Structural Dynamics and Interfacial Properties of Elastomer Nano-composites

The combined effect of filler networking and reduced chain mobility close to the filler interface on the dynamic-mechanical properties of elastomers is analyzed based on investigations of the relaxation dynamics of solution styrene butadiene rubber filled with different loadings of silica. Dynamic-mechanical and dielectric spectra are studied in a wide frequency and temperature range. For the creation of dynamic-mechanical master curves frequency dependent measurements at different temperatures are applied to cover a larger frequency range. It is demonstrated that the time-temperaturesuperposition (TTS)-principle is not fulfilled for filled elastomers and the introduction of vertical shift factors is necessary to obtain viscoelastic master curves. The changes in the dynamic-mechanical properties by the incorporation of fillers and the failure of the TTS-principle in the low frequency (high temperature) regime are shown to be related to the superimposed dynamics of the filler network. It is governed by the viscoelastic response of glassy-like polymer bridges between adjacent filler particles, which differs from that of the polymer matrix. The reduced chain mobility close to the filler interface becomes apparent by a broadening of the glass transition on the high temperature side.