A Coarse-Grained Implicit Solvent Model for Poly(ethylene oxide), CnEm Surfactants, and Hydrophobically End-Capped Poly(ethylene oxide) and Its Application to Micelle Self-Assembly and Phase Behavior

We parametrize a molecular dynamics force field for poly(ethylene oxide) (PEO) within the Dry Martini coarse-grained (CG) implicit solvent model and show that it yields similar distributions of bond lengths, angles and torsional angles, and a similar dependence of radius of gyration on PEO chain length as those obtained from atomistic and explicit solvent CG simulations. We apply these new parameters to simulate self-assembly of long-chain single-end-capped CnEm surfactants and double-end-capped telechelic polymers CnEmCn, where n is the number of alkane carbons and m the number of ethylene oxide monomers. We determine that the average equilibrium micelle aggregation number at high concentrations is around 23 hydrophobes for C12E100, C12E100C12, and C12E200C12, consistent with experimental/theoretical results. However, for EO block less than 200 monomers at 300 K, for example, for C12E45C12 and C12E136C12, telechelic polymers phase separate to form a polymer dense phase at low concentrations due to the formation of bridged flower-like micelles, with critical concentrations for phase separation also in agreement with experimental values.