Conformation of a Lennard-Jones Chain in Explicit Solvent: A Solvation Potential Approach

Computer modeling of polymer systems is important both for developing new materials and understanding how biological macromolecules function. This type of modeling is made difficult by the large system sizes required to study a polymer chain in solvent. The problem can be formally simplified by mapping the ``many-body'' chain-in-solvent system to a single chain plus a ``few-body'' effective potential that mimics the role of the solvent. This few-body potential (where few = the number of chain monomers) depends on the instantaneous conformation of the chain and is, in general, not practical to compute. Thus, one generally assumes a two-site decomposition of this potential. Here we use Monte Carlo simulation techniques to study a Lennard-Jones chain-in-solvent system. We construct a set of ``exact'' two-site solvation potentials for a 5-mer chain thereby demonstrating the validity of the two-site approximation. We then construct approximate solvation potentials for long chains, which combine exact short chain results with the pure solvent potential of mean force. Our solvation potential results compare well with simulation results for the full chain-in-solvent systems.