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_∞+(ε_s–ε_∞)/(1 + iωτ₀)^ξ.

The temperature dependence of the relative static permittivity (ε_s) is accurately described by the empirical relation, ε_s=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 ε_s 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.