CO2 in lyotropic liquid crystals: Monoethanolamine-facilitated uptake and swelling

Abstract

Ternary systems consisting of amphiphilic block copolymers/water/monoethanolamine (MEA) have been studied as potential solvents for carbon capture and storage (CCS). The phase behavior of two poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymers with average compositions (EO)8(PO)47(EO)8 (L92) and (EO)3(PO)50(EO)3 (L81) have been investigated by cross-polarized visual observation and small angle X-ray scattering (SAXS). The respective ternary phase diagrams have been studied for systems containing MEA and the equivalent systems containing CO2-loaded MEA. The presence of MEA loaded with CO2 hinders self-association, preventing the formation of liquid crystalline phases. One-phase liquid crystalline regions were found at low MEA concentrations (below 20 wt %) in L92. In the case of L81, only one one-phase region consisting of coexisting lamellar and disordered aggregates was found at 5 wt % MEA. The swelling of the liquid crystalline phases with MEA was investigated along designated dilution lines. The lattice parameters of L92 liquid crystals decrease upon addition of MEA, whereas L81 aggregates show the opposite behavior.