Aggregation Behavior of Cetyltrimethylammonium Bromide in Aqueous Sodium Hydroxide

Tariq Ahmad Wagay, Abhishek Mukherjee and K. Ismail

Department of Chemistry, NEHU, Shillong-793022

Email: twagay@gmail.com

Abstract:

Understanding the effect of external additives on the aggregation and adsorption behavior of aqueous surfactant solutions is of immense importance due to widespread applications of surfactant-based systems. The cetyltrimethylammonium bromide (CTAB) – sodium hydroxide system is important due to its involvement in the preparation of nanoparticles and hydrolysis of many organic molecules particularly esters. Therefore, critical micelle concentration (cmc) values of CTAB in water in the presence of varying amounts of sodium hydroxide were determined at 25 ◦C by the conductivity and surface  tension  methods.  The  values  of  surface  properties  like  maximum  surface  excess  and minimum area per molecule were computed from the surface tension data. The cmc values of CTAB in aqueous NaOH have been found to be similar to that in aqueous KBr. The Corrin-Harkins equation and also the modified Corrin-Harkins equation provide linear plots indicating that cmc of CTAB in aqueous NaOH depends mostly on the total counterion concentration and very less on the specific type of the anionic counterions (bromide and hydroxyl) present in the solution. The aqueous CTAB + NaOH system also exhibits unusual conductivity behavior.

Keywords:  Cetyltrimethylammonium  bromide;  sodium  hydroxide,  surface  tension,  critical  micelle concentration