(319g) Solvent Effect on Morphology of Crystals

Certain solutes crystallized from different classes of solvents exhibit different crystal size and morphology. For example carboxylic acids such as succinic acid and ibuprofen are known to exhibit varying morphologies from solvents. This work presents a comprehensive study of size and shape of different carboxylic acids in solvents ranging from non polar to highly polar. Crystallization experiments we carried out and size and morphology were analyzed through optical microscope and SEM pictures. The results suggest that for carboxylic acids non-polar solvents tends to give smaller size and higher aspect ratio (ratio between two major dimensions) crystals while polar solvents tend to give larger size and lower aspect ratio crystals. It is our view that hydrogen bonding between the solute carboxylic groups and the solvent plays an important role in the crystal morphology. Another interesting observation is that solutes having higher solubility parameter values tend to form larger size and lower aspect ratio crystals in a given solvent. This observation is consistent to both non-polar and polar solvents. We believe this comprehensive experimental study and the subsequent analysis will help us better understand this phenomenon.