Molecular dynamics simulation of tracer diffusion of acetonitril in polyacrylamide hydrogels

The diffusional motion of individual acetonitril molecules in polyacrylamid e hydrogels has been investigated by molecular dynamics simulation. The mob ility and the reorientation of the probe particles depend on their location within the polymer network. It can be separated between slow bound molecul es and faster unbound molecules. To uncover the change in diffusion mechani sm, we have followed the motion of individual probe molecules. Strong polym er-solute interactions, which an dominated by hydrogen bonding, result in a significant retardation of the transport properties. In the solvent-rich p ores of the polymer matrix the acetonitril molecules can move freely as in pure water. A comparison of calculated diffusion coefficients reveals good agreement of the MD simulation results with experimental data.