Mixed gas water vapor/N2 transport in poly(ethylene oxide) poly(butylene terephthalate) block copolymers

Water starts to cluster at higher concentrations of water in the polymer, as revealed by a Zimm and Lundberg cluster analysis of the sorption isotherm and by FTIR-ATR. The latter technique shows that the interactions between water and the polymer become weaker as the amount of water in the block copolymer increases. This observation suggests that the decrease in interaction energy between water and the polymer must be compensated by an entropy gain, because the solubility of water vapor increases with an increase of activity.