The physical and chemical properties of polyurethane nano-composites have attracted much attention due to their promising applications in optoelectronictechnologies. Thin films of polyurethane nano-composites with luminescent properties could be used as potential materials for document protection. The materials for optoelectronic applications should fulfill specific requirements such as: high intensity of photoemission and high transmittance. Both characteristics depend on the quantity and good dispersion of luminophores in polymer matrix. Inorganic nanofillers have a strong inclination to agglomeration in polymers because of physical interaction between organic polymer matrix and inorganic filler.

      The aim of this study was to evaluate the influence of nanofiller type on the structure and properties of the polyurethane composites.

      For polyurethane synthesis the following chemicals were used: polycaprolactone diol, 4,4’-dicyclohexymethane diisocyanates and two chain extenders. As a nanofiller yttrium-aluminum-garnet (YAG) doped with 10mol.% of Tb³⁺ was used. The fillers were prepared using two different methods: the Pechinie method and the thermal decomposition. The filler was added to the polyurethane matrix in the proportion 0.1 wt. %. Nanocomposites were synthesized by prepolymer method.

     A series of nano-composites with various amounts of nano-filler were obtained which exhibited high luminescence and intensity of emissions. The microstructure of these composites was investigated via Atomic Force Microscopy in a Tapping Mode and High Resolution Scanning Electron Microscopy (HRSEM). The size analysis of nano-fillers was performed with HRSEM and TEM. The mechanical and electro-optical properties of the specimens have been correlated to their microstructure.