Crystallization of organic compounds in reversed micelles. II. Crystallization of glycine and l-phenylalanine in water-isooctane-AOT microemulsions

The crystallization of glycine and I-phenylalanine from water-isooctane mic roemulsions stabilized by AOT (sodium di-2-ethylhexyl sulfosuccinate) has b een investigated. Crystallization phenomena were strongly affected by the l ocalization of the solubilized molecules within the microemulsion droplets. In the case of glycine, which is solubilized within the water pools, a sig nificant reduction in crystal size was observed in the temperature range in vestigated (T-i = 35 degreesC, T-c = 5 degreesC). While crystals formed in aqueous solution usually grow to millimeter sizes, glycine crystals grown f rom;microemulsions were submicron to micron in size. In addition, the alpha -form was only observed from aqueous solution, while the gamma -form was t he predominant form from microemulsions. In the case of phenylalanine molec ules, which are located primarily at the W/O interface, morphology and poly morphism were also affected in addition to crystal size. While phenylalanin e crystallizes from aqueous solution in the form of two polymorphs, i.e., t he needlelike alpha -form and platelike beta -form, upon crystallization fr om microemulsions, only the beta -form appeared. The different crystallizat ion mechanisms of the two amino acids are discussed.