Morphological effect of dispersed phase on gas permeation properties through heterophase polymer membrane: theoretical and experimental approaches

The possibility of the continuous channel formation of the dispersed phase in immiscible polymer blends was numerically simulated by adopting the perc olation concept. The numerical simulation showed that the formation probabi lity of the continuous channels increased with the increase in the amount o f the dispersed phase. Further, it increased with the decrease in the domai n size of the dispersed phase at a given blend composition. The effect of t he presence of the continuous channels of the dispersed phase across the me mbranes on gas transport properties was investigated experimentally. The do main size of the dispersed polyisoprene phase of poly(phenylene oxide)/poly isoprene (PPO/PI) blend membranes was controlled by adding the styrene-isop rene-styrene (SIS) block copolymer. When the SIS block copolymer was added at 4 wt% in PPO/PI membranes in the range of the PI content of 20-30 wt%, t he domain size of the dispersed phase was reduced markedly and its permeabi lity was consequently increased. From the theoretical and experimental resu lts, it could be concluded that the abrupt increase in gas permeability of the blend membranes at 20-30 wt% of PI phase may result from the formation of the continuous channels of the more permeable dispersed phase when the b lock copolymer is added. (C) 1999 Elsevier Science Ltd. All rights reserved .