Characterizing the Interplay between Polymer Solvation and Conformation

Abstract

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.