Kinetic study of the thermal degradation of PS/MMT nanocomposites prepared with imidazolium surfactants

Styrene and montmorillonite organically modified with imidazolium surfactants (MMT) at various alkyl chain lengths (C-12, C-16 and C-18) were used to prepare the corresponding PS/MMT/C-12, PS/MMT/C-16 and PS/MMT/C-18 nanocomposites by in situ polymerization. XRD and TEM analyses evidenced the formation of both intercalated and exfoliated structures. The glass transition temperatures (T-8) of nanocomposites, as well as that of neat PS, were obtained by DSC measurements. The thermal degradations were carried out in the scanning mode, in both inert and oxidative environments, and the initial temperatures of decomposition (T-i) and the apparent activation energies of degradation (E-a) were determined. Due to an oxidative degradation mechanism, the Ti and E. values in air atmosphere were lower than those under nitrogen. The results indicated that nanocomposites are more thermally stable than polystyrene, and suggested an increasing degree of exfoliation as a function of alkyl chain length of surfactant, associated with enhancing thermal stability.