All-atom and coarse-grained force fields for polydimethylsiloxane

By combining the bottom-up and top-down approaches, we have developed a new all-atom (AA) force field from quantum mechanics and experimental data and a new coarse grained (CG) force field from AA simulation and experimental data, for polydimethylsiloxane (PDMS). The AA force field is developed based on the TEAM force field database. The CG force field uses a mapping rule that splits the connecting oxygen into neighbouring CG beads to maintain the charge neutrality of the beads, analytical functional forms including anharmonic terms in the valence terms, and the temperature-dependent free-energy functional form to describe the inter-bead interactions. Broad range of thermodynamic properties of PDMS including density, surface tension, solubility parameter, radius of gyration and glass transition temperature are calculated to validate the force fields, and good agreements with the experimental data are obtained.