When polyamide 6 (PA) films are exposed for different time to acidified solutions of sodium trithionate, Na₂S₃O₆, and sodium tetrathionate, Na₂S₄O₆, and later to alkalified solution of Tl₂SO₄, Tl_xS layers on PA films are formed. A study of IR and UV absorption spectra has shown that pentathionate, S₅O₆^2–, ions are sorbed from acidified water solutions of potassium pentathionate, K₂S₅O₆, by PA films. The concentration of pentathionate ions sorbed into a polymer increases with increasing the concentration of K₂S₅O₆ solution, as well as the temperature and duration of treatment. A layer of nonstoichiometric thallium sulfide, Tl_xS, was obtained after treating sulfurized PA with a solution of Tl₂SO₄. The concentration of thallium increased when the concentration and temperature of the pentathionate solution had been increased. Supposedly, a compact Tl_xS layer forms on the PA film, which terminates the further diffusion of Tl⁺ ions from Tl(I) salt solution. The water solution of dodecathionic acid, H₂S₁₂O₆, acts effectively as a sulfurization agent of PA. The values of sulfur concentration in PA increase with increasing the duration of treatment and the temperature of H₂S₁₂O₆ solution. Tl_xS layers are formed on the surface of PA film if a polymer sulfurized in H₂S₁₂O₆ solution is treated with alkalified solution of Tl₂SO₄. The concentration of thallium in the polyamide film increases with increasing the duration and temperature of initial sulfurization. Four thallium sulfide phases, TlS, Tl₂S₂, Tl₄S₃ and Tl₂S₅, were identified in the composition of the layers by X-ray diffraction. The determined regularities enable formation by the sorption–diffusion method of thallium sulfide layers of a desirable composition, using dodecathionic acid as a PA sulfurization agent. The XPS analysis of Tl_xS layers, formed by using H₂S₁₂O₆ solution as a precursor, showed various thallium, sulfur and oxygen compounds: Tl₂O₃, Tl₂S₃, Tl₂S, S₈, Tl₂SO₄ and Tl(OH)₃. Studies of Tl_xS layer surface morphology by the AFM method have shown that, depending on the temperature of the initial polyamide sulfurization in K₂S₅O₆ or H₂S₁₂O₆ solution (in the same “thalliumizing” conditions of sulfurized PA), thallium sulfide layers are formed unevenly as islands which grow into bigger agglomerates. The surface of the coatings is rather uneven and rough.

Keywords: review, polythionates, polyamide, thallium sulfide layer