Electrochemical, conductive, and magnetic properties of 2,7-carbazole-based conjugated polymers

Novel poly(2,7-carbazole)s (i.e., poly(N-octyl-2,7-carbazolediyl) and poly(N-(4-hexylbenzoyl)2,7-carbazolediyl)) and their alternating thiophene, bithiophene, and 3,4-ethylenedioxy-2,5-thienylene copolymers have been investigated by cyclic voltammetry, UV-vis spectroelectrochemistry, electrochemical quartz crystal microbalance, in-situ electron spin resonance, and in-situ conductivity techniques. All polymer films undergo reversible oxidation and partially reversible reduction processes. In poly(N-octyl-2,7-carbazolediyl), two isoelectronic oxidation processes produce radical cations and dications with charge localization at the carbazole subunits. The presence of a strong electron-withdrawing substituent onto the nitrogen atom in the homopolymer leads to an increase by 3 orders of magnitude of the conductivity (i.e., 1 x 10(-2) S/cm). Similarly, in alternating copolymers, the oxidative charge is more delocalized over the polyconjugated backbone with in-situ conductivities in the range of 4 x 10(-2)-4 x 10(-3) S/cm.