  Conformational transitions of flexible molecules, especially those driven by
hydrophobic effects, tend to be hindered by desolvation barriers. For such
transitions, it is thus important to characterize and understand the interplay
between solvation and conformation. Using specialized molecular simulations,
here we perform such a characterization for a hydrophobic polymer solvated in
water. We find that an external potential, which unfavorably perturbs the
polymer hydration waters, can trigger a coil-to-globule or collapse transition,
and that the relative stabilities of the collapsed and extended states can be
quantified by the strength of the requisite potential. Our results also provide
mechanistic insights into the collapse transition, highlighting that polymer
collapse proceeds through the formation of a sufficiently large non-polar
cluster, and that collective water density fluctuations play an important role
in stabilizing such a cluster. We also study the collapse of the hydrophobic
polymer in octane, a non-polar solvent, and interestingly, we find that the
mechanistic details of the transition are qualitatively similar to that in
water.
