Gas permeation of poly(amide-6-b-ethylene oxide) copolymer

Block copolymers exhibit a different gas permeation behavior from that of homopolymers. In the diffusion process, the fraction of impermeable regions in the block copolymer decreases the diffusivity and the permeability. As the amount of impermeable regions in the block copolymer increases, the flow paths for the gas diffusion are restricted. Poly(amide-6-b-ethylene oxide) (PEBAX^®) copolymer consists of a regular linear chain of rigid polyamide for hard segment interspaced with flexible polyether for soft segment. PEBAX^® copolymer shows a typical permeation behavior of rubbery polymers. The permeability of CO₂ increases with the pressure originating from the increment of the sorbed CO₂ amounts. PEBAX^® copolymer shows the high permeability and the high selectivity for polarizable/nonpolar gas pairs. Particularly, the selectivity of CO₂ over N₂ is 61 and that of SO₂ over N₂ is 500. For small and nonpolar gases (i.e. He, H₂, O₂ and N₂), the permeability decreases with increasing the molecular size or volume of gases. On the other hand, for polarizable and larger gases (i.e. CO₂ and SO₂), it shows the high permeability. The high permeability and permselectivity of PEBAX^® copolymer are attributed of polarizable gases to polyether segment in PEBAX^®.