Polypyrrole-coated melamine sponge as a precursor for conducting macroporous nitrogen-containing carbons

Abstract

Macroporous open-cell melamine sponges were coated with a conducting polymer, polypyrrole, during in-situ oxidative polymerization of pyrrole. Two samples, differing in polypyrrole content, 8.2 and 27.4 wt%, were prepared. They were exposed to various temperatures up to 700 degrees C in an inert atmosphere. The macroporous structure and mechanical integrity were preserved after this process. This converted both the polypyrrole coating and the melamine sponge to macroporous nitrogen-containing carbons. The changes in molecular structure in the course of carbonization were followed by elemental analysis and FTIR and Raman spectra. The specific surface area of polypyrrole-coated sponge increased from ca. 90 to ca. 300 m(2) g(-1) along with accompanying increase in the porosity. The conductivity of the sponges was recorded as a function of compression in a newly developed apparatus. The sponge containing 27.4 wt% pyrrole had conductivity of the order of 10(-2) S center dot cm(-1) at 0.1 MPa pressure, which was reduced by four orders of magnitude when exposed to 400-500 degrees C and nearly recovered after the temperature reached 700 degrees C. The sponges were tested in electromagnetic radiation shielding and displayed both radiation absorption and, to a lower extent, radiation reflection proportional mainly to the samples' conductivity.