A Transferable MARTINI Model of Polyethylene Oxide

Motivated by the deficiencies of the previous MARTINI models of polyethylene oxide (PEO), we present a new model featuring a high degree of transferability. The model parameterization is based 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 of the polymer 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 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 non-ionic surfactants in water; (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.