Dynamics of interfacial layers—Experimental feasibilities of adsorption kinetics and dilational rheology

• Published in: Advances in colloid and interface science 2011-10, Vol.168 (1), p.167-178
• Main Authors: Mucic, N., Javadi, A., Kovalchuk, N.M., Aksenenko, E.V., Miller, R.
• Format: Article
• Language: English
• Subjects: Adsorption; Capillary pressure; Capillary pressure tensiometry; Diffusion controlled adsorption; Dilational rheology; Drop profile analysis tensiometry; Dynamic surface tension; Dynamics; Feasibility Studies; Impact tests; Kinetics; Langmuir isotherm; Liquids; Maximum bubble pressure method; Models, Theoretical; Oscillating drop method; Rheology; Rheology - methods; Surface-Active Agents - chemistry; Surfactants; Windows (intervals)
• ISSN: 0001-8686; 1873-3727
• DOI: 10.1016/j.cis.2011.06.001

Each experimental method has a certain range of application, and so do the instruments for measuring dynamic interfacial tension and dilational rheology. While the capillary pressure tensiometry provides data for the shortest adsorption times starting from milliseconds at liquid/gas and tens of milliseconds at liquid/liquid interfaces, the drop profile tensiometry allows measurements in a time window from seconds to many hours. Although both methods together cover a time range of about eight orders of magnitude (10 − 3 s to 10 5 s), not all surfactants can be investigated with these techniques in the required concentration range. The same is true for studies of the dilational rheology. While drop profile tensiometry allows oscillations between 10 − 3 Hz and 0.2 Hz, which can be complemented by measurements with capillary pressure oscillating drops and the capillary wave damping method (up to 10 3 Hz) these six orders of magnitude in frequency are often insufficient for a complete characterization of interfacial dilational relaxations of surfactant adsorption layers. The presented analysis provides a guide to select the most suitable experimental method for a given surfactant to be studied. The analysis is based on a diffusion controlled adsorption kinetics and a Langmuir adsorption model. The frequency dependence of the dilational rheology is a very sensitive characteristic for each surfactant. The maximum in the dilational viscosity is directly related to the characteristic frequency of this surfactant, and it depends on the surfactant bulk concentration. [Display omitted] ►The adsorption isotherm spans over two to four orders of magnitude of bulk concentration. ►The dynamic interfacial tension and the dilational rheology describe the adsorption dynamics. ►-To measure the dynamic interfacial tensions typically one experimental method is not sufficient. ► The bubble/drop profile analysis tensiometry and capillary pressure tensiometry are complement. ► Oscillating drops/bubbles based on shape analysis or capillary pressure measurements represent the best techniques for studies of the dilation rheology. ► On the basis of the Langmuir adsorption model the optimum selection of techniques can be proposed.