Anisotropic Molecular Organization at a Liquid/Vapor Interface Promotes Crystal Nucleation with Polymorph Selection

Area of Science:

• Physical Chemistry
• Materials Science
• Crystallization Science

Background:

• Molecular organization and dynamics at liquid surfaces differ from the bulk.
• These interfacial differences can influence crystal nucleation and polymorphism.
• The precise impact of surface effects on nucleation remains poorly understood.

Purpose of the Study:

• To investigate and quantify the effect of liquid surfaces on crystal nucleation and polymorphic selection.
• To elucidate the mechanisms behind surface-enhanced nucleation.
• To explore methods for controlling surface-induced crystallization.

Main Methods:

• Studied nucleation in pure liquid d-arabitol.
• Quantified nucleation rates at the surface versus the bulk.
• Investigated the influence of temperature and a second surface-active component.
• Analyzed molecular packing at the interface.

Main Results:

• Surface nucleation of d-arabitol was enhanced by 12 orders of magnitude compared to bulk.
• A different polymorph was selected at the surface.
• The surface effect intensified with cooling.
• A dilute surface-active component inhibited the surface nucleation enhancement.

Conclusions:

• Anisotropic molecular packing at interfaces significantly enhances and alters crystal nucleation.
• Surface-induced crystallization is controllable via temperature and additives.
• Findings are relevant for crystallization in systems with significant interfaces, like nanodroplets and atmospheric water.