Investigations on some selected conducting polymers and polymer ...

Chapter-L
gels. In thixotropic gels, polymer-polymer interactions are greater than
polymer-solvent interactions. Thixotropic gels can be broken to a
certain extent by simple stirring. But a thixotropic gel, once redissolved
will re-form upon sitting. Another method to break a thixotropic gel is
to add a suitable second solvent. Hsu etal [54] reported that gels of
PANI (EB) in NMP could be redissolved by exposing to gaseous
ammonia. The gels can either be doped in the gel form itself and then
cast into a film or it can be first cast into a film and then doped [9].
1.7 PANI fibers
PANI could also be processed in the form of fibers. A polymer
can be considered as spinnable, if it is capable of assuming large
irreversible deformations on applying uniaxial stress [9].But all
spinnable fluids do not form fibers. Examples include honey and highly
viscous mineral oils. The spinning solution (spin dope) should have
considerable molecular weight also in addition to being spinnable. The
spin dope must be capable of forming some type of chain-chain
interactions such as hydrogen bonding, dispersion interactions,
mechanical entanglement of the polymer chains, or some combination
ofthese or other mechanisms.
Generally fiber spinning IS of two types-melt spmnmg and
solution spinning [9].In melt spinning, the polymer softens and
interchain interactions are minimized upon heating. Thus deformation
of the polymer is facilitated without deterioration of the chains. Such
materials are referred to as thermoplastics. The fiber forming material
is spun through a device called spinnerette, Spinnerette is a highly