Thermodynamics of glyme-sodium dodecyl sulfate (SDS) mixed micelle formation via isoperibol solution calorimetry: Temperature, and concentration effects

The enthalpies of mixed micelle formation (ΔmicH) for a number of sodium dodecyl sulfate (SDS)/glycol ether (glyme) systems were determined as a function of the concentration of the glycol ether in the mixed solvent systems and temperature via isoperibol solution calorimetry. The glycol ethers investigated in the present work were diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TEGDME), tetraethylene glycol dimethyl ether (TetraEGDME), and diethylene glycol diethyl ether (DEGDEE). The data from the isoperibol solution calorimeter was also used to directly determine the CMC values of the SDS/glyme mixed micelles. The entropies and Gibbs energies of mixed micellization (ΔmicSandΔmicG) were calculated by the application of the charged pseudo-phase separation model to the calorimetric enthalpies and CMC values. In general, CMC values and mixed micelle formation enthalpies depended strongly on the glyme structure and its concentration in the mixed solvents. The relative contributions to micelle thermodynamics by the ethylene oxide groups and the alkyloxy chain endcaps, and how the locus of solubilization influences the intramicellar surfactant/cosurfactant interactions, are interpreted in terms of alkyl chain interactions, hydrophobic effects, and electrostatic contributions. [Display omitted] •Micelle formation enthalpies for SDS/glycol ether mixed micelles are strongly dependent on glycol ether structure and concentration.•CMC values and mixed micelle formation entropies also depended strongly on the glyme structure and concentration in the mixed solvents.•Significant enthalpy-entropy compensation effects were observed.•Locus of solubilization of glyme strongly influences the intramicellar surfactant/cosurfactant interactions.