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Updated: Jul 19, 2026

Environmentally-controlled Microtensile Testing of Mechanically-adaptive Polymer Nanocomposites for ex vivo Characterization
Published on: August 20, 2013
Dynamics and internal stress at the nanoscale related to unique thermomechanical behavior in polymer nanocomposites
R Aravinda Narayanan1, P Thiyagarajan, S Lewis
1Intense Pulsed Neutron Source Division, Argonne National Laboratory, Argonne, Illinois 60439, USA. raghavanan@ornl.gov
Abstract:
A small amount of alumina nanoparticles in polymethylmethacrylate causes a sharp depression of the glass transition temperature (Tg) accompanied by a toughening of the composite. We investigated this phenomenon using multispeckle x-ray photon correlation spectroscopy. Measurements reveal a dynamic structure factor that has the form exp[-(t/taua)beta], with beta greater than 1. We show for the first time that beta(T) tracks the internal stress at the polymer-particle interface. The internal stress, which we propose arises due to the entropic penalty that the polymer faces in the presence of the nanoparticles, engenders temporally heterogeneous dynamics. In the jammed glassy state, we show that the dominant fast relaxation mode--taumax--aided by a weak dewetting interface relieves the stress and follows the variations in Tg.
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