Effects of Additives on the Morphology of Thiamine Nitrate: The Great Difference of Two Kinds of Similar Additives

Abstract

The growth of thiamine nitrate, in supersaturated aqueous solutions in the absence and presence of sodium alkyl sulfates CH3(CH2)nSO4Na and sodium alkyl sulfonates CH3(CH2)nSO3Na was studied by a single seed crystal growth experiment. It was surprisingly found that the growth of the a-axis of thiamine nitrate is significantly inhibited by CH3(CH2)nSO4Na, thus reducing the aspect ratio of thiamine nitrate, while the aspect ratio of thiamine nitrate in the presence of CH3(CH2)nSO3Na remains almost constant. Furthermore, the mechanism of additives to modify the crystal morphology is proposed: both additives can inhibit the growth of thiamine nitrate by hindering the solute diffusion. However, their unusual behavior is due to the selective adsorption, which was caused by electrostatic and hydrogen bond interactions between solute and additive molecules. In particular, the anionic groups exposed at the end of the additives demonstrate an interesting case in which a small variation in the charge density and hyd...