With global warming, green chemistry has experienced a great development. In this context, fatty acids are surfactants of particular interest since they can be extracted from agricultural resources. The use of an organic counter-ion enables their solubilization in aqueous solution at room temperature where they self-assemble into different supramolecular structures.
Stearic Acid (SA), one of the most common fatty acids in nature, self-assembles in lamellar phases in water. In the other hand, the 12-Hydroxy-Stearic-Acid( 12-HSA) fatty acid, self-assembles (using the same counter ion) in micrometric long multilamellar tubes. Their packing parameter is very similar, and both structures are thermo-sensitive with a transition towards spherical micelles above a threshold temperature, which is however very different from SA to HSA.
In this sense, we have studied the behaviour of SA/12-HSA mixtures in order to find out how this OH group in 12-HSA’s main chain influences thermally, structurally and mechanically the self-assemblies. To determine the structure and thermal properties of the SA/12-HSA self-assemblies, we used different techniques such as DSC, transmittance measurements and SANS experiments. We demonstrated that a doping of SA by a few amount 12-HSA molecules induces strong structural rearrangements whereas the reverse, i.e. doping 12-HSA by SA, almost does not change the structure. By rheology we have found three different modules (G’ and G") states according to the SA/12-HSA ratio.
- Wenlong Xu, Hongyao Gu, Xionglu Zhu, Yingping Zhong, Liwen Jiang, Mengxin Xu, Aixin Song, and Jingcheng Hao, Langmuir, 2015, 5758−5766
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