Dynamic Light Scattering and Small-Angle Neutron Scattering Studies on the Poly(ethylene oxide)/Sodium Dodecyl Sulfate/Polystyrene Latex System

Abstract

Dynamic light scattering and small-angle neutron scattering measurements have been performed on aqueous polystyrene latex dispersions with physisorbed polymer, poly(ethylene oxide), in the presence of the surfactant sodium dodecyl sulfate (SDS). Dynamic light scattering measurements suggested that the polymer layer is partially desorbed at surfactant concentrations close to the critical micelle concentration. At surfactant concentrations above the normal critical micelle concentration, the hydrodynamic thickness increased close to the value in the absence of surfactant. Small-angle neutron scattering measurements suggested that as the normal critical micelle concentration of the surfactant was approached, very thin layers were formed. It was possible to obtain the volume fraction profiles of the adsorbed polymer layer, along with information on the structure of the surfactant micelles. Two types of SDS structures were observed, one corresponding to SDS existing bound to bulk polymer and the other to SDS bound to adsorbed polymer.

Polymer/Surfactant Interaction: Interfacial Aspects

“…What is surprising is that beyond the cmc the layer thickness increases again, suggesting that SDS micelles are bound by the residually attached PEO chains. In general terms these results were confirmed by similar measurements on polystyrene latex particles on which the PEO was either adsorbed or grafted (53,54), and also by SANS measurements (54).…”

Applications of Dissipative Particle Dynamics

“…Chari et al [54] obtained the swelling exponent ν = 0.65 for a saturated PEO/SDS system as we find here. Thompson et al [57] study the thickness of an adsorbed layer of PEO, and find an initial decrease, followed by a subsequent increase when the SDS concentration is increased, very similar to the present simulation results. In the previous simulations, the number of surfactant molecules in the system was varied.…”

“…Fluorescence measurements on the same system indicate that the aggregation number of SDS is low at the onset of binding, but increases with surfactant concentration where the aggregate forms an elongated rod [55]. For PEO/SDS (PEO = polyethyleneoxide) mixtures it is also found that on increasing SDS concentration the polymer initially reduces in size, but when the surfactant concentration is increased beyond a certain point the polymer swells again [56,57]. [49] To predict when in a polymer-surfactant system such molecular bottlebrushes are formed, and when the surfactant adsorbs as micelles, Groot employed the DPD technique [58].…”

Neutron and light scattering studies of light-harvesting photosynthetic antenna complexes

“…Further, DLS requires a much shorter time (within 1-2 min) than SANS measurements (minutes to hours) for probing the particle size and other structural information, so one can probe the near real-time structural information of particles and biomolecules with minimal sample preparation (see below). Combinations of SANS and DLS have been used to characterize self-assembled polymers and the structural features of biomolecules and protein (or polymer)-surfactant complexes (Borsali et al 1998;Chodankar et al 2007;Hanson et al 2001;Inomoto et al 2009;Mears et al 1998;Okabe et al 2004;Romer et al 2003;Yajima et al 1998). In summary, SANS has great potential to assist structural investigation for biological systems that will not crystallize and/or have little hope of acquiring atomic-resolution structures (some examples are illustrated below).…”