Pénétration d'alcools à chaîne courte dans les couches monomoléculaires d'alkyl benzène sulfonates adsorbées à l'interface eau-décane. Influence sur l'abaissement de la tension interfaciale

Laboratoire de Chimie Physique, LA 176, Université Pierre et Marie Curie, 11, rue Pierre et Marie Curie, 75 231 Paris, Cedex 05, France.

Résumé

La composition de la couche adsorbée à l'interface eau-décane en présence d’alkyl benzène sulfonâtes et d'alcools à chaine courte est déterminée par application de la relation de Gibbs dans des conditions données de salinité et de température. On met en évidence une forte interaction entre sulfonâtes et alcool qui, cependant, ne semble pas permettre d'attribuer à la seule adsorption de l'alcool à l'interface l'abaissement de tension considérable observé dans certains cas par action de cet additif.

Abstract

As well known, short chain alcohols added as co surfactants extensively decrease the tension at the hydrocarbon — water interfaces with concentrated alkyl benzene sulfonates as surfactants. These compounds can act either by solubilization in the phases or by adsorption at the interface. Whether or not the adsorption process is determining is investigated. The composition of the monolayer adsorbed at the water — decane interface with dodecylbenzene sulfonate and butanol is determined by use of Gibb’s relationship, under given temperature and salinity. The lowest interfacial tension obtained near the cmc, from the most condensed monolayer, is not very low, what means that the adsorption of alcohol alone cannot explain a very low tension. However, the variation of the mean area versus the mole fraction of alcohol in this adsorbed layer shows strong interaction between sulfonate and alcohol so promoting the formation of mixed micelles. It is concluded that micelles are absolutely required for very low interfacial tension and that alcohol probably makes easier the micellization and the solubilization of decane by mixed micelles.