The Coarse-grained models of poly(ethylene oxide) and poly(propylene oxide) homopolymers and poloxamers in big multipole water (BMW) and MARTINI framework
Polyethylene oxide (PEO) and poly(propylene oxide) (PPO), especially their tri-block copolymers PEO-PPO-PEO (poloxamers), have a broad range of applications in biotechnology and medical sciences. Understanding their interaction with biomembranes is the key to unveil the unique features of poloxamers either as membrane-healing or membrane pore-forming agents. Based on the coarse-graining convention of MARTINI force field and the big multipole water (BMW) model, which has a three charged site topology and can reproduce correct dipole moment of four-water clusters, we generated coarse-grained (CG) models with analytical as well as numerical potentials for PEO, PPO, and their block copolymers in dilute solutions. The effective bonded interaction potentials between CG beads were determined from probability distribution of bond lengths, angles and dihedrals that are determined from atomistic simulations. The nonbonded interaction potentials were fine-tuned to reproduce conformational properties of atomistic PEO and PPO homopolymers and poloxamers via extensive CG simulations of PEO and PPO homopolymers and poloxamers in BMW water environment. The reported CG models provide a promising framework for describing poloxamers in explicit water environment, and for studying delicate interactions of poloxamers with biomembranes in future work.