Surface tension of aqueous amphiphiles.
Surface tension measurements show that at low concentrations a surfactant bearing two ester groups in its chain assembles into small aggregates or else rearranges at the air/water interface to occupy less area per molecule. Only at higher surfactant concentrations do bona fide micelles form. The air/water interface, it is argued, saturates abruptly and cooperatively (as does the aggregation into micelles at the higher concentrations) to give a "critical monolayer concentration". Yet saturation does not reduce the surface tension a great deal. The bulk of surface tension reduction is imparted by monomeric surfactant in the solution via a mechanism that is obscure but may be related in part to the mechanical perturbation of the saturated film during measurement.
Menger
Fredric M
FM
Department of Chemistry, Emory University, Atlanta, GA 30322, USA. menger@emory.edu
Galloway
Ashley L
AL
Chlebowski
Mary E
ME
D000327:Adsorption; D000388:Air; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008823:Micelles; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D017155:Wettability
D008823:Micelles; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; D014867:Water; C022806:dodecyltrimethylammonium; D002266:Carboxymethylcellulose Sodium