Polyhedral oligomeric silsesquioxanes (POSS) are hybrid molecules consisting of a rigid inorganic core composed of 8, 10 or 12 silicon atoms linked by oxygen atoms, with organic substituents attached at the comers of the silica cage.Although first synthesised in 1946, POSS have recently begun to attract serious attention as a filler in polymer nanocomposites, due to the enhanced mechanical and thermal properties these nano-sized molecules impart.