Slow, nondiffusive dynamics in concentrated nanoemulsions.
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.
Guo
H
H
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.
Wilking
J N
JN
Liang
D
D
Mason
T G
TG
Harden
J L
JL
Leheny
R L
RL