Long-time interfacial relaxation in aqueous butanol solutions

The long-time relaxation of the dynamic surface tension (DST) in aqueous so lutions of four structural isomers of butyl alcohol has been observed with the aid of the maximum bubble pressure technique. Diffusion-controlled kine tics was found to allow an apparently successful tin terms of the quality o f fitting) description of the observed DST dynamics, but it leads to an unr ealistically low value of the diffusion coefficient, 10(-11)-10(-13) m(2) s (-1). Conversely, the activation-controlled kinetics fails to explain the s low damping of DST curves observed over long time periods. A comprehensive theoretical analysis supported by numerical simulations has conclusively sh own that neither diffusion nor mixed diffusion-activation kinetics can adeq uately account for the observed slower DST relaxation. As an alternative ex planation, the presence of packing defects in the adsorbed layer is propose d.