Showing papers by "Peter Schurtenberger published in 1994"

Understanding colloidal charge renormalization from surface chemistry: Experiment and theory

Abstract: In this paper we report on the charging behavior of latex particles in aqueous suspensions. We use static light scattering and acid–base titrations as complementary techniques to observe both effective and bare particle charges. Acid–base titrations at various ionic strengths provide the pH dependent charging curves. The surface chemical parameters (dissociation constant of the acidic carboxylic groups, total density of ionizable sites and Stern capacitance) are determined from fits of a Stern layer model to the titration data. We find strong evidence that the dissociation of protons is the only specific adsorption process. Effective particle charges are determined by fits of integral equation calculations of the polydisperse static structure factor to the static light scattering data. A generalization of the Poisson–Boltzmann cell model including the dissociation of the acidic surface groups and the autodissociation of water is used to predict effective particle charges from the surface chemical parameters determined by the titration experiments. We find that the light scattering data are best described by a model where a small fraction of the ionizable surface sites are sulfate groups which are completely dissociated at moderate pH. These effective charges are comparable to the predictions by a basic cell model where charge regulation is absent.

The static and dynamic structure factor of polymer-like lecithin reverse micelles

Abstract: We report a detailed analysis of the static and dynamic structure factor of polymer-like lecithin reverse micelles. We previously demonstrated that one can directly apply the results from conformation space renormalization group theory for semi-dilute polymer solutions to «equilibrium polymers» such as worm-like micelles or microemulsions, if one takes into account the fact that their size distribution is concentration dependent [1]. The present study confirms these findings and shows that this approach can be extended to the Q- and c-dependence of the static (S(Q)) and dynamic (S(Q, t)) structure factor

Spontaneous vesiculation: mixed lecithin-bile salt solutions as a biologically relevant model system

Abstract: Spontaneous formation of vesicles which occurs upon dilution of lecithin-bile salt mixed micellar solutions was studied using static (SLS) and dynamic (DLS) light scattering. Special attention was paid to the properties of the vesicles formed, and also to the mixed micellar precursors, since the structure of these mixed micelles is still controversial. We show how a self-consistent interpretation of the SLS and DLS data can be achieved using concepts from colloid and polymer physics and incorporating the effects of polydispersity and interparticle interactions. The micelle to vesicle transition is interpreted within the framework of current theoretical models for the spontaneous formation of vesicles.