Kinetic Polymer Arrest in Percolated SWNT Networks

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Particle-polymer interactions create heterogeneities in polymer dynamics, affecting material properties.
• Anisotropic nanoparticles in composites can lead to low percolation thresholds and complex dynamics.
• Interfacial effects are typically confined to polymer segments near particles.

Purpose of the Study:

• Investigate polymer dynamics in percolated single-wall carbon nanotube (SWNT) / PMMA nanocomposites.
• Understand how a percolated network influences polymer relaxation behavior.
• Examine dynamics beyond the immediate interfacial regions.

Main Methods:

• Neutron spectroscopy was employed to measure polymer dynamics.
• The study focused on a system of percolated SWNTs within a PMMA matrix.
• Analysis considered both interfacial and non-interfacial polymer segments.

Main Results:

• An interfacial polymer layer was observed to be transiently pinned to SWNT surfaces.
• The percolated SWNT network acts as a kinetic cage, restricting polymer motion.
• Both local and cooperative relaxations of non-interfacial polymer segments are significantly hindered.

Conclusions:

• Percolated networks in nanocomposites induce complex polymer dynamics.
• Kinetic caging by nanoparticles affects polymer segments far from the interface.
• Findings inform theories and simulations of hierarchical polymer dynamics in nanocomposites.