Spontaneous microstructure formation at water/paraffin oil interfaces

Mickaël Antoni (1) , Murielle Schmitt (1) , Ritu Toor , Renaud Denoyel (1)

1 MADIREL - Matériaux divisés, interfaces, réactivité, électrochimie

An experimental investigation of spontaneous emulsification is proposed with water drops pendant in a paraffin oil (PO) solution loaded with a surfactant (SPAN80). Optical microscopy in 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 due to interface modification with a characteristic time that depends upon the SPAN80 concentration. For low concentrations, spontaneous emulsification is slow and produces micrometer sized droplets while 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 the process, they appear as deformed objects surrounded by a loose membrane.

Keywords: SPAN80; water/oil interfaces; Spontaneous emulsification; water transport.; microstructures

Domains: Chemical Sciences; Material chemistry

Mickaël Antoni, Murielle Schmitt, Ritu Toor, Renaud Denoyel. Spontaneous microstructure formation at water/paraffin oil interfaces. Langmuir, In press, ⟨10.1021/acs.langmuir.7b02549⟩. ⟨hal-01651056⟩