Synthesis of electrically conductive polypyrrole-polystyrene composites using supercritical carbon dioxide: I. Effects of the blending conditions

The electrical conductivity for a polymer composite consisting of polypyrrole (PPy) and an insulating host polystyrene (PS) is reported in this study. The host polymer was blended with pyrrole monomer using either supercritical carbon dioxide (SCCO₂) or high-pressure liquid carbon dioxide (HPLCO₂) as the carrying solvent. After the blending process, the blended host polymer was soaked in an oxidant solution. This process is compared with that of oxidant impregnation. With the same processing conditions, a polymer composite with much higher conductivity was obtained when the blending process was carried out before doping in an oxidant agent. Scanning electron microscope (SEM) and elemental analysis reveal that polymerization proceeded when the blended host polymer was soaking in the oxidant solution. It is observed that SCCO₂ provides better conditions for blending the host polymer with pyrrole monomer than HPLCO₂ at the same density. The maximum conductivity of the polymer composites also increases with temperature and pressure at the same SCCO₂ density.