Controlling the dynamics of a bidimensional gel above and below its percolation transition

Abstract

The morphology and the microscopic internal dynamics of a bidimensional gel formed by spontaneous aggregation of gold nanoparticles confined at the water surface are investigated by a suite of techniques, including grazing-incidence x-ray photon correlation spectroscopy (GI-XPCS). The range of concentrations studied spans across the percolation transition for the formation of the gel. The dynamical features observed by GI-XPCS are interpreted in view of the results of microscopical imaging; an intrinsic link between the mechanical modulus and internal dynamics is demonstrated for all the concentrations. Our work presents, to the best of our knowledge, the first example of a transition from stretched to compressed correlation function actively controlled by quasistatically varying the relevant thermodynamic variable. Moreover, by applying a model proposed time ago by Duri and Cipelletti [A. Duri and L. Cipelletti, Europhys. Lett. 76, 972 (2006)] we are able to build a novel master curve for the shape parameter, whose scaling factor allows us to quantify a 'long time displacement length'. This characteristic length is shown to converge, as the concentration is increased, to the 'short time localization length' determined by pseudo Debye-Waller analysis of the initial contrast. Finally, the intrinsic dynamics of the system are then compared with that induced by means of a delicate mechanical perturbation applied to the interface.

References in corpus (8)

• Atomic-scale relaxation dynamics and aging in a metallic glass probed by X-ray photon correlation spectroscopy
• Length scale dependence of dynamical heterogeneity in a colloidal fractal gel
• Anomalous dynamical light scattering in soft glassy gels
• Dichotomic Aging Behaviour in a Colloidal Glass
• Heterogeneous and anisotropic dynamics of a 2D gel
• Subdiffusion and intermittent dynamic fluctuations in the aging regime of concentrated hard spheres
• Slow dynamics in an azopolymer molecular layer studied by x-ray photon correlation spectroscopy
• Equilibrium and out-of-equilibrium dynamics in a molecular layer of azopolymer floating on water studied by Interfacial Shear Rheology

Cited by in corpus (5)

• Unveiling the structural arrangements responsible for the atomic dynamics in metallic glasses during physical aging
• Relaxation in yield stress systems through elastically interacting activated events
• Liquid-liquid transition revealed by quasi-static cooling of an ultra-viscous metallic liquid
• Wave vector dependence of the dynamics in supercooled metallic liquids
• Multiple dynamic regimes in a coarsening foam