Adsorption and grafting on colloidal interfaces studied by scattering techniques

Abstract

The adsorption of polymer and surfactant molecules onto colloidal particles or droplets in solution can be characterized non-destructively by scattering techniques. In a first part, the general framework of Dynamic Light Scattering, Small Angle Neutron and X-ray Scattering for the determination of the structure of adsorbed layers, and namely of the density profile, is presented. We then review recent studies of layers of the model polymer poly(ethylene oxide), as homopolymer or part of a block copolymer. In this field, scattering with contrast variation has been shown to be a powerful tool to obtain a detailed description of the layer structure. Adsorption of chemically more complex systems, including polyelectrolytes, polymer complexes, grafted chains and biomacromolecules are also discussed in this review, as well as surfactant adsorption.

Introduction to soft matter and neutron scattering

“…Another complex but common situation is the conformation of macromolecules on a surface. If the surface is a nanoparticle, then small-angle scattering can be used to access the polymer structure [81,[127][128][129][130]. If on the other hand, the surface is flat, then reflectometry and possibly GISANS are the methods of choice [95,[131][132][133].…”

Probing effects of polymer adsorption in colloidal particle suspensions by light scattering as relevant for the aquatic environment: An overview

“…Small-angle neutron scattering experiments have been successfully used to study this property (Mears et al, 1998;Hone et al, 2002;Oberdisse, 2007;Vaccaro et al, 2009). This technique has the advantage that simultaneous measurements of the adsorbed amount and of the layer thickness are possible.…”

Reduced colloidal repulsion imparted by adsorbed polymer of particle dimensions

“…For noninteracting particles in the dilute limit, there is no spatial correlation between different particles. The particle size and shape can, in principle, be unraveled by comparing the scattering data with analytic theories on form factor [33]. For concentrated samples, colloidal interactions introduce spatial correlations over distances considerably greater than the particle diameter and thus contribute additionally to the total scattering intensity.…”

“…For this purpose, centrifugal depletion methods were often employed to separate non-adsorbed polymer chains and the polymer-coated particles, and the amount of polymer adsorption was later determined by a mass balance [3] or UV spectroscopy [52]. Alternatively, a combination of various optical-scattering experiments (typically, DLS and SAXS or SANS) has been employed for a similar purpose [33,44,53]. In this study, DLS analysis was first utilized to determine the adsorption isotherm for PEO-coated particles.…”