Physical aging and compressed exponential behaviors in a model soft colloidal system

Abstract

Compressed exponential g2(t) does not require super-diffusive MSD behavior.

Linear and nonlinear viscoelasticity of concentrated thermoresponsive microgel suspensions

“…Thus, at T>37℃ we expect particles have effectively collapsed to an essentially temperature independent size. At low temperature, the microgel diameter changes linearly with heating until very close to LCST, per dynamic light scattering measurements [37]. This initial linear diameter decrease with heating dependence can be modeled as [37],…”

“Dense diffusion” in colloidal glasses: short-ranged long-time self-diffusion as a mechanistic model for relaxation dynamics

“…While we aim to accomplish this by rapidly increasing the pressure of a hard-sphere system to compress the solvent, such experiments are still in development. To make progress, we use sudden swelling of microgel particles to increase volume fraction [103][104][105][106][107] , but the swollen particles are substantially softer. Softness complicates the calculation of volume fraction and introduces elastic deformation and relaxation that shift the random close packing (and presumably the glass transition) point to higher volume fractions.…”

“…In the present work, we combine large-scale dynamic simulations with experiments to carry out constant-volume, constantnumber-density particle-size jumps from a colloidal liquid state to varying depths near and beyond the putative glass transition. Experimental realization of a similar protocol to trigger the glass transition was recently implemented with thermo-responsive microgel particles [103][104][105][106][107] ; the first in silico modeling of a size-jump volume-fraction quench was implemented recently in our study of time-concentration superposition 108 . Here we expand that model to interrogate detailed particle-scale dynamics.…”

Multiple dynamic regimes in a coarsening foam

“…At large enough q, our results denote that compressed exponential relaxations are associated to a ballisticlike dispersion relation. Such combination has been found in a variety of non-equilibrium systems [5,6,21,22,23,11,24,7], and has been rationalized in terms of a heuristic model, originally developed for colloidal gels [25] [8]. This model entailed that randomly distributed local rearrangement events would lead to stress inhomogeneities that act as dipolar forces, inducing strain fields that would give rise to ultraslow yet continuous ballistic-like motion of the gel strands.…”

“…Such stress-driven dynamics has been inferred to be at the origin of residual activity in a number of aging soft matter systems [4,5]. Experimental evidence for this scenario were obtained in dynamic light scattering experiments, yielding intermediate scattering functions displaying compressed exponential decays with relaxation rates Γ(q) depending linearly on the scattering wavevector q, reminiscent of ballistic motion [5,6,7].…”