Smart ionic liquid/water mixture system with dual stimuli-response to temperature and CO_(2)

Stimuli-responsive materials have important applications in chemistry and chemical engineering.Here,we synthesized five different polyetheramine-fatty acids(PEFA)ionic liquids(ILs),possessing the dual stimuli-responsive ability to temperature and CO_(2).These PEFA ILs have reversible lower critical solution temperature(LCST)phase behavior over a wide temperature range of 37-91℃,and reversible heterogeneous-homogeneous phase transition towards the addition and removal of CO_(2).Furthermore,the droplet size of the IL-water mixture system increased from 6.5 to 21.0 nm as the temperature increased from 25 to 56℃,and then recovered to 6.5 nm when the temperature decreased to 25℃.The addition and removal of CO_(2)also reversibly modulated the droplet size of the system.Results from nuclear magnetic resonance(NMR)and Fourier transform infrared(FTIR)spectra further showed that the temperature-dependent conformation of polyether amine chain in the cation dominates the temperature response,while the reversible formation of bicarbonate and fatty acids(FA)from CO_(2)and anion controls the CO_(2)-based reversible phase transition.Molecular simulations revealed a microscopic response mechanism of the IL-water system to temperature and CO_(2),and a synergistic effect between the dual stimuli of temperature and CO_(2).These findings may provide a basis for the rational design and understanding of ILs-based stimuli-responsive materials and nanoreactors.