Conformation of a flexible polymer in explicit solvent: Accurate solvation potentials for Lennard-Jones chains

Abstract

The conformation of a polymer chain in solution is coupled to the local structure of the surrounding solvent and can undergo large changes in response to variations in solvent density and temperature. The many-body effects of solvent on the structure of an n-mer polymer chain can be formally mapped to an exact n-body solvation potential. Here, we use a pair decomposition of this n-body potential to construct a set of two-body potentials for a Lennard-Jones (LJ) polymer chain in explicit LJ solvent. The solvation potentials are built from numerically exact results for 5-mer chains in solvent combined with an approximate asymptotic expression for the solvation potential between sites that are distant along the chain backbone. These potentials map the many-body chain-in-solvent problem to a few-body single-chain problem and can be used to study a chain of arbitrary length, thereby dramatically reducing the computational complexity of the polymer chain-in-solvent problem. We have constructed solvation potentials at a large number of state points across the LJ solvent phase diagram including the vapor, liquid, and super-critical regions. We use these solvation potentials in single-chain Monte Carlo (MC) simulations with n ≤ 800 to determine the size, intramolecular structure, and scaling behavior of chains in solvent. To assess our results, we have carried out full chain-in-solvent MC simulations (with n ≤ 100) and find that our solvation potential approach is quantitatively accurate for a wide range of solvent conditions for these chain lengths.

Study of Hydrophobic Clustering in Partially Sulfonated Polystyrene Solutions with a Systematic Coarse-Grained Model

“…We note that the validity of a pairwise decomposition of the n-body solvation potential has previously been successfully tested for flexible chains in a model solvent, showing that the effects of solvation on chain conformations can be captured with effective two-body interactions. 67,68 We further show that the rescaling approach proposed in the present work provides a way to realistically describe the conformations of partially collapsed polyelectrolyte chains. The dependence of the rescaling factor on the chain length has been theoretically derived and confirmed by results of coarse-grained and extensive, detailed-atomistic, simulations.…”

“…Although an appropriately rescaled pairwise interaction potential does not capture the full multibody nature of hydrophobic clustering in aqueous solution, and needs to be tested for other systems, we herein demonstrate that it is accurate enough to reproduce the properties of an atomistic system composed of partially sulfonated polystyrene chains. We note that the validity of a pairwise decomposition of the n -body solvation potential has previously been successfully tested for flexible chains in a model solvent, showing that the effects of solvation on chain conformations can be captured with effective two-body interactions. , We further show that the rescaling approach proposed in the present work provides a way to realistically describe the conformations of partially collapsed polyelectrolyte chains. The dependence of the rescaling factor on the chain length has been theoretically derived and confirmed by results of coarse-grained and extensive, detailed-atomistic, simulations.…”

Flory-type theories of polymer chains under different external stimuli

“…At present, the main instruments for theoretical investigation of the equilibrium properties of real single polymer chains in the solvent media are still represented by the methods of molecular dynamics (MD) and Monte-Carlo (MC) computer simulations [30][31][32][33][34][35]. Nevertheless, despite the availability of modern powerful supercomputers, full atomistic computer simulations of quite long polymer chains in the explicit solvent still lead to high computational costs.…”

“…Nevertheless, despite the availability of modern powerful supercomputers, full atomistic computer simulations of quite long polymer chains in the explicit solvent still lead to high computational costs. Thus, for the efficient application of these methods to modelling real polymer chains one needs to have (1) a rather accurate coarse-grained model of the macromolecule [35][36][37] and (2) a method of accounting for the solvent effects on the polymer chain conformation [34,38,39]. However, both of these factors of reducing the computational complexity are associated with serious difficulties [34,38,39].…”

Dynamic Feature of Incipient Polymer Collapse below the Theta Point

“…Thus, it is hard to explore theta point dynamics systematically by experiment. In contrast to the experimental method, molecular simulation is a straightforward approach to study the system of this problem. − It is easy to prepare many independent samples. The time evolution for the position of a polymer segment is a direct output.…”