Shear-induced delocalization of polarons in polyaniline-surfactant complexes

A transition for a random coil to an extended chain conformation in dilute polyaniline solutions has been shown to induce delocalization of polarons and to increase the conductivity in the solid state by MacDiarmid et al. We have investigated a similar chain extension during a transition from isotropic to a liquid crystalline phase of polyaniline (PANi). We now report the use of an extra additive, the zinc salt of the dopant, to improve the viscoelastic behavior of the doped PANi complex by applying external force, shearing for the possibility of chain alignment. PANi was initially doped with dinonyl-naphthalenesulfonic acid (DNNSAH), and then controlled amounts of the zinc salt of DNNSAH were added to this doped PANi complex in the solution state. The addition of zinc salt improved the viscoelastic behavior, and we were able to apply manual shear to the solid samples at elevated temperatures. The shearing was shown to induce chain alignment as seen by strong birefringence under the optical microscope and with the layered structure defined by X-ray diffraction experiments at room temperature in the cooled samples only after the shearing of the samples. The delocalization of polarons with free carrier tail extending to the near-infrared (NIR) was observed by UV-NIR spectroscopy to confirm the observed chain extension under the presented conditions. The electrical conductivity increased 3 orders of magnitude after the shear.