Computational Studies of Structure and Dynamics of Clathrate Inhibitor Monomers in Solution

Theoretical studies of five monomer constituents of gas clathrate inhibitorsvinylpyrrolidone, vinylvalerolactam, l-proline (LP), 1-formylpyrrolidine, and (dimethylaminoethyl)methacrylate (DMAEMA)are performed
in the presence of water, with the solvent treated both explicitly and as a continuum. The binding energy
increases as the inhibitor is more polarized, but no clear relationship is found between polarization and free
energy of solvation values. Comparison of the binding energies of the inhibitor−water complexes and analysis
of the hydration shells around the inhibitor sites indicate that short-range interactions influence the clathrate
inhibitor effect more than long-range ones do. The balance of hydrophobic and hydrophilic moieties is found
to be a determinant factor in the behavior of the inhibitor. In contrast to the other monomers, analyses of the
DMAEMA and LP behaviors show that the N site can be associated with the hydrophilic moiety. Besides,
DMAEMA has the best hydrophobic solvation around its methyl groups, resembling clathrate formation around
methane. The time evolution of the mean square displacement and the power spectrum calculated from velocity
autocorrelation functions reveal slight changes in the dynamic behavior of water that are not strong enough
to be considered decisive in the inhibition efficiency.