Structural and thermodynamic signatures of marine microlayer surfactant films
In: Journal of Sea Research. Elsevier/Netherlands Institute for Sea Research: Amsterdam; Den Burg. ISSN 1385-1101; e-ISSN 1873-1414, more Also appears in:Ohlson, M.; Omstedt, A.; Turner, D. (Ed.) (2003). Proceedings of the 22nd Conference of the Baltic Oceanographers (CBO), Stockholm, Sweden, 25-29 November 2001. Journal of Sea Research, 49(4). Elsevier: Amsterdam. 227-374 pp., more | |
Keywords | Agents > Surfactants Physics > Mechanics > Dynamics > Structural dynamics Properties > Physical properties > Thermodynamic properties Properties > Physical properties > Thermodynamic properties > Enthalpy Properties > Physical properties > Thermodynamic properties > Entropy Surface films ANE, Baltic, Gdansk Gulf [Marine Regions] Marine/Coastal | Author keywords | southern Baltic; Gulf of Gdansk; surfactant films; isotherm scaling;surface thermodynamics; visco-elasticity |
Authors | | Top | - Pogorzelski, S.J.
- Kogut, A.D.
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Abstract | Natural surface film experiments in inland waters and shallow offshore regions of the Baltic and Mediterranean Seas were carried out in the time period 1990-1999 under calm sea conditions using a novel device for sampling and force-area studies. The sampler-Langmuir trough-Wilhelmy filter paper plate system `cuts out' an undisturbed film-covered sea area to perform pi-A studies without any initial physico-chemical sample processing. The limiting specific area Alim (2.68-31.57 nm2/molecule) and mean molecular mass Mw (0.65-9.7 kDa) of microlayer surfactants were determined from the 2D virial equation of state applied to the isotherms. Enthalpy deltaH and entropy deltaSt of the 2D first-order phase transitions were evaluated using the Clausius-Clapeyron equation applied to the isotherms. Miscibility of film components and film structure evolution is expressed by the scaling exponent y adopting the 2D polymer film scaling theory. The stress-relaxation measurements revealed a two-step relaxation process at the interface with characteristic times T1=1.1-2.8 and T2=5.6-25.6 seconds suggesting the presence of diffusion-controlled and structural organisation relaxation phenomena. The obtained results suggest that natural films are a complex mixture of biomolecules covering a wide range of solubilities, surface activity and molecular masses with an apparent structural organisation exhibiting a spatial and temporal variability. |
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