Investigations on some selected conducting polymers and polymer ...

more, many of the solutions of these substituted polymers are unstable
and precipitation occurs after some time. Derivitazed polythiophenes
form an exemption in this regard [42-46].Adding substituents on the
polythiophene chain has only a minor effect on chain planarity. Alkyl
substituted thiophenes have good mechanical and electrical properties
in film and fiber forms. The major hurdle in this regard is the tedious
synthesis procedure ofmodified monomers and limited solubility ofthe
doped polythiophene derivatives[9].
Another method involves the inclusion ofsolubilizing monomeric
structures along a modified chain[47]. Though this method increases
the solubility to certain extent, it adversely affects the conductivity,
because charge transport along the chain gets hindered. The
morphology and crystallanity of the polymer may also be adversely
affected by this process[9].
The precursor polymer approach is another recently explored
method for synthesizing soluble conducting polymers. The steps
adopted in this method are outlined below[47].
a) A precursor polymer is prepared.
b) It is converted to the form ofthe desired end product.
c) Finally it is transformed into dopable Intrinsically Conducting
Polymer (ICP), usually by the application ofheat.
Most of the precursor polymers used in this approach have a
polyelectrolyte structure, which is highly water soluble. Usually films
10