Синтез и физико-химическое исследование сульфатированных производных йота-каррагинана

The efficiency of different approaches to iota-carrageenan sulfation with sulfamic acid (in the presence of urea over Amberlite® and Pyrolite® catalysts), sodium pyrosulfite, sodium sulfite, and ammonium sulfamate has been compared. It has been established that the highest product yield (79.25 %) and the maximum sulfur content (14.2 %) hare obtained in the processes involving sulfamic acid and an urea activator in a 1,4-dioxane medium at a process temperature of 90 °C and a process time of 3 h. The poorest results have been obtained when the sulfation process occurred with the participation of sodium sulfite (yield 4.25 % and S content 7.7 %) and sodium pyrosulfite (yield 10.5‒12.1 % and S content 11.5–11.6 %). The synthesized derivatives have been then characterized by the advanced analysis that included several physical and chemical techniques: Fourier-transform infrared spectroscopy, X-ray diffractometry, TG-DSC simultaneous thermal analysis, atomic force microscopy, and gel permeation chromatography. It has been demonstrated that sulfation noticeably enhances the number of sulfo groups and reduces the molecular weight Mw (from 682547 to 47108 g/mol) and the degree of polydispersity (from 4.61 to 5.83) and induces the polysaccharide structure amorphization. The reported results are of great importance for the creation of powerful techniques for modifying polysaccharides in the way of synthesis of novel materials with required biological, physical, and chemical characteristics.