Interfacial effect of molecules on nucleation kinetics

Abstract

Interfacial effects of molecules on nucleation kinetics of paracetamol were systematically examined for the first time. The effects can be classified into (a) the interfacial nucleation barrier lowering effects, described by a so-called interracial correlation parameter, f(m,R′); and (b) the kink integration effect, described by kink kinetic coefficient βkink. The second effect includes that the effect of desolvation of additives or impurities from the adsorption sites of embryo surface, and the induced pre-ordering of liquid at the substrate-fluid interface. Additives m-acetamidophenol and p-acetoxyacetanilide inhibit paracetamol nucleation by adsorbing on the surface of paracetamol, which suppresses the interface epitaxial effect (the nucleation barrier lowering effect) (f(m,R′) → 1) and enhancing the desolvation energy barrier (βkink → 0), whereas p-hydroxybenzoic acid methyl ester only inhibits paracetamol nucleation by enhancing slightly the desolvation energy barrier. Polysaccharide, which forms strains in the solution, will promote nucleation in terms of the induced pre-ordering of liquid molecules. This interface induced pre-ordering effect, identified first time in this work, is different from the classic epitaxial effect. This effect can in principle be utilized to engineer the micro-and nano structure of complex materials.