Question

In addition to spherical micelles and lamellar phases, a binary amphiphile-water mixture can also form extended cylindrical rolls, with the hydrophilic groups pointing out and the hydrophobic chains on the interior. Over what composition range are such cylinders most likely to be found relative to spherical micelles and planar layers?

Short answer

Cylindrical rolls are formed in a composition range between spherical micelles and planar layers.

Step-by-step solution

Spherical micelles

Spherical micelles come under the class of nanoparticles that has a simple core-shell structure and can form complex nanomaterials.

The structure of a spherical micelle is given below:

The hydrophobic and hydrophilic groups are marked on the diagram.

Lamellar phases

Lamellar phases are the bilayer sheet-like surfactants that have weakly repulsive head groups.

Composition range

When we consider molecular packing, a cylinder comes in between a sphere and a plane layer. The volume fraction of spherical micelles is less than 1/3, cylindrical micelles are between 1/3 and ½, and lamellar micelles are between ½ and 1. So, we can say that the cylinder rolls have a composition range between that of spherical micelles and planar phases.