Orientation and conductivity in polyaniline .1.

Films of polyaniline doped with (+/-)-camphor sulfonic acid, cast from nz-cresol, exhibit considerable metallic properties. Such films are partially crystalline, but appear macroscopically disordered when probed by X-rays. Changing the X-ray geometry to probe molecular trajectories within the thickness of such films reveals considerable anisotropy; the molecules statistically adopt a chain direction parallel to the film surface. Some degree of ordering is also noted perpendicular to this, i.e. in the direction of the film thickness, indicating some alignment of the polymer/counter ion complex. We believe that the origin of this orientation lies in a complex interaction between molecule, dopant and solvent whereby the polymer adopts an extended, swollen conformation in solution. On removal of solvent these structures deposit as 'stiff logs'. Such orientation increases the intrinsic ordering within the materials, thus allowing metallic properties to be revealed. By selecting only one enantiomer for doping, less steric disruption is found and a more ordered structure with greater orientation can develop. Such materials exhibit a greater conductivity and enhanced metallic features as compared to polymers doped by (+/-)-camphor sulfonic acid. (C) 1997 Elsevier Science Ltd.