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. Cross-linked 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 type cross-linking and in situ membrane casting. The developed membranes display excellent CO2 separation performance with CO2 permeability ranging from 301 to 561 Barrer with excellent CO2/N2 selectivity ranging from 50 to 59, overcoming the Robeson upper bound (2008). The key finding underlying the excellent performance of the newly developed cross-linked 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 antiaging performance of up to eight months and antiplasticization behavior up to 25 atm pressure.