Anomaly in temperature dependence of thermal transport of two hydrogen-bonded glass-forming liquids

Abstract

The thermal conductivity of two molecular glasses (ethanol and 1-propanol) decrease with increasing temperature up to their glass transitions at ${T}_{g}\ensuremath{\approx}97$ and $98\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, respectively. Within their supercooled liquid phases, the conductivity increases with rising temperature up to a maximum which roughly coincides with the liquidus (or melting temperatures ${T}_{m}\ensuremath{\approx}159\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and ${T}_{m}\ensuremath{\approx}149\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, respectively). From there on, the conductivity decreases with increasing temperature, a behavior common to most liquids examined so far, exception made of liquid water. The origin of the rather different dependencies with temperature of thermal transport is understood as a competition between phonon-assisted and diffusive transport effects which are amenable to experiments using high resolution quasielastic neutron scattering and visible and ultraviolet Brillouin light-scattering spectroscopies.