Temperature Comparative Studies on Self-Assembly of Sodium Dodecyl Sulphate and Didodecyl Dimethyl Ammonium Bromide in Aqueous,Brine, and Trifluoroethanol Media

An approach based on experimental and theoretical methods was used to compare the self-assembly [i.e., determination of the critical micelle concentration (CMC), degree of ionization (α) and counterion binding (β)] of sodium dodecyl sulfate (SDS) and didodecyl dimethyl ammonium bromide (DDAB) in deionized water and 10 mM NaCl and 10 (vol) % trifluoroethanol solutions. Experimental methods consisted of electrical conductometry, tensiometry, fluorimetry, and determination of Krafft temperature. A critical analysis of the thermodynamics of self-assembly by the Gibbs–Helmholtz equation and the van't-Hoff rationale provided values of several parameters, such as the change of Gibbs free energy and enthalpy change of micellization ( and , respectively) and the Gibbs free energy of surfactant tail groups (∆G⁰_trans). Interfacial properties, aggregation number (N_agg), micropolarity (I₁/I₃), microviscosity (η), packing parameter (P), dielectric constant (D), anisotropy (r), and Stern–Volmer binding constant (K_SV) for SDS and DDAB in different temperatures and different systems were determined.