Hello

CTAB can act in a variety of different ways, but I would guess that "microemulsions" are the best way to explain the formation of nano-rods.

I attached the handout, which I use in one of my classes on this subject.

The information might be a little on the short side, but I would think it is sufficient to get a rough idea.

Cylindrical micelles form a hexagonal structure ("logs", folded together along the length). If they are formed in water, then inside the cylinders are hydrocarbon groups. Around the micelles is water. It can be converted into solid gel additives. If the surfactant micelles are removed with a solvent, then a porous cylindrical structure is obtained.

If hexagonal structures are formed in oil, they are called reverse micelles or microemulsions. Inside the cylinders is water. These are microreactors, in which it is possible to obtain rod-shaped gold crystals by various reactions for the reduction of gold ions.

Best regards.

CTAB is  amphiphilic molecule, which creates highly anisotropic interfacial regions lining the boundary formed by the highly polar aqueous and nonpolar hydrocarbon regions.

CTAB forms micelles or microheterogenous environments in solution.  These micelles have an aggregation number around 80.Usually, surfactants in aqueous solutions form spherical micelles, but some surfactants like CTAB, further associate into rod-like micelles with increasing surfactant concentration. In the case of ionic surfactants, rod-like micelles can only form above a certain additive salt concentration threshold.