Thermal studies of conducting electroactive polymers

234 Pages·2013·4.65 MB·English

University of Wollongong
Research Online
University of Wollongong Thesis Collection University of Wollongong Thesis Collections
1995
Thermal studies of conducting electroactive
polymers
Reza Ansari
University of Wollongong
Recommended Citation
Ansari, Reza, Thermal studies of conducting electroactive polymers, Doctor of Philosophy thesis, Department of Chemistry,
University of Wollongong, 1995. http://ro.uow.edu.au/theses/1210
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I
THERMAL STUDIES Of CONDUCTING
ELECTROACTIVE POLYMERS
A thesis submitted in fulfilment of the
requirements for the award of the degree of
DOCTOR OF PHILOSOPHY
from
THE UNIVERSITY OF WOLLONGONG
by
REZA ANSARI, BSc, MSc
CHEMISTRY DEPARTMENT
January, 1995
II
IN THE NAME OF GOD,
THE MOST BENEFICENT, THE MERCIFUL
Ill
This is to certify that the work described in this thesis has not been
submitted for a higher degree at any other University or Institution.
Reza Ansari
sign
IV
DEDICATED TO:
1- The martyres who gave their lives for the Islamic
Republic of IRAN.
2- My Parent and my Family
V
ACKNOWLEDGEMENTS
I would like to express my gratitude to my supervisor Professor
Gordon G. Wallace for his guidance and continuous supervision during
the course of the project.
1 would like to express my sincere thanks to my co-supervisor Dr.
William Price for his help and encouragement throughout the
completion of my thesis.
The technical assistance of the staff of Electronic, Mechanical and
Glass Blowing Workshops of the Faculty of Science is greatly
appreciated.
I appreciate the help and friendship of my colleagues and staff of the
Chemistry Department, in particular, Kerry Gilmore.
I would like to express my gratitude to Trevor Lewis, Norman Barisci,
Chee O. Too, Mark Imisides and Daniela Organato for proof-reading
parts of this thesis.
I am deeply indebted to my family for their continued support and
enormous endurance over the years.
Finally, I acknowledge the financial support provided by the
Scholarship Department of the Ministry of Culture and Higher
Education of Iran during the course of this work.
VI
PUBLICATIONS
1- Effect of thermal treatment on electroactivity of polypyrrole
conducting polymers.
R.Ansari, G.G. Wallace, Polymer, Vol. 35, No. 11, 1994
2- Effect of thermal treatment on electroactivity of polyaniline
conducting polymers (submitted).
R.Ansari, W.E. Price and G.G. Wallace.
3-Thermal treatment of polypyrrole membranes,
(3rd Pacific Polymer Conference, Gold Coast, Australia, Dec. 1993
R. Ansari, W. E. Price and G. G. Wallace.
4- Effect of thermal treatment on electrochemical properties of
polypyrrole conducting polymers,
(9th Australisian Electrochemistry Conference, Feb. 1994,
Wollongong, Australia)
R. Ansari, W. E. Price and G. G. Wallace.
5- Novel conducting polymer containing polyelectrolytes: a new
Dimension in Responsive Materials (In preparation).
R.Ansari, A. Mirmohseni A., J. Hodgson, G. G. Wallace
6- Effect of electrolyte temperature on transport properties of
polypyrrole conducting polymer membranes (In preparation).
R. Ansari, W. E. Price and G. G. Wallace.
VII
ABSTRACT
Conducting polymers have in the past been plagued by either poor
environmental or poor thermal stability. Indeed, many of the
applications envisioned for these materials require a high level of
conductivity, thermal and environmental stability. In all these
applications, the long-term stability of the polymer determines the
limits of its use. This stability is then assessed in terms of the property
of interest, such as: conductivity, electroactivity, chemical or
mechanical properties.
The present work is concerned with thermal studies based on
polypyrrole and polyaniline conducting polymers. The effect of
exposing conducting polymerss to elevated temperatures on the
electroactivity and conductivity of the polymers has been considered.
Polypyrrole conducting polymers were prepared as coated electrodes
or free standing films, then the effect of thermal treatment on the
electrochemical or electrical conductivity was investigated in different
media. It was found that the redox properties and conductivity could be
improved with mild heating but degraded at higher temperatures.
In all cases, it was found that the nature of the dopant plays the greatest
role in determining the stability of Polypyrrole conducting polymers at
elevated temperatures.
In the application part of this project polypyrrole films were prepared
as free standing films or membranes. The effect of solution
temperature on the transport properies of these polymers which are
based on their unique electrochemical properties was investigated. It
VIII
was found that PPy membranes doped with small mobile counterions
show higher transport of ions at low temperatures. By contrast, the
PPy membranes doped with immobile counterion showed higher flux
at elevated solution temperatures.
Cyclic voltammetry, quartz crystal microbalance, and resistometry
techniques, have been employed to study the effect of solution
temperature on the properties of polypyrrole films.
It was also found that dry state thermal treatment of polypyrrole
membranes under appropriate conditions, in spite of improving the
conductivity or electroactivity, did not result any improvement in the
transport properties of the polypyrrole membranes.
Polyaniline films were also coated on electrodes by chemical and
electrochemical means in order to investigate the thermal stability of
the electroactivity in air and nitrogen atmospheres. Polyaniline was
also synthesised chemically and cast as a membrane. It was found that
the electroactivity and conductivity of the films was stable up to
150°C. Exposure to higher temperatures leads to a decrease in
electroactivity and conductivity, although use of a nitrogen atmosphere
has less effect on the properties than air.
It was found that the electrochemical cell developed in our research
laboratory for transport studies can be easily used for in-situ
characterisation of conducting polymer membranes. Using this cell set
up, allows a wide range of electrochemical techniques to be used for
characterisation of conducting polymers that can be prepared as free
standing films.