Pseudopeptide bioconjugate additives for CO2 separation membranes

1:1α/α‐N^α‐Bn‐hydrazino] pseudopeptide?polymer bioconjugates were synthesized and investigated as additives in a reference gas separation membrane (Pebax®) for CO₂ capture. Pebax® is a polyether block amide thermoplastic elastomer provided by Arkema and is already well known for its good performance for CO₂ separations. First, dimer and tetramer pseudopeptides were synthesized and their terminal amine was modified into a ‘clickable’ alkyne group in view of coupling. Second, an α‐azido acrylic poly(ethylene glycol)‐based oligomer was obtained by single‐electron transfer living radical polymerization and the two partners were coupled using copper(I) catalyzed alkyne‐azide cycloaddition (CuAAC) ‘click’ chemistry. The pseudopeptides and their bioconjugates were then assessed as original additives in Pebax® membranes for CO₂/CH₄ and CO₂/N₂ separations. The permeation data were analyzed according to the solution‐diffusion model. Compared to pseudopeptides, the pseudopeptide?polymer bioconjugates enabled the membrane properties to be greatly improved with better permeability (×1.5) and a good constant selectivity for CO₂ capture. The best membrane properties were obtained with 3 eq. wt% of the tetramer‐based bioconjugate with a CO₂ permeability of 194 Barrer (+46% compared to that of Pebax®) and constant selectivity (αCO₂/N₂ = 44 and αCO₂/CH₄ = 13). © 2016 Society of Chemical Industry