Dielectric study of propylene carbonate/toluene mixtures and dipole moment of supercooled propylene carbonate

The authors present results of a dielectric experimental study on binary polar/nonpolar mixtures, propylene carbonate (PC) toluene or methylbenzene (MB), down to their glass transition temperatures. The values obtained for static permittivity made it possible to estimate the dipole moment of propylene carbonate from 60°C down to T _g=119.8°C. The Kirkwood correlation factor was then deduced over this temperature range in order to determine the short-range effects on propylene carbonate molecules near T_g. In addition, the temperature dependence of the dielectric relaxation time of [PC]_x[MB]_1-x mixtures was studied. Dipolar molecules of PC may be considered as molecular probes lost in a nonpolar matrix (MB) when the dilution becomes infinite. The extrapolation to zero molar concentration χ leads to an evaluation of the MB molecular relaxation time