CO2-Selective Gas Separation Membranes Based on Crosslinked Poly(ethylene oxide) Copolymer Networks

The economic separation of CO2/light gas mixtures is a crucial component in many energy-related processes, both for the purification of desired products (e.g. H2, CH4) and the potential sequestration of carbon dioxide. In recent years, there has been increasing interest in developing membrane materials capable of such separations. Crosslinked rubbery networks with high ethylene oxide content have been shown to display high CO2 permeability and strongly preferential selectivity for CO2 over other light gas components, offering a viable alternative for the removal and capture of CO2 from these mixtures.

The molecular relaxation characteristics of three series of copolymer membrane networks based on bisphenol A ethoxylate diacrylate [BPA-EDA] crosslinker have been investigated using dynamic mechanical analysis and broadband dielectric spectroscopy. The networks were prepared via UV photopolymerization of BPA-EDA with mono-functional acrylates of varying molecular weight, leading to the insertion of ethylene oxide pendant groups along the network backbone. The influence of co-monomer content and pendant length on the glass-rubber and sub-glass relaxation properties of the networks was assessed by dynamic mechanical and dielectric methods. The insertion of increasing amounts of co-monomer branches produced an increase in network fractional free volume that correlated with the measured permeability of the polymers.