Dynamics and internal stress at the nanoscale related to unique thermomechanical behavior in polymer nanocomposites

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 s...

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Bibliographic Details
Published in:Physical review letters 2006-08, Vol.97 (7), p.075505-075505, Article 075505
Main Authors: Narayanan, R Aravinda, Thiyagarajan, P, Lewis, S, Bansal, A, Schadler, L S, Lurio, L B
Format: Article
Language:English
Subjects:
ALUMINIUM OXIDES
COMPOSITE MATERIALS
GLASS
INTERFACES
MATERIALS SCIENCE
NANOSTRUCTURES
PARTICLES
POLYMERS
STRESSES
STRUCTURE FACTORS
TRANSITION TEMPERATURE
X-RAY SPECTROSCOPY
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Summary: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.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.97.075505