Physical Properties of Polyhedral Oligomeric Silsesquioxanes–Cycloolefin Copolymer Nanocomposites

Properties of cycloolefin copolymer (COC)– polyhedral oligomeric silsesquioxanes (POSS) nanocomposites, prepared by melt compounding, have been investigated. Composites retained the optical transparency of the matrix up to a nanofiller content of 5 wt %. whereas for higher percentages the formation of a crystalline phase, due to the presence of agglomerated nanoparticles, was revealed by X-Ray diffraction (XRD). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) evidenced a significant decrease of the glass transition temperature (Tg) and of the thermal decomposition rate, with the POSS content. Similarly, at increasing filler content, both quasi-static tensile tests in the solid state and rheological measurements on melts showed a decrease of measured parameters (elastic modulus, ultimate elongation, loss and storage shear modulus, viscosity). These results were attributed to the formation of a soft interphase at the nanoparticles/polymer boundary due to the presence of isobutylic groups on POSS nanoparticles that limited the stress transfer process and acted in the COC matrix as a molecular lubricant agent. A small increase of the receding contact angle with the nanofiller content was also detected from dynamic contact angle (DCA) measurements. VC 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: