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CN-121975040-A - Preparation method of chitosan with narrow molecular weight distribution

CN121975040ACN 121975040 ACN121975040 ACN 121975040ACN-121975040-A

Abstract

The invention discloses a preparation method of chitosan with narrow molecular weight distribution, which comprises the following steps of (1) synthesizing a eutectic solvent, (2) presoaking high-concentration alkali, (3) initial alkali treatment and (4) eutectic solvent-alkali cooperative treatment. The invention provides a preparation method of chitosan with narrow molecular weight distribution, which comprises the steps of pre-soaking chitin by strong alkali, performing initial alkali treatment stage and performing subsequent co-processing by eutectic solvent (DES) -NaOH, wherein the chitosan can effectively inhibit random chain breakage while obtaining medium deacetylation degree, so that narrower molecular weight distribution is realized, and finally, the chitosan with relatively narrow molecular weight distribution is prepared, an effective strategy is provided for controllable adjustment of MWD of chitosan, and new knowledge is provided for structural evolution and degradation behavior relation in the deacetylation process of polysaccharide.

Inventors

  • MIAO WENHUA
  • CHEN SIJIA
  • ZHAO YADONG
  • ZHENG BIN

Assignees

  • 浙江海洋大学

Dates

Publication Date
20260505
Application Date
20260206

Claims (5)

  1. 1. The preparation method of the chitosan with narrow molecular weight distribution is characterized by comprising the following steps of: (1) Synthesizing a eutectic solvent, namely mixing choline chloride and glycerin, heating and stirring to form transparent liquid, cooling to room temperature, and then placing in a dryer for storage to obtain the eutectic solvent; (2) High-concentration alkali presoaking, namely mixing chitin powder with a sodium hydroxide solution with the mass concentration of 50%, and stirring to obtain chitin suspension; (3) Initial alkali treatment, namely heating and refluxing the chitin suspension to react under the condition of continuous stirring, and obtaining a reactant after the reaction is finished; (4) And (3) the eutectic solvent-alkali synergistic treatment, namely adding the eutectic solvent into the reactant, continuously carrying out heating reflux reaction on the reactant under the condition of continuous stirring, adding absolute ethyl alcohol after the reaction is finished, precipitating the reactant to a solid, washing the obtained solid to be neutral by using distilled water, and carrying out vacuum freeze drying to obtain the chitosan with narrow molecular weight distribution.
  2. 2. The method for preparing chitosan with narrow molecular weight distribution according to claim 1, wherein in the step (1), the molar ratio of choline chloride to glycerin is 1:2, and the heating is performed to 100 ℃.
  3. 3. The method for preparing chitosan with narrow molecular weight distribution according to claim 1, wherein in the step (2), the mass ratio of the chitin powder to the sodium hydroxide solution with the mass concentration of 50% is 1:20, and stirring is performed under the condition of room temperature.
  4. 4. The method for preparing chitosan with narrow molecular weight distribution according to claim 1, wherein in the step (3), the reflux reaction temperature is 100 ℃ and the reaction time is 4 hours.
  5. 5. The method for preparing chitosan with narrow molecular weight distribution according to claim 1, wherein in the step (4), the eutectic solvent is added in an amount equal to that of the sodium hydroxide solution with the mass concentration of 50% in the step (2), the reflux reaction temperature is 100 ℃, and the reaction time is 8 hours.

Description

Preparation method of chitosan with narrow molecular weight distribution Technical Field The invention relates to a preparation method of chitosan, in particular to a preparation method of chitosan with narrow molecular weight distribution. Background Chitosan has been widely paid attention to the fields of biological medicine, food packaging, functional materials and the like because of its good biocompatibility, antibacterial property and regenerability. However, in practical applications, chitosan obtained under different sources or preparation conditions often shows significant performance differences, which limits the application thereof in fields with high requirements on refinement and repeatability. For example, coatings prepared from chitosan of different molecular weights are significantly different in corrosion resistance and swelling behavior, affecting their practical performance in protective materials. Chitosan and derivatives of different molecular weights also show significant differences in antioxidant activity. Similar phenomena are observed in polymeric material systems, and it has been reviewed that different molecular weight distributions (MolecularWeightDistribution, MWD) have a significant impact on the crystalline structure, thermal stability and mechanical properties of the polymer. And the width of the molecular weight distribution has important influence on the mechanical strength, the thermal stability and even the surface quality of the injection molded polymer. These property differences may be closely related to the difficulty in precisely controlling the molecular weight and molecular weight distribution of the polymer during the preparation process. Both molecular weight and molecular weight distribution are important structural parameters that determine the stability of the material properties. Studies have shown that molecular weight can significantly affect the solubility, mechanical properties and functional performance of chitosan, for example, as the molecular weight of chitosan increases, the solubility of its modified product in water decreases significantly. In packaging and film forming applications, high molecular weight chitosan can impart higher mechanical strength and structural stability to the material. In drug delivery systems, the molecular weight also affects carrier particle size, stability, and bioactivity. However, describing chitosan structures solely in terms of molecular weight is often insufficient to reflect their true chain structural features. In contrast, molecular weight distribution can more fully characterize the distribution state of different segments in a polymer system, which is usually expressed in terms of dispersion coefficient [ ]) Quantitative description is performed. In the field of synthetic polymers, a great deal of research has proved that the width and distribution morphology of molecular weight distribution can still significantly influence the rheological behavior, mechanical properties and processing stability of materials even under the same molecular weight condition. For example, the processability and mechanical properties of the material can be balanced to a certain extent by controlling the ratio of the high molecular weight component to the low molecular weight component in the polylactic acid system. Engineering regulation of the molecular weight distribution of the filaments during extrusion additive manufacturing has proven to significantly improve the stiffness and young's modulus of the printing member. Therefore, in view of the important influence of molecular weight distribution on polymer performance, the establishment of a controllable chitosan molecular weight distribution regulation strategy is an important research direction worthy of deep exploration. The traditional chitosan deacetylation method generally adopts strong alkali conditions, and the process is often accompanied by chain degradation and structural damage, so that the molecular weight is difficult to maintain, the molecular weight distribution is remarkably widened, and the sample conforming to the definition of chitosan is difficult to stably obtain. Based on this, it is necessary to design and develop a chitosan preparation method having a relatively narrow molecular weight distribution. Disclosure of Invention The invention provides a preparation method of chitosan with narrow molecular weight distribution, which aims to solve the problems that the molecular weight is difficult to maintain, the molecular weight distribution is obviously widened, and a sample conforming to the definition of chitosan is difficult to obtain stably due to chain degradation and structural damage of a chitosan deacetylation preparation method of chitosan in the prior art, and has the advantages of simple process steps, mild and controllable process and capability of preparing chitosan with relatively narrow molecular weight distribution. In order to achieve the