STUDY OF THE REGULARITIES OF SYNTHESIS AND COMPARATIVE PHYSICAL-CHEMICAL CHARACTERISTICS OF DIALDEHYDES CHITOSAN

Experimental data on the principles of synthesis and comparative physical-chemical characteristics of dialdehydes chitosan are presented. The preliminary purpose of the study was to identify optimal reaction conditions for the periodate oxidation of chitosan. For this purpose, modification of the polysaccharide was carried out at different concentrations of the oxidizing agent, time, temperature and pH of the environment. Studies have established that the degree of oxidation of chitosan derivatives depends on the reaction conditions and can vary widely. The study of the molecular weight characteristics of dialdehydes chitosan has proven that the destruction of chitosan macromolecules occurs during the oxidation process. In this case, with an increase in the content of aldehyde groups, the average molecular weight of chitosan decreases from 23.0 to 6.4 kDa. The results on the amine nitrogen content and zeta potential of oxidized chitosan derivatives are presented. In this case, an increase in the number of aldehyde groups in dialdehydes chitosan led to a decrease in amine nitrogen and a shift in the zeta potential from positive to negative. A significant difference was found in the hydrodynamic size distributions of chitosan particles and dialdehyde chitosan samples. In contrast to the original chitosan, the hydrodynamic diameter of dialdehyde chitosan particles turned out to be much smaller and was characterized by a bi- and polymodal state. The presence of aldehyde groups in the composition of oxidized chitosan was substantiated using FTIR and UV spectroscopy methods. In the FTIR spectrum of dialdehyde chitosan with a limiting degree of oxidation, a characteristic absorption related to aldehyde groups was detected. With an increase in the quantitative content of oxidized elementary units in the chitosan composition, an increase in the absorption intensity was observed at λmax=310-328 nm in the UV region of the spectra. Analysis of X-ray diffraction patterns showed that the introduction of aldehyde groups into chitosan macromolecules leads to a decrease or disappearance of crystalline regions and promotes the amorphization of reaction products. For citation: Akhmedov O.R., Abdurakhmanov J.A., Shomurotov S.A., Turaev A.S. Study of the regularities of synthesis and comparative physical-chemical characteristics of dialdehydes chitosan. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 5. P. 128-136. DOI: 10.6060/ivkkt.20256805.7089.