Elastic Modulus and Thermal Conductivity of Thiolene/TiO₂ Nanocomposites

Abstract

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.

Temperature-Dependent Thermoelastic Anisotropy of the Phenyl Pyrimidine Liquid Crystal

“…We adopted the BLS-measured sound velocities as the phonon group velocities. 31 Figure 5a depicts the temperature dependencies of the phonon MFPs in the ∥ m and ⊥ m directions. In the liquid phase, the phonon MFPs are similar in both directions.…”

Well-defined metal-polymer nanocomposites: The interplay of structure, thermoplasmonics, and elastic mechanical properties

“…The Wood's law's prediction (solid red line) with no adjustable parameters is a monotonic increase of M L,eff with Ag volume fraction. The computed M L,eff assuming the particular ρ eff (ϕ) does not capture the observed decrease at low experimental Ag content; an effective lower density for Ag would be needed [33].…”

“…Interestingly, Wood's law failed to predict the increase of c L,eff (ϕ) in a TiO 2 polymer nanocomposite [33], where a soft interlayer had to be introduced [34]. The longitudinal elastic modulus, M L,eff = ρ eff c 2 L,eff , an important material property, is shown in Fig.…”

Robustness of elastic properties in polymer nanocomposite films examined over the full volume fraction range

“…Polymer nanocomposites are of current interest due to the possibility of tuning material properties by varying size and volume fractions of included nanoparticles 1 , 2 . In particular, the elastic modulus is an important property for applications and knowledge of the component moduli is not sufficient for predicting it, effective medium theories being often unreliable 3 , 4 . Thus, the combination of the two materials can sometimes exceed the bulk behavior of the constituents, owing to a synergistic interplay between the two components.…”

“…From our previous study 3 , we know that nanoparticle films can display lower sound velocities than their bulk constituent material, depending on the contact stiffness between the nanoparticles 4 , 14 . This was unexpected behavior, since polymer nanocomposites are generally stiffer than their constituent polymers 15 – 17 .…”