Dynamics of equilibrium linked colloidal gels

Abstract

Colloids that attractively bond to only a few neighbors (e.g., patchy particles) can form equilibrium gels with distinctive dynamic properties that are stable in time. Here, we use a coarse-grained model to explore the dynamics of linked networks of patchy colloids whose average valence is macroscopically, rather than microscopically, constrained. Simulation results for the model show dynamic hallmarks of equilibrium gel formation and establish that the colloid-colloid bond persistence time controls the characteristic slow relaxation of the self-intermediate scattering function. The model features re-entrant network formation without phase separation as a function of linker concentration, centered at the stoichiometric ratio of linker ends to nanoparticle surface bonding sites. Departures from stoichiometry result in linker-starved or site-starved networks with reduced connectivity and shorter characteristic relaxation times with lower activation energies. Underlying the re-entrant trends, dynamic properties vary monotonically with the number of effective network bonds per colloid, a quantity that can be predicted using Wertheim's thermodynamic perturbation theory. These behaviors suggest macroscopic in situ strategies for tuning the dynamical response of colloidal networks.

25 pages, 9 figures

References in corpus (10)

• Phase diagram of patchy colloids: towards empty liquids
• Theoretical and numerical study of the phase diagram of patchy colloids: ordered and disordered patch arrangements
• Percolation in a Model Transient Network: Rheology and Dynamic Light Scattering
• Equilibrium gels of limited valence colloids
• Robust Phase Behavior of Model Transient networks
• Assembling Inorganic Nanocrystal Gels
• The physics of Empty Liquids: from Patchy particles to Water
• Origin and Detection of Microstructural Clustering in Fluids with Spatial-Range Competitive Interactions
• Effects of linker flexibility on phase behavior and structure of linked colloidal gels
• Percolation in binary mixtures of linkers and particles: chaining {\it {vs}} branching