5, and further drying the chitosan hydrogel prepared in claim 1 or the organogel prepared in claim 5 to remove liquid, thereby obtaining chitosan aerogel; the drying method comprises supercritical drying, normal pressure drying or freeze drying.
7. A method for preparing hydrophobic chitosan aerogel, which comprises the method for preparing chitosan organogel of claim 5, and further performing hydrophobic modification on the chitosan organogel prepared in claim 5 to obtain hydrophobic chitosan aerogel.
8. The preparation method of claim 7, wherein the hydrophobic modification method is to deposit or graft or coat a hydrophobic compound with lower surface chemical energy on the surface of the chitosan rich in hydroxyl and amino groups by chemical vapor deposition or chemical grafting or physical coating.
9. The method of claim 8, wherein the compound having a low surface chemical energy comprises inorganic oxides, silanes, long-chain alkane acid chlorides, and fluorides.
10. A preparation method of carbon aerogel, which is characterized by comprising the preparation method of the chitosan aerogel in claim 6, and further carrying out heat treatment on the chitosan aerogel prepared in claim 6 at the temperature of more than 150 ℃ under the protection of inert atmosphere to obtain the carbon aerogel.
11. A preparation method of a functional chitosan hydrogel or aerogel material is characterized by comprising the following steps: the method for preparing the chitosan hydrogel or the aerogel of claim 6 comprises the steps of adding functional organic or inorganic additives and low-dimensional nano materials in the preparation process, or introducing natural macromolecules or synthetic macromolecules to blend to prepare the hydrogel or the aerogel materials.
12. The method of claim 11, wherein: the functional organic or inorganic additive is selected from one or more of a plasticizer, a reinforcing agent, a refractory material additive, a dye, an optical stabilizer, an antibacterial bacteriostatic agent, a conductive material and a surfactant; the low-dimensional nano material is selected from graphene and derivatives thereof, carbon nanotubes and derivatives thereof, metal or metal oxide nanoparticles, organic framework compounds or layered nano materials.
13. The method of claim 11, wherein: the natural polymer and the synthetic polymer are selected from polymer nanofiber, animal protein, vegetable protein, alginate, cellulose and derivatives thereof, conductive polymer, polyvinyl alcohol or polyethylene glycol.
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