The mechanical reinforcement of polymer nanocomposites above their glass transition temperature has been extensively studied. However, much less is known about the origin of this effect when composite is vitrified. In the present talk, we unravel the effect of polymer molecular weight on the mechanism of reinforcement in glassy nanocomposites with attractive interaction between polymer and filler. Mechanical properties were measured using Brillouin light scattering. Our results demonstrate that the increase of molecular weight of the polymer matrix results in a decrease in the mechanical properties in the composite. We ascribe this phenomenon to the reported earlier reduction of density in the interfacial region formed around the nanoparticles with increase of molecular weight of the matrix. Based on this result, we hypothesize that densification of the interfacial region might be an effective way to improve the mechanical properties in composite with high molecular weight. The latter can be achieve by mixing in a small amount of polymer of low molecular weight. Indeed, our results demonstrate a significant improvement in mechanical performance of the composite that contain high molecular weight with small addition of the low molecular weight polymer. This finding is important for the design of materials with the desired mechanical properties.

Improving mechanical properties in glassy polymer nanocomposites: effect of molecular weight

255th National Meeting (2018)

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