Dynamic surface activity of phenylalanine glycerol-ether surfactant solutions measured by a differential maximum bubble pressure tensiometer |
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Authors: | Kalogianni Eleni P Varka Evi M Karapantsios Thodoris D Pegiadou Sofia |
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Institution: | Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece. |
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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. |
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