Water Transport in PS-B-PEO Copolymer Membranes

Nanostructured polymer membranes are promising materials for CO₂ separation, water purification, and lithium air batteries. Poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO) is an example of such nanostructured membrane with polar phase PEO component; mechanically robust PEO spherulites and hydrophobic PS component. Water transport is an essential parameter needed to properly model the performance of this membrane in various applications. We present the results of sorption, diffusion and desorption of water in PS-b-PEO at various water activities using gravimetric sorption measurements and Fourier transform infrared – attenuated total reflectance (FTIR-ATR) spectroscopy. A direct comparison with PEO homopolymer membrane shows that the presence of water affects both molecular structure and thermal properties of membranes at high water activities. Due to these structural changes, water sorption was found to increase exponentially at high water activity. The crystalline content of the PEO and the presence of glassy PS lamellae will be used to explain the transport results.