Influence of Perfluorohexane‐Enriched Atmosphere on Viscoelasticity and Structural Order of Self‐Assembled Semifluorinated Alkanes at the Air‐Water Interface

Abstract

Semifluorinated alkanes FnHm self‐assemble into nanometer‐sized surface micelles at the air‐water interface. In this study, we investigated how an atmosphere enriched with perfluorohexane (PFH) influences the interfacial viscoelasticity and structural order of a monolayer of FnHm by the combination of dilational rheology and grazing‐incidence small‐angle X‐ray scattering (GISAXS). The monolayers behaved predominantly elastic which can be attributed to the strong dipole repulsions of the surface domains. Enrichment of the atmosphere with PFH lead to an increase of the compressibility and a decrease of the elastic modulus without altering the structural ordering of the FnHm molecules into highly correlated nanodomains, suggesting the adsorption of PFH molecules to the free spaces between the domains. The capability of FnHm domains to retain the structural integrity in the presence of PFH gas is promising for the fabrication of stable microbubbles for sonographic imaging.

Impact of Fluorocarbon Gaseous Environments on the Permeability of Foam Films to Air

“…Contrary to most previous studies, the partial pressure of C 6 F 14 is not constant in our experiments. Linking the additional membrane resistance due to adsorbed fluorinated molecules to their partial pressure is a difficult task, which likely requires neutron or X-ray reflectometry studies. , It is well beyond the scope of this work. However, for the sake of simplicity, it can be assumed that adsorption is reversible and rapid in view of the characteristic gas transfer time (of the order of L / k ∼ 10 s).…”

“…Linking the additional membrane resistance due to adsorbed fluorinated molecules to their partial pressure is a difficult task, which likely requires neutron or X-ray reflectometry studies well beyond the scope of this work. 51,52 However, for the sake of simplicity, it can be assumed that adsorption is reversible and rapid in view of the characteristic gas transfer time (of the order of L/k ∼ 10 s). Under this assumption, the concentration of adsorbed molecules on the membrane as well as the permeability would only depend on the fluorinated gas pressure in compartment 2, P C 6 F 14 ,2 .…”

Influence of Semifluorinated Alkane Surface Domains on Phase Behavior and Linear and Nonlinear Viscoelasticity of Phospholipid Monolayers

“…Recent studies demonstrated that the self-assembled FnHm hemimicelles confined at the air/water interface possess unique viscoelastic properties. ,− Dilational and shear rheology measurements revealed that the system is predominantly elastic, which can be attributed to very poor compressibility (∼7 m/N) and strong dipole repulsions between the micelles . A possible explanation for the low interfacial viscosity is the strong hydrophobic nature of the semifluorinated alkanes, which results in a low friction between FnHm monolayers and the water subphase …”

“…3,11−13 Dilational 10 and shear 9 rheology measurements revealed that the system is predominantly elastic, which can be attributed to very poor compressibility (∼7 m/N) and strong dipole repulsions between the micelles. 12 A possible explanation for the low interfacial viscosity is the strong hydrophobic nature of the semifluorinated alkanes, which results in a low friction between FnHm monolayers and the water subphase. 12 Such unique mechanical properties of surface domains of semifluorinated alkanes open up a broad variety of biomedical applications.…”

“…12 A possible explanation for the low interfacial viscosity is the strong hydrophobic nature of the semifluorinated alkanes, which results in a low friction between FnHm monolayers and the water subphase. 12 Such unique mechanical properties of surface domains of semifluorinated alkanes open up a broad variety of biomedical applications. One potential application is to stabilize microbubbles that are used as contrast agents for ultrasound imaging and drug delivery.…”