Synthesis, thermal behavior and physicochemical characterization of ZrO2/PEG inorganic/organic hybrid materials via sol–gel technique

Six zirconia–polyethylene glycol (ZrO2/PEG) inorganic/organic hybrid materials were synthesized by the sol–gel technique with different amount of polyethylene glycol (PEG) (corresponding to 6, 12, 24, 50, 60 and 70 mass%). Scanning electron microscopy and Fourier transform infrared spectroscopic (FT-IR) techniques were used in a recent study to characterize the materials with PEG content up to 50 mass%, while in the present one this characterization was extended to the more promising materials with higher PEG content (60 and 70 mass%). All the six materials confirmed their nanocomposite hybrid nature and the formation of hydrogen bonds between the inorganic zirconia matrix and the water-soluble organic component, which involve the Zr–OH groups and both the terminal OH groups and oxygen atoms in the ethereal units of the polymer chains. Moreover, the occurrence of interactions between PEG and acetylacetone, an inhibitor used during the sol–gel synthesis, was observed in the samples with high polymer content. The thermal behavior of all six hybrid materials was studied for the first time by thermogravimetry and differential thermal analysis from room temperature to 1023 K, aiming at identifying all physical and chemical processes occurring in these interesting materials, with particular reference to the decomposition of PEG to establish their thermal stabilities and the most suitable temperature condition for a further thermal treatment. The results revealed that PEG degradation occurs in the range temperature 473–873 K, and the degradation temperature decreases with increasing the PEG content. A probable explanation for PEG-rich materials is due to free PEG (not involved in the formation of H bonds) not affected by the stabilizing effect of the linkage with the inorganic matrix that causes a shift of degradation temperature toward lower values.