J. Maron et al., PROCESSING-INDUCED CHANGES IN THE LOCAL-STRUCTURE OF AMORPHOUS POLYANILINE BY RADIAL-DISTRIBUTION FUNCTION-ANALYSIS OF X-RAY-SCATTERING DATA, Macromolecules, 28(13), 1995, pp. 4475-4486
The local molecular structure of amorphous polyaniline (PANI) film in
the emeraldine oxidation state has been studied using radial distribut
ion function analysis of X-ray scattering data in combination with mod
el calculations. As-cast emeraldine base (EB) films exhibit an interch
ain ordering that is significantly poorer than that for the intrachain
structure. Protonic acid (HBr or HCl) doping of these films, to yield
the electrically conductive emeraldine salt (ES) form of PANI, leads
to significant changes in both the intrachain and interchain structure
of the polymer chains. Structural changes in the intrachain ordering
are found to be essentially reversible on undoping since, after all of
the dopant is removed from ES films by immersion in a strong base sol
ution, the original as-cast EB intrachain features become more pronoun
ced. In contrast, evidence of irreversible changes in the interchain.
packing is observed during this doping/undoping process following the
treatment with base. These changes in the EB local molecular ordering
may be intimately coupled to the electronic properties intrinsic to co
nducting polymers and they occur in such a way that subsequent exposur
e to protonic acids initiates a highly site-specific redoping of the p
olymer host. These findings shed light on the doping-induced variation
s of the physical properties in conducting polymers such as charge and
mass transport through polyaniline films.