Dielectric relaxation in non-aqueous solutions. Part 5.—Propylene carbonate (4-methyl-1,3-dioxolan-2-one)
Abstract
The permittivity (ε′) and loss (ε″) of propylene carbonate (4-methyl-1,3-dioxolan-2-one) have been measured at several temperatures between 0° and 50°C in the frequency range 0.5 to 35 GHz. The overall frequency response of the complex permittivity is unsymmetrical but can be satisfactorily represented by the equation ε′(ω)– iε″(ω)=ε∞+(εs–ε∞)/(1 + iωτ0)ξ.
The temperature dependence of the relative static permittivity (εs) is accurately described by the empirical relation, εs=A exp(–LT), with A= 195.6 and L= 3.681 × 10–3 K–1, although the dielectric relaxation times (τ0) do not fit the usual Arrhenius expression. The distribution parameter (ξ) and high frequency limiting permittivity (ε∞) both vary in an irregular manner with increasing temperature. Propylene carbonate also absorbs in the far infra-red between 20 and 170 cm–1 with a maximum absorption at about 70 cm–1.
Values of the Kirkwood correlation parameter (g) calculated from εs indicate that short range order is not significant in liquid propylene carbonate. The unsymmetrical frequency response of (ε′– iε″) has been discussed in terms of current molecular theories.