On the outside are left the polar and charged residues, which form energetically favorable interactions with the water. As a result, nonpolar (also called hydrophobic) residues tend to cluster inside of a protein, protected from the water. These, when surrounded by water, form the same clathrates. In a protein, there are 'oily' residues, those which are nonpolar such as leucine, phenylalanine, valine, etc. As a result, oil association occurs more often than oil solvation. However, there is a much smaller penalty for two oil molecules to associate, and some energetic gain from dispersion. Hence, there is both an entropic penalty and no energetic gain. Additionally, because oil is nonpolar, there is no energetic benefit to water associating. When water meets a nonpolar molecule, it forms highly ordered clathrates similar to those found in ice. Systems tend to greater entropy, unless energy is put into the system to impose order on it. Entropy can be thought of as the state of disorder of a system. The force that drives the oil molecules to associated and separate from the water isn't really an energetic force in the regular sense. Hence, you can't dissolve oil (or hexane) in water. Nonpolar molecules in an aqueous environment are likely self-associate rather than remain solvated. The adage - 'oil and water don't mix' is a manifestation of the hydrophobic effect. The 'force' that sequesters nonpolar sidechains into the hydrophobic core of a protein.

Hydrophobic effect entropy