Variously substituted phenyl hepta cyclopentyl-polyhedral oligomeric silsesquioxane (ph,hcp-POSS)/polystyrene (PS) nanocomposites The influence of substituents on the thermal stability

A comparative study concerning the thermal stability of polystyrene (PS) and six POSS/PS nanocomposites of general formula R7R'(SiO1.5)(8)/PS (where R = cyclopentyl and R' = phenyl, 4-methoxyphenyl, 4-tolyl, 3,5-xilyl, 4-fluorophenyl, and 2,4-difluorophenyl) was carried out in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Nanocomposites were prepared by in situ polymerization of styrene in the presence of 5 % w/w of POSS, but the actual filler concentration in the obtained nanocomposites, determined by H-1 NMR spectroscopy, was in all cases slightly higher than that in the reactant mixtures. FTIR spectra of nanocomposites evidenced the presence of filler-polymer interactions. Inherent viscosity (eta (inh)) determinations indicated that the average molar mass of polymer in methylated and fluorinated derivatives was lower than neat PS, and were in agreement with calorimetric glass transition temperature (T (g)) measurements. Degradations were performed into a thermobalance, in the scanning mode, at 10 A degrees C min(-1), and the temperatures at 5 % mass loss (T (5 %)), of various nanocomposites were determined. The effects of various substituents of the POSS phenyl group on the thermal stability of nanocomposites were evaluated. The results were discussed and interpreted.