Physico-Chemical Investigations of Mixed Micelles of Cationic Gemini and Conventional Surfactants: a Conductometric Stud
- PDF / 342,016 Bytes
- 8 Pages / 595.276 x 790.866 pts Page_size
- 21 Downloads / 176 Views
REVIEW ARTICLE
Physico-Chemical Investigations of Mixed Micelles of Cationic Gemini and Conventional Surfactants: a Conductometric Study Naved Azum • Malik Abdul Rub • Abdullah M. Asiri Aftab Aslam Parwaz Khan • Anish Khan
•
Received: 5 February 2012 / Accepted: 17 July 2012 Ó AOCS 2012
Abstract The interaction of cationic gemini and cationic conventional surfactants by conductivity was systematically overviewed, paying attention to synergism observed in micellization. These mixed systems were found to show remarkable synergism in micelle formation. The experimental critical micelle concentration values being lower than the value predicted by ideal solution theory indicate that the mixed micellization is due to attractive interaction between the two components. Gemini/conventional systems form mixed micelle due to attractive interactions (negative b values). The values of micellar mole fraction of constituent 1 (X1) in surfactant mixtures are more than in the ideal state (Xideal ), 1 which means that, the mixed micelles are rich in conventional surfactants in comparison to that in the ideal state. Keywords Mixed surfactant systems Conventional surfactants Gemini surfactants Interaction parameters Synergism Regular solution theory
Introduction The gemini surfactants [1, 2] (also known as dimeric surfactants [3, 4]), have generated interest in colloid chemistry due to
N. Azum (&) M. A. Rub A. M. Asiri A. A. P. Khan A. Khan Center of Excellence for Advanced Materials Research, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia e-mail: [email protected] N. Azum M. A. Rub A. M. Asiri A. A. P. Khan A. Khan Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia
their superior performance over conventional surfactants in various applications. Menger et al. [5–7] assigned the term ‘‘gemini’’ to the bis-surfactants having a rigid spacer such as benzene or stilbene. The term was then extended to other bis or double tailed surfactants, irrespective of the nature of the spacer. Geminis are considerably more surface active than conventional monomeric surfactants. All geminis possess at least two hydrophobic chains with two ionic or polar head groups having different spacers [8], such as short or long flexible chains of methylene groups, rigid (stilbene), polar (polyether) and non-polar (aliphatic, aromatic) groups (Fig. 1). The head group can be positive (ammonium) or negative (phosphate, sulfate, carboxylate) whereas the polar nonionics may be polyether or sugar-based. The majority of geminis have a symmetrical structure with two identical head groups and two identical chains. Some unsymmetrical geminis with three or more polar groups or tails have recently been reported [9–15]. In contrast to the conventional surfactants (single head/ single tail), the gemini surfactants with their unique chemical structures have been found to possess properties which are superior to those of the former. These include low critical mic
Data Loading...
