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 impr egnating a PU foam with ferric trifluoromethane sulfonate (ferric triflate) using supercritical carbon dioxide (scCO(2)) containing 0.2-1.3 vol.% etha nol as a cosolvent, and then exposing the foam to pyrrole vapor. Polypyrrol e (PPy) was formed in situ by an chemical oxidative polymerization. The con ductivity of the composite foams ranged from 10(-7) to 10(-2) S/cm, dependi ng on the amount of ethanol and impregnation time used. The amount of PPy p roduced depended on the amount of oxidant absorbed by the foam. For low eth anol concentrations and/or short impregnation time, the PPy produced was co ncentrated at or near the surfaces of the foam sample. The dispersion of th e PPy in the foam was improved by increasing the amount of ethanol and the impregnation time. Ferric trifluoroacetate was more soluble in the scCO(2)/ ethanol solutions, but produced foams with much lower conductivity than did ferric triflate. (C) 2001 Elsevier Science B.V. All rights reserved.