Nucleation inhibitors, design

The supramolecular assembly process can be controlled so that the precursor nuclei in solution adopt a structure that resembles the structure of the desired crystalline modification. " This concept has been used in the design of nucleation inhibitors to prevent growth of the stable polymorph and enhance the growth of the metastable polymorph. Davey and coworkers have explained the solvent dependent polymorph appearance of sulfathiazole by analyzing the intermolecular interactions in the various polymorphic structures, and comparing them with the supramolecular assemblies that could exist in the different solvents. In this case, however, the solvent dependent selective crystallization of a polymorph was not correlated with solubility. 

Torbeev, V.Yu., Shavit, E., Weissbuch, Leiserowitz, L Lahav, M. Control of crystal polymorphism by tuning the structure of auxihary molecules as nucleation inhibitors. The /3-polymorph of glycine grown in aqueous soluhons, Crystal Growth Design. 5(6) (2005) 2190-2196. 

Knowledge concerning the mechanism of hydrates formation is important in designing inhibitor systems for hydrates. The process of formation is believed to occur in two steps. The first step is a nucleation step and the second step is a growth reaction of the nucleus. Experimental results of nucleation are difficult to reproduce. Therefore, it is assumed that stochastic models would be useful in the mechanism of formation. Hydrate nucleation is an intrinsically stochastic process that involves the formation and growth of gas-water clusters to critical-sized, stable hydrate nuclei. The hydrate growth process involves the growth of stable hydrate nuclei as solid hydrates [129]. 

Molecular recognition of crystal interfaces makes possible the control of crystal growth processes in that suitably designed auxiliary molecules aci as promoters or inhibitors of crystal nucleation inducing, for instance, the resolution of enantiomers or Ihe crystallization of desired polymorphs and crystal habits. 

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