Abstract
In this communication, the single element version of the fractional Maxwell model (single-FMM or Scott–Blair model) is adopted to quantify the observed behavior of the linear interfacial dilational viscoelasticity. This mathematical tool is applied to the results obtained by capillary pressure experiments under low-gravity conditions aboard the International Space Station, for adsorption layers at the hydrocarbon/water interface. Two specific experimental sets of steady-state harmonic oscillations of interfacial area are reported, respectively: a drop of pure water into a Span-80 surfactant/paraffin-oil matrix and a pure n-hexane drop into a C13DMPO/TTAB mixed surfactants/aqueous-solution matrix. The fractional constitutive single-FMM is demonstrated to embrace the standard Maxwell model (MM) and the Lucassen–van-den-Tempel model (L–vdT), as particular cases. The single-FMM adequately fits the Span-80/paraffin-oil observed results, correctly predicting the frequency dependence of the complex viscoelastic modulus and the inherent phase-shift angle. In contrast, the single-FMM appears as a scarcely adequate tool to fit the observed behavior of the mixed-adsorption surfactants for the C13DMPO/TTAB/aqueous solution matrix (despite the single-FMM satisfactorily comparing to the phenomenology of the sole complex viscoelastic modulus). Further speculations are envisaged in order to devise combined FMM as rational guidance to interpret the properties and the interfacial structure of complex mixed surfactant adsorption systems.
Highlights
We report the application of the single element fractional Maxwell model (FMM) to the interfacial dilational viscoelastic results, obtained by capillary pressure experiments under low-gravity conditions aboard the International Space Station, for adsorption layers at the hydrocarbon/water interface
The reported experimental findings show that the fitting values of a single-element fractional Maxwell model (FMM) almost perfectly compare with the observed experimental results of interfacial dilational viscoelasticity, obtained for a sequence of harmonic steady-state oscillations of Span-80 adsorption layers at a water drop interface formed in a paraffin–oil matrix
The behavior of a pure n-hexane drop immersed in an aqueous matrix containing mixed C13DMPO and trimethyl ammonium bromide (TTAB) surfactants cannot be described by a single-element FMM
Summary
A large variety of natural materials and industrial products exhibit a viscoelastic behavior when subjected to periodic or transient stress-strain perturbations, responding to the imposed perturbations with typical frequency spectra or evolving along peculiar time scales [1]. Sharma et al suggested the possible coupling of bulk and interfacial viscoelasticity in case of particular soft matters, where the interfacial contribution is eventually significant to the 3D-viscoelasticity results [19]. In this communication, we report the application of the single element FMM to the interfacial dilational viscoelastic results, obtained by capillary pressure experiments under low-gravity conditions aboard the International Space Station, for adsorption layers at the hydrocarbon/water interface. The experiments with single water-in-oil and oil-in-water drops are important for deeper understanding the fundamental laws governing the dynamic behavior of adsorption layers occurring in real emulsions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
