Thermal evolution of PEG-based and BRIJ-based hybrid organo-inorganic materials. FT-IR studies

This work presents the application of FT-IR spectroscopy to study the thermal evolution of PEG-based nanocomposites prepared using montmorillonite STx intercalated with polyethylene oxides PEG 1500 and PEG 4000 and polyethylene oxide BRIJ. The effect of different polymer molecular weights and polymer loadings has been evaluated by means of diagnostic mid-IR bands. PEG fragmentation through the cleavage of the C-O bond appears to be the main reaction step, leading to the formation of short chain carbonyl adsorbed species (such as acetaldehyde), alcohols (ethanol and methanol) and, to a lesser extent, esters species, characterized by the frequency of the carbonyl stretching band. The detection of carbonyl band evidenced the formation of partial oxidation products as first step of the thermal degradation. Increasing polymer loadings, as well as increasing polymer molecular weight leads to lower temperature of formation of the first oxidation products. No clear indication of the effect of the chemical nature for the intercalated polymers can be obtained. BRIJ thermal decomposition seems to be mainly driven by the PEG-like moiety chemistry. CH stretching bands detected at 450-500 C for the samples intercalated with PEG samples indicated the formation of residual organic compounds resisting oxidation, possibly char species preserved from further oxidation by the interlayer galleries. (C) 2014 Elsevier B.V. All rights reserved.