Аннотация:The thermal stability of dibenzo-21-crown-7 and of MN-200 organic matrix based on styrene–divinylbenzene in inert and oxidizing atmosphere at temperatures of up to 600°С was studied. Solid extractants (SEs) were prepared from these components. These SEs are stable up to 300°С in inert atmosphere and up to 180–250°С in oxidizing atmosphere, depending on the presence of an additional diluent, fluorinated alcohol, in the SE. At higher temperatures, the SEs undergo exothermic processes accompanied by the formation of such major gaseous products as toluene, styrene, benzaldehyde, 1-ethyl-4-methylbenzene, and 1,3-dioxolane. Their yield depends on the type of the gaseous atmosphere used.