Modelling the interaction between the poly(octadecyl acrylate) inhibitor and an n-octacosane crystal

The interaction between a growth inhibitor (poly(octadecyl acrylate)) and the surfaces of a paraffin crystal has been modelled using a molecular dynamics technique. A dimer unit of the inhibitor was found to interact strongly with the paraffin crystal surfaces, with good crystallographic matching, and it was readily incorporated into the crystal. The inhibitor introduced some distortion into the local alkane structure and there was an increase in the average energy of the alkane molecules close to the inhibitor. Crystal growth was simulated by the addition of molecules to the surface; both single molecule addition and crystal layer addition were considered. During the growth simulations the open conformation of the inhibitor was found to stabilize a configuration in which a number of alkane molecules spanned the gap between the crystal lamellae. Such an extended defect may play a significant role in the inhibitor mechanism.