Thermal Study on Phenyl, Hepta Isobutyl-Polyhedral Oligomeric Silsesquioxane/Polystyrene Nanocomposites

A comparative study concerning the thermal stability of Polystyrene (PS) and three Polyhedral Oligomeric Silsesquioxane/Polystyrene (POSS/PS) nanocomposites of formula R7R’(SiO1.5)8/PS (where R = Isobutyl and R’ = Phenyl), at various (3%, 5% and 10%) POSS concentration was carried out in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Nanocomposites were synthesized by in situ polymerization of styrene in the presence of POSS and the experimental filler concentration in the obtained compounds, determined by 1H NMR spectroscopy, was in all cases slightly higher than that in the reactant mixtures. Inherent viscosity (inh) determinations indicated that the average molar mass of polymer in the nanocomposites was practically the same than neat PS and were in agreement with calorimetric glass transition temperature (Tg) measurements. The temperature at 5% mass loss (T5%) and the activation energy (Ea) of degradation process of synthesized nanocomposites were determined and compared with each other and with those of unfilled PS. On the basis of the results from thermal and IR Spectroscopy characterizations the nanocomposite with 5% of molecular filler appears the most thermally stable. The results were also compared with literature data on similar PS based nanocomposites.