Utilization of Surface Equilibria for Controlling Heterogeneous Nucleation: Making the “Disappeared” Polymorph of 3-Aminobenzensulfonic Acid “Reappear”

Abstract

The ability to control crystal form is essential for the development of materials with desired properties. The rational design of heterosurfaces to control nucleation is one such approach. Heterosurfaces are commonly selected based on their chemistry and/or crystallography and/or morphology. However, the heterosurface is almost always considered to be in equilibrium with the crystallization medium during nucleation. This may lead to an inaccurate description of the epitaxial mechanisms responsible for controlling nucleation. Herein, we discuss controlling the surface equilibria of sparingly soluble crystals to control heterogeneous nucleation and crystal form. The heterogeneous crystallization of 3-aminobenzensulfonic acid (3-ABSA) on seeds of 1,5-diaminonaphthalene (DAN) was investigated. The DAN crystal faces were determined to be in a nonequilibrium state upon suspension in an aqueous solution of 3-ABSA, resulting in significant changes in surface morphology. Controlling the kinetics of surface equilibration resulted in DAN seeds with differing surface morphologies. Seeding with these different surface morphologies led to the nucleation of different crystal forms of 3-ABSA, including the so-called “disappeared” polymorph, Form I. Utilizing surface equilibria to control heterogeneous nucleation represents a highly novel approach to controlling the crystal form.