(224a) Polymorph Control of Nanosized Organic Molecular Crystals On the Engineered Surfaces

Nanosized crystals are of great interest in a variety of fields. In pharmaceutics, nanosized particle are of great interest in application since enhanced solubility and dissolution rate can potentially enhance bioavailability. Methods to produce nano-sized organic molecular crystals include both ?top down' and ?bottom up'. Top down methods such as milling and high pressure homogenization employ crystal or particle breakage and bottom up methods such as supercritical fluid crystallization and impinging jet crystallization employ high supersaturation. Recently there has been increased interest in employing methods which confine the crystallization volume such as emulsions and the crystallization in nano-pourous material.

In this work we employ patterned surface engineered surfaces that allow us to crystallize from 500 nm droplets while controlling the supersaturation. Results show that we can produce organic molecular nanosized crystals directly from solution with relatively low supersaturation when compared to bulk crystallization with a uniform sizes. 500nm sized bifucntional (hydrophilic and hydrophobic) patterned surfaces were prepared using lithography and Self Assembled Monolayers (SAMs) for depositing droplets of solution to be crystallized upon. By control of solution temperature and solvent evaporation rate, nano-sized crystals are formed on each island. Glycine crystals under 200nm have been generated and characterized by atomic force and Raman microscopy. Polymorphic outcome is shown to depend on supersaturation the generation rate. In addition, our observations suggest that this technique can be used for studying the other physical/chemical properties of nano-sized crystals such as melting point and solubility.