Polyelectrolyte-mediated surface interactions.
ABSTRACT The current understanding of interactions between surfaces coated with polyelectrolytes is reviewed. Experimental data obtained with various surface force techniques are reported and compared with theoretical predictions. The majority of the studies concerned with interactions between polyelectrolyte-coated surfaces deal with polyelectrolytes adsorbed to oppositely charged surfaces, and this is also the main focus of this review. However, we also consider polyelectrolytes adsorbed to uncharged surfaces and to similarly charged surfaces, areas where theoretical predictions are available, but relevant experimental data are mostly lacking. We also devote sections to interactions between polyelectrolyte brush-layers and to interactions due to non-adsorbing polyelectrolytes. Here, a sufficient amount of both theoretical and experimental studies are reported to allow us to comment on the agreement between theory and experiments. A topic of particular interest is the presence of trapped non-equilibrium states that often is encountered in experiments, but difficult to treat theoretically.
- SourceAvailable from: ncsu.edu[show abstract] [hide abstract]
ABSTRACT: The interactions between nonpolar surfaces coated with the nonionic surfactant hexaoxyethylene dodecyl ether C12E6 were investigated using two techniques and three different types of surfaces. As nonpolar surfaces, the air/water interface, silanated negatively charged glass, and thiolated uncharged gold surfaces were chosen. The interactions between the air/water interfaces were measured with a thin film pressure balance in terms of disjoining pressure as a function of film thickness. The interactions between the solid/liquid interfaces were determined using a bimorph surface force apparatus. The influence of the nature of the surface on the interaction forces was investigated at surfactant concentrations below and above the cmc. The adsorption of the nonionic surfactant on the uncharged thiolated surface does not, as expected, lead to any buildup of a surface charge. On the other hand, adsorption of C12E6 on the charged silanated glass and the charged air/water interface results in a lowering of the surface charge density. The reduction of the surface charge density on the silanated glass surfaces is rationalized by changes in the dielectric permittivity around the charged silanol groups. The reason for the surface charge observed at the air/water interface as well as its decrease with increasing surfactant concentration is discussed and a new mechanism for generation of OH- ions at this particular interface is proposed.Langmuir 07/2004; 20(12):4977-88. · 4.19 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Using small angle neutron scattering techniques, we have determined the interfacial density profile of polyelectrolyte brushes. We show that in pure water the density profile has a Gaussian shape whose characteristic length appears to be a decreasing function of the grafting density. Upon the addition of salt, the layers shrink but never collapse. Even at very high ionic strength, the chains remain stretched and the density profile is eventually parabolic.Physical Review Letters 11/1995; 75(15):2863-2866. · 7.94 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Free-standing black films drawn from a diblock copolymer aqueous solution were studied by x-ray reflectivity. Because of the hydrophilic part of the copolymer which is a highly charged polyelectrolyte (NaPSS), such films behave as two opposing charged brushes. Above a determined threshold the thickness of the double brush decreases slowly as electrolyte is added. These results are in good agreement with recent mean-field theories.Physical Review Letters 06/1995; 74(18):3628-3631. · 7.94 Impact Factor