title: Dynamic surface activity of phenylalanine glycerol-ether surfactant solutions measured by a differential maximum bubble pressure tensiometer.
abstract: A refined differential maximum bubble pressure tensiometer was used for measuring the dynamic surface tension at various concentrations of a nonconventional surfactant, a member of a new homologous series of phenylalanine glycerol-ether amphiphiles, with 10 carbon atoms to the hydrophobic alkyl chain (C(10)-PhGE). The effective bubble formation frequency for the examined surfactant concentrations was varied from 2 bubbles per second to 1 bubble per 20 s. The variation of equilibrium surface tension with concentration as well as the critical micelle concentration were determined by a Wilhelmy plate technique. Comparisons between dynamic and equilibrium surface tension values demonstrate that, under the employed surface deformation rates, the equilibrium surface tension is a misleading indicator of surface activity. This is also supported by simple surface rheology considerations. Results based on a diffusion-controlled kinetic analysis provide further evidence on the strong dependence of surface activity on the particular time scale of deformation.
authors.affiliation: Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece.
authors.forename: Eleni P
authors.initials: EP
authors.lastname: Kalogianni
authors.forename: Evi M
authors.initials: EM
authors.lastname: Varka
authors.forename: Thodoris D
authors.initials: TD
authors.lastname: Karapantsios
authors.forename: Sofia
authors.initials: S
authors.lastname: Pegiadou