Energetic, surface-chemical and hydrodynamic studies on cetyltrimethylammonium bromide and sodium salicylate

Abstract

<span style="font-size:12.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-in;mso-fareast-language:en-in;mso-bidi-language:ar-sa"="" lang="EN-IN">Molecular interaction between cetyltrimethylammonium bromide (CTAS) and sodium salicylate (NaSal) has been investigated. A 1:1 complex is formed in solution. The mixed solution at this composition micellizes at 0.12 mmol dm^-3 at <span style="mso-bidi-font-style:italic">30^oC<i> </i>, and the mixed micelle binds nearly 55% counter-ions. The molecular complex formation between CTAS and NaSal combination is an exothermic process. The micellization of CTAS-NaSal combination is also exothermic and a two-step process, the overall enthalpy values falling in the range of 10-15 kJ mol^-1 at 30^o C. The micellization process is prominently entropy controlled. The surface excess of CTAB and its minimum area at the air-water interface in NaSal, NaCI and NaSr environments have been determined. The CTAS-NaSal system is non-Newtonian and viscoelastic, and show shear thinning properties.</span></span>