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Role of CoBr2 on the structural, optical and magnetic properties of polyvinyl alcohol films



Polyvinyl alcohol (PVA) films filled with different concentrations of CoBr2 were prepared using the casting method. These films were characterized by FTIR, UV–visible, XRD, and ESR techniques. FTIR spectra were used to clarify the structural variations due to the filling level from CoBr2. The observed bands at 3484, 1733, and 1640 cm−1 were assigned to O[BOND]H, C[DOUBLE BOND]O, and C[DOUBLE BOND]C stretching vibrations, respectively. UV–visible spectra shows the absorption band at 280 nm which is assigned to π → π* transition. This indicates the presence of unsaturated bonds in tail to head of PVA. Optical energy gap decreased with increasing the concentration of CoBr2. X-ray diffraction scans show some decrease in the degree of crystallinity in the filled films which reveals an increase in amorphous phase of PVA due to the interaction between Co+2 and polymeric matrix causing a molecular rearrangement within the amorphous phase of PVA. The observed complex ESR spectrum due to hyperfine interactions confirms the role of free radicals. Spectroscopic and magnetic properties of PVA/CoBr2 composite films were investigated and compared with those of PVA alone. The results show that the change of the structure due to the interaction of filler with the polymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010