Dynamically asymmetric binary glass formers studied by dielectric and NMR spectroscopy

Area of Science:

• Materials Science
• Physical Chemistry
• Condensed Matter Physics

Background:

• Binary glass formers exhibit complex dynamics influenced by component interactions.
• Understanding component dynamics is crucial for designing materials with specific properties.

Purpose of the Study:

• To investigate the component dynamics in asymmetric binary glass formers.
• To analyze the dielectric spectra and relaxation behavior of high-Tg and low-Tg components.

Main Methods:

• Dielectric spectroscopy was used to measure the dielectric spectra of m-tricresyl phosphate and quinaldine mixed with toluene.
• A generalized Cole-Davidson (CD) function was applied to analyze the broadened spectra.
• Stimulated echo experiments and NMR relaxation data were used to confirm findings.

Main Results:

• Broadened spectra could not be described by standard Kohlrausch or CD functions, necessitating a generalized CD function.
• Increasing toluene concentration led to common spectral broadening and failure of frequency-temperature superposition.
• The high-Tg component showed atypical weak relaxation broadening, while the low-Tg component displayed pronounced dynamic heterogeneities.

Conclusions:

• A universal evolution of dynamics for both high-Tg and low-Tg components is suggested for mixtures with high Tg contrast.
• Isodynamic points revealed different concentration dependencies and time scales for each component.
• The study highlights significant dynamic heterogeneities in the faster-relaxing low-Tg component.