Thermodynamics of micellization of ammoniumdodecyl sulfate in aqueous solutions of symmetrical tetraalkylammonium bromides: Clouding in presence of tetrabutylammonium bromide salt

摘要

The critical micellization concentration (CMC) of ammoniumdodecyl sulfate (ADS) in different tetraalkylammonium bromides (TAAB) viz., tetramethylammonium bromide (TMAB), tetraethylammonium bromide (TEAB), tetrapropylammonium bromide (TPAB), and tetrabutylammonium bromide (TBAB), in the concentration range of 0.0005 to 0.005M were measured by electrical conductivity method. Micelle formation of ADS in these electrolyte media favours CMC reduction in the order TBAB>TPAB>TEAB>TMAB. The thermodynamic parameters of micellization, ΔG°_(mic), ΔH°_(mic), and ΔS°_(mic), were evaluated in 0.001M of different TAAB solutions in the temperature range of 288.15 to 318.15 K. Large positive ΔS°_(mic) values suggest the overall micellization to be entropy driven. ΔH°_(mic) and ΔS°_(mic) compensate each other with compensation temperature of 304±2K. ADS solution manifests clouding in presence of TBAB. With fixed [ADS] and varying [TBAB], CP decreases steeply at the initial [TBAB], but changes little above [TBAB]/[ADS] mole ratio of 1:1. The results have been explained in terms of electrostatic and increased hydrophobic interactions between electrolytes and ADS micelle.