Interfacial Dynamics in Supported Ultrathin Polymer Films-From the Solid to the Free Interface

Area of Science:

• Polymer Physics
• Materials Science
• Surface Science

Background:

• Understanding molecular dynamics in thin polymer films is crucial for advanced material applications.
• Interfacial effects significantly influence polymer behavior, deviating from bulk properties.

Purpose of the Study:

• To investigate molecular dynamics in ultrathin polymer layers.
• To characterize relaxation times and mobilities in interfacial zones.
• To determine the temperature dependence of molecular motion near interfaces.

Main Methods:

• Broadband dielectric spectroscopy using nanostructured electrodes.
• Atomistic molecular dynamics simulations.
• Analysis of relaxation time distributions above the glass transition temperature (Tg).

Main Results:

• Segmental relaxation rates remain bulklike down to 12 nm film thickness.
• Modified molecular mobilities are observed in interfacial zones (~1.5 nm each).
• Both adsorbed and free interface segments exhibit non-Arrhenius temperature activation.

Conclusions:

• Interfacial regions in ultrathin polymer films display distinct molecular dynamics.
• Non-Arrhenius behavior of interfacial segments is independent of molecular weight and film thickness.
• Findings are relevant for polymer applications in adhesion, coatings, and nanocomposites.