Interfacial properties, and micellization of surface-active ionic liquid in presence of polymeric solutions

Abstract

Interfacial properties of newly synthesized surface-active ionic liquid 1-tetradecyl-3-methylimidazolium bromide [C₁₄mim]Br were studied in aqueous solutions of non-ionic polymeric co-solute polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG-200). The interfacial and micellization properties of [C₁₄mim]Br were determined considering various concentrations of PVP and PEG. The critical micelle concentration (CMC) was evaluated using conductivity, contact angle, and surface tension measurements. Thermodynamic properties such as standard enthalpy of micellization, ΔH°_m, standard Gibb's free energy of micellization, ΔG°_m, and standard entropy of micellization ΔS°_m, calculated from micellization and degree of counterion binding (α) values. As the concentration of PEG-200 polymer increased from 1 wt% to 2 wt%, the CMC of SAIL decreased, but CMC increased with temperatures. However, in the case of PVP polymer, the CMC values increased with PVP concentration and temperature. This observation illustrates how the electrostatic and hydrophobic interactions of SAIL with polymers (PEG-200 and PVP) influence SAIL micellization. From the surface tension measurements, CMC, surface tension at CMC (γ_cmc), surface excess concentration (Г_max), surface pressure (π_cmc), and minimum surface area per molecule (A_min) have also been evaluated in water and the presence of polymers (PEG-200 and PVP).