Chain Flexibility and the Segmental Dynamics of Polymers

Area of Science:

• Polymer physics
• Computational materials science

Background:

• Simulations of freely rotating and freely jointed chains often fail to capture complex polymer dynamics observed experimentally.
• Understanding polymer dynamics is crucial for designing materials with specific mechanical and thermal properties.

Purpose of the Study:

• To investigate the role of torsional rigidity in polymer dynamics using molecular dynamics simulations.
• To identify the common origin of experimentally observed phenomena absent in simplified chain models.

Main Methods:

• Employing molecular dynamics simulations to model polymer chains with varying lengths and torsional potentials.
• Analyzing segmental dynamics, pressure effects, and relaxation time behaviors.

Main Results:

• Torsional rigidity was identified as the common origin for reduced volume effects on segmental dynamics, pressure densification, and non-constant Johari-Goldstein relaxation times.
• These effects become more pronounced with increasing chain rigidity.
• Discrepancies between simulation and experimental observations in simplified models were explained.

Conclusions:

• Torsional rigidity is a critical factor in accurately simulating polymer dynamics.
• Molecular dynamics simulations incorporating torsional potentials provide deeper insights into polymer behavior under varying conditions.
• The findings offer a more realistic model for polymer dynamics, bridging simulation and experimental data.