Synthesis of Conductive Elastomeric Foams by an In Situ Polymerization of Pyrrole Using Supercritical Carbon Dioxide and Ethanol Cosolvents
Electrically conductive polyurethane (PU) foams were prepared by first impregnating a PU foam with ferric trifluoromethane sulfonate (ferric triflate) using supercritical carbon dioxide (scCO2) containing 0.2–1.3 vol.% ethanol as a cosolvent, and then exposing the foam to pyrrole vapor. Polypyrrole (PPy) was formed in situ by an chemical oxidative polymerization. The conductivity of the composite foams ranged from 10−7 to 10−2 S/cm, depending on the amount of ethanol and impregnation time used. The amount of PPy produced depended on the amount of oxidant absorbed by the foam. For low ethanol concentrations and/or short impregnation time, the PPy produced was concentrated at or near the surfaces of the foam sample. The dispersion of the PPy in the foam was improved by increasing the amount of ethanol and the impregnation time. Ferric trifluoroacetate was more soluble in the scCO2/ethanol solutions, but produced foams with much lower conductivity than did ferric triflate.