Characterizing the Interplay between Polymer Solvation and Conformation

TL;DR

This study investigates how solvation influences the conformational transitions of hydrophobic polymers, revealing that external perturbations can induce collapse and that water density fluctuations are key to this process, with similar mechanisms in water and octane.

Contribution

It provides a detailed mechanistic understanding of polymer collapse driven by solvation effects using specialized molecular simulations, highlighting the role of water density fluctuations.

Findings

External potential can trigger coil-to-globule transition.

Collapse involves formation of non-polar clusters.

Similar collapse mechanisms in water and octane.

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.