Model for the hydration of nonpolar compounds and polymers

We introduce an exactly solvable statistical-mechanical model of the hydration of nonpolar compounds, based on grouping water molecules in clusters where hydrogen bonds and isotropic interactions occur; interactions between clusters are neglected. Analytical results show that an effective strengthening of hydrogen bonds in the presence of the solute, together with a geometric reorganization of water molecules, are enough to yield hydrophobic behavior. We extend our model to describe a nonpolar homopolymer in aqueous solution, obtaining a clear evidence of both “cold” and “warm” swelling transitions. This suggests that our model could be relevant to describe some features of protein folding.