阅读说明：本技术 水凝胶制备及其性能测试的方法 (Hydrogel preparation and performance test method thereof ) 是由 夏海明 于 2018-08-28 设计创作，主要内容包括：本发明提供了化学领域内的水凝胶制备及其性能测试的方法,包括以下步骤,(1)准备实验材料；(2)取2.5g纤维素粉末加入到50mL的85%浓磷酸中,在0℃下机械搅拌；(3)入氮气吹扫30 min后彻底排出体系内的空气；(4)在纤维素溶液中加入100mg APS和50 mg MBA,将混合物在0℃下搅拌均匀；(5)用滴液漏斗滴加不同量的单体AA,连续搅拌2h后,将反应混合物转移至直径为6 mm的玻璃管中,在0℃下继续聚合反应24 h；(6)得到圆柱形状的条状水凝胶,将新鲜的水凝胶切成2～3mm厚度的圆片,用去离子水洗去残留原料和副产物；本发明操作简单,温度控制容易。(The invention provides a method for preparing hydrogel and testing the performance of the hydrogel in the chemical field, which comprises the following steps of (1) preparing experimental materials; (2) adding 2.5g of cellulose powder into 50mL of 85% concentrated phosphoric acid, and mechanically stirring at 0 ℃; (3) blowing with nitrogen for 30 min, and completely discharging air; (4) adding 100mg APS and 50 mg MBA to the cellulose solution, and stirring the mixture at 0 deg.C; (5) dripping different amounts of monomer AA by using a dropping funnel, continuously stirring for 2h, transferring the reaction mixture into a glass tube with the diameter of 6 mm, and continuously carrying out polymerization reaction for 24 h at the temperature of 0 ℃; (6) obtaining cylindrical strip-shaped hydrogel, cutting fresh hydrogel into wafers with the thickness of 2-3 mm, and washing away residual raw materials and byproducts by deionized water; the invention has simple operation and easy temperature control.)

1. The hydrogel preparation and performance test method is characterized by comprising the following steps:

(1) preparing experimental materials;

(2) 2.5g of cellulose powder was added to 50mL of 85% concentrated phosphoric acid and mechanically stirred at 0 ℃ until the mixture became a homogeneous, translucent gum;

(3) blowing with nitrogen for 30 min, and completely discharging air;

(4) adding 100mg of APS (as initiator) and 50 mg of MBA (as cross-linking agent) to the cellulose solution, and stirring the mixture sufficiently at 0 ℃ until uniform;

(5) slowly dripping different amounts of monomer AA (dripping off within about 30 min) by using a constant-pressure dropping funnel, continuously stirring for 2h, transferring the reaction mixture into a glass tube (serving as a micro-reactor) with the diameter of 6 mm, and continuously carrying out polymerization reaction for 24 h at the temperature of 0 ℃;

(6) obtaining cylindrical strip-shaped hydrogel, cutting fresh hydrogel into wafers with the thickness of 2-3 mm, washing away residual raw materials and byproducts by using a large amount of deionized water, and drying in a drying oven at 50 ℃ to constant weight for later use;

(7) and (3) carrying out performance test on the dried hydrogel, and analyzing the results obtained by the test, wherein the results comprise SEM analysis, FTIR analysis, conductivity titration determination of carboxyl content, determination of C-g-AA gel swelling behavior in different solvent media and C-g-AA gel cationic dye adsorption determination.

2. The method for preparing hydrogel and testing the performance thereof according to claim 1, wherein the SEM analysis specifically comprises:

(1) freeze-drying the C-g-AA hydrogel wafer which is swelled and balanced in advance at-45 ℃ for two days until all water is sublimated;

(2) rapidly freezing the gel wafer in liquid nitrogen, cracking the gel wafer into fragments, and spraying gold on the cracked surfaces;

(3) surface morphology images of fractured samples were recorded by a scanning electron microscope (Quanta 200, FEI Company) with a working voltage of 3 kV and a resolution of 10 nm, and five different positions were selected for each sample for scanning and pictures with repetitive features were selected for analysis.

3. Method for hydrogel preparation and its performance testing according to claim 1 or 2, characterized in that said FTIR analysis is in particular:

(1) grinding the fully dried C-g-AA hydrogel into powder, and fully mixing the powder with spectrum-grade potassium bromide (KBr) powder in an agate mortar;

(2) pressing the powder mixture into a transparent sheet in a tablet press;

(3) an FTIR spectrogram of the gel is recorded and measured by a Bruker Vector 33 infrared spectrometer, and the measuring wavelength range is 4000-500 cm^-1；

(4) Pure cellulose was tabletted with KBr as a control for the experiment.

4. The method for preparing hydrogel and testing the performance of the hydrogel according to claim 2 or 3, wherein the conductivity titration determination of the carboxyl content is specifically as follows:

(1) fully dispersing gel powder in 0.01 mol/L hydrochloric acid solution, and reacting with H in the solution⁺

Ion exchange of cation, fully exchange for 6H, and then use deionized water to remove residual H⁺Washing the ions until the solution is neutral;

(2) ensuring complete equilibrium between the aqueous phase and the gel phase by slow acid-base titration and obtaining quantitative data;

(3) the cellulose powder is processed in the same way to obtain a blank titration curve;

(4) each sample was titrated three times and the arithmetic mean was taken.

5. The method for preparing hydrogel and testing the performance thereof according to claim 2 or 3, wherein the swelling behavior of C-g-AA gel in different solvent media is determined by:

(1) placing the fully dried C-g-AA hydrogel wafer in different solutions including deionized water, pH buffer solution (pH: 2.0-11.0, ionic strength: I = 0.2M), and salt solution (NaCl or CaCl)₂0.01-2.5 mol/L) of the raw material;

(2) taking out the gel in swelling at regular intervals, sucking off the water on the surface by using filter paper and weighing, then immersing the hydrogel into the original solution again for swelling, and taking out again after a preset time interval for operating as above and weighing.

6. The method for preparing the hydrogel and testing the performance of the hydrogel according to any one of claims 1 to 5, wherein the C-g-AA gel cationic dye adsorption assay specifically comprises:

(1) placing the accurately weighed xerogel in deionized water for 24 hours until the gel is in swelling balance, then soaking the gel in swelling balance in MB solution, and placing the gel in a rotary shaking table (30 ℃, 85 rpm) to fully contact for 36 hours;

(2) MB absorbance at 664 nm was measured by an ultraviolet-visible spectrophotometer (Hitachi Z-5000, Japan) as adsorption quantitative data.

Technical Field

The invention belongs to the field of chemistry, and particularly relates to a method for preparing hydrogel and testing performance of the hydrogel.

Background

Oxidized cellulose is a renewable, biodegradable, green resource with abundant reserves. Various derivatives of cellulose have been widely used in the fields of paper making, food, medical and health, cosmetics, petroleum industry, and the like. The hydrogel as a biomaterial with a cross-linked three-dimensional network structure only swells but does not dissolve in a solvent, can be applied to a plurality of fields such as drug release carriers, wound dressing, agriculture and forestry breeding and the like, and the preparation of the functional hydrogel by using a natural high polymer material has important environmental protection significance and economic significance.

lithium/N, N '-dimethylacetamide (LiCl/DMAC) is a green solvent which is recognized to be very effective, less in fiber degradation and environment-friendly at present, and the main defects of the lithium/N, N' -dimethylacetamide are that the reaction temperature is high (110 ℃) and the reaction time is long (4-5 hours).

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to overcome the defects in the prior art and provides a method for preparing hydrogel and testing the performance of the hydrogel.

The purpose of the invention is realized as follows: the hydrogel preparation and performance test method comprises the following steps:

(1) preparing experimental materials;

(2) 2.5g of cellulose powder was added to 50mL of 85% concentrated phosphoric acid and mechanically stirred at 0 ℃ until the mixture became a homogeneous, translucent gum;

(3) blowing with nitrogen for 30 min, and completely discharging air;

(4) adding 100mg of APS (as initiator) and 50 mg of MBA (as cross-linking agent) to the cellulose solution, and stirring the mixture sufficiently at 0 ℃ until uniform;

(5) slowly dripping different amounts of monomer AA (dripping off within about 30 min) by using a constant-pressure dropping funnel, continuously stirring for 2h, transferring the reaction mixture into a glass tube (serving as a micro-reactor) with the diameter of 6 mm, and continuously carrying out polymerization reaction for 24 h at the temperature of 0 ℃;

(6) obtaining cylindrical strip-shaped hydrogel, cutting fresh hydrogel into wafers with the thickness of 2-3 mm, washing away residual raw materials and byproducts by using a large amount of deionized water, and drying in a drying oven at 50 ℃ to constant weight for later use;

(7) and (3) carrying out performance test on the dried hydrogel, and analyzing the results obtained by the test, wherein the results comprise SEM analysis, FTIR analysis, conductivity titration determination of carboxyl content, determination of C-g-AA gel swelling behavior in different solvent media and C-g-AA gel cationic dye adsorption determination.

As a further improvement of the present invention, the SEM analysis specifically includes:

(1) freeze-drying the C-g-AA hydrogel wafer which is swelled and balanced in advance at-45 ℃ for two days until all water is sublimated;

(2) rapidly freezing the gel wafer in liquid nitrogen, cracking the gel wafer into fragments, and spraying gold on the cracked surfaces;

(3) surface morphology images of fractured samples were recorded by a scanning electron microscope (Quanta 200, FEI Company) with a working voltage of 3 kV and a resolution of 10 nm, and five different positions were selected for each sample for scanning and pictures with repetitive features were selected for analysis.

As a further improvement of the present invention, said FTIR analysis is specifically:

(1) grinding the fully dried C-g-AA hydrogel into powder, and fully mixing the powder with spectrum-grade potassium bromide (KBr) powder in an agate mortar;

(2) pressing the powder mixture into a transparent sheet in a tablet press;

(3) an FTIR spectrogram of the gel is recorded and measured by a Bruker Vector 33 infrared spectrometer, and the measuring wavelength range is 4000-500 cm^-1；

(4) Pure cellulose was tabletted with KBr as a control for the experiment.

As a further improvement of the invention, the conductivity titration determination of the carboxyl content is specifically as follows:

(1) fully dispersing gel powder in 0.01 mol/L hydrochloric acid solution, and reacting with H in the solution⁺

Ion exchange of cation, fully exchange for 6H, and then use deionized water to remove residual H⁺Washing the ions until the solution is neutral;

(2) ensuring complete equilibrium between the aqueous phase and the gel phase by slow acid-base titration and obtaining quantitative data;

(3) the cellulose powder is processed in the same way to obtain a blank titration curve;

(4) each sample was titrated three times and the arithmetic mean was taken.

As a further improvement of the invention, the determination of the gel swelling behavior of C-g-AA in different solvent media is specifically as follows:

(1) placing the fully dried C-g-AA hydrogel wafer in different solutions including deionized water, pH buffer solution (pH: 2.0-11.0, ionic strength: I = 0.2M), and salt solution (NaCl or CaCl)₂0.01-2.5 mol/L) of the raw material;

(2) taking out the gel in swelling at regular intervals, sucking off the water on the surface by using filter paper and weighing, then immersing the hydrogel into the original solution again for swelling, and taking out again after a preset time interval for operating as above and weighing.

As a further improvement of the invention, the adsorption determination of the C-g-AA gel cationic dye specifically comprises the following steps:

(1) placing the accurately weighed xerogel in deionized water for 24 hours until the gel is in swelling balance, then soaking the gel in swelling balance in MB solution, and placing the gel in a rotary shaking table (30 ℃, 85 rpm) to fully contact for 36 hours;

(2) MB absorbance at 664 nm was measured by an ultraviolet-visible spectrophotometer (Hitachi Z-5000, Japan) as adsorption quantitative data.

Drawings

FIG. 1 is a diagram showing a mechanism of hydrogel synthesis.

FIG. 2 is an FTIR spectrum of raw cotton linters and C-g-AA hydrogel.

Detailed Description

The hydrogel preparation and performance test method comprises the following steps:

(1) preparing experimental materials shown in table 1;

(2) 2.5g of cellulose powder was added to 50mL of 85% concentrated phosphoric acid and mechanically stirred at 0 ℃ until the mixture became a homogeneous, translucent gum;

(3) blowing with nitrogen for 30 min, and completely discharging air;

(4) adding 100mg of APS (as initiator) and 50 mg of MBA (as cross-linking agent) to the cellulose solution, and stirring the mixture sufficiently at 0 ℃ until uniform;

(5) slowly dripping different amounts of monomer AA (dripping off within about 30 min) by using a constant-pressure dropping funnel, continuously stirring for 2h, transferring the reaction mixture into a glass tube (serving as a micro-reactor) with the diameter of 6 mm, and continuously carrying out polymerization reaction for 24 h at the temperature of 0 ℃;

(6) obtaining cylindrical strip-shaped hydrogel, cutting fresh hydrogel into wafers with the thickness of 2-3 mm, washing away residual raw materials and byproducts by using a large amount of deionized water, and drying in a drying oven at 50 ℃ to constant weight for later use;

(7) and (3) carrying out performance test on the dried hydrogel, and analyzing the results obtained by the test, wherein the results comprise SEM analysis, FTIR analysis, conductivity titration determination of carboxyl content, determination of C-g-AA gel swelling behavior in different solvent media and C-g-AA gel cationic dye adsorption determination.

The SEM analysis specifically comprises:

(1) freeze-drying the C-g-AA hydrogel wafer which is swelled and balanced in advance at-45 ℃ for two days until all water is sublimated;

(2) rapidly freezing the gel wafer in liquid nitrogen, cracking the gel wafer into fragments, and spraying gold on the cracked surfaces;

(3) surface morphology images of fractured samples were recorded by a scanning electron microscope (Quanta 200, FEI Company) with a working voltage of 3 kV and a resolution of 10 nm, and five different positions were selected for each sample for scanning and pictures with repetitive features were selected for analysis.

FTIR analysis specifically was:

(1) grinding the fully dried C-g-AA hydrogel into powder, and fully mixing the powder with spectrum-grade potassium bromide (KBr) powder in an agate mortar;

(2) pressing the powder mixture into a transparent sheet in a tablet press;

(3) an FTIR spectrogram of the gel is recorded and measured by a Bruker Vector 33 infrared spectrometer, and the measuring wavelength range is 4000-500 cm^-1；

(4) Pure cellulose was tabletted with KBr as a control for the experiment.

The conductivity titration determination of carboxyl content specifically comprises:

(1) fully dispersing gel powder in 0.01 mol/L hydrochloric acid solution, and reacting with H in the solution⁺

Ion exchange of cation, fully exchange for 6H, and then use deionized water to remove residual H⁺Washing the ions until the solution is neutral;

(2) ensuring complete equilibrium between the aqueous phase and the gel phase by slow acid-base titration and obtaining quantitative data;

(3) the cellulose powder is processed in the same way to obtain a blank titration curve;

(4) each sample was titrated three times and the arithmetic mean was taken.

The determination of the gel swelling behavior of C-g-AA in different solvent media specifically comprises the following steps:

(1) placing the fully dried C-g-AA hydrogel wafer in different solutions including deionized water, pH buffer solution (pH: 2.0-11.0, ionic strength: I = 0.2M), and salt solution (NaCl or CaCl)₂0.01-2.5 mol/L) of the raw material;

(2) taking out the gel in swelling at regular intervals, sucking off the water on the surface by using filter paper and weighing, then immersing the hydrogel into the original solution again for swelling, and taking out again after a preset time interval for operating as above and weighing.

The specific measurement of the adsorption of the C-g-AA gel cationic dye is as follows:

(1) placing the accurately weighed xerogel in deionized water for 24 hours until the gel is in swelling balance, then soaking the gel in swelling balance in MB solution, and placing the gel in a rotary shaking table (30 ℃, 85 rpm) to fully contact for 36 hours;

(2) MB absorbance at 664 nm was measured by an ultraviolet-visible spectrophotometer (Hitachi Z-5000, Japan) as adsorption quantitative data.

TABLE 1 amounts of raw materials for preparing gels

。

The C-g-AA hydrogel samples, CA10, CA15 and CA20, are successfully prepared by experiments, the cellulose/AA molar ratios are respectively 1:2, 1:4 and 1:6, the appearance of the hydrogel is semitransparent, the surface of the hydrogel is smooth, soft and elastic, and SEM analysis is carried out on a gel fracture surface, the result shows that the hydrogel has a highly porous network structure, and the structure is favorable for diffusion of water molecules and subsequent adsorption of dye ions and metal ions; further experiments have shown that when the AA content of the hydrogel is too high, for example a cellulose/AA molar ratio of 1:8, the gel formed is so weak that it is difficult to shape.

In FIG. 2, it is shown that both samples have distinct absorption peaks at 3355 cm-1 and 3448 cm-1, which are characteristic peaks of hydrogen-bonded-OH groups in cellulose. Both also showed a characteristic peak at 2900 cm-1, which is the result of the asymmetric stretching of-CH 2-in the cellulose-CH 2OH group; the C-g-AA hydrogel has a broad peak in the range of 1710-1569 cm-1, which is generated by the stretching vibration of C = O in-COOH groups on grafted acrylic acid branched chains; while the sharp characteristic peak at 1411cm-1 is attributed to the symmetric stretching vibration of the-COO-group; the absorption peaks at 710-1569 cm-1 and 1411cm-1 demonstrate the presence of carboxyl groups in the hydrogel structure after polymerization. Furthermore, the intensity of the absorption peak at 1069 cm-1 of the C-g-AA hydrogel, here the C-O stretching vibration peak in the-CH 2OH group, was significantly reduced compared to the absorption peak at 1060cm-1 of the raw cotton linter, indicating that the graft polymerization reaction occurred predominantly at the primary hydroxyl sites of the cellulose, where the reaction reduced the number of hydroxyl groups.

However, the presence of carboxyl groups may also be due to the incorporation of AA monomers or the presence of acrylic acid homopolymers, rather than being grafted onto the cellulose hydrogel. To demonstrate this, the hydrogel was soaked thoroughly in 0.01 mol/L NaOH solution for 48 h, then freeze dried and ground to a powder for FTIR observation. The results show that the hydrogels showed identical FTIR spectra regardless of whether they were washed with dilute alkali solution or not. This further demonstrates that the successful grafting of AA monomer onto the cellulose backbone, the reaction synthesizes a completely new polymer.

The present invention is not limited to the above embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts based on the disclosed technical solutions, and these substitutions and modifications are all within the protection scope of the present invention.