Effect of temperature and additives on the critical micelle concentration and thermodynamics of micelle formation of sodium dodecyl benzene sulfonate and dodecyltrimethylammonium bromide in aqueous solution: A conductometric study

Specific conductance of (0.3 to 3.0) mmol center dot kg (1) sodium dodecyl benzene sulfonate (SDBS) and (3.0 to 30.0) mmol center dot kg (1) dodecyltrimethylammonium bromide (DTAB) has been determined in water and in the presence of (0.01, 0.05 and 0.10) mol center dot kg (1) aqueous solution of glutamine/histidine/methionine at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K. From the conductivity data, the critical micellar concentration (CMC) and thermodynamic parameters of micellization (Delta G degrees(m), Delta H degrees(m) and Delta S degrees(m)) have been computed by applying the mass action model. Enthalpy-entropy compensation effect has also been observed. The effect of amino acid on the micellar properties of SDBS and DTAB depends upon their nature, concentration, as well as on temperature and has been used to study the interactions present in the micellar systems. There occurs a gradual increase in the value of CMC with temperature in case of SDBS while in case of DTAB, it passes through a broad minimum and then tends to increase with increase in temperature. Increase of amino acid concentration is found to decrease CMC in both the surfactants. The Delta G degrees(m) values are negative and the feasibility of the micellization is found to increase with rise in temperature. The magnitude of hydrophilic and hydrophobic dehydration determines whether the CMC values increase or decrease with rise in temperature. (C) 2013 Elsevier Ltd. All rights reserved.