Investigations on some selected conducting polymers and polymer ...

Chaptet -L
PANI powder. Metallic transport over the whole range of temperatures
below room temperature has been reported in dispersion polymerized
PANI [17] where PANI is prepared by self-stabilized dispersion
polymerization (SSDP). In contrast to conventional homogeneous/
dispersion polymerization using an aqueous medium containing aniline,
acid and oxidant, this new polymerization is carried out in a
heterogeneous biphasic (organic and aqueous) mixture without any
stabilizers. Aniline dissolved in acid solution is like a surfactant, with a
polar hydrophilic part and an organic hydrophobic part. The monomers
and growing polymer chains act as interfacial stabilizers, resulting in
excellent dispersion of the organic phase inside the aqueous reaction
medium. The aniline monomers and grown PANI chains are separated
from the reactive ends of the chain in the aqueous phase by the organic
phase and thereby the undesirable side reactions are suppressed. The
reaction mixture is filtered, washed and deprotonated to the emeraldine
base (EB) form, and then dried. Thus high quality PANI (EB) samples
with low density of structural defects can be produced. The resulting
PANI (EB) powder, doped with Camphor Sulphonic Acid (CSA) can
be cast into free-standing films from solution in meta-cresol. The
highest conducting samples synthesized by this method has recorded a
room temperature D.C electrical conductivity value of around
1300S/cm with a positive temperature co-efficient of resistance from
300K to 5K.The exciting results obtained may be due to the improved
molecular structure of the samples, as revealed from the X-ray
Diffraction(XRD) studies.