Bonded Potentials of Coarse-Grained Polymer Models

In most coarse-grained (CG) polymer models, bonded interactions are heuristically taken to be analogous to those in atomistic models, which consist of bond stretch (two-body), angle bend (three-body), and sometimes torsion (four-body) potentials, but among consecutive CG segments (superatoms), instead of atoms, on the same chain. These bonded potentials are used to reproduce only the local intrachain structures. Also, they and non-bonded CG potentials are often obtained sequentially, sometimes even independently. In our recent work [D. Yang and Q. Wang, Soft Matter 11, 7109 (2015)], however, we showed that bonded CG potentials (taken to be isotropic pair potentials), in the most commonly used structure-based coarse graining (which reproduces some distribution functions of the original system), need to reproduce the intrachain segment pair correlations functions at all length scales, and that bonded and non-bonded CG potentials are coupled and need to be obtained simultaneously. Here we show how to achieve these in various ways by combining theories and simulations, for the case where each CG segment represents the center-of-mass of a group of consecutive monomers on the same chain.