Percolation behavior of gas permeability in rigid-flexible block copolymermembranes

Transport of permeates through copolymer membranes with rigid and flexible block was investigated based on the percolation concept. In terms of the mo rphology, the percolation approach provided a rationale for the property of gas permeation behavior of block copolymer consisting of the rigid amideim ide block and the flexible siloxane block. The permeability of oxygen throu gh poly(amideimide)siloxane (SPAI) membranes containing different siloxane contents showed a peculiar permeation behavior, indicating that there exist ed a percolation threshold of the gas permeation at around 0.2-0.3 volume f raction of SPAI. At above the threshold volume fraction, the gas permeabili ty of this block copolymer was proportional to the probability of spanning siloxane phase. We confirmed that an addition of flexible domains in the ri gid matrix enhanced the rate of gas permeation, and the permeability of SPA I obeyed a simple power law above and near the percolation threshold. In or der to inspect the present system, the percolation concept was reinterprete d to elucidate the change of gas permeability through polymeric membranes w ith rigid and flexible block. (C) 2000 Elsevier Science B.V. All rights res erved.