PEG/PPG–PDMS-Based Cross-Linked Copolymer Membranes Prepared by ROMP and In Situ Membrane Casting for CO₂ Separation: An Approach to Endow Rubbery Materials with Properties of Rigid Polymers

Rubbery polymer membranes prepared from CO2-philic PEO and/or highly permeable PDMS are desired for efficient CO2 separation from light gases (CH4 and N2). Poor mechanical properties and size-sieving ability, however, limit their application in gas separation applications. Crosslinked rubbery polymer-based gas separation membranes with a low Tg based on both PEG/PPG and PDMS units with various compositions between these two units are prepared for the first time in this work by ring-opening metathesis polymerization (ROMP) type crosslinking and in situ membrane casting. The developed membranes display excellent CO2 separation performance with CO2 permeability ranging from 300 to 561 Barrer with excellent CO2/N2 selectivity ranging from 50 to 58, overcoming the Robeson upper bound (2008). The key finding underlying the excellent performance of the newly-developed crosslinked x(PEG/PPG:PDMS) membranes is the formation of a well-connected interlocked network structure, which endows the rubbery materials with the properties of rigid polymers, e.g. size-sieving ability and high thermomechanical stability. Moreover, the membrane shows long term anti-aging performance of up to eight months and anti-plasticization behavior up to 25 atm pressure.