Study of the structure of polyphenylsiloxanes containing the metal-ions by physical–chemical methods

Abstract

The study of the structure of polylphenylsiloxanes containing magnesium, cobalt, nickel, and zinc has been performed by the methods of PAS, XRD, and XPS. Using the XRD data, the areas of cross-section of polymer molecules (according to the Miller–Boyer method) and coherent scattering (CS) volumes have been calculated. The data of positron annihilation spectroscopy (PAS) allowed calculation of the specific volumes of positron (Ve+) and positronium (Vps) “traps”. A direct proportional dependence of the volume of the “trap”, in which single positron annihilation takes place, on the positron lifetime and an inverse dependence on the density of metal-siloxanes have was demonstrated. The number of positron annihilations per elementary unit volume has been calculated. Here, for polycobaltphenyl-siloxane and polyphenyl-siloxane the number of oxane fragments, in which annihilation takes place, is equal to 3, whereas for polynickel- and polyzincphenyl-siloxane it is equal to 4. The number of elementary units (e.u.) in the CS volume for magnesium, cobalt, and polyphenyl-siloxane is equal to 10, while for nickel and zinc – to 12, which must be related to higher density in case of nickel-siloxane and to larger CS volume for zinc-siloxane.The Т3 and Т2 values in the 29Si NMR spectrum for polyphenyl-siloxane coincide with the respective data for polynickel- and polycobaltphenyl-siloxanes and differ significantly from those for polyzincphenyl-siloxane. The increase of the number of Т1-and Т2-fragments for zinc is related to the increase of the percentage of octahedral polyhedra of these ions, while for nickel and cobalt – to a greater degree, to the tetrahedral structure of these ions.The study of polyzincphenyl-siloxane by the method of X-ray photoelectron spectroscopy has been performed, and the presence of two types of zinc atoms has been demonstrated: the content of zinc atoms with 2p3/2 was 64.3%; the content of those with 2p1/2 was 35.7%. The latter corresponds to the content of the tetrahedral surrounding of Т1 and Т2 silicon atoms in the 29Si NMR spectrum.