Thermal degradation in bulk and thin films of 2-, 4-, and 6-arm polystyrene stars with a C60 core

The thermal stability (TS) of hexa-, tetra-, and di-arm polystyrene (PS) stars with a C60 core was studied by thermal gravimetric analysis and mass-spectrometry. The quantitative production of volatile products, their composition and their formation kinetics during heating of (PSxC60) are reported. A bimodal release of styrene is observed. The first release takes place about 100 °C before the depolymerization temperature of styrene and all the C60 comes out at this lower temperature. That results from a complete breaking of the weak PS-C60 bonds followed by a partial depolymerization of the PS arms initiated by the so formed radicals. The amount of PS 'surviving' this first depolymerization step increases with the length of the arms and its TS is close to that of pure PS. The thermal stability of the PSxC60 stars decreases if the number of arms increases and, from the activation energy of the release of styrene and C60, it was possible to estimate the PS-C60 bond strength for these three adducts.