title: Slow, nondiffusive dynamics in concentrated nanoemulsions.
abstract: Using multispeckle x-ray photon correlation spectroscopy, we have measured the slow, wave-vector-dependent dynamics of concentrated, disordered nanoemulsions composed of silicone oil droplets in water. The intermediate scattering function possesses a compressed exponential line shape and a relaxation time that varies inversely with wave vector. We interpret this dynamics as strain in response to local stress relaxation. The motion includes a transient component whose characteristic velocity decays exponentially with time following a mechanical perturbation of the nanoemulsions and a second component whose characteristic velocity is essentially independent of time. The steady-state characteristic velocity is surprisingly insensitive to the droplet volume fraction in the concentrated regime, indicating that the strain motion is only weakly dependent on the droplet-droplet interactions.
authors.affiliation: Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: H
authors.initials: H
authors.lastname: Guo
authors.forename: J N
authors.initials: JN
authors.lastname: Wilking
authors.forename: D
authors.initials: D
authors.lastname: Liang
authors.forename: T G
authors.initials: TG
authors.lastname: Mason
authors.forename: J L
authors.initials: JL
authors.lastname: Harden
authors.forename: R L
authors.initials: RL
authors.lastname: Leheny