Tuning Crystal Morphology of Succinic Acid Using a Polymer Additive

The effect of the triblock copolymer Pluronic P123 (PP123) on the growth of succinic acid crystals from aqueous solutions is reported at two batch process scales: 10 and 350 mL. The presence of small quantities of PP123 is shown to modify the crystal morphology from plate-like crystals to block-like crystals, in a fully reproducible manner. Increasing the quantity of polymer present, or the concentration of succinic acid used, produces needle-like crystals that are less favorable for processing. In-line process analytical tools (FBRM, PVM, and Raman) were implemented for the larger volume batch processes, allowing the crystallization to be monitored in real time. The effect of the polymer on the metastable zone width (MSZW) has also been determined in designing the crystallization experiments and is presented. In addition, the effect of the individual blocks of the copolymer, poly(ethylene glycol) and poly(propylene glycol), on the crystal morphology was examined, and these findings, together with face indexing and knowledge of the underlying crystal structure, have allowed a possible mechanism to be constructed for the interaction of the polymer with the crystal surface. This mechanism is supported by subsequent recrystallization experiments following washing of the block-like crystals with a nonpolar solvent.