mz500636s_si_001.pdf (546.07 kB)
Kinetic Polymer Arrest in Percolated SWNT Networks
journal contribution
posted on 2014-12-16, 00:00 authored by Rana Ashkar, Mansour Abdul Baki, Madhusudan Tyagi, Antonio Faraone, Paul Butler, Ramanan KrishnamoortiParticle–polymer attractions
in nanocomposites can cause
significant heterogeneities in the polymer dynamics and remarkably
impact the material properties. Dynamical perturbations are generally
expected to be limited to interfacial polymer segments. However, composites
with highly anisotropic nanoparticles usually exhibit very low percolation
thresholds. In such systems, the overlapping interfacial regions could
result in a complex polymer relaxation behavior that is unanticipated
from dilute nanoparticle dispersions in polymer matrices. To understand
this behavior, we examine a system of percolated single-wall carbon
nanotubes (SWNT) in a polymer matrix, PMMA, which is known to have
strong interfacial binding. Neutron spectroscopy measurements on the
composites reveal not only an interfacial polymer layer that is transiently
pinned to the SWNT surface, but suggest that the percolated network
forms a kinetic cage that dramatically restricts both local and cooperative
relaxations of noninterfacial polymer segments. These findings should
help guide theories and simulations of hierarchical polymer dynamics
in nanocomposites.