Crystal morphology control

CHIRALITY IMPROVEMENT WITH CRYSTAL MORPHOLOGY CONTROL... 

I. Weissbuch, M. Lahav, and L. Leiserowitz, Crystal morphology control with tailor-made additives A stereochemical approach, Adv. Cryst. Growth Res., 381 00 (2001). 

Mesocrystals are a very interesting form of colloidal crystal, as they extend the so far known colloidal crystals with spherical building units to those with non-spherical building units. This offers new possibilities of superstructme formation due to the anisotropic particle shape of the nanoparticle building units [113]. Thus, mesocrystals are colloidal crystals but with extended possibihties for their self-assembled superstructure, offering new handles for crystal morphology control. 

Kurimura, S. and Nakamura, R. (2005) Control of crystal morphology in dewetted films of thienyl dyes. Appl. Phys. A, 80, 903-906. 

Li S, Xu J, Luo G (2007) Control of crystal morphology through supersaturation ratio and mixing conditions. J Cryst Growth 304(l) 219-224... 

Cao, S.W. and Zhu, Y.J. (2009) Iron oxide hollow spheres microwave-hydrothermal ionic liquid preparation, formation mechanism, crystal phase and morphology control and properties. Acta Materialia, 57 (7), 2154-2165. 

The use of tailor made additives holds great promise in the area of crystal growth and morphology control. The routine selection and use of these type of additives will require a fundamental understanding of the mechanism which the additives work on a molecular basis. At the same time, the effect of solvent molecules on the crystal growth process is another related and important problem. In both instances, the relationship between internal aystal structure, aystal growth rate, solvent and impurities are needed to predict the habit of a crystal and thus allow seleaion of the proper conditions and components required to obtain a desired habit... 

The overall rate of growth depends upon the slowest step in this sequence. Crystal growth may be controlled either by the transport processes or by the chemical reaction at the surface. The mechanism of growth and the resulting crystal morphology... 

If we consider NaOH, KOH, and NaF, which act as mineralizers, to be the solvent components, and other minor amounts of elements such as Fe +and Al " to be impurity elements, then the partitioning of these impurity elements is controlled principally by kinetics. The impurity partitioning is related to color, or radiation-induced color, and crystal morphology. 

Similar polycondensation giving crystals was attained by the reaction of 4-hydroxybenzoic acid with 4-ethoxybenzoic acid anhydride, which immediately affords 4-(4-ethoxybenzoyloxy)benzoic acid, a monomer, and monofunctional compound [260]. Polyesters with a DP of 38-76 were obtained even if 30-60 mol % of the anhydride was added to the reaction mixture (Scheme 67). This polycondensation is noteworthy not only as a stoichio-metrically imbalanced polycondensation, but also as a valuable method for morphology control of condensation polymers during polymerization [261]. 

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