Micellization Behavior of Cetyltrimethylammonium Bromide with and Without Triton X—100 in Acetonitrile‐Water Mixed Solvents at Different Temperatures: A Conductometric Study

ABSTRACT The micellization behavior of cetyltrimethylammonium bromide (CTAB) and its mixture with Triton X‐100 (TX100) was studied in pure water and in acetonitrile‐water ( ACN − W) mixed solvents with acetonitrile volume fractions ( VF ) of 0.10, 0.20, 0.30, and 0.40, using conductivity measurements at 298.15, 308.15, 313.15, and 318.15 K. The CTAB concentration ranged from 4.0 × 10 −4 M to 1.0 × 10 −2 M in presence of 2.3 × 10 −5 M TX100. From conductivity data, the critical micelle concentration ( CMC ) and degree of ionization (α) were determined. Both CMC and α increased with increase in temperature and ACN content. Thermodynamic parameter including standard Gibbs free energy of micellization , standard enthalpy of micellization , standard entropy of micellization , and the standard free energy of surfactant tail transfer were calculated. The decreasing in solvent dielectric constant and cohesive forces with increasing VF of ACN content significantly influenced micellization. The negative values confirm the micellization is thermodynamically favorable at equilibrium., while exothermic nature is supported by values of .