Molecular dynamics calculations of N-methylpyrrolidone in liquid water

A comprehensive molecular dynamics study has been carried out on the structural and dynamical behaviour of N-methylpyrrolidone (MeP) in water. The impetus for these calculations derives from the growing interest in kinetic hydrate inhibitors, of which polyvinylpyrrolidone (PVP) is the prototype. Study of the smallest unit of this polymer provides valuable insight into the effect of the pyrrolidone ring on water. The present study indicates a strong structuring effect of MeP on surrounding water molecules, with up to four solvation shells being clearly discernible around the solute and markedly slower dynamics for water in the vicinity of MeP. Synergistic solvation effects were found to arise from the conjunction of hydrophobic solvation around the methyl group, and hydrophilic solvation around the amide oxygen; this synergism is likely to be important in understanding the role of pyrrolidone, and other lactam rings, in inhibiting clathrate hydrate formation.