Systematic and Simulation-Free Coarse-Graining of Polymer Melts using Soft Potentials

Full atomistic simulations of many-chain systems such as polymer melts are not feasible at present due to their formidable computational requirements. Coarse-grained models have to be used instead, where the segments interact with soft potentials that allow complete overlapping. This enables systematic coarse-graining with different $N$ (number of segments on each chain) at constant invariant degree of polymerization controlling the system fluctuations. In this work we use integral-equation theories and a relative entropy framework for coarse-graining to investigate how the soft potential varies with $N$ and how well the coarse-grained models can reproduce both structural and thermodynamic properties of the original system. This will provide us with a quantitative basis for choosing small $N$-values that can still capture the chain conformational entropy, a characteristics of polymers.