Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The micellization of two silicone ionic liquids, 1-methyl-1-[tri(trimethylsiloxy)]- silylpropylpyrrolidinium nitrate (Si4pyNO3) and 1-methyl-1-[tri(trimethylsiloxy)]- silylpropylpyrrolidinium acetate (Si4pyAc), with different counterions was systematically investigated by surface tension and electrical conductivity. Surface tension of water can be reduced almost to 20 mN*m 1 with the addition of the silicone ionic liquids, indicating that the silicone ionic liquids exhibit excellent surface activity. The critical micelle concentration (CMC) values of Si4pyNO3 are less than those of Si4pyAc. Electrical conductivity measurements show that the degree of counterion binding (ss) for Si4pyNO3 is twice as large as that for Si4pyAc. Thermodynamic parameters (?Hm0, ?Sm0, and ?Gm0) of micellization derived from electrical conductivities indicate that the micellization for both Si4pyNO3 and Si4pyAc is enthalpy-driven process. The heat capacities, ?cm,p0, are negative for the two silicone ionic liquids relating to the removal of water accessible nonpolar surfaces. The addition of sodium halides in the aqueous solution decreases CMC remarkably; however, the surface tension at CMC stays the same with the salt-free system.