Generalized phase behavior of small molecules and nanoparticles.

Area of Science:

• Physical Chemistry
• Materials Science
• Chemical Physics

Background:

• Predicting phase transitions in molecular systems requires understanding intermolecular interactions, which are challenging to determine a priori.
• Complex molecules and functionalized nanoparticles present particular difficulties in characterizing these interactions.
• Solvent temperature and composition significantly influence these crucial interactions.

Purpose of the Study:

• To introduce a novel method for probing intermolecular interactions in molecular systems.
• To establish a correlation between solubility and a key diffusion metric.
• To provide a generalized understanding of phase behavior in hydrogen-bonding systems.

Main Methods:

• Utilizing pulsed-field gradient spin-echo nuclear magnetic resonance (PFG-SE-NMR).
• Measuring the pair contribution to long-time self-diffusivity (D2).
• Analyzing a diverse range of hydrogen-bonding solutes undergoing crystallization.

Main Results:

• Demonstrated that scaled long-time self-diffusivity (D2) values correlate with material solubility.
• Observed that materials with high solubility exhibit D2 values near hard sphere limits.
• Found that D2 decreases as solubility diminishes, indicating stronger attractive interactions.

Conclusions:

• Established a remarkable correlation between solubility and D2 for hydrogen-bonding solutes.
• Explained generalized phase behavior through attractive forces with short-range extent.
• Highlighted PFG-SE-NMR as a powerful tool for characterizing intermolecular interactions and predicting phase transitions.