ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Micellization of dimethylbenzyldodecylammonium bromide and the micelle association with bromide counterions studied by potentiometry and cryoscopy

F. Kopecký, M. Vojteková, P. Stopjaková, and J. Oremusová

Department of Physical Chemistry, Faculty of Pharmacy, Comenius University, CS-83232 Bratislava

Abstract: Activities of both cations and anions of the antimicrobial surfactant dimethylbenzyldodecylammonium (benzododecinium) bromide were measured in aqueous solutions above critical micelle concentration (CMC) up to 0.1 mol dm^-3 potentiometrically with ion-selective electrodes at 25°C. The concentrations of the free ions in the micellar region and the degree of association  of the micelles of benzododecinium cations with bromide counterions were calculated from the activities. CMC 0.0024 mol dm^-3 was found and it decreased upon the addition of KBr, approximately after Shinoda equation. Cryoscopically measured osmotic coefficients β of the benzododecinium bromide solutions combined with potentiometric results suggested continuously increasing size of the relatively small micelles above CMC, while the concentrations of the free benzododecinium cations decreased.

Full paper in Portable Document Format: 454a463.pdf

Chemical Papers 45 (4) 463–472 (1991)