Influences and the Mechanism of Additives on Intensifying Nucleation and Growth of <i>p</i>-Methylacetanilide

Abstract

Effectively manipulating crystal nucleation and growth is an essential issue for controlling the crystal morphology. In this work, the effect of additives on promoting crystal nucleation and growth was investigated from both thermodynamic and kinetic perspectives by using p-methylacetanilide as the model compound. Two additives with amide-terminal and halogen-terminal were selected, and it was found that they can promote the nucleation and crystal growth of p-methylacetanilide. It was found that the existence of 4-bromoacetanilide or 4-chloroacetanilide could decrease the solubility and the interfacial energy of p-methylacetanilide in ethanol, thus leading to an easier nucleation process. Furthermore, by measuring the growth rates of the (1 1 0) and (0 1̅ 1) faces of p-methylacetanilide in the absence and presence of additives, it was found that the raised supersaturation was not the only factor for crystal growth intensification. Molecular simulations revealed that the promotion effect was because the amide-terminal of additives bring the halogen-terminal to the proximity of the p-methylacetanilide surface and disrupt the absorbed ethanol layer, thus eliminating the negative influence of solvent on the surface diffusion of p-methylacetanilide.