Enhanced electrical properties of rigid-rod polymer incorporated with electroactive triarylamino moieties

Oxidatively stable and electrically insulating rigid-rod polymer poly(p-phenylenebenzobisthiazole) (PBT), was incorporated with electroactive triarylamino (TPA) moieties, (R)TPA-PBT with R = NMe2 and Me. Copolymers or homopolymers were synthesized with various TPA fractions changing the polymers to segmentally rigid configuration, and fabricated into films. On cast films, x-ray scattering revealed that the copolymers were random copolymers, microscopy showed "template effect'' from the rigid segments. Iodine activation of the incorporated polymers led consistently to more than five order-of-magnitude increases in electrical conductivity. The activated conductivity also increased with TPA fraction. A conductivity value as high as 4.1 x 10(-4) S/cm was realized for the activated (NMe2)TPA-PBT homopolymer. However, temporal stabilities were observed for the conductivity, which seemed to depend on the polymer composition and film morphology. Spectroscopic examination detected no new electronic state generated by iodine doping. Instead, optical absorbance was drastically increased for h nu greater than 2 eV with a change in film color. Both enhanced conductivity and absorbance were not exhibited by the iodine-activated PBT polymer. (C) 1999 American Institute of Physics. [S0021-8979(99)04001-3].