MEASUREMENT OF CONDUCTING ION MOBILITY AND CONCENTRATION IN ION-CONTAINING POLYMERS

Open Access
Author:
Choi, U Hyeok
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 09, 2009
Committee Members:
  • Ralph H Colby, Thesis Advisor
Keywords:
  • Ion-containing polymers
  • Ion concentration
  • Ion Mobility
Abstract:
In this study, we focus on how to measure conducting ion mobility and conducting ion number density in ion-containing polymers. From a fundamental side, we do not yet understand how to design the ion-containing polymers to have a large and rapid ion response to an applied field. It is therefore necessary to develop precise measurement of number density and mobility of charge carriers. That can give rise to better understand the generation and transport processes of ionic carriers in these polymers. On the practical side, the fundamental performance characteristics make it possible to optimize the design of ion-containing polymers for advanced devices. We studied dielectric properties and ion conduction of poly(ethylene oxide) (PEO) based polyester copolymer ionomers, with and without crown ether, using dielectric relaxation spectroscopy. Addition of crown ether to PE600-0.5Li enhanced ionic conductivity. A physical model of electrode polarization enabled the ionic conductivity to be separated into conducting ion mobility and conducting ion concentration. The formation of Li-complex with crown ether causes a large increase in the static dielectric constant as well. The increase of the static dielectric constant boosts the number density of conducting ions, and this has the largest contribution to increased conductivity. In addition to the dielectric relaxation spectroscopy measurement, we suggested that a Hall Effect measurement may be able to directly measure both number density of conducting ions and their mobility even though the method has only been extensively used for the characterization of classical semiconductor materials. We defined and discussed fundamental equations of d.c. and a.c. Hall effect. Furthermore, the essential components of an apparatus for ionic Hall Effect measurements are investigated in several ionic systems. With these theoretical and experimental results, we tried to estimate Hall voltage of PE600-0.1Na using d.c. Hall Effect measurement.