Investigations on some selected conducting polymers and polymer ...

Chapter-I
Acid(DBSA) and Napthalene Sulphonic Acid(NSA) has resulted in
enhanced conductivities and a weaker temperature dependence of
conductivity[8-9].This group of doped conducting polymers exhibit
a significant positive Temperature Co-efficient of Resistance (TCR)
in the temperature range 160-300K [8-9,29-31].Recently polyaniline
samples prepared using self-stabilised dispersion polymerization
[32], are found to have room temperature conductivities in excess of
lOOOS/cm with a monotonic decrease in conductivity from room
temperature to 5K[ 17]. However a lot of work is still left to be done
in improving the microscopic and macroscopic order in these
polymers.
1.5 Synthesis
Chemical oxidative polymerization [33] is a common method
employed to synthesise conducting polymers in bulk form. Here the
monomer is dissolved in the dopant acid solution .The oxidant
dissolved in appropriate solvent (water is the commonly used solvent)
is added dropwise to the mixture with continuous stirring for 4-5 hours.
The precipitate obtained is filtered, washed and dried. This is one ofthe
easiest methods adopted for synthesizing conducting polymers in bulk
form and is used to prepare conducting polymers such as polyaniline,
polypyrrole etc.