Dielectric Spectroscopy Applied to Polymers

Since the beginning of the XX ^{n the} century, considerable efforts have been made to develop techniques for characterizing all kinds of mobility within polymeric materials, from the scale of a structural unit to the size of a spherulite. Indeed, variations in the electrical properties of polymers are the response, on a macroscopic scale, to movements occurring on a molecular scale, involving all or part of the molecule.

In the study of an insulating polymer material, an analysis of its dielectric properties, and more specifically the study of molecular mobility induced by relaxation phenomena and charge dynamics triggered by conductive mechanisms, can prove to be an interesting tool for assessing the state of the material and quantifying its evolution under the influence of various physical stresses.

In addition to fundamental studies of the dielectric and electrical behavior of polymers, dielectric spectroscopy provides information relevant to sectors using polymers as dielectric materials. This includes applications as varied as electrical engineering, power electronics, microelectronics, nanoelectronics, biology and pharmaceuticals. This experimental technique provides direct, practical information on ..:

• the electrical insulation properties of amorphous polymers, traditionally used for cable insulation in the frequency -range from mHz to MHz, as well as for the passivation layers of modern electronic devices such as microchips;

• the reliability of polymers in the presence of water for electrical insulation applications used in transformers and alternators;

• to monitor the state of degradation of polymer-based insulators used in transformers following ageing or electrical, mechanical, thermal or thermomechanical stress;

• the electrical performance of a polymer before it is integrated into an electronic device, especially when it is used as a low-permittivity material in Very-Large-Scale Integration (VLSI) applications;

• the structural state of the polymer before and after its glass transition.

This article presents a fundamental study correlated with experimental analyses using the dielectric spectroscopy technique (impedance spectrometer) to unlock the property/structure relationship of polymers. via understanding the various relaxation and conduction mechanisms.