The influence of the nature of POSSs cage's periphery on the thermal stability of a series of new bridged POSS/PS nanocomposites

The thermal degradation of three hepta cyclopentyl bridged Polyhedral Oligomeric Silsesquioxanes (POSS)/Polystyrene (PS) nanocomposites, at different POSS content (1%, 3% and 5%), was studied and compared with that of similar hepta isobutyl bridged POSS/PS nanocomposites previously studied, in order to investigate the influence of the nature of POSSs cage's periphery on the thermal stability of the obtained materials. Nanocomposites were synthesized by in situ polymerization of styrene in the presence of POSS and the actual filler concentration in the obtained nanocomposites was checked by 1H NMR and FT-IR spectroscopy. The glass transition temperatures (Tg) were determined by Differential Scanning Calorimetry (DSC) while degradations were carried out into a thermobalance, in the scanning mode, at various heating rates in flowing nitrogen and in a static air atmosphere. The characteristic parameters of thermal stability, namely temperature at 5% mass loss (T5%) and the activation energy (Ea) of degradation, of the various nanocomposites were determined and showed a large improvement of thermal stability in respect to those of PS and of analogous isobutyl bridged POSS/PS ones. The results were discussed and interpreted.