Zwitterion/BrOnsted Acid Mixtures Showing Controlled Lower Critical Solution Temperature-Type Phase Changes with Water

摘要

A new ammonium-type zwitterion (ZI), N,N-dihexyl-N-monopentyl-3-sulfonyl-1-propaneammonium (N(665)C3S) with adequate hydrophobicity showed reversible and highly temperature-sensitive lower critical solution temperature (LCST)-type phase transitions after being mixed with pure water. Generally for such compounds, those with longer alkyl chains were immiscible with water and those with shorter chains were miscible with water, regardless of temperature. A slightly more hydrophobic ZI than N(665)C3S showed LCST-type phase behavior with water when it was mixed with equimolar amounts of a BrOnsted acid such as trifluoromethanesulfonic acid (HTfO). The phase-transition temperature of the ZI/BrOnsted acid mixed aqueous solution was controllable by water content.