An experimental investigation of spontaneous emulsification is proposed with a water drop pendant in a paraffin oil (PO) solution loaded with a surfactant (SPAN80). Optical microscopy in a transmission mode is employed for high-spatial-resolution image recording. The kinetics of spontaneous emulsification is studied. It is shown to generate a darkening of the drops because of interface modification with a characteristic time that depends upon the SPAN80 concentration. For low concentrations, spontaneous emulsification is slow and produces micrometer-sized droplets, whereas for large concentrations, it is fast and bush-like microstructures are observed. These microstructures increase in size and progressively invade the complete water/PO interfaces, detach, and finally migrate into the PO phase. This transport phenomenon withdraws water from the drops and leads to a gradual shrinking of their volume. At the end of this process, they appear as deformed objects surrounded by a loose membrane.

The kinetics of spontaneous emulsification is investigated on aqueous pendant drops in paraffin oil. Optical microscopy in transmission mode is used for high-spatial-resolution image recording. The influence of a lipophilic surfactant (Span 80) and two water-soluble surfactants (CTAB and SDS) is investigated. As time runs, the drop interface turns opaque due to the formation of microstructures associated with spontaneous emulsification. The time evolution of this phenomenon is shown to depend upon temperature and surfactant concentration, which leads to an overall shrinkage due to gradual water uptake and transport into paraffin oil. Spontaneous emulsification kinetics depends upon the chemical composition. Higher concentrations of Span 80 and CTAB (resp. SDS) are shown to promote (resp. hinder) water transport. This work provides new insights into the understanding of spontaneous emulsification when combining the properties of non-ionic and ionic surfactants.

Among non-covalent bonds, the host-guest interaction is an attractive way to attach biomolecules to solid surfaces since the binding strength can be tuned by the nature of host and guest partners or through the valency of the interaction. For that purpose, we synthesized cyclodecapeptide scaffolds exhibiting in a spatially controlled manner two independent domains enabling the multimeric presentation of guest molecules on one face and the other face enabling the potential grafting of a biomolecule of interest. In this work, we were interested in the β-cyclodextrin/ferrocene inclusion complex formed on β-CD monolayers functionalized surfaces. By using surface sensitive techniques such as quartz crystal microbalance and surface plasmon resonance, we quantified the influence of the guest valency on the stability of the inclusion complexes. The results show a drastic enhancement of the affinity with the gradual increase of guest valency. Considering that the sequential binding events are equal and independent, we applied the multivalent model developed by the Huskens group to extract intrinsic binding constants and an effective concentration of host.