Please login first
Influence of Crystallization Additives on Morphology of Selected Benzoic Acids – a Molecular Dynamics (MD) Simulation Study
* ,
1  University of Latvia

Published: 06 November 2020 by MDPI in The 2nd International Online Conference on Crystals session Crystal Engineering
Abstract:

Two model substances were used in the study – 2,6-dimethoxybenzoic acid (2,6MeOBA) and 3-hydroxybenzoic acid (3OHBA), each having two polymorphic forms, including a form without carboxylic acid homodimers in their crystal structure. For each polymorph 2-3 largest crystal faces were selected for MD simulations and the crystal was cut along these planes by preparing simulation box with these planes facing towards solution. In the performed study it was determined which additives potentially can influence the crystal morphology (based on the selected planes) and possibly also the obtained polymorph achieved by significantly changing crystal growth rate by adsorbing on the surface. For the study 4-5 additives providing different intermolecular interaction possibilities were selected. Growth of both explored surfaces of 2,6MeOBA form I are best inhibited by urea in 1,4-dioxane, while in methanol all explored additives act almost equally. All the studied surfaces of form II dissolved, indicating the very low stability of this. A different effect of urea and para-aminobenzoic acid (PABA) on the morphology of 3OHBA form I was found. In 1,4-dioxane different sorption results were observed for both additives. The growth of {011} surface could be inhibited by urea, but the {020} surface by PABA. The simulations showed that urea could not play a decisive role in the discrimination of 3OHBA polymorphic forms, as it was well sorbed on surfaces of both forms. Meanwhile the simulations showed that trans-stilbene has the potential to inhibit the formation of {110} surface of 3OHBA form II in methanol due to a strong π-π interactions. It was also observed that solvent has notable effect on the sorption of additives. The sorption of the studied additives was notably different in 1,4-dioxane, but in the methanol sorption of all additives was rather similar. Based on the results 1,4-dioxane is probably a better solvent for inhibition of growth of surfaces where hydrogen bonds are the dominant type of interactions. Among the studied additives urea showed the mot complete sorption and the longest residence time on surfaces for both substances with the exceptions of some specific planes. Meanwhile, complete and irreversible adsorption on crystal could also indicate on the possibility of formation of a mixed phase (co-crystal) in the presence of these additives.

Keywords: molecular dynamic simulations; polymorphism; additives; crystal engineering; 2,6-dimethoxybenzoic acid; 3-hydroxybenzoic acid
Comments on this paper
Rocco Caliandro
Relevant paper
This is a relevant paper, where the effect of additives on the crystallization process has been highlighted by detailed simulation studies. Very useful information was derived.



 
 
Top