阅读说明：本技术 一种基于席夫碱的聚氨酯/壳聚糖自愈合水凝胶及其制备方法 (Polyurethane/chitosan self-healing hydrogel based on Schiff base and preparation method thereof ) 是由 吉晓莉 易曌 吴力立 于 2020-05-11 设计创作，主要内容包括：本发明公开了一种基于席夫碱的聚氨酯/壳聚糖自愈合水凝胶,以醛基化聚氨酯和壳聚糖为原料,通过亚胺键交联制备而成；所述醛基化聚氨酯中醛基和壳聚糖中氨基的摩尔比为1:1-3；所述自愈合水凝胶的固含量为8%-12%。本发明所述基于席夫碱的聚氨酯/壳聚糖自愈合水凝胶具有良好的力学性能和优越的抗菌性能,以及良好的自愈合性能、溶胀性能以及pH响应性,既可方便使用,又可延长其使用寿命。(The invention discloses polyurethane/chitosan self-healing hydrogel based on Schiff base, which is prepared by taking aldehyde polyurethane and chitosan as raw materials and cross-linking through imine bonds; the molar ratio of aldehyde groups in the aldehyde polyurethane to amino groups in the chitosan is 1: 1-3; the solid content of the self-healing hydrogel is 8-12%. The polyurethane/chitosan self-healing hydrogel based on the Schiff base has good mechanical property, excellent antibacterial property, good self-healing property, swelling property and pH responsiveness, and can be conveniently used and prolong the service life.)

1. Polyurethane/chitosan self-healing hydrogel based on Schiff base is characterized in that aldehyde polyurethane and chitosan are used as raw materials and are prepared by cross-linking through imine bonds; the molar ratio of aldehyde groups in the aldehyde polyurethane to amino groups in the chitosan is 1: 1-3; the solid content of the self-healing hydrogel is 8-12%.

2. A preparation method of polyurethane/chitosan self-healing hydrogel based on Schiff base is characterized by mainly comprising the following steps:

(1) uniformly mixing polyethylene glycol and isophorone diisocyanate in acetone, and adding an organic tin catalyst to obtain a polyurethane prepolymer solution;

(2) uniformly mixing an acetone solution of 2, 4-dihydroxy benzaldehyde with the polyurethane prepolymer solution prepared in the step (1), then dropwise adding an acetone solution of a basic catalyst, reacting to obtain an orange-red viscous liquid, and drying to obtain an aldehyde polyurethane solid;

(3) dissolving the aldehyde polyurethane prepared in the step (2) with water to obtain an aldehyde polyurethane solution; dissolving chitosan with acetic acid solution to obtain chitosan solution;

(4) and (3) mixing the aldehyde polyurethane solution prepared in the step (3) with the chitosan solution, adding alkali to adjust the pH value to 5.0-6.5, and curing at room temperature to obtain the polyurethane/chitosan self-healing hydrogel based on Schiff base.

3. The preparation method of the schiff base-based polyurethane/chitosan self-healing hydrogel according to claim 2, wherein the molecular weight of the polyethylene glycol is 1500-; the molar ratio of the polyethylene glycol to the isophorone diisocyanate is 1: 1-1.5.

4. The preparation method of the Schiff base-based polyurethane/chitosan self-healing hydrogel according to claim 2, wherein in the step (1), the total solid content of the polyethylene glycol and the isophorone diisocyanate in acetone is 60-85%.

5. The preparation method of the Schiff base-based polyurethane/chitosan self-healing hydrogel according to claim 2, wherein in the step (1), the organotin catalyst is dibutyltin dilaurate, and the amount of the organotin catalyst is 0.01 to 0.02 percent of the total mass of the polyethylene glycol and the isophorone diisocyanate; (ii) a After adding the organic tin catalyst, keeping the temperature of 55-60 ℃ for reaction for 20-40 minutes.

6. The preparation method of the schiff base-based polyurethane/chitosan self-healing hydrogel according to claim 2, wherein the molar ratio of the 2, 4-dihydroxybenzaldehyde added in the step (2) to the isophorone diisocyanate in the step (1) is 1: 2-3; the mass percentage concentration of the acetone solution of the 2, 4-dihydroxy benzaldehyde is 5-10%.

7. The preparation method of the Schiff base-based polyurethane/chitosan self-healing hydrogel according to claim 2, wherein in the step (2), the basic catalyst is 1, 8-diazabicyclo [5.4.0] undec-7-ene, and the amount of the basic catalyst is 0.6-0.65% of the total mass of the polyethylene glycol and the isophorone diisocyanate; the mass percentage concentration of the acetone solution of the alkaline catalyst is 1-2.5%.

8. The preparation method of the schiff base-based polyurethane/chitosan self-healing hydrogel according to claim 2, wherein in the step (2), the reaction temperature is 60-80 ℃, the reaction time is 4-6 hours, and acetone is continuously added in the reaction process to reduce the viscosity of the reaction system; in the step (1) and the step (2), the total amount of acetone accounts for 50-80% of the total mass of the reaction system.

9. The preparation method of the schiff base-based polyurethane/chitosan self-healing hydrogel according to claim 2, wherein in the step (3), the aldehydized polyurethane is dissolved in water for 2-3 days to obtain an aldehydized polyurethane solution, the mass fraction of which is 10% -15%; the mass fraction of the chitosan solution is 2-3.5%; wherein, when preparing the chitosan solution, the mass fraction of the acetic acid solution is 1-3%, the deacetylation degree of the chitosan is more than or equal to 95%, and the molecular weight is 200000-5000000.

10. The preparation method of the schiff base-based polyurethane/chitosan self-healing hydrogel according to claim 2, wherein in the step (4), the ratio of the aldehyde-based polyurethane solution to the chitosan solution is calculated by the molar ratio of the amino groups in the chitosan to the aldehyde groups in the aldehyde-based polyurethane being 1: 1-3; the curing time at room temperature is 6-12 hours.

Technical Field

The invention belongs to the technical field of high polymer materials and biomedical materials, and particularly relates to polyurethane/chitosan self-healing hydrogel based on Schiff base and a preparation method thereof.

Background

The hydrogel is a polymer with a three-dimensional microstructure, can swell in water without losing the structural integrity, has excellent softness, biocompatibility and permeability, and is one of the most promising materials in the biomedical field at present. However, the hydrogel is easily damaged by external factors during processing and use, and microcracks are generated inside the hydrogel, thereby shortening the service life. Therefore, the self-healing function is introduced into the hydrogel material, so that the service life of the material is prolonged, and the safety of the material is improved. The nature of the self-healing hydrogel is based on dynamic covalent bonds or non-covalent bonds, wherein, due to the combination of reversibility of the non-covalent bonds and stability of the covalent bonds, researches on designing and preparing the self-healing hydrogel through the dynamic covalent bonds are more and more emphasized, and the self-healing hydrogel based on phenylboronate, disulfide bonds, hydrazide and imine is reported at present. Among these dynamic covalent bonds, imine bonds can be formed between amino and aldehyde groups simply and efficiently under mild conditions, and thus, the self-healing hydrogel based on schiff bases has a wide potential for biomedical applications.

Chitosan is the only positively charged basic polysaccharide known at present and is obtained by deacetylating chitin in hot alkaline solution. Compared with other natural polysaccharides, the chitosan has the advantages of good biocompatibility, low cytotoxicity, good antibacterial performance, accelerated blood coagulation, wound repair and the like, and is developed very rapidly in the biomedical field. The inherent reactive amino group of the chitosan facilitates the preparation of the chitosan self-healing hydrogel based on Schiff base crosslinking. Recently, chitosan hydrogels based on schiff bases often use small-molecule dialdehydes, which limit biological applications because of their toxicity, or polyaldehydes, which are most representative of aldehydized polyethylene glycols, but are mostly used for injectable hydrogels because of their poor mechanical properties, as cross-linkers.

The polyurethane material can be cut due to the molecular structure, the performance is easy to regulate, the biocompatibility and the mechanical performance are good, the cytotoxicity is low, and the flexibility and the air permeability are proper, so that the polyurethane material occupies an important position in the research and application of the biomedical field in recent years. However, the poor antibacterial performance and self-healing performance of the polyurethane hydrogel are problems to be solved urgently during application, and many reports are currently reported for endowing the polyurethane hydrogel with antibacterial performance by using inorganic nano-particle compounding, such as nano-silver, nano-titanium dioxide and the like, but the problems that the shape and the particle size distribution of the inorganic nano-particles are not easy to control, the requirement of high dispersion degree is difficult to achieve and the like still exist. Polyurethane hydrogels based on schiff base crosslinking are also less common for self-healing properties.

Disclosure of Invention

The invention aims to solve the technical problem of providing polyurethane/chitosan self-healing hydrogel based on Schiff base and a preparation method thereof so as to obtain hydrogel with good mechanical property, excellent antibacterial property and self-healing property.

The technical scheme adopted by the invention for solving the problems is as follows:

polyurethane/chitosan self-healing hydrogel based on Schiff base is prepared by taking aldehyde polyurethane and chitosan as raw materials and performing cross-linking through imine bonds; the molar ratio of aldehyde groups in the aldehyde polyurethane to amino groups in the chitosan is 1: 1-3; the solid content of the self-healing hydrogel is 8-12%.

The invention also provides a preparation method of the polyurethane/chitosan self-healing hydrogel based on Schiff base, which comprises the following steps:

(1) dissolving polyethylene glycol and isophorone diisocyanate in acetone at 55-60 ℃, dropwise adding an organic tin catalyst after full dissolution, and keeping the temperature at 55-60 ℃ to continue reacting for 20-40 minutes to obtain a colorless and transparent polyurethane prepolymer solution;

(2) adding an acetone solution of 2, 4-dihydroxybenzaldehyde into the polyurethane prepolymer solution prepared in the step (1), after fully dissolving the 2, 4-dihydroxybenzaldehyde, dropwise adding an acetone solution of a basic catalyst into a reaction system, heating to 60-80 ℃, reacting for 4-6 hours, continuously adding acetone in the reaction process to reduce the viscosity of the reaction system to obtain orange-red viscous liquid, and then drying in vacuum at 45-55 ℃ to constant weight to obtain aldehyde polyurethane solid;

(3) dissolving the aldehyde polyurethane prepared in the step (2) with deionized water at room temperature for 2-3 days to obtain a yellow transparent aldehyde polyurethane solution; completely dissolving chitosan in an acetic acid solution at room temperature to obtain a colorless and transparent chitosan solution;

(4) stirring and mixing the aldehyde polyurethane solution prepared in the step (3) and the chitosan solution prepared in the step (3) to obtain light yellow transparent viscous liquid, then dropwise adding a sodium hydroxide aqueous solution to adjust the pH value to 5.0-6.5, then injecting into a mold to cure at room temperature for 6-12 hours, and demolding to obtain the polyurethane/chitosan self-healing hydrogel based on Schiff base.

According to the scheme, the molecular weight of the polyethylene glycol is 1500-3000.

According to the scheme, in the step (1), the molar ratio of the polyethylene glycol to the isophorone diisocyanate is 1: 1-1.5; the total solid content (by mass percent) of the polyethylene glycol and the isophorone diisocyanate in the acetone is 60-80%.

According to the scheme, in the step (1), the organotin catalyst is dibutyltin dilaurate, and the using amount of the organotin catalyst is 0.01-0.02% of the total mass of the monomers (namely the total mass of the polyethylene glycol and the isophorone diisocyanate).

According to the scheme, in the step (2), the molar ratio of the addition amount of the 2, 4-dihydroxy benzaldehyde to the isophorone diisocyanate in the step (1) is 1: 2-3.5; the mass percentage concentration of the acetone solution of the 2, 4-dihydroxy benzaldehyde is 5-10%.

According to the scheme, in the step (2), the basic catalyst is 1, 8-diazabicyclo [5.4.0] undec-7-ene, and the using amount of the basic catalyst is 0.6-0.65% of the total mass of the monomer; the mass percentage concentration of the acetone solution of the alkaline catalyst is 1-2.5%.

According to the scheme, in the step (1) and the step (2), the total dosage of acetone accounts for 50-80% of the total mass of the reaction system.

According to the scheme, in the step (3), the mass fraction of the aldehyde polyurethane solution is 10-15%; the mass fraction of the chitosan solution is 2-3.5%. Wherein, when preparing the chitosan solution, the mass fraction of the acetic acid solution is 1-3%, the deacetylation degree of the chitosan is more than or equal to 95%, and the molecular weight is 200000-5000000.

According to the scheme, in the step (4), the proportion of the aldehyde polyurethane solution to the chitosan solution is calculated by the molar ratio of the amino group in the chitosan to the aldehyde group in the aldehyde polyurethane being 1: 1-3.

According to the scheme, in the step (4), the concentration of the sodium hydroxide aqueous solution is 20g/100mL-30g/100 mL. Preferably, a certain amount of pigment is added for dyeing before the sodium hydroxide aqueous solution is added, so that the observation can be facilitated.

Compared with the prior art, the invention has the beneficial effects that:

(1) the polyurethane/chitosan self-healing hydrogel based on Schiff base takes aldehyde polyurethane and chitosan as raw materials, and the prepared hydrogel is endowed with good mechanical property and excellent antibacterial property, so that the hydrogel is suitable for biomedical materials (such as wound dressings).

(2) The hydrogel is prepared by imine bond crosslinking. As a dynamic covalent bond, the reversibility of a non-covalent bond and the stability of a covalent bond are combined by imine bonds, and meanwhile, the imine bonds are synthesized simply and efficiently. Therefore, the hydrogel prepared by the invention has good self-healing performance, swelling performance and pH responsiveness, is convenient to use and can prolong the service life.

Drawings

FIG. 1 is a swelling curve of the Schiff base-based polyurethane/chitosan self-healing hydrogel obtained in example 1 in deionized water at 25 ℃.

Fig. 2 is a stress-strain curve of the schiff base-based polyurethane/chitosan self-healing hydrogel obtained in example 2.

Detailed Description

In order to better understand the present invention, the following examples are further provided to illustrate the content of the present invention, but the present invention is not limited to the following examples.

In the examples below, the molecular weight of the polyethylene glycol was 2000; the mass concentration of the acetic acid solution is 2.1 percent; the deacetylation degree of the chitosan is more than or equal to 95 percent, and the molecular weight is 200000-5000000.