Preparation and Thermal Characterization of Three Different Series of Novel Polyhedral Oligomeric Silsesquioxanes (POSSs)/Polystyrene (PS) Nanocomposites

The resistance to the thermal degradation of some polystyrene (PS) based nanocomposites, loaded with 5% w/w of one of nine novel POSSs of general formula R7R′(SiO1.5)8, where R = isobutyl, cyclopentyl or phenyl and R′ = -(CH2)5-CH3, -(CH2)7-CH3 or -(CH2)9-CH3, was studied in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Nanocomposites were prepared by in-situ polymerization of styrene in the presence of the appropriate POSS and were characterized by differential scanning calorimetry (DSC), to determine the glass transition temperature (Tg), and by nuclear magnetic resonance (1H NMR) spectroscopy, to determine the actual filler content which, in all cases, was slightly higher than in the starting mixtures. Nanocomposites were degraded in a thermobalance, in both selected atmospheres, in the 25–700°C temperature range with the formation of small quantities of solid residue at 700°C. The temperatures of 5% mass loss (T5%) were determined to evaluate the resistance to the thermal degradation; the results were higher than for PS. The data obtained were then compared with each other in order to verify if and how much the nature of R and R′ can influence the thermal stability of the corresponding nanocomposites.