Capacitive Compactness and Surface Charge Density Variation in Pluronic (F-127) Micelles using Small-Angle X-ray Scattering

The spatial extent of a charged colloid or an electrode is usually characterized by its Debye length which is independent of important physical features including colloidal charge and electrostatic ion correlations. To describe the colloidal stability of electrified nanoparticles more accurately we need tools to study the structure of the electrical double layer. Colloidal particles can be used in diverse technological applications involving colloidal stability of charged solutions, or storage capacity of electrical energy in batteries or supercapacitors. Capacitive compactness is a novel description of the diffuse electrical double layer extension in terms of an effective capacitor and has ability to consider important physical characteristics of the solute. We have chosen Pluronic F-127 in this work because it is a temperature responsive triblock copolymer with well-known adsorption and colloidal properties. In this work, we studied the surface charge density of Pluronic F-127 micelles at different concentration and pH to understand how interparticle interactions relate to capacitive compactness. Small-angle x-ray scattering results were used to analyze the micelle-micelle structure factor and relate it to pH dependent changes in the capacitive compactness.