Charged colloids and polyelectrolytes: from statics to electrokinetics

Abstract

Experimental study of granular convection in (real) two-dimension Brazil-nut effect H A C Wibowo, T N Ain, Y P Nugraha et al. Abstract.A review is given on recent studies of charged colloidal suspensions and polyelectrolytes both in static and non-equilibrium situations. As far as static equilibrium situations are concerned, we discuss three different problems: 1) Sedimentation density profiles in charged suspensions are shown to exhibit a stretched non-bariometric wing at large heights and binary suspensions under gravity can exhibit an analog of the brazil-nut effect known from granular matter, i.e. the heavier particles settle on top of the lighter ones. 2) Soft polyelectrolyte systems like polyelectrolyte stars and microgels show an ultra-soft effective interaction and this results into an unusual equilibrium phase diagram including reentrant melting transitions and stable open crystalline lattices.3) The freezing transition in bilayers of confined charged suspensions is discussed and a reentrant behaviour is obtained. As far as nonequilibrium problems are concerned, we discuss an interface instability in oppositely driven colloidal mixtures and discuss possible approaches to simulate electrokinetic effects in charged suspensions.

Design principles for Bernal spirals and helices with tunable pitch

“…2 shows that the pitch length can be controlled by modulating the range of the screened electrostatic interactions, which can be tuned experimentally by changing the salt concentration of the medium. 48 It is evident that the pitch of the helix changes by nearly 30% upon varying k over a range accessible in experiments for both N ¼ 9 and N ¼ 20. The slight difference between the two sizes arises due to additional (attractive) dipolar interactions when more dumbbells are present in the cluster.…”

“…A single helical strand is observed without any predetermined chirality for clusters up to at least N = 20 for the set of parameters investigated. Figure 1 shows that the pitch length can be controlled by modulating the range of the screened electrostatic interactions, which can be tuned experimentally by changing the salt concentration of the medium [46]. It is evident that the pitch of the helix changes by nearly 30% upon varying κ over a range accessible in experiments for both N = 9 and N = 20.…”

Self-Organization at Aqueous Colloid-Membrane Interfaces and an Optical Method to Measure the Kinetics of Exclusion Zone Formation

“…Such a model would require a more sophisticated theoretical treatment than those that have been previously published. A very large number of parameters combined with electrostatics and hydrodynamics and their coupling, including electro-osmosis and electro-hydrodynamic convection, would be involved [16]. Parameters including van der Waals interactions, Brownian motion, surface interactions from the glass or charged hydrophilic membrane boundaries, parameters characterizing the applied electromagnetic field, gravity, properties of the solvent, ions, and the size and shape of colloidal particles, must all be considered.…”

Gauss law constraints on Debye-Hückel screening

“…These areas include classical electrodynamics [1], equilibrium statistical mechanics [2,3], nonequilibrium transport processes [4], plasma physics [5][6][7], relativistic heavy-ion collisions [8][9][10] and chemical electrolytes/colloids [11][12][13][14].…”