CHARGE-TRANSFER INTERACTIONS AND REDOX STATES IN RING-SUBSTITUTED POLYANILINES AND THEIR COMPLEXES

Oxidative chemical polymerizations of halogen and alkyl ring-substituted aniline in aqueous acids and organic solvent media have been carried out. X-ray photoelectron spectroscopic data suggest that, with the exception of 2-chloroaniline polymer prepared in an aprotic solvent, the ring-substituted aniline polymers generally have a lower intrinsic oxidation state (imine/amine ratio) than that of their unsubstituted emeraldine counterpart. Nevertheless, protonation levels close to 50% are readily achieved when the 2-chloroaniline, 3-chloroaniline and 2-ethylaniline base polymers are loaded with excess non-volatile HClO4. Sulfonation of the ring-substituted polymer readily gives rise to a self-protonated polymer. The extent of sulfonation, however, is limited by the substituent at the ortho-position of the ring. The halogen substituent at the ortho-position is more susceptible to elimination than that at the meta-position during reprotonation and sulfonation. The ring substituent also severely hinders the charge transfer interactions of the polymer with bulky organic acceptors, such as o-chloranil and o-bromanil.