Paul Winsor

Dielectric relaxation of 1-propanol/water solutions

Abstract Time domain measurements of solutions at seven compositions and 25°C have been Fourier transformed to obtain complex permittivities in the range 50 MHz to 8 GHz. These can be represented by a sum of two Debye relaxation functions. The principal, slower, one has a relaxation time changing smoothly from 320 ps for 1-propanol to 8 ps for water (by extrapolation from 0.75 mole fraction of water). The second is quite small for 1-propanol, but increases with added water, and remarkably has a relaxation time of ca. 20 ps which is independent of concentration to within the accuracy of the data and fitting. The significance of the behavior is discussed in terms of diffusion like models for molecular reorientations and local conformational changes in hydrogen bonding, with the conclusion that the latter provides a more likely explanation, particularly of the faster relaxation.

Fourier Transform Dielectric Spectroscopy

This paper is primarily concerned with the techniques usually described as time domain spectroscopy (TDS) or time domain reflectometry (TDR). These have been most commonly applied to studies of time or frequency dependent behavior of dielectrics with negligible ohmic or d. c. conductance, but can be used for substances with appreciable conductance and indeed for studies of any electrical properties which can be characterized by an effective admittance or impedance.

Time domain dielectric measurements of conducting glasses

Dielectric measurements of ionically conducting glasses in the family 0.2Li2O ⋅ yLiF ⋅ B2O3 with y=0,0.1,0.2,0.3,0.4,0.5,0.6, and 0.7, have been made in the 107–1010 Hz region by time domain reflectometry (TDR) at six temperatures in the 25–375 °C range. The presence of a plateau in E’ in the ∼107–109 Hz region below an absorptive process near 109 Hz constitutes a static permittivity, Es, whose temperature coefficient leads to the result that (∂S/∂E2)T is positive and, thus, that the system becomes more disordered upon application of the electric field.

Dielectric and C-13 NMR relaxation in solutions of the sulphone copolymers and terpolymers of but-2-ene and of but-1-ene.

Abstract We describe studies made with a time domain system of the high frequency dielectric relaxation of solutions in chloroform and in dioxane of the polyolefins sulphones of but-2-ene and but-1-ene, and of the terpolymers of intermediate composition. The correlation times for transverse dipole relaxation are compared with the values obtained here or elsewhere by dynamic NMR means for the hydrocarbon segments of the main chain in the same solvents. Solvent viscosity is not an important factor controlling segmental motions. In chloroform the high frequency motions of the chains rich in 1-olefin units have similar dipole and NMR correlation times, which is consistent with the simple helical model of the terpolymers, but in the less polar dioxane a specific solvent effect may sufficiently disrupt dipole ordering to produce a different chain dynamics. The dielectric measurements indicate a wide range of correlation times for dipole movement. Differences between the dielectric and NMR correlation times in the disordered chains may arise from a greater sensitivity of the NMR T1 relaxation process to the high frequency components in the spectral distribution function.