Highly Selective Oxygen Permeation through a Poly(vinylidene dichloride)−Cobalt Porphyrin Membrane:  Hopping Transport of Oxygen via the Fixed Cobalt Porphyrin Carrier

A combination membrane having both gas barrier properties and selective oxygen-absorbing and -carrying capability was prepared by complexing poly(vinylidene dichloride- co -vinylimidazole) and meso -tetrakis(α,α,α,α- o -pivalamidophenyl)porphyrinatocobalt (CoP). The vinylidene dichloride copolymer was selected because of its low physical gas permeability and its dense and tough thin-membrane formability even after the CoP complexation. Oxygen permeation was selectively facilitated with the CoP carrier fixed in the membrane, and high oxygen permselectivity (facilitation factor > 25, oxygen/nitrogen permselectivity > 100, permeability 10 -10 cm 3 (STP) cm cm -2 s -1 cmHg -1 ) was observed, e.g., for the membrane containing > 20 wt % CoP at an upstream oxygen partial pressure of 0.5 cmHg. The facilitated oxygen transport was properly analyzed by a dual-mode model to give permeation parameters of the membrane such as the postulated diffusion coefficient of oxygen hopping via the fixed CoP carrier ( D C ). D C was inversely proportional to the average distance between the CoP carrier sites.