Ionic glass formers show an inverted relation between fragility and non-exponential alpha-relaxation

Area of Science:

• Materials Science
• Polymer Chemistry
• Physical Chemistry

Background:

• Supercooled liquids transform into amorphous solids at the glass transition temperature.
• Glass formers are classified as strong or fragile based on viscosity changes.
• A correlation between liquid fragility and relaxation non-exponentiality is established but debated.

Purpose of the Study:

• To investigate the relationship between fragility and relaxation in ionic materials.
• To explore the role of ionic interactions in the glass transition.
• To identify new materials with combined processability and mechanical dissipation.

Main Methods:

• Synthesis of charged polymers cross-linked via ionic interactions.
• Characterization of glass transition and mechanical relaxation dynamics.
• Survey of ionic liquids, polymerized ionic liquids, and ionomers.

Main Results:

• Ionic materials exhibit an inverted relationship between fragility and relaxation non-exponentiality.
• Highly charged polymers show a strong glass transition with stretched mechanical relaxation.
• Charged materials universally display a trend opposite to non-charged counterparts.

Conclusions:

• Long-ranged ionic interactions play a crucial role in vitrification.
• The findings challenge the generality of existing correlations in glass-forming materials.
• This research paves the way for designing novel materials with tailored properties.