Dielectric Spectroscopy in Analysis of Polymers
Polymers and Rubbers
Published Online: 15 SEP 2006
Copyright © 2000 John Wiley & Sons, Ltd. All rights reserved.
Encyclopedia of Analytical Chemistry
How to Cite
Schultz, J. W. 2006. Dielectric Spectroscopy in Analysis of Polymers. Encyclopedia of Analytical Chemistry.
- Published Online: 15 SEP 2006
Dielectric spectroscopy is the measurement of complex permittivity (or “dielectric constant”) as a function of frequency. This measurement can also be done as a function of temperature or time at fixed frequencies to determine various physical and chemical properties of a given polymer. The permittivity is usually measured by placing the sample in contact with electrodes and applying a sinusoidal voltage. Permanent and induced dipoles, and also ion or electron conduction, all contribute to the dielectric response of a material. Dielectric spectroscopy can be used to probe molecular relaxation processes in polymers such as the glass transition or phase transitions such as a melt. For many of the relaxations, it is among the most sensitive of the thermal analysis techniques. Dielectric spectroscopy can also be used to follow chemical changes in polymer systems, such as polymer cure or aging. Because of its enormous frequency range (10−6–1012 Hz), dielectric spectroscopy can follow a wide variety of phenomena. However, since it requires either dipole rotation or charge transport, there are some molecular processes that may not be dielectrically active. In addition, analysis of the measured data can be difficult when there are different phenomena occurring simultaneously.