Structure and thermochemical properties of copper-containing birch xylan sulfates obtained by the ion exchange method

For the first time, the synthesis of water-soluble copper-containing xylan sulfates (Cu-XS) was carried out by ion exchange method. The composition and structure of the obtained polymers were studied by chemical analysis, X-ray spectral microanalysis, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, electron spin resonance, and atomic force microscopy. The samples Cu-XS and sodium salt of xylan sulfate have an amorphous structure, while the original xylan tends to form crystalline structure. The interaction of copper with xylan sulfate leads to the formation of isolated and exchange-coupled copper (II) ions which correspond to isotropic and anisotropic signals in the EPR spectrum. According to AFM method, the surface of the Cu-XS films was formed by homogeneous particles of a spherical or extended form with sizes of about 100 nm. The introduction of copper ions into xylan sulfate reduces its thermal stability and the activation energy of the thermal decomposition process.