Mechanism of Micelle to Vesicle Transition in Cationic−Anionic Surfactant Mixtures

• Published in: Langmuir Vol. 14; no. 14; pp. 3778 - 3782
• Main Authors: Salkar, R. A, Mukesh, D, Samant, S. D, Manohar, C
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 07-07-1998
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Micelles. Thin films; MO method; Molecular packing; Conformational dynamics; Cationic surfactant; Theoretical study; Sodium compound; NMR spectrometry; Experimental study; Lauryl sulfate; Quaternary ammonium compound; Anionic surfactant; Solution structure; Organic sulfate; Aqueous solution
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la971024v

The present paper investigates the cationic−anionic surfactant mixtures with a view to understand the role of polar head packing in bringing about a vesicle to micelle transition. Differences in behavior between addition of sodium dodecylbenzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS) to cetyltrimethylammonium-p-toluenesulfonate (CTAPTS) solutions are investigated by NMR and molecular modeling techniques. It is concluded that the complex formed between SDS and CTAPTS is more tightly bound than that between SDBS and CTAPTS, leading to precipitation rather than vesicle formation in the latter case. Molecular modeling shows that the SDBS chain has a bend in the molecule, and this facilitates loose packing of the complex neccessary for the formation of vesicles.