Microscopic view of accelerated dynamics in deformed polymer glasses

Area of Science:

• Polymer Physics
• Materials Science
• Computational Chemistry

Background:

• Aging polymer glasses exhibit complex relaxation dynamics.
• Understanding these dynamics is crucial for predicting material behavior under stress.
• Molecular dynamics simulations offer a powerful tool to probe these phenomena at the segmental level.

Purpose of the Study:

• To determine the full relaxation time spectrum of aging polymer glasses.
• To investigate the effects of different deformation protocols on relaxation dynamics.
• To identify universal behaviors in relaxation processes.

Main Methods:

• Utilizing molecular dynamics simulations to analyze segmental trajectories.
• Calculating the complete relaxation time spectrum from simulation data.
• Applying three distinct deformation protocols to aging polymer glasses.

Main Results:

• Observed acceleration of dynamics by several orders of magnitude, consistent with experimental findings.
• Directly observed narrowing of relaxation time distributions during creep.
• Computed an acceleration factor showing universal dependence on strain, irrespective of age or deformation protocol.

Conclusions:

• Molecular dynamics simulations accurately capture the complex relaxation behavior of aging polymer glasses.
• The identified universal strain dependence provides a key parameter for understanding and predicting material response.
• Findings offer fundamental insights into the aging and deformation mechanisms of amorphous polymers.