Supercritical carbon dioxide aided preparation of conductive polyurethane–polypyrrole composites

Conductive polyurethane (PU) foams were prepared using a two-step procedure. First, PU foams were impregnated with the oxidant I2 from a scCO2 solution. Subsequently, the foams were subjected to pyrrole vapor, which polymerized within the foam in the presence of the oxidant. The reduced form of iodine as a result of the oxidative polymerization of pyrrole functions as a dopant. The conductivities of the foams ranged from 10−7 to 10−2 S/cm and the foams were flexible and not brittle. The concentration of conductive polypyrrole, i.e. the PPy–I2 charge-transfer complex, needed to achieve a conductivity of 10−4–10−3 S/cm was about 22% w/w. The solubility of I2 in scCO2 and the partition coefficients of I2 between PU foam and scCO2 solution were determined.