COLL 85 |
| Tatiana F. Svitova and Clayton J. Radke. Chemical Engineering Dept, U of CA, Tan Hall, Berkeley, CA 94720-1462 |
| We extend classical drop-shape tensiometry by immersing a pinned sessile drop/bubble in an optical cell with continuous stirring and flow through the cell. Ideal mixing eliminates mass transfer resistance and permits detection of sorption kinetic barriers to and from the external aqueous phase with time constants longer than ~ 1 min. Ad/desorption is instantaneous for monodisperse nonionic CnEm surfactants. These surfactants below their CMC exhibit no detectable sorption-activation barriers on time scales studied. Polydisperse nonionic surfactants load in good agreement with local-equilibrium theory but show deviation from the theoretical washout curves, presumably due to slow desorption water-insoluble components. The nonionic block copolymer Pluronics® exhibit almost complete irreversible adsorption at the air/water interface over a molecular-weight range from 3.0 to 14 kDa. The new continuous-flow tensiometer (CFT) provides a powerful tool for sorption dynamics investigations at fluid/fluid interfaces. |
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ACS Award in Colloid and Surface Chemistry Symposium Honoring Clay Radke
Division of Colloid and Surface Chemistry |