Monolayers of gemini surfactants and their catanionic mixtures with sodium dodecyl sulfate at the air-water interface: Chain length and composition effects

• Type: Article in International Scientific Journal
• Date: 2008

Authors

Yujie J Wang (Author) Other; Eduardo F Marques (Author) FCUP; Carlos M Pereira (Author) FCUP

Journal

Title: Thin Solid Films

Vol. 516 No. 1

Pages: 7458-7466

ISSN: 0040-6090

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 28 Citations

Scopus - 28 Citations

Scientific classification

FOS: Engineering and technology > Materials engineering

Other information

Authenticus ID: P-003-WVZ

DOI: 10.1016/j.tsf.2008.03.029

Abstract (EN): Monolayers of cationic gemini surfactants and their catanionic mixtures with sodium dodecyl sulfate (SDS), have been investigated with the Langmuir trough technique, at the air-water interface. The gemini surfactants are of the alkanediyl-alpha,omega-bis(alkyldimethylammonium) type, here designated as m-2-m, where m and 2 are the alkyl chain and spacer lengths, respectively. For the neat geminis, the stability of the monolayer increases as the chain length increases, starting from soluble films of 12-2-12 to stable films of 18-2-18. For the equicharged m-2-m/SDS mixtures (with m=12, 14, 16 and 18), stable monolayers are obtained. The effect of the gemini chain length on the phase behavior and molecular organization of the films is discussed on the basis of pressure-area isotherms for compression or compression-expansion cycles. The pressure-temperature plots, at constant trough area, yield the desorption temperature and suggest the desorption mechanism of the film molecules. Furthermore, the effect of the mixing molar ratio between m-2-m and SDS on the isotherms, for m = 12 and 14, has also been investigated. It is concluded from the mean area per molecule that the gemini molecules when in excess with respect to equicharged composition desorb from the film, so that the electroneutral composition is maintained.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9