Self-Assembly of Chiral Menthol Molecules from a Liquid Film into Ring-Banded Spherulites

• Published in: Crystal growth & design Vol. 19; no. 7; pp. 4063 - 4069
• Main Authors: Kovács, Tamás, Szűcs, Rózsa, Holló, Gábor, Zuba, Zita, Molnár, János, Christenson, Hugo K, Lagzi, István
• Format: Journal Article
• Language: English
• Published: American Chemical Society 03.07.2019
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/acs.cgd.9b00465

We investigate the growth of spherulites in the wake of a solidification front in a thin film of liquid menthol. We observed that the two enantiomeric forms of menthol ((−)-menthol and (+)-menthol)) form ring-banded spherulites, in which needle-like crystals self-assemble into high- and low-density crystal regions. Interestingly, the racemic mixture produces nonbanded spherulites consisting of closely packed plate-like crystals. In the ring-banded spherulitic growth, we could clearly identify the curvature effect of the solidification front on the pattern formation on a millimeter spatial scale. We developed a numerical model based on the Cahn–Hilliard equation, which qualitatively describes the main features observed in experiments, namely, the formation of periodic ring-banded structures and the curvature effect of the propagating solidification front.