Dissolution and diffusion of oxygen in and through poly(octyl methacrylate-co-vinylimidazole)/cobaltporphyrin complexed membranes

The dissolution and diffusion processes of oxygen in and through poly (octyl methacrylate-co-vinylimidazole)(OIm)/cobaltporphyrin complexed membranes were discussed. Facilitated oxygen transport through a polymer membrane containing meso-α , α , α , α-tetrakis(o- pivalamidophenyl) porphyrinatocobalt (CoP) as a fixed oxygen carrier was analyzed by a dual-mode transport model. It was found that CoP fixed in the solid membrane rapidly and reversibly bound with oxygen and the oxygen-binding equilibrium constants of CoP (K) was 14 mol^-1 L. The oxygen absorption for the CoP-OIm membrane obeyed a Langmuir-type isotherm, while the nitrogen absorption showed a proportional increase with nitrogen pressure according to Henry's law. The physical solubility coefficient of oxygen (k _D) in the polymer matrix was calculated to be 4.4 × 10 ^-5 cm³ (STP) cm^-3 Pa^-1 according to the adsorption results. Oxygen permeability coefficients (P_o2) of the OIm-CoP membranes steeply increased with a decrease in the pressure difference (p_o2), while P_o2 for the control membrane composed of inactive (oxidized) Co(III)P was small and independent of p_o2, indicating that the CoP carrier fixed in the membrane interacts with oxygen and facilitates oxygen transport. The facilitation factor (G) that indicates the degree of facilitated transport was 9. The ratio of the diffusion coefficient of oxygen for hopping between the fixed carriers (D_c) to the physical diffusion coefficient of oxygen through the matric polymer (D_D) was 0.08.