Fluid Micellar Threads

Multilayered scrolls, which are commonly formed from water-insoluble lipids upon swelling, offer no possibilities for supramolecular ordering and most of their molecular constituents have no contact with water. Furthermore, the position of dissolved or surface-attached functional molecules can neither be fixed nor determined with any certainty. Thinner surfactant rods are more promising. 

More work is required in order to clarify the molecular structure of these fascinating molecular assemblies which seem to be on the borderline between fluid and solid micellar rods. Their formation develops through a certain type of precipitation, also typical for solid micellar fibres. However, the binding forces between the head group molecules (tetraalkylammonium and phenol) are weak, meaning that the fibres are not as stiff and uniform as the crystalline fibres described later. Aqueous suspensions of the described fibres dissolve massive amounts of small hydrocarbon molecules, e.g. 20 mol % of hexane, but the dissolving of hydrophobic porphyrins in them has not yet been achieved. 

It may be that the polar and disordered spherical micelles and vesicle surfaces are the only parts of molecular assemblies which provide strong solvation power. More ordered structures, even if still liquid, may not have such an effect. 

The mono-tetramethylammonium salt of 2-dodecylmalonic acid also forms rod-like micelles as seen by their viscoelasticity . The concentration range here is 1.4-13 mM. Light microscopy also reveals extremely long threads in sonicated sodium myristate solutions at millimolar concentrations .  

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Figure 5.4 Electron micrographs of fluid micellar threads of cetyltrimethylammonium salicylate.

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