XPCS Study of Temporal Dynamic Heterogeneity in a Rubber Nanocomposite

In situ X-ray Photon Correlation Spectroscopy can be used to characterize the temporal heterogeneity in the dynamics of silica filler movement when a highly filled rubber nanocomposite is strained.  After a step strain the motions of the filler particles and network do not necessarily develop in a temporally uniform way.  The relaxation of the stress can involve sudden slowing down of the particle movement and sudden speeding up of the movement.  There are various means of visualizing and describing this intriguing dynamic heterogeneity.  The heterogeneity is seen to be less prevalent when a silane coupling agent is added to the rubber.  Also, the character of the heterogeneity varies when the type of silica filler is varied.  The variation in the intensity and duration of the heterogeneity with direction (e.g. strain direction vs. perpendicular to strain) can also be resolved.