UNUSUAL GAS-TRANSPORT SELECTIVITY IN A PARTIALLY OXIDIZED FORM OF THECONDUCTIVE POLYMER POLYPYRROLE

Prior investigations have shown that polypyrrole has low gas-transport selectivity. This has been attributed to the microporous morphology o btained when thin films of this polymer are prepared by conventional s ynthetic methods. In this paper we show that polypyrrole with a dense (as opposed to microporous) morphology can be prepared by slowing down the rate of the polymerization reaction. We further demonstrate that a partially oxidized form of this material shows extraordinary gas-tra nsport properties. When the Volume percent of O-2 in the feed-gas stre am was 100% (i.e., pure O-2), this partially oxidized form of polypyrr ole showed an O-2 vs N-2 gas-transport selectivity coefficient of 18. This is one of the highest gas-transport selectivity coefficients to b e reported to date for a polymeric material. The O-2 vs Nz selectivity coefficient was found to increase with decreasing partial pressure of O-2 in the feed-gas stream. When the partial pressure of O-2 was 0.1% (99.9% N-2), the O-2 vs N-2 selectivity coefficient increased to 92. There is no precedent in the Literature for selectivity coefficients o f this magnitude for polymeric materials. The data are consistent with facilitated transport of O-2 in this unique partially oxidized form o f polypyrrole.