Multiscale structural characterizations of fatty acid multilayered tubes with a temperature-tunable diameter

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Physical Chemistry

Background:

• 12-hydroxystearic acid forms self-assembled supramolecular tubes via ion-pairing.
• These tubes exhibit temperature-dependent diameter variations, notably a large increase at a specific temperature threshold (T(Ø↑)).

Purpose of the Study:

• To investigate the influence of different counterions on the self-assembly of 12-hydroxystearic acid tubes.
• To understand the relationship between counterion nature, temperature, and tube diameter variation.

Main Methods:

• Systematic measurement of structural parameters using phase contrast microscopy and small-angle neutron scattering (SANS).
• Thermodynamic studies were conducted using differential scanning calorimetry (DSC).

Main Results:

• The temperature threshold (T(Ø↑)) for diameter increase is sensitive to the counterion used.
• No DSC peak correlated with the diameter variation was observed.
• SANS analysis revealed significant softening of multilayer tube walls at T(Ø↑) for all counterions.
• Interlayer spacing and bilayer thickness varied but were not directly related to T(Ø↑).

Conclusions:

• The counterion's nature is a critical factor in the self-assembly and temperature-induced diameter changes of these supramolecular tubes.
• The observed diameter variation is linked to the counterion and the elastic properties of the bilayer stack.