Facilitated oxygen transport in poly(alkylmethacrylate-co-vinylimidazole)-cobaltprophyrin membranes

Poly(alkylmethacrylate-co-vinylimidazole) membranes, containing a cobaltporphyrin complex (CoP) which binds specifically and reversibly with molecular oxygen, were prepared. The spectroscopically determined apparent oxygen-binding equilibrium constant was greater for the membrane composed of the methacrylate copolymer with a longer alkyl side chain, which showed lower glass transition temperature (T_g) and larger oxygen solubility coefficient. The apparent oxygen-binding and-dissociation rate constants also increased with decreasing T_g of the membrane. The permeability coefficient and the time lag (low-pressure permeation measurement) increased with decreasing upstream gas pressure. This behavior was analyzed by a dual mode transport model. The oxygen permeability coefficient increased with the length of the alkyl side chain, because the longer chain increases oxygen diffusivity.