PEG/PPG-PDMS-Based Cross-Linked Copolymer Membranes Prepared by ROMP and In Situ Membrane Casting for CO 2 Separation: An Approach to Endow Rubbery Materials with Properties of Rigid Polymers.

Rubbery polymer membranes prepared from CO ₂ -philic PEO and/or highly permeable PDMS are desired for efficient CO ₂ separation from light gases (CH ₄ and N ₂ ). 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 T _g 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 CO ₂ separation performance with CO ₂ permeability ranging from 301 to 561 Barrer with excellent CO ₂ /N ₂ 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.