Modeling hydration water and its role in polymer folding

The hydrophobic effect is the dominant force which drives a protein towards its native state, but its physics has not been thoroughly understood yet. We introduce an exactly solvable model of the solvation of non-polar molecules in water, which shows that the reduced number of allowed configurations of water molecules when the solute is present is enough to give rise to hydrophobic behaviour. We apply our model to a non-polar homopolymer in aqueous solution, obtaining a clear evidence of both ``cold'' and ``warm'' collapse transitions that recall those of proteins. Finally we show how the model can be adapted to describe the solvation of aromatic and polar molecules.