X-RAY STRUCTURE OF THE POLYANILINE DERIVATIVE POLY(ORTHO-TOLUIDINE) - THE STRUCTURAL ORIGIN OF CHARGE LOCALIZATION

We investigate the structural features of the polyaniline derivative poly(o-toluidine)(POT). In the base form POT is amorphous, with an X-ray diffraction pattern similar to that of emeraldine base EB-I. We estimate from the position of the broad peaks in the amorphous pattern that the interchain spacing is larger in POT-EB than in EB-I. POT hydrochloride is partially crystalline with a diffraction pattern resembling that of emeraldine hydrochloride ES-I. Analysis of the data shows that the crystalline part of POT hydrochloride adopts the ES-I-like structure, with increased zigzag angle of the polymer chain and larger interchain spacing, together with an increased disorder, possibly due to defects in the stacking of polymer chains caused by the bulky CH3 groups. Structure and percent crystallinity evolve with doping level in the same way as in the EB-I-ES-I emeraldine system. These structural results correlate with difference in the electronic properties of POT-ES as compared with ES-I. In particular, the 10(3) decrease in room temperature conductivity of POT-ES compared to ES-I and concomitant localization of conduction electrons in POT-ES as compared with PAN-ES are attributed to the increased separation and decreased coherence between polymer chains leading to quasi-one-dimensional localization of conduction electrons.