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Updated: Sep 23, 2025
09:32
Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films
Published on: January 26, 2016
8.3K
Simple Rules for Complex Near-Glass-Transition Phenomena in Medium-Sized Schiff Bases
Andrzej Nowok1, Wioleta Cieślik2, Joanna Grelska3,4
1Department of Experimental Physics, Wrocław University of Science and Technology, Wybrzeże Stanisława Wyspiańskiego 27, 50-370 Wrocław, Poland.
International Journal of Molecular Sciences
|May 14, 2022
Summary
Schiff bases exhibit remarkable stability in their supercooled liquid states, even under high pressure. Researchers derived rules for predicting glass transition temperature and identified key interactions governing molecular dynamics.
Area of Science:
- Materials Science
- Organic Chemistry
- Physical Chemistry
Background:
- Glass-forming ability is crucial for organic compounds in optoelectronics.
- Understanding vitrification and near-glass-transition phenomena in Schiff bases is essential.
- Schiff bases, specifically glycine imino esters, are a key family for study.
Purpose of the Study:
- To investigate near-glass-transition phenomena and molecular dynamics of glycine imino esters.
- To explore the stability of the supercooled liquid phase under ambient and high-pressure conditions.
- To establish structure-property relationships and general rules for vitrification in this compound family.
Main Methods:
- Differential scanning calorimetry (DSC)
- Broadband dielectric spectroscopy (BDS)
- X-ray diffraction (XRD)
- Quantum density functional theory (DFT) calculations
- Ambient and high-pressure molecular dynamics simulations
Main Results:
- Exceptional stability of the supercooled liquid phase was observed, even under high pressure.
- Atypical self-organization into stable centrosymmetric dimers through bifurcated hydrogen bonds was confirmed.
- A mathematical formula was derived to predict and tune the glass transition temperature (Tg) and its pressure coefficient (dTg/dp).
- Van der Waals and dipole-dipole interactions were identified as the primary drivers of molecular dynamics and dielectric properties, surprisingly overriding hydrogen bonding effects.
Conclusions:
- General rules governing molecular dynamics and near-glass transition phenomena for glycine imino esters were established.
- The derived formula provides a tool for designing materials with specific thermal properties.
- The study highlights the dominant role of non-hydrogen bonding interactions in the dielectric and dynamic behavior of these Schiff bases.
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