Nanocomposites and nanomaterials

The influence of metal nature on the structure and properties of composites with polyaniline  
O. Aksimentyeva, Ya. Koren, P. Demchenko, O. Konopelnyk, Yu. Horbenko

Ivan Franko National University of Lviv, 6/8 Kyryla&Mefodia , 79005, Ukraine; E-mail: aksimen@ukr.net

Interest in polymer-metal nanosystems is due to the possibility of obtaining materials with new, enhanced functional properties that can be found in sensor and medical chemistry, electrocatalysis and biotechnology. 
The purpose of the work was to study the influence of the nature of the metal (Ag, Au, Pt, Pd) on the patterns of synthesis and structure of composites with polyaniline (PAN) obtained in conditions of emulsion polymerization. The idea of synthesis was that due to the change in the oxidation degree of the newly formed polymer chains, the ions of the metal are recovered, forming nanosized particles. XPD structural studies and a scanning electron microscopy with energy-dispersive spectroscopy showed that the PAN-Au composite is characterized by the formation of uniformly distributed metallic grains in the polymer with the size of 12.6 ± 3.4 nm. In the PAN-Ag composited the main mass of metal with an average particle size of 30.5 ± 3.5 nm is included in the polymer matrix. The diffractogram of the PAN-Pt composite has only an amorphous halo, which is inherent to the polymer, while the energy-dispersion spectroscopy indicates the presence of metal in the composite. Obviously, platinum is in a completely amorphous state (the size of the particles of its phase grains is ~2 nm). The most interesting was the PAN-Pd composite, for which there are well-formed reflexes that may belong to the individual phase of  Pdx ((C6H7N)n) y. Separate sections of the metallic phase have not been recorded on the CEM images, which suggests the formation of chemical compounds. Consequently, the metal fragment is included in the polymer chain or covalently, or in coordination with the polymer ligands (Pt, Pd). Part of the metal enters the composite in the form of nanoparticles (Au, Ag) uniformly distributed in the polymer matrix. Depending on the nature of the inclusion of the metal in the polymer matrix, the metal center affects both the type of bond and the degree of polymerization.