Micellization parameters of cationic surfactants consisting of the [1-(ethoxycarbonyl)-pentadecyl]trimethylammonium ion and various anions I. Effect of temperature and type of anion on the critical micelle concentration and thermodynamic functions of

摘要

The effect of temperature on the critical micelle concentration of five quarternary ammonium surfactants (SX), having a common [1-(methoxycarbonyl)-pentadecyl]-trimethylammonium cation and bromide, chloride, iodide, rhodanide and hydroxide anions (four of them-SCI, SI, SSCN and SOH-newly synthesized), were studied in aqueous solutions using conductometric and UV spectrophotometric techniques. From the conductometric dependences measured over the temperature range 15-50 deg C (25-50 deg C for iodide salt), the critical micelle concentrations, degrees of counterion binding, and thermodynamic functions of micellization (standard molar Gibbs energy, enthalpy, entropy of micellization and molar heat of micellization) were determined and compared. It was found that the critical micelle concentration increases with temperature in the order SCN < SI < SBr < SCI < SOH. For comparative purposes the critical micelle concentrations for all compounds were also determined by UV-spectroscopy. Conductometry and UV - spectroscopy gave closely similar values for critical micelle concentration.