Modified chain dynamics in poly(dimethylsiloxane)/silica nanocomposites

The molecular dynamics of a series of poly(dimethylsiloxane) networks filled with silica nanoparticles synthesized in situ was studied using dielectric relaxation spectroscopy. In addition to the α-relaxation associated with the glass transition of the polymer matrix, we observe a slower α-relaxation. This behavior is discussed in terms of a gradual increase of relaxation times close to the surface of the nanoparticles. The range of this effect is estimated to be around 3 nm at Tg, decreasing slightly with increasing temperature. The results are discussed in relation to molecular dynamics simulations of supercooled liquids close to an interface, as well as experimental studies of nanoconfined glass forming liquids and thin polymer films.