Semiconductive and electrically conductive layers of copper sulfides on the polyamide 6 (PA) surface were formed using the sorption–diffusion method and a water solution of potassium pentathionate, K₂S₅O₆, as a precursor of polymer sulfurization. Pentathionate anions containing chains of divalent sulfur atoms of low oxidation state, ^–O₃S–S–S–S–SO₃^–, are sorbed-diffused into PA films if they are treated with K₂S₅O₆ solution. The concentration of sorbed sulfur increases with an increase of the temperature and concentration of the precursor solution and the duration of PA treatment. Cu_xS layers are formed on the surface of PA film when a sulfurized polymer is treated with the water solution of copper(II / I) salt: pentathionate anions react with copper ions. The concentration of copper increases (up to ~40 mg · g^–1) with increasing the concentration and temperature of the precursor solution. XRD results confirmed the formation of Cu_xS layers on the surface of PA. The phase composition of Cu_xS layer depends on the concentration and temperature of potassium pentathionate solution and on the duration of initial treatment in the K₂S₅O₆ solution. The layers are composed of the low-conductive tetragonal chalcocite, Cu_1.96S, monoclinic djurleite, Cu_1.9375S, electrically conductive rhomhedral digenite, Cu₉S₅, orthorhombic anilite, Cu₇S₄, and cubic CuS₂. The phase composition determines the electrical characteristics of the layers obtained: the sheet resistance varies from 0.104 to 1.52 · 10³ KΩ / □. X-ray photoelectron spectroscopy confirmed formation of copper sulfides of various phases. The regularities established in the present work enable formation of Cu_xS layers of a desirable composition and conductivity.

Keywords: potassium pentathionate, polyamide, copper sulfide layer