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Carboxymethyl chitosan (CMC) is one of the derivatives of chitosan which have been most studied. Due to its enhanced water-soluble, it has film-forming, moisturizing, chelating and other characteristics, which can be widely applied in medicine,wastewater treatment, anti-bacterial, biological sensing and other fields. While Carboxymethyl sulfochitosan is similar to heparin in its active groups.This article explores and determines the preparation craft of carboxymethyl chitosans substituted in three different locations(N,O-CMC, O-CMC, N-CMC) through experiments. Then the products are analyzed and characterized from the degree of substitution (DS), infrared radiation (IR) and nuclear magnetic resonance (NMR) etc, which lay the foundation on the further study of their biological activity and structure-activity relationship. During the experiments, the synthesized O-CMC is used as raw materials, Carboxymethyl sulfochitosan and low-molecular-weight carboxymethyl sulfochitosan are prepared. The main study of contents and results are as follows:(1)Change the conditions of reaction, various N,O-CMC products with different degree of substitution are synthesized. Protecting groups are introduced. Aldimine is formed by adding benzaldehyde into the reaction system to react with amino groups of chitosan. And then, in order to prepare 6O-CMC, deprotection is carried under acidic conditions after carboxymethylation,finally the O-CMC are acquired. Glyoxylate is used to react with amino groups of chitosan to form aldimine and reduced in alkaline environment to get 2N- Carboxymethyl chitosan.(2)DMF-chlorosulfonic acid is used as sulfonation reagent, for the sulfonation of low-molecular-weight chitosan. On the basis of the experiments, Carboxymethyl sulfochitosan and low-molecular-weight Carboxymethyl sulfochitosan are prepared successfully, with sulfated ester group contents 16.78% and 19.06%. Its IR and NMR characterization show that the main product is 6O-Carboxymethyl-2N-sulfochitosan.
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