Elastic Modulus and Thermal Conductivity of Thiolene/TiO₂ Nanocomposites

Metal oxide based polymer nanocomposites find diverse applications as functional materials, and in particular thiol-ene/TiO₂ nanocomposites are promising candidates for dental restorative materials. The important mechanical and thermal properties of the nanocomposites, however, are still not well understood. In this study, the elastic modulus and thermal conductivity of thiol-ene/TiO₂ nanocomposite thin films with varying weight fractions of TiO₂ nanoparticles are investigated by using Brillouin light scattering spectroscopy and 3ω measurements, respectively. As the TiO₂ weight fraction increases from 0 to 90%, the effective elastic longitudinal modulus of the films increases from 6.2 to 37.5 GPa, and the effective thermal conductivity from 0.04 to 0.76 W/m K. The former increase could be attributed to the covalent cross-linking of the nanocomposite constituents. The latter one could be ascribed to the addition of high thermal conductivity TiO₂ nanoparticles and the formation of possible conductive channels at high TiO₂ weight fractions. The linear dependence of the thermal conductivity on the sound velocity, reported for amorphous polymers, is not observed in the present nanocomposite system.