Relationship+of+entropy+to+hydrophobic+effect

Basically water cannot form hydrogen bonds with hydrophobic surfaces. As a result, the water molecules are forced to reorient themselves in an ordered fashion to form a hydration shell around the hydrophobic surface. This hydration shell decreases the entropy of the solution which is unfavored. When the hydrophobic molecules or surfaces aggregate together, they reduce the surface area exposed to water and minimize the size of the organized hydration shell that must be formed thus maximizing the possible entropy of the solution.

here's an excerpt from the wikipedia article on the hydrophobic effect http://en.wikipedia.org/wiki/Hydrophobic_effect#The_origin_of_hydrophobic_effect

The hydrophobic interaction is mostly an [|entropic] effect originating from the disruption of highly dynamic [|hydrogen bonds] between molecules of liquid water by the nonpolar solute[|[][|9][|]]. A hydrocarbon chain or a similar nonpolar region or a big molecule is incapable of forming hydrogen bonds with water, introduction of such a non-hydrogen bonding surface into water causes disruption of the hydrogen bonding network between water molecules. The hydrogen bonds are reoriented tangential to such a surface to minimize disruption of the hydrogen bonded 3D network of water molecules and thus leads to a structured water "cage" around the nonpolar surface. The water molecules that form the "cage" (or [|solvation shell]) have restricted mobilities. In the solvation shell of small nonpolar particles, the restriction amounts to some 10%, e.g. in the case of dissolved Xe at room temperature, a mobility restriction of 30% has been found.[|[][|10][|]] In the case of larger nonpolar molecules the reorientational and translational motion of the water molecules in the solvation shell may be restricted by a factor of two to four. Thus at 25°C the reorientational correlation time of water increases from 2 to 4-8 picoseconds. Generally, this leads to significant losses in translational and rotational [|entropy] of water molecules and makes the process unfavorable in terms of [|free energy] of the system.[|[][|11][|]] By aggregating together, nonpolar molecules reduce the [|surface area exposed to water]and minimize their disruptive effect.