The Polymer Society of Korea

Abstract

Membrane-based CO₂ capture systems often suffer from reduced CO₂ permeability under humid conditions. Although this degradation is commonly attributed to polymer plasticization or competitive sorption by water, the underlying transport mechanism remains unclear. So, we investigate the effect of water vapor on CO₂ transport in PDMS membranes by decoupling changes in sorption behavior and transport kinetics through sorption uptake and permeation measurements under humid condition. The results show that water vapor significantly suppresses CO₂ transport, accompanied by reduced CO₂ uptake and slowed transport kinetics. Based on a gas–gas interaction–based mechanistic interpretation, this behavior suggests thermodynamically unfavorable coexistence between CO₂ and H₂O within PDMS rather than plasticization. These findings provide mechanistic insight into humidity-induced transport losses and guidance for membrane design under realistic separation conditions.