The article presents the results of studies on the synthesis of a new sorption material with a cross-linked structure (with a yield 94%) based on a ternary co-oligomer of 4-isopropenylphenol (I), styrene (II) and maleic anhydride (III) - their structuring (crosslinking) with ethylenediamine. The process was carried out in a block, at a temperature of 800C and a time of 3 hours. The ratio of co-oligomer and ethylenediamine is 1:2 mol. The initial co-oligomers were obtained by co-oligomerization of I, II and III at their equimolar ratio in the presence of the initiator di-tert-butyl peroxide (2% of the mixture of initial components). Temperature 1400C, time 10 hours. The gel chromatography data confirmed the formation of mainly co-oligomeric compounds under these conditions (87% are co-oligomers with Mw 575 and 980, and Mn 400 and 450, respectively). 13% are co-oligomers with Mw 3585 and Mn 2900. A study of the sorption properties of three-dimensional copolymers as sorbents for the extraction of uranyl ions from model aqueous systems (depending on the pH of the medium, the initial concentration of the said ions, and the holding time of the system) in statistical mode showed that they are highly effective. The degree of extraction (R) of uranyl ions at an optimal pH of 7 is more than 84.2%, while the sorption capacity (q) is 216.5 mg/g.