A temperature-dependent implicit-solvent model of polyethylene glycol in aqueous solution

TL;DR

This paper develops a temperature-dependent coarse-grained model for polyethylene glycol in water, accurately capturing thermodynamic properties across a wide temperature range using a combined bottom-up and top-down approach.

Contribution

It introduces a novel T-dependent implicit-solvent model with pair potentials derived from atomistic simulations and refined with experimental data, ensuring transferability in temperature space.

Findings

Successfully reproduces the equation of state for PEG solutions.

Accurately predicts the cloud point temperature.

Model is transferable across a wide temperature range.

Abstract

A temperature (T)-dependent coarse-grained (CG) Hamiltonian of polyethylene glycol/oxide (PEG/PEO) in aqueous solution is reported to be used in implicit-solvent material models in a wide temperature (i.e., solvent quality) range. The T-dependent nonbonded CG interactions are derived from a combined "bottom-up" and "top-down" approach. The pair potentials calculated from atomistic replica-exchange molecular dynamics simulations in combination with the iterative Boltzmann inversion are post-refined by benchmarking to experimental data of the radius of gyration. For better handling and a fully continuous transferability in T-space, the pair potentials are conveniently truncated and mapped to an analytic formula with three structural parameters expressed as explicit continuous functions of T. It is then demonstrated that this model without further adjustments successfully reproduces other experimentally known key thermodynamic properties of semi-dilute PEG solutions such as the full equation of state (i.e., T-dependent osmotic pressure) for various chain lengths as well as their cloud point (or collapse) temperature.