Abstract
Aim: The micellization behavior of cationic surfactants has been studied in the presence of food additives.
Objectives: Micellization behaviour of cationic surfactants, Cetyltrimethylammonium Bromide (CTAB) and Tetradecyltrimethylammonium Bromide (TTAB) has been studied in water and in various concentrations of salts (food additives) L-glutamic acid, sodium propionate, sodium citrate tribasic dihydrate and disodium tartrate dihydrate at (298.15, 308.15 and 318.15) K.
Methods: Two methods used in the present study are specific conductance measurements and spectroscopy (NMR) studies.
Results: From the specific conductance(κ), various parameters such as Critical Micelle Concentration (CMC), degree of ionization of micelle (α), standard Gibbs free energy (ΔG°m), enthalpy (ΔH°m), and entropy (ΔS°m) of micellization have also been calculated. Thermodynamic parameters related to the micellization process were also analyzed through NMR studies.
Conclusion: The CMC values are influenced by the presence of food additive. The magnitude of CMC values increases with an increase in the concentration of food additive. In all the cases, enthalpy of micellization, ΔH°m values are found to be negative, whereas entropy of micellization, ΔS°m values are positive, which indicates that hydrophobic interactions play a major role in the micellization process. Moreover, NMR studies reveal that tartrate and citrate are more hydrated than glutamic acid and propionate, resulting in a more downfield shift.
Keywords: Cetyltrimethylammonium bromide, critical micelle concentration, enthalpy of micelle formation, entropy of micellization, standard gibbs free energy of micellization, tetradecyltrimethylammonium bromide.
Graphical Abstract
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