Optical and Structural Properties of Composites Based on Poly(urethane) and TiO(2) Nanowires

This article’s objective is the synthesis of new composites based on thermoplastic polyurethane (TPU) and TiO(2) nanowires (NWs) as free-standing films, highlighting their structural and optical properties. The free-standing TPU–TiO(2) NW films were prepared by a wet chemical method accompanied by a thermal treatment at 100 °C for 1 h, followed by air-drying for 2 h. X-ray diffraction (XRD) studies indicated that the starting commercial TiO(2) NW sample contains TiO(2) tetragonal anatase (A), cubic Ti(0.91)O (C), and orthorhombic Ti(2)O(3) (OR), as well as monoclinic H(2)Ti(3)O(7) (M). In the presence of TPU, an increase in the ratio between the intensities of the diffraction peaks at 43.4° and 48° belonging to the C and A phases of titanium dioxide, respectively, is reported. The increase in the intensity of the peak at 43.4° is explained to be a consequence of the interaction of TiO(2) NWs with PTU, which occurs when the formation of suboxides takes place. The variation in the ratio of the absorbance of the IR bands peaked at 765–771 cm(−1) and 3304–3315 cm(−1) from 4.68 to 4.21 and 3.83 for TPU and the TPU–TiO(2) NW composites, respectively, with TiO(2) NW concentration equal to 2 wt.% and 17 wt.%, indicated a decrease in the higher-order aggregates of TPU with a simultaneous increase in the hydrogen bonds established between the amide groups of TPU and the oxygen atoms of TiO(2) NWs. The decrease in the ratio of the intensity of the Raman lines peaked at 658 cm(−1) and 635 cm(−1), which were assigned to the vibrational modes E(g) in TiO(2) A and E(g) in H(2)Ti(3)O(7) (I(TiO2-A)/I(H2Ti3O7)), respectively, from 3.45 in TiO(2) NWs to 0.94–0.96 in the TPU–TiO(2) NW composites, which indicates that the adsorption of TPU onto TiO(2) NWs involves an exchange reaction of TPU in the presence of TiO(2) NWs, followed by the formation of new hydrogen bonds between the -NH- of the amide group and the oxygen atoms of Ti(x)O(2x-mn), Ti(2)O(3), and Ti(0.91)O. Photoluminescence (PL) studies highlighted a gradual decrease in the intensity of the TPU emission band, which is situated in the spectral range 380–650 nm, in the presence of TiO(2) NW. After increasing the TiO(2) NW concentration in the TPU–TiO(2) NW composite mass from 0 wt.% to 2 wt.% and 17 wt.%, respectively, a change in the binding angle of the TPU onto the TiO(2) NW surface from 12.6° to 32° and 45.9°, respectively, took place.