Surface adsorption and thermodynamic properties of mixed system of ionic liquid surfactants with cetyltrimethyl ammonium bromide

摘要

The effects of temperature and concentration of CTAB added into imidazolium-based ionic liquids (C(n)mimBr, n = 10, 12, 16) solution were investigated, and surface active parameters and aggregation of these surfactants were explored by surface tension and conductivity measurements, which include critical micelle concentration (CMC), maximum surface excess concentration (Gamma(max)), minimum surface area per surfactant molecule (A(min)), surface tension at the CMC (gamma(CMC)), adsorption efficiency (pC(20)), and surface pressure (Pi(CMC)), as well as thermodynamic parameters of micellization. The results were reported in the presence of CTAB at 0, 4, 8, 12, and 16 mM for C(10)mimBr, 0, 0.2, 0.4, 0.8, and 1.2 mM for C(12)mimBr, and 0, 0.04, 0.08, 0.12, and 0.16 mM for C(16)mimBr in mixed systems. The increase of the CMCs with temperature were observed, while pC(20), Gamma(max), and standard entropy of aggregation were decreased, indicating that the aggregation is an enthalpy-driven process within the temperature limits of the present study. FT-IR and H-1 NMR measurements revealed that the changes mentioned above were controlled by the electrostatic effect and hydrophobic interactions between CTAB and ILs molecules.