Evolution of local dynamics and mechanical aging in soft solids

James Harden, The Johns Hopkins University

This talk presents studies of the local dynamics and mechanics of nanoparticle suspensions that form soft, gel-like materials. A combination of dynamic light scattering, diffusing wave spectroscopy, neutron spin echo, SANS, and X-ray photon correlation spectroscopy were used to monitor the local dynamics and the formation, aging, and rejuvenation of these soft glassy phases. Specific systems to be discussed include Laponite (a suspension of repulsive discoidal particles), depletion gels of spherical silica nanoparticles in polymer solutions, and cubic mesophases of block copolymer micelles. In these very different attractive and repulsive systems, we observe a number of common features in the collective dynamics and aging behavior, which we discuss within the general theoretical framework of soft glassy materials.

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