Structural relaxation in glassy polymers predicted by soft modes: a quantitative analysis

Area of Science:

• Materials Science
• Computational Physics
• Polymer Physics

Background:

• Polymer glasses exhibit complex structural dynamics, including localized rearrangements.
• Understanding the relationship between vibrational modes and structural changes is crucial for predicting material properties.

Purpose of the Study:

• To quantitatively analyze the correlation between low-energy vibrational modes and structural relaxation events in polymer glasses.
• To investigate the temperature and age dependence of this correlation.
• To determine if soft modes can predict the direction of molecular rearrangements.

Main Methods:

• Computer simulations of quiescent, thermal polymer glasses.
• Quantitative analysis of quasi-localized, low-energy vibrational modes.
• Studying systems in supercooled and aging regimes.

Main Results:

• Soft modes identify regions with up to 7 times higher probability of irreversible rearrangements.
• Correlation between soft modes and rearrangements shows temperature and age dependence.
• Soft modes predict the direction of molecular rearrangements.
• Soft regions are long-lived structural features, persisting for significant system evolution.

Conclusions:

• Quasi-localized, low-energy vibrational modes are reliable indicators of future structural relaxation events in polymer glasses.
• Soft modes provide insights into the spatial and directional aspects of molecular rearrangements.
• These findings enhance our understanding of the dynamics governing the glassy state.