CN103923428A - Starch-based porous hydrogel and preparation method thereof - Google Patents

Abstract

The invention discloses a starch-based porous hydrogel prepared from a starch liquid, an initiating agent, a monomer and a cross-linking agent. The preparation method comprises the following steps: adding the initiating agent, the monomer and cross-linking agent into the starch liquid; after each component is added, mixing uniformly, and heating for full reaction, thereby obtaining a starch-based hydrogel; and washing and swelling the obtained starch-based hydrogel, immerging the washed and swelled starch-based hydrogel into an organic solvent-water mixed solution with specific components so as to perform gradient solvent exchange, and drying, thereby obtaining the starch-based porous hydrogel. The starch-based porous hydrogel has the characteristics of simple and convenient preparation method, good open pore property, controllable porous structure and stable three-dimensional structure.

Description

A kind of starch-based porous hydrogel and preparation method thereof

technical field

The invention relates to the technical field of polymer materials, in particular to a starch-based porous hydrogel and a preparation method thereof.

Background technique

Hydrogel is a kind of hydrophilic and water-insoluble polymer, which can rapidly swell to swelling equilibrium in water, and its three-dimensional structure and shape remain unchanged. It has been widely used in the fields of food processing, medicine, and materials. application. Compared with traditional hydrogels, porous hydrogels have a large number of pore structures inside, with larger spaces and larger internal surface areas, so they have better swelling properties, faster swelling kinetics, and more external contact. Features of quick response.

Starch is a renewable natural resource with abundant sources, low price, renewable resources, low toxicity, biocompatibility and biodegradability. However, starch itself has disadvantages such as strong crystallinity, difficulty in processing and forming, etc. Therefore, starch is usually modified physically or chemically to improve the structure and performance of starch and broaden the application fields of starch. In recent years, starch and other natural polymers, as renewable and sustainable green materials, have been more widely and deeply researched and applied in the fields of chemical industry, medicine, and environment.

At present, the commonly used methods for preparing porous hydrogels are: foaming method, porogen method, phase separation method, freeze-drying method, and solvent exchange method. The foaming method utilizes the gas generated by the foaming agent reaction or the volatilization of the organic solvent gas to form cells inside the material. For example, CN103044703A uses air as the foaming agent to prepare porous foam colloid, which is used as a component of wound dressings. CN102492093A, CN1264321 A, CN1757662 A, CN1488331 A, CN1763123A, CN1768920A, CN102633956 B, etc. use carbonate or bicarbonate as a blowing agent, react under acidic conditions to generate gaseous carbon dioxide, and form a porous structure after volatilization. CN102702559A uses microorganisms—dried yeast as a foaming agent, and generates gas through its fermentation to form a porous hydrogel. CN102167763A A low-boiling-point solvent is used as a foaming agent to prepare a porous hydrogel by low-temperature photopolymerization. CN101588790A, CN1527860A etc. utilize the gas generated during the polymerization reaction as a foaming agent to leave holes in the hydrogel matrix. CN1763124A and CN102406595A adopt the microcapsule prepared by the sharp-hole coagulation bath method as a foaming agent to generate a cell structure in the hydrogel. The porogenic method is to dope the porogen into the polymer body and place the polymer in water. If the porogen dissolves in water but the polymer does not dissolve, holes will be left inside the polymer, such as the preparation of polyacrylamide/potassium acrylate interpenetrating network porous hydrogel with ethanol as porogen (Materials Report, 2011, 25 (10), 28-31). The phase separation method utilizes that the polymer is insoluble in the solvent, and the polymer phase and the solvent phase are separated, and then during the drying process, the solvent volatilizes, leaving holes in the polymer matrix, such as Zhang et al. with sucrose solution and 1,4 PNIPA porous hydrogel was prepared with dioxane mixture as solvent (Macromolecular Chemistry and Physics, 2004, 205 (1), 107-113.). The freeze-drying method is to volatilize the solvent in the polymer under low-temperature vacuum conditions, thereby leaving holes in the polymer. For example, CN103094596A utilizes the freeze-drying method to prepare porous hydrogel as a carrier of the proton membrane.

In these methods of preparing porous hydrogels, there are usually some problems: such as the gas volatilization rate is fast, the degree of reaction and the pore structure are often difficult to control; when the solvent volatilizes or phase separation forms pores, the three-dimensional structure of the hydrogel usually changes. When the porous hydrogel is destroyed, the structure, size and shape of the pores are difficult to control, the porosity is poor, and the three-dimensional size of the porous hydrogel usually changes drastically before and after swelling. When the structure is used, the application will be limited. The solvent exchange method uses an organic solvent to exchange and replace the swollen water in the hydrogel, and then volatilizes the organic solvent to obtain a porous structure. This method can be processed at room temperature, the conditions are mild, and the method is simple, but when water molecules are exchanged by organic solvents, due to the action of hydrogen bonds between water molecules and the action of polar bonds in the hydrogel structure, the pore structure will seriously occur. shrinkage or collapse.

Contents of the invention

In order to overcome the deficiencies in the above-mentioned prior art, the present invention provides a gradient solvent exchange method. Using a specific composition of organic solvent-water mixed solution, will not destroy the original pore structure, can maintain the three-dimensional structure of the hydrogel, and is easy to operate, good porosity, three-dimensional structure stable starch-based porous hydrogel and its Preparation.

The purpose of the present invention is achieved like this:

A starch-based porous hydrogel includes starch solution, initiator, monomer and cross-linking agent.

The preparation method of the starch-based porous hydrogel is as follows: adding an initiator, a monomer and a crosslinking agent into the starch solution, and mixing evenly after each component is added, heating to make it fully react, and then obtaining Starch-based hydrogel: after the obtained starch-based hydrogel is washed and swollen, immersed in an organic solvent-water mixed solution for gradient solvent exchange, and dried, the starch-based porous hydrogel can be obtained.

The starch in the starch solution is soluble starch, cornstarch, carboxymethyl starch, hydroxyethyl starch; the starch solution is: the aqueous solution of starch or the dimethyl sulfoxide solution of starch; the initiator is: Potassium persulfate, ammonium persulfate, azobisisobutyronitrile; the monomer is: at least one of acrylamide, acrylic acid, acrylate and methacrylic acid; the crosslinking agent is: polydimethyl At least one of ethylene glycol acrylate, N,N-methylenebisacrylamide, glutaraldehyde and epichlorohydrin; the organic solvent-water mixed solution is: ethanol-water mixed solution or acetone —Water mixed solution; the gradient solvent exchange refers to: immerse the starch-based hydrogel sequentially in the ethanol-water mixed solution or acetone-water mixed solution with a gradient distribution of volume concentration from small to large, and perform solvent exchange sequentially .

The mass concentration of the starch solution is 1%-5%.

The mass ratio of the starch to the monomer is 1:1-1:8.

When the cross-linking agent is polyethylene glycol dimethacrylate or N,N-methylenebisacrylamide, the process route is: add initiator, monomer and cross-linking agent to the starch solution, and After each component is added, mix evenly, heat to make it fully react, and the starch-based hydrogel can be obtained; after soaking, washing and swelling the obtained starch-based hydrogel in water, immerse it in an organic solvent-water Gradient solvent exchange is carried out in the mixed solution, and after drying, the starch-based porous hydrogel can be obtained.

When the cross-linking agent is glutaraldehyde or epichlorohydrin, the process route is: add initiator and monomer to the starch solution, mix evenly, heat it to react for a certain period of time, then add the cross-linking agent to continue the reaction , the starch-based hydrogel can be obtained. After soaking, washing and swelling the obtained starch-based hydrogel in water, immersing the obtained starch-based hydrogel in an organic solvent-water mixed solution for gradient solvent exchange and drying, the starch-based porous hydrogel can be obtained.

For the ethanol-water mixed solution and the acetone-water mixed solution, the volume concentration of the mixed solution is distributed in a gradient from 10% to 100%, and the setting of the volume concentration is suitable if the hydrogel does not appear obvious volume shrinkage.

Positive and beneficial effects: the advantages of the present invention are: 1. Grafting and copolymerizing starch and monomers to form starch graft polymers, and chemically modifying starch can not only improve the performance of starch, but also make starch-based porous hydrogel The formation of the starch-based hydrogel is easier and the structure is more stable; 2. The starch-based hydrogel is subjected to gradient solvent exchange with an organic solvent-water mixed solution, which is easy to form a starch-based porous hydrogel with an open-pore structure, and can better maintain the starch-based hydrogel. Three-dimensional structure of hydrogels.

Description of drawings

Fig. 1 is the starch-acrylamide porous hydrogel cross-sectional electron micrograph that embodiment 1 prepares;

Fig. 2 is the starch-acrylic acid amide porous hydrogel cross-sectional electron micrograph that embodiment 2 prepares;

Fig. 3 is the cross-sectional electron microscope image of the starch-acrylic acid-butyl acrylate porous hydrogel prepared in Example 6.

Detailed ways

Below in conjunction with specific embodiment, the present invention will be further described:

A starch-based porous hydrogel includes starch solution, initiator, monomer and cross-linking agent.

The preparation method of the starch-based porous hydrogel is as follows: adding an initiator, a monomer and a crosslinking agent into the starch solution, and mixing evenly after each component is added, heating to make it fully react, and then obtaining Starch-based hydrogel: after the obtained starch-based hydrogel is washed and swollen, immersed in an organic solvent-water mixed solution for gradient solvent exchange, and dried, the starch-based porous hydrogel can be obtained.

The starch in the starch solution is soluble starch, cornstarch, carboxymethyl starch, hydroxyethyl starch; the starch solution is: the aqueous solution of starch or the dimethyl sulfoxide solution of starch; the initiator is: Potassium persulfate, ammonium persulfate, azobisisobutyronitrile; the monomer is: at least one of acrylamide, acrylic acid, acrylate and methacrylic acid; the crosslinking agent is: polydimethyl At least one of ethylene glycol acrylate, N,N-methylenebisacrylamide, glutaraldehyde and epichlorohydrin; the organic solvent-water mixed solution is: ethanol-water mixed solution or acetone —Water mixed solution; the gradient solvent exchange refers to: immerse the starch-based hydrogel sequentially in the ethanol-water mixed solution or acetone-water mixed solution with a gradient distribution of volume concentration from small to large, and perform solvent exchange sequentially .

The mass concentration of the starch solution is 1%-5%.

The mass ratio of the starch to the monomer is 1:1-1:8.

When the cross-linking agent is polyethylene glycol dimethacrylate or N,N-methylenebisacrylamide, the process route is: add initiator, monomer and cross-linking agent to the starch solution, and After each component is added, mix evenly, heat to make it fully react, and the starch-based hydrogel can be obtained; after soaking, washing and swelling the obtained starch-based hydrogel in water, immerse it in an organic solvent-water Gradient solvent exchange is carried out in the mixed solution, and after drying, the starch-based porous hydrogel can be obtained.

When the cross-linking agent is glutaraldehyde or epichlorohydrin, the process route is: add initiator and monomer to the starch solution, mix evenly, heat it to react for a certain period of time, then add the cross-linking agent to continue the reaction , the starch-based hydrogel can be obtained. After soaking, washing and swelling the obtained starch-based hydrogel in water, immersing the obtained starch-based hydrogel in an organic solvent-water mixed solution for gradient solvent exchange and drying, the starch-based porous hydrogel can be obtained.

For the ethanol-water mixed solution and the acetone-water mixed solution, the volume concentration of the mixed solution is distributed in a gradient from 10% to 100%, and the setting of the volume concentration is suitable if the hydrogel does not appear obvious volume shrinkage.

Example 1

Add 2.00 g of starch and 40 mL of distilled water into a round bottom flask, stir well, heat to 85°C to fully gelatinize the starch, and then cool to room temperature. Add 4.00 g of monomer acrylamide, 0.08 g of potassium persulfate, and 1.00 g of cross-linking agent polyethylene glycol dimethacrylate to the starch solution in sequence, and heat for 2.5 h to obtain starch-based hydrogel. The hydrogel is taken out, repeatedly soaked in distilled water, swelled, and washed several times to obtain a pure hydrogel. The swollen hydrogel was sequentially immersed in ethanol-water mixed solutions with volume concentrations of 20%, 40%, 50%, 60%, 65%, 70%, 75%, 80%, and 100%. Shake for 2 hours. Oscillate in 100% ethanol for more than 12 hours, take the hydrogel hardened and no longer elastic as the standard, and then dry it in a drying oven to obtain a starch-based porous hydrogel, as shown in Figure 1. Electron micrograph of the section of acrylamide porous hydrogel.

Example 2

Add 2.00 g of starch and 40 mL of distilled water into a round bottom flask, stir well, heat to 85°C to fully gelatinize the starch, and then cool to room temperature. Add 4.00 g of monomer acrylamide and 0.08 g of potassium persulfate in turn to the starch solution, and keep the temperature at 75 °C for 1 hour. Add dilute hydrochloric acid to adjust the pH of the solution to 1, add 4.00 g of glutaraldehyde as a cross-linking agent, and heat to 50°C for a certain period of time to obtain a starch-based hydrogel. The hydrogel is taken out, repeatedly soaked in distilled water, swelled, and washed several times to obtain a pure hydrogel. The swollen hydrogel was sequentially immersed in ethanol-water mixed solutions with volume concentrations of 20%, 40%, 50%, 60%, 65%, 70%, 75%, 80%, and 100%. Shake for 2 hours. Oscillate in 100% ethanol for more than 12 hours, take the hydrogel hardened and no longer elastic as the standard, and then dry it in a drying oven to obtain a starch-based porous hydrogel, as shown in Figure 2. Electron micrograph of the section of acrylamide porous hydrogel.

Example 3

Weigh 3.0 g of acrylic acid, add corresponding amount of 25% sodium hydroxide solution to neutralize acrylic acid (neutralization degree 60%), and cool to room temperature. Put 1.0 g of starch and 10 mL of distilled water in a beaker, heat to 70 °C, and react for 0.5 h. Then add the above-mentioned acrylic acid solution with a neutralization degree of 60%, 1 mL of 0.9% N,N-methylenebisacrylamide solution, and 3 mL of 2.0% potassium persulfate solution in sequence, and heat for 1.5 h to obtain a starch-based hydrogel. . The hydrogel is taken out, repeatedly soaked in distilled water, swelled, and washed several times to obtain a pure hydrogel. The fully swollen hydrogels were immersed in the ethanol-water mixed solutions with volume concentrations of 20%, 40%, 50%, 60%, 65%, 70%, 75%, 80%, and 100% in sequence, and each immersion , Shake for 2 hours. Then it is placed in a drying oven to dry to obtain the starch-based porous hydrogel.

Example 4

Weigh 3.0 g of acrylic acid, add corresponding amount of 25% sodium hydroxide solution to neutralize acrylic acid (neutralization degree 60%), and cool to room temperature. Put 1.0 g of starch and 10 mL of distilled water in a beaker, heat to 70 °C, and react for 0.5 h. Then add the above-mentioned acrylic acid solution with a neutralization degree of 60%, 1 mL of 0.9% N,N-methylenebisacrylamide solution, and 3 mL of 2.0% potassium persulfate solution in sequence, and heat for 1.5 h to obtain a starch-based hydrogel. . The hydrogel is taken out, repeatedly soaked in distilled water, swelled, and washed several times to obtain a pure hydrogel. The fully swollen hydrogels were immersed in the acetone-water mixed solutions with volume concentrations of 35%, 70%, 73%, 76%, 79%, 82%, 90%, and 100% in sequence, each soaking and shaking for 2 Hour. Then place it in a drying oven to dry to obtain the starch-based porous hydrogel.

Example 5

Put 1.0 g of starch and 10 mL of distilled water in a beaker, heat to 70 °C, and react for 0.5 h. Then add acrylic acid and acrylamide in sequence, the mass ratio of starch, acrylic acid, and acrylamide is 1:3:6, 0.9% N,N-methylenebisacrylamide solution 1mL, 2.0% potassium persulfate solution 3mL, heat After reacting for 1.5 h, the starch-based hydrogel was obtained. The starch-based hydrogel is taken out, repeatedly soaked in distilled water, swelled, and washed several times to obtain a pure hydrogel. The fully swollen hydrogels were immersed in the acetone-water mixed solutions with volume concentrations of 35%, 70%, 73%, 76%, 79%, 82%, 90%, and 100% in sequence, each soaking and shaking for 2 Hour. Then place it in a drying oven to dry to obtain the starch-based porous hydrogel.

Example 6

Add 20 mL of dimethyl sulfoxide and 2.0 g of starch into a round bottom flask, heat and stir at 85° C. to dissolve, and then cool to room temperature.

Add 0.34g of crosslinking agent polyethylene glycol dimethacrylate, 6.0g of acrylic acid and 2.0g of butyl acrylate, 0.34g of initiator azobisisobutyronitrile to the solution successively, heat to 65°, and react for 1.5h, A starch-based hydrogel is obtained. The prepared starch-based hydrogel is taken out, soaked and washed repeatedly with distilled water, and impurities including solvents can be removed, thereby obtaining a relatively pure starch-based hydrogel. The swollen hydrogel was taken out of the water, placed in ethanol with a volume fraction of 20%, and then the ethanol-water mixed solution was changed every 2 hours, and the volume fractions were 40%, 50%, 60%, 65%, 70%, 75%, 80%, 100%, the last time should be placed for more than 4 hours. It is better to place it in a water bath constant temperature shaker. Subject to the unchanged gel volume, after meeting the requirements, put it in a vacuum drying oven and dry it to a constant weight to obtain a starch-based porous hydrogel, as shown in Figure 3. The cross-section of the starch-acrylic acid-butyl acrylate porous hydrogel Electron micrograph.

The advantages of the present invention are: 1. Graft copolymerization of starch and monomers to form starch graft polymers, chemical modification of starch can not only improve the performance of starch, but also make the formation of starch-based porous hydrogel easier , the structure is more stable; 2. The starch-based hydrogel is subjected to gradient solvent exchange with an organic solvent-water mixed solution, which is easy to form a starch-based porous hydrogel with an open-pore structure, and can better maintain the structure of the starch-based hydrogel. three-dimensional structure.

The above implementation cases are only used to illustrate the preferred implementation of the present invention, but the present invention is not limited to the above-mentioned implementation, within the scope of knowledge of those of ordinary skill in the art, any modifications made within the spirit and principles of the present invention , equivalent substitutions and improvements, etc., should all be regarded as the scope of protection of this application.

Claims (8)

1. A starch-based porous hydrogel, characterized in that: comprising starch solution, initiator, monomer and crosslinking agent. 2. the preparation method of starch-based porous hydrogel as claimed in claim 1 is characterized in that: add initiator, monomer and crosslinking agent in starch solution, and mix after every kind of component adds, Heating to make it react fully, you can get starch-based hydrogel; wash and swell the obtained starch-based hydrogel, immerse in organic solvent-water mixed solution for gradient solvent exchange, after drying, you can get starch-based porous Hydrogels. 3. the preparation method of a kind of starch-based porous hydrogel according to claim 2, is characterized in that: the starch in described starch solution is soluble starch, corn starch, carboxymethyl starch, hydroxyethyl starch; Said starch solution is: starch aqueous solution or starch dimethyl sulfoxide solution; said initiator is: potassium persulfate, ammonium persulfate, azobisisobutyronitrile; said monomer is: acrylamide, At least one of acrylic acid, acrylate and methacrylic acid; the crosslinking agent is: polyethylene glycol dimethacrylate, N,N-methylenebisacrylamide, glutaraldehyde and epoxy chloride At least one of propane; the organic solvent-water mixed solution is: ethanol-water mixed solution or acetone-water mixed solution; the gradient solvent exchange refers to: the starch-based hydrogel is sequentially immersed to the volume concentration In the ethanol-water mixed solution or acetone-water mixed solution distributed in a gradient from small to large, solvent exchange is performed in sequence. 4. The preparation method of a starch-based porous hydrogel according to claim 2, characterized in that: the mass concentration of the starch solution is 1%-5%. 5. The preparation method of a starch-based porous hydrogel according to claim 3, characterized in that: the mass ratio of the starch to the monomer is 1:1-1:8. 6. the preparation method of a kind of starch-based porous hydrogel according to claim 2, is characterized in that: described linking agent is poly(ethylene glycol dimethacrylate), N,N-methylene dimethacrylate For acrylamide, the process route is: add initiator, monomer and cross-linking agent to the starch solution, mix evenly after each component is added, heat it to fully react, and then obtain starch-based hydrogel ; Soak, wash and swell the obtained starch-based hydrogel in water, immerse it in an organic solvent-water mixed solution for gradient solvent exchange, and dry to obtain the starch-based porous hydrogel. 7. the preparation method of a kind of starch-based porous hydrogel according to claim 2 is characterized in that: when described linking agent is glutaraldehyde, epichlorohydrin, its operational route is: in starch solution Add initiator and monomer to the mixture, mix evenly, heat to react for a certain period of time, then add cross-linking agent to continue the reaction to obtain starch-based hydrogel; soak, wash and swell the obtained starch-based hydrogel in water Finally, it is immersed in an organic solvent-water mixed solution for gradient solvent exchange, and after drying, the starch-based porous hydrogel can be obtained. 8. the preparation method of a kind of starch-based porous hydrogel according to claim 3 is characterized in that: described ethanol-water mixed solution and acetone-water mixed solution, the volume concentration of mixed solution is by 10% to 100% % presents a gradient distribution, and the setting of the volume concentration is appropriate when the hydrogel does not show obvious volume shrinkage.