Structure-properties relationships of polyhedral oligomeric silsesquioxane (POSS) filled PS nanocomposites

The polyhedral oligomeric silsesquioxane (POSS) additivated polystyrene (PS) based nanocomposites were preparedby melt processing and the structure-properties relationships of the POSS-PS systems were compared to those of theneat PS. In order to investigate the effect of these structural parameters on the final properties of the polymer nanocomposites,five different kinds of POSS samples were used, in particular, POSS with different inorganic cage and with differentorganic pendent groups. The rheological investigation suggests clearly that the POSS acts as a plasticizer and that theprocessability of the PS was positively modified. The affinity between the POSS samples and the PS matrix was estimatedby the calculated theoretical solubility parameters, considering the Hoy’s method and by morphology analysis. Minor differencebetween the solubility parameter of POSS and the matrix means better compatibility and no aggregation tendency.Furthermore, the POSS loading leads to a decrease of the rigidity, of the glass transition temperature and of the dampingfactor of the nanocomposite systems. The loading of different POSS molecules with open cage leads to a more pronouncedeffect on all the investigated properties that the loading of the POSS molecules with closed cage. Moreover, the melt propertiesare significantly influenced by the type of inorganic framework, by the type of the pendent organic groups and by theinteraction between the POSS organic groups and the host matrix, while, the solid state properties appears to be influencedmore by the kind of cage.