Intramolecular dynamic coupling slows surface relaxation of polymer glasses.

Area of Science:

• Materials Science
• Polymer Physics
• Surface Chemistry

Background:

• Studies over three decades show mobile surface layers with steep gradients on glass surfaces.
• Polymers exhibit unique surface dynamics due to intramolecular interactions and chain connectivity, but their role remains unclear.

Purpose of the Study:

• To investigate the fundamental role of intramolecular dynamics and chain connectivity in polymer surface dynamics.
• To understand how polymer chain architecture influences surface mobility and thermal properties.

Main Methods:

• Devised polymer surfaces with varying chain loop penetration depths.
• Conducted surface dissipation experiments.
• Performed Monte Carlo simulations.

Main Results:

• Demonstrated that intramolecular dynamic coupling along surface chains suppresses fast surface dynamics in polymers.
• Observed that accelerated segmental relaxation on polymer glass surfaces significantly slows as chain loops penetrate deeper into the film.
• Found that surface mobility suppression reduces the decrease in glass transition temperature typically seen in thin films.

Conclusions:

• Intramolecular coupling in polymer chains is a key factor controlling surface dynamics.
• Tailoring polymer chain architecture, specifically loop depth, can enhance thermal stability and modify properties at interfaces and under confinement.