ELECTRON-LOCALIZATION EFFECTS ON THE CONDUCTING AND MAGNETIC STATES IN POLYANILINE COPOLYMERS

The methyl-ring-substituted derivative of polyaniline shows increased electron localization compared to polyaniline, and the mechanism for t his increased localization has been proposed as due to a decrease in t he interchain diffusion rate caused mainly by enhanced disorder due to random positioning of the methyl groups. We have investigated this is sue by studying the magnetic and transport behavior of the copolymer p oly(aniline)x(p-fluoroaniline)1-x at five values of x. We find that th e electron-localization length in the copolymer is nearly equal to the conjugation length, and it decreases on decreasing x. The comparison of this behavior with that for poly(o-toluidine) and other alkyl-ring- substituted derivatives of polyaniline shows that the primary cause of electron localization in the polyaniline derivatives is enhanced inte rchain disorder. Our results also seem to provide some support for a m odel of polyaniline comprised of metallic islands consisting of single , isolated strands of the polymer.