Transferable MARTINI Model of Poly(ethylene Oxide)

TL;DR

This paper introduces a new MARTINI coarse-grained model for poly(ethylene oxide) that is highly transferable and accurately predicts properties across various solvents, phases, and copolymer systems, outperforming previous models.

Contribution

A novel MARTINI PEO model with enhanced transferability, calibrated on transfer free energies, chain dimensions, and atomistic distributions, applicable to diverse systems.

Findings

Accurately predicts densities and phase behavior of PEO oligomers.

Reproduces chain dimensions in multiple solvents over broad molecular weights.

Models lipid bilayers and surfactant phase behavior effectively.

Abstract

Motivated by the deficiencies of the previous MARTINI models of poly(ethylene oxide) (PEO), we present a new model featuring a high degree of transferability. The model is parametrized on (a) a set of 8 free energies of transfer of dimethoxyethane (PEO dimer) from water to solvents of varying polarity; (b) the radius of gyration in water at high dilution; and (c) matching angle and dihedral distributions from atomistic simulations. We demonstrate that our model behaves well in five different areas of application: (1) it produces accurate densities and phase behavior or small PEO oligomers and water mixtures; (2) it yields chain dimensions in good agreement with the experiment in three different solvents (water, diglyme, and benzene) over a broad range of molecular weights (1.2 kg/mol to 21 kg/mol); (3) it reproduces qualitatively the structural features of lipid bilayers containing PEGylated lipids in the brush and mushroom regime; (4) it is able to reproduce the phase behavior of several PEO-based nonionic surfactants in water; and (5) it can be combined with the existing MARTINI PS to model PS/PEO block copolymers. Overall, the new PEO model outperforms previous models and features a high degree of transferability.