Radiation Induced Conductivity in the Composites of Polyaniline-base with Chloral Hydrate

Polyaniline (PANI) is one of the most widely studied conducting polymers due to its relative high conductivity and easier processing with respect to other conductive polymers. The various intrinsic redox states of polyaniline polymers, fully oxidized pernigraniline, fully reduced leucoemeraldine and 50% oxidized emeraldine can be given. The base form of emeraldine (PANI-base) is non-conductive (10-10 S cm-1) and the salt form emeraldine (PANI-salt) is the most conducting (1 S cm-1) form of polyaniline. PANI-base can be doped to increase its conductivity either by protonation with a protonic acid or by charge transfer using an oxidation agent. In a series of studies from this laboratory we have used radiation as a tool to release HCl from appropriate additives to PANI. The protonic acid (HCl) doping has been extensively studied by blending of PANI-base with poly(vinyl chloride), vinyl chloride/vinyl acetate copolymer (PVC-co-PVAc) and chlorinated poly(propylene) (PPCl), where HCl was obtained by irradiation induced degradation of these chlorine containing polymers. As it is well known, chlorine containing polymers release HCl, when they are exposed to ionizing radiation, which can be captured by the PANI molecules thus enhancing the electrical conductivity of blends. In this study, chlorine containing compound chloral hydrate (C2H3Cl3O2) (ClH) was used instead of chlorine containing polymers. Polyaniline base (PANI-base) composites with ClH were prepared and radiation induced conductivity was studied. The samples with different composition were prepared by grinding proper amounts of components and pelletizing under 5 ton press. The pellets were irradiated in 60Co gamma cell in air at room temperature to different doses up to 200 kGy. Electrical conductivity of the pelletized composites was measured before and after irradiation using four and two probe techniques. Increasing radiation dose resulted in a logarithmic increase in conductivity of PANI-ClH composites up to 100 kGy and beyond this value a decrease was observed. The conductivity change was observed in the range of 10-10 -10-4 S cm-1 up to 200 kGy