CO₂ in Lyotropic Liquid Crystals: Phase Equilibria Behavior and Rheology

The CO₂ absorption of liquid crystalline phases of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (Pluronic L92, (EO)₈(PO)₄₇(EO)₈), monoethanolamine (MEA), and water, with a composition of 60% L92/10% MEA/30% water has been investigated to assess potential use in carbon capture and storage applications. Vapor⁻liquid equilibrium data of the liquid crystalline system with CO₂ was recorded up to a CO₂ partial pressure of 6 bar, where a loading of 38.6 g CO₂/kg sample was obtained. Moreover, the phase transitions occurring during the loading process were investigated by small angle X-ray scattering (SAXS), presenting a transition from lamellar + hexagonal phase to hexagonal (at 25 °C). In addition, the rheology of samples with varying loadings was also studied, showing that the viscosity increases with increasing CO₂-loading until the phase transition to hexagonal phase is completed. Finally, thermal stability experiments were performed, and revealed that L92 does not contribute to MEA degradation.