The linear elastic properties of isotropic
materials of polymer tethered nanoparticles (NPs) are
evaluated using noncontact Brillouin light spectroscopy.
While the mechanical properties of dense brush materials
follow predicted trends with NP composition, a surprising
increase in elastic moduli is observed in the case of sparsely
grafted particle systems at approximately equal NP filling
ratio. Complementary molecular dynamics simulations reveal
that the stiffening is caused by the coil-like conformations of
the grafted chains, which lead to stronger polymer?polymer
interactions compared to densely grafted NPs with short
chains. Our results point to novel opportunities to enhance
the physical properties of composite materials by the strategic
design of the “molecular architecture” of constituents to benefit from synergistic effects relating to the organization of the
polymer component
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