2025 AIChE Annual Meeting

Evidence for a ? Polymorph of Suberic Acid: Influence of Solvent Concentration on Crystallization Pathways

Polymorphism occurs when a single substance can crystallize into more than one crystal structure. These polymorphs exhibit distinct properties due to their differing atomic arrangements. For example, both diamond and graphite are pure carbon: diamond forms a three-dimensional tetrahedral network that makes it extremely hard, whereas graphite consists of stacked, planar sheets that slide easily—hence why graphite writes in pencils while a diamond would not.

Polymorphism is especially important in pharmaceuticals. Clinicians and formulators must ensure that a drug is present in its intended polymorphic form, as using the incorrect form can alter its performance and potentially compromise patient safety.

Suberic acid is an organic molecule used in drug synthesis and delivery, medical implants, and skin treatments. Two polymorphs are well established, α and β, with β generally more stable, but evidence suggests a third, γ, can form under certain conditions. We are investigating this γ polymorph by dissolving suberic acid in various organic solvents, aerosolizing the solutions, drying the resulting particles, collecting the crystals by impaction, and characterizing them with X-ray diffraction (XRD). We also measure particle size distributions with a scanning mobility particle sizer (SMPS).

For suberic acid in acetone at 5 g/L, 1 g/L, 0.5 g/L, and 0.2 g/L, the XRD peaks assigned to the γ polymorph became more prominent as concentration decreased.