Adsorption of MultiLamellar tubes with a temperature tunable diameter at the air-water interface: a process driven by the bulk properties

TL;DR

This study investigates how multilamellar tubes made of ethanolamine salt of 12-hydroxy stearic acid behave at the air-water interface as temperature varies, revealing reversible structural transitions driven by bulk properties.

Contribution

It demonstrates that the temperature-dependent behavior of bulk multilamellar tubes also occurs at the air-water interface, including a reversible unfolding into multilamellar layers around 50°C.

Findings

Tubes exhibit temperature-tunable diameters at the interface.

Unfolding into multilamellar layers occurs around 50°C.

Structural transitions are highly reversible.

Abstract

The behavior at the air/water interface of multilamellar tubes made of the ethanolamine salt of the 12-hydroxy stearic acid as a function of the temperature has been investigated using Neutron Reflectivity. Those tubes are known to exhibit a temperature tunable diameter in the bulk. We have observed multilamellar tubes adsorbed at the air/water interface by specular neutron reflectivity. Interestingly, at the interface, the adsorbed tubes exhibit the same behavior than in the bulk upon heating. There is however a peculiar behavior at around 50\degree for which the increase of the diameter of the tubes at the interface yields an unfolding of those tubes into a multilamellar layer. Upon further heating, the tubes re-fold and their diameter re-decrease after what they melt as observed in the bulk. All structural transitions at the interface are nevertheless shown to be quasi-completely reversible. This provides to the system a high interest for its interfacial properties because the structure at the air/water interface can be tuned easily by the temperature.