Showing papers by "Andrew Doherty published in 2000"
TL;DR: The long-time self-diffusion coefficients of Triton X-100 micelles have been determined as a function of surfactant and electrolyte concentrations using rotating disk electrode voltammetry in conju... as discussed by the authors.
Abstract: The long-time self-diffusion coefficients of Triton X-100 micelles have been determined as a function of surfactant and electrolyte concentrations using rotating disk electrode voltammetry in conju...
70 citations
TL;DR: In this article, cyclic voltammetry, chronoamperometry, and the rotating disk electrode (RDE) were used for the determination of micellar hydrodynamic radii and showed that only the steady-state RDE yields values directly comparable with nonelectrochemical techniques.
Abstract: Self-assembled systems such as micelles and liquid crystals are currently of interest as templates for the controlled formation of nanoscale structures. Knowledge of the mesophase structure, structural evolution, and interparticle interaction is of great importance in understanding the behavior of such systems especially for applications such as nanoreactors. Here, we compare the use of cyclic voltammetry, chronoamperometry, and the rotating disk electrode (RDE) for the determination of micellar hydrodynamic radii and show that only the steady-state RDE yields values directly comparable with nonelectrochemical techniques. The RDE is applied for the determination of cetyltrimethylammonium chloride micellar structure and observing micellar structural evolution as well as evaluating the usual intermicellar interactions. The results clearly show (a) the collapse of the micellar shear plane toward the hard-sphere surface with increasing electrolyte concentration, (b) the electrolyte-dependent spherical expansion of the micellar hard-spheres due to increasing aggregation (N) number, (c) the structural transition from spherical to rodlike micelles, and (d) micellar elongation. As well as structural evolution, the evolutionary changes in interaction processes are also observed, i.e. the transition from Coulombic interactions to excluded volume interaction. This paper describes in detail the voltammetric measurement of these processes and explicates the necessary experimental conditions for successful observation of micellar structural evolution.
36 citations
TL;DR: In this article, the authors measured the long-time self-diffusion coefficients (Ds) of AOT (AOT = sodium bis-2-ethylhexylsulfosuccinate) reverse micelles in isooctane using K3Fe(CN)6 as a micelle-immobilized electroactive probe.
Abstract: Microelectrode voltammetry has been used to measure the long-time self-diffusion coefficients (Ds) of AOT (AOT = sodium bis-2-ethylhexylsulfosuccinate) reverse micelles in isooctane using K3Fe(CN)6 as a micelle-immobilized electroactive probe. Ds values were found to be a function of both reverse micellar volume fraction (φmic) and probe concentration. The results show that increasing the probe concentration results in a decrease in Ds, suggesting an increase in attractive intermicellar interaction upon addition of probe. This has been interpreted in terms of attenuated surfactant tail-group reorganization facilitating interpenetrating of the surfactant tails. Increasing the micellar volume fraction is seen to diminish attractive interaction which indicates the presence of entropy-driven solvent mediated depletion forces. Self-diffusion coefficients at the limit of zero probe concentration ( ) were found to be micellar volume fraction dependent, and the behavior conformed to the linear interaction theory ...
33 citations