Effect of nanoconfinement on polymer dynamics: surface layers and interphases

Area of Science:

• Polymer Physics
• Materials Science
• Surface Science

Background:

• Understanding polymer dynamics near surfaces is crucial for material properties.
• Previous studies suggested a glassy, immobile surface layer in confined polymer melts.
• The exact nature of polymer-surface interactions and their impact on dynamics remains debated.

Purpose of the Study:

• To investigate the dynamic phenomena in polymer melts induced by confining surfaces.
• To clarify the structure and mobility of polymer layers at interfaces.
• To challenge existing models of polymer behavior under confinement.

Main Methods:

• Neutron spin echo (NSE) experiments were employed.
• The study focused on polymer melts interacting with a confining surface.
• Analysis centered on dynamic phenomena and chain mobility.

Main Results:

• An anchored surface layer was identified, exhibiting high internal mobility, contrary to glassy models.
• Polymer dynamics under confinement are governed by two distinct phases: bulk-like and surface-anchored.
• A topological interaction between the anchored phase and nearby chains creates an interphase, hindering full chain relaxation.

Conclusions:

• The concept of a glassy surface layer in polymer melts is challenged.
• Polymer dynamics at surfaces are characterized by a mobile anchored layer and a distinct interphase.
• Topological interactions play a key role in mediating polymer dynamics in confined systems.