Entropy and Fragility in Supercooling Liquids

Area of Science:

• Materials Science
• Physical Chemistry
• Polymer Science

Background:

• The Kauzmann paradox highlights the challenge of understanding the glassy state.
• Structural glassformers exhibit complex energy landscapes and relaxation dynamics.

Purpose of the Study:

• To review the Kauzmann paradox and its implications for glassformer energy hypersurfaces.
• To demonstrate how the Adam-Gibbs relaxation model explains liquid and polymeric glassformer phenomenology.
• To explore the connection between relaxation time pre-exponents and quasi-lattice vibrations.

Main Methods:

• Review of theoretical frameworks (Kauzmann paradox, Adam-Gibbs theory, WLF equation).
• Analysis of extended temperature range relaxation studies.
• Application of boundary conditions to Vogel-Fulcher-Tammann and WLF equations.

Main Results:

• Adam-Gibbs theory qualitatively accounts for strong/fragile liquid patterns and non-ergodic behavior.
• Relaxation time pre-exponents align with quasi-lattice vibration timescales.
• Imposing this boundary condition on VFT fittings yields T0-TK correspondence across a wide Tg range.
• WLF equation fitting under this condition yields polymer fragility measures.

Conclusions:

• The Adam-Gibbs model, constrained by vibrational timescales, provides a unified framework for glassformer relaxation.
• This approach connects thermodynamic and dynamic properties, offering insights into polymer fragility.
• The study provides a consistent interpretation of diverse glassforming systems, including unfolding proteins.