Role of Dynamical Heterogeneities on the Mechanical Response of Confined Polymer

Polymer near their glassy transition are known to exhibit dynamical heterogeneities. By “dynamical heterogeneities” one means that local relaxation times can vary of 4 order of magnitude from place to place in the sample, with a characteristic length scale of a few nanometer.
 
Glassy polymer, when confined up to nanometric gaps, exhibits a mechanical relaxation that can be very different from the bulk one. This is very important for filled rubbers (used in tires for instance) where the polymer confined in between nano-particles is known to control the mechanical macroscopic properties.
 
In this paper we prove that this heterogeneous dynamics is responsible for the modification of the apparent mechanical response when the system is confined. We compare quantitatively the results of our theoretical description with experimental data on confined system. We conclude that dynamical heterogeneities are completely at the origin of confinement effect on the polymer dynamics if the characteristic length scale is about 5 nm.
 
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R. J. Masurel, P. Gelineau, S. Cantournet, A. Dequidt, D. R. Long, F. Lequeux, and H. Montes. Physics review letters 118, 047801 (2017)
 
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.047801