Morphology and Growth of Methyl Stearate as a Function of Crystallization Environment

Abstract

In situ studies of methyl stearate growing from supersaturated n-dodecane, kerosene, and toluene solutions reveal strong evidence that solvent choice influences the crystal morphology and crystal growth kinetics. Crystals with similar habit are observed in all solvents, with the exception of lower supersaturations in kerosene, where a less symmetric morphology was observed. BFDH analysis based on the monoclinic C2 crystal structure of methyl stearate yielded the morphological indexation to be (110), (1–10), (−110), and (−1–10) for the dominant observed habit and (110) (1–10) (−1–10) (−240) (−3–10) for the less symmetric habit observed in kerosene solvent. Measurements of the growth rate for the (110) and (1–10) faces are similar for all solutions ranging from 0.02 to 1.13 μm/s, for significantly lower values of supersaturation in the case of toluene. The tendency of the growth rate dependence on σ was consistent with the Burton-Cabrera-Frank (BCF) growth mechanism in n-dodecane, the Birth and Spread (B&S) mechanism in kerosene and diffusion controlled in toluene solvent.

Examination of inequivalent wetting on the crystal habit surfaces of RS-ibuprofen using grid-based molecular modelling

“…17 However, the enhanced supersaturations that are often employed in solution crystallisation and variations in crystalline surface chemistries, can result in different crystalline surfaces growing according to different growth mechanisms, which can strongly impact upon the resultant 'as grown' crystal morphology. 1,22,23 Though there has been some evidence for some surface reconstruction of conformationally flexible molecules, 24 the surface to bulk equivalence assumption has been effectively used to model the crystal morphology of organic materials. 12,14,19,[25][26][27] However, molecular modelling techniques have been developed to calculate bulk solution and interfacial intermolecular interactions of a crystal in contact with a solution, 28,29 hence attempting to address the equivalent wetting and proportionality assumptions.…”

Temperature-induced polymorphism in methyl stearate

“…Finally, we should comment on the almost identical lattice parameters of form IV identified in this study and the monoclinic form reported in ref. 18. The only difference is in the assignment of space group (C2/c for form IV compared with C2 in the previous report).…”

“…However, no further structural details were reported. 18 Form II contains one molecule in the asymmetric unit. There are four molecular layers in the unit cell, packed in a tilted manner and forming roof-like "ripples" along the c-axis (Fig.…”

Morphological population balance modelling of the effect of crystallisation environment on the evolution of crystal size and shape of para-aminobenzoic acid

“…3, it can be seen that the diffusion related term with a value of 8.65  10 -4 is over 2 times magnitude larger than that for the surface integration term (5  10 -6 ). Therefore the rate of crystal growth of face {011} is diffusion limited by diffusion mass transfer (Camacho et al, 2016), i.e. the crystal growth is controlled by how fast the solute molecules in bulk solution diffuses from the bulk solution and across the solid/solution boundary layer for integrating with (growing on) the crystal face.…”