Reversible capture and release of carbon dioxide by binary system of polyamidine and polyethylene glycol

CO₂ absorbents were prepared from polyethylene glycol and the polyamidines having N,N′-disubstituted amidine structure in the main chain synthesized through acid-catalyzed melt polycondensation of orthoesters and α,ω-diamines. The homogeneous binary mixtures with the polyamidines captured CO₂ much more efficiently under CO₂ flow than the one with polyethyleneimine. Furthermore, we investigated the CO₂ capture and release by the binary mixtures in terms of effects of the volatility and the structure of polyamidines, temperature, and polyethylene glycol. Taking into consideration the results thus obtained, we conducted CO₂ capture/release cycles with the CO₂ capture step at 40 °C and with the CO₂ releasing step at 80 °C in an alternating manner, thereby demonstrating the repeatability of CO₂ capture and release by the binary system of the polyamidine and polyethylene glycol.